A Commericial Sunscreen Modulates Aryl Hydrocarbon Receptor-Signaling in Keratinocytes and Inhibits CYP1A1 and CYP1B1 Enzyme Activities

This topic involves gene-environment interactions. Octinoxate (a sunscreen) is the “environmental signal”, and genetic activation via aryl hydrocarbon receptor (AHR)-signaling represents the “response to the signal.”

We are constantly exposed to varying levels of ultraviolet radiation (UVR) from the sun — which includes two main wavelength differences, UVA (320–400 nm) and UVB (280–320 nm). This exposure elicits beneficial effects (e.g. enhancing our vitamin D levels); however, UVB exposure is well known to cause increased risk of skin cancer (via DNA mutagenic lesions). To decrease this risk, sunscreens are now widely used to protect our skin. Commercially available sunscreens usually contain a mixture of organic and/or inorganic compounds that function as UVR filters (by either absorbing or reflecting UVR away from skin). Despite this protection, studies suggest UVR filters do not stay exclusively on the skin surface (i.e. several sunscreens are known to penetrate through the outer layers of epidermis and reach systemic circulation at measurable concentrations).

In fact, it recently has been shown that, under maximal application conditions, plasma levels of selected UVR sunscreens “exceeded FDA-allowed thresholds in specific toxicological tests.” Authors [see attached article] believe it is important to determine if UVR filters have significant “off-target effects” (i.e. affecting pathways that are better off not being affected) — which could negatively impact human health; this is particularly important for babies and young children, because their skin is thinner than that of adults and usually contains lower levels of melanin (pigment).

Many UVR filters are hydrophobic and contain aromatic rings — making them potential candidates for interacting with AHR, a ligand-activated transcription factor that regulates expression of various enzymes involved in metabolizing both foreign and endogenous compounds (and also has been shown to be important in immune function and skin integrity). In fact, AHR-CYP1 signaling, which is already active in embryonic stem cells, appears to be involved in virtually every cell-type of the body, participating in many dozens of critical-life functions [reviewed in Progr Lipid Res 2017; 67: 38-57].

Authors [see attached article] demonstrated that the UVR sunscreen, octinoxate, potentiated the ability of a known AHR ligand, 6-formylindolo[3,2-b]carbazole (FICZ), to activate AHR. Co-treatment of HaCaT cells (a human immortalized keratinocyte cell line — commonly used in keratinocyte and skin studies) — with octinoxate and FICZ induced cytochrome P450 1A1 (CYP1A1) and P4501B1 (CYP1B1) mRNA transcripts — in an AHR-dependent fashion. Octinoxate was also shown to be an inhibitor of CYP1A1 and CYP1B1 enzyme activity, but with IC50 values of approximately 1 mM and 586 nM, respectively (which are not in a physiologically relevant range, in the eyes of these GEITP pages). Topical application of octinoxate and FICZ on mouse skin also increased CYP1A1 and CYP1B1 mRNA levels. Thus, octinoxate is able to activate AHR-signaling, as well as inhibiting CYP1A1 and CYP1B1 enzyme function at very high concentrations — which (the authors say) “may have important downstream consequences for metabolism of various compounds and skin integrity.” Octinoxate interference with critically-important AHR-dependent pathways, however, is probably far more important than “inhibition of enzyme activities.” 😊
DwN

Toxicol Sci Sept 2020; 177: 188-201

COMMENT:
This recent review seems to be pretty thorough:
Aryl Hydrocarbon Receptor in Atopic Dermatitis and Psoriasis
Masutaka Furue, Akiko Hashimoto-Hachiya, Gaku Tsuji
Int J Mol Sci 2019 Nov; 20: 5424. PMCID: PMC6862295

I just glanced through it, but I hope to find time soon to read it 🙂

I can’t answer what would happen with low doses, especially in the context of low-affinity ligands. I would guess nothing of significance, but that’s kind of my bias. There is some evidence to suggest that low-level activation of AHR by high-affinity ligands increases Th17 cells, instead of Tr1 cells. We published those data, but the effect was not very strong and it was not related to topical exposure. Also, if you have a compound that activates AHR enough to induce metabolism of the ligand — who knows what the metabolites might do locally.
Let me know if you want to discuss this further…

COMMENTs:
on PubMed I entered “AHR contact sensitivity” — and got 36 hits.

https://pubmed.ncbi.nlm.nih.gov/?term=ahr+contact+sensitivity

Even including UVR-induced immunosuppression… I suppose I could even find more articles if I added “psoriasis” to the mix.

DwN

Do you have references handy, demonstrating that lower levels of AHR activation in skin inhibits contact sensitivity and suppresses psoriasis? Do you think that low-level dermal exposure to AHR agonists (doses that modestly elevate AHR activity in skin, e.g ~ 10%) — could be beneficial for psoriasis?

Hi John, I didn’t pay attention to the fact that CYPs are inhibited at high concentrations. I was just thinking about known effects from topical application of several AHR ligands (which would presumably result in increasing CYP activities).

Hi Nancy. Would you predict dermal application of ‘any” inhibitor of CYP1A /CYP1B might have similar beneficial effects, in enhancing the AHR activation?
John

I would predict that epidermal administration of Octinoxate might result in beneficial effects — because topical application of AHR ligands is known to inhibit contact hypersensitivity, as well as to suppress development of psoriasis. 😊

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new binding target for SARS-CoV-2

Exciting new breakthrough in our understanding? These articles might be of interest to some of you.

SARS-CoV-2 binds not only to ACE, but also to neuropilin receptor-1.
—DwN

In silico identification and validation of inhibitors of the interaction between neuropilin receptor 1 and SARS-CoV-2 Spike protein.

Perez-Miller S, Patek M, Moutal A, Cabel CR, Thorne CA, Campos SK, Khanna R.bioRxiv. 2020 Sep 23:2020.09.22.308783. doi: 10.1101/2020.09.22.308783. Preprint.PMID: 32995772 Free PMC article.

Neuropilin‑1 as a new potential SARS‑CoV‑2 infection mediator implicated in the neurologic features and central nervous system involvement of COVID‑19.

Davies J, Randeva HS, Chatha K, Hall M, Spandidos DA, Karteris E, Kyrou I.Mol Med Rep. 2020 Nov;22(5):4221-4226. doi: 10.3892/mmr.2020.11510. Epub 2020 Sep 15.PMID: 33000221 Free PMC article.

COMMENT:
Thanks, Dan. Here is another paper on NRP1: https://www.biorxiv.org/content/10.1101/2020.06.07.137802v3, whose summary states—

The causative agent of the current pandemic and coronavirus disease 2019 (COVID-19) is the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Understanding how SARS-CoV-2 enters and spreads within human organs is crucial for developing strategies to prevent viral dissemination. For many viruses, tissue tropism is determined by the availability of virus receptors on the surface of host cells. Both SARS-CoV and SARS-CoV-2 use angiotensin-converting enzyme 2 (ACE2) as a host receptor, yet, their tropisms differ. Here, we found that the cellular receptor neuropilin-1 (NRP1), known to bind furin-cleaved substrates, significantly potentiates SARS-CoV-2 infectivity, which was inhibited by a monoclonal blocking antibody against the extracellular b1b2 domain of NRP1. NRP1 is abundantly expressed in the respiratory and olfactory epithelium, with highest expression in endothelial cells and in the epithelial cells facing the nasal cavity. Neuropathological analysis of human COVID-19 autopsies revealed SARS-CoV-2 infected NRP1-positive cells in the olfactory epithelium and bulb. In the olfactory bulb, infection was detected particularly within NRP1-positive endothelial cells of small capillaries and medium-sized vessels. Studies in mice demonstrated, after intranasal application, NRP1-mediated transport of virus-sized particles into the central nervous system. Thus, NRP1 could explain the enhanced tropism and spreading of SARS-CoV-2.

Mutated SARS-CoV-2, however, does not appear even to need NRP1. Oh my! ☹

And this publication came out yesterday in Science from the same research group:

Cantuti-Castelvetri L (and 28 additional authors). Neuropilin-1 facilitates SARS-CoV-2 cell entry and infectivity. Science 20 Oct 2020; eabd2985. doi: 10.1126/science.abd2985. Epub ahead of print. PMID: 33082293.

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Effects of Arsenic (+3 Oxidation State) Methyltransferase Gene Polymorphisms and Risk of Bladder Cancer

Bladder cancer ranks as the ninth most common malignant tumor worldwide. Cigarette smoking is among factors known to be associated with increased risk — with smokers exhibiting 3-fold higher risk of developing bladder cancer than nonsmokers. In addition, chronic exposure to chemicals in the environment, more specifically occupational exposure (e.g. workers in the dye industry) is another factor that might increase bladder cancer risk. Inorganic arsenic (As) is a known human carcinogen, commonly ingested by human populations in contaminated water and food, as well as inhalation of particulate matter in polluted air (such as that seen in recent wildfires in the US). In humans, As is reduced to arsenite (AsIII); after methylation by S-adenosylmethionine, AsIII is converted to monomethylated arsenate (MMA) and dimethylated arsenate (DMA), both of which are excreted in urine. Compared with As, MMA and DMA are far more chemically reactive (and therefore more toxic) and more likely to result in bladder cancer.

Heritable differences in the AS3MT gene encoding the arsenic (+3 oxidation state) methyltransferase enzyme (AS3MT) exist in human populations; this could be an additional parameter, when considering risk of AS-induced bladder cancer. Several studies have assessed the possible association of AS3MT polymorphisms with high vs low enzyme activity. To this end, eight single-nucleotide variants (SNVs) have been extensively studied [rs1046778, rs11191439, rs3740393, rs11191438, rs10748835, rs3740391, rs3740392, and rs11191454; see attached article for more details]; authors therefore queried whether AS3MT expression might influence the clinicopathologic characteristics, risk, and prognosis of bladder cancer.

Authors reviewed “eligible” case-control studies of AS3MT polymorphisms and bladder cancer by meta-analysis. They also conducted a series of analyses, based on The Cancer Genome Atlas (TGCA) dataset. Five articles were recruited; authors state that the “pooled results demonstrated that rs3740393 and rs11191438 polymorphisms are related to bladder cancer risk in the overall population (P <0.05) and that GG and GC genotypes in rs3740393, and GG genotype in rs11191438, might be susceptibility genotypes for bladder cancer.” Authors also state that “results, based on 168 bladder cancer samples from TGCA, indicated that patients with higher AS3MT expression had poorer overall survival time (i.e. AS3MT expression is an independent indicator for bladder cancer prognosis).” However, these kinds of “P <0.05 studies” very often are identifying false positives, due to the >3 billion nucleotides in the haploid genome of each individual, thereby requiring a P-value of <5.0 x 10–8 (also denoted as <5.0e–08) in order to reach statistical significance. The title of this [attached] paper was exciting — which was the reason these GEITP pages chose to highlight it. Sadly, however, this “meta-analysis paper” was improperly reviewed and should never have been accepted for publication. Alternatively, authors might have concluded from their meta-analysis that “no statistically significant association was found.” The sizes of the cohorts were likely far too small to reach statistical significance (i.e. perhaps statistical significance of <5.0e-08 could be achieved — assigning AS3MT as a small-effect gene contributing to bladder cancer risk — if one had 100,000 cases of bladder cancer, compared with 100,000 controls?). * * * * * * * * * * In comparison, consider a genome-wide association study (GWAS) of 1,313 As-exposed Bangladeshi individuals, in which five highly significant SNVs in and near the AS3MT gene showed independent associations with As-induced toxicity at a significance level of P <5.0e–08, with five SNVs showing independent associations. Expression quantitative trait locus (eQTL) analyses of genome-wide expression data from 950 individuals’ lymphocyte RNA also suggested that several of these identified SNVs represent cis-eQTLs for AS3MT (P = 1.0e-12) and for neighboring gene C10orf32 (P = 10e-44), which is involved in C10orf32-AS3MT read-through transcription [PLoS Genet 2012; 8: e1002522].This paper is commendable 😊, especially compared to the [attached] article. ☹ DwN Toxicol Sci Sept 2020; 77: 27-40 COMMENT: I think this is interesting. Arsenic is known to induce bladder cancer, so it makes sense that the AS3MT gene encoding As3MT is likely to be associated with this increased risk of bladder cancer. So, they simply need a larger cohort to prove this. It is also interesting that this gene was demonstrated in 2012 to be associated with arsenic-induced toxicity. Sooner or later, a GWAS will show an association between SNVs in and near the AS3MT gene and arsenic-induced skin cancer. In the past we discovered aquaporin-9 (AQP9) transports arsenic. However, I don’t see yet any GWAS results to show an association between the AQP9 gene and arsenic-related diseases...

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A Commericial Sunscreen Modulates Aryl Hydrocarbon Receptor-Signaling in Keratinocytes and Inhibits CYP1A1 and CYP1B1 Enzyme Activities

This topic involves gene-environment interactions. Octinoxate (a sunscreen) is the “environmental signal”, and genetic activation via aryl hydrocarbon receptor (AHR)-signaling represents the “response to the signal.”

We are constantly exposed to varying levels of ultraviolet radiation (UVR) from the sun — which includes two main wavelength differences, UVA (320–400 nm) and UVB (280–320 nm). This exposure elicits beneficial effects (e.g. enhancing our vitamin D levels); however, UVB exposure is well known to cause increased risk of skin cancer (via DNA mutagenic lesions). To decrease this risk, sunscreens are now widely used to protect our skin. Commercially available sunscreens usually contain a mixture of organic and/or inorganic compounds that function as UVR filters (by either absorbing or reflecting UVR away from skin). Despite this protection, studies suggest UVR filters do not stay exclusively on the skin surface (i.e. several sunscreens are known to penetrate through the outer layers of epidermis and reach systemic circulation at measurable concentrations).

In fact, it recently has been shown that, under maximal application conditions, plasma levels of selected UVR sunscreens “exceeded FDA-allowed thresholds in specific toxicological tests.” Authors [see attached article] believe it is important to determine if UVR filters have significant “off-target effects” (i.e. affecting pathways that are better off not being affected) — which could negatively impact human health; this is particularly important for babies and young children, because their skin is thinner than that of adults and usually contains lower levels of melanin (pigment).

Many UVR filters are hydrophobic and contain aromatic rings — making them potential candidates for interacting with AHR, a ligand-activated transcription factor that regulates expression of various enzymes involved in metabolizing both foreign and endogenous compounds (and also has been shown to be important in immune function and skin integrity). In fact, AHR-CYP1 signaling, which is already active in embryonic stem cells, appears to be involved in virtually every cell-type of the body, participating in many dozens of critical-life functions [reviewed in Progr Lipid Res 2017; 67: 38-57].

Authors [see attached article] demonstrated that the UVR sunscreen, octinoxate, potentiated the ability of a known AHR ligand, 6-formylindolo[3,2-b]carbazole (FICZ), to activate AHR. Co-treatment of HaCaT cells (a human immortalized keratinocyte cell line — commonly used in keratinocyte and skin studies) — with octinoxate and FICZ induced cytochrome P450 1A1 (CYP1A1) and P4501B1 (CYP1B1) mRNA transcripts — in an AHR-dependent fashion. Octinoxate was also shown to be an inhibitor of CYP1A1 and CYP1B1 enzyme activity, but with IC50 values of approximately 1 mM and 586 nM, respectively (which are not in a physiologically relevant range, in the eyes of these GEITP pages). Topical application of octinoxate and FICZ on mouse skin also increased CYP1A1 and CYP1B1 mRNA levels. Thus, octinoxate is able to activate AHR-signaling, as well as inhibiting CYP1A1 and CYP1B1 enzyme function at very high concentrations — which (the authors say) “may have important downstream consequences for metabolism of various compounds and skin integrity.” Octinoxate interference with critically-important AHR-dependent pathways, however, is probably far more important than “inhibition of enzyme activities.” 😊

DwN

Toxicol Sci Sept 2020; 177: 188-201

COMMENT:
I would predict that epidermal administration of Octinoxate might result in beneficial effects — because topical application of AHR ligands is known to inhibit contact hypersensitivity, as well as to suppress development of psoriasis. 😊

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Changes in regeneration-responsive enhancers affect regenerative capacities in vertebrates

This topic is within the theme of gene-environment interactions. The “environmental signal” is — loss of a body part. ☹ The “response to that signal” is — let’s mobilize our transcription factors and regulatory elements and activate our genetic networks to make a new body part. 😊

Everyone knows that (if that body part is lost), salamanders can regenerate a tail, and some fish can regenerate a fin. However, mammals (e.g. humans, mice) cannot regenerate a limb. In certain species, the ability to regenerate can be limited only to early developmental stages, and not later in life. Changes in cis-regulatory elements, or enhancers (i.e. short DNA segments usually near to the gene they are regulating) are a major source of morphological diversity. Emerging evidence suggests that activation of injury-dependent gene expression may be controlled by injury-responsive enhancer elements. Two such elements, leptin-b (lepb) enhancer in zebrafish (Danio rerio), and the WNT gene cluster (BRV118) enhancer in fruit flies (Drosophila melanogaster), modulate gene expression after injury. However, ablation of lepb in zebrafish, or ablation of the fly WNT enhancer — does not impede regeneration, suggesting that these injury-responsive components might be necessary but not essential for regeneration. Therefore, whether conserved regeneration-responsive, rather than injury-responsive, elements exist in vertebrate genomes and how they evolve have not been conclusively demonstrated.

Identification of enhancers across species is complicated by the fact that these elements mutate rapidly during evolution. A recent study showed that limb and fin regeneration share a deep evolutionary origin. Thus, authors [see attached article] hypothesized that if genetic mechanisms driving regeneration are evolutionarily conserved in distantly related species (subjected to different selective pressures), then it should be possible to distinguish between species-specific and conserved regeneration-responsive enhancers (RREs).

Robust differences in life history — and the ~230 million years of evolutionary divergence — between zebrafish and African killifish Nothobranchius furzeri provide an exclusive biological context in which to test this hypothesis. Both species can regenerate missing body parts, following amputation; however, whereas zebrafish are found in moderately flowing freshwater habitats in Southern Asia, killifish inhabit temporal ponds subjected to annual desiccation in southeast Africa. Strong selective pressure of seasonal desiccation has driven killifish to evolve interesting features — including rapid sexual maturation (as short as 2 weeks), diapause embryos (delays in embryonic growth), and an extremely short life span (4 to 6 months).

Authors [see attached article] (comparing epigenetic and transcriptional changes during early stages of regeneration), discovered an evolutionarily conserved regeneration program involving the fin and heart. Authors also provide evidence that elements of this program have been subjected to evolutionary changes in vertebrate species (which have limited or no regenerative capacities). Among several conserved regeneration-responsive enhancers (RREs), authors found an element — upstream of inhibin beta A (inhba), which is a known effector of vertebrate regeneration. This element activated expression in regenerating transgenic fish, and its genomic deletion perturbed caudal fin regeneration and blocked cardiac regeneration altogether. This enhancer is present in mammals, shares functionally essential activator protein-1 (AP1)–binding motifs, and responds to injury; however, this mammalian element was unable to rescue regeneration in fish. These data suggest that evolutionary alterations in AP1–enriched RREs are likely a crucial source of the loss of regenerative capacities in vertebrates. 😊 ☹

DwN

Science 4 Sept 2020; 369: 1207 eaaz3090

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Regulation of sleep homeostasis mediator (adenosine) in the mouse — mostly by glutamatergic neurons

At first glance, this topic might not seem to be related to the GEITP theme of gene-environment interactions. However, the “environmental signal” (in this case, an endogenous compound from cells other than the target neurons) is a “somnogenic factor” and the gene response in these neurons is to induce sleep in the animal. Homeostatic regulation is a fundamental phenomenon of the sleep-wake cycle, whereby sleep-promoting “somnogenic factors” accumulate in the brain during our waking hours, ultimately inducing sleep. Several extracellular or cytoplasmic factors and associated genetic pathways that contribute to this phenomenon have been identified. Different patterns of neural activity in the brain control the sleep-wake cycle — but how this neural activity contributes to sleep homeostasis — remains largely unknown.

Among various processes implicated in controlling sleep homeostasis, release of adenosine in the basal forebrain is a prominent physiological mediator of sleep homeostasis. Authors [see attached article] used a genetically encoded adenosine sensor to examine in detail the mechanisms underlying increases in adenosine concentration in the basal forebrain. To record the dynamics of extracellular adenosine levels in the basal forebrain during the sleep-wake cycle with high temporal resolution and high specificity and sensitivity, authors designed, and optimized, a G protein–coupled receptor (GPCR)–activation–based (GRAB) sensor for adenosine (GRABAdo) — in which the amount of extracellular adenosine is indicated by the intensity of fluorescence produced by green fluorescent protein (GFP).

Authors [see attached article] then used human embryonic kidney 293T (HEK293T) cultured cells — to show unequivocal membrane-trafficking of adenosine when a saturated concentration of adenosine (100 mM) was administered to the cells in culture; in contrast, a non–ligand-binding mutant form of the sensor showed no detectable response. Using this newly developed genetically-designed adenosine sensor, authors found an activity-dependent rapid increase in extracellular adenosine levels — most specifically in mouse basal forebrain.

Although activity of both cholinergic and glutamatergic neurons in the basal forebrain correlated with changes in the adenosine concentrations, activation of neurons at physiological firing frequencies showed that glutamatergic neurons contributed much greater to the increased adenosine. Mice — having selective ablation of basal forebrain glutamatergic neurons — exhibited a much diminished adenosine-induced response, as well as impaired sleep homeostasis regulation. Therefore, these data show that cell type–specific neural activity in the basal forebrain is most important in dynamically controling sleep homeostasis. 😊

DwN

Science 4 Sept 2020; 369: 1208 eabb0556

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The pandemic—from the virus’ point-of-view

This timely article (surprisingly, from The New York Times) fits very nicely with GEITP’s gene-environment interactions theme. The author writes very clearly and eloquently, with elegant similes. And his approach (in this article) is the same way that we should all think, i.e. “outside the box.” Instead of “thinking of evolution” only in terms of us humans, we should always look at evolution from the point-of-view of the virus, the bacterium, the cancer cell, the tiny mustard plant, the large oak tree, the fungus, the ant, fly, worm, reptile, bird, etc.

Every species (that arises via ‘speciation’) is in this game for their own survival. It is all part of Darwin’s BIG picture. 😊

DwN

The pandemic—from the virus’ point-of-view

The career of the coronavirus so far is, in Darwinian terms, a great success story.

By David Quammen

· Sept. 19, 2020

o

No sensible person can dispute that COVID-19 is a great tragedy for humanity — a tragedy even in the ancient Greek sense, as defined by Aristotle, with the disastrous ending contingent on some prideful flaw in the protagonist. This time it’s not Oedipus or Agamemnon. This time it’s we who are that cocky protagonist, having brought disaster on ourselves. The scope and the devastation of the pandemic reflect bad luck, yes, and a dangerous world, yes, but also catastrophic failures of human foresight, communal will, and leadership.

But look past that record of human failures for a moment, and consider this whole event from the point-of-view of the virus. Measure it by the cold logic of evolution: The career of SARS-CoV-2 so far is, in Darwinian terms, a great success story.

This now-notorious coronavirus was once an inconspicuous creature, lurking quietly in its natural host: some population of animals, possibly bats, in the caves and remnant forests of southern China. The existence of such a living hide-out — also known as a reservoir host — is logically necessary when any new virus appears suddenly as a human infection.

Why? Because everything comes from somewhere, and viruses come from cellular creatures, such as animals, plants or fungi. (A viral particle isn’t a cell; it’s just a strip of genomic instructions enclosed in a protein capsule — a message in a bottle.) A virus can only replicate itself, function as though it were alive and abide over time — if it inhabits the cells of a more complex creature, like a sort of genetic parasite.

Generally, the relationship between virus and reservoir host represents an ancient evolutionary accommodation. The virus persists at a low profile, without causing trouble, without proliferating explosively, and in return it gets long-term security. Its horizons are modest: relatively small population, limited geographical scope.

But this guest-host arrangement is not imperturbably stable, or the end of the story. If another sort of creature comes in close contact with the host — by preying on it, by capturing it, or maybe only by sharing the same cave — the virus might be jostled from its comfort zone and into a new situation: a new potential host.

Suddenly it’s like a gaggle of rats that jump ashore from a ship onto a remote island. The virus might thrive in this new habitat, or it might fail and die out. If it happens to thrive, if by chance it finds the new situation hospitable, then it might establish itself not just in the first new individual — but in the new population.

It might discover itself capable of entering some of the new host’s cells, replicating abundantly, and getting itself transmitted from that individual to others. That jump is called host-switching or, by a slightly more vivid term, spillover. If the spillover results in disease among a dozen or two dozen people, you have an outbreak. If it spreads countrywide, an epidemic. If it spreads worldwide, a pandemic.

Imagine again that gaggle of rats on a previously rat-free island. To their delight, they find the island inhabited by several endemic species of birds, naïve and trusting, accustomed to laying their eggs on the ground. The rats eat those eggs. Soon the island has lost its terns and its rails and its dotterels, but it has an abundance of rats.

Over time, the rats also acquire the ability to dig lizards out of their hiding places amid rocks and logs, and eat them. They develop an improved agility at tree climbing, and eat eggs from birds’ nests up there, too. Now you might as well call the place Rat Island. For the rats, this is a tale of evolutionary success.

If the remote island of habitat is a human being newly colonized by a virus from a nonhuman animal, we call that virus a zoonosis. The resulting infection is a zoonotic disease. More than 60 percent of human infectious diseases, including COVID-19, fall into this category of zoonoses that have succeeded. Some zoonotic diseases are caused by bacteria (such as the bacillus responsible for bubonic plague) or other kinds of pathogen, but most are viral.

Viruses have no malice against us. They have no purposes, no schemes. They follow the same simple Darwinian imperatives as do rats or any other creature driven by a genome: to extend themselves as much as possible in abundance, in geographical space and in time. Their primal instinct is to do just what God commanded to his newly created humans in Genesis 1:28: “Be fruitful and multiply, and fill the earth, and subdue it.”

For an obscure virus, abiding within its reservoir host — a bat or a monkey in some remote region of Asia or Africa, or maybe a mouse in the American Southwest — spilling over into humans offers the opportunity to comply. Not every successful virus will “subdue” the planet, but some go a fair way toward subduing at least humans.

This is how the AIDS pandemic happened. A chimpanzee virus now known as SIVcpz passed from a single chimp into a single human, possibly by blood contact during mortal combat, and took hold in the human. Molecular evidence developed by two teams of scientists, one led by Dr. Beatrice H. Hahn, the other by Michael Worobey, tells us that this most likely happened more than a century ago, in the southeastern corner of Cameroon, in Central Africa, and that the virus took decades to attain proficiency at human-to-human transmission.

By 1960 that virus had traveled downriver to big cities such as Léopoldville (now Kinshasa, the capital of the Democratic Republic of Congo); then it spread to the Americas and burst into notice in the early 1980s. Now we call it “H.I.V.-1 group M”: It’s the pandemic strain, accounting for most of the 71 million known human infections to date.

Chimpanzees were a species in decline, alas, because of habitat loss and killing by humans; humans were a species in ascendance. The SIVcpz virus reversed its own evolutionary prospects by getting into us and adapting well to the new host. It jumped from a sinking lifeboat onto a luxury cruise ship.

SARS-CoV-2 has done likewise, though its success has occurred much more quickly. It has now infected more than 30 million people, just under half as many as the number of people infected by H.I.V., and in 10 months rather than 10 decades. It’s not the most successful human-infecting virus on the planet — that distinction lies elsewhere, possibly with the Epstein-Barr virus, a very transmissible species of herpesvirus, which may reside within at least 90 percent of all humans, causing syndromes in some, and lying latent in most. But SARS-CoV-2 is off to a roaring start.

Now, for purposes of illustration, imagine a different scenario, involving a different virus. In the mountain forests of Rwanda lives a small, insectivorous bat known as Hill’s horseshoe bat (Rhinolophus hilli). This bat is real, but it has been glimpsed only rarely and is classified as critically endangered. Posit a coronavirus, for which this bat serves as reservoir host. Call the virus RhRW19 (a coded abbreviation of the sort biologists use), because it was detected within the species Rhinolophus hilli (Rh), in Rwanda (RW), in 2019 (19).

The virus is hypothetical, but it’s plausible, given that coronaviruses are known to occur in many kinds of horseshoe bats around the world. RhRW19 is on the brink of extinction, because the rare bat is its sole refuge. The lifeboat is leaking badly and nearly swamped.

But then a single Rwandan farmer, needing fertilizer for his crops on a meager patch of dirt, enters a cave and shovels up some bat guano. The guano has come from Hill’s horseshoe bats and it contains the virus. In the process of shoveling and breathing, the farmer becomes infected with RhRW19. He passes it to his brother, and the brother carries it to a provincial clinic where he works as a nurse. The virus circulates for weeks among employees of the clinic and their contacts, making some sick, killing one person, while natural selection improves its capacity to replicate within cells of the human respiratory tract and transmit between people.

A visiting doctor becomes infected, and she carries the virus back to Kigali, the capital. Soon it is at the airport, in the airways of people who don’t yet feel symptoms and are boarding flights for Kinshasa, Doha and London. Now you can give the improved virus a different name: SARS-CoV-3. It’s a success story that hasn’t happened yet but very easily could.

Coronaviruses are an exceptionally dangerous group. The journal Cell recently published a paper on pandemic diseases and how COVID-19 has come upon us, by a scientist named Dr. David M. Morens and one coauthor. Dr. Morens, a prolific author and keen commentator, serves as senior scientific adviser to the director of the National Institute of Allergy and Infectious Diseases, Dr. Anthony Fauci. His coauthor on this paper is Dr. Fauci.

The paper says, among other things, that coronaviruses harbored in various mammalian species “may essentially be preadapted to human infectivity.” Not just bats but other mammals — pangolins, palm civets, cats, ferrets, mink, who knows what — contain cells that are susceptible to the same viral hooks that allow coronaviruses to catch hold of some human cells. Existing within those reservoir hosts may prepare the viruses nicely for infecting us.

The closest known relative of SARS-CoV-2 is a virus discovered seven years ago, in a bat captured at a mine shaft in Yunnan Province, China, by a team under the leadership of Dr. Zhengli Shi, of the Wuhan Institute of Virology. This virus carries the moniker RaTG13. It is about 96 percent similar to SARS-CoV-2, but that four percentage point difference represents decades of evolutionary divergence, possibly in a different population of bats. In other words, RaTG13 and our nemesis bug are not the same virus; they are like cousins who have lived all their adult lives in separate towns.

What happened, during those decades of evolutionary divergence, to bring a still-undiscovered bat coronavirus to the brink of spillover into humans and enable it to become SARS-CoV-2? We don’t yet know. Scientists in China will keep looking for that closer-match virus. The evidence gathered so far is mixed and incomplete, complicated by the fact that coronaviruses are capable of a nifty evolutionary trick: recombination.

This means that — when two strains of coronavirus infect the same individual animal, they may swap sections and emerge as a composite — possibly (by sheer chance) encompassing the most aggressive, adaptive sections of the two. SARS-CoV-2 may be such a composite, built by happenstance and natural selection from components known to exist among other viruses in the wild, and emerging from its nonhuman host with a fearsome capacity to grab, enter and replicate within certain human cells.

Bad luck for us. But evolution is not rigged to please Homo sapiens.

SARS-CoV-2 has made a great career move, spilling over from its reservoir host into humans. It already has achieved two of the three Darwinian imperatives: expanding its abundance and extending its geographical range. Only the third imperative remains as a challenge: to perpetuate itself in time.

Will we ever be rid of it entirely, now that it’s a human virus? Probably not. Will we ever get past the travails of this COVID-19 emergency? Yes.

Dr. Morens has recently been a co-author of another paper examining how coronaviruses have come at us. In it, he and his colleagues nod to the eminent molecular biologist Joshua Lederberg, a Nobel Prize laureate in 1958, at age 33, who later wrote: “The future of humanity and microbes likely will unfold as episodes of a suspense thriller that could be titled ‘Our Wits Versus Their Genes.’ ”

Dr. Morens is on target, and Dr. Lederberg was right. Viruses can evolve, quickly and efficaciously. But we humans are smart — sometimes.

David Quammen is an author and journalist whose books include “Spillover: Animal Infections and the Next Human Pandemic.”

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Antihistamines May Help Calm COVID-19 Cytokine Storm

This study might be of interest to some GEITP’ers. Perhaps the most significant news in this study — is that both drugs are already FDA-approved, over-the-counter (OTC), and easy to acquire. 😊

DwN

Antihistamines May Help Calm COVID-19 Cytokine Storm

By David Douglas

September 11, 2020

NEW YORK (Reuters Health) – Dual histamine-receptor blockade — with cetirizine and famotidine — appears to reduce pulmonary symptoms and may have other benefits in patients with COVID-19, according to a new study.

“We are excited about the global potential application of this unique approach to the cytokine storm which drives morbidity and mortality in this pandemic,” Dr. Reed B. Hogan II of GI Associates, in Flowood, Mississippi, told Reuters Health by email.

In a paper in Pulmonary Pharmacology and Therapeutics, Dr. Hogan and colleagues note that antihistamines are safe and effective treatments for reducing inflammation and cytokine release. They might thus be of help in reducing the respiratory distress associated with COVID-19.

Histamine-1 (H1)-receptor antagonists such as cetirizine are administered for allergies, and histamine-2 (H2)-receptor antagonists such as famotidine are used to control stomach acid and heartburn. Urticaria has been successfully treated with dual histamine-receptor blockade since the 1970s.

Both classes of agents are safe and available — both by prescription and over-the-counter, worldwide. To investigate the potential utility of this approach, the researchers studied 110 COVID-19-positive patients with severe and critical pulmonary symptoms. Eleven of the patients had “do not resuscitate” (DNR) directives.

Their median age was 63.7 years, and among the most common comorbidities were hypertension (78%), obesity and morbid obesity (58%), and diabetes (43%).

As well as standard-of-care treatment, they were also given cetirizine 10 mg and famotidine 20 mg twice daily for at least 48 hours; this resulted in the rate of intubation falling from an initial 16.4% to 7.3%.

The inpatient mortality rate was 15.5% overall and 8.2% after exclusion of the DNR patients. The average number of days to discharge was 11.0.

In another group of 12 patients at the same hospital who did not receive cetirizine and famotidine — the intubation rate was 41.7%, there were five deaths (41.7%) and the average hospital stay was 19.0 days. The researchers observe that these and other numbers “were not deemed sufficient for comparative statistical analysis,” but “are consistent with high symptom severity and high rate of inpatient fatality in the overall admitted patient population.”

Studies in the U.S., the U.K. and China have shown inpatient fatality rates — ranging from 21% to 28%. Thus, say the researchers, “In essence, we observed an approximately one third reduction in inpatient deaths in the cetirizine – famotidine cohort, relative to well documented clinical studies.”

They are now treating most of their COVID-19 patients with the cetirizine and famotidine combination.

“The science is solid,” said Dr. Hogan, “and combined with these early results is suggestive of significant potential benefit in the early disease states to blunt the inflammatory cascade and avoid hospitalization and deterioration. We are seeing many using this approach prophylactically, especially among some healthcare providers.”

Dr. Hogan has applied for a US patent on dual histamine-receptor blockade in the treatment of COVID-19. He has patents on dual histamine-receptor blockade in the treatment of diarrhea and owns a related biomedical business.

SOURCE: https://bit.ly/2Fjp7Ms Pulmonary Pharmacology and Therapeutics, online August 29, 2020

COMMENT:
Dan: [1] Most of my patients are on this H1/H2 dual histamine receptor blockade regimen — for hives/angioedema or mast cell-related issues.

[2] I’m not sure that the statistics are very significant in this paper.

And [3] how can Dr. Douglas patent OTC-drugs for the treatment of COVID-19? I don’t think that is possible.

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Prion-like domain in ELF3 acts as a thermosensor in the plant Arabidopsis

Today we have a “natural” as a topic for gene-environment interactions. And “prions” are mentioned again — just after an article about prions 2-3 days ago in these GEITP pages. Today the “environmental signal” is temperature (heat vs cold), and the “gene response to the environmental signal” (in the genome of the plant, Arabidopsis thaliana) involves a prion-like domain (PrD) in the thermosensor protein called ELF3, encoded by the EARLY FLOWERING-3 gene.

Unlike animals, plants cannot move (or, for humans, remove or add clothing) to escape harsh conditions. Consequently, plants must continuously monitor their environment and, when exposed to high temperatures, quickly adjust their expression of developmental- and growth-related genes. Authors [see attached article & editorial] describe a molecular process that appears to underlie this temperature responsiveness. Expression of developmental- and growth-related genes in animals and plants typically occurs in a rhythmic fashion over a 24-hour cycle. Such daily oscillations are controlled by a molecular loop of protein activity that provides what is termed “the circadian clock.” Clock-induced transcriptional changes enable plants to anticipate daily environmental changes.

In the tiny mustard plant A. thaliana, one component of the circadian clock is a protein assembly called the evening

complex, which is maximally active at dusk and represses expression of many genes important for plant development. The evening complex comprises the transcription-factor protein ELF3, a peptide known as ELF4 (a small α-helical protein), and a protein called LUX (a DNA-binding protein required to recruit the evening complex to transcriptional targets). Plants with mutations that disable the ELF gene tend to flower earlier than normal during development and grow longer embryonic stems (termed “hypocotyls”) — indicating that ELF3 has a key developmental role. ELF3 contains a polyglutamine (polyQ) repeat — embedded within a predicted prion domain (PrD). Authors [see attached article] discovered that the length of the polyQ repeat — correlates with thermal responsiveness.

Authors found that ELF3 proteins in plants from hotter climates — with no detectable PrD — are active at high temperatures, and lack thermal responsiveness. Temperature sensitivity of ELF3 is also modulated by ELF4 levels, indicating that ELF4 can stabilize the function of ELF3. In both Arabidopsis and a heterologous system, authors fused ELF3 with the intracellular marker, green fluorescent protein (GFP), and demonstrated that speckles are formed, within minutes, in response to higher temperatures — in a PrD-dependent manner. A purified peptide fragment — encompassing the ELF3 PrD — was found to reversibly form liquid droplets in response to increasing temperatures in cell culture, indicating that these properties reflect a direct biophysical response conferred by the PrD. This study shows that the ability of temperature to rapidly shift ELF3 between active and inactive states, via phase transition, represents a previously unknown thermosensory mechanism. 😊

DwN

Nature 10 Sept 2020; 585: 256-260 & editorial pp 191-192

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Accumulation of storage proteins in plant seeds is mediated by amyloid formation

Just as “prions” were first discovered in humans — and now are realized to exist in not only all animals but also yeast, fungi and plants — and carry out important functions — so we learn [from the attached article] that “amyloid”, discovered early on in human disease — also exists not only in all animals but also in plants — and even bacteria(!!) and carries out important critical-life functions. In fact, prions represent a subset of amyloids. [By the way, discoveries such as these create a very strong case for evolution of life on this planet from a common ancestor.] 😊 The present study [see attached] shows that amyloid participates in transfer of “environmental signal(s)” to elicit a “response by the genome” in carrying out an important function in plants.

Amyloids (seen under pathological conditions such as Alzheimer disease, Parkinson disease, Creutzfeldt–Jakob disease, motor neuron diseases, the large group of polyglutamine disorders including Huntington’s disease, as well as diseases of peripheral tissue such as hATTR amyloidosis and familial amyloid polyneuropathy) — represent protein aggregates having an unusual structure formed by intermolecular beta-sheets and stabilized by numerous hydrogen bonds. Such a structure (called “cross-β”) gives amyloids the morphology of predominantly unbranched fibrils with unique physicochemical properties.

The biological significance of amyloids is thus based on two aspects, i.e. pathological and functional. Besides amyloid deposition being associated with development of more than 40 incurable human and animal diseases — amyloids also have important intracellular functions as well. A growing number of studies demonstrate that amyloids play vital roles in archaeabacteria and eubacteria, and in eukaryotes (i.e. having chromosomal pairs) including humans. Amyloids in prokaryotes (i.e. having single unpaired chromosomes) fulfill mostly structural (biofilm and sheath formation) and storage (toxicant accumulation) functions. In fungi, infectious amyloids (called prions) are beneficial in that they regulate heterokaryon incompatibility (a fungal nonself-recognition system), multicellularity, and drug resistance. In animals, amyloid formation is important for various functions (e.g. long-term memory potentiation, melanin polymerization, hormone storage, and programmed necrosis). On the other hand, plants remain poorly studied in the field of amyloid biology.

The term “amyloid” was initially introduced in 1838 to describe plant cell carbohydrates, but then attributed to Rudolf Virchow in 1854 for forming pathological protein deposits in human tissues. Early studies (from the 1920s through the 1950s) led to hypotheses on the existence of amyloids in plant seeds; however, these structures turned out to be xyloglucans (the major cell wall matrix polysaccharides). Nevertheless, recently, some plant proteins were shown to form fibrils (having properties of amyloids under denaturing conditions), suggesting that plants might form bona fide amyloids in vivo. Authors [see attached article] thus hypothesized that amyloid formation might occur at seed maturation to stabilize storage proteins, thus preventing their degradation and misfolding during seed dormancy. In order to test this hypothesis, authors analyzed whether amyloid proteins are present in seeds of the garden pea, Pisum sativum L.

Authors showed that 7S globulin vicilin (the most abundant amyloid-like aggregates of storage proteins) forms bona fide amyloids in vivo and in cell culture. Full-length vicilin contains two evolutionary conserved β-barrel domains that self-assemble in vitro into amyloid fibrils with physicochemical properties similar to amyloids. In vivo, vicilin forms amyloids in cotyledon cells that bind amyloid-specific dyes and are resistant to detergents and proteases. Vicilin amyloid accumulation increases during seed maturation, and wanes at germination. Vicilin amyloids resist digestion by gastrointestinal enzymes (which persist in canned peas), and exhibit toxicity for yeast and mammalian cells. This study thus demonstrates that amyloid formation plays an important role in accumulation of storage proteins in plant seeds. 😊

DwN

PLoS Biol July 2020; 18: e3000564

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