The cocaine-binding aptamer is unusual in that it tightly binds molecules other than the ligand it was selected for. Here, we study the interaction of the cocaine-binding aptamer with one of these off-target ligands, quinine. Isothermal titration calorimetry was used to quantify the quinine-binding affinity and thermodynamics of a set of sequence variants of the cocaine-binding aptamer. We find that the affinity of the cocaine-binding aptamer for quinine is 30-40 times stronger than it is for cocaine. Competitive-binding studies demonstrate that both quinine and cocaine bind at the same site on the aptamer. The ligand-induced structural-switching binding mechanism of an aptamer variant that contains three base pairs in stem 1 is retained with quinine as a ligand. The short stem 1 aptamer is unfolded or loosely folded in the free form and becomes folded when bound to quinine. This folding is confirmed by NMR spectroscopy and by the short stem 1 construct having a more negative change in heat capacity of quinine binding than is seen when stem 1 has six base pairs. Small-angle X-ray scattering (SAXS) studies of the free aptamer and both the quinine- and the cocaine-bound forms show that, for the long stem 1 aptamers, the three forms display similar hydrodynamic properties, and the ab initio shape reconstruction structures are very similar. For the short stem 1 aptamer there is a greater variation among the SAXS-derived ab initio shape reconstruction structures, consistent with the changes expected with its structural-switching binding mechanism.

Epidemiological data in COVID-19 mortality indicate that men are more prone to die of SARS-CoV2 infection than women, but biologic causes for this sexual dimorphism are unknown. We discuss the prospective behavioral and biological differences between the sexes that could be attributed to this gender-based differentiation. The female sex hormones and the immune stimulatory genes including toll-like receptors, interleukins, micro-RNAs present on X-chromosome may impart lesser infectivity and mortality of the SARS-CoV-2 in females over males. The sex hormone estrogen interacts with the Renin-Angiotensin-Aldosterone System, one of the most critical pathways in COVID-19 infectivity, and modulate the vasomotor homeostasis. Testosterone on the contrary enhances the levels of the two most critical molecules angiotensin converting enzyme 2 (ACE2) and the transmembrane protease, serine-type 2 (TMPRSS2), transcriptionally and post-translationally, thereby increasing viral load and delaying viral clearance in men as compared to women. We propose that modulating sex hormones, either by increasing estrogen or anti-androgen, may be a therapeutic option to reduce mortality from SARS-CoV-2.

total number of manuscript pages -41 • total number of figures -4 • word count for the body of the text -7834 • type of contribution -review article AbstractHigh-altitude pulmonary edema (HAPE) occurs most frequently in non-acclimatized low landers on exposure to altitude ≥2500m. HAPE is a complex condition that involves perturbation of signaling pathways in vasoconstrictors, vasodilators, anti-diuretics and vascular growth factors. Genetic variations are instrumental in regulating these pathways and evidence is accumulating for a role of epigenetic modification in hypoxic responses. This review focuses on the crosstalk between HAPE-associated genetic variants and transcription factors, comparing high-altitude adapted and HAPE-afflicted subjects. This approach might ultimately yield biomarker information both to understand and to design therapies for high altitude adaptation.Evolution and physiological adaptation have permitted survival at the highest topographically elevated regions of the world. [1][2][3][4][5] Reduced air pressure at high-altitude decreases the partial pressure of inspired oxygen, affecting lungs, brain, heart and blood and can lead to a spectrum of high-altitude disorders including high-altitude pulmonary edema (HAPE), acute mountain sickness (AMS) and high-altitude cerebral edema (HACE). 6,7 This review focuses on HAPE. HAPE is a consequence of hypoxic pulmonary vasoconstriction leading to increased pulmonary arterial pressure and capillary stress failure. 8-11 HAPE victims have lower arterial oxygen saturation (SaO2) and higher heart rate, pulmonary vascular resistance and pulmonary vascular resistance index 12,13 than do unaffected sojourners to altitude. Clinically HAPE is characterized by dyspnoea, elevated body temperature, pink frothy sputum, tachypnoea, tachycardia, persistent cough and cyanosis. [14][15][16][17] Chest X-rays and CT scans show increased lung vascular markings and patchy shadows. 18,19 There have been great strides in understanding the clinical and physiological mechanisms of HAPE that has led to the discovery of successful treatments. Information on genetic contributions to this disorder has also grown rapidly over the last decade, partly to the development and implementation of newer genetic techniques. Candidate-gene approaches, advanced techniques such as Next-GenerationSequencing and Genome-Wide Association Studies have led to association of multiple genetic variants with high-altitude adaptation or maladaptation. [20][21][22][23][24][25][26] The majority of these genes belong to multiple, frequently related pathways. These include the renin-angiotensin aldosterone system, apelin signaling, nitric oxide signaling, and hypoxia induced signaling.These pathways regulate vasoactive molecules including angiotensin II, apelin, nitric oxide, aldosterone, and beta-adrenergics. [27][28][29][30][31] In addition to genetic variation, epigenetics plays prominent role in HAPE and other diseases. [32][33][34][35] DNA methylation, acetylation, histone modifications/chromatin rem...

Dexamethasone can be taken prophylactically to prevent hypobaric hypoxia-associated disorders of high-altitude. While dexamethasone-mediated protection against high-altitude disorders has been clinically evaluated, detailed sex-based mechanistic insights have not been explored. As part of our India-Leh-Dexamethasone-expedition-2020 (INDEX 2020) programme, we examined the phenotype of control (n = 14) and dexamethasone (n = 13) groups, which were airlifted from Delhi (∼225 m elevation) to Leh, Ladakh (∼3,500 m), India, for 3 days. Dexamethasone 4 mg twice daily significantly attenuated the rise in blood pressure, heart rate, pulmonary pressure, and drop in SaO2 resulting from high-altitude exposure compared to control-treated subjects. Of note, the effect of dexamethasone was substantially greater in women than in men, in whom the drug had relatively little effect. Thus, for the first time, this study shows a sex-biased regulation by dexamethasone of physiologic parameters resulting from the hypoxic environment of high-altitude, which impacts the development of high-altitude pulmonary hypertension and acute mountain sickness. Future studies of cellular contributions toward sex-specific regulation may provide further insights and preventive measures in managing sex-specific, high-altitude–related disorders.

Endothelin 1 (EDN1) encodes a potent endogenous vasoconstrictor, ET1, to maintain vascular homeostasis and redistribution of tissue blood flow during exercise. One of the EDN1 missense polymorphisms, rs5370 G/T, has strongly been associated with cardiopulmonary diseases. This study investigated the impact of rs5370 polymorphism in high-altitude pulmonary oedema (HAPE) disorder or maladaptation and adaptation physiology in a well-characterized case–control study of high-altitude and low-altitude populations comprising 310 samples each of HAPE-patients, HAPE-free controls and native highlanders. The rs5370 polymorphism was genotyped, and the gene expression and plasma level of EDN1 were evaluated. The functional relevance of each allele was investigated in the human embryonic kidney 293 cell line after exposure to hypoxia and computationally. The T allele was significantly more prevalent in HAPE-p compared to HAPE-f and HLs. The EDN1 gene expression and ET1 bio-level were significantly elevated in HAPE-p compared to controls. Compared to the G allele, the T allele was significantly associated with elevated levels of ET-1 in all three study groups and cells exposed to hypoxia. The in silico studies further confirmed the stabilizing effect of the T allele on the structural integrity and function of ET1 protein. The ET1 rs5370 T allele is associated with an increased concentration of ET-1 in vivo and in vitro, establishing it as a potent marker in the adaptation/maladaptation physiology under the high-altitude environment. This could also be pertinent in endurance exercises at high altitudes.

Background SARS-CoV-2 has affected every demography disproportionately, including even the native highland populations. Hypobaric-hypoxic settings at high-altitude (HA, >2,500 masl) present an extreme environment that impacts the survival of permanent residents, possibly including SARS-CoV-2. Conflicting hypotheses have been presented for COVID-19 incidence and fatality at HA. Objectives To evaluate protection or risk against COVID-19 incidence and fatality in humans under hypobaric-hypoxic environment of high-altitude (>2,501 masl). Methods Global COVID-19 data of March 2020-21, employed from official websites of the Indian Government, John Hopkins University, and Worldometer were clustered into 6 altitude categories. Clinical cofactors and comorbidities data were evaluated with COVID-19 incidence and fatality. Extensive comparisons and correlations using several statistical tools estimated the risk and protection. Results Of relevance, data analyses revealed four distinct responses, namely, partial risk, total risk, partial protection, and total protection from COVID-19 at high-altitude indicating a mixed baggage and complexity of the infection. Surprisingly, it included the countries within the same geographic region. Moreover, body mass index, hypertension, and diabetes correlated significantly with COVID-19 incidence and fatality rate (P ≤ 0.05). Conclusions Varied patterns of protection and risk against COVID-19 incidence and fatality were observed among the high-altitude populations. It is though premature to generalize COVID-19 effects on any particular demography without further extensive studies.

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