Sex-Specific Modulation of Blood Pressure and the Renin-Angiotensin System by ACE (Angiotensin-Converting Enzyme) 2

Salt-Responsive Gut Microbiota Induces Sex-Specific Blood Pressure Changes

BACKGROUND

Tryptophan metabolism is important in blood pressure regulation. The tryptophan-indole pathway is exclusively mediated by the gut microbiota. ACE2 (angiotensin-converting enzyme 2) participates in tryptophan absorption, and a lack of ACE2 leads to changes in the gut microbiota. The gut microbiota has been recognized as a regulator of blood pressure. Furthermore, there is ample evidence for sex differences in the gut microbiota. However, it is unclear whether such sex differences impact blood pressure differentially through the tryptophan-indole pathway.

METHODS

To study the sex-specific mechanisms of gut microbiota-mediated tryptophan-indole pathway in hypertension, we generated a novel rat model with Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats-associated protein 9)-targeted deletion of Ace2 in the Dahl salt-sensitive rat. Cecal microbiota transfers from donors of both sexes to female S recipients were performed. Also, Dahl salt-sensitive rats of both sexes were orally gavaged with indole to investigate blood pressure response.

RESULTS

The female gut microbiota and its tryptophan-indole pathway exhibited greater buffering capacity when exposed to tryptophan, due to Ace2 deficiency, and salt. In contrast, the male gut microbiota and its tryptophan-indole pathway were more vulnerable. Female rats with male cecal microbiota responded to salt with a higher blood pressure increase compared with those with female cecal microbiota. Indole, a tryptophan-derived metabolite produced by gut bacteria, increased blood pressure in male but not in female rats. Moreover, salt altered host-mediated tryptophan metabolism, characterized by reduced serum serotonin of both sexes and higher levels of kynurenine derivatives in the females.

CONCLUSIONS

We uncovered a novel sex-specific mechanism in the gut microbiota-mediated tryptophan-indole pathway in blood pressure regulation. Salt tipped the tryptophan metabolism between the host and gut microbiota in a sex-dependent manner. Our study provides evidence for a novel concept that gut microbiota and its metabolism play sex-specific roles in the development of salt-sensitive hypertension.

Angiotensin-Converting Enzyme 2 Posttranslational Modifications and Implications for Hypertension and SARS-CoV-2: 2023 Lewis K. Dahl Memorial Lecture

ACE2 (angiotensin-converting enzyme 2), a multifunctional transmembrane protein, is well recognized as an important member of the (RAS) renin-angiotensin system with important roles in the regulation of cardiovascular function by opposing the harmful effects of Ang-II (angiotensin II) and AT1R (Ang-II type 1 receptor) activation. More recently, ACE2 was found to be the entry point for the SARS-CoV-2 virus into cells, causing COVID-19. This finding has led to an exponential rise in the number of publications focused on ACE2, albeit these studies often have opposite objectives to the preservation of ACE2 in cardiovascular regulation. However, notwithstanding accumulating data of the role of ACE2 in the generation of angiotensin-(1-7) and SARS-CoV-2 internalization, numerous other putative roles of this enzyme remain less investigated and not yet characterized. Currently, no drug modulating ACE2 function or expression is available in the clinic, and the development of new pharmacological tools should attempt targeting each step of the lifespan of the protein from synthesis to degradation. The present review expands on our presentation during the 2023 Lewis K. Dahl Memorial Lecture Sponsored by the American Heart Association Council on Hypertension. We provide a critical summary of the current knowledge of the mechanisms controlling ACE2 internalization and intracellular trafficking, the mutual regulation with GPCRs (G-protein-coupled receptors) and other proteins, and posttranslational modifications. A major focus is on ubiquitination which has become a critical step in the modulation of ACE2 cellular levels.

Candesartan upregulates angiotensin-converting enzyme 2 in kidneys of male animals by decreased ubiquitination

Candesartan is a common angiotensin-II receptor-1 blocker used for patients with cardiovascular and renal diseases. Angiotensin-converting enzyme 2 (ACE2) is a negative regulator of blood pressure (BP), and also a major receptor for coronaviruses. To determine whether and how candesartan upregulates ACE2, we examined BP and ACE2 in multi-organs from male and female C57BL/6J mice treated with candesartan (1 mg/kg, i.p.) for 7 days. Relative to the vehicle, candesartan lowered BP more in males than females; ACE2 protein abundances were increased in kidneys, not lungs, hearts, aorta, liver, spleen, brain, or serum, only from males. Ace2-mRNA was similar in kidneys. Candesartan also decreased BP in normal, hypertensive, and nephrotic male rats. The renal ACE2 was increased by the drug in normal and nephrotic male rats but not spontaneously hypertensive ones. In male mouse kidneys, ACE2 was distributed at sodium-hydrogen-exchanger-3 positive proximal-convoluted-tubules; ACE2-ubiquitination was decreased by candesartan, accompanied with increased ubiquitin-specific-protease-48 (USP48). In candesartan-treated mouse renal proximal-convoluted-tubule cells, ACE2 abundances and activities were increased while ACE2-ubiquitination and colocalization with lysosomal and proteosomal markers were decreased. The silence of USP48 by siRNA caused a reduction of ACE2 in the cells. Thus, the sex-differential ACE2 upregulation by candesartan in kidney from males may be due to the decreased ACE2-ubiquitination, associated with USP48, and consequent degradation in lysosomes and proteosomes. This is a novel mechanism and may shed light on candesartan-like-drug choice in men and women prone to coronavirus infections.

Sex differences in blood pressure regulation and hypertension: renal, hemodynamic, and hormonal mechanisms

The teleology of sex differences has been argued since at least as early as Aristotle's controversial Generation of Animals more than 300 years BC, which reflects the sex bias of the time to contemporary readers. Although the question "why are the sexes different" remains a topic of debate in the present day in metaphysics, the recent emphasis on sex comparison in research studies has led to the question "how are the sexes different" being addressed in health science through numerous observational studies in both health and disease susceptibility, including blood pressure regulation and hypertension. These efforts have resulted in better understanding of differences in males and females at the molecular level that partially explain their differences in vascular function and renal sodium handling and hence blood pressure and the consequential cardiovascular and kidney disease risks in hypertension. This review focuses on clinical studies comparing differences between men and women in blood pressure over the life span and response to dietary sodium and highlights experimental models investigating sexual dimorphism in the renin-angiotensin-aldosterone, vascular, sympathetic nervous, and immune systems, endothelin, the major renal sodium transporters/exchangers/channels, and the impact of sex hormones on these systems in blood pressure homeostasis. Understanding the mechanisms governing sex differences in blood pressure regulation could guide novel therapeutic approaches in a sex-specific manner to lower cardiovascular risks in hypertension and advance personalized medicine.

Circadian gene expression in mouse renal proximal tubule

Circadian variability in kidney function is well recognized but is often ignored as a potential confounding variable in physiological experiments. Here, we have created a data resource consisting of expression levels for mRNA transcripts in microdissected proximal tubule segments from mice as a function of the time of day. Small-sample RNA sequencing was applied to microdissected S1 proximal convoluted tubules and S2 proximal straight tubules. After stringent filtering, the data were analyzed using JTK-Cycle to detect periodicity. The data set is provided as a user-friendly webpage at https://esbl.nhlbi.nih.gov/Databases/Circadian-Prox2/. In proximal convoluted tubules, 234 transcripts varied in a circadian manner (4.0% of the total). In proximal straight tubules, 334 transcripts varied in a circadian manner (5.3%). Transcripts previously known to be associated with corticosteroid action and with increased flow were found to be overrepresented among circadian transcripts peaking during the "dark" portion of the day [zeitgeber time (ZT)14-22], corresponding to peak levels of corticosterone and glomerular filtration rate in mice. To ask whether there is a time-of-day dependence of protein abundances in the kidney, we carried out LC-MS/MS-based proteomics in whole mouse kidneys at ZT12 and ZT0. The full data set (n = 6,546 proteins) is available at https://esbl.nhlbi.nih.gov/Databases/Circadian-Proteome/. Overall, 293 proteins were differentially expressed between ZT12 and ZT0 (197 proteins greater at ZT12 and 96 proteins greater at ZT0). Among the regulated proteins, only nine proteins were found to be periodic in the RNA-sequencing analysis, suggesting a high level of posttranscriptional regulation of protein abundances.NEW & NOTEWORTHY Circadian variation in gene expression can be an important determinant in the regulation of kidney function. The authors used RNA-sequencing transcriptomics and LC-MS/MS-based proteomics to identify gene products expressed in a periodic manner. The data were used to construct user-friendly web resources.

Innate immunity to SARS-CoV-2 infection: a review

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, first notified in China, has spread around the world causing high morbidity and mortality, which is due to factors such as the subversion of the immune response. The aims of the study are to summarise and present the immunopathological relationship of COVID-19 with innate immunity. This is a systematic review conducted by the National Library of Medicine - National Institutes of Health, USA (PUBMED), Latin American and Caribbean Literature on Health Sciences (LILACS), Medical Literature Analysis and Retrieval System Online (MEDLINE) and Scientific Electronic Library Online (SCIELO) databases with clinical trials, in vitro assays, case-controls, cohort studies, systematic reviews and meta-analyses between February 2020 and July 2021. The version 2 of the Cochrane risk-of-bias tool for RCTs (RoB 2), Joana Briggs Institute (JBI) Critical Appraisal (for the review articles) and the Risk of Bias in Non-randomised Studies of Interventions (ROBINS-I) tools were used to evaluate the quality and the risk of bias of the studies included in this review. The innate immune response through the generation of interferons, alternative pathways and complement system lectins and the joint action of innate immune cells and cytokines and chemokines lead to different clinical outcomes, taking into account the exacerbated inflammatory response and pathogenesis. Then, in addition to interacting as a bridge for adaptive immunity, the innate immune response plays an essential role in primary defense and is one of the starting points for immune evasion by SARS-CoV-2.

AT1 Receptors: Their Actions from Hypertension to Cognitive Impairment

Hypertension is one of the most prevalent cardiovascular disorders worldwide, affecting 1.13 billion people, or 14% of the global population. Hypertension is the single biggest risk factor for cerebrovascular dysfunction. According to the American Heart Association, high blood pressure (BP), especially in middle-aged individuals (~ 40 to 60 years old), is associated with an increased risk of dementia, later in life. Alzheimer’s disease and cerebrovascular disease are the two leading causes of dementia, accounting for around 80% of the total cases and usually combining mixed pathologies from both. Little is known regarding how hypertension affects cognitive function, so the impact of its treatment on cognitive impairment has been difficult to assess. The brain renin-angiotensin system (RAS) is essential for BP regulation and overactivity of this system has been established to precede the development and maintenance of hypertension. Angiotensin II (Ang-II), the main peptide within this system, induces vasoconstriction and impairs neuro-vascular coupling by acting on brain Ang-II type 1 receptors (AT₁R). In this review, we systemically analyzed the association between RAS and biological mechanisms of cognitive impairment, from the perspective of AT₁R located in the central nervous system. Additionally, the possible contribution of brain AT₁R to global cognition decline in COVID-19 cases will be discussed as well.

The Identikit of Patient at Risk for Severe COVID-19 and Death: The Dysregulation of Renin-Angiotensin System as the Common Theme

Since the first months of the coronavirus disease 2019 (COVID-19) pandemic, several specific physiologic traits, such as male sex and older age, or health conditions, such as overweight/obesity, arterial hypertension, metabolic syndrome, and type 2 diabetes mellitus, have been found to be highly prevalent and associated with increased risk of adverse outcomes in hospitalized patients. All these cardiovascular morbidities are widespread in the population and often coexist, thus identifying a common patient phenotype, characterized by a hyper-activation of the "classic" renin-angiotensin system (RAS) and mediated by the binding of angiotensin II (Ang II) to the type 1-receptor. At the same time, the RAS imbalance was proved to be crucial in the genesis of lung injury after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, where angiotensin-converting-enzyme-2 (ACE2) is not only the receptor for SARS-CoV-2, but its down-regulation through internalization and shedding, caused by the virus binding, leads to a further dysregulation of RAS by reducing angiotensin 1-7 (Ang 1-7) production. This focused narrative review will discuss the main available evidence on the role played by cardiovascular and metabolic conditions in severe COVID-19, providing a possible pathophysiological link based on the disequilibrium between the two opposite arms of RAS.

Immunoreactivity of the SARS-CoV-2 entry proteins ACE-2 and TMPRSS-2 in murine models of hormonal manipulation, ageing, and cardiac injury

Previous work indicates that SARS-CoV-2 virus entry proteins angiotensin-converting enzyme 2 (ACE-2) and the cell surface transmembrane protease serine 2 (TMPRSS-2) are regulated by sex hormones. However, clinical studies addressing this association have yielded conflicting results. We sought to analyze the impact of sex hormones, age, and cardiovascular disease on ACE-2 and TMPRSS-2 expression in different mouse models. ACE-2 and TMPRSS-2 expression was analyzed by immunostaining in a variety of tissues obtained from FVB/N mice undergoing either gonadectomy or sham-surgery and being subjected to ischemia-reperfusion injury or transverse aortic constriction surgery. In lung tissues sex did not have a significant impact on the expression of ACE-2 and TMPRSS-2. On the contrary, following myocardial injury, female sex was associated to a lower expression of ACE-2 at the level of the kidney tubules. In addition, after myocardial injury, a significant correlation between younger age and higher expression of both ACE-2 and TMPRSS-2 was observed for lung alveoli and bronchioli, kidney tubules, and liver sinusoids. Our experimental data indicate that gonadal hormones and biological sex do not alter ACE-2 and TMPRSS-2 expression in the respiratory tract in mice, independent of disease state. Thus, sex differences in ACE-2 and TMPRSS-2 protein expression observed in mice may not explain the higher disease burden of COVID-19 among men.

Cardiac and Renal SARS-CoV-2 Viral Entry Protein Regulation by Androgens and Diet: Implications for Polycystic Ovary Syndrome and COVID-19

The susceptibility and the severity of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are associated with hyperandrogenism, obesity, and preexisting pulmonary, metabolic, renal, and cardiac conditions. Polycystic ovary syndrome (PCOS), the most common endocrine disorder in premenopausal women, is associated with obesity, hyperandrogenism, and cardiometabolic dysregulations. We analyzed cardiac, renal, circulatory, and urinary SARS-CoV-2 viral entry proteins (ACE2, TMPRSS2, TMPRSS4, furin, cathepsin L, and ADAM17) and androgen receptor (AR) expression, in a peripubertal androgen exposure model of PCOS. Peripubertal female mice were treated with dihydrotestosterone (DHT) and low (LFD) or high (HFD) fat diet for 90 days. HFD exacerbated DHT-induced increase in body weight, fat mass, and cardiac and renal hypertrophy. In the heart, DHT upregulated AR protein in both LFD and HFD, ACE2 in HFD, and ADAM17 in LFD. In the kidney, AR protein expression was upregulated by both DHT and HFD. Moreover, ACE2 and ADAM17 were upregulated by DHT in both diets. Renal TMPRSS2, furin, and cathepsin L were upregulated by DHT and differentially modulated by the diet. DHT upregulated urinary ACE2 in both diets, while neither treatment modified serum ACE2. Renal AR mRNA expression positively correlated with Ace2, Tmprss2, furin, cathepsin L, and ADAM17. Our findings suggest that women with PCOS could be a population with a high risk of COVID-19-associated cardiac and renal complications. Furthermore, our study suggests that weight loss by lifestyle modifications (i.e., diet) could potentially mitigate COVID-19-associated deleterious cardiorenal outcomes in women with PCOS.

Male bias in ACE2 basic science research: missed opportunity for discovery in the time of COVID-19

Throughout the world, including the United States, men have worse outcomes from COVID-19 than women. SARS-CoV-2, the causative virus of the COVID-19 pandemic, uses angiotensin-converting enzyme 2 (ACE2) to gain cellular entry. ACE2 is a member of the renin-angiotensin system (RAS) and plays an important role in counteracting the harmful effects mediated by the angiotensin type 1 receptor. Therefore, we conducted Ovid MEDLINE and Embase database searches of basic science studies investigating the impact of the biological variable of sex on ACE2 expression and regulation from 2000, the year ACE2 was discovered, through December 31, 2020. Out of 2,131 publications, we identified 853 original research articles on ACE2 conducted in primary cells, tissues, and/or whole mammals excluding humans. The majority (68.7%) of these studies that cited the sex of the animal were conducted in males, while 11.2% were conducted solely in females; 9.26% compared ACE2 between the sexes, while 10.8% did not report the sex of the animals used. General findings are that sex differences are tissue-specific and when present, are dependent upon gonadal state. Renal, cardiac, and adipose ACE2 is increased in both sexes under experimental conditions that model co-morbidities associated with worse COVID-19 outcomes including hypertension, obesity, and renal and cardiovascular diseases; however, ACE2 protein was generally higher in the males. Studies in Ace2 knockout mice indicate ACE2 plays a greater role in protecting the female from developing hypertension than the male. Studying the biological variable of sex in ACE2 research provides an opportunity for discovery in conditions involving RAS dysfunction and will shed light on sex differences in COVID-19 severity.

A comprehensive guide to the pharmacologic regulation of angiotensin converting enzyme 2 (ACE2), the SARS-CoV-2 entry receptor

The recent emergence of coronavirus disease-2019 (COVID-19) as a global pandemic has prompted scientists to address an urgent need for defining mechanisms of disease pathology and treatment. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent for COVID-19, employs angiotensin converting enzyme 2 (ACE2) as its primary target for cell surface attachment and likely entry into the host cell. Thus, understanding factors that may regulate the expression and function of ACE2 in the healthy and diseased body is critical for clinical intervention. Over 66% of all adults in the United States are currently using a prescription drug and while earlier findings have focused on possible upregulation of ACE2 expression through the use of renin angiotensin system (RAS) inhibitors, mounting evidence suggests that various other widely administered drugs used in the treatment of hypertension, heart failure, diabetes mellitus, hyperlipidemias, coagulation disorders, and pulmonary disease may also present a varied risk for COVID-19. Specifically, we summarize mechanisms on how heparin, statins, steroids and phytochemicals, besides their established therapeutic effects, may also interfere with SARS-CoV-2 viral entry into cells. We also describe evidence on the effect of several vitamins, phytochemicals, and naturally occurring compounds on ACE2 expression and activity in various tissues and disease models. This comprehensive review aims to provide a timely compendium on the potential impact of commonly prescribed drugs and pharmacologically active compounds on COVID-19 pathology and risk through regulation of ACE2 and RAS signaling.

Angiotensin-converting enzyme 2 and COVID-19: patients, comorbidities, and therapies

On March 11, 2020, the World Health Organization declared coronavirus disease 2019 (COVID-19) a pandemic, and the reality of the situation has finally caught up to the widespread reach of the disease. The presentation of the disease is highly variable, ranging from asymptomatic carriers to critical COVID-19. The availability of angiotensin-converting enzyme 2 (ACE2) receptors may reportedly increase the susceptibility and/or disease progression of COVID-19. Comorbidities and risk factors have also been noted to increase COVID-19 susceptibility. In this paper, we hereby review the evidence pertaining to ACE2's relationship to common comorbidities, risk factors, and therapies associated with the susceptibility and severity of COVID-19. We also highlight gaps of knowledge that require further investigation. The primary comorbidities of respiratory disease, cardiovascular disease, renal disease, diabetes, obesity, and hypertension had strong evidence. The secondary risk factors of age, sex, and race/genetics had limited-to-moderate evidence. The tertiary factors of ACE inhibitors and angiotensin II receptor blockers had limited-to-moderate evidence. Ibuprofen and thiazolidinediones had limited evidence.

Androgens, the kidney, and COVID-19: an opportunity for translational research

Coronavirus disease 2019 (COVID-19) has reached pandemic proportions, affecting millions of people worldwide. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the causative agent of COVID-19. Epidemiological reports have shown that the severity of SARS-CoV-2 infection is associated with preexisting comorbidities such as hypertension, diabetes mellitus, cardiovascular diseases, and chronic kidney diseases, all of which are also risk factors for acute kidney injury (AKI). The kidney has emerged as a key organ affected by SARS-CoV-2. AKI is associated with increased morbidity and mortality in patients with COVID-19. Male sex is an independent predictor for AKI, and an increased death rate has been reported in male patients with COVID-19 worldwide. The mechanism(s) that mediate the sex discrepancy in mortality due to COVID-19 remain(s) unknown. Angiotensin-converting enzyme (ACE)2 is the receptor for SARS-CoV-2. Alterations in the ACE-to-ACE2 ratio have been implicated in renal diseases. This perspective aims to discuss data that suggest that androgens, via alterations in the intrarenal renin-angiotensin system, impair renal hemodynamics, predisposing patients to AKI during COVID-19 infection, which could explain the higher mortality observed in men with COVID-19. Clinicians should ensure early and effective cardiometabolic control for all patients to ameliorate the compensatory elevation of ACE2 and alterations in the ACE-to-ACE2 ratio. A better understanding of the role of androgens in SARS-CoV-2-associated AKI and mortality is imperative. The kidney could constitute a key organ that may explain the sex disparities of the higher mortality and worst outcomes associated with COVID-19 in men.

Sex differences in COVID-19: candidate pathways, genetics of ACE2, and sex hormones

Biological sex is increasingly recognized as a critical determinant of health and disease, particularly relevant to the topical COVID-19 pandemic caused by the SARS-CoV-2 coronavirus. Epidemiological data and observational reports from both the original SARS epidemic and the most recent COVID-19 pandemic have a common feature: males are more likely to exhibit enhanced disease severity and mortality than females. Sex differences in cardiovascular disease and COVID-19 share mechanistic foundations, namely, the involvement of both the innate immune system and the canonical renin-angiotensin system (RAS). Immunological differences suggest that females mount a rapid and aggressive innate immune response, and the attenuated antiviral response in males may confer enhanced susceptibility to severe disease. Furthermore, the angiotensin-converting enzyme 2 (ACE2) is involved in disease pathogenesis in cardiovascular disease and COVID-19, either to serve as a protective mechanism by deactivating the RAS or as the receptor for viral entry, respectively. Loss of membrane ACE2 and a corresponding increase in plasma ACE2 are associated with worsened cardiovascular disease outcomes, a mechanism attributed to a disintegrin and metalloproteinase (ADAM17). SARS-CoV-2 infection also leads to ADAM17 activation, a positive feedback cycle that exacerbates ACE2 loss. Therefore, the relationship between cardiovascular disease and COVID-19 is critically dependent on the loss of membrane ACE2 by ADAM17-mediated proteolytic cleavage. This article explores potential mechanisms involved in COVID-19 that may contribute to sex-specific susceptibility focusing on the innate immune system and the RAS, namely, genetics and sex hormones. Finally, we highlight here the added challenges of gender in the COVID-19 pandemic.

Sex differences in COVID-19: candidate pathways, genetics of ACE2, and sex hormones

Biological sex is increasingly recognized as a critical determinant of health and disease, particularly relevant to the topical COVID-19 pandemic caused by the SARS-CoV-2 coronavirus. Epidemiological data and observational reports from both the original SARS epidemic and the most recent COVID-19 pandemic have a common feature: males are more likely to exhibit enhanced disease severity and mortality than females. Sex differences in cardiovascular disease and COVID-19 share mechanistic foundations, namely, the involvement of both the innate immune system and the canonical renin-angiotensin system (RAS). Immunological differences suggest that females mount a rapid and aggressive innate immune response, and the attenuated antiviral response in males may confer enhanced susceptibility to severe disease. Furthermore, the angiotensin-converting enzyme 2 (ACE2) is involved in disease pathogenesis in cardiovascular disease and COVID-19, either to serve as a protective mechanism by deactivating the RAS or as the receptor for viral entry, respectively. Loss of membrane ACE2 and a corresponding increase in plasma ACE2 are associated with worsened cardiovascular disease outcomes, a mechanism attributed to a disintegrin and metalloproteinase (ADAM17). SARS-CoV-2 infection also leads to ADAM17 activation, a positive feedback cycle that exacerbates ACE2 loss. Therefore, the relationship between cardiovascular disease and COVID-19 is critically dependent on the loss of membrane ACE2 by ADAM17-mediated proteolytic cleavage. This article explores potential mechanisms involved in COVID-19 that may contribute to sex-specific susceptibility focusing on the innate immune system and the RAS, namely, genetics and sex hormones. Finally, we highlight here the added challenges of gender in the COVID-19 pandemic.

Covid-19 Kills More Men Than Women: An Overview of Possible Reasons

The high mortality observed in Covid-19 patients may be related to unrecognized pulmonary embolism, pulmonary thrombosis, or other underlying cardiovascular diseases. Recent data have highlighted that the mortality rate of Covid-19 seems to be higher in male patients compared to females. In this paper, we have analyzed possible factors that may underline this sex difference in terms of activity of the immune system and its modulation by sex hormones, coagulation pattern, and preexisting cardiovascular diseases as well as effects deriving from smoking and drinking habits. Future studies are needed to evaluate the effects of sex differences on the prevalence of infections, including Covid-19, its outcome, and the responses to antiviral treatments.

Let's talk about sex in the context of COVID-19

In recent months, the coronavirus disease 2019 (COVID-19) pandemic has sent many countries into crisis. Studies have shown that this virus causes worse outcomes and a higher mortality in men than in women. It has been recognized that sex can affect the immune response to a pathogenic agent, as well as the susceptibility for some respiratory diseases. These different responses in males and females may be related to the actions of sex hormones. Angiotensin-converting enzyme 2 (ACE2) acts as the receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which causes COVID-19. The expression of ACE2 is influenced by sex hormones; therefore, we discuss in this article that this could be one of the reasons why COVID-19 is more prevalent in men than in women.