Enhanced expression of angiotensin-converting enzyme 2 in psoriatic skin and its upregulation in keratinocytes by interferon-γ: implication of inflammatory milieu in skin tropism of SARS-CoV-2

The Renin-Angiotensin System: The Challenge behind Autoimmune Dermatological Diseases

Autoimmune dermatological diseases (AIDD) encompass a diverse group of disorders characterized by aberrant immune responses targeting the skin and its associated structures. In recent years, emerging evidence suggests a potential involvement of the renin-angiotensin system (RAS) in the pathogenesis and progression of these conditions. RAS is a multicomponent cascade, primarily known for its role in regulating blood pressure and fluid balance. All of the RAS components play an important role in controlling inflammation and other immune responses. Angiotensin II, the main effector, acts on two essential receptors: Angiotensin Receptor 1 and 2 (AT1R and AT2R). A disturbance in the axis can lead to many pathological processes, including autoimmune (AI) diseases. AT1R activation triggers diverse signaling cascades involved in inflammation, fibrosis and tissue remodeling. Experimental studies have demonstrated the presence of AT1R in various cutaneous cells and immune cells, further emphasizing its potential contribution to the AI processes in the skin. Furthermore, recent investigations have highlighted the role of other RAS components, beyond angiotensin-converting enzyme (ACE) and Ang II, that may contribute to the pathophysiology of AIDD. Alternative pathways involving ACE2, Ang receptors and Ang-(1-7) have been implicated in regulating immune responses and tissue homeostasis within the skin microenvironment. Understanding the intricate involvement of the RAS in AIDD may provide novel therapeutic opportunities. Targeting specific components of the RAS, such as angiotensin receptor blockers (ARBs), ACE inhibitors (ACEIs) or alternative RAS pathway modulators, could potentially ameliorate inflammatory responses, reduce tissue damage and lessen disease manifestations. Further research is warranted to outline the exact mechanisms underlying RAS-mediated immune dysregulation in AIDD. This abstract aims to provide a concise overview of the intricate interplay between the RAS and AIDD. Therefore, we elaborate a systematic review of the potential challenge of RAS in the AIDD, including psoriasis, systemic sclerosis, vitiligo, lupus erythematosus and many more.

Single-cell RNA sequencing analysis of a COVID-19-associated maculopapular rash in a patient with psoriasis treated with ustekinumab

Coronavirus disease 2019 (COVID-19) primarily affects the respiratory system but extrapulmonary manifestations, including the skin, have been well documented. However, transcriptomic profiles of skin lesions have not been performed thus far. Here, we present a single-cell RNA sequencing analysis in a patient with COVID-19 infection with a maculopapular skin rash while on treatment with the interleukin (IL)-12/IL-23 blocker ustekinumab for his underlying psoriasis. Results were compared with healthy controls and untreated psoriasis lesions. We found the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral entry receptors ACE2 and TMPRSS2 in keratinocytes of the patient with COVID-19, while ACE2 expression was low to undetectable in psoriasis lesions and healthy skin. Among all cell types, ACE2+ keratinocyte clusters showed the highest levels of transcriptomic dysregulation in COVID-19, expressing type 1-associated immune markers such as CXCL9 and CXCL10. In line with a generally type 1-skewed immune microenvironment, cytotoxic lymphocytes showed increased expression of the IFNG gene and other T-cell effector genes, while type 2, type 17, or type 22 T-cell activation was largely absent. Conversely, downregulation of several anti-inflammatory mediators was observed. This first transcriptomic description of a COVID-19-associated rash identifies ACE2+ keratinocytes displaying profound transcriptional changes, and inflammatory immune cells that might help to improve the understanding of SARS-CoV-2-associated skin conditions.

COVID-19 Among Patients with Psoriasis: A Single-Center Retrospective Cross-Sectional Study

Objective

Psoriasis patients may have been affected by COVID-19 differently than the normal population due to using different types of treatments, including immunosuppressive agents and biological therapies, the probability of lower effectiveness, and different side effects of the vaccines. This study aimed to evaluate the epidemiologic and clinical features of COVID-19 and the effect of the psoriasis treatment on it.

Materials and Methods

Psoriasis patients followed up in our clinic between March 2020 and July 2022 were evaluated in terms of clinicodemographic characteristics, treatment methods, and COVID-19 vaccination status and compared regarding COVID-19 history.

Results

A total of 110 patients (female:male ratio=1:1.2) with a mean age of 45.6±14.3 years were evaluated. Thirty patients (27.2%) developed COVID-19 during psoriasis treatment. Unvaccinated patients had COVID-19 (6/11, 55%) more frequently than vaccinated ones (24/99, 24%), but it was not statistically significant (p=0.067). Although patients who received biological therapy were also more frequently infected with SARS-CoV-2 than patients who received other types of therapies (18/53 [34%] versus 12/57 [21%], respectively), the difference was again not statistically significant.A patient with hypertension using acitretin was hospitalized for pulmonary involvement because of COVID-19. No exacerbation of psoriasis was observed in patients who developed COVID-19, while psoriasis flares occurred following COVID-19 mRNA vaccination in two patients.

Conclusion

Patients with psoriasis should get vaccinated against COVID-19, as vaccination prevents the disease and does not result in serious side effects. Although using biological agents for the treatment of psoriasis could be related to a higher risk of getting COVID-19, these agents do not increase the risk of severe COVID-19. Therefore, they may be beneficial in reducing the risk of both psoriasis exacerbations and severe COVID-19 due to the cytokine storm among patients using biological for psoriasis.However, large-scale and controlled studies are needed to support our conclusions.

Receptors and Cofactors That Contribute to SARS-CoV-2 Entry: Can Skin Be an Alternative Route of Entry?

To prevent the spread of SARS-CoV-2, all routes of entry of the virus into the host must be mapped. The skin is in contact with the external environment and thus may be an alternative route of entry to transmission via the upper respiratory tract. SARS-CoV-2 cell entry is primarily dependent on ACE2 and the proteases TMPRSS2 or cathepsin L but other cofactors and attachment receptors have been identified that may play a more important role in specific tissues such as the skin. The continued emergence of new variants may also alter the tropism of the virus. In this review, we summarize current knowledge on these receptors and cofactors, their expression profile, factors modulating their expression and their role in facilitating SARS-CoV-2 infection. We discuss their expression in the skin and their possible involvement in percutaneous infection since the presence of the virus has been detected in the skin.

SARS-CoV-2 and Skin: New Insights and Perspectives

The SARS-CoV-2 pandemic has disrupted global health systems and brought the entire globe to its knees. Although born as a disease of the respiratory system, COVID-19 can affect different parts of the body, including the skin. Reports of ongoing skin manifestations of COVID-19 have gradually multiplied, pushing researchers to investigate the etiopathogenic mechanisms underlying these phenomena in more depth. In an attempt to investigate the possible association between SARS-CoV-2, ACE2, TMPRSS2 and skin manifestations, we performed immunohistochemical investigations of the ACE2 receptor and TMPRSS2 in nine skin samples from SARS-CoV-2-positive patients compared to a cohort of healthy controls. Furthermore, after consulting public databases regarding ACE2 mRNA expression in various cell populations resident in the skin, we conducted a literature review aimed at outlining the current state of this topic. We did not find statistically different immuno-expression of ACE2 and TMPRSS2 between the group of SARS-CoV-2-positive patients (nine skin biopsies) and the control group. Regarding ACE2, major immunolabeling was present in the epidermal keratinocytes and, rarely, in the fibroblasts and in the adenomeres of the eccrine sweat glands. Regarding the immune expression of TMPRSS2, we found no significant differences between the two groups, with a weak immune staining only in some skin cytotypes. From the review of the literature, we isolated 35 relevant articles according to the inclusion criteria adopted. ACE2 appears to be a target of SARS-CoV-2, although, other receptor molecules may potentially be implicated, such as TMPRSS2. Future studies with large cases and different molecular investigative methods are needed to further elucidate the mechanisms underlying the skin manifestations of SARS-CoV-2.

IL-33 Enhances ACE2 Expression on Epidermal Keratinocytes in Atopic Dermatitis: A Plausible Issue for SARS-CoV-2 Transmission in Inflamed Atopic Skin

Background: Interleukin-33 (IL-33) is an important cytokine in the pathophysiology of atopic dermatitis (AD) and in the progression of COVID-19. Angiotensin converting enzyme 2 (ACE2), the entry receptor for SARS-CoV-2, is expressed in epidermal keratinocytes. Whether IL-33 could regulate the expression of ACE2 mechanistically in keratinocytes warrants investigation. Objective: We questioned whether the ACE2 expression is increased in AD skin. We also questioned whether ACE2 is expressed in keratinocytes; if so, would its expression be enhanced mechanistically by IL-33. Methods: We measured and compared the expression of ACE2 in skin from patients with AD, patients with psoriasis, and healthy controls using immunohistochemistry. Flow cytometry, immunofluorescent exam, and quantitative RT-PCR were used for measuring the ACE2 expression in cultured keratinocytes treated with IL-33 and IL-17. Blocking antibodies were utilized to study the intracellular signaling pathways governing the ACE2 expression using cytokines. Results: The results showed that the ACE2 expression is increased in AD compared with that in healthy skin and psoriasis. In primary epidermal keratinocytes, ACE2 is constitutively expressed. IL-33 induces a time-dependent increase in ACE2 expression in cultured keratinocytes through quantitative PCR, flow cytometry, and immunofluorescent examinations. Furthermore, pretreatment of an ERK inhibitor, but not a STAT3 inhibitor, eliminated the increases in ACE2 by IL-33 in keratinocytes, indicating that IL-33 enhances ACE2 expression through ERK on epidermal keratinocytes. Conclusion: This is the first study to reveal that IL-33 enhances ACE2 expression on keratinocytes via ERK. Although further mechanistic studies are required, the increased ACE2 expression in IL-33 might have a biological implication on the transmission of SARS-CoV-2 in patients with AD.

Angiotensin-Converting Enzyme 2 Expression Is Detectable in Keratinocytes, Cutaneous Appendages, and Blood Vessels by Multiplex RNA In Situ Hybridization

OBJECTIVE

The angiotensin-converting enzyme 2 (ACE2) receptor mediates uptake of SARS-CoV-2, the virus responsible for COVID-19. Previous work analyzing publicly available bulk RNA-sequencing data sets has shown the expression of ACE2 in human keratinocytes. This finding is potentially relevant for the etiology of COVID-19-associated rashes and might also suggest a possible entry mechanism for the SARS-CoV-2 virus. In this study, the authors examined the spatial localization of ACE2 mRNA in vivo.

METHODS AND RESULTS

The authors analyzed several publicly available single-cell RNA-sequencing data sets. They determined spatial localization of ACE2 mRNA using multiplex RNA in situ hybridization in human skin.

CONCLUSIONS

Both analyses supported ACE2 expression in keratinocytes and skin vasculature, which could reflect a potential cutaneous entry point for SARS-CoV-2, particularly in damaged or broken skin. Moreover, ACE2 expression in vascular endothelial cells may support direct, virally mediated mechanisms in the etiology of the chilblain-like acral eruption that is seen in patients with COVID-19.

Angiotensin converting enzyme and angiotensin converting enzyme inhibitors in dermatology: a narrative review

INTRODUCTION

Angiotensin converting enzyme inhibitors (ACEI) are commonly used for cardiovascular diseases. The evidence supporting the use of ACEI in dermatology is limited.

AREAS COVERED

This review article was divided into three parts. The first part discusses ACEI in clinical use in dermatology. The second part reveals the relationship between angiotensin converting enzyme (ACE) and immune diseases, and further discusses the possible relationship between ACEI in clinical use in these diseases and ACE. The third part focuses on cutaneous adverse reactions of ACEI.

EXPERT OPINION

The use of ACEI in dermatology is mainly based on its properties as regulation of renin angiotensin system (RAS), but currently, with limited clinical use. The association of ACE and several diseases are well discussed, including COVID-19, psoriasis, sarcoidosis, systemic lupus erythematosus and vitiligo. The main cutaneous adverse effects of ACEI include angioedema, psoriasis and pemphigus. Plausible factors for these adverse reactions include accumulation of vasoactive mediators, preventing angiotension from binding to AT₁ receptor and AT₂ receptor and presence of circulating antibodies.

SARS-CoV-2 might transmit through the skin while the skin barrier function could be the mediator

During the coronavirus disease 2019 (COVID-19) pandemic, it were reported that COVID-19 patients could have cutaneous symptoms, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was observed on the skin of COVID-19 patients, which indicated that the skin is one target of SARS-CoV-2. Meanwhile, reports about SARS-CoV-2 transmission through food cold-chain overpacks emerged. With the fact that SARS-CoV-2 could survive on the skin for more than 9 h, the skin could be implicated in SARS CoV-2 transmission. Angiotensin-converting enzyme 2 (ACE2), a critical membrane protein for SARS-CoV-2 that enters a host cell, was recognized to be associated with the risk of SARS-CoV-2 infection. Therefore, tissues that express ACE2 might have the potential to be infected by and transmit SARS-CoV-2. The skin is one such tissue that expresses ACE2. However, unlike the lung that expresses ACE2 on the upper-most epithelial layer, the skin is composed of different layers of cells that function as a barrier, and cells under the top epidermal layer express ACE2. Since the skin barrier is the first line of protection, the typical position of ACE2-expressing cells in the skin implies that the skin barrier function could be the mediator of SARS-CoV-2. In our study, we found that ACE2 could be expressed in the skin, and its expression level is increased in psoriasis, an inflammatory disease of the skin with barrier dysfunction. Additionally, by applying the SARS-CoV-2 pseudovirus on mouse models with or without deteriorated skin barrier, we found that the SARS-CoV-2 pseudovirus could infect the skin and lungs of mouse models, and when the skin barrier was impaired, more SARS-CoV-2-infected cells could be found. Thus, we hypothesized that a deteriorated condition of the skin barrier might increase the risk of SARS-CoV-2 infection through the skin.

Biologics for Psoriasis During the COVID-19 Pandemic

Coronavirus disease 2019 (COVID-19), a new form of acute infectious respiratory syndrome first reported in 2019, has rapidly spread worldwide and has been recognized as a pandemic by the WHO. It raised widespread concern about the treatment of psoriasis in this COVID-19 pandemic era, especially on the biologics use for patients with psoriasis. This review will summarize key information that is currently known about the relationship between psoriasis, biological treatments, and COVID-19, and vaccination-related issues. We also provide references for dermatologists and patients when they need to make clinical decisions. Currently, there is no consensus on whether biological agents increase the risk of coronavirus infection; however, current research shows that biological agents have no adverse effects on the prognosis of patients with COVID-19 with psoriasis. In short, it is not recommended to stop biological treatment in patients with psoriasis to prevent the infection risk, and for those patients who tested positive for SARS-CoV-2, the decision to pause biologic therapy should be considered on a case-by-case basis, and individual risk and benefit should be taken into account. Vaccine immunization against SARS-CoV-2 is strictly recommendable in patients with psoriasis without discontinuation of their biologics but evaluating the risk-benefit ratio of maintaining biologics before vaccination is mandatory at the moment.

Skin Aging, Cellular Senescence and Natural Polyphenols

The skin, being the barrier organ of the body, is constitutively exposed to various stimuli impacting its morphology and function. Senescent cells have been found to accumulate with age and may contribute to age-related skin changes and pathologies. Natural polyphenols exert many health benefits, including ameliorative effects on skin aging. By affecting molecular pathways of senescence, polyphenols are able to prevent or delay the senescence formation and, consequently, avoid or ameliorate aging and age-associated pathologies of the skin. This review aims to provide an overview of the current state of knowledge in skin aging and cellular senescence, and to summarize the recent in vitro studies related to the anti-senescent mechanisms of natural polyphenols carried out on keratinocytes, melanocytes and fibroblasts. Aged skin in the context of the COVID-19 pandemic will be also discussed.

Multifunctional angiotensin converting enzyme 2, the SARS-CoV-2 entry receptor, and critical appraisal of its role in acute lung injury

The recent emergence of coronavirus disease-2019 (COVID-19) as a pandemic affecting millions of individuals has raised great concern throughout the world, and the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was identified as the causative agent for COVID-19. The multifunctional protein angiotensin converting enzyme 2 (ACE2) is accepted as its primary target for entry into host cells. In its enzymatic function, ACE2, like its homologue ACE, regulates the renin-angiotensin system (RAS) critical for cardiovascular and renal homeostasis in mammals. Unlike ACE, however, ACE2 drives an alternative RAS pathway by degrading Ang-II and thus operates to balance RAS homeostasis in the context of hypertension, heart failure, and cardiovascular as well as renal complications of diabetes. Outside the RAS, ACE2 hydrolyzes key peptides, such as amyloid-β, apelin, and [des-Arg9]-bradykinin. In addition to its enzymatic functions, ACE2 is found to regulate intestinal amino acid homeostasis and the gut microbiome. Although the non-enzymatic function of ACE2 as the entry receptor for SARS-CoV-2 has been well established, the contribution of enzymatic functions of ACE2 to the pathogenesis of COVID-19-related lung injury has been a matter of debate. A complete understanding of this central enzyme may begin to explain the various symptoms and pathologies seen in SARS-CoV-2 infected individuals, and may aid in the development of novel treatments for COVID-19.

Response to Tembhre et al.: 'Enhanced expression of angiotensin-converting enzyme 2 in psoriatic skin and its upregulation in keratinocytes by interferon-γ: implication of inflammatory milieu in skin tropism of SARS-CoV-2'

Linked Article: Tembhre et al. Br J Dermatol 2021; 184:577–579.