Protective Effect of Angiotensin (1-7) on Silicotic Fibrosis in Rats

Involvement of the ACE2/Ang-(1-7)/MasR Axis in Pulmonary Fibrosis: Implications for COVID-19

Pulmonary fibrosis is a chronic, fibrotic lung disease affecting 3 million people worldwide. The ACE2/Ang-(1–7)/MasR axis is of interest in pulmonary fibrosis due to evidence of its anti-fibrotic action. Current scientific evidence supports that inhibition of ACE2 causes enhanced fibrosis. ACE2 is also the primary receptor that facilitates the entry of SARS-CoV-2, the virus responsible for the current COVID-19 pandemic. COVID-19 is associated with a myriad of symptoms ranging from asymptomatic to severe pneumonia and acute respiratory distress syndrome (ARDS) leading to respiratory failure, mechanical ventilation, and often death. One of the potential complications in people who recover from COVID-19 is pulmonary fibrosis. Cigarette smoking is a risk factor for fibrotic lung diseases, including the idiopathic form of this disease (idiopathic pulmonary fibrosis), which has a prevalence of 41% to 83%. Cigarette smoke increases the expression of pulmonary ACE2 and is thought to alter susceptibility to COVID-19. Cannabis is another popular combustible product that shares some similarities with cigarette smoke, however, cannabis contains cannabinoids that may reduce inflammation and/or ACE2 levels. The role of cannabis smoke in the pathogenesis of pulmonary fibrosis remains unknown. This review aimed to characterize the ACE2-Ang-(1–7)-MasR Axis in the context of pulmonary fibrosis with an emphasis on risk factors, including the SARS-CoV-2 virus and exposure to environmental toxicants. In the context of the pandemic, there is a dire need for an understanding of pulmonary fibrotic events. More research is needed to understand the interplay between ACE2, pulmonary fibrosis, and susceptibility to coronavirus infection.

Angiotensin-Converting Enzyme 2 (ACE2) in the Context of Respiratory Diseases and Its Importance in Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection

Angiotensin-Converting Enzyme 2 (ACE2) is an 805 amino acid protein encoded by the ACE2 gene expressed in various human cells, especially in those located in the epithelia. The primary function of ACE2 is to produce angiotensin (1–7) from angiotensin II (Ang II). The current research has described the importance of ACE2 and Ang (1–7) in alternative routes of the renin-angiotensin system (RAS) that promote the downregulation of fibrosis, inflammation, and oxidative stress processes in a great variety of diseases, such as hypertension, acute lung injury, liver cirrhosis, and kidney abnormalities. Investigations into the recent outbreak of the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have revealed the importance of ACE2 during infection and its role in recognizing viral binding proteins through interactions with specific amino acids of this enzyme. Additionally, the ACE2 expression in several organs has allowed us to understand the clinical picture related to the infection caused by SARS-CoV-2. This review aims to provide context for the functions and importance of ACE2 with regards to SARS-CoV-2 in the general clinical aspect and its impact on other diseases, especially respiratory diseases.

Dahuang Zhechong Pills Suppress Silicosis Fibrosis Progression via p38 MAPK/TGF-β1/Smad Pathway In Vitro

Background

Dahuang Zhechong pills (DHZCP) is a classic Chinese medicinal prescription in “Treatise on Cold Pathogenic and Miscellaneous Diseases (Shanghan Zabing Lun),” and it has the function of tonifying blood, nourishing Yin, and removing blood stasis. Previous studies have shown that DHZCP could alleviate SiO₂ induced pulmonary fibrosis in mice. This study aims to further explore the preventive and therapeutic effects of DHZCP against silicosis fibrosis and the underlying mechanisms in vitro.

Methods

We used the experimental model of SiO₂-induced MH-S cells to evaluate the therapeutic potential of DHZCP. MH-S cells induced by SiO₂ were intervened with the drug-containing serum of DHZCP, and the effects of drug-containing serum of DHZCP on the MH-S cells were detected by CCK8, ELISA, flow cytometry, western blot, and immunofluorescence.

Results

DHZCP improved cell viability by reducing apoptosis. It also decreased the levels of TNF-α, IL-1β, IL-6 in the supernatant of MH-S cells induced by SiO₂, inhibited the expression of p38 MAPK, blocked the activation of NF-κB, and controlled the upstream inflammatory response by multiple targeting. Concomitantly, we observed upregulation of Smad7 and a marked decline in TGF-β1, α-SMA, Smad2, Smad3 expression in MH-S cells treated with DHZCP.

Conclusion

To sum up, we conclude that DHZCP protects against SiO₂-induced silicosis by reducing the persistent irritation of inflammation, regulating the p38 MAPK/TGF-β1/Smad pathway.

Comparative proteomic analysis of silica-induced pulmonary fibrosis in rats based on tandem mass tag (TMT) quantitation technology

Silicosis is a systemic disease characterized by chronic persistent inflammation and incurable pulmonary fibrosis with the underlying molecular mechanisms to be fully elucidated. In this study, we employed tandem mass tag (TMT) based on quantitative proteomics technology to detect differentially expressed proteins (DEPs) in lung tissues of silica-exposed rats. A total of 285 DEPs (145 upregulated and 140 downregulated) were identified. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were performed to predict the biological pathway and functional classification of the proteins. Results showed that these DEPs were mainly enriched in the phagosome, lysosome function, complement and the coagulation cascade, glutathione metabolism, focal adhesion and ECM-receptor interactions. To validate the proteomics data, we selected and analyzed the expression trends of six proteins including CD14, PSAP, GM2A, COL1A1, ITGA8 and CLDN5 using parallel reaction monitoring (PRM). The consistent result between PRM and TMT indicated the reliability of our proteomic data. These findings will help to reveal the pathogenesis of silicosis and provide potential therapeutic targets. Data are available via ProteomeXchange with identifier PXD020625.

Angiotensin-converting enzyme 2 expression in COPD and IPF fibroblasts: the forgotten cell in COVID-19

The COVID-19 pandemic is associated with severe pneumonia and acute respiratory distress syndrome leading to death in susceptible individuals. For those who recover, post-COVID-19 complications may include development of pulmonary fibrosis. Factors contributing to disease severity or development of complications are not known. Using computational analysis with experimental data, we report that idiopathic pulmonary fibrosis (IPF)- and chronic obstructive pulmonary disease (COPD)-derived lung fibroblasts express higher levels of angiotensin-converting enzyme 2 (ACE2), the receptor for SARS-CoV-2 entry and part of the renin-angiotensin system that is antifibrotic and anti-inflammatory. In preclinical models, we found that chronic exposure to cigarette smoke, a risk factor for both COPD and IPF and potentially for SARS-CoV-2 infection, significantly increased pulmonary ACE2 protein expression. Further studies are needed to understand the functional implications of ACE2 on lung fibroblasts, a cell type that thus far has received relatively little attention in the context of COVID-19.

ACE2 in the Era of SARS-CoV-2: Controversies and Novel Perspectives

Angiotensin-converting enzyme 2 (ACE2) is related to ACE but turned out to counteract several pathophysiological actions of ACE. ACE2 exerts antihypertensive and cardioprotective effects and reduces lung inflammation. ACE2 is subjected to extensive transcriptional and post-transcriptional modulation by epigenetic mechanisms and microRNAs. Also, ACE2 expression is regulated post-translationally by glycosylation, phosphorylation, and shedding from the plasma membrane. ACE2 protein is ubiquitous across mammalian tissues, prominently in the cardiovascular system, kidney, and intestine. ACE2 expression in the respiratory tract is of particular interest, in light of the discovery that ACE2 serves as the initial cellular target of severe acute respiratory syndrome (SARS)-coronaviruses, including the recent SARS-CoV2, responsible of the COronaVIrus Disease 2019 (COVID-19). Since the onset of the COVID-19 pandemic, an intense effort has been made to elucidate the biochemical determinants of SARS-CoV2-ACE2 interaction. It has been determined that SARS-CoV2 engages with ACE2 through its spike (S) protein, which consists of two subunits: S1, that mediates binding to the host receptor; S2, that induces fusion of the viral envelope with the host cell membrane and delivery of the viral genome. Owing to the role of ACE2 in SARS-CoV2 pathogenicity, it has been speculated that medical conditions, i.e., hypertension, and/or drugs, i.e., ACE inhibitors and angiotensin receptor blockers, known to influence ACE2 density could alter the fate of SARS-CoV-2 infection. The debate is still open and will only be solved when results of properly designed experimental and clinical investigations will be made public. An interesting observation is, however that, upon infection, ACE2 activity is reduced either by downregulation or by shedding. These events might precipitate the so-called "cytokine storm" that characterizes the most severe COVID-19 forms. As evidence accumulates, ACE2 appears a druggable target in the attempt to limit virus entry and replication. Strategies aimed at blocking ACE2 with antibodies, small molecules or peptides, or at neutralizing the virus by competitive binding with exogenously administered ACE2, are currently under investigations. In this review, we will present an overview of the state-of-the-art knowledge on ACE2 biochemistry and pathophysiology, outlining open issues in the context of COVID-19 disease and potential experimental and clinical developments.