The effect of endogenous angiotensin II on alveolar fluid clearance in rats with acute lung injury

Epigenetic perspectives associated with COVID-19 infection and related cytokine storm: an updated review

PURPOSE

The COVID-19 pandemic caused by the novel Severe Acute Respiratory Syndrome Corona Virus 2 (SARS-CoV-2) has put the world in a medical crisis for the past three years; nearly 6.3 million lives have been diminished due to the virus outbreak. This review aims to update the recent findings on COVID-19 infections from an epigenetic scenario and develop future perspectives of epi-drugs to treat the disease.

METHODS

Original research articles and review studies related to COVID-19 were searched and analyzed from the Google Scholar/PubMed/Medline databases mainly between 2019 and 2022 to brief the recent work.

RESULTS

Numerous in-depth studies of the mechanisms used by SARS-CoV-2 have been going on to minimize the consequences of the viral outburst. Angiotensin-Converting Enzyme 2 receptors and Transmembrane serine protease 2 facilitate viral entry to the host cells. Upon internalization, it uses the host machinery to replicate viral copies and alter the downstream regulation of the normal cells, causing infection-related morbidities and mortalities. In addition, several epigenetic regulations such as DNA methylation, acetylation, histone modifications, microRNA, and other factors (age, sex, etc.) are responsible for the regulations of viral entry, its immune evasion, and cytokine responses also play a major modulatory role in COVID-19 severity, which has been discussed in detail in this review.

CONCLUSION

Findings of epigenetic regulation of viral pathogenicity open a new window for epi-drugs as a possible therapeutical approach against COVID-19.

Exploring the Network between Adipocytokines and Inflammatory Response in SARS-CoV-2 Infection: A Scoping Review

Adipose tissue is actually regarded as an endocrine organ, rather than as an organ that merely stores energy. During the COVID-19 pandemic, obesity has undoubtedly emerged as one of the most important risk factors for disease severity and poor outcomes related to SARS-CoV-2 infection. The aberrant production of cytokine-like hormones, called adipokines, may contribute to alterations in metabolism, dysfunction in vascular endothelium and the creation of a state of general chronic inflammation. Moreover, chronic, low-grade inflammation linked to obesity predisposes the host to immunosuppression and excessive cytokine activation. In this respect, understanding the mechanisms that link obesity with the severity of SARS-CoV-2 infection could represent a real game changer in the development of new therapeutic strategies. Our review therefore examines the pathogenic mechanisms of SARS-CoV-2, the implications with visceral adipose tissue and the influences of the adipose tissue and its adipokines on the clinical behavior of COVID-19.

Targeting the renin angiotensin system for respiratory diseases

Renin-angiotensin system (RAS) plays an indispensable role in regulating blood pressure through its effects on fluid and electrolyte balance. As an aside, cumulative evidence from experimental to clinical studies supports the notion that dysregulation of RAS contributes to the pro-inflammatory, pro-oxidative, and pro-fibrotic processes that occur in pulmonary diseases like asthma, chronic obstructive pulmonary disease (COPD), idiopathic pulmonary fibrosis (IPF), and acute lung injury (ALI). Pharmacological intervention of the various RAS components can be a novel therapeutic strategy for the treatment of these respiratory diseases. In this chapter, we first give a recent update on the RAS, and then compile, review, and analyse recent reports on targeting RAS components as treatments for respiratory diseases. Inhibition of the pro-inflammatory renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and Ang II type 1 receptor (AT1R) axis, and activation of the protective ACE2, AT2R, Ang (1-7), and Mas receptor axis have demonstrated varying degrees of efficacies in experimental respiratory disease models or in human trials. The newly identified alamandine/Mas-related G-protein-coupled receptor member D pathway has shown some therapeutic promise as well. However, our understanding of the RAS ligand-and-receptor interactions is still inconclusive, and the modes of action and signaling cascade mediating the newly identified RAS receptors remain to be better characterized. Clinical data are obviously lacking behind the promising pre-clinical findings of certain well-established molecules targeting at different pathways of the RAS in respiratory diseases. Translational human studies should be the focus for RAS drug development in lung diseases in the next decade.

The Renin-Angiotensin System as a Component of Biotrauma in Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a major concern in critical care medicine with a high mortality of over 30%. Injury to the lungs is caused not only by underlying pathological conditions such as pneumonia, sepsis, or trauma, but also by ventilator-induced lung injury (VILI) resulting from high positive pressure levels and a high inspiratory oxygen fraction. Apart from mechanical factors that stress the lungs with a specific physical power and cause volutrauma and barotrauma, it is increasingly recognized that lung injury is further aggravated by biological mediators. The COVID-19 pandemic has led to increased interest in the role of the renin-angiotensin system (RAS) in the context of ARDS, as the RAS enzyme angiotensin-converting enzyme 2 serves as the primary cell entry receptor for severe acute respiratory syndrome (SARS) coronavirus (CoV)-2. Even before this pandemic, studies have documented the involvement of the RAS in VILI and its dysregulation in clinical ARDS. In recent years, analytical tools for RAS investigation have made major advances based on the optimized precision and detail of mass spectrometry. Given that many clinical trials with pharmacological interventions in ARDS were negative, RAS-modifying drugs may represent an interesting starting point for novel therapeutic approaches. Results from animal models have highlighted the potential of RAS-modifying drugs to prevent VILI or treat ARDS. While these drugs have beneficial pulmonary effects, the best targets and application forms for intervention still have to be determined to avoid negative effects on the circulation in clinical settings.

Mechanisms contributing to adverse outcomes of COVID-19 in obesity

A growing amount of epidemiological data from multiple countries indicate an increased prevalence of obesity, more importantly central obesity, among hospitalized subjects with COVID-19. This suggests that obesity is a major factor contributing to adverse outcome of the disease. As it is a metabolic disorder with dysregulated immune and endocrine function, it is logical that dysfunctional metabolism contributes to the mechanisms behind obesity being a risk factor for adverse outcome in COVID-19. Emerging data suggest that in obese subjects, (a) the molecular mechanisms of viral entry and spread mediated through ACE2 receptor, a multifunctional host cell protein which links to cellular homeostasis mechanisms, are affected. This includes perturbation of the physiological renin-angiotensin system pathway causing pro-inflammatory and pro-thrombotic challenges (b) existent metabolic overload and ER stress-induced UPR pathway make obese subjects vulnerable to severe COVID-19, (c) host cell response is altered involving reprogramming of metabolism and epigenetic mechanisms involving microRNAs in line with changes in obesity, and (d) adiposopathy with altered endocrine, adipokine, and cytokine profile contributes to altered immune cell metabolism, systemic inflammation, and vascular endothelial dysfunction, exacerbating COVID-19 pathology. In this review, we have examined the available literature on the underlying mechanisms contributing to obesity being a risk for adverse outcome in COVID-19.

Angiotensin Receptor Blockers Are Not Just for Hypertension Anymore

Beyond blood pressure control, angiotensin receptor blockers reduce common injury mechanisms, decreasing excessive inflammation and protecting endothelial and mitochondrial function, insulin sensitivity, the coagulation cascade, immune responses, cerebrovascular flow, and cognition, properties useful to treat inflammatory, age-related, neurodegenerative, and metabolic disorders of many organs including brain and lung.

Scientific Hypothesis for Treatment of COVID-19's Lung Lesions by Adjusting ACE/ACE2 Imbalance

In March 2019 began the global pandemic COVID-19 caused by the new Coronavirus SARS-CoV-2. The first cases of SARS-CoV-2 infection occurred in November-19 in Wuhan, China. The preventive measures taken did not prevent the rapid spread of the virus to all countries around the world. To date, there are about 2.54 million deaths, effective vaccines are in clinical trials. SARS-CoV-2 uses the ACE-2 protein as an intracellular gateway. ACE-2 is a key component of the Renin Angiotensin (RAS) system, a key regulator of cardiovascular function. Considering the key role of ACE-2 in COVID-19 infection, both as an entry receptor and as a protective role, especially for the respiratory tract, and considering the variations of ACE-2 and ACE during the stages of viral infection, it is clear the important role that the pharmacological regulation of RAS and ACE-2 can assume. This biological knowledge suggests different pharmacological approaches to treat COVID-19 by modulating RAS, ACE-2 and the ACE/ACE2 balance that we describe in this article.

COVID-19 and Oxidative Stress

Pathogenesis of the novel coronavirus infection COVID-19 is the subject of active research around the world. COVID-19 caused by the SARS-CoV-2 is a complex disease in which interaction of the virus with target cells, action of the immune system and the body’s systemic response to these events are closely intertwined. Many respiratory viral infections, including COVID-19, cause death of the infected cells, activation of innate immune response, and secretion of inflammatory cytokines. All these processes are associated with the development of oxidative stress, which makes an important contribution to pathogenesis of the viral infections. This review analyzes information on the oxidative stress associated with the infections caused by SARS-CoV-2 and other respiratory viruses. The review also focuses on involvement of the vascular endothelium in the COVID-19 pathogenesis.

An Open Label Trial to Assess Safety of Losartan for Treating Worsening Respiratory Illness in COVID-19

Rationale: Coronavirus disease 2019 (COVID-19) can cause disruption of the renin-angiotensin system in the lungs, possibly contributing to pulmonary capillary leakage. Thus, angiotensin receptor blockers (ARBs) may improve respiratory failure. Objective: Assess safety of losartan for use in respiratory failure related to COVID-19 (NCT04335123). Methods: Single arm, open label trial of losartan in those hospitalized with respiratory failure related to COVID-19. Oral losartan (25 mg daily for 3 days, then 50 mg) was administered from enrollment until day 14 or hospital discharge. A post-hoc external control group with patients who met all inclusion criteria was matched 1:1 to the treatment group using propensity scores for comparison. Measures: Primary outcome was cumulative incidence of any adverse events. Secondary, explorative endpoints included measures of respiratory failure, length of stay and vital status. Results: Of the 34 participants enrolled in the trial, 30 completed the study with a mean age SD of 53.8 ± 17.7 years and 17 males (57%). On losartan, 24/30 (80%) experienced an adverse event as opposed to 29/30 (97%) of controls, with a lower average number of adverse events on losartan relative to control (2.2 vs. 3.3). Using Poisson regression and controlling for age, sex, race, date of enrollment, disease severity at enrollment, and history of high-risk comorbidities, the incidence rate ratio of adverse events on losartan relative to control was 0.69 (95% CI: 0.49-0.97) Conclusions: Losartan appeared safe for COVID-19-related acute respiratory compromise. To assess true efficacy, randomized trials are needed.

Are losartan and imatinib effective against SARS-CoV2 pathogenesis? A pathophysiologic-based in silico study

Proposing a theory about the pathophysiology of cytokine storm in COVID19, we were to find the potential drugs to treat this disease and to find any effect of these drugs on the virus infectivity through an in silico study. COVID-19-induced ARDS is linked to a cytokine storm phenomenon not explainable solely by the virus infectivity. Knowing that ACE2, the hydrolyzing enzyme of AngII and SARS-CoV2 receptor, downregulates when the virus enters the host cells, we hypothesize that hyperacute AngII upregulation is the eliciting factor of this ARDS. We were to validate this theory through reviewing previous studies to figure out the role of overzealous activation of AT1R in ARDS. According to this theory losartan may attenuate ARDS in this disease. Imatinib, has previously been elucidated to be promising in modulating lung inflammatory reactions and virus infectivity in SARS and MERS. We did an in silico study to uncover any probable other unconsidered inhibitory effects of losartan and imatinib against SARS-CoV2 pathogenesis. Reviewing the literature, we could find that over-activation of AT1R could explain precisely the mechanism of cytokine storm in COVID19. Our in silico study revealed that losartan and imatinib could probably: (1) decline SARS-CoV2 affinity to ACE2. (2) inhibit the main protease and furin, (3) disturb papain-like protease and p38MAPK functions. Our reviewing on renin-angiotensin system showed that overzealous activation of AT1R by hyper-acute excess of AngII due to acute downregulation of ACE2 by SARS-CoV2 explains precisely the mechanism of cytokine storm in COVID-19. Besides, based on our in silico study we concluded that losartan and imatinib are promising in COVID19.

Should ACE2 be given a chance in COVID-19 therapeutics: A semi-systematic review of strategies enhancing ACE2

The severe acute respiratory syndrome corona virus-2 (SARS-CoV-2) has resulted in almost 28 million cases of COVID-19 (Corona virus disease-2019) and more than 900000 deaths worldwide since December 2019. In the absence of effective antiviral therapy and vaccine, treatment of COVID-19 is largely symptomatic. By making use of its spike (S) protein, the virus binds to its primary human cell receptor, angiotensin converting enzyme 2 (ACE2) which is present in the pulmonary epithelial cells as well as other organs. SARS-CoV-2 may cause a downregulation of ACE2. ACE2 plays a protective role in the pulmonary system through its Mas-receptor and alamandine-MrgD-TGR7 pathways. Loss of this protective effect could be a major component of COVID-19 pathogenesis. An attractive strategy in SARS-CoV-2 therapeutics would be to augment ACE2 either directly by supplementation or indirectly through drugs which increase its levels or stimulate its downstream players. In this semi-systematic review, we have analysed the pathophysiological interplay between ACE and ACE2 in the cardiopulmonary system, the modulation of these two proteins by SARS-CoV-2, and potential therapeutic avenues targeting ACE-Ang II and ACE2-Ang (1-7) axes, that can be utilized against COVID-19 disease progression.

ACE2: Evidence of role as entry receptor for SARS-CoV-2 and implications in comorbidities

Pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus 19 disease (COVID-19) which presents a large spectrum of manifestations with fatal outcomes in vulnerable people over 70-years-old and with hypertension, diabetes, obesity, cardiovascular disease, COPD, and smoking status. Knowledge of the entry receptor is key to understand SARS-CoV-2 tropism, transmission and pathogenesis. Early evidence pointed to angiotensin-converting enzyme 2 (ACE2) as SARS-CoV-2 entry receptor. Here, we provide a critical summary of the current knowledge highlighting the limitations and remaining gaps that need to be addressed to fully characterize ACE2 function in SARS-CoV-2 infection and associated pathogenesis. We also discuss ACE2 expression and potential role in the context of comorbidities associated with poor COVID-19 outcomes. Finally, we discuss the potential co-receptors/attachment factors such as neuropilins, heparan sulfate and sialic acids and the putative alternative receptors, such as CD147 and GRP78.

A hypothesis for pathobiology and treatment of COVID-19: The centrality of ACE1/ACE2 imbalance

Angiotensin Converting Enzyme2 is the cell surface binding site for the coronavirus SARS-CoV-2, which causes COVID-19. We propose that an imbalance in the action of ACE1- and ACE2-derived peptides, thereby enhancing angiotensin II (Ang II) signalling is primary driver of COVID-19 pathobiology. ACE1/ACE2 imbalance occurs due to the binding of SARS-CoV-2 to ACE2, reducing ACE2-mediated conversion of Ang II to Ang peptides that counteract pathophysiological effects of ACE1-generated ANG II. This hypothesis suggests several approaches to treat COVID-19 by restoring ACE1/ACE2 balance: (a) AT receptor antagonists; (b) ACE1 inhibitors (ACEIs); (iii) agonists of receptors activated by ACE2-derived peptides (e.g. Ang (1-7), which activates MAS1); (d) recombinant human ACE2 or ACE2 peptides as decoys for the virus. Reducing ACE1/ACE2 imbalance is predicted to blunt COVID-19-associated morbidity and mortality, especially in vulnerable patients. Importantly, approved AT antagonists and ACEIs can be rapidly repurposed to test their efficacy in treating COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Candesartan could ameliorate the COVID-19 cytokine storm

BACKGROUND

Angiotensin receptor blockers (ARBs) reducing inflammation and protecting lung and brain function, could be of therapeutic efficacy in COVID-19 patients.

METHODS

Using GSEA, we compared our previous transcriptome analysis of neurons injured by glutamate and treated with the ARB Candesartan (GSE67036) with transcriptional signatures from SARS-CoV-2 infected primary human bronchial epithelial cells (NHBE) and lung postmortem (GSE147507), PBMC and BALF samples (CRA002390) from COVID-19 patients.

RESULTS

Hundreds of genes upregulated in SARS-CoV-2/COVID-19 transcriptomes were similarly upregulated by glutamate and normalized by Candesartan. Gene Ontology analysis revealed expression profiles with greatest significance and enrichment, including proinflammatory cytokine and chemokine activity, the NF-kappa B complex, alterations in innate and adaptive immunity, with many genes participating in the COVID-19 cytokine storm.

CONCLUSIONS

There are similar injury mechanisms in SARS-CoV-2 infection and neuronal injury, equally reduced by ARB treatment. This supports the hypothesis of a therapeutic role for ARBs, ameliorating the COVID-19 cytokine storm.

Role of Renin-Angiotensin System in Acute Lung Injury Caused by Viral Infection

The renin-angiotensin system (RAS) is the most important regulatory system of electrolyte homeostasis and blood pressure and acts through angiotensin-converting enzyme (ACE)/angiotensin II (Ang II)/Ang II type 1 (AT1) receptor axis and angiotensin-converting enzyme 2 (ACE2)/angiotensin (1-7)/MAS receptor axis. RAS dysfunction is related to the occurrence and development of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) and causes a serious prognosis and even death. ALI/ARDS can be induced by various ways, one of which is viral infections, such as SARS-CoV, SARS-CoV-2, H5N1, H7N9, and EV71. This article reviews the specific mechanism on how RAS dysfunction affects ALI/ARDs caused by viral infections. SARS-CoV and SARS-CoV-2 enter the host cells by binding with ACE2. H5N1 and H7N9 avian influenza viruses reduce the ACE2 level in the body, and EV71 increases Ang II concentration. Treatment with angiotensin-converting enzyme inhibitor and angiotensin AT1 receptor blocker can alleviate ALI/ARDS symptoms. This review provides suggestions for the treatment of lung injury caused by viral infections.

Angiotensin-converting enzyme 2, the complement system, the kallikrein-kinin system, type-2 diabetes, interleukin-6, and their interactions regarding the complex COVID-19 pathophysiological crossroads

Because of the current COVID-19-pandemic, the world is currently being held hostage in various lockdowns. ACE2 facilitates SARS-CoV-2 cell-entry, and is at the very center of several pathophysiological pathways regarding the RAAS, CS, KKS, T2DM, and IL-6. Their interactions with severe COVID-19 complications (e.g. ARDS and thrombosis), and potential therapeutic targets for pharmacological intervention, will be reviewed.

Comprehensive analysis of drugs to treat SARS‑CoV‑2 infection: Mechanistic insights into current COVID‑19 therapies (Review)

The major impact produced by the severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) focused many researchers attention to find treatments that can suppress transmission or ameliorate the disease. Despite the very fast and large flow of scientific data on possible treatment solutions, none have yet demonstrated unequivocal clinical utility against coronavirus disease 2019 (COVID‑19). This work represents an exhaustive and critical review of all available data on potential treatments for COVID‑19, highlighting their mechanistic characteristics and the strategy development rationale. Drug repurposing, also known as drug repositioning, and target based methods are the most used strategies to advance therapeutic solutions into clinical practice. Current in silico, in vitro and in vivo evidence regarding proposed treatments are summarized providing strong support for future research efforts.

Application of System Biology to Explore the Association of Neprilysin, Angiotensin-Converting Enzyme 2 (ACE2), and Carbonic Anhydrase (CA) in Pathogenesis of SARS-CoV-2

Background

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) appears with common symptoms including fever, dry cough, and fatigue, as well as some less common sysmptoms such as loss of taste and smell, diarrhea, skin rashes and discoloration of fingers. COVID-19 patients may also suffer from serious symptoms including shortness of breathing, chest pressure and pain, as well as loss of daily routine habits, pointing out to a sever reduction in the quality of life. COVID-19 has afftected almost all countries, however, the United States contains the highest number of infection (> 1,595,000 cases) and deaths cases (> 95,000 deaths) in the world until May 21, 2020. Finding an influential treatment strategy against COVID-19 can be facilitated through better understanding of the virus pathogenesis and consequently interrupting the biochemical pathways that the virus may play role in human body as the current reservoir of the virus.

Results

In this study, we combined system biology and bioinformatic approaches to define the role of coexpression of angiotensin-converting enzyme 2 (ACE2), neprilysin or membrane metallo-endopeptidase (MME), and carbonic anhydrases (CAs) and their association in the pathogenesis of SARS-CoV-2. The results revealed that ACE2 as the cellular attachment site of SARS-CoV-2, neprilysin, and CAs have a great contribution together in the renin angiotensin system (RAS) and consequently in pathogenesis of SARS-CoV-2 in the vital organs such as respiratory, renal, and blood circulation systems. Any disorder in neprilysin, ACE2, and CAs can lead to increase of CO₂ concentration in blood and respiratory acidosis, induction of pulmonary edema and heart and renal failures.

Conclusions

Due to the presence of ACE2-Neprilysin-CA complex in most of vital organs and as a receptor of COVID-19, it is expected that most organs are affected by SARS-CoV-2 such as inflammation and fibrosis of lungs, which may conversely affect their vital functions, temporary or permanently, sometimes leading to death. Therefore, ACE2-Neprilysin-CA complex could be the key factor of pathogenesis of SARS-CoV-2 and may provide us useful information to find better provocative and therapeutic strategies against COVID-19.

A hypothesis for pathobiology and treatment of COVID-19: The centrality of ACE1/ACE2 imbalance

Angiotensin Converting Enzyme2 is the cell surface binding site for the coronavirus SARS-CoV-2, which causes COVID-19. We propose that an imbalance in the action of ACE1- and ACE2-derived peptides, thereby enhancing angiotensin II (Ang II) signalling is primary driver of COVID-19 pathobiology. ACE1/ACE2 imbalance occurs due to the binding of SARS-CoV-2 to ACE2, reducing ACE2-mediated conversion of Ang II to Ang peptides that counteract pathophysiological effects of ACE1-generated ANG II. This hypothesis suggests several approaches to treat COVID-19 by restoring ACE1/ACE2 balance: (a) AT receptor antagonists; (b) ACE1 inhibitors (ACEIs); (iii) agonists of receptors activated by ACE2-derived peptides (e.g. Ang (1-7), which activates MAS1); (d) recombinant human ACE2 or ACE2 peptides as decoys for the virus. Reducing ACE1/ACE2 imbalance is predicted to blunt COVID-19-associated morbidity and mortality, especially in vulnerable patients. Importantly, approved AT antagonists and ACEIs can be rapidly repurposed to test their efficacy in treating COVID-19. LINKED ARTICLES: This article is part of a themed issue on The Pharmacology of COVID-19. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.21/issuetoc.

Maresin Conjugates in Tissue Regeneration 1 improves alveolar fluid clearance by up-regulating alveolar ENaC, Na, K-ATPase in lipopolysaccharide-induced acute lung injury

Maresin Conjugates in Tissue Regeneration 1 (MCTR1) is a newly identified macrophage‐derived sulfido‐conjugated mediator that stimulates the resolution of inflammation. This study assessed the role of MCTR1 in alveolar fluid clearance (AFC) in a rat model of acute lung injury (ALI) induced by lipopolysaccharide (LPS). Rats were intravenously injected with MCTR1 at a dose of 200 ng/rat, 8 hours after administration of 14 mg/kg LPS. The level of AFC was then determined in live rats. Primary rat ATII (Alveolar Type II) epithelial cells were also treated with MCTR1 (100 nmol/L) in a culture medium containing LPS for 8 hours. MCTR1 treatment improved AFC (18.85 ± 2.07 vs 10.11 ± 1.08, P < .0001) and ameliorated ALI in rats. MCTR1 also significantly promoted AFC by up‐regulating epithelial sodium channel (ENaC) and Na⁺‐K⁺‐adenosine triphosphatase (Na, K‐ATPase) expressions in vivo. MCTR1 also activated Na, K‐ATPase and elevated phosphorylated‐Akt (P‐Akt) by up‐regulating the expression of phosphorylated Nedd4‐2 (P‐Nedd4‐2) in vivo and in vitro. However, BOC‐2 (ALX inhibitor), KH7 (cAMP inhibitor) and LY294002 (PI3K inhibitor) abrogated the improved AFC induced by MCTR1. Based on the findings of this study, MCTR1 may be a novel therapeutic approach to improve reabsorption of pulmonary oedema during ALI/acute respiratory distress syndrome (ARDS).

Soluble Epoxide Hydrolase Plays a Vital Role in Angiotensin II-Induced Lung Injury in Mice

BACKGROUND

Angiotensin II plays a vital role in the pathogenesis of acute respiratory distress syndrome (ARDS). However, its mechanism is not well defined. Angiotensin II upregulates the expression of soluble epoxide hydrolase (sEH; Ephx2). sEH is suggested as a potential pharmacologic target for ARDS. The present study investigates whether the sEH is involved in the angiotensin II-triggered pulmonary inflammation and edema using an angiotensin II-induced lung injury animal model.

METHODS

Lung injury was induced by angiotensin II intratracheally instillation in wild-type or Ephx2 deficient mice.

RESULTS

sEH activities were markedly increased in wild-type mice treated with angiotensin II. Angiotensin II markedly increased the levels of tumor necrosis factor-α and interleukin-1β in bronchoalveolar lavage fluid, worsened alveolar capillary protein leak and lung histological alterations, and elevated activity of activator protein-1 and nuclear factor-κB. However, these changes were significantly improved in Ephx2 deficient mice. Moreover, Losartan, an angiotensin II receptor 1 antagonist, abolished the sEH induction and improved mortality.

CONCLUSIONS

Angiotensin II-induced lung injury was improved in sEH gene deleted mice. The angiotensin II-triggered pulmonary inflammation is mediated, at least in part, through the sEH.

AVE 0991 Attenuates Pyroptosis and Liver Damage after Heatstroke by Inhibiting the ROS-NLRP3 Inflammatory Signalling Pathway

We previously demonstrated that angiotensin-(1-7) (Ang-(1-7)), an essential endocrine factor, inhibits the NLRP3 inflammasome by regulating reactive oxygen species (ROS) in fibrotic livers. We also demonstrated that the NLRP3 inflammasome contributes to the liver damage induced by pyroptosis after heatstroke. However, the role of Ang-(1-7) in the hepatocytes under heat stress remains uncertain. We aimed to examine the change in angiotensin peptides in the livers affected by heatstroke and the effect on the ROS-NLRP3 inflammatory signalling pathway. In vivo, increased angiotensin II (Ang II) and decreased Ang-(1-7) in the serum of heatstroke patients suffering from hepatic dysfunction were observed. The change in angiotensin peptides was considered a potential biomarker that could be used to predict hepatic dysfunction. Enhanced Ang II and attenuated Ang-(1-7) levels were also observed in the liver tissue of heatstroke rats, which were consistent with their receptors and converting enzymes. Hepatic damage associated with increased ROS and protein expression levels of NOX4, NLRP3, caspase-1, and IL-1β was attenuated by AVE 0991, an analogue of Ang-(1-7). In vitro, pyroptosis, characterized by activated caspase-1 and IL-1β, was observed in hepatocytes under heat stress, which was enhanced by Ang II and attenuated by antioxidants, NOX4 siRNA, and AVE 0991. In summary, AVE 0991 attenuates pyroptosis and liver damage induced by heat stress by inhibiting the ROS-NLRP3 inflammatory signalling pathway.

Protectin DX increases alveolar fluid clearance in rats with lipopolysaccharide-induced acute lung injury

Acute respiratory distress syndrome is a life-threatening critical syndrome resulting largely from the accumulation of and the inability to clear pulmonary edema. Protectin DX, an endogenously produced lipid mediator, is believed to exert anti-inflammatory and pro-resolution effects. Protectin DX (5 µg/kg) was injected i.v. 8 h after LPS (14 mg/kg) administration, and alveolar fluid clearance was measured in live rats (n = 8). In primary rat ATII epithelial cells, protectin DX (3.605 × 10⁻³ mg/l) was added to the culture medium with LPS for 6 h. Protectin DX improved alveolar fluid clearance (9.65 ± 1.60 vs. 15.85 ± 1.49, p < 0.0001) and decreased pulmonary edema and lung injury in LPS-induced lung injury in rats. Protectin DX markedly regulated alveolar fluid clearance by upregulating sodium channel and Na, K-ATPase protein expression levels in vivo and in vitro. Protectin DX also increased the activity of Na, K-ATPase and upregulated P-Akt via inhibiting Nedd4–2 in vivo. In addition, protectin DX enhanced the subcellular distribution of sodium channels and Na, K-ATPase, which were specifically localized to the apical and basal membranes of primary rat ATII cells. Furthermore, BOC-2, Rp-cAMP, and LY294002 blocked the increased alveolar fluid clearance in response to protectin DX. Protectin DX stimulates alveolar fluid clearance through a mechanism partly dependent on alveolar epithelial sodium channel and Na, K-ATPase activation via the ALX/PI3K/Nedd4–2 signaling pathway.

Treatment that involves boosting levels of a signaling molecule could help reduce fluid on the lungs in acute respiratory distress syndrome (ARDS). This condition usually affects critically ill patients with illnesses such as pneumonia or sepsis, and leads to severe inflammation and flooding of the lungs with fluid. This prevents microscopic air sacs called aveoli from processing oxygen and carbon dioxide effectively. At present there is no effective management for the condition. Now, Sheng-Wei Jin at Wenzhou Medical University, China, and co-workers have shown that boosting levels of a signaling molecule called protectin DX can help with aveolar fluid clearance in rats. They found that protectin DX activates sodium channels within the aveoli, helping clear fluid, and also acts as an anti-inflammatory and pro-resolving mediator to protect lung tissues from further injury.

Unravelling the Lesser Known Facets of Angiotensin II Type 1 Receptor

PURPOSE OF REVIEW

Hypertension is an important risk factor in various pathologies. Despite enormous advancements in health sciences, the number of hypertensive individuals is increasing worldwide. The complex interplay between genetic and epigenetic factors seems to be a promising pathway to exploring the pathophysiology of hypertension.

RECENT FINDINGS

Various single gene and genome wide association studies have generated huge but non-reproducible data that highlights the role of some additional but as yet unidentified factor(s) in disease outcome. Dietary pattern and epigenetic mechanism (mainly DNA methylation) have shown a profound effect on blood pressure regulation. Angiotensin II and its receptors are known to play an important role in maintaining blood pressure; hence, a larger section of antihypertensive drugs targets the renin-angiotensin system (RAS). Angiotensin II type 1 receptor (AT1R), besides maintaining blood pressure, also has a role in cancer progression. Besides other pathways, RAS still remains the main player in blood pressure regulation. Additionally, AT1R has recently emerged as a molecule with diverse roles ranging from physiologic to cancer progression.

Attenuation of pulmonary ACE2 activity impairs inactivation of des-Arg9 bradykinin/BKB1R axis and facilitates LPS-induced neutrophil infiltration

Angiotensin-converting enzyme 2 (ACE2) is a terminal carboxypeptidase with important functions in the renin-angiotensin system and plays a critical role in inflammatory lung diseases. ACE2 cleaves single-terminal residues from several bioactive peptides such as angiotensin II. However, few of its substrates in the respiratory tract have been identified, and the mechanism underlying the role of ACE2 in inflammatory lung disease has not been fully characterized. In an effort to identify biological targets of ACE2 in the lung, we tested its effects on des-Arg⁹ bradykinin (DABK) in airway epithelial cells on the basis of the hypothesis that DABK is a biological substrate of ACE2 in the lung and ACE2 plays an important role in the pathogenesis of acute lung inflammation partly through modulating DABK/bradykinin receptor B1 (BKB1R) axis signaling. We found that loss of ACE2 function in mouse lung in the setting of endotoxin inhalation led to activation of the DABK/BKB1R axis, release of proinflammatory chemokines such as C-X-C motif chemokine 5 (CXCL5), macrophage inflammatory protein-2 (MIP2), C-X-C motif chemokine 1 (KC), and TNF-α from airway epithelia, increased neutrophil infiltration, and exaggerated lung inflammation and injury. These results indicate that a reduction in pulmonary ACE2 activity contributes to the pathogenesis of lung inflammation, in part because of an impaired ability to inhibit DABK/BKB1R axis-mediated signaling, resulting in more prompt onset of neutrophil infiltration and more severe inflammation in the lung. Our study identifies a biological substrate of ACE2 within the airways, as well as a potential new therapeutic target for inflammatory diseases.

JAK2/STAT3 Pathway Was Associated with the Protective Effects of IL-22 On Aortic Dissection with Acute Lung Injury

Patients with aortic dissection (AD) may present acute lung injury (ALI) that may affect the prognosis. In this study, we aim to investigate the roles and mechanism of IL-22 in the pathogenesis of AD complicated with ALI. Six hundred and twenty-one AD patients were included, and the incidence of ALI and pulmonary CT findings were analyzed. Mouse ALI model was established through AngII, and then IL-22 injection and AG490 were given. The pathological changes, infiltration of inflammatory cells, and expression of STAT3 were determined. For the in vitro experiment, cultivated pulmonary microvascular endothelial cells (PMVECs) were treated by angiotensin II (AngII), followed by treating with IL-22 and/or AG490. The expression and migration of STAT3 was determined. Flow cytometry was carried out to evaluate the apoptosis. IL-22 contributed to the expression of STAT3 in lung tissues and attenuation of ALI. IL-22 obviously inhibited the apoptosis of PMVECs mediated by AngII and downregulated the expression and intranuclear transmission of STAT3. Such phenomenon was completely inhibited upon administration of AG490, an inhibitor of JAK2. Our data showed IL-22 contributed to the inhibition of PMVEC apoptosis mediated by AngII through activating the JAK2/STAT3 signaling pathway, which may attenuate the ALI induced by AngII.

Maresin1 stimulates alveolar fluid clearance through the alveolar epithelial sodium channel Na,K-ATPase via the ALX/PI3K/Nedd4-2 pathway

Maresin1 (MaR1) is a new docosahexaenoic acid-derived pro-resolving agent that promotes the resolution of inflammation. In this study, we sought to investigate the effect and underlining mechanisms of MaR1 in modulating alveolar fluid clearance (AFC) on LPS-induced acute lung injury. MaR1 was injected intravenously or administered by instillation (200 ng/kg) 8 h after LPS (14 mg/kg) administration and AFC was measured in live rats. In primary rat alveolar type II epithelial cells, MaR1 (100 nM) was added to the culture medium with lipopolysaccharide for 6 h. MaR1 markedly stimulated AFC in LPS-induced lung injury, with the outcome of decreased pulmonary edema and lung injury. In addition, rat lung tissue protein was isolated after intervention, and we found MaR1 improved epithelial sodium channel (ENaC), Na,K-adenosine triphosphatase (ATPase) protein expression and Na,K-ATPase activity. MaR1 down-regulated Nedd4-2 protein expression though PI3k/Akt but not though PI3k/SGK1 pathway in vivo. In primary rat alveolar type II epithelial cells stimulated with LPS, MaR1-upregulated ENaC and Na,K-ATPase protein abundance in the plasma membrane. Finally, the lipoxin A4 Receptor inhibitor (BOC-2) and PI3K inhibitor (LY294002) not only blocked MaR1's effects on cAMP/cGMP, the expression of phosphorylated Akt and Nedd4-2, but also inhibited the effect of MaR1 on AFC in vivo. In conclusion, MaR1 stimulates AFC through a mechanism partly dependent on alveolar epithelial ENaC and Na,K-ATPase activation via the ALX/PI3K/Nedd4-2 signaling pathway. Our findings reveal a novel mechanism for pulmonary edema fluid reabsorption and MaR1 may provide a new therapy for the resolution of ALI/ARDS.

Formaldehyde impairs transepithelial sodium transport

Unsaturated oxidative formaldehyde is a noxious aldehyde in cigarette smoke that causes edematous acute lung injury. However, the mechanistic effects of formaldehyde on lung fluid transport are still poorly understood. We examined how formaldehyde regulates human epithelial sodium channels (ENaC) in H441 and expressed in Xenopus oocytes and exposed mice in vivo. Our results showed that formaldehyde reduced mouse transalveolar fluid clearance in vivo. Formaldehyde caused a dose-dependent inhibition of amiloride-sensitive short-circuit Na+ currents in H441 monolayers and of αβγ-ENaC channel activity in oocytes. α-ENaC protein was reduced, whereas phosphorylation of the extracellular regulated protein kinases 1 and 2 (ERK1/2) increased significantly post exposure. Moreover, both α- and γ-ENaC transcripts were down-regulated. Reactive oxygen species (ROS) was elevated significantly by formaldehyde in addition to markedly augmented membrane permeability of oocytes. These data suggest that formaldehyde contributes to edematous acute lung injury by reducing transalveolar Na+ transport, through decreased ENaC activity and enhanced membrane depolarization, and by elevating ROS production over long-term exposure.

Captopril pretreatment protects the lung against severe acute pancreatitis induced injury via inhibiting angiotensin II production and suppressing Rho/ROCK pathway

Acute pancreatitis (AP) usually causes acute lung injury, which is also known as acute pancreatitis associated lung injury (APALI). This study aimed to investigate whether captopril pretreatment was able to protect lung against APALI via inhibiting angiotensin II (Ang II) production and suppressing Rho/ROCK (Rho kinase) pathway in rats. Severe AP (SAP) was introduced to rats by bile-pancreatic duct retrograde injection of 5% sodium taurocholate. Rats were randomly divided into three groups. In the sham group, sham operation was performed; in the SAP group, SAP was introduced; in the pre-cpl + SAP group, rats were intragastrically injected with 5 mg/kg captopril 1 hour prior to SAP induction. Pathological examination of the lung and pancreas, evaluation of pulmonary vascular permeability by wet/dry ratio and Evans Blue staining, detection of serum amylase, Western blot assay for Ang II receptor type 1 (AT1), RhoA, ROCK (Rho kinase), and MLCK (myosin light chain kinase) were performed after the animals were sacrificed at 24 hours. After the surgery, characteristic findings of pancreatitis were observed, accompanied by lung injury. The serum amylase, Ang II, and lung expression of AT1, RhoA, ROCK, and MLCK increased dramatically in SAP rats. However, captopril pretreatment improved the histological changes, reduced the pathological score of the pancreas and lung, inhibited serum amylase and Ang II production, and decreased expression of AT1, RhoA, ROCK, and MLCK in the lung. These findings suggest that captopril pretreatment is able to protect the lung against APALI, which is, at least partially, related to the inhibition of Ang II production and the suppression of the Rho/ROCK pathway.

Endotoxin-induced skeletal muscle wasting is prevented by angiotensin-(1-7) through a p38 MAPK-dependent mechanism

Skeletal muscle atrophy induced during sepsis syndrome produced by endotoxin in the form of LPS (lipopolysaccharide), is a pathological condition characterized by the loss of strength and muscle mass, an increase in MHC (myosin heavy chain) degradation, and an increase in the expression of atrogin-1 and MuRF-1 (muscle-specific RING-finger protein 1), two ubiquitin E3 ligases belonging to the ubiquitin-proteasome system. Ang-(1-7) [Angiotensin-(1-7)], through its Mas receptor, has beneficial effects in skeletal muscle. We evaluated in vivo the role of Ang-(1-7) and Mas receptor on the muscle wasting induced by LPS injection into C57BL/10J mice. In vitro studies were performed in murine C2C12 myotubes and isolated myofibres from EDL (extensor digitorum longus) muscle. In addition, the participation of p38 MAPK (mitogen-activated protein kinase) in the Ang-(1-7) effect on the LPS-induced muscle atrophy was evaluated. Our results show that Ang-(1-7) prevents the decrease in the diameter of myofibres and myotubes, the decrease in muscle strength, the diminution in MHC levels and the induction of atrogin-1 and MuRF-1 expression, all of which are induced by LPS. These effects were reversed by using A779, a Mas antagonist. Ang-(1-7) exerts these anti-atrophic effects at least in part by inhibiting the LPS-dependent activation of p38 MAPK both in vitro and in vivo. We have demonstrated for the first time that Ang-(1-7) counteracts the skeletal muscle atrophy induced by endotoxin through a mechanism dependent on the Mas receptor that involves a decrease in p38 MAPK phosphorylation. The present study indicates that Ang-(1-7) is a novel molecule with a potential therapeutic use to improve muscle wasting during endotoxin-induced sepsis syndrome.