Implication of mitochondrial ROS-NLRP3 inflammasome axis during two-hit mediated acute lung injury in mice.

Acute lung injury (ALI) caused by acid aspiration often accompanies bacterial components leading to exaggerated inflammation and can result in acute respiratory distress syndrome (ARDS), but the underlying mechanisms behind such an exacerbation remain unclear. NLRP3 inflammasome and mitochondrial ROS (mtROS) have been implicated in ALI but its role in injury caused through two hit i.e. Hydrochloric acid (HCl) + Lipopolysaccharide (LPS) is not known. Therefore, the present study is designed to elucidate the role of mtROS-NLPR3 inflammasome upon "two-hit" mediated ALI. Our data showed that "two-hit" induced ALI results in aggravated lung inflammation as compared to either of single hit(s) as reflected by a steep increase in inflammatory cells particularly neutrophils in bronchoalveolar lavage fluid (BALF). Further, enhanced inflammation was associated with increased mtROS as depicted by data on mean fluorescence intensity (MFI) of MitoSOX+ neutrophils and macrophages in BALF of two-hit simulated mice. Importantly, ALI results in activation of NLRP3 inflammasome as reflected by active caspase-1 protein expression and IL-1ß levels. Interestingly, NLRP3 inflammasome inhibitor, MCC950 suppressed the lung inflammation remarkably. Further, Mito-tempo, a mitochondrial-targeted antioxidant, halted "two-hit" mediated NLRP3 inflammasome activation and IL-1ß release followed by amelioration of lung inflammation. Suppression in MFI of MitoSOX+ stained neutrophils and macrophages by Mito-tempo was associated with down-regulation of phospho-p65-NF-κB and its dependent genes (IL-1ß/TNF-α/IL-6). Overall, our data suggest that NLRP3 inflammasome activation by mtROS plays a critical role in pathogenesis of exaggerated inflammation and therefore targeting mtROS-NLRP3 inflammasome axis may be an attractive option for combating ALI/ARDS.

COVID-19 and ARDS: Update on Preventive and Therapeutic Venues.

A novel coronavirus SARS-CoV-2, which initially originated in China, has outstretched to all nations and turned out to be an intense global concern for both the governments and the public. In addition to the health concerns, the COVID-19 pandemic has caused a tremendous impact on the economic and political conditions of every nation. Ever since the start of the pandemic, the physicians were constrained to rely on the management strategies due to a lack of clear understanding of the disease pathogenesis caused by SARS-CoV-2 infection. Scientists are working tirelessly to gather maximum information about the deadly virus and come up with various strategies, which can be used against COVID-19 infection in terms of therapeutics and vaccine development. It is quite evident that the virus infection leads to acute respiratory distress syndrome (ARDS), and most of the deaths occur due to respiratory failure. As the virus spreads through respiratory droplets, the strenuous exercise of preventive measures and diagnosis at a large scale has been in practice across the globe to prevent transmission. This review amalgamates the various updates and acts as an umbrella to provide insights on SARS-CoV-2 mediated ARDS pathogenesis, the impact of co-morbidities, diagnostics, current progress in vaccine development, and promising therapeutics and immuno-modulatory strategies, highlighting various concerns and gaps that need to be addressed to fight current and future pandemics effectively.

Gallic acid ameliorates COPD-associated exacerbation in mice.

COPD is an inflammatory lung disease, which is often exacerbated with microbial infections resulting in worsening of respiratory symptoms. Gallic acid (GA), a naturally occurring phenolic compound is known to possess anti-oxidant/anti-inflammatory activity. We have recently reported that GA protects against the elastase (ET) induced lung inflammation and emphysema and the present work was designed to investigate the beneficial effects of Gallic acid against ET + Lipopolysachharide (LPS) induced COPD exacerbation like condition in mice model. Our data showed that i.t. administration of LPS at 21 days after ET instillation resulted in significant infiltration of inflammatory cells particularly neutrophils (p < 0.0001) into the lungs along with elevated levels of pro-inflammatory cytokines like TNF-α, IL-1ß and IL-6 (p < 0.0001). Interestingly, daily administration of GA (200 mg/Kg b. wt.) starting 7 days before ET instillation, significantly blunted the ET + LPS induced inflammation as indicated by reduced number of inflammatory cells particularly neutrophils (p < 0.0001) in BALF along with suppression of myeloperoxidase activity (p = 0.0009) and production of pro-inflammatory cytokines (p < 0.0001). Further, GA also restored the redox imbalance in the lungs towards normal. Additionally, phosphorylation of p65-NF-κB was found to be reduced (p = 0.015), which was associated with downregulation in the gene expression of IL-1ß (p = 0.022) and TNF-α (p = 0.04). Conversely, GA treatment resulted in increased protein levels of Nrf2 (p = 0.021) with concomitant increase in transcription of its downstream target genes HO-1 (p = 0.033) and Prdx-1 (p = 0.006). Overall, our data show that GA effectively modulates COPD exacerbation manifestations in mice potentially by restoring redox imbalance in lungs.

COVID-19 Severity: Lung-Heart Interplay.

In December 2019, a novel COVID-19 infection caused by SARS-CoV-2 has emerged as a global emergency. In a few months, the pathogen has infected millions of people in the world. Primarily SARS-CoV-2 infects the pulmonary system which ultimately leads to ARDS and lung failure. The majority of patients develop milder symptoms but the infection turns severe in a huge number of people, which ultimately results in enhanced mortality in COVID-19 patients. Co-morbid conditions, primarily cardiovascular complications and diabetes, have been reported to show a strong correlation with COVID-19 severity. Further, the onset of myocardial injury secondary to pulmonary damage has been observed in critically ill patients who have never reported heart-related ailments before. Due to drastic health risks associated with virus infection, the unprecedented disruption in normal business throughout the world has caused economic misery. Apparently, newer treatments are urgently needed to combat the virus particularly to reduce the severity burden. Therefore, understanding the crosstalk between lung and heart during COVID-19 might give us better clarity for early diagnosis followed by appropriate treatment in patients with the likelihood of developing severe symptoms. Accordingly, the present review highlights the potential mechanisms that may explain the crosstalk between lung and heart so that effective treatment/management strategies can be evolved swiftly in this direction.

Critical role of mitochondrial oxidative stress in acid aspiration induced ALI in mice.

Acute lung injury (ALI) is a pulmonary inflammatory disorder which causes significant mortality in critically ill patients. Intracellular oxidative stress has been considered to be the major component in the pathogenesis of ALI but exact source of intracellular ROS is not clearly known. The present study has been designed to elucidate the role of NADPH oxidase system and/or mitochondrial oxidative stress and its downstream pathway NLRP3 inflammasomes in mouse model of acid aspiration mediated ALI. Our data showed that acid aspiration induced lung inflammation was associated with enhanced oxidative stress as evident by data on MDA levels, nitrite levels and redox imbalance. Further acid aspiration resulted in elevation of expression of NADPH oxidase subunits (gp91 phox/p22 phox/p67 phox) as well as mitochondrial oxidative stress as reflected by aconitase activity, mitochondrial ROS levels. Interestingly, NADPH oxidase inhibitor, apocynin did not alter lung inflammation upon HCl instillation. Conversely, mitochondrial antioxidant mito-tempo resulted in significant amelioration of lung inflammation as indicated by suppression of pulmonary neutrophils and inflammatory cytokines namely IL-1ß, TNF-α, IL-6 in BALF. Analysis of mitochondrial enzymes aconitase/mitochondrial ROS/Mn-SOD confirmed that reduction in lung inflammation by mito-tempo was associated with normalization of oxidative stress in mitochondria. Further, mito-tempo administration blunted phosphorylation of p65- NF-κB at Ser 536. Finally, mito-tempo downregulated HCl-induced NF-κB-dependent pro-inflammatory cytokines (IL-1ß, TNF-α, IL-6) drastically at mRNA levels. Overall, our data support that mitochondrial oxidative stress is crucial in modulating the HCl induced lung inflammation and identifies mitochondrial-targeted antioxidant as a potential therapeutic agent.