Mitochondria-Targeted Antioxidants as a Therapeutic Strategy for Chronic Obstructive Pulmonary Disease.

Oxidative stress is a major hallmark of COPD, contributing to inflammatory signaling, corticosteroid resistance, DNA damage, and accelerated lung aging and cellular senescence. Evidence suggests that oxidative damage is not solely due to exogenous exposure to inhaled irritants, but also endogenous sources of oxidants in the form of reactive oxygen species (ROS). Mitochondria, the major producers of ROS, exhibit impaired structure and function in COPD, resulting in reduced oxidative capacity and excessive ROS production. Antioxidants have been shown to protect against ROS-induced oxidative damage in COPD, by reducing ROS levels, reducing inflammation, and protecting against the development of emphysema. However, currently available antioxidants are not routinely used in the management of COPD, suggesting the need for more effective antioxidant agents. In recent years, a number of mitochondria-targeted antioxidant (MTA) compounds have been developed that are capable of crossing the mitochondria lipid bilayer, offering a more targeted approach to reducing ROS at its source. In particular, MTAs have been shown to illicit greater protective effects compared to non-targeted, cellular antioxidants by further reducing apoptosis and offering greater protection against mtDNA damage, suggesting they are promising therapeutic agents for the treatment of COPD. Here, we review evidence for the therapeutic potential of MTAs as a treatment for chronic lung disease and discuss current challenges and future directions.

Advanced models for respiratory disease and drug studies.

The global burden of respiratory diseases is enormous, with many millions of people suffering and dying prematurely every year. The global COVID-19 pandemic witnessed recently, along with increased air pollution and wildfire events, increases the urgency of identifying the most effective therapeutic measures to combat these diseases even further. Despite increasing expenditure and extensive collaborative efforts to identify and develop the most effective and safe treatments, the failure rates of drugs evaluated in human clinical trials are high. To reverse these trends and minimize the cost of drug development, ineffective drug candidates must be eliminated as early as possible by employing new, efficient, and accurate preclinical screening approaches. Animal models have been the mainstay of pulmonary research as they recapitulate the complex physiological processes, Multiorgan interplay, disease phenotypes of disease, and the pharmacokinetic behavior of drugs. Recently, the use of advanced culture technologies such as organoids and lung-on-a-chip models has gained increasing attention because of their potential to reproduce human diseased states and physiology, with clinically relevant responses to drugs and toxins. This review provides an overview of different animal models for studying respiratory diseases and evaluating drugs. We also highlight recent progress in cell culture technologies to advance integrated models and discuss current challenges and present future perspectives.

Role of oxidative stress in the pathogenesis of COPD.

Chronic inhalation of cigarette smoke is a prominent cause of chronic obstructive pulmonary disease (COPD) and provides an important source of exogenous oxidants. In addition, several inflammatory and structural cells are a source of endogenous oxidants in the lower airways of COPD patients, even in former smokers. This suggests that oxidants play a key role in the pathogenesis of COPD. This oxidative stress is counterbalanced by the protective effects of the various endogenous antioxidant defenses of the lower airways. A large amount of data from animal models and patients with COPD have shown that both the stable phase of the disease, and during exacerbations, have increased oxidative stress in the lower airways compared with age-matched smokers with normal lung function. Thus, counteracting the increased oxidative stress may produce clinical benefits in COPD patients. Smoking cessation is currently the most effective treatment of COPD patients and reduces oxidative stress in the lower airways. In addition, many drugs used to treat COPD have some antioxidant effects, however, it is still unclear if their clinical efficacy is related to pharmacological modulation of the oxidant/antioxidant balance. Several new antioxidant compounds are in development for the treatment of COPD.

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.

Role of Lung Microbiome in Innate Immune Response Associated With Chronic Lung Diseases.

Respiratory diseases such as asthma, chronic obstructive pulmonary disease (COPD), lung fibrosis, and lung cancer, pose a huge socio-economic burden on society and are one of the leading causes of death worldwide. In the past, culture-dependent techniques could not detect bacteria in the lungs, therefore the lungs were considered a sterile environment. However, the development of culture-independent techniques, particularly 16S rRNA sequencing, allowed for the detection of commensal microbes in the lung and with further investigation, their roles in disease have since emerged. In healthy individuals, the predominant commensal microbes are of phylum Firmicutes and Bacteroidetes, including those of the genera Veillonella and Prevotella. In contrast, pathogenic microbes (Haemophilus, Streptococcus, Klebsiella, Pseudomonas) are often associated with lung diseases. There is growing evidence that microbial metabolites, structural components, and toxins from pathogenic and opportunistic bacteria have the capacity to stimulate both innate and adaptive immune responses, and therefore can contribute to the pathogenesis of lung diseases. Here we review the multiple mechanisms that are altered by pathogenic microbiomes in asthma, COPD, lung cancer, and lung fibrosis. Furthermore, we focus on the recent exciting advancements in therapies that can be used to restore altered microbiomes in the lungs.

Gallic acid protects against the COPD-linked lung inflammation and emphysema in mice.

OBJECTIVE AND DESIGN: Gallic acid (GA) a naturally occurring phenolic compound, known to possess antioxidant/anti-inflammatory activities. The aim of the present work was to investigate the beneficial effects of GA against COPD-linked lung inflammation/emphysema by utilizing elastase (ET) and cigarette smoke (CS)-induced mice model. MATERIALS: Male BALB/c mice were treated with ET (1U/mouse) or exposed to CS (9 cigarettes/day for 4 days). GA administration was started 7 days (daily) prior to ET/CS exposure. Broncho-alveolar lavage was analyzed for inflammatory cells and pro-inflammatory cytokines. Lung homogenate was assessed for MPO activity/GSH/MDA/protein carbonyls. Further, Lung tissue was subjected to semi-quantitative RT-PCR, immunoblotting, and histological analysis. RESULTS: GA suppressed the ET-induced neutrophil infiltration, elevated MPO activity and production of pro-inflammatory cytokines (IL-6/TNF-α/IL-1ß) at 24 h. Reduced inflammation was accompanied with normalization of redox balance as reflected by ROS/GSH/MDA/protein carbonyl levels. Further, GA suppressed phosphorylation of p65NF-κB and IκBα along with down-regulation of IL-1ß/TNF-α/KC/MIP-2/GCSF genes. Furthermore, GA offered protection against ET-induced airspace enlargement and ameliorated MMP-2/MMP-9. Finally, GA suppressed the CS-induced influx of neutrophils and macrophages and blunted gene expression of TNF-α/MIP-2/KC. CONCLUSION: Overall, our data show that GA effectively modulates pulmonary inflammation and emphysema associated with COPD pathogenesis in mice.

PARP-1 inhibition provides protection against elastase-induced emphysema by mitigating the expression of matrix metalloproteinases.

In our previous study, we have shown that PARP-1 inhibition (genetic or pharmacological) ameliorates elastase-induced inflammation and emphysema. Since matrix metalloproteinases (MMPs) particularly MMP-2 and MMP-9 are known to play a critical role in emphysema development, the present work was designed to evaluate the effects of PARP-1 inhibition on their expression utilizing elastase-induced mouse model of emphysema. Our data show that olaparib administration at a dose of 5 mg/kg b.wt. (daily) significantly prevented the elastase-induced inflammation as indicated by decreased inflammatory cells particularly macrophages in BALF at 1 week post-injury. In addition, the drug restored the altered redox balance in the lungs of elastase-treated mice toward normal. Further, PCR data show that olaparib administration ameliorates the elastase-induced expression of MMP-2 and MMP-9 without having much effect on the expressions of their inhibitors TIMP-1 and TIMP-2. Next, our data on immunoblot, gelatin zymography, and immunohistochemical analysis indeed confirm that olaparib reduced the elastase-induced expression of MMP-2 and MMP-9. Reduction in the expression of metalloproteinases correlate well with the PARP activity as olaparib treatment suppressed the elastase-induced expression of PAR modified proteins markedly. Overall, our data strongly suggest that PARP-1 inhibition blunts elastase-induced MMP-2 and MMP-9 expression, which may be partly responsible for prevention of emphysema.

PARP-1 inhibition ameliorates elastase induced lung inflammation and emphysema in mice.

COPD is associated with high morbidity and mortality and no effective treatment is available till date. We have previously reported that PARP-1 plays an important role in the establishment of airway inflammation associated with asthma and ALI. In the present work, we have evaluated the beneficial effects of PARP-1 inhibition on COPD pathogenesis utilizing elastase induced mouse model of the disease. Our data show that PARP-1 inhibition by olaparib significantly reduced the elastase-induced recruitment of inflammatory cells particularly neutrophils in the lungs of mice when administered at a dose of 5 mg/kg b.wt (i.p.). Reduction in the lung inflammation was associated with suppressed myeloperoxidase activity. Further, the drug restored the redox status in the lung tissues towards normal as reflected by the levels of ROS, GSH and MDA. Olaparib administration prior to elastase instillation blunted the phosphorylation of P65-NF-κB at Ser 536 without altering phosphorylation of its inhibitor IκBα in the lungs. Furthermore, olaparib down regulated the elastase-induced expression of NF-κB dependent pro-inflammatory cytokines (TNF-A, IL-6), chemokine (MIP-2) and growth factor (GCSF) severely both at the mRNA and protein levels. Additionally, PARP-1 heterozygosity suppressed the recruitment of inflammatory cells and production of TNF-A, IL-6, MIP-2 and GCSF in the BALF to the similar extent as exhibited by olaparib administration. Finally, PARP-1 inhibition by olaparib or gene deletion protected against elastase-induced emphysema markedly. Overall, our data strongly suggest that PARP-1 plays a critical role in elastase induced lung inflammation and emphysema, and thus may be a new drug target candidate in COPD.

Poly(ADP-Ribose)Polymerase-1 in Lung Inflammatory Disorders: A Review.

Asthma, acute lung injury (ALI), and chronic obstructive pulmonary disease (COPD) are lung inflammatory disorders with a common outcome, that is, difficulty in breathing. Corticosteroids, a class of potent anti-inflammatory drugs, have shown less success in the treatment/management of these disorders, particularly ALI and COPD; thus, alternative therapies are needed. Poly(ADP-ribose)polymerases (PARPs) are the post-translational modifying enzymes with a primary role in DNA repair. During the last two decades, several studies have reported the critical role played by PARPs in a good of inflammatory disorders. In the current review, the studies that address the role of PARPs in asthma, ALI, and COPD have been discussed. Among the different members of the family, PARP-1 emerges as a key player in the orchestration of lung inflammation in asthma and ALI. In addition, PARP activation seems to be associated with the progression of COPD. Furthermore, PARP-14 seems to play a crucial role in asthma. STAT-6 and GATA-3 are reported to be central players in PARP-1-mediated eosinophilic inflammation in asthma. Interestingly, oxidative stress-PARP-1-NF-κB axis appears to be tightly linked with inflammatory response in all three-lung diseases despite their distinct pathophysiologies. The present review sheds light on PARP-1-regulated factors, which may be common or differential players in asthma/ALI/COPD and put forward our prospective for future studies.