Melatonin induced suppression of ER stress and mitochondrial dysfunction inhibited NLRP3 inflammasome activation in COPD mice

Natural autophagy modulators in non-communicable diseases: from autophagy mechanisms to therapeutic potential

Non-communicable diseases (NCDs) are defined as a kind of diseases closely related to bad behaviors and lifestyles, e.g., cardiovascular diseases, cancer, and diabetes. Driven by population growth and aging, NCDs have become the biggest disease burden in the world, and it is urgent to prevent and control these chronic diseases. Autophagy is an evolutionarily conserved process that degrade cellular senescent or malfunctioning organelles in lysosomes. Mounting evidence has demonstrated a major role of autophagy in the pathogenesis of cardiovascular diseases, cancer, and other major human diseases, suggesting that autophagy could be a candidate therapeutic target for NCDs. Natural products/phytochemicals are important resources for drugs against a wide variety of diseases. Recently, compounds from natural plants, such as resveratrol, curcumin, and ursolic acid, have been recognized as promising autophagy modulators. In this review, we address recent advances and the current status of the development of natural autophagy modulators in NCDs and provide an update of the latest in vitro and in vivo experiments that pave the way to clinical studies. Specifically, we focus on the relationship between natural autophagy modulators and NCDs, with an intent to identify natural autophagy modulators with therapeutic potential.

Understanding the impact of ER stress on lung physiology

Human lungs consist of a distinctive array of cell types, which are subjected to persistent challenges from chemical, mechanical, biological, immunological, and xenobiotic stress throughout life. The disruption of endoplasmic reticulum (ER) homeostatic function, triggered by various factors, can induce ER stress. To overcome the elevated ER stress, an adaptive mechanism known as the unfolded protein response (UPR) is activated in cells. However, persistent ER stress and maladaptive UPR can lead to defects in proteostasis at the cellular level and are typical features of the lung aging. The aging lung and associated lung diseases exhibit signs of ER stress-related disruption in cellular homeostasis. Dysfunction resulting from ER stress and maladaptive UPR can compromise various cellular and molecular processes associated with aging. Hence, comprehending the mechanisms of ER stress and UPR components implicated in aging and associated lung diseases could enable to develop appropriate therapeutic strategies for the vulnerable population.

Melatonin antagonizes oxidative stress-induced apoptosis in retinal ganglion cells through activating the thioredoxin-1 pathway

This study aimed to explore the role of melatonin in oxidative stress-induced injury on retinal ganglion cells and the underlying mechanisms. The immortalized RGC-5 cells were treated with H2O2 to induce oxidative injury. Cell viability was measured by Cell Counting Kit-8, and apoptosis was determined by flow cytometry and western blot assays. Reactive oxygen species (ROS), lactate dehydrogenase (LDH), and malondialdehyde (MDA) levels were examined to evaluate oxidative stress levels. In addition, Thioredoxin-1 (Trx1) was silenced in RGC-5 cells using small interfering RNA followed by signaling pathway examination to explore the underlying mechanisms of melatonin in alleviating oxidative injury. Melatonin pre-treatment significantly alleviated H2O2-induced apoptosis in RGC-5 cells. Melatonin also markedly reversed the upregulation of cleaved-caspase 3, cleaved-caspase 9, and Bax expression and downregulation of Bcl-2 expression induced by H2O2. Further analyses presented that melatonin significantly attenuated the increase of ROS, LDH, and MDA levels in RGC-5 cells after H2O2 treatment. Melatonin also abolished the downregulated expression of Superoxide dismutase type 1, Trx1, and Thioredoxin reductase 1, and the reduced activity of thioredoxin reductase in RGC-5 cells after H2O2 treatment. Notably, Trx1 knockdown significantly mitigated the protective effect of melatonin in alleviating H2O2-induced apoptosis and oxidative stress, while administration of compound C, a common inhibitor of c-Jun N-terminal kinase (JNK) signaling, partially reversed the effect of Trx1 silencing, thereby ameliorating the apoptosis and oxidative injury induced by H2O2 in RGC-5 cells. Melatonin could significantly alleviate oxidative stress-induced injury of retinal ganglion cells via modulating Trx1-mediated JNK signaling pathway.

TXNIP regulates pulmonary inflammation induced by Asian sand dust

Asian sand dust (ASD), a seasonal dust storm originating from the deserts of China and Mongolia, affects Korea and Japan during the spring, carrying soil particles and a variety of biochemical components. Exposure to ASD has been associated with the onset and exacerbation of respiratory disorders, although the underlying mechanisms remain unclear. This study investigates ASD-induced pulmonary toxicity and its mechanistic pathways, focusing on the role of thioredoxin-interacting protein (TXNIP). Using TXNIP knock-out (KO) mice and adeno-associated virus (AAV)-mediated TXNIP overexpression transgenic mice, we explored how TXNIP modulates ASD-induced pulmonary inflammation. Mice were exposed to ASD via intranasal administration on days 1, 3, and 5 to induce inflammation. ASD exposure led to significant pulmonary inflammation, evidenced by increased inflammatory cell counts and elevated cytokine levels in bronchoalveolar lavage fluid, as well as heightened protein expression of the TXNIP/NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome. TXNIP KO mice exhibited attenuated airway inflammation and downregulation of the NLRP3 inflammasome compared to wild-type controls, while AAV-mediated TXNIP overexpression mice showed exacerbated inflammatory responses, including elevated NLRP3 inflammasome expression, compared to AAV-GFP controls. These findings suggest that TXNIP is a key regulator of ASD-induced pulmonary inflammation.

Naringenin can Inhibit the Pyroptosis of Osteoblasts by Activating the Nrf2/HO-1 Signaling Pathway and Alleviate the Differentiation Disorder of Osteoblasts Caused by Microgravity

Naringenin (4,5,7-trihydroxyflavone, NAR) is an effective active ingredient in Rhizoma Drynariae, which has many biological functions, encompassing anti-inflammatory and -oxidant functions. Prior research has shown that NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasomes possessed a significant contribution to osteoporosis. However, the NAR impact on bone loss caused by microgravity remains unclear. Classical microgravity simulation methods were used to induce simulated microgravity (SMG) in mice and cells. Microcomputed tomography, immunohistochemical examination, and hematoxylin and eosin staining were implemented to ascertain alterations in bone microstructure and morphology in mice subsequent to NAR gavage. Cellular investigations were implemented encompassing quantitative real-time polymerase chain reaction, Western blotting, and immunofluorescence labeling to investigate the molecular mechanism behind NAR resistance to microgravity-induced bone loss. Our research has shown that NAR can significantly enhance the SMG-stimulated alterations in bone microstructure and morphology in mice, mainly by increasing the trabecular thickness, bone volume fraction, and trabecular number while increasing the bone trabecula number. Cell experiments also showed that SMG caused the activation of inflammatory corpuscles of NLRP3 and induced pyroptosis simultaneously, which can be confirmed by the upregulation of protein and mRNA expression levels such as those of NLRP3, cleaved caspase-1, gasdermin D, and apoptosis-associated speck-like protein. The occurrence of pyroptosis further led to the disorder of osteogenic differentiation, which showed that the osteopontin, Runt-related transcription factor 2, bone morphogenetic protein 2, and alkaline phosphatase expression levels were decreased. The intervention of NAR can activate the nuclear factor erythroid 2-related factor 2/heme oxygenase-1 (Nrf2/HO-1) pathway, reverse this phenomenon via controlling the reactive oxygen species generation in cells and correcting mitochondrial malfunction, weaken the pyroptosis of osteoblasts (OBs), and promote osteogenic differentiation. In summary, NAR could hinder the pyroptosis of OBs caused by SMG and promote osteogenic differentiation via activating the Nrf2/HO-1 pathway. This provides a unique view for inhibiting bone loss under weightlessness and confirms the NAR capacity in treating microgravity-stimulated bone loss, giving new ideas and methods for future space medicine development.

Phikud navakot extract acts as an ER stress inhibitor to ameliorate ER stress and neuroinflammation

The prevalence of neurological disorders (NDs) such as Alzheimer's disease (AD) is increasing globally, and the lack of effective pharmacological interventions presents a significant health risk. Multiple mechanisms including the activation of oxidative stress, amyloid pathway, ER stress, and neuroinflammation have been implicated in AD; therefore, multi-targeted agents against these mechanisms may be preferable to single-target agents. Phikud Navakot (PN), a Thai traditional medicine combining nine herbs, has been shown to reduce oxidative stress and neuroinflammation of neuronal and microglia cells and the coculture between them, indicating the promising role of PN extract as anti-AD. This study evaluated the neuroprotective effects of PN extract against oxidative stress, amyloid pathway, endoplasmic reticulum stress (ER stress), and neuroinflammation using neuronal and microglia cells, as well as in a Drosophila model of AD. Results showed that PN extract reduced oxidative stress, lipid peroxidation, pro-inflammatory cytokines, amyloid pathway, and ER stress induced by aluminum chloride (AlCl3, AD-induced agent) or thapsigargin (TG, an ER stress activator) in both neurons and microglia cells. PN extract also reduced oxidative stress, ER-stress-related genes, and neurotoxic peptides (amyloid beta) in a Drosophila model of AD. Data indicated that PN extract may function as an anti-AD agent by targeting multiple mechanisms as described. This research also revealed for the first time that PN extract acted as an ER stress inhibitor.

Copper oxide nanoparticles exacerbate chronic obstructive pulmonary disease by activating the TXNIP-NLRP3 signaling pathway

BACKGROUND

Although copper oxide nanoparticles (CuONPs) offer certain benefits to humans, they can be toxic to organs and exacerbate underlying diseases upon exposure. Chronic obstructive pulmonary disease (COPD), induced by smoking, can worsen with exposure to various harmful particles. However, the specific impact of CuONPs on COPD and the underlying mechanisms remain unknown. In this study, we investigated the toxic effects of CuONPs on the respiratory tract, the pathophysiology of CuONPs exposure-induced COPD, and the mechanism of CuONPs toxicity, focusing on thioredoxin-interacting protein (TXNIP) signaling using a cigarette smoke condensate (CSC)-induced COPD model.

RESULTS

In the toxicity study, CuONPs exposure induced an inflammatory response in the respiratory tract, including inflammatory cell infiltration, cytokine production, and mucus secretion, which were accompanied by increased TXNIP, NOD-like receptor protein 3 (NLRP3), caspase-1, and interleukin (IL)-1β. In the COPD model, CuONPs exposure induced the elevation of various indexes related to COPD, as well as increased TXNIP expression. Additionally, TNXIP-knockout (KO) mice showed a significantly decreased expression of NLRP3, caspase-1, and IL-1β and inflammatory responses in CuONPs-exposed COPD mice. These results were consistent with the results of an in vitro experiment using H292 cells. By contrast, TNXIP-overexpressed mice had a markedly increased expression of NLRP3, caspase-1, and IL-1β and inflammatory responses in CuONPs-exposed COPD mice.

CONCLUSIONS

We elucidated the exacerbating effect of CuONPs exposure on the respiratory tract with underlying COPD, as well as related signaling transduction via TXNIP regulation. CuONPs exposure significantly increased inflammatory responses in the respiratory tract, which was correlated with elevated TXNIP-NLRP3 signaling.

Melatonin regulates endoplasmic reticulum stress in diverse pathophysiological contexts: A comprehensive mechanistic review

The endoplasmic reticulum (ER) is crucial for protein quality control, and disruptions in its function can lead to various diseases. ER stress triggers an adaptive response called the unfolded protein response (UPR), which can either restore cellular homeostasis or induce cell death. Melatonin, a safe and multifunctional compound, shows promise in controlling ER stress and could be a valuable therapeutic agent for managing the UPR. By regulating ER and mitochondrial functions, melatonin helps maintain cellular homeostasis via reduction of oxidative stress, inflammation, and apoptosis. Melatonin can directly or indirectly interfere with ER-associated sensors and downstream targets of the UPR, impacting cell death, autophagy, inflammation, molecular repair, among others. Crucially, this review explores the mechanistic role of melatonin on ER stress in various diseases including liver damage, neurodegeneration, reproductive disorders, pulmonary disease, cardiomyopathy, insulin resistance, renal dysfunction, and cancer. Interestingly, while it alleviates the burden of ER stress in most pathological contexts, it can paradoxically stimulate ER stress in cancer cells, highlighting its intricate involvement in cellular homeostasis. With numerous successful studies using in vivo and in vitro models, the continuation of clinical trials is imperative to fully explore melatonin's therapeutic potential in these conditions.

Determination of beneficial effects of cuminaldehyde on hyperglycemia associated kidney malfunctions

Type 1 diabetes mellitus is defined by the autoimmune destruction of pancreatic β cells, with diabetic nephropathy being a significant consequence. Recently, cuminaldehyde has been shown protective ability against various pathophysiology. However, its nephroprotective and anti-diabetic potential has not yet been fully understood. We, therefore, conducted the present study to evaluate the anti-hyperglycemic potential of cuminaldehyde in NRK52E cells without (control) or with high glucose medium to emulate hyperglycemic conditions. Cuminaldehyde pre-treatment at an optimal concentration of 175 μM prior to high glucose addition restricted excessive reactive oxygen species (ROS) production and maintained cellular morphology to almost normal. The inhibitor study using N-acetyl-l-cysteine confirmed that blocking of ROS assists NRK52E cells in evading apoptosis. In addition, hyperglycemia was induced in 6-week-old Swiss albino mice in this investigation through the intraperitoneal injection of streptozotocin (150 mg kg-1 body weight). Hyperglycemia increased the kidney-to-body weight ratio, lowered serum insulin levels, and led to significant renal tissue damage compared to control mice. Moreover, hyperglycemia disturbs cellular redox equilibrium by decreasing antioxidant enzyme functions and promoting inflammatory cytokines in kidney tissue. Administering cuminaldehyde at a dosage of 10 mg kg-1 body weight for 5 weeks daily after the onset of diabetes effectively ameliorated the aforementioned anomalies and reversed kidney damage by regulating inflammation-induced cell death. Overall, the research demonstrated that cuminaldehyde has hypoglycemic, antioxidant, anti-inflammatory, and anti-apoptotic properties. We believe that after conducting extensive research, this unique molecule can be used in clinical trials against diabetic nephropathy in future.

Gene Expression Regulation and the Signal Transduction of Programmed Cell Death

Cell death is of great significance in maintaining tissue homeostasis and bodily functions. With considerable research coming to the fore, it has been found that programmed cell death presents in multiple modalities in the body, which is not only limited to apoptosis, but also can be divided into autophagy, pyroptosis, ferroptosis, mitotic catastrophe, entosis, netosis, and other ways. Different forms of programmed cell death have disparate or analogous characteristics with each other, and their occurrence is accompanied by multiple signal transduction and the role of a myriad of regulatory factors. In recent years, scholars across the world have carried out considerable in-depth research on programmed cell death, and new forms of cell death are being discovered continually. Concomitantly, the mechanisms of intricate signaling pathways and regulators have been discovered. More critically, cancer cells tend to choose distinct ways to evade cell death, and different tumors adapt to different manners of death. Therefore, targeting the cell death network has been regarded as an effective tumor treatment strategy for a long time. The objective of our paper is to review the signaling pathways and gene regulation in several typical types of programmed cell death and their correlation with cancer.

Particulate matter-induced oxidative stress - Mechanistic insights and antioxidant approaches reported in in vitro studies

Inhaled particulate matter (PM) is a key factor in millions of yearly air pollution-related deaths worldwide. The oxidative potential of PM indicates its ability to promote an oxidative environment. Excessive reactive oxygen species (ROS) can cause cell damage via oxidative stress, leading to inflammation, endoplasmic reticulum stress, airway remodeling, and various cell death modes (apoptosis, ferroptosis, pyroptosis). ROS can also interact with macromolecules, inducing DNA damage and epigenetic modifications, disrupting homeostasis. These effects have been studied extensively in vitro and confirmed in vivo. This review explores the oxidative potential of airborne particles and PM-induced ROS-mediated cellular damage observed in vitro, highlighting the link between oxidative stress, inflammation, and cell death modes described in the latest literature. The review also analyzes the effects of ROS on DNA damage, repair, carcinogenicity, and epigenetics. Additionally, the latest developments on the potential of antioxidants to prevent ROS's harmful effects are described, providing future perspectives on the topic.

Mitochondria and NLRP3 inflammasome in cardiac hypertrophy

Cardiac hypertrophy is the main adaptive response of the heart to chronic loads; however, prolonged or excessive hypertrophy promotes myocardial interstitial fibrosis, systolic dysfunction, and cardiomyocyte death, especially aseptic inflammation mediated by NLRP3 inflammasome, which can aggravate ventricular remodeling and myocardial damage, which is an important mechanism for the progression of heart failure. Various cardiac overloads can cause mitochondrial damage. In recent years, the mitochondria have been demonstrated to be involved in the inflammatory response during the development of cardiac hypertrophy in vitro and in vivo. As the NLRP3 inflammasome and mitochondria are regulators of inflammation and cardiac hypertrophy, we explored the potential functions of the NLRP3 inflammasome and mitochondrial dysfunction in cardiac hypertrophy. In particular, we proposed that the induction of mitochondrial dysfunction in cardiomyocytes may promote NLRP3-dependent inflammation during myocardial hypertrophy. Further in-depth studies could prompt valuable discoveries regarding the underlying molecular mechanisms of cardiac hypertrophy, reveal novel anti-inflammatory therapies for cardiac hypertrophy, and provide more desirable therapeutic outcomes for patients with cardiac hypertrophy.

TROP2 promotes PINK1-mediated mitophagy and apoptosis to accelerate the progression of senile chronic obstructive pulmonary disease by up-regulating DRP1 expression

Chronic obstructive pulmonary disease (COPD) is a chronic airway inflammatory disease characterised by irreversible airflow limitation. The elderly are a vulnerable population for developing COPD. With the growth of age, physiological degenerative changes occur in the thorax, bronchus, lung and vascular wall, which can lead to age-related physiological attenuation of lung function in the elderly, so the prevalence of COPD increases with age. Its pathogenesis has not yet been truly clarified. Mitophagy plays an important role in maintaining the stability of mitochondrial function and intracellular environment by scavenging damaged mitochondria. Currently, studies have shown that trophoblast antigen 2 (TROP2) expression is up-regulated in airway basal cells of patients with COPD, suggesting that TROP2 is involved in the progression of COPD. However, whether it is involved in disease progression by regulating mitochondrial function remains unclear. In this study, compared with non-smoking non-COPD patients, the expression of TROP2 in lung tissues of smoking non-COPD patients and patients with COPD increased, and TROP2 expression in patients with COPD was higher than that in smoking non-COPD patients. To further explore the role of TROP2, we stimulated BEAS-2B with cigarette smoke to construct an in vitro model. We found that TROP2 expression increased, whereas TROP2 silencing reversed the cigarette smoke extract-induced decrease in mitochondrial membrane potential, increased reactive oxygen species content, decreased adenosine triphosphate (ATP) production, increased inflammatory factor secretion and increased apoptosis. In addition, we searched online bioinformatics and screened the gene dynamin-related protein 1 (DRP1) related to mitophagy as the research object. Co-IP assay verified the binding relationship between DRP1 and TROP2. Further study found that TROP2 promoted mitophagy and apoptosis of BEAS-2B cells by up-regulating the expression of DRP1. In addition, PTEN-induced putative kinase 1 (PINK1) is a potential binding protein of DRP1, and DRP1 accelerated mitophagy and apoptosis of BEAS-2B cells by promoting the expression of PINK1. We established a COPD SD rat model by cigarette smoke exposure and LPS instillation and treated it by intraperitoneal injection of si-TROP2. The results showed that TROP2 silencing restored lung function and reduced the secretion of inflammatory factors in bronchoalveolar lavage fluid. In conclusion, TROP2 can be used as a new reference for COPD treatment.

Andrographolide Attenuates NLRP3 Inflammasome Activation and Airway Inflammation in Exacerbation of Chronic Obstructive Pulmonary Disease

Purpose

The aim of this study is to uncover the anti-inflammatory propertity of andrographolide (AGP) in acute exacerbation of chronic obstructive pulmonary disease (AECOPD) and the underlying mechanisms related to the nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome pathway.

Methods

An in vivo experiment was conducted on murine model of AECOPD through endotracheal atomization of elastase and lipopolysaccharide (LPS). Intraperitoneal AGP was administered four times. NLRP3 inflammasome pathway molecules were examined using real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis. By using enzyme-linked immunosorbent assay (ELISA), we tested interleukin (IL)-1β levels in bronchoalveolar lavage fluid. An in vitro study was conducted to determine how AGP impacts the NLRP3 inflammasome in THP-1 derived macrophages. The levels of molecules involved in the pathway were measured. Furthermore, molecular docking analyses were carried out to investigate the interactions between AGP and pathway targets.

Results

In the in vivo study, NLRP3 inflammasome activation was observed in mice experiencing AECOPD. The administration of high-dose AGP demonstrated a mitigating effect on inflammatory cells infiltration in the lungs. Moreover, AGP administration effectively suppressed the expression of NLRP3, apoptosis associated speck-like protein that contains a CARD (PYCARD), cysteinyl aspartate-specific protease-1 (Caspase-1), IL-1β, and IL-18 at both the genetic and protein levels. In the in vitro experiment, IL-1β levels were significantly elevated in THP-1 derived macrophages with activated inflammasome compared to the control group. Furthermore, the downregulation of NLRP3, CASP1, and IL1B genes was observed upon the inhibition of NLRP3 expression through small interfering RNA (siRNA). AGP demonstrated inhibitory effects on the gene expression and protein levels of NLRP3, Caspase-1, and IL-1β. Additionally, molecular docking analysis confirmed that AGP exhibited a favorable binding affinity with all five targets of the pathway.

Conclusion

AGP effectively inhibited NLRP3 inflammasome activation and mitigated the inflammatory reaction of AECOPD both in animal models and in vitro experiments, highlighting the potential of AGP as a treatment for AECOPD with anti-inflammatory properties.

NADH Intraperitoneal Injection Prevents Lung Inflammation in a BALB/C Mice Model of Cigarette Smoke-Induced Chronic Obstructive Pulmonary Disease

Cigarette smoke is one of the main factors in Chronic Obstructive Pulmonary Disease (COPD), a respiratory syndrome marked by persistent respiratory symptoms and increasing airway obstruction. Perturbed NAD+/NADH levels may play a role in various diseases, including lung disorders like COPD. In our study, we investigated the preventive effect of NADH supplementation in an experimental model of COPD induced by cigarette smoke extract (CSE). N = 64 mice randomly distributed in eight groups were injected with NADH (two doses of 100 mg/kg or 200 mg/kg) or dexamethasone (2 mg/kg) before being exposed to CSE for up to 9 weeks. Additionally, NADH supplementation preserved lung antioxidant defenses by preventing the functional loss of key enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase, and the expression levels of glutathione (GSH) (n = 4, p < 0.001). It also reduced oxidative damage markers, such as malondialdehyde (MDA) and nitrites (n = 4, p < 0.001). A marked increase in tissue myeloperoxidase activity was assessed (MPO), confirming neutrophils implication in the inflammatory process. The latter was significantly ameliorated in the NADH-treated groups (p < 0.001). Finally, NADH prevented the CSE-induced secretion of cytokines such as Tumor Necrosis Factor alpha (TNF-α), IL-17, and IFN-y (n = 4, p < 0.001). Our study shows, for the first time, the clinical potential of NADH supplementation in preventing key features of COPD via its unique anti-inflammatory and antioxidant properties.

Engineering of VCAM-1-targeted nanostructured lipid carriers for delivery of melatonin against acute lung injury through SIRT1/NLRP3 mediated pyroptosis signaling pathway

Acute lung injury (ALI) is a prevalent and critical condition in clinical practice. Although certain pharmacological interventions have demonstrated benefits in preclinical studies, none have been proven entirely effective thus far. Therefore, the development of more efficient treatment strategies for ALI is imperative. In this study, we prepared nanostructured lipid carriers (NLCs) conjugated with anti-VCAM-1 antibodies to encapsulate melatonin (MLT), resulting in VCAM/MLT NLCs. This approach aimed to enhance the distribution of melatonin in lung vascular endothelial cells. The VCAM/MLT NLCs had an average diameter of 364 nm, high drug loading content, and a sustained drug release profile. Notably, the NLCs conjugated with anti-VCAM-1 antibodies demonstrated more specific cellular delivery mediated by the VCAM-1 receptors, increased cellular internalization, and enhanced accumulation in lung tissues. Treatment with VCAM/MLT NLCs effectively alleviated pulmonary inflammation by activating NLRP3 inflammasome-dependent pyroptosis through up-regulation of Sirtuin 1. Our findings suggest that VCAM/MLT NLCs demonstrate remarkable therapeutic effects on ALI in both in vitro and in vivo settings, making them a promising and efficient treatment strategy for ALI.

The role of lysosomes in airborne particulate matter-induced pulmonary toxicity

An investigation of the potential role of lysosomes in airborne particulate matter (APM) induced health risks is essential to fully comprehend the pathogenic mechanisms of respiratory diseases. It is commonly accepted that APM-induced lung injury is caused by oxidative stress, inflammatory responses, and DNA damage. In addition, there exists abundant evidence that changes in lysosomal function are essential for cellular adaptation to a variety of particulate stimuli. This review emphasizes that disruption of the lysosomal structure/function is a key step in the cellular metabolic imbalance induced by APMs. After being ingested by cells, most particles are localized within lysosomes. Thus, lysosomes become the primary locus where APMs accumulate, and here they undergo degradation and release toxic components. Recent studies have provided incontrovertible evidence that a wide variety of APMs interfere with the normal function of lysosomes. After being stimulated by APMs, lysosome rupture leads to a loss of lysosomal acidic conditions and the inactivation of proteolytic enzymes, promoting an inflammatory response by activating the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome. Moreover, APMs interfere with autophagosome production or block autophagic flux, resulting in autophagy dysfunction. Additionally, APMs disrupt the normal function of lysosomes in iron metabolism, leading to disruption on iron homeostasis. Therefore, understanding the impacts of APM exposure from the perspective of lysosomes will provide new insights into the detrimental consequences of air pollution.

COX-2/sEH-Mediated Macrophage Activation Is a Target for Pulmonary Protection in Mouse Models of Chronic Obstructive Pulmonary Disease

Effective inhibition of macrophage activation is critical for resolving inflammation and restoring pulmonary function in patients with chronic obstructive pulmonary disease (COPD). In this study, we identified the dual-enhanced cyclooxygenase-2 (COX-2)/soluble epoxide hydrolase (sEH) as a novel regulator of macrophage activation in COPD. Both COX-2 and sEH were found to be increased in patients and mice with COPD and in macrophages exposed to cigarette smoke extract. Pharmacological reduction of the COX-2 and sEH by 4-(5-phenyl-3-{3-[3-(4-trifluoromethylphenyl)-ureido]-propyl}-pyrazol-1-yl)-benzenesulfonamide (PTUPB) effectively prevented macrophage activation, downregulated inflammation-related genes, and reduced lung injury, thereby improving respiratory function in a mouse model of COPD induced by cigarette smoke and lipopolysaccharide. Mechanistically, enhanced COX-2/sEH triggered the activation of the NACHT, LRR, and PYD domains-containing protein 3 inflammasome, leading to the cleavage of pro-IL-1β into its active form in macrophages and amplifying inflammatory responses. These findings demonstrate that targeting COX-2/sEH-mediated macrophage activation may be a promising therapeutic strategy for COPD. Importantly, our data support the potential use of the dual COX-2 and sEH inhibitor PTUPB as a therapeutic drug for the treatment of COPD.

GSTP1 rs4147581 C>G and NLRP3 rs3806265 T>C as Risk Factors for Chronic Obstructive Pulmonary Disease: A Case-Control Study

Background

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory ailment influenced by a blend of genetic and environmental factors. Inflammatory response and an imbalance in oxidative-antioxidant mechanisms constitute the primary pathogenesis of COPD. Glutathione S-transferase P1(GSTP1) plays a pivotal role as an antioxidant enzyme in regulating oxidative-antioxidant responses in the pulmonary system. The activation of the NOD-like receptor thermal protein domain (NLRP3) inflammatory vesicle can trigger an inflammatory response. Several investigations have implicated GSTP1 and NLRP3 in the progression of COPD; nonetheless, there remains debate regarding this mechanism.

Methods

Employing a case-control study design, 312 individuals diagnosed with COPD and 314 healthy controls were recruited from Gansu Province to evaluate the correlation between GSTP1 (rs4147581C>G and rs1695A>G) and NLRP3 (rs3806265T>C and rs10754558G>C) polymorphisms and the susceptibility to COPD.

Results

The presence of the GSTP1 rs4147581G allele substantially elevated the susceptibility to COPD (CGvs.CC:OR=3.11,95% CI=1.961-4.935, P<0.001;GGvs.CC:OR=2.065,95% CI=1.273-3.350, P=0.003; CG+GGvs.CC:OR=2.594,95% CI=1.718-3.916, P<0.001). Similarly, the NLRP3rs3806265T allele significantly increased the susceptibility to COPD (TC:TT:OR=0.432,95% CI=0.296-0.630; TC+CCvs.TT:OR=2.132,95% CI=1.479-3.074, P<0.001). However, no statistically significant association was discerned between the rs1695A>G and rs10754558G>C polymorphisms and COPD susceptibility (P>0.05).

Conclusion

In summary, this study ascertained that the GSTP1 rs4147581C>G polymorphism is associated with increased COPD susceptibility, with the G allele elevating the risk of COPD. Similarly, the NLRP3 rs3806265T>C polymorphism is linked to elevated COPD susceptibility, with the T allele heightening the risk of COPD.

Nrf2/HO-1 signaling activation alleviates cigarette smoke-induced inflammation in chronic obstructive pulmonary disease by suppressing NLRP3-mediated pyroptosis

BACKGROUND

This study examined the effect of the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway on chronic obstructive pulmonary disease (COPD) and the potential molecular mechanism.

METHODS

A COPD mouse model was established by cigarette smoke exposure and administered with either ML385 or dimethyl fumarate (DMF). Airway resistance of mice was detected. IL-1β and IL-6 levels in mice alveolar lavage fluid were examined by enzyme-linked immunosorbent assay. Hematoxylin and eosin staining and immunohistochemical of lung tissues were utilized to detect lung injury and NLRP3 expression. DMF was used to treat COPD cell model constructed by exposing normal human bronchial epithelial (NHBE) cells to cigarette smoke extract. NHBE cells were transfected by NLRP3-expression vectors. Expression of proteins was detected by Western blot.

RESULTS

COPD mice showed the enhanced airway resistance, the inactivated Nrf2/HO-1 pathway and the overexpressed NLRP3, Caspase-1 and GSDMD-N proteins in lung tissues, and the increased IL-1β and IL-6 levels in alveolar lavage fluid. ML385 treatment augmented these indicators and lung injury in COPD mice. However, DMF intervention attenuated these indicators and lung injury in COPD mice. Nrf2/HO-1 pathway inactivation and overexpression of NLRP3, Caspase-1 and GSDMD-N proteins were observed in COPD cells. DMF intervention activated Nrf2/HO-1 pathway and down-regulated NLRP3, Caspase-1 and GSDMD-N proteins in COPD cells. However, NLRP3 overexpression abolished the effect of DMF on COPD cells.

CONCLUSION

Nrf2/HO-1 pathway activation may alleviate inflammation in COPD by suppressing the NLRP3-related pyroptosis. Activating the Nrf2/HO-1 pathway may be an effective method to treat COPD.

The potential influence of melatonin on mitochondrial quality control: a review

Mitochondria are critical for cellular energetic metabolism, intracellular signaling orchestration and programmed death regulation. Therefore, mitochondrial dysfunction is associated with various pathogeneses. The maintenance of mitochondrial homeostasis and functional recovery after injury are coordinated by mitochondrial biogenesis, dynamics and autophagy, which are collectively referred to as mitochondrial quality control. There is increasing evidence that mitochondria are important targets for melatonin to exert protective effects under pathological conditions. Melatonin, an evolutionarily conserved tryptophan metabolite, can be synthesized, transported and metabolized in mitochondria. In this review, we summarize the important role of melatonin in the damaged mitochondria elimination and mitochondrial energy supply recovery by regulating mitochondrial quality control, which may provide new strategies for clinical treatment of mitochondria-related diseases.

METTL14 Regulates the m6A Modification of TRAF6 to Suppress Mitochondrial Dysfunction and Ferroptosis in Dopaminergic Neurons via the cGAS-STING Pathway

OBJECTIVES

The degeneration of dopaminergic (DA) neurons has emerged as a crucial pathological characteristic in Parkinson's disease (PD). To enrich the related knowledge, we aimed to explore the impact of the METTL14-TRAF6-cGASSTING axis in mitochondrial dysfunction and ferroptosis underlying DA neuron degeneration.

METHODS

1-methyl-4-phenylpyridinium ion (MPP+) was used to treat DA neuron MN9D to develop the PD cell models. Afterward, a cell counting kit, flow cytometer, DCFH-DA fluorescent probe, and Dipyrromethene Boron Difluoride staining were utilized to measure the cell viability, iron concentration, ROS level, and lipid peroxidation, respectively. Meanwhile, the mitochondrial ultrastructure, the activity of mitochondrial respiratory chain complexes, and levels of malondialdehyde and glutathione were monitored. In addition, reverse transcription-quantitative polymerase chain reaction and western blot assays were adopted to measure the expression of related genes. cGAS ubiquitylation and TRAF6 messenger RNA (mRNA) N6-methyladenosine (m6A) levels, the linkages among METTL14, TRAF6, and the cGAS-STING pathway were also evaluated.

RESULTS

METTL14 expression was low, and TRAF6 expression was high after MPP+ treatment. In MPP+-treated MN9D cells, METTL14 overexpression reduced ferroptosis, ROS generation, mitochondrial injury, and oxidative stress (OS) and enhanced mitochondrial membrane potentials. TRAF6 overexpression had promoting impacts on mitochondrial dysfunction and ferroptosis in MPP+-treated MN9D cells, which was reversed by further overexpression of METTL14. Mechanistically, METTL14 facilitated the m6A methylation of TRAF6 mRNA to down-regulate TRAF6 expression, thus inactivating the cGAS-STING pathway.

CONCLUSION

METTL14 down-regulated TRAF6 expression through TRAF6 m6A methylation to inactivate the cGAS-STING pathway, thereby relieving mitochondrial dysfunction and ferroptosis in DA neurons.

Multiomics was used to clarify the mechanism by which air pollutants affect chronic obstructive pulmonary disease: A human cohort study

Exposure to air pollutants has been associated with various adverse health outcomes, including chronic obstructive pulmonary disease (COPD). However, the precise underlying mechanism by which air pollution impacts COPD through remains insufficiently understood. To elucidated the molecular mechanism by which air pollutant exposure contributes to alterations in the gut microbiome and metabolism in AECOPD patients, we employed metagenomics and untargeted metabolomics to analyse the gut microbial, faecal, and serum metabolites. The correlations among air pollutants, gut microbes, serum metabolites, and blood biochemical markers were assessed using generalised additive mixed models and Spearman correlation analysis. The findings revealed that for every 10 μg/m3 increase in PM2.5 concentration, the α-diversity of the gut flora decreased by 2.16% (95% CI: 1.80%-2.53%). We found seven microorganisms that were significantly associated with air pollutants, of which Enterococcus faecium, Bacteroides fragilis, Ruthenibacterium lactatiformans, and Subdoligranulum sp.4_3_54A2FAA were primarily associated with glycolysis. We identified 13 serum metabolites and 17 faecal metabolites significantly linked to air pollutants. Seven of these metabolites, which were strongly associated with air pollutants and blood biochemical indices, were found in both serum and faecal samples. Some of these metabolites, such as 2,5-furandicarboxylic acid, C-8C1P and melatonin, were closely associated with disturbances in lipid and fatty acid metabolism in AECOPD patients. These findings underscore the impact of air pollutants on overall metabolism based on influencing gut microbes and metabolites in AECOPD patients. Moreover, these altered biomarkers establish the biologic connection between air pollutant exposure and AECOPD outcomes.The identification of pertinent biomarkers provides valuable insights for the development of precision COPD prevention strategies.

Identification of Genes Related to Endoplasmic Reticulum Stress (ERS) in Chronic Obstructive Pulmonary Disease (COPD) and Clinical Validation

Objective

Endoplasmic reticulum stress (ERS) is key in chronic obstructive pulmonary disease (COPD) incidence and progression. This study aims to identify potential ERS-related genes in COPD through bioinformatics analysis and clinical experiments.

Methods

We first obtained a COPD-related mRNA expression dataset (GSE38974) from the Gene Expression Omnibus (GEO) database. The R software was then used to identify potential differentially expressed genes (DEGs) of COPD-related ERS (COPDERS). Subsequently, the identified DEGs were subjected to protein-protein interaction (PPI), correlation, Gene Ontology (GO) enrichment, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Following that, qRT-PCR was used to examine the RNA expression of six ERS-related DEGs in blood samples obtained from the COPD and control groups. The genes were also subjected to microRNA analysis. Finally, a correlation analysis was performed between the DEGs and key clinical indicators.

Results

Six ERS-related DEGs (five upregulated and one downregulated) were identified based on samples drawn from 23 COPD patients and nine healthy individuals enrolled in the study. Enrichment analysis revealed multiple ERS-related pathways. The qRT-PCR and mRNA microarray bioinformatics analysis results showed consistent STC2, APAF1, BAX, and PTPN1 expressions in the COPD and control groups. Additionally, hsa-miR-485-5p was identified through microRNA prediction and DEG analysis. A correlation analysis between key genes and clinical indicators in COPD patients demonstrated that STC2 was positively and negatively correlated with eosinophil count (EOS) and lymphocyte count (LYM), respectively. On the other hand, PTPN1 showed a strong correlation with pulmonary function indicators.

Conclusion

Four COPDERS-related key genes (STC2, APAF1, BAX, and PTPN1) were identified through bioinformatics analysis and clinical validation, and the expressions of some genes exhibited a significant correlation with the selected clinical indicators. Furthermore, hsa-miR-485-5p was identified as a potential key target in COPDERS, but its precise mechanism remains unclear.

Mitochondrial damage-associated molecular patterns in chronic obstructive pulmonary disease: Pathogenetic mechanism and therapeutic target

Chronic obstructive pulmonary disease (COPD) is a common inflammatory airway disease characterized by enhanced inflammation. Recent studies suggest that mitochondrial damage-associated molecular patterns (DAMPs) may play an important role in the regulation of inflammation and are involved in a serial of inflammatory diseases, and they may also be involved in COPD. This review highlights the potential role of mitochondrial DAMPs during COPD pathogenesis and discusses the therapeutic potential of targeting mitochondrial DAMPs and their related signaling pathways and receptors for COPD. Research progress on mitochondrial DAMPs may enhance our understanding of COPD inflammation and provide novel therapeutic targets.

Endoplasmic reticulum stress: a vital process and potential therapeutic target in chronic obstructive pulmonary disease

BACKGROUND

Chronic obstructive pulmonary disease (COPD), a chronic and progressive disease characterized by persistent respiratory symptoms and progressive airflow obstruction, has attracted extensive attention due to its high morbidity and mortality. Although the understanding of the pathogenesis of COPD has gradually increased because of increasing evidence, many questions regarding the mechanisms involved in COPD progression and its deleterious effects remain unanswered. Recent advances have shown the potential functions of endoplasmic reticulum (ER) stress in causing airway inflammation, emphasizing the vital role of unfolded protein response (UPR) pathways in the development of COPD.

METHODS

A comprehensive search of major databases including PubMed, Scopus, and Web of Science was conducted to retrieve original research articles and reviews related to ER stress, UPR, and COPD.

RESULTS

The common causes of COPD, namely cigarette smoke (CS) and air pollutants, induce ER stress through the generation of reactive oxygen species (ROS). UPR promotes mucus secretion and further plays a dual role in the cell apoptosis-autophagy axis in the development of COPD. Existing drug research has indicated the potential of UPR as a therapeutic target for COPD.

CONCLUSIONS

ER stress and UPR activation play significant roles in the etiology, pathogenesis, and treatment of COPD and discuss whether related genes can be used as biomarkers and therapeutic targets.

Melatonin promotes gut anti-oxidative status in perinatal rat by remodeling the gut microbiome

Gut health is important for nutrition absorption, reproduction, and lactation in perinatal and early weaned mammals. Although melatonin functions in maintaining circadian rhythms and preventing obesity, neurodegenerative diseases, and viral infections, its impact on the gut microbiome and its function in mediating gut health through gut microbiota remain largely unexplored. In the present study, the microbiome of rats was monitoring after fecal microbiota transplantation (FMT) and foster care (FC). The results showed that FMT and FC increased intestinal villus height/crypt depth in perinatal rats. Mechanistically, the melatonin-mediated remodeling of gut microbiota inhibited oxidative stress, which led to attenuation of autophagy and inflammation. In addition, FMT and FC encouraged the growth of more beneficial intestinal bacteria, such as Allobaculum, Bifidobacterium, and Faecalibaculum, which produce more short-chain fatty acids to strengthen intestinal anti-oxidation. These findings suggest that melatonin-treated gut microbiota increase the production of SCFAs, which improve gut health by reducing oxidative stress, autophagy and inflammation. The transfer of melatonin-treated gut microbiota may be a new and effective method by which to ameliorate gut health in perinatal and weaned mammals.

Chronic obstructive pulmonary disease and emerging ER stress-related therapeutic targets

COPD pathogenesis is frequently associated with endoplasmic reticulum stress (ER stress) progression. Targeting the major unfolded protein response (UPR) branches in the ER stress pathway may provide pharmacotherapeutic selection strategies for treating COPD and enable relief from its symptoms. In this study, we aimed to systematically review the potential role of the ER stress inhibitors of major UPR branches (IRE1, PERK, and ATF6) in COPD-related studies and determine the current stage of knowledge in this field. The systematic review was carried out adhering to the PRISMA checklist based on published studies obtained from specific keyword searches of three databases, namely PubMed, ScienceDirect and Springer Database. The search was limited to the year 2000-2022 which includes all in vitro studies, in vivo studies and clinical trials related to the application of ER stress inhibitors toward COPD-induced models and disease. The risk of bias was evaluated using the QUIN, SYRCLE, revised Cochrane risk of bias tool for randomized trials (RoB 2.0) and NIH tool respectively. A total of 7828 articles were screened from three databases and a final total of 37 studies were included in the review. The ER stress and UPR pathways are potentially useful to prevent COPD progression and attenuate the exacerbation of COPD and related symptoms. Interestingly, the off-target effects from inhibition of the UPR pathway may be desirable or undesirable depending on context and therapeutic applications. Targeting the UPR pathway could have complex consequences as the production of ER molecules involved in folding may be impaired which could continuously provoke misfolding of proteins. Although several emerging compounds were noted to be potentially useful for targeted therapy against COPD, clinical studies have yet to be thoroughly explored.

GSPE attenuates CSE-induced lung inflammation and emphysema by regulating autophagy via the reactive oxygen species/TFEB signaling pathway

Cigarette smoke can enhance reactive oxygen species (ROS) production in inflammatory and epithelial cells. Subsequently, ROS enhance autophagy-induced inflammation due to alveolar macrophages (AMs), the primary source of cytokines implicated in chronic obstructive pulmonary disease (COPD) pathogenesis. Therefore, we hypothesized that grape seed proanthocyanidin extract (GSPE), an effective antioxidant, could inhibit emphysema and airway inflammation by ameliorating cigarette smoke extract (CSE)-induced autophagy via suppressing oxidative stress in macrophages. We observed that GSPE significantly attenuated histological changes observed in CSE-induced emphysema and airway inflammation in the lungs of mice. Moreover, GSPE ameliorated lung inflammation by reducing the number of cells, macrophages, and neutrophils and the tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6 levels measured in bronchioloalveolar lavage fluid. ROS levels increased after CSE instillation and significantly decreased with in vitro GSPE treatment. GSPE decreased transcription factor EB (TFEB) oxidation by reducing ROS, inhibiting TFEB nuclear translocation. Furthermore, GSPE inhibited ROS-induced autophagy in RAW 264.7 cells, bone marrow-derived macrophages, and AMs. Inhibiting autophagy through GSPE treatment diminishes CSE-induced lung inflammation by inhibiting the NLRP3 inflammasome. This study demonstrates that GSPE can ameliorate CSE-induced inflammation and emphysema via autophagy-induced NLRP3 inflammasome regulation through the ROS/TFEB signaling pathway in a COPD mouse model.

The roles of autophagy and mitophagy in corneal pathology: current knowledge and future perspectives

The cornea is the clear dome that covers the front portion of the globe. The primary functions of the cornea are to promote the refraction of light and to protect the eye from invading pathogens, both of which are essential for the preservation of vision. Homeostasis of each cellular layer of the cornea requires the orchestration of multiple processes, including the ability to respond to stress. One mechanism whereby cells respond to stress is autophagy, or the process of "self-eating." Autophagy functions to clear damaged proteins and organelles. During nutrient deprivation, amino acids released from protein breakdown via autophagy are used as a fuel source. Mitophagy, a selective form of autophagy, functions to clear damaged mitochondria. Thus, autophagy and mitophagy are important intracellular degradative processes that sustain tissue homeostasis. Importantly, the inhibition or excessive activation of these processes result in deleterious effects on the cell. In the eye, impairment or inhibition of these mechanisms have been associated with corneal disease, degenerations, and dystrophies. This review summarizes the current body of knowledge on autophagy and mitophagy at all layers in the cornea in both non-infectious and infectious corneal disease, dystrophies, and degenerations. It further highlights the critical gaps in our understanding of mitochondrial dysfunction, with implications for novel therapeutics in clinical practice.

Role of mitochondrial stress and the NLRP3 inflammasome in lung diseases

BACKGROUND

As an organelle essential for intracellular energy supply, mitochondria are involved in intracellular metabolism and inflammation, and cell death. The interaction of mitochondria with the NLRP3 inflammasome in the development of lung diseases has been extensively studied. However, the exact mechanism by which mitochondria mediate the activation of the NLRP3 inflammasome and trigger lung disease is still unclear.

METHODS

The literatures related to mitochondrial stress, NLRP3 inflammasome and lung diseases were searched in PubMed.

RESULTS

This review aims to provide new insights into the recently discovered mitochondrial regulation of the NLRP3 inflammasome in lung diseases. It also describes the crucial roles of mitochondrial autophagy, long noncoding RNA, micro RNA, altered mitochondrial membrane potential, cell membrane receptors, and ion channels in mitochondrial stress and regulation of the NLRP3 inflammasome, in addition to the reduction of mitochondrial stress by nuclear factor erythroid 2-related factor 2 (Nrf2). The effective components of potential drugs for the treatment of lung diseases under this mechanism are also summarized.

CONCLUSION

This review provides a resource for the discovery of new therapeutic mechanisms and suggests ideas for the development of new therapeutic drugs, thus promoting the rapid treatment of lung diseases.

Effects of Z-VaD-Ala-Asp-Fluoromethyl Ketone (Z-VAD-FMK) and Acetyl-Asp-Glu-Val-Asp-Aldehyde(Ac-DEVD-CHO) on Inflammation and Mucus Secretion in Mice Exposed to Cigarette Smoke

Background and Objectives

Smoking can lead to airway inflammation and mucus secretion through the nucleotide-binding domain-like receptor protein 3/caspase-1 pathway. In this study, z-VaD-Ala-Asp-fluoromethyl ketone(Z-VAD), a pan-caspase inhibitor, and acetyl-Asp-Glu-Val-Asp-aldehyde(Ac-DEVD), a caspase-3 inhibitor, were used to investigate the effect of caspase inhibitors on the expression of interleukin(IL)-1β and IL-8, airway inflammation, and mucus secretion in mice exposed to cigarette smoke(CS).

Methods

Thirty-two C57BL/6J male mice were divided into a control group, Smoke group, Z-VAD group, and Ac-DEVD group. Except for the control group, the animals were all exposed to CS for three months. After the experiment, lung function was measured and hematoxylin and eosin staining and periodic acid-Schiff staining were performed. The levels of IL-1β, IL-8, and mucin 5ac(Muc5ac) in serum and bronchoalveolar lavage fluid(BALF) were determined by enzyme-linked immunosorbent assay.

Results

Compared with the control group, the lung function of mice exposed to smoke was poorer, with a large number of inflammatory cells infiltrating around the airway, collapse of alveoli, expansion and fusion of distal alveoli, and formation of emphysema. The Z-VAD group was relieved compared with the smoke group. Airway inflammation was also reduced in the Ac-DEVD group compared with the Smoke group, but the degree of emphysema was not significantly improved. Although Z-VAD relieved airway inflammation and emphysema, Ac-DEVD only relieved inflammation. Z-VAD and Ac-DEVD decreased serum IL-1β and IL-8 levels. In BALF, IL-1β was decreased in Z-VAD group and IL-8 was highest in Smoke +Ac-DEVD group compared with control group and Ac-DEVD group. There was no significant difference in the expression of Muc5ac in serum. However, in BALF, levels of Muc5ac were higher in the smoking group and the lowest in the Ac-DEVD group.

Conclusion

Mice exposed to smoke had decreased lung function and significant cilia lodging, epithelial cell shedding, and inflammatory cell infiltration, with significant emphysema formation. The pan-caspase inhibitor, Z-VAD, improved airway inflammation and emphysema lesions in the mice exposed to smoke and reduced IL-1β and IL-8 levels in serum. The caspase-3 inhibitor, Ac-DEVD, reduced airway inflammation, serum IL-1β and IL-8 levels, and Muc5ac levels in BALF, but it did not improve emphysema.

Associative analysis of multi-omics data indicates that acetylation modification is widely involved in cigarette smoke-induced chronic obstructive pulmonary disease

We aimed to study the molecular mechanisms of chronic obstructive pulmonary disease (COPD) caused by cigarette smoke more comprehensively and systematically through different perspectives and aspects and to explore the role of protein acetylation modification in COPD. We established the COPD model by exposing C57BL/6J mice to cigarette smoke for 24 weeks, then analyzed the transcriptomics, proteomics, and acetylomics data of mouse lung tissue by RNA sequencing (RNA-seq) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), and associated these omics data through unique algorithms. This study demonstrated that the differentially expressed proteins and acetylation modification in the lung tissue of COPD mice were co-enriched in pathways such as oxidative phosphorylation (OXPHOS) and fatty acid degradation. A total of 19 genes, namely, ENO3, PFKM, ALDOA, ACTN2, FGG, MYH1, MYH3, MYH8, MYL1, MYLPF, TTN, ACTA1, ATP2A1, CKM, CORO1A, EEF1A2, AKR1B8, MB, and STAT1, were significantly and differentially expressed at all the three levels of transcription, protein, and acetylation modification simultaneously. Then, we assessed the distribution and expression in different cell subpopulations of these 19 genes in the lung tissues of patients with COPD by analyzing data from single-cell RNA sequencing (scRNA-seq). Finally, we carried out the in vivo experimental verification using mouse lung tissue through quantitative real-time PCR (qRT-PCR), Western blotting (WB), immunofluorescence (IF), and immunoprecipitation (IP). The results showed that the differential acetylation modifications of mouse lung tissue are widely involved in cigarette smoke-induced COPD. ALDOA is significantly downregulated and hyperacetylated in the lung tissues of humans and mice with COPD, which might be a potential biomarker for the diagnosis and/or treatment of COPD.

Endoplasmic Reticulum Stress in Elderly Patients with COVID-19: Potential of Melatonin Treatment

Aging processes, including immunosenescence, inflammation, inflammasome formation, genomic instability, telomeric attrition, and altered autophagy, are involved in viral infections and they may contribute to increased pathophysiological responses to the SARS-CoV-2 infection in the elderly; this poses additional risks of accelerated aging, which could be found even after recovery. Aging is associated with oxidative damage. Moreover, SARS-CoV-2 infections may increase the production of reactive oxygen species and such infections will disturb the Ca++ balance via an endoplasmic reticulum (ER) stress-mediated unfolded protein response. Although vaccine development and anti-inflammation therapy lower the severity of COVID-19, the prevalence and mortality rates are still alarming in some countries worldwide. In this review, we describe the involvement of viral proteins in activating ER stress transducers and their downstream signals and in inducing inflammation and inflammasome formation. Furthermore, we propose the potential of melatonin as an ER stress modulator, owing to its antioxidant, anti-inflammatory, and immunoregulatory effects in viral infections. Considering its strong safety profile, we suggest that additive melatonin supplementation in the elderly could be beneficial in treating COVID-19.

The role of the NLRP3 inflammasome in chronic inflammation in asthma and chronic obstructive pulmonary disease

Asthma and chronic obstructive pulmonary disease (COPD) are lung diseases characterized by airflow limitation and chronic inflammation. More and more studies have shown that the occurrence and development of asthma and COPD are related to abnormal immune responses caused by dysregulation of many genetic and environmental factors. The exact pathogenesis of the disease is still unclear. A large number of studies have shown that the NLRP3 inflammasome is involved in the process of chronic airway inflammation in asthma and COPD. Here, we summarize recent advances in the mechanism of NLRP3 inflammasome activation and regulation and its role in the pathogenesis of inflammatory lung diseases such as asthma and COPD. Meanwhile we propose possible therapeutic targets in asthma and COPD.

Melatonin alleviates lead-induced intestinal epithelial cell pyroptosis in the common carps (Cyprinus carpio) via miR-17-5p/TXNIP axis

Lead (Pb) has been concerned as one of the most severe hazardous contaminants, because it can cause pyroptosis in multiple tissues of mammals and birds. Melatonin (Mel) has attracted much interest for its role in governing intestinal injury via microRNAs (miRNAs). To explore the effect of Mel on Pb exposure-induced intestinal epithelial cell pyroptosis in common carps by regulating miR-17-5p/TXNIP axis, the Pb exposure and Pb-Mel treated models were constructed in vivo. The results elucidated that the suppressed expression of miR-17-5p and intensified level of TXNIP were primarily detected in Pb-exposed gut tissues, and both abolished with Mel addition, along with downregulated Pb-mediated elevated expression of NLRP3, CASP1, IL1β and GSDMD. Additionally, the targeting relationship between miR-17-5p and TXNIP were demonstrated by dual-luciferase reporter assay, and on this basis, miR-17-5p NC, mimic and inhibitor cell models were established. Thereby, Thereby, the expression of TXNIP in the miR-17-5p mimic groups was significant lower in the Pb-exposure but still elevated than the Control group, and the expression of NLRP3 and NLRP3-dependent pyrotposis-related genes performed consistent alterations. Noticeably, the expression of TXNIP suppressed with Mel addition even in the miR-17-5p inhibitor cell model, resulting in the inactivation of NLRP3 inflammasome-dependent pyroptosis. Overall, we draw the conclusion as Mel attenuates Pb-induced intestinal epithelial cell pyroptosis via miR-17-5p/TXNIP axis. The present study provides a novel perspective for toxicological mechanism of Pb, and new insights for the detoxification mechanism of Mel.

Endoplasmic Reticulum Stress in Chronic Obstructive Pulmonary Disease: Mechanisms and Future Perspectives

The endoplasmic reticulum (ER) is an integral organelle for maintaining protein homeostasis. Multiple factors can disrupt protein folding in the lumen of the ER, triggering ER stress and activating the unfolded protein response (UPR), which interrelates with various damage mechanisms, such as inflammation, apoptosis, and autophagy. Numerous studies have linked ER stress and UPR to the progression of chronic obstructive pulmonary disease (COPD). This review focuses on the mechanisms of other cellular processes triggered by UPR and summarizes drug intervention strategies targeting the UPR pathway in COPD to explore new therapeutic approaches and preventive measures for COPD.

Targeting the mitochondria in chronic respiratory diseases

Mitochondria are one of the basic essential components for eukaryotic life survival. It is also the source of respiratory ATP. Recently published studies have demonstrated that mitochondria may have more roles to play aside from energy production. There is an increasing body of evidence which suggest that mitochondrial activities involved in normal and pathological states contribute to significant impact to the lung airway morphology and epithelial function in respiratory diseases such as asthma, COPD, and lung cancer. This review summarizes the pathophysiological pathways involved in asthma, COPD, lung cancer and highlights potential treatment strategies that target the malfunctioning mitochondria in such ailments. Mitochondria are responsive to environmental stimuli such as infection, tobacco smoke, and inflammation, which are essential in the pathogenesis of respiratory diseases. They may affect mitochondrial shape, protein production and ultimately cause dysfunction. The impairment of mitochondrial function has downstream impact on the cytosolic components, calcium control, response towards oxidative stress, regulation of genes and proteins and metabolic activities. Several novel compounds and alternative medicines that target mitochondria in asthma and chronic lung diseases have been discussed here. Moreover, mitochondrial enzymes or proteins that may serve as excellent therapeutic targets in COPD are also covered. The role of mitochondria in respiratory diseases is gaining much attention and mitochondria-based treatment strategies and personalized medicine targeting the mitochondria may materialize in the near future. Nevertheless, more in-depth studies are urgently needed to validate the advantages and efficacy of drugs that affect mitochondria in pathological states.

The NLRP3 inflammasome as a new target in respiratory disorders treatment

In recent years a continuous increase in new cases of respiratory disorders, such as rhinitis, asthma, and chronic obstructive pulmonary disease (COPD), has been observed. The exact pathomechanism of these diseases is still blurry, resulting in the lack of targeted and effective therapy. The conventional use of treatment strategies, such as antihistamine drugs and/or glucocorticosteroids act mainly symptomatically and have significant side effects. Specific allergen immunotherapy is only useful in the management of specific allergies and selected patients. Therefore, new therapeutic solutions are constantly being sought. The novelty of recent years has been the association between NLRP3 inflammasome activation and the development of airway inflammatory diseases. This seems to be an interesting therapeutic target that may support or even replace traditional therapies in the future. The review presented, discusses the contribution of NLRP3 inflammasome to the development of allergic rhinitis, allergic asthma, and COPD. Moreover, the modulatory properties of probiotics as potential inhibitors of NLRP3 inflammasome are emphasised.

Cigarette smoke-induced gasdermin D activation in bronchoalveolar macrophages and bronchial epithelial cells dependently on NLRP3

Chronic pulmonary inflammation and chronic obstructive pulmonary disease (COPD) are major health issues largely due to air pollution and cigarette smoke (CS) exposure. The role of the innate receptor NLRP3 (nucleotide-binding domain and leucine-rich repeat containing protein 3) orchestrating inflammation through formation of an inflammasome complex in CS-induced inflammation or COPD remains controversial. Using acute and subchronic CS exposure models, we found that Nlrp3-deficient mice or wild-type mice treated with the NLRP3 inhibitor MCC950 presented an important reduction of inflammatory cells recruited into the bronchoalveolar space and of pulmonary inflammation with decreased chemokines and cytokines production, in particular IL-1β demonstrating the key role of NLRP3. Furthermore, mice deficient for Caspase-1/Caspase-11 presented also decreased inflammation parameters, suggesting a role for the NLRP3 inflammasome. Importantly we showed that acute CS-exposure promotes NLRP3-dependent cleavage of gasdermin D in macrophages present in the bronchoalveolar space and in bronchial airway epithelial cells. Finally, Gsdmd-deficiency reduced acute CS-induced lung and bronchoalveolar space inflammation and IL-1β secretion. Thus, we demonstrated in our model that NLRP3 and gasdermin D are key players in CS-induced pulmonary inflammation and IL-1β release potentially through gasdermin D forming-pore and/or pyroptoctic cell death.

Synthesis, characterization, and evaluation of in vitro cytotoxicity and in vivo antitumor activity of asiatic acid-loaded poly lactic-co-glycolic acid nanoparticles: A strategy of treating breast cancer

Asiatic acid (AA), an aglycone of pentacyclic triterpene glycoside, obtained from the leaves of Centella asiatica exerts anticancer effects by inhibiting cellular proliferation and inducing apoptosis in a wide range of carcinogenic distresses. However, its chemotherapeutic efficacy is dampened by its low bioavailability. Polymeric nanoparticles (NPs) exhibit therapeutic efficacy and compliance by improving tissue penetration and lowering toxicity. Thus, to increase the therapeutic effectiveness of AA in the treatment of breast cancer, AA-loaded poly lactic-co-glycolic acid (PLGA) NPs (AA-PLGA NPs) have been formulated. The AA-PLGA NPs were characterized on the basis of their average particle size, zeta potential, electron microscopic imaging, drug loading, and entrapment efficiency. The NPs exhibited sustained drug release profile in vitro. Developed NPs exerted dose-dependent cytotoxicity to MCF-7 and MDA-MB-231 cells without damaging normal cells. The pro-oxidant and pro-apoptotic properties of AA-PLGA NPs were determined by the study of the cellular levels of SOD, CAT, GSH-GSSG, MDA, protein carbonylation, ROS, mitochondrial membrane potential, and FACS analyses on MCF-7 cells. Immunoblotting showed that AA-PLGA NPs elicited an intrinsic pathway of apoptosis in MCF-7 cells. In vivo studies on female BALB/c mice exhibited reduced volume of mammary pad tumor tissues and augmented expression of caspase-3 when administered with AA-PLGA NPs. No systemic adverse effect of AA-PLGA NPs was observed in our studies. Thus, AA-PLGA NPs can act as an efficient drug delivery system against breast cancer.

Melatonin counteracts necroptosis and pulmonary edema in cadmium-induced chronic lung injury through the inhibition of angiotensin II

The renin-angiotensin system (RAS) is an important regulator in pulmonary physiology. In our study, we identified the efficacy of melatonin to control the RAS in cadmium (Cd) induced chronic lung injury in a mouse model. Swiss albino mice exposed to CdCl₂ intraperitoneally (I.P.) (1 mg/kg b.w.; 12 weeks) showed increased release of lactate dehydrogenase in bronchoalveolar lavage fluid, generating reactive oxygen species, impaired antioxidant enzymes function, and disrupted alveolar structure along with increased expression of Angiotensin-II (Ang-II) in lung tissue. Cd-induced angiotensin-converting enzyme-2-Ang-II axis imbalance triggered the onset of Ang-II induced tumour necrosis factor alpha  (TNF-α) mediated necroptosis by upregulating the signalling molecules RIP-1, RIP-3, and p-mixed lineage kinase domain-like. In an in vitro study, colocalization of Ang-II-RIP-3 molecule in Cd intoxicated L-132 cells (human alveolar epithelial cell line), as well as pretreatment of Cd exposed cells with the inhibitor's captopril (10 μM), necrostatin-1 (50 μM), and etanercept (5 μg/ml) indicated TNF-α induced necroptotic cell death via activation of the key molecule, Ang-II. Moreover, Ang-II disrupted the alveolar-capillary barrier by decreasing tight junctional proteins (zonula occludens-1 and occludin) and endothelial VE-cadherin expression. The use of human umbilical vein endothelial cells as a model of junctional protein-expressing cells showed that captopril pretreatment (25 μM) restored VE-cadherin expression in Cd-treated human umbilical vein endothelial cells. In CdCl₂ intoxicated mice, melatonin pretreatment (10 mg/kg b.w.; 12 weeks, I.P.) inhibited inflammatory mediators (TNF-α, interleukin [IL]-1β, and IL-6) release and effectively suppressed (Cd-induced) Ang-II mediated necroptotic cell death and alveolar-capillary breaching due to Cd toxicity.

Pyroptosis in inflammation-related respiratory disease

Pyroptosis is commonly induced by the gasdermin (GSDM) family and is accompanied by the release of inflammatory cytokines such as IL-1β and IL-18. Recently, increasing evidence suggests that pyroptosis plays a role in respiratory diseases. This review aimed to summarize the roles and mechanisms of pyroptosis in inflammation-related respiratory diseases. There are several pathways involved in pyroptosis, such as the canonical inflammasome-induced pathway, non-canonical inflammasome-induced pathway, caspase-1/3/6/7/GSDMB pathway, caspase-8/GSDMC pathway, caspase-8/GSDMD pathway, and caspase-3/GSEME pathway. Pyroptosis may be involved in asthma, chronic obstructive pulmonary disease (COPD), lung cancer, acute lung injury (ALI), silicosis, pulmonary hypertension (PH), and tuberculosis (TB), in which the NLRP3 inflammasome-induced pathway is mostly highlighted. Pyroptosis contributes to the deterioration of asthma, COPD, ALI, silicosis, and PH. In addition, pyroptosis has dual effects on lung cancer and TB. Additionally, whether pyroptosis participates in cystic fibrosis (CF) and sarcoidosis or not is largely unknown, though the activation of NLRP3 inflammasome is found in CF and sarcoidosis. In conclusion, pyroptosis may play a role in inflammation-related respiratory diseases, providing new therapeutic targets.

Polyphenols, flavonoids and inflammasomes: the role of cigarette smoke in COPD

COPD is predicted to become the third leading cause of morbidity and mortality worldwide by 2030. Cigarette smoking (active or passive) is one of its chief causes, with about 20% of cigarette smokers developing COPD from cigarette smoke (CS)-induced irreversible damage and sustained inflammation of the airway epithelium. Inflammasome activation leads to the cleavage of pro-interleukin (IL)-1β and pro-IL-18, along with the release of pro-inflammatory cytokines via gasdermin D N-terminal fragment membrane pores, which further triggers acute phase pro-inflammatory responses and concurrent pyroptosis. There is currently intense interest in the role of nucleotide-binding oligomerisation domain-like receptor family, pyrin domain containing protein-3 inflammasomes in chronic inflammatory lung diseases such as COPD and their potential for therapeutic targeting. Phytochemicals including polyphenols and flavonoids have phyto-medicinal benefits in CS-COPD. Here, we review published articles from the last decade regarding the known associations between inflammasome-mediated responses and ameliorations in pre-clinical manifestations of CS-COPD via polyphenol and flavonoid treatment, with a focus on the underlying mechanistic insights. This article will potentially assist the development of drugs for the prevention and therapy of COPD, particularly in cigarette smokers.

This review compiles current investigations into the role of polyphenols/flavonoids in the alleviation of cigarette smoke-induced inflammasome; notably it provides a promising hit for rectifying the treatment of COPD.https://bit.ly/36OcUO9

The NLRP3 Inflammasome Pathway: A Review of Mechanisms and Inhibitors for the Treatment of Inflammatory Diseases

The NLRP3 inflammasome is a multiprotein complex that plays a pivotal role in regulating the innate immune system and inflammatory signaling. Upon activation by PAMPs and DAMPs, NLRP3 oligomerizes and activates caspase-1 which initiates the processing and release of pro-inflammatory cytokines IL-1β and IL-18. NLRP3 is the most extensively studied inflammasome to date due to its array of activators and aberrant activation in several inflammatory diseases. Studies using small molecules and biologics targeting the NLRP3 inflammasome pathway have shown positive outcomes in treating various disease pathologies by blocking chronic inflammation. In this review, we discuss the recent advances in understanding the NLRP3 mechanism, its role in disease pathology, and provide a broad review of therapeutics discovered to target the NLRP3 pathway and their challenges.

Melatonin attenuates LPS-induced pyroptosis in acute lung injury by inhibiting NLRP3-GSDMD pathway via activating Nrf2/HO-1 signaling axis

Acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS) is featured by intensive inflammatory responses and oxidative stress, which lead to cytokine storms and pyroptosis. Here, we aimed to investigate whether melatonin was capable of alleviating LPS-induced ALI via activating the nuclear factor erythroid 2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signaling axis and inhibiting pyroptosis. Mice were injected with melatonin (30 mg/kg) intraperitoneally for consecutive five days before LPS instillation intratracheally, and human alveolar epithelial cell (AECⅡ) A549 cell lines and murine macrophages Raw264.7 cell lines were pretreated with melatonin (400 μM) before LPS (10 μg/ml) stimulation. The result demonstrated that LPS induced obvious lung injury characterized by alveolar damage, neutrophil infiltration and lung edema as well as the reduction of the survival rate of mice, which were totally reversed by melatonin pretreatment. Mechanistically, melatonin pretreatment activated nuclear factor erythroid2-related factor (Nrf) 2 signaling, subsequently, drove antioxidant pathways including significant increases in the expression of Nrf2, HO-1, NQO1, Mn-SOD and Catalase in vivo and in vitro. Simultaneously, melatonin inhibited ROS and MDA overproduction, iNOS expression as well as TNF-α and IL-1β expression and release. Furthermore, melatonin inhibited LPS-induced pyroptosis by reversing the overexpression of NLRP3, Caspase-1, IL-1β, IL-18 and GSDMD-N, as well as LDH release and TUNEL-positive cells in A549 cells and Raw264.7 cells. Overall, the current study suggests that melatonin exerts protective roles on LPS-induced ALI and pyroptosis by inhibiting NLRP3-GSDMD pathway via activating Nrf2/HO-1 signaling axis.

Enhancement of anti-neoplastic effects of cuminaldehyde against breast cancer via mesoporous silica nanoparticle based targeted drug delivery system

AIMS

Synthesis of novel drug delivery system for targeted delivery of cuminaldehyde to breast cancer cells and the subsequent analyses of anti-neoplastic potential of the drug.

MAIN METHODS

3-carboxy-phenyl boronic acid (PBA) conjugated and polyacrylic acid (PAA) gated mesoporous silica nanoparticles (MSNs) were synthesized for the targeted delivery of cuminaldehyde (CUM) to breast cancer cells. Enhancement of anti-neoplastic effects of cuminaldehyde (4-isopropylbenzaldehyde) by the nanoconjugates was assessed.

KEY FINDINGS

The anti-cancer effects of non-targeted and targeted drug-nanoconjugates were examined in vitro and in vivo. The targeted drug-nanoconjugates caused cell cycle arrest and induced the intrinsic pathway of apoptosis in MCF-7 cells through mitochondrial damage. In vivo intravenous injection of the targeted drug-nanoconjugates led to effective reduction in growth of 4 T1 induced mammary pad tumor in female BALB/c mice via augmented accumulation of cuminaldehyde. The drug-nanoconjugates did not exhibit any systemic toxicity.

SIGNIFICANCE

Therefore, MSN-PBA-CUM-PAA represents a potent therapeutic model for breast cancer treatment.

HSP60 regulates the cigarette smoke-induced activation of TLR4-NF-κB-MyD88 signalling pathway and NLRP3 inflammasome

Chronic obstructive pulmonary disease (COPD) is characterized by increased cellular stress and inflammation. Heat shock protein 60 (HSP60) is a highly conserved stress protein that acts as a cellular "danger" signal for immune reactions. In this study, we investigated the role of HSP60 in COPD and explored the underlying mechanisms. Expression levels of HSP60 in patients with acute exacerbation of COPD (AECOPD), stable COPD, and healthy people were detected by Western blotting and enzyme-linked immunosorbent assay (ELISA). Moreover, the effect and molecular mechanism of HSP60 in COPD were studied in cigarette smoke (CS)-treated C57BL/6 mice and macrophages. The results showed significant upregulation of HSP60 expression in the peripheral blood mononuclear cells (PBMCs) and sera of patients with AECOPD compared to those with stable COPD or healthy people. CS induced the expression of HSP60 in the COPD mouse model, accelerated the activation of toll-like receptor 4 (TLR4) and NLR family pyrin domain containing 3 (NLRP3) signalling pathways, promoted the increase of inflammatory cells in alveolar lavage fluid and serum inflammatory factors, and induced destruction of lung tissue structure. Furthermore, HSP60 knockdown affected TLR4 and MyD88 expression, IκBα degradation, and nuclear localization of NF-κB and NLRP3 inflammasome activity. Our study revealed that CS stimulates the expression of HSP60, activating the TLR4-MyD88-NF-κB signalling pathway and the NLRP3 inflammasome.

Fabrication of phenyl boronic acid modified pH-responsive zinc oxide nanoparticles as targeted delivery of chrysin on human A549 cells

Recently, different natural bioactive compounds have been used as anticancer agents for their various therapeutic benefits and non-toxic nature to other organs. However, they have various restrictions in preclinical and clinical studies due to their non-targeting nature and insufficient bioavailability. As a result, a zinc oxide nanoparticle (ZnO) based drug delivery medium was constructed which has good bio-compatibility and bio-degradability. It also displays cancer cell-specific drug delivery in a targeted and controlled way. In the present study, phenylboronic acid (PBA) tagged ZnO nanoparticles (ZnO-PBA) was fabricated and in the next step, chrysin (a natural bio-active molecule) was loaded to it to form the nanoconjugate (ZnO-PBA-Chry). Different characterization techniques were used to confirm the successful fabrication of ZnO-PBA-Chry. PBA-tagging to the nanoparticle helps in targeted delivery of chrysin in lung cancer cells (A549) as PBA binds with sialic acid receptors which are over-expressed on the surface of A549 cells. As ZnO dissociates in acidic pH, it shows stimuli-responsive release of chrysin in tumor microenvironment. Application of ZnO-PBA-Chry nanohybrid in lung cancer cell line A549 caused oxidative stress mediated intrinsic cell death and cell cycle arrest. ZnO-PBA-Chry downregulated MMP-2 and VE-Cadherin, thereby inhibiting metastasis and the invasive property of A549 cells.

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pH-responsive PBA functionalized ZnO nanoparticle was fabricated.

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Chrysin was loaded as a bioactive anticancer agent into ZnO nanoparticle.

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ZnO-PBA-Chry induced intrinsic cell death and cell cycle arrest in A549 cells.

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It inhibited metastasis and invasive properties of A549 cells.