Hydrogen ameliorates lung injury in a rat model of subacute exposure to concentrated ambient PM2.5 via Aryl hydrocarbon receptor

Toxicological Response of the BEAS-2B Cell After Acute Exposure at the Air-Liquid Interface to Ethylbenzene and m-Xylene Alone and in Binary Mixtures

Benzene, toluene, ethylbenzene, and xylenes (o-, m-, and p-xylenes) constitute a family, named BTEX, of volatile organic compounds (VOCs) known for its toxicity. This study aimed to study the acute in vitro toxicity of ethylbenzene and m-xylene on human bronchial epithelial cells exposed at the air-liquid interface (ALI). The cells were exposed to VOCs alone and in a mixture for 1 h, followed by 5, 23, and 47 h of incubation. The kinetics of the cell response was characterized, including cytotoxicity, xenobiotic biotransformation, antioxidant defense system, inflammatory response, and apoptosis. The gene expression results showed major differences between these two compounds, even though their chemical structure is very similar. Ethylbenzene did not appear to be metabolized in BEAS-2B cells, as it inhibited gene expression of xenobiotic metabolizing enzymes (XME) and did not induce antioxidant defense systems or apoptosis. However, a slight inflammatory response was observed after exposure. m-Xylene was metabolized in BEAS-2B cells, inducing several XMEs and upregulating enzymes involved in the antioxidant defense system, as well as markers of inflammation and apoptosis. Co-exposure to the binary mixture resulted in an inhibition phenomenon, resulting in the inhibition of toxic action mechanisms studied. The results provide new information on the toxicity of ethylbenzene and m-xylene and highlight the importance of conducting ALI exposures to mixtures of toxicants.

Anti-inflammatory and antioxidant activity of high concentrations of hydrogen in the lung diseases: a systematic review and meta-analysis

As a small molecule, hydrogen is colorless, odorless and lightest. Many studies conducted that hydrogen can protect almost every organ, including the brain, heart muscle, liver, small intestine, and lungs. To verify whether high concentrations of hydrogen (HCH) has anti-inflammatory and antioxidant activities on respiratory system, we product a systematic review and meta-analysis. We investigated MEDLINE-PubMed, Cochrane Library, ScienceDirect, Wiley and SpringerLink database and selected in vivo studies related to the anti-inflammatory or antioxidant effects of HCH in the lung diseases which were published until September 2023. We firstly identified 437 studies and only 12 met the inclusion criteria. They all conducted in rodents. The results showed that HCH had a positive effect on the reduction of tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-4, IL-8, malondialdehyde (MDA), superoxide dismutase (SOD) and reactive oxygen species (ROS); but there is no effect on IL-6, we speculated that may contribute to the test results for different body fluids and at different points in time. This meta-analysis discovered the protective effects on inflammation and oxidative stress, but whether there exists more effects on reduction of inflammatory and oxidant mediators needs to be further elucidated.

The Impact of the Aryl Hydrocarbon Receptor on Antenatal Chemical Exposure-Induced Cardiovascular-Kidney-Metabolic Programming

Early life exposure lays the groundwork for the risk of developing cardiovascular-kidney-metabolic (CKM) syndrome in adulthood. Various environmental chemicals to which pregnant mothers are commonly exposed can disrupt fetal programming, leading to a wide range of CKM phenotypes. The aryl hydrocarbon receptor (AHR) has a key role as a ligand-activated transcription factor in sensing these environmental chemicals. Activating AHR through exposure to environmental chemicals has been documented for its adverse impacts on cardiovascular diseases, hypertension, diabetes, obesity, kidney disease, and non-alcoholic fatty liver disease, as evidenced by both epidemiological and animal studies. In this review, we compile current human evidence and findings from animal models that support the connection between antenatal chemical exposures and CKM programming, focusing particularly on AHR signaling. Additionally, we explore potential AHR modulators aimed at preventing CKM syndrome. As the pioneering review to present evidence advocating for the avoidance of toxic chemical exposure during pregnancy and deepening our understanding of AHR signaling, this has the potential to mitigate the global burden of CKM syndrome in the future.

Effects of environmental exposure to iron powder on healthy and elastase-exposed mice

Prolonged exposure to iron powder and other mineral dusts can threaten the health of individuals, especially those with COPD. The goal of this study was to determine how environmental exposure to metal dust from two different mining centers in Brazil affects lung mechanics, inflammation, remodeling and oxidative stress responses in healthy and elastase-exposed mice. This study divided 72 male C57Bl/6 mice into two groups, the summer group and the winter group. These groups were further divided into six groups: control, nonexposed (SAL); nonexposed, given elastase (ELA); exposed to metal powder at a mining company (SAL-L1 and ELA-L1); and exposed to a location three miles away from the mining company (SAL-L2 and ELA-L2) for four weeks. On the 29th day of the protocol, the researchers assessed lung mechanics, bronchoalveolar lavage fluid (BALF), inflammation, remodeling, oxidative stress, macrophage iron and alveolar wall alterations (mean linear intercept-Lm). The Lm was increased in the ELA, ELA-L1 and ELA-L2 groups compared to the SAL group (p < 0.05). There was an increase in the total number of cells and macrophages in the ELA-L1 and ELA-L2 groups compared to the other groups (p < 0.05). Compared to the ELA and SAL groups, the exposed groups (ELA-L1, ELA-L2, SAL-L1, and SAL-L2) exhibited increased expression of IL-1β, IL-6, IL-10, IL-17, TNF-α, neutrophil elastase, TIMP-1, MMP-9, MMP-12, TGF-β, collagen fibers, MUC5AC, iNOS, Gp91phox, NFkB and iron positive macrophages (p < 0.05). Although we did not find differences in lung mechanics across all groups, there were low to moderate correlations between inflammation remodeling, oxidative stress and NFkB with elastance, resistance of lung tissue and iron positive macrophages (p < 0.05). Environmental exposure to iron, confirmed by evaluation of iron in alveolar macrophages and in air, exacerbated inflammation, initiated remodeling, and induced oxidative stress responses in exposed mice with and without emphysema. Activation of the iNOS, Gp91phox and NFkB pathways play a role in these changes.

Evaluation of the effect of enriched hydrogen saline solution on distant organ (lung) damage in skeletal muscle ischemia reperfusion in rats

INTRODUCTION

Ischemia-reperfusion (IR) injury is a major concern that frequently occurs during vascular surgeries. Hydrogen-rich saline (HRS) solution exhibits antioxidant and anti-inflammatory properties. This study aimed to examine the effects of HRS applied before ischemia in the lungs of rats using a lower extremity IR model.

MATERIAL AND METHODS

After approval was obtained from the ethics committee, 18 male Wistar albino rats weighing 250-280 g were randomly divided into three groups: control (C), IR and IR-HRS. In the IR and IR-HRS groups, an atraumatic microvascular clamp was used to clamp the infrarenal abdominal aorta, and skeletal muscle ischemia was induced. After 120 min, the clamp was removed, and reperfusion was achieved for 120 min. In the IR-HRS group, HRS was administered intraperitoneally 30 min before the procedure. Lung tissue samples were examined under a light microscope and stained with hematoxylin-eosin (H&E). Malondialdehyde (MDA) levels, total sulfhydryl (SH) levels, and histopathological parameters were evaluated in the tissue samples.

RESULTS

MDA and total SH levels were significantly higher in the IR group than in the control group (p < 0.0001 and p = 0.001, respectively). MDA and total SH levels were significantly lower in the IR-HRS group than in the IR group (p < 0.0001 and p = 0.013, respectively). A histopathological examination revealed that neutrophil infiltration/aggregation, alveolar wall thickness, and total lung injury score were significantly higher in the IR group than in the control group (p < 0.0001, p = 0.001, and p < 0.0001, respectively). Similarly, alveolar wall thickness and total lung injury scores were significantly higher in the IR-HRS group than in the control group (p = 0.009 and p = 0.004, respectively). A statistically significant decrease was observed in neutrophil infiltration/aggregation and total lung injury scores in the IR-HRS group compared to those in the IR group (p = 0.023 and p = 0.022, respectively).

CONCLUSION

HRS at a dose of 20 mg/kg, administered intraperitoneally 30 min before ischemia in rats, reduced lipid peroxidation and oxidative stress, while also reducing IR damage in lung histopathology. We believe that HRS administered to rats prior to IR exerts a lung-protective effect.

Exercise ameliorates fine particulate matter-induced metabolic damage through the SIRT1/AMPKα/PGC1-α/NRF1 signaling pathway

Air pollution, particularly fine particulate matter (PM2.5), poses a major threat to human health. Exercise has long been recognized as a beneficial way to maintain physical health. However, there is limited research on whether exercise can mitigate the damage caused by PM2.5 exposure. In this study, the mice were exercised on the IITC treadmill for 1 h per day, then exposed to concentrated PM2.5 for 8 h. After 2, 4 and 6-month exercise and PM2.5 exposure, the glucose tolerance and insulin tolerance were determined. Meanwhile, the corresponding indicators in epididymal white adipose tissue (eWAT), brown adipose tissue (BAT) and skeletal muscle were detected. The results indicated that PM2.5 exposure significantly increased insulin resistance (IR), while exercise effectively attenuated this response. The observations of muscle, BAT and eWAT by transmission electron microscopy (TEM) showed that PM2.5 significantly reduced the number of mitochondria in all of the three tissues mentioned above, and decreased the mitochondrial area in skeletal muscle and BAT. Exercise reversed the changes in mitochondrial area in all of the three tissues, but had no effect on the reduction of mitochondrial number in skeletal muscle. At 2 months, the expressions of Mfn2, Mfn1, OPA1, Drp1 and Fis1 in eWAT of the PM mice showed no significant changes when compared with the corresponding FA mice. However, at 4 months and 6 months, the expression levels of these genes in PM mice were higher than those in the FA mice in skeletal muscle. Exercise intervention significantly reduced the upregulation of these genes induced by PM exposure. The study indicated that PM2.5 may impact mitochondrial biogenesis and dynamics by inhibiting the SIRT1/AMPKα/PGC1-α/NRF1 pathway, which further lead to IR, glucose and lipid disorders. However, exercise might alleviate the damages caused by PM2.5 exposure.

Irisin Ameliorates PM2.5-Induced Acute Lung Injury by Regulation of Autophagy Through AMPK/mTOR Pathway

Background

PM2.5 exposure is one of the major inducements of various respiratory diseases and related mortality. Meanwhile, irisin, a metabolism and thermogenesis-related hormone, is found to be protective against acute lung injury induced by LPS, which indicates its therapeutic function in lung injury. However, the function and underlying mechanism of irisin in PM2.5-induced acute lung injury (ALI) are still unclear. This study is aimed to discover the potential mechanisms of irisin in PM2.5-induced acute lung injury.

Methods

Atg5 deficient mice and cells were established to clarify the relationship between irisin and autophagy in PM2.5-induced ALI. We also used Ad-mCherry-GFP-LC3B as a monitor of autophagy flux to claim the effects of irisin on autophagy. Western blotting and qPCR were used to reveal the molecular mechanism.

Results

As a result, PM2.5 exposure induced lung injury whereas mitigated by irisin. Moreover, PM2.5 hampered autophagy flux, characterized by accumulation of p62, and autophagosomes, as well as blocked autolysosomes. Irisin improved the disturbed autophagy flux, which was abrogated by deficiency of Atg5. Additionally, we demonstrated that irisin activated AMPK and inhibited mTOR, which indicated the enhanced autophagy. Moreover, blockage of AMPK by compound C terminated irisin's induction of autophagy in cultured MH-S cells.

Conclusion

Our findings reveal that irisin performs protective effects against PM2.5-induced ALI by activating autophagy through AMPK/mTOR signaling pathway.

A comparison of fine particulate matter (PM2.5) in vivo exposure studies incorporating chemical analysis

The complex, variable mixtures present in fine particulate matter (PM_2.5) have been well established, and associations between chemical constituents and human health are expanding. In the past decade, there has been an increase in PM_2.5 toxicology studies that include chemical analysis of samples. This investigation is a crucial component for identifying the causal constituents for observed adverse health effects following exposure to PM_2.5. In this review, investigations of PM_2.5 that used both in vivo models were explored and chemical analysis with a focus on respiratory, cardiovascular, central nervous system, reproductive, and developmental toxicity was examined to determine if chemical constituents were considered in the interpretation of the toxicity findings. Comparisons between model systems, PM_2.5 characteristics, endpoints, and results were made. A vast majority of studies observed adverse effects in vivo following exposure to PM_2.5. While limited, investigations that explored connections between chemical components and measured endpoints noted significant associations between biological measurements and a variety of PM_2.5 constituents including elements, ions, and organic/elemental carbon, indicating the need for such analysis. Current limitations in available data, including relatively scarce statistical comparisons between collected toxicity and chemical datasets, are provided. Future progress in this field in combination with epidemiologic research examining chemical composition may support regulatory standards of PM_2.5 to protect human health.

Role of air pollutants in airway epithelial barrier dysfunction in asthma and COPD

Chronic exposure to environmental pollutants is a major contributor to the development and progression of obstructive airway diseases, including asthma and COPD. Understanding the mechanisms underlying the development of obstructive lung diseases upon exposure to inhaled pollutants will lead to novel insights into the pathogenesis, prevention and treatment of these diseases. The respiratory epithelial lining forms a robust physicochemical barrier protecting the body from inhaled toxic particles and pathogens. Inhalation of airborne particles and gases may impair airway epithelial barrier function and subsequently lead to exaggerated inflammatory responses and airway remodelling, which are key features of asthma and COPD. In addition, air pollutant-induced airway epithelial barrier dysfunction may increase susceptibility to respiratory infections, thereby increasing the risk of exacerbations and thus triggering further inflammation. In this review, we discuss the molecular and immunological mechanisms involved in physical barrier disruption induced by major airborne pollutants and outline their implications in the pathogenesis of asthma and COPD. We further discuss the link between these pollutants and changes in the lung microbiome as a potential factor for aggravating airway diseases. Understanding these mechanisms may lead to identification of novel targets for therapeutic intervention to restore airway epithelial integrity in asthma and COPD.

Exposure to air pollution induces airway epithelial barrier dysfunction through several mechanisms including increased oxidative stress, exaggerated cytokine responses and impaired host defence, which contributes to development of asthma and COPD. https://bit.ly/3DHL1CA

Molecular hydrogen is a promising therapeutic agent for pulmonary disease

Molecular hydrogen exerts biological effects on nearly all organs. It has anti-oxidative, anti-inflammatory, and anti-aging effects and contributes to the regulation of autophagy and cell death. As the primary organ for gas exchange, the lungs are constantly exposed to various harmful environmental irritants. Short- or long-term exposure to these harmful substances often results in lung injury, causing respiratory and lung diseases. Acute and chronic respiratory diseases have high rates of morbidity and mortality and have become a major public health concern worldwide. For example, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic. An increasing number of studies have revealed that hydrogen may protect the lungs from diverse diseases, including acute lung injury, chronic obstructive pulmonary disease, asthma, lung cancer, pulmonary arterial hypertension, and pulmonary fibrosis. In this review, we highlight the multiple functions of hydrogen and the mechanisms underlying its protective effects in various lung diseases, with a focus on its roles in disease pathogenesis and clinical significance.

Hydrogen, a Novel Therapeutic Molecule, Regulates Oxidative Stress, Inflammation, and Apoptosis

Molecular hydrogen (H₂) is a colorless and odorless gas. Studies have shown that H₂ inhalation has the therapeutic effects in many animal studies and clinical trials, and its application is recommended in the novel coronavirus pneumonia treatment guidelines in China recently. H₂ has a relatively small molecular mass, which helps it quickly spread and penetrate cell membranes to exert a wide range of biological effects. It may play a role in the treatment and prevention of a variety of acute and chronic inflammatory diseases, such as acute pancreatitis, sepsis, respiratory disease, ischemia reperfusion injury diseases, autoimmunity diseases, etc.. H₂ is primarily administered via inhalation, drinking H₂-rich water, or injection of H₂ saline. It may participate in the anti-inflammatory and antioxidant activity (mitochondrial energy metabolism), immune system regulation, and cell death (apoptosis, autophagy, and pyroptosis) through annihilating excess reactive oxygen species production and modulating nuclear transcription factor. However, the underlying mechanism of H₂ has not yet been fully revealed. Owing to its safety and potential efficacy, H₂ has a promising potential for clinical use against many diseases. This review will demonstrate the role of H₂ in antioxidative, anti-inflammatory, and antiapoptotic effects and its underlying mechanism, particularly in coronavirus disease-2019 (COVID-19), providing strategies for the medical application of H₂ for various diseases.

PM2.5 activated NLRP3 inflammasome and IL-1β release in MH-S cells by facilitating autophagy via activating Wnt5a

Particulate matter 2.5 (PM2.5)-induced pulmonary inflammation is an important issue worldwide. NLRP3 inflammasome activation has been found to be involved in pulmonary inflammation development. However, whether PM2.5 induces pulmonary inflammation by activating the NLRP3 inflammasome has not yet been fully elucidated. This study researched whether PM2.5 induces the NLRP3 inflammasomes activation to trigger pulmonary inflammation.

Mice and MH-S cells were exposed to PM2.5, BOX5, and Rapamycin. Hematoxylin and eosin staining was performed on the lung tissues of mice. M1 macrophage marker CD80 expression in the lung tissues of mice and LC3B expression in MH-S cells was detected by immunofluorescence. IL-1β level in the lavage fluid and MH-S cells were detected by enzyme-linked immunosorbent assay. Protein expression was detected by Western blot. Autophagy assay in MH-S cells was performed by LC3B-GFP punctae experiment.PM2.5 exposure induced the lung injury of mice and increased NLRP3, P62, Wnt5a, LC3BII/I, and CD80 expression and IL-1β release in the lung tissues. PM2.5 treatment increased NLRP3, pro-caspase-1, cleaved caspase-1, Pro-IL-1β, Pro-IL-18, P62, LC3BII/I, and Wnt5a expression, IL-1β release, and LC3B-GFP punctae in MH-S cells. However, BOX5 treatment counteracted this effect of PM2.5 on lung tissues of mice and MH-S cells. Rapamycin reversed the effect of BOX5 on PM2.5-induced lung tissues of mice and MH-S cells.PM2.5 activated the NLRP3 inflammasome and IL-1β release in MH-S cells by facilitating the autophagy via activating Wnt5a. The findings of this study provided a new clue for the treatment of pulmonary inflammation caused by PM2.5.

Interleukin-37 inhibits inflammation activation and disease severity of PM2.5-induced airway hyperresponsiveness

We have shown in the past studies that fine particulate matter (PM2.5) exposure increases airway hyperresponsiveness and leads to lung inflammation damage. Interleukin (IL)-37 plays a inhibitory role in inflammation activation and maintenance. However, the function of IL-37 in the above processes keep unclear. We aim to explore the role of IL-37 in PM2.5-induced airway hyperresponsiveness in this study. A nose-only PM2.5 online concentration, enrichment and exposure instrument was also applied to generate mice model of airway hyperresponsiveness. A transgenic mice strain using a CMV promoter to express human IL-37b (hIL-37tg) was obtained. PM2.5 exposure was shown to increase airway resistance, followed by lung inflammation and IL-1β, TNFα, and IL-6 release, which was inhibited by IL-37tg mice and mice administrated recombinant human IL-37 intranasally (i.n). Moreover, expression of the proliferation-related protein PCNA and migration-related proteins MMP-2, MMP-9, and Vimentin was reduced in lung tissues of IL-37tg mice and mice given recombinant human IL-37 i.n. Abnormal cell contraction, proliferation, and migration of human airway smooth muscle cells (hASMCs) incubated with PM2.5 were also decreased by IL-37 treatment. In addition, IL-37 intervention of hASMCs before PM2.5 incubation decreased cytoplasmic calcium level and expression of PCNA, MMP-2, MMP-9 and Vimentin. Finally, knockdown of the IL-37 receptor IL-1R8 gene eliminated the protective effects of IL-37 in the above responses. We conclude that IL-37 inhibits inflammation activation and disease severity of airway hyperreactivity by PM2.5 induction.

Amelioration of Ambient Particulate Matter (PM2.5)-Induced Lung Injury in Rats by Aerobic Exercise Training

Ambient particulate matter (PM_2.5), as an inflammation-inducing factor, increases the prevalence of lung injury. The aim of this study was to examine the protective effect and mechanism of aerobic exercise on PM_2.5 exposure-induced lung injury. Forty Wistar rats were randomly divided into four groups: sedentary+PM_2.5 exposure, exercise+PM_2.5 exposure, sedentary, and exercise groups. All rats in the exercise-related groups underwent 8-week aerobic interval treadmill training (5daysweek⁻¹, 1hday⁻¹). PM-exposed rats were exposed to ambient PM_2.5 (6h day⁻¹) for 3weeks after the 8-week exercise intervention. Then, ventilation function, histopathological changes, and inflammation responses of pulmonary tissue were examined. Results showed that PM_2.5 exposure induced lung injury as manifested by decreased pulmonary function, abnormal histopathological changes, and increased pro-inflammatory cytokine levels (tumor necrosis factor-α and Interleukin-1α). Aerobic exercise alleviated the airway obstruction, reduced respiratory muscle strength, bronchial mucosal exfoliation, ultrastructure damage, and inflammatory responses induced by PM_2.5 in exercise-related groups. The benefits of exercise were related with the downregulation of p38-mitogen-activated protein kinase (MAPK), and the subsequent inhibition of the pathways of the cyclooxygenase 2 (COX-2) product, prostaglandin E₂ (PGE₂). Thus, pre-exercise training may be an effective way to protect against PM_2.5-induced lung inflammatory injury in rats.

High concentration of hydrogen ameliorates lipopolysaccharide-induced acute lung injury in a sirt1-dependent manner

The aim of this study was to investigate the efficacy and underlying mechanism of high concentration of hydrogen on lipopolysaccharide (LPS)-induced acute lung injury (ALI). We have established a corresponding mouse model and examined the function of hydrogen inhalation on lung pathology and pulmonary edema induced by LPS, as well as contents of IL-1β, TNF-α and IL-8. The pulmonary microvascular permeability and 66.7 % hydrogen on the expression of sirt1 and its downstream signaling molecules were tested. Results showed that 66.7 % hydrogen alleviated lung pathological changes and pulmonary edema caused by LPS, and reduced the degree of ALI by inhibiting pro-inflammatory cytokine release and oxidative stress response, thereby decreasing the expression of molecules related to intercellular adhesion. sirt1 contributed to the repair of LPS-induced ALI by hydrogen through the regulation of NF-κB and catalase expression. In conclusion, 66.7 % hydrogen protected against LPS-induced ALI by suppressing inflammatory response and oxidative stress mediated by NF-κB and catalase in a sirt1-dependent manner.

Astragaloside IV Protects from PM2.5-Induced Lung Injury by Regulating Autophagy via Inhibition of PI3K/Akt/mTOR Signaling in vivo and in vitro

Introduction

Prolonged exposure to air polluted with airborne fine particulate matter (PM2.5) can increase respiratory disease risk. Astragaloside IV (AS-IV) is one of the main bioactive substances in the traditional Chinese medicinal herb, Astragalus membranaceus Bunge. AS-IV has numerous pharmacological properties; whereas there are few reports on the prevention of PM2.5-induced lung injury by AS-IV through modulation of the autophagic pathway. This study aimed to investigate the protective effects and the underlying mechanisms of AS-IV in PM2.5-induced lung injury rats and rat alveolar macrophages (NR8383 cells).

Methods

The pneumotoxicity model was established by intratracheal injection of PM2.5 in rats, and PM2.5 challenge in NR8383 cells. The severity of lung injury was evaluated by wet weight to dry weight ratio and McGuigan pathology scoring. Inflammatory factors and oxidative stress were detected through ELISA. The expressions of p-PI3K, p-Akt, and p-mTOR proteins were analyzed by immunohistochemistry. Immunofluorescence and transmission electron microscopy were used to detect autophagosomes. The expressions of autophagy marker protein (LC3B and p62), PI3K/Akt/mTOR signaling and NF-κB translocation were detected by Western blot in lung tissue and NR8383 cells.

Results

After PM2.5 stimulation, rats showed severe inflammation and oxidative stress, along with inhibition of autophagy in lung tissue. AS-IV not only decreased pulmonary inflammation and oxidative stress by inhibiting nuclear factor kappa B translocation, but also regulated autophagy by inhibiting PI3K/Akt/mTOR signaling. After treatment with 3-methyladenine (a classic PI3K inhibitor, blocking the formation of autophagosomes), the protective effect of AS-IV on PM2.5-induced lung injury was further strengthened. In parallel, using Western blot, immunohistochemistry, and transmission electron microscopy, we demonstrated that AS-IV restore autophagic flux mainly through regulating the degradation of autophagosomes rather than suppressing the formation in vivo and in vitro.

Conclusion

Our data indicated that AS-IV protects from PM2.5-induced lung injury in vivo and in vitro by inhibiting the PI3K/Akt/mTOR pathway to regulate autophagy and inflammation.

Aerobic exercise ameliorates particulate matter-induced lung injury in aging rats

Particulate matter 2.5 (PM_2.5) is an inflammatory-inducing factor that is considered to be related to many adverse respiratory problems, especially in the elderly. This study aimed to examine whether pre-exercise training could prevent pulmonary injury induced by urban PM_2.5 in aging rats and investigate its relationship with inflammatory pathways. Male Wistar rats (aged 16 months) were randomly divided into four groups: sedentary, exercise, sedentary + PM_2.5 exposure, and exercise + PM_2.5 exposure. All rats in exercise-related groups were treadmill-trained for 8 weeks (65%-75% VO_2max for 30 min every other day). Sedentary groups' rats lived freely in cages without exercise intervention. Rats in the PM-related groups were exposed to ambient PM_2.5 (4 h day^-1) for 2 weeks after an 8-week exercise intervention or sedentary treatment. Finally, all rats' pulmonary function, lung morphology, degree of inflammation, and relevant protein and mRNA transcript expression levels were examined. The results indicated that PM_2.5 exposure induced lung injury in the sedentary + PM_2.5 exposure group, as evidenced by the deterioration of pulmonary function, histopathological characteristics, and inflammatory changes. Aerobic exercise alleviated PM_2.5-induced airway obstruction, deterioration of pulmonary function, bronchial mucosal exfoliation, and inflammatory responses in aging rats. These effects in exercise groups were associated with the increased expression of intracellular 70 kDa heat shock protein (iHSP70) and the suppression of nuclear transcription factor-κB (NF-κB) activation, as confirmed by increased expression of inhibitor of NF-κB (IκBα) and a reduction in phospho-IKBα (p-IκBα), which is regulated by inhibiting kappa B kinase beta (IKKβ). Taken together, aerobic pre-exercise had protective effects on lung injury and reduced vulnerability to inflammation induced by PM_2.5 exposure, possibly through the toll-like receptor 4 (TLR4)/NF-κB signaling pathways mediated by the extracellular-to-intracellular HSP70 ratio. Pre-exercise training may be an effective way to protect against PM_2.5-induced lung toxicity in aging individuals.

lncRNA Gm16410 Mediates PM2.5-Induced Macrophage Activation via PI3K/AKT Pathway

PM₂.₅ refers to atmospheric particulate matters with a diameter of less than 2.5 μm. The deposit of PM₂.₅ in lung cells can cause oxidative stress, leading to changes in macrophage polarity, which can subsequently cause pulmonary inflammation. Long-chain non-coding RNA (lncRNA) is a class of transcripts that regulate biological processes through multiple mechanisms. However, the role of lncRNA in PM₂.₅-induced lung inflammation has not been established. In this study, the biological effects and associated mechanism of lncRNA in PM₂.₅-induced change in macrophage polarity were investigated. The lncRNA-mediated PM₂.₅-induced macrophage inflammation and lung inflammation-associated injury were also determined. Mice were exposed to chronic levels of PM₂.₅, and changes in the expression of lncRNA in the lung were measured by lncRNA microarray. lncRNAs that showed significant changes in expression in response to PM₂.₅ were identified. lncRNA showing the biggest change was subjected to further analysis to determine its functional roles and mechanisms with respect to macrophage activation. The result showed that a significant reduction in expression of one lncRNA, identified as lncGm16410, was observed in the lung of mice and RAW264.7 cells following exposure to PM₂.₅. lncGm16410 suppressed PM₂.₅-induced macrophage activation via the SRC protein-mediated PI3K/AKT signaling pathway. PM₂.₅ promoted lung inflammation by downregulating the expression of lncGm16410, enhancing the activation of macrophages. Thus, lncGm16410 might provide new insight into the prevention of PM₂.₅ injury.

Fine particulate matter increases airway hyperresponsiveness through kallikrein-bradykinin pathway

Epidemiological studies have reported short-term fine particulate matter (PM2.5) exposure to increase incidence of asthma, related to the increase of airway hyperresponsiveness (AHR); however, the underlying mechanism remains unclear. Aim of this study was to elucidate the role of kallikrein in PM2.5-induced airway hyperresponsiveness and understand the underlying mechanism. Nose-only PM2.5 exposure system was used to generate a mouse model of airway hyperresponsiveness. Compared with the control group, PM2.5 exposure could significantly increase airway resistance, lung inflammation, kallikrein expression of bronchi-lung tissue and bradykinin (BK) secretion. However, these changes could be alleviated by kallikrein inhibitor. In addition，PM2.5 could increase the viability of human airway smooth muscle cells (hASMCs), accompanied by increased expression of kallikrein 14 (Klk14), bradykinin 2 receptor (B2R), bradykinin secretion and cytosol calcium level, while kallikrein 14 gene knockdown could significantly amelioratethe above response induced by PM2.5. Taken together, the data suggested kallikrein to play a key role in PM2.5-induced airway hyperresponsiveness, and that it could be a potential therapeutic target in asthma.