PM2.5 induces autophagy-mediated cell death via NOS2 signaling in human bronchial epithelium cells

Airborne particulate matter (PM2.5) triggers ocular hypertension and glaucoma through pyroptosis

Background

Particulate matter (PM) is strongly linked to human health and has detrimental effects on the eye. Studies have, however, focused on the ocular surface, with limited research on the impact of PM_2.5 on intraocular pressure (IOP).

Methods

To investigate the impact of PM_2.5 on IOP and the associated mechanism, C57BL/6 mouse eyes were topically exposed to a PM_2.5 suspension for 3 months, and human trabecular meshwork (HTM) cells were subjected to various PM_2.5 concentrations in vitro. Cell viability, NLRP3/caspase-1, IL-1β, and GSDMD expression, reactive oxygen species (ROS) production and cell contractility were measured by western blot, ELISA, cell counting kit-8, ROS assay kit or a cell contractility assay. ROS scavenger N-acetyl-L-cysteine (NAC) and caspase-1 inhibitor VX-765 were used to intervene in PM_2.5-induced damages.

Results

The results revealed that the IOP increased gradually after PM_2.5 exposure, and upregulations of the NLRP3 inflammasome, caspase-1, IL-1β, and GSDMD protein levels were observed in outflow tissues. PM_2.5 exposure decreased HTM cell viability and affected contraction. Furthermore, elevated ROS levels were observed as well as an activation of the NLRP3 inflammasome and downstream inflammatory factors caspase-1 and IL-1β. NAC improved HTM cell viability, inhibited the activation of the NLRP3 inflammasome axis, and HTM cell contraction by scavenging ROS. VX-765 showed similar protection against the PM_2.5 induced adverse effects.

Conclusion

This study provides novel evidence that PM_2.5 has a direct toxic effect on intraocular tissues and may contribute to the initiation and development of ocular hypertension and glaucoma. This occurs as a result of increased oxidative stress and the subsequent induction of NLRP3 inflammasome mediated pyroptosis in trabecular meshwork cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00403-4.

SARS-CoV-2 infection, COVID-19 pathogenesis, and exposure to air pollution: What is the connection?

Exposure to air pollutants has been previously associated with respiratory viral infections, including influenza, measles, mumps, rhinovirus, and respiratory syncytial virus. Epidemiological studies have also suggested that air pollution exposure is associated with increased cases of SARS-CoV-2 infection and COVID-19-associated mortality, although the molecular mechanisms by which pollutant exposure affects viral infection and pathogenesis of COVID-19 remain unknown. In this review, we suggest potential molecular mechanisms that could account for this association. We have focused on the potential effect of exposure to nitrogen dioxide (NO2 ), ozone (O3 ), and particulate matter (PM) since there are studies investigating how exposure to these pollutants affects the life cycle of other viruses. We have concluded that pollutant exposure may affect different stages of the viral life cycle, including inhibition of mucociliary clearance, alteration of viral receptors and proteases required for entry, changes to antiviral interferon production and viral replication, changes in viral assembly mediated by autophagy, prevention of uptake by macrophages, and promotion of viral spread by increasing epithelial permeability. We believe that exposure to pollutants skews adaptive immune responses toward bacterial/allergic immune responses, as opposed to antiviral responses. Exposure to air pollutants could also predispose exposed populations toward developing COIVD-19-associated immunopathology, enhancing virus-induced tissue inflammation and damage.

Airway hyperresponsiveness development and the toxicity of PM2.5

Airway hyperresponsiveness (AHR) is characterized by excessive bronchoconstriction in response to nonspecific stimuli, thereby leading to airway stenosis and increased airway resistance. AHR is recognized as a key characteristic of asthma and is associated with significant morbidity. At present, many studies on the molecular mechanisms of AHR have mainly focused on the imbalance in Th1/Th2 cell function and the abnormal contraction of airway smooth muscle cells. However, the specific mechanisms of AHR remain unclear and need to be systematically elaborated. In addition, the effect of air pollution on the respiratory system has become a worldwide concern. To date, numerous studies have indicated that certain concentrations of fine particulate matter (PM2.5) can increase airway responsiveness and induce acute exacerbation of asthma. Of note, the concentration of PM2.5 does correlate with the degree of AHR. Numerous studies exploring the toxicity of PM2.5 have mainly focused on the inflammatory response, oxidative stress, genotoxicity, apoptosis, autophagy, and so on. However, there have been few reviews systematically elaborating the molecular mechanisms by which PM2.5 induces AHR. The present review separately sheds light on the underlying molecular mechanisms of AHR and PM2.5-induced AHR.

Autophagy attenuates particulate matter 2.5-induced damage in HaCaT cells

Background

Keratinocyte is a key component of the skin barrier and maintains skin homeostasis. As an environmental pathogenic factor, PM2.5 can cause epidermal cell damage, but the mechanism remains to be elucidated. The present study aimed to evaluate the effect caused by PM2.5 in HaCaT cells and investigate the underlying mechanisms.

Methods

HaCaT cells were treated with PM2.5 for 12 h or 24 h, either alone or combined with UVB irradiation. A Cell Counting Kit (CCK-8) assay was carried out to detect the effect of PM2.5 on HaCaT cell viability. Flow cytometry, Western Blot, and AO staining were employed to detect the changes of apoptosis and autophagy. The changes of cytotoxicity and apoptosis in HaCaT cells were analyzed by CCK-8 and flow cytometry after pretreatment with autophagy inhibitor 3-MA.

Results

The results showed that PM2.5 induced cytotoxicity by increasing cell apoptosis and activating autophagy. Apoptosis was determined to be increased significantly after autophagy inhibition. Moreover, solar radiation intensified PM2.5-induced damage in HaCaT cells, which further enhanced the autophagy. However, there was no significant difference in apoptosis after inhibition of autophagy in combined treatment.

Conclusions

Our data reveals that PM2.5 induces damage in HaCaT cells, and autophagy plays a protective role to promote cell survival.

PM2.5-related cell death patterns

With the increasingly serious problem of environmental pollution, the health problems caused by PM2.5 are gradually coming into our line of sight. Previous researches have indicated that air pollution is nearly related to various diseases, but few studies have focused on the exact function mediated by particulate matter less than 2.5 (PM2.5) in these diseases. PM2.5 is known to induce multiple ways of cell death, including autophagy, necrosis, apoptosis, pyroptosis and ferroptosis. Therefore, it is of much importance to understand the different ways of cell death caused by PM2.5 in the pathogenesis and treatment of PM2.5-related diseases. This present review is an insight of multiple ways of PM2.5‑induced cell death in different diseases.

microRNA-146a-5p negatively modulates PM2.5 caused inflammation in THP-1 cells via autophagy process

Ambient fine particulate matter (PM_2.5) can change the expression profile of microRNAs (miRs), which may play important roles in mediating inflammatory responses. The present study attempts to investigate the roles of miR-146a-5p in regulating cytokine expression in a human monocytic leukemia cell line (THP-1). Four types of PM_2.5 extracts obtained from Beijing, China, were subjected to cytotoxic tests in THP-1 cells. These four PM_2.5 extracts included two water extracts collected from non-heating and heating season (WN and WH), and two organic extracts from non-heating and heating season (DN and DH). Firstly, the four PM_2.5 extracts caused cytotoxicity, oxidative stress responses, cytokine gene expressions and interleukin 8 (IL-8) release in THP-1 cells, with WH showing the highest cytotoxicity, WN showing the highest oxidative stress and inflammatory responses. Additionally, we observed expression of miR-146a-5p was significantly increased, with the maximal response of six folds in WN group. Cellular autophagy was initiated by PM_2.5 indicated by related protein and gene expressions. Both RNA interference and autophagy inhibitor were applied to interrupt autophagy process in THP-1 cells. Autophagy dysfunction could alleviate IL-8 expression, suggesting autophagy process regulated cytokine expression and inflammatory response caused by PM_2.5. A chemical inhibitor was applied to inhibit the function of miR-146a-5p, and then the expressions of IL-8 and autophagic genes were significantly aggravated. Meanwhile, two target genes of miR-146a-5p, interleukin-1 associated-kinase-1 (IRAK1) and tumor-necrosis factor receptor-associated factor-6 (TRAF6) were increased dramatically, which also played important roles in regulation of autophagy. These data suggested miR-146a-5p negatively modulated cytokine expression caused by PM_2.5 via autophagy process through the target genes of IRAK1 and TRAF6. Our findings raised the concerns of the changes of miR expression profile and following responses caused by PM_2.5.

PM2.5 induces autophagy-mediated cell apoptosis via PI3K/AKT/mTOR signaling pathway in mice bronchial epithelium cells

Air pollution can highly impact the respiratory system in healthy individuals. Studies have indicated that particles with an aerodynamic diameter of ≤2.5 µm (PM2.5) can be considered to be harmful for lung alveoli and bronchial epithelium cells. PM2.5 can be directly inhaled and can deeply penetrate into the lung alveoli, causing lung dysfunction. However, the toxicological mechanism mediated by PM2.5 for respiratory disease has still not been clearly determined. The purpose of the current study was to investigate the effects of PM2.5 on mouse bronchial epithelium cells (MBECs) and explored the possible mechanism mediated by PM2.5 in MBECs. The results of the current study indicated that PM2.5 markedly decreased lung function, including total lung capacity, residual volume, vital capacity and airway resistance in experimental mice. The results demonstrated that PM2.5 markedly induced inflammatory responses, oxidative injury and MBEC apoptosis. PM2.5 increased interleukin (IL)-1β and IL-6 expression, and reactive oxygen species production in MBECs. Furthermore, PM2.5 specifically induced PI3K, AKT and mTOR expression in MBECs. Disruption of PI3K/AKT/mTOR signaling was also indicated to effectively inhibit apoptosis of MBECs. In conclusion, the results of the current study systematically demonstrated the role of apoptosis-mediated MBEC apoptosis in PM2.5-treated mice, and provides a potential strategy for preclinical intervention in patients with PM2.5-induced lung diseases.

Identification of Toxicity Parameters Associated with Combustion Produced Soot Surface Chemistry and Particle Structure by in Vitro Assays

Air pollution has become the world's single biggest environmental health risk of the past decade, causing millions of yearly deaths worldwide. One of the dominant air pollutants is fine particulate matter (PM2.5), which is a product of combustion. Exposure to PM2.5 has been associated with decreased lung function, impaired immunity, and exacerbations of lung disease. Accumulating evidence suggests that many of the adverse health effects of PM2.5 exposure are associated with lung inflammation and oxidative stress. While the physical structure and surface chemistry of PM2.5 are surrogate measures of particle oxidative potential, little is known about their contributions to negative health effects. In this study, we used functionalized carbon black particles as surrogates for atmospherically aged combustion-formed soot to assess the effects of PM2.5 surface chemistry in lung cells. We exposed the BEAS-2B lung epithelial cell line to different soot at a range of concentrations and assessed cell viability, inflammation, and oxidative stress. Our results indicate that exposure to soot with varying particle surface composition results in differential cell viability rates, the expression of pro-inflammatory and oxidative stress genes, and protein carbonylation. We conclude that particle surface chemistry, specifically oxygen content, in soot modulates lung cell inflammatory and oxidative stress responses.

Transcriptomic profiling of human corneal epithelial cells exposed to airborne fine particulate matter (PM2.5)

PURPOSE

To explore the molecular mechanisms of PM_2.5-induced dysfunction in human corneal epithelial cells (HCECs) and the potential role of the plasminogen activator inhibitor type-2 (PAI-2) in PM_2.5-induced autophagy in vitro and in vivo.

METHODS

RNA-Seq was performed to identify the differentially expressed genes (DEGs) in PM_2.5-exposed HCECs compared to unexposed condition, followed by validation via real-time PCR (qRT-PCR). Corneal fluorescein staining and tear secretion were assessed in the PM_2.5-exposed rat model. The expression of PAI-2 and autophagy-related markers were examined via immunoblotting, immunofluorescence staining and/or qRT-PCR in PM_2.5-exposed or unexposed HCECs and rat corneas. PAI-2-knockdown HCECs were generated to study PAI-2's role in the PM_2.5-induced autophagy in HCECs.

RESULTS

A total of 434 DEGs-240 up-regulated and 194 down-regulated-were identified in PM_2.5-exposed HCECs rather than unexposed HCECs. The expression of a few genes related to proliferation, inflammation, and aryl hydrocarbon stimulation were significantly altered by PM_2.5 exposure. PAI-2 expression was up-regulated in PM_2.5-exposed HCECs, sharing a similar fluctuation trend with autophagy-related markers LC3B II and BECN1 according to various exposure periods. Moreover, PAI-2 knockdown significantly suppressed the expression of LC3B and BECN1 in PM_2.5-exposed HCECs. The corneal fluorescein staining was enhanced and tear secretion was significantly reduced in PM_2.5-exposed rat eyes. PAI-2 expression was also increased in PM_2.5-exposed rat corneas, together with the up-regulation of several autophagy-related markers.

CONCLUSION

The present study identified the altered expression of hundreds of genes in PM_2.5-exposed HCECs, which suggests the importance of PM_2.5 for cornea health. The involvement of PAI-2 was discovered in the PM_2.5-induced autophagy in HCECs as well as likely in rat corneas, which implied that PAI-2 may become a potential target of clinical treatment of PM_2.5-associated ocular surface diseases.

PM2.5 induces autophagy and apoptosis through endoplasmic reticulum stress in human endothelial cells

Endothelial cells integrally form a crucial interface that maintains homeostasis of the cardiovascular system. As a vulnerable target of PM2.5, the underlying mechanisms of endothelial cell damage have yet to be fully elucidated. In the current study, two types of cell death, including autophagy and apoptosis, and an important organelle of the endoplasmic reticulum (ER) were focalized following PM2.5 exposure. As a result, the internalization of PM2.5 has the ability to induce excess ER stress, which is a crucial step for further autophagy and apoptosis in human endothelial cells, as confirmed by the pre-treatment with the inhibitor of ER stress (4-PBA) which effectively mitigates the apoptosis rate and LC3II expression. Intriguingly, crosstalk between ER stress and autophagy demonstrated that ER stress is probably involved in autophagic events, whereas autophagy has no significant effect on ER stress but confer a protective role against PM2.5-induced endothelial cell apoptosis. Moreover, PM2.5 results in blockage of autophagic flux (failed fusion between autophagosomes and lysosomes), which is detrimental to endothelial cell survival. In conclusion, our findings provide a valuable insight into the relation between autophagy and apoptosis under PM2.5-induced ER stress conditions, where the interplay between them ultimately determines cell fate.

Brain lipid profiles in the spontaneously hypertensive rat after subchronic real-world exposure to ambient fine particulate matter

Recent studies have illustrated an association between ambient fine particulate matter (PM_2.5) exposure and neuronal toxicity in epidemiological studies and animal models. However, the possible molecular effects on brains under real-world exposure to PM_2.5 remain unclear. In this pilot study, male spontaneously hypertensive rats were whole-bodily exposed to ambient air from the outdoor environment of Taipei City for 3 months, while the control rats inhaled HEPA-filtered air. The PM_2.5-induced phosphatidylcholine and sphingomyelin profiles in the hippocampus, cortex, medulla, cerebellum, and olfactory bulb were assessed by mass spectrometry (MS)-based lipidomics. Partial least squares discriminant analysis (PLS-DA) and the Wilcoxon rank sum test were used to examine the lipid changes between the exposed and control groups. The PLS-DA models showed that phosphatidylcholine and sphingomyelin profiles of the PM_2.5 exposure group were different from those of the control group in each brain region except the cortex. More lipid changes were found in the hippocampus, while fewer lipid changes were observed in the olfactory bulb. The lipid alteration in the hippocampus may strengthen membrane integrity, modulate signaling pathways, and avoid accumulation of lipofuscin to counter the PM_2.5-induced stress. The lipid changes in the cortex and medulla may respond to PM_2.5-induced injury and inflammation; while the lipid changes in the cerebellum were associated with neuron protection. This study suggests that the MS-based lipidomics is a powerful approach to discriminate the brain lipid profiles even at the environmental level of ambient PM_2.5 and has the potential to suggest possible adverse health effects in long-term PM_2.5 exposure studies.

PM2.5 exposure induces vascular dysfunction via NO generated by iNOS in lung of ApoE-/- mouse

PM2.5 exposure exacerbates cardiovascular diseases via oxidative stress and inflammation, the detailed mechanism of which is unclear. In this study, the effects of oxidative stress and inflammation, as well as vascular structure and function were studied by multiple PM2.5 exposure model of ApoE-/- mice. The results indicated that NO produced by iNOS not cNOS might play important roles in inducing vascular dysfunction after PM2.5 exposure. The occurrence order and causality among NO, other oxidative stress indicators and inflammation is explored by single PM2.5 exposure. The results showed that NO generated by iNOS occurred earlier than that of other oxidative stress indicators, which was followed by the increased inflammation. Inhibition of NOS could effectively block the raise of NO, oxidative stress and inflammation after PM2.5 exposure. All in all, we firstly confirmed that NO was the initiation factor of PM2.5 exposure-induced oxidative stress, which led to inflammation and the following vascular dysfunction.

Environmental Exposures and Asthma Development: Autophagy, Mitophagy, and Cellular Senescence

Environmental pollutants and allergens induce oxidative stress and mitochondrial dysfunction, leading to key features of allergic asthma. Dysregulations in autophagy, mitophagy, and cellular senescence have been associated with environmental pollutant and allergen-induced oxidative stress, mitochondrial dysfunction, secretion of multiple inflammatory proteins, and subsequently development of asthma. Particularly, particulate matter 2.5 (PM2.5) has been reported to induce autophagy in the bronchial epithelial cells through activation of AMP-activated protein kinase (AMPK), drive mitophagy through activating PTEN-induced kinase 1(PINK1)/Parkin pathway, and induce cell cycle arrest and senescence. Intriguingly, allergens, including ovalbumin (OVA), Alternaria alternata, and cockroach allergen, have also been shown to induce autophagy through activation of different signaling pathways. Additionally, mitochondrial dysfunction can induce cell senescence due to excessive ROS production, which affects airway diseases. Although autophagy and senescence share similar properties, recent studies suggest that autophagy can either accelerate the development of senescence or prevent senescence. Thus, in this review, we evaluated the literature regarding the basic cellular processes, including autophagy, mitophagy, and cellular senescence, explored their molecular mechanisms in the regulation of the initiation and downstream signaling. Especially, we highlighted their involvement in environmental pollutant/allergen-induced major phenotypic changes of asthma such as airway inflammation and remodeling and reviewed novel and critical research areas for future studies. Ultimately, understanding the regulatory mechanisms of autophagy, mitophagy, and cellular senescence may allow for the development of new therapeutic targets for asthma.

Resveratrol alleviates chronic "real-world" ambient particulate matter-induced lung inflammation and fibrosis by inhibiting NLRP3 inflammasome activation in mice

BACKGROUND

Inhalation of fine particulate matter (PM_2.5) induces the occurrence of lung inflammation and fibrosis, but its molecular mechanism remains unclear. Resveratrol (RES) is known to have anti-inflammatory properties in many pulmonary diseases. Here, we aimed to investigate the effect of long-term "real-world" ambient PM exposure on lung inflammation and fibrosis and further explore the protective effect and mechanism of RES.

METHODS AND RESULTS

RES (50 and 100 mg/kg.bw) was administered to C57BL/6J mice that were exposed to ambient PM for 5 months. The control group breathed filtered air without RES, and the PM group was exposed to PM without RES. The inflammatory cytokine levels in bronchoalveolar lavage fluid (BALF) and lung fibrosis were evaluated by enzyme-linked immune sorbent assay (ELISA) kits and Masson's trichrome staining. The real-time PCR and Western blot analysis were used to determine the signal pathway. In vivo, PM exposure markedly elevated the levels of inflammatory cytokines and TGF-β1 in BALF, induced lung fibrosis. Meanwhile, PM exposure triggered autophagy process and activated the nucleotide-binding domain and leucine-rich repeat protein 3 (NLRP3) inflammasome in lung. Also, RES treatment abolished PM-induced lung inflammation and fibrosis, and inhibited autophagic process and NLRP3 inflammasome activation. In vitro, PM_2.5-induced cytotoxicity in BEAS-2B cells dose-dependently. Besides, RES alleviated PM_2.5-induced cytotoxicity, inhibited autophagic process and NLRP3 inflammasome activity and decreased IL-1β production in BEAS-2B cells.

CONCLUSION

Long-term PM exposure induced lung inflammation and fibrosis, and RES intervention alleviated these adverse effects via inhibiting autophagy-related NLRP3 inflammasome activation.

PM2.5-induced ADRB2 hypermethylation contributed to cardiac dysfunction through cardiomyocytes apoptosis via PI3K/Akt pathway

BACKGROUND

Long-term exposure to fine particulate matter (PM_2.5) can causally contribute to progression of atherosclerosis, risk of ischemic heart disease and death, but the underlying mechanism is little known. Since DNA methylation impacts the process of heart disease, it might be useful in exploring potential mechanistic pathways linking PM_2.5 exposure and heart disease.

OBJECTIVES

Here, we investigated the PM_2.5-induced ADRB2 hypermethylation and the involving epigenetic mechanism of PM_2.5-induced cardiomyocytes apoptosis and cardiac dysfunction.

METHODS AND RESULTS

In vitro, PM_2.5 markedly augmented cardiotoxicity including oxidative damage and apoptosis in cardiomyocytes AC16 as well as epigenetic alteration. DNA methylation profiling revealed a significant gene-ADRB2 was involved in the cardiac relative GO and KEGG pathways. Methylation chip and Bisulfite Sequencing PCR (BSP) both identified the hypermethylation status of ADRB2 which encodes β2-Adrenergic receptor (β2AR). Mechanistic study showed ADRB2 hypermethylation-induced down-regulation of β2AR inhibited PI3K/Akt and then activated Bcl-2/BAX and p53 pathway in AC16. The transgenic cell lines showed over-expression of ADRB2 weakened the PM_2.5-induced cardiomyocytes apoptosis in opposite way, but was augmented by PI3K inhibitor (LY294002). In vivo, echocardiography showed the heart contractile function was decreased after SD rats intratracheal instillation of PM_2.5 for 30 days. The myocardial interstitial edema, myocardial gap expansion and myofibril disorder in PM_2.5 treated group were observed in rats heart tissue. What's more, basal expression of β2AR and VEGFR2 decreased in heart tissue as the dosage of PM_2.5 increasing, meanwhile PM_2.5 markedly attenuated PI3K/Akt pathway followed by augmented Bcl-2/BAX and p53 pathway, thus caused a greater number of TUNEL positive cardiomyocytes resulted in cardiac dysfunction in vivo.

CONCLUSIONS

PM_2.5 exposure could cause the myocardial ADRB2 hypermethylation and activate the β2AR/PI3K/Akt pathway, resulted in PM_2.5-induced cardiomyocytes apoptosis and cardiac dysfunction. Our study suggested that the ADRB2 demethylation or ADRB2/β2AR activation may serve as a potential pathway to prevent cardiac dysfunction induced by PM_2.5 exposure.

Extracellular vesicles degradation pathway based autophagy lysosome pathway

As an ancient intracellular degradation pathway, the autophagy lysosome pathway exists in various cells continuously and stably and maintains cellular homeostasis by degrading damaged organelles and misfolded proteins that are prejudicial to cells. Extracellular vesicles (EVs) including microparticles and exosomes, are derived from varieties of mammalian tissue cells such as platelets, endothelial cells, cardiomyocytes. Through large quantity of active substances carried by EVs, EVs exert momentous biological functions. Recent researches have revealed the molecular mechanism of the interaction between extracellular vesicles and autophagy. In this review, we first elaborate that extracellular vesicles are identified and internalized by target cells by means of receptor-ligand. Since extracellular vesicles contain multiple functional molecules, we subsequently describe the process of intracellular autophagy pathway induced by extracellular vesicles, which activates autophagy-related pathways or delivers autophagy-associated molecules. Finally, we introduced the effects of extracellular vesicle-induced autophagy on extracellular vesicles and target cells respectively. In conclusion, this article integrates relevant theoretical knowledge of autophagy caused by extracellular vesicles and provides a new direction for the study of extracellular vesicles in the future.

Modifications of autophagy influenced the Alzheimer-like changes in SH-SY5Y cells promoted by ultrafine black carbon

Ambient ultrafine black carbon (uBC) can potentially cross blood-brain barrier, however, very little is currently known about the effects they may have on central nervous system. This study aimed to explore the roles of autophagy in Alzheimer-like pathogenic changes promoted by uBC in SH-SY5Y cells. We firstly found uBC could cause cytotoxicity and oxidative stress in SH-SY5Y cells. Additionally we found uBC initiated progressive development of Alzheimer's disease (AD) associated features, mainly including neuro-inflammation and phosphorylation of tau protein (p-Tau) accumulation. Meanwhile, autophagy process was activated by uBC probably through phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway. RNA interference and autophagosome-lysosome fusion inhibitor were applied to block autophagy process at different stages. Autophagy dysfunction at the initial membrane expansion stage could aggravate p-Tau accumulation and other Alzheimer-like changes in SH-SY5Y cells promoted by uBC. However, autophagy inhibition at the final stage could alleviate p-Tau accumulation caused by uBC. This suggested that inhibition of the infusion of autophagosome and lysosome could possibly activate ubiquitination degradation pathway to regulate p-Tau equilibrium in SH-SY5Y cells. Our findings further raise the concerns about the effects of uBC on the risk of AD and indicate potential roles of autophagy in early Alzheimer-like pathogenic changes caused by ambient uBC.

PM2.5 Exposure Induces More Serious Apoptosis of Cardiomyocytes Mediated by Caspase3 through JNK/ P53 Pathway in Hyperlipidemic Rats

Exposure to airborne particulate matter with an aerodynamic diameter less than or equivalent to 2.5 microns (PM_2.5) easily induces acute myocardial infarction in populations with high-risk cardiovascular diseases such as hyperlipidemia, but its mechanism remains unclear. In this study, hyperlipidemic rats were used to examine the effects of PM_2.5 exposure on the cardiovascular system and the mechanism for its induction of cardiovascular events. We found that PM_2.5 exposure resulted in bigger changes in the myocardial enzyme profile (cTnI, LDH, CK, CK-MB) in hyperlipidemic rats than that of control rats, as well as a significant increase in the C-reactive protein (CRP) level and a decrease in the superoxide dismutase (SOD) activity. It promoted a hypercoagulable state, significantly increased blood pressure and heart rate, while decreased the variability of heart rate in hyperlipidemic rats. In addition, pathological test showed that PM_2.5 exposure more easily deteriorated myocardial injury in hyperlipidemic rats. It upregulated the phosphorylation levels of myocardial c-Jun NH2-terminal kinase (JNK) and P53, resulting in the elevated expression of downstream effector protein Bax and the decreased expression of Bcl-2, and then increased caspase3 level leading to cardiomyocyte apoptosis, while little change of caspase2 was observed. Taken together, PM_2.5 exposure induced more serious inflammation and oxidative stress in the circulation system of hyperlipidemic rats, promoted a hypercoagulable state and triggered cardiomyocyte apoptosis, in which JNK/P53 pathway played a key role.