Airborne particulate matter (PM2.5) triggers cornea inflammation and pyroptosis via NLRP3 activation

Diesel exhaust exposure induced squamous metaplasia of corneal epithelium via yes-associated protein activation

Atmospheric pollution has been demonstrated to be associated with ocular surface diseases characterized by corneal epithelial damage, including impaired barrier function and squamous metaplasia. However, the specific mechanisms underlying the impact of atmospheric pollution on corneal damage are still unknow. To address this gap in knowledge, we conducted a study using a whole-body exposure system to investigate the detrimental effects of traffic-related air pollution, specifically diesel exhaust (DE), on corneal epithelium in C57BL/6 mice over a 28-day period. Following DE exposure, the pathological alterations in corneal epithelium, including significant increase in corneal thickness and epithelial stratification, were observed in mice. Additionally, exposure to DE was also shown to disrupt the barrier functions of corneal epithelium, leading to excessive proliferation of basal cells and even causing squamous metaplasia in corneal epithelium. Further studies have found that the activation of yes-associated protein (YAP), characterized by nuclear translocation, may play a significant role in DE-induced corneal squamous metaplasia. In vitro assays confirmed that DE exposure triggered the YAP/β-catenin pathway, resulting in squamous metaplasia and destruction of barrier functions. These findings provide the preliminary evidence that YAP activation is one of the mechanisms of the damage to corneal epithelium caused by traffic-related air pollution. These findings contribute to the knowledge base for promoting eye health in the context of atmospheric pollution.

The association between airborne particulate matter (PM2.5) exposure level and primary open-angle glaucoma

The eye is vulnerable to the adverse effects of air pollution. Previous experimental study found that fine particulate matter (PM2.5) had a direct toxic effect on intraocular tissues. However, clinical evidence for the impact of air pollutants exposure on functional and structural changes in glaucoma remains scarce. A total of 120 patients with primary open-angle glaucoma (POAG) who met the inclusion criteria were included in this retrospective study. The standardized ophthalmic examination, such as intraocular pressure (IOP), visual field, optical coherence tomography, and comprehensive physical examination, were performed. The air pollution data, including PM2.5 concentration and air quality index (AQI), were collected. PM2.5 and AQI for the day of the medical examination, as well as one month, and three months before the medical examination date, were investigated. In our results, higher average exposure levels for one-month and three-month, were associated with increased IOP (r=0.229, P=0.013; r=0.204, P=0.028, respectively) and decreased visual field mean sensitivity (MS) (r=-0.212, P=0.037; r=-0.305, P=0.002, respectively). PM2.5 concentrations for the day of the medical examination was not significantly associated with ocular parameters. In multiple linear regression analysis adjusted for demographic and clinical factors, higher PM2.5 exposure for one month was associated with elevated IOP (P=0.040, β=0.173, 95 %CI=0.008-0.337). We also found an association between PM2.5 and MS (one-month exposure: β=-0.160, P=0.029; three-month exposure: β=-0.238, P=0.002). The logistic regression analysis found that three-month average PM2.5 exposure level was significantly associated with the disease severity (β=0.043, P=0.025, 95 %CI=1.005-1.084). In conclusion, this study is the first to investigate the relationship between air pollution and detailed ocular parameters of POAG patients in Shanghai over a three-year period, and to explore the effects of different exposure times of PM2.5 on glaucoma. This study found that PM2.5 exposure was correlated with elevated IOP and decreased MS. The one-month PM2.5 exposure level had the most significant effects on IOP. The three-month PM2.5 exposure level was an independent risk factor for POAG severity. Current evidence suggests there may be an association between PM2.5 exposure and POAG.

The effects of fine particulate matter on the blood-testis barrier and its potential mechanisms

With the rapid expansion of industrial scale, an increasing number of fine particulate matter (PM2.5) has bringing health concerns. Although exposure to PM2.5 has been clearly associated with male reproductive toxicity, the exact mechanisms are still unclear. Recent studies demonstrated that exposure to PM2.5 can disturb spermatogenesis through destroying the blood-testis barrier (BTB), consisting of different junction types, containing tight junctions (TJs), gap junctions (GJs), ectoplasmic specialization (ES) and desmosomes. The BTB is one of the tightest blood-tissue barriers among mammals, which isolating germ cells from hazardous substances and immune cell infiltration during spermatogenesis. Therefore, once the BTB is destroyed, hazardous substances and immune cells will enter seminiferous tubule and cause adversely reproductive effects. In addition, PM2.5 also has shown to cause cells and tissues injury via inducing autophagy, inflammation, sex hormones disorder, and oxidative stress. However, the exact mechanisms of the disruption of the BTB, induced by PM2.5, are still unclear. It is suggested that more research is required to identify the potential mechanisms. In this review, we aim to understand the adverse effects on the BTB after exposure to PM2.5 and explore its potential mechanisms, which provides novel insight into accounting for PM2.5-induced BTB injury.

Impact of inflammasomes on the ocular surface

PURPOSE OF REVIEW

The ocular surface is prone to inflammation due to exposure to environmental irritants and pathogens. Inflammasomes are intracellular, multiprotein complexes that communicate potentially dangerous signals to the immune system. The identification of inflammasomes in various inflammatory ocular surface conditions can aid in the development of therapeutics to treat these chronic inflammatory conditions.

RECENT FINDINGS

Several inflammasomes have been associated with ocular surface disorders including dry eye disease, keratitis, and allergies. Mechanisms for activation of these inflammasomes with regards to specific disorders have been explored in models to aid in the development of targeted treatments.

SUMMARY

Research efforts continue to characterize the types of inflammasomes and activators of these in inflammatory ocular surface conditions. Various therapies targeting specific inflammasome types or pyroptosis are being tested preclinically to assess effects on decreasing the associated chronic inflammation.

TBHQ Alleviates Particulate Matter-Induced Pyroptosis in Human Nasal Epithelial Cells

Pyroptosis represents a type of cell death mechanism notable for its cell membrane disruption and the subsequent release of proinflammatory cytokines. The Nod-like receptor family pyrin domain containing inflammasome 3 (NLRP3) plays a critical role in the pyroptosis mechanism associated with various diseases resulting from particulate matter (PM) exposure. Tert-butylhydroquinone (tBHQ) is a synthetic antioxidant commonly used in a variety of foods and products. The aim of this study is to examine the potential of tBHQ as a therapeutic agent for managing sinonasal diseases induced by PM exposure. The occurrence of NLRP3 inflammasome-dependent pyroptosis in RPMI 2650 cells treated with PM < 4 µm in size was confirmed using Western blot analysis and enzyme-linked immunosorbent assay results for the pyroptosis metabolites IL-1β and IL-18. In addition, the inhibitory effect of tBHQ on PM-induced pyroptosis was confirmed using Western blot and immunofluorescence techniques. The inhibition of tBHQ-mediated pyroptosis was abolished upon nuclear factor erythroid 2-related factor 2 (Nrf2) knockdown, indicating its involvement in the antioxidant mechanism. tBHQ showed potential as a therapeutic agent for sinonasal diseases induced by PM because NLRP3 inflammasome activation was effectively suppressed via the Nrf2 pathway.

Inflammatory Cytokines and Chemokines Are Synergistically Induced in a ROS-Dependent Manner by a Co-Culture of Corneal Epithelial Cells and Neutrophil-like Cells in the Presence of Particulate Matter

Ocular exposure to particulate matter (PM) causes local inflammation; however, the influence of neutrophils on PM-induced ocular inflammation is still not fully understood. In this study, we constructed a system to investigate the role of PM in ocular inflammation using a co-culture of human corneal epithelial cells (HCE-T) and differentiation-induced neutrophils (dHL-60). To investigate whether HCE-T directly endocytosed PM, we performed a holographic analysis, which showed the endocytosis of PM in HCE-T. The cytokines and chemokines produced by HCE-T were measured using an ELISA. HCE-T treated with PM produced IL-6 and IL-8, which were inhibited by N-Acetyl-L-cysteine (NAC), suggesting the involvement of ROS. Their co-culture with dHL-60 enhanced their production of IL-6, IL-8, and MCP-1. This suggests an inflammatory loop involving intraocular corneal epithelial cells and neutrophils. These cytokines and chemokines are mainly regulated by NF-κB. Therefore, this co-culture system was examined in the presence of an IKK inhibitor known to downregulate NF-κB activity. The IKK inhibitor dramatically suppressed the production of these factors in co-culture supernatants. The results suggest that the inflammatory loop observed in the co-culture is mediated through ROS and the transcription factor NF-κB. Thus, the co-culture system is considered a valuable tool for analyzing complex inflammations.

Mechanisms of PM10 Disruption of the Nrf2 Pathway in Cornea

We have previously shown that PM10 exposure causes oxidative stress and reduces Nrf2 protein levels, and SKQ1 pre-treatment protects against this damage in human corneal epithelial cells (HCE-2). The current study focuses on uncovering the mechanisms underlying acute PM10 toxicity and SKQ1-mediated protection. HCE-2 were pre-treated with SKQ1 and then exposed to 100 μg/mL PM10. Cell viability, oxidative stress markers, programmed cell death, DNA damage, senescence markers, and pro-inflammatory cytokines were analyzed. Nrf2 cellular location and its transcriptional activity were determined. Effects of the Nrf2 inhibitor ML385 were similarly evaluated. Data showed that PM10 decreased cell viability, Nrf2 transcriptional activity, and mRNA levels of antioxidant enzymes, but increased p-PI3K, p-NFκB, COX-2, and iNOS proteins levels. Additionally, PM10 exposure significantly increased DNA damage, phosphor-p53, p16 and p21 protein levels, and β-galactosidase (β-gal) staining, which confirmed the senescence. SKQ1 pre-treatment reversed these effects. ML385 lowered the Nrf2 protein levels and mRNA levels of its downstream targets. ML385 also abrogated the protective effects of SKQ1 against PM10 toxicity by preventing the restoration of cell viability and reduced oxidative stress. In conclusion, PM10 induces inflammation, reduces Nrf2 transcriptional activity, and causes DNA damage, leading to a senescence-like phenotype, which is prevented by SKQ1.

Consequences of exposure to particulate matter on the ocular surface: Mechanistic insights from cellular mechanisms to epidemiological findings

Exposure to air pollutants, especially in the case of particulate matter (PM), poses significant health risks throughout the body. The ocular surface is directly exposed to atmospheric PM making it challenging to avoid. This constant exposure makes the ocular surface a valuable model for investigating the impact of air pollutants on the eyes. This comprehensive review assembles evidence from across the spectrum, from in vitro and in vivo investigations to clinical studies and epidemiological studies, offering a thorough understanding of how PM10 and PM2.5 affect the health of the ocular surface. PM has been primarily found to induce inflammatory responses, allergic reactions, oxidative stress, DNA damage, mitochondrial impairment, and inhibit the proliferation and migration of ocular surface cells. In toto these effects ultimately lead to impaired wound healing and ocular surface damage. In addition, PM can alter tear composition. These events contribute to ocular diseases such as dry eye disease, blepharitis, conjunctivitis, keratitis, limbal stem cell deficiency and pterygium. Importantly, preexisting ocular conditions such as dry eye, allergic conjunctivitis, and infectious keratitis can be worsened by PM exposure. Adaptive responses may partially alleviate the mentioned insults, resulting in morphological and physiological changes that could be different between periods of short-term and long-term exposure. Particle size is not the only determinant of the ocular effect of PM, the composition and solubility of PM also play critical roles. Increasing awareness of how PM affects the ocular surface is crucial in the field of public health, and mechanistic insights of these adverse effects may provide guidelines for preventive and therapeutic strategies in dealing with a polluted environment.

Association between air pollution and emergency room admission for eye diseases in Rome, Italy: A time-series analysis

Eye diseases impose a significant burden on health services due to high case numbers. However, exposure to outdoor air pollution is seldom mentioned as potential harmful factor. We conducted a time-series analysis in Rome, Italy, to estimate the association between daily mean concentration of NO2, PM10 and PM2.5 and daily number of emergency room (ER) admissions for a selected cluster of eye diseases from 2006 to 2016. We used Poisson regression adjusted for time trend, population decrease during summer vacations and holidays, day of week, apparent temperature (hot and cold) and daily concentration of nine pollen species. We observed 581,868 ER admissions during the study period. 44.74% of cases were observed in subjects with less than 20 years, 19.50% in 51-65 age category and 13.4% among children (0-14 years). No differences between sexes were recorded. Mean values of pollutant concentrations were 54.75, 31.01 and 18.14 μg/m3 for NO2, PM10 and PM2.5 respectively. The air temperature ranged from -1 °C to 32.5 °C, with a mean value of 16 °C (SD = 6.88). The apparent temperature spaced from -3.58 °C to 34.08 °C (mean = 15.61 °C, SD = 8.5). The highest percent risk increases for 10 μg/m3 increases of the three pollutants were observed at lag0-1 day (1.3%, 0.63-1.98 for PM2.5; 1.03%, 0.56-1.51 for PM10 and 0.6%, 0.13-1.07 for NO2). Risk increased significantly also at lag0 and lag0-5 day for each pollutant. Secondary analyses showed higher effects in the elderly compared to younger subjects. No differences emerged between sexes. The dose response analysis suggested of possible effects on ER admission risk also at low-level concentrations of PM2.5. A strong confounding effect of pollen was not detected. RESULTS: of this study are coherent with previous analyses. Speculation can be done about the biological mechanisms that link air pollution to eye damage.

Effects of particulate matter exposure on the expression of the SARS-CoV-2 ACE2 receptor in ocular surface tissues and cells

Particulate matter (PM) has been reported to be one of the risk factor for COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). However, although the ocular surface is deeply affected by both PM exposure and SARS-COV-2 infection, no studies have investigated the effects of PM exposure on the ocular route of SARS-COV-2 infection. To this end, we explored the effects of PM on the expression of SARS-COV-2-associated receptors and proteins in ocular surface. Herein, short- and long-term PM-exposed rat models were established by topically administering PM for 3 and 10 days, respectively. Immortalized human corneal epithelial cells (HCECs) and human conjunctival epithelial cells (HCjECs) were exposed to PM. ACE2, TMPRSS2, CD147, and ADAM17 expression levels were measured by western blot analysis. Our results show that short-term PM exposure had little effect on the expressions of ACE2, TMPRSS2, and CD147 in ocular surface tissues. However, long-term PM exposure decreased the ACE2 expression in conjunctival tissues and increased the CD147 expression in corneal or conjunctival tissues. PM exposure reduced the ACE2 expression by increasing the ADAM17 expression and ACE2 shedding level in HCECs and HCjECs. Our findings suggest that long-term PM exposure down-regulate the expression of the SARS-CoV-2 receptor ACE2 in conjunctival tissues through ADAM17-dependent ACE2 shedding. However, long-term PM exposure up-regulates the expression of another SARS-CoV-2 receptor CD147 in ocular surface tissues, accompanied by ocular surface damage and cytotoxicity. This study provides a new insight into uncovering potential risk factors for infection with SARS-CoV-2 via the ocular route.

Atmospheric pollutant black carbon induces ocular surface damage in mice

The threats of air pollution to human health have been gradually discovered, including its effects on eyes. The purpose of the study is to investigate the potential correlation between ocular surface exposure to black carbon and ocular surface structural damage as well as tear film dysfunction. To achieve this goal, 60 6-8-week-aged male BALB/C mice were randomly divided into 4 groups (n = 15). 0.5 mg/ml (group A), 1 mg/ml (group B), 5 mg/ml (group C) black carbon suspension droplets and PBS solution (group D) were used in the right eyes, 4 μl per time of three times per day. Tear break-up time, corneal fluorescein staining scores, and tear volume were assessed before treatment (day 0) and on days 4, 7, 10, and 14 after treatment. On day 14, the mice were sacrificed, and corneal and conjunctival tissues were collected for histological analysis. As the exposure time increased, there were no significant changes in the measured parameters from PBS-treated group of mice (P > 0.05). However, in the black carbon-treated group, there were significant decreases in tear film break-up time, significant increases in corneal fluorescein staining scores, and significant reductions in tear secretion (all P < 0.05). After 14 days, H&E staining of the corneal epithelium showed that in the PBS-treated group of mice, the corneal epithelial cells were neatly arranged, with no inflammatory cell infiltration, while in the black carbon-treated group, the corneal epithelium was significantly thickened, the basal cell arrangement was disrupted, the number of cell layers increased, and there was evidence of inflammatory cell infiltration. In the ultrastructure of the corneal epithelium, it could be observed that the black carbon-treated group had an increased amount of corneal epithelial cell detachment compared to the PBS-treated group, at the same time, the intercellular connections were looser, and there was a decrease in the number of microvilli and desmosomes in the black carbon-treated group. The results indicate that the ocular surface exposure to black carbon can result in a decrease in tear film stability and tear secretion in mice. Moreover, it can induce alterations in the corneal structure.

Urban Particulate Matter Triggers Meibomian Gland Dysfunction

Purpose

The meibomian gland (MG), as the largest modified sebaceous gland, is potentially damaged by urban particulate matter (UPM) based on epidemiological evidence, but the specific experimental mechanisms remain unknown. This study investigated the effects of UPM on MG dysfunction (MGD) in rodent models.

Methods

Female C57BL/6J mice received eye drops containing UPM suspension or PBS for 14 days. The proliferative capacity and progenitor of MG were evaluated by immunofluorescence. Cell apoptosis was confirmed by TUNEL assay, along with the analysis of caspase family expression. Lipid accumulation was visualized by Oil Red O staining and LipidTox staining. Ductal hyperkeratinization, neutrophil infiltration, and pyroptosis activation were detected through immunostaining. The relative gene expression and signaling pathway activation were determined by Western blot analysis.

Results

Administration of UPM caused MGD-like clinical signs, manifested as distinct corneal epithelial erosion, increased MG orifice occlusion, and glandular dropout. UPM exposure significantly induced progenitor loss, cellular apoptosis, and lipogenic disorder in MG, by reducing P63/Lrig1 expression and increasing cleaved caspase-8, -9, and -3 and meibum lipogenic protein (HMGCR/SREBP-1) expression. UPM-treated mice exhibited ductal hyperkeratinization and neutrophil recruitment. Simultaneously, pyroptosis was motivated, as indicated by the heightened expression of NLRP3 and the cleavage of caspase-1 and -4 and gasdermin D, as well as the increase in IL-1β and IL-18 downstream. The underlying pathological mechanisms of UPM involve the phosphorylation of mitogen-activated protein kinase and nuclear factor-κB.

Conclusions

These results provided direct evidence for the toxicity of UPM in MG. UPM-induced activation of pyroptosis and mitogen-activated protein kinase/nuclear factor-κB signaling pathway might account for the inflammatory MGD.

The Cellular Accumulation of Vehicle Exhaust Particulates Changes the Acidic pH Environment of Lysosomes in BEAS-2B Airway Epithelial Cells

Many people are exposed every day to vehicle exhaust particulates (VEPs), which are thought to be taken up by epithelial cells that are the first barrier in our biological defense. The study aim was to investigate how VEPs are processed in the lysosomal degradation system. BEAS-2B airway epithelial cells easily ingest VEPs and have been shown to accumulate in cells for several days, but no elevated cytotoxicity was observed over that time period. An analysis of 3D images confirmed the presence of VEPs in or near lysosomes, and an accumulation of VEPs resulted in an increase in the normal acidic pH in lysosomes and the extracellular release of the lysosomal enzyme β-hexosaminidase. Epithelial cells were thought to activate the lysosome-mediated secretion of extracellular vesicles to avoid damage caused by non-degradable foreign substances, such as VEPs, and as a side reaction, the acidic pH environment of the lysosomes could not be maintained.

PM2.5 induces renal tubular injury by activating NLRP3-mediated pyroptosis

Fine particulate matter (PM2.5)-related health issues have received increasing attention as a worldwide public health problem, and PM2.5-related chronic kidney disease (CKD) has been emerging over the years. Limited research has focused on the mechanism of PM2.5-induced kidney disease. To investigate the impact of PM2.5 on the kidney and its potential mechanism, we generated a PM2.5-exposed C57BL/6 mouse model by using Shanghai Meteorological and Environment Animal Exposure System (Shanghai-METAS) for 12 weeks, urine, blood and kidney tissues were collected. The pathological changes and the function of the kidney were measured after PM2.5 exposure for 12 weeks. Along with glomerular damage, tubular damage was also severe in PM2.5-induced mice. The results of mRNA-seq indicate that pyroptosis is involved. Pyroptosis is defined as caspase-1-dependent programmed cell death in response to insults. The expression of the nucleotide-binding and oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3), Caspase-1, gasdermin D (GSDMD) and IL-1β was detected. NLRP3 inflammasome activation and subsequent pyroptosis were observed in PM2.5-exposed kidney tissues and PM2.5-exposed Bumpt cells too. At the meantime, the inhibitors of NLRP3 and caspase-1 were applied to the PM2.5 exposed Bumpt cells. It turned out to have a significant rescue effect of the inhibitors. This study revealed new insights into PM2.5-induced kidney injury and specific kidney pathological damage, as well as morphological changes, and defined the important role of pyroptosis in PM2.5-induced kidney dysfunction.

Long-term PM2.5 exposure disrupts corneal epithelial homeostasis by impairing limbal stem/progenitor cells in humans and rat models

BACKGROUND

Limbal stem/progenitor cells (LSPCs) play a crucial role in maintaining corneal health by regulating epithelial homeostasis. Although PM2.5 is associated with the occurrence of several corneal diseases, its effects on LSPCs are not clearly understood.

METHODS

In this study, we explored the correlation between PM2.5 exposure and human limbal epithelial thickness measured by Fourier-domain Optical Coherence Tomography in the ophthalmologic clinic. Long- and short-term PM2.5 exposed-rat models were established to investigate the changes in LSPCs and the associated mechanisms.

RESULTS

We found that people living in regions with higher PM2.5 concentrations had thinner limbal epithelium, indicating the loss of LSPCs. In rat models, long-term PM2.5 exposure impairs LSPCs renewal and differentiation, manifesting as corneal epithelial defects and thinner epithelium in the cornea and limbus. However, LSPCs were activated in short-term PM2.5-exposed rat models. RNA sequencing implied that the circadian rhythm in LSPCs was perturbed during PM2.5 exposure. The mRNA level of circadian genes including Per1, Per2, Per3, and Rev-erbα was upregulated in both short- and long-term models, suggesting circadian rhythm was involved in the activation and dysregulation of LSPCs at different stages. PM2.5 also disturbed the limbal microenvironment as evidenced by changes in corneal subbasal nerve fiber density, vascular density and permeability, and immune cell infiltration, which further resulted in the circadian mismatches and dysfunction of LSPCs.

CONCLUSION

This study systematically demonstrates that PM2.5 impairs LSPCs and their microenvironment. Moreover, we show that circadian misalignment of LSPCs may be a new mechanism by which PM2.5 induces corneal diseases. Therapeutic options that target circadian rhythm may be viable options for improving LSPC functions and alleviating various PM2.5-associated corneal diseases.

PM2.5 induces the inflammatory response in rat spleen lymphocytes through autophagy activation of NLRP3 inflammasome

Recent evidence has suggested that fine particulate matter (PM2.5) can induce inflammatory injury in spleen. However, the underlying mechanisms of injury remain enigmatic. In this study, we aim to clarify the inflammatory injury mechanisms of PM2.5 through investigating the crosstalk between autophagy and nod-like receptor protein 3 (NLRP3) inflammasome. The spleen lymphocytes were extracted from SD rats and subjected to PM2.5 and its water-soluble components. The CCK-8 assay was utilized to explore the effects of PM2.5 and its water-soluble components on lymphocytes. Then, the effects of PM2.5 and its water-soluble components exposure on autophagy and NLRP3 inflammasome were detected by qRT-PCR, western blotting, and immunofluorescence staining. The autophagosome production was observed under the transmission electron microscope. The autophagy inhibitor 3-methyladenine (3MA) following PM2.5 water-soluble components was used to investigate the regulation of NLRP3 inflammasome by autophagy. We found that PM2.5 and its water-soluble components decreased the viability of spleen lymphocytes in a dose-dependent manner. PM2.5 exposure and its water-soluble components exposure activated the autophagy and NlRP3 inflammasome, as indicated by an increased expression of LC3, P62, NLRP3, Caspase-1 p10, and increased release of IL-1β. Furthermore, the treatment with autophagy inhibitor 3MA attenuated the production of autophagosome and NLRP3 inflammasome induced by PM2.5 water-soluble components with decreased expression of NLRP3, Caspase-1 p10, and diminished production of IL-1β. These results suggested that PM2.5 and its water-soluble components could induce autophagy and inflammatory response through NLRP3 inflammasome in spleen lymphocytes, while the NLRP3 inflammasome induced by PM2.5 could be significantly alleviated by inhibition of autophagy, further providing new insights for the understanding of spleen injury caused by PM2.5.

Impacts and potential mechanisms of fine particulate matter (PM2.5) on male testosterone biosynthesis disruption

Exposure to PM2.5 is the most significant air pollutant for health risk. The testosterone level in male is vulnerable to environmental toxicants. In the past, researchers focused more attention on the impacts of PM2.5 on respiratory system, cardiovascular system, and nervous system, and few researchers focused attention on the reproductive system. Recent studies have reported that PM2.5 involved in male testosterone biosynthesis disruption, which is closely associated with male reproductive health. However, the underlying mechanisms by which PM2.5 causes testosterone biosynthesis disruption are still not clear. To better understand its potential mechanisms, we based on the existing scientific publications to critically and comprehensively reviewed the role and potential mechanisms of PM2.5 that are participated in testosterone biosynthesis in male. In this review, we summarized the potential mechanisms of PM2.5 triggering the change of testosterone level in male, which involve in oxidative stress, inflammatory response, ferroptosis, pyroptosis, autophagy and mitophagy, microRNAs (miRNAs), endoplasmic reticulum (ER) stress, and N6-methyladenosine (m6A) modification. It will provide new suggestions and ideas for prevention and treatment of testosterone biosynthesis disruption caused by PM2.5 for future research.

The role of regulated necrosis in inflammation and ocular surface diseases

In recent decades, numerous types of regulated cell death have been identified, including pyroptosis, ferroptosis and necroptosis. Regulated necrosis is characterized by a series of amplified inflammatory responses that result in cell death. Therefore, it has been suggested to play an essential role in the pathogenesis of ocular surface diseases. The cell morphological features and molecular mechanisms of regulated necrosis are discussed in this review. Furthermore, it summarizes the role of ocular surface diseases, such as dry eye, keratitis, and cornea alkali burn, as potential disease prevention and treatment targets.

BPDE exposure promotes trophoblast cell pyroptosis and induces miscarriage by up-regulating lnc-HZ14/ZBP1/NLRP3 axis

Environmental Benzo(a)pyrene (BaP) and its ultimate metabolite BPDE (benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide) are typical persistent organic pollutants and endocrine disrupting chemicals. BaP/BPDE exposure might cause human trophoblast cell dysfunctions and induce miscarriage. However, the underlying mechanisms remain largely elusive. In this study, we found that BPDE exposure induced human trophoblast cell pyroptosis by up-regulating NLRP3/Caspase1/GSDMD pathway. We also identified that lnc-HZ14 was highly expressed in BPDE-exposed trophoblast cells and in recurrent miscarriage (RM) vs healthy control (HC) villous tissues. Lnc-HZ14 promoted trophoblast cell pyroptosis by promoting IRF1-mediated ZBP1 transcription, increasing METTL3-mediated m6A methylation on NLRP3 mRNA and its stability, and also enhancing ZBP1/NLRP3 protein interactions. Knockdown of lnc-HZ14/ZBP1/NLRP3 axis could efficiently alleviate BPDE-induced trophoblast cell pyroptosis. Higher level of pyroptosis, as indicated by the up-regulation of lnc-HZ14/ZBP1/NLRP3 axis, was found in RM vs HC villous tissues. In BaP-exposed mouse model, BaP exposure induced placental tissue pyroptosis and miscarriage by up-regulating murine Zbp1/Nlrp3 axis, and knockdown of Nlrp3 could efficiently reduce placenta pyroptosis and alleviate BaP-induced mouse miscarriage. Serum IL-1β protein level might act as a promising indicator to predict the risk of miscarriage. These findings provided new insights into BaP/BPDE-induced trophoblast cell pyroptosis and miscarriage and might be helpful for further assessment of the toxicological effects of BaP/BPDE on the female reproduction.

Effects of TCPP and TCEP exposure on human corneal epithelial cells: Oxidate damage, cell cycle arrest, and pyroptosis

Tris(2-chloroisopropyl) phosphate (TCPP) and Tris(2-chloroethyl) phosphate (TCEP) are the widely used organophosphorus flame retardants indoors and easily accessible to the eyes as the common adhesive components of dust and particle matter, however, hardly any evidence has demonstrated their corneal toxicity. In this study, the adverse effects of TCPP, TCEP, and TCPP + TCEP exposure on human corneal epithelial cells (HCECs) were investigated. The cell viability and morphology, intracellular reactive oxygen species (ROS), cell cycle, and the expressions of cell cycle and pyroptosis-related genes were assessed to explain the underlying mechanisms. Compared to individual exposure, co-exposure to TCPP₂₀+TCEP₂₀ showed higher cytotoxicity with a sharp decrease of >30% in viability and more serious oxidative damage by increasing ROS production to 110.92% compared to the control group. Furthermore, the cell cycle arrested at the S phase (36.20%) was observed after combined treatment, evidenced by the upregulation of cyclin D1, CDK2, CDK4, CDK6, p21, and p27. Interestingly, pyroptosis-related genes GSDMD, Caspase-1, NLRP3, IL-1β, IL-18, NLRP1, and NLRC4 expressions were promoted with cell swelling and glowing morphology. Oxidative stress and cell cycle arrest probably acted as a key role in TCPP₂₀+TCEP₂₀-induced cytotoxicity and pyroptosis in HCECs. Our results suggested that TCPP₂₀+TCEP₂₀ co-exposure induced severer corneal damage, further illustrating its significance in estimating indoor health hazards to humans.

ROS generation and p-38 activation contribute to montmorillonite-induced corneal toxicity in vitro and in vivo

BACKGROUND

Montmorillonite (Mt) and its derivatives are now widely used in industrial and biomedical fields. Therefore, safety assessments of these materials are critical to protect human health after exposure; however, studies on the ocular toxicity of Mt are lacking. In particular, varying physicochemical characteristics of Mt may greatly alter their toxicological potential. To explore the effects of such characteristics on the eyes, five types of Mt were investigated in vitro and in vivo for the first time, and their underlying mechanisms studied.

RESULTS

The different types of Mt caused cytotoxicity in human HCEC-B4G12 corneal cells based on analyses of ATP content, lactate dehydrogenase (LDH) leakage, cell morphology, and the distribution of Mt in cells. Among the five Mt types, Na-Mt exhibited the highest cytotoxicity. Notably, Na-Mt and chitosan-modified acidic Na-Mt (C-H-Na-Mt) induced ocular toxicity in vivo, as demonstrated by increases corneal injury area and the number of apoptotic cells. Na-Mt and C-H-Na-Mt also induced reactive oxygen species (ROS) generation in vitro and in vivo, as indicated by 2',7'-dichlorofluorescin diacetate and dihydroethidium staining. In addition, Na-Mt activated the mitogen-activated protein kinase signaling pathway. The pretreatment of HCEC-B4G12 cells with N-acetylcysteine, an ROS scavenger, attenuated the Na-Mt-induced cytotoxicity and suppressed p38 activation, while inhibiting p38 activation with a p38-specific inhibitor decreased Na-Mt-induced cytotoxicity.

CONCLUSIONS

The results indicate that Mt induces corneal toxicity in vitro and in vivo. The physicochemical properties of Mt greatly affect its toxicological potential. Furthermore, ROS generation and p38 activation contribute at least in part to Na-Mt-induced toxicity.

The inflammasome pathway: A key player in ocular surface and anterior segment diseases

Inflammasomes are multicomplex molecular regulators with an emerging importance in regulating ocular surface and anterior segment health and disease. Key components found in the eye include NF-κB, NLRP3, NLRC4, NLRP6, ASC, IL-1β, IL-18, and caspase-1. The role of NLRP1, NLRC4, AIM2, and NLRP3 inflammasomes in the pathogenesis of infectious ulcers, DED, uveitis, glaucoma, corneal edema, and other diseases is being studied with many developments. Attenuation of these diseases has been explored by blocking various molecules along the inflammasome pathway with agents like NAC, polydatin, calcitriol, glyburide, YVAD, and disulfiram. We provide a background on the inflammasome pathway as it relates to the ocular surface and anterior segment of the eye, discuss the role of inflammasomes in the above diseases in animals and humans, investigate new therapeutic targets, and explore the efficacy of new anti-inflammasome therapies.

Pollutant-induced pyroptosis in humans and other animals

Pyroptosis is a form of lytic cell death with pro-inflammatory characteristics, induced upon the activation of certain inflammatory caspases by inflammasome complexes such as NLRP3 inflammasome. Gasdermin proteins as the mediators of pyroptosis form cell membrane pores upon activation, which release certain cellular contents into the extracellular space including inflammatory cytokines such as IL-1β and IL-18, and also damage the integrity of the cell membrane. Gasdermins have been implicated in autoimmune and inflammatory diseases, infectious diseases, deafness and cancer. Mostly in the last 2 years, diverse pollutant types including particulate matter, cadmium and polystyrene microplastics were reported to induce pyroptotic cell death in diverse tissues from mammals to birds. In the present study, we review our current understanding of pollutant-induced pyroptosis as well as current knowledge of upstream events leading to pyroptotic cell death upon exposure to pollutants.

On the Need for Human Studies of PM Exposure Activation of the NLRP3 Inflammasome

Particulate matter air pollution is associated with blood inflammatory biomarkers, however, the biological pathways from exposure to periferal inflammation are not well understood. We propose that the NLRP3 inflammasome is likely stimulated by ambient particulate matter, as it is by some other particles and call for more research into this pathway.

AES-CSFS: an automatic evaluation system for corneal sodium fluorescein staining based on deep learning

Background

Corneal fluorescein sodium staining is a valuable diagnostic method for various ocular surface diseases. However, the examination results are highly dependent on the subjective experience of ophthalmologists.

Objectives

To develop an artificial intelligence system based on deep learning to provide an accurate quantitative assessment of sodium fluorescein staining score and the size of cornea epithelial patchy defect.

Design

A prospective study.

Methods

We proposed an artificial intelligence system for automatically evaluating corneal staining scores and accurately measuring patchy corneal epithelial defects based on corneal fluorescein sodium staining images. The design incorporates two segmentation models and a classification model to forecast and assess the stained images. Meanwhile, we compare the evaluation findings from the system with ophthalmologists with varying expertise.

Results

For the segmentation task of cornea boundary and cornea epithelial patchy defect area, our proposed method can achieve the performance of dice similarity coefficient (DSC) is 0.98/0.97 and Hausdorff distance (HD) is 3.60/8.39, respectively, when compared with the manually labeled gold standard. This method significantly outperforms the four leading algorithms (Unet, Unet++, Swin-Unet, and TransUnet). For the classification task, our algorithm achieves the best performance in accuracy, recall, and F1-score, which are 91.2%, 78.6%, and 79.2%, respectively. The performance of our developed system exceeds seven different approaches (Inception, ShuffleNet, Xception, EfficientNet_B7, DenseNet, ResNet, and VIT) in classification tasks. In addition, three ophthalmologists were selected to rate corneal staining images. The results showed that the performance of our artificial intelligence system significantly outperformed the junior doctors.

Conclusion

The system offers a promising automated assessment method for corneal fluorescein staining, decreasing incorrect evaluations caused by ophthalmologists' subjective variance and limited knowledge.

Joint effects of meteorological factors and PM2.5 on age-related macular degeneration: a national cross-sectional study in China

BACKGROUND

Weather conditions are a possible contributing factor to age-related macular degeneration (AMD), a leading cause of irreversible loss of vision. The present study evaluated the joint effects of meteorological factors and fine particulate matter (PM_2.5) on AMD.

METHODS

Data was extracted from a national cross-sectional survey conducted across 10 provinces in rural China. A total of 36,081 participants aged 40 and older were recruited. AMD was diagnosed clinically by slit-lamp ophthalmoscopy, fundus photography, and spectral domain optical coherence tomography (OCT). Meteorological data were calculated by European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis and were matched to participants' home addresses by latitude and longitude. Participants' individual PM_2.5 exposure concentrations were calculated by a satellite-based model at a 1-km resolution level. Multivariable-adjusted logistic regression models paired with interaction analysis were performed to investigate the joint effects of meteorological factors and PM_2.5 on AMD.

RESULTS

The prevalence of AMD in the study population was 2.6% (95% CI 2.42-2.76%). The average annual PM_2.5 level during the study period was 63.1 ± 15.3 µg/m³. A significant positive association was detected between AMD and PM_2.5 level, temperature (T), and relative humidity (RH), in both the independent and the combined effect models. For PM_2.5, compared with the lowest quartile, the odds ratios (ORs) with 95% confidence intervals (CIs) across increasing quartiles were 0.828 (0.674,1.018), 1.105 (0.799,1.528), and 2.602 (1.516,4.468). Positive associations were observed between AMD and temperature, with ORs (95% CI) of 1.625 (1.059,2.494), 1.619 (1.026,2.553), and 3.276 (1.841,5.830), across increasing quartiles. In the interaction analysis, the estimated relative excess risk due to interaction (RERI) and the attributable proportion (AP) for combined atmospheric pressure and PM_2.5 was 0.864 (0.586,1.141) and 1.180 (0.768,1.592), respectively, indicating a synergistic effect between PM_2.5 and atmospheric pressure.

CONCLUSIONS

This study is among the first to characterize the coordinated effects of meteorological factors and PM_2.5 on AMD. The findings warrant further investigation to elucidate the relationship between ambient environment and AMD.

The Potential Role of Regulated Cell Death in Dry Eye Diseases and Ocular Surface Dysfunction

The research on new treatments for dry eye diseases (DED) has exponentially grown over the past decades. The increased prevalence of dry eye conditions, particularly in the younger population, has received much attention. Therefore, it is of utmost importance to identify novel therapeutical targets. Regulated cell death (RCD) is an essential process to control the biological homeostasis of tissues and organisms. The identification of different mechanisms of RCD stimulated the research on their involvement in different human pathologies. Whereas apoptosis has been widely studied in DED and included in the DED vicious cycle, the role of RCD still needs to be completely elucidated. In this review, we will explore the potential roles of different types of RCD in DED and ocular surface dysfunction. Starting from the evidence of oxidative stress and inflammation in dry eye pathology, we will analyse the potential therapeutic applications of the following principal RCD mechanisms: ferroptosis, necroptosis, and pyroptosis.

IL-1β and Allergy: Focusing on Its Role in Allergic Rhinitis

Allergic rhinitis (AR) is a chronic upper airway immune-inflammation response mediated by immunoglobulin E (IgE) to allergens and can seriously affect the quality of life and work efficiency. Previous studies have shown that interleukin-1β (IL-1β) acts as a key cytokine to participate in and promote the occurrence and development of allergic diseases. It has been proposed that IL-1β may be a potential biomarker of AR. However, its definitive role and potential mechanism in AR have not been fully elucidated, and the clinical sample collection and detection methods were inconsistent among different studies, which have limited the use of IL-1β as a clinical diagnosis and treatment marker for AR. This article systematically summarizes the research advances in the roles of IL-1β in allergic diseases, focusing on the changes of IL-1β in AR and the possible interventions. In addition, based on the findings by our team, we provided new insights into the use of IL-1β in AR diagnosis and treatment, in an attempt to further promote the clinical application of IL-1β in AR and other allergic diseases.

Fibroblast growth factor 10 protects against particulate matter-induced lung injury by inhibiting oxidative stress-mediated pyroptosis via the PI3K/Akt/Nrf2 signaling pathway

Particulate matter (PM) is a major environmental contaminant that causes and worsens respiratory diseases. Fibroblast growth factor 10 (FGF10), a paracrine fibroblast growth factor that specifically stimulates repair and regeneration after injury, has been shown to protect against PM-induced lung injury. However, the underlying mechanisms are still unclear. In this study, the protective effects of FGF10 were investigated using a PM-induced lung injury mouse model in vivo and BEAS-2B cells in vitro. According to the findings, FGF10 treatment alleviated PM-induced oxidative damage and pyroptosis in vivo and in vitro. Mechanistically, FGF10 activated antioxidative Nrf2 signaling. Inhibition of PI3K signaling with LY294002 or Nrf2 signaling with ML385 revealed that FGF10-mediated lung protection was mediated by the PI3K/Akt/Nrf2 pathway. These results collectively indicate that FGF10 inhibits oxidative stress-mediated pyroptosis via the PI3K/Akt/Nrf2 pathway, suggesting a possible therapy for PM-induced lung injury.

Wood smoke particulate matter (WSPM2.5) induces pyroptosis through both Caspase-1/IL-1β/IL-18 and ATP/P2Y-dependent mechanisms in human bronchial epithelial cells

Emerging evidences have linked the air pollution particulate matters, especially the fine particulate matter PM2.5, to the disease development of chronic obstructive pulmonary disease (COPD). Our previous studies reported that biofuel PM2.5 can induce devastated damage of human bronchial epithelial cells, this study aims to further investigate the underlying molecular mechanisms how biofuel PM2.5 induces bronchial epithelial cell death and dysfunction. In this study, biofuel PM2.5 extracted from wood smoke (WSPM2.5) was used according to our previous publication. A 16-HBE cell line was used as the cell model. Results showed that: Firstly, WSPM2.5 induced significant pyroptosis in 16-HBE cells, reflected by the typical changes including elevated release of lactate dehydrogenase release (LDH) and activated activity and expression of Caspase-1/IL-1β/IL-18 signaling pathway. Then, specific inhibitors for both Caspases (Z-VAD-FMK) and Caspase-1 (VX-765), as well as specific siRNA knockdown of IL-1β all effectively attenuated the WSPM2.5-induced upregulation of downstream inflammatory cytokines and chemokines (IL-6, IL-8, CXCL-1, CXCL-2, etc), respectively. Notably, WSPM2.5 caused a novel increase of intracellular-to-extracellular ATP secretion, which could also contribute to the WSPM2.5-induced pyroptosis and inflammation by activating the Caspase-1/IL-1β/IL-18 signaling pathway through possible autocrine and/or paracrine mechanisms. Antagonism of ATP (Apyrase) or specific siRNA knockdown against ATP receptors (P2Y2 and P2Y7) both significantly inhibited the WSPM2.5-induced pyroptosis and inflammation. These results add up to the current knowledge and bring up novel insights that WSPM2.5 could induce significant pyroptosis and inflammation of human bronchial epithelial cells, through both a classic NLRP3/Caspase-1/IL-1β-dependent and a novel ATP/P2Y-dependent mechanisms.

Acute exposure to air pollutants increase the risk of acute glaucoma

Background

Ambient air pollution is related to the onset and progression of ocular disease. However, the effect of air pollutants on the acute glaucoma remains unclear.

Objective

To investigate the effect of air pollutants on the incidence of acute glaucoma (acute angle closure glaucoma and glaucomatocyclitic crisis) among adults.

Methods

We conducted a time-stratified case-crossover study based on the data of glaucoma outpatients from January, 2015 to Dec, 2021 in Shanghai, China. A conditional logistic regression model combined with a polynomial distributed lag model was applied for the statistical analysis. Each case serves as its own referent by comparing exposures on the day of the outpatient visit to the exposures on the other 3–4 control days on the same week, month and year. To fully capture the delayed effect of air pollution, we used a maximum lag of 7 days in main model.

Results

A total of 14,385 acute glaucoma outpatients were included in this study. We found exposure to PM_2.5, PM₁₀, nitrogen dioxide (NO₂) and carbon monoxide (CO) significantly increased the odds of outpatient visit for acute glaucoma. Wherein the odds of acute glaucoma related to PM_2.5 and NO₂ were higher and more sustained, with OR of 1.07 (95%CI: 1.03–1.11) and 1.12 (95% CI: 1.08–1.17) for an IQR increase over lag 0–3 days, than PM₁₀ and CO over lag 0–1 days (OR:1.03; 95% CI: 1.01–1.05; OR: 1.04; 95% CI: 1.01–1.07).

Conclusions

This case-crossover study provided first-hand evidence that air pollutants, especially PM_2.5 and NO₂, significantly increased risk of acute glaucoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-022-14078-9.

Smoke and the eyes: A review of the harmful effects of wildfire smoke and air pollution on the ocular surface

Wildfires are occurring worldwide with greater frequency and intensity. Wildfires, as well as other sources of air pollution including environmental tobacco smoke, household biomass combustion, agricultural burning, and vehicular emissions, release large amounts of toxic substances into the atmosphere. The ocular surface is constantly exposed to the ambient air and is hence vulnerable to damage from air pollutants. This review describes the detrimental effects of wildfire smoke and air pollution on the ocular surface and resultant signs and symptoms. The latest relevant evidence is synthesised and critically evaluated. A mechanism for the pathophysiology of ocular surface damage will be proposed considering the existing literature on respiratory effects of air pollution. Current strategies to reduce human exposure to air pollutants are discussed and specific possible approaches to protect the ocular surface and manage air pollution induced ocular surface damage are suggested. Further avenues of research are suggested to understand how acute and chronic air pollution exposure affects the ocular surface including the short and long-term implications.

SIRT1 Protects Against Particulate Matter-Induced Oxidative Stress in Human Corneal and Conjunctival Epithelial Cells

Purpose

Sirtuin1 (SIRT1) as a hot therapeutic target for oxidative stress–associated diseases that has been extensively studied. This study aimed to determine the changes in SIRT1 expression in particulate matter (PM)–induced corneal and conjunctival epithelial cell damage and explore potential drugs to reduce PM-associated ocular surface injury.

Methods

Immortalized human corneal epithelial cells (HCECs) and human conjunctival epithelial cells (HCjECs) were exposed to an ambient PM sample. Cytotoxicity was evaluated by water-soluble tetrazolium salt–8 assay. SIRT1 expression was measured by Western blot analysis. Reactive oxygen species (ROS) production, cell apoptosis, mitochondrial function, and cell senescence were assessed by using 2ʹ,7ʹ-dichlorofluorescein diacetate assay, annexin V apoptosis assay, tetramethylrhodamine ethyl ester assay, and senescence β-galactosidase staining, respectively.

Results

PM-induced cytotoxicity of HCECs and HCjECs occurred in a dose-dependent manner. Increased ROS production, as well as decreased SIRT1 expression, were observed in HCECs and HCjECs after 200 µg/mL PM exposure. In addition, PM induced oxidative stress-mediated cellular damage, including cell apoptosis, mitochondrial damage, and cell senescence. Interestingly, SRT1720, a SIRT1 activator, increased SIRT1 expression and decreased ROS production and attenuated PM-induced cell damage in HCECs and HCjECs.

Conclusions

This study determined that SIRT1 was involved in PM-induced oxidative stress in HCECs and HCjECs and found that ROS overproduction may a key factor in PM-induced SIRT1 downregulation. The SIRT1 activator, SRT1720, can effectively upregulate SIRT1 expression and inhibit ROS production, thereby reversing PM-induced cell damage. This study provides a new potential target for clinical treatment of PM-associated ocular surface diseases.

Spotlight on pyroptosis: role in pathogenesis and therapeutic potential of ocular diseases

Pyroptosis is a programmed cell death characterized by swift plasma membrane disruption and subsequent release of cellular contents and pro-inflammatory mediators (cytokines), including IL‐1β and IL‐18. It differs from other types of programmed cell death such as apoptosis, autophagy, necroptosis, ferroptosis, and NETosis in terms of its morphology and mechanism. As a recently discovered form of cell death, pyroptosis has been demonstrated to be involved in the progression of multiple diseases. Recent studies have also suggested that pyroptosis is linked to various ocular diseases. In this review, we systematically summarized and discussed recent scientific discoveries of the involvement of pyroptosis in common ocular diseases, including diabetic retinopathy, age-related macular degeneration, AIDS-related human cytomegalovirus retinitis, glaucoma, dry eye disease, keratitis, uveitis, and cataract. We also organized new and emerging evidence suggesting that pyroptosis signaling pathways may be potential therapeutic targets in ocular diseases, hoping to provide a summary of overall intervention strategies and relevant multi-dimensional evaluations for various ocular diseases, as well as offer valuable ideas for further research and development from the perspective of pyroptosis.

Fine particulate matter exposure aggravates ischemic injury via NLRP3 inflammasome activation and pyroptosis

Aims

Accumulating evidence has suggested that airborne fine particulate matter (PM2.5) exposure is associated with an increased risk of ischemic stroke. However, the underlying mechanisms have not been fully elucidated. In this study, we aim to investigate the role and mechanisms of NLRP3 inflammasome and pyroptosis in ischemic stroke after PM2.5 exposure.

Methods

The BV‐2 and HMC‐3 microglial cell lines were established and subjected to oxygen–glucose deprivation and reoxygenation (OGD/R) with or without PM2.5 exposure. We used the CCK‐8 assay to explore the effects of PM2.5 on cell viability of BV‐2 and HMC‐3 cells. Then, the effects of PM2.5 exposure on NLRP3 inflammasome and pyroptosis following OGD/R were detected by western blotting, ELISA, and the confocal immunofluorescence staining. Afterwards, NLRP3 was knocked down to further validate the effects of PM2.5 on cell viability, NLRP3 inflammasome activation, and pyroptosis after OGD/R in HMC‐3 cells. Finally, the intracellular reactive oxygen species (ROS) was measured and the ROS inhibitor N‐acetyl‐L‐cysteine (NAC) was used to investigate whether ROS was required for PM2.5‐induced NLRP3 inflammasome activation and pyroptosis under ischemic conditions.

Results

We found that PM2.5 exposure decreased the viability of BV‐2 and HMC‐3 cells in a dose‐ and time‐dependent manner under ischemic conditions. Furthermore, PM2.5 exposure aggravated NLRP3 inflammasome activation and pyroptosis after OGD/R, as indicated by an increased expression of NLRP3, ASC, pro‐caspase‐1, Caspase‐1, GSDMD, and GSDMD‐N; increased production of IL‐1β and IL‐18; and enhanced Caspase‐1 activity and SYTOX green uptake. However, shRNA NLRP3 treatment attenuated the effects of PM2.5 on cell viability, NLRP3 inflammasome activation, and pyroptosis. Moreover, we observed that PM2.5 exposure increased the production of intracellular ROS following OGD/R, while inhibiting ROS production with NAC partially attenuated PM2.5‐induced NLRP3 inflammasome activation and pyroptosis under ischemic conditions.

Conclusion

These results suggested that PM2.5 exposure triggered the activation of NLRP3 inflammasome and pyroptosis under ischemic conditions, which may be mediated by increased ROS production after ischemic stroke. These findings may provide a more enhanced understanding of the interplay between PM2.5 and neuroinflammation and cell death, and reveal a novel mechanism of PM2.5‐mediated toxic effects after ischemic stroke.

The role of the PI3K/AKT signalling pathway in the corneal epithelium: recent updates

Phosphatidylinositol 3 kinase (PI3K)/AKT (also called protein kinase B, PKB) signalling regulates various cellular processes, such as apoptosis, cell proliferation, the cell cycle, protein synthesis, glucose metabolism, and telomere activity. Corneal epithelial cells (CECs) are the outermost cells of the cornea; they maintain good optical performance and act as a physical and immune barrier. Various growth factors, including epidermal growth factor receptor (EGFR) ligands, insulin-like growth factor 1 (IGF1), neurokinin 1 (NK-1), and insulin activate the PI3K/AKT signalling pathway by binding their receptors and promote antiapoptotic, anti-inflammatory, proliferative, and migratory functions and wound healing in the corneal epithelium (CE). Reactive oxygen species (ROS) regulate apoptosis and inflammation in CECs in a concentration-dependent manner. Extreme environments induce excess ROS accumulation, inhibit PI3K/AKT, and cause apoptosis and inflammation in CECs. However, at low or moderate levels, ROS activate PI3K/AKT signalling, inhibiting apoptosis and stimulating proliferation of healthy CECs. Diabetes-associated hyperglycaemia directly inhibit PI3K/AKT signalling by increasing ROS and endoplasmic reticulum (ER) stress levels or suppressing the expression of growth factors receptors and cause diabetic keratopathy (DK) in CECs. Similarly, hyperosmolarity and ROS accumulation suppress PI3K/AKT signalling in dry eye disease (DED). However, significant overactivation of the PI3K/AKT signalling pathway, which mediates inflammation in CECs, is observed in both infectious and noninfectious keratitis. Overall, upon activation by growth factors and NK-1, PI3K/AKT signalling promotes the proliferation, migration, and anti-apoptosis of CECs, and these processes can be regulated by ROS in a concentration-dependent manner. Moreover, PI3K/AKT signalling pathway is inhibited in CECs from individuals with DK and DED, but is overactivated by keratitis.

Roles and Mechanisms of Regulated Necrosis in Corneal Diseases: Progress and Perspectives

Regulated necrosis is defined as cell death characterized by loss of the cell membrane integrity and release of the cytoplasmic content. It contributes to the development and progression of some diseases, including ischemic stroke injury, liver diseases, hypertension, and cancer. Various forms of regulated necrosis, particularly pyroptosis, necroptosis, and ferroptosis, have been implicated in the pathogenesis of corneal disease. Regulated necrosis of corneal cells enhances inflammatory reactions in the adjacent corneal tissues, leading to recurrence and aggravation of corneal disease. In this review, we summarize the molecular mechanisms of pyroptosis, necroptosis, and ferroptosis in corneal diseases and discuss the roles of regulated necrosis in inflammation regulation, tissue repair, and corneal disease outcomes.

PM2.5 exposure inducing ATP alteration links with NLRP3 inflammasome activation

Fine particulate matter (PM_2.5) has been the primary air pollutant and the fourth leading risk factor for disease and death in the world. Exposure to PM_2.5 is related to activation of the NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, but the mechanism of PM_2.5 affecting the NLRP3 inflammasome is still unclear. Previous studies have shown that PM_2.5 can cause alterations in adenosine triphosphate (ATP), and an increase in extracellular ATP and a decrease in intracellular ATP can trigger the activation process of the NLRP3 inflammasome. Therefore, we emphasize that ATP changes may be the central link and key mechanism of PM_2.5 exposure that activates the NLRP3 inflammasome. This review briefly elucidates and summarizes how PM_2.5 acts on ATP and subsequently further impacts the NLRP3 inflammasome. Investigation of ATP changes due to exposure to PM_2.5 may be essential to regulate NLRP3 inflammasome activation and treat inflammation-related diseases such as coronavirus disease 2019 (COVID-19).

TBHQ alleviates pyroptosis and necroptosis in chicken alveolar epithelial cells induced by fine particulate matter from broiler houses

Fine particulate matter (PM2.5) from poultry houses has adverse effects on the health of animals and workers. Tert-butylhydroquinone (TBHQ), an antioxidant, is widely used in feed additives. The present study investigated the effects of TBHQ on broiler house PM2.5-induced damage in chicken primary alveolar epithelial cells (AECII) extracted from 16-day-old chicken embryos using the method of differential adhesion. AECII were exposed to PM2.5 and TBHQ alone or in combination, and then, cell membrane integrity, pyroptosis, and necroptosis were detected. Our results showed that PM2.5 from broiler houses caused cell rupture and loss of cell membrane integrity. This result was confirmed by the obvious increases in lactate dehydrogenase (LDH) release and propidium iodide (PI)-positive cells compared to the control group. In addition, the intracellular reactive oxygen species (ROS) levels and the expression levels of pyroptosis-related genes (NLRP3, IL-18, IL-1β) and necroptosis-related genes (RIPK3) were also significantly enhanced. However, TBHQ significantly inhibited intracellular ROS, improved cell viability, and reduced the release of LDH and the number of PI-positive cells compared to those in the PM2.5 group. The expression levels of pyroptosis-related genes (Caspase-1, NLRP3, IL-18, IL-1β) and necroptosis-related genes (RIPK3) were also significantly decreased in the co-treatment group. In summary, these results indicated that TBHQ can alleviate PM2.5-mediated cell pyroptosis and necroptosis in chicken AECII and provide a basis for overcoming the danger that air pollutants from broiler houses pose to the health of chickens.

Salidroside prevents PM2.5-induced BEAS-2B cell apoptosis via SIRT1-dependent regulation of ROS and mitochondrial function

PM2.5 is a harmful air pollutant currently threatening public health. It has been closely linked to increased morbidity of bronchial asthma and lung cancer worldwide. Salidroside (Sal), an active component extracted from Rhodiola rosea, has been reported to ameliorate the progression of asthma. However, there are few studies on the protective effect of salidroside on PM2.5-induced bronchial epithelial cell injury, and the related molecular mechanism is not clear. Here, we aimed to explore the protective effect and related mechanism of Sal on PM2.5 bronchial injury. We chose 50 μg/mL PM2.5 for 24 h as a PM2.5-induced cell damage model. After that BEAS-2B cells were pretreated with 40, 80, 160 µM Sal for 24 h and then exposed to 50 μg/mL PM2.5 for 24 h. We found that Sal pretreatment significantly inhibited the decrease of cell viability induced by PM2.5. Sal was effective in preventing PM2.5-induced apoptotic features, including Ca²⁺ overload, the cleavages of caspase 3, and the increases in levels of caspase 9 and Bcl-2-associated X protein (Bax), ultimately, Sal significantly inhibited PM2.5-induced apoptosis. Sal improved mitochondrial membrane potential, inhibited the release of cytochrome c from the mitochondria to cytoplasm. Sal alleviated ROS production, decreased the level of MDA, prevented the reduction of CAT, SOD and GSH-Px and increased the expression of NF-E2-related factor 2 (Nrf2), HO-1 and superoxide dismutase 1 (SOD1) in cells exposed to PM2.5. Furthermore, Sal improved the decrease of SIRT1 and PGC-1 α expression levels caused by PM2.5. In addition, inhibition of SIRT1 by EX527 (SIRT1 inhibitor) reversed the protective effects of Sal, including the decrease of ROS level, the increase of membrane potential level and the decrease of apoptosis level. Thus, Sal may be regarded as a potential drug to prevent PM2.5-induced apoptosis of bronchial epithelial cells and other diseases with similar pathological mechanisms.

A Novel Rat Model of Dry Eye Induced by Aerosol Exposure of Particulate Matter

Purpose

The purpose of this study was to introduce a novel dry eye rat model induced by aerosol exposure of particulate matter (PM).

Methods

A total of 30 female Sprague Dawley (SD) rats divided into 3 groups: the control group, the low-level exposed group, and the high-level exposed group. The rats in the experience groups were directly exposed to PM samples in the exposure chamber over 14 days. The clinical observation, including tear volume, corneal fluorescein staining, breakup time (BUT), inflammation index, corneal irregularity score, and corneal confocal microscopy. Eyeballs were collected on day 14 for hematoxylin and eosin (H&E) staining and PAS staining. TUNEL assay, CD45, and Ki67 immunostaining was performed and corneal ultrastructural changes were detected by electron microscopy. IL-1β, TNF-α, IFN-γ, and NF-κB Western blot analysis were used to observe the possible pathogenesis.

Results

In the PM-treated groups, the number of layers in the corneal epithelium and corneal nerve fiber length were significantly decreased compared with that of the control group. The number of corneal epithelial microvilli and chondriosome/desmosomes were drastically reduced in PM-treated groups. Confocal microscopy and CD45 immunohistochemistry showed inflammatory cell infiltration in the PM-treated groups. PM caused apoptosis of corneal and conjunctival epithelial cells while leading to abnormal epithelial cell proliferation, meanwhile, conjunctival goblet cells in the PM-treated group were also significantly reduced. PM significantly increased the levels of IL-1β, TNF-α, IFN-γ, and p-NF-κB-p65 in the cornea.

Conclusions

Aerosol exposure of PM can reduce the stability of tear film and cause the change of ocular surface, which is similar to the performance of human dry eye, suggesting a novel animal model of dry eye.

Magnetic resonance imaging investigations reveal that PM2.5 exposure triggers visual dysfunction in mice

OBJECTIVES

To investigate how PM_2.5 exposure affects the microstructure, metabolites or functions of the visual system.

METHODS

C57BL/6J mice were randomly assigned to groups exposed to the filtered air (the control group) or the concentrated ambient PM_2.5 (the PM_2.5 group). Visual evoked potentials (VEP), electroretinograms (ERG), diffusion tensor imaging (DTI), proton magnetic resonance spectroscopy (¹H-MRS) and resting-state functional MRI (rsfMRI) were performed. Parameters were obtained and compared between the two groups, including latencies and amplitudes of the P1 wave, N1 wave and P2 wave from VEP, latencies and amplitudes of the a wave and b wave from ERG, fractional anisotropy (FA), mean diffusion (MD), axial diffusivity (AD) and radial diffusivity (RD) from DTI, visual cortex (VC) metabolites from ¹H-MRS, and regional homogeneity (ReHo) from rsfMRI.

RESULTS

Compared with the values of the control group, the PM_2.5 group showed a prolonged N1 latency (43.11 ± 7.94 ms vs. 38.75 ± 4.60 ms) and lowered P1 amplitude (5.62 ± 4.38 μV vs. 8.56 ± 5.92 μV) on VEP (all p < 0.05). On ERG, the amplitude of the a wave was lowered (- 91.39 ± 56.29 μV vs. - 138.68 ± 89.05 μV), the amplitude of the b wave was lowered (194.38 ± 126.27 μV vs. 284.72 ± 170.99 μV), and the latency of the b wave was prolonged (37.78 ± 10.72 ms vs. 33.01 ± 4.34 ms) than the values of the control group (all p < 0.05). DTI indicated FA increase in the bilateral piriform cortex (Pir), FA decrease in the bilateral somatosensory cortex (S) and the bilateral striatum (Stri), AD decrease in the bilateral VC, the right S and the bilateral Pir, MD decrease in the bilateral Pir, and RD decrease in the bilateral Pir in the PM_2.5 mice (all p < 0.05, Alphasim corrected). ¹H-MRS showed Glutamate (Glu) increase and Phosphocholine (PCh) increase in the VC of the PM_2.5 group than those of the control group (PCh 1.63 ± 0.25 vs. 1.50 ± 0.25; PCh/total creatine(tCr) 0.19 ± 0.03 vs. 0.18 ± 0.03; Glu 10.46 ± 1.50 vs. 9.60 ± 1.19; Glu/tcr 1.23 ± 0.11 vs. 1.12 ± 0.11) (all p < 0.05). rsfMRI showed higher ReHo in the PM_2.5 mice in the left superior colliculus, the left motor cortex, the hippocampus, the periaqueductal gray and the right mesencephalic reticular formation (all p < 0.01, AlphaSim corrected).

CONCLUSIONS

This study revealed that PM_2.5 exposure triggered visual dysfunction, and altered microstructure, metabolite and function in the retina and visual brain areas along the visual system.

The Application of Nitric Oxide for Ocular Hypertension Treatment

Despite of various therapeutic methods for treating ocular hypertension and glaucoma, it still remains the leading cause of irreversible blindness. Intraocular pressure (IOP) lowering is the most effective way to slow disease progression and prevent blindness. Among the ocular hypotensive drugs currently in use, only a couple act on the conventional outflow system, which is the main pathway for aqueous humor outflow and the major lesion site resulting in ocular hypertension. Nitric oxide (NO) is a commendable new class of glaucoma drugs that acts on the conventional outflow pathway. An increasing number of nitric oxide donors have been developed for glaucoma and ocular hypertension treatment. Here, we will review how NO lowers IOP and the types of nitric oxide donors that have been developed. And a brief analysis of the advantages and challenges associated with the application will be made. The literature used in this review is based on Pubmed database search using ‘nitric oxide’ and ‘glaucoma’ as key words.

Lifetime exposure of ambient PM2.5 elevates intraocular pressure in young mice

Epidemiological studies suggest that ambient particulate matter exposure may be a new risk factor of glaucoma, but it lacks solid experimental evidence to establish a causal relationship. In this study, young mice (4 weeks old) were exposed concentrated ambient PM2.5 (CAP) for 9 months, which is throughout most of the life span of a mouse under heavy pollution. CAP was introduced using a versatile aerosol concentration enrichment system which mimics natural PM2.5 exposure. CAP exposure caused a gradual elevation of intraocular pressure (IOP) and an increase in aqueous humor outflow resistance. In the conventional outflow tissues that regulates IOP, inducible nitric oxide synthase (iNOS) was up-regulated and 3-nitrotyrosine (3-NT) formation increased. At the cellular level, PM2.5 exposure increased the transendothelial electrical resistance of cells that control IOP (AAP cells). This is accompanied by increased reactive oxygen species (ROS), iNOS and 3-NT levels. Peroxynitrite scavenger MnTMPyP successfully treated the IOP elevation and restored it to normal levels by reducing 3-NT formation in outflow tissues. This study provides the novel evidence that in young mice, lifetime whole-body PM2.5 exposure has a direct toxic effect on intraocular tissues, which imposes a significant risk of IOP elevation and may initiate the development of ocular hypertension and glaucoma. This occurs as a result of protein nitration of conventional aqueous humor outflow tissues.

Research advances in pathogenic mechanisms underlying air pollution-induced ocular surface diseases

Background

The harmful effect of aerial fine particulate matter（PM2.5）has been a serious public health issue and has attracted worldwide attention, especially in developing countries.

Main Text

Numerous previous clinical and experimental studies have demonstrated that PM2.5 has a clear pathogenic effect on diseases related to the respiratory and cardiovascular systems. Recent researches have pointed out that PM2.5 plays a pivotal role in the occurrence and progression of ocular surface diseases. The current studies have shown that PM2.5 may promote the appearance of conjunctivitis, keratitis, blepharitis, dry eye, meibomian gland dysfunction（MGD） and other ocular surface diseases through regulating a series of mechanisms such as inflammation, immune reaction, oxidative stress, autophagy, cell migration, and epigenetics.

Conclusions

This review aims to summarize the current research progress on the pathogenic mechanism of PM2.5-related ocular surface diseases.

The Protective Effect of Topical Spermidine on Dry Eye Disease with Retinal Damage Induced by Diesel Particulate Matter2.5

Air pollutants, especially ambient fine particulate matter2.5, may contribute to various ocular surface disorders, including dry eye disease, keratitis and conjunctivitis. A natural polyamine spermidine has a protective effect on the retina and optic nerve; however, no study has been conducted on the application of spermidine in particulate matter2.5-induced dry eye disease. In the present study, we investigated the effect of spermidine eye drops in topically exposed particulate matter2.5-induced dry eye models of Sprague-Dawley rats, by hematological, biochemical and histological evaluation. Spermidine eye drops attenuated the particulate matter2.5 exposure-induced reduction of tear secretion and corneal epithelial damage. Furthermore, spermidine protected against conjunctival goblet cell loss and retinal ganglion cell loss induced by particulate matter2.5. Additionally, spermidine markedly prevented particulate matter2.5-induced infiltration of cluster of differentiation3⁺ and cluster of differentiation4⁺ T lymphocytes and F4/80⁺ macrophages on lacrimal gland. Moreover, over expression of pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-6 and interleukin-17 in the lacrimal gland and cornea. Meanwhile, the levels of serum total cholesterol and low-density lipoprotein cholesterol were markedly increased by topical exposure to particulate matter2.5, but this change in the lipid profile was decreased by spermidine. Taken together, spermidine may have protective effects against particulate matter2.5-induced dry eye symptoms via stabilization of the tear film and suppression of inflammation and may in part contribute to improving retinal function and lipid metabolism disorder.

Forgotten but not gone: Particulate matter as contaminations of mucosal systems

A decade ago, environmental issues, such as air pollution and the contamination of the oceans with microplastic, were prominently communicated in the media. However, these days, political topics, as well as the ongoing COVID-19 pandemic, have clearly taken over. In spite of this shift in focus regarding media representation, researchers have made progress in evaluating the possible health risks associated with particulate contaminations present in water and air. In this review article, we summarize recent efforts that establish a clear link between the increasing occurrence of certain pathological conditions and the exposure of humans (or animals) to airborne or waterborne particulate matter. First, we give an overview of the physiological functions mucus has to fulfill in humans and animals, and we discuss different sources of particulate matter. We then highlight parameters that govern particle toxicity and summarize our current knowledge of how an exposure to particulate matter can be related to dysfunctions of mucosal systems. Last, we outline how biophysical tools and methods can help researchers to obtain a better understanding of how particulate matter may affect human health. As we discuss here, recent research has made it quite clear that the structure and functions of those mucosal systems are sensitive toward particulate contaminations. Yet, our mechanistic understanding of how (and which) nano- and microparticles can compromise human health via interacting with mucosal barriers is far from complete.

The Protective Effect of Oral Application of Corni Fructus on the Disorders of the Cornea, Conjunctiva, Lacrimal Gland and Retina by Topical Particulate Matter 2.5

Particulate matter 2.5 (PM_2.5) may aggravate dry eye disease (DED). Corni Fructus (CF), which is fruit of Cornus officinalis Sieb. et Zucc., has been reported to have various beneficial pharmacological effects, whereas the effect of CF on the eye is still unknown. Therefore, in this study, we investigated the effect of oral administration of water extract of CF (CFW) on the eye, hematology, and biochemistry in a DED model induced by topical exposure to PM_2.5. Furthermore, the efficacy of CFW compared with cyclosporine (CsA), an anti-inflammatory agent, and lutein, the posterior eye-protective agent. Sprague-Dawley rats were topically administered 5 mg/mL PM_2.5 in both eyes four times daily for 14 days. During the same period, CFW (200 mg/kg and 400 mg/kg) and lutein (4.1 mg/kg) were orally administered once a day. All eyes of rats in the 0.05% cyclosporine A (CsA)-treated group were topically exposed to 20 μL of CsA, twice daily for 14 days. Oral administration of CFW attenuated the PM_2.5-induced reduction of tear secretion and corneal epithelial damage. In addition, CFW protected against goblet cell loss in conjunctiva and overexpression of inflammatory factors in the lacrimal gland following topical exposure to PM_2.5. Furthermore, CFW markedly prevented PM_2.5-induced ganglion cell loss and recovered the thickness of inner plexiform layer. Meanwhile, CFW treatment decreased the levels of total cholesterol and low-density lipoprotein cholesterol in serum induced by PM_2.5. Importantly, the efficacy of CFW was superior or similar to that of CsA and lutein. Taken together, oral administration of CFW may have protective effects against PM_2.5-induced DED symptoms via stabilization of the tear film and suppression of inflammation. Furthermore, CFW may in part contribute to improving retinal function and lipid metabolism disorder.

Targeting the NLRP3 Inflammasome in Glaucoma

Glaucoma is a group of optic neuropathies characterised by the degeneration of retinal ganglion cells, resulting in damage to the optic nerve head (ONH) and loss of vision in one or both eyes. Increased intraocular pressure (IOP) is one of the major aetiological risk factors in glaucoma, and is currently the only modifiable risk factor. However, 30–40% of glaucoma patients do not present with elevated IOP and still proceed to lose vision. The pathophysiology of glaucoma is therefore not completely understood, and there is a need for the development of IOP-independent neuroprotective therapies to preserve vision. Neuroinflammation has been shown to play a key role in glaucoma and, specifically, the NLRP3 inflammasome, a key driver of inflammation, has recently been implicated. The NLRP3 inflammasome is expressed in the eye and its activation is reported in pre-clinical studies of glaucoma. Activation of the NLRP3 inflammasome results in IL-1β processing. This pro inflammatory cytokine is elevated in the blood of glaucoma patients and is believed to drive neurotoxic inflammation, resulting in axon degeneration and the death of retinal ganglion cells (RGCs). This review discusses glaucoma as an inflammatory disease and evaluates targeting the NLRP3 inflammasome as a therapeutic strategy. A hypothetical mechanism for the action of the NLRP3 inflammasome in glaucoma is presented.

Black carbon induces complement activation via NLRP3 inflammasome in human corneal epithelial cells

PURPOSE

To investigate the effect of black carbon (BC) particles on complement activation in human corneal epithelial cells (HCECs), and determine whether this effect can be attenuated by inhibiting the NLPR3 inflammasome pathway.

MATERIALS AND METHODS

HCECs were treated with fresh BC (FBC) or ozone-oxidized BC (OBC) particles at a concentration of 200 μg/ml for 72hours. Complement activation was observed by detecting C5b-9 protein level in cell culture supernatant using ELISA. HCECs were transfected with duplexes of siRNA targeting NLRP3 (NLRP3-siRNA) at 0.1 pmol/µL for 24 hours to inhibit the NLPR3 inflammasome pathway. RT-qPCR was performed to examine the efficacy of NLRP3-siRNA for inhibition; a random siRNA duplex was used for control siRNA.

RESULTS

Both FBC exposure and OBC exposure for 72 hours significantly increased the C5b-9 protein level compared to negative control cells (all P < .05). However, the difference in C5b-9 level after FBC exposure and OBC exposure was not statistically significant (P> .05). NLRP3-siRNA transfection reduced C5b-9 protein levels in FBC treated and OBC treated HCECs compared to control (lowered by 27% in the FBC treated group and by 23% in the OBC treated group, all P < .05).

CONCLUSIONS

BC particles, including FBC and OBC, triggered complement activation, increasing the protein level of C5b-9 in cultured HCECs. siRNA targeting NLRP3 to inhibit NLRP3 generation reduced C5b-9 protein level in HCECs treated with FBC or OBC particles, indicating that BC induces complement activation potentially through the NLRP3 inflammasome in HCECs.