Environmental pollutants induce NLRP3 inflammasome activation and pyroptosis: Roles and mechanisms in various diseases

An Overview of Hexavalent Chromium-Induced Necroptosis, Pyroptosis, and Ferroptosis

Heavy metals are common environmental industrial pollutants. Due to anthropogenic activity, chromium, especially its hexavalent form [Cr(VI)], is a widespread environmental contaminant that poses a threat to human health. In this review paper, we summarize the currently reported molecular mechanisms involved in chromium toxicity with a focus on the induction of pro-inflammatory non-apoptotic cell death pathways such as necroptosis, pyroptosis, and ferroptosis. The review highlights the ability of chromium to induce necroptosis, pyroptosis, and ferroptosis revealing the signaling pathways involved. Cr(VI) can induce RIPK1/RIPK3-dependent necroptosis both in vitro and in vivo. Chromium toxicity is associated with pyroptotic NLRP3 inflammasome/caspase-1/gasdermin D-dependent secretion of IL-1β and IL-18. Furthermore, this review emphasizes the role of redox imbalance and intracellular iron accumulation in Cr(VI)-induced ferroptosis. Of note, the crosstalk between the investigated lethal subroutines in chromium-induced toxicity is primarily mediated by reactive oxygen species (ROS), which are suggested to act as a rheostat determining the cell death pathway in cells exposed to chromium. The current study provides novel insights into the pro-inflammatory effects of chromium, since necroptosis, pyroptosis, and ferroptosis affect inflammation owing to their immunogenic properties linked primarily with damage-associated molecular patterns. Inhibition of these non-apoptotic lethal subroutines can be considered a therapeutic strategy to reduce the toxicity of heavy metals, including chromium.

Gray Frequency-Based Methodology for Assessing Cell Damage

Cell biology techniques offer a solid foundation for evaluating and forecasting the danger of pollutants in the investigations of environmental toxicology. Studies on ecological toxicity, medication development, and illness diagnosis depend on evaluating cellular damage. The morphology of stimulated cells can alter the light scattering and reflection, and the brightness of microscopic images of the cells. This study demonstrated that stimulation-damaged and normal cells had distinct gray value distributions which led to the proposal of a novel theory to measure cellular damage by image brightness. Second, various cell types were used to confirm the method's applicability. Additionally, an evaluation technique based on gray frequency analysis can be created to determine the extent of cellular damage. This approach provides an effective and helpful tool for cellular damage visualization and quantitative evaluation in environmental toxicity assessment.

Life-threatening risk factors contribute to the development of diseases with the highest mortality through the induction of regulated necrotic cell death

Chronic diseases affecting the cardiovascular system, diabetes mellitus, neurodegenerative diseases, and various other organ-specific conditions, involve different underlying pathological processes. However, they share common risk factors that contribute to the development and progression of these diseases, including air pollution, hypertension, obesity, high cholesterol levels, smoking and alcoholism. In this review, we aim to explore the connection between four types of diseases with different etiologies and various risk factors. We highlight that the presence of risk factors induces regulated necrotic cell death, leading to the release of damage-associated molecular patterns (DAMPs), ultimately resulting in sterile inflammation. Therefore, DAMP-mediated inflammation may be the link explaining how risk factors can lead to the development and maintenance of chronic diseases. To explore these processes, we summarize the main cell death pathways activated by the most common life-threatening risk factors, the types of released DAMPs and how these events are associated with the pathophysiology of diseases with the highest mortality. Various risk factors, such as smoking, air pollution, alcoholism, hypertension, obesity, and high cholesterol levels induce regulated necrosis. Subsequently, the release of DAMPs leads to chronic inflammation, which increases the risk of many diseases, including those with the highest mortality rates.

Computational insights into exploring the potential effects of environmental contaminants on human health

With rapid industrialization and urbanization, the increasing prevalence of air and water pollutants poses a significant threat to public health. Traditional research methods, such as epidemiological studies and in vitro/in vivo experiments, provide valuable biological insights but are often costly, time-consuming, and limited in scale. To address this gap, this study develops a machine learning-based approach to predict the carcinogenicity of pollutants. Using the dataset of carcinogenic and non-carcinogenic molecules that we collected, the pretrained KPGT model trained with molecular fingerprints and descriptors achieved an AUC of 0.83, surpassing traditional machine learning models. To validate this model, common pollutants from air and water sources were analyzed. Further clustering classified these pollutants into five distinct groups. Target prediction analysis identified key genes associated with representative pollutant molecules, such as MAPK1, MTOR, and PTPN11. GO and KEGG pathway analyses, along with survival analysis, revealed potential carcinogenic mechanisms and prognostic implications. Our findings contribute to improved pollution risk assessment and evidence-based environmental policy development, ultimately aiding in the mitigation of pollutant-related health risks.

The role of NLRP3 inflammasome activation in proinflammatory and cytotoxic effects of metal nanoparticles

Exposure to metal nanoparticles (NPs) is known to induce inflammatory responses in various tissues, thus limiting their therapeutic potential. NOD-like receptor protein 3 (NLRP3) inflammasome activation is an essential component of innate immunity playing a significant role in inflammation and development of inflammatory diseases. Therefore, the objective of the present review was to summarize data on the role of NLRP3 inflammasome in proinflammatory effects induced by metal NPs, and to discuss the underlying molecular mechanisms, including its dependence on the physical and chemical properties of metal NPs. Titanium, zinc, silver, aluminum, iron, cobalt, nickel, vanadium, and tungsten nanoparticles, as well as metal-based quantum dots have all been shown to induce NLRP3 inflammasome activation in vitro in macrophages and monocytes, dendritic cells, keratinocytes, hepatocytes, enterocytes, microglia, astrocytes, lung epithelial cells, endotheliocytes, as well as certain types of cancer cells. In vivo studies confirmed the role of NLRP3 pathway activation in development of colitis, pulmonary inflammation, liver damage, osteolysis, and neuroinflammation induced by various metal nanoparticles. Briefly, particle endocytosis with subsequent lysosomal damage, induction of ROS formation, K+ efflux, increased intracellular Ca2+ levels, and NF-κB pathway activation results in NLRP3 inflammasome complex assembly, caspase-1 activation, and cleavage of pro-IL-1β and pro-IL-18 to mature proinflammatory cytokines, while gasdermin D cleavage induces pyroptotic cell death. Moreover, small-sized and rod-shaped metal NPs exert a more profound stimulatory effect on NLRP3 inflammasome activation, but contrary findings have also been reported. Taken together, it is concluded that NLRP3 inflammasome may mediate both adverse proinflammatory effects of metal nanoparticles, as well as their beneficial effect when used as antitumor agents.

Short-Chain Chlorinated Paraffins May Induce Ovarian Damage in Mice via AIM2- and NLRP12-PANoptosome

Humans may intake 0.02 mg/kg/day of short-chain chlorinated paraffins (SCCPs), and no study is available on mammalian ovarian damage caused by low-level SCCPs. In this study, four groups of 5-week-old female Institute of Cancer Research (ICR) mice were orally administered 0, 0.01, 0.1, and 1.0 mg/kg/day SCCPs for 21 consecutive days, and serum and ovaries were collected 20 h after the last SCCPs-administration. SCCPs at ≥0.1 mg/kg/day were found to reduce follicle counts at each stage, induce dose-dependent oxidative stress in mice, and lower serum E2 and ovarian anti-Müllerian hormone levels. The data indicated that cellular PANoptosis increased in the ovaries of all SCCP-treated mice. Furthermore, AIM2- and NLRP12-PANoptosome gene and protein levels were considerably elevated. Female germline stem cells (FGSCs) in the cortical portion of the ovary exhibited substantial damage in all SCCP groups, additionally, the expression of FGSC marker genes and major marker proteins was diminished in the ovaries. Oral administration of SCCPs with 0.01, 0.1, and 1.0 mg/kg/day to mice resulted in PANoptosis of the ovaries. Therefore, it was suggested that the oral administration of ≥0.1 mg/kg/day of SCCPs suppressed ovarian function, which may be attributed to the fact that SCCPs induced the generation of AIM2- and NLRP12-PANoptosome in ovary cells.

Mechanisms of Metal-Induced Hepatic Inflammation

PURPOSE OF REVIEW

Worldwide, there is an increasing prevalence of hepatic diseases. The most common diseases include alcoholic-associated liver disease (ALD), metabolic dysfunction-associated fatty liver disease/ metabolic dysfunction-associated steatohepatitis (MAFLD/MASH) and viral hepatitis. While there are many important mediators of these diseases, there is increasing recognition of the importance of the inflammatory immune response in hepatic disease pathogenesis.

RECENT FINDINGS

Hepatic inflammation triggers the onset and progression of liver diseases. Chronic and sustained inflammation can lead to fibrosis, then cirrhosis and eventually end-stage cancer, hepatocellular carcinoma. Importantly, growing evidence suggest that metal exposure plays a role in hepatic disease pathogenesis. While in recent years, studies have linked metal exposure and hepatic steatosis, studies emphasizing metal-induced hepatic inflammation are limited. Hepatic inflammation is an important hallmark of fatty liver disease. This review aims to summarize the mechanisms of arsenic (As), cadmium (Cd) and chromium (Cr)-induced hepatic inflammation as they contribute to hepatic toxicity and to identify data gaps for future investigation.

PM2.5-mediated cardiovascular disease in aging: Cardiometabolic risks, molecular mechanisms and potential interventions

Air pollution, particularly fine particulate matter (PM2.5) with <2.5 μm in diameter, is a major public health concern. Studies have consistently linked PM2.5 exposure to a heightened risk of cardiovascular diseases (CVDs) such as ischemic heart disease (IHD), heart failure (HF), and cardiac arrhythmias. Notably, individuals with pre-existing age-related cardiometabolic conditions appear more susceptible. However, the specific impact of PM2.5 on CVDs susceptibility in older adults remains unclear. Therefore, this review addresses this gap by discussing the factors that make the elderly more vulnerable to PM2.5-induced CVDs. Accordingly, we focused on physiological aging, increased susceptibility, cardiometabolic risk factors, CVDs, and biological mechanisms. This review concludes by examining potential interventions to reduce exposure and the adverse health effects of PM2.5 in the elderly population. The latter includes dietary modifications, medications, and exploration of the potential benefits of supplements. By comprehensively analyzing these factors, this review aims to provide a deeper understanding of the detrimental effects of PM2.5 on cardiovascular health in older adults. This knowledge can inform future research and guide strategies to protect vulnerable populations from the adverse effects of air pollution.

Copper induced cytosolic escape of mitochondrial DNA and activation of cGAS-STING-NLRP3 pathway-dependent pyroptosis in C8-D1A cells

Copper, a vital mineral nutrient, possesses redox qualities that make it both beneficial and toxic to organisms. Excessive environmental copper exposure can result in neurological damage and cognitive decline in humans. Astrocytes, the predominant glial cells in the brain, are particularly vulnerable to pollutants, but the mechanism of copper-induced damage to astrocytes remains elusive. The aim of this study was to determine the role of the cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway in initiating NLRP3 inflammasome-induced astrocyte pyroptosis and chronic inflammation under conditions of copper overload. Our findings indicated that copper exposure elevated mitochondrial ROS (mtROS) levels, resulting in mitochondrial damage in astrocytes. This damage caused the release of mitochondrial DNA (mtDNA) into the cytoplasm, which subsequently activated the cGAS-STING pathway. This activation resulted in interactions between STING and NLRP3 proteins, facilitating the assembly of the NLRP3 inflammasome and inducing pyroptosis. Furthermore, depletion of mtROS mitigated copper-induced mitochondrial damage in astrocytes and reduced mtDNA leakage. Pharmacological inhibition of STING or STING transfection further reversed copper-induced pyroptosis and the inflammatory response. In conclusion, this study demonstrated that the leakage of mtDNA into the cytoplasm and the subsequent activation of the cGAS-STING-NLRP3 pathway may be potential mechanisms underlying copper-induced pyroptosis in astrocytes. These findings provided new insights into the toxicity of copper.

Imbalance of mitochondrial quality control regulated by STING and PINK1 affects cyfluthrin-induced neuroinflammation

Nervous system diseases are a global health problem, and with the increase in the elderly population around the world, their incidence will also increase. Harmful substances in the environment are closely related to the occurrence of nervous system diseases. China is a large agricultural country, and thus the insecticide cyfluthrin has been widely used. Cyfluthrin is neurotoxic, but the mechanism of this injury is not clear. Inflammation is an important mechanism for the occurrence of nervous system diseases. Mitochondria are the main regulators of the inflammatory response, and various cellular responses, including autophagy, directly affect the regulation of inflammatory processes. Mitochondrial damage is related to mitochondrial quality control (MQC) and PTEN-induced kinase 1 (PINK1). As an anti-inflammatory factor, stimulator of interferon genes (STING) participates in the regulation of inflammation. However, the relationship between STING and mitochondria in the process of cyfluthrin-induced nerve injury is unclear. This study established in vivo and in vitro models of cyfluthrin exposure to explore the role of MQC and to clarify the mechanism of action of STING and PINK1. Our results showed that cyfluthrin can increase the reactive oxygen species (ROS) level, resulting in mitochondrial damage and inflammation. In this process, an imbalance in MQC leads to the aggravation of mitochondrial damage, and high STING expression drives the occurrence of inflammation. We established a differential expression model of STING and PINK1 to further determine the underlying mechanism and found that the interaction between STING and PINK1 regulates MQC to affect the levels of mitochondrial damage and inflammation. When STING and PINK1 expression are downregulated, mitochondrial damage and STING-induced inflammation are significantly alleviated. In summary, a synergistic effect between STING and PINK1 on cyfluthrin-induced neuroinflammation may exist, which leads to an imbalance in MQC by inhibiting mitochondrial biogenesis and division/fusion, and PINK1 can reduce STING-driven inflammation.

Attenuation of PM2.5-Induced Lung Injury by 4-Phenylbutyric Acid: Maintenance of [Ca2+]i Stability between Endoplasmic Reticulum and Mitochondria

Fine particulate matter (PM2.5) is a significant cause of respiratory diseases and associated cellular damage. The mechanisms behind this damage have not been fully explained. This study investigated two types of cellular damage (inflammation and pyroptosis) induced by PM2.5, focusing on their relationship with two organelles (the endoplasmic reticulum and mitochondria). Animal models have demonstrated that PM2.5 induces excessive endoplasmic reticulum stress (ER stress), which is a significant cause of lung damage in rats. This was confirmed by pretreatment with an ER stress inhibitor (4-Phenylbutyric acid, 4-PBA). We found that, in vitro, the intracellular Ca2+ ([Ca2+]i) dysregulation induced by PM2.5 in rat alveolar macrophages was associated with ER stress. Changes in mitochondria-associated membranes (MAMs) result in abnormal mitochondrial function. This further induced the massive expression of NLRP3 and GSDMD-N, which was detrimental to cell survival. In conclusion, our findings provide valuable insights into the relationship between [Ca2+]i dysregulation, mitochondrial damage, inflammation and pyroptosis under PM2.5-induced ER stress conditions. Their interactions ultimately have an impact on respiratory health.

Pyroptosis, gasdermins and allergic diseases

Pyroptosis is an inflammatory form of programmed cell death that is distinct from necrosis and apoptosis. Pyroptosis is primarily mediated by the gasdermin family of proteins (GSDMA-E and PVJK), which, when activated by proteolytic cleavage, form pores in the plasma membrane, leading to cell death. While much of the past research on pyroptosis has focused on its role in cancer, metabolic disorders, and infectious diseases, recent experimental and observational studies have begun to implicate pyroptosis in allergic diseases. These studies suggest that gasdermin-mediated pyroptosis contributes to the development of allergic conditions and could offer novel targets for therapy. Here, we review our current understanding of pyroptosis with an emphasis on the role of gasdermins as executioners of pyroptosis and potential mediators to allergic disease. We highlight new discoveries that establish a mechanistic link between the biochemical actions of gasdermins and the onset of allergic diseases. Additionally, we discuss how pyroptosis and gasdermins might contribute to the dysfunction of epithelial barrier, a key factor believed to initiate the progression of various allergic diseases.

Homotherapy for heteropathy: therapeutic effect of Butein in NLRP3-driven diseases

BACKGROUND

Aberrant inflammatory responses drive the initiation and progression of various diseases, and hyperactivation of NLRP3 inflammasome is a key pathogenetic mechanism. Pharmacological inhibitors of NLRP3 represent a potential therapy for treating these diseases but are not yet clinically available. The natural product butein has excellent anti-inflammatory activity, but its potential mechanisms remain to be investigated. In this study, we aimed to evaluate the ability of butein to block NLRP3 inflammasome activation and the ameliorative effects of butein on NLRP3-driven diseases.

METHODS

Lipopolysaccharide (LPS)-primed bone-marrow-derived macrophages were pretreated with butein and various inflammasome stimuli. Intracellular potassium levels, ASC oligomerization and reactive oxygen species production were also detected to evaluate the regulatory mechanisms of butein. Moreover, mouse models of LPS-induced peritonitis, dextran sodium sulfate-induced colitis, and high-fat diet-induced non-alcoholic steatohepatitis were used to test whether butein has protective effects on these NLRP3-driven diseases.

RESULTS

Butein blocks NLRP3 inflammasome activation in mouse macrophages by inhibiting ASC oligomerization, suppressing reactive oxygen species production, and upregulating the expression of the antioxidant pathway nuclear factor erythroid 2-related factor 2 (Nrf2). Importantly, in vivo experiments demonstrated that butein administration has a significant protective effect on the mouse models of LPS-induced peritonitis, dextran sodium sulfate-induced colitis, and high-fat diet-induced non-alcoholic steatohepatitis.

CONCLUSION

Our study illustrates the connotation of homotherapy for heteropathy, i.e., the application of butein to broaden therapeutic approaches and treat multiple inflammatory diseases driven by NLRP3.

Immune-mediated disease caused by climate change-associated environmental hazards: mitigation and adaptation

Global warming and climate change have increased the pollen burden and the frequency and intensity of wildfires, sand and dust storms, thunderstorms, and heatwaves - with concomitant increases in air pollution, heat stress, and flooding. These environmental stressors alter the human exposome and trigger complex immune responses. In parallel, pollutants, allergens, and other environmental factors increase the risks of skin and mucosal barrier disruption and microbial dysbiosis, while a loss of biodiversity and reduced exposure to microbial diversity impairs tolerogenic immune development. The resulting immune dysregulation is contributing to an increase in immune-mediated diseases such as asthma and other allergic diseases, autoimmune diseases, and cancer. It is now abundantly clear that multi-sectoral, multidisciplinary, and transborder efforts based on Planetary Health and One Health approaches (which consider the dependence of human health on the environment and natural ecosystems) are urgently needed to adapt to and mitigate the effects of climate change. Key actions include reducing emissions and improving air quality (through reduced fossil fuel use), providing safe housing (e.g., improving weatherization), improving diets (i.e., quality and diversity) and agricultural practices, and increasing environmental biodiversity and green spaces. There is also a pressing need for collaborative, multidisciplinary research to better understand the pathophysiology of immune diseases in the context of climate change. New data science techniques, biomarkers, and economic models should be used to measure the impact of climate change on immune health and disease, to inform mitigation and adaptation efforts, and to evaluate their effectiveness. Justice, equity, diversity, and inclusion (JEDI) considerations should be integral to these efforts to address disparities in the impact of climate change.

Glycyrrhizin and the Related Preparations: An Inspiring Resource for the Treatment of Liver Diseases

Liver diseases and their related complications endanger the health of millions of people worldwide. The prevention and treatment of liver diseases are still serious challenges both in China and globally. With the improvement of living standards, the prevalence of metabolic liver diseases, including non-alcoholic fatty liver disease and alcoholic liver disease, has increased at an alarming rate, resulting in more cases of end-stage liver disease. Therefore, the discovery of novel therapeutic drugs for the treatment of liver diseases is urgently needed. Glycyrrhizin (GL), a triterpene glycoside from the roots of licorice plants, possesses a wide range of pharmacological and biological activities. Currently, GL preparations (GLPs) have certain advantages in the treatment of liver diseases, with good clinical effects and fewer adverse reactions, and have shown broad application prospects through multitargeting therapeutic mechanisms, including antisteatotic, anti-oxidative stress, anti-inflammatory, immunoregulatory, antifibrotic, anticancer, and drug interaction activities. This review summarizes the currently known biological activities of GLPs and their medical applications in the treatment of liver diseases, and highlights the potential of these preparations as promising therapeutic options and their alluring prospects for the treatment of liver diseases.

Ferroptosis Induced by Pollutants: An Emerging Mechanism in Environmental Toxicology

Environmental pollutants have been recognized for their ability to induce various adverse outcomes in both the environment and human health, including inflammation, apoptosis, necrosis, pyroptosis, and autophagy. Understanding these biological mechanisms has played a crucial role in risk assessment and management efforts. However, the recent identification of ferroptosis as a form of programmed cell death has emerged as a critical mechanism underlying pollutant-induced toxicity. Numerous studies have demonstrated that fine particulates, heavy metals, and organic substances can trigger ferroptosis, which is closely intertwined with lipid, iron, and amino acid metabolism. Given the growing evidence linking ferroptosis to severe diseases such as heart failure, chronic obstructive pulmonary disease, liver injury, Parkinson's disease, Alzheimer's disease, and cancer, it is imperative to investigate the role of pollutant-induced ferroptosis. In this review, we comprehensively analyze various pollutant-induced ferroptosis pathways and intricate signaling molecules and elucidate their integration into the driving and braking axes. Furthermore, we discuss the potential hazards associated with pollutant-induced ferroptosis in various organs and four representative animal models. Finally, we provide an outlook on future research directions and strategies aimed at preventing pollutant-induced ferroptosis. By enhancing our understanding of this novel form of cell death and developing effective preventive measures, we can mitigate the adverse effects of environmental pollutants and safeguard human and environmental health.

Molecular Foundations of Inflammatory Diseases: Insights into Inflammation and Inflammasomes

Inflammatory diseases are a global health problem affecting millions of people with a wide range of conditions. These diseases, including inflammatory bowel disease (IBD), rheumatoid arthritis (RA), osteoarthritis (OA), gout, and diabetes, impose a significant burden on patients and healthcare systems. A complicated interaction between genetic variables, environmental stimuli, and dysregulated immune responses shows the complex biological foundation of various diseases. This review focuses on the molecular mechanisms underlying inflammatory diseases, including the function of inflammasomes and inflammation. We investigate the impact of environmental and genetic factors on the progression of inflammatory diseases, explore the connection between inflammation and inflammasome activation, and examine the incidence of various inflammatory diseases in relation to inflammasomes.

CD14 down-modulation as a real-time biomarker in Kawasaki disease

Objectives

The objectives of this study were to investigate the pathophysiology of Kawasaki disease (KD) from immunological and oxidative stress perspectives, and to identify real-time biomarkers linked to innate immunity and oxidative stress in KD.

Methods

We prospectively enrolled 85 patients with KD and 135 patients with diverse conditions including immune, infectious and non-infectious diseases for this investigation. Flow cytometry was used to analyse the surface expression of CD14, CD38 and CD62L on monocytes, along with a quantitative assessment of CD14 down-modulation. Additionally, oxidative stress levels were evaluated using derivatives of reactive oxygen metabolites (d-ROMs) and antioxidant capacity measured by a free radical elective evaluator system.

Results

During the acute phase of KD, we observed a prominent CD14 down-modulation on monocytes, reflecting the indirect detection of circulating innate immune molecular patterns. Moreover, patients with KD showed a significantly higher CD14 down-modulation compared with infectious and non-infectious disease controls. Notably, the surface expression of CD14 on monocytes was restored concurrently with responses to intravenous immunoglobulin and infliximab treatment in KD. Furthermore, d-ROM levels in patients with KD were significantly elevated compared with patients with infectious and non-infectious diseases. Following intravenous immunoglobulin treatment, oxidative stress levels decreased in patients with KD.

Conclusion

Monitoring CD14 down-modulation on monocytes in real-time is a valuable strategy for assessing treatment response, distinguishing KD relapse from concomitant infections and selecting second-line therapy after IVIG treatment in KD patients. The interplay between inflammation and oxidative stress likely plays a crucial role in the development of KD.