NLRP3 inflammasome blocked the glycolytic pathway via targeting to PKLR in arsenic-induced hepatic insulin resistance

Angiogenin-mediated tsRNAs control inflammation and metabolic disorder by regulating NLRP3 inflammasome

The cellular stress response system in immune cells plays a crucial role in regulating the development of inflammatory diseases. In response to cellular damage or microbial infection, the assembly of the NLRP3 inflammasome induces pyroptosis and the release of inflammatory cytokines. Meanwhile, Angiogenin (Ang)-mediated transfer RNA-derived small RNAs (tsRNAs) promote cell survival under stressful conditions. While both tsRNAs and inflammasomes are induced under stress conditions, the interplay between these two systems and their implications in regulating inflammatory diseases remains poorly understood. In this study, it was demonstrated that Ang deficiency exacerbated sodium arsenite-induced activation of NLRP3 inflammasome and pyroptosis. Moreover, Ang-induced 5'-tsRNAs inhibited NLRP3 inflammasome activation and pyroptosis. Mechanistically, 5'-tsRNAs recruit DDX3X protein into stress granules (SGs), consequently inhibiting the interaction between DDX3X and NLRP3, thus leading to the suppression of NLRP3 inflammasome activation. Furthermore, in vivo results showed that Ang deficiency led to the downregulation of tsRNAs, ultimately leading to an exacerbation of NLRP3 inflammasome-dependent inflammation, including lipopolysaccharide-induced systemic inflammation and type-2 diabetes-related inflammation. Altogether, our study sheds a new light on the role of Ang-induced 5'-tsRNAs in regulating NLRP3 inflammasome activation via SGs, and highlights tsRNAs as a promising target for the treatment of NLRP3 inflammasome-related diseases.

Down-regulation of O-GlcNAcylation alleviates insulin signaling pathway impairment following arsenic exposure via suppressing the AMPK/mTOR-autophagy pathway

Impairment of the insulin signaling pathway is a key contributor to insulin resistance under arsenic exposure. Specifically, O-GlcNAcylation, an important post-translational modification, plays a crucial role in insulin resistance. Nevertheless, the concrete effect and mechanism of O-GlcNAcylation in arsenic-induced impairment of the insulin signaling pathway remain elusive. Herein, C57BL/6 mice were continuously fed arsenic-containing food, with a total arsenic concentration of 30 mg/kg. We observed that the IRS/Akt/GSK-3β insulin signaling pathway was impaired, and autophagy was activated in mouse livers and HepG2 cells exposed to arsenic. Additionally, O-GlcNAcylation expression in mouse livers and HepG2 cells was elevated, and the key O-GlcNAcylation homeostasis enzyme, O-GlcNAc transferase (OGT), was upregulated. In vitro, non-targeted metabolomic analysis showed that metabolic disorder was induced, and inhibition of O-GlcNAcylation restored the metabolic profile of HepG2 cells exposed to arsenic. In addition, we found that the compromised insulin signaling pathway was dependent on AMPK activation. Inhibition of AMPK mitigated autophagy activation and impairment of insulin signaling pathway under arsenic exposure. Furthermore, down-regulation of O-GlcNAcylation inhibited AMPK activation, thereby suppressing autophagy activation, and improving the impaired insulin signaling pathway. Collectively, our findings indicate that arsenic can impair the insulin signaling pathway by regulating O-GlcNAcylation homeostasis. Importantly, O-GlcNAcylation inhibition alleviated the impaired insulin signaling pathway by suppressing the AMPK/mTOR-autophagy pathway. This indicates that regulating O-GlcNAcylation may be a potential intervention for the impaired insulin signaling pathway induced by arsenic.

m6A methylation-mediated PGC-1α contributes to ferroptosis via regulating GSTK1 in arsenic-induced hepatic insulin resistance

Arsenic exposure has been closely linked to hepatic insulin resistance (IR) and ferroptosis with the mechanism elusive. Peroxisome proliferator γ-activated receptor coactivator 1-α (PGC-1α) is essential for glucose metabolism as well as for the production of reactive oxygen species (ROS). However, it was unclear whether there is a regulatory connection between PGC-1α and ferroptosis. Besides, the definitive mechanism of arsenic-induced hepatic IR progression remains to be determined. Here, we found that hepatic insulin sensitivity impaired by sodium arsenite (NaAsO2) could be reversed by inhibiting ferroptosis. Mechanistically, we found that PGC-1α suppression inhibited the protein expression of glutathione s-transferase kappa 1 (GSTK1) via nuclear respiratory factor 1 (NRF1), thereby increasing ROS accumulation and promoting ferroptosis. Furthermore, we showed that NaAsO2 induced hepatic IR and ferroptosis via methyltransferase-like 14 (METTL14) and YTH domain-containing family protein 2 (YTHDF2)-mediated N6-methyladenosine (m6A) of PGC-1α mRNA. In conclusion, NaAsO2-mediated PGC-1α suppression was m6A methylation-dependent and induced ferroptosis via the PGC-1α/NRF1/GSTK1 pathway in hepatic IR. The data might provide insight into potential targets for diabetes prevention and treatment.

Rotundic acid improves nonalcoholic steatohepatitis in mice by regulating glycolysis and the TLR4/AP1 signaling pathway

BACKGROUND

Steatosis and inflammation are the hallmarks of nonalcoholic steatohepatitis (NASH). Rotundic acid (RA) is among the key triterpenes of Ilicis Rotundae Cortex and has exhibited multipronged effects in terms of lowering the lipid content and alleviating inflammation. The study objective is to systematically evaluate the potential mechanisms through which RA affects the development and progression of NASH.

METHODS

Transcriptomic and proteomic analyses of primary hepatocytes isolated from the control, high-fat diet-induced NASH, and RA treatment groups were performed through Gene Ontology analysis and pathway enrichment. Hub genes were identified through network analysis. Integrative analysis revealed key RA-regulated pathways, which were verified by gene and protein expression studies and cell assays.

RESULTS

Hub genes were identified and enriched in the Toll-like receptor 4 (TLR4)/activator protein-1 (AP1) signaling pathway and glycolysis pathway. RA reversed glycolysis and attenuated the TLR4/AP1 pathway, thereby reducing lipid accumulation and inflammation. Additionally, lactate release in L-02 cells increased with NaAsO2-treated and significantly decreased with RA treatment, thus revealing that RA had a major impact on glycolysis.

CONCLUSIONS

RA is effective in lowering the lipid content and reducing inflammation in mice with NASH by ameliorating glycolysis and TLR4/AP1 pathways, which contributes to the existing knowledge and potentially sheds light on the development of therapeutic interventions for patients with NASH.

The crosstalk between M1 macrophage polarization and energy metabolism disorder contributes to polystyrene nanoplastics-triggered testicular inflammation

Ubiquitous microplastics have become a threat to animal and human health, due to their potential toxicity, persistent nature and consequent bioaccumulation. Supporting evidence elucidates that polystyrene nanoplastics (PS-NPs) can destroy blood-testis barrier integrity, thus causing testicular hypoplasia and impairment of spermatogenesis. Nevertheless, how PS-NPs modulate macrophage polarization-energy metabolism crosstalk has not been fully investigated in testicular tissue. Here, we observed that polystyrene PS-NPs exposure contributes to severe vacuolization in the seminiferous tubules, accompanied by apoptosis of testicular tissue and infiltration of M1 macrophages. Meanwhile, we found that PS-NPs could trigger the M1 polarization phenotype, which activated ROS-macrophage migration inhibitory factor (MIF)/NF-κB signaling that in turn induced apoptosis of GC2 cells in the GC2-macrophage cell coculture model. Simultaneously, we confirmed that PS-NPs exposure increased 3-phospho-D-glycerate, phosphoenolpyruvate and lactate concentrations, accompanied by decreased pyruvate and adenosine triphosphate (ATP) production, likely due to downregulated pyruvate kinase M2 (PKM2) dimer expression. In conclusion, the mechanism of PS-NPs-induced testicular inflammation can be mediated by promoting the infiltration of M1 macrophages, thereby resulting in an ROS burst and subsequent induction of energy metabolism disorders. The current study will provide new insights into PS-NPs-induced male reproductive toxicity and highlight the context-specific roles of testicular macrophages.

Association between Heavy Metals, Metalloids and Metabolic Syndrome: New Insights and Approaches

Metabolic syndrome (MetS) is an important public health issue that affects millions of people around the world and is growing to pandemic-like proportions. This syndrome is defined by the World Health Organization (WHO) as a pathologic condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Moreover, the etiology of MetS is multifactorial, involving many environmental factors, including toxicant exposures. Several studies have associated MetS with heavy metals exposure, which is the focus of this review. Environmental and/or occupational exposure to heavy metals are a major risk, contributing to the development of chronic diseases. Of particular note, toxic metals such as mercury, lead, and cadmium may contribute to the development of MetS by altering oxidative stress, IL-6 signaling, apoptosis, altered lipoprotein metabolism, fluid shear stress and atherosclerosis, and other mechanisms. In this review, we discuss the known and potential roles of heavy metals in MetS etiology as well as potential targeted pathways that are associated with MetS. Furthermore, we describe how new approaches involving proteomic and transcriptome analysis, as well as bioinformatic tools, may help bring about an understanding of the involvement of heavy metals and metalloids in MetS.

Role of NLRP3 inflammasome and oxidative stress in hepatic insulin resistance and the ameliorative effect of phytochemical intervention

NLRP3 inflammasome has a key role in chronic low-grade metabolic inflammation, and its excessive activation may contribute to the beginning and progression of several diseases, including hepatic insulin resistance (hIR). Thus, this review aims to highlight the role of NLRP3 inflammasome and oxidative stress in the development of hIR and evidence related to phytochemical intervention in this context. In this review, we will address the hIR pathogenesis related to reactive oxygen species (ROS) production mechanisms, involving oxidized mitochondrial DNA (ox-mtDNA) and thioredoxin interacting protein (TXNIP) induction in the NLRP3 inflammasome activation. Moreover, we discuss the inhibitory effect of bioactive compounds on the insulin signaling pathway, and the role of microRNAs (miRNAs) in the phytochemical target mechanism in ameliorating hIR. Although most of the research in the field has been focused on evaluating the inhibitory effect of phytochemicals on the NLRP3 inflammasome pathway, further investigation and clinical studies are required to provide insights into the mechanisms of action, and, thus, encourage the use of these bioactive compounds as an additional therapeutic strategy to improve hIR and correlated conditions.

Annexin A1 inhibition facilitates NLRP3 inflammasome activation in arsenic-induced insulin resistance in rat liver

Hepatic insulin resistance (IR) is the primary pathology of type 2 diabetes (T2D). The role of the NOD-like receptor protein 3 (NLRP3) inflammasome in arsenic-induced hepatic IR has been previously demonstrated. However, the mechanism of the arsenic-induced activation of the NLRP3 inflammasome is still unclear. Here, we demonstrate that NaAsO₂ downregulated the mRNA and protein level of Annexin A1 (AnxA1), an anti-inflammatory factor, in rat livers and L-02 cells. Moreover, AnxA1 overexpression significantly alleviated arsenic-induced NLRP3 inflammasome activation and IR in L-02 cells. Importantly, Co-immunoprecipitation (Co-IP) results showed that AnxA1 1-190 peptide could bind to the domain encompassing amino acids 1-210 and 211-550 of NLRP3. In conclusion, our experiments demonstrated that arsenic exposure could activate the NLRP3 inflammasome and IR by inhibiting the AnxA1 activity. These findings suggest that AnxA1 may be a promising therapeutic target of arsenicosis.

Hsp47 acts as a bridge between NLRP3 inflammasome and hepatic stellate cells activation in arsenic-induced liver fibrosis

The activation of hepatic stellate cells (HSCs) is a key event during the progression of liver fibrosis (LF). We have previously indicated that NLRP3 inflammasome plays a crucial role in arsenic-induced HSCs activation. However, the mechanism of cascade responses between NLRP3 inflammasome and HSCs activation is unclear. Here, we showed that the transcription and protein level of Hsp47 was upregulated after 4μM arsenic treatment, both in vivo and in vitro. Additionally, arsenic-induced HSCs activation was remarkably alleviated by the interference of Hsp47. Furthermore, blockage of NLRP3 significantly mitigated the activation of the NLRP3 inflammasome and decreased the expression of Hsp47, thereby attenuating the arsenic-induced HSCs activation. However, the ablation of Hsp47 did not affect the activation of the NLRP3 inflammasome. Notably, the protein-protein interaction between NLRP3 and Hsp47 was observed both in vivo and in vitro, and the target amino acid sequences were further identified. In summary, the present study indicated that NaAsO₂ induced HSCs activation via the NLRP3 inflammasome-Hsp47 pathway. These findings provide direct evidence that Hsp47 may be a potential therapeutic target for arsenic-induced LF.

Thioredoxin-1 Activation by Pterostilbene Protects Against Doxorubicin-Induced Hepatotoxicity via Inhibiting the NLRP3 Inflammasome

Background: Doxorubicin (DOX) has been widely used in cancer treatment. However, DOX can cause a range of significant side effects, of which hepatotoxicity is a common one, and therefore limits its clinical use. Pterostilbene (PTS) has been shown to exhibit anti-oxidant and anti-inflammatory effects in the treatment of liver diseases but whether PTS could protect against hepatotoxicity in DOX-treated mice is unknown.

Methods: In our study, we use C57/BL6J mice and the HepG2 cell line. We divided the mice in 4 groups: the control, the PTS treatment, the DOX treatment, and the DOX + PTS treatment group. Liver histopathology was judged by performing hematoxylin–eosin and Masson staining. Immunohistochemistry was used to perform the expression of NLRP3. The levels of serum alanine transaminase (ALT) and aspartate transaminase (AST) were evaluated. Levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH), and DCFH-DA staining were used to evaluate the oxidative injury. Western blot and real-time PCR were applied to evaluate the expressions of proteins and mRNA. MTT was used to evaluate DOX-induced cell injury and the protective effects of PTS. Recombinant Trx-1 was used to analyze the mechanism of PTS. A TUNEL assay was used to detect apoptosis in DOX-induced HepG2 cells and the protective effects of PTS.

Results: PTS ameliorated DOX-induced liver pathological changes and the levels of AST and ALT. PTS also decreased the level of MDA, increased the level of SOD, GSH, and the expression of Trx-1 in DOX-treated mice. PTS decreased the levels of NLRP3 and IL-1β mRNA and the expressions of their proteins in DOX-treated mice. In addition, PTS also decreased the expression of Cleaved Caspase-3 and BAX and increased the expression of BCL-2. In vitro, after treatment with recombinant Trx-1, ROS and NLRP3 inflammasome were both decreased. Treatment with PTS could rescue the downregulation of Trx-1, decreased the ROS level and the NLRP3 inflammasome, and protected HepG2 cells against DOX-induced apoptosis.

Conclusion: The results show that PTS exhibits protective effects against DOX-induced liver injuries via suppression of oxidative stress, fibrosis, NLRP3 inflammasome stimulation, and cell apoptosis which might lead to a new approach of preventing DOX-induced hepatotoxicity.

Is Arsenic Exposure a Risk Factor for Metabolic Syndrome? A Review of the Potential Mechanisms

Exposure to arsenic in drinking water is a worldwide health problem. This pollutant is associated with increased risk of developing chronic diseases, including metabolic diseases. Metabolic syndrome (MS) is a complex pathology that results from the interaction between environmental and genetic factors. This condition increases the risk of developing type 2 diabetes, cardiovascular diseases, and cancer. The MS includes at least three of the following signs, central obesity, impaired fasting glucose, insulin resistance, dyslipidemias, and hypertension. Here, we summarize the existing evidence of the multiple mechanisms triggered by arsenic to developing the cardinal signs of MS, showing that this pollutant could contribute to the multifactorial origin of this pathology.