Ferroptosis contributing to cardiomyocyte injury induced by silica nanoparticles via miR-125b-2-3p/HO-1 signaling.

BACKGROUND: Amorphous silica nanoparticles (SiNPs) have been gradually proven to threaten cardiac health, but pathogenesis has not been fully elucidated. Ferroptosis is a newly defined form of programmed cell death that is implicated in myocardial diseases. Nevertheless, its role in the adverse cardiac effects of SiNPs has not been described. RESULTS: We first reported the induction of cardiomyocyte ferroptosis by SiNPs in both in vivo and in vitro. The sub-chronic exposure to SiNPs through intratracheal instillation aroused myocardial injury, characterized by significant inflammatory infiltration and collagen hyperplasia, accompanied by elevated CK-MB and cTnT activities in serum. Meanwhile, the activation of myocardial ferroptosis by SiNPs was certified by the extensive iron overload, declined FTH1 and FTL, and lipid peroxidation. The correlation analysis among detected indexes hinted ferroptosis was responsible for the SiNPs-aroused myocardial injury. Further, in vitro tests, SiNPs triggered iron overload and lipid peroxidation in cardiomyocytes. Concomitantly, altered expressions of TfR, DMT1, FTH1, and FTL indicated dysregulated iron metabolism of cardiomyocytes upon SiNP stimuli. Also, shrinking mitochondria with ridge fracture and ruptured outer membrane were noticed. To note, the ferroptosis inhibitor Ferrostatin-1 could effectively alleviate SiNPs-induced iron overload, lipid peroxidation, and myocardial cytotoxicity. More importantly, the mechanistic investigations revealed miR-125b-2-3p-targeted HO-1 as a key player in the induction of ferroptosis by SiNPs, probably through regulating the intracellular iron metabolism to mediate iron overload and ensuing lipid peroxidation. CONCLUSIONS: Our findings firstly underscored the fact that ferroptosis mediated by miR-125b-2-3p/HO-1 signaling was a contributor to SiNPs-induced myocardial injury, which could be of importance to elucidate the toxicity and provide new insights into the future safety applications of SiNPs-related nano products.

Amorphous silica nanoparticles caused lung injury through the induction of epithelial apoptosis via ROS/Ca2+/DRP1-mediated mitochondrial fission signaling.

The adverse effects of amorphous silica nanoparticles (SiNPs) exposure on the respiratory system were increasingly recognized, however, its potential pathogenesis still remains not fully elucidated. So, this study aimed to explore its effects on pulmonary injury, and to investigate related mechanisms. Histological investigations illustrated SiNPs triggered the lung injury, mainly manifested as alveolar structure destruction, collagen deposition, and mitochondrial ultrastructural injury. In particular, SiNPs greatly enhanced pulmonary ROS and TUNEL positive rate in lungs, both of which were positively correlated with lung impairments. Further, the underlying mechanisms were investigated in cultured human bronchial epithelial cells (16HBE). Consistent with the in vivo findings, SiNPs caused the impairments on mitochondrial structure, as well as the activation of ROS generation and oxidative injury. Upon SiNPs stimuli, mitochondrial respiration was greatly inhibited, while Ca2+ overload in cytosol and mitochondria owing to ER calcium release was noticed, resulting in mitochondrial-dependent epithelial apoptosis. More importantly, mitochondrial dynamics was imbalanced toward a fission type, as evidenced by upregulated DRP1 and its phosphorylation at Ser616 (DRP1s616), while downregulated DRP1s637, and also MFN1, MFN2. Mechanistic investigations revealed that the activation of ROS/Ca2+ signaling promoted DRP1-mediated mitochondrial fission by SiNPs, forming a vicious cycle, and ultimately contributing to apoptosis in 16HBE. In summary, our results disclosed SiNPs caused pulmonary injury through the induction of epithelial apoptosis via a ROS/Ca2+/DRP1-mediated mitochondrial fission axis.

Long-term respiratory exposure to amorphous silica nanoparticles promoted systemic inflammation and progression of fibrosis in a susceptible mouse model.

Exposure to amorphous silica nanoparticles (SiNPs) has increased dramatically, and concerns are growing about their potential health effects. However, their long-term systemic toxicity profile and underlying mechanisms following respiratory exposure still remains unexplored. It is well documented that the inhalation of ultrafine particles is firmly associated with adverse effects in humans. Environmental pollutants may contribute to diverse adverse effect or comorbidity in susceptible individuals. Thereby, we examined the long-term systemic effects of inhaled SiNPs using a sensitive mouse model (ApoE-/-) fed by a western diet. Male ApoE-/- mice were intratracheally instilled with SiNPs suspension at a dose of 1.5, 3.0 and 6.0 mg/kg·bw, respectively, once per week, 12 times in total. The histological analysis was conducted. The serum cytokine levels were quantified by RayBiotech antibody array. As a result, systemic histopathological alterations were noticed, mainly characterized by inflammation and fibrosis. More importantly, cytokine array analysis indicated the key role of mast cells accumulation in systemic inflammation and fibrosis progression induced by inhaled SiNPs. Collectively, our study firstly demonstrated that long-term exposure to inhaled SiNPs promoted the mast cell-dominated activation of inflammatory response, not only in the lung but also in heart, liver and kidney, etc., eventually leading to the progression of tissue fibrosis in ApoE-/- mice.

Myocardial toxicity induced by silica nanoparticles in a transcriptome profile.

The deleterious effects of silica nanoparticles (SiNPs) on human health and the ecological system have gradually gained attention owing to their heavy annual output and extensive global flux. The updated epidemiological or experimental investigations have demonstrated the potential myocardial toxicity triggered by SiNPs, but the underlying mechanisms and long-lasting cardiac effects are still poorly understood. Here, a rat model of sub-chronic respiratory exposure to SiNPs was conducted, and the histopathological analysis and ultrastructural investigation of heart tissues were carried out. More importantly, a comprehensive analysis of whole-genome transcription was utilized in rat heart to uncover key biological and cellular mechanisms triggered by SiNPs. The widening of myocardial space and partial fiber rupture were clearly manifested in rat heart after prolonged SiNPs exposure, particularly accompanied by mitochondrial swelling and cristae rupture. With the aid of Affymetrix GeneChips, 3153 differentially expressed genes (DEGs) were identified after SiNPs exposure, including 1916 down- and 1237 up-regulated genes. GO and KEGG analysis illustrated many important biological processes and pathways perturbed by SiNPs, mainly specializing in cellular stress, energy metabolism, actin filament dynamics and immune response. Signal-net analysis revealed that Prkaca (PKA) plays a core role in the cardiac toxification process of prolonged exposure of SiNPs to rats. Furthermore, qRT-PCR verified that PKA-mediated calcium signaling is probably responsible for SiNPs-induced cardiac injury. Conclusively, our study revealed that SiNPs caused myocardial injury, and particularly, provided transcriptomic insight into the role of PKA-calcium signaling triggered by SiNPs, which would facilitate SiNPs-based nanosafety assessment and biomedicine development.

Biomarkers for the adverse effects on respiratory system health associated with atmospheric particulate matter exposure.

Large amounts of epidemiological evidence have confirmed the atmospheric particulate matter (PM2.5) exposure was positively correlated with the morbidity and mortality of respiratory diseases. Nevertheless, its pathogenesis remains incompletely understood, probably resulting from the activation of oxidative stress, inflammation, altered genetic and epigenetic modifications in the lung upon PM2.5 exposure. Currently, biomarker investigations have been widely used in epidemiological and toxicological studies, which may help in understanding the biologic mechanisms underlying PM2.5-elicited adverse health outcomes. Here, the emerging biomarkers to indicate PM2.5-respiratory system interactions were summarized, primarily related to oxidative stress (ROS, MDA, GSH, etc.), inflammation (Interleukins, FENO, CC16, etc.), DNA damage (8-OHdG, γH2AX, OGG1) and also epigenetic modulation (DNA methylation, histone modification, microRNAs). The identified biomarkers shed light on PM2.5-elicited inflammation, fibrogenesis and carcinogenesis, thus may favor more precise interventions in public health. It is worth noting that some inconsistent findings may possibly relate to the inter-study differentials in the airborne PM2.5 sample, exposure mode and targeted subjects, as well as methodological issues. Further research, particularly by -omics technique to identify novel, specific biomarkers, is warranted to illuminate the causal relationship between PM2.5 pollution and deleterious lung outcomes.

Oxidative stress- and mitochondrial dysfunction-mediated cytotoxicity by silica nanoparticle in lung epithelial cells from metabolomic perspective.

Quantities of researches have demonstrated silica nanoparticles (SiNPs) exposure inevitably induced damage to respiratory system, nonetheless, knowledge of its toxicological behavior and metabolic interactions with the cellular machinery that determines the potentially deleterious outcomes are limited and poorly elucidated. Here, the metabolic responses of lung bronchial epithelial cells (BEAS-2B) under SiNPs exposure were investigated using ultra performance liquid chromatography-mass spectrum (UPLC-MS)-based metabolomics research. Results revealed that even with low cytotoxicity, SiNPs disturbed global metabolism. Five metabolic pathways were significantly perturbed, in particular, oxidative stress- and mitochondrial dysfunction-related GSH metabolism and pantothenate and coenzyme A (CoA) biosynthesis, where the identified metabolites glutathione (GSH), glycine, beta-alanine, cysteine, cysteinyl-glycine and pantothenic acid were included. In support of the metabolomics profiling, SiNPs caused abnormality in mitochondrial structure and mitochondrial dysfunction, as evidenced by the inhibition of cellular respiration and ATP production. Moreover, SiNPs triggered oxidative stress as confirmed by the dose-dependent ROS generation, down-regulated nuclear factor erythroid 2-related factor 2 (NRF2) signaling, together with GSH depletion in SiNPs-treated BEAS-2B cells. Oxidative DNA damage and cell membrane dis-integrity were also detected in response to SiNPs exposure, which was correspondingly in agreed with the elevated 8-hydroxyguanosine (8-OHdG) and decreased phospholipids screened through metabolic analysis. Thereby, we successfully used the metabolomics approaches to manifest SiNPs-elicited toxicity through oxidative stress, mitochondrial dysfunction, DNA damage and rupture of membrane integrity in BEAS-2B cells. Overall, our study provided novel insights into the mechanism underlying SiNPs-induced pulmonary toxicity.

Disturbed mitochondrial quality control involved in hepatocytotoxicity induced by silica nanoparticles.

The extensive application of silica nanoparticles (SiNPs) brings about inevitable occupational, environmental, and even iatrogenic exposure for human beings. The liver, which is rich in mitochondria, is one of the target organs of SiNPs, but the underlying mechanisms by which these nanoparticles (NPs) interact with liver mitochondria and affect their functions still remain unclear. In the present study, we examined silicon nanoparticle (SiNP)-induced mitochondrial dysfunction, and further revealed its negative effects on mitochondrial quality control (MQC) in the human liver cell line L-02, including mitochondrial dynamics, mitophagy and biogenesis. Consequently, SiNPs induced cellular injury, accompanied by mitochondrial dysfunction, including mitochondrial reactive oxygen generation and mitochondrial membrane potential collapse. In line with the transmission electron microscopy (TEM)-observed abnormalities in the mitochondrial morphology and length distribution, a fission phenotype was manifested in the mitochondria of SiNP-exposed cells, and up-regulated DRP1 and FIS1, and down-regulated MFN1, were detected. Furthermore, the enhanced LC3II level, colocalization of the mitochondria and lysosomes, activated PINK1/Parkin signaling, and accumulated p62 in the SiNP-exposed cells suggested mitophagy disorder triggered by SiNPs. In addition, SiNPs inhibited mito-biogenesis, as evidenced by the reduced mitochondrial mass and mtDNA copy number, as well as the suppressed PGC1α-NRF1-TFAM signaling pathway. Overall, the study demonstrates that SiNPs trigger hepatocytotoxicity through interfering with the MQC process, bringing in excessive mitochondrial fission, mitophagy disorder and suppressed mito-biogenesis, leading to mitochondrial dysfunction and ensuing cell damage, and ultimately contributing to the occurrence and development of liver diseases. Our research could provide important experimental evidence related to safety assessments of SiNPs, especially in the field of biomedical applications.

PM2.5 triggered apoptosis in lung epithelial cells through the mitochondrial apoptotic way mediated by a ROS-DRP1-mitochondrial fission axis.

Epidemiological studies revealed a sharp increase in respiratory diseases attributed to PM2.5. However, the underlying mechanisms remain unclear. Evidence suggested mitochondrion as a sensitive target upon the stimulus of PM2.5, and the centrality in the pathological processes and clinical characterization of lung diseases. To investigate cell fate and related mechanisms caused by PM2.5, we exposed human lung epithelial cells (BEAS-2B) to PM2.5 (0-100 µg/mL). Consequently, PM2.5 components were found in cytoplasm, and morphological and functional alterations in mitochondria occurred, as evidenced by loss of cristae, vacuolization and even the outer mitochondrial membrane rupture, mitochondrial membrane potential collapse, enhanced reactive oxygen species (ROS)/mtROS level, calcium overload, suppressed cellular respiration and ATP production in PM2.5-treated cells. Further, disturbed dynamics toward fission was clearly observed in PM2.5-treated mitochondria, associated with DRP1 mitochondrial translocation and phosphorylation. Besides, PM2.5 induced mitochondria-mediated apoptosis. More importantly, mechanistic results revealed ROS- and DRP1-mediated mitochondrial fission in a reciprocal way, and DRP1 inhibitor (Mdivi-1) significantly alleviated the pro-apoptotic effect of PM2.5 through reversing the activated mitochondrial apoptotic pathway. In summary, our results firstly revealed PM2.5 induced apoptosis in lung epithelial cells through a ROS-DRP1-mitochodrial fission axis-mediated mitochondrial apoptotic pathway, ultimately contributing to the onset and development of pulmonary diseases.