Silica nanoparticles induce lung inflammation in mice via ROS/PARP/TRPM2 signaling-mediated lysosome impairment and autophagy dysfunction

Background Wide applications of nanoparticles (NPs) have raised increasing concerns about safety to humans. Oxidative stress and inflammation are extensively investigated as mechanisms for NPs-induced toxicity. Autophagy and lysosomal dysfunction are emerging molecular mechanisms. Inhalation is one of the main pathways of exposing humans to NPs, which has been reported to induce severe pulmonary inflammation. However, the underlying mechanisms and, more specifically, the interplays of above-mentioned mechanisms in NPs-induced pulmonary inflammation are still largely obscure. Considered that NPs exposure in modern society is often unavoidable, it is highly desirable to develop effective strategies that could help to prevent nanomaterials-induced pulmonary inflammation. Results Pulmonary inflammation induced by intratracheal instillation of silica nanoparticles (SiNPs) in C57BL/6 mice was prevented by PJ34, a poly (ADP-ribose) polymerase (PARP) inhibitor. In human lung bronchial epithelial (BEAS-2B) cells, exposure to SiNPs reduced cell viability, and induced ROS generation, impairment in lysosome function and autophagic flux. Inhibition of ROS generation, PARP and TRPM2 channel suppressed SiNPs-induced lysosome impairment and autophagy dysfunction and consequent inflammatory responses. Consistently, SiNPs-induced pulmonary inflammation was prevented in TRPM2 deficient mice. Conclusion The ROS/PARP/TRPM2 signaling is critical in SiNPs-induced pulmonary inflammation, providing novel mechanistic insights into NPs-induced lung injury. Our study identifies TRPM2 channel as a new target for the development of preventive and therapeutic strategies to mitigate nanomaterials-induced lung inflammation

Role of autophagy in response to titanium dioxide nanoparticles

International audienceThe development and the increasing production of manufactured nanoparticles (NP) are raising safety concerns because of the potential effects of NP on human health, particularly at the respiratory level. Several studies have shown that exposure to manufactured NP can induce pathogenic biological effects, with lung remodelling (fibrosis, emphysema…), depending on the physicochemical characteristics of the NP. Currently, oxidative stress and inflammation are the most widely accepted paradigms of NP toxicity; however, the exact underlying mechanisms in the biological effects of NP still remain unknown. Autophagy is a physiological process that allows the autodigestion of the subcellar components and which is also involved in the elimination of intracellular pathogens. It has been shown that this process can negatively regulate inflammation and oxidative stress. Thus, the hypothesis of this study is that a defective autophagy could be a new mechanism explaining, at least in part, NP effects. We choose to focus on TiO2 NP since it is one of the most abundantly produced and widely used NP. We used seven TiO2 NPs presenting different physicochemicals properties (size, crystal phase, surface embedding) and compared their effects to those of micron-size TiO2 and carbon black (CB - for chemical composition effects). NPs were characterized by electron microscopy, dynamic light scattering and X-ray diffraction. Murine macrophages (RAW cell line) were exposed to 50 μg/mL TiO2 and CB NP for 6 hours. Effects of NP on the autophagy process were analysed by looking at the expression of autophagy markers (LC3-II and p62) and lysosomal proteins (LAMPs and cathepsins). We also analysed the cytoskeleton network by fluorescence microscopy. Moreover, expression of inflammatory cytokines was determined in macrophages exposed to NP. All particles, except the micrometric one, induced an increase of LC3-II protein expression, indicating an accumulation of autophagosomes. These particles also increased p62 protein level, suggesting an autophagy blockade. This perturbation of the autophagy process by NP does not seem to result from a disruption of the cytoskeleton but from a defect in the lysosome function as suggested by a decrease of mature cathepsins expression. Moreover, preliminary results showed that exposure to TiO2 NP induce inflammation, at different levels depending on their physicochemicals characteristics. These results suggest that some TiO2 NP, depending on their physicochemical properties, can block the autophagy process. The future work will be to understand the mechanisms explaining this autophagy dysfunction and to determine its consequence on the toxicity induced by these NP

Exposure to welding fumes and lower airway infection with Streptococcus pneumoniae

Background Welders are at increased risk of pneumococcal pneumonia. The mechanism for this association is not known. The capacity of pneumococci to adhere to and infect lower airway cells is mediated by host-expressed platelet-activating factor receptor (PAFR). Objective We sought to assess the effect of mild steel welding fumes (MS-WF) on PAFR-dependent pneumococcal adhesion and infection to human airway cells in vitro and on pneumococcal airway infection in a mouse model. Methods The oxidative potential of MS-WF was assessed by their capacity to reduce antioxidants in vitro. Pneumococcal adhesion and infection of A549, BEAS-2B, and primary human bronchial airway cells were assessed by means of quantitative bacterial culture and expressed as colony-forming units (CFU). After intranasal instillation of MS-WF, mice were infected with Streptococcus pneumoniae, and bronchoalveolar lavage fluid (BALF) and lung CFU values were determined. PAFR protein levels were assessed by using immunofluorescence and immunohistochemistry, and PAFR mRNA expression was assessed by using quantitative PCR. PAFR was blocked by CV-3988, and oxidative stress was attenuated by N-acetylcysteine. Results MS-WF exhibited high oxidative potential. In A549 and BEAS-2B cells MS-WF increased pneumococcal adhesion and infection and PAFR protein expression. Both CV-3988 and N-acetylcysteine reduced MS-WF–stimulated pneumococcal adhesion and infection of airway cells. MS-WF increased mouse lung PAFR mRNA expression and increased BALF and lung pneumococcal CFU values. In MS-WF–exposed mice CV-3988 reduced BALF CFU values. Conclusions Hypersusceptibility of welders to pneumococcal pneumonia is in part mediated by the capacity of welding fumes to increase PAFR-dependent pneumococcal adhesion and infection of lower airway cells

Evidence for caveolin-1 as a new susceptibility gene regulating tissue fibrosis in systemic sclerosis

Caveolin-1 (CAV1) is an inhibitor of tissue fibrosis and has been implicated in the pathogenesis of systemic sclerosis (SSc). The aim of the study was to analyse the possible association of CAV1 gene single nucleotide polymorphisms (SNP) with SSc. METHODS: A total population of 3974 individuals (1355 SSc patients, 2619 controls) was studied. Genotype data for 23 SNP spanning the CAV1-CAV2 gene locus were obtained from a genome-wide scan conducted in a French population (564 SSc patients, 1776 controls). Three CAV1 SNP (rs926198, rs959173, rs9920) displaying the most significant associations with SSc and/or clinical phenotypes were then genotyped in an Italian population (791 SSc patients, 843 controls). CAV1 protein expression in skin biopsies was investigated by immunohistochemistry and western blotting. RESULTS: In the French population, the CAV1 rs959173 C minor allele showed a significant protective association with susceptibility to SSc (OR 0.71, 95% CI 0.59 to 0.86, p(adjusted)=0.009), and with the subset of patients with limited cutaneous SSc (OR 0.71, 95% CI 0.56 to 0.89, p(adjusted)=0.018). The association was replicated in the Italian population and strengthened in the combined populations through Cochran-Mantel-Haenszel meta-analysis (SSc: pooled OR 0.81, 95% CI 0.71 to 0.92, p=0.0018; limited cutaneous SSc: pooled OR 0.80, 95% CI 0.69 to 0.93, p=0.0053). Genotype/protein expression correlations revealed that the rs959173 C protective allele was associated with increased CAV1 protein expression. CONCLUSIONS: These results add CAV1 to the list of SSc susceptibility genes and provide further evidence for the contribution of this pathway in the fibrotic process that characterises SSc pathogenesis

Brief report: candidate gene study in systemic sclerosis identifies a rare and functional variant of the TNFAIP3 locus as a risk factor for polyautoimmunity

Systemic lupus erythematosus (SLE) and systemic sclerosis (SSc) share some pathophysiologic bases as evidenced by individual and familial polyautoimmunity and common susceptibility genetic factors. With regard to the latter, there has been a recent shift from the "common variant" to the "rare variant" paradigm, since rare variants of TNFAIP3 and TREX1 with large effect sizes have recently been discovered in SLE. The present study was undertaken to investigate whether rare variants of TNFAIP3 and TREX1 are also associated with SSc. METHODS: TREX1 single-nucleotide polymorphisms (SNPs) rs3135946, rs7626978, rs3135943, and rs11797 and TNFAIP3 SNPs rs9494883, rs72063345, rs5029939, rs2230926, rs117480515, and rs7749323 were genotyped in a discovery set (985 SSc patients and 1,011 controls), and replication analysis of the most relevant results was performed in a second set (622 SSc patients and 493 controls). RESULTS: No association between TREX1 variants and SSc was observed. For TNFAIP3, we first demonstrated that a low-frequency variant, rs117480515, tagged the recently identified TT>A SLE dinucleotide. In the discovery sample, we observed that all tested TNFAIP3 variants were in linkage disequilibrium and were associated with SSc and various SSc subsets, including the polyautoimmune phenotype. We subsequently genotyped rs117480515 in the replication sample and found it to be associated solely with the SSc polyautoimmune subset (odds ratio 3.51 [95% confidence interval 2.28-5.41], P = 8.58 7 10(-9) ) in the combined populations. Genotype-messenger RNA (mRNA) expression correlation analysis revealed that the TNFAIP3 rs117480515 risk allele was associated with decreased mRNA expression. CONCLUSION: The present findings establish the TNFAIP3 locus as a susceptibility factor for the subset of SSc with a polyautoimmune phenotype. Our results support the implication of rare/low-frequency functional variants and the critical role of A20 in autoimmunity

Evidence for caveolin-1 as a new susceptibility gene regulating tissue fibrosis in systemic sclerosis

Objective Caveolin-1 (CAV1) is an inhibitor of tissue fibrosis and has been implicated in the pathogenesis of systemic sclerosis (SSc). The aim of the study was to analyse the possible association of CAV1 gene single nucleotide polymorphisms (SNP) with SSc. Methods A total population of 3974 individuals (1355 SSc patients, 2619 controls) was studied. Genotype data for 23 SNP spanning the CAV1-CAV2 gene locus were obtained from a genome-wide scan conducted in a French population (564 SSc patients, 1776 controls). Three CAV1 SNP (rs926198, rs959173, rs9920) displaying the most significant associations with SSc and/or clinical phenotypes were then genotyped in an Italian population (791 SSc patients, 843 controls). CAV1 protein expression in skin biopsies was investigated by immunohistochemistry and western blotting. Results In the French population, the CAV1 rs959173 C minor allele showed a significant protective association with susceptibility to SSc (OR 0.71, 95% CI 0.59 to 0.86, p(adjusted)=0.009), and with the subset of patients with limited cutaneous SSc (OR 0.71, 95% CI 0.56 to 0.89, p(adjusted)=0.018). The association was replicated in the Italian population and strengthened in the combined populations through Cochran-Mantel-Haenszel meta-analysis (SSc: pooled OR 0.81, 95% CI 0.71 to 0.92, p=0.0018; limited cutaneous SSc: pooled OR 0.80, 95% CI 0.69 to 0.93, p=0.0053). Genotype/protein expression correlations revealed that the rs959173 C protective allele was associated with increased CAV1 protein expression. Conclusions These results add CAV1 to the list of SSc susceptibility genes and provide further evidence for the contribution of this pathway in the fibrotic process that characterises SSc pathogenesis

Evidence for caveolin-1 as a new susceptibility gene regulating tissue fibrosis in systemic sclerosis

OBJECTIVE: Caveolin-1 (CAV1) is an inhibitor of tissue fibrosis and has been implicated in the pathogenesis of systemic sclerosis (SSc). The aim of the study was to analyse the possible association of CAV1 gene single nucleotide polymorphisms (SNP) with SSc. METHODS: A total population of 3974 individuals (1355 SSc patients, 2619 controls) was studied. Genotype data for 23 SNP spanning the CAV1-CAV2 gene locus were obtained from a genome-wide scan conducted in a French population (564 SSc patients, 1776 controls). Three CAV1 SNP (rs926198, rs959173, rs9920) displaying the most significant associations with SSc and/or clinical phenotypes were then genotyped in an Italian population (791 SSc patients, 843 controls). CAV1 protein expression in skin biopsies was investigated by immunohistochemistry and western blotting. RESULTS: In the French population, the CAV1 rs959173 C minor allele showed a significant protective association with susceptibility to SSc (OR 0.71, 95% CI 0.59 to 0.86, p(adjusted)=0.009), and with the subset of patients with limited cutaneous SSc (OR 0.71, 95% CI 0.56 to 0.89, p(adjusted)=0.018). The association was replicated in the Italian population and strengthened in the combined populations through Cochran-Mantel-Haenszel meta-analysis (SSc: pooled OR 0.81, 95% CI 0.71 to 0.92, p=0.0018; limited cutaneous SSc: pooled OR 0.80, 95% CI 0.69 to 0.93, p=0.0053). Genotype/protein expression correlations revealed that the rs959173 C protective allele was associated with increased CAV1 protein expression. CONCLUSIONS: These results add CAV1 to the list of SSc susceptibility genes and provide further evidence for the contribution of this pathway in the fibrotic process that characterises SSc pathogenesis