Myeloid cell-specific deletion of Capns1 prevents macrophage polarization toward the M1 phenotype and reduces interstitial lung disease in the bleomycin model of systemic sclerosis

Relationships between systemic sclerosis and atherosclerosis: screening for mitochondria-related biomarkers

Background

Patients with systemic sclerosis (SSc) are known to have higher incidence of atherosclerosis (AS). Mitochondrial injuries in SSc can cause endothelial dysfunction, leading to AS; thus, mitochondria appear to be hubs linking SSc to AS. This study aimed to identify the mitochondria-related biomarkers of SSc and AS.

Methods

We identified common differentially expressed genes (DEGs) in the SSc (GSE58095) and AS (GSE100927) datasets of the Gene Expression Omnibus (GEO) database. Considering the intersection between genes with identical expression trends and mitochondrial genes, we used the least absolute shrinkage and selection operator (LASSO) as well as random forest (RF) algorithms to identify four mitochondria-related hub genes. Diagnostic nomograms were then constructed to predict the likelihood of SSc and AS. Next, we used the CIBERSORT algorithm to evaluate immune infiltration in both disorders, predicted the transcription factors for the hub genes, and validated these genes for the two datasets.

Results

A total of 112 genes and 13 mitochondria-related genes were identified; these genes were then significantly enriched for macrophage differentiation, collagen-containing extracellular matrix, collagen binding, antigen processing and presentation, leukocyte transendothelial migration, and apoptosis. Four mitochondria-related hub DEGs (IFI6, FSCN1, GAL, and SGCA) were also identified. The nomograms showed good diagnostic values for GSE58095 (area under the curve (AUC) = 0.903) and GSE100927 (AUC = 0.904). Further, memory B cells, γδT cells, M0 macrophages, and activated mast cells were significantly higher in AS, while the resting memory CD4+ T cells were lower and M1 macrophages were higher in SSc; all of these were closely linked to multiple immune cells. Gene set enrichment analysis (GSEA) showed that IFI6 and FSCN1 were involved in immune-related pathways in both AS and SSc; GAL and SGCA are related to mitochondrial metabolism pathways in both SSc and AS. Twenty transcription factors (TFs) were predicted, where two TFs, namely BRCA1 and PPARγ, were highly expressed in both SSc and AS.

Conclusion

Four mitochondria-related biomarkers were identified in both SSc and AS, which have high diagnostic value and are associated with immune cell infiltration in both disorders. Hence, this study provides new insights into the pathological mechanisms underlying SSc and AS. The specific roles and action mechanisms of these genes require further clinical validation in SSc patients with AS.

Environmental pollutants and phosphoinositide signaling in autoimmunity

Environmental pollution stands as one of the most critical challenges affecting human health, with an estimated mortality rate linked to pollution-induced non-communicable diseases projected to range from 20% to 25%. These pollutants not only disrupt immune responses but can also trigger immunotoxicity. Phosphoinositide signaling, a pivotal regulator of immune responses, plays a central role in the development of autoimmune diseases and exhibits high sensitivity to environmental stressors. Among these stressors, environmental pollutants have become increasingly prevalent in our society, contributing to the initiation and exacerbation of autoimmune conditions. In this review, we summarize the intricate interplay between phosphoinositide signaling and autoimmune diseases within the context of environmental pollutants and contaminants. We provide an up-to-date overview of stress-induced phosphoinositide signaling, discuss 14 selected examples categorized into three groups of environmental pollutants and their connections to immune diseases, and shed light on the associated phosphoinositide signaling pathways. Through these discussions, this review advances our understanding of how phosphoinositide signaling influences the coordinated immune response to environmental stressors at a biological level. Furthermore, it offers valuable insights into potential research directions and therapeutic targets aimed at mitigating the impact of environmental pollutants on the pathogenesis of autoimmune diseases. SYNOPSIS: Phosphoinositide signaling at the intersection of environmental pollutants and autoimmunity provides novel insights for managing autoimmune diseases aggravated by pollutants.

ACSL4 inhibition prevents macrophage ferroptosis and alleviates fibrosis in bleomycin-induced systemic sclerosis model

BACKGROUND

Systemic sclerosis (SSc), with unclear pathophysiology, is a paradigmatic rheumatic disease of immunity dysfunction-driven multi-organ inflammation and ultimate fibrosis. Pathogenesis breakthroughs are urgently needed for available treatments halting its unremitting stiffness. This study aims to investigate whether ferroptosis can regulate the progressive SSc fibrosis.

METHODS

In vivo, bleomycin (BLM)-induced mice model was subjected to ferroptosis detection using western blotting, malondialdehyde (MDA), and glutathione (GSH) assays. Pharmacological inhibitor of the acyl-CoA synthetase long-chain family member 4 (ACSL4) was utilized to explore its potential therapeutic effects for fibrosis, from histological, biochemical, and molecular analyses. In vitro, bone marrow-derived macrophages (BMDM) were activated into inflammatory phenotype and then the relationship was evaluated between activation level and ferroptosis sensitivity in lipopolysaccharide (LPS) incubation with gradient concentrations. The potential calpain/ACSL4 axis was analyzed after calpain knockdown or over-expression in Raw264.7.

RESULTS

Both skin and lung tissue ferroptosis were present in SSc mice with enhanced ACSL4 expression, while ACSL4 inhibition effectively halted fibrosis progressing and provides protection from inflammatory milieu. Meanwhile, a positive regulation relationship between LPS-induced macrophage activity and ferroptosis sensitivity can be observed. After calpain knockdown, both inflammatory macrophage ferroptosis sensitivity and ACSL4 expression decreased, while its over-expression renders ACSL4-envoking condition. Also, calpain pharmacological inhibition reduced both ferroptosis and fibrosis aptitude in mice.

CONCLUSIONS

ACSL4 induces inflammatory macrophage ferroptosis to aggravate fibrosis progressing. ACSL4 and its upregulators of calpains may be potential therapeutic targets for BLM model of SSc.

Myeloid-specific deletion of Capns1 attenuates myocardial infarction injury via restoring mitochondrial function and inhibiting inflammasome activation

BACKGROUND

Mitochondrial dysfunction of macrophage-mediated inflammatory response plays a key pathophysiological process in myocardial infarction (MI). Calpains are a well-known family of calcium-dependent cysteine proteases that regulate a variety of processes, including cell adhesion, proliferation, and migration, as well as mitochondrial function and inflammation. CAPNS1, the common regulatory subunit of calpain-1 and 2, is essential for the stabilization and activity of the catalytic subunit. Emerging studies suggest that calpains may serve as key mediators in mitochondria and NLRP3 inflammasome. This study investigated the role of myeloid cell calpains in MI.

METHODS

MI models were constructed using myeloid-specific Capns1 knockout mice. Cardiac function, cardiac fibrosis, and inflammatory infiltration were investigated. In vitro, bone marrow-derived macrophages (BMDMs) were isolated from mice. Mitochondrial function and NLRP3 activation were assessed in BMDMs under LPS stimulation. ATP5A1 knockdown and Capns1 knock-out mice were subjected to MI to investigate their roles in MI injury.

RESULTS

Ablation of calpain activities by Capns1 deletion improved the cardiac function, reduced infarct size, and alleviated cardiac fibrosis in mice subjected to MI. Mechanistically, Capns1 knockout reduced the cleavage of ATP5A1 and restored the mitochondria function thus inhibiting the inflammasome activation. ATP5A1 knockdown antagonized the protective effect of Capns1 mKO and aggravated MI injury.

CONCLUSION

This study demonstrated that Capns1 depletion in macrophages mitigates MI injury via maintaining mitochondrial homeostasis and inactivating the NLRP3 inflammasome signaling pathway. This study may offer novel insights into MI injury treatment.