Simvastatin Reduces NETosis to Attenuate Severe Asthma by Inhibiting PAD4 Expression.

Objective: Patients with severe asthma respond poorly to corticosteroids, and their care accounts for more than 60% of the total costs attributed to asthma. Neutrophils form neutrophil extracellular traps (NETs), which play a crucial role in severe asthma. Statins have shown anti-inflammatory effects by reducing NETosis. In this study, we investigate if simvastatin can attenuate severe asthma by reducing NETosis and the underlying mechanism. Methods: Mice were concomitantly sensitized with ovalbumin (OVA), house dust mite (HDM), and lipopolysaccharide (LPS) during sensitization to establish a mouse model of severe asthma with neutrophil predominant inflammation (OVA+LPS mice) and treated with or without simvastatin. In inflammatory response, proportions of Th2, Th17, and Treg cells in lung tissue were detected by flow cytometry, and the levels of cytokines, dsDNA, and MPO-DNA in bronchoalveolar lavage fluid (BALF) were analyzed by ELISA. Citrullinated histone H3 (CitH3) and peptidyl arginine deiminase 4 (PAD4) in lung tissue were determined by Western blot and immunofluorescence imaging. PAD4 mRNA was determined by quantitative PCR (qPCR). HL-60 cells were differentiated into neutrophil-like cells by 1.25% DMSO. The neutrophil-like cells were treated with or without LPS, and simvastatin was then stimulated with PMA. CitH3 and PAD4 expressions were determined. Results: Sensitization with OVA, HDM, and LPS resulted in neutrophilic inflammation and the formation of NETs in the lungs. Simvastatin treatment reduced the inflammation score, cytokine levels, total cells, and neutrophil counts in the BALF and reduced proportions of Th2 and Th17 but increased Treg cells in lungs of OVA+LPS mice. Simvastatin-treated OVA+LPS mice show reduced NET formation in BALF and lung tissue compared to control mice. Adoptive transfer of neutrophils was sufficient to restore NETosis and neutrophilic inflammation in simvastatin-treated OVA+LPS mice. Simvastatin reduced PAD4 mRNA and protein expression in lung tissues and neutrophils isolated from lungs of OVA+LPS mice and consequent NET formation. In vitro, simvastatin reduced LPS-induced PAD4 upregulation and NETosis in HL-60-differentiated neutrophil-like cells. Furthermore, PAD4-overexpressed lentiviral transduction was sufficient to restore PAD4 protein expression and NETosis in simvastatin-treated HL-60-differentiated neutrophil-like cells. Conclusions: Simvastatin reduces Th17-mediated neutrophilic inflammation and airway hyperreactivity by reducing PAD4 expression and inhibiting NETosis in a mouse model of severe asthma. Severe asthmatic patients with high levels of circulating NETs or sputum NETs may show improved responses to statin treatment.

Long non-coding RNA MALAT1 sponges miR-149 to promote inflammatory responses of LPS-induced acute lung injury by targeting MyD88.

Acute lung injury (ALI) caused by sepsis occurs early and the condition is severe, and is also an important reason for accelerating the death of patients. Increasing evidence has identified long non-coding RNA (lncRNA) metastasis associated in lung adenocarcinoma transcript 1 (MALAT1) as a regulator of ALI. However, the potential mechanism underlying MALAT1 on ALI still needs further identification. To explore the mechanisms of gene regulation expression mediated by MALAT1 through miR-149/MyD88 in lung injury inflammation, we constructed a lung injury inflammatory model using the lipopolysaccharides (LPS)-induced method and quantificated the cytokines and signaling cascade molecules as well as miR-149. The MALAT1, myeloid differentiation factor 88 (MyD88), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and IL-6 levels were significantly increased, and the nuclear factor-κB (NF-κB) pathway was activated, but the miR-149 level was decreased in the LPS-induced ALI model. miR-149 directly targeted both lncRNA MALAT1 and the MyD88 gene. Knockdown of MALAT1 down-regulated the levels of MyD88, TNF-α, IL-1ß, and IL-6, and inhibited the NF-κB pathway. However, MALAT1 knockdown up-regulated the expression of miR-149. Overexpression of miR-149 down-regulated MyD88, TNF-α, IL-1ß, and IL-6 levels, and inhibited the NF-κB pathway. MALAT1 acts as a pro-inflammatory factor in ALI via the miR-149/MyD88/NF-κB axis and is therefore a potential novel therapeutic target for ALI treatment.

Hypomethylation of perforin regulatory elements in CD4+ T cells from rat spleens contributes to the development of autoimmune emphysema.

BACKGROUND AND OBJECTIVE: It is widely accepted that perforin regulatory elements are hypomethylated in CD4+ T cells from patients with active lupus, but whether this is the case in autoimmune emphysema is not known. METHODS: Twenty rats were randomly divided into a normal control group and an emphysema group. Rat models of emphysema were established by intraperitoneal injection with xenogeneic endothelial cells. The levels of tumour necrosis factor-α, interleukin-8 and matrix metalloproteinase (MMP)-9 in bronchoalveolar lavage fluid (BALF) were measured, lung mean linear intercept and destructive index measured. Mean methylation of perforin gene promoter in CD4+ T cells and the expression of perforin were investigated. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling methods were used to examine the percentage of apoptotic cells in the alveolar septa. RESULTS: The levels of MMP-9 in BALF were higher in emphysema group than in control group (P < 0.05). The mean linear intercept and destructive index were higher in emphysema group than in control group (P < 0.05). The mean perforin gene promotor methylation of emphysema group was significantly decreased as compared with control group, while the expression levels of perforin gene were relatively higher (P < 0.05). There were more terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling-positive cells in the alveolar septa in control group than in emphysema group. CONCLUSIONS: Hypomethylation of perforin regulatory elements in CD4+ T cells may result in the lung septal cell apoptosis associated with the development of experimental autoimmune emphysema. MMP-9 may play an important role in the pathogenesis of this kind of disease.