Vitamin D protects silica particles induced lung injury by promoting macrophage polarization in a KLF4-STAT6 manner.

Silicosis is one of the severest occupational diseases worldwide, manifesting as infiltration of inflammatory cells, excessive secretion of pro-inflammatory mediators and pulmonary diffuse fibrosis. Macrophages polarization to M2 is one of the major strategies that attenuates inflammatory response. Our previous study found that vitamin D could protect against silica-induced lung injury by damping the secretion of pro-inflammatory cytokines. Here we further identified that vitamin D attenuated silica particles-induced lung inflammation by regulating macrophage polarization in a KLF4-STAT6 manner. Myeloid-specific Stat6 knockout (cKO) mice were generated for in vivo studies. Primary macrophages purified from bronchoalveolar lavage fluid (BALF) of wildtype or Stat6 cKO mice and differentiated THP-1 cells were used for in vitro studies. Vitamin D was found to promote alveolar macrophage polarizing to M2 phenotype through the STAT6 signaling pathway, as demonstrated by worse lung inflammation and ablated protection of vitamin D in silica particles-instilled Stat6 cKO mice. Mechanismly, vitamin D upregulated KLF4 expression in the alveolar macrophage, which synergistically activated STAT6. Additionally, KLF4 was found to upregulate macrophages autophagy, which protected them from silica particles-induced oxidative stress and cell apoptosis. The protective effects of vitamin D were dismissed by silencing KLF4. Our study demonstrates the potential mechanism of vitamin D-mediated macrophage polarization and reveals the therapeutic application of vitamin D in inflammatory disease.

Melatonin protects against nonylphenol caused pancreatic ß-cells damage through MDM2-P53-P21 axis.

Nonylphenol (NP) is an endocrine disrupting chemical, which widely exists in environment and can result in multiple system dysfunction. Pancreas as one of the most important organs is sensitive to NP, while the detail toxic effect is still less studied. Previously, we unveiled nonylphenol causes pancreatic damage in rats, herein, we further explore the potential mechanism and seek protection strategy in vitro. Insulinoma (INS-1) cells exposed to NP were observed to suffer oxidative stress and mitochondrial dysfunction, as reflected by the abnormal levels of reactive oxygen species, malonic dialdehyde, superoxide dismutase, Ca2+, and mitochondrial membrane potential. Melatonin (MT) was found to alleviate NP-induced mitochondrial dysfunction and oxidative stress, further inhibit apoptosis and restore pancreas function. Mechanically, MT induced the MDM2-P53-P21 signaling, which upregulated the Nrf2 signaling pathway. In summary, our study clarified NP-induced INS-1 cells mitochondrial dysfunction and oxidative stress, which could be ameliorated by MT through MDM2-P53-P21 axis.

STAT6 inhibits ferroptosis and alleviates acute lung injury via regulating P53/SLC7A11 pathway.

Compelling evidences have revealed the emerging role of ferroptosis in the pathophysiological process of acute lung injury (ALI), but its modulation is not clear. Here, we identified that STAT6 acted as a critical regulator of epithelium ferroptosis during ALI. Firstly, STAT6 expression and activity were increased in the ALI mice models caused by crystalline silica (CS), LPS and X-ray exposure. Followed by confirming the contribution of ferroptosis in the above ALI with ferrostatin-1 and deferoxamine intervention, bioinformatic analyses revealed that STAT6 expression was negatively correlated with ferroptosis. Consistently, lung epithelium-specific depletion of STAT6 in mice or STAT6 knockdown in cultured epithelial cells exacerbated ferroptosis in the above ALI. While overexpression of STAT6 in lung epithelial cells attenuated the ferroptosis. Mechanistically, SLC7A11 is a typical ferroptosis-related gene and negatively regulated by P53. CREB-binding protein (CBP) is a critical acetyltransferase of P53 acetylation, showing valuable regulation on targets' transcription. Herein, we found that STAT6 negatively regulates ferroptosis through competitively binding with CBP, which inhibits P53 acetylation and transcriptionally restores SLC7A11 expression. Finally, pulmonary-specific STAT6 overexpression decreased the ferroptosis and attenuated CS and LPS induced lung injury. Our findings revealed that STAT6 is a pivotal regulator of ferroptosis, which may be a potential therapeutic target for the treatment of acute lung injury.

STAT6/VDR Axis Mitigates Lung Inflammatory Injury by Promoting Nrf2 Signaling Pathway.

Lung inflammatory injury is a global public health concern. It is characterized by infiltration of diverse inflammatory cells and thickening of pulmonary septum along with oxidative stress to airway epithelial cells. STAT6 is a nuclear transcription factor that plays a crucial role in orchestrating the immune response, but its function in tissue inflammatory injury has not been comprehensively studied. Here, we demonstrated that STAT6 activation can protect against particle-induced lung inflammatory injury by resisting oxidative stress. Specifically, genetic ablation of STAT6 was observed to worsen particle-induced lung injury mainly by disrupting the lungs' antioxidant capacity, as reflected by the downregulation of the Nrf2 signaling pathway, an increase in malondialdehyde levels, and a decrease in glutathione levels. Vitamin D receptor (VDR) has been previously proved to positively regulate Nrf2 signals. In this study, silencing VDR expression in human bronchial epithelial BEAS-2B cells consistently suppressed autophagy-mediated activation of the Nrf2 signaling pathway, thereby aggravating particle-induced cell damage. Mechanically, STAT6 activation promoted the nuclear translocation of VDR, which increased the transcription of autophagy-related genes and induced Nrf2 signals, and silencing VDR abolished these effects. Our research provides important insights into the role of STAT6 in oxidative damage and reveals its potential underlying mechanism. This information not only deepens the appreciation of STAT6 but also opens new avenues for the discovery of therapies for inflammatory respiratory system disorders.

Upregulation of autophagy in M2 macrophage by vitamin D alleviates crystalline silica-induced pulmonary inflammatory damage.

Crystalline silica (CS) is a universal environmental pollutant, which causes a typical inflammatory lung injury. Vitamin D shows huge potential against particles-induced lung injury, while little known about the molecular mechanism involved in macrophage autophagy. In this study, we aim to identify the protective effects of vitamin D on CS caused lung inflammatory injury and clarify the detail mechanism. After exposure to CS (3 mg/mice in 50 µl PBS), wildtype and Atg7flox/flox Lyz2-cre mice were treated with or without vitamin D3 (40,000 IU/kg). The results indicated that exposure to CS caused an obvious lung injury, manifesting as pathological structural changes, macrophage-dominated inflammatory cell infiltration and increased pro-inflammatory cytokines. Remarkably, these damages were more serious in Atg7flox/flox Lyz2-cre mice. Vitamin D was found to inverse CS-induced inflammatory cell infiltration and restored anti-inflammatory M2 macrophages by inducing autophagy, which attenuated lung injury, as determined by decreased levels of apoptosis and inflammatory response. While, this effects of vitamin D were slashed in Atg7flox/flox Lyz2-cre mice. This study reveals the adverse effect of CS on lung tissue and the protective mechanism of vitamin D involved in M2 macrophages autophagy, which attenuates CS-caused lung injury.