The initiation and regulation of pulmonary fibrosis are not well understood. IL-33, an important cytokine for respiratory diseases, is overexpressed in the lungs of patients with idiopathic pulmonary fibrosis. We aimed to determine the effects and mechanism of IL-33 on the development and severity of pulmonary fibrosis in murine bleomycin-induced fibrosis. Lung fibrosis was induced by bleomycin in wild-type or Il33r (St2)(-/-) C57BL/6 mice treated with the recombinant mature form of IL-33 or anti-IL-33 antibody or transferred with type 2 innate lymphoid cells (ILC2s). The development and severity of fibrosis was evaluated based on lung histology, collagen levels, and lavage cytology. Cytokine and chemokine levels were quantified by using quantitative PCR, ELISA, and cytometry. IL-33 is constitutively expressed in lung epithelial cells but is induced in macrophages by bleomycin. Bleomycin enhanced the production of the mature but reduced full-length form of IL-33 in lung tissue. ST2 deficiency, anti-IL-33 antibody treatment, or alveolar macrophage depletion attenuated and exogenous IL-33 or adoptive transfer of ILC2s enhanced bleomycin-induced lung inflammation and fibrosis. These pathologic changes were accompanied, respectively, by reduced or increased IL-33, IL-13, TGF-β1, and inflammatory chemokine production in the lung. Furthermore, IL-33 polarized M2 macrophages to produce IL-13 and TGF-β1 and induced the expansion of ILC2s to produce IL-13 in vitro and in vivo. IL-33 is a novel profibrogenic cytokine that signals through ST2 to promote the initiation and progression of pulmonary fibrosis by recruiting and directing inflammatory cell function and enhancing profibrogenic cytokine production in an ST2- and macrophage-dependent manner.

The nucleotide-binding domain, leucine-rich repeat containing family caspase recruitment domain containing 4 (NLRC4) inflammasome can be activated by pathogenic bacteria via products translocated through the microbial type III secretion apparatus (T3SS). Recent work has shown that activation of the NLRP3 inflammasome is downregulated by autophagy, but the influence of autophagy on NLRC4 activation is unclear. We set out to determine how autophagy might influence this process, using the bacterium Pseudomonas aeruginosa, which activates the NLRC4 inflammasome via its T3SS. Infection resulted in T3SS-dependent mitochondrial damage with increased production of reactive oxygen intermediates and release of mitochondrial DNA. Inhibiting mitochondrial reactive oxygen release or degrading intracellular mitochondrial DNA abrogated NLRC4 inflammasome activation. Moreover, macrophages lacking mitochondria failed to activate NLRC4 following infection. Removal of damaged mitochondria by autophagy significantly attenuated NLRC4 inflammasome activation. Mitochondrial DNA bound specifically to NLRC4 immunoprecipitates and transfection of mitochondrial DNA directly activated the NLRC4 inflammasome; oxidation of the DNA enhanced this effect. Manipulation of autophagy altered the degree of inflammasome activation and inflammation in an in vivo model of P. aeruginosa infection. Our results reveal a novel mechanism contributing to NLRC4 activation by P. aeruginosa via mitochondrial damage and release of mitochondrial DNA triggered by the bacterial T3SS that is downregulated by autophagy.

Background: Inflammatory bowel disease (IBD) patients may be at risk of vitamin B12 and folate insufficiencies, as these micronutrients are absorbed in the small intestine, which is affected by IBD. However, a consensus has not been reached on the association between IBD and serum folate and vitamin B12 concentrations. Methods: In this study, a comprehensive search of multiple databases was performed to identify studies focused on the association between IBD and serum folate and vitamin B12 concentrations. Studies that compared serum folate and vitamin B12 concentrations between IBD and control patients were selected for inclusion in the meta-analysis. Results: The main outcome was the mean difference in serum folate and vitamin B12 concentrations between IBD and control patients. Our findings indicated that the average serum folate concentration in IBD patients was significantly lower than that in control patients, whereas the mean serum vitamin B12 concentration did not differ between IBD patients and controls. In addition, the average serum folate concentration in patients with ulcerative colitis (UC) but not Crohn’s disease (CD) was significantly lower than that in controls. This meta-analysis identified a significant relationship between low serum folate concentration and IBD. Conclusions: Our findings suggest IBD may be linked with folate deficiency, although the results do not indicate causation. Thus, providing supplements of folate and vitamin B12 to IBD patients may improve their nutritional status and prevent other diseases.

The microglia cell transfer has been shown to play a protective role in ischemic stroke. Microglia cells may play this nerve-protective role via the promotion of angiogenesis. However, the underlying mechanisms are largely unknown and need further investigation. The aim of this study was to investigate the pro-angiogenesis effects of unpolarized, interleukin-4 (IL-4)-polarized or lipopolysaccharide (LPS)-polarized BV2 microglia cells both in vivo and in vitro. We also investigated the potential mechanisms of these pro-angiogenesis effects. BV2 cells were polarized using phosphate-buffered saline (PBS), LPS or IL-4, respectively. The gene expression pattern was analyzed by reverse transcription polymerase chain reaction (RTPCR). The transfer of polarized BV2 cells was performed with an intravenous injection into mice 45 min after the middle cerebral artery (MCA) occlusion. Angiogenin expression was assessed by immunofluorescence. We also examined the angiogenesis effect of polarized BV2 cells and their exosomes through 3-dimensional co-cultures in vitro. Finally, the microRNA (miRNA) profiles of exosomes released by BV2 cells under different polarization conditions were examined using miRNA microarray. The IL-4-polarized BV2 transplantation promoted angiogenin expression in the ischemic brain. Interleukin-4-polarized microglia increased the tube formation of endothelial cells by secreting exosomes. The miRNA profiles of exosomes released by BV2 cells under different polarization conditions were different. Exosomes from IL-4-polarized BV2 cells contained higher amounts of miRNA-26a compared to those from the LPS-polarized and unpolarized BV2 cells. Interleukin-4-polarized microglia cells might ameliorate the damage caused by ischemic stroke by promoting angiogenesis through the secretion of exosomes containing miRNA-26a.