Interleukin-18 promotes fibroblast senescence in pulmonary fibrosis through down-regulating Klotho expression.

Idiopathic pulmonary fibrosis (IPF) is a lethal disease of unknown aetiology that largely presents in the elderly. The mechanisms related to aging such as fibroblast senescence have been strongly implicated in pathology of IPF. We have previously demonstrated the protective effects of IL-18 binding protein (IL-18BP) against bleomycin (BLM)-induced pulmonary fibrosis (PF) via inhibition of epithelial-to-mesenchymal transition. However, the role of IL-18 in fibroblast senescence in PF is still unknown. The aim of this study was to investigate the effects of IL-18 on fibroblast senescence in the development of PF. We found that SA-ß-gal positive cells, the proportion of cells in G1 phase, and expressions of p21 and p53 were increased in primary lung fibroblasts isolated from BLM-challenged mice, while the fibroblasts from IL-18BP-treated mice showed decreased senescence propensity. We further demonstrated that IL-18 was sufficient to trigger senescence of primary lung fibroblasts. The senescence-associated secretory phenotype (SASP) of fibroblasts treated with IL-18 robustly stimulated a fibrotic phenotype in pulmonary fibroblasts. Moreover, the expression of Klotho, an anti-senescence protein, was down-regulated after IL-18 treatment in primary lung fibroblasts. Overexpression of Klotho reversed the senescence and SASP induced by IL-18 in lung fibroblasts. In summary, we reported for the first time that IL-18 promoted the lung fibroblast senescence and SASP in PF through blocking Klotho pathway. Neutralize IL-18 by IL-18BP exhibited antifibrotic effects partly by suppressing lung fibroblast senescence in PF. It contributes to the growing evidence that IL-18 could be a therapeutic target for PF.

Neutralization of IL-18 by IL-18 binding protein ameliorates bleomycin-induced pulmonary fibrosis via inhibition of epithelial-mesenchymal transition.

Idiopathic pulmonary fibrosis (IPF) is a fatal parenchymal lung disease with limited effective therapies. Interleukin (IL)-18 belongs to a rather large IL-1 gene family and is a proinflammatory cytokine, which acts in both acquired and innate immunity. We have previously reported that IL-18 play an important role in lipopolysaccharide-induced acute lung injury in mice. Persistent inflammation often drives fibrotic progression in the bleomycin (BLM) injury model. However, the role of IL-18 in pulmonary fibrosis (PF) is still unknown. IL-18 binding protein (IL-18BP) is able to neutralize IL-18 biological activity and has a protective effect against renal fibrosis. The aim of this study was to investigate the effects of IL-18BP on BLM-induced PF. In the present study, we found that IL-18 was upregulated in lungs of BLM-injured mice. Neutralization of IL-18 by IL-18BP improved the survival rate and ameliorated BLM-induced PF in mice, which was associated with attenuated pathological changes, reduced collagen deposition, and decreased content of transforming growth factor-ß1 (TGF-ß1). We further demonstrated that IL-18BP treatment suppressed the BLM-induced epithelial mesenchymal transition (EMT), characterized by decreased α-smooth muscle actin (α-SMA) and increased E-cadherin (E-cad) in vivo. In addition, we provided in vitro evidence demonstrating that IL-18 promoted EMT through upregulation of Snail-1 in A549 cells. In conclusion, our findings raise the possibility that the increase of IL-18 is involved in the development of BLM-induced PF through modulating EMT in a Snail-1-dependent manner. IL-18BP may be a worthwhile candidate option for PF therapy.

Interleukin-18 binding protein attenuates lipopolysaccharide-induced acute lung injury in mice via suppression NF-κB and activation Nrf2 pathway.

Interleukin (IL)-18 belongs to a rather large IL-1 gene family and is a proinflammatory cytokine. IL-18 plays important roles in lung injury. IL-18 binding protein (IL-18BP), a natural antagonist of IL-18, binds IL-18 with high affinity. IL-18BP is able to neutralize IL-18 biological activity and has a protective effect against renal fibrosis. The aim of this study was to evaluate the potential protective effect of IL-18BP on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice and to illuminate the underlying mechanisms. Results indicated that pretreatment with IL-18BP significantly attenuated LPS-induced pulmonary pathological injury. Meanwhile, IL-18BP pretreatment markedly inhibited infiltration of inflammatory cell and release of inflammatory factor in ALI mice in vivo and in primary macrophages after LPS insult in vitro. IL-18BP treatment dramatically reduced oxidative stress through increasing superoxide dismutase (SOD) and glutathione (GSH) contents, and decreasing the levels of malondialdehyde (MDA) and reactive oxygen species (ROS) in LPS-induced ALI mice and primary macrophages. Additionally, IL-18BP was also observed to markedly decreased the activation of nuclear factor-kappa B (NF-κB) and upregulated the nuclear factor erythroid 2-related factor 2 (Nrf2). Taken together, IL-18BP possessed protective effect against LPS-induced ALI, which might be associated with its regulation of NF-κB and Nrf2 activities. The results rendered IL-18BP worthy of further development into a pharmaceutical drug for the treatment of ALI.

Sema 3A as a biomarker of the activated mTOR pathway during hexavalent chromium-induced acute kidney injury.

Semaphorin 3A (sema 3A) is one of a class of secretory proteins belonging to a family of axon-directed factors found in podocytes, distal tubules, and collecting tubes of the kidney. It is considered to be a potential target molecule involved in the mammalian target of the rapamycin (mTOR) pathway in renal injury or renal diseases, but it has an unknown role in the course of hexavalent chromium-Cr(VI) induced nephrotoxicity. In the present study, an acute kidney injury (AKI) model in rats or cultured tubular epithelial HK-2 cells was employed for Cr(VI) exposure alone or in combination with rapamycin (Rap) or N-acetyl-l-cysteine (NAC) or recombinant sema 3A. The methods of histopathology, biochemics, and western blotting were applied to evaluate tubular injury and the role of sema 3A. The results showed that a significant increase of urinary sema 3A indicates an early occurrence of AKI exposed to Cr(VI), accompanied with a significant increase of tubular injury score and phosphorylated mTOR proteins. Further, Cr(VI) treatment, in combination with pretreatment of the mTOR pathway inhibitor, Rap, showed a considerably stronger protective effect of Rap in protecting against Cr(VI)-induced nephrotoxicity than that seen with the free radical scavenger NAC, highlighting the dominant renal protective role of the mTOR pathway in inhibiting toxicity by downregulating the expressed levels of sema 3A in renal tissue. This study has demonstrated that an increased expression of sema 3A occurs in Cr(VI)-induced AKI resulting from activation of the mTOR pathway, and that inhibition of this pathway has been shown to decrease the severity of the toxicity. In conclusion, this study has shown that increased urinary sema 3A is indicative of an activated mTOR pathway and is a valuable biomarker of the early AKI induced by Cr(VI) exposure.