The Effect And Mechanism Of Interleukin22in Patients With Polymyositis/Dermatomyositis Complicated Interstitial Lung Disease

Interleukin22(IL-22) is a cytokine which has both anti-inflammatory and proinflammatory properties. It can be produced by multiple immune cells. The IL-22receptor is composed of the IL-22R and IL-10R2subunits. IL-10R2is ubiquity, but IL-22R is found on cells of nonimmune origin in the skin, kidney, liver, lung, and gut. So IL-22exerts its functions on periphery tissues. Polymyositis/dermatomyositis (PM/DM) is often complicated with interstitial lung disease (ILD), which usually leads to a high mortality rate. Idiopathic pulmonary fibrosis (IPF) is defined as a specific form of chronic, progressive fibrosing interstitial pneumonia of unknown cause. It is associated with a poor prognosis with a median survival time from2to3years. Animal experiments demonstrated that IL-22had an important role in the regulation of pulmonary inflammation and fibrosis. Although IL-22expression in muscle biopsies of DM patients was high, and which may be associated with muscle inflammation and fibrosis, the effect and mechanism of IL-22in PM/DM-ILD remained unclear.Firstly, in vivo, the expressions of IL-22and transforming growth factor betal (TGF-β1), the profibrotic cytokine in patients with IPF and PM/DM-ILD were assessed by immunohistochemisty. Plasma levels of IL-17A, IL-6and TNF-α, the important inflammatory cytokines which involved in the pathogenesis of ILD were measured by enzyme linked immunosorbent assay (ELISA) and/or fluorescence quantitative real time polymerase chain reaction (RT-FQ-OCR). We found that the expressions of IL-22in the muscle tissues of patients with PM/DM-ILD were increased significantly compared with controls. However, IL-22expressed in lung tissues and serum IL-22levels both decreased in PM/DM-ILD and IPF patients. TGF-β1expression in the lung tissues of these patients were increased significantly. The plasma concentrations and the mRNA expressions of IL-17A in peripheral blood mononuclear cells (PBMCs) of IPF patients were increased significantly, while decreased significantly in PM/DM-ILD patients. Plasma levels of IL-6and TNF-a in the patients with PM/DM-ILD and IPF increased significantly. Plasma IL-22levels were negatively correlated with the levels of IL-6and TNF-α in PM/DM-ILD patients.Secondly, the regulation and mechanism of IL-22on myoilbroblast were investigated in vitro. Morphological changes of human alveolar epithelial cell (A549) and human embryo fibroblast (HELF) lines stimulated by recombinant human (rh) TGF-β1or/and rhIL-22at different times and concentrations have been observed. The expressions of E-cadherin (E-cad) and a-smooth muscle actin (a-SMA) on A549and fibronectin (FN) and a-SMA on HELF were measured by Western blot. The expressions of TGF-βR2, total Smad2/3, phosphorylation Smad2/3(P-Smad2/3), total Stat3and P-Stat3were also assessed after the A549and HELF lines were treated by rhIL-22. The expressions of IL-22RA1, total Smad2/3, P-Smad2/3, total Stat3and P-Stat3were detected after the cells were treated by rhTGF-β1. We observed that A549cells became spindle-shape from cobble-stone shape after treatment by rhTGF-β1, with down-regulated E-cad and up-regulated a-SMA. The HELF cells were slender spindle-shape after stimulation by rhTGF-β1, with down-regulated FN and up-regulated a-SMA. The morphology of the two cell lines did not change compared with controls after stimulation by rhIL-22, but the expressions of E-cad on A549and FN on HELF cells were up-regulated, with the expression of a-SMA down-regulated. On morphology, after costimulated by rhIL-22and rhTGF-β1, both cell lines had a tendency of being stretched, but were less than the extents of TGF-β1groups. The expressions of surface markers on both lines did not change after costimulation. The moderate concentrations of rhIL-22(10ng/ml) could inhibit the transdifferentiation from A549and HELF cells into myofibroblasts, but also have no effect on their normal morphological changes. The expressions of TGF-PR2and P-Smad2/3of both cell lines were down-regulated significantly after treatment with rhIL-22, but the expressions of P-Stat3were up-regulated. The expressions of IL-22RA1and P-Smad2/3on the two lines increased after stimulation by rhTGF-β1, but the expressions of P-Stat3did not change.In conclusion, the low expressions of IL-22in PM/DM-ILD and IPF patients may be related to the pathogenesis of lung interstitial disease. IL-22can mediate the development of pulmonary fibrosis through inhibiting the transdifferentiations from A549and HELF cells into myofibroblasts. The mechanisms may be due to the inhibition of Smad2/3signal pathway and activation of Stat3signaling, which make the expressions of E-cad on A549and FN on HELF up-regulated and a-SMA on both lines down-regulated. The findings of our experiments in vitro and in vivo suggested that IL-22may be a novel target for treatment of idiopathic and secondary interstitial lung diseases, but the effect and mechanism of pulmonary inflammation and fibrosis mediated by IL-22in animal models need to be further explored.