Function And Application Of PTP1B In Inflammation Diseases

More and more studies have showed that signaling pathway of tyrosine phosphatase 1B(PTP1B)mediate pathogenesis in many inflammatory-related diseases,including ulcerative colitis and diabetic complications.However,the biological function and mechanism of PTP1B was not yet understood.Firstly,we studied the function and mechanism of PTP1B in ulcerative colitis induced by dextran sulfate sodium(DSS).Knockout or activity reduction of PTP1B could promote and activate the proliferation and function of myeloid-derived immunosuppressive cells(MDSC),and effectively resist DSS-induced ulcerative colitis.In this study,we found that PTP1B-/-mice could effectively resist inflammation compared with wild-type mice under the same concentration of DSS treatment.The disease activity index(DAI),pathological structural analysis,inflammatory cell infiltration and inflammatory cytokines levels in serum of PTP1B-/-mice were significantly lower than wild-type mice.To illustrate this phenomenon,we did further research and found that MDSC from bone marrow,spleen and peripheral blood of PTP1B-/-mice significantly increased.During the process of inducing bone marrow cells to MDSC with the stimulation of cytokine IL-6 and GM-CSF,we found that induction rate of PTP1B-/-mice bone marrow was faster,and MDSC percentage was higher at the same time point.In addition,assay of CD4+,CD8+T cell and Th17 cells in vivo and test of MDSC co-cultured with T cells in vitro indicated that exhibited MDSC originated from PTP1B-/-mice had a stronger inhibition effect on proliferation of T cells.These results validate that PTP1B plays a negative role in the regulation of proliferation and function of MDSC,and MDSC expansion leads to resistance of DSS-induced ulcerative colitis.Then,we implanted induced MDSC by intravenous injection,and found equal effect on inflammation reducion.With treatment of glucocorticoid,the percentage of MDSC in mouse bone marrow,spleen and peripheral blood increased significantly.Together with the results of decreased percentage of body weight,histological scores,inflammatory cell infiltration and inflammatory cytokine levels assay,we also could made a conclusion that glucocorticoids could resist ulcerative colitis by increasing the proliferation and function of MDSC.At the same time,we studied the mechanism of PTP1B mediated MDSC upregulation in inflammation resistance.We found that PTP1B downregulation could increase the phosphorylation levels of JAK2/STAT3,and then increased signaling pathway activity.leading to upregulated MDSC function,such as enhancing its suppression on T cells,reducing immune cells infiltration and decreasing damage to the body tissues.Finally,it could achieve the purpose of inflammation relief and resistance.Our research provides strong evidence for PTP1B application in the treatment of ulcerative colitis as a biological target.Secondly,we studied the function and mechanism of PTP1B in diabetic wound healing.The increased PTP1B expression in diabetes hindered the process of angiogenesis and wound healing by increasing VEGFR2 dephosphorylation.In our research we found that PTP1B expression was extremely higher in wild type mice treated by STZ and spontaneous diabetes ob/ob mice compared with the normal mice.As a specific marker of angiogenesis,CD31 positive rate was significantly decreased,indicating the angiogenesis of diabetic mice capacity was obviously decreased.The daily observation and pathological results also showed that wound healing rate of diabetic mice was significantly slowly.By contrast,PTP1B-/-diabetic mice showed an accelerated angiogenesis and wound healing process.From healing-process wound photos and pathological results,we found that the PTP1B inhibitor could effectively enhance the capacity of angiogenesis and wound healing.In addition,we stimulated endothelial cells,HMEC-1,with high concentration of glucose in vitro.We found this treatment could induce PTP1B highly expression,and inhibited VEGF-stimulated HMEC-1 tube formation,proliferation and migration.While treating HMEC-1 cells with high.concentration of glucose and PTP1B inhibitors at the same time,the ability of tube formation,proliferation and migration was enhanced.Then we studied the mechanism of PTP1B overexpression with the stimulation of high concentration of glucose.We found that this treatment could significantly increase ROS production,thus improving NF?B expression.With the treatment of ROS or NF?B inhibitors,PTP1B expression did not increase.These results suggested that PTP1B overexpression induced by high glucose might be acvtivated by ROS-NF?B pathway.Then we found that the highly expressed PTP1B significantly reduced vascular endothelial growth factor receptor 2(VEGFR2)phosphorylation level,resulting in a declined binding activity in VEGF and VEGFR2,and blocking angiogenesis,thus made the wound healing delay.Under high concentration of glucose condition,VEGFR2 phosphorylation level in HMEC-1 was significantly decreased.By in vivo and in vitro experiments we found that PTP1B inhibitors could significantly improve the VEGFR2 phosphorylation level.In order to further confirm the mechanism of PTP1B mediated VEGFR2 phosphorylation activity,we transfected HMEC-1 cells with siRNA against VEGFR2.When VEGFR2 was knocked-down,tube formation,proliferation and migration of HMEC-1 significantly reduced.Overexpression or inhibition the activity of PTP1B could not influence VEGFR2 phosphorylation level,as well as tube formation,cell proliferation or migration.In conclusion,our study demonstrated that high PTP1B expression could reduce VEGFR2 phosphorylation level,and thus prevent angiogenesis and diabetic wound healing.PTP1B inhibitor could effectively accelerate diabetic wound healing.Our research provids a new angle of view for the pathogenesis of diabetic wound,and a new train of thought for PTP1B as a novel biological target in clinical diabetic wound therapy.In summary,this thesis certificates and expounds the significant biological function and mechanism of the enzyme PTP1B played in inflammatory diseases,such as ulcerative colitis and diabetes.Our study provides strong evidence and a new point of view for clinical treatment of this kind of disease and has important clinical significance.