Study On The Function And Mechanism Of MTOR Signaling Pathway In Kidney Disease

ObjectiveCrescent formation is a common pathologic change in many glomerular diseases. Recently, studies have demonstrated that podocytes play a key role in the formation of cellular crescents in experimental and human diseases. However, the underlying mechanisms for podocytes in promoting crescent formation need further investigation. mTORC1 signaling plays an important role in cell growth and proliferation. Here we hypothesis that mTORC1 activation in podocytes may contribute to the cellular crescent formation.Methods1. Human kidney specimens were obtained. Immunohistochemistry of p-S6、 p-4EBP1 and HIF1-α was performed. 2. The podocyte specific Tsc1 knockout mice were generated by crossbreeding Tsc1 floxed mice andPodocin-Cre transgenic mice. There were three groups:the control mice-, the KO mice and the KO mice with rapamycin treatment. For rapamycin treatment, mice were injected with rapamycin at 1 mg/kg by intraperitoneally every other day for 5 weeks. Then, the control、KO and rapamycin treatment mice were sacrificed at 7weeks and 12 weeks old, urine and blood samples were collected at each time point. The renal cross sections were stained with PAS, the urine albumin and renal function were detected;Immunohistochemistry of p-S6、 p-4EBP1、HIF1-α、WT1 and CXCR4 was perfomed.Results1. p-S6, p-4E BP1 as well as HIFlalpha are induced in cellular crescents from patients with crescentic glomerular disease.2. Cellular or mixed cellular and fibrous crescents are developed in podo-Tsc1-/-mice.3. Podocytes with mTORC1 activation participate in crescent formation involving HIF1alpha and Cxcr4 induction.4. Blocking mTORC1 signaling with rapamycin abolishes crescent formation in podo-Tsc1-/- mice.ConclusionThis study suggests that podocyte specific activation of mTORC1 promotes crescent formation and kidney dysfunction and blocking this signaling may be of therapeutic value for treating patients with crescentic glomerular disease.ObjectiveTubular injury occurs in many forms of renal disease. After injury, tubular cells release chemokines such as TNF-alpha、MCP-land Rantes, these chemokines contribute to renal interstitial inflammation and promote the development of renal disease. Pten/PI3K/Akt signaling pathway plays an important role in inflammation and the production of chemokines. In this study, we investigated the role of Pten/PI3K/Akt signaling in renal tubular jnjury and inflammation.Methods1. The tubular cell specific Pten knockout mice were generated by crossbreeding Pten floxed mice and CDH16-Cre transgenic mice, urine、blood and kidney samples were collected at 8weeks and 24 weeks after mice born.;2. The UUO model was established in tubule-Pten-/-and control mice at the age of 8weeks,Then, the control and tubule-Pten-/-mice were sacrificed at 3days and 7 days after UUO, kidney samples were collected,The renal cross sections were stained with PAS, the urine albumin and renal function were detected;3. Knonck down the Pten gene in rat tubular cells in vitro.Results1. Tubule-Pten-/- mice developed albuminuria at the age of 8 weeks and 24 weeks; and at the age of 24 weeks, the level of NAG in urine and the renal chemokines was higher in KO mice than in control mice.2. Tubule-Pten-/- mice developed more severe tubule dilation than control mice at 3 days and 7 days after UUO operation; and the mRNA level of chemokines was much higer in tubule-Pten-/- mice at 7days after UUO operation.3. Knockdown Pten gene in rat tubular cells induced the expression of chemokins,and after the stimulation of TNF-alpha, the mRNA level of chemokines was much higer.ConclusionPten deletion in tubular cells induced the tubular cell injury and promoted the production of chemokines in tubular cells.