Glucagon­like peptide­1 protects mouse podocytes against high glucose­induced apoptosis, and suppresses reactive oxygen species production and proinflammatory cytokine secretion, through sirtuin 1 activation in vitro.

Glucagon­like peptide­1 (GLP­1) is a gut incretin hormone that is considered to be a promising target for the treatment of patients with type 2 diabetes. However, the mechanisms underlying the protective effects of GLP­1 on diabetic nephropathy are yet to be fully elucidated. Sirtuin (SIRT)1 encodes a member of the SIRT family of proteins that serves an important role in mitochondrial function and is reported to be associated with the pathogenesis of chronic kidney disease. The present study treated mouse podocytes with various concentrations of D­glucose to establish a high glucose (HG)­induced model of renal injury. The results of a 2',7'­dichlorodihydrofluorescein diacetate assay, Annexin V/propidium iodide staining and ELISA demonstrated that treatment of podocytes with HG significantly enhanced the production of reactive oxygen species (ROS), promoted cell apoptosis and increased the secretion of proinflammatory cytokines, respectively. The cytokines increased following HG treatment included tumor necrosis factor­α, interleukin (IL)­1ß and IL­6. Notably, treatment with GLP­1 attenuated HG­induced increases in ROS production and podocyte apoptosis, which may occur via downregulation of the expression of caspase­3 and caspase­9, and increased expression of nephrin, podocin and SIRT1, as determined by reverse transcription­quantitative polymerase chain reaction and western blot analysis. Treatment with GLP­1 led to protective effects in podocytes that were similar to those of resveratrol. Furthermore, SIRT1 knockdown using short hairpin RNA significantly enhanced the expression of caspase­3 and caspase­9 in mouse podocytes, compared with normal mouse podocytes. SIRT1 knockdown with or without GLP­1 administration significantly decreased the expression of caspase­3 and caspase­9 in mouse podocytes, compared with SIRT1 knockdown mouse podocytes. In conclusion, the results of the present study indicated that GLP­1 may be a promising target for the development of novel therapeutic strategies for HG­induced nephropathy, and may function through the activation of SIRT1.

SIRT4 overexpression protects against diabetic nephropathy by inhibiting podocyte apoptosis.

Diabetic nephropathy is a diabetic complication associated with capillary damage and increased mortality. Sirtuin 4 (SIRT4) plays an important role in mitochondrial function and the pathogenesis of metabolic diseases, including aging kidneys. The aim of the present study was to investigate the association between SIRT4 and diabetic nephropathy in a glucose-induced mouse podocyte model. A CCK-8 assay showed that glucose simulation significantly inhibited podocyte proliferation in a time- and concentration-dependent manner. Reverse transcription-quantitative polymerase chain reaction and western blot analysis showed that the mRNA and protein levels of SIRT4 were notably decreased in a concentration-dependent manner in glucose-simulated podocytes. However, SIRT4 overexpression increased proliferation and suppressed apoptosis, which was accompanied by increases in mitochondrial membrane potential and reduced production of reactive oxygen species (ROS). Notably, SIRT4 overexpression downregulated the expression of apoptosis-related proteins NOX1, Bax and phosphorylated p38 and upregulated the expression of Bcl-2 in glucose-simulated podocytes. In addition, SIRT4 overexpression significantly attenuated the inflammatory response, indicated by reductions in the levels of TNF-α, IL-1ß and IL-6. These results demonstrate for the first time that the overexpression of SIRT4 prevents glucose-induced podocyte apoptosis and ROS production and suggest that podocyte apoptosis represents an early pathological mechanism leading to diabetic nephropathy.

Silencing of USP22 suppresses high glucose-induced apoptosis, ROS production and inflammation in podocytes.

Ubiquitin-specific protease 22 (USP22) has been reported to mediate various cellular processes, including cell proliferation and apoptosis. However, its role in high glucose-induced podocytes and diabetic rats remains unknown. In the current study, podocytes were treated with different concentrations of d-glucose to establish a high glucose-induced injury model. Additionally, intravenous tail injection of rats with 65 mg kg(-1) of streptozotocin (STZ) was performed to establish a diabetic rat model. Our findings showed that the treatment of podocytes with high d-glucose significantly increased the USP22 expression level. Silencing of USP22 in podocytes attenuated high d-glucose-induced apoptosis and inflammatory responses, evidenced by increases in proliferation and MMP levels and decreases in the apoptotic rate, ROS production, the Bax/Bcl-2 ratio, caspase-3 expression and secretion of TNF-α, IL-1ß, IL-6 and TGF-ß1. In addition, podocytes with USP22 overexpression significantly enhanced the effect of high d-glucose-induced apoptosis and inflammatory responses. Similar to the protective effect of USP22 knockdown, resveratrol (RSV) depressed not only high d-glucose- and USP22 overexpression-induced cytotoxicity, but also the secretion of TNF-α, IL-1ß, IL-6 and TGF-ß1. Notably, silencing of USP22 in diabetic rats conferred a similar protective effect against high glucose-induced apoptosis and inflammation. Taken together, the findings of the present study have demonstrated for the first time that USP22 inhibition attenuates high glucose-induced podocyte injuries and inflammation.

[Thrombin and angiogenesis of cancer--review].

Thrombin is the most important factor in hemostasis. In recent years, it has been found that thrombin is a potent mitogen capable of inducing cellular functions. Therefore, it is proved to be of importance in promoting the growth, metastasis and angiogenesis of cancer. Anticoagulant therapy not only reduce the characteristic hypercoagulability of cancer, but also inhibits growth and metastasis of cancer, and alters the fundamental biology of cancer. In this paper thrombin and its receptor, relationship of thrombin and its receptor with cancer growth, metastasis and angiogenesis, the mechanisms of thrombin influence on cancer angiogenesis, as well as application prospects on anti-angiogenesis and anti-coagulation therapy were reviewed.