ag-490 and Diabetic-Nephropathies

Topics: Animals; beta Catenin; Cell Proliferation; Cells, Cultured; Diabetic Nephropathies; Fibronectins; Fibrosis; Kidney; Male; Mesangial Cells; Mice; Mice, Inbred C57BL; Mucin-1; Signal Transduction; STAT Transcription Factors; Sulfonamides; Tyrphostins

Diabetic nephropathy (DN) is a serious and one of the most common microvascular complications of diabetes. There is accumulating evidence to indicate that advanced glycation end products (AGEs), senescent macroprotein derivatives formed at an accelerated rate under conditions of diabetes, play a role in DN. In this study, we found that the serum and urine levels of C-X-C motif chemokine ligand 9 (CXCL9) were significantly elevated in patients with DN compared with healthy controls. Based on an in vitro model of mouse podocyte injury, AGEs decreased the proliferation of podocytes and increased the expression of CXCL9 and C-X-C motif chemokine receptor 3 (CXCR3), and promoted the activation of signal transducer and activator of transcription 3 (STAT3). The knockdown of CXCL9 by the transfection of mouse podoyctes with specific siRNA significantly increased the proliferation and decreased the apoptosis of the podoyctes. Moreover, the levels of inflammatory factors, such as tumor necrosis factor (TNF)‑α and interleukin (IL)‑6 were also decreased in the podoyctes transfected with siRNA-CXCL9, accompanied by the increased expression of nephrin and podocin, and decreased levels of Bax/Bcl-2 and activated caspase-3. The knockdown of CXCL9 also led to the inactivation of the Janus kinase 2 (JAK2)/STAT3 pathway. Importantly, the use of the JAK2 inhibitor, AG490, and valsartan (angiotensin II receptor antagonist) attenuated the injury induced to mouse podoyctes by AGEs. On the whole, and to the best of our knowledge, this study demonstrates for the first time that AGEs exert pro-apoptotic and pro-inflammatory effects in mouse podoyctes through the CXCL9-mediated activation of the JAK2/STAT3 pathway. Thus, our data provide a potential therapeutic target for DN.

Topics: Animals; Apoptosis; bcl-2-Associated X Protein; Cell Line; Chemokine CXCL9; Diabetic Nephropathies; Gene Expression Regulation; Glycation End Products, Advanced; Humans; Interleukin-6; Intracellular Signaling Peptides and Proteins; Janus Kinase 2; Membrane Proteins; Mice; Podocytes; Proto-Oncogene Proteins c-bcl-2; Receptors, Angiotensin; Receptors, CXCR3; RNA, Small Interfering; Signal Transduction; STAT3 Transcription Factor; Tumor Necrosis Factor-alpha; Tyrphostins; Valsartan

Clinical and animal studies show that treatment with angiotensin-converting enzyme (ACE) inhibitors or ANG II-receptor antagonists slows progression of nephropathy in diabetes, indicating ANG II plays an important role in its development. We previously reported that hyperglycemia augments both ANG II-induced growth and activation of Janus kinase (JAK)2 and signal transducers and activators of transcription (STAT) proteins in cultured rat mesangial cells. Furthermore, we demonstrated that the tyrosine kinase enzyme JAK2 plays a key role in both ANG II- and hyperglycemia-induced growth in these cells. We hypothesized that the ACE inhibitor captopril and the ANG II-receptor antagonist candesartan would hinder hyperglycemic-induced activation of JAK and STAT proteins in rat glomeruli, demonstrating that ANG II plays an important role in the activation of these proteins in vivo. Adult male Sprague-Dawley rats were given either streptozotocin (STZ; 60 mg/kg iv) or vehicle, and glomeruli were isolated 2 wk later. Activation of JAK and STAT proteins was evaluated by Western blot analysis for specific tyrosine phosphorylation. Groups of rats were given captopril (75-85 mg x kg(-1) x day(-1)), candesartan (10 mg x kg(-1) x day(-1)), or the JAK2 inhibitor AG-490 (5 mg x kg(-1) x day(-1)) for the study's duration. STZ stimulated glomerular phosphorylation of JAK2, STAT1, STAT3, and STAT5. Phosphorylation was reduced in rats treated with captopril, candesartan, and AG-490. Furthermore, both candesartan and AG-490 inhibited STZ-induced increases in urinary protein excretion. In conclusion, our studies demonstrate that hyperglycemia induces activation of JAK2 and the STATs in vivo via an ANG II-dependent mechanism and that these proteins may be involved in the early kidney damage associated with diabetes.

Topics: Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Antihypertensive Agents; Benzimidazoles; Biphenyl Compounds; Diabetic Nephropathies; DNA-Binding Proteins; Enzyme Inhibitors; Hyperglycemia; Intracellular Signaling Peptides and Proteins; Janus Kinase 2; Kidney Glomerulus; Male; Milk Proteins; Protein Tyrosine Phosphatase, Non-Receptor Type 1; Protein Tyrosine Phosphatase, Non-Receptor Type 11; Protein Tyrosine Phosphatase, Non-Receptor Type 6; Protein Tyrosine Phosphatases; Protein-Tyrosine Kinases; Proto-Oncogene Proteins; Rats; Rats, Sprague-Dawley; Signal Transduction; STAT1 Transcription Factor; STAT3 Transcription Factor; STAT5 Transcription Factor; Tetrazoles; Trans-Activators; Transcription, Genetic; Tyrphostins