Previous studies suggest that TGF contributes to

Previous studies suggest that TGF-β contributes to the pathogenesis of diabetic renal injury [47]. TGF-β stimulates matrix production and prevents matrix degradation, which leads to increase collagen deposition and glomerulosclerosis [48]. In the current study ABT702 significantly reduced renal collagen deposition and collagen excretion suggesting that adenosine kinase inhibition may halt the progression of renal injury by slowing the development of glomerulosclerosis in diabetic mice. Studies support a potential role of macrophages in diabetic renal injury as increased kidney macrophages infiltration correlates with the severity of renal injury in diabetes [49], [50]. Increasing evidence also indicates a role for various inflammatory molecules, including chemokines, adhesion molecules, and pro-inflammatory cytokines, in diabetic complications [50]. For example, MCP-1 is produced by mesangial and tubular epithelial ulixertinib to direct monocytes to the site of inflammation mediating renal interstitial inflammation, tubular atrophy and interstitial fibrosis [51], [52]. Increased MCP-1 excretion levels, which is known to reflect kidney MCP-1 production, correlates with the elevation in proteinuria in diabetes [52]. Activation of NFκB inflammatory signal is also known to exacerbate renal injury in diabetic animal models as phosphorylation of NFκB and its nuclear translocation activates down-stream inflammatory cytokines such as MCP-1 perturbing inflammatory cascade [12]. Elsherbiny et al. recently showed that ABT702 significantly reduced retinal inflammation and inhibited the elevation in ICAM-1 and TNF-α expression levels in the retina of streptozotocin-induced diabetic mice [25]. ABT702 also inhibited TNF-α release in vitro in the retinal microglia treated with Amadori-glycated albumin [25]. Consistent with these findings, the current study demonstrated that ABT702 reduced renal inflammation as evident by the reduction in renal macrophage infiltration, NFκB phosphorylation and MCP-1 excretion. Since hyperglycemia is known to increase inflammation via an MAPK/ERK-dependent signaling pathway [13], [53], inhibition of adenosine kinase could improve glomerular permeability and barrier function in cultured HGECs under normal and high glucose conditions via decreased inflammation. ABT702 reduced high glucose-induced elevation in FITC-dextran permeability and MAPK phosphorylation and improved glomerular occludin expression in vitro in HGECs. Thus, the ability of adenosine kinase inhibition to reduce macrophage infiltration and cytokines levels is likely a key element in the renal protection against diabetic insult. Collectively, these data suggest that ABT702-induced inhibition of adenosine kinase provides anti-inflammatory properties which could be a potential mechanism for alleviating diabetic-induced renal injury. Reactive oxygen species (ROS) are considered a causal link between elevated glucose levels and the development of diabetic renal injury [54], [55]. ABT702 inhibited oxidative and nitrosative stress in diabetic retina as it decreased superoxide and nitrotyrosine levels [25]. Treating diabetic mice with ABT702 also significantly reduced retinal neuronal cell death [25]. Accordingly, ABT702's anti-inflammatory effects could be attributed to its antioxidant properties. NAD(P)H oxidase is the main source of superoxide production in the vasculature and hyperglycemia is known to activate NAD(P)H oxidase generating reactive oxygen species which in turn increase lipid peroxidation and membrane damage [54], [55]. Consistent with these data, ABT702 treatment reduced the elevation in urinary TBARS excretion, a marker of lipid peroxidation, and renal NAD(P)H oxidase activity in diabetic mice highlighting the potential antioxidant ability of adenosine kinase inhibition as a reno-protective mechanism in diabetes. Increased superoxide production not only reduces NO availability but also scavenges NO, generating peroxynitrite which is known to induce deleterious effects on the vascular function and aggravate renal injury during diabetes [56], [57]. In the current study, ABT702 increased eNOS expression and nitrate/nitrite excretion in diabetic mice suggesting that inhibition of adenosine kinase could also improve vascular function via the reduction in NADPH-derived superoxide production as well as the improvement in NO availability alleviating the progression of renal injury in diabetic mice.