Adenosine receptors as emerging therapeutic targets for diabetic kidney disease.

Diabetic kidney disease (DKD) is now a pandemic worldwide, and novel therapeutic options are urgently required. Adenosine, an adenosine triphosphate metabolite, plays a role in kidney homeostasis through interacting with four types of adenosine receptors (ARs): A1AR, A2AAR, A2BAR, and A3AR. Increasing evidence highlights the role of adenosine and ARs in the development and progression of DKD: 1) increased adenosine in the plasma and urine of diabetics with kidney injury, 2) increased expression of each of the ARs in diabetic kidneys, 3) the protective effect of coffee, a commonly ingested nonselective AR antagonist, on DKD, and 4) the protective effect of AR modulators in experimental DKD models. We propose AR modulators as a new therapeutic option to treat DKD. Detailed mechanistic studies on the pharmacology of AR modulators will help us to develop effective first-in-class AR modulators against DKD.

Impact of acute kidney injury on long-term adverse outcomes in obstructive uropathy.

Obstructive uropathy is known to be associated with acute kidney injury (AKI). This study aimed to investigate the etiologies, clinical characteristics, consequences and also assess the impact of AKI on long-term outcomes. This multicenter, retrospective study of 1683 patients with obstructive uropathy who underwent percutaneous nephrostomy (PCN) analyzed clinical characteristics, outcomes including progression to end-stage kidney disease (ESKD), overall mortality, and the impact of AKI on long-term outcomes. Obstructive uropathy in adults was most commonly caused by malignancy, urolithiasis, and other causes. AKI was present in 78% of the patients and was independently associated with preexisting chronic kidney disease (CKD). Short-term recovery was achieved in 56.78% after the relief of obstruction. ESKD progression rate was 4.4% in urolithiasis and 6.8% in other causes and older age, preexisting CKD, and stage 3 AKI were independent factors of progression. The mortality rate (34%) was highly attributed to malignant obstruction (52%) stage 3 AKI was also an independent predictor of mortality in non-malignant obstruction. AKI is a frequent complication of adult obstructive uropathy. AKI negatively affects long-term kidney outcomes and survival in non-malignant obstructions. A better understanding of the epidemiology and prognostic factors is needed for adult obstructive uropathy.

LPS-Induced Acute Kidney Injury Is Mediated by Nox4-SH3YL1.

Cytosolic proteins are required for regulation of NADPH (nicotinamide adenine dinucleotide phosphate) oxidase (Nox) isozymes. Here we show that Src homology 3 (SH3) domain-containing YSC84-like 1 (SH3YL1), as a Nox4 cytosolic regulator, mediates lipopolysaccharide (LPS)-induced H2O2 generation, leading to acute kidney injury. The SH3YL1, Ysc84p/Lsb4p, Lsb3p, and plant FYVE proteins (SYLF) region and SH3 domain of SH3YL1 contribute to formation of a complex with Nox4-p22phox. Interaction of p22phox with SH3YL1 is triggered by LPS, and the complex induces H2O2 generation and pro-inflammatory cytokine expression in mouse tubular epithelial cells. After LPS injection, SH3YL1 knockout mice show lower levels of acute kidney injury biomarkers, decreased secretion of pro-inflammatory cytokines, decreased infiltration of macrophages, and reduced tubular damage compared with wild-type (WT) mice. The results strongly suggest that SH3YL1 is involved in renal failure in LPS-induced acute kidney injury (AKI) mice. We demonstrate that formation of a ternary complex of p22phox-SH3YL1-Nox4, leading to H2O2 generation, induces severe renal failure in the LPS-induced AKI model.

Renoprotective Effects of a Highly Selective A3 Adenosine Receptor Antagonist in a Mouse Model of Adriamycin-induced Nephropathy.

The concentration of adenosine in the normal kidney increases markedly during renal hypoxia, ischemia, and inflammation. A recent study reported that an A3 adenosine receptor (A3AR) antagonist attenuated the progression of renal fibrosis. The adriamycin (ADX)-induced nephropathy model induces podocyte injury, which results in severe proteinuria and progressive glomerulosclerosis. In this study, we investigated the preventive effect of a highly selective A3AR antagonist (LJ1888) in ADX-induced nephropathy. Three groups of six-week-old Balb/c mice were treated with ADX (11 mg/kg) for four weeks and LJ1888 (10 mg/kg) for two weeks as following: 1) control; 2) ADX; and 3) ADX + LJ1888. ADX treatment decreased body weight without a change in water and food intake, but this was ameliorated by LJ1888 treatment. Interestingly, LJ1888 lowered plasma creatinine level, proteinuria, and albuminuria, which had increased during ADX treatment. Furthermore, LJ1888 inhibited urinary nephrin excretion as a podocyte injury marker, and urine 8-isoprostane and kidney lipid peroxide concentration, which are markers of oxidative stress, increased after injection of ADX. ADX also induced the activation of proinflammatory and profibrotic molecules such as TGF-ß1, MCP-1, PAI-1, type IV collagen, NF-κB, NOX4, TLR4, TNFα, IL-1ß, and IFN-γ, but they were remarkably suppressed after LJ1888 treatment. In conclusion, our results suggest that LJ1888 has a renoprotective effect in ADX-induced nephropathy, which might be associated with podocyte injury through oxidative stress. Therefore, LJ1888, a selective A3AR antagonist, could be considered as a potential therapeutic agent in renal glomerular diseases which include podocyte injury and proteinuria.

DA-1229, a dipeptidyl peptidase IV inhibitor, protects against renal injury by preventing podocyte damage in an animal model of progressive renal injury.

Although dipeptidyl peptidase IV (DPPIV) inhibitors are known to have renoprotective effects, the mechanism underlying these effects has remained elusive. Here we investigated the effects of DA-1229, a novel DPPIV inhibitor, in two animal models of renal injury including db/db mice and the adriamycin nephropathy rodent model of chronic renal disease characterized by podocyte injury. For both models, DA-1229 was administered at 300 mg/kg/day. DPPIV activity in the kidney was significantly higher in diabetic mice compared with their nondiabetic controls. Although DA-1229 did not affect glycemic control or insulin resistance, DA-1229 did improve lipid profiles, albuminuria and renal fibrosis. Moreover, DA-1229 treatment resulted in decreased urinary excretion of nephrin, decreased circulating and kidney DPPIV activity, and decreased macrophage infiltration in the kidney. In adriamycin-treated mice, DPPIV activity in the kidney and urinary nephrin loss were both increased, whereas glucagon-like peptide-1 concentrations were unchanged. Moreover, DA-1229 treatment significantly improved proteinuria, renal fibrosis and inflammation associated with decreased urinary nephrin loss, and kidney DPP4 activity. In cultured podocytes, DA-1229 restored the high glucose/angiotensin II-induced increase of DPPIV activity and preserved the nephrin levels in podocytes. These findings suggest that activation of DPPIV in the kidney has a role in the progression of renal disease, and that DA-1229 may exert its renoprotective effects by preventing podocyte injury.

Effects of Toll-like receptor antagonist 4,5-dihydro-3-phenyl-5-isoxasole acetic acid on the progression of kidney disease in mice on a high-fat diet.

BACKGROUND: Obesity-related metabolic disorders are closely associated with inflammation induced by innate immunity. Toll-like receptors (TLRs) play a pivotal role in the innate immune system by activating proinflammatory signaling pathways. GIT27 (4,5-dihydro-3-phenyl-5-isoxasole acetic acid) is an active immunomodulatory agent that primarily targets macrophages and inhibits secretion of tumor necrosis factor α [as well as interleukin (IL)-1ß, IL-10, and interferon γ]. However, the effect of TLR antagonist on kidney diseases has rarely been reported. We investigated whether the TLR antagonist GIT27 has beneficial effects on the progression of kidney disease in obese mice on a high-fat diet (HFD). METHODS: Six-week-old male C57BL/6 mice were divided into three groups: mice fed with normal chow diet (N=4); mice fed with a HFD (60% of total calories from fat, 5.5% from soybean oil, and 54.5% from lard, N=4); and GIT27-treated mice fed with a HFD (N=7). RESULTS: Glucose intolerance, oxidative stress, and lipid abnormalities in HFD mice were improved by GIT27 treatment. In addition, GIT27 treatment decreased the urinary excretion of albumin and protein in obesity-related kidney disease, urinary oxidative stress markers, and inflammatory cytokine levels. This treatment inhibited the expression of proinflammatory cytokines in the kidneys and adipose tissue, and improved extracellular matrix expansion and tubulointerstitial fibrosis in obesity-related kidney disease. CONCLUSION: TLR inhibition by administering GIT27 improved metabolic parameters. GIT27 ameliorates abnormalities of lipid metabolism and may have renoprotective effects on obesity-related kidney disease through its anti-inflammatory properties.

Sulodexide improves renal function through reduction of vascular endothelial growth factor in type 2 diabetic rats.

AIMS: Sulodexide is a promising therapeutic drug for the management of diabetic nephropathy. Although sulodexide has demonstrated a renoprotective effect through its ability to restore glomerular ionic permselectivity, the exact mechanism is still not clear. We investigated the effects of long-term sulodexide treatment on diabetic nephropathy in Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats. MAIN METHODS: Diabetic rats were treated with or without sulodexide at 10mg/kg/day in the drinking water for nine months. Renal morphology and changes in VEGF and p38 mitogen-activated protein kinase (p38 MAPK), urinary levels of albumin (UAE) and urinary VEGF excretion were determined. To define the direct effects of sulodexide, we performed an in vitro experiment using podocytes. KEY FINDINGS: UAE was significantly higher in OLETF rats than in control LETO rats, and the sulodexide group showed significantly decreased UAE after six months of treatment. Interestingly, urinary VEGF levels were also significantly decreased in the sulodexide-treated group. In accordance with UAE and urinary VEGF changes, the renal expression of profibrotic molecules was significantly decreased after sulodexide treatment. In addition, the activation of p38 MAPK, assessed by measuring the level of phospho-specific p38 MAPK, increased in diabetic renal tissues and was markedly suppressed by sulodexide treatment. In cultured podocytes, sulodexide treatment significantly decreased high glucose-induced p38 MAPK activation and VEGF synthesis. SIGNIFICANCE: Sulodexide directly suppresses VEGF synthesis through the p38 MAPK pathway in podocytes, and these results suggest that sulodexide may provide renoprotection via suppression of renal VEGF synthesis independently of glomerular basement membrane ionic permselectivity in type 2 diabetic rats.

Glucocorticoids attenuate septic acute kidney injury.

BACKGROUND: The incidence and mortality of septic acute kidney injury (AKI) remains high, whereas our understanding of pathogenesis for septic AKI is still limited. Glucocorticoids (GCs) have been clinically recommended for treatment of septic shock and also have showed favorable effect on septic AKI in several animal experiments. The aim of this study is to investigate the pathophysiology of septic AKI and the effect of GCs on septic AKI. METHODS: We induced septic AKI using cecal ligation and puncture (CLP) model in 8-10 wk-old male C57BL/6 mice. Saline or dexamethasone (2.5 mg/kg) dissolved in saline was administered after surgery. Hemodynamic, biochemical and histological changes were examined in a time-course manner. RESULTS: CLP resulted in hyperdynamic warm shock with multiple organ dysfunction including AKI. Despite renal dysfunction, light microscopy showed scanty acute tubular necrosis and inflammation. Instead, CLP induced significant increase in apoptosis of the kidney and spleen cells. In addition, septic kidneys showed mitochondrial injury and alterations in Bcl2 family proteins in the renal tubular cells. Dexamethasone treatment attenuated renal dysfunction, but it was not associated with improvement of hemodynamic parameters. Dexamethasone-induced organ protective effect was associated with reduced mitochondrial injury with preserved cytochrome c oxidase and suppression of proapoptotic proteins as well as reduced cytokine release. CONCLUSIONS: Mitochondrial damage and subsequent apoptosis are thought to play important role in the development of septic AKI. GCs might be a useful therapeutic strategy for septic AKI by reducing mitochondrial damage and apoptosis.

Adipose-derived stem cells improve renal function in a mouse model of IgA nephropathy.

T-cell dysregulation plays an important role in the pathogenesis of immunoglobulin A nephropathy (IgAN). Adipose-derived stem cells (ASCs) have been reported to be able to prevent tissue damage through immune-modulating effects. To evaluate the effects of ASCs in high IgA ddY (HIGA) mice, ASCs were isolated from HIGA mice with different stages of IgAN before and after disease onset. ASCs were injected at a dose of 5×10(6) cells/kg body weight through the tail vein every 2 weeks for 3 months. Although the administered ASCs were rarely detected in the glomeruli, 24-h proteinuria was markedly decreased in all ASC-treated groups. Although glomerular deposition of IgA was not significantly different among groups, mesangial proliferation and glomerulosclerosis were dramatically decreased in most ASC treatment groups. In addition, levels of fibrotic and inflammatory molecules were markedly decreased by ASC treatment. Interestingly, ASC therapy significantly decreased Th1 cytokine activity in the kidney and caused a shift to Th2 responses in spleen T-cells as determined by FACS analysis. Furthermore, conditioned media from ASCs abrogated aggregated IgA-induced Th1 cytokine production in cultured HIGA mesangial cells. These results suggest that the beneficial effects of ASC treatment in IgAN occur via paracrine mechanisms that modulate the Th1/Th2 cytokine balance. ASCs are therefore a promising new therapeutic agent for the treatment of IgAN.

Aliskiren improves insulin resistance and ameliorates diabetic vascular complications in db/db mice.

BACKGROUND: Aliskiren is a direct renin inhibitor (DRI) and provides an organ-protective effect in human and animal experiments. However, there is no current evidence of the effect of DRI on insulin resistance and metabolic abnormalities in type 2 diabetic animals. Methods. We investigated the effects and molecular mechanism of aliskiren in db/db mice and cultured mesangial cells (MCs). RESULTS: Aliskiren treatment for 3 months at a dose of 25 mg/kg/day via an osmotic mini-pump did not induce significant changes in blood glucose levels, systolic blood pressure, serum creatinine and electrolyte levels. However, aliskiren treatment improved insulin resistance confirmed by insulin tolerance test and various biomarkers including homeostasis model assessment index levels and lipid abnormalities. The treated group also exhibited significant improvement in cardiac functional and morphological abnormalities including left ventricular hypertrophy, and induced phenotypic changes in adipose tissue. Aliskiren treatment also markedly decreased urinary albumin excretion, glomerulosclerosis and suppressed profibrotic and proinflammatory cytokine synthesis and improved renal lipid metabolism. In cultured MCs, high glucose stimulation increased MC renin concentration. Furthermore, renin treatment directly up-regulates synthesis of proinflammatory and profibrotic cytokines, which were abolished by prior treatment with aliskiren and angiotensin receptor (AT1) antagonist. These results suggest that the beneficial effect of aliskiren is mediated by an angiotensin-dependent mechanism. CONCLUSIONS: Together, these results imply that aliskiren provides an organ-protective effect through improvement in insulin resistance and lipid abnormality, as well as direct anti-fibrotic effect in target organ in db/db mice. Aliskiren may be a useful new therapeutic agent in the treatment of type 2 diabetes mellitus and diabetic nephropathy.