8-11-14-eicosatrienoic-acid and Diabetic-Nephropathies

Diabetic nephropathy (DN), a major complication of diabetes, is characterized by hypertrophy, extracellular matrix accumulation, fibrosis and proteinuria leading to loss of renal function. Hypertrophy is a major factor inducing proximal tubular epithelial cells injury. However, the mechanisms leading to tubular injury is not well defined. In our study, we show that exposure of rats proximal tubular epithelial cells to high glucose (HG) resulted in increased extracellular matrix accumulation and hypertrophy. HG treatment increased ROS production and was associated with alteration in CYPs 4A and 2C11 expression concomitant with alteration in 20-HETE and EETs formation. HG-induced tubular injury were blocked by HET0016, an inhibitor of CYPs 4A. In contrast, inhibition of EETs promoted the effects of HG on cultured proximal tubular cells. Our results also show that alteration in CYPs 4A and 2C expression and 20HETE and EETs formation regulates the activation of the mTOR/p70S6Kinase pathway, known to play a major role in the development of DN. In conclusion, we show that hyperglycemia in diabetes has a significant effect on the expression of Arachidonic Acid (AA)-metabolizing CYPs, manifested by increased AA metabolism, and might thus alter kidney function through alteration of type and amount of AA metabolites.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Blotting, Western; Cells, Cultured; Cytochrome P-450 CYP4A; Cytochrome P-450 Enzyme System; Diabetic Nephropathies; Glucose; Hydroxyeicosatetraenoic Acids; Hypertrophy; Kidney Tubules, Proximal; Oxidative Stress; Rats; Reactive Oxygen Species; Ribosomal Protein S6 Kinases, 70-kDa; TOR Serine-Threonine Kinases

Cytochrome P-450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play important roles in regulating cardiovascular functions. The anti-inflammatory, antiapoptotic, proangiogenic, and antihypertensive properties of EETs suggest a beneficial role for EETs in diabetic nephropathy. Endogenous EET levels are maintained by a balance between synthesis by CYP epoxygenases and hydrolysis by epoxide hydrolases into physiologically less active dihydroxyeicosatrienoic acids. Genetic disruption of soluble epoxide hydrolase (sEH/EPHX2) results in increased EET levels through decreased hydrolysis. This study investigated the effects of sEH gene disruption on diabetic nephropathy in streptozotocin-induced diabetic mice. Streptozotocin-induced diabetic manifestations were attenuated in sEH-deficient mice relative to wild-type controls, with significantly decreased levels of Hb A(1c), creatinine, and blood urea nitrogen and urinary microalbumin excretion. The sEH-deficient diabetic mice also had decreased renal tubular apoptosis that coincided with increased levels of antiapoptotic Bcl-2 and Bcl-xl, and decreased levels of the proapoptotic Bax. These effects were associated with activation of the PI3K-Akt-NOS3 and AMPK signaling cascades. sEH gene inhibition and exogenous EETs significantly protected HK-2 cells from TNFα-induced apoptosis in vitro. These findings highlight the beneficial role of the CYP epoxygenase-EETs-sEH system in the pathogenesis of diabetic nephropathy and suggest that the sEH inhibitors available may be potential therapeutic agents for this condition.

Topics: 8,11,14-Eicosatrienoic Acid; Albuminuria; Animals; Apoptosis; Apoptosis Regulatory Proteins; Cell Line, Transformed; Cytoplasm; Diabetic Nephropathies; Disease Models, Animal; Epoxide Hydrolases; Gene Silencing; Humans; Hyperglycemia; Kidney Cortex; Kidney Tubules, Proximal; Mice; Molecular Targeted Therapy; RNA, Small Interfering; Signal Transduction; Streptozocin; Tumor Necrosis Factor-alpha

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid into epoxyeicosatrienoic acids (EETs), which play important and diverse roles in the cardiovascular system. The anti-inflammatory, anti-apoptotic, pro-angiogenic, and anti-hypertensive properties of EETs in the cardiovascular system suggest a beneficial role for EETs in diabetic nephropathy. This study investigated the effects of endothelial specific overexpression of CYP2J2 epoxygenase on diabetic nephropathy in streptozotocin-induced diabetic mice. Endothelial CYP2J2 overexpression attenuated renal damage as measured by urinary microalbumin and glomerulosclerosis. These effects were associated with inhibition of TGF-β/Smad signaling in the kidney. Indeed, overexpression of CYP2J2 prevented TGF-β1-induced renal tubular epithelial-mesenchymal transition in vitro. These findings highlight the beneficial roles of the CYP epoxygenase-EET system in the pathogenesis of diabetic nephropathy.

Topics: 8,11,14-Eicosatrienoic Acid; Animals; Arachidonic Acid; Cell Line; Cytochrome P-450 CYP2J2; Cytochrome P-450 Enzyme System; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Epithelial-Mesenchymal Transition; Gene Expression; Kidney; Kidney Function Tests; Mice; Mice, Transgenic; Signal Transduction; Smad Proteins; Streptozocin; Transforming Growth Factor beta1

The early stage of diabetic nephropathy (DN) is linked to proteinuria. Transforming growth factor (TGF)-beta1 increases glomerular permeability to albumin (P(alb)), whereas 20-HETE and EETs reduce P(alb). To investigate the impact of hyperglycemia and hyperlipidemia on 20-HETE, EETs, and TGF-beta1 in the glomeruli, rats were divided into four groups: ND rats were fed a normal diet, HF rats were fed a high-fat diet, STZ rats were treated with 35 mg/kg of streptozotocin, and HF/STZ rats were fed a HF diet and treated with STZ. After 10 wk on these regimens, blood glucose, urinary albumin, serum cholesterol, serum triglyceride levels, and the kidney-to-body weight ratio were significantly elevated in STZ and HF/STZ rats compared with HF and ND rats. STZ and HF/STZ rats had histopathologic changes and abnormal renal hemodynamics. Expression of glomerular CYP4A, enzymes for 20-HETE production, was significantly decreased in STZ rats, whereas expression of glomerular CYP2C and CYP2J, enzymes for EETs production, was significantly decreased in both STZ and HF/STZ rats. Moreover, glomerular TGF-beta1 levels were significantly greater in STZ and HF/STZ rats than in HF and ND rats. Five-week treatment of STZ rats with clofibrate induced glomerular CYP4A expression and 20-HETE production, but reduced glomerular TGF-beta1 and urinary protein excretion. These results demonstrate that hyperglycemia increases TGF-beta1 but decreases 20-HETE and EETs production in the glomeruli, changes that may be important in causing glomerular damage in the early stage of DN.

Topics: 8,11,14-Eicosatrienoic Acid; Amino Acids; Animals; Clofibrate; Cytochrome P-450 CYP4A; Diabetes Mellitus, Experimental; Diabetic Nephropathies; Epoxide Hydrolases; Epoxy Compounds; Hydroxyeicosatetraenoic Acids; Hyperglycemia; Hyperlipidemias; Kidney; Kidney Glomerulus; Male; Polymerase Chain Reaction; Protein Isoforms; Proteinuria; Rats; Rats, Sprague-Dawley; Renal Circulation; Streptozocin; Transforming Growth Factor beta1