We previously showed that inhibition of soluble epoxide hydrolase (sEH) increased epoxyeicosatrienoic acids (EETs) levels and reduced renal injury in diabetic mice and these changes were associated with induction of hemeoxygenase-1 (HO-1). The present study determines whether the inhibition of HO negates the reno-protective effect of sEH inhibition in diabetic spontaneously hypertensive rats as a model of diabetic nephropathy in which hypertension coexists with diabetes. After six weeks of induction of diabetes with streptozotocin, SHR were divided into the following groups: untreated, treated with the sEH inhibitor,
trans
-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid (AUCB), treated with the HO inhibitor, stannous mesoporphyrin (SnMP), and treated with both inhibitors for four more weeks; non diabetic SHR served as a control group. Although inhibition of sEH increased renal EETs/DHETEs ratio and HO-1 activity in diabetic SHR, it did not significantly alter blood pressure (plasma EETs/DHETEs ratio was 0.5± 0.1 in AUCB-treated
vs.
0.1± 0.01 in untreated diabetic SHR, P<0.05). Treatment of diabetic SHR with AUCB reduced the elevation in urinary albumin and nephrin excretion (albuminuria was 6.5± 0.5 in AUCB-treated diabetic SHR vs. 9± 1.7 mg/day in untreated diabetic SHR and nephrinuria was 70±11 in AUCB-treated diabetic SHR vs. 111± 9 μg/day in untreated diabetic SHR, P<0.05) whereas co-administration of SnMP with AUCB prevented these changes (albuminuria was 10.6± 0.6 mg/day and nephrinuria was 91±11 μg/day). Immunohistochemical analysis revealed elevations in renal fibrosis and apoptosis as evidenced by increased renal TGF-β, fibronectin and annexin V expression in diabetic SHR and these changes were reduced with sEH inhibition. Co-administration of SnMP with AUCB prevented its ability to reduce renal fibrosis and apoptosis in diabetic SHR. In addition, SnMP treatment also prevented AUCB-induced decreases in renal macrophage infiltration and renal TGF-β, NFκB and MCP-1 levels in diabetic SHR. These data suggest that HO-1 induction is involved in the protective effect of sEH inhibition against diabetic renal injury.
Angiotensin Type 2 Receptor Agonist Compound 21 Reduces Vascular Injury and Myocardial Fibrosis in Stroke-Prone Spontaneously Hypertensive Rats
