Soluble epoxide hydrolase gene deletion attenuates renal injury and inflammation with DOCA-salt hypertension

Inhibition of soluble epoxide hydrolase (sEH) has been shown to be renal protective in rat models of salt-sensitive hypertension. Here, we hypothesize that targeted disruption of the sEH gene (Ephx2) prevents both renal inflammation and injury in deoxycorticosterone acetate plus high salt (DOCA-salt) hypertensive mice. Mean arterial blood pressure (MAP) increased significantly in the DOCA-salt groups, and MAP was lower in Ephx2-/- DOCA-salt (129 +/- 3 mmHg) compared with wild-type (WT) DOCA-salt (145 +/- 2 mmHg) mice. Following 21 days of treatment, WT DOCA-salt urinary MCP-1 excretion increased from control and was attenuated in the Ephx2-/- DOCA-salt group. Macrophage infiltration was reduced in Ephx2-/- DOCA-salt compared with WT DOCA-salt mice. Albuminuria increased in WT DOCA-salt (278 +/- 55 microg/day) compared with control (17 +/- 1 microg/day) and was blunted in the Ephx2-/- DOCA-salt mice (97 +/- 23 microg/day). Glomerular nephrin expression demonstrated an inverse relationship with albuminuria. Nephrin immunofluorescence was greater in the Ephx2-/- DOCA-salt group (3.4 +/- 0.3 RFU) compared with WT DOCA-salt group (1.1 +/- 0.07 RFU). Reduction in renal inflammation and injury was also seen in WT DOCA-salt mice treated with a sEH inhibitor {trans-4-[4-(3-adamantan-1-yl-ureido)-cyclohexyloxy]-benzoic acid; tAUCB}, demonstrating that the C-terminal hydrolase domain of the sEH enzyme is responsible for renal protection with DOCA-salt hypertension. These data demonstrate that Ephx2 gene deletion decreases blood pressure, attenuates renal inflammation, and ameliorates glomerular injury in DOCA-salt hypertension.

Soluble epoxide inhibition is protective against cerebral ischemia via vascular and neural protection

Inhibition of soluble epoxide hydrolase (SEH), the enzyme responsible for degradation of vasoactive epoxides, protects against cerebral ischemia in rats. However, the molecular and biological mechanisms that confer protection in normotension and hypertension remain unclear. Here we show that 6 weeks of SEH inhibition via 2 mg/day of 12-(3-adamantan-1-yl-ureido) dodecanoic acid (AUDA) in spontaneously hypertensive stroke-prone (SHRSP) rats protects against cerebral ischemia induced by middle cerebral artery occlusion, reducing percent hemispheric infarct and neurodeficit score without decreasing blood pressure. This level of cerebral protection was similar to that of the angiotensin-converting enzyme inhibitor, enalapril, which significantly lowered blood pressure. SEH inhibition is also protective in normotensive Wistar-Kyoto (WKY) rats, reducing both hemispheric infarct and neurodeficit score. In SHRSP rats, SEH inhibition reduced wall-to-lumen ratio and collagen deposition and increased cerebral microvessel density, although AUDA did not alter middle cerebral artery structure or microvessel density in WKY rats. An apoptosis mRNA expression microarray of brain tissues from AUDA-treated rats revealed that AUDA modulates gene expression of mediators involved in the regulation of apoptosis in neural tissues of both WKY and SHRSP rats. Hence, we conclude that chronic SEH inhibition protects against cerebral ischemia via vascular protection in SHRSP rats and neural protection in both the SHRSP and WKY rats, indicating that SEH inhibition has broad pharmacological potential for treating ischemic stroke.

Secreted protein acidic and rich in cysteine deficiency ameliorates renal inflammation and fibrosis in angiotensin hypertension

The matricellular protein secreted protein acidic and rich in cysteine (SPARC) modulates cell adhesion, proliferation, matrix deposition, and tissue remodeling. SPARC has been shown to regulate the expression of collagen type I and transforming growth factor-beta1 in mesangial cells and to be highly expressed during tubulointerstitial fibrosis in rat angiotensin (ANG) II infusion models. We hypothesized that SPARC is a downstream effector of ANG II and that loss of host SPARC function provides a protective effect on renal damage and fibrosis associated with ANG II hypertension. Our results revealed that cultured primary mesangial cells displayed a concentration-dependent increase in SPARC expression in response to ANG II. After a 14-day chronic infusion of ANG II, hypertensive SPARC-null mice exhibited significantly attenuated levels of urinary and renal indicators of oxidative stress and inflammation and decreased renal perivascular and tubulointerstitial fibrosis relative to wild-type hypertensive controls. Moreover, the observed renal protective changes in SPARC-null mice were found to be independent of blood pressure. These results identify SPARC as an effector of ANG II signaling and suggest an important role for SPARC in mediating ANG II-induced oxidative stress, inflammation, and fibrosis.

Angiotensin II hypertension is attenuated in interleukin-6 knockout mice

Plasma levels of IL-6 correlate with high blood pressure under many circumstances, and ANG II has been shown to stimulate IL-6 production from various cell types. This study tested the role of IL-6 in mediating the hypertension caused by high-dose ANG II and a high-salt diet. Male C57BL6 and IL-6 knockout (IL-6 KO) mice were implanted with biotelemetry devices and placed in metabolic cages to measure mean arterial pressure (MAP), heart rate (HR), sodium balance, and urinary albumin excretion. Baseline MAP during the control period averaged 114 +/- 1 and 109 +/- 1 mmHg for wild-type (WT) and IL-6 KO mice, respectively, and did not change significantly when the mice were placed on a high-salt diet (HS; 4% NaCl). ANG II (90 ng/min sc) caused a rapid increase in MAP in both groups, to 141 +/- 9 and 141 +/- 4 in WT and KO mice, respectively, on day 2. MAP plateaued at this level in KO mice (134 +/- 2 mmHg on day 14 of ANG II) but began to increase further in WT mice by day 4, reaching an average of 160 +/- 4 mmHg from days 10 to 14 of ANG II. Urinary albumin excretion on day 4 of ANG II was not different between groups (9.18 +/- 4.34 and 8.53 +/- 2.85 microg/2 days for WT and KO mice). By day 14, albumin excretion was nearly fourfold greater in WT mice, but MAP dropped rapidly back to control levels in both groups when the ANG II was stopped after 14 days. Thus the approximately 30 mmHg greater ANG II hypertension in the WT mice suggests that IL-6 contributes significantly to ANG II-salt hypertension. In addition, the early separation in MAP, the albumin excretion data, and the rapid, post-ANG II recovery of MAP suggest an IL-6-dependent mechanism that is independent of renal injury.

Bremazocine increases C-type natriuretic peptide levels in aqueous humor and enhances outflow facility

A relatively selective agonist of kappa opioid receptors (KOR), bremazocine (BRE), lowers intraocular pressure in rabbits, in part, by increasing natriuretic peptide levels in aqueous humor and by enhancing total outflow facility (TOF). Natriuretic peptide (NP) levels [atrial NP (ANP), brain NP (BNP), and C-type NP (CNP)] were measured in aqueous humor of rabbits either by radioimmunoassay or enzyme immunoassay. TOF was determined in rabbits by two-level constant pressure perfusion of the anterior chamber. Experimental regimens included topical treatment with BRE in the presence or absence of KOR antagonist (norbinaltorphimine), protein kinase C inhibitor (chelerythrine), and natriuretic peptide receptor antagonist (isatin). The rank order of basal NP levels in aqueous humor of rabbits was BNP CNP > ANP. Topical administration of BRE (1-100 microg) caused dose-related elevations of CNP levels in aqueous humor that were inhibited by topical pretreatment with either norbinaltorphimine (100 microg, bilaterally) or chelerythrine (10 microg, bilaterally). Topically administered BRE (100 microg) also elevated levels of ANP and BNP in aqueous humor and evoked an 80% increase in TOF. The increase in TOF was antagonized by topical pretreatment with either norbinaltorphimine (100 microg, bilaterally) or isatin (100 microg, bilaterally). Bremazocine induced an increase in NP (ANP, BNP, and CNP) levels and TOF in rabbits by activating KOR. The increase in CNP levels elicited by BRE was inhibited by norbinaltorphimine and chelerythrine; therefore, this event is most likely mediated by a KOR-linked activation of protein kinase C. These data provide evidence that the increase in TOF elicited by BRE was mediated by a KOR-activated paracrine effect of NPs on tissues within ocular outflow tract(s).