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Genome-wide association studies have found a number of potential genes involved in blood pressure regulation; however, the functional role of many of these candidates has yet to be established. One such candidate gene is CLCN6, which encodes the transmembrane protein, chloride channel 6 (ClC-6). Although the CLCN6 locus has been widely associated with human blood pressure regulation, the mechanistic role of ClC-6 in blood pressure homeostasis at the molecular, cellular, and physiological levels is completely unknown. In this study, we demonstrate that rats with a functional knockout of ClC-6 on the Dahl Salt-Sensitive rat background (SS-Clcn6) have lower diastolic but not systolic blood pressures. The effect of diastolic blood pressure attenuation was independent of dietary salt exposure in knockout animals. Moreover, SS-Clcn6 rats are protected from hypertension-induced cardiac hypertrophy and arterial stiffening; however, they have impaired vasodilation and dysregulated intracellular calcium handling. ClC-6 is highly expressed in vascular smooth muscle cells where it is targeted to the Golgi apparatus. Using bilayer electrophysiology, we provide evidence that recombinant human ClC-6 protein can function as a channel. Last, we demonstrate that loss of ClC-6 function reduces Golgi calcium stores, which may play a previously unidentified role in vascular contraction and relaxation signaling in vascular smooth muscle cells. Collectively, these data indicate that ClC-6 may modulate blood pressure by regulating Golgi calcium reserves, which in turn contribute to vascular smooth muscle function. [ABSTRACT FROM AUTHOR]

Epoxyeicosatrienoic acids (EETs) are epoxy fatty acids that have biological actions that are essential for maintaining water and electrolyte homeostasis. An inability to increase EETs in response to a high-salt diet results in salt-sensitive hypertension. Vasodilation, inhibition of epithelial sodium channel, and inhibition of inflammation are the major EET actions that are beneficial to the heart, resistance arteries, and kidneys. Genetic and pharmacological means to elevate EETs demonstrated antihypertensive, anti-inflammatory, and organ protective actions. Therapeutic approaches to increase EETs were then developed for cardiovascular diseases. sEH (soluble epoxide hydrolase) inhibitors were developed and progressed to clinical trials for hypertension, diabetes mellitus, and other diseases. EET analogs were another therapeutic approach taken and these drugs are entering the early phases of clinical development. Even with the promise for these therapeutic approaches, there are still several challenges, unexplored areas, and opportunities for epoxy fatty acids. [ABSTRACT FROM AUTHOR]

The article offers information on epoxyeicosatrienoic acids (EETs) based drugs to treat hypertension and kidney disease. Topics discussed include generation of EETs from the substrate arachidonic acid by cytochrome P450 (CYP) epoxygenase enzymes, the role of EETs in vascular endothelial function, and the antihypertensive and kidney protective abilities of the EET and Soluble epoxide hydrolase (sEH) enzyme-based drugs.

Salt-sensitive hypertension leads to kidney injury. The Dahl salt-sensitive hypertensive rat (Dahl SS) is a model of salt-sensitive hypertension and progressive kidney injury. The current set of experimental studies evaluated the kidney protective potential of a novel epoxyeicosatrienoic acid analog (EET-B) in Dahl SS hypertension. Dahl SS rats receiving high-salt diet were treated with EET-B (10 mg/kg per day) or vehicle in drinking water for 14 days. Urine, plasma, and tissue samples were collected at the end of the treatment protocol to assess kidney injury, oxidative stress, inflammation, and endoplasmic reticulum stress. EET-B treatment in Dahl SS rats markedly reduced urinary albumin and nephrin excretion by 60% to 75% along with 30% to 60% reductions in glomerular injury, intratubular cast formation, and kidney fibrosis without affecting blood pressure. In Dahl SS rats, EET-B treatment further caused marked reduction in oxidative stress with 25% to 30% decrease in kidney malondialdehyde content along with 42% increase of nitrate/nitrite and a 40% reduction of 8-isoprostane. EET-B treatment reduced urinary monocyte chemoattractant protein-1 by 50% along with a 40% reduction in macrophage infiltration in the kidney. Treatment with EET-B markedly reduced renal endoplasmic reticulum stress in Dahl SS rats with reduction in the kidney mRNA expressions and immunoreactivity of glucose regulatory protein 78 and C/EBP homologous protein. In summary, these experimental findings reveal that EET-B provides kidney protection in Dahl SS rats by reducing oxidative stress, inflammation, and endoplasmic reticulum stress, and this protection was independent of reducing blood pressure. [ABSTRACT FROM AUTHOR]

Obesity and hypertension have been identified as cardiovascular risk factors that contribute to the progression of end-stage renal disease. To examine the mechanisms by which a high-fat diet and hypertension contribute to endothelial dysfunction and renal injury, 8-week-old male spontaneously hypertensive rats and Wistar rats were fed a high-fat (36% fat) or a normal-fat (7% fat) diet for 10 weeks. The high-fat diet increased body weight in Wistar and hypertensive rats by 25 and 31 g, respectively. Systolic blood pressure was higher in the hypertensive rats compared with Wistar rats; however, blood pressure was unaltered by the high-fat diet. Afferent arteriole response to acetylcholine was impaired in the high-fat groups after just 3 weeks. Renal macrophage infiltration was increased in the hypertensive high-fat group compared with others, and monocyte chemoattractant protein-1 excretion was increased in both of the high-fat-fed groups. Renal PCR arrays displayed significant increases in 2 inflammatory genes in hypertensive rats fed a normal diet, 1 gene was increased in high-fat-fed Wistar rats, whereas 12 genes were increased in high-fat-fed hypertensive rats. Urinary albumin excretion was increased in the hypertensive rats compared with the Wistar rats, which was further exacerbated by the high-fat diet. Glomerular nephrin expression was reduced and desmin was increased by the high-fat diet in the hypertensive rats. Our results indicate that endothelial dysfunction precedes renal injury in normotensive and spontaneously hypertensive rats fed a high-fat diet, and hypertension with obesity induces a powerful inflammatory response and disruption of the renal filtration barrier. [ABSTRACT FROM AUTHOR]

The present study was designed to determine whether chemokine receptor 2b (CCR2b) contributes to the development of renal injury in salt-sensitive angiotensin II (ANG) hypertension. Rats were infused with ANG and fed a high-salt diet (HS) for 14 days. Rats were divided into 4 groups: HS; HS administered the CCR2b antagonist, RS102895; Ang/HS hypertensive; and Ang/HS hypertensive administered RS102895. CCR2b inhibition slowed the progression of blood pressure elevation during the first week of ANG/HS hypertension; however, it did not alter blood pressure in the HS group. At 2 weeks, arterial pressure was not significantly different between ANG/HS and ANG/HS hypertensive rats administered RS102895. Renal cortical nuclear factor kappaB activity increased in ANG/HS hypertension compared with the HS group (0.11+/-0.006 versus 0.08+/-0.003 ng of activated nuclear factor kappaB per microgram of protein), and RS102895 treatment lowered nuclear factor kappaB activity in ANG/HS hypertension (0.08+/-0.005 ng of activated nuclear factor kappaB per microgram of protein). Renal tumor necrosis factor-alpha and intercellular adhesion molecule-1 expression increased, and Cyp2c23 expression decreased in ANG/HS hypertension compared with the HS group, and CCR2b inhibition reduced tumor necrosis factor-alpha and intercellular adhesion molecule-1 and increased Cyp2c23 expression. Histological immunostaining revealed increased renal monocyte and macrophage infiltration in ANG/HS hypertensive rats with decreased infiltration in rats receiving RS102895 treatment. Albuminuria and cortical collagen staining also increased in ANG/HS hypertensive rats, and RS102895 treatment lowered these effects. Afferent arteriolar autoregulatory responses to increasing renal perfusion pressure were blunted in ANG/HS hypertension, and RS102895 treatment improved this response. These data suggest that CCR2b inhibition protects the kidney in hypertension by reducing inflammation and delaying the progression of hypertension. [ABSTRACT FROM AUTHOR]

The article presents a study which examined whether chemokine receptor 2b (CCR2b) contributes to the development of renal injury in salt-sensitive angiotensin II (ANG) hypertension. The authors hypothesized that the activation of the CCR2b receptor by monocyte chemoattractant protein-1 is involved in the development of high blood pressure and renal injury in the ANG/high-salt diet model of hypertension via the increase in inflammation and macrophage infiltration.

To determine the mechanism(s) involved in vasorelaxation of small arteries from hypertensive rats, normotensive (NORM), angiotensin II-infused (ANG), high-salt (HS), ANG high-salt (ANG/HS), placebo, and deoxycorticosterone acetate-salt rats were studied. Third-order mesenteric arteries from ANG or ANG/HS displayed decreased sensitivity to acetylcholine (ACh)-induced vasorelaxation compared with NORM or HS, respectively. Maximal relaxations were comparable between groups. Blockade of Ca(2+)-activated K(+) channels had no effect on ANG versus blunting relaxation in NORM (log EC(50): -6.8+/-0.1 versus -7.2+/-0.1 mol/L). NO synthase (NOS) inhibition abolished ACh-mediated relaxation in small arteries from ANG, ANG/HS, and deoxycorticosterone acetate-salt versus blunting relaxation in NORM, HS, and placebo (% maximal relaxation: ANG: 2.7+/-1.8; ANG/HS: 7.2+/-3.2; NORM: 91+/-3.1; HS: 82.1+/-13.3; deoxycorticosterone acetate-salt: 35.2+/-17.7; placebo: 79.3+/-10.3), indicating that NOS is the primary vasorelaxation pathway in these arteries from hypertensive rats. We hypothesized that NO/cGMP signaling and NOS-dependent H(2)O(2) maintains vasorelaxation in small arteries from ANG. ACh increased NOS-dependent cGMP production, indicating that NO/cGMP signaling is present in small arteries from ANG (55.7+/-6.9 versus 30.5+/-5.1 pmol/mg), and ACh stimulated NOS-dependent H(2)O(2) production (ACh: 2.8+/-0.2 micromol/mg; N(omega)-nitro-l-arginine methyl ester hydrochloride+ACh: 1.8+/-0.1 micromol/mg) in small arteries from ANG. H(2)O(2) induced vasorelaxation and catalase blunted ACh-mediated vasorelaxation. In conclusion, Ca(2+)-activated K(+) channel-mediated relaxation is dysfunctional in small mesenteric arteries from hypertensive rats, and the NOS pathway compensates to maintain vasorelaxation in these arteries through NOS-mediated cGMP and H(2)O(2) production. [ABSTRACT FROM AUTHOR]

The article presents the findings of a study on nitric oxide synthase-dependent mechanism of vasorelaxation in small arteries from hypertensive rats. Systolic blood pressure increased in rats which received angiotensin II (ANG) and ANG/high-salt (HS) than with normotensive (NORM) and HS. Third-order mesentric arteries from ANG were less sensitive to acetylcholine (ACh) than arteries from NORM. There was less cyclic guanosine monophosphate (cGMP) content in small mesenteric arteries from ANG.

The author examines the findings of several studies on the role of adenosine receptors and epoxyeicosatrieoic acids (EET) on the regulation of blood pressure and salt in the body. He cites findings that increasing dietary salt in Dahl salt-resistant rats demonstrated increased EET levels in the cortex and medulla show signs of hypertension. Another study found that decreased tubular sodium reabsorption resulted from increased sodium excretion in response to dietary salt.

The author discusses the effect of 20-hydroxyeicosatetraeonoic acid (HETE) generated by increased endothelial CYP4A2 expression to angiotensin-converting enzyme (ACE) and angiotensin-dependent hypertension. It references a study by K. Sodhi and colleagues published in the 2010 issue of "Hypertension." The results show a new positive feedback system whereby 20-HETE and angiotensin II could result in severe vascular dysfunction in hypertension. Questions remain such as the endothelial cell signaling mechanisms which 20-HETE uses to increase ACE expression.

The proximal nephron reabsorbs 60% to 70% of the fluid and sodium and most of the filtered bicarbonate via Na/H exchanger 3. Enhanced proximal nephron transport is implicated in hypertension. Our findings show that a fructose-enriched diet causes salt sensitivity. We hypothesized that fructose stimulates luminal Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. Na/H exchange was measured in rat proximal tubules as the rate of intracellular pH (pHi) recovery in fluorescent units/s. Replacing 5 mmol/L glucose with 5 mmol/L fructose increased the rate of pHi recovery (1.8±0.6 fluorescent units/s; P<0.02; n=8). Staurosporine, a protein kinase C inhibitor, blocked this effect. We studied whether this effect was because of the addition of fructose or removal of glucose. The basal rate of pHi recovery was first tested in the presence of a 0.6-mmol/L glucose and 1, 3, or 5 mmol/L fructose added in a second period. The rate of pHi recovery did not change with 1 mmol/L but it increased with 3 and 5 mmol/L of fructose. Adding 5 mmol/L glucose caused no change. Removal of luminal sodium blocked pHi recovery. With 5.5 mmol/L glucose, angiotensin II (1 pmol/L) did not affect the rate of pHi recovery (change, -1.1±0.5 fluorescent units/s; n=9) but it increased the rate of pHi recovery with 0.6 mmol/L glucose/5 mmol/L fructose (change, 4.0±2.2 fluorescent units/s; P<0.02; n=6). We conclude that fructose stimulates Na/H exchange activity and sensitizes the proximal tubule to angiotensin II. This mechanism is likely dependent on protein kinase C. These results may partially explain the mechanism by which a fructose diet induces hypertension. [ABSTRACT FROM AUTHOR]

Azilsartan, an angiotensin II receptor blocker, demonstrated anti-hypertensive and organ protective effects in hypertension. We investigated if azilsartan can be utilized in ameliorating kidney damage associated with cardiometabolic syndrome using Zucker Diabetic Fatty (ZDF) rats. Two groups of 6-8 week-old male ZDF rats were treated with vehicle or azilsartan (10 mg/kg/d, p.o.) for 8 weeks. A set of male Zucker Diabetic Lean (ZDL) rats were used as the control group. At the end of the treatment period, urine and plasma samples were collected for biochemical analysis while kidney tissues were collected for histopathological examination (n=6/group). ZDF rats were diabetic with fasting blood glucose levels averaging 287±45 mg/dL compared to 107±6 mg/dL in ZDL rats. Azilsartan treatment ameliorated hyperglycemia in ZDF rats (167±46 mg/dL). ZDF rats were also hypertensive compared to ZDL rats (181±4 vs 126±4 mmHg), and azilsartan treatment attenuated blood pressure in ZDF rats (109±4 mmHg). ZDF rats demonstrated marked renal damage compared to ZDL with elevated urinary excretion of albumin (ZDF vs ZDL, 92±47 vs 4±2 mg/d) and nephrin (842±364 vs 16±4 μg/d). ZDF rats also had 2-4-fold higher tubular cast formation and glomerular injury compared to ZDL rats. In ZDF rats, azilsartan treatment markedly reduced renal injury by attenuating elevated urinary albumin (7±2 mg/d) and nephrin (73±28 ug/d) along with a reduction in renal tubular cast formation and glomerular injury index. ZDF rats demonstrated increased inflammation and oxidative stress with elevated urinary monocyte chemoattaractant protein-1 (MCP-1) excretion (ZDF vs ZDL, 645±373 vs 319±76 ng/d) and kidney malondialdehyde (MDA) content (5±1 vs 10±1 μmol/mg). Azilsartan treatment reduced inflammation and oxidative stress in ZDF rats by reducing MCP-1 (335±80 ng/d) and kidney MDA content (6±1 ug/d). In summary, we demonstrate marked kidney protective, anti-inflammatory, and anti-oxidative effects of azilsartan in cardiometabolic syndrome ZDF rats.Support provided by Takeda Pharmaceuticals Inc., USA [ABSTRACT FROM AUTHOR]

Renal injury is associated with salt-sensitive hypertension. The Dahl salt-sensitive hypertensive rat (Dahl SS) is a model of salt-sensitive hypertension and the related kidney injury. The kidney injury in Dahl SS hypertension is associated with oxidative stress, inflammation and ER stress. We have recently developed orally active epoxyecosatrienoic acid (EET) analogs that provide organ protection in hypertension and other pathologies through multiple signaling pathways. We hypothesized that these EET analogs with their anti-inflammatory, anti-oxidant and anti-ER stress effects will protect the kidney in Dahl SS hypertension. Dahl SS rats received high salt diet and treated either with an EET analog (10 mg/kg/d) or vehicle (0.05% EtOH+0.1% PEG 400) in drinking water for 14 days. Blood pressure (SBP) was measured by tail-cuff plethysmography and urine, plasma and tissue samples were collected at the end of the treatment protocol. Urinary creatinine, albumin, nephrin, and renal tissue TBARS content were measured using ELISA or colorimetric assays. Renal expression of oxidative, inflammatory and ER stress marker genes were examined using RT-PCR. Histological analysis was done to assess renal injury. In Dahl SS rats, EET analog treatment did not affect the SBP compared to vehicle (183±6 vs. 185±12 mmHg). Interestingly, the EET analog treatment in Dahl SS reduced albumin-creatinine ratio (49±17 vs. 12±3) and nephrinuria (11±1 vs. 4±1 mg/d). EET analog treatment also reduced glomerular injury, intra-tubular cast formation and kidney fibrosis by 30-60% in Dahl SS rats compared to vehicle. In Dahl SS rats, EET analog treatment caused a 40% reduction in kidney TBARS content compared to vehicle. Moreover, the EET analog treatment in Dahl SS rats resulted 2-3 fold attenuation in the renal expression of oxidative (p47PHOX), inflammation (IL-6, TGF-β), and ER stress (CHOP, GADD34) genes. These data, demonstrate that a novel orally active EET analog provides kidney protection in Dahl SS hypertension by reducing oxidative stress, inflammation and ER stress, and this kidney protection was independent of blood pressure reduction. [ABSTRACT FROM AUTHOR]

Soluble epoxide hydrolase (sEH) inhibitors have been demonstrated to have cardiovascular protective actions. This hydrolase enzyme converts fatty acid epoxides to their corresponding diols, and this conversion can alter the biologic activity of these metabolites. We hypothesized that 12-(3-adamantan-1-yl-ureido)dodecanoic acid (AUDA), a sEH inhibitor, would protect stroke-prone spontaneously hypertensive rats from cerebral ischemia. AUDA was administered to 6-week-old male rats for 6 weeks, during which blood pressure was measured by telemetry. Cerebral ischemia was induced by middle cerebral artery occlusion, the size of the cerebral infarct was assessed after 6 hours of ischemia, and the results were expressed as a percentage of the hemisphere infarcted (%HI). Vascular structure and function were assessed using a pressurized arteriograph. Plasma levels of AUDA at the end of the treatment period averaged 5.0 +/- 0.4 ng/mL, and the urinary excretion rate was 99 +/- 21 ng/d. AUDA-treated rats had significantly smaller cerebral infarcts than control rats (36 +/- 4% vs 53 +/- 4% HI, treated versus control, P < 0.05, n = 6). This difference occurred independently of changes in blood pressure. AUDA treatment increased the passive compliance of the cerebral vessels but had no effect on vascular structure. The results of this study provide novel evidence suggesting that the sEH inhibitor AUDA is a possible therapeutic agent for ischemic stroke.