DOCA-salt Hypertensive Rats Research Articles

Tubastatin A suppresses renal fibrosis via regulation of epigenetic histone modification and Smad3-dependent fibrotic genes

Inflammation and fibrosis are implicated in the pathogenesis of hypertensive kidney damage. We previously demonstrated that a nonspecific histone deacetylase (HDAC) inhibitor attenuates cardiac fibrosis in deoxycorticosterone acetate-salt hypertensive rats, which induces HDAC6 protein and enzymatic activity. However, the HDAC inhibitor's effect and mechanism have not yet been demonstrated. We sought to determine whether an HDAC6-selective inhibitor could treat hypertension and kidney damage in angiotensin II-infused mice. Hypertension was induced by infusion of ANG in mice. Tubastatin A, an HDAC6 selective inhibitor, did not regulate blood pressure. Hypertensive stimuli enhanced the expression of HDAC6 in vivo and in vitro. We showed that the inhibition of HDAC6 prevents fibrosis and inflammation as determined by quantitative real-time PCR, western blot, and immunohistochemistry. Small interfering RNA (siRNA) against HDAC6 or Smad3 attenuated hypertensive stimuli-induced fibrosis and inflammation, whereas Smad2 siRNA failed to inhibit fibrosis. Interestingly, the combination of the HDAC6 inhibitor and Smad3 knockdown synergistically blocked transforming growth factor β (TGF-β) or ANG-induced fibrosis. We also demonstrated for the first time, to our knowledge, that acetylation of collagen type I can be regulated by HDAC6/p300 acetyltransferase. The chromatin immunoprecipitation assay revealed that the HDAC6 inhibitor suppressed TGF-β-induced acetylated histone H4 or phospho-Smad2/3 to Smad3 binding elements in the fibrosis-associated gene promoters including collagen type I. These results suggest that HDAC6 may be a valuable therapeutic target for the treatment of hypertension-induced kidney fibrosis and inflammation.

Supplementation of apelin increase plasma levels of nesfatin-1 in normal and DOCA-salt hypertensive rats.

We aimed to observe the effects of apelin supplementation on the plasma levels of nesfatin-1 in DOCA-salt hypertensive and normal rats. For this purpose, 28 young Wistar albino male rats were divided into four groups; Control (C), Control + Apelin (C+A), Hypertension (HT) and Hypertension + Apelin (HT+A). Hypertension was induced by injection of DOCA-salt (25 mg/kg, s.c.) twice weekly, 4 weeks, whereas intraperitoneal apelin was administered (200 µg.kg-1) for 17 days. Plasma nesfatin-1 and apelin levels were measured with ELISA. Systolic blood pressure was monitored using a tail cuff system. The relationships between plasma nesfatin levels and blood pressure were assessed. Plasma nesfatin-1 levels was found lower in control animals compared to C+A, HT and HT+A groups (p = 0.002, p = 0.026 and p = 0.011, respectively). Systolic blood pressures were similar in the C and C+A groups, but systolic blood pressures of the HT and HT+A groups was found significantly higher than the C and C+A groups. In conclusion, apelin administration induced an increment of nesfatin-1 in normal rats and plasma levels of nesfatin-1 increase in DOCA-salt hypertension rats. But apelin addition in hypertension did not cause an extra increase in nesfatin-1 levels. This is the first report to investigate the effect of apelin administration on plasma nesfatin levels of normal and hypertensive rats (Fig. 2, Ref. 44).

Effect of aminoguanidine on cardiovascular responses and survival time during blood loss: A study in normotensive and deoxycorticosterone acetate-salt hypertensive rats.

Introduction:Hemorrhagic shock causes more circulatory disturbances and mortality in hypertensive than normotensive subjects. In the late phase of hemorrhagic shock, nitric oxide (NO) overproduction leads to vascular decompensation. In this study, we evaluated the effect of inducible NO synthase (iNOS) inhibitor, aminoguanidine (AG), on hemodynamic parameters and serum nitrite concentration in decompensated hemorrhagic shock model in normotensive and hypertensive male rats.Materials and Methods:Twenty-four male rats were divided into hypertensive and normotensive groups (n = 12 each). Hypertension was induced by subcutaneous injection of deoxycorticoesterone acetate (DOCA), 30 mg/kg in uninephrectomized rats. Decompensated hemorrhagic shock was induced by withdrawing blood until the mean arterial pressure (MAP) reached 40 mmHg. After 120 min, each group was assigned to aminguanidine (100 mg/kg) and control group. Hemodynamic parameters were monitored for next 60 min. Blood samples were taken before and after shock period and 60 min after treatment. Survival rate was monitored for 72 h.Results:Infusion of AG in normotensive animals caused a transient increase in MAP and increase of heart rate, whereas it did not affect those parameters in hypertensive animals. Hemorrhagic shock caused a significant rise in serum nitrite concentration in normotensive and hypertensive rats and infusion of AG did not significantly change it in both groups. No significant differences observed in survival rate between AG-treated and not treated groups.Conclusion:It seems that inhibition of iNOS with AG does not have beneficial effects on hemodynamatic parameters and survival rate during decompensated hemorrhagic shock in normotensive and hypertensive animals.

Novel role of kallistatin in vascular repair by promoting mobility, viability, and function of endothelial progenitor cells.

BackgroundKallistatin exerts pleiotropic activities in inhibiting inflammation, apoptosis, and oxidative stress in endothelial cells. Because endothelial progenitor cells (EPCs) play a significant role in vascular repair, we investigated whether kallistatin contributes to vascular regeneration by enhancing EPC migration and function.Methods and ResultsWe examined the effect of endogenous kallistatin on circulating EPCs in a rat model of vascular injury and the mechanisms of kallistatin on EPC mobility and function in vitro. In deoxycorticosterone acetate–salt hypertensive rats, we found that kallistatin depletion augmented glomerular endothelial cell loss and diminished circulating EPC number, whereas kallistatin gene delivery increased EPC levels. In cultured EPCs, kallistatin significantly reduced tumor necrosis factor‐α–induced apoptosis and caspase‐3 activity, but kallistatin's effects were blocked by phosphoinositide 3‐kinase inhibitor (LY294002) and nitric oxide (NO) synthase inhibitor (l‐NAME). Kallistatin stimulated the proliferation, migration, adhesion and tube formation of EPCs; however, kallistatin's actions were abolished by LY294002, l‐NAME, endothelial NO synthase–small interfering RNA, constitutively active glycogen synthase kinase‐3β, or vascular endothelial growth factor antibody. Kallistatin also increased Akt, glycogen synthase kinase‐3β, and endothelial NO synthase phosphorylation; endothelial NO synthase, vascular endothelial growth factor, and matrix metalloproteinase‐2 synthesis and activity; and NO and vascular endothelial growth factor levels. Kallistatin's actions on phosphoinositide 3‐kinase–Akt signaling were blocked by LY294002, l‐NAME, and anti–vascular endothelial growth factor antibody.ConclusionsEndogenous kallistatin plays a novel role in protection against vascular injury in hypertensive rats by promoting the mobility, viability, and vasculogenic capacity of EPCs via enhancing NO and vascular endothelial growth factor levels through activation of phosphoinositide 3‐kinase–Akt signaling. Kallistatin therapy may be a promising approach in the treatment of vascular diseases.

Discovery of 6-[5-(4-fluorophenyl)-3-methyl-pyrazol-4-yl]-benzoxazin-3-one derivatives as novel selective nonsteroidal mineralocorticoid receptor antagonists

In the course of our study on selective nonsteroidal mineralocorticoid receptor (MR) antagonists, a series of novel benzoxazine derivatives possessing an azole ring as the core scaffold was designed for the purpose of attenuating the partial agonistic activity of the previously reported dihydropyrrol-2-one derivatives. Screening of alternative azole rings identified 1,3-dimethyl pyrazole 6a as a lead compound with reduced partial agonistic activity. Subsequent replacement of the 1-methyl group of the pyrazole ring with larger lipophilic side chains or polar side chains targeting Arg817 and Gln776 increased MR binding activity while maintaining the agonistic response at the lower level. Among these compounds, 6-[1-(2,2-difluoro-3-hydroxypropyl)-5-(4-fluorophenyl)-3-methyl-1H-pyrazol-4-yl]-2H-1,4-benzoxazin-3(4H)-one (37a) showed highly potent in vitro activity, high selectivity versus other steroid hormone receptors, and good pharmacokinetic profiles. Oral administration of 37a in deoxycorticosterone acetate-salt hypertensive rats showed a significant blood pressure-lowering effect with no signs of antiandrogenic effects.

Effect of Scurrula atropurpurea on nitric oxide, endothelial damage, and endothelial progenitor cells of DOCA-salt hypertensive rats.

To know whether Scurrula atropurpurea is able to modulate total plasma nitrate/nitrite levels, decrease endothelial damage, and increase endothelial progenitor cells (EPCs) in hypertensive rats. The rats were divided in 5 groups: control (normotensive) group, Desoxy cortico sterone (DOCA)-salt hypertensive group, and three DOCA-salt hypertensive groups. All 5 groups received methanolic extract of S. atropurpurea (MESA) at a dosage of 50; 100; and 200 mg/KgBW. Serum nitric oxide (NO) was assayed by colorimetric. Circulating endothelial cells (CECs) and EPCs were assayed using flow cytometry. The administration of MESA100 and MESA200 elevated the total plasma nitrate/nitrite levels but cannot reach the level in control group. MESA100 and MESA200 also elevated the EPCs number compared with hypertensive group. The administration of MESA significantly (P< 0.05) decreased the CECs number compared to hypertensive groups. Methanolic extract of S. atropurpurea is able to modulate total plasma nitrate/nitrite levels and diminish endothelial damage via increasing EPCs.

Endothelin receptor blockade ameliorates renal injury by inhibition of RhoA/Rho-kinase signalling in deoxycorticosterone acetate-salt hypertensive rats

Excessive production of fibrosis is a feature of hypertension-induced renal injury. Activation of RhoA/Rho-kinase (ROCK) axis has been shown in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We assessed whether selective endothelin receptor blockers can attenuate renal fibrosis by inhibiting RhoA/ROCK axis in DOCA-salt rats. At 4 weeks after the start of DOCA-salt treatment and uninephrectomization, male Wistar rats were randomized into three groups for 4 weeks: vehicle, ABT-627 (endothelin-A receptor inhibitor) and A192621 (endothelin-B receptor inhibitor). DOCA-salt was characterized by increased blood pressure, decreased renal function, increased proteinuria, increased glomerulosclerosis and tubulointerstitial fibrosis with myofibroblast accumulation, increased renal endothelin-1 levels and RhoA activity along with increased expression of connective tissue growth factor at both mRNA and protein levels as compared with uninephrectomized control male Wistar rats. Treatment with a selective mineralocorticoid receptor antagonist, eplerenone, ameliorated proteinuria. Impaired renal function and histological changes were overcome by treatment with ABT-627, but not with A192621. The beneficial effects of bosentan, a nonspecific endothelin receptor blocker, on proteinuria, RhoA activity, and connective tissue growth factor levels were similar to ABT-627. Furthermore, in an isolated perfuse kidney, a RhoA inhibitor, C3 exoenzyme, and two ROCK inhibitors, fasudil and Y-27632, significantly attenuated connective tissue growth factor levels. These results indicate that DOCA-salt elevates renal endothelin-1 levels and RhoA activity via activation of mineralocorticoid receptor, resulting in renal fibrosis and proteinuria. Endothelin-A receptor blockade can attenuate DOCA-salt-induced renal fibrosis probably through the inhibition of RhoA/ROCK activity and connective tissue growth factor expression.

Rostafuroxin ameliorates endothelial dysfunction and oxidative stress in resistance arteries from deoxycorticosterone acetate-salt hypertensive rats

Endogenous ouabain is elevated in patients and experimental models of hypertension and is associated with elevated mortality. In this context, it is reasonable to assume that a new antihypertensive drug that inhibits the deleterious effects of endogenous ouabain may be a specific pharmacological tool for hypertension treatment. Here, we investigated the effects of rostafuroxin (ROSTA), an ouabain inhibitor, on SBP, endothelial dysfunction and oxidative stress in deoxycorticosterone acetate (DOCA)-salt rats. A hypertensive model was established in uninephrectomized Wistar rats using DOCA-salt. After SBP stabilization, DOCA-salt rats were divided into two groups: DOCA-salt (control) and DOCA-salt treatment with ROSTA (1 mg/kg per day gavage, 3 weeks). The SBP was measured using the tail-cuff method, and vascular function was assessed in mesenteric-resistance arteries (MRAs) using a wire myograph. Nitric oxide and reactive oxygen species production were investigated. Western blot was performed to quantify protein expression. Our results indicated that ROSTA treatment decreased SBP, improved acetylcholine-induced relaxation via enhanced nitric oxide synthesis and bioavailability, decreased superoxide anion generation from NAD(P)H oxidase and cyclooxygenase-2 and reduced cytoplasmic tyrosine kinase Src phosphorylation without changes in NaKATPase activity in MRA from DOCA-salt rats. This study reports the critical role of endogenous ouabain in volume-dependent hypertension. In MRA from DOCA-salt rats, the binding of endogenous ouabain to NaK-ATPase results in downstream c-SRC activation, oxidative stress and endothelial dysfunction. Endogenous ouabain is a putative target for the treatment of hypertension, and ROSTA may represent a novel therapeutic approach.

Antioxidative and blood pressure-lowering effects of Scurrula atropurpurea on deoxycorticosterone acetate–salt hypertensive rats

This study aimed to investigate whether a methanolic extract of Scurrula atropurpurea (BL.) Dans. (MESA) was able to reduced oxidative stress and systolic blood pressure (SBP) in deoxycorticosterone acetate–salt hypertensive rats. Twenty-five male Wistar were divided into the control group and four hypertensive groups that received the MESA at a doses of 50 mg/kg, 100 mg/kg, or 200 mg/kg bodyweight, or received no MESA. SBP was recorded by tail cuff methods. The levels of serum malondialdehyde (MDA) and superoxide dismutase (SOD) were analyzed by colorimetry. SBP was increased significantly in the hypertensive group compared to the sham group (p < 0.05). Administration of MESA significantly decreased SBP, but not to reach the level of the sham group. The level of MDA was significantly higher in the hypertensive group compared to the sham group (p < 0.05). Administration of MESA200 significantly decreased the MDA levels compared to HR groups (p < 0.05). The SOD level was significantly decreased in HR compared to the sham group (p < 0.05). Administration of MESA50 elevated the SOD levels to reach the level in the sham group. The SOD levels in MESA100 and MESA200 were significantly higher compared to the sham group (p < 0.05). In conclusion, Scurulla atropurpurea is able to modulate SOD, diminish oxidative stress, and decrease SBP in deoxycorticosterone acetate–salt hypertensive rats.

Apelin-induced hemorheological alterations in DOCA-salt hypertensive rats

Apelin is a hypotensive peptide. Red blood cell (RBC) deformability and aggregation were previously demonstrated to be altered in various hypertension (HT) models. In the present study, we investigated possible alterations in RBC deformability and aggregation in response to apelin in DOCA-salt hypertensive rats. Rats were randomly divided into 4 groups: Control (C), Hypertension (HT), Apelin, and Apelin + Hypertension (Apelin + HT). HT was induced by injection of DOCA-salt (25 mg/kg, s.c.) twice weekly for 4 weeks, whereas apelin was administered (200 μg/kg i.p.) for 17 days. RBC deformability and aggregation were determined using an ektacytometer. Blood pressure was monitored using a tail cuff system. Systolic blood pressure was decreased in the Apelin and Apelin + HT groups and increased in the HT group. RBC deformability was not significantly altered in the HT group. Apelin administration induced a statistically significant increase in RBC deformability in control animals, whereas erythrocytic deformability in the Apelin + HT group was decreased compared to the Apelin group. RBC aggregation of hypertensive animals was reduced compared to controls. Apelin administration induced increased RBC aggregation in hypertensive rats. Our results showed favorable effects of apelin on RBC deformability in control animals, but not in hypertensive rats.

Effect of Visfatin on Blood Pressure in Normal and DOCA-Salt Hypertensive Rats

Effect of Visfatin on Blood Pressure in Normal and DOCA-Salt Hypertensive Rats

Aliskiren Augments the Activities of Anti-Oxidant Enzymes in Liver Homogenates of DOCA Salt-Induced Hypertensive Rats

Hypertension is a serious problem that is recently thought to be associated with damaging effects on target organs partially via oxidative stress. On the other hand, there is accumulating literature describing some sort of therapeutic interaction between antioxidant enzymes in vital organs and hypertension. Therefore, the aim of this study is to investigate the possible effect of a direct renin inhibitor, aliskiren, used in treatment of hypertension via renin-angiotensin-aldosterone system (RAAS), on selected anti-oxidant enzymes in hepatic homogenates in DOCA salt-induced hypertesnive albino rats. Thirty male wister albino rats were assigned randomly into 3 groups (n = 10/ group). Group 1 received no treatement and serves as control. Group 2 received 0.5% carboxymethylcellulose sodium ip as a solvent of aliskiren, as a direct renin inhibitor (DRI). Group 3 received aliskiren 100 mg/kg/day ip for 4 weeks through gastric tube. Systolic blood pressure (SBP) was measured every week and its mean was recorded at the end of the study. Superoxide dismutase (SOD) enzyme in RBCs lysates, activities of catalase (CAT) and glutathione peroxidase enzymes and thiobarbituric acid reactive substance (TBARS), as a marker of lipid peroxidation, in hepatic homogenates were measured at the end of the study. DRI produced a marked reduction in mean SBP of hypertensive rats. It also significantly (p < 0.05) increased the activities of measured anti-oxidant enzymes while it significantly (p < 0.05) reduced TBARS in liver homogenates. These results indicated that renin possesses an oxidative effect in the liver in hypertensive rats. Aliskiren, in addition to its powerful anti-hypertensive effect, it could induce a great anti-oxidant effect in liver homogenates of DOCA salt-hypertensive rats.

Abstract 447: Intracerebroventricular Administration of Autologous Bone Marrow-derived Cells Attenuates Sympathetic Hyperactivity in Deoxycorticosterone Acetate-salt Hypertensive Rats

Objectives: Administration of deoxycorticosterone acetate (DOCA) in combination with salt loading and surgical removal of one kidney induces hypertension. Central mechanism is involved in this hypertension. Bone marrow-derived cells (BMCs) include mesenchymal stem cells play critical role in repairing damaged tissue and anti-inflammation. We hypothesized that increase in number of BMCs in the brain would attenuate the DOCA-salt hypertension. Methods: Sprague-Dawley rats underwent unilateral nephrectomy were divided into following 4 groups: rats received sham treatment with intracerebroventricular (icv) administration of medium (S/M group, n=5); rats received sham treatment with icv administration of BMCs (S/B group, n=5); rats received DOCA-salt treatment with icv administration of medium (D/M group, n=4); rats received DOCA-salt treatment with icv administration of BMCs (D/B group, n=7). Three weeks following the initiation of DOCA-salt treatment, rats had surgery to implant arterial and venous catheters. Resting mean arterial pressure (MAP) of rats was recorded in conscious unrestrained state and resting sympathetic tone was evaluated with a peak depressor response produced by hexamethonium (C6) injection. Results: Resting MAPs of S/M, S/B, D/M and D/B group were 116±4, 120±5, 194±4, 172±9 mmHg, respectively. DOCA-salt treatment significantly increased MAP in both D/M and D/B group. D/B group tended to have lower MAP than D/M group, however, post hoc analysis did not reach significant. The peak depressor responses to C6 injection in S/M, S/B, D/M and D/B group were 41±2, 46±5, 97±10, 69±5 mmHg, respectively. DOCA-salt treatment significantly increased the peak depressor response to C6 and icv administration of BMCs attenuated the increase in peak depressor response. Conclusion: BMCs in the brain may have protective role against sympathetic hyperactivity caused by DOCA-salt treatment.

Increased Catecholamine Secretion from Single Adrenal Chromaffin Cells in DOCA-Salt Hypertension Is Associated with Potassium Channel Dysfunction

The mechanism of catecholamine release from single adrenal chromaffin cells isolated from normotensive and DOCA-salt hypertensive rats was investigated. These cells were used as a model for sympathetic nerves to better understand how exocytotic release of catecholamines is altered in this model of hypertension. Catecholamine secretion was evoked by local application of acetylcholine (1 mM) or high K+ (70 mM), and continuous amperometry was used to monitor catecholamine secretion as an oxidative current. The total number of catecholamine molecules secreted from a vesicle, the total number of vesicles fusing and secreting, and the duration of secretion in response to a stimulus were all significantly greater for chromaffin cells from hypertensive rats as compared to normotensive controls. The greater catecholamine secretion from DOCA-salt cells results, at least in part, from functionally impaired large conductance, Ca2+-activated (BK) and ATP-sensitive K+ channels. This work reveals that there is altered vesicular release of catecholamines from these cells (and possibly from perivascular sympathetic nerves) and this may contribute to increased vasomotor tone in DOCA-salt hypertension.

Cardiovascular Effects of the Essential Oil of Croton Zehntneri Leaves in DOCA-salt Hypertensive, Conscious Rats

This study investigated the cardiovascular effects of the essential oil of Croton zehntneri (EOCZ) in deoxycorticosterone-acetate (DOCA)-salt hypertensive rats. Furthermore, in vitro experiments using isolated thoracic aortic rings were performed to assess the vascular effects of the EOCZ. In conscious hypertensive rats, intravenous (i.v.) injections of EOCZ (1-20 mg/kg) induced rapid (2-4 s) and dose-dependent hypotension and bradycardia (phase 1). The hypotension was followed by a significant pressor effect that was more evident at the higher doses (10 and 20 mg/kg) of EOCZ. Hypotension and bradycardia of EOCZ (phase 1) were abolished and respectively reversed into pressor and tachycardiac effects by methylatropine (1 mg/kg, i.v.) pretreatment. In isolated endothelium-intact aortic preparations, increasing concentrations (1-1000 microg/mL) of EOCZ relaxed the potassium-induced contraction in a concentration-dependent manner with an IC50 (geometric mean [95% confidence interval]) value of 202.0 [92.0-443.7] microg/mL. This vasorelaxant effect remained unaffected by either mechanical removal of functional vascular endothelium (IC50 = 189.0 [159.4-224.7] microg/mL) or the addition of atropine (1 microM) (IC50 = 158.6 [79.8-316.2] microg/mL) in the perfusion medium. These data show that i.v. administration of EOCZ in DOCA-salt hypertensive rats induces a vago-vagal reflex decreases in heart rate and blood pressure (phase 1). EOCZ may induce a second and delayed hypotension due to its direct endothelium-independent vasorelaxant effects, but it seems to be buffered by the pressor component (subsequent to phase 1) of EOCZ. This pattern of blood pressure and heart rate responses to EOCZ seems unaltered by DOCA-salt hypertension, as was similar to that previously reported in conscious normotensive rats.

Enhanced uridine adenosine tetraphosphate-induced contraction in renal artery from type 2 diabetic Goto-Kakizaki rats due to activated cyclooxygenase/thromboxane receptor axis

The dinucleotide uridine adenosine tetraphosphate (Up4A), which has both purine and pyrimidine moieties, was reported as a novel endothelium-derived contracting factor. Recently, growing evidence has suggested that Up4A plays an important role in regulation of the cardiovascular function. We previously demonstrated that Up4A-induced vasoconstrictions are altered in arteries from DOCA-salt hypertensive rats. We have assessed responses to Up4A shown by renal arteries from type 2 diabetic Goto-Kakizaki (GK) rats (42-46weeks old) and identified the molecular mechanisms involved. Concentration-dependent contractions to Up4A were greater in renal arterial rings from the GK than age-matched control Wistar group. In both groups, the inhibition of nitric oxide synthase (with N (G)-nitro-L-arginine) increased the response to Up4A, whereas the inhibition of cyclooxygenase (COX) (with indomethacin) decreased the response. Specific inhibitors of COX-1 (valeroyl salicylate) and COX-2 (NS398), a thromboxane (TX) receptor (TP) antagonist (SQ29548), and P2 receptor antagonist (suramin) also decreased the response to Up4A. Protein expressions of COXs in renal arteries were greater in the GK than Wistar group. The production of TXB2 (a metabolite of TXA2) by Up4A did not differ between these groups. Concentration-dependent contractions to U46619, an agonist of the TP receptor, were greater in renal arteries from the GK than Wistar group. The expression of P2X1 and P2Y2 receptors did not differ between these groups. These results suggest that enhancement of the Up4A-induced contraction in renal arteries from GK rats may be attributable to the increased activation of COXs/TP receptor signaling.

Enhanced Assymetrical Noradrenergic Transmission in the Olfactory Bulb of Deoxycorticosterone Acetate-Salt Hypertensive Rats

The ablation of olfactory bulb induces critical changes in dopamine, and monoamine oxidase activity in the brain stem. Growing evidence supports the participation of this telencephalic region in the regulation blood pressure and cardiovascular activity but little is known about its contribution to hypertension. We have previously reported that in the olfactory bulb of normotensive rats endothelins enhance noradrenergic activity by increasing tyrosine hydroxylase activity and norepinephrine release. In the present study we sought to establish the status of noradrenergic activity in the olfactory bulb of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Different steps in norepinephrine transmission including tyrosine hydroxylase activity, neuronal norepinephrine release and uptake were assessed in the left and right olfactory bulb of DOCA-salt hypertensive rats. Increased tyrosine hydroxylase activity, and decreased neuronal norepinephrine uptake were observed in the olfactory bulb of DOCA-salt hypertensive rats. Furthermore the expression of tyrosine hydroxylase and its phosphorylated forms were also augmented. Intriguingly, asymmetrical responses between the right and left olfactory bulb of normotensive and hypertensive rats were observed. Neuronal norepinephrine release was increased in the right but not in the left olfactory bulb of DOCA-salt hypertensive rats, whereas non asymmetrical differences were observed in normotensive animals. Present findings indicate that the olfactory bulb of hypertensive rats show an asymmetrical increase in norepinephrine activity. The observed changes in noradrenergic transmission may likely contribute to the onset and/or progression of hypertension in this animal model.

Mechanism of the Antihypertensive and Vasorelaxant Effects of the Flavonoid Tiliroside in Resistance Arteries

Hypertension is a leading cause of death and disability globally, and its prevalence continues to accelerate. The cardiovascular effects of the flavonoid tiliroside have never been reported. In this work, using complementary in vivo and in vitro approaches, we describe the antihypertensive effect of tiliroside and the underlying mechanisms involved in the reduction of blood pressure. Tiliroside (1, 5 or 10 mg/kg) induced a dose-dependent long-lasting decrease in blood pressure in conscious DOCA-salt hypertensive rats that was accompanied by an increased heart rate. Tiliroside also induced a concentration-dependent vasodilation of mesenteric resistance arteries precontracted with phenylephrine. Removal of the endothelium or pretreatment of the preparation with L-NAME or indomethacin did not modify the vasodilator response for tiliroside. When vessels were precontracted with a high K⁺ (50 mM) solution, tiliroside exhibited a vasodilator effect similar to that observed in vessels precontracted with phenylephrine. Experiments carried out in nominally Ca²⁺-free solution showed that tiliroside antagonized CaCl₂-induced contractions. Moreover, tiliroside reduced the rise in intracellular Ca²⁺ concentration induced by membrane depolarization in vascular smooth muscle cells. Finally, tiliroside decreased the voltage-activated peak amplitude of the L-type Ca²⁺ channel current in freshly dissociated vascular smooth muscle cells from mesenteric arteries. Altogether, our results point to an antihypertensive effect of tiliroside due to a reduction in peripheral resistance through blockage of voltage-activated peak amplitude of the L-type Ca²⁺ channel in smooth muscle cells.

Comparative Effects of Ficus exasperata Aqueous Leaf Extract and Furosemide on Urinary Excretion in DOCA-salt Hypertensive Rat

Comparative Effects of Ficus exasperata Aqueous Leaf Extract and Furosemide on Urinary Excretion in DOCA-salt Hypertensive Rat

Differential contribution of pannexin‐1 channels to agonist and neurogenic constriction of mesenteric arteries and veins from normotensive and DOCA‐salt hypertensive rats

Norepinephrine (NE) and ATP are constrictor transmitters released from perivascular sympathetic nerves. ATP efflux through smooth muscle pannexin‐1 channels contributes to á1 adrenergic receptor (α1‐AR) mediated arterial constriction. We tested the hypotheses that pannexin‐1 contributes to: 1) α1‐AR mediated constriction of mesenteric veins (MV); 2) neurogenic constriction of mesenteric arteries (MA) and MV; 3) pannexin‐1 mechanisms are impaired in DOCA‐salt hypertension in rats. We used MA and MV in vitro. Drugs were added to organ bath solutions. Constrictions were measured using video microscopy. Perivascular nerves were activated by focal electrical stimulation. Western blot was used to measure pannexin‐1 protein. Phenylephrine (PE) concentration‐response curves (CRCs) were similar in MA and MV from sham and DOCA‐salt rats. PE‐CRCs were right‐shifted to a similar extent by mefloquine (1 μM, pannexin‐1 blocker) in MA but not MV from sham and DOCA‐salt rats. Mefloquine did not alter neurogenic constrictions in MA or MV. Pannexin‐1 protein was expressed in MA and MV. These data indicate that pannexin‐1 mechanisms contribute to agonist but not neurogenic constriction of MA in normotensive and hypertensive rats. This mechanism does not contribute to adrenergic constriction of MV. Nerve released and exogenous NE may access different constrictor mechanisms in MA. (Supported by P01HL070687)