Hepatoprotective and cardioprotective effects of empagliflozin in spontaneously hypertensive rats fed a high-fat diet.

A combination of liver and heart dysfunction worsens the prognosis of human survival. The aim of this study was to investigate whether empagliflozin (a sodium-glucose transporter-2 inhibitor) has beneficial effects not only on cardiac and renal function but also on hepatic function. Adult (6-month-old) male spontaneously hypertensive rats (SHR) were fed a high-fat diet (60% fat) for four months to induce hepatic steatosis and mild heart failure. For the last two months, the rats were treated with empagliflozin (empa, 10 mg.kg-1.day-1 in the drinking water). Renal function and oral glucose tolerance test were analyzed in control (n=8), high-fat diet (SHR+HF, n=10), and empagliflozin-treated (SHR+HF+empa, n=9) SHR throughout the study. Metabolic parameters and echocardiography were evaluated at the end of the experiment. High-fat diet feeding increased body weight and visceral adiposity, liver triglyceride and cholesterol concentrations, and worsened glucose tolerance. Although the high-fat diet did not affect renal function, it significantly worsened cardiac function in a subset of SHR rats. Empagliflozin reduced body weight gain but not visceral fat deposition. It also improved glucose sensitivity and several metabolic parameters (plasma insulin, uric acid, and HDL cholesterol). In the liver, empagliflozin reduced ectopic lipid accumulation, lipoperoxidation, inflammation and pro-inflammatory HETEs, while increasing anti-inflammatory EETs. In addition, empagliflozin improved cardiac function (systolic, diastolic and pumping) independent of blood pressure. The results of our study suggest that hepatoprotection plays a decisive role in the beneficial effects of empagliflozin in preventing the progression of cardiac dysfunction induced by high-fat diet feeding.

Changes in cardiovascular autonomic control induced by chronic inhibition of acetylcholinesterase during pyridostigmine or donepezil treatment of spontaneously hypertensive rats.

Chronic treatment with acetylcholinesterase inhibitors may be a promising therapeutic strategy for treatment of cardiovascular diseases. The aim of our study was to analyze the changes in blood pressure (BP) and heart rate (HR) during 14 days of treatment with two different acetylcholinesterase inhibitors - pyridostigmine (PYR) having only peripheral effects or donepezil (DON) with both peripheral and central effects. In addition, we studied their effects on the cardiovascular response to restraint stress and on sympathovagal control of HR in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). SHR were characterized by elevated BP and increased low-frequency component of systolic BP variability (LF-SBPV), but their cardiac vagal tone and HR variability (HRV) were reduced compared with WKY. Chronic treatment with either acetylcholinesterase inhibitor decreased HR and increased HRV in both strains. PYR treatment slightly decreased BP and LF-SBPV in the dark phase of the day. Neither drug significantly altered BP response to stress, but PYR attenuated HR increase during restraint stress. Regarding sympathovagal balance, acute methylatropine administration caused a greater increase of HR in WKY than in SHR. Chronic PYR or DON treatment enhanced HRV and HR response to methylatropine (vagal tone) in WKY, whereas PYR but not DON treatment potentiated HRV and vagal tone in SHR. In conclusion, vagal tone was lower in SHR compared with WKY, but was enhanced by chronic PYR treatment in both strains. Thus, chronic peripheral, but not central, acetylcholinesterase inhibition has major effects on HR and its variability in both normotensive and hypertensive rats.

Impaired vascular ß-adrenergic relaxation in spontaneously hypertensive rats: The differences between conduit and resistance arteries.

It was suggested that impaired ß-adrenergic relaxation in spontaneously hypertensive rats (SHR) might contribute to their high blood pressure (BP). Our study was focused on isoprenaline-induced dilatation of conduit femoral or resistance mesenteric arteries and on isoprenaline-induced BP reduction in SHR and Wistar-Kyoto rats (WKY). We confirmed decreased ß-adrenergic relaxation of SHR femoral arteries due to the absence of its endothelium-independent component, whereas endothelium-dependent component of ß-adrenergic smooth muscle relaxation was similar in both strains. Conversely, isoprenaline-induced relaxation of resistance mesenteric arteries was similar in both strains and this was true for endothelium-dependent and endothelium-independent components. We observed moderately reduced sensitivity of SHR mesenteric arteries to salmeterol (ß2-adrenergic agonist) and this strain difference disappeared after endothelium removal. However, there was no difference in mesenteric arteries relaxation by dobutamine (ß1-adrenergic agonist) which was independent of endothelium. The increasing isoprenaline doses elicited similar BP decrease in both rat strains, although BP sensitivity to isoprenaline was slightly decreased in SHR. The blockade of cyclooxygenase (indomethacin) and NO synthase (L-NAME) further reduced BP sensitivity to isoprenaline in SHR. On the other hand, salmeterol elicited similar BP decrease in both strains and the blockade of cyclooxygenase and NO synthase increased BP sensitivity to salmeterol in SHR as compared to WKY. In conclusion, attenuated ß-adrenergic vasodilatation of conduit arteries of SHR but similar ß-adrenergic relaxation of resistance mesenteric arteries from WKY and SHR and their similar BP response to ß-adrenergic agonists do not support major role of altered ß-adrenergic vasodilatation for high BP in genetic hypertension.

Empagliflozin Is Not Renoprotective in Non-Diabetic Rat Models of Chronic Kidney Disease.

Gliflozins (sodium-glucose transporter-2 inhibitors) exhibited renoprotective effects not only in diabetic but also in non-diabetic patients with chronic kidney disease (CKD). Controversial results were reported in experimental non-diabetic models of CKD. Therefore, we examined empagliflozin effects in three CKD models, namely, in fawn-hooded hypertensive (FHH) rats, uninephrectomized salt-loaded (UNX + HS) rats, and in rats with Goldblatt hypertension (two-kidney, one-clip 2K1C) that were either untreated or treated with empagliflozin (10 mg/kg/day) for eight weeks. Plethysmography blood pressure (BP) was recorded weekly, and renal parameters (proteinuria, plasma urea, creatinine clearance, and sodium excretion) were analyzed three times during the experiment. At the end of the study, blood pressure was also measured directly. Markers of oxidative stress (TBARS) and inflammation (MCP-1) were analyzed in kidney and plasma, respectively. Body weight and visceral adiposity were reduced by empagliflozin in FHH rats, without a significant effect on BP. Experimentally induced CKD (UNX + HS and 2K1C) was associated with a substantial increase in BP and relative heart and kidney weights. Empagliflozin influenced neither visceral adiposity nor BP in these two models. Although empagliflozin increased sodium excretion, suggesting effective SGLT-2 inhibition, it did not affect diuresis in any experimental model. Unexpectedly, empagliflozin did not provide renoprotection because proteinuria, plasma urea, and plasma creatinine were not lowered by empagliflozin treatment in all three CKD models. In line with these results, empagliflozin treatment did not decrease TBARS or MCP-1 levels in either model. In conclusion, empagliflozin did not provide the expected beneficial effects on kidney function in experimental models of CKD.

Beneficial Effects of Empagliflozin Are Mediated by Reduced Renal Inflammation and Oxidative Stress in Spontaneously Hypertensive Rats Expressing Human C-Reactive Protein.

Gliflozins (inhibitors of sodium-glucose cotransporter 2) show many beneficial actions beyond their antidiabetic effects. The underlying mechanisms of these additional protective effects are still not well understood, especially under non-diabetic conditions. Therefore, we analyzed the effects of empagliflozin in young (3-month-old) and adult (12-month-old) male spontaneously hypertensive rats (SHR) expressing human C-reactive protein (CRP) in the liver. SHR-CRP rats are a non-diabetic model of metabolic syndrome, inflammation, and organ damage. Empagliflozin was given in a daily dose of 10 mg/kg body weight for 8 weeks. Both age groups of SHR-CRP rats treated with empagliflozin had lower body weight, decreased weight of fat depots, reduced ectopic fat accumulation in the liver and kidneys, and decreased levels of plasma insulin and ß-hydroxybutyrate. Empagliflozin effectively reduced ectopic renal fat accumulation, and was associated with decreased inflammation. Exclusively in young rats, decreased microalbuminuria after empagliflozin treatment was accompanied by attenuated oxidative stress. In adult animals, empagliflozin also improved left ventricle function. In conclusion, in young animals, the beneficial renoprotective effects of empagliflozin could be ascribed to reduced lipid deposition in the kidney and the attenuation of oxidative stress and inflammation. In contrast, hepatic lipid metabolism was ameliorated in adult rats.

Both central sympathoexcitation and peripheral angiotensin II-dependent vasoconstriction contribute to hypertension development in immature heterozygous Ren-2 transgenic rats.

Recently, we demonstrated that chronic blockade of the renin-angiotensin system (RAS) lowered the blood pressure (BP) of adult Ren-2 transgenic rats (TGR) mainly through the attenuation of central sympathoexcitation. However, the participation of central and peripheral mechanisms in the development of high BP in immature TGR remains unclear. In the present study, 6-week-old heterozygous TGR males were chronically treated with intracerebroventricular (ICV) or intraperitoneal (IP) infusions of the AT1 receptor inhibitor losartan (1 or 2 mg/kg/day) for 4 weeks. The influence of these treatments on sympathetic- and angiotensin II-dependent BP components (BP response to pentolinium or captopril, respectively) as well as on BP response to exogenous angiotensin II were determined to evaluate the participation of central and peripheral RAS in hypertension development. Chronic IP losartan administration (1 or 2 mg/kg/day) lowered the BP of immature TGR by reducing both sympathetic and angiotensin II-dependent BP components. The central action of IP-administered losartan was indicated by a reduced BP response to acute ICV angiotensin II injection. Chronic ICV administration of a lower losartan dose (1 mg/kg/day) reduced only the sympathetic BP component, whereas a higher ICV administered dose (2 mg/kg/day) was required to influence the angiotensin II-dependent BP component. Accordingly, chronic ICV losartan administration of 2 mg/kg/day (but not 1 mg/kg/day) attenuated the BP response to acute intravenous angiotensin II application. In conclusion, central sympathoexcitation seems to play an important role in hypertension development in immature TGR. Central sympathoexcitation is highly susceptible to inhibition by low doses of RAS-blocking agents, whereas higher doses also affect peripheral angiotensin II-dependent vasoconstriction.

Antihypertensive and metabolic effects of empagliflozin in Ren-2 transgenic rats, an experimental non-diabetic model of hypertension.

The new antidiabetic drugs, gliflozins, inhibit sodium-glucose transporter-2 in renal proximal tubules promoting glucose and sodium excretion. This leads not only to a significant improvement of glucose control but also to the reduction of blood pressure and body weight in both diabetic patients and experimental models. We examined whether these beneficial effects can also be achieved in a non-diabetic hypertensive model, namely in Ren-2 transgenic rats (TGR). Adult 6-month-old hypertensive TGR and their normotensive controls (Hannover Sprague-Dawley rats), were either untreated or treated with empagliflozin (10 mg/kg/day) for two months. Telemetric blood pressure monitoring, renal parameters as well as cardiac function via echocardiography were analyzed during the experiment. At the end of the study, the contribution of major vasoactive systems to blood pressure maintenance was studied. Metabolic parameters and markers of oxidative stress and inflammation were also analyzed. Empagliflozin had no effect on plasma glucose level but partially reduced blood pressure in TGR. Although food consumption was substantially higher in empagliflozin-treated TGR compared to the untreated animals, their body weight and the amount of epididymal and perirenal fat was decreased. Empagliflozin had no effect on proteinuria, but it decreased plasma urea, attenuated renal oxidative stress and temporarily increased urinary urea excretion. Several metabolic (hepatic triglycerides, non-esterified fatty acids, insulin) and inflammatory (TNF-α, leptin) parameters were also improved by empagliflozin treatment. By contrast, echocardiography did not reveal any effect of empagliflozin on cardiac function. In conclusion, empagliflozin exerted beneficial antihypertensive, anti-inflammatory and metabolic effects also in a non-diabetic hypertensive model.

Cooperation of augmented calcium sensitization and increased calcium entry contributes to high blood pressure in salt-sensitive Dahl rats.

Salt hypertensive Dahl rats are characterized by sympathoexcitation and relative NO deficiency. We tested the hypothesis that the increased blood pressure (BP) response to fasudil in salt hypertensive Dahl rats is due to augmented calcium sensitization in the salt-sensitive strain and/or due to their decreased baroreflex efficiency. BP reduction after acute administration of nifedipine (an L-type voltage-dependent calcium channel blocker) or fasudil (a Rho kinase inhibitor) was studied in conscious intact rats and in rats subjected to acute NO synthase inhibition or combined blockade of the renin-angiotensin system (captopril), sympathetic nervous system (pentolinium), and NO synthase (L-NAME). Intact salt-sensitive (SS) Dahl rats fed a low-salt diet had greater BP responses to nifedipine (-31 ± 6 mmHg) or fasudil (-34 ± 7 mmHg) than salt-resistant (SR) Dahl rats (-16 ± 4 and -17 ± 2 mmHg, respectively), and a high-salt intake augmented the BP response only in SS rats. These BP responses were doubled after acute NO synthase inhibition, indicating that endogenous NO attenuates both calcium entry and calcium sensitization. Additional pentolinium administration, which minimized sympathetic compensation for the drug-induced BP reduction, magnified the BP responses to nifedipine or fasudil in all groups except for salt hypertensive SS rats due to their lower baroreflex efficiency. The BP response to the calcium channel blocker nifedipine can distinguish SS and SR rats even after calcium sensitization inhibition by fasudil, which was not seen when fasudil was administered to nifedipine-pretreated rats. Thus, enhanced calcium entry (potentiated by sympathoexcitation) in salt hypertensive Dahl rats is the abnormality that is essential for their BP increase, which was further augmented by increased calcium sensitization in salt-sensitive Dahl rats.

Hyper-reactivity of HPA axis in Fischer 344 rats is associated with impaired cardiovascular and behavioral adaptation to repeated restraint stress.

Fischer 344 (F344) rats are characterized by the hyper-reactive hypothalamic-pituitary-adrenal axis to stressful stimuli, while Lewis (LEW) rats are considered to be hypo-reactive. We studied stress-induced cardiovascular, neuroendocrine, and behavioral responses of adult male F344 and LEW rats subjected to the single (120 min) or the repeated restraint stress (daily 120 min for 1 week). Mean arterial pressure (MAP) and heart rate (HR) were measured in the restrained rats (n = 7-8 for each group) via a catheter inserted into the femoral artery. Baroreceptor sensitivity was evaluated using NO donor sodium nitroprusside and α1-adrenoceptor agonist phenylephrine. The plasma levels of adrenocorticotropic hormone (ACTH), corticosterone, aldosterone, and adrenaline were determined before and during the restraint. Exploratory behavior was tested in open field test. F344 rats exerted the augmented stress-induced increase in plasma ACTH, corticosterone, and adrenaline as well as the impaired endocrine adaptation to the repeated stress compared to LEW rats. F344 rats exhibited higher MAP than LEW rats during single and repeated restraint. Moreover, repeatedly restrained F344 showed elevated HR and diminished baroreflex sensitivity. F344 and LEW rats exhibited similar total locomotor activity and the time spent in the center of open field arena, both parameters being decreased by the repeated restraint. The detailed analysis revealed altered pattern of locomotor behavior in F344 rats subjected to repeated restraint. In conclusion, F344 rats showed the impaired endocrine adaptation that resulted in allostatic overload, which might contribute to the impaired cardiovascular and behavioral adaptation to chronic stress observed in this strain. Lay summary F344 rats, characterized by HPA axis hyper-reactivity, exhibited higher blood pressure during restraint than LEW rats. Moreover, repeatedly restrained F344 rats showed elevated heart rate and impaired baroreflex sensitivity. It can be concluded that a poor adaptation to the repeated stress in F344 rats is not only limited to the neuroendocrine response but also has important cardiovascular consequences.

Renoprotection Provided by Additional Diuretic Treatment in Partially Nephrectomized Ren-2 Transgenic Rats Subjected to the Combined RAS and ETA Blockade.

OBJECTIVE: Our previous study in heterozygous Ren-2 transgenic rats (TGR) demonstrated that long-term treatment with endothelin receptor A (ETA) blocker atrasentan added to the renin-angiotensin system (RAS) blockade had renoprotective effects in a model of chronic kidney disease (CKD) induced by partial nephrectomy. Since ETA blockade is known to cause edema, we were interested whether diuretic treatment added to this therapy would be beneficial. DESIGN AND METHODS: Partial nephrectomy (NX) was performed at the age of 3 months in TGR rats which were subjected to: (i) RAS blockade alone (angiotensin receptor blocker losartan and angiotensin converting enzyme inhibitor trandolapril), (ii) combined RAS (losartan and trandolapril) and ETA receptor blockade (atrasentan), or (iii) diuretic (hydrochlorothiazide) added to the combined RAS + ETA blockade for 50 weeks following NX. RESULTS: At the end of the study systolic blood pressure and cardiac hypertrophy were similarly decreased in all treated groups. Survival was significantly improved by ETA receptor blockade added to RAS blockade with no further effects of diuretic treatment. However, additional diuretic treatment combined with RAS + ETA blockade decreased body weight and had beneficial renoprotective effects - reductions of both kidney weight and kidney damage markers. Proteinuria gradually increased in rats treated with RAS blockade alone, while it was substantially lowered by additional ETA blockade. In rats treated with additional diuretic, proteinuria was progressively reduced throughout the experiment. CONCLUSION: A diuretic added to the combined RAS and ETA blockade has late renoprotective effects in CKD induced by partial nephrectomy in Ren-2 transgenic rats. The diuretic improved: renal function (evaluated as proteinuria and creatinine clearance), renal morphology (kidney mass, glomerular volume), and histological markers of kidney damage (glomerulosclerosis index, tubulointerstitial injury).

Sympathectomy-induced blood pressure reduction in adult normotensive and hypertensive rats is counteracted by enhanced cardiovascular sensitivity to vasoconstrictors.

The effect of chemical sympathectomy on cardiovascular parameters and the compensatory role of adrenal hormones, the renin-angiotensin system, and cardiovascular sensitivity to vasoconstrictors were studied in spontaneously hypertensive rats (SHRs) and normotensive Wistar-Kyoto (WKY) rats. Sympathectomy was induced in 20-week-old rats by daily intraperitoneal guanethidine administration (30 mg/kg b.w.) for 2 weeks. Basal blood pressure (BP), heart rate (HR), and restraint stress-induced cardiovascular changes were measured by radiotelemetry. The BP response to catecholamines was determined in rats with implanted catheters. Sympathectomy decreased BP only transiently, and after 14-day guanethidine treatment, BP returned to basal values in both strains. Sympathectomy permanently lowered HR, improved baroreflex sensitivity, and decreased the low-frequency domain of systolic blood pressure variability (a marker of vascular sympathetic activity). Guanethidine also attenuated the BP and HR responses to restraint stress. On the other hand, the BP response to catecholamines was augmented in sympathectomized rats, and this was not due to the de novo synthesis of vascular adrenergic receptors. Sympathectomy caused adrenal enlargement, enhanced the expression of adrenal catecholamine biosynthetic enzymes, and elevated plasma adrenaline levels in both strains, especially in WKY rats. Guanethidine also increased the plasma levels of aldosterone and corticosterone in WKY rats only. In conclusion, sympathectomy produced a transient decrease in BP, a chronic decrease in HR and improvement in baroreflex sensitivity. The effect of sympathectomy on BP was counteracted by increased vascular sensitivity to catecholamines in WKY rats and SHRs and/or by the enhanced secretion of adrenal hormones, which was more pronounced in WKY rats.

Role of angiotensin II in chronic blood pressure control of heterozygous Ren-2 transgenic rats: Peripheral vasoconstriction versus central sympathoexcitation.

Our previous studies demonstrated that chronic systemic blockade of renin-angiotensin system (RAS) lowered blood pressure (BP) of Ren-2 transgenic rats (TGR) by the attenuation of both angiotensin II-dependent and sympathetic vasoconstriction. Since systemic RAS blockade also inhibits brain RAS, we were interested which effects on these two types of vasoconstriction will have the central RAS blockade in hypertensive TGR rats. Adult male heterozygous TGR rats and their Hannover Sprague Dawley (HanSD) controls were subjected to chronic systemic or intracerebroventricular administration of either angiotensin type 1 receptor blocker losartan or direct renin inhibitor aliskiren for 4 weeks. Additional groups of TGR and HanSD rats were used for the evaluation of acute peripheral and brain effects of angiotensin II. Both chronic systemic and intracerebroventricular administrations of losartan or aliskiren normalized BP of TGR animals. BP effect of brain RAS blockade was based solely on the reduced sympathetic vasoconstriction, while systemic RAS blockade attenuated both angiotensin II-dependent and sympathetic vasoconstriction. Surprisingly, neither peripheral nor central pressor effects of acute angiotensin II administration were enhanced in TGR compared to HanSD rats. In conclusion, sympathoinhibition represents the main mechanism of BP reduction in heterozygous TGR rats subjected to chronic brain or systemic RAS blockade, while peripheral attenuation of angiotensin II-dependent vasoconstriction during systemic RAS blockade is less important. Our data suggest that the participation of angiotensin II in BP control of adult heterozygous TGR rats is shifted from peripheral vasoconstriction to central sympathoexcitation. Similar mechanisms cannot be excluded in human essential hypertension.

Which sympathoadrenal abnormalities of adult spontaneously hypertensive rats can be traced to a prehypertensive stage?

Alterations of sympathoadrenal and sympathoneural systems have been suggested to be involved in the pathogenesis of hypertension in spontaneously hypertensive rats (SHR). To evaluate the ontogenetic changes of these systems, mRNA and protein expressions of catecholaminergic system genes were measured in adrenal glands and sympathetic ganglia, and the catecholamine levels were determined in adrenal glands, sympathetic ganglia and plasma of prehypertensive (4-week-old) and hypertensive (24-week-old) SHR. Vascular sympathetic innervation was visualized in the femoral artery by glyoxylic acid. In the adrenal glands of prehypertensive SHR, the expression of catecholamine biosynthetic enzymes Ddc, Dbh and Pnmt was lower than in aged-matched Wistar-Kyoto rats. In contrast, the adrenal content of dopamine, noradrenaline and adrenaline was higher in prehypertensive SHR (141%, 123% and 120% of Wistar-Kyoto rats, respectively, p < 0.01). In the adrenal glands of adult SHR, the expression of catecholamine biosynthetic enzymes Th, Ddc, Dbh and Pnmt was decreased along the amounts of dopamine and noradrenaline (50% and 38%, respectively, p < 0.001). The expression levels of Ddc and Dbh enzymes were also downregulated in the sympathetic ganglia of both prehypertensive and adult SHR. At both ages, the density of sympathetic innervation was twofold higher in SHR compared to Wistar-Kyoto rats (p < 0.001). In conclusion, adrenal catecholamine content was increased in prehypertensive SHR, whereas it was reduced in SHR with established hypertension. Surprisingly, downregulation of catecholamine biosynthetic enzymes was observed in both the adrenal medulla and sympathetic ganglia of SHR at both ages. Thus, this downregulation might be a compensatory mechanism that counteracts the vascular sympathetic hyperinnervation seen in SHR of both ages.

Exaggerated blood pressure response to fasudil or nifedipine in hypertensive Ren-2 transgenic rats: role of altered baroreflex.

Basal calcium sensitization is decreased in spontaneously hypertensive rats, although their blood pressure (BP) response to acute Rho-kinase inhibition is enhanced. Using fasudil (Rho-kinase inhibitor) or nifedipine (L-VDCC blocker), we evaluated the contribution of calcium sensitization and calcium entry to BP maintenance in hypertensive transgenic Ren-2 rats (TGR) focusing on the influence of major vasoactive systems and/or baroreflex efficiency on BP responses to these two drugs. Homozygous TGR and normotensive Hannover Sprague-Dawley (HanSD) control rats aged 5, 11, or 22 weeks were used. The acute BP-lowering effects of fasudil or nifedipine were studied in intact rats, nitric oxide-deficient L-NAME-pretreated rats and rats subjected to combined blockade of the renin-angiotensin system (RAS), sympathetic nervous system (SNS) and nitric oxide synthase (NOS). Fasudil- or nifedipine-induced BP reduction increased during hypertension development in TGR. By contrast, the nifedipine-induced BP response decreased, whereas the fasudil-induced BP response increased with age in HanSD controls. Our data indicated a major contribution of nifedipine-sensitive calcium entry and relative attenuation of calcium sensitization in hypertensive rats compared with normotensive controls. The BP responses to fasudil or nifedipine were enhanced by NOS inhibition and combined blockade in normotensive HanSD rats but not in hypertensive TGR. In conclusion, calcium  sensitization is attenuated by endogenous nitric oxide in normotensive HanSD rats but not in hypertensive TGR. Moreover, BP reduction elicited by acute Rho-kinase inhibition is partially compensated by enhanced sympathetic vasoconstriction. The decreased compensation in hypertensive rats with impaired baroreflex efficiency explains their greater BP response to fasudil than in normotensive animals.

Hemodynamic Response to Gabapentin in Conscious Spontaneously Hypertensive Rats.

Ligands of auxiliary α2δ subunit of voltage-dependent calcium channels (VDCCs) decrease elevated L-type VDCCs surface expression in arterial myocytes and arterial constriction in spontaneously hypertensive rats (SHR). However, their effect on blood pressure (BP) is unclear. In this study, we investigated the hemodynamic response to acute and chronic administration of gabapentin, a ligand of auxiliary α2δ subunit of VDCCs, in adult SHR with established neurogenic hypertension. The acute gabapentin administration lowered BP and heart rate more in conscious SHR than Wistar-Kyoto rats. Both nifedipine (L-type VDCCs blocker) and ω-conotoxin GVIA (N-type VDCCs blocker) also decreased BP more in SHR, but only gabapentin and ω-conotoxin GVIA abolished the nitroprusside-induced reflex tachycardia of baroreceptor-heart rate control. Hypotensive effect of gabapentin was accompanied by a reduction of (1) plasma norepinephrine level, (2) depressor response to ganglionic blocker pentolinium, (3) power of low frequency component of systolic BP variability, and (4) pressor response of mesenteric vascular bed to periarterial nerve stimulation, suggesting the decrease of peripheral sympathetic nerve transmission. Moreover, gabapentin effects on BP and baroreflex were absent in sympathectomized rats. In conclusion, the acute (but not chronic) administration of gabapentin lowered BP more in SHR than in Wistar-Kyoto rats. Besides the known L-type VDCCs involvement in the vascular effect of gabapentin, our data revealed the important role of N-type VDCCs in acute gabapentin effect on sympathetic control of BP. Gabapentin-induced changes of sympathetic nerve transmission indicated major hemodynamic mechanism of the acute response to this drug.

20-Hydroxyeicosatetraenoic acid antagonist attenuates the development of malignant hypertension and reverses it once established: a study in Cyp1a1-Ren-2 transgenic rats.

We hypothesized that vascular actions of 20-hydroxyeicosatetraenoic acid (20-HETE), the product of cytochrome P450 (CYP450)-dependent ω-hydroxylase, potentiate prohypertensive actions of angiotensin II (ANG II) in Cyp1a1-Ren-2 transgenic rats, a model of ANG II-dependent malignant hypertension. Therefore, we evaluated the antihypertensive effectiveness of 20-HETE receptor antagonist (AAA) in this model. Malignant hypertension was induced in Cyp1a1-Ren-2 transgenic rats by activation of the renin gene using indole-3-carbinol (I3C), a natural xenobiotic. Treatment with AAA was started either simultaneously with induction of hypertension or 10 days later, during established hypertension. Systolic blood pressure (SBP) was monitored by radiotelemetry, indices of renal and cardiac injury, and kidney ANG II levels were determined. In I3C-induced hypertensive rats, early AAA treatment reduced SBP elevation (to 161 ± 3 compared with 199 ± 3 mmHg in untreated I3C-induced rats), reduced albuminuria, glomerulosclerosis index, and cardiac hypertrophy (P<0.05 in all cases). Untreated I3C-induced rats showed augmented kidney ANG II (405 ± 14 compared with 52 ± 3 fmol/g in non-induced rats, P<0.05) which was markedly lowered by AAA treatment (72 ± 6 fmol/g). Remarkably, in TGR with established hypertension, AAA also decreased SBP (from 187 ± 4 to 158 ± 4 mmHg, P<0.05) and exhibited organoprotective effects in addition to marked suppression of kidney ANG II levels. In conclusion, 20-HETE antagonist attenuated the development and largely reversed the established ANG II-dependent malignant hypertension, likely via suppression of intrarenal ANG II levels. This suggests that intrarenal ANG II activation by 20-HETE is important in the pathophysiology of this hypertension form.

Erratum to "Contribution of Ca2+-Dependent Cl- Channels to Norepinephrine-Induced Contraction of Femoral Artery Is Replaced by Increasing EDCF Contribution during Ageing".

[This corrects the article DOI: 10.1155/2014/289361.].

Basal and Activated Calcium Sensitization Mediated by RhoA/Rho Kinase Pathway in Rats with Genetic and Salt Hypertension.

Calcium sensitization mediated by RhoA/Rho kinase pathway can be evaluated either in the absence (basal calcium sensitization) or in the presence of endogenous vasoconstrictor systems (activated calcium sensitization). Our aim was to compare basal and activated calcium sensitization in three forms of experimental hypertension with increased sympathetic tone and enhanced calcium entry-spontaneously hypertensive rats (SHR), heterozygous Ren-2 transgenic rats (TGR), and salt hypertensive Dahl rats. Activated calcium sensitization was determined as blood pressure reduction induced by acute administration of Rho kinase inhibitor fasudil in conscious rats with intact sympathetic nervous system (SNS) and renin-angiotensin system (RAS). Basal calcium sensitization was studied as fasudil-dependent difference in blood pressure response to calcium channel opener BAY K8644 in rats subjected to RAS and SNS blockade. Calcium sensitization was also estimated from reduced development of isolated artery contraction by Rho kinase inhibitor Y-27632. Activated calcium sensitization was enhanced in all three hypertensive models (due to the hyperactivity of vasoconstrictor systems). In contrast, basal calcium sensitization was reduced in SHR and TGR relative to their controls, whereas it was augmented in salt-sensitive Dahl rats relative to their salt-resistant controls. Similar differences in calcium sensitization were seen in femoral arteries of SHR and Dahl rats.

Altered contractile responses of arteries from spontaneously hypertensive rat: The role of endogenous mediators and membrane depolarization.

AIMS: The goal of our study was to reveal the important mechanism(s) responsible for the enhanced contractility of isolated arteries from animals suffering genetic hypertension. MAIN METHODS: Contractile force of endothelium-denuded arteries, modulated by various interventions, was measured by wire myography. KEY FINDINGS: Spontaneously hypertensive rat (SHR) and Wistar-Kyoto rat (WKY) arteries were stimulated by norepinephrine, increased extracellular K+ or tyramine. Strain difference was not observed in the contraction elicited by exogenous norepinephrine but SHR arteries responded more to tyramine (causing endogenous norepinephrine release from neuronal varicosities). K+-induced contraction was enhanced in SHR arteries, with no involvement of endogenous catecholamines. The α-adrenoceptor blockade lowered tyramine-induced contraction more in SHR arteries; similar effect was achieved by guanethidine-induced sympathectomy. Partial depolarization of WKY arteries by 20mM K+ enhanced its contraction to SHR level. The blockade of ß-adrenoceptors by propranolol or selective ß2-antagonist ICI-118,551 induced contraction of SHR endothelium-denuded arteries but was without significant effects on WKY arteries unless they were stimulated with K+. Both tyramine-induced and propranolol-induced contractions were attenuated by flupirtine and abolished by nifedipine. SIGNIFICANCE: The differences of SHR and WKY arteries were not related to vascular expression of α- and ß-adrenoceptors or G-proteins. Enhanced contractility of SHR arteries is related to both increased presence of endogenous norepinephrine in vascular wall and also to altered vascular smooth muscle membrane potential.

The Regulatory Role of Nuclear Factor Kappa B in the Heart of Hereditary Hypertriglyceridemic Rat.

Activation of nuclear factor-κB (NF-κB) by increased production of reactive oxygen species (ROS) might induce transcription and expression of different antioxidant enzymes and also of nitric oxide synthase (NOS) isoforms. Thus, we aimed at studying the effect of NF-κB inhibition, caused by JSH-23 (4-methyl-N (1)-(3-phenyl-propyl)-benzene-1,2-diamine) injection, on ROS and NO generation in hereditary hypertriglyceridemic (HTG) rats. 12-week-old, male Wistar and HTG rats were treated with JSH-23 (bolus, 10 µmol, i.v.). After one week, blood pressure (BP), superoxide dismutase (SOD) activity, SOD1, endothelial NOS (eNOS), and NF-κB (p65) protein expressions were higher in the heart of HTG rats compared to control rats. On the other hand, NOS activity was decreased. In HTG rats, JSH-23 treatment increased BP and heart conjugated dienes (CD) concentration (measured as the marker of tissue oxidative damage). Concomitantly, SOD activity together with SOD1 expression was decreased, while NOS activity and eNOS protein expression were increased significantly. In conclusion, NF-κB inhibition in HTG rats led to decreased ROS degradation by SOD followed by increased oxidative damage in the heart and BP elevation. In these conditions, increased NO generation may represent rather a counterregulatory mechanism activated by ROS. Nevertheless, this mechanism was not sufficient enough to compensate BP increase in HTG rats.