Effects of telmisartan, hydrochlorothiazide and their combination on blood pressure and renal excretory parameters in spontaneously hypertensive rats

Catechin Reduces Blood Pressure in Spontaneously Hypertensive Rats through Modulation of Arachidonic Acid Metabolism

(1) Background: hypertension affects approximately half of the adults in the United States (roughly 116 million). The cytochrome P450 (CYP)-mediated metabolism of arachidonic acid (AA) in the kidney has been found to play a major role in the pathogenesis of hypertension. This study examines the anti-hypertensive effect of the natural polyphenolic compound catechin (CAT) and investigates if it impacts the metabolism of AA in the kidney in comparison to captopril (CAP): a commonly used antihypertensive drug. (2) Methods: spontaneously hypertensive rats (SHR) were randomly divided into five groups. The treatment groups were administered CAT in drinking water at doses of 10 and 50 mg/kg. A positive control group received CAP at a dose of 10 mg/kg in the drinking water, and one group received both CAP and CAT at doses of 10 mg/kg and 50 mg/kg, respectively. Blood pressure was monitored weekly for five weeks. The activity of the two major enzymes involved in AA metabolism in the kidney, namely CYP4A and soluble epoxide hydrolase (sEH), were analyzed. (3) Results: CAP monotherapy was found to reduce blood pressure compared to the control untreated rats but did not demonstrate any effect on AA metabolism. Low- and high-dose CAT resisted the rise in blood pressure observed in the untreated SHR and significantly lowered blood pressure compared to the control group, respectively. Only rats treated with high CAT doses demonstrated significant inhibition of CYP4A and sEH enzyme activities. The coadministration of CAP and a high dose of CAT resulted in more pronounced blood pressure-lowering effects, but no more significant effects on AA metabolism were found compared to a high dose of CAT alone. (4) Conclusion: the modulation of AA metabolism in the kidney contributes, at least partially, to the blood pressure-lowering effect of CAT in SHR rats.

Transcriptomic Response in the Heart and Kidney to Different Types of Antihypertensive Drug Administration

Certain classes of antihypertensive drug may exert specific, blood pressure (BP)-independent protective effects on end-organ damages such as left ventricular hypertrophy, although the overall evidence has not been definitive in clinical trials. To unravel antihypertensive drug-induced gene expression changes that are potentially related to the amelioration of end-organ damages, we performed in vivo phenotypic evaluation and transcriptomic analysis on the heart and the kidney, with administration of antihypertensive drugs to two inbred strains (ie, hypertensive and normotensive) of rats. We chose 6 antihypertensive classes: enalapril (angiotensin-converting enzyme inhibitor), candesartan (angiotensin receptor blocker), hydrochlorothiazide (diuretics), amlodipine (calcium-channel blocker), carvedilol (vasodilating β-blocker), and hydralazine. In the tested rat strains, 4 of 6 drugs, including 2 renin-angiotensin system inhibitors, were effective for BP lowering, whereas the remaining 2 drugs were not. Besides BP lowering, there appeared to be some interdrug heterogeneity in phenotypic changes, such as suppressed body weight gain and body weight-adjusted heart weight reduction. For the transcriptomic response, a considerable number of genes showed prominent mRNA expression changes either in a BP-dependent or BP-independent manner with substantial diversity between the target organs. Noticeable changes of mRNA expression were induced particularly by renin-angiotensin system blockade, for example, for genes in the natriuretic peptide system (Nppb and Corin) in the heart and for those in the renin-angiotensin system/kallikrein-kinin system (Ren and rat Klk1 paralogs) and those related to calcium ion binding (Calb1 and Slc8a1) in the kidney. The research resources constructed here will help corroborate occasionally inconclusive evidence in clinical settings.

The Antihypertensive Effect of Quercetin in Young Spontaneously Hypertensive Rats; Role of Arachidonic Acid Metabolism

Hypertension affects almost 50% of the adult American population. Metabolites of arachidonic acid (AA) in the kidney play an important role in blood pressure regulation. The present study investigates the blood pressure-lowering potential of quercetin (QR), a naturally occurring polyphenol, and examines its correlation to the modulation of AA metabolism. Spontaneously hypertensive rats (SHR) were randomly divided into four groups. Treatment groups were administered QR in drinking water at concentrations of 10, 30, and 60 mg/L. Blood pressure was monitored at seven-day intervals. After a total of seven weeks of treatment, rats were killed and kidney tissues were collected to examine the activity of the two major enzymes involved in AA metabolism in the kidney, namely cytochrome P450 (CYP)4A and soluble epoxide hydrolase (sEH). Medium- and high-dose QR resisted the rise in blood pressure observed in the untreated SHR and significantly inhibited the activity of the CYP4A enzyme in renal cortical microsomes. The activity of the sEH enzyme in renal cortical cytosols was significantly inhibited only by the high QR dose. Our data not only demonstrate the antihypertensive effect of QR, but also provide a novel mechanism for its underlying cardioprotective properties.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

Neurovascular protection by telmisartan via reducing neuroinflammation in stroke-resistant spontaneously hypertensive rat brain after ischemic stroke

Telmisartan is a highly lipid-soluble angiotensin receptor blocker (ARB), which improves insulin sensitivity and reduces triglyceride levels and, thus, is called metabo-sartan. We examined the effects of telmisartan on neurovascular unit (N-acetylglucosamine oligomer [NAGO], collagen IV, and glial fibrillary acidic protein [GFAP]) and neuroinflammation (matrix metalloproteinase-9 [MMP-9] and inflammasome) in brain of stroke-resistant spontaneously hypertensive rat (SHR-SR). At 12 weeks of age, SHR-SR received transient middle cerebral artery occlusion (tMCAO) for 90 minutes and were divided into the following 3 groups, that is, vehicle group, low-dose telmisartan group (.3 mg/kg/d), and high-dose telmisartan group (3 mg/kg/d, postoral). Immunohistologic analysis at ages 6, 12, and 18 months showed progressive decreases of NAGO-positive endothelium and collagen IV-positive basement membrane and progressive increases of MMP-9-positive neurons, GFAP-positive astrocytes, and NLRP3-positive inflammasome in the cerebral cortex of vehicle group. Low-dose telmisartan reduced such changes without lowering blood pressure (BP), and high-dose telmisartan further improved such changes with lowering BP. The present findings suggest that a persistent hypertension caused a long-lasting inflammation after tMCAO in SHR-SR, which accelerated neurovascular disruption and emergent inflammasome, and that telmisartan greatly reduced such inflammation and protected the neurovascular unit via its pleiotropic effects in living hypertensive rat brain after ischemic stroke.

Effect of aliskiren, telmisartan and torsemide on cardiac dysfunction in l-nitro arginine methyl ester (l-NAME) induced hypertension in rats

Comparative study of cardio protective effect of aliskiren, telmisartan, and torsemide was carried out on l-nitro arginine methyl ester (l-NAME) induced hypertension in rats. The three drugs were given daily for 8 weeks simultaneously with l-NAME, with a control group for each drug and l-NAME. The degree of protection was assessed by measurement of systolic blood pressure and heart rate of animals every two weeks. At the end of the experimental period blood sampling was carried out for estimation of the level of NO2 (-)/NO3 (-). After which animals were sacrificed for heart dissection to detect collagen types I and III gene expression. Histopathological study was done to evaluate the extension of collagen deposits. The study revealed that the three drugs decreased blood pressure significantly compared to l-NAME. There was no significant difference between aliskiren and telmisartan in all measurements, but there was significant decrease in measurements of both aliskiren and telmisartan treated groups compared to torsemide starting from 4th week. There were insignificant changes in pulse rate values between the three l-NAME treated groups through the experiment. The three drugs significantly increased NO compared to l-NAME. Collagen I and III gene expression was significantly decreased by the three drugs but the highest percentage of inhibition was with telmisartan compared to l-NAME. Comparing the percentage inhibition of cardiac fibrosis, there was insignificant difference between telmisartan and torsemide treated groups while both were superior to aliskiren. In conclusion, further experimental studies are required to elucidate the potential cardioprotective mechanisms of aliskiren, telmisartan and torsemide, and assess their efficacy in treatment of heart failure.

Protective effect of telmisartan against progressive oxidative brain damage and synuclein phosphorylation in stroke-resistant spontaneously hypertensive rats

Previously, we reported that reactive oxygen species and signaling molecules of angiotensin II produced lipid peroxides, degenerated proteins, and injured DNA after cerebral ischemia in normotensive Wistar rats. Here, we investigated the long-term effect of the angiotensin II type I receptor blocker telmisartan on oxidative stress and hyperphosphorylated α-synuclein accumulation in stroke-resistant spontaneously hypertensive rats (SHR-SR). At the age of 3 months, SHR-SR were divided into 3 treatment groups: SHR-SR vehicle (SHR/Ve), SHR-SR low-dose telmisartan (.3 mg/kg/day) (SHR/low), and SHR-SR high-dose telmisartan (3 mg/kg/day) (SHR/high). Immunohistologic analyses were conducted in these groups and Wistar rats at the age of 6, 12, and 18 months. The SHR/Ve group demonstrated more progressive increase in advanced glycation end product (AGE)-, 4-hydroxy-2-nonenal (4-HNE)-, and phosphorylated α-synuclein (pSyn)-positive cells in the cerebral cortex and hippocampus compared with the Wistar group at 18 months. These expressions were reduced in the SHR/low group even without lowering blood pressure (BP), and expressions were dramatically suppressed in the SHR/high group with lowering of BP. These data suggest that persistent hypertension in SHR-SR strongly potentiate the markers of oxidative damage (AGEs and 4-HNE) and abnormal accumulation of pSyn, which were greatly suppressed by telmisartan in a dose-dependent manner without and with lowering of BP.

Pharmacokinetic-pharmacodynamic model of the antihypertensive interaction between telmisartan and hydrochlorothiazide in spontaneously hypertensive rats

OBJECTIVES

The goal of this study was to establish an integrated indirect response pharmacokinetic-pharmacodynamic model between telmisartan and hydrochlorothiazide to describe the antihypertensive interaction of these two drugs in spontaneously hypertensive rats.

METHODS

The blood pressure and plasma concentrations were measured by the tail-cuff test and high performance liquid chromatography-mass spectrometry, respectively, in spontaneously hypertensive rats. The current pharmacokinetic-pharmacodynamic model was based on the non-competitive pharmacodynamic interaction of two drugs acting on different physiological processes.

KEY FINDINGS

This model was able to acquire the temporal changes in drug concentration and blood pressure after administration of telmisartan or hydrochlorothiazide. The noncompetitive pharmacodynamic interaction assumed that the decreased blood pressure was attributed to the inhibitory function of telmisartan and stimulatory function of hydrochlorothiazide after administration of these two drugs. There was no significant pharmacokinetic change of telmisartan and hydrochlorothiazide in the different groups tested. The model predicted a synergistic pharmacodynamic interaction when telmisartan was administered in combination with hydrochlorothiazide, which was notably stronger than if the effects were additive.

CONCLUSION

The results showed that the presented pharmacokinetic-pharmacodynamic model was suitable for describing the antihypertensive interaction between telmisartan and hydrochlorothiazide.

Telmisartan/hydrochlorothiazide: a new fixed dose combination

Many patients with hypertension require two or more antihypertensive drugs with complementary mechanisms of action to lower their blood pressure and attain the therapeutic goals specified in internationally accepted guidelines. Yet, these latter guidelines offer the choice of fixed dose combinations as possible first-step therapies. The angiotensin II type 1-receptor antagonist telmisartan and the diuretic hydrochlorothiazide are two antihypertensive agents that have a well-recognized clinical efficacy. Their combination was shown in randomized, controlled trials to be more effective than each agent alone in lowering blood pressure, due to a dual and synergistic mechanism. Indeed, combining telmisartan with hydrochlorothiazide enhances the antihypertensive efficacy of telmisartan in almost two-thirds of hypertensive patients with mild-to-moderate hypertension. The pharmacokinetics and -dynamics of the combination are similar to monotherapy, and the addition of hydrochlorothiazide to telmisartan does not modify the excellent tolerability profile of the drug.

The pharmacokinetic-pharmacodynamic assessment of the hypotensive effect after coadministration of losartan and hydrochlorothiazide in spontaneously hypertensive rats

The interactive hypotensive effect of the combination treatment of losartan (LOS) and hydrochlorothiazide (HCTZ) was assessed using a pharmacokinetic-pharmacodynamic (PK-PD) model in spontaneously hypertensive rats. Intravenous coadministration of these drugs showed a prolonged and enhanced time-course of the hypotensive effect. A population PK analysis revealed the delayed elimination of LOS after coadministration. The time-course of the plasma renin activity (PRA) was measured, and showed a more continuative time profile after coadministration compared with the administration of LOS alone. An indirect response model was applied to describe the relationship between the PK of LOS and the PRA profile, and the E(max) value for the increase of the PRA by LOS was increased with the dose of HCTZ. Blood pressure was linked to the PRA through an effect compartment. The model successfully described the relationship between the doses of LOS and HCTZ and their interactive hypotensive effect. These results indicate that the interaction for blood pressure in the combination treatment of LOS and HCTZ can be estimated using the doses of the drugs and the PRA-mediated PK-PD model.

Telmisartan/Hydrochlorothiazide: a review of its use as fixed-dose combinations in essential hypertension

Fixed-dose combinations of telmisartan and hydrochlorothiazide (HCTZ) [Micardis Plus, Micardis HCT, PritorPlus] are available in many countries for the treatment of patients with essential hypertension. Combining the angiotensin II receptor antagonist (angiotensin II receptor blocker [ARB]) telmisartan with the thiazide diuretic HCTZ provides antihypertensive therapy with complementary mechanisms of action. In the US and EU, telmisartan/HCTZ is approved for patients whose hypertension is not adequately controlled with telmisartan monotherapy; US labelling for the fixed-dose combination also includes inadequate control of blood pressure (BP) with HCTZ monotherapy.The antihypertensive efficacy of once-daily telmisartan/HCTZ has been demonstrated in several large, randomized trials in patients with stages 1 and 2 hypertension. The addition of HCTZ to telmisartan achieved significant reductions in BP in nonresponders to telmisartan monotherapy, and the antihypertensive efficacy of telmisartan/HCTZ was similar to or significantly greater than that of various comparator agents. Moreover, in studies that used ambulatory BP monitoring, telmisartan/HCTZ provided consistent 24-hour BP reductions throughout morning, daytime and night-time periods. The BP-lowering efficacy over the entire 24-hour dose administration interval is consistent with the pharmacokinetic profile of telmisartan, which has the longest elimination half-life among currently available ARBs and a unique chemical structure. Adverse events with telmisartan/HCTZ in clinical trials were typically mild and transient, and no unexpected events occurred that had not been previously reported with either telmisartan or HCTZ. Extensive tolerability data are available for telmisartan, in particular from the ONTARGET study, the largest clinical outcomes trial with an ARB. As such, fixed-dose combinations of telmisartan/HCTZ provide an effective, rational and generally well tolerated treatment option for the management of patients with hypertension.

Superiority of combination of thiazide with angiotensin-converting enzyme inhibitor or AT1-receptor blocker over thiazide alone on renoprotection inl-NAME/SHR

The renal and glomerular dynamic effects of combining thiazide and angiotensin antagonists have not been reported. The present study was designed to examine the effects of hydrochlorothiazide (HCTZ) alone or in combination with an angiotensin-converting enzyme inhibitor or ANG II type 1-receptor blocker on renal hemodynamics, glomerular dynamics, renal function, and renal histopathology in the Nω-nitro-l-arginine methyl ester-treated spontaneously hypertensive rat (l-NAME/SHR) model. HCTZ (80 mg·kg−1·day−1) alone or in combination with enalapril (30 mg·kg−1·day−1) or losartan (30 mg·kg−1·day−1) or enalapril (15 mg·kg−1·day−1) plus losartan (15 mg·kg−1·day−1) was administered to l-NAME/SHR (5.0 ± 0.10 mg·kg−1·day−1) for 3 wk. Mean arterial pressure, total peripheral resistance, renal plasma flow, glomerular filtration rate, glomerular hydrostatic pressure, afferent and efferent glomerular arteriolar resistances, single nephron plasma flow, single nephron glomerular filtration rate, serum creatinine concentration, 24-h urinary protein excretion, and glomerular and arteriolar injury scores were determined. HCTZ reduced mean arterial pressure, total peripheral resistance, glomerular hydrostatic pressure, and afferent and efferent glomerular arteriolar resistances ( P < 0.05, at least) but slightly increased renal plasma flow and single nephron plasma flow associated with reduced serum creatinine concentration, urinary protein excretion, and arteriolar injury score compared with l-NAME/SHR control. However, the combination of enalapril and/or losartan with HCTZ markedly improved each of these functions. These results demonstrated minor benefits of HCTZ monotherapy and a marked superiority of its combination with enalapril and/or losartan over HCTZ monotherapy on renoprotection in l-NAME/SHR, thereby providing strong evidence of their clinical benefits for hypertensive patients with renal functional impairment.

[Pharmacological and clinical profile of telmisartan, a selective angiotensin II type-1 receptor blocker]

Telmisartan (Micardis) is a potent, long-lasting, nonpeptide angiotensin II type-1 (AT(1)) receptor blocker (ARB) that is indicated for the treatment of essential hypertension. In receptor binding studies, telmisartan showed a high affinity and selectivity for the human AT(1) receptors compared with AT(2) receptors and a slower dissociation rate from the human AT(1) receptor than those of ARBs. In isolated aorta rings, telmisartan was shown to be an insurmountable antagonist of AII-induced contractions. The inhibitory effects of telmisartan on AII-induced contraction persisted even after wash-out procedures. In animal models such as spontaneous hypertension rats and renovascular hypertensive rats, telmisartan produced the consistent reduction of blood pressure. Furthermore, there were no rebound phenomenon and no tolerance to the drug developed in the repeated oral administration. Telmisartan has a longer terminal elimination half-life (about 24 h) than the other ARBs. In patients with mild-moderate hypertension, trough/peak ratios for telmisartan were above 80%. In Japanese patients with mild-moderate hypertension, telmisartan produced a significant reduction in blood pressure (effective rate: 76.0%) with a good safety profile. Therefore, telmisartan is expected to be effective in the treatment of hypertension, producing sustained 24-h blood pressure control.

Telmisartan/hydrochlorothiazide: in the treatment of essential hypertension

Oral telmisartan/hydrochlorothiazide (HCTZ) combines two antihypertensive agents, a selective angiotensin II receptor antagonist with a long half-life and once-daily administration, and a thiazide diuretic. In two large, 8-week, double-blind trials, patients with hypertension unresponsive to monotherapy who received combined telmisartan/HCTZ 80/12.5 or 40/12.5 mg/day, achieved significantly larger reductions in diastolic and systolic blood pressure (BP), than recipients of continued telmisartan monotherapy (p < 0.05 for all). Compliance with telmisartan/HCTZ 80/12.5 mg/day was 98.9%. In patients with hypertension, telmisartan/HCTZ resulted in similar BP reductions to oral enalapril/HCTZ and atenolol/HCTZ in 26-week double-blind trials and greater reductions than oral losartan/HCTZ 50/12.5 mg/day in a 6-week randomised open-label trial (p < 0.001). Up to one-third of patients with hypertension initially responsive to telmisartan 40 or 80 mg/day in a 4-year study required the eventual addition of HCTZ 12.5 or 25 mg/day and/or another agent to maintain BP control. BP was controlled in about 75% of these by adding only HCTZ. In clinical trials of up to 4 years, including elderly patients, telmisartan/HCTZ had similar tolerability to placebo, with few reports of hypokalaemia. Most adverse events were mild to moderate.