Effects of low-dose ketanserin on blood pressure variability, baroreflex sensitivity and end-organ damage in spontaneously hypertensive rats

Arterial Baroreflex Dysfunction Promotes Neuroinflammation by Activating the Platelet CD40L/Nuclear Factor Kappa B Signaling Pathway in Microglia and Astrocytes

Arterial baroreflex (ABR) dysfunction has previously been associated with neuroinflammation, the most common pathological feature of neurological disorders. However, the mechanisms mediating ABR dysfunction-induced neuroinflammation are not fully understood. In the present study, we investigated the role of platelet CD40 ligand (CD40L) in neuroinflammation in an in vivo model of ABR dysfunction, and microglia and astrocyte activation in vitro. ABR dysfunction was induced in Sprague‒Dawley rats by sinoaortic denervation (SAD). We used ELSA and immunofluorescence to assess the effect of platelet CD40L on glial cell polarization and the secretion of inflammatory factors. By flow cytometry, we found that rats subjected to SAD showed a high level of platelet microaggregation and upregulation of CD40L on the platelet surface. The promotion of platelet invasion and accumulation was also observed in the brain tissues of rats subjected to SAD. In the animal model and cultured N9 microglia/C6 astrocytoma cells, platelet CD40L overexpression promoted neuroinflammation and activated M1 microglia, A1 astrocytes, and the nuclear factor kappa B (NFκB) signaling pathway. These effects were partially blocked by inhibiting platelet activity with clopidogrel or inhibiting CD40L-mediated signaling. Our results suggest that during ABR dysfunction, CD40L signaling in platelets converts microglia to the M1 phenotype and astrocytes to the A1 phenotype, activating NFκB and resulting in neuroinflammation. Thus, our study provides a novel understanding of the pathogenesis of ABR dysfunction-induced neuroinflammation and indicates that targeting platelet CD40L is beneficial for treating central nervous system (CNS) disorders associated with ABR dysfunction.

Characteristic enhancement of blood pressure V-shaped waves in sinoaortic-denervated rats in a conscious and quiet state

A hemodynamic feature of chronic sinoaortic-denervated (SAD) rats is the increase in blood pressure variability (BPV) without significant changes in the average level of blood pressure (BP). The current study was designed to investigate the changes in BP V-shaped waves (V waves) in SAD rats. Sprague-Dawley (SD) rats were divided into 2 groups: SAD rats and sham-operated rats (n=13). Hemodynamics measurements were obtained in conscious, freely moving rats, four weeks after sinoaortic denervation or sham operation. V wave indices were evaluated in rats in both conscious and quiet states. Additionally, normal and high BPV was simulated by the production of V waves with different amplitudes. The results showed that the V wave amplitude was dramatically increased, with a significantly prolonged duration and reduced frequency in SAD rats. V wave BPV in SAD rats was significantly increased, though BP remained unchanged. The twenty-four hour BPV in all rats was positively correlated with amplitude, duration time and V wave BPV and negatively correlated with frequency. The systolic BP spectral powers in the low frequency range (0.38-0.45 Hz) were significantly reduced in the V waves of SAD rats. Moreover, there was a remarkable increase in mean BPV and a normal mean BP after simulating high BPV in SAD rats. These results suggest that enhancement of V waves might be a waveform character of BP in SAD rats in both the conscious and quiet states. These types of V waves appear to be related to a depression of sympathetic regulation of BP induced by sinoaortic denervation.

Baroreflex deficiency aggravates atherosclerosis via α7 nicotinic acetylcholine receptor in mice

OBJECTIVE

Inflammation and oxidative stress play a key role in the initiation, propagation, and development of atherosclerosis. Arterial baroreflex (ABR) dysfunction induced by sinoaortic denervation (SAD) promoted the development of atherosclerosis in ApoE^-/- mice. The present work was designed to examine whether ABR deficiency affected inflammation and oxidative stress via α7 nicotinic acetylcholine receptor (α7nAChR) leading to the aggravation of atherosclerosis in mice.

METHODS AND RESULTS

ApoE^-/- mice were fed with a high-cholesterol diet for 6weeks and half of the mice received sinoaortic denervation that destroyed ABR. We studied the expression of vesicular acetylcholine transporter (VAChT), α7nAChR and levels of inflammatory response and oxidative stress. The results showed that baroreflex dysfunction could promote atherosclerosis, meanwhile, decrease the expression of VAChT and α7nAChR and significantly increase the levels of oxidative stress and inflammation in SAD mice. After treated with PNU-282987 (a selective α7nAChR agonist, 0.53mg/kg/day) for 6weeks in SAD and Sham mice, we found that PNU-282987 could attenuate atherosclerosis and significantly decreased oxidative stress and inflammation after SAD. In addition, α7nAChR^+/+ and α7nAChR^-/- mice fed with a high-cholesterol diet for 8weeks were co-treated with ketanserin (0.6mg/kg/day), a drug that can enhance baroreflex sensitivity (BRS). Ketanserin could alleviate atherosclerosis and markedly decrease oxidative stress and inflammation in α7nAChR^+/+ mice. But there were no effects in α7nAChR knockout mice.

CONCLUSIONS

Our results demonstrate that ABR dysfunction aggravates atherosclerosis in mice via the vagus-ACh-α7nAChR-inflammation and oxidative stress pathway.

Ketanserin improves cardiac performance after myocardial infarction in spontaneously hypertensive rats partially through restoration of baroreflex function

AIM

Baroreflex dysfunction is associated with a higher rate of sudden death after myocardial infarction (MI). Ketanserin enhances baroreflex function in rats. The present work was designed to examine whether ketanserin improves the post-MI cardiac function and to explore the possible mechanism involved.

METHODS

Spontaneously hypertensive rats (SHR) were treated with ketanserin (0.3 mg·kg(-1)·d(-1)). Two weeks later, blood pressure and baroreflex function were measured, followed by a ligation of the left coronary artery. The expressions of vesicular acetylcholine transporter (VAChT) and α7 nicotinic acetylcholine receptor (α7-nAChR) in ischemic myocardium, angiogenesis, cardiac function, and left ventricular (LV) remodeling were evaluated subsequently.

RESULTS

Ketanserin significantly improved baroreflex sensitivity (0.62±0.21 vs 0.34±0.12 ms/mmHg, P<0.01) and vagal tonic activity (heart rate changes in response to atropine, 54.8±16.2 vs 37.6±13.4 bpm, P<0.01) without affecting the blood pressure or basic heart rate in SHR. Treatment of SHR with ketanserin prominently improved cardiac function and alleviated LV remodeling, as reflected by increases in the ejection fraction, fractional shortening, and LV systolic pressure as well as decreases in LV internal diameter and LV relative weight. The capillary density, vascular endothelial growth factor expression, and blood flow in the ischemic myocardium were significantly higher in the ketanserin-treated group. In addition, ketanserin markedly increased the expression of VAChT and α7-nAChR in ischemic myocardium.

CONCLUSION

Ketanserin improved post-MI cardiac function and angiogenesis in ischemic myocardium. The findings provide a mechanistic basis for restoring baroreflex function using ketanserin in the treatment of MI.

Role of serotonin 5-HT2A receptors in the development of cardiac hypertrophy in response to aortic constriction in mice

Serotonin, in addition to its fundamental role as a neurotransmitter, plays a critical role in the cardiovascular system, where it is thought to be involved in the development of cardiac hypertrophy and failure. Indeed, we recently found that mice with deletion of monoamine oxidase A had enhanced levels of blood and cardiac 5-HT, which contributed to exacerbation of hypertrophy in a model of experimental pressure overload. 5-HT2A receptors are expressed in the heart and mediate a hypertrophic response to 5-HT in cardiac cells. However, their role in cardiac remodeling in vivo and the signaling pathways associated are not well understood. In the present study, we evaluated the effect of a selective 5-HT2A receptor antagonist, M100907, on the development of cardiac hypertrophy induced by transverse aortic constriction (TAC). Cardiac 5-HT2A receptor expression was transiently increased after TAC, and was recapitulated in cardiomyocytes, as observed with 5-HT2A in situ labeling by immunohistochemistry. Selective blockade of 5-HT2A receptors prevented the development of cardiac hypertrophy, as measured by echocardiography, cardiomyocyte area and heart weight-to-body weight ratio. Interestingly, activation of calmodulin kinase (CamKII), which is a core mechanism in cardiac hypertrophy, was reduced in cardiac samples from M100907-treated TAC mice compared to vehicle-treated mice. In addition, phosphorylation of histone deacetylase 4 (HDAC4), a downstream partner of CamKII was significantly diminished in M100907-treated TAC mice. Thus, our results show that selective blockade of 5-HT2A receptors has beneficial effect in the development of cardiac hypertrophy through inhibition of the CamKII/HDAC4 pathway.

Effects of ketanserin on endotoxic shock and baroreflex function in rodents

BACKGROUND

Ketanserin, a 5-hydroxytryptamine receptor antagonist, is clinically used as an antihypertensive agent and could enhance baroreflex function. The present work tested the hypothesis that restoration of baroreflex function is an effective treatment for lipopolysaccharide (LPS)-induced shock.

METHODS

Kunming mice were injected with LPS (30 mg/kg; intraperitoneal) to induce endotoxic shock. Ketanserin (0.3, 1, 3, or 10 mg/kg; intraperitoneal) was administered immediately after LPS injection. Survival time was monitored, and serum cytokines were analyzed after the onset of LPS. Effects of ketanserin were also examined in IL-10-deficient mice and mice with sinoaortic denervation. Finally, effects of ketanserin on blood pressure, heart rate, and baroreflex sensitivity were examined in Wistar-Kyoto (WKY) rats with endotoxic shock.

RESULTS

Ketanserin significantly increased survival time and decreased serum levels of tumor necrosis factor α and interleukin (IL) 1β in mice with endotoxic shock. At a dose of 10 mg/kg, ketanserin also significantly increased serum IL-10 concentration. The antishock effect of ketanserin was also apparent in IL-10-knockout mice. In mice with sinoaortic denervation, however, ketanserin had little antishock effects. In WKY rats, ketanserin significantly prevented the baroreflex impairment induced by LPS and prolonged the survival time.

CONCLUSIONS

Ketanserin could ameliorate endotoxic shock by restoring baroreflex function.

Ketanserin-induced baroreflex enhancement in spontaneously hypertensive rats depends on central 5-HT(2A) receptors

1. Ketanserin may influence baroreflex function by blocking 5-HT(2A) receptors and/or alpha(1)-adrenoceptors through central and/or peripheral mechanisms. 2. In the present study, we tested the hypothesis that the baroreflex sensitivity (BRS)-enhancing effects of ketanserin are mediated by central 5-HT(2A) receptors in spontaneously hypertensive rats (SHR). 3. Using a conjugate of a monoclonal antibody to the serotonin reuptake transporter (SERT) and the toxin saporin (anti-SERT-SAP), which specifically eliminates the neurons that express SERT, the effects of ketanserin (0.3 and 3.0 mg/kg, i.g.) on BRS, blood pressure (BP), heart period (HP) and blood pressure variability (BPV) were compared between conscious intact SHR and SHR pretreated with anti-SERT-SAP. 4. Immunochemistry showed that, 2 weeks after intracerebroventricular injection of the toxin, 5-HT expression was strikingly attenuated in the brain, whereas values of BRS, BPV and BP were similar to those in the sham group. In intact SHR, 0.3 mg/kg ketanserin significantly improved BRS (191% control) and reduced BPV without affecting BP; at 3.0 mg/kg, ketanserin significantly increased BRS (197% control) and decreased BPV and BP. In toxin-pretreated SHR, only the high dose of ketanserin improved BRS (132% control), neither of the ketanserin doses reduced BPV, but both significantly decreased BP. 5. We conclude that the BRS-enhancing effects of ketanserin are mediated largely by central 5-HT(2A) receptors, whereas the antihypertensive effect of ketanserin persists even after destruction of serotonergic neurons in the central nervous system.

Inhibition of Rho-kinase attenuates nephrosclerosis and improves survival in salt-loaded spontaneously hypertensive stroke-prone rats

OBJECTIVES

We examined whether the Rho/Rho-kinase pathway is involved in the pathogenesis of nephrosclerosis in severely hypertensive rats and assessed the effects of long-term treatment with a Rho-kinase inhibitor, fasudil, on kidney function, histological findings, gene expressions, and survival. We also attempted to elucidate the mechanisms involved.

METHODS

We studied the following four groups: control Wistar-Kyoto rats (WKY), untreated salt-loaded spontaneously hypertensive stroke-prone rats (SHR-SP), low-dose fasudil (15 mg/kg per day)-treated SHR-SP, and high-dose fasudil (30 mg/kg per day)-treated SHR-SP. After 8 weeks' treatment, the effects of fasudil were examined.

RESULTS

Untreated SHR-SP were characterized by increased blood pressure without circadian variation, decreased kidney function, abnormal renal morphological findings, and increased messenger RNA expression levels of transforming growth factor beta, collagen I, collagen III, p40phox, p47phox, plasminogen activator inhibitor 1, and intracellular adhesion molecule 1 in the renal cortex, compared with WKY. Long-term high-dose fasudil treatment significantly improved renal function (serum creatinine -32%, creatine clearance +39%), proteinuria (-92%) and histological findings (glomerular injury score -57%, arteriolar injury score -55%, fibrous area -40%, ED-1-positive cells -43%) without changing blood pressure or circadian variation, compared with untreated SHR-SP. In addition, fasudil significantly improved increased mRNA expression levels in the renal cortex. Furthermore, high-dose fasudil significantly prolonged survival time compared with untreated SHR-SP (P < 0.01). Low-dose fasudil treatment improved these variables slightly, but did not affect most significantly.

CONCLUSION

The Rho/Rho-kinase pathway participates in the pathogenesis of nephrosclerosis in SHR-SP independently of blood pressure-lowering activity, partly by upregulation of the gene expressions of extracellular matrix, oxidative stress, adhesion molecules, and antifibrinolysis.

Treatment of hypertension based on measurement of blood pressure variability: lessons from animal studies

PURPOSE OF REVIEW

Blood pressure variability, a quantitative index for the spontaneous variation in blood pressure, has been proposed as a risk factor for end-organ damage and to determine the efficacy of hypertension treatment.

RECENT FINDINGS

Animal studies indicate that blood pressure variability is as important as blood pressure level in determining end-organ damage, and that high blood pressure variability is associated with end-organ damage, including myocardial lesions, aortic hypertrophy, vascular remodeling and renal damage. Although the organ damage induced by high blood pressure variability was similar to that induced by hypertension, comparative studies in sinoaortic-denervated and spontaneously hypertensive rats revealed that aortic hypertrophy is a sensitive index of high blood pressure variability, and left ventricular hypertrophy is a sensitive index of high blood pressure level. The possible mechanisms for high blood pressure variability-induced end-organ damage include: direct endothelial lesions, renin-angiotensin system activation, inflammation initiation and cardiomyocyte apoptosis augmentation. Blood pressure variability reduction contributes importantly to the organ-protective effect of some antihypertensive drugs.

SUMMARY

Although animal studies suggest some advantages in blood pressure variability measurements, clinical trials are necessary before the widespread use of blood pressure variability as a predictor of hypertensive organ damage and a new strategy for the treatment of hypertension.

Blood pressure variability is more important than blood pressure level in determination of end-organ damage in rats

OBJECTIVE

This study was designed to determine how important a novel risk factor of elevated blood pressure variability (BPV) is in the determination of end-organ damage by comparison with the classic risk factor of a high blood pressure (BP) level.

METHODS AND RESULTS

The effects of haemodynamics on cardiovascular morphology were evaluated by univariate and multivariate regression analysis in two different rat models with an enlarged distribution of haemodynamics. In male sham-operated and sinoaortic-denervated Wistar-Kyoto rats and spontaneously hypertensive rats (n = 34), BPV was more important than BP in cardiac and renal damage and aortic hypertrophy. BPV and BP had independent effects, explaining 59.4% of the variation in damage to these organs. In male (n = 44) and female (n = 46) F1 hybrids of Sprague-Dawley rats and spontaneously hypertensive rats, the greater importance of BPV than BP was further demonstrated in left ventricular hypertrophy, glomerular damage and aortic hypertrophy. The phenomenon was more evident in females than males for cardiovascular hypertrophy. BPV and BP or BPV alone had independent effects, explaining 46.9% (male) or 37.5% (female) of the variation in damage to these organs.

CONCLUSION

BPV is a more critical determinant than BP level for cardiac damage, renal lesions and aortic hypertrophy in rats, strongly suggesting the significance of BPV control for the protection of these organs.

Effects of nine antihypertensive drugs on blood pressure variability in sinoaortic-denervated rats

AIM

The present work was designed to investigate the effects of nine commonly used antihypertensive drugs on blood pressure (BP) and blood pressure variability (BPV) in conscious sinoaortic-denervated (SAD) rats.

METHODS

Seventy-two SAD rats were randomly divided into nine groups. They were respectively given nifedipine 3 mg/kg, nitrendipine 5 mg/kg, amlodipine 1 mg/kg, clonidine 10 mug/kg, prazosin 0.5 mg/kg, atenolol 20 mg/kg, telmisartan 20 mg/kg, hydrochlorothiazide 40 mg/kg or captopril 50 mg/kg. The drugs were given via a catheter previously implanted into the stomach. BP was recorded for 5 h from 1 h before drug administration to 4 h after drug administration in conscious, freely moving rats.

RESULTS

It was found that all these nine drugs significantly decreased BP in SAD rats. Six of these drugs (nifedipine, nitrendipine, amlodipine, clonidine, prazosin and atenolol) significantly decreased BPV in SAD rats, but the remaining three drugs did not. Clonidine and atenolol increased the heart period and the others did not. No drugs affected the heart period variability.

CONCLUSION

Among nine antihypertensive drugs from different classes, calcium antagonists and sympathetic inhibitors decreased BPV in SAD rats.

Effects of Long-Term Treatment with Candesartan on Hemodynamics and Organ Damage in Spontaneously Hypertensive Rats

This study was designed to investigate the effects of candesartan on blood pressure (BP) and blood pressure variability (BPV) reductions, baroreflex sensitivity (BRS) amelioration, and organ protection in spontaneously hypertensive rats (SHR).

METHODS

Studies were performed in two groups of SHR (n = 13 for control rats; and n = 20 for candesartan-treated rats) and one group of WKY rats (n = 13). Candesartan (3 mg /kg/d) was given in rat chow for 4 months. BP was then continuously recorded for 24 hours in conscious state. After the determination of BRS, rats were killed for organ-damage evaluation.

RESULTS

Long-term treatment with candesartan significantly reduced BP and BPV expressed by both standard deviation and variation coefficient of BP, enhanced BRS and produced obvious organ protection. Compared with BP level, BPV and BRS values showed a closer or similar relationship with organ-damage parameters in SHR. Multiple regression analysis showed that the decrease in left ventricular hypertrophy was most closely associated with the increase in BRS, whereas the decrease in aortic hypertrophy was most closely associated with the decrease in 24-hour systolic BPV, and the amelioration in renal lesions, with the increase in BRS and the decrease in 24-hour systolic BPV.

CONCLUSION

long-term treatment with candesartan results in organ protection in SHR. Besides BP reduction, the decrease in BPV and the restoration of BRS are significantly related to this organ protection.

Reduction of blood pressure variability: a new strategy for the treatment of hypertension

The main aims of the treatment of hypertension are to prevent end-organ damage (EOD) and to avoid consequent lethal complications associated with hypertension. Blood pressure level is a well-known determinant of EOD. However, recent studies suggest that blood pressure variability (BPV) is as important as blood pressure level in determining EOD. The reduction of BPV is an important contributory factor of the organ protection provided by some antihypertensive drugs. Thus, reduction of BPV might represent a new strategy for the treatment of hypertension.