Effects of low-dose ketanserin on atherosclerosis in rats and rabbits

Contribution of platelets to disruption of the blood-brain barrier during arterial baroreflex dysfunction

BACKGROUND

Arterial baroreflex dysfunction, like many other central nervous system disorders, involves disruption of the blood-brain barrier, but what causes such disruption in ABR dysfunction is unclear. Here we explored the potential role of platelets in this disruption.

METHODS

ABR dysfunction was induced in rats using sinoaortic denervation, and the effects on integrity of the blood-brain barrier were explored based on leakage of Evans blue or FITC-dextran, while the effects on expression of CD40L in platelets and of key proteins in microvascular endothelial cells were explored using immunohistochemistry, western blotting and enzyme-linked immunosorbent assay. Similar experiments were carried out in rat brain microvascular endothelial cell line, which we exposed to platelets taken from rats with ABR dysfunction.

RESULTS

Sinoaortic denervation permeabilized the blood-brain barrier and downregulated zonula occludens-1 and occludin in rat brain, while upregulating expression of CD40L on the surface of platelets and stimulating platelet aggregation. Similar effects of permeabilization and downregulation were observed in healthy rats that received platelets from animals with ABR dysfunction, and in rat brain microvascular endothelial cells, but only in the presence of lipopolysaccharide. These effects were associated with activation of NF-κB signaling and upregulation of matrix metalloprotease-9. These effects of platelets from animals with ABR dysfunction were partially blocked by neutralizing antibody against CD40L or the platelet inhibitor clopidogrel.

CONCLUSION

During ABR dysfunction, platelets may disrupt the blood-brain barrier when CD40L on their surface activates NF-kB signaling within cerebral microvascular endothelial cells, leading to upregulation of matrix metalloprotease-9. Our findings imply that targeting CD40L may be effective against cerebral diseases involving ABR dysfunction.

Inhibition of RAGE by FPS-ZM1 alleviates renal injury in spontaneously hypertensive rats

The current study was designed to examine the protection of RAGE-specific inhibitor FPS-ZM1 against renal injury in spontaneously hypertensive rats (SHR) and investigate the underlying mechanism. The adult male SHR were treated with FPS-ZM1 via oral gavages for 12 weeks, and age-matched male Wistar-Kyoto rats (WKY) were used as control. Treatment of SHR with FPS-ZM1 slightly reduced blood pressure, and significantly improved baroreflex sensitivity in SHR. Treatment of SHR with FPS-ZM1 improved renal function, evidenced by increased glomerular filtration rate and renal blood flow, and reduced plasma creatinine, blood urea nitrogen and urine albumin excretion rate. Histology results revealed that treatment of SHR with FPS-ZM1 alleviated renal injury and reduced tubulointerstitial fibrosis. Treatment of SHR with FPS-ZM1 suppressed activation of NF-κB and reduced expression of pro-inflammatory cytokines including Tnf, Il6, and Il1b. Treatment of SHR with FPS-ZM1 abated oxidative stress and downregulated mRNA levels of components of NADPH oxidase (Nox) including Cyba, Nox1, Nox2, Nox4 and Ncf1 in kidneys. In addition, treatment of SHR with FPS-ZM1 reduced renal AngII levels, downregulated mRNA expression of Ace and upregulated expression of Agtr2. In conclusion, treatment with FPS-ZM1 alleviated hypertension-related renal dysfunction, possibly by suppressing NF-κB-mediated inflammation, abating Nox-mediated oxidative stress, and improving local renal renin-angiotensin system (RAS).

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.

NADPH oxidase contributes to the left ventricular dysfunction induced by sinoaortic denervation in rats

The aim of this work was to investigate the role nicotinamide adenine dinucleotide phosphate (NADPH) oxidase on left ventricular dysfunction of rats submitted to sinoaortic denervation (SAD). Experiment 1: 8 weeks after SAD of rats, NADPH oxidase in left ventricles was assayed by Western blotting analysis. Experiment 2: Rats were subjected to SAD and received treatment with apocynin (an NADPH oxidase inhibitor, 30 mg/kg/day, intragastric administration) for 8 weeks; 8 weeks after SAD, Nox2 and Nox4 expressions and Rac1 activity of left ventricles were higher in SAD rats than those in sham-operated rats. Although treatment of SAD rats with apocynin did not affect blood pressure, blood pressure variability (BPV), and baroreflex function, it significantly attenuated left ventricular hypertrophy marked by reduced expression of atrial natriuretic factor and β-myosin heavy chain. Treatment of SAD rats with apocynin abated oxidative stress marked by reduced malondialdehyde formation and suppressed nuclear factor-kappa B (NFκB) activation; inflammation marked by reduced monocyte chemoattractant protein-1 expression and myeloperoxidase activity; attenuated endoplasmic reticulum stress marked by reduced expression of CCAAT-enhancer-binding protein homologous protein, chaperone-glucose-regulated protein 78, and X-box protein 1; and alleviated cardiac fibrosis marked by reduced mRNA levels of collagens I and III and transforming growth factor beta. In conclusion, exaggerated BPV induces chronic myocardial oxidative stress and thereby aggravates cardiac remodeling in rats. These data suggest a potential role of NADPH oxidases in the pathogenesis of cardiac dysfunction induced by exaggerated BPV.

Baroreflex and cerebral autoregulation are inversely correlated

BACKGROUND

The relative stability of cerebral blood flow is maintained by the baroreflex and cerebral autoregulation (CA). We assessed the relationship between baroreflex sensitivity (BRS) and CA in patients with atherosclerotic carotid stenosis or occlusion.

METHODS AND RESULTS

Patients referred for assessment of atherosclerotic unilateral >50% carotid stenosis or occlusion were included. Ten healthy volunteers served as a reference group. BRS was measured using the sequence method. CA was quantified by the correlation coefficient (Mx) between slow oscillations in mean arterial blood pressure and mean cerebral blood flow velocities from transcranial Doppler. Forty-five patients (M/F: 36/9), with a median age of 68 years (IQR:17) were included. Thirty-four patients had carotid stenosis, and 11 patients had carotid occlusion (asymptomatic: 31 patients; symptomatic: 14 patients). The median degree of carotid steno-occlusive disease was 90% (IQR:18). Both CA (P=0.02) and BRS (P<0.001) were impaired in patients as compared with healthy volunteers. CA and BRS were inversely and strongly correlated with each other in patients (rho=0.58, P<0.001) and in healthy volunteers (rho=0.939; P<0.001). Increasing BRS remained strongly associated with impaired CA on multivariate analysis (P=0.004).

CONCLUSIONS

There was an inverse correlation between CA and BRS in healthy volunteers and in patients with carotid stenosis or occlusion. This might be due to a relative increase in sympathetic drive associated with weak baroreflex enhancing cerebral vasomotor tone and CA.

Consumption of hydrogen-rich water alleviates renal injury in spontaneous hypertensive rats

In hypertensive animals and patients, oxidative stress represents the primary risk factor for progression of renal disease. Recently, it has been demonstrated that hydrogen, as a novel antioxidant, can selectively reduce hydroxyl radicals and peroxynitrite anion to exert therapeutic antioxidant activity. Herein, we investigated the protective effect of hydrogen-rich water (HW) against renal injury in spontaneously hypertensive rats (SHR). The 8-week-old male SHR and age-matched Wistar-Kyoto rats were randomized into HW-treated (1.3 ± 0.2 mg/l for 3 months, drinking) and vehicle-treated group. Although treatment with HW had no significant effect on blood pressure, it significantly ameliorated renal injury in SHR. Treatment with HW lowered reactive oxygen species formation, upregulated the activities of superoxide dismutase, glutathione peroxidase, glutathione-S-epoxide transferase, and catalase, and suppressed NADPH oxidase activity. Treatment with HW in SHR depressed pro-inflammatory cytokines expression including TNF-α, IL-6, IL-1β, and macrophage chemoattractant protein 1, which might be mediated by suppressing nuclear factor-κB activation. In addition, treatment with HW had protective effect on mitochondrial function including adenosine triphosphate formation and membrane integrity in SHR. In conclusion, consumption of HW is a promising strategy to alleviate renal injury as a supplement for anti-hypertensive therapy.

Activation of receptor for advanced glycation end products contributes to aortic remodeling and endothelial dysfunction in sinoaortic denervated rats

OBJECTIVE

The aim of present study was to test the hypothesis that activation of receptor for advanced glycation end products (RAGE) pathway contributes to aortic remodeling and endothelial dysfunction in sinoaortic denervated (SAD) rats.

METHODS AND RESULTS

Experiment 1: 8 weeks after sinoaortic denervation, aortas were removed for measurement of AGE/RAGE pathway. Sinoaortic denervation in rats resulted in enhanced activity of aldose reductase, reduced activity of glyoxalase 1, accumulation of methylglyoxal and AGE, and upregulated expression of RAGE in aortas. Experiment 2: 5 weeks after sinoaortic denervation, the rats received intraperitoneal injections of 500 μg soluble RAGE (sRAGE) daily for 3 weeks. Treatment of SAD rats with sRAGE attenuated aortic remodeling, marked by reduction in AW/length, wall thickness, proliferation of SMC, and collagen deposition, and improvement of endothelial function. Treatment of SAD rats with sRAGE abated aortic oxidative stress, marked by reduction in formation of malondialdehyde, reactive oxygen species, superoxide, peroxynitrite and 3-nitrotyrosine, and enhancement of ratio of GSH/GSSG. Treatment of SAD rats with sRAGE attenuated aortic mitochondrial dysfunction. Treatment of SAD rats with sRAGE suppressed aortic NFκB nuclear translocation and inflammation. Treatment of SAD rats with sRAGE restored aortic NO formation through upregulating eNOS and dimethylarginine dimethylaminohydrolase-2 and downregulating protein arginine methyltransferase-1.

CONCLUSION

Activated RAGE contributed to aortic remodeling and endothelial dysfunction in SAD rats, possibly via induction of oxidative stress and inflammation, impairment of mitochondrial function, and reduction in NO bioavailability.

Contribution of hydrogen sulfide and nitric oxide to exercise-induced attenuation of aortic remodeling and improvement of endothelial function in spontaneously hypertensive rats

It is well known that exercise training attenuates aortic remodeling and improves endothelial function in spontaneously hypertensive rats (SHR). However, the underlying molecular mechanism remains unclear. Hydrogen sulfide (H(2)S) and nitric oxide (NO), as two established physiologic messenger molecules, have important roles in the development of aortic remodeling and endothelial dysfunction in hypertensive animals and patients. In this work, it was found that exercise training had no significant effect on blood pressure, but effectively attenuated baroreflex dysfunction in SHR. Exercise training in SHR attenuated aortic remodeling and improved endothelium-mediated vascular relaxations of aortas in response to acetylcholine. Interestingly, exercise training in SHR restored plasma H(2)S levels and aortic H(2)S formation and enhanced levels of mRNA for cystathionine γ-lyase in aortas. Furthermore, exercise training in SHR resulted in augmentation of nitrite and nitrate (NOx) contents and reduction of asymmetric dimethylarginine contents of aortas, upregulation of dimethylarginine dimethylaminohydrolase 2, and phosphorylation of nitric oxide synthase 3, but had no significant effect on protein levels of NOS3. In addition, exercise training could effectively reduce malondialdehyde production and suppressed formation of O(2) (-), and OONO(-) in aortas of SHR through enhancing activities of superoxide dismutase and catalase, and suppressing NADPH oxidase activity. In conclusion, exercise training ameliorates aortic hypertrophy and endothelial dysfunction, possibly via restoring bioavailabilities of hydrogen sulfide and nitric oxide in SHR.

Chronic hydrogen-rich saline treatment reduces oxidative stress and attenuates left ventricular hypertrophy in spontaneous hypertensive rats

In hypertensive animals and patients, oxidative stress represents the primary risk factor for progression of left ventricular hypertrophy. Recently, it has been demonstrated that hydrogen, as a novel antioxidant, can selectively reduce hydroxyl radicals and peroxynitrite anion to exert therapeutic antioxidant activity. In the current study, we explored the effect of chronic treatment with hydrogen-rich saline (HRS) on left ventricular hypertrophy in spontaneously hypertensive rats (SHR). The 8-week-old male SHR and age-matched Wistar-Kyoto rats (WKY) were randomized into HRS-treated (6 ml/kg/day for 3 months, i.p.) and vehicle-treated groups. HRS treatment had no significant effect on blood pressure, but it effectively attenuated left ventricular hypertrophy in SHR. HRS treatment abated oxidative stress, restored the activity of antioxidant enzymes including GPx, GST, catalase, and SOD, suppressed NADPH oxidase activity and downregulated Nox2 and Nox4 expression in left ventricles of SHR. HRS treatment suppressed pro-inflammatory cytokines including IL-1β, IL-6, TNF-α, and MCP-1, and inhibited NF-κB activation through preventing IκBα degradation in left ventricles of SHR. HRS treatment preserved mitochondrial function through restoring electron transport chain enzyme activity, repressing ROS formation, and enhancing ATP production in left ventricles of SHR. Moreover, HRS treatment suppressed ACE expression and locally reduced angiotensin II generation in left ventricles of SHR. In conclusion, HRS treatment attenuates left ventricular hypertrophy through abating oxidative stress, suppressing inflammatory process, preserving mitochondrial function, in which suppression of HRS on angiotensin II in left ventricles locally might be involved.

Chronic hydrogen-rich saline treatment attenuates vascular dysfunction in spontaneous hypertensive rats

In hypertensive patients, increased oxidative stress is thought to be one important cause of vascular dysfunction. Recently, it has been suggested that hydrogen exerts a therapeutic antioxidant activity by selectively reducing hydroxyl radical and peroxynitrite, the most cytotoxic chemicals of reactive oxygen species (ROS). Herein, we investigated the protective effect of chronic treatment with hydrogen-rich saline (HRS) against vascular dysfunction in SHR and the underlying mechanism. The 8-week-old spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto rats (WKY) were randomized into HRS-treated (6ml/kg/day for 3 months, i.p.) and vehicle treated group. Treatment with HRS ameliorated vascular dysfunction including aortic hypertrophy and endothelial function in SHR. Treatment with HRS had no significant effect on blood pressure, but it significantly improved baroreflex function in SHR. Treatment with HRS abated oxidative stress, restored antioxidant enzymes including superoxide dismutase, glutathione peroxidase, and catalase, and suppressed NADPH oxidase. Furthermore, treatment with HRS depressed pro-inflammatory cytokines expression including IL-6 and IL-1β and suppressed NF-κB activation, restored mitochondrial function including ATP formation and membrane integrity. In addition, although treatment with HRS had no significant effect on nitric oxide amount in circulating or aorta, it suppressed endothelial nitric oxide synthase expression and upregulated dimethylarginine dimethylaminohydrolase 2 expression in SHR. In conclusion, treatment with HRS alleviates vascular dysfunction through abating oxidative stress, restoring baroreflex function, suppressing inflammation, preserving mitochondrial function, and enhancing nitric oxide bioavailability.