Xiu-Juan Ma

Sodium tanshinone IIA sulfonate protects cardiomyocytes against oxidative stress-mediated apoptosis through inhibiting JNK activation.

Sodium tanshinone IIA sulfonate (STS) is a water-soluble derivative of tanshinone IIA, a well-known Chinese medicine for treating cardiovascular disorders. Cardiomyocyte apoptosis plays a major role in the development of cardiovascular diseases. The present study was designed to investigate the effects of STS on cardiomyocyte apoptosis induced by in vivo acute myocardial infarction (MI) in adult rats and by in vitro H2O2-treated neonatal rat ventricular myocytes. In MI rats, STS significantly reduced the infarct sizes, the blood lactate dehydrogenase (LDH) level, and the number of apoptotic cardiomyocytes in the infarcted hearts. In the in vitro study, STS reversed the decreased effect of cell viability induced by H2O2. In addition, STS also markedly inhibited H2O2-induced cardiomyocyte apoptosis. C-Jun N-terminal kinases/stress-activated protein kinases (JNKs/SAPKs) and p38 MAPK are classic oxidative stress-activated protein kinases. Our further mechanistic study revealed that increased JNK phosphorylation stimulated by H2O2 was abolished by STS treatment. In conclusion, inhibition of JNK activation plays a significant role in cardioprotective effects of STS.

Dysfunction of the Cholinergic Anti-Inflammatory Pathway Mediates Organ Damage in Hypertension

Inflammatory responses are associated with the genesis and progression of end-organ damage (EOD) in hypertension. A role for the &agr;7 nicotinic acetylcholine receptor (&agr;7nAChR) in inflammation has recently been identified. We tested the hypothesis that &agr;7nAChR dysfunction contributes to hypertensive EOD. In both spontaneously hypertensive rats (SHRs) and rats with abdominal aorta coarctation–induced hypertension, atropine-induced tachycardia was blunted compared with normotensive controls. Both models of hypertension were associated with deficits in expression of the vesicular acetylcholine transporter and the &agr;7nAChR in cardiovascular tissues. In hypertension induced by abdominal aorta coarctation, deficits in aortic vesicular acetylcholine transporter and &agr;7nAChR were present both above and below the coarctation site, indicating that they were independent of the level of arterial pressure itself. Hypertension in 40-week-old SHRs was associated with cardiac and aortic hypertrophy. Morphological abnormalities consistent with EOD, along with elevated tissue levels of proinflammatory cytokines (tumor necrosis factor-&agr;, interleukin-1&bgr;, and interleukin-6) were observed in the heart, kidney, and aorta. Chronic treatment of SHRs with the &agr;7nAChR agonist PNU-282987 relieved EOD and inhibited tissue levels of proinflammatory cytokines and activation of nuclear factor &kgr;B. Greater serum levels of proinflammatory cytokines and more severe damage in the heart, aorta, and kidney were seen in &agr;7nAChR−/− mice subjected to 2-kidney-1-clip surgery than in wild-type mice. A deficit in the cholinergic anti-inflammatory pathway appears to contribute to the pathogenesis of EOD in models of hypertension of varying etiology. This pathway may provide a new target for preventing cardiovascular disease resulting from hypertension.

Arterial Baroreflex: A Novel Target for Preventing Stroke in Rat Hypertension

Background and Purpose— Arterial baroreflex is one of the most important mechanisms in the regulation of cardiovascular activities. Arterial baroreflex function can be expressed as baroreflex sensitivity (BRS). The present study was designed to test 2 hypotheses: (1) BRS is a new independent predictor for the incidence of stroke in hypertension, and (2) restoration of BRS can prevent stroke in hypertension. Methods— First, 82 stroke-prone spontaneously hypertensive rats (SHR-SP) aged 28 to 30 weeks were used. After measuring blood pressure and BRS, the survival time was observed. Second, 12 SHR-SP aged 8 months were used. Blood pressure and BRS were determined separately before and after intragastric administration of ketanserin (0.3 and 3.0 mg/kg). Third, SHR-SP aged 5 months were treated with ketanserin for 12 weeks (0.3 mg and 3.0 mg/kg per day). At the end of the treatment, blood pressure and BRS were determined and the end-organ damage was evaluated. Last, SHR-SP aged 3 months were treated with ketanserin (0.3 and 3.0 mg/kg per day) for life and the survival time was recorded. Results— Stroke was significantly delayed in rats with high BRS than those with low BRS (time to 50% death was 1.47-fold longer than low BRS group; P<0.01). Ketanserin of 3.0 mg/kg per day decreased blood pressure and enhanced BRS, whereas 0.3 mg/kg per day only enhanced the BRS. Fatal stroke incidences were markedly reduced by treatment with both doses (P<0.0001 versus control group). Conclusions— The present study provides evidence that BRS is an independent predictor for stroke in hypertension. Restoration of BRS may be a new strategy for the prevention of stroke.

A Systematic Review of Angiotensin Receptor Blockers in Preventing Stroke

Background and Purpose— Angiotensin receptor blockers are widely used in patients at high risk of cardiocerebrovascular events. The aim of this meta-analysis was to investigate the effects of angiotensin receptor blockers on the risk of stroke. Methods— Electronic searches of MEDLINE, EMBASE, and the Cochrane central register of controlled trials were performed. A total of 20 randomized clinical trials with 108 286 patients reporting stroke were available for this clinical outcome analysis. Results— Angiotensin receptor blockers were associated with a significant reduction in the risk of stroke than placebo with an OR of 0.91 (0.84 to 0.98). Angiotensin receptor blockers were associated with no significant reduction in the risk of stroke compared with angiotensin-converting enzyme inhibitors (OR, 0.93; 0.84 to 1.03) and calcium antagonists (OR, 1.16; 0.91 to 1.48). Conclusions— Evidence of the benefit of angiotensin receptor blockers on the risk of stroke is provided when compared with placebo. There was no evidence of the benefit when comparing angiotensin receptor blockers with angiotensin-converting enzyme inhibitors and with calcium antagonists.

E-selectin deficiency attenuates brain ischemia in mice.

To determine whether E‐selectin deficiency can attenuate brain ischemia in a mouse model of focal cerebral ischemia.

Clonidine, moxonidine, folic acid, and mecobalamin improve baroreflex function in stroke-prone, spontaneously hypertensive rats

AbstractAim:To investigate the effect of clonidine, moxonidine, folic acid, and mecobalamin on arterial baroreflex (ABR) function in stroke-prone spontaneously hypertensive rats (SHR-SP) and the possible mechanisms involved.Methods:Eighty-one SHR-SP were divided into 7 groups. Four groups were designated for the intragastric (ig) administration of clonidine (1.0 and 10.0 μg/kg), moxonidine (0.1 and 1.0 mg/kg), folic acid (1.0 mg/kg), and mecobalamin (1.0 mg/kg). Three groups were for the intracerebroventricular (icv) injection of clonidine (4 μg/4 μL), moxonidine (5 μg/4 μL), and mecobalamin (20 μg/4 μL). Blood pressure (BP) was recorded in the conscious state for 30 min and baroreflex sensitivity (BRS) was determined respectively before and after drug administration.Results:Clonidine and moxonidine significantly decreased BP, prolonged the heart period (HP), and increased BRS when administered as either ig or icv injections. Both BP and HP were unchanged by ig folic acid or mecobalamin injection. However, BRS was significantly increased by both.Conclusion:Clonidine, moxonidine, folic acid, and mecobalamin improved impaired ABR function in SHR-SP. The central mechanism was involved in this effect of either clonidine or moxonidine. Mecobalamin improved ABR function through the peripheral mechanism.

Blood Pressure Reduction Combining Baroreflex Restoration for Stroke Prevention in Hypertension in Rats

Blood pressure reduction is an important and effective strategy in stroke prevention in hypertensives. Recently, we found that baroreflex restoration was also crucial in stroke prevention. The present work was designed to test the hypothesis that a combination of blood pressure reduction and baroreflex restoration may be a new strategy for stroke prevention. In Experiment 1, the effects of ketanserin (0.3, 1, 3, 10 mg/kg), amlodipine (0.3, 1, 2, 3 mg/kg) and their combination (1 + 0.3, 1 + 1, 1 + 2, 1 + 3 mg/kg) on blood pressure and baroreflex sensitivity (BRS) of stroke-prone spontaneously hypertensive rats (SHR-SP) were determined under conscious state. It was found that both amlodipine and ketanserin decreased blood pressure dose-dependently. Ketanserin enfanced BRS from a very small dose but amlodipine enfanced BRS only at largest dose used. At the dose of 1 + 2 mg/kg (ketanserin + amlodipine), the combination possessed the largest synergism on blood pressure reduction. In Experiments 2 and 3, SHR-SP and two-kidney, two-clip (2K2C) renovascular hypertensive rats received life-long treatments with ketanserin (1 mg/kg) and amlodipine (2 mg/kg) or their combination (0.5 + 1, 1 + 2, 2 + 4 mg/kg). The survival time was recorded and the brain lesion was examined. It was found that all kinds of treatments prolonged the survival time of SHR-SP and 2K2C rats. The combination possessed a significantly better effect on stroke prevention than mono-therapies. In conclusion, combination of blood pressure reduction and baroreflex restoration may be a new strategy for the prevention of stroke in hypertension.

Effects of allisartan, a new AT1 receptor blocker, on blood pressure and end-organ damage in hypertensive animals

AbstractAim:To investigate the effects of allisartan, a new angiotensin II type 1 (AT1) receptor antagonist, on blood pressure (BP) and end-organ damage (EOD) in hypertensive rats and dogs.Methods:First, a single dose of allisartan was given intragastrically to evaluate the BP reduction in spontaneously hypertensive rats (SHRs), two kidney-one clip (2K1C) renovascular hypertensive rats and dogs, and Beagle dogs with angiotensin II-induced hypertension. Second, allisartan was mixed in rat chow for long-term treatment. After 4 months of drug administration, rats were instrumented to determine BP and baroreflex sensitivity (BRS). Observation of morphologic changes was used to estimate EOD. Third, the acute toxicity of allisartan was compared with that of losartan in mice.Results:BP was significantly decreased after intragastric administration of allisartan in SHRs, 2K1C rats, 2K1C dogs and Beagle dogs with angiotensin II-induced hypertension. Compared with the control, SHRs that received long-term treatment with allisartan exhibited an improved BRS and organ protective effects. Mice who were administered allisartan experienced less acute toxicity than those treated with losartan.Conclusion:Allisartan is highly effective for BP reduction and organ protection with low toxicity.

NLRP3 inflammasome activation mediates radiation-induced pyroptosis in bone marrow-derived macrophages.

A limit to the clinical benefit of radiotherapy is not an incapacity to eliminate tumor cells but rather a limit on its capacity to do so without destroying normal tissue and inducing inflammation. Recent evidence reveals that the inflammasome is essential for mediating radiation-induced cell and tissue damage. In this study, using primary cultured bone marrow-derived macrophages (BMDM) and a mouse radiation model, we explored the role of NLRP3 inflammasome activation and the secondary pyroptosis underlying radiation-induced immune cell death. We observed an increasing proportion of pyroptosis and elevating Caspase-1 activation in 10 and 20 Gy radiation groups. Nlrp3 knock out significantly diminished the quantity of cleaved-Caspase-1 (p10) and IL-1β as well as the proportion of pyroptosis. Additionally, in vivo research shows that 9.5 Gy of radiation promotes Caspase-1 activation in marginal zone cells and induces death in mice, both of which can be significantly inhibited by knocking out Nlrp3. Thus, based on these findings, we conclude that the NLRP3 inflammasome activation mediates radiation-induced pyroptosis in BMDMs. Targeting NLRP3 inflammasome and pyroptosis may serve as effective strategies to diminish injury caused by radiation.

Synergism of telmisartan and amlodipine on blood pressure reduction and cardiorenal protection in hypertensive rats.

Aim: This study was designed to investigate the effects of telmisartan and amlodipine on reduction of blood pressure (BP), myocardial hypertrophy, and renal injury in hypertensive rats. Method: In acute experiments, the BP was measured in conscious freely moving rats. Spontaneously hypertensive rats were treated with intragastric administration of amlodipine (1, 2, 4 mg/kg), telmisartan (4, 8, 12, 16, 20 mg/kg), and their different combinations (4 + 4, 2 + 4, 4 + 8, 4 + 12, 1 + 4, 2 + 8, 4 + 16, 2 + 12, 1 + 8, 2 + 16, 2 + 20, 1 + 12, 1 + 16, 1 + 20 mg/kg). The probability sum test (q test) was used to evaluate the synergistic action on BP reduction. In two-kidney, one-clip rats, the effects of amlodipine (1 mg/kg), telmisartan (6 mg/kg) and their combination on BP reduction were observed. In the chronic study, spontaneously hypertensive rats were treated with amlodipine (1 mg/kg), telmisartan (6 mg/kg), and their combination for 4 months. Histopathologic examinations were performed after the determination of BP and BP variability. Results: There is a synergistic interaction between amlodipine and telmisartan on BP reduction. The optimal dose ratio was found at 1:6. The synergistic effect of this dose ratio (1:6) was also seen in two-kidney, one-clip rats. Long-term treatment with this combination results in a beneficial effect on the reduction of BP and BP variability. The end-organ damage, including myocardial hypertrophy, glomerular atrophy, and fibrosis, was significantly attenuated by this combination. Conclusion: The optimal dose ratio of amlodipine and telmisartan on BP was 1:6. This combination is beneficial for the BP and BP variability reduction and end-organ damage prevention.