Serotonergic mechanisms in hypertension

Common Metabolites in Two Different Hypertensive Mouse Models: A Serum and Urine Metabolome Study

Recent metabolomics studies have identified a wide array of microbial metabolites and metabolite pathways that are significantly altered in hypertension. However, whether these metabolites play an active role in pathogenesis of hypertension or are altered because of this has yet to be determined. In the current study, we hypothesized that metabolite changes common between hypertension models may unify hypertension's pathophysiology with respect to metabolites. We utilized two common mouse models of experimental hypertension: L-arginine methyl ester hydrochloride (L-NAME)/high-salt-diet-induced hypertension (LSHTN) and angiotensin II induced hypertension (AHTN). To identify common metabolites that were altered across both models, we performed untargeted global metabolomics analysis in serum and urine and the resulting data were analyzed using MetaboAnalyst software and compared to control mice. A total of 41 serum metabolites were identified as being significantly altered in any hypertensive model compared to the controls. Of these compounds, 14 were commonly changed in both hypertensive groups, with 4 significantly increased and 10 significantly decreased. In the urine, six metabolites were significantly altered in any hypertensive group with respect to the control; however, none of them were common between the hypertensive groups. These findings demonstrate that a modest, but potentially important, number of serum metabolites are commonly altered between experimental hypertension models. Further studies of the newly identified metabolites from this untargeted metabolomics analysis may lead to a greater understanding of the association between gut dysbiosis and hypertension.

Electroencephalographical effects of sarpogrelate hydrochloride versus ticlopidine hydrochloride in elderly patients with peripheral atherosclerosis

The aim was to determine the efficacy of sarpogrelate (a selective 5-hydroxytryptamine-2-serotonergic receptor antagonist) on cerebrovascular function and mean blood pressure (mBP) in elderly patients (> 60 years old). Patients with peripheral circulatory disorders were studied using electroencephalogram (EEG) and mBP measurements before and after 2 years' treatment with either sarpogrelate (n = 31) or ticlopidine (n = 43). Ticlopidine had no significant effect on the whole brain. Sarpogrelate decreased the percentage of slow waves (%slow), but not significantly, and was associated with a smaller change in the percentage of slow waves (delta slow). In the anterior area, neither drug caused significant EEG changes. In the posterior area, sarpogrelate significantly decreased the %slow and increased the %alpha values, and was associated with a significantly higher delta alpha value than ticlopidine. The results suggest that sarpogrelate hydrochloride can suppress serotonin-induced pathological processes in peripheral circulatory disorders and may be recommended as an anti-platelet agent, even in elderly patients with subclinical arteriosclerosis.

A depressed myocardium

BACKGROUND

Venlafaxine is a potent neuronal serotonin and noradrenaline re-uptake inhibitor, and to a lesser extent an inhibitor of dopamine reuptake. Paroxetine is a potent selective inhibitor of serotonin reuptake.

CASE REPORT

A 27-year-old man ingested 1987.5 mg of venlafaxine and 360 mg of paroxetine. He subsequently developed systolic and diastolic hypertension, transient electrocardiographic abnormalities, and an area of persistent myocardial damage. He recovered from his overdose with his blood pressure and electrocardiogram returning to normal. The area of myocardial damage was documented on echocardiogram as an area of marked hypokinesia at the basal anterior septum. Despite the absence of confirming blood levels or the absolute exclusion of cocaine, this case indicates that venlafaxine and paroxetine have the potential for serious cardiotoxicity when taken in overdose.

Hypertension incidence is predicted by high levels of hopelessness in Finnish men

Recent studies have reported that hopelessness is an important factor in cardiovascular morbidity and mortality, including ischemic heart disease, acute myocardial infarction, and atherosclerotic progression. This study examined the relationship between hopelessness and incident hypertension in a population-based sample of 616 initially normotensive, middle-aged men from eastern Finland, an area with high rates of cardiovascular disease. Participants completed a medical examination and a series of psychological questionnaires at baseline and at the 4-year follow-up. Hopelessness was measured by 2 items assessing negative expectancy about the future and one's goals. A logistic regression model with adjustments for age, body mass index, baseline resting blood pressure, physical activity, smoking, alcohol consumption, education, parental history of hypertension, and self-reported depressive symptoms revealed that men reporting high levels of hopelessness at baseline were 3 times more likely to become hypertensive (systolic blood pressure > or =165 mm Hg and/or a diastolic blood pressure > or =95 mm Hg or confirmed use of antihypertensive medication) in the intervening 4 years than men who were not hopeless (odds ratio, 3.22; 95% confidence interval, 1. 56, 6.67). Men reporting moderate levels of hopelessness were not at a significantly increased risk of hypertension (odds ratio, 1.27; 95% confidence interval, 0.79, 2.07). This is the first study to identify a significant relationship between hopelessness and incident hypertension. Research is needed to explore the neuroendocrine and central nervous system mechanisms underlying this association.

Serotonin: Ubiquitous Neuromodulator in the Failing Heart

Serotonin exhibits various cardiovascular effects and evidence of its role in various cardiovascular disorders is emerging. Serotonin levels in whole blood and the platelet serotonin uptake were significantly increased in patients with heart failure compared to control subjects. However, the intraplatelet serotonin content was not significantly different in the two groups. We conclude that serotonin is involved in the syndrome of heart failure both directly and indirectly through its action on cardiac contractility, heart rate, preload, and afterload.

Monoamine responses to acute and chronic aerobic exercise in normotensive and hypertensive subjects

OBJECTIVES

The purpose of the present study was to compare the plasma and serum monoamine levels in sedentary, untrained normotensive and hypertensive men at rest with levels measured after an acute bout of exercise and to compare similar measurements following a 12-week aerobic training program. PLACE OF STUDY: The data obtained for this study was collected from a clinic for the prevention of heart disease and cardiac rehabilitation (FITCOR) and analyzed in the Federal University of São Paulo (EPM), Laboratory of Experimental Neurology.

SUBJECTS

Two groups of untrained male subjects, i.e., normotensive (N = 16) and hypertensive (N = 19), were submitted to an acute bout of exercise to analyze the acute effect of exercise on the monoamine levels. To study the chronic effect of exercise (physical training program), some individuals of each group were arranged in two other groups; normotensive (N = 11) and hypertensive (N = 8).

MEASUREMENT

Plasma catecholamines and serum serotonin levels were determined by high performance liquid chromatography coupled with electrochemical detection.

RESULTS

A significant reduction in diastolic blood pressure at rest was observed in the hypertensive group after the physical training program (p < 0.05). Only the mean plasma noradrenaline concentration increased significantly post-exercise in all groups of individuals (acute effect of exercise--p < 0.01 for untrained normotensive and hypertensive; chronic effect of exercise--p < 0.001 for untrained and trained normotensive, p < 0.01 for untrained and trained hypertensive).

CONCLUSION

These data show the beneficial effect of physical exercise in reducing the blood pressure in hypertensive patients, which does not seem to be related to changes in circulating monoamines.

Anteroventral third ventricle lesions attenuate pressor responses to serotonin in anesthetized rats

When administered intravenously, serotonin (5-hydroxytryptamine; 5-HT) evokes a triphasic blood pressure response, consisting of the Bezold-Jarisch-associated depressor response, a pressor action, and long-lasting depressor response. Because the pressor response may, in part, be caused by central nervous system (CNS) activation by 5-HT, we predicted that destruction of the anteroventral third ventricle (AV3V) region, an area rich in 5-HT receptors, would attenuate increases in blood pressure to intravenous 5-HT. In anesthetized sham-lesioned and AV3V-lesioned Sprague-Dawley rats, we measured mean arterial pressure (MAP), heart rate (HR), and lumbar sympathetic nerve activity (SNA) to increasing bolus doses of intravenous 5-HT (1, 2.5, 5, 10, 25 mu g/kg), before and after blockade of bradycardia using methylatropine (200 mu g/kg). In all rats, bolus injections of 5-HT elicited bradycardia accompanied by a fall in lumbar SNA and an initial hypotension followed by a pressor response and a longer lasting hypotensive response. The bradycardia, reduction in lumbar SNA, and both depressor responses were equivalent in sham-lesioned and AV3V-lesioned groups. Importantly, AV3V lesions attenuated pressor responses to increasing doses of 5-HT (3 +/- 1, 6 +/- 4, 6 +/- 4, 17 -/+ 4 35 +/- 3 mmHg) compared to sham-lesioned controls (6 +/- 3, 16 +/- 7, 33 +/- 5, 54 +/- 4, 51 +/- 6 mmHg; P < 0.0001). This attenuation was conserved following blockade of bradycardia with methylatropine (P < 0.01). In summary, pressor responses to intravenous 5-HT are diminished by AV3V lesions. These data indicate that the pressor component of the blood pressure response to intravenous 5-HT is partly dependent upon interaction with the CNS.

Arachidonate metabolites and serotonin contraction of femoral arteries from DOCA-salt hypertensive rats

Serotonin stimulates phospholipase A(2)(PLA(2)) leading to the production of prostaglandin products, several of which are vasoconstrictors. We hypothesised that the elevated vascular responsiveness to serotonin in deoxycorticosterone acetate (DOCA)-hypertensive rats is due in part to augmented production of vasoconstrictor cyclooxygenase products (e.g. PGF(2)alpha). Denuded helical strips of femoral arteries from DOCA-salt hypertensive rats (SBP 183 +/- 7 mmHg) and normotensive control rats (SBP 115 +/- 2) were used in all experiments. EC(50) values for several agonists were significantly reduced in DOCA arteries compared with controls (in mu mol/L, control vs. DOCA): PGF(2)alpha (0.99 vs. 0.23), PGE(2) (0.72 vs. 0.22), arachidonate (1.52 vs. 0.73), serotonin (0.19 vs. 0.07), noradrenaline (0.029 vs. 0.013), KCl (40.1 vs. 27.0 mmol/L) and AlF(4) (2.3 vs. 1.4 mmol/L). Treatment with indomethacin (14 mu mol/L) inhibited the responses to serotonin in DOCA arteries (EC(50) values 0.07 untreated vs. 0.70) and eliminated the responses to arachidonate but did not affect KCl or AlF(4-)contractions. Cyclooxygenase inhibitors shifted concentration response curves to serotonin in sham and DOCA tissues equally. Thus increased sensitivity to serotonin in DOCA arteries persisted following cyclooxygenase blockade. Therefore, although arachidonate products contribute to the serotonergic contraction in femoral arteries, the augmented response in arteries from DOCA hypertensive rats is not due to increased production of or sensitivity to cyclooxygenase products. Furthermore,arachidonate metabolites do not contribute to the contraction induced by either AlF(4-)or KCl in this preparation.

The role of platelets in essential hypertension

Recent research is helping us understand the complex interactions that occur between platelets and their environment. The several intracellular events that occur during platelet activation are being identified as ar their effects on other platelets, the endothelium and coagulation factors. Heightened platelet activation is seen early in essential hypertension and probably plays an important role in the initiation and progression of atherosclerosis and the disorders associated with it. This review identifies some of the changes in platelet structure and function in essential hypertension and their role in the pathogenesis of hypertensive vascular disease.