Role of angiotensin II in the response to endothelin-1 of goat cerebral arteries after ischemia-reperfusion

Molecular mechanisms underlying some major common risk factors of stroke

Ischemic and hemorrhagic strokes are the most common known cerebrovascular disease which can be induced by modifiable and non-modifiable risk factors. Age and race are the most common non-modifiable risk factors of stroke. However, hypertension, diabetes, obesity, dyslipidemia, physical inactivity, and cardiovascular disorders are major modifiable risk factors. Understanding the molecular mechanism mediating each of these risk factors is expected to contribute significantly to reducing the risk of stroke, preventing neural damage, enhancing rehabilitation, and designing suitable treatments. Abnormalities in the structure of the blood-brain barrier and blood vessels, thrombosis, vasoconstriction, atherosclerosis, reduced cerebral blood flow, neural oxidative stress, inflammation, and apoptosis, impaired synaptic transmission, excitotoxicity, altered expression/activities of many channels and signaling proteins are the most knows mechanisms responsible for stroke induction. However, the molecular role of risk factors in each of these mechanisms is not well understood and requires a lot of search and reading. This review was designed to provide the reader with a single source of information that discusses the current update of the prevalence, pathophysiology, and all possible molecular mechanisms underlying some major risk factors of stroke namely, hypertension, diabetes mellitus, dyslipidemia, and lipid fraction, and physical inactivity. This provides a full resource for understanding the molecular effect of each of these risk factors in stroke.

The importance of comorbidities in ischemic stroke: Impact of hypertension on the cerebral circulation

Comorbidities are a hallmark of stroke that both increase the incidence of stroke and worsen outcome. Hypertension is prevalent in the stroke population and the most important modifiable risk factor for stroke. Hypertensive disorders promote stroke through increased shear stress, endothelial dysfunction, and large artery stiffness that transmits pulsatile flow to the cerebral microcirculation. Hypertension also promotes cerebral small vessel disease through several mechanisms, including hypoperfusion, diminished autoregulatory capacity and localized increase in blood-brain barrier permeability. Preeclampsia, a hypertensive disorder of pregnancy, also increases the risk of stroke 4-5-fold compared to normal pregnancy that predisposes women to early-onset cognitive impairment. In this review, we highlight how comorbidities and concomitant disorders are not only risk factors for ischemic stroke, but alter the response to acute ischemia. We focus on hypertension as a comorbidity and its effects on the cerebral circulation that alters the pathophysiology of ischemic stroke and should be considered in guiding future therapeutic strategies.

Role of angiotensin and endothelin in testicular ischemia reperfusion injury

OBJECTIVES

To determine whether angiotensin and endothelin have any role in testicular ischemia reperfusion injury by investigating the effects of the angiotensin converting enzyme inhibitor enalapril, selective non-peptide angiotensin-II type I blocker losartan and dual endothelin receptor blocker bosentan.

METHODS

Rats were anesthetized with thiopental sodium (50 mg/kg i.p.) before the operation. The left testicular artery and vein of rats were occluded for 1 h; before the bilateral orchiectomy, the organ was allowed to reperfuse for 3 h or 24 h. Enalapril (20 mg/kg i.p.), losartan (30 mg/kg i.p.), bosentan (10 mg/kg i.p.) or vehicle (saline) were given 30 min before reperfusion. Malondialdehyde level was measured in testicular tissue after 3 h of reperfusion. Histological examination was carried out after 24 h of reperfusion.

RESULTS

Ischemia reperfusion caused a significant increase in malondialdehyde level of ipsilateral testis, and histopathological injury in both ipsilateral and contralateral testes. Enalapril, losartan and bosentan treatments prevented the ischemia reperfusion-induced augmentation in malondialdehyde levels. Only bosentan treatment ameloriated ischemia reperfusion-induced histopathological alterations.

CONCLUSIONS

Endothelin might play a more important role in pathogenesis of testicular ischemia reperfusion injury when compared with angiotensin.