Prevention by the new Ca2+ channel antagonist, AJ-3941, of loss of endothelium-dependent relaxation after subarachnoid hemorrhage in rats

Diastereoselective Formal [5+2] Cycloaddition of Diazo Arylidene Succinimides-Derived Rhodium Carbenes and Aldehydes: A Route to 2-Benzoxepines

We report on a facile method for the preparation of 2-benzoxepine derivatives as a result of Rh(II)-catalyzed decomposition of diazo arylidene succinimides in the presence of aldehydes. The process is thought to involve the formation of styryl carbonyl ylide which undergoes 1,7-electrocyclization and subsequent 1,5-hydrogen shift. In some cases, the competition of the target reaction and [3+2] dipolar cycloaddition of the intermediate carbonyl ylide to another molecule of diazo substrate was observed. Generally, the desired 2-benzoxepines were isolated in good to high yields and high diastereoselectivity. The developed original approach toward a 2-benzoxepine core via formal [5+2] cycloaddition of styryl carbenoids and aldehydes significantly expands the arsenal of synthetic methods for producing this scaffold.

Calpeptin Reduces Neurobehavioral Deficits and Neuronal Apoptosis Following Subarachnoid Hemorrhage in Rats

BACKGROUND

Inhibition of calpain activity provides neuroprotection in multiple central nervous system injury, but the role and mechanism of calpain in subarachnoid hemorrhage (SAH) remain unclear. This study was undertaken to determine the effects of inhibition of calpain on neurological deficit and neuronal apoptosis following experimental SAH.

METHODS

The endovascular perforation model of SAH was produced in male Sprague-Dawley rats. Rats were administered calpeptin 50 μg, intracerebroventricular injection, 30 minutes before induction of SAH. After 72 hours, the method of Evans blue dye extravasation and wet/dry method were used for determination of blood-brain barrier permeability and brain edema, Western blot analysis and immunohistological staining were used to evaluate neuronal apoptosis.

RESULTS

The intracellular Ca²⁺ level and calpain activity was significantly elevated in basal cortex after SAH. Calpain inhibitor calpeptin reduces brain water content and Evans blue dye extravasation, improves neurobehavioral deficits after SAH. Importantly, calpeptin treatment significantly reduces activation of caspase-3, caspase-9, caspase-12 and poly ADP ribose polymerase and the number of apoptotic neurons in basal cortex after SAH.

CONCLUSION

The present study suggested that calpeptin is neuroprotective in early brain injury after SAH through antiapoptotic effect.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Impaired cerebral vasodilator responses to NO and PDE V inhibition after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is associated with impaired nitric oxide (NO)-mediated cerebral vasodilatation. We tested the hypothesis that SAH causes alterations in the production of, hydrolysis of, or responsiveness to cGMP in the rat basilar artery in vivo. Rats were injected with saline or autologous blood into the cisterna magna. Two days later, effects of vasoactive drugs on basilar artery diameter were examined using a cranial window preparation. Vasodilator responses to ACh, sodium nitroprusside (SNP), and low concentrations (</=10(-5) M) of zaprinast, an inhibitor of phosphodiesterase V (PDE V), were impaired in SAH rats (P < 0.05). In contrast, vasodilator responses to adenosine and 8-BrcGMP were similar in control and SAH rats. Vasoconstrictor responses to 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one, an inhibitor of soluble guanylate cyclase, were unaffected by SAH. In the presence of zaprinast (10(-5)-10(-4) M), responses to ACh and SNP were equivalent in control and SAH rats. Thus an increased rate of cGMP hydrolysis by PDE V may be a major factor contributing to the impairment of NO-mediated cerebral vasodilatation after SAH.

Subarachnoid haemorrhage: what happens to the cerebral arteries?

1. Subarachnoid haemorrhage (SAH) is a unique disorder and a major clinical problem that most commonly occurs when an aneurysm in a cerebral artery ruptures, leading to bleeding and clot formation. Subarachnoid haemorrhage results in death or severe disability of 50-70% of victims and is the cause of up to 10% of all strokes. Delayed cerebral vasospasm, which is the most critical clinical complication that occurs after SAH, seems to be associated with both impaired dilator and increased constrictor mechanisms in cerebral arteries. Mechanisms contributing to development of vasospasm and abnormal reactivity of cerebral arteries after SAH have been intensively investigated in recent years. In the present review we focus on recent advances in our knowledge of the roles of nitric oxide (NO) and cGMP, endothelin (ET), protein kinase C (PKC) and potassium channels as they relate to SAH. 2. Nitric oxide is produced by the endothelium and is an important regulator of cerebral vascular tone by tonically maintaining the vasculature in a dilated state. Endothelial injury after SAH may interfere with NO production and lead to vasoconstriction and impaired responses to endothelium-dependent vasodilators. Inactivation of NO by oxyhaemoglobin or superoxide from erythrocytes may also occur in the subarachnoid space after SAH. 3. Nitric oxide stimulates activity of soluble guanylate cyclase in vascular muscle, leading to intracellular generation of cGMP and relaxation. Subarachnoid haemorrhage appears to cause impaired activity of soluble guanylate cyclase, resulting in reduced basal levels of cGMP in cerebral vessels and often decreased responsiveness of cerebral arteries to NO. 4. Endothelin is a potent, long-lasting vasoconstrictor that may contribute to the spasm of cerebral arteries after SAH. Endothelin is present in increased levels in the cerebrospinal fluid of SAH patients. Pharmacological inhibition of ET synthesis or of ET receptors has been reported to attenuate cerebral vasospasm. Production of and vasoconstriction by ET may be due, in part, to the decreased activity of NO and formation of cGMP. 5. Protein kinase C is an important enzyme involved in the contraction of vascular muscle in response to several agonists, including ET. Activity of PKC appears to be increased in cerebral arteries after SAH, indicating that PKC may be critical in the development of cerebral vasospasm. Recent evidence suggests that PKC activation may occur in cerebral arteries after SAH as a result of decreased negative feedback influence of NO/cGMP. 6. Cerebral arteries are depolarized after SAH, possibly due to decreased activity of potassium channels in vascular muscle. Decreased basal activation of potassium channels may be due to several mechanisms, including impaired activity of NO (and/or cGMP) or increased activity of PKC. Vasodilator drugs that produce hyperpolarization, such as potassium channel openers, appear to be unusually effective in cerebral arteries after SAH. 7. Thus, endothelial damage and reduced activity of NO may contribute to cerebral vascular dysfunction after SAH. Potassium channels may represent an important therapeutic target for the treatment of cerebral vasospasm after SAH.