Uncoupling force and calcium flux to develop novel therapeutics for subarachnoid hemorrhage-induced vasospasm

Abstract

Subarachnoid hemorrhage (SAH) affects approximately 30,000 people each year and accounts for 1-7% of all strokes. Spontaneous SAH occurs due to the rupture of a cerebral aneurysm. SAH is characterized primarily by loss of cerebral autoregulation, development of delayed cerebral vasospasm and subsequent ischemia. Neurological deficits that are direct sequelae of vasospastic events are the most common cause of morbidity and mortality in patients with SAH. Current treatments for the ensuing vasospasm do not successfully reverse or prevent the spasm, as cellular mechanisms are not fully understood. The purpose of this thesis is to better understand thin and thick filaments that govern smooth muscle function in order to develop effective therapeutics for spastic arteries by uncoupling calcium signaling and myosin light chain phosphorylation with force generation. This novel ability to uncouple the two processes suggests that there are indeed calcium-independent mechanisms of relaxation. This work provides insight into mechanisms that regulate smooth muscle tone and may provide therapeutic angles to treat SAH-induced vasospasm. Recent findings have shown that there are biochemical changes in the vascular tissue that undergoes vasospasm. Among them are the down regulation of the actin associated proteins heat shock protein 20 (HSP20) and increased phosphorylation of heat shock protein 27 (HSP27). By down-regulating HSP20 and increasing the amount of HSP27 this study modeled the vasoactive changes that occur in the spastic vessels. This approach is direct and specific for the treatment of SAH-induced vasospasm. Hence targeting phosphorylated HSP20 and HSP27 should specifically modulate SAH-induced vasospastic vessels without causing ensuing hypotension. Engineered delivery techniques were used to enhance the uptake of siRNA and peptides to smooth muscle, in order to modulate HSP20. Taken together, this work provides novel insight into mechanisms that regulate smooth muscle tone and may provide therapeutic angles to treat SAH-induced vasospasm.