Formation of Double Stranded RNA Provokes Smooth Muscle Contractions and Structural Modifications in Bladder Ischemia

Abstract

Purpose Growing evidence suggests that ischemia provokes detrusor overactivity and degenerative responses in the bladder. Underlying mechanisms appear to involve modification of smooth muscle contractile rudiments by hypoxia, redox, cellular stress and cell survival signaling. Downstream pathways of cellular stress and stress response molecules eliciting bladder dysfunction in ischemia remain largely elusive. Our goal was to define the role of double stranded RNA (dsRNA), a stress response molecule provoked by redox, in ischemia mediated bladder dysfunction. Methods A rat model of pelvic ischemia along with a cell culture hypoxia model were used to investigate the expression levels, functional consequences, structural aspects, and regulatory mechanisms of dsRNA in the bladder. Gene and protein expression were examined by reverse transcription polymerase chain reaction (RT-PCR), dot blot, and Western blotting, respectively. Tissue structure and function were assessed using histological staining and organ bath. Regulatory mechanisms were analyzed in cultured bladder smooth muscle cells. Results The data presented here provide the first evidence of the formation of dsRNA in the overactive bladder. dsRNA is a cellular stress response molecule that sensitizes smooth muscle and regulates inflammatory and degenerative rejoinders. Our data suggest that the production of dsRNA in the bladder is provoked by ischemia. Formation of dsRNA appears to augment bladder smooth muscle contractions and provoke fibrotic and apoptotic responses. Downstream actions of dsRNA in the bladder may involve upregulation of dsRNA-activated protein kinase R (PKR) and caspase-3, the executioner of apoptosis. Conclusion Activation of dsRNA/PKR pathway may play a role in sensitization of bladder smooth muscle cells to contractile stimuli, whereas dsRNA and caspase-3 crosstalk appear to modulate cellular stress and instigate degenerative responses in bladder ischemia. These observations suggest the role of dsRNA in bladder dysfunction and may open new perspectives to overcome overactive smooth muscle contractions and structural damage in the bladder.

Differential Post-Translational Modifications of Proteins in Bladder Ischemia

“…Several other studies have shown that human bladder blood flow decreases with aging in both men and women, and decreased bladder blood flow significantly correlates with reduced bladder compliance and the development of LUTS . Studies of animal models have revealed that ischemia compromises the bladder proteomic profiles and instigates a cascade of downstream signaling pathways with critical structural and functional consequences [37][38][39][40][41]. These observations, cumulatively, suggest that therapeutic strategies to improve bladder perfusion could prevent or reverse detrusor overactivity and LUTS in patients with pelvic ischemia.…”

“…These observations, cumulatively, suggest that therapeutic strategies to improve bladder perfusion could prevent or reverse detrusor overactivity and LUTS in patients with pelvic ischemia. Downstream mechanisms mediating overactivity and structural damage in bladder ischemia appear to involve disruption of cellular energy homeostasis, cellular stress, and cell survival signaling [37][38][39][40][41]. It is thought that the upregulation of cellular stress response molecules by ischemia activates homeostatic mechanisms to signal nutrient deficiency, hypoxic stressors, and cell danger [42][43][44][45][46][47][48][49][50].…”

“…Our study suggests a close link between the interruption of nutrients and oxygen delivery to the ischemic cells, the accumulation of free radicals and metabolic waste, and differential (post-translational) modifications of the stress response proteins in bladder ischemia. The cell's fate after exposure to stressful conditions such as ischemia depends on the severity and duration of ischemia and the cell's defensive capacity to confine stress, eliciting molecular responses including PTMs [37][38][39]. Cellular stress sensors may play a key role in regulating molecular responses and protein modifications in the ischemic bladder [37][38][39].…”

“…The cell's fate after exposure to stressful conditions such as ischemia depends on the severity and duration of ischemia and the cell's defensive capacity to confine stress, eliciting molecular responses including PTMs [37][38][39]. Cellular stress sensors may play a key role in regulating molecular responses and protein modifications in the ischemic bladder [37][38][39].…”