Acute Stress and Intravesical Corticotropin-Releasing Hormone Induces Mast Cell Dependent Vascular Endothelial Growth Factor Release From Mouse Bladder Explants

Purpose: Corticotropin-releasing hormone is typically released from the hypothalamus but it has proinflammatory effects outside of the brain, possibly through the activation of mast cells. These cells express corticotropin-releasing hormone receptors with selective secretion of vascular endothelial growth factor, which may be involved in the pathogenesis of painful bladder syndrome/interstitial cystitis. This condition is characterized by bladder inflammation and worsened by stress. We investigated the effect of intravesical corticotropin-releasing hormone and acute restraint stress on vascular endothelial growth factor release from mouse bladder explants and the role of mast cells. Materials and Methods: The bladder of C57BL/6 mast cell deficient (W/W^v) and normal congenic (+/+) female mice (Jackson Laboratories, Bar Harbor, Maine) at ages 10 to 12 weeks was catheterized using anesthesia. After emptying urine 1) normal saline or corticotropin-releasing hormone was introduced for 45 minutes, urine was collected and the mice were allowed to recover for 4 hours before sacrifice or 2) the mice were stressed by placing them in a restrainer for 4 hours before sacrifice and urine was collected 2 hours after stress. The bladder was removed 4 hours after stress and processed for corticotropin-releasing hormone immunohistochemical staining. In other experiments the bladder was removed, minced into 1 mm² pieces and cultured with or without corticotropin-releasing hormone overnight. Urine and medium were frozen for histamine, interleukin-6, tumor necrosis factor-α and vascular endothelial growth factor assay. Results: Corticotropin-releasing hormone (100 nM) or acute restraint stress (4 hours) increased histamine release in urine and vascular endothelial growth factor release in medium without increasing interleukin-6 or tumor necrosis factor-α in the bladder explants of C57BL/6 or +/+ but not W/W^v mice. No vascular endothelial growth factor, interleukin-6 or tumor necrosis factor-α was detected in urine before or after stimulation. Corticotropin-releasing hormone immunoreactivity was present in control bladders but it increased dramatically in the bladder of stressed mice. Conclusions: Intravesical corticotropin-releasing hormone and acute restraint stress induced mast cell dependent vascular endothelial growth factor release from bladder explants. These findings suggest that stress, corticotropin-releasing hormone, mast cells and vascular endothelial growth factor might participate in the pathogenesis of painful bladder syndrome/interstitial cystitis, which is worsened by stress, and provide for new therapeutic targets.