REGULATION OF BLADDER NGF BY ESTROGEN

University Of Wisconsin Madison, Madison WI

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Abstract

The incidence of many painful inflammatory disorders is significantly greater in women than in men, and women comprise 90 percent of patients with interstitial cystitis, a painful bladder disorder of uncertain etiology. The severity of symptoms of interstitial cystitis fluctuates with the menstrual cycle and may improve during pregnancy. The proposed research will test the hypothesis that the sex hormone estrogen increases nerve growth factor (NGF) release and uptake in the bladder, thereby predisposing to bladder inflammation and accounting for gender-related differences in the incidence of painful bladder disorders. NGF has been shown to be a potent mediator of pain, particularly pain associated with inflammation. The hypothesis that estrogen regulates bladder NGF is supported by exciting preliminary data indicating that in vivo treatment of mice with an estrogen antagonist significantly reduced bladder NGF mRNA. Estrogen also stimulated increased NGF synthesis in primary cultures of human urothelial cells. Lipopolysaccharide, a proinflammatory component of the cell wall of gram negative bacteria, stimulates increased NGF in the mouse bladder. Thus, while increased bladder NGF in response to estrogen may or may not independently result in inflammation or hyperalgesia, upregulation of NGF by estrogen may augment pain and inflammation in response to inflammatory stimuli. This hypothesis will be tested in intact and ovariectomized mice, using hormone replacement and blockade of the estrogen receptor, as well as mice with a genetic disruption of estrogen receptor alpha (ERKOa), and in primary cultures of human urothelial cells. The mechanisms by which estrogen modulates NGF release by the mouse bladder and cultured human uothelial cells will be investigated in the presence and absence of E. coli lipopolysaccharide. The results of these investigations will provide a better understanding of the role of estrogen in bladder inflammation and should suggest new strategies for prevention or amelioration of pain associated with cystitis.