Regulation of eNOS by S-Nitrosylation in Diet Associated Erectile Dysfunction

Johns Hopkins University, Baltimore MD

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Abstract

PROJECT SUMMARY A diet abundant in sugar and fats derived from animal sources and cheap vegetable oils has been termed the Western diet. Consumption of the Western diet is now prevalent in the United States and has been spreading throughout the world over the past 15 years. Consumption of a Western style diet is implicated in the etiology of erectile dysfunction (ED), a condition strongly associated with reduced quality of life. Nitric oxide is a primary mediator of penile erection, which is produced by nitric oxide synthase. Under conditions of excessive oxidative stress, endothelial nitric oxide synthase (eNOS) may become uncoupled, whereby superoxide is produced rather than nitric oxide, which propagates further oxidative stress. It is thought that eNOS coupling status is regulated by adequate presence of co-factors and substrates. However, recent data indicate that eNOS uncoupling and dysfunctionality may be promoted by S-nitrosylation, which may be dependent on an oxidative shift in cellular redox state. Additionally, the mammalian target of rapamycin (mTOR) is a cellular signaling molecule that may induce oxidative stress in response to excessive fat and sugar consumption. The primary hypothesis of this proposal is that an oxidative shift in the penile redox environment, mediated by mTOR- dependent nutrient signaling in response to the Western diet promotes erectile dysfunction due to eNOS dysregulation via excessive S-nitrosylation induced by impairment of the denitrosylation system. Specific aims for the proposal are: 1) to determine if Western diet-induced ED is mediated by an oxidative shift in redox state dependent upon mTOR signaling; 2) to determine if the mTOR dependent shift in redox state exerts alteration of S-nitrosylation; 3) to determine if regulation of S-nitrosylation controls erectile function in a diet-dependent manner. The proposed research plan includes the use of a Western style rodent diet in combination with pharmacologic, molecular, proteomic, and physiological studies. These studies utilize the Western diet in combination with pharmacologic shifts in redox state, inhibition of mTOR, and genetic manipulation of proteins that regulate denitrosylation. Molecular studies proposed include assessment of protein structure, function, and post-translational modifications influencing eNOS, the mTOR signaling pathway, and the proteins that regulate cellular S-nitrosylation. Proteomic studies proposed include assessment of S-nitrosylation status of the penile proteome, as well as S-nitrosylation of individual thiol groups of penile eNOS. Molecular and proteomic studies will be enriched by physiologic erectile function measurements in response to these perturbations. The proposed studies include the use of a genetic mouse model where the regulation of S-nitrosylation is manipulated, and a rat model where the regulation of S-nitrosylation is manipulated specifically in the penis. It is anticipated that the findings of this proposal will provide greater understanding of molecular events leading to Western diet associated ED, and provide a basis for enhanced treatment.