S-nitrosylation of endothelial nitric oxide synthase impacts erectile function

Area of Science:

• Physiology
• Biochemistry
• Urology

Background:

• Nitric oxide synthases (NOS), including neuronal (nNOS) and endothelial (eNOS), are crucial for erectile function.
• S-nitrosylation is a key post-translational modification that regulates NOS activity.
• The role of S-nitrosylated NOS in penile tissue and its impact on erectile function require further investigation.

Purpose of the Study:

• To investigate the presence and function of S-nitrosylated NOS in the penis.
• To examine the impact of NOS S-nitrosylation and denitrosylation on erectile function.
• To determine the role of S-nitrosoglutathione reductase (GSNO-R) in regulating eNOS S-nitrosylation.

Main Methods:

• Biotin-switch assay followed by western blot analysis to detect S-nitrosylated NOS.
• Continuous cavernous nerve electrical stimulation (CCNES) to assess erectile function in wild-type, GSNO^+/-, and GSNO^-/- mice.
• Intracorporal injection of glutathione ethyl ester (GSHee) to modulate S-nitrosylated NOS levels.
• Immunohistological and immunofluorescence analyses to localize eNOS and GSNO-R in corporal tissue.

Main Results:

• Both eNOS and nNOS were found to be S-nitrosylated in unstimulated mouse penises.
• CCNES induced a time-dependent increase in eNOS S-nitrosylation, peaking during detumescence.
• S-nitrosylated nNOS levels remained unchanged during CCNES.
• GSHee administration reduced S-nitrosylated eNOS levels and enhanced the time to maximum intracavernous pressure (ICP).
• GSNO-R^+/- and GSNO-R^-/- mice exhibited impaired ability to maintain elevated ICP during CCNES.
• eNOS and GSNO-R were co-localized in the endothelium of the corpus cavernosum in both mouse and human tissues.

Conclusions:

• eNOS S-nitrosylation and denitrosylation represent a critical regulatory mechanism for eNOS activity during erectile function.
• GSNO-R is identified as a key enzyme responsible for eNOS denitrosylation.
• Increased eNOS S-nitrosylation during tumescence may initiate detumescence, suggesting a potential link to erectile dysfunction.
• Imbalances in S-nitrosylation/denitrosylation may contribute to the pathophysiology of erectile dysfunction.