Testicular ischemia/reperfusion injury (TI/RI) is a significant clinical contributor to subfertility and infertility resulting from testicular torsion and subsequent detortion. Insufficient nitric oxide (NO) synthesis in TI/RI can result in endothelial dysfunction, as the vascular endothelium fails to produce sufficient NO to sustain appropriate vasodilation and blood perfusion. Many studies have found that NO plays an important role in the I/RI and its increase or decrease can affect the progression and outcome of I/RI. However, the role of NO in I/RI is controversial and complicated. NO derived by endothelial NO synthase (eNOS) shows a protective role in I/RI, while excessive NO derived by inducible NO synthase (iNOS) accelerates inflammation and increases oxidative stress, further aggravating I/RI. Nevertheless, the overexpression of eNOS may exacerbate I/RI. Here we try to investigate the new progress in the understanding of the roles of NO during I/RI. This study examined the interplay between cytotoxic and cytoprotective mechanisms underpinning NO produced from L-citrulline (L-Cit) on TI/R injured rats. Thirty-two adult Sprague-Dawley albino rats were equally randomized into the following groups: normal control group, sham group, TI/R group (3 h/4 h), and TI/R + L-Cit group (600 mg/kg) orally at 1 h before reperfusion. Compared to the TI/R-operated group, the injection of L-Cit markedly enhanced serum concentrations of reproductive hormones (p < 0.05). Elevated SOD, CAT, and GPx activity, along with reduced MDA and NO concentrations, indicated a diminished oxidative stress. The testicular levels of TNF-α, IL-1β, caspase-3, BAX, eNOS, iNOS, and NF-κB p65 were markedly reduced. Histopathological analysis corroborated the protective effect of L-Cit. The findings confirmed molecular models, demonstrating that L-Cit inhibited eNOS, iNOS, and IKKβ. The results showed that giving torsioned rats NO made from L-Cit protected them against hormonal imbalance, oxidative stress, inflammation, and apoptosis in I/RI. This makes L-Cit even more important for protecting against tissue I/RI during surgery. L-Cit not only promoted NO synthesis through eNOS activation, but it also facilitated the neutralization of iNOS production and its pathogenic NO levels during the reperfusion phase in I/R-injured rats.
Keywords: L‐citrulline; endothelial nitric oxide synthase; inducible nitric oxide synthase; nitric oxide; nuclear factor‐kappa B; testicular ischemia/reperfusion injury.
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