Ale Ebenezer Morayo, Kade Ige Joseph, Timothy Mgbede Joy, Boyi Richard-Harris Nsenreuti, Asuelimen Steve Osagie, Ayo Victoria Ifeoluwa, Toluwalase Ebenezer Kayode, Abah Moses Adondua, Nnamani Emmanuela Onyebuchi
Department of Biochemistry, Faculty of Pure and Applied Sciences, Federal University, Wukari, Taraba State, Nigeria.
Department of Biochemistry, School of Sciences, Federal University of Technology, Akure, Ondo State, Nigeria.
Sci Rep. 2025 May 20;15(1):17482. doi: 10.1038/s41598-024-77767-y.
Diphenyl diselenide (DPDS) is an organoselenium which has garnered profound interest due to its reported antioxidant viz-a-viz glutathione peroxidase (GPx) mimetic activity which is ultimately speculated to rely on oxidation of free thiols or protein thiols critical to the activities of some sulfhydryl proteins or enzymes. However, this hypothesis has not been fully established. This study was therefore carried out to investigate the antioxidant effect as well the possible involvement of proteins thiols in the in vitro GPx mimicry of DPDS. The effect of DPDS on Fe (10 µM) and HO (1mM)-induced lipid peroxidation and the possible involvement of thiols of cerebral sodium pump (Na/K-ATPase) and hepatic delta-aminolevulinic acid dehydratase (δ-ALAD) in the GPx mimicry of DPDS were evaluated in the cerebral and hepatic tissue homogenates of rat in the presence of thiol alkylating agent, iodoacetamide (IA, 2 mM). The results revealed that DPDS exerted marked (p < 0.05) inhibitory effect on Thiobarbituric acid reactive species (TBARS) production induced by Fe and HO in the rats hepatic and cerebral tissues and this effect was significant (p < 0.05) when compared with the control. However, IA profoundly (p < 0.05) counteracted the inhibitory action of DPDS on the TBARS production process. Furthermore, results also showed that DPDS inhibited the sulfhydryl enzymes, cerebral Na/K-ATPase and hepatic δ-ALAD as well as TBARS production in the same reaction system. Finally, we further established the involvement of thiols in the DPDS inhibition of sulfhydryl enzymes by assaying for pump and δ-ALAD activities in the presence of exogenous thiols [dithiothreitol (DTT) and glutathione (GSH)]. Interestingly DPDS did not inhibit the activity of these enzymes when pre-incubated or post-incubated with DTT or GSH indicating that DPDS switched from proteins/enzymes thiols to the oxidation of exogenous thiols. It is therefore apparent that the GPx mimicry/antioxidant action of DPDS is related to the loss of enzymes' activities. Consequently, we conclude that the in vitro GPx mimicry/ antioxidant mechanism of DPDS is largely dependent on the oxidation of essential thiols of sulfydryl proteins and that DPDS could be an effective therapeutic candidate for oxidative stress-mediated conditions in which endogenous GSH level is depleted.
二苯基二硒化物（DPDS）是一种有机硒化合物，因其具有与谷胱甘肽过氧化物酶（GPx）模拟活性相关的抗氧化作用而备受关注，最终推测其依赖于对某些巯基蛋白或酶活性至关重要的游离巯基或蛋白质巯基的氧化。然而，这一假说尚未完全确立。因此，本研究旨在探讨DPDS的抗氧化作用以及蛋白质巯基在其体外GPx模拟作用中的可能参与情况。在存在巯基烷基化剂碘乙酰胺（IA，2 mM）的情况下，评估了DPDS对铁（10 µM）和过氧化氢（1 mM）诱导的大鼠脑和肝组织匀浆中脂质过氧化的影响，以及脑钠泵（Na/K-ATP酶）和肝δ-氨基乙酰丙酸脱水酶（δ-ALAD）的巯基在DPDS的GPx模拟作用中的可能参与情况。结果显示，DPDS对铁和过氧化氢诱导的大鼠肝和脑组织中硫代巴比妥酸反应性物质（TBARS）的产生具有显著（p < 0.05）抑制作用，与对照组相比，该作用具有统计学意义（p < 0.05）。然而，IA显著（p < 0.05）抵消了DPDS对TBARS产生过程的抑制作用。此外，结果还表明，DPDS在同一反应体系中抑制了巯基酶、脑Na/K-ATP酶和肝δ-ALAD以及TBARS的产生。最后，我们通过在外源巯基[二硫苏糖醇（DTT）和谷胱甘肽（GSH）]存在的情况下检测钠泵和δ-ALAD的活性，进一步确定了巯基在DPDS对巯基酶抑制作用中的参与情况。有趣的是，当与DTT或GSH预孵育或后孵育时，DPDS并未抑制这些酶的活性，这表明DPDS从蛋白质/酶巯基转向了对外源巯基的氧化。因此，很明显DPDS的GPx模拟/抗氧化作用与酶活性的丧失有关。因此，我们得出结论，DPDS的体外GPx模拟/抗氧化机制在很大程度上依赖于巯基蛋白必需巯基的氧化，并且DPDS可能是内源性谷胱甘肽水平耗尽的氧化应激介导疾病的有效治疗候选药物。
