| Aging is usually associated with a progressive disruption of the redox balance leading to recurrent damage resulting from oxidative stress. Oxidative stress resulting from excessive free-radical release is likely implicated in the initiation and progression of motor behavior disorders. Therefore, antioxidant therapies have received considerable attention in motor behavior defects treatment. The nuclear factor erythroid 2-related factor 2(Nrf2) binds to antioxidant response element(ARE) to induce antioxidant and phase II detoxification enzymes under conditions of oxidative stress, which reduces oxidative stress and accumulation of toxic metabolites. Testosterone has many physiological and behavioral effects throughout the lifespan and shown to affect motor behavior in adult male rats and gonadectomized rats. However, whether Nrf2-ARE pathway is activated after testosterone administration has not been studied in aged rats. The tilting-plane test and the horizontal-wire test as well as the oxidative stress parameters, the expression of Nrf2, heme oxygenase-1(HO-1) and NAD(P)H: quinone oxidoreductase-1(NQO1) and the number of tyrosine hydroxylase immunoreactive(TH-ir) cells in brain were examined in aged rats following chronic subcutaneous injections of testosterone propionate(TP). Our study showed that chronic TP supplement significantly ameliorated the decline of balancing reactions and muscular strength associated with aging. Oxidative stress parameters were ameliorate, the expression of Nrf2, HO-1 and NQO1 at protein or gene levels and the number of TH-ir cells significantly increased in substantia nigra or caudate putamen after TP treatment in aged rats. Our findings demonstrated that chronic TP treatment activated Nrf2-ARE pathway may influence the maintenance of the balancing reactions and muscular strength and reduce TH-ir cells death in aged rats. Therefore, TP supplement have shown for therapeutic strategies in the treatment and modification of motor behavior disorders.Objective: To study the effect of subcutaneous administration of TP on the expression of Nrf2-ARE pathway and motor behavior in aged rats, it is hoped subcutaneous administration of TP could be used in adjutant for the incidence and treatment-related neuropsychiatric disorders.Methods: Male Wistar rats were randomly divided into four groups. Aged male rats were tested at 24 months of age following treatment with either subcutaneous testosterone propionate injection at the age of 21 months(24Mon-TP, n = 15), or the sesame oil as vehicle(24Mon, n = 15). A group of rats tested at 6 months of age were treated with the sesame oil vehicle(6Mon, n = 15) at the age of 3 months. The supplement of TP or vehicle continued for 12 weeks(84-day). A final group of rats remained naive(24Mon-N, n = 5), which were the same age as rats in 24 Mon group and received handling as well as exposure to the chamber on the habituation and training days but did not receive drug or vehicle, were used as paired control to tilting-plane test and horizontal-wire test studies. Following behavioral tests, subgroups of rats(n = 5/group) were used for reduced glutathione(GSH) and malondialdehyde(MDA) assay, Western blot and real-time fluorescence quantitative PCR analysis, and immunohistochemical analysis.Results:1 The effect of TP on tilting-plane test behavior in aged rats The angle of sliding off significantly decreased in 24 Mon rats than in 6Mon rats, the frequency of sliding off at 50? angle significantly increased in 24 Mon rats than in 6Mon rats. The angle of sliding off was increased in 24Mon-TP rats than that in 24 Mon rats by 10.4%, as well as the frequency of sliding off at 50? angle was decreased in 24Mon-TP rats than that in 24 Mon rats by 34.0%(P < 0.01) after TP treatment. The angle of sliding off in 24Mon-TP rats was still significantly lower than that in 6Mon rats(P < 0.01) and the frequency of sliding off at 50? angle in 24Mon-TP rats was still significantly higher than that in 6Mon rats(P < 0.01).2 The effect of TP on horizontal-wire test behavior in aged rats the duration time of hanging was significantly shorter in 24 Mon rats than in 6Mon rats and that the duration time of hanging was increased in 24Mon-TP rats than that in 24 Mon rats by 103.7%(P < 0.01) after TP supplement. The duration time of hanging in 24Mon-TP rats was still significantly lower than that in 6Mon rats(P < 0.01).3 The effect of TP on the level of MDA and GSH in aged ratsAs shown in Fig. 3, there are group differences found among the 6Mon, 24 Mon and 24Mon-TP rats both in SN and in CPu on the level of GSH and MDA. The post hoc test revealed that the level of GSH in SN as well as in CPu of 24 Mon rats was significantly reduced compared to 6Mon rats and the level of MDA in SN as well as in CPu of 24 Mon rats was significantly increased compared to 6Mon rats. The level of GSH in SN and in CPu of 24Mon-TP rats were higher than that of 24 Mon rats by 24.5%(P < 0.01) and 16.5%(P < 0.01) respectively after TP administration. The level of MDA in SN and in CPu of 24Mon-TP rats were lower than that of 24 Mon rats by 13.9%(P < 0.01) and 13.4%(P < 0.01) respectively after TP treatment, and the level of GSH and MDA in SN as well as in CPu of 24Mon-TP rats were not restored to the level of 6Mon rats(P < 0.01).4 The effect of TP on expression of Nrf2, HO-1 and NQO1 proteins in aged rats the expression of Nrf2(P < 0.01), HO-1(P < 0.01) and NQO1(P < 0.01) in SN as well as in CPu of 24 Mon rats was significantly reduced compared to 6Mon rats. The expression of Nrf2, HO-1 and NQO1 in SN of 24Mon-TP rats were higher than that of 24 Mon rats by 31.6%(P < 0.01), 30.3%(P < 0.01) and 24.2%(P < 0.01) respectively, and the expression of HO-1 and NQO1 in CPu of 24Mon-TP rats were higher than that of 24 Mon rats by 36.8%(P < 0.01) and 13.6%(P < 0.01) respectively after TP administration. The expression of Nrf2, HO-1 and NQO1 in SN as well as the expression of HO-1 and NQO1 in CPu of 24Mon-TP rats were not restored to the level of 6Mon rats(P < 0.01)5 The effect of TP on expression Nrf2, HO-1 and NQO1 m RNA in aged ratsThe expression of Nrf2 m RNA(P < 0.01), HO-1 m RNA(P < 0.01) and NQO1 m RNA(P < 0.01) in 24 Mon rats was significantly reduced compared to 6Mon rats. The expression of Nrf2 m RNA, HO-1 m RNA and NQO1 m RNA in 24Mon-TP rats were higher than that of 24 Mon rats by 21.4%(P < 0.01), 19.2%(P < 0.01) and 20.9%(P < 0.01) respectively after TP supplement, and expression of Nrf2 m RNA, HO-1 m RNA and NQO1 m RNA of 24Mon-TP rats were not restored to the level of 6Mon rats(P < 0.01).6 The effect of TP on the number of TH-ir cells in aged ratsThe number of TH-ir cells decreased in 24 Mon rats and that the number of TH-ir cells increased in 24Mon-TP rats compared to 24 Mon rats by 38.5% after TP administration. The number of TH-ir cells in SN of 24Mon-TP rats were not restored to the level of 6Mon rats(P < 0.01).Conclusion:the present study shows that the Nrf2-ARE pathway were been activated after chronic testosterone propionate the Nrf2-ARE pathway activity can ameliorate behavioral and oxidative stress parameters and protect the TH-ir cells in SN in aged rats treatment. |
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