SIRT2 and FOXO3a expressions in the cerebral cortex and hippocampus of young and aged male rats: antioxidant and anti-apoptotic effects of melatonin.

Melatonin has antioxidant, anti-apoptotic and anti-aging effects in the brain. Sirtuin2 (SIRT2) accumulates in the central nervous system with aging, and its inhibition appears to be protective in aging and aging-related neurodegenerative diseases. Forkhead Box-class O3a (FOXO3a) transcription factor is one of the main targets of SIRT2, and SIRT2-mediated FOXO3a deacetylation is closely related to aging, oxidative stress, and apoptosis. This study aimed to investigate the effects of melatonin on SIRT2 and FOXO3a expressions in the cerebral cortex and hippocampus of aged rats. Young (3 months, n = 18) and aged (22 months, n = 18) male Wistar rats were divided into control (4% DMSO-PBS, sc, for 21 days), melatonin (10 mg/kg, sc, for 21 days) and salermide (1 mM; 25 µl/100 g bw, ip, for 21 days) groups. SIRT2, FOXO3a, Bcl-2, Bax and Bim expressions in the cerebral cortex and hippocampus were demonstrated by Western blotting. SIRT2 and FOXO3a protein levels were also measured by a sandwich ELISA method. Oxidative stress index (OSI) was calculated by measuring total oxidant status (TOS) and total antioxidant status (TAS). Aging increased SIRT2, FOXO3a, Bim (only in the cerebral cortex), Bax (only in the hippocampus), TOS, and OSI, while decreasing Bcl-2, Bcl-2/Bax and TAS in both brain regions. Melatonin decreased SIRT2, FOXO3a, oxidative stress parameters and pro-apoptotic proteins, while increasing TAS, Bcl-2 and Bcl-2/Bax, more specifically in the hippocampus of the aged brain. Our results indicate that inhibition of SIRT2 and FOXO3a expressions appears to be involved in the protective effects of melatonin in the hippocampus of aged rats.

The protective role of melatonin and curcumin in the testis of young and aged rats.

We aimed to investigate the effect of melatonin and curcumin treatment on oxidative stress, apoptosis, and histology of testicular tissue in our study. Four groups were formed using young (4 months old, n = 6) and aged (20-22 months old, n = 18) male Wistar albino rats: (a) Young control (1% ethanol:phosphate-buffered saline [PBS], subcutaneously [s.c.]); (b) Aged control (CTL; n = 6, 1% ethanol:PBS, s.c.); (c) Aged Melatonin (MLT; n = 6, 10 mg/kg, s.c.); (d) Aged Curcumin (CUR; n = 6, 30 mg/kg, i.p.). At the end of 21 days, the rats were sacrificed, and testicular tissues were removed. Malondialdehyde (MDA) in the testicular tissue was determined with thiobarbituric acid reactive substances formation, and glutathione (GSH) was determined with modified Ellman method; testosterone level was determined with chemiluminescence method and histologic changes were determined with Haematoxylin-Eosin and Johnsen's scoring; Apoptotic cell counts were made with TUNEL staining of seminiferous tubule in testis. With ageing, MDA level increased in testicular tissue, but GSH and blood testosterone levels decreased. Melatonin treatment for aged rats significantly decreased Paired total testicular/body weight ratio compared to aged control group (p < 0.05). Curcumin treatment for aged rats significantly increased GSH level compared to the aged control group (p < 0.05). Besides, melatonin and curcumin treatment significantly decreased the number of apoptotic cells and significantly increased Johnsen's score (p < 0.05).

The effects of melatonin and curcumin on the expression of SIRT2, Bcl-2 and Bax in the hippocampus of adult rats.

OBJECTIVE: Though the mechanisms are not clearly understood, melatonin and curcumin have been reported to have neuroprotective effects. However, the mechanisms of neuroprotective effects of melatonin and curcumin in the brain are not clearly understood. In the current study, we investigated the effects of melatonin and curcumin treatments on oxidative stress parameters, the expression of SIRT2, Bcl-2 and Bax in the hippocampus. METHODS: A total of thirty adult (13 months-old) male Wistar rats were divided into five groups: Control (1% ethanol:PBS), s.c. for 30 days), dimethyl sulfoxide (10%, s.c. for 30 days), Melatonin (10 mg/kg/day, s.c. for 30 days), Curcumin (30 mg/kg/day, i.p. for 30 days) and Salermide (100 µM, i.p. for 30 days). The levels of malondialdehyde (MDA) glutathione (GSH) were measured as oxidative stress parameters in the hippocampus. The expression levels of SIRT2, Bcl-2 and Bax proteins were tested by western blotting and the SIRT2 protein levels of the hippocampal region was measured by a sandwich ELISA method. RESULTS: Melatonin and curcumin significantly decreased MDA and SIRT2 expression in the hippocampus (p < 0.05). Accordingly, a significant increase in the GSH levels of curcumin-treated group and melatonin-treated group was observed. Melatonin, but not curcumin, significantly increased the Bcl-2 expression of the hippocampal region. There was a significant correlation between SIRT2 and MDA levels (p < 0.05). DISCUSSION: In conclusion, our results suggest that melatonin may increase cell survival in the hippocampus via decreasing oxidative stress and SIRT2 expression and increasing Bcl-2 expression.