Changing dynamics in daily rhythms of oxidative stress indicators in SCN and extra-SCN brain regions with aging in male Wistar rats.

The suprachiasmatic nucleus (SCN) in the hypothalamus regulates circadian timing system (CTS) by co-ordinating peripheral tissue clocks and extra-SCN oscillators in the brain. Aging disrupts the CTS, impairing physiological functions and reducing antioxidant defences, which contribute to neurodegeneration. The brain is vulnerable to oxidative damage due to its high metabolic activity, oxygen consumption, and levels of iron and lipids. Antioxidant enzymes, such as catalase (CAT), glutathione S-transferase (GST), superoxide dismutase (SOD), and lipid peroxidation (LPO), help against oxidative damage. In this study, we examined the temporal patterns of these antioxidant stress indicators in the SCN and extra-SCN brain regions (frontal cortex, cerebellum, and hippocampus) at various time points in male Wistar rats 3, 12, and 24 months. The rhythmicity of GST and LPO levels persisted across brain regions with aging, while CAT rhythmicity was lost in the SCN and hippocampus of older rats. SOD rhythmicity persisted in cortex, cerebellum, and hippocampus but was lost in the SCN. The daily rhythm parameters of CAT were affected most significantly, followed by SOD, GST, and LPO. Our findings demonstrate that aging leads to desynchronization of oxidative stress indicators potentially contributing to neurodegeneration and circadian dysfunction with varying effects across different brain tissues.