Melatoninergic Agonists and Omega-3 Fatty Acids in Circadian Rhythm and Neuroprotection: from Cellular, Animal, to Clinical Research

Background: Circadian rhythm dysregulation is associated with clinical manifestation and pathogenesis in psychiatric disorders. Melatonin plays a crucial role in circadian clock gene regulation for sleep-wake cycles in anxiety and depression disorders. Melatonin receptor agonists, including ramelteon (RMT) and agomelatine (AGO), could induce phase shifts and have recently available for treatment of anxiety, depression and sleep disorders, which have been associated with pathophysiological changes in both oxidative stress pathways and neurodegenerative mechanisms. The conventional antidepressant agent, e.g. selective serotonin reuptake inhibitors (SSRIs), and the novel natural antidepressants, e.g. omega-3 polyunsaturated fatty acids (omega-3 or n-3 PUFAs) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), could reverse oxidative and neuro-inflammatory effects in clinical and preclinical studies. However, the interaction between oxidation/inflammation and circadian gene regulation at the transcriptional level are not yet clear. Thus, this project aims to investigate individual and synergistic regulation of melatonin receptor agonists and n-3 PUFAs, as compared with fluoxetine, on antioxidant and neuroprotective actions and circadian rhythm related biomarkers in both clinical and cellular models. Method: In cellular and animal experiments, we will investigate the rescue and prevention effects of melatonin agonists RMT and AGO, the SSRI fluoxetine, and n-3 PUFAs EPA and DHA, on cell viability in SH-SY5Y cells under oxidative stress (H202), as well as the circadian rhythm dysregulations in animal models of chronic stress and depression. The key cellular markers for oxidative stress, inflammatory and neuroprotection will be analyzed using western blotting and immunocytochemistry. The epigenetic molecular mechanisms will be investigated. There are 2 parts in clinical experiments. In the observational study, we would recruit eligible patients with sleep disturbance comorbid with anxiety and depressive disorders and perform comprehensive clinical and peripheral biomarkers in a 12-week follow-up study. The patients will receive pharmacological treatments based on the mutual decision between clinicians and patients. The participants who receive RMT (8-16 mg/day, n=30) or AGO (25-50 mg/day, n=30) or fluoxetine (20-40 mg/day, n=30) will be consent for laboratory analyses. Furthermore, 60 informed consent subjects will be enrolled to participate in a 12 week randomized, double-blind, placebo-controlled trial of n-3 PUFAs comprising three parallel groups (EPA: 2.3 g/day, n=20; DHA 2.2 g/day, n=20; placebo: soybean oil, n=20). The peripheral blood and urine samples from both the clinical studies will be collected at weeks 0, and 12 for biological markers related to melatonin metabolism and circadian functions. In both cellular and clinical study, oxidative stress-related circadian clock genes will be quantified to substantiate that oxidative stress and inflammation can alter circadian regulation at the transcriptional level. Anticipated outcomes: In preclinical experiments, we will identify the oxidative stress related circadian clock related genes expression and also common and different antioxidant and inflammatory pathways modified by different agents to imply the specific biological mechanisms for individual therapeutic and preventive effects. In clinical experiments, the role of melatonin agonists in circadian rhythm, oxidative stress related circadian-clock-related genes and melatonin metabolisms could provide new insights of the role melatonin in neuropsychiatric disorders.