Significance of Melatonin in the Regulation of Circadian Rhythms and Disease Management.

Melatonin, the 'hormone of darkness' is a neuronal hormone secreted by the pineal gland and other extra pineal sites. Responsible for the circadian rhythm and seasonal behaviour of vertebrates and mammals, melatonin is responsible for regulating various physiological conditions and the maintenance of sleep, body weight and the neuronal activities of the ocular sites. With its unique amphiphilic structure, melatonin can cross the cellular barriers and elucidate its activities in the subcellular components, including mitochondria. Melatonin is a potential scavenger of oxygen and nitrogen-reactive species and can directly obliterate the ROS and RNS by a receptor-independent mechanism. It can also regulate the pro- and anti-inflammatory cytokines in various pathological conditions and exhibit therapeutic activities against neurodegenerative, psychiatric disorders and cancer. Melatonin is also found to show its effects on major organs, particularly the brain, liver and heart, and also imparts a role in the modulation of the immune system. Thus, melatonin is a multifaceted candidate with immense therapeutic potential and is still considered an effective supplement on various therapies. This is primarily due to rectification of aberrant circadian rhythm by improvement of sleep quality associated with risk development of neurodegenerative, cognitive, cardiovascular and other metabolic disorders, thereby enhancing the quality of life.

Cascade of immune mechanism and consequences of inflammatory disorders.

Inflammatory responses arise as an outcome of tissues or organs exposure towards harmful stimuli like injury, toxic chemicals or pathogenic microorganism. It is a complex cascade of immune mechanism to overcome from tissue injury and to initiate the healing process by recruiting various immune cells, chemical mediators such as the vasoactive peptides and amines, pro-inflammatory cytokines, eicosanoids and acute-phase proteins to prevent tissue damage and ultimately complete restoration of the tissue function. The cytokines exhibits a central function in communication between the cells, inflammatory response initiation, amplification and their regulation. This review covers the importance of inflammatory responses; the significance of cytokines in inflammation and numerous inflammatory disorders/ailments due to the abrupt expression of cytokines and the hyper-inflammatory response or cytokine storm associated with poor prognosis in COVID-19 pandemic. Also highlighting the importance of naturally derived anti-inflammatory metabolites to overcome the side-effects of currently prevailing anti-inflammatory drugs.