Therapeutic aspects of melatonin in bone marrow and thyroid associated immune regulation

Abstract

The immune system is functionally compartmentalized and is collectively modulated by various internal factors such as hormones, cytokines and externally by seasonal variations in day-length. Neuro-hormone melatonin serves as a "Timezyme" (marker of day-length variation) and a connecting link between the neuro-immuno-endocrine circuits. The role of melatonin in regulating immune functions is well documented. Previous studies have reported that the process of hematopoiesis is regulated by the peripheral levels of melatonin as well as the melatonin synthesized within the microenvironment of bone marrow. The bone marrow granulocyte macrophage colony forming cells (CFU-GM) rhythmically proliferates during the dark hours coinciding with the higher circulatory levels of melatonin. Melatonin acts through its highly specific receptor MT1 present on the surface of progenitor immuno-competent cells (B- and T-cells). Literature suggests that the thyroid hormone(s) also play a key role in regulation of immune functions by acting on immuno-competent cells through its receptor TR-a. Altered thyroid status is responsible for imbalances in antioxidant-pro-oxidant level in lymphoid organs. Melatonin being a well-known endogenous antioxidant effectively combats oxidative stress in lymphoid tissues induced by altered thyroid hormones. Most of evidences exist supporting that melatonin influences CFU-GM function. How the thyroid gland dysfunction influences immune status and bone marrow CFU-GM function is a question for neuro-endocrinologists as melatonin and thyroid hormone both influences immunity. The review encompasses the role of melatonin in regulation of bone marrow function and thyroid function whose interaction is finally responsible in regulation of immunity in normal and clinical conditions. These interactions can be easily judged by the expression of MT1 and TR-a in lymphoid organ which can throw a light in multifarious hypothesis of immune regulation to explain various clinical challenges. Thus, having diverse beneficial functions melatonin could be a potent therapeutic agent to treat the immuno-compromised state of an individual. © 2017 Nova Science Publishers, Inc.