Melatonin: Its microbicidal properties and clinical applications

Abstract

Melatonin is a versatile molecule, synthesized mainly by the pineal gland and in small amounts by other organs like retina, gastrointestinal tract, thymus, bone marrow, and lymphocytes. Other than its important role in various body functions like sleep and circadian rhythm regulation, antioxidant functions, and control of reproductive functions, melatonin has been found to be effective in combating infections by various bacteria including chlamydia and Mycobacterium tuberculosis, as well as by viruses. Molecular mechanisms of antimicrobial actions of melatonin have been proposed to be due to its effects on free radical formation, direct regulation of bacterial duplication, and depletion of intracellular substrates like iron. It also has protective effect against sepsis as shown in various animal models of septic shock. This protective effect is suggested to be due to its antioxidant, immunomodulating, and inhibitory actions against the production and activation of pro-inflammatory mediators. Clinical studies have shown the potential beneficial use of melatonin in treating septic shock with severe respiratory distress syndrome and associated multiorgan failure in addition to its antimicrobial and antiviral actions.