Abstract

Melatonin is a hormone with antioxidant properties. In the body, melatonin is involved in regulation of circadian biological rhythm. However, receptors for melatonin are expressed on disparate organs and they can be found on immune cells as well. The present experiment is focused on research whether melatonin would regulate pathogenesis caused by a model intracellular pathogen, Francisella tularensis. For this reason, laboratory mice BALB/c were chosen as a suitable model and they were infected with F. tularensis. Melatonin was given in two doses: 10 and 100 µg/kg. Animals were sacrificed after either three or five days. Spleen and liver were sampled for bacterial burden. Interferon gamma (IFN-γ), interleukin 2 (IL-2) and total immunoglobulins were assayed from plasma samples. The results showed administration of melatonin reduced bacterial burden in the organs in a dose response manner. Surprisingly, IFN-γ and IL-2 levels were reduced as well, while immunoglobulins remained unchanged. We conclude our experiment that melatonin is potent to reduce tularemia progression.

Key words: Melatonin, Francisella tularensis, tularemia, interferon gamma, interleukin 2, oxidative stress, pineal gland, inflammation.