Influence of melatonin therapy and orchiectomy on T cell subsets in male Wistar rats infected with Trypanosoma cruzi

Melatonin: A look at protozoal and helminths

Melatonin is a pleiotropic neurohormone found in different animal, plant, and microorganism species. It is a product resulting from tryptophan metabolism in the pineal gland and is widely known for its ability to synchronize the circadian rhythm to antitumor functions in different types of cancers. The molecular mechanisms responsible for its immunomodulatory, antioxidant and cytoprotective effects involve binding to high-affinity G protein-coupled receptors and interactions with intracellular targets that modulate signal transduction pathways. In vitro and in vivo studies have reported the therapeutic potential of melatonin in different infectious and parasitic diseases. In this review, the protective and pathophysiological roles of melatonin in fighting protozoan and helminth infections and the possible mechanisms involved against these stressors will be discussed.

Melatonin decreases circulating Trypanosoma cruzi load with no effect on tissue parasite replication

Cardiac damage during the acute phase of Chagas disease (CD) is associated with an increase in pro-inflammatory markers and oxidative stress. Melatonin (MEL) has emerged as a promising therapy for CD due to its antioxidant and immunomodulatory properties; however, the protective action of MEL in the cardiac tissue, as well as its direct action on the parasite cycle, is not fully understood. We investigated the effects of MEL on heart parasitism in mice infected with Trypanosoma cruzi and also its effects on the parasitic proliferation in vitro. Our in vivo study showed that MEL reduced circulating parasitemia load, but did not control tissue (heart, liver, and spleen) parasitism in mice. MEL did not prevent the redox imbalance in the left ventricle of infected mice. Our in vitro findings showed that MEL did not inhibit parasites replication within cells, but rather increased their release from cells. MEL did not control parasitism load in the heart or prevent the cardiac redox imbalance induced by acute T. cruzi infection. The hormone controlled the circulating parasitic load, but within cells MEL accelerated parasitic release, a response that can be harmful.

Plasma melatonin and urinary 6-hydroxymelatonin levels in patients with pulmonary tuberculosis

Tuberculosis (TB) is the second most frequent cause of death in the world, after AIDS. Delay in diagnosing TB is an important worldwide problem. It seriously threatens public health. Cell-mediated immune responses play an important role in the pathogenesis of TB infection. The course of Mycobacterium tuberculosis (MTb) infection is regulated by two distinct T cell cytokine patterns. Melatonin is a biomolecule (mainly secreted by the pineal gland) with free radical scavenging, antioxidant and immunoregulatory properties. Melatonin has both its direct and indirect immunomodulatory effects on the immune system. In this study, we measured plasma melatonin and urine 6-hydroxy melatonin sulphate (6-HMS) concentrations in patients with newly diagnosed TB for the purpose of investigating whether there was a relationship between their levels and MTb infection. Thirty-one newly diagnosed patients presenting with active TB and 31 healthy subjects as the control group were included in this study. Blood and 24-h urine samples were collected from all individuals. Plasma melatonin levels and urine 6-HMS were measured. Our results show that in patients with TB, mean melatonin and 6-HMS concentrations were significantly lower than in the control subjects (p = 0.037, p < 0.001, respectively). We believe that the treatment of TB patients with melatonin might result in a wide range of health benefits including improved quality of life and reduced severity of infection in these patients. Supplementation with melatonin may be considered as an adjunctive therapy to classic treatment of pulmonary TB, especially during the acute phase of infection.

Progesterone induces mucosal immunity in a rodent model of human taeniosis by Taenia solium

More than one quarter of human world's population is exposed to intestinal helminth parasites. The Taenia solium tapeworm carrier is the main risk factor in the transmission of both human neurocysticercosis and porcine cysticercosis. Sex steroids play an important role during T. solium infection, particularly progesterone has been proposed as a key immunomodulatory hormone involved in susceptibility to human taeniosis in woman and cysticercosis in pregnant pigs. Thus, we evaluated the effect of progesterone administration upon the experimental taeniosis in golden hamsters (Mesocricetus auratus). Intact female adult hamsters were randomly divided into 3 groups: progesterone-subcutaneously treated; olive oil-treated as the vehicle group; and untreated controls. Animals were treated every other day during 4 weeks. After 2 weeks of treatment, all hamsters were orally infected with 4 viable T. solium cysticerci. After 2 weeks post infection, progesterone-treated hamsters showed reduction in adult worm recovery by 80%, compared to both vehicle-treated and non-manipulated infected animals. In contrast to control and vehicle groups, progesterone treatment diminished tapeworm length by 75% and increased proliferation rate of leukocytes from spleen and mesenteric lymph nodes of infected hamsters by 5-fold. The latter exhibited high expression levels of IL-4, IL-6 and TNF-α at the duodenal mucosa, accompanied with polymorphonuclear leukocytes infiltration. These results support that progesterone protects hamsters from the T. solium adult tapeworm establishment by improving the intestinal mucosal immunity, suggesting a potential use of analogues of this hormone as novel inductors of the gut immune response against intestinal helminth infections and probably other bowel-related disorders.

The role of melatonin in parasite biology

Regarded as the circadian hormone in mammals, melatonin is a highly conserved molecule, present in nearly all species. In this review, we discuss the role of this indolamine and its precursors in the cell biology of parasites and the role of the molecule in the physiology of the host. In Plasmodium, melatonin can modulate intracellular concentrations of calcium and cAMP, which in turn can regulate kinase activity and cell cycle. In Trypanosoma infections, modulation of the immune system by melatonin is extremely important in controlling the parasite population. Melatonin also contributes to the inflammatory response to Toxoplasma gondii infection. Thus, there are a number of unique adaptations involving intricate connections between melatonin and the biology of the parasite-host relationship.

Curcumin, myrecen and cineol modulate the percentage of lymphocyte subsets altered by 2,3,7, 8-tetracholorodibenzo-p-dioxins (TCDD) in rats

The aim of this study was to investigate the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a persistent environmental pollutant, on the percentage of T-cell subsets and B-lymphocyte and effectiveness of curcumin, β-myrcene (myrcene) and 1,8-cineole (cineol) on this toxicity in rats. Rats (n = 112) were divided randomly into 8 equal groups. One group was kept as control and given corn oil as carrier. TCDD was orally administered at the dose of 2 µg/kg/week. Curcumin, myrcene and cineol were orally administered by gavages at the doses of 100, 200 and 100 mg/kg/day, respectively, dissolved in corn oil with and without TCDD. The blood samples were taken from half of the rats on day 30 and from the rest on day 60 for the determination of lymphocyte subsets (CD3(+), CD4(+), CD8(+), CD161(+), CD45RA, CD4(+)CD25(+) and total lymphocyte). The results indicated that although TCDD significantly (p < 0.05) decreased the percentage of CD3(+), CD4(+), CD161(+), CD45RA, CD4(+)CD25(+) and total lymphocyte, it caused a significant increase in the percentage of CD8(+) cells. In contrast, curcumin, myrcene and cineol significantly decreased CD8(+) cells levels but increased CD3(+), CD4(+), CD161(+), CD45RA, CD4(+)CD25(+) and total lymphocyte cells populations. The beneficial effects of curcumin, myrcene and cineol and the toxic effects of TCDD were increased at day 60 compared to day 30. In conclusion, curcumin, myrcene and cineol showed immunomodulatory effects and eliminated TCDD-induced immune suppressive effects in rats.