Showing papers by "Chandana Haldar published in 2012"

Daily variation in antioxidant enzymes and lipid peroxidation in lungs of a tropical bird Perdicula asiatica: role of melatonin and nuclear receptor RORα.

Abstract: The wild animals are exposed in nature to more oxidative stress than any laboratory animals. Studies on oxidative stress of brain, liver and kidney are quite common while very less reports are available on respiratory system when it is the most susceptible organ to various stressors. We checked the oxidative stress of lung tissue of a wild seasonally breeding bird Perdicula asiatica by noting down the daily variation in antioxidant enzymes (superoxide dismutase and catalase) levels, lipid peroxidation in terms of malondialdehyde level and total antioxidant status during reproductively active (RAP) and inactive phase (RIP). On the other hand melatonin has been accepted as free radical scavenger acting via receptor (nuclear receptor) or non receptor pathway. To pin point the role of melatonin in regulation of antioxidant enzymes via non receptor mediated pathway in lungs of bird, we checked variation in the nuclear melatonin receptor RORα. Antioxidant enzymes (superoxide dismutase and catalase) exhibited a marked 24h rhythm in lungs being high during night time and coincided almost with the peak of melatonin and total antioxidant status where as malondialdehyde level and nuclear receptor RORα showed inverse relationship with all the above mentioned parameters. These findings suggest that melatonin might be acting as an antioxidant for the free radical load of lung tissue of a tropical bird P. asiatica and its action might be via nuclear receptor RORα.

Age dependent expression of melatonin membrane receptor (MT1, MT2) and its role in regulation of nitrosative stress in tropical rodent Funambulus pennanti

Abstract: Age-dependent declining level of melatonin induces free radical load and thereby deteriorates immune function. However, reports are lacking about age-dependent melatonin membrane receptor (MT1 & MT2) expression, their role in regulation of reactive nitrogen species (RNS) and eventually how they affect immunity of a tropical rodent F. pennanti . We checked MT1R, MT2R and iNOS expression in lymphoid organs of young middle and old aged squirrels. Nitrite and nitrate ion concentration (NOx) in lymphoid organs, testes and plasma, lymphocyte proliferation and IL-2 level was recorded. Age-dependent decrease in MT1 and MT2 receptor expression, lymphocyte proliferation, IL-2 level and increased RNS in lymphoid organs, testes and plasma was observed with decreased circulatory melatonin. Androgen and AR expression was increased in middleaged while declined in old-aged squirrels. Present study suggests that age associated immunosenescence is consequence of increased RNS which might have important relationship with melatonin membrane receptors in F. pennanti .

Melatonin membrane receptor type MT1 modulates cell-mediated immunity in the seasonally breeding tropical rodent Funambulus pennanti.

Abstract: Objective: Despite the evidence for melatonin membrane receptors (MT1R and MT2R) on lymphoid tissues in a wide range of seasonal breeders, their specific potency has never been compared and correlated with cell-mediated immunity. Methods: We used luzindole, a nonselective MT2R antagonist, and 4-phenyl-2-propionamidotetralin (4P-PDOT), a selective MT2R antagonist, to assess the potency of the melatonin receptors MT1 and MT2 in melatonin-induced immunity under both in vivo as well as in vitro conditions. Results: Physiological doses (25 µg/100 g body weight in vivo and 100 and 500 pg/ml in vitro) of melatonin upregulated both MT1R and MT2R expression as well as splenocyte proliferation, while higher doses (100 and 500 µg/100 g body weight in vivo and 1 ng/ml in vitro) downregulated splenocyte proliferation and the expression of both receptors. Luzindole antagonized the expression of both MT1R and MT2R in a dose-dependent manner under in vivo as well as in vitro conditions, while 4P-PDOT blocked the expression of MT2R only during both experimental conditions. Splenocyte proliferation and IL-2 secretion (in vitro) followed the MT1R expression pattern, while the MT2R expression pattern showed no definite relation with either splenocyte proliferation or IL-2 secretion under in vivo and in vitro conditions. Conclusion: Immune function in tropical rodents is directly regulated by melatonin via its high-affinity membrane receptor MT1. MT1R plays a directive role in mediating splenocyte proliferation and IL-2 release, while the MT2R subtype appears not to be required for the immunoenhancing role of melatonin.

L-5-hydroxytryptophan resets the circadian locomotor activity rhythm of the nocturnal Indian pygmy field mouse, Mus terricolor.

Abstract: We report that l-5-hydroxytryptophan (5-HTP), a serotonin precursor, resets the overt circadian rhythm in the Indian pygmy field mouse, Mus terricolor, in a phase- and dose-dependent manner. We used wheel running to assess phase shifts in the free-running locomotor activity rhythm. Following entrainment to a 12:12 h light–dark cycle, 5-HTP (100 mg/kg in saline) was intraperitoneally administered in complete darkness at circadian time (CT)s 0, 3, 6, 9, 12, 15, 18, and 21, and the ensuing phase shifts in the locomotor activity rhythm were calculated. The results show that 5-HTP differentially shifts the phase of the rhythm, causing phase advances from CT 0 to CT 12 and phase delays from CT 12 to CT 21. Maximum advance phase shift was at CT 6 (1.18 ± 0.37 h) and maximum delay was at CT 18 (−2.36 ± 0.56 h). No extended dead zone is apparent. Vehicle (saline) at any CT did not evoke a significant phase shift. Investigations with different doses (10, 50, 100, and 200 mg/kg) of 5-HTP revealed that the phase resetting effect is dose-dependent. The shape of the phase–response curve (PRC) has a strong similarity to PRCs obtained using some serotonergic agents. There was no significant increase in wheel-running activity after 5-HTP injection, ruling out behavioral arousal-dependent shifts. This suggests that this phase resetting does not completely depend on feedback of the overt rhythmic behavior on the circadian clock. A mechanistic explanation of these shifts is currently lacking.

Immune responses to lipopolysaccharide challenge in a tropical rodent (Funambulus pennanti): photoperiod entrainment and sex differences.

Abstract: Annual variation in day length (photoperiod) triggers changes in the immune system of seasonal breeders. The rationale behind this study was to delineate any sex differences in immune responses of photoperiodically entrained animals challenged against lipopolysaccharide (LPS)-induced inflammatory stress. We observed that photoperiodically entrained [short day, SD, 10 h light (L):14 h dark (D); long day, LD, 16 h L:8 h D; and natural day length, NDL, 12 h L:12 h D] male and female Indian palm squirrels, Funambulus pennanti, presented sexual dimorphism in immune status after LPS-induced stress. Females presented high humoral (anti-keyhole limpet hemocyanin immunoglobulin) and cellular immunity (lymphocyte proliferation) compared with the males of all photoperiodic conditions. Female squirrels showed reduced pro-inflammatory cytokine levels (interleukin-1β, interleukin-6, and tumor necrosis factor-α) than the males suggesting their high efficiency to recover from LPS-induced inflammatory stress. Increased du...

Peripheral autonomic nerves of human pineal organ terminate on vessels, their supposed role in the periodic secretion of pineal melatonin.

Abstract: Nonvisual pineal and retinal photoreceptors are synchronizing circadian and circannual periodicity to the environmental light periods in the function of various organs. Melatonin of the pineal organ is secreted at night and represents an important factor of this periodic regulation. Night illumination suppressing melatonin secretion may result in pathological events like breast and colorectal cancer. Experimental works demonstrated the role of autonomic nerves in the pineal melatonin secretion. It was supposed that mammalian pineals have lost their photoreceptor capacity that is present in submammalians, and sympathetic fibers would mediate light information from the retina to regulate melatonin secretion. Retinal afferentation may reach the organ by central nerve fibers via the pineal habenulae as well. In our earlier works we have found that the pineal organ developing from lobular evaginations of the epithalamus differs from peripheral endocrine glands and is composed of a retina-like central nervous tissue that is comprised of cone-like pinealocytes, secondary pineal neurons and glial cells. Their autonomic nerves in submammalians as well as in mammalian animals do not terminate on pineal cells, rather, they run in the meningeal septa among pineal lobules and form vasomotor nerve endings. Concerning the adult human pineal there are no detailed fine structural data about the termination of autonomic fibers, therefore, in the present work we investigated the ultrastructure of the human pineal peripheral autonomic nerve fibers. It was found, that similarly to other parts of the brain, autonomic nerves do not enter the human pineal nervous tissue itself but separated by glial limiting membranes take their course in the meningeal septa of the organ and terminate on vessels by vasomotor endings. We suppose that these autonomic vasomotor nerves serve the regulation of the pineal blood supply according to the circadian and circannual changes of the metabolic activity of the organ and support by this effect the secretion of pineal neurohormones including melatonin.

Eco-Immunology: Role of Melatonin in Avian Immune Defense

Abstract: Avian immunology is a fascinating and growing field. Ecologists are now taking an interest in measuring immune-competence and determining its importance as a heritable trait for the survival of the wild species. Seasonally breeding animals encounter different environmental challenges throughout the year. In order to survive in specific environments these animals have developed various strategies that help them to find food, protect themselves from the tough environments, and also reproduce accordingly. Indeed, wild birds are continually challenged with different natural stressors such as shortage of food (during winter and rainy season), lack of water during summer, predator pressure in social system, sudden change in weather, season-bound diseases, infection (like avian influenza), etc. Only a few ecological studies have analyzed the stress and general immunity in wild birds that might have a link with the anti-stress hormone melatonin. Therefore, approaches improving our understanding of the stress-induced immune depression and their interrelationship in birds are most desirable. Unfortunately, our knowledge of the immune system has advanced at a much faster pace for mammals while immunology of wild birds received less attention. The purpose of this review is to bring together the current knowledge on the biological effects of melatonin on avian immune defense with special emphasis on new immerging area of neuro-immuno-endocrinology i.e., eco-immunology.