Effects and mechanisms of melatonin on immune responses in mice of different months.
OBJECTIVE
To study the effects and mechanisms of melatonin (MT) on immune responses in mice of different months.


METHODS
Thymocyte proliferation and IL-2 activity were assayed by 3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) and activated mouse splenocyte proliferation methods, respectively; cAMP and methionine-enkephalin (met-Enk) level was determined by competitive protein binding assay and radioimmunoassay, respectively.


RESULTS
The function of lymphocytes, obtained from BALB/c mice aged 6 and 11 months were decreased, which was restored by melatonin at the dose of 5 mg/kg or 30 mg/kg. In vitro, proliferation of lymphocytes in 11-month-old mice was decreased and cAMP level was increased. Melatonin (0.1 nmol/L or 1 micromol/L) had negative regulation to this. Forskolin (10 micromol/L) enhanced the cAMP level of lymphocytes in 2- and 11-month-old mice (P<0.01), which was antagonized partially by melatonin and this effect of melatonin was also abolished by pertussis toxin (1 mg/L) completely. Melatonin (1 micromol/L and 0.1 nmol/L) increased the content of met-Enk of lymphocytes in 2- and 11-month-old mice, respectively (P<0.01), which was blocked by nifedipine (1 micromol/L).


CONCLUSIONS
Melatonin exerted an effect on immune responses in mice of different months, which might be mediated by G protein-AC-cAMP signal transduction pathway and regulation of met-Enk level.
Wei
Wei
W
Institute of Clinical Pharmacology, Anhui Medical University, Hefei 230032, China. wwei@ahmu.edu.cn
Shen
Yu-Xian
YX
Dai
Min
M
Chen
Qun
Q
D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000367:Age Factors; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002469:Cell Separation; D000242:Cyclic AMP / Q000096:biosynthesis; D004744:Enkephalin, Methionine / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D007109:Immunity / Q000187:drug effects* / Q000276:immunology; D007376:Interleukin-2 / Q000096:biosynthesis; D008214:Lymphocytes / Q000187:drug effects* / Q000276:immunology; D008550:Melatonin / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D051381:Rats; D015398:Signal Transduction
D000276:Adjuvants, Immunologic; D007376:Interleukin-2; D004744:Enkephalin, Methionine; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D008550:Melatonin