| Research Abstract |
To clarify the regulatory mechanism of neurotransmitter in the immune system and the neuroimmune interaction, we have been investigated the presence of muscarinic acetylcholine (mACh) receptors and the transmembrane control in human T lymphocytes. In Jurkat cells which is a cloned human T lymphocyte, muscarinic agonist oxotremorine-M (Oxo-M) caused a transient rise of intracellular concentration of Ca^<2+> ([Ca^<2+>]_i). In addition, Oxo-M stimulated a formation of inositol-1, 4, 5-trisphosphate (IP_3) but did not affect the cyclic AMP level. Oxo-M-induced [Ca^<2+>]_i rise was not affected by omission of Ca^<2+> in the medium and by pretreatment with pertussis, cholera or botulinus toxin. While, Gpp (NH) p and IP_3 caused [Ca^<2+>]_i in digitonin-permeabilized cells. Scatchard analysis of [ ^3H]QNB binding in Jurkat cells indicated : K_D=14 nM and Bmax=45, 000 sites/cell. In addition, Northern blot analysis showed to be expressed m3 type of mACh receptor mRNA. These results suggest tha
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t M_3-mACh receptors exist in human T lymphocytes and the activation of the receptors causes Ca^<2+> mobilization from intracellular Ca^<2+> stores via bacterial toxin-insensitive GTP-binding proteins (probably Gq-like GTP-binding proteins), phospholipase C (PLC) activation and IP_3 formation. Furthermore, to clarify the physiological function of M_3-mACh receptors in the immune system, we then examined effects of M_3-mACh receptor activation on interleukin-2 (IL-2) production from human peripheral blood T lymphocytes.
In electrophysiological assay system using Xenopus oocytes into which rat brain mRNA were microinjected, we identified novel type of IL-2 receptors. The receptors seem to activate PLC via GTP-binding proteins in the brain. We are now planning the cDNA cloning of the novel IL-2 receptors.
MPP^+, a selective neurotoxin to dopamine (DA) neurons, which causes Parkinsonism-like syndromes, decreased the DA content in PC12 cells, a DA neuron-model. IL-6 inhibited MPP^+-induced decrease in the DA content. IL-6 also enhanced the expression of tyrosine hydroxylase mRNA, suggesting that IL-6 exerts protective effects to neurons in the central nervous system. Less
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