Cholinergic System in Lymphocytes

ESANDI MC; DE ROSA MJ; BOUZAT C

New Immunology Research Developments

Nova Science Publications

Año: 2008; p. 1 - 21

Acetylcoline (ACh) plays an important role as a neurotransmitter of the central and peripheral nervous systems. Interestingly, this molecule and its synthesizing enzyme, choline acetyltransferase, are present in lymphocytes. In addition, several types of nicotinic (nAChR) and muscarinic (mAChR) receptors have been identified in these blood cells. These findings have provided evidence that lymphocytes have most of the essential components needed to constitute and independent, non neuronal cholinergic system. Probably, ACh acts as an immunomodulator. It might be that activated immune cells use the released ACh in selfmodulating autocrine and paracrine loops. However, up to this time, controversial results about the distribution of cholinergic receptors in lymphocytes are found in the literature. Due to this variability, the identification of the exact role of this extraneuronal cholinergic system is poorly understood. We have consistently observed the expression of a7 nicotinic receptors mRNA in peripheral human lymphocytes. After incubation of lymphocyte with the agonist nicotine, upregulation of the nicotinic receptors is systematically observed. Same effect was described using the antagonist a-bungarotoxine. In addition, these drugs protect lymphocytes from cortisol-induced apoptosis, suggesting that a7 is involved in the modulation of this process. Apoptosis is important in maintaining homeostasis in the immune system, where cells are continually being generated and destroyed. Other studies have demonstrated that an increment of ACh secretion occurs upon PHA stimulation of human lymphocytes (Fujii et al, 1996; Rinner et al, 1998; Fujii et al, 1998). These data suggest that lymphocyte activation induces ACh synthesis and this neurotransmitter might modulate cell proliferation. All these results contribute to determine the role of the ACh and its receptors in lymphocytes, and propose that the immune function is not only regulated by the cytokine network but is also under the control of an independent cholinergic system.