Regulation of m 1 muscarinic receptors and nNOS mRNA levels by autoantibodies from schizophrenic patients

Abstract

In this paper we demonstrate that, circulating antibodies from schizophrenic patients interacting with cerebral M 1 muscarinic acetylcholine receptors (M 1 mAChRs), can act as an inducer of m 1 mAChR-mRNA, and neuronal nitric oxide synthase (nNOS) mRNA gene expression of rat frontal cortex. The different signaling pathways involved in the autoantibody's actions, were characterized. As previously reported serum autoantibodies from schizophrenic patients reacted against neural cells surface inhibiting the binding of the specific mAChR radioligand to rat cerebral frontal cortex membrane. Moreover, by ELISA using M 1 synthetic peptide (with identical aminoacid sequence to human M 1 mAChR) as coating antigen we demonstrated the reactivity against the second extracellular loop of human cerebral M 1 mAChR. The corresponding affinity-purified anti M 1 peptide IgG (anti M 1 peptide IgG) from schizophrenic patients by stimulation of M 1 mAChR exerted an increase in m 1 mAChR-mRNA and nNOS-mRNA levels, that significantly correlated with the accumulation of phosphoinositides (IPs) and activation of NOS (α = 0.05). All these effects were blunted by pirenzepine and mimicked the action of the authentic agonist. Concurrent analysis of the effects of nNOS, phospholipase C (PLC) and calcium/calmodulin (CaM) inhibition on both, m 1 mAChR-mRNA and nNOS-mRNA levels, showing that antibody up-regulation mRNA level is under the control of endogenous nitric oxide (NO) signaling system. On the basis of our results, the activation of M 1 mAChR by schizophrenic autoantibody appears to induce nNOS-mRNA expression and reciprocally, the activation of NOS up-regulates m 1 mAChR gene expression. These results gave support to the participation of an autoimmune process in a particular group of chronic schizophrenic patients.