APOPTOTIC EFFECT OF SERUM ANTIBODIES FROM PATIENTS WITH PRIMARY SJÖGREN SYNDROME - ROLE OF CHOLINERGIC MUSCARINIC RECEPTORS

SILVIA REINA, LEONOR STERIN-BORDA, ENRI BORDA

Buenos Aires, Argentina

Congreso; 3rd Latin American Congress on Autoimmunity; 2010

LACA International

Previously we have shown the presence of autoantibodies against the muscarinic acetylcholine receptor (mAChR) in the serum of patients with primary Sjögren Syndrome (SSp). It is known that G protein-coupled receptors, like the mAChR, modulate the programmed cell death or apoptosis.The aim of this work was to investigate whether the serum immunoglobulin from patients with SSp (IgG SSp) was capable of promoting the apoptotic process, interacting with mAChR of normal human gingival fibroblasts.By primary cell culture techniques and the terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labelling (T.U.N.E.L.) procedure we studied the fragmentation of the DNA in individual culture cells as an apoptotic signal.The IgG SSp shows the concentration-dependent and time-dependent increase the apoptotic process with respect to the baseline.This effect was inhibited by 50% ± 4.8 with 4-DAMP and by 25% ± 2.4 with pirenzepine, blockers for the M1 and M3 mAChR subtypes respectively, and by 83.6% ± 7.4 with M3 synthetic peptide. Also normal lgG, used as a control, showed no effect.The apoptotic process stimulated by IgG SSp was inhibited by 75% ± 7.6 with U-73122 (5x10-6M), a phospholipase C inhibitor, by 50% ± 4.5 with staurosporina (1x10-9M), a protein kinase inhibitor, and by 40% ± 3.5 trifluoperazine (5x10-6M), a calcium-calmodulin inhibitor.We conclude that in the serum of patients with SSp there are antibodies against mAChR, capable of stimulating the apoptotic phenomenon via PCL/Ca2+ pathways, which shows a new evidence of the role of these antibodies in the pathogenesis of the SSp.