Sylvain Bougoin, Nicole Kerlero de Rosbo, Sonia Berrih-Aknin Muscle pathophysiology: Anti-AChR antibodies increase IL-6 production by myoblasts and myotubes in vitro Sylvain Bougoin, Nicole Kerlero de Rosbo, Sonia Berrih-Aknin UMR CNRS-UPS 8162, Centre chirurgical Marie Lannelongue, Le Plessis Robinson, France International Conference on Myasthenia Gravis, December 1-2, 2009

Understanding the consequences of the autoimmune attack on the muscle function Anti-AChR antibodies MIR : Main Immunogenic Region Accelerated degradation of AChR (Drachman et al. 1977) Complement mediated damage (Engel et al. 1976) Blocking antibodies (Howard et al. 1987) MG Muscle (Adapted from Drachman et al, 1994) Control Muscle

Transcriptome analysis of rat and human muscle Rat / EAMG Rat (Feferman, Fuchs, Souroujon) Human Control / MG List of dysregulated genes List of dysregulated genes Muscle structural genes regulated Genes coding for heat-shock proteins Signaling pathways Ex: IL-6 Abs effect on IL-6 production?

Why IL-6? Important role in the immune system:  Differentiation of the B cells (Klashman DJ. et al, 1991)  Differentiation, proliferation and survival of lymphocytes (Smol'nikova V.V. et al, 2000) High IL-6 gene expression and production by cultured human thymic epithelial cells from patients with myasthenia gravis (Cohen-Kaminsky S. et al, 1993) IL-6 has a role in muscular contraction and is a regulator of Skeletal Muscle Hypertrophy (McKay R. et al, 2009; Serrano L. et al, 2008) No MG induction in IL-6-/- mice (Deng C. et al, 2002)

Methods Internalisation (Alpha-Bgt binding) IL-6 production (ELISA assays) Sera (Control, SPMG, SNMG) Mabs (198, 155) (S. Tzartos) Mab 198 Mab 155 Extracellular Intracellular Human myogenic cell line (LHCN) (V. Mouly ) Myoblasts Myotubes

Effects of patient sera on IL-6 production Kinetics of IL-6 production IL-6 production at 48 hours p<0.01 p<0.05 Patient sera induce the production of IL-6 by myoblasts Is the serum effect due to anti-AChR antibodies ?

Effects of monoclonal anti-AChR antibodies on IL-6 production MAbs: monoclonal antibodies (Rat) Kinetics of IL-6 production IL-6 production at 48 hours p<0.001 p<0.01 Anti-AChR antibody 198 induces the production of IL-6 by myoblasts Is the IL-6 production due to AChR internalization?

Ab 198 induces both a strong internalization and IL-6 production Effects of Mab anti-AChR on human myotubes AChR expression at 12 hours Kinetics of IL-6 production p<0.01 Ab 198 induces both a strong internalization and IL-6 production

Effect of MG sera on surface AChR levels AChR expression Kinetics of IL-6 production Poea S. et al, 2000 SNMG SPMG CONTROLS Surprisingly, sera from patients with anti-AChR antibodies do not induce significant production of IL-6, while sera with undetectable antibodies do Production of IL-6 and internalization appear to be independent events Mechanisms involved?

Work in progress: Signaling Pathways NF-κB… Ca2+ Release 10µM Ca2+ Release Signaling Pathways NF-κB… 2µM 5µM Il-6 production

IL-6 production A new action mechanism of anti-AChR on muscular cells Conclusion: Sera (Control, SPMG, SNMG) Mabs (198, 155) (S. Tzartos) Myotubes Myoblasts IL-6 production A new action mechanism of anti-AChR on muscular cells

Future work MG: Regenerative capacity of satellite cells Ca2+ Release ? ? Satellites cells proliferation Il-6 production Cyclin D1 JAK2/STAT3 Mc Kay et al. 2009 ? Local immune role