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IL-6 and Akt are involved in muscular pathogenesis in myasthenia gravis.

Maurer M, Bougoin S, Feferman T, Frenkian M, Bismuth J, Mouly V, Clairac G, Tzartos S, Fadel E, Eymard B, Fuchs S, Souroujon MC, Berrih-Aknin S - Acta Neuropathol Commun (2015)

Bottom Line: Furthermore, Akt phosphorylation in response to insulin was decreased in the presence of monoclonal anti-AChR antibodies.IL-6 is a myokine with known effects on signaling pathways such as Akt/mTOR (mammalian Target of Rapamycin).Since Akt plays a key role in multiple cellular processes, the reduced phosphorylation of Akt by the anti-AChR antibodies may have a significant impact on the muscle fatigability observed in MG patients.

View Article: PubMed Central - PubMed

Affiliation: Sorbonne Universités, UPMC Univ Paris 06, Myology Research Center UM76, Paris, F-75013, France. sonia.berrih-aknin@upmc.fr.

ABSTRACT

Introduction: Anti-acetylcholine receptor (AChR) autoantibodies target muscles in spontaneous human myasthenia gravis (MG) and its induced experimental autoimmune model MG (EAMG). The aim of this study was to identify novel functional mechanisms occurring in the muscle pathology of myasthenia.

Results: A transcriptome analysis performed on muscle tissue from MG patients (compared with healthy controls) and from EAMG rats (compared with control rats) revealed a deregulation of genes associated with the Interleukin-6 (IL-6) and Insulin-Like Growth Factor 1 (IGF-1) pathways in both humans and rats. The expression of IL-6 and its receptor IL-6R transcripts was found to be altered in muscles of EAMG rats and mice compared with control animals. In muscle biopsies from MG patients, IL-6 protein level was higher than in control muscles. Using cultures of human muscle cells, we evaluated the effects of anti-AChR antibodies on IL-6 production and on the phosphorylation of Protein Kinase B (PKB/Akt). Most MG sera and some monoclonal anti-AChR antibodies induced a significant increase in IL-6 production by human muscle cells. Furthermore, Akt phosphorylation in response to insulin was decreased in the presence of monoclonal anti-AChR antibodies.

Conclusions: Anti-AChR antibodies alter IL-6 production by muscle cells, suggesting a putative novel functional mechanism of action for the anti-AChR antibodies. IL-6 is a myokine with known effects on signaling pathways such as Akt/mTOR (mammalian Target of Rapamycin). Since Akt plays a key role in multiple cellular processes, the reduced phosphorylation of Akt by the anti-AChR antibodies may have a significant impact on the muscle fatigability observed in MG patients.

No MeSH data available.


Related in: MedlinePlus

Monoclonal anti-AChR antibodies increase IL-6 production by muscle cells. The LHCNM2 cells were cultured as described in the Materials and Methods section, as myoblasts or after differentiation into myotubes. (A) IL-6 production was measured by ELISA and normalized to controls (without antibody). Myotubes were treated with anti-AChR antibodies (198, 155, 35 and Acrys), their isotype controls (IgG2a, IgG1), or left untreated (Ctl). The data come from four experiments, each including 4–6 replicates. (B) For some antibodies, the effect on myotubes (black bars) and myoblasts (white bars) was compared. The data come from three experiments, each including 2–4 replicates. (C) The expression of AChR subunits in myotubes (black bars) and myoblasts (white bars) was assessed by Q-RT-PCR (n = 4). (D) Addition of the anti-AChR mAb 198 was performed at several time points and all supernatants were analyzed at 72 h. mAb 198 was added once (bar A), twice (bars B and C), or at three consecutive time points (bar D). The results shown are from two wells for each condition in a representative experiment. Bars and error bars represent mean ± SEM. ***p < 0.001; **p < 0.01; *p < 0.05.
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Fig4: Monoclonal anti-AChR antibodies increase IL-6 production by muscle cells. The LHCNM2 cells were cultured as described in the Materials and Methods section, as myoblasts or after differentiation into myotubes. (A) IL-6 production was measured by ELISA and normalized to controls (without antibody). Myotubes were treated with anti-AChR antibodies (198, 155, 35 and Acrys), their isotype controls (IgG2a, IgG1), or left untreated (Ctl). The data come from four experiments, each including 4–6 replicates. (B) For some antibodies, the effect on myotubes (black bars) and myoblasts (white bars) was compared. The data come from three experiments, each including 2–4 replicates. (C) The expression of AChR subunits in myotubes (black bars) and myoblasts (white bars) was assessed by Q-RT-PCR (n = 4). (D) Addition of the anti-AChR mAb 198 was performed at several time points and all supernatants were analyzed at 72 h. mAb 198 was added once (bar A), twice (bars B and C), or at three consecutive time points (bar D). The results shown are from two wells for each condition in a representative experiment. Bars and error bars represent mean ± SEM. ***p < 0.001; **p < 0.01; *p < 0.05.

Mentions: To investigate whether these effects on IL-6 production were due to anti-AChR antibodies, we tested the effect of several anti-AChR monoclonal antibodies (Figure 4). For each antibody, the relevant isotype control was used for normalization (IgG2a or IgG1). MAb 198 and mAb 35 are directed against the main immunogenic region on the extracellular part of the alpha subunit and are known to cause not only antigenic modulation but also passive transfer EAMG [25]. MAb 155 has been described to bind to a major epitope of the cytoplasmic side of the α-subunit [25]. The Acris mAb, a commercial monoclonal antibody, reacts with an unknown epitope of the human AChR. We observed that mAb 198 had a larger effect on IL-6 production by myotubes than mAb 35, mAb 155 or Acris mAb (Figure 4A). These data suggest that the induction of IL-6 by anti-AChR mAbs is dependent on the epitope recognized by the antibody.Figure 4


IL-6 and Akt are involved in muscular pathogenesis in myasthenia gravis.

Maurer M, Bougoin S, Feferman T, Frenkian M, Bismuth J, Mouly V, Clairac G, Tzartos S, Fadel E, Eymard B, Fuchs S, Souroujon MC, Berrih-Aknin S - Acta Neuropathol Commun (2015)

Monoclonal anti-AChR antibodies increase IL-6 production by muscle cells. The LHCNM2 cells were cultured as described in the Materials and Methods section, as myoblasts or after differentiation into myotubes. (A) IL-6 production was measured by ELISA and normalized to controls (without antibody). Myotubes were treated with anti-AChR antibodies (198, 155, 35 and Acrys), their isotype controls (IgG2a, IgG1), or left untreated (Ctl). The data come from four experiments, each including 4–6 replicates. (B) For some antibodies, the effect on myotubes (black bars) and myoblasts (white bars) was compared. The data come from three experiments, each including 2–4 replicates. (C) The expression of AChR subunits in myotubes (black bars) and myoblasts (white bars) was assessed by Q-RT-PCR (n = 4). (D) Addition of the anti-AChR mAb 198 was performed at several time points and all supernatants were analyzed at 72 h. mAb 198 was added once (bar A), twice (bars B and C), or at three consecutive time points (bar D). The results shown are from two wells for each condition in a representative experiment. Bars and error bars represent mean ± SEM. ***p < 0.001; **p < 0.01; *p < 0.05.
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Related In: Results  -  Collection

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Fig4: Monoclonal anti-AChR antibodies increase IL-6 production by muscle cells. The LHCNM2 cells were cultured as described in the Materials and Methods section, as myoblasts or after differentiation into myotubes. (A) IL-6 production was measured by ELISA and normalized to controls (without antibody). Myotubes were treated with anti-AChR antibodies (198, 155, 35 and Acrys), their isotype controls (IgG2a, IgG1), or left untreated (Ctl). The data come from four experiments, each including 4–6 replicates. (B) For some antibodies, the effect on myotubes (black bars) and myoblasts (white bars) was compared. The data come from three experiments, each including 2–4 replicates. (C) The expression of AChR subunits in myotubes (black bars) and myoblasts (white bars) was assessed by Q-RT-PCR (n = 4). (D) Addition of the anti-AChR mAb 198 was performed at several time points and all supernatants were analyzed at 72 h. mAb 198 was added once (bar A), twice (bars B and C), or at three consecutive time points (bar D). The results shown are from two wells for each condition in a representative experiment. Bars and error bars represent mean ± SEM. ***p < 0.001; **p < 0.01; *p < 0.05.
Mentions: To investigate whether these effects on IL-6 production were due to anti-AChR antibodies, we tested the effect of several anti-AChR monoclonal antibodies (Figure 4). For each antibody, the relevant isotype control was used for normalization (IgG2a or IgG1). MAb 198 and mAb 35 are directed against the main immunogenic region on the extracellular part of the alpha subunit and are known to cause not only antigenic modulation but also passive transfer EAMG [25]. MAb 155 has been described to bind to a major epitope of the cytoplasmic side of the α-subunit [25]. The Acris mAb, a commercial monoclonal antibody, reacts with an unknown epitope of the human AChR. We observed that mAb 198 had a larger effect on IL-6 production by myotubes than mAb 35, mAb 155 or Acris mAb (Figure 4A). These data suggest that the induction of IL-6 by anti-AChR mAbs is dependent on the epitope recognized by the antibody.Figure 4

Bottom Line: Furthermore, Akt phosphorylation in response to insulin was decreased in the presence of monoclonal anti-AChR antibodies.IL-6 is a myokine with known effects on signaling pathways such as Akt/mTOR (mammalian Target of Rapamycin).Since Akt plays a key role in multiple cellular processes, the reduced phosphorylation of Akt by the anti-AChR antibodies may have a significant impact on the muscle fatigability observed in MG patients.

View Article: PubMed Central - PubMed

Affiliation: Sorbonne Universités, UPMC Univ Paris 06, Myology Research Center UM76, Paris, F-75013, France. sonia.berrih-aknin@upmc.fr.

ABSTRACT

Introduction: Anti-acetylcholine receptor (AChR) autoantibodies target muscles in spontaneous human myasthenia gravis (MG) and its induced experimental autoimmune model MG (EAMG). The aim of this study was to identify novel functional mechanisms occurring in the muscle pathology of myasthenia.

Results: A transcriptome analysis performed on muscle tissue from MG patients (compared with healthy controls) and from EAMG rats (compared with control rats) revealed a deregulation of genes associated with the Interleukin-6 (IL-6) and Insulin-Like Growth Factor 1 (IGF-1) pathways in both humans and rats. The expression of IL-6 and its receptor IL-6R transcripts was found to be altered in muscles of EAMG rats and mice compared with control animals. In muscle biopsies from MG patients, IL-6 protein level was higher than in control muscles. Using cultures of human muscle cells, we evaluated the effects of anti-AChR antibodies on IL-6 production and on the phosphorylation of Protein Kinase B (PKB/Akt). Most MG sera and some monoclonal anti-AChR antibodies induced a significant increase in IL-6 production by human muscle cells. Furthermore, Akt phosphorylation in response to insulin was decreased in the presence of monoclonal anti-AChR antibodies.

Conclusions: Anti-AChR antibodies alter IL-6 production by muscle cells, suggesting a putative novel functional mechanism of action for the anti-AChR antibodies. IL-6 is a myokine with known effects on signaling pathways such as Akt/mTOR (mammalian Target of Rapamycin). Since Akt plays a key role in multiple cellular processes, the reduced phosphorylation of Akt by the anti-AChR antibodies may have a significant impact on the muscle fatigability observed in MG patients.

No MeSH data available.


Related in: MedlinePlus