Toll-Like Receptors Differentially Regulate CC and CXC Chemokines in Skeletal Muscle via NF- B and Calcineurin

Respiratory Division, Room L411, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, Quebec H3A 1A1, Canada.
Infection and Immunity (Impact Factor: 3.73). 01/2007; 74(12):6829-38. DOI: 10.1128/IAI.00286-06
Source: PubMed


Immunologically active molecules such as cytokines and chemokines have been implicated in skeletal muscle weakness during sepsis as well as recovery from muscle injury. In sepsis, Toll-like receptors (TLRs) act as key sentinel molecules of the innate immune system. Here we determined skeletal muscle cell responses of two prototypical CC and CXC chemokine genes (monocyte chemoattractant protein 1 [MCP-1] and KC, respectively), to stimulation with specific TLR ligands. In addition, we examined whether NF-kappaB and calcineurin signaling are involved in these responses. Differentiated myotubes and intact whole muscles expressed TLR2, TLR4, TLR5, and TLR9. Stimulation with ligands for TLR2 (peptidoglycan) or TLR4 (LPS) elicited robust and equivalent levels of MCP-1 and KC mRNA expression, whereas stimulation of TLR5 (by flagellin) required gamma interferon priming to induce similar effects. Although both TLR2 and TLR4 ligands activated the NF-kappaB pathway, NF-kappaB reporter activity was approximately 20-fold greater after TLR4 stimulation than after TLR2 stimulation. Inhibitory effects of NF-kappaB blockade on TLR-mediated chemokine gene expression, by either pharmacological (pyrrolidine dithiocarbamate) or molecular (IKKbeta dominant-negative transfection) methods, were also more pronounced during TLR4 stimulation. In contrast, inhibitory effects on TLR-mediated chemokine expression of calcineurin blockade (by FK506) were greater for TLR2 than for TLR4 stimulation. MCP-1 and KC mRNA levels also demonstrated differential responses to NF-kappaB and calcineurin blockade during stimulation with specific TLR ligands. We conclude that skeletal muscle cells differentially utilize the NF-kappaB and calcineurin pathways in a TLR-specific manner to enable complex regulation of CC and CXC chemokine gene expression.

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Available from: Basil Petrof, Apr 13, 2014
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    • "TLRs are expressed on multiple cell types (such as dendritic cells and macrophages) and generally respond to " danger signals " (e.g., pathogens and damage associated molecules) triggering the production of inflammatory cytokines and chemokines. In vitro studies demonstrated that murine myotubes express TLR2, TLR4, TLR5, and TLR9 [53]. Notably, a study showed that TLR3 is expressed in muscle biopsies of patients with chronic myopathies and that TLR3 activation on human myoblasts triggers a downstream cascade leading to NF-í µí¼…B activation and ultimately IL-8 production [54]. "
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    • "In order to confirm the direct effect of each cytokine on NF-κB activation, and also the importance of this activation in IL-1β and TNF-α induced proliferation, PDTC was used to block NF-κB. PDTC is a known inhibitor of NF-κB in many cell types [70], [72], [98], [99], and Hayakawa et al. [98] discovered that it works through blocking the polyubiquitylation of IκB. In the present study, a concentration of 50 μM PDTC completely inhibited cytokine-induced NF-κB activity, resulting in decreased myoblast proliferation. "
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    • "j o u r n a l ho m e p a g e : w w w . e l s e v i e r. c o m / l oc a t e / t o x i c o n production by myoblasts (Boyd et al., 2006; Frost et al., 2006; Lang et al., 2003). Moreover, evidences from in vitro and in vivo studies also showed that lipopolysaccharide (LPS), a specific TLR4 ligand, activates the classical NFkB pathway in muscle cells leading to the production of TNFa, IL-1b, and IL-6 proinflammatory cytokines (Frost and Lang, 2008; Frost et al., 2004; Marino et al., 2011). "
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