FYN‐dependent muscle–immune interaction after sciatic nerve injury

Abstract

Denervation of skeletal muscles results in loss of muscle mass and contractile force. Recent evidence suggests that local immune system activation plays a key role in these processes, but the mechanisms underlying muscle-immune system cross-talk are not understood. The purpose of this study was to address the mechanisms by which muscle responds to denervation and to elucidate the specific role played by FYN in local immune system activation. We studied initial events taking place in the gastrocnemius of wild-type and Fyn(-/-) mice following sciatic nerve transection. Discontinuous sucrose gradient centrifugation was used to prepare lipid rafts at different time-points (1, 7, and 14 days) after surgery. Activation of FYN, cytokine expression (IL-1beta and TNF-alpha), and T-cell activation (CD3 and IL-15) were followed by in vitro kinase assays, enzyme-linked immunoassay (ELISA), Western blotting, and immunoprecipitation. Sciatic nerve injury resulted in increased SRC kinase activity in gastrocnemius lipid rafts. Production of both IL-1beta and TNF-alpha was increased, peaking after 1 day, followed after 7 and 14 days by upregulation of IL-15 and CD3 expression and the development of caveolin-3 and CD3 complexes. The integrity of lipid rafts and the upregulation of SRC kinase activity, cytokine expression, and T-cell activation and cross-talk with muscle cells following denervation were abolished in Fyn(-/-) mice. The integrity of FYN-dependent lipid rafts is required for local immune system activation within denervated muscle, and lipid rafts are implicated in orchestrating muscle-immune-cell cross-talk. These results are likely to provide new insights into the therapy of neuromuscular injury.

Age-Dependent Neuroimmune Modulation of IGF-1R in the Traumatic Mice

“…We have already known that, In the central nervous system (CNS), Fyn controls switches in a variety of signal transduction pathways governing cell growth, division, differentiation, and survival [33] by assembling a unique platform, lipid rafts [34]. It has also been noted that the principle of Fyn activation appears to be realized by its affinity with receptors for growth factors, especially, IGF-1R, and the specialized cellular communication within the lipid rafts.…”

De novo expression of connexin hemichannels in denervated fast skeletal muscles leads to atrophy

“…Inflammasome. Denervation induces an early and transient increase in muscle levels of TNF-α and IL-1β (20), which are products of inflammasome activation (21). Because activation of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), a transcription factor, induces muscle atrophy (1), we decided to evaluate levels of the phosphorylated form of p65 (P-p65), an active subunit of NF-κB (22).…”

Rab1-Dependent G<i>β</i>1<i>γ</i>2 Trafficking during Muscle Mobilization

“…As reported, growth factors usually result in a quick and adaptive response, and mediate changes allowing an animal to effec-tively face mobilization [3]- [7]. Coincidently, we have characterized that Fyn, one of Src kinases, represented the predominant signaling in VEGFR-2 activation and VEGFR-1 shuttling between membrane and ER, which initiated stereotypic inflammation and muscle-T cell interaction during muscle denervation [8]- [10]. Therefore, it was proposed that subcellular communication might form a viable link to functional muscular stabilization.…”

“…Previously, we reported that timely Fyn activation triggered a particular microenvironment in the denervated gastrocnemius, which evoked early muscular inflammation and later local immunological changes via specific subcellular communication [8] [9]. Herein, gastrocnemius mobilization was established and it was observed that extracellular calcium level was elevated, which happened rapidly and sustained within one week of operation.…”

“…It was previously reported that ER is associated with protein synthesis [26] [27], the functional alteration was proposed to implicate in the cellular responses during prolonged muscle denervation [8] [9]. In the present study, Fyn (+/−) mice were undergone leg casting, gastrocnemius was separated, Figure 2(a) revealed that protein synthesis in membrane was markedly decreased by day 14 following muscle mobilization, however, protein breakdown was increased in the same time (Figure 2(b), Figure 2(c)).…”