Nitric oxide synthase inhibition prevents activity‐induced calcineurin–NFATc1 signalling and fast‐to‐slow skeletal muscle fibre type conversions

Abstract

Key points• Exercise is known to trigger skeletal muscle structural and functional adaptations.• Control of these adaptive alterations is a complex process involving multiple signalling pathways and levels of regulation.• The well-characterized calcineurin-nuclear factor of activated T-cells (NFATc1) signalling pathway is involved in the regulation of activity-dependent alterations in skeletal muscle myosin heavy chain expression. Myosin heavy chain is a contractile protein that largely dictates a muscle's speed of contraction.• We show that a signalling molecule called nitric oxide may be regulating alterations in myosin heavy chain expression via activity-modulated calcineurin-NFATc1 signalling.• These findings increase our understanding of how skeletal muscle adaptive alterations are regulated. AbstractThe calcineurin-NFAT (nuclear factor of activated T-cells) signalling pathway is involved in the regulation of activity-dependent skeletal muscle myosin heavy chain (MHC) isoform type expression. Emerging evidence indicates that nitric oxide (NO) may play a critical role in this regulatory pathway. Thus, the purpose of this study was to investigate the role of NO in activity-induced calcineurin-NFATc1 signalling leading to skeletal muscle faster-to-slower fibre type transformations in vivo. Endogenous NO production was blocked by administering L-NAME (0.75 mg ml −1 ) in drinking water throughout 0, 1, 2, 5 or 10 days of chronic low-frequency stimulation (CLFS; 10 Hz, 12 h day −1 ) of rat fast-twitch muscles (L+Stim; n = 30) and outcomes were compared with control rats receiving only CLFS (Stim; n = 30). Western blot and immunofluorescence analyses revealed that CLFS induced an increase in NFATc1 dephosphorylation and nuclear localisation, sustained by glycogen synthase kinase (GSK)-3β phosphorylation in Stim, which were all abolished in L+Stim. Moreover, real-time RT-PCR revealed that CLFS induced an increased expression of MHC-I, -IIa and -IId(x) mRNAs in Stim that was abolished in L+Stim. SDS-PAGE and immunohistochemical analyses revealed that CLFS induced faster-to-slower MHC protein and fibre type transformations, respectively, within the fast fibre population of both Stim and L+Stim groups. The final fast type IIA to slow type I transformation, however, was prevented in L+Stim. It is concluded that NO regulates activity-induced MHC-based faster-to-slower fibre type transformations at the transcriptional level via inhibitory GSK-3β-induced facilitation of calcineurin-NFATc1 nuclear accumulation in vivo, whereas transformations within the fast fibre population may also involve translational control mechanisms independent of NO signalling.

Endothelial nitric oxide synthase g894t (rs1799983) gene polymorphism in polish athletes

“…Interestingly, it appears that the role of nitric oxide in these categories is modest [8]. On the other hand, NO exerts several distinct effects on various aspects of skeletal muscle structure and function that could possibly be favourable in strength/power sports, such as excitation-contraction coupling [9], skeletal muscle fiber type conversion (faster-to-slower fiber type) [10], modulation of mitochondrial energy production [11] and glucose metabolism [12]. Further, animal studies provided evidence that nitric oxide may promote exercise-induced muscle hypertrophy [14,[46][47][48], stretch-induced proliferation of myoblasts [49] and prevent muscle atrophy [50].…”

“…Nitric oxide has been shown to be one of the most important intrinsic factors in regulating basal vascular tone, a balance between constrictor and dilator influences, however, the results regarding the increase in muscle blood flow with exercise (hyperamia) are less concordant [8]. Moreover, NO has been shown to exert several other distinct effects on various aspects of skeletal muscle structure and function, such as excitation-contraction coupling [9], skeletal muscle fiber type conversion (faster-to-slower fiber type) [10], mitochondrial energy production [11], glucose metabolism [12], and autoregulation of blood flow [13].…”

Exercise-Induced Skeletal Muscle Remodeling and Metabolic Adaptation: Redox Signaling and Role of Autophagy

“…ROS also mediate c-Jun N-terminal kinase ( JNK) signaling activation triggered by acute exercise (141). In addition, it has recently been shown that the xanthine oxidase inhibitor allopurinol is able to attenuate skeletal muscle signaling after acute exercise (namely, the increased phosphorylation of p38 MAPK and extracellular-signal-regulated kinase [ERK]), although this inhibitor does not impair mitochondrial adaptations to endurance training (PGC-1a, GLUT4, and superoxide dismutase [SOD] increase) (87,116,189). Moreover, some authors suggest that NOS are activated by both Ca 2 + and AMPK.…”

Creatine loading elevates the intracellular phosphorylation potential and alters adaptive responses of rat fast-twitch muscle to chronic low-frequency stimulation

“…CLFS (10 Hz, impulse width 380 s, 12 h/day) was applied as previously described (Putman et al 2004(Putman et al , 2007Martins et al 2012). While rats were under general anaesthesia, bipolar electrodes were implanted lateral to the common peroneal nerve of the left hind limb, externalised, and connected to a small portable stimulator; animals recovered for 7 days.…”

“…Thus, the purpose of the present study was to extend our previous work by investigating the effects of maximum Cr loading on the whole-muscle IPP and related phenotypic changes induced by 10 days of CLFS, a critical stimulation period in this model of forced contractile activity that is known to induce the maximum rate of fast-to-slow fibre type transitions (Conjard et al 1998;Martins et al 2012). Because fibre contraction is a determinant of Cr uptake (Snow and Murphy 2003), and CLFS imposes the same contraction parameters onto all fibres (Pette and Vrbová 1999), we reasoned that Cr uptake by muscle fibres would be ubiquitous, resulting in greater intracellular Cr accretion.…”