RESUMO

Bites by viperid snakes belonging to Bothrops genus produce fast and intense local edema, inflammation, bleeding and myonecrosis. In this study, we investigated the role of Myogenic Regulatory Factors (MRFs: MyoD; Myog), negatively regulated by GDF-8 (Myostatin), and ubiquitin-proteasome system pathway (UPS: MuRF-1; Fbx-32) in gastrocnemius muscle regeneration after Bothrops jararacussu snake venom (Bjussu) or its isolated phospholipase A2 myotoxins, BthTx-I (Lys-49 PLA2) and BthTx-II (Asp-49 PLA2) injection. Male Swiss mice received a single intra-gastrocnemius injection of crude Bjussu, at a dose/volume of 0.83 mg/kg/20 µl, and BthTx-I or BthTx-II, at a dose/volume of 2.5 mg/kg/20 µl. Control mice (Sham) received an injection of sterile saline solution (NaCl 0.9%; 20 µl). At 24, 48, 72 and 96 h post injection, right gastrocnemius was collected for protein expression analyses. Based on the temporal expressional dynamics of MyoD, Myog and GDF-8/Myostatin, it was possible to propose that the myogenesis pathway was impacted most badly by BthTx-II followed by BthTx-I and lastly by B. jararacussu venom, thus suggesting that catalytic activity has likely inhibitory role on the satellite cells-mediated reparative myogenesis pathway. Inversely, the catalytic activity seems to be not a determinant for the activation of proteins ubiquitination by MuRF-1 and Fbx-32/Atrogin-1 E3 proteasome ligases, given proteolysis pathway through UPS was activated neither after Bjussu, nor after BthTx-II, but just after the catalytically-inactive BthTx-I Lys-49 PLA2-homologue exposure. The findings of this study disclose interesting perspective for further mechanistic studies about pathways that take part in the atrophy and repair after permanent damage induced by bothropic snakebites.

Assuntos

RESUMO

The aim of this study was to investigate the effects of an acute bout of eccentric actions, performed at fast velocity (210º.s-1) and at slow velocity (20º.s-1), on the gene expression of regulatory components of the myostatin (MSTN) signalling pathway. Participants performed an acute bout of eccentric actions at either a slow or a fast velocity. Muscle biopsy samples were taken before, immediately after, and 2 h after the exercise bout. The gene expression of the components of the MSTN pathway was assessed by real-time PCR. No change was observed in MSTN, ACTRIIB, GASP-1 or FOXO-3a gene expression after either slow or fast eccentric actions (p > 0.05). However, the MSTN inhibitors follistatin (FST), FST-like-3 (FSTL3) and SMAD-7 were significantly increased 2 h after both eccentric actions (p < 0.05). No significant difference between bouts was found before, immediately after, or 2 h after the eccentric actions (slow and fast velocities, p > 0.05). The current findings indicate that a bout of eccentric actions activates the expression of MSTN inhibitors. However, no difference was observed in MSTN inhibitors' gene expression when comparing slow and fast eccentric actions. It is possible that the greater time under tension induced by slow eccentric (SE) actions might compensate the effect of the greater velocity of fast eccentric (FE) actions. Additional studies are required to address the effect of eccentric action (EA) velocities on the pathways related to muscle hypertrophy.

RESUMO

In this study, the developmental expression pattern of myostatin (mstn) in the spotted rose snapper Lutjanus guttatus under culture conditions is presented. The full coding sequence of mstn from L. guttatus was isolated from muscle tissue, obtaining 1134 nucleotides which encode a peptide of 377 amino acids. The phylogenetic analysis indicated that this sequence corresponds to mstn-1. mstn expression was detected in embryonic stages, and maintained at low levels until 28 days post-hatch, when it showed a significant increase, coinciding with the onset of metamorphosis. After that, expression was fluctuating, coinciding probably with periods of rapid and slow muscle growth or individual growth rates. mstn expression was also analysed by body mass with higher levels detected in smaller animals, irrespective of age. mstn was also expressed in other tissues from L. guttatus, presenting higher levels in brain, eye and gill. In brain for instance, two variants of mstn were isolated, both coding sequences were identical to muscle, except that one of them contained a 75 nucleotide deletion in exon 1, maintaining the reading frame but deleting two conserved cysteine residues. Phylogenetic analysis indicated that this brain variant was also mstn-1. The function of this variant is not clear and needs further investigation. These results indicate that mstn-1 participates in different physiological processes other than muscle growth in fishes.

Assuntos

RESUMO

Non-invasive biological indicators of the absence/presence or progress of the disease that could be used to support diagnosis and to evaluate the effectiveness of treatment are of utmost importance in Duchenne Muscular Dystrophy (DMD). This neuromuscular disorder affects male children, causing weakness and disability, whereas female relatives are at risk of being carriers of the disease. A biomarker with both high sensitivity and specificity for accurate prediction is preferred. Until now creatine kinase (CK) levels have been used for DMD diagnosis but these fail to assess disease progression. Herein we examined the potential applicability of serum levels of matrix metalloproteinase 9 and matrix metalloproteinase 2, tissue inhibitor of metalloproteinases 1, myostatin (GDF-8) and follistatin (FSTN) as non-invasive biomarkers to distinguish between DMD steroid naïve patients and healthy controls of similar age and also for carrier detection. Our data suggest that serum levels of MMP-9, GDF-8 and FSTN are useful to discriminate DMD from controls (p < 0.05), to correlate with some neuromuscular assessments for DMD, and also to differentiate between Becker muscular dystrophy (BMD) and Limb-girdle muscular dystrophy (LGMD) patients. In DMD individuals under steroid treatment, GDF-8 levels increased as FSTN levels decreased, resembling the proportions of these proteins in healthy controls and also the baseline ratio of patients without steroids. GDF-8 and FSTN serum levels were also useful for carrier detection (p < 0.05). Longitudinal studies with larger cohorts are necessary to confirm that these molecules correlate with disease progression. The biomarkers presented herein could potentially outperform CK levels for carrier detection and also harbor potential for monitoring disease progression.

Assuntos

RESUMO

Myostatin (MSTN) is a protein of the Transforming Growth Factor-ß (TGF-ß) superfamily and plays a crucial role in muscular development for higher vertebrates. However, its biological function in marine invertebrates remains undiscovered. This study characterizes the full-length sequence of the Mytilus chilensis myostatin gene (Mc-MSTN). Furthermore, tissue transcription patterns and putative single nucleotide polymorphisms (SNPs) were also identified. The Mc-MSTN cDNA sequence showed 3528 base pairs (bp), consisting of 161 bp of 5' UTR, 2,110 bp of 3' UTR, and an open reading frame of 1,257 bp encoding for 418 amino acids and with an RXXR proteolytic site and nine cysteine-conserved residues. Gene transcription analysis revealed that the Mc-MSTN has ubiquitous expression among several tissues, with higher expression in the gonads and mantle than in the digestive gland, gills, and hemolymph. Furthermore, high levels of polymorphisms were detected (28 SNPs in 3'-UTR and 9 SNPs in the coding region). Two SNPs were non-synonymous and involved amino acid changes between Glu/Asp and Thr/Ile. Until now, the MSTN gene has been mainly related to muscle growth in marine bivalves. However, the present study suggests a putative biological function not entirely associated to muscle tissue and contributes molecular evidence to the current debate about the function of the MSTN gene in marine invertebrates.

Assuntos