TNF-like weak inducer of apoptosis (TWEAK) and its sole receptor fibroblast growth factor-inducible 14 (Fn14) are involved in various inflammatory conditions. This study was performed to investigate the potential role of TWEAK/Fn14 in immune-mediated necrotizing myopathy (IMNM).
Muscle biopsies from patients with IMNM (n = 37) and controls (n = 11) were collected. Human muscle cells were treated with TWEAK in vitro. Muscle biopsies and cultured muscle cells were analysed by immunostaining and quantitative PCR. Serum levels of TWEAK and Fn14 were detected by ELISA.
TWEAK and Fn14 were overexpressed in IMNM muscle biopsies. The percentage of Fn14-positive myofibers correlated with disease severity, myonecrosis, regeneration and inflammation infiltrates. Fn14-positive myofibers tended to be surrounded or invaded by CD68+ macrophages. TWEAK treatment had a harmful effect on cultured muscle cells by inducing the production of multiple chemokines and pro-inflammatory cytokines. Serum Fn14 levels were increased in patients with IMNM and correlated with muscle weakness.
TWEAK/Fn14 signalling was activated in IMNM, most likely aggravating muscle damage via amplifying inflammatory response and macrophages chemotaxis. Fn14 seems to be a biomarker for assessing disease severity in IMNM. In addition, Fn14 may also contribute to muscle injury repair.

BACKGROUND: Bothrops moojeni snake venom (VBm) has toxins that cause pronounced tissue damage and exacerbated inflammatory reaction. Cannabis sativa L. is a plant species that produces an oil (CSO) rich in unsaturated fatty acids. Nano-emulsions have several advantages, such as better stability and higher penetrating power in membranes. Therefore, this study evaluated the effect of a nano-emulsion based on this herbal derivative (NCS) against VBm-induced inflammation in Wistar rats.
METHODS: The CSO and NCS were submitted to physicochemical characterization. The inflammatory process was induced by the VBm (0.10 mg/kg) as follows: rat paw edema, peritonitis, analysis of leukocyte infiltrate in gastrocnemius muscle of rats and formation of granulomatous tissue.
RESULTS: No significant changes were observed when the NCS was submitted to the centrifugation and thermal stress tests. There was no phase separation, changes in density (0.978 ± 0.01 g/cm3) and viscosity (0.889 ± 0.15). The droplet diameter ranged from 119.7 ± 065 to 129.3 ± 0.15 nm and the polydispersity index ranged from 0.22 ± 0.008 to 0.23 ± 0.011. The results showed that treatments with CSO (200 and 400 mg/kg) and NCS (100 mg/kg) were able to decrease significantly (p < 0.001) the formation of edema and granulomatous tissue. The CSO and NCS groups significantly attenuated (p < 0.001) the recruitment of inflammatory cells in the tests for peritonitis and leukocyte infiltrate. The histopathological analysis of the gastrocnemius muscle showed a reduction in tissue damage caused by VBm.
CONCLUSIONS: The results obtained in this study showed anti-inflammatory activity of the CSO which may be due to a high UFA content. The nanosizing, as evidenced by the incorporation of the CSO in the NCS improved the effect and opens the perspective for the obtainment of a nanomedicine in which a kinetic stable phytotherapic can be used at low doses.

Skeletal muscle regeneration after myonecrosis involves the activation, proliferation and fusion of myogenic cells, and a coordinated inflammatory response encompassing phagocytosis of necrotic cell debris, and the concerted synthesis of cytokines and growth factors. Myonecrosis often occurs in snakebite envenomings. In the case of venoms that cause myotoxicity without affecting the vasculature, such as those of many elapid snakes, regeneration proceeds successfully. In contrast, in envenomings by most viperid snakes, which affect the vasculature and extracellular matrix in addition to muscle fibers, regeneration is largely impaired and, therefore, the muscle mass is reduced and replaced by fibro-adipose tissue. This review discusses possible causes for such poor regenerative outcome including: (a) damage to muscle microvasculature, which causes tissue hypoxia and affects the inflammatory response and the timely removal of necrotic tissue; (b) damage to intramuscular nerves, which results in atrophy of regenerating fibers; (c) degradation of muscle cell basement membrane, compromising the spatial niche for proliferating myoblasts; (d) widespread degradation of the extracellular matrix; and (e) persistence of venom components in the damaged tissue, which may affect myogenic cells at critical points in the regenerative process. Understanding the causes of poor muscle regeneration may pave the way for the development of novel therapeutic interventions aimed at fostering the regenerative process in envenomed patients.

SaPLIγ is a novel gamma phospholipase A2 inhibitor (PLI) recently isolated from Sinonatrix annularis, a Chinese endemic non-venomous snake. To explore the neutralization effects of saPLIγ in snakebite envenomation, a dose equivalent to LD50 of Deinagkistrodon acutus, Agkistrodon halys and Naja atra venom with/without saPLIγ was inoculated into the gastrocnemius muscle of female Kunming mice. The ability of saPLIγ to inhibit myonecrosis and systemic toxicity were evaluated through investigations of muscle histopathology, and determination of the serum levels of creatine kinase (CK), lactate dehydrogenase isoenzyme1 (LDH1) and aspartate transferase (AST). Edema of the gastrocnemius muscle was evaluated by calculating the width difference between the inoculated limb and the contralateral leg. Desmin loss in the gastrocnemius muscle was determined by Western blot analysis. Co-immunoprecipitation and shotgun LC-MS/MS analyses were performed to identify venom proteins that interact with saPLIγ. All the envenomed mice had significantly elevated serum CK, LDH1 and AST levels, whereas the levels were decreased significantly in the presence of saPLIγ. Histopathological evaluation of gastrocnemius muscle sections showed severe snake venom-induced damage, characterized by leukocyte infiltration and erythrocyte leakage, leading to local edema. Myonecrosis, hemorrhage and desmin loss were significantly attenuated by saPLIγ. SaPLIγ interacted with a wide range of venom proteins, including PLA2s, metalloproteinases and C type lectins, which may contribute to broad anti-venom effects.