RESUMO
A rapid in vitro cytolytic effect of some myotoxic phospholipases A2 (PLA2s) isolated from the venoms of Viperidae snakes has been previously described. This study was undertaken to investigate if cytolytic activity is a common property of the myotoxic proteins from this group. Murine endothelial cells (tEnd) and skeletal muscle myotubes (C2C12) were utilized as targets. The release of lactic dehydrogenase was quantified as a measure of cell damage, 3 h after exposure of cells to the different PLA2s, including representatives from the genera Bothrops, Agkistrodon, Trimeresurus, Crotalus (family Viperidae), and Notechis (family Elapidae). All of the group II myotoxic PLA2s tested displayed rapid cytolytic activity when tested in the micromolar range of concentrations (8-32 microM). In contrast, the group I myotoxic PLA2 notexin was devoid of this activity. Aspartate-49 and lysine-49 PLA2 group II variants showed a comparable cytolytic effect. Skeletal muscle myotubes, obtained after fusion and differentiation of C2C12 myoblasts, were significantly more susceptible to the cytolytic action of myotoxins than endothelial cells, previously reported to be more susceptible than undifferentiated myoblasts under the same assay conditions. Cytolytic activity appears to be a common characteristic of group II myotoxic PLA2s of the Viperidae. Bee venom PLA2, a group III enzyme of known myotoxicity, also displayed cytotoxic activity on C2C12 myotubes, being devoid of activity on endothelial cells. These results suggest that in vitro differentiated skeletal muscle myotubes may represent a suitable model target for the study of myotoxic PLA2s of the structural group II found in snake venoms.
Assuntos
Endotélio Vascular/citologia , Músculo Esquelético/citologia , Fosfolipases A/toxicidade , Animais , Venenos de Abelha/toxicidade , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Venenos de Crotalídeos/toxicidade , Venenos Elapídicos/toxicidade , Endotélio Vascular/efeitos dos fármacos , Endotélio Vascular/enzimologia , Isoenzimas/toxicidade , L-Lactato Desidrogenase/metabolismo , Camundongos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/enzimologia , Neurotoxinas/toxicidade , Fosfolipases A2RESUMO
A 47-year-old Japanese man suffering from T-cell leukemia was examined for multiple subcutaneous abscesses followed to abrasion wound on his right knee. The causative organism was clustered, fine-branched filaments in pus aspirated from the lesions, identified as Nocardia brasiliensis. Most of the lesions regressed from the combined therapy of sulfamethoxazole and trimethoprim, leaving an ulcer on the patient's left leg. The nocardiosis cases in Japan until 1984, including this one, were briefly surveyed.