Mn(2+) ions reduce the enzymatic and pharmacological activities of bothropstoxin-I, a myotoxic Lys49 phospholipase A(2) homologue from Bothrops jararacussu snake venom.
Bothropstoxin-I (BthTX-I), a myotoxic Lys49 phospholipase A(2) (PLA(2)) homologue isolated from Bothrops jararacussu snake venom, causes a range of biological effects, including myonecrosis, mouse paw edema, irreversible neuromuscular blockade and lysis of cell cultures. Among eight divalent cations assayed, Mn(2+) was the most effective in reducing mouse paw edema induced by BthTX-I (25 microg). Preincubating BthTX-I with Mn(2+) (1.0mM) reduced mouse paw edema by 70% and myotoxicity by 60% in mice injected i.m. with 50 microg toxin. Mn(2+) (50 microl of a 1mM solution) administered within 1min at the site of toxin injection was still but less effective in antagonising BthTX-I-induced myotoxicity. Mn(2+) (1.0mM) completely prevented BthTX-I (1.4 microM)-induced neuromuscular blockade in the mouse phrenic-nerve diaphragm preparation. Mn(2+) (0.25mM) protected about 85% of NB41A3 cells from lysis when coincubated with BthTX-I (1.0 microM) for 25h. Preincubation with 0.25mM Mn(2+) increased the sensitivity of the cells to subsequent lysis by BthTX-I in the absence of Mn(2+). BthTX-I (1 microM) caused extensive fatty acid release (from 0.8% of the total radiolabeled lipid in control cells to 56% with toxin) when incubated with the NB41A3 cell line for 25h. PLA(2) activity observed in cell cultures after addition of BthTX-I was considerably reduced by 0.25mM Mn(2+). Mn(2+) ions constitute a promising agent to assess the action mechanism and the effects of enzymatic inhibition on the pharmacological activity of Lys49 PLA(2) homologues.
Soares
Andreimar M
AM
Departamento de Bioquímica e Imunologia, Faculdade de Medicina, Universidade de São Paulo, 14049-900-, SP, Ribeirão Preto, Brazil.
Oshima-Franco
Yoko
Y
Vieira
Carlos A
CA
Leite
Gildo B
GB
Fletcher
Jeffrey E
JE
Jiang
M-S
MS
Cintra
Adelia C O
AC
Giglio
José R
JR
Rodrigues-Simioni
Léa
L
D000818:Animals; D017837:Bothrops; D002413:Cations, Divalent / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D003435:Crotalid Venoms / Q000201:enzymology* / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004487:Edema / Q000139:chemically induced; D066298:In Vitro Techniques; D007273:Injections, Intramuscular; D007700:Kinetics; D008055:Lipids / Q000032:analysis; D008297:Male; D008345:Manganese / Q000378:metabolism*; D051379:Mice; D018482:Muscle, Skeletal / Q000187:drug effects / Q000503:physiopathology; D009336:Necrosis; D009447:Neuroblastoma / Q000473:pathology; D019148:Neuromuscular Blockade; D010741:Phospholipases A / Q000737:chemistry* / Q000187:drug effects; D010791:Phrenic Nerve / Q000187:drug effects / Q000502:physiology; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured
D002413:Cations, Divalent; D003435:Crotalid Venoms; D008055:Lipids; C078097:bothropstoxin; D008345:Manganese; D010741:Phospholipases A