Factors influencing the hemolysis of human erythrocytes by cardiotoxins from Naja naja kaouthia and Naja naja atra venoms and a phospholipase A 2 with cardiotoxin-like activities from Bungarus fasciatus venom

Abstract

M. Jiang, J. E. Fletcher and L. A. Smith. Factors influencing the hemolysis of human erythrocytes by cardiotoxins from Naja naja kaouthia and Naja naja atra venoms and a phospholipase A 2 with cardiotoxin-like activities from Bungarus fasciatus venom. Toxicon 27, 247–257, 1989.—The effects of red blood cell age and incubation conditions (temperature, divalent cation type and concentration, pH and glucose) on hemolysis induced by cardiotoxin fractions from Naja naja atra and Naja naja kaouthia venoms, a phospholipase A 2 with cardiotoxin-like activities from Bungarus fasciatus venom and bee venom phospholipase A 2 were examined. Hemolysis by the snake venom toxins was dependent on red blood cell age (aged more susceptible than fresh) and the temperature of incubation (37°C⦔20°C). Divalent cations at 0.5–2.0 mM enhanced (Ca 2+) or slightly decreased (Sr 2+, Ba 2+) hemolysis due to N. n. kaouthia and N. n. atra toxins, and greatly decreased (Ca 2+, Sr 2+, Ba 2+) hemolysis by these toxins at higher concentrations (5–40 mM). For the B. fasciatus phospholipase A 2, Ba 2+ and Sr 2+ could not fully support hemolysis in any concentration while both low (<0.5 mM) and high (>40 mM) Ca 2+ enhanced hemolysis. Bee venom phospholipase A 2 only induced hemolysis (>10% at >40 mM) at high concentrations of Ca 2+. Increasing the pH from 7.5 to 8.5 greatly increased the levels of hemolysis by the snake venom toxins and enzyme. Glucose (5.3 mM) increased hemolysis by the snake venom components at low concentrations of divalent cations (2 mM) and slightly decreased hemolysis at high concentrations (40 mM). Treatment with p-bromophenacyl bromide abolished phospholipase A 2 activity of bee venom and B.fasciatus phospholipases, but did not affect hemolytic potency of N. n. kaouthia or B. fasciatus toxins. A similar mechanism, which is independent of phospholipase A 2 activity, may be involved in hemolysis by the N. n. kaouthia and N. n. atra cardiotoxins. The B. fasciatus cardiotoxin-like phospholipase A 2 appears to have two mechanisms of hemolysis; the first is similar to that of the two typical cardiotoxins and the second appears dependent on phospholipase A 2 activity and is only evident at high Ca 2+ concentrations.