Faculty Bibliography

Human neuroblastoma cells were exposed to ethanol (EtOH; 100 mM) in culture for various time periods. It was found that chronic EtOH exposure increased the arachidonyl-specific phospholipase A2 (PLA2) activity significantly in both cytosol (1.6-fold) and membrane (2.2-fold) fractions when 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphocholine was used as a substrate. This arachidonyl-specific PLA2 activity progressively increased with increasing duration of EtOH exposure and reached peak level at 72-hr EtOH exposure (chronic). A significant amount of the PLA2 activity was associated with the membrane fraction. No significant difference in PLA2 activity was observed when 1-palmitoyl-2 oleoyl or linoleoyl-sn-glycero-3-phosphocholine was used as a substrate. It was also found that co-treatment of neuroblastoma cells with ganglioside GM1 reduced the EtOH-induced activation of arachidonyl-specific PLA2 activity. The present results indicate that arachidonic acid-specific PLA2 may play a role in adaptation mechanisms to chronic EtOH in cultured neuroblastoma cells. Ganglioside GM1, in part, may exert its neuroprotective effects by modulating arachidonyl-specific PLA2 activity in chronic EtOH-exposed neuroblastoma cells

Rabbit antibodies were prepared against purified phospholipase A2 (NN-XIa-PLA2) from Indian cobra (Naja naja naja) venom. The PLA2 has haemolytic, neurotoxic, myotoxic, cytotoxic and oedema-inducing activities apart from the catalytic activity. The immunological cross-reactivity of structurally similar neurotoxic PLA2s was investigated using enzyme-linked immunosorbent assay (ELISA) and immunodiffusion. Anti-NN-XIa-PLA2 IgG cross-reacted with other purified neurotoxic PLA2s from the same venom. Immunochemical cross-reactions of anti-NN-XIa-PLA2 IgG with NN-XIa-PLA2, NN-XIb-PLA2, NN-XIII-PLA2, NN-IVb1-PLA2 and NN-Vb-PLA2 were shown by a very high ELISA titre and a single precipitin band on double immunodiffusion agarose plates. The catalytic activity of these PLA2s was inhibited dose-dependently by anti-NN-XIa-PLA2 IgG but was unable to neutralize lethality and neurotoxic symptoms in experimental animals injected with neurotoxic PLA2. Anti-NN-XIa-PLA2 IgG fails to neutralize myotoxicity and oedema-inducing activities of NN-XIa-PLA2 and NN-XIII-PLA2. Anti-NN-XIa-PLA2 IgG inhibited cytotoxic effects of NN-XIa-PLA2 dose-dependently, but failed to inhibit NN-XIII-PLA2-induced cytotoxicity. Direct haemolytic activity of NN-XIa-PLA2 and NN-XIII-PLA2 was inhibited dose-dependently by these antibodies. The results indicate the presence of separate catalytic and pharmacologic site(s).

Indian cobra venom contains many phospholipase A2 (PLA2) toxins. In the present study two toxic PLA2s have been purified from the Indian cobra (Naja naja naja) venom by column chromatography. The NN-XIa-and NN-XIb-PLA2s have mol. wts between 10,700 and 15,000. The NN-XIa-PLA2 induces myotoxic effects, oedema and neurotoxicity in mice and has an i.p. LD50 of 8.5 mg/kg body weight. The NN-XIa-PLA2 is also cytotoxic to Ehrlich ascites tumour cells. The other PLA2, NN-XIb, in contrast has an i.p. LD50 of 0.22 mg/kg body weight, and it induces acute neurotoxicity. The NN-XIb-PLA2 is devoid of the other biological activities which are exhibited by NN-XIa-PLA2.