We investigated the in vitro process of cell death caused by Egyptian cobra venom on primary human embryonic kidney (293T) and mouse myoblast (C2C12) cell lines. The aim of these studies was to provide further information about triggering cell death, and suggest methods for eliminating unwanted cells, such as tumour cells. Both cell lines were treated with 10, 20, and 50 m g/ml of Egyptian cobra (Naja haje) venom in serum free media (SFM) and incubated for 8 hours. Total activities of the lactate dehydrogenase (LDH) and creatine kinase (CK) released in the culture during venom incubation were used as an indicator of the venom in vitro cytotoxicity. Cell injury was morphologically recognized and apoptosis determined by a Fluorescing Apoptosis Detection System and confirmed by staining nuclear DNA with DAPI. Our data clearly demonstrated marked cytotoxic effects and acute cell injury for both cell lines. Release of LDH and CK into the culture media induced by the venom correlates well with the morphological changes and extent of cell death. Mostly, these consequences were time and dose-dependent in both cell lines. The results obtained from this study indicated that cobra venom cause cell death by two different mechanisms: necrosis and induction of apoptosis. The apoptotic mechanism, accompanied by cell necrosis, mediated cell destruction of both tested cell lines; however, necrosis was predominant in the C2C12 cell line while apoptosis, in 293T cells. This unusual form of cell death induced by cobra venom may represent a combination of apoptosis and necrosis within the same cell. This is a first-hand investigation showing the apoptotic effects of N. haje venom at the cellular level. However, the contribution of the apoptotic pathway may be dependent on concentration and/or time of exposure to snake venom.

Scorpion venom toxicity is of major concern due to its influence on human activities and public health. The cytotoxicity and apoptosis induced by scorpion L. quinquestriatus venom on two established eukaryotic cell lines (293T and C2C12) were analyzed. Both cultured cell lines were incubated with varying doses (10, 20, and 50 µg/ml) of scorpion venom in serum free medium (SFM) for 0.5, 1, 2, 4, and 8 hours at 37°C. The percentage of total lactate dehydrogenase (LDH) released in the culture during venom incubation was used as an index of cell damage. Control culture was treated with an equal amount of SFM. Cell injury was recognized morphologically and apoptosis was researched by a Fluorescing Apoptosis Detection System using the principle of TUNEL (TdT-mediated dUTP Nick-End Labelling) assay and confirmed by another assay concerning nuclear DNA staining with DAPI stain. Cytotoxicity was remarkable and cell survival highly reduced at the highest tested concentration (50 µg/ml). These effects were rapid and observed within 30 minutes. The apparent initial damage to the nucleus and lysis of the plasmalemma and/or organelle membranes, which was evident by a significant increase in cytosolic LDH release, suggested that this toxin acts at the membrane level. The morphological changes that occurred in apoptotic cells include condensation and compartmentalization of nuclear and cytoplasmic materials into structurally preserved membrane-bound fragments or blebs. The cytotoxic effects are dose and time dependent and cell death by apoptosis was more characteristic of 293T cells than C2C12 cells. The apoptotic effects were more prominent and clear in the early stages of toxicity, while other forms of cell damage such as swelling, rupture, and/or necrosis occurred at later stages.