Modification of Substrate Inhibition of Synaptosomal Acetylcholinesterase by Cardiotoxins

Biochemistry of envenomation

Venoms and toxins are of significant interest due to their ability to cause a wide range of pathophysiological conditions that can potentially result in death. Despite their wide distribution among plants and animals, the biochemical pathways associated with these pathogenic agents remain largely unexplored. Impoverished and underdeveloped regions appear especially susceptible to increased incidence and severity due to poor socioeconomic conditions and lack of appropriate medical treatment infrastructure. To facilitate better management and treatment of envenomation victims, it is essential that the biochemical mechanisms of their action be elucidated. This review aims to characterize downstream envenomation mechanisms by addressing the major neuro-, cardio-, and hemotoxins as well as ion-channel toxins. Because of their use in folk and traditional medicine, the biochemistry behind venom therapy and possible implications on conventional medicine will also be addressed.

Mechanisms of cardiotoxin lll-induced apoptosis in human colorectal cancer colo205 cells

Cardiotoxin III (CTX III) is a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom. This is the first report on the mechanism of the anticancer effect of CTX III in human colorectal cancer Colo205 cells. 2. Cardiotoxin III-induced Colo205 cell apoptosis was confirmed by DNA fragmentation (DNA ladder and sub-G1 formation) with an IC(50) of 4 mg/mL at 48 h. 3. Further mechanistic analysis demonstrate that CTX III induced the loss of mitochondrial membrane potential (Dym), cytochrome c release from mitochondria into the cytosol and activation of capase-9, caspase 3, as well as markedly enhancing the expression of Bax, but not Bcl-2, protein in the cells. Moreover, the CTX III-induced apoptosis was significantly blocked by the broad-spectrum caspase inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone. 4. However, CTX III did not generate the formation of reactive oxygen species and anti-oxidants, including N-acetylcysteine, and catalase could not block CTX III-induced apoptosis in the Colo205 cells. 5. Taken together, these results suggest that CTX III may induce apoptosis through a mitochondrial- and caspase-dependent mechanism and alteration of Bax/Bcl-2 ratio in human colorectal Colo205 cancer cells.