Characterization of the insulinotropic action of a phospholipase A2 isolated from Crotalus durissus collilineatus rattlesnake venom on rat pancreatic islets

Abstract

The ability of PLA 2 and crotapotin, isolated from Crotalus durissus collilineatus rattlesnake venom, to stimulate insulin secretion from isolated rat islets was examined. PLA 2 and crotapotin stimulated insulin secretion at 2.8 mmol/L glucose, whereas at a high glucose concentrations (16.7 mmol/L) only PLA 2 stimulated secretion. Nifedipine (10 mmol/L) did not alter the ability of PLA 2 to increase insulin secretion stimulated by a depolarizing concentration of K C (30 mmol/L). PLA 2 did not affect 14 CO 2 production but significantly increased the efflux of arachidonic acid from isolated islets. These results indicate that PLA 2 -stimulated secretion is not dependent on an additional influx of Ca 2C through L-type Ca 2C -channels but rather is associated with arachidonic acid formation in pancreatic islets. q

Isolation and characterisation of insulin-releasing compounds from Crotalus adamanteus, Crotalus vegrandis and Bitis nasicornis venom

“…This is in agreement with the work of Yamamoto et al (1983) and Nogueira et al (2005), which report the insulinotropic action of exogenous phospholipase A 2 from C. adamanteus and C. durissus collilineatus, in rat islets. In both instances cell viability was maintained, therefore excluding the possibility of mere leakage of insulin from cells undergoing lysis.…”

“…Exposure to PLA 2 causes hydrolysis of membrane phospholipids with the subsequent production of arachidonic acid and metabolism into lipoxygenase products which are key to elevation of cytosolic Ca 2þ levels and PLA 2 -induced insulin secretion (Persaud et al, 2007). The link between arachidonic acid and insulin secretion by C. durissus collilineatus venom was confirmed by Nogueira et al (2005) when efflux in arachidonic acid was shown to be significantly higher in PLA 2 treated islets compared to control islets. Furthermore, given that 14 CO 2 production in islets was not altered, the authors hypothesized that the increase in insulin secretion following PLA 2 exposure could not be attributed to changes in glucose metabolism.…”

“…The neurotoxin crotoxin fractionated from the crude venom was further purified to isolate its two individual constituents, crotapotin and PLA 2. Crotoxin, crotapotin and PLA 2 enhanced insulin secretion at the lower glucose concentration but only crotoxin and PLA 2 potentiated insulin secretion at the high glucose concentration (Nogueira et al, 2005). Yamamoto et al (1983) also described a positive concentration-dependent insulinotropic response for exogenous phospholipase A 2 from C. adamanteus when incubated in rat islets.…”

“…CTX-1 has been shown to stimulate insulin secretion from INS-1E cells with no evidence of cytotoxic action or cell lysis (Nguyen et al, 2012). Cell viability was also maintained following treatment with exogenous PLA 2 from C. durissus collilineatus and C. adamanteus (Nogueira et al, 2005;Yamamoto et al, 1983). Supported by existing literature on the ability of various snake venom components to stimulate insulin secretion, we chose to investigate three snakes belonging to the Viperidae family, C. adamanteus, C. vegrandis and Bitis nasicornis.…”

Expression of secretory phospholipase A2in insulitis of human transplanted pancreas and its insulinotropic effect on isolated rat islets

“…In addition, it was reported that sPLA 2 derived from bee venom, snake venom and porcine pancreas elicited insulin secretion in vitro, although the mechanism ShOrt repOrt ShOrt repOrt has not been fully understood. [8][9][10][11] Therefore, we also investigated the effects of exogenous sPLA 2 on insulin secretion, intracellular free Ca 2+ concentration ([Ca 2+ ]i) and lysophospholipid contents in isolated rat islets.…”