Pharmacological characterization of the mechanism underlying the inflammatory response in dermonecrosis induced by Cerastes cerastes venom

H Oussedik-Oumehdi1,2, F Laraba-Djebari1,2. 1USTHB, Faculty of Biological Sciences, Department of Cellular and Molecular Biology, Algeria, 2Pasteur Institute of Algeria, Laboratory of Research and Development on venoms, Algeria

The life-threatening systemic effects associated with snake envenomations are efficiently neutralized by antivenoms, whereas the local effects are scarcely neutralized. Tissue damage and necrosis can induce definitive sequelae to the bitten victims consisting in the loss of tissue mass and organ function. Cerastes cerastes venom induces a dose-dependent necrotic activity with a minimum necrotic dose (MND) of 19 µg/20 g of mice body mass. This activity is abolished when venom is co-incubated, prior to injection, with metal chelators (Na2CaEDTA and 1,10 Phenanthroline), indicating that SVMPs (Snake venom metalloproteinases) are involved in tissue necrosis. To evaluate the mechanisms involved in dermonecrosis induced by venom, different pharmacological drugs were administered to groups of 8 adult male NMRI mice (20 ± 2 g; n = 8) : dexamethasone (inhibitor of PLA2 activity, 1 mg/kg, i.p.), indomethacin (a non selective inhibitor of both COX-1 and COX-2, 1mg/kg, i.p.) and pentoxifylline (inhibitor of TNFα synthesis, 0.17 mg/kg, i.p.) 30 min before i.d. injection of a sublethal dose of venom (30 µg/20 g of mice body mass). The pharmacological drugs were re-administered 36 h after the envenomation, in order to block the inflammatory pathway involved. After 72 h, the animals were humanely sacrificed and the dorsal skin was removed for histological assessment and for the evaluation of the amount of NO and MPO activity in tissue homogenates (Student t-test was used for statistical analysis of data). Histological sections of skin obtained 3 days after envenomation, showed disintegrated epidermis which also increased in thickness (acanthosis) and a deep alteration of the dermis where hair follicles and glandular structures were altered. Edema was observed in the epidermo-dermic junction and in the dermis. Hemorrhage and inflammatory infiltrate were also observed in the dermis. The use of dexamethasone induced a marked decrease of necrotic and hemorrhagic lesions. Indomethacin and pentoxifylline showed a slight decrease of tissue alterations. Dexamethasone also reduced NO and MPO levels of 68.5 % (14.72 ± 0.13 nmole/mg, p<0.05, n=8) and 66.58 % (0.093 ± 0.01 IU/mg, p<0.05, n=8). Pentoxifylline and indomethacin induced, respectively, level decrease of NO production of 31.44 % (22.63 ± 0.35 nmole/mg, p<0.05, n=8) and 40.29 % (19.71 ± 0.48 nmole/mg, p<0.05, n=8) and MPO activity decrease of 53.58 % (0.13 ± 0.021 IU/mg, p<0.05, n=8) and 35.72 % (0.18 ± 0.027 IU/mg, p<0.05, n=8). Results indicated that acid-arachidonic metabolism pathways, cyclo-oxygenase pathway and TNFα are involved in the pathogenesis of the induced tissue damage by the venom. Pre-treating animals with drugs interfering in different inflammatory pathways induced a partial reduction of tissue damage. This could be ascribed to the complexity of the venom composition that contains several peptides and proteins acting with high specificity and high potency on different molecular and cell targets.