Role of Toll-like receptors in local effects in a model of experimental envenoming induced by Bothrops jararacussu snake venom and by two phospholipases A2

Abstract

Literature shows that phospholipases A2 isolated from snake venoms of the genus Bothrops are involved in the local inflammatory response. However, the mechanisms by which these enzymes trigger this process have not yet been clarified. Toll-Like receptors (TLRs) are transmembrane proteins that recognize pathogens associated molecular patterns (PAMPs), or even damage associated molecular patterns (DAMPs). After this recognition, an innate immune response is activated resulting in cytokines liberation contributing to inflammation. Thus, the purpose of this work was to study the participation of different TLRs during the local inflammatory process induced by B. jararacussu snake venom and by two isolated phospholipases A2, BthTX-I or BthTX-II, from this venom in a model of experimental envenoming. For this, sub-lethal doses of B. jararacussu venom (BjussuV), BthTX-I or BthTX-II were injected in the gastrocnemius muscle. Myotoxic activity was evaluated by histological analysis and by quantification of plasma levels of total-creatine kinase (CK). The pro-inflammatory cytokines TNF-α and IL-1β was measured in both muscle tissue homogenate and plasma. A quantification of the gene expression of TLRs 2, 4, 5 and 9 in muscle tissue homogenate was performed by the real-time polymerase chain reaction (RTq-PCR). According to the results, it can be observed that, when compared to the control, there was a significant increase of CK and TNF-α in the bloodstream of the animals injected with both BjussuV, BthTX-I and BthTX-II. In muscle tissue homogenate, it was observed a significant increase in both cytokines, TNF-α and IL-1β, levels compared to the control animals. The results point to an important increase in the gene expression of TLR2 and TLR4, suggesting that these TLRs can be important targets for the development of future therapies for local treatment for victims of snakebites.