Efeito da doação e da inibição farmacológica do H2S sobre a inflamação na região orofacial em ratos

Abstract

Orofacial pain is defined as all pain symptoms associated to soft and mineralized tissues (skin, blood vessels, bones, teeth, glands or muscles) of oral cavity and face. Temporomandibular Disorders (TMD) are the main no-odontogenic causes of orofacial pain and consist of a group of disorders involving masticatory muscles, temporomandibular joint and adjacent tissues. One of the treatments for TMD is based on the use of nonsteroidal anti-inflammatory drugs (NSAIDs), however new possibilities for therapeutic interventions are needed. In this way, the aim of this study is to evaluate the effect of hydrogen sulfide H2S on orofacial inflammation, since this gas, that is also produced endogenously, has been reported in the literature as mediator of the inflammatory process. In this study Wistar rats were divided into groups that received Carrageenan (3%) or saline injection into the masseter muscle. Animals were treated with an inhibitor of endogenous formation of H2S or with a donor of H2S by the local intramuscular administration (into the masseter muscle). The induction was realized in the right masseter muscle and animals were euthanized 6 hours thereafter. After 5 hours of induction, hyperalgesia was evaluated by using the electronic von Frey. At the end of the experiment, tissue samples were excised for the evaluation of myeloperoxidase (MPO) activity, lipid peroxidation and edema index. The results showed an increase of MPO activity in carrageenan group (p<0,05) when compared with saline group, confirming the induction of orofacial inflammation in masseter muscle. The treatment with sodium hydrosulfide (NaHS), an H2S donor, at doses of 5 and 10 μmol, decreased MPO activity when compared with carrageenan-injected animals (p<0,05). The treatment with H2S inhibitor, DL-proparlgylglycine (PAG) did not modify MPO activity when compared to carrageenan group. These results are consistent with the proctetive role of H2S locally injected in the masseter muscle. However, more studies are need in order to better characterize the effects of H2S on the orofacial inflammation.