Tabernaemontana catharinensis apresenta atividade anti-inflamatória tópica em modelos de dermatite de contato irritante em camundongos

Abstract

Tabernaemontana catharinensis A. DC (Apocynaceae family) is popularly known as cobrina and used on leaf infusions form as an anti-inflammatory, antidote to snake bites, against insect bites, among other applications. These effects are due to a diversity of chemical constituents already identified in several parts of the plant. However, no study was performed to confirm its topical anti-inflammatory activity in inflammatory skin diseases. All procedures were approved by Ethics Committee for Animal Research of the Federal University of Santa Maria (Process number 23081.018655/2014-91 and 5199270616/2016). To evaluate this effect, were performed acute irritant contact dermatitis (ICD) models induced by cinnamadehyde (4 μg/ear), capsaicin (200 μg/ear), arachidonic acid (200 μg/ear), phenol (10% v/v/ear) and croton oil (1000 μg/ear) and a chronic ICD model induced by croton oil repeated applications using male Swiss mice (25-30g). We assessed: 1) The topical effect of T. catharinensis leaves crude extract (CETc) (0.0001-10 μg/ear) on acute ICD models induced by different irritant agents; 2) The topical effect of CETc isolated fractions (dichloromethane, n-butanol and ethyl acetate) (0.0001-10 μg/ear) and CETc gel formulations (0.001-3%; 0.15g/ear) in an acute ICD model induced by croton oil; 3) The topical effect of CETc repeated treatment (10 μg/ear) in a chronic ICD model croton oil-induced. These effects were evaluated through inflammatory parameters as ear edema and polymorphonuclear cells infiltration. Moreover, we assessed the CETc topical effect on pro-inflammatory cytokines (MIP-2, IL-1β and TNF-α), the NF-κB transcription pathway and glucocorticoid receptor involvement on its anti-inflammatory effect, as well as the toxicity development by CETc repeated (14 days) topical treatment. The CETc inhibited the acute ear edema induced by cinnamaldehyde, capsaicin, arachidonic acid, phenol and croton oil with an inhibitory dose 50% (ID50) of 0.061 (0.02-0.2); 0.37 (0.21-0.67); 0.002 (0.0008-0.003); 0.0009 (0.0005-0.002) and 0.006 (0.003-0.013) μg/ear, respectively, and a maximum inhibition (Imáx) of 100% (10 μg/ear) in the ICD model induced by cinnamaldehyde, arachidonic acid, phenol and croton oil and 75±6% (10 μg/ear) in the ICD induced by capsaicin. CETc (0.0001-10 μg/ear) significantly reduced the polymorphonuclear cells infiltration (verified by myeloperoxidase - MPO activity and histological analysis), as well as pro-inflammatory cytokines levels (MIP-2, IL-1β and TNF-α) induced by all irritant agents evaluated. The dichloromethane, n-butanol and ethyl acetate fractions decreased the ear edema with an ID50 of 0.061 (0.03-0.136); 0.002 (0.0006-0.005) and 0.001 (0.0004-0.004) μg/ear and an Imáx of 85±4%, 83±6% e 86±6% (10 μg/ear), respectively, while the CETc gel formulation reduced the ear edema in 96±3% (3%; 0.15 g/ear). Furthermore, all these treatments decreased the polymorphonuclear cells infiltration. The CETc (10 μg/ear) repeated application also reduced the ear edema induced by croton oil multiple administration from 1st day of treatment, with an Imáx de 66±6% (9th day of experiment) even as the polymorphonuclear cells infiltration. The CETc topical treatment reduced all inflammatory parameters evaluated by glucocorticoid receptor-dependent mechanism, but NF-κB transcription pathway-independent, without causing adverse effects, since the CETc repeated treatment did not alter behavioral and biochemical parameters evaluated. Our study suggests that formulations containing T. catharinensis can be effective as a topical anti-inflammatory to treating of ICD.