Gamma-Terpinene Modulation of LPS-Stimulated Macrophages is Dependent on the PGE2/IL-10 Axis.

Gamma-terpinene is a monoterpene present in the essential oils of several plants, including those from the Eucalyptus genus. This molecule was recently described as anti-inflammatory and microbiocidal, but little is known about the mechanisms behind its effects. The aim of the present study was to investigate the effect of gamma-terpinene on the lipopolysaccharide-induced production of cytokines by murine peritoneal macrophages. Gamma-terpinene treatment was found to reduce the production of proinflammatory cytokines, such as interleukin-1ß and interleukin-6, and enhance that of the anti-inflammatory cytokine interleukin-10. This was accompanied by increased levels of the enzyme cycloxygenase-2 and its product, the lipid mediator prostaglandin E2. Inhibition of cycloxygenase-2 with nimesulide abolished the potentiating effect of gamma-terpinene on interleukin-10 production. Moreover, nimesulide treatment also abrogated the inhibitory effect of gamma-terpinene on interleukin-1ß and interleukin-6. Furthermore, in macrophages from mice deficient in the interleukin-10 gene, gamma-terpinene failed to inhibit interleukin-1ß and interleukin-6 production. These results suggest that this monoterpene promotes the prostaglandin E2/interleukin-10 axis, which inhibits the production of these proinflammatory cytokines.

Synthesis, toxicity study and anti-inflammatory effect of MHTP, a new tetrahydroisoquinoline alkaloid.

The alkaloid 2-methoxy-4-(7-methoxy-1,2,3,4-tetrahydroisoquinolin-1-yl)phenol (MHTP) was synthesized to prospect new compounds with therapeutic properties. Thus, the goal of this study was to evaluate the MHTP anti-inflammatory effect by in vivo and in vitro assays. The MHTP toxicity was analyzed. We found that MHTP pre-treatment (2.5-10 mg/kg) showed antiedematogenic effect (p < 0.05) in carrageenan-induced paw edema by inhibiting the PGE2 action independently of mast cell degranulation or histamine activity. MHTP also diminished (p < 0.01) total leukocyte migration in 41.5% into peritoneal cavity during carrageenan-induced peritonitis, reducing polymorphonuclear cells (PMNs) (59.6%) and proteins levels (29.4%). MHTP in an experimental model of acute lung injury inhibited (p < 0.001) total inflammatory cell migration into the lungs and PMNs in 58% and 67.5%, respectively. Additionally, MHTP did not present cytotoxicity at concentrations of 10, 25 or 50 µM but decreased (p < 0.001) the NO production in 24%, 47% and 39%, respectively. The alkaloid also reduced (p < 0.001, in lipopolysaccharide (LPS)-stimulated macrophages (1 µg/mL), IL-1ß, IL-6 and IL-10 levels in 35.7%, 31.0% and 33.4%, respectively. The results obtained in this study allow us to conclude that the inedited synthetic alkaloid, MHTP has anti-inflammatory effect by inhibiting PGE2 function as well as inhibiting inflammatory cell migration to the inflamed site and attenuated the acute lung injury disease by inhibiting the migration of neutrophil to the lung. However, further studies will be carried out to demonstrate the mechanisms of action of the molecule and explore its potential as a future drug to treat inflammatory processes.