Dilodendron bipinnatum Radlk. inhibits pro-inflammatory mediators through the induction of MKP-1 and the down-regulation of MAPKp38/JNK/NF-κB pathways and COX-2 in LPS-activated RAW 264.7 cells.

ETHNOPHARMACOLOGICAL RELEVANCE: The stem bark of Dilodendron bipinnatum Radlk. (Sapindaceae), a tree native to Pantanal of Mato Grosso, Brazil, popularly known as "mulher-pobre" (poor woman), has been historically used by the locals, after decoction and maceration, for the treatment of inflammatory conditions. We have recently shown that these preparations indeed possess anti-inflammatory properties, which are mediated by the inhibition of cell migration and the modulation of Th1 and Th2 cytokines. The NO pathway was not affected.

AIM OF THE PRESENT STUDY: The aim of the present study was to further investigate the mechanisms responsible for the anti-inflammatory properties of the hydroethanolic extract of the stem bark of Dilodendron bipinnatum (HEDb).

MATERIALS AND METHODS: HEDb was obtained by maceration of the stem bark of D. bipinnatum as previously described. The corresponding effects on a macrophage-like cell line, RAW 264.7, were investigated. The apoptosis of RAW 264.7 upon treatment with LPS, HEDb and N-acetyl-L-cysteine (NAC) was assessed by flow cytometry, using an Annexin V-PE kit. The production of inflammatory cytokines (TNF-α, IL-1β and IL-10) and PGE2 were evaluated by ELISA, after cell challenge with LPS. The intracellular redox state and changes in mitochondrial membrane potential were also assessed by flow cytometry, using DCFH-DA and JC-1 as probes. The protein expression levels of MAPK p-p38, p-ERK, p-JNK, MKP-1 and COX-2 were analysed by western blotting. Nuclear translocation of NF-қB was assessed by immunofluorescence microscopy. The quantified results are presented as a nuclear:cytoplasmic ratio.

RESULTS: LPS, HEDb and NAC did not appear to decrease the number of viable cells in comparison to control treatment. HEDb attenuated the production of pro-inflammatory cytokines (IL-1β and TNF-α) and PGE2 induced by LPS but did not affect IL-10. The production of ROS was also inhibited by HEDb (1, 5 or 20µg/mL), even at the lowest concentration; at 20µg/mL, HEDb was more effective than NAC, which was used as a positive control (74.1% and 66.2% inhibition of LPS's effect, respectively). LPS induced an increase in ΔΨm (19.2%, p<0.001), while HEDb inhibited the change in ΔΨm (7.7% at 20µg/mL, p<0.001). The results of western blotting showed that HEDb inhibited the expression of MAPK p-p38, p-JNK and COX-2, while the expression of MKP-1 was increased. p-ERK was not affected. LPS promoted the nuclear translocation of NF-қB p65 (67%, p<0.01) in RAW 264.7 cells, in comparison to baseline (33%). Pre-treatment with HEDb inhibited this translocation of NF-κB p65 (58% at 20µg/mL, p<0.001).

CONCLUSION: HEDb has a potent anti-inflammatory activity and acts on multiple targets and biological pathways of potential therapeutic relevance.