Cannabidiol (CBD): a killer for inflammatory rheumatoid arthritis synovial fibroblasts.

Cannabidiol (CBD) is a non-intoxicating phytocannabinoid from cannabis sativa that has demonstrated anti-inflammatory effects in several inflammatory conditions including arthritis. However, CBD binds to several receptors and enzymes and, therefore, its mode of action remains elusive. In this study, we show that CBD increases intracellular calcium levels, reduces cell viability and IL-6/IL-8/MMP-3 production of rheumatoid arthritis synovial fibroblasts (RASF). These effects were pronounced under inflammatory conditions by activating transient receptor potential ankyrin (TRPA1), and by opening of the mitochondrial permeability transition pore. Changes in intracellular calcium and cell viability were determined by using the fluorescent dyes Cal-520/PoPo3 together with cell titer blue and the luminescent dye RealTime-glo. Cell-based impedance measurements were conducted with the XCELLigence system and TRPA1 protein was detected by flow cytometry. Cytokine production was evaluated by ELISA. CBD reduced cell viability, proliferation, and IL-6/IL-8 production of RASF. Moreover, CBD increased intracellular calcium and uptake of the cationic viability dye PoPo3 in RASF, which was enhanced by pre-treatment with TNF. Concomitant incubation of CBD with the TRPA1 antagonist A967079 but not the TRPV1 antagonist capsazepine reduced the effects of CBD on calcium and PoPo3 uptake. In addition, an inhibitor of the mitochondrial permeability transition pore, cyclosporin A, also blocked the effects of CBD on cell viability and IL-8 production. PoPo3 uptake was inhibited by the voltage-dependent anion-selective channel inhibitor DIDS and Decynium-22, an inhibitor for all organic cation transporter isoforms. CBD increases intracellular calcium levels, reduces cell viability, and IL-6/IL-8/MMP-3 production of RASF by activating TRPA1 and mitochondrial targets. This effect was enhanced by pre-treatment with TNF suggesting that CBD preferentially targets activated, pro-inflammatory RASF. Thus, CBD possesses anti-arthritic activity and might ameliorate arthritis via targeting synovial fibroblasts under inflammatory conditions.

Arsenic trioxide inhibits osteosarcoma cell invasiveness via MAPK signaling pathway.

Arsenic trioxide (As(2)O(3)) is an active ingredient in traditional Chinese medicine. Recent studies showed that it causes apoptosis in several cancer cells. However, research of As(2)O(3) in osteosarcoma is sparse. In our present study, an inhibitory effect of As(2)O(3) on osteosarcoma cell adhesion and metastasis was observed with a cell adhesion, migration and invasion test. The impact of As(2)O(3) on the activities of MMP-9 and MAPK pathway-related downstream factors was analyzed by western blotting. Our results showed that As(2)O(3) significantly inhibited motility, migration and invasion in HOS and MNNG cells in a concentration-dependent manner at concentrations ranging from 0.5-2 µM, and led to cytoskeletal rearrangements. As(2)O(3) exerted an inhibitory effect on the phosphorylation of ERK1/2 and MEK, which are the members of the MAPK family. Additionally, treatment with As(2)O(3) in combination with inhibitors specific for MEK (U0126) in HOS and MNNG cells resulted in a marked inhibition of cell invasion and As(2)O(3) could significantly reduce PMA-induced invasion. In conclusion, we demonstrate the inhibitory effects of As(2)O(3) on the invasiveness of HOS and MNNG cells, which may be due at least partly to inactivation of the MAPK signaling pathway.