Fig. 1.

The effects of bromelain on NO production in LPS-stimulated microglial cells. Primary microglial cells were incubated in the absence (-) or presence (+) of 1 µg/ml LPS. The cells were pretreated with various amounts of bromelain (5, 10, 20, and 30 µg/ml) for one hour prior to LPS addition. Following 48 h of incubation, the cultures were subjected to a nitrite assay (A) and a cell viability assay (B). The LPS-stimulated microglial cells showed a remarkable increase in NO levels in the cell-conditioned media when compared to those in the control. Pretreatment of microglial cells with bromelain (at 5-30 µg/ml) significantly reduced NO production in the LPS-stimulated primary microglia in a dose-dependent manner. The MTT assay indicates that the inhibitory effects of bromelain on LPS-stimulated NO production are not due to cytotoxic action of bromelain on primary microglia. *P<0.01 as compared with the LPS-treated group without bromelain