Luteolin inhibits LPS-stimulated inducible nitric oxide synthase expression in BV-2 microglial cells.

Overproduction of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) acts as a neurotoxic effector in the central nervous system, resulting in neurodegenerative diseases. From the alcoholic extracts of Perilla frutescens, we have purified an inhibitor of NO production in lipopolysaccharide (LPS)-activated microglia by activity-guided purification. The active compound was identified as luteolin by spectral analysis. Luteolin inhibited the NO production in LPS-activated microglia in a dose-dependent manner (IC50=6.9 microM). Luteolin also suppressed the degradation of I-kappaB-alpha, the expression of protein and mRNA of iNOS in LPS-activated microglia as observed in Western blot analysis and RT-PCR experiments. Luteolin may have beneficial effects in the treatment of neuro-inflammatory diseases through the inhibition of iNOS expression.