Luteolin reduces primary hippocampal neurons death induced by neuroinflammation.

Objectives: This study examined whether luteolin may exert an anti-inflammatory effect in microglia and may be neuroprotective by regulating microglia activation.

Methods: We treated BV2 microglia with 1.0 μg/ml lipopolysaccharide (LPS) after incubation with luteolin for 1 hour, the nitric oxide (NO) levels were determined by a Griess reaction, the inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-alpha (TNF-alpha), and interleukin 1beta (IL-1beta) mRNA expression were determined by real-time PCR analysis, the iNOS and COX-2 protein induction were determined by Western blot analysis, and the levels of prostaglandin E(2) (PGE(2)), TNF-alpha, and IL-1beta were determined by enzyme-linked immunosorbent assay (ELISA) kits. Rat primary hippocampal neurons were co-cultured with LPS-activated BV2 microglia with 20 μM luteolin for 24 hours, the hippocampal neurons viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and the number of apoptotic hippocampal neurons was determined by immunofluorescence detection.

Results: Luteolin significantly inhibited the expression of iNOS and COX-2 in LPS-induced BV2 microglia. Moreover, the compound down-regulated the proinflammatory cytokines (TNF-alpha and IL-1beta) as well as the production of NO and PGE(2) in these cells. When hippocampal neurons were co-cultured with LPS-stimulated BV2 microglia, the administration of 20 μM luteolin increased the neurons viability and reduced the number of apoptotic neurons.

Conclusion: These data demonstrate that anti-inflammatory activity of luteolin in microglia contributes to its neuroprotective effect and suggest that it may have a potential therapeutic application in the treatment of neurodegenerative diseases.