Anti-inflammatory effects of Perilla frutescens leaf extract on lipopolysaccharide-stimulated RAW264.7 cells

Perilla leaves are widely used in Chinese herbal medicine and in Japanese herbal agents used to treat respiratory diseases. This study aimed to investigate the anti-inflammatory effects and the underlying mechanisms of Perilla frutescens leaf extract (PLE). Murine macrophage RAW264.7 cells were used as a model. Cell viability and morphological changes were studied by the MTT assay and microscopy. mRNA expression of pro-inflammatory mediators was assessed by both semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and quantitative (q) RT-PCR. Nitric oxide (NO) and prostaglandin E2 (PGE2) production were analyzed by the Griess test and sandwich enzyme-linked immunosorbent assay (ELISA), respectively. The activation of kinase cascades was studied by immunoblotting. Our findings showed that PLE slightly affects cell viability, but alleviates LPS-induced activation of RAW264.7 cells. Furthermore, PLE significantly reduced the LPS-induced mRNA expression of the interleukin (IL)-6, IL-8, tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), genes in a dose-dependent manner. In addition, PLE reduced NO production and PGE2 secretion induced by LPS. PLE also inhibited activation of mitogen-activated protein kinases (MAPKs), increased the cytosolic IκBα level, and reduced the level of nuclear factor (NF)-κB. Taken together, these findings indicate that PLE significantly decreases the mRNA expression and protein production of pro-inflammatory mediators, via the inhibition of extracellular-signal-regulated kinase (ERK)1/2, c-Jun N-terminal kinase (JNK), p38, as well as NF-κB signaling in RAW264.7 cells stimulated with LPS.