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

ABSTRACT

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 anti­inflammatory 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 pro­inflammatory mediators was assessed by both semi­quantitative reverse transcription­polymerase chain reaction (RT­PCR) and quantitative (q) RT­PCR. Nitric oxide (NO) and prostaglandin E2 (PGE2) production were analyzed by the Griess test and sandwich enzyme­linked immunosorbent assay (ELISA), respectively. The activation of kinase cascades was studied by immunoblotting. Our findings showed that PLE slightly affects cell viability, but alleviates LPS­induced activation of RAW264.7 cells. Furthermore, PLE significantly reduced the LPS­induced mRNA expression of the interleukin (IL)­6, IL­8, tumor necrosis factor­α (TNF­α), cyclooxygenase­2 (COX­2) and inducible nitric oxide synthase (iNOS), genes in a dose­dependent manner. In addition, PLE reduced NO production and PGE2 secretion induced by LPS. PLE also inhibited activation of mitogen­activated 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 pro­inflammatory mediators, via the inhibition of extracellular­signal­regulated kinase (ERK)1/2, c­Jun N­terminal kinase (JNK), p38, as well as NF­κB signaling in RAW264.7 cells stimulated with LPS.