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.