Abutilon avicennae seed coat extract inhibits the lipopolysaccharide-induced inflammatory response in macrophages by multiple mechanisms

Abstract

Abutilon avicennae is used in Korean folk medicine to treat middle ear infection, diarrhea, and inflammation of the lymphatic glands. The anti-inflammatory abilities of abutilon avicennae have not been investigated in detail. Therefore, we undertook the present study to examine whether an extract of the seed coat of abutilon avicennae (SCAA) could suppress LPS-stimulated inflammatory responses in RAW 264.7 cells and to determine the mechanisms by which it did so. We found that SCAA completely suppressed NO production in LPS-stimulated RAW 264.7 cells in a dose-dependent manner. We also confirmed that SCAA was not cytotoxic to RAW 264.7 cells at any of the concentrations we used in this study. Molecular analysis demonstrated that SCAA inhibited mRNA and protein expression of both iNOS and COX-2 in a dose-dependent manner. In addition, SCAA reduced the mRNA levels of the pro-inflammatory cytokines interleukin-1β (IL-1β) and interleukin-6 (IL-6). Moreover, SCAA suppressed the phosphorylation of mitogen-activated protein kinases (MAPKs; JNK, ERK1/2 and p38), whereas it had no effect on the phosphorylation status of Akt. SCAA suppressed the LPS-stimulated degradation of IkBα in a concentration-dependent manner, thereby preventing translocation of nuclear factor-kB (NF-kB) into the nucleus. Taken together, these results suggest that SCAA exerted its anti-inflammatory effects in LPS-stimulated RAW 264.7 cells by inhibiting IkBk degradation, and inhibiting the transcription of proinflammatory mediators and cytokines. Key words: Inflammation, abutilon avicennae, nuclear factor-kB, RAW 264.7.