Inhibitory activities of ethanolic extract of perilla frutescens seed residue on inflammation and cancer promotion of colon in rats

Abstract

Nga-kee-mon (Perilla frutescens; PF) is a plant in the mint family. Its leaves and seeds are mostly consumed in the Northern of Thailand. In the production of PF seed oil, PF seed residue remained largely are useless and not interesting to use. Although, the nutrients and bioactive compounds of PF seed residue are previously reported, the biological activities of PF seed residue are limited. Therefore, this study aimed to investigate the chemoprotective action of PF seed residue crude ethanolic extract (PCE) on the inflammatory induced promotion stage of rat colon carcinogenesis and cell culture models. To determine the effect of PCE on aberrant crypt foci (ACF) progression, male Wistar rats were initiated ACF formation by injection with 40 mg/kg body weight of dimethylhydrazine (DMH) once a week for 2 weeks. After that, rats were induced inflammation to promote ACF growth by drinking 1% w/v of dextran sulfate sodium (DSS) instead of drinking water for 1 week. After 2 weeks of DSS administration, rats were orally administrated by PCE at 0.1 and 1 g/kg body weight /day until week 15. Then all rats were sacrificed and the number, the distribution and multiplicity of ACF were determined. During experimental period, the blood samples were taken in week-3 (after received DMH), week-5 (after 2-week DSS administration) and week-10 (after 5-week oral gavage with PCE) to evaluate serum pro-inflammatory cytokines including interleukin-6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor alpha (TNF-α). The results shown that PCE 1 g/kg body weight exhibited the reduction of ACF number (66.46%) compared to DMH+DSS alone (P<0.01), whereas rats received PCE at 0.1g/kg body weight the ACF count was approximately 35.2% (P˂0.01) lower than the group of DMH and DSS alone. However, there was a downward trend of ACF multiplicity in rats which were received PCE, but there was not statistical difference. When measuring the serum level of inflammatory cytokine of rats treated with DMH and DSS, the levels of IL-6, IL-1β, and TNF-α were significantly increased when compared to the control group. Whereas, after 5-week oral gavage with PCE, the serum level of all cytokines was significantly decreased (P<0.01). In addition, the study of PCE on the expression of inflammatory cytokines in rat colonic epithelial cells by real-time PCR showed that the expression of IL-6, IL-1β, and TNF-α were down regulated by a high dose of PCE feeding in DMH+DSS rats. The results suggested that PCE might inhibit ACF promotion from DMH and DSS induction via the modulation of inflammatory microenvironment in rat colon. Additionally, the mechanism of PCE on inflammation and cancer growth induced by inflammatory cytokines was investigated in vitro. The results showed that PCE could inhibit all cytokines secretion (IL-6, IL-1β and TNF-α) in cell culture media of lipopolysaccharide (LPS)-induced RAW 264.7 cell. Then, the effect of PCE on inflammatory-response of human colon cancer cell lines (HCT-116 and HT-29) was determined. The results demonstrated that PCE inhibited IL-6-induced cell proliferation in both HCT-116 and HT-29. Therefore, PCE could either modulate the inflammation induced by bacterial toxin or suppress the proliferation of cancer cell line which was induced by inflammatory process. In conclusion, the active components in Perilla frutescens seed residue showed the preventive effect on the aberrant colonic epithelial cell progression by modulating inflammatory microenvironment from the infiltrated macrophage or inflammatory response of aberrant cells. Therefore, the mechanisms study of PF seed residue against inflammation and inflammatory-induced colon cancer progression needs to be further investigate.