The anti-cancer and anti-inflammatory effects of polyacetylenes from carrots and their mechanisms of action in the APCMin/+ mouse colon cancer model and primary macrophages

Abstract

Diets rich in vegetables, including the Apiaceae family are associated with improved health outcomes and a reduced risk of chronic diseases like inflammation and cancer. Bioactive phytochemicals in Apiaceae vegetables such as polyphenols, carotenoids, and polyacetylenes (PAs) have been suggested to be responsible for the protective effects of these vegetables. Falcarinol (FaOH), falcarindiol (FaDOH), and falcarindiol 3-acetate (FaDOH3Ac) are cytotoxic polyacetylenic oxylipins naturally found in carrots. FaOH and FaDOH purified from carrots have demonstrated anti-inflammatory and chemopreventive effects on colorectal cancer precursor lesions in rats. In addition, observational studies on humans suggest that higher intakes of carrots reduce the risk of cancer. However, the health-promoting effects of polyacetylenes have not been thoroughly studied. Also, there is little knowledge of the physiological functions that the polyacetylenic phytochemicals may affect. The present study sought to elucidate the potential anti-inflammatory and immunomodulatory effects of PAs for their ability to downregulate the interferons (IFNs) pathway and the nuclear factor κB (NF-κB) pathway by pre-treating bone marrow derived macrophages (BMDMs) with 5μM of a mixture of PAs, pure FaOH, and pure FaDOH for 24h prior to the induction of inflammation via lipopolysaccharide (LPS) and 2′3′-Cyclic GMP-AMP (cGAMP). Moreover, the possible anti- tumour effect on colorectal cancer was investigated by treating APCMin/+ mice with diet-achievable doses of the mixed PAs (5 mg/kg body weight) daily for 10 weeks. The results found that each of the treatments (mixed PAs, FaOH, and FaDOH) were potent anti-inflammatories, downregulating cGAMP-induced proinflammatory IL6 gene expression (6 hours), and proinflammatory IL6 and TNF𝛼 cytokines (6 and 24 hours) and the effect was less in LPS induced inflammation. Moreover, all polyacetylene treatments upregulated cGAMP induced heme oxygenase 1 (HO-1) in mRNA levels; and the mixed PAs, but not FaOH or FaDOH, upregulated LPS induced HO-1. No phytochemicals upregulated NAD(P)H quinone oxireductase (NQO1) or nuclear factor E2-related factor (Nrf2), after both LPS and cGAMP stimulation. The mixture of PAs, FaOH and FaDOH each downregulated NF-κβ in mRNA levels and its downstream inflammatory markers: inhibitor of kappa β (Iκβ), cyclooxygenase 2 (COX-2), and nitric oxide synthase (NOS). A novel finding of this study is that polyacetylenes at low doses were potent anti-inflammatories by inhibiting the IFNs pathway in both gene and protein expressions. Polyacetylenes inhibited the neoplastic formation of aberrant crypt foci (ACF) and substantially reduced the total number of macroscopic neoplasms in mice. In conclusion, PAs exerted a range of anti-inflammatory, anti-mitotic, and antiproliferative effects, indicating the mechanisms through which they suppress neoplastic growth.