Effects of dietary supplementation of Angelica gigas Nakai root powder on heat shock gene expression of peripheral blood mononuclear cells (PBMC) isolated from broiler chickens grown under normal and heat stressed environment

Abstract

The study was undertaken to assess the difference in the heat response of Ross broiler chickens subjected to heat stress with varying amounts of Angelica gigas Nakai (AGN) root powder supplemented in the diet. A total of one hundred ninety‐two, day old broiler chicks were randomly divided into two groups: control (29°C) and heat stressed (36°C for 5 hours). The two groups were divided into four subgroups having different treatments composed of the control (no AGN feed supplementation), 0.1%, 0.3% and 0.5% AGN root powder supplementation. After 4 weeks, animals were sacrificed and samples were collected for analysis. PBMC was isolated using Ficoll‐Paque Plus density gradient centrifugation of blood samples collected from the brachial vein. PBMC cultures were stimulated with LPS then subjected to cell viability assay, RT‐PCR and Western blot analyses (Hsf1, Hsp70, Hsp90, IL‐1β, IL‐2, IL‐6, IL‐8, TGF‐β, iNOS and IFNγ). Cell viability assay showed that AGN root powder promoted cell proliferation on PBMC (with or without LPS stimulation) of broiler chickens under normal temperature conditions. More importantly, the plant also alleviates heat shock through both cytotoxicity prevention and dose dependent cell proliferation on PBMCs (with or without LPS stimulation) of heat stressed broilers. Both RT‐PCR and Western blot analysis showed enhanced expression of heat shock genes and proteins Hsf1, Hsp90 and Hsp70. Immunomodulatory activity of AGN was also demonstrated through upregulated mRNA and protein expressions of cytokines IL‐1β, IL‐6, IL‐8 and IFNγ and down regulation of IL‐2, TGF‐β and iNOS. These findings suggest the potential of AGN root powder as a feed supplement in broiler chickens to enhance cellular tolerance against heat shock through the enhancement of heat shock genes and protein expressions in addition to its immunomodulatory activity on avian PBMC.