Arsenic affects inflammatory cytokine expression in Gallus gallus brain tissues

Abstract

Background: The heavy metal arsenic is widely distributed in nature and posses a serious threat to organism's health. However, little is known about the arsenic-induced inflammatory response in the brain tissues of birds and the relationship and mechanism of the inflammatory response. The purpose of this study was to explore the effects of dietary arsenic on the expression of inflammatory cytokines in the brains of Gallus gallus.

Results: Seventy-two 1-day-old male Hy-line chickens were divided into a control group, a low arsenic trioxide (As₂O₃)-treated (7.5 mg/kg) group, a middle As₂O₃-treated (15 mg/kg) group, and a high As₂O₃-treated (30 mg/kg) group. Arsenic exposure caused obvious ultrastructural changes. The mRNA levels of the transcription factor nuclear factor-κB (NF-κB) and of pro-inflammatory cytokines, including inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and prostaglandin E synthase (PTGEs), in chicken brain tissues (cerebrum, cerebellum, thalamus, brainstem and myelencephalon) on days 30, 60 and 90, respectively, were measured by real-time PCR. The protein expression of iNOS was detected by western blot. The results showed that after being treated with As₂O_3, the levels of inflammatory-related factor NF-κB and pro-inflammatory cytokines in chicken brain tissues increased (P < 0.05).

Conclusions: Arsenic exposure in the chickens triggered host defence and induced an inflammatory response by regulating the expression of inflammatory-related genes in the cerebrum, cerebellum, thalamus, brainstem and myelencephalon. These data form a foundation for further research on arsenic-induced neurotoxicity in Gallus gallus.

Keywords: Arsenic; Brain tissues; Chickens; Inflammatory cytokines; NF-κB.

Fig. 1

Ultrastructural observations in the brain tissues of chickens. Panels A, B, C, D and E were the histology of the cerebrum, cerebellum, thalamus, brainstem and myelencephalon tissue in the control group, respectively. Panels a, b, c, d and e represented the histology of the cerebrum, cerebellum, thalamus, brainstem, and myelencephalon tissue in the As₂O₃ treated groups at 90 d (H groups)

Fig. 2

Effects of As₂O₃ on the NF-κB mRNA levels in the brain tissues. a-e represented the NF-κB mRNA levels in the cerebrum, cerebellum, thalamus, brainstem and myelencephalon tissue, respectively. Each value represented the means ± SD of six individuals. The bars with a star at the same sampling time were significantly different (P < 0.05)

Fig. 3

Effects of As₂O₃ on the iNOS mRNA levels in the brain tissues. a-e represented the iNOS mRNA levels in the cerebrum, cerebellum, thalamus, brainstem and myelencephalon tissue, respectively. Each value represented the means ± SD of six individuals. The bars with a star at the same sampling time were significantly different (P < 0.05)

Fig. 4

Effects of As₂O₃ on the COX-2 mRNA levels in the brain tissues. a-e represented the COX-2 mRNA levels in the cerebrum, cerebellum, thalamus, brainstem and myelencephalon tissue, respectively. Each value represented the means ± SD of six individuals. The bars with a star at the same sampling time were significantly different (P < 0.05)

Fig. 5

Effects of As₂O₃ on the PTGEs mRNA levels in the brain tissues. a-e represented the PTGEs mRNA levels in the cerebrum, cerebellum, thalamus, brainstem and myelencephalon tissue, respectively. Each value represented the means ± SD of six individuals. The bars with a star at the same sampling time were significantly different (P < 0.05)

Fig. 6

Effects of As₂O₃ on the iNOS protein expressions in the brain tissues. a-e represented the western blot results of the expression of the iNOS and GADPH proteins and iNOS/GADPH ratio in the cerebrum, cerebellum, thalamus, brainstem and myelencephalon tissue, respectively. C30 and H30 represented the C and H groups at 30 d, respectively, the notations for the C60, H60, C90 and H90 groups are similar. Each value represented the means ± SD of six individuals. The bars with a star at the same sampling time were significantly different (P < 0.05)