Effects of oral exposure to naturally-occurring and synthetic deoxynivalenol congeners on proinflammatory cytokine and chemokine mRNA expression in the mouse

Abstract

The foodborne mycotoxin deoxynivalenol (DON) induces a ribotoxic stress response in mononuclear phagocytes that mediate aberrant multi-organ upregulation of TNF-α, interleukins and chemokines in experimental animals. While other DON congeners also exist as food contaminants or pharmacologically-active derivatives, it is not known how these compounds affect expression of these cytokine genes in vivo. To address this gap, we compared in mice the acute effects of oral DON exposure to that of seven relevant congeners on splenic expression of representative cytokine mRNAs after 2 and 6h. Congeners included the 8-ketotrichothecenes 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), fusarenon X (FX), nivalenol (NIV), the plant metabolite DON-3-glucoside (D3G) and two synthetic DON derivatives with novel satiety-inducing properties (EN139528 and EN139544). DON markedly induced transient upregulation of TNF-α IL-1β, IL-6, CXCL-2, CCL-2 and CCL-7 mRNA expressions. The two ADONs also evoked mRNA expression of these genes but to a relatively lesser extent. FX induced more persistent responses than the other DON congeners and, compared to DON, was: 1) more potent in inducing IL-1β mRNA, 2) approximately equipotent in the induction of TNF-α and CCL-2 mRNAs, and 3) less potent at upregulating IL-6, CXCL-2, and CCL-2 mRNAs. EN139528's effects were similar to NIV, the least potent 8-ketotrichothecene, while D3G and EN139544 were largely incapable of eliciting cytokine or chemokine mRNA responses. Taken together, the results presented herein provide important new insights into the potential of naturally-occurring and synthetic DON congeners to elicit aberrant mRNA upregulation of cytokines associated with acute and chronic trichothecene toxicity.

Keywords: 8-Ketotrichothecenes; Chemokine; Cytokine; Deoxynivalenol-3-glucoside; EN139528; EN139544.

Fig. 1

Structures of 8-ketotrichothecene DON congeners.

Fig. 2

Structures of natural DON plant metabolite D3G (A) and synthetic DON congeners. (EN139528 (B) and EN139544 (C).

Fig. 3

Experimental design.

Fig. 4

Comparative effects of DON congeners on IL-1β mRNA expression. Mice were orally gavaged with 8-ketotrichothecenes (A,B) and D3G, EN139528, EN139544 (C,D) at 2.5 mg/kg bw and then spleens removed at 2 h (A,C) or 6 h (B,D) post administration IL-1β mRNA expression was determined by real-time PCR. Data are mean ± SEM (n=6/gp) of mRNA fold change relative to vehicle control and were analyzed as described in Fig. 4 legend

Fig. 5

Comparative effects of DON congeners on IL-6 mRNA expression. Mice were orally gavaged with 8-ketotrichothecenes (A,B) and D3G, EN139528, EN139544 (C,D) at 2.5 mg/kg bw and then spleens removed at 2 h (A,C) or 6 h (B,D) post administration IL-6 mRNA expression was determined by real-time PCR. Data are mean ± SEM (n=6/gp) of mRNA fold change relative to vehicle control and were analyzed as described in Fig. 4 legend.

Fig. 6

Comparative effects of DON congeners on TNF-α mRNA expression. Mice were orally gavaged with 8-ketotrichothecenes (A,B) and D3G, EN139528, EN139544 (C,D) at 2.5 mg/kg bw and then spleens removed at 2 h (A,C) or 6 h (B,D) post administration TNF-α mRNA expression was determined by real-time PCR. The letter ^a indicates significant differences between responses to DON or DON congener and vehicle control (p ≤ 0.05). The letter ^b indicates significant differences between responses to congener and DON (p ≤ 0.05).

Fig. 7

Comparative effects of DON congeners on CXCL-2 mRNA expression. Mice were orally gavaged with 8-ketotrichothecenes (A,B) and D3G, EN139528, EN139544 (C,D) at 2.5 mg/kg bw and then spleens removed at 2 h (A,C) or 6 h (B,D) post administration CXCL-2 mRNA expression was determined by real-time PCR. Data are mean ± SEM (n=6/gp) of mRNA fold change relative to vehicle control and were analyzed as described in Fig. 4 legend.

Fig. 8

Comparative effects of DON congeners on CCL-2 mRNA expression. Mice were orally gavaged with 8-ketotrichothecenes (A,B) and D3G, EN139528, EN139544 (C,D) at 2.5 mg/kg bw and then spleens removed at 2 h (A,C) or 6 h (B,D) post administration CCL-2 mRNA expression was determined by real-time PCR. Data are mean ± SEM (n=6/gp) of mRNA fold change relative to vehicle control and were analyzed as described in Fig. 4 legend.

Fig. 9

Comparative effects of DON congeners on CCL-7 mRNA expression. Mice were orally gavaged with 8-ketotrichothecenes (A,B) and D3G, EN139528, EN139544 (C,D) at 2.5 mg/kg bw and then spleens removed at 2 h (A,C) or 6 h (B,D) post administration CCL-7 mRNA expression was determined by real-time PCR. Data are mean ± SEM (n=6/gp) of mRNA fold change relative to vehicle control and were analyzed as described in Fig. 4 legend.