S-adenosylmethionine prevents the up regulation of Toll-like receptor (TLR) signaling caused by chronic ethanol feeding in rats

Abstract

Toll-like receptors (TLR) play a role in mediating the proinflammatory response, fibrogenesis and carcinogenesis in chronic liver diseases such as alcoholic liver disease, non-alcoholic liver disease, hepatitis C and hepatocellular carcinoma. This is true in experimental models of these diseases. For this reason, we investigated the TLR proinflammatory response in the chronic intragastric tube feeding rat model of alcohol liver disease. The methyl donor S-adenosylmethionine was also fed to prevent the gene expression changes induced by ethanol. Ethanol feeding tended to increase the up regulation of the gene expression of TLR2 and TLR4. SAMe feeding prevented this. TLR4 and MyD88 protein levels were significantly increased by ethanol and this was prevented by SAMe. This is the first report where ethanol feeding induced TLR2 and SAMe prevented the induction by ethanol. CD34, FOS, interferon responsive factor 1 (IRF-1), Jun, TLR 1,2,3,4,6 and 7 and Traf-6 were found to be up regulated as seen by microarray analysis where rats were sacrificed at high blood alcohol levels compared to pair fed controls. Il-6, IL-10 and IFNγ were also up regulated by high blood levels of ethanol. The gene expression of CD14, MyD88 and TNFR1SF1 were not up regulated by ethanol but were down regulated by SAMe. The gene expression of IL-1R1 and IRF1 tended to be up regulated by ethanol and this was prevented by feeding SAMe. The results suggest that SAMe, fed chronically prevents the activation of TLR pathways caused by ethanol. In this way the proinflammatory response, fibrogenesis, cirrhosis and hepatocellular carcinoma formation due to alcohol liver disease could be prevented by SAMe.

Fig 1

qRT-PCR analysis of TLR2 (A) and TLR4 (B), gene expression tended to be increased by ethanol, but not TLR3 (C), TLR9 (D) and TLR5 (E). This increase or the expression of mRNA was down regulated when SAMe was supplemented with ethanol. (Mean ± SEM, n=3). (C: Dex vs. SAMe+EtOH p=0.049) (D: Dex vs. SAMe+EtOH p=0.04; EtOH vs. SAMe+dex p=0.006).

Fig 1

qRT-PCR analysis of TLR2 (A) and TLR4 (B), gene expression tended to be increased by ethanol, but not TLR3 (C), TLR9 (D) and TLR5 (E). This increase or the expression of mRNA was down regulated when SAMe was supplemented with ethanol. (Mean ± SEM, n=3). (C: Dex vs. SAMe+EtOH p=0.049) (D: Dex vs. SAMe+EtOH p=0.04; EtOH vs. SAMe+dex p=0.006).

Figure 2

qRT-PCR analysis of CD14 (A) and MyD88 (B) gene expression. Note that there was no change in CD14 expression in the liver of rats fed ethanol but there was a small decrease in MyD88 expression in the liver of ethanol fed rats. SAMe down regulated the expression of MyD88 with or without ethanol. (Mean ± SEM, n=3) (B: Dex vs. SAMe+Dex p=0.002; EtOH vs. SAMe+Dex p=0.003)

Figure 3

Protein levels analyzed by Western blot showed that TLR4 and MyD88 were increased by ethanol feeding. SAMe supplementation prevented this increase.

Fig 4

qRT-PCR analysis of IL-1R1 (A), IRF1 (B) and TNFR1SF1a (C) gene expression. Note that ethanol feeding tended to increase the mRNA levels of IL-R1 and IRF-1. SAMe supplementation tended to decrease this up regulation. TNFR1SF1a expression was not significantly increased by ethanol feeding although SAMe supplementation tended to decrease the expression of TNFRISF1a.. (Mean ±SEM, n=3)

Fig 4

qRT-PCR analysis of IL-1R1 (A), IRF1 (B) and TNFR1SF1a (C) gene expression. Note that ethanol feeding tended to increase the mRNA levels of IL-R1 and IRF-1. SAMe supplementation tended to decrease this up regulation. TNFR1SF1a expression was not significantly increased by ethanol feeding although SAMe supplementation tended to decrease the expression of TNFRISF1a.. (Mean ±SEM, n=3)