Inhibitory effect of TNF-α on the intestinal absorption of galactose

✍ Scribed by P. Amador; J. García-Herrera; M.C. Marca; J. de la Osada; S. Acín; M.A. Navarro; M.T. Salvador; M.P. Lostao; M.J. Rodríguez-Yoldi

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 247 KB
• Volume: 101
• Category: Article
• ISSN: 0730-2312
• DOI: 10.1002/jcb.21168

✦ Synopsis

Abstract

Sepsis is a systemic response to infection in which toxins, such as bacterial lipopolysaccharide (LPS), stimulate the production of inflammatory mediators like the cytokine tumor necrosis factor alpha (TNF‐α). Previous studies from our laboratory have revealed that LPS inhibits the intestinal absorption of L‐leucine and D‐fructose in rabbit when it was intravenously administered, and that TNF‐α seems to mediate this effect on amino acid absorption. To extend this work, the present study was designed to evaluate the possible effect of TNF‐α on D‐galactose intestinal absorption, identify the intracellular mechanisms involved and establish whether this cytokine mediates possible LPS effects. Our findings indicate that TNF‐α decreases D‐galactose absorption both in rabbit intestinal tissue preparations and brush‐border membrane vesicles. Western blot analysis revealed reduced amounts of the Na^+^/glucose cotransporter (SGLT1) protein in the plasma membrane attributable to the cytokine. On the contrary, TNF‐α increased SGLT1 mRNA levels. Specific inhibitors of the secondary messengers PKC, PKA, the MAP kinases p38 MAP, JNK, MEK1/2 as well as the proteasome, diminished the TNF‐α‐evoked inhibitory effect. LPS inhibition of the uptake of the sugar was blocked by a TNF‐α antagonist. In conclusion, TNF‐α inhibits D‐galactose intestinal absorption by decreasing the number of SGLT1 molecules at the enterocyte plasma membrane through a mechanism in which several protein‐like kinases are involved. J. Cell. Biochem. 101: 99–111, 2007. © 2006 Wiley‐Liss, Inc.