Short- and Long-term Regulation of Intestinal Na+/H+ exchange by TLR4 in intestinal epithelial cells

The ability of recognizing microbiological infections is largely dependent on toll-like receptors (TLR). TLR4 is expressed in the cell membrane and is activated by bacterial lipopolysaccharide, one of components of the outer membrane of Gram-negative bacteria. Aims: To evaluate the effect of TLR4 activation by Monophosphoryl Lipid A (MPLA) on Na+/H+ exchanger (NHE) activity in T84 cells as well the signal transduction set in motion. Material and methods: NHE activity and kinetics were measured using fluorimetric assays and protein expression was determined by western blot analysis. Results: Short- and long-term MPLA (0.01 to 50 µg/ml) exposure induced an NHE1 concentration dependent inhibition (st -4.9±5 to -25.2±5 %; lt -3.9± to -31.9±4 %) without any effect over NHE membrane protein expression. The cell signal triggered AC3, PKA, PLC and PKC signal molecules. Long-term exposure induced changes in NHE activity but affecting different NHE isoforms depending on MPLA concentration, lower MPLA induced NHE3 i...