Recovery from heat shock injury by activation of Na+-glucose cotransporter in renal epithelial cells

Abstract

Exposure of cells or organs to sublethal physical or chemical stresses induces disruption of cellular structures and functions. Here, we examined whether Na(+)-glucose cotransporter (SGLT1) is involved in the recovery from heat shock (HS) injury in porcine renal epithelial LLC-PK(1) cells. Recovery from HS (42 degrees C for 3 h, then 37 degrees C for 12 h) increased SGLT1 activity, assessed by [14C]alpha-methyl glucopyranoside uptake, and a maximal transport rate (V(max)) from 2.4 to 5.9 nmol/mg protein/30 min, but did not alter an apparent affinity constant (K(m)). Protein distribution of SGLT1 in apical membrane fraction was also increased after recovery from HS without changing in total membrane fraction. Membrane integrity assessed by calcein accumulation was decreased by HS, and then returned to basal level. This recovery was inhibited by phloridzin, a potent SGLT1 inhibitor, and nonmetabolizable glucose analogues. Anti-transforming growth factor-beta 1 (TGF-beta 1) antibody inhibited both elevation of SGLT1 distribution in apical membrane and recovery of calcein accumulation induced by HS. Taken together, HS increases in the number of SGLT1 protein in apical membrane mediated via TGF-beta 1 signaling pathway. The increase of glucose uptake is necessary to repair plasma membrane integrity.

Rosmarinic acid, major phenolic constituent of Greek sage herbal tea, modulates rat intestinal SGLT1 levels with effects on blood glucose

“…In order to shed light on the mechanisms of S. fruticosa and RA on translocation to the BBM of SGLT1, Hsp70 and PKC were quantified. Hsp70 has been reported to increase both translocation of SGLT1 to the BBM and transport activity, through the formation of Hsp70/SGLT1 complexes 43, 44. Our results show that Hsp70 levels profile in BBM was similar to that of SGLT1.…”

Reorganization of ZO‐1 by sodium‐dependent glucose transporter activation after heat stress in LLC‐PK1 cells

“…HS decreased the accumulation of a fluorescent dye, calcein, in LLC‐PK 1 cells, indicating that plasma membrane was damaged by HS (Ikari et al, 2003). The subsequent incubation of cells at 37°C led to recovery of the calcein accumulation that was inhibited by phloridzin.…”

“…The extract was completely collected (Triton X‐100 soluble fraction) and the residue (Triton X‐100 insoluble fraction) was dissolved in lysis buffer (1% Triton X‐100, 150 mM NaCl, 1 mM EDTA, 20 mM Tris‐HCl, pH7.4, 0.1% SDS) containing protease inhibitors. Total membrane fraction was prepared as described previously (Ikari et al, 2003). These fractions were dissolved in sample buffer for SDS‐polyacrylamide gel electrophoresis.…”

Effect on cell membrane structural integrity of xylitol‐coated probiotics when stabilised with milk solids – A FTIR study

“…It has been shown that lethal damage to bacterial cells because of heat injury is very much linked to protein denaturation and inactivation of the membrane‐bound enzymes (Ikari et al . 2003). Heat injury can further aggravate or alleviate the damage depending on the pH and the composition of the environment.…”