SGLT-1-mediated glucose uptake protects intestinal epithelial cells against LPS-induced apoptosis and barrier defects: a novel cellular rescue mechanism?

FASEB J. 2005 Nov;19(13):1822-35. doi: 10.1096/fj.05-4226com.

Abstract

Excessive apoptosis induced by enteric microbes leads to epithelial barrier defects. This mechanism has been implicated in the pathogenesis of inflammatory bowel diseases (IBD) and bacterial enteritis. The sodium-dependent glucose cotransporter (SGLT-1) is responsible for active glucose uptake in enterocytes. The aim was to investigate the effects of SGLT-1 glucose uptake on enterocyte apoptosis and barrier defects induced by bacterial lipopolysaccharide (LPS). SGLT-1-transfected Caco-2 cells were treated with LPS (50 mug/mL) in low (5 mM) or high (25 mM) glucose media. LPS in low glucose induced caspase-3 cleavage, DNA fragmentation, and increased paracellular permeability to dextran in epithelial cells. These phenomena were significantly attenuated in high glucose. LPS increased SGLT-1 activity in high, but not low glucose media. Addition of phloridzin, which competitively binds to SGLT-1, inhibited the cytoprotection mediated by high glucose. Western blot showed that LPS in high glucose increased the levels of anti-apoptotic Bcl-2 and Bcl-X(L,) and did not change proapoptotic Bax. Differential extraction of membranous vs. cytosolic cell components demonstrated that high glucose inhibits mitochondrial cytochrome c translocation to cytosol. Collectively, SGLT-1-mediated glucose uptake increases anti-apoptotic proteins, and protects enterocytes from LPS-induced apoptosis and barrier defects. The understanding of this novel glucose-mediated rescue mechanism may lead to therapeutic interventions for various enteric diseases.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Binding, Competitive
  • Biological Transport
  • Blotting, Western
  • Caco-2 Cells
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • Caspases / metabolism
  • Cell Membrane / metabolism
  • Cytochromes c / metabolism
  • Cytosol / metabolism
  • DNA Fragmentation
  • Enterocytes / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • Epithelial Cells / cytology*
  • Glucose / metabolism
  • Humans
  • Inflammatory Bowel Diseases / pathology
  • Intestines / cytology*
  • Intestines / pathology
  • Lipopolysaccharides / metabolism*
  • Membrane Potentials
  • Membrane Proteins / chemistry
  • Microscopy, Fluorescence
  • Models, Biological
  • Models, Statistical
  • Occludin
  • Permeability
  • Phlorhizin / pharmacology
  • Protein Binding
  • Protein Transport
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Sodium-Glucose Transporter 1 / metabolism
  • Sodium-Glucose Transporter 1 / physiology*
  • Time Factors
  • Transfection
  • Up-Regulation
  • Voltage-Dependent Anion Channels / metabolism
  • bcl-X Protein / metabolism

Substances

  • Lipopolysaccharides
  • Membrane Proteins
  • OCLN protein, human
  • Occludin
  • Proto-Oncogene Proteins c-bcl-2
  • SLC5A1 protein, human
  • Sodium-Glucose Transporter 1
  • Voltage-Dependent Anion Channels
  • bcl-X Protein
  • Cytochromes c
  • Phlorhizin
  • CASP3 protein, human
  • CASP8 protein, human
  • CASP9 protein, human
  • Caspase 3
  • Caspase 8
  • Caspase 9
  • Caspases
  • Glucose