Glutamine deprivation facilitates tumour necrosis factor induced bacterial translocation in Caco-2 cells by depletion of enterocyte fuel substrate.
Level 5 - mechanism / opinion, no new human data
In vitro laboratory bench research using cultured cell lines.
PubMed 12524404 · doi:10.1136/gut.52.2.224
What was done
The authors investigated the effects of tumour necrosis factor alpha (TNF-alpha; 20 ng/ml basolaterally for six hours) on Escherichia coli C25 translocation across Caco-2 epithelial monolayers under glutamine depletion and with various metabolic products or pathway inhibitors. Paracellular pathway integrity was measured using transepithelial electrical resistance (TEER) and lucifer yellow flux, enterocyte membrane integrity was assessed by lactate dehydrogenase release, enterocyte ATP levels were measured, and cell monolayers were imaged using transmission electron microscopy.
What was found
TNF-alpha induced E. coli translocation across Caco-2 monolayers only when accompanied by simultaneous glutamine depletion (p<0.01). Translocation was inhibited by adding glutamine for two hours (p<0.01), whereas an isonitrogenous mixture of non-glutamine amino acids had no inhibitory effect. Inhibiting glutamine conversion to alpha-ketoglutarate also induced translocation in the presence of TNF-alpha, whereas blockade of glutathione or polyamine synthesis did not. All conditions inducing translocation were associated with marked reductions in enterocyte ATP levels. No effect was observed on TEER, lucifer yellow flux, or lactate dehydrogenase release. Electron microscopy showed bacteria within enterocyte vacuoles rather than the paracellular space. Exact numerical values for translocation rates and ATP levels were not reported in the abstract.
Why it matters
This study demonstrates that enterocyte ATP depletion from glutamine starvation allows cytokine-mediated, transcellular bacterial passage across the intestinal epithelium without disrupting paracellular tight junctions.
Limits
Findings are limited to an in vitro single-cell line (Caco-2) model lacking in vivo vascular, neural, immune, and complex microbiota interactions. Replicate counts (n) and exact baseline/post-treatment numerical values were not provided in the abstract.
Cited by
- supports Glutamine is metabolized into glutamate for cellular energy and into alpha-ketoglutarate, which serves as an energy substrate for gut cells.