Proinflammatory cytokines increase the rate of glycolysis and adenosine-5'-triphosphate turnover in cultured rat enterocytes.
OBJECTIVE
Measurements of steady-state adenosine-5'-triphosphate (ATP) levels in tissue samples from patients or experimental animals with sepsis or endotoxemia provide little information about the rate of ATP production and consumption in these conditions. Accordingly, we sought to use an in vitro "reductionist" model of sepsis to test the hypothesis that proinflammatory cytokines modulate ATP turnover rate.


METHODS
In vitro "reductionist" model of sepsis.


METHODS
University laboratory.


METHODS
Cultured rat enterocyte-like cells.


METHODS
IEC-6 nontransformed rat enterocytes were studied under control conditions or following incubation for 24 or 48 hrs with cytomix, a mixture of tumor necrosis factor-alpha (10 ng/mL), interleukin-1beta (1 ng/mL), and interferon-gamma (1000 units/mL). To measure ATP turnover rate, ATP synthesis was acutely blocked by adding to the cells a mixture of 2-deoxyglucose (10 mM), potassium cyanide (8 mM), and antimycin A (1 microM). ATP content was measured at baseline (before metabolic inhibition) and 0.5, 1, 2, 5, and 10 mins later. Log-linear ATP decay curves were generated and the kinetics of ATP utilization thereby calculated.


RESULTS
ATP consumption rate was higher in cytomix-stimulated compared with control cells (3.11 +/- 1.39 vs. 1.25 +/- 0.66 nmol/min, respectively; p <.01). Similarly, the half-time for ATP disappearance was shorter in cytomix-stimulated compared with control cells (2.63 +/- 1.00 vs. 6.21 +/- 3.49; p <.05). In contrast to these findings, the rate of ATP disappearance was similar in cytokine-naïve and immunostimulated IEC-6 cells when protein and nucleic acid synthesis were inhibited by adding 50 microg/mL cycloheximide and 5 microg/mL actinomycin D to cultures for 4 hrs. The rates of glucose consumption and lactate production were significantly greater in cytomix-stimulated compared with controls cells.


CONCLUSIONS
Incubation of IEC-6 cells with cytomix significantly increased ATP turnover. Increased ATP turnover rate was supported by increases in the rate of anaerobic glycolysis. These findings support the view that proinflammatory mediators impose a metabolic demand on visceral cells. In sepsis, cells may be more susceptible to dysfunction on the basis of diminished oxygen delivery and/or mitochondrial dysfunction.
Berg
Sören
S
Department of Cardiothoracic Anesthesia (SB), Linköping University, Linköping, Sweden.
Sappington
Penny L
PL
Guzik
Lynda J
LJ
Delude
Russell L
RL
Fink
Mitchell P
MP
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D016207:Cytokines / Q000494:pharmacology*; D020895:Enterocytes / Q000378:metabolism* / Q000502:physiology; D005947:Glucose / Q000378:metabolism; D006019:Glycolysis / Q000187:drug effects*; D018836:Inflammation Mediators / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D051381:Rats; D018805:Sepsis / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D016207:Cytokines; D018836:Inflammation Mediators; D007375:Interleukin-1; D011506:Proteins; D014409:Tumor Necrosis Factor-alpha; D019344:Lactic Acid; D012313:RNA; D007371:Interferon-gamma; D000255:Adenosine Triphosphate; D005947:Glucose