TY - JOUR
T1 - Cytoprotection by fructose and other ketohexoses during bile salt- induced apoptosis of hepatocytes
AU - Zeid, Iyad M.
AU - Bronk, Steven F.
AU - Fesmier, Patricia J.
AU - Gores, Gregory J.
PY - 1997/1
Y1 - 1997/1
N2 - Toxic bile salts cause hepatocyte necrosis at high concentrations and apoptosis at lower concentrations. Although fructose prevents bile salt- induced necrosis, the effect of fructose on bile salt-induced apoptosis is unclear. Our aim was to determine if fructose also protects against bile salt-induced apoptosis. Fructose inhibited glycochenodeoxycholate (GCDC)- induced apoptosis in a concentration-dependent manner with a maximum inhibition of 72% ± 10% at 10 mmol/L. First, we determined if fructose inhibited apoptosis by decreasing adenosine triphosphate (ATP) and intracellular pH (pH(i)). Although fructose decreased ATP to <25% of basal values, oligomycin (an ATP synthase inhibitor) did not inhibit apoptosis despite decreasing ATP to similar values. Fructose (10 mmol/L) decreased intracellular pH (pH(i)) by 0.2 U. However, extracellular acidification (pH 6.8), which decreased hepatocyte pH(i) 0.35 U and is known to inhibit necrosis, actually potentiated apoptosis 1.6-fold. Fructose cytoprotection also could not be explained by induction of bcl-2 transcription or metal chelation. Because we could not attribute fructose cytoprotection to metabolic effects, alterations in the expression of bcl-2, or metal chelation, we next determined if the poorly metabolized ketohexoses, tagatose and sorbose, also inhibited apoptosis; unexpectedly, both ketohexoses inhibited apoptosis. Because bile salt-induced apoptosis and necrosis are inhibited by fructose, these data suggest that similar processes initiate bile salt-induced hepatocyte necrosis and apoptosis. In contrast, acidosis, which inhibits necrosis, potentiates apoptosis. Thus, ketohexose-sensitive pathways appear to initiate both bile salt-induced cell apoptosis and necrosis, whereas dissimilar, pH-sensitive, effector mechanisms execute these two different cell death processes.
AB - Toxic bile salts cause hepatocyte necrosis at high concentrations and apoptosis at lower concentrations. Although fructose prevents bile salt- induced necrosis, the effect of fructose on bile salt-induced apoptosis is unclear. Our aim was to determine if fructose also protects against bile salt-induced apoptosis. Fructose inhibited glycochenodeoxycholate (GCDC)- induced apoptosis in a concentration-dependent manner with a maximum inhibition of 72% ± 10% at 10 mmol/L. First, we determined if fructose inhibited apoptosis by decreasing adenosine triphosphate (ATP) and intracellular pH (pH(i)). Although fructose decreased ATP to <25% of basal values, oligomycin (an ATP synthase inhibitor) did not inhibit apoptosis despite decreasing ATP to similar values. Fructose (10 mmol/L) decreased intracellular pH (pH(i)) by 0.2 U. However, extracellular acidification (pH 6.8), which decreased hepatocyte pH(i) 0.35 U and is known to inhibit necrosis, actually potentiated apoptosis 1.6-fold. Fructose cytoprotection also could not be explained by induction of bcl-2 transcription or metal chelation. Because we could not attribute fructose cytoprotection to metabolic effects, alterations in the expression of bcl-2, or metal chelation, we next determined if the poorly metabolized ketohexoses, tagatose and sorbose, also inhibited apoptosis; unexpectedly, both ketohexoses inhibited apoptosis. Because bile salt-induced apoptosis and necrosis are inhibited by fructose, these data suggest that similar processes initiate bile salt-induced hepatocyte necrosis and apoptosis. In contrast, acidosis, which inhibits necrosis, potentiates apoptosis. Thus, ketohexose-sensitive pathways appear to initiate both bile salt-induced cell apoptosis and necrosis, whereas dissimilar, pH-sensitive, effector mechanisms execute these two different cell death processes.
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U2 - 10.1002/hep.510250115
DO - 10.1002/hep.510250115
M3 - Article
C2 - 8985269
AN - SCOPUS:0031012851
VL - 25
SP - 81
EP - 86
JO - Hepatology
JF - Hepatology
SN - 0270-9139
IS - 1
ER -