ACUTE-PHASE RESPONSE FACTOR, INCREASED BINDING, AND TARGET GENE-TRANSCRIPTION DURING LIVER-REGENERATION

Background & Aims: The acute-phase response may contribute and influen ce cell-cycle progression in hepatocytes. The aim of this study was to examine the regulation of the alpha(2)-macroglobulin gene during live r regeneration and molecular mechanisms that influence its expression, Methods: Partial hepatectomy or sham surgery was performed in Sprague -Dawley rats, At different time points after surgery blood was taken f rom the liver vein, and nuclear extracts and RNA were prepared, Northe rn blot analysis, run-off assays, gel shift experiments, and cytokine assays were performed. Results: Increased transcription of the alpha(2 )-macroglobuln gene was found 12-24 hours posthepatectomy and not afte r sham surgery, Increased levels of alpha(2)-macroglobulin messenger R NA correlated with enhanced binding of acute-phase response factor/sig nal transducer and activator of transcription 3 (APRF/Stat3) towards t he cognate DNA sequence in the alpha(2)-macroglobulin promoter and dra matically increased interleukin-6 levels in the liver vein, In contras t, nuclear translocation of APRF/Stat3 was detected as early as a hour after hepatectomy and up to 48 hours posthepatectomy. Therefore, two events can be distinguished in the regulation of APRF/Stat3: its nucle ar translocation and increased DNA binding, Conclusions: increased alp ha(2)-macroglobulin transcription posthepatectomy is achieved by incre ased levels of interleukin 6 and consecutive binding of APRF/Stat3 to the alpha(2)-macroglobulin promoter, A two-step event is suggested for APRF/Stat3-dependent gene activation in hepatocytes.