Yang J, Dong L W, Tang C, Liu M S
Department of Pharmacological and Physiological Science, St. Louis University School of Medicine, St. Louis, Missouri 63104, USA.
Am J Physiol. 1999 Jul;277(1):R132-9. doi: 10.1152/ajpregu.1999.277.1.R132.
Changes in beta(2)-adrenergic receptor (beta(2)-AR) gene expression in the rat liver during different phases of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). Septic rats exhibit two metabolically distinct phases: an initial hyperglycemic (9 h after CLP; early sepsis) followed by a hypoglycemic phase (18 h after CLP; late sepsis). The [(3)H]dihydroalprenolol binding studies show that the density of beta(2)-AR was decreased by 12 and 35% during the early and late phases of sepsis, respectively. Western blot analyses depict that the beta(2)-AR protein level was reduced by 37 and 72% during early and late sepsis, respectively. The reverse transcription polymerase chain reaction and Southern blot analyses reveal that the steady-state level of beta(2)-AR mRNA was decreased by 37% during early phase and 77% during late phase of sepsis. Nuclear run-off assays show that the rate of transcription of beta(2)-AR mRNA was reduced by 36% during early sepsis and 64% during late sepsis. The stability assays indicate that the half-life of beta(2)-AR mRNA was shortened by 21 and 50% during the early and late phases of sepsis, respectively, indicating that the rate of degradation of beta(2)-AR mRNA was progressively enhanced during sepsis. These findings demonstrate that the beta(2)-AR gene was underexpressed in the liver during the progression of sepsis, and, furthermore, the underexpression of the beta(2)-AR gene was the result of a reduction in the rate of transcription coupled with an enhancement in the rate of degradation of beta(2)-AR gene transcripts. Thus our findings that the transcriptional and posttranscriptional regulation of beta(2)-AR gene associated with decreases in beta(2)-AR number and its protein expression may provide a molecular mechanistic explanation for the development of hypoglycemia during the late stage of sepsis.
研究了脓毒症不同阶段大鼠肝脏中β₂-肾上腺素能受体（β₂-AR）基因表达的变化。采用盲肠结扎穿刺术（CLP）诱导脓毒症。脓毒症大鼠呈现出两个代谢明显不同的阶段：最初的高血糖阶段（CLP后9小时；早期脓毒症），随后是低血糖阶段（CLP后18小时；晚期脓毒症）。[³H]二氢阿普洛尔结合研究表明，在脓毒症的早期和晚期阶段，β₂-AR的密度分别降低了12%和35%。蛋白质免疫印迹分析显示，在早期和晚期脓毒症期间，β₂-AR蛋白水平分别降低了37%和72%。逆转录聚合酶链反应和Southern印迹分析显示，在脓毒症的早期阶段，β₂-AR mRNA的稳态水平降低了37%，在晚期阶段降低了77%。细胞核转录分析表明，在早期脓毒症期间，β₂-AR mRNA的转录速率降低了36%，在晚期脓毒症期间降低了64%。稳定性分析表明，在脓毒症的早期和晚期阶段，β₂-AR mRNA的半衰期分别缩短了21%和50%，这表明在脓毒症期间β₂-AR mRNA的降解速率逐渐加快。这些发现表明，在脓毒症进展过程中，肝脏中的β₂-AR基因表达不足，此外，β₂-AR基因表达不足是转录速率降低与β₂-AR基因转录本降解速率加快共同作用的结果。因此，我们发现β₂-AR基因的转录和转录后调控与β₂-AR数量及其蛋白表达的减少相关，这可能为脓毒症晚期低血糖的发生提供分子机制解释。
