Smith T J, Piscatelli J J, Andersen V, Wang H S, Lance P
Division of Molecular and Cellular Medicine, Department of Medicine, Albany Medical College, NY 12208, USA.
Hepatology. 1996 Apr;23(4):866-71. doi: 10.1002/hep.510230430.
n-Butyrate, a short-chain aliphatic carboxylic acid with pleiotropic actions, is present at high concentrations in the portal circulation and thus may play an important role in the regulation of specific gene expression in the mammalian liver. We report here that n-butyrate can increase substantially the level of plasminogen activator inhibitor type 1 (PAI-1) messenger RNA (mRNA) in Hep G2 cells, up to eightfold above control cultures. Maximal effects occurred at a concentration of 3 mmol/L n-butyrate and with a treatment period of 8 to 12 hours. Increases in PAI-1 mRNA were accompanied by modest increases (twofold) in the encoded protein as assessed by specific enzyme-linked immunosorbent assay and by [35S]methionine incorporation into immunoprecipitable PAI-1 in the culture medium. Nuclear run-on studies showed that the rate of transcription of the PAI-1 gene did not appear altered by treatment with 3 mmol/L n-butyrate for 6 hours. The increases in steady-state PAI-1 mRNA caused by exposure to n-butyrate can be blocked by cycloheximide. Enhanced stability of mature PAI-1 transcript could not be demonstrated in Hep G2 cells treated with the carboxylic acid. We have reported previously that n-butyrate can reduce the level of beta-galactoside alpha 2,6-sialyltransferase expression in Hep G2 cells. That effect was attenuated with inhibitors of protein and RNA synthesis and was mediated at the post-transcriptional level. Thus, n-butyrate can influence the expression of multiple genes in this hepatoblastoma cell through its actions on events that appear to be posttranscriptional. These observations may be relevant to the normal physiology of the mammalian liver because of the high concentrations of n-butyrate and related compounds to which the organ is ordinarily exposed.
正丁酸盐是一种具有多种作用的短链脂肪族羧酸，在门静脉循环中浓度很高，因此可能在哺乳动物肝脏中特定基因表达的调控中发挥重要作用。我们在此报告，正丁酸盐可使Hep G2细胞中纤溶酶原激活物抑制剂1（PAI - 1）信使核糖核酸（mRNA）的水平大幅增加，比对照培养物高出多达八倍。最大效应出现在3 mmol/L正丁酸盐浓度及8至12小时的处理时间。通过特异性酶联免疫吸附测定以及[35S]甲硫氨酸掺入培养基中可免疫沉淀的PAI - 1来评估，PAI - 1 mRNA的增加伴随着编码蛋白适度增加（两倍）。细胞核连续转录研究表明，用3 mmol/L正丁酸盐处理6小时后，PAI - 1基因的转录速率似乎未改变。用放线菌酮可阻断因暴露于正丁酸盐而导致的稳态PAI - 1 mRNA增加。在用该羧酸处理的Hep G2细胞中，未证实成熟PAI - 1转录本的稳定性增强。我们之前曾报道正丁酸盐可降低Hep G2细胞中β - 半乳糖苷α2,6 - 唾液酸转移酶的表达水平。该效应因蛋白质和RNA合成抑制剂而减弱，且在转录后水平介导。因此，正丁酸盐可通过对似乎是转录后事件的作用来影响该肝癌细胞中多个基因的表达。由于该器官通常暴露于高浓度的正丁酸盐及相关化合物，这些观察结果可能与哺乳动物肝脏的正常生理学相关。
