Sandnes Dagny, Müller Kristin M, Akhtar Kanwal, Johansen Ellen Johanne, Christoffersen Thoralf, Thoresen G Hege
Department of Pharmacology, Medical Faculty, University of Oslo, Oslo, Norway.
Cell Physiol Biochem. 2010;25(4-5):523-32. doi: 10.1159/000303056. Epub 2010 Mar 23.
BACKGROUND/AIMS: Liver regeneration factor 1 (LRF-1/ATF3) is an early response gene which is rapidly induced upon partial hepatectomy in rats, and by growth factors and G protein-coupled receptor (GPCR) agonists in cultured rat hepatocytes. The aim of the present study was to examine the mechanisms involved in induction of LRF-1/ATF3 by the GPCR agonist vasopressin.
Primary cultures of rat hepatocytes were treated with vasopressin, TPA, and the Ca2+-elevating agents thapsigargin and A23187. LRF-1/ATF3 mRNA and protein were measured by Northern blot analysis or RT-PCR and immunoblotting. Signalling pathways were examined by immunoblots and kinase assays.
While elevation of intracellular calcium induced LRF-1/ATF3 expression, treatment with TPA did not. Inhibition of phospholipase C, protein kinase C, or pretreatment with calcium chelators did not affect vasopressin-induced expression of LRF-1/ATF3. Inhibition of each of the MAP kinases ERK1/2, JNK or p38 did not affect vasopressin-induced LRF-1/ATF3 expression. Combined inhibition of JNK and p38, and of ERK1/2 and either JNK or p38 suppressed vasopressin-induced expression of LRF-1/ATF3.
Vasopressin induces LRF-1/ATF3 expression by mechanisms that differ from those activated by Ca2+-elevating agents. The results suggest that partly redundant, complex MAP kinase networks are involved in induction of LRF-1/ATF3 by vasopressin in hepatocytes.
背景/目的：肝再生因子1（LRF-1/ATF3）是一种早期反应基因，在大鼠部分肝切除术后迅速被诱导，在培养的大鼠肝细胞中也可被生长因子和G蛋白偶联受体（GPCR）激动剂诱导。本研究的目的是探讨GPCR激动剂血管加压素诱导LRF-1/ATF3的机制。
用血管加压素、佛波酯（TPA）以及升高钙离子的试剂毒胡萝卜素和A23187处理原代培养的大鼠肝细胞。通过Northern印迹分析、RT-PCR或免疫印迹法检测LRF-1/ATF3 mRNA和蛋白。通过免疫印迹和激酶分析检测信号通路。
虽然细胞内钙离子升高诱导了LRF-1/ATF3的表达，但用TPA处理则未诱导。抑制磷脂酶C、蛋白激酶C或用钙螯合剂预处理均不影响血管加压素诱导的LRF-1/ATF3表达。抑制丝裂原活化蛋白激酶（MAPK）ERK1/2、JNK或p38中的任何一种均不影响血管加压素诱导的LRF-1/ATF3表达。联合抑制JNK和p38以及ERK1/2与JNK或p38中的一种可抑制血管加压素诱导的LRF-1/ATF3表达。
血管加压素通过不同于升高钙离子试剂激活的机制诱导LRF-1/ATF3表达。结果表明，部分冗余、复杂的MAPK网络参与了血管加压素在肝细胞中诱导LRF-1/ATF3的过程。
