Leptin as a novel profibrogenic cytokine in hepatic stellate cells: mitogenesis and inhibition of apoptosis mediated by extracellular regulated kinase (Erk) and Akt phosphorylation
Leptin as a novel profibrogenic cytokine in hepatic stellate cells: mitogenesis and inhibition of apoptosis mediated by extracellular regulated kinase (Erk) and Akt phosphorylation
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DOI：
10.1096/fj.04-1847fje
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发表时间：
2004-08-01
期刊：
影响因子：
4.8
通讯作者：
Anania, FA
中科院分区：
文献类型：
--
作者：
Saxena, NK;Titus, MA;Anania, FA
肝纤维化分子发病机制的一个关键特征是需要通过增殖和抑制凋亡来维持活化的肝星状细胞（HSC）表型。我们提供的证据表明，瘦素是一种有效的HSC有丝分裂原，并显着抑制星状细胞凋亡。通过溴脱氧尿苷（BrdU）掺入分离的原代HSC中进行评估，瘦素被证明是与血小板衍生生长因子（PDGF）一样有效的HSC有丝分裂原;使用荧光碘化丙啶（PI）摄取的数据显示，瘦素与PDGF一样，增加了细胞周期S期和G（2）/M期的HSC数量。瘦素导致细胞周期蛋白D1表达的强烈增加。使用Janus激酶2（Jak 2）活性的化学抑制剂AG 490和细胞因子信号传导抑制因子3（SOCS-3）的过表达，我们发现，瘦素受体（Ob-Rb）磷酸化的阻断阻断瘦素诱导的HSC增殖。瘦素相关的细胞外调节激酶（p44/p42，Erk）和Akt的磷酸化也被禁止。此外，发现PI-3激酶抑制剂LY 294002和MAPK抑制剂PD 98059显著降低瘦素诱导的HSC增殖，从而表明瘦素诱导的HSC增殖是Akt和Erk依赖性的。Akt对HSC凋亡也有保护作用。瘦素废除环己酰亚胺诱导和肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导的细胞凋亡，表现为减少caspase-3活性，HSC-TUNEL染色，DNA片段。我们的结论是，瘦素作为一个直接的肝星状细胞存活激动剂。重要的是，我们已经证明瘦素诱导的HSC增殖和存活的Ob-Rb磷酸化都是ERK和Akt依赖性的。
A key feature in the molecular pathogenesis of liver fibrosis requires maintenance of the activated hepatic stellate cell (HSC) phenotype by both proliferation and inhibition of apoptosis. We provide evidence that leptin is a potent HSC mitogen and dramatically inhibits stellate cell apoptosis. Leptin proved to be as potent an HSC mitogen as platelet-derived growth factor ( PDGF) as assessed by bromodeoxyuridine ( BrdU) incorporation in isolated primary HSCs; data using fluorescent propidium iodide ( PI) uptake revealed that leptin, like PDGF, increased HSC populations in the S- and G(2)/M-phases of the cell cycle. Leptin resulted in a robust increase in cyclin D1 expression. Using the chemical inhibitor of Janus kinase 2 (Jak2) activity, AG 490, and overexpression of the suppressor of cytokine signaling 3 (SOCS-3), we show that blockade of leptin receptor (Ob-Rb) phosphorylation blocks leptin-induced HSC proliferation. Leptin-associated phosphorylation of both extracellular regulated kinase (p44/p42, Erk) and Akt is also prohibited. Further, the PI-3 kinase inhibitor LY294002 and MAPK inhibitor PD98059 were found to significantly reduce leptin-induced HSC proliferation, thereby indicating that leptin induced HSC proliferation is Akt- and Erk-dependent. Akt was also protective against HSC apoptosis. Leptin abolished both cycloheximide-induced and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-induced apoptosis, demonstrated by reduced caspase-3 activity, HSC-TUNEL staining, and DNA fragmentation. We conclude that leptin acts as a direct hepatic stellate cell survival agonist. Importantly, we have demonstrated that leptin-induced HSC proliferation and survival by Ob-Rb phosphorylation are both Erk- and Akt- dependent.