PNPLA3 I148M Variant Impairs Liver X Receptor Signaling and Cholesterol Homeostasis in Human Hepatic Stellate Cells
PNPLA3 I148M Variant Impairs Liver X Receptor Signaling and Cholesterol Homeostasis in Human Hepatic Stellate Cells
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DOI：
10.1002/hep4.1395
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发表时间：
2019-09-01
影响因子：
5.1
通讯作者：
Trauner, Michael
中科院分区：
文献类型：
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作者：
Bruschi, Francesca Virginia;Claudel, Thierry;Trauner, Michael
马铃薯糖蛋白样磷脂酶结构域蛋白3（PNPLA 3）I148 M变异体易导致肝脂肪变性和进展为晚期肝损伤，并发展为纤维化、肝硬化和癌症。肝星状细胞（HSC）驱动对慢性损伤的伤口愈合反应，并且缺乏肝X受体（LXR）信号传导通过损害HSC胆固醇稳态而加剧肝纤维化。然而，I148 M变体对这一过程的贡献仍然未知。我们根据PNPLA 3基因型（野生型[WT]与I148 M）分析了原代人HSC和过表达LX-2细胞中的LXR表达和转录活性。在这里，我们证明了LXR α蛋白的增加，而LXR靶基因的表达减少在体外激活原代人HSC。值得注意的是，与WT相比，原代I148 M HSC中的LXR α水平和信号传导降低，如LXR靶基因表达降低所示。此外，胆固醇流出和产生氧固醇的酶的表达减少与较高的总胆固醇和游离胆固醇积累相关，而内源性胆固醇合成和摄取在I148 M HSC中减少。对LXR反应元件的荧光素酶测定证实了I148 M HSC中LXR转录活性降低;相反，合成的LXR激动剂T0901317补充了LXR功能，由三磷酸腺苷结合盒亚家族A成员1（ABCA 1）诱导支持，并降低了胶原1 α 1和趋化因子（C-C基序）配体5表达。相反，过氧化物酶体增殖物激活受体γ（PPAR γ）激动剂罗格列酮对LXR靶基因ABCA 1仅具有部分作用，并且既不减少促炎细胞因子的表达，也不增加I148 M HSC中的新生脂肪生成基因。结论：作为降低的PPAR γ活性的结果，携带I148 M PNPLA 3的HSC显示受损的LXR信号传导，导致胆固醇积累。使用特定的LXR激动剂显示出减少持续HSC活化和肝纤维化发生的有益效果。
The patatin-like phospholipase domain-containing protein 3 (PNPLA3) I148M variant predisposes to hepatic steatosis and progression to advanced liver injury with development of fibrosis, cirrhosis, and cancer. Hepatic stellate cells (HSCs) drive the wound healing response to chronic injury, and lack of liver X receptor (LXR) signaling exacerbates liver fibrogenesis by impairing HSC cholesterol homeostasis. However, the contribution of the I148M variant to this process is still unknown. We analyzed LXR expression and transcriptional activity in primary human HSCs and overexpressing LX-2 cells according to PNPLA3 genotype (wild type [WT] versus I148M). Here we demonstrate that LXR alpha protein increased whereas LXR target gene expression decreased during in vitro activation of primary human HSCs. Notably, LXR alpha levels and signaling were reduced in primary I148M HSCs compared to WT, as displayed by decreased expression of LXR target genes. Moreover, reduced expression of cholesterol efflux and enzymes generating oxysterols was associated with higher total and free cholesterol accumulation whereas endogenous cholesterol synthesis and uptake were diminished in I148M HSCs. Luciferase assays on LXR response element confirmed decreased LXR transcriptional activity in I148M HSCs; in contrast the synthetic LXR agonist T0901317 replenished LXR functionality, supported by adenosine triphosphate-binding cassette subfamily A member 1 (ABCA1) induction, and reduced collagen1 alpha 1 and chemokine (C-C motif) ligand 5 expression. Conversely, the peroxisome proliferator-activated receptor gamma (PPAR gamma) agonist rosiglitazone had only partial effects on the LXR target gene ABCA1, and neither diminished expression of proinflammatory cytokines nor increased de novo lipogenic genes in I148M HSCs. Conclusion: As a consequence of reduced PPAR gamma activity, HSCs carrying I148M PNPLA3 show impaired LXR signaling, leading to cholesterol accumulation. The use of a specific LXR agonist shows beneficial effects for diminishing sustained HSC activation and development of liver fibrogenesis.