Department of Pathophysiology, Key Lab for Shock and Microcirculation Research of Guangdong, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, PR China.
Department of Pathophysiology, Key Lab for Shock and Microcirculation Research of Guangdong, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, PR China.
Int Immunopharmacol. 2022 Jul;108:108741. doi: 10.1016/j.intimp.2022.108741. Epub 2022 Apr 6.
BACKGROUND & AIMS: Hyperlipidemia is a lipid metabolism disorder associated with elevated serum triglyceride (TG) and/or cholesterol. Over the years, studies have shown that hyperlipidemia is associated with combordities, incluing diabetes and obesity, gradually becoming a public health concern. Current treatment approaches remain limited due to the lack of effective drugs. Here we investigated the function of recombinant humanized IgG1 in maintaining liver TG homeostasis and the underlying mechanisms.
ApoE mice were fed a high-fat diet (HFD) for 20 weeks to induce hyperlipidemia. RNA sequencing (RNA-Seq) was performed to identify differences in gene expression in different groups of ApoE mice liver. In vitro lipid accumulation in primary mouse hepatocytes was induced using a free fatty acid (FFA) mixture. Gene and protein expression were assessed in primary mouse hepatocytes by qPCR and Western blot. Gene reporter assays and ChIP-PCR were used to determine arylacetamide deacetylase (Aadac) promoter activity.
Recombinant humanized IgG1 could significantly decrease the serum level of TG and low-density lipoproteins (LDL-C). Moreover, hepatic TG and lipid droplets were also reduced compared to the HFD group. Mouse liver RNA-Seq revealed that administration of recombinant humanized IgG1 significantly elevated the expression of Aadac. In vitro, knock-down of Aadac could nullify the effect of recombinant humanized IgG1 on decreasing the lipid droplets induced by FFA in primary mouse hepatocytes. Gene Reporter assays and ChIP-PCR demonstrated that the foxa1 response element in the Aadac promoter played a key role in Aadac expression induced by recombinant humanized IgG1. Moreover, recombinant humanized IgG1 repressed phosphorylation of PKCδ and resulted in foxa1 elevation. Finally, neonatal Fc receptor (FcRn) knock-down reversed the effect of recombinant humanized IgG1 on the expression of PKCδ phosphorylation, foxa1 and Aadac.
Our findings suggest that recombinant humanized IgG1 plays an important role in maintaining liver TG homeostasis via the FcRn/PKCδ/foxa1/Aadac pathway.
高脂血症是一种与血清甘油三酯（TG）和/或胆固醇升高有关的脂质代谢紊乱。多年来的研究表明，高脂血症与包括糖尿病和肥胖症在内的多种合并症相关，逐渐成为一个公共卫生关注点。由于缺乏有效的药物，目前的治疗方法仍然有限。在这里，我们研究了重组人源化 IgG1 在维持肝脏 TG 稳态中的作用及其潜在机制。
用高脂肪饮食（HFD）喂养载脂蛋白 E（ApoE）小鼠 20 周，以诱导高脂血症。对不同组别的 ApoE 小鼠肝脏进行 RNA 测序（RNA-Seq），以鉴定基因表达的差异。用游离脂肪酸（FFA）混合物诱导原代小鼠肝细胞中的脂质积累。通过 qPCR 和 Western blot 评估原代小鼠肝细胞中的基因和蛋白表达。采用基因报告基因测定和 ChIP-PCR 来确定芳基乙酰胺脱乙酰酶（Aadac）启动子活性。
重组人源化 IgG1 可显著降低血清 TG 和低密度脂蛋白胆固醇（LDL-C）水平。此外，与 HFD 组相比，肝 TG 和脂滴也减少了。小鼠肝 RNA-Seq 显示，给予重组人源化 IgG1 可显著上调 Aadac 的表达。在体外，敲低 Aadac 可消除重组人源化 IgG1 对 FFA 诱导的原代小鼠肝细胞中脂滴减少的作用。基因报告基因测定和 ChIP-PCR 表明，Aadac 启动子中的 foxa1 反应元件在重组人源化 IgG1 诱导的 Aadac 表达中起关键作用。此外，重组人源化 IgG1 抑制 PKCδ 的磷酸化，导致 foxa1 升高。最后，新生儿 Fc 受体（FcRn）敲低逆转了重组人源化 IgG1 对 PKCδ 磷酸化、foxa1 和 Aadac 表达的影响。
我们的研究结果表明，重组人源化 IgG1 通过 FcRn/PKCδ/foxa1/Aadac 途径在维持肝脏 TG 稳态方面发挥重要作用。
