Myeloid peroxisome proliferator-activated receptor α deficiency accelerates liver regeneration via IL-6/STAT3 pathway after 2/3 partial hepatectomy in mice

Guomin Xie; Yanting Song; Na Li; Zhenzhen Zhang; Xia Wang; Ye Liu; Shiyu Jiao; Ming Wei; Baoqi Yu; Yan Wang; Hua Wang; Aijuan Qu

doi:10.21037/hbsn-20-688

Myeloid peroxisome proliferator-activated receptor α deficiency accelerates liver regeneration via IL-6/STAT3 pathway after 2/3 partial hepatectomy in mice

Hepatobiliary Surg Nutr. 2022 Apr;11(2):199-211. doi: 10.21037/hbsn-20-688.

Authors

Guomin Xie^{1

2}, Yanting Song^{1

2}, Na Li³, Zhenzhen Zhang⁴, Xia Wang^{1

2}, Ye Liu^{1

2}, Shiyu Jiao^{1

2}, Ming Wei^{1

2}, Baoqi Yu^{1

2}, Yan Wang⁴, Hua Wang⁵, Aijuan Qu^{1

2}

Affiliations

¹ Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Capital Medical University, Beijing, China.
² Key Laboratory of Remodeling-Related Cardiovascular Diseases, Ministry of Education, Beijing, China.
³ Department of Endocrinology, Beijing Chaoyang Hospital Affiliated to Capital Medical University, Beijing, China.
⁴ Department of Infectious Diseases, Peking University First Hospital, Beijing, China.
⁵ Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei, China.

Abstract

Background: Liver regeneration is a fundamental process for sustained body homeostasis and liver function recovery after injury. Emerging evidence demonstrates that myeloid cells play a critical role in liver regeneration by secreting cytokines and growth factors. Peroxisome proliferator-activated receptor α (PPARα), the target of clinical lipid-lowering fibrate drugs, regulates cell metabolism, proliferation, and survival. However, the role of myeloid PPARα in partial hepatectomy (PHx)-induced liver regeneration remains unknown.

Methods: Myeloid-specific PPARa-deficient (Ppara ^Mye-/-) mice and the littermate controls (Ppara ^fl/fl) were subjected to sham or 2/3 PHx to induce liver regeneration. Hepatocyte proliferation and mitosis were assessed by immunohistochemical (IHC) staining for 5-bromo-2'-deoxyuridine (BrdU) and Ki67 as well as hematoxylin and eosin (H&E) staining. Macrophage and neutrophil infiltration into livers were reflected by IHC staining for galectin-3 and myeloperoxidase (MPO) as well as flow cytometry analysis. Macrophage migration ability was evaluated by transwell assay. The mRNA levels for cell cycle or inflammation-related genes were measured by quantitative real-time RT-PCR (qPCR). The protein levels of cell proliferation related protein and phosphorylated signal transducer and activator of transcription 3 (STAT3) were detected by Western blotting.

Results: Ppara ^Mye-/- mice showed enhanced hepatocyte proliferation and mitosis at 32 h after PHx compared with Ppara ^fl/fl mice, which was consistent with increased proliferating cell nuclear antigen (Pcna) mRNA and cyclinD1 (CYCD1) protein levels in Ppara ^Mye-/- mice at 32 h after PHx, indicating an accelerated liver regeneration in Ppara ^Mye-/- mice. IHC staining showed that macrophages and neutrophils were increased in Ppara ^Mye-/- liver at 32 h after PHx. Livers of Ppara ^Mye-/- mice also showed an enhanced infiltration of M1 macrophages at 32 h after PHx. In vitro, Ppara-deficient bone marrow-derived macrophages (BMDMs) exhibited markedly enhanced migratory capacity and upregulated M1 genes Il6 and Tnfa but downregulated M2 gene Arg1 expressions. Furthermore, the phosphorylation of STAT3, a key transcript factor mediating IL6-promoted hepatocyte survival and proliferation, was reinforced in the liver of Ppara ^Mye-/- mice after PHx.

Conclusions: This study provides evidence that myeloid PPARα deficiency accelerates PHx-induced liver regeneration via macrophage polarization and consequent IL-6/STAT3 activation, thus providing a potential target for manipulating liver regeneration.

Keywords: Liver regeneration; interleukin 6 (IL-6); myeloid cell; peroxisome proliferator-activated receptor α (PPARα); signal transducer and activator of transcription 3 (STAT3).