Guomin Xie1,2, Yanting Song1,2, Na Li3, Zhenzhen Zhang4, Xia Wang1,2, Ye Liu1,2, Shiyu Jiao1,2, Ming Wei1,2, Baoqi Yu1,2, Yan Wang4, Hua Wang5, Aijuan Qu1,2. 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. 2022 Hepatobiliary Surgery and Nutrition. All rights reserved.
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. 2022 Hepatobiliary Surgery and Nutrition. All rights reserved.
Entities:
Keywords:
Liver regeneration; interleukin 6 (IL-6); myeloid cell; peroxisome proliferator-activated receptor α (PPARα); signal transducer and activator of transcription 3 (STAT3)
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