Related Experiment Video
Updated: Aug 20, 2025
Author Spotlight: THP-1 Macrophage Response to LPS/ATP — Unveiling the Pyroptosis, Apoptosis, and Necroptosis Spectrum
Published on: May 3, 2024
Melatonin Suppresses Macrophage M1 Polarization and ROS-Mediated Pyroptosis via Activating ApoE/LDLR Pathway in
Meng-Meng Xu1,2, Jia-Ying Kang1,2, Shuang Ji1,2
1Department of Respiratory and Critical Care Medicine, The First Affiliated Hospital of Anhui Medical University, Hefei, 230022 Anhui, China.
Abstract:
Influenza virus infection is one of the strongest pathogenic factors for the development of acute lung injury (ALI)/ acute respiratory distress syndrome (ARDS). However, the underlying cellular and molecular mechanisms have not been clarified. In this study, we aim to investigate whether melatonin modulates macrophage polarization, oxidative stress, and pyroptosis via activating Apolipoprotein E/low-density lipoprotein receptor (ApoE/LDLR) pathway in influenza A-induced ALI. Here, wild-type (WT) and ApoE-/- mice were instilled intratracheally with influenza A (H3N2) and injected intraperitoneally with melatonin for 7 consecutive days. In vitro, WT and ApoE-/- murine bone marrow-derived macrophages (BMDMs) were pretreated with melatonin before H3N2 stimulation. The results showed that melatonin administration significantly attenuated H3N2-induced pulmonary damage, leukocyte infiltration, and edema; decreased the expression of proinflammatory M1 markers; enhanced anti-inflammatory M2 markers; and switched the polarization of alveolar macrophages (AMs) from M1 to M2 phenotype. Additionally, melatonin inhibited reactive oxygen species- (ROS-) mediated pyroptosis shown by downregulation of malonaldehyde (MDA) and ROS levels as well as inhibition of the NLRP3/GSDMD pathway and lactate dehydrogenase (LDH) release. Strikingly, the ApoE/LDLR pathway was activated when melatonin was applied in H3N2-infected macrophages and mice. ApoE knockout mostly abrogated the protective impacts of melatonin on H3N2-induced ALI and its regulatory ability on macrophage polarization, oxidative stress, and pyroptosis. Furthermore, recombinant ApoE3 (re-ApoE3) inhibited H3N2-induced M1 polarization of BMDMs with upregulation of MT1 and MT2 expression, but re-ApoE2 and re-ApoE4 failed to do this. Melatonin combined with re-ApoE3 played more beneficial protective effects on modulating macrophage polarization, oxidative stress, and pyroptosis in H3N2-infected ApoE-/- BMDMs. Our study indicated that melatonin attenuated influenza A- (H3N2-) induced ALI by inhibiting the M1 polarization of pulmonary macrophages and ROS-mediated pyroptosis via activating the ApoE/LDLR pathway. This study suggested that melatonin-ApoE/LDLR axis may serve as a novel therapeutic strategy for influenza virus-induced ALI.
Insights
Melatonin treatment reduces lung injury from influenza A by shifting macrophage polarization and inhibiting pyroptosis through the Apolipoprotein E/low-density lipoprotein receptor pathway.
Area of Science:
- Immunology and Virology
- Molecular Mechanisms of Lung Injury
- Therapeutic Strategies for Infectious Diseases
Background:
- Influenza A virus is a major cause of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).
- The precise cellular and molecular pathways underlying influenza-induced ALI remain incompletely understood.
- Macrophage polarization, oxidative stress, and pyroptosis are key pathological processes in ALI.
Purpose of the Study:
- To investigate if melatonin modulates macrophage polarization, oxidative stress, and pyroptosis in influenza A-induced ALI.
- To determine the role of the Apolipoprotein E/low-density lipoprotein receptor (ApoE/LDLR) pathway in melatonin's effects.
- To explore the potential of the melatonin-ApoE/LDLR axis as a therapeutic strategy for influenza-induced ALI.
Main Methods:
- Utilized wild-type and ApoE knockout mice infected with influenza A (H3N2) and treated with melatonin.
- In vitro studies involved melatonin pretreatment of bone marrow-derived macrophages (BMDMs) followed by H3N2 stimulation.
- Assessed pulmonary damage, leukocyte infiltration, M1/M2 macrophage markers, reactive oxygen species (ROS), pyroptosis markers (NLRP3/GSDMD, LDH), and ApoE/LDLR pathway activation.
Main Results:
- Melatonin significantly reduced H3N2-induced lung damage, edema, and leukocyte infiltration.
- Melatonin promoted a shift from M1 to M2 macrophage polarization and inhibited ROS-mediated pyroptosis.
- Melatonin activated the ApoE/LDLR pathway; ApoE knockout largely abolished melatonin's protective effects.
Conclusions:
- Melatonin attenuates influenza A-induced ALI by inhibiting M1 macrophage polarization and ROS-mediated pyroptosis.
- These protective effects are mediated through the activation of the ApoE/LDLR pathway.
- The melatonin-ApoE/LDLR axis represents a promising novel therapeutic target for influenza virus-induced ALI.
