Melatonin Suppresses Macrophage M1 Polarization and ROS-Mediated Pyroptosis via Activating ApoE/LDLR Pathway in Influenza A-Induced Acute Lung Injury

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.

Melatonin improves influenza virus infection-induced acute exacerbation of COPD by suppressing macrophage M1 polarization and apoptosis

“…In COPD, pathogens infection may further evoke abnormal polarization of AMs, exacerbate lung damages of COPD patients [ 15 , 40 ]. In our previous study, acute IAV infection was found only up-regulated the M1 polarization of pulmonary macrophages [ 18 ]. We speculate that, while macrophages are in resting status, acute IAV infection dominantly polarizes them into pro-inflammatory M1 phenotype.…”

“…The IAV samples were amplified in Madin-Darby canine kidney (MDCK) cells and specific pathogen-free embryonated chicken eggs. Virus titers were assayed via the standard plaque assay on MDCK cells according to previous description [ 18 , 29 ]. MDCK cells were infected with diluted virus samples 1–2 h at 37 °C.…”

“…The difference of airway microenvironments determines the proportion of M1 and M2 macrophages, also affects the process of “injuries-repairments” of lung tissues [ 16 , 17 ]. Our recent study revealed that acute IAV infection induced acute lung injury (ALI) via enhanced the M1 polarization of pulmonary macrophages, and inhibiting M2 polarization [ 18 ]. However, in cigarette smoke-exposed lung tissues, the effects of in acute IAV infection on pulmonary macrophage polarization remain to be clarified.…”

“…Moreover, melatonin is also capable to resist virus infection, such as influenza virus and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection [ 27 , 28 ]. Our recent study demonstrated that melatonin alleviated IAV infection-induced ALI by inhibiting the M1 polarization of AMs with the decreased expression of iNOS, MCP1 and CD86 [ 18 ]. However, the effects of melatonin on IAV infection-induced AECOPD remain unknown.…”

Secretion of related factors and AMPK/PGC-1 α signal pathway by alveolar macrophages in viral acute lung injury

“…more serious, it is called acute respiratory distress syndrome (ARDS) (1). Respiratory virus infection, gastric acid inhalation, sepsis and other pathogenic factors can lead to ALI, including influenza A virus, avian influenza virus, coronavirus and novel coronavirus, which caused the global pandemic (2). Viral ALI (VALI) is usually caused by diffuse capillary endothelial and alveolar epithelial injury after severe injury.…”