Mitochondrial dysfunction in macrophages promotes inflammation and suppresses repair after myocardial infarction
Shanshan Cai, Mingyue Zhao, Bo Zhou, Akira Yoshii, Darrian Bugg, Outi Villet, Anita Sahu, Gregory S. Olson, Jennifer Davis, Rong Tian
Shanshan Cai, Mingyue Zhao, Bo Zhou, Akira Yoshii, Darrian Bugg, Outi Villet, Anita Sahu, Gregory S. Olson, Jennifer Davis, Rong Tian
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Research Article Cardiology Metabolism

Mitochondrial dysfunction in macrophages promotes inflammation and suppresses repair after myocardial infarction

Abstract

Innate immune cells play important roles in tissue injury and repair following acute myocardial infarction (MI). Although reprogramming of macrophage metabolism has been observed during inflammation and resolution phases, the mechanistic link to macrophage phenotype is not fully understood. In this study, we found that myeloid-specific deletion (mKO) of mitochondrial complex I protein, encoded by Ndufs4, reproduced the proinflammatory metabolic profile in macrophages and exaggerated the response to LPS. Moreover, mKO mice showed increased mortality, poor scar formation, and worsened cardiac function 30 days after MI. We observed a greater inflammatory response in mKO mice on day 1 followed by increased cell death of infiltrating macrophages and blunted transition to the reparative phase during post-MI days 3–7. Efferocytosis was impaired in mKO macrophages, leading to lower expression of antiinflammatory cytokines and tissue repair factors, which suppressed the proliferation and activation of myofibroblasts in the infarcted area. Mitochondria-targeted ROS scavenging rescued these impairments, improved myofibroblast function in vivo, and reduced post-MI mortality in mKO mice. Together these results reveal a critical role of mitochondria in inflammation resolution and tissue repair via modulation of efferocytosis and crosstalk with fibroblasts. These findings have potential significance for post-MI recovery as well as for other inflammatory conditions.

Authors

Shanshan Cai, Mingyue Zhao, Bo Zhou, Akira Yoshii, Darrian Bugg, Outi Villet, Anita Sahu, Gregory S. Olson, Jennifer Davis, Rong Tian

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Figure 1

Deletion of the mitochondrial complex I protein Ndufs4 mimics the metabolic profile of inflammatory macrophages and exacerbates the response to LPS.

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Deletion of the mitochondrial complex I protein Ndufs4 mimics the metabo...
(A) Ndufs4 protein expression levels in BMDMs from WT, LysMcre, f/f, mKO, and KO mice were detected by Western blotting. (B) Representative tracings of the OCR of BMDMs from the indicated groups of mice (left). The group average of basal and maximal (Max.) OCRs are shown (right). Vertical lines indicate time of addition of mitochondrial inhibitors oligomycin A (OA) (5 μM), FCCP (3 μM), or rotenone/antimycin A (R/A) (1 μM/1 μM). Experiments were repeated in 3 mice per group. (C and D) Mitochondrial respiration and glycolysis were measured according to the OCR (C) and the ECAR (D) in BMDMs treated with LPS (10 ng/mL) or vehicle for 6 hours. OCR and ECAR tracings are shown on the left. Average values at basal state and during maximum respiration or glycolysis (glycolytic capacity) are presented on the right. Experiments were repeated in 3–5 mice per group. (E) mtROS levels were measured by flow cytometry. MitoSOX was used as the ROS-sensitive dye in WT and KO macrophages pretreated with LPS (10 ng/mL) or vehicle for 6 hours. Representative flow cytometric analysis of MitoSOX fluorescence (upper) and the average of MitoSOXhi percentage (lower) are shown. Experiments were repeated in 5–8 mice per group. SSC-H, side scatter height. (F–H) Protein levels in BMDMs treated with vehicle (PBS, control [Ctrl]) and LPS 100 ng/mL for 6 hours. IL-6 (F), TNF-α (G) levels were detected by ELISA, and IL-1β levels (H) were detected by Western blotting. Experiments were repeated in 4–5 mice per group. (I and J) Relative mRNA level of iNOS (I) and Icam1 (J) in WT and KO BMDMs treated with 100 ng/mL LPS or PBS for 6 hours (n = 3/group). (K) Representative plots and quantification of CD80+ macrophages (percentage) in BMDMs treated with 100 ng/mL LPS or PBS for 24 hours. (L) Representative flow cytometry histogram and average (MFI) of CD80 staining. Experiments were repeated in 4 mice per group. All Data are presented as the mean ± SEM. *P < 0.05, **P < 0.01, ***P < 0.001, and ****P < 0.0001, by 1- or 2-way ANOVA.