Melatonin inhibits cytosolic mitochondrial DNA–induced neuroinflammatory signaling in accelerated aging and neurodegeneration
Abhishek Jauhari, … , Diane L. Carlisle, Robert M. Friedlander
Abhishek Jauhari, … , Diane L. Carlisle, Robert M. Friedlander
Published March 17, 2020
Citation Information: J Clin Invest. 2020;130(6):3124-3136. https://doi.org/10.1172/JCI135026.
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Research Article Inflammation Neuroscience

Melatonin inhibits cytosolic mitochondrial DNA–induced neuroinflammatory signaling in accelerated aging and neurodegeneration

Abstract

Chronic inflammation is a pathologic feature of neurodegeneration and aging; however, the mechanism regulating this process is not understood. Melatonin, an endogenous free radical scavenger synthesized by neuronal mitochondria, decreases with aging and neurodegeneration. We proposed that insufficient melatonin levels impair mitochondrial homeostasis, resulting in mitochondrial DNA (mtDNA) release and activation of cytosolic DNA-mediated inflammatory response in neurons. We found increased mitochondrial oxidative stress and decreased mitochondrial membrane potential, with higher mtDNA release in brain and primary cerebro-cortical neurons of melatonin-deficient aralkylamine N-acetyltransferase (AANAT) knockout mice. Cytosolic mtDNA activated the cGAS/STING/IRF3 pathway, stimulating inflammatory cytokine generation. We found that Huntington’s disease mice had increased mtDNA release, cGAS activation, and inflammation, all inhibited by exogenous melatonin. Thus, we demonstrated that cytosolic mtDNA activated the inflammatory response in aging and neurodegeneration, a process modulated by melatonin. Furthermore, our data suggest that AANAT knockout mice are a model of accelerated aging.

Authors

Abhishek Jauhari, Sergei V. Baranov, Yalikun Suofu, Jinho Kim, Tanisha Singh, Svitlana Yablonska, Fang Li, Xiaomin Wang, Patrick Oberly, M. Beth Minnigh, Samuel M. Poloyac, Diane L. Carlisle, Robert M. Friedlander

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Figure 2

AANAT-KO induces mtDNA release and subsequent inflammation in PCNs.

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AANAT-KO induces mtDNA release and subsequent inflammation in PCNs. (A) ...
(A) Analysis of MMP by TMRM in WT and AANAT-KO PCNs at DIV21 (21 days in vitro) with or without melatonin (5 μM) in culture medium. TMRM fluorescence is plotted relative to WT PCN after normalization to nuclear stain (n = 5). (B) qPCR analysis of cytosolic mtDNA in WT and AANAT-KO PCNs using primers for mt-CO1, mt-Dloop1, and mt-Dloop3. Cytosolic mtDNA is plotted relative to amount of WT PCN after normalization to β-actin from the corresponding total DNA lysate (n = 3). (C) Representative immunoblot and (D) quantitation for cGAS, STING, IRF3, caspase-1, and β-actin in WT and AANAT-KO. β-actin was a loading control and data are expressed relative to untreated WT (n = 3). (E) Cytokine ELISA in culture medium of WT and AANAT-KO PCNs expressed as pg cytokine per mL of culture medium. PCNs grown with or without 5 μM melatonin (n = 3). All experiments were performed at DIV21, expressed as the mean ± SD, analyzed by ANOVA followed by Tukey’s test. *P < 0.05; **P < 0.01; ***P < 0.001.