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 5

DNAse1 decreases expression of proinflammatory cytokine secretion in HD.

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DNAse1 decreases expression of proinflammatory cytokine secretion in HD....
(A) qPCR analysis of cytosolic mtDNA in differentiated Q7 and Q111 cells transfected with DNAse 1 or lactate dehydrogenase (LDH) as a control using mt-CO1, mt-Dloop1, and mt-Dloop3. Cytosolic mtDNA is plotted relative to the control transfected Q7-differentiated neurons after normalization to β-actin in the corresponding total DNA sample (n = 3). (B) Analysis of mitochondrial ROS by Mitosox in Q7- and Q111-differentiated neurons transfected with control LDH or DNAse 1. Mitosox fluorescence intensity is presented relative to fluorescence in Q7-differentiated neurons transfected with LDH (n = 3). (C) Analysis of MMP by TMRM in Q7- and Q111-differentiated neurons transfected with LDH control or DNAse 1 (n = 3). (D) Representative immunoblots and quantification of cGAS, IRF3, STING, and β-actin in Q7- and Q111-differentiated neurons transfected with LDH or DNAse 1 (n = 3). β-actin was used as endogenous normalization control. (E) Cytokine ELISA secretion in culture medium of differentiated Q7 and Q111 neurons transfected with LDH or DNAse1, shown as pg cytokine per mL culture medium (n = 3). Data are expressed as mean ± SD and analyzed by ANOVA followed by Tukey’s test. *P < 0.05; **P < 0.01; ***P < 0.001.