Melatonin inhibits cytosolic mitochondrial DNA‚Äìinduced neuroinflammatory signaling in accelerated aging and neurodegeneration
Authors: Sergei V Baranov
Fang Li
Xiaomin Wang
Yalikun Suofu
Abhishek Jauhari
Robert M Friedlander
Samuel M Poloyac
Jinho Kim
Tanisha Singh
Patrick Oberly
M Beth Minnigh
Svitlana Yablonska
Diane L Carlisle
Journal: Journal of Clinical Investigation (2020)
Discipline: CLINICAL MEDICINE
Keywords: Inflammation; Mitochondria; Neurodegeneration; Neuroscience.
Affiliations: Department of Neurological Surgery and., Department of Pharmaceutical Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

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. 

Retracted: No

PubPeer comments:
 Beta-actin was recycled in different blots in Figure 4-C  , 
 Great work Dr Friedlander! I have a concern about WB images. Could the author explain the use of the same beta-actin with different intensities for normalization of different proteins in fig 2? Can the author share full-length blot images. Thanks.  , 
 Unfortunately, we did not receive any response from the authors yet. However, having the same beta-actin with different intensities, as shown in Fig. 2, may change the conclusion of Fig. 2 and the overall conclusion of the manuscript. Dear authors, A more careful reading of the manuscript also revealed that the quantitative analysis for STING and IRF3 was identical, although the WB for these two proteins is different in Fig. 7E.  In Fig 2, not only the graphs but also the **SD values** for IL-1B and IL-18 are the same. However, the significance (p-value) in the graph for IL-1B was different than in the graph for IL-18. I would appreciate it if you, please explain this data more in detail with original values and statistical calculations for further understanding of the results present within the manuscript.  Furthermore, it isn t easy to understand how the caspase-1 activity was monitored throughout the manuscript. In Figure 1F, cleaved caspase-1 was observed in the form of p45, although the full-length pro-Caspase 1 is also p45. In figure 2, cleaved caspase-1 was monitored by p20; however, in figure 4, cleaved caspase 1 is indicated by p10. Can you please explain which one is correct? If all are correct, why were different fragments chosen to represent the cleaved caspase 1 activity throughout the published article? Considering that the mol wt of p10 and p20 are very close to each other, can you please explain how you validated the results presented within the published paper. , 
 A corrigendum is posted. https: www.jci.org articles view 150328 We identified errors in seven figure panels in this manuscript: Figures 1F, 2C, 2E, 3C, and 7E and Supplemental Figures 1E and 7A. These errors were identified as the result of a thorough review of each figure panel after discrepancies were noted by a reader after publication. When the concern was brought to our attention, we reviewed all the data for every panel in the publication. In the data review, we reexamined the original raw data for each figure. We informed the JCI of the errors in these panels and provided the raw data to the editors for their review. This information was also provided for an independent institutional evaluation. The correct data are consistent with the conclusions made in the original article. In this Corrigendum, the seven incorrect figure panels are replaced with the correct panels made from the original raw data. In addition, anti-caspase 1 antibody (catalog 22915-1-AP, Proteintech), which was omitted from the reagent list in Supplemental Table 2, has been added to the updated supplemental file. We regret the errors. In Figure 1F the band labeled u201ccleaved caspase-1 (p45)u201d should have been labeled u201ccleaved caspase-1 (p10).u201d The correctly labeled image is below.  In Figure 2C, the u03b2-actin Western blot image was inadvertently duplicated. The correct corresponding u03b2-actin images are shown below with their respective Western blots.  In Figure 2E, the IL-18 data were inadvertently replaced with a duplicate of the IL-1u03b2 data. The correct panel for IL-18 is shown below.  In Figure 3C, the IRF3 data were inadvertently replaced with a duplicate of the cGAS data. The correct IRF3 panel is shown below.  In Figure 7E, the IRF3 panel was inadvertently replaced with a duplicate of the STING panel. The correct panel for IRF3 densitometric quantification is shown below.  In Supplemental Figure 1E, 20-week IL-6 data were inadvertently replaced with a duplicate of the IL-1u03b2 data. The 8-week data were correct. The correct panel for IL-6 is shown below.  In Supplemental Figure 7A, the panel on the far right was inadvertently mislabeled as IRF3 rather than STING. The correct panel is shown below.  ,