MUTYH promotes oxidative microglial activation and inherited retinal degeneration
Shunji Nakatake, … , Yusaku Nakabeppu, Koh-Hei Sonoda
Shunji Nakatake, … , Yusaku Nakabeppu, Koh-Hei Sonoda
Published September 22, 2016
Citation Information: JCI Insight. 2016;1(15):e87781. https://doi.org/10.1172/jci.insight.87781.
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Research Article Inflammation Ophthalmology

MUTYH promotes oxidative microglial activation and inherited retinal degeneration

Abstract

Oxidative stress is implicated in various neurodegenerative disorders, including retinitis pigmentosa (RP), an inherited disease that causes blindness. The biological and cellular mechanisms by which oxidative stress mediates neuronal cell death are largely unknown. In a mouse model of RP (rd10 mice), we show that oxidative DNA damage activates microglia through MutY homolog–mediated (MUYTH-mediated) base excision repair (BER), thereby exacerbating retinal inflammation and degeneration. In the early stage of retinal degeneration, oxidative DNA damage accumulated in the microglia and caused single-strand breaks (SSBs) and poly(ADP-ribose) polymerase activation. In contrast, Mutyh deficiency in rd10 mice prevented SSB formation in microglia, which in turn suppressed microglial activation and photoreceptor cell death. Moreover, Mutyh-deficient primary microglial cells attenuated the polarization to the inflammatory and cytotoxic phenotype under oxidative stress. Thus, MUTYH-mediated BER in oxidative microglial activation may be a novel target to dampen the disease progression in RP and other neurodegenerative disorders that are associated with oxidative stress.

Authors

Shunji Nakatake, Yusuke Murakami, Yasuhiro Ikeda, Noriko Morioka, Takashi Tachibana, Kohta Fujiwara, Noriko Yoshida, Shoji Notomi, Toshio Hisatomi, Shigeo Yoshida, Tatsuro Ishibashi, Yusaku Nakabeppu, Koh-Hei Sonoda

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Figure 1

Mutyh deficiency protected photoreceptors against cell death and suppressed microglial activation in rd10 mice.

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Mutyh deficiency protected photoreceptors against cell death and suppre...
(A) Western blot analysis for MUTYH protein in the retinas from WT, rd10;Mutyh+/+, and rd10;Mutyh−/− mice. β-Actin was used as the loading control. (B and C) TUNEL (green) and DAPI (blue) staining (B) and quantification of TUNEL-positive photoreceptor cells (C) in the retinas of P21 rd10;Mutyh+/+ mice (n = 8) and rd10;Mutyh−/− mice (n = 7). INL, inner nuclear layer; ONL, outer nuclear layer. Scale bar: 50 μm. (D and E) Histological findings of the retina (D) and quantitative analysis of photoreceptor cells (E) in the ONL in P26 rd10;Mutyh+/+ mice (n = 10) and rd10;Mutyh−/− mice (n = 9). The number of photoreceptor nuclei in the 10,000-μm2 area was counted at the peripheral, mid-peripheral, and central regions of the retina. Scale bars: 50 μm. (F and G) PNA staining (F) and quantification of PNA-positive cone photoreceptor cells (G) in the retinas of P42 rd10;Mutyh+/+ mice (n = 8) and rd10;Mutyh−/− mice (n = 6). Scale bar: 20 μm. (H and I) Iba-1 staining (H) and quantification of Iba-1–positive microglia (I) in the retinas of P21 rd10;Mutyh+/+ mice (n = 7) and rd10;Mutyh−/− mice (n = 7). Scale bar: 50 μm. (J and K) Iba-1 staining (J) and quantification of Iba-1–positive microglia (K) in the retinas of P42 rd10;Mutyh+/+ mice (n = 6) and rd10;Mutyh−/− mice (n = 6). Scale bar: 50 μm. Data shown are the combined results for all mice in 2–4 experiments. Data are presented as whisker-box plots. The central horizontal bars indicate the medians, boxes indicate 25th to 75th percentiles, and whiskers indicate 1.5 times the interquartile range from the bottom and the top of the box. Outliers are shown as dots. Wilcoxon rank sum tests were performed to assess significance. *P < 0.05, **P < 0.01.