calpain-inhibitor-iii and 8-hydroxyguanine

8-Oxoguanine (8-oxoG), a common DNA lesion caused by reactive oxygen species, is associated with carcinogenesis and neurodegeneration. Although the mechanism by which 8-oxoG causes carcinogenesis is well understood, the mechanism by which it causes neurodegeneration is unknown. Here, we report that neurodegeneration is triggered by MUTYH-mediated excision repair of 8-oxoG-paired adenine. Mutant mice lacking 8-oxo-2'-deoxyguanosine triphosphate-depleting (8-oxo-dGTP-depleting) MTH1 and/or 8-oxoG-excising OGG1 exhibited severe striatal neurodegeneration, whereas mutant mice lacking MUTYH or OGG1/MUTYH were resistant to neurodegeneration under conditions of oxidative stress. These results indicate that OGG1 and MTH1 are protective, while MUTYH promotes neurodegeneration. We observed that 8-oxoG accumulated in the mitochondrial DNA of neurons and caused calpain-dependent neuronal loss, while delayed nuclear accumulation of 8-oxoG in microglia resulted in PARP-dependent activation of apoptosis-inducing factor and exacerbated microgliosis. These results revealed that neurodegeneration is a complex process caused by 8-oxoG accumulation in the genomes of neurons and microglia. Different signaling pathways were triggered by the accumulation of single-strand breaks in each type of DNA generated during base excision repair initiated by MUTYH, suggesting that suppression of MUTYH may protect the brain under conditions of oxidative stress.

Topics: Animals; Apoptosis Inducing Factor; Benzamides; Calpain; Cell Nucleus; Corpus Striatum; Dipeptides; DNA Breaks, Single-Stranded; DNA Glycosylases; DNA Repair; DNA, Mitochondrial; Guanine; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Microglia; Mitochondria; Motor Activity; Neurodegenerative Diseases; Nitro Compounds; Oxidative Stress; Phosphoric Monoester Hydrolases; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerase Inhibitors; Poly(ADP-ribose) Polymerases; Propionates