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Figure 4. RET activation in human AD subjects and role of APP.C99 in RET deregulation in AD models. (A) Measurements of NAD⁺/NADH ratio and H₂O₂ level in brain tissue lysates of non-AD control, low ADNC, intermediate ADNC, and high ADNC individuals. Bar graphs show quantification of individual samples and pooled data from low, intermediate, and high ADNC samples; (B) In vitro RET assays using brain mitochondria purified from non-AD control, low ADNC, intermediate ADNC, and high ADNC individuals. Bar graphs show quantification of individual samples and pooled data from low, intermediate, and high ADNC samples; (C) Immunoblots showing presence of APP.C99 in mitochondrial fraction and co-IP assay showing physical interaction between APP.C99 and NDUFV1 and NDUFS3; (D) Co-IP assay and data quantification showing altered NDUFS3 interaction with NDUFV1 in APP.C99 transgenic flies and the effect of CPT treatment in restoring such interaction; (E) Co-IP assay and data quantification showing altered NDUFS3 interaction with NDUFV1 in 5xFAD transgenic mouse brain tissues and the effect of CPT treatment in restoring such interaction; (F) Immunoblots and data quantification showing the effect of CPT treatment on full-length APP and APP.C99 levels in 5xFAD transgenic mouse brain tissues. *P < 0.05, **P < 0.01, ***P < 0.001 in Student’s t-test or one-way ANOVA test. AD: Alzheimer’s disease; RET: reverse electron transport; ADNC: Alzheimer’s disease neuropathologic change; CPT: CPT2008, 6-chloro-3-(2,4-dichloro-5-methoxyphenyl)-2-mecapto-7-methoxyquinazolin-4(3H)-one; FAD: familial Alzheimer’s disease.