Pathogenic mechanisms of charcot–marie–tooth disease type 1a (CMT1A) and therapeutic potential of NAD⁺ modulation|RISS 상세보기

다국어 초록 (Multilingual Abstract)

Charcot–Marie–Tooth disease type 1A （CMT1A） is the most common inherited peripheral neuropathy caused by duplication of the peripheral myelin protein 22 （PMP22） gene. Although PMP22 overexpression induces Schwann cell （SC） dysfunction and demyelination, the metabolic mechanisms underlying disease progression remain poorly understood. This study investigated the role of mitochondrial metabolism and NAD⁺ redox homeostasis in the pathogenesis of CMT1A and evaluated the therapeutic potential of targeting these pathways.
Using primary rat SCs, I found that PMP22 overexpression selectively impaired mitochondrial function during SC differentiation, leading to metabolic dysregulation, NAD⁺ redox imbalance, and defective SC differentiation. These findings indicate a stage-specific metabolic vulnerability to PMP22 overexpression. Pharmacological inhibition of NAD⁺ biosynthesis using the NAMPT inhibitor FK866 recapitulated mitochondrial dysfunction and impaired SC differentiation, highlighting the critical role of NAD⁺ metabolism in CMT1A pathogenesis. PMP22-overexpressing SCs also exhibited marked intracellular PMP22 aggregation, indicating impaired proteostasis.
To restore NAD⁺ redox homeostasis, I used NADB2, an NAD⁺ modulator that targets NAD（P）H: quinone oxidoreductase 1 （NQO1）. NADB2 treatment restored mitochondrial function, reduced oxidative stress and PMP22 aggregation, and rescued SC differentiation defects in vitro. In a CMT1A mouse model, NADB2 improved neurological function, nerve conduction, and remyelination, with sustained therapeutic effects observed after treatment withdrawal. Importantly, the beneficial effects of NADB2 were completely abolished under NQO1-deficient conditions both in vitro and in vivo. Furthermore, NQO1 deficiency itself exacerbated neuropathic phenotypes in CMT1A mice, establishing NQO1 as a key regulator of mitochondrial homeostasis and disease progression under conditions of metabolic stress.
Collectively, this study supports the emerging concept that CMT1A is a metabolic neuropathy characterized by mitochondrial dysfunction, oxidative stress, and proteostasis disruption, and highlights NQO1-mediated modulation of NAD⁺ metabolism as a promising therapeutic strategy for CMT1A and other demyelinating neuropathies.

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목차 (Table of Contents)

Ⅰ. Introduction 1
Ⅱ. Materials and Methods 10
2.1. Reagents 10
2.2. Cell culture and in vitro experiments 10
2.3. Animal models and in vivo experiments 18

Ⅰ. Introduction 1
Ⅱ. Materials and Methods 10
2.1. Reagents 10
2.2. Cell culture and in vitro experiments 10
2.3. Animal models and in vivo experiments 18
2.4. Behavioral assessment 20
2.5. Histopathological and biochemical analysis 22
2.6. Statistical analysis 24
Ⅲ. Results 28
3.1. PMP22 overexpression impairs mitochondrial respiration during SC differentiation 28
3.2. PMP22 overexpression disrupts NAD⁺ redox balance and induces metabolic switch during SC differentiation 32
3.3. PMP22 overexpression induces mitochondrial dysfunction, oxidative stress, and differentiation defects 35
3.4. Antioxidant treatment rescues mitochondrial dysfunction and cellular phenotypes 43
3.5. NAD⁺ depletion is sufficient to induce mitochondrial dysfunction and differentiation failure during SC differentiation 48
3.6. Restoration of NAD⁺ metabolism rescues mitochondrial function and reverses metabolic defects during SC differentiation 54
3.7. NAD⁺ restoration reduces mitochondrial oxidative stress and rescues cellular phenotypes during SC differentiation 59
3.8. A novel NAD⁺ modulator （NADB2） improves motor and sensory function in a CMT1A transgenic mouse model 65
3.9. NADB2 restores electrophysiological function in a CMT1A mouse model 69
3.10. NADB2 promotes structural remyelination and attenuates demyelinating pathologies in a CMT1A mouse model 71
3.11. NADB2 provides sustained therapeutic effects after treatment withdrawal in a CMT1A mouse model 76
3.12. NADB2 restores mitochondrial function and metabolic homeostasis in PMP22-overexpressing SCs during SC differentiation 84
3.13. NADB2 alleviates mitochondrial oxidative stress and proteostatic defects in PMP22-overexpressing SCs during SC differentiation 89
3.14. NADB2 rescues mitochondrial function in an NQO1-dependent manner during differentiation of PMP22-overexpressing SCs 95
3.15. NQO1 restores mitochondrial redox balance and cellular homeostasis during differentiation of PMP22-overexpressing SCs 99
3.16. NQO1 regulates the SC differentiation program 102
3.17. Ablation of NQO1 exacerbates the neuropathic phenotype in C3-PMP22 mice 105
3.18. NQO1 is required for NADB2–mediated therapeutic effects in vivo 113
Ⅳ. Discussion 121
References 130
국문초록 144