NAC blocks Cystatin C amyloid complex aggregation in a cell system and in skin of HCCAA patients
Michael E March1, Alvaro Gutierrez-Uzquiza1,2, Asbjorg Osk Snorradottir3,4
1The Center for Applied Genomics, The Children's Hospital of Philadelphia, Philadelphia, PA, USA.
Insights
N-acetyl-cysteine (NAC) treatment reduced amyloid deposits in hereditary cystatin C amyloid angiopathy patients. This suggests reducing agents can target the L68Q-hCC mutation, offering a potential therapeutic strategy for this rare, inherited neurological disease.
Area of Science:
- Neuroscience
- Genetics
- Biochemistry
Background:
- Hereditary cystatin C amyloid angiopathy (HCCAA) is a rare, dominantly inherited disease.
- It is caused by a leucine to glutamine variant (L68Q) in human cystatin C (hCC).
- The L68Q-hCC mutation leads to amyloid deposits in brain arteries, causing severe neurological deficits and early death.
Purpose of the Study:
- To investigate the potential of reducing agents to interfere with L68Q-hCC aggregation.
- To assess the cellular toxicity of L68Q-hCC and the effect of reducing agents.
- To evaluate the in vivo efficacy of N-acetyl-cysteine (NAC) in reducing L68Q-hCC deposits in patients.
Main Methods:
- Generated cell lines expressing wild-type (WT) and L68Q-hCC to study protein aggregation.
- Incubated L68Q-hCC with reducing agents like glutathione and NAC to observe effects on oligomers.
- Analyzed skin biopsies from six L68Q-hCC carriers before and after NAC treatment to quantify hCC deposit reduction.
Main Results:
- High-molecular weight complexes of L68Q-hCC were detected in cell cultures.
- Reducing agents, including NAC, effectively broke down L68Q-hCC oligomers into monomers.
- Five out of six treated HCCAA carriers showed a significant reduction (50-90%) in L68Q-hCC skin deposits after NAC administration.
Conclusions:
- L68Q-hCC forms amyloidogenic aggregates that are susceptible to reduction.
- N-acetyl-cysteine (NAC) demonstrates potential as a therapeutic agent for hereditary cystatin C amyloid angiopathy.
- L68Q-hCC is a viable clinical target for treatment with reducing agents.
Abstract:
Hereditary cystatin C amyloid angiopathy is a dominantly inherited disease caused by a leucine to glutamine variant of human cystatin C (hCC). L68Q-hCC forms amyloid deposits in brain arteries associated with micro-infarcts, leading ultimately to paralysis, dementia and death in young adults. To evaluate the ability of molecules to interfere with aggregation of hCC while informing about cellular toxicity, we generated cells that produce and secrete WT and L68Q-hCC and have detected high-molecular weight complexes formed from the mutant protein. Incubations of either lysate or supernatant containing L68Q-hCC with reducing agents glutathione or N-acetyl-cysteine (NAC) breaks oligomers into monomers. Six L68Q-hCC carriers taking NAC had skin biopsies obtained to determine if hCC deposits were reduced following NAC treatment. Remarkably, ~50-90% reduction of L68Q-hCC staining was observed in five of the treated carriers suggesting that L68Q-hCC is a clinical target for reducing agents.
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