NAC blocks Cystatin C amyloid complex aggregation in a cell system and in skin of HCCAA patients

Michael E March,Alvaro Gutierrez-Uzquiza,Asbjorg Osk Snorradottir,Birkir Thor Bragason,Patrick M A Sleiman,Helgi J Isaksson,Elias Olafsson,Charlly Kao,Hakon Hakonarson,Thorgeir Gestsson,Noelia Fonseca Balvis,Astridur Palsdottir,Kenny Nguyen,Leticia S Matsuoka

doi:10.1038/s41467-021-22120-4

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.

Highlights

Hereditary cystatin C amyloid angiopathy (HCCAA) is a dominantly inherited disease caused by a leucine 68 to glutamine variant of human cystatin C1
HCCAA is classified as a cerebral amyloid angiopathy (CAA), a group of diseases in which amyloid deposits form on the walls of blood vessels in the central nervous system (CNS)
Previous investigations have suggested that preventing domain swapping of human cystatin C (hCC) might be used for treatment of HCCAA24; Nilsson et al.[26] developed variants of WT hCC and L68Q-hCC with intra-chain-stabilizing disulfide bonds preventing domain swapping; stabilized molecules could not form dimers

Summary

Introduction

Hereditary cystatin C amyloid angiopathy is a dominantly inherited disease caused by a leucine to glutamine variant of human cystatin C (hCC). Hereditary cystatin C amyloid angiopathy (HCCAA) is a dominantly inherited disease caused by a leucine 68 to glutamine variant of human cystatin C (hCC, L68QhCC)[1]. Previous investigations have suggested that preventing domain swapping of hCC might be used for treatment of HCCAA24; Nilsson et al.[26] developed variants of WT hCC and L68Q-hCC with intra-chain-stabilizing disulfide bonds preventing domain swapping; stabilized molecules could not form dimers. These results suggest that the knowledge of the molecular mechanism causing the transition of physiologically normal and soluble proteins to toxic oligomers and insoluble fibrils is essential for the development of treatment strategies

Methods

Results

Conclusion