Pigmentation Chemistry and Radical‐Based Collagen Degradation in Alkaptonuria and Osteoarthritic Cartilage
Open Access
- 26 March 2020
- journal article
- research article
- Published by Wiley in Angewandte Chemie
- Vol. 59 (29), 11937-11942
- https://doi.org/10.1002/anie.202000618
Abstract
Alkaptonuria (AKU) is a rare disease characterized by high levels of homogentisic acid (HGA); patients suffer from tissue ochronosis: dark brown pigmentation, especially of joint cartilage, leading to severe early osteoarthropathy. No molecular mechanism links elevated HGA to ochronosis; the pigment's chemical identity is still not known, nor how it induces joint cartilage degradation. Here we give key insight on HGA‐derived pigment composition and collagen disruption in AKU cartilage. Synthetic pigment and pigmented human cartilage tissue both showed hydroquinone‐resembling NMR signals. EPR spectroscopy showed that the synthetic pigment contains radicals. Moreover, we observed intrastrand disruption of collagen triple helix in pigmented AKU human cartilage, and in cartilage from patients with osteoarthritis. We propose that collagen degradation can occur via transient glycyl radicals, the formation of which is enhanced in AKU due to the redox environment generated by pigmentation.Keywords
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Funding Information
- H2020 Research Infrastructures (iNEXT, grant number 653706 (PID 1952))
- University of Liverpool
- Agilent Technologies
- Deutscher Akademischer Austauschdienst
- Leibniz-Gemeinschaft
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