N‐acetylcysteine (NAC) differentially affects arterial medial calcification and bone formation: The role of l‐cysteine and hydrogen sulphide

• Published in: Journal of cellular physiology Vol. 237; no. 1; pp. 1070 - 1086
• Main Authors: Bourne, Lucie E., Patel, Jessal J., Davies, Bethan K., Neven, Ellen, Verhulst, Anja, D'Haese, Patrick C., Wheeler‐Jones, Caroline P. D., Orriss, Isabel R.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01-01-2022
• Subjects: Acetylcysteine; Acetylcysteine - pharmacology; Antioxidants; Arteries; Arteries - metabolism; Biomedical materials; bone formation; Bone growth; Calcification; Calcium phosphates; Cell death; Cysteine; Deacetylation; Glutathione; Glutathione - metabolism; Hydrogen sulfide; Hydrogen Sulfide - metabolism; Hydrogen Sulfide - pharmacology; hydrogen sulphide; l‐cysteine; Molecular modelling; Muscles; N‐acetylcysteine; Osteoblastogenesis; Osteoblasts; Osteoblasts - metabolism; Osteogenesis; Physiology; Smooth muscle; Sulfides; vascular calcification; bone formation; l-cysteine; hydrogen sulphide; vascular calcification; N-acetylcysteine
• ISSN: 0021-9541; 1097-4652
• DOI: 10.1002/jcp.30605

Arterial medial calcification (AMC) is the deposition of calcium phosphate in the arteries. AMC is widely thought to share similarities with physiological bone formation; however, emerging evidence suggests several key differences between these processes. N‐acetylcysteine (NAC) displays antioxidant properties and can generate hydrogen sulphide (H2S) and glutathione (GSH) from its deacetylation to l‐cysteine. This study found that NAC exerts divergent effects in vitro, increasing osteoblast differentiation and bone formation by up to 5.5‐fold but reducing vascular smooth muscle cell (VSMC) calcification and cell death by up to 80%. In vivo, NAC reduced AMC in a site‐specific manner by 25% but had no effect on the bone. The actions of l‐cysteine and H2S mimicked those of NAC; however, the effects of H2S were much less efficacious than NAC and l‐cysteine. Pharmacological inhibition of H2S‐generating enzymes did not alter the actions of NAC or l‐cysteine; endogenous production of H2S was also unaffected. In contrast, NAC and l‐cysteine increased GSH levels in calcifying VSMCs and osteoblasts by up to 3‐fold. This suggests that the beneficial actions of NAC are likely to be mediated via the breakdown of l‐cysteine and the subsequent GSH generation. Together, these data show that while the molecular mechanisms driving the actions of NAC appear similar, the downstream effects on cell function differ significantly between osteoblasts and calcifying VSMCs. The ability of NAC to exert these differential actions further supports the notion that there are differences between the development of pathological AMC and physiological bone formation. NAC could represent a therapeutic option for treating AMC without exerting negative effects on bone.
This study found that N‐acetylcysteine (NAC) exerts divergent effects in vitro, increasing osteoblast differentiation and bone formation but reducing vascular smooth muscle cell calcification and death. These data show that whilst the molecular mechanisms driving the actions of NAC appear similar, the downstream effects on cell function differ significantly between osteoblasts and calcifying vascular smooth muscle cells. The ability of NAC to exert these differential actions further supports the notion that there are differences between the development of pathological arterial medial calcification and physiological bone formation.