d-Amino acids differentially trigger an inflammatory environment in vitro

Yap, Siew Hwei and Lee, Cheng Siang and Zulkifli, Nur Diyana and Suresh, Darshinie and Hamase, Kenji and Das, Kumitaa Theva and Rajasuriar, Reena and Leong, Kok Hoong (2024) d-Amino acids differentially trigger an inflammatory environment in vitro. Amino Acids, 56 (1). p. 6. ISSN 0939-4451, DOI https://doi.org/10.1007/s00726-023-03360-8.

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Official URL: https://doi.org/10.1007/s00726-023-03360-8

Abstract

Studies in vivo have demonstrated that the accumulation of D-amino acids (D-AAs) is associated with age-related diseases and increased immune activation. However, the underlying mechanism(s) of these observations are not well defined. The metabolism of D-AAs by D-amino oxidase (DAO) produces hydrogen peroxide (H2O2), a reactive oxygen species involved in several physiological processes including immune response, cell differentiation, and proliferation. Excessive levels of H2O2 contribute to oxidative stress and eventual cell death, a characteristic of age-related pathology. Here, we explored the molecular mechanisms of D-serine (D-Ser) and D-alanine (D-Ala) in human liver cancer cells, HepG2, with a focus on the production of H2O2 the downstream secretion of pro-inflammatory cytokine and chemokine, and subsequent cell death. In HepG2 cells, we demonstrated that D-Ser decreased H2O2 production and induced concentration-dependent depolarization of mitochondrial membrane potential (MMP). This was associated with the upregulation of activated NF-& kcy;B, pro-inflammatory cytokine, TNF-alpha, and chemokine, IL-8 secretion, and subsequent apoptosis. Conversely, D-Ala-treated cells induced H2O2 production, and were also accompanied by the upregulation of activated NF-& kcy;B, TNF-alpha, and IL-8, but did not cause significant apoptosis. The present study confirms the role of both D-Ser and D-Ala in inducing inflammatory responses, but each via unique activation pathways. This response was associated with apoptotic cell death only with D-Ser. Further research is required to gain a better understanding of the mechanisms underlying D-AA-induced inflammation and its downstream consequences, especially in the context of aging given the wide detection of these entities in systemic circulation.

Item Type: Article
Funders: Fundamental Research Grant Scheme, Ministry of Higher Education, Government of Malaysia (FRGS/1/2019/SKK08/UM/02/7), International Centre for Genetic Engineering and Biotechnology (CRP/MYS17-05), Agilent Technologies, Inc (PV018-2017)
Uncontrolled Keywords: d-Amino acid oxidase; <sc>d</sc>-Serine; <sc>d</sc>-Alanine; Inflammation; TNF-alpha
Subjects: R Medicine > R Medicine (General)
R Medicine > RM Therapeutics. Pharmacology
Divisions: Faculty of Medicine > Medicine Department
Centre for Internship & Academic Enrichment (CITRA)
Faculty of Pharmacy > Department of Pharmaceutical Chemistry
Depositing User: Ms. Juhaida Abd Rahim
Date Deposited: 08 Nov 2024 06:47
Last Modified: 08 Nov 2024 06:47
URI: http://eprints.um.edu.my/id/eprint/45663

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