d-Amino acids differentially trigger an inflammatory environment in vitro

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) produce...

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Main Authors: Siew Hwei Yap, Cheng Siang Lee, Nur Diyana Zulkifli, Darshinie Suresh, Kenji Hamase, Kumitaa Theva Das, Reena Rajasuriar, Kok Hoong Leong
Format: Article
Language:English
Published: Springer 2024-02-01
Series:Amino Acids
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Online Access:https://doi.org/10.1007/s00726-023-03360-8
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author Siew Hwei Yap
Cheng Siang Lee
Nur Diyana Zulkifli
Darshinie Suresh
Kenji Hamase
Kumitaa Theva Das
Reena Rajasuriar
Kok Hoong Leong
author_facet Siew Hwei Yap
Cheng Siang Lee
Nur Diyana Zulkifli
Darshinie Suresh
Kenji Hamase
Kumitaa Theva Das
Reena Rajasuriar
Kok Hoong Leong
author_sort Siew Hwei Yap
collection DOAJ
description 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-кB, pro-inflammatory cytokine, TNF-α, 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-кB, TNF-α, 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.
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spelling doaj-art-61d46c25585641e983ed3b4fb8589c122024-12-22T12:34:21ZengSpringerAmino Acids1438-21992024-02-0156111310.1007/s00726-023-03360-8d-Amino acids differentially trigger an inflammatory environment in vitroSiew Hwei Yap0Cheng Siang Lee1Nur Diyana Zulkifli2Darshinie Suresh3Kenji Hamase4Kumitaa Theva Das5Reena Rajasuriar6Kok Hoong Leong7Centre of Excellence for Research in AIDS (CERiA), Universiti MalayaCentre of Excellence for Research in AIDS (CERiA), Universiti MalayaDepartment of Biomedical Sciences, Advanced Medical and Dental Institute, Universiti Sains MalaysiaDepartment of Biomedical Sciences, Advanced Medical and Dental Institute, Universiti Sains MalaysiaGraduate School of Pharmaceutical Sciences, Kyushu UniversityDepartment of Biomedical Sciences, Advanced Medical and Dental Institute, Universiti Sains MalaysiaCentre of Excellence for Research in AIDS (CERiA), Universiti MalayaDepartment of Pharmaceutical Chemistry, Faculty of Pharmacy, Universiti MalayaAbstract 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-кB, pro-inflammatory cytokine, TNF-α, 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-кB, TNF-α, 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.https://doi.org/10.1007/s00726-023-03360-8d-Amino acid oxidased-Serined-AlanineInflammationTNF-α
spellingShingle Siew Hwei Yap
Cheng Siang Lee
Nur Diyana Zulkifli
Darshinie Suresh
Kenji Hamase
Kumitaa Theva Das
Reena Rajasuriar
Kok Hoong Leong
d-Amino acids differentially trigger an inflammatory environment in vitro
Amino Acids
d-Amino acid oxidase
d-Serine
d-Alanine
Inflammation
TNF-α
title d-Amino acids differentially trigger an inflammatory environment in vitro
title_full d-Amino acids differentially trigger an inflammatory environment in vitro
title_fullStr d-Amino acids differentially trigger an inflammatory environment in vitro
title_full_unstemmed d-Amino acids differentially trigger an inflammatory environment in vitro
title_short d-Amino acids differentially trigger an inflammatory environment in vitro
title_sort d amino acids differentially trigger an inflammatory environment in vitro
topic d-Amino acid oxidase
d-Serine
d-Alanine
Inflammation
TNF-α
url https://doi.org/10.1007/s00726-023-03360-8
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