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Diekman BO, Loeser RF. DNA Damage and Cellular Senescence in Osteoarthritis: An Unexpected Role for Interferon Regulatory Factor 1 in Chondrocyte DNA Repair. Arthritis Rheumatol 2024; 76:842-844. [PMID: 38343350 PMCID: PMC11136596 DOI: 10.1002/art.42822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 02/03/2024] [Accepted: 02/08/2024] [Indexed: 02/29/2024]
Affiliation(s)
- Brian O Diekman
- University of North Carolina, Chapel Hill, and North Carolina State University, Raleigh
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2
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Du X, Fan R, Kong J. What improvements do general exercise training and traditional Chinese exercises have on knee osteoarthritis? A narrative review based on biological mechanisms and clinical efficacy. Front Med (Lausanne) 2024; 11:1395375. [PMID: 38841568 PMCID: PMC11150680 DOI: 10.3389/fmed.2024.1395375] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2024] [Accepted: 04/22/2024] [Indexed: 06/07/2024] Open
Abstract
Background Knee osteoarthritis (KOA) is a disease that significantly affects the quality of life of patients, with a complex pathophysiology that includes degeneration of cartilage and subchondral bone, synovitis, and associations with mechanical load, inflammation, metabolic factors, hormonal changes, and aging. Objective This article aims to comprehensively review the biological mechanisms and clinical effects of general exercise training and traditional Chinese exercises (such as Tai Chi and Qigong) on the treatment of KOA, providing references for the development of clinical exercise prescriptions. Methods A systematic search of databases including PubMed, Web of Science, Google Scholar, and China National Knowledge Infrastructure (CNKI) was conducted, reviewing studies including randomized controlled trials (RCTs), observational studies, systematic reviews, and meta-analyses. Keywords included "knee osteoarthritis," "exercise therapy," "physical activity," and "traditional Chinese exercise." Results and conclusion General exercise training positively affects KOA by mechanisms such as promoting blood circulation, improving the metabolism of inflammatory factors, enhancing the expression of anti-inflammatory cytokines, and reducing cartilage cell aging. Traditional Chinese exercises, like Tai Chi and Qigong, benefit the improvement of KOA symptoms and tissue repair by regulating immune function and alleviating joint inflammation. Clinical studies have shown that both types of exercise can improve physical function, quality of life, and pain relief in patients with KOA. Both general exercise training and traditional Chinese exercises are non-pharmacological treatment options for KOA that can effectively improve patients' physiological function and quality of life. Future research should further explore the long-term effects and biological mechanisms of these exercise interventions and develop personalized exercise programs based on the specific needs of patients.
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Affiliation(s)
- Xingbin Du
- Shandong Huayu University of Technology, Dezhou, China
- Faculty of Education, Qufu Normal University, Qufu, China
| | - Rao Fan
- College of Sports Science, Qufu Normal University, Qufu, China
| | - Jianda Kong
- College of Sports Science, Qufu Normal University, Qufu, China
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3
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Diekman BO, Loeser RF. Aging and the emerging role of cellular senescence in osteoarthritis. Osteoarthritis Cartilage 2024; 32:365-371. [PMID: 38049031 PMCID: PMC10984800 DOI: 10.1016/j.joca.2023.11.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/22/2023] [Revised: 11/21/2023] [Accepted: 11/29/2023] [Indexed: 12/06/2023]
Abstract
OBJECTIVE The correlation between age and incidence of osteoarthritis (OA) is well known but the causal mechanisms involved are not completely understood. This narrative review summarizes selected key findings from the past 30 years that have elucidated key aspects of the relationship between aging and OA. METHODS The peer-reviewed English language literature was searched on PubMed using keywords including senescence, aging, cartilage, and osteoarthritis, for original studies and reviews published from 1993 to 2023 with a major focus on more recent studies. Manuscripts most relevant to aging and OA that examined one or more of the hallmarks of aging were selected for further review. RESULTS All proposed hallmarks of aging have been observed in articular cartilage and some have also been described in other joint tissues. Hallmarks include genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, disabled macroautophagy, chronic inflammation, and dysbiosis. There is evidence that these age-related changes contribute to the development of OA in part by promoting cellular senescence. Senescence may therefore serve as a downstream mediator that connects numerous aging hallmarks to OA, likely through the senescence-associated secretory phenotype that is characterized by increased production of proinflammatory cytokines and matrix metalloproteinases. CONCLUSIONS Progress over the past 30 years has provided the foundation for emerging therapies, such as senolytics and senomorphics, that hold promise for OA disease modification. Mechanistic studies utilizing physiologically-aged animals and cadaveric human joint tissues will be important for continued progress.
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Affiliation(s)
- Brian O Diekman
- Thurston Arthritis Research Center, University of North Carolina School of Medicine, Chapel Hill, NC, 27599, USA; Joint Department of Biomedical Engineering, University of North Carolina at Chapel Hill and North Carolina State University, Raleigh, NC, 27599, USA.
| | - Richard F Loeser
- Thurston Arthritis Research Center, University of North Carolina School of Medicine, Chapel Hill, NC, 27599, USA; Division of Rheumatology, Allergy, and Immunology, University of North Carolina, Chapel Hill, NC, 27599, USA.
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4
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Roelofs AJ, De Bari C. Osteoarthritis year in review 2023: Biology. Osteoarthritis Cartilage 2024; 32:148-158. [PMID: 37944663 DOI: 10.1016/j.joca.2023.11.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Revised: 10/25/2023] [Accepted: 11/02/2023] [Indexed: 11/12/2023]
Abstract
Great progress continues to be made in our understanding of the multiple facets of osteoarthritis (OA) biology. Here, we review the major advances in this field and progress towards therapy development over the past year, highlighting a selection of relevant published literature from a PubMed search covering the year from the end of April 2022 to the end of April 2023. The selected articles have been arranged in themes. These include 1) molecular regulation of articular cartilage and implications for OA, 2) mechanisms of subchondral bone remodelling, 3) role of synovium and inflammation, 4) role of age-related changes including cartilage matrix stiffening, cellular senescence, mitochondrial dysfunction, metabolic dysfunction, and impaired autophagy, and 5) peripheral mechanisms of OA pain. Progress in the understanding of the cellular and molecular mechanisms responsible for the multiple aspects of OA biology is unravelling novel therapeutic targets for disease modification.
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Affiliation(s)
- Anke J Roelofs
- Arthritis and Regenerative Medicine Laboratory, Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, Aberdeen, UK
| | - Cosimo De Bari
- Arthritis and Regenerative Medicine Laboratory, Centre for Arthritis and Musculoskeletal Health, University of Aberdeen, Aberdeen, UK.
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5
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Mao LW, Jiang QY, Meng N, Xiao L, Zhang Q, Chen YX, Liu LJ, Wang L. Sirt6 promotes DNA damage repair in osteoarthritis chondrocytes by activating the Keap1/Nrf2/HO-1 signaling pathway. Cell Cycle 2024; 23:205-217. [PMID: 38389322 PMCID: PMC11037281 DOI: 10.1080/15384101.2024.2316493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2023] [Accepted: 02/06/2024] [Indexed: 02/24/2024] Open
Abstract
The aim of this study was to explore the effect and mechanism of Sirt6 on DNA damage repair in OA chondrocytes. Cartilage tissues were collected from OA patients with knee arthroplasty and traumatic amputation patients without OA. Besides, 7-week-old male C57BL/6 mice were randomly divided into Control and OA groups; CHON-001 cells of corresponding groups were treated with 10 ng/ml interleukin (IL)-1β, respectively. Subsequently, Sirt6 or siNrf2 was over-expressed in CHON-001 cells to observe the effect of Sirt6 on DNA damage and senescence of chondrocytes by IL-1β through the nuclear factor E2-related factor 2 (Nrf2) signaling pathway. The expression level of Sirt6 in human and mouse OA cartilage tissues was significantly decreased. However, 24 h of treatment with IL-1β significantly decreased the expression of Sirt6 in chondrocytes, induced DNA damage, and promoted cellular senescence. In addition, over-expression of Sirt6 promoted DNA damage repair and inhibited cellular senescence in IL-1β-induced chondrocytes. Moreover, the overexpression of Sirt6 activated the Keap1/Nrf2/HO-1 signaling pathway in chondrocytes, while knockdown of Nrf2 expression inhibited the DNA damage repair and anti-senescence effects of Sirt6 on IL-1β-treated chondrocytes. Sirt6 may reduce DNA damage and cellular senescence in OA chondrocytes induced by IL-1β through activating the Keap1/Nrf2/HO-1 signaling pathway.
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Affiliation(s)
- Ling-Wei Mao
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Qin-Yi Jiang
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Nan Meng
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Li Xiao
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Qi Zhang
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Yong-Xin Chen
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Lin-Juan Liu
- Department of Stomatology, Affiliated Hospital of Jiangsu University, Zhenjiang, China
| | - Lei Wang
- Department of Orthopedics, The Affiliated People’s Hospital with Jiangsu University, Zhenjiang, China
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Copp ME, Shine J, Brown HL, Nimmala KR, Hansen OB, Chubinskaya S, Collins JA, Loeser RF, Diekman BO. Sirtuin 6 activation rescues the age-related decline in DNA damage repair in primary human chondrocytes. Aging (Albany NY) 2023; 15:13628-13645. [PMID: 38078876 PMCID: PMC10756124 DOI: 10.18632/aging.205394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 11/15/2023] [Indexed: 12/21/2023]
Abstract
While advanced age is widely recognized as the greatest risk factor for osteoarthritis (OA), the biological mechanisms behind this connection remain unclear. Previous work has demonstrated that chondrocytes from older cadaveric donors have elevated levels of DNA damage as compared to chondrocytes from younger donors. The purpose of this study was to determine whether a decline in DNA repair efficiency is one explanation for the accumulation of DNA damage with age, and to quantify the improvement in repair with activation of Sirtuin 6 (SIRT6). After acute damage with irradiation, DNA repair was shown to be more efficient in chondrocytes from young (≤45 years old) as compared to middle-aged (50-65 years old) or older (>70 years old) cadaveric donors. Activation of SIRT6 with MDL-800 improved the repair efficiency, while inhibition with EX-527 reduced the rate of repair and increased the percentage of cells that retain high levels of damage. In addition to affecting repair after acute damage, treating chondrocytes from older donors with MDL-800 for 48 hours significantly reduced the amount of baseline DNA damage. Chondrocytes isolated from the knees of mice between 4 months and 22 months of age revealed both an increase in DNA damage with aging, and a decrease in DNA damage following MDL-800 treatment. Lastly, treating murine cartilage explants with MDL-800 lowered the percentage of chondrocytes with high p16 promoter activity, which supports the concept that using SIRT6 activation to maintain low levels of DNA damage may prevent the initiation of senescence.
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Affiliation(s)
- Michaela E. Copp
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC 27606, USA
| | - Jacqueline Shine
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Hannon L. Brown
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC 27606, USA
| | - Kirti R. Nimmala
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC 27606, USA
| | - Oliver B. Hansen
- School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Susan Chubinskaya
- Department of Pediatrics, Rush University Medical Center, Chicago, IL 60612, USA
| | - John A. Collins
- Department of Orthopedic Surgery, Thomas Jefferson University, Philadelphia, PA 19144, USA
| | - Richard F. Loeser
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Division of Rheumatology, Allergy, and Immunology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Brian O. Diekman
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC 27606, USA
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Ni W, Zhang H, Mei Z, Hongyi Z, Wu Y, Xu W, Ma Y, Yang W, Liang Y, Gu T, Su Y, Fan S, Shen S, Hu Z. An inducible long noncoding RNA, LncZFHX2, facilitates DNA repair to mediate osteoarthritis pathology. Redox Biol 2023; 66:102858. [PMID: 37633048 PMCID: PMC10472307 DOI: 10.1016/j.redox.2023.102858] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Revised: 08/06/2023] [Accepted: 08/17/2023] [Indexed: 08/28/2023] Open
Abstract
Cartilage homeostasis is essential for chondrocytes to maintain proper phenotype and metabolism. Because adult articular cartilage is avascular, chondrocytes must survive in low oxygen conditions, and changing oxygen tension can significantly affect metabolism and proteoglycan synthesis in these cells. However, whether long noncoding RNA participate in cartilage homeostasis under hypoxia has not been reported yet. Here, we first identified LncZFHX2 as a lncRNA upregulated under physiological hypoxia in cartilage, specifically by HIF-1α. LncZFHX2 knockdown simultaneously accelerated cellular senescence, targeted multiple components of extracellular matrix metabolism, and increased DNA damage in chondrocytes. Through a series of in vitro and in vivo experiments, we identified that LncZFHX2 performed a novel function that regulated RIF1 expression through forming a transcription complex with KLF4 and promoting chondrocyte DNA repair. Moreover, chondrocyte-conditional knockout of LncZFHX2 accelerated injury-induced cartilage degeneration in vivo. In conclusion, we identified a hypoxia-activated DNA repair pathway that maintains matrix homeostasis in osteoarthritis cartilage.
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Affiliation(s)
- Weiyu Ni
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Haitao Zhang
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Zixuan Mei
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Zhou Hongyi
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Yizheng Wu
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Wenbin Xu
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Yan Ma
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Wentao Yang
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Yi Liang
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Tianyuan Gu
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Yingfeng Su
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China
| | - Shunwu Fan
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China.
| | - Shuying Shen
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China.
| | - Ziang Hu
- Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, Zhejiang University School of Medicine, 3 East Qingchun Road, Hangzhou, Zhejiang Province, China; Key Laboratory of Musculoskeletal System Degeneration and Regeneration Translational Research of Zhejiang Province, China.
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8
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Riegger J, Schoppa A, Ruths L, Haffner-Luntzer M, Ignatius A. Oxidative stress as a key modulator of cell fate decision in osteoarthritis and osteoporosis: a narrative review. Cell Mol Biol Lett 2023; 28:76. [PMID: 37777764 PMCID: PMC10541721 DOI: 10.1186/s11658-023-00489-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 09/11/2023] [Indexed: 10/02/2023] Open
Abstract
During aging and after traumatic injuries, cartilage and bone cells are exposed to various pathophysiologic mediators, including reactive oxygen species (ROS), damage-associated molecular patterns, and proinflammatory cytokines. This detrimental environment triggers cellular stress and subsequent dysfunction, which not only contributes to the development of associated diseases, that is, osteoporosis and osteoarthritis, but also impairs regenerative processes. To counter ROS-mediated stress and reduce the overall tissue damage, cells possess diverse defense mechanisms. However, cellular antioxidative capacities are limited and thus ROS accumulation can lead to aberrant cell fate decisions, which have adverse effects on cartilage and bone homeostasis. In this narrative review, we address oxidative stress as a major driver of pathophysiologic processes in cartilage and bone, including senescence, misdirected differentiation, cell death, mitochondrial dysfunction, and impaired mitophagy by illustrating the consequences on tissue homeostasis and regeneration. Moreover, we elaborate cellular defense mechanisms, with a particular focus on oxidative stress response and mitophagy, and briefly discuss respective therapeutic strategies to improve cell and tissue protection.
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Affiliation(s)
- Jana Riegger
- Division for Biochemistry of Joint and Connective Tissue Diseases, Department of Orthopedics, Ulm University Medical Center, 89081, Ulm, Germany.
| | - Astrid Schoppa
- Institute of Orthopedic Research and Biomechanics, Ulm University Medical Center, 89081, Ulm, Germany
| | - Leonie Ruths
- Division for Biochemistry of Joint and Connective Tissue Diseases, Department of Orthopedics, Ulm University Medical Center, 89081, Ulm, Germany
| | - Melanie Haffner-Luntzer
- Institute of Orthopedic Research and Biomechanics, Ulm University Medical Center, 89081, Ulm, Germany
| | - Anita Ignatius
- Institute of Orthopedic Research and Biomechanics, Ulm University Medical Center, 89081, Ulm, Germany
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9
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Janik-Karpinska E, Ceremuga M, Niemcewicz M, Synowiec E, Sliwinski T, Stela M, Bijak M. DNA Damage Induced by T-2 Mycotoxin in Human Skin Fibroblast Cell Line-Hs68. Int J Mol Sci 2023; 24:14458. [PMID: 37833905 PMCID: PMC10572149 DOI: 10.3390/ijms241914458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/17/2023] [Accepted: 09/19/2023] [Indexed: 10/15/2023] Open
Abstract
T-2 mycotoxin is the most potent representative of the trichothecene group A and is produced by various Fusarium species, including F. sporotrichioides, F. poae, and F. acuminatum. T-2 toxin has been reported to have toxic effects on various tissues and organs, and humans and animals alike suffer a variety of pathological conditions after consumption of mycotoxin-contaminated food. The T-2 toxin's unique feature is dermal toxicity, characterized by skin inflammation. In this in vitro study, we investigated the molecular mechanism of T-2 toxin-induced genotoxicity in the human skin fibroblast-Hs68 cell line. For the purpose of investigation, the cells were treated with T-2 toxin in 0.1, 1, and 10 μM concentrations and incubated for 24 h and 48 h. Nuclear DNA (nDNA) is found within the nucleus of eukaryotic cells and has a double-helix structure. nDNA encodes the primary structure of proteins, consisting of the basic amino acid sequence. The alkaline comet assay results showed that T-2 toxin induces DNA alkali-labile sites. The DNA strand breaks in cells, and the DNA damage level is correlated with the increasing concentration and time of exposure to T-2 toxin. The evaluation of nDNA damage revealed that exposure to toxin resulted in an increasing lesion frequency in Hs68 cells with HPRT1 and TP53 genes. Further analyses were focused on mRNA expression changes in two groups of genes involved in the inflammatory and repair processes. The level of mRNA increased for all examined inflammatory genes (TNF, INFG, IL1A, and IL1B). In the second group of genes related to the repair process, changes in expression induced by toxin in genes-LIG3 and APEX were observed. The level of mRNA for LIG3 decreased, while that for APEX increased. In the case of LIG1, FEN, and XRCC1, no changes in mRNA level between the control and T-2 toxin probes were observed. In conclusion, the results of this study indicate that T-2 toxin shows genotoxic effects on Hs68 cells, and the molecular mechanism of this toxic effect is related to nDNA damage.
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Affiliation(s)
- Edyta Janik-Karpinska
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (E.J.-K.); (M.N.); (M.S.)
| | - Michal Ceremuga
- Military Institute of Armament Technology, Prymasa Stefana Wyszyńskiego 7, 05-220 Zielonka, Poland;
| | - Marcin Niemcewicz
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (E.J.-K.); (M.N.); (M.S.)
| | - Ewelina Synowiec
- Laboratory of Medical Genetics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (E.S.); (T.S.)
| | - Tomasz Sliwinski
- Laboratory of Medical Genetics, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (E.S.); (T.S.)
| | - Maksymilian Stela
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (E.J.-K.); (M.N.); (M.S.)
| | - Michal Bijak
- Biohazard Prevention Centre, Faculty of Biology and Environmental Protection, University of Lodz, Pomorska 141/143, 90-236 Lodz, Poland; (E.J.-K.); (M.N.); (M.S.)
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10
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Chen Z, Song J, Xie L, Xu G, Zheng C, Xia X, Lu F, Ma X, Zou F, Jiang J, Wang H. N6-methyladenosine hypomethylation of circGPATCH2L regulates DNA damage and apoptosis through TRIM28 in intervertebral disc degeneration. Cell Death Differ 2023; 30:1957-1972. [PMID: 37438603 PMCID: PMC10406905 DOI: 10.1038/s41418-023-01190-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 05/31/2023] [Accepted: 06/29/2023] [Indexed: 07/14/2023] Open
Abstract
Circular RNAs (circRNAs) are a class of noncoding RNAs that have been found to be involved in intervertebral disc degeneration (IVDD) progression, and N6-methyladenosine (m6A) broadly exists in circRNAs. Here, we identified circGPATCH2L with a low m6A methylation level to be upregulated in degenerative nucleus pulposus tissues. Mechanistically, as a protein decoy for tripartite motif containing 28 (TRIM28) within aa 402-452 region, circGPATCH2L abrogates the phosphorylation of TRIM28 and inhibits P53 degradation, which contributes to DNA damage accumulation and cellular apoptosis and leads to IVDD progression. Moreover, m6A-methylated circGPATCH2L is recognised and endoribonucleolytically cleaved by a YTHDF2-RPL10-RNase P/MRP complex to maintain the physiological state of nucleus pulposus cells. Thus, our data show the physiological significance of m6A modification in regulating circRNA abundance and provide a potentially effective therapeutic target for the treatment of IVDD.
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Affiliation(s)
- Zhenhao Chen
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
| | - Jian Song
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
| | - Lin Xie
- Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430000, China
| | - Guangyu Xu
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
| | - Chaojun Zheng
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
| | - Xinlei Xia
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
| | - Feizhou Lu
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, 200000, China
| | - Xiaosheng Ma
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China
| | - Fei Zou
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China.
| | - Jianyuan Jiang
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China.
| | - Hongli Wang
- Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, 200000, China.
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11
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Floramo JS, Molchanov V, Liu H, Liu Y, Craig SEL, Yang T. An Integrated View of Stressors as Causative Agents in OA Pathogenesis. Biomolecules 2023; 13:biom13050721. [PMID: 37238590 DOI: 10.3390/biom13050721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Revised: 04/14/2023] [Accepted: 04/20/2023] [Indexed: 05/28/2023] Open
Abstract
Cells in the body are exposed to dynamic external and internal environments, many of which cause cell damage. The cell's response to this damage, broadly called the stress response, is meant to promote survival and repair or remove damage. However, not all damage can be repaired, and sometimes, even worse, the stress response can overtax the system itself, further aggravating homeostasis and leading to its loss. Aging phenotypes are considered a manifestation of accumulated cellular damage and defective repair. This is particularly apparent in the primary cell type of the articular joint, the articular chondrocytes. Articular chondrocytes are constantly facing the challenge of stressors, including mechanical overloading, oxidation, DNA damage, proteostatic stress, and metabolic imbalance. The consequence of the accumulation of stress on articular chondrocytes is aberrant mitogenesis and differentiation, defective extracellular matrix production and turnover, cellular senescence, and cell death. The most severe form of stress-induced chondrocyte dysfunction in the joints is osteoarthritis (OA). Here, we summarize studies on the cellular effects of stressors on articular chondrocytes and demonstrate that the molecular effectors of the stress pathways connect to amplify articular joint dysfunction and OA development.
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Affiliation(s)
- Joseph S Floramo
- Laboratory of Skeletal Biology, Department of Cell Biology, Van Andel Institute, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
| | - Vladimir Molchanov
- Laboratory of Skeletal Biology, Department of Cell Biology, Van Andel Institute, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
| | - Huadie Liu
- Laboratory of Skeletal Biology, Department of Cell Biology, Van Andel Institute, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
| | - Ye Liu
- Laboratory of Skeletal Biology, Department of Cell Biology, Van Andel Institute, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
| | - Sonya E L Craig
- Laboratory of Skeletal Biology, Department of Cell Biology, Van Andel Institute, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
| | - Tao Yang
- Laboratory of Skeletal Biology, Department of Cell Biology, Van Andel Institute, 333 Bostwick Ave NE, Grand Rapids, MI 49503, USA
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Copp ME, Shine J, Brown HL, Nimmala KR, Chubinskaya S, Collins JA, Loeser RF, Diekman BO. SIRT6 activation rescues the age-related decline in DNA damage repair in primary human chondrocytes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.02.27.530205. [PMID: 36909504 PMCID: PMC10002640 DOI: 10.1101/2023.02.27.530205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/04/2023]
Abstract
While advanced age has long been recognized as the greatest risk factor for osteoarthritis (OA), the biological mechanisms behind this connection remain unclear. Previous work has demonstrated that chondrocytes from older cadaveric donors have elevated levels of DNA damage as compared to chondrocytes from younger donors. The purpose of this study was to determine whether a decline in DNA repair efficiency is one explanation for the accumulation of DNA damage with age, and to quantify the improvement in repair with activation of Sirtuin 6 (SIRT6). Using an acute irradiation model to bring the baseline level of all donors to the same starting point, this study demonstrates a decline in repair efficiency during aging when comparing chondrocytes from young (≤45 years old), middle-aged (50-65 years old), or older (>70 years old) cadaveric donors with no known history of OA or macroscopic cartilage degradation at isolation. Activation of SIRT6 in middle-aged chondrocytes with MDL-800 (20 μM) improved the repair efficiency, while inhibition with EX-527 (10 μM) inhibited the rate of repair and the increased the percentage of cells that retained high levels of damage. Treating chondrocytes from older donors with MDL-800 for 48 hours significantly reduced the amount of DNA damage, despite this damage having accumulated over decades. Lastly, chondrocytes isolated from the proximal femurs of mice between 4 months and 22 months of age revealed both an increase in DNA damage with aging, and a decrease in DNA damage following MDL-800 treatment.
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Affiliation(s)
- Michaela E Copp
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC
| | - Jacqueline Shine
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
| | - Hannon L Brown
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC
| | - Kirti R Nimmala
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC
| | - Susan Chubinskaya
- Department of Pediatrics, Rush University Medical Center, Chicago, IL
| | - John A Collins
- Department of Orthopedic Surgery, Thomas Jefferson University
| | - Richard F Loeser
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
- Division of Rheumatology, Allergy, and Immunology, University of North Carolina
| | - Brian O Diekman
- Thurston Arthritis Research Center, University of North Carolina at Chapel Hill, Chapel Hill, NC
- Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, NC
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Zhang X, Xiang S, Zhang Y, Liu S, Lei G, Hines S, Wang N, Lin H. In vitro study to identify ligand-independent function of estrogen receptor-α in suppressing DNA damage-induced chondrocyte senescence. FASEB J 2023; 37:e22746. [PMID: 36622202 PMCID: PMC10369926 DOI: 10.1096/fj.202201228r] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 11/29/2022] [Accepted: 12/19/2022] [Indexed: 01/10/2023]
Abstract
In osteoarthritis (OA), chondrocytes undergo many pathological alternations that are linked with cellular senescence. However, the exact pathways that lead to the generation of a senescence-like phenotype in OA chondrocytes are not clear. Previously, we found that loss of estrogen receptor-α (ERα) was associated with an increased senescence level in human chondrocytes. Since DNA damage is a common cause of cellular senescence, we aimed to study the relationship among ERα levels, DNA damage, and senescence in chondrocytes. We first examined the levels of ERα, representative markers of DNA damage and senescence in normal and OA cartilage harvested from male and female human donors, as well as from male mice. The influence of DNA damage on ERα levels was studied by treating human chondrocytes with doxorubicin (DOX), which is an often-used DNA-damaging agent. Next, we tested the potential of overexpressing ERα in reducing DNA damage and senescence levels. Lastly, we explored the interaction between ERα and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway. Results indicated that the OA chondrocytes contained DNA damage and displayed senescence features, which were accompanied by significantly reduced ERα levels. Overexpression of ERα reduced the levels of DNA damage and senescence in DOX-treated normal chondrocytes and OA chondrocytes. Moreover, DOX-induced the activation of NF-κB pathway, which was partially reversed by overexpressing ERα. Taken together, our results demonstrated the critical role of ERα in maintaining the health of chondrocytes by inhibiting DNA damage and senescence. This study also suggests that maintaining the ERα level may represent a new avenue to prevent and treat OA.
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Affiliation(s)
- Xiurui Zhang
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.,Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Shiqi Xiang
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Yiqian Zhang
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.,Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Silvia Liu
- Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Guanghua Lei
- Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Sophie Hines
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Ning Wang
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.,Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Hang Lin
- Department of Orthopaedic Surgery, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.,Department of Bioengineering, University of Pittsburgh Swanson School of Engineering, Pittsburgh, Pennsylvania, USA.,McGowan Institute for Regenerative Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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Toth D, Reglodi D, Schwieters L, Tamas A. Role of endocrine PACAP in age-related diseases. Front Endocrinol (Lausanne) 2023; 14:1118927. [PMID: 36967746 PMCID: PMC10033946 DOI: 10.3389/fendo.2023.1118927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Accepted: 02/24/2023] [Indexed: 03/11/2023] Open
Abstract
Pituitary adenylate cyclase activating polypeptide (PACAP) is a conserved neuropeptide, which confers diverse anti-aging endocrine and paracrine/autocrine effects, including anti-apoptotic, anti-inflammatory and antioxidant action. The results of the in vivo and in vitro experiments show that increasing emphasis is being placed on the diagnostic/prognostic biomarker potential of this neuropeptide in a wide array of age-related diseases. After the initial findings regarding the presence and alteration of PACAP in different body fluids in physiological processes, an increasing number of studies have focused on the changes of its levels in various pathological conditions associated with advanced aging. Until 2016 - when the results of previous human studies were reviewed - a vast majority of the studies had dealt with age-related neurological diseases, like cerebrovascular and neurodegenerative diseases, multiple sclerosis, as well as some other common diseases in elderly such as migraine, traumatic brain injury and post-traumatic stress disorder, chronic hepatitis and nephrotic syndrome. The aim of this review is to summarize the old and the new results and highlight those 'classical' and emerging clinical fields in which PACAP may become subject to further investigation as a diagnostic and/or prognostic biomarker in age-related diseases.
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Affiliation(s)
- Denes Toth
- Department of Forensic Medicine, University of Pécs Medical School, Pécs, Hungary
| | - Dora Reglodi
- Department of Anatomy, ELKH-PTE PACAP Research Team, Centre for Neuroscience, University of Pécs Medical School, Pécs, Hungary
| | - Lili Schwieters
- Department of Anatomy, ELKH-PTE PACAP Research Team, Centre for Neuroscience, University of Pécs Medical School, Pécs, Hungary
| | - Andrea Tamas
- Department of Anatomy, ELKH-PTE PACAP Research Team, Centre for Neuroscience, University of Pécs Medical School, Pécs, Hungary
- *Correspondence: Andrea Tamas,
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Guang Z, Min Z, Jun-Tan L, Tian-Xu D, Xiang G. Single-cell protein activity analysis reveals a novel subpopulation of chondrocytes and the corresponding key master regulator proteins associated with anti-senescence and OA progression. Front Immunol 2023; 14:1077003. [PMID: 37033917 PMCID: PMC10077735 DOI: 10.3389/fimmu.2023.1077003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2022] [Accepted: 03/09/2023] [Indexed: 04/11/2023] Open
Abstract
Background Osteoarthritis (OA) is a prevalent senescence-related disease with substantial joint pain, loss of joint function, and cartilage degeneration. Because of the paucity of single-cell studies of OA and the gene dropout problem of single-cell RNA sequencing, it is difficult to acquire an in-depth understanding of the molecular characteristics of various chondrocyte clusters. Methods Here, we aimed to provide new insights into chondrocyte senescence and a rationale for the development of effective intervention strategies for OA by using published single-cell RNA-sequencing data sets and the metaVIPER algorithm (Virtual Inference of Protein activity by Enriched Regulon). This algorithm was employed to present a proteome catalog of 62,449 chondrocytes from the cartilage of healthy individuals and OA patients at single-cell resolution. Furthermore, histopathologic analysis was carried out in cartilage samples from clinical patients and experimental mouse models of OA to validate above results. Results We identified 16 protein-activity-based chondrocyte clusters as well as the underlying master regulators in each cluster. By assessing the enrichment score of each cluster in bulk RNA-sequencing data, followed by gene-set variation analysis, we preliminarily identified a novel subpopulation of chondrocytes (cluster 3). This clinically relevant cluster was predicted to be the main chondrocyte cluster responsible for maintaining cellular homeostasis and anti-senescence. Specifically, we uncovered a set of the key leading-edge proteins of cluster 3 by validating the robustness of the above results using another human chondrocyte single-cell RNA-sequencing data set, consisting of 24,675 chondrocytes. Furthermore, cartilage samples from clinical patients and experimental mouse models of OA were used to evaluate the expression patterns of these leading-edge proteins, and the results indicated that NDRG2, TSPYL2, JMJD6 and HMGB2 are closely associated with OA pathogenesis and might play critical roles in modulating cellular homeostasis and anti-senescence in chondrocytes. Conclusion Our study revealed a novel subpopulation of chondrocytes that are critical for anti-progression of OA and the corresponding master regulator proteins, which might serve as therapeutic targets in OA.
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Affiliation(s)
- Zhao Guang
- Department of Orthopedics, The Fourth Hospital of China Medical University, Shenyang, China
| | - Zhang Min
- Department of Obstetrics, The Fourth Hospital of China Medical University, Shenyang, China
| | - Li Jun-Tan
- Department of Sport Medicine and Joint Surgery, The First Hospital of China Medical University, Shenyang, China
| | - Dou Tian-Xu
- Department of Sport Medicine and Joint Surgery, The First Hospital of China Medical University, Shenyang, China
| | - Gao Xiang
- Department of Orthopedics, The Fourth Hospital of China Medical University, Shenyang, China
- *Correspondence: Gao Xiang,
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Nutrition Strategies Promoting Healthy Aging: From Improvement of Cardiovascular and Brain Health to Prevention of Age-Associated Diseases. Nutrients 2022; 15:nu15010047. [PMID: 36615705 PMCID: PMC9824801 DOI: 10.3390/nu15010047] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 12/19/2022] [Accepted: 12/21/2022] [Indexed: 12/24/2022] Open
Abstract
BACKGROUND An increasing number of studies suggest that diet plays an important role in regulating aging processes and modulates the development of the most important age-related diseases. OBJECTIVE The aim of this review is to provide an overview of the relationship between nutrition and critical age-associated diseases. METHODS A literature review was conducted to survey recent pre-clinical and clinical findings related to the role of nutritional factors in modulation of fundamental cellular and molecular mechanisms of aging and their role in prevention of the genesis of the diseases of aging. RESULTS Studies show that the development of cardiovascular and cerebrovascular diseases, neurodegenerative diseases, cognitive impairment and dementia can be slowed down or prevented by certain diets with anti-aging action. The protective effects of diets, at least in part, may be mediated by their beneficial macro- (protein, fat, carbohydrate) and micronutrient (vitamins, minerals) composition. CONCLUSIONS Certain diets, such as the Mediterranean diet, may play a significant role in healthy aging by preventing the onset of certain diseases and by improving the aging process itself. This latter can be strengthened by incorporating fasting elements into the diet. As dietary recommendations change with age, this should be taken into consideration as well, when developing a diet tailored to the needs of elderly individuals. Future and ongoing clinical studies on complex anti-aging dietary interventions translating the results of preclinical investigations are expected to lead to novel nutritional guidelines for older adults in the near future.
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Adverse Effect of Blue Light on DNA Integrity Is Accelerated by 5-Aminolevulinic Acid in HaCaT Human Keratinocyte Cells and B16F1 Murine Melanoma Cells. BIOLOGY 2022; 11:biology11121743. [PMID: 36552253 PMCID: PMC9774801 DOI: 10.3390/biology11121743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2022] [Revised: 11/21/2022] [Accepted: 11/29/2022] [Indexed: 12/05/2022]
Abstract
Several studies have suggested the potential benefits of 5-aminolevulinic acid (5-ALA)-based photodynamic therapy (PDT). 5-ALA is a precursor of heme, which generates reactive oxygen species (ROS) following photoirradiation. Some reports indicate that blue light induces intracellular ROS production. In the present study, we elucidated the effects of blue light and 5-ALA on DNA integrity in B16F1 murine melanoma and human keratinocyte HaCaT cells using a variety of comet assay techniques. Co-treatment with blue light and 5-ALA significantly decreased cell viability in both cell lines. A neutral comet assay was performed to assess DNA double-strand break (DSB) formation and blue light and 5-ALA caused DSBs. We also performed an alkali comet assay to detect single-strand breaks (SSB) and alkali labile sites (ALS). The results indicated that 5-ALA accelerated blue light-induced SSB formation. In addition, modified comet assays were done using two types of enzymes to evaluate oxidative DNA damages. The results indicated that blue light and 5-ALA generated oxidized purine and pyrimidines in both cell lines. In summary, co-treatment with 5-ALA and photoirradiation may cause unexpected DNA damage in cells and tissues.
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