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  1. Article ; Online: Re-thinking osteoarthritis pathogenesis: what can we learn (and what do we need to unlearn) from mouse models about the mechanisms involved in disease development.

    Poulsen, Raewyn C / Jain, Lekha / Dalbeth, Nicola

    Arthritis research & therapy

    2023  Volume 25, Issue 1, Page(s) 59

    Abstract: Efforts to develop effective disease-modifying drugs to treat osteoarthritis have so far proved unsuccessful with a number of promising drug candidates from pre-clinical studies failing to show efficacy in clinical trials. It is therefore timely to re- ... ...

    Abstract Efforts to develop effective disease-modifying drugs to treat osteoarthritis have so far proved unsuccessful with a number of promising drug candidates from pre-clinical studies failing to show efficacy in clinical trials. It is therefore timely to re-evaluate our current understanding of osteoarthritis pathogenesis and the similarities and differences in disease development between commonly used pre-clinical mouse models and human patients. There is substantial heterogeneity between patients presenting with osteoarthritis and mounting evidence that the pathways involved in osteoarthritis (e.g. Wnt signalling) differ between patient sub-groups. There is also emerging evidence that the pathways involved in osteoarthritis differ between the STR/ort mouse model (the most extensively studied mouse model of spontaneously occurring osteoarthritis) and injury-induced osteoarthritis mouse models. For instance, while canonical Wnt signalling is upregulated in the synovium and cartilage at an early stage of disease in injury-induced osteoarthritis mouse models, this does not appear to be the case in the STR/ort mouse. Such findings may prove insightful for understanding the heterogeneity in mechanisms involved in osteoarthritis pathogenesis in human disease. However, it is important to recognise that there are differences between mice and humans in osteoarthritis pathogenesis. A much more extensive array of pathological changes are evident in osteoarthritic joints in individual mice with osteoarthritis compared to individual patients. There are also specified differences in the pathways involved in disease development. For instance, although increased TGF-β signalling is implicated in osteoarthritis development in both mouse models of osteoarthritis and human disease, in mice, this is mainly mediated through TGF-β3 whereas in humans, it is through TGF-β1. Studies in other tissues have shown TGF-β1 is more potent than TGF-β3 in inducing the switch to SMAD1/5 signalling that occurs in osteoarthritic cartilage and that TGF-β1 and TGF-β3 have opposing effects on fibrosis. It is therefore possible that the relative contribution of TGF-β signalling to joint pathology in osteoarthritis differs between murine models and humans. Understanding the similarities and differences in osteoarthritis pathogenesis between mouse models and humans is critical for understanding the translational potential of findings from pre-clinical studies.
    MeSH term(s) Mice ; Humans ; Animals ; Transforming Growth Factor beta1/metabolism ; Cartilage, Articular/pathology ; Transforming Growth Factor beta3/metabolism ; Osteoarthritis/metabolism ; Disease Models, Animal
    Chemical Substances Transforming Growth Factor beta1 ; Transforming Growth Factor beta3
    Language English
    Publishing date 2023-04-12
    Publishing country England
    Document type Journal Article ; Review ; Research Support, Non-U.S. Gov't
    ZDB-ID 2107602-9
    ISSN 1478-6362 ; 1478-6354
    ISSN (online) 1478-6362
    ISSN 1478-6354
    DOI 10.1186/s13075-023-03042-6
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: N-methyl-D-aspartate receptor regulates the circadian clock in megakaryocytic cells and impacts cell proliferation through BMAL1.

    Hearn, James I / Alhilali, Mariam / Kim, Minah / Kalev-Zylinska, Maggie L / Poulsen, Raewyn C

    Platelets

    2023  Volume 34, Issue 1, Page(s) 2206918

    Abstract: Peripheral circadian clocks control cell proliferation and survival, but little is known about their role and regulation in megakaryocytic cells. N-methyl-D-aspartate receptor (NMDAR) regulates the central clock in the brain. The purpose of this study ... ...

    Abstract Peripheral circadian clocks control cell proliferation and survival, but little is known about their role and regulation in megakaryocytic cells. N-methyl-D-aspartate receptor (NMDAR) regulates the central clock in the brain. The purpose of this study was to determine whether NMDAR regulates the megakaryocytic cell clock and whether the megakaryocytic clock regulates cell proliferation and cell death. We found that both the Meg-01 megakaryocytic cell line and native murine megakaryocytes expressed circadian clock genes. Megakaryocyte-directed deletion of Grin1 in mice caused significant disruption of the circadian rhythm pathway at the transcriptional level and increased expression of BMAL1 at the protein level. Similarly, both pharmacological (MK-801) and genetic (GRIN
    MeSH term(s) Mice ; Animals ; Circadian Clocks/genetics ; ARNTL Transcription Factors/genetics ; ARNTL Transcription Factors/metabolism ; Receptors, N-Methyl-D-Aspartate/genetics ; Gene Expression Regulation ; Circadian Rhythm/physiology ; Cell Proliferation
    Chemical Substances ARNTL Transcription Factors ; Receptors, N-Methyl-D-Aspartate
    Language English
    Publishing date 2023-06-10
    Publishing country England
    Document type Journal Article
    ZDB-ID 1034283-7
    ISSN 1369-1635 ; 0953-7104
    ISSN (online) 1369-1635
    ISSN 0953-7104
    DOI 10.1080/09537104.2023.2206918
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Elevated glucose promotes MMP13 and ADAMTS5 production by osteoarthritic chondrocytes under oxygenated but not hypoxic conditions.

    Jain, Lekha / Bolam, Scott M / Monk, Paul / Munro, Jacob T / Tamatea, Jade / Dalbeth, Nicola / Poulsen, Raewyn C

    Journal of cellular physiology

    2024  

    Abstract: Type 2 diabetes is linked with increased incidence and severity of osteoarthritis. The purpose of this study was to determine the effect of extracellular glucose within the normal blood glucose and hyperglycemic range on catabolic enzyme production by ... ...

    Abstract Type 2 diabetes is linked with increased incidence and severity of osteoarthritis. The purpose of this study was to determine the effect of extracellular glucose within the normal blood glucose and hyperglycemic range on catabolic enzyme production by chondrocytes isolated from osteoarthritic (OA) and macroscopically normal (MN) human cartilage under oxygenated (18.9% oxygen) and hypoxic (1% oxygen) conditions. OA and MN chondrocytes were maintained in 4, 6, 8, or 10 mM glucose for 24 h. Glucose consumption, GLUT1 glucose transporter levels, MMP13 and ADAMTS5 production, and levels of RUNX2, a transcriptional regulator of MMP13, ADAMTS5, and GLUT1, were assessed by enzyme-linked assays, RT-qPCR and/or western blot. Under oxygenated conditions, glucose consumption and GLUT1 protein levels were higher in OA but not MN chondrocytes in 10 mM glucose compared to 4 mM. Both RNA and protein levels of MMP13 and ADAMTS5 were also higher in OA but not MN chondrocytes in 10 mM compared to 4 mM glucose under oxygenated conditions. Expression of RUNX2 was overall lower in MN than OA chondrocytes and there was no consistent effect of extracellular glucose concentration on RUNX2 levels in MN chondrocytes. However, protein (but not RNA) levels of RUNX2 were elevated in OA chondrocytes maintained in 10 mM versus 4 mM glucose under oxygenated conditions. In contrast, neither RUNX2 levels or MMP13 or ADAMTS5 expression were increased in OA chondrocytes maintained in 10 mM compared to 4 mM glucose in hypoxia. Elevated extracellular glucose leads to increased glucose consumption and increased RUNX2 protein levels, promoting production of MMP13 and ADAMTS5 by OA chondrocytes in oxygenated but not hypoxic conditions. These findings suggest that hyperglycaemia may exacerbate chondrocyte-mediated cartilage catabolism in the oxygenated superficial zone of cartilage in vivo in patients with undertreated type 2 diabetes, contributing to increased OA severity.
    Language English
    Publishing date 2024-04-09
    Publishing country United States
    Document type Journal Article
    ZDB-ID 3116-1
    ISSN 1097-4652 ; 0021-9541
    ISSN (online) 1097-4652
    ISSN 0021-9541
    DOI 10.1002/jcp.31271
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Monosodium urate crystals alter the circadian clock in macrophages leading to loss of NLRP3 inflammasome repression: Implications for timing of the gout flare.

    Popov, Dmitry / Jain, Lekha / Alhilali, Mariam / Dalbeth, Nicola / Poulsen, Raewyn C

    FASEB journal : official publication of the Federation of American Societies for Experimental Biology

    2023  Volume 37, Issue 6, Page(s) e22940

    Abstract: Gout is caused by monosodium urate (MSU) crystal deposition within joints. This leads to acute episodes of inflammation ("gout flares") driven by NLRP3 inflammasome activation in macrophages. Gout flares are frequently present during late night/early ... ...

    Abstract Gout is caused by monosodium urate (MSU) crystal deposition within joints. This leads to acute episodes of inflammation ("gout flares") driven by NLRP3 inflammasome activation in macrophages. Gout flares are frequently present during late night/early morning. The reason for this timing is unclear. Recent evidence suggests the NLRP3 inflammasome is under circadian control. The purpose of this study was to determine whether MSU crystals cause changes in the circadian clock in macrophages leading to time-of-day differences in NLRP3 inflammasome activation. Levels of circadian clock components were measured in undifferentiated "monocytic" and PMA-differentiated "macrophagic" THP-1 cells cultured with/without MSU crystals. Caspase-1 activity was measured to assess NLRP3 inflammasome activity. MSU crystal exposure resulted in minimal effects on clock genes in THP-1 monocytes but BMAL1, CRY1, PER2, and REV-ERBα showed altered expression with reduced protein levels of BMAL1 and REV-ERBα in THP-1 macrophages. REV-ERBα activation or BMAL1 over-expression resulted in reduced MSU crystal-induced caspase-1 activity. BMAL1 knockdown resulted in a further increase in MSU crystal-induced caspase-1 activity, but only at times of day when BMAL1 levels were naturally high. MSU crystal-induced NLRP3 inflammasome activation was greatest at the time of day when BMAL1 levels were naturally low. MSU crystals alter the expression of circadian clock components in THP-1 macrophages leading to loss of BMAL1 and REV-ERBα-mediated repression of NLRP3 inflammasome activity and time-of-day differences in susceptibility to inflammasome activation. Our findings suggest that the nocturnal risk of gout flare is at least partially a consequence of altered circadian control of immune cell function.
    MeSH term(s) Humans ; Gout/genetics ; Inflammasomes/metabolism ; Uric Acid/metabolism ; NLR Family, Pyrin Domain-Containing 3 Protein/genetics ; NLR Family, Pyrin Domain-Containing 3 Protein/metabolism ; ARNTL Transcription Factors/metabolism ; Circadian Clocks/genetics ; Symptom Flare Up ; Macrophages/metabolism ; Caspases/metabolism ; Interleukin-1beta/metabolism
    Chemical Substances Inflammasomes ; Uric Acid (268B43MJ25) ; NLR Family, Pyrin Domain-Containing 3 Protein ; ARNTL Transcription Factors ; Caspases (EC 3.4.22.-) ; Interleukin-1beta
    Language English
    Publishing date 2023-05-26
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 639186-2
    ISSN 1530-6860 ; 0892-6638
    ISSN (online) 1530-6860
    ISSN 0892-6638
    DOI 10.1096/fj.202202035R
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: The circadian clock: a central mediator of cartilage maintenance and osteoarthritis development?

    Poulsen, Raewyn C / Hearn, James I / Dalbeth, Nicola

    Rheumatology (Oxford, England)

    2021  Volume 60, Issue 7, Page(s) 3048–3057

    Abstract: The circadian clock is a specialized cell signalling pathway present in all cells. Loss of clock function leads to tissue degeneration and premature ageing in animal models demonstrating the fundamental importance of clocks for cell, tissue and organism ... ...

    Abstract The circadian clock is a specialized cell signalling pathway present in all cells. Loss of clock function leads to tissue degeneration and premature ageing in animal models demonstrating the fundamental importance of clocks for cell, tissue and organism health. There is now considerable evidence that the chondrocyte circadian clock is altered in OA. The purpose of this review is to summarize current knowledge regarding the nature of the change in the chondrocyte clock in OA and the implications of this change for disease development. Expression of the core clock component, BMAL1, has consistently been shown to be lower in OA chondrocytes. This may contribute to changes in chondrocyte differentiation and extracellular matrix turnover in disease. Circadian clocks are highly responsive to environmental factors. Mechanical loading, diet, inflammation and oxidative insult can all influence clock function. These factors may contribute to causing the change in the chondrocyte clock in OA.
    MeSH term(s) ARNTL Transcription Factors/metabolism ; CLOCK Proteins/metabolism ; Cartilage, Articular/cytology ; Cartilage, Articular/metabolism ; Cartilage, Articular/physiopathology ; Cell Differentiation ; Cell Proliferation ; Cell Survival ; Chondrocytes/metabolism ; Chondrogenesis ; Circadian Clocks ; Cryptochromes/metabolism ; Diet ; Extracellular Matrix/metabolism ; Humans ; Inflammation ; Osteoarthritis/metabolism ; Osteoarthritis/physiopathology ; Oxidative Stress ; Period Circadian Proteins/metabolism ; Suprachiasmatic Nucleus/metabolism ; Weight-Bearing
    Chemical Substances ARNTL Transcription Factors ; Cryptochromes ; Period Circadian Proteins ; CLOCK Proteins (EC 2.3.1.48)
    Language English
    Publishing date 2021-02-24
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Review
    ZDB-ID 1464822-2
    ISSN 1462-0332 ; 1462-0324
    ISSN (online) 1462-0332
    ISSN 1462-0324
    DOI 10.1093/rheumatology/keab197
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Concentration-dependent effects of leptin on osteoarthritis-associated changes in phenotype of human chondrocytes.

    Primrose, Julia Gb / Jain, Lekha / Bolam, Scott M / Monk, A Paul / Munro, Jacob T / Dalbeth, Nicola / Poulsen, Raewyn C

    Connective tissue research

    2023  Volume 64, Issue 5, Page(s) 457–468

    Abstract: Metabolic syndrome is a risk factor for osteoarthritis. Elevated leptin levels have been implicated as a potential cause of this association. Previous studies have shown that supra-physiological leptin concentrations can induce osteoarthritis-like ... ...

    Abstract Metabolic syndrome is a risk factor for osteoarthritis. Elevated leptin levels have been implicated as a potential cause of this association. Previous studies have shown that supra-physiological leptin concentrations can induce osteoarthritis-like changes in chondrocyte phenotype. Here, we tested the effects of leptin in the concentration range found in synovial fluid on chondrocyte phenotype. Chondrocytes isolated from macroscopically normal regions of cartilage within osteoarthritic joints from patients undergoing knee arthroplasty, all with body mass index >30 kg/m
    MeSH term(s) Humans ; Female ; Leptin/pharmacology ; Chondrocytes/metabolism ; Metabolic Syndrome/metabolism ; Osteoarthritis/metabolism ; Phenotype ; Cartilage, Articular/metabolism ; Cells, Cultured
    Chemical Substances Leptin
    Language English
    Publishing date 2023-05-17
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 185551-7
    ISSN 1607-8438 ; 0091-1690 ; 0300-8207
    ISSN (online) 1607-8438
    ISSN 0091-1690 ; 0300-8207
    DOI 10.1080/03008207.2023.2214249
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  7. Article: Redox Homeostasis in Ocular Tissues: Circadian Regulation of Glutathione in the Lens?

    Lim, Julie C / Suzuki-Kerr, Haruna / Nguyen, Tai X / Lim, Christopher J J / Poulsen, Raewyn C

    Antioxidants (Basel, Switzerland)

    2022  Volume 11, Issue 8

    Abstract: Accumulating evidence in tissues suggests an interconnection between circadian clocks and redox regulation. Diurnal variations in antioxidant levels, circadian rhythms of antioxidant enzyme activity, and differences in oxidative stress markers at ... ...

    Abstract Accumulating evidence in tissues suggests an interconnection between circadian clocks and redox regulation. Diurnal variations in antioxidant levels, circadian rhythms of antioxidant enzyme activity, and differences in oxidative stress markers at different times of the day all indicate that oxidative stress responses follow a circadian rhythm. Disruptions of circadian rhythms are linked to a number of age-related diseases, including those in the eye. Typically, ocular tissues contain a robust antioxidant defence system to maintain redox balance and minimise oxidative stress and damage. The lens, in particular, contains remarkably high levels of the antioxidant glutathione (GSH). However, with advancing age, GSH levels deplete, initiating a chain of biochemical events that ultimately result in protein aggregation, light scattering, and age-related cataracts. While there is evidence that the lens exhibits circadian rhythms in the synthesis and release of melatonin, little is known about the regulation or function of timekeeping mechanisms in the lens. Since circadian rhythms are disrupted with age, and the depletion of GSH in the lens is a known initiating factor in the development of age-related cataracts, understanding the mechanisms involved in regulating GSH levels may lead to the future development of approaches to manipulate the clock to restore GSH levels and redox balance in the lens, and protect the lens from cataracts.
    Language English
    Publishing date 2022-08-03
    Publishing country Switzerland
    Document type Journal Article ; Review
    ZDB-ID 2704216-9
    ISSN 2076-3921
    ISSN 2076-3921
    DOI 10.3390/antiox11081516
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  8. Article ; Online: Differential Effects of Hypoxia versus Hyperoxia or Physoxia on Phenotype and Energy Metabolism in Human Chondrocytes from Osteoarthritic Compared to Macroscopically Normal Cartilage.

    Jain, Lekha / Bolam, Scott M / Monk, A Paul / Munro, Jacob T / Chen, Even / Tamatea, Jade / Dalbeth, Nicola / Poulsen, Raewyn C

    International journal of molecular sciences

    2023  Volume 24, Issue 8

    Abstract: Chondrocyte phenotype and energy metabolism are altered in osteoarthritis (OA). However, most studies characterising the change in human chondrocyte behaviour in OA have been conducted in supraphysiological oxygen concentrations. The purpose of this ... ...

    Abstract Chondrocyte phenotype and energy metabolism are altered in osteoarthritis (OA). However, most studies characterising the change in human chondrocyte behaviour in OA have been conducted in supraphysiological oxygen concentrations. The purpose of this study was to compare phenotype and energy metabolism in chondrocytes from macroscopically normal (MN) and OA cartilage maintained in 18.9% (standard tissue culture), 6% (equivalent to superficial zone of cartilage in vivo) or 1% oxygen (equivalent to deep zone of cartilage in vivo). MMP13 production was higher in chondrocytes from OA compared to MN cartilage in hyperoxia and physoxia but not hypoxia. Hypoxia promoted SOX9, COL2A1 and ACAN protein expression in chondrocytes from MN but not OA cartilage. OA chondrocytes used higher levels of glycolysis regardless of oxygen availability. These results show that differences in phenotype and energy metabolism between chondrocytes from OA and MN cartilage differ depending on oxygen availability. OA chondrocytes show elevated synthesis of cartilage-catabolising enzymes and chondrocytes from MN cartilage show reduced cartilage anabolism in oxygenated conditions. This is relevant as a recent study has shown that oxygen levels are elevated in OA cartilage in vivo. Our findings may indicate that this elevated cartilage oxygenation may promote cartilage loss in OA.
    MeSH term(s) Humans ; Chondrocytes/metabolism ; Hyperoxia/metabolism ; Osteoarthritis/metabolism ; Phenotype ; Cartilage, Articular/metabolism ; Hypoxia/metabolism ; Energy Metabolism ; Oxygen/metabolism ; Cells, Cultured
    Chemical Substances Oxygen (S88TT14065)
    Language English
    Publishing date 2023-04-19
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2019364-6
    ISSN 1422-0067 ; 1422-0067 ; 1661-6596
    ISSN (online) 1422-0067
    ISSN 1422-0067 ; 1661-6596
    DOI 10.3390/ijms24087532
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  9. Article ; Online: REST, RCOR1 and RCOR2 expression is reduced in osteoarthritic chondrocytes and contributes to increasing MMP13 and ADAMTS5 expression through upregulating HES1.

    Primrose, Julia G B / Jain, Lekha / Alhilali, Mariam / Bolam, Scott M / Monk, A Paul / Munro, Jacob T / Dalbeth, Nicola / Poulsen, Raewyn C

    Cellular signalling

    2023  Volume 109, Page(s) 110800

    Abstract: Expression of key transcriptional regulators is altered in chondrocytes in osteoarthritis (OA). This contributes to an increase in production of cartilage-catabolizing enzymes such as MMP13 and ADAMTS5. RCOR1 and RCOR2, binding partners for the ... ...

    Abstract Expression of key transcriptional regulators is altered in chondrocytes in osteoarthritis (OA). This contributes to an increase in production of cartilage-catabolizing enzymes such as MMP13 and ADAMTS5. RCOR1 and RCOR2, binding partners for the transcriptional repressor REST, have previously been found to be downregulated in OA chondrocytes although their function in chondrocytes is unclear. HES1 is a known REST/RCOR1 target gene and HES1 has been shown to promote MMP13 and ADAMTS5 expression in murine OA chondrocytes. The purpose of this study was to determine whether reduced REST/RCOR levels leads to increased HES1 expression in human OA chondrocytes and whether HES1 also promotes ADAMTS5 and MMP13 expression in these cells. Chondrocytes were isolated from osteoarthritic and adjacent macroscopically normal cartilage obtained from patients undergoing total knee arthroplasty. RNA and protein levels of REST, RCOR1 and RCOR2 were lower, but levels of HES1 higher, in chondrocytes isolated from osteoarthritic compared to macroscopically normal cartilage. Over-expression of either REST, RCOR1 or RCOR2 resulted in reduced HES1 levels in OA chondrocytes whereas knockdown of REST, RCOR1 or RCOR2 led to increased HES1 expression in chondrocytes from macroscopically normal cartilage. In OA chondrocytes, ADAMTS5 and MMP13 expression were reduced following HES1 knockdown, but further enhanced following HES1 over-expression. Levels of phosphorylated CaMKII were higher in chondrocytes from OA cartilage consistent with previous findings that HES1 only promotes gene transcription in the presence of active CaMKII. These findings identify the REST/RCOR/HES1 pathway as a contributing factor leading to increased ADAMTS5 and MMP13 expression in OA chondrocytes.
    MeSH term(s) Humans ; Mice ; Animals ; Chondrocytes/metabolism ; Matrix Metalloproteinase 13/genetics ; Calcium-Calmodulin-Dependent Protein Kinase Type 2/metabolism ; Osteoarthritis/metabolism ; RNA/metabolism ; Cells, Cultured ; Transcription Factor HES-1/metabolism ; ADAMTS5 Protein/genetics ; ADAMTS5 Protein/metabolism ; Nerve Tissue Proteins/metabolism ; Co-Repressor Proteins/metabolism
    Chemical Substances Matrix Metalloproteinase 13 (EC 3.4.24.-) ; Calcium-Calmodulin-Dependent Protein Kinase Type 2 (EC 2.7.11.17) ; RNA (63231-63-0) ; HES1 protein, human (149348-15-2) ; Transcription Factor HES-1 ; ADAMTS5 protein, human (EC 3.4.24.-) ; ADAMTS5 Protein (EC 3.4.24.-) ; RCOR1 protein, human ; Nerve Tissue Proteins ; Co-Repressor Proteins ; MMP13 protein, human (EC 3.4.24.-)
    Language English
    Publishing date 2023-07-11
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 1002702-6
    ISSN 1873-3913 ; 0898-6568
    ISSN (online) 1873-3913
    ISSN 0898-6568
    DOI 10.1016/j.cellsig.2023.110800
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  10. Article: Redox Homeostasis in Ocular Tissues: Circadian Regulation of Glutathione in the Lens?

    Lim, Julie C. / Suzuki-Kerr, Haruna / Nguyen, Tai X. / Lim, Christopher J. J. / Poulsen, Raewyn C.

    Antioxidants. 2022 Aug. 03, v. 11, no. 8

    2022  

    Abstract: Accumulating evidence in tissues suggests an interconnection between circadian clocks and redox regulation. Diurnal variations in antioxidant levels, circadian rhythms of antioxidant enzyme activity, and differences in oxidative stress markers at ... ...

    Abstract Accumulating evidence in tissues suggests an interconnection between circadian clocks and redox regulation. Diurnal variations in antioxidant levels, circadian rhythms of antioxidant enzyme activity, and differences in oxidative stress markers at different times of the day all indicate that oxidative stress responses follow a circadian rhythm. Disruptions of circadian rhythms are linked to a number of age-related diseases, including those in the eye. Typically, ocular tissues contain a robust antioxidant defence system to maintain redox balance and minimise oxidative stress and damage. The lens, in particular, contains remarkably high levels of the antioxidant glutathione (GSH). However, with advancing age, GSH levels deplete, initiating a chain of biochemical events that ultimately result in protein aggregation, light scattering, and age-related cataracts. While there is evidence that the lens exhibits circadian rhythms in the synthesis and release of melatonin, little is known about the regulation or function of timekeeping mechanisms in the lens. Since circadian rhythms are disrupted with age, and the depletion of GSH in the lens is a known initiating factor in the development of age-related cataracts, understanding the mechanisms involved in regulating GSH levels may lead to the future development of approaches to manipulate the clock to restore GSH levels and redox balance in the lens, and protect the lens from cataracts.
    Keywords Lens ; antioxidant activity ; antioxidant enzymes ; circadian rhythm ; enzyme activity ; eyes ; glutathione ; homeostasis ; melatonin ; oxidative stress
    Language English
    Dates of publication 2022-0803
    Publishing place Multidisciplinary Digital Publishing Institute
    Document type Article
    ZDB-ID 2704216-9
    ISSN 2076-3921
    ISSN 2076-3921
    DOI 10.3390/antiox11081516
    Database NAL-Catalogue (AGRICOLA)

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