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Park SC, Lee YS, Cho KA, Kim SY, Lee YI, Lee SR, Lim IK. What matters in aging is signaling for responsiveness. Pharmacol Ther 2023; 252:108560. [PMID: 37952903 DOI: 10.1016/j.pharmthera.2023.108560] [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: 06/04/2023] [Revised: 10/03/2023] [Accepted: 11/06/2023] [Indexed: 11/14/2023]
Abstract
Biological responsiveness refers to the capacity of living organisms to adapt to changes in both their internal and external environments through physiological and behavioral mechanisms. One of the prominent aspects of aging is the decline in this responsiveness, which can lead to a deterioration in the processes required for maintenance, survival, and growth. The vital link between physiological responsiveness and the essential life processes lies within the signaling systems. To devise effective strategies for controlling the aging process, a comprehensive reevaluation of this connecting loop is imperative. This review aims to explore the impact of aging on signaling systems responsible for responsiveness and introduce a novel perspective on intervening in the aging process by restoring the compromised responsiveness. These innovative mechanistic approaches for modulating altered responsiveness hold the potential to illuminate the development of action plans aimed at controlling the aging process and treating age-related disorders.
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Affiliation(s)
- Sang Chul Park
- The Future Life & Society Research Center, Advanced Institute of Aging Science, Chonnam National University, Gwangju 61469, Republic of Korea.
| | - Young-Sam Lee
- Department of New Biology, DGIST, Daegu 42988, Republic of Korea; Well Aging Research Center, Division of Biotechnology, DGIST, Daegu 42988, Republic of Korea.
| | - Kyung A Cho
- Department of Biochemistry, Chonnam National University Medical School, Jeollanam-do 58128, Republic of Korea
| | - Sung Young Kim
- Department of Biochemistry, Konkuk University School of Medicine, Seoul 05029, Republic of Korea
| | - Yun-Il Lee
- Well Aging Research Center, Division of Biotechnology, DGIST, Daegu 42988, Republic of Korea; Interdisciplinary Engineering Major, Department of Interdisciplinary Studies, DGIST, Daegu 42988, Republic of Korea
| | - Seung-Rock Lee
- Department of Biochemistry, Chonnam National University Medical School, Jeollanam-do 58128, Republic of Korea; Department of Biomedical Sciences, Research Center for Aging and Geriatrics, Research Institute of Medical Sciences, Chonnam National University Medical School, Gwangju 61469, Republic of Korea
| | - In Kyoung Lim
- Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon 16499, Republic of Korea
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Bivalent Ligand UDCA-LPE Inhibits Pro-Fibrogenic Integrin Signalling by Inducing Lipid Raft-Mediated Internalization. Int J Mol Sci 2018; 19:ijms19103254. [PMID: 30347788 PMCID: PMC6214129 DOI: 10.3390/ijms19103254] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 01/07/2023] Open
Abstract
Ursodeoxycholyl lysophosphatidylethanolamide (UDCA-LPE) is a synthetic bile acid-phospholipid conjugate with profound hepatoprotective and anti-fibrogenic functions in vitro and in vivo. Herein, we aimed to demonstrate the inhibitory effects of UDCA-LPE on pro-fibrogenic integrin signalling. UDCA-LPE treatment of human embryonic liver cell line CL48 and primary human hepatic stellate cells induced a non-classical internalization of integrin β1 resulting in dephosphorylation and inhibition of SRC and focal adhesion kinase (FAK). Signalling analyses suggested that UDCA-LPE may act as a heterobivalent ligand for integrins and lysophospholipid receptor1 (LPAR1) and co-immunoprecipitation demonstrated the bridging effect of UDCA-LPE on integrin β1 and LPAR1. The disruption of either the UDCA-moiety binding to integrins by RGD-containing peptide GRGDSP or the LPE-moiety binding to LPAR1 by LPAR1 antagonist Ki16425 reversed inhibitory functions of UDCA-LPE. The lack of inhibitory functions of UDCA-PE and UDCA-LPE derivatives (14:0 and 12:0, LPE-moiety containing shorter fatty acid chain) as well as the consistency of the translocation of UDCA-LPE and integrins, which co-fractionated with LPE but not UDCA, suggested that the observed UDCA-LPE-induced translocation of integrins was mediated by LPE endocytic transport pathway.
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Lysophosphatidic acid enhances PGE2 to PGF2α ratio and nitric oxide level in nonpregnant buffalo uterus. Theriogenology 2018; 120:47-55. [PMID: 30092374 DOI: 10.1016/j.theriogenology.2018.07.014] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2018] [Revised: 07/10/2018] [Accepted: 07/16/2018] [Indexed: 01/24/2023]
Abstract
Lysophosphatidic acid (LPA) is a small ubiquitous lipid exerting diverse biological functions. Its role in reproduction in different species has created great interest in recent times. In the present study, we aimed to elucidate LPA signaling in nonpregnant buffalo uterus by in vitro studies. Standard techniques like real-time PCR (for mRNA expression of LPARs and COX-2 and iNOS), Western blot (for PPARγ protein expression), sandwich ELISA (for PGE2 and PGF2α assay) and histopathology (for assessment of endometrial architecture in culture) were used in this study. The buffalo uterine tissues were collected from the local slaughterhouse and were selected for the study on the basis of the presence of corpus luteum on the ovary (n = 5). The LPAR3 receptor was the highest expressed receptor as compared to LPAR1 and LPAR6 in non-pregnant uterine tissues after 6 h incubation in Dulbecco's Modified Eagle Medium (DMEM). 50 μM LPA increased the mRNA expressions of COX-2 and iNOS enzymes which were attenuated by the treatment of LPAR1/3 antagonist Ki16425. PPARγ antagonist GW9662 prevented the LPA-induced increase in iNOS mRNA expression but did not alter the COX-2 expression. LPA also enhanced the PGE2 to PGF2α ratio in uterine tissue homogenates which was inhibited by all the receptor antagonists as well as by the inhibitors of COX-2 and iNOS. LPA also increased the total nitrite level in tissue homogenates in LPAR1/3- and iNOS-dependent manner. Additionally, we demonstrate PPARγ mRNA and protein expressions in nonpregnant buffalo endometrium. In conclusion, the results of the present study suggest that LPA acts as a luteotropic factor during the estrus cycle in nonpregnant buffalo uterus by enhancing PGE2 to PGF2α ratio and NO level through multiple receptors.
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Rolewska P, Simm A, Silber RE, Bartling B. Reduced expression level of the cyclic adenosine monophosphate response element-binding protein contributes to lung aging. Am J Respir Cell Mol Biol 2014; 50:201-11. [PMID: 23991634 DOI: 10.1165/rcmb.2013-0057oc] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Lung aging is associated with morphological and physiological changes in which alterations in transcription factors, including the cyclic adenosine monophosphate response element-binding protein (CREB), could play a role. We studied CREB in lung tissue from mice at different ages and in response to known age-related factors (e.g., cellular senescence and matrix modifications with advanced glycation end-products [AGEs]). Our study shows that protein but not mRNA levels of CREB are reduced in the lungs of old mice. CREB reduction was also observed in senescent human lung fibroblasts (WI-38, LuFi) and human lung epithelial cells (A549) cultured on AGE-modified collagen matrix. Reduction of CREB protein is partially based on pre- and posttranslational modifications as exhibited by an increase in the CREB-regulating microRNA 34b and CREB ubiquitination. Permanent down-regulation of CREB in lung cells impaired cell proliferation and viability and increased the number of cells with senescence-associated β-galactosidase activity. CREB down-regulation was accompanied by the reduced expression of 165 genes in WI-38 fibroblasts and A549 epithelial cells, of which 15 genes showed a reduced expression in lung tissues of old mice. The CREB-dependent reduction in RAB27A coding for the Ras-related protein Rab27A and IGFBP3 coding for the insulin-like growth factor-binding protein 3 has been confirmed for aged lung tissue, senescent fibroblasts, and lung epithelial cells on AGE-modified collagen. Our data demonstrate that the reduced protein expression of CREB might play a significant role in lung aging by modifying the transcription of RAB27A, IGFBP3, and other target genes.
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Affiliation(s)
- Paulina Rolewska
- 1 Department of Cardio-Thoracic Surgery, University Hospital Halle/Saale, Martin Luther University Halle-Wittenberg, Halle/Saale, Germany
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Park EY, Lee CH, Lee EK, Kim JH, Cova A, Lee SK, Cho SC, Kwak CS, Song KY, Park SC, Jun HS, Kim KT. HNF4α contributes to glucose formation in aged rat hepatocytes. Exp Gerontol 2013; 48:1518-25. [PMID: 24177414 DOI: 10.1016/j.exger.2013.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Revised: 10/18/2013] [Accepted: 10/22/2013] [Indexed: 11/18/2022]
Abstract
Aging-dependent physiological conditions are attributed to parenchymal structural changes to cellular functions in aged organisms. Compared to the young animals, the primary hepatocytes from old rats showed a higher glucose output and a higher expression of the key gluconeogenesis-regulating enzyme, phosphoenol pyruvate carboxykinase (PEPCK). The primary hepatocytes from old rats showed a higher glucose output and a higher expression of the key gluconeogenesis-regulating enzyme, phosphoenol pyruvate carboxykinase (PEPCK), compared with those from the young animals. The in situ hybridization study showed increased PEPCK mRNA expression in the aged liver tissues. The livers from old rats showed loosened hexagonal hepatic lobular structures, increased collagen accumulation, and high expression of the hypoxia marker hypoxia-inducible factor 1α (HIF1α). Hypoxia increased the PEPCK mRNA and protein expression levels in accordance with the HIF1α expression. PEPCK promoter luciferase reporter assay showed that hypoxia increased PEPCK through transcriptional activation. Furthermore, the hepatocyte nuclear factor α (HNF4α) protein, but not the HNF4α mRNA level, increased in parallel with the PEPCK mRNA expression under hypoxic conditions. Glucose production increased under hypoxic conditions, but this increment diminished by HNF4α siRNA in young hepatocytes. Moreover, increased glucose production from old rat hepatocytes was reversed by the down-regulation of HNF4α through a specific siRNA. This study suggests that the mild hypoxic conditions in response to aging-dependent hepatic structural changes may contribute to the induction of the gluconeogenic enzyme PEPCK through HNF4α protein stabilization.
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Affiliation(s)
- Eun Young Park
- College of Pharmacy and Gachon Institute of Pharmaceutical Science, Gachon University, Yeonsu-ku, Incheon 406-840, South Korea; Lee Gil Ya Cancer and Diabetes Institute, Gachon University, Yeonsu-ku, Incheon 406-840, South Korea
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Nuclear barrier hypothesis of aging as mechanism for trade-off growth to survival. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 720:3-13. [PMID: 21901614 DOI: 10.1007/978-1-4614-0254-1_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
When the aging-dependent cellular behaviors toward growth factors and toxic stress have been analyzed, the perinuclear accumulation of the activated signals, either mitogenic or apoptotic, has been observed, suggesting the aging-dependent inefficiency of the nucleocytoplasmic trafficking of the signals. Thereby, it would be natural to assume the operation of the functional nuclear barrier in aging-dependent manner, which would be designated as "Park and Lim's Barrier." And for the ultimate transcriptional factor for these aging-dependent changes of the functional nuclear barrier, Sp1 transcriptional factor has been suggested to be the most probable candidate. This novel mechanism of aging-dependent operation of the functional nuclear barrier is proposed as the ultimate checking mechanism for cellular protection against toxic environment and the general mechanism for the trade-off growth to survival in aging.
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Involvement of IGF binding protein 5 in prostaglandin E(2)-induced cellular senescence in human fibroblasts. Biogerontology 2010; 12:239-52. [PMID: 21191810 DOI: 10.1007/s10522-010-9318-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Accepted: 12/21/2010] [Indexed: 12/25/2022]
Abstract
Inflammation is an underlying basis for the molecular alterations that link aging and age-related pathological processes. In a previous study, we found that secretory phospholipase A(2) (sPLA(2)) induced cellular senescence in human dermal fibroblasts (HDFs). To further investigate the association of inflammation with cellular senescence, the effects of PGE(2) on cellular senescence in HDFs were investigated, since PGE(2) is the most abundant prostanoid. PGE(2) treatment induces cellular senescence, as determined by a decrease in cell proliferation and an increase in senescence-associated β-galactosidase staining. Notably, PGE(2) treatment increased the IGFBP5 protein level. While treatment with PGE(2) antagonists repressed PGE(2)-induced cellular senescence, increasing intracellular cAMP accelerated cellular senescence. Down-regulation of IGFBP5 inhibited PGE(2)-induced cellular senescence. Taken together, these results suggest that PGE(2) may play an important role in controlling cellular senescence of HDFs through the regulation of IGFBP5 and therefore may contribute to inflammatory disorders associated with aging.
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Rhim JH, Jang IS, Kwon ST, Song KY, Yeo EJ, Park SC. Activation of Wound Healing in Aged Rats by Altering the Cellular Mitogenic Potential. J Gerontol A Biol Sci Med Sci 2010; 65:704-11. [DOI: 10.1093/gerona/glq065] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
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Moon EY, Kim HS, Im YS. Gi-protein inhibitor, guanosine 5'-O-(2-thiodiphosphate), induces senescence-associated beta-galactosidase positive cell formation through CREB phosphorylation. Life Sci 2010; 86:683-90. [PMID: 20193693 DOI: 10.1016/j.lfs.2010.02.020] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Revised: 02/06/2010] [Accepted: 02/22/2010] [Indexed: 11/28/2022]
Abstract
AIMS We evaluated Gi-protein inhibitor, guanosine 5'-O-(2-thiodiphosphate)(GOT)-induced senescence-associated(SA)-beta-galactosidase(Gal) positive cell formation to determine if it occurred through phosphorylation of cyclic AMP-dependent response element binding protein (CREB). MAIN METHODS IMR-90 human lung fibroblast cells were used. SA-beta-Gal positive cells and senescence-associated heterochromatic foci (SAHF) were determined by assessing blue color formation of substrate, X-gal inside cells and DAPI staining, respectively. Cell cycle and hypodiploid cell formation were assessed by flow cytometry analysis. CREB phosphorylation and molecular changes were analyzed by western blot. KEY FINDINGS GOT treatment led to SA-beta-Gal positive cell formation and SAHF. CREB phosphorylation increased in response to GOT treatment but then decreased over 24h. SA-beta-Gal positive cell formation increased in response to transient transfection of pS6-RSV-CREB and no changes were detected following CREB knockdown with CREB-siRNA. In addition, CREB phosphorylation was delayed by treatment with the anti-cellular senescence agents, clitocybins which also reduced the number of SA-beta-Gal positive cells. Collectively, our data showed that GOT-induced CREB phosphorylation initiated SA-beta-Gal positive cell formation after which decreased in SA-beta-Gal positive cells. SIGNIFICANCE These findings suggest for the first time that CREB phosphorylation by GOT could induce cellular senescence as judged by SA-beta-Gal positive cell formation.
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Affiliation(s)
- E Y Moon
- Department of Bioscience and Biotechnology, Sejong University, Seoul 143-747, Republic of Korea
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Jeong JH, Cho S, Pak YK. Sterol-independent repression of low density lipoprotein receptor promoter by peroxisome proliferator activated receptor gamma coactivator-1alpha (PGC-1alpha). Exp Mol Med 2009; 41:406-16. [PMID: 19322023 DOI: 10.3858/emm.2009.41.6.046] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Peroxisome proliferator activated receptor (PPAR) gamma coactivator-1alpha (PGC-1alpha) may be implicated in cholesterol metabolism since PGC-1alpha co-activates estrogen receptor alpha (ERalpha) transactivity and estrogen/ERalpha induces the transcription of LDL receptor (LDLR). Here, we show that overexpression of PGC-1alpha in HepG2 cells represses the gene expression of LDLR and does not affect the ERalpha-induced LDLR expression. PGC-1alpha suppressed the LDLR promoter-luciferase (pLR1563- luc) activity regardless of cholesterol or functional sterol-regulatory element-1. Serial deletions of the LDLR promoter revealed that the inhibition by PGC-1alpha required the LDLR promoter regions between -650 bp and -974 bp. Phosphorylation of PGC-1alpha may not affect the suppression of LDLR expression because treatment of SB202190, a p38 MAP kinase inhibitor, did not reverse the LDLR down-regulation by PGC-1alpha. This may be the first report showing the repressive function of PGC-1alpha on gene expression. PGC-1alpha might be a novel modulator of LDLR gene expression in a sterol-independent manner, and implicated in atherogenesis.
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Affiliation(s)
- Jae Hoon Jeong
- Department of Physiology, Kyung Hee University College of MedicineSeoul 130-701, Korea
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Kim DY, Song HJ, Jeong JH, Suh JS, Sohn UD. Regulation of lysophosphatidic acid-induced COX-2 expression by ERK1/2 activation in cultured feline esophageal epithelial Cells. Arch Pharm Res 2008; 31:1331-8. [DOI: 10.1007/s12272-001-2114-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 09/23/2008] [Accepted: 10/06/2008] [Indexed: 11/29/2022]
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Rhim JH, Jang IS, Song KY, Ha MK, Cho SC, Yeo EJ, Park SC. Lysophosphatidic Acid and Adenylyl Cyclase Inhibitor Increase Proliferation of Senescent Human Diploid Fibroblasts by Inhibiting Adenosine Monophosphate-Activated Protein Kinase. Rejuvenation Res 2008; 11:781-92. [DOI: 10.1089/rej.2008.0709] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Affiliation(s)
- Ji-Heon Rhim
- Department of Biochemistry and Molecular Biology, Aging and Apoptosis Research Center, Seoul National University College of Medicine, Seoul, South Korea
| | - Ik-Soon Jang
- Korea Basic Science Institute Gwangju Center, Gwangju, South Korea
| | - Kye-Yong Song
- Department of Pathology, Chung-Ang University College of Medicine, Seoul, South Korea
| | - Moon-Kyung Ha
- Department of Biochemistry and Molecular Biology, Aging and Apoptosis Research Center, Seoul National University College of Medicine, Seoul, South Korea
| | - Sung-Chun Cho
- Department of Biochemistry and Molecular Biology, Aging and Apoptosis Research Center, Seoul National University College of Medicine, Seoul, South Korea
| | - Eui-Ju Yeo
- Department of Biochemistry, Gachon University of Medicine and Science, Incheon, South Korea
| | - Sang Chul Park
- Department of Biochemistry and Molecular Biology, Aging and Apoptosis Research Center, Seoul National University College of Medicine, Seoul, South Korea
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Rhim JH, Jang IS, Yeo EJ, Song KY, Park SC. Role of protein kinase C-dependent A-kinase anchoring proteins in lysophosphatidic acid-induced cAMP signaling in human diploid fibroblasts. Aging Cell 2006; 5:451-61. [PMID: 17081159 DOI: 10.1111/j.1474-9726.2006.00239.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Previously, we reported that lysophosphatidic acid (LPA)-induced adenosine 3',5'-cyclic monophosphate (cAMP) production by human diploid fibroblasts depends on the age of the fibroblasts. In this study, we examined the role of A-kinase anchoring proteins (AKAP) in the regulation of LPA-stimulated cAMP production in senescent fibroblasts. We found that levels of protein kinase C (PKC)-dependent AKAPs, such as Gravin and AKAP79, were elevated in senescent cells. Co-immunoprecipitation experiments revealed that Gravin and AKAP79 do not associate with adenylyl cyclase type 2 (AC2) but bind to AC4/6, which interacts with calcium-dependent PKCs alpha/beta both in young and senescent fibroblasts. When the expression of Gravin and AKAP79 was blocked by small interference RNA transfection, the basal level of cAMP was greatly reduced and the cAMP status after LPA treatment was also reversed. Protein kinase A showed a similar pattern in terms of its basal activity and LPA-dependent modulation. These data suggest that Gravin and to a lesser extent, AKAP79, may play important roles in maintaining the basal AC activity and in coupling the AC systems to inhibitory signals such as Gialpha in young cells, and to stimulatory signals such as PKCs in senescent cells. This study also demonstrates that Gravin is especially important for the long-term activation of PKC by LPA in senescent cells. We conclude that LPA-dependent increased level of cAMP in senescent human diploid fibroblasts is associated with increases in Gravin levels resulting in its increased binding with and activation of calcium-dependent PKC alpha/beta and AC4/6.
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Affiliation(s)
- Ji-Heon Rhim
- Department of Biochemistry and Molecular Biology, Aging and Apoptosis Research Center, Seoul National University College of Medicine, Seoul 110-799, South Korea
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Di Giulio C, Rapino M, Zingariello M, Antonucci A, Cataldi A. PKC alpha-mediated CREB activation is oxygen and age-dependent in rat myocardial tissue. Histochem Cell Biol 2006; 127:327-33. [PMID: 17120015 DOI: 10.1007/s00418-006-0245-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/06/2006] [Indexed: 02/02/2023]
Abstract
Both hypoxia and aging affect the morphology and the function of rat myocardial tissue. Moreover the heart tries to counteract the impaired function by activating specific signalling cascades. Here we report the involvement of CREB protein in "in vivo" response to hypoxic challenge and during aging in rat hearts. CREB is activated in parallel to HIF-1alpha nuclear translocation in the young after hypoxia exposure followed by reoxygenation, while this kind of response is not so dramatic in the old, neither in terms of CREB activation, neither in terms of HIF-1alpha expression and translocation, suggesting in the old the existence of an impaired oxygen-sensing mechanism or an adaptation of the cells to hypoxia. Moreover in the young a PKC alpha/Erk pathway seems to be involved in the activation of HIF-1alpha along with CREB, suggesting an attempt of the young to counteract the damage evoked by hypoxia, while in the old a PKC alpha/p38 MAPK/CREB pathway could determine the occurrence of both aging and aged cell hypoxia response.
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Affiliation(s)
- Camillo Di Giulio
- Dipartimento di Scienze Mediche di Base ed Applicate, Università G. d'Annunzio, Chieti-Pescara, Chieti, Italy
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Abstract
New-onset diabetes mellitus in a previously non-diabetic transplant recipient is a serious adverse event that confers significant morbidity and mortality. The most significant consequences of post-transplant diabetes mellitus (PTDM) in solid organ transplant recipients include decreased patient and graft survival, an increased risk of infectious complications, and morbid cardiovascular events. The development of PTDM in the elderly is of particular concern because this group is already at increased risk of progression of cardiovascular disease. Because the elderly, especially those aged >65 years, are the fastest-growing segment of the renal transplant population, attention needs to be given to PTDM risk reduction and post-transplant management. PTDM develops as a consequence of both impaired insulin production and enhanced peripheral insulin resistance. A number of non-modifiable factors such as age, race, family history, hepatitis C, polycystic kidney disease and emerging genetic causes have been identified as risk factors for PTDM. However, a number of modifiable factors can be targets for intervention in high-risk patients, including bodyweight (through dietary restriction and exercise), hypertension, hyperlipidaemia and the effects of certain immunosuppressive agents. The two agents most responsible for PTDM are tacrolimus and corticosteroids, especially when used in combination. Attempts to modify doses and regimens designed to eliminate or avoid these drugs should be considered. Use of HMG-CoA reductase inhibitors ('statins') and ACE inhibitors is particularly helpful in controlling hypertension and hyperlipidaemia in the elderly because these agents confer protection against future adverse cardiovascular events. Bisphosphonates are also advantageous in controlling the progression of osteoporosis and possible increased risk of bone fractures. Future trials in the elderly should focus on such endpoints as PTDM, post-transplant neoplasia, cardiovascular events and bone fracture events in order to identify the safest regimens that provide the optimal control of rejection while limiting the morbidity from these secondary events.
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Affiliation(s)
- Alain Duclos
- Transplant Center/Glickman Urological Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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