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Li Y, Pan Y, Cao S, Sasaki K, Wang Y, Niu A, Fan X, Wang S, Zhang MZ, Harris RC. Podocyte EGFR Inhibits Autophagy Through Upregulation of Rubicon in Type 2 Diabetic Nephropathy. Diabetes 2021; 70:562-576. [PMID: 33239448 PMCID: PMC7881855 DOI: 10.2337/db20-0660] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/27/2020] [Accepted: 11/17/2020] [Indexed: 02/06/2023]
Abstract
Renal epidermal growth factor receptor (EGFR) signaling is activated in models of diabetic nephropathy (DN), and inhibition of the EGFR signaling pathway protects against the development of DN. We have now determined that in cultured podocytes, high glucose led to increases in activation of EGFR signaling but decreases in autophagy activity as indicated by decreased beclin-1 and inhibition of LC3B autophagosome formation as well as increased rubicon (an autophagy inhibitor) and SQSTM1 (autophagy substrate). Either genetic (small interfering [si]EGFR) or pharmacologic (AG1478) inhibition of EGFR signaling attenuated the decreased autophagy activity. In addition, rubicon siRNA knockdown prevented high glucose-induced inhibition of autophagy in podocytes. We further examined whether selective EGFR deletion in podocytes affected the progression of DN in type 2 diabetes. Selective podocyte EGFR deletion had no effect on body weight or fasting blood sugars in either db/db mice or nos3 -/-; db/db mice, a model of accelerated type 2 DN. However selective podocyte EGFR deletion led to relative podocyte preservation and marked reduction in albuminuria and glomerulosclerosis, renal proinflammatory cytokine/chemokine expression, and decreased profibrotic and fibrotic components in nos3 -/-; db/db mice. Podocyte EGFR deletion led to decreased podocyte expression of rubicon, in association with increased podocyte autophagy activity. Therefore, activation of EGFR signaling in podocytes contributes to progression of DN at least in part by increasing rubicon expression, leading to subsequent autophagy inhibition and podocyte injury.
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Affiliation(s)
- Yan Li
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
- Division of Nephrology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Yu Pan
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
- Division of Nephrology, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shirong Cao
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Kensuke Sasaki
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Yinqiu Wang
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Aolei Niu
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Xiaofeng Fan
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Suwan Wang
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Ming-Zhi Zhang
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
| | - Raymond C Harris
- Division of Nephrology and Hypertension, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Vanderbilt Center for Kidney Disease, Vanderbilt University School of Medicine, Nashville, TN
- Department of Veterans Affairs, Nashville, TN
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Song M, Finley SD. ERK and Akt exhibit distinct signaling responses following stimulation by pro-angiogenic factors. Cell Commun Signal 2020; 18:114. [PMID: 32680529 PMCID: PMC7368799 DOI: 10.1186/s12964-020-00595-w] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2019] [Accepted: 05/11/2020] [Indexed: 02/07/2023] Open
Abstract
Background Angiogenesis plays an important role in the survival of tissues, as blood vessels provide oxygen and nutrients required by the resident cells. Thus, targeting angiogenesis is a prominent strategy in many different settings, including both tissue engineering and cancer treatment. However, not all of the approaches that modulate angiogenesis lead to successful outcomes. Angiogenesis-based therapies primarily target pro-angiogenic factors such as vascular endothelial growth factor-A (VEGF) or fibroblast growth factor (FGF) in isolation, and there is a limited understanding of how these promoters combine together to stimulate angiogenesis. Targeting one pathway could be insufficient, as alternative pathways may compensate, diminishing the overall effect of the treatment strategy. Methods To gain mechanistic insight and identify novel therapeutic strategies, we have developed a detailed mathematical model to quantitatively characterize the crosstalk of FGF and VEGF intracellular signaling. The model focuses on FGF- and VEGF-induced mitogen-activated protein kinase (MAPK) signaling to promote cell proliferation and the phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway, which promotes cell survival and migration. We fit the model to published experimental datasets that measure phosphorylated extracellular regulated kinase (pERK) and Akt (pAkt) upon FGF or VEGF stimulation. We validate the model with separate sets of data. Results We apply the trained and validated mathematical model to characterize the dynamics of pERK and pAkt in response to the mono- and co-stimulation by FGF and VEGF. The model predicts that for certain ranges of ligand concentrations, the maximum pERK level is more responsive to changes in ligand concentration compared to the maximum pAkt level. Also, the combination of FGF and VEGF indicates a greater effect in increasing the maximum pERK compared to the summation of individual effects, which is not seen for maximum pAkt levels. In addition, our model identifies the influential species and kinetic parameters that specifically modulate the pERK and pAkt responses, which represent potential targets for angiogenesis-based therapies. Conclusions Overall, the model predicts the combination effects of FGF and VEGF stimulation on ERK and Akt quantitatively and provides a framework to mechanistically explain experimental results and guide experimental design. Thus, this model can be utilized to study the effects of pro- and anti-angiogenic therapies that particularly target ERK and/or Akt activation upon stimulation with FGF and VEGF. Video Abstract
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Affiliation(s)
- Min Song
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA
| | - Stacey D Finley
- Department of Biomedical Engineering, University of Southern California, Los Angeles, CA, USA. .,Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, CA, USA. .,Department of Biological Sciences, University of Southern California, Los Angeles, CA, USA.
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Fractalkine Regulates HEC-1A/JEG-3 Interaction by Influencing the Expression of Implantation-Related Genes in an In Vitro Co-Culture Model. Int J Mol Sci 2020; 21:ijms21093175. [PMID: 32365902 PMCID: PMC7246682 DOI: 10.3390/ijms21093175] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 04/24/2020] [Accepted: 04/29/2020] [Indexed: 12/15/2022] Open
Abstract
Embryo implantation is a complex process regulated by a network of biological molecules. Recently, it has been described that fractalkine (CX3CL1, FKN) might have an important role in the feto-maternal interaction during gestation since the trophoblast cells express fractalkine receptor (CX3CR1) and the endometrium cells secrete fractalkine. CX3CR1 controls three major signalling pathways, PLC-PKC pathway, PI3K/AKT/NFκB pathway and Ras-mitogen-activated protein kinases (MAPK) pathways regulating proliferation, growth, migration and apoptosis. In this study, we focused on the molecular mechanisms of FKN treatment influencing the expression of implantation-related genes in trophoblast cells (JEG-3) both in mono-and in co-culture models. Our results reveal that FKN acted in a concentration and time dependent manner on JEG-3 cells. FKN seemed to operate as a positive regulator of implantation via changing the action of progesterone receptor (PR), activin receptor and bone morphogenetic protein receptor (BMPR). FKN modified also the expression of matrix metalloproteinase 2 and 9 controlling invasion. The presence of HEC-1A endometrial cells in the co-culture contributed to the effect of fractalkine on JEG-3 cells regulating implantation. The results suggest that FKN may contribute to the successful attachment and implantation of embryo.
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Wang Y, Gao C, Zhang Y, Gao J, Teng F, Tian W, Yang W, Yan Y, Xue F. Visfatin stimulates endometrial cancer cell proliferation via activation of PI3K/Akt and MAPK/ERK1/2 signalling pathways. Gynecol Oncol 2016; 143:168-178. [PMID: 27473926 DOI: 10.1016/j.ygyno.2016.07.109] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 07/18/2016] [Accepted: 07/21/2016] [Indexed: 01/24/2023]
Abstract
OBJECTIVE Endometrial carcinoma is one of the most common malignancies of the female reproductive system, but the aetiology and pathogenesis are not well understood, although adipokines such as visfatin may be involved. Our study provides insight into the mechanism underlying the tumorigenic effects of visfatin in endometrial carcinoma. METHODS We investigated the effect of visfatin on endometrial carcinoma cell proliferation, cell cycle, and apoptosis using well-differentiated Ishikawa cells and poorly differentiated KLE cells. We also assessed the effect of visfatin on tumour growth in vivo. RESULTS Visfatin stimulated the proliferation of both Ishikawa and KLE cells, and visfatin treatment promoted G1/S phase progression and inhibited endometrial carcinoma cell apoptosis. Visfatin promoted endometrial carcinoma tumour growth in BALB/c-nu mice. Transplanted tumour tissues from an endometrial carcinoma mouse model were analysed using immunohistochemical staining, which revealed much stronger positive signals for Ki-67 with over-abundant visfatin. Western blot analysis revealed that insulin receptor (IR), insulin receptor substrate (IRS)1/2 and key components of the phosphoinositide 3-kinase (PI3K)/AKT and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK)1/2 signalling pathways were highly expressed in endometrial carcinoma cells exposed to visfatin. Treated cells showed increased C-MYC and cyclin D1 and reduced caspase-3 expression. The effects of visfatin on proliferation and apoptosis were abrogated by treatment with the PI3K inhibitor LY294002 and MEK inhibitor U0126. CONCLUSIONS Visfatin promotes the malignant progression of endometrial carcinoma via activation of IR and PI3K/Akt and MAPK/ERK signalling. Visfatin may serve as a therapeutic target in the treatment of endometrial carcinoma.
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Affiliation(s)
- Yingmei Wang
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Chao Gao
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Yanfang Zhang
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Jinping Gao
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Fei Teng
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Wenyan Tian
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Wen Yang
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Ye Yan
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China
| | - Fengxia Xue
- Department of Gynecology and Obstetrics, Tianjin Medical University General Hospital, Tianjin, China.
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Cheng Q, Dong W, Qian L, Wu J, Peng Y. Visfatin inhibits apoptosis of pancreatic β-cell line, MIN6, via the mitogen-activated protein kinase/phosphoinositide 3-kinase pathway. J Mol Endocrinol 2011; 47:13-21. [PMID: 21471274 DOI: 10.1530/jme-10-0106] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Visfatin is an adipocytokine that plays an important role in attenuating insulin resistance by binding to insulin receptor. It has been suggested that visfatin plays a role in the regulation of cell apoptosis and inflammation by an as yet unidentified mechanism. This study investigated the protective effects of visfatin on palmitate-induced islet β-cell apoptosis in the clonal mouse pancreatic β-cell line MIN6. The cells were treated with palmitate and/or recombinant visfatin. An 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan assay was used to detect cell proliferation, V-FITC/propidium iodide staining was used to measure cell apoptosis and necrosis, and western blot analysis was used to detect the expression of proapoptotic proteins. The incubation of the cells with visfatin led to a concentration-dependent increase of cell proliferation (1.55-fold at 10(-7) M and 24 h compared with control, P<0.05). Visfatin significantly reduced the cell apoptosis induced by palmitate and caused a significant change in the expression of several proapoptotic proteins, including upregulation of Bcl-2 and a marked downregulation of cytochrome c and caspase 3. Visfatin also activated the ERK1/2 and the phosphoinositide 3-kinase (PI3K)/AKT signaling pathways in a time- and concentration-dependent manner, and the effect of visfatin on apoptosis was blocked by the specific ERK1/2 and PI3K/AKT inhibitors, PD098059 and LY294002. We conclude that visfatin can increase β-cell proliferation and prevent apoptosis, activate intracellular signaling, and regulate the expression of proapoptotic proteins. The antiapoptotic action of visfatin is mediated by activation of mitogen-activated protein kinase-dependent and PI3K-dependent signaling pathways.
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Affiliation(s)
- Qun Cheng
- Diabetes Research Laboratory, Department of Endocrinology and Metabolism, Shanghai Jiaotong University Affiliated First People's Hospital, 100 Hainin Road, Shanghai 200080, People's Republic of China
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Low-level laser therapy (LLLT; 780 nm) acts differently on mRNA expression of anti- and pro-inflammatory mediators in an experimental model of collagenase-induced tendinitis in rat. Lasers Med Sci 2010; 26:85-94. [PMID: 20737183 DOI: 10.1007/s10103-010-0811-z] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Accepted: 06/24/2010] [Indexed: 12/15/2022]
Abstract
Low-level laser therapy (LLLT) has been found to produce anti-inflammatory effects in a variety of disorders. Tendinopathies are directly related to unbalance in expression of pro- and anti-inflammatory cytokines which are responsible by degeneration process of tendinocytes. In the current study, we decided to investigate if LLLT could reduce mRNA expression for TNF-α, IL-1β, IL-6, TGF-β cytokines, and COX-2 enzyme. Forty-two male Wistar rats were divided randomly in seven groups, and tendinitis was induced with a collagenase intratendinea injection. The mRNA expression was evaluated by real-time PCR in 7th and 14th days after tendinitis. LLLT irradiation with wavelength of 780 nm required for 75 s with a dose of 7.7 J/cm(2) was administered in distinct moments: 12 h and 7 days post tendinitis. At the 12 h after tendinitis, the animals were irradiated once in intercalate days until the 7th or 14th day in and them the animals were killed, respectively. In other series, 7 days after tendinitis, the animals were irradiated once in intercalated days until the 14th day and then the animals were killed. LLLT in both acute and chronic phases decreased IL-6, COX-2, and TGF-β expression after tendinitis, respectively, when compared to tendinitis groups: IL-6, COX-2, and TGF-β. The LLLT not altered IL-1β expression in any time, but reduced the TNF-α expression; however, only at chronic phase. We conclude that LLLT administered with this protocol reduces one of features of tendinopathies that is mRNA expression for pro-inflammatory mediators.
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IGF-I regulates tight-junction protein claudin-1 during differentiation of osteoblast-like MC3T3-E1 cells via a MAP-kinase pathway. Cell Tissue Res 2008; 334:243-54. [PMID: 18855015 DOI: 10.1007/s00441-008-0690-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Accepted: 08/27/2008] [Indexed: 12/18/2022]
Abstract
Insulin-like growth factor I (IGF-I) is expressed in many tissues, including bone, and acts on the proliferation and differentiation of osteoblasts as an autocrine/paracrine regulator. Tight-junction proteins have been detected in osteoblasts, and direct cell-to-cell interactions may modulate osteoblast function with respect, for example, to gap junctions. In order to investigate the regulation of expression of tight-junction molecules and of function during bone differentiation, osteoblast-like MC3T3-E1 cells and osteocyte-like MLO-Y4 cells were treated with IGF-I. In both MC3T3-E1 cells and MLO-Y4 cells, the tight-junction molecules occludin, claudin-1, -2, and -6, and the gap-junction molecule connexin 43 (Cx43) were detected by reverse transcription with polymerase chain reaction. In MC3T3-E1 cells but not MLO-Y4 cells, mRNAs of claudin-1, -2, and -6, Cx43, and type I collagen, and proteins of claudin-1 and Cx43 were increased after treatment with IGF-I. Such treatment significantly decreased paracellular permeability in MC3T3-E1 cells. The expression of claudin-1 in MC3T3-E1 cells after IGF-I treatment was mainly upregulated via a mitogen-activated protein (MAP)-kinase pathway and, in part, modulated by a PI3-kinase pathway, whereas Cx43 expression and the mediated gap-junctional intercellular communication protein did not contribute to the upregulation. Furthermore, in MC3T3-E1 cells during wound healing, upregulation of claudin-1 was observed together with an increase of IGF-I and type I collagen. These findings suggest that the induction of tight-junction protein claudin-1 and paracellular permeability during the differentiation of osteoblast-like MC3T3-E1 cells after treatment with IGF-I is regulated via a MAP-kinase pathway, but not with respect to gap junctions.
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Terashima M, Takahashi M, Shimoyama M, Tanigawa Y, Urano T, Tsuchiya M. Glycosylphosphatidylinositol-anchored arginine-specific ADP-ribosyltransferase7.1 (Art7.1) on chicken B cells: the possible role of Art7 in B cell receptor signalling and proliferation. Mol Cell Biochem 2008; 320:93-100. [DOI: 10.1007/s11010-008-9902-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Accepted: 07/25/2008] [Indexed: 11/28/2022]
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Phosphoinositide 3-kinase inhibitors protect mouse kidney cells from cyclosporine-induced cell death. Kidney Int 2008; 73:77-85. [DOI: 10.1038/sj.ki.5002638] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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Li Y, Chan EY, Katze MG. Functional genomics analyses of differential macaque peripheral blood mononuclear cell infections by human immunodeficiency virus-1 and simian immunodeficiency virus. Virology 2007; 366:137-49. [PMID: 17507074 PMCID: PMC2082051 DOI: 10.1016/j.virol.2007.04.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Revised: 03/23/2007] [Accepted: 04/05/2007] [Indexed: 11/28/2022]
Abstract
The pathogenicity of the primate lentiviruses, human, and simian immunodeficiency viruses, is host-specific. Previous studies indicated that the highly pathogenic human lentivirus HIV-1 has markedly reduced pathogenicity compared to the pathogenic simian lentivirus SIV in pigtail macaques (Macaca nemestrina). We therefore hypothesized that the pigtail macaque peripheral blood mononuclear cells (mPBMCs) would respond differently to infections of HIV-1 and pathogenic SIV. To elucidate the cellular responses to the infections of HIV-1 and SIV, we infected mPBMC with these two viruses. Like infections in vivo, HIV-1 and SIV demonstrated distinct replication kinetics in mPBMCs, with HIV-1 replicating at significantly lower levels. Similarly, gene expression profiling facilitated by macaque-specific oligonucleotide microarrays also revealed distinct expression patterns of genes between the HIV-1- and SIV-infected mPBMCs; in particular, genes associated with the antigen presentation, T cell receptor, ERK/MAPK signaling, Wnt/beta-catenin signaling, and natural killer cell signaling pathways were differentially regulated between these two viruses. Most interestingly, despite the lower levels of replication, HIV-1 triggered a more robust regulation of immune response genes early after infection; the converse was true in SIV-infected mPBMCs. Our results therefore suggest that macaques may be controlling the infection of HIV-1 at an early stage through coordinated regulation of host defense pathways.
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Affiliation(s)
- Yu Li
- Department of Microbiology and Washington National Primate Research Center, University of Washington, Box 358070, Seattle, WA 98195-8070, USA
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Scott A, Cook JL, Hart DA, Walker DC, Duronio V, Khan KM. Tenocyte responses to mechanical loading in vivo: a role for local insulin-like growth factor 1 signaling in early tendinosis in rats. ACTA ACUST UNITED AC 2007; 56:871-81. [PMID: 17328060 DOI: 10.1002/art.22426] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE To investigate tenocyte regulatory events during the development of overuse supraspinatus tendinosis in rats. METHODS Supraspinatus tendinosis was induced by running rats downhill at 1 km/hour for 1 hour a day. Tendons were harvested at 4, 8, 12, and 16 weeks and processed for brightfield, polarized light, or transmission electron microscopy. The development of tendinosis was assessed semiquantitatively using a modified Bonar histopathologic scale. Apoptosis and proliferation were examined using antibodies against fragmented DNA or proliferating cell nuclear antigen, respectively. Insulin-like growth factor 1 (IGF-1) expression was determined by computer-assisted quantification of immunohistochemical reaction. Local IGF-1 signaling was probed using antibodies to phosphorylated insulin receptor substrate 1 (IRS-1) and ERK-1/2. RESULTS Tendinosis was present after 12 weeks of downhill running and was characterized by tenocyte rounding and proliferation as well as by glycosaminoglycan accumulation and collagen fragmentation. The proliferation index was elevated in CD90+ tenocytes in association with tendinosis and correlated with increased local IGF-1 expression by tenocytes and phosphorylation of IRS-1 and ERK-1/2. Both apoptosis and cellular inflammation were absent at all time points. CONCLUSION In this animal model, early tendinosis was associated with local stimulation of tenocytes rather than with extrinsic inflammation or apoptosis. Our data suggest a role for IGF-1 in the load-induced tenocyte responses during the pathogenesis of overuse tendon disorders.
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Affiliation(s)
- Alexander Scott
- University of British Columbia, Vancouver, British Columbia, Canada
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Lian Ø, Scott A, Engebretsen L, Bahr R, Duronio V, Khan K. Excessive apoptosis in patellar tendinopathy in athletes. Am J Sports Med 2007; 35:605-11. [PMID: 17244903 DOI: 10.1177/0363546506295702] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BACKGROUND The pathogenesis of tendon overuse injuries is poorly understood. The histopathology underlying tendinopathy at various anatomical locations is similar and may reflect a common pathologic process. HYPOTHESIS Apoptosis contributes to the pathophysiology in patellar tendinopathy. STUDY DESIGN Case control study; Level of evidence, 3. METHODS We compared biopsy specimens from the patellar tendon in patients with patellar tendinopathy diagnosed clinically and with typical magnetic resonance image findings with biopsy specimens from a control group without any previous or current knee complaints to suggest patellar tendinopathy. The presence of apoptosis was examined with immunohistochemical methods using a polyclonal antibody recognizing active caspase-3, confirmed by labeling DNA strand breaks (F7-26 antibody) and nuclear morphology (fragmentation and condensation). RESULTS The number of apoptotic cells per unit area (4.5 mm(2)) was 0.91 +/- 0.81 (SD) in tendinopathic samples and 0.21 +/- 0.21 in controls (P = .026). Although the tendinopathic samples displayed increased cellularity (average 162.5 nuclei/mm(2) vs 98.9 nuclei/mm(2)), the apoptotic index was higher (0.42% vs 0.17%, P = .014). CONCLUSION Increased apoptotic cell death is a feature of patellar tendinosis. The role of apoptosis within the broader framework and time course of tendon overuse injury remains to be established.
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Affiliation(s)
- Øystein Lian
- Oslo Sport Trauma Research Center, Department of Sports Medicine, Norwegian School of Sport Sciences, Ullevål Stadion, Oslo, Norway.
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Bitko V, Shulyayeva O, Mazumder B, Musiyenko A, Ramaswamy M, Look DC, Barik S. Nonstructural proteins of respiratory syncytial virus suppress premature apoptosis by an NF-kappaB-dependent, interferon-independent mechanism and facilitate virus growth. J Virol 2006; 81:1786-95. [PMID: 17151097 PMCID: PMC1797585 DOI: 10.1128/jvi.01420-06] [Citation(s) in RCA: 128] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The two nonstructural (NS) proteins NS1 and NS2 of respiratory syncytial virus (RSV) are abundantly expressed in the infected cell but are not packaged in mature progeny virions. We found that both proteins were expressed early in infection, whereas the infected cells underwent apoptosis much later. Coincident with NS protein expression, a number of cellular antiapoptotic factors were expressed or activated at early stages, which included NF-kappaB and phosphorylated forms of protein kinases AKT, phosphoinositide-dependent protein kinase, and glycogen synthase kinase. Using specific short interfering RNAs (siRNAs), we achieved significant knockdown of one or both NS proteins in the infected cell, which resulted in abrogation of the antiapoptotic functions and led to early apoptosis. NS-dependent suppression of apoptosis was observed in Vero cells that are naturally devoid of type I interferons (IFN). The siRNA-based results were confirmed by the use of NS-deleted RSV mutants. Early activation of epidermal growth factor receptor (EGFR) in the RSV-infected cell did not require NS proteins. Premature apoptosis triggered by the loss of NS or by apoptosis-promoting drugs caused a severe reduction of RSV growth. Finally, recombinantly expressed NS1 and NS2, individually and together, reduced apoptosis by tumor necrosis factor alpha, suggesting an intrinsic antiapoptotic property of both. We conclude that the early-expressed nonstructural proteins of RSV boost viral replication by delaying the apoptosis of the infected cell via a novel IFN- and EGFR-independent pathway.
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Affiliation(s)
- Vira Bitko
- Department of Biochemistry and Molecular Biology, University of South Alabama, College of Medicine, 307 University Blvd., Mobile, AL 36688-0002, USA
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Xu D, Guthrie JR, Mabry S, Sack TM, Truog WE. Mitochondrial aldehyde dehydrogenase attenuates hyperoxia-induced cell death through activation of ERK/MAPK and PI3K-Akt pathways in lung epithelial cells. Am J Physiol Lung Cell Mol Physiol 2006; 291:L966-75. [PMID: 16782756 DOI: 10.1152/ajplung.00045.2006] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Oxygen toxicity is one of the major risk factors in the development of the chronic lung disease or bronchopulmonary dysplasia in premature infants. Using proteomic analysis, we discovered that mitochondrial aldehyde dehydrogenase (mtALDH or ALDH2) was downregulated in neonatal rat lung after hyperoxic exposure. To study the role of mtALDH in hyperoxic lung injury, we overexpressed mtALDH in human lung epithelial cells (A549) and found that mtALDH significantly reduced hyperoxia-induced cell death. Compared with control cells (Neo-A549), the necrotic cell death in mtALDH-overexpressing cells (mtALDH-A549) decreased from 25.3 to 6.5%, 50.5 to 9.1%, and 52.4 to 15.1% after 24-, 48-, and 72-h hyperoxic exposure, respectively. The levels of intracellular and mitochondria-derived reactive oxygen species (ROS) in mtALDH-A549 cells after hyperoxic exposure were significantly lowered compared with Neo-A549 cells. mtALDH overexpression significantly stimulated extracellular signal-regulated kinase (ERK) phosphorylation under normoxic and hyperoxic conditions. Inhibition of ERK phosphorylation partially eliminated the protective effect of mtALDH in hyperoxia-induced cell death, suggesting ERK activation by mtALDH conferred cellular resistance to hyperoxia. mtALDH overexpression augmented Akt phosphorylation and maintained the total Akt level in mtALDH-A549 cells under normoxic and hyperoxic conditions. Inhibition of phosphatidylinositol 3-kinase (PI3K) activation by LY294002 in mtALDH-A549 cells significantly increased necrotic cell death after hyperoxic exposure, indicating that PI3K-Akt activation by mtALDH played an important role in cell survival after hyperoxia. Taken together, these data demonstrate that mtALDH overexpression attenuates hyperoxia-induced cell death in lung epithelial cells through reduction of ROS, activation of ERK/MAPK, and PI3K-Akt cell survival signaling pathways.
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Affiliation(s)
- Dong Xu
- Neonatology Research Laboratory, Children's Mercy Hospital, Pediatric Research Center, 4th Floor, 2401 Gillham Rd., Kansas City, MO 64108, USA.
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Fitau J, Boulday G, Coulon F, Quillard T, Charreau B. The adaptor molecule Lnk negatively regulates tumor necrosis factor-alpha-dependent VCAM-1 expression in endothelial cells through inhibition of the ERK1 and -2 pathways. J Biol Chem 2006; 281:20148-59. [PMID: 16644735 DOI: 10.1074/jbc.m510997200] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Lnk, with APS and SH2-B (Src homology 2-B), belongs to a family of SH2-containing proteins with potential adaptor functions. Lnk regulates growth factor and cytokine receptor-mediated pathways implicated in lymphoid, myeloid, and platelet homeostasis. We have previously shown that Lnk is expressed and up-regulated in vascular endothelial cells (ECs) in response to tumor necrosis factor-alpha (TNFalpha). In this study, we have shown that, in ECs, Lnk down-regulates the expression, at both mRNA and protein levels, of the proinflammatory molecules VCAM-1 and E-selectin induced by TNFalpha. Mechanistically, our data indicated that, in response to TNFalpha, NFkappaB/p65 phosphorylation and translocation as well as IkappaBalpha phosphorylation and degradation were unchanged, suggesting that Lnk does not modulate NFkappaB activity. However, Lnk activates phosphatidylinositol 3-kinase (PI3K) as reflected by Akt phosphorylation. Our results identify endothelial nitric-oxide synthase as a downstream target of Lnk-mediated activation of the PI3K/Akt pathway and HO-1 as a new substrate of Akt. We found that sustained Lnk-mediated activation of PI3K in TNFalpha-activated ECs correlated with the inhibition of ERK1/2 phosphorylation, whereas phosphorylation of p38 and c-Jun NH(2)-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs) was unchanged. ERK1/2 inhibition decreases VCAM-1 expression in TNFalpha-treated ECs. Collectively, our results identify the adaptor Lnk as a negative regulator in the TNFalpha-signaling pathway mediating ERK inhibition and suggest a role for Lnk in the interplay between PI3K and ERK triggered by TNFalpha in ECs.
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