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Jepsen-Grant K, Pollard RE, Johnson LR. Vertebral heart scores in eight dog breeds. Vet Radiol Ultrasound 2012; 54:3-8. [PMID: 22994206 DOI: 10.1111/j.1740-8261.2012.01976.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 07/13/2012] [Indexed: 11/29/2022] Open
Abstract
The vertebral heart score (VHS) measurement is commonly used to provide a more objective measurement of cardiomegaly in canines. However, several studies have shown significant breed variations from the value previously established by Buchanan and Bücheler (9.7 ± 0.5). This study describes VHS measurements in Pug, Pomeranian, Yorkshire Terrier, Dachshund, Bulldog, Shih Tzu, Lhasa Apso, and Boston Terrier dog breeds. Dogs with two or three view thoracic radiographs, no subjective radiographic evidence of cardiomegaly, and no physical examination findings of heart murmurs or gallop rhythms were included in the study. The Pug, Pomeranian, Bulldog, and Boston Terrier groups were found to have a VHS significantly greater than 9.7 ± 0.5 (P < 0.00001, P = 0.0014, P < 0.0001, P < 0.00001, respectively). Body condition score (BCS) was found to have a significant effect on the VHS of Lhasa Apso group. Anomalous vertebrae in the thoracic column were associated with a significant increase in VHS of the Bulldog (P = 0.028) and Boston Terrier (P = 0.0004) groups. Thoracic depth to width ratio did not have a significant effect on VHS.
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Alman AC, Johnson LR, Calverley DC, Grunwald GK, Lezotte DC, Hokanson JE. Diagnostic capabilities of fractal dimension and mandibular cortical width to identify men and women with decreased bone mineral density. Osteoporos Int 2012; 23:1631-6. [PMID: 21633828 DOI: 10.1007/s00198-011-1678-y] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 03/30/2011] [Indexed: 10/18/2022]
Abstract
UNLABELLED Dental panoramic radiographs could be used to screen for osteopenia. We found the fractal dimension to be a good discriminator of osteopenia in both men and women but that the mandibular cortical width (MCW) did not perform as well in men. The fractal dimension may be a valid screening tool. INTRODUCTION The aim of this study was to assess the diagnostic capability of the fractal dimension and MCW measured from dental panoramic radiographs in identifying men and women with decreased bone mineral density (BMD). METHODS The MCW and fractal dimension were measured from dental panoramic radiographs as surrogates for BMD. These measures were then compared to the results from dual-energy X-ray absorptiometry (DXA) performed for clinical purposes. A total of 56 subjects with the panoramic radiograph taken within 6 months of the DXA exam were used in the analysis for this study. RESULTS The area under the curve of the fractal dimension for identifying low BMD (T-score <-1.0) was 0.81 (0.67, 0.95) and 0.78 (0.49, 1.00) for men and women, respectively. For the MCW, the area under the curve was found to be 0.53 (0.34, 0.72) and 0.80 (0.58, 1.00) for men and women, respectively. CONCLUSIONS In this largely male study population, the fractal dimension was found to be a good discriminator of low BMD in both men and women. The MCW did not perform as well in men.
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Ray RM, Li C, Bhattacharya S, Naren AP, Johnson LR. Spermine, a molecular switch regulating EGFR, integrin β3, Src, and FAK scaffolding. Cell Signal 2012; 24:931-42. [PMID: 22227249 PMCID: PMC3334284 DOI: 10.1016/j.cellsig.2011.12.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2011] [Accepted: 12/19/2011] [Indexed: 12/21/2022]
Abstract
Intracellular polyamine levels are highly regulated by the activity of ornithine decarboxylase (ODC), which catalyzes the first rate-limiting reaction in polyamine biosynthesis, producing putrescine, which is subsequently converted to spermidine and spermine. We have shown that polyamines regulate proliferation, migration, and apoptosis in intestinal epithelial cells. Polyamines regulate key signaling events at the level of the EGFR and Src. However, the precise mechanism of action of polyamines is unknown. In the present study, we demonstrate that ODC localizes in lamellipodia and in adhesion plaques during cell spreading. Spermine regulates EGF-induced migration by modulating the interaction of the EGFR with Src. The EGFR interacted with integrin β3, Src, and focal adhesion kinase (FAK). Active Src (pY418-Src) localized with FAK during spreading and migration. Spermine prevented EGF-induced binding of the EGFR with integrin β3, Src, and FAK. Activation of Src and FAK was necessary for EGF-induced migration in HEK293 cells. EGFR-mediated Src activation in live HEK293 cells using a FRET based Src reporter showed that polyamine depletion significantly increased Src kinase activity. In vitro binding studies showed that spermine directly binds Src, and preferentially interacts with the SH2 domain of Src. The physical interaction between Src and the EGFR was severely attenuated by spermine. Therefore, spermine acts as a molecular switch in regulating EGFR-Src coupling both physically and functionally. Upon activation of the EGFR, integrin β3, FAK and Src are recruited to EGFR leading to the trans-activation of both the EGFR and Src and to the Src-mediated phosphorylation of FAK. The activation of FAK induced Rho-GTPases and subsequently migration. This is the first study to define mechanistically how polyamines modulate Src function at the molecular level.
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Ray RM, Viar MJ, Johnson LR. Amino acids regulate expression of antizyme-1 to modulate ornithine decarboxylase activity. J Biol Chem 2011; 287:3674-90. [PMID: 22157018 DOI: 10.1074/jbc.m111.232561] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In a glucose-salt solution (Earle's balanced salt solution), asparagine (Asn) stimulates ornithine decarboxylase (ODC) activity in a dose-dependent manner, and the addition of epidermal growth factor (EGF) potentiates the effect of Asn. However, EGF alone fails to activate ODC. Thus, the mechanism by which Asn activates ODC is important for understanding the regulation of ODC activity. Asn reduced antizyme-1 (AZ1) mRNA and protein. Among the amino acids tested, Asn and glutamine (Gln) effectively inhibited AZ1 expression, suggesting a differential role for amino acids in the regulation of ODC activity. Asn decreased the putrescine-induced AZ1 translation. The absence of amino acids increased the binding of eukaryotic initiation factor 4E-binding protein (4EBP1) to 5'-mRNA cap and thereby inhibited global protein synthesis. Asn failed to prevent the binding of 4EBP1 to mRNA, and the bound 4EBP1 was unphosphorylated, suggesting the involvement of the mammalian target of rapamycin (mTOR) in the regulation of AZ1 synthesis. Rapamycin treatment (4 h) failed to alter the expression of AZ1. However, extending the treatment (24 h) allowed expression in the presence of amino acids, indicating that AZ1 is expressed when TORC1 signaling is decreased. This suggests the involvement of cap-independent translation. However, transient inhibition of mTORC2 by PP242 completely abolished the phosphorylation of 4EBP1 and decreased basal as well as putrescine-induced AZ1 expression. Asn decreased the phosphorylation of mTOR-Ser(2448) and AKT-Ser(473), suggesting the inhibition of mTORC2. In the absence of amino acids, mTORC1 is inhibited, whereas mTORC2 is activated, leading to the inhibition of global protein synthesis and increased AZ1 synthesis via a cap-independent mechanism.
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Ray RM, Bhattacharya S, Johnson LR. Mdm2 inhibition induces apoptosis in p53 deficient human colon cancer cells by activating p73- and E2F1-mediated expression of PUMA and Siva-1. Apoptosis 2011; 16:35-44. [PMID: 20812030 DOI: 10.1007/s10495-010-0538-0] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Camptothecin (CPT) and Nutlin-3 caused apoptosis by increasing p53 protein and its activation in intestinal epithelial cells (IEC-6). We studied the effectiveness of these inducers on apoptosis in human colon cancer cells (Caco2) lacking p53 expression. CPT failed to activate caspase-3 and cause apoptosis in these cells. The absence of p53 expression, higher basal Bcl-xL and lower Bax proteins prevented CPT-induced apoptosis. However, the Mdm2 antagonist Nutlin-3 induced apoptosis in a dose dependent manner by activating caspases-9 and -3. Nutlin-3 prevented the activation of AKT via PTEN-mediated inhibition of the PI3K pathway. Nutlin-3 increased the phosphorylation of retinoblastoma protein causing E2F1 release leading to induction of Siva-1. Nutlin-3-mediated degradation of Mdm2 caused the accumulation of p73, which induced the expression of p53 up-regulated modulator of apoptosis (PUMA). E2F1 and p73 knockdown decreased the expression of Siva and PUMA, respectively and abolished Nutlin-3-induced caspase-3 activation. Cycloheximide (CHX) inhibited Nutlin-3-induced Siva, Noxa, and PUMA expression and inhibited apoptosis in IEC-6 and Caco2 cells. These results indicate that translation of mRNAs induced by Nutlin-3 is critical for apoptosis. In summary, apoptosis in Caco2 cells lacking functional p53 occurred following the disruption of Mdm2 binding with p73 and Rb leading to the expression of pro-apoptotic proteins, PUMA, Noxa, and Siva-1.
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Ray RM, Bavaria MN, Bhattacharya S, Johnson LR. Activation of Dbl restores migration in polyamine-depleted intestinal epithelial cells via Rho-GTPases. Am J Physiol Gastrointest Liver Physiol 2011; 300:G988-97. [PMID: 21372162 PMCID: PMC3119111 DOI: 10.1152/ajpgi.00409.2010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Integrin binding to the extracellular matrix (ECM) activated Rho GTPases, Src, and focal adhesion kinase in intestinal epithelial cells (IEC)-6. Polyamine depletion inhibited activities of Rac1, RhoA, and Cdc42 and thereby migration. However, constitutively active (CA) Rac1 expression abolished the inhibitory effect of polyamine depletion, indicating that polyamines are involved in a process upstream of Rac1. In the present study, we examined the role of polyamines in the regulation of the guanine nucleotide exchange factor, diffuse B-cell lymphoma (Dbl), for Rho GTPases. Polyamine depletion decreased the level as well as the activation of Dbl protein. Dbl knockdown by siRNA altered cytoskeletal structure and decreased Rac1 activity and migration. Cells expressing CA-Dbl increased migration, Rac1 activity, and proliferation. CA-Dbl restored migration in polyamine-depleted cells by activating RhoA, Rac1, and Cdc42. CA-Dbl caused extensive reorganization of the F-actin cortex into stress fibers. Inhibition of Rac1 by NSC23766 significantly decreased migration of vector-transfected cells and CA-Dbl-transfected cells. However, the inhibition of migration was significantly higher in the vector-transfected cells compared with that seen in the CA-Dbl-transfected cells. Dbl localized in the perinuclear region in polyamine-depleted cells, whereas it localized with the stress fibers in control cells. CA-Dbl localized with stress fibers in both the control and polyamine-depleted cells. These results suggest that polyamines regulate the activation of Dbl, a membrane-proximal process upstream of Rac1.
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Ray RM, Jin S, Bavaria MN, Johnson LR. Regulation of JNK activity in the apoptotic response of intestinal epithelial cells. Am J Physiol Gastrointest Liver Physiol 2011; 300:G761-70. [PMID: 21350193 PMCID: PMC3094148 DOI: 10.1152/ajpgi.00405.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
We have studied apoptosis of gastrointestinal epithelial cells by examining the receptor-mediated and DNA damage-induced pathways using TNF-α and camptothecin (CPT), respectively. TNF-α requires inhibition of antiapoptotic protein synthesis by cycloheximide (CHX). CHX also results in high levels of active JNK, which are necessary for TNF-induced apoptosis. While CPT induces apoptosis, the increase in JNK activity was not proportional to the degree of apoptosis. Thus the mechanism of activation of JNK and its role in apoptosis are unclear. We examined the course of JNK activation in response to a combination of TNF-α and CPT (TNF + CPT), which resulted in a three- to fourfold increase in apoptosis compared with CPT alone, indicating an amplification of apoptotic signaling pathways. TNF + CPT caused apoptosis by activating JNK, p38, and caspases-8, -9, and -3. TNF-α stimulated a transient phosphorylation of JNK1/2 and ERK1/2 at 15 min, which returned to basal by 60 min and remained low for 4 h. CPT increased JNK1/2 activity between 3 and 4 h. TNF + CPT caused a sustained and robust JNK1/2 and ERK1/2 phosphorylation by 2 h, which remained high at 4 h, suggesting involvement of MEKK4/7 and MEK1, respectively. When administered with TNF + CPT, SP-600125, a specific inhibitor of MEKK4/7, completely inhibited JNK1/2 and decreased apoptosis. However, administration of SP-600125 at 1 h after TNF + CPT failed to prevent JNK1/2 phosphorylation, and the protective effect of SP-600125 on apoptosis was abolished. These results indicate that the persistent activation of JNK might be due to inhibition of JNK-specific MAPK phosphatase 1 (MKP1). Small interfering RNA-mediated knockdown of MKP1 enhanced TNF + CPT-induced activity of JNK1/2 and caspases-9 and -3. Taken together, these results suggest that MKP1 activity determines the duration of JNK1/2 and p38 activation and, thereby, apoptosis in response to TNF + CPT.
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Bhattacharya S, Ray RM, Chaum E, Johnson DA, Johnson LR. Inhibition of Mdm2 sensitizes human retinal pigment epithelial cells to apoptosis. Invest Ophthalmol Vis Sci 2011; 52:3368-80. [PMID: 21345989 DOI: 10.1167/iovs.10-6991] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
PURPOSE Because recent studies indicate that blocking the interaction between p53 and Mdm2 results in the nongenotoxic activation of p53, the authors sought to investigate whether the inhibition of p53-Mdm2 binding activates p53 and sensitizes human retinal epithelial cells to apoptosis. METHODS Apoptosis was evaluated by the activation of caspases and DNA fragmentation assays. The Mdm2 antagonist Nutlin-3 was used to dissociate p53 from Mdm2 and, thus, to increase p53 activity. Knockdown of p53 expression was accomplished by using p53 siRNA. RESULTS ARPE-19 and primary RPE cells expressed high levels of the antiapoptotic proteins Bcl-2 and Bcl-xL. Exposure of these cells to camptothecin (CPT) or TNF-α/ cycloheximide (CHX) failed to induce apoptosis. In contrast, treatment with the Mdm2 antagonist Nutlin-3 in the absence of CPT or TNF-α/CHX increased apoptosis. Activation of p53 in response to Nutlin-3 also increased levels of Noxa, p53-upregulated modulator of apoptosis (PUMA), and Siva-1, decreased expression of Bcl-2 and Bcl-xL, and simultaneously increased caspases-9 and -3 activities and DNA fragmentation. Knockdown of p53 decreased the basal expression of p21Cip1 and Bcl-2, inhibited the Nutlin-3-induced upregulation of Siva-1 and PUMA expression, and consequently inhibited caspase-3 activation. CONCLUSIONS These results indicate that the normally available pool of intracellular p53 is predominantly engaged in the regulation of cell cycle checkpoints by p21Cip1 and does not trigger apoptosis in response to DNA-damaging agents. However, the blockage of p53 binding to Mdm2 frees a pool of p53 that is sufficient, even in the absence of DNA-damaging agents, to increase the expression of proapoptotic targets and to override the resistance of RPE cells to apoptosis.
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Ray RM, Bavaria MN, Bhattacharya S, Johnson LR. Polyamine dependent activation of Dbl Restores Migration via Rho‐GTPases. FASEB J 2011. [DOI: 10.1096/fasebj.25.1_supplement.1120.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Johnson LR, Sharp ZD, Galewsky J, Strong M, Van Pelt AD, Dong F, Noone D. Hydrogen isotope correction for laser instrument measurement bias at low water vapor concentration using conventional isotope analyses: application to measurements from Mauna Loa Observatory, Hawaii. RAPID COMMUNICATIONS IN MASS SPECTROMETRY : RCM 2011; 25:608-616. [PMID: 21290447 DOI: 10.1002/rcm.4894] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The hydrogen and oxygen isotope ratios of water vapor can be measured with commercially available laser spectroscopy analyzers in real time. Operation of the laser systems in relatively dry air is difficult because measurements are non-linear as a function of humidity at low water concentrations. Here we use field-based sampling coupled with traditional mass spectrometry techniques for assessing linearity and calibrating laser spectroscopy systems at low water vapor concentrations. Air samples are collected in an evacuated 2 L glass flask and the water is separated from the non-condensable gases cryogenically. Approximately 2 µL of water are reduced to H(2) gas and measured on an isotope ratio mass spectrometer. In a field experiment at the Mauna Loa Observatory (MLO), we ran Picarro and Los Gatos Research (LGR) laser analyzers for a period of 25 days in addition to periodic sample collection in evacuated flasks. When the two laser systems are corrected to the flask data, they are strongly coincident over the entire 25 days. The δ(2)H values were found to change by over 200‰ over 2.5 min as the boundary layer elevation changed relative to MLO. The δ(2)H values ranged from -106 to -332‰, and the δ(18)O values (uncorrected) ranged from -12 to -50‰. Raw data from laser analyzers in environments with low water vapor concentrations can be normalized to the international V-SMOW scale by calibration to the flask data measured conventionally. Bias correction is especially critical for the accurate determination of deuterium excess in dry air.
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Johnson LR, Vernau W. Bronchoscopic findings in 48 cats with spontaneous lower respiratory tract disease (2002-2009). J Vet Intern Med 2011; 25:236-43. [PMID: 21314731 DOI: 10.1111/j.1939-1676.2011.00688.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND Diagnosis of lower respiratory disease requires collection of airway samples to confirm the etiology of disease. Bronchoscopic evaluation is commonly performed in dogs but less information is available in cats. HYPOTHESIS The presence and number of bronchoscopic abnormalities visualized during bronchoscopic evaluation of cats with lower respiratory disease will correlate with the type of disease and total and differential cell counts in bronchoalveolar lavage (BAL) fluid. ANIMALS Forty-eight cats prospectively evaluated by a single bronchoscopist. METHODS Bronchoscopy was performed during clinical evaluation of cats presenting with cough, respiratory distress, or both. Cats were evaluated for airway hyperemia, stenosis, or collapse, mucus accumulation, bronchiectasis, and epithelial irregularities. Cats were placed into groups of bronchitis/"asthma," pneumonia, or neoplasia based on BAL findings, histopathology, and response to appropriate medical therapy. Summation of bronchial abnormalities and total and differential cell counts were compared among groups. RESULTS Endobronchial abnormalities were common in cats with feline bronchitis/asthma, pneumonia, and neoplasia and no differentiating features were found. Excessive mucus accumulation was common (83%), followed by stenosis of bronchial openings and nodular epithelial irregularities (56%), airway hyperemia (54%), airway collapse (48%), and bronchiectasis (27%). Total bronchoscopic score and total cell count did not differ among groups, although differential cell counts were significantly different. A weak correlation (R² = 0.16, P= .006) between age and total bronchoscopic score was noted. CONCLUSIONS AND CLINICAL RELEVANCE Bronchoscopic abnormalities are common in cats with lower respiratory tract disease, and visualization of the airways provides additional nonspecific clinical information in cats.
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Bavaria MN, Ray RM, Johnson LR. The phosphorylation state of MRLC is polyamine dependent in intestinal epithelial cells. Am J Physiol Cell Physiol 2010; 300:C164-75. [PMID: 21068360 DOI: 10.1152/ajpcell.00247.2010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cell migration is important to the integrity of the gastrointestinal tract for the normal movement of cells from crypt to villi and the healing of wounds. Polyamines are essential to cell migration, mucosal restitution, and, hence, healing. Polyamine depletion by α-difluoromethyl ornithine (DFMO) inhibited migration by decreasing lamellipodia and stress fiber formation and preventing the activation of Rho-GTPases. Polyamine depletion increased the association of the thick F-actin cortex with phosphorylated myosin regulatory light chain (pMRLC). In this study, we determined why MRLC is constitutively phosphorylated as part of the actin cortex. Inhibition of myosin light chain kinase (MLCK) decreased RhoA and Rac1 activities and significantly inhibited migration. Polyamine depletion increased phosphorylation of MRLC (Thr18/Ser19) and stabilized the actin cortex and focal adhesions. The Rho-kinase inhibitor Y27632 increased spreading and migration by decreasing the phosphorylation of MRLC, remodeling focal adhesions, and by activating Rho-GTPases. Thus phosphorylation of MRLC appears to be the rate-limiting step during the migration of IEC-6 cells. In addition, increased localization of RhoA with the actin cortex in polyamine-depleted cells appears to activate Rho-kinase. In the absence of polyamines, activated Rho-kinase phosphorylates myosin phosphatase targeting subunit 1 (MYPT1) at serine-668 leading to its inactivation and preventing the recruitment of phosphatase (protein phosphastase, PP1cδ) to the actomyosin cortex. In this condition, MRLC is constitutively phosphorylated and cycling does not occur. Thus activated myosin binds F-actin stress fibers and prevents focal adhesion turnover, Rho-GTPase activation, and the remodeling of the cytoskeleton required for migration.
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Elias BC, Bhattacharya S, Ray RM, Johnson LR. Polyamine-dependent activation of Rac1 is stimulated by focal adhesion-mediated Tiam1 activation. Cell Adh Migr 2010; 4:419-30. [PMID: 20448461 DOI: 10.4161/cam.4.3.12043] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Integrin receptors cluster on the cell surface and bind to extra cellular matrix (ECM) proteins triggering the formation of focal contacts and the activation of various signal transduction pathways that affect the morphology, motility, gene expression and survival of adherent cells. Polyamine depletion prevents the increase in autophosphorylation of focal adhesion kinase (FAK) and Src during attachment. Rac activity also shows a steady decline, and its upstream guanine nucleotide exchange factor (GEF), Tiam1 also shows a reduction in total protein level when cells are depleted of polyamines. When Tiam1 and Rac1 interaction was inhibited by NSC-23766, there was not only a decrease in Rac1 activity as expected but also a decrease in FAK auto-phosphorylation. Inhibition of Src activity by PP2 also reduced FAK autophosphorylation, which implies that Src modulates FAK autophosphorylation. From the data obtained in this study we conclude that FAK and Src are rapidly activated upon fibronectin mediated signaling leading to Tiam1-mediated Rac1 activation and that intracellular polyamines influence the signaling strength by modulating interaction of Src with Tiam1 using focal adhesion kinase as a scaffolding site.
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Ray RM, Viar MJ, Johnson LR. Amino acids regulate expression of Antizyme‐1 and modulate Ornithine Decarboxylase Activation. FASEB J 2010. [DOI: 10.1096/fasebj.24.1_supplement.1010.5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Elias BC, Ray RM, Johnson LR. Polyamines regulate integrin mediated signaling during IEC‐6 cell attachment and spreading. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.979.2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Jin S, Ray RM, Johnson LR. Caspase‐8 activation requires functional mitochondria in camptothecin‐induced apoptosis in intestinal epithelial cells. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.618.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bhattacharya S, Ray RM, Johnson LR. Mdm2 antagonist Nutlin‐3 induces apoptosis in p53 mutant human colon carcinoma cells. FASEB J 2009. [DOI: 10.1096/fasebj.23.1_supplement.618.12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bhattacharya S, Ray RM, Johnson LR. Role of polyamines in p53-dependent apoptosis of intestinal epithelial cells. Cell Signal 2009; 21:509-22. [DOI: 10.1016/j.cellsig.2008.12.003] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Revised: 12/05/2008] [Accepted: 12/08/2008] [Indexed: 01/18/2023]
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Jin S, Ray RM, Johnson LR. TNF-alpha/cycloheximide-induced apoptosis in intestinal epithelial cells requires Rac1-regulated reactive oxygen species. Am J Physiol Gastrointest Liver Physiol 2008; 294:G928-37. [PMID: 18218673 DOI: 10.1152/ajpgi.00219.2007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Previously we have shown that both Rac1 and c-Jun NH(2)-terminal kinase (JNK1/2) are key proapoptotic molecules in tumor necrosis factor (TNF)-alpha/cycloheximide (CHX)-induced apoptosis in intestinal epithelial cells, whereas the role of reactive oxygen species (ROS) in apoptosis is unclear. The present studies tested the hypothesis that Rac1-mediated ROS production is involved in TNF-alpha-induced apoptosis. In this study, we showed that TNF-alpha/CHX-induced ROS production and hydrogen peroxide (H(2)O(2))-induced oxidative stress increased apoptosis. Inhibition of Rac1 by a specific inhibitor NSC23766 prevented TNF-alpha-induced ROS production. The antioxidant, N-acetylcysteine (NAC), or rotenone (Rot), the mitochondrial electron transport chain inhibitor, attenuated mitochondrial ROS production and apoptosis. Rot also prevented JNK1/2 activation during apoptosis. Inhibition of Rac1 by expression of dominant negative Rac1 decreased TNF-alpha-induced mitochondrial ROS production. Moreover, TNF-alpha-induced cytosolic ROS production was inhibited by Rac1 inhibition, diphenyleneiodonium (DPI, an inhibitor of NADPH oxidase), and NAC. In addition, DPI inhibited TNF-alpha-induced apoptosis as judged by morphological changes, DNA fragmentation, and JNK1/2 activation. Mitochondrial membrane potential change is Rac1 or cytosolic ROS dependent. Lastly, all ROS inhibitors inhibited caspase-3 activity. Thus these results indicate that TNF-alpha-induced apoptosis requires Rac1-dependent ROS production in intestinal epithelial cells.
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Bhattacharya S, Ray RM, Johnson DA, Johnson LR. Camptothecin induced expression and phosphorylation of p53 regulates apoptosis in epithelial cells. FASEB J 2008. [DOI: 10.1096/fasebj.22.1_supplement.1189.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Bhattacharya S, Guo H, Ray RM, Johnson LR. Basic helix-loop-helix protein E47-mediated p21Waf1/Cip1 gene expression regulates apoptosis of intestinal epithelial cells. Biochem J 2008; 407:243-54. [PMID: 17617061 PMCID: PMC2049013 DOI: 10.1042/bj20070293] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Inhibition of ornithine decarboxylase by DFMO (alpha-difluromethylornithine) and subsequent polyamine depletion increases p21Cip1 protein, induces cell cycle arrest and confers resistance to apoptosis on intestinal epithelial cells. However, the mechanism by which polyamines regulate p21Cip1 expression and apoptosis is unknown. On the basis of the involvement of p21Cip1 as an anti-apoptotic protein, we tested the role of p21Cip1 in providing protection from apoptosis. Simultaneously, we investigated the role of E47, a basic helix-loop-helix protein, in the regulation of p21Cip1 gene transcription. Gene-specific siRNA (small interfering RNA) decreased E47 protein levels, increased p21Cip1 promoter activity and protein levels and protected cells from TNFalpha (tumour necrosis factor alpha)-induced apoptosis. Knockdown of p21Cip1 protein by siRNA resulted in cells becoming more susceptible to apoptosis. In contrast, incubation with EGF (epidermal growth factor) stimulated p21Cip1 mRNA and protein levels and rescued cells from apoptosis. During apoptosis, the level of E47 mRNA increased, causing a concomitant decrease in p21Cip1 mRNA and protein levels. Polyamine depletion decreased E47 mRNA levels and cell survival. Caspase 3-mediated cleavage of p130Cas has been implicated in p21Cip1 transcription. The progression of apoptosis led to a caspase 3-dependent cleavage of p130Cas and generated a 31 kDa fragment, which translocated to the nucleus, associated with nuclear E47 and inhibited p21Cip1 transcription. Polyamine depletion inhibited all these effects. Transient expression of the 31 kDa fragment prevented the expression of p21Cip1 protein and increased apoptosis. These results implicate p21Cip1 as an anti-apoptotic protein and suggest a role for polyamines in the regulation of p21Cip1 via the transcription repressor E47. Caspase-mediated cleavage of p130Cas generates a 31 kDa fragment, inhibits p21Cip1 transcription and acts as an amplifier of apoptotic signalling.
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Bhattacharya S, Ray RM, Johnson LR. Decreased apoptosis in polyamine depleted IEC-6 cells depends on Akt-mediated NF-kappaB activation but not GSK3beta activity. Apoptosis 2007; 10:759-76. [PMID: 16133867 DOI: 10.1007/s10495-005-2943-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The PI3-kinase/Akt pathway promotes cell survival in many different cell types including intestinal epithelial cells. Increased AKT activation in polyamine depleted intestinal epithelial cells correlated well with the decrease in TNF-alpha-induced apoptosis. Increased Akt activation and GSK3beta (Ser 9) phosphorylation without significant effect on Bad (Ser136) phosphorylation indicate that Akt-mediated protection is independent of Bad phosphorylation but may depend on GSK3beta. Pretreatment of polyamine-depleted cells with LY294002 increased caspase-9 and caspase-3 activation and decreased basal levels of GSK-3beta phosphorylation. Inhibition of GSK3beta activity using AR-A014418 or lithium chloride or siRNA-mediated downregulation of its expression had no effect on apoptosis. Inhibition of PI3-kinase and over-expression of dominant negative Akt (DN-AKT), significantly increased apoptosis in polyamine depleted cells. DN-Akt expression reversed the protective effect of polyamine depletion on apoptosis. DN-Akt, as well as the PI3-kinase inhibitors, prevented Akt activation and subsequent translocation of NF-kappaB to the nucleus. Constitutively active Akt (CA-AKT) expression increased resistance to TNF-alpha-induced apoptosis. Constitutively active-Akt expression increased nuclear staining of NF-kappaB. Moreover, polyamine depletion of DN-Akt cells prevented basal and TNF-alpha-induced IkappaBalpha phosphorylation. Prevention of NF-kappaB activation in DN-IkappaBalpha-transfected cells increased apoptosis in control cells and restored it in polyamine-depleted cells to control levels. These data indicate that Akt regulates the mitochondrial pathway, preventing activation of caspase-9 and thereby caspase-3 via NF-kappaB and these effects are independent of GSK-3beta activity.
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Ray RM, Bhattacharya S, Johnson LR. EGFR plays a pivotal role in the regulation of polyamine-dependent apoptosis in intestinal epithelial cells. Cell Signal 2007; 19:2519-27. [PMID: 17825525 PMCID: PMC2699668 DOI: 10.1016/j.cellsig.2007.08.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2007] [Accepted: 08/06/2007] [Indexed: 11/16/2022]
Abstract
Intracellular polyamine synthesis is regulated by the enzyme ornithine decarboxylase (ODC), and its inhibition by alpha-difluromethylornithine (DFMO), confers resistance to apoptosis. We have previously shown that DFMO leads to the inhibition of de novo polyamine synthesis, which in turn rapidly activates Src, STAT3 and NF-kappaB via integrin beta3 in intestinal epithelial cells. One mechanism to explain these effects involves the activation of upstream growth factor receptors, such as the epidermal growth factor receptor (EGFR). We therefore hypothesized that EGFR phosphorylation regulates the early response to polyamine depletion. DFMO increased EGFR phosphorylation on tyrosine residues 1173 (pY1173) and 845 (pY845) within 5 min. Phosphorylation declined after 10 min and was prevented by the addition of exogenous putrescine to DFMO containing medium. Phosphorylation of EGFR was concomitant with the activation of ERK1/2. Pretreatment with either DFMO or EGF for 1 h protected cells from TNF-alpha/CHX-induced apoptosis. Exogenous addition of polyamines prevented the protective effect of DFMO. In addition, inhibition of integrin beta3 activity (with RGDS), Src activity (with PP2), or EGFR kinase activity (with AG1478), increased basal apoptosis and prevented protection conferred by either DFMO or EGF. Polyamine depletion failed to protect B82L fibroblasts lacking the EGFR (PRN) and PRN cells expressing either a kinase dead EGFR (K721A) or an EGFR (Y845F) mutant lacking the Src phosphorylation site. Conversely, expression of WT-EGFR (WT) restored the protective effect of polyamine depletion. Fibronectin activated the EGFR, Src, ERKs and protected cells from apoptosis. Taken together, our data indicate an essential role of EGFR kinase activity in MEK/ERK-mediated protection, which synergizes with integrin beta3 leading to Src-mediated protective responses in polyamine depleted cells.
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Deng W, Shuyu E, Tsukahara R, Valentine WJ, Durgam G, Gududuru V, Balazs L, Manickam V, Arsura M, Vanmiddlesworth L, Johnson LR, Parrill AL, Miller DD, Tigyi G. The lysophosphatidic acid type 2 receptor is required for protection against radiation-induced intestinal injury. Gastroenterology 2007; 132:1834-51. [PMID: 17484878 PMCID: PMC3446791 DOI: 10.1053/j.gastro.2007.03.038] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2006] [Accepted: 01/24/2007] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS We recently identified lysophosphatidic acid (LPA) as a potent antiapoptotic agent for the intestinal epithelium. The objective of the present study was to evaluate the effect of octadecenyl thiophosphate (OTP), a novel rationally designed, metabolically stabilized LPA mimic, on radiation-induced apoptosis of intestinal epithelial cells in vitro and in vivo. METHODS The receptors and signaling pathways activated by OTP were examined in IEC-6 and RH7777 cell lines and wild-type and LPA(1) and LPA(2) knockout mice exposed to different apoptotic stimuli. RESULTS OTP was more efficacious than LPA in reducing gamma irradiation-, camptothecin-, or tumor necrosis factor alpha/cycloheximide-induced apoptosis and caspase-3-8, and caspase-9 activity in the IEC-6 cell line. In RH7777 cells lacking LPA receptors, OTP selectively protected LPA(2) but not LPA(1) and LPA(3) transfectants. In C57BL/6 and LPA(1) knockout mice exposed to 15 Gy gamma irradiation, orally applied OTP reduced the number of apoptotic bodies and activated caspase-3-positive cells but was ineffective in LPA(2) knockout mice. OTP, with higher efficacy than LPA, enhanced intestinal crypt survival in C57BL/6 mice but was without any effect in LPA(2) knockout mice. Intraperitoneally administered OTP reduced death caused by lethal dose (LD)(100/30) radiation by 50%. CONCLUSIONS Our data indicate that OTP is a highly effective antiapoptotic agent that engages similar prosurvival pathways to LPA through the LPA(2) receptor subtype.
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MESH Headings
- Administration, Oral
- Animals
- Apoptosis/drug effects
- Apoptosis/physiology
- Apoptosis/radiation effects
- Cell Line
- Cells, Cultured
- Dose-Response Relationship, Drug
- Female
- GTP-Binding Proteins/physiology
- Gamma Rays/adverse effects
- Gene Expression Regulation
- Injections, Intraperitoneal
- Intestinal Mucosa/metabolism
- Intestinal Mucosa/pathology
- Intestinal Mucosa/radiation effects
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mitogen-Activated Protein Kinases/physiology
- Nerve Tissue Proteins/pharmacology
- Organophosphorus Compounds/administration & dosage
- Organophosphorus Compounds/pharmacology
- Phosphatidylinositol 3-Kinases/physiology
- Radiation Injuries, Experimental/metabolism
- Radiation Injuries, Experimental/pathology
- Radiation Injuries, Experimental/prevention & control
- Receptors, Lysophosphatidic Acid/genetics
- Receptors, Lysophosphatidic Acid/physiology
- Signal Transduction/physiology
- Tumor Necrosis Factor-alpha/pharmacology
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