D A Fullerton

University of Colorado, Denver, CO, United States

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Publications (173)555.55 Total impact

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    ABSTRACT: Background Lower extremity paralysis continues to complicate aortic interventions. The lack of understanding of the underlying pathology has hindered advancements to decrease the occurrence this injury. The current model demonstrates reproducible lower extremity paralysis following thoracic aortic occlusion. Methods Adult male C57BL6 mice were anesthetized with isoflurane. Through a cervicosternal incision the aorta was exposed. The descending thoracic aorta and left subclavian arteries were identified without entrance into pleural space. Skeletonization of these arteries was followed by immediate closure (Sham) or occlusion for 4 min (moderate ischemia) or 8 min (prolonged ischemia). The sternotomy and skin were closed and the mouse was transferred to warming bed for recovery. Following recovery, functional analysis was obtained at 12 hr intervals until 48 hr. Results Mice that underwent sham surgery showed no observable hind limb deficit. Mice subjected to moderate ischemia for 4 min had minimal functional deficit at 12 hr followed by progression to complete paralysis at 48 hr. Mice subjected to prolonged ischemia had an immediate paralysis with no observable hind-limb movement at any point in the postoperative period. There was no observed intraoperative or post operative mortality. Conclusion Reproducible lower extremity paralysis whether immediate or delayed can be achieved in a murine model. Additionally, by using a median sternotomy and careful dissection, high survival rates, and reproducibility can be achieved.
    Journal of Visualized Experiments 01/2014;
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    ABSTRACT: Postoperative atrial fibrillation (POAF) is a well-recognized complication of cardiac surgery; however, its management remains a challenge, and the implementation and outcomes of various strategies in clinical practice remain unclear. We hypothesize that treatment for POAF is variable, and that it is associated with particular morbidity and mortality following cardiac surgery. We compared patient characteristics, operative procedures, postoperative management, and outcomes between patients with and without POAF following coronary artery bypass grafting (CABG) in the Society of Thoracic Surgeons multicenter Contemporary Analysis of Perioperative Cardiovascular Surgical Care (CAPS-Care) registry (2004-2005). Of 2390 patients who underwent CABG, 676 (28%) had POAF. Compared with patients without POAF, those with POAF were older (median age 74 vs 71 years, P < 0.0001) and more likely to have hypertension (86% vs 83%, P = 0.04) and impaired renal function (median estimated glomerular filtration rate 56.9 vs 58.6 mL/min/1.73 m(2) , P = 0.0001). A majority of patients with POAF were treated with amiodarone (77%) and β-blockers (68%); few (9.9%) underwent cardioversion. Patients with POAF were more likely to experience complications (57% vs 41%, P < 0.0001), including acute limb ischemia (1.0% vs 0.4%, P = 0.03), stroke (4.0% vs 1.9%, P = 0.002), and reoperation (13% vs 7.9%, P < 0.0001). Length of stay (median 8 days vs 6 days, P < 0.0001), in-hospital mortality (6.8% vs 3.7%, P = 0.001), and 30-day mortality (7.8 vs 3.9, P < 0.0001) were all worse for patients with POAF. In adjusted analyses, POAF remained associated with increased length of stay following surgery (adjusted ratio of the mean: 1.27, 95% confidence interval: 1.2-1.34, P < 0.0001). Postoperative AF is common following CABG, and such patients continue to have higher rates of postoperative complications. Postoperative AF is significantly associated with increased length of stay following surgery.
    Clinical Cardiology 12/2013; · 1.83 Impact Factor
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    ABSTRACT: Dexmedetomidine, an α-2a adrenergic agonist, given pre- and postoperatively was previously shown to attenuate neuronal injury in a murine model of spinal cord ischemia-reperfusion. In the brain, α-2 agonists have been shown to induce the phosphorylation of cyclic AMP response-element binding protein (CREB), a transcription factor necessary for neuron survival. We hypothesized that the α-2a adrenergic agonist given preoperatively increases CREB-mediated neuroprotective proteins, attenuating neuronal injury and cytoarchitectural decay. Mice (ie, C57BL/6 mice) underwent 5 minutes of aortic occlusion via median sternotomy. Mice received 25 μg/kg dexmedetomidine or equivalent normal saline at 24 hours, 12 hours, and 30 minutes preoperatively. Functional outcomes were recorded at 6 to 48 hours postoperatively when spinal cords were removed for histologic analysis. Spinal cords were examined for protein kinase B, CREB, B-cell lymphoma 2, and brain-derived neurotrophic factor following treatment alone or ischemia-reperfusion surgery. Following aortic occlusion, mice in the treatment group had preserved neurologic function at all time points (P < .05). Histologic analysis showed preserved cytoarchitecture and decreased neuronal injury in the treatment group when compared with ischemic controls. Additionally, analysis of spinal cord homogenate following surgery and pretreatment revealed a significant (P < .05) increase in B-cell lymphoma 2 and brain-derived neurotrophic factor expression and protein kinase B and CREB phosphorylation with α-2a adrenergic agonist pretreatment. Pretreatment with the α-2a agonist dexmedetomidine preserved neurologic function and attenuated neuronal injury following thoracic aortic occlusion in mice. This relationship was associated with an increased phosphorylation of protein kinase B and CREB and subsequent up-regulation of antiapoptotic factor B-cell lymphoma 2 and brain-derived neurotrophic factor. Thus, α-2a receptor agonism-induced CREB phosphorylation and contributes to dexmedetomidine's protective mechanism in the spinal cord following ischemia.
    The Journal of thoracic and cardiovascular surgery 09/2013; · 3.41 Impact Factor
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    ABSTRACT: Paraplegia continues to complicate thoracoabdominal aortic interventions. The elusive mechanism of spinal cord ischemia-reperfusion injury has delayed the development of pharmacological adjuncts. Microglia, the resident macrophages of the central nervous system, can have pathological responses after a variety of insults. This can occur through toll-like receptor 4 (TLR-4) in stroke models. We hypothesize that spinal cord ischemia-reperfusion injury after aortic occlusion results from TLR-4-mediated microglial activation in mice. TLR-4 mutant and wild-type mice underwent aortic occlusion for 5 minutes, followed by 60 hours of reperfusion when spinal cords were removed for analysis. Spinal cord cytokine production and microglial activation were assessed at 6 and 36 hours after surgery. Isolated microglia from mutant and wild-type mice were subjected to oxygen and glucose deprivation for 24 hours, after which the expression of TLR-4 and proinflammatory cytokines was analyzed. Mice without functional TLR-4 demonstrated decreased microglial activation and cytokine production and had preserved functional outcomes and neuronal viability after thoracic aortic occlusion. After oxygen and glucose deprivation, wild-type microglia had increased TLR-4 expression and production of proinflammatory cytokines. The absence of functional TLR-4 attenuated neuronal injury and microglial activation after thoracic aortic occlusion in mice. Furthermore, microglial upregulation of TLR-4 occurred after oxygen and glucose deprivation, and the absence of functional TLR-4 significantly attenuated the production of proinflammatory cytokines. In conclusion, TLR-4-mediated microglia activation in the spinal cord after aortic occlusion is critical in the mechanism of paraplegia after aortic cross-clamping and may provide targets for pharmacological intervention.
    Circulation 09/2013; 128(26 Suppl 1):S152-6. · 15.20 Impact Factor
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    ABSTRACT: Risk of atrial fibrillation (AF) after coronary artery bypass grafting (CABG) is high, yet the effectiveness of guideline-recommended preoperative prophylaxis in clinical practice remains uncertain. We determined the utilization and variation of preoperative AF prevention and assessed the comparative effectiveness of alternative drugs using the Society of Thoracic Surgeons multicenter Contemporary Analysis of Perioperative Cardiovascular Surgical Care (CAPS-Care) registry. Among 2,177 patients who underwent high-risk CABG and/or valve surgery, the mean age was 71 ± 9, 66% were men, 26% had chronic lung disease, and 21% had cerebrovascular disease. Overall use of AF prophylaxis was 84% and varied across sites (range 52% to 100%). The most common preventive agents were beta blockers (72%), followed by calcium antagonists (17%). Postoperatively, 30% (n = 646) developed AF at a median of 2 (25th to 75th percentiles: 1 to 3) days after surgery. Increasing age, height, white race, body mass index >35, New York Heart Association class IV heart failure, preoperative dialysis, and concomitant aortic valve replacement were associated with greater odds of postoperative AF (p <0.05 for all). Preoperative amiodarone use was associated with a trend to reduction of postoperative AF (26%, adjusted odds ratio 0.72 [95% confidence interval 0.51 to 1.00], p = 0.052). After adjustment, the odds of postoperative AF were not statistically different across agents. In conclusion, use of AF prophylaxis before surgery varied significantly. In this high-risk population, we were unable to demonstrate that any of the commonly used preventive agents were associated with lower rates of AF compared with alternatives or no treatment.
    The American journal of cardiology 07/2013; · 3.58 Impact Factor
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    ABSTRACT: Despite investigation into preventable pharmacologic adjuncts, paraplegia continues to complicate thoracoabdominal aortic interventions. The alpha 2a adrenergic receptor agonist, dexmedetomidine, has been shown to preserve neurologic function and neuronal viability in a murine model of spinal cord ischemia reperfusion, although the mechanism remains elusive. We hypothesize that dexmedetomidine will blunt postischemic inflammation in vivo following thoracic aortic occlusion with in vitro demonstration of microglial inhibition following lipopolysaccharide (LPS) stimulation. Adult male C57BL/6 mice underwent 4 minutes of aortic occlusion. Mice received 25 μg/kg intraperitoneal dexmedetomidine (n = 8) or 0.9% normal saline (n = 7) at reperfusion and 12-hour intervals postoperatively until 48 hours. Additionally, sham mice (n = 3), which had aortic arch exposed with no occlusion, were included for comparison. Functional scoring was done at 6 hours following surgery and 12-hour intervals until 60 hours when spinal cords were removed and examined for neuronal viability and cytokine production. Additional analysis of microglia activation was done in 12 hours following surgery. Age- and sex-matched mice had spinal cord removed for microglial isolation culture. Cells were grown to confluence and stimulated with toll-like receptor-4 agonist LPS 100 ng/mL in presence of dexmedetomidine or vehicle control for 24 hours. Microglia and media were then removed for analysis of protein expression. Dexmedetomidine treatment at reperfusion significantly preserved neurologic function with mice in treatment group having a Basso Score of 6.3 in comparison to 2.3 in ischemic control group. Treatment was associated with a significant reduction in microglia activation and in interleukin-6 production. Microglial cells in isolation when stimulated with LPS had an increased production of proinflammatory cytokines and markers of activation. Treatment with dexmedetomidine significantly attenuated microglial activation and proinflammatory cytokine production in vitro with a greater than twofold reduction in tumor necrosis factor-α. Alpha 2a agonist, dexmedetomidine treatment at reperfusion preserved neurologic function and neuronal viability. Furthermore, dexmedetomidine treatment resulted in an attenuation of microglial activation and proinflammatory cytokine production both in vivo and in vitro following LPS stimulation. This finding lends insight into the mechanism of paralysis following thoracic aortic interventions and may guide future pharmacologic targets for attenuating spinal cord ischemia and reperfusion.
    Journal of vascular surgery: official publication, the Society for Vascular Surgery [and] International Society for Cardiovascular Surgery, North American Chapter 07/2013; · 3.52 Impact Factor
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    ABSTRACT: BACKGROUND: Mechanisms of inflammation have been implicated in the pathogenesis of aortic stenosis. When stimulated, human aortic valve interstitial cells (AVICs) have been shown to become inflammatory cells. Increased levels of interleukin (IL)-1β have been found in the leaflets of stenotic aortic valves. The purpose of this study was to determine the effects of IL-1β on isolated human AVICs and to determine the intracellular signaling pathway by which the effects are mediated. The results of this study demonstrated that IL-1β induces an inflammatory phenotype in human AVICs. METHODS: Human AVICs were isolated from normal aortic valves from explanted hearts of patients undergoing cardiac transplantation (n = 4) and grown in culture. When grown to confluence, the cells were treated with IL-1β (10 ng/mL). Cell culture media was analyzed for IL-6, IL-8, and monocyte chemoattractant protein-1 (enzyme-linked immunosorbent assay). Cell lysates were analyzed for intercellular adhesion molecule-1 (immunoblot). Inhibition of nuclear factor-κβ was by Bay 11-7085 (5 μM). Inhibition of extracellular signal regulated kinase-1/2 was by PD098059 (20 nM). Statistics were by analysis of variance, with p less than 0.05 significant. RESULTS: Interluekin-1β induced an inflammatory phenotype in human AVICs. The IL-1β stimulation resulted in significantly increased production of the inflammatory cytokines, IL-6 and IL-8, the chemokine monocyte chemoattractant protein-1, and intercellular adhesion molecule-1. Inhibition of nuclear factor-κβ prevented these changes, whereas inhibition of extracellular signal regulated kinase-1/2 had no effect. CONCLUSIONS: Interleukin-1β induced an inflammatory phenotype in human AVICs, which was prevented by inhibition of nuclear factor-κβ. These data implicate IL-1β in the pathogenesis of aortic stenosis.
    The Annals of thoracic surgery 06/2013; · 3.74 Impact Factor
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    ABSTRACT: The aortic valve interstitial cell (AVIC) has been implicated in the pathogenesis of calcific aortic stenosis. When appropriately stimulated, AVICs undergo a phenotypic change from that of a myofibroblast to that of a bone-forming-like cell. An elevated blood level of low-density lipoprotein (LDL) cholesterol is a clinical risk factor for aortic stenosis, and oxidized LDL (ox-LDL) cholesterol has been consistently found in calcified aortic valve leaflets. However, whether it plays a role in the pathogenesis of aortic stenosis is unknown. The process of aortic valve leaflet calcification has been associated with the deposition of calcium phosphate, mediated in part by the phosphate inorganic transporter 1 (PiT-1), a sodium-phosphate ion cotransporter. Therefore, we hypothesized that ox-LDL induces an osteogenic change in human AVICs marked by the induction of PiT-1. Using isolated human AVICs, the purpose of the present study was to examine the effect of ox-LDL on the expression of PiT-1 and the osteogenic factor bone morphogenetic protein 2 (BMP-2), which is a protein necessary for bone formation. Human AVICs were isolated from nonstenotic aortic valves obtained from the explanted hearts of patients undergoing cardiac transplantation (n = 4) and grown in culture. The cells were treated with serum-free media, serum-free media with dimethyl sulfoxide (vehicle control), 40 μg/mL of ox-LDL, or 40 μg/mL of ox-LDL plus 2.5 mM phosphonoformate hexahydrate acid. Phosphonoformate hexahydrate acid is a competitive inhibitor of PiT-1 by mimicking inorganic phosphate. Cell lysis was performed at 24 h after treatment. Cell lysates were analyzed using immunoblot and densitometry for PiT-1 and BMP-2. Statistical analysis was performed using analysis of variance. P < 0.05 was significant. ox-LDL stimulation of AVICs induced an increase in PiT-1 and BMP-2. ox-LDL induced increased production of the phosphate transporter, PiT-1, and the osteogenic factor, BMP-2. Inhibition of PiT-1 with phosphonoformate hexahydrate acid prevented ox-LDL-induced BMP-2 expression. These data offer mechanistic insight into the pathogenesis of calcific aortic stenosis.
    Journal of Surgical Research 05/2013; · 2.02 Impact Factor
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    ABSTRACT: OBJECTIVE: Calcific aortic valve disease is a leading cardiovascular disease in the elderly, and progressive calcification results in the failure of valvular function. Aortic valve interstitial cells (AVICs) from stenotic valves express higher levels of bone morphogenetic protein-2 in response to Toll-like receptor 4 stimulation. We recently found that Toll-like receptor 4 interacts with Notch1 in human AVICs. This study tests the hypothesis that Notch1 promotes the pro-osteogenic response of human AVICs. APPROACH AND RESULTS: AVICs isolated from diseased human valves expressed higher levels of bone morphogenetic protein-2 and alkaline phosphatase after lipopolysaccharide stimulation. The augmented pro-osteogenic response is associated with elevated cellular levels of Notch1 and enhanced Notch1 cleavage in response to lipopolysaccharide stimulation. Inhibition or silencing of Notch1 suppressed the pro-osteogenic response in diseased cells, and the Notch 1 ligand, Jagged1, enhanced the response in AVICs isolated from normal human valves. Interestingly, ERK1/2 and nuclear factor-κB phosphorylation induced by lipopolysaccharide was markedly reduced by inhibition or silencing of Notch1 and enhanced by Jagged1. Inhibition of ERK1/2 or nuclear factor-κB also reduced bone morphogenetic protein-2 and alkaline phosphatase expression induced by lipopolysaccharide. CONCLUSIONS: Notch1 mediates the pro-osteogenic response to Toll-like receptor 4 stimulation in human AVICs. Elevated Notch1 levels and enhanced Notch1 activation play a major role in augmentation of the pro-osteogenic response of AVICs of stenotic valves through modulation of ERK1/2 and nuclear factor-κB activation. These pathways could be potential therapeutic targets for prevention of the progression of calcific aortic valve disease.
    Arteriosclerosis Thrombosis and Vascular Biology 05/2013; · 6.34 Impact Factor
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    ABSTRACT: BACKGROUND: Traditionally, cardiothoracic residency programs are 2 or 3 years in length and require the completion of a general surgery residency. Six-year integrated programs (IP) that directly match fourth-year medical students have been recently developed. Our objective was to examine the curricula of traditional 2-year (T2) and 3-year (T3) programs and compare them to the curricula of IP. METHODS: We requested curricula from the directors of all IP, T2, and T3 programs participating in the 2011 to 2012 match. We compared the median number of months spent on a cardiothoracic (CT) rotation, an adult cardiac rotation, a thoracic rotation, and a congenital rotation, as well as time spent on "other" nonsurgical rotations. Traditional programs were categorized into 1 of 3 pathways: combined cardiothoracic (CCT), adult cardiac (AC), or general thoracic (GT). RESULTS: Integrated programs spend more time on general thoracic rotations when compared with CCT-T2, CCT-T3, AC-T2, and AC-T3 pathways (p = 0.009, p = 0.046, p = 0.001 and p = 0.028, respectively). The IP spend a similar amount of time on CT, adult cardiac, and congenital rotations when compared when 2- and 3-year CCT, AC, and GT pathways. Of note, IP spend significantly more time on "other" nonsurgical rotations than all other pathways (p < 0.001 to 0.008). CONCLUSIONS: Integrated programs should not be considered "cardiac pathways" as they spend a significant amount of time on thoracic rotations. Additional nonsurgical rotations provide an opportunity for residents in IP to develop unique skills not currently provided in traditional programs.
    The Annals of thoracic surgery 04/2013; · 3.74 Impact Factor
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    ABSTRACT: Background/Aim: Secretory phospholipase-A2 (sPLA2) mediates growth and proliferation of human esophageal adenocarcinoma cells (HEAC). Two major molecular pathways of cancer growth regulation include extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase-B (AKT). Phospholipase enzymes have been demonstrated to significantly influence these two growth regulating pathways in other tumor cells. We hypothesize sPLA2 to mediate HEAC growth control through ERK 1/2 and AKT. Verified HEAC (FLO-1), treated with either the mitogen-activated protein kinase kinase selective inhibitor (PD98059) or with group IIa sPLA2-specific inhibitor, were assessed for ERK1/2 phosphorylation and AKT activation after tumor necrosis factor-alpha stimulation, as well as for viability, proliferation, and apoptosis responses. PD98059 significantly inhibited ERK 1/2 activation, reduced cell viability, and reduced proliferation (p<0.05). sPLA2 inhibition attenuated ERK 1/2 activation (p<0.01) but had no effect on AKT activation or apoptosis. Specific inhibition of group IIa sPLA2 directly reduces HEAC viability and proliferation by attenuating ERK 1/2 activation with no effect on AKT activation or apoptosis. This may indicate that the mechanism of action of sPLA2 is mainly the induction of growth arrest.
    Anticancer research 04/2013; 33(4):1337-42. · 1.71 Impact Factor
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    ABSTRACT: BACKGROUND: Paraplegia remains a devastating complication of thoracoabdominal aortic procedures resulting from spinal cord ischemia and reperfusion injury (SCIR). Pharmacologic interventions have not proven efficacious in attenuating this injury, with poor understanding of the underlying mechanisms. The resident macrophages, or microglia in the spinal cord, may play a significant role in SCIR. The macrolide antibiotic, minocycline, has been shown in stroke models to inhibit microglial activation. This study hypothesized that microglial inhibition by minocycline after SCIR will attenuate injury with preservation of motor function. METHODS: Mature male C57Bl/6 mice underwent 4 minutes of thoracic aortic occlusion with reperfusion. Mice receiving minocycline 30 minutes before ischemia and daily thereafter (90 mg/kg and 45 mg/kg, respectively) were compared with mice receiving vehicle controls. Hind-limb motor function was measured at 12-hour intervals, with spinal cord harvest for histologic and immunologic comparison at 60 hours. RESULTS: Minocycline treatment significantly preserved hind limb motor function in all mice (n = 7) compared with complete paralysis in all untreated mice (n = 8), reaching significance from 24 hours of reperfusion through 60 hours. Immunofluorescent staining for Iba-1 revealed significant inhibition of microglial activation by minocycline treatment. Vehicle control sections demonstrated a greater degree of apoptosis compared with minocycline-treated spinal cord sections. CONCLUSIONS: Minocycline limits microglial activation, paralleling functional preservation after aortic cross-clamping. These data suggest functional microglia contribute to reperfusion injury after spinal cord ischemia. The effects of minocycline demonstrate a potential pharmacological therapy as well as demonstrating a potential cellular target in preventing paraplegia after aortic intervention.
    The Annals of thoracic surgery 03/2013; · 3.74 Impact Factor
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    ABSTRACT: Ghrelin is a small endogenous peptide principally produced and secreted by the gastric mucosa, with a major role in appetite and metabolism regulation. We hypothesized that anti-inflammatory therapy, as produced by exogenous administration of ghrelin, would decrease the myocardial inflammatory response to global hypothermia I/R, thereby affording myocardial protection. Heterotopic cervical heart transplantation that allows to subject donor hearts to global hypothermic ischemia and blood reperfusion, which very closely stimulates I/R conditions associated with cardiac surgical operations. Ghrelin administration prior to blood reperfusion significantly decreased serum concentrations of cTn-I versus animals subjected I/R alone, with a significantly attenuated VCAM-1 expression in I/R animals pre-treated with ghrelin. The tissue concentrations of pro-inflammatory cytokines (IL-6, IL-1β, and MCP-1) were ameliorated by the administration of ghrelin prior to reperfusion versus the concentrations observed in animals subjected to I/R alone. Significantly fewer monocytes in the tissue sections of I/R+ghrelin animals versus those subjected to I/R alone. Exogenous ghrelin administration prior to reperfusion of an ischemic heart resulted in a significant reduction in myocardial injury as measured by cTn-I. The reduced myocardial injury was accompanied by an attenuated tissue expression of several pro-inflammatory mediators, including VCAM-1, IL-6, IL-1β, and MCP-1. Key Words: Global ischemia/reperfusion, Ghrelin, cTn-I, Pro-inflammatory cytokines, VCAM-1
    AJBM. 01/2013; 1(2):38-48.
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    ABSTRACT: Group IIa secretory phospholipase A2 (sPLA2 IIa) plays a role in the malignant potential of several epithelial cancers. Nuclear factor kappa B (NF-κB) regulates cancer cell growth and is modulated by phospholipase activity in many cancer cells. We hypothesized that knockdown of sPLA2 in lung cancer cells would reduce cell proliferation and NF-κB activity in vitro and attenuate tumor growth in vivo. Two human non-small cell lung cancer cell lines (A549 and H358) were transduced with short hairpin RNA targeting sPLA2 group IIa. Quantitative reverse transcriptase-polymerase chain reaction and immunoblotting confirmed knockdown of sPLA2 IIa messenger RNA and protein, respectively. Cell proliferation was evaluated by the 5-bromo-2'-deoxyuridine DNA labeling assay. NF-κB phosphorylation was assayed by western blot. 1 × 10(6) of A549 or A549 sPLA2 knockdown cells were injected into the left flanks of nude mice (aged 6 to 8 weeks). Tumors were followed for 23 days, then removed and stained with hematoxylin and eosin, stained with Ki-67, and analyzed for sPLA2 IIa messenger RNA expression. sPLA2 knockdown reduced NF-κB phosphorylation and tumor growth in vivo. A549 wild-type tumors grew twice as fast as knockdown tumors. Ki-67 staining was more prominent throughout the wild-type tumors compared with knockdown tumors. Explanted knockdown tumors maintained lower sPLA2 levels compared with wild-type, confirmed by reverse transcriptase-polymerase chain reaction. Knockdown of sPLA2 IIa suppresses lung cancer growth in part by attenuating NF-κB activity. These findings justify further investigation into the cellular mechanisms of sPLA2 in lung cancer and its potential role as a therapeutic target.
    The Journal of thoracic and cardiovascular surgery 11/2012; 144(5):1185-91. · 3.41 Impact Factor
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    ABSTRACT: OBJECTIVE: Irradiation of the chest or chest wall has been shown to cause calcific aortic stenosis. However, the mechanisms are unknown. Aortic valve interstitial cells have been implicated in the pathogenesis of aortic stenosis; they have been shown to change from the phenotype of a myofibroblast to an osteoblastlike cell. We therefore hypothesized that irradiation of human aortic valve interstitial cells induces an osteogenic phenotype. In isolated human aortic valve interstitial cells, our purpose was to determine the effect of irradiation on the production of osteogenic factors: (1) bone morphogenetic protein 2, (2) osteopontin, (3) alkaline phosphatase, and (4) the transcription factor Runx2. METHODS: Human aortic valve interstitial cells were isolated from normal aortic valves obtained from explanted hearts of patients undergoing cardiac transplantation (n = 4) and were grown in culture. The cells were grown to confluence, irradiated with 10 Gy using a cesium-137 irradiator, and then lysed 24 hours after irradiation. Cell lysates were analyzed via immunoblot and densitometry for bone morphogenetic protein 2, osteopontin, alkaline phosphatase, and Runx2. Statistical analysis was performed using analysis of variance, with P < .05 indicating significance. RESULTS: Irradiation induced an osteogenic phenotype in human aortic valve interstitial cells. Irradiation induced a 2-fold increase in bone morphogenetic protein 2, a 7-fold increase in osteopontin, a 3-fold increase in alkaline phosphatase, and a 2-fold increase in Runx2. CONCLUSIONS: Radiation induces an osteogenic phenotype in human aortic valve interstitial cells. The irradiated cells had a significantly increased expression of the osteogenic factors bone morphogenetic protein 2, osteopontin, alkaline phosphatase, and Runx2. These data offer mechanistic insight into the pathogenesis of radiation-induced valvular heart disease.
    The Journal of thoracic and cardiovascular surgery 09/2012; · 3.41 Impact Factor
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    ABSTRACT: OBJECTIVE: There are currently no targeted therapies against lung tumors with oncogenic K-ras mutations that are found in 25% to -40% of lung cancers and are characterized by their resistance to epidermal growth factor receptor inhibitors. The isozyme group IIa secretory phospholipase A(2) (sPLA(2)IIa) is a potential biomarker and regulator of lung cancer cell invasion; however, the relationship between K-ras mutations and sPLA(2)IIa has yet to be investigated. We hypothesize that sPLA(2)IIa modulates lung cancer cell growth in K-ras mutant cells and that sPLA(2)IIa expression in human lung tumors is increased in K-ras mutant tumors. METHODS: Baseline sPLA(2)IIa expression in K-ras mutant lung cancer cell lines (A549, SW1573, H358, H2009) was assessed. Cells were treated with a specific sPLA(2)IIa inhibitor and evaluated for apoptosis and cell viability. Nuclear factor kappa-b (NF-κB) and extracellular signal-regulated kinase 1/2 activity were detected by Western blot. Human tumor samples were evaluated for sPLA(2)IIa mRNA expression by quantitative reverse-transcription polymerase chain reaction. RESULTS: Cytotoxicity of sPLA(2)IIa inhibition correlates with sPLA(2)IIa expression. Apoptosis in response to sPLA(2) inhibition parallels attenuation in NF-κB activity. In addition, sPLA(2)IIa expression in human tumors correlates with squamous cell pathology and increasing stage of K-ras mutant lung tumors. CONCLUSIONS: Baseline sPLA(2)IIa expression predicts response to sPLA(2)IIa inhibition in some K-ras mutant lung cancer cells. This finding is independent of p53 mutation status. Furthermore, squamous tumors and advanced-stage K-ras mutant tumors express more sPLA(2)IIa. These data support a role for sPLA(2)IIa as a potential global therapeutic target in the treatment of lung cancer.
    The Journal of thoracic and cardiovascular surgery 09/2012; · 3.41 Impact Factor
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    ABSTRACT: Although biglycan (BGN) and oxidized low-density lipoprotein (oxLDL) accumulation has been observed in calcific, stenotic aortic valves, their role in the pathogenesis of calcific aortic valve disease is poorly understood. We hypothesized that soluble BGN induces the osteogenic response in human aortic valve interstitial cells via Toll-like receptor (TLR) 2 and TLR4 and mediates the proosteogenic effect of oxLDL. Aortic valve interstitial cells of stenotic valves express higher levels of BGN. Stimulation of cells from normal valves with BGN increased the expression of bone morphogenetic protein-2 (BMP-2) and alkaline phosphatase (ALP) among the chondrogenic/osteogenic markers examined and caused accumulation of calcium deposits. TLR2 silencing, but not TLR4 silencing, reduced BMP-2 and ALP levels after BGN stimulation although coimmunoprecipitation revealed that BGN interacts with both TLR2 and TLR4. BGN induced the phosphorylation of extracellular signal-regulated protein kinase-1/2, p38 mitogen-activated protein kinase and nuclear factor-κB. Inhibition of extracellular-regulated kinase-1/2 markedly reduced the upregulation of BMP-2 and ALP expression by BGN whereas inhibition of p38 mitogen-activated protein kinase or nuclear factor-κB had a moderate effect. Stimulation of aortic valve interstitial cells with oxLDL upregulated BGN expression and release. Knockdown and neutralization of BGN reduced the effect of oxLDL on BMP-2 and ALP expression. Extracellular soluble BGN induces the expression of BMP-2 and ALP in human aortic valve interstitial cells primarily via TLR2 and contributes to the proosteogenic effect of oxLDL. These findings highlight the potential role of soluble BGN and oxLDL in the development of calcific aortic valve disease.
    Arteriosclerosis Thrombosis and Vascular Biology 09/2012; 32(11):2711-20. · 6.34 Impact Factor
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    ABSTRACT: Calcific aortic stenosis is a chronic inflammatory disease, and aortic valve interstitial cells (AVIC) play an important role in valvular inflammation. Whereas AVIC from stenotic aortic valves exhibit an augmented response to Toll-like receptor 4 (TLR4) stimulation, the underlying mechanism is unclear. This study tested the hypothesis that an excessive cross-talk between the TLR4 and Notch1 pathways is responsible for augmentation of the inflammatory response to lipopolysaccharide (LPS) in AVIC of stenotic valves. Human AVIC were isolated from normal and stenotic leaflets. Nuclear factor kappa-B (NF-κB) activation and production of interleukin-8, monocyte chemoattactrant protein-1, and intercellular adhesion molecule-1 were analyzed after treatment with LPS. The role of Notch1 in the inflammatory response was determined using inhibitor, siRNA, and specific ligand. Cells from diseased valves produced greater levels of chemokines and intercellular adhesion molecule-1 that are associated with enhanced NF-κB activation. Interestingly, diseased cells exhibited augmented Jagged1 release and Notch1 activation after TLR4 stimulation. Inhibition and silencing of Notch1 each resulted in greater suppression of the TLR4-induced inflammatory response in diseased cells. Conversely, activation of Notch1 with a specific ligand, Jagged1, enhanced the LPS-induced inflammatory response in normal AVIC. Further, Notch1 intracellular domain was coimmunoprecipited with the inhibitor of NF-κB kinase after LPS stimulation, and inhibition of Notch1 abrogated the difference in the level of NF-κB activation between diseased and normal cells. Notch1 enhances the inflammatory response to TLR4 stimulation in human AVIC through modulating NF-κB activation. Excessive cross-talk between the TLR4 and Notch1 pathways is responsible for augmentation of the TLR4 response in AVIC of stenotic valves.
    Circulation 09/2012; 126(11 Suppl 1):S222-30. · 15.20 Impact Factor
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    ABSTRACT: Paraplegia remains a devastating complication of thoracic aortic surgery. The mechanism of the antecedent spinal cord ischemia and reperfusion injury (IR) remains poorly described. IR involves 2 injuries, an initial ischemic insult and subsequent inflammatory amplification of the injury. This mechanism is consistent with the clinical phenomenon of delayed onset paraplegia. This study sought to characterize the inflammatory response in the spinal cord after IR and hypothesized that this would support a bimodal mechanism of injury. Male C57Bl/6 mice were subjected to 5 minutes of aortic arch and left subclavian occlusion with subsequent reperfusion to generate spinal cord ischemia. Functional outcomes were scored at 12-hour intervals. Spinal cords were harvested after 0, 6, 12, 18, 24, 36, and 48 hours of reperfusion. Cytokine levels were analyzed using a mouse magnetic bead-based multiplex immunoassay. Inflammatory chemokine concentrations (interleukin [IL]-1β, IL-6, keratinocyte-derived cytokine, macrophage inflammatory protein-1α, monocyte chemotactic protein-1, RANTES, and tumor necrosis factor-α) peaked at 6 hours and 36 to 48 hours after reperfusion. Functional scores reflected initial gain in function with subsequent decline, inversely proportional to cytokine levels. Immunofluorescent staining demonstrated microglia activation at 12 and 48 hours. Spinal cord ischemia and reperfusion injury occurs in 2 phases, correlating to increases in inflammatory chemokines release and microglial activation. These observations chronologically parallel the too-common clinical syndrome of delayed-onset paraplegia. Understanding the molecular pathogenesis of this injury may allow future intervention to prevent this devastating complication.
    Circulation 09/2012; 126(11 Suppl 1):S110-7. · 15.20 Impact Factor
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    ABSTRACT: Background/Aim: Group IIa secretory phospholipase A2 (sPLA2 IIa) has been implicated in the regulation of metastasis of non-small cell lung cancer (NSCLC) and the present study investigates its contribution to lung cancer growth and progression. PLA2s initiate signaling in several pathways that mediate cell survival including phosphatidylinositol 3-kinase-AKT (PI3K-AKT), p38 mitogen-activated protein kinase (p38 MAPK), extracellular-signal-regulated kinase (ERK) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). Human NSCLC cell lines (A549 and NCI-H358) were treated with a specific sPLA2 IIa inhibitor. Cells were assayed for apoptosis, viability, proliferation and changes in cell morphology. Effects on AKT, p38 MAPK, ERK1/2 and NF-κB signaling pathways were investigated. sPLA2 IIa inhibition reduced proliferation and increased apoptosis. NF-κB activity was attenuated, whereas AKT, ERK1/2, p38 MAPK were variably affected by sPLA2 IIa inhibition. NF-κB inhibitor-associated apoptosis confirmed the dominant role of NF-κB. sPLA2 IIa attenuates growth and promotes apoptosis predominantly via its effects on NF-κB activity.
    Anticancer research 09/2012; 32(9):3601-7. · 1.71 Impact Factor

Publication Stats

2k Citations
555.55 Total Impact Points

Institutions

  • 1991–2013
    • University of Colorado
      • • Division of Cardiothoracic Surgery
      • • Department of Surgery
      Denver, CO, United States
  • 1999–2002
    • University of Illinois at Chicago
      Chicago, Illinois, United States
  • 1997–2002
    • Northwestern University
      • • Division of Thoracic Surgery
      • • Feinberg Cardiovascular Research Institute
      Evanston, IL, United States
  • 1993–1996
    • Childrens Hospital of Pittsburgh
      • Cardiothoracic Surgery Division
      Pittsburgh, Pennsylvania, United States
  • 1990–1993
    • Loma Linda University
      • Department of Cardiovascular and Thoracic Surgery
      Loma Linda, CA, United States
  • 1992
    • Boston Children's Hospital
      Boston, Massachusetts, United States