Study Protocol: The Feeding Exercise Randomized Trial among Overweight and Obese Adolescents in Greece.

Background: This paper describes the study protocol used in the Feeding Exercise Clinical Trial in Adolescents in the region of Larissa in Greece, a randomized controlled clinical trial, among overweight/obese adolescents. Methods: The main aim of the study was to comparatively evaluate the effectiveness of 2 different clinical interventions among 12 to 18-year-old overweight and obese adolescents. The first group participated in an exercise program and the second group in a combined dietary and exercise program. The third group was the control group. The study was conducted between 2014 and 2015. All adolescents aged 12 to 18 years old from public schools of Larisa and also their parents asked to participate. The effects of the intervention program will be analyzed by repeated-measures analysis of variance or the Friedman test. Changes in lifestyle behaviors from the baseline to the end of the intervention will be assessed using a chi-square test for categorical variables. A Pearson or a Spearman correlation coefficient and a linear regression analysis will be performed to explore any associations between quantitative variables. The following parameters were measured among adolescents: height, weight, body mass index, waist circumference, systolic and diastolic pressure, pulse rate, dietary and exercise habits of the adolescents and their parents. Conclusion: This is the first clinical trial in Greece investigating the impact of clinical interventions on obesity among adolescents. It is expected that the results will provide useful insights into the effectiveness of clinical interventions among overweight and obese adolescents in Greece.

Effects of Ranolazine and its Combination with Amiodarone on Rapid Pacing-induced Reentrant Atrial Tachycardia in Rabbits.

Ranolazine (RAN) has previously been shown to lower the onset of cholinergic atrial fibrillation in intact animals; however, its efficacy in the setting of atrial tachycardia (AT) is unknown. The purpose of this study was to investigate the effects of RAN alone or in combination with amiodarone (AMIO) on rapid pacing-evoked right AT in rabbit hearts. Right atrial monophasic action potentials (MAPs) were recorded in 11 anesthetized rabbits, using combination MAP pacing catheters. Vulnerability to AT was tested by employing consecutive trains of rapid burst pacing prior to and after 2.4 mg/kg of RAN alone delivered intravenously and then in combination with 3 mg/kg of AMIO as a 15-minute infusion. Primary endpoints were postdrug AT reproducibility as well as cycle length (CL) and tachycardia duration. MAP duration at 75% repolarization and the effective refractory period (ERP) were assessed during programmed pacing to calculate the atrial postrepolarization refractoriness (aPRR = ERP - MAPD75%). AT was elicited in eight out of 11 rabbits; only these animals were included for further investigation. RAN did not abolish the inducibility of AT in any experiment; however, it prolonged its CL (baseline vs. RAN: 120 ± 16 ms vs. 138 ± 18 ms; p = 0.053). Supplemental AMIO further increased the AT CL (baseline vs. RAN + AMIO: 120 ± 16 ms vs. 152 ± 23 ms; p = 0.006), without affecting arrhythmia reinducibility. Slowing of the tachycardia after RAN or RAN + AMIO was associated with spontaneous termination of the arrhythmia. RAN prolonged the aPRR significantly, while AMIO in addition to RAN potentiated this effect. Neither RAN alone nor its combination with AMIO abolished the elicitation of AT in this model. However, both agents synergistically prolonged the aPRR, resulting in the slowing of AT and promoting spontaneous termination of the arrhythmia.

Silver Nanoparticles Alter Cell Adhesion and Proliferation of Sheep Primary Mesothelial Cells.

BACKGROUND: Human exposure to engineered nanoparticles has been linked to pleural effusion, inflammation and fibrosis. Silver nanoparticles (AgNPs) are widely used in medical and domestic products, increasing the risk of occupational and domestic exposure. We assessed the influence of AgNPs on adhesion and proliferation of sheep primary pleural mesothelial cells. MATERIALS AND METHODS: Cells were used for cell adhesion (90 min) and proliferation experiments (3 days) while exposed to 20 nm and 60 nm AgNPs (0.2 µg/ml and 2 µg/ml) using colorimetric assays. RESULTS: Exposure to 0.2 µg/ml of 20 nm and 60 nm AgNPs significantly increased cell adhesion, while at 2 µg/ml this effect was not elicited. Cell proliferation was significantly increased by both 20 nm and 60 nm AgNPs at 0.2 µg/ml, while at 2 µg/ml this effect was only elicited by the 60 nm AgNPs. CONCLUSION: AgNPs alter the adhesive and proliferative properties of primary pleural mesothelial cells.

Silver nanoparticles alter the permeability of sheep pleura and of sheep and human pleural mesothelial cell monolayers.

Nanoparticles have been implicated in the development of pleural effusions in exposed factory workers while in experimental animal studies it has been shown that they induce inflammation, fibrosis and carcinogenesis in the pleura. The scope of this study was to investigate the direct effects of silver nanoparticles exposure on the membrane permeability of sheep parietal pleura, of primary sheep pleural cell monolayers and on a human mesothelial cell line. Our findings suggest that acute (30min) exposure increases the pleural permeability ex vivo, while longer (24h) exposure in vivo leads to late decrease of the pleural cell monolayers permeability.

Influence of AQP1 on cell adhesion, migration, and tumor sphere formation in malignant pleural mesothelioma is substratum- and histological-type dependent.

Malignant pleural mesothelioma (MPM) is an aggressive cancer. MPM cells express aquaporin-1 (AQP1) that in other cancers has been shown to participate in the tumor metastasis processes. However, in MPM patients AQP1 overexpression is an independent prognostic factor favoring survival. In this study we aimed at evaluating the role of AQP1 in cell adhesion, migration, and tumor sphere formation in nonmalignant mesothelial cells (MeT-5A) and in epithelioid (M14K) and sarcomatoid (ZL34) MPM cell lines. We used fibronectin (FN) or homologous cell-derived extracellular martrix (ECM) substratum to investigate the role of AQP1 in these experimental phenotypes, inhibiting AQP1 by 10(-5) M mercury chloride (MC). Deposited ECM during cell culture exhibited significant concentration differences among cell types. ZL34 cell adhesion was significantly higher than MeT-5A or M14K cells on FN and ECM. MeT-5A and M14K cell adhesion on FN was sensitive to AQP1 inhibition, whereas AQP1 inhibition on ECM was limited to M14K cells. Wound healing in ZL34 cells was significantly higher than MeT-5A and M14K cells on FN and ECM. AQP1 inhibition significantly lowered cell migration in ZL34 cells on FN and ECM. Sphere formation was not dependent on FN or ECM in the media. AQP1 inhibition in FN media reduced sphere formation in M14K cells, whereas, in ECM, all three cell types were sensitive to AQP1 inhibition.

Transcriptional over-expression of chloride intracellular channels 3 and 4 in malignant pleural mesothelioma.

BACKGROUND: Chloride Intracellular Channels (CLICs) are contributing to the regulation of multiple cellular functions. CLICs have been found over-expressed in several malignancies, and therefore they are currently considered as potential drug targets. The goal of our study was to assess the gene expression levels of the CLIC's 1-6 in malignant pleural mesothelioma (MPM) as compared to controls. METHODS: We used gene expression data from a publicly available microarray dataset comparing MPM versus healthy tissue in order to investigate the differential expression profile of CLIC 1-6. False discovery rates were calculated and the interactome of the significantly differentially expressed CLICs was constructed and Functional Enrichment Analysis for Gene Ontologies (FEAGO) was performed. RESULTS: In MPM, the gene expressions of CLIC3 and CLIC4 were significantly increased compared to controls (p=0.001 and p<0.001 respectively). A significant positive correlation between the gene expressions of CLIC3 and CLIC4 (p=0.0008 and Pearson's r=0.51) was found. Deming regression analysis provided an association equation between the CLIC3 and CLIC4 gene expressions: CLIC3=4.42CLIC4-10.07. CONCLUSIONS: Our results indicate that CLIC3 and CLIC4 are over-expressed in human MPM. Moreover, their expressions correlate suggesting that they either share common gene expression inducers or that their products act synergistically. FAEGO showed that CLIC interactome might contribute to TGF beta signaling and water transport.

Computational genomic analysis of PARK7 interactome reveals high BBS1 gene expression as a prognostic factor favoring survival in malignant pleural mesothelioma.

The aim of our study was to assess the differential gene expression of Parkinson protein 7 (PARK7) interactome in malignant pleural mesothelioma (MPM) using data mining techniques to identify novel candidate genes that may play a role in the pathogenicity of MPM. We constructed the PARK7 interactome using the ConsensusPathDB database. We then interrogated the Oncomine Cancer Microarray database using the Gordon Mesothelioma Study, for differential gene expression of the PARK7 interactome. In ConsensusPathDB, 38 protein interactors of PARK7 were identified. In the Gordon Mesothelioma Study, 34 of them were assessed out of which SUMO1, UBC3, KIAA0101, HDAC2, DAXX, RBBP4, BBS1, NONO, RBBP7, HTRA2, and STUB1 were significantly overexpressed whereas TRAF6 and MTA2 were significantly underexpressed in MPM patients (network 2). Furthermore, Kaplan-Meier analysis revealed that MPM patients with high BBS1 expression had a median overall survival of 16.5 vs. 8.7 mo of those that had low expression. For validation purposes, we performed a meta-analysis in Oncomine database in five sarcoma datasets. Eight network 2 genes (KIAA0101, HDAC2, SUMO1, RBBP4, NONO, RBBP7, HTRA2, and MTA2) were significantly differentially expressed in an array of 18 different sarcoma types. Finally, Gene Ontology annotation enrichment analysis revealed significant roles of the PARK7 interactome in NuRD, CHD, and SWI/SNF protein complexes. In conclusion, we identified 13 novel genes differentially expressed in MPM, never reported before. Among them, BBS1 emerged as a novel predictor of overall survival in MPM. Finally, we identified that PARK7 interactome is involved in novel pathways pertinent in MPM disease.

Physiology of pericardial fluid production and drainage.

The pericardium is one of the serosal cavities of the mammals. It consists of two anatomical structures closely connected, an external sac of fibrous connective tissue, that is called fibrous pericardium and an internal that is called serous pericardium coating the internal surface of the fibrous pericardium (parietal layer) and the heart (visceral layer) forming the pericardial space. Between these two layers a small amount of fluid exists that is called pericardial fluid. The pericardial fluid is a product of ultrafiltration and is considered to be drained by lymphatic capillary bed mainly. Under normal conditions it provides lubrication during heart beating while the mesothelial cells that line the membrane may also have a role in the absorption of the pericardial fluid along with the pericardial lymphatics. Here, we provide a review of the the current literature regarding the physiology of the pericardial space and the regulation of pericardial fluid turnover and highlight the areas that need to be further investigated.

Airways microbiota: Hidden Trojan horses in asbestos exposed individuals?

Malignant pleura mesothelioma (MPM) is a rare type of cancer with devastating prognosis, which develops in the pleural cavity from transformed mesothelium. MPM has been directly associated with asbestos exposure however there are aspects of the pathophysiology involved in the translocation of asbestos fibers in the pleura that remain unclear. Here, we propose and discuss that certain proteins secreted by airways symbiotic microbiota create membrane pores to the airway epithelial cells, through which asbestos fibers can penetrate the lung parenchyma and reach the sub-pleural areas. We evaluate this hypothesis using data from the published literature regarding the airways microbiota toxins such as cholesterol-dependent cytolysins (CDCs).

VEGF increases the permeability of sheep pleura ex vivo through VEGFR2 stimulation.

Vascular endothelial growth factor (VEGF), a cytokine that increases vascular permeability to water and proteins and induces angiogenesis, has been implicated in the development of pleural effusions. Inflammatory and malignant pleural effusions are rich in VEGF content while mesothelial cells produce and excrete VEGF. In this report we aimed at investigating by means of electrophysiology the direct effects of VEGF on the parietal and visceral sheep pleura as well as the type of receptors that mediate this effect. Our findings show that VEGF has a direct effect on the pleural mesothelium rendering it more permeable and this effect is mediated through the stimulation of VEGF receptor 2. Our findings shed more light to the role of VEGF in the pathogenesis of pleural effusions and provide functional evidence for a role of VEGFR2 on the pleural mesothelium that has never been studied before.

Long-term exposure to muscarinic agonists decreases expression of contractile proteins and responsiveness of rabbit tracheal smooth muscle cells.

BACKGROUND: Chronic airway diseases, like asthma or COPD, are characterized by excessive acetylcholine release and airway remodeling. The aim of this study was to investigate the long-term effect of muscarinic agonists on the phenotype and proliferation of rabbit tracheal airway smooth muscle cells (ASMCs). METHODS: ASMCs were serum starved before treatment with muscarinic agonists. Cell phenotype was studied by optical microscopy and indirect immunofluorescence, using smooth muscle α-actin, desmin and SM-Myosin Heavy Chain (SM-MHC) antibodies. [N-methyl-3H]scopolamine binding studies were performed in order to assess M3 muscarinic receptor expression on isolated cell membranes. Contractility studies were performed on isolated ASMCs treated with muscarinic agonists. Proliferation was estimated using methyl-[3H]thymidine incorporation, MTT or cell counting methods. Involvement of PI3K and MAPK signalling pathways was studied by cell incubation with the pathway inhibitors LY294002 and PD98059 respectively. RESULTS: Prolonged culture of ASMCs with acetylcholine, carbachol or FBS, reduced the expression of α-actin, desmin and SM-MHC compared to cells cultured in serum free medium. Treatment of ASMCs with muscarinic agonists for 3-15 days decreased muscarinic receptor expression and their responsiveness to muscarinic stimulation. Acetylcholine and carbachol induced DNA synthesis and increased cell number, of ASMCs that had acquired a contractile phenotype by 7 day serum starvation. This effect was mediated via a PI3K and MAPK dependent mechanism. CONCLUSIONS: Prolonged exposure of rabbit ASMCs to muscarinic agonists decreases the expression of smooth muscle specific marker proteins, down-regulates muscarinic receptors and decreases ASMC contractile responsiveness. Muscarinic agonists are mitogenic, via the PI3K and MAPK signalling pathways.

Ranolazine enhances the antiarrhythmic activity of amiodarone by accelerating conversion of new-onset atrial fibrillation after cardiac surgery.

Ranolazine is a relatively novel antiischemic/antianginal compound with antiarrhythmic properties. We investigated its ability to shorten the time to conversion of postoperative atrial fibrillation (POAF) when added to amiodarone after coronary artery bypass graft (CABG) surgery. In this prospective, randomized, allocation-concealed, single-blind, single-site clinical trial, we enrolled consecutive eligible patients who developed POAF after elective on-pump CABG surgery. Participants were randomized to receive either ranolazine 375 mg twice daily orally plus intravenous amiodarone (active group) or intravenous amiodarone alone (control group). We enrolled 41 patients; 20 in the active and 21 in the control group. There were no significant differences between the groups in terms of age, procedural duration, extracorporeal circulation time, and aortic cross-clamp time. Mean time of conversion was significantly shorter in the active group (19.9 ± 3.2 vs 37.2 ± 3.9 hours, P < .001), suggesting that compared to amiodarone alone, the ranolazine-amiodarone combination had a superior antiarrhythmic effect against POAF.

Endothelin-1 acutely reduces the permeability of visceral sheep peritoneum in vitro through both endothelin-A and endothelin-B receptors.

Mesothelium is an important part of the peritoneal barrier for water and ion transport, essential for effective peritoneal dialysis (PD). Peritoneal fibrosis has been associated with PD treatment failure. Endothelin-1 (ET-1) is a potent vasoactive peptide, involved in pathologic fibrotic processes. Its action is mediated mainly by endothelin type A (ETA ) and type B (ETB ) receptors. The aim of this study was to investigate, by Ussing chamber experiments, the effect of ET-1 on the transmesothelial electrical resistance (RTM ) of the isolated visceral sheep peritoneum. Intact sheets of visceral peritoneum were obtained from 40 adult sheep and mounted in Ussing-type chambers. ET-1 (10(-7) M), BQ-123 (ETA receptor antagonist; 10(-6) M), BQ-788 (ETB receptor antagonist; 10(-6) M), and their combinations were added on the apical and the basolateral side of the peritoneum. RTM was measured before and serially after addition of the substances, and changes were registered as percentage (ΔRTM %). RTM increased within 1 min after addition of ET-1 apically (ΔRTM 65.03 ± 15.87%; P < 0.05) or basolaterally (ΔRTM 85.5 ± 20.86%; P < 0.05). BQ-123 and BQ-788 and their combination significantly reduced (P < 0.05) the effect of ET-1 to a similar degree in all cases. These results clearly indicate that ET-1 reduces ionic permeability of the visceral sheep peritoneum in vitro. Additionally, it is obvious that this inhibitory effect is mediated through both ETA and ETB receptors.

TNFα induces expression of HIF-1α mRNA and protein but inhibits hypoxic stimulation of HIF-1 transcriptional activity in airway smooth muscle cells.

Airway smooth muscle cells (ASMCs) participate in tissue remodeling characteristic of airway inflammatory diseases like asthma. Inflammation and hypoxia pathways are often interconnected and the regulatory subunit of the hypoxia inducible factor, HIF-1α, has been recently shown to be induced by cytokines. Here we investigate the effect of individual or combined treatment of ASMCs with the inflammatory mediator TNFα and/or hypoxia on the expression of HIF-1α, HIF-1 targets and inflammation markers. TNFα enhances HIF-1α protein and mRNA levels, under both normoxia and hypoxia. TNFα-mediated induction of HIF-1α gene transcription is repressed by inhibition of the NF-κB pathway. Despite the up-regulation of HIF-1α protein, the transcription of HIF-1 target genes remains low in the presence of TNFα at normoxia and is even reduced at hypoxia. We show that the reduction in HIF-1 transcriptional activity by TNFα is due to inhibition of the interaction of HIF-1α with ARNT and subsequent blocking of its binding to HREs. Comparison between hypoxia and TNFα for their effects on the expression of inflammatory markers shows significant differences: hypoxia up-regulates the expression of IL-6, but not RANTES or ICAM, and reduces the induction of VCAM by TNFα. Finally, ex vivo treatment of rabbit trachea strips with TNFα increases HIF-1α protein levels, but reduces the expression of HIF-1 targets under hypoxia. Overall, TNFα induces HIF-1α mRNA synthesis via an NF-κB dependent pathway but inhibits binding of HIF-1α to ARNT and DNA, while hypoxia and TNFα have distinct effects on ASMC inflammatory gene expression.

Gene expression profile of aquaporin 1 and associated interactors in malignant pleural mesothelioma.

Overexpression of AQP1 has recently been shown to be an independent prognostic factor in pleural mesothelioma favoring survival. This paper presents a data mining and bioinformatics approach towards the evaluation of the gene expression profile of AQP1 in malignant pleural mesothelioma and of AQP1 associated markers in the context of mesothelioma disease phenotype, CDKN2A gene deletion, sex and asbestos exposure. The data generated were thus again subjected to differential expression profile analysis. Here we report that AQP1 is overexpressed in epithelioid mesothelioma and identify TRIP6 and EFEMP2 as candidate genes for further investigation in mesothelioma.

Endothelial progenitor cells in the pathogenesis of idiopathic pulmonary fibrosis: an evolving concept.

BACKGROUND: Idiopathic pulmonary fibrosis (IPF) has been associated with abnormal vascular remodeling. Bone marrow derived endothelial progenitor cells (EPCs) are considered to possess lung tissue repair and vascular remodeling properties. OBJECTIVES: The study aimed to assess early EPCs levels and EPCs endogenous vascular endothelial growth factor (VEGF) expression in IPF. In order to examine alterations in the mobilization of EPCs from the bone marrow we measured plasma VEGF. MAIN RESULTS: Twenty-three patients with IPF and fifteen healthy subjects were included. The number of early EPCs colonies was markedly reduced in IPF patients vs controls (6.00±6.49 vs 49.68±16.73, respectively, p<0.001). EPCs were further decreased in patients presenting systolic pulmonary arterial pressure (sPAP)≥35 mmHg. The number of colonies per well correlated negatively with P((A-a))O(2) (r =  -0.750, p<0.001). Additionally, VEGF mRNA levels were significantly increased in IPF patients. There were no differences observed in VEGF plasma levels in IPF patients when compared to controls. CONCLUSIONS: The current data suggest that inadequate levels of early EPCs may potentially contribute to suppressed repair and recovery of the damaged pulmonary endothelium and thereby may drive the sequence of events in profibrogenic direction. Increased VEGFmRNA levels in the clinical context of IPF may represent a compensatory mechanism to overcome reduced EPCs levels.

Ranolazine-induced postrepolarization refractoriness suppresses induction of atrial flutter and fibrillation in anesthetized rabbits.

Ranolazine (Ran) is a novel anti-ischemic agent with electrophysiologic properties mainly attributed to the inhibition of late Na(+) current and atrial-selective early Na(+) current. However, there are only limited data regarding its efficacy and mechanism of action against atrial flutter (Afl) and atrial fibrillation (AF) in intact animals. Therefore, we aimed to investigate the electrophysiologic mechanism of Ran in a rabbit model of inducible atrial tachyarrhythmias elicited by acetylcholine (ACh). Arrhythmias were produced in 19 rabbits by rapid atrial burst pacing during control, after intravenous ACh and after Ran + ACh administration. Recording of right atrial monophasic action potentials (MAPs) and programmed stimulation were utilized to determine the duration of atrial repolarization at various cycle lengths and voltage levels of action potential, including 75% of total MAP duration (MAPD75), effective refractory period (ERP), and postrepolarization refractoriness (PRR = ERP - MAPD75) prior to and after Ran. Control stimulation yielded no arrhythmias or maximal nonsustained runs of Afl/AF. Upon ACh, 17 of 19 rabbits exhibited sustained Afl and AF as well as mixed forms of Afl/AF, while 2 animals revealed none or short runs of nonsustained arrhythmias and were excluded from the study. High-frequency burst pacing during the first 30 minutes after Ran + ACh failed to induce any arrhythmia in 13 of 17 rabbits (76%), while 2 animals displayed sustained Afl/AF and 2 other animals nonsustained Afl/AF. At basic stimulation cycle length of 250 milliseconds, Ran prolonged baseline atrial ERP (80 ± 8 vs 120 ± 9 milliseconds, P < .001) much more than MAPD75 (65 ± 7 vs 85 ± 7 milliseconds, P < .001), leading to atrial PRR which was more pronounced after Ran compared with control measurements (35 ± 11 vs 15 ± 10 milliseconds, P < .001). This in vivo study demonstrates that Ran exerts antiarrhythmic activity by suppressing inducibility of ACh-mediated Afl/AF in intact rabbits. Its action may predominantly be related to a significant increase in atrial PRR, resulting in depressed electrical excitability and impediment of arrhythmia initiation.

Effect of ranolazine in preventing postoperative atrial fibrillation in patients undergoing coronary revascularization surgery.

BACKGROUND/OBJECTIVE: Ranolazine is a new anti-ischemic agent approved for chronic angina with additional electrophysiologic properties. The purpose of the present trial was to investigate its effect in preventing postoperative atrial fibrillation (POAF) after on-pump coronary artery bypass graft (CABG) surgery. METHODS: In the current prospective, randomized, (1 active: 2 control), single-blind (outcome assessors), single-centre clinical trial we recruited consecutive eligible patients scheduled for elective on-pump CABG. Participants were assigned to receive either oral ranolazine 375 mg twice daily for 3 days prior to surgery and until discharge, or to receive usual care. Patients were monitored for the development of POAF. RESULTS: We enrolled 102 patients. Significantly lower incidence of POAF was noted in the ranolazine group compared with the control group (3 out of 34 patients, 8.8%, vs 21 out of 68 patients, 30.8%; p< 0.001). Mean values of left atrial diameter and left ventricular ejection fraction between the control and the ranolazine group were not significantly different. CONCLUSION: Our findings suggest a protective role of oral ranolazine when administered in a moderate dose preoperatively in patients undergoing on-pump CABG surgery. Future studies based on a wider sample of patients will eventually support our conclusions.

Pleural fluid protein is inversely correlated with age in uncomplicated parapneumonic pleural effusions.

OBJECTIVES: Assess whether age influences standard biochemical parameters used in the differential diagnosis of transudative and exudative pleural effusions. DESIGN AND METHODS: We retrospectively analyzed data from the database of our clinic from 225 patients with pleural effusions categorized based on their final diagnosis in 5 groups: transudates 41 (18%), uncomplicated parapneumonic 26 (12%), complicated parapneumonic 20 (9%), tuberculosis 35 (15%) and lung cancer 103 (46%). We tested whether age correlated with pleural fluid protein or lactate dehydrogenase. RESULTS: There was a statistically significant inverse correlation only between the age and the pleural fluid protein content in patients with uncomplicated parapneumonic effusions with correlation coefficient r=-0.6 [(95% CI=-0.8 to -0.28); p=0.001]. Linear regression analysis showed that this association is given by the equation: age=101.998-10.03 protein. In the same group of patients age was not correlated with serum protein content. CONCLUSIONS: Our study shows that age may be a confounding factor in the differential diagnosis of transudative and exudative pleural effusions. Clinicians should be aware of this finding especially when dealing with elders.

Matrix metalloproteinases 2 and 9 increase permeability of sheep pleura in vitro.

BACKGROUND: Matrix metalloproteinases (MMPs) 2 and 9 are two gelatinase members which have been found elevated in exudative pleural effusions. In endothelial cells these MMPs increase paracellular permeability via the disruption of tight junction (TJ) proteins occludin and claudin. In the present study it was investigated if MMP2 and MMP9 alter permeability properties of the pleura tissue by degradation of TJ proteins in pleural mesothelium. RESULTS: In the present study the transmesothelial resistance (RTM) of sheep pleura tissue was recorded in Ussing chambers after the addition of MMP2 or MMP9. Both enzymes reduced RTM of the pleura, implying an increase in pleural permeability. The localization and expression of TJ proteins, occludin and claudin-1, were assessed after incubation with MMPs by indirect immunofluorescence and western blot analysis. Our results revealed that incubation with MMPs did not alter neither proteins localization at cell periphery nor their expression. CONCLUSIONS: MMP2 and MMP9 increase the permeability of sheep pleura and this finding suggests a role for MMPs in pleural fluid formation. Tight junction proteins remain intact after incubation with MMPs, contrary to previous studies which have shown TJ degradation by MMPs. Probably MMP2 and MMP9 augment pleural permeability via other mechanisms.