Evgeniy I. Solenov

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.

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.

Regulatory volume decrease of rat kidney principal cells after successive hypo-osmotic shocks

Outer Medullary Collecting Duct (OMCD) principal cells are exposed to significant changes of the extracellular osmolarity and thus the analysis of their regulatory volume decrease (RVD) function is of great importance in order to avoid cell membrane rupture and subsequent death. In this paper we provide a sub-second temporal analysis of RVD events occurring after two successive hypo-osmotic challenges in rat kidney OMCD principal cells. We performed experimental cell volume measurements and created a mathematical model based on our experimental results. As a consequence of RVD the cell expels part of intracellular osmolytes and reduces the permeability of the plasma membrane to water. The next osmotic challenge does not cause significant RVD if it occurs within a minute after the primary shock. In such a case the cell reacts as an ideal osmometer. Through our model we provide the basis for further detailed studies on RVD dynamical modeling.

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.

The water permeability reduction after successive hypo-osmotic shocks in kidney principal cells is apically regulated.

Background/Aims: Renal principal cells maintain their intracellular water and electrolyte content despite significant fluctuations of the extracellular water and salt concentrations. Their water permeability decreases rapidly (within a few seconds) after successive hypo-osmotic shocks. Our aim was to investigate the contribution of the apical and basolateral surface to this effect and the potential influence of fast reduction in AQP-2, -3 or -4 plasma membrane content. Methods: Rat principal cells of kidney collecting duct fragments underwent hypo-osmotic challenge applied apically or basolaterally and the regulatory volume decrease (RVD) was measured by the calcein quenching method. The AQP -2, -3 and -4 content of the plasma membrane fraction was quantified by Western blotting. Results: The hypo-osmotic shock applied apically causes rapid swelling with high apparent water permeability and fast RVD. An identical successive shock after 15-20 sec causes significantly lower swelling rate with 3-fold reduction in apparent water permeability. This reaction is accompanied by AQP2 decrease in the plasma membrane while AQP3 and AQP4 are unaffected. The contribution of the basolateral cell surface to RVD is significantly lower than the apical. Conclusion: These results indicate that in principal cells the effective mechanism of RVD is mainly regulated by the apical cell plasma membrane.

Study of the reaction of kidney collecting duct principal cells to hypotonic shock. Experiment and mathematical model

The reaction of rat kidney collecting duct principal cells to hypotonic shock was studied. The changes in cell relative volume were measured using fluorescent dye calcein, and a mathematical model based on our experimental results was developed. It was shown that regulatory volume decrease is mainly provided by significant release of osmolytes from the cell and decrease of the plasma membrane water permeability. Using our model, we calculated the membrane water permeability and found it to decrease from 2 · 10−1 to 2 · 10−2 cm/s. We conclude that for effective RVD to occur, a dramatic increase in the membrane permeability to K+, Cl− and organic anions is necessary.

Quantitative estimation of transmembrane ion transport in rat renal collecting duct principal cells.

Kidney collecting duct principal cells play a key role in regulated tubular reabsorption of water and sodium and secretion of potassium. The importance of this function for the maintenance of the osmotic homeostasis of the whole organism motivates extensive study of the ion transport properties of collecting duct principal cells. We performed experimental measurements of cell volume and intracellular sodium concentration in rat renal collecting duct principal cells from the outer medulla (OMCD) and used a mathematical model describing transmembrane ion fluxes to analyze the experimental data. The sodium and chloride concentrations ([Na+]in = 37.3 ± 3.3 mM, [Cl-]in = 32.2 ± 4.0 mM) in OMCD cells were quantitatively estimated. Correspondence between the experimentally measured cell physiological characteristics and the values of model permeability parameters was established. Plasma membrane permeabilities and the rates of transmembrane fluxes for sodium, potassium and chloride ions were estimated on the basis of ion substitution experiments and model predictions. In particular, calculated sodium (PNa), potassium (PK) and chloride (PCl) permeabilities were equal to 3.2 × 10-6 cm/s, 1.0 × 10-5 cm/s and 3.0 × 10-6 cm/s, respectively. This approach sets grounds for utilization of experimental measurements of intracellular sodium concentration and cell volume to quantify the ion permeabilities of OMCD principal cells and aids us in understanding the physiology of the adjustment of renal sodium and potassium excretion.

Age-Related Changes in Water Transport by Corneal Endothelial Cells in Rats

Senescence-associated alterations in the structure and function of the cornea make it more sensitive to such external agents as surgery, traumas, and disease, resulting in edema and vision impairment that can be corrected only by cornea transplantation. The role of aquaporins for cornea endothelium functioning, as well as age-related changes in their activity, is not entirely understood. We have studied age-related changes in the water permeability (Pf) of corneal endothelium plasma membranes and the mRNA expression levels of aquaporins aqp1 and aqp3 genes in Wistar and senescence-accelerated OXYS rats. At the age of 3 to 18 months, Pf increased in Wistar rats and decreased in OXYS rats, becoming two times lower than in the Wistar line. The expression of AQP1 mRNA (studied by real-time PCR) in the endothelium was the same in Wistar and OXYS rats at the age of 3 months. By the age of 18 months, it increased only in Wistar rats and became two times higher than in OXYS rats. The expression of aqp3 mRNA in the endothelium of 3-month-old OXYS rats was half that of Wistar rats and did not change with age, while it decreased in Wistar rats and at 18 months was four times lower than at 3 months. We propose that the increased water permeability of endothelial cells in Wistar rats is adaptive and compensates for the decrease in endothelial cell density with age, while the accelerated aging of OXYS rats eliminates this compensation.

Transcriptomic Analysis of the Claudin Interactome in Malignant Pleural Mesothelioma: Evaluation of the Effect of Disease Phenotype, Asbestos Exposure, and CDKN2A Deletion Status

Malignant pleural mesothelioma (MPM) is a highly aggressive tumor primarily associated with asbestos exposure. Early detection of MPM is restricted by the long latency period until clinical presentation, the ineffectiveness of imaging techniques in early stage detection and the lack of non-invasive biomarkers with high sensitivity and specificity. In this study we used transcriptome data mining in order to determine which CLAUDIN (CLDN) genes are differentially expressed in MPM as compared to controls. Using the same approach we identified the interactome of the differentially expressed CLDN genes and assessed their expression profile. Subsequently, we evaluated the effect of tumor histology, asbestos exposure, CDKN2A deletion status, and gender on the gene expression level of the claudin interactome. We found that 5 out of 15 studied CLDNs (4, 5, 8, 10, 15) and 4 out of 27 available interactors (S100B, SHBG, CDH5, CXCL8) were differentially expressed in MPM specimens vs. healthy tissues. The genes encoding the CLDN-15 and S100B proteins present differences in their expression profile between the three histological subtypes of MPM. Moreover, CLDN-15 is significantly under-expressed in the cohort of patients with previous history of asbestos exposure. CLDN-15 was also found significantly underexpressed in patients lacking the CDKN2A gene. These results warrant the detailed in vitro investigation of the role of CDLN-15 in the pathobiology of MPM.

Role of the low-selective organic anion transport in regulation of osmotic balance of renal collecting duct principal cells under hypo-osmotic conditions

In the course of adaptation of the rat kidney collecting duct cells to hypo-osmotic medium, the organic anion transporter inhibitor probenecid reduced significantly the regulatory cell volume decrease in response to a hypotonic shock. Both probenecid and hypotonic shock delayed significantly the entry into a cell of the fluorescent dye calcein, which exists as anion at neutral pH. Thus, the organic osmolyte transport plays an important role in the regulatory decrease of the principal cell volume under the hypo-osmotic conditions.