Increase In Water Permeability Research Articles

Effect of mobile cation on zeolite-polyamide thin film nanocomposite membranes

Hybrid zeolite-polyamide thin film nanocomposite (TFN) reverse osmosis membranes were synthesized by incorporating Linde type A (LTA)-type zeolite molecular sieve nanocrystals in the interfacial polymerization reaction used to form polyamide thin films. Nanocrystals were prepared with two different mobile cations (Na+ and Ag+) exchanged within the LTA crystal matrix. Incorporation of molecular sieve nanocrystals into polyamide thin films during interfacial polymerization was verified by infrared spectroscopy. Both TFN membranes exhibited higher water permeability, while maintaining similar salt rejection to pure polyamide thin film composite membranes. Nanocomposite thin films containing LTA nanocrystals in the silver form (AgA) produced a greater increase in water permeability than those in the sodium form (NaA). Furthermore, AgA-TFN membranes exhibited more hydrophilic and smooth interfaces, which appeared to inhibit adhesion of bacteria cells onto the membranes. The AgA nanocrystals exhibited significant bactericidal activity; however, when encapsulated within polyamide thin films the antimicrobial activity was significantly reduced.

Regulation of water permeability of collecting ducts in mouse kidney during postnatal development

Water permeability of epithelial cells and response to vasopressin was studied on isolated fragments of collecting ducts in the kidney of C57BL/6J mice of three age groups (9, 18, and 60–90 days). The coefficient of osmotic water permeability P f was evaluated from the rate of cell swelling after medium osmolality was changed from 300 to 200 mOsm/l. The P f value proved to be significantly lower in mice at the age of 9 days than at the age of 18 days, i.e., after the transition to mixed feeding; although P f at the age of 18 days does not reach the level of adult animals (58.6 ± 7.7, 94.5 ± 8.8, and 168.4 ± 11.8 μM/s, respectively). The antagonist of vasopressin V2 receptors desmopressin at 1 nM significantly increased P f in both 18-day-old and adult mice but induced no changes in 9-day-old animals. The inhibitor of protein kinase C Ro-31-8220 in the concentration of 100 nM inhibited the desmopressin effect on P f in 18 day-old and adult mice but did not inhibit the effect of the analog of the vasopressin secondary messenger cAMP, N6,O2-dibutyryl cyclic monophosphate, on P f of the plasma membrane in collecting duct cells. Thus, the response of collecting duct cells to vasopressin appears at the end of wining and correlates with the increase in unstimulated osmotic water permeability of the plasma membrane in collecting duct cells. The vasopressin signal transduction via V2 receptors is proposed to require the activity of protein kinase C and calcium-dependent systems of intercellular mediators apart from the cAMP-mediated mechanism.

Effects of feed water temperature on separation performance and organic fouling of brackish water RO membranes

Data are presented from a series of laboratory experiments designed to evaluate separation performance and humic acid fouling for two RO membranes treating brackish water at temperatures of 15, 25, and 35°C. A model is proposed that considers changes only to solute and solvent properties. Model results and experimental data confirm that solute concentration polarization decreases, while water permeability and salt permeability increase with temperature. Overall, higher feed water temperature reduces energy consumption and observed salt rejection to a greater extent than that predicted by the model, which suggests that RO transport models must be developed for predicting changes in solution and membrane properties. At all temperatures, salt rejection increases after introduction of humic acid, probably due to membrane modification and sealing of thin film defects. Humic acid colloidal size decreases with increasing temperature. At higher temperatures, humic acid rejection is lower (as measured by TOC) due to changes in the membrane structure and in the fraction of dissolved TOC. Flux decline is much more severe at 15°C, but practically identical at 25 and 35°C. The mass of humic acid accumulated on the membranes is essentially the same at all temperatures, but specific cake resistance increases as temperature decreases; hence, specific cake resistance increases with increasing humic acid colloid size. These results have important implications for engineering efforts to mitigate membrane fouling and reduce energy consumption in brackish water desalination.

Caprock and overburden processes in geological CO2 storage: An experimental study on sealing efficiency and mineral alterations

A comprehensive set of experimental and analytical methods has been used to characterise the sealing and fluid -transport properties of fine-grained (pelitic) sedimentary rocks under the pressure and temperature conditions of geological CO2 storage. The flow experiments were carried out on cylindrical sample plugs of 28.5 or 38 mm diameter and 10–20 mm length. The capillary sealing effici ncy of the lithotypes was determined by repetitive gas breakthrough experiments to test for reproducibility and to detect petrophysical changes of the rock samples resulting from CO2/water/rock interactions. These tests were performed with both, Helium and sc CO2 on the initially water-saturated sample plugs. Although molecular diffusion is not considered as an efficient leakage mechanism it represents a rate-determining step in mineral reactions and reactive transport. Therefore repetitive CO2 diffusion experiments were carried out on selected samples in the water-saturated state. These measurements provide information on the molecular mobility of CO2 and its hydrolysis products and on the physical and chemical storage capacity of the rock for these species. Before and after each experiment a steady -state fluid flow of water was established across the samples by applying high pressure gradients. This procedure ensured a defined state of saturation. Permeability coefficients derived from these tests were used to detect changes in the transport properties resulting from exposure to CO2. The fluid transport experiments were complemented by petrophysical (BET specific surface area, mercury porosimetry) and mineralogical analyses (X-ray diffraction; XRD ) of the original and post -experiment samples. The experiments revealed significant changes in the transport properties and the sealing efficiency of the samples. The gas breakthrough tests resulted in reduced capillary entry pressures and increased effective gas permeability as a result of repetitive exposure to CO2. Repeated diffusion tests revealed a faster diffusive transport in the second experiment. An increase in water permeability was consistently observed after both, capillary breakthrough tests and diffusi on experiments with CO2. The BET and mercury porosimetry results were not significantly affected by the CO2 treatment. XRD measurements before and after CO2 treatment revealed significant variations in the mineral compositions of the samples upon exposure to CO2.

Fibrinogen-γ C-Terminal Fragments Induce Endothelial Barrier Dysfunction and Microvascular Leak via Integrin-Mediated and RhoA-Dependent Mechanism

The purposes of this study were to characterize the direct effect of the C-terminal fragment of fibrinogen gamma chain (gammaC) on microvascular endothelial permeability and to examine its molecular mechanism of action. Intravital microscopy was performed to measure albumin extravasation in intact mesenteric microvasculature, followed by quantification of hydraulic conductivity in single perfused microvessels. Transendothelial electric resistance was measured in microvascular endothelial cells in combination with immunoblotting and immunocytochemistry. The results show that gammaC induced time- and concentration-dependent increases in protein transvascular flux and water permeability and decreases in endothelial barrier function, coupled with Rho GTPase activation, myosin light chain phosphorylation, and stress fiber formation. Depletion of RhoA via siRNA knockdown or pharmacological inhibition of RhoA signaling attenuated gammaC-induced barrier dysfunction. Imaging analyses demonstrated binding of gammaC to endothelial cells; the interaction was inhibited during blockage of the alphavbeta3 integrin. Furthermore, in vivo experiments showed that the microvascular leak response to gammaC was attenuated in integrin beta3(-/-) animals. Fibrinogen-gamma C terminus directly interacts with the microvascular endothelium causing fluid and protein leak. The endothelial response to gammaC involves an integrin receptor-mediated RhoA-dependent signaling pathway that leads to paracellular hyperpermeability.

Preparation of PVDF/PMMA blend hollow fiber membrane via thermally induced phase separation (TIPS) method

Porous poly(vinylidene fluoride) (PVDF)/poly(methyl methacrylate) (PMMA) blend hollow fiber membranes were prepared via thermally induced phase separation (TIPS) process. From the measurement of X-ray diffraction, the crystalline structure of PVDF hardly changed by blending with PMMA. When total polymer concentration was fixed at 30 wt%, water permeability of the blend membrane increased by increasing PMMA concentration. However, when PVDF concentration was fixed at 25 wt%, the trend of water permeability with the increase of PMMA concentration was contrary to the former case. Treating with acetone was applied to extract the PMMA from the obtained blend membranes. The extraction of PMMA was effective to increase water permeability. In addition, the extraction of PMMA brought about the improvement for the membrane elongation. The PVDF crystallinity was found to increase with the PMMA extraction due to the secondary crystallization. This was the reason for the elongation enhancement.

Acceleration of Vacuolar Regeneration and Cell Growth by Overexpression of an Aquaporin NtTIP1;1 in Tobacco BY-2 Cells

Aquaporin is a water channel that increases water permeability through membranous structures. In plants, vacuoles are essential organelles that undergo dynamic volume changes during cell growth. To understand the contribution of aquaporins to plant cell growth, we developed a transgenic tobacco BY-2 cell line overexpressing the tonoplast intrinsic protein (TIP), gammaTIP. Vacuolar membranes of isolated vacuoles from gammaTIP-overexpressing cells showed higher water permeation activities than those from wild-type cells. We then examined the role of gammaTIP in vacuolar regeneration of evacuolated tobacco BY-2 protoplasts (miniprotoplasts). Vacuolar regeneration from thin to thick tube-network vacuoles and subsequent development of large vacuoles was accelerated in miniprotoplasts of this cell line. A parallel increase in the rate of cell expansion indicated a tight relationship between vacuolar development and cellular volume increases. Interestingly, overexpression of tobacco gammaTIP also enhanced cell division. Thus, increased vacuolar aquaporin activity may accelerate both cell expansion and cell division by increasing water permeability through the vacuolar membrane.

New Benzylureas as a Novel Series of Potent, Nonpeptidic Vasopressin V2 Receptor Agonists

Vasopressin (AVP) is a hormone that stimulates an increase in water permeability through activation of V2 receptors in the kidney. The analogue of AVP, desmopressin, has proven an effective drug for diseases where a reduction of urine output is desired. However, its peptidic nature limits its bioavailability. We report herein the discovery of potent, nonpeptidic, benzylurea derived agonists of the vasopressin V2 receptor. We describe substitutions on the benzyl group to give improvements in potency and subsequent modifications to the urea end group to provide improvements in solubility and increased oral efficacy in a rat model of diuresis. The lead compound 20e (VA106483) is reported for the first time and has been selected for clinical development.

ATP and adenosine in the local regulation of water transport and homeostasis by the kidney

Regulation of body water homeostasis is critically dependent on the kidney and under the control of AVP, which is released from the neurohypophysis. In the collecting duct (CD) of the kidney, AVP activates adenylyl cyclase via vasopressin V2 receptors. cAMP-dependent activation of protein kinase A phosphorylates the water channel aquaporin-2 and increases water permeability by insertion of aquaporin-2 into the apical cell membrane. However, local factors modulate the effects of AVP to fine tune its effects, accelerate responses, and potentially protect the integrity of CD cells. Nucleotides like ATP belong to these local factors and act in an autocrine and paracrine way to activate P2Y2 receptors on CD cells. Extracellular breakdown of ATP and cAMP forms adenosine, the latter also induces specific effects on the CD by activation of adenosine A1 receptors. Activation of both receptor types can inhibit the cAMP-triggered activation of protein kinase A and reduce water permeability and transport. This review focuses on the role and potential interactions of the ATP and adenosine system with regard to the regulation of water transport in the CD. We address the potential stimuli and mechanisms involved in nucleotide release and adenosine formation, and discuss the corresponding signaling cascades that are activated. Potential interactions between the ATP and adenosine system, as well as other factors involved in the regulation of CD function, are outlined. Data from pharmacological studies and gene-targeted mouse models are presented to demonstrate the in vivo relevance to water transport and homeostasis.

Wettability Alteration in Gas-Condensate Reservoirs To Mitigate Well Deliverability Loss by Water Blocking

Summary Liquid blocking in some gas-condensate reservoirs is a serious problem when the permeability is low (for example, of the order of 10 md or less). The current practice centers mainly on hydraulic fracturing to improve gas flow. In most cases, the frequency of application results in high costs. An alternative is the permanent alteration of wettability from liquid-wetting to preferentially gaswetting. In this work, we present an experimental study of wettability alteration to preferential gas-wetting using a multifunctional surfactant and polymer synthesized for this particular application. The treatments are performed with an alcohol-based-surfactant/ polymer solution. We treat Berea cores and reservoir-rock samples from two gas-condensate reservoirs. In one of the reservoirs, water blocking has resulted in a significant reduction of well deliverabil-ity. The treatment provides significant improvement on the phase mobility. In this study, our focus is the investigation of water/gas two-phase flow at high temperatures (80 and 140°C). Basic measurements such as contact angle, spontaneous imbibition, and the effect on the absolute permeability are discussed. The initial liquid saturation at the time of treatment may have an influence on the wettability alteration. The results of the treatment on oil-saturated and water-saturated cores are presented. The treatment by alcohol without using the polymer is compared and discussed. Two-phase-flow tests in single-phase and two-phase injections are performed before and after the treatment using brine and gas. Relative permeabilities of gas and water are measured, and the improvement after the treatment is presented. Various measurements in our work show that water and gas relative permeability increase significantly in a wide range, especially at high liquid saturation.

Adaptation of the sea-bass ( Dicentrarchus labrax) to fresh water: Role of aquaporins and Na +/K +-ATPases

Sea-bass ( Dicentrarchus labrax) grow under different salinity regimes, from the open sea to lagoons and even rivers, but some mortality has been recorded in juvenile stages when exposed to low salinity water. Changes in water permeability of different osmoregulatory tissues could be the cause of reduction in blood osmotic pressure and death in some fish in fresh water (FW). In order to explore this condition, we have studied the changes of aquaporins (AQP1 and AQP3), α1 and α4 Na +/K +-ATPase transcript levels in the digestive tract, kidney and gills after a long-term exposure of juvenile sea-bass to sea water (SW) and FW fish able to survive in SW and FW are called SW-adapted fish (SWS), FW successfully-adapted fish (FWS) respectively, while fish that die in FW are called FW unsuccessfully-adapted fish (FWU). AQP1 was highly expressed in SWS digestive tract and kidney, suggesting its involvement in water absorption. In FWU, AQP1 transcript levels in the digestive tract were higher than in FWS, suggesting higher water absorption. AQP3 transcript levels in gills were higher in FWS compared to SWS, suggesting a role in FW adaptation. AQP3 transcript levels in gills were higher in FWU than in FWS, suggesting an increase in gill water permeability or other solutes. Transfer to FW was followed in gills by an increase in α1 and α4 Na +/K +-ATPase levels in FWS and FWU, supporting the current model of ion absorption through the gills.

Effect of the addition of the surfactant Tetronic 1307 on poly(ether sulfone) porous hollow‐fiber membrane formation

AbstractPoly(ether sulfone) (PES) hollow‐fiber membrane was prepared via a nonsolvent‐induced phase‐separation method, and the effect of the addition of the surfactant Tetronic 1307 on the membrane performance and characteristics was investigated. The phase diagram of the PES/N‐methyl‐2‐pyrrolidone (NMP)/water system was clarified. When the polymer solution involved Tetronic 1307, the amount of water required to induce the phase separation decreased, which indicated that Tetronic 1307 was one kind of nonsolvent. The kinetics of phase separation for the PES/NMP/Tetronic 1307 system were studied by light‐scattering measurements. With the addition of Tetronic 1307, delayed phase separation was observed, and the structure growth rate decreased. Scanning electron microscopy images for all of the membranes showed the formation of fingerlike macrovoids through the cross section. Membrane surface morphologies were measured by atomic force microscopy. The obtained results indicated that membrane with 7 wt % Tetronic 1307 had higher roughness parameters than original membrane without the addition of surfactant. Ultrafiltration experiment results showed that the addition of Tetronic 1307 brought about an increase in water permeability and decreased the rejection of dextran with a molecular weight of about 10,000. The contact angles of water on the membrane outer surface decreased with the addition of Tetronic 1307. This mean the membrane surface became more hydrophilic. Thus, the addition of Tetronic 1307 was useful for improving the water permeability and for obtaining a hydrophilic membrane surface. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Renal dysfunction and water channels in fresh water unadapted European sea‐bass (Dicentrarchus labrax)

The euryhalin teleost D. labrax is able to live within a wide salinity range between fresh water (FW) and sea water. However some juvenile individuals are unable to adapt to FW (FWU‐fish). The expression of aquaporins (AQP1 & AQP3) and Na+/K+‐ATPase expression was evaluated in osmoregulatory organs. The structure of gills, gut and kidney were analysed by histology. Overexpression of AQP1 in gut and of AQP3 in gills in FWU‐fish compared to FW‐adapted fish suggest an increase in water permeability of these organs. The presence of renal bodies in distended collecting duct and urinary bladder of FWU‐fish, as well as a lower Na+/K+‐ATPase activity in FWU kidney indicate a renal failure as the origin of lower osmotic blood pressure which leads to fish die. Fish dyes 48 h after the occurrence of abnormal behavior in the shoal. FWU‐fish survive if they are transferred to 10 ppt (340 mOms.kg−1)or more.

Activator Protein-1 Contributes to High NaCl-induced Increase in Tonicity-responsive Enhancer/Osmotic Response Element-binding Protein Transactivating Activity

Tonicity-responsive enhancer/osmotic response element-binding protein (TonEBP/OREBP) is a Rel protein that activates transcription of osmoprotective genes at high extracellular NaCl. Other Rel proteins NFAT1-4 and NF-kappaB complex with activator protein-1 (AP-1) to transactivate target genes through interaction at composite NFAT/NF-kappaB.AP-1 sites. TonEBP/OREBP target genes commonly have one or more conserved AP-1 binding sites near TonEBP/OREBP cognate elements (OREs). Also, TonEBP/OREBP and the AP-1 proteins c-Fos and c-Jun are all activated by high NaCl. We now find, using an ORE.AP-1 reporter from the target aldose reductase gene or the same reporter with a mutated AP-1 site, that upon stimulation by high extracellular NaCl, 1) the presence of a wild type, but not a mutated, AP-1 site contributes to TonEBP/OREBP-dependent transcription and 2) AP-1 dominant negative constructs inhibit TonEBP/OREBP-dependent transcription provided the AP-1 site is not mutated. Using supershifts and an ORE.AP-1 probe, we find c-Fos and c-Jun present in combination with TonEBP/OREBP. Also, c-Fos and c-Jun coimmunoprecipitate with TonEBP/OREBP, indicating physical association. Small interfering RNA knockdown of either c-Fos or c-Jun inhibits high NaCl-induced increase of mRNA abundance of the TonEBP/OREBP target genes AR and BGT1. Furthermore, a dominant negative AP-1 also reduces high NaCl-induced increase of TonEBP/OREBP transactivating activity. Inhibition of p38, which is known to stimulate TonEBP/OREBP transcriptional activity, reduces high NaCl-dependent transcription of an ORE.AP-1 reporter only if the AP-1 site is intact. Thus, AP-1 is part of the TonEBP/OREBP enhanceosome, and its role in high NaCl-induced activation of TonEBP/OREBP may require p38 activity.

A fruit‐specific plasma membrane aquaporin subtype PIP1;1 is regulated during strawberry (Fragaria × ananassa) fruit ripening

Despite the advances in the physiology of fruit ripening, the role and contribution of water pathways are still barely considered. Our aim was therefore to characterize aquaporins, proteins that render the molecular basis for putative regulatory mechanisms in water transport. We focused our work on strawberry (Fragaria xananassa) fruit, a non-climacteric fruit of special interest because of its forced brief commercial shelf life. A full-length cDNA was isolated with high homology with plasma membrane (PM) intrinsic proteins (named FaPIP1;1), showing a profile with high expression in fruit, less in ovaries and no detection at all in other parts. Its cellular localization was confirmed at the PM. As reported in other plasma membrane intrinsic proteins subtype 1 (PIP1s), when expressing the protein in Xenopus leavis oocytes, FaPIP1;1 shows low water permeability values that only increased when it is coexpressed with a plasma membrane intrinsic protein subtype 2. Northern blotting using total RNA shows that its expression increases during fruit ripening. Moreover, functional characterization of isolated PM vesicles from red stage fruit unequivocally demonstrates the presence of active water channels, i.e. high water permeability values and a low Arrhenius activation energy, both evidences of water transport mediated by proteins. Interestingly, as many ripening-related strawberry genes, the expression pattern of FaPIP1;1 was also repressed by the presence of auxins. We therefore report a fruit specific PIP1 aquaporin with an accumulation pattern tightly associated to auxins and to the ripening process that might be responsible for increasing water permeability at the level of the PM in ripe fruit.

Propriedades físico-hídricas de um Latossolo Vermelho submetido a diferentes sistemas de manejo

Uma das práticas mecânicas que podem ser adotadas também em solos sob plantio direto (PD) é a escarificação, que tem por objetivos reduzir a densidade do solo e a sua resistência mecânica à penetração das raízes e aumentar a permeabilidade do solo. O efeito dessas alterações sobre o crescimento e desenvolvimento das plantas e o rendimento de grãos é dependente das condições climáticas vigentes. Em condições de umidade do solo ideal, as limitações físicas tendem a não se manifestar com muita intensidade. Este trabalho teve por objetivo estudar as alterações nas propriedades físico-hídricas de um Latossolo Vermelho distrófico típico, conduzido sob PD e submetido à descompactação por escarificação. Avaliaram-se a densidade do solo, a densidade máxima e umidade ótima de compactação, a densidade relativa, a infiltração da água e a condutividade hidráulica do solo saturado (K0) e não-saturado (Kteta), por meio de tensiometria a campo. Os resultados indicaram que a área com escarificação (PDE) apresentou infiltração de água e K0 superiores aos do PD, demonstrando ser uma alternativa para conservação do solo e da água, com efeitos que permaneceram por mais de um ano. A densidade do solo não apresentou diferenças entre os manejos, e o PDE mostrou menor densidade relativa. Conclui-se que a escarificação em solos sob PD tem efeitos por até 24 meses e melhora as condições para conservação do solo e da água.

Breakdown of Paraendothelial Barrier Function during Marburg Virus Infection Is Associated with Early Tyrosine Phosphorylation of Platelet Endothelial Cell Adhesion Molecule–1

Marburg virus (MARV) infection often causes fulminant shock due to pathologic immune responses and alterations of the vascular system. Cytokines released from virus-infected monocytes/macrophages provoke endothelial activation and vascular hyperpermeability and contribute to the development of shock. Tyrosine phosphorylation of cell-junction proteins is important for the regulation of paraendothelial barrier function. We showed that mediators released from MARV-infected monocytes/macrophages, as well as recombinant tumor necrosis factor (TNF)- alpha /H2O2 and interferon (IFN)- gamma , caused tyrosine phosphorylation of platelet endothelial cell adhesion molecule-1 (PECAM-1) but not of the vascular endothelial (VE) cadherin/catenin complex proteins. Tyrosine phosphorylation of PECAM-1 was associated with delayed opening of interendothelial junctions. Interestingly, we observed an early increase in water permeability in response to TNF- alpha /H2O2 that was not due to an opening of the interendothelial junctions. These data indicate 2 distinct mechanisms for the TNF- alpha /H2O2-mediated decrease in endothelial barrier function involving tyrosine phosphorylation of PECAM-1 but not requiring tyrosine phosphorylation of VE-cadherin or catenin proteins.

Aquaporin-1 Channel Function Is Positively Regulated by Protein Kinase C

Aquaporin-1 (AQP1) channels contribute to osmotically induced water transport in several organs including the kidney and serosal membranes such as the peritoneum and the pleura. In addition, AQP1 channels have been shown to conduct cationic currents upon stimulation by cyclic nucleotides. To date, the short term regulation of AQP1 function by other major intracellular signaling pathways has not been studied. In the present study, we therefore investigated the regulation of AQP1 by protein kinase C. AQP1 wild type channels were expressed in Xenopus oocytes. Water permeability was assessed by hypotonic challenges. Activation of protein kinase C (PKC) by 1-oleoyl-2-acetyl-sn-glycerol (OAG) induced a marked increase of AQP1-dependent water permeability. This regulation was abolished in mutated AQP1 channels lacking both consensus PKC phosphorylation sites Thr(157) and Thr(239) (termed AQP1 DeltaPKC). AQP1 cationic currents measured with double-electrode voltage clamp were markedly increased after pharmacological activation of PKC by either OAG or phorbol 12-myristate 13-acetate. Deletion of either Thr(157) or Thr(239) caused a marked attenuation of PKC-dependent current increases, and deletion of both phosphorylation sites in AQP1 DeltaPKC channels abolished the effect. In vitro phosphorylation studies with synthesized peptides corresponding to amino acids 154-168 and 236-250 revealed that both Thr(157) and Thr(239) are phosphorylated by PKC. Upon stimulation by cyclic nucleotides, AQP1 wild type currents exhibited a strong activation. This regulation was not affected after deletion of PKC phosphorylation sites in AQP1 DeltaPKC channels. In conclusion, this is the first study to show that PKC positively regulates both water permeability and ionic conductance of AQP1 channels. This new pathway of AQP1 regulation is independent of the previously described cyclic nucleotide pathway and may contribute to the PKC stimulation of AQP1-modulated processes such as endothelial permeability, angiogenesis, and urine concentration.

Activation of the α7 nAChR Reduces Acid-Induced Acute Lung Injury in Mice and Rats

New evidence indicates that neural mechanisms can down-regulate acute inflammation. In these studies, we tested the potential role of the alpha7 nicotinic acetylcholine receptor (alpha7 nAChR) in a rodent model of acid-induced acute lung injury. We first determined that the alpha7 nAChR was expressed by alveolar macrophages and lung epithelial cells. Then, using an acid-induced acute lung injury mouse model, we found that nicotine, choline, and PNU-282,987 (a specific alpha7 nAChR agonist) decreased excess lung water and lung vascular permeability, and reduced protein concentration in the bronchoalveolar lavage (BAL). Deficiency of alpha7 nAChR resulted in a 2-fold increase in excess lung water and lung vascular permeability. The reduction of proinflammatory cytokines (macrophage inflammatory protein-2 and TNF-alpha) in the BAL with nicotine probably resulted from the suppression of NF-kappaB activation in alveolar macrophages. The beneficial effect of nicotine was also tested in rat model of acid-induced acute lung injury in which BAL protein and receptor for advanced glycation end products (RAGE), a marker of type I cell injury, were reduced by nicotine treatment. These results indicate that activation of alpha7 nAChR may provide a new therapeutic pathway for the treatment of acute lung injury.

Functional expression of aquaporins in embryonic, postnatal, and adult mouse lenses.

Aquaporin 0 (AQP0) and AQP1 are expressed in the lens, each in a different cell type, and their functional roles are not thoroughly understood. Our previous study showed that these two AQPs function as water transporters. In order to further understand the functional significance of these two different aquaporins in the lens, we investigated their initiation and continued expression. AQP0 transcript and protein were first detected at embryonic stage (E) 11.25 in the differentiating primary fiber cells of the developing lens; its synthesis continued through the adult stage in the secondary fiber cells. Low levels of AQP1 expression were first seen in lens anterior epithelial cells at E17.5; following postnatal day (P) 6.5, the expression gradually progressed towards the equatorial epithelial cells. In the postnatal lens, the increase in membrane water permeability of epithelial cells and lens transparency coincides with the increase in AQP1 expression. AQP1 expression reaches its peak at P30 and continues through the adult stage both in the anterior and equatorial epithelial cells. The enhancement in AQP1 expression concomitant with the increase in the size of the lens suggests the progression in the establishment of the lens microcirculatory system. In vitro and in vivo studies show that both aquaporins share at least one important function, which is water transport in the lens microcirculatory system. However, the temporal expression of these two AQPs suggests an apparently unique role/s in lens development and transparency. To our knowledge, this is the first report on the expression patterns of AQP0 and AQP1 during lens development and differentiation and their relation to lens transparency.