Montelukast improves symptoms of seasonal allergic rhinitis over a 4-week treatment period.

BACKGROUND: Proinflammatory mediators such as the cysteinyl leukotrienes are important in the pathophysiology of allergic rhinitis. This study evaluated the efficacy and tolerability of montelukast, a cysteinyl leukotriene receptor antagonist, given once daily in the morning for treatment of seasonal (fall) allergic rhinitis for 4 weeks. METHODS: This was a randomized, double-blind trial with a placebo run-in and a 4-week treatment period. Patients (n = 1079) with a history of allergic rhinitis and a positive skin test to seasonal pollen allergens were assigned to placebo, montelukast 10 mg, or loratadine 10 mg. Symptoms were assessed with a daily diary. RESULTS: Montelukast was more effective than placebo in improving scores for the primary endpoint of daytime nasal symptoms (P = 0.003) and the secondary endpoints of night-time, composite, and daytime eye symptoms, patient's and physician's global evaluations of allergic rhinitis, and rhinoconjunctivitis quality-of-life (P

Activation of hepatocyte growth factor (HGF) by endogenous HGF activator is required for metanephric kidney morphogenesis in vitro.

The interaction of hepatocyte growth factor (HGF) with c-Met has been implicated in morphogenesis of the kidney, lung, mammary gland, liver, placenta, and limb bud. HGF is secreted as an inactive zymogen and must be cleaved by a serine protease to initiate Met signaling. We show here that a serine protease specific for HGF, HGF activator (HGFA), is expressed and activated by the ureteric bud of the developing kidney in vivo and in vitro. Inhibition of HGFA activity with serine protease inhibitors reduced ureteric bud branching and inhibited glomerulogenesis and nephrogenesis. Activated HGF rescued developing kidneys from the effects of inhibitors. HGFA was localized around the tips of the ureteric bud in developing kidneys, while HGF was expressed diffusely throughout the mesenchyme. These data show that expression of HGF is not sufficient for development, but that its activation is also required. The localization of HGFA to the ureteric bud and the mesenchyme immediately adjacent to it suggests that HGFA creates a gradient of HGF activity in the developing kidney. The creation and shape of gradients of activated HGF by the localized secretion of HGF activators could play an important role in pattern formation by HGF responsive tissues.

Cardiac defects and renal failure in mice with targeted mutations in Pkd2.

PKD2, mutations in which cause autosomal dominant polycystic kidney disease (ADPKD), encodes an integral membrane glycoprotein with similarity to calcium channel subunits. We induced two mutations in the mouse homologue Pkd2 (ref.4): an unstable allele (WS25; hereafter denoted Pkd2WS25) that can undergo homologous-recombination-based somatic rearrangement to form a null allele; and a true null mutation (WS183; hereafter denoted Pkd2-). We examined these mutations to understand the function of polycystin-2, the protein product of Pkd2, and to provide evidence that kidney and liver cyst formation associated with Pkd2 deficiency occurs by a two-hit mechanism. Pkd2-/- mice die in utero between embryonic day (E) 13.5 and parturition. They have structural defects in cardiac septation and cyst formation in maturing nephrons and pancreatic ducts. Pancreatic ductal cysts also occur in adult Pkd2WS25/- mice, suggesting that this clinical manifestation of ADPKD also occurs by a two-hit mechanism. As in human ADPKD, formation of kidney cysts in adult Pkd2WS25/- mice is associated with renal failure and early death (median survival, 65 weeks versus 94 weeks for controls). Adult Pkd2+/- mice have intermediate survival in the absence of cystic disease or renal failure, providing the first indication of a deleterious effect of haploinsufficiency at Pkd2on long-term survival. Our studies advance our understanding of the function of polycystin-2 in development and our mouse models recapitulate the complex human ADPKD phenotype.

Polycystin-1, the PKD1 gene product, is in a complex containing E-cadherin and the catenins.

Autosomal dominant polycystic kidney disease (ADPKD) is a common human genetic disease characterized by cyst formation in kidney tubules and other ductular epithelia. Cells lining the cysts have abnormalities in cell proliferation and cell polarity. The majority of ADPKD cases are caused by mutations in the PKD1 gene, which codes for polycystin-1, a large integral membrane protein of unknown function that is expressed on the plasma membrane of renal tubular epithelial cells in fetal kidneys. Because signaling from cell-cell and cell-matrix adhesion complexes regulates cell proliferation and polarity, we speculated that polycystin-1 might interact with these complexes. We show here that polycystin-1 colocalized with the cell adhesion molecules E-cadherin and alpha-, beta-, and gamma-catenin. Polycystin-1 coprecipitated with these proteins and comigrated with them on sucrose density gradients, but it did not colocalize, coprecipitate, or comigrate with focal adhesion kinase, a component of the focal adhesion. We conclude that polycystin-1 is in a complex containing E-cadherin and alpha-, beta-, and gamma-catenin. These observations raise the question of whether the defects in cell proliferation and cell polarity observed in ADPKD are mediated by E-cadherin or the catenins.

The role of the polycystins in kidney development.

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disease that affects both adults and children. Renal cysts are the cardinal sign of the disease that also causes cysts in liver, pancreas, testis, and ovary, as well as cardiac valvular insufficiency and arterial aneurysms. At least three genes cause ADPKD in humans. PKD1 and PKD2 have been cloned and sequenced, both code for novel proteins. Analyses of their primary structures suggest that polycystin-1, the PKD1 gene product, is a receptor, while similarities between the polycystins and calcium channel subunits suggest that these proteins are subunits of a novel channel. Individuals with mutations in PKD1 or PKD2 have identical phenotypes, which present at a later age in PKD2 patients. Recent evidence suggests that the two polycystins interact, providing a biochemical basis for the similarity of disease caused by mutations in PKD1 and PKD2. Consistent with its protean manifestations, polycystin-1 is widely expressed in both epithelial and nonepithelial tissues during embryological development. Mice with targeted mutations of either the PKD1 or the PKD2 genes die during embryogenesis. Thus, the PKD genes are required for normal fetal development. The observation that loss of polycystin-1 or -2 function causes death during embryogenesis suggests that PKD1 and PKD2 might be part of a morphoregulatory pathway.

Peptides from the PKD repeats of polycystin, the PKD1 gene product, modulate pattern formation in the developing kidney.

Mutations in the PKD1 gene cause the majority of cases of autosomal dominant polycystic kidney disease. The PKD1 gene codes for a protein of unknown function, polycystin-1, that is predicted to be a receptor. Its large extracellular domain contains 16 copies of novel motif, the PKD repeat, that is likely to be a ligand binding domain based on its similarity to immunoglobulin domains. These observations suggested that soluble fragments of the extracellular domain of polycystin-1 could be used as competitive inhibitors of polycystin function in a suitable model system. Polycystin-1 is highly expressed in the ureteric bud and other branching epithelia during development and interacts with beta-catenin, a molecule known to play a role in branching morphogenesis. These data suggested that polycystin-1 might play a role in branching morphogenesis. I show here that peptides derived from the PKD repeats of polycystin-1 caused an asymmetric pattern of ureteric bud branching in cultured kidney rudiments. Treatment of kidney rudiments with experimental but not control peptides reduced both the number of ureteric bud branches and the number of nephrons. Experimental peptides produced significant morphogenetic effects at concentrations < or = 0.1 mM. These data suggest that polycystin-1 plays a role in branching morphogenesis by the ureteric bud.

Protein targeting: the molecular basis of vectorial transport in the kidney.

The renal tubular epithelium maintains different sets of transport proteins in plasma membrane domains facing the lumenal and mucosal fluids and limits diffusion between these two compartments. This asymmetry is generated by directing transporters to the appropriate membrane domain, a process that requires both an intracellular machinery that sorts out proteins destined for different domains and cues that create the addresses to which these proteins are sorted. Interactions with the extracellular environment convey the positional information that creates the plasma membrane domains. These interactions are mediated by macromolecular assemblies of cell adhesion molecules, cytoskeleton, and signaling molecules. This review focuses on the mechanisms by which these complexes create polarized membrane domains.

The effect of apical and basolateral lipids on the function of the band 3 anion exchange protein.

Although many polarized proteins are sorted to the same membrane domain in all epithelial tissues, there are some that exhibit a cell type-specific polarity. We recently found that band 3 (the anion exchanger AE1) was present in the apical membrane of a renal intercalated cell line when these cells were seeded at low density, but its targeting was reversed to the basolateral membrane under the influence of an extracellular matrix protein secreted when the cells were seeded at high density. Because apical and basolateral lipids differ in epithelia, we asked what effect might these lipids have on band 3 function. This question is especially interesting since apical anion exchange in these cells is resistant to disulfonic stilbene inhibitors while basolateral anion exchange is quite sensitive. Furthermore, the apical anion exchanger cannot be stained by antibodies that readily identify the basolateral protein. We used short chain sphingolipid analogues and found that sphingomyelin was preferentially targeted to the basolateral domain in the intercalated cell line. The ganglioside GM1 (Gal 1beta1, 3GalNAcbeta1, 4Gal-NeuAcalpha2, 3Galbeta1, 4Glc ceramide) was confined to the apical membrane as visualized by confocal microscopy after addition of fluorescent cholera toxin to filter grown cells. We reconstituted erythrocyte band 3 into liposomes using apical and basolateral types of lipids and examined the inhibitory potency of 4, 4'-dinitorsostilbene-2,2'-disulfonic acid (DNDS; a reversible stilbene) on 35SO4/SO4 exchange. Although anion exchange in sphingomyelin liposomes was sensitive to inhibition, the addition of increasing amounts of the ganglioside GM1 reduced the potency of the inhibitor drastically. Because these polarized lipids are present in the exofacial surface of the bilayer, we propose that the lipid structure might influence the packing of the transmembrane domains of band 3 in that region, altering the binding of the stilbenes to these chains. These results highlight the role of polarized lipids in changing the function of unpolarized proteins or of proteins whose locations differ in different epithelia.

Protection of perfused lung from oxidant injury by inhibitors of anion exchange.

Hyperoxic lung injury is enhanced in isolated perfused lungs (IPL) in the presence of L-arginine. Reactive O2 species such as superoxide anion (O2-.) produced during hyperoxia are known to react with nitric oxide to form the strong oxidant species peroxynitrite. The appearance of O2-. in red blood cell membranes in vitro and in buffer-perfused lung preparations can be inhibited by the stilbene compound 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) DIDS also inhibits anion exchange across the cell membrane regulated by a family of anion exchange proteins (AE). In this study, we hypothesized that anion exchange inhibitors would prevent lung injury from hyperoxia and L-arginine (O2 + L-Arg) by decreasing O2-. flux into the vascular space of the IPL. We found that both DIDS and a structurally distinct anion transport blocker, dipyridamole, protected the rabbit IPL from pulmonary hypertension and edema produced by O2 + L-Arg. The protective effect was associated with increased nitrite concentrations in the perfusate. Protection also was conferred when sodium bicarbonate in the perfusion buffer was replaced with either sodium thiosulfate or N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). In lungs perfused with thiosulfate or HEPES-containing buffer, protection from O2 and L-arginine was also associated with diminished detection of reducing activity consistent with O2-. in the vascular space. Western blot analysis of lung protein and immunocytochemical staining of lung sections using antibodies against rabbit red blood cell AE1 and mouse gastric AE2 peptide showed that lung contains membrane protein antigenically similar to gastric AE2. These data suggest the possibility that inhibition of AE or other anion transporters may play an important role in mediating oxidative lung injury.

Polycystin expression is temporally and spatially regulated during renal development.

Mutations in PKD1 cause autosomal dominant polycystic kidney disease (ADPKD), a common genetic disease in which cysts form from kidney tubules. The predicted product of this gene is a novel protein with cell-adhesive and membrane-spanning domains. To test the hypothesis that polycystin, the product of the PKD1 gene, is a cell adhesion molecule, we raised antibodies against peptides derived from the unduplicated, membrane-spanning portion of the predicted amino acid sequence. These antibodies recognized membrane-associated polypeptides of 485 and 245 kDa in human fetal kidney homogenates. Expression was greater in fetal than adult kidney by both Western blot analysis and immunofluorescence. In fetal kidney, polycystin was localized to the plasma membranes of ureteric bud and comma and S-shaped bodies. However, in more mature tubules in fetal kidney, in adult kidney, and in polycystic kidney, the majority of polycystin staining was intracellular. The temporal and spatial regulation of polycystin expression during renal development lead us to speculate that polycystin may play a role in nephrogenesis.

Analysis of the role of membrane polarity in polycystic kidney disease of transgenic SBM mice.

Altered membrane polarity has been proposed as an important pathogenetic factor in the development of renal cysts in polycystic kidney disease. To determine whether this alteration in epithelial phenotype is a primary or secondary phenomenon, we examined the epithelial membrane polarity of SBM transgenic mice, in which epithelial proliferation mediated by the c-myc oncogene is an established primary event. Kidneys from 32 transgenic mice and 10 age-matched controls from fetal to adult age were immunostained with antibodies to Na,K-ATPase, fodrin, ankyrin, E-cadherin, and tubule segment-specific lectins. In normal control mice, Na,K-ATPase localization was apical in fetal kidneys but became translocated to the basolateral membrane at maturity. Early microcysts in fetal transgenic kidneys displayed similar (95 to 100%) apical Na,K-ATPase. In young and newborn transgenic mice (1 to 8 days of age), Na,K-ATPase localization was extremely heterogeneous. Noncystic tubules demonstrated either apical (mean 23 to 28%), basolateral (mean 48 to 58%), mixed (mean 4 to 15%), or absent (mean 10 to 13%) staining for Na,K-ATPase. Apical Na,K-ATPase was more frequently observed in early cysts (mean 55%) in young transgenic mice but became less prevalent in adult mice (mean 22%), where 30% of cysts had basolateral staining, 39% mixed patterns, and 9% absent staining. Macrocysts typically lost all Na,K-ATPase reactivity. At all ages, Na,K-ATPase colocalized well with cytoskeletal proteins ankyrin and fodrin. These heterogeneous patterns of Na,K-ATPase staining indicate that although altered cell polarity is frequent in early cystic epithelium of SBM mice, it is not a prerequisite to cystogenesis or progressive cyst enlargement. In conclusion, our results support the view that altered cystic membrane polarity is not a primary process, but represents the persistence of an immature epithelial phenotype characteristic of proliferative polycystic kidney disease epithelia.

The PKD1 gene produces a developmentally regulated protein in mesenchyme and vasculature.

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common human genetic diseases. In addition to polycystic kidneys, the disease can cause cystic changes in liver and other organs, cardiac valvular insufficiency and cerebral arterial aneurysms. Using antibodies raised against the predicted gene product of PKD1, which is mutated in about 85% of ADPKD cases, we show that PKD1 is a 530-kD protein localized to the extracellular matrix of kidney, liver and cerebral blood vessels. We discovered that the PKD1 protein was highly expressed in the mesenchyme of developing kidney and liver, transiently localized in the developing glomerulus and juxtaglomerular apparatus and restricted to perivascular, extraglomerular areas in adult renal cortex. These data suggest that the PKD1 protein plays a role in renal and hepatic morphogenesis.

Murine polycystic kidney epithelial cell lines have increased integrin-mediated adhesion to collagen.

Polycystic kidney disease (PKD), in which epithelial cysts arise from or instead of normal renal tubules, is one of the most common genetic diseases. It has both autosomal dominant and autosomal recessive inheritance in humans and in experimental animals. Epithelial cells lining the cysts have an increased rate of proliferation, abnormal polarity of Na-K-adenosinetriphosphatase, which is localized to apical and sometimes lateral membrane domains, and an abnormal extracellular matrix. One hypothesis that explains the simultaneous acquisition of these characteristics as the result of several different genetic mutations is that cell-matrix interactions, which are known to regulate cell proliferation and cell polarity, are altered in PKD. I have created immortalized renal epithelial cell lines from C57Bl/6Jcpk mice with PKD, an autosomal recessive trait in these animals, and from their phenotypically normal littermates. Using these cell lines, I show that polycystic cells have increased adhesion to collagens and laminin mediated by an integrin. These results demonstrate that cell-matrix interactions are defective in PKD and suggest that these interactions may be involved in the abnormalities of cell polarity and cell proliferation seen in these disorders.

An induced extracellular matrix protein reverses the polarity of band 3 in intercalated epithelial cells.

The intercalated epithelial cell exists in two interconvertible forms in vivo, one where band 3 protein is apical and the other where it is basolateral. We seeded an immortalized clone of these cells at low density and found that band 3 was apical at confluence. There was little or no apical endocytosis. But when the cells were plated at high density, band 3 was basolateral, and there was vigorous apical endocytosis. Extracellular matrix produced by high density cells was able to retarget band 3 in low density cells and to induce apical endocytosis, as did a 230 kd protein partially purified from this matrix. Therefore, polarized targeting of some proteins is determined by external cues that might determine their polarity by reorganizing the cytoplasm.

The apical Cl/HCO3 exchanger of beta intercalated cells.

There are two types of intercalated cells of the renal collecting duct; one secretes H+ and the other secretes HCO3-. The H(+)-secreting form has an apical vacuolar H(+)-ATPase and a basolateral Cl/HCO3 exchanger that cross-reacts with antibodies to band 3, the product of the AE1 gene. The HCO3(-)-secreting form has a basolateral vacuolar H(+)-ATPase and an apical Cl/HCO3 exchanger, whose identity has not been established previously. Apical membrane vesicles of beta intercalated cells purified from rabbit kidney cortex contain both an electroneutral Cl/HCO3 exchange activity and polypeptides that react with antibodies to band 3 on Western blots. Furthermore, both primary cultures of HCO3(-)-secreting intercalated cells and an immortalized cell line derived from these cells express AE1 and have an apical Cl/HCO3 exchanger. Apical membranes purified from these cells contain a 100-kDa polypeptide that cross-reacts with antibody to the cytoplasmic domain of band 3. These data suggest that the apical Cl/HCO3 exchanger of HCO3(-)-secreting intercalated cells is band 3.

Conditional immortalization of bicarbonate-secreting intercalated cells from rabbit.

We have derived an immortalized cell line from primary cultures of bicarbonate-secreting intercalated cells from rabbit. Cells were transfected with a plasmid encoding a temperature-sensitive large T antigen of SV40 plus the neomycin resistance gene under the control of an SV40 promoter. Transfectants were selected for resistance to G418. One stably transfected clone, designated IC250, was subcloned to ensure clonality, and a subclone (clone C) was characterized in detail. The cells divide continuously at permissive temperature. At restrictive temperature, they cease dividing and assume morphological and transport properties of true bicarbonate-secreting intercalated cells. They express appropriate ultrastructural features, bind peanut lectin in an apical pattern, are rich in carbonic anhydrase, stain for proton-adenosinetriphosphatase in a basolateral pattern, and do not stain with antibodies to erythrocyte band 3. Most monolayers of transformed type B intercalated cells do not achieve a significant transepithelial resistance; those monolayers that are sufficiently electrically tight for electrophysiological studies are capable of chloride-dependent bicarbonate transport.

Isolation and culture of HCO3- -secreting intercalated cells.

Intercalated cells of the distal nephron secrete either H+ or HCO3-. We have succeeded in isolating HCO3- -secreting intercalated cells from the rabbit kidney. When seeded onto collagen-coated permeable supports, these cells form monolayers with a resistance of 595 +/- 75 omega.cm2. The monolayers maintain the characteristics of an epithelium, with apical microvillae and tight junctions. They display the same polarity as do HCO3- -secreting intercalated cells in vivo, namely apical peanut lectin binding and apical Cl- -HCO3- exchange. The monolayers are capable of transepithelial HCO3- transport via this exchanger. The rate of Cl- -dependent transepithelial HCO3- transport is 4 +/- 0.4 nmol.min-1.cm-2. Transepithelial HCO3- transport is completely abolished by 50 microM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid applied to the apical side of the monolayer. These cultured HCO3- -secreting intercalated cells should prove useful for defining the cellular regulation of HCO3- secretion.