Cyclosporin A disrupts bradykinin signaling through superoxide

Cyclosporin A (CsA) is used to reduce transplant rejection rates. Chronic use, however, has a destructive toxic effect on the kidney, resulting in hypertension. In this study, we investigated the effects of CsA treatment on the bradykinin/soluble guanylate cyclase signaling cascade and the involvement of superoxide in LLC-PK1 porcine kidney proximal tubule cells. Treatment with 1 micromol/L CsA for 24 hours increased basal cGMP levels by 41%, whereas CsA inhibited bradykinin-stimulated cGMP production by 26%. Western blotting showed increased expression of eNOS, but no other protein in the bradykinin/soluble guanylate cyclase (sGC) pathway was affected. Using lucigenin-dependent chemiluminescence, we found that CsA treatment significantly increased superoxide production. Production of O2- was not significantly reduced by 10 micromol/L oxypurinol or 30 micromol/L ketoconazole. However, it was inhibited by the NADPH oxidase inhibitor diphenyleneiodonium chloride (10 micromol/L) as well as the O2- scavenger superoxide dismutase (SOD) (100 U). On treatment with 50 micromol/L quercetin, 10 mmol/L N-acetyl-cysteine, both antioxidants, as well as the O2- scavenger Tiron (10 mmol/L), concomitant with 1 micromol/L CsA for 24 hours the activation of cGMP production, was restored in combination with a reduction in O2-. Incubation with 100 micromol/L menadione, a reactive oxygen generator, and 10 nmol/L bradykinin showed similar effects on the level of cGMP as with CsA. CsA treatment was found to increase nitrotyrosine levels. These findings suggest that CsA activates a NADPH oxidase that releases O2- and disrupts the bradykinin/soluble guanylate cyclase pathway, probably by binding with NO to form peroxynitrite (ONOO-).

Quercetin, a phytoestrogen and dietary flavonoid, activates different membrane-bound guanylate cyclase isoforms in LLC-PK1 and PC12 cells

Accumulated evidence suggests that quercetin, a dietary flavonoid, has beneficial effects in protection against cardiovascular diseases and in the inhibition of tumour growth. We have recently shown that antioxidants such as 17beta-estradiol, resveratrol, dithiothreitol and vitamin C activate membrane-bound guanylate cyclase GC-A, a receptor for atrial natriuretic factor (ANF). Since quercetin is a phytoestrogen and potent antioxidant, it is possible that it may activate GC-A or other guanylate cyclase isoforms. We examined whether quercetin activates GC-A or GC-B (the receptor for C-type natriuretic peptide, CNP) in PC12 and porcine kidney proximal tubular LLC-PK1 cells. The results showed that quercetin activated a guanylate cyclase isoform in both cell types. Quercetin inhibited CNP-stimulated GC-B activity, but had little effect on ANF-stimulated GC-A activity in PC12 cells, suggesting that quercetin mainly activates GC-B in PC12 cells. In contrast, CNP had no effect on guanylate cyclase activity in LLC-PK1 cells, indicating that GC-B is not expressed in LLC-PK1 cells. Furthermore, quercetin had a small effect on ANF-stimulated GC-A activity and had no effect on soluble guanylate cyclase activity in LLC-PK1 cells, suggesting that quercetin does not activate GC-A, GC-B or soluble guanylate cyclase in LLC-PK1 cells. However, quercetin did stimulate membrane-bound guanylate cyclase activity in LLC-PK1 cell membranes. These results indicate that quercetin activates the GC-B isoform in PC12 cells, but activates an unknown membrane-bound guanylate cyclase isoform in LLC-PK1 cells.

GCMa regulates the syncytin-mediated trophoblastic fusion

The human placental trophoblast cell can be classified as either a cytotrophoblast or a syncytiotrophoblast. Cytotrophoblasts can function as stem cells for the development of the syncytiotrophoblast layer via cell fusion. An envelope gene of the human endogenous retrovirus family W (HERV-W) called syncytin is specifically expressed in the syncytiotrophoblast layer. Syncytin is a fusogenic membrane protein; therefore, it can mediate the fusion of cytotrophoblasts into the syncytiotrophoblast layer, which is essential for pregnancy maintenance. GCMa is a placenta-specific transcription factor and is required for placental development. To study the placenta-specific fusion mediated by syncytin, we tested whether GCMa is involved in this process by regulating syncytin gene expression. In this report, we demonstrate that GCMa was able to regulate syncytin gene expression via two GCMa-binding sites upstream of the 5'-long terminal repeat of the syncytin-harboring HERV-W family member in BeWo and JEG3 cells but not in HeLa cells. Furthermore, adenovirus-directed expression of GCMa enhanced syncytin gene expression and syncytin-mediated cell fusion in BeWo and JEG3 cells but not in HeLa cells. Therefore, the integration site of the syncytin-harboring HERV-W family member in the human genome is close to the functional GCMa-binding sites by which GCMa can specifically transactivate syncytin gene expression in trophoblast cells. Our results may help to explain the mechanism underlying the cell fusion event specific for syncytiotrophoblast formation.

A functional composite cis-element for NF kappa b and RBJ kappa in the rat pregnancy-specific glycoprotein gene

The rat pregnancy-specific glycoprotein gene rnCGM3 is primarily expressed in the placenta. Previously, three DNase I footprinting sites (FPI, FPII, and FPIII) were identified in the rnCGM3 promoter region, a yeast one-hybrid screen was performed to identify the nuclear factors binding to the FPIII (5'-GCCTGGGAAAAAACTC-3') element, and RBPJ kappa, a downstream effector of the Notch signaling pathway, was identified as one of the FPIII-binding factors. In the present study, the NF kappa B member p65 was identified as another FPIII-binding factor. Electrophoretic mobility shift assays showed that NF kappa B members, including p50 and p65, bound to the FPIII site. The core binding sequence in the FPIII element for p50 and p65 is GGGAAA, which overlaps with that for RBPJ kappa. Competition exists between p50 and RBPJ kappa for binding to the FPIII element. Transient expression analyses revealed that p65 significantly stimulated the expression of a reporter gene directed by the NF kappa B core sequence in the FPIII element. However, RBPJ kappa could block this stimulation. These results suggest that the regulation of rnCGM3 expression involves both NF kappa B and RBPJ kappa, and they are mutually exclusive in the FPIII element.

Simultaneous immunoblotting analysis with activity gel electrophoresis in a single polyacrylamide gel

We describe here that a simple diffusion blotting method can couple immunoblotting analysis with another biochemical technique in a single polyacrylamide gel. The efficiency of protein transfer was evaluated by serial dilutions of nephrosin, a metalloproteinase of the astacin family, and by immunodetection. It is estimated that diffusion blotting produces 25-50% of the signal intensity compared to the classical electrophoretic transfer method. However, with diffusion blotting it is possible to generate several replicas from a single gel. In addition, a protein blot can be obtained from a sodium dodecyl sulfate (SDS)-polyacrylamide gel for zymography assay or from a native polyacrylamide gel for electrophoretic mobility shift assay (EMSA). In this regard, a particular signal in zymography or EMSA can be confirmed by simultaneous immunoblotting analysis with a corresponding antiserum. Therefore, diffusion blotting allows a direct comparison of signals between gels and replicas in zymography assay and EMSA. These advantages make diffusion blotting desirable when partial loss of transfer efficiency can be tolerated or be compensated by a more sensitive immunodetection reaction using enhanced chemiluminescence substrates.

Purification and cloning of carp nephrosin, a secreted zinc endopeptidase of the astacin family

We have purified a secreted proteinase of 23 kDa from carp head kidney by sequential column chromatography on a Reactive Blue 72-agarose dye affinity column and an FPLC Mono-P column. The secretion of this proteinase from carp head kidney can be stimulated by high concentrations of potassium. Since the carp proteinase is present mainly in the head kidney, kidney, and spleen (all of which are lymphohematopoietic organs), it is named nephrosin. The carp nephrosin is most sensitive to metal chelators, but not to inhibitors specific for other classes of proteinases. A cDNA clone has been isolated from a carp head kidney cDNA library by immunoscreening with a polyclonal antiserum raised against purified nephrosin. The cloned cDNA is 1086 base pairs in length and has an open reading frame encoding a protein of 273 amino acids, including a 19-amino acid signal peptide and 56-amino acid propeptide. The deduced amino acid sequence shows moderate levels of identity to medaka HCE1 (52.5%), medaka LCE (50.7%), crayfish astacin (33.2%), murine meprin-alpha (34%), and murine meprin-beta (33.5%), all members of the astacin family of zinc endopeptidases. Nephrosin is the first member of the astacin family found in lymphohematopoietic tissues.

Expression, characterization, and genomic structure of carp JAK1 kinase gene

A 3.7-kb cDNA encodes the carp JAK1 kinase of 1,156 amino acid residues. The overall amino acid sequence identity between carp JAK1 and murine JAK1, JAK2, JAK3, and human TYK2 is 57%, 35.5%, 31.3%, and 42.4%, respectively. In addition, carp JAK1 shows higher sequence homology to mammalian JAK1 in both the kinase-like (JH2) and kinase (JH1) domains (approximately 70% identity). Therefore, carp JAK1 is a homolog of mammalian JAK1. To investigate the possible function of JH2 domain, full-length, and various truncated forms of carp JAK1 were produced in the baculovirus system. Our results demonstrate that c-JH1 and c-JH2 associate with each other and c-JH2 can be tyrosine-phosphorylated by c-JAK1 and by c-JH(1 + 2). The JAK1 gene was also isolated from a carp genomic library and characterized. This gene is divided into 24 exons spanning at least 31 kb of genomic DNA. Exon 1 contains the 5'-untranslated region and exon 2 contains the putative translation initiation site. The 2.5-kb DNA region upstream of the transcription initiation site contains numerous potential binding sites for transcription factors including NF-IL6, HNF-5, AP1, GHF-5, and E2A. When this DNA fragment was placed upstream of the chloramphenicol acetyltransferase (CAT) reporter gene and transfected into a carp CF cell line, it could drive the synthesis of CAT enzyme 16 times more efficiently than the promoterless pCAT-Basic. Deletion analysis defined a positive regulatory region between -1,023 and -528. A smaller region (-181 to +59) without any typical TATA-box sequences, G + C-rich sequences, or other binding sequences for known transcription factors still had promoter activity. Constructs without this region did not have detectable promoter activity. This suggests that this region of DNA may play an important role in the expression of carp JAK1 gene.

Genomic structure of carp mitogen-activated protein kinase kinase 1 gene

Carp mitogen-activated protein kinase kinase 1 (cMKK1) gene was isolated from a liver genomic library. The sequence around the exon-intron boundaries and 2 kb of the promoter region were determined. Our data indicate that this gene is composed of 11 exons and 10 introns spanning about 9 kb. Multiple potential transcription initiation sites were located by primer extension analysis. Examination of 2 kb of 5'-flanking sequence revealed potential binding sites for a variety of transcription factors such as E2F, Ets-1, GATA-1, Myb, NF-IL6, Sp1, and NF-kB.

Purification and molecular cloning of carp ovarian cystatin

The ovarian fluid of carp consists of many components. Using the antiserum against carp serum, Western blot analysis of ovarian fluid was done in order to distinguish substances synthesized by the ovary from those derived from the serum. Several ovary-specific substances were detected including a protein of 12 kDa (p12), which was purified to homogeneity. Purified p12 displays a single band in SDS-PAGE under nonreducing condition and it can inhibit the enzymatic activity of papain with an apparent inhibition constant of 0.01 nM. The primary structure of p12 was partially determined by Edman degradation and fully elucidated by molecular cloning. A cDNA of 531 bp encoding p12 was obtained. The precursor of p12 has 129 residues, including a signal peptide of 18 residues and a mature protein of 111 residues. The N- and C-terminus of p12 are threonine and methionine, respectively. The p12 shares many common features of the family 2 cystatins of other species, including the similarity of the protein size (in the range of 110 to 120 residues), the presence of 4 cysteine residues and the occurrence of invariant residues throughout the molecule.

Studies on the structure and function of the carp gonadotropin alpha subunit by site-directed mutagenesis

There are two genes encoding the alpha subunit of carp gonadotropin (alpha 1 and alpha 2 subunits). Our previous data have demonstrated that both alpha 1 and alpha 2 subunits expressed in insect cells are able to associate with the beta subunit, but only the alpha 1/beta heterodimer displays biological activity. In the mature protein, there are only four amino-acid residues different between the alpha 1 and alpha 2 subunits. In this study we used site-directed mutagenesis and expressed different mutant alpha subunits in insect cells to identify which residue might be important for biological activity of the alpha subunit. Our results suggested that the change of Arg-71 to Gln-71 affected the activity of the carp gonadotropin alpha subunit.

A protease inhibitor of the serpin family is a major protein in carp perimeningeal fluid: I. Protein purification and characterization

Two isoforms of a protease inhibitor of the serpin family (p62) have been purified from bighead carp perimeningeal fluid. Both isoforms migrate with an apparent molecular mass of 62 kDa on reducing and nonreducing sodium dodecyl sulfate-polyacrylamide gels. Both proteins inhibited the activities of bovine trypsin, bovine chymotrypsin, and porcine pancreatic elastase. They also formed complexes with these proteases that were resistant to sodium dodecyl sulfate treatment. p62 exists in the extracts of all tissues examined, including brain, head kidney, kidney, liver, muscle, ovary, pituitary, and spleen. It is also present in serum, ovarian fluid, and milt as well as perimeningeal fluid. The protease inhibitor is a glycoprotein, and its carbohydrate moiety could be removed by endoglycosidase F. Because p62 resembles mammalian alpha 1-antitrypsin in many aspects, it is likely a fish equivalent of alpha 1-antitrypsin.

A protease inhibitor of the serpin family is a major protein in carp perimeningeal fluid: II. cDNA cloning, sequence analysis, and Escherichia coli expression

A cDNA clone, pCP9, has been isolated from a common carp liver cDNA library by immunoscreening with polyclonal antiserum raised against purified bighead carp alpha 1-antitrypsin. This clone is 1,396 bp in length and has an open reading frame encoding a protein of 410 amino acid residues. The deduced amino acid sequence shows moderate homology to human alpha 1-antitrypsin (38%), guinea pig contrapsin (35%), human alpha 1-antichymotrypsin (34%), and human proteinase C inhibitor (31%), all members of the serine protease inhibitor (serpin) family. To confirm further that the cDNA clone was derived from the authentic carp alpha 1-antitrypsin gene, the presumptive mature protein of pCP9 was expressed in Escherichia coli. The molecular mass of the recombinant protein matched that predicted from the nucleotide sequence. This recombinant protein, which was recognized by antiserum against native alpha 1-antitrypsin, was capable of formation of serpin-enzyme complexes with trypsin, chymotrypsin, and elastase. Therefore, we conclude that the protein encoded by the pCP9 clone is indeed carp alpha 1-antitrypsin. Expression of alpha 1-antitrypsin in brain was confirmed by reverse transcription and polymerase chain reaction performed on mRNA derived from both common carp and bighead carp brain.

Molecular cloning and sequencing of a carp cDNA encoding mitogen-activated protein kinase kinase

We have cloned a full-length cDNA encoding the mitogen-activated protein kinase kinase (MKK) from a carp liver cDNA library. The cDNA contains 1970 bp with a single open reading frame encoding a 397 amino acid protein. By comparing with known MKK sequences from other species, carp MKK is 78%, 80%, 76% and 58% identical to rat MKK1, rat MKK2, Xenopus MKK and Drosophila MKK.

Structural requirements of mastoparan for activation of membrane-bound guanylate cyclase

Mastoparan activated membrane-bound guanylate cyclase and potentiated the effect of atrial natriuretic factor (ANF) and ATP on guanylate cyclase activity in rat lung membranes. Mastoparan is a cationic, amphiphilic tetradecapeptide with an amidated carboxyl terminus. It takes the alpha-helical conformation upon interacting with the membrane. Several analogs were synthesized to study the role of the positive charges, the carboxyl amino group and the alpha-helical conformation of mastoparan in the activation of guanylate cyclase. The results showed that substitution of the C-terminal amide group of mastoparan with a carboxyl group significantly reduced its potency on the activation of guanylate cyclase. Replacement of three lysine residues of mastoparan with aspartic acid or serine residues completely abolished the stimulatory effect of mastoparan. When the alanine at position 10 of mastoparan was substituted by a proline, the resulting analog had no effect on guanylate cyclase activity. These results demonstrate that the positive charges and the helical structure of mastoparan are critical determinants for the activation of guanylate cyclase.

Expression of two forms of carp gonadotropin alpha subunit in insect cells by recombinant baculovirus

There are two types of cDNA clones (designated alpha 1 and alpha 2) encoding the alpha subunit of carp gonadotropin. These two cDNAs are derived from different genes and encode proteins that differ by seven amino acid residues (three in the signal peptide and four in the mature polypeptide). Expression of these two cDNAs in insect cells by recombinant baculovirus revealed that the alpha 1 subunit, after noncovalent association with the beta subunit, has the same potency as the native alpha subunit purified from the pituitary. In contrast, the alpha 2 subunit can associate with the beta subunit, but only to form an inactive gonadotropin. Competition of the alpha 2 subunit with the alpha 1 subunit for association with the beta subunit decreases the gonadotropin activity of the alpha/beta complex. In addition, both alpha 1 and alpha 2 subunits are secreted into the culture medium by insect cells and have an apparent molecular mass approximately 5 kDa higher than that of the native alpha subunit. These results indicate that the insect cell-derived alpha 1 subunit is biologically active and that those four amino acid changes in the mature of alpha 2 protein affect the biological activity and thus provide valuable clues for the study of the structure-function relationship of the alpha subunit of glycoprotein hormones.

Studies of the in vivo catabolism of exogenous dopamine as infused through a push-pull cannula implanted in the rat caudate nucleus

In this report, using a push-pull perfusion technique, we examined in vivo the effects of exogenous dopamine (DA) on the output of neurochemical substances from the caudate nucleus (CN) of freely behaving rats. Exogenous DA, at concentrations of 10(-5) M, 5 x 10(-5) M and 10(-4) M, in modified Krebs-Ringer phosphate medium (KRP) was infused directly into the CN for 15 min each. Exogenous DA at the doses tested elicited increases in 3,4-dihydroxyphenylacetic acid (DOPAC) output in a dose-dependent manner. In addition, the higher two doses of exogenous DA also induced increases in homovanillic acid (HVA) output from the rat CN. The increases in DOPAC output by 5 x 10(-5) M DA was partially blocked by the inclusion of 10(-3) M nomifensine in KRP. Interestingly, exogenous DA-induced increases in HVA output were little affected by the nomifensine treatment. However, the catabolism of exogenous DA was almost completely eliminated by a prior 6-hydroxydopamine lesion in the ipsilateral substantia nigra. Furthermore, infusions of exogenous DA did not change 5-hydroxyindoleacetic acid output from the CN. In conclusion, our results confirm in vivo that (a) DA catabolic pathway via DOPAC intermediate predominates over the alternative pathway via 3-methoxytyramine, (b) increases in extracellular DA will lead to increases in DOPAC and HVA levels in extracellular space and (c) the majority of the DA is oxidized by intradopaminergic monoamine oxidase.

A potent dopamine-releasing factor is present in high concentrations in the rat adrenal gland

The present study shows that a novel, protease-sensitive factor present in a partially purified preparation from the rat adrenal gland selectively stimulates the release of dopamine from the rat striatal tissue superfused in vitro in a dose-dependent manner. Biological activity is also found to be present in much lower concentrations in the neocortex, striatum and cerebellum but absent in liver or spleen. This putative dopamine releasing factor is probably a glycoprotein, resistent to boiling, partially inactivated by trypsin and completely inactivated by the non-specific protease pronase E.

Effects on dopamine metabolism of MPTP and MPP+ infused through a push-pull cannula into the caudate nucleus of awake adult male rats

Our previous data demonstrated that both 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 1-methyl-4-phenylpyridinium ion (MPP+) exerted potent inhibition on endogenous 3,4-dihydroxyphenylacetic acid (DOPAC) output and potent stimulation on endogenous dopamine (DA) release from the rat corpus striatum superfused in vitro. In this report, using a push-pull perfusion technique, we examined in vivo the acute effects of MPTP and MPP+ on DA metabolism in the rat caudate nucleus (CN). MPTP or MPP+ in modified Krebs-Ringer phosphate buffer at concentrations of 10(-6), 10(-5) and 10(-4) M was administered directly into the CN for 15 min, each 90 min apart. Thirty minutes after the infusion of 10(-6) M MPP+, DOPAC output was reduced to a significantly lower value and subsequent infusions of high concentrations of MPP+ further decreased DOPAC output. Homovanillic acid (HVA) output was also decreased by MPP+ infusions, however, at higher concentrations. In respect to DA release, 1 of 10, 4 of 10 and 7 of 10 animals responded with significant increases to 10(-6), 10(-5) and 10(-4) M MPP+, respectively. On the other hand, MPTP was effective in reducing DOPAC output only at 10(-4) M and ineffective in altering DA and HVA output at all doses tested. In addition, neither drugs had a significant effect on 5-hydroxyindoleacetic acid. Accompanying the dramatic changes in DA metabolism caused by MPP+, two uncommon behavioral syndromes were also observed; tremor-body twist and body shaking.(ABSTRACT TRUNCATED AT 250 WORDS)

The mechanism of action of MPTP and MPP+ on endogenous dopamine release from the rat corpus striatum superfused in vitro

In this paper, using an in vitro superfusion system, we examined in the rat corpus striatum (CS) the action of N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and N-methylphenylpyridine (MPP+) on dopamine (DA) metabolism. MPTP, at at 10(-5) M and 10(-4) M, caused decreases in 3,4-dihydroxyphenylacetic acid (DOPAC) output in a dose-dependent manner. In addition, at 10(-4) M, MPTP caused an increase in DA release from CS. On the other hand, at 10(-6) M and 10(-5) M, MPP+ exerted very potent and rapid inhibition on DOPAC output and stimulated DA release in a dose-dependent manner. Furthermore, pretreatment of MPP+ markedly potentiated K+-stimulated DA release from CS. From the present data, we propose that MPP+ (the active metabolite of MPTP) inhibits DA reuptake system and/or monoamine oxidase (MAO) activity, increases readily releasable pool of DA and stimulates DA release from dopaminergic terminals.

Separation of subunits of pike eel gonadotropin by hydrophobic interaction chromatography

Subunits of pike eel gonadotropin were dissociated in propionic acid and separated by hydrophobic interaction chromatography on phenyl-Sepharose CL-4B with a high yield (79%). Isolated subunits were homogeneous, as tested by sodium dodecyl sulphate disc electrophoresis and by N-terminal analysis. The biological activities of two subunits, S-I and S-II, were 0% and 2.8% of native molecule, respectively, as assayed by stimulation of androgen production on carp testes. Reassociated molecules restored about 75% activity.