Clearance of circulating endothelin-1 by ETB receptors in rats

Exogenous endothelin (ET) is rapidly cleared from the circulation. We investigated which ET receptor subtypes (ETA and ETB) participate in ET-1 clearance. Following an intravenous (i.v.) bolus dose of [125I]ET-1 in anesthetized rats, radioactivity was rapidly cleared from the circulation and trapped by the lungs, kidneys and liver. Tissue distribution of the radioactivity was significantly inhibited in the lungs and kidneys, but not in the liver by infusion of the ETB antagonist BQ-788 (0.1 mg/kg/min i.v.), and the ET-1 clearance rate was reduced, while the ETA antagonist BQ-123 had no such effect. Furthermore, in isolated perfused rat lungs, about 80% of bolus-injected [125I]ET-1 was retained by the lungs after one passage. The retention of ET-1 was significantly inhibited by infusion of 1 microM BQ-788, but not BQ-123. These results suggest that ETB receptors play an important role in the clearance of ET-1.

Biochemical and pharmacological profile of a potent and selective endothelin B-receptor antagonist, BQ-788

We describe the characteristics of a potent and selective endothelin (ET) B-receptor antagonist, BQ-788 [N-cis-2,6-dimethylpiperidinocarbonyl-L-gamma-methylleucyl-D -1- methoxycarbonyltryptophanyl-D-norleucine]. In vitro, this compound potently and competitively inhibits 125I-labeled endothelin 1 (ET-1) binding to ETB receptors on human Girardi heart cells (IC50, 1.2 nM) but only poorly inhibits the binding to ETA receptors on human neuroblastoma cell line SK-N-MC cells (IC50, 1300 nM). In isolated rabbit pulmonary arteries, BQ-788 shows no agonist activity up to 10 microM and competitively antagonizes the vasoconstriction induced by an ETB-selective agonist, BQ-3020 (pA2, 8.4). In rat, an ETA-selective antagonist, BQ-123 (1 mg/kg, i.v.), does not affect transient depressor response to ET-1 (0.3 nmol/kg, i.v.) but potently inhibits following sustained pressor response; vice versa, BQ-788 (1 mg/kg, i.v.) abolishes the depressor response, resulting in a rapid onset of apparently enhanced pressor response. Thus, being a potent and selective ETB receptor antagonist, BQ-788 may be considered as a powerful tool for investigating the role of ET in physiological and pathological processes.

Runx3 controls the axonal projection of proprioceptive dorsal root ganglion neurons

Dorsal root ganglion (DRG) neurons specifically project axons to central and peripheral targets according to their sensory modality. The Runt-related genes Runx1 and Runx3 are expressed in DRG neuronal subpopulations, suggesting that they may regulate the trajectories of specific axons. Here we report that Runx3-deficient (Runx3(-/-)) mice displayed severe motor uncoordination and that few DRG neurons synthesized the proprioceptive neuronal marker parvalbumin. Proprioceptive afferent axons failed to project to their targets in the spinal cord as well as those in the muscle. NT-3-responsive Runx3(-/-) DRG neurons showed less neurite outgrowth in vitro. However, we found no changes in the fate specification of Runx3(-/-) DRG neurons or in the number of DRG neurons that expressed trkC. Our data demonstrate that Runx3 is critical in regulating the axonal projections of a specific subpopulation of DRG neurons.

A potential role for immune complex pathogenesis in drusen formation

Drusen are abnormal extracellular deposits that accumulate between the retinal pigmented epithelium and Bruch's membrane and are commonly associated with age-related macular degeneration. Our recent work has identified a number of plasma proteins as molecular components of drusen. Of interest is the fact that many of these drusen-associated molecules are acute phase reactant proteins and some have established roles in mediating immune responsiveness. As immune and inflammatory responses appear to play a role in the formation of other pathologic age-related deposits, we examined the distribution of immunoglobulin molecules and terminal complement complexes at sites of drusen deposition. Here, we report that concentrations of immunoglobulin G and terminal C5b-9 complement complexes are present in drusen. In addition, we observe that retinal pigmented epithelial cells overlying or directly adjacent to drusen, as well as some within apparently normal epithelia, exhibit cytoplasmic immunoreactivity for immunoglobulin and the C5 component of complement. Taken together, these results suggest that drusen biogenesis may be a byproduct of immune responsiveness, and they implicate immune complex-mediated pathogenesis involving retinal pigmented epithelial cells as an initiating event in drusen formation.

Aggressive natural killer-cell leukemia revisited: large granular lymphocyte leukemia of cytotoxic NK cells

Aggressive natural killer-cell leukemia (ANKL) is a rare form of large granular lymphocyte leukemia, which is characterized by a systemic proliferation of NK cells. The clinical features of 22 ANKL cases were analyzed. Hepatomegaly (64%), splenomegaly (55%) and lymphadenopathy (41%) were also frequently observed. Leukemic cells were identified as CD1-, CD2+, surface CD3-, CD4-, CD5-, CD7+, CD8+/-, CD10-, CD11b+/-, CD13-, CD16+, CD19-, CD20-, CD25-, CD33(-), CD34-, CD38+, CD56+, CD122+, HLA-DR+ and TCR-. Two of the 16 cases examined for CD57 were positive and three of the seven cases examined for cytoplasmic CD3. Epstein-Barr virus was detected in the tumor cells of 11 of the 13 cases examined. No common cytogenetic abnormalities were identified and 6q anomaly was detected in only one. Three of 13 patients treated with chemotherapy containing anthracycline/anthraquinone attained complete remission, in contrast to none of the eight who were treated with regimens without anthracycline. Although the overall prognosis was poor with a median survival of 58 days, those who attained remission showed better prognosis (P=0.005). These findings suggest that ANKL is an entity of mature cytotoxic NK-cell neoplasms with distinct phenotype and disease presentations. Intensive treatment for ANKL may result in a better prognosis.

A transgenic model of autoimmune hemolytic anemia

We made double transgenic mice bearing immunoglobulin heavy and light chain genes encoding an autoantibody against the mouse erythrocyte by the cross of C57BL/6 mice carrying the transgene for each chain of the immunoglobulin. Although no obvious disorders were found in the single-chain transgenic mice, severely anemic symptoms were found in some of the double transgenic mice, in which most B cells express, at least on their surface, the autoantibody reactive to self-antigens on the erythrocyte. Individual double-transgenic mice showed a wide variation of phenotypes between severe anemia and no symptoms. Both deletion and anergy of autoreactive B cells were seen in each individual mouse, but their relative contribution to self-tolerance was variable and not directly related to the severity of anemia or the amount of the autoantibody produced. This transgenic system provides a good autoimmune disease model for exploring its onset mechanism, and means of its treatment and prevention.

Local cellular sources of apolipoprotein E in the human retina and retinal pigmented epithelium: implications for the process of drusen formation

PURPOSE

The inheritance of specific apolipoprotein E allelles has been linked to atherosclerosis, Alzheimer disease, and, most recently, to the incidence of age-related macular degeneration. Apolipoprotein E is a common component of the extracellular plaques and deposits characteristic of these disorders, including drusen, which are a hallmark of age-related macular degeneration. Accordingly, we assessed the potential biosynthetic contribution of local ocular cell types to the apolipoprotein E found in drusen.

METHODS

We measured apolipoprotein E mRNA levels in human donor tissues using a quantitative assay of apolipoprotein E transcription, and we localized apolipoprotein E protein to specific cell types and compartments in the neural retina, retinal pigmented epithelium, and choroid using laser scanning confocal immunofluorescence microscopy.

RESULTS

Apolipoprotein E immunoreactivity is associated with photoreceptor outer segments, the retinal ganglion cell layer, the retinal pigmented epithelium basal cytoplasm and basal lamina, and with both collagenous layers of Bruch membrane. Apolipoprotein E appears to be a ubiquitous component of drusen, irrespective of clinical phenotype. It also accumulates in the cytoplasm of a subpopulation of retinal pigmented epithelial cells, many of which overlie or flank drusen. Mean levels of apolipoprotein E mRNA in the adult human retina are 45% and 150% of the levels measured in liver and adult brain, the two most abundant biosynthetic sources of apolipoprotein E. Apolipoprotein E mRNA levels are highest in the inner retina, and lowest in the outer retina where photoreceptors predominate. Significant levels of apolipoprotein E mRNA are also present in the retinal pigmented epithelium/choroid complex and in cultured human retinal pigmented epithelial cells.

CONCLUSIONS

Apolipoprotein E protein is strategically located at the same anatomic locus where drusen are situated, and the retinal pigmented epithelium is the most likely local biosynthetic source of apolipoprotein E at that location. Age-related alteration of lipoprotein biosynthesis and/or processing at the level of the retinal pigmented epithelium and/or Bruch membrane may be a significant contributing factor in drusen formation and age-related macular degeneration pathogenesis.

Molecular cloning and characterization of a surface antigen preferentially overexpressed on multiple myeloma cells

HM1.24 antigen has been identified as a surface molecule preferentially expressed on terminally differentiated B cells, and its overexpression is observed in multiple myeloma cells. The HM1.24 antigen is, therefore, expected as a most potent target molecule for antibody-based immunotherapy for multiple myeloma. Here, we have identified the cDNA for human HM1.24 antigen and also analyzed its gene structure including the promoter region. The HM1.24 antigen is a type II membrane glycoprotein, which has been reported as a bone marrow stromal cell surface antigen BST2, and may exist as a homodimer on myeloma cell surface. Although a reason for the overexpression in myeloma cells is not understood, very interestingly, the promoter region of the HM1.24 gene has a tandem repeat of three cis elements for a transcription factor, STAT3, which mediates interleukin-6 (IL-6) response gene expression. Since IL-6 is a differentiation factor for B cells, and known as a paracrine/autocrine growth factor for multiple myeloma cells, the expression of HM1.24 antigen may be regulated by the activation of STAT3. Importantly, a humanized anti-HM1.24 antibody effectively lysed the CHO transformants which expressed HM1.24 antigen as high as human multiple myeloma cells, but not the cells with lower antigen expression. This evaluation shows that ADCC heavily depends on the expression level of target antigens and, therefore, the immunotherapy targeting the HM1.24 antigen should have a promising potential in clinical use.

A pleckstrin homology domain specific for phosphatidylinositol 4, 5-bisphosphate (PtdIns-4,5-P2) and fused to green fluorescent protein identifies plasma membrane PtdIns-4,5-P2 as being important in exocytosis

Kinetically distinct steps can be distinguished in the secretory response from neuroendocrine cells with slow ATP-dependent priming steps preceding the triggering of exocytosis by Ca(2+). One of these priming steps involves the maintenance of phosphatidylinositol 4, 5-bisphosphate (PtdIns-4,5-P(2)) through lipid kinases and is responsible for at least 70% of the ATP-dependent secretion observed in digitonin-permeabilized chromaffin cells. PtdIns-4,5-P(2) is usually thought to reside on the plasma membrane. However, because phosphatidylinositol 4-kinase is an integral chromaffin granule membrane protein, PtdIns-4,5-P(2) important in exocytosis may reside on the chromaffin granule membrane. In the present study we have investigated the localization of PtdIns-4,5-P(2) that is involved in exocytosis by transiently expressing in chromaffin cells a pleckstrin homology (PH) domain that specifically binds PtdIns-4, 5-P(2) and is fused to green fluorescent protein (GFP). The PH-GFP protein predominantly associated with the plasma membrane in chromaffin cells without any detectable association with chromaffin granules. Rhodamine-neomycin, which also binds to PtdIns-4,5-P(2), showed a similar subcellular localization. The transiently expressed PH-GFP inhibited exocytosis as measured by both biochemical and electrophysiological techniques. The results indicate that the inhibition was at a step after Ca(2+) entry and suggest that plasma membrane PtdIns-4,5-P(2) is important for exocytosis. Expression of PH-GFP also reduced calcium currents, raising the possibility that PtdIns-4,5-P(2) in some manner alters calcium channel function in chromaffin cells.

Intravenous cyclophosphamide therapy for progressive interstitial pneumonia in patients with polymyositis/dermatomyositis

OBJECTIVES

To study the efficacy and safety of monthly intravenous pulse cyclophosphamide (IVCYC) therapy for progressive interstitial pneumonia in polymyositis/dermatomyositis (PM/DM).

METHODS

Seventeen patients with PM/DM/amyopathic DM (mean age 51.4 +/- 10.4, mean follow-up 32 months) who received IVCYC for progressive interstitial pneumonia between August 1993 and October 2002 were studied. Nine patients had failed to respond to previous treatment with high-dose steroid and/or immunosuppressant. Cyclophosphamide (300-800 mg/m2) was given at least six times every 4 weeks. Oral prednisolone (0.5-1 mg/kg/day) was administered for the first 2 weeks and was gradually tapered. Response to treatment was evaluated based on the degree of exertional dyspnea, pulmonary function test and high-resolution computed tomography (HRCT).

RESULTS

Eleven of 17 patients showed improvement in their dyspnea; six out of seven patients who had required oxygen treatment before IVCYC no longer did so after IVCYC. Eight of 17 patients had >or=10% improvement of vital capacity (VC)% and 9/17 had >or=10 point reduction in their HRCT score. Twelve patients had exhibited at least one result. Two patients with anti-Jo-1 antibodies showed a flare-up of interstitial pneumonia or myositis. After the IVCYC therapy, mean VC% improved by 15% (from 68 to 83%, P = 0.0034). The extent of abnormal lesions in HRCT was reduced from 24 to 13% (P = 0.0055). There was neither death nor severe toxicities observed.

CONCLUSIONS

In this open-label study, IVCYC improved symptoms, pulmonary function tests and HRCT findings in patients with PM/DM. Longitudinal controlled studies are required to further confirm the efficacy of IVCYC.

Platelet-derived growth factor activates protein kinase C epsilon through redundant and independent signaling pathways involving phospholipase C gamma or phosphatidylinositol 3-kinase

Protein kinase C (PKC), a major cellular receptor for tumor-promoting phorbol esters and diacylglycerols (DGs), appears to be involved in a variety of cellular functions, although its activation mechanism in vivo is not yet fully understood. To evaluate the signaling pathways involved in the activation of PKC epsilon upon stimulation by platelet-derived growth factor (PDGF) receptor (PDGFR), we used a series of PDGFR "add-back" mutants. Activation of a PDGFR mutant (Y40/51) that binds and activates phosphatidylinositol 3-kinase (PI 3-kinase) caused translocation of PKC epsilon from the cytosol to the membrane in response to PDGF. A PDGFR mutant (Y1021) that binds and activates phospholipase C gamma (PLC gamma), but not PI 3-kinase, also caused the PDGF-dependent translocation of PKC epsilon. The translocation of PKC epsilon upon stimulation of PDGFR (Y40/51) was inhibited by wortmannin, an inhibitor of PI 3-kinase. Activation of PKC epsilon was further confirmed in terms of PKC epsilon-dependent expression of a phorbol 12-tetradecanoate 13-acetate response element (TRE)-luciferase reporter. Further, purified PKC epsilon was activated in vitro by either DG or synthetic phosphatidylinositol 3,4,5-trisphosphate. These results clearly demonstrate that PKC epsilon is activated through redundant and independent signaling pathways which most likely involve PLC gamma or PI 3-kinase in vivo and that PKC epsilon is one of the downstream mediators of PI 3-kinase whose downstream targets remain to be identified.

In vitro and in vivo pharmacological characterization of J-113397, a potent and selective non-peptidyl ORL1 receptor antagonist

1-[(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl -1, 3-dihydro-2H-benzimidazol-2-one (J-113397) was found to be the first potent nonpeptidyl ORL1 receptor antagonist (K(i): cloned human ORL1=1.8 nM) with high selectivity over other opioid receptors (K(i): 1000 nM for human mu-opioid receptor, >10,000 nM for human delta-opioid receptor, and 640 nM for human kappa-opioid receptor). In vitro, J-113397 inhibited nociceptin/orphanin FQ-stimulated [35S]guanosine 5'-O-(gamma-thio)triphosphate (GTP gamma S) binding to Chinese Hamster Ovary (CHO) cells expressing ORL1 (CHO-ORL1) with an IC(50) value of 5.3 nM but had no effect on [35S]GTP gamma S binding by itself. Schild plot analysis of the [35S]GTP gamma S binding assay and cAMP assay using CHO-ORL1 indicated competitive antagonism of J-113397 on the ORL1 receptor. In CHO cells expressing mu-, delta- or kappa-opioid receptors, J-113397 had no effects on [35S]GTP gamma S binding up to a concentration of 100 nM, indicating selective antagonism of the compound on the ORL1 receptor. In vivo, J-113397, when administered subcutaneously (s.c.), dose-dependently inhibited hyperalgesia elicited by intracerebroventricular (i.c.v.) administration of nociceptin/orphanin FQ in a tail-flick test with mice. An in vitro binding study using mouse brains indicated that J-113397 possesses high affinity for the mouse ORL1 receptor (K(i): 1.1 nM) as well as the human receptor. In summary, J-113397 is the first potent, selective ORL1 receptor antagonist that may be useful in elucidating the physiological roles of nociceptin/orphanin FQ.

Enhanced apoptosis relates to bile duct loss in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is characterized by an immune-mediated destruction of intrahepatic small bile ducts. Apoptosis, a unique pattern of cell death, has been suggested to be responsible for the biliary destruction in PBC. To address this issue, we attempted to detect the apoptosis of biliary epithelial cells by in situ nick-end labeling and by the expression of apoptosis-related proteins using immunohistochemistry in patients with various hepatobiliary diseases, including PBC. The data was noteworthy for several reasons. First, apoptosis was occasionally detected on biliary cells in all liver specimens; however, the positive rate was high in PBC and relatively low in other livers. Strong expression of CD95 was frequently observed in the epithelial cells of the injured bile ducts of PBC, which accompanied high intensity CD95 ligand-expressing mononuclear cells. Perforin and granzyme B immunoreactivities were occasionally found on the bile ducts in control liver diseases as well as PBC, but granzyme B-positive biliary cells were prominent in PBC. In contrast, Lewis Y expression, as detected using BM-1 antibody, was consistently present in the injured bile ducts of PBC. These data suggest that apoptosis, via the perforin/granzyme B pathway, may be associated with the degrading fraction of cell cycle regulation in the small-sized biliary tree under physiological and pathological liver conditions. Moreover, enhanced apoptosis, mediated by CD95/CD95 ligand interaction, may contribute to the bile duct injury and loss observed in PBC.

Intracellular delivery of phosphoinositides and inositol phosphates using polyamine carriers

Phosphoinositide signaling regulates events in endocytosis and exocytosis, vesicular trafficking of proteins, transduction of extracellular signals, remodeling of the actin cytoskeleton, regulation of calcium flux, and apoptosis. Obtaining mechanistic insights in living cells is impeded by the membrane impermeability of these anionic lipids. We describe a carrier system for intracellular delivery of phosphoinositide polyphosphates (PIP(n)s) and fluorescently labeled PIP(n)s into living cells, such that intracellular localization can be directly observed. Preincubation of PIP(n)s or inositol phosphates with carrier polyamines produced complexes that entered mammalian, plant, yeast, bacterial, and protozoal cells in seconds to minutes via a nonendocytic mechanism. Time-dependent transit of both PIP(n)s and the carrier to specific cytosolic and nuclear compartments was readily visualized by fluorescence microscopy. Platelet-derived growth factor treatment of NIH 3T3 fibroblasts containing carrier-delivered phosphatidylinositol 4,5-bisphosphate [PtdIns(4, 5)P(2)]-7-nitrobenz-2-oxa-1,3-diazole resulted in the redistribution of the fluorescent signal, suggesting that fluorescent PtdIns(4, 5)P(2) was a substrate for phospholipase C. We also observed a calcium flux in NIH 3T3 cells when complexes of carrier and PtdIns(4, 5)P(2) or inositol 1,4,5-trisphosphate were added extracellularly. This simple intracellular delivery system allows for the efficient translocation of biologically active PIP(n)s, inositol phosphates, and their fluorescent derivatives into living cells in a physiologically relevant context.

Spontaneous motoneuronal activity mediated by glycine and GABA in the spinal cord of rat fetuses in vitro

1. Spontaneous motoneuronal activity was monitored from the lumbar ventral roots in an isolated spinal cord preparation from rat fetuses at embryonic days (E) 13.5-18.5. 2. Spontaneous bursts that were synchronized in both left and right ventral roots were observed periodically (mean interval, 1.5-2.6 min) from E14.5 to 17.5. This activity was abolished in Ca(2+)-free saline or by application of tetrodotoxin (1 microM), indicating that it was synaptically mediated. 3. The glutamate receptor blocker kynurenate (4 mM) failed to block spontaneous bursts at E14.5-15.5, though it completely abolished them at E17.5. The glycine receptor antagonist strychnine (10 microM) completely blocked spontaneous bursts at E14.5-15.5. Bicuculline, a GABAA receptor antagonist, reduced the amplitude of the spontaneous bursts. 4. At E15.5, a brief application of glycine (250 microM to 2 mM) evoked excitatory responses resembling the spontaneous bursts in both time course and amplitude. Such glycine-induced responses were not observed under Ca(2+)-free conditions, suggesting that they were synaptically evoked. These synaptic responses were not blocked by kynurenate (4 mM), but they were abolished by strychnine (10 microM). 5. It is concluded that glycine and GABA generate the earliest spontaneous motor activity of the fetus and function transiently as excitatory transmitters in the embryonic spinal cord.

Leptin inhibits stress-induced apoptosis of T lymphocytes

Leptin, which is secreted by adipocytes, the placenta and the stomach, not only controls appetite through leptin receptors in the hypothalamus but also regulates cell-mediated immunity. In this study we have demonstrated that continuous injection of leptin prevents the reduction in lymphocyte numbers normally observed in fasted and steroid-injected mice. Consistent with leptin-induced protection, we observed up-regulation of the bcl-xL gene as a result of signal transduction via leptin receptors on lymphocytes. We suggest that leptin might contribute to the recovery of immune suppression in malnourished mice by inhibiting lymphocyte apoptosis.

Endothelin receptor subtypes in human versus rabbit pulmonary arteries

We studied which endothelin (ET) receptor subtypes mediate ET-1-induced vasocontraction in the human pulmonary artery (PA) compared with the rabbit PA. ET-1 produced potent contraction in both human and rabbit isolated PAs. In human PA, ET-1-induced contraction was competitively antagonized by BQ-123 (an ETA receptor antagonist) with a pA2 value of 7.68. In rabbit PA, however, even a high concentration of BQ-123 (1 microM) did not affect the contraction. BQ-3020 (an ETB receptor agonist) produced potent contraction in rabbit PA but not in human PA. Binding assays of the membrane preparations showed that human and rabbit PAs contained ETA and ETB receptors in ratios of 93:7 and 23:77, respectively. These results suggest interspecies differences in the ET receptor subtypes that mediate ET-1-induced vasocontraction; ETA receptors are dominant in the human PA, whereas ETB receptors are dominant in the rabbit PA. Furthermore, the predominance of ETA receptors in human PA was supported by autoradiographical studies. If ET-1 acts as a physiological and/or pathophysiological vasocontractor in the human pulmonary circulation, an ETA receptor antagonist would function as a pulmonary vasodilator in humans.

Potent neuropeptide Y Y1 receptor antagonist, 1229U91: blockade of neuropeptide Y-induced and physiological food intake

Neuropeptide Y (NPY) is thought to increase food intake through the action of Y1 (-like) receptors in the hypothalamus. To confirm the involvement of Y1 receptors in feeding behavior, selective and potent antagonists for Y1 receptors are required. In the present study, we showed that a peptide, 1229U91 [(Ile,Glu,Pro,Dpr,Tyr,Arg,Leu,Arg, Tyr-NH2)2 cyclic (2,4'),(2',4)-diamide], is a potent and selective antagonist for Y1 receptors. 1229U91 displaced [125I]peptide YY (PYY) binding to membranes of human neuroblastoma-derived SK-N-MC cells that predominantly express Y1 receptors with a K1 value 0.10 nM and inhibited the NPY-induced increase in intracellular calcium levels(IC50 = 0.27 nM). In contrast, the K1 values for [125I]PYY binding to Y2 receptors in membranes of human neuroblastoma-derived SK-N-BE2 cells and rat hypothalamus were 700 nM and more than 1 microM, respectively. Although [125I]PYY could not detect Y1 receptors in the rat hypothalamic membranes, [125I]1229U91 revealed binding sites with a high affinity (Kd = 18 pM), indicating the presence of Y1 receptors in the hypothalamus. Intracerebroventricular injection of 1229U91 (30 micrograms) into male Sprague-Dawley rats completely inhibited NPY (5 micrograms)-induced food intake without any other behavioral change. Furthermore, intracerebroventricular injection of 1229U91 significantly suppressed physiological feeding behavior after overnight fasting. These results indicate that Y1 receptors in the rat hypothalamus mediate NPY-induced food intake, and that physiological feeding behavior after overnight fasting may be largely regulated by NPY via Y1 receptors. 1229U91 may be useful for further elucidating the pathophysiological roles of NPY in feeding behavior.

A novel radioligand [125I]BQ-3020 selective for endothelin (ETB) receptors

A linear endothelin (ET) analog, N-acetyl-LeuMetAspLysGluAlaValTyrPheAlaHisLeu-AspIleIleTrp (BQ-3020), is highly selective for ETB receptors. BQ-3020 displaces [125I]ET-1 binding to ETB receptors (nonselective to ET isopeptides) in porcine cerebellar membranes (IC50: 0.2nM) at a concentration 4,700 times lower than that to ETA receptors (selective to ET-1) on aortic vascular smooth muscle cells (VSMC) (IC50: 940nM). BQ-3020 as well as ET-1 and ET-3 elicits vasoconstriction in the rabbit pulmonary artery. The ETA antagonist BQ-123 failed to inhibit this BQ-3020-induced vasoconstriction. Furthermore, BQ-3020 elicits endothelium-dependent vasodilation. These data indicate that BQ-3020 has ETB agonistic activity. The radioligand [125I]BQ-3020 binds to cerebellar membranes at single high affinity sites (Kd = 34.4pM), whereas it scarcely binds to VSMC. [125I]BQ-3020 binding to the cerebellum was displaced by BQ-3020, ET-1 and ET-3 in a nonselective manner (IC50: 0.07-0.17nM). However, the binding of [125I]BQ-3020 was insensitive to the ETA antagonist BQ-123 and other bioactive peptides. Both [125I]ET-1 and [125I]BQ-3020 show slow onset and offset binding kinetics to ETB receptors. These data indicate that the radioligand [125I]BQ-3020 selectively labels ETB receptors and that the slow binding kinetics of ET-1 are dependent on the peptide sequence from Leu6 to Trp21, but not on the structure formed by its two disulfide bridges.

Isolation and characterization of CA XIV, a novel membrane-bound carbonic anhydrase from mouse kidney

Carbonic anhydrase (CA) is involved in various physiological processes such as acid-base balance and transport of carbon dioxide and ions. In this study, we have succeeded in the isolation of a novel CA from the mouse kidney by use of the signal sequence trap method. It is a 337-amino acid polypeptide with a calculated molecular mass of 37.5 kDa, consisting of a putative amino-terminal signal sequence, a CA domain, a transmembrane domain, and a short hydrophilic carboxyl terminus, which we designated CA XIV. The CA domain of CA XIV is highly homologous with those of known CAs, especially extracellular CAs including CA XII, IX, VI, and IV. The expression study of an epitope-tagged protein has suggested that CA XIV is located on the plasma membrane. When expressed in COS-7 cells, CA XIV exhibits CA activity that is predominantly associated with the membrane fraction. By Northern blot analysis, the gene expression of CA XIV is most abundant in the kidney and heart, followed by the skeletal muscle, brain, lung, and liver. In situ hybridization has revealed that, in the kidney, the gene is expressed intensely in the proximal convoluted tubule, which is the major segment for bicarbonate reabsorption and also in the outer border of the inner stripe of the outer medulla. In conclusion, we have cloned a functional cDNA encoding a novel membrane-bound CA. This study will bring new insights into our understanding of carbon dioxide metabolism and acid-base balance.

Involvement of Th1 cells and heat shock protein 60 in the pathogenesis of intestinal Behcet's disease

Involvement of excessive Th1 cell functions and heat shock protein expression in the pathogenesis of Behcet's disease (BD) has been reported. In this study we have characterized immune responses in intestinal lesions of BD. Peripheral blood lymphocytes (PBL) of BD and healthy controls (HC) and tissue specimens of intestinal Behcet's disease (intestinal BD), Crohn's disease (CD) and ulcerative colitis (UC) were analysed for mRNA and protein expression by reverse transcriptase-polymerase chain reaction (PCR) and immunohistochemistry, respectively. PBL of BD patients expressed the Th1-related chemokine receptor, CCR5 and CXCR3 preferentially compared with those of healthy controls. Intestinal lesions of BD expressed interferon (IFN)-gamma, tumour necrosis factor (TNF)-alpha and interleukin (IL)-12 mRNA, indicating Th1 skewed responses in vivo. mRNA of Txk, a Tec family tyrosine kinase specific to Th1 cells, was expressed in the lesions, suggesting its contribution to the Th1-dominant responses. In the intestinal samples, CCR5 was detected in all the cases with BD, whereas Th2-related CCR3 and CCR4 were detected randomly, mainly in the cases with inactive BD and those receiving large amounts of prednisolone, indicating the Th1-dominant immune responses in the intestinal lesions. As the ligands of CCR5, MIP1alpha and MIP1beta were detected, whereas RANTES was not. Heat shock protein (HSP) 60 was expressed in PBL and intestinal tissues of BD. Th1-dominant immune responses and HSP60 expression may induce the inflammatory responses and thus be associated with the pathogenesis of intestinal BD.