Biomedical subjects

Alicia Rivera

Publications and source records attributed to Alicia Rivera.

At least 19 recordsLinked to original sources

PubMed2006

Effect of complete protein 4.1R deficiency on ion transport properties of murine erythrocytes.

Moderate hemolytic anemia, abnormal erythrocyte morphology (spherocytosis), and decreased membrane stability are observed in mice with complete deficiency of all erythroid protein 4.1 protein isoforms (4.1(-/-); Shi TS et al. J Clin Invest 103: 331, 1999). We have examined the effects of erythroid protein 4.1 (4.1R) deficiency on erythrocyte cation transport and volume regulation. 4.1(-/-) mice exhibited erythrocyte dehydration that was associated with reduced cellular K and increased Na content. Increased Na permeability was observed in these mice, mostly mediated by Na/H exchange with normal Na-K pump and Na-K-2Cl cotransport activities. The Na/H exchange of 4.1(-/-) erythrocytes was markedly activated by exposure to hypertonic conditions (18.2 +/- 3.2 in 4.1(-/-) vs. 9.8 +/- 1.3 mmol/10(13) cell x h in control mice), with an abnormal dependence on osmolality (EC(50) = 417 +/- 42 in 4.1(-/-) vs. 460 +/- 35 mosmol/kgH(2)O in control mice), suggestive of an upregulated functional state. While the affinity for internal protons was not altered (K(0.5) = 489.7 +/- 0.7 vs. 537.0 +/- 0.56 nM in control mice), the V(max) of the H-induced Na/H exchange activity was markedly elevated in 4.1(-/-) erythrocytes (V(max) 91.47 +/- 7.2 compared with 46.52 +/- 5.4 mmol/10(13) cell x h in control mice). Na/H exchange activation by okadaic acid was absent in 4.1(-/-) erythrocytes. Altogether, these results suggest that erythroid protein 4.1 plays a major role in volume regulation and physiologically downregulates Na/H exchange in mouse erythrocytes. Upregulation of the Na/H exchange is an important contributor to the elevated cell Na content of 4.1(-/-) erythrocytes.

Animals↗

PubMed2006

Uncoupling protein-2 promotes nigrostriatal dopamine neuronal function.

Uncoupling protein 2 (UCP2) is known to promote neuroprotection in many forms of neurological pathologies including Parkinson's disease. Here, we examined the hypothesis that UCP2 also mediates aspects of normal nigrostriatal dopamine (DA) function. Mice lacking UCP2 exhibited reduced dopamine turnover in the striatum as measured by the 3,4-dihydoxyphenylacetic acid/dopamine (DOPAC/DA) ratio, reduced tyrosine hydroxylase immunoreactivity (TH IR) in the substantia nigra pars compacta (SNc) and reticulata, striatum and nucleus accumbens. UCP2-knockout (KO) mice also had reduced dopamine transporter immunoreactivity (DAT IR) in the SNc but not other brain regions examined. In order to determine if these biochemical deficits are transcribed into behavioural deficits, we examined locomotor function in UCP2-KO mice compared to wild-type (WT) controls. UCP2-KO mice exhibited significantly reduced total movement distance, movement velocity and increased rest time compared to wild-type controls. These results suggest that UCP2 is an important mitochondrial protein that helps to maintain normal nigrostriatal dopamine neuronal function and a reduction in UCP2 levels may predispose individuals to environmental causes of Parkinson's disease.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2006

Galanin-neuropeptide Y (NPY) interactions in central cardiovascular control: involvement of the NPY Y receptor subtype.

The interactions between neuropeptide Y (NPY), specifically through NPY Y(1) and Y(2) receptor subtypes, and galanin [GAL(1-29)] have been analysed at the cardiovascular level. The cardiovascular effects of intracisternal coinjections of GAL(1-29) with NPY or NPY Y(1) or Y(2) agonists, as well as quantitative receptor autoradiography of the binding characteristics of NPY Y(1) and Y(2) receptor subtypes in the nucleus of the solitary tract (NTS), in the presence or absence of GAL(1-29), have been investigated. The effects of coinjections of GAL(1-29) and the NPY Y(1) agonist on the expression of c-FOS immunoreactivity in the NTS were also studied. The coinjection of NPY with GAL(1-29) induced a significant vasopressor and tachycardic action with a maximum 40% increase (P < 0.001). The coinjection of the NPY Y(1) agonist and GAL(1-29) induced a similar increase in mean arterial pressure and heart rate as did NPY plus GAL(1-29), actions that were not observed with the NPY Y(2) agonist plus GAL(1-29). GAL(1-29), 3 nm, significantly and substantially (by approximately 40%) decreased NPY Y(1) agonist binding in the NTS. This effect was significantly blocked (P < 0.01) in the presence of the specific galanin antagonist M35. The NPY Y(2) agonist binding was not modified in the presence of GAL(1-29). At the c-FOS level, the coinjection of NPY Y(1) and GAL(1-29) significantly reduced the c-FOS-immunoreactive response induced by either of the two peptides. The present findings suggest the existence of a modulatory antagonistic effect of GAL(1-29) mediated via galanin receptors on the NPY Y(1) receptor subtype and its signalling within the NTS.

Animals↗

PubMed2005

Evidence for a protective role of the Gardos channel against hemolysis in murine spherocytosis.

It has been shown that mice with complete deficiency of all 4.1R protein isoforms (4.1-/-) exhibit moderate hemolytic anemia, with abnormal erythrocyte morphology (spherocytosis) and decreased membrane stability. Here, we characterized the Gardos channel function in vitro and in vivo in erythrocytes of 4.1-/- mice. Compared with wild-type, the Gardos channel of 4.1-/- erythrocytes showed an increase in Vmax (9.75 +/- 1.06 vs 6.08 +/- 0.09 mM cell x minute; P < .04) and a decrease in Km (1.01 +/- 0.06 vs 1.47 +/- 1.02 microM; P < .03), indicating an increased sensitivity to activation by intracellular calcium. In vivo function of the Gardos channel was assessed by the oral administration of clotrimazole, a well-characterized Gardos channel blocker. Clotrimazole treatment resulted in worsening of anemia and hemolysis, with decreased red cell survival and increased numbers of circulating hyperchromic spherocytes and microspherocytes. Clotrimazole induced similar changes in 4.2-/- and band 3+/- mice, indicating that these effects of the Gardos channel are shared in different models of murine spherocytosis. Thus, potassium and water loss through the Gardos channel may play an important protective role in compensating for the reduced surface-membrane area of hereditary spherocytosis (HS) erythrocytes and reducing hemolysis in erythrocytes with cytoskeletal impairments.

Anemia, Hemolytic↗

PubMed2005

Functional expression of beta-chemokine receptors in osteoblasts: role of regulated upon activation, normal T cell expressed and secreted (RANTES) in osteoblasts and regulation of its secretion by osteoblasts and osteoclasts.

The expression and functions of receptors for the beta-chemokine, regulated upon activation, normal T cell expressed, and secreted (RANTES)/CCL5, were investigated in osteoblasts. Both primary osteoblasts and the MC3T3-E1 osteoblast cell line express the RANTES receptors, CCR1, 3, 4, and 5 (by RT-PCR), which encode functional receptors in osteoblasts as shown by [125I]-RANTES binding followed by Scatchard analysis. Expression of all four RANTES receptor mRNAs in osteoblast is in contrast to the reports of expression of CCR1 being the only RANTES receptor expressed by osteoclasts. Exogenous RANTES elicits chemotaxis of osteoblasts and promotes cell survival via phosphatidylinositol 3-kinase with attendant phosphorylation of Akt. Osteoclastic RANTES, obtained from the conditioned medium of receptor activator of nuclear factor-kappa B ligand-differentiated RAW264.7 cells also induces chemotaxis of MC3T3-E1 cells. Incubating the conditioned medium with an anti-RANTES neutralizing antibody attenuated this effect. RANTES secretion from osteoblast is inhibited by differentiation promoting hormones, e.g. 1,25 (OH)2D3 and dexamethasone, whereas macrophage inflammatory protein-1 alpha (but not macrophage inflammatory protein-1 beta) and elevated calcium induce it. Elevated calcium also stimulated RANTES secretion by osteoclasts. Therefore, RANTES is an osteoblast chemoattractant and a survival-promoting molecule whose regulation in osteoblast is varied. Furthermore, RANTES secreted from osteoclasts induces osteoblast chemotaxis. Therefore, expression of RANTES and its receptors in both osteoblasts and osteoclasts could enable this chemokine to act in autocrine/paracrine modes.

Animals↗

PubMed2005

Na+/Ca2+ exchanger activity modulates connective tissue growth factor mRNA expression in transforming growth factor beta1- and Des-Arg10-kallidin-stimulated myofibroblasts.

Transforming growth factor (TGF)-beta and des-Arg(10)-kallidin stimulate the expression of connective tissue growth factor (CTGF), a matrix signaling molecule that is frequently overexpressed in fibrotic disorders. Because the early signal transduction events regulating CTGF expression are unclear, we investigated the role of Ca(2+) homeostasis in CTGF mRNA expression in TGF-beta1- and des-Arg(10)-kallidin-stimulated human lung myofibroblasts. Activation of the kinin B1 receptor with des-Arg(10)-kallidin stimulated a rise in cytosolic Ca(2+) that was extracellular Na(+)-dependent and extracellular Ca(2+)-dependent. The des-Arg(10)-kallidin-stimulated increase of cytosolic Ca(2+) was blocked by KB-R7943, a specific inhibitor of Ca(2+) entry mode operation of the plasma membrane Na(+)/Ca(2+) exchanger. TGF-beta1 similarly stimulated a KB-R7943-sensitive increase of cytosolic Ca(2+) with kinetics distinct from the des-Arg(10)-kallidin-stimulated Ca(2+) response. We also found that KB-R7943 or 2',4'-dichlorobenzamil, an amiloride analog that inhibits the Na(+)/Ca(2+) exchanger activity, blocked the TGF-beta1- and des-Arg(10)-kallidin-stimulated increases of CTGF mRNA. Pretreatment with KB-R7943 also reduced the basal and TGF-beta1-stimulated levels of alpha1(I) collagen and alpha smooth muscle actin mRNAs. These data suggest that, in addition to regulating ion homeostasis, Na(+)/Ca(2+) exchanger acts as a signal transducer regulating CTGF, alpha1(I) collagen, and alpha smooth muscle actin expression. Consistent with a more widespread role for Na(+)/Ca(2+) exchanger in fibrogenesis, we also observed that KB-R7943 likewise blocked TGF-beta1-stimulated levels of CTGF mRNA in human microvascular endothelial and human osteoblast-like cells. We conclude that Ca(2+) entry mode operation of the Na(+)/Ca(2+) exchanger is required for des-Arg(10)-kallidin- and TGF-beta1-stimulated fibrogenesis and participates in the maintenance of the myofibroblast phenotype.

Blotting, Northern↗

PubMed2005

Protection but maintained dysfunction of nigral dopaminergic nerve cell bodies and striatal dopaminergic terminals in MPTP-lesioned mice after acute treatment with the mGluR5 antagonist MPEP.

The mGluR5 antagonist MPEP was used to study the role of mGluR5 in MPTP-induced injury of the nigrostriatal DA neurons. The findings indicate that acute blockade of mGluR5 may result in neuroprotective actions against MPTP neurotoxicity on nigral DA cell bodies and striatal DA terminals using stereological analysis of TH immunoreactivity and microdensitometry. Biochemical analysis showed no restoration of DA levels and metabolism indicating a maintained reduction of DA transmission.

Animals↗

PubMed2004

Abnormal regulation of Mg2+ transport via Na/Mg exchanger in sickle erythrocytes.

Erythrocyte magnesium (Mg2+) deficiency has been demonstrated in sickle cell disease to contribute to erythrocyte dehydration, K loss, and thus sickling. No studies have assessed the functional properties of the Na/Mg exchanger in sickle cell disease. Using Mg(2+)-loaded erythrocytes, we measured Mg2+ efflux induced by extracellular Na+. We estimated that the Na/Mg exchanger had higher maximal velocity, higher affinity for Na+, and lower cooperativity for Mg2+ in sickle than in normal erythrocytes. The activity of the exchanger was markedly decreased by hypotonic and hypertonic conditions in normal erythrocytes but not in sickle erythrocytes. Studies of density-separated erythrocytes showed that the activity of the exchanger decreased as the mean cellular hemoglobin concentration increased in normal but not in sickle erythrocytes. Inhibition of protein kinase C (PKC) activity by calphostin C and chelerythrine increased the activity of the exchanger in normal but not in sickle erythrocytes. Inhibition of serine/threonine phosphatases did not affect the activity of the exchanger in either normal or sickle erythrocytes. Altogether, these data indicate that the Na/Mg exchanger is abnormally regulated in sickle erythrocytes. Therefore, Mg2+ depletion in sickle erythrocytes might be mediated by an up-regulated Na/Mg exchanger, possibly by dephosphorylation of the transporter or a closely associated regulator.

Anemia, Sickle Cell↗

PubMed2004

SOD2-deficiency anemia: protein oxidation and altered protein expression reveal targets of damage, stress response, and antioxidant responsiveness.

SOD2 is an antioxidant protein that protects cells against mitochondrial superoxide. Hematopoietic stem cells (HSCs) lacking SOD2 are capable of rescuing lethally irradiated hosts, but reconstituted animals display a persistent hemolytic anemia characterized by increased oxidative damage to red cells, with morphologic similarity to human "sideroblastic" anemia. We report further characterization of this novel SOD2-deficiency anemia. Electron micrographs of SOD2-deficient reticulocytes reveal striking mitochondrial proliferation and mitochondrial membrane thickening. Peripheral blood smears show abundant iron-stainable granules in mature red cells (siderocytes). Fluorescence-activated cell sorting (FACS) analysis of cells labeled with oxidation-sensitive dyes demonstrates enhanced production of superoxide and hydrogen peroxide by SOD2-deficient cells. Oxidative damage to proteins is increased in SOD2-deficient cells, with much of the damage affecting membrane/insoluble proteins. Red cell proteome analysis demonstrates that several proteins involved in folding/chaperone function, redox regulation, adenosine triphosphate (ATP) synthesis, and red cell metabolism show altered expression in SOD2-deficient cells. This data, combined with information on how protein expression levels change upon antioxidant therapy, will aid in identification of proteins that are sensitive to oxidative damage in this model, and by extension, may have a role in the regulation of red cell lifespan in other hemolytic disorders.

Adenosine Triphosphate↗

PubMed2004

Na+/Mg2+ exchange is functionally coupled to the insulin receptor.

Regulation of cellular Mg(2+) levels by insulin has been shown in various tissues. However, the mechanisms for hormonal regulation of cellular Mg(2+) have not been well described. We studied the effect of insulin on Na(+)/Mg(2+) exchange in normal human cells, measuring Na(+)/Mg(2+) exchange activity as net total Mg(2+) efflux driven by an inward Na(+) gradient in Mg(2+)-loaded red blood cells (RBCs). Na(+)/Mg(2+) exchange was increased significantly by the addition of 2.4 nmol/L of insulin to the flux medium (from 0.60 +/- 0.06 mmol/L cell x h to 0.75 +/- 0.08 mmol/L cell x h [P = 0.0098, n = 44]). A dose-response curve for the effects of insulin on the exchanger activity gave an estimated EC(50) for insulin of 0.95 +/- 0.31 nmol/L and a V(max) of 0.86 +/- 0.12 mmol/L cell x h (n = 7). Kinetics of the Na(+)/Mg(2+) exchange were characterized by measuring its activity as a function of Mg(2+) and Na(+) concentrations. The K(0.5) for cellular Mg(2+) was not affected by incubation with insulin. However, the K(0.5) for extracellular Na(+) decreased from 69.9 +/- 6.3 to 40.3 +/- 8.4 mol/L (n = 5, P = 0.03) in the presence of insulin. We also studied the effect of wortmannin (WT), a PI 3-kinase inhibitor, on activity of the exchanger. WT significantly blocked the insulin-stimulated Na(+)/Mg(2+) activity (n = 6, P = 0.048), with an IC(50) of 0.5 nmol/L. LY294002, another PI 3-kinase inhibitor, likewise blocked the insulin-stimulated activity of the exchanger. Therefore, insulin regulates cellular Mg(2+) metabolism in part via an increase in the affinity for Na(+) of the Na(+)/Mg(2+) exchange and PI 3-kinase activation, suggesting another role for the PI 3-kinase pathway in insulin-mediated cellular events.

Antiporters↗

PubMed2004

Anxiogenic-like activity of 3,4-methylenedioxy-methamphetamine ("Ecstasy") in the social interaction test is accompanied by an increase of c-fos expression in mice amygdala.

3,4-Methylenedioxymethamphetamine (MDMA) is a synthetic amphetamine popularly known as "Ecstasy." Animal studies examining acute effects of MDMA on anxiety are unclear because although an anxiolytic-like action of MDMA in different animal models of anxiety has been described, there is also substantial evidence supporting an anxiogenic-like effect of this drug. To date, several studies have examined c-fos expression following MDMA administration in rats. However, there is no information about the MDMA-induced c-fos expression in mice previously tested in an animal model of anxiety. In this study, male mice were injected with MDMA (1, 8 and 15 mg/kg ip) and assessed for changes on anxiety and for the expression of the immediate early gene c-fos in the amygdala (central, basolateral and basomedial). Anxiety was evaluated by the "social interaction test." Ten behavioral categories were recorded: body care, digging, nonsocial exploration, exploration from a distance, social investigation, threat, attack, avoidance/flee, defense/submission and immobility. As compared with the control group, mice treated with MDMA (all doses) showed a decrease in mean duration and total time spent in social investigation behaviors, whereas avoidance/flee behaviors were significantly increased after treatment with this compound (8 and 15 mg/kg). Likewise, a significant increase in c-fos expression was found in the basolateral (all doses) and central (15 mg/kg) amygdala after MDMA administration. Overall, these findings indicate that MDMA exhibits an anxiogenic-like profile in the social interaction test in mice, and that central and basolateral amygdala might be involved in these anxiogenic-like effects of the drug.

Amygdala↗

PubMed2004

In vivo reduction of erythrocyte oxidant stress in a murine model of beta-thalassemia.

BACKGROUND AND OBJECTIVES: Oxidant damage is an important contributor to the premature destruction of erythrocytes and anemia in thalassemias. To assess the extent of oxidant damage of circulating erythrocytes and the effects of antioxidant therapy on erythrocyte characteristics and anemia, we used a mouse model of human beta-thalassemia intermedia (b1/b2 deletion). DESIGN AND METHODS: Several parameters indicative of oxidant damage were measured at baseline and following administration of the semi-synthetic flavonoid antioxidant, 7-monohydroxyethylrutoside (monoHER), to beta-thalassemic mice at a dose of either 500 mg/kg i.p. once a day (n=6) or 250 mg/kg i.p. twice a day (n=6) for 21 days. RESULTS: Significant erythrocyte oxidant damage at baseline was indicated by: (i) dehydration, reduced cell K content, and up-regulated K-Cl co-transport; (ii) marked membrane externalization of phosphatidylserine; (iii) reduced plasma and membrane content of vitamin E; and (iv) increased membrane bound IgG. MonoHER treatment increased erythrocyte K content, and markedly improved all cellular indicators of oxidant stress and of lipid membrane peroxidation. While anemia did not improve, monoHER therapy reduced reticulocyte counts, improved survival of a fraction of red cells, and reduced ineffective erythropoiesis with decreased total bilirubin, lactate dehydrogenase and plasma iron. INTERPRETATION AND CONCLUSIONS: Antioxidant therapy reverses several indicators of oxidant damage in vivo. These promising antioxidant effects of monoHER should be investigated further.

Animals↗

PubMed2003

Expression of D4 dopamine receptors in striatonigral and striatopallidal neurons in the rat striatum.

Recent studies have reported the regional distribution of D(4) dopamine receptors in the rat striatum at the cellular and subcellular levels. However, the precise identity of the striatal neurons that express these receptors remains unknown. We have studied the expression of D(4) receptors in the striatal interneurons as well as in the output regions of the striatum using immunohistochemistry. Furthermore, we have evaluated the contribution of the striatum to D(4) receptor immunoreactivity in these areas by means of ibotenic acid lesion of the striatum. D(4) receptors were observed in the substantia nigra pars reticulata (SNr), the entopeduncular nucleus (EP) and the globus pallidus (GP), and they were found, using electron microscopy, to be located presynaptically. D(4) immunoreactivity in the striatal output nuclei was observed to dramatically decrease following lesion of the striatum with ibotenic acid. Striatal interneurons were not found to express D(4) receptors. These results demonstrate that D(4) receptors are located almost exclusively in striatal projection neurons, in both striatonigral and striatopallidal neurons.

Animals↗

PubMed2003

D5 (not D1) dopamine receptors potentiate burst-firing in neurons of the subthalamic nucleus by modulating an L-type calcium conductance.

Dopamine is a crucial factor in basal ganglia functioning. In current models of basal ganglia, dopamine is postulated to act on striatal neurons. However, it may also act on the subthalamic nucleus (STN), a key nucleus in the basal ganglia circuit. The data presented here were obtained in brain slices using whole-cell patch clamp. They reveal that D5 dopamine receptors strengthen electrical activity in the subset of subthalamic neurons endowed with burst-firing capacity, resulting in longer discharges of spontaneous or evoked bursts. To distinguish between D1 and D5 subtypes, the action of agonists in the D1/D5 receptor family was first investigated on rat subthalamic neurons. Single-cell reverse transcription-PCR profiling showed that burst-competent neurons only expressed D5 receptors. Accordingly, receptors localized in postsynaptic membranes within the STN were labeled by a D5-specific antibody. Second, agonists in the D1/D5 family were tested in mouse brain slices. It was found that these agonists were active in D1 receptor knock-out mice in a similar way to wild-type mice or rats. This proved that D5 rather than D1 receptors were involved. Pharmacological tools (dihydropyridines, omega-conotoxins, and calciseptine) were used to identify the target of D5 receptors as an L-type channel. This was reached via G-protein and protein kinase A. The action of dopamine on D5 receptors therefore shapes neuronal activity. It contributes to normal information processing in basal ganglia outside striatum. This finding may be useful in drug therapy for various disorders involving changes in STN activity, such as Parkinson's disease and related disorders.

Animals↗

PubMed2002

Propranolol blocks the tachycardia induced by galanin (1-15) but not by galanin (1-29).

The efferent pathways involved in the tachycardia induced by intracisternal injections of the N-terminal galanin fragment (1-15) (GAL (1-15)) and galanin (GAL (1-29)) has been evaluated in rats pretreated with the cholinergic antagonist atropine or the beta-antagonist propranolol. The pretreatment with propranolol significantly blocked the tachycardic and vasopressor effect produced by intracisternal injection of GAL (1-15) (p<0.05), but the pretreatment with atropine did not modify these cardiovascular effects. However, the cardiovascular response elicited by GAL (1-29) is modified by the pretreatment with atropine (p<0.05) but not by propranolol. These findings demonstrate that the central cardiovascular action of GAL (1-15), but not GAL (1-29), is mediated by beta-receptor stimulation and this suggests the existence of a different pathway involved in the cardiovascular response produced by the N-terminal galanin fragment as compared with the parent molecule GAL (1-29).

Animals↗

PubMed2002

Headpiece domain of dematin is required for the stability of the erythrocyte membrane.

Dematin is an actin-binding and bundling protein of the erythrocyte membrane skeleton. Dematin is localized to the spectrin-actin junctions, and its actin-bundling activity is regulated by phosphorylation of cAMP-dependent protein kinase. The carboxyl terminus of dematin is homologous to the "headpiece" domain of villin, an actin-bundling protein of the microvillus cytoskeleton. The headpiece domain contains an actin-binding site, a cAMP-kinase phosphorylation site, plays an essential role in dematin self-assembly, and bundles F-actin in vitro. By using homologous recombination in mouse embryonic stem cells, the headpiece domain of dematin was deleted to evaluate its function in vivo. Dematin headpiece null mice were viable and born at the expected Mendelian ratio. Hematological evaluation revealed evidence of compensated anemia and spherocytosis in the dematin headpiece null mice. The headpiece null erythrocytes were osmotically fragile, and ektacytometry/micropore filtration measurements demonstrated reduced deformability and filterability. In vitro membrane stability measurements indicated significantly greater membrane fragmentation of the dematin headpiece null erythrocytes. Finally, biochemical characterization, including the vesicle/cytoskeleton dissociation, spectrin self-association, and chemical crosslinking measurements, revealed a weakened membrane skeleton evidenced by reduced association of spectrin and actin to the plasma membrane. Together, these results provide evidence for the physiological significance of dematin and demonstrate a role for the headpiece domain in the maintenance of structural integrity and mechanical properties of erythrocytes in vivo.

Actins↗

PubMed2002

Modulation of Gardos channel activity by cytokines in sickle erythrocytes.

It has recently been shown that the Gardos channel activity of mouse erythrocytes can be modified by endothelins, suggesting a functional linkage between endothelin receptors and the Gardos channel. Using (86)Rubidium ((86)Rb) influx, effects were estimated of proinflammatory molecules such as platelet activator factor (PAF), endothelin-1 (ET-1), interleukin-10 (IL-10), and regulated on activation normal T cells expressed and secreted (RANTES) on the Gardos channel activity in human normal and sickle red cells. It was found that PAF (EC(50): 15 +/- 7 nM), RANTES (EC(50), 9 +/- 6 ng/mL [1.2 +/- 0.8 nM]), IL-10 (EC(50), 11 +/- 8 ng/mL [204 +/- 148 nM]), and ET-1 (EC(50), 123 +/- 34 nM) induce a significant increase in Gardos channel activity-between 28% and 84%-over the control. In addition, these agents modify the Gardos channel affinity for internal Ca(++) (K(0.5)) by 2- to 6-fold. Biochemical evidence is provided for the presence of ET receptor subtype B in sickle and normal red cells. Furthermore, it was found that ET-1, PAF, RANTES, and IL-10 induce a significant increase in red cell density (P <.05). These data suggest that activation of the Gardos channel is functionally coupled to receptor motifs such as C-X-C (PAF), C-C (RANTES), and ET receptor subtype B. Thus, cell volume regulation or erythrocyte hydration states might be altered by activation of the Gardos channel by cytokines in vivo. The role of these mediators in promoting sickle cell dehydration in vivo is under investigation.

Anemia, Sickle Cell↗

PubMed2002

Molecular dissection of dopamine receptor signaling.

The use of genetically engineered mice has provided substantial new insights into the functional organization of the striatum. Increasing evidence suggests that specific genes expressed within the striatum contribute to its functional activity. We studied the dopamine (DA) D1 receptor gene and one of its downstream targets, the transcription factor c-Fos. We have evaluated the functional interaction between the D1 and D2 DA receptor subtypes at the cellular and behavioral levels. Our results show that haloperidol, a DA D2-class receptor antagonist, activates c-Fos predominantly in enkephalin-positive striatal neurons, which project to the globus pallidus and are thought to mediate motor inhibition. Deletion of the DA D1 receptor increased the responsiveness of enkephalin neurons to haloperidol, in that haloperidol-induced increases in c-Fos and catalepsy were enhanced in D1 receptor knockout mice. These results suggest a functionally opposing role of the D1 receptor against the D2 DA-class receptors in the striatum.

Animals↗