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S C Robson

Publications and source records attributed to S C Robson.

At least 19 recordsLinked to original sources
PubMed2006

Effect of low oxygen concentrations on trophoblast-like cell line invasion.

The applicability of trophoblast-like cell lines to the study of trophoblast function has been widely debated. The present study investigated the effect of oxygen on the invasiveness, apoptosis, proliferation and secreted proteases of four different trophoblast cell lines; HTR-8/SVneo, SGHPL-4, JEG3 and JAR. All experiments were performed at 20% and 3% oxygen for 24, 48 and 72h. Immunostaining for integrins alpha1, alpha6 and beta3, cytokeratin 7 and HLA-G was used to determine the phenotype of the different cell lines. Invasion was assessed using the Matrigel invasion assay. Immunostaining for M30 and Ki67 determined levels of apoptosis and proliferation, respectively. Gelatin and casein/plasminogen zymography were performed on conditioned media to determine levels of secreted matrix metalloproteinase (MMP) 2 and MMP9 and urokinase plasminogen activator (uPA), respectively. None of the cell lines immunostained for all markers normally expressed by extravillous trophoblast cells. Invasiveness of HTR-8/SVneo and JEG3 cells cultured in 3% oxygen was increased after 24h but was inhibited by 72h in culture. Invasion of SGHPL-4 cells was inhibited after culture in 3% oxygen for 24h. Invasion by JAR cells was not affected by changes in oxygen concentration. The different cell lines also displayed different responses to culture period in 3% oxygen with respect to apoptosis, proliferation and secreted proteases. Care should be taken before results obtained using cell lines as a model for EVT are extrapolated to extravillous trophoblast cell behaviour in vivo.

Animals↗
PubMed2006

Nucleoside triphosphate diphosphohydrolase-2 (NTPDase2/CD39L1) is the dominant ectonucleotidase expressed by rat astrocytes.

Inflammatory and degenerative pathophysiological processes within the CNS are important causes of human disease. Astrocytes appear to modulate these reactions and are a major source of inflammatory mediators, e.g. extracellular adenine nucleotides, in nervous tissues. Actions following extracellular nucleotides binding to type 2 purinergic receptors are regulated by ectonucleotidases, including members of the CD39/ecto-nucleoside triphosphate diphosphohydrolase family. The ectonucleotidases of astrocytes expressed by rat brain rapidly convert extracellular ATP to ADP, ultimately to AMP. RT-PCR, immunocytochemistry as well as Western blotting analysis demonstrated expression of multiple ecto-nucleoside triphosphate diphosphohydrolase family members at both the mRNA and protein level. By quantitative real-time PCR, we identified Entpd2 (CD39L1) as the dominant Entpd gene expressed by rat hippocampal, cortical and cerebellar astrocytes. These data in combination with the elevated ecto-ATPase activity observed in these brain regions, suggest that NTPDase2, an ecto-enzyme that preferentially hydrolyzes ATP, is the major ecto-nucleoside triphosphate diphosphohydrolase expressed by rat astrocytes. NTPDase2 may modulate inflammatory reactions within the CNS and could represent a useful therapeutic target in human disease.

Adenosine Diphosphate↗
PubMed2006

Early embryonic demise: no evidence of abnormal spiral artery transformation or trophoblast invasion.

Invasion by extravillous trophoblast of uterine decidua and myometrium and the associated spiral artery 'transformation' are essential for the development of normal pregnancy. Small pilot studies of placental bed and basal plate tissues from miscarriages have suggested that impaired interstitial and endovascular trophoblast invasion may play a role in the pathogenesis of miscarriage. The hypothesis that early miscarriage is associated with reduced extravillous trophoblast invasion and spiral artery transformation was tested in a large series of placental bed biopsies containing decidua and myometrium and at least one spiral artery from early, karyotyped embryonic miscarriages (<or=12 weeks' gestation; n = 50) dated from the last menstrual period and ultrasound scan dated normal pregnancies (n = 78). Frozen sections were immunostained to demonstrate trophoblast (cytokeratin), myometrium and spiral artery medial smooth muscle (desmin), and endothelium (von Willebrand factor). Trophoblast invasion and individual features of spiral artery transformation were assessed histologically in spiral arteries of miscarriages (n = 176) and controls (n = 246) and analysed statistically using a logistic regression model. Trophoblast invasion of uterine tissues and spiral artery transformation did not differ between euploid and aneuploid early miscarriage and also did not differ significantly from normal pregnancy. These findings suggest that failed trophoblast invasion and spiral artery transformation do not have a pivotal role in the pathogenesis of early miscarriage.

Abortion, Spontaneous↗
PubMed2006

Late sporadic miscarriage is associated with abnormalities in spiral artery transformation and trophoblast invasion.

Trophoblast invasion of uterine decidua and myometrium, and spiral artery transformation, are essential for the development of normal pregnancy; this process is impaired in pre-eclampsia, fetal growth restriction, and pre-term labour. The hypothesis that late miscarriage is associated with reduced trophoblast invasion and spiral artery transformation was tested in a large series of placental bed biopsies containing decidua and myometrium from late, karyotyped, embryonic miscarriage (>or=13 weeks' gestation; n = 26; n = 96 spiral arteries) and gestationally matched ultrasound-dated normal pregnancies (n = 74; n = 236 spiral arteries). Cryostat sections were immunostained using an avidin-biotin peroxidase technique for cytokeratin, desmin, and von Willebrand factor to detect trophoblast, myometrium, and vascular smooth muscle and endothelium, respectively. Trophoblast invasion and individual features of spiral artery transformation were assessed and analysed using a logistic regression model. Compared with normal pregnancy, myometrial spiral arteries in late miscarriage showed reduced endovascular (4% vs. 31%, p = 0.001) and intramural trophoblast (76% vs. 88%, p = 0.05), and less extensive fibrinoid change (4% vs. 18%, p = 0.01). In contrast, endovascular trophoblast in decidual spiral arteries was increased (40% vs. 66%, p = 0.04). These findings suggest that, in common with pre-eclampsia, late sporadic miscarriage may be associated with reduced trophoblast invasion and inadequate transformation of myometrial spiral arteries.

Abortion, Spontaneous↗
PubMed2005

Does antenatal pelvic dilation predict renal scarring?

Moderate antenatal renal pelvic dilation (5-15 mm) may suggest vesicoureteric reflux, but it is not known to predict renal scarring. Dimercaptosuccinic acid scans on such children aged over 4 years showed a scarring rate (0/133 boys, 1/56 girls) similar to our local population. Investigation and treatment of moderate dilation may not be required.

Adolescent↗
PubMed2004

Noise exposure induces up-regulation of ecto-nucleoside triphosphate diphosphohydrolases 1 and 2 in rat cochlea.

Extracellular ATP acting via P2 receptors in the inner ear initiates a variety of signaling pathways that may be involved in noise-induced cochlear injury. Nucleoside triphosphate diphosphohydrolase (NTPDase)1/CD39 and NTPDase2/CD39L1 are key elements for regulation of extracellular nucleotide concentrations and P2 receptor signaling in the cochlea. This study characterized the effect of noise exposure on regulation of NTPDase1 and NTPDase2 expression in the cochlea using a combination of real-time RT-PCR, immunohistochemistry and functional studies. Adult Wistar rats were exposed to broad band noise at 90 dB and 110 dB sound pressure level (SPL) for 72 h. Exposure to 90 dB SPL induced a small and temporary change of auditory thresholds (temporary threshold shift), while exposure to 110 dB SPL induced a robust and permanent change of auditory thresholds (permanent threshold shift). NTPDase1 and NTPDase2 mRNA transcripts were upregulated in the cochlea exposed to 110 dB SPL, while mild noise (90 dB SPL) altered only NTPDase1 mRNA expression levels. Changes in NTPDases expression did not correlate with levels of circulating corticosterone, implying that the up-regulation of NTPDases expression was not stress-related. Semi-quantitative immunohistochemistry in the cochlea exposed to 110 dB SPL localized the increased NTPDase1 and NTPDase2 immunostaining in the stria vascularis and up-regulation of NTPDase2 in the intraganglionic spiral bundle. In contrast, NTPDase1 was down-regulated in the cell bodies of the spiral ganglion neurones. Distribution of NTPDases was not altered in the cochlea exposed to 90 dB SPL. Functional studies revealed increased ectonucleotidase activities in the cochlea after exposure to 110 dB SPL, consistent with up-regulation of NTPDases. The changes in NTPDases expression may reflect adaptive response of cochlear tissues to limit ATP signaling during noise exposure.

Acoustic Stimulation↗
PubMed2004

Interleukin-8 is involved in cervical dilatation but not in prelabour cervical ripening.

Our aim was to determine the amount and source of interleukin (IL)-8 and to study IL-8 receptor expression in the human cervix during pregnancy and after labour. Cervical biopsies were obtained from six non-pregnant women, eight women undergoing pregnancy termination, 17 women undergoing elective caesarean section and 11 women after vaginal delivery. IL-8 levels were compared in women with and without a ripe cervix, as determined by cervical Bishop score and cervicovaginal fetal fibronectin levels. Levels of IL-8 and IL-1beta, a regulator of IL-8 expression, were determined by enzyme-linked immunosorbent assay (ELISA). IL-8, IL-1beta and IL-8 receptor proteins were localized by immunohistochemistry. Compared with late pregnancy, IL-8 levels increased after labour and vaginal delivery (P < 0.01) but there was no correlation with cervical ripening. IL-8 was localized to stromal cells, macrophages and granulocytes. There were no significant differences in IL-1beta levels between groups. IL-8 receptors were expressed primarily on granulocytes and macrophages after vaginal delivery. We conclude that IL-8 is involved in cervical dilatation but not in cervical ripening.

Cervical Ripening↗
PubMed2002

Protective effects of recombinant human antithrombin III in pig-to-primate renal xenotransplantation.

Delayed rejection of pig kidney xenografts by primates is associated with vascular injury that may be accompanied by a form of consumptive coagulopathy in recipients. Using a life-supporting pig-to-baboon renal xenotransplantation model, we have tested the hypothesis that treatment with recombinant human antithrombin III would prevent or at least delay the onset of rejection and coagulopathy. Non-immunosuppressed baboons were transplanted with transgenic pig kidneys expressing the human complement regulators CD55 and CD59. Recipients were treated with an intravenous infusion of antithrombin III eight hourly (250 units per kg body weight), with or without low molecular weight heparin. Antithrombin-treated recipients had preservation of normal renal function for 4-5 days, which was twice as long as untreated animals, and developed neither thrombocytopenia nor significant coagulopathy during this period. Thus, recombinant antithrombin III may be a useful therapeutic agent to ameliorate both early graft damage and the development of systemic coagulation disorders in pig-to-human xenotransplantation.

Animals↗
PubMed2002

Transforming growth factor beta expression in human placenta and placental bed during early pregnancy.

Normal human pregnancy depends on physiological transformation of spiral arteries. Pre-eclampsia and fetal growth restriction are associated with impaired trophoblast invasion and spiral artery transformation. Recent data obtained from studies on placenta suggest that temporal changes in expression of TGF-beta3 play a key role in trophoblast invasion and that over-expression of TGF-beta3 in pre-eclampsia is responsible for inadequate trophoblast invasion. There are, however, no studies of specific TGF-betas in the placental bed throughout pregnancy although this is where the invasive trophoblast and spiral arteries are located. In this study we have used immunohistochemistry, Western blot analysis, ELISA and RT-PCR to examine the expression of TGF-beta1, TGF-beta2 and TGF-beta3 in placental bed biopsies and placentas from 7--19 weeks' gestation. The results show that TGF-beta1, 2 and 3 are expressed in the placenta throughout this time but the striking temporal changes in TGF-beta3 expression previously reported were not observed. Extravillous trophoblast within the placental bed expressed TGF-beta2 but not TGF-beta1 or TGF-beta3 while extracellular TGF-beta1 and cytoplasmic TGF-beta2 were detected in decidua. These data suggest that TGF-beta1 and TGF-beta2 but not TGF-beta3 may play a role in trophoblast invasion.

Adult↗
PubMed2001

Pig kidney transplantation in baboons: anti-Gal(alpha)1-3Gal IgM alone is associated with acute humoral xenograft rejection and disseminated intravascular coagulation.

BACKGROUND: Kidneys harvested from miniature swine or pigs transgenic for human decay-accelerating factor (hDAF) were transplanted into baboons receiving an anti-CD154 monoclonal antibody (mAb) and either a whole body irradiation (WBI)- or cyclophosphamide (CPP)-based immunosuppressive regimen. METHODS: Group 1 baboons (n=3) underwent induction therapy with WBI and thymic irradiation, pretransplantation antithymocyte globulin, and immunoadsorption of anti-Gal(alpha)1-3Gal (Gal) antibody (Ab). After transplantation of a miniature swine kidney, maintenance therapy comprised cobra venom factor, mycophenolate mofetil, and an anti-CD154 mAb (for 14-28 days). In group 2 (n=2), WBI was replaced by CPP in the induction protocol. Group 3 (n=3) animals received the group 2 regimen, but underwent transplantation with hDAF pig kidneys. RESULTS: Group 1 and 2 animals developed features of disseminated intravascular coagulation (DIC), with reductions of fibrinogen and platelets and increases of prothrombin time, partial thromboplastin time, and fibrin split products. Graft survival was for 6-13 days. Histology showed mild acute humoral xenograft rejection (AHXR) of the kidneys, but severe rejection of the ureters. Group 3 animals developed features of DIC in two of three cases during the fourth week, with AHXR in the third case. Graft survival was for 28 (n=1) or 29 (n=2) days. Histology of day 15 biopsy specimens showed minimal focal mononuclear cellular infiltrates, with predominantly CD3+ cells. By days 28 and 29, kidneys showed mild-to-moderate features of AHXR. In all groups, the humoral response was manifest by reappearance of anti-Gal IgM below baseline level, with no or low return of anti-Gal IgG. All excised kidneys showed IgM deposition, but no complement and no or minimal IgG deposition. No baboon showed a rebound of anti-Gal Ab immediately after excision of the graft, and anti-Gal Ab increased over pretransplantation levels only when anti-CD154 mAb was discontinued. CONCLUSIONS: DIC was observed with WBI- or CPP-based therapy, and after miniature swine or hDAF kidney transplantation. AHXR+/-DIC was observed in all recipients even in the absence of complement and no or low levels of anti-Gal IgG, but was significantly delayed in the hDAF recipients. These results confirm our earlier observation that CD154 blockade prevents T cell-dependent sensitization in baboons to pig antigens, but that baseline natural anti-Gal Ab production is not inhibited. We suggest that IgM deposition, even in the absence of IgG and complement, leads to endothelial cell activation with the development of DIC, even when there are only minimal histologic changes of AHXR.

Acute Disease↗
PubMed2001

A training model for external cephalic version.

The Royal College of Obstetricians and Gynaecologists (RCOG) has recommended that all women with an uncomplicated pregnancy and a breech presentation at term should be offered external cephalic version (ECV) but only 43% of consultants in England practice ECV. There is a need to train clinicians to perform ECV safely and effectively. A model abdomen is described which fulfils these requirements. The model is adjustable to represent a continuum from an easy procedure to an impossible procedure. The model was used to train and assess two midwives in the technique of ECV. This model is a valuable method of both training a clinician to perform ECV and also providing an objective method of assessing their technique. It has the potential to maximise the success rate of the newly trained clinician prior to performing ECV on women.

Breech Presentation↗
PubMed2001

Modulation of platelet aggregation in baboons: implications for mixed chimerism in xenotransplantation. I. The roles of individual components of a transplantation conditioning regimen and of pig peripheral blood progenitor cells.

BACKGROUND: The induction of tolerance to pig antigens in primates may facilitate the development of successful clinical xenotransplantation protocols. The infusion of mobilized porcine peripheral blood leukocytes (PBPCs, comprised of approximately 2% peripheral blood progenitor cells) into splenectomized preconditioned baboons, intended to induce mixed hematopoietic cell chimerism, however, results in a severe thrombotic microangiopathy (TM) that includes pronounced thrombocytopenia. Because the mechanisms responsible for this phenomenon are unclear, we have explored the effects of individual components of the conditioning regimen, of therapeutic adjuncts, and of PBPCs on platelet aggregation. METHODS: Groups of splenectomized baboons (n = at least 2 in each group) were treated with single components of the conditioning regimen--whole body irradiation (WBI), antithymocyte globulin (ATG), extracorporeal immunoadsorption (EI), mycophenolate mofetil (MMF), anti-CD40L monoclonal antibody (mAb), cobra venom factor (CVF), pig hematopoietic growth factors (interleukin-3 (pIL3) and stem cell factor (pSCF))--or with potential adjuncts, prostacyclin (PGI2), heparin, methylprednisolone, and eptifibatide (a GPIIb/IIIa antagonist). Blood samples were collected and platelet-rich plasma (PRP) was prepared. Using light transmission aggregometry, the extent of aggregation induced by platelet agonists (thrombin, adenosine diphosphate (ADP), collagen, ristocetin, and arachidonic acid) was determined in vitro. PRP was also prepared from untreated baboons, PBPCs were added, and platelet aggregation was measured in the absence of exogenous platelet agonists. RESULTS: WBI, ATG, MMF, anti-CD40L mAb, CVF, pIL3, pSCF, and PGI2 had no effect on purified baboon platelet aggregation profiles in vitro. Eptifibatide markedly inhibited platelet aggregation induced by all standard agonists. EI or heparin inhibited thrombin-induced platelet aggregation, and methylprednisolone inhibited ADP-induced aggregation to some extent. In vitro addition of PBPCs to PRP stimulated platelet aggregation in the absence of any agonists. Prior treatment of baboons with eptifibatide, however, inhibited this effect by 70% to 80%. CONCLUSIONS: Aggregation of baboon platelets and TM is directly induced by PBPCs, but not by individual components of the conditioning regimen. GPIIb/IIIa antagonists, such as eptifibatide, interfere directly with xenogeneic PBPC-platelet interactions and may further ameliorate TM in the pig-to-primate model.

Animals↗
PubMed2001

Modulation of platelet aggregation in baboons: implications for mixed chimerism in xenotransplantation. II. The effects of cyclophosphamide on pig peripheral blood progenitor cell-induced aggregation.

BACKGROUND: The induction of tolerance to pig antigens in primates may facilitate the development of successful clinical xenotransplantation protocols. The infusion of mobilized porcine peripheral blood leukocytes (PBPCs, comprised of approximately 2% peripheral blood progenitor cells) into splenectomized preconditioned (whole body irradiation (WBI)-based) baboons, intended to induce mixed hematopoietic cell chimerism, however, results in a severe thrombotic microangiopathy (TM) that includes pronounced thrombocytopenia. Previous studies have indicated that the infused PBPCs initiate platelet aggregation, but that the various individual components of the conditioning regimen are not associated with the development of aggregation. We have now investigated the effects of cyclophosphamide (CPP) as an alternative to WBI on platelet aggregation. METHODS: Splenectomized baboons (n=3) were treated with CPP. Blood samples were collected and platelet-rich plasma (PRP) was prepared. Using light transmission aggregometry, the extent of aggregation induced by platelet agonists (thrombin, adenosine diphosphate (ADP), collagen, ristocetin, and arachidonic acid) was determined in vitro. PRP was also prepared from untreated baboons and from baboons receiving CPP, PBPCs were added, and platelet aggregation was measured in the absence of exogenous platelet agonists. RESULTS: CPP markedly inhibited platelet aggregation induced by all standard agonists. In vitro addition of PBPCs to PRP stimulated platelet aggregation in the absence of any agonists. Prior treatment of baboons with CPP, however, inhibited this effect by 55% to 65%. TM was not evident in baboons receiving a conditioning regimen that included CPP instead of WBI. CONCLUSIONS: Aggregation of baboon platelets and TM is directly induced by PBPCs. CPP has direct anti-aggregatory properties and may provide an alternative strategy to WBI in this pig-to-primate model intended to induce mixed hematopoietic cell chimerism.

Animals↗
PubMed2001

Mechanisms of thrombotic microangiopathy following xenogeneic hematopoietic progenitor cell transplantation.

INTRODUCTION: Attempts to induce tolerance though mixed hematopoietic chimerism in the discordant pig-to-baboon xenotransplantation model are sometimes complicated by a potentially fatal thrombotic microangiopathy in the recipient baboons. This state develops immediately after the infusion of porcine mobilized peripheral blood leukocytes, containing progenitor cells (PBPC). In our study, we examined the interaction of infused porcine PBPC with recipient platelets in vivo in baboons and investigated the underlying mechanisms using an in vitro model. METHODS: Two naïve baboons and six baboons preconditioned with irradiation and immunosuppression that received porcine PBPC were evaluated in vivo. The interaction of porcine and baboon PBPC with baboon platelets was investigated by an in vitro platelet aggregation assay. Fresh and cryopreserved PBPC were evaluated as well as PBPC obtained from growth-factor mobilized and unmobilized pigs. Furthermore, cellular subsets of PBPC were assessed for potential to induce platelet aggregation. Immunohistochemical staining was performed on platelet-leukocyte aggregates and potential inhibition of aggregation with anti-P-selectin and anti-CD154 mAbs, or eptifibatide (a GPIIb/IIIa receptor antagonist), was tested. RESULTS: All baboons that received porcine PBPC rapidly developed marked thrombocytopenia (<20,000/microl), elevated serum lactate dehydrogenase (>1,500U/liter), schistocytosis, and platelet aggregates on blood smear. Three baboons died (two untreated and one preconditioned), and substantive platelet aggregates containing porcine leukocytes were observed in the microvasculature of lungs and kidneys. In vitro, porcine, but not baboon, PBPC induced aggregation of baboon platelets in a dose-dependent manner. Immunohistological examination of these aggregates confirmed the incorporation of porcine leukocytes. Cryopreserved PBPC caused less aggregation than fresh PBPC, and growth-factor-mobilized PBPC induced less aggregation than unmobilized PBPC. Aggregation was fully abrogated by the addition of eptifibatide, and modulated by anti-P-selectin and anti-CD154 monoclonal antibodies that recognize adhesion receptors on activated platelets. Purified fractions (granulocytes, CD2+, and CD- cells) of porcine PBPC did not initiate aggregation, whereas addition of exogenous porcine PBPC membranes (erythrocytes, dead cells, and/or platelets) to the purified fractions exacerbated the aggregation response. CONCLUSIONS: These data indicate that porcine PBPC mediate aggregation of baboon platelets. This process likely contributes to the thrombotic microangiopathy observed after PBPC transplantation in the pig-to-baboon model. Eptifibatide can fully abrogate platelet aggregation induced by porcine PBPC in vitro. Purification of the progenitor cells from porcine PBPC and/or treatment of baboons with eptifibatide may be beneficial.

Animals↗
PubMed2001

Effects of nitric oxide (NO) and soluble nucleoside triphosphate diphosphohydrolase (NTPDase) on inhibition of platelet deposition in vitro.

Vascular thrombosis is regulated via the release of several constituents from the vascular endothelium, including nucleoside triphosphate diphosphohydrolases (NTPDases or ectonucleotidases), nitric oxide (NO), and eicosanoids. Currently, it is unknown how these constituents interact in the inhibition of platelet aggregation and adhesion. To investigate the combined effects of NO and NTPDase on platelet deposition sequestration, an in vitro study was performed to compare inhibition of platelet deposition to a biomaterial by NO in the absence or presence of soluble NTPDase. Results of the platelet inhibition studies with NO and NTPDase conclusively show that the inhibitory effects of NTPDase and NO are additive. The platelet inhibitory potency in the presence of NO was enhanced by NTPDase in a dose-dependent manner, for a given NO exposure. This augmentation is independent of aspirin; the ability of NTPDase or NO alone to inhibit platelet deposition is also independent of aspirin. Clearly, NO and NTPDase independently contribute to platelet inhibition via different mechanisms. The inaction of NO on the activity of NTPDase confirmed that NO or reaction products in the presence of O(2) do not interact with NTPDase directly.

Acid Anhydride Hydrolases↗
PubMed2001

P2Y(6) nucleotide receptor mediates monocyte interleukin-8 production in response to UDP or lipopolysaccharide.

Extracellular nucleotides are autocrine and paracrine cellular mediators that signal through P2 nucleotide receptors. Monocytic cells express several P2Y receptors but the role of these G protein-coupled receptors in monocytes is not known. Here, we present evidence that P2Y(6) regulates chemokine production and release in monocytes. We find that UDP, a selective P2Y(6) agonist, stimulates interleukin (IL)-8 release in human THP-1 monocytic cells whereas other nucleotides are relatively inactive. P2 receptor antagonists or P2Y(6) antisense oligonucleotides inhibit IL-8 release induced by UDP. Furthermore, UDP specifically activated IL-8 production in astrocytoma 1321N1 cells transfected with human P2Y(6). Since lipopolysaccharide has been suggested to activate P2 receptors via nucleotide release, we tested whether IL-8 production stimulated by lipopolysaccharide might result from P2Y(6) activation. P2 antagonists or apyrase, an enzyme which hydrolyzes nucleotides including UDP, inhibit IL-8 production induced by lipopolysaccharide but not by other stimuli. Furthermore, IL-8 gene expression activated by lipopolysaccharide is enhanced by P2Y(6) overexpression and inhibited by P2Y(6) antisense oligonucleotides. Thus, UDP activates IL-8 production via P2Y(6) in monocytic cells. Furthermore, lipopolysaccharide mediates IL-8 production at least in part by autocrine P2Y(6) activation. These findings indicate a novel role for P2Y(6) in innate immune defenses.

Cell Line↗
PubMed2001

Carbon monoxide generated by heme oxygenase-1 suppresses the rejection of mouse-to-rat cardiac transplants.

Mouse-to-rat cardiac transplants survive long term after transient complement depletion by cobra venom factor and T cell immunosuppression by cyclosporin A. Expression of heme oxygenase-1 (HO-1) by the graft vasculature is critical to achieve graft survival. In the present study, we asked whether this protective effect was attributable to the generation of one of the catabolic products of HO-1, carbon monoxide (CO). Our present data suggests that this is the case. Under the same immunosuppressive regimen that allows mouse-to-rat cardiac transplants to survive long term (i.e., cobra venom factor plus cyclosporin A), inhibition of HO-1 activity by tin protoporphyrin, caused graft rejection in 3--7 days. Rejection was associated with widespread platelet sequestration, thrombosis of coronary arterioles, myocardial infarction, and apoptosis of endothelial cells as well as cardiac myocytes. Under inhibition of HO-1 activity by tin protoporphyrin, exogenous CO suppressed graft rejection and restored long-term graft survival. This effect of CO was associated with inhibition of platelet aggregation, thrombosis, myocardial infarction, and apoptosis. We also found that expression of HO-1 by endothelial cells in vitro inhibits platelet aggregation and protects endothelial cells from apoptosis. Both these actions of HO-1 are mediated through the generation of CO. These data suggests that HO-1 suppresses the rejection of mouse-to-rat cardiac transplants through a mechanism that involves the generation of CO. Presumably CO suppresses graft rejection by inhibiting platelet aggregation that facilitates vascular thrombosis and myocardial infarction. Additional mechanisms by which CO overcomes graft rejection may involve its ability to suppress endothelial cell apoptosis.

Acute Disease↗