Activation of adenosine receptor on gingival fibroblasts

CD73 (ecto-5'-nucleotidase) on human gingival fibroblasts plays a role in the regulation of intracellular cAMP levels through the generation of adenosine, which subsequently activates adenosine receptors. In this study, we examined the involvement of ecto-adenosine deaminase, which can be anchored to CD26 on human gingival fibroblasts, in metabolizing adenosine generated by CD73, and thus attenuating adenosine receptor activation. Ecto-adenosine deaminase expression on fibroblasts could be increased by pre-treatment with a lysate of Jurkat cells, a cell line rich in cytoplasmic adenosine deaminase. Interestingly, the cAMP response to adenosine generated from 5'-AMP via CD73 and the ability of 5'-AMP to induce hyaluronan synthase 1 mRNA were significantly decreased by the pre-treatment of fibroblasts with Jurkat cell lysate. This inhibitory effect was reversed by the specific adenosine deaminase inhibitor. These results suggest that ecto-adenosine deaminase metabolizes CD73-generated adenosine and regulates adenosine receptor activation.

Involvement of CD73 (ecto-5'-nucleotidase) in adenosine generation by human gingival fibroblasts

Adenosine has various biological effects on human gingival fibroblasts (HGF) and epithelial cells closely associated with inflammation, such as cytokine production and cell adhesion. However, the mechanism of adenosine formation in periodontal tissues is not yet defined. In this study, we examined the involvement of CD73 (ecto-5'-nucleotidase) in adenosine generation by HGF. CD73 was detected on in vitro-maintained HGF by immunocytochemistry and flow cytometric analysis. Adenosine production was observed following the addition of 5'-AMP, the substrate of CD73-associated ecto-5'-nucleotidase. Moreover, the addition of 5'-AMP to cultured HGF resulted in the elevation of cyclic adenosine monophosphate (cAMP). The 5'-AMP-induced increase in intracellular cAMP level was inhibited markedly by xanthine amine congener, an adenosine receptor antagonist, and partially by alpha,beta-methylene adenosine 5'-diphosphate, an ecto-5'-nucleotidase inhibitor. These results suggest that CD73 on HGF is a critical enzyme responsible for the generation of adenosine, an immunomodulator that activates adenosine receptors.

Activation of adenosine-receptor-enhanced iNOS mRNA expression by gingival epithelial cells

A series of reports has revealed that adenosine has a plethora of biological actions toward a large variety of cells. In this study, we investigated the influence of adenosine receptor activation on iNOS mRNA expression in human gingival epithelial cells (HGEC) and SV-40-transformed HGEC. HGEC expressed adenosine receptor subtypes A1, A2a, and A2b, but not A3 mRNA. Ligation of adenosine receptors by a receptor agonist, 2-chloroadenosine (2CADO), enhanced iNOS mRNA expression by both HGEC and transformed HGEC. In addition, the adenosine receptor agonist enhanced the production of NO(2)(-)/NO(3)(-), NO-derived stable end-products. An enhanced expression of iNOS mRNA and NO(2)(-)/NO(3)(-) was also observed when SV40-transformed HGEC were stimulated with CPA or CGS21680, A1- or A2a-selective adenosine receptor agonists, respectively. These results provide new evidence for the possible involvement of adenosine in the regulation of inflammatory responses by HGEC in periodontal tissues.

Increased leukocyte activity as a predictor for flow-limiting coronary lesions in patients with angina pectoris

Myocardial ischemia initiates an acute inflammatory response, in which polymorphonuclear leukocytes (PMNs) are major participants. We investigated whether increased PMN activity in the peripheral blood is a marker for high-grade coronary artery stenosis in patients with angina pectoris. PMN activity was examined in 45 patients by measuring the luminol-dependent chemiluminescence (CL) response of the peripheral blood upon addition of phorbol myristate acetate (PMA). The CL of patients with angiographic filling delay was 1.6-fold higher than in patients without delay (480+/-54 vs. 302+/-33 counts/PMN, P<0.01). The CL of patients with a filling delay of the left anterior descending artery (LAD) was 1.7-fold higher than in patients without an LAD filling delay (537+/-79 vs. 317+/-27 counts/PMN, P<0.01). With the CL cut-off at 400 counts/PMN, the sensitivity and specificity for detecting an angiographic filling delay of the LAD were 69 and 75%, respectively. These data indicate that PMN activity in the peripheral blood is increased with the presence of a flow-limiting coronary lesion showing an angiographic filling delay. Measuring PMN activity may be a useful approach to assess indications for and timing of angiography and/or adjunctive invasive therapies in patients with angina pectoris.

Platelet aggregability under shear is enhanced in patients with unstable angina pectoris who developed acute myocardial infarction

The study investigated whether patients hospitalized for unstable angina pectoris (UAP), who subsequently develop complete coronary thrombosis (acute transmural myocardial infarction (AMI)) despite medical treatment, exhibit platelet hyperaggregability in an assay system that does not employ agonist stimulation. The study comprised 89 patients with UAP (Braunwald type B). Unfractionated heparin and nitrate were administered to all patients via continuous intravenous drip together with aspirin taken orally. Citrated platelet-rich plasma (230-250x 10(3)/microl) was obtained on admission and again, in some patients, following the AMI. Platelet aggregability was measured in an optically modified cone-plate viscometer that enables the detection of platelet aggregation without agonist stimulation. A continuous shear rate of 1,200/s was employed. Of the 89 patients, 85 were finally stabilized, while 4 developed an AMI accompanied by persistent ST-segment elevation with increased levels of plasma creatine kinase within 3 h after starting the treatment. The extent of platelet aggregation on admission was significantly greater in these 4 patients compared with the 85 who were stabilized (87.8+/-6.8%, n=4 vs 26.8+/-9.1%, n=85; mean+/-SD). These data suggest that platelet hyperaggregability mediated mainly by fibrinogen binding to the activated glycoprotein IIb/IIIa complex occurs before a complete thrombotic occlusion and this evaluation may provide important information before the onset of myocardial infarction.

[Advanced breast cancer with multiple bone metastases successfully treated with combined chemoendocrine-therapy of CEF (cyclophosphamide, epirubicin, 5-fluorouracil) and 5'-DFUR (5'-deoxy-5-fluorouridine) + MPA (medroxyprogesterone acetate)--a case report]

We report the case of a 51-year-old female with stage IV advanced breast cancer accompanied by multiple bone metastases. A hard mass of about 3.0 cm in diameter was palpated just below the nipple. An excisional biopsy was performed and histological examination revealed infiltrated solid tubular adenocarcinoma. There were no estrogen or progesterone receptors in the tumor. Modified radical mastectomy was performed in October, 1998. Postoperative adjuvant therapy with 10 cycles of CEF therapy was undertaken for one year. Combined chemoendocrine therapy with 5'-DFUR and MPA was also conducted for 11 months. Bone scintigraphy showed that all bone metastatic lesions disappeared completely one year after the operation. Mild bone marrow suppression, alopecia and body weight gain were observed as side effects. It is suggested that this combination therapy may be useful for advanced breast cancer patients with multiple bone metastases.

Adenosine regulates the production of interleukin-6 by human gingival fibroblasts via cyclic AMP/protein kinase A pathway

Adenosine has been reported to alter a variety functions of the cells that participate in inflammatory responses. However, the effect(s) of adenosine on human gingival fibroblasts (HGF), one of the immunomodulator cells in inflamed periodontal lesions, remains to be established. In this study, we examined the influence of adenosine on the production of interleukin (IL)-6 by HGF. Ligation of adenosine receptors with adenosine or its related analogue, 2-chloroadenosine (2-CADO), increased IL-6 production by HGF without any other stimuli. In addition, adenosine and 2-CADO enhanced the cyclic AMP (cAMP) level in HGF as did prostaglandin E1 (PGE1) and forskolin. Interestingly, these cAMP-arising reagents and the permeable cAMP analogue, dibutyryl cAMP (dbtcAMP), also increased IL-6 production by HGF. These results suggest that cAMP is involved in adenosine-induced IL-6 production by HGF. Adenosine-induced IL-6 production was suppressed by protein kinase A (PKA) inhibitor, H89, indicating that cAMP/PKA pathway is involved in the induction. Moreover, the experiments using antagonists specific for adenosine receptor subtypes revealed that the adenosine-induced IL-6 production by HGF was, at least in part, mediated by the adenosine A2b receptor. These results provide new evidence for the possible effects of adenosine or its related analogue as an immunomodulator in inflammatory periodontal lesions.

Analogs of cyclic nucleotides in rat liver preservation

BACKGROUND

Cyclic nucleotides mediate intracellular signal transduction of several vasodilators. In addition to its vascular relaxant effects, cAMP is known to protect endothelial cells and to suppress Kupffer cell activation. On the other hand, cGMP potently ameliorates adhesion of leukocytes and platelets. We tested the effects of two analogs of cyclic nucleotides (8bromo cyclic adenosine monophosphate [8br-cAMP] and 8bromo cyclic guanosine monophosphate [8br-cGMP]) in rat liver preservation.

METHODS

In experiment 1, either analog (0.1-1.0 mM) alone was added to University of Wisconsin (UW) solution in a survival study. In experiment 2, donors and recipients were also treated with 8br-cAMP or 8br-cGMP, with the following three groups tested: group 1=control; group 2=administration of 8br-cAMP to donors, UW solution, and recipients; group 3=administration of 8br-cGMP to donors, UW solution, and recipients. Experiment 3 tested combined treatments: group 4=administration of 8br-cGMP to donors and UW solution, and cAMP to recipients; group 5=administration of 8br-cAMP to donors and UW solution, and 8br-cGMP to recipients. To elucidate the roles of each nucleotide, two further groups were tested: group 6=administration of 8br-cAMP to donors and UW solution; group 7=administration of 8br-cGMP to recipients. In experiment 4, rats in groups 1, 5, 6, and 7 were killed at several time points after reperfusion, and percent graft blood flow (%BF), number of accumulated neutrophils, plasma levels of tumor necrosis factor-alpha and interleukin-1, and serum alanine aminotransferase levels were examined.

RESULTS

In experiments 1 and 2, no significant effect was observed on animal survival. In experiment 3, a significant increase in animal survival was observed only in group 5 (100%, 7/7, P=0.0004 vs. group 1: 16.7%, 2/12). In group 5, no improvement of %BF was observed during the early phase of reperfusion (15 and 30 min) compared with that in group 1. On the other hand, the %BF of group 5 was significantly higher in the later phase (6 hr), consistent with the decrease in accumulation of neutrophils observed then. Production of tumor necrosis factor-alpha and serum alanine aminotransferase levels were also reduced with this treatment. Histologically, the bleeding and segmental necrosis, observed in group 1, were completely prevented in group 5.

CONCLUSIONS

We conclude that restoration of grafts with cAMP and administration of cGMP to recipients led to successful transplantation, and that the two analogs acted synergistically in opposing preservation and reperfusion injury without improvement of graft blood flow during the early phase of reperfusion. The effect was due to their regulation of neutrophil activation and sequestration.

Lymphoid/nonlymphoid compartmentalization of donor leukocyte chimerism in rat recipients of heart allografts, with or without adjunct bone marrow

BACKGROUND

The role of leukocyte migration and chimerism in organ allograft acceptance has been obscured by the lack of information about the late localization of the donor cells.

METHODS

Male Lewis rat-->female Brown Norway abdominal heart transplantation was performed under tacrolimus immunosuppression (days 0-13, 20, and 27) with or without donor bone marrow and (in bone marrow subgroups) a 1-week postoperative course of a possibly chimerism-enhancing drug. Using rat sex-determining region-Y-specific oligonucleotide primers, we determined the donor DNA concentration by polymerase chain reaction in serial venous blood samples for 100 days and in tissue specimens when animals were killed.

RESULTS

Chimerism was detected out to 56 days in 89% of the blood samples but in none of the samples at 100 days. However, donor DNA was detected when animals were killed in 95% of the native hearts, 80% of the skin biopsy specimens, and 23% of the spleens. The presence and quantity of early and late chimerism were strongly correlated the administration of adjunct bone marrow and with a reduction in the vasculopathy and inflammation index in the cardiac allografts. Marginally significant further increases in chimerism and/or reductions in chronic heart rejection beyond those achieved with adjunct bone marrow alone were associated with additional treatment with the growth factors Flt-3 ligand, granulocyte colony-stimulating factor, and a recombinant molecular variant of interleukin-6 (interleukin-6 mutein) but not with hepatocyte growth factor or lisofylline.

CONCLUSIONS

The previously suspected shift of early chimerism in the blood and lymphoid organs to dominance in host nonlymphoid tissues is consistent with the dual mechanisms of clonal exhaustion and immune indifference, governed by antigen migration and localization, that have been postulated elsewhere to account for organ allograft acceptance.

Effect in supralethally irradiated rats of granulocyte colony-stimulating factor and lisofylline on hematopoietic reconstitution by syngeneic bone marrow or whole organ passenger leukocytes

We have previously shown the existence of migratory hematopoietic stem cells in adult solid organs. This study demonstrates that granulocyte colony-stimulating factor (G-CSF) and lisofylline, a phosphatidic acid inhibitor that suppresses hematopoiesis-inhibiting cytokines, can enhance the engraftment of organ-based hematopoietic stem cells. When syngeneic heart grafts or liver nonparenchymal cells were transplanted into lethally irradiated (9.5 Gy) Lewis rats, complete hematopoietic reconstitution and animal survival were significantly improved by treating the recipient with G-CSF or, to a lesser extent, with lisofylline. Pretreatment of hepatic nonparenchymal cell donors with G-CSF, but not lisofylline, also resulted in striking improvement of recipient survival which was associated with an augmented subpopulation of donor stem cells. The results suggest that these drugs can be used to enhance the chimerism that we postulate to be the basis of organ allograft acceptance.

Angiotropic B-cell lymphoma presenting with progressive dementia: an autopsy case and review of the literature in Japan

We report an autopsy case of angiotropic lymphoma and review the literature in Japan. A 68-year-old female presented with transient right facial nerve palsy, right hemiplegia and progressive dementia. Laboratory studies showed raised erythrocyte sedimentation rate, C-reactive protein and serum lactate dehydrogenase. Computed tomography of the brain did not show any abnormal density areas but on T2-weighted magnetic resonance imaging high signal areas were recognized at the basal ganglia. She was diagnosed as having dementia caused by cerebrovascular insufficiency. She soon developed a febrile state and died of respiratory failure within three months of presentation. Postmortem examination showed widespread angiotropic B-cell lymphoma.

Polyamine metabolism in the rat liver after orthotopic liver transplantation

We examined the polyamine metabolism in liver transplanted after cold ischemia and effects of putrescine administration on liver injury, liver regeneration, and survival rate after orthotopic liver transplantation in the rat. Male Wistar rats were used as donors and recipients. Grafts were stored in Euro-Collins solution for 6 h at 4 degrees C. Orthotopic liver transplantation was performed by the three cuff technique. The activities of aspartate aminotransferase, alanine aminotransferase and lactate dehydrogenase elevated and peaked 4 h after liver transplantation. Hepatic ornithine decarboxylase and spermidine/spermine N1-acetyltransferase activities were also elevated and peaked 8 h after the operation. In agreement with the increases in ornithine decarboxylase and spermidine/spermine N1-acetyltransferase activities, the putrescine content increased and spermidine content decreased in the transplanted liver. Putrescine administrated intraperitoneally improved the survival rate, decreased serum transaminase level and increased the [3H]thymidine incorporation into the liver DNA. These findings suggest that both biosynthetic and biodegradative pathways are stimulated in liver transplantation, resulting in the increase in the formation of putrescine from ornithine and from spermidine, and that putrescine administration improve the survival rate by protecting the damaged graft after cold ischemia and reperfusion and by stimulating liver regeneration.

Increased spermidine or spermine level is essential for hepatocyte growth factor-induced DNA synthesis in cultured rat hepatocytes

BACKGROUND/AIMS

Hepatocyte growth factor is a potent mitogen for mature hepatocytes and seems to act as a trigger for liver regeneration. Hepatocyte growth factor was first purified from human and rabbit plasma and rat platelets. Additionally, putrescine, spermidine, and spermine are widely distributed in many different cells; intracellular concentrations of these polyamines are closely related to cell proliferation. The present study examined whether polyamine metabolism is involved in hepatocyte growth factor-induced DNA synthesis in primary cultured rat hepatocytes.

METHODS

Hepatocytes were isolated from rats by the collagenase perfusion method. Ornithine decarboxylase and S-adenosylmethionine decarboxylase activities were measured as the release of 14CO2 from L-[1-14C]ornithine and S-adenosyl-L-[carboxyl-14C]methionine, respectively.

RESULTS

alpha-Difluoromethylornithine inhibited hepatocyte growth factor-induced DNA synthesis by only 21%. On the other hand, methylglyoxal bis(guanylhydrazone) completely inhibited hepatocyte growth factor-induced DNA synthesis to nontreated control level. The inhibitory effect of methylglyoxal bis(guanylhydrazone) on hepatocyte growth factor-induced DNA synthesis was reversed by exogenously added spermidine or spermine.

CONCLUSIONS

Spermidine or spermine is essential for hepatocyte growth factor-induced DNA synthesis in primary cultured rat hepatocytes.

The effect of hepatic ischemia-reperfusion on polyamine metabolism in some organs of the rat

Hepatic ischemia was produced by clamping the portal venous and hepatic arterial blood supply to the left lateral and median lobes of the rat liver. Hepatic ornithine decarboxylase (ODC) and spermidine/spermine N1-acetyltransferase (SAT) activities in ischemic and nonischemic regions were increased and, respectively, peaked by 6 hr and 3 hr after 1 hr of hepatic ischemia. Hepatic putrescine contents in ischemic and nonischemic regions were increased and peaked by 6 hr. However, hepatic spermidine and spermine were not increased. an increase in ODC activity was also observed in the spleen and the kidney after 1 hr of hepatic ischemia. [3H]thymidine incorporation into DNA was observed in the liver and the spleen--however it was not observed in the kidney--after hepatic ischemia.

Increase in ornithine decarboxylase activity caused by hepatocyte growth factor in primary cultured adult rat hepatocytes

The effect of hepatocyte growth factor on ornithine decarboxylase activity was studied in primary cultured adult rat hepatocytes. Ornithine decarboxylase activity was increased 3 hr after the addition of hepatocyte growth factor and remained at a high level until 12 hr; thereafter it decreased, and it returned to the control level by 24 hr. Enzyme activity began to increase with 1 ng/ml hepatocyte growth factor and reached its maximum with 5 ng/ml hepatocyte growth factor. When insulin or epidermal growth factor was added with hepatocyte growth factor, enzyme activity was further stimulated. The level of ornithine decarboxylase messenger RNA did not increase with addition of hepatocyte growth factor. The half-time of ornithine decarboxylase activity was prolonged about twofold by hepatocyte growth factor treatment. These results suggest that hepatocyte growth factor treatment of cells enhanced ornithine decarboxylase activity posttranslationally.