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At least 595 records · Page 33Linked to original sources
PubMed1995

Hypotensive effect of 13-hydroxylinoleic acid in the rat: mediation via the release of a CGRP-like mediator from capsaicin-sensitive nerves.

1. The effect of 13-hydroxylinoleic acid (13-HODE) on changes in blood pressure in the rat was measured. 2. 13-HODE (0.1 - 100 micrograms kg-1) had no direct effect on blood pressure in the rat and had no effect on histamine (0.1 - 1000 micrograms kg-1)-induced changes in blood pressure. In contrast, it was found that 13-HODE itself induced a decrease in diastolic arterial blood pressure when it was injected intravenously after either a single dose of histamine (10, 100 or 1000 micrograms kg-1) or after a dose-response curve of histamine (0.1 - 1000 micrograms kg-1). 3. This hypotensive effect of 13-HODE was not observed after administration of the endothelium-dependent vasodilator, acetylcholine (0.1 - 10 micrograms kg-1), the endothelium-independent vasodilator, sodium nitroprusside (0.1 - 100 micrograms kg-1) or the inflammatory mediator, leukotriene B4 (0.1 - 300 micrograms kg-1). However, prior injection of bradykinin (0.1 - 100 micrograms kg-1) allowed a dose-dependent hypotensive effect of 13-HODE to be revealed. 4. The hypotensive effect of 13-HODE after histamine and bradykinin could be inhibited by neonatal capsaicin treatment of the rats (50 mg kg-1, s.c. on day 1 and 2 after birth). 5. Ruthenium red (120 micrograms kg-1 min-1), an inhibitor of excitatory effects on sensory nerves, and the CGRP antagonist, CGRP8-37 (1-3 micrograms kg-1 min-1) also inhibited the hypotensive effect of 13-HODE. 6. It is concluded that the hypotensive effect of 13-HODE in the rat after histamine and bradykinin is due to the release of a CGRP-like substance from sensory nerves. These results highlight the possibility that endogenous 13-HODE could be involved in the neurogenic regulation of blood pressure.

Acetylcholine↗
PubMed2006

Saliva can mediate HIV-1-specific antibody-dependent cell-mediated cytotoxicity.

HIV is not usually transmitted by saliva from HIV-1-infected individuals. Antiviral substances in saliva responsible for this may include HIV-1-specific antibody-dependent cell-mediated cytotoxicity (ADCC). We evaluated saliva ADCC titers of 62 HIV-1-infected women from the Women's Interagency HIV Study (WIHS) and 55 uninfected individuals. HIV-1-infected women were less likely to have ADCC activity in saliva than in serum or cervical lavage fluid (CVL). 24% of HIV-1-positive women and a similar percentage of uninfected women had HIV-1-specific saliva ADCC activity. A significant amount of saliva ADCC activity in infected women was HIV-gp120-specific. These studies demonstrate that HIV-specific ADCC activity can be present in saliva. This activity may contribute to host defence against initial infection with HIV.

Antibody Specificity↗
PubMed1994

Differentiation of the peripherally mediated from the centrally mediated influences of adenosine in the rat during systemic hypoxia.

In two groups of Saffan-anaesthetized, spontaneously breathing rats we have attempted to identify the peripheral influences of adenosine in mediating the responses evoked by hypoxia by using an adenosine receptor antagonist, 8-sulphophenyltheophylline (8-SPT, 20 mg kg-1 i.v., Group 1) and adenosine deaminase (ADA, 500 units in 0.04 ml infused into the tail artery for 10 min, Group 2); neither of these drugs crosses the blood-brain barrier. Recordings were made of respiration, heart rate, arterial pressure, blood flow and vascular conductance in the femoral artery, with ankle ligated (FBF and FVC, respectively) and in the carotid artery with all branches except the internal carotid ligated (CBF and CVC, respectively, Group 1 only) in order to indicate responses in skeletal muscle and cerebral vasculature. Hypoxia (breathing 8 or 10% O2 for 10 min) evoked an increase followed by a secondary decrease in respiration, tachycardia followed by secondary bradycardia, a fall in arterial pressure, an increase in FVC and CVC and an increase, followed by a decrease, in CBF. Neither 8-SPT nor ADA had any significant effect on the secondary decrease in respiration. The secondary bradycardia was unaffected by 8-SPT, but abolished by ADA. Both drugs reduced the fall in arterial pressure and the increase in FVC; 8-SPT had no significant effect on the increase in CVC, but CBF no longer fell with arterial pressure. We propose that adenosine contributes to the hypoxia-induced fall in arterial pressure by causing vasodilatation in skeletal muscle and possibly by causing bradycardia by a direct action on the heart; other evidence suggests that adenosine contributes to the secondary decrease in respiration by acting on central respiratory neurones. The possibility that the fall in arterial pressure and the secondary falls in CBF, respiration and heart rate, can become interdependent in a positive feedback manner is discussed.

2-Chloroadenosine↗
PubMed2002

Negative and positive regulatory epitopes in the C-terminal domains of the human B1 and B2 bradykinin receptor subtypes determine receptor coupling efficacy to G(q/11)-mediated [correction of G(9/11)-mediated] phospholipase Cbeta activity.

The human B1 bradykinin (BK) receptor (B1R) is more efficacious than the human B2 BK receptor (B2R) in both ligand-independent and agonist-dependent coupling to G(q/11)-mediated phospholipase Cbeta activity. In fact, B1R is constitutively active, whereas B2R exhibits little if any constitutive activity. To evaluate the role of the C-terminal domain in receptor G(q/11) coupling, we constructed chimeric and C-terminally truncated receptors. The slopes of the increase in basal and agonist-dependent cellular phosphoinositide hydrolysis as a function of receptor density in transiently transfected human embryonic kidney 293 cells provided parameters of receptor coupling. Exchanging the C-terminal domains between the two receptors revealed that these domains are largely responsible for the difference in coupling. B1R truncation showed that this receptor does not directly depend on the C-terminal domain for efficient coupling, although coupling is dramatically augmented by residues in the membrane-distal portion of the domain downstream from Tyr(327). On the other hand, coupling of B2R is absolutely dependent on a membrane-proximal epitope in the C-terminal domain upstream from Lys(315). This epitope is adjacent to a basic residue, Arg(311), which exerts an inhibitory effect on coupling. Arg(311) is not conserved in B1R, and complementary mutations in B2R and B1R showed that this residue, together with previously identified serines and threonines, acts to attenuate the coupling efficacy of B2R. Therefore, the C-terminal domain participates intimately in the efficacy of B1R and B2R G(q/11) coupling by contributing both positive and negative regulatory epitopes.

Amino Acid Sequence↗
PubMed2003

Carboxylesterase-mediated sensitization of human tumor cells to CPT-11 cannot override ABCG2-mediated drug resistance.

The recently introduced camptothecin-derived chemotherapeutic agents have demonstrated remarkable promise in cancer therapy and as such have been approved for use in humans for the treatment of ovarian, lung, and colon cancer. CPT-11 is a prodrug that is activated by esterases to yield the potent topoisomerase I inhibitor, SN-38. Considerable success has been achieved in the treatment of both naïve and drug-resistant colon cancer with CPT-11. However, mechanisms of resistance to this agent have not been explored in detail. The role of the ATP-dependent drug transporter ABCG2 in CPT-11 cytotoxicity is unclear because some ABCG2 mutants confer camptothecin resistance, whereas others do not. Because CPT-11 is activated by carboxylesterases (CEs), we assessed the relative contribution of each protein in mediating CPT-11 toxicity by both drug accumulation and cell growth-inhibition assays. Our results indicate that the expression of ABCG2 protects cells from CPT-11 toxicity, even in the presence of high levels of a rabbit liver carboxylesterase (rCE), which can efficiently activate the drug. However, this can be partially overcome by the ABCG2 inhibitor reserpine. These studies indicate that overexpression of ABCG2 in vivo would probably overcome any increased drug activation that might be achieved by gene delivery or antibody-directed enzyme prodrug therapy methods using rCE.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed1977

Mechanisms of resistant of herpesviruses: comparison of the effectiveness of different cell types in mediating antibody-dependent cell-mediated cytotoxicity.

Enriched populations of polymorphonuclear leukocytes (PMN) and macrophages obtained from the mammary gland and of granulocytes (PBG) and lymphocytes (PBL) prepared from peripheral blood of the same animal were compared for their ability to mediate antibody-dependent cell cytotoxocity against antibody-sensitized infectious bovine rhinotracheitis virus-infected target cells (IBR-GBK) and antibody-sensitized chicken erythrocyte targest (CRBC). The order of effectiveness was PMN leads to macrophages leads to PBG leads to PBL. The reason why PBG (86% PMN) were less than 50% as active as mammary PMN (99% PMN) was explored and discussed. The findings that PMN were more effective on a cell-to-cell basis, required less antiserum to sensitize for cytotoxicity, and destroyed IBR-GBK cells faster and more completely than other cell types could mean that PMN may be the cell type most importnat in causing early recovery from herpesvirus infections.

Animals↗
PubMed1986

Presence of a macrophage-mediated suppressor cell mechanism during cell-mediated immune response in experimental visceral leishmaniasis.

In susceptible BALB/c mice, systemic intracellular infection with Leishmania donovani provokes generation of adherent spleen cells which can suppress both mitogen- and specific-antigen-stimulated T-cell responses. To characterize the responsible suppressor cell, we irradiated (2,000 R) adherent spleen cells from L. donovani-infected mice or treated them with anti-Thy-1.2 antibody plus complement. Neither anti-T-cell treatment diminished the capacity to inhibit lymphocyte proliferative activity. In addition, as judged by morphologic and functional criteria, 80 to 90% of the adherent cells appeared to be macrophages. Four observations suggested an immunopathogenic role for these suppressor macrophages. (i) Their appearance and disappearance paralleled the establishment and resolution of L. donovani visceral infection in vivo. (ii) Suppressive effects included inhibition of production of the macrophage-activating lymphokine gamma interferon (IFN-gamma). (iii) On transfer into immune mice, suppressor macrophages impaired naturally acquired resistance to L. donovani. (iv) Inhibition of macrophage prostaglandin metabolism by indomethacin reduced suppressor activity in vitro and resulted in a 50% decrease in parasite visceral replication in vivo. In addition, prophylactic cyclophosphamide treatment inhibited the development of suppressor macrophages, and under these conditions visceral infection was rapidly controlled. These results suggested that disseminated L. donovani infection provokes a macrophage-mediated suppressor mechanism which appears to contribute to establishment of visceral leishmaniasis in a susceptible host.

Animals↗
PubMed1994

Analysis of Bacillus subtilis hut operon expression indicates that histidine-dependent induction is mediated primarily by transcriptional antitermination and that amino acid repression is mediated by two mechanisms: regulation of transcription initiation and inhibition of histidine transport.

Expression of the Bacillus subtilis hut operon is induced by histidine and subject to regulation by carbon catabolite repression and amino acid repression. A set of hut-lacZ transcriptional fusions was constructed and used to identify the cis-acting sites required for histidine induction and amino acid repression. Histidine induction was found to be primarily mediated by transcriptional antitermination at a palindromic sequence located immediately downstream of the first structural gene in the hut operon, hutP. High levels of histidine induction were observed only in hut-lacZ fusions which contained this palindromic sequence. The hutC1 mutation, which results in constitutive expression of the hut operon, was sequenced and found to contain a GC to TA transversion located within the stem-loop structure. Transcription of hut DNA in vitro revealed that the palindromic structure functions as a transcriptional terminator with wild-type hut DNA but not with hutC1 DNA. Two sites were found to be involved in amino acid repression of hut expression: (i) an operator, hutOA, which lies downstream of the hut promoter, and (ii) the hut terminator. The rate of [14C]histidine uptake in amino acid-grown cells was sixfold lower than that seen in cells grown without amino acids. Thus, inhibition of histidine transport in amino acid-grown cells indirectly regulates hut expression by interfering with histidine induction at the hut terminator.

Bacillus subtilis↗
PubMed1999

Induction of antiviral antibodies by DNA immunization requires neither perforin-mediated nor CD8(+)-T-cell-mediated lysis of antigen-expressing cells.

DNA immunization induces antibodies to the encoded protein, which indicates that the protein must gain access to the extracellular milieu, allowing it to interact with naïve B lymphocytes. It has been suggested that antigen release may be effected by cytotoxic-T-lymphocyte-mediated lysis of transfected antigen-expressing cells; this might be particularly important for the induction of responses to a noncytopathic, cytosolic protein. Here we show that the induction of antibody responses to one such DNA-encoded protein required neither perforin nor CD8(+) T cells. In addition, there was no skewing of the immunoglobulin G isotypes in the absence of perforin.

Animals↗
PubMed2001

Socs-1 inhibits TEL-JAK2-mediated transformation of hematopoietic cells through inhibition of JAK2 kinase activity and induction of proteasome-mediated degradation.

TEL-JAK2 fusion proteins, which are a result of t(9;12)(p24;p13) translocations associated with human leukemia, activate Stat5 in vitro and in vivo and cause a myelo- and lymphoproliferative disease in a murine bone marrow transplant model. We report that Socs-1, a member of the SOCS family of endogenous inhibitors of JAKs and STATs, inhibits transformation of Ba/F3 cells by TEL-JAK2 but has no effect on Ba/F3 cells transformed by BCR-ABL, TEL-ABL, or TEL-platelet-derived growth factor receptor beta. TEL-JAK2, in addition to activating Stat5, associates with Shc and Grb2 and induces activation of Erk2, and expression of Socs-1 inhibits engagement of each of these signaling molecules. TEL-JAK2 kinase activity is inhibited by Socs-1, as assessed by in vitro kinase assays. In addition, Socs-1 induces proteasomal degradation of TEL-JAK2. Mutational analysis indicates that the SOCS box of Socs-1 is required for proteasomal degradation and for abrogation of growth of TEL-JAK2-transformed cells. Furthermore, murine bone marrow transplant assays demonstrate that expression of Socs-1 prolongs latency of TEL-JAK2-mediated disease in vivo. Collectively, these data indicate that Socs-1 inhibits TEL-JAK2 in vitro and in vivo through inhibition of kinase activity and induction of TEL-JAK2 protein degradation.

Animals↗
PubMed1992

A mediator derived from arginine mediates inhibitory junction potentials and relaxations in lower esophageal sphincter: an independent role for vasoactive intestinal peptide.

This study provides mechanical and electrophysiological evidence to show that a metabolite of arginine, not vasoactive intestinal peptide (VIP), is the putative nonadrenergic noncholinergic (NANC) inhibitory mediator in canine and opossum lower esophageal sphincters (LES). Relaxations of spontaneous active tension by electrical field stimulation (FS) at parameters that induced tetrodotoxin (TTX)-sensitive responses were abolished by L-N omega-arginine methyl ester (L-NAME) at 10(-4) M and restored by L-arginine (10(-3) M) but not D-arginine (10(-3) M). TTX-insensitive relaxations to 5-ms pulses were unaffected by L-NAME, L- or D-arginine. VIP (10(-6) M) caused maximum relaxations of basal tension in both the opossum and canine LES. However these relaxations, unlike those from FS were unaffected by L-NAME. Methylene blue (5 x 10(-5)M) increased basal tension of the LES in each species, and did not inhibit the relaxation to FS or VIP, but often increased the amplitudes of these responses due to the increase in basal tension. In parallel experiments NANC inhibition of body circular muscle from opossum esophagus was abolished by methylene blue. Electrophysiological studies using micro-electrodes revealed that NANC inhibition was associated with inhibitory junction potentials in the canine LES. These were inhibited by L-NAME and restored by L-arginine but not D-arginine. In contrast, 10(-6) M VIP in canine LES did not induce any change in membrane potential during a 20-min superfusion. Sodium nitroprusside also hyperpolarized sphincteric muscle and its effects were not affected by L-NAME.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Cyclic ADP ribose-mediated Ca2+ signaling in mediating endothelial nitric oxide production in bovine coronary arteries.

The present study tested the hypothesis that cyclic ADP ribose (cADPR) serves as a novel second messenger to mediate intracellular Ca2+ mobilization in coronary arterial endothelial cells (CAECs) and thereby contributes to endothelium-dependent vasodilation. In isolated and perfused small bovine coronary arteries, bradykinin (BK)-induced concentration-dependent vasodilation was significantly attenuated by 8-bromo-cADPR (a cell-permeable cADPR antagonist), ryanodine (an antagonist of ryanodine receptors), or nicotinamide (an ADP-ribosyl cyclase inhibitor). By in situ simultaneously fluorescent monitoring, Ca2+ transient and nitric oxide (NO) levels in the intact coronary arterial endothelium preparation, 8-bromo-cADPR (30 microM), ryanodine (50 microM), and nicotinamide (6 mM) substantially attenuated BK (1 microM)-induced increase in intracellular [Ca2+] by 78%, 80%, and 74%, respectively, whereas these compounds significantly blocked BK-induced NO increase by about 80%, and inositol 1,4,5-trisphosphate receptor blockade with 2-aminethoxydiphenyl borate (50 microM) only blunted BK-induced Ca2+-NO signaling by about 30%. With the use of cADPR-cycling assay, it was found that inhibition of ADP-ribosyl cyclase by nicotinamide substantially blocked BK-induced intracellular cADPR production. Furthermore, HPLC analysis showed that the conversion rate of beta-nicotinamide guanine dinucleotide into cyclic GDP ribose dramatically increased by stimulation with BK, which was blockable by nicotinamide. However, U-73122, a phospholipase C inhibitor, had no effect on this BK-induced increase in ADP-ribosyl cyclase activity for cADPR production. In conclusion, these results suggest that cADPR importantly contributes to BK- and A-23187-induced NO production and vasodilator response in coronary arteries through its Ca2+ signaling mechanism in CAECs.

Animals↗
PubMed2004

Gialpha3 protein-coupled dopamine D3 receptor-mediated inhibition of renal NHE3 activity in SHR proximal tubular cells is a PLC-PKC-mediated event.

This study evaluated the transduction pathway associated with type 3 Na(+)/H(+) exchanger (NHE3) activity-induced inhibition during dopamine D(3) receptor activation in immortalized renal proximal tubular epithelial cells from the spontaneously hypertensive rat. The dopamine D(3) receptor agonist 7-OH-DPAT decreased NHE3 activity, which was prevented by the D(2)-like receptor antagonist S-sulpiride, pertussis toxin (PTX; overnight treatment), and the PKC inhibitor chelerythrine, but not by cholera toxin (overnight treatment), the MAPK inhibitor PD-098059, or the p38 inhibitor SB-203580. The PKA inhibitor H-89 abolished the inhibitory effects of forskolin on NHE3 activity, but not that of 7-OH-DPAT. The phospholipase C (PLC) inhibitor U-73122 prevented the inhibitory effects of 7-OH-DPAT, whereas PDBu and 7-OH-DPAT increased PLC activity and reduced NHE3 activity; downregulation of PKC abolished the inhibitory effects of both PDBu and 7-OH-DPAT on NHE activity. The inhibition of NHE3 activity by GTPgammaS and the prevention of the effect of 7-OH-DPAT by PTX suggest an involvement of a G(i/o) protein coupled to the dopamine D(3) receptor. Indeed, the 7-OH-DPAT-induced decrease in NHE3 activity was abolished in cells treated overnight with the anti-G(i)alpha3 antibody, but not in cells treated with antibodies against G(q/11), G(s)alpha, G(beta), and G(i)alpha1,2 proteins. The calcium ionophore A-23187 and the Ca(2+)-ATPase inhibitor thapsigargin increased intracellular Ca(2+) but did not affect NHE3 activity. However, the inhibitory effects of PDBu and 7-OH-DPAT on NHE3 activity were completely abolished by A-23287 and thapsigargin. It is concluded that inhibition of NHE3 activity by dopamine D(3) receptors coupled to G(i)alpha3 proteins is a PLC-PKC-mediated event, modulated by intracellular Ca(2+).

Animals↗
PubMed1988

Clinical studies on cell-mediated immunity in patients with urinary bladder carcinoma. Depression of cell-mediated immunity by adherent cells.

Lymphocyte blastogenesis by stimulation with phytohemagglutinin was compared in 10 control subjects and 20 patients with bladder cancer. Blastogenesis was measured by the incorporation of 3H-thymidine into lymphocytes using microplate assay. As a result, blastogenesis was significantly decreased in high stage patients compared to control subjects and low stage patients. When the nylon wool adherent cells were removed, lymphocyte blastogenesis was increased in high stage patients, while it was decreased in control subjects and low stage patients. This study provides evidence that in most bladder cancer patients with in vitro immunodepression, adherent suppressor cells are detectable, and that these cells may mediate the noted immunodepression.

Aged↗
PubMed1974

Cell-mediated immune response of ragweed-sensitive patients to ragweed antigen E. In vitro lymphocyte transformation and elaboration of lymphocyte mediators.

The in vivo and in vitro responses to ragweed antigen E were evaluated in 28 untreated atopic patients with ragweed hayfever. The methods employed included direct skin testing, measurement of total serum IgE, measurement of specific IgE anti-ragweed antibodies, leukocyte histamine release, lymphocyte transformation, and release of lymphocyte mediators (migration inhibitory factor and mitogenic factor). The patients could be divided into sensitive and insensitive groups on the basis of their in vitro reactivity to antigen E. 20 patients in the sensitive group had statistically higher levels of total serum IgE, higher levels of specific IgE anti-ragweed antibodies, and greater leukocyte sensitivity as measured by antigen-induced histamine release than did eight patients in the insensitive group. Lymphocytes from sensitive patients produced greater amounts of migration inhibitory factor and mitogenic factor when challenged by antigen E than did lymphocytes from insensitive patients. A possible role for the lymphocyte in this allergic disease is discussed. The results of this study indicate that the immune response to ragweed antigen is complex and involves components of both immediate and delayed hypersensitivity.

Adolescent↗
PubMed1978

Impaired cell-mediated immunity in Hodgkin's disease mediated by suppressor lymphocytes and monocytes.

In Hodgkin's disease a possible mechanism for impaired cellular immunity is cell-mediated suppression, defined as the inhibitory interaction between suppressor cells and effector lymphocytes. To test for the presence of suppressor cells in peripheral blood, we have modified the standard, one-way mixed lymphocyte culture by adding mitomycin C-treated mononuclear cells from the responder. Suppression, expressed as a percent of the base-line mixed lymphocyte culture in which these extra cells are not present, results in a reduction of thymidine incorporated in the modified culture (i.e., 100% suppression = no net thymidine incorporation; 0% suppression = identical thymidine incorporation in both the modified and baseline culture). Suppression was found to be significantly increased in patients with both active Hodgkin's disease (78+/-4.6%) and remission Hodgkin's disease (58+/-9.3%) compared to normal individuals (21+/-6.9%) (mean+/-SE). The degree and frequency of suppression were not influenced by disease stage or prior therapy. Cell purification techniques revealed (in 10 patients studied) the suppressor cell to be a monocyte in 6, and a thymus-derived lymphocyte in 4. Possible genetic restriction of the suppressor cell interaction was indicated by a failure of suppressor cells to alter the response of lymphocytes from unrelated individuals, but suppression was obtained with lymphocytes from a histocompatible sibling. Although mononuclear cells from normal individuals suppress less frequently than cells from patients with Hodgkin's disease, normals may demonstrate suppression comparable to that observed in Hodgkin's patients. This finding suggests that suppression is a normal immunoregulatory mechanism which is altered in Hodgkin's disease.

Adolescent↗
PubMed2003

P2Y6 receptor mediates colonic NaCl secretion via differential activation of cAMP-mediated transport.

Extracellular nucleotides are important regulators of epithelial ion transport. Here we investigated nucleotide-mediated effects on colonic NaCl secretion and the signal transduction mechanisms involved. Basolateral UDP induced a sustained activation of Cl(-) secretion, which was completely inhibited by 293B, a specific inhibitor of cAMP-stimulated basolateral KCNQ1/KCNE3 K(+) channels. We therefore speculated that a basolateral P2Y(6) receptor could increase cAMP. Indeed UDP elevated cAMP in isolated crypts. We identified an epithelial P2Y(6) receptor using crypt [Ca(2+)](i) measurements, RT-PCR, and immunohistochemistry. To investigate whether the rat P2Y(6)elevates cAMP, we coexpressed the P2Y(1) or P2Y(6) receptor together with the cAMP-regulated cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel in Xenopus oocytes. A two-electrode voltage clamp was used to monitor nucleotide-induced Cl(-) currents. In oocytes expressing the P2Y(1) receptor, ATP transiently activated the endogenous Ca(2+)-activated Cl(-) current, but not CFTR. In contrast, in oocytes expressing the P2Y(6)receptor, UDP transiently activated the Ca(2+)-activated Cl(-) current and subsequently CFTR. CFTR Cl(-) currents were identified by their halide conductance sequence. In summary we find a basolateral P2Y(6) receptor in colonic epithelial cells stimulating sustained NaCl secretion by way of a synergistic increase of [Ca(2+)](i) and cAMP. In support of these data P2Y(6) receptor stimulation differentially activates CFTR in Xenopus oocytes.

1-Methyl-3-isobutylxanthine↗
PubMed2001

Complement-mediated cell death induced by rituximab in B-cell lymphoproliferative disorders is mediated in vitro by a caspase-independent mechanism involving the generation of reactive oxygen species.

Mechanisms involving the in vitro effect of rituximab in cells from 55 patients with B-cell lymphoproliferative disorders were investigated. No cytotoxic effect was observed when cells were incubated with rituximab alone, but in the presence of human AB serum rituximab induced complement-dependent cell death (R-CDC). A cytotoxic effect was observed in cells from 9 of 33 patients with B-cell chronic lymphocytic leukemia, 16 of 16 patients with mantle-cell lymphoma, 4 of 4 patients with follicular lymphoma, and 2 of 2 patients with hairy-cell leukemia. R-CDC was observed in cells from patients expressing more than 50 x 10(3) CD20 molecules per cell, and directly correlated with the number of CD20 molecules per cell. Preincubation with anti-CD59 increased the cytotoxic effect of rituximab and sensitized cells from nonsensitive cases. Neither cleavage of poly-ADP ribose polymerase (PARP) nor activation of caspase-3 was observed in R-CDC. In addition, no cells with a hypodiploid DNA content were detected and R-CDC was not prevented by a broad-spectrum caspase inhibitor, suggesting a caspase-independent mechanism. Incubation with rituximab in the presence of AB serum induced a rapid and intense production of reactive oxygen species (ROS). R-CDC was blocked by the incubation of cells with N-acetyl-L-cysteine (NAC) or Tiron, 2 ROS scavengers, indicating that the cytotoxic effect was due to the generation of superoxide (O) radicals. In conclusion, the results of the present study suggest that CD20, CD59, and complement have a role in the in vitro cytotoxic effect of rituximab, which is mediated by a caspase-independent process that involves ROS generation.

Adult↗