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Biomedical subjects

A H Esa

Publications and source records attributed to A H Esa.

17 recordsLinked to original sources
PubMed1996

Nordihydroguaiaretic acid blocks IL-2-independent lymphocyte proliferation and enhances responses to PPD.

The authors examined the mechanism by which the non-specific lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) inhibits human lymphocyte proliferative responses and compared its effects with those of cyclosporine (CsA). It was found that CsA-resistant proliferative responses induced by direct PK-C activators such as mitogenic concentrations of the phorbol ester TPA or the putative antitumour agent bryostatin 1 (bryo 1) were inhibited in a concentration-dependent manner by NDGA (IC50 = 2 microM). In contrast, CsA-sensitive IL-2-dependent proliferative responses induced by PHA, anti-CD3 or the purified protein derivative (PPD) of M. tuberculosis were not significantly inhibited by NDGA concentrations as high as 8 microM. The expression of the IL-2R by lymphocytes was also resistant to NDGA concentrations that effectively blocked the mitogenic effects of TPA or bryostatin, but could be inhibited by higher concentrations of NDGA (IC50 = 8 microM). In addition, NDGA, but not CsA, blocked the production of IL-6 by human mononuclear cells. Furthermore, PPD-induced proliferation was significantly enhanced by NDGA. These data would suggest that NDGA at concentrations below 8 microM selectively inhibits IL-2-independent proliferation. NDGA's ability to inhibit IL-6 while enhancing the proliferative response to PPD may indicate an anti-inflammatory therapeutic potential of antioxidants in mycobacterial infections.

Adjuvants, Immunologic↗
PubMed1993

Late cyclosporine treatment ameliorates established coronary graft disease in rat allografts.

The development of post-transplantation coronary graft disease (CGD) is a major cause of late morbidity and mortality. Recent reports have suggested that CGD is a type of chronic vascular rejection, possibly enhanced by cofactors such as concurrent CMV infection and hyperlipidemia. It remains controversial whether established CGD can be improved by modifications in immunosuppressive therapy. The purpose of this study was to examine whether CsA could reverse or halt the progression of CGD after it was already established. Lewis to Fisher (F-344) heterotopic heart allografts develop CGD resembling human disease. Group 1 (n = 29) had no CsA therapy for chronic rat CMV (RCMV) infection in recipients for 8 weeks before transplant. Group 2 (n = 17) had chronic RCMV infection along with CsA therapy from days 15 to 28 post-transplant. Allografts were killed at 2 and 4 weeks and 90 days post-transplantation. In group 1, leukocyte adhesion to arterial endothelium and intimal hyperplasia were well established at 2 weeks and progressed to stenotic, proliferative arterial lesions at 4 weeks. In group 2, CsA therapy was effective in significantly reversing histologic parameters of vascular rejection such as leukocyte adhesion, intimal proliferation, and periarterial edema at 4 weeks. By 90 days, however, arterial pathology was as severe as in group 1. In conclusion, these results support the hypothesis that CGD is a form of chronic vascular rejection, and once established, can be significantly modified by CsA therapy. These effects are not permanent, and progressive CGD recurs after CsA therapy is discontinued.

Animals↗
PubMed1991

Successful treatment of murine melanoma with bryostatin 1.

Bryostatins are a novel class of protein kinase C activators which were isolated from the marine bryozoan Bugula neritina and found to possess both antineoplastic and immunoenhancing properties. In this report, we examined the relationship between the in vivo and in vitro antineoplastic effects of bryostatin 1. The in vivo antitumor activity of bryostatin 1 was demonstrated in a B16 melanoma pulmonary metastases model, in which treatment of tumor-bearing C57BL/6 mice with 5 days of bryostatin 1 resulted in a significant reduction in of the number of lung nodules (control, 87; bryostatin, 7). There was a clear dose-response effect, with the optimal antimelanoma dose being 100 micrograms/kg/day, but even low doses of bryostatin 1 of 1 micrograms/kg/day resulted in a 53% reduction in the number of metastases. Although bryostatin 1 shares many biological properties with the phorbol esters, parallel treatment with 12-O-tetradecanoyl 13-phorbol acetate was ineffective against B16 melanoma in vivo. Using a clonogenic assay, bryostatin 1 was found to have a direct antiproliferative effect against B16 melanoma. This inhibition occurred at relatively high bryostatin 1 concentrations (10(-6) M), in comparison with a sensitive cell line REH (10(-10) M). Treatment of mice with bryostatin 1 or preincubation of normal spleen cells with bryostatin 1 failed to enhance nonspecific cell-mediated cytotoxicity against B16 melanoma in vitro. Moreover, bryostatin 1 was found to inhibit both natural killer cell activity and interleukin 2 generation of lymphokine-activated killer cells. Thus, a role for an in vivo immune enhancement mechanism as the basis for the antimelanoma activity observed with bryostatin 1 cannot be invoked from these experiments. These findings indicate that bryostatin 1 may act directly on the B16 melanoma pulmonary metastases. The precise mechanism whereby bryostatin exerts its antimelanoma effects remains unclear.

Animals↗
PubMed1990

Activation of T-cells by bryostatins: induction of the IL-2 receptor gene transcription and down-modulation of surface receptors.

Bryostatins are macrocyclic lactones isolated from the marine bryozoan Bugula neritina. They are currently evaluated for putative antineoplastic activity. Bryostatins bind and activate protein kinase C (PK-C), the cellular receptor for the phorbol ester, and elicit PK-D-dependent cellular functions. Such functions include the expression of the interleukin-2 receptor (IL-2R). Northern blot hybridization with a human IL-2R and an IL-2 cDNA showed that bryostatin 1 (bryo 1), like the phorbol ester, PMA, activates the IL-2R gene. Activation with bryo 1 or PMA in the presence of a calcium ionophore, A23187, increased IL-2 message. These findings indicate that calcium mobilization is necessary for bryo 1 or PMA induced IL-2 gene expression. Unlike PMA, bryo 1 did not cause a vigorous proliferative response of T-lymphocytes unless A23187 was added to the cultures. A bryostatin congener, bryo 13, was inactive in the above assays. Short-term treatment of T-cells with bryo 1 and PMA resulted in an equivalent down-regulation of surface CD3 and CD4 receptors without affecting the CD8 receptor. Bryo 1 or PMA mediated expression of surface IL-2R and T-cell proliferation induced by bryo 1 or PMA were sensitive to inhibition by the PK-C antagonists staurosporine (Sts) and H-7. In contrast, CD4 and CD3 down-regulation were resistant to H-7, but could be blocked by Sts, although the Sts concentration required to block bryo 1 or PMA-induced down-modulation was 2.5-fold higher than required to inhibit IL-2R expression and T-cell proliferation. These results indicate that bryostatins activate T-cell through PK-C.

Antigens, Surface↗
PubMed1989

Successful in vitro graft-versus-tumor effect against an Ia-bearing tumor using cyclosporine-induced syngeneic graft-versus-host disease in the rat.

Lethally irradiated LouM rats reconstituted with syngeneic bone marrow and then treated with cyclosporine (CsA) for 40 consecutive days following transplant developed a graft-v-host disease (GVHD)-like syndrome after CsA cessation. This model of GVHD was used to define and characterize a graft-v-tumor (GVT) effect against a syngeneic plasmacytoma CRL1662 cell line which expresses class II major histocompatibility (MHC) antigen (Ia). Nylon wool-nonadherent spleen cells from animals who developed syngeneic GVHD were capable of significant lysis against chromium-labeled tumor target cells in a four-hour chromium released cell mediated lympholysis assay; maximum lysis occurred five days following cessation of CsA when clinical signs first appeared. Cytolytic activity declined to baseline as GVHD symptoms resolved. Fractionation of splenocytes into lymphocyte subsets demonstrated that cytolytic lymphocytes (CTLs) of the OX8 phenotype (non-helper T) were capable of significant lysis against tumor target cells. Lysis of tumor cells was blocked by preincubation with monoclonal antibodies (MoAb) specific for the rat anti-class II MHC antigen but not with MoAb against class I. Incubation of tumor cells with gamma-interferon increased expression of tumor class II MHC antigens and significantly increased their susceptibility to lysis by nylon wool-nonadherent splenocytes from animals with syngeneic GVHD. These studies have demonstrated an in vitro GVT of syngeneic GVHD against an Ia-bearing tumor; the effector cell is a CTL of the OX8 phenotype specific for the class II MHC antigen.

Animals↗
PubMed1988

Activation of human T lymphocytes by bryostatin.

The immunologic effects of bryostatin (Bryo), a PKC activator with antineoplastic activity, were assessed and compared to PMA. Bryo induced IL-2R expression on CD4+ and CD8+ human T lymphocytes with a dose response comparable to PMA. However, Bryo induced only a marginal proliferative response as compared with the vigorous response induced by PMA. Bryo mediated functional receptor expression because the proliferative response was enhanced by addition of rIL-2. Furthermore, the proliferative response was inhibited by the relatively specific Ca+, phospholipid-dependent protein kinase (PKC) inhibitor, H-7, indicating a role of PKC in Bryo-induced activation. Addition of the calcium ionophore, ionomycin, to Bryo-stimulated lymphocytes resulted in the production and secretion of IL-2 with a concomitant proliferative response. This effect of the calcium ionophore could be inhibited by cyclosporine with identical results obtained in PMA-stimulated cultures. A most intriguing finding was that Bryo could effectively antagonize PMA-induced T cell proliferation. Although this mechanism of inhibition is unclear, a discussion with respect to differential effects on potential intracellular PKC isoforms is provided. These studies indicated that Bryo has potent immunopotentiating properties that share some similar effects of the phorbol ester, PMA, but offers the additional property of modulating other phorbol ester effects on proliferation.

Adjuvants, Immunologic↗
PubMed1988

Immunotoxicity of organophosphorus compounds. Modulation of cell-mediated immune responses by inhibition of monocyte accessory functions.

Several organophosphorus compounds (OP) used commercially as flame retardants and plasticizers and related chemicals were evaluated for their effects on human in vitro cell-mediated immune responses. At nontoxic concentrations ranging from 0.1 to 20 microM, two of the tested compounds, triphenylphosphine oxide (TPPO) and tetra-o-cresylpiperazinyl diphosphoamidate (TCPD) caused significant suppression of antigen-specific lymphocyte proliferation (P less than 0.01). Mitogenesis was less sensitive to OP treatment and was affected only by TCPD. When monocytes and lymphocytes were treated separately with OP, washed, and recombined, it appeared that these OP mediated their suppressive effects by interfering with a monocyte function rather than acting directly on lymphocytes. Further, triphenyl phosphate (TPP), triphenyl thiophosphate (TPTP) as well as TPPO and TCPD were tested for direct inhibition of monocyte antigen presentation, and all four compounds were found to cause significant inhibition at concentrations as low as 1 microM (P less than 0.001).

Antigen-Presenting Cells↗
PubMed1987

Cyclosporine inhibits soluble antigen and alloantigen presentation by human monocytes in vitro.

We examined whether cyclosporine (CsA) interferes with human monocyte processing and presentation of soluble and particulate antigens. Human monocytes were pulsed in the presence of CsA with one of three antigens: tetanus toxoid (TT), diphtheria toxoid (DIP) or cytomegalovirus (CMVx). When these monocytes were co-cultured with immunocompetent T-lymphocytes they were found to be impaired in the induction of proliferative and cytotoxic T-cell responses. At CsA concentrations higher that 0.5 micrograms/ml, proliferation induced by the particulate CMVx antigen was markedly more sensitive than that induced by the soluble TT antigen. In the allogeneic mixed lymphocyte reaction (MLR), pretreatment of responder haplotype monocytes alone with CsA led to reduced reactivity as determined in both proliferative (P less than 0.01) and cell-mediated lympholysis (P less than 0.001) assays. These effects of CsA were not due to direct CsA action of residual CsA carried over with treated monocytes, and were not apparently due to inhibition of interleukin-1 (IL-1) production since exogenous IL-1 could not restore normal responses.

Antigen-Presenting Cells↗
PubMed1987

Antineoplastic bryostatins are multipotential stimulators of human hematopoietic progenitor cells.

The bryostatins are macrocyclic lactones, extracted from the marine bryozoan Bugula neritina, and have been reported to be potent antineoplastic agents. Results described here demonstrate that the bryostatins may also be useful as stimulators of normal human hematopoietic cells since they can (i) directly stimulate bone marrow progenitor cells to form colonies in vitro and (ii) functionally activate neutrophils. Structure-activity studies with bryostatin congeners indicate that these stimulatory properties may be dependent on the chain length and the unsaturated nature of the acylated group at carbons 20 and 7 of the bryostatin molecule. These stimulatory properties demonstrate that the naturally occurring bryostatins can mimic many of the biological effects of multipotential granulocyte-macrophage colony-stimulating factor. Thus, the coupling of antineoplastic activity with stimulatory growth properties for normal hematopoietic cells makes this agent an excellent probe to dissect the mechanism(s) of normal hematopoiesis. In addition, bryostatin may represent a clinically attractive agent useful for treating bone marrow failure states.

Antineoplastic Agents↗
PubMed1986

Cyclosporine and the immune response: basic aspects.

Cyclosporine (CsA) is a novel immunosuppressive agent currently used clinically, to prevent rejection of solid organ allografts and to prevent graft-vs.-host disease. Early studies in a variety of animal models exhibited transplantation tolerance after limited treatment with this unique agent. The apparent specific immunological unresponsiveness induced by CsA is thought to be maintained by antigen-specific suppressor T lymphocytes. Studies attempting to dissect the mechanism of action of this unique agent suggested that CsA selectively affected different T lymphocyte populations. Cyclosporine was very effective at inhibiting the production of interleukin-2 (IL-2), a soluble lymphokine known to amplify cytotoxic T cell responses and was also capable of preventing IL-2 receptor expression on the precursor cytotoxic T lymphocyte. In contrast, to the effect on T helper cells and on the precursor cytotoxic T lymphocyte, studies in vitro and in vivo demonstrated that CsA had a sparing effect on suppressor T cell induction. More recent studies have indicated that CsA allows for the amplification of suppressor T lymphocytes independent of interleukin-2 indicating that other cellular and/or soluble factors are important for potentiation of suppressor T lymphocyte activity. However, the molecular action of CsA at the cellular level still remains unresolved. Thus, CsA is not only a useful drug in clinical transplantation but it has become increasingly important as an immunologic probe allowing the dissection of complex cellular interactions involved in the immune response.

Animals↗
PubMed1986

Immunological heterogeneity of human monocyte subsets prepared by counterflow centrifugation elutriation.

Human peripheral blood mononuclear cells were separated into three fractions by means of counterflow centrifugation elutriation (CCE). The first fraction, eluted at a flow rate of 24 ml/min, was composed of lymphocytes with less than 2% contaminating esterase-positive cells. The cells in this fraction were incapable of responding to either soluble antigen (tetanus toxoid) or particulate antigen (cytomegalovirus-infected fibroblasts) unless recombined with accessory cells. The second fraction, eluted at a flow rate of 28 ml/min, was composed predominantly (72%) of small Ia, leu M3, and esterase-positive monocytes, which stained weakly with leu 10 antibody. Cells in this fraction efficiently presented soluble and particulate antigens to monocyte-depleted lymphocytes. Of the remaining cells, 87% were large esterase-positive monocytes that labelled strongly with Ia, leu M3, and leu 10. These cells were less efficient in antigen presentation than the small monocytes. However, lymphocytes activated with antigen-pulsed large monocytes exhibited more suppressor cell activity than those activated with antigen-pulsed small monocytes.

Antigen-Presenting Cells↗
PubMed1985

Influences of nutrition on immunity and susceptibility to mouse hepatitis virus type 2.

Resistance to mouse hepatitis virus (MHV) in C3H mice is a genetic trait which appears 3-4 weeks after birth. However, when these animals were weaned on a low protein diet (8% casein), they remained susceptible to MHV-2 infection until they reached 8-9 weeks of age. During this period, the protein-restricted C3H mice were as susceptible to MHV-2 as the genetically susceptible congenic C3Hss strain. The delay in the emergence of resistance in the protein-restricted mice could be corrected by injecting these animals with spleen cells from 6-week-old C3H mice. Thymocytes from normal C3H mice, and splenocytes and thymocytes from protein-restricted C3H mice, were not protective. However, spleen cells from the protein-restricted mice were more responsive to phytohaemagglutinin, lipopolysaccharide and concanavalin A than spleen cells from normal C3H. The enhanced lymphoproliferative response in spleen cells from protein-restricted mice was abrogated by the addition of plastic-adherent cells obtained from normal C3H spleens. Spleen cells from protein-restricted and from genetically susceptible C3Hss mice also possessed more spontaneous cytotoxicity against MHV-infected 3T3 fibroblasts.

Animals↗
PubMedDate not supplied

Bryostatins trigger human polymorphonuclear neutrophil and monocyte oxidative metabolism: association with in vitro antineoplastic activity.

Bryostatin-1-but not bryostatin-13-a macrocyclic lactone isolated from the marine bryozoan Bugula neritina, triggered human polymorphonuclear neutrophil (PMN) and monocyte release of reactive oxygen radicals, as measured by the generation of lucigenin chemiluminescence and by the ferricytochrome c reduction assay. The release of oxygen radicals by bryostatins was sensitive to inhibitors of protein kinases, but resistant to the inhibition of phospholipase A2 activity and arachidonic acid metabolism (prior treatment with mepacrine or indomethacin). Comparison of the effect of protein kinase (PK) inhibitors H-8, H-7 and staurosporine on bryostatin-1-induced neutrophil oxygen radical release further suggested a requirement for activation of phospholipid-dependent PKC, but not for cGMP- or cAMP-dependent PK. In cytostatic assays, PMNs treated with bryostatin-1 inhibited the growth of the erythroleukaemic cell line K562 in a concentration-dependent manner. These findings suggest that the reported antineoplastic effect of bryostatins may result at least in part from activation of PMNs and monocytes.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗