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Biomedical subjects

F H Bach

Publications and source records attributed to F H Bach.

At least 73 records · Page 4Linked to original sources
PubMed1997

Inhibition of bovine endothelial cell activation in vitro by regulated expression of a transdominant inhibitor of NF-kappa B.

The activation of endothelial cells is a recurrent phenomenon linked to pathologic conditions such as inflammation, chronic arthritis, allo- and xenograft rejection. To inhibit endothelial cell activation we have constructed a transactivation-deficient derivative of the p65/RelA subunit of NF-kappa B, a transcription factor known to be crucial for the induction of adhesion molecules, cytokines and procoagulants in activated endothelial cells. This protein (p65RHD) comprises the Rel homology domain of the RelA subunit, retaining dimerization, DNA binding, and nuclear localization functions, but is deficient in transcriptional activation, and acts as a competitive inhibitor of NF-kappa B. Our data demonstrate that p65RHD is a potent and specific inhibitor of NF-kappa B-mediated induction of a number of genes, such as I kappa B alpha, IL-8, E-selectin, P-selectin, and tissue factor in endothelial cells. Furthermore, tetracycline-inducible expression of p65RHD in stably transfected primary endothelial cells inhibits the induction of gene expression equally well. This regulated system of gene expression provides the basis for a novel therapeutic approach to the pathologic effects of endothelial cell activation, especially in delayed xenograft rejection, by using transgenic animals as organ donors.

Animals↗
PubMed1997

Loss of ATP diphosphohydrolase activity with endothelial cell activation.

Quiescent endothelial cells (EC) regulate blood flow and prevent intravascular thrombosis. This latter effect is mediated in a number of ways, including expression by EC of thrombomodulin and heparan sulfate, both of which are lost from the EC surface as part of the activation response to proinflammatory cytokines. Loss of these anticoagulant molecules potentiates the procoagulant properties of the injured vasculature. An additional thromboregulatory factor, ATP diphosphohydrolase (ATPDase; designated as EC 3.6.1.5) is also expressed by quiescent EC, and has the capacity to degrade the extracellular inflammatory mediators ATP and ADP to AMP, thereby inhibiting platelet activation and modulating vascular thrombosis. We describe here that the antithrombotic effects of the ATPDase, like heparan sulfate and thrombomodulin, are lost after EC activation, both in vitro and in vivo. Because platelet activation and aggregation are important components of the hemostatic changes that accompany inflammatory diseases, we suggest that the loss of vascular ATPDase may be crucial for the progression of vascular injury.

Adenosine Diphosphate↗
PubMed1997

Protective genes expressed in endothelial cells: a regulatory response to injury.

Endothelial cells (ECs) have evolved to guard against insults that incite inflammation. Response to injury is an active process that, if uncontrolled, can progress to EC death (apoptosis). Here Fritz Bach and colleagues suggest that ECs have a balancing component to their proinflammatory response: they upregulate a set of protective genes, including anti-apoptotic genes, that serve to limit the activation process and thereby regulate the response to injury.

Animals↗
PubMed1997

Accommodation of vascularized xenografts: expression of "protective genes" by donor endothelial cells in a host Th2 cytokine environment.

Organ xenografts under certain circumstances survive in the presence of anti-graft antibodies and complement, a situation referred to as "accommodation." We find that the endothelial cells (ECs) in hamster hearts that accommodate themselves in rats express genes, such as A20 and bcl-2, that in vitro protect ECs from apoptosis and prevent upregulation in those cells of proinflammatory genes such as cytokines, procoagulant and adhesion molecules. Hearts that are rejected do not express these genes. In addition, vessels of rejected hearts show florid transplant arteriosclerosis whereas those of accommodated hearts do not. Accommodated xenografts have an ongoing T helper cell type 2 (Th2) cytokine immune response, whereas the rejected grafts have a Th1 response. We propose a model for factors that contribute to the survival of xenografts and the avoidance of transplant arteriosclerosis.

Animals↗
PubMed1997

Modulation of vascular ATP diphosphohydrolase by fatty acids.

Endothelial cells (EC) possess several protective thromboregulatory mechanisms that may be perturbed by cell activation or injury. Vascular ATP-diphosphohydrolase (ATPDase) has been demonstrated on both aortic EC and smooth muscle cells and may play a key regulatory role in hemostasis and platelet reactivity by converting extracellular ATP and ADP to AMP. We have examined the role of exogenous saturated or unsaturated fatty acids in the modulation of EC associated ATPDase activity in vitro. EC growth was not dramatically influenced by supplementation with fatty acids whereas viability was enhanced by oleic, butyrate and eicosapentaenoic acid. EC cultures supplemented with saturated or a monounsaturated (oleic acid) fatty acid(s) had markedly increased ATPDase activity, whereas those exposed to polyunsaturated fatty acids showed substantive decreases. Exogenous oleic acid could also protect against the significant loss of ATPDase activity, following exposure to reactive oxygen intermediates in vitro. We conclude that endothelial ATPDase activity may be regulated by exogenous fatty acids and that underlying mechanisms include alterations in the nature of the phospholipid composition of EC membranes that influence responses to oxidative stress reactions.

Animals↗
PubMed1997

Results of allogeneic bone marrow transplants for leukemia using donors other than HLA-identical siblings.

PURPOSE: To compare outcomes of bone marrow transplants for leukemia from HLA-identical siblings, haploidentical HLA-mismatched relatives, and HLA-matched and mismatched unrelated donors. PATIENTS: A total of 2,055 recipients of allogeneic bone marrow transplants for chronic myelogenous leukemia (CML), acute myelogenous leukemia (AML), and acute lymphoblastic leukemia (ALL) were entered onto the study. Transplants were performed between 1985 and 1991 and reported to the International Bone Marrow Transplant Registry (IBMTR). Donors were HLA-identical siblings (n = 1,224); haploidentical relatives mismatched for one (n = 238) or two (n = 102) HLA-A, -B, or -DR antigens; or unrelated persons who were HLA-matched (n = 383) or mismatched for one HLA-A, -B, or -DR antigen (n = 108). HLA typing was performed using serologic techniques. RESULTS: Transplant-related mortality was significantly higher after alternative donor transplants than after HLA-identical sibling transplants. Among patients with early leukemia (CML in chronic phase or acute leukemia in first remission), 3-year transplant-related mortality (+/-SE) was 21% +/- 2% after HLA-identical sibling transplants and greater than 50% after all types of alternative donor transplants studied. Among patients with early leukemia, relative risks of treatment failure (inverse of leukemia-free survival), using HLA-identical sibling transplants as the reference group, were 2.43 (P < .0001) with 1-HLA-antigen-mismatched related donors, 3.79 (P < .0001) with 2-HLA-antigen-mismatched related donors, 2.11 (P < .0001) with HLA-matched unrelated donors, and 3.33 (P < .0001) with 1-HLA-antigen-mismatched unrelated donors. For patients with more advanced leukemia, differences in treatment failure were less striking: 1-HLA-antigen-mismatched relatives, 1.22 (P = not significant [NS]); 2-HLA-antigen-mismatched relatives, 1.81 (P < .0001); HLA-matched unrelated donors, 1.39 (P = .002); and 1-HLA-antigen-mismatched unrelated donors, 1.63 (P = .002). CONCLUSION: Although transplants from alternative donors are effective in some patients with leukemia, treatment failure is higher than after HLA-identical sibling transplants. Outcome depends on leukemia state, donor-recipient relationship, and degree of HLA matching. In early leukemia, alternative donor transplants have a more than twofold increased risk of treatment failure compared with HLA-identical sibling transplants. This difference is less in advanced leukemia.

Age Factors↗
PubMed1997

Gem, a GTP-binding protein from mitogen-stimulated T cells, is induced in endothelial cells upon activation by inflammatory cytokines.

Using differential screening of cytokine-activated versus resting porcine aortic endothelial cells (PAEC), we have isolated a member of the family of Ras/GTP-binding proteins. The cDNA encodes a 34-kilodalton protein showing 97% homology to Gem, a gene recently isolated from activated T cells, likely representing its porcine homologue. The amino acid sequence differs from the Ras consensus by the absence of a C-terminal isoprenylation site and a glycine to glutamic acid substitution in the third GTP-binding domain. We report here, that pigGem mRNA is strongly inducible in PAEC upon activation by either IL-1 alpha, TNF alpha or lipopolysaccharide (LPS). Low constitutive expression is found in several organs. Epitope-tagged pigGem transfected into endothelial cells (EC) localizes to the cytoplasm and to the inner side of the plasma membrane. Structural features of Gem and its inducibility apparently restricted to T cells and endothelial cells, together with Rad, a GTPase overexpressed in skeletal muscle cells of type II diabetic individuals, define a new branch within the superfamily of GTP-binding proteins.

Amino Acid Sequence↗
PubMed1997

Tumor infiltrating lymphocytes in squamous cell carcinoma of the head and neck: mechanisms of enhancement using prostaglandin synthetase inhibitors.

Indomethacin has been shown clinically to inhibit growth of SCCHN (Panje, 1981). This inhibition appears to be due to augmentation of cellular immunity. The inhibitory effect of indomethacin may act by limiting tumor associated prostaglandin E2 production, thereby allowing return of costimulatory cytokines by antigen presenting cells. This would have the net result of relief from host unresponsiveness and promotion of B-cell and CTL differentiation, allowing the individual to mount an effective response. The enhancement of tumor infiltrating lymphocytes in SCCHN seen with indomethacin administration could presumably be further augmented when given in combination with cytokine therapy. Future investigation may allow the biochemical staging of an individuals' tumor to determine the optimal combination of cytokine therapy and prostaglandin inhibition through selective use of NSAID's. The effect of NSAID manipulation of prostaglandin and leukotriene metabolism on prevention of metastatic disease in SCCHN has yet to be studied. Given that a preselected, potentially responsive subset of immunocytes exists within the tumor tissue and lymph nodes, the development of the LAK phenomenon in TIL's and tumor draining lymph nodes from surgical specimens is a viable and exceedingly interesting area for future investigations in autologous LAK immunotherapy. The potential exists to harvest a preselected population of tumor infiltrating (Boscia, 1988) or tumor draining immunocytes (McKinnon, 1990). These can then potentially be returned to a state of antigen responsiveness with a combination of cytokine exposure (e.g. rIL-2) and systemic cytokine therapy. With subsequent inhibition of tumor associated prostaglandin synthesis by the systemic administration of prostaglandin synthesis inhibitors, it may be possible to successfully alter the host response to tumor.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Apyrase administration prolongs discordant xenograft survival.

Platelet thrombi and vascular inflammation are prominent features of discordant xenograft rejection. The purinergic nucleotides ATP and ADP, which are secreted from platelets and released by injured endothelial cells (EC), are important mediators of these reactions. Quiescent EC express the ectoenzyme ATP-diphosphohydrolase (ATPDase; an apyrase), which exerts an important thromboregulatory function by hydrolyzing both ATP and ADP. We have shown that ATPDase activity is rapidly lost from the surface of the EC following ischemia-reperfusion injury and during xenograft rejection. The aim of this study was to supplement ATPDase activity within xenografts by infusion of soluble apyrases, and thereby validate the importance of local ATPDase activity in the modulation of xenograft rejection. Lewis rats underwent heterotopic cardiac xenografting from guinea pigs and apyrase was administered intravenously (200 U/kg) as a single dose to evaluate effects on hyperacute rejection (HAR). This initial dose was followed by a continuous apyrase infusion (8.0 U/kg/hr) directly into the graft aorta in combination with systemic cobra venom factor (CVF) administration to deplete complement when delayed xenograft rejection (DXR) was studied. Functional apyrase levels in vivo were assessed by the capacity of blood samples taken at the time of surgery and rejection to inhibit platelet aggregation in vitro. Apyrase administration significantly prolonged graft survival in HAR and DXR. Functional assays showed inhibition of platelet aggregation suggesting effective systemic antiaggregatory effects of the administered apyrases. Histologic studies showed that apyrase administration abrogated local platelet aggregation and activation in HAR and DXR. Our data demonstrate that local administration of apyrase prolonged discordant xenograft survival. These observations emphasize the potential importance of purinergic mediators in platelet activation during xenograft rejection.

Adenosine Diphosphate↗
PubMed1996

T cell independence of macrophage and natural killer cell infiltration, cytokine production, and endothelial activation during delayed xenograft rejection.

Rejection of guinea pig cardiac grafts in rats depleted of complement takes place in 3-4 days and involves progressive mononuclear cell infiltration and cytokine expression, fibrin and antibody deposition, and endothelial cell up-regulation of adhesion and procoagulant molecules, a process termed delayed xenograft rejection (DXR). The relative contribution of each effector mechanism and the role of T cells in this complex process are unknown, although small numbers of interleukin (IL) 2 receptor-positive T cells are present at the time of rejection. We investigated the importance of T cells in DXR by comparing discordant xenograft responses of nude rats, which lack T cell receptor (TCR)-alpha/beta+ cells, with those of normal Lewis rats. Nude or Lewis rats receiving guinea pig cardiac grafts were assigned to one of three groups: no therapy, daily administration of cobra venom factor (CVF), or splenectomy plus daily CVF. All untreated rats rejected their xenografts within 10-15 min, whereas grafts in complement-depleted recipients survived a further 3-4 days; splenectomy had no significant additional effect upon graft survival. Immunohistologic analysis in CVF-treated nude recipients with or without splenectomy showed: (1) considerable leukocyte infiltration of xenografts (mean +/- SD, 76+/-14 and 71+/-16 leukocytes/field, respectively, at 72 hr, compared with 68+/-17 in Lewis rats), consisting largely of macrophages (>75% of total leukocytes) plus small numbers of natural killer cells (10-20%) with no detectable B or T cells (TCR-alpha/beta or TCR-gamma/delta); (2) at least 10-fold lower levels of intragraft IgM or IgG deposition than in corresponding Lewis recipients; and (3) considerable cytokine expression by intragraft macrophages (IL-12, tumor necrosis factor-alpha, monocyte chemoattractant protein-1, IL-1beta, IL-6, IL-7, IL-12) and natural killer cells (interferon-gamma), as well as up-regulation of tissue factor expression and dense fibrin deposition. Analysis of recipient sera of both control and nude rats by ELISA, for the binding of IgG or IgM to guinea pig platelets, showed a rapid rise after transplantation in the titers of IgM and IgG antibodies, which was abrogated by prior splenectomy; i.e., data from splenectomized xenograft recipients reflect the presence of only basal levels of IgM and IgG. Thus, our data in nude rats show rejection times and intragraft features of DXR comparable to those in immunocompetent Lewis recipients, despite a lack of detectable host T cells, and, in the case of splenectomized rats, only about one tenth of normal xenoreactive antibody levels. Our data document a new model in which to analyze the immunopathogenesis of DXR.

Animals↗
PubMed1996

Identification and characterization of CD39/vascular ATP diphosphohydrolase.

Vascular ATP diphosphohydrolase (ATPDase) is a plasma membrane-bound enzyme that hydrolyses extracellular ATP and ADP to AMP. Analysis of amino acid sequences available from various mammalian and avian ATPDases revealed their close homology with CD39, a putative B-cell activation marker. We, therefore, isolated CD39 cDNA from human endothelial cells and expressed this in COS-7 cells. CD39 was found to have both immunological identity to, and functional characteristics of, the vascular ATPDase. We also demonstrated that ATPDase could inhibit platelet aggregation in response to ADP, collagen, and thrombin, and that this activity in transfected COS-7 cells was lost following exposure to oxidative stress. ATPDase mRNA was present in human placenta, lung, skeletal muscle, kidney, and heart and was not detected in brain. Multiple RNA bands were detected with the CD39 cDNA probe that most probably represent different splicing products. Finally, we identified an unique conserved motif, DLGGASTQ, that could be crucial for nucleotide binding, activity, and/or structure of ATPDase. Because ATPDase activity is lost with endothelial cell activation, overexpression of the functional enzyme, or a truncated mutant thereof, may prevent platelet activation associated with vascular inflammation.

Adenosine Triphosphatases↗
PubMed1996

The intron-exon structure of the porcine E-selectin-encoding gene.

We have cloned and sequenced the gene encoding porcine E-selectin. The gene comprises 12 exons and 11 introns. Two pseudoexons are contained within intron 4 and intron 6. These sequences are similar to the corresponding exons in the human E-selectin sequence; however, they are not present in the porcine E-selectin-encoding cDNA. Transcription starts at position -498 relative to the translation initiation site. The first ATG is located within exon 2. Translation stops in exon 11 leaving exon 12 untranslated in its entirety.

Amino Acid Sequence↗
PubMed1996

Adenoviral-mediated overexpression of I(kappa)B(alpha) in endothelial cells inhibits natural killer cell-mediated endothelial cell activation.

Activated natural killer (NK) cells have been found in rejecting discordant xenografts and may contribute to endothelial cell (EC) activation and damage. The transcription of genes associated with EC activation, such as E-selectin and interleukin (IL)-8, is regulated by the transcription factor NF-kappaB. In resting EC, NF-kappaB is complexed within the cytoplasm to I(kappa)B(alpha), and EC activation leads to dissociation of the I(kappa)B(alpha)-NF-kappaB complex and nuclear translocation of NF-kappaB. We investigated whether overexpression of I(kappa)B(alpha) in EC, using adenoviral gene transfer, could block NF-kappaB translocation, thereby inhibiting NK cell-mediated EC activation. Co-culture of human NK cells with porcine EC resulted in a threefold increase in E-selectin expression after 4 hr and secretion of greater than 650 pg/ml porcine IL-8 over 24 hr. Overexpression of I(kappa)B(alpha) inhibited the NK cell-mediated induction of E-selectin expression and IL-8 secretion, whereas overexpression of P-galactosidase did not. The inhibition of EC activation was not due to variation in NK-EC adhesion, as the level of adhesion was similar between adenovirally infected and noninfected EC over 4 hr. The level of NK cell-mediated EC cytotoxicity was not significantly different after 4 hr of co-culture, but after 24 hr, cytotoxicity was increased in virally infected cells. Cytotoxicity was more marked in cells overexpressing I(kappa)B(alpha) than cells overexpressing beta-galactosidase. SLA class I and the induction of SLA class II antigen in response to interferon-gamma treatment were reduced in cells infected with adeno-I(kappa)B(alpha) and empty adenovirus, demonstrating that viral infection alone can influence EC biology. Overexpression of I(kappa)B(alpha) using adenovirus provides a novel approach to inhibiting NK cell-mediated EC activation, but additional strategies will be required to inhibit NK cell-mediated cytotoxicity.

Adenoviridae↗