Gemifloxacin inhibits cytokine secretion by lipopolysaccharide stimulated human monocytes at the post-transcriptional level

The fluroquinolone gemifloxacin was examined for its capacity to modulate secretion of cytokines by human monocytes stimulated with lipopolysaccharide (LPS). Monocytes from six male and two female healthy volunteers were stimulated with LPS, exposed to gemifloxacin and the amounts of secreted IL-1 alpha, IL-1 beta, IL-6, IL-10 and TNF-alpha measured at 3, 6 and 24 h. The results revealed that LPS alone increased secretion of each cytokine significantly. Treatment of the LPS-stimulated monocytes with gemifloxacin resulted in a significant inhibition (p < 0.01) of secretion of each of the cytokines from monocytes of the eight volunteers. Nuclear extracts of the human monocyte cell line, THP-1, were used in the electrophoretic mobility shift assay to determine whether gemifloxacin affects nuclear factor-kappa B (NF-kappa B) activation. In addition, RNA from THP-1 cells was used in Northern blots to determine whether inhibition of secretion of IL-1 beta and TNF-alpha by gemifloxacin occurred at the transcription or translation level. Whereas LPS induced a rapid increase in NF-kappa B activation, gemifloxacin alone did not. Gemifloxacin did not affect the kinetics or decrease the extent of activation. Northern blots indicated that the inhibitory activity of gemifloxacin occurred post-transcription. Thus, gemifloxacin may modulate the immune response by altering secretion of cytokines by human monocytes. Although the concentrations of gemifloxacin used were higher than those observed in the serum of human volunteers treated with the dose under clinical development, it should be taken into consideration that concentrations at tissue and intracellular levels may be considerably higher than serum concentrations.

Dendritic cell-based xenoantigen vaccination for prostate cancer immunotherapy

Many tumor-associated Ags represent tissue differentiation Ags that are poorly immunogenic. Their weak immunogenicity may be due to immune tolerance to self-Ags. Prostatic acid phosphatase (PAP) is just such an Ag that is expressed by both normal and malignant prostate tissue. We have previously demonstrated that PAP can be immunogenic in a rodent model. However, generation of prostate-specific autoimmunity was seen only when a xenogeneic homolog of PAP was used as the immunogen. To explore the potential role of xenoantigen immunization in cancer patients, we performed a phase I clinical trial using dendritic cells pulsed with recombinant mouse PAP as a tumor vaccine. Twenty-one patients with metastatic prostate cancer received two monthly vaccinations of xenoantigen-loaded dendritic cells with minimal treatment-associated side effects. All patients developed T cell immunity to mouse PAP following immunization. Eleven of the 21 patients also developed T cell proliferative responses to the homologous self-Ag. These responses were associated with Ag-specific IFN-gamma and/or TNF-alpha secretion, but not IL-4, consistent with induction of Th1 immunity. Finally, 6 of 21 patients had clinical stabilization of their previously progressing prostate cancer. All six of these patients developed T cell immunity to human PAP following vaccination. These results demonstrate that xenoantigen immunization can break tolerance to a self-Ag in humans, resulting in a clinically significant antitumor effect.

Altered peptide ligand vaccination with Flt3 ligand expanded dendritic cells for tumor immunotherapy

Most tumor-associated antigens represent self-proteins and as a result are poorly immunogenic due to immune tolerance. Here we show that tolerance to carcinoembryonic antigen (CEA), which is overexpressed by the majority of lethal malignancies, can be reversed by immunization with a CEA-derived peptide. This peptide was altered to make it a more potent T cell antigen and loaded onto dendritic cells (DCs) for delivery as a cellular vaccine. Although DCs are rare in the blood, we found that treatment of advanced cancer patients with Flt3 ligand, a hematopoietic growth factor, expanded DCs 20-fold in vivo. Immunization with these antigen-loaded DCs induced CD8 cytotoxic T lymphocytes that recognized tumor cells expressing endogenous CEA. Staining with peptide-MHC tetramers demonstrated the expansion of CD8 T cells that recognize both the native and altered epitopes and possess an effector cytotoxic T lymphocyte phenotype (CD45RA(+)CD27(-)CCR7(-)). After vaccination, two of 12 patients experienced dramatic tumor regression, one patient had a mixed response, and two had stable disease. Clinical response correlated with the expansion of CD8 tetramer(+) T cells, confirming the role of CD8 T cells in this treatment strategy.

Dendritic cells injected via different routes induce immunity in cancer patients

Dendritic cells (DC) represent potent APCs that are capable of generating tumor-specific immunity. We performed a pilot clinical trial using Ag-pulsed DC as a tumor vaccine. Twenty-one patients with metastatic prostate cancer received two monthly injections of DC enriched and activated from their PBMC. DC were cocultured ex vivo with recombinant mouse prostatic acid phosphatase as the target neoantigen. Following enrichment, DC developed an activated phenotype with up-regulation of CD80, CD86, and CD83 expression. During culture, the DC maintained their levels of various adhesion molecules, including CD44, LFA-1, cutaneous lymphocyte-associated Ag, and CD49d, up-regulated CCR7, but lost CD62 ligand and CCR5. In the absence of CD62 ligand, such cells would not be expected to prime T cells efficiently if administered i.v. due to their inability to access lymphoid tissue via high endothelial venules. To assess this possibility, three patient cohorts were immunized with Ag-pulsed DC by i.v., intradermal (i.d.), or intralymphatic (i.l.) injection. All patients developed Ag-specific T cell immune responses following immunization, regardless of route. Induction of IFN-gamma production, however, was seen only with i.d. and i.l. routes of administration, and no IL-4 responses were seen regardless of route, consistent with the induction of Th1-type immunity. Five of nine patients who were immunized by the i.v. route developed Ag-specific Abs compared with one of six for i.d. and two of six for i.l. routes. These results suggest that while activated DC can prime T cell immunity regardless of route, the quality of this response and induction of Ag-specific Abs may be affected by the route of administration.

Fetoplacental growth in sheep administered progesterone during the first three days of pregnancy

We have previously shown that administration of progesterone during early pregnancy in sheep enhances fetal weight and crown-rump length. The present study examined the effect of this treatment on individual fetal organ weights and on placental growth and structure. Embryos that had been exposed to either a normal or a high concentration of progesterone on days 1-3 in initial recipient ewes were transferred at random to final recipient ewes that had or had not been treated with progesterone on days 1-3. Embryos in an additional group of ewes were exposed to progesterone on days 1-3 with oviducts of the ewes ligated. An increase in fetal weight was observed in the final recipient group that had been treated with progesterone (P< 0.01) but not in the initial group treated with progesterone. Fetal weight was increased (P< 0.05) in the initial recipients treated with progesterone plus ligation. Placental weight did not differ between any of the treatments in either initial or final recipients, while placental volumes of chorionic membrane and maternal crypts were increased by progesterone, with and without ligation, in initial recipients (P< 0.05). The responses of fetal weight in final recipients were associated with increases in the weight and linear dimensions of specific fetal components (e.g. brain, kidney, heart, spleen, total gut, head width, thorax circumference). Proportionate increases were observed for most parameters with the exception of brain, heart and M tibialis anterior weight; adjusted least squares means indicated disproportionate increases in these of 5 per cent, 32 per cent and 26 per cent respectively. Enhanced fetal weight in the progesterone plus ligation group was associated with increased (P< 0.05) heart weight; a disproportionate increase of 39 per cent was recorded. Increased fetal weight and fetal heart, skeletal muscle and brain weight were correlated with increased volumes and surface area of the fetal trophectoderm and maternal fetomaternal syncytium in the final recipients treated with progesterone. It is concluded that alteration of the embryo's environment during the first few days of development enhances fetal growth disproportionately, in close association with increased abundance of the exchange epithelia in the placenta.

Differentiation of myeloid dendritic cells into CD8alpha-positive dendritic cells in vivo

Bone marrow-derived dendritic cells (DC) represent a family of antigen-presenting cells (APC) with varying phenotypes. For example, in mice, CD8alpha(+) and CD8alpha(-) DC are thought to represent cells of lymphoid and myeloid origin, respectively. Langerhans cells (LC) of the epidermis are typical myeloid DC; they do not express CD8alpha, but they do express high levels of myeloid antigens such as CD11b and FcgammaR. By contrast, thymic DC, which derive from a lymphoid-related progenitor, express CD8alpha but only low levels of myeloid antigens. CD8alpha(+) DC are also found in the spleen and lymph nodes (LN), but the origin of these cells has not been determined. By activating and labeling CD8alpha(-) epidermal LC in vivo, it was found that these cells expressed CD8alpha on migration to the draining LN. Similarly, CD8alpha(-) LC generated in vitro from a CD8 wild-type mouse and injected into the skin of a CD8alphaKO mouse expressed CD8alpha when they reached the draining LN. The results also show that CD8alpha(+) LC are potent APC. After migration from skin, they localized in the T-cell areas of LN, secreted high levels of interleukin-12, interferon-gamma, and chemokine-attracting T cells, and they induced antigen-specific T-cell activation. These results demonstrate that myeloid DC in the periphery can express CD8alpha when they migrate to the draining LN. CD8alpha expression on these DC appears to reflect a state of activation, mobilization, or both, rather than lineage. (Blood. 2000;96:1865-1872)

Dendritic cells in cancer immunotherapy

The potential to harness the potency and specificity of the immune system underlies the growing interest in cancer immunotherapy. One such approach uses bone marrow-derived dendritic cells, phenotypically distinct and extremely potent antigen-presenting cells, to present tumor-associated antigens and thereby generate tumor-specific immunity. Support for this strategy comes from animal studies that have demonstrated that dendritic cells, when loaded ex vivo with tumor antigens and administered to tumor-bearing hosts, can elicit T cell-mediated tumor destruction. These observations have led to clinical trials designed to investigate the immunologic and clinical effects of antigen-loaded dendritic cells administered as a therapeutic vaccine to patients with cancer. In the design and conduct of such trials, important considerations include antigen selection, methods for introducing the antigen into MHC class I and II processing pathways, methods for isolating and activating dendritic cells, and route of administration. Although current dendritic cell-based vaccination methods are cumbersome, promising results from clinical trials in patients with malignant lymphoma, melanoma, and prostate cancer suggest that immunotherapeutic strategies that take advantage of the antigen presenting properties of dendritic cells may ultimately prove both efficacious and widely applicable to human tumors.

Induction of immunity to antigens expressed by recombinant adeno-associated virus depends on the route of administration

Recombinant adeno-associated virus (rAAV) is a replication-defective parvovirus which is being explored as a vector for gene therapy because of its broad host range, excellent safety profile, and durable transgene expression in infected hosts. rAAV has also been reported by several groups to induce little or no immune response to its encoded transgene products. In this study we examined the immunogenicity of rAAV by studying the immune response of C57BL/6 mice to a single dose of rAAV-encoding ovalbumin (AAV-Ova) administered by a variety of routes. Mice injected with AAV-Ova intraperitoneally (ip), intravenously, or subcutaneously developed potent ovalbumin-specific cytotoxic T lymphocytes (CTL) as well as anti-ovalbumin antibodies and antibodies to AAV. In contrast, mice injected with AAV-Ova intramuscularly developed a humoral response to the virus and the transgene but minimal ovalbumin-specific CTLs. The induced CTL response after ip administration of AAV-Ova protected mice against a subsequent tumor challenge with an ovalbumin-transfected B16 melanoma cell line. Studies of the mechanism by which AAV-Ova induces CTL confirmed that the virus delivers the transgene product into the classical MHC class I pathway of antigen processing. Mice that previously had been exposed to rAAV vectors failed to develop ovalbumin-specific CTL following administration of AAV-Ova. Analysis of these mice revealed the presence of circulating anti-AAV antibodies that blocked rAAV transduction in vitro and inhibited CTL induction in vivo. These results suggest a possible role for rAAV in the immunotherapy of malignancies and viral infections, although induced antibody responses to AAV may limit its ability to be administered for repeated vaccinations.

Characterization of circulating T cells specific for tumor-associated antigens in melanoma patients

We identified circulating CD8+ T-cell populations specific for the tumor-associated antigens (TAAs) MART-1 (27-35) or tyrosinase (368-376) in six of eleven patients with metastatic melanoma using peptide/HLA-A*0201 tetramers. These TAA-specific populations were of two phenotypically distinct types: one, typical for memory/effector T cells; the other, a previously undescribed phenotype expressing both naive and effector cell markers. This latter type represented more than 2% of the total CD8+ T cells in one patient, permitting detailed phenotypic and functional analysis. Although these cells have many of the hallmarks of effector T cells, they were functionally unresponsive, unable to directly lyse melanoma target cells or produce cytokines in response to mitogens. In contrast, CD8+ T cells from the same patient were able to lyse EBV-pulsed target cells and showed robust allogeneic responses. Thus, the clonally expanded TAA-specific population seems to have been selectively rendered anergic in vivo. Peptide stimulation of the TAA-specific T-cell populations in other patients failed to induce substantial upregulation of CD69 expression, indicating that these cells may also have functional defects, leading to blunted activation responses. These data demonstrate that systemic TAA-specific T-cell responses can develop de novo in cancer patients, but that antigen-specific unresponsiveness may explain why such cells are unable to control tumor growth.

[Study on the status of methylation of Rb gene promoter in human esophageal cancer and effect of NMBzA on Rb gene promoter in monkey esophageal epithelium]

OBJECTIVE

To elucidate the cause of abnormal Rb expression in esophageal cancer (EC).

METHODS

Methylation of Rb gene promoter was examined with restriction endonuclease digestion and PCR amplification.

RESULTS

Of the 30 specimens of EC, 10 (33.3%) had Msp I type hypermethylation of the Rb gene promoter while 12 (40.0%) had Hpa II type hypermethylation and one had both type of hypermethylation. In monkey fed with a single dose of NMBzA (30 mg/kg) on day 0, increasing hypermethylation of both types of the Rb gene promoter in esophageal epithelium was found on day 1, 2 and 3 but reduced on day 5.

CONCLUSION

These data suggest that abnoromal expression of Rb gene may be related to hypermethylation of its promoter and carcinogen NMBzA can induce such hypermethylation in monkey esophageal epithelium.

Donor blood monocytes but not T or B cells facilitate long-term allograft survival after total lymphoid irradiation

BACKGROUND

Previous studies showed that a combination of posttransplant total lymphoid irradiation (TLI), rabbit antithymocyte globulin (ATG), and a single donor blood transfusion induced tolerance to ACI heart allografts in Lewis rats. All three modalities were required to achieve tolerance. The objective of the current study was to determine the subset(s) of cells in the donor blood that facilitated long-term allograft survival.

METHODS

Lewis hosts received TLI, ATG, and donor cell infusion after heart transplantation. Graft survival, mixed leukocyte reaction (MLR), and intragraft cytokine mRNA were studied.

RESULTS

The intravenous injection of 25 x 10(6) ACI peripheral blood mononuclear cells (PBMC) significantly prolonged graft survival as compared with that of Lewis hosts given TLI and ATG alone. Injection of highly enriched blood T cells or splenic B cells adjusted for the number contained in 25 x 10(6) PBMC failed to induce significant graft prolongation. Unexpectedly, depletion of monocytes (CD11b+ cells) from PBMC resulted in the loss of graft prolongation activity. Enriched populations of monocytes obtained by plastic adherence were more efficient in prolonging graft survival than PBMC on a per cell basis. Hosts with long-term grafts (>100-day survival) showed evidence of immune deviation, because the MLR to ACI stimulator cells was vigorous, but secretion of interferon-gamma in the MLR was markedly reduced. In situ hybridization studies of long-term grafts showed markedly reduced levels of interferon-gamma mRNA as compared with rejecting grafts.

CONCLUSION

Infusion of donor monocytes facilitated graft prolongation via immune deviation.

Induction of tissue-specific autoimmune prostatitis with prostatic acid phosphatase immunization: implications for immunotherapy of prostate cancer

Prostatic acid phosphatase (PAP) is uniquely expressed in prostatic tissue and prostate cancer. In this study, the immunogenicity of PAP was investigated in a male rat model. We show that immunization with recombinant rat or human PAP in CFA leads to a significant Ab response, but does not generate CTL or result in autoimmune prostatitis. In contrast, immunization with recombinant vaccinia expressing human PAP, but not rat PAP, generates a CTL response and tissue-specific prostatitis in the absence of detectable PAP-specific Abs. These findings suggest that a cellular immune response to PAP, rather than Abs, mediates destructive autoimmune prostatitis. Thus, xenogeneic forms of PAP are a new tool for the induction of prostate-specific immunity and may prove useful for the immunotherapy of prostate cancer.

Induction of tissue-specific autoimmune prostatitis with prostatic acid phosphatase immunization: implications for immunotherapy of prostate cancer

Prostatic acid phosphatase (PAP) is uniquely expressed in prostatic tissue and prostate cancer. In this study, the immunogenicity of PAP was investigated in a male rat model. We show that immunization with recombinant rat or human PAP in CFA leads to a significant Ab response, but does not generate CTL or result in autoimmune prostatitis. In contrast, immunization with recombinant vaccinia expressing human PAP, but not rat PAP, generates a CTL response and tissue-specific prostatitis in the absence of detectable PAP-specific Abs. These findings suggest that a cellular immune response to PAP, rather than Abs, mediates destructive autoimmune prostatitis. Thus, xenogeneic forms of PAP are a new tool for the induction of prostate-specific immunity and may prove useful for the immunotherapy of prostate cancer.

Introduction of soluble proteins into the MHC class I pathway by conjugation to an HIV tat peptide

Protection against most intracellular pathogens requires T cells that recognize pathogen-derived peptides in association with MHC class I molecules on the surface of infected cells. However, because exogenous proteins do not ordinarily enter the cytosol and access the MHC class I-processing pathway, protein-based vaccines that induce class I-restricted CTL responses have proved difficult to design. We have addressed this problem by conjugating proteins, such as OVA, to a short cationic peptide derived from HIV-1 tat (residues 49-57). When APC were exposed in vitro to such protein conjugates, they processed and presented the peptides in association with MHC class I molecules and stimulated CD8+ Ag-specific T cells. Moreover, Ag-specific CTLs were generated in vivo by immunizing mice with histocompatible dendritic cells that had been exposed to protein-tat conjugates.

Introduction of soluble proteins into the MHC class I pathway by conjugation to an HIV tat peptide

Protection against most intracellular pathogens requires T cells that recognize pathogen-derived peptides in association with MHC class I molecules on the surface of infected cells. However, because exogenous proteins do not ordinarily enter the cytosol and access the MHC class I-processing pathway, protein-based vaccines that induce class I-restricted CTL responses have proved difficult to design. We have addressed this problem by conjugating proteins, such as OVA, to a short cationic peptide derived from HIV-1 tat (residues 49-57). When APC were exposed in vitro to such protein conjugates, they processed and presented the peptides in association with MHC class I molecules and stimulated CD8+ Ag-specific T cells. Moreover, Ag-specific CTLs were generated in vivo by immunizing mice with histocompatible dendritic cells that had been exposed to protein-tat conjugates.

Overexpression of hormone-sensitive lipase in Chinese hamster ovary cells leads to abnormalities in cholesterol homeostasis

Hormone-sensitive lipase (HSL) is an intracellular enzyme that functions as both a neutral triglyceride and cholesteryl ester hydrolase. In order to explore the effects of HSL on cholesterol homeostasis, Chinese hamster ovary (CHO) cells were transfected with rat HSL and several different stable cell lines that overexpress HSL mRNA, HSL protein, and HSL activity approximately 600-fold were isolated. Cells transfected with HSL contained less cholesteryl esters and unesterified cholesterol than control cells. HSL transfectants expressed 20-60% fewer LDL receptors than control cells when grown in lipid-depleted media or in the presence of mevinolin, as assessed by binding and degradation of LDL and immunoblotting of LDL receptors. In contrast, the rate of cholesterol synthesis and the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase were increased 3- to 14-fold in HSL transfectants grown in sterol replete media. The rate of cholesterol synthesis and the activity of HMG-CoA reductase increased when cells were grown in lipid-depleted media, and remained markedly elevated compared to control cells. These results show that the regulation of LDL receptor expression and cholesterol synthesis can be dissociated through the actions of HSL and suggest multiple control mechanisms for sterol-responsive genes.

Experience of radiotherapy in lethal midline granuloma with special emphasis on centrofacial T-cell lymphoma: a retrospective analysis covering a 34-year period

Lethal midline granuloma (LMG) is characterized by progressive ulceration and destruction of the midfacial tissue. It occurs more frequently in Oriental than in Western populations. Because of the progress in clinical pathology and immunohistochemistry, most cases have been proven to be malignant lymphomas, especially of T-cell lineage. We describe 92 cases of lethal midline granuloma or centrofacial malignant lymphoma in the period 1959-1993. All received complete courses of radiotherapy. Twenty of them also received combination chemotherapy. Thirty-six cases had specimens available for immunohistochemical study; 25 (69%) of these had a T-cell phenotype, and 6 (17%) were of B-cell lineage. The dose to the nasal region was in the range of 3000-7500 cGy in 11-58 days, and to the neck 3000-6400 cGy in 11-48 days. The overall survival rate for the LMGs was 59.5% at 5 years and 56.2% at 10 years (Kaplan-Meier). Combined chemotherapy seemed not to improve the overall survival in this study (p = 0.63), but the patient number was too small to make a firm conclusion. Based on the results of this study, we recommend a dose of 4500-5000 cGy to the midfacial region, since a higher dosage did not improve the treatment results (p = 0.88). Irradiation has a definite role in good locoregional control of this disease. The recent clarification of the disease nature and the recognition of the background clinicopathological features should provide valuable information for future patient management and prospective studies.

Chromosome aberrations induced in human lymphocytes after partial-body irradiation

Chromosomal aberrations in peripheral blood lymphocytes obtained from two patients before and after they received one fraction of partial-body irradiation for palliative treatment were analyzed. Blood samples were taken 30 min and 24 h after radiation treatment. The yield of dicentrics obtained from case A 30 min after a partial-body (about 21%) treatment with 8 Gy was 0.066/cell, while the yield obtained 24 h after radiation treatment was 0.071/cell. The fraction of irradiated lymphocytes that reached metaphase at 52 h was 0.08 as evaluated by mixing cultures of in vitro irradiated and unirradiated blood. The yield of dicentrics for blood from case B 30 min after 6 Gy partial-body (about 24%) irradiation was 0.655/cell, while the yield 24 h after irradiation was 0.605/cell. The fraction of irradiated cells was 0.29. Estimation of doses and irradiated fractions for the two cases using the method proposed by Dolphin and the Qdr method is discussed. Although there was no significant difference between the mean yields of dicentrics per cell obtained 30 min and 24 h after radiation treatment, the data obtained at 24 h seemed more useful for the purpose of dose estimation. When a higher dose (8 Gy) was delivered to a smaller percentage of the body, underestimation of the dose was encountered.

Immunohistochemical analysis of in vivo patterns of Bcl-X expression

The in vivo patterns of bcl-X gene expression were assessed in human and mouse tissues using an immunohistochemical approach. Polyclonal antisera were raised against synthetic peptides corresponding to amino acids 46-66 and 61-79 of the human Bcl-X protein and were shown to be specific for detection of human and mouse Bcl-X-L and Bcl-X-S proteins by immunoblotting. Bcl-X immunoreactivity was detected in a wide variety of cell types and was typically present in the cytosol in a punctate pattern suggestive of association with intracellular organelles. Among the cell types with prominent Bcl-X immunostaining were: (a) a variety of neuronal populations in the brain as well as sensory neurons in dorsal root ganglia; (b) cortical (but not medullary) thymocytes and activated lymphocytes and plasma cells in lymph nodes; (c) several types of cells in the bone marrow, including megakaryocytes, red cell precursors, and some types of differentiating myeloid cells; (d) reproductive tissues, including the spermatocytes and spermatids in the testes and germinal epithelium of the ovary; and (e) a variety of epithelial cells including mammary epithelium, the secretory epithelial and basal cells of the prostate, uterine endometrium, gastric and intestinal epithelial cells, renal tubule epithelium, and differentiated keratinocytes in the upper layers of the epidermis but not in the basal cells. In many cases, these patterns of Bcl-X expression were strikingly different from those reported previously for Bcl-2, suggesting that Bcl-X and Bcl-2 regulate cell life and death at different stages of cell differentiation through tissue-specific control of their expression.

Interactions among members of the Bcl-2 protein family analyzed with a yeast two-hybrid system

Interactions of the Bcl-2 protein with itself and other members of the Bcl-2 family, including Bcl-X-L, Bcl-X-S, Mcl-1, and Bax, were explored with a yeast two-hybrid system. Fusion proteins were created by linking Bcl-2 family proteins to a LexA DNA-binding domain or a B42 trans-activation domain. Protein-protein interactions were examined by expression of these fusion proteins in Saccharomyces cerevisiae having a lacZ (beta-galactosidase) gene under control of a LexA-dependent operator. This approach gave evidence for Bcl-2 protein homodimerization. Bcl-2 also interacted with Bcl-X-L and Mcl-1 and with the dominant inhibitors Bax and Bcl-X-S. Bcl-X-L displayed the same pattern of combinatorial interactions with Bcl-2 family proteins as Bcl-2. Use of deletion mutants of Bcl-2 suggested that Bcl-2 homodimerization involves interactions between two distinct regions within the Bcl-2 protein, since a LexA protein containing Bcl-2 amino acids 83-218 mediated functional interactions with a B42 fusion protein containing Bcl-2 amino acids 1-81 but did not complement a B42 fusion protein containing Bcl-2 amino acids 83-218. In contrast to LexA/Bcl-2 fusion proteins, expression of a LexA/Bax protein was lethal to yeast. This cytotoxicity could be abrogated by B42 fusion proteins containing Bcl-2, Bcl-X-L, or Mcl-1 but not those containing Bcl-X-S (an alternatively spliced form of Bcl-X that lacks a well-conserved 63-amino acid region). The findings suggest a model whereby Bax and Bcl-X-S differentially regulate Bcl-2 function, and indicate that requirements for Bcl-2/Bax heterodimerization may be different from those for Bcl-2/Bcl-2 homodimerization.

Elevated 1,25-dihydroxyvitamin D levels in patients with chronic obstructive pulmonary disease treated with prednisone

Glucocorticoid administration is a well established cause of osteopenia. Mechanisms underlying the deleterious effect of glucocorticoids on bone may include direct inhibition of bone formation as well as indirect effects through changes in intestinal calcium absorption, renal calcium excretion, and/or levels of the calciotropic hormones. To further examine the potential role of the calciotropic hormones we measured serum levels of PTH and 1,25 dihydroxyvitamin D [1,25(OH)2D], as well as serum and urine levels of calcium and vertebral bone density in patients with chronic obstructive pulmonary disease being managed with or without prednisone. Patients treated with prednisone had lower spinal bone density (53 vs. 106 mg/cm3) and higher serum calcium (2.40 vs. 2.33 mmol/l), urine calcium (6.9 vs. 2.7 mmol/24h), and 1,25(OH)2D levels (147 vs. 95 pmol/L). Compared to the patients not treated with glucocorticoids. PTH levels also tended to be higher (33 vs. 26 microliters-eq/ml), but the difference was not significant. Serum and urine calcium levels correlated positively with 1,25(OH)2D levels, but none of these measurements correlated with PTH levels. Our results suggest that prednisone treatment alters the regulation of 1,25(OH)2D production, and this may contribute to the loss of bone mineral induced by prednisone.

Gastric and oesophageal carcinogenesis: models for the identification of risk and protective factors

Male weanling rats of the Charles River Sprague-Dawley strain were exposed to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in the water for 3 months at the concentration of 75 ml/litre. Other real or potential risk factors were administered, alone or in combination with MNNG. When MNNG was administered in combination with NaCl, bile acids, aspirin or BHA, forestomach tumours were enhanced. MNNG-induced tumours were inhibited by selenium or by difluoromethylornithine, an ornithine decarboxylase inhibitor. BHA alone caused forestomach tumours. When BHA was administered by dietary means or by gavage, alone or in combination with MNNG, the gavage method resulted in greater tumorigenesis than dietary exposure. This increase was associated with increased [3H]thymidine labelling of forestomach epithelium and increased hyperplasia. Oesophageal carcinogenesis induced by methylbenzylnitrosamine (MBN) was enhanced by zinc deficiency, alcohol and 13-cis-retinoic acid. Zinc deficiency also resulted in oesophageal tumours in rats exposed to the hepatocarcinogen dimethylnitrosamine. Riboflavin deficiency injured oral and oesophageal epithelium and increased sensitivity to MBN-induced oesophageal tumours.

II. In vitro restoration by levamisole of mitogen responsiveness in zinc-deprived rats

The effect of levamisole on the in vitro responses of splenic and peripheral blood lymphocytes to phytohemagglutinin were investigated in zinc-deprived and pair-fed control rats. The in vitro response of lymphocytes from zinc-deprived rats was markedly impaired in comparison with that of controls. The addition of levamisole to cultures of zinc-deprived splenic lymphocytes significantly improved their response to phytohemagglutinin by 54%. The addition of levamisole to cultures of zinc-deprived peripheral blood lymphocytes significantly improved their response by 116.2%. The addition of levamisole to control lymphocyte culture had no effect. This study may be the first to evaluate the beneficial effect of an immunomodulating agent on immune function in a nutritionally deprived host.

I. Depressed immunological function in zinc-deprived rats as measured by mitogen response of spleen, thymus, and peripheral blood

The in vitro responses of splenic, thymic, and peripheral blood lymphocytes to two T-cell mitogens (phytohemagglutinin and concanavalin A) and one B-cell mitogen (pokeweed mitogen) were investigated in zinc-deprived and pair-fed control rats. The responses to phytohemagglutinin of splenic, thymic, and peripheral blood lymphocytes from zinc-deprived animals were depressed by at least 50% in comparison with those of controls, and the difference between the two groups was significant for each tissue (P = 0.05). The responses to concanavalin A of splenic and peripheral blood lymphocytes were suppressed in zinc-deprived animals, and splenic and thymic responses to pokeweed mitogen were depressed by about 50% in comparison with those of controls; these results were significant at the P = 0.05 level. This study is the first to evaluate the effects of diet-induced zinc deprivation on lymphocyte transformation and immune function in rats.