Receptor-mediated modulation of human monocyte, neutrophil, lymphocyte, and platelet function by phorbol diesters.

The tumor promoting phorbol diesters elicit a variety of responses from normal and leukemic blood cells in vitro by apparently interacting with cellular receptors. The biologically active ligand [20-(3)H] phorbol 12,13-dibutyrate ([(3)H]PDBu) bound specifically to intact human lymphocytes, monocytes, polymorphonuclear leukocytes (PMN), and platelets, but not to erythrocytes. Binding, which was comparable for all four blood cell types, occurred rapidly at 23 degrees and 37 degrees C, reaching a maximum by 20-30 min usually followed by a 30-40% decrease in cell associated radioactivity over the next 30-60 min. The time course for binding was temperature dependent with equilibrium binding occurring after 120-150 min at 4 degrees C, with no subsequent loss of cell-associated radioactivity at this temperature. Bound [(3)H]PDBu could be eluted by addition of unlabeled PDBu. Scatchard analysis of data from 4 degrees C binding studies revealed linear plots with high affinity receptors in these cell types with dissociation constants and receptors per cell of 60 nM and 7.8 x 10(5)/cell for lymphocytes, 51 nM and 15.5 x 10(5)/cell for monocytes, 38 nM and 4.0 x 10(5)/cell for PMN, and 19 nM and 2.9 x 10(4)/cell for platelets. Structure-activity studies using unlabeled phorbol-related compounds demonstrated a close correlation between their abilities to inhibit binding of [(3)H]PDBu to cells and their abilities to induce cellular responses (monocyte and PMN H(2)O(2) secretion, lymphocyte (3)HTdR incorporation, and platelet tritiated serotonin release); phorbol and 4-alpha phorbol were inactive while phorbol 12-myristate 13-acetate (PMA), PDBu, mezerein, and phorbol 12,13-diacetate (in decreasing order of potency) inhibited [(3)H]PDBu binding and elicited the various responses. Thus, these high affinity, specific receptors for the phorbol diesters, present on monocytes, lymphocytes, PMN, and platelets, mediate the pleiotypic effects induced by these ligands.

Human leukemia cell lines with comparable receptor binding characteristics but different phenotypic responses to phorbol diesters.

Phorbol diester (PDE) tumor promoters have differing effects on normal and neoplastic hematopoietic cells in vitro. The effects of PDEs on cells are apparently mediated by specific cellular receptors for these ligands. The purpose of this study was to determine if the different phenotypic responses of cells of different human leukemia cell lines were due to differences in the PDE receptors in these cells. All cells of the different lines studied [HL-60 (promyelocytic), HL-60Bll (undifferentiated blastic), U-937 (monoblastic), H-SB2 (T-lymphoblastoid), and SB (B-lymphoblastoid) bound the [20-3H]phorbol-12,13-dibutyrate in a specific manner. The ligand bound to the cells rapidly, reaching a maximum by 10 to 20 min at 37 degrees or by 60 min at 4 degrees. The bound [20-3H]phorbol-12,13-dibutyrate could be fully dissociated from the cells by adding unlabeled phorbol-12,13-dibutyrate; the kinetics of this dissociation paralleled association kinetics. Scatchard analysis of the binding data, derived from experiments done at 4 degrees, revealed linear plots, indicating, most likely, that only single classes of receptors existed on all of these lines. The dissociation constants for binding were all comparable (46 to 152 nM), and the calculated numbers of binding sites were comparable (4.8 to 8.1 X 10(5)/cell). None of the cells could degrade [20-3H]phorbol-12-myristate-13-acetate or [20-3H]phorbol-12,13-dibutyrate as determined by thin-layer chromatographic analysis of cells or supernatants of the cell cultures. PDEs inhibited the proliferation of U-937 and HL-60 cells but not that of the HL-60Bll, SB, or H-SB2 cells. The incorporation of tritiated thymidine into HL-60 cells (but not HL-60Bll cells) was dramatically inhibited by various PDEs, and the potency in causing this inhibition paralleled that known for the potency of the phorbol analogues to cause tumor promotion in vivo or to elicit other in vitro responses from hematopoietic cells. [20-3H]Phorbol-12-myristate-13-acetate caused the HL-60 and U-937 cells to adhere to the plastic, spread, and develop vacuoles, but the other cells displayed no changes. These results suggest that the differing phenotypic responses to PDEs are most likely related to postreceptor factors.

Separate and interactive regulation of cytochrome P450 3A4 by triiodothyronine, dexamethasone, and growth hormone in cultured hepatocytes.

CYP3A4, the predominant cytochrome P450 expressed in human liver, is responsible for the metabolism of endogenous steroids and many drugs. On the basis of pharmacokinetic studies in patients with hormonal derangements and the effects of replacement therapy, it has been suggested that iodothyronines decrease CYP3A4-mediated drug metabolism, whereas glucocorticoids and GH enhance CYP3A4 activity. The aim of the present study, using well differentiated human hepatocytes in primary culture, was to examine directly whether hormonal factors regulate CYP3A4 gene expression. Addition of T3 to primary hepatocytes resulted in a marked reduction of CYP3A4-catalyzed testosterone 6 beta-hydroxylase activity and corresponding levels of CYP3A4 protein and messenger ribonucleic acid compared to those in untreated cells. Conversely, both dexamethasone and GH treatment substantially increased CYP3A4 gene expression. None of the hormones studied consistently altered the expression of other human cytochrome P450 genes. We conclude that iodothyronines, glucocorticoids, and GH act directly on human hepatocytes to regulate the expression of CYP3A4, and these effects appear to be exerted at a pretranslational level. Altered regulation of hepatic CYP3A4 is, therefore, likely to account for previous observations concerning the effects of endocrine diseases and hormonal treatments on human cytochrome P450-mediated drug and steroid metabolism.

Soya protein antibodies in man: their occurrence and possible relevance in coeliac disease.

Circulating antibodies to soya-derived protein antigens have been measured in patients with duodenitis, Crohn's disease, ulcerative colitis and coeliac disease. Significantly raised antibody titres were found frequently in the coeliac group, particularly those patients showing a suboptimal response to a gluten-free diet, but rarely in subjects with other gastrointestinal diseases. Antisoya activity was not necessarily accompanied by antibodies to other common dietary antigens. We suggest that some coeliacs may have an associated dietary soya sensitivity which could adversely influence their response to gluten withdrawal.

Spatiotemporal variation in a Lyme disease host and vector: black-legged ticks on white-footed mice.

We monitored population density of white-footed mice (Peromyscus leucopus), burdens of immature black-legged ticks (Ixodes scapularis) on mice, and infection prevalence of host-seeking ticks on six forest plots in southeastern New York State from 1995 through 1999. Despite densities of mice that fluctuated two orders of magnitude, average larval and nymphal tick burdens per mouse remained remarkably constant. Spatial variability in mouse density and tick burdens was modest. The total number of larval and nymphal ticks that fed on the mouse population each year depended strongly on population density of mice; a steady increase was observed in both mouse density and total tick meals on mice from 1996 through 1999. The result was a steady increase in the infection prevalence of nymphal and adult ticks with the etiological agent of Lyme disease, Borrelia burgdorferi, over this time. We suggest that fluctuations in population density of mice, combined with possible regulation of tick burdens on mice, may influence risk of human exposure to Lyme disease.

Painful palmar and plantar erythema associated with hepatic artery infusion of 5-fluoro-2'deoxyuridine.

Painful palmar and plantar erythema is an uncommon systemic complication of chemotherapy and has been reported in association with methotrexate, cystosine arabinoside, doxorubicin, and 5-fluorouracil. The authors report a case in which the syndrome was precipitated by hepatic artery infusion of 5-FUdR. The previous recommendation that treatment of patients developing painful palmar-plantar erythema from other drugs may be successfully resumed using intrahepatic arterial infusion of FUdR must be reconsidered in light of the present report.

Specific receptors for phorbol diesters on freshly isolated human myeloid and lymphoid leukemia cells: comparable binding characteristics despite different cellular responses.

Freshly isolated human leukemia cells have been shown in the past to display varying in vitro responses to phorbol diesters, depending on their cell type. Specific receptors for the phorbol diesters have been demonstrated on numerous different cells. This study was designed to characterize the receptors for phorbol diesters on leukemia cells freshly isolated from patients with different kinds of leukemia and to determine if differences in binding characteristics for tritium-labeled phorbol 12,13-dibutyrate (3H-PDBu) accounted for the different cellular responses elicited in vitro by phorbol diesters. Cells from 26 patients with different kinds of leukemia were studied. PDBu or phorbol 12-myristate 13-acetate (PMA) caused cells from patients with acute myeloblastic leukemia (AML), acute promyelocytic (APML), acute myelomonocytic (AMML), acute monocytic (AMoL), acute erythroleukemia (AEL), chronic myelocytic leukemia (CML) in blast crisis (myeloid), acute undifferentiated leukemia (AUL), and hairy cell leukemia (HCL) (n = 15) to adhere to plastic and spread. However, they caused no adherence or spreading and only slight aggregation of cells from patients with acute lymphocytic leukemia (ALL), chronic lymphocytic leukemia (CLL), or CML-blast crisis (lymphoid) (n = 11). All leukemia cells studied, irrespective of cellular type, displayed specific receptors for 3H-PDBu. The time courses for binding by all leukemia types were similar, with peak binding at 5-10 min at 37 degrees C and 120 min at 4 degrees C. The binding affinities were similar for patients with ALL (96 +/- 32 nM, n = 4), CLL (126 +/- 32 nM, n = 6), and acute nonlymphoid leukemia (73 +/- 14 nM, n = 11). Likewise, the numbers of specific binding sites/cell were comparable for the patients with ALL (6.2 +/- 1.3 X 10(5) sites/cell, n = 4), CLL (5.0 +/- 2.0 X 10(5) sites/cell, n = 6), and acute nonlymphoid leukemia (4.4 +/- 1.9 X 10(5) sites/cell, n = 11). Thus, the differing responses to phorbol diesters of various types of freshly isolated leukemia cells appear to be due to differences other than initial ligand-receptor binding.

A reversible enteropathy complicating continuous hepatic artery infusion chemotherapy with 5-fluoro-2-deoxyuridine.

This article describes two patients with hepatic metastases from colorectal cancer in whom a reversible enteropathy developed during the administration of hepatic artery infusion chemotherapy with 5-fluoro-2-deoxyuridine (5-FUdR) via an Infusaid Series 400 pump (Infusaid Corp., Sharon, MA). Both patients had severe diarrhea and signs that suggested small bowel obstruction. Barium studies revealed a distinctive radiologic appearance of severe narrowing of the ileum associated with complete loss of normal mucosal patterns. Results of an extensive evaluation for an infectious or toxin-related enterocolitis were negative. Perfusion studies confirmed the appropriate position of the catheters and revealed no extrahepatic perfusion. Systemic shunting of the 5-FUdR through the liver or tumor bed is postulated as the primary event, with the small bowel manifesting the major toxicity.