Intimal hyperplasia after balloon injury is attenuated by blocking selectins.

BACKGROUND: Cell adhesion molecules facilitate the adherence of platelets and leukocytes to the vascular endothelium in response to injury. Restenosis after balloon angioplasty is thought to represent the response to vascular injury. The role of cell adhesion in this process is unclear. METHODS AND RESULTS: This study was performed in New Zealand White rabbits that underwent balloon angioplasty of the iliac artery. Expression of the cell adhesion molecule E-selectin on endothelium was determined by immunohistochemistry and increased at 6 hours with a peak expression 24 to 48 hours after balloon injury, returning to baseline by 1 week. The expression of L-selectin on circulating leukocytes, measured by flow cytometry, was significantly increased at 48 hours, with return to baseline by 1 week. In seven animals, the selectins were blocked with an analogue of sialyl-Lewis(x) given as an I.V. bolus of 10 mg/kg followed by 2 mg x kg(-1) x h(-1) I.P. infusion for 7 days. After 4 weeks, compared with control animals, the study group had a larger lumen area (57.7 versus 44.7 mm2, P<.05), smaller intima area (9.0 versus 19.2 mm2, P<.01), smaller intima/media ratio (0.4 versus 1.0, P<.01), and a smaller percent area stenosis (15.6% versus 34.3%, P<.01). CONCLUSIONS: The cell adhesion molecules E-selectin and L-selectin are expressed after balloon injury. Blockade of the selectins has a favorable effect on the response to vascular injury.

Phenotypic instability of Salmonella strain YG1024 during mutagenicity assays of arylamine promutagens.

During spot tests using Salmonella TA98 derivatives (YG1021, YG1024) and TA100 derivatives (YG1026, YG1029), a unique response of O-acetyltransferase (OAT)-enhanced strains YG1024 and YG1029 to arylamines was observed. On plates containing rat-liver S9, these strains yielded revertant colonies induced in two separate concentric rings around the site of application, while the parent (TA98, TA100) and nitroreductase-enhanced strains (YG1021, YG1026) did not exhibit this response. The inner ring of revertants was accompanied by cytotoxicity and microcolony formation, with the outer ring in a region without background lawn toxicity. Addition of tetracycline to the top agar eliminated formation of the inner ring of YG1024 revertants in spot tests and reduced the revertant count in preincubation assays at cytotoxic dose levels of 2-aminoanthracene, 2-aminofluorene, 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline. Tetracycline sensitivity indicates that mutant colonies developing at high concentration/toxicity arose, in effect, from TA98 regenerated by functional loss of the tetracycline-resistance plasmid (pYG219) from YG1024. Mutant colonies found at low concentration/toxicity arose from normal plasmid-bearing YG1024. These results indicate the need to consider coincidental toxicity-induced instability in YG1024 during quantitative mutagenicity assays of arylamines and uncharacterized complex mixtures.

In vitro chromosome aberration assay of formulated recombinant human granulocyte-macrophage colony-stimulating factor in human peripheral blood lymphocytes.

The clastogenic potential of a recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) therapeutic protein formulation was assessed in human peripheral blood lymphocyte (HPBL) cultures. Final formulation, rather than pure protein, was evaluated to simulate exposure conditions encountered in man. Because the formulation excipients (citric acid, sodium phosphate, mannitol, human serum albumin and polyethylene glycol) were found to alter cell-cycle kinetics and interfere with S-9 metabolic activation in vitro, a novel testing sequence and protocol were used to distinguish between rhGM-CSF and excipient effects and to guard against false negative results. Initial trials were performed to establish the volume of formulation alone (with and without rhGM-CSF) that would not cause severe cell-cycle delay, interfere with S-9 metabolic activation or inhibit positive control responses. This maximum tolerated volume of formulation was then incorporated in all dosed and control groups of each respective assay phase to give the same extent of cell-cycle delay. In the main assay, 24-hr HPBL cultures were exposed to dose levels of 0, 50, 100, 200 and 350 mug rhGM-CSF/ml for 24 hr in -S-9 phases and 0, 200, 350, 500 and 650 mug/ml for 2 hr in +S-9 phases, and harvested 24 hr later. No significant increases in the percentage of cells with structural chromosomal aberrations were found in either test phase. These results show that rhGM-CSF is not clastogenic in HPBL at greater than 17,000 times human exposure levels, and demonstrate that valid cytogenetic assay data with formulations containing cytotoxic excipient can be obtained in vitro.

Nonmutagenicity of maleic acid and its sodium salts in salmonella assays.

Maleic acid (cis-butenedioic acid) and its mono- and disodium salts are shown to be non-mutagenic in the standard Ames Salmonella/mammalian microsome assay in the absence and presence of Aroclor-1254-induced rat liver S9. This lack of activity occurred despite depression of top agar pH in accordance with the degree of protonation of this polybasic acid. These results indicate that when chemical compounds which are maleate salts show activity in this assay, the effect is attributable to the base moiety rather than maleate or pH depression per se.

The neurotoxicity of cyclotrimethylenetrinitramine (RDX) in a child: a clinical and pharmacokinetic evaluation.

Cyclotrimethylenetrinitramine (RDX) is a highly explosive compound frequently used for both military and civilian purposes. Previously reported cases of human RDX intoxication were limited to wartime settings and have described no human pharmacokinetic data. We report the first human intoxication to occur in a non-wartime setting. This intoxication presented with status epilepticus in a child and permitted the description of RDX human pharmacokinetics. It also suggested a strong association between central nervous system dysfunction and RDX intoxication.

Absence of in vitro genotoxicity of pyrvinium pamoate in sister-chromatid exchange, chromosome aberration, and HGPRT-locus mutation bioassays.

A single preparation of U.S.P. pyrvinium pamoate that exhibited promutagen activity in Salmonella/mammalian microsome reverse mutation assays was subjected to in vitro mammalian cell bioassays. Cytotoxicity limiting doses of dimethyl sulfoxide-solubilized drug were without effect in the absence and/or presence of liver S9 fraction from Aroclor-1254-induced rats in an in vitro Chinese hamster ovary (CHO) cell assay for chromosome aberration and sister-chromatid exchange induction at concentrations of 0.025-0.78 microgram/ml. Forward gene mutation at the hypoxanthine-guanine phosphoribosyl-transferase (HGPRT) locus in Chinese hamster (V-79) cells was studied with and without exogenous metabolic activation at concentrations ranging from 0.3 to 10 micrograms/ml. In concurrent promutagen controls, dimethylnitrosamine, benzo[a]pyrene, and cyclophosphamide caused significant (p less than 0.05) increases over controls in each respective assay endpoint under the metabolic activations used. These results suggest that intrinsic mutagenic activity manifested in lower microbial systems does not have a corresponding effect in mammalian cells. Coupled with the lack of solubility and poor absorption in vivo, we concluded that the drug, when used In the single oral dose mode of administration, possesses a negligible somatic and germinal genotoxicity risk.

Carcinogen bioassay and mutagenicity studies with the hypolipidemic agent gemfibrozil.

Gemfibrozil, a novel hypolipidemic agent identified chemically as 2,2-dimethyl-5-(2,5-xylyoxy) valeric acid, was evaluated for mutagenic potential in in vitro assays with Salmonella typhimurium. For evaluation of tumorigenic potential, gemfibrozil was administered in the diet (0.30, and 300 mg gemfibrozil/kg) to groups of noninbred CD-1 mice (72/sex) and noninbred CD rats (50/sex) for 78 and 104 weeks, respectively. In the bacterial mutagenesis assays, between 100 and 2,500 microgram gemfibrozil/plate failed to induce a significant increase in revertant bacterial colonies. Neither was a mutagenic response in bacterial assays induced at concentrations up to 300 microgram of five in vivo metabolites of gemifibrozil isolated from rat urine/plate. In mice, gemfibrozil did not significantly increase the frequency or the mean latency period of tumors. In rats, the statistically significant increases in hepatocellular tumors and interstitial cell tumors of the testes were dose related. Adrenal medullary and pancreatic acinar tumors were increased in male rats but were inversely dose related. Under the conditions of this assay, gemfibrozil did not elicit a tumorigenic potential in mice and female rats. In male rats and related to the hepatocellular tumor response, the peroxisome proliferation seen did not occur in humans chronically administered hypolipidemics.

Chemical carcinogen induction of DNA-repair synthesis in human peripheral blood monocytes.

Fresh ex vivo cultures of normal human peripheral blood monocytes, which are nonreplicative and known to possess cytochrome P-450 associated mixed-function oxidase activity, were used to assay DNA-excision repair manifested as augmented [3H]thymidine (dThd) incorporation following treatment in culture with diverse mutagenic carcinogens. Untreated monocyte cultures established from pools of 3-6 normal donors incorporated a low level of cytoplasmic [3H]dThd throughout a majority of the cells during an 18-h incubation. This background incorporation into whole cells was 80-90% inhibited by hydroxyurea (HU) at concentrations greater than 5 mM. Dose-related increases in the cumulative 18-h [3H]dThd incorporation in monocytes were observed following treatment with UV, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), methyl methanesulfonate (MMS), mitomycin C (MMC), N-acetoxy-acetylaminofluorene (NA-AAF), aflatoxin B1 (AFB1), benzo[a]pyrene (BaP), and dimethylnitrosamine (DMN). The presence of HU during chemical treatment and throughout this 18 h of incubation with [3H]dThd did not influence the dose-response curves obtained with UV, MMS, NA-AAF and BaP but it increased the input dose of MNNG, MMC, DMN and AFB1 required to give peak repair incorporation. When HU was added to cultures following MNNG damage no interference with repair response was observed. HU apparently influences the extent of DNA damage by direct reactivity with these chemicals or their endogenously generated metabolites rather than inhibiting DNA-repair processes. These results provide evidence that monocytes are enzymatically proficient in base and nucleotide excision pathways and have endogenous capacity to metabolize BaP, AFB1 and DMN to DNA-damaging metabolites. As such, the monocyte is a potentially useful human cell type for detecting genotoxic chemicals and studying individuality in chemical-biological interactions.

Limitations of metabolic activation systems used with in vitro tests for carcinogens.

Important differences between the metabolic activation of 7,12-dimethylbenz[a]anthracene in intact cellular systems and in liver homogenates suggest that the use of homogenates in conjunction with short-term assays for carcinogens could yield misleading results.

Heteroploid conversion of human skin cells by methylcholanthrene.

Cultured epithelial cells from human skin generally had 3- to 30-fold more hydrocarbon-metabolizing activity than fibroblasts from skin of the same donor. This activity was constant for up to 55 days in primary culture but was lost rapidly upon physical subdivision of the cultures. Treatment of primary mixed fibroblasts and epithelial cell cultures with methylcholanthrene, but not phenanthrene, led to development of actively growing fibroblastic cultures with many heteroploid cells. Unique marker chromosomes, stable over a number of cell population doublings, were identified in several of the heteroploid cell strains. Pure cultures of fibroblasts from the same donors did not undergo heteroploid conversion in response to methylcholanthrene. Spontaneously occurring heteroploidy in logarithmic phase human fibroblasts is a rare event; thus, heteroploid conversion may be a useful marker for chemical transformation of human cells. Because methylcholanthrene seems to have little transforming effect on human skin fibroblasts, human skin epithelial cells, because of their hydrocarbon-metabolizing activity, may serve to convert methylcholanthrene from a distal to an ultimate carcinogenic form.

Further characterization of the F1-histone phosphokinase of metaphase-arrested animal cells.

Exponentially growing Chinese hamster cells are found to contain two major phosphokinase activities with specificity for the phosphorylation of F1 (lysine-rich) histone. These two activities, designated KI and KII, were extracted with 0.35 M NaCl and fractionated in 0.2 M NaCl by Sephadex G-200 gel filtration. KI, which is similar to the ubiquitous cyclic 3',5'-adenosine monophosphate (cAMP)-dependent phosphokinase, differs from KII by several criteria. KII is mol wt 90,000, cAMP independent, rapidly turned over in vivo, low K(m) for ATP, and phosphorylates F1 histone at several unique sites. Comparative examination of metaphase-arrested (M) and counterpart interphase (I) cells for these two activities reveals that KII is responsible for the overall high activity in M-arrested cells. Pulse labeling of cells with (32)P during traverse of the G(2)-M phase of the cell cycle reveals an in vivo tryptic-phosphopeptide pattern in whole unfractionated F1 which is unique to M cells. Seven major phosphopeptides derived by in vitro phosphorylation of F1 with the KII enzyme correspond to these M cell-specific phosphorylation sites observed in vivo. It is suggested that KII activity predominates during the G(2)-M transition and that F1 is its natural in vivo substrate.