Pharmacokinetics and pharmacodynamics of recombinant FGF-2 in a phase I trial in coronary artery disease

Fibroblast growth factor-2 (FGF-2) is a heparin-binding protein capable of inducing angiogenesis in multiple animal models of chronic ischemia. The pharmacokinetics and pharmacodynamics of a single dose of recombinant FGF-2 (rFGF-2) administered by intracoronary or intravenous infusion were evaluated in a Phase I trial in 66 patients with severe coronary artery disease. rFGF-2 displayed biphasic elimination with a mean studywide distribution t1/2 of 21 minutes and a mean apparent terminal elimination t1/2 of 7.6 hours. Systemic exposure to rFGF-2 was comparable following intracoronary or intravenous administration. Peak plasma concentration and area under the concentration-time curve increased proportionally with dose, indicating linear pharmacokinetics over the dose range examined (0.33 to 48.0 micrograms/kg). Greater systemic exposure was observed when heparin was administered closer to rFGF-2 infusion, consistent with slower clearance of heparin/rFGF-2 complexes. Infusion of rFGF-2 was associated with changes in acute hemodynamics. While a clear PK/PD dose-response relationship was not established, a trend toward hypotension and tachycardia with higher rFGF-2 doses was observed.

Comparative skin phototoxicity in mice with two photosensitizing drugs: benzoporphyrin derivative monoacid ring A and porfimer sodium (Photofrin)

Benzoporphyrin derivative monoacid ring A (BPD-MA) and Photofrin (porfimer sodium) are photodynamic anticancer agents. The chemical structures of the two regioisomers of BPD-MA are 9-methyl trans-(+/-)-18-ethenyl-4,4 alpha-dihydro-3,4- bis(methoxycarbonyl)-4 alpha, 8,14,19-tetramethyl-4,4 alpha-dihydro-3,4- bis(methoxycarbonyl)-4 alpha, 8,14,19-tetramethyl-23H,25H-benzo(b)porphine- 9,13-dipropanoate and 13-methyl-trans-(+/-)-18-ethenyl-4,4 alpha-dihydro-3,4- bis(methoxycarbonyl)-4 alpha, 8,14,19-tetramethyl-23H,25H-benzo(b)porphine- 9,13-dipropanoate. Photofrin (a registered trademark of American Cyanamid Co.) is a polyporphrin oligomer containing ester and ether linkages. The ability of BPD-MA or Photofrin to cause skin phototoxicity was investigated in mice exposed to simulated sunlight (light) 3, 24, or 48 hr after receiving a single intravenous injection of vehicle or 2, 10, or 20 mg/kg of BPD-MA or Photofrin. The data were from two studies conducted using male and female CD1 mice (approximately 7 weeks old). The hair of the dorsal thoracic area was clipped 24 hr prior to exposure to light. Mice were exposed to light for 5 min. The clipped area of skin was the primary site for the evaluation of phototoxicity. Mice were observed for 2 weeks after treatment. There were no significant findings in controls or in mice given 2 mg/kg of BPD-MA. When mice were exposed to light 3 hr after dosing, both BPD-MA (10 or 20 mg/kg) and Photofrin (2, 10 or 20 mg/kg) caused phototoxicity. Death occurred in all mice given 20 mg/kg of BPD-MA or Photofrin, and in the majority of mice given 10 mg/kg of Photofrin.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow cytometric analysis of xenobiotic metabolism activity in isolated rat hepatocytes

Flow cytometry offers great potential for the study of xenobiotic metabolism in intact cells. We explored this application by the use of ethoxyfluorescein ethyl ester (EFEE) and isolated rat hepatocytes, a classic system for studying such reactions. EFEE is only weakly fluorescent and it diffuses freely into viable cells, where it is metabolized to fluorescein by a process dependent upon mixed-function oxidase activity. In the current study, viable hepatocytes were first identified by flow cytometric assessment of fluorescein diacetate staining. The viable subpopulation was also identifiable on the basis of forward and right angle light scattering properties alone, and it was in this fraction that EFEE metabolism was measured. Metabolism of EFEE to fluorescein was quantified by flow cytometry. SKF 525A, alpha-naphthoflavone, and metyrapone, classic inhibitors of mixed-function oxidation, each inhibited the metabolism of EFEE. These results demonstrate the potential of EFEE for use in flow cytometric studies of drug metabolism, such as in multiparameter mechanistic assays of cellular xenobiotic metabolism and toxicity, and in the isolation by fluorescence-activated cell sorting of subpopulations which differ in this activity.

Adhesion and proliferation are enhanced in vitro in Schwann cells from nerve undergoing Wallerian degeneration

Proliferation of Schwann cells during nerve degeneration or regeneration is well documented in vivo. We investigated whether the proliferative response of Schwann cells to injury is retained in vitro. Using 5-month-old male C57BL mice, Schwann cells were isolated from sciatic nerves under 3 experimental conditions: (1) uninjured, (2) after permanent nerve-transection, or (3) after nerve-crush, which permits axonal regeneration. Schwann cells rarely attached to polylysine-coated coverslips when isolated from uninjured or 1 day posttransection/crush nerves. The number of adherent cells increased when Schwann cells were isolated 3 days after nerve-transection or -crush. When cells were isolated from transected nerves, cell adhesion reached a peak 2 weeks after the injury and then declined. Maximal attachment of Schwann cells occurred when the cells were isolated 2-4 weeks after nerve-crush. The percentage of Schwann cells with spreading processes corresponded closely with the number of thymidine-labeled cells at 1 day in vitro. The in vitro capacity of cells to spread and incorporate thymidine reached maximal levels at 5 days posttransection/crush. Capacity of cells to spread and incorporate thymidine subsequently decreased with time following transection. However, a biphasic elevation in cell spreading and thymidine incorporation was observed in Schwann cells isolated from crushed nerves. Maximal growth of Schwann cells in vitro occurred at 1-2 weeks posttransection and at 1-4 weeks postcrush. Adhesion and spreading of Schwann cells were promoted by coating coverslips with laminin or fibronectin. Preincubation of Schwann cells with soluble laminin or fibronectin prevented the initial cell attachment induced by the corresponding protein. Our results suggest that Schwann cells from injured nerves possess binding sites for laminin and fibronectin, which are, in part, responsible for the enhanced adhesion of Schwann cells in vitro. This study provides a new method for preparation of Schwann cells from peripheral nerves of adult mice.

Lipid metabolism during early stages of Wallerian degeneration in the rat sciatic nerve

We examined changes in biosynthetic capacity of sciatic nerve during the early stages of Wallerian degeneration, utilizing a model that permits exclusion of nonresident cells from degenerating nerve. Sciatic nerve segments were placed in either 5-microns pore (allowing infiltration of nonresident cells) or 0.22-microns pore (excluding nonresident cells) Millipore diffusion chambers and then implanted in the peritoneal cavity of the same 32-34-day-old rat. At times up to 7 days postsurgery, nerve segments from the chambers, as well as control segments from the contralateral sciatic nerve, were removed and their capacity to incorporate radioactive precursors into lipids and proteins assayed in vitro. In nerve segments from both the 0.22- and 5-microns pore chambers, incorporation of [14C]acetate into total lipids was decreased relative to control by 50% at 12 h postsurgery and by 85% at day 3. This decreased incorporation of [14C]acetate reflects primarily decreased de novo synthesis of cholesterol and of fatty acyl residues incorporated into glycerolipids and sphingolipids. There was a preferentially decreased synthesis of cerebrosides and cholesterol (components enriched in myelin) relative to other lipids, while cholesterol esters and free fatty acids (products of membrane degradation) accounted for a greater proportion of the greatly reduced levels of total lipid label. In contrast to [14C]acetate, incorporation of [3H]glycerol into lipids was increased up to fourfold, relative to control, 1 day after nerve transection.(ABSTRACT TRUNCATED AT 250 WORDS)

Macrophage-like cells from explant cultures of rat sciatic nerve produce apolipoprotein E

Apolipoprotein E is synthesized and secreted by degenerating peripheral nerve, but the role of resident endoneurial cells in this process is not clear. To exclude the involvement of nonresident cells, we examined the cellular source of endoneurial apolipoprotein E in explant cultures of rat sciatic nerve. The cellular outgrowth from these explant cultures released apolipoprotein E into the culture medium. The cellular outgrowth contained fibroblasts, Schwann cells, and a population of cells with many phenotypic characteristics of macrophages, including the production of apolipoprotein E. No other cell type in the cultures appeared to contribute to this production. These data suggest that apolipoprotein E is produced by resident endoneurial cells in explant cultures and that these cells are macrophages.

Mechanisms of rodent liver carcinogenesis

Stimulation of DNA synthesis by peroxisome proliferators, including DEHP, should be viewed differently from the stimulation of DNA synthesis by xenobiotic chemicals which stimulate restorative hyperplasia after hepatic necrosis induced by the toxicity of the chemical. The emerging picture of the control mechanisms for hepatocyte proliferation suggests that rather few and distinct factors are involved. The stimulation of DNA synthesis by peroxisome proliferators should be examined in the context of the effects of these factors. Comparisons with other xenobiotics show that induction of DNA synthesis at rates comparable to those of peroxisome proliferators is not sufficient to explain the rates of carcinogenicity associated with peroxisome proliferators. These considerations lead to the conclusion that although DNA synthesis enhances the incidence of neoplasia, it should not be viewed as a complete carcinogen, nor should it be considered as resulting in initiation at rates that can explain the carcinogenic potency of compounds such as peroxisome proliferators.

In vitro colonization ability appears soon after initiation of hepatocarcinogenesis in the rat

Hepatocytes were isolated from rat livers at various intervals after initiating hepatocarcinogenesis by a single administration of methyl(acetoxymethyl)nitrosamine after a partial hepatectomy. Proliferative hepatocyte colonies were regularly observed in primary cultures derived from initiated livers when these cultures were incubated in medium containing the liver tumor promoter, phenobarbital. Fewer colonies generally were observed in initiated cell cultures that were incubated without phenobarbital and in phenobarbital-induced cultures derived from non-initiated control livers. Because in vitro proliferative activity is a characteristic of malignant hepatocytes these results suggest that the feature of in vitro colonization may characterize a population of carcinogen-altered hepatocytes.

Promoting effect of nicotinamide on the development of renal tubular cell tumors in rats initiated with diethylnitrosamine

Nicotinamide administered in the drinking water of male Fischer 344 rats increased the number of renal tubular cell tumors of rats treated with an i.p. injection of diethylnitrosamine (DEN) (25-mg/kg body weight). The incidence of kidneys with tumors in rats treated with DEN alone was 5%. In rats which received DEN and then were promoted with either 30 or 6.7 mM nicotinamide in their drinking water, the incidence of kidneys with tumors rose to 59 and 28%, respectively. Rats which were on 30 mM nicotinamide but did not receive DEN had no kidney tumors present. These results show that nicotinamide promoted DEN-induced renal tubular cell tumorigenesis.

Inhibition of DNA synthesis by chemical carcinogens in cultures of initiated and normal proliferating rat hepatocytes

Rat hepatocytes in primary culture can be stimulated to replicate under the influence of rat serum and sparse plating conditions. Higher replication rates are induced by serum from two-thirds partially hepatectomized rats (Michalopoulos, G., Cianciulli, H. D., Novotny, A. R., Kligerman, A. D., Strom, S. C., and Jirtle, R. L. Cancer Res., 42: 4673-4682, 1982). The effects of carcinogens and noncarcinogens on the ability of hepatocytes to synthesize DNA were examined by measuring the incorporation of [3H]thymidine by liquid scintillation counting and autoradiography. Hepatocyte DNA synthesis was not decreased by ethanol or dimethyl sulfoxide at concentrations less than 0.5%. No effect was observed when 0.1 mM ketamine, Nembutal, hypoxanthine, sucrose, ascorbic acid, or benzo(e)pyrene was added to cultures of replicating hepatocytes. Estrogen, testosterone, tryptophan, and vitamin E inhibited DNA synthesis by approximately 50% at 0.1 mM, a concentration at which toxicity was noticeable. Several carcinogens requiring metabolic activation as well as the direct-acting carcinogen N-methyl-N'-nitro-N-nitrosoguanidine interfered with DNA synthesis. Aflatoxin B1 inhibited DNA synthesis by 50% (ID50) at concentrations between 1 X 10(-8) and 1 X 10(-7) M. The ID50 for 2-acetylaminofluorene was between 1 X 10(-7) and 1 X 10(-6) M. Benzo(a)pyrene and 3'-methyl-4-dimethylaminoazobenzene inhibited DNA synthesis 50% between 1 X 10(-5) and 1 X 10(-4) M. Diethylnitrosamine and dimethylnitrosamine (ID50 between 1 X 10(-4) and 5 X 10(-4) M) and 1- and 2-naphthylamine (ID50 between 1 X 10(-5) and 5 X 10(-4) M) caused inhibition of DNA synthesis at concentrations which overlapped with concentrations that caused measurable toxicity. The ability of hepatocytes to activate 2-acetylaminofluorene to reactive intermediates capable of binding to DNA and inhibiting new DNA synthesis decreased as a function of time in culture. gamma-Glutamyl-transferase-positive hepatocytes from diethylnitrosamine-treated rats were observed to be relatively insensitive to carcinogen inhibition of DNA synthesis.

Establishment of two rat hepatoma cell strains produced by a carcinogen initiation, phenobarbital promotion protocol

Two Fischer 344 rat hepatoma cell strains, JM1 and JM2, have been isolated from a primary hepatocellular carcinoma. Primary tumor formation was induced in a two-thirds partially hepatectomized rat by a single low dose (70 mg/kg of diethylnitrosamine followed by chronic phenobarbital administration (0.1 g/100 ml drinking water). The primary tumors were passed three times by subcutaneous implantation of tumor fragments into the inguinal region of syngeneic recipients. The fourth pass was by injection of tumor cells directly into the livers of recipient rats. Several weeks later, the tumor-containing rat livers were subjected to collagenase perfusion. Two cell lines emerged from tissue culture of the cells isolated by perfusion. Each cell line was cloned by serial dilution. Cells JM1 and JM2 were tumorigenic when injected into syngeneic rats. The tumors, which arose from injected cell strains, exhibited several characteristics of hepatocellular carcinoma. Morphology was examined by light and electron microscopy. Histochemical studies of JM1 and JM2 cells grown in vitro and in vivo were done. The levels of tyrosine aminotransferase and three microsomal enzymes of importance to drug and carcinogen metabolism were investigated. To our knowledge, this is the first report of cell strains derived from an initiation promotion protocol in rats.

Human hepatocyte-mediated mutagenesis and DNA repair activity

Combined cultures of human hepatocytes and human fibroblasts constitute a system composed entirely of normal human cells that can be used to investigate the mutagenicity of chemicals requiring metabolic activation. Addition of diethylnitrosamine (DEN) to this system resulted in mutations at the hypoxanthine-guanine phosphoribosyltransferase locus of the human fibroblasts. In separate experiments with cultures of hepatocytes alone, DEN induced unscheduled DNA synthesis (UDS) in the human hepatocytes. A comparative analysis of UDS and hepatocyte-mediated mutagensis indicates a great degree of similarity between the human and previously studied rat hepatocytes in their response to DEN in vitro.

Isolation, culture, and transplantation of human hepatocytes

The in situ two-step collagenase perfusion technique used for the isolation of hepatocytes from rat liver was adapted into a procedure applicable to pieces of human liver obtainable from surgical procedures. Human hepatocytes obtained by this method were maintained in primary culture for 10 days. The cellular changes observed at the light microscopic and electron microscopic levels are described. The changes in microsomal enzymes as a function of the age of the cultures were also measured. Exposure of the human hepatocytes to procarcinogens known to be metabolized by rodent liver resulted in unscheduled DNA synthesis. The isolated hepatocytes were also transplanted into two-thirds partially hepatectomized athymic nude mice. The transplanted cells formed nodules with characteristic hepatic architecture. These studies demonstrate that hepatocytes obtained from human liver by the described modified collagenase technique can be used for in vitro studies in chemical carcinogenesis.

Cryopreservation of isolated rat hepatocytes

Isolated parenchymal hepatocytes from adult rats were frozen in media containing 10% glycerol, 10% dimethylsulfoxide (DMSO), 20% DMSO. Thus microsome-associated functions were compared in nonfrozen cells and cells frozen in each of the above cryoprotectant solutions. Freezing in DMSO maintains cytochromes P-450 and b5 and NADPH-cytochrome C reductase at levels nearer to control values than does freezing in glycerol. Cells frozen and subsequently thawed and cultured for 24 h lose a greater amount of cytochrome P-450 than do nonfrozen cultured cells. The levels of cytochrome b5 and reductase in frozen-thawed cells remain close to control values. Cell viability (trypan blue dye exclusion and percentage of attached cells) after freezing is maintained better using DMSO as a cryoprotectant. Dimethylsulfoxide protects the hepatocytes from freeze-induced damage to the extent that many viable cells attach to collagen-coated petri dishes, survive for at least 24 h, and still maintain significant levels of enzymes of importance to drug and carcinogen metabolism.

Mutagenesis induced by procarcinogens at the hypoxanthine-guanine phosphoribosyl transferase locus of human fibroblasts cocultured with rat hepatocytes

The addition of diethylnitrosamine or cyclophosphamide in cultures of hepatocytes overlaid on confluent diploid human fibroblasts resulted in a dose-dependent increase in the frequency of hypoxanthine-guanine phosphoribosyl transferase human fibroblast mutants with both chemicals. Different toxicity patterns for the two cell types were seen. Diethylnitrosamine was more toxic to the hepatocytes, whereas cyclophosphamide was more toxic to the fibroblasts. These data open the possibility of using strains of human fibroblasts as in vitro screens for mutagenicity of procarcinogens.