Subacute toxicity assessment of diflubenzuron, an insect growth regulator, in adult male rats

Diflubenzuron (DFB), an insecticide and acaricide insect growth regulator, can be used in agriculture against insect predators and in public health programs, to control insects and vectors, mainly Aedes aegypti larvae. Due to the lack of toxicological assessments of this compound, the objective of the present study was to evaluate the toxicological effects of subacute exposure to the DFB insecticide in adult male rats. Adult male rats were exposed (gavage) to 0, 2, 4, or 8 mg/kg of DFB for 28 days. No clinical signs of toxicity were observed in the DFB-treated animals of the experimental groups. However, there was an increase in serum levels of alanine aminotransferase in the group that received 8 mg/kg/DFB/day and urea at doses of 4 and 8 mg/kg/DFB/day, without altering other biochemical or hematological parameters. The subacute exposure to the lowest dose of DFB caused significant decrease in testis weight, daily sperm production, and in number of sperm in the epididymis in relation to the control group. However, no alterations were observed in the sperm morphology, testicular, epididymis, liver and kidney histology, or testosterone levels. These findings unveiled the hazardous effects of DFB on male reproduction after the subacute exposure and special attention should be addressed to the effects of low doses of this pesticide.

Molecular mechanism of mutagenesis induced by olaquindox using a shuttle vector pSP189/mammalian cell system

Olaquindox, a quinoxaline 1,4-dioxide derivative from quindoxin, is widely used as an animal growth promoter in China. We tested olaquindox as a mutagen in a SV40-based shuttle vector pSP189 and African green kidney cell (Vero E6 cell line) system to define the safety of olaquindox as a food-additive for animals. When applied at 6.6 microg/ml, olaquindox caused 12 times higher mutation frequency in comparison to untreated controls. More than 70% of base substitutions happened at G:C base pairs featuring G:C to T:A or G:C to A:T conversions. Frequency of point mutations for in vitro modified plasmids was also dramatically increased from the spontaneous background level. Olaquindox-induced mutations did not occur randomly along the supF shuttle vector, but instead, had a hot spot at base pair #155 which accounts for 37% of total mutations. Olaquindox-induced mutations also showed sequence-specificity in which most point mutations occurred at site N in a 5'-NNTTNN-3' sequence while most tandem bases deletion and rearrangement were seen at the 5'-ANGGCCNAAA-3' sequence. We conclude that olaquindox induces DNA mutation, therefore, should not be used as an additive to promote animal growth.

Effects of the androgenic growth promoter 17-beta-trenbolone on fecundity and reproductive endocrinology of the fathead minnow

Trenbolone acetate is a synthetic steroid that is extensively used in the United States as a growth promoter in beef cattle. The acetate is administered to livestock via slow-release implants; some is converted by the animal to 17-beta-trenbolone, a relatively potent androgen receptor agonist in mammalian systems. Recent studies indicate that excreted 17-beta-trenbolone is comparatively stable in animal waste, suggesting the potential for exposure to aquatic animals via direct discharge, runoff, or both. However, little is known concerning the toxicity of trenbolone to fish. Our goal was to assess the effects of 17-beta-trenbolone on reproductive endocrinology of the fathead minnow (Pimephales promelas). An in vitro competitive binding study with the fathead minnow androgen receptor demonstrated that 17-beta-trenbolone had a higher affinity for the receptor than that of the endogenous ligand, testosterone. Male and female fish were exposed for 21 d to nominal (target) concentrations of 17-beta-trenbolone ranging from 0.005 to 50 microg/L. Fecundity of the fish was significantly reduced by exposure to measured test concentrations > or = 0.027 microg/ L. The 17-beta-trenbolone was clearly androgenic in vivo at these concentrations, as evidenced by the de novo production in females of dorsal (nuptial) tubercles, structures normally present only on the heads of mature males. Plasma steroid (testosterone and beta-estradiol) and vitellogenin concentrations in the females all were significantly reduced by exposure to 17-beta-trenbolone. The 17-beta-trenbolone also altered reproductive physiology of male fathead minnows, albeit at concentrations much higher than those producing effects in females. Males exposed to 17-beta-trenbolone at 41 microg/L (measured) exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of beta-estradiol and vitellogenin. Overall, our studies indicate that 17-beta-trenbolone is a potent androgen and reproductive toxicant in fish. Given the widespread use of trenbolone acetate as a growth promoter, and relative stability of its metabolites in animal wastes, further studies are warranted to assess potential ecological risk.

IL-25 induces IL-4, IL-5, and IL-13 and Th2-associated pathologies in vivo

We have characterized a cytokine produced by Th2 cells, designated as IL-25. Infusion of mice with IL-25 induced IL-4, IL-5, and IL-13 gene expression. The induction of these cytokines resulted in Th2-like responses marked by increased serum IgE, IgG(1), and IgA levels, blood eosinophilia, and pathological changes in the lungs and digestive tract that included eosinophilic infiltrates, increased mucus production, and epithelial cell hyperplasia/hypertrophy. In addition, our studies show that IL-25 induces Th2-type cytokine production by accessory cells that are MHC class II(high), CD11c(dull), and lineage(-). These results suggest that IL-25, derived from Th2 T cells, is capable of amplifying allergic type inflammatory responses by its actions on other cell types.

Mechanisms of the antimetastatic effect in the liver and of the hepatocyte injury induced by alpha-galactosylceramide in mice

The role of mouse liver NK1.1 Ag(+) T (NKT) cells in the antitumor effect of alpha-galactosylceramide (alpha-GalCer) has been unclear. We now show that, whereas alpha-GalCer increased the serum IFN-gamma concentration and alanine aminotransferase activity in NK cell-depleted C57BL/6 (B6) mice and B6-beige/beige mice similarly to its effects in control B6 mice, its enhancement of the antitumor cytotoxicity of liver mononuclear cells (MNCs) was abrogated. Depletion of both NK and NKT cells in B6 mice reduced all these effects of alpha-GALCER: Injection of Abs to IFN-gamma also inhibited the alpha-GalCer-induced increase in antitumor cytotoxicity of MNCS: alpha-GalCer induced the expression of Fas ligand on NKT cells in the liver of B6 mice. Whereas alpha-GalCer did not increase serum alanine aminotransferase activity in B6-lpr/lpr mice and B6-gld/gld mice, it increased the antitumor cytotoxicity of liver MNCS: The alpha-GalCer-induced increase in survival rate apparent in B6 mice injected intrasplenically with B16 tumor cells was abrogated in beige/beige mice, NK cell-depleted B6 mice, and B6 mice treated with Abs to IFN-gamma. Depletion of CD8(+) T cells did not affect the alpha-GalCer-induced antitumor cytotoxicity of liver MNCs but reduced the effect of alpha-GalCer on the survival of B6 mice. Thus, IFN-gamma produced by alpha-GalCer-activated NKT cells increases both the innate antitumor cytotoxicity of NK cells and the adaptive antitumor response of CD8(+) T cells, with consequent inhibition of tumor metastasis to the liver. Moreover, NKT cells mediate alpha-GalCer-induced hepatocyte injury through Fas-Fas ligand signaling.

Mechanisms of cell transformation in the Syrian hamster embryo (SHE) cell transformation system

The Syrian hamster embryo (SHE) cell transformation system has been used for investigational studies of basic mechanisms of neoplastic transformation, as well as determining the carcinogenic potential of chemical, physical, and biological agents. Many of these investigations utilize an intermediate step in the SHE cell neoplastic transformation process, known as morphological transformation, as an indicator that the cells have acquired an increased potential to progress to malignancy. While the nature of the morphologically transformed phenotype is not completely understood, it is believed to result from a block in the cellular differentiation of stem cells present within the SHE cell population. In terms of determination of the transforming potential of biological/chemical/physical agents, more than 500 agents have been tested in the SHE cell transformation assay with an 80-90% correlation between MT and carcinogenic potential. As such, the SHE cell transformation assay has utility as a test to provide short-term information on the carcinogenic potential of chemicals. One class of agents of current interest with regard to SHE cell transformation assay utilization consists of growth and differentiation factors (GDFs). Analysis of the SHE cell transformation potential of the GDFs, epidermal growth factor (EGF), fibroblast growth factor 4 (FGF-4), platelet-derived growth factor AA (PDGF AA), PDGF AB, PDGF BB, and the antimitogenic GDF, transforming growth factor beta one (TGF-beta1), was performed. All GDFs, with the exception of TGF-beta1, induced SHE cell transformation. However, an interesting difference between the GDFs was observed--PDGF A/B and PDGF B/B, but not PDGF A/A, EGF, or FGF-4, induced transformation after both a transient 1-day exposure and a continuous 7-day exposure, while continuous 7-day exposure was required for transformation by PDGF A/A, EGF, and FGF-4. Interestingly, both transient 1-day and continuous 7-day TGF-beta1 exposure resulted in suppression of transformation induced by a variety of transforming agents including growth factors, Ames assay-positive carcinogens, Ames assay-negative carcinogens, and spontaneous transformation. Interestingly TGF-beta1 was not able to suppress transformation by the tumor promoter, TPA. Together, these data demonstrate the utility of the Syrian hamster embryo cell transformation system for analyzing the transforming potential of GDFs and for characterizing differences in transforming mechanisms between different GDFs.

Dual effect of pseudorabies virus growth factor (PRGF) displayed on actin cytoskeleton

Pseudorabies virus growth factor (PRGF) was shown to possess transforming activity as well as transformation repressing activity in in vitro systems. In order to better understand these phenomena we studied actin cytoskeleton and its alterations induced by PRGF using normal human fibroblasts VH-10 and transformed cell line HeLa. For specific detection of filamentous actin cells were stained with phalloidin conjugated with fluorescein isothiocyanate (FITC)-phalloidin. PRGF was applied to VH-10 cells for various length of time from 10 min up to 48 h. The effect was very fast and changes in actin filament composition could be detected already after 10 min. In comparison to untreated cells the staining of treated cells was more diffuse and a number of actin microfilaments in individual stress fibers became reduced. After 30 min thick short actin bundles appeared in the perinuclear region. A 24-h exposure resulted in a large reduction of actin bundles. After additional 24 h a partial restoration of actin cytoskeleton in cells was observed. In transformed HeLa cells PRGF induced opposite process than in normal cells: the number of filamentous actin structures increased. We hypothesise that PRGF may act as a transcription-like factor and may initiate changes in gene expression which consequently result in actin cytoskeleton alterations.

FGF7/KGF triggers cell transformation and invasion on immortalised human prostatic epithelial PNT1A cells

Fibroblast growth factor 7 (FGF7/KGF) is synthesized exclusively by fibroblasts in normal tissues; it acts as a potent mitogen on epithelial cells, through interaction with the FGF7-specific receptor FGFR2/IIIb. To examine the importance of this growth factor both to prostate physiology and to prostate-cancer progression, we have tested the exogenous effect of FGF7. Thus, by mimicking the paracrine pathway (on proliferation, growth in soft agar and invasion) on the human prostatic epithelial cell line PNT1A positively checked for FGFR2/IIIb expression, FGF7 significantly enhanced cell proliferation at an optimal concentration of 7.5 x 10(-11) M, but no significant invasion or growth in soft agar were observed. To confirm FGF7 properties on human prostatic epithelial cells, we constitutively expressed FGF7 by transfecting PNT1A cells with FGF7-cDNA. The FGF7-transfected clones, PNT1A/ FGF7-T5 and PNT1A/FGF7-T6, were stable and expressed FGF7. Analysis of the FGF7-autocrine loop on the non-tumorigenic epithelial cells PNT1A showed acquired invasive potential in in vitro extracellular-matrix migration assays, specifically inhibited by an FGF7-neutralizing antibody, and over-expressed factors implicated in the migration process: the metalloproteinase MMP-1 and the plasminogen activator uPA. Taken together, these results demonstrate a role for FGF7 in triggering invasion of human prostatic epithelial cells. Furthermore, these FGF7-transfected clones exhibited functional and physiological differences from the original PNT1A cell line: anchorage-independent growth, growth in serum-free media and increased proliferation. These data confirm the oncogenic function of FGF7 in prostate progression potentially acting through paracrine and/or autocrine regulatory pathways.

Keratinocyte growth factor administered before conditioning ameliorates graft-versus-host disease after allogeneic bone marrow transplantation in mice

Keratinocyte growth factor (KGF) is important in tissue repair and wound healing and its administration can abrogate chemical- and radiation-induced tissue damage in rodents. We investigated KGF as a therapeutic agent for the prevention of graft-versus-host disease (GVHD)-induced tissue damage, morbidity, and mortality in an established murine allogeneic bone marrow transplantation (BMT) model. B10.BR (H2(k)) recipient mice were lethally irradiated and transplanted with C57BL/6 (H2(b)) bone marrow (BM) with spleen cells (BMS) as a source of GVHD-causing T cells. KGF-treated mice (5 mg/kg/d subcutaneously days -6, -5, and -4 pre-BMT) receiving BMS exhibited better survival than those not receiving KGF (P =.0027). Cyclophosphamide (Cy), a common component of total body irradiation (TBI)-containing regimens, was administered to other cohorts of mice at a dose of 120 mg/kg/d intraperitoneally on days -3 and -2 before BMT. KGF-treated mice again exhibited a better survival rate than those not receiving KGF (P =.00086). However, KGF-treated recipients receiving TBI or Cy/TBI BMS were not GVHD-free, as shown by lower body weights compared with BM groups. GVHD target tissues were assessed histologically during a 38-day post-BMT observation period. KGF ameliorated GVHD-induced tissue damage in the liver, skin, and lung (completely in some recipients) and moderately so in the spleen, colon, and ileum, even with Cy conditioning. These studies demonstrate that KGF administration, completed before conditioning, has potential as an anti-GVHD therapeutic agent.

Betacellulin-Pseudomonas toxin fusion proteins bind but are not cytotoxic to cells expressing HER4; correlation of EGFR for cytotoxic activity

Betacellulin (BTC) is a member of the EGF ligand family that directly binds to both EGFR and HER4 and induces the growth of certain epithelial cell types. Fusion proteins composed of the terminal 48 or 50 amino acids of mature betacellulin and a binding defective form of Pseudomonas exotoxin (BTC-TX48 and BTC-TX50, respectively), have been produced. BTC-TX50 induced tyrosine phosphorylation of both EGFR and HER4, whereas BTC-TX48 induced phosphorylation of HER4 but to a much lesser extent EGFR, indicating that the presence of two additional amino acid residues, Arg62 and Lys63, contribute to full kinase activity. BTC-TX50 was up to 300-fold more active at inhibiting protein synthesis than BTC-TX48 on cell lines expressing EGFR, most likely due to the >tenfold higher affinity of BTC-TX50. MDA-MB-453 breast carcinoma cells which express HER4 but not EGFR, were not sensitive to either BTC-TX form. These data indicate that despite the ability of BTC-TX to bind and phosphorylate HER4, it was only cytotoxic to cells expressing EGFR. The inability of BTC-TX to kill cells was likely due to its failure to internalize through HER4.

The effects of platelet-derived growth factor-BB and insulin-like growth factor-1 on epithelial dysplasia

Growth factors are multi-functional and multi-targeted proteins which play a significant role in wound healing. Platelet-derived growth factor B-chain homodimer (PDGF-BB) and insulin-like growth factor-1 (IGF-1) have demonstrated efficacy for periodontal regeneration in animal models. Although primarily associated with wound healing, PDGF-BB and IGF-1 also facilitate growth of a number of malignant neoplasms. Of particular concern to periodontists is epithelial dysplasia, a necessary precursor to squamous cell carcinoma, the most common oral malignancy. Certain risk factors for oral cancer, such as tobacco, age, and alcohol, are also associated with an increased incidence of periodontal disease. The effects of the combination of PDGF-BB and IGF-1 on epithelial dysplasia have not previously been reported. The purpose of this study was to examine the effects of the combination of PDGF-BB and IGF-1 on epithelial dysplasia induced in the buccal cheek pouch of the Syrian golden hamster. A total of 66 hamsters received 18 applications of 0.5% dimethylbenzanthracene (DMBA), a topical carcinogen, over a 6-week period for the induction of dysplasia. The hamsters were subsequently divided into a baseline and 3 experimental groups (growth factors, saline vehicle, untreated control). Following the final DMBA application (day 0), the baseline group (N = 6) was sacrificed, the growth factor group (N = 21) received a single injection in the cheek pouch containing 4 micrograms of PDGF-BB and 4 micrograms of IGF-1 in saline, the saline group (N = 19) received an injection in the cheek pouch containing the saline vehicle only, and the untreated control group (N = 20) received no injection. Animals in experimental groups were sacrificed on days 3, 6, and 10. The cheek pouches were harvested for histologic and histochemical evaluation. Dysplasia was histologically graded from 0 to 4. Statistical analysis of the histologic data revealed no significant differences either by sacrifice date or by group. Histochemical evaluation, via staining for gamma-glutamyl transpeptidase (GGT), a marker for dysplastic cell colonies, revealed that the density of GGT-positive cells in experimental groups differed significantly from baseline levels. No significant differences were detected between experimental groups. There was poor correlation between the density of GGT-positive cells and the histologic grading of dysplasia. It is concluded that exposure to PDGF-BB and IGF-1 had no demonstrable effect on epithelial dysplasia in this hamster model.

Non-major histocompatibility complex antigen class I-regulatory molecule for cytotoxicity by natural killer cells

The mechanism of the cytotoxicity by natural killer (NK) cells is not known. It is speculated that there exist several positively regulated and negatively regulated target molecules expressed on the target cell surface. Although one of the latter is considered to be major histocompatibility complex antigen (MHC) class I, in this study we described a novel non-MHC class I molecule that may negatively regulate the NK cytotoxicity. This antigen is defined by monoclonal antibody Cho-1 and is composed of noncovalently associated antigens that are 40 and 200 kilodaltons in molecular size. The expression of this antigen is reduced along with the cell growth induced by growth factors and/or oncogenes. Thus, Cho-1-defined antigen appears to be involved as one of the resistant molecules in the cytotoxic mechanism of NK cells.

Antiangiogenic treatment with linomide as chemoprevention for prostate, seminal vesicle, and breast carcinogenesis in rodents

There are two distinct phases during prostatic carcinogenesis with regard to tumor blood vessel development. During the first or prevascular phase, which may persist for years, cells that have undergone some but not all of the transformation steps undergo a limited amount of net growth, producing premalignant prostatic intraepithelial neoplastic (PIN) lesions. Most of these PIN lesions do not continue net growth and do not progress to produce histologically detectable cancer. Even the PIN lesions that do progress to cancer remain of limited virulence unless they undergo conversion to the second or angiogenic phase. Once this angiogenic phase is reached, new blood vessel development is greatly enhanced within the cancer. It is this enhanced tumor angiogenesis which allows these cancers both to grow continuously and to metastasize. Thus, inhibition of angiogenesis should be an effective chemopreventive approach for prostatic carcinogenesis. Linomide is a low molecular weight, water-soluble agent with excellent p.o. absorption and bioavailability. We have previously demonstrated that daily p.o. treatment with Linomide has antiangiogenic abilities against a series of rat and human prostatic cancer xenografts growing in vivo. In the present studies, we have demonstrated using Matrigel in in vivo angiogenesis assays that daily p.o. Linomide at 25 mg/kg/day inhibits angiogenesis induced by tumor necrosis factor alpha, acidic fibroblast growth factor, basic fibroblast growth factor, and vascular endothelial growth factor. Using an N-methylnitrosourea initiation-androgen promotion model, Linomide was given p.o. at a daily dose as high as 25 mg/kg/day for at least 1 year without major toxicity while inhibiting the development of seminal vesicle/prostate cancers in male rats by >50%. Dose-response analysis demonstrated that a Linomide blood level of 50-100 microM is optimal for such chemoprevention. In addition, Linomide treatment at a dose of 25 mg/kg/day was able to inhibit by approximately 60% the incidence of N-methylnitrosourea and approximately 50% of 7,12-dimethyl-benz(a)anthracine-induced mammary carcinogenesis in female rats.

Inhibition of PAF-, LPS-, and cytokine-induced granulocyte accumulation in guinea pig lung by dexamethasone: evidence that inhibition of IL-5 release is responsible for the selective inhibition of eosinophilia by glucocorticoids in guinea-pigs

The potency of dexamethasone has been determined as an inhibitor of intratracheally administered platelet activating factor- (PAF), or interleukin (IL)-5-induced eosinophilia, and of lipopolysaccharide-(LPS), tumour necrosis factor alpha-(TNF alpha) or cytokine-induced neutrophil chemoattractant- (CINC) induced neutrophilia in guinea-pig lungs. Dexamethasone was a potent inhibitor of PAF- induced eosinophil accumulation, but higher doses of dexamethasone were required to inhibit IL-5-induced eosinophilia. LPS-induced neutrophilia was less sensitive to the inhibitory effects of dexamethasone, than PAF-induced eosinophilia. Both LPS- and TNF alpha-induced neutrophilia were inhibited by the same doses of dexamethasone. In contrast, higher doses of dexamethasone were required to inhibit CINC-induced neutrophilia. Since data in the literature show that PAF-induced eosinophilia in guinea-pig lungs is dependent on the generation of IL-5, it is concluded that inhibition of this response, by dexamethasone, is due to inhibition of release of IL-5. Similarly, although data in the literature show that LPS-induced neutrophilia is dependent on the generation of TNF alpha, it is concluded that inhibition of this response, by glucocorticoids, is due to an action on an event which occurs after the release of TNF alpha, possibly through inhibition of chemokine release.

Activin disrupts epithelial branching morphogenesis in developing glandular organs of the mouse

We report that activin profoundly alters epithelial branching morphogenesis of embryonic mouse salivary gland, pancreas and kidney rudiments in culture, indicating that it may play a role as a morphogen during mammalian organogenesis. In developing pancreas and salivary gland rudiments, activin causes severe disruption of normal lobulation patterns of the epithelium whereas follistatin, an activin-binding protein, counteracts the effect of activin. In the kidney, activin delays branching of the ureter bud and reduces the number of secondary branches. TGF-beta induces a pattern of aberrant branching in the ureter bud derived epithelium distinct from that seen for activin. Reverse-transcriptase polymerase chain reaction, Northern hybridization and in situ hybridization analyses indicate that these developing tissues express the mRNA transcripts for activin subunits, follistatin or activin receptors. Our results are suggestive of a potential role for the activin-follistatin system as an intrinsic regulator of epithelial branching morphogenesis during mammalian organogenesis.

Negative regulators of cell proliferation

Cell proliferation is governed by the influence of both mitogens and inhibitors. Although cell contact has long been thought to play a fundamental role in cell cycling regulation, and negative regulators have long been suspected to exist, their isolation and purification has been complicated by a variety of technical difficulties. Nevertheless, over recent years an ever-expanding list of putative negative regulators have emerged. In many cases, their biological inhibitory activities are consistent with density-dependent growth inhibition. Most likely their interactions with mitogenic agents, at an intracellular level, are responsible for either mitotic arrest or continued cell cycling. A review of naturally occurring cell growth inhibitors is presented with an emphasis on those factors shown to be residents of the cell surface membrane. Particular attention is focused on a cell surface sialoglycopeptide, isolated from intact bovine cerebral cortex cells, which has been shown to inhibit the proliferation of an unusually wide range of target cells. The glycopeptide arrest cells obtained from diverse species, both fibroblasts and epithelial cells, and a broad variety of transformed cells. Signal transduction events and a limited spectrum of cells that are refractory to the sialoglycopeptide have provided insight into the molecular events mediated by this cell surface inhibitor.

Observations on the effects of long-term withdrawal on carcass composition and residue concentrations in clenbuterol-medicated cattle

The detection of the illegal use of clenbuterol (CBL) as a growth promoter has relied on detecting residual concentrations of the drug in body fluids or tissues. Analysis of retinal extracts has recently been shown to considerably extend the detection period following withdrawal. The withdrawal periods required to eliminate residues from the liver and retina were investigated by medicating 20 cattle with CBL for 30 days; 6 control animals remained unmedicated. Residual concentrations were monitored throughout this period and for the subsequent 140 days. Concurrent changes in muscle areas and backfat thicknesses were recorded by ultrasound. CBL was detectable in liver up to the 56th day of withdrawal (0.35 ng/g, SD = 0.5), but retinal concentrations remained well above detectable concentrations throughout the withdrawal period (22.5 ng/g, SD = 6.5). There were small gains (3-4%) in the muscle areas of treated cattle during medication as compared to controls (p > 0.05). These comparative gains remained during withdrawal. Backfat thicknesses in treated animals were 40% lower than in controls at the end of medication (p < 0.01). However, by 70 days after withdrawal this difference had disappeared (p > 0.05) owing to accelerated fat deposition in the treated group. The retina has been shown to be a highly effective target matrix for detecting CBL administration after long withdrawal periods.

Role of Porphyromonas gingivalis-derived fibroblast-activating factor in bone resorption

A 24-kDa protein was isolated from the outer membrane vesicles of Porphyromaonas gingivalis W50. This protein, referred to as fibroblast-activating factor (FAF), was examined for its bone-resorptive ability by the rat long-bone assay and the mouse bone marrow cell culture system. FAF resulted in a significant release of 45Ca from cultured bones, as well as the formation of tartrate-resistant acid phosphatase-positive monocytes. These cultures were compared with control cells. FAF therefore might be considered a significant bacterially expressed protein which could affect and modulate the resorption or destruction of tissue and alveolar bone in the local periodontal environment.

Conclusions of the satellite symposium of the Eurotox '91 Congress on Safety Aspects of Biotechnology-Derived Drugs

This satellite symposium, arranged as a workshop, was organized by B. Ryffel and R.A. Ettlin (Sandoz Pharma Ltd., Basel). It was attended by 58 participants from Europe, the USA, Asia and New Zealand. The highlights of the meeting and its provocative and creative discussions are summarized below.

FDA regulations for growth factors and related products

Biological products, including the majority of growth factors, are regulated by the Center for Biologics Evaluation and Research (CBER) in the U.S. Food and Drug Administration (U.S.FDA) under two statutes; U.S. Federal Food Drug and Cosmetics (FDC) act and the U.S. Public Health Service act. As stipulated in the U.S. Code of Federal Regulations (21 CFR) under the FDC act, the testing of new products in humans is conducted under an Investigational New Drug (IND) application. The primary objective of the FDA in all Phases of an investigation is assure safety of human subjects. During phase II and phase III studies, additional assurance regarding the scientific quality of the clinical investigation is required. A marketing approval is granted by CBER following the review of Product License Applications (PLA) and Establishment License Applications (ELA). CBER's review process provides guidance to the manufacturers of biological products towards the development of safe and effective biological products for human use. Information pertinent to preclinical issues and clinical trial design is presented here with a special emphasis on the non-hematopoietic growth factors.

A phase I/II trial of recombinant granulocyte-macrophage colony-stimulating factor for children with aplastic anemia

Nine pediatric patients (median age, 8 years; range, 0.7 to 19 years), eight with refractory aplastic anemia and one with newly diagnosed aplasia, were enrolled in a phase I/II trial of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) administered via continuous intravenous infusion. Doses ranged from 8 to 32 micrograms/kg/d. Six of eight evaluable patients responded with a significant rise in neutrophil count (median fourfold increase; range, 2.5- to 31-fold) during the 28-day induction period. Five patients completed 2 further months of therapy (maintenance) with persistent or improved neutrophil responses. Three patients had bone marrow aspirates suggestive of increased erythropoiesis, although only one patient had improvement in peripheral hematocrit and platelet count. In the five patients completing maintenance, three experienced a rapid return to baseline counts after rhGM-CSF was discontinued, one maintained a neutrophil response for 2 months after drug discontinuation, and one has maintained a trilineage response for greater than 1 year off study. Drug therapy was well tolerated. Toxicity was minimal at doses from 8 to 16 micrograms/kg/d. Fever and rash were more commonly seen at 32 micrograms/kg/d. No patient developed an infection during the course of rhGM-CSF administration. These results demonstrate that rhGM-CSF increases peripheral neutrophil counts in children with refractory and newly diagnosed aplastic anemia and may be able to stimulate a multilineage response in a more limited number. Randomized, prospective trials are necessary to determine if rhGM-CSF administration will impact favorably on the morbidity and mortality of severe aplastic anemia.

Subcutaneous recombinant granulocyte-macrophage colony-stimulating factor used as a single agent and in an alternating regimen with azidothymidine in leukopenic patients with severe human immunodeficiency virus infection

We investigated the effects of recombinant human granulocyte-macrophage colony-stimulating factor (rGM-CSF) administered by the subcutaneous route, first alone and then alternating with azidothymidine (AZT), in leukopenic patients with severe human immunodeficiency virus (HIV) infection. Ten patients with acquired immunodeficiency syndrome (AIDS) or related disorders, five of whom could not tolerate conventional doses of AZT, were administered rGM-CSF subcutaneously for 12 days. They then were administered an alternating regimen using AZT for 1 week, followed by 5 days of subcutaneous rGM-CSF and 2 days without any medication. During the initial 12 days of GM-CSF administration, there was an increase in the mean white blood cell (WBC) value. In addition, rGM-CSF stimulated circulating monocytes as evidenced by an increase in superoxide anion production and expression of surface HLA-DR antigen. However, at the same time rGM-CSF increased the serum HIV p24 antigen in each of the six evaluable patients from 189 x/divided by 2.02 pg/mL (geometric mean x/divided by SEM) at entry to 375 x/divided by 2.11 pg/mL (P less than .05). During the subsequent period of alternating AZT and rGM-CSF treatment, serum HIV p24 antigen fell below the day 14 value in most patients, particularly after the weeks of AZT administration. The mean T4 cell value increased in patients who had not previously received AZT, but generally did not change in those who had prior AZT exposure. Hematologic toxicity appeared to be somewhat reduced compared with continuous full-dose AZT therapy, and two patients with previous AZT hematologic toxicity tolerated this alternating regimen for 25 weeks. Additional regimens simultaneously combining these two agents are worth exploring.

Use of recombinant human granulocyte-macrophage colony-stimulating factor in graft failure after bone marrow transplantation

The effect of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) was evaluated in 37 patients with marrow graft failure after allogeneic (n = 15), autologous (n = 21), or syngeneic (n = 1) bone marrow transplantation. rhGM-CSF was administered by 2-hour infusion at doses between 60 and 1,000 micrograms/m2/d for 14 or 21 days. At doses of less than 500 micrograms/m2, rhGM-CSF was well-tolerated and did not exacerbate graft-versus-host disease in allogeneic transplant recipients. No patient with myelogenous leukemia relapsed while receiving rhGM-CSF. Twenty-one patients reached an absolute neutrophil count (ANC) greater than or equal to 0.5 x 10(9)/L within 2 weeks of starting therapy while 16 did not. None of seven patients who received chemically purged autologous marrow grafts responded to rhGM-CSF. The survival rates of GM-CSF-treated patients were significantly better than those of a historical control group.

Phase I/II study with GM-CSF in patients with myelodysplastic syndromes

The availability of rh GM-CSF has allowed the in vivo treatment of patients with cytopenia. Therefore a phase I/II trial was initiated to study the effect of rh GM-CSF in patients with myelodysplastic syndromes who were not eligible for other kinds of therapy. rh GM-CSF has been tested in 10 patients in doses from 15 micrograms/m2 to 150 micrograms/m2 given intravenously over 8 hours for a cycle of 7 days followed by an interval of 14 days and a second 7-day treatment course. A dose dependent increase in leukocyte count was observed in 9 out of 10 patients. No change in reticulocyte numbers was seen and only one patient experienced an increase in platelet count. Toxicity mainly consisted of mild local phlebitis at the site of infusion and sternal pain after bolus injection. An increase in blast cell counts in some patients necessitated the start of low dose Ara-C therapy.

A phase I study of therapy with recombinant granulocyte-macrophage colony-stimulating factor administered by IV bolus or continuous infusion

Sixteen patients with primary or secondary bone marrow failure were treated with recombinant human granulocyte-macrophage colony-stimulating factor (rGM-CSF) given as either an intravenous bolus or by continuous infusion. The dose range studied was from 15 micrograms/m2/d to 960 micrograms/m2/d. Administration of rGM-CSF on a bolus schedule failed to elicit a hematologic response, but resulted in side effects of epigastric distress and eructation in over 30% of administered courses. Administration of rGM-CSF by continuous infusion resulted in a dose-dependent increase in the total leukocyte, granulocyte, and eosinophil counts. The mean maximal rise in granulocyte count was 8.5-fold. After cessation of therapy, blood counts returned to near baseline in most patients by 7 days. A 36 percent decrease from baseline in mean serum cholesterol level was observed in the continuous infusion group, but not in patients receiving rGM-CSF as an IV bolus. Fever, fatigue, and bone pain were dose-limiting in the continuous infusion group at a dose of 240 micrograms/m2/d. The maximally tolerated dose was 480 micrograms/m2/d. No life-threatening toxicities were observed in either group. Our data demonstrate that continuous infusion rGM-CSF is biologically active and non-toxic at a dose of 120 micrograms/m2/d in patients with bone marrow failure.

Phase I/II study of recombinant human granulocyte-macrophage colony-stimulating factor (GM-CSF) in bone marrow failure

We performed a Phase I/II study of the administration of recombinant human GM-CSF to patients suffering from severe bone marrow failure, either due to aplastic anemia or myelodysplastic syndrome. Doses ranging from 15 micrograms/m2 to 480 micrograms/m2 were administered as an intravenous infusion daily for 7 days. Temporary improvements were seen in granulocyte counts, monocyte counts and reticulocyte counts. There was no reduction in erythrocyte transfusion requirements and no effect was observed on platelet counts. There was only minimal toxicity consisting of transient low back discomfort, anorexia, myalgias/arthralgias, and low grade fever. Our data suggest that prolonged use of GM-CSF might benefit some patients with severe marrow failure.

The effects of recombinant human granulocyte-macrophage colony-stimulating factor on phagocyte kinetics in man

Four patients with advanced resistant malignant disease received recombinant human granulocyte-macrophage colony stimulating factor (rhGM-CSF) for 10 days. All developed a moderate neutrophilia and monocytosis over this period. A transient phagocytopenia was observed during the first hour of administration. Radionuclide labelling studies showed that this cytopenia was due to sequestration predominantly within the lungs and that the recovery was due to re-entry of the same cells into the circulation. Studies of neutrophil lobularity during this time showed no reduction in lobe count suggesting that there had been little if any release of immature cells from bone marrow reserves. Skin window responses were present in 2 out of 3 patients during the period of neutropenia showing that cells were also present in the marginated pool of the skin at this time.

Granulocyte-macrophage colony-stimulating factor induces the expression of the CD11b surface adhesion molecule on human granulocytes in vivo

The CD11b (Mol) molecule is a member of a family of surface glycoproteins that are essential for adhesion-dependent granulocyte functions. Brief exposure of granulocytes to human granulocyte-macrophage colony-stimulating factor (GM-CSF) in vitro increases the surface expression of CD11b and increases granulocyte adhesiveness. To assess the possible in vivo significance of these observations we studied the effect of GM-CSF on CD11b, CD11a (LFA-1), and CD11c (gp 150, 95) expression on granulocytes from nine adult patients with sarcoma who were receiving GM-CSF as part of a phase I trial. GM-CSF was administered as a continuous infusion at a dose of 32 or 64 micrograms/kg/d. Granulocyte CD11b, CD11a, and CD11c expression was determined by indirect immunofluorescence staining of whole blood, thereby minimizing in vitro manipulation. A transient leukopenia developed within 15 minutes of initiation of GM-CSF treatment that was associated with a marked increase in the surface antigen density of CD11b. A mean 1.7-fold increase (P = .001) in the percentage of CD11b-positive granulocytes and a mean 2.1-fold increase (P = .002) in CD11b surface antigen density was noted after 12 hours of treatment. No change in CD11a or CD11c expression was observed over the first 12 hours. The level of CD11b expression was followed in six patients for up to 5 days of treatment with GM-CSF. Compared with the 12-hour value, three of six patients showed a subsequent decrease in CD11b expression, two remained constant, and one showed a continued increase in CD11b surface density. Fluorescence-activated cell sorting of granulocytes into high- and low-density CD11b-positive groups revealed a preponderance of immature myeloid forms in the low-density CD11b fraction, which suggests that the late decrease in CD11b expression in some patients may be related to a greater proportion of circulating immature myeloid forms in the peripheral blood. This study suggests that GM-CSF administered as a continuous infusion rapidly upregulates the expression of granulocyte CD11b in vivo. The influence of this phenomenon on in vivo granulocyte aggregation may be clinically relevant with regard to the toxicity of GM-CSF and deserves further investigation.

Recombinant granulocyte/macrophage-colony stimulating factor in human and murine bone marrow transplantation

Recombinant granulocyte/macrophage-colony stimulating factor (rGM-CSF) is a protein that mediates a broad range of biological activities including inducing proliferation of bone marrow progenitor cells and up-regulating the functional capabilities of neutrophils, monocytes, and macrophages. We have administered rGM-CSF in vivo in the context of allogeneic (murine) and autologous (human) bone marrow transplantation (BMT). In a murine allogeneic model of T-cell depletion constructed to favor graft failure/rejection of donor marrow, ex vivo treatment of marrow with rGM-CSF significantly promoted engraftment. However, when rGM-CSF was infused in vivo, engraftment was significantly impaired. We have initiated a phase I clinical trial of rGM-CSF in human autologous BMT for patients with acute lymphoblastic leukemia (ALL). rGM-CSF has been administered for 14-21 days in a dose escalation study (16-128 micrograms/M2/day). At high doses of rGM-CSF, neutrophil recovery has returned earlier and to higher levels than previously observed in historical controls. rGM-CSF related toxicity in this study has been mild.

Phase I study of recombinant DNA granulocyte macrophage colony stimulating factor

In this Phase I study of rh GM-CSF three patients have been entered at each of the following dose levels--0.3, 1, 3, 10 and 30 micrograms/kg/day. The mean total white cell count (x 10(9)/l) over the first ten days of rh GM-CSF rose from 11 to 14 at 3 micrograms/kg, 8 to 23 at 10 micrograms/kg and 7 to 27 at 30 micrograms/kg. Side effects included transient pyrexias after the first two infusions of rh GM-CSF and bone pains which were severe and required analgesia in two patients receiving 30 micrograms/kg and one receiving 10 micrograms/kg. No neutralizing antibodies to rh GM-CSF have been detected in the six patients tested to date. Patients are now being studied at 60 micrograms/kg/day.

Potential role of granulocyte-macrophage colony stimulating factor in patients with HIV infection

Abnormalities in leukocyte number and function contribute to the high incidence of infection in patients with HIV infection. Leukopenia is a frequent occurrence in patients with AIDS and AIDS-related diseases and is a major dose limiting factor in the treatment of HIV infected individuals with antiviral compounds and chemotherapy. Granulocyte-macrophage colony stimulating factor (GM-CSF) is a hematopoietic hormone that stimulates the growth and differentiation of myeloid progenitor cells in vitro and enhances the function of mature monocytes and neutrophils. Studies on the effects of this agent in patients with AIDS, indicate that GM-CSF causes increased production of neutrophils, monocytes, and eosinophils in a dose dependent fashion. Leukocytes produced in response to GM-CSF function normally as judged by in vitro tests. The effects of GM-CSF on HIV replication and expression in vivo are uncertain. Studies of the use of GM-CSF alone and in combination with antiretroviral, antimicrobial, antineoplastic agents or other hematopoietins and cytokines will help define its ultimate clinical utility in patients with HIV infection.

Principles of a full 'relay toxicity' experiment and results conducted with carbadox, a feed additive used as growth promoter for growing swine

Relay toxicity is a new approach which permits an evaluation of the harmlessness of residues found in tissue, for the human consumer. Farm animals, swine for example, received high quantities of the additive over a long period. The swine were sacrificed without any withdrawal. Their meat and liver were added to the feed ration of laboratory animals to study the eventual problems of residue and metabolites. The following experiments were performed using carbadox:--Levels of carbadox up to 200 ppm were added to the swine ration (a maximum of 20 ppm is authorized). The meat and dehydrated liver were given in doses of 20% and 10% respectively, in the rat feed for 2 years or 3 generations.--The fresh meat, frozen then thawed at the time of use, was distributed to dogs daily for 7 1/2 years. No abnormalities were found, either in the growth of the animals or in their descendants. No abnormalities were observed macroscopically or microscopically after sacrifice. Relay toxicity gives high coefficients of security when the additive is used without withdrawal up to the time of sacrifice. This study demonstrated that the use of carbadox in swine doesn't present any disadvantage to the human consumer.

[Toxicity by relay. II. A method for the asessment of safety to human consumers of carbadox, a growth-promoting additive to the feed of slaughter pigs]

A toxicity by relay. II. A method for the assessment of safety to human consumers of carbadox, a growth-promoting additive to the feed of slaughter pigs. A new methodology called "toxicity by relay" has been used to assess the potential hazard to humans of incorporating an additive into animal feeds. This methodology considers a farm-reared animal as a "relay" between the food additive and the human consumer, and employs laboratory animals as "pseudo-consumers". These laboratory animals are fed throughout their entire lives with the meat or organs of the "relay" animals which have been reared on feeds supplemented with various levels of the additive. In the present study, the toxicity of carbadox was assessed in this way. In pigs, where it is used as a growth promoter, carbadox is metabolised into serveal different products, and so an assessment of its safety using traditional methods of studying the toxicity of a substance and tis known metabolites, would perhaps be subject to error. A safety factor for man, in relation to the safety factors for rats and dogs, was calculated using (a) the comparative consumption of the laboratory animals and man; (b) an assessment of the highest dosage likely to be consumed in normal circumstances compared to the laboratory dosage, and (c) the consideration that in the laboratory there is no period of withdrawal from feeding before sacrifice as is the case with animals for slaughter. Pigs were used as "relays" in the present study by supplementing their feed with carbadox. The meat and/or livers of these animals were then fed daily to (a) rats for a period of 3 generations; (b) rats for 24-25 months, and (c) dogs for 60 months. No abnormalities were observed at the termination of the experiments. We may therefore conclude that there is no hazard for the human consumer from the use of carbadox as a pig-feed additive.