Urinary antigens as markers of papillary toxicity. II: Application of monoclonal antibodies for the determination of papillary antigens in rat urine

We have previously reported the preparation of monoclonal antibodies specific for antigens localized in the rat renal papilla. Three of the monoclonal antibodies reacting with antigens localized in papillary and cortical collecting duct epithelia were selected for the development of enzyme-linked immunosorbent assay (ELISA)-type assays. The papillary antigens ('PapA') determined in these tests were designated PapAl (applying the monoclonal antibody PapX 5C10), PapA2 (applying the monoclonal antibody PapX 12F6), and PapA3 (applying the monoclonal antibody PapXI 3C7). Using these assays antigen excretion was determined in the urine of rats. Depending on the test compound used. the application route, and the dose, the observed antigen release patterns differed. Whereas after a single intraperitoneal application of 2-bromoethanamine or of propyleneimine an increased release of PapA1 but not of the two other antigens was observed oral application of bromoethanamine had minor effects. In contrast, both a single intraperitoneal application or repeated oral applications of indomethacin resulted in an increased release of all the three antigens. Daily application of ipsapirone in the diet or in drinking water resulted in significantly elevated urinary release of PapAl which increased incrementally for the duration of the application. Release of PapA2 and PapA3 was not affected and remained in the normal range. These results show that with the tests developed changes in the rat renal papilla caused by xenobiotics can be detected early by urinary analysis and monitored during follow-up studies. Moreover. the different antigen release patterns obtained after application of the different compounds suggest a possible differing mode of action.

Preclinical safety evaluation of moxifloxacin, a novel fluoroquinolone

The toxicity of moxifloxacin (BAY 12-8039), a novel fluoroquinolone with a broad spectrum of antibacterial activity, was evaluated in a comprehensive programme of toxicological studies that included single and multiple dose toxicity studies in rats, mice, dogs and monkeys, reproductive system toxicity studies in rats and monkeys and in-vitro and in-vivo mutagenicity assays. Although moxifloxacin is not intended for long-term clinical use, an accelerated bioassay in target organs to assess carcinogenesis was performed in rats. In addition to the routine toxicological programme required for the development of a drug intended for short-term administration, a major part of the preclinical programme for moxifloxacin comprised studies designed specifically to address the safety issues known to be features of fluoroquinolones, i.e. adverse effects on the central nervous and cardiovascular systems, phototoxicity, arthrotoxicity and oculotoxicity. The results of the toxicological investigations confirmed that the safety profile of moxifloxacin is comparable to those of other fluoroquinolones.

Damage to mitochondrial DNA induced by the quinolone Bay y 3118 in embryonic turkey liver

Quinolones are a class of antibiotics that induce damage to and loss of DNA from bacteria. The structural organization of bacterial DNA is more similar to eukaryotic mitochondrial DNA (mtDNA) than to eukaryotic chromosomal or nuclear DNA (nDNA). Antibiotics affecting the bacterial genome may therefore preferentially damage mtDNA rather than nDNA. We investigated the effect of a quinolone on mtDNA in avian embryonic hepatocytes in ovo. The quinolone Bay y 3118 (1-cyclopropyl-7-(2,8-diazabicyclo[4.3.0]non-8-yl) 6-fluoro-8-chloro-1,4-dihydro-4-oxo-3-quinolinecarboxylic acid hydrochloride, chemical structure see Bremm et al. [K.D. Bremm, U. Petersen, K.G. Metzger, R. Endermann, In vitro evaluation of Bay-y 3118, a new full-spectrum fluoroquinolone, Chemotherapy 38 (1992) 376-387] was injected into fertilized turkey eggs 8 days before hatching at doses of 1, 3, 10 and 30 mg per egg. The embryos were removed from the eggs after 4 days and liver samples were shock frozen. Mitochondrial DNA was purified from samples of the embryonic liver. The integrity of mtDNA was investigated by electrophoresis on agarose gels with native mtDNA and with ribonuclease-treated mtDNA. Fluorescent staining of the electrophoresis gels allows the densitometric quantification of the mtDNA of the regular band at 16 kilobases (kb) and the amount of DNA fragments of irregular size (smear). The genotoxic nitrosamine nitrosodiethylamine (NDEA) has previously been shown to reduce the content of mtDNA of the regular size of 16 kb and to induce the occurrence of smaller fragments of mtDNA [H. Enzmann, C. Kühlem, E. Löser, P. Bannasch, Damage to mitochondrial DNA induced by the hepatocarcinogen, diethylnitrosamine in ovo, Mutation Res. 329 (1995) 113-120]. After exposure to 10 and 30 mg Bay y 3118, a dose-dependent induction of damage to the mtDNA was found, whereas exposure to 3 and 1 mg showed no effect. NDEA (25 mg) was used as positive control. Testing chemical compounds in the in ovo model is a simple and rapid approach for investigations on chemically induced alterations of mtDNA.

Preclinical safety evaluation of cerivastatin, a novel HMG-CoA reductase inhibitor

Cerivastatin is a new but structurally distinct 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor ("statin"). It effectively decreases low-density lipoprotein (LDL) cholesterol at 1% of the doses of other currently available statins. The toxicology of cerivastatin was evaluated in a comprehensive program of studies including: (1) single- and multiple-dose toxicity studies in rats, mice, minipigs, dogs, and monkeys; (2) reproductive toxicity studies in rats and rabbits; (3) in vitro and in vivo mutagenicity assays in rats and mice; and (4) carcinogenicity studies in rats and mice. In addition, studies were undertaken to investigate the effects of cerivastatin on lens opacity, testicular tissue, and hemorrhage in dogs. Oral administration of single and multiple doses of cerivastatin over periods ranging from 4 weeks to 24 months was generally well tolerated. Adverse effects were similar to those observed with other statins and primarily involved the liver and muscle tissue. At the high doses used in the toxicologic studies, cerivastatin caused elevations in serum transaminases and creatine phosphokinase levels as well as some degeneration of muscle fibers in rats, mice, dogs, and minipigs. In dogs, the species most sensitive to statins, cerivastatin caused erosions and hemorrhages in the gastrointestinal tract, bleeding in the brain stem with fibroid degeneration of vessel walls in the choroid plexus, and lens opacity. Apart from minor morphologic changes in the testicular tissue of dogs--the only organ for which a comparably low margin of safety was observed--cerivastatin had no significant effects on the male or female reproductive system. Cerivastatin also caused no primary embryotoxic or teratogenic effects. With the exception of cerivastatin-induced effects on the eyes and testicles, administration of mevalonic acid reversed the toxicologic effects of cerivastatin, indicating that the toxic effects were related to its mode of action and not to any intrinsic toxicity of the molecule itself. There was no evidence that cerivastatin had any mutagenic effects and, in contrast to other statins, high doses of cerivastatin did not induce tumors in rats. The main metabolite of cerivastatin was well tolerated systemically in all animals, including dogs. Overall, cerivastatin has a similar toxicologic profile to other statins and is a well-tolerated HMG-CoA reductase inhibitor.

Determination of the excitatory potencies of fluoroquinolones in the central nervous system by an in vitro model

Fluoroquinolones have been reported to induce central nervous system side effects, including seizures and psychiatric events. Although relatively rare in patients up to now, the proconvulsant activity depends on the chemical structure and might be a critical endpoint of some new representatives of this valuable class of antimicrobials. The electrophysiological determination of field potentials in the CA1 region of the rat hippocampus slice allowed an assessment of the excitatory potential of fluoroquinolones and might be predictive for their neurotoxic potency in vivo. An optimization of this method and its extension to other fluoroquinolones resulted in a defined rank order. Well-known already-marketed quinolones as well as some fluoroquinolones under evaluation and development were used. The dose range tested was between 0.5 and 4 mumol/liter, which was comparable to the therapeutic concentration in the brain. All tested compounds increased the population spike amplitude in a concentration-dependent manner, and the resulting excitatory potency was highly dependent on the chemical structure, with compounds ranging from least to most excitatory as follows: ofloxacin, ciprofloxacin, nalidixic acid, moxifloxacin, BAY x 8843, [corrected] fleroxacin, lomefloxacin, enoxacin, clinafloxacin (much more excitatory than enoxacin), tosufloxacin, trovafloxacin, BAY 15-7828, and BAY x 9181 (much more excitatory than BAY 15-7828). The proposed hippocampus slice model not only is suitable for giving valuable alerts as to convulsive potential during candidate selection but also enables mechanistic investigations. These investigations pointed to the N-methyl-D-aspartate receptor as the probable target of the fluoroquinolone effects.

Calcium channel blockers and the risk of cancer: a preclinical assessment

The preclinical evidence for a potential influence of calcium channel blockers (CCBs) on carcinogenesis is discussed in the light of a broad database from rodent carcinogenicity studies as well as literature data. In all bioassays performed in rats and mice on the dihydropyridine CCBs--nifedipine, nimodipine, nisoldipine, and nitrendipine--no evidence was found for a carcinogenic potential of these compounds. Calcium is an essential intracellular signal for cell proliferation and apoptosis. The crucial role of increased cell proliferation in all stages of carcinogenesis is well documented. Some indirect experimental evidence also points to a role of defective apoptosis in tumor promotion. CCBs uniformly inhibit cell proliferation, whereas the influence of CCBs on apoptosis is inconsistent, resulting in an inhibition or increase in apoptosis dependent on cell type. Accordingly, antitumorigenic effects of CCBs have been reported based on their antiproliferative action. A tumor-promoting effect of CCBs based on inhibition of apoptosis, however, remains purely speculative and, in fact, can be denied based on the results of in vivo bioassays. It is therefore concluded that there is no preclinical evidence that should give rise to concern over the carcinogenic potential of dihydropyridine-type CCBs.

Calcium channel blockers and cancer: is there preclinical evidence for an association?

The preclinical evidence for a potential influence of calcium channel blockers (CCB) on carcinogenesis is discussed in the light of rodent carcinogenicity studies as well as mechanistic data. In the bioassays performed in rats and mice on the dihydropyridine CCB nifedipine, nimodipine, nisoldipine and nitrendipine, no evidence was found for a carcinogenic potential of these compounds. Moreover, the mechanistic knowledge on the influence of CCB on the fundamental processes of cell proliferation and apoptosis is not in favor of a tumor-promoting activity of these compounds. It is, therefore, concluded that there is no preclinical evidence that the therapeutic use of CCB of the dihydropyridine class is associated with an increased risk of cancer.

Quinolone antibiotic photodynamic production of 8-oxo-7, 8-dihydro-2'-deoxyguanosine in cultured liver epithelial cells

To study the basis for the phototoxicity of quinolones, a class of synthetic antibacterials, the photodynamic ability to mediate 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) formation in cultured cells was measured for lomefloxacin (LMX), which is strongly associated with clinical phototoxicity in humans, and ciprofloxacin (CFX), which has few reports of phototoxicity. Adult rat liver (ARL-18) cells were exposed to the quinolones in the presence of UVA and DNA was extracted and analyzed by HPLC with electrochemical detection. Low levels of 8-oxo-dG were found in the DNA of nonirradiated ARL-18 cells and this was increased up to 6-fold in the presence of either LMX (50-400 microM) or up to 3.6-fold in the presence of CFX (50-400 microM) and UVA (20 J/cm2) when compared to the UVA control. Comparing separate experiments with LMX and CFX, LMX produced greater levels of 8-oxo-dG either after dark exposure or after UVA exposure at 20 J/cm2. Also, LMX and CFX were both shown to photodegrade in the presence of UVA, and it was determined that UVA photoinstability alone does not reflect phototoxic potential. These data suggest that the photodynamic potential of LMX and CFX to produce 8-oxo-dG may relate to their human clinical phototoxicity profile. We suggest that the observed clinical phototoxicity is mediated through a UVA photodynamic effect on the quinolone to form reactive oxygen species in the presence of molecular oxygen. The findings indicate that 8-oxo-dG formation can serve as a marker for the potential phototoxicity of new quinolones.

Specific binding of a 47-kilodalton protein to the 3' untranslated region of rat transition protein 2 messenger ribonucleic acid

The synthesis of transition protein (TNP) 2, one of the predominant nuclear proteins of mammalian spermatids, was shown to be posttranscriptionally regulated, by storing the untranslated mRNA for about 3-5 days in the cytoplasm of differentiating spermatids. It has been proposed that binding of a cytoplasmic protein to a conserved motif of 8 nucleotides (nt) in the 3' untranslated region (3'UTR) of TNP2 mRNA is involved in this translational control mechanism. In this report, we show that deletion or variation of the conserved 8-nt motif (GCCAT-CAC) in rat TNP2-3'UTR abolishes the capacity of the in vitro-transcribed RNA to reconstitute specific RNA-protein complexes in RNA bandshift assays. Using Northwestern analysis, we identified specific binding to the TNP2-3'UTR of four proteins of 45, 47, 49, and 60 kDa, all of which are stage-specifically regulated in male germ cell differentiation. Deletion of the 8-nt motif in the 3'UTR specifically prevented binding of the 47-kDa protein, the interaction of which is thought to be mediated by the RNA secondary structure. Analysis of the RNA secondary structure revealed that the 8-nt motif is an essential element of a specific stem-loop structure that is predicted for rat wild-type TNP2-3'UTR. Therefore we assume that the 47-kDa protein plays an important role in specific RNA-protein complex formation of rat TNP2-3'UTR that may be a central event in the translational control of rat TNP2 mRNA.

An in vitro model for toxicological investigations of environmental neurotoxins in primary neuronal cell cultures

Currently, most neurotoxicological investigations are still conducted using various animal models (e.g. chickens, rodents). In this report, alternative strategies of testing were examined to detect the neurotoxic potency of foreign compounds. Primary neuronal cell cultures from fetal rats are already an accepted model for mechanistic and pharmacological studies in drug research. Their suitability for neurotoxicological studies was examined by using industrial model compounds, which are well-known inductors of neuropathies: acrylamide, hexachlorophene, paraquat, n-hexane, and its neurotoxic metabolites acetylaceton and 2,5-hexandione. As a control compound, the nonneurotoxic solvent n-heptane was used. General cytotoxicity and the intracellular content of glial fibrillary acid protein, neuron-specific enolase, and neurofilaments were measured. n-Heptane induced an acute cytotoxicity and acrylamide and 2,5-hexandione produced a delayed cytotoxicity in primary neuronal cells, whereas the others showed no cytotoxic potency in the tested concentration range. These results were in agreement with the quantification of neurons by neuron-specific enolase. In contrast, with the exception of acetylaceton, glia cells were significantly affected by all neurotoxins at the later time. Signs of axonopathies were demonstrated for acrylamide, n-hexane and its metabolites, as well as for hexachlorophene and paraquat in vitro, by determining the intracellular neurofilament level. Therefore, the determination of cell-specific end points is necessary to detect the neurotoxic potency and quality of a compound, whereas the cytotoxicity assay limited the tested concentration range.

Stage and developmental specific gene expression during mammalian spermatogenesis

Spermatogenesis is a complex developmental process which involves amplification of germinal stem cells, their differentiation into spermatocytes, meiotic division and finally transformation into mature spermatozoa. Therefore, spermatogenesis provides an interesting system for examining the regulation of gene expression during development and differentiation. The genes expressed during spermatogenesis can be divided into two main groups: diploid and haploid expressed genes. In this review, we report about the regulation of expression of a diploid expressed gene, namely the proacrosin gene, and that of a haploid expressed gene, the transition protein 2 gene.

Urinary antigens as markers of papillary toxicity. I. Identification and characterization of rat kidney papillary antigens with monoclonal antibodies

Monoclonal antibodies were prepared in an attempt to develop diagnostic tools for the identification of toxic damage to the rat renal papilla. One IgG and five IgM monoclonal antibodies, reacting with antigens localized in the papilla were obtained. Three of the IgM class and the IgG class monoclonal antibodies were found to be specific for antigens localized in collecting ducts, two of them staining papillary collecting ducts more intensely than cortical collecting ducts. The IgG class antibody, termed Pap X 5C10, recognizes an antigen located at high density on the luminal side of papillary collecting duct epithelial cells and at lower density in cortical collecting duct cells. One of the IgM class monoclonal antibodies reacts with an antigen localized in epithelial cells as ascending and descending loops of Henle and of connecting tubules. Another of the IgM class monoclonal antibodies reacts with an antigen localized in the interstices of the inner medulla. All these monoclonal antibodies react with their antigens in native frozen as well as in Bouin-fixed and paraffin-embedded tissue slices. Molecular properties of the Pap X 5C10 antigen have been investigated by gel permeation chromatography, SDS-PAGE, Western blotting, and isoelectric focusing. The results indicate that the antigen in both its tissue-derived and urinary form is of large (150-200 kDa) molecular size and can be separated into two molecular species with isoelectric points of pH 7.2 and 7.3 respectively. In the urine the antigens recognized by the monoclonal antibodies form large complexes with Tamm-Horsfall protein. The antigen-containing complexes can be extracted from urine by adsorption to diatomaceous earth and elution with SDS-containing buffer. Using sandwich ELISA-type assays it is possible to determine the concentration of the antigens. In preliminary experiments we were able to show that at least three of the antigens are detected in the urine following toxic insults to the kidney. The monoclonal antibodies prepared and the tests developed thus may provide direct diagnostic access to the renal papilla and allow, for the first time, early detection of papillary damage.

Sequence analysis of the conserved protamine gene cluster shows that it contains a fourth expressed gene

Structural data are presented on the protamine gene cluster (PGC) of human, mouse, rat, and bull. By restriction mapping we demonstrate that the organization of the protamine cluster is conserved throughout all four species, i.e., the genes are situated in a head to tail arrangement in the order: protamine 1-protamine 2-transition protein 2. Further, we established the nucleotide sequence of the entire human PGC (25 kb in total) and the 3' portion of the rat protamine cluster (PRM2 and TNP2 genes and intergenic region). In addition, a 1 kb fragment of the bovine and murine protamine cluster, situated between PRM2 and TNP2, was sequenced. This fragment is conserved regarding sequence, position, and orientation in all species examined, and was classified as likely coding region by gene recognition program GRAIL. Using the rat fragment as a probe in RNA blots, we detected a testis-specific signal of about 0.5 kb. Finally, we demonstrate a high density of Alu elements, both full and fragmented copies, in the human PGC and discuss their localization with respect to evolutionary and functional aspects.

The rat Prm3 gene is an intronless member of the protamine gene cluster and is expressed in haploid male germ cells

We have cloned and sequenced the cDNA of a novel gene from the rat protamine gene cluster. This gene, preliminarily referred to as Prm3, is intronless and resides between the genes for protamine 2 and transition protein 2. Prm3 is transcribed from the same strand as these genes and is expressed in haploid stages of spermatogenesis. The 410-bp-long cDNA possesses an ORF, coding for a putative 104-amino acid polypeptide with a high content of glutamic acid.

Electrically evoked potentials in the rat hippocampus slice in the presence of aminophylline alone and in combination with quinolones

The excitability of brain matter was tested bt electrically evoked field potentials in the CA1 region of the rat hippocampus in vitro. In contrast to the quinolones which only increased the amplitudes of electrically evoked potentials, aminophylline induced spontaneous firing in the pyramidal cell layer without stimulation in addition to its dose-dependent effects on the amplitudes of the evoked potentials. Threshold doses of the quinolones tested (0.25 microM) increased the amplitudes of evoked potentials in the presence of an otherwise ineffective concentration of aminophylline (0.5 microM) to different degrees, ranging from 135.3% for ciprofloxacin to 223.8% for nalidixic acid. The rank order of potency of CNS side effects reported in the literature correlates very well with the increase of the population spike amplitude in the hippocampus slice preparation. This feature could be important during the development of new chemical analogues of quinolones.

An 87 bp deletion in exon 5 of the LDL receptor gene in a mother and her son with familial hypercholesterolemia

DNA analysis of the low density lipoprotein receptor (LDLR) gene was performed in two persons with familial hypercholesterolemia (FH). Southern blot experiments indicated the heterozygous loss of an EcoRI site in exon 5 of the LDLR gene. Upon amplification and sequencing of exon 5 in both probands, an 87-bp deletion in a heterozygous state could be evaluated. This is a novel mutation, most probably leading to the formation of a nonfunctional LDLR. Analysis of the deletion breakpoints revealed the presence of a six-base-pair consensus sequence 5'TGA/GA/GG/TA/C3', which is characteristic of small deletions in different genetic defects.

A conserved 8 bp motif (GCYATCAY) in the 3'UTR of transition protein 2 as a putative target for a transcript stabilizing protein factor

The 3'UTR of the transition protein 2 gene of several mammalian species was sequenced and the transcript level of this gene was determined by Northern blots. In all species tested so far, a Northern blot detectable transcript level was associated with the presence of a conserved 8 bp motif (GCYATCAY) 50 bp downstream of the stop codon. RNA-bandshift experiments indicate that this region is capable of binding a cytosolic protein factor from rat testis. These findings support our hypothesis that the low transcript level of the transition protein 2 gene in human is due to insufficient storage of the mRNA as ribonucleic/protein particle.

Chondrotoxicity of quinolones in vivo and in vitro

Chondrotoxicity is a rare toxicological finding which is observed in dogs after administration of quinolone antibacterials. To study this effect chondrocytes from articular cartilage of dogs were isolated, and incubated with quinolone derivatives. The effects on cell viability, mitochondrial dehydrogenase, and proteoglycan synthesis were determined. These results were compared with in vivo findings in dogs treated with these quinolones. It was concluded that inhibition of mitochondrial dehydrogenase activity and of proteoglycan synthesis are major reasons for cartilage damage. Therefore this in vitro model is capable of identifying strongly arthropathogenic quinolones without the need of performing animal studies.

The gene for human transition protein 2: nucleotide sequence, assignment to the protamine gene cluster, and evidence for its low expression

We have isolated the gene for transition protein 2 (TNP2) from a human cosmid clone that contains the genes for protamines 1 and 2. A nucleotide sequence of 1776 bp that comprises 268 bp of the 5'-noncoding region, 400 bp of exon 1, 849 bp of an intron, 17 bp of exon 2, and 242 bp of the 3'-noncoding region was determined. A modified CAT box, a TATAA box, and two possible polyadenylation sites were identified. Transcripts in testicular RNA could be detected only by RT-PCR and RNase protection assays. By direct sequencing of the PCR products, a cDNA sequence was established. It can be deduced from these results that, in contrast to other mammalian genes, the human TNP2 gene is expressed at a very low level. The human gene differs from that of other mammalian species by the absence of a conserved GCCATCAC nucleotide sequence in the 3'-untranslated region. Since both protamine genes are known to be localized on chromosome 16p13.3, this chromosomal localization holds true for the human TNP2 gene as well. The genes for both protamines and TNP2 are arranged in a DNA stretch of 13 kb.

The genes for protamine 1 and 2 (PRM1 and PRM2) and transition protein 2 (TNP2) are closely linked in the mammalian genome

The genes for two protamines (PRM1 and PRM2) and for two transition proteins (TNP1 and TNP2) have been characterized in several mammalian species. In the human, boar, and bull, the genes for PRM1, PRM2, and TNP2 are closely linked over a stretch of DNA 13-15 kb long. Although similar data are not yet available for the mouse and rat, our results suggest that the three genes are similarly linked in these species. The gene for TNP1 in all species studied is located on another chromosome.