Mechanisms of antiviral action and toxicities of ipecac alkaloids: Emetine and dehydroemetine exhibit anti-coronaviral activities at non-cardiotoxic concentrations

The emergence of highly infectious pathogens with their potential for triggering global pandemics necessitate the development of effective treatment strategies, including broad-spectrum antiviral therapies to safeguard human health. This study investigates the antiviral activity of emetine, dehydroemetine (DHE), and congeneric compounds against SARS-CoV-2 and HCoV-OC43, and evaluates their impact on the host cell. Concurrently, we assess the potential cardiotoxicity of these ipecac alkaloids. Significantly, our data reveal that emetine and the (-)-R,S isomer of 2,3-dehydroemetine (designated in this paper as DHE4) reduce viral growth at nanomolar concentrations (i.e., IC50 ∼ 50-100 nM), paralleling those required for inhibition of protein synthesis, while calcium channel blocking activity occurs at elevated concentrations (i.e., IC50 ∼ 40-60 µM). Our findings suggest that the antiviral mechanisms primarily involve disruption of host cell protein synthesis and is demonstrably stereoisomer specific. The prospect of a therapeutic window in which emetine or DHE4 inhibit viral propagation without cardiotoxicity renders these alkaloids viable candidates in strategies worthy of clinical investigation.

Additive Effects of Arsenic and Aristolochic Acid in Chemical Carcinogenesis of Upper Urinary Tract Urothelium

BACKGROUND

Aristolochic acids (AA) and arsenic are chemical carcinogens associated with urothelial carcinogenesis. Here we investigate the combined effects of AA and arsenic toward the risk of developing upper tract urothelial carcinoma (UTUC).

METHODS

Hospital-based (n = 89) and population-based (2,921 cases and 11,684 controls) Taiwanese UTUC cohorts were used to investigate the association between exposure to AA and/or arsenic and the risk of developing UTUC. In the hospital cohort, AA exposure was evaluated by measuring aristolactam-DNA adducts in the renal cortex and by identifying A>T TP53 mutations in tumors. In the population cohort, AA exposure was determined from prescription health insurance records. Arsenic levels were graded from 0 to 3 based on concentrations in well water and the presence of arseniasis-related diseases.

RESULTS

In the hospital cohort, 43, 26, and 20 patients resided in grade 0, 1+2, and 3 arseniasis-endemic areas, respectively. Aristolactam-DNA adducts were present in >90% of these patients, indicating widespread AA exposure. A>T mutations in TP53 were detected in 28%, 44%, and 22% of patients residing in grade 0, 1+2, and 3 arseniasis-endemic areas, respectively. Population studies revealed that individuals who consumed more AA-containing herbs had a higher risk of developing UTUC in both arseniasis-endemic and nonendemic areas. Logistic regression showed an additive effect of AA and arsenic exposure on the risk of developing UTUC.

CONCLUSIONS

Exposure to both AA and arsenic acts additively to increase the UTUC risk in Taiwan.

IMPACT

This is the first study to investigate the combined effect of AA and arsenic exposure on UTUC.

Effect of sequence context on Polζ-dependent error-prone extension past (6-4) photoproducts

The (6-4) pyrimidine-pyrimidone photoproduct [(6-4)PP] is a major DNA lesion induced by ultraviolet radiation. (6-4)PP induces complex mutations opposite its downstream bases, in addition to opposite 3' or 5' base, as has been observed through a site-specific translesion DNA synthesis (TLS) assay. The mechanism by which these mutations occur is not well understood. To elucidate the mechanisms underlying mutagenesis induced by (6-4)PP, we performed an intracellular TLS assay using a replicative vector with site-specific T(thymidine)-T (6-4)PP. Rev3^-/-p53^-/- mouse embryonic fibroblast (MEF) cells (defective in Polζ) were almost completely defective in bypassing T-T (6-4)PP, whereas both Rev1^-/- and Polh^-/-Poli^-/-Polk^-/- MEF cells (defective in Polη, Polι, and Polκ) presented bypassing activity comparable to that of wild-type cells, indicating that Y-family TLS polymerases are dispensable for bypassing activity, whereas Polζ plays an essential role, probably at the extension step. Among all cells tested, misincorporation occurred most frequently just beyond the lesion (position +1), indicating that the Polζ-dependent extension step is crucial for (6-4)PP-induced mutagenesis. We then examined the effects of sequence context on T-T (6-4)PP bypass using a series of T-T (6-4)PP templates with different sequences at position +1 or -1 to the lesion, and found that the dependency of T-T (6-4)PP bypass on Polζ is not sequence specific. However, the misincorporation frequency at position +1 differed significantly among these templates. The misincorporation of A at position +1 occurred frequently when a purine base was located at position -1. These results indicate that Polζ-dependent extension plays a major role in inducing base substitutions in (6-4)PP-induced mutagenesis, and its fidelity is affected by sequence context surrounding a lesion.

A simple and rapid method for measuring human natural killer cell function in whole blood by anti-NKp30-conjugated nanoparticles

Natural killer (NK) cells play a central role as innate immune effector cells to virus infected cells and tumor cells. The standard assay to evaluate NK activity is 51Cr release assay using radio-labeled K562 cells, however, new methods using fluorescence-labeled targets or flow cytometry to examine degranulation markers have been developed recently. In addition to cytotoxicity, NK cells enable to produce various cytokines to regulate the adaptive immune responses in infection, inflammation and cancer. Here we generated nanoparticles conjugated with various antibody for NK receptors and examined to stimulate human whole blood with these nanoparticles instead of K562 target cells. We found that various cytokines such as IFN-γ, IL-6, IL-1β and CCL2 were produced by NK cells in whole blood by anti-NKp30-conjugated nanoparticles in dose-dependent manner more than by anti-NKp46 or anti-NKG2D nanoparticles. Production of IFN-γ was detected within 4 hours and reached maximum level at 24 hours after stimulation. IFN-γ production was relatively high at incubation temperature of 37°C, but that was significantly decreased over 39°C. Importantly, we could evaluate the reproducible cytokine production in same donors at another blood collection date because of the stable stimulus of nanoparticles and less variation data by human manipulation for lymphocyte separation. Additionally, cytokine secretion did not correlate with NK cell-mediated lysis of K562 target cells and NK cell numbers in whole blood. These data indicated that this method using NKp30 nanoparticles might be useful for measurement of individual differences of NK function especially correlated in adaptive immune response and inflammation.

Effects of Motor Imagery on Cognitive Function and Prefrontal Cortex Activity in Normal Adults Evaluated by NIRS

Recent near-infrared spectroscopy (NIRS) studies demonstrated that physical exercise enhances working memory (WM) performance and prefrontal cortex (PFC) activity during WM tasks in normal adults. Interestingly, the effects of rehabilitation (i.e. physiotherapy) on post-stroke patients could be enhanced by motor imagery (MI), an active process during which the specified action is reproduced within WM without any actual physical movement. However, it is not known whether MI can enhance cognitive function and associated brain activity. To clarify these issues, we evaluated the effect of MI on WM performance and PFC activity during WM tasks in normal adults, employing NIRS. We studied 10 healthy adults. The present study was a crossover comparison test; the MI training and control condition (rest) were applied to the subjects at random. The Time Up and Go method was used for MI training: the subject sat on a chair and conducted MI for 3 min, three times. Neuronal activity (oxyhemoglobin concentration) in the bilateral PFC was measured using 2-CH NIRS during WM tasks. We found that MI improved the behavioral performance of WM compared with the control (p < 0.01). NIRS revealed that MI enhanced PFC activity induced by the WM task compared with the control task (p < 0.01). These results suggest that MI can improve cognitive function and increase associated PFC activity in normal adults.

Sulfotransferase-1A1-dependent bioactivation of aristolochic acid I and N-hydroxyaristolactam I in human cells

Aristolochic acids (AA) are implicated in the development of chronic renal disease and upper urinary tract carcinoma in humans. Using in vitro approaches, we demonstrated that N-hydroxyaristolactams, metabolites derived from partial nitroreduction of AA, require sulfotransferase (SULT)-catalyzed conjugation with a sulfonyl group to form aristolactam-DNA adducts. Following up on this observation, bioactivation of AA-I and N-hydroxyaristolactam I (AL-I-NOH) was studied in human kidney (HK-2) and skin fibroblast (GM00637) cell lines. Pentachlorophenol, a known SULT inhibitor, significantly reduced cell death and aristolactam-DNA adduct levels in HK-2 cells following exposure to AA-I and AL-I-NOH, suggesting a role for Phase II metabolism in AA activation. A gene knockdown, siRNA approach was employed to establish the involvement of selected SULTs and nitroreductases in AA-I bioactivation. Silencing of SULT1A1 and PAPSS2 led to a significant decrease in aristolactam-DNA levels in both cell lines following exposure to AA-I, indicating the critical role for sulfonation in the activation of AA-I in vivo Since HK-2 cells proved relatively resistant to knockdown with siRNAs, gene silencing of xanthine oxidoreductase, cytochrome P450 oxidoreductase and NADPH:quinone oxidoreductase was conducted in GM00637 cells, showing a significant increase, decrease and no effect on aristolactam-DNA levels, respectively. In GM00637 cells exposed to AL-I-NOH, suppressing the SULT pathway led to a significant decrease in aristolactam-DNA formation, mirroring data obtained for AA-I. We conclude from these studies that SULT1A1 is involved in the bioactivation of AA-I through the sulfonation of AL-I-NOH, contributing significantly to the toxicities of AA observed in vivo.

Effects of Physical Exercise on Working Memory and Prefrontal Cortex Function in Post-Stroke Patients

Physical exercise enhances prefrontal cortex activity and improves working memory performance in healthy older adults, but it is not clear whether this remains the case in post-stroke patients. Therefore, the aim of this study was to examine the acute effect of physical exercise on prefrontal cortex activity in post-stroke patients using near-infrared spectroscopy (NIRS). We studied 11 post-stroke patients. The patients performed Sternberg-type working memory tasks before and after moderate intensity aerobic exercise (40 % of maximal oxygen uptake) with a cycling ergometer for 15 min. We measured the NIRS response at the prefrontal cortex during the working memory task. We evaluated behavioral performance (response time and accuracy) of the working memory task. It was found that physical exercise improved behavioral performance of the working memory task compared with the control condition (p < 0.01). In addition, NIRS analysis indicated that physical exercise enhanced prefrontal cortex activation, particularly in the right prefrontal cortex (p < 0.05), during the working memory task compared with the control condition. These findings suggest that the moderate-intensity aerobic exercise enhances prefrontal cortex activity and improves working memory performance in post-stroke patients.

Physical interaction between SLX4 (FANCP) and XPF (FANCQ) proteins and biological consequences of interaction-defective missense mutations

SLX4 (FANCP) and XPF (FANCQ) proteins interact with each other and play a vital role in the Fanconi anemia (FA) DNA repair pathway. We have identified a SLX4 region and several amino acid residues that are responsible for this interaction. The study has revealed that the global minor allele, SLX4(Y546C), is defective in this interaction and cannot complement Fancp knockout mouse cells in mitomycin C-induced cytotoxicity or chromosomal aberrations. These results highly suggest this allele, as well as SLX4(L530Q), to be pathogenic. The interacting partner XPF is involved in various DNA repair pathways, and certain XPF mutations cause progeria, Cockayne syndrome (CS), and/or FA phenotypes. Because several atypical xeroderma pigmentosum (XP) phenotype-causing XPF missense mutations are located in the SLX4-interacting region, we suspected the disruption of the interaction with SLX4 in these XPF mutants, thereby causing severer phenotypes. The immunoprecipitation assay of cell extracts revealed that those XPF mutations, except XPF(C236R), located in the SLX4-interacting region cause instability of XPF protein, which could be the reason for the FA, progeria and/or CS phenotypes.

Mutational signature of aristolochic acid exposure as revealed by whole-exome sequencing

In humans, exposure to aristolochic acid (AA) is associated with urothelial carcinoma of the upper urinary tract (UTUC). Exome sequencing of UTUCs from 19 individuals with documented exposure to AA revealed a remarkably large number of somatic mutations and an unusual mutational signature attributable to AA. Most of the mutations (72%) in these tumors were A:T-to-T:A transversions, located predominantly on the nontranscribed strand, with a strong preference for deoxyadenosine in a consensus sequence (T/CAG). This trinucleotide motif overlaps the canonical splice acceptor site, possibly accounting for the excess of splice site mutations observed in these tumors. The AA mutational fingerprint was found frequently in oncogenes and tumor suppressor genes in AA-associated UTUC. The AA mutational signature was observed in one patient's tumor from a UTUC cohort without previous indication of AA exposure. Together, these results directly link an established environmental mutagen to cancer through genome-wide sequencing and highlight its power to reveal individual exposure to carcinogens.

Analysis of TP53 mutation spectra reveals the fingerprint of the potent environmental carcinogen, aristolochic acid

Genetic alterations in cancer tissues may reflect the mutational fingerprint of environmental carcinogens. Here we review the pieces of evidence that support the role of aristolochic acid (AA) in inducing a mutational fingerprint in the tumor suppressor gene TP53 in urothelial carcinomas of the upper urinary tract (UUT). Exposure to AA, a nitrophenathrene carboxylic acid present in certain herbal remedies and in flour prepared from wheat grain contaminated with seeds of Aristolochia clematitis, has been linked to chronic nephropathy and UUT. TP53 mutations in UUT of individuals exposed to AA reveal a unique pattern of mutations characterized by A to T transversions on the non-transcribed strand, which cluster at hotspots rarely mutated in other cancers. This unusual pattern, originally discovered in UUTs from two different populations, one in Taiwan, and one in the Balkans, has been reproduced experimentally by treating mouse cells that harbor human TP53 sequences with AA. The convergence of molecular epidemiological and experimental data establishes a clear causal association between exposure to the human carcinogen AA and UUT. Despite bans on the sale of herbs containing AA, their use continues, raising global public health concern and an urgent need to identify populations at risk.

Aristolochic acid-induced upper tract urothelial carcinoma in Taiwan: clinical characteristics and outcomes

Aristolochic acid (AA), a component of all Aristolochia-based herbal medicines, is a potent nephrotoxin and human carcinogen associated with upper urinary tract urothelial carcinoma (UUC). To investigate the clinical and pathological characteristics of AA-induced UUC, this study included 152 UUC patients, 93 of whom had been exposed to AA based on the presence of aristolactam-DNA adducts in the renal cortex. Gene sequencing was used to identify tumors with A:T-to-T:A transversions in TP53, a mutational signature associated with AA. Cases with both aristolactam-DNA adducts and A:T-to-T:A transversions in TP53 were defined as AA-UUC, whereas patients lacking both of these biomarkers were classified as non-AA-UUC. Cases with either biomarker were classified as possible-AA-UUC. Forty (26%), 60 (40%), and 52 (34%) patients were classified as AA-UUC, possible-AA-UUC and non-AA-UUC, respectively. AA-UUC patients were younger (median ages: 64, 68, 68 years, respectively; p=0.189), predominately female (65%, 42%, 35%, respectively; p=0.011), had more end-stage renal disease (28%, 10%, 12%, respectively; p=0.055), and were infrequent smokers (5%, 22%, 33%, respectively; p=0.07) compared to possible-AA-UUC and non-AA-UUC patients. All 14 patients who developed contralateral UUC had aristolactam-DNA adducts; ten of these also had signature mutations. The contralateral UUC-free survival period was shorter in AA-UUC compared to possible- or non-AA-UUC (p=0.019 and 0.002, respectively), whereas no differences among groups were observed for bladder cancer recurrence. In conclusion, AA-UUC patients tend to be younger and female, and have more advanced renal disease. Notably, AA exposure was associated with an increased risk for developing synchronous bilateral and metachronous contralateral UUC.

The vital role of polymerase ζ and REV1 in mutagenic, but not correct, DNA synthesis across benzo[a]pyrene-dG and recruitment of polymerase ζ by REV1 to replication-stalled site

The DNA synthesis across DNA lesions, termed translesion synthesis (TLS), is a complex process influenced by various factors. To investigate this process in mammalian cells, we examined TLS across a benzo[a]pyrene dihydrodiol epoxide-derived dG adduct (BPDE-dG) using a plasmid bearing a single BPDE-dG and genetically engineered mouse embryonic fibroblasts (MEFs). In wild-type MEFs, TLS was extremely miscoding (>90%) with G → T transversions being predominant. Knockout of the Rev1 gene decreased both the TLS efficiency and the miscoding frequency. Knockout of the Rev3L gene, coding for the catalytic subunit of pol ζ, caused even greater decreases in these two TLS parameters; almost all residual TLS were error-free. Thus, REV1 and pol ζ are critical to mutagenic, but not accurate, TLS across BPDE-dG. The introduction of human REV1 cDNA into Rev1(-/-) MEFs restored the mutagenic TLS, but a REV1 mutant lacking the C terminus did not. Yeast and mammalian three-hybrid assays revealed that the REV7 subunit of pol ζ mediated the interaction between REV3 and the REV1 C terminus. These results support the hypothesis that REV1 recruits pol ζ through the interaction with REV7. Our results also predict the existence of a minor REV1-independent pol ζ recruitment pathway. Finally, although mutagenic TLS across BPDE-dG largely depends on RAD18, experiments using Polk(-/-) Polh(-/-) Poli(-/-) triple-gene knockout MEFs unexpectedly revealed that another polymerase(s) could insert a nucleotide opposite BPDE-dG. This indicates that a non-Y family polymerase(s) can insert a nucleotide opposite BPDE-dG, but the subsequent extension from miscoding termini depends on REV1-polζ in a RAD18-dependent manner.

TP53 Mutational signature for aristolochic acid: an environmental carcinogen

This study was designed to establish the TP53 mutational spectrum of aristolochic acid (AA), examined in the context of endemic (Balkan) nephropathy, an environmental disease associated with transitional cell (urothelial) carcinomas of the upper urinary tract (UUC). Tumor tissue was obtained from residents of regions in Bosnia, Croatia and Serbia where endemic nephropathy has been prevalent for over 50 years. Fifty-nine TP53 mutations were detected in 42 of the 97 tumors analyzed. Mutational spectra were dominated by A:T to T:A transversions with the mutated adenines located almost exclusively on the nontranscribed strand. This marked strand bias is attributed to selective processing of aristolactam-dA adducts by transcription-coupled nucleotide excision repair. Hotspots for A:T to T:A mutations include codons 131 and 179 and the 5'-AG acceptor splice site of intron 6. The unique TP53 mutational signature for AA identified in this study can be used to explore the hypothesis that botanical products containing this human carcinogen and nephrotoxin are responsible, in part, for the high prevalence of UUC and chronic renal disease in countries where Aristolochia herbal remedies traditionally have been used for medicinal purposes.

The roles of DNA polymerases κ and ι in the error-free bypass of N2-carboxyalkyl-2'-deoxyguanosine lesions in mammalian cells

To counteract the deleterious effects of DNA damage, cells are equipped with specialized polymerases to bypass DNA lesions. Previous biochemical studies revealed that DinB family DNA polymerases, including Escherichia coli DNA polymerase IV and human DNA polymerase κ, efficiently incorporate the correct nucleotide opposite some N(2)-modified 2'-deoxyguanosine derivatives. Herein, we used shuttle vector technology and demonstrated that deficiency in Polk or Poli in mouse embryonic fibroblast (MEF) cells resulted in elevated frequencies of G→T and G→A mutations at N(2)-(1-carboxyethyl)-2'-deoxyguanosine (N(2)-CEdG) and N(2)-carboxymethyl-2'-deoxyguanosine (N(2)-CMdG) sites. Steady-state kinetic measurements revealed that human DNA polymerase ι preferentially inserts the correct nucleotide, dCMP, opposite N(2)-CEdG lesions. In contrast, no mutation was found after the N(2)-CEdG- and N(2)-CMdG-bearing plasmids were replicated in POLH-deficient human cells or Rev3-deficient MEF cells. Together, our results revealed that, in mammalian cells, both polymerases κ and ι are necessary for the error-free bypass of N(2)-CEdG and N(2)-CMdG. However, in the absence of polymerase κ or ι, other translesion synthesis polymerase(s) could incorporate nucleotide(s) opposite these lesions but would do so inaccurately.

Abstract LB-401: TP-53 mutational signature of a urothelial carcinogen

Aristolochic acid (AA), a powerful nephrotoxin and human carcinogen, was shown recently (PNAS, 102, 12129 (2007)) to be the causative agent in endemic (Balkan) nephropathy (EN). This devastating environmental disease is associated with a &gt;50% incidence of urothelial carcinomas of the upper urinary tract (UUC). Following metabolic activation, AA reacts with genomic DNA to form covalent adducts (AL-DNA). These mutagenic lesions persist for decades in the renal cortex where they serve as robust biomarkers of exposure to AA. In EN, exposure occurs through ingestion of bread prepared from flour contaminated with AA. In China and other Asian countries, a significant fraction of the population also is exposed to AA, in this case through the medicinal use of herbal medicines prepared from Aristohchia plants. Such exposure, well-documented in Taiwan (JNCI, 102 1 (2009)) raises an important question: Do AA-induced cancers occur globally as a silent iatrogenic disease? To address this public health issue, we undertook a systematic study of 75 UUC patients residing in regions of Croatia, Bosnia and Serbia where EN and UUC are prevalent. DNA was obtained, with informed consent, from renal cortex and tumor tissues following nephroureterectomy. AL-DNA adducts were quantified by 32P- post-labeling techniques. Chip-sequencing technology was utilized to detect base substitutions in the TP-53 gene. Adducts were found in the renal cortex of 65% of patients with UUC. The TP53 mutation spectrum was dominated by A: TàT: A transversions located almost exclusively on the non-transcribed DNA strand. Twenty-five of these mutations occurred in exons and 12 mutations at 5′AG splice sites. Additionally, we identified several A: T àT: A mutational hotspots, including the first base of codon 131. TP53 gene mutations at this position have not previously been reported. The mechanism underlying the marked strand bias appears to be a selective failure to excise AL-DNA adducts by global genomic nucleotide excision repair. This factor also may account for the remarkable persistence of these adducts in human tissues, in some cases, for more than 50 years. Thus, AA joins vinyl chloride and aflatoxin as human chemical carcinogens with a definitive mutational signature. This information, coupled with the use of AL-DNA adducts as a biomarker, may be used to establish the role of AA ingestion in countries with a high prevalence of UUC and chronic renal disease. Importantly, public health authorities in countries where Aristolochia herbal preparations are in use should implement measures to reduce human exposure to this toxic and carcinogenic herb. (Supported by grant ES-04068 from NIEHS and the Croatian Ministry of Science)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-401.

Mechanism of the anti-obesity effects induced by a novel melanin-concentrating hormone 1-receptor antagonist in mice

BACKGROUND AND PURPOSE

Melanin-concentrating hormone (MCH) is an orexigenic neuropeptide expressed in the lateral hypothalamus that is involved in feeding and body weight regulation. Intracerebroventricular infusion of a peptidic MCH1 receptor antagonist ameliorated obesity in murine models. Recently, small molecule MCH1 receptor antagonists have been developed and characterized for the treatment of obesity. However, little is known of the mechanism of the anti-obesity effects of MCH1 receptor antagonists.

EXPERIMENTAL APPROACH

To examine the mechanisms of action of the anti-obesity effect of MCH1 receptor antagonists more precisely, we conducted a pair-feeding study in mice with diet-induced obesity (DIO), chronically treated with an orally active and highly selective MCH1 receptor antagonist and examined changes in mRNA expression levels in liver, brown and white adipose tissues. We also assessed the acute effects of the MCH1 receptor antagonist in energy expenditure under thermoneutral conditions.

KEY RESULTS

Treatment with the MCH1 receptor antagonist at 30 mg.kg(-1) for 1 month moderately suppressed feeding and significantly reduced body weight by 24%. In contrast, pair-feeding resulted in a smaller weight reduction of 10%. Treatment with the MCH1 receptor antagonist resulted in a higher body temperature compared with the pair-fed group. TaqMan and calorimetry data suggested that the MCH1 receptor antagonist also stimulated thermogenesis.

CONCLUSIONS AND IMPLICATIONS

Our results indicate that an MCH1 receptor antagonist caused anti-obesity effects im mice by acting on both energy intake and energy expenditure.

DNA adducts of aristolochic acid II: total synthesis and site-specific mutagenesis studies in mammalian cells

Aristolochic acids I and II (AA-I, AA-II) are found in all Aristolochia species. Ingestion of these acids either in the form of herbal remedies or as contaminated wheat flour causes a dose-dependent chronic kidney failure characterized by renal tubulointerstitial fibrosis. In ∼50% of these cases, the condition is accompanied by an upper urinary tract malignancy. The disease is now termed aristolochic acid nephropathy (AAN). AA-I is largely responsible for the nephrotoxicity while both AA-I and AA-II are genotoxic. DNA adducts derived from AA-I and AA-II have been isolated from renal tissues of patients suffering from AAN. We describe the total synthesis, de novo, of the dA and dG adducts derived from AA-II, their incorporation site-specifically into DNA oligomers and the splicing of these modified oligomers into a plasmid construct followed by transfection into mouse embryonic fibroblasts. Analysis of the plasmid progeny revealed that both adducts blocked replication but were still partly processed by DNA polymerase(s). Although the majority of coding events involved insertion of correct nucleotides, substantial misincorporation of bases also was noted. The dA adduct is significantly more mutagenic than the dG adduct; both adducts give rise, almost exclusively, to misincorporation of dA, which leads to AL-II-dA→T and AL-II-dG→T transversions.

Two distinct translesion synthesis pathways across a lipid peroxidation-derived DNA adduct in mammalian cells

Translesion DNA synthesis (TLS) of damaged DNA templates is catalyzed by specialized DNA polymerases. To probe the cellular TLS mechanism, a host-vector system consisting of mouse fibroblasts and a replicating plasmid bearing a single DNA adduct was developed. This system was used to explore the TLS mechanism of a heptanone-etheno-dC (H-epsilondC) adduct, an endogenous lesion produced by lipid peroxidation. In wild-type cells, H-epsilondC almost exclusively directed incorporation of dT and dA. Whereas knockout of the Y family TLS polymerase genes, Polh, Polk, or Poli, did not qualitatively affect these TLS events, inactivation of the Rev3 gene coding for a subunit of polymerase zeta or of the Rev1 gene abolished TLS associated with dA, but not dT, insertion. The analysis of results of the cellular studies and in vitro TLS studies using purified polymerases has revealed that the insertion of dA and dT was catalyzed by different polymerases in cells. While insertion of dT can be catalyzed by polymerase eta, kappa, and iota, insertion of dA is catalyzed by an unidentified polymerase that cannot catalyze extension from the resulting dA terminus. Therefore, the extension from this terminus requires the activity of polymerase zeta-REV1. These results provide new insight into how cells use different TLS pathways to overcome a synthesis block.

A 12 month in vivo study on the response of bone to a hydroxyapatite–polymethylmethacrylate cranioplasty composite

We investigated the osteoconductivity and biocompatibility in vivo of a new hydroxyapatite-polymethylmethacrylate (HA-PMMA) composite developed for use as an implant material for cranioplasty, which is expected to have the good osteoconductivity of HA together with the strength and ease of handling of PMMA. The HA-PMMA composites were implanted in eight full-grown beagles and then 6, 12, 24 weeks and 1 year after implantation, the animals were sacrificed and the implanted materials removed along with the surrounding tissues. Extirpated specimens were studied using an optical microscope and micro-computed tomography (micro-CT). Fibrous connective tissue was prominent in the interface of the composite at 6 weeks. New bone formation was seen around the implant, 12 and 24 weeks after operation. At 1 year, new bone filled in the interface of the HA-PMMA composite and adhered to the surrounding autogenous bone. Mixing HA and PMMA did not interfere with the osteoconductivity of the HA component. In micro-CT findings, the new bone growing on the HA-PMMA composite could be seen attaching preferentially to HA particles exposed at the composite surface, rather than the PMMA. This study demonstrated that this HA-PMMA composite is a good candidate for cranial bone implants due to its good osteoconductivity and biocompatibility.

Aristolochic acid and the etiology of endemic (Balkan) nephropathy

Endemic (Balkan) nephropathy (EN), a devastating renal disease affecting men and women living in rural areas of Bosnia, Bulgaria, Croatia, Romania, and Serbia, is characterized by its insidious onset, invariable progression to chronic renal failure and a strong association with transitional cell (urothelial) carcinoma of the upper urinary tract. Significant epidemiologic features of EN include its focal occurrence in certain villages and a familial, but not inherited, pattern of disease. Our experiments test the hypothesis that chronic dietary poisoning by aristolochic acid is responsible for EN and its associated urothelial cancer. Using (32)P-postlabeling/PAGE and authentic standards, we identified dA-aristolactam (AL) and dG-AL DNA adducts in the renal cortex of patients with EN but not in patients with other chronic renal diseases. In addition, urothelial cancer tissue was obtained from residents of endemic villages with upper urinary tract malignancies. The AmpliChip p53 microarray was then used to sequence exons 2-11 of the p53 gene where we identified 19 base substitutions. Mutations at A:T pairs accounted for 89% of all p53 mutations, with 78% of these being A:T --> T:A transversions. Our experimental results, namely, that (i) DNA adducts derived from aristolochic acid (AA) are present in renal tissues of patients with documented EN, (ii) these adducts can be detected in transitional cell cancers, and (iii) A:T --> T:A transversions dominate the p53 mutational spectrum in the upper urinary tract malignancies found in this population lead to the conclusion that dietary exposure to AA is a significant risk factor for EN and its attendant transitional cell cancer.

Replication-coupled repair of crotonaldehyde/acetaldehyde-induced guanine-guanine interstrand cross-links and their mutagenicity

The repair of acetaldehyde/crotonaldehyde-induced guanine (N2)-guanine (N2) interstrand cross-links (ICLs), 3-(2-deoxyribos-1-yl)-5,6,7,8-(N2-deoxyguanosyl)-6(R or S)-methylpyrimido[1,2-alpha]purine-10(3H)-one, was studied using a shuttle plasmid bearing a site-specific ICL. Since the authentic ICLs can revert to monoadducts, a chemically stable model ICL, 1,3-bis(2'-deoxyguanos-N2-yl)butane derivative, was also employed to probe the ICL repair mechanism. Since the removal of ICL depends on the nucleotide excision repair (NER) mechanism in Escherichia coli, the plasmid bearing the model ICL failed to yield transformants in NER-deficient host cells, proving the stability of this ICL in cells. The authentic ICLs yielded transformants in the NER-deficient hosts; therefore, these transformants are produced by plasmid bearing spontaneously reverted monoadducts. In contrast, in NER-deficient human cells, the model ICL was removed by an NER-independent repair pathway, which is unique to higher eukaryotes. This repair did not associate with a transcriptional event, but with replication. The analysis of repaired molecules revealed that the authentic and model ICLs were repaired mostly (>94%) in an error-free manner in both hosts. The major mutations that were observed were G --> T transversions targeting the cross-linked dG located in the lagging strand template. These results support one of the current models for the mammalian NER-independent ICL repair mechanism, in which a DNA endonuclease(s) unhooks an ICL from the leading strand template at a stalled replication fork site by incising on both sides of the ICL and then translesion synthesis is conducted across the "half-excised" ICL attached to the lagging strand template to restore DNA synthesis.

Beneficial effect of interferon-β treatment in patients with multiple sclerosis is associated with transient increase in serum IL-6 level in response to interferon-β injection

In order to predict the clinical benefit of interferon-beta (IFN-beta) to patients with multiple sclerosis (MS), the following markers were investigated; (1) chronological change of cytokines (IFN-gamma, TNF-alpha, IL-6, IL-10, and TGF-beta) after administration of IFN-beta, (2) untoward effects of IFN-beta such as headache and arthralgia, (3) backgrounds of the patients such as age and relapse rate, (4) efficacy of IFN-beta therapy assessed by the change of relapse rate and progression of disability. Chronological blood sampling was performed 0, 10, and 24 h after injection of IFN-beta. The increase of serum IL-6 level in response to IFN-beta administration was associated with headache, arthralgia, relapse rate before treatment, and disability score at the initiation of the therapy. Significant association of change of serum TNF-alpha with age and headache was also observed. The important finding in this study was that patients with a transient increase in IL-6 in response to IFN-beta showed a slow disease progression. This result suggests that this transient increase in the serum IL-6 predicts favorable response to IFN-beta treatment.

Translesion DNA Synthesis across the Heptanone−Etheno-2‘-Deoxycytidine Adduct in Cells

4-Oxo-2(E)-nonenal, a lipid peroxidation-derived product, reacts with dG, dA, and dC in DNA to form heptanone (H)-etheno (epsilon) adducts. Among the three adducts, H-epsilondC is formed in the greatest abundance in in vitro reactions, and it has been detected in the C57BL/6JAPC(min) mouse model of colorectal cancer. To establish the genotoxic properties of this adduct, a site-specifically modified oligonucleotide was synthesized and incorporated into a shuttle vector. The modified vector was replicated in Escherichia coli and human cells. Analysis of the progeny plasmid has revealed that H-epsilondC strongly blocks DNA synthesis and markedly miscodes in both hosts. The miscoding frequency was 40-50% in bacteria and more than 90% in three human cell lines (xeroderma pigmentosum A and variant cells, and DNA repair wild-type cells). There was a drastic difference in coding events in these two hosts: dG and dC were almost exclusively inserted opposite the lesion in E. coli, while dA and dT were the preferential choices in human cells. These results indicate that this endogenous DNA adduct is very genotoxic to both organisms.

Genotoxicity of acetaldehyde- and crotonaldehyde-induced 1,N2-propanodeoxyguanosine DNA adducts in human cells

Reaction of crotonaldehyde or two molecules of acetaldehyde with DNA generates 3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxy-6-methylpyrimido[1,2-a]purine-10(3H)one (2, Scheme 1), which occurs in (6R, 8R) and (6S, 8S) configurations (Fig. 1). These diastereomers were site-specifically incorporated into oligonucleotides, which were then inserted into a double-stranded DNA vector for genotoxicity studies. Modified DNA was introduced into human xeroderma pigmentosum A (XPA) cells to allow replication. Analysis of progeny plasmid revealed that these DNA adducts inhibit DNA synthesis to similar degrees. (6S, 8S)-2 miscodes more frequently than (6R, 8R)-2: 10% versus 5%. For both adducts, major miscoding events were G-->T transversions, but G-->A transitions were also observed at a comparable level for (6R, 8R)-2. G-->C transversions were the second most common events for (6S, 8S)-2. Comparison of these results with those of other 1,N2-propanodeoxyguanosine (PdG) adducts, which were evaluated by the same system, indicates that (i) their synthesis inhibiting potencies are stronger than that of the unsubstituted analog, 3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-8-hydroxypyrimido[1,2-a]purine-10(3H)one (1, Scheme 1), but weaker than that of 3-(2'-deoxyribos-1'-yl)-5,6,7,8-tetrahydro-6-hydroxypyrimido[1,2-a]purine-10(3H)one (3, Scheme 1); (ii) both isomers of 2 are more miscoding than 1; (iii) the miscoding potency of (6S, 8S)-2 is comparable to those of 3 and a model PdG 4 lacking a hydroxyl and a methyl group (Fig. 1). Therefore, considering the fact that 2 are formed endogenously as well as exogenously, they may play a significant role in aging and cancer in humans.

The effect of hematoma removal for reducing the development of brain edema in cases of putaminal hemorrhage

INTRODUCTION

Surgical intervention in putaminal hemorrhage has been a controversial issue. The aim of this research is to evaluate the benefits of surgery for reducing the development of brain edema.

MATERIALS AND METHODS

Sixteen cases of putaminal hemorrhage were examined. Eight patients were treated conservatively (C group), and the other 8 patients were treated surgically (S group). Head CT scans were performed on the day of onset (day 0) in C group or performed just after surgery (day 0) in S group, and performed again once per period on days 1-7, 8-14, and 15-21. The volume of the mass including hematoma and edema (H + E) was measured using CT scans and the (H + E)/H0 ratios were calculated (H0; hematoma volume on day 0). The (H + E)/H0 ratios for each period were compared statistically between the 2 groups using a t-test.

RESULTS

The mean values of(H + E)/H0 ratios at each period were 2.19, 2.63, 2.53 in C group, and 1.29, 1.29, 0.66 in S group. The values in S group were significantly lower as compared with C group in every period (p < 0.01, < 0.05, < 0.01).

CONCLUSIONS

Hematoma volume reduction by surgery reduced the development of brain edema.

Progressive expression of vascular endothelial growth factor (VEGF) and angiogenesis after chronic ischemic hypoperfusion in rat

Cerebrovascular stenosis caused by arteriosclerosis induces failure of the cerebral circulation. Even if chronic cerebral hypoperfusion does not induce acute neuronal cell death, cerebral hypoperfusion may be a risk factor for neurodegenerative diseases. The purpose of this study was to determine if vasodilation, expression of VEGF, and neovascularization are homeostatic signs of cerebral circulation failure after permanent common carotid artery occlusion (CCAO) in the rat. Neuronal cell death in neocortex was observed 2 weeks after CCAO and gradually increased in a time-dependent manner. The diameter of capillaries and expression of VEGF also increased progressively after CCAO. Moreover, we observed unusual irregular angiogenic vasculature at 4 weeks. In conclusion, chronic hypoperfusion results in mechanisms to compensate for insufficiency in blood flow including vasodilation, VEGF expression, and neovascularization in the ischemic region. These results suggest that angiogenesis might be induced in adult brain through the support of growth factors and transplantation of vascular progenitor cells, and that neovascularization might be a therapeutic strategy for children and adults with diseases such as vascular dementia.

Analysis of parameter variations in L-Q equations for river runoff processes from the viewpoint of spatial and temporal conditions

This study aims to find out variation characteristics of the parameters of 'a' and 'b' in L = a x Q(b), an empirical equation for run-off loading (L) and flow rate (Q), by evaluating the effects of flow conditions and regional properties of the watersheds on the values. We selected the Kamo River basin (155 km2) as a study field, and conducted various kinds of investigations, such as 80 day high frequency observations, continuous monitoring for more than 2 years, storm event surveys, and simultaneous surveys of 39 stations. Then, we obtained 7-170 data in each of 39 sampling stations. The main results obtained are as follows: (1) L-Q equation with a range of 'a' can express L-Q relation in most of the WQIs (water quality indices); (2) 'a' receives temporal (flow condition) effects more in SS, VSS and Al, while it receives regional effect more in inorganic carbon, TN, Ca and Fe; (3) both of flow change in storm events, and base flow levels affect the L-Q relation, and their effects can classify the WQIs into several groups; (4) the effects of regional properties were obviously observed in 'a', and quantitatively evaluated, especially for density of population.

Estimation of annual pollutant loadings in two small catchments and examination of their differences caused by regional properties

A series of runoff surveys was conducted for more than one year in two small catchments of the Kamo River basin (75.4 km2) and the Takano River basin (66.8 km2) in Kyoto, Japan, which adjoin each other, and may have the same precipitation pattern. The investigation consisted of a high-frequency periodic survey, a long-term regular survey and a storm event survey. The survey results were compared with the regional properties of the basins, and the following results were obtained. (1) Pollutant loadings were successfully estimated as two portions of base discharge and storm events discharge from the survey results. (2) Estimated annual loading of the sites was 2.9-4.5, 1.3-1.8, 17-27, 1.3-2.2, 0.076-0.97 t/km2/y, respectively for COD(Mn), DOC, SS, TN and TP. (3) 52-53% of the whole flow, which was caused by rainfall events, conveyed 81-87, 68-73, 92-95, 64-67, 76-81% of the whole loading, respectively for COD(Mn), DOC, SS, TN and TP. (4) Differences of regional properties in two basins cause different runoff patterns, but the differences in runoff patterns also depend on the rainfall patterns. In general, a more urbanized basin receives early and strong influence of precipitation on the storm event runoff.

Futile short-patch DNA base excision repair of adenine:8-oxoguanine mispair

8-oxo-7, 8-dihydrodeoxyguanosine (8-oxo-dG), one of the representative oxidative DNA lesions, frequently mispairs with the incoming dAMP during mammalian DNA replication. Mispaired dA is removed by post-replicative base excision repair (BER) initiated by adenine DNA glycosylase, MYH, creating an apurinic (AP) site. The subsequent mechanism ensuring a dC:8-oxo-dG pair, a substrate for 8-oxoguanine DNA glycosylase (OGG1), remains to be elucidated. At the nucleotide insertion step, none of the mammalian DNA polymerases examined exclusively inserted dC opposite 8-oxo-dG that was located in a gap. AP endonuclease 1, which possesses 3'-->5' exonuclease activity and potentially serves as a proofreader, did not discriminate dA from dC that was located opposite 8-oxo-dG. However, human DNA ligases I and III joined 3'-dA terminus much more efficiently than 3'-dC terminus when paired to 8-oxo-dG. In reconstituted short-patch BER, repair products contained only dA opposite 8-oxo-dG. These results indicate that human DNA ligases discriminate dC from dA and that MYH-initiated short-patch BER is futile and hence this BER must proceed to long-patch repair, even if it is initiated as short-patch repair, through strand displacement synthesis from the ligation-resistant dC terminus to generate the OGG1 substrate, dC:8-oxo-dG pair.

Comparative evaluation of the bioreactivity and mutagenic spectra of acrolein-derived alpha-HOPdG and gamma-HOPdG regioisomeric deoxyguanosine adducts

Acrolein is a bifunctional electrophile, present as an ubiquitous environmental pollutant and an endogenous cellular product of lipid peroxidation. Reaction of acrolein with deoxyguanosine produces two regioisomeric DNA adducts, specifically gamma-hydroxypropanodeoxyguanosine (gamma-HOPdG) and alpha-hydroxypropanodeoxyguanosine (alpha-HOPdG). While previous investigations have focused on the major gamma-HOPdG adduct, little is known about the properties of the minor alpha-HOPdG adduct. Therefore, this comparative investigation has assessed the following: the ability of each adduct to undergo secondary chemical reactions with biomolecules to form various cross-linked species, in vitro translesion DNA synthesis, and mutagenic properties, following replication in mammalian cells. In contrast to gamma-HOPdG, which is capable of forming DNA-DNA, DNA-peptide, and DNA-protein cross-links, alpha-HOPdG did not form any of these cross-linked species. These results can be attributed to the inability of the alpha-HOPdG adduct to undergo ring opening, whereas the gamma-HOPdG adduct forms the ring open, acyclic N(2) oxopropyl in duplex DNA, which readily reacts with nucleophilic functions. Consistent with this interpretation, when polymerase eta replication bypass of DNA containing alpha-HOPdG was assayed, this lesion posed a stronger block to replication than the gamma-HOPdG adduct, closely resembling the results for polymerase eta bypass of propanodeoxyguanosine in which the exocyclic adduct remains permanently ring-closed. Cellular replication and mutagenesis assays in COS-7 cells using single-stranded DNA containing a site specific alpha-HOPdG revealed that this adduct was significantly mutagenic, yielding a nearly identical frequency and spectrum of mutations as compared with the gamma-HOPdG adduct.

Mammalian translesion DNA synthesis across an acrolein-derived deoxyguanosine adduct. Participation of DNA polymerase eta in error-prone synthesis in human cells

alpha-OH-PdG, an acrolein-derived deoxyguanosine adduct, inhibits DNA synthesis and miscodes significantly in human cells. To probe the cellular mechanism underlying the error-free and error-prone translesion DNA syntheses, in vitro primer extension experiments using purified DNA polymerases and site-specific alpha-OH-PdG were conducted. The results suggest the involvement of pol eta in the cellular error-prone translesion synthesis. Experiments with xeroderma pigmentosum variant cells, which lack pol eta, confirmed this hypothesis. The in vitro results also suggested the involvement of pol iota and/or REV1 in inserting correct dCMP opposite alpha-OH-PdG during error-free synthesis. However, none of translesion-specialized DNA polymerases catalyzed significant extension from a dC terminus when paired opposite alpha-OH-PdG. Thus, our results indicate the following. (i) Multiple DNA polymerases are involved in the bypass of alpha-OH-PdG in human cells. (ii) The accurate and inaccurate syntheses are catalyzed by different polymerases. (iii) A modification of the current eukaryotic bypass model is necessary to account for the accurate bypass synthesis in human cells.

Mutagenesis by acrolein-derived propanodeoxyguanosine adducts in human cells

Acrolein, which is widely spread in the environment and is produced by lipid peroxidation in cells, reacts with DNA to form two exocyclic 1,N2-propanodeoxyguanosine (PdG) adducts. To establish their relative contribution to the acrolein mutagenicity, the genotoxic properties of alpha-OH-PdG and gamma-OH-PdG together with their model DNA adduct, PdG, were studied in human cells. DNA adducts were incorporated site-specifically into a SV40/BK virus origin-based shuttle vector and replicated in xeroderma pigmentosum complementation group A (XPA) cells. Analysis of progeny plasmid revealed that alpha-OH-PdG and PdG strongly block DNA synthesis and that both adducts induced base substitutions with G --> T transversions predominating. Primer extension studies, catalyzed by the 3'-->5' exonuclease-deficient Klenow fragment of Escherichia coli pol I, revealed limited extension from the 3' primer termini opposite these two adducts. In contrast, gamma-OH-PdG did not strongly block DNA synthesis or miscode in XPA cells. Primer extension from a dC terminus opposite gamma-OH-PdG was much more efficient than that opposite alpha-OH-PdG or PdG. These results indicate that the minor alpha-OH-PdG adduct is more genotoxic than the major gamma-OH-PdG. Furthermore, experiments using a HeLa whole cell extract indicate that all three DNA adducts are not efficiently removed from DNA by base excision repair.

The acceleration of cosmic-ray protons in the supernova remnant RX J1713.7-3946

Protons with energies up to approximately 10(15) eV are the main component of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking. Electrons are known to be accelerated to cosmic-ray energies in supernova remnants, and the shock waves associated with such remnants, when they hit the surrounding interstellar medium, could also provide the energy to accelerate protons. The signature of such a process would be the decay of pions (pi(0)), which are generated when the protons collide with atoms and molecules in an interstellar cloud: pion decay results in gamma-rays with a particular spectral-energy distribution. Here we report the observation of cascade showers of optical photons resulting from gamma-rays at energies of approximately 10(12) eV hitting Earth's upper atmosphere, in the direction of the supernova remnant RX J1713.7-3946. The spectrum is a good match to that predicted by pion decay, and cannot be explained by other mechanisms.

Genotoxic mechanism for the major acrolein-derived deoxyguanosine adduct in human cells

Acrolein, widely distributed in the environment and also produced endogenously, forms deoxyguanosine adducts in DNA. The genotoxicity of the major acrolein-dG adduct, 8alpha and 8beta isomers of 3H-8-hydroxy-3-(beta-D-2'-deoxyribofuranosyl)-5,6,7,8-tetrahydropyrido[3,2-a]purine-9-one (gamma-OH-PdG), and the model adduct, PdG, which lacks the hydroxy group of gamma-OH-PdG, was investigated in human cells. The adducts were site-specifically incorporated into a SV40/BK origin-based shuttle vector. Estimated efficiencies of translesion DNA synthesis were 73% for gamma-OH-PdG and 25% for PdG when compared with dG control. Gamma-OH-PdG was marginally miscoding (<or=1%), inducing G-->T and G-->A base substitutions in HeLa and xeroderma pigmentosum complementation group A (XP-A) and variant (XP-V) cells. There was no significant difference in the miscoding frequency when the adduct was inserted in the leading or lagging strand. PdG was more miscoding than gamma-OH-PdG by inducing targeted base substitutions (G-->T, A, or C) at a frequency of 7.5% in XP-A cells. Thus, the authentic major adduct, gamma-OH-PdG, is less blocking to DNA synthesis and less miscoding than the model adduct, PdG.

Dicationic dithiocarbamate carbapenems with anti-MRSA activity

A new class of 1 beta-methylcarbapenems bearing a doubly quaternarized 1,4-diazabicyclooctane (DABCO) substituted dithiocarbamate moiety at the C-2 side chain was prepared, and the biological profiles of the compounds, including in vitro and in vivo anti-MRSA activity and DHP-I susceptibility, were evaluated to identify a carbapenem derivative that was superior to BO-3482 (1). As a result, we discovered a 1 beta-methyl-2-[4-(4-carbamoylmethyl-1,4-diazabicyclo[2,2,2]octanediium-1-yl)methyl-1,2,3,6-tetrahydropyridinylthiocarbonylthio]carbapenem, 14a showing greater than 2-fold better anti-MRSA activity in a mouse infection model and 3-fold better DHP-I susceptibility as compared with BO-3482 (1).

Translesion DNA Synthesis Catalyzed by Human Pol η and Pol κ across 1,N 6-Ethenodeoxyadenosine

1,N(6)-Ethenodeoxyadenosine, a DNA adduct generated by exogenous and endogenous sources, severely blocks DNA synthesis and induces miscoding events in human cells. To probe the mechanism for in vivo translesion DNA synthesis across this adduct, in vitro primer extension studies were conducted using newly identified human DNA polymerases (pol) eta and kappa, which have been shown to catalyze translesion DNA synthesis past several DNA lesions. Steady-state kinetic analyses and analysis of translesion products have revealed that the synthesis is >100-fold more efficient with pol eta than with pol kappa and that both error-free and error-prone syntheses are observed with these enzymes. The miscoding events include both base substitution and frameshift mutations. These results suggest that both polymerases, particularly pol eta, may contribute to the translesion DNA synthesis events observed for 1,N(6)-ethenodeoxyadenosine in human cells.

Responses to the major acrolein-derived deoxyguanosine adduct in Escherichia coli

Acrolein, a reactive alpha,beta-unsaturated aldehyde found ubiquitously in the environment and formed endogenously in mammalian cells, reacts with DNA to form an exocyclic DNA adduct, 3H-8-hydroxy-3-(beta-D-2'-deoxyribofuranosyl)-5,6,7,8-tetrahydropyrido[3,2-a]purine-9-one (gamma-OH-PdG). The cellular processing and mutagenic potential of gamma-OH-PdG have been examined, using a site-specific approach in which a single adduct is embedded in double-strand plasmid DNA. Analysis of progeny plasmid reveals that this adduct is excised by nucleotide excision repair. The apparent level of inhibition of DNA synthesis is approximately 70% in Escherichia coli DeltarecA, uvrA. The block to DNA synthesis can be overcome partially by recA-dependent recombination repair. Targeted G --> T transversions were observed at a frequency of 7 x 10(-4)/translesion synthesis. Inactivation of polB, dinB, and umuD,C genes coding for "SOS" DNA polymerases did not affect significantly the efficiency or fidelity of translesion synthesis. In vitro primer extension experiments revealed that the Klenow fragment of polymerase I catalyzes error-prone synthesis, preferentially incorporating dAMP and dGMP opposite gamma-OH-PdG. We conclude from this study that DNA polymerase III catalyzes translesion synthesis across gamma-OH-PdG in an error-free manner. Nucleotide excision repair, recombination repair, and highly accurate translesion synthesis combine to protect E. coli from the potential genotoxicity of this DNA adduct.

Escherichia coli responses to a single DNA adduct

To study the mechanisms by which Escherichia coli modulates the genotoxic effects of DNA damage, a novel system has been developed which permits quantitative measurements of various E. coli pathways involved in mutagenesis and DNA repair. Events measured include fidelity and efficiency of translesion DNA synthesis, excision repair, and recombination repair. Our strategy involves heteroduplex plasmid DNA bearing a single site-specific DNA adduct and several mismatched regions. The plasmid replicates in a mismatch repair-deficient host with the mismatches serving as strand-specific markers. Analysis of progeny plasmid DNA for linkage of the strand-specific markers identifies the pathway from which the plasmid is derived. Using this approach, a single 1, N(6)-ethenodeoxyadenosine adduct was shown to be repaired inefficiently by excision repair, to inhibit DNA synthesis by approximately 80 to 90%, and to direct the incorporation of correct dTMP opposite this adduct. This approach is especially useful in analyzing the damage avoidance-tolerance mechanisms. Our results also show that (i) progeny derived from the damage avoidance-tolerance pathway(s) accounts for more than 15% of all progeny; (ii) this pathway(s) requires functional recA, recF, recO, and recR genes, suggesting the mechanism to be daughter strand gap repair; (iii) the ruvABC genes or the recG gene is also required; and (iv) the RecG pathway appears to be more active than the RuvABC pathway. Based on these results, the mechanism of the damage avoidance-tolerance pathway is discussed.

Immunohistochemical detection of calmodulin and calmodulin-dependent protein kinase II in the mouse testis

We reported previously that in mouse testis calmodulin-dependent protein phosphatase (calcineurin) is localised in the nuclei of round and elongating spermatids (Cell Tissue Res. 1995; 281: 273-81). In this study, we studied the immunohistochemical localisation of calcium/calmodulin-dependent protein kinase (CaM kinase II) using antibodies against CaM kinase IIgamma from chicken gizzard and specific antibodies raised against the amino acid sequence Ileu480-Ala493 of this enzyme, and compared it with the distribution of calmodulin. Indirect immunofluorescence was most concentrated in early spermatocytes and localised in the outermost layer of seminiferous tubules where the calmodulin level was relatively low. Measurements of immuno-gold particle densities on electron micrographs revealed that CaM kinase II is transiently increased in the nucleus of zygotene spermatocytes. These observations suggest the involvement of CaM kinase II in the meiotic chromosomal pairing process. An extremely high concentration of calmodulin in spermatogenic cells undergoing meiosis may not be directly related to activation of calmodulin-dependent kinases and phosphatases.

Mutagenesis induced by a single 1,N6-ethenodeoxyadenosine adduct in human cells

To study the genotoxic properties of 1,N6-ethenodeoxyadenosine (epsilondA) in human cells, a novel site-specific mutagenesis approach was developed, in which a single DNA adduct was uniquely placed in either strand of a shuttle plasmid vector. The analysis of progeny plasmid derived from the modified strand shows that epsilondA, when incorporated into the position of the second A of 5'-CAA (codon 61 of the ras gene), is mutagenic in human cells, inducing A-->T, A-->G, and A-->C mutations. The efficient induction of A-->T transversions in experiments using modified double- and singlestranded DNA substrates supports the hypothesis that A:T-->T:A transversions in human and animal tumors induced by vinyl compounds reflect misinsertion of dAMP opposite this adduct. Mutagenic events were similar when the adduct was incorporated into either the leading or the lagging strand. EpsilondA was more mutagenic than 8-oxodeoxyguanosine, which induced targeted G-->T transversions in HeLa cells. In Escherichia coli, epsilondA did not significantly miscode (<0.27%) even in the presence of induced SOS functions.

Ultrastructure and 18S rDNA sequence analysis of Wobblia lunata gen. et sp. nov., a new heterotrophic flagellate (Stramenopiles, Incertae sedis)

A new heterotrophic flagellate Wobblia lunata gen. et sp. nov. is described. This organism usually attaches to the substratum showing a wobbling motion, and sometimes glides on the substratum or swims freely in the medium. W. lunata has various features characteristic of the stramenopiles. These include a hairy flagellum with tripartite tubular hairs, a mitochondrion with tubular cristae, arrangement of flagellar apparatus components and a double helix in the flagellar transition zone. W. lunata shares a double helix with heterotrophic stramenopiles, including Developayella elegans, oomycetes, hyphochytrids, opalinids and proteromonads, and could be placed in the phylum Bigyra Cavalier-Smith. However, from 18S rDNA tree analysis, these organisms form two distantly-related clades in the stramenopiles, and Wobblia appears at the base of the stramenopiles. Evaluation of morphological features and comparison of 18S rDNA sequences indicate that W. lunata is a member of the stramenopiles, but it is distinct from any other stramenopiles so far described. Its phylogenetic position within the stramenopiles is uncertain and therefore W. lunata is described as a stramenopile incertae sedis.

Cellular response to exocyclic DNA adducts

The mutagenic potential of three exocyclic DNA adducts was studied in Escherichia coli and simian kidney cells by incorporating them into single-stranded DNA. Differences in the mutagenic potency of the adducts were observed between hosts: 1,N6-ethenodeoxyadenosine and 3,N4-ethenodeoxycytidine were more mutagenic in simian cells, whereas 1,N2-(1,3-propan-1,3-diyl)-2'-deoxyguanosine was more mutagenic in E. coli. To investigate the cellular response to DNA adducts, a double-stranded DNA vector system was developed. Use of this system showed that 1,N6-ethenodeoxyadenosine blocks DNA synthesis strongly, and DNA synthesis past this adduct was highly accurate in E. coli. The blockage of DNA synthesis was overcome in an error-free manner by the recombination repair mechanism (daughter-strand gap repair).

[A patient presented with atypical paroxysmal kinesigenic choreoathetosis and Becker muscular dystrophy]

A 22-year-old man had choreatic movements in upper limbs, neck and trunk for over twelve years which were associated with dystonia in lower limbs upon initiating voluntary movements. The choreatic movement lasted for a few seconds and the dystonia lasted for a few minutes. He also had high serum CK levels and hypertrophic calf muscles. His muscle strength and deep tendon reflexes were normal. His choreatic movements fulfill the criteria for paroxysmal kinesigenic choreoathetosis (PKC). However, it was unclear what the symptom of dystonia was due to. From a muscle biopsy and DNA analysis, he was diagnosed as having Becker muscular dystrophy. Administration of anticonvulsant improved the dystonia as well as the choreatic movement, which showed that the dystonia was a symptom of PKC. Coincidence of choreatic movements and dystonias which had different lasting time in a patient of PKC was atypical and had not previously reported.