Kinetics of HTT lowering in brain of YAC 128 mice following single and repetitive intranasal dosing of siRNA packaged in chitosan-based nanoparticle.

This report describes the kinetics of Huntington's Disease (HD) gene (HTT) lowering in brains of YAC 128 mice. Lowering (or "knock-down") of HTT mRNA expression was achieved by intranasal administration of specially designed siRNA loaded into chitosan nanoparticles. Kinetic patterns of HTT lowering observed in different brain regions allowed calculation of cumulative lowering effects that result from multiple consecutive administrations. Mathematical modeling generated dosing schedules for approaching a steady knock-down effect and for prediction of magnitude and duration of HTT lowering. Kinetic modeling of HTT lowering with our algorithm will be useful in determining intranasal dosing schedules to produce chronic, therapeutically significant lowering effect of gene expression.

The expression of the transcription factor TAF1 is modified by the HPV16 E2 protein.

High-risk human papillomaviruses (e.g., HPV16 and 18) are associated with cervical cancer occurrence and development. The early viral gene E2 encodes a protein involved in several key processes in HPV biology, such as replication, genome segregation, and viral gene transcription. E2's presence also affects the expression of a variety of cellular genes involved in a wide range of biological processes, including cell cycle regulation and apoptosis, which are mediated by E2's interaction with cellular proteins. In this report, a lentiviral system was used to express the HPV16 E2 gene in the HPV-negative C-33A cell line for several weeks. E2 expression was measured by RT-qPCR and its biological activity was evaluated using a reporter gene. In HPV16 E2-positive cells, we observed a statistically significant increase in mRNA and protein levels of TAF1 and p27, a basal transcription factor and one of its target genes, respectively. To our knowledge, this is the first study showing that the viral protein HPV16 E2 upregulates TAF1 expression. This suggests that E2's expression promotes a transcriptionally-favorable cellular environment that allows HPV to successfully complete its replication cycle. Keywords: HPV16; E2 protein; transcription; TAF1 regulation.

Clinical markers of asthma and IgE assessed in parents before conception predict asthma and hayfever in the offspring.

BACKGROUND: Mice models suggest epigenetic inheritance induced by parental allergic disease activity. However, we know little of how parental disease activity before conception influences offspring's asthma and allergy in humans. OBJECTIVE: We aimed to assess the associations of parental asthma severity, bronchial hyperresponsiveness (BHR), and total and specific IgEs, measured before conception vs. after birth, with offspring asthma and hayfever. METHODS: The study included 4293 participants (mean age 34, 47% men) from the European Community Respiratory Health Survey (ECRHS) with information on asthma symptom severity, BHR, total and specific IgEs from 1991 to 1993, and data on 9100 offspring born 1972-2012. Adjusted relative risk ratios (aRRR) for associations of parental clinical outcome with offspring allergic disease were estimated with multinomial logistic regressions. RESULTS: Offspring asthma with hayfever was more strongly associated with parental BHR and specific IgE measured before conception than after birth [BHR: aRRR = 2.96 (95% CI: 1.92, 4.57) and 1.40 (1.03, 1.91), respectively; specific IgEs: 3.08 (2.13, 4.45) and 1.83 (1.45, 2.31), respectively]. This was confirmed in a sensitivity analysis of a subgroup of offspring aged 11-22 years with information on parental disease activity both before and after birth. CONCLUSION & CLINICAL RELEVANCE: Parental BHR and specific IgE were associated with offspring asthma and hayfever, with the strongest associations observed with clinical assessment before conception as compared to after birth of the child. If the hypothesis is confirmed in other studies, parental disease activity assessed before conception may prove useful for identifying children at risk for developing asthma with hayfever.

Premenstrual asthma and leukotriene variations in the menstrual cycle.

BACKGROUND: Several authors have reported an increase in leukotriene C4 in the premenstrual phase in women with severe premenstrual asthma, indicating that antileukotrienes could be used in treatment. OBJECTIVE: To analyse the role of leukotrienes in premenstrual asthma. METHODS: A questionnaire on respiratory symptoms and peak flow during one complete menstrual cycle was given to women of fertile age to define them as asthmatics who suffered from premenstrual asthma or not. Premenstrual asthma (PMA) was defined as a clinical or functional deterioration (≥20%) in the premenstrual phase compared with the preovulatory phase. Blood samples to measure leukotriene C4 were taken during the preovulatory and premenstrual phases. RESULTS: Blood samples were taken in 62 asthmatic women, 34 of whom (54.3%) presented PMA criteria, all with a premenstrual deterioration of between 20 and 40%. There was no difference in leukotriene C4 levels between the preovulatory and premenstrual phases in the women who suffered from PMA (1.50ng/mL vs. 1.31ng/mL; p=0.32) and those who did not (1.40ng/mL vs. 1.29ng/mL; p=0.62). Neither were there any differences in leukotriene levels between women with or without PMA. The results were similar for each category of asthma severity. CONCLUSIONS: Our data show that leukotriene C4 does not appear to be involved in the pathogenesis of premenstrual asthma, or support the use of anti-leukotrienes in the specific treatment of premenstrual asthma, at least in women with a moderate premenstrual deterioration. No differences appeared in any of the categories of asthma severity.

Evaluation of a heart failure knowledge questionnaire and its use in guiding the educational intervention.

INTRODUCTION AND OBJECTIVE: Patient education by nurses is a cornerstone of any heart failure (HF) program, but the models are widely heterogeneous and few specific instruments exist. Our objective is to evaluate our own questionnaire and its utility as a guide for educational intervention. METHODS: This work is a prospective cohort study of patients followed-up on in a specialized unit after diagnosis of HF. The intervention group received educational sessions guided according to their knowledge using the questionnaire and was compared to a group which received standard education. The validity and reliability of the questionnaire was evaluated. The utility of the educational model was determined by the primary composite endpoint of death and/or hospital admission or emergency care for HF. RESULTS: A total of 152 patients were included, 88 which received guided education and 64 which received standard education, with a mean follow-up time of 16±4 months. In the guided education group, the evaluation questionnaire score (qs) rose from 59% to 78.5% (p=0.018), which was associated with greater self-care (28.5-0.6*qs, p=0.04), a tendency toward better quality of life (51.1-1.1*qs, p=0.09), and adherence (5.02+0.04*qs, p=0.06), with acceptable reliability (Cronbach's alpha 0.75). The primary composite endpoint was met in 12 patients (13.6%) in the intervention group compared to 19 (29.7%) in the control group (hazard ratio: 0.46; 95% confidence interval: 0.24-0.88; p=0.019). Only educational level, age, NT-proBNP, and atrial fibrillation were predictors in the multivariate analysis. CONCLUSION: The HF knowledge questionnaire proposed is a valid, reliable tool and allows for quantifying learning. Its utility in guiding education requires a certain degree of skill from the patient that determines a group with better prognosis.

Clinical vignettes in Parkinson's disease: a collection of unusual medication-induced hallucinations, delusions, and compulsive behaviours.

Hallucinations, delusions, and compulsive behaviors are frequent iatrogenic complications of the treatment of motor dysfunction in Parkinson's disease (PD). Although these have been studied, and the phenomenology described, there are few detailed descriptions of the various psychiatric problems our treated PD patients live with that allow physicians who do not have a great deal of experience with PD patients to appreciate the extent of their altered lives. This report is a compilation of vignettes describing these behavioral problems that the treating neurologist or psychiatrist attributed to the medications used for treating PD.

Variability in the prevalence of premenstrual asthma.

Our aim is to analyse the differences in the prevalence of premenstrual asthma (PMA) according to a set of criteria, the relationship between them and the influence of asthma severity. The answer "Yes" to "Does your asthma get worse before menstruation?" was considered subjective PMA. A daily respiratory symptoms register of fertile asthmatic females was taken during two consecutive menstrual cycles. For the semi-objective diagnosis, an exacerbation of > or =20% was required in the symptoms register. Objective diagnosis was a premenstrual worsening of > or =20% of peak flow. We selected 103 patients. Subjective premenstrual deterioration was perceived in 43.7%. The semi-objective deterioration of symptoms in the first cycle occurred in 44.7%, and in 22.3% in both cycles. A total of 54.3% of females with semi-objective criteria in the first cycle perceived a subjective deterioration of symptoms, versus 35.1% of those without semi-objective criteria (p = 0.05). PMA was present at all levels of asthma severity, with no clear link to the degree of severity. The detection of PMA prevalence, the subjective perception of this deterioration and its presence at all levels of asthma severity lead us to urge research into possible premenstrual deterioration in all fertile asthmatic females.

Correlation of transforming growth factor ß-1 vitreous levels with clinical severity of proliferative vitreoretinopathy in patients with rhegmatogenous retinal detachment. / Correlación de niveles del factor de crecimiento transformante ß-1 con severidad de vitreorretinopatía proliferativa en pacientes con desprendimiento de retina regmatógeno.

OBJECTIVE: To correlate the vitreous concentration of transforming growth factor ß-1 (TGF ß-1) with the degree of clinical severity of proliferative vitreoretinopathy (PVR). DESIGN: A prospective, observational, cross-sectional study carried out on cases and controls. PARTICIPANTS: The study included 40 patients with a diagnosis of PVR secondary to rhegmatogenous retinal detachment. METHODS: Vitreous was obtained in patients undergoing pars plana vitrectomy by rhegmatogenous retinal detachment, who were treated during the period from August 2015 to June 2016, in a national reference centre for ophthalmological care in Mexico City, Mexico. The levels of TGFß-1 were quantified by ELISA technique. An ANOVA test was performed for the comparison of the different groups, together with a post-hoc Dunns test. A statistically significant difference was considered when obtaining P <.05. RESULTS: The levels of TGFß-1 were quantified, and the following means were found for each group: In the group with PVR grade A, 1150.6 ± 452.08 pg / ml, PVR grade B: 1129.6 ± 365.54 pg / ml, and PVR grade C: 1146.4 ± 330.21 pg / ml. The statistical analysis did not find significant differences when comparing the different PVR groups. (P=.53). However, when performing the differential analysis for each level of severity, a statistically significant increase in the expression of TGFß-1 was observed in the group of patients with PVR-A at a greater number of days of evolution of the detachment. (P=.03). There were no statistically significant differences for PVR-B and PVR-C (P=.16 and P=.16, respectively). CONCLUSION: Although the levels of TGFß-1 are not directly related to the clinical severity grade, suggesting that there must be other factors involved in the advanced stages of PVR, TGFß-1 may have greater relevance during the initial stages of the clinical course by promoting the epithelial-mesenchymal transition due to its greater expression in PVR-A. Thus, it can be concluded that each isoform plays a very particular role in the complex process of PVR.

Study of the metabolomic relationship between lung cancer and chronic obstructive pulmonary disease based on direct infusion mass spectrometry.

The high prevalence of lung cancer (LC) has triggered the search of biomarkers for early diagnosis of this disease. For this purpose the study of metabolic changes related to the development of lung cancer could provide interesting information about its early diagnosis. In this sense, chronic obstructive pulmonary disease (COPD), a disease associated with tumor development, is a comorbidity that increases the risk of onset and progression of lung neoplasia and has also to be considered in the study of pathology related to lung cancer. This work develop a metabolomic approach based on direct infusion mass spectrometry using a hybrid triple quadrupole-time of flight mass spectrometer (DI-ESI-QqQ-TOF-MS) in order to identify altered metabolites from serum of LC and COPD patients and evaluate its relationship and implication in the progression of LC. This methodology has been applied to 30 serum samples from LC, 30 healthy patients used as controls (HC) and 30 serum samples from COPD to found altered metabolites from both LC and COPD diseases. In addition, some metabolic differences and similarities were found in Pulmonary Emphysema and Chronic Bronchitis patients. On the other hand, altered metabolites were studied in different stages of LC (II, III and IV) to evaluate the perturbation of them throughout the progression of disease. The sample treatment consisted of the extraction of polar and non-polar metabolites from serum that was later infused into the mass spectrometer using an electrospray ionization source in positive and negative mode. Partial least squares discriminant analysis (PLS-DA) allowed a classification between LC, HC and COPD groups in all acquisition modes. A total of 35 altered and common metabolites between LC and COPD, including amino acids, fatty acids, lysophospholipids, phospholipids and triacylglycerides were identified, being alanine, aspartate and glutamate metabolism the most altered. Finally, ROC curves were applied to the dataset and metabolites with AUC value higher than 0.70 were considered as relevant in the progression of LC.

[Inter-observer variability in the diagnosis and classification of diabetic retinopathy through biomicroscopy]. / Variabilidad interobservador en el diagnóstico y clasificación de la retinopatía diabética mediante biomicroscopía.

OBJECTIVE: Analysis of the inter-observer variability of biomicroscopy used for the diagnosis of Diabetic Retinopathy. METHODS: This was a descriptive study. Parallel observer-blind evaluations of the degree of retinopathy in type 2 diabetic patients, as defined on biomicroscopic photographs, were performed by two ophthalmologists. The sample size required for the Kappa index among ophthalmologists with a disagreement ratio of 15%, precision ratio of 5% and confidence level of 95% is n=196 (<> being the number of eyes). The only variable measured was the degree of Diabetic Retinopathy, according to the modified Early Treatment Diabetic Research Study (ETDRS) classification. RESULTS: The average age of the 217 patients photographed was of 65.42 years (SE= 9.91). In 191 instances there was total agreement between the 2 ophthalmologists. In 24 instances the discrepancy was only of one degree of the classification of the ETDRS, and in 2 the discrepancy was of two degrees. In no case was it greater than this. (Quadratic weighed Kappa = 0.876, IC95%: 0.655-0.952 and linear weighed Kappa = 0.804, IC95%: 0.729-0.878). CONCLUSIONS: The Weighed Kappa index demonstrated a <> agreement of the degree of diabetic retinopathy. The discrepancies were slight, were of no clinical importance, and would not have affected treatment decisions. The results indicate that this examination, performed by a single ophthalmologist, can be utilised as a reference standard in Diabetic Retinopathy diagnosis.

Analgesic effect of a single-dose of perineural dexamethasone on ultrasound-guided femoral nerve block after total knee replacement. / Eficacia analgésica de una dosis única de dexametasona perineural en el bloqueo ecoguiado del nervio femoral en cirugía de prótesis total de rodilla.

INTRODUCTION: Total knee replacement is usually a very painful procedure. A single-dose of femoral nerve block has been shown to provide similar analgesia to an epidural, with fewer side effects, but limited in time. OBJECTIVE: To compare the analgesia provided by dexamethasone used at perineural level in the femoral nerve block after total knee replacement with the one used at intravenous level, and with that of a control group. MATERIAL AND METHODS: A prospective, randomised, double-blind controlled trial was conducted on 81 patients randomly assigned to one of three groups: 1)IV dexamethasone (8mg); 2)perineural dexamethasone (8mg), and 3)placebo. All patients received 20ml of ropivacaine 0.5% for femoral nerve block. The primary outcome was the duration of the sensory-analgesic block of the femoral nerve block. The secondary outcomes included pain intensity measurements, patient satisfaction, and incidence of complications. RESULTS: Randomisation was effective. Analgesia duration was significantly higher (P<.0001) in the perineural dexamethasone group (mean 1152.2min, 95% confidence interval [95% CI]: 756.9-1547.6) in comparison with the control group (mean 186min, 95%CI: 81.2-292) and dexamethasone IV group (mean 159.4min, 95%CI: 109.8-209). Postoperative pain, complications and side effects were also lower in this group. CONCLUSIONS: Dexamethasone prolongs sensory block of single dose of femoral nerve block using ropivacaine. It also provides better analgesia and patient satisfaction, with fewer side effects.

Can low level exposure to ochratoxin-A cause parkinsonism?

Mycotoxins are fungal metabolites with pharmacological activities that have been utilized in the production of antibiotics, growth promoters, and other classes of drugs. Some mycotoxins have been developed as biological and chemical warfare agents. Bombs and ballistic missiles loaded with aflatoxin were stockpiled and may have been deployed by Iraq during the first Gulf War. In light of the excess incidence of amyotrophic lateral sclerosis (ALS) in veterans from Operation Desert Storm, the potential for delayed neurotoxic effects of low doses of mycotoxins should not be overlooked. Ochratoxin-A (OTA) is a common mycotoxin with complex mechanisms of action, similar to that of the aflatoxins. Acute administration of OTA at non-lethal doses (10% of the LD(50)) have been shown to increase oxidative DNA damage in brain up to 72 h, with peak effects noted at 24 h in midbrain (MB), caudate/putamen (CP) and hippocampus (HP). Levels of dopamine (DA) and its metabolites in the striatum (e.g., CP) were shown to be decreased in a dose-dependent manner. The present study focused on the effects of chronic low dose OTA exposure on regional brain oxidative stress and striatal DA metabolism. Continuous administration of low doses of OTA with implanted subcutaneous Alzet minipumps caused a small but significant decrease in striatal DA levels and an upregulation of anti-oxidative systems and DNA repair. It is possible that low dose exposure to OTA will result in an earlier onset of parkinsonism when normal age-dependent decline in striatal DA levels are superimposed on the mycotoxin-induced lesion.

Acute neurotoxic effects of the fungal metabolite ochratoxin-A.

Ochratoxin-A (OTA) is a fungal metabolite with potential toxic effects on the central nervous system that have not yet been fully characterized. OTA has complex mechanisms of action that include evocation of oxidative stress, bioenergetic compromise, inhibition of protein synthesis, production of DNA single-strand breaks and formation of OTA-DNA adducts. The time course of acute effects of OTA were investigated in the context of DNA damage, DNA repair and global oxidative stress across six brain regions. Oxidative DNA damage, as measured with the "comet assay", was significantly increased in the six brain regions at all time points up to 72 h, with peak effects noted at 24 h in midbrain (MB), CP (caudate/putamen) and HP (hippocampus). Oxidative DNA repair activity (oxyguanosine glycosylase or OGG1) was inhibited in all regions at 6 h, but recovered to control levels in cerebellum (CB) by 72 h, and showed a trend to recovery in other regions of brain. Other indices of oxidative stress were also elevated. Lipid peroxidation and superoxide dismutase (SOD) increased over time throughout the brain. In light of the known vulnerability of the nigro-striatal dopaminergic neurons to oxidative stress, levels of striatal dopamine (DA) and its metabolites were also measured. Administration of OTA (0-6 mg/kg i.p.) to mice resulted in a dose-dependent decrease in striatal DA content and turnover with an ED50 of 3.2 mg/kg. A single dose of 3.5 mg/kg decreased the intensity of tyrosine hydroxylase immunoreactivity (TH(+)) in fibers of striatum, TH(+) cells in substantia nigra (SN) and TH(+) cells of the locus ceruleus. TUNEL staining did not reveal apoptotic profiles in MB, CP or in other brain regions and did not alter DARPP32 immunoreactivity in striatum. In conclusion, OTA caused acute depletion of striatal DA on a background of globally increased oxidative stress and transient inhibition of oxidative DNA repair.

Neuroanatomical mapping of DNA repair and antioxidative responses in mouse brain: Effects of a single dose of MPTP.

The primary objective of this study was to map the normal distribution of the base excision enzyme oxyguanosine glycosylase (OGG1) across mouse-brain regions as a prelude to assessing the effects of various neurotoxicants, ranging from highly selective molecules like MPTP to more global toxic agents. This research is based on the hypothesis that regional brain vulnerability to a toxicant is determined, in part, by variation in the intrinsic capacity of cellular populations to successfully repair oxidative DNA damage. After mapping the normal distributions of OGG1 and superoxide dismutase (SOD) across 44 loci dissected from mouse brain, MPTP, a mitochondrial toxicant with selective dopamine (DA) neuron cytotoxicity was used to elicit focal oxidative stress and DNA repair responses. A single dose of MPTP (20mg/kg, i.p.) elicited time- and region-dependent changes in both SOD and OGG1, with early increases in DNA repair and anti-oxidant activities throughout all regions of brain. In some sampled loci, notably the substantia nigra (SN) and hippocampus, the heightened DNA repair and antioxidant responses were not maintained beyond 48h. Other loci from cerebellum, cerebral cortex and pons maintained high levels of activity up to 72h. Levels of dopamine (DA) were decreased significantly at all time points and remained below control levels in nigro-striatal and mesolimbic systems (ventral tegmental area and nucleus accumbens). Assessment of apoptosis by TUNEL staining revealed a significant increase in number of apoptotic nuclei in the substantia nigra at 72h and not in other loci. The marked degree of apoptosis that became evident in SN at 72h was associated with large decreases in SOD and DNA repair activity at that locus. In conclusion, MPTP elicited global effects on DNA repair and antioxidant activity in all regions of brain, but the most vulnerable loci were unable to maintain elevated DNA repair and antioxidant responses.

Intravenous administration of human umbilical cord blood reduces behavioral deficits after stroke in rats.

BACKGROUND AND PURPOSE: Human umbilical cord blood cells (HUCBC) are rich in stem and progenitor cells. In this study we tested whether intravenously infused HUCBC enter brain, survive, differentiate, and improve neurological functional recovery after stroke in rats. In addition, we tested whether ischemic brain tissue extract selectively induces chemotaxis of HUCBC in vitro. METHODS: Adult male Wistar rats were subjected to transient (2-hour) middle cerebral artery occlusion (MCAO). Experimental groups were as follows: group 1, MCAO alone (n=5); group 2, 3x10(6) HUCBC injected into tail vein at 24 hours after MCAO (n=6) (animals of groups 1 and 2 were killed at 14 days after MCAO); group 3, MCAO alone (n=5); group 4, MCAO injected with PBS at 1 day after stroke (n=8); and group 5, 3x10(6) HUCBC injected into tail vein at 7 days after MCAO (n=5). Rats of groups 3, 4, and 5 were killed at 35 days after MCAO. Behavioral tests (rotarod and Modified Neurological Severity Score [mNSS]) were performed. Immunohistochemical staining was used to identify cells derived from HUCBC. Chemotactic activity of ischemia brain tissue extracts toward HUCBC at different time points was evaluated in vitro. RESULTS: Treatment at 24 hours after MCAO with HUCBC significantly improved functional recovery, as evidenced by the rotarod test and mNSS (P<0.05). Treatment at 7 days after MCAO with HUCBC significantly improved function only on the mNSS (P<0.05). Some HUCBC were reactive for the astrocyte marker glial fibrillary acidic protein and the neuronal markers NeuN and microtubule-associated protein 2. In vitro, significant HUCBC migration activity was present at 24 hours after MCAO (P<0.01) compared with normal brain tissue. CONCLUSIONS: Intravenously administered HUCBC enter brain, survive, migrate, and improve functional recovery after stroke. HUCBC transplantation may provide a cell source to treat stroke.

A dual role for nitric oxide in NMDA-mediated toxicity in vivo.

Nitric oxide has been implicated in N-methyl-D-aspartate (NMDA)-mediated damage in vitro; however, its role in excitotoxic damage in vivo is not clear. In the present study we evaluated the histopathological and hemodynamic consequences of intrastriatal injections of various doses of NMDA and determined the effects of nitric oxide synthase inhibition on these changes. NMDA was injected into the striatum at doses of 50, 150, and 300 nmol with or without N omega-nitro-L-arginine methyl ester (L-NAME; 100 micrograms, locally). Three days following injections histopathological assessment was performed by morphometric analysis of the lesion area in multiple sections taken from the anterior to the posterior borders of the lesion. In animals injected with 150 and 300 nmol of NMDA (+/- L-NAME), local CBF (lCBF) was determined 30 min following injections using 14C-iodoantipyrine autoradiography. All NMDA-treated animals showed a well-demarcated lesion extending beyond the injection site. The volume of the lesion correlated significantly with the NMDA dose injected. The effects of L-NAME on lesion size were dependent on the dose of the NMDA. The lesion induced by 50 nmol of NMDA was not affected by L-NAME. With a dose of 150 nmol of NMDA, L-NAME induced a 43% increase in lesion volume. In contrast, a 38% decrease in lesion size was observed in animals treated with 300 nmol of NMDA combined with L-NAME. At a dose of 150 nmol, NMDA induced a significant elevation in lCBF, which was restricted to regions close to the injection site including the center areas of the anterior and middle striatum. The increase in lCBF observed with 150 nmol of NMDA was significantly attenuated in the NMDA + L-NAME-treated group. The lCBF changes induced by 300 nmol of NMDA were not significantly different from those in the 150-nmol group; however, the extent of the regions involved was larger. The increases in lCBF were observed in all striatal regions including the central and peripheral areas. L-NAME did not have a significant effect on the lCBF changes induced by NMDA at a dose of 300 nmol. These data suggest that in vivo the involvement of nitric oxide in NMDA toxicity depends on the NMDA dose and on the participation of hemodynamic mechanisms secondary to NMDA exposure.

Attenuation of age-dependent oxidative damage to DNA and protein in brainstem of Tg Cu/Zn SOD mice.

Age-dependent accumulation of oxidative DNA and protein damage in brainstem and striatum was assessed in normal and transgenic (tg) mice which overexpress human Cu/Zn superoxide dismutase (h-SOD1). A marker of oxidative DNA damage, 8-hydroxy-2'-deoxyguanosine (oxo8dG), was measured at 3, 12, and 18 months of age in control and tg mice. Cu/Zn SOD, but not MnSOD, activities in brainstems and striata from tg mice were increased compared to controls at all ages. At 18 months, oxo8dG levels were increased by 58% in brainstem and by 21% in striatum of control mice. In the tg mice, brainstem and striatal oxo8dG levels were increased to a lesser extent than in the corresponding controls. Protein oxidation (carbonyl content), was increased by 59% at 18 months in control brainstem, but not in striatum, and the increase was significantly attenuated in the tg mice. In summary, oxidative damage to DNA and protein increased with age in brainstem (and to a lesser extent in striatum), and augmented Cu/Zn SOD activity modified the extent of DNA and protein damage.

DNA damage, repair, and antioxidant systems in brain regions: a correlative study.

8-Hydroxy-2'-deoxyguanosine (oxo(8)dG) has been used as a marker of free radical damage to DNA and has been shown to accumulate during aging. Oxidative stress affects some brain regions more than others as demonstrated by regional differences in steady state oxo(8)dG levels in mouse brain. In our study, we have shown that regions such as the midbrain, caudate putamen, and hippocampus show high levels of oxo(8)dG in total DNA, although regions such as the cerebellum, cortex, and pons and medulla have lower levels. These regional differences in basal levels of DNA damage inversely correlate with the regional capacity to remove oxo(8)dG from DNA. Additionally, the activities of antioxidant enzymes (Cu/Zn superoxide dismutase, mitochondrial superoxide dismutase, and glutathione peroxidase) and the levels of the endogenous antioxidant glutathione are not predictors of the degree of free radical induced damage to DNA in different brain regions. Although each brain region has significant differences in antioxidant defenses, the capacity to excise the oxidized base from DNA seems to be the major determinant of the steady state levels of oxo(8)dG in each brain region.

Comparison of base-excision repair capacity in proliferating and differentiated PC 12 cells following acute challenge with dieldrin.

Dieldrin, an organochlorine pesticide and known neurotoxicant, is ubiquitously distributed in the environment. Dieldrin depletes brain monoamines in some animal species and is toxic for dopaminergic neurons in vitro. Dieldrin interferes with mitochondrial electron transport and increases generation of superoxide anion. Reactive oxygen species have been shown to produce oxidative lesions to DNA bases, i.e., 8-hydroxy-2'-deoxyguanosine (8-oxodGuo). Accumulation of 8-oxodGuo has been shown to be promutagenic in proliferating cells, and can lead to degeneration in fully differentiated cells. The objective of this study was to determine the effects of dieldrin exposure on the activity of the enzyme responsible for removing 8-oxodGuo, OGG1, from undifferentiated (untreated with NGF) and differentiated (NGF-treated) PC 12 cells. Proliferating PC 12 cells exhibited a mild upregulation of glycosylase activity, reaching a maximum by 1 h and returning to baseline by 6 h. Differentiated (+) NGF cells showed a time-dependent decline in activity reaching a nadir at 3 h with a return towards baseline by 6 h. Levels of the damaged base, 8-oxodGuo, in the differentiated PC12 cells appeared to be regulated by the activity of OGG1. In contrast, levels of the damaged base in actively proliferating cells were independent of the OGG1 activity. This difference between actively dividing and differentiated cells in the regulation of base-excision repair and DNA damage accumulation explains, in part, the vulnerability of postmitotic neurons to oxidative stresses and neurotoxins.