Neurotoxicity from glutathione depletion is mediated by Cu-dependent p53 activation

Loss of intracellular neuronal glutathione (GSH) is an important feature of neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The consequences of GSH depletion include increased oxidative damage to proteins, lipids, and DNA and subsequent cytotoxic effects. GSH is also an important modulator of cellular copper (Cu) homeostasis and altered Cu metabolism is central to the pathology of several neurodegenerative diseases. The cytotoxic effects of Cu in cells depleted of GSH are not well understood. We have previously reported that depletion of neuronal GSH levels results in cell death from trace levels of extracellular Cu due to elevated Cu(I)-mediated free radical production. In this study we further examined the molecular pathway of trace Cu toxicity in neurons and fibroblasts depleted of GSH. Treatment of primary cortical neurons or 3T3 fibroblasts with the glutathione synthetase inhibitor buthionine sulfoximine resulted in substantial loss of intracellular GSH and increased cytotoxicity. We found that both neurons and fibroblasts revealed increased expression and activation of p53 after depletion of GSH. The increased p53 activity was induced by extracellular trace Cu. Furthermore, we showed that in GSH-depleted cells, Cu induced an increase in oxidative stress resulting in DNA damage and activation of p53-dependent cell death. These findings may have important implications for neurodegenerative disorders that involve GSH depletion and aberrant Cu metabolism.     

Polymorphisms in cytokine genes and risk of Helicobacter pylori infection among Jamaican children

Background: Infection by Helicobacter pylori is often acquired during childhood. Recent studies suggest that inflammatory cytokines may play a role in susceptibility to, and disease phenotype caused by, H. pylori infection, but the association of host genetic variability with risk of H. pylori infection has not been studied in children. Methods: We investigated the relationship between the risk of H. pylori antibody positivity and cytokine gene polymorphisms among 199 two‐year‐old Jamaicans. H. pylori seropositivity was determined by a validated research enzyme‐linked immunosorbent assay. Real‐time Taqman® polymerase chain reaction was used to determine variants at 17 loci in 11 cytokine genes (IL1A, IL1B, IL2, TNF, TLR4, IL4, IL6, IL10, IL10RA, IL12A and IL13). We estimated the odds ratio and the 95% confidence interval for the association of genetic polymorphisms with H. pylori seropositivity, using logistic regression. Results: Forty (20.1%) of 199 children were seropositive. Children's H. pylori seropositivity correlated highly with maternal H. pylori seropositivity (OR = 7.98, 95% CI = 1.05–60.60, p = .02). Children carrying IL1A?889T had a lower risk of H. pylori positivity, compared to those carrying ?889C, with each T allele associated with 43% risk reduction (OR = 0.57, 95% CI = 0.33–0.99, p‐trend = .05). No other loci we examined were associated with the risk of H. pylori seropositivity. Conclusions: The IL1A?889 T allele, known to express a higher level of cytokine IL‐1α, is associated with a lower risk of H. pylori infection among Jamaican children. Our finding supports the hypothesis that an upregulation of pro‐inflammatory cytokines may protect against persistent H. pylori colonization.     

From the mountains to the sea: assemblage structure and dynamics in Chironomidae (Insecta: Diptera) in the Clyde River estuarine gradient, New South Wales, south-eastern Australia

Abstract  Chironomidae (Insecta: Diptera: non-biting midges) were surveyed at five shallow riffle stations along the estuarine gradient of the Clyde River, southern New South Wales (35°45'S, 150°15'E). Benthic populations were sampled seasonally between April 2001 and January 2002, between an uppermost fully fresh station and 7 km south of the tidal limit at Shallow Crossing, encompassing a 23 km stretch. Biological structure and integrity of chironomid assemblages, which are essentially unknown in eastern Australia's estuarine environments, were elucidated. Assemblages were diverse: from 5732 chironomid larvae, 45 species belonging to four subfamilies were identified from riffles. All chironomid assemblages were strongly structured and non-random with respect to spatial position along the salinity gradient although relatively random with respect to temporal shifts between the five seasonal samples. Generally, the salinity gradient had strong effects on assemblage composition but no discrete brackish fauna was identifiable, and the abundance of many species declined gradually with distance from the freshest station. Dominant taxa in the brackish zone were Parakiefferiella ' variegatus ' and two species of Cladotanytarsus . Notably, the little-known Semiocladius crassipennis Skuse (Orthocladiinae) was abundant at the most marine-influenced station. Taxa present exclusively in freshwaters included several Tanypodinae notably absent from sites below Shallow Crossing at salinities normally tolerated in athalassic waters. Other species restricted to freshwaters included Nanocladius sp., Demicryptochironomus (Irmakia) sp., Polypedilum vespertinus (Skuse), Zavrelliella fuscoguttata (Kieffer), Riethia stictoptera (Kieffer) and Podonomopsis sp.     

Characterization of cDNA clones for differentially expressed genes in embryos of dormant and nondormant Avena fatua L. caryopses

The molecular regulation of seed dormancy was investigated using differential display to visualize and isolate cDNAs representing differentially expressed genes during early imbibition of dormant and nondormant Avena fatua L. embryos. Of about 3000 cDNA bands examined, 5 cDNAs hybridized with mRNAs exhibiting dormancy-associated expression patterns during the first 48 h of imbibition, while many more nondormancy-associated cDNAs were observed. Dormancy-associated clone AFD1 hybridized with a 1.5 kb mRNA barely detectable in dry dormant and nondormant embryos that became more abundant in dormant embryos after 24 h of imbibition. Clone AFD2 hybridized with two mRNAs, a 1.3 kb message constitutively expressed in dormant and nondormant embryos and a 0.9 kb message present at higher levels in dormant embryos after 3 h of imbibition. Nondormancy-associated clones AFN1, AFN2 and AFN3 hybridized with 1.5 kb, 1.7 kb and 1.1 kb mRNAs, respectively, that were more abundant in nondormant embryos during imbibition. Expression patterns of some mRNAs in dormant embryos induced to germinate by GA₃ treatment were different than water controls, but were not identical to those observed in nondormant embryos. DNA sequence analysis revealed 76% sequence identity between clone AFN3 and a Citrus sinensis glutathione peroxidase-like cDNA, while significant sequence similarities with known genes were not found for other clones. Southern hybridization analyses showed that all clones represent low (1 to 4) copy number genes.     

Spontaneous Periodic Hypothermia: Diencephalic Epilepsy

The case of a patient with episodic hypothermia and profuse sweating believed to be due to diencephalic epilepsy is reported. Despite intensive investigations no other manifestations of hypothalamic dysfunction were found. Conventional antiepileptic drugs were without effect but the patient was successfully treated by total sympathectomy.     

In-patient Tolvaptan use in SIADH: care audit,therapy observation and outcome analysis

Background

Indications for use of tolvaptan in SIADH-associated hyponatraemia remain controversial. We audited our local guidelines for Tolvaptan use in this situation to review treatment implications including drug safety, hospital admission episode analysis (episodes of liver toxicity, CNS myelinolysis, sodium-related re-admission rates), morbidity; mortality and underlying aetiologies.

Methods

We report a retrospective case series analysis of on-going treatment outcomes (case-note review) for 31 patients (age 73.3 ± 10.5 years, 55% females) consecutively treated with Tolvaptan as in-patient for confirmed SIADH with persistent S/Na⁺ < 125 mmol/L despite removal of reversible causes and 24-48 h fluid restriction, and include longer-term outcome data (re-treatment/readmissions/mortality) for up to 4 years of follow-up. A minimum of 6 months follow-up data were reviewed unless the patient died before that period.

Results

Short-term outcomes were favourable; 94%-achieved treatment targets after a mean of 3.48 ± 2.46 days. There was statistically significant rise in S/Na⁺ level after Tolvaptan treatment (before treatment: mean sodium 117.8 ± 3.73, 108–121 mmol/L and after treatment: mean sodium 128.7 ± 3.67, 125–135.2 mmol/L, P < .001). Although the target S/Na⁺ level was >125 mmol/L in fact one third (35%) of the patients achieved a S/Na⁺ level of >130 mmol/L by the time of hospital discharge. No patient experienced S/Na⁺ rise >12 mmol/L/24 h, drug-associated liver injury or CNS-myelinolysis. The average length of hospital stay following start of Tolvaptan treatment was 3.2 days. Relapse of hyponatraemia occurred in 26% of the patients, requiring retreatment with Tolvaptan. In all patients where either relapse of hyponatraemia occurred or readmission was necessary, SIADH was associated with malignancy, which was present overall in 60% of the group studied.

Conclusions

This study confirms the safety and efficacy of Tolvaptan in the treatment of SIADH-related significant, symptomatic hyponatraemia when used under specialist guidance and strict monitoring. A sodium level relapsing below the treatment threshold by 1 week after discontinuation is a good indicator of a patient group with re-treatment/longer-term therapy needs, all of whom had underlying malignancy. The criteria set locally in our trust to initiate Tolvaptan use also identifies a group where further investigation for underlying malignancy should be considered.