Mitochondrial alterations triggered by repeated exposure to fine (PM2.5-0.18) and quasi-ultrafine (PM0.18) fractions of ambient particulate matter

Nowadays ambient particulate matter (PM) levels still regularly exceed the guideline values established by World Health Organization in most urban areas. Numerous experimental studies have already demonstrated the airway toxicity of the fine fraction of PM (FP), mainly triggered by oxidative stress-induced airway inflammation. However, only few studies have actually paid close attention to the ultrafine fraction of PM (UFP), which is likely to be more easily internalized in cells and more biologically reactive. Mitochondria are major endogenous sources of reactive oxygen species (ROS) through oxidative metabolism, and coordinate many critical cellular signaling processes. Mitochondria have been often studied in the context of PM toxicity and generally associated with apoptosis activation. However, little is known about the underlying adaptation mechanisms that could occur following exposure at sub-apoptotic doses of ambient PM. Here, normal human bronchial epithelial BEAS-2B cells were acutely or repeatedly exposed to relatively low doses (5 µg.cm^-2) of FP (PM_2.5-0.18) or quasi-UFP (Q-UFP; PM_0.18) to better access the critical changes in mitochondrial morphology, functions, and dynamics. No significant cytotoxicity nor increase of apoptotic events were reported for any exposure. Mitochondrial membrane potential (ΔΨm) and intracellular ATP content were also not significantly impaired. After cell exposure to sub-apoptotic doses of FP and notably Q-UFP, oxidative phosphorylation was increased as well as mitochondrial mass, resulting in increased production of mitochondrial superoxide anion. Given this oxidative boost, the NRF2-ARE signaling pathway was significantly activated. However, mitochondrial dynamic alterations in favor of accentuated fission process were observed, in particular after Q-UFP vs FP, and repeated vs acute exposure. Taken together, these results supported mitochondrial quality control and metabolism dysfunction as an early lung underlying mechanism of toxicity, thereby leading to accumulation of defective mitochondria and enhanced endogenous ROS generation. Therefore, these features might play a key role in maintaining PM-induced oxidative stress and inflammation within lung cells, which could dramatically contribute to the exacerbation of inflammatory chronic lung diseases. The prospective findings of this work could also offer new insights into the physiopathology of lung toxicity, arguably initiate and/or exacerbate by acutely and rather repeated exposure to ambient FP and mostly Q-UFP.

Abstract AS20: DNA-PKcs is amplified in high grade serous ovarian cancer (HGSC), correlates with poor outcome and drives resistance to platinum therapy via the AKT signaling pathway

High grade serous ovarian cancer is typified by p53 mutation, high degrees of genomic instability and the development of chemo-resistance. Genomic translocations result from incorrectly repaired DNA double strand breaks (DSBs). DNA-PKcs is a central catalytic component of the error prone non-homologous end joining (NHEJ) DSB repair mechanism. We report here that DNA-PKcs is frequently amplified in copy number in HGSC and that amplification correlates with higher DNA-PKcs gene expression and poorer patient outcome (PFS/OS) using both in-house and publicly available datasets (TCGA). Targeting DNA-PKcs, pharmacologically or by RNAi, enhances apoptosis in response to platinum treatment in platinum resistant cell lines and primary models. Furthermore we report that inhibition of DNA-PK restores response to cisplatin in chemoresistant ovarian cancer cells in vivo. SKOV-3 tumor xenografts were implanted subcutaneously into Balb/c Nu/Nu mice and treated with DNA-PKcs inhibitor NU7441 for 2 weeks alone or in combination with cisplatin. DNA-PK inhibition or cisplatin treatment alone were ineffective however in combination they decreased tumor growth at 14 days by 90%, relative to platinum only treatment. On investigating the mechanism of DNA-PKcs mediated chemoresistance we revealed that, in response to DNA damage, DNA-PKcs phosphorylates AKT on serine residue 473 in the nucleus of platinum resistant ovarian tumor cells, but not sensitive cells from the same patient. Phosphorylation at AKT threonine 308 is unaffected and DNA-PK inhibition does not interfere with insulin-mediated phosphorylation of AKT S473. DNA-PK mediated AKT activation in chemoresistant cells results in inhibitory phosphorylation of the pro-apoptotic protein BAD and stabilisation of the anti-apoptotic Bcl-2 protein resulting in the observed attenuation of apoptotic response to platinum treatment. DNA-PK inhibition is an attractive therapeutic strategy for resensitising resistant tumors to platinum based therapy, directly linking the DNA damage caused by platinum to the pro-survival AKT pathway, without interfering with normal physiological roles of AKT.

Citation Format: Curry E, Cheraghchi-Bashi-Astaneh A, Chen M, Cunnea P, De Sousa C, Maginn E, Dai Y, Liu E, Wasan H, Mills G, Bowtell D, Gabra H & Stronach EA. DNA-PKcs is amplified in high grade serous ovarian cancer (HGSC), correlates with poor outcome and drives resistance to platinum therapy via the AKT signaling pathway [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS20.

Contaminated sites: the Canadian situation in an international context

Over the last 2 decades, policy-makers have been giving increasing attention to the remediation and redevelopment of contaminated sites, especially those located in urban areas commonly referred to as brownfields. Traditionally, private developers have tended to ignore these sites on account of a series of obstacles of a structural-political nature, including variability in regulatory processes, lack of information on soil quality, impractical clean up standards, fear of liability, and limited funding resources for clean ups. This paper examines the types of policy-making measures that are currently being taken in Canada to overcome these obstacles, comparing them to those being taken in the US and Europe. It is argued that the contaminated site-related policies and programs employed to overcome each obstacle, both within Canada and internationally, are converging in style and content as governments are becoming more aware of the types of costs and risks they must share in order to solve the problem effectively. It is also argued that this trend is unfolding in a relatively predictable way, and that policy-making in Canada is evolving more slowly than it is in the other jurisdictions examined.

Cerebellitis presenting as acute hydrocephalus

A 14-year-old boy presented acutely with occipital headache, nausea and vomiting. MRI showed obstructive hydrocephalus and marked bilateral cerebellar swelling with increased signal on T2-weighted imaging. Following treatment with oral corticosteroids, the clinical and radiological signs resolved. The clinical course and radiological appearances were consistent with cerebellitis associated with a significant mass effect and hydrocephalus.

Carnitine and weakness in haemodialysis patients

Weakness in haemodialysis patients has been attributed to several factors including carnitine deficiency. Malnutrition, neuropathy, uraemic myopathy and parathyroid hormone excess may all be important. Six haemodialysis patients were shown to have reduced muscle power compared with a normal population, and to be malnourished by dietary assessment, and features of their weakness were investigated. Total carnitine was normal in plasma but elevated in muscle, with an excess of esterified carnitine in both plasma and muscle and diminished free plasma carnitine. Muscle biopsy showed no features of carnitine deficiency and electromyography showed a non-specific neuropathy with additional myopathic changes in some. Dietary supplementation with L-carnitine (2 g/day) for 6 weeks in a placebo-controlled trial showed a redistribution of carnitine fractions but no subjective or objective improvement in muscle function. There was no improvement in the plasma lipid profile. The weakness of haemodialysis patients is multifactorial. We have not demonstrated total carnitine depletion in either muscle or plasma, and oral supplementation of L-carnitine has no demonstrable effect in this group.