PINK1/Parkin Mediated Mitophagy, Ca2+ Signalling, and ER-Mitochondria Contacts in Parkinson's Disease

Endoplasmic reticulum (ER)-mitochondria contact sites are critical structures for cellular function. They are implicated in a plethora of cellular processes, including Ca2+ signalling and mitophagy, the selective degradation of damaged mitochondria. Phosphatase and tensin homolog (PTEN)-induced kinase (PINK) and Parkin proteins, whose mutations are associated with familial forms of Parkinson's disease, are two of the best characterized mitophagy players. They accumulate at ER-mitochondria contact sites and modulate organelles crosstalk. Alterations in ER-mitochondria tethering are a common hallmark of many neurodegenerative diseases including Parkinson's disease. Here, we summarize the current knowledge on the involvement of PINK1 and Parkin at the ER-mitochondria contact sites and their role in the modulation of Ca2+ signalling and mitophagy

Evaluation of poly (ADP-ribose) polymerase inhibitor ABT-888 combined with radiotherapy and temozolomide in glioblastoma

This is the final version. Available from the publisher via the DOI in this record.Background: The cytotoxicity of radiotherapy and chemotherapy can be enhanced by modulating DNA repair. PARP is a family of enzymes required for an efficient base-excision repair of DNA single-strand breaks and inhibition of PARP can prevent the repair of these lesions. The current study investigates the trimodal combination of ABT-888, a potent inhibitor of PARP1-2, ionizing radiation and temozolomide(TMZ)-based chemotherapy in glioblastoma (GBM) cells.Methods: Four human GBM cell lines were treated for 5 h with 5 μM ABT-888 before being exposed to X-rays concurrently with TMZ at doses of 5 or 10 μM for 2 h. ABT-888′s PARP inhibition was measured using immunodetection of poly(ADP-ribose) (pADPr). Cell survival and the different cell death pathways were examined via clonogenic assay and morphological characterization of the cell and cell nucleus.Results: Combining ABT-888 with radiation yielded enhanced cell killing in all four cell lines, as demonstrated by a sensitizer enhancement ratio at 50% survival (SER50) ranging between 1.12 and 1.37. Radio- and chemo-sensitization was further enhanced when ABT-888 was combined with both X-rays and TMZ in the O6-methylguanine-DNA-methyltransferase (MGMT)-methylated cell lines with a SER50 up to 1.44. This effect was also measured in one of the MGMT-unmethylated cell lines with a SER50 value of 1.30. Apoptosis induction by ABT-888, TMZ and X-rays was also considered and the effect of ABT-888 on the number of apoptotic cells was noticeable at later time points. In addition, this work showed that ABT-888 mediated sensitization is replication dependent, thus demonstrating that this effect might be more pronounced in tumour cells in which endogenous replication lesions are present in a larger proportion than in normal cells.Conclusions: This study suggests that ABT-888 has the clinical potential to enhance the current standard treatment for GBM, in combination with conventional chemo-radiotherapy. Interestingly, our results suggest that the use of PARP inhibitors might be clinically significant in those patients whose tumour is MGMT-unmethylated and currently derive less benefit from TMZ. © 2013 Barazzuol et al.; licensee BioMed Central Ltd.European Union: European Community’s Seventh Framework Programm

A split-GFP tool reveals differences in the sub-mitochondrial distribution of wt and mutant alpha-synuclein

Parkinson's disease (PD), the second most common neurodegenerative disorder, is characterized by dopaminergic neuronal loss that initiates in the substantia nigra pars compacta and by the formation of intracellular inclusions mainly constituted by aberrant \u3b1-synuclein (\u3b1-syn) deposits known as Lewy bodies. Most cases of PD are sporadic, but about 10% are familial, among them those caused by mutations in SNCA gene have an autosomal dominant transmission. SNCA encodes \u3b1-syn, a small 140-amino acids protein that, under physiological conditions, is mainly localized at the presynaptic terminals. It is prevalently cytosolic, but its presence has been reported in the nucleus, in the mitochondria and, more recently, in the mitochondria-associated ER membranes (MAMs). Whether different cellular localizations may reflect specific \u3b1-syn activities is presently unclear and its action at mitochondrial level is still a matter of debate. Mounting evidence supports a role for \u3b1-syn in several mitochondria-derived activities, among which maintenance of mitochondrial morphology and modulation of complex I and ATP synthase activity. \u3b1-syn has been proposed to localize at the outer membrane (OMM), in the intermembrane space (IMS), at the inner membrane (IMM) and in the mitochondrial matrix, but a clear and comparative analysis of the sub-mitochondrial localization of WT and mutant \u3b1-syn is missing. Furthermore, the reasons for this spread sub-mitochondrial localization under physiological and pathological circumstances remain elusive. In this context, we decided to selectively monitor the sub-mitochondrial distribution of the WT and PD-related \u3b1-syn mutants A53T and A30P by taking advantage from a bimolecular fluorescence complementation (BiFC) approach. We also investigated whether cell stress could trigger \u3b1-syn translocation within the different mitochondrial sub-compartments and whether PD-related mutations could impinge on it. Interestingly, the artificial targeting of \u3b1-syn WT (but not of the mutants) to the mitochondrial matrix impacts on ATP production, suggesting a potential role within this compartment

Mitophagy induction improves salivary gland stem/progenitor cell function by reducing senescence after irradiation

BACKGROUND AND PURPOSE: Patients undergoing radiotherapy for head and neck cancer often experience a decline in their quality of life due to the co-irradiation of salivary glands. Radiation-induced cellular senescence is a key factor contributing to salivary gland dysfunction. Interestingly, mitochondrial dysfunction and cellular senescence have been reported to be strongly interconnected and thus implicated in several aging-related diseases. This study aims to investigate the role of mitochondrial dysfunction in senescence induction in salivary gland stem/progenitor cells after irradiation.MATERIALS AND METHODS: A dose of 7 Gy photons was used to irradiate mouse salivary gland organoids. Senescent markers and mitochondrial function were assessed using rt-qPCR, western blot analysis, SA-β-Gal staining and flow cytometry analysis. Mitochondrial dynamics-related proteins were detected by western blot analysis while Mdivi-1 and MFI8 were used to modulate the mitochondrial fission process. To induce mitophagy, organoids were treated with Urolithin A and PMI and subsequently stem/progenitor cell self-renewal capacity was assessed as organoid forming efficiency.RESULTS: Irradiation led to increased senescence and accumulation of dysfunctional mitochondria. This was accompanied by a strong downregulation of mitochondrial fission-related proteins and mitophagy-related genes. After irradiation, treatment with the mitophagy inducer Urolithin A attenuated the senescent phenotype and improved organoid growth and stem/progenitor cell self-renewal capacity.CONCLUSION: This study shows the important interplay between senescence and mitochondrial dysfunction after irradiation. Importantly, activation of mitophagy improved salivary gland stem/progenitor cell function thereby providing a novel therapeutic strategy to restore the regenerative capacity of salivary glands following irradiation.</p

Mitophagy induction improves salivary gland stem/progenitor cell function by reducing senescence after irradiation

BACKGROUND AND PURPOSE: Patients undergoing radiotherapy for head and neck cancer often experience a decline in their quality of life due to the co-irradiation of salivary glands. Radiation-induced cellular senescence is a key factor contributing to salivary gland dysfunction. Interestingly, mitochondrial dysfunction and cellular senescence have been reported to be strongly interconnected and thus implicated in several aging-related diseases. This study aims to investigate the role of mitochondrial dysfunction in senescence induction in salivary gland stem/progenitor cells after irradiation.MATERIALS AND METHODS: A dose of 7 Gy photons was used to irradiate mouse salivary gland organoids. Senescent markers and mitochondrial function were assessed using rt-qPCR, western blot analysis, SA-β-Gal staining and flow cytometry analysis. Mitochondrial dynamics-related proteins were detected by western blot analysis while Mdivi-1 and MFI8 were used to modulate the mitochondrial fission process. To induce mitophagy, organoids were treated with Urolithin A and PMI and subsequently stem/progenitor cell self-renewal capacity was assessed as organoid forming efficiency.RESULTS: Irradiation led to increased senescence and accumulation of dysfunctional mitochondria. This was accompanied by a strong downregulation of mitochondrial fission-related proteins and mitophagy-related genes. After irradiation, treatment with the mitophagy inducer Urolithin A attenuated the senescent phenotype and improved organoid growth and stem/progenitor cell self-renewal capacity.CONCLUSION: This study shows the important interplay between senescence and mitochondrial dysfunction after irradiation. Importantly, activation of mitophagy improved salivary gland stem/progenitor cell function thereby providing a novel therapeutic strategy to restore the regenerative capacity of salivary glands following irradiation.</p

Establishment of the New Particle Therapy Research Center (PARTREC) at UMCG Groningen

After 25 years of successful research in the nuclear and radiation physics domain, the KVI-CART research center in Groningen is upgraded and re-established as the PARticle Therapy REsearch Center (PARTREC). Using the superconducting cyclotron AGOR and being embedded within the University Medical Center Groningen, it operates in close collaboration with the Groningen Proton Therapy Center. PARTREC uniquely combines radiation physics, medical physics, biology and radiotherapy research with an R&D program to improve hadron therapy technology and advanced radiation therapy for cancer. A number of further upgrades, scheduled for completion in 2023, will establish a wide range of irradiation modalities, such as pencil beam scanning, shoot-through with high energy protons and SOBP for protons, helium and carbon ions. Delivery of spatial fractionation (GRID) and dose rates over 300 Gy/s (FLASH) are envisioned. In addition, PARTREC delivers a variety of ion beams and infrastructure for radiation hardness experiments conducted by scientific and commercial communities, and nuclear science research in collaboration with the Faculty of Science and Engineering of the University of Groningen

The rate of X-ray-induced DNA double-strand break repair in the embryonic mouse brain is unaff ected by exposure to 50 Hz magnetic fi elds

Following in utero exposure to low dose radiation (10 – 200 mGy), we recently observed a linear induction of DNA double-strand breaks (DSB) and activation of apoptosis in the embryonic neuronal stem/progenitor cell compartment. No signifi cant induction of DSB or apoptosis was observed following exposure to magnetic fi elds (MF). In the present study, we exploited this in vivo system to examine whether exposure to MF before and after exposure to 100 mGy X-rays impacts upon DSB repair rates. Materials and methods : 53BP1 foci were quantifi ed following combined exposure to radiation and MF in the embryonic neuronal stem/progenitor cell compartment. Embryos were exposed in utero to 50 Hz MF at 300 m T for 3 h before and up to 9 h after exposure to 100 mGy X-rays. Controls included embryos exposed to MF or X-rays alone plus sham exposures. Results : Exposure to MF before and after 100 mGy X-rays did not impact upon the rate of DSB repair in the embryonic neuronal stem cell compartment compared to repair rates following radiation exposure alone. Conclusions : We conclude that in this sensitive system MF do not exert any signifi cant level of DNA damage and do not impede the repair of X-ray induced damage

Effects of proton therapy on regional [¹⁸F]FDG uptake in non-tumor brain regions of patients treated for head and neck cancer

Background and purpose: Previous pre-clinical research using [18F]FDG-PET has shown that whole-brain photon-based radiotherapy can affect brain glucose metabolism. This study, aimed to investigate how these findings translate into regional changes in brain [18F]FDG uptake in patients with head and neck cancer treated with intensity-modulated proton therapy (IMPT). Materials and methods: Twenty-three head and neck cancer patients treated with IMPT and available [18F]FDG scans before and at 3 months follow-up were retrospectively evaluated. Regional assessment of the [18F]FDG standardized uptake value (SUV) parameters and radiation dose in the left (L) and right (R) hippocampi, L and R occipital lobes, cerebellum, temporal lobe, L and R parietal lobes and frontal lobe were evaluated to understand the relationship between regional changes in SUV metrics and radiation dose. Results: Three months after IMPT, [18F]FDG brain uptake calculated using SUVmean and SUVmax, was significantly higher than that before IMPT. The absolute SUVmean after IMPT was significantly higher than before IMPT in seven regions of the brain (p ≤ 0.01), except for the R (p = 0.11) and L (p = 0.15) hippocampi. Absolute and relative changes were variably correlated with the regional maximum and mean doses received in most of the brain regions. Conclusion: Our findings suggest that 3 months after completion of IMPT for head and neck cancer, significant increases in the uptake of [18F]FDG (reflected by SUVmean and SUVmax) can be detected in several individual key brain regions, and when evaluated jointly, it shows a negative correlation with the mean dose. Future studies are needed to assess whether and how these results could be used for the early identification of patients at risk for adverse cognitive effects of radiation doses in non-tumor tissues.</p