Regulation of mitochondrial permeability transition pore by PINK1

Background: Loss-of-function mutations in PTEN-induced kinase 1 (PINK1) have been linked to familial Parkinson’s disease, but the underlying pathogenic mechanism remains unclear. We previously reported that loss of PINK1 impairs mitochondrial respiratory activity in mouse brains. Results: In this study, we investigate how loss of PINK1 impairs mitochondrial respiration using cultured primary fibroblasts and neurons. We found that intact mitochondria in PINK1−/− cells recapitulate the respiratory defect in isolated mitochondria from PINK1−/− mouse brains, suggesting that these PINK1−/− cells are a valid experimental system to study the underlying mechanisms. Enzymatic activities of the electron transport system complexes are normal in PINK1−/− cells, but mitochondrial transmembrane potential is reduced. Interestingly, the opening of the mitochondrial permeability transition pore (mPTP) is increased in PINK1−/− cells, and this genotypic difference between PINK1−/− and control cells is eliminated by agonists or inhibitors of the mPTP. Furthermore, inhibition of mPTP opening rescues the defects in transmembrane potential and respiration in PINK1−/− cells. Consistent with our earlier findings in mouse brains, mitochondrial morphology is similar between PINK1−/− and wild-type cells, indicating that the observed mitochondrial functional defects are not due to morphological changes. Following FCCP treatment, calcium increases in the cytosol are higher in PINK1−/− compared to wild-type cells, suggesting that intra-mitochondrial calcium concentration is higher in the absence of PINK1. Conclusions: Our findings show that loss of PINK1 causes selective increases in mPTP opening and mitochondrial calcium, and that the excessive mPTP opening may underlie the mitochondrial functional defects observed in PINK1−/− cells

Clinical Implications of Diurnal Variations in Physiological, Psychological and Behavioral Measures in Patients with Chronic Obstructive Pulmonary Disease

The aim of this thesis was to investigate the clinical implications of diurnal variations in physiological, behavioral and psychological measures in a Chronic Obstructive Pulmonary Disease (COPD) population. In a sample of 14 moderate-to-severe COPD participants we first evaluated the effect of time of day on the acute response to incremental exercise in COPD. We found that a majority of individuals exceeded clinically significant changes in their pulmonary function and peak exercise capacity measures. A peak in exercise capacity was observed in the afternoon in the subgroup of individuals who demonstrated increased variability, similar to the timing of peak exercise performance previously documented in healthy individuals. We then investigated if high or low relative amplitude (RA), a marker of internal synchronization, was associated with disease severity or prognosis in COPD. Lower RA was associated with higher ratings of dyspnea and worse scores on prognostic indexes. The amplitude difference between the two sub-groups appears to be due to increased physical activity at midday in the high-RA sub-group. Lastly, we investigated whether diurnal variation in depression symptoms would be associated with depression symptoms severity. We found larger diurnal variation in depression symptoms to be associated with worse depression symptom severity in COPD patients. This association seemed independent of pulmonary function and exercise capacity. The results presented in this thesis were the first to report on diurnal variations in various common clinical measures in COPD and to explore the link between amplitude of the rest-activity cycle and indexes of disease prognosis. Based on our findings, accounting for the timing of repeated exercise testing is suggested. RA of the rest-activity cycle may be a useful marker in COPD prognosis. Lastly, identifying diurnal variation in depressive symptoms may help detect depression in COPD

Regulation of mitochondrial permeability transition pore by PINK1

Background: Loss-of-function mutations in PTEN-induced kinase 1 (PINK1) have been linked to familial Parkinson’s disease, but the underlying pathogenic mechanism remains unclear. We previously reported that loss of PINK1 impairs mitochondrial respiratory activity in mouse brains. Results: In this study, we investigate how loss of PINK1 impairs mitochondrial respiration using cultured primary fibroblasts and neurons. We found that intact mitochondria in PINK1−/− cells recapitulate the respiratory defect in isolated mitochondria from PINK1−/− mouse brains, suggesting that these PINK1−/− cells are a valid experimental system to study the underlying mechanisms. Enzymatic activities of the electron transport system complexes are normal in PINK1−/− cells, but mitochondrial transmembrane potential is reduced. Interestingly, the opening of the mitochondrial permeability transition pore (mPTP) is increased in PINK1−/− cells, and this genotypic difference between PINK1−/− and control cells is eliminated by agonists or inhibitors of the mPTP. Furthermore, inhibition of mPTP opening rescues the defects in transmembrane potential and respiration in PINK1−/− cells. Consistent with our earlier findings in mouse brains, mitochondrial morphology is similar between PINK1−/− and wild-type cells, indicating that the observed mitochondrial functional defects are not due to morphological changes. Following FCCP treatment, calcium increases in the cytosol are higher in PINK1−/− compared to wild-type cells, suggesting that intra-mitochondrial calcium concentration is higher in the absence of PINK1. Conclusions: Our findings show that loss of PINK1 causes selective increases in mPTP opening and mitochondrial calcium, and that the excessive mPTP opening may underlie the mitochondrial functional defects observed in PINK1−/− cells

Amplitude of the rest–activity cycle in chronic obstructive pulmonary disease: an exploratory study

In chronic obstructive pulmonary disease (COPD), there is large individual variability in the progression of the disease. Low amplitude of rest–activity rhythms has been associated with worse prognosis in a variety of diseases, but it has not been investigated in COPD. The first aim of this exploratory study was to compare disease severity and prognosis indicators between COPD patients with relatively high or low amplitude of their rest–activity cycle, as measured with actigraphy. As a second objective, 24-hour profiles of both activity levels and nighttime-sleep quality were compared between the two subgroups to assess the relative contribution of day- and night-activity levels to high and low rest–activity rhythm amplitude in this population. Rest–activity rhythms were measured with 8–14 days of wrist actigraphy in 14 patients (nine men), aged 58–79 years, suffering from moderate-to-severe COPD. Relative amplitude of 24-hour activity profiles ranged from 0.72 to 0.98. Participants were divided at the median into high-amplitude (mean ± standard deviation 0.9±0.04) and low-amplitude (0.79±0.05) subgroups. There was no significant difference between the two subgroups for pulmonary function or exercise capacity. However, the low-amplitude group had more severe symptoms of dyspnea and worse prognostic scores than the high-amplitude group (P<0.05). The 24-hour activity profiles revealed higher levels of activity in the high-amplitude group for the 12–3 pm interval (P<0.05). There was no significant difference between the two groups for subjective or actigraphic estimates of sleep quality, sleep duration, or proportion of daytime sleep. This exploratory study is a first step toward the identification of larger rest–activity rhythm amplitude as a marker of better prognosis in COPD and as another potential target for exercise-based rehabilitation programs in this population

Suppressor of K+ transport growth defect 1 (SKD1) interactswith RING-type ubiquitin ligase and sucrose non-fermenting1-related protein kinase (SnRK1) in the halophyte ice plant

SKD1 (suppressor of K+ transport growth defect 1) is an AAA-type ATPase that functions as a molecular motor. It was previously shown that SKD1 accumulates in epidermal bladder cells of the halophyte Mesembryanthemum crystallinum. SKD1 knock-down Arabidopsis mutants showed an imbalanced Na+/K+ ratio under salt stress. Two enzymes involved in protein post-translational modifications that physically interacted with McSKD1 were identified. McCPN1 (copine 1), a RING-type ubiquitin ligase, has an N-terminal myristoylation site that links to the plasma membrane, a central copine domain that interacts with McSKD1, and a C-terminal RING domain that catalyses protein ubiquitination. In vitro ubiquitination assay demonstrated that McCPN1 was capable of mediating ubiquitination of McSKD1. McSnRK1 (sucrose non-fermenting 1-related protein kinase) is a Ser/Thr protein kinase that contains an N-terminal STKc catalytic domain to phosphorylate McSKD1, and C-terminal UBA and KA1 domains to interact with McSKD1. The transcript and protein levels of McSnRK1 increased as NaCl concentrations increased. The formation of an SKD1–SnRK1–CPN1 ternary complex was demonstrated by yeast three-hybrid and bimolecular fluorescence complementation. It was found that McSKD1 preferentially interacts with McSnRK1 in the cytosol, and salt induced the re-distribution of McSKD1 and McSnRK1 towards the plasma membrane via the microtubule cytoskeleton and subsequently interacted with RING-type E3 McCPN1. The potential effects of ubiquitination and phosphorylation on McSKD1, such as changes in the ATPase activity and cellular localization, and how they relate to the functions of SKD1 in the maintenance of Na+/K+ homeostasis under salt stress, are discussed

Using Continuous Data Tracking Technology to Study Exercise Adherence in Pulmonary Rehabilitation

Pulmonary rehabilitation is widely recognized in the management of respiratory diseases. A key component to successful pulmonary rehabilitation is adherence to the recommended exercise training. The purpose of the present protocol is to describe how continuous data tracking technology can be used to precisely measure adherence to a prescribed aerobic training intensity

Amplitude of the rest-activity cycle in chronic obstructive pulmonary disease: an exploratory study

In chronic obstructive pulmonary disease (COPD), there is large individual variability in the progression of the disease. Low amplitude of rest–activity rhythms has been associated with worse prognosis in a variety of diseases, but it has not been investigated in COPD. The first aim of this exploratory study was to compare disease severity and prognosis indicators between COPD patients with relatively high or low amplitude of their rest–activity cycle, as measured with actigraphy. As a second objective, 24-hour profiles of both activity levels and nighttime-sleep quality were compared between the two subgroups to assess the relative contribution of day- and night-activity levels to high and low rest–activity rhythm amplitude in this population. Rest–activity rhythms were measured with 8–14 days of wrist actigraphy in 14 patients (nine men), aged 58–79 years, suffering from moderate-to-severe COPD. Relative amplitude of 24-hour activity profiles ranged from 0.72 to 0.98. Participants were divided at the median into high-amplitude (mean ± standard deviation 0.9±0.04) and low-amplitude (0.79±0.05) subgroups. There was no significant difference between the two subgroups for pulmonary function or exercise capacity. However, the low-amplitude group had more severe symptoms of dyspnea and worse prognostic scores than the high-amplitude group (P<0.05). The 24-hour activity profiles revealed higher levels of activity in the high-amplitude group for the 12–3 pm interval (P<0.05). There was no significant difference between the two groups for subjective or actigraphic estimates of sleep quality, sleep duration, or proportion of daytime sleep. This exploratory study is a first step toward the identification of larger rest–activity rhythm amplitude as a marker of better prognosis in COPD and as another potential target for exercise-based rehabilitation programs in this population

A Comprehensive Phenotypic and Functional Immune Analysis Unravels Circulating Anti-Phospholipase A2 Receptor Antibody Secreting Cells in Membranous Nephropathy Patients

Introduction: Primary membranous nephropathy (MN) is characterized by the presence of antipodocyte antibodies, but studies describing phenotypic and functional abnormalities in circulating lymphocytes are limited. Methods: We analyzed 68 different B- and T-cell subsets using flow cytometry in 30 MN patients (before initiating immunosuppression) compared with 31 patients with non-immune-mediated chronic kidney disease (CKD) and 12 healthy individuals. We also measured 19 serum cytokines in MN patients and in healthy controls. Lastly, we quantified the ex vivo production of phospholipase A2 receptor (PLA2R)-specific IgG by plasmablasts (measuring antibodies in culture supernatants and by the newly developed FluoroSpot assay [AutoImmun Diagnostika, Strasberg, Germany]) and assessed the circulating antibody repertoire by phage immunoprecipitation sequencing (PhIP-Seq). Results: After adjusting for multiple testing, plasma cells and regulatory B cells (BREG) were significantly higher (P < 0.05) in MN patients compared with both control groups. The percentages of circulating plasma cells correlated with serum anti-PLA2R antibody levels (P = 0.042) and were associated with disease activity. Ex vivo-expanded PLA2R-specific IgG-producing plasmablasts generated from circulating PLA2R-specific memory B cells (mBCs) correlated with serum anti-PLA2R IgG antibodies (P < 0.001) in MN patients. Tumor necrosis factor-alpha (TNF-alpha) was the only significantly increased cytokine in MN patients (P < 0.05), whereas there was no significant difference across study groups in the autoantibody and antiviral antibody repertoire. Conclusion: This extensive phenotypic and functional immune characterization shows that autoreactive plasma cells are present in the circulation of MN patients, providing a new therapeutic target and a candidate biomarker of disease activity