ABSTRACT
In an effort to stem the loss of Ontario's late career nurses, the Ontario Ministry of Health and Long-Term Care introduced the Late Career Nurse Initiative (LCNI) to implement a 0.20 full-time equivalent reduction of physically or psychologically demanding duties of nurses aged 55 or over and repurposing this time to enriching and less demanding activities. Fifty-nine nurse leaders were interviewed to explore their perceptions associated with implementing the LCNI in their respective organizations. Following a qualitative directed content analysis approach, three themes emerged: (1) having a strategic approach, (2) leveraging staff expertise and (3) securing organizational support.
Subject(s)
Attitude of Health Personnel , Career Mobility , Clinical Competence , Leadership , Personnel Turnover , Population Dynamics , Workload , Career Choice , Female , Humans , Middle Aged , Ontario , Work Schedule ToleranceABSTRACT
Epithelial-to-mesenchymal transition (EMT) contributes to renal fibrosis in chronic kidney disease. Endoplasmic reticulum (ER) stress, a feature of many forms of kidney disease, results from the accumulation of misfolded proteins in the ER and leads to the unfolded protein response (UPR). We hypothesized that ER stress mediates EMT in human renal proximal tubules. ER stress is induced by a variety of stressors differing in their mechanism of action, including tunicamycin, thapsigargin, and the calcineurin inhibitor cyclosporine A. These ER stressors increased the UPR markers GRP78, GRP94, and phospho-eIF2α in human proximal tubular cells. Thapsigargin and cyclosporine A also increased cytosolic Ca(2+) concentration and T cell death-associated gene 51 (TDAG51) expression, whereas tunicamycin did not. Thapsigargin was also shown to increase levels of active transforming growth factor (TGF)-ß1 in the media of cultured human proximal tubular cells. Thapsigargin induced cytoskeletal rearrangement, ß-catenin nuclear translocation, and α-smooth muscle actin and vinculin expression in proximal tubular cells, indicating an EMT response. Subconfluent primary human proximal tubular cells were induced to undergo EMT by TGF-ß1 treatment. In contrast, tunicamycin treatment did not produce an EMT response. Plasmid-mediated overexpression of TDAG51 resulted in cell shape change and ß-catenin nuclear translocation. These results allowed us to develop a two-hit model of ER stress-induced EMT, where Ca(2+) dysregulation-mediated TDAG51 upregulation primes the cell for mesenchymal transformation via Wnt signaling and then TGF-ß1 activation leads to a complete EMT response. Thus the release of Ca(2+) from ER stores mediates EMT in human proximal tubular epithelium via the induction of TDAG51.
Subject(s)
Epithelium/metabolism , Kidney Tubules, Proximal/metabolism , Mesoderm/metabolism , Transcription Factors/physiology , Animals , Calcium/metabolism , Cell Line , Cell Shape , Cells, Cultured , Chelating Agents/pharmacology , Cytosol/drug effects , Cytosol/metabolism , Egtazic Acid/analogs & derivatives , Egtazic Acid/pharmacology , Electrophoresis, Polyacrylamide Gel , Endoplasmic Reticulum/drug effects , Endoplasmic Reticulum/metabolism , Endoplasmic Reticulum Chaperone BiP , Enzyme-Linked Immunosorbent Assay , Fibrosis , Humans , Indicators and Reagents , Mice , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Fluorescence , Plasmids/genetics , Spectrometry, Fluorescence , Transcription Factors/genetics , Transfection , Transforming Growth Factor beta1/biosynthesis , Up-Regulation/drug effects , Up-Regulation/physiology , beta Catenin/metabolismABSTRACT
The integrated stress response mediated by eukaryotic translation initiation factor 2α (eIF2α) phosphorylation maintains cellular homeostasis under endoplasmic reticulum (ER) stress. eIF2α phosphorylation induces activating transcription factor 4 (ATF4), a basic leucine zipper transcription factor that regulates the expression of genes responsible for amino acid metabolism, cellular redox state, and anti-stress responses. Cystathionine γ-lyase (CSE) and cystathionine ß-synthase are critical enzymes in the transsulfuration pathway, which also regulate cellular redox status by modulating glutathione (GSH) levels. To determine the link between the integrated stress response and the transsulfuration pathway, we used homocysteine (Hcy) as an inducer of eIF2α phosphorylation and ATF4 gene induction. Mouse embryonic fibroblasts (MEFs) lacking ATF4 (ATF4(-/-)) had reduced GSH levels and increased reactive oxygen species and were susceptible to apoptotic cell death under normal culture conditions. Further, ATF4(-/-) MEFs were more sensitive to Hcy-induced cytotoxicity and showed significantly reduced intracellular GSH levels associated with apoptosis. ATF4(-/-) MEFs could be rescued from l-Hcy-induced apoptosis by ß-mercaptoethanol medium supplementation that increases cysteine levels and restores GSH synthesis. ATF4(-/-) MEFs showed little or no CSE protein but did express cystathionine ß-synthase. Further, ER stress-inducing agents, including tunicamycin and thapsigargin, induced the expression of CSE in ATF4(+/+) MEFs. Consistent with ATF4(-/-) MEFs, CSE(-/-) MEFs showed significantly greater apoptosis when treated with tunicamycin, thapsigargin, and l-Hcy, compared with CSE(+/+) MEFs. Liver and kidney GSH levels were also reduced in CSE(-/-) mice, suggesting that CSE is a critical factor in GSH synthesis and may act to protect the liver and kidney from a variety of conditions that cause ER stress.
