ADP-Ribosylation Factor-Interacting Protein 2 Acts as a Novel Regulator of Mitophagy and Autophagy in Podocytes in Diabetic Nephropathy

(1) Background: Differentiated podocytes are particularly vulnerable to oxidative stress and cellular waste products. The disease-related loss of postmitotic podocytes is a direct indicator of renal disease progression and aging. Podocytes use highly specific regulated networks of autophagy and endocytosis that counteract the increasing number of damaged protein aggregates and help maintain cellular homeostasis. Here, we demonstrate that ARFIP2 is a regulator of autophagy and mitophagy in podocytes both in vitro and in vivo. (2) Methods: In a recent molecular regulatory network analysis of mouse glomeruli, we identified ADP-ribosylation factor-interacting protein 2 (Arfip2), a cytoskeletal regulator and cofactor of ATG9-mediated autophagosome formation, to be differentially expressed with age. We generated an Arfip2-deficient immortalized podocyte cell line using the CRISPR/Cas technique to investigate the significance of Arfip2 for renal homeostasis in vitro. For the in vivo analyses of Arfip2 deficiency, we used a mouse model of Streptozotozin-induced type I diabetes and investigated physiological data and (patho)histological (ultra)structural modifications. (3) Results: ARFIP2 deficiency in immortalized human podocytes impedes autophagy. Beyond this, ARFIP2 deficiency in human podocytes interferes with ATG9A trafficking and the PINK1-Parkin pathway, leading to the compromised fission of mitochondria and short-term increase in mitochondrial respiration and induction of mitophagy. In diabetic mice, Arfip2 deficiency deteriorates autophagy and leads to foot process effacement, histopathological changes, and early albuminuria. (4) Conclusions: In summary, we show that ARFIP2 is a novel regulator of autophagy and mitochondrial homeostasis in podocytes by facilitating ATG9A trafficking during PINK1/Parkin-regulated mitophagy.

A YAP/TAZ-ARHGAP29-RhoA Signaling Axis Regulates Podocyte Protrusions and Integrin Adhesions

Glomerular disease due to podocyte malfunction is a major factor in the pathogenesis of chronic kidney disease. Identification of podocyte-specific signaling pathways is therefore a prerequisite to characterizing relevant disease pathways and developing novel treatment approaches. Here, we employed loss of function studies for EPB41L5 (Yurt) as a central podocyte gene to generate a cell type-specific disease model. Loss of Yurt in fly nephrocytes caused protein uptake and slit diaphragm defects. Transcriptomic and proteomic analysis of human EPB41L5 knockout podocytes demonstrated impaired mechanotransduction via the YAP/TAZ signaling pathway. Further analysis of specific inhibition of the YAP/TAZ-TEAD transcription factor complex by TEADi led to the identification of ARGHAP29 as an EPB41L5 and YAP/TAZ-dependently expressed podocyte RhoGAP. Knockdown of ARHGAP29 caused increased RhoA activation, defective lamellipodia formation, and increased maturation of integrin adhesion complexes, explaining similar phenotypes caused by loss of EPB41L5 and TEADi expression in podocytes. Detection of increased levels of ARHGAP29 in early disease stages of human glomerular disease implies a novel negative feedback loop for mechanotransductive RhoA-YAP/TAZ signaling in podocyte physiology and disease.

α-Parvin Defines a Specific Integrin Adhesome to Maintain the Glomerular Filtration Barrier

BACKGROUND

The cell-matrix adhesion between podocytes and the glomerular basement membrane is essential for the integrity of the kidney's filtration barrier. Despite increasing knowledge about the complexity of integrin adhesion complexes, an understanding of the regulation of these protein complexes in glomerular disease remains elusive.

METHODS

We mapped the in vivo composition of the podocyte integrin adhesome. In addition, we analyzed conditional knockout mice targeting a gene (Parva) that encodes an actin-binding protein (α-parvin), and murine disease models. To evaluate podocytes in vivo, we used super-resolution microscopy, electron microscopy, multiplex immunofluorescence microscopy, and RNA sequencing. We performed functional analysis of CRISPR/Cas9-generated PARVA single knockout podocytes and PARVA and PARVB double knockout podocytes in three- and two-dimensional cultures using specific extracellular matrix ligands and micropatterns.

RESULTS

We found that PARVA is essential to prevent podocyte foot process effacement, detachment from the glomerular basement membrane, and the development of FSGS. Through the use of in vitro and in vivo models, we identified an inherent PARVB-dependent compensatory module at podocyte integrin adhesion complexes, sustaining efficient mechanical linkage at the filtration barrier. Sequential genetic deletion of PARVA and PARVB induces a switch in structure and composition of integrin adhesion complexes. This redistribution of these complexes translates into a loss of the ventral actin cytoskeleton, decreased adhesion capacity, impaired mechanical resistance, and dysfunctional extracellular matrix assembly.

CONCLUSIONS

The findings reveal adaptive mechanisms of podocyte integrin adhesion complexes, providing a conceptual framework for therapeutic strategies to prevent podocyte detachment in glomerular disease.

A Novel Model for Nephrotic Syndrome Reveals Associated Dysbiosis of the Gut Microbiome and Extramedullary Hematopoiesis

Glomerular kidney disease causing nephrotic syndrome is a complex systemic disorder and is associated with significant morbidity in affected patient populations. Despite its clinical relevance, well-established models are largely missing to further elucidate the implications of uncontrolled urinary protein loss. To overcome this limitation, we generated a novel, inducible, podocyte-specific transgenic mouse model (Epb41l5^fl/fl*Nphs1-rtTA-3G*tetOCre), developing nephrotic syndrome in adult mice. Animals were comprehensively characterized, including microbiome analysis and multiplexed immunofluorescence imaging. Induced knockout mice developed a phenotype consistent with focal segmental glomerular sclerosis (FSGS). Although these mice showed hallmark features of severe nephrotic syndrome (including proteinuria, hypoalbuminemia and dyslipidemia), they did not exhibit overt chronic kidney disease (CKD) phenotypes. Analysis of the gut microbiome demonstrated distinct dysbiosis and highly significant enrichment of the Alistipes genus. Moreover, Epb41l5-deficient mice developed marked organ pathologies, including extramedullary hematopoiesis of the spleen. Multiplex immunofluorescence imaging demonstrated red pulp macrophage proliferation and mTOR activation as driving factors of hematopoietic niche expansion. Thus, this novel mouse model for adult-onset nephrotic syndrome reveals the significant impact of proteinuria on extra-renal manifestations, demonstrating the versatility of this model for nephrotic syndrome-related research.

SRGAP1 Controls Small Rho GTPases To Regulate Podocyte Foot Process Maintenance

BACKGROUND

Previous research demonstrated that small Rho GTPases, modulators of the actin cytoskeleton, are drivers of podocyte foot-process effacement in glomerular diseases, such as FSGS. However, a comprehensive understanding of the regulatory networks of small Rho GTPases in podocytes is lacking.

METHODS

We conducted an analysis of podocyte transcriptome and proteome datasets for Rho GTPases; mapped in vivo, podocyte-specific Rho GTPase affinity networks; and examined conditional knockout mice and murine disease models targeting Srgap1. To evaluate podocyte foot-process morphology, we used super-resolution microscopy and electron microscopy; in situ proximity ligation assays were used to determine the subcellular localization of the small GTPase-activating protein SRGAP1. We performed functional analysis of CRISPR/Cas9-generated SRGAP1 knockout podocytes in two-dimensional and three-dimensional cultures and quantitative interaction proteomics.

RESULTS

We demonstrated SRGAP1 localization to podocyte foot processes in vivo and to cellular protrusions in vitro. Srgap1^fl/fl*Six2Cre but not Srgap1^fl/fl*hNPHS2Cre knockout mice developed an FSGS-like phenotype at adulthood. Podocyte-specific deletion of Srgap1 by hNPHS2Cre resulted in increased susceptibility to doxorubicin-induced nephropathy. Detailed analysis demonstrated significant effacement of podocyte foot processes. Furthermore, SRGAP1-knockout podocytes showed excessive protrusion formation and disinhibition of the small Rho GTPase machinery in vitro. Evaluation of a SRGAP1-dependent interactome revealed the involvement of SRGAP1 with protrusive and contractile actin networks. Analysis of glomerular biopsy specimens translated these findings toward human disease by displaying a pronounced redistribution of SRGAP1 in FSGS.

CONCLUSIONS

SRGAP1, a podocyte-specific RhoGAP, controls podocyte foot-process architecture by limiting the activity of protrusive, branched actin networks. Therefore, elucidating the complex regulatory small Rho GTPase affinity network points to novel targets for potentially precise intervention in glomerular diseases.

Preliminary investigation of extracellular vesicles in mammary cancer of dogs and cats: Identification and characterization

Extracellular vesicles (EVs) are membrane-bound vesicles produced by cells, known to play a key role in cell-to-cell communication. They exert pleiotropic biological functions via the horizontal transfer of bioactive molecules (DNA, RNAs, proteins, and lipids) within the tumour microenvironment and throughout the body. In human cancer, EVs are known to interfere with pathways that lead to tumour progression and are used as novel cancer biomarkers. In veterinary medicine, very little is known on cancer-derived EVs. In this study, we preliminarily characterized EVs in mammary gland cancer of dogs and cats. EVs were isolated by ultracentrifugation from canine (CYPp), feline (FMCp) and human (MCF7) mammary tumour cell lines. EVs were visualized by transmission electron microscopy (TEM), counted using nanoparticle tracking analysis (NTA) and characterized by immunogold (CD63 and Alix) and western blot (Alix and TSG101). Additionally, EV production by "donor" cells (palmtdTomato⁺ ) and uptake by "recipient" cells (GFP⁺ ) were assessed. EVs were successfully isolated from all 3 cell lines by ultracentrifugation. Membrane-bound structures (50-400 nm) were identified by TEM and were positive for both CD63 and Alix at immunogold. Western blot showed positivity of EVs to Alix and TSG101. NTA analysis detected EVs from cell culture media ranging from 1.67 to 2.56 × 10² as number of EVs/cell and from 80 to 600 nm in size. Confocal microscopy identified the presence of palmtdTomato⁺ EVs into the cytoplasm of GFP⁺ cells. This preliminary study identified and characterized canine and feline mammary tumour cell-derived EVs, opening in veterinary medicine a new interesting unexplored field with several applications and limitless potential.

Drug utilization, safety, and effectiveness of exenatide, sitagliptin, and vildagliptin for type 2 diabetes in the real world: data from the Italian AIFA Anti-diabetics Monitoring Registry

BACKGROUND AND AIMS

In Italy, the reimbursed use of incretin mimetics and incretin enhancers was subject to enrollment of patients into a web-based system recording the general demographic and clinical data of patients. We report the utilization data of glucagon-like peptide 1 (GLP1) receptor agonists and dipeptidylpeptidase-4 (DPP4) inhibitors in clinical practice as recorded by the Italian Medicines Agency (AIFA) Monitoring Registry.

METHODS AND RESULTS

From February 2008 to August 2010, 75,283 patients with type 2 diabetes were entered into the registry and treated with exenatide, sitagliptin, or vildagliptin. The treatment was administered to patients in a wide range of ages (≥75 years, n = 6125 cases), body mass index (BMI) (≥35 kg/m(2), n = 22,015), and metabolic control (HbA(1c) ≥ 11% ((96 mmol/mol), n = 3151). Overall, 1116 suspected adverse drug reactions were registered, including 12 cases of acute pancreatitis (six on exenatide). Hypoglycemic episodes mainly occurred in combination with sulfonylureas. Treatment discontinuation for the three drugs (logistic regression analysis) was negatively associated with the male gender and positively with baseline HbA1c, diabetes duration, and, limitedly to DPP-4 inhibitors, with BMI. Treatment discontinuation (including loss to follow-up, accounting for 21-26%) was frequent. Discontinuation for treatment failure occurred in 7.7% of cases (exenatide), 3.8% (sitagliptin), and 4.1% (vildagliptin), respectively, corresponding to 27-40% of all discontinuations, after excluding lost to follow-up. HbA1c decreased on average by 0.9-1.0% (9 mmol/mol). Body weight decreased by 3.5% with exenatide and by 1.0-1.5% with DPP-4 inhibitors.

CONCLUSIONS

In the real world of Italian diabetes centers, prescriptions of incretins have been made in many cases outside the regulatory limits. Nevertheless, when appropriately utilized, incretins may grant results at least in line with pivotal trials.

[The use of procedures volume indicators in an Italian Teaching Hospital]

In a context of continuous spread health technologies, in which particular intensive procedures are performed, the use of procedure volume indicators supports the decision making process in monitoring and improving the healthcare quality. The aim of our work focuses on the evaluation of the association between the volume of procedures performed by organizational units inside an Italian University Hospital and the results in terms of mortality and prolonged length of stay (LOS). Volume indicators concerning esophageal resection, pancreatic resection, abdominal aortic aneurysm repair, coronary artery bypass graft and percutaneous transluminal coronary angioplasty were analysed according to the Agency of Health Care Research and Quality's criteria. A retrospective observational study was conducted analysing hospital discharged databases and operating room records for the period 2000-2005. Descriptive and inferential statistical analysis were performed using SPSS software 13.0 version. Regarding prolonged LOS, a statistical significant difference emerged among high and low volume organizational units for pancreatic resections, bypass, and angioplasty with respectively adjusted OR at 2.4 (C.I. 95% 1.04-5.53); 1.67 (C.I. 95% 1.29-2.16) and 3.34 (CI 95% 2.60-4.28). For mortality, a statistical significant difference emerged for abdominal aortic aneurysm repair and bypass with respectively OR at 21.02 (C.I. 95% 2.22-199.64) and 26.55 (C.I. 95% 15.30 - 46.07). The use of procedure volume indicators could help hospital administrators and medical professionals balance competing values such as control of cost and continuous quality improvement.

Psychosocial stages and quality of life of women with breast cancer

Certain issues are universal for all women with breast cancer, irrespective of age, ethnic group, or stage of disease. Yet, along with common concerns, experiences, and anxieties, each woman may encounter a unique set of problems. Ultimately, each woman's adaptation and choices will be strongly influenced by her personal history, her psychosocial stage, and her life-cycle concerns. Changes in the criteria norms for the psychosocial stages of women's lives and their subsequent influence on quality of life are issues that have substantial implications for nursing and other healthcare professions. Younger and older women have different needs, concerns, and quality of life issues in a context of psychosocial life stages that have changed significantly across the post-World War II generations. The experience of breast cancer is perceived differently by women of distinct psychosocial life stages. At each critical life stage, the unique emerging problems require specific psychosocial supports that can reduce or avert the ensuing emotional distress. The planning and implementation of care must be tailored to address the differences demonstrated by age and psychosocial life stage, and to enhance quality of life outcomes for survivors of breast cancer, both young and old.

Perceived social support, uncertainty, and quality of life of younger breast cancer survivors

This study investigated the relationship between perceived social support, uncertainty, and quality of life among younger breast cancer survivors. Proposed hypotheses predicted a significant positive correlation between perceived social support and quality of life, a significant negative correlation between uncertainty and quality of life, and that perceived social support and uncertainty, considered together, will explain more of the variance of quality of life than either variable considered independently. A sample of 101 breast cancer survivors below age 50 completed the Social Support Questionnaire, Mishel Uncertainty in Illness Scale--Community Form, and Ferrans and Powers Quality of Life Index--Cancer Version. Data were analyzed using Pearson product-moment correlation and stepwise multiple regression. All three hypotheses were supported. Additional findings revealed a significant positive correlation between support and network size, and between network size and the socioeconomic domain of quality of life. Significant negative correlations were found between perceived social support and uncertainty, between network size and time since diagnosis and treatment, and between network size and uncertainty. Study results demonstrated that although perceived social support and uncertainty accounted for a significant amount (27.2%) of variance of quality of life, a large amount of variance remains unexplained. Further research is needed in this area.