Absence of miR-146a in Podocytes Increases Risk of Diabetic Glomerulopathy via Up-regulation of ErbB4 and Notch-1.

Podocyte injury is an early event in diabetic kidney disease and is a hallmark of glomerulopathy. MicroRNA-146a (miR-146a) is highly expressed in many cell types under homeostatic conditions, and plays an important anti-inflammatory role in myeloid cells. However, its role in podocytes is unclear. Here, we show that miR-146a expression levels decrease in the glomeruli of patients with type 2 diabetes (T2D), which correlates with increased albuminuria and glomerular damage. miR-146a levels are also significantly reduced in the glomeruli of albuminuric BTBR ob/ob mice, indicating its significant role in maintaining podocyte health. miR-146a-deficient mice (miR-146a-/-) showed accelerated development of glomerulopathy and albuminuria upon streptozotocin (STZ)-induced hyperglycemia. The miR-146a targets, Notch-1 and ErbB4, were also significantly up-regulated in the glomeruli of diabetic patients and mice, suggesting induction of the downstream TGFß signaling. Treatment with a pan-ErbB kinase inhibitor erlotinib with nanomolar activity against ErbB4 significantly suppressed diabetic glomerular injury and albuminuria in both WT and miR-146a-/- animals. Treatment of podocytes in vitro with TGF-ß1 resulted in increased expression of Notch-1, ErbB4, pErbB4, and pEGFR, the heterodimerization partner of ErbB4, suggesting increased ErbB4/EGFR signaling. TGF-ß1 also increased levels of inflammatory cytokine monocyte chemoattractant protein-1 (MCP-1) and MCP-1 induced protein-1 (MCPIP1), a suppressor of miR-146a, suggesting an autocrine loop. Inhibition of ErbB4/EGFR with erlotinib co-treatment of podocytes suppressed this signaling. Our findings suggest a novel role for miR-146a in protecting against diabetic glomerulopathy and podocyte injury. They also point to ErbB4/EGFR as a novel, druggable target for therapeutic intervention, especially because several pan-ErbB inhibitors are clinically available.

High-content screening assay-based discovery of paullones as novel podocyte-protective agents.

Podocyte dysfunction and loss is an early event and a hallmark of proteinuric kidney diseases. A podocyte's normal function is maintained via its unique cellular architecture that relies on an intracellular network of filaments, including filamentous actin (F-actin) and microtubules, that provides mechanical support. Damage to this filamentous network leads to changes in cellular morphology and results in podocyte injury, dysfunction, and death. Conversely, stabilization of this network protects podocytes and ameliorates proteinuria. This suggests that stabilization of podocyte architecture via its filamentous network could be a key therapeutic strategy for proteinuric kidney diseases. However, development of podocyte-directed therapeutics, especially those that target the cell's filamentous network, is still lacking, partly because of unavailability of appropriate cellular assays for use in a drug discovery environment. Here, we describe a new high-content screening-based methodology and its implementation on podocytes to identify paullone derivatives as a novel group of podocyte-protective compounds. We find that three compounds, i.e., kenpaullone, 1-azakenpaullone, and alsterpaullone, dose dependently protect podocytes from puromycin aminonucleoside (PAN)-mediated injury in vitro by reducing PAN-induced changes in both the filamentous actin and microtubules, with alsterpaullone providing maximal protection. Mechanistic studies further show that alsterpaullone suppressed PAN-induced activation of signaling downstream of GSK3ß and p38 mitogen-activated protein kinase. In vivo it reduced ADR-induced glomerular injury in a zebrafish model. Together, these results identify paullone derivatives as novel podocyte-protective agents for future therapeutic development.

Dynamin Autonomously Regulates Podocyte Focal Adhesion Maturation.

Rho family GTPases, the prototypical members of which are Cdc42, Rac1, and RhoA, are molecular switches best known for regulating the actin cytoskeleton. In addition to the canonical small GTPases, the large GTPase dynamin has been implicated in regulating the actin cytoskeleton via direct dynamin-actin interactions. The physiologic role of dynamin in regulating the actin cytoskeleton has been linked to the maintenance of the kidney filtration barrier. Additionally, the small molecule Bis-T-23, which promotes actin-dependent dynamin oligomerization and thus, increases actin polymerization, improved renal health in diverse models of CKD, implicating dynamin as a potential therapeutic target for the treatment of CKD. Here, we show that treating cultured mouse podocytes with Bis-T-23 promoted stress fiber formation and focal adhesion maturation in a dynamin-dependent manner. Furthermore, Bis-T-23 induced the formation of focal adhesions and stress fibers in cells in which the RhoA signaling pathway was downregulated by multiple experimental approaches. Our study suggests that dynamin regulates focal adhesion maturation by a mechanism parallel to and synergistic with the RhoA signaling pathway. Identification of dynamin as one of the essential and autonomous regulators of focal adhesion maturation suggests a molecular mechanism that underlies the beneficial effect of Bis-T-23 on podocyte physiology.

CFTR Controls the Activity of NF-κB by Enhancing the Degradation of TRADD.

BACKGROUND/AIMS: Chronic lung infection in cystic fibrosis leads to an inflammatory response that persists because of the chronic presence of bacteria and ultimately leads to a catastrophic failure of lung function. METHODS: We use a combination of biochemistry, cell and molecular biology to study the interaction of TRADD, a key adaptor molecule in TNFα signaling, with CFTR in the regulation of NFκB. RESULTS: We show that Wt CFTR binds to and colocalizes with TRADD. TRADD is a key signaling intermediate connecting TNFα with activation of NFκB. By contrast, ΔF508 CFTR does not bind to TRADD. NF-κB activation is higher in CFBE expressing ΔF508 CFTR than in cells expressing Wt CFTR. However, this differential effect is abolished when TRADD levels are knocked down. Transfecting Wt CFTR into CFBE cells reduces NF-κB activity. However the reduction is abolished by the CFTR chloride transport inhibitor-172. Consistently, transfecting in the correctly trafficked CFTR conduction mutants G551D or S341A also fail to reduce NFκB activity. Thus CFTR must be functional if it is to regulate NF-κB activity. We also found that TNFα produced a greater increase in NF-κB activity in CFBE cells than in the same cell when Wt CFTR-corrected. Consistently, the effect is also abolished when TRADD is knocked down by shRNA. Thus, Wt CFTR control of TRADD modulates the physiological activation of NF-κB by TNFα. Based on studies with proteosomal and lysosomal inhibitors, the mechanism by which Wt CFTR, but not ΔF508 CFTR, suppresses TRADD is by lysosomal degradation. CONCLUSION: We have uncovered a novel mechanism whereby Wt CFTR regulates TNFα signaling by enhancing TRADD degradation. Thus by reducing the levels of TRADD, Wt CFTR suppresses downstream proinflammatory NFκB signaling. By contrast, suppression of NF-κB activation fails in CF cells expressing ΔF508 CFTR.

A Podocyte-Based Automated Screening Assay Identifies Protective Small Molecules.

Podocyte injury and loss mark an early step in the pathogenesis of various glomerular diseases, making these cells excellent targets for therapeutics. However, cell-based high-throughput screening assays for the rational development of podocyte-directed therapeutics are currently lacking. Here, we describe a novel high-content screening-based phenotypic assay that analyzes thousands of podocytes per assay condition in 96-well plates to quantitatively measure dose-dependent changes in multiple cellular features. Our assay consistently produced a Z' value >0.44, making it suitable for compound screening. On screening with >2100 pharmacologically active agents, we identified 24 small molecules that protected podocytes against injury in vitro (1% hit rate). Among the identified hits, we confirmed an ß1-integrin agonist, pyrintegrin, as a podocyte-protective agent. Treatment with pyrintegrin prevented damage-induced decreases in F-actin stress fibers, focal adhesions, and active ß1-integrin levels in cultured cells. In vivo, administration of pyrintegrin protected mice from LPS-induced podocyte foot process effacement and proteinuria. Analysis of the murine glomeruli showed that LPS administration reduced the levels of active ß1 integrin in the podocytes, which was prevented by cotreatment with pyrintegrin. In rats, pyrintegrin reduced peak proteinuria caused by puromycin aminonucleoside-induced nephropathy. Our findings identify pyrintegrin as a potential therapeutic candidate and show the use of podocyte-based screening assays for identifying novel therapeutics for proteinuric kidney diseases.

A high-content screen of FDA approved drugs to enhance CAR T cell function: ingenol-3-angelate improves B7-H3-CAR T cell activity by upregulating B7-H3 on the target cell surface via PKCα activation.

BACKGROUND: CAR T cell therapy is a promising approach to improve outcomes and decrease toxicities for patients with cancer. While extraordinary success has been achieved using CAR T cells to treat patients with CD19-positive malignancies, multiple obstacles have so far limited the benefit of CAR T cell therapy for patients with solid tumors. Novel manufacturing and engineering approaches show great promise to enhance CAR T cell function against solid tumors. However, similar to single agent chemotherapy approaches, CAR T cell monotherapy may be unable to achieve high cure rates for patients with difficult to treat solid tumors. Thus, combinatorial drug plus CAR T cell approaches are likely required to achieve widespread clinical success. METHODS: We developed a novel, confocal microscopy based, high-content screen to evaluate 1114 FDA approved drugs for the potential to increase expression of the solid tumor antigen B7-H3 on the surface of osteosarcoma cells. Western blot, RT-qPCR, siRNA knockdown and flow cytometry assays were used to validate screening results and identify mechanisms of drug-induced B7-H3 upregulation. Cytokine and cytotoxicity assays were used to determine if drug pre-treatment enhanced B7-H3-CAR T cell effector function. RESULTS: Fifty-five drugs were identified to increase B7-H3 expression on the surface of LM7 osteosarcoma cells using a novel high-content, high-throughput screen. One drug, ingenol-3-angelate (I3A), increased B7-H3 expression by up to 100%, and was evaluated in downstream experiments. Validation assays confirmed I3A increased B7-H3 expression in a biphasic dose response and cell dependent fashion. Mechanistic studies demonstrated that I3A increased B7-H3 (CD276) mRNA, total protein, and cell surface expression via protein kinase C alpha activation. Functionally, I3A induced B7-H3 expression enhanced B7-H3-CAR T cell function in cytokine production and cytotoxicity assays. CONCLUSIONS: This study demonstrates a novel high-content and high-throughput screen can identify drugs to enhance CAR T cell activity. This and other high-content technologies will pave the way to develop clinical trials implementing rational drug plus CAR T cell combinatorial therapies. Importantly, the technique could also be repurposed for an array of basic and translational research applications where drugs are needed to modulate cell surface protein expression.

CYP3A5 unexpectedly regulates glucose metabolism through the AKT-TXNIP-GLUT1 axis in pancreatic cancer.

CYP3A5 is a cytochrome P450 (CYP) enzyme that metabolizes drugs and contributes to drug resistance in cancer. However, it remains unclear whether CYP3A5 directly influences cancer progression. In this report, we demonstrate that CYP3A5 regulates glucose metabolism in pancreatic ductal adenocarcinoma. Multi-omics analysis showed that CYP3A5 knockdown results in a decrease in various glucose-related metabolites through its effect on glucose transport. A mechanistic study revealed that CYP3A5 enriches the glucose transporter GLUT1 at the plasma membrane by restricting the translation of TXNIP, a negative regulator of GLUT1. Notably, CYP3A5-generated reactive oxygen species were proved to be responsible for attenuating the AKT-4EBP1-TXNIP signaling pathway. CYP3A5 contributes to cell migration by maintaining high glucose uptake in pancreatic cancer. Taken together, our results, for the first time, reveal a role of CYP3A5 in glucose metabolism in pancreatic ductal adenocarcinoma and identify a novel mechanism that is a potential therapeutic target.

Genome-wide mapping of cancer dependency genes and genetic modifiers of chemotherapy in high-risk hepatoblastoma.

A lack of relevant genetic models and cell lines hampers our understanding of hepatoblastoma pathogenesis and the development of new therapies for this neoplasm. Here, we report an improved MYC-driven hepatoblastoma-like murine model that recapitulates the pathological features of embryonal type of hepatoblastoma, with transcriptomics resembling the high-risk gene signatures of the human disease. Single-cell RNA-sequencing and spatial transcriptomics identify distinct subpopulations of hepatoblastoma cells. After deriving cell lines from the mouse model, we map cancer dependency genes using CRISPR-Cas9 screening and identify druggable targets shared with human hepatoblastoma (e.g., CDK7, CDK9, PRMT1, PRMT5). Our screen also reveals oncogenes and tumor suppressor genes in hepatoblastoma that engage multiple, druggable cancer signaling pathways. Chemotherapy is critical for human hepatoblastoma treatment. A genetic mapping of doxorubicin response by CRISPR-Cas9 screening identifies modifiers whose loss-of-function synergizes with (e.g., PRKDC) or antagonizes (e.g., apoptosis genes) the effect of chemotherapy. The combination of PRKDC inhibition and doxorubicin-based chemotherapy greatly enhances therapeutic efficacy. These studies provide a set of resources including disease models suitable for identifying and validating potential therapeutic targets in human high-risk hepatoblastoma.

Magnetic resonance histology of age-related nephropathy in the Sprague Dawley rat.

Magnetic resonance histology (MRH) has become a valuable tool in evaluating drug-induced toxicity in preclinical models. However, its application in renal injury has been limited. This study tested the hypothesis that MRH could detect image-based biomarkers of chronic disease, inflammation, or age-related degeneration in the kidney, laying the foundation for more extensive use in evaluating drug toxicity. We examined the entire intact kidney in a spontaneous model of chronic progressive nephropathy. Kidneys from male Sprague Dawley rats were imaged at 8 weeks (n = 4) and 52 weeks (n =4) on a 9.4 T system dedicated to MR microscopy. Several potential contrast mechanisms were explored to optimize the scanning protocols. Full coverage of the entire kidney was achieved with isotropic spatial resolution at 31 microns (voxel volume = 30 pL) using a gradient recalled echo sequence. Isotropic spatial resolution of 15 microns (voxel volume < 4 pL) was achieved in a biopsy core specimen. Qualitative age-related structural changes, such as renal cortical microvasculature, tubular dilation, interstitial fibrosis, and glomerular architecture, were apparent. The nondestructive 3D images allowed measurement of quantitative differences of kidney volume, pelvis volume, main vessel volume, glomerular size, as well as thickness of the cortex, outer medulla, and inner medulla.

Nonimmune cell-derived ICOS ligand functions as a renoprotective αvß3 integrin-selective antagonist.

Soluble urokinase receptor (suPAR) is a circulatory molecule that activates αvß3 integrin on podocytes, causes foot process effacement, and contributes to proteinuric kidney disease. While active integrin can be targeted by antibodies and small molecules, endogenous inhibitors haven't been discovered yet. Here we report what we believe is a novel renoprotective role for the inducible costimulator ligand (ICOSL) in early kidney disease through its selective binding to podocyte αvß3 integrin. Contrary to ICOSL's immune-regulatory role, ICOSL in nonhematopoietic cells limited the activation of αvß3 integrin. Specifically, ICOSL contains the arginine-glycine-aspartate (RGD) motif, which allowed for a high-affinity and selective binding to αvß3 and modulation of podocyte adhesion. This binding was largely inhibited either by a synthetic RGD peptide or by a disrupted RGD sequence in ICOSL. ICOSL binding favored the active αvß3 rather than the inactive form and showed little affinity for other integrins. Consistent with the rapid induction of podocyte ICOSL by inflammatory stimuli, glomerular ICOSL expression was increased in biopsies of early-stage human proteinuric kidney diseases. Icosl deficiency in mice resulted in an increased susceptibility to proteinuria that was rescued by recombinant ICOSL. Our work identified a potentially novel role for ICOSL, which serves as an endogenous αvß3-selective antagonist to maintain glomerular filtration.

Pseudomonas aeruginosa ExoS Induces Intrinsic Apoptosis in Target Host Cells in a Manner That is Dependent on its GAP Domain Activity.

Pseudomonas aeruginosa is a Gram-negative opportunistic pathogen that causes serious infections in immunocompromised individuals and cystic fibrosis patients. ExoS and ExoT are two homologous bifunctional Type III Secretion System (T3SS) virulence factors that induce apoptosis in target host cells. They possess a GTPase Activating Protein (GAP) domain at their N-termini, which share ~76% homology, and an ADP-ribosyltransferase (ADPRT) domain at their C-termini, which target non-overlapping substrates. Both the GAP and the ADPRT domains contribute to ExoT's cytotoxicity in target epithelial cells, whereas, ExoS-induced apoptosis is reported to be primarily due to its ADPRT domain. In this report, we demonstrate that ExoS/GAP domain is both necessary and sufficient to induce mitochondrial apoptosis. Our data demonstrate that intoxication with ExoS/GAP domain leads to enrichment of Bax and Bim into the mitochondrial outer-membrane, disruption of mitochondrial membrane and release of and cytochrome c into the cytosol, which activates initiator caspase-9 and effector caspase-3, that executes cellular death. We posit that the contribution of the GAP domain in ExoS-induced apoptosis was overlooked in prior studies due to its slower kinetics of cytotoxicity as compared to ADPRT. Our data clarify the field and reveal a novel virulence function for ExoS/GAP as an inducer of apoptosis.

A High-Content Screening Technology for Quantitatively Studying Podocyte Dynamics.

Podocytes form the visceral layer of a kidney glomerulus and express a characteristic octopus-like cellular architecture specialized for the ultrafiltration of blood. The cytoskeletal dynamics and structural elasticity of podocytes rely on the self-organization of highly interconnected actin bundles, and the maintenance of these features is important for the intact glomerular filtration. Development of more differentiated podocytes in culture has dramatically increased our understanding of the molecular mechanisms regulating podocyte actin dynamics. Podocytes are damaged in a variety of kidney diseases, and therapies targeting podocytes are being investigated with increasing efforts. Association between podocyte damage and disease severity-or between podocyte recovery and the performance of therapeutic molecules-have been the venues of research for years. In this perspective, more standardized high--content screening has emerged as a powerful tool for visualization and analysis of podocyte morphology. This high-throughput fluorescence microscopy technique is based on an automated image analysis with simultaneous detection of various phenotypes (multiplexing) across multiple phenotypic parameters (multiparametric). Here, we review the principles of high-content screening technology and summarize efforts to carry out small compound screen using podocytes.

CD11b activation suppresses TLR-dependent inflammation and autoimmunity in systemic lupus erythematosus.

Genetic variations in the ITGAM gene (encoding CD11b) strongly associate with risk for systemic lupus erythematosus (SLE). Here we have shown that 3 nonsynonymous ITGAM variants that produce defective CD11b associate with elevated levels of type I interferon (IFN-I) in lupus, suggesting a direct link between reduced CD11b activity and the chronically increased inflammatory status in patients. Treatment with the small-molecule CD11b agonist LA1 led to partial integrin activation, reduced IFN-I responses in WT but not CD11b-deficient mice, and protected lupus-prone MRL/Lpr mice from end-organ injury. CD11b activation reduced TLR-dependent proinflammatory signaling in leukocytes and suppressed IFN-I signaling via an AKT/FOXO3/IFN regulatory factor 3/7 pathway. TLR-stimulated macrophages from CD11B SNP carriers showed increased basal expression of IFN regulatory factor 7 (IRF7) and IFN-ß, as well as increased nuclear exclusion of FOXO3, which was suppressed by LA1-dependent activation of CD11b. This suggests that pharmacologic activation of CD11b could be a potential mechanism for developing SLE therapeutics.

A tripartite complex of suPAR, APOL1 risk variants and αvß3 integrin on podocytes mediates chronic kidney disease.

Soluble urokinase plasminogen activator receptor (suPAR) independently predicts chronic kidney disease (CKD) incidence and progression. Apolipoprotein L1 (APOL1) gene variants G1 and G2, but not the reference allele (G0), are associated with an increased risk of CKD in individuals of recent African ancestry. Here we show in two large, unrelated cohorts that decline in kidney function associated with APOL1 risk variants was dependent on plasma suPAR levels: APOL1-related risk was attenuated in patients with lower suPAR, and strengthened in those with higher suPAR levels. Mechanistically, surface plasmon resonance studies identified high-affinity interactions between suPAR, APOL1 and αvß3 integrin, whereby APOL1 protein variants G1 and G2 exhibited higher affinity for suPAR-activated avb3 integrin than APOL1 G0. APOL1 G1 or G2 augments αvß3 integrin activation and causes proteinuria in mice in a suPAR-dependent manner. The synergy of circulating factor suPAR and APOL1 G1 or G2 on αvß3 integrin activation is a mechanism for CKD.

Insulin-like growth factor 1 (IGF-1) enhances the protein expression of CFTR.

Low levels of insulin-like growth factor 1 (IGF-1) have been observed in the serum of cystic fibrosis (CF) patients. However, the effects of low serum IGF-1 on the cystic fibrosis transmembrane conductance regulator (CFTR), whose defective function is the primary cause of cystic fibrosis, have not been studied. Here, we show in human cells that IGF-1 increases the steady-state levels of mature wildtype CFTR in a CFTR-associated ligand (CAL)- and TC10-dependent manner; moreover, IGF-1 increases CFTR-mediated chloride transport. Using an acceptor photobleaching fluorescence resonance energy transfer (FRET) assay, we have confirmed the binding of CAL and CFTR in the Golgi. We also show that CAL overexpression inhibits forskolin-induced increases in the cell-surface expression of CFTR. We found that IGF-1 activates TC10, and active TC10 alters the functional association between CAL and CFTR. Furthermore, IGF-1 and active TC10 can reverse the CAL-mediated reduction in the cell-surface expression of CFTR. IGF-1 does not increase the expression of ΔF508 CFTR, whose processing is arrested in the ER. This finding is consistent with our observation that IGF-1 alters the functional interaction of CAL and CFTR in the Golgi. However, when ΔF508 CFTR is rescued with low temperature or the corrector VRT-325 and proceeds to the Golgi, IGF-1 can increase the expression of the rescued ΔF508 CFTR. Our data support a model indicating that CAL-CFTR binding in the Golgi inhibits CFTR trafficking to the cell surface, leading CFTR to the degradation pathway instead. IGF-1-activated TC10 changes the interaction of CFTR and CAL, allowing CFTR to progress to the plasma membrane. These findings offer a potential strategy using a combinational treatment of IGF-1 and correctors to increase the post-Golgi expression of CFTR in cystic fibrosis patients bearing the ΔF508 mutation.

Adiponectin regulates bone mass via opposite central and peripheral mechanisms through FoxO1.

The synthesis of adiponectin, an adipokine with ill-defined functions in animals fed a normal diet, is enhanced by the osteoblast-derived hormone osteocalcin. Here we show that adiponectin signals back in osteoblasts to hamper their proliferation and favor their apoptosis, altogether decreasing bone mass and circulating osteocalcin levels. Adiponectin fulfills these functions, independently of its known receptors and signaling pathways, by decreasing FoxO1 activity in a PI3-kinase-dependent manner. Over time, however, these local effects are masked because adiponectin signals in neurons of the locus coeruleus, also through FoxO1, to decrease the sympathetic tone, thereby increasing bone mass and decreasing energy expenditure. This study reveals that adiponectin has the unusual ability to regulate the same function in two opposite manners depending on where it acts and that it opposes, partially, leptin's influence on the sympathetic nervous system. It also proposes that adiponectin regulation of bone mass occurs through a PI3-kinase-FoxO1 pathway.