Biology subjects

Waller, A. P.

Publications and source records attributed to Waller, A. P..

4 recordsLinked to original sources

bioRxiv2025

Hypoalbuminemia Increases Fibrin Clot Density and Impairs Fibrinolysis

BackgroundHypoalbuminemia is a thrombotic disease risk biomarker. Albumin is a negative acute phase reactant and may thus be an indirect biomarker of thromboinflammation. However, nephrotic syndrome (resulting from non-inflammatory proteinuric glomerular disease) causes both hypoalbuminemia and elevated thrombotic risk. Hypofibrinolysis has been observed in nephrotic syndrome and published data suggest that albumin may directly enhance fibrinolysis. These observations suggest that albumin may directly influence thrombotic risk. ObjectiveTo test the hypothesis that hypoalbuminemia impairs fibrinolysis. MethodsHypoalbuminemic blood and plasma from nephrotic syndrome rat models and nephrotic patients were analyzed by thromboelastometry, clot lysis assays, fibrin clot turbidity, confocal microscopy, and immunoblotting. Some studies were conducted without vs. with albumin repletion. Plasma from an analbuminemic mutant rat model was used to confirm albumin-dependent observations. ResultsHypoalbuminemia was associated with hypofibrinolysis in nephrotic whole blood. Albumin levels were positively associated with fibrinolysis in both nephrotic rat and patient plasma. Hypoalbuminemia accelerated fibrin clot formation in nephrotic rat plasma. Dense fibrin clots are known to be resistant to fibrinolysis and fibrin clot network density was increased in hypoalbuminemic plasma clots from both nephrotic rats and patients. Clots formed from hypoalbuminemic plasma contained less albumin than controls, and repletion with recombinant albumin to healthy control levels corrected both fibrin network density and fibrinolysis in nephrotic and analbuminemic rat plasma. ConclusionThese data show that albumin directly increases fibrin network porosity and enhances fibrinolysis. Hypoalbuminemia may mechanistically contribute to nephrotic syndrome thrombotic complications and may similarly increase thrombotic risk in other hypoalbuminemic conditions.

physiology↗

bioRxiv2023

Prothrombin Knockdown Protects Podocytes and Reduces Proteinuria in Glomerular Disease

Chronic kidney disease (CKD) is a leading cause of death, and its progression is driven by glomerular podocyte injury and loss, manifesting as proteinuria. Proteinuria includes urinary loss of coagulation zymogens, cofactors, and inhibitors. Importantly, both CKD and proteinuria significantly increase the risk of thromboembolic disease. Prior studies demonstrated that anticoagulants reduced proteinuria in rats and that thrombin injured cultured podocytes. Herein we aimed to directly determine the influence of circulating prothrombin on glomerular pathobiology. We hypothesized that (pro)thrombin drives podocytopathy, podocytopenia, and proteinuria. Glomerular proteinuria was induced with puromycin aminonucleoside (PAN) in Wistar rats. Circulating prothrombin was either knocked down using a rat-specific antisense oligonucleotide or elevated by serial intravenous infusions of prothrombin protein, which are previously established methods to model hypo- (LoPT) and hyper-prothrombinemia (HiPT), respectively. After 10 days (peak proteinuria in this model) plasma prothrombin levels were determined, kidneys were examined for (pro)thrombin co-localization to podocytes, histology, and electron microscopy. Podocytopathy and podocytopenia were determined and proteinuria, and plasma albumin were measured. LoPT significantly reduced prothrombin colocalization to podocytes, podocytopathy, and proteinuria with improved plasma albumin. In contrast, HiPT significantly increased podocytopathy and proteinuria. Podocytopenia was significantly reduced in LoPT vs. HiPT rats. In summary, prothrombin knockdown ameliorated PAN-induced glomerular disease whereas hyper-prothrombinemia exacerbated disease. Thus, (pro)thrombin antagonism may be a viable strategy to simultaneously provide thromboprophylaxis and prevent podocytopathy-mediated CKD progression.

physiology↗

bioRxiv2021

Selective Modulator of Nuclear Receptor PPARy with Reduced Adipogenic Potential Ameliorates Experimental Nephrotic Syndrome

BackgroundGlomerular disease, often manifesting as nephrotic syndrome (NS) with high proteinuria, can be refractory to standard treatment and is typically associated with hypoalbuminemia, hypercholesterolemia and hypercoagulopathy. We hypothesized that the nuclear receptor PPAR{gamma} can be selectively modulated using a novel partial agonist, GQ-16, to gain therapeutic advantage over traditional PPAR{gamma} agonists (e.g. thiazolidinediones) for the treatment of glomerular disease. MethodsNephropathy was induced with puromycin amino-nucleoside (PAN) in Wistar rats and treated with Pioglitazone (Pio) or GQ-16. Plasma, serum, and urine chemistries were performed, and kidneys, glomeruli, liver, and white adipose tissue (WAT) were harvested. Lipid accumulation and adipogenic gene expression were measured in adipocytes. ResultsPAN-induced proteinuria was significantly reduced with Pio to 64% of PAN-value. It was reduced robustly with GQ-16 to 81% of PAN, which was comparable to controls. While both GQ-16 and Pio restored glomerular Nphs1 and hepatic Pcsk9 expression and reduced hypercholesterolemia, GQ-16 also restored glomerular Nrf2, and reduced hypoalbuminemia and hypercoagulopathy. Furthermore, RNA-seq analysis identified both common and distinct restored glomerular genes downstream of Pio and GQ-16. Pio but not GQ-16 significantly induced aP2 (fatty acid binding protein) in adipocytes and in WAT. Pio induced more lipid accumulation than GQ-16 in differentiated adipocytes. Both, Pio and GQ-16 induced insulin sensitizing adipokines in WAT with varying degrees. ConclusionsSelective modulation of PPAR{gamma} by a partial agonist, GQ-16, is more advantageous than pioglitazone in reducing proteinuria and NS associated co-morbidities, while reducing the adipogenic side-effects conferred by traditional PPAR{gamma} full agonists. Translational StatementThe authors have previously reported that type-II diabetes drugs, thiazolidinediones (PPAR{gamma} agonists), also provide beneficial effects in reducing podocyte and glomerular injury. However, these drugs are associated with adverse effects such as weight gain, and their effects on glomerular disease-associated features are largely unexplored. Their current findings demonstrate that PPAR{gamma} can be selectively modulated by its partial agonist, GQ-16, which reduces proteinuria and improves nephrotic syndrome (NS) with reduced side-effects typically conferred by thiazolidinediones. These findings not only deepen our molecular understanding of the role of PPAR{gamma} in glomerular disease and underscore the potential for partial agonists of PPAR{gamma}, such as GQ-16 as a treatment modality for NS, but also lend the possibility of its potential benefits in diabetic nephropathy.

molecular biology↗

bioRxiv2020

Nephrotic Syndrome-Associated Hypercoagulopathy is Alleviated by Nuclear Receptor Agonist Therapy with both Pioglitazone and Glucocorticoids

BackgroundThrombosis is a potentially life-threatening nephrotic syndrome (NS) complication. We have previously demonstrated that hypercoagulopathy is proportional to NS severity in rat models and that pioglitazone (Pio) reduces proteinuria both independently and in combination with methylprednisolone (MP), a glucocorticoid (GC). However, the effect of these treatments on NS-associated hypercoagulopathy remains unknown. We thus sought to determine the ability of Pio and GC to alleviate NS-associated hypercoagulopathy. MethodsPuromycin aminonucleoside-induced rat NS was treated with sham, Low- or High-dose MP, Pio, or combination (Pio+Low-MP) and plasma was collected at day 11. Plasma samples were collected from children with steroid-sensitive NS (SSNS) and steroid-resistant NS (SRNS) upon presentation and after 7 weeks of GC therapy. Plasma endogenous thrombin potential (ETP), antithrombin (AT) activity, and albumin (Alb) were measured using thrombin generation, amidolytic, and colorimetric assays, respectively. ResultsIn a rat model of NS, both High-MP and Pio improved proteinuria and corrected hypoalbuminemia, ETP and AT activity (P<0.05). Proteinuria (P=0.005) and hypoalbuminemia (P<0.001) were correlated with ETP. In childhood NS, while ETP was not different at presentation, GC therapy improved proteinuria, hypoalbuminemia, and ETP in children with SSNS (P<0.001) but not SRNS (P=0.330). ConclusionsBoth Pio and GC diminish proteinuria and significantly alleviate hypercoagulopathy. Both Pio and MP improved hypercoagulopathy in rats, and successful GC therapy (SSNS) also improved hypercoagulopathy in childhood NS. These data suggest that even a partial reduction in proteinuria may reduce NS-associated thrombotic risk. SIGNIFICANCE STATEMENTNephrotic syndrome (NS) is characterized by massive proteinuria and is complicated by a complex, acquired hypercoagulopathy that markedly increases the risk for potentially life-threatening venous thromboembolism (VTE). This study demonstrates a strong correlation between proteinuria reduction and improvement of an established VTE-risk biomarker, in both a well-established animal model and in childhood NS before and after steroid treatment. We show that nuclear receptor agonists with known disparate mechanisms of action successfully reduce proteinuria and simultaneously improve NS-associated hypercoagulopathy. These data suggest that complete or partial proteinuria reduction by any therapeutic modality may concurrently reduce NS-associated thrombotic risk.

pathology↗