Proximal Tubular Epithelium Research Articles

CHIP drives proteasomal degradation of NUR77 to alleviate oxidative stress and intrinsic apoptosis in cisplatin-induced nephropathy

Carboxy-terminus of Hsc70-interacting protein (CHIP), an E3 ligase, modulates the stability of its targeted proteins to alleviate various pathological perturbations in various organ systems. Cisplatin is a widely used chemotherapeutic agent, but it is also known for its alarming renal toxicity. The role of CHIP in the pathogenesis of cisplatin-induced acute kidney injury (AKI) has not been adequately investigated. Herein, we demonstrated that CHIP was abundantly expressed in the renal proximal tubular epithelia, and its expression was downregulated in cisplatin-induced AKI. Further investigation revealed that CHIP overexpression or activation alleviated, while its gene disruption promoted, oxidative stress and apoptosis in renal proximal tubular epithelia induced by cisplatin. In terms of mechanism, CHIP interacted with and ubiquitinated NUR77 to promote its degradation, which consequently shielded BCL2 to maintain mitochondrial permeability of renal proximal tubular cells in the presence of cisplatin. Also, we demonstrated that CHIP interacted with NUR77 via its central coiled-coil (CC) domain, a non-canonical interactive pattern. In conclusion, these findings indicated that CHIP ubiquitinated and degraded its substrate NUR77 to attenuate intrinsic apoptosis in cisplatin-treated renal proximal tubular epithelia, thus providing a novel insight for the pathogenesis of cisplatin-induced AKI.

Clonal monocytosis of renal significance

Clonal monocytosis reflects a preneoplastic or neoplastic sustained increase in the absolute monocyte count in the absence of reactive causes. Causes of clonal monocytosis include clonal cytopenias with monocytosis and acute and chronic myeloid neoplasms. Chronic myelomonocytic leukemia is a prototypical myelodysplastic/myeloproliferative overlap neoplasm in adults, characterized by sustained peripheral blood monocytosis. Renal abnormalities, including acute kidney injury and chronic kidney disease, are frequent in patients with chronic myelomonocytic leukemia and are predictors of worse outcomes. In addition, acute kidney injury/chronic kidney disease often limits eligibility for allogeneic stem cell transplantation or enrollment in clinical trials. In this review, we highlight clonal monocytosis-related etiologies that give rise to acute kidney injury and chronic kidney disease, with special emphasis on chronic myelomonocytic leukemia and lysozyme-induced nephropathy. Monocytes produce lysozyme, which, in excess, can accumulate in and damage the proximal renal tubular epithelium. Early identification of this etiology and a timely reduction in monocyte counts can salvage renal function. Other etiologies of renal injury associated with clonal monocytosis include direct renal infiltration by monocytes, renal extramedullary hematopoiesis, myeloproliferative neoplasm-associated glomerulopathy, autoimmune (membranous nephropathy, minimal change disease) and paraneoplastic manifestations, thrombotic microangiopathy, obstructive nephropathy due to myeloproliferation, and urate nephropathy due to tumor lysis syndrome. We propose to group these mechanistic etiologies of renal injury as clonal monocytosis of renal significance and provide guidance on their diagnosis and management.

Mechanistic study on lncRNA XIST/miR-124-3p/ITGB1 axis in renal fibrosis in obstructive nephropathy

ObjectiveThe purpose of this study was to investigate the role and possible mechanism of lncRNA XIST in renal fibrosis and to provide potential endogenous targets for renal fibrosis in obstructive nephropathy (ON). MethodsThe study included 50 cases of ON with renal fibrosis (samples taken from patients undergoing nephrectomy due to ON) and 50 cases of normal renal tissue (samples taken from patients undergoing total or partial nephrectomy due to accidental injury, congenital malformations, and benign tumors). Treatment of human proximal renal tubular epithelium (HK-2) cells with TGF-β1 simulated renal fibrosis in vitro. Cell viability and proliferation were measured by CCK-8 and EdU, and cell migration was measured by transwell. XIST, miR-124-3p, ITGB1, and epithelial-mesenchymal transition (EMT)-related proteins (E-cadherin, α-SMA, and fibronectin) were detected by PCR and immunoblot. The targeting relationship between miR-124-3p and XIST or ITGB1 was verified by starBase and dual luciferase reporter gene experiments. In addition, The left ureter was ligated in mice as a model of unilateral ureteral obstruction (UUO), and the renal histopathology was observed by HE staining and Masson staining. ResultsON patients with renal fibrosis had elevated XIST and ITGB1 levels and reduced miR-124-3p levels. The administration of TGF-β1 exhibited a dose-dependent promotion of HK-2 cell viability, proliferation, migration, and EMT. Conversely, depleting XIST or enhancing miR-124-3p hindered HK-2 cell viability, proliferation, migration, and EMT in TGF-β1-damaged HK-2 cells HK-2 cells. XIST functioned as a miR-124-3p sponge. Additionally, miR-124-3p negatively regulated ITGB1 expression. Elevating ITGB1 weakened the impact of XIST depletion on TGF-β1-damaged HK-2 cells. Down-regulating XIST improved renal fibrosis in UUO mice. ConclusionXIST promotes renal fibrosis in ON by elevating miR-124-3p and reducing ITGB1 expressions.

A case of acute kidney injury and Fanconi syndrome while taking multiple supplements, including Red Yeast Rice Cholesterol Help®.

A 62-year-old man visited his primary care physician with the complaints of loss of appetite and fatigue. He was admitted to our hospital based on a diagnosis of acute kidney injury, Fanconi syndrome as indicated by hypokalemia, hypouricemia, hypophosphatemia, elevated glucose levels in urine, and aminoaciduria. He had been taking multiple supplements, including Red Yeast Rice Cholesterol Help®, for one and a half years. After admission, all the supplements were stopped. Blood samples were collected; however, the samples were negative for diseases that could cause Fanconi syndrome. Renal biopsy revealed renal proximal tubular damage, mainly characterized by simplification of the proximal tubular epithelium. The mycotoxin, citrinin, which is reported to be produced by the mold used for producing red yeast rice, but not the mold Monascus pilosus used for Red Yeast Rice Cholesterol Help®, reportedly causes proximal tubular damage. However, although the causative agent has not been identified, it was thought that a substance similar to citrinin, produced by the mold used for Red Yeast Rice Cholesterol Help®, caused proximal tubular damage, leading to acute kidney injury and Fanconi syndrome. Hence, all supplements were stopped, and the patient was treated with oral potassium and phosphorus preparations, leading to gradual recovery of his kidney function. We herein report the first case of acute kidney injury and Fanconi syndrome in a patient taking multiple health supplements, including Red Yeast Rice Cholesterol Help®. Early discontinuation of the oral supplements was probably useful in improving the patient's kidney function.

Uptake of Fluorescein via a pH-Dependent Monocarboxylate Transporter by Human Kidney 2 (HK-2) Cells.

Herein, we investigated whether a fluorescent probe for an organic anion transporter (OAT), fluorescein (FLS), could be accumulated by human kidney 2 (HK-2) cells derived from human kidney proximal tubular epithelia. HK-2 cells took up FLS in a pH-dependent and concentration-dependent manner. FLS accumulation by HK-2 cells was inhibited by monocarboxylic acids, ibuprofen, rosuvastatin, and indoleacetic acid but not by typical substrates for OATs. A typical protonophore, carbonyl cyanide p-trichloromethoxyphenylhydrazone completely abolished FLS accumulation by HK-2 cells. The FLS efflux process from the preloaded HK-2 cells exhibited substantial trans-stimulation by the excess amount of extracellular FLS transport inhibitable monocarboxylate compounds such as 2,4-dichloro phenoxyacetic acid, fluvastatin, ibuprofen, indoleacetic acid, salicylic acid and rosuvastatin, indicating that the FLS transporter can recognize and accumulate them into the cells in a pH-dependent manner. The involvement of the FLS transporter in the reabsorption of monocarboxylic compounds was indicated by demonstrating that the pH-dependent FLS uptake is inhibited by various monocarboxylates in rabbit renal brush border membrane vesicles. pH-dependent FLS uptake was trans-stimulated by the inhibitable monocarboxylates. Collectively, the present data indicate that the pH-dependent transporters expressed in HK-2 cells are involved in the reabsorption of monocarboxylates from the urinary fluid into the tubular epithelia.

Differential expression of epithelial and smooth muscle lineage-specific markers of metanephros in one-humped camel foetuses.

The development of the metanephros in one-humped camels involves a complex series of interactions between epithelial and mesenchymal cells. As a result, there is a synchronized differentiation process of stromal, vascular and epithelial cell types during glomerulogenesis, angiogenesis and tubulogenesis. In the current work, the metanephros of camel foetuses were divided into four stages where kidneys from each stage were processed and immunoassayed, followed by quantitative analysis to determine target protein intensities throughout metanephrogenesis in the camel. This study demonstrated robust expression of α-smooth muscle actin (α-SMA) in the glomerular mesangium, as well as in interlobular and glomerular arterioles during the earlier stages of development. However, in the late stages, α-SMA expression became more localized around the blood capillaries in both the cortex and medulla. Strong expression of CD34 was observed in the immature glomerular and peritubular endothelial cells within the subcapsular zone, as well as in the glomerular, proximal tubular and distal tubular epithelium of stage one foetuses, although its expression gradually diminished with foetal maturation. The expression pattern of osteopontin was prominently observed in the distal convoluted tubules throughout all stages, however, no expression was detected in the proximal tubules, glomeruli and arterioles. E-cadherin was detected in the developing renal tubular epithelial cells but not in the glomeruli. In conclusion, this study reveals the spatiotemporal distribution of key proteins, including α-SMA, CD34, Osteopontin and E-cadherin, which play a crucial role in metanephrogenesis in camel foetuses.

Renal glomerular and tubular responses to glutaraldehyde- polymerized human hemoglobin.

Hemoglobin-based oxygen carriers (HBOCs) are being developed as oxygen and volume replacement therapeutics, however, their molecular and cellular effects on the vasculature and different organ systems are not fully defined. Using a guinea pig transfusion model, we examined the renal glomerular and tubular responses to PolyHeme, a highly characterized glutaraldehyde-polymerized human hemoglobin with low tetrameric hemoglobin content. PolyHeme-infused animals showed no major changes in glomerular histology or loss of specific markers of glomerular podocytes (Wilms tumor 1 protein, podocin, and podocalyxin) or endothelial cells (ETS-related gene and claudin-5) after 4, 24, and 72 h. Relative to sham controls, PolyHeme-infused animals also showed similar expression and subcellular distribution of N-cadherin and E-cadherin, two key epithelial junctional proteins of proximal and distal tubules, respectively. In terms of heme catabolism and iron-handling responses, PolyHeme induced a moderate but transient expression of heme oxygenase-1 in proximal tubular epithelium and tubulointerstitial macrophages that was accompanied by increased iron deposition in tubular epithelium. Contrary to previous findings with other modified or acellular hemoglobins, the present data show that PolyHeme does not disrupt the junctional integrity of the renal glomerulus and tubular epithelium, and triggers moderate activation of heme catabolic and iron sequestration systems likely as part of a renal adaptive response.

Immunoglobulin G deposition on proximal tubules and the tubular basement membrane in acute tubular injury complicated with focal segmental glomerulosclerosis (FSGS): A possible prediction tool for subclinical FSGS

Immunofluorescent deposition of immunoglobulin G (IgG) in the tubular basement membrane (TBM) has been evaluated in the diagnosis of various diseases; however, few studies have investigated the immunofluorescence of acute tubular injury (ATI). Herein, we attempted to clarify IgG expression in the proximal tubular epithelium and TBM in ATI due to various causes. Patients with ATI with nephrotic-range proteinuria, including focal segmental glomerulosclerosis (FSGS, n = 18) and minimal change nephrotic syndrome (MCNS, n = 8), ATI with ischemia (n = 6), and drug-induced ATI (n = 7), were enrolled. ATI was evaluated by light microscopy. CD15 and IgG double staining and IgG subclass staining were performed to evaluate immunoglobulin deposition in the proximal tubular epithelium and TBM. IgG deposition was identified in the proximal tubules only in the FSGS group. Furthermore, IgG deposition in the TBM was observed in the FSGS group showing severe ATI. IgG3 was predominantly deposited by the IgG subclass study. Our results indicate that IgG deposition in the proximal tubular epithelium and TBM suggests the leaking of IgG from the glomerular filtration barrier and its reabsorption by proximal tubules, which may predict disruption of the glomerular size barrier, including subclinical FSGS. FSGS with ATI should be included as a differential diagnosis when IgG deposition in TBM is observed.

Protein Arginine Methyltransferases Refine the Classification of Clear Cell Renal Cell Carcinoma with Distinct Prognosis and Tumor Microenvironment Characteristics.

Background: Clear cell renal cell carcinoma (ccRCC) is an aggressive urological cancer that originates from the proximal tubular epithelium. As one of the most common post-translational modification, protein arginine methylation plays a pivotal role in various cancer-associated biological functions, especially in cancer immunity. Therefore, constructing a protein arginine methylation-related prognostic signature would be beneficial in guiding better personalized clinical management for patients with ccRCC. Methods: Based on the multi-omics profiling of the expression levels of eight protein arginine methyltransferases (PRMTs) in 763 ccRCC samples (from TCGA, CPTAC, EMBL, and ICGC databases), we established a scoring system with machine-learning algorithms to quantify the modification patterns on clinical and immunological characterizations of individual ccRCC patient, which was termed as PRMTScore. Moreover, we utilized two external clinical cohorts receiving immunotherapy (n=302) to validate the reliability of the PRMTScore system. Multiplex immunohistochemistry (mIHC) was performed to characterize the cellular composition of 30 paired ccRCC samples. The proteomic profiling of 232 ccRCC samples obtained from Fudan University Shanghai Cancer Center (FUSCC) was analyzed to validate the protein expression of PRMT5 in ccRCC. Finally, CCK-8, transwell, and wound healing assays were conducted to elucidate the role of PRMT5 in ccRCC in vitro. Results: A total of 763 ccRCC patients with available multi-omics profiling were stratified into two clusters (PRMTCluster A and B) with distinctive prognosis, genomic alterations, tumor microenvironment (TME) characteristics, and fundamental biological mechanisms. Subsequently, protein arginine methylation-related prognostic signature (PRMTScore) was constructed and consisted of SLC16A12, HRH2, F2RL3, and SAA1. The PRMTScore showed remarkable differences in outcomes, immune and stromal fractions, expressions of immune checkpoints, the abundance of immune cells, and immunotherapy response in ccRCC patients. Additionally, preliminary insights unveiled the tumor-suppressive role of PRMT5 in ccRCC, and the signal of PRMT5low significantly predicted aggressive prognosis and the high abundance of PD1+ CD8+ cells in ccRCC. Conclusion: We constructed a PRMTScore system, which showed the potent ability to assess the prognosis, TME characteristics, and immunotherapy response for patients with ccRCC. Moreover, this is the first study to propose that PRMT5 acts as a cancer suppressor in ccRCC.

MicroRNA antagonist therapy during normothermic machine perfusion of donor kidneys

Normothermic machine perfusion (NMP) is a novel clinical approach to overcome the limitations of traditional hypothermic organ preservation. NMP can be used to assess and recondition organs prior to transplant and is the subject of clinical trials in solid organ transplantation. In addition, NMP provides an opportunity to deliver therapeutic agents directly to the organ, thus avoiding many limitations associated with systemic treatment of the recipient. We report the delivery of oligonucleotide-based therapy to human kidneys during NMP, in this case to target microRNA function (antagomir). An antagomir targeting mir-24-3p localized to the endothelium and proximal tubular epithelium. Endosomal uptake during NMP conditions facilitated antagomir co-localization with proteins involved in the RNA-induced silencing complex (RISC) and demonstrated engagement of the miRNA target. This pattern of uptake was not seen during cold perfusion. Targeting mir-24-3p action increased expression of genes controlled by this microRNA, including heme oxygenase-1 and sphingosine-1-phosphate receptor 1. The expression of genes not under the control of mir-24-3p was unchanged, indicating specificity of the antagomir effect. In summary, this is the first report of ex vivo gymnotic delivery of oligonucleotide to the human kidney and demonstrates that NMP provides the platform to bind and block detrimental microRNAs in donor kidneys prior to transplantation.

Response to: Hypouricaemia and acute kidney injury: a hereditary condition should be considered.

First, we would like to thank Dr Martin for his insightful comments. We agree that we should evaluate the mutations in the gene that caused renal hypouricemia (RHUC) in the patient in this report.1 The patient was of Japanese ethnicity with no family history of nephrolithiasis or exercise-induced acute kidney injury (EIAKI), and this was the first instance that they noticed symptoms suggesting EIAKI. At discharge, we recommended sufficient hydration during exercise and avoiding strenuous activity. After kidney function recovery, the patient’s uric acid (UA) level was as low as it was at hospitalization, but the fractional excretion of UA remained high. Although we did not mention it in our report, we diagnosed this case as RHUC and excluded diseases that could cause hypouricemia with increased UA excretion, such as the syndrome of inappropriate secretion of antidiuretic hormone and Fanconi syndrome.1 UA is excreted from the renal glomerulus into the renal tubules and reabsorbed via UA transporters, such as urate transporter 1 (encoded by the URAT1/SLC22A12 gene) and glucose transporter 9 (encoded by the GLUT9/SLC2A9 gene), expressed in the proximal tubular epithelium. Dysfunction of these transporters causes RHUC, and nephrolithiasis or EIAKI are known complications of RHUC; however, the exact frequencies of these complications remain unknown. It is postulated that there are genes other than URAT1/SLC22A12 and GLUT9/SLC2A9 that cause RHUC.2,3 The genetic test could have been performed to discover the causative gene. Although allopurinol might prevent EIAKI in patients with RHUC, its administration remains controversial, and the dosage and dosing period are unclear.2,4 Therefore, we did not administer allopurinol.

Analysis of mRNA and protein kidney injury Molecule-1 (KIM-1) expression in a kidney model during the initiation phase of ischemia reperfusion injury

BackgroundKidney injury molecule-1 (KIM-1) is a transmembrane glycoprotein expressed predominantly on the proximal tubular epithelium. ObjectiveWe wanted to see if there was a critical time for increased tubular damage and its related biomarker, KIM-1 mRNA, and protein expressions during the first 24 h of ischemia-reperfusion injury. MethodAn Experimental research used five male Rattus Norvegicus rats in each group. Bulldog clamp was used to clamp renal arteries and veins to create renal ischemia. Immunohistochemistry was used for the analysis of KIM-1 protein expression. While Tubular Injury Score was examined by Histopathology. RT-PCR was used for KIM-1 mRNA expression. ResultsTubular Injury Score (TIS) was significantly higher in ischemia than control. TIS remained similar after IR 30 min, peaked at IR 2 h, and decreased to the level of IR 30 min at IR 24 h.The KIM-1 mRNA expression was also higher in ischemia than in control. Similarly, KIM-1 mRNA expression increased more after IR 30 min, IR 2 h, and IR 24 h.The KIM-1 protein expression was higher in ischemia than in control. KIM-1 protein increased more after IR 30 min, IR for 2 h, and remained similar at IR for 24 h.KIM-1 mRNA and protein expressions at IR 2 h were significantly different compared to ischemia but not significantly different compared to that in IR 24 h. ConclusionsKIM-1 mRNA and protein expressions increased within 24 h IR with the critical time was in the 2 h IR.

Direct evidence of proximal tubular proliferation in early diabetic nephropathy

Kidney hypertrophy is a common clinical feature in patients with diabetes and is associated with poor renal outcomes. Initial cell proliferation followed by cellular hypertrophy are considered the responsible mechanisms for diabetic kidney hypertrophy. However, whether similar responses against hyperglycemia continue in the chronic phase in diabetes is unclear. We performed lineage tracing analysis of proximal tubular epithelia using novel type 2 diabetic mice with a tamoxifen-inducible proximal tubule-specific fluorescent reporter. Clonal analysis of proximal tubular epithelia demonstrated that the labeled epithelia proliferated in type 2 diabetic mice. Based on the histological analysis and protein/DNA ratio of sorted labeled tubular epithelia, there was no evidence of cellular hypertrophy in type 2 diabetic mice. Lineage tracing and histological analyses of streptozocin-induced type 1 diabetes also revealed that cellular proliferation occurs in the chronic phase of type 1 diabetes induction. According to our study, epithelial proliferation accompanied by SGLT2 upregulation, rather than cellular hypertrophy, predominantly occurs in the hypertrophic kidney in both type 1 and type 2 diabetes. An increased number of SGLT2+ tubular epithelia may be an adaptive response against hyperglycemia, and linked to the hyper-reabsorption of sodium and glucose observed in type 2 diabetes patients.

Preclinical safety profile of a liver-localized mitochondrial uncoupler: OPC-163493.

Mitochondrial uncouplers (mUncouplers) are known to exhibit a variety of toxic effects in animals. Here we report a safety profile of an mUncoupler, OPC-163493, recently synthesized at Otsuka Pharmaceutical Co, Ltd, and its development as a therapeutic agent for treating diabetes. To understand the acute and subchronic toxicity of OPC-163493, single and repeated oral dose studies in rats, dogs, and monkeys were performed. In the rat studies, rigor mortis and increased body temperatures were observed in the high dose group. Focal necrosis, fatty change, and granular eosinophilic cytoplasm of the hepatocytes were also observed in the high dose group. In the dog studies, gastrointestinal manifestations were observed with decreased body weight and decreased food consumption in the high dose group. Necrotizing arteritis was observed in multiple organs as well as meningitis with hemorrhage in the brain. In the monkey studies, vomiting, decreased food consumption, and decreased locomotor activity were observed in the high dose group. Degeneration of the proximal convoluted tubules and the straight tubular epithelium, regeneration of the proximal tubular epithelium, and degeneration of the collecting tubular epithelium were observed. The target organs of OPC-163493 were liver, blood vessels, and kidney in rats, dogs, and monkeys, respectively. In rats, dogs, and monkeys, safety ratios were 100:1, 13:1, and 20:1, respectively, in terms of total exposure (AUC24h). These safety ratios showed clear separation between exposure to OPC-163493 in animals at NOAEL and the exposure at the effective dose in ZDF rats. This information should contribute to the drug development of new and effective mUncoupler candidates.

Kidney-Targeted Redox Scavenger Therapy Prevents Cisplatin-Induced Acute Kidney Injury.

Cisplatin-induced acute kidney injury (CI-AKI) is a significant co-morbidity of chemotherapeutic regimens. While this condition is associated with substantially lower survival and increased economic burden, there is no pharmacological agent to effectively treat CI-AKI. The disease is hallmarked by acute tubular necrosis of the proximal tubular epithelial cells primarily due to increased oxidative stress. We investigated a drug delivery strategy to improve the pharmacokinetics of an approved therapy that does not normally demonstrate appreciable efficacy in CI-AKI, as a preventive intervention. In prior work, we developed a kidney-selective mesoscale nanoparticle (MNP) that targets the renal proximal tubular epithelium. Here, we found that the nanoparticles target the kidneys in a mouse model of CI-AKI with significant damage. We evaluated MNPs loaded with the reactive oxygen species scavenger edaravone, currently used to treat stroke and ALS. We found a marked and significant therapeutic benefit with edaravone-loaded MNPs, including improved renal function, which we demonstrated was likely due to a decrease in tubular epithelial cell damage and death imparted by the specific delivery of edaravone. The results suggest that renal-selective edaravone delivery holds potential for the prevention of acute kidney injury among patients undergoing cisplatin-based chemotherapy.

Effect of Lycopene on Histological Alterations of Basement Membrane & Fibrosis in Renal Interstitial Tissue of Celebrex Induced Albino Rats; An Experimental Study

Objective: To assess the histological alterations in basement membrane and fibrosis in renal interstitium of albino rats due to celebrex with enhancement by lycopene. 
 Study Design: Experimental study.
 Abode of Study: Animal House of Jinnah Postgraduate institute, Karachi,
 Materials and Methods: COX-2 inhibitor and antioxidant medicines were used in this research work. These medications were orally administered in 40 male albino rats weighing 200-220gm for experimentation. Rats were housed in separate pens at 23ºC. Rats were arranged into 4 groups including control horde and three experimental hordes. The medications were dose up orally by gastric tube daily for one month. At completion of experiment, animals were dissected and tissues were well-preserved for staining.
 Results: In second horde PAS stained kidney segments showed disrupted basement membrane of distended proximal convoluted tubules & ill-defined brush border and fibrosis in renal interstitium, but 3rd horde had intact basement membrane & well-define brush border at the luminal surface of proximal tubular epithelium and there was mild fibrosis in renal interstitium.
 Conclusion: This study divulges that lycopene convalesce the disrupted basement membrane and fibrosis in second horde.

A Monoclonal Antibody Targeting ALK2 As a Potential Therapeutic Agent for Anemia of Inflammation

Background: Iron homeostasis is primarily regulated by hepcidin, a hormone predominantly expressed in the liver. Hepcidin activates the degradation of the transmembrane iron exporter ferroportin, thereby downregulating the release of iron from cells. Hepcidin expression is, at least partly, regulated in response to signaling of the type I TGF-β receptor ALK2, via SMAD2/3 phosphorylation. IL-6, which is commonly elevated in chronic kidney disease (CKD) and other inflammatory conditions, upregulates hepcidin expression and reduces serum iron bioavailability. As a result, chronic inflammatory conditions are often accompanied by secondary anemia of inflammation (AI).We have previously demonstrated that ALK2 inhibition suppressed hepcidin expression in rodents, monkeys and healthy humans. We further described that administration of a selective small molecule ALK2 kinase inhibitor (KTI-2338) reversed changes in hepcidin and iron in a mouse model of CKD, supporting the potential benefit of ALK2 inhibition in AI. Another approach to targeting ALK2 signaling is use of a neutralizing antibody. KTI-018 is a neutralizing ALK2 antibody with high affinity and selectivity for ALK2. This biologic has been demonstrated to reduce serum hepcidin and increase serum iron in healthy non-human primates.Aims: To further elucidate the specific contribution of ALK2 signaling as a driver in AI, and to determine the therapeutic potential of the antibody in this type of anemia, we assessed the effect of KTI-018 in the CKD mouse model.Methods: The study was conducted with 6-week-old male C57Bl/6 mice. Mice in the CKD cohort (CKD) were treated with once daily oral administration of adenine, a compound that metabolizes to 2,8-dihydroxyadenine, forming crystals in the proximal tubular epithelia and causing inflammation and fibrosis in the kidneys. Mice in the control cohort (healthy) received once daily oral administration of vehicle.Upon confirmation of disease, the CKD cohort was subdivided into two groups. The treatment group received twice weekly intraperitoneal treatment with KTI-018 (CKD-KTI-018), and the control group received tris-buffered saline (CKD-TBS). Healthy mice received TBS only. All mice were maintained on their assigned daily adenine or vehicle regimen. At day 53, the study was terminated and hematologic parameters, serum hepcidin, iron, and IL-6 levels were assessed.Results: After 42 days of adenine or vehicle administration, serum hepcidin, serum iron, and hematologic parameters were assessed in representative cohorts of CKD-TBS and healthy mice. The CKD-TBS cohort experienced changes associated with anemia of inflammation as compared to the healthy mice, including increased hepcidin, decreased serum iron, and decreased hematologic parameters. The differences between the healthy and CKD-TBS groups were maintained through the duration of the study.At study termination, CKD-TBS mice had increased serum IL-6 levels (218%), elevated serum hepcidin (149%), and reduced serum iron (-30%) as compared to the healthy mice. Laboratory findings characteristic of anemia were present in the CKD-TBS group, including decreased red blood cells (-6.1%), hemoglobin (-13.2%), and reticulocyte hemoglobin content (-9.3%) as compared to healthy mice.In contrast, CKD-KTI-018 mice had decreased serum hepcidin (-25%) and increased serum iron (59%) as compared to CKD-TBS mice. This restoration of serum iron corresponded to improvements in red blood cells, hemoglobin, and reticulocyte hemoglobin content, which were increased by 7.6%, 9.6%, and 6.7%, respectively, in the CKD-KTI-018 mice as compared to the CKD-TBS mice. These results demonstrate that, by decreasing serum hepcidin, KTI-018 increased the bioavailability of iron, which led to the restoration of hematologic parameters and appeared to reverse AI in mice.Discussion: In this study, a neutralizing ALK2 antibody decreased serum hepcidin, increased serum iron and consequently reversed AI in a mouse model of CKD. These results support the role of ALK2 signaling in AI and suggest that inhibition of ALK2 may be a potential treatment approach for anemia resulting from CKD and other chronic inflammatory diseases. Future studies will explore if ALK2 inhibition may prevent or treat progression of CKD itself, and the role that ALK2 inhibition may play in other chronic inflammatory conditions associated with elevated hepcidin. DisclosuresMedeiros: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company. Backus: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company. Materna: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company. Fisher: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company. Lachey: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company, Membership on an entity's Board of Directors or advisory committees. Seehra: Keros Therapeutics: Current Employment, Current equity holder in publicly-traded company.

Cumulative DNA damage by repeated low-dose cisplatin injection promotes the transition of acute to chronic kidney injury in mice

Cisplatin is a commonly used anticancer drug, but nephrotoxicity is a dose-limiting adverse effect. Recent experimental and clinical observations have demonstrated that multiple injections of cisplatin induce the transition to chronic kidney disease; however, the underlying mechanisms remain unclear. We found that multiple injections of higher doses of cisplatin in a shorter interval affected the severity of kidney injury, causing kidney fibrosis to develop at a later time point. An additional injection of cisplatin during the recovery period after a prior injury, when proximal tubule epithelia are actively proliferating, induced substantial tubular injury by inducing more severe DNA damage than that induced by a single injection. Lineage tracing analysis of proximal tubular epithelia demonstrated that the tubular epithelia that underwent multiple rounds of cell division after multiple injections of cisplatin existed at the chronic phase, and these populations often expressed vcam1 + , suggesting the induction of proinflammatory failed-repair tubular epithelia. Our study revealed that as cisplatin exerts cytotoxic effects on actively proliferating cells, additional cisplatin injections before the completion of tubular repair exacerbates kidney injury through cumulative DNA damage. Appropriate both the setting of dosage and dosing intervals, with careful monitoring, are essential to prevent nephrotoxicity of repeated cisplatin treatment in cancer patients.

Enhanced Renal Clearance of Heme Triggers Acute Kidney Injury in Sickle Cell Disease

Circulating heme is scavenged primarily by hemopexin (Hx) for degradation in the liver, while alpha-1-microglobulin (A1M) binds heme for urinary clearance. Individuals with sickle cell disease (SCD) have acquired Hx deficiency. Hitherto, it has not been determined whether the low Hx in SCD results in a disproportionately large amount of heme exposure in the kidneys sufficient to promote acute tissue injury. Acute kidney injury (AKI) is a common downstream complication of acute chest syndrome (ACS) and vaso-occlusive pain crisis (VOC). Emerging evidence indicates acute elevations in circulating heme contributes to both ACS and VOC. Therefore, we tested the hypothesis that acute hemolytic crisis triggers AKI in SCD. We found that steady-state plasma A1M is raised significantly in SCD patients compared to controls (SS: 0.27±0.03, AA: 0.18±0.02 mg/ml p<0.05; n=12), and we determined that the molar A1M/Hx ratio is 14-fold higher in transgenic homozygous SCD (SS) mice compared to control (AA) littermates (n=6; p<0.05). Infusion of a non-lethal dose of purified heme (20 μmoles/kg) raised the concentration of heme in the liver but not in the kidneys of AA mice in 48 hours. On the contrary, the heme infusion over the same duration raised the total heme concentration in the kidneys but not in the liver of the SS mice (p<0.05). The SS mice but not the control AA mice developed severe renal tissue damage, defined by tubular atrophy and cast formation, loss of epithelial brush borders and apoptosis of the proximal tubular epithelium, within 48 hours of the heme infusion. Clinical detection of AKI is typically defined by elevation in serum creatinine and urinary albumin creatinine ratio (uACR). The acute elevation in circulating heme increased the plasma creatinine by 4-fold (p<0.001) with a 2-fold elevation in uACR (p<0.01) exclusively in the SS mice but not in control AA mice. Urinary kidney injury molecule-1 (KIM-1), which is a reliable predictor of AKI increased ~3-fold in the SS mice following the heme infusion, while no alteration of KIM-1 was evident in AA mice treated with the same challenge (n=6). To define the relationship between AKI in SCD and the hepatic and renal mechanisms of heme clearance, we measured plasma A1M and Hx, and urinary KIM-1 in a cohort of Ghanaian SCD patients aged 1-14 years (n=40). The molar ratio of A1M/Hx correlated positively with KIM-1 in this patient population (Pearson r=0.54; p=0.0003). Together, our data supports the conclusion that acute elevation of circulating heme triggers AKI in SCD. Clinically, the relative molar concentrations of plasma A1M and Hx can be developed as a biomarker to assess AKI risk in SCD patients. Finally, our data suggest acute infusions of Hx may protect SCD patients from AKI during episodes of hemolytic crisis. DisclosuresOfori-Acquah:NuvOx Pharma: Patents & Royalties.

MO1048PHYTOTHERAPY ON RENAL HYPOXIA: THE PREVENTIVE EFFECTS OF HYDROXYTYROSOL - PRELIMINARY IN VITRO RESULTS

Abstract Background and Aims Renal hypoxia plays a key role in the pathophysiology of acute kidney injury and in the progression of chronic kidney disease, potentiating other important risk factors for renal disease, such as oxidative stress, renal fibrosis, and inflammation. Hydroxytyrosol (HT) is a phenolic compound extracted from olives and olive-derived products, that has been shown to detain potent in vitro antioxidant and anti-inflammatory activity. The aim of this study was to evaluate the preventive therapeutic potential of HT on a cellular model of renal hypoxia. Method A cell line of normal adult proximal tubular epithelium (HK-2 cell line) was used to determine the effects of the chemical induction of hypoxia with cobalt chloride (CoCl2), as well as the preventive potential of HT on the elicited effects. For this purpose, HK-2 cells were exposed for 24 h to 254 µM CoCl2, to mimic the hypoxic conditions, or pre-incubated for 1 h with 5 µM HT and further exposed to the CoCl2 for 24 h more. Cell viability was assessed by the thiazolyl blue tetrazolium bromide reduction assay. Oxidative status was evaluated by the measurement of reactive oxygen and nitrogen species (ROS and RNS) and reduced glutathione (GSH) levels, by using standardized fluorometric and colorimetric assays. The expression of several genes related to the hypoxic, inflammatory, and fibrotic responses was determined by quantitative polymerase chain reaction (PCR). Results CoCl2-exposed HK-2 cells (hypoxic conditions) showed a significant decrease in cell viability (p &amp;lt; 0.0001 vs. control), and a disruption of the oxidative status, characterized by an increase of ROS and RNS production of about 6-fold over control cells (p &amp;lt; 0.0001) and a decrease in GSH intracellular levels of nearly 50 % (p &amp;lt; 0.05). Although the pre-exposure to HT showed no significant effects on the loss of cell viability elicited by CoCl2, the presence of HT prior to induction of hypoxia reduced the generation of ROS and RNS (p &amp;lt; 0.05 for HT + CoCl2 vs. CoCl2) and prevented the GSH depletion (GSH levels for HT + CoCl2 were similar to those of control) elicited by CoCl2. When compared to control cells, CoCl2-exposed HK-2 cells also showed increased expression of genes related to hypoxia (HIF1A, p &amp;lt; 0.05; GAPDH, p &amp;lt; 0.0001), as well as of modulators of inflammation (IL6, p &amp;lt; 0.0001) and fibrosis (TGFB1, p &amp;lt; 0.05). Importantly, the expression of these genes was partially or even totally suppressed by the pre-exposure of cells to HT (GAPDH, p &amp;lt; 0.01 for HT + CoCl2 vs. CoCl2; expression of HIF1A, IL6 and TGFB1 for HT + CoCl2 was similar to that of control). Conclusion Our data supports the potential for a multiplicity of preventive effects of HT, providing antioxidant, anti-inflammatory and anti-fibrotic defenses to renal cells under hypoxic conditions. Importantly, the development of safe and effective therapeutic approaches based on phytochemicals such as HT, may present substantial advantages for renal patients over synthetic drugs, including fewer side effects, significantly lower price, and ease of administration in the form of dietary supplements. Acknowledgments This work was supported by Applied Molecular Biosciences Unit (UCIBIO), financed by national funds from FCT/MCTES (UIDB/04378/2020), by North Portugal Regional Coordination and Development Commission (CCDR-N)/NORTE2020/Portugal 2020 (Norte-01-0145-FEDER-000024), and co-financed by FCT/MCTES (PTDC/OCE-ETA/32492/2017) and FEDER/COMPETE 2020 (POCI-01-0145-FEDER-032492).