Proximal Tubule Research Articles

Renal Proximal Tubule Cell-specific Megalin Deletion Does Not Affect Atherosclerosis But Induces Tubulointerstitial Nephritis in Mice Fed Western Diet.

Pharmacological inhibition of megalin (also known as low-density lipoprotein receptor-related protein 2: LRP2) attenuates atherosclerosis in hypercholesterolemic mice. Since megalin is abundant in renal proximal tubule cells (PTCs), the purpose of this study was to determine whether PTC-specific deletion of megalin reduces hypercholesterolemia-induced atherosclerosis in mice. Female Lrp2 f/f mice were bred with male Ndrg1-Cre ERT2 +/0 mice to develop PTC-LRP2 +/+ and -/- littermates. To study atherosclerosis, all mice were bred to an LDL receptor -/- background and fed a Western diet to induce atherosclerosis. PTC-specific megalin deletion did not attenuate atherosclerosis in LDL receptor -/- mice in either sex. Serendipitously, we discovered that PTC-specific megalin deletion led to interstitial infiltration of CD68+ cells and tubular atrophy. The pathology was only evident in male PTC-LRP2 -/- mice fed the Western diet, but not in mice fed a normal laboratory diet. Renal pathologies were also observed in male PTC-LRP2 -/- mice in an LDL receptor +/+ background fed the same Western diet, demonstrating that the renal pathologies were dependent on diet and not hypercholesterolemia. In contrast, female PTC-LRP2 -/- mice had no apparent renal pathologies. In vivo multiphoton microscopy demonstrated that PTC-specific megalin deletion dramatically diminished albumin accumulation in PTCs within 10 days of Western diet feeding. RNA sequencing analyses demonstrated the upregulation of inflammation-related pathways in kidney. PTC-specific megalin deletion does not affect atherosclerosis, but leads to tubulointerstitial nephritis in mice fed Western diet, with severe pathologies in male mice.

Sodium-Glucose Cotransporter-2 Inhibitors In Heart Failure

Heart failure (HF) is a serious problem in a modern world, with increasing prevalence among ageing populations. The use of sodium-glucose cotransporter-2 (SGLT2) inhibitors, originally intended to treat type 2 diabetes, has revolutionised the treatment of HF. In this review article, we present the latest evidence on the mechanism of action of SGLT2 inhibitors, also called flosins, in HF. The primary mechanism of action of flosins is to reduce glucose reabsorption from glomerular filtration in the proximal renal tubule with a concomitant reduction in sodium reabsorption, leading to urinary glucose excretion and osmotic diuresis. Based on experimental findings, several pleiotropic effects of SGLT2 inhibitors have been proposed. Mechanisms also include regulation of inflammatory and oxidative pathways along with improved endothelial function. Recent multicentre studies of SGLT2 inhibitors have shown that they reduce hospitalisations for heart failure after their use, regardless of type 2 diabetes and the degree of cardiac systolic dysfunction.

Identification of Differentially Expressed Genes in Cold Storage-associated Kidney Transplantation.

Although it is acknowledged that ischemia-reperfusion injury is the primary pathology of cold storage-associated kidney transplantation, its underlying mechanism is not well elucidated. To extend the understanding of molecular events and mine hub genes posttransplantation, we performed bulk RNA sequencing at different time points (24 h, day 7, and day 14) on a murine kidney transplantation model with prolonged cold storage (10 h). In the present study, we showed that genes related to the regulation of apoptotic process, DNA damage response, cell cycle/proliferation, and inflammatory response were steadily elevated at 24 h and day 7. The upregulated gene profiling delicately transformed to extracellular matrix organization and fibrosis at day 14. It is prominent that metabolism-associated genes persistently took the first place among downregulated genes. The gene ontology terms of particular note to enrich are fatty acid oxidation and mitochondria energy metabolism. Correspondingly, the key enzymes of the above processes were the products of hub genes as recognized. Moreover, we highlighted the proximal tubular cell-specific increased genes at 24 h by combining the data with public RNA-Seq performed on proximal tubules. We also focused on ferroptosis-related genes and fatty acid oxidation genes to show profound gene dysregulation in kidney transplantation. The comprehensive characterization of transcriptomic analysis may help provide diagnostic biomarkers and therapeutic targets in kidney transplantation.

RIPK4 promotes oxidative stress and ferroptotic death through the downregulation of ACSM1

One of the most critical axes for cell fate determination is how cells respond to excessive reactive oxygen species (ROS)-oxidative stress. Extensive lipid peroxidation commits cells to death via a distinct cell death paradigm termed ferroptosis. However, the molecular mechanism regulating cellular fates to distinct ROS remains incompletely understood. Through siRNA against human receptor-interacting protein kinase (RIPK) family members, we found that RIPK4 is crucial for oxidative stress and ferroptotic death. Upon ROS induction, RIPK4 is rapidly activated, and the kinase activity of RIPK4 is indispensable to induce cell death. Specific ablation of RIPK4 in kidney proximal tubules protects mice from acute kidney injury induced by cisplatin and renal ischemia/reperfusion. RNA sequencing revealed the dramatically decreased expression of acyl-CoA synthetase medium-chain (ACSM) family members induced by cisplatin treatment which is compromised in RIPK4-deficient mice. Among these ACSM family members, suppression of ACSM1 strongly augments oxidative stress and ferroptotic cell death with induced expression of ACS long-chain family member 4, an important component for ferroptosis execution. Our lipidome analysis revealed that overexpression of ACSM1 leads to the accumulation of monounsaturated fatty acids, attenuation of polyunsaturated fatty acid (PUFAs) production, and thereby cellular resistance to ferroptosis. Hence, knockdown of ACSM1 resensitizes RIPK4 KO cells to oxidative stress and ferroptotic death. In conclusion, RIPK4 is a key player involved in oxidative stress and ferroptotic death, which is potentially important for a broad spectrum of human pathologies. The link between the RIPK4-ASCM1 axis to PUFAs and ferroptosis reveals a unique mechanism to oxidative stress-induced necrosis and ferroptosis.

5-Hydroxytryptamine 1F Receptor Agonist Lasmiditan Differentially Regulates Successful Repair and Failed Repair Genes in a Mouse Model of Acute Kidney Injury.

Increasing evidence substantiates the role of mitochondrial dysfunction, inflammation, fibrosis, and cell senescence in the onset and progression of acute kidney injury (AKI) to chronic kidney disease . The underlying governing cellular and transcriptional events, however, are not fully understood. Recently, the key factors that regulate successful and failed repair states in the proximal tubule have been identified at a single-cell resolution following bilateral ischemia-reperfusion (I/R) in a mouse model of AKI. Previously, our group showed that treatment with the FDA-approved selective 5-hydroxytryptamine receptor 1F agonist lasmiditan following AKI induces mitochondrial biogenesis , restores renal mitochondrial function, and increases renal and vascular recovery in vivo. Here, we assessed the effect of lasmiditan on transcriptional and translational changes that are responsible for successful repair, injury, and failed repair states in the renal cortex following I/R-induced AKI. Increased levels of successful repair genes such as acyl-coA synthase medium-chain family member 2a, low-density lipoprotein receptor-related protein 2, solute carrier family 5 member 12, and hepatocyte nuclear factor 4 alpha were observed with 6 and 12 days of lasmiditan treatment following AKI compared to vehicle control. While 6 days of lasmiditan treatment had no effect on failed repair genes, the administration of lasmiditan for 12 days decreased the levels of vascular cell adhesion protein 1, tumor necrosis factor α, and interleukin-1β, which drive maladaptive repair. These data reveal that lasmiditan treatment post-AKI differentially regulates successful and failed repair gene expression in the renal cortex, likely contributing to the restoration of renal function and providing a potential targeted therapeutic pathway for the treatment of AKI.

COMMD5 counteracts cisplatin-induced nephrotoxicity by maintaining tubular epithelial integrity and autophagy flux.

Oxidative stress mediated by reactive oxygen species (ROS) contributes to apoptosis of tubular epithelial cells (TECs) and renal inflammation during acute kidney injury (AKI). Copper metabolism MURR1 domain-containing 5 [COMMD5/hypertension-related, calcium-regulated gene (HCaRG)] shows strong cytoprotective properties. COMMD5 is highly expressed in proximal tubules (PTs), where it controls cell differentiation. We assessed its role in cisplatin-induced AKI using transgenic mice in which COMMD5 is overexpressed in the PTs. Cisplatin caused the accumulation of damaged mitochondria and cellular waste in PTs, thus increasing the apoptosis of TECs. COMMD5 overexpression effectively protected TECs from cisplatin nephrotoxicity by decreasing intracellular ROS levels, mitochondrial dysfunction, and apoptosis through the preservation of tubular epithelial integrity, thus alleviating morphological and functional kidney damage. Excessive ROS production by hydrogen peroxide led to long-term autophagy activation through an increased burden on the autophagy/lysosome degradation system in TECs, and autophagic elimination of damaged mitochondria and cellular waste was compromised. COMMD5 attenuated oxidative injury by increasing autophagy flux, possibly due to a reduction of intracellular ROS levels through maintained tubular epithelial integrity, which decreased JNK/caspase-3-dependent apoptosis. Meanwhile, COMMD5 inhibition by siRNA reduced the resistance of TECs to cisplatin cytotoxicity, as shown by disrupted tubular epithelial integrity and cell viability. These data indicated that COMMD5 protects TECs from drug-induced oxidative stress and toxicity by maintaining tubular epithelial integrity and autophagy flux and ultimately decreases mitochondrial dysfunction and apoptosis. Increasing COMMD5 content in PTs is proposed as a new protective and therapeutic strategy against AKI.NEW & NOTEWORTHY Oxidative stress overload by drug treatment causes the accumulation of damaged mitochondria that could contribute to tubulopathy. However, effective preventive treatment for drug-induced acute kidney injury remains incompletely understood. Our study showed that copper metabolism MURR1 domain-containing 5 (COMMD5) reduced mitochondrial dysfunction and increased autophagy flux by alleviating reactive oxygen species production through maintaining tubular epithelial integrity when tubular epithelial cells were under oxidative stress, thus ameliorating renal function in cisplatin-treated mice. These results uncover a novel renoprotective mechanism underlying tubular epithelial integrity and autophagy flux.

Distinct and overlapping RGS14 and RGS12 actions regulate NPT2A-mediated phosphate transport

Parathyroid hormone (PTH) and fibroblast growth factor-23 (FGF23) control serum phosphate levels by downregulating the renal Na-phosphate transporter NPT2A, thereby decreasing phosphate absorption and augmenting urinary excretion. This mechanism requires NHERF1, a PDZ scaffold protein, and is governed by the regulator of G protein signaling-14 (RGS14), which harbors a carboxy-terminal PDZ ligand that binds NHERF1. RGS14 is part of a triad of structurally related RGS proteins that includes RGS12 and RGS10. Like RGS14, RGS12 contains a class 1 PDZ ligand. However, unlike RGS14, the larger RGS12 contains an upstream PDZ-binding domain. The studies outlined here examined and characterized the binding of RGS12 with NHERF1 and NPT2A and its function on hormone-regulated phosphate transport. Immunoblotting experiments revealed RGS12 C-terminal PDZ ligand binding to NHERF1. Further structural analysis disclosed that NPT2A engaged full-length RGS12 and the upstream fragment containing the PDZ domain. Neither the downstream RGS12 portion nor RGS14 interacted with NPT2A. PTH and FGF23 profoundly inhibited phosphate uptake in opossum kidney proximal tubule cells. Transfection with human RGS14, or human RGS12, abolished hormone-sensitive phosphate transport as reported for human proximal tubule cells. RGS12 inhibitory activity resides in the downstream region and is comparable to RGS14. The carboxy-terminal RGS12(667–1447) splice variant is prominently expressed in the kidney and may contribute to regulating hormone-sensitive phosphate transport.

Podocyte-specific KLF6 primes proximal tubule CaMK1D signaling to attenuate diabetic kidney disease

Diabetic kidney disease (DKD) is the main cause of chronic kidney disease worldwide. While injury to the podocytes, visceral epithelial cells that comprise the glomerular filtration barrier, drives albuminuria, proximal tubule (PT) dysfunction is the critical mediator of DKD progression. Here, we report that the podocyte-specific induction of human KLF6, a zinc-finger binding transcription factor, attenuates podocyte loss, PT dysfunction, and eventual interstitial fibrosis in a male murine model of DKD. Utilizing combination of snRNA-seq, snATAC-seq, and tandem mass spectrometry, we demonstrate that podocyte-specific KLF6 triggers the release of secretory ApoJ to activate calcium/calmodulin dependent protein kinase 1D (CaMK1D) signaling in neighboring PT cells. CaMK1D is enriched in the first segment of the PT, proximal to the podocytes, and is critical to attenuating mitochondrial fission and restoring mitochondrial function under diabetic conditions. Targeting podocyte-PT signaling by enhancing ApoJ-CaMK1D might be a key therapeutic strategy in attenuating the progression of DKD.

Single-nucleus sequencing unveils heterogeneity in renal cell carcinomas microenvironment: Insights into pathogenic origins and treatment-responsive cellular subgroups

BackgroundDifferent individuals with renal cell carcinoma (RCC) exhibit substantial heterogeneity in histomorphology, genetic alterations in the proteome, immune cell infiltration patterns, and clinical behavior. ObjectivesThis study aims to use single-nucleus sequencing on ten samples (four normal, three clear cell renal cell carcinoma (ccRCC), and three chromophobe renal cell carcinoma (chRCC)) to uncover pathogenic origins and prognostic characteristics in patients with RCC. MethodsBy using two algorithms, inferCNV and k-means, the study explores malignant cells and compares them with the normal group to reveal their origins. Furthermore, we explore the pathogenic factors at the gene level through Summary-data-based Mendelian Randomization and co-localization methods. Based on the relevant malignant markers, a total of 212 machine-learning combinations were compared to develop a prognostic signature with high precision and stability. Finally, the study correlates with clinical data to investigate which cell subtypes may impact patients’ prognosis. Results & conclusionTwo main origin tumor cells were identified: Proximal tubule cell B and Intercalated cell type A, which were highly differentiated in epithelial cells, and three gene loci were determined as potential pathogenic genes. The best malignant signature among the 212 prognostic models demonstrated high predictive power in ccRCC: (AUC: 0.920 (1-year), 0.920 (3-year) and 0.930 (5-year) in the training dataset; 0.756 (1-year), 0.828 (3-year), and 0.832 (5-year) in the testing dataset. In addition, we confirmed that LYVE1+ tissue-resident macrophage and TOX+ CD8 significantly impact the prognosis of ccRCC patients, while monocytes play a crucial role in the prognosis of chRCC patients.

Spns1 is an iron transporter essential for megalin-dependent endocytosis.

Proximal tubule endocytosis is essential to produce protein free urine as well as to regulate system wide metabolic pathways, such as the activation of Vitamin D. We have determined that the proximal tubule expresses an endolysosomal membrane protein, protein spinster homolog1 (Spns1), which engenders a novel iron conductance that is indispensable during embryonic development. Conditional knockout of Spns1 with a novel Cre-LoxP construct specific to megalin-expressing cells led to the arrest of megalin receptor-mediated endocytosis as well as dextran pinocytosis in proximal tubules. The endocytic defect was accompanied by changes in megalin phosphorylation as well as enlargement of lysosomes confirming previous findings in Drosophila and Zebrafish. The endocytic defect was also accompanied by iron overload in proximal tubules. Remarkably, iron levels regulated the Spns1 phenotypes, because feeding an iron deficient diet or mating Spns1 knockout with divalent metal transporter1 (DMT1) knockout rescued the phenotypes. Conversely, iron loading wild type mice reproduced the endocytic defect, These data demonstrate a reversible, negative feedback for apical endocytosis, and raise the possibility that regulation of endocytosis, pinocytosis, megalin activation, and organellar size and function is nutrient-responsive.

Insoluble HIFa protein aggregates by cadmium disrupt hypoxia-prolyl hydroxylase (PHD)-hypoxia inducible factor (HIFa) signaling in renal epithelial (NRK-52E) and interstitial (FAIK3-5) cells.

The kidney is the main organ that senses changes in systemic O2 pressure by hypoxia-PHD-HIFa (HPH) signaling, resulting in adaptive target gene activation, including erythropoietin (EPO). The non-essential transition metal cadmium (Cd) is nephrotoxic and disrupts the renal HPH pathway, which may promote Cd-associated chronic renal disease (CKD). A deeper molecular understanding of Cd interference with renal HPH signaling is missing, and no data with renal cell lines are available. In rat kidney NRK-52E cells, which model the proximal tubule, and murine fibroblastoid atypical interstitial kidney (FAIK3-5) cells, which mimic renal EPO-producing cells, the chemical hypoxia mimetic dimethyloxalylglycine (DMOG; 1 mmol/l) or hypoxia (1% O2) activated HPH signaling. Cd2+ (2.5-20 µmol/l for ≤ 24h) preferentially induced necrosis (trypan blue uptake) of FAIK3-5 cells at high Cd whereas NRK-52E cells specially developed apoptosis (PARP-1 cleavage) at all Cd concentrations. Cd (12.5 µmol/l) abolished HIFa stabilization and prevented upregulation of target genes (quantitative real-time polymerase chain reaction and immunoblotting) induced by DMOG or hypoxia in both cell lines, which was caused by the formation of insoluble HIFa aggregates. Strikingly, hypoxic preconditioning (1% O2 for 18h) reduced apoptosis of FAIK3-5 and NRK-52E cells at low Cd concentrations and decreased insoluble HIFa proteins. Hence, drugs mimicking hypoxic preconditioning could reduce CKD induced by chronic low Cd exposure.

Pik3c3 expression profiling in the mouse kidney and its role in proximal tubule cell physiology.

The class 3 phosphatidylinositol 3-kinase (Pik3c3) plays critical roles in regulating autophagy, endocytosis, and nutrient sensing, but its expression profile in the kidney remains undefined. Recently, we validated a Pik3c3 antibody through immunofluorescence staining of kidney tissues from cell type-specific Pik3c3 knockout mice. Immunohistochemistry unveiled significant disparities in Pik3c3 expression levels across various kidney cell types. Notably, renal interstitial cells exhibit minimal Pik3c3 expression. Further, coimmunofluorescence staining, utilizing nephron segment- or cell type-specific markers, revealed nearly undetectable levels of Pik3c3 expression in glomerular mesangial cells and endothelial cells. Intriguingly, although podocytes exhibit the highest Pik3c3 expression levels among all kidney cell types, the renal proximal tubule cells (RPTCs) express the highest level of Pik3c3 among all renal tubules. RPTCs are known to express the highest level of the epidermal growth factor receptor (EGFR) in adult kidneys; however, the role of Pik3c3 in EGFR signaling within RPTCs remains unexplored. Therefore, we conducted additional cell culture studies. The results demonstrated that Pik3c3 inhibition significantly delayed EGF-stimulated EGFR degradation and the termination of EGFR signaling in RPTCs. Mechanistically, Pik3c3 inhibition surprisingly did not affect the initial endocytosis process but instead impeded the lysosomal degradation of EGFR. In summary, this study defines, for the first time, the expression profile of Pik3c3 in the mouse kidney and also highlights a pivotal role of Pik3c3 in the proximal tubule cells. These findings shed light on the intricate mechanisms underlying Pik3c3-mediated regulation of EGFR signaling, providing valuable insights into the role of Pik3c3 in renal cell physiology. NEW & NOTEWORTHY This is the first report defining the class 3 phosphatidylinositol 3-kinase (Pik3c3) expression profile in the kidney. Pik3c3 is nearly absent in renal interstitial cells, glomerular mesangial cells, and endothelial cells. Remarkably, glomerular podocytes express the highest Pik3c3 level in the kidney. However, the proximal tubule exhibits the highest expression level among all renal tubules. This study also unveils the pivotal role of Pik3c3 in regulating EGFR degradation and signaling termination in RPTCs, furthering our understanding of Pik3c3 in renal cell physiology.

A Focus on the Proximal Tubule Dysfunction in Dent Disease Type 1.

Dent disease type 1 is a rare X-linked recessive inherited renal disorder affecting mainly young males, generally leading to end-stage renal failure and for which there is no cure. It is caused by inactivating mutations in the gene encoding ClC-5, a 2Cl-/H+ exchanger found on endosomes in the renal proximal tubule. This transporter participates in reabsorbing all filtered plasma proteins, which justifies why proteinuria is commonly observed when ClC-5 is defective. In the context of Dent disease type 1, a proximal tubule dedifferentiation was shown to be accompanied by a dysfunctional cell metabolism. However, the exact mechanisms linking such alterations to chronic kidney disease are still unclear. In this review, we gather knowledge from several Dent disease type 1 models to summarize the current hypotheses generated to understand the progression of this disorder. We also highlight some urinary biomarkers for Dent disease type 1 suggested in different studies.

Spatial transcriptomics defines injury specific microenvironments and cellular interactions in kidney regeneration and disease

Kidney injury disrupts the intricate renal architecture and triggers limited regeneration, together with injury-invoked inflammation and fibrosis. Deciphering the molecular pathways and cellular interactions driving these processes is challenging due to the complex tissue structure. Here, we apply single cell spatial transcriptomics to examine ischemia-reperfusion injury in the mouse kidney. Spatial transcriptomics reveals injury-specific and spatially-dependent gene expression patterns in distinct cellular microenvironments within the kidney and predicts Clcf1-Crfl1 in a molecular interplay between persistently injured proximal tubule cells and their neighboring fibroblasts. Immune cell types play a critical role in organ repair. Spatial analysis identifies cellular microenvironments resembling early tertiary lymphoid structures and associated molecular pathways. Collectively, this study supports a focus on molecular interactions in cellular microenvironments to enhance understanding of injury, repair and disease.

Evaluating nephrotoxicity reduction in a novel polymyxin B formulation: insights from a 3D kidney-on-a-chip model.

This study aimed to assess the nephrotoxicity associated with VRP-034 (novel formulation of polymyxin B [PMB]) compared to marketed PMB in a three-dimensional (3D) kidney-on-a-chip model. To model the human kidney proximal tubule for analysis, tubular structures were established using 23 triple-channel chips seeded with RPTEC/hTERT1 cells. These cells were exposed to VRP-034 or PMB at seven concentrations (1-200 µM) over 12, 24, and 48 h. A suite of novel kidney injury biomarkers, cell health, and inflammatory markers were quantitatively assessed in the effluent. Additionally, caspase and cytochrome C levels were measured, and cell viability was evaluated using calcein AM and ethidium homodimer-1 (EthD-1). Exposure to marketed PMB resulted in significantly elevated levels (P < 0.05) of four key biomarkers (KIM-1, cystatin C, clusterin, and OPN) compared to VRP-034, particularly at clinically relevant concentrations of ≥10 µM. At 25 µM, all biomarkers demonstrated a significant increase (P < 0.05) with marketed PMB exposure compared to VRP-034. Inflammatory markers (interleukin-6 and interleukin-8) increased significantly (P < 0.05) with marketed PMB at concentrations of ≥5 µM, relative to VRP-034. VRP-034 displayed superior cell health outcomes, exhibiting lower lactate dehydrogenase release, while ATP levels remained comparable. Morphological analysis revealed that marketed PMB induced more severe damage, disrupting tubular integrity. Both treatments activated cytochrome C, caspase-3, caspase-8, caspase-9, and caspase-12 in a concentration-dependent manner; however, caspase activation was significantly reduced (P < 0.05) with VRP-034. This study demonstrates that VRP-034 significantly reduces nephrotoxicity compared to marketed PMB within a 3D microphysiological system, suggesting its potential to enable the use of full therapeutic doses of PMB with an improved safety profile, addressing the need for less nephrotoxic polymyxin antibiotics.

Decoding 11-Oxygenated Androgen Synthesis: Insights from Enzyme Gene Expression and LC‒MS/MS Quantification.

Adrenal-origin and peripheral tissue-transformed 11-oxygenated androgens are recognized as significant androgens. However, our current understanding of the synthesis of 11-oxygenated androgens, including the organs and cell types involved, remains limited. We performed comprehensive analyses on an extensive dataset of normal human tissues, which included bulk RNA data from 30 tissues, single-cell RNA sequencing (scRNA) data from 16 tissues and proteomics data from 29 tissues, to characterize the expression profiles of enzyme-encoding genes. To validate the findings, immunohistochemical and liquid chromatography-tandem mass spectrometry (LC‒MS/MS) techniques were employed. Our investigation revealed that the gene expression levels of the enzymes HSD11B2 and AKR1C3 were notably elevated in the kidney and intestines. Intriguingly, within these organs, we observed an increasing trend in enzyme expression with age in women, while a decreasing trend was apparent in men. Sc-RNA analysis revealed that HSD11B2 was predominantly expressed in collecting duct principal cells in the kidney, while AKR1C3 was primarily expressed in the proximal tubules. Intriguingly, nearly all epithelial cells in the intestine expressed these key enzymes. Further analysis using LC‒MS/MS revealed that the kidney exhibited the highest levels of 11-ketoandrostenedione (11KA4) and 11-ketotestosterone (11KT) among the seven tissues examined, and substantial synthesis of 11KA4 and 11KT was also observed in the intestine. Finally, we developed the TransMap website (http://gxmujyzmolab.cn:16245/TransMap/) to provide comprehensive visualization of all currently available transcriptome data. This study offers an overarching perspective on tracing the synthesis of 11-oxygenated androgens in peripheral tissues, thereby providing valuable insights into the potential role of these androgens in humans.

Oridonin Attenuates Diabetes‑induced Renal Fibrosis via the Inhibition of TXNIP/NLRP3 and NF‑κB Pathways by Activating PPARγ in Rats.

Oridonin possesses remarkable anti-inflammatory, immunoregulatory properties. However, the renoprotective effects of oridonin and the underlying molecular mechanisms in diabetic nephropathy (DN). We hypothesized that oridonin could ameliorate diabetes‑induced renal fibrosis. Streptozocin (STZ)-induced diabetic rats were provided with a high-fat diet to establish a type 2 diabetes mellitus (T2DM) animal model, and then treated with Oridonin (10, 20 mg/kg/day) for two weeks. Kidney function and renal fibrosis were assessed. High glucose-induced human renal proximal tubule epithelial cells (HK-2) were also treated with oridonin. The expression of inflammatory factors and fibrotic markers were analyzed. Oridonin treatment preserved kidney function and markedly limited the renal fibrosis size in diabetic rats. The renal fibrotic markers were inhibited in the oridonin 10 mg/kg/day and 20 mg/kg/day groups compared to the T2DM group. The expression of thioredoxin-interacting proteins/ nod-like receptor protein-3 (TXNIP/NLRP3) and nuclear factor (NF)‑κB pathway decreased, while that of peroxisome proliferator-activated receptor-gamma (PPARγ) increased in the oridonin treatment group compared to the non-treated group. In vitro, PPARγ intervention could significantly regulate the effect of oridonin on the high glucose-induced inflammatory changes in HK-2 cells. Oridonin reduces renal fibrosis and preserves kidney function via the inhibition of TXNIP/NLRP3 and NF‑κB pathways by activating PPARγ in rat T2DM model, which indicates potential effect of oridonin in the treatment of DN.

Abstract 08: Genome-wide Maps of Human Kidney Proximal Tubules and Thick Ascending Limbs of Henle reveal an Enrichment for Human Blood Pressure associated Polymorphisms

GWAS has identified &gt;1,000 blood pressure (BP)-associated sentinel SNPs, most of which (&gt;90%) are intronic and intergenic. How they regulate BP-relevant genes remains an open question. We hypothesized many SNPs would reside within cis -regulatory elements specific to nephron segments critical to sodium resorption such as proximal tubule (PT) and thick ascending limb (TAL). To address this, we developed chromatin state (ATAC-seq) and transcriptome (RNA-seq) maps from manually dissected human PT and medullary TAL (mTAL) segments. We identified 216,168 and 179,467 open regions in PT and mTAL, respectively, with the majority (70%) being unique to one tissue. Interestingly, peaks shared between the two segments resided more frequently in promoters, whereas unique peaks were more often found in distal introns or intergenic regions, suggesting they lie within enhancers ( Figure 1A ). Both chromatin state and transcriptomic data demonstrated a correlation between open chromatin peaks within gene promoters and mRNA levels (r=0.11; p&lt;4.6e-16). This correlation was weaker at open regions distal to the promoter, illustrating the difficulty of mapping distal open regions to the gene(s) they regulate. We hypothesized these open regions would be enriched for BP-relevant SNPs. We curated 1,071 bp-associated SNPs and found 87 and 67 in mTAL and PT, open regions respectively, many of which are near BP-relevant genes. This enrichment was significant based on 10 4 randomizations (pValue 10 -4 ) ( Figure 1B ). We conclude that these novel tissue-specific chromatin maps can be used to identify potential mechanisms by which SNPs influence gene expression and BP. Additional studies will be needed to demonstrate both causality and molecular mechanisms.

Abstract P367: Cross-Species Epigenomic Maps of Intergenic Loci for Hypertension and Blood Pressure

Many non-coding SNPs identified in Genome-Wide Association Studies (GWAS) likely affect BP-related gene expression through epigenetic mechanisms. This study analyzes the comparative genomic and epigenomic landscapes in human and rat kidney tissues, including kidney proximal tubule (PT) and medullary thick ascending limb (mTAL), focusing on the major challenge of identifying conserved regulatory elements in intergenic regions. The purpose of our study is to identify BP gene regulatory elements in intergenic regions that are conserved from human to rat for in vivo validation and mechanistic studies. Our ultimate goal is to generate high-resolution, genome-wide epigenomic maps of key BP-relevant tissues, using ATAC-seq, Hi-C, CUT&amp;Tag, DNA methylation profiling and RNA-seq. We are creating visualization hubs for human and rat, integrating our data within the UCSC Genome Browser environment. UCSC contains extensive data for humans but very little for rats, particularly for the updated genome assemblies. To address this gap, we integrated our results with data from the Rat Genome Database (RGD). To date, we harmonized ATAC-seq data from human and rat PT and mTAL and displayed these data in RGD’s JBrowse2 genome browser for unique comparative genome views. Based on our initial analysis of data density and intensity, we are developing a novel pattern recognition algorithm to identify epigenomic marks that are conserved across rat and human genomes. Existing algorithms predominantly focus on the conservation of coding genes, gene families, and genomic sequences. Here, average normalized peak intensities for ATAC-seq data across tissues were subject to canonical correlation between human and rat to identify conserved epigenomic patterns within the BP GWAS loci. Here we present an example of a human BP locus in the intergenic region between NPR3 and TARS1 on chromosome 5 which has a region of conserved synteny with rat chromosome 2. Comparative analysis and visualization of this region show significant correlation between ATAC-seq peaks from rat and human PT and mTAL at this locus, with predicted conserved regulatory elements. These visualizations can uncover novel biological insights and identify potential regulatory targets for intervention. This work underscores the importance of advanced visualization techniques in understanding hypertension pathogenesis, facilitating cross-species comparisons, and enhancing the utility of genomic databases.

Abstract 06: Role of the Atrial Natriuretic Peptide in Mitochondria-mediated Proximal Tubule Epithelial Oxidative Stress in Type 1 Diabetic Kidney Disease

Introduction: Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. Most studies of DKD are glomerulo-centric. The recent progress in the control of renal glucose handling by SGLT2i makes the proximal tubule (PT) a prime candidate. Mitochondrial (mito) dysfunction and mito-induced oxidative stress in DKD is well-studied and is known to accelerate tubular injury. Some studies have suggested the role of the Atrial Natriuretic Peptide (ANP) in DKD. ANP is a hormone that regulates renal salt/water homeostasis and renal hemodynamics. We hypothesize that in DKD, ANP is a beneficial factor that improves proximal tubule mitochondrial function via protection from oxidative stress-induced ferroptosis. Methods: Using male ANP knock-out (SS NPPA-/- ) and wild-type (SS WT ) rats on the Dahl SS background, T1DKD was induced by streptozotocin (STZ; 75mg/kg) at 9-10 weeks of age. Baseline, midpoint, and endpoint blood glucose, urine, and body weights were collected. Western blotting was done on isolated cortical tissue and tissue fibrosis was measured in PicroSirius Red staining. ANOVA through Origin 2019b was used for comparisons. Results: STZ- SS WT and STZ-SS NPPA-/- groups exhibited similar body weight (231.7 ± 14.8 vs. 230.9 ± 8.4 g, respectively), two-kidney weight to body weight ratio (31.8 ± 0.9 vs. 28.4 ± 1.5 mg/g), and endpoint hyperglycemia (with blood glucose levels &gt;650 mg/dL). Both, STZ- SS WT and STZ-SS NPPA-/- groups had high diuresis (59.9 ± 3.1 vs. 52.7 ± 3.2 mL/24hr/100gTBW). Histological analysis revealed elevated cortical fibrosis in the STZ-SS NPPA-/- compared to STZ- SS WT (4.6 ± 0.2 vs. 3.1 ± 0.2 % area, respectively, p&lt;0.05). Moreover, in the kidney cortex, STZ-SS NPPA-/- rats compared to STZ- SS WT rats exhibit a significant increase in OXPHOS complexes IV and V (p&lt;0.05) and a decrease in glutathione peroxidase 4 (GPX4; a core regulator of ferroptosis) abundance (1.5 ± 0.2 vs. 1.9 ± 0.1 a.u., respectively, p&lt;0.05). Conclusion: Data showed that lack of ANP may promote DKD-related tubulointerstitial fibrosis and suggested a relationship with renal cortical mitochondrial function. Future studies will provide mechanistic insight into the role of ANP in mito-related oxidative stress and further assess the role of ANP in PT ferroptosis.