Egr-1 deficiency protects from renal inflammation and fibrosis

Autophagy activates EGR1 via MAPK/ERK to induce FGF2 in renal tubular cells for fibroblast activation and fibrosis during maladaptive kidney repair

Macroautophagy/autophagy contributes to maladaptive kidney repair by inducing pro-fibrotic factors such as FGF2 (fibroblast growth factor 2), but the underlying mechanism remains elusive. Here, we show that EGR1 (early growth response 1) was induced in injured proximal tubules after ischemic acute kidney injury (AKI) and this induction was suppressed by autophagy deficiency in inducible, renal tubule-specific atg7 (autophagy related 7) knockout (iRT-atg7 KO) mice. In cultured proximal tubular cells, TGFB1 (transforming growth factor beta 1) induced EGR1 and this induction was also autophagy dependent. Egr1 knockdown in tubular cells reduced FGF2 expression during TGFB1 treatment, leading to less FGF2 secretion and decreased paracrine effects on fibroblasts. ChIP assay detected an increased binding of EGR1 to the Fgf2 gene promoter in TGFB1-treated tubular cells. Both Fgf2 and Egr1 transcription was inhibited by FGF2 neutralizing antibody, suggesting a positive feedback for EGR1-mediated FGF2 autoregulation. This feedback was confirmed using fgf2-deficient tubular cells and fgf2-deficient mice. Upstream of EGR1, autophagy deficiency in mice suppressed MAPK/ERK (mitogen-activated protein kinase) activation in post-ischemic renal tubules. This inhibition correlated with SQSTM1/p62 (sequestosome 1) aggregation and its sequestration of MAPK/ERK. SQSTM1/p62 interacted with MAPK/ERK and blocked its activation during TGFB1 treatment in autophagy-deficient tubular cells. Inhibition of MAPK/ERK suppressed EGR1 and FGF2 expression in maladaptive tubules, leading to the amelioration of renal fibrosis and improvement of renal function. These results suggest that autophagy activates MAPK/ERK in renal tubular cells, which induces EGR1 to transactivate FGF2. FGF2 is then secreted into the interstitium to stimulate fibroblasts for fibrogenesis.Abbreviation: 3-MA: 3-methyladenine; ACTA2/α-SMA: actin alpha 2, smooth muscle, aorta; ACTB/β-actin: actin, beta; AKI: acute kidney injury; aa: amino acid; ATG/Atg: autophagy related; BUN: blood urea nitrogen; ChIP: chromatin immunoprecipitation; CKD: chronic kidney disease; CM: conditioned medium; COL1A1: collagen, type I, alpha 1; COL4A1: collagen, type IV, alpha 1; CQ: chloroquine; DBA: dolichos biflorus agglutinin; EGR1: early growth response 1; ELK1: ELK1, member of ETS oncogene family; FGF2: fibroblast growth factor 2; FN1: fibronectin 1; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HAVCR1/KIM-1: hepatitis A virus cellular receptor 1; IP: immunoprecipitation; LIR: LC3-interacting region; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MAP2K/MEK: mitogen-activated protein kinase kinase; MAPK: mitogen-activated protein kinase; NFKB: nuclear factor kappa B; PB1: Phox and Bem1; PFT: pifithrin α; PPIB/cyclophilin B: peptidylprolyl isomerase B; RT-qPCR: real time-quantitative PCR; SQSTM1/p62: sequestosome 1; TGFB1/TGF-β1: transforming growth factor beta 1; VIM: vimentin.

Endothelial NOX5 Obliterates the Reno-Protective Effect of Nox4 Deletion by Promoting Renal Fibrosis via Activation of EMT and ROS-Sensitive Pathways in Diabetes

Chronic hyperglycemia induces intrarenal oxidative stress due to the excessive production of reactive oxygen species (ROS), leading to a cascade of events that contribute to the development and progression of diabetic kidney disease (DKD). NOX5, a pro-oxidant NADPH oxidase isoform, has been identified as a significant contributor to renal ROS in humans. Elevated levels of renal ROS contribute to endothelial cell dysfunction and associated inflammation, causing increased endothelial permeability, which can disrupt the renal ecosystem, leading to progressive albuminuria and renal fibrosis in DKD. This study specifically examines the contribution of endothelial cell-specific human NOX5 expression in renal pathology in a transgenic mouse model of DKD. This study additionally compares NOX5 with the previously characterized NADPH oxidase, NOX4, in terms of their relative roles in DKD. Regardless of NOX4 pathway, this study found that endothelial cell-specific expression of NOX5 exacerbates renal injury, albuminuria and fibrosis. This is attributed to the activation of the endothelial mesenchymal transition (EMT) pathway via enhanced ROS formation and the modulation of redox-sensitive factors. These findings underscore the potential therapeutic significance of NOX5 inhibition in human DKD. The study proposes that inhibiting NOX5 could be a promising approach for mitigating the progression of DKD and strengthens the case for the development of NOX5-specific inhibitors as a potential therapeutic intervention.

Early growth response 1/Krüppel-like factor 5 pathway inhibitor alleviates lipopolysaccharide-induced lung injury by promoting autophagy

Early transcription factors play critical roles in the development of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Early growth response 1 (EGR1) is a transcription factor essential for various biological processes, including regulation of metabolism, differentiation, and inflammation. However, its role in ALI has been poorly reported. In this study, we aimed to determine the effect of EGR1 on ALI to gain insights into the theoretical basis for further treatment of ALI. By employing concerted molecular biology techniques, we showed that EGR1 protein was upregulated in mice. EGR1 protein was upregulated in mice and human lung epithelial cells in response to lipopolysaccharide (LPS) stimulation. EGR1 knockdown promoted autophagy and reduced LPS-induced pro-inflammatory mediator production. EGR1 was preferentially bound to the GCGTGGGCG motif region and EGR1-binding peak-related genes were mainly enriched in autophagy and injury stress-related pathways. Additionally, EGR1 promoted Krüppel-like factor 5 (KLF5) transcription by binding to the KLF5 promoter region, and KLF5 knockdown significantly decreased inflammatory damage, suggesting that EGR1 promotes ALI progression by regulating KLF5 expression. Furthermore, ML264, an inhibitor of the EGR1/KLF5 pathway axis, displayed a protective role in ALI to reduce inflammation. In conclusion, our findings demonstrate the potential of EGR1 knockdown to inhibit KLF5 and promote autophagy, further reducing the inflammatory response to mitigate ALI/ARDS. The EGR1/KLF5 pathway axis may be a valuable therapeutic target for the treatment of ALI/ARDS.

Liproxstatin-1 Alleviated Ischemia/Reperfusion-Induced Acute Kidney Injury via Inhibiting Ferroptosis

Ferroptosis, as a novel regulable cell death, is characterized by iron overload, glutathione depletion, and an accumulation of lipid peroxides. Recently, it has been discovered that ferroptosis is involved in ischemia/reperfusion (I/R)-induced acute kidney injury (AKI) and plays a crucial role in renal tubular cell death. In this study, we tried to investigate the effect and mechanism of liproxstatin-1 (Lip-1) in I/R-induced AKI and seek the key regulator of ferroptosis in I/R-induced AKI. Mice were administrated with clamping bilateral renal pedicles for 30 min. We found that early growth response 1 (EGR1) might be a key regulator of ferroptosis, and Lip-1 could suppress ferroptosis via EGR1. Meanwhile, Lip-1 could reduce macrophage recruitment and the release of inflammatory cytokines. These findings indicated that Lip-1 alleviated I/R-induced AKI via regulating EGR1, and it might pave the theoretical basis of a new therapeutic strategy for I/R-induced AKI.

Egr-1 is a key regulator of the blood-brain barrier damage induced by meningitic Escherichia coli

Bacterial meningitis remains a leading cause of infection-related mortality worldwide. Although Escherichia coli (E. coli) is the most common etiology of neonatal meningitis, the underlying mechanisms governing bacterial blood-brain barrier (BBB) disruption during infection remain elusive. We observed that infection of human brain microvascular endothelial cells with meningitic E. coli triggers the activation of early growth response 1 (Egr-1), a host transcriptional activator. Through integrated chromatin immunoprecipitation sequencing and transcriptome analysis, we identified Egr-1 as a crucial regulator for maintaining BBB integrity. Mechanistically, Egr-1 induced cytoskeletal changes and downregulated tight junction protein expression by directly targeting VEGFA, PDGFB, and ANGPTL4, resulting in increased BBB permeability. Meanwhile, Egr-1 also served as a master regulator in the initiation of neuroinflammatory response during meningitic E. coli infection. Our findings support an Egr-1-dependent mechanism of BBB disruption by meningitic E. coli, highlighting a promising therapeutic target for bacterial meningitis.

Early growth response 1 as a podocyte injury marker in human glomerular diseases

Background

In human glomerular diseases, visualizing podocyte injury is desirable since podocytes do not regenerate and podocyte injury leads to podocyte loss. Herein, we investigated the utility of immunostaining for early growth response 1 (EGR1), which is expressed in injured podocytes from the early stages of injury in animal experiments, as a podocyte injury marker in human glomerular diseases.

Methods

This study included 102 patients with biopsy-proven glomerular diseases between 2018 and 2021. The proportion of EGR1 expression in podocytes (%EGR1pod) was analyzed in relation to clinical and histopathological features, including glomerular and urinary podocyte-specific markers.

Results

%EGR1pod correlated significantly with the urinary protein:creatinine ratio, urinary nephrin and podocin mRNA levels, and glomerular podocin staining (rho = 0.361, 0.514, 0.487 and -0.417, respectively; adjusted P = .002, <.001, <.001 and <.001, respectively). Additionally, %EGR1pod correlated with cellular/fibrocellular crescents (rho = 0.479, adjusted P <.001). %EGR1pod was high in patients with glomerulonephritis, such as immunoglobulin A nephropathy (IgAN), lupus nephritis and antineutrophil cytoplasmic antibody-associated glomerulonephritis, and in those with podocytopathies, such as membranous nephropathy and primary focal segmental glomerulosclerosis, while %EGR1pod was low in patients with minimal change disease. In a subgroup analysis of IgAN, %EGR1pod was higher in Oxford C1 patients than in C0 patients. However, unexpectedly, patients with higher %EGR1pod were more prone to attain proteinuria remission, suggesting that EGR1 in the context of IgAN reflects reversible early injury.

Conclusions

Our findings indicate that EGR1 is a promising potential marker for identifying active early podocyte injury in human glomerular diseases.

HK-2 cell response to TGF-β highly depends on cell culture medium formulations

The immortalized human renal proximal tubular epithelial cell line HK-2 is most commonly used to study renal cell physiology and human kidney diseases with tubulointerstitial fibrosis such as diabetic nephropathy, obstructive uropathy or allograft fibrosis. Epithelial-to-mesenchymal transition (EMT) is the main pathological process of tubulointerstitial fibrosis in vitro. Transforming growth factor-beta (TGF-β) is a key inducer of EMT. Several pro-fibrotic gene expression differences have been observed in a TGF-β-induced EMT model of HK-2 cells. However, growth conditions and medium formulations might greatly impact these differences. We investigated gene and protein expression of HK-2 cells cultured in six medium formulations. TGF-β1 increased the expression of ACTA2, TGFB1, COL4A1, EGR2, VIM and CTGF genes while reducing PPARG in all medium formulations. Interestingly, TGF-β1 treatment either increased or decreased EGR1, FN, IL6 and C3 gene expression, depending on medium formulations. The cell morphology was slightly affected, but immunoblots revealed TGFB1 and vimentin protein overexpression in all media. However, fibronectin expression as well as the nuclear translocation of EGR1 was medium dependent. In conclusion, our study demonstrates that, using the HK-2 in vitro model of EMT, the meticulous selection of appropriate cell culture medium formulation is essential to achieve reliable scientific results.

Montelukast Attenuates Retraction of Expanded Flap by Inhibiting Capsule Formation around Silicone Expander through TGF-β1 Signaling

BACKGROUND

Tissue expansion has tremendous applications in plastic surgery, but flap retraction provides insufficient tissue for use. Inspired by the use of montelukast to suppress capsular contracture, the authors investigated the effects of montelukast on capsule formation around the expander and retraction of the expanded scalp of the rat.

METHODS

Thirty-six male Sprague-Dawley rats were randomly divided into control and montelukast groups. In each group, 12 expanded flaps with or without capsules were harvested for histologic and molecular analysis; the six remaining expanded flaps were transferred to repair defects. Myofibroblast and transforming growth factor-β1 expression in the capsule was determined using immunofluorescence. Capsule ultrastructure was observed using transmission electron microscopy. Related protein expression in the capsules was detected using Western blot analysis.

RESULTS

A comparison of control and montelukast groups revealed that areas of the harvested expanded flaps with capsules were greater (2.04 ± 0.11 cm 2 versus 2.42 ± 0.12 cm 2 , respectively; P = 0.04); the retraction rate decreased (41.3% ± 2.16% versus 28.13% ± 2.17%, respectively; P < 0.01). However, the increased areas and decreased retraction disappeared after capsule removal. The number of myofibroblasts declined. Thin, sparse collagen fibers were observed in the capsules. The expression of COL1, COL3, TGF-β1, EGR1, and phosphorylated ERK1/2 in the capsules decreased. Furthermore, the recipient area repaired by the transferred expanded flap was increased from 4.25 ± 0.39 cm 2 to 6.58 ± 0.31 cm 2 ( P < 0.01).

CONCLUSION

Montelukast attenuates retraction of the expanded flap by inhibiting capsule formation through suppressing transforming growth factor-β1 signaling.

CLINICAL RELEVANCE STATEMENT

This study provides novel insights into a method for increasing the area of the expanded flap.

Early Growth Response 1 Contributes to Renal IR Injury by Inducing Proximal Tubular Cell Apoptosis

Renal ischemia-reperfusion (IR) causes acute kidney injury due to oxidative stress, tubular inflammation, and apoptosis. Early growth response 1 (Egr-1) is a transcription factor belonging to the immediate early gene family and is known to regulate cell proliferation, differentiation, and survival. Egr-1 expression is induced during renal IR; however, its pathogenic role and underlying mechanisms remain elusive. Here, we investigated the function of Egr-1 during renal IR using C57BL/6 mice and cultured renal proximal tubular HK-2 cells. Egr-1 expression increased immediately, 1-4 h after IR, whereas plasma creatinine and oxidative stress increased progressively over 24 h after IR. Egr-1 overexpression showed greater increases in plasma creatinine, renal tubular injury, and apoptosis than in the control after IR. Egr-1 overexpression also showed significant neutrophil infiltration and increased pro-inflammatory cytokines (TNF-α, MIP-2, and IL-6) after IR. Consistently, proximal tubular HK-2 cells showed immediate induction of Egr-1 at 1 h after hypoxia and reoxygenation, where its downstream target, p53, was also increased. Interestingly, Egr-1 overexpression enhanced p53 levels and tubular apoptosis, while the knockdown of Egr-1 reduced p53 levels and tubular apoptosis after H2O2 treatment. Egr-1 was recruited to the p53 promoter, which activates p53 transcription, and Egr-1 induction occurred through Erk/JNK signaling kinases, as the specific inhibitors blocked its expression. Taken together, these results show that Egr-1 is upregulated in proximal tubular cells and contributes to renal IR injury by inducing tubular apoptosis, mediated by p53 transcriptional activation. Thus, Egr-1 could be a potential therapeutic target for renal IR injury.

IRX2 regulates angiotensin II-induced cardiac fibrosis by transcriptionally activating EGR1 in male mice

Cardiac fibrosis is a common feature of chronic heart failure. Iroquois homeobox (IRX) family of transcription factors plays important roles in heart development; however, the role of IRX2 in cardiac fibrosis has not been clarified. Here we report that IRX2 expression is significantly upregulated in the fibrotic hearts. Increased IRX2 expression is mainly derived from cardiac fibroblast (CF) during the angiotensin II (Ang II)-induced fibrotic response. Using two CF-specific Irx2-knockout mouse models, we show that deletion of Irx2 in CFs protect against pathological fibrotic remodelling and improve cardiac function in male mice. In contrast, Irx2 gain of function in CFs exaggerate fibrotic remodelling. Mechanistically, we find that IRX2 directly binds to the promoter of the early growth response factor 1 (EGR1) and subsequently initiates the transcription of several fibrosis-related genes. Our study provides evidence that IRX2 regulates the EGR1 pathway upon Ang II stimulation and drives cardiac fibrosis.

S14G-Humanin ameliorates ovalbumin-induced airway inflammation in asthma mediated by inhibition of toll-like receptor 4 (TLR4) expression and the nuclear factor κ-B (NF-κB)/early growth response protein-1 (Egr-1) pathway

Asthma is a chronic inflammatory disease with a high morbidity rate in children and significantly impacts their healthy growth. It is reported that Th2 cell-mediated airway inflammation and activated oxidative stress are involved in the pathogenesis of asthma. S14G-humanin (HNG) is a derivative of Humanin with higher activity. The present study proposes to explore the potential treating property of HNG on asthma. An asthma model was constructed in mice using ovalbumin (OVA), the mice were treated with 2.5 mg/kg and 5 mg/kg HNG for 16 days. Dramatically increased lung weight index, elevated number of monocytes, eosinophils, and neutrophils, promoted production of Th2 cytokines including interleukin-4 (IL-4), interleukin-5 (IL-5), and interleukin-13 (IL-13), and severe histological pathology were observed in OVA-challenged mice, all of which were extremely alleviated by 2.5 mg/kg and 5 mg/kg HNG. Furthermore, the increased malondialdehyde (MDA) level and declined superoxide dismutase (SOD) activity in OVA-challenged mice were abolished by 2.5 mg/kg and 5 mg/kg HNG. Lastly, the upregulated TLR4, p-NF-κB p65, and early growth response 1 (Egr-1) in lung tissues of OVA-challenged mice were pronouncedly downregulated by 2.5 mg/kg and 5 mg/kg HNG. Collectively, our data suggested that HNG ameliorated airway inflammation in asthma partially due to NF-κB and Egr-1-mediated responses.

Lysophosphatidic Acid Induces Podocyte Pyroptosis in Diabetic Nephropathy by an Increase of Egr1 Expression via Downregulation of EzH2

Podocyte damage and renal inflammation are the main features and pathogenesis of diabetic nephropathy (DN). Inhibition of lysophosphatidic acid (LPA) receptor 1 (LPAR1) suppresses glomerular inflammation and improves DN. Herein, we investigated LPA-induced podocyte damage and its underlying mechanisms in DN. We investigated the effects of AM095, a specific LPAR1 inhibitor, on podocytes from streptozotocin (STZ)-induced diabetic mice. E11 cells were treated with LPA in the presence or absence of AM095, and the expression of NLRP3 inflammasome factors and pyroptosis were measured. A chromatin immunoprecipitation assay and Western blotting were performed to elucidate underlying molecular mechanisms. Gene knockdown by transfecting small interfering RNA was used to determine the role of the transcription factor Egr1 (early growth response protein 1) and histone methyltransferase EzH2 (Enhancer of Zeste Homolog 2) in LPA-induced podocyte injury. AM095 administration inhibited podocyte loss, NLRP3 inflammasome factor expression, and cell death in STZ-induced diabetic mice. In E11 cells, LPA increased NLRP3 inflammasome activation and pyroptosis via LPAR1. Egr1 mediated NLRP3 inflammasome activation and pyroptosis in LPA-treated E11 cells. LPA decreased H3K27me3 enrichment at the Egr1 promoter in E11 cells by downregulating EzH2 expression. EzH2 knockdown further increased LPA-induced Egr1 expression. In podocytes from STZ-induced diabetic mice, AM095 suppressed Egr1 expression increase and EzH2/H3K27me3 expression reduction. Collectively, these results demonstrate that LPA induces NLRP3 inflammasome activation by downregulating EzH2/H3K27me3 and upregulating Egr1 expression, resulting in podocyte damage and pyroptosis, which may be a potential mechanism of DN progression.

Identification of AKI signatures and classification patterns in ccRCC based on machine learning

Background

Acute kidney injury can be mitigated if detected early. There are limited biomarkers for predicting acute kidney injury (AKI). In this study, we used public databases with machine learning algorithms to identify novel biomarkers to predict AKI. In addition, the interaction between AKI and clear cell renal cell carcinoma (ccRCC) remain elusive.

Methods

Four public AKI datasets (GSE126805, GSE139061, GSE30718, and GSE90861) treated as discovery datasets and one (GSE43974) treated as a validation dataset were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed genes (DEGs) between AKI and normal kidney tissues were identified using the R package limma. Four machine learning algorithms were used to identify the novel AKI biomarkers. The correlations between the seven biomarkers and immune cells or their components were calculated using the R package ggcor. Furthermore, two distinct ccRCC subtypes with different prognoses and immune characteristics were identified and verified using seven novel biomarkers.

Results

Seven robust AKI signatures were identified using the four machine learning methods. The immune infiltration analysis revealed that the numbers of activated CD4 T cells, CD56^dim natural killer cells, eosinophils, mast cells, memory B cells, natural killer T cells, neutrophils, T follicular helper cells, and type 1 T helper cells were significantly higher in the AKI cluster. The nomogram for prediction of AKI risk demonstrated satisfactory discrimination with an Area Under the Curve (AUC) of 0.919 in the training set and 0.945 in the testing set. In addition, the calibration plot demonstrated few errors between the predicted and actual values. In a separate analysis, the immune components and cellular differences between the two ccRCC subtypes based on their AKI signatures were compared. Patients in the CS1 had better overall survival, progression-free survival, drug sensitivity, and survival probability.

Conclusion

Our study identified seven distinct AKI-related biomarkers based on four machine learning methods and proposed a nomogram for stratified AKI risk prediction. We also confirmed that AKI signatures were valuable for predicting ccRCC prognosis. The current work not only sheds light on the early prediction of AKI, but also provides new insights into the correlation between AKI and ccRCC.

Single-cell RNA sequencing reveals the transcriptomic landscape of kidneys in patients with ischemic acute kidney injury

BACKGROUND

Ischemic acute kidney injury (AKI) is a common syndrome associated with considerable mortality and healthcare costs. Up to now, the underlying pathogenesis of ischemic AKI remains incompletely understood, and specific strategies for early diagnosis and treatment of ischemic AKI are still lacking. Here, this study aimed to define the transcriptomic landscape of AKI patients through single-cell RNA sequencing (scRNA-seq) analysis in kidneys.

METHODS

In this study, scRNA-seq technology was applied to kidneys from two ischemic AKI patients, and three human public scRNA-seq datasets were collected as controls. Differentially expressed genes (DEGs) and cell clusters of kidneys were determined. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis, as well as the ligand-receptor interaction between cells, were performed. We also validated several DEGs expression in kidneys from human ischemic AKI and ischemia/reperfusion (I/R) injury induced AKI mice through immunohistochemistry staining.

RESULTS

15 distinct cell clusters were determined in kidney from subjects of ischemic AKI and control. The injured proximal tubules (PT) displayed a proapoptotic and proinflammatory phenotype. PT cells of ischemic AKI had up-regulation of novel pro-apoptotic genes including USP47 , RASSF4 , EBAG9 , IER3 , SASH1 , SEPTIN7 , and NUB1 , which have not been reported in ischemic AKI previously. Several hub genes were validated in kidneys from human AKI and renal I/R injury mice, respectively. Furthermore, PT highly expressed DEGs enriched in endoplasmic reticulum stress, autophagy, and retinoic acid-inducible gene I (RIG-I) signaling. DEGs overexpressed in other tubular cells were primarily enriched in nucleotide-binding and oligomerization domain (NOD)-like receptor signaling, estrogen signaling, interleukin (IL)-12 signaling, and IL-17 signaling. Overexpressed genes in kidney-resident immune cells including macrophages, natural killer T (NKT) cells, monocytes, and dendritic cells were associated with leukocyte activation, chemotaxis, cell adhesion, and complement activation. In addition, the ligand-receptor interactions analysis revealed prominent communications between macrophages and monocytes with other cells in the process of ischemic AKI.

CONCLUSION

Together, this study reveals distinct cell-specific transcriptomic atlas of kidney in ischemic AKI patients, altered signaling pathways, and potential cell-cell crosstalk in the development of AKI. These data reveal new insights into the pathogenesis and potential therapeutic strategies in ischemic AKI.

Lipid Deposition Profiles Influence Foreign Body Responses

Fibrosis remains a significant cause of failure in implanted biomedical devices and early absorption of proteins on implant surfaces has been shown to be a key instigating factor. However, lipids can also regulate immune activity and their presence may also contribute to biomaterial-induced foreign body responses (FBR) and fibrosis. Here it is demonstrated that the surface presentation of lipids on implant affects FBR by influencing reactions of immune cells to materials as well as their resultant inflammatory/suppressive polarization. Time-of-flight secondary ion mass spectroscopy (ToF-SIMS) is employed to characterize lipid deposition on implants that are surface-modified chemically with immunomodulatory small molecules. Multiple immunosuppressive phospholipids (phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, and sphingomyelin) are all found to deposit preferentially on implants with anti-FBR surface modifications in mice. Significantly, a set of 11 fatty acids is enriched on unmodified implanted devices that failed in both mice and humans, highlighting relevance across species. Phospholipid deposition is also found to upregulate the transcription of anti-inflammatory genes in murine macrophages, while fatty acid deposition stimulated the expression of pro-inflammatory genes. These results provide further insights into how to improve the design of biomaterials and medical devices to mitigate biomaterial material-induced FBR and fibrosis.

Fibulin7 aggravates calcium oxalate-induced acute kidney injury by binding to calcium oxalate crystals

Fibulin7 (Fbln7) is a matricellular protein that is structurally similar to short fibulins but does not possess elastogenic abilities. Fbln7 is localized on the cell surface of the renal tubular epithelium in the adult kidney. We previously reported that Fbln7 binds artificial calcium phosphate particles in vitro, and that heparin counteracts this binding by releasing Fbln7 from the cell surface. Fbln7 gene (Fbln7) deletion in vivo decreased interstitial fibrosis and improved renal function in a high phosphate diet-induced chronic kidney disease mouse model. However, the contribution of Fbln7 during acute injury response remains largely unknown. We hypothesized that Fbln7 serves as an exacerbating factor in acute kidney injury (AKI). We employed three AKI models in vivo and in vitro, including unilateral ureteral obstruction (UUO), cisplatin-induced AKI, and calcium oxalate (CaOx)-induced AKI. Here, we report that Fbln7KO mice were protected from kidney damage in a CaOx-induced AKI model. Using HEK293T cells, we found that Fbln7 overexpression enhanced the CaOx-induced upregulation of EGR1 and LAMB3, and that heparin treatment canceled this effect. Interestingly, the protective function observed in Fbln7KO kidneys was limited to the CaOx-induced AKI model, while Fbln7KO mice were not protected against UUO-induced renal fibrosis or cisplatin-induced renal tubular damage. Taken together, our study indicates that Fbln7 mediates the local deposition of CaOx and damages the renal tubular epithelium. Releasing Fbln7 from the cell surface via heparin/heparin derivatives or Fbln7 inhibitory antibodies may provide a general strategy to mitigate calcium crystal-induced kidney injuries.

Single-cell profiling of peripheral blood and muscle cells reveals inflammatory features of juvenile dermatomyositis

Introduction: Juvenile dermatomyositis (JDM) is a rare yet serious childhood systemic autoimmune condition that primarily causes skin rashes and inflammatory myopathy of the proximal muscles. Although the associated immune response involves the innate and adaptive arms, a detailed analysis of the pertinent immune cells remains to be performed. This study aims to investigate the dynamic changes of cell type, cell composition and transcriptional profiles in peripheral blood and muscle tissues, and in order to clarify the involvement of immune cells in the pathogenesis of JDM and provide a theoretical reference for JDM. Methods: Single-cell RNA sequencing combined with bioinformatic analyses were used to investigate the dynamic changes in cell composition and transcriptional profiles. Results: Analysis of 45,859 cells revealed nine and seven distinct cell subsets in the peripheral blood and muscle tissues respectively. IFITM2+ and CYP4F3+ monocytes were largely produced, and CD74⁺ smooth muscle cells (SMCs) and CCL19+ fibroblasts were identified as inflammatory-related cell subtypes in JDM patients, exhibiting patient-specific cell population heterogeneity.The dynamic gene expression patterns presented an enhanced type I interferon response in peripheral blood monocytes and T-cells, and SMCs and fibroblasts in muscle of untreated JDM patients. EGR1 and IRF7 may play central roles in the inflammation in both CD74⁺ SMCs and CCL19+ fibroblasts. Moreover, inflammatory-related monocytes could regulate T-cells, and the interaction between immune cells and SMCs or fibroblasts in muscle was enhanced under the inflammatory state. Conclusions: Immune dysregulation is one of the key pathogenic factors of JDM, and type I interferon responses are significantly enhanced in peripheral blood Monos and T cells as well as SMCs and fibroblasts. EGR1 and IRF7 may play central roles in the inflammation and are considered as potential therapeutic targets for JDM.

Calycosin attenuates renal ischemia/reperfusion injury by suppressing NF-κB mediated inflammation via PPARγ/EGR1 pathway

Renal ischemia reperfusion injury (IRI) is a leading and common cause of acute kidney injury (AKI), and inflammation is a critical factor in ischemic AKI progression. Calycosin (CAL), a major active component of Radix astragali, has been reported to have anti-inflammatory effect in multiple organs. However, whether CAL can alleviate renal IRI and its mechanism remain uncertain. In the present study, a renal IRI model is established by bilateral renal pedicles occlusion for 35 min in male C57BL/6 mice, and the effect of CAL on renal IRI is measured by serum creatinine and pathohistological assay. Hypoxia/reoxygenation (H/R) stimulated human renal tubular epithelial cells HK-2 were applied to explore the regulatory mechanisms of CAL. Luciferase reporter assay and molecular docking were applied to identify the CAL's target protein and pathway. In the mice with renal IRI, CAL dose dependently alleviated the renal injury and decreased nuclear factor kappa B (NF-κB) mediated inflammatory response. Bioinformatics analysis and experiments showed that early growth response 1 (EGR1) increased in mice with renal IRI and promoted NF-κB mediated inflammatory processes, and CAL dose-dependably reduced EGR1. Through JASPAR database and luciferase reporter assay, peroxisome proliferator-activated receptor γ (PPARγ) was predicted to be a transcription factor of EGR1 and repressed the expression of EGR1 in renal tubular epithelial cells. CAL could increase PPARγ in a dose dependent manner in mice with renal IRI and molecular docking predicted CAL could bind stably to PPARγ. In HK-2 cells after H/R, CAL increased PPARγ, decreased EGR1, and inhibited NF-κB mediated inflammatory response. However, PPARγ knockdown by siRNA transfection abrogated the anti-inflammation therapeutic effect of CAL. CAL produced a protective effect on renal IRI by attenuating NF-κB mediated inflammatory response via PPARγ/EGR1 pathway.

Fucoidan-Mediated Inhibition of Fibrotic Properties in Oral Submucous Fibrosis via the MEG3/miR-181a/Egr1 Axis

Oral submucous fibrosis (OSF) is a chronic fibrotic remodeling disease that can progress to oral cancer. However, efficient clinical diagnosis and treatment methods for OSF are still lacking. This study investigated the anti-fibrotic effect of fucoidan on oral fibrosis. To evaluate the fibrotic ability (myofibroblast activities), we performed wound-healing, Transwell migration, and collagen contraction assays by using patient-derived normal and fibrotic buccal submucous fibroblasts (BMFs and fBMFs, respectively). RNA-sequencing and dual-luciferase reporter and RNA immunoprecipitation chip assays were performed to identify the clinical significance and molecular mechanism of non-coding RNAs. Fucoidan suppressed the myofibroblast activities and inhibited the MEG3 in fBMFs. MEG3 was overexpressed in the OSF tissue and was positively associated with myofibroblast markers. Knockdown of MEG3 markedly inhibited myofibroblast activities, which were restored by inhibiting miR-181a and overexpressing Egr1. The results from luciferase reporter and RIP assays confirmed that MEG3 functioned as a competing endogenous RNA (ceRNA) and could directly target miR-181a, thereby preventing the miR-181a-mediated translational repression of Egr1. This study demonstrated that MEG3 exerts a profibrotic effect on OSF by targeting miR-181a/Egr1. Therefore, the administration of fucoidan may serve as a potential therapeutic strategy for OSF by targeting the overexpression of MEG3.

miR‑let‑7c‑3p targeting on Egr‑1 contributes to the committed differentiation of leukemia cells into monocyte/macrophages

In preliminary experiments, it was found that the expression of early growth response-1 (Egr-1) was upregulated during the committed differentiation of leukemia cells into monocytes/macrophages. The cross-analysis of gene chip detection and database prediction indicated that Egr-1 was associated with upstream microRNA (miR)-let-7c-3p, thus the present study focused on the role of the miR-let-7c-3p/Egr-1 signaling axis in the committed differentiation of leukemia cells into monocytes/macrophages. Phorbol 12-myristate 13-acetate (PMA) was used to induce the directed differentiation of human K562 leukemia cells into monocytes/macrophages and the differentiation of K562 leukemia cells was determined by cell morphology observation and expression of differentiation antigens CD11b and CD14 by flow cytometry. The expression levels of Egr-1 and miR-let-7c-3p were detected by reverse transcription-quantitative PCR and the protein expression of Egr-1 was detected by western blotting. The effect of Egr-1 on the differentiation of K562 cells was detected by short interfering (si)RNA interference assay. A dual-luciferase reporter assay was used to detect target binding of miR-let-7c-3p on the 3′UTR of Egr-1. Cell transfection of miR-let-7c-3p mimics and inhibitors was used to modulate the expression of miR-let-7c-3p, as indicated by RT-qPCR assays. Western blotting was also used to examine the effect of miR-let-7c-3p on Egr-1 expression. The PMA-induced differentiation of K562 cells was transfected with miR-let-7c-3p and the expression of differentiation antigen was detected by flow cytometry. A differentiation model of K562 leukemia cells into monocytes/macrophages was induced by PMA, which was indicated by morphological observations and upregulation of CD11b and CD14 antigens. The gene or protein expression of Egr-1 was significantly higher compared with that of the control group, while the expression of miR-let-7c-3p was significantly lower compared with that of the control group. siRNA interference experiments showed that the expression of cell differentiation antigen CD14 in the 100 µg/ml PMA + si-Egr-1 group was significantly lower compared with that in the 100 µg/ml PMA + si-ctrl group. The dual luciferase reporter gene results showed that the luciferase activity of the co-transfected mimic and Egr-1 WT groups was significantly lower than that of the NC control group, while the luciferase activity of the co-transfected mimic and Egr-1 MUT groups was comparable to that of the NC control group. Therefore, the dual-luciferase reporter gene assay confirmed that miR-let-7c-3p can target Egr-1. Western blotting showed that the expression of Egr-1 following transfection with miR-let-7c-3p inhibitor was significantly higher compared with that of the negative control and the expression of Egr-1 after transfection with miR-let-7c-3p mimic was significantly lower than that of the negative control. Following exposure to PMA, the expressions of CD11b and CD14 in the miR-let-7c-3p inhibitor group were significantly higher than those in the miR-let-7c-3p NC group, as indicated by CD11b and CD14 respectively. In conclusion, miR-let-7c-3p could bind to the 3′UTR of Egr-1 and negatively regulated Egr-1 expression. The miR-let-7c-3p/Egr-1 signaling axis was closely associated with the committed differentiation of K562 cells from leukemia cells to monocytes/macrophages.

Genetic or siRNA inhibition of MBD2 attenuates the UUO- and I/R-induced renal fibrosis via downregulation of EGR1

DNA methylation plays a pivotal role in the progression of renal fibrosis. Methyl-CpG–binding domain protein 2 (MBD2), a protein reader of methylation, is involved in the development of acute kidney injury (AKI) caused by vancomycin. However, the role and mechanism of action of MBD2 in renal remain unclear. In this study, MBD2 mediated extracellular matrix (ECM) production induced by TGF-β1 in Boston University mouse proximal tubule (BUMPT) cells，and upregulated the expression EGR1 to promote ECM production in murine embryonic NIH 3T3 fibroblasts. ChIP analysis demonstrated that MBD2 physically interacted with the promoter region of the CpG islands of EGR1 genes and then activated their expression by inducing hypomethylation of the promoter region. In vivo, PT-MBD2-KO attenuated unilateral ureteral obstruction (UUO)-induced renal tubulointerstitial fibrosis via downregulation of EGR1, which was demonstrated by the downregulation of fibronectin (FN), collagen I and IV, α-SMA, and EGR1. Injection of MBD2-siRNA attenuated the UUO- and I/R-induced renal fibrosis. Those molecular changes were verified by biopsies from patients with obstructive nephropathy (OB). These data collectively demonstrated that inhibition of MBD2 reduces renal fibrosis via downregulating EGR1, which could be a target for treatment of fibrotic kidney disease.

EGR1 Upregulation during Encephalitic Viral Infections Contributes to Inflammation and Cell Death

Early growth response 1 (EGR1) is an immediate early gene and transcription factor previously found to be significantly upregulated in human astrocytoma cells infected with Venezuelan equine encephalitis virus (VEEV). The loss of EGR1 resulted in decreased cell death but had no significant impact on viral replication. Here, we extend these studies to determine the impacts of EGR1 on gene expression following viral infection. Inflammatory genes CXCL3, CXCL8, CXCL10, TNF, and PTGS2 were upregulated in VEEV-infected cells, which was partially dependent on EGR1. Additionally, transcription factors, including EGR1 itself, as well as ATF3, FOS, JUN, KLF4, EGR2, and EGR4 were found to be partially transcriptionally dependent on EGR1. We also examined the role of EGR1 and the changes in gene expression in response to infection with other alphaviruses, including eastern equine encephalitis virus (EEEV), Sindbis virus (SINV), and chikungunya virus (CHIKV), as well as Zika virus (ZIKV) and Rift Valley fever virus (RVFV), members of the Flaviviridae and Phenuiviridae families, respectively. EGR1 was significantly upregulated to varying degrees in EEEV-, CHIKV-, RVFV-, SINV-, and ZIKV-infected astrocytoma cells. Genes that were identified as being partially transcriptionally dependent on EGR1 in infected cells included ATF3 (EEEV, CHIKV, ZIKV), JUN (EEEV), KLF4 (SINV, ZIKV, RVFV), CXCL3 (EEEV, CHIKV, ZIKV), CXCL8 (EEEV, CHIKV, ZIKV, RVFV), CXCL10 (EEEV, RVFV), TNF-α (EEEV, ZIKV, RVFV), and PTGS2 (EEEV, CHIKV, ZIKV). Additionally, inhibition of the inflammatory gene PTGS2 with Celecoxib, a small molecule inhibitor, rescued astrocytoma cells from VEEV-induced cell death but had no impact on viral titers. Collectively, these results suggest that EGR1 induction following viral infection stimulates multiple inflammatory mediators. Managing inflammation and cell death in response to viral infection is of utmost importance, especially during VEEV infection where survivors are at-risk for neurological sequalae.

Independent of Renox, NOX5 Promotes Renal Inflammation and Fibrosis in Diabetes by Activating ROS-Sensitive Pathways

Excessive production of renal reactive oxygen species (ROS) plays a major role in diabetic kidney disease (DKD). Here, we provide key findings demonstrating the predominant pathological role of the pro-oxidant enzyme NADPH oxidase 5 (NOX5) in DKD, independent of the previously characterized NOX4 pathway. In patients with diabetes, we found increased expression of renal NOX5 in association with enhanced ROS formation and upregulation of ROS-sensitive factors early growth response 1 (EGR-1), protein kinase C-α (PKC-α), and a key metabolic gene involved in redox balance, thioredoxin-interacting protein (TXNIP). In preclinical models of DKD, overexpression of NOX5 in Nox4-deficient mice enhances kidney damage by increasing albuminuria and augmenting renal fibrosis and inflammation via enhanced ROS formation and the modulation of EGR1, TXNIP, ERK1/2, PKC-α, and PKC-ε. In addition, the only first-in-class NOX inhibitor, GKT137831, appears to be ineffective in the presence of NOX5 expression in diabetes. In vitro, silencing of NOX5 in human mesangial cells attenuated upregulation of EGR1, PKC-α, and TXNIP induced by high glucose levels, as well as markers of inflammation (TLR4 and MCP-1) and fibrosis (CTGF and collagens I and III) via reduction in ROS formation. Collectively, these findings identify NOX5 as a superior target in human DKD compared with other NOX isoforms such as NOX4, which may have been overinterpreted in previous rodent studies.

The protective effects of cabozantinib against high glucose-induced damages in in vitro renal glomerular endothelial cells model via inhibition of early growth response-1 (Egr-1)

Cabozantinib is a tyrosine kinase inhibitor with anti-tumor activity in kidney cancer. However, the efficacy of cabozantinib in other renal diseases has never been reported. Here, we focused on exploring the effect of cabozantinib on diabetic nephropathy (DN). The biofunctions of cabozantinib in human renal glomerular endothelial cells (hGECs) under high glucose conditions have been investigated. We found that cabozantinib ameliorated high glucose-induced oxidative stress in hGECs with decreased production of mitochondrial reactive oxygen species (ROS) and increased glutathione peroxidase (GSH-PX) activity. Cabozantinib ameliorated high glucose-induced reduction in the expression of endothelial nitric oxide synthase (eNOS) and the production of nitric oxide (NO) in hGECs. It also suppressed the expression of pro-inflammatory mediators, interleukin-6 (IL-6) and monocyte chemokine protein 1 (MCP-1), against high glucose exposure in hGECs. Cabozantinib reduced the expression of early growth response-1 (Egr-1) in high glucose-treated hGECs, while Egr-1 overexpression abolished the protective effects of cabozantinib against high glucose in hGECs. In conclusion, cabozantinib protected hGECs from high glucose-induced oxidative stress, NO deficiency, and inflammation via regulating Egr-1. These findings suggest that cabozantinib might be used as an adjuvant to control DN.

GPR43 activation-mediated lipotoxicity contributes to podocyte injury in diabetic nephropathy by modulating the ERK/EGR1 pathway

Background: G-protein-coupled receptor 43 (GPR43) is a posttranscriptional regulator involved in cholesterol metabolism. This study aimed to investigate the possible roles of GPR43 activation in podocyte lipotoxicity in diabetic nephropathy (DN) and explore the potential mechanisms.

Methods: The experiments were conducted by using diabetic GPR43-knockout mice and a podocyte cell culture model. Lipid deposition and free cholesterol levels in kidney tissues were measured by BODIPY staining and quantitative cholesterol assays, respectively. The protein expression of GPR43, LC3II, p62, beclin1, low-density lipoprotein receptor (LDLR) and early growth response protein 1 (EGR1) in kidney tissues and podocytes was measured by real-time PCR, immunofluorescent staining and Western blotting.

Results: There were increased LDL cholesterol levels in plasma and cholesterol accumulation in the kidneys of diabetic mice. However, GPR43 gene knockout inhibited these changes. An in vitro study further demonstrated that acetate treatment induced cholesterol accumulation in high glucose-stimulated podocytes, which was correlated with increased cholesterol uptake mediated by LDLR and reduced cholesterol autophagic degradation, as characterized by the inhibition of LC3 maturation, p62 degradation and autophagosome formation. Gene knockdown or pharmacological inhibition of GPR43 prevented these effects on podocytes. Furthermore, GPR43 activation increased extracellular regulated protein kinases 1/2 (ERK1/2) activity and EGR1 expression in podocytes, which resulted in an increase in cholesterol influx and autophagy inhibition. In contrast, after GPR43 deletion, these changes in podocytes were improved, as shown by the in vivo and in vitro results.

Conclusion: GPR43 activation-mediated lipotoxicity contributes to podocyte injury in DN by modulating the ERK/EGR1 pathway.

Identification of miRNA-mRNA network and immune-related gene signatures in IgA nephropathy by integrated bioinformatics analysis

BACKGROUND

IgA nephropathy (IgAN) is the most common form of primary glomerulonephritis worldwide, and its diagnosis depends mainly on renal biopsy. However, there is no specific treatment for IgAN. Moreover, its causes and underlying molecular events require further exploration.

METHODS

The expression profiles of GSE64306 and GSE93798 were downloaded from the Gene Expression Omnibus (GEO) database and used to identify the differential expression of miRNAs and genes, respectively. The StarBase and TransmiR databases were employed to predict target genes and transcription factors of the differentially expressed miRNAs (DE-miRNAs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were conducted to predict biological functions. A comprehensive analysis of the miRNA-mRNA regulatory network was constructed, and protein-protein interaction (PPI) networks and hub genes were identified. CIBERSORT was used to examine the immune cells in IgAN, and correlation analyses were performed between the hub genes and infiltrating immune cells.

RESULTS

Four downregulated miRNAs and 16 upregulated miRNAs were identified. Forty-five and twelve target genes were identified for the upregulated and downregulated DE-miRNAs, respectively. CDKN1A, CDC23, EGR1, HIF1A, and TRIM28 were the hub genes with the highest degrees of connectivity. CIBERSORT revealed increases in the numbers of activated NK cells, M1 and M2 macrophages, CD4 naive T cells, and regulatory T cells in IgAN. Additionally, HIF1A, CDC23, TRIM28, and CDKN1A in IgAN patients were associated with immune cell infiltration.

CONCLUSIONS

A potential miRNA-mRNA regulatory network contributing to IgAN onset and progression was successfully established. The results of the present study may facilitate the diagnosis and treatment of IgAN by targeting established miRNA-mRNA interaction networks. Infiltrating immune cells may play significant roles in IgAN pathogenesis. Future studies on these immune cells may help guide immunotherapy for IgAN patients.

Early Growth Response-1, an Integrative Sensor in Cardiovascular and Inflammatory Disease

Early growth response‐1 (Egr‐1) is a master regulator and transcriptional sensor in vascular dysfunction and disease. This article reviews recent developments in our understanding of the regulatory roles this zinc finger protein and product of an immediate‐early gene plays in a range of cardiovascular and inflammatory disorders. Egr‐1 can amplify pathologic signals from the extracellular environment by serving as a molecular conduit in the inducible expression of proliferative, migratory and proinflammatory genes driving disease progression. Strategies targeting Egr‐1 may provide therapeutic benefit in cardiovascular and inflammatory disorders.

The Role of Short-Chain Fatty Acids of Gut Microbiota Origin in Hypertension

Hypertension is a significant risk factor for cardiovascular and cerebrovascular diseases, and its development involves multiple mechanisms. Gut microbiota has been reported to be closely linked to hypertension. Short-chain fatty acids (SCFAs)-the metabolites of gut microbiota-participate in hypertension development through various pathways, including specific receptors, immune system, autonomic nervous system, metabolic regulation and gene transcription. This article reviews the possible mechanisms of SCFAs in regulating blood pressure and the prospects of SCFAs as a target to prevent and treat hypertension.

Multi-omics approaches for revealing the complexity of cardiovascular disease

The development and progression of cardiovascular disease (CVD) can mainly be attributed to the narrowing of blood vessels caused by atherosclerosis and thrombosis, which induces organ damage that will result in end-organ dysfunction characterized by events such as myocardial infarction or stroke. It is also essential to consider other contributory factors to CVD, including cardiac remodelling caused by cardiomyopathies and co-morbidities with other diseases such as chronic kidney disease. Besides, there is a growing amount of evidence linking the gut microbiota to CVD through several metabolic pathways. Hence, it is of utmost importance to decipher the underlying molecular mechanisms associated with these disease states to elucidate the development and progression of CVD. A wide array of systems biology approaches incorporating multi-omics data have emerged as an invaluable tool in establishing alterations in specific cell types and identifying modifications in signalling events that promote disease development. Here, we review recent studies that apply multi-omics approaches to further understand the underlying causes of CVD and provide possible treatment strategies by identifying novel drug targets and biomarkers. We also discuss very recent advances in gut microbiota research with an emphasis on how diet and microbial composition can impact the development of CVD. Finally, we present various biological network analyses and other independent studies that have been employed for providing mechanistic explanation and developing treatment strategies for end-stage CVD, namely myocardial infarction and stroke.

Aging, inflammation and DNA damage in the somatic testicular niche with idiopathic germ cell aplasia

Molecular mechanisms associated with human germ cell aplasia in infertile men remain undefined. Here we perform single-cell transcriptome profiling to highlight differentially expressed genes and pathways in each somatic cell type in testes of men with idiopathic germ cell aplasia. We identify immaturity of Leydig cells, chronic tissue inflammation, fibrosis, and senescence phenotype of the somatic cells, as well markers of chronic inflammation in the blood. We find that deregulated expression of parentally imprinted genes in myoid and immature Leydig cells, with relevant changes in the ratio of Lamin A/C transcripts and an active DNA damage response in Leydig and peritubular myoid cells are also indicative of senescence of the testicular niche. This study offers molecular insights into the pathogenesis of idiopathic germ cell aplasia.

Molecular mechanisms associated with human germ cell aplasia in infertile men remain undefined. Here the authors perform single-cell transcriptome profiling to highlight differentially expressed genes and pathways in each somatic cell type in testes of men with idiopathic germ cell aplasia.

Long Non-coding RNA: An Emerging Contributor and Potential Therapeutic Target in Renal Fibrosis

Renal fibrosis (RF) is a pathological process that culminates in terminal renal failure in chronic kidney disease (CKD). Fibrosis contributes to progressive and irreversible decline in renal function. However, the molecular mechanisms involved in RF are complex and remain poorly understood. Long non-coding RNAs (lncRNAs) are a major type of non-coding RNAs, which significantly affect various disease processes, cellular homeostasis, and development through multiple mechanisms. Recent investigations have implicated aberrantly expressed lncRNA in RF development and progression, suggesting that lncRNAs play a crucial role in determining the clinical manifestation of RF. In this review, we comprehensively evaluated the recently published articles on lncRNAs in RF, discussed the potential application of lncRNAs as diagnostic and/or prognostic biomarkers, proposed therapeutic targets for treating RF-associated diseases and subsequent CKD transition, and highlight future research directions in the context of the role of lncRNAs in the development and treatment of RF.

Epigenetic regulation of TXNIP-mediated oxidative stress and NLRP3 inflammasome activation contributes to SAHH inhibition-aggravated diabetic nephropathy

S-adenosylhomocysteine (SAH) is hydrolyzed by SAH hydrolase (SAHH) to homocysteine and adenosine. Increased plasma SAH levels were associated with disturbed renal function in patients with diabetes. However, the role and mechanism of SAHH in diabetic nephropathy is still unknown. In the present study, we found that inhibition of SAHH by using its inhibitor adenosine dialdehyde (ADA) accumulates intracellular or plasma SAH levels and increases high glucose-induced podocyte injury and aggravates STZ-induced diabetic nephropathy, which is associated with Nod-like receptor protein 3 (NLRP3) inflammasome activation. Inhibition or knockout of NLRP3 attenuates SAHH inhibition-aggravated podocyte injury and diabetic nephropathy. Additionally, SAHH inhibition increases thioredoxin-interacting protein (TXNIP)-mediated oxidative stress and NLRP3 inflammasome activation, but these effects were not observed in TXNIP knockout mice. Mechanistically, SAHH inhibition increased TXNIP by inhibiting histone methyltransferase enhancer of zeste homolog 2 (EZH2) and reduced trimethylation of histone H3 lysine 27 and its enrichment at promoter of early growth response 1 (EGR1). Moreover, EGR1 is activated and enriched at promoters of TXNIP by SAHH inhibition and is essential for SAHH inhibition-induced TXNIP expression. Inhibition of EGR1 protected against SAHH inhibition-induced NLRP3 inflammasome activation and oxidative stress and diabetic nephropathy. Finally, the harmful effects of SAHH inhibition on inflammation and oxidative stress and diabetic nephropathy were also observed in heterozygote SAHH knockout mice. These findings suggest that EZH2/EGR1/TXNIP/NLRP3 signaling cascade contributes to SAHH inhibition-aggravated diabetic nephropathy. Our study firstly provides a novel insight into the role and mechanism of SAHH inhibition in diabetic nephropathy.

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SAHH inhibition accumulates SAH levels and aggravates podocyte injury and diabetic nephropathy.

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SAHH inhibition induces TXNIP-mediated oxidative stress and NLRP3 inflammasome activation.

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SAHH inhibition increases TXNIP by inhibiting EZH2 and reducing H3K27me3 and its enrichment at promoter of EGR1.

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EGR1 is required for SAHH inhibition-induced TXNIP and NLRP3 inflammasome activation and diabetic nephropathy.

Klotho prevents epithelial-mesenchymal transition through Egr-1 downregulation in diabetic kidney disease

INTRODUCTION

As a key event leading to tubulointerstitial fibrosis in diabetic kidney disease (DKD), epithelial-mesenchymal transition (EMT) has drawn increasing attention from researchers. The antiaging protein Klotho attenuates renal fibrosis in part by inhibiting ERK1/2 signaling in DKD. Early growth response factor 1 (Egr-1), which is activated mainly by ERK1/2, has been shown to play an important role in EMT. However, whether Klotho prevents EMT by inhibiting ERK1/2-dependent Egr-1 expression in DKD is unclear.The aim of this study was to investigate whether Klotho prevents EMT through Egr-1 downregulation by inhibiting the ERK1/2 signaling pathway in DKD.

RESEARCH DESIGN AND METHODS

Male C57BL/6J mice fed an high-fat diet for 4 weeks received 120 mg/kg streptozotocin (STZ), which was injected intraperitoneally. Klotho and Egr-1 expression was detected in the renal cortices of these mice on their sacrifice at 6 and 12 weeks after STZ treatment. In In vitro studies, we incubated HK2 cells under high-glucose (HG) or transforming growth factor-β1 (TGF-β1) conditions to mimic DKD. We then transfected the cells with an Klotho-containing plasmid, Klotho small interfering RNA.

RESULTS

Klotho expression was significantly decreased in the renal cortices of mice with diabetes mellitus (DM) compared with the renal cortices of control mice at 6 weeks after treatment and even more significantly decreased at 12 weeks. In contrast, Egr-1 expression was significantly increased in mice with DM compared with control mice only at 12 weeks. We also found that Klotho overexpression downregulated Egr-1 expression and the (p-ERK1/2):(ERK1/2) ratio in HG-treated or TGF-β1-treated HK2 cells. Conversely, Klotho silencing upregulated Egr-1 expression and the (p-ERK1/2):(ERK1/2) ratio in HG-treated or TGF-β1-treated HK2 cells. Moreover, the effects of si-Klotho were abolished by the ERK1/2 inhibitor PD98059.

CONCLUSIONS

Klotho prevents EMT during DKD progression, an effect that has been partially attributed to Egr-1 downregulation mediated by ERK1/2 signaling pathway inhibition.

Adult Zebrafish Model for Screening Drug-Induced Kidney Injury

Drug-induced kidney injury is a serious safety issue in drug development. In this study, we evaluated the usefulness of adult zebrafish as a small in vivo system for detecting drug-induced kidney injury. We first investigated the effects of typical nephrotoxicants, gentamicin and doxorubicin, on adult zebrafish. We found that gentamicin induced renal tubular necrosis with increased lysosome and myeloid bodies, and doxorubicin caused foot process fusion of glomerular podocytes. These findings were similar to those seen in mammals, suggesting a common pathogenesis. Second, to further evaluate the performance of the model in detecting drug-induced kidney injury, adult zebrafish were treated with 28 nephrotoxicants or 14 nonnephrotoxicants for up to 4 days, euthanized 24 h after the final treatment, and examined histopathologically. Sixteen of the 28 nephrotoxicants and none of the 14 nonnephrotoxicants caused drug-induced kidney injury in zebrafish (sensitivity, 57%; specificity, 100%; positive predictive value, 100%; negative predictive value, 54%). Finally, we explored genomic biomarker candidates using kidneys isolated from gentamicin- and cisplatin-treated zebrafish using microarray analysis and identified 3 candidate genes, egr1, atf3, and fos based on increased expression levels and biological implications. The expression of these genes was upregulated dose dependently in cisplatin-treated groups and was > 25-fold higher in gentamicin-treated than in the control group. In conclusion, these results suggest that the adult zebrafish has (1) similar nephrotoxic response to those of mammals, (2) considerable feasibility as an experimental model for toxicity studies, and (3) applicability to pathological examination and genomic biomarker evaluation in drug-induced kidney injury.

Roles of Krüppel-like factor 5 in kidney disease

Transcription factor Krüppel-like factor 5 (KLF5) is a member of the Krüppel-like factors' (KLFs) family. KLF5 regulates a number of cellular functions, such as apoptosis, proliferation and differentiation. Therefore, KLF5 can play a role in many diseases, including, cancer, cardiovascular disease and gastrointestinal disorders. An important role for KLF5 in the kidney was recently reported, such that KLF5 regulated podocyte apoptosis, renal cell proliferation, tubulointerstitial inflammation and renal fibrosis. In this review, we have summarized the available information in the literature with a brief description on how transcriptional, post-transcriptional and post-translational modifications of KLF5 modulate its function in a variety of organs including the kidney with a focus of its importance on the pathogenesis of various kidney diseases. Furthermore, we also have outlined the current and possible mechanisms of KLF5 activation in kidney diseases. These studies suggest a need for more systemic investigations, particularly for generation of animal models with renal cell-specific deletion or overexpression of KLF5 gene to examine direct contributions of KLF5 to various kidney diseases. This will promote further experimentation in the development of therapies to prevent or treat various kidney diseases.

Early Growth Response Protein 1 Knockdown Alleviates the Cerebral Injury in Rats with Intracerebral Hemorrhage (ICH) via STAT3/NF-κB Pathway by Reducing RXRα Acetylation Level

Brain EGR1 (early growth response protein 1) overexpression aggravates focal ischemic brain injury, but its role in intracerebral hemorrhage (ICH) induced cerebral injury remains obscure. In this study, a rat ICH model was established by injecting type VII collagenase into the brain, and EGR1 knockdown reversed the increase of hematoma area, neurological function score, brain water content, blood-brain barrier (BBB) permeability, inflammation, p300 and retinoid a X receptor-α (RXRα) protein levels, as well as RXRα acetylation level induced by ICH. EGR1 expression was up-regulated in primary brain microvascular endothelial cells (BMECs), neurons, and astrocytes after ICH induction, and the up-regulation was most significant in BMECs. We also found that EGR1 promoted RXRα acetylation level by regulating p300 in BMECs. Subsequently, the BMECs were treated with OGD (oxygen glucose deprivation) plus hemin to simulate ICH condition. And silencing EGR1 rescued the upregulation of cell inflammation and the reduction of cell viability and TEER (transendothelial electric resistance) caused by OGD plus hemin via p300-mediated RXRα acetylation. Furthermore, the STAT3/NF-κB pathway was activated after treatment with OGD plus hemin, which was suppressed by silencing EGR1. And treatment with Stattic (an inhibitor of STAT3) restrained the effect of OGD plus hemin on NF-κB pathway activity, inflammation, cell viability and TEER. In conclusion, EGR1 increased RXRα acetylation level by regulating p300, thereby aggravating brain damage in ICH rat model and dysfunction in BMECs, which might through the STAT3/NF-κB pathway.

Integrative genomic meta-analysis reveals novel molecular insights into cystic fibrosis and ΔF508-CFTR rescue

Cystic fibrosis (CF), caused by mutations to CFTR, leads to severe and progressive lung disease. The most common mutant, ΔF508-CFTR, undergoes proteasomal degradation, extinguishing its anion channel function. Numerous in vitro interventions have been identified to partially rescue ΔF508-CFTR function yet remain poorly understood. Improved understanding of both the altered state of CF cells and the mechanisms of existing rescue strategies could reveal novel therapeutic strategies. Toward this aim, we measured transcriptional profiles of established temperature, genetic, and chemical interventions that rescue ΔF508-CFTR and also re-analyzed public datasets characterizing transcription in human CF vs. non-CF samples from airway and whole blood. Meta-analysis yielded a core disease signature and two core rescue signatures. To interpret these through the lens of prior knowledge, we compiled a "CFTR Gene Set Library" from literature. The core disease signature revealed remarkably strong connections to genes with established effects on CFTR trafficking and function and suggested novel roles of EGR1 and SGK1 in the disease state. Our data also revealed an unexpected mechanistic link between several genetic rescue interventions and the unfolded protein response. Finally, we found that C18, an analog of the CFTR corrector compound Lumacaftor, induces almost no transcriptional perturbation despite its rescue activity.

Interleukin-22 attenuates renal tubular cells inflammation and fibrosis induced by TGF-β1 through Notch1 signaling pathway

Transforming growth factor-β1 (TGF-β1) is a crucial factor implicated in the development of renal inflammation and tubulointerstitial fibrosis (TIF). The cytokine interleukin 22 (IL-22) was previously reported to involve in the pathogenesis of chronic inflammatory diseases, however recent studies showed that IL-22 could reduced inflammatory responses and tissue damage. In the present study, we aim to investigate the role and mechanisms of IL-22 in renal tubular cells inflammation and fibrosis induced by TGF-β1. HK-2 cells were treated with TGF-β1 in the presence of IL-22 or the Notch pathway inhibitor dibenzazepine (DBZ) for 48 h. Collagen I (Col I), fibronectin (FN), α-smooth muscle actin (α-SMA), vimentin and E-Cadherin were detected by western blot, proinflammatory factors (TNF-α, IL-6) and chemokines (MCP-1, RANTES) were evaluated by ELISA. Jagged1, Notch1, NICD1, and Hes1 were also detected by western blot. We found TGF-β1 increased the levels of Col I, FN, α-SMA and vimentin in HK-2 cells compared with control, and decreased E-Cadherin level, however, IL-22 restored their expressions partly. IL-22 reduced overexpression of proinflammatory factors (TNF-α, IL-6) and chemokines (MCP-1, RANTES) levels induced by TGF-β1, along with down-regulation of Jagged1, Notch, NICD1 and Hes1. Fibrosis and inflammation in renal tubular cells induced by TGF-β1 could be attenuated by IL-22, and the effects were similar to DBZ treatment. Collectively, our study shows that IL-22 exerts a protective role in renal fibrotic and inflammatory responses induced by TGF-β1 in vitro, which may be through inhibiting Jagged1/Notch1 signaling pathway activation.

Tocilizumab mimotope alleviates kidney injury and fibrosis by inhibiting IL-6 signaling and ferroptosis in UUO model

AIMS

Previously we identified four Tocilizumab mimotopes and antibodies induced by these mimotopes could bind to IL-6R (interleukin-6 receptor) and regulate the downstream signaling pathways. On the basis of obtained research data, we sought to investigate whether the therapeutic strategies by Tocilizumab mimotope vaccination could be effective in the renal fibrosis model and show the desired activity by inhibiting IL-6 signaling in current study.

MAIN METHODS

We immunized the mice with the Tocilizumab mimotope and then performed the unilateral ureteric obstruction (UUO) surgery. Masson-trichrome staining and immunohistochemistry were performed to evaluate the renal fibrosis. The activations and differentiations of F4/80+ cells in the spleens and kidneys were detected by flow cytometry, immunohistochemistry and immunofluorescence. Signaling pathways involved IL-6, pro-fibrotic and ferroptosis were analyzed by immunoblot assay. The free iron and lipid oxidation end product were performed by Prussian blue staining and immunohistochemistry. The injury and apoptosis in the kidneys were evaluated by immunofluorescence.

KEY FINDINGS

The results showed the mimotope vaccination could reduce the level of fibrosis, injury and apoptosis by down-regulating the pro-fibrotic proteins, alleviating the activations and differentiations of macrophage F4/80+ cells in UUO models. IL-6/ERK signaling pathway was inhibited with the mimotope vaccination. The ferroptosis inhibited proteins significantly increased after the mimotope vaccination. On the contrary, the levels of free iron and lipid oxidation end product were observed to decrease in the mimotope treatment group.

SIGNIFICANCE

Our results suggested that the Tocilizumab mimotope vaccination might be an alternative therapy to against renal fibrosis.

Effects of Egr1 on pancreatic acinar intracellular trypsinogen activation and the associated ceRNA network

Acute pancreatitis (AP) is a common digestive disorder with high morbidity and mortality. The present study aimed to investigate the expression of early growth response protein 1 (Egr1), and the effect of competing endogenous (ce)RNA network on trypsinogen activation. Pancreatic acinar intracellular trypsinogen activation (PAITA) is an important event in the early stage of AP; however, the underlying mechanisms remain unclear. The present study used taurolithocholic acid 3-sulfate (TLC-S)-treated AR42J cells (pancreatic cell line) to establish a PAITA model. A gene microarray and bioinformatics analysis was performed to identify the potential key targets in PAITA. The results demonstrated that Egr1, an important transcription factor, was significantly overexpressed in PAITA. In Egr1 small interfering (si)RNA-transfected cells, Egr1 expression was decreased and trypsinogen activation was significantly decreased compared with negative control siRNA-transfected cells, indicating that in TLC-S-induced PAITA, overexpression of Egr1 enhanced trypsinogen activation. A ceRNA network [mRNA-microRNA (miRNA/miR)-long non-coding (lnc)RNA] generated using the PAITA model revealed that the effects of Egr1 on PAITA may be regulated by multiple ceRNA pairs, and the lncRNAs (including NONRATT022624 and NONRATT031002) and miRNAs [including Rattus norvegicus (rno)-miR-214-3p and rno-miR-764-5p] included in the ceRNA pairs may serve roles in PAITA by regulating the expression of Egr1. The results of the present study may provide novel targets for researching the underlying mechanisms of, and developing treatments for AP.

Nuclear Factor Kappa B Signaling Complexes in Acute Inflammation

Significance: Nuclear factor kappa B (NF-κB) is a master regulator of the inflammatory response and represents a key regulatory node in the complex inflammatory signaling network. In addition, selective NF-κB transcriptional activity on specific target genes occurs through the control of redox-sensitive NF-κB interactions. Recent Advances: The selective NF-κB response is mediated by redox-modulated NF-κB complexes with ribosomal protein S3 (RPS3), Pirin (PIR). cAMP response element-binding (CREB)-binding protein (CBP)/p300, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), activator protein-1 (AP-1), signal transducer and activator of transcription 3 (STAT3), early growth response protein 1 (EGR-1), and SP-1. NF-κB is cooperatively coactivated with AP-1, STAT3, EGR-1, and SP-1 during the inflammatory process, whereas NF-κB complexes with CBP/p300 and PGC-1α regulate the expression of antioxidant genes. PGC-1α may act as selective repressor of phospho-p65 toward interleukin-6 (IL-6) in acute inflammation. p65 and nuclear factor erythroid 2-related factor 2 (NRF2) compete for binding to coactivator CBP/p300 playing opposite roles in the regulation of inflammatory genes. S-nitrosylation or tyrosine nitration favors the recruitment of specific NF-κB subunits to κB sites. Critical Issues: NF-κB is a redox-sensitive transcription factor that forms specific signaling complexes to regulate selectively the expression of target genes in acute inflammation. Protein-protein interactions with coregulatory proteins, other transcription factors, and chromatin-remodeling proteins provide transcriptional specificity to NF-κB. Furthermore, different NF-κB subunits may form distinct redox-sensitive homo- and heterodimers with distinct affinities for κB sites. Future Directions: Further research is required to elucidate the whole NF-κB interactome to fully characterize the complex NF-κB signaling network in redox signaling, inflammation, and cancer.

Impact of Heparanse on Organ Fibrosis

Organ fibrosis is defined as a deregulated wound-healing process characterized by a progressive accumulation of fibrous tissue and by reduced remodeling that can lead to the loss of functionality of the affected organ. This pathological process is quite common in several parenchymal organs such as kidneys, liver, and lungs and represents a real health emergency in developed western countries since a real anti-fibrotic therapy is not yet available in most cases. Heparanase (HPSE), which is the enzyme that cuts off the side chains of heparan sulfate (HS) proteoglycan, appears to be involved in the aetiopathogenesis of fibrosis in all these organs, even if with different mechanisms. Here we discuss how the interplay between HPSE and components of the immune and inflammatory responses can activate recruitment, proliferation, and activation of myofibroblasts which represent the main cell type responsible for the deposition of fibrous matrix. Finally, bearing in mind that once the activity of HPSE is inhibited no other molecule is able to perform the same function, it is desirable that this enzyme could prove to be a suitable pharmacological target in anti-fibrotic therapy.

EGR1 Transcription Factor is a Multifaceted Regulator of Matrix Production in Tendons and Other Connective Tissues

Although the transcription factor EGR1 is known as NGF1-A, TIS8, Krox24, zif/268, and ZENK, it still has many fewer names than biological functions. A broad range of signals induce Egr1 gene expression via numerous regulatory elements identified in the Egr1 promoter. EGR1 is also the target of multiple post-translational modifications, which modulate EGR1 transcriptional activity. Despite the myriad regulators of Egr1 transcription and translation, and the numerous biological functions identified for EGR1, the literature reveals a recurring theme of EGR1 transcriptional activity in connective tissues, regulating genes related to the extracellular matrix. Egr1 is expressed in different connective tissues, such as tendon (a dense connective tissue), cartilage and bone (supportive connective tissues), and adipose tissue (a loose connective tissue). Egr1 is involved in the development, homeostasis, and healing processes of these tissues, mainly via the regulation of extracellular matrix. In addition, Egr1 is often involved in the abnormal production of extracellular matrix in fibrotic conditions, and Egr1 deletion is seen as a target for therapeutic strategies to fight fibrotic conditions. This generic EGR1 function in matrix regulation has little-explored implications but is potentially important for tendon repair.

Egr1 Knockdown Combined with an ACE Inhibitor Ameliorates Diabetic Kidney Disease in Mice: Blockade of Compensatory Renin Increase

BACKGROUND

Increased compensatory intrarenal renin diminishes the efficacy of angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) in the treatment of diabetic kidney disease (DKD). Early growth response-1 (Egr1) is a crucial transcriptional factor in the progress of DKD and is a potential transcription factor of intrarenal renin according to bioinformatic analysis. However, whether inhibition of Egr1 can suppress compensatory renin increase in DKD is unclear.

METHODS

We generated a high-fat diet (HFD)/streptozotocin (STZ)-induced diabetic mouse model. The mice were treated with either enalapril (an ACEI) or enalapril combined with a shEgr1 plasmid, and age-matched DKD mice were used as controls. Urine microalbumin, urinary renin and kidney TGF-β1 were determined by enzyme-linked immunosorbent assay (ELISA). Hematoxylin and eosin (H&E) and Masson staining were used to determine renal pathological changes. Egr1, renin, TNF-α, and FN were measured by real-time quantitative PCR, Western blot, and immunohistochemistry. The SV40-MES13 murine mesangial cell line was transfected with pENTER-Egr1 plasmid and siEgr1.

RESULTS

Our results showed that enalapril increased the renin level of urinary and renal in DKD mice, while shEgr1 attenuated this effect. In addition, enalapril treatment reduced the levels of urinary microalbumin, TNF-α, TGF-β1 and FN, and alleviated the pathological changes, while shEgr1 strengthened these effects. The protein and mRNA expression of renin in the SV40 MES13 cells was upregulated and downregulated following overexpression and silence of Egr1, respectively.

CONCLUSION

Silence of Egr1 could alleviate renal injury in DKD by downregulating intrarenal renin.

Characterisation of transcription factor profiles in polycystic kidney disease (PKD): identification and validation of STAT3 and RUNX1 in the injury/repair response and PKD progression

Abstract

Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, caused in the majority of the cases by a mutation in either the PKD1 or the PKD2 gene. ADPKD is characterised by a progressive increase in the number and size of cysts, together with fibrosis and distortion of the renal architecture, over the years. This is accompanied by alterations in a complex network of signalling pathways. However, the underlying molecular mechanisms are not well characterised. Previously, we defined the PKD Signature, a set of genes typically dysregulated in PKD across different disease models from a meta-analysis of expression profiles. Given the importance of transcription factors (TFs) in modulating disease, we focused in this paper on characterising TFs from the PKD Signature. Our results revealed that out of the 1515 genes in the PKD Signature, 92 were TFs with altered expression in PKD, and 32 of those were also implicated in tissue injury/repair mechanisms. Validating the dysregulation of these TFs by qPCR in independent PKD and injury models largely confirmed these findings. STAT3 and RUNX1 displayed the strongest activation in cystic kidneys, as demonstrated by chromatin immunoprecipitation (ChIP) followed by qPCR. Using immunohistochemistry, we showed a dramatic increase of expression after renal injury in mice and cystic renal tissue of mice and humans. Our results suggest a role for STAT3 and RUNX1 and their downstream targets in the aetiology of ADPKD and indicate that the meta-analysis approach is a viable strategy for new target discovery in PKD.

Key messages

We identified a list of transcription factors (TFs) commonly dysregulated in ADPKD.

Out of the 92 TFs identified in the PKD Signature, 35% are also involved in injury/repair processes.

STAT3 and RUNX1 are the most significantly dysregulated TFs after injury and during PKD progression.

STAT3 and RUNX1 activity is increased in cystic compared to non-cystic mouse kidneys.

Increased expression of STAT3 and RUNX1 is observed in the nuclei of renal epithelial cells, also in human ADPKD samples.

Electronic supplementary material

The online version of this article (10.1007/s00109-019-01852-3) contains supplementary material, which is available to authorized users.

Soluble Klotho regulates bone differentiation by upregulating expression of the transcription factor EGR-1

Klotho is a transmembrane protein known to regulate aging and lifespan. Soluble Klotho (sKL), a truncated form of Klotho, regulates various cell signaling pathways, including bone development. Here, we investigated the relationship between sKL and the zinc finger transcription factor early growth response protein 1 (EGR-1) on bone formation. We find that sKL induces the expression of EGR-1 mRNA and protein. Through mutational analysis, we identify the 130 bp region on the EGR-1 promoter that is responsive to sKL overexpression. Additionally, sKL induces the expression of markers of bone differentiation (BMP2, RUNX2, ALP, COL1A, and osteocalcin) in osteoblast MC3T3 cells. EGR-1 siRNA decreases the bone mineralization induced by sKL or ascorbic acid/glycerol 2-phosphate in MC3T3 cells. Our results suggest that sKL may regulate bone development through EGR-1 expression.

Proximal Tubule Translational Profiling during Kidney Fibrosis Reveals Proinflammatory and Long Noncoding RNA Expression Patterns with Sexual Dimorphism

BACKGROUND

Proximal tubule injury can initiate CKD, with progression rates that are approximately 50% faster in males versus females. The precise transcriptional changes in this nephron segment during fibrosis and potential differences between sexes remain undefined.

METHODS

We generated mice with proximal tubule-specific expression of an L10a ribosomal subunit protein fused with enhanced green fluorescent protein. We performed unilateral ureteral obstruction surgery on four male and three female mice to induce inflammation and fibrosis, collected proximal tubule-specific and bulk cortex mRNA at day 5 or 10, and sequenced samples to a depth of 30 million reads. We applied computational methods to identify sex-biased and shared molecular responses to fibrotic injury, including up- and downregulated long noncoding RNAs (lncRNAs) and transcriptional regulators, and used in situ hybridization to validate critical genes and pathways.

RESULTS

We identified >17,000 genes in each proximal tubule group, including 145 G-protein-coupled receptors. More than 700 transcripts were differentially expressed in the proximal tubule of males versus females. The >4000 genes displaying altered expression during fibrosis were enriched for proinflammatory and profibrotic pathways. Our identification of nearly 150 differentially expressed proximal tubule lncRNAs during fibrosis suggests they may have unanticipated regulatory roles. Network analysis prioritized proinflammatory and profibrotic transcription factors such as Irf1, Nfkb1, and Stat3 as drivers of fibrosis progression.

CONCLUSIONS

This comprehensive transcriptomic map of the proximal tubule revealed sexually dimorphic gene expression that may reflect sex-related disparities in CKD, proinflammatory gene modules, and previously unappreciated proximal tubule-specific bidirectional lncRNA regulation.

Zn(ii)-Curcumin supplementation alleviates gut dysbiosis and zinc dyshomeostasis during doxorubicin-induced cardiotoxicity in rats

Doxorubicin is a powerful anticancer agent used to treat a variety of human neoplasms. However, the clinical use of doxorubicin is hampered by cardiotoxicity and effective cardioprotective adjuvants do not exist. Dietary zinc, an essential nutrient, is required to maintain steady-state tissue zinc levels and intestinal homeostasis and may yield therapeutic benefits in diseases associated with zinc dysregulation or gut dysbiosis. Here, we investigated the effects of dietary Zn(ii)-curcumin (ZnCM) solid dispersions on gut dysbiosis and zinc dyshomeostasis during doxorubicin-induced cardiotoxicity in rats. Rats were injected with multiple low doses of doxorubicin and orally administered ZnCM daily over four weeks. Daily administration of ZnCM not only alleviated Dox-induced gut dysbiosis-as indicated by the increased Firmicutes-to-Bacteroidetes ratio and the maintenance of the relative abundances of major beneficial bacteria including Clostridium_XIVa, Clostridium_IV, Roseburia, Butyricicoccus and Akkermansia-but also maintained intestinal barrier integrity and decreased the lipopolysaccharide (LPS) contents of feces and plasma. ZnCM also significantly attenuated doxorubicin-induced zinc dyshomeostasis, which was mirrored by preservation of zinc levels and expression of zinc-related transporters. Furthermore, ZnCM significantly improved heart function and reduced cardiomyocyte apoptosis and myocardial injury in doxorubicin-treated rats. Notably, the regulation of zinc homeostasis and cardioprotective and microbiota-modulating effects of ZnCM were transmissible through horizontal feces transfer from ZnCM-treated rats to normal rats. Thus, ZnCM supplementation has potential as an effective therapeutic strategy to alleviate gut dysbiosis and zinc dyshomeostasis during doxorubicin-induced cardiotoxicity.

DPP-4 inhibition by linagliptin prevents cardiac dysfunction and inflammation by targeting the Nlrp3/ASC inflammasome

We compared the effects of linagliptin (Lina, a DPP4 inhibitor) and GLP-1 receptor activation by exenatide followed by exendin-4 in an infusion pump (EX) on infarct size (IS), post-infarction activation of the inflammasome and remodeling in wild-type (WT) and db/db diabetic mice. Mice underwent 30 min ischemia followed by 24 h reperfusion. IS was assessed by TTC. Additional mice underwent permanent coronary artery occlusion. Echocardiography was performed 2w after infarction. Activation of the inflammasome in the border zone of the infarction was assessed by rt-PCR and ELISA 2w after reperfusion. Further in vitro experiments were done using primary human cardiofibroblasts and cardiomyocytes exposed to simulated ischemia-reoxygenation. Lina and EX limited IS in both the WT and the db/db mice. Lina and EX equally improved ejection fraction in both the WT and the db/db mice. mRNA levels of ASC, NALP3, IL-1β, IL-6, Collagen-1, and Collagen-3 were higher in the db/db mice than in the WT mice. Infarction increased these levels in the WT and db/db mice. Lina more than EX attenuated the increase in ASC, NALP3, IL-1β, IL-6, Collagen-1 and Collagen-3, TNFα and IL-1β, and decreased apoptosis, especially in the db/db mice. In vitro experiments showed that Lina, but not EX, attenuated the increase in TLR4 expression, an effect that was dependent on p38 activation with downstream upregulation of Let-7i and miR-146b levels. Lina and EX had similar effects on IS and post-infarction function, but Lina attenuated the activation of the inflammasome and the upregulation of collagen-1 and collagen-3 more than direct GLP-1 receptor activation. This effect depends on p38 activation with downstream upregulation of miR-146b levels that suppresses TLR4 expression.