CXCR4 inhibition attenuates calcium oxalate crystal deposition-induced renal fibrosis

The role of epithelial cells in fibrosis: Mechanisms and treatment

Fibrosis is a pathological process that affects multiple organs and is considered one of the major causes of morbidity and mortality in multiple diseases, resulting in an enormous disease burden. Current studies have focused on fibroblasts and myofibroblasts, which directly lead to imbalance in generation and degradation of extracellular matrix (ECM). In recent years, an increasing number of studies have focused on the role of epithelial cells in fibrosis. In some cases, epithelial cells are first exposed to external physicochemical stimuli that may directly drive collagen accumulation in the mesenchyme. In other cases, the source of stimulation is mainly immune cells and some cytokines, and epithelial cells are similarly altered in the process. In this review, we will focus on the multiple dynamic alterations involved in epithelial cells after injury and during fibrogenesis, discuss the association among them, and summarize some therapies targeting changed epithelial cells. Especially, epithelial mesenchymal transition (EMT) is the key central step, which is closely linked to other biological behaviors. Meanwhile, we think studies on disruption of epithelial barrier, epithelial cell death and altered basal stem cell populations and stemness in fibrosis are not appreciated. We believe that therapies targeted epithelial cells can prevent the progress of fibrosis, but not reverse it. The epithelial cell targeting therapies will provide a wonderful preventive and delaying action.

Epithelial-mesenchymal plasticity in kidney fibrosis

Epithelial-mesenchymal transition (EMT) is an important biological process contributing to kidney fibrosis and chronic kidney disease. This process is characterized by decreased epithelial phenotypes/markers and increased mesenchymal phenotypes/markers. Tubular epithelial cells (TECs) are commonly susceptible to EMT by various stimuli, for example, transforming growth factor-β (TGF-β), cellular communication network factor 2, angiotensin-II, fibroblast growth factor-2, oncostatin M, matrix metalloproteinase-2, tissue plasminogen activator (t-PA), plasmin, interleukin-1β, and reactive oxygen species. Similarly, glomerular podocytes can undergo EMT via these stimuli and by high glucose condition in diabetic kidney disease. EMT of TECs and podocytes leads to tubulointerstitial fibrosis and glomerulosclerosis, respectively. Signaling pathways involved in EMT-mediated kidney fibrosis are diverse and complex. TGF-β1/Smad and Wnt/β-catenin pathways are the major venues triggering EMT in TECs and podocytes. These two pathways thus serve as the major therapeutic targets against EMT-mediated kidney fibrosis. To date, a number of EMT inhibitors have been identified and characterized. As expected, the majority of these EMT inhibitors affect TGF-β1/Smad and Wnt/β-catenin pathways. In addition to kidney fibrosis, these EMT-targeted antifibrotic inhibitors are expected to be effective for treatment against fibrosis in other organs/tissues.

The SOX4/EZH2/SLC7A11 signaling axis mediates ferroptosis in calcium oxalate crystal deposition-induced kidney injury

Epigenetic regulation is reported to play a significant role in the pathogenesis of various kidney diseases, including renal cell carcinoma, acute kidney injury, renal fibrosis, diabetic nephropathy, and lupus nephritis. However, the role of epigenetic regulation in calcium oxalate (CaOx) crystal deposition-induced kidney injury remains unclear. Our study demonstrated that the upregulation of enhancer of zeste homolog 2 (EZH2)-mediated ferroptosis facilitates CaOx-induced kidney injury. CaOx crystal deposition promoted ferroptosis in vivo and in vitro. Usage of liproxstatin-1 (Lip-1), a ferroptosis inhibitor, mitigated CaOx-induced kidney damage. Single-nucleus RNA-sequencing, RNA-sequencing, immunohistochemical and western blotting analyses revealed that EZH2 was upregulated in kidney stone patients, kidney stone mice, and oxalate-stimulated HK-2 cells. Experiments involving in vivo EZH2 knockout, in vitro EZH2 knockdown, and in vivo GSK-126 (an EZH2 inhibitor) treatment confirmed the protective effects of EZH2 inhibition on kidney injury and ferroptosis. Mechanistically, the results of RNA-sequencing and chromatin immunoprecipitation assays demonstrated that EZH2 regulates ferroptosis by suppressing solute carrier family 7, member 11 (SLC7A11) expression through trimethylation of histone H3 lysine 27 (H3K27me3) modification. Additionally, SOX4 regulated ferroptosis by directly modulating EZH2 expression. Thus, this study demonstrated that SOX4 facilitates ferroptosis in CaOx-induced kidney injury through EZH2/H3K27me3-mediated suppression of SLC7A11.

STAT6 promoting oxalate crystal deposition-induced renal fibrosis by mediating macrophage-to-myofibroblast transition via inhibiting fatty acid oxidation

OBJECTIVE AND DESIGN

Kidney stones commonly occur with a 50% recurrence rate within 5 years, and can elevate the risk of chronic kidney disease. Macrophage-to-myofibroblast transition (MMT) is a newly discovered mechanism that leads to progressive fibrosis in different forms of kidney disease. In this study, we aimed to investigate the role of MMT in renal fibrosis in glyoxylate-induced kidney stone mice and the mechanism by which signal transducer and activator of transcription 6 (STAT6) regulates MMT.

METHODS

We collected non-functioning kidneys from patients with stones, established glyoxylate-induced calcium oxalate stone mice model and treated AS1517499 every other day in the treatment group, and constructed a STAT6-knockout RAW264.7 cell line. We first screened the enrichment pathway of the model by transcriptome sequencing; detected renal injury and fibrosis by hematoxylin eosin staining, Von Kossa staining and Sirius red staining; detected MMT levels by multiplexed immunofluorescence and flow cytometry; and verified the binding site of STAT6 at the PPARα promoter by chromatin immunoprecipitation. Fatty acid oxidation (FAO) and fibrosis-related genes were detected by western blot and real-time quantitative polymerase chain reaction.

RESULTS

In this study, we found that FAO was downregulated, macrophages converted to myofibroblasts, and STAT6 expression was elevated in stone patients and glyoxylate-induced kidney stone mice. The promotion of FAO in macrophages attenuated MMT and upregulated fibrosis-related genes induced by calcium oxalate treatment. Further, inhibition of peroxisome proliferator-activated receptor-α (PPARα) eliminated the effect of STAT6 deletion on FAO and fibrosis-associated protein expression. Pharmacological inhibition of STAT6 also prevented the development of renal injury, lipid accumulation, MMT, and renal fibrosis. Mechanistically, STAT6 transcriptionally represses PPARα and FAO through cis-inducible elements located in the promoter region of the gene, thereby promoting MMT and renal fibrosis.

CONCLUSIONS

These findings establish a role for STAT6 in kidney stone injury-induced renal fibrosis, and suggest that STAT6 may be a therapeutic target for progressive renal fibrosis in patients with nephrolithiasis.

Human Wharton's jelly-derived mesenchymal stem cells prevent pregnancy loss in a rat by JAK/STAT-mediated immunomodulation

AIM

Spontaneous abortion (SA) is a multiple-original syndrome with immune imbalance as one of its major risk factors. As Wharton's jelly-mesenchymal stem cells (WJ-MSCs) are considered to be able to prevent abortion, this study aims to explore the currently poorly understood underlining molecular signaling pathways and regulatory mechanisms of WJ-MSCs in pregnancy maintenance.

METHODS

Abortion mode is established by subcutaneous injection of bromocriptine in rat on day 9 and abortion prevention is achieved by WJ-MSCs injection via tail vein. WJ-MSCs were cultured with/without the inhibitors of JAK/STAT or NF-κB. The uterus was collected on the 14th day of gestation and the rate of embryo absorption was calculated. The expression of Th1/Th2/Th3 cytokines in decidual, placental tissue, and peripheral blood was analyzed.

RESULTS

WJ-MSCs treatment significantly reduced the abortion rate in bromocriptine-treated pregnancy such that it was not significantly different from a normal pregnancy. JAK/STAT inhibition abolished pregnancy preserving effects of WJ-MSCs but NF-κB inhibition did not. The levels of Th1-related cytokines and mRNA levels in the bromocriptine abortion model were significantly higher than the normal pregnancy group and ethanol control group, while levels of the Th2-related cytokines and mRNA levels significantly decreased. WJ-MSCs transfusion into the abortion model restored cytokine profiles such that they were not significantly different from the normal pregnancy group and ethanol control group. JAK/STAT inhibition of WJ-MSCs prevented their effect on cytokine and mRNA levels, but NF-κB inhibition did not.

CONCLUSIONS

WJ-MSCs significantly lower the rate of embryo resorption of spontaneous abortion by reducing Th1-related cytokines while increasing Th2 and Th3-related cytokines in JAK/STAT-dependent manner.

p53 deacetylation alleviates calcium oxalate deposition-induced renal fibrosis by inhibiting ferroptosis

Calcium oxalate (CaOx) stones are among the most common types of kidney stones and are associated with renal tubular damage, interstitial fibrosis, and chronic kidney disease. The mechanism of CaOx crystal-induced renal fibrosis remains unknown. Ferroptosis, a type of regulated cell death, is characterised by iron-dependent lipid peroxidation, and the tumour suppressor p53 is a key regulator of ferroptosis. In the present study, our results demonstrated that ferroptosis was significantly activated in patients with nephrolithiasis and hyperoxaluric mice as well as verified the protective effects of ferroptosis inhibition on CaOx crystal-induced renal fibrosis. Moreover, the single-cell sequencing database, RNA-sequencing, and western blot analysis revealed that the expression of p53 was increased in patients with chronic kidney disease and the oxalate-stimulated human renal tubular epithelial cell line, HK-2. Additionally, the acetylation of p53 was enhanced by oxalate stimulation in HK-2 cells. Mechanistically, we found that the induction of p53 deacetylation, owing to either the SRT1720-induced activation of deacetylase sirtuin 1 or the triple mutation of p53, inhibited ferroptosis and alleviated renal fibrosis caused by CaOx crystals. We conclude that ferroptosis is one of the critical mechanisms contributing to CaOx crystal-induced renal fibrosis, and the pharmacological induction of ferroptosis via sirtuin 1-mediated p53 deacetylation may be a potential target for preventing renal fibrosis in patients with nephrolithiasis.

Effect of transmembrane protein 100 on prostate cancer progression by regulating SCNN1D through the FAK/PI3K/AKT pathway

The effects of transmembrane (TMEM) proteins in the progression of prostate cancer (PCa) remain unknown. This study aims to explore the functions of TMEM100 in PCa. To explore the expression, regulation, and effects of TMEM100 in PCa, two PCa cell lines and 30 PCa tissue samples with adjacent control tissues were examined. Online databases, immunohistochemistry, immunofluorescence, western blot, flow cytometry, colony formation, wound healing, transwell assays, and xenograft mouse models were used to explore effects of TMEM100 relevant to PCa. TMEM100 expression was shown to decrease in PCa patients, and low TMEM100 expression was associated with tumor stage and metastasis. Overexpression of TMEM100 suppressed PCa progression by inhibiting the FAK/PI3K/AKT signaling pathway. Tumor size was smaller in TMEM100 overexpressing PCa cells in xenograft mice than in control mice. We also found that TMEM100 could regulate SCNN1D by inhibiting FAK/PI3K/AKT signaling in PCa cell lines. Taken together, our findings indicate that TMEM100 is a tumor suppressor that plays a vital role in preventing PCa proliferation, migration, and invasion through inhibition of FAK/PI3K/AKT signaling. These studies suggest that TMEM100 can be used as a predictive biomarker and therapeutic target.

Ferrostatin‑1 alleviates oxalate‑induced renal tubular epithelial cell injury, fibrosis and calcium oxalate stone formation by inhibiting ferroptosis

The present study aimed to evaluate the role and mechanism of ferrostatin-1 (Fer-1) in oxalate (Ox)-induced renal tubular epithelial cell injury, fibrosis, and calcium oxalate (CaOx) stone formation. A CaOx model in mice kidneys was established via intraperitoneal injection of 80 mg/kg glyoxylic acid for 14 days. The mice were randomly divided into three groups (n=6), namely, the control (Con), the CaOx group, and the CaOx + Fer-1 group. Cultured human renal tubular epithelial cells (HK-2 cells) were randomly divided into three groups (n=3), namely, the control (Con), the Ox group, and the Ox + Fer-1 group. The levels of heme oxygenase 1 (HO-1), superoxide dismutase 2 (SOD2), glutathione peroxidase 4 (GPX4), and solute carrier family 7 member 11 (SLC7A11) were assessed by immunofluorescence and western blot analysis. Renal tubular injury and apoptosis were evaluated by H&E and TUNEL staining. Kidney interstitial fibrosis was evaluated by Masson and Sirius red staining, and the levels of E-cadherin, vimentin and α-SMA were detected by immunofluorescence or western blot analysis. Mitochondrial structure was observed using a transmission electron microscope. The levels of reactive oxygen species (ROS) were determined by flow cytometry and CaOx stone formation was evaluated by von Kossa staining. The results revealed that in comparison with the Con group, mitochondrial injury under glyoxylic acid treatment was observed by TEM. The expression of GPX4 and SLC7A11 in the CaOx and Ox groups was downregulated (P<0.05), whereas the expression of HO-1 and SOD2 was upregulated (P<0.05). Renal tissue damage, apoptosis of renal tubular epithelial cells, and interstitial fibrosis were increased in the CaOx and Ox groups (P<0.05). In comparison with the CaOx or Ox group, the expression of GPX4 and SLC7A11 in the CaOx + Fer-1 or Ox + Fer-1 group was upregulated (P<0.05), whereas that of HO-1 and SOD2 was downregulated (P<0.05). Renal tissue damage, apoptosis of renal tubular epithelial cells and interstitial fibrosis were decreased following Fer-1 treatment (P<0.05). The ROS level was also decreased following Fer-1 treatment. Moreover, CaOx stone formation was decreased in the CaOx + Fer-1 group (P<0.05). In conclusion, Fer-1 alleviated Ox-induced renal tubular epithelial cell injury, fibrosis, and CaOx stone formation by inhibiting ferroptosis.

Suppressing the activity of CXCR4 down-regulates the expression of renal fibrosis related genes in primary glomerular cells

BACKGROUND

C-X-C chemokine receptor type 4 (CXCR4) has a certain effect on renal fibrosis, and there are few specific studies in cells. We want to investigate the impact of suppressing CXCR4 activity on the expression of renal fibrosis-related genes in primary glomerular endothelial cells, mesangial cells, and podocytes.

METHODS

Immunofluorescence assays were used to determine the purity of isolated glomerular endothelial cells, mesangial cells, and podocytes. CXCR4 knockdown cell lines were established by transfecting the short hairpin (sh)RNA against CXCR4. T140 and AMD3100 were used to inhibit the activity of CXCR4. LY294002 was used to inhibit the activity of phosphoinositide 3-kinase (PI3K). The mRNA expression of CXCR4 was determined by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The protein expression of CXCR4, collagen IV, matrix metallopeptidase (MMP)-9, PI3K, Rac1, and vascular cell adhesion protein 1 (VCAM-1) was evaluated by Western blot analysis.

RESULTS

High purity was observed on isolated primary glomerular endothelial cells and podocytes. However, the purity of isolated mesangial cells was relatively low. The mRNA expression of CXCR4 was significantly suppressed by the transfection of shRNA. Compared to control cells, the expression of CXCR4, collagen IV, MMP-9, PI3K, Rac1, and VCAM-1 were dramatically downregulated in cell lines transfected with shRNA against CXCR4. Furthermore, cell lines treated with T140, AMD3100, or LY294002 also showed downregulated expression of these proteins compared to untreated cells. No significant differences were observed in the protein expression of these proteins between control cells and cells transfected with the shRNA negative control (NC).

CONCLUSIONS

Suppressing the activity of CXCR4 downregulated the expression of renal fibrosis-related genes in primary glomerular cells, even under a non-inflammatory state.