CXCL16 Deficiency Attenuates Renal Injury and Fibrosis in Salt-Sensitive Hypertension

The role of the CXCR6/CXCL16 axis in the pathogenesis of fibrotic disease

CXC chemokine receptor 6 (CXCR6), a seven-transmembrane domain G-protein-coupled receptor, plays a pivotal regulatory role in inflammation and tissue damage through its interaction with CXC chemokine ligand 16 (CXCL16). This axis is implicated in the pathogenesis of various fibrotic diseases and correlates with clinical parameters that indicate disease severity, activity, and prognosis in organ fibrosis, including afflictions of the liver, kidney, lung, cardiovascular system, skin, and intestines. Soluble CXCL16 (sCXCL16) serves as a chemokine, facilitating the migration and recruitment of CXCR6-expressing cells, while membrane-bound CXCL16 (mCXCL16) functions as a transmembrane protein with adhesion properties, facilitating intercellular interactions by binding to CXCR6. The CXCR6/CXCL16 axis is established to regulate the cycle of damage and repair during chronic inflammation, either through modulating immune cell-mediated intercellular communication or by independently influencing fibroblast homing, proliferation, and activation, with each pathway potentially culminating in the onset and progression of fibrotic diseases. However, clinically exploiting the targeting of the CXCR6/CXCL16 axis requires further elucidation of the intricate chemokine interactions within fibrosis pathogenesis. This review explores the biology of CXCR6/CXCL16, its multifaceted effects contributing to fibrosis in various organs, and the prospective clinical implications of these insights.

PROSTATE CELL HETEROGENEITY AND CXCL17 UPREGULATION IN MOUSE STEROID HORMONE IMBALANCE

Benign prostatic hyperplasia (BPH) is a prevalent age-related condition often characterized by debilitating urinary symptoms. Its etiology is believed to stem from hormonal imbalance, particularly an elevated estradiol-to-testosterone ratio and chronic inflammation. Our previous studies using a mouse steroid hormone imbalance model identified a specific increase in macrophages that migrate and accumulate in the prostate lumen where they differentiate into lipid-laden foam cells in mice implanted with testosterone and estradiol pellets, but not in sham animals. The current study focused on further characterizing the cellular heterogeneity of the prostate in this model as well as identifying the specific transcriptomic signature of the recruited foam cells. Moreover, we aimed to identify the epithelia-derived signals that drive macrophage infiltration and luminal translocation. Male C57BL/6J mice were implanted with slow-release testosterone and estradiol pellets (T+E2) and harvested the ventral prostates two weeks later for scRNA-seq analysis, or performed sham surgery. We identified Ear2+ and Cd72+ macrophages that were elevated in response to steroid hormone imbalance, whereas a Mrc1+ resident macrophage population did not change. In addition, an Spp1+ foam cell cluster was almost exclusively found in T+E2 mice. Further markers of foam cells were also identified, including Gpnmb and Trem2, and GPNMB was confirmed as a novel histological marker with immunohistochemistry. Foam cells were also shown to express known pathological factors Vegf, Tgfb1, Ccl6, Cxcl16 and Mmp12. Intriguingly, a screen for chemokines identified the upregulation of epithelial-derived Cxcl17, a known monocyte attractant, in T+E2 prostates suggesting that it might be responsible for the elevated macrophage number as well as their translocation to the lumen. Our study identified macrophage subsets that respond to steroid hormone imbalance as well as further confirmed a potential pathological role of luminal foam cells in the prostate. These results underscore a pathological role of the identified prostate foam cells and suggests CXCL17-mediated macrophage migration as a critical initiating event.

Renal transcriptome analysis of uninephrectomized db/db mice identified a mechanism for the transition to severe diabetic nephropathy

Diabetic nephropathy (DN), included in diabetic kidney disease (DKD), is a primary driver of end-stage renal disease (ESRD) leading to dialysis treatment. To develop new therapeutic drugs to prevent ESRD and avoid dialysis treatment, insight into DKD pathophysiology and animal models suitable for drug efficacy testing are needed. In this study, transcriptome analysis of kidneys from 26-week-old and 35-week-old uninephrectomized (UNX) db/db mice was used to identify the pathways that affect the deterioration of renal function in db/db mice. Differentially expressed genes suggested that there was increased interferon (IFN)-γ signaling during the 26 to 35-week period. Modules that changed between 26 and 35 weeks of age extracted by weighted gene co-expression network analysis (WGCNA) suggested increased the tumor necrosis factor (TNF)-α and nuclear factor-kappa B (NF-κB) signaling pathway in component cells of glomeruli. The protein-protein interaction (PPI) network analysis identified Cxcl16 as a hub gene for those signaling pathways, and it was shown that the pathways in this module changed when the glomerular filtration rate decreased in patients with DN. These results suggested the possibility that signaling mediated by Cxcl16 induced by IFN-γ and TNF-α between 26 and 35 weeks of age leads to renal fibrosis, resulting in severe disease. Drugs that target such pathways can be options for developing drugs for DN. We also think that the uninephrectomized db/db mouse can be used as an animal model of severe DKD and to evaluate efficacy in patients with DN.

Advances in understanding and treating diabetic kidney disease: focus on tubulointerstitial inflammation mechanisms

Diabetic kidney disease (DKD) is a serious complication of diabetes that can lead to end-stage kidney disease. Despite its significant impact, most research has concentrated on the glomerulus, with little attention paid to the tubulointerstitial region, which accounts for the majority of the kidney volume. DKD's tubulointerstitial lesions are characterized by inflammation, fibrosis, and loss of kidney function, and recent studies indicate that these lesions may occur earlier than glomerular lesions. Evidence has shown that inflammatory mechanisms in the tubulointerstitium play a critical role in the development and progression of these lesions. Apart from the renin-angiotensin-aldosterone blockade, Sodium-Glucose Linked Transporter-2(SGLT-2) inhibitors and new types of mineralocorticoid receptor antagonists have emerged as effective ways to treat DKD. Moreover, researchers have proposed potential targeted therapies, such as inhibiting pro-inflammatory cytokines and modulating T cells and macrophages, among others. These therapies have demonstrated promising results in preclinical studies and clinical trials, suggesting their potential to treat DKD-induced tubulointerstitial lesions effectively. Understanding the immune-inflammatory mechanisms underlying DKD-induced tubulointerstitial lesions and developing targeted therapies could significantly improve the treatment and management of DKD. This review summarizes the latest advances in this field, highlighting the importance of focusing on tubulointerstitial inflammation mechanisms to improve DKD outcomes.

JMJD3 ablation in myeloid cells confers renoprotection in mice with DOCA/salt-induced hypertension

Hypertension-induced renal injury is characterized by robust inflammation and tubulointerstitial fibrosis. Jumonji domain containing-3 (JMJD3) is closely linked with inflammatory response and fibrogenesis. Here we examined the effect of myeloid JMJD3 ablation on kidney inflammation and fibrosis in deoxycorticosterone acetate (DOCA)/salt hypertension. Our results showed that JMJD3 is notably induced in the kidneys with hypertensive injury. DOCA/salt stress causes an elevation in blood pressure that was no difference between myeloid specific JMJD3-deficient mice and wild-type control mice. Compared with wild-type control mice, myeloid JMJD3 ablation ameliorated kidney function and injury of mice in response to DOCA/salt challenge. Myeloid JMJD3 ablation attenuated collagen deposition, extracellular matrix proteins expression, and fibroblasts activation in injured kidneys following DOCA/salt treatment. Furthermore, myeloid JMJD3 ablation blunts inflammatory response in injured kidneys after DOCA/salt stress. Finally, myeloid JMJD3 ablation precluded myeloid myofibroblasts activation and protected against macrophages to myofibroblasts transition in injured kidneys. These beneficial effects were accompanied by reduced expression of interferon regulator factor 4. In summary, JMJD3 ablation in myeloid cells reduces kidney inflammation and fibrosis in DOCA salt-induced hypertension. Inhibition of myeloid JMJD3 may be a novel potential therapeutic target for hypertensive nephropathy. Myeloid JMJD3 deficiency reduces inflammatory response, myeloid fibroblasts activation, macrophages to myofibroblasts transition, and delays kidney fibrosis progression.

Interferon regulatory factor 4 deletion protects against kidney inflammation and fibrosis in deoxycorticosterone acetate/salt hypertension

BACKGROUND

Inflammation and renal interstitial fibrosis are the main pathological features of hypertensive nephropathy. Interferon regulatory factor 4 (IRF-4) has an important role in the pathogenesis of inflammatory and fibrotic diseases. However, its role in hypertension-induced renal inflammation and fibrosis remains unexplored.

METHOD AND RESULTS

We showed that deoxycorticosterone acetate (DOCA)-salt resulted in an elevation of blood pressure and that there was no difference between wild-type and IRF-4 knockout mice. IRF-4 -/- mice presented less severe renal dysfunction, albuminuria, and fibrotic response after DOCA-salt stress compared with wild-type mice. Loss of IRF-4 inhibited extracellular matrix protein deposition and suppressed fibroblasts activation in the kidneys of mice subjected to DOCA-salt treatment. IRF-4 disruption impaired bone marrow-derived fibroblasts activation and macrophages to myofibroblasts transition in the kidneys in response to DOCA-salt treatment. IRF-4 deletion impeded the infiltration of inflammatory cells and decreased the production of proinflammatory molecules in injured kidneys. IRF-4 deficiency activated phosphatase and tensin homolog and weakened phosphoinositide-3 kinase/AKT signaling pathway in vivo or in vitro . In cultured monocytes, TGFβ1 also induced expression of fibronectin and α-smooth muscle actin and stimulated the transition of macrophages to myofibroblasts, which was blocked in the absence of IRF-4. Finally, macrophages depletion blunted macrophages to myofibroblasts transition, inhibited myofibroblasts accumulation, and ameliorated kidney injury and fibrosis.

CONCLUSION

Collectively, IRF-4 plays a critical role in the pathogenesis of kidney inflammation and fibrosis in DOCA-salt hypertension.

JNK and Jag1/Notch2 co-regulate CXCL16 to facilitate cypermethrin-induced kidney damage

Cypermethrin (CYP), a widely-used composite pyrethroid pesticide, has underlying nephrotoxic effects. To elucidate potential roles of the MAPK pathway, the Jag/Notch pathway, and miRNAs in CYP-mediated kidney lesion, Sprague-Dawley rats and glomerular mesangial cells were used in this work. Results displayed that β-CYP abnormally altered renal histomorphology and ultrastructures, induced renal DNA damage, and impaired renal functions, as evidenced by the increase in plasma levels of Cys-C and β2-Mg. β-CYP activated the JNK/c-Jun pathway by inducing ROS and oxidative stress. Meanwhile, β-CYP changed the miRNA expression profile, miR-21-5p showing the most significant increase. Moreover, the Jag1/Notch2/Hes1 pathway was directly targeted by miR-21-5p, the mRNA and protein expression of Jag1, Notch2, and Hes1 being declined in vivo and in vitro. The chemokine CXCL16 was induced by β-CYP, accompanied by the inflammatory factor production and inflammatory cell infiltration in kidneys. The specific JNK inhibitor, Jag1 overexpression, Hes1 overexpression, bidirectional Co-IP, ChIP, and CXCL16 silencing demonstrated that CXCL16 co-regulated by the JNK/c-Jun and Jag1/Notch2/Hes1 pathways elicited renal inflammation. Collectively, our findings indicate that β-CYP is of nephrotoxicity and it not only directly changes renal histomorphology and ultrastructures, but induces CXCL16 to trigger renal inflammation via the JNK/c-Jun and Jag1/Notch2/Hes1 pathways, finally synergistically contributing to kidney damage.

Single-cell analysis identifies the interaction of altered renal tubules with basophils orchestrating kidney fibrosis

Inflammation is an important component of fibrosis but immune processes that orchestrate kidney fibrosis are not well understood. Here we apply single-cell sequencing to a mouse model of kidney fibrosis. We identify a subset of kidney tubule cells with a profibrotic-inflammatory phenotype characterized by the expression of cytokines and chemokines associated with immune cell recruitment. Receptor-ligand interaction analysis and experimental validation indicate that CXCL1 secreted by profibrotic tubules recruits CXCR2+ basophils. In mice, these basophils are an important source of interleukin-6 and recruitment of the TH17 subset of helper T cells. Genetic deletion or antibody-based depletion of basophils results in reduced renal fibrosis. Human kidney single-cell, bulk gene expression and immunostaining validate a function for basophils in patients with kidney fibrosis. Collectively, these studies identify basophils as contributors to the development of renal fibrosis and suggest that targeting these cells might be a useful clinical strategy to manage chronic kidney disease.

Myeloid PTEN deficiency aggravates renal inflammation and fibrosis in angiotensin II-induced hypertension

Hypertension is a major cause of chronic kidney disease. However, the pathogenesis of hypertensive kidney disease is not fully understood. Recently, we have shown that CXCL16/phosphoinositide-3 kinase γ (PI3Kγ) plays an important role in the development of renal inflammation and fibrosis in angiotensin II (AngII) induced hypertensive nephropathy. In the present study, we examined the role of phosphatase and tensin homolog (PTEN), a major regulator of PI3K signaling, in the pathogenesis of renal inflammation and fibrosis in an experimental model of hypertension induced by AngII. We generated myeloid PTEN conditional knockout mice by crossing PTEN^flox/flox mice with LysM-driven Cre mice. Littermate LysM-Cre^-/- PTEN^flox/flox mice were used as a control. Both myeloid PTEN knockout mice and their littermate control mice exhibited similar blood pressure at baseline. AngII treatment resulted in an increase in blood pressure that was comparable between myeloid PTEN knockout mice and littermate control mice. Compared with littermate control mice, myeloid PTEN knockout mice developed more severe kidney dysfunction, proteinuria, and fibrosis following AngII treatment. Furthermore, myeloid PTEN deficiency exacerbated total collagen deposition and extracellular matrix protein production and enhanced myeloid fibroblast accumulation and myofibroblast formation in the kidney following AngII treatment. Finally, myeloid PTEN deficiency markedly augmented infiltration of F4/80⁺ macrophages and CD3⁺ T cells into the kidneys of AngII-treated mice. Taken together, these results indicate that PTEN plays a crucial role in the pathogenesis of renal inflammation and fibrosis through the regulation of infiltration of myeloid fibroblasts, macrophages, and T lymphocytes into the kidney.

SARS-CoV-2 spike promotes inflammation and apoptosis through autophagy by ROS-suppressed PI3K/AKT/mTOR signaling

Background

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection-induced inflammatory responses are largely responsible for the death of novel coronavirus disease 2019 (COVID-19) patients. However, the mechanism by which SARS-CoV-2 triggers inflammatory responses remains unclear. Here, we aimed to explore the regulatory role of SARS-CoV-2 spike protein in infected cells and attempted to elucidate the molecular mechanism of SARS-CoV-2-induced inflammation.

Methods

SARS-CoV-2 spike pseudovirions (SCV-2-S) were generated using the spike-expressing virus packaging system. Western blot, mCherry-GFP-LC3 labeling, immunofluorescence, and RNA-seq were performed to examine the regulatory mechanism of SCV-2-S in autophagic response. The effects of SCV-2-S on apoptosis were evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), Western blot, and flow cytometry analysis. Enzyme-linked immunosorbent assay (ELISA) was carried out to examine the mechanism of SCV-2-S in inflammatory responses.

Results

Angiotensin-converting enzyme 2 (ACE2)-mediated SCV-2-S infection induced autophagy and apoptosis in human bronchial epithelial and microvascular endothelial cells. Mechanistically, SCV-2-S inhibited the PI3K/AKT/mTOR pathway by upregulating intracellular reactive oxygen species (ROS) levels, thus promoting the autophagic response. Ultimately, SCV-2-S-induced autophagy triggered inflammatory responses and apoptosis in infected cells. These findings not only improve our understanding of the mechanism underlying SARS-CoV-2 infection-induced pathogenic inflammation but also have important implications for developing anti-inflammatory therapies, such as ROS and autophagy inhibitors, for COVID-19 patients.

C-C Motif Chemokine Ligand-17 as a Novel Biomarker and Regulator of Epithelial Mesenchymal Transition in Renal Fibrogenesis

CCL17, a chemotactic cytokine produced by macrophages, is known to promote inflammatory and fibrotic effects in multiple organs, but its role in mediating renal fibrosis is unclear. In our study cohort of 234 chronic kidney disease (CKD) patients and 65 healthy controls, human cytokine array analysis revealed elevated CCL17 expression in CKD that correlated negatively with renal function. The area under the receiver operating characteristic curve of CCL17 to predict the development of CKD stages 3b–5 was 0.644 (p < 0.001), with the optimal cut-off value of 415.3 ng/mL. In vitro over-expression of CCL17 in HK2 cells had no effect on cell viability, but increased cell motility and the expression of α-SMA, vimentin and collagen I, as shown by western blot analysis. In a unilateral ureteral obstruction (UUO) mouse model, we observed significantly increased interstitial fibrosis and renal tubule dilatation by Masson’s Trichrome and H&E staining, and markedly increased expression of CCL17, vimentin, collagen I, and α-SMA by IHC stain, qRTPCR, and western blotting. CCL17 induced renal fibrosis by promoting the epithelial-mesenchymal transition, resulting in ECM accumulation. CCL17 may be a useful biomarker for predicting the development of advanced CKD.

STAT6 Deficiency Attenuates Myeloid Fibroblast Activation and Macrophage Polarization in Experimental Folic Acid Nephropathy

Renal fibrosis is a pathologic feature of chronic kidney disease, which can lead to end-stage kidney disease. Myeloid fibroblasts play a central role in the pathogenesis of renal fibrosis. However, the molecular mechanisms pertaining to myeloid fibroblast activation remain to be elucidated. In the present study, we examine the role of signal transducer and activator of transcription 6 (STAT6) in myeloid fibroblast activation, macrophage polarization, and renal fibrosis development in a mouse model of folic acid nephropathy. STAT6 is activated in the kidney with folic acid nephropathy. Compared with folic-acid-treated wild-type mice, STAT6 knockout mice had markedly reduced myeloid fibroblasts and myofibroblasts in the kidney with folic acid nephropathy. Furthermore, STAT6 knockout mice exhibited significantly less CD206 and PDGFR-β dual-positive fibroblast accumulation and M2 macrophage polarization in the kidney with folic acid nephropathy. Consistent with these findings, STAT6 knockout mice produced less extracellular matrix protein, exhibited less severe interstitial fibrosis, and preserved kidney function in folic acid nephropathy. Taken together, these results have shown that STAT6 plays a critical role in myeloid fibroblasts activation, M2 macrophage polarization, extracellular matrix protein production, and renal fibrosis development in folic acid nephropathy. Therefore, targeting STAT6 may provide a novel therapeutic strategy for fibrotic kidney disease.

IRF-4 deficiency reduces inflammation and kidney fibrosis after folic acid-induced acute kidney injury

The chronic phase following toxin-induced acute kidney injury (AKI) is characterized by robust inflammation and progressive kidney fibrosis. Interferon regulatory factor 4 (IRF-4) is a type of multifunctional transcription factor that has been deeply linked to inflammation and fibrotic diseases. However, the role of IRF-4 in kidney damage and renal fibrosis after toxin-induced AKI remain to be explored. In this work, we examined the effect of IRF-4 deficiency on inflammation and kidney fibrosis in an AKI-chronic kidney disease (CKD) transition model induced by folic acid (FA) injury. We showed that FA treatment resulted in severe acute tubular injury followed by inflammatory reaction and interstitial fibrosis in wild-type mice. A sharp elevation of IRF-4 levels was observed in FA-injured kidneys. IRF-4 knockout led to a substantial reduction of extracellular matrix (ECM) proteins deposition and inhibited myofibroblasts transformation in the kidneys of mice subjected to FA treatment. In addition, IRF-4 ablation impaired F4/80+ macrophages and CD3+ T lymphocytes infiltration into the FA-injured kidneys. Loss of IRF-4 reduced the production of inflammatory molecules such as CXCL16, IL-18, IL-6, and TGF-β1 in the kidneys in response to FA stress. Following FA injury, the kidneys of IRF-4 knockout mice had fewer bone marrow-derived myofibroblasts than wild-type controls. Moreover, IRF-4 disruption inhibited macrophages to myofibroblasts differentiation in the kidneys in response to FA stimuli. In vitro, IL-4 stimulated expression of α-smooth muscle actin and ECM proteins and promoted M2 macrophages to myofibroblasts transition in mouse bone marrow-derived monocytes, which was abolished in the absence of IRF-4. Thus, we identified an important role of IRF-4 in the pathogenesis of progressive CKD following FA-induced AKI.

Deficiency of MicroRNA-181a Results in Transcriptome-Wide Cell-Specific Changes in the Kidney and Increases Blood Pressure

[Figure: see text].

Urinary chemokine C-X-C motif ligand 16 and endostatin as predictors of tubulointerstitial fibrosis in patients with advanced diabetic kidney disease

BACKGROUND

Interstitial fibrosis and tubular atrophy (IFTA) is a well-recognized risk factor for poor renal outcome in patients with diabetic kidney disease (DKD). However, a noninvasive biomarker for IFTA is currently lacking. The purpose of this study was to identify urinary markers of IFTA and to determine their clinical relevance as predictors of renal prognosis.

METHODS

Seventy patients with biopsy-proven isolated DKD were enrolled in this study. We measured multiple urinary inflammatory cytokines and chemokines by multiplex enzyme-linked immunosorbent assay in these patients and evaluated their association with various pathologic features and renal outcomes.

RESULTS

Patients enrolled in this study exhibited advanced DKD at the time of renal biopsy, characterized by moderate to severe renal dysfunction [mean estimated glomerular filtration rate (eGFR) 36.1 mL/min/1.73 m2] and heavy proteinuria (mean urinary protein:creatinine ratio 7.8 g/g creatinine). Clinicopathologic analysis revealed that higher IFTA scores were associated with worse baseline eGFR (P < 0.001) and poor renal outcome (P = 0.002), whereas glomerular injury scores were not. Among measured urinary inflammatory markers, C-X-C motif ligand 16 (CXCL16) and endostatin showed strong correlations with IFTA scores (P = 0.001 and P < 0.001, respectively), and patients with higher levels of urinary CXCL16 and/or endostatin experienced significantly rapid renal progression compared with other patients (P < 0.001). Finally, increased urinary CXCL16 and endostatin were independent risk factors for poor renal outcome after multivariate adjustments (95% confidence interval 1.070-3.455, P = 0.029).

CONCLUSIONS

Urinary CXCL16 and endostatin could reflect the degree of IFTA and serve as biomarkers of renal outcome in patients with advanced DKD.

Pharmacological inhibition of SETD7 by PFI-2 attenuates renal fibrosis following folic acid and obstruction injury

Renal fibrosis is the common pathological hallmark of chronic kidney disease, and SET domain containing lysine methyltransferase 7 (SETD7) promote considerably renal fibrosis. However, the signaling mechanisms underlying SETD7 driving renal fibrosis are not fully understood. Here, we investigated the role of SETD7 in M2 macrophages-myofibroblasts transition and the myeloid fibroblasts activation in folic acid and obstruction-induced renal fibrosis. Mice treated with PFI-2, an inhibitor of SETD7, presented less bone marrow-derived myofibroblasts, fewer CD206+/α-smooth muscle actin + cells and developed less renal fibrosis (P＜0.01). Furthermore, SETD7 inhibition reduced the infiltration of inflammatory cells and decreased the production of pro-inflammatory cytokines and chemokines in the kidneys after folic acid treatment (P＜0.01). Finally, SETD7 inhibition suppressed the accumulation of NF-κB p65+ cells in folic acid nephropathy (P＜0.01). Taken together, SETD7 mediates M2 macrophages-myofibroblasts transition, bone marrow-derived myofibroblasts activation, and inflammation response in the development of renal fibrosis.

Mechanisms of Cisplatin-Induced Acute Kidney Injury: Pathological Mechanisms, Pharmacological Interventions, and Genetic Mitigations

Administration of the chemotherapeutic agent cisplatin leads to acute kidney injury (AKI). Cisplatin-induced AKI (CIAKI) has a complex pathophysiological map, which has been linked to cellular uptake and efflux, apoptosis, vascular injury, oxidative and endoplasmic reticulum stress, and inflammation. Despite research efforts, pharmaceutical interventions, and clinical trials spanning over several decades, a consistent and stable pharmacological treatment option to reduce AKI in patients receiving cisplatin remains unavailable. This has been predominately linked to the incomplete understanding of CIAKI pathophysiology and molecular mechanisms involved. Herein, we detail the extensively known pathophysiology of cisplatin-induced nephrotoxicity that manifests and the variety of pharmacological and genetic alteration studies that target them.

Phosphoinositide 3-kinase γ deficiency attenuates kidney injury and fibrosis in angiotensin II-induced hypertension

BACKGROUND

We have shown that the CXCL16/CXCR6 axis plays a critical role in recruiting inflammatory cells and bone marrow-derived fibroblasts into the kidney leading to renal injury and fibrosis. However, the underlying signaling mechanisms are not known.

METHODS

In the present study, we examined the role of phosphoinositide-3 kinase γ (PI3Kγ) signaling in the recruitment of inflammatory cells and bone marrow-derived fibroblasts into the kidney and development of renal injury and fibrosis in an experimental model of hypertension induced by angiotensin II.

RESULTS

Blood pressure was comparable between wild-type (WT) and PI3Kγ knockout (KO) mice at baseline. Angiotensin II treatment led to an increase in blood pressure that was similar between WT and PI3Kγ KO mice. Compared with WT mice, PI3Kγ KO mice were protected from angiotensin II-induced renal dysfunction and injury and developed less proteinuria. PI3Kγ deficiency suppressed bone marrow-derived fibroblast accumulation and myofibroblast formation in the kidney and inhibited total collagen deposition and extracellular matrix protein production in the kidney in response to angiotensin II. PI3Kγ deficiency inhibited the infiltration of F4/80+ macrophages and CD3+ T cells into the kidney and reduced gene expression levels of pro-inflammatory cytokines in the kidney following angiotensin II treatment. Finally, inhibition of PI3Kγ suppressed CXCL16-induced monocyte migration in vitro.

CONCLUSION

These results indicate that PI3Kγ mediates the influx of macrophages, T cells and bone marrow-derived fibroblasts into the kidney resulting in kidney injury and fibrosis.

EGFR-rich extracellular vesicles derived from highly metastatic nasopharyngeal carcinoma cells accelerate tumour metastasis through PI3K/AKT pathway-suppressed ROS

Nasopharyngeal carcinoma (NPC) is the most common cancer with high metastatic potential that occurs in the epithelial cells of the nasopharynx. Distant metastases are the primary cause for treatment failure and mortality of NPC patients. However, the underlying mechanism responsible for the initiation of tumour cell dissemination and tumour metastasis in NPC is not well understood. Here, we demonstrated that epidermal growth factor receptor (EGFR) was highly expressed in tumour tissues of NPC patients with distant metastases and was associated with a decrease in reactive oxygen species (ROS). We also revealed that extracellular vesicles (EVs) transfer occurred from highly to poorly metastatic NPC cells, mediating cell-cell communication and enhancing the metastatic potential of poorly metastatic NPC cells. Further experiments indicated that EVs derived from highly metastatic NPC cells induced the up-regulation of EGFR and down-regulation of ROS in low metastatic NPC cells. Mechanistically, EGFR-rich EVs-mediated EGFR overexpression down-regulated intracellular ROS levels through the PI3K/AKT pathway, thus promoting the metastatic potential of poorly metastatic NPC cells. Strikingly, treatment with EVs secreted from highly metastatic NPC cells was significantly associated with rapid NPC progression and shorter survival in xenografted mice. These findings not only improve our understanding of EVs-mediated NPC metastatic mechanism but also have important implications for the detection and treatment of NPC patients accompanied by aberrant EGFR-rich EVs transmission.

Ameliorative effect of phosphodiesterase 4 and 5 inhibitors in deoxycorticosterone acetate-salt hypertensive uni-nephrectomized KKAy mice

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease (ESRD). Hypertension increases kidney stress, which deteriorates function, and leads to peripheral renal vascular resistance. Long-term hypoperfusion promotes interstitial fibrosis and glomerular sclerosis, resulting in nephrosclerosis. Although hypertension and DN are frequent ESRD complications, relevant animal models remain unavailable. We generated a deoxycorticosterone acetate (DOCA)-salt hypertensive uni-nephrectomized (UNx) KKA^y mouse model demonstrating hypertension, hyperglycemia, cardiac hypertrophy, kidney failure, increased urinary albumin creatinine ratio (UACR), and increased renal PDE4D and cardiac PDE5A mRNA levels. We hypothesized that the novel PDE4 selective inhibitor, compound A, and PDE5 inhibitor, sildenafil, exhibit nephroprotective, and cardioprotective effects in this new model. Compound A, sildenafil, and the angiotensin II receptor blocker, irbesartan, significantly reduced ventricular hypertrophy and pleural effusion volume. Meanwhile, compound A and sildenafil significantly suppressed the UACR, urinary kidney injury molecule-1, and monocyte chemoattractant protein-1 levels, as well as that of renal pro-fibrotic marker mRNAs, including collagen 1A1, fibronectin, and transforming growth factor-beta (TGF-β). Moreover, compound A significantly suppressed TGF-β-induced pro-fibrotic mRNA expression in vitro in all major kidney lesions, including within the glomerular mesangial region, podocytes, and epithelial region. Hence, PDE4 and PDE5 inhibitors may be promising treatments, in combination with irbesartan, for DN with hypertension as they demonstrate complementary mechanisms.

Pharmacological inhibition of the NLRP3 inflammasome reduces blood pressure, renal damage, and dysfunction in salt-sensitive hypertension

Aims

Renal inflammation, leading to fibrosis and impaired function is a major contributor to the development of hypertension. The NLRP3 inflammasome mediates inflammation in several chronic diseases by processing the cytokines pro-interleukin (IL)-1β and pro-IL-18. In this study, we investigated whether MCC950, a recently-identified inhibitor of NLRP3 activity, reduces blood pressure (BP), renal inflammation, fibrosis and dysfunction in mice with established hypertension.

Methods and results

C57BL6/J mice were made hypertensive by uninephrectomy and treatment with deoxycorticosterone acetate (2.4 mg/day, s.c.) and 0.9% NaCl in the drinking water (1K/DOCA/salt). Normotensive controls were uninephrectomized and received normal drinking water. Ten days later, mice were treated with MCC950 (10 mg/kg/day, s.c.) or vehicle (saline, s.c.) for up to 25 days. BP was monitored by tail-cuff or radiotelemetry; renal function by biochemical analysis of 24-h urine collections; and kidney inflammation/pathology was assessed by real-time PCR for inflammatory gene expression, flow cytometry for leucocyte influx, and Picrosirius red histology for collagen. Over the 10 days post-surgery, 1K/DOCA/salt-treated mice became hypertensive, developed impaired renal function, and displayed elevated renal levels of inflammatory markers, collagen and immune cells. MCC950 treatment from day 10 attenuated 1K/DOCA/salt-induced increases in renal expression of inflammasome subunits (NLRP3, ASC, pro-caspase-1) and inflammatory/injury markers (pro-IL-18, pro-IL-1β, IL-17A, TNF-α, osteopontin, ICAM-1, VCAM-1, CCL2, vimentin), each by 25–40%. MCC950 reduced interstitial collagen and accumulation of certain leucocyte subsets in kidneys of 1K/DOCA/salt-treated mice, including CD206⁺ (M2-like) macrophages and interferon-gamma-producing T cells. Finally, MCC950 partially reversed 1K/DOCA/salt-induced elevations in BP, urine output, osmolality, [Na⁺], and albuminuria (each by 20–25%). None of the above parameters were altered by MCC950 in normotensive mice.

Conclusion

MCC950 was effective at reducing BP and limiting renal inflammation, fibrosis and dysfunction in mice with established hypertension. This study provides proof-of-concept that pharmacological inhibition of the NLRP3 inflammasome is a viable anti-hypertensive strategy.

Inflammatory macrophages in the kidney contribute to salt-sensitive hypertension

This review will highlight recent studies that have investigated the relationship between Na⁺, renal macrophage polarization, and renal damage. A hyperosmotic environment drives the macrophage toward a proinflammatory phenotype and away from an anti-inflammatory phenotype. Animal models of salt-sensitive hypertension demonstrate a characteristic infiltration of macrophages into the kidney that is greatly reduced when blood pressure is lowered. Because general immunosuppression or macrophage depletion leads to a host of adverse side effects, more recent studies have modulated the interaction of specific signaling molecules, including NOD-like receptor family pyrin domain-containing 3, chemokine (C-X-C motif) ligand 16, and VEGF, to prevent the end-organ renal damage that accumulates in salt-sensitive disease.

Disruption of CXCR6 Ameliorates Kidney Inflammation and Fibrosis in Deoxycorticosterone Acetate/Salt Hypertension

Circulating cells have a pathogenic role in the development of hypertensive nephropathy. However, how these cells infiltrate into the kidney are not fully elucidated. In this study, we investigated the role of CXCR6 in deoxycorticosterone acetate (DOCA)/salt-induced inflammation and fibrosis of the kidney. Following uninephrectomy, wild-type and CXCR6 knockout mice were treated with DOCA/salt for 3 weeks. Blood pressure was similar between wild-type and CXCR6 knockout mice at baseline and after treatment with DOCA/salt. Wild-type mice develop significant kidney injury, proteinuria, and kidney fibrosis after three weeks of DOCA/salt treatment. CXCR6 deficiency ameliorated kidney injury, proteinuria, and kidney fibrosis following treatment with DOCA/salt. Moreover, CXCR6 deficiency inhibited accumulation of bone marrow–derived fibroblasts and myofibroblasts in the kidney following treatment with DOCA/salt. Furthermore, CXCR6 deficiency markedly reduced the number of macrophages and T cells in the kidney after DOCA/salt treatment. In summary, our results identify a critical role of CXCR6 in the development of inflammation and fibrosis of the kidney in salt-sensitive hypertension.

CXCL16/CXCR6 axis promotes bleomycin-induced fibrotic process in MRC-5 cells via the PI3K/AKT/FOXO3a pathway

OBJECTIVE

Interstitial lung disease (ILD) is a progressive and irreversible lung disease with very limited therapeutic options. Previous studies have found that chemokine ligands CXCL16 and CXCR6 play critical roles in organ fibrosis. However, whether CXCL16 and CXCR6 are also involved in the pathogenesis of ILD, as well as their regulatory role in pulmonary fibrosis, has not been reported.

METHODS

In this study, we detected CXCL16 levels in patients with rheumatoid arthritis-associated ILD (RA-ILD) and examined the critical role of the CXCL16/CXCR6 axis in the proliferation and collagen production of human pulmonary fibroblasts (MRC-5 cells). The effect of anti-CXCL16 antibody on the bleomycin-induced fibrogenesis in cultured MRC-5 cells was also evaluated.

RESULTS

Our results indicated that serum soluble CXCL16 was significantly higher in RA-ILD patients and also associated with the severity of lung fibrosis. CXCL16 facilitates fibrosis by enhancing proliferation, migration, and collagen production of MRC-5 cells. Furthermore, a synergistic fibrogenic effect of CXCL16 and bleomycin has been found. CXCL16 stimulated the activation of PI3K/AKT/FOXO3a signaling pathway in MRC-5 cells, and the inhibition by specific inhibitors Wortmannin and LY294002, or knockdown of CXCR6 by siRNA also suppressed the biological functions of MRC-5 cells mediated by CXCL16. Similarly, down-regulation of CXCR6 also partly blocked BLM-induced fibrogenesis in MRC-5 cells.

CONCLUSIONS

CXCL16/CXCR6 axis promotes proliferation and collagen production of MRC-5 cells by the PI3K/AKT/FOXO3a signaling pathway, and inhibition of the CXCL16/CXCR6 axis may provide a new therapeutic strategy targeting pulmonary fibrosis.

CXCL16 is activated by p-JNK and is involved in H2O2-induced HK-2 cell injury via p-ERK signaling

Acute kidney injury (AKI) leads to an abrupt deterioration of renal function. CXC chemokine ligand 16 (CXCL16) is a CXC-soluble chemokine and a cell surface scavenger receptor that is involved in tissue injury and inflammation. It is induced in AKI patients, but the molecular mechanism remains unclear. In this study, we have worked to determine the function of CXCL16 and to investigate the involvement of ERK and JNK signaling in AKI. We used H₂O₂ and recombinant human CXCL16 protein (rh CXCL16) to treat the human renal tubular epithelial cell line, HK-2, in vitro. The present results indicate that H₂O₂ inhibits proliferation, induces apoptosis, and up-regulates expression of CXCL16 and the CXCL16 receptor, CXCR6, in HK-2 cells. Furthermore, H₂O₂-induced proliferation inhibition, apoptosis, and inflammation in HK-2 cells were ameliorated by NAC (N-acetyl cysteine, the ROS scavenger) and SP600125 (the JNK inhibitor). The expression levels of CXCL16 and CXCR6 were also positively correlated with the phosphorylation level of JNK (p-JNK). Additionally, rh CXCL16 treatment led to effects like those of H₂O₂ treatment in HK-2 cells, with symptoms being effectively improved by CXCR6 siRNA and the ERK inhibitor (PD98059). In addition, rh CXCL16-induced HK-2 cell apoptosis, inflammation, and collagen deposition were lessened by CXCR6 siRNA and PD98059 treatment. In summary, the present results have indicated that CXCL16 is involved in H₂O₂-induced HK-2 cell injury, that CXCL16 is activated by p-JNK, and that the regulatory function of CXCL16 is involved in the phosphorylation of ERK.

The chemokine receptor CX3CR1 reduces renal injury in mice with angiotensin II-induced hypertension

The role of CX₃CR1, also known as fractalkine receptor, in hypertension is unknown. The present study determined the role of the fractalkine receptor CX₃CR1 in hypertensive renal and cardiac injury. Expression of CX₃CR1 was determined using CX₃CR1^GFP/+ mice that express a green fluorescent protein (GFP) reporter in CX₃CR1⁺ cells. FACS analysis of leukocytes isolated from the kidney showed that 34% of CD45⁺ cells expressed CX₃CR1. Dendritic cells were the majority of positive cells (67%) followed by macrophages (10%), NK cells (6%), and T cells (10%). With the use of confocal microscopy, the receptor was detected in the kidney only on infiltrating cells but not on resident renal cells. To evaluate the role of CX₃CR1 in hypertensive end-organ injury, an aggravated model of hypertension was used. Unilateral nephrectomy was performed followed by infusion of angiotensin II (ANG II, 1.5 ng·g^-1·min^-1) and a high-salt diet in wild-type ( n = 15) and CX₃CR1-deficient mice ( n = 18). CX₃CR1 deficiency reduced the number of renal dendritic cells and increased the numbers of renal CD11b/F4/80⁺ macrophages and CD11b/Ly6G⁺ neutrophils in ANG II-infused mice. Surprisingly, CX₃CR1-deficient mice exhibited increased albuminuria, glomerular injury, and reduced podocyte density in spite of similar levels of arterial hypertension. In contrast, cardiac damage as assessed by increased heart weight, cardiac fibrosis, and expression of fetal genes, and matrix components were not different between both genotypes. Our findings suggest that CX₃CR1 exerts protective properties by modulating the invasion of inflammatory cells in hypertensive renal injury. CX₃CR1 inhibition should be avoided in hypertension because it may promote hypertensive renal injury.

Macrophage Depletion Lowered Blood Pressure and Attenuated Hypertensive Renal Injury and Fibrosis

Monocyte/macrophage recruitment is closely associated with the degree of hypertensive renal injury. We investigated the direct role of macrophages using liposome-encapsulated clodronate (LEC) to deplete monocytes/macrophages in hypertensive renal injury. C57BL/6 mice were treated with a pressor dose of angiotensin (Ang, 1.4 mg/kg/day) II plus LEC or the PBS-liposome for 2 weeks. Ang II mice developed hypertension, albuminuria, glomerulosclerosis, and renal fibrosis. LEC treatment reduced systolic blood pressure (SBP), albuminuria, and protected against renal structural injury in Ang II mice. Ang II significantly increased renal macrophage infiltration (MOMA2⁺ cells) and the expression of renal tumor necrosis factor α and interleukin β1, which were significantly reduced in Ang II/LEC mice. Ang II increased renal oxidative stress and the expression of profibrotic factors transforming growth factor (TGF) β1 and fibronectin. Ang II also inhibited the phosphorylation of endothelial nitric oxide synthase [phospho-endothelial nitric oxide synthesis (eNOS), ser1177]. LEC treatment reduced renal oxidative stress and TGFβ1 and fibronectin expressions, and increased phospho-eNOS expression in the Ang II mice. In Dahl rats of salt-sensitive hypertension, LEC treatment for 4 weeks significantly attenuated the elevation of SBP induced by high salt intake and protected against renal injury and fibrosis. Our results demonstrate that renal macrophages play a critical role in the development of hypertension and hypertensive renal injury and fibrosis; the underlying mechanisms may be involved in the reduction in macrophage-driven renal inflammation and restoration of the balance between renal oxidative stress and eNOS. Therefore, macrophages should be considered as a potential therapeutic target to reduce the adverse consequences of hypertensive renal diseases.

Pharmacological Inhibition of PTEN Aggravates Acute Kidney Injury

Renal ischemia/reperfusion is a major cause of acute kidney injury. However, the pathogenic mechanisms underlying renal ischemia/reperfusion injury (IRI) are not fully defined. Here, we investigated the role of PTEN, a dual protein/lipid phosphatase, in the development of ischemic AKI in mice. Pharmacological inhibition of PTEN with bpV(HOpic) exacerbated renal dysfunction and promoted tubular damage in mice with IRI compared with vehicle-treated mice with IRI. PTEN inhibition enhanced tubular cell apoptosis in kidneys with IRI, which was associated with excessive caspase-3 activation. Furthermore, PTEN inhibition expanded the infiltration of neutrophils and macrophages into kidneys with IRI, which was accompanied by increased expression of the proinflammatory molecules. These results have demonstrated that PTEN plays a crucial role in the pathogenesis of ischemic acute kidney injury through regulating tubular cell apoptosis and inflammation suggesting PTEN could be a potential therapeutic target for acute kidney injury.

Protection of tubular epithelial cells during renal injury via post-transcriptional control of BMP7

Severe injury of renal tubular epithelial cells may cause acute renal failure, the progression of which results in renal fibrosis, and obstructive nephropathy. Transforming growth factor β 1 and bone morphogenic protein 7 (BMP7) play contradicting roles in and coordinate the process of epithelial-to-mesenchymal transition of renal tubular epithelial cells, but the molecular regulation of BMP7 remains ill-defined. Here, we addressed this question. We found that after induction of unilateral ureteral obstruction (UUO) in mice, the increases in BMP7 mRNA were much more pronounced than BMP7 protein in kidney, suggesting the presence of post-transcriptional control of BMP7. Moreover, significant increases in a BMP7-targeting microRNA, miR-384-5p, were detected in the mouse kidney post UUO. Overexpression of miR-384-5p significantly decreased BMP7 protein, while depletion of miR-384-5p significantly increased BMP7 protein in renal epithelial cells. Bioinformatics study showed that miR-384-5p appeared to suppress BMP7 protein translation, through its direct binding to the 3'-UTR of BMP7 mRNA. Furthermore, suppression of miR-384-5p in vivo attenuated severity of renal injury by UUO. Together, our study sheds light on miR-384-5p as a crucial factor that regulates the fibrosis-related pathogenesis after renal injury, and points to miR-384-5p as a promising innovative therapeutic target for prevention of renal fibrosis.

Recent Advances in Magnetic Resonance Imaging Assessment of Renal Fibrosis

CKD is a global public health problem. Renal fibrosis is a final common pathway leading to progressive loss of function in CKD. The degree of renal fibrosis predicts the prognosis of CKD. Recent studies have shown that bone marrow-derived fibroblasts contribute significantly to the development of renal fibrosis, which may yield novel therapeutic strategy for fibrotic kidney disease. Therefore, it is imperative to accurately assess the degree of renal fibrosis noninvasively to identify those patients who can benefit from antifibrotic therapy. In this review, we summarize recent advances in the assessment of renal fibrosis by magnetic resonance imaging.

The role of chemokines in hypertension and consequent target organ damage

Immune cells infiltrate the kidney, vasculature, and central nervous system during hypertension, consequently amplifying tissue damage and/or blood pressure elevation. Mononuclear cell motility depends partly on chemokines, which are small cytokines that guide cells through an increasing concentration gradient via ligation of their receptors. Tissue expression of several chemokines is elevated in clinical and experimental hypertension. Likewise, immune cells have enhanced chemokine receptor expression during hypertension, driving immune cell infiltration and inappropriate inflammation in cardiovascular control centers. T lymphocytes and monocytes/macrophages are pivotal mediators of hypertensive inflammation, and these cells migrate in response to several chemokines. As powerful drivers of diapedesis, the chemokines CCL2 and CCL5 have long been implicated in hypertension, but experimental data highlight divergent, context-specific effects of these chemokines on blood pressure and tissue injury. Several other chemokines, particularly those of the CXC family, contribute to blood pressure elevation and target organ damage. Given the significant interplay and chemotactic redundancy among chemokines during disease, future work must not only describe the actions of individual chemokines in hypertension, but also characterize how manipulating a single chemokine modulates the expression and/or function of other chemokines and their cognate receptors. This information will facilitate the design of precise chemotactic immunotherapies to limit cardiovascular and renal morbidity in hypertensive patients.

CXCL16 regulates renal injury and fibrosis in experimental renal artery stenosis

Recent studies have shown that inflammation plays a critical role in the initiation and progression of hypertensive kidney disease, including renal artery stenosis. However, the signaling mechanisms underlying the induction of inflammation are poorly understood. We found that CXCL16 was induced in the kidney in a murine model of renal artery stenosis. To determine whether CXCL16 is involved in renal injury and fibrosis, wild-type and CXCL16 knockout mice were subjected to renal artery stenosis induced by placing a cuff on the left renal artery. Wild-type and CXCL16 knockout mice had comparable blood pressure at baseline. Renal artery stenosis caused an increase in blood pressure that was similar between wild-type and CXCL16 knockout mice. CXCL16 knockout mice were protected from RAS-induced renal injury and fibrosis. CXCL16 deficiency suppressed bone marrow-derived fibroblast accumulation and myofibroblast formation in the stenotic kidneys, which was associated with less expression of extracellular matrix proteins. Furthermore, CXCL16 deficiency inhibited infiltration of F4/80(+) macrophages and CD3(+) T cells in the stenotic kidneys compared with those of wild-type mice. Taken together, our results indicate that CXCL16 plays a pivotal role in the pathogenesis of renal artery stenosis-induced renal injury and fibrosis through regulation of bone marrow-derived fibroblast accumulation and macrophage and T-cell infiltration.