Stiffness sensing via Piezo1 enhances macrophage efferocytosis and promotes the resolution of liver fibrosis.

Tissue stiffening is a predominant feature of fibrotic disorders, but the response of macrophages to changes in tissue stiffness and cellular context in fibrotic diseases remains unclear. Here, we found that the mechanosensitive ion channel Piezo1 was up-regulated in hepatic fibrosis. Macrophages lacking Piezo1 showed sustained inflammation and impaired spontaneous resolution of early liver fibrosis. Further analysis revealed an impairment of clearance of apoptotic cells by macrophages in the fibrotic liver. Macrophages showed enhanced efferocytosis when cultured on rigid substrates but not soft ones, suggesting stiffness-dependent efferocytosis of macrophages required Piezo1 activation. Besides, Piezo1 was involved in the efficient acidification of the engulfed cargo in the phagolysosomes and affected the subsequent expression of anti-inflammation genes after efferocytosis. Pharmacological activation of Piezo1 increased the efferocytosis capacity of macrophages and accelerated the resolution of inflammation and fibrosis. Our study supports the antifibrotic role of Piezo1-mediated mechanical sensation in liver fibrosis, suggesting that targeting PIEZO1 to enhance macrophage efferocytosis could induce fibrosis regression.

Vinblastine resets tumor-associated macrophages toward M1 phenotype and promotes antitumor immune response.

BACKGROUND: Massive tumor-associated macrophage (TAM) infiltration is observed in many tumors, which usually display the immune-suppressive M2-like phenotype but can also be converted to an M1-like antitumor phenotype due to their high degree of plasticity. The macrophage polarization state is associated with changes in cell shape, macrophage morphology is associated with activation status. M1 macrophages appeared large and rounded, while M2 macrophages were stretched and elongated cells. Manipulating cell morphology has been shown to affect the polarization state of macrophages. The shape of the cell is largely dependent on cytoskeletal proteins, especially, microtubules. As a microtubule-targetting drug, vinblastine (VBL) has been used in chemotherapy. However, no study to date has explored the effect of VBL on TAM shape changes and its role in tumor immune response. METHOD: We used fluorescent staining of the cytoskeleton and quantitative analysis to reveal the morphological differences between M0, M1, M2, TAM and VBL-treated TAM. Flow cytometry was used to confirm the polarization states of these macrophages using a cell surface marker-based classification. In vivo antibody depletion experiments in tumor mouse models were performed to test whether macrophages and CD8+ T cell populations were required for the antitumor effect of VBL. VBL and anti-PD-1 combination therapy was then investigated in comparison with monotherapy. RNA-seq of TAM of treated and untreated with VBL was performed to explore the changes in pathway activities. siRNA mediated knockdown experiments were performed to verify the target pathway that was affected by VBL treatment. RESULTS: Here, we showed that VBL, an antineoplastic agent that destabilizes microtubule, drove macrophage polarization into the M1-like phenotype both in vitro and in tumor models. The antitumor effect of VBL was attenuated in the absence of macrophages or CD8+ T cells. Mechanistically, VBL induces the activation of NF-κB and Cyba-dependent reactive oxygen species generation, thus polarizing TAMs to the M1 phenotype. In parallel, VBL promotes the nuclear translocation of transcription factor EB, inducing lysosome biogenesis and a dramatic increase in phagocytic activity in macrophages. CONCLUSIONS: This study explored whether manipulating cellular morphology affects macrophage polarization and consequently induces an antitumor response. Our data reveal a previously unrecognized antitumor mechanism of VBL and suggest a drug repurposing strategy combining VBL with immune checkpoint inhibitors to improve malignant tumor immunotherapy.

Oxidized mitochondrial DNA induces gasdermin D oligomerization in systemic lupus erythematosus.

Although extracellular DNA is known to form immune complexes (ICs) with autoantibodies in systemic lupus erythematosus (SLE), the mechanisms leading to the release of DNA from cells remain poorly characterized. Here, we show that the pore-forming protein, gasdermin D (GSDMD), is required for nuclear DNA and mitochondrial DNA (mtDNA) release from neutrophils and lytic cell death following ex vivo stimulation with serum from patients with SLE and IFN-γ. Mechanistically, the activation of FcγR downregulated Serpinb1 following ex vivo stimulation with serum from patients with SLE, leading to spontaneous activation of both caspase-1/caspase-11 and cleavage of GSDMD into GSDMD-N. Furthermore, mtDNA oxidization promoted GSDMD-N oligomerization and cell death. In addition, GSDMD, but not peptidyl arginine deiminase 4 is necessary for extracellular mtDNA release from low-density granulocytes from SLE patients or healthy human neutrophils following incubation with ICs. Using the pristane-induced lupus model, we show that disease severity is significantly reduced in mice with neutrophil-specific Gsdmd deficiency or following treatment with the GSDMD inhibitor, disulfiram. Altogether, our study highlights an important role for oxidized mtDNA in inducing GSDMD oligomerization and pore formation. These findings also suggest that GSDMD might represent a possible therapeutic target in SLE.

PD-L1 negatively regulates antifungal immunity by inhibiting neutrophil release from bone marrow.

Programmed death ligand 1 (PD-L1) has been shown to be inducibly expressed on neutrophils to suppress host immunity during polymicrobial sepsis, virus and parasite infections. However, the role of PD-L1 on neutrophil-mediated antifungal immunity remains wholly unknown. Here, we show that the expression of PD-L1 on murine and human neutrophils was upregulated upon the engagement of C-type lectin receptor Dectin-1 with its ligand ß-glucans, exposed on fungal pathogen Candida albicans yeast. Moreover, ß-glucan stimulation induced PD-L1 translocation into nucleus to regulate the production of chemokines CXCL1 and CXCL2, which control neutrophil mobilization. Importantly, C. albicans infection-induced expression of PD-L1 leads to neutrophil accumulation in bone marrow, through mediating their autocrine secretion of CXCL1/2. Furthermore, neutrophil-specific deficiency of PD-L1 impaired CXCL1/2 secretion, which promoted neutrophil migration from bone marrow into the peripheral circulation, thereby conferring host resistance to C. albicans infection. Finally, either PD-L1 blockade or pharmacological inhibition of PD-L1 expression significantly increased neutrophil release from bone marrow to enhance host antifungal immunity. Our data together indicate that activation of Dectin-1/PD-L1 cascade by ß-glucans inhibits neutrophil release from bone marrow reserve, contributing to the negative regulation of antifungal innate immunity, which functions as a potent immunotherapeutic target against life-threatening fungi infections.

Ferritin triggers neutrophil extracellular trap-mediated cytokine storm through Msr1 contributing to adult-onset Still's disease pathogenesis.

Hyperferritinemic syndrome, an overwhelming inflammatory condition, is characterized by high ferritin levels, systemic inflammation and multi-organ dysfunction, but the pathogenic role of ferritin remains largely unknown. Here we show in an animal model that ferritin administration leads to systemic and hepatic inflammation characterized by excessive neutrophil leukocyte infiltration and neutrophil extracellular trap (NET) formation in the liver tissue. Ferritin-induced NET formation depends on the expression of peptidylarginine deiminase 4 and neutrophil elastase and on reactive oxygen species production. Mechanistically, ferritin exposure increases both overall and cell surface expression of Msr1 on neutrophil leukocytes, and also acts as ligand to Msr1 to trigger the NET formation pathway. Depletion of neutrophil leukocytes or ablation of Msr1 protect mice from tissue damage and the hyperinflammatory response, which further confirms the role of Msr1 as ferritin receptor. The relevance of the animal model is underscored by the observation that enhanced NET formation, increased Msr1 expression and signalling on neutrophil leukocytes are also characteristic to adult-onset Still's disease (AOSD), a typical hyperferritinemic syndrome. Collectively, our findings demonstrate an essential role of ferritin in NET-mediated cytokine storm, and suggest that targeting NETs or Msr1 may benefit AOSD patients.

Disulfiram bolsters T-cell anti-tumor immunity through direct activation of LCK-mediated TCR signaling.

Activation of the T-cell antigen receptor (TCR)-CD3 complex is critical to induce the anti-tumor response of CD8+ T cells. Here, we found that disulfiram (DSF), an FDA-approved drug previously used to treat alcohol dependency, directly activates TCR signaling. Mechanistically, DSF covalently binds to Cys20/Cys23 residues of lymphocyte-specific protein tyrosine kinase (LCK) and enhances its tyrosine 394 phosphorylation, thereby promoting LCK kinase activity and boosting effector T cell function, interleukin-2 production, metabolic reprogramming, and proliferation. Furthermore, our in vivo data revealed that DSF promotes anti-tumor immunity against both melanoma and colon cancer in mice by activating CD8+ T cells, and this effect was enhanced by anti-PD-1 co-treatment. We conclude that DSF directly activates LCK-mediated TCR signaling to induce strong anti-tumor immunity, providing novel molecular insights into the therapeutic effect of DSF on cancer.

Caspase-11 promotes NLRP3 inflammasome activation via the cleavage of pannexin1 in acute kidney disease.

Ischemia/reperfusion (I/R) injury is a major cause of acute kidney injury (AKI) in clinic. The activation of NLRP3 inflammasome is associated with inflammation and renal injury in I/R-induced AKI. In the current study we explored the molecular and cellular mechanisms for NLRP3 inflammasome activation following renal I/R. Mice were subjected to I/R renal injury by clamping bilateral renal pedicles. We showed that I/R injury markedly increased caspase-11 expression and the cleavage of pannexin 1 (panx1) in the kidneys accompanied by NLRP3 inflammasome activation evidenced by the activation of caspase-1 and interlukin-1ß (IL-1ß) maturation. In Casp-11-/- mice, I/R-induced panx1 cleavage, NLRP3 inflammasome activation as well as renal functional deterioration and tubular morphological changes were significantly attenuated. In cultured primary tubular cells (PTCs) and NRK-52E cells, hypoxia/reoxygenation (H/R) markedly increased caspase-11 expression, NLRP3 inflammasome activation, IL-1ß maturation and panx1 cleavage. Knockdown of caspase-11 attenuated all those changes; similar effects were observed in PTCs isolated from Casp-11-/- mice. In NRK-52E cells, overexpression of caspase-11 promoted panx1 cleavage; pretreatment with panx1 inhibitor carbenoxolone or knockdown of panx1 significantly attenuated H/R-induced intracellular ATP reduction, extracellular ATP elevation and NLRP3 inflammasome activation without apparent influence on H/R-induced caspase-11 increase; pretreatment with P2X7 receptor inhibitor AZD9056 also attenuated NLRP3 inflammasome activation. The above results demonstrate that the cleavage of panx1 by upregulated caspase-11 is involved in facilitating ATP release and then NLRP3 inflammasome activation in I/R-induced AKI. This study provides new insight into the molecular mechanism of NLRP3 inflammasome activation in AKI.

FoxM1 promotes Wnt/ß-catenin pathway activation and renal fibrosis via transcriptionally regulating multi-Wnts expressions.

The activation of Wnt/ß-catenin pathway plays a pivotal role in promoting renal fibrosis. The activation of Wnt/ß-catenin pathway relies on the binding of Wnts to Frizzled receptors on cell membrane. However, the factor regulating Wnts production remains unclear. Here, we demonstrated that transcriptional factor FoxM1 was significantly increased in obstructed kidneys and patients' kidneys with fibrosis. The up-regulation of FoxM1 mainly distributed in tubular epithelial cells. Pharmacological inhibition of FoxM1 down-regulated multi-Wnts elevation in UUO mice and attenuated renal fibrosis. In cultured renal tubular epithelial cells, overexpression of FoxM1 promoted 8 Wnts expression, while knock-down on FoxM1-suppressed multi-Wnts including Wnt1, Wnt2b and Wnt3 expression induced by Ang II. Chromatin immunoprecipitation PCR confirmed that FoxM1 bound to Wnt1, Wnt2b, Wnt3 promoters and luciferase assay further identified that the transcriptions of Wnt1, Wnt2b and Wnt3 were regulated by FoxM1. Thus, our findings show that multi-Wnt family members were regulated by transcriptional factor FoxM1. FoxM1 might be a key switch for activating ß-catenin pathway and renal fibrosis. Therefore, FoxM1 might be a potential therapeutic target in manipulating renal fibrosis.

RIG-I aggravates interstitial fibrosis via c-Myc-mediated fibroblast activation in UUO mice.

Progressive tubulointerstitial fibrosis is the common final outcome for all kidney diseases evolving into chronic kidney disease (CKD), whereas molecular mechanisms driving fibrogenesis remain elusive. Retinoic acid-inducible gene-I (RIG-I), an intracellular pattern recognition receptor, is originally identified participating in immune response by recognizing virus RNA. Here, we revealed for the first time that RIG-I was induced in unilateral ureteral obstruction (UUO) and folic acid (FA) renal fibrosis models and moderate-degree renal fibrosis patients. Besides, we found RIG-I was mainly located in renal tubular epithelial cells and promoted the production and release of inflammatory cytokines, such as interleukin (IL)-1ß and IL-6 through activation of NF-κB. Inflammatory cytokines released by tubular epithelial cells activated c-Myc-mediated TGF-ß/Smad signaling in fibroblasts, which in turn aggravated interstitial fibrosis by promoting fibroblast activation and production of extracellular matrix components (ECM). Deficiency of RIG-I attenuated renal fibrosis by the regulation of inflammatory responses, c-Myc expression, and fibroblast activation. Besides, gene silencing of RIG-I reduced inflammatory cytokines in cultured tubular epithelial cells treated with Angiotensin II. Knockdown of c-Myc or c-Myc inhibitor blocked IL-1ß-induced fibroblast activation. Collectively, our study demonstrates that RIG-I plays a significant role in the progress of renal fibrosis via regulating c-Myc-mediated fibroblast activation. KEY MESSAGES: • RIG-I was constantly elevated in kidneys from renal fibrotic mice. • RIG-I facilitated inflammatory cytokine production in tubular epithelial cells. • RIG-I aggravated renal fibrosis via c-Myc-mediated TGF-ß/Smad activation.

The cleavage of gasdermin D by caspase-11 promotes tubular epithelial cell pyroptosis and urinary IL-18 excretion in acute kidney injury.

Inflammation and tubular cell death are the hallmarks of acute kidney injury. However, the precise mechanism underlying these effects has not been fully elucidated. Here we tested whether caspase-11, an inflammatory member of the caspase family, was increased in cisplatin or ischemia-reperfusion-induced acute kidney injury. Caspase-11 knockout mice after cisplatin treatment exhibited attenuated deterioration of renal functional, reduced tubular damage, reduced macrophage and neutrophil infiltration, and decreased urinary IL-18 excretion. Mechanistically, the upregulation of caspase-11 by either cisplatin or ischemia-reperfusion cleaved gasdermin D (GSDMD) into GSDMD-N, which translocated onto the plasma membrane, thus triggering cell pyroptosis and facilitated IL-18 release in primary cultured renal tubular cells. These results were further confirmed in GSDMD knockout mice that cisplatin-induced renal morphological and functional deterioration as well as urinary IL-18 excretion were alleviated. Furthermore, deficiency of GSDMD significantly suppressed cisplatin-induced IL-18 release but not the transcription and maturation level of IL-18 in tubular cells. Thus, our study indicates that caspase-11/GSDMD dependent tubule cell pyroptosis plays a significant role in initiating tubular cell damage, urinary IL-18 excretion and renal functional deterioration in acute kidney injury.

NIX-mediated mitophagy protects against proteinuria-induced tubular cell apoptosis and renal injury.

Proteinuria, the most common symptom of renal injury, is an independent factor for renal tubular injury. However, the underlying mechanism remains to be fully elucidated. Mitochondrion is an important target for proteinuria-induced renal tubular cell injury. Insufficient mitophagy exacerbates cell injury by initiating mitochondrial dysfunction-related cell apoptosis. In the experiment, the role of NIP3-like protein X (NIX)-mediated mitophagy was investigated in proteinuria-induced renal injury. In this study, we demonstrated that NIX expression was reduced in renal tubules and correlated with the decline of estimated glomerular filtration rate and increase of the proteinuria in patients. In proteinuric mice, NIX-mediated mitophagy was significantly suppressed. Meanwhile, the proteinuric mice exhibited renal dysfunction, increased mitochondrial fragmentation, and tubular cell apoptosis. Overexpression of NIX attenuated those disruptions in proteinuric mice. In cultured renal tubular epithelial cells, albumin induced a decrease in NIX-mediated mitophagy and an increase in cell apoptosis. Overexpression of NIX attenuated albumin-induced cell apoptosis, whereas NIX siRNA aggravated these perturbations. These results indicate that proteinuria suppresses NIX-mediated mitophagy in the renal tubular epithelial cell, which triggers the cell undergoing mitochondria-dependent cell apoptosis. Collectively, our finding suggests that restoration of NIX-mediated mitophagy might be a novel therapeutic target for alleviating proteinuria-induced kidney injury.

Caspase-11 promotes renal fibrosis by stimulating IL-1ß maturation via activating caspase-1.

Caspase-11 is a key upstream modulator for activation of inflammatory response under pathological conditions. In this study, we investigated the roles of caspase-11 in the maturation of interleukin-1ß (IL-1ß) and development of renal interstitial fibrosis in vivo and in vitro. Mice were subjected to unilateral ureteral obstruction (UUO). The mice were treated with either caspase-11 inhibitor wedelolactone (Wed, 30 mg/kg/day, ig) for 7 days or caspase-11 siRNA (10 nmol/20 g body weight per day, iv) for 14 days. The mice were euthanized on day 14, their renal tissue and blood sample were collected. We found that the obstructed kidney had significantly higher caspase-11 levels and obvious tubular injury and interstitial fibrosis. Treatment with Wed or caspase-11 siRNA significantly mitigated renal fibrosis in UUO mice, evidenced by the improved histological changes. Furthermore, caspase-11 inhibition significantly blunted caspase-1 activation, IL-1ß maturation, transforming growth factor-ß (TGF-ß), fibronectin, and collagen I expressions in the obstructed kidney. Renal tubular epithelial NRK-52E cells were treated in vitro with angiotensin (Ang, 1 µmol/L), which stimulated caspase-11 activation and IL-1ß maturation. Treatment with IL-1ß (20 ng/ml) significantly increased the expression of TGF-ß, fibronectin, and collagen I in the cells. Ang II-induced expression of TGF-ß, fibronectin, and collagen I were suppressed by caspase-11 siRNA or Wed. Finally, we revealed using co-immunoprecipitation that caspase-11 was able to interact with caspase-1 in NRK-52E cells. These results suggest that caspase-11 is involved in UUO-induced renal fibrosis. Elevation of caspase-11 in the obstructed kidney promotes renal fibrosis by stimulating caspase-1 activation and IL-1ß maturation.

c-Myc promotes tubular cell apoptosis in ischemia-reperfusion-induced renal injury by negatively regulating c-FLIP and enhancing FasL/Fas-mediated apoptosis pathway.

c-Myc plays an important role in cell proliferation, differentiation, and cell apoptosis. FasL/Fas pathway is a key regulator of cell apoptosis. This study was aimed to investigate the effects of c-Myc on the FasL/Fas pathway in ischemia-reperfusion (I/R)-induced renal injury. Rats were objected to bilateral renal ischemia for 60 min and reperfused for 24 or 48 h. NRK-52E cells were treated with hypoxia-reoxygenation (H/R) or FasL. Immunohistochemistry was used to identify the distribution of c-Myc. Cell apoptosis was assessed by TUNEL staining. Ad-c-Myc and recombinant pcDAN 3.0 were used to overexpress c-Myc and c-FLIP, respectively. ChIP assay and luciferase assay were used to detect the binding of c-Myc to c-FLIP promoter. In I/R rats, c-Myc was increased significantly and mainly located in renal tubular epithelial cells; meanwhile, c-FLIP was decreased, cleaved caspase-8, cleaved caspase-3 and TUNEL-positive staining cells were increased. Treatment of I/R rats with c-Myc inhibitor 10058-F4 significantly attenuated the decrease in c-FLIP, the increase in cleaved caspase-8, cleaved caspase-3, TUNEL-positive cells, Scr and BUN in I/R rats. In NRK-52E cells, hypoxia and reoxygen induced the increase in c-Myc and decrease in c-FLIP. ChIP and luciferase assay results indicated that c-Myc binds to the promoter region of c-FLIP gene. Overexpression of c-Myc markedly decreased c-FLIP. Overexpression of c-FLIP inhibited the increase in cleaved caspase-8 and caspase-3 induced by FasL. Data indicated that c-Myc is increased in kidneys of I/R rats and negatively regulates the expression of c-FLIP, then enhanced FasL-induced cell apoptosis in I/R stress.

SND p102 promotes extracellular matrix accumulation and cell proliferation in rat glomerular mesangial cells via the AT1R/ERK/Smad3 pathway.

SND p102 was first described as a transcriptional co-activator, and subsequently determined to be a co-regulator of Pim-1, STAT6 and STAT5. We previously reported that SND p102 expression was increased in high glucose-treated mesangial cells (MCs) and plays a role in the extracellular matrix (ECM) accumulation of MCs by regulating the activation of RAS. In this study, we further examined the roles of SND p102 in diabetic nephropathy (DN)-induced glomerulosclerosis. Rats were injected with STZ (50 mg/kg, ip) to induce diabetes. MCs or isolated glomeruli were cultured in normal glucose (NG, 5.5 mmol/L)- or high glucose (HG, 25 mmol/L)-containing DMEM. We found that SND p102 expression was significantly increased in the diabetic kidneys, as well as in HG-treated isolated glomeruli and MCs. In addition, HG treatment induced significant fibrotic changes in MCs evidenced by enhanced protein expression of TGF-ß, fbronectin and collagen IV, and significantly increased the proliferation of MCs. We further revealed that overexpression of SND p102 significantly increased the protein expression of angiotensin II (Ang II) type 1 receptor (AT1R) in MCs by increasing its mRNA levels via directly targeting the AT1R 3'-UTR, which resulted in activation of the ERK/Smad3 signaling and subsequently promoted the up-regulation of fbronectin, collagen IV, and TGF-ß in MCs, as well as the cell proliferation. These results demonstrate that SND p102 is a key regulator of AT1R-mediating ECM synthesis and cell proliferation in MCs. Thus, small molecule inhibitors of SND p102 may be a novel therapeutic strategy for DN.

Caspase-11 promotes cisplatin-induced renal tubular apoptosis through a caspase-3-dependent pathway.

Renal tubular injury is the hallmark of cisplatin-induced nephrotoxicity. Caspase-11, a member of the caspase family, plays an important role in inflammation and cell death. However, its role in cisplatin-induced renal tubular injury remains unclear. In cisplatin-treated mice, caspase-11 expression was significantly elevated and the expression of caspase-11 was mainly located in renal tubule. Inhibition of caspase-11 by small-interference RNA or its inhibitor wedelolactone attenuated cisplatin-induced renal dysfunction and tubular injury. In cultured primary renal tubular epithelial cells, cisplatin significantly promoted the expression and activation of caspase-11. Inhibition of caspase-11 by small-interference RNA reduced cisplatin-induced cell apoptosis. Overexpression of caspase-11 promoted cell apoptosis by activating the caspase-3-related cell apoptosis. Furthermore, coimmunoprecipitation results showed there was a direct interaction between caspase-11 and caspase-3, and the interaction was enhanced by cisplatin. The fluorescence confocal microscopy results showed that caspase-11 and caspase-3 were colocalized in the cytoplasm of renal tubular epithelial cells. These results demonstrate that caspase-11 plays an important role in cisplatin-induced renal tubular injury. Caspase-11 promotes renal epithelial cell apoptosis by activating the caspase-3-dependent apoptotic pathway. Caspase-11 might be a potential target for therapeutic treatment against cisplatin-induced nephrotoxicity.

c-Myc promotes renal fibrosis by inducing integrin αv-mediated transforming growth factor-ß signaling.

Fibrogenesis involves the activation of renal fibroblasts upon kidney injury. However, the mechanisms underlying renal fibroblast activation are poorly characterized. c-Myc is a predominant oncogene encoding a pleiotropic transcription factor that participates in the regulation of various genes, including genes vital for regulating the cell cycle, cell proliferation, and apoptosis. Here we tested whether renal fibrosis in unilateral ureteral obstruction and folic acid-induced renal fibrosis mouse models are associated with the overexpression of c-Myc. Transforming growth factor-ß (TGF-ß) has been identified as a key mediator of renal fibrosis, and it is secreted in an inactive form as a complex with latency-associated peptide and latent TGF-ß-binding proteins. Five αv-containing integrins with different ß -subunits can activate TGF-ß, and consistent with this we found that c-Myc bound directly to the promoter of integrin αv in renal fibroblasts activating its transcription. This, in turn, induced activation of TGF-ß signaling. Pharmacological blockade of c-Myc attenuated renal fibrosis in vivo in the ureteral obstruction and folic acid-treated mouse models and inhibited the proliferation and activation of renal fibroblasts in vitro. Thus, c-Myc overexpression stimulated proliferation and activation of renal fibroblasts by inducing integrin αv -mediated TGF-ß signaling. Hence, targeting c-Myc may have clinical utility in the treatment of renal fibrosis.

N-acetylcysteine alleviates angiotensin II-mediated renal fibrosis in mouse obstructed kidneys.

AIM: To investigate the effects of ROS scavenger N-acetylcysteine (NAC) on angiotensin II (Ang II)-mediated renal fibrosis in vivo and in vitro. METHODS: Mice were subjected to unilateral ureteral obstruction (UUO), and then treated with vehicle or NAC (250 mg/kg, ip) for 7 days. Histological changes of the obstructed kidneys were observed with Masson's trichrome staining. ROS levels were detected with DHE staining. The expression of relevant proteins in the obstructed kidneys was assessed using Western blotting assays. Cultured rat renal fibroblast NRK-49F cells were used for in vitro experiments. RESULTS: In the obstructed kidneys, Ang II levels were significantly elevated, and collagen I was accumulated in the interstitial spaces. Furthermore, ROS production and the expression of p47 (a key subunit of NADPH oxidase complexes) were increased in a time-dependent manner; the expression of fibronectin, α-SMA and TGF-ß were upregulated. Administration of NAC significantly alleviated the fibrotic responses in the obstructed kidneys. In cultured NRK-49F cells, treatment with Ang II (0.001-10 µmol/L) increased the expression of fibronectin, collagen I, α-SMA and TGF-ß in dose-dependent and time-dependent manners. Ang II also increased ROS production and the phosphorylation of Smad3. Pretreatment with NAC (5 µmol/L) blocked Ang II-induced oxidative stress and ECM production in the cells. CONCLUSION: In mouse obstructed kidneys, the fibrotic responses result from Ang II upregulation can be alleviated by the ROS scavenger N-acetylcysteine.

Involvement of spliced X-box binding protein 1 in renal fibrosis induced by unilateral ureteral obstruction in mice.

Endoplasmic reticulum (ER) stress is involved in the process of kidney fibrosis. Spliced X-box binding protein 1 (XBP1S) is the key mediator of ER stress while its role in fibrosis is still poorly understood. This study was aimed to investigate the role of XBP1S in renal fibrosis and evaluate whether valsartan could alleviate fibrosis through XBP1S. Renal interstitial fibrosis was induced by unilateral ureteral obstruction (UUO) in C57BL/6 mice, and UUO mice were daily administered with valsartan (20 mg/kg) through oral gavage. After 7 days of UUO, at euthanasia, left kidney was collected to examine the histological alteration by using haematoxylin-eosin staining, Masson's trichrome staining, Sirius red staining and immunohistochemistry. Western blot was used to assess XBP1S, targets of XBP1S, fibronectin, α-SMA, BAX and BCL2 protein levels. Real-time polymerase chain reaction was performed to assess NADPH oxidase subunits p47-phox and p67-phox mRNA levels. The results showed that XBP1S expression was decreased by about 70% in the UUO mice compared with that in sham mice (P < 0.01), which was reversed by valsartan administration (P < 0.05). Meanwhile, UUO-induced renal interstitial fibrosis was attenuated by valsartan treatment. In addition, the protein levels of fibronectin and α-SMA were upregulated by UUO induction (P < 0.01), and valsartan administration inhibited the protein levels of fibronectin and α-SMA in UUO mice (P < 0.05). Western blot analysis showed that the ratio of BAX to BCL2 protein level was increased in UUO model compared with that in sham mice, and the increment also was diminished by valsartan treatment (P < 0.05). Finally, UUO-induced mRNA levels of p47-phox and p67-phox were significantly attenuated by valsartan administration (P < 0.05). These results showed that valsartan at least partly restores renal interstitial fibrosis by enhancing XBP1S activation through inhibiting oxidative stress and apoptosis in the UUO mice. These results suggest that XBP1S could be a potential therapeutic target for kidney fibrosis.

Renalase attenuates hypertension, renal injury and cardiac remodelling in rats with subtotal nephrectomy.

Chronic kidney disease is associated with higher risk of cardiovascular complication and this interaction can lead to accelerated dysfunction in both organs. Renalase, a kidney-derived cytokine, not only protects against various renal diseases but also exerts cardio-protective effects. Here, we investigated the role of renalase in the progression of cardiorenal syndrome (CRS) after subtotal nephrectomy. Sprague-Dawley rats were randomly subjected to sham operation or subtotal (5/6) nephrectomy (STNx). Two weeks after surgery, sham rats were intravenously injected with Hanks' balanced salt solution (sham), and STNx rats were randomly intravenously injected with adenovirus-ß-gal (STNx+Ad-ß-gal) or adenovirus-renalase (STNx+Ad-renalase) respectively. After 4 weeks of therapy, Ad-renalase administration significantly restored plasma, kidney and heart renalase expression levels in STNx rats. We noticed that STNx rats receiving Ad-renalase exhibited reduced proteinuria, glomerular hypertrophy and interstitial fibrosis after renal ablation compared with STNx rats receiving Ad-ß-gal; these changes were associated with significant decreased expression of genes for fibrosis markers, proinflammatory cytokines and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase components. At the same time, systemic delivery of renalase attenuated hypertension, cardiomyocytes hypertrophy and cardiac interstitial fibrosis; prevented cardiac remodelling through inhibition of pro-fibrotic genes expression and phosphorylation of extracellular signal-regulated kinase (ERK)-1/2. In summary, these results indicate that renalase protects against renal injury and cardiac remodelling after subtotal nephrectomy via inhibiting inflammation, oxidative stress and phosphorylation of ERK-1/2. Renalase shows potential as a therapeutic target for the prevention and treatment of CRS in patients with chronic kidney disease.