STAT1 regulates macrophage number and phenotype and prevents renal fibrosis after ischemia-reperfusion injury

Fluorinated apelin-13 mediates neuroprotective effects in multiple sclerosis models

Multiple sclerosis (MS) is an autoimmune and neurodegenerative disease leading to demyelination and axonal loss. Current treatments are immunomodulatory or immunosuppressive drugs acting on the inflammatory component. However, these treatments do not adequately address the crucial aspect of neuroprotection. Recently, an association between an altered balance of adipokines and MS has been proposed as both a risk factor for developing MS and a chronic disease aggravating factor. Specifically, a decrease of apelin plasma levels in MS patients compared to controls correlates with the number of relapses and disease severity. Here we report a dramatic downregulation of apelin levels in the CNS of EAE mice which is also detected in MS patients brain samples compared to controls. Exploiting innovative design and synthesis techniques, we engineered a novel fluorinated apelin-13 peptide characterized by enhanced plasmatic stability compared to its native counterpart. With this peptide, we assessed the potential therapeutic benefits of apelin preventive supplementation in the EAE mouse model. We show that the fluorinated Apelin-13 peptide ameliorates EAE clinical score and preserves myelin content in the EAE MOG model recapitulating the progressive form of disease. These results combined with ex-vivo experiments in brain organotypic slices and in vitro studies in neurons and primary microglia and macrophages suggest that apelin has neuroprotective effects and influences the microglia/macrophages function.

Renal biopsies from donors with acute kidney injury show different molecular patterns according to the post-transplant function

The utilization of kidneys from donors with acute kidney injury (AKI) is often limited by unpredictable post-transplantation outcomes. The aim of our study was to identify protein mediators implicated in either recovery or failure of these organs. Forty kidney biopsies from donors with (20) and without AKI (20) were selected and then subdivided according to the post-transplant outcome defined as a threshold of 45 ml/min for the eGFR at 1 year from transplantation. Tissue homogenates were analysed by western blot to assess how the levels of 17 pre-selected proteins varied across the four groups. Samples from AKI kidneys with a poor outcome showed a fourfold increase in the levels of PPARg and twofold reduction of STAT1 compared to the other groups (p < 0.05). On the contrary, antioxidant enzymes including TRX1 and PRX3 were increased in the AKI kidneys with a good outcome (p < 0.05). An opposite trend was observed for the detoxifying enzyme GSTp which was significantly increased in the AKI group with poor versus good outcome (p < 0.05). The importance of lipid metabolism (PPARg) and inflammatory signals (STAT1) in the function recovery of these kidneys hints to the therapeutical targeting of the involved pathways in the setting of organ reconditioning.

CircSOD2 polarizes macrophages towards the M1 phenotype to alleviate cisplatin resistance in gastric cancer cells by targeting the miR-1296/STAT1 axis

Cisplatin is the first-line drug for gastric cancer (GC). Cisplatin resistance is the most important cause of poor prognosis for GC. Increasing evidence has identified the important role of macrophage polarization in chemoresistance. CircRNAs are newly discovered non-coding RNAs, characterized by covalently closed loops with high stability. Previous studies have reported a significant difference between circRNA profiles expressed in classically activated M1 macrophages, and those expressed in alternatively activated M2 macrophages. However, the underlying mechanism behind the regulation of GC cisplatin resistance by macrophages remains unclear. In our study, we observed the aberrant high expression of circSOD2 in M1 macrophages derived from THP-1. These expression patterns were confirmed in macrophages from patients with GC. Detection of the M1 and M2 markers confirmed that overexpression of circSOD2 enhances M1 polarization. The viability of cisplatin-treated GC cells was significantly reduced in the presence of macrophages overexpressing circSOD2, and cisplatin-induced apoptosis increased dramatically. In vivo experiments showed that macrophages expressing circSOD2 enhanced the effect of cisplatin. Moreover, we demonstrated that circSOD2 acts as a microRNA sponge for miR-1296 and regulates the expression of its target gene STAT1 (signal transducer and activator of transcription 1). CircSOD2 exerts its function through the miR-1296/STAT1 axis. Inhibition of circSOD2/miR-1296/STAT1 may therefore reduce M1 polarization. Overexpression of circSOD2 promotes the polarization of M1 macrophages and enhances the effect of cisplatin in GC. CircSOD2 is a novel positive regulator of M1 macrophages and may serve as a potential target for GC chemotherapy.

Discovery of Biomarkers Related to Interstitial Fibrosis and Tubular Atrophy among Kidney Transplant Recipients by mRNA-Sequencing

Interstitial fibrosis and tubular atrophy (IF/TA) after kidney transplantation causes a chronic deterioration of graft function. IF/TA can be diagnosed by means of a graft biopsy, which is a necessity as non-invasive diagnostic methods are unavailable. In this study, we identified IF/TA-related differentially expressed genes (DEGs) through next-generation sequencing using peripheral blood mononuclear cells. Blood samples from kidney transplant recipients undergoing standard immunosuppressive therapy (tacrolimus/mycophenolate mofetil or mycophenolate sodium/steroid) and diagnosed as IF/TA (n = 41) or normal (controls; n = 41) at their one-year protocol biopsy were recruited between January of 2020 and August of 2020. DEGs were derived through mRNA sequencing and validated by means of a quantitative real-time polymerase chain reaction. We identified 34 DEGs related to IF/TA. ADAMTS2, PLIN5, CLDN9, and KCNJ15 demonstrated a log2(fold change) of >1.5 and an area under the receiver operating characteristic curve (AUC) value of >0.6, with ADAMTS2 showing the largest AUC value and expression levels, which were 3.5-fold higher in the IF/TA group relative to that observed in the control group. We identified and validated DEGs related to IF/TA progression at one-year post-transplantation. Specifically, we identified ADAMTS2 as a potential IF/TA biomarker.

Uremic Toxin Indoxyl Sulfate Promotes Macrophage-Associated Low-Grade Inflammation and Epithelial Cell Senescence

In this study, we investigated the impact of the uremic toxin indoxyl sulfate on macrophages and tubular epithelial cells and its role in modulating the response to lipopolysaccharide (LPS). Indoxyl sulfate accumulates in the blood of patients with chronic kidney disease (CKD) and is a predictor of overall and cardiovascular morbidity/mortality. To simulate the uremic condition, primary macrophages and tubular epithelial cells were incubated with indoxyl sulfate at low concentrations as well as concentrations found in uremic patients, both alone and upon LPS challenge. The results showed that indoxyl sulfate alone induced the release of reactive oxygen species and low-grade inflammation in macrophages. Moreover, combined with LPS (proinflammatory conditions), indoxyl sulfate significantly increased TNF-α, CCL2, and IL-10 release but did not significantly affect the polarization of macrophages. Pre-treatment with indoxyl sulfate following LPS challenge induced the expression of aryl hydrocarbon receptor (Ahr) and NADPH oxidase 4 (Nox4) which generate reactive oxygen species (ROS). Further, experiments with tubular epithelial cells revealed that indoxyl sulfate might induce senescence in parenchymal cells and therefore participate in the progression of inflammaging. In conclusion, this study provides evidence that indoxyl sulfate provokes low-grade inflammation, modulates macrophage function, and enhances the inflammatory response associated with LPS. Finally, indoxyl sulfate signaling contributes to the senescence of tubular epithelial cells during injury.

Cold Storage Followed by Transplantation Induces Interferon-Gamma and STAT-1 in Kidney Grafts

Cold storage (CS)-mediated inflammation, a reality of donor kidney processing and transplantation, can contribute to organ graft failure. However, the mechanisms by which this inflammation is perpetuated during and after CS remain unclear. Here, we examined the immunoregulatory roles of signal transducer and activator of transcription (STAT) family proteins, most notably STAT1 and STAT3, with our in vivo model of renal CS and transplant. Donor rat kidneys were exposed to 4 h or 18 h of CS, which was then followed by transplantation (CS + transplant). STAT total protein level and activity (phosphorylation) were evaluated via Western blot analysis and mRNA expression was tabulated using quantitative RT-PCR after organ harvest on day 1 or day 9 post-surgery. In vivo assays were further corroborated via similar analyses featuring in vitro models, specifically proximal tubular cells (human and rat) as well as macrophage cells (Raw 264.7). Strikingly, gene expression of IFN-γ (a pro-inflammatory cytokine inducer of STAT) and STAT1 were markedly increased after CS + transplant. STAT3 dephosphorylation was additionally observed after CS, a result suggestive of dysregulation of anti-inflammatory signaling as phosphorylated STAT3 acts as a transcription factor in the nucleus to increase the expression of anti-inflammatory signaling molecules. In vitro, IFN-γ gene expression as well as amplification of downstream STAT1 and inducible nitric oxide synthase (iNOS; a hallmark of ischemia reperfusion injury) was remarkably increased after CS + rewarming. Collectively, these results demonstrate that aberrant induction of STAT1 is sustained in vivo post-CS exposure and post-transplant. Thus, Jak/STAT signaling may be a viable therapeutic target during CS to mitigate poor graft outcomes when transplanting kidneys from deceased donors.

A systems biology approach identifies the role of dysregulated PRDM6 in the development of hypertension

Genetic variants in the third intron of the PRDM6 gene have been associated with BP traits in multiple GWAS. By combining fine mapping, massively parallel reporter assays, and gene editing, we identified super enhancers that drive the expression of PRDM6 and are partly regulated by STAT1 as the causal variants for hypertension. The heterozygous disruption of Prdm6 in mice expressing Cre recombinase under the control of mouse smooth muscle cell protein 22-α promoter (Prdm6fl/+ SM22-Cre) exhibited a markedly higher number of renin-producing cells in the kidneys at E18.5 compared with WT littermates and developed salt-induced systemic hypertension that was completely responsive to the renin inhibitor aliskiren. Strikingly, RNA-Seq analysis of the mouse aortas identified a network of PRDM6-regulated genes that are located in GWAS-associated loci for blood pressure, most notably Sox6, which modulates renin expression in the kidney. Accordingly, the smooth muscle cell-specific disruption of Sox6 in Prdm6fl/+ SM22-Cre mice resulted in a dramatic reduction of renin. Fate mapping and histological studies also showed increased numbers of neural crest-derived cells accompanied by increased collagen deposition in the kidneys of Prdm6fl/+ Wnt1Cre-ZsGreen1Cre mice compared with WT mice. These findings establish the role of PRDM6 as a regulator of renin-producing cell differentiation into smooth muscle cells and as an attractive target for the development of antihypertensive drugs.

Role of SUMOylation of STAT1 in tubular epithelial‑mesenchymal transition induced by high glucose

Tubulointerstitial fibrosis (TIF) is an important pathological change that occurs during the development of diabetic kidney disease. The epithelial‑mesenchymal transition (EMT) of renal tubular epithelial cells is a manifestation of TIF. STAT1, a member of the STAT family of transcription factors, can be modified by the small ubiquitin‑related modifier (SUMO), thus affecting the activity of STAT1. The present study investigated the role of STAT1 SUMOylation in high glucose‑induced tubular EMT by western blotting, immunocytochemistry, immunofluorescence, co‑immunoprecipitation and dual luciferase reporter analysis. The results indicated that in the process of high glucose‑induced EMT, STAT1 activation protected the cells from EMT. However, high glucose also increased the SUMOylation of STAT1, which prevented STAT1 from exerting an effective protective role by inhibiting its activity.

Effects of contralateral nephrectomy timing and ischemic conditions on kidney fibrosis after unilateral kidney ischemia-reperfusion injury

Acute kidney injury (AKI) is an important cause of chronic kidney disease (CKD), but the underlying mechanisms are unclear. Animal models are tools for studying the AKI-CKD progression. Kidney ischemia-reperfusion injury (IRI) models, especially the unilateral IRI (uIRI) model with delayed contralateral kidney resection, are commonly used to induce fibrotic progression to CKD after AKI. However, in previous studies, we found that details of the operation had a significant impact on the long-term outcomes of the kidney in this uIRI model. In this study, we investigated the effects of resection timing of the contralateral intact kidney, core body temperatures during ischemia, and time length of kidney ischemia on kidney function, histological injury and kidney fibrosis after AKI, using a mouse uIRI model with delayed contralateral nephrectomy. The results showed that all these parameters significantly affected the AKI-CKD transition. The post-AKI fibrosis worsened and the survival rate declined with a longer interval between contralateral nephrectomy and uIRI, higher ischemic body temperature, or longer ischemic duration when the other two variables were fixed. In conclusion, in the uIRI model with delayed contralateral nephrectomy, kidney fibrosis after AKI is influenced by many factors. Strictly controlling the experimental conditions is very important for the stability and consistency of the model.

STAT1 is regulated by TRIM24 and promotes immunosuppression in head and neck squamous carcinoma cells, but enhances T cell antitumour immunity in the tumour microenvironment

BACKGROUND

Head and neck squamous cell carcinoma (HNSCC) is a significant problem and is frequently resistant to current treatments. STAT1 is important in anti-tumour immune responses against HNSCC. However, the role of STAT1 expression by tumour cells and its regulation during HNSCC is unclear.

METHODS

We determined the effects of STAT1 inhibition on tumour development and immunity in CAL27 and UMSCC22A HNSCC cell lines in vitro and in a HNSCC carcinogen-induced model in vivo.

RESULTS

STAT1 siRNA knockdown in human HNSCC cells impaired their proliferation and expression of the immunosuppressive marker PD-L1. Stat1-deficient mice displayed increased oral lesion incidence and multiplicity during tumour carcinogenesis in vivo. Immunosuppressive markers PD-1 in CD8+ T cells and PD-L1 in monocytic MDSCs and macrophages were reduced in oral tumours and draining lymph nodes of tumour-bearing Stat1-deficient mice. However, STAT1 was required for anti-tumour functions of T cells during HNSCC in vivo. Finally, we identified TRIM24 to be a negative regulator of STAT1 that plays a similar tumorigenic function to STAT1 in vitro and thus may be a potential target when treating HNSCC.

CONCLUSION

Our findings indicate that STAT1 activity plays an important role in tumorigenicity and immunosuppression during HNSCC development.

Computational Prediction of Biomarkers, Pathways, and New Target Drugs in the Pathogenesis of Immune-Based Diseases Regarding Kidney Transplantation Rejection

Background

The diagnosis of graft rejection in kidney transplantation (KT) patients is made by evaluating the histological characteristics of biopsy samples. The evolution of omics sciences and bioinformatics techniques has contributed to the advancement in searching and predicting biomarkers, pathways, and new target drugs that allow a more precise and less invasive diagnosis. The aim was to search for differentially expressed genes (DEGs) in patients with/without antibody-mediated rejection (AMR) and find essential cells involved in AMR, new target drugs, protein-protein interactions (PPI), and know their functional and biological analysis.

Material and Methods

Four GEO databases of kidney biopsies of kidney transplantation with/without AMR were analyzed. The infiltrating leukocyte populations in the graft, new target drugs, protein-protein interactions (PPI), functional and biological analysis were studied by different bioinformatics tools.

Results

Our results show DEGs and the infiltrating leukocyte populations in the graft. There is an increase in the expression of genes related to different stages of the activation of the immune system, antigenic presentation such as antibody-mediated cytotoxicity, or leukocyte migration during AMR. The importance of the IRF/STAT1 pathways of response to IFN in controlling the expression of genes related to humoral rejection. The genes of this biological pathway were postulated as potential therapeutic targets and biomarkers of AMR. These biological processes correlated showed the infiltration of NK cells and monocytes towards the allograft. Besides the increase in dendritic cell maturation, it plays a central role in mediating the damage suffered by the graft during AMR. Computational approaches to the search for new therapeutic uses of approved target drugs also showed that imatinib might theoretically be helpful in KT for the prevention and/or treatment of AMR.

Conclusion

Our results suggest the importance of the IRF/STAT1 pathways in humoral kidney rejection. NK cells and monocytes in graft damage have an essential role during rejection, and imatinib improves KT outcomes. Our results will have to be validated for the potential use of overexpressed genes as rejection biomarkers that can be used as diagnostic and prognostic markers and as therapeutic targets to avoid graft rejection in patients undergoing kidney transplantation.

Regulator of Cell Cycle Protein (RGCC/RGC-32) Protects against Pulmonary Fibrosis

Some previous studies in tissue fibrosis have suggested a profibrotic contribution from elevated expression of a protein termed either RGCC (regulator of cell cycle) or RGC-32 (response gene to complement 32 protein). Our analysis of public gene expression datasets, by contrast, revealed a consistent decrease in RGCC mRNA levels in association with pulmonary fibrosis. Consistent with this observation, we found that stimulating primary adult human lung fibroblasts with transforming growth factor (TGF)-β in cell cultures elevated collagen expression and simultaneously attenuated RGCC mRNA and protein levels. Moreover, overexpression of RGCC in cultured lung fibroblasts attenuated the stimulating effect of TGF-β on collagen levels. Similar to humans with pulmonary fibrosis, the levels of RGCC were also decreased in vivo in lung tissues of wild-type mice challenged with bleomycin in both acute and chronic models. Mice with constitutive RGCC gene deletion accumulated more collagen in their lungs in response to chronic bleomycin challenge than did wild-type mice. RNA-Seq analyses of lung fibroblasts revealed that RGCC overexpression alone had a modest transcriptomic effect, but in combination with TGF-β stimulation, induced notable transcriptomic changes that negated the effects of TGF-β, including on extracellular matrix-related genes. At the level of intracellular signaling, RGCC overexpression delayed early TGF-β-induced Smad2/3 phosphorylation, elevated the expression of total and phosphorylated antifibrotic mediator STAT1, and attenuated the expression of a profibrotic mediator STAT3. We conclude that RGCC plays a protective role in pulmonary fibrosis and that its decline permits collagen accumulation. Restoration of RGCC expression may have therapeutic potential in pulmonary fibrosis.

Macrophage-Specific MCPIP1/Regnase-1 Attenuates Kidney Ischemia-Reperfusion Injury by Shaping the Local Inflammatory Response and Tissue Regeneration

Sterile inflammation either resolves the initial insult or leads to tissue damage. Kidney ischemia/reperfusion injury (IRI) is associated with neutrophilic infiltration, enhanced production of inflammatory mediators, accumulation of necrotic cells and tissue remodeling. Macrophage-dependent microenvironmental changes orchestrate many features of the immune response and tissue regeneration. The activation status of macrophages is influenced by extracellular signals, the duration and intensity of the stimulation, as well as various regulatory molecules. The role of macrophage-derived monocyte chemoattractant protein-induced protein 1 (MCPIP1), also known as Regnase-1, in kidney ischemia-reperfusion injury (IRI) and recovery from sterile inflammation remains unresolved. In this study, we showed that macrophage-specific Mcpip1 deletion significantly affects the kidney phenotype. Macrophage-specific Mcpip1 transgenic mice displayed enhanced inflammation and loss of the tubular compartment upon IRI. We showed that MCPIP1 modulates sterile inflammation by negative regulation of Irf4 expression and accumulation of IRF4+ cells in the tissue and, consequently, suppresses the post-ischemic kidney immune response. Thus, we identified MCPIP1 as an important molecular sentinel of immune homeostasis in experimental acute kidney injury (AKI) and renal fibrosis.

Macrophage p47phox regulates pressure overload-induced left ventricular remodeling by modulating IL-4/STAT6/PPARγ signaling

NADPH oxidase (Nox) mediates ROS production and contributes to cardiac remodeling. However, macrophage p47^phox, a Nox subunit regulating cardiac remodeling, is unclear. We aimed to investigate the role of macrophage p47^phox in hypertensive cardiac remodeling. Pressure-overload induced by Angiotensin II (AngII) for two weeks in young adult male p47^phox deficient (KO) mice showed aggravated cardiac dysfunction and hypertrophy as indicated from echocardiographic and histological studies in comparison with wild-type littermates (WT). Additionally, LV of AngII-infused KO mice showed augmented interstitial fibrosis, collagen deposition and, myofibroblasts compared to AngII-infused WT mice. Moreover, these changes in AngII-infused KO mice correlated well with the gene analysis of hypertrophic and fibrotic markers. Similar results were also found in the transverse aortic constriction model. Further, AngII-infused KO mice showed elevated circulating immunokines and increased LV leukocytes infiltration and CD206⁺ macrophages compared to AngII-infused WT mice. Likewise, LV of AngII-infused KO mice showed upregulated mRNA expression of anti-inflammatory/pro-fibrotic M2 macrophage markers (Ym1, Arg-1) compared to AngII-infused WT mice. AngII and IL-4 treated bone marrow-derived macrophages (BMDMs) from KO mice showed upregulated M2 macrophage markers and STAT6 phosphorylation (Y641) compared to AngII and IL-4 treated WT BMDMs. These alterations were at least partly mediated by macrophage as bone marrow transplantation from KO mice into WT mice aggravated cardiac remodeling. Mechanistically, AngII-infused KO mice showed hyperactivated IL-4/STAT6/PPARγ signaling and downregulated SOCS3 expression compared to AngII-infused WT mice. Our studies show that macrophage p47^phox limits anti-inflammatory signaling and extracellular matrix remodeling in response to pressure-overload.

SS-31 Protects Liver from Ischemia-Reperfusion Injury via Modulating Macrophage Polarization

Ischemia-reperfusion injury (IRI) is a common complication in liver surgeries. It is a focus to discover effective treatments to reduce ischemia-reperfusion injury. Previous studies show that oxidative stress and inflammation response contribute to the liver damage during IRI. SS-31 is an innovated mitochondrial-targeted antioxidant peptide shown to scavenge reactive oxygen species and decrease oxidative stress, but the protective effects of SS-31 against hepatic IRI are not well understood. The aim of our study is to investigate whether SS-31 could protect the liver from damages induced by IRI and understand the protective mechanism. The results showed that SS-31 treatment can significantly attenuate liver injury during IRI, proved by HE staining, serum ALT/AST, and TUNEL staining which can assess the degree of liver damage. Meanwhile, we find that oxidative stress and inflammation were significantly suppressed after SS-31 administration. Furthermore, the mechanism revealed that SS-31 can directly decrease ROS production and regulate STAT1/STAT3 signaling in macrophages, thus inhibiting macrophage M1 polarization. The proinflammation cytokines are then significantly reduced, which suppress inflammation response in the liver. Taken together, our study discovered that SS-31 can regulate macrophage polarization through ROS scavenging and STAT1/STAT3 signaling to ameliorate liver injury; the protective effects against hepatic IRI suggest that SS-31 may be an appropriate treatment for liver IRI in the clinic.

Construction of a immune-associated genes based prognostic signature in bladder cancer

Current studies indicated that immune-associated genes (IAGs) have important roles in the occurrence and development of bladder cancer (BC). The current work aims to identify the prognostic values of IAGs in BC and establish a prognostic signature based on IAGs. RNA sequencing data and protein expression data were used to identify differentially expressed IAGs in BC. An IAGs based signature was further constructed and the prognostic and predictive values of the signature were evaluated by survival analysis and nomogram. RNA isolation and reverse transcription-quantitative PCR (RT-qPCR) were further performed to investigate the expression levels of IAGs in BC cells and were used to explore the relationship between IAGs and M2 tumour-associated macrophages (TAMs) secreted transforming growth factor-β1 (TGF-β1) in BC cells. We selected five IAGs to develop an IAGs signature model, which were significantly related to survival outcomes of BC patients. RT-qPCR showed that five IAGs were significantly differentially expressed and three IAGs were positively correlated with M2 TAMs secreted TGF-β1 in T24 cells. We identified and validated an IAGs based signature to predict the prognosis of BC patients. Furthermore, M2 TAMs may promote the expression of IAGs in BC via the TGF-β1 signalling pathway.

Renoprotective effect of Stat1 deletion in murine aristolochic acid nephropathy

Injured tubule epithelium stimulates a profibrotic milieu that accelerates loss of function in chronic kidney disease (CKD). This study tested the role of signal transducer and activator of transcription 1 (STAT1) in the progressive loss of kidney function in aristolochic acid (AA) nephropathy, a model of CKD. Mean serum creatinine concentration increased in wild-type (WT) littermates treated with AA, whereas Stat1-/- mice were protected. Focal increases in the apical expression of kidney injury molecule (KIM)-1 were observed in the proximal tubules of WT mice with AA treatment but were absent in Stat1-/- mice in the treatment group as well as in both control groups. A composite injury score, an indicator of proximal tubule injury, was reduced in Stat1-/- mice treated with AA. Increased expression of integrin-β6 and phosphorylated Smad2/3 in proximal tubules as well as interstitial collagen and fibronectin were observed in WT mice following AA treatment but were all decreased in AA-treated Stat1-/- mice. The data indicated that STAT1 activation facilitated the development of progressive kidney injury and interstitial fibrosis in AA nephropathy.

Exosomal MicroRNA-374b-5p From Tubular Epithelial Cells Promoted M1 Macrophages Activation and Worsened Renal Ischemia/Reperfusion Injury

Tubular epithelial cells (TECs) represent the primary site of renal ischemia/reperfusion injury (RIRI). However, whether the damage of TECs could drive the initiation of inflammation was unclear. Here we investigated the role of the TECs and macrophages during RIRI. Increased expression of inflammation response and activated M1 macrophage were determined in the mice model of RIRI. Moreover, we demonstrated global miRNA expression profiling of renal exosomes, and miR-374b-5p was most upregulated in these exosomes in vivo. Inhibition of miR-374b-5p in the mice upon RIR operation would alleviate the kidney injury via decreasing the production of proinflammatory cytokines and suppressing the macrophage activation. Similar results were also identified in the hypoxia-induced cell model where exosomal miR-374b-5p was dramatically upregulated. Uptake of exosomes derived from the hypoxic TECs by macrophages would trigger M1 polarization via transferring miR-374b-5p. Besides, we confirmed that miR-374b-5p could directly bind to Socs1 using a dual-luciferase reporter assay. Notably, when we injected the miR-374b-5p-enriched exosomes into mice, a high-level inflammatory response and M1 macrophage activation were performed. Our studies demonstrated that exosomal miR-374b-5p played an essential role in the communication between injured TECs and macrophages, resulting in the M1 macrophage activation during RIRI. The blockage of the release of such exosomes may serve as a new therapeutic strategy for RIRI.

STAT signaling in polycystic kidney disease

The most common form of polycystic kidney disease (PKD) in humans is caused by mutations in the PKD1 gene coding for polycystin1 (PC1). Among the many identified or proposed functions of PC1 is its ability to regulate the activity of transcription factors of the STAT family. Most STAT proteins that have been investigated were found to be aberrantly activated in kidneys in PKD, and some have been shown to be drivers of disease progression. In this review, we focus on the role of signal transducer and activator of transcription (STAT) signaling pathways in various renal cell types in healthy kidneys as compared to polycystic kidneys, on the mechanisms of STAT regulation by PC1 and other factors, and on the possibility to target STAT signaling for PKD therapy.

The Roles of Immune Cells in the Pathogenesis of Fibrosis

Tissue injury and inflammatory response trigger the development of fibrosis in various diseases. It has been recognized that both innate and adaptive immune cells are important players with multifaceted functions in fibrogenesis. The activated immune cells produce various cytokines, modulate the differentiation and functions of myofibroblasts via diverse molecular mechanisms, and regulate fibrotic development. The immune cells exhibit differential functions during different stages of fibrotic diseases. In this review, we summarized recent advances in understanding the roles of immune cells in regulating fibrotic development and immune-based therapies in different disorders and discuss the underlying molecular mechanisms with a focus on mTOR and JAK-STAT signaling pathways.