Project description:The aim of this study was to identify miRNAs that regulate AKI and develop their applications as diagnostic biomarkers and therapeutic agents. First, kidney tissues from two different AKI mouse models, namely, AKI induced by the administration of lipopolysaccharide (LPS) causing sepsis (LPS-AKI mice) and AKI induced by renal ischemia–reperfusion injury (IRI-AKI mice), were exhaustively screened for their changes of miRNA expression compared with that of control mice by microarray analysis.
Project description:The aim of this study was to identify miRNAs that regulate AKI and develop their applications as diagnostic biomarkers and therapeutic agents. First, kidney tissues from two different AKI mouse models, namely, AKI induced by the administration of lipopolysaccharide (LPS) causing sepsis (LPS-AKI mice) and AKI induced by renal ischemia–reperfusion injury (IRI-AKI mice), were exhaustively screened for their changes of miRNA expression compared with that of control mice by microarray analysis.
Project description:Ischemic acute kidney injury (AKI), a complication that frequently occurs in hospital settings, is often associated with hemodynamic compromise, sepsis, cardiac surgery or exposure to nephrotoxicants. AKI is associated with immune cell infiltration into the kidney stroma, which causes acute tubular injury. Here, using a murine renal ischemic-reperfusion injury (IRI) model we show that intercalated cells (ICs) rapidly adopt a pro-inflammatory phenotype post IRI. During the early phase of AKI, we demonstrate that either blocking the pro-inflammatory P2Y14 receptor located on the apical membrane of ICs, or ablation of the gene encoding the P2Y14 receptor in ICs: 1) inhibits IRI-induced chemokine expression increase in ICs; 2) reduces neutrophil and monocyte renal infiltration; 3) reduces the extent of kidney dysfunction; and 4) attenuates proximal tubule (PT) damage. These observations indicate that the P2Y14 receptor participates in the very first inflammatory steps associated with ischemic AKI. In addition, we show that the concentration of the P2Y14 receptor ligand, uridine diphosphate-glucose (UDP-Glc), is higher in urine samples from intensive care unit patients who developed AKI when compared with urine from patients without AKI. In particular, we observed a strong correlation between UDP-Glc concentration and the development of AKI in cardiac surgery patients. Our study identifies the UDP-Glc/P2Y14 receptor axis as a potential target for the prevention and/or attenuation of ischemic-AKI.
Project description:Incomplete repair after acute kidney injury (AKI) is associated with progressive loss of tubular cell function and development of chronic kidney disease (CKD). Here, we compared the kidney single-cell transcriptomes from the mice subjected to either unilateral ischemia-reperfusion kidney injury with contralateral nephrectomy (IRI/CL-NX, in which tubule repair predominates) or unilateral IRI with contralateral kidney intact (U-IRI, in which fibrosis and atrophy predominates) to investigate the mechanism(s) underlying transition to CKD following AKI.
Project description:Acute kidney disease caused by ischemia-reperfusion (IRI-AKI) is characterized by ectopic inflammation and tubular injury, in which macrophage infiltration and inflammatory activation play a critical pathogenic role. Calycosin is an active flavone from the root of Astragalus membranaceus and shows anti-inflammatory effects in various diseases. In this study, we investigated the renoprotective role of calycosin against IRI-AKI and the underlying mechanism. Our results showed that calycosin treatment reduced the levels of serum creatinine and urea nitrogen along with attenuated tubular necrosis and cast formation in IRI-AKI mice. Calycosin significantly suppressed the activation of NF-κB signaling and the expression of inflammatory mediators IL-1β and TNF-α in IRI-AKI kidneys. In vitro, calycosin inhibited LPS-induced inflammatory activation in RAW 264.7 cells. Interestingly, RNA-seq revealed that calycosin remarkably down-regulated chemotaxis-related pathways in RAW 264.7 cells. Among the differentially expressed genes, Ccl2/MCP-1, a critical chemokine mediating macrophage inflammatory chemotaxis, was down-regulated in both LPS-stimulated RAW 264.7 cells and IRI-AKI kidneys. Consistently, calycosin treatment attenuated macrophage infiltration in the IRI-AKI kidneys. Importantly, in combination with target prediction, molecular docking, and surface plasmon resonance, we showed that calycosin can directly bind to macrophage migration inhibitory factor (MIF). Functionally, calycosin abrogated MIF-stimulated NF-κB signaling activation and Ccl2 expression and MIF-mediated chemotaxis in RAW 264.7 cells without influencing its expression. Collectively, calycosin protects from IRI-AKI by suppressing MIF-mediated macrophage inflammatory chemotaxis. Calycosin could be a promising candidate medicine for clinical treatment of IRI-AKI.
Project description:Renal hypoxia is widespread in acute kidney injury (AKI) of various aetiologies. Hypoxia adaptation, conferred through the hypoxia-inducible factor (HIF), appears to be insufficient. Here we show that HIF activation in renal tubules through Pax8-rtTA-based inducible knockout of von Hippel-Lindau protein (VHL-KO) protects from rhabdomyolysis-induced AKI. In this model, histological observations indicate that injury mainly affects proximal convoluted tubules, with 5% necrosis at d1 and 40% necrosis at d2. HIF-1alpha up-regulation in distal tubules reflects renal hypoxia. However, lack of HIF in proximal tubules suggests insufficient adaptation by HIF. AKI in VHL-KO mice leads to prominent HIF activation in all nephron segments, as well as to reduced serum creatinine, serum urea, tubular necrosis, and apoptosis marker caspase-3 protein. At d1 after rhabdomyolysis, when tubular injury is potentially reversible, HIF mediated protection in AKI is associated with activated glycolysis, cellular glucose uptake and utilization, autophagy, vasodilation, and proton removal as demonstrated by qPCR, pathway enrichment analysis and immunohistochemistry. Together, our data provide evidence for a HIF-orchestrated multi-level shift towards glycolysis as a major mechanism for protection against acute tubular injury. All experiments were carried out in transgenic mice in which selective renal tubular VHL knockout (VHL-KO) was inducible by doxycycline (Reference: Mathia S, Paliege A, Koesters R, Peters H, Neumayer HH, Bachmann S, Rosenberger C. Action of hypoxia-inducible factor in liver and kidney from mice with Pax8-rtTA-based deletion of von Hippel-Lindau protein. Acta Physiol (Oxf). 2013; 207(3):565-76.). Four groups of animals were used: 1) controls: untreated mice; 2) VHL-KO: injected with doxycycline (0.1 mg per 10 g body weight SC), 4 days prior to sacrifice; 3) AKI: rhabdomyolysis; 4) VHL-KO/AKI: doxycycline plus rhabdomyolysis. To induce AKI, 50% glycerol (0.05 ml per 10 g body weight) was injected IM into the left hind limb under isoflurane narcosis. Drinking water was withdrawn between 20 h prior and 24 h after glycerol injection.
Project description:Retinoic acid (RA) signaling is activted in proximal tubular epithelial cells (PTECs) after acute kidney injury (AKI). In these studies we evaluated the functional role of this by inducing ischemia reperfusion-induced AKI (IRI-AKI) in mice after inhibiting RA signaling in PTECs genetically. Here we evaluated the effects of this on the activation of renal mononuclear cells (MNCs) by evaluating RNA expression in CD11B+ cells isolated from kidneys after IRI-AKI. Compared with control mice, there was a reducion in expression of inflammatory marker gene expression 3 days after IRI-AKI in mice with inhibition of RAR signaling in PTECs. These findings suggest a mechanism by which inhibition of RAR signaling in PTECs is protective against AKI.
Project description:Acute kidney injury (AKI) represents a common complication in critically ill patients that is associated with an increased morbidity and mortality. Currently, no effective treatment options are available. Here, we show that glutamine significantly attenuates leukocyte recruitment and inflammatory signaling in human and murine tubular epithelial cells (TECs). In a murine AKI model induced by ischemia-reperfusion-injury (IRI) we show that glutamine causes transcriptomic and proteomic reprogramming in renal TECs and neutrophils, resulting in decreased epithelial apoptosis, neutrophil recruitment and improved mitochondrial functionality and respiration provoked by an ameliorated oxidative phosphorylation. We identify the proteins glutamine gamma glutamyltransferase 2 (Tgm2) and apoptosis signal-regulating kinase (Ask1) as the major targets of glutamine in apoptotic signaling. Increased Tgm2 expression and reduced Ask1 activation result in decreased JNK activation leading to a diminished mitochondrial intrinsic apoptosis in kidneys upon IRI-induced AKI and under hypoxia or following TNFα-treatment of TECs. Consequently, glutamine administration attenuated kidney injury in vivo during AKI progression as well as TEC viability in vitro under inflammatory and hypoxic conditions.
Project description:Because exosomes have gained attention as a source of biomarkers, we investigated if miRNAs in exosomes (exo-miRs) can report the disease progression of organ injury. Using renal ischemia-reperfusion injury (IRI) as a model of acute kidney injury (AKI), we determined temporally-released exo-miRs in urine during IRI and found that these exo-miRs could reliably mirror the progression of AKI. From the longitudinal measurements of miRNA expression in kidney and urine, we found that release of exo-miRs was regulated sorting process, rather than simply representing their intracellular biosynthesis. In the injury state, miR-16, miR-24, and miR-200c were increased in the urine. Interestingly, expression of target mRNAs of these exo-miRs was significantly altered in renal medulla. Next, in the early recovery state, urinary exo-miRs (miR-9a, miR-141, miR-200a, miR-200c, miR-429), which shares Zeb1/2 as a common target mRNA, were upregulated, indicating that they reflect TGF--associated renal fibrosis. Finally, release of exo-miRs (miR-125a, miR-351) was regulated by TGF-1 and was able to differentiate the sham and IRI even after the injured kidneys were functionally recovered. Altogether, these data indicate that exo-miRs released in renal IRI are largely associated with TGF- signaling. Temporal release of exo-miRs which share targets might be a regulatory mechanism to control the disease progression of AKI.