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:Brain pericytes are important to maintain vascular integrity of the neurovascular unit under both, physiological and ischemic conditions. Ischemic stroke is known to induce an inflammatory and hypoxic response due to the lack of oxygen and glucose in the brain tissue. How this early response to ischemia is molecularly regulated in pericytes is largely unknown but may be of importance for future therapeutic targets .Here we evaluate the transcriptional responses in in vitro cultured human brain pericytes after oxygen and/or glucose deprivation. Hypoxia has been widely known to stabilise the transcription factor hypoxia inducible factor 1-alpha (HIF1alpha) and mediate the induction of hypoxic transcriptional programs after ischemia. However, we find that the transcription factors Jun Proto-Oncogene (c-JUN), Nuclear Factor Of Kappa Light Polypeptide Gene Enhancer In B-Cells (NFkappaB) and signal transducer and activator of transcription 3 (STAT3) bind genes regulated after 2 hours of omitted glucose and oxygen before HIF1alpha. Potent HIF1alpha responses require 6 hours of hypoxia to substantiate transcriptional regulation comparable to either c-JUN or STAT3. We show that STAT3 and c-JUN are regulating their bound genes before HIF1alpha after 2 hours of hypoxia or omitted glucose and oxygen, suggesting that HIF1alpha is not the initiating trans-acting factor in the response of pericytes to ischemia.
Project description:CD4+ T cells mediate the pathogenesis of ischemic and nephrotoxic acute kidney injury (AKI), as well as acute injury to other organs. However, the underlying mechanisms of CD4+ T cell-mediated pathogenesis are largely unknown. We therefore conducted unbiased RNA-sequencing to discover novel mechanistic pathways of kidney CD4+ T cells post-ischemia compared to normal mouse kidney. Unexpectedly, lipocalin-2 (Lcn2) gene, which encodes neutrophil gelatinase-associated lipocalin (NGAL) had the highest (~60)-fold increase. The NGAL increase in CD4+ T cells during AKI was confirmed at the mRNA level with real-time PCR and at the protein level with ELISA. NGAL is a potential biomarker for the early detection of AKI and has multiple potential biological functions during organ injury. However, the role of NGAL produced by CD4+ T cells has not been investigated. We found that ischemic AKI in NGAL knockout (KO) mice had worse renal outcomes compared to wild type (WT) mice. Adoptive transfer of NGAL-deficient CD4+ T cells from NGAL KO mice into CD4 KO or WT mice led to worse renal function than transfer of WT CD4+ T cells. In vitro simulated ischemia reperfusion showed that NGAL-deficient CD4+ T cells express higher levels of IFN-γ mRNA compared to WT CD4+ T cells. In vitro differentiation of naive CD4+ T cells to Th17, Th1 and Th2 cells led to significant increase in Lcn2 expression. Human kidney CD4+ T cell NGAL also increased significantly post-ischemia. These results demonstrate an important role for CD4+ T cell NGAL as a mechanism by which CD4+ T cells mediate AKI and extend the importance of NGAL in AKI beyond diagnostics.
Project description:Trypanosoma brucei, the etiological agent of sleeping sickness, has particular peroxisome-like organelles called glycosomes where several metabolic pathways are compartmentalized, including glycolysis. Many enzymes from sugar nucleotide biosynthetic pathways are located in this organelle, contrasting with the cytosolic localisation reported in the eukaryota domain. The UDP-glucose pyrophosphorylase (UGP), the enzyme responsible for UDP-glucose (UDP-Glc) production, is essential for growth and survival of trypanosomes. In addition, UGP is localized in both glycosomes and cytosol, raising questions about why would these parasites maintain a pathway functional in two different subcellular compartments. UGP is imported into glycosomes by piggybacking on the glycosomal protein PEPCK, which is the first evidence of piggybacking involving two proteins not functionally related, and the first report in trypanosomatids. The dataset demonstrates that UGP is present in the total cellular extract and the glycocomal fraction of the wild-type trypanosomes, while only in the total cellular extract of the PEPCK null mutant.
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: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:<p><strong>BACKGROUND:</strong> Ischemia/reperfusion injury (IRI) is the leading cause of acute kidney injury (AKI). The current standard of care focuses on supporting kidney function, stating the need for more efficient and targeted therapies to enhance repair. Mesenchymal Stromal Cells (MSCs) and their secretome, either as conditioned medium (CM) or extracellular vesicles (EVs), have emerged as promising options for regenerative therapy, however, their full potential in treating AKI remains unknown.</p><p><strong>METHODS:</strong> In this study, we employed an in vitro model of chemically-induced ischemia using antimycin A combined with 2-deoxy-D-glucose to induce ischemic injury in proximal tubule epithelial cells. Afterwards, we evaluated the effects of MSC secretome, CM or EVs obtained from adipose tissue, bone marrow and umbilical cord, on ameliorating the detrimental effects of ischemia. To assess the damage and treatment outcomes, we analyzed cell morphology, mitochondrial health parameters (mitochondrial activity, ATP production, mass and membrane potential) and overall cell metabolism by metabolomics.</p><p><strong>RESULTS:</strong> Our findings show that ischemic injury caused cytoskeletal changes confirmed by disruption of the F-actin network, energetic imbalance as revealed by a 50% decrease in the oxygen consumption rate, increased oxidative stress, mitochondrial dysfunction and reduced cell metabolism. Upon treatment with MSC secretome, the morphological derangements were partly restored and ATP production increased by 40-50%, with umbilical cord-derived EVs being most effective. Furthermore, MSC treatment led to phenotype restoration as indicated by an increase in cell bioenergetics, including increased levels of glycolysis intermediates, as well as an accumulation of antioxidant metabolites.</p><p><strong>CONCLUSION:</strong> Our in vitro model effectively replicated the in vivo-like morphological and molecular changes observed during ischemic injury. Additionally, treatment with MSC secretome ameliorated proximal tubule damage, highlighting its potential as a viable therapeutic option for targeting AKI.</p>
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.