Changes In Acute Kidney Injury Research Articles

Trajectory pattern of serially measured acute kidney injury biomarkers in critically ill patients: a prospective observational study

BackgroundThe clinical value of the trajectory of temporal changes in acute kidney injury (AKI) biomarkers has not been well established among intensive care unit (ICU) patients.MethodsThis is a single-center, prospective observational study, performed at a mixed ICU in a teaching medical institute in Tokyo, Japan. Adult ICU patients with an arterial line and urethral catheter were enrolled from September 2014 to March 2015. Patients who stayed in the ICU for less than 48 h and patients with known end-stage renal disease were excluded from the study. Blood and urine samples were collected for measurement of AKI biomarkers at 0, 12, 24, and 48 h after ICU admission. The primary outcome was major adverse kidney events (MAKE) at discharge, defined as a composite of death, dialysis dependency, and persistent loss of kidney function (≥ 25% decline in eGFR).ResultsThe study included 156 patients. Serum creatinine-based estimated glomerular filtration rate (eGFR), plasma neutrophil gelatinase-associated lipocalin (NGAL), and urinary liver-type fatty acid-binding protein (uL-FABP) were serially measured and each variable was classified into three groups based on group-based trajectory modeling analysis. While the trajectory curves moved parallel to each other (i.e., “low,” “middle,” and “high”) for eGFR and plasma NGAL, the uL-FABP curves showed distinct trajectory patterns and moved in different directions (“low and constant,” “high and exponential decrease,” and “high and exponential increase”). These trajectory patterns were significantly associated with MAKE. MAKE occurred in 16 (18%), 16 (40%), and 9 (100%) patients in the “low and constant,” “high and exponential decrease,” and “high and exponential increase” groups, respectively, based on uL-FABP levels (p-value < 0.001). The initial value and the 12-h change in uL-FABP were both significantly associated with MAKE, even after adjusting for eGFR [Odds ratio (95% confidence interval): 1.45 (1.17–1.83) and 1.43 (1.12–1.88) for increase of initial value and 12-h change of log-transformed uL-FABP by 1 point, respectively].ConclusionsTrajectory pattern of serially measured urinary L-FABP was significantly associated with MAKE in ICU patients.

Dynamic cellular changes in acute kidney injury caused by different ischemia time

Ischemia reperfusion injury (IRI), often related to surgical procedures, is one of the important causes of acute kidney injury (AKI). To decipher the dynamic process of AKI caused by IRI (with prolonged ischemia phase), we performed single-cell RNA sequencing (scRNA-seq) of clinically relevant IRI murine model with different ischemic intervals. We discovered that Slc5a2hi proximal tubular cells were susceptible to AKI and highly expressed neutral amino acid transporter gene Slc6a19, which was dramatically decreased over the time course. With the usage of mass spectrometry-based metabolomic analysis, we detected that the level of neutral amino acid isoleucine dropped off in AKI mouse plasma metabolites. And the reduction of plasma isoleucine was also verified in patients with cardiac surgery-associated acute kidney injury (CSA-AKI). The findings advanced the understanding of dynamic process of AKI and introduced reduction of isoleucine as a potential biomarker for CSA-AKI.

Neferine mitigates cisplatin-induced acute kidney injury in mice by regulating autophagy and apoptosis.

The nephrotoxicity caused by cisplatin severely limits the application and affects related platinum-based therapeutics. Neferine is a dibenzylisoquinoline alkaloid extracted from a Chinese medicinal herb (Nelumbo nucifera Gaertn), which can decrease cisplatin-induced apoptosis of NRK-52E cells by activating autophagy in vitro in our previous study. In this article, we aimed to further investigate the protective effect of neferine, against to the cispltain-induced kidney damage in mice. Six groups were designed in our study. Renal index, mice serum creatinine and blood urea nitrogen levels were detected after the mice were killed. HE staining was used to observe the pathological changes of each group. The apoptosis of mouse kidney tissue was detected by TUNEL. Immunofluorescence and Western blot were used to detect the expression of cleaved-caspase3 and LC3. The transmission electron microscope was used to reveal the changes of apoptosis and autophagy of renal tubular epithelial cells in different groups. In our findings, the pathological changes of acute kidney injury were easily observed in cisplatin-treated mice while those in the neferine-pretreated groups were significantly alleviated. The apoptosis induced by cisplatin in mice increased evidently compared with the control group, which was decreased in the mice with neferine pretreatment. What' more, we found that autophagy increased obviously in mice pretreated by neferine contrast to the cisplatin-treated mice. In our study, neferine can effectively alleviate cisplatin-induced renal injury in mice, as well act as an autophagy-regulator in kidney protection.

Probing the viscosity changes of acute kidney injury by fluorescence imaging

Elucidating the viscosity level under the pathology of acute kidney injury (AKI) is of great significance. However, this necessary and interesting work has never been explored. In view of this, a near-infrared (NIR) emission fluorescent probe MI-F was developed to visualize the viscosity level of AKI and evaluate the intervention ability of reduced glutathione on AKI. With MI-F, the increase of viscosity under the pathology of AKI was revealed. It also proved that the early intake of reduced glutathione has a certain inhibitory and preventive effect on the degree of kidney organ damage during AKI process. In addition, no obvious changes in the fluorescence intensity of other organs including the heart, liver, spleen and lung have been found, revealing the early stage of AKI may have less impact on other organs. Therefore, our work will provide pathological guidance for clinical studies of AKI such as diagnosis, prevention and treatment.

Single Cell Dissection of Epithelial-Immune Cellular Interplay in Acute Kidney Injury Microenvironment.

BackgroundUnderstanding the acute kidney injury (AKI) microenvironment changes and the complex cellular interaction is essential to elucidate the mechanisms and develop new targeted therapies for AKI.MethodsWe employed unbiased single-cell RNA sequencing to systematically resolve the cellular atlas of kidney tissue samples from mice at 1, 2 and 3 days after ischemia-reperfusion AKI and healthy control. The single-cell transcriptome findings were validated using multiplex immunostaining, western blotting, and functional experiments.ResultsWe constructed a systematic single-cell transcriptome atlas covering different AKI timepoints with immune cell infiltration increasing with AKI progression. Three new proximal tubule cells (PTCs) subtypes (PTC-S1-new/PTC-S2-new/PTC-S3-new) were identified, with upregulation of injury and repair-regulated signatures such as Sox9, Vcam1, Egr1, and Klf6 while with downregulation of metabolism. PTC-S1-new exhibited pro-inflammatory and pro-fibrotic signature compared to normal PTC, and trajectory analysis revealed that proliferating PTCs were the precursor cell of PTC-S1-new, and part of PTC-S1-new cells may turn into PTC-injured and then become fibrotic. Cellular interaction analysis revealed that PTC-S1-new and PTC-injured interacted closely with infiltrating immune cells through CXCL and TNF signaling pathways. Immunostaining validated that injured PTCs expressed a high level of TNFRSF1A and Kim-1, and functional experiments revealed that the exogenous addition of TNF-α promoted kidney inflammation, dramatic injury, and specific depletion of TNFRSF1A would abrogate the injury.ConclusionsThe single-cell profiling of AKI microenvironment provides new insight for the deep understanding of molecular changes of AKI, and elucidates the mechanisms and developing new targeted therapies for AKI.

Identifying of miRNA-mRNA Regulatory Networks Associated with Acute Kidney Injury by Weighted Gene Co-Expression Network Analysis.

BackgroundAcute kidney injury (AKI) is a clinical emergency characterized by a dramatic decline in renal function and the accumulation of metabolic waste products in the body, with a high morbidity and mortality rate. The pathogenesis of AKI remains unclear and there are no effective treatment options.MethodsWe aimed to identify critical genes involved in the pathogenesis of AKI and construct a miRNA–mRNA regulatory network using gene expression data downloaded from Gene Expression Omnibus (GSE85957) for 38 kidneys of AKI and 19 control rats and cisplatin treated kidneys of 3 AKI and 3 control rats. Data in GSE85957 were processed using weighted gene co-expression network analysis (WGCNA), and biological function analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were used to analyze the functions associated with critical genes.ResultsTwenty-eight modules in the GSE85957 dataset were identified by WGCNA, of which 103 genes in the orange module and 30 genes in the black module were closely associated with AKI and dose. Biological function analysis of genes in the orange and black modules revealed that skeletal muscle cell differentiation, tissue development and organ development were involved in the pathological changes of AKI. Combining with our experimentally processed AKI rat kidney data, eight genes (Atf3, Egr1, Egr2, Fos, Fosb, Gdf15, Serpine1 and Nr1d1) were identified as potential biomarkers of AKI, and miRNA–mRNA regulatory networks were constructed based on the above eight critical genes. Further tissue validation revealed that Egr1 and Fos were highly expressed in AKI.ConclusionOur study identified potential biomarkers of AKI and constructed an associated miRNA–mRNA regulatory network, which may provide new insights into the molecular pathogenesis of AKI.

Sugar or Fat? Renal Tubular Metabolism Reviewed in Health and Disease.

The kidney is a highly metabolically active organ that relies on specialized epithelial cells comprising the renal tubules to reabsorb most of the filtered water and solutes. Most of this reabsorption is mediated by the proximal tubules, and high amounts of energy are needed to facilitate solute movement. Thus, proximal tubules use fatty acid oxidation, which generates more adenosine triphosphate (ATP) than glucose metabolism, as its preferred metabolic pathway. After kidney injury, metabolism is altered, leading to decreased fatty acid oxidation and increased lactic acid generation. This review discusses how metabolism differs between the proximal and more distal tubular segments of the healthy nephron. In addition, metabolic changes in acute kidney injury and chronic kidney disease are discussed, as well as how these changes in metabolism may impact tubule repair and chronic kidney disease progression.

Multimodal Analgesia and Decreased Opioid Use in Adult Trauma Patients.

There is an opioid epidemic in the United States. With the increased concern of over-prescribing opioids, physicians are seeking alternative pain management strategies. The purpose of this study is to review the impact of instituting a multimodal analgesia (MMA) guideline on decreasing opioid use in trauma patients at a Level 1 trauma center. In 2017, an MMA guideline was developed and included anti-inflammatories, muscle relaxants, neuropathic agents, and local analgesics in addition to opioids. Staff were educated and the guideline was implemented. A retrospective review of medications prescribed to patients admitted from 2016 through 2018 was performed. Patients admitted in 2016 served as the control group (before MMA). In 2018, all patients received multimodal pain therapy as standard practice, and served as the comparison group. A total of 10 340 patients were admitted to the trauma service from 2016 through 2018. There were 3013 and 3249 patients for review in 2016 and 2018, respectively. Total morphine milligram equivalents were 2 402 329 and 1 975 935 in 2016 and 2018, respectively, a 17.7% decrease (P < .001). Concurrently, there was a statistically significant increase in the use of multimodal pain medications. A secondary endpoint was studied to evaluate for changes in acute kidney injury; there was not a statistically significant increase (0.56% versus 0.68%, P = .55). Implementation of an MMA guideline significantly reduced opioid use in trauma patients. The use of nonopioid MMA medications increased without an increased incidence of acute kidney injury.

The crosstalk between hypoxia-inducible factor-1α and microRNAs in acute kidney injury.

Acute kidney injury (AKI) is a common critical clinical disease that is characterized by a rapid decline in renal function and reduced urine output. Ischemia and hypoxia are dominant pathophysiological changes in AKI that are induced by many factors, and the role of the “master” regulator hypoxia-inducible factor-1α (HIF-1α) is well recognized in AKI-related studies. MicroRNAs have been found to act as critical regulators of AKI pathophysiological process. More studies now have reported mutual interactions between HIF-1α and microRNAs in AKI. Therefore, in this brief review, we look into the mutual regulatory mechanisms between HIF-1α and microRNAs and discuss their function in the process of AKI. Recent studies demonstrated that HIF-1α is involved in the regulation of multiple functional microRNAs in AKI, and in turn, the level of HIF-1α is regulated by specific microRNAs. However, the role of the interactions between HIF-1α and microRNAs in AKI are controversial, and whether interventions targeting relevant mechanisms could achieve clinical benefits is not clear. Much work remains to further explore the value of targeting the HIF-1α-microRNA pathway in AKI treatment. Impact statement At first, we have discussed the role of hypoxia-inducible factor-1α (HIF-1α) and microRNAs in the acute kidney injury (AKI) pathophysiology. Then we have summarized the interactions between HIF-1α and microRNAs reported by AKI-related studies and concluded their regulatory effects in AKI process. Finally, we have made a vision of HIF-1α/microRNAs pathway’s potential as the intervention target in AKI. The mini review provides a systematic understanding of the crosstalk between HIF-1α and microRNAs in AKI and their effects on AKI pathophysiology and treatment.

Evolution of diagnostic criteria for acute kidney injury in patients with decompensated cirrhosis: A prospective study in a tertiary university hospital

Recently, changes in acute kidney injury (AKI) diagnostic criteria have been proposed (ICA-AKI criteria). However, in Brazil there is a paucity of data and analyses that evaluate AKI in patients with cirrhosis and determine the impact of the implemented AKI criteria changes. Therefore, this study sought to evaluate the incidence of AKI in patients with cirrhosis; to evaluate the agreement between traditional and ICA-AKI criteria; and to assess its clinical and laboratory characteristics, etiologies, risk factors and outcomes. This is a prospective cohort study in hospitalized patients with cirrhosis and acute decompensation. The total number of hospitalizations was evaluated using the PWP statistical model for recurring events; P values<0.05 were considered significant. A total of 154 admissions of 75 patients were included in the study. Among the hospitalizations, 89 (57.79%) met the ICA-AKI criteria. There was substantial agreement between both AKI classifications (Kappa 0.7293). The main etiology of AKI was pre-renal (59.55%), followed by renal (26.96%) and hepatorenal syndrome (10.11%). A multivariate analysis uncovered risk factors for ICA-AKI, including the MELD score (P=0.0162, RR:1.055, 95%CI:1.010-1.101) and the use of furosemide (P=0.001,RR:2.360, 95% CI:1.417-3.931). A univariate analysis found an association between in-hospital mortality and serum creatinine (sCr)≥1.5mg/dL(P=0.0373), MELD (P=0.0296), bilirubin (P=0.0064), and infection (P=0.0045), while in the multivariate analysis, the bilirubin levels (P=0.0030, RR:1.077, 95%CI: 1.025-1.130) and the presence of shock (P=0.0002, RR:8.511, 95%CI: 2.746-26.377) were associated with in-hospital mortality. Among the hospitalizations with AKI, death was significantly associated with non-response to treatment and dialysis. Initial stage 1A-AKI had lower in-hospital mortality than stage 1B-AKI. AKI incidence was high in this cohort of patients with decompensated cirrhosis, and substantial agreement between AKI definitions was observed. In-hospital mortality was associated with worse liver function, AKI, infection and the presence of shock. Also, sCr>1,5mg/dL remained an important prognostic factor.

Changes in acute kidney injury epidemiology in critically ill patients: a population-based cohort study in Korea

BackgroundAlthough no specific treatment facilitates renal tubular regeneration in acute kidney injury (AKI), the rapid increase in aging populations with more comorbidities and advances in critical care management are expected to change the epidemiology of AKI. However, few recent studies dissected the current epidemiologic characteristics of critically ill patients with AKI. We investigated recent epidemiologic changes in severe AKI in critically ill patients.MethodsAll adult admissions to intensive care units (ICUs) in Korea from 2008 to 2015 were screened using the national health insurance review and assessment database, and 1,744,235 patients were included. Clinical characteristics and changes in AKI incidence and mortality rate were analyzed.ResultsThe incidence of AKI increased from 7.4% in 2008 to 8.3% in 2015 (p for trend < 0.001). Age-standardized AKI rate was 7018.6 per 100,000 person-years. In-hospital mortality significantly decreased from 39.1% in 2008 to 37.2% in 2015 (p for trend < 0.001) with 2427.6 deaths per 100,000 person-years. Patients with AKI showed higher in-hospital mortality, prolonged ICU length of stay, and higher total cost. Multivariable analysis showed increased risk of in-hospital mortality (adjusted odds ratio [OR] 3.74), mechanical ventilation (OR 2.87), ECMO (OR 6.99), and vasopressor requirement (OR 2.75) in patients with AKI.ConclusionsRecent advances in medical management for AKI have improved in-hospital mortality of critically ill patients with AKI despite increases in the elderly population and AKI incidence.

Methylation-Demethylation Dynamics: Implications of Changes in Acute Kidney Injury.

Over the years, the epigenetic landscape has grown increasingly complex. Until recently, methylation of DNA and histones was considered one of the most important epigenetic modifications. However, with the discovery of enzymes involved in the demethylation process, several exciting prospects have emerged that focus on the dynamic regulation of methylation and its crucial role in development and disease. An interplay of the methylation-demethylation machinery controls the process of gene expression. Since acute kidney injury (AKI), a major risk factor for chronic kidney disease and death, is characterised by aberrant expression of genes, understanding the dynamics of methylation and demethylation will provide new insights into the intricacies of the disease. Research on epigenetics in AKI has only made its mark in the recent years but has provided compelling evidence that implicates the involvement of methylation and demethylation changes in its pathophysiology. In this review, we explore the role of methylation and demethylation machinery in cellular epigenetic control and further discuss the contribution of methylomic changes and histone modifications to the pathophysiology of AKI.

Science to Practice: Can Functional MR Imaging Be Useful in the Evaluation of Cardiorenal Syndrome?

Functional magnetic resonance (MR) imaging of the kidneys has gained interest recently, especially in the detection of early changes in acute kidney injury or to predict progression of chronic kidney disease (CKD). The application of these methods to cardiorenal syndrome (CRS) is novel. CRS is widely accepted as a complex clinical problem routinely faced by clinicians. In this issue, Chang et al ( 1 ) present their preliminary experience applying blood oxygen level-dependent (BOLD) MR imaging to the kidneys in mice with experimental myocardial infarction. They showed that R2* in the kidney increases after induced myocardial infarction and that the response was higher in animals with larger infarcts and over time. The authors also for the first time correlated the BOLD MR imaging findings against hypoxia-inducible factor-1α (HIF-1α) expression, an independent marker of renal hypoxia. In addition, they showed evidence for renal injury by using a kidney injury marker, kidney injury molecule-1 (KIM-1). The results of their study support the use of renal BOLD MR imaging in subjects with heart failure, in whom the risk of subsequent renal ischemia and/or hypoxia is known to exist. These results, along with those of other recent reports ( 2 ), suggest that functional imaging methods could play a key role in evaluating changes in both the primary and secondary organs involved in complex disease processes such as CRS. Availability of such methods could facilitate translation to the clinic and improve the mechanistic understanding of the complicated and interrelated pathophysiology.

Hyperpolarized 13 C,15 N2 -urea T2 relaxation changes in acute kidney injury.

To investigate the correlation between renal ischemia and 13 C-urea T2 relaxation rate in an acute kidney injury (AKI) rat model. Six rats subjected to unilateral renal ischemia were investigated. Creatinine clearance, urine output, plasma creatinine as well as blood-urea nitrogen (BUN) values were acquired before and after the procedure. 1 H T2* mapping was acquired using blood oxygenation level dependent (BOLD) MRI and hyperpolarized 13 C-urea T2 mapping was acquired using a 2D golden-angle radial approach. Kidney perfusion was estimated using noncontrast flow alternating inversion recovery arterial spin labeling. All rats showed clinical signs of AKI with increased plasma creatinine and increased BUN. Whole kidney 13 C-urea T2 significantly decreased 26% (P = 0.001) 24 h after reperfusion. A significantly different (3.7 times steeper; P = 0.008) osmolality gradient was observed in the contralateral kidney (P = 0.008; R2 = 0.86) compared with the postischemic kidney (P = 0.0004, R2 =0.97). Whole kidney T2* signal (P = 0.14) and T2* gradient (P = 0.26) was similar between the two kidneys. Oxygen availability dependency on 13 C-urea T2 was investigated by means of the correlation between the BOLD and T2 signals; a statistically significant difference (P = 0.03) was found in the contralateral kidney (P = 0.0001; R2 = 0.95), but not in the postischemic kidney (P = 0.31; R2 = 0.25). We demonstrate that hyperpolarized [13 C,15 N2 ]urea T2 relaxation correlates with renal oxygen tension ( T2*) in the healthy contralateral kidney, but not in the postischemic kidney. The whole kidney T2 relaxation difference between the postischemic and contralateral kidney may originate from altered blood volume in the postischemic kidney. Magn Reson Med 80:696-702, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Dynamic Contrast-Enhanced Computed Tomography: A New Diagnostic Tool to Assess Renal Perfusion After Ischemia-Reperfusion Injury in Mice: Correlation of Perfusion Deficit to Histopathologic Damage.

The aim of this study was to investigate the value of dynamic contrast-enhanced computed tomography (CT) in the assessment of renal perfusion parameters after ischemia-reperfusion (I/R) injury in an experimental murine model. Balb/cJ wildtype mice were subjected to 45 minutes (AKI45) or 60 minutes (AKI60) of unilateral warm I/R injury by clamping the pedicle of the right kidney. Two, 7, and 18 days after right I/R injury, renal blood flow (RBF), renal volume of distribution (RVD), and mean transit time were quantitatively assessed in the cortex of both kidneys by dynamic contrast-enhanced CT. Acute tubular injury (ATI) was assessed by histologic analysis using a semiquantitative sum score (score, 0-18) and correlated with RBF, RVD, and mean transit time. Histologic signs of ATI could be detected in the clamped kidneys in both groups already at day 2. Pathologic features of ATI worsened in AKI60 until day 18 (score, 7 ± 0), whereas mice in AKI45 group showed amelioration over time (score, 4 ± 2). Renal blood flow was significantly reduced in ischemic kidneys in AKI45 (287 ± 32 mL/100 mL per minute; P < 0.01) and AKI60 group (249 ± 73 mL/100 mL per minute; P < 0.01) as compared with that in healthy kidneys (402 ± 49 mL/100 mL per minute) on day 2. It decreased further at day 7 in both groups (AKI45: 165 ± 44 mL/100 mL per minute, P < 0.01; AKI60: 151 ± 72 mL/100 mL per minute, P < 0.05) and improved at day 18 in AKI45 (261 ± 11 mL/100 mL per minute, P < 0.05) and to a lesser degree in AKI60 (197 ± 52 mL/100 mL per minute, P > 0.05). Values of RVD paralleled RBF at all time points. Renal blood flow (r = -0.79; P < 0.01) and RVD (r = -0.8; P < 0.01) significantly correlated with the histological damage score (Spearman rank correlation). Dynamic contrast-enhanced CT is a noninvasive method to determine renal perfusion changes in acute kidney injury. It might be a valuable diagnostic tool to predict outcome or monitor treatment effects of renal I/R injury.

Early lipid changes in acute kidney injury using SWATH lipidomics coupled with MALDI tissue imaging

Acute kidney injury (AKI) is one of the leading causes of in-hospital morbidity and mortality, particularly in critically ill patients. Although our understanding of AKI at the molecular level remains limited due to its complex pathophysiology, recent advances in both quantitative and spatial mass spectrometric approaches offer new opportunities to assess the significance of renal metabolomic changes in AKI models. In this study, we evaluated lipid changes in early ischemia-reperfusion (IR)-related AKI in mice by using sequential window acquisition of all theoretical spectra (SWATH)-mass spectrometry (MS) lipidomics. We found a significant increase in two abundant ether-linked phospholipids following IR at 6 h postinjury, a plasmanyl choline, phosphatidylcholine (PC) O-38:1 (O-18:0, 20:1), and a plasmalogen, phosphatidylethanolamine (PE) O-42:3 (O-20:1, 22:2). Both of these lipids correlated with the severity of AKI as measured by plasma creatinine. In addition to many more renal lipid changes associated with more severe AKI, PC O-38:1 elevations were maintained at 24 h post-IR, while renal PE O-42:3 levels decreased, as were all ether PEs detected by SWATH-MS at this later time point. To further assess the significance of this early increase in PC O-38:1, we used matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) to determine that it occurred in proximal tubules, a region of the kidney that is most prone to IR injury and also rich in the rate-limiting enzymes involved in ether-linked phospholipid biosynthesis. Use of SWATH-MS lipidomics in conjunction with MALDI-IMS for lipid localization will help in elucidating the role of lipids in the pathobiology of AKI.

Elevation of miR-21, through targeting MKK3, may be involved in ischemia pretreatment protection from ischemia-reperfusion induced kidney injury.

Ischemia-reperfusion (IR) causes acute kidney injury (AKI), and ischemia pretreatment may exert protection. Mitogen-activated protein kinase kinase 3 (MKK3), which is involved in the signal transduction pathway in IR-induced injury, is a potential target of miR-21. We aimed to verify the targeting regulation of miR-21 on MKK3 and to explore the effects of miR-21-mediated MKK3 expression changes in AKI. Vectors containing the MKK3 3'UTR and mutated MKK3-3U-M were constructed and co-transfected with nonsense miR, miR-21-5p mimics or inhibitor in HEK293 cells. Gene expressions were detected by dual luciferase reporter assay. The effects of miR-21 on mRNA and protein of MKK3 were investigated in HK-2 cells. Male C57BL/6J mice were treated with ischemic preconditioning (IPC) and IR. Kidney functions were assessed through monitoring serum creatinine (Scr) and blood urea nitrogen (BUN). Pathological changes were observed and scored with histological samples of kidney. Expression levels of miR-21, MKK3, interleukin (IL)-6, tumor necrosis factor (TNF)-α before and after IPC and IR were examined by real-time polymerase chain reaction and/or immunohistochemistry. miR-21 regulated the expression of MKK3 via 3'UTR. Following IR, MKK3, IL-6 and TNF-α levels were increased. Scr, BUN and pathological injuries were aggravated, and miR-21 expression was increased. IPC increased miR-21 levels ahead of IR and inhibited the increases in MKK3, IL-6 and TNF-α levels and the aggravation of Scr, BUN and pathological injuries. miR-21 targets MKK3 in vivo and in vitro, inhibiting the downstream factors IL-6 and TNF-α. Therefore, miR-21 might be involved in protection of IPC against IR of the kidney.

Glomerular changes and alterations of zonula occludens-1 in the kidneys of Plasmodium falciparum malaria patients.

BackgroundThe process of cytoadhesion in Plasmodium falciparum malaria infection causes signaling processes that lead to structural and functional changes at the cellular level. Histopathological changes of acute kidney injury (AKI) in P. falciparum malaria often involve glomerular proliferation, thickening of the glomerular basement membrane, acute tubular necrosis, and interstitial inflammation. Focusing on the glomeruli, this study aimed to investigate glomerular and tight junction-associated protein- zonula occludens-1 (ZO-1) changes in P. falciparum malaria patients.MethodsKidney tissues were grouped into P. falciparum with AKI (Cr ≥ 265 μmol/L or 3 mg/dl), P. falciparum without AKI (Cr < 265 μmol/L), and normal kidney tissues (control group). Glomerular cells and the glomerular area were quantified and compared in three experimental groups. The tight junction was investigated immunohistochemically using tight junction-associated protein, ZO-1, protein marker. A further immunofluorescence study was performed in an endothelial cell (EC)-parasitized red blood cell (PRBC) co-culture system, to evaluate the tight junction protein.ResultsGlomerular cell proliferation was significant in P. falciparum with AKI (Cr ≥ 265 μmol/L). By contrast, the glomerular area decreased significantly. ZO-1 expression was significantly decreased in the AKI group compared with normal kidneys, and in kidney tissues without AKI (p < 0.05). This was further confirmed by the depletion in ZO-1 localization in ECs co-cultured with PRBCs.ConclusionsIn P. falciparum malaria with AKI, the decrease in glomerular area, despite glomerular cell proliferation, could be due to the collapse of cellular structures secondary to damaged tight junction-associated protein, ZO-1.

Assessing intrarenal nonperfusion and vascular leakage in acute kidney injury with multinuclear 1H/19F MRI and perfluorocarbon nanoparticles

We sought to develop a unique sensor-reporter approach for functional kidney imaging that employs circulating perfluorocarbon nanoparticles and multinuclear (1) H/(19) F MRI. (19) F spin density weighted and T1 weighted images were used to generate quantitative functional mappings of both healthy and ischemia-reperfusion (acute kidney injury) injured mouse kidneys. (1) H blood-oxygenation-level-dependent (BOLD) MRI was also employed as a supplementary approach to facilitate the comprehensive analysis of renal circulation and its pathological changes in acute kidney injury. Heterogeneous blood volume distributions and intrarenal oxygenation gradients were confirmed in healthy kidneys by (19) F MRI. In a mouse model of acute kidney injury, (19) F MRI, in conjunction with blood-oxygenation-level-dependent MRI, sensitively delineated renal vascular damage and recovery. In the cortico-medullary junction region, we observed 25% lower (19) F signal (P < 0.05) and 70% longer (1) H T2* (P < 0.01) in injured kidneys compared with contralateral kidneys at 24 h after initial ischemia-reperfusion injury. We also detected 71% higher (19) F signal (P < 0.01) and 40% lower (1) H T2* (P < 0.05) in the renal medulla region of injured kidneys compared with contralateral uninjured kidneys. Integrated (1) H/(19) F MRI using perfluorocarbon nanoparticles provides a multiparametric readout of regional perfusion defects in acutely injured kidneys.

Assessment of arterial stiffness, oxidative stress and inflammation in acute kidney injury

BackgroundIt is well know that arterial stiffness, oxidative stress and inflammation are features of chronic kidney disease. The arterial changes have a multitude of potential interconnected causes including endothelial dysfunction, oxidative stress, inflammation, atherosclerosis and vascular calcification. There is evidence that arterial stiffness becomes progressively worse as CKD progresses. The contribution of the biochemical changes of uremic toxicity to arterial stiffness is less clear. The aim of this study is to elucidate the vascular changes in acute kidney injury. We hypothesise that arterial stiffness will be increased during acute kidney injury and this will return to normal after kidney function recovers.Methods/DesignOne hundred and forty four patients with acute kidney injury defined as an acute increase in serum creatinine to > 133 μmol/l or urea > 14.3 mmol/l or urine output < 410 ml/day will be recruited. Baseline measures of aortic pulse wave velocity, augmentation index, and brachial and central blood pressure will be recorded along with blood measures for oxidative stress and inflammation. Repeat measures will be taken at six and 12 months after the onset of the acute kidney injury.DiscussionThe role and contribution of the biochemical changes to arterial stiffness in the acute phase of kidney disease is not known. This study will primarily assess the time course changes in pulse wave velocity from the onset of acute kidney injury and after recovery. In addition it will assess augmentation index, central blood pressure and oxidative stress and inflammation. This may shed light on the contribution of biochemical kidney toxins on arterial stiffness in both acute kidney injury and chronic kidney disease.Trial RegistrationACTRN 12609000285257