Acute kidney injury: a paradigm for miRNA regulation of the cell cycle

Ischemic preconditioning-induced protective effect for promoting angiogenesis in renal ischemia-reperfusion injury by regulating miR-376c-3p/HIF-1α/VEGF axis in male rats

OBJECTIVE

Ischemic preconditioning (IPC) is defined as a well-established phenomenon in which brief exposure to sublethal episodes of ischemia and reperfusion induces a tolerance to injurious effects of prolonged ischemia by exploiting intrinsic defence mechanisms. The present study was performed to determine the protective effect of IPC on the rat renal ischemia-reperfusion injury (IRI) via miR-376c-3p/HIF-1α/VEGF axis.

METHODS

In vivo, these male Sprague-Dawley rats were treated by IRI and IPC. Meanwhile, these rats from different treatment groups were also injected subcutaneously with 2 nmol agomir-376c-3p and/or 10 nmol recombinant rat HIF-1α. At 72 h after reperfusion, serum samples were respectively collected for renal function. Besides, kidney tissues were harvested to observe renal morphology changes. Subsequently, the expression levels of CD31, HIF-1α and VEGF in the kidney tissues were measured using immunohistochemical staining, quantitative real-time PCR, as well as Western blotting analysis at the indicated time points after reperfusion. In vitro, HK-2 cells were used to detect the cell activity by CCK-8 and transfection of mir-376c-3p mimic in Hypoxia/Reoxygenation (H/R) group.

RESULTS

In vivo, the pathological changes were significantly relieved in the rats with IPC group, compared to the IRI group. Rats which were treated IPC significantly reduced the levels of blood urea nitrogen (BUN), serum creatinine (Scr) at 24 h after operation, compared to IRI group. After IPC treatment, the expression level of CD31 was obviously decreased, compared to IRI group. A total of differently expressed microRNAs were screened out by microRNA microarray assay in rat renal ischemia tissue, especially showing that miR-376c-3p was selected as the target miRNA. Compared to IRI group, the expression level of miR-376c-3p were obviously higher in IPC-treated group. Double-luciferase reporter assay demonstrated that miR-376c-3p directly targeted HIF-1α. In vitro, IPC significantly increased cell viability of HK-2, and promoted the angiogenesis via up-regulating miR-376c-3p/HIF-1α/VEGF axis. Furthermore, the expression level of HIF-1α was apparently decreased in HK-2 treated with H/R after miR-376c-3p mimic transfection respectively, as well as the increased expression level of VEGF.

CONCLUSIONS

Our study provided a novel insight for investigating the protective effect of IPC on renal IRI. Consequently, miR-376c-3p played an important role in renal IRI by promoting angiogenesis via targeting HIF-1α/VEGF pathway in male rats.

Determination of a microRNA signature of protective kidney ischemic preconditioning originating from proximal tubules

Ischemic preconditioning (IPC) is effective in limiting subsequent ischemic acute kidney injury in experimental models. MicroRNAs are an important class of post-transcriptional regulator and show promise as biomarkers of kidney injury. We evaluated the time- and dose-dependence of benefit from IPC in a rat model of functional (bilateral) ischemia–reperfusion injury (IRI). We found optimal protection from subsequent injury following short, repetitive sequences of preconditioning insult. We subsequently used hybridization array and microRNA sequencing to characterize microRNA signatures of protective IPC and of IRI. These approaches identified a profile of microRNA changes consequent on IRI, that were limited by prior IPC. To localize these signals within the kidney, we used laser capture microdissection and RT-qPCR to measure microRNA abundance in nephron segments, pinpointing microRNA changes principally to glomeruli and proximal tubules. Our data describe a unique microRNA signature for IRI in the rat kidney. Pulsatile IPC reduces kidney damage following IRI and diminishes this microRNA signal. We have also identified candidate microRNAs that may act as biomarkers of injury and therapeutic targets in this context.

MEG3 aggravates hypoxia/reoxygenation induced apoptosis of renal tubular epithelial cells via the miR-129-5p/HMGB1 axis

The apoptosis of renal tubular epithelial cells (TECs) during ischemia/reperfusion (I/R) facilitates the progression of acute kidney injury (AKI). This study aimed to probe the role of long noncoding RNA maternally expressed 3 (MEG3) in I/R-induced apoptosis of TECs. In this study, with CoCl₂ and hypoxia/reoxygenation treatments, cell models were established to mimic I/R using the human kidney tubular cell line HK-2. In HK-2 cells, expression of MEG3 detected using quantitative real-time polymerase chain reaction (qRT-PCR), was significantly upregulated after CoCl₂ treatment and hypoxia/reoxygenation treatment. The results of cell counting kit-8 assay and flow cytometry suggested that knockdown of MEG3 significantly increased the viability of HK-2 cells but inhibited its apoptosis, while overexpression of MEG3 exerted the reverse effects. Additionally, expression levels of interleukin 6 and tumor necrosis factor-α in the medium were elevated after MEG3 was overexpressed in HK-2 cells. Together with qRT-PCR and Western blot analysis, a dual-luciferase reporter gene assay was used to verify the interactions among MEG3, miR-129-5p, and HMGB1. The results demonstrated that in HK-2 cells, miR-129-5p was a target of MEG3, and HMGB1 served as a target gene of miR-129-5p. Besides this, compared with the control group, the expression levels of MEG3 and HMGB1 in samples derived from AKI patients were remarkably upregulated, and the expression of miR-129-5p was downregulated. Therefore, taken together, we conclude that the overexpression of MEG3 induced by I/R promotes apoptosis of TECs via regulating the miR-129-5p/HMGB1 axis.

Epigenetic regulation in AKI and kidney repair: mechanisms and therapeutic implications

Acute kidney injury (AKI) is a major public health concern associated with high morbidity and mortality. Despite decades of research, the pathogenesis of AKI remains incompletely understood and effective therapies are lacking. An increasing body of evidence suggests a role for epigenetic regulation in the process of AKI and kidney repair, involving remarkable changes in histone modifications, DNA methylation and the expression of various non-coding RNAs. For instance, increases in levels of histone acetylation seem to protect kidneys from AKI and promote kidney repair. AKI is also associated with changes in genome-wide and gene-specific DNA methylation; however, the role and regulation of DNA methylation in kidney injury and repair remains largely elusive. MicroRNAs have been studied quite extensively in AKI, and a plethora of specific microRNAs have been implicated in the pathogenesis of AKI. Emerging research suggests potential for microRNAs as novel diagnostic biomarkers of AKI. Further investigation into these epigenetic mechanisms will not only generate novel insights into the mechanisms of AKI and kidney repair but also might lead to new strategies for the diagnosis and therapy of this disease.

Expression patterns and prognostic value of miR-210, miR-494, and miR-205 in middle-aged and old patients with sepsis-induced acute kidney injury

Septic patients suffer a 'cytokine storm' from proinflammatory cytokines, chemokines and other inflammatory mediators, resulting in acute kidney injury (AKI) and death. The purpose of the present study was to determine the expression patterns of microRNA-210 (miR-210), miR-494, and miR-205 in middle-aged and old patients with sepsis-induced AKI and to evaluate their association with patient prognosis. Serum blood urea nitrogen (BUN), creatinine (Cr) and cystatin C levels were determined in peripheral venous blood collected from 110 patients with sepsis-induced AKI and 110 healthy controls. The expression profile of 30 miRNAs was analyzed by TaqMan low-density array (TLDA) in plasma samples from patients and controls. Association of miRNAs with prognosis and survival of patients was analyzed by Spearman's rank correlation coefficient, Cox multivariate analysis, and ROC curve analysis. TILDA analysis showed 11 upregulated and 11 downregulated miRNAs in patients with sepsis-induced AKI. MiR-210 and miR-494 were the most upregulated and miR-205 was the most downregulated miRNA. High expression of miR-210 and miR-494 was positively correlated with BUN, Cr and cystatin C levels of patients, while low expression of miR-205 was negatively correlated. MiR-210 and miR-494 expression was significantly decreased and miR-205 expression was increased in survivors with sepsis-induced AKI (28-day survival, n = 68) vs. non-survivors (n = 42). BUN, Cr, and miR-205 were independent risk factors for prognosis in sepsis-induced AKI. Our study showed the predictive value of miR-210, miR-494, and miR-205 in prognosis and survival of patients with sepsis-induced AKI. MiR-205 is an independent risk factor for sepsis-induced AKI and its decreased expression is associated with shorter patient survival.

A urinary microRNA panel that is an early predictive biomarker of delayed graft function following kidney transplantation

Predicting immediate and subsequent graft function is important in clinical decision-making around kidney transplantation, but is difficult using available approaches. Here we have evaluated urinary microRNAs as biomarkers in this context. Profiling of 377 microRNAs in the first urine passed post-transplantation identified 6 microRNAs, confirmed to be upregulated by RT-qPCR in an expanded cohort (miR-9, -10a, -21, -29a, -221, and -429, n = 33, P < 0.05 for each). Receiver operating characteristic analysis showed Area Under the Curve 0.94 for this panel. To establish whether this early signal was sustained, miR-21 was measured daily for 5 days post-transplant, and was consistently elevated in those developing Delayed Graft Function (n = 165 samples from 33 patients, p < 0.05). The biomarker panel was then evaluated in an independent cohort, sampled at varying times in the first week post-transplantation in a separate transplant center. When considered individually, all miRs in the panel showed a trend to increase or a significant increase in those developing delayed Graft Function (miR-9: P = 0.068, mIR-10a: P = 0.397, miR-21: P = 0.003, miR-29a: P = 0.019, miR-221: P = 0.1, and miR-429: P = 0.013, n = 47) with Area Under the Curve 0.75 for the panel. In conclusion, combined measurement of six microRNAs had predictive value for delayed graft function following kidney transplantation.

Identification of microRNA-mRNA networks involved in cisplatin-induced renal tubular epithelial cells injury

Cisplatin is a widely used chemotherapeutic drug that often causes acute kidney injury (AKI) in cancer patients. The contribution of miRNAs to the cisplatin-induced renal tubular epithelial cell injury remains largely unknown. Here we performed an integrative network analysis of miRNA and mRNA expression profiles to shed light into the underlying mechanism of cisplatin-induced renal tubular epithelial cell injury. Microarray analysis identified 47 differentially expressed miRNAs, among them 26 were upregulated and 21 were downregulated. Moreover, integrating dysregulated miRNAs target prediction and altered mRNA expression enabled us to identify 1181 putative target genes for further bioinformatics analysis. Gene ontology (GO) analysis revealed that the putative target genes were involved in apoptosis process and regulation of transcription. Pathway analysis indicated that the top upregulated pathways included MAPK and p53 signaling pathway, while the top downregulated pathways were PI3K-Akt and Wnt signaling pathway. Further network analysis showed that MAPK signaling pathway and apoptosis with the highest degree were identified as core pathways, hsa-miR-9-3p and hsa-miR-371b-5p as the most critical miRNAs, and CASK, ASH1L, CDK6 etc. as hub target genes. In addition, the expression level change of selected five microRNAs (hsa-miR-4299, hsa-miR-297, hsa-miR-3135b, hsa-miR-9-3p, and hsa-miR-371b-5p) and two mRNAs( CASK and CDK6) were validated in cisplatin-induced HK-2 cells. Furthermore, a similar trend of expression level change was observed in NRK-52E cells by cisplatin treatment. Overall, our results provide the molecular basis and potential targets for the treatment of cisplatin-induced renal tubular cell injury.

Epithelial Cell Cycle Behaviour in the Injured Kidney

Acute kidney injury (AKI), commonly caused by ischemia-reperfusion injury, has far-reaching health consequences. Despite the significant regenerative capacity of proximal tubular epithelium cells (PTCs), repair frequently fails, leading to the development of chronic kidney disease (CKD). In the last decade, it has been repeatedly demonstrated that dysregulation of the cell cycle can cause injured kidneys to progress to CKD. More precisely, severe AKI causes PTCs to arrest in the G1/S or G2/M phase of the cell cycle, leading to maladaptive repair and a fibrotic outcome. The mechanisms causing these arrests are far from known. The arrest might, at least partially, be attributed to DNA damage since activation of the DNA-damage response pathway leads to cell cycle arrest. Alternatively, cytokine signalling via nuclear factor kappa beta (NF-κβ) and p38-mitogen-activated protein kinase (p38-MAPK) pathways, and reactive oxygen species (ROS) can play a role independent of DNA damage. In addition, only a handful of cell cycle regulators (e.g., p53, p21) have been thoroughly studied during renal repair. Still, why and how PTCs decide to arrest their cell cycle and how this arrest can efficiently be overcome remain open and challenging questions. In this review we will discuss the evidence for cell cycle involvement during AKI and development of CKD together with putative therapeutic approaches.

Exosomes from patients with septic shock convey miRNAs related to inflammation and cell cycle regulation: new signaling pathways in sepsis?

Background

Exosomes isolated from plasma of patients with sepsis may induce vascular apoptosis and myocardial dysfunction by mechanisms related to inflammation and oxidative stress. Despite previous studies demonstrating that these vesicles contain genetic material related to cellular communication, their molecular cargo during sepsis is relatively unknown. In this study, we evaluated the presence of microRNAs (miRNAs) and messenger RNAs (mRNAs) related to inflammatory response and redox metabolism in exosomes of patients with septic shock.

Methods

Blood samples were collected from 24 patients with septic shock at ICU admission and after 7 days of treatment. Twelve healthy volunteers were used as control subjects. Exosomes were isolated by ultracentrifugation, and their miRNA and mRNA content was evaluated by qRT-PCR array.

Results

As compared with healthy volunteers, exosomes from patients with sepsis had significant changes in 65 exosomal miRNAs. Twenty-eight miRNAs were differentially expressed, both at enrollment and after 7 days, with similar kinetics (18 miRNAs upregulated and 10 downregulated). At enrollment, 35 differentially expressed miRNAs clustered patients with sepsis according to survival. The pathways enriched by the miRNAs of patients with sepsis compared with control subjects were related mostly to inflammatory response. The comparison of miRNAs from patients with sepsis according to hospital survival demonstrated pathways related mostly to cell cycle regulation. At enrollment, sepsis was associated with significant increases in the expression of mRNAs related to redox metabolism (myeloperoxidase, 64-fold; PRDX3, 2.6-fold; SOD2, 2.2-fold) and redox-responsive genes (FOXM1, 21-fold; SELS, 16-fold; GLRX2, 3.4-fold). The expression of myeloperoxidase mRNA remained elevated after 7 days (65-fold).

Conclusions

Exosomes from patients with septic shock convey miRNAs and mRNAs related to pathogenic pathways, including inflammatory response, oxidative stress, and cell cycle regulation. Exosomes may represent a novel mechanism for intercellular communication during sepsis.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2003-3) contains supplementary material, which is available to authorized users.

Micro RNA-155 inhibitor as a potential therapeutic strategy for the treatment of acute kidney injury (AKI): a nanomedicine perspective

In this study, we have prepared miR-155 inhibitor-loaded liposome vesicles for the effective treatment of acute kidney injury. The efficacy of liposomal miR-155 inhibitor in the expression of miR-155, mortality in animals, the expression of TNF-α-IL6, and the expression of SOCS1–STAT1 were evaluated. The loading of miR-155 inhibitor into liposomes conferred the much needed colloidal stability and efficient delivery to the renal tissues. The study clearly shows that miR-I-LV significantly decreases the expression of miR-155 in kidneys compared to LPS. Administration of miR-I-LV remarkably reduced the pathological concerns of the kidneys with a marked decrease in inflammatory cell infiltration. Scrambled miR-155 did not have any effect on the expression of these markers; however miR-I-LV showed a remarkable ability to decrease the expression of TNF-α and IL-6 in kidney tissues indicating an ability to treat acute kidney infections. Overall, administration of miR-155 inhibitor effectively alleviated LPS-induced kidney injury by significantly suppressing TNF-α and IL-6 in kidney tissue and by remarkably increasing the expression of mRNA of SOCS1 and STAT1. The present results suggest that miR-155 inhibitor could be used in an effective targeting strategy for the treatment of acute kidney injury (AKI).

In this study, we have prepared miR-155 inhibitor-loaded liposome vesicles for the effective treatment of acute kidney injury.

Systematic analysis of the expression profile of non-coding RNAs involved in ischemia/reperfusion-induced acute kidney injury in mice using RNA sequencing

Acute kidney injury (AKI) is a common and serious disease characterized by a rapid decline in renal function and has an unacceptably high mortality rate with no effective treatment beyond supportive care. AKI can be induced by many factors such as ischemia/reperfusion (IR), sepsis, and drug-induced nephrotoxicity. However, the molecular mechanisms of AKI are poorly understood. A non-coding RNA (ncRNA) is a RNA molecule that is not translated into a protein. NcRNAs play multiple roles in cellular processes, and mutations or imbalances of these molecules within the body can cause a variety of diseases. Although growing evidence has supported the key role of ncRNAs in AKI, the specific mechanism remains largely unknown. In this study, the second-generation gene sequencing was performed to investigate the expression patterns of ncRNAs, including microRNA (miRNA), long non-coding RNAs, and circular RNAs, in the kidneys of mice subjected to IR-induced AKI. This information will contribute to future research of the mechanism of ncRNAs in the pathogenesis of AKI and facilitate the identification of novel therapeutic targets of ncRNAs.

Dynamic and Modularized MicroRNA Regulation and Its Implication in Human Cancers

MicroRNA is responsible for the fine-tuning of fundamental cellular activities and human disease development. The altered availability of microRNAs, target mRNAs, and other types of endogenous RNAs competing for microRNA interactions reflects the dynamic and conditional property of microRNA-mediated gene regulation that remains under-investigated. Here we propose a new integrative method to study this dynamic process by considering both competing and cooperative mechanisms and identifying functional modules where different microRNAs co-regulate the same functional process. Specifically, a new pipeline was built based on a meta-Lasso regression model and the proof-of-concept study was performed using a large-scale genomic dataset from ~4,200 patients with 9 cancer types. In the analysis, 10,726 microRNA-mRNA interactions were identified to be associated with a specific stage and/or type of cancer, which demonstrated the dynamic and conditional miRNA regulation during cancer progression. On the other hands, we detected 4,134 regulatory modules that exhibit high fidelity of microRNA function through selective microRNA-mRNA binding and modulation. For example, miR-18a-3p, -320a, -193b-3p, and -92b-3p co-regulate the glycolysis/gluconeogenesis and focal adhesion in cancers of kidney, liver, lung, and uterus. Furthermore, several new insights into dynamic microRNA regulation in cancers have been discovered in this study.

Inhibiting microRNA-449 Attenuates Cisplatin-Induced Injury in NRK-52E Cells Possibly via Regulating the SIRT1/P53/BAX Pathway

Background

Acute kidney injury (AKI) is quite common in the patients who frequently use the anticancer drug cisplatin. microRNAs (miRNAs) are powerful tools in modulating the expression of key factors in disease progression, but little is known about roles of miRNAs in AKI. This study explored the expression and function of miR-449 in cisplatin-induced AKI.

Material/Methods

Rat renal proximal tubular cell line NRK-52E was used for cisplatin treatment and miR-449 sponge transfection. MTT assay and flow cytometry were performed to detect cell viability and apoptosis in different cell groups. Protein expression of sirtuin 1 (SIRT1), acetylated p53, and BCL-associated X protein (BAX) was detected to deduce the possible regulatory mechanism of miR-449.

Results

Results showed that cisplatin treatment in NRK-52E cells significantly up-regulated miR-449 levels (P<0.05), inhibited cell viability (P<0.05), accelerated cell apoptosis (P<0.05), and changed SIRT1, acetylated p53, and BAX protein levels (P<0.01). However, inhibiting miR-449 by its sponge transfection in cisplatin-treated cells significantly promoted cell viability (P<0.05), suppressed cell apoptosis (P<0.05), elevated SIRT1 expression (P<0.01), and inhibited acetylated p53 and BAX protein levels (P<0.001).

Conclusions

These results indicate that inhibiting miR-449 allows the attenuation of cisplatin-induced injury in NRK-52E cells, suggesting that miR-449 is a potential target for treating AKI. miR-449 regulates the SIRT1/p53/BAX pathway, which may be its possible mechanism in modulating cell apoptosis of cisplatin-induced AKI. Further verification and a thorough understanding are necessary for targeting miR-449 in AKI treatment.

Global miRNA expression is temporally correlated with acute kidney injury in mice

MicroRNAs (miRNAs) are negative regulators of gene expression and protein abundance. Current evidence shows an association of miRNAs with acute kidney injury (AKI) leading to substantially increased morbidity and mortality. Here, we investigated whether miRNAs are inductive regulators responsible for the pathological development of AKI. Microarray analysis was used to detect temporal changes in global miRNA expression within 48 h after AKI in mice. Results indicated that global miRNA expression gradually increased over 24 h from ischemia reperfusion injury after 24 h, and then decreased from 24 h to 48 h. A similar trend was observed for the index of tubulointerstitial injury and the level of serum creatinine, and there was a significant correlation between the level of total miRNA expression and the level of serum creatinine (p < 0.05). This expression-phenotype correlation was validated by quantitative reverse transcription PCR on individual miRNAs, including miR-18a, -134, -182, -210 and -214. Increased global miRNA expression may lead to widespread translational repression and reduced cellular activity. Furthermore, significant inflammatory cytokine release and peritubular capillary loss were observed, suggesting that the initiation of systematic destruction programs was due to AKI. Our findings provide new understanding of the dominant role of miRNAs in promoting the pathological development of AKI.