MicroRNA-188 aggravates contrast-induced apoptosis by targeting SRSF7 in novel isotonic contrast-induced acute kidney injury rat models and renal tubular epithelial cells

Contrast-induced acute kidney injury: a review of definition, pathogenesis, risk factors, prevention and treatment

Contrast-induced acute kidney injury (CI-AKI) has become the third leading cause of hospital-acquired AKI, which seriously threatens the health of patients. To date, the precise pathogenesis of CI-AKI has remained not clear and may be related to the direct cytotoxicity, hypoxia and ischemia of medulla, and oxidative stress caused by iodine contrast medium, which have diverse physicochemical properties, including cytotoxicity, permeability and viscosity. The latest research shows that microRNAs (miRNAs) are also involved in apoptosis, pyroptosis, and autophagy which caused by iodine contrast medium (ICM), which may be implicated in the pathogenesis of CI-AKI. Unfortunately, effective therapy of CI-AKI is very limited at present. Therefore, effective prevention of CI-AKI is of great significance, and several preventive options, including hydration, antagonistic vasoconstriction, and antioxidant drugs, have been developed. Here, we review current knowledge about the features of iodine contrast medium, the definition, pathogenesis, molecular mechanism, risk factors, prevention and treatment of CI-AKI.

The clinical predictive value and regulation mechanism of microRNA-188-5p in contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CI-AKI), also known as contrast-induced nephropathy (CIN), has become the third leading cause of iatrogenic AKI. Serum creatinine (Scr) is currently used in CIN clinical diagnosis. Patients with increased Scr have developed severe kidney injury, so there is an urgent need to find a bio-marker for CIN early diagnosis. To investigate the changes in circulating microRNA-188-5p (miR-188-5p) after coronary angiography and its predictive value for the CIN occurrence, miR-188-5p expression in CIN rats from the GEO database and CIN patients and control patients from Lianshui People's Hospital was analyzed. The results showed that miR-188-5p expression in plasma and renal was higher in CIN group than in control group. Further, a total of 36 CIN patients and 108 non-CIN patients were included. There were significant differences in age, hypertension, diabetes, and contrast agent dosage. After 12 h of contrast agent application, circulating miR-188-5p expression in CIN group was higher than control group. Univariate and multivariate logistic regression analysis showed that age, hypertension, diabetes, contrast media dosage and postoperative miR-188-5p expression were closely related to CIN occurrence. For in vitro experiments, intracellular miR-188-5p expression was decreased with ioversol treatment, while miR-188-5p expression in supernatant was increased. To explore the potential mechanism of miR-188-5p in CIN, HK-2 cells were treated with NC mimic, ioversol, or miR-188-5p mimic. The results showed that the application of miR-188-5p mimic reduced apoptosis, reactive oxygen species and MDA, enhanced SOD and GSH contents. Further, it was confirmed that mRNA and protein levels of PTEN were up-regulated in ioversol-treated HK-2 cells, and down-regulated after miR-188-5p administration. Dual-luciferase reporter gene assay confirmed that PTEN was direct target gene of miR-188-5p. Above results suggest that circulating miR-188-5p has the potential to serve as a predictor of CIN.

Contrast-Associated Acute Kidney Injury: Definitions, Epidemiology, Pathophysiology, and Implications

Acute kidney injury (AKI) is a common occurrence after contrast media administration. Hemodynamic changes, direct tubular injury, and reactive oxygen species are the proposed mechanisms involved in AKI. However, in most scenarios, it is not possible to establish causality despite extensive clinical evaluation, therefore, contrast-associated AKI (CA-AKI) has become a widely accepted term to define AKI postcontrast. CA-AKI is associated with worse clinical outcomes including cardiovascular events and mortality; however, discussions are ongoing whether CA-AKI is a marker of an increased risk of adverse outcomes or a mediator of such outcomes.

MicroRNAs as Biomarkers and Therapeutic Targets for Acute Kidney Injury

Acute kidney injury (AKI) is a clinical syndrome where a rapid decrease in kidney function and/or urine output is observed, which may result in the imbalance of water, electrolytes and acid base. It is associated with poor prognosis and prolonged hospitalization. Therefore, an early diagnosis and treatment to avoid the severe AKI stage are important. While several biomarkers, such as urinary L-FABP and NGAL, can be clinically useful, there is still no gold standard for the early detection of AKI and there are limited therapeutic options against AKI. miRNAs are non-coding and single-stranded RNAs that silence their target genes in the post-transcriptional process and are involved in a wide range of biological processes. Recent accumulated evidence has revealed that miRNAs may be potential biomarkers and therapeutic targets for AKI. In this review article, we summarize the current knowledge about miRNAs as promising biomarkers and potential therapeutic targets for AKI, as well as the challenges in their clinical use.

MicroRNAs in kidney injury and disease

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression by degrading or repressing the translation of their target messenger RNAs. As miRNAs are critical regulators of cellular homeostasis, their dysregulation is a crucial component of cell and organ injury. A substantial body of evidence indicates that miRNAs are involved in the pathophysiology of acute kidney injury (AKI), chronic kidney disease and allograft damage. Different subsets of miRNAs are dysregulated during AKI, chronic kidney disease and allograft rejection, which could reflect differences in the physiopathology of these conditions. miRNAs that have been investigated in AKI include miR-21, which has an anti-apoptotic role, and miR-214 and miR-668, which regulate mitochondrial dynamics. Various miRNAs are downregulated in diabetic kidney disease, including the miR-30 family and miR-146a, which protect against inflammation and fibrosis. Other miRNAs such as miR-193 and miR-92a induce podocyte dedifferentiation in glomerulonephritis. In transplantation, miRNAs have been implicated in allograft rejection and injury. Further work is needed to identify and validate miRNAs as biomarkers of graft function and of kidney disease development and progression. Use of combinations of miRNAs together with other molecular markers could potentially improve diagnostic or predictive power and facilitate clinical translation. In addition, targeting specific miRNAs at different stages of disease could be a promising therapeutic strategy.

Capsaicin Prevents Contrast-Associated Acute Kidney Injury through Activation of Nrf2 in Mice

Capsaicin, a transient receptor potential vanilloid 1 channel agonist, possesses antioxidative properties through activating nuclear factor-erythroid 2-related factor 2 (Nrf2). As oxidative stress is a major contributor to the development of contrast-associated acute kidney injury (CA-AKI), we investigated the protective effect of capsaicin against CA-AKI via Nrf2. C57BL/6J mice were treated with dehydration and iodixanol to establish the model of CA-AKI. For pretreatment, capsaicin (0.3 mg/kg) was given via intraperitoneal injection one hour before iodixanol injection. Nrf2-specific siRNA was given through the tail vein to knock down Nrf2. The CA-AKI mouse model had remarkable mitochondrial fragmentation and dysfunction and apoptosis of tubular cells, overproduction of superoxide in renal tubules, increased renal malondialdehyde, tubular epithelial cell injury, and renal dysfunction. Importantly, pretreatment with capsaicin significantly ameliorated tubular cell injury and renal dysfunction with decreased superoxide, renal malondialdehyde, and apoptotic tubular cells and improved mitochondrial morphology and function in the CA-AKI mouse model. The expression of Nrf2 was increased in the kidney from the CA-AKI mouse model and was further enhanced by capsaicin. Administration of siRNA through the tail vein successfully decreased Nrf2 expression in the kidney, and knockdown of Nrf2 by siRNA abolished the beneficial effects of capsaicin on CA-AKI. The present study demonstrated a protective effect of capsaicin pretreatment against CA-AKI via Nrf2.

Circ_0006006 facilitates non-small cell lung cancer progression by modulating miR-924/SRSF7 axis

BACKGROUND

Non-small cell lung cancer (NSCLC) is an aggressive tumor with high mortality. Circular RNAs (CircRNAs) played crucial roles in the development of cancers, including NSCLC. In this study, the action of circ_0006006 in NSCLC was investigated.

METHODS

Using real-time quantitative PCR (RT-qPCR), the relative gene expression was detected. The structure of circ_0006006 was identified using RNase R digestion and Actinomycin D treatment. The functional role of circ_0006006 in cell proliferation, migration, invasion, apoptosis and angiogenesis was explored using Cell Counting Kit-8 (CCK-8), EdU, colony formation, wound healing, transwell, flow cytometry, and tube formation assays, respectively. Using western blot, the relative proteins expression was measured. Dual-luciferase reporter and RNA immunoprecipitation (RIP) assays were employed to verify the correlation between microRNA-924 (miR-924) and circ_0006006 or serine/arginine-rich splicing factor 7 (SRSF7). Xenograft tumor experiment was used to investigate the effect of circ_0006006 on tumor growth in vivo. Immunohistochemistry (IHC) assay was performed to detect Ki-67, Bax, Bcl-2 and SRSF7 expression in tissues of mice.

RESULTS

Circ_0006006 was increased in NSCLC tissues and cells. Loss-of-function assays demonstrated that circ_0006006 silencing repressed the proliferative ability, cell migration and invasion, angiogenesis, and promoted cell apoptosis in A549 and H1299 cells. Follow-up mechanism experiments depicted that circ_0006006 sponged miR-924 and miR-924 inhibitor rescued circ_0006006 knockdown-mediated inhibition effect on the progression of NSCLC. Additionally, the inhibition effect of circ_0006006 knockdown on SRSF7 expression was reversed by miR-924 inhibitor. Moreover, the suppressive effect of miR-924 on NSCLC progression was reversed by SRSF7 overexpression. Xenograft tumor experiment unveiled that circ_0006006 knockdown inhibited tumor growth in vivo.

CONCLUSION

Circ_0006006 stimulated NSCLC progression by targeting miR-924 to regulate SRSF7 expression.

miRNA-Based Regulation of Alternative RNA Splicing in Metazoans

Alternative RNA splicing is an important regulatory process used by genes to increase their diversity. This process is mainly executed by specific classes of RNA binding proteins that act in a dosage-dependent manner to include or exclude selected exons in the final transcripts. While these processes are tightly regulated in cells and tissues, little is known on how the dosage of these factors is achieved and maintained. Several recent studies have suggested that alternative RNA splicing may be in part modulated by microRNAs (miRNAs), which are short, non-coding RNAs (~22 nt in length) that inhibit translation of specific mRNA transcripts. As evidenced in tissues and in diseases, such as cancer and neurological disorders, the dysregulation of miRNA pathways disrupts downstream alternative RNA splicing events by altering the dosage of splicing factors involved in RNA splicing. This attractive model suggests that miRNAs can not only influence the dosage of gene expression at the post-transcriptional level but also indirectly interfere in pre-mRNA splicing at the co-transcriptional level. The purpose of this review is to compile and analyze recent studies on miRNAs modulating alternative RNA splicing factors, and how these events contribute to transcript rearrangements in tissue development and disease.

Antagonist targeting miR‑106b‑5p attenuates acute renal injury by regulating renal function, apoptosis and autophagy via the upregulation of TCF4

Acute renal injury (ARI) is a life‑threatening condition and a main contributor to end‑stage renal disease, which is mainly caused by ischemia‑reperfusion (I/R). miR‑106b‑5p is a kidney function‑related miRNA; however, whether miR‑106b‑5p regulates the progression of ARI remains unclear. The present study thus aimed to examine the effects of miR‑106b‑5p antagonist on the regulation of ARI progression. It was found that miR‑106b‑5p expression was upregulated in the renal tissue of rats with I/R‑induced ARI and in NRK‑52E rat renal proximal tubular epithelial cells subjected to hypoxia‑reoxygenation (H/R). In vitro, H/R induction suppressed the proliferation, and promoted the apoptosis and autophagy of NRK‑52E cells, whereas miR‑106b‑5p antagonist (inhibition of miR‑106b‑5p) promoted the proliferation, and attenuated the apoptosis and autophagy of NRK‑52E cells under the H/R condition. Dual luciferase reporter gene assay validated that transcription factor 4 (TCF4) was a target of miR‑106b‑5p. It was further found that TCF4 overexpression promoted the proliferation, and inhibited the apoptosis and autophagy of NRK‑52E cells subjected to H/R. Moreover, the effects of miR‑106b‑5p antagonist on NRK‑52E cell proliferation, apoptosis and autophagy were mediated through the regulation of TCF4. In vivo, miR‑106b‑5p antagonist reduced the severity of renal injury, decreased cell proliferation in renal tissues and lowered the serum creatinine (Scr) and blood urea nitrogen (BUN) levels in the blood samples from rats with I/R‑induced ARI. On the whole, the findings presented herein demonstrate that miR‑106b‑5p antagonist attenuates ARI by promoting the proliferation, and suppressing the apoptosis and autophagy of renal cells via upregulating TCF4.

MiR-429 prohibited NF-κB signalling to alleviate contrast-induced acute kidney injury via targeting PDCD4

MiR-429 was reported to be downregulated in contrast-induced acute kidney injury (CI-AKI). However, whether miR-429 is functionally relevant with CI-AKI needs further investigation. Human renal tubular epithelial cell (HK-2) cells were stimulated with contrast media iodixanol to establish in vitro CI-AKI model. Cell Counting Kit-8 (CCK-8) was applied to access cell viability. Flow cytometry was performed to determine apoptosis. Quantitative real-time polymerase chain reaction (qRT-PCR) was applied to evaluate level of programmed cell death 4 (PDCD4) mRNA and miR-429 while western blot was applied to evaluate level of proteins including PDCD4, B-cell leukaemia/lymphoma 2 (Bcl-2), BCL2-associated X protein (Bax), cleaved caspase 3, cleaved caspase 9, p65, phosphorylated p65. Dual luciferase assay was used to validate miR-429 targeting PDCD4. MiR-429 was downregulated whereas PDCD4 was upregulated in contrast media iodixanol-stimulated HK-2 cells. MiR-429 overexpression elevated cell viability and attenuated cell apoptosis. Moreover, the activation of nuclear factor kappa-B (NF-κB) signalling was suppressed after miR-429 overexpression, while PDCD4 overexpression reversed these effects. MiR-429 directly targeted PDCD4 and negatively regulated its expression. CI-AKI induced NF-κB signalling activation and PDCD4 overexpression further promoted NF-κB signalling activation. However, the treatment of BAY11-7082 reversed above results. Overexpression of miR-429 attenuated apoptosis and elevated cell viability in a CI-AKI cell model via targeting PDCD4 and thus restraining NF-κB signalling.

Erratum to microRNA-188 aggravates contrast-induced apoptosis by targeting SRSF7 in novel isotonic contrast-induced acute kidney injury rat models and renal tubular epithelial cells

[This corrects the article DOI: 10.21037/atm.2019.07.20.].

TUNEL Assay: A Powerful Tool for Kidney Injury Evaluation

Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay is a long-established assay used to detect cell death-associated DNA fragmentation (3'-OH DNA termini) by endonucleases. Because these enzymes are particularly active in the kidney, TUNEL is widely used to identify and quantify DNA fragmentation and cell death in cultured kidney cells and animal and human kidneys resulting from toxic or hypoxic injury. The early characterization of TUNEL as an apoptotic assay has led to numerous misinterpretations of the mechanisms of kidney cell injury. Nevertheless, TUNEL is becoming increasingly popular for kidney injury assessment because it can be used universally in cultured and tissue cells and for all mechanisms of cell death. Furthermore, it is sensitive, accurate, quantitative, easily linked to particular cells or tissue compartments, and can be combined with immunohistochemistry to allow reliable identification of cell types or likely mechanisms of cell death. Traditionally, TUNEL analysis has been limited to the presence or absence of a TUNEL signal. However, additional information on the mechanism of cell death can be obtained from the analysis of TUNEL patterns.

Ranolazine alleviates contrast-associated acute kidney injury through modulation of calcium independent oxidative stress and apoptosis

This study investigates the role of ranolazine in contrast-associated acute kidney injury (CA-AKI) and potential mechanisms. For in vivo studies, mouse models of CA-AKI and control mice were treated with ranolazine or vehicle. Blood urea nitrogen (BUN) and serum creatinine were detected by spectrophotometry. Anti-T-cell immunoglobulin and mucin domain 1 (TIM 1) and anti-lipocalin 2 antibody (LCN2) were detected by immunofluorescence. Hemodynamic parameters were detected via invasive blood pressure measurement and renal artery color doppler ultrasound, capillary density was measured by CD31 immunofluorescence, vascular permeability assay was performed by Evans blue dye. The expressions of oxidative stress and apoptotic markers were measured and analyzed by immunofluorescence and western blotting. For in vitro studies, intracellular calcium concentration of HUVECs was measured with Fluo 3-AM under confocal microscopy. Results show that compared with control mice, serum BUN, creatinine, TIM 1 and LCN2 levels were elevated in CA-AKI mice, but this effect was alleviated by ranolazine-pretreatment. Safe doses of ranolazine (less than 64 mg/kg) had no significant effect on overall blood pressure, but substantially improved renal perfusion, reduced contrast-induced microcirculation disturbance, improved renal capillary density and attenuated renal vascular permeability in ranolazine-pretreated CA-AKI mice. Mechanistically, ranolazine markedly down-regulated oxidative stress and apoptosis markers compared to CA-AKI mice. Intracellularly, ranolazine attenuated calcium overload in HUVECs. These results indicate that ranolazine alleviates CA-AKI through modulation of calcium independent oxidative stress and apoptosis.

MicroRNA as an early diagnostic biomarker for contrast-induced acute kidney injury

Contrast-induced acute kidney injury (CI-AKI) is a common clinical complication and an important cause of increased mortality, prolonged hospitalization, and increased medical costs. For taking effective interventions in CI-AKI, early diagnosis and active prevention are of key importance. Currently, early CI-AKI detection depends on serum creatinine (Scr) levels, which lags behind the actual time of renal injury and seriously affects early diagnosis and interventions. MicroRNA (miRNA) has been found to be a useful biomarker in early CI-AKI diagnosis. Several studies have reported on tissue and time-specific miRNAs in AKI as effective diagnostic biomarkers and potential therapeutic targets, but there are only a few studies on miRNA in CI-AKI. However, these studies are preliminary exploratory investigations on changes in miRNA expression in CI-AKI, and whether these specific miRNAs can be used as biomarkers for early CI-AKI diagnosis and as clinical therapeutic targets requires systematic and in-depth studies. Therefore, more sensitive and specific miRNAs of CI-AKI could be discovered, providing newer options and development directions for early diagnosis and intervention in clinical CI-AKI practice. This review evaluates the research progress on specific miRNAs in the early diagnosis of CI-AKI with an aim of providing basic data for the clinical application of these molecular markers in CI-AKI.

Advances in the pathogenesis and prevention of contrast-induced nephropathy

With the increasing application of medical imaging contrast materials, contrast-induced nephropathy has become one of the leading causes of iatrogenic renal insufficiency. The underlying mechanism is associated with renal medullary hypoxia, direct toxicity of contrast agents, oxidative stress, apoptosis, immune/inflammation and epigenetic regulation in contrast-induced nephropathy. Up to date, there is no effective therapy for contrast-induced nephropathy, and thus risk predication and effective preventive strategies are keys to reduce the occurrence of contrast-induced nephropathy. It was found that the proper use of contrast medium, personalized hydration, and high-dose statins may reduce the occurrence of contrast-induced nephropathy, while antioxidants have not shown significant therapeutic benefits. Additionally, the role of remote ischemia preconditioning and vasodilators in the prevention of contrast-induced nephropathy needs further study. This review aims to discuss the incidence, pathogenesis, risk prediction, and preventive strategies for contrast-induced nephropathy.

The Role of MicroRNA in Contrast-Induced Nephropathy: A Scoping Review and Meta-Analysis

Objective

Early diagnosis of contrast-induced nephropathy (CIN) remains crucial for successful treatment; unfortunately, the widely used serum creatinine is elevated only in the late stage of CIN. The circulating microRNAs (miRNAs) are stable biomarker that might be useful. The aim of this scoping review and meta-analysis is to assess the role of miRNAs in CIN.

Methods

We performed a systematic literature search on topics that assess the role of miRNAs in CIN from several electronic databases.

Results

There were 6 preclinical studies and 2 of them validated their findings in human. Only miR-30a, miR-30c, miR-30e, and miR-188 have been validated in human models. Meta-analysis showed that increase in miR-30a expression was associated with higher incidence of CIN (OR 4.48 [1.52, 13.26],  p = 0.007; I²: 94%, p < 0.001). An increase in miR-30e expression was associated with higher incidence of CIN (OR 2.34 [1.70, 3.20], p < 0.001; I²: 0%, p = 0.76). There is an indication that miR-188 is associated with contrast-induced apoptosis and might potentially be a drug target in the future.

Conclusion

This study highlighted the importance of certain miRNAs in CIN pathophysiology. Future researches should explore on the prognostic and therapeutic implication of miRNA in CIN.

Pathophysiology of Contrast-Induced Acute Kidney Injury

Passing contrast media through the renal vascular bed leads to vasoconstriction. The perfusion decrease leads to ischemia of tubular cells. Through ischemia and direct toxicity to renal tubular cells, reactive oxygen species formation is increased, enhancing the effect of vasoconstrictive mediators and decreasing the bioavailability of vasodilative mediators. Reactive oxygen species formation leads to oxidative damage to tubular cells. These interacting pathways lead to tubular necrosis. In the pathophysiology of contrast-induced acute kidney injury, low osmolar and iso-osmolar agents have theoretic advantages and disadvantages; however, clinically the difference in incidence of contrast-induced acute kidney injury has not changed.