miR-21 contributes to xenon-conferred amelioration of renal ischemia-reperfusion injury in mice

Research progress on miR-124-3p in the field of kidney disease

MicroRNAs (miRNAs) are 18-25 nucleotides long, single-stranded, non-coding RNA molecules that regulate gene expression. They play a crucial role in maintaining normal cellular functions and homeostasis in organisms. Studies have shown that miR-124-3p is highly expressed in brain tissue and plays a significant role in nervous system development. It is also described as a tumor suppressor, regulating biological processes like cancer cell proliferation, apoptosis, migration, and invasion by controlling multiple downstream target genes. miR-124-3p has been found to be involved in the progression of various kidney diseases, including diabetic kidney disease, calcium oxalate kidney stones, acute kidney injury, lupus nephritis, and renal interstitial fibrosis. It mediates these processes through mechanisms like oxidative stress, inflammation, autophagy, and ferroptosis. To lay the foundation for future therapeutic strategies, this research group reviewed recent studies on the functional roles of miR-124-3p in renal diseases and the regulation of its downstream target genes. Additionally, the feasibility, limitations, and potential application of miR-124-3p as a diagnostic biomarker and therapeutic target were thoroughly investigated.

Physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated in underlying of ischemia/reperfusion injury in different organs

Ischemia-reperfusion (I/R) injury, as a pathological phenomenon, takes place when blood supply to an organ is disrupted and then aggravated during restoration of blood flow. Ischemic preconditioning (IPC) is a potent method for attenuating subsequent events of IR damage in numerous organs. IPC protocol is determined by a brief and sequential time periods of I/R before the main ischemia. MicroRNAs are endogenous non-coding RNAs that regulate post-transcriptionally target mRNA translation via degrading it and/or suppressing protein synthesis. This review introduces the physiological and cellular mechanisms of ischemic preconditioning microRNAs-mediated after I/R insult in different organs such as the liver, kidney, heart, brain, and intestine. Data of this review have been collected from the scientific articles published in databases such as Science Direct, Scopus, PubMed, Web of Science, and Scientific Information Database from 2000 to 2023. Based on these literature studies, IPC/IR intervention can affect cellular mechanisms including oxidative stress, apoptosis, angiogenesis, and inflammation through up-regulation or down-regulation of multiple microRNAs and their target genes.

Injury Site Specific Xenon Delivered by Platelet Membrane-Mimicking Hybrid Microbubbles to Protect Against Acute Kidney Injury via Inhibition of Cellular Senescence

Inhalation of xenon gas improves acute kidney injury (AKI). However, xenon can only be delivered through inhalation, which causes non-specific distribution and low bioavailability of xenon, thus limiting its clinical application. In this study, xenon is loaded into platelet membrane-mimicking hybrid microbubbles (Xe-Pla-MBs). In ischemia-reperfusion-induced AKI, intravenously injected Xe-Pla-MBs adhere to the endothelial injury site in the kidney. Xe-Pla-MBs are then disrupted by ultrasound, and xenon is released to the injured site. This release of xenon reduced ischemia-reperfusion-induced renal fibrosis and improved renal function, which are associated with decreased protein expression of cellular senescence markers p53 and p16, as well as reduced beta-galactosidase in renal tubular epithelial cells. Together, platelet membrane-mimicking hybrid microbubble-delivered xenon to the injred site protects against ischemia-reperfusion-induced AKI, which likely reduces renal senescence. Thus, the delivery of xenon by platelet membrane-mimicking hybrid microbubbles is a potential therapeutic approach for AKI.

The Versatile Role of miR-21 in Renal Homeostasis and Diseases

MicroRNAs (miRNAs) are small, non-coding RNA species that control gene expression and confer robustness to biological processes. Over the last two decades, their important roles during kidney development, homeostasis and the treatment of diseases have been established, in particular during the onset and progression of various forms of acute and chronic renal disorders. In recent years, miR-21, one of the best-characterized miRNAs to date, has received much attention in renal physiology in particular given its high degree of conservation and expression in kidneys, as well as its potent pathogenic role in various debilitating renal diseases. This review summarizes the current knowledge on miR-21’s involvement in both renal homeostasis and diseases, in particular its double-edged-sword role in acute versus chronic kidney injuries. Finally, we also discuss the potential of miR-21 as a biomarker and therapeutic target in renal diseases.

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.

LncRNA IRAR regulates chemokines production in tubular epithelial cells thus promoting kidney ischemia-reperfusion injury

Increasing evidence demonstrates that long noncoding RNAs (lncRNAs) play an important role in several pathogenic processes of the kidney. However, functions of lncRNAs in ischemic acute kidney injury (AKI) remain undefined. In this study, global lncRNA profiling indicated that many lncRNA transcripts were deregulated in kidney after ischemia reperfusion (IR). Among them, we identified IRAR (ischemia-reperfusion injury associated RNA) as a potential lncRNA candidate, which was mostly expressed by the tubular epithelial cells (TECs) after IR, involved in the development of AKI. GapmeR-mediated silencing and viral-based overexpression of IRAR were carried out to assess its function and contribution to IR-induced AKI. The results revealed that in vivo silencing of IRAR significantly reduced IR-induced proinflammatory cells infiltration and AKI. IRAR overexpression induced chemokine CCL2, CXCL1 and CXCL2 expression both in mRNA and protein levels in TECs, while, silencing of IRAR resulted in downregulation of these chemokines. RNA immunoprecipitation and RNA pulldown assay validated the association between IRAR and CCL2, CXCL1/2. Further examination revealed that specific ablation of CCL2 in TECs reduced macrophages infiltration and proinflammatory cytokine production, attenuated renal dysfunction in IR mice. Inhibition of CXC chemokine receptor 2 (receptor of CXCL1/2) reduced neutrofils infiltration, but had no overt effect on kidney function. To explore the mechanism of IRAR upregulation in kidney during IR, we analyzed promoter region of IRAR and predicted a potential binding site for transcription factor C/EBP β on IRAR promoter. Silencing of C/EBP β reduced IRAR expression in TECs. A dual-luciferase reporter assay and chromatin immunoprecipitation (ChIP) confirmed that IRAR was a transcriptional target of the C/EBP β. Altogether, our findings identify IRAR as a new player in the development of ischemic AKI through regulating chemokine production and immune cells infiltration, suggesting that IRAR is a potential target for prevention and/or attenuation of AKI.

Longitudinal Impact of WTC Dust Inhalation on Rat Cardiac Tissue Transcriptomic Profiles

First responders (FR) exposed to the World Trade Center (WTC) Ground Zero air over the first week after the 9/11 disaster have an increased heart disease incidence compared to unexposed FR and the general population. To test if WTC dusts were causative agents, rats were exposed to WTC dusts (under isoflurane [ISO] anesthesia) 2 h/day on 2 consecutive days; controls received air/ISO or air only. Hearts were collected 1, 30, 240, and 360 d post-exposure, left ventricle total RNA was extracted, and transcription profiles were obtained. The data showed that differentially expressed genes (DEG) for WTC vs. ISO rats did not reach any significance with a false discovery rate (FDR) < 0.05 at days 1, 30, and 240, indicating that the dusts did not impart effects beyond any from ISO. However, at day 360, 14 DEG with a low FDR were identified, reflecting potential long-term effects from WTC dust alone, and the majority of these DEG have been implicated as having an impact on heart functions. Furthermore, the functional gene set enrichment analysis (GSEA) data at day 360 showed that WTC dust could potentially impact the myocardial energy metabolism via PPAR signaling and heart valve development. This is the first study showing that WTC dust could significantly affect some genes that are associated with the heart/CV system, in the long term. Even > 20 years after the 9/11 disaster, this has potentially important implications for those FR exposed repeatedly at Ground Zero over the first week after the buildings collapsed.

PTEN alleviates maladaptive repair of renal tubular epithelial cells by restoring CHMP2A-mediated phagosome closure

Phosphatase and Tensin Homolog on chromosome Ten (PTEN) has emerged as a key protein that governs the response to kidney injury. Notably, renal adaptive repair is important for preventing acute kidney injury (AKI) to chronic kidney disease (CKD) transition. To test the role of PTEN in renal repair after acute injury, we constructed a mouse model that overexpresses PTEN in renal proximal tubular cells (RPTC) by crossing PTEN^fl-stop-fl mice with Ggt1-Cre mice. Mass spectrometry-based proteomics was performed after subjecting these mice to ischemia/reperfusion (I/R). We found that PTEN was downregulated in renal tubular cells in mice and cultured HK-2 cells subjected to renal maladaptive repair induced by I/R. Renal expression of PTEN negatively correlated with NGAL and fibrotic markers. RPTC-specific PTEN overexpression relieved I/R-induced maladaptive repair, as indicated by alleviative tubular cell damage, apoptosis, and subsequent renal fibrosis. Mass spectrometry analysis revealed that differentially expressed proteins in RPTC-specific PTEN overexpression mice subjected to I/R were significantly enriched in phagosome, PI3K/Akt, and HIF-1 signaling pathway and found significant upregulation of CHMP2A, an autophagy-related protein. PTEN deficiency downregulated CHMP2A and inhibited phagosome closure and autolysosome formation, which aggravated cell injury and apoptosis after I/R. PTEN overexpression had the opposite effect. Notably, the beneficial effect of PTEN overexpression on autophagy flux and cell damage was abolished when CHMP2A was silenced. Collectively, our study suggests that PTEN relieved renal maladaptive repair in terms of cell damage, apoptosis, and renal fibrosis by upregulating CHMP2A-mediated phagosome closure, suggesting that PTEN/CHMP2A may serve as a novel therapeutic target for the AKI to CKD transition.

Pirfenidone Attenuates Renal Tubulointerstitial Fibrosis through Inhibiting miR-21

BACKGROUND

Our previous studies had shown pirfenidone (PFD) not only improved tubulointerstitial fibrosis (TIF) but also inhibited the expression of microRNA-21 (miR-21) in the renal tissue of unilateral urethral obstruction (UUO) rats. This study aims to investigate whether PFD can attenuate TIF through inhibiting miR-21 in UUO rats.

METHODS

Sprague Dawley rats were divided randomly into sham-operated group, UUO group, and PFD and olmesartan (Olm) treatment groups. Samples were collected on day 14. Expression of miR-21, TGF-β1, Smad3, and Smad7 mRNA in the renal tissue was detected using real-time quantitative PCR. Immunohistochemistry was performed to assess the protein expressions of collagen III, E-cadherin, and α-SMA. Automated capillary Western blotting was used to detect the quantitative expression of TGF-β1, Smad3, p-Smad3, Smad7, collagen III, E-cadherin, and α-SMA in renal tissues. The expression of miR-21 and Smad7 mRNA and the protein levels of collagen III and α-SMA were examined in the miR-21-overexpressing cell line, NRK-52E.

RESULTS

Compared with the UUO group, both PFD and Olm inhibited renal tubular dilation, diffused epithelial cell degeneration and necrosis, and reduced renal interstitial edema, inflammatory cell infiltration, and collagen fiber deposition, while no significant difference between PFD group and Olm group. Informatics-based approaches identified Smad7 as a likely candidate for regulation by miR-21. Compared with the sham group, miR-21 expression was upregulated in the UUO group resulting in the downregulation of Smad7 expression due to degradation. The overexpression of miR-21 in the in vitro model downregulated Smad7 and promoted EMT and ECM accumulation. Protein levels of TGF-β1, Smad3, p-Smad3, collagen III, and α-SMA were upregulated, while E-cadherin protein was downregulated in the UUO group than in the sham group. PFD rather than Olm decreased the expression of miR-21 and increased the expression level of Smad7 mRNA and then inhibited the TGF-β1/Smad3 signaling pathway. Olm only downregulated the TGF-β1/Smad3 signaling pathway.

CONCLUSIONS

PFD improves TIF by downregulating the expression of miR-21, then elevating Smad7, and finally inhibiting the activation of the TGF-β1/Smad3 signaling pathway in UUO rats.

Longitudinal impact on rat cardiac tissue transcriptomic profiles due to acute intratracheal inhalation exposures to isoflurane

Isoflurane (ISO) is a widely used inhalation anesthetic in experiments with rodents and humans during surgery. Though ISO has not been reported to impart long-lasting side effects, it is unknown if ISO can influence gene regulation in certain tissues, including the heart. Such changes could have important implications for use of this anesthetic in patients susceptible to heart failure/other cardiac abnormalities. To test if ISO could alter gene regulation/expression in heart tissues, and if such changes were reversible, prolonged, or late onset with time, SHR (spontaneously hypertensive) rats were exposed by intratracheal inhalation to a 97.5% air/2.5% ISO mixture on two consecutive days (2 hr/d). Control rats breathed filtered air only. On Days 1, 30, 240, and 360 post-exposure, rat hearts were collected and total RNA was extracted from the left ventricle for global gene expression analysis. The data revealed differentially-expressed genes (DEG) in response to ISO (compared to naïve control) at all post-exposure timepoints. The data showed acute ISO exposures led to DEG associated with wounding, local immune function, inflammation, and circadian rhythm regulation at Days 1 and 30; these effects dissipated by Day 240. There were other significantly-increased DEG induced by ISO at Day 360; these included changes in expression of genes associated with cell signaling, differentiation, and migration, extracellular matrix organization, cell-substrate adhesion, heart development, and blood pressure regulation. Examination of consistent DEG at Days 240 and 360 indicated late onset DEG reflecting potential long-lasting effects from ISO; these included DEG associated with oxidative phosphorylation, ribosome, angiogenesis, mitochondrial translation elongation, and focal adhesion. Together, the data show acute repeated ISO exposures could impart variable effects on gene expression/regulation in the heart. While some alterations self-resolved, others appeared to be long-lasting or late onset. Whether such changes occur in all rat models or in humans remains to be investigated.

Perilipin 2 Impacts Acute Kidney Injury via Regulation of PPARα

Renal ischemia-reperfusion (I/R) can induce oxidative stress and injury via the generation of reactive oxygen species (ROS). Renal proximal tubular cells are susceptible to oxidative stress, and the dysregulation of renal proximal tubular cellular homeostasis can damage cells via apoptotic pathways. A recent study showed that the generation of ROS can increase perilipin 2 (Plin2) expression in HepG2 cells. Some evidence has also demonstrated the association between Plin2 expression and renal tumors. However, the underlying mechanism of Plin2 in I/R-induced acute kidney injury (AKI) remains elusive. Here, using a mouse model of I/R-induced AKI, we found that ROS generation was increased and the expression of Plin2 was significantly upregulated. An in vitro study further revealed that the expression of Plin2, and the generation of ROS were significantly upregulated in primary tubular cells treated with hydrogen peroxide. Accordingly, Plin2 knockdown decreased apoptosis in renal proximal tubular epithelial cells treated with hydrogen peroxide, which depended on the activation of peroxisome proliferator-activated receptor α (PPARα). Overall, the present study demonstrated that Plin2 is involved in AKI; knockdown of this marker might limit apoptosis via the activation of PPARα. Consequently, the downregulation of Plin2 could be a novel therapeutic strategy for AKI.

Argon inhibits reactive oxygen species oxidative stress via the miR-21-mediated PDCD4/PTEN pathway to prevent myocardial ischemia/reperfusion injury

The objective of this study was to explore the effect of argon preconditioning on myocardial ischemia reperfusion (MI/R) injury and its mechanism. Cardiomyocytes H2C9 were pre-treated with 50% argon, and a cell model of oxygen-glucose deprivation (OGD) was established. CCK-8 and cytotoxicity detection kits were used to detect cell viability and lactate dehydrogenase (LDH) release. The miR-21 expression was detected using quantitative real-time polymerase chain reaction. Western blot analysis was performed to detect the expression of programmed cell death protein 4 (PDCD4) and homologous phosphatase and tensin homolog (PTEN) proteins. The levels of inflammatory factors (IL-1β, IL-6, and IL-8) and oxidative stress factors (reactive oxygen species ROS], malondialdehyde [MDA], and superoxide dismutase [SOD]) were measured using an enzyme-linked immunosorbent assay. The effect of argon on cell apoptosis was detected using flow cytometry. Argon increased the proliferation of cardiomyocytes induced by OGD, decreased the release of LDH in cell culture medium, increased miR-21 expression in cells, decreased the expression of miR-21 target proteins PDCD4 and PTEN, decreased the levels of inflammatory factors (interleukin-1β [IL-1β], interleukin-6 [IL-6], and interleukin-8 [IL-8]) and oxidative stress factors (ROS and MDA), increased the SOD content, and decreased the cell apoptosis rate. Our results suggest that argon preconditioning inhibited the PDCD4/PTEN pathway via miR-21, thereby inhibiting ROS oxidative stress and preventing MI/R injury.

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.

Regulation of microRNAs in high-fat diet induced hyperlipidemic hamsters

Dyslipidemia is a documented risk factor for cardiovascular diseases and other metabolic disorders. Therefore, the analysis of hyperlipidemia (HL)-related miRNAs is a potential approach for achieving new prognostic markers in lipid-metabolism related diseases. We aimed to analyze specific distribution of miRNAs in different tissues from HL animals. Golden Syrian hamsters were fed either regular chow (NL) or high-fat diet (HL) for 12 weeks. Microarray miRNAs profiling was performed in liver, heart and small intestine and data analyzed by R-studio software. Functional enrichment bioinformatics analysis was performed using miRWalk and DAVID tools. We observed a dysregulation of miRNAs in HL tissues evidencing a discrete distribution in the heart-liver axis and three lipid metabolism-related miRNAs were identified: hsa-miR-223-3p, hsa-miR-21-5p, and hsa-miR-146a-5p. Expression levels of these miRNAs were increased in HL livers and hearts. Functional bioinformatics analysis showed involvement of these miRNAs in the regulation of biological processes altered in HL conditions such as lipid metabolic process, fat cell differentiation, regulation of smooth muscle cells and cardiac septum development. We identified a set of miRNAs dysregulated in different tissues of HFD-induced HL hamsters. These findings motivate further studies aiming to investigate novel molecular mechanisms of lipid metabolism and atherogenic HL.

Total Glucosides of Paeony Alleviate Cell Apoptosis and Inflammation by Targeting the Long Noncoding RNA XIST/MicroRNA-124-3p/ITGB1 Axis in Renal Ischemia/Reperfusion Injury

OBJECTIVE

Renal ischemia/reperfusion injury (RI/RI) is the main cause of acute kidney injury. Total glucosides of paeony (TGP) are a traditional Chinese medicine. This study was aimed at exploring the role of TGP in RI/RI and its underlying mechanism of action.

METHODS

Rat RI/RI models were constructed by surgical operation. Serum creatinine (Scr) and blood urea nitrogen (BUN) were used to evaluate renal function. The levels of proinflammatory cytokines were detected by ELISA. RI/RI was simulated by hypoxia/reoxygenation (H/R) treatment in renal cells in vitro. The lncRNA XIST (XIST) expression was analyzed by qRT-PCR. Then, the viability and apoptosis of renal cells were detected by MTT and flow cytometry assay. Additionally, dual-luciferase reporter assay was used to determine the interactions among XIST, microRNA-124-3p (miR-124-3p), and ITGB1.

RESULTS

TGP improved renal function and inhibited inflammatory responses after RI/RI. XIST expression was highly expressed in rat RI/RI models and H/R-treated renal cells, whereas treatment with TGP downregulated the XIST expression. Additionally, TGP increased viability and attenuated apoptosis and inflammation of H/R-treated renal cells via inhibiting XIST. Moreover, XIST was competitively bound to miR-124-3p, and ITGB1 was a target of miR-124-3p. miR-124-3p overexpression or ITGB1 inhibition rescued the reduction effect on viability and mitigated the promoting effects on cell apoptosis and inflammation caused by XIST overexpression in H/R-treated renal cells.

CONCLUSIONS

In vivo, TGP attenuated renal dysfunction and inflammation in RI/RI rats. In vitro, TGP inhibited XIST expression to modulate the miR-124-3p/ITGB1 axis, alleviating the apoptosis and inflammation of H/R-treated renal cells.

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.

Depletion of miR-21 in dendritic cells aggravates renal ischemia-reperfusion injury

Dendritic cells (DCs) play an important role in the pathophysiology of renal ischemia-reperfusion injury (IRI). The mechanisms underlying DCs phenotypic modulation and their function are not fully understood. In this study, we examined the effect of miR-21 on the phenotypic modulation of DCs in vitro and in vivo, and further investigated the impact of miR-21-overexpression DC or miR-21-deficient DC on renal IRI. We found that treatment with hypoxia/reoxygenation (H/R) suppressed miR-21 expression in bone marrow-derived dendritic cells (BMDCs), and significantly increased the percentage of mature DCs (CD11c⁺ /MHC-II⁺ /CD80⁺ ). Using a selection of microRNA mimics, we successfully induced the upregulation of miR-21 in BMDCs, which induced immature DC phenotype and an anti-inflammatory DC response. However, deletion of miR-21 in BMDCs promoted maturation of DCs under H/R. Adoptive transfer of miR-21-overexpression BMDCs could alleviate renal IR-induced pro-inflammatory cytokines production and acute kidney injury (AKI). Mice with miR-21 deficiency in DCs subjected to renal IR showed more severe renal dysfunction and inflammatory response compared with wild-type mice. In addition, chemokine C receptor 7 (CCR7), a surface marker of mature DC, was a target gene of miR-21, and silencing of CCR7 in BMDCs led to reduced mature DCs under H/R. In conclusion, our findings highlight miR-21 as a key regulator of DCs subset phenotype and a potential therapeutic target in renal IRI.

Xenon blunts NF-κB/NLRP3 inflammasome activation and improves acute onset of accelerated and severe lupus nephritis in mice

Xenon, an inert anesthetic gas, is increasingly recognized to possess desirable properties including cytoprotective and anti-inflammatory effects. Here we evaluated the effects of xenon on the progression of lupus nephritis (LN) in a mouse model. A two hour exposure of either 70% xenon or 70% nitrogen balanced with oxygen was administered daily for five weeks to female NZB/W F1 mice that had been induced to develop accelerated and severe LN. Xenon treatment improved kidney function and renal histology, and decreased the renal expression of neutrophil chemoattractants, thereby attenuating glomerular neutrophil infiltration. The effects of xenon were mediated primarily by deceasing serum levels of anti-double stranded DNA autoantibody, inhibiting reactive oxygen species production, NF-κB/NLRP3 inflammasome activation, ICAM-1 expression, glomerular deposition of IgG and C3 and apoptosis, in the kidney; and enhancing renal hypoxia inducible factor 1-α expression. Proteomic analysis revealed that the treatment with xenon downregulated renal NLRP3 inflammasome-mediated cellular signaling. Similarly, xenon was effective in improving renal pathology and function in a spontaneous LN model in female NZB/W F1 mice. Thus, xenon may have a therapeutic role in treating LN but further studies are warranted to determine applicability to patients.

LncRNA GAS5 promotes apoptosis as a competing endogenous RNA for miR-21 via thrombospondin 1 in ischemic AKI

Mounting evidence has indicated that long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) played important roles in renal ischemia/reperfusion (I/R) injury. However, the involvement of lncRNA growth arrest specific 5 (GAS5) in acute kidney injury (AKI) remained largely unexplored. This study aimed to determine possible mechanisms of GAS5 in the renal I/R process. We found that GAS5, noticeably upregulated by renal I/R injury, was further suppressed by delayed IPC while knockdown of miR-21 in vivo before IPC could significantly increased the GAS5 levels. Concurrently, TSP-1 was negatively regulated by miR-21 in vivo and vitro. Additionally, Reciprocal repression of GAS5 and miR-21 was identified. Knockdown of miR-21 in H6R0.5 treated HK-2 cells promoted apoptosis. Co-transfection of miR-21 mimic and pcDNA-GAS5 or pcDNA-Vector were performed, results of which showed that inhibition of miR-21 on TSP-1 could be rescued by overexpression of GAS5. This study suggested that GAS5 facilitated apoptosis by competitively sponging miR-21, which negatively regulated TSP-1 in renal I/R injury. This novel regulatory axis could act as a therapeutic target for AKI in the future.

Acute Kidney Injury Associated with Cardiac Surgery: a Comprehensive Literature Review

Objective

To comprehensively understand cardiac surgeryassociated acute kidney injury (CSA-AKI) and methods of prevention of such complication in cardiac surgery patients.

Methods

A comprehensive literature search was performed using the electronic database to identify articles describing acute kidney injury (AKI) in patients that undergone cardiac surgery. There was neither time limit nor language limit on the search. The results were narratively summarized.

Results

All the relevant articles have been extracted; results have been summarized in each related section. CSA-AKI is a serious postoperative complication and it can contribute to a significant increase in perioperative morbidity and mortality rates. Optimization of factors that can reduce CSA-AKI, therefore, contributes to a better postoperative outcome.

Conclusion

Several factors can significantly increase the rate of AKI; identification and minimization of such factors can lead to lower rates of CSA-AKI and lower perioperative morbidity and mortality rates.

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.

Uncoupling protein 1 inhibits mitochondrial reactive oxygen species generation and alleviates acute kidney injury

BACKGROUND

Uncoupling protein 1 (UCP1) is predominantly found in brown adipose tissue mitochondria, and mediates energy dissipation to generate heat rather than ATP via functional mitochondrial uncoupling. However, little is known about its expression and function in kidney.

METHODS

We carried out a mRNA microarray analysis in mice kidneys with ischemia reperfusion (IR) injury. The most dramatically downregulated gene UCP1 after IR was identified, and its role in generation of mitochondrial reactive oxygen species (ROS) and oxidative stress injury was assessed both in vitro and in vivo. Genetic deletion of UCP1 was used to investigate the effects of UCP1 on ischemia or cisplatin-indued acute kidney injury (AKI) in mice.

FINDINGS

UCP1 was located in renal tubular epithelial cells in kidney and downregulated in a time-dependent manner during renal IR. Deletion of UCP1 increased oxidative stress in kidneys and aggravated ischemia or cisplatin induced AKI in mice.Viral-based overexpression of UCP1 reduced mitochondrial ROS generation and apoptosis in hypoxia-treated tubular epithelial cells. Furthermore, UCP1 expression was regulated by peroxisome proliferator-activator receptor (PPAR) γ in kidneys during renal IR. Overexpression of PPAR-γ resembled UCP1-overexpression phenotype in vitro. Treatment with PPAR-γ agonist could induce UCP1 upregulation and provide protective effect against renal IR injury in UCP1^+/+mice, but not in UCP1^-/-mice.

INTERPRETATION

UCP1 protects against AKI likely by suppressing oxidative stress, and activation of UCP1 represents a potential therapeutic strategy for AKI. FUND: National Natural Science Foundation of China grants, Science and Technology Commission of Shanghai.

Better haemodynamic stability under xenon anaesthesia than under isoflurane anaesthesia during partial nephrectomy - a secondary analysis of a randomised controlled trial

Background

Renal dysfunction following intraoperative arterial hypotension is mainly caused by an insufficient renal blood flow. It is associated with higher mortality and morbidity rates. We hypothesised that the intraoperative haemodynamics are more stable during xenon anaesthesia than during isoflurane anaesthesia in patients undergoing partial nephrectomy.

Methods

We performed a secondary analysis of the haemodynamic variables collected during the randomised, single-blinded, single-centre PaNeX study, which analysed the postoperative renal function in 46 patients who underwent partial nephrectomy. The patients received either xenon or isoflurane anaesthesia with 1:1 allocation ratio. We analysed the duration of the intraoperative systolic blood pressure decrease by > 40% from baseline values and the cumulative duration of a mean arterial blood pressure (MAP) of < 65 mmHg as primary outcomes. The secondary outcomes were related to other blood pressure thresholds, the amount of administered norepinephrine, and the analysis of confounding factors on the haemodynamic stability.

Results

The periods of an MAP of < 65 mmHg were significantly shorter in the xenon group than in the isoflurane group. The medians [interquartile range] were 0 [0–10.0] and 25.0 [10.0–47.5] minutes, for the xenon and isoflurane group, respectively (P = 0.002). However, the cumulative duration of a systolic blood pressure decrease by > 40% did not significantly differ between the groups (P = 0.51). The periods with a systolic blood pressure decrease by 20% from baseline, MAP decrease to values < 60 mmHg, and the need for norepinephrine, as well as the cumulative dose of norepinephrine were significantly shorter and lower, respectively, in the xenon group. The confounding factors, such as demographic data, surgical technique, or anaesthesia data, were similar in the two groups.

Conclusion

The patients undergoing xenon anaesthesia showed a better haemodynamic stability, which might be attributed to the xenon properties. The indirect effect of xenon anaesthesia might be of importance for the preservation of renal function during renal surgery and needs further elaboration.

Trial registration

ClinicalTrials.gov: NCT01839084. Registered 24 April 2013.

Electronic supplementary material

The online version of this article (10.1186/s12871-019-0799-2) contains supplementary material, which is available to authorized users.

Exosomes from human-bone-marrow-derived mesenchymal stem cells protect against renal ischemia/reperfusion injury via transferring miR-199a-3p

Renal ischemia/reperfusion (I/R) injury is the main reason for acute kidney injury (AKI) and is closely related to high morbidity and mortality. In this study, we found that exosomes from human-bone-marrow-derived mesenchymal stem cells (hBMSC-Exos) play a protective role in hypoxia/reoxygenation (H/R) injury. hBMSC-Exos were enriched in miR-199a-3p, and hBMSC-Exo treatment increased the expression level of miR-199a-3p in renal cells. We further explored the function of miR-199a-3p on H/R injury. miR-199a-3p was knocked down in hBMSCs with a miR-199a-3p inhibitor. HK-2 cells cocultured with miR-199a-3p-knockdown hBMSCs were more susceptible to H/R injury and showed more apoptosis than those cocultured with hBMSCs or miR-199a-3p-overexpressing hBMSCs. Meanwhile, we found that HK-2 cells exposed to H/R treatment incubated with hBMSC-Exos decreased semaphorin 3A (Sema3A) and activated the protein kinase B (AKT) and extracellular-signal-regulated kinase (ERK) pathways. However, HK-2 cells cocultured with miR-199a-3p-knockdown hBMSCs restored Sema3A expression and blocked the activation of the AKT and ERK pathways. Moreover, knocking down Sema3A could reactivate the AKT and ERK pathways suppressed by a miR-199a-3p inhibitor. In vivo, we injected hBMSC-Exos into mice suffering from I/R injury; this treatment induced functional recovery and histologic protection and reduced cleaved caspase-3 and Sema3A expression levels, as shown by immunohistochemistry. On the whole, this study demonstrated an antiapoptotic effect of hBMSC-Exos, which protected against I/R injury, via delivering miR-199a-3p to renal cells, downregulating Sema3A expression and thereby activating the AKT and ERK pathways. These findings reveal a novel mechanism of AKI treated with hBMSC-Exos and provide a therapeutic method for kidney diseases.

miR‑27a suppresses TLR4‑induced renal ischemia‑reperfusion injury

Ischemia reperfusion injury (IRI) is one of the primary causes of acute renal injury and even acute renal failure. An increasing body of evidence has indicated that the aberrant expression of microRNAs (miRNA/miR) is closely associated with the progression of IRI. In the process of renal IRI, inflammatory reactions, cell adhesion and the death of renal tubular epithelial cells serve important roles. The present study investigated the expression of renal miRNAs following renal IRI in an attempt to identify the miRNAs that exert pivotal functions in renal IRI. The present study revealed that miR-27a, which was downregulated in IRI, and the 3′-untranslated region (UTR) of Toll-like receptor 4 (TLR4) have associated binding sites. The levels of TLR4, miR-27a and specific associated proteins in the renal tissues of gestational rats were determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis, immunohistochemistry and western blotting. The associations between miR-27a and TLR4 were analyzed, and the regulatory effect of miR-27a on TLR4 was detected via a luciferase reporter gene assay, western blotting and RT-qPCR in vivo and in vitro. In addition, the present study demonstrated that miR-27a suppressed the expression of TLR4 by binding to the 3′UTR of TLR4. The overexpression of miR-27a downregulated the expression of TLR4, which in turn inhibited the inflammation, cell adhesion and cell death in IRI. Therefore, miR-27a inhibited inflammation in IRI by decreasing the expression of TLR4.

Gcm1 is involved in cell proliferation and fibrosis during kidney regeneration after ischemia-reperfusion injury

In acute kidney injury (AKI), the S3 segment of the proximal tubule is particularly damaged, as it is most vulnerable to ischemia. However, this region is also involved in renal tubular regeneration. To deeply understand the mechanism of the repair process after ischemic injury in AKI, we focused on glial cells missing 1 (Gcm1), which is one of the genes expressed in the S3 segment. Gcm1 is essential for the development of the placenta, and Gcm1 knockout (KO) is embryonically lethal. Thus, the function of Gcm1 in the kidney has not been analyzed yet. We analyzed the function of Gcm1 in the kidney by specifically knocking out Gcm1 in the kidney. We created an ischemia-reperfusion injury (IRI) model to observe the repair process after AKI. We found that Gcm1 expression was transiently increased during the recovery phase of IRI. In Gcm1 conditional KO mice, during the recovery phase of IRI, tubular cell proliferation reduced and transforming growth factor-β1 expression was downregulated resulting in a reduction in fibrosis. In vitro, Gcm1 overexpression promoted cell proliferation and upregulated TGF-β1 expression. These findings indicate that Gcm1 is involved in the mechanisms of fibrosis and cell proliferation after ischemic injury of the kidney.

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.

Inhibition of MicroRNA-23 Contributes to the Isoflurane-Mediated Cardioprotection Against Oxidative Stress

Isoflurane is one of the most frequently used volatile anesthetics in clinical practice for inhalational anesthesia. It is widely studied that isoflurane mediates cardioprotection during multiple pathological processes. However, the precise mechanisms have not been fully elucidated. Neonatal cardiomyocytes were isolated and cultured, followed by treatments with isoflurane at 0, 50, 100 or 200 µM. Rat cardiomyoblast cell line, H9c2, was treated with H₂O₂. Expression of miR-23 was measured by qRT-PCR. The cell survival rate of H9c2 in response to H₂O₂ treatments was evaluated by MTT assay. The ROS and GSH/GSSG levels were measured using Superoxide Detection Kit and GSH/GSSG Ratio Detection Assay Kit. In this study, we report an isoflurane-miR-23-antioxidant axis in cardiomyocyte. We observed that miR-23 was suppressed by isoflurane treatments at 50, 100 or 200 µM. Moreover, cardiomyocyte with isoflurane exposure was insensitive to H₂O₂ treatment in vitro. Inhibition of miR-23 protected cardiomyocyte against oxidative stress induced by H₂O₂ treatments at 30, 60, 90 or 120 µM. In addition, overexpression of miR-23 induced ROS generation over twofolds and rendered cardiomyocyte sensitive to H₂O₂ treatments. We demonstrate that miR-23 inhibited intracellular GSH, an antioxidant against oxidative stress. Our results reveal that with isoflurane exposure, overexpression of miR-23 rendered cardiomyocyte sensitive to H₂O₂ treatments at 20, 30, 40, 50 µM. Pretreatments with GSH in miR-23 overexpressing cells rescued the cell death under oxidative stress. In summary, our results illustrate that the isoflurane-mediated protection of cardiomyocytes under oxidative stress is through inhibition of miR-23. This study provides an aspect for the miRNAs-modulated cardiomyocyte sensitivity to oxidative stress, contributing to the development of therapeutic agents.

RhoA/rho-kinase, nitric oxide and inflammatory response in LIMA during OPCABG with isoflurane preconditioning

Background

Grafting vessel with LIMA to the left anterior descending coronary artery plays a most important role in the long-term prognosis of OPCABG surgery. The aim of this study was to compare the effects of isoflurane preconditioning on miRs and mRNAs levels in the left internal mammary arterie (LIMA) graft with propofol in patients undergoing off-pump coronary artery bypass surgery (OPCABG).

Methods

Patients were randomly assigned to receive either propofol (n = 15), or interrupted isoflurane (n = 15). In group P, propofol administration was continued at 3–5 mg/kg/h intravenous injection for the duration of surgery. Five minutes prior to incision, patients of the isoflurane group (group Iso) received 2 cycles of 1 MAC isoflurane.

Results

miR-221 were significantly lower in group Iso (P < 0 .05). E-selectin mRNA, RhoA mRNA and ROK mRNA were significantly lower at specimens of LIMA in group Iso compared with those in group P patients (P < 0 .05). The expression of NOS3 mRNA was significantly higher in group Iso patients (P < 0 .05).

Conclusion

Our findings provide some insight that prior interrupted isoflurane administration could regulate miR-221, and downstream effectors (mRNAs) and resulted in actual attenuation of inflammation and spasm of LIMA in patients undergoing OPCABG surgery.

Trial registration

NCT No. (ClinicalTrials.gov): NCT02678650; Registration date: January 23, 2016.

Xenon anesthesia and beyond: pros and cons

Xenon is a colorless and odorless noble gas, licensed for human use as an anesthetic gas as well as a radiological marker. The MAC of this gas is about 63% but xenon anesthesia is associated with fast recovery of cognitive function and cardiovascular stability. Nevertheless, postoperative nausea and vomiting (PONV) incidence for xenon anesthesia is very high. It has been reported that Xenon has cytoprotective effects that may have therapeutic values in both CNS protection, and in organ graft preservation. Currently, there are few studies about the effect of xenon on ischemia reperfusion injury of transplantable organs and insufficient clinical data upon its effect on intracranial and cerebral perfusion pressure. We shortly review the pros and cons of xenon as an anesthetic agent.

miR-21 Protects Against Ischemia/Reperfusion-Induced Acute Kidney Injury by Preventing Epithelial Cell Apoptosis and Inhibiting Dendritic Cell Maturation

Renal tubular injury and innate immune responses induced by hypoxia contribute to acute kidney injury. Accumulating evidence suggests that miR-21 overexpression protects against kidney ischemia injury. Additionally, miR-21 emerges as a key inhibitor in dendritic cell maturation. Thus, we hypothesized that miR-21 protects the kidney from IR injury by suppressing epithelial cell damage and inflammatory reaction. In this study, we investigated effects of miR-21 and its signaling pathways (PTEN/AKT/mTOR/HIF, PDCD4/NFκ-B) on kidney ischemia/reperfusion (IR) injury in vitro and in vivo. The results revealed that IR increased miR-21, HIF1α, and 2α expression in vivo and in vitro. MiR-21 interacted with HIF1α and 2α through the PTEN/AKT/mTOR pathway. Moreover, inhibition of miR-21 activated PDCD4/NFκ-B pathways, which are critical for dendritic cell maturation. Renal IR triggers local inflammation by inducing the dendritic cell maturation and promoting the secretion of IL-12, IL-6, and TNF-α cytokines. Knockdown of miR-21 intensified the effect of IR on tubular epithelial cell apoptosis and dendritic cell maturation. Our results suggested that IR-inducible miR-21 protects epithelial cells from IR injury via a feedback interaction with HIF (PTEN/AKT/mTOR/HIF/miR-21) and by inhibiting maturation of DCs through the PDCD4/NF-κB pathway. These findings highlight new therapeutic opportunities in AKI.

Postconditioning effects of argon or xenon on early graft function in a porcine model of kidney autotransplantation

BACKGROUND

Ischaemia-reperfusion injury is inevitable during renal transplantation and can lead to delayed graft function and primary non-function. Preconditioning, reconditioning and postconditioning with argon and xenon protects against renal ischaemia-reperfusion injury in rodent models. The hypothesis that postconditioning with argon or xenon inhalation would improve graft function in a porcine renal autotransplant model was tested.

METHODS

Pigs (n = 6 per group) underwent left nephrectomy after 60 min of warm ischaemia (renal artery and vein clamping). The procured kidney was autotransplanted in a separate procedure after 18 h of cold storage, immediately after a right nephrectomy. Upon reperfusion, pigs were randomized to inhalation of control gas (70 per cent nitrogen and 30 per cent oxygen), argon (70 per cent and 30 per cent oxygen) or xenon (70 per cent and 30 per cent oxygen) for 2 h. The primary outcome parameter was peak plasma creatinine; secondary outcome parameters included further markers of graft function (creatinine course, urine output), graft injury (aspartate aminotransferase, heart-type fatty acid-binding protein, histology), apoptosis and autophagy (western blot, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining), inflammatory mediators and markers of cell survival/growth (mRNA and tissue protein quantification), and animal survival. Results are presented as median (i.q.r.). ANOVA and Kruskal-Wallis tests were used where indicated.

RESULTS

Peak plasma creatinine levels were similar between the groups: control 20·8 (16·4-23·1) mg/dl, argon 21·4 (17·1-24·9) mg/dl and xenon 19·4 (17·5-21·0) mg/dl (P = 0·607). Xenon was associated with an increase in autophagy and proapoptotic markers. Creatinine course, urine output, injury markers, histology, survival and inflammatory mediators were not affected by the intervention.

CONCLUSION

Postconditioning with argon or xenon did not improve kidney graft function in this experimental model. Surgical relevance Ischaemia-reperfusion injury is inevitable during renal transplantation and can lead to delayed graft function and primary non-function. Based on mainly small animal experiments, noble gases (argon and xenon) have been proposed to minimize this ischaemia-reperfusion injury and improve outcomes after transplantation. The hypothesis that postconditioning with argon or xenon inhalation would improve graft function was tested in a porcine kidney autotransplantation model. The peak plasma creatinine concentration was similar in the control, argon and xenon groups. No other secondary outcome parameters, including animal survival, were affected by the intervention. Xenon was associated with an increase in autophagy and proapoptotic markers. Despite promising results in small animal models, postconditioning with argon or xenon in a translational model of kidney autotransplantation was not beneficial. Clinical trials would require better results.

miR-21 contributes to renal protection by targeting prolyl hydroxylase domain protein 2 in delayed ischaemic preconditioning

AIM

Upregulation of miR-21 in renal ischaemic preconditioning (IPC) was associated with increased hypoxia inducible factor (HIF)-1α expression. Hypoxic induction of HIF-1α is mediated by inhibition of prolyl hydroxylase domain protein 2 (PHD2) .We hypothesized that miR-21 regulated HIF-1α by targeting PHD2 in the renal IPC.

METHODS

Luciferase reporter assay examined if miR-21 target the 3'-untranslated region of PHD2. In vitro, human proximal tubular cell line (HK-2) was incubated in hypoxia or hypoxia/ reoxygenation condition. Kidneys of Mice were respectively subjected to ischaemia/reperfusion injury (IRI) and IPC. Locked nucleic acid (LNA) modified anti-miR-21 was used to knockdown miR-21. Serum creatinine and histological changes estimated the renal injury. Levels of HIF-1α, PHD2, VEGF and miR-21 were examined by western blot or real-time PCR.

RESULT

miR-21 targeting of PHD2 was confirmed by 3'-untranslated region reporter assay. miR-21 was significantly upregulated by hypoxia/reoxygenation in HK-2 cell, while PHD2 protein level decreased significantly. LNA anti-miR-21 significantly repressed miR-21 levels and increased the abundance of PHD2. In vivo, IPC upregulated miR-21 expression 24 h after the second ischaemia, while PHD2 expression decreased significantly with upregulation of HIF-1α protein and VEGF mRNA. MiR-21 induced by delayed IPC was effectively inhibited by the LNA anti-miR-21. With downregulation of miR-21, the protection of delayed IPC was attenuated and PHD2 protein was increased. Furthermore, upregulation of HIF-1α and VEGF were abolished after the LNA anti-miR-21 treatment.

CONCLUSION

miR-21 could protect kidney against IRI via HIF-1α by inhibiting its target PHD2.The study suggested a new relationship between miR-21 and HIF-1α.

Renal Protection Mediated by Hypoxia Inducible Factor-1α Depends on Proangiogenesis Function of miR-21 by Targeting Thrombospondin 1

Background

Angiogenesis contributes to the repair process after renal ischemia/reperfusion (I/R) injury. In the present study, we tested the role of miR-21 in the angiogenesis induced by hypoxia inducible factor (HIF)-1α through inhibiting a predicted target gene thrombospondin 1 (TSP-1).

Methods

To stabilize HIF-1α, hypoxia (1% O₂ for 24 hours) was performed in human umbilical vein endothelial cells and cobalt chloride (CoCl₂) was pretreated intraperitoneally 24 hours before renal I/R in mice. Locked nucleic acid modified anti-miR-21 and scrambled control was transfected with hypoxic cells or delivered into the mice via tail vein 1 hour before CoCl₂ injection. The kidneys and blood were collected at 24 hours after reperfusion.

Results

HIF-1α induced by hypoxia and CoCl₂ upregulated vascular endothelial growth factor and miR-21, and increased angiogenesis. It was found that expression of TSP-1 was inversely related with miR-21 in vitro and in vivo. Targeting of TSP-1 by miR-21 was further confirmed in vitro. Furthermore, HIF-1α improved renal function, accompanied with increased angiogenesis after I/R injury in mice. The protective effect of HIF-1α was attenuated by inhibition of miR-21.

Conclusions

HIF-1α induced angiogenesis by upregulating not only vascular endothelial growth factor but also miR-21 via inhibiting a novel target gene TSP-1. Both of them may contribute to the protective effect of HIF-1α on renal I/R injury.

Hypoxia induces HIF-1α which upregulates not only VEGF but also miR-21, and this last one inhibits a novel target gene, thrombospondin 1. Angiogenesis induced by hypoxia depends at least partially on production of VEGF and inhibition of thrombospondin 1 through miR-21.

Dual Role of MiR-21-Mediated Signaling in HUVECs and Rat Surgical Flap under Normoxia and Hypoxia Condition

Restoring sufficient vascularity of the ischemia/hypoxia flap is always the critical issue in flap surgeries. In a previous studies microRNA-21 (miR-21) expression was upregulated after rat skin flap surgery. MiR-21 has been reported to be induced by hypoxia and the function of miR-21 involves in the process of angiogenesis. However, the precise regulatory mechanisms in miR-21-mediated pathways are still unclear. These issues were investigated via in vitro and in vivo experiments in this study. In human umbilical vein endothelial cells (HUVEC), the expression of hsa-miR-21-5p was induced after hypoxic culture and the induction of hsa-miR-21-5p was suppressed after sequential normoxic culture. Moreover, transfection of hsa-miR-21-5p mimic enhanced tube formation capacity in normoxia, but attenuated it in hypoxia. Furthermore, bioinformatic analysis suggested that SMAD7 was a predicted target of hsa-miR-21-5p. Our results demonstrated the effect of hsa-miR-21-5p was different on SMAD7 expression in normoxia and hypoxia. In rat skin flaps, blockage of miR-21-5p significantly increased angiogenesis via analysis of color laser Doppler imaging and repressed SMAD7 expression in ischemic skin tissue. Our study showed the opposite effect of miR-21-5p mediating angiogenesis in normoxia and hypoxia, providing important implications regarding the design of novel miRNA-based therapeutic strategies in flap surgeries.

miR‑21 attenuates contrast‑induced renal cell apoptosis by targeting PDCD4

Contrast medium (CM) is widely used in cardiac catheterization; however, it may induce acute kidney injury or renal failure, although the underlying mechanism remains to be elucidated. MicroRNA‑21 (miR‑21) is involved in renal disease and has been indicated to regulate cellular apoptosis and fibrosis, although its role in CM‑induced renal cell injury is unknown. The present study examined the expression and potential targets of miR‑21 in human renal proximal tubular epithelial (HK‑2) cells following CM treatment. CM induced renal cell apoptosis and decreased miR‑21 expression. The expression level of the apoptosis regulator protein, B‑cell lymphoma 2 (Bcl‑2) was upregulated, whereas that of the apoptosis regulator, Bcl‑2‑associated X protein (Bax) was downregulated upon transfection of miR‑21 mimics; miR‑21 overexpression additionally directly inhibited the expression of programmed cell death protein 4 (PDCD4), as determined by a dual luciferase reporter assay, and PDCD4 silencing reduced the rate of HK‑2 cell apoptosis. The results of the present study indicated that miR‑21 protected renal cells against CM‑induced apoptosis by regulating PDCD4 expression.

Renal function following xenon anesthesia for partial nephrectomy-An explorative analysis of a randomized controlled study

Background

Perioperative preservation of renal function has a significant impact on morbidity and mortality in kidney surgery. Nephroprotective effects of the anesthetic xenon on ischemia-reperfusion injury were found in several experimental studies.

Objective

We aimed to explore whether xenon anesthesia can reduce renal damage in humans undergoing partial nephrectomy and to gather pilot data of possible nephroprotection in these patients.

Design

A prospective randomized, single-blinded, controlled study.

Setting

Single-center, University Hospital of Aachen, Germany between July 2013-October 2015.

Patients

Forty-six patients with regular renal function undergoing partial nephrectomy.

Interventions

Patients were randomly assigned to receive xenon- (n = 23) or isoflurane (n = 23) anesthesia.

Main outcome measures

Primary outcome was the maximum postoperative glomerular filtration rate (GFR) decline within seven days after surgery. Secondary outcomes included intraoperative and tumor-related data, assessment of further kidney injury markers, adverse events and optional determination of renal function after 3–6 months.

Results

Unexpected radical nephrectomy was performed in 5 patients, thus they were excluded from the per-protocol analysis, but included in the intention-to-treat analysis. The maximum postoperative GFR decline was attenuated by 45% in the xenon-group (10.9 ml min^-1 1.73 cm^-2 versus 19.7 ml min^-1 1.73 cm^-2 in the isoflurane group), but without significance (P = 0.084). Occurrence of adverse events was reduced (P = 0.003) in the xenon group. Renal function was similar among the groups after 3–6 months.

Conclusion

Xenon anesthesia was feasible and safe in patients undergoing partial nephrectomy with regard to postoperative renal function. We found no significant effect on early renal function but less adverse events in the xenon group. Larger randomized controlled studies in more heterogeneous collectives are required, to confirm or refute the possible clinical benefit on renal function by xenon.

Trial registration

ClinicalTrials.gov NCT01839084 and EudraCT 2012-005698-30

Tissue-Specific MicroRNA Expression Patterns in Four Types of Kidney Disease

MicroRNAs contribute to the development of kidney disease. Previous analyses of microRNA expression in human kidneys, however, were limited by tissue heterogeneity or the inclusion of only one pathologic type. In this study, we used laser-capture microdissection to obtain glomeruli and proximal tubules from 98 human needle kidney biopsy specimens for microRNA expression analysis using deep sequencing. We analyzed specimens from patients with diabetic nephropathy (DN), FSGS, IgA nephropathy (IgAN), membranoproliferative GN (MPGN) (n=19-23 for each disease), and a control group (n=14). Compared with control glomeruli, DN, FSGS, IgAN, and MPGN glomeruli exhibited differential expression of 18, 12, two, and 17 known microRNAs, respectively. The expression of several microRNAs also differed between disease conditions. Specifically, compared with control or FSGS glomeruli, IgAN glomeruli exhibited downregulated expression of hsa-miR-3182. Furthermore, in combination, the expression levels of hsa-miR-146a-5p and hsa-miR-30a-5p distinguished DN from all other conditions except IgAN. Compared with control proximal tubules, DN, FSGS, IgAN, and MPGN proximal tubules had differential expression of 13, 14, eight, and eight microRNAs, respectively, but expression of microRNAs did not differ significantly between the disease conditions. The abundance of several microRNAs correlated with indexes of renal function. Finally, we validated the differential glomerular expression of select microRNAs in a second cohort of patients with DN (n=19) and FSGS (n=21). In conclusion, we identified tissue-specific microRNA expression patterns associated with several kidney pathologies. The identified microRNAs could be developed as biomarkers of kidney diseases and might be involved in disease mechanisms.

Noncoding RNA and epigenetic gene regulation in renal diseases

Kidneys have a major role in normal physiology and metabolic homeostasis. Loss or impairment of kidney function is a common occurrence in several metabolic disorders, including hypertension and diabetes. Chronic kidney disease (CKD) affect nearly 10% of the population worldwide; ranks 18th in the list of causes of death; and contributes to a significant proportion of healthcare costs. The tissue repair and regenerative potential of kidneys are limited and they decline during aging. Recent studies have demonstrated a key role for epigenetic processes and players, such as DNA methylation, histone modifications, noncoding (nc)RNA, and so on, in both kidney development and disease. In this review, we highlight these recent findings with an emphasis on aberrant epigenetic changes that accompany renal diseases, key targets, and their therapeutic value.

MicroRNAs in acute kidney injury

Acute kidney injury (AKI) is an important clinical issue that is associated with significant morbidity and mortality. Despite research advances over the past decades, the complex pathophysiology of AKI is not fully understood. The regulatory mechanisms underlying post-AKI repair and fibrosis have not been clarified either. Furthermore, there is no definitively effective treatment for AKI. MicroRNAs (miRNAs) are endogenous single-stranded noncoding RNAs of 19~23 nucleotides that have been shown to be crucial to the post-transcriptional regulation of various cellular biological functions, including proliferation, differentiation, metabolism, and apoptosis. In addition to being fundamental to normal development and physiology, miRNAs also play important roles in various human diseases. In AKI, some miRNAs appear to act pathogenically by promoting inflammation, apoptosis, and fibrosis, while others may act protectively by exerting anti-inflammatory, anti-apoptotic, anti-fibrotic, and pro-angiogenic effects. Thus, miRNAs have not only emerged as novel biomarkers for AKI; they also hold promise to be potential therapeutic targets.

MicroRNAs and drug-induced kidney injury

Drug-induced kidney injury (DIKI) is a severe complication in hospitalized patients associated with higher probabilities of developing progressive chronic kidney disease or end-stage renal diseases. Furthermore, DIKI is a problem during preclinical and clinical phases of drug development leading to high rates of project terminations. Understanding the molecular perturbations caused by DIKI would pave the way for a new class of therapeutics to mitigate the damage. Yet, another approach to ameliorate DIKI is identifying sensitive and specific translational biomarkers that outperform the current diagnostic analytes like serum creatinine and facilitate early diagnosis. MicroRNAs (miRNAs), a class of non-coding RNAs, are increasingly being recognized to have a two-pronged approach toward DIKI management: 1) miRNAs have a regulatory role in gene expression and signaling pathways thereby making them novel interventional targets and 2) miRNAs enable diagnosis and prognosis of DIKI because of their stable presence in biofluids. In this review, apart from summarizing the literature on miRNAs in DIKI, we report small RNA sequencing results showing miRNA expression profiles at baseline in normal kidney samples from mice and humans. Additionally, we also compared the miRNA expression in biopsies of normal human kidneys to patients with acute tubular necrosis, and found 76 miRNAs significantly downregulated and 47 miRNAs upregulated (FDR adjusted p<0.05, +/-2-fold change). In summary, we highlight the transformative potential of miRNAs in therapeutics and translational medicine with a focus on drug-induced kidney damage.

MicroRNAs in Pathogenesis of Acute Kidney Injury

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression mainly by repressing their target gene translation. A large spectrum of human diseases is associated with significant changes in miRNAs. Many miRNAs are induced in diseases, whereas some others are downregulated. The significance of miRNAs has been demonstrated in renal development and physiology, and in major kidney diseases such as acute kidney injury (AKI). Recent studies have further implicated specific miRNAs in the pathogenesis of AKI. miRNAs also have the potential to become new diagnostic biomarkers of AKI. Further investigation will identify the key pathogenic miRNAs in various types of AKI and test miRNA-based therapeutics and diagnosis. © 2016 S. Karger AG, Basel.

Xenon Protects Against Septic Acute Kidney Injury via miR-21 Target Signaling Pathway

Objectives:

Septic acute kidney injury is one of the most common and life-threatening complications in critically ill patients, and there is no approved effective treatment. We have shown xenon provides renoprotection against ischemia-reperfusion injury and nephrotoxicity in rodents via inhibiting apoptosis. Here, we studied the effects of xenon preconditioning on septic acute kidney injury and its mechanism.

Design:

Experimental animal investigation.

Setting:

University research laboratory.

Subjects:

Experiments were performed with male C57BL/6 mice, 10 weeks of age, weighing 20–25 g.

Interventions:

We induced septic acute kidney injury by a single intraperitoneal injection of Escherichia coli lipopolysaccharide at a dose of 20 mg/kg. Mice were exposed for 2 hours to either 70% xenon or 70% nitrogen, 24 hours before the onset of septic acute kidney injury. In vivo knockdown of miR-21 was performed using locked nucleic acid-modified anti-miR, the role of miR-21 in renal protection conferred by the xenon preconditioning was examined, and miR-21 signaling pathways were analyzed.

Measurements and Main Results:

Xenon preconditioning provided morphologic and functional renoprotection, characterized by attenuation of renal tubular damage, apoptosis, and a reduction in inflammation. Furthermore, xenon treatment significantly upregulated the expression of miR-21 in kidney, suppressed proinflammatory factor programmed cell death protein 4 expression and nuclear factor-κB activity, and increased interleukin-10 production. Meanwhile, xenon preconditioning also suppressed the expression of proapoptotic protein phosphatase and tensin homolog deleted on chromosome 10, activating protein kinase B signaling pathway, subsequently increasing the expression of antiapoptotic B-cell lymphoma-2, and inhibiting caspase-3 activity. Knockdown of miR-21 upregulated its target effectors programmed cell death protein 4 and phosphatase and tensin homolog deleted on chromosome 10 expression, resulted in an increase in apoptosis, and exacerbated lipopolysaccharide-induced acute kidney injury.

Conclusion:

Our findings demonstrated that xenon preconditioning protected against lipopolysaccharide-induced acute kidney injury via activation of miR-21 target signaling pathways.

Up-regulation of microRNA-21 mediates isoflurane-induced protection of cardiomyocytes

BACKGROUND

Anesthetic cardioprotection reduces myocardial infarct size after ischemia-reperfusion injury. Currently, the role of microRNA in this process remains unknown. MicroRNAs are short, noncoding nucleotide sequences that negatively regulate gene expression through degradation or suppression of messenger RNA. In this study, the authors uncovered the functional role of microRNA-21 (miR-21) up-regulation after anesthetic exposure.

METHODS

MicroRNA and messenger RNA expression changes were analyzed by quantitative real-time polymerase chain reaction in cardiomyocytes after exposure to isoflurane. Lactate dehydrogenase release assay and propidium iodide staining were conducted after inhibition of miR-21. miR-21 target expression was analyzed by Western blot. The functional role of miR-21 was confirmed in vivo in both wild-type and miR-21 knockout mice.

RESULTS

Isoflurane induces an acute up-regulation of miR-21 in both in vivo and in vitro rat models (n = 6, 247.8 ± 27.5% and 258.5 ± 9.0%), which mediates protection to cardiomyocytes through down-regulation of programmed cell death protein 4 messenger RNA (n = 3, 82.0 ± 4.9% of control group). This protective effect was confirmed by knockdown of miR-21 and programmed cell death protein 4 in vitro. In addition, the protective effect of isoflurane was abolished in miR-21 knockout mice in vivo, with no significant decrease in infarct size compared with nonexposed controls (n = 8, 62.3 ± 4.6% and 56.2 ± 3.2%).

CONCLUSIONS

The authors demonstrate for the first time that isoflurane mediates protection of cardiomyocytes against oxidative stress via an miR-21/programmed cell death protein 4 pathway. These results reveal a novel mechanism by which the damage done by ischemia/reperfusion injury may be decreased.

MicroRNAs in Kidney Transplantation: Living up to Their Expectations?

Since the discovery of microRNAs, ample research has been conducted to elucidate their involvement in an array of (patho)physiological conditions. Ischemia reperfusion injury is a major problem in kidney transplantation and its mechanism is still not fully known, nor is there an effective therapy. Furthermore, no biomarker is available to specifically measure (ischemic) damage after kidney transplantation or predict transplantation outcome. In this review, we summarize studies conducted on microRNAs in renal ischemia reperfusion injury and kidney transplantation. Although the number of publications on miRNAs in different areas of nephrology is increasing every year, only a limited number of reports that address the role of miRNAs in relation to ischemia reperfusion injury or kidney transplantation are available. All reports up to June 2014 on microRNAs in renal IRI, kidney transplantation, and renal allograft status were included. Design of the studies was highly variable and there was limited overlap between microRNAs found in these reports. No single microRNA expression pattern could be found, although multiple microRNAs involved in the immune response seem to be altered after ischemia reperfusion injury and kidney transplantation. Although there is a growing interest in microRNA research in kidney transplantation aiming to identify biomarkers and therapeutical targets, to date, no specific microRNA has been demonstrated to be applicable as either one, mostly because of lack of specificity. More systematical research is needed to determine whether microRNAs can be applied as biomarker, therapeutic target, or therapeutic agent in kidney transplantation.

MicroRNA-21 attenuates renal ischemia reperfusion injury via targeting caspase signaling in mice

BACKGROUND

MicroRNAs (miR) have come into focus as powerful regulators of gene expression and potential diagnostic tools during renal ischemia reperfusion injury (IRI). The aim of this study was to investigate the molecular regulation and function of miR-21, and to analyze the relationship between caspases and miR-21 expression levels in an experimental model of renal IRI.

METHODS

IRI was induced by bilateral renal ischemia for 45 min followed by reperfusion. The male BALB/c mice were randomly assigned to the following groups: pre-miR-21 + IRI group, antagomiR-21 + IRI group, PBS + IRI group, pre-miR-21 + sham operation group, antagomiR-21 + sham operation group, PBS + sham operation group. The pre-miR-21 or antagomiR-21 was administered intraperitoneally (200 ng/kg weight) 24 and 6 h before induction of ischemia. Renal function, histological damage, renal cell apoptosis proteins were evaluated at 24 h after reperfusion.

RESULTS

Mice upregulated miR-21 had lower plasma levels of blood urea nitrogen (BUN) and creatinine, lower histopathological scores and a decrease in programmed cell death 4 (PDCD4) mRNA and active caspase-3, caspase-8 proteins expressions.

CONCLUSIONS

miR-21 is endowed with anti-apoptotic properties by suppressing the expression of PDCD4 gene and active caspase 3/8 fragments in the condition of renal IRI. miR-21 exerts significant functional protection in our renal murine model of IRI.