MiR-20a-5p mediates hypoxia-induced autophagy by targeting ATG16L1 in ischemic kidney injury

Critical role of miR-21/exosomal miR-21 in autophagy pathway

Activation of autophagy, a process of cellular stress response, leads to the breakdown of proteins, organelles, and other parts of the cell in lysosomes, and can be linked to several ailments, such as cancer, neurological diseases, and rare hereditary syndromes. Thus, its regulation is very carefully monitored. Transcriptional and post-translational mechanisms domestically or in whole organisms utilized to control the autophagic activity, have been heavily researched. In modern times, microRNAs (miRNAs) are being considered to have a part in post-translational orchestration of the autophagic activity, with miR-21 as one of the best studied miRNAs, it is often more than expressed in cancer cells. This regulatory RNA is thought to play a major role in a plethora of processes and illnesses including growth, cancer, cardiovascular disease, and inflammation. Different studies have suggested that a few autophagy-oriented genes, such as PTEN, Rab11a, Atg12, SIPA1L2, and ATG5, are all targeted by miR-21, indicating its essential role in the regulation.

Exosomal microRNA profiling revealed enhanced autophagy suppression and anti-tumor effects of a combination of compound Phyllanthus urinaria and lenvatinib in hepatocellular carcinoma

BACKGROUND

Compound Phyllanthus urinaria (CP), a traditional Chinese herbal remedy, possesses strong anti-cancer effects and is extensively employed in the clinical management of hepatocellular carcinoma (HCC). While lenvatinib and other oral tyrosine kinase inhibitors have been authorized as initial treatments for advanced unresectable HCC, the survival of patients is ultimately restricted due to the gradual development of drug resistance. Fortunately, the co-administration of CP and lenvatinib holds promise for anti-cancer applications.

PURPOSE

Our objective was to understand the molecular-level mechanisms of bioactive phytocompounds in CP, in order to explore the anti-HCC effects of combining CP and lenvatinib treatment and reveal the underlying mechanisms. Furthermore, we discovered new miRNAs associated with autophagy that are common to both HepG2-derived exosomes and HepG2 cells. These miRNAs play a role in the advancement of HCC and were identified through the utilization of CP and lenvatinib.

METHODS

To assess the anti-HCC effects of CP in combination with lenvatinib, both an in vitro CCK-8 assay and an in vivo xenograft model assay were performed. TEM, NTA, and nano-flow cytometry were employed for the identification of isolated exosomes. To ascertain the miRNA expression patterns in HepG2 cells and HepG2-derived exosomes, miRNA-sequencing analysis was conducted. Further investigation involved the use of real-time PCR, examination of the fusion protein GFP-mRFP-LC3, TEM analysis, and western blotting.

RESULTS

In vitro and in vivo, the combination of CP and lenvatinib showed a stronger and more powerful impact on HCC compared to either CP or lenvatinib alone. The combination of CP and lenvatinib had a significant impact on autophagy-related miRNAs in HepG2-derived exosomes and HepG2 cells, as demonstrated by cellular and exosomal miRNA sequencing. Additional tests indicated that the increased inhibition of autophagy in HepG2 cells subjected to CP treatment, as well as the combination of CP and lenvatinib, was accomplished through the regulation of Beclin-1, LC3-II, and P62 expression.

CONCLUSION

In conclusion, our results indicate that the combination of CP and lenvatinib can effectively inhibit HCC by promoting the exosome-mediated suppression of autophagy. This novel therapeutic option is highly efficient and durable, making it a promising treatment for HCC. Moreover, the miRNAs that are differentially expressed and associated with exosome-mediated autophagy, which have been discovered in this study, could potentially be targeted for clinical treatment of HCC.

Holistic expression of miR-17-92 cluster in obesity, kidney diseases, cardiovascular diseases, and diabetes

miR-17-92 cluster encodes six micro RNAs (miRNAs) and plays a crucial role in the regulation of various cellular processes. Aberrant expression of this cluster may result in the onset of several diseases. Initially, the role of miR-17-92 cluster in tumorigenesis was discovered but recent research has also uncovered its role in other diseases. Members of the cluster may serve as potential biomarkers in the prognosis, diagnosis, and treatment of several diseases and their complications. In this article, we have reviewed the recent research carried out on the expression pattern of miR-17-92 cluster in non-communicable diseases i.e., obesity, cardiovascular diseases (CVD), kidney diseases (KD) and diabetes mellitus (DM). We examined miR-17-92 role in pathological processes and their potential importance as biomarkers. Each member of the cluster miR-17-92 was upregulated in obesity. miR-18a, miR-19b-3p, miR20a, and miR92a were significantly upregulated in CVD. An equal fraction of the cluster was dysregulated (upregulated and downregulated) in diabetes; however, miR-17-92 was downregulated in most studies on CKD.

Identification and validation of aging-related gene signatures and their immune landscape in diabetic nephropathy

Background

Aging and immune infiltration have essential role in the physiopathological mechanisms of diabetic nephropathy (DN), but their relationship has not been systematically elucidated. We identified aging-related characteristic genes in DN and explored their immune landscape.

Methods

Four datasets from the Gene Expression Omnibus (GEO) database were screened for exploration and validation. Functional and pathway analysis was performed using Gene Set Enrichment Analysis (GSEA). Characteristic genes were obtained using a combination of Random Forest (RF) and Support Vector Machine Recursive Feature Elimination (SVM-RFE) algorithm. We evaluated and validated the diagnostic performance of the characteristic genes using receiver operating characteristic (ROC) curve, and the expression pattern of the characteristic genes was evaluated and validated. Single-Sample Gene Set Enrichment Analysis (ssGSEA) was adopted to assess immune cell infiltration in samples. Based on the TarBase database and the JASPAR repository, potential microRNAs and transcription factors were predicted to further elucidate the molecular regulatory mechanisms of the characteristic genes.

Results

A total of 14 differentially expressed genes related to aging were obtained, of which 10 were up-regulated and 4 were down-regulated. Models were constructed by the RF and SVM-RFE algorithms, contracted to three signature genes: EGF-containing fibulin-like extracellular matrix (EFEMP1), Growth hormone receptor (GHR), and Vascular endothelial growth factor A (VEGFA). The three genes showed good efficacy in three tested cohorts and consistent expression patterns in the glomerular test cohorts. Most immune cells were more infiltrated in the DN samples compared to the controls, and there was a negative correlation between the characteristic genes and most immune cell infiltration. 24 microRNAs were involved in the transcriptional regulation of multiple genes simultaneously, and Endothelial transcription factor GATA-2 (GATA2) had a potential regulatory effect on both GHR and VEGFA.

Conclusion

We identified a novel aging-related signature allowing assessment of diagnosis for DN patients, and further can be used to predict immune infiltration sensitivity.

Liquid Biopsies Poorly miRror Renal Ischemia-Reperfusion Injury

Acute kidney injury (AKI) is the rapid reduction in renal function. It is often difficult to detect at an early stage. Biofluid microRNAs (miRs) have been proposed as novel biomarkers due to their regulatory role in renal pathophysiology. The goal of this study was to determine the overlap in AKI miRNA profiles in the renal cortex, urine, and plasma samples collected from a rat model of ischemia-reperfusion (IR)-induced AKI. Bilateral renal ischemia was induced by clamping the renal pedicles for 30 min, followed by reperfusion. Urine was then collected over 24 h, followed by terminal blood and tissue collection for small RNA profiling. Differentially expressed (IR vs. sham) miRs within the urine and renal cortex sample types demonstrated a strong correlation in normalized abundance regardless of injury (IR and sham: R2 = 0.8710 and 0.9716, respectively). Relatively few miRs were differentially expressed in multiple samples. Further, there were no differentially expressed miRs with clinically relevant sequence conservation common between renal cortex and urine samples. This project highlights the need for a comprehensive analysis of potential miR biomarkers, including analysis of pathological tissues and biofluids, with the goal of identifying the cellular origin of altered miRs. Analysis at earlier timepoints is needed to further evaluate clinical potential.

Disturbance of Hypoxia Response and Its Implications in Kidney Diseases

Significance: The disturbance of the hypoxia response system is closely related to human diseases, because it is essential for the maintenance of homeostasis. Given the significant role of the hypoxia response system in human health, therapeutic applications targeting prolyl hydroxylase-hypoxia-inducible factor (HIF) signaling have been attempted. Thus, systemically reviewing the hypoxia response-based therapeutic strategies is of great significance. Recent Advances: Disturbance of the hypoxia response is a characteristic feature of various diseases. Targeting the hypoxia response system is, thus, a promising therapeutic strategy. Interestingly, several compounds and drugs are currently under clinical trials, and some have already been approved for use in the treatment of certain human diseases. Critical Issues: We summarize the molecular mechanisms of the hypoxia response system and address the potential therapeutic implications in kidney diseases. Given that the effects of hypoxia response in kidney diseases are likely to depend on the pathological context, specific cell types, and the differences in the activation pattern of HIF isoforms, the precise application is critical for the treatment of kidney diseases. Although HIF-PHIs (HIF-PHD inhibitors) have been proven to be effective and well tolerated in chronic kidney disease patients with anemia, the potential on-target consequence of HIF activation and some outstanding questions warrant further consideration. Future Direction: The mechanism of the hypoxia response system disturbance remains unclear. Elucidation of the molecular mechanism of hypoxia response and its precise effects on kidney diseases warrants clarification. Considering the complexity of the hypoxia response system and multiple biological processes controlled by HIF signaling, the development of more specific inhibitors is highly warranted. Antioxid. Redox Signal. 37, 936-955.

Regulatory mechanism of miR-20a-5p expression in Cancer

MicroRNAs(miRNAs) are non-coding single-stranded RNA molecules encoded by endogenous genes with a length of about 22 nucleotides. The dysregulation of miRNAs has been proven to be one of the vital causes of cancer, which makes them a biomarker for cancer diagnosis and prognosis. Compared with surgery and chemotherapy, nucleic acid therapy targeting specific miRNAs is a promising candidate for cancer treatment. miR-20a-5p plays an anticancer role in high-incidence human cancers such as cervical cancer, breast cancer and leukemia, which is of great importance in the diagnosis of cancers. The up-regulation and down-regulation of miR-20a-5p offers a possible breakthrough for the treatment of cancers. In this paper, we aim to investigate the functional significance of miR-20a-5p in different cancers, reviewing the expression differences of miR-20a-5p in cancer, while systematically summarizing the changes of circRNA-miR-20a-5p networks, and probe how it promotes messenger RNA (mRNA) degradation or inhibits mRNA translation to regulate downstream gene expression. We've also summarized the biogenesis mechanism of miRNAs, and emphasized its role in cell proliferation, cell apoptosis and cell migration. On this basis, we believe that miR-20a-5p is a promising and effective marker for cancer diagnosis, prognosis and treatment.

Circulating microRNA sequencing revealed miRNome patterns in hematology and oncology patients aiding the prognosis of invasive aspergillosis

Invasive aspergillosis (IA) may occur as a serious complication of hematological malignancy. Delays in antifungal therapy can lead to an invasive disease resulting in high mortality. Currently, there are no well-established blood circulating microRNA biomarkers or laboratory tests which can be used to diagnose IA. Therefore, we aimed to define dysregulated miRNAs in hematology and oncology (HO) patients to identify biomarkers predisposing disease. We performed an in-depth analysis of high-throughput small transcriptome sequencing data obtained from the whole blood samples of our study cohort of 50 participants including 26 high-risk HO patients and 24 controls. By integrating in silico bioinformatic analyses of small noncoding RNA data, 57 miRNAs exhibiting significant expression differences (P < 0.05) were identified between IA-infected patients and non-IA HO patients. Among these, we found 36 differentially expressed miRNAs (DEMs) irrespective of HO malignancy. Of the top ranked DEMs, we found 14 significantly deregulated miRNAs, whose expression levels were successfully quantified by qRT-PCR. MiRNA target prediction revealed the involvement of IA related miRNAs in the biological pathways of tumorigenesis, the cell cycle, the immune response, cell differentiation and apoptosis.

MicroRNA-20a-5p Inhibits the Autophagy and Cisplatin Resistance in Ovarian Cancer via Regulating DNMT3B-mediated DNA Methylation of RBP1

Ovarian cancer (OvCa) is the third most common female malignancy worldwide and poses great threats on women health. Chemotherapy is the most recommended post-surgery treatment for OvCa patients; but, cisplatin resistance is a main cause of chemotherapy failure. In addition, autophagy modulates the sensitivity of tumor cells to chemotherapeutic agents. Hence, it is significant to explore the molecular mechanism concerning the autophagy and cisplatin resistance in OvCa. In this study, quantitative real-time PCR (qRT-PCR) was used to detect miR-20a-5p expression and western blot to measure RBP1 expression. A series of assays were conducted to explore the gain-of-function effects of miR-20a-5p. Luciferase reporter assay was applied to determine the downstream target of miR-20a-5p. The results proved that miR-20a-5p represses malignant phenotypes and autophagy in cisplatin-resistant OvCa cells. In addition, DNMT3B mediates DNA methylation of RBP1 to impair the promoting effects of RBP1 on carcinogenesis and autophagy in OvCa. Through rescue experiments, we certified that miR-20a-5p inhibits the autophagy and cisplatin resistance in OvCa via DNMT3B-mediated DNA methylation of RBP1. Collectively, we demonstrated that miR-20a-5p plays a crucial role in the modulation of autophagy and cisplatin resistance in OvCa, which might offer novel insights into developing effective treatment strategies for OvCa.

MiR-20a-5p Negatively Regulates NR4A3 to Promote Metastasis in Bladder Cancer

Metastasis is the leading cause of death in cancer patients. Therefore, the prediction and treatment of metastasis are critical in improving the survival of patients with bladder cancer. In this study, we aimed to investigate the role of miR-20a-5p and NR4A3 in bladder cancer and the regulatory relationship between them. The high expression of miR-20a-5p in the bladder cancer (BCa) tissues and cells was determined by qRT-PCR. Exogenous miR-20a-5p overexpression promoted the proliferation, migration, and invasion of BCa cells. MiR-20a-5p inhibition inhibited the BCa cell proliferation, invasion, and migration. NR4A3 was proved to be the target gene of miR-20a-5p by the double luciferase reporter assay. In addition, the reduction of NR4A3 could promote the proliferation, invasion, and clonal formation of the bladder cancer cells 5637 and T24. NR4A3 overexpression could reverse the carcinogenic effect of miR-20a. We further confirmed that the oncogenic effect of miR-20a was achieved by promoting EMT in tumor cells. MiR-20a-5p promoted the growth and metastasis of the bladder cancer cells by inhibiting the expression of the tumor suppressor gene NR4A3 and played a carcinogenic role in BCa. Thus, miR-20a-5p may become a potential therapeutic target for BCa treatment.

miR-17-5p attenuates kidney ischemia-reperfusion injury by inhibiting the PTEN and BIM pathways

Background

Kidney ischemia-reperfusion (I/R) injury is an independent risk factor for delayed graft function after kidney transplantation with long-term graft survival deterioration. Previously, we found that the upregulated expression of miR-17-5p exerts a protective effect in kidney I/R injury, but the mechanism has not been clearly studied.

Methods

A kidney I/R injury model was induced in adult C57BL/6 male mice (20–22 g) by clamping both kidney pedicles for 30 min. The miR-17-5p agomir complex was injected into mice 24 h before surgery via the tail vein at a total injection volume of 10 µL/g body weight. The mice were euthanized on post-I/R injury day 2, and kidney function, apoptosis, autophagy, and related molecules were then detected. Human kidney-2 (HK-2) cells, which underwent hypoxia/reoxygenation, were treated with the miR-17-5p agomir, miR-17-5p antagomir, and small interfering ribonucleic acids (siRNAs). Cell viability, apoptosis, autophagy, and molecules were also examined.

Results

Autophagy, miR-17-5p expression, and kidney function damage were significantly more increased in the I/R group than in the sham group. In the cultured HK-2 cells underwent hypoxia/reoxygenation, the miR-17-5p agomir directly inhibited the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Bcl-2 like protein 11 (BIM), and attenuated apoptosis and autophagy. Further, miR-17-5p inhibited autophagy by activating the protein kinase B (Akt)/Beclin1 pathway, which was suppressed by siRNAs. Additionally, the administration of miR-17-5p agomir greatly improved kidney function in the I/R mice group by inhibiting autophagy and apoptosis.

Conclusions

These findings suggest a new possible therapeutic strategy for the prevention and treatment of kidney I/R injury. The upregulation of miR-17-5p expression appears to inhibit apoptosis and autophagy by suppressing PTEN and BIM expression, which in turn upregulates downstream Akt/Beclin1 expression.

Regulation of autophagy by miRNAs in human diseases

Autophagy is a homeostatic process designed to eliminate dysfunctional and aging organelles and misfolded proteins through a well-concerted pathway, starting with forming a double-membrane vesicle and culminating in the lysosomal degradation of the cargo enclosed inside the mature vesicle. As a vital sentry of cellular health, autophagy is regulated in every human disease condition and is an essential target for non-coding RNAs like microRNAs (miRNAs). miRNAs are short oligonucleotides that specifically bind to the 3'-untranslated region (UTR) of target mRNAs, thus leading to mRNA silencing, degradation, or translation blockage. This review summarizes the recent findings regarding the regulation of autophagy and autophagy-related genes by different miRNAs in various pathological conditions, including cancer, kidney and liver disorders, neurodegeneration, cardiovascular disorders, infectious diseases, aging-related conditions, and inflammation-related diseases. As miRNAs are being identified as prime regulators of autophagy in human disease, pharmacological molecules and traditional medicines targeting these miRNAs are also being tested in disease models, thus initiating a new series of therapeutic interventions targeting autophagy.

MicroRNA-590-3p relieves hypoxia/reoxygenation induced cardiomyocytes apoptosis and autophagy by targeting HIF-1α

Autophagy and apoptosis are key factors in myocardial ischemia/reperfusion (I/R) injury. MicroRNAs (miRNAs or miRs) participate in occurrence and development of myocardial I/R injury by regulating autophagy and apoptosis. The purpose of the present study was to investigate the role of miR-590-3p in the regulation of autophagy and apoptosis in hypoxia/reoxygenation (H/R)-treated cardiomyocytes. Following 6 h hypoxia and 6 h reoxygenation in primary rat cardiomyocytes, miR-590-3p was downregulated. Transfection of miR-590-3p mimic inhibited the increased autophagy and apoptosis following H/R treatment. Subsequent experiments demonstrated that miR-590-3p regulated induction of autophagy and apoptosis by targeting hypoxia inducible factor (HIF)-1α. Forced expression of HIF-1α rescued the protective effect of miR-590-3p on H/R-induced cardiomyocytes. In summary, the present study showed that miR-590-3p exhibited a protective effect on H/R-induced cardiomyocyte injury and may be a novel target for the treatment of myocardial ischemia disease.

VEGF-mediated angiogenesis in retinopathy of prematurity is co-regulated by miR-17-5p and miR-20a-5p

The microRNAs miR-17-5p and miR-20a-5p play important roles on angiogenesis; however, it is arguable whether they regulate the formation of retinal blood vessels in retinopathy of prematurity (ROP). We used a mouse model of oxygen-induced retinopathy (OIR) to simulate the development of retinas in mice suffering from ROP, and the expression levels of miR-20a-5p, miR-17-5p, hypoxia-inducible factor 1-alpha (HIF-1α), and vascular endothelial growth factor (VEGF) were measured by RT-qPCR and Western blotting. Cell proliferation, apoptosis, and angiogenesis in the OIR model mice were measured using MTT assays, flow cytometry, and Matrigel assays, respectively. The interaction between HIF-1α/VEGF and miR-20a-5p/miR-17-5p were further validated using dual-luciferase reporter assays, biotin-labeled RNA-pulldown, and RNA immunoprecipitation (RIP) assays. In our OIR model, retinal angiogenesis in the mice was associated with down-regulation of miR-20a-5p and miR-17-5p, as well as up-regulation of HIF-1α and VEGF. In addition, the miR-20a-5p and miR-17-5p inhibited cell proliferation and angiogenesis through regulating HIF-1α and VEGF in the retinal cells of the OIR model mice. Moreover, it was found that miR-20a-5p and miR-17-5p bind to HIF-1α and VEGF at the 3'UTR, and there was a combined effect between miR-20a-5p and miR-17-5p on the regulation of HIF-1α and VEGF. It is worth noting that miR-17-5p and miR-20a-5p can preferentially regulate HIF-1α, then act on VEGF, thereby affecting the angiogenesis associated with ROP.

miR‑30a‑5p mitigates autophagy by regulating the Beclin‑1/ATG16 pathway in renal ischemia/reperfusion injury

Renal ischemia/reperfusion (I/R) injury often occurs during multiple organ failure and sepsis, and autophagy may serve a role in I/R injury. The aim of the present study was to explore the effect of microRNA (miR)-30a-5p on autophagy in renal I/R injury. miR-30a-5p and autophagy-related protein expression levels in renal I/R injury mouse models and in hypoxia/re-oxygenation HK-2 cell models were determined using reverse transcription-quantitative PCR or western blotting; apoptosis was analyzed using flow cytometry. The effects of miR-30a-5p, Beclin-1 and autophagy-related gene 16 (ATG16) on the proliferation and autophagy of HK-2 cells were analyzed through gain- and loss-of-function studies. miR-30a-5p expression was significantly decreased after renal I/R injury in the in vivo and in vitro experiments. Renal I/R injury led to upregulated expression of autophagy-related proteins microtubule-associated protein light chain 3 (LC3)-II and Beclin-1, and downregulated expression of p62. miR-30a-5p overexpression decreased the number of LC3 punctae, decreased HK-2 cell apoptosis, increased p62 expression and decreased LC3-II and Beclin-1 expression. Inhibition of miR-30a-5p exhibited the opposite effects. A luciferase reporter assay demonstrated that miR-30a-5p targeted Beclin-1. Beclin-1 overexpression led to a significant increase in LC3-II expression and a decrease in p62 expression, as well as a significant increase in apoptosis. Beclin-1 overexpression also increased the protein expression level of ATG16. Downregulation of Beclin-1 decreased the expression of LC3-II, elevated the p62 level and decreased apoptosis. ATG16 knockdown showed similar effects as those of Beclin-1 downregulation. In conclusion, miR-30a-5p was increased in renal I/R injury and might mitigate autophagy by regulating the Beclin-1/ATG16 pathway.

miR-20a-5p ameliorates ovalbumin (OVA)-induced mouse model of allergic asthma through targeting ATG7-regulated cell death, fibrosis and inflammation

Autophagy plays an essential role in modulating asthma progression. MiR-20a-5p can regulate autophagy, but its effects on allergic asthma are still unclear. The aim of this study was to explore the potential of miR-20a-5p on autophagy-modulated airway remodeling and to reveal the underlying molecular mechanisms. We found that miR-20a-5p expression was markedly down-regulated in lung of ovalbumin (OVA)-induced mouse model with allergic asthma and in cells stimulated by OVA. Meanwhile, autophagy, apoptosis, fibrosis and inflammatory response were detected in pulmonary tissues from OVA-treated mice. Importantly, luciferase assays showed that ATG7 was a target of miR-20a-5p. We also found that miR-20a-5p over-expression markedly reduced ATG7, while its inhibition promoted ATG7 in cells. In addition, over-expressing miR-20a-5p in OVA-treated cells significantly decreased ATG7 expression levels, along with markedly reduced autophagy, apoptotic cell death, fibrosis and inflammatory response. These results were similar to the effects of autophagy inhibitor 3-Methyladenine (3-MA), indicating that miR-20a-5p was involved in autophagy-induced apoptosis, fibrosis and inflammation. In vivo experiments further demonstrated that miR-20a-5p over-expression was associated with ATG7 reduction in parallel with the alleviated airway remodeling in OVA-treated mice also through suppressing collagen accumulation, apoptosis and inflammation. Similarly, animal studies further confirmed that miR-20a-5p functioned as an autophagy inhibitor to mitigate allergic asthma development. Therefore, miR-20a-5p may be a promising biomarker and therapeutic target during asthma progression by regulating ATG7-modulated autophagy.

Activation of the angiotensin II receptor promotes autophagy in renal proximal tubular cells and affords protection from ischemia/reperfusion injury

Roles of the renin-angiotensin system in autophagy and ischemia/reperfusion (I/R) injury in the kidney have not been fully characterized. Here we examined the hypothesis that modest activation of the angiotensin II (Ang II) receptor upregulates autophagy and increases renal tolerance to I/R injury. Sprague-Dawley rats were assigned to treatment with a vehicle or a non-pressor dose of Ang II (200 ng/kg/min) for 72 h before 30-min renal I/R. LC3-immunohistochemistry showed that Ang II treatment increased autophagosomes in proximal tubular cells by 2.7 fold. In Ang II-pretreated rats, autophagosomes were increased by 2.5 fold compared to those in vehicle-treated rats at 4 h after I/R, when phosphorylation of Akt and S6 was suppressed and ULK1-Ser555 phosphorylation was increased. Serum creatinine and urea nitrogen levels, incidence of oliguria, and histological score of tubular necrosis at 24 h after I/R were attenuated by Ang II-pretreatment. In NRK-52E cells, Ang II induced LC3-II upregulation, which was inhibited by losartan but not by A779. The results indicate that a non-pressor dose of Ang-II promotes autophagy via ULK1-mediated signaling in renal tubular cells and attenuates renal I/R injury. The AT1 receptor, but not the Mas receptor, contributes to Ang-II-induced autophagy and presumably also to the renoprotection.

Differentially expressed urinary exo-miRs and clinical outcomes in kidney recipients on short-term tacrolimus therapy: a pilot study

Aim: To analyze the expression of urinary exosome-derived miRNAs (exo-miRs) in kidney recipients on tacrolimus-based therapy. Patients & methods: Clinical and drug monitoring data were recorded from 23 kidney recipients. Expression of 93 exo-miRs was measured by quantitative PCR array and mRNA targets were explored. Results: 16 exo-miRs were differentially expressed, including marked upregulation of miR-155-5p, and downregulation of miR-223-3p and miR-1228-3p. Expression of miR-155-5p and miR-223-3p correlated with tacrolimus dose (p < 0.05), miR-223-3p with serum creatinine (p < 0.05), and miR-223-3p and miR-1228-3p with blood leukocytes (p < 0.05). 12 miRNAs have predicted targets involved in cell proliferation, apoptosis, stress response, PIK3/AKT/mTOR and TGF-β signaling pathways. Conclusion: Differentially expressed urinary exo-miRs may be useful markers to monitor tacrolimus therapy and graft function in kidney transplantation.

miR-20a-5p promotes pulmonary artery smooth muscle cell proliferation and migration by targeting ABCA1

BACKGROUND

The function of miR-20a-5p in pulmonary artery smooth muscle cells (PASMCs) and the underlying mechanism remains largely unknown.

METHODS

C57BL/6J mice and PASMCs were used for constructing pulmonary artery hypertension (PAH) animal and cell models, respectively. Reverse transcription polymerase chain reaction (RT-PCR) was employed to detect miR-20a-5p and ATP-binding cassette subfamily A member 1 (ABCA1) messenger RNA expression. CCK-8, Transwell, and TUNEL experiments were used to determine PASMCs proliferation, migration, and apoptosis. The relationship between miR-20a-5p and ABCA1 was detected by luciferase reporter experiment, Western blot analysis, and qRT-PCR.

RESULTS

miR-20a-5p was remarkably elevated in PASMCs of PAH mice and human PASMCs treated by hypoxia, while ABCA1 was remarkably decreased. After transfection of miR-20a-5p mimics, PASMCs proliferation and migration were promoted and PASMCs apoptosis was suppressed. ABCA1 was confirmed to be a target of miR-20a-5p and restoration of ABCA1 reversed the function of miR-20a-5p.

CONCLUSION

miR-20a-5p enhances the proliferation and migration of PASMCs to promote the development of PAH via targeting ABCA1.

Targeting the MicroRNA-490-3p-ATG4B-Autophagy Axis Relieves Myocardial Injury in Ischemia Reperfusion

We investigated the potential role of miR-490-3p in ischemia reperfusion (IR) injury. We first determined the expression of miR-490-3p and autophagy-related 4B cysteine (ATG4B) in IR. Then, to explore whether miR-490-3p would affect autophagy, apoptosis, and IR injury, we evaluated apoptosis, autophagy, and infarct size via gain- and loss-of-function experiments. Furthermore, we used adenovirus to enhance or inhibit the expression of ATG4B, and then measured autophagy, apoptosis, and IR injury. miR-490-3p was downregulated in the hearts during the process of IR, while ATG4B was upregulated. The inhibition of miR-490-3p or overexpression of ATG4B could promote the expression of LC3II, increase the autolysosomes, inhibit the expression of p62, and reduce infarct size. On all accounts, the inhibition of miR-490-3p could promote autophagy to reduce myocardial IR injury by upregulating ATG4B, a finding that provides new insights for the protective mechanism of autophagy in IR. Graphical Abstract.

MicroRNAs as major regulators of the autophagy pathway

Autophagy is a cellular stress response mechanism activation of which leads to degradation of cellular components, including proteins as well as damaged organelles in lysosomes. Defects in autophagy mechanisms were associated with several pathologies (e.g. cancer, neurodegenerative diseases, and rare genetic diseases). Therefore, autophagy regulation is under strict control. Transcriptional and post-translational mechanisms that control autophagy in cells and organisms studied in detail. Recent studies introduced non-coding small RNAs, and especially microRNAs (miRNAs) in the post-translational orchestration of the autophagic activity. In this review article, we analyzed in detail the current status of autophagy-miRNA connections. Comprehensive documentation of miRNAs that were directly involved in autophagy regulation resulted in the emergence of common themes and concepts governing these complex and intricate interactions. Hence, a better and systematic understanding of these interactions reveals a central role for miRNAs in the regulation of autophagy.

Protective Effects of miR-126 Specifically Regulates Nrf2 Through Ischemic Postconditioning on Renal Ischemia/Reperfusion Injury in Mice

The protective effects of ischemic postconditioning on renal ischemia/reperfusion injury in mice and the role of miR-126 and Nrf2 signaling pathway in the process were the focus of this study. Mice were classified into 5 groups: sham-operation, I/R6h, I/R24h, postconditioning (POC), and miR-126 agomir. Serum creatinine, renal histopathology changes, and oxidative stress were examined. The expression of miR-126 and Nrf2 were detected. We also treated NRK52E cells with hypoxia reoxygenation. The I/R group showed significant renal injury and increased generation of oxidative stress. However, the severity of renal injury and oxidative stress were markedly attenuated in the POC group. MiR-126 was downregulated, and Nrf2 was upregulated in NRK52E cells subjected to hypoxia/reoxygenation (H/R) and in mouse kidneys subjected to POC. Oxidative stress was higher and Nrf2 was lower in the mouse miR-126 agomir group; apoptosis were higher in H/R-treated NRK52E cells transfected with Nrf2 siRNA and lower in anti-miR-126. These findings demonstrate that after renal ischemic postconditioning, miR-126 inhibits oxidative stress by inducing Nrf2 and suppresses injury.

Profiling and bioinformatic analysis reveal differential microRNA expression in the left and right kidneys in normal mice

Physiological and pathophysiological differences exist between the left and right kidneys; however, the molecular bases for these differences remain unknown. Since miRNAs are involved in kidney function and the development of kidney diseases, we examined their differential expression through miRNA profiling of the left and right kidneys of normal mice. We find that 36 miRNAs exhibit higher expression, whereas 22 miRNAs show lower expression in the left than the right kidneys in mice under physiological condition. Ten miRNAs were further examined by quantitative PCR assays, and four of them with high expression level were confirmed by Northern blot. Through bioinformatic analysis, we dissected the function and network of the differentially expressed miRNAs, providing insights into the physiological and pathophysiological differences between the left and the right kidneys.

MiR-20a-containing exosomes from umbilical cord mesenchymal stem cells alleviates liver ischemia/reperfusion injury

Mesenchymal stem cells (MSCs) have been proved to exert considerable therapeutic effects on ischemia-reperfusion (I/R)-induced injury, but the underlying mechanism remains unknown. In this study, we aimed to explore the potential molecular mechanism underlying the therapeutic effect of MSCs-derived exosome reinforced with miR-20a in reversing liver I/R injury. Quantitative real-time polymerase chain reaction, Western blot, and IHC were carried out to compare the differential expressions of miR-20a, Beclin-I, FAS, Caspase-3, mTOR and P62 in IR rats and normal rats. TUNEL was performed to assess IR-induced apoptosis in IR rats, and luciferase assay was used to confirm the inhibitory effect of miR-20a on Beclin-I and FAS expression. Among the 12 candidate microRNAs (miRNAs), miR-486, miR-25, miR-24, miR-20a,miR-466 and miR-433-3p were significantly downregulated in I/R. In particular, miR-20a, a miRNA highly expressed in umbilical cord-derived mesenchymal stem cells, was proved to bind to the 3' UTR of Beclin-I and FAS to exert an inhibitory effect on their expressions. Since Beclin-I and FAS were aberrantly upregulated in IR, exosomes separated from UC-MSCs showed therapeutic efficacy in reversing I/R induced apoptosis. In addition, exosomes reinforced with miR-20a and separated from UC-MSCs almost fully alleviated I/R injury. Furthermore, our results showed that miR-20a could alleviate the abnormal expression of genes related to apoptosis and autophagy, such as active Caspase-3, mTOR, P62, and LC3II. This study presented detailed evidence to clarify the mechanism underlying the therapeutic efficacy of UC-MSCs in the treatment of I/R injury.

Exosomes from miR-20b-3p-overexpressing stromal cells ameliorate calcium oxalate deposition in rat kidney

Hyperoxaluria-induced calcium oxalate (CaOx) deposition is the key factor in kidney stone formation, for which adipose-derived stromal cells (ADSCs) have been used as a therapeutic treatment. Studies revealed that miR-20b-3p is down-regulated in hypercalciuric stone-forming rat kidney. To investigate whether ADSC-derived miR-20b-3p-enriched exosomes protect against kidney stones, an ethylene glycol (EG)-induced hyperoxaluria rat model and an in vitro model of oxalate-induced NRK-52E cells were established to explore the protective mechanism of miR-20b-3p. The results showed that miR-20b-3p levels were decreased following hyperoxaluria in the urine of patients and in kidney tissues from animal models. Furthermore, treatment with miR-20b-3p-enriched exosomes from ADSCs protected EG-induced hyperoxaluria rats, and cell experiments confirmed that co-culture with miR-20b-3p-enriched exosomes alleviated oxalate-induced cell autophagy and the inflammatory response by inhibiting ATG7 and TLR4. In conclusion, ADSC-derived miR-20b-3p-enriched exosomes protected against kidney stones by suppressing autophagy and inflammatory responses.

Advances on Cell Autophagy and Its Potential Regulatory Factors in Renal Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a major reason for acute kidney injury and various kidney diseases. Autophagy plays an important role during renal ischemia-reperfusion injury (RIRI), but it remains controversial whether autophagy contributes to cell survival or ischemia-reperfusion-induced cell death. In the review, we summarized the function of autophagy in the progression of acute ischemic kidney injury, as well as its related molecular mechanisms. While analyzing the opposite roles of autophagy in RIRI, it was concluded that the protective or detrimental function of autophagy was depending on the timing and amount of the activation of cell autophagy. We also summarized the regulatory agents, including active compounds, proteins, or microRNAs (miRNAs), which regulated the cell autophagy during renal acute ischemic kidney injury process. This explained why the opposite conclusion occurred when cell autophagy was studied in the RIRI models from different researchers. Therefore, the article provided a hypothesis to control cell autophagy at the appropriate timing and intensity so as to alleviate renal injury and sustain cell survival of the renal cell.

miR-20a suppresses chondrogenic differentiation of ATDC5 cells by regulating Atg7

Both the miR-17-92 cluster and autophagy have been suggested as critical regulators of bone development, but the potential correlation between the two factors is largely unknown. Hence, we investigated whether members of this cluster can regulate chondrogenesis through an autophagy-related signalling pathway. In this study, the expression of miR-17-92 cluster members and the level of autophagic activity were investigated during chondrogenic induction in ATDC5 cells. miR-17, miR-18a, miR-20a, and miR-92-1 showed significant changes, and the level of autophagic activity was enhanced. Among the miR-17-92 cluster members, miR-20a showed the most significant change. Histological, cellular and molecular analyses were performed after the regulation of miR-20a and autophagy. miR-20a and autophagy had the opposite effect on chondrogenic differentiation, and there was a negative correlation between them. Moreover, the expression of the autophagy regulatory gene Atg7 was inhibited by miR-20a. siRNA was then used to knock down Atg7, and the results further indicated that Atg7 might be a potential target of miR-20a in chondrogenic differentiation. In conclusion, miR-20a is a critical negative regulator of chondrogenic differentiation because it inhibits autophagy via Atg7. Other members of the miR-17-92 cluster may have a similar effect, but this hypothesis requires further investigation.

RNA-binding protein, human antigen R regulates hypoxia-induced autophagy by targeting ATG7/ATG16L1 expressions and autophagosome formation

Autophagy, a prosurvival mechanism offers a protective role during acute kidney injury. We show novel findings on the functional role of RNA binding protein, HuR during hypoxia-induced autophagy in renal proximal tubular cells-2 (HK-2). HK-2 cells showed upregulated expressions of HuR and autophagy-related proteins such as autophagy related 7 (ATG7), autophagy related 16 like 1 (ATG16L1), and LC3II under hypoxia. Increased autophagosome formation was visualized as LC3 puncta in hypoxic cells. Further, short hairpin-RNA-mediated loss of HuR function in HK-2 cells significantly decreased ATG7 and ATG16L1 protein expressions. Bioinformatics prediction revealed HuR motif binding on the coding region of ATG7 and AU-rich element at 3'UTR ATG16L1 messnger RNA (mRNA). The RNA immunoprecipitation study showed that HuR was predominantly associated with ATG7 and ATG16L1 mRNAs under hypoxia. In addition, HuR enhanced autophagosome formation by regulating LC3II expressions. These results show that HuR regulates ATG7 and ATG16L1 expressions and thereby mediate autophagy in HK-2 cells. Importantly, HuR knockdown cells underwent apoptosis during hypoxia as observed through the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. Collectively, these findings show the crucial role of HuR under hypoxia by regulating autophagy and suppressing apoptosis in renal tubular cells.

The neuroprotective effects of curcumin are associated with the regulation of the reciprocal function between autophagy and HIF-1α in cerebral ischemia-reperfusion injury

Purpose

The beneficial, neuroprotective effects of curcumin against ischemia-reperfusion injury have been demonstrated. In the present study, whether curcumin exerts neuroprotective effects associated with the inhibition of autophagy and hypoxia inducible factor-1α (HIF-1α) was investigated.

Materials and methods

PC12 cellular model of oxygen glucose deprivation/reperfusion (OGD/R) has been developed to mimic cerebral ischemia-reperfusion injury. Cell viability was evaluated using the CellTiter 96^® AQueous One Solution Cell Proliferation Assay. Apoptosis was assessed using flow cytometry. The expression levels of HIF-1α and autophagy-associated proteins, LC3 and P62, were examined using Western blot. The autophagy flux was quantitatively estimated based on the number of autophagic compartments using fluorescence microscopy. In addition, 3-methyladenine (3-MA) was administered to PC12 cells to investigate how autophagy affects HIF-1α. Moreover, the inhibitory effects of HIF-1α on autophagy activation level were examined.

Results

In this study, curcumin decreased the death and apoptosis of cells, and inhibited autophagy and HIF-1α under OGD/R conditions, consistent with 3-MA treatment or HIF-1α downregulation. Moreover, inhibition of autophagy caused a decrease in HIF-1α, and the attenuation of HIF-1α induced autophagy suppression under OGD/R conditions.

Conclusion

The results of this study showed that curcumin exerts neuroprotective effects against ischemia-reperfusion, which is associated with the regulation of the reciprocal function between autophagy and HIF-1α.

miR-20a inhibits hypoxia-induced autophagy by targeting ATG5/FIP200 in colorectal cancer

Autophagy is a highly conserved lysosome-mediated protective cellular process in which cytosolic components, including damaged organelles and long-lived proteins, are cleared. Many studies have shown that autophagy was upregulated in hypoxic regions. However, the precise molecular mechanism of hypoxia-induced autophagy in colorectal cancer (CRC) is still elusive. In this study, we found that miR-20a was significantly downregulated under hypoxia in colon cancer cells, and overexpression of miR-20a alleviated hypoxia-induced autophagy. Moreover, miR-20a inhibits the hypoxia-induced autophagic flux by targeting multiple key regulators of autophagy, including ATG5 and FIP200. Furthermore, by dual-luciferase assay we demonstrated that miR-20a directly targeted the 3'-untranslated region of ATG5 and FIP200, regulating their messenger RNA and protein levels. In addition, reintroduction of exogenous ATG5 or FIP200 partially reversed miR-20a-mediated autophagy inhibition under hypoxia. A negative correlation between miR-20a and its target genes is observed in the hypoxic region of colon cancer tissues. Taken together, our findings suggest that hypoxia-mediated autophagy was regulated by miR-20a/ATG5/FI200 signaling pathway in CRC. miR-20a-mediated autophagy defect that might play an important role in hypoxia-induced autophagy during colorectal tumorigenesis.

Mir223 restrains autophagy and promotes CNS inflammation by targeting ATG16L1

Microglia are innate immune cells in the central nervous system (CNS), that supplies neurons with key factors for executing autophagosomal/lysosomal functions. Macroautophagy/autophagy is a cellular catabolic process that maintains cell balance in response to stress-related stimulation. Abnormal autophagy occurs with many pathologies, such as cancer, and autoimmune and neurodegenerative diseases. Hence, clarification of the mechanisms of autophagy regulation is of utmost importance. Recently, researchers presented microRNAs (miRNAs) as novel and potent modulators of autophagic activity. Here, we found that Mir223 deficiency significantly ameliorated CNS inflammation, demyelination and the clinical symptoms of experimental autoimmune encephalomyelitis (EAE) and increased resting microglia and autophagy in brain microglial cells. In contrast, the autophagy inhibitor 3-methylademine (3-MA) aggravated the clinical symptoms of EAE in wild-type (WT) and Mir223-deficienct mice. Furthermore, it was confirmed that Mir223 deficiency in mice increased the protein expression of ATG16L1 (autophagy related 16-like 1 [S. cerevisiae]) and LC3-II in bone marrow-derived macrophage cells compared with cells from WT mice. Indeed, the cellular level of Atg16l1 was decreased in BV2 cells upon Mir223 overexpression and increased following the introduction of antagomirs. We also showed that the 3’ UTR of Atg16l1 contained functional Mir223-responsive sequences and that overexpression of ATG16L1 returned autophagy to normal levels even in the presence of Mir223 mimics. Collectively, these data indicate that Mir223 is a novel and important regulator of autophagy and that Atg16l1 is a Mir223 target in this process, which may have implications for improving our understanding of the neuroinflammatory process of EAE.

Abbreviations: 3-MA: 3-methylademine; ACTB/β-actin: actin, beta; ATG: autophagy related; ATG16L1: autophagy related 16-like 1 (S. cerevisiae); BECN1: beclin 1, autophagy related; CNR2: cannabinoid receptor 2 (macrophage); CNS: central nervous system; CQ: chloroquine; EAE: experimental autoimmune encephalomyelitis; FOXO3: forkhead box O3; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; H&E: hematoxylin and eosin; ITGAM: integrin alpha M; LPS: lipoplysaccharide; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; miRNAs: microRNAs; MS: multiple sclerosis; PPARG: peroxisome proliferator activated receptor gamma; PTPRC: protein tyrosine phosphatase, receptor type, C; RA: rheumatoid arthritis; SQSTM1: sequestosome 1; TB: tuberculosis; TIMM23: translocase of inner mitochondrial membrane 23; TLR: toll-like receptor.

Telmisartan attenuates kidney apoptosis and autophagy-related protein expression levels in an intermittent hypoxia mouse model

Purpose

Obstructive sleep apnea (OSA) is associated with renal impairs. As a novel pathophysiological hallmark of OSA, chronic intermittent hypoxia (CIH) enhances apoptosis and autophagy. The present study aims to evaluate the effect of telmisartan on CIH-induced kidney apoptosis and autophagy in a mouse model of OSA.

Materials and methods

Mice were randomly allocated to normoxia, CIH, and CIH+telmisartan groups (n = 12 in each group). The CIH exposure duration was 12 weeks. Mice in the CIH+telmisartan group received telmisartan administration. The terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and western blotting of Bax and cleaved caspase-3 were conducted for evaluating apoptosis in kidney tissue. While the autophagy-related proteins, beclin-1 and LC3, were also observed via western blotting.

Results

The percentage of apoptotic cell in the CIH group was significantly higher than that of normoxia group; meanwhile, Bax and cleaved caspase-3 protein levels were increased in the CIH group than those of normoxia group (all p < 0.05). Compared with the normoxia group, mice in the CIH group had greater autophagy-related proteins (beclin-1 and LC3) expression. When compared to the CIH group, both the renal apoptosis and autophagy in the CIH+telmisartan group were decreased.

Conclusion

The CIH accelerates renal apoptosis and autophagy levels. Telmisartan ameliorating those levels suggests that it might prevent renal impairs from the CIH in OSA patients.

Plasma microRNA signature of patients with IgA nephropathy

We looked for differentially expressed MicroRNAs (miRNAs) in Immunoglobulin A nephropathy (IgAN). Forty-eight miRNAs were identified through the initial screening phase (2 IgAN pools vs. 1 normal control (NC) pool) using quantitative reverse transcription polymerase chain reaction (qRT-PCR) based Exiqon panel (miRCURY-Ready-to-Use-PCR-Human-panel-I + II-V₁.M). By qRT-PCR, these miRNAs were further assessed in the training (32 IgAN VS. 31 NCs) and testing stages (51 IgAN VS. 51 NCs). The renal pathological lesions of patients with IgAN were evaluated according to Lee's grading system. We discovered a plasma miRNA signature including four up-regulated miRNAs (miR-148a-3p, miR-150-5p, miR-20a-5p and miR-425-3p) and the areas under the receiver operating characteristic (ROC) curve (AUC) were 0.80 and 0.76 for the training and testing stage, respectively. The expression of the four miRNAs in IgAN grade I-II subgroups (according to Lee's grading system) was obviously higher than that in IgAN grade III-V (P < .05). In summary, the plasma expression of miR-148a-3p, miR-150-5p, miR-20a-5p and miR-425-3p were up-regulated in patients with IgAN, especially the early-stage disease. Further studies are needed to explore the roles of the four miRNAs in the pathogenesis and progression of IgAN.

MiR-20a-5p suppresses tumor proliferation by targeting autophagy-related gene 7 in neuroblastoma

Background

Neuroblastoma (NB) is the most common malignant tumor originating from the extracranial sympathetic nervous system in children. The molecular mechanisms underlying this disease are complex, and not completely understood.

Methods

Quantitative real-time PCR (qRT-PCR) was applied to quantify the expression of miR-20a-5p and its target gene ATG7 in clinical NB tissues. The biological function of miR-20a-5p and ATG7 in SH-SY5Y cells was investigated through in vitro studies (Real-Time cell kinetic analyzer, colony formation assay, caspase-Glo 3/7 assay and western blotting). The luciferase reporter assay was conducted to verify the biological relationship between miR-20a-5p and ATG7.

Results

Here we found that miR-20a-5p expression was significantly downregulated whereas its target autophagy-related gene 7 (ATG7) was increased along with clinical staging of NB progression. Correlation analysis showed that miR-20a-5p had a negative correlation trend with ATG7. In SH-SY5Y cells, forced expression of miR-20a-5p suppressed ATG7 expression, autophagy initiation and cellular proliferation while promoted apoptosis, suggesting a potential association between miR-20a-5p and ATG7. Further bioinformatic target prediction combined with protein expression and luciferase reporter assay verified that miR-20a-5p inhibited ATG7 by directly binding to its 3′-UTR, confirming the involvement of miR-20a-5p in the regulation of ATG7 in NB.

Conclusions

These results clarified that miR-20a-5p inhibited cell proliferation and promoted apoptosis through negative regulation of ATG7 and thus autophagy suppression in SH-SY5Y cells. Therefore, defining the context-specific roles of autophagy in NB and regulatory mechanisms involved will be critical for developing autophagy-targeted therapeutics against NB. Both miR-20a-5p and ATG7 would be potential therapeutic targets for future NB treatment.

Role of microRNA in the detection, progression, and intervention of acute kidney injury

Acute kidney injury, characterized by sharply decreased renal function, is a common and important complication in hospitalized patients. The pathological mechanism of acute kidney injury is mainly related to immune activation and inflammation. Given the high morbidity and mortality rates of hospitalized patients with acute kidney injury, the identification of biomarkers useful for assessing risk, making an early diagnosis, evaluating the prognosis, and classifying the injury severity is urgently needed. Furthermore, investigation into the development of acute kidney injury and potential therapeutic targets is required. While microRNA was first discovered in Caenorhabditis elegans, Gary Ruvkun's laboratory identified the first microRNA target gene. Together, these two important findings confirmed the existence of a novel post-transcriptional gene regulatory mechanism. Considering that serum creatinine tests often fail in the early detection of AKI, testing for microRNAs as early diagnostic biomarkers has shown great potential. Numerous studies have identified microRNAs that can serve as biomarkers for the detection of acute kidney injury. In addition, as microRNAs can control the expression of multiple proteins through hundreds or thousands of targets influencing multiple signaling pathways, the number of studies on the functions of microRNAs in AKI progression is increasing. Here, we mainly focus on research into microRNAs as biomarkers and explorations of their functions in acute kidney injury. Impact statement Firstly, we have discussed the potential advantages and limitations of miRNA as biomarkers. Secondly, we have summarized the role of miRNA in the progress of AKI. Finally, we have made a vision of miRNA's potential and advantages as therapeutic target intervention AKI.

MicroRNA-17-5p mediates hypoxia-induced autophagy and inhibits apoptosis by targeting signal transducer and activator of transcription 3 in vascular smooth muscle cells

The aim of the present study was to investigate hypoxia-induced apoptosis and autophagy in vascular smooth muscle cells (VSMCs) and the underlying molecular mechanisms of microRNA (miR)-17-5p responses in an anaerobic environment. The results revealed that miR-17-5p expression was significantly upregulated in VSMCs subjected to hypoxic conditions (P<0.05) and lower miR-17-5p levels were observed in ethyl 3,4-dihydroxybenzoate-treated and hypoxia inducible factor-1 loss-of-function cells. Additionally, it was demonstrated that miR-17-5p is associated with hypoxia-induced autophagy, which was confirmed by upregulating the light chain 3-II/LC3-I ratio and downregulating nucleoporin p62. Cell apoptosis was inhibited in response to hypoxia, and levels of pro-apoptotic proteins B-cell lymphoma 2-associated X protein and p-caspase were markedly decreased when VSMCs were subjected to hypoxic conditions. Furthermore, expression of signal transducer and activator of transcription 3 (STAT3) decreased when cells were transfected with overexpressing miR-17-5p and subjected to hypoxic conditions, and the combination of miR-17-5p loss-of-function and hypoxia induced greater upregulation in the protein expression of STAT3 compared with a single treatment for hypoxia in VSMCs. In conclusion, miR-17-5p may be a novel hypoxia-responsive miR and hypoxia may induce protective autophagy and anti-apoptosis in VSMCs by targeting STAT3.

Induction of microRNA-17-5p by p53 protects against renal ischemia-reperfusion injury by targeting death receptor 6

Renal ischemia-reperfusion injury is a leading cause of acute kidney injury; the pathogenesis of which remains poorly understood and effective therapies are still lacking. Here we tested whether microRNAs, identified as critical regulators of cell health and disease, are involved in this process. We found that miR-17-5p was significantly up-regulated during renal ischemia-reperfusion injury in mice and during hypoxia in cultured renal tubular cells. In cultured cells, miR-17-5p directly inhibited the expression of death receptor 6 (DR6) and attenuated apoptosis during hypoxia. Blockade of miR-17-5p abolished the suppression of DR6 and facilitated caspase activation and apoptosis. In vivo, an miR-17-5p mimic suppressed DR6 expression and protected against renal ischemia-reperfusion injury. We further verified that miR-17-5p induction during renal ischemia-reperfusion injury was dependent on p53. Inhibition of p53 with pifithrin-α or a dominant-negative mutant led to the repression of miR-17-5p expression under hypoxia in vitro. Moreover, miR-17-5p induction during renal ischemia-reperfusion injury was attenuated in proximal tubule p53 knockout mice, supporting the role of p53 in miR-17-5p induction in vivo. Thus, p53/miR-17-5p/DR6 is a new protective pathway in renal ischemia-reperfusion injury and may be targeted for the prevention and treatment of ischemic acute kidney injury.

microRNA-20a Inhibits Autophagic Process by Targeting ATG7 and ATG16L1 and Favors Mycobacterial Survival in Macrophage Cells

Autophagy plays important roles in the host immune response against mycobacterial infection. Mycobacterium tuberculosis (M. tuberculosis) can live in macrophages owing to its ability to evade attacks by regulating autophagic response. MicroRNAs (miRNAs) are small noncoding, endogenously encoded RNA which plays critical roles in precise regulation of macrophage functions. Whether miRNAs specifically influence the activation of macrophage autophagy during M. tuberculosis infection are largely unknown. In this study, we demonstrate that BCG infection of macrophages resulted in enhanced expression of miRNA-20a, which inhibits autophagic process by targeting ATG7 and ATG16L1 and promotes BCG survival in macrophages. Forced overexpression of miR-20a decreased the expression levels of LC3-II and the number of LC3 puncta in macrophages, and promoted BCG survival in macrophages, while transfection with miR-20a inhibitor had the opposite effect. Moreover, the inhibitory effect of miR-20a on autophagy was further confirmed by transmission electron microscopy (TEM) analysis. Quantification of autophagosomes per cellular cross-section revealed a significant reduction upon transfection with miR-20a mimic, but transfection with miR-20a inhibitor increased the number of autophagosomes per cellular cross-section. Moreover, silencing of ATG7 significantly inhibited autophagic response, and transfection with ATG7 siRNA plus miR-20a mimic could further decrease autophagic response. Collectively, our data reveal that miR-20a inhibits autophagic response and promotes BCG survival in macrophages by targeting ATG7 and ATG16L1, which may have implications for a better understanding of pathogenesis of M. tuberculosis infection.

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.

Autophagy and Tubular Cell Death in the Kidney

Many common renal insults such as ischemia and toxic injury primarily target the tubular epithelial cells, especially the highly metabolically active proximal tubular segment. Tubular epithelial cells are particularly dependent on autophagy to maintain homeostasis and respond to stressors. The pattern of autophagy in the kidney has a unique spatial and chronologic signature. Recent evidence has shown that there is complex cross-talk between autophagy and various cell death pathways. This review specifically discusses the interplay between autophagy and cell death in the renal tubular epithelia. It is imperative to review this topic because recent discoveries have improved our mechanistic understanding of the autophagic process and have highlighted its broad clinical applications, making autophagy a major target for drug development.

MicroRNA-20a-5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression

Recently, it is implicated that aberrant expression of microRNAs (miRs) is associated with insulin resistance. However, the role of miR‐17 family in hepatic insulin resistance and its underlying mechanisms remain unknown. In this study, we provided mechanistic insight into the effects of miR‐20a‐5p, a member of miR‐17 family, on the regulation of AKT/GSK pathway and glycogenesis in hepatocytes. MiR‐20a‐5p was down‐regulated in the liver of db/db mice, and NCTC1469 cells and Hep1‐6 cells treated with high glucose, accompanied by reduced glycogen content and impaired insulin signalling. Notably, inhibition of miR‐20a‐5p significantly reduced glycogen synthesis and AKT/GSK activation, whereas overexpression of miR‐20a‐5p led to elevated glycogenesis and activated AKT/GSK signalling pathway. In addition, miR‐20a‐5p mimic could reverse high glucose‐induced impaired glycogenesis and AKT/GSK activation in NCTC1469 and Hep1‐6 cells. P63 was identified as a target of miR‐20a‐5p by bioinformatics analysis and luciferase reporter assay. Knockdown of p63 in the NCTC1469 cells and the Hep1‐6 cells by transfecting with siRNA targeting p63 could increase glycogen content and reverse miR‐20a‐5p inhibition‐induced reduced glycogenesis and activation of AKT and GSK, suggesting that p63 participated in miR‐20a‐5p‐mediated glycogenesis in hepatocytes. Moreover, our results indicate that p63 might directly bind to p53, thereby regulating PTEN expression and in turn participating in glycogenesis. In conclusion, we found novel evidence suggesting that as a member of miR‐17 family, miR‐20a‐5p contributes to hepatic glycogen synthesis through targeting p63 to regulate p53 and PTEN expression.

MicroRNA-495 regulates starvation-induced autophagy by targeting ATG3

The functions of some essential autophagy genes are regulated by microRNAs. However, an ATG3-modulating microRNA has never been reported. Here we show that the transcription of miR-495 negatively correlates with the translation of ATG3 under nutrient-deprived or rapamycin-treated conditions. miR-495 targets ATG3 and regulates its protein levels under starvation conditions. miR-495 also inhibits starvation-induced autophagy by decreasing the number of autophagosomes and by preventing LC3-I-to-LC3-II transition and P62 degradation. These processes are reversed by the overexpression of an endogenous miR-495 inhibitor. Re-expression of Atg3 without miR-495 response elements restores miR-495-inhibited autophagy. miR-495 sustains cell viability under starvation conditions but has no effect under hypoxia. Moreover, miR-495 inhibits etoposide-induced cell death. In conclusion, miR-495 is involved in starvation-induced autophagy by regulating Atg3.

MiR-20a and miR-20b negatively regulate autophagy by targeting RB1CC1/FIP200 in breast cancer cells

AIMS

RB1CC1/FIP200 was essential for autophagosome formation. Therefore, RB1CC1/FIP200 cellular levels are critical for the activation of the autophagy pathways. Following the screen of miRNAs affecting RB1CC1/FIP200 level and rapamycin-induced autophagy, we discovered miR-20a and miR-20b could regulate autophagy by targeting RB1CC1/FIP200.

MAIN METHODS

Inhibitory effect of miR-20a and 20b on basal and rapamycin-stimulated autophagy was demonstrated using various autophagic tests including GFP-LC3 puncta analysis, LC3II/LC3I gel shift and TEM observation.

KEY FINDINGS

We discovered RB1CC1/FIP200 as cellular targets of miR-20a and miR-20b. Upon miR-20a and miR-20b overexpression, both mRNA and protein levels of RB1CC1/FIP200 decreased. miR-20a and miR-20b target sequences present in the 3' UTR of RB1CC1/FIP200 mRNAs and introduction of mutations abolished the miR-20a and miR-20b responsiveness. In MCF7 and MDA-MB-231 breast cancer cells, miR-20a and miR-20b over-expression attenuated basal and rapamycin-induced autophagy; while suppression of miR-20a or miR-20b by specific antagomir showed normal rapamycin-induced autophagic activity.

SIGNIFICANCE

To our knowledge, this is the first study showing the significance of miR-20a and miR-20b regulating autophagy by targeting RB1CC1/FIP200.