Junjie Xiao

miR-21-3p controls sepsis-associated cardiac dysfunction via regulating SORBS2

Cardiac dysfunction with sepsis is a major cause of death in intensive care units. Several lines of evidence have revealed the potential of microRNAs (miRNAs, miRs) as biomarkers for detecting sepsis, though direct evidence of their functional roles in septic cardiac dysfunction is still lacking. In this study, C57BL/6 mice were exposed to lipopolysaccharide (LPS) to induce sepsis-associated cardiac dysfunction, as evidenced by reduced fractional shortening (FS) and ejection fraction (EF) and detrimental changes in cardiac contractility, inflammation, and energy metabolism. Microarray analysis and qRT-PCRs revealed that miR-21-3p was significantly induced in heart samples challenged with LPS. Impressively, pharmacological inhibition of miR-21-3p using antagomiR was able to preserve FS and EF and prevent mitochondria ultrastructural damage and autophagy in LPS-treated mice, while forced expression of miR-21-3p using agomiR aggravated that. Besides that, miR-21-3p antagomiR improved the survival of mice treated with LPS. Meanwhile, our data showed that SH3 domain-containing protein 2 (SORBS2) was inversely correlated with miR-21-3p expression level in mice hearts, and was repressed in hearts challenged with LPS, suggesting SORBS2 as a target gene of miR-21-3p. Additionally, plasma miR-21-3p was markedly elevated in septic patients with cardiac dysfunction as compared to septic patients without cardiac dysfunction. The ROC curve showed that plasma miR-21-3p could be a specific predictor of septic patients developing cardiac dysfunction with an area under the curve of 0.939. Collectively, the present study provides strong evidence that miR-21-3p controls sepsis-associated cardiac dysfunction via regulating SORBS2. Inhibition of miR-21-3p might be a protective strategy to treat sepsis-induced cardiac dysfunction.

miR-382 targeting PTEN-Akt axis promotes liver regeneration

Liver regeneration is a highly orchestrated process which can be regulated by microRNAs (miRNAs, miRs), though the mechanisms are largely unclear. This study was aimed to identify miRNAs responsible for hepatocyte proliferation during liver regeneration. Here we detected a marked elevation of miR-382 in the mouse liver at 48 hrs after partial hepatectomy (PH-48h) using microarray analysis and qRT-PCRs. miR-382 overexpression accelerated the proliferation and the G1 to S phase transition of the cell cycle both in mouse NCTC1469 and human HL7702 normal liver cells, while miR-382 downregulation had inverse effects. Moreover, miR-382 negatively regulated PTEN expression and increased Akt phosphorylation both in vitro and in vivo. Using PTEN siRNA and Akt activator/inhibitor, we further found that PTEN inhibition and Akt phosphorylation were essential for mediating the promotive effect of miR-382 in the proliferation and cell growth of hepatocytes. Collectively, our findings identify miR-382 as a promoter for hepatocyte proliferation and cell growth via targeting PTEN-Akt axis which might be a novel therapeutic target to enhance liver regeneration capability.

miR‐212 downregulation contributes to the protective effect of exercise against non‐alcoholic fatty liver via targeting FGF‐21

Non‐alcoholic fatty liver disease (NAFLD) is associated with obesity and lifestyle, while exercise is beneficial for NAFLD. Dysregulated microRNAs (miRs) control the pathogenesis of NAFLD. However, whether exercise could prevent NAFLD via targeting microRNA is unknown. In this study, normal or high‐fat diet (HF) mice were either subjected to a 16‐week running program or kept sedentary. Exercise attenuated liver steatosis in HF mice. MicroRNA array and qRT‐PCR demonstrated that miR‐212 was overexpressed in HF liver, while reduced by exercise. Next, we investigated the role of miR‐212 in lipogenesis using HepG2 cells with/without long‐chain fatty acid treatment (±FFA). FFA increased miR‐212 in HepG2 cells. Moreover, miR‐212 promoted lipogenesis in HepG2 cells (±FFA). Fibroblast growth factor (FGF)‐21, a key regulator for lipid metabolism, was negatively regulated by miR‐212 at protein level in HepG2 cells. Meanwhile, FFA downregulated FGF‐21 both at mRNA and protein levels in HepG2 cells. Also, FGF‐21 protein level was reduced in HF liver, while reversed by exercise in vivo. Furthermore, siRNA‐FGF‐21 abolished the lipogenesis‐reducing effect of miR‐212 inhibitor in HepG2 cells (±FFA), validating FGF‐21 as a target gene of miR‐212. These data link the benefit of exercise and miR‐212 downregulation in preventing NAFLD via targeting FGF‐21.

Inhibition of miR-155 Protects Against LPS-induced Cardiac Dysfunction and Apoptosis in Mice.

Sepsis-induced myocardial dysfunction represents a major cause of death in intensive care units. Dysregulated microRNAs (miR)-155 has been implicated in multiple cardiovascular diseases and miR-155 can be induced by lipopolysaccharide (LPS). However, the role of miR-155 in LPS-induced cardiac dysfunction is unclear. Septic cardiac dysfunction in mice was induced by intraperitoneal injection of LPS (5 mg/kg) and miR-155 was found to be significantly increased in heart challenged with LPS. Pharmacological inhibition of miR-155 using antagomiR improved cardiac function and suppressed cardiac apoptosis induced by LPS in mice as determined by echocardiography, terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay, and Western blot for Bax and Bcl-2, while overexpression of miR-155 using agomiR had inverse effects. Pea15a was identified as a target gene of miR-155, mediating its effects in controlling apoptosis of cardiomyocytes as evidenced by luciferase reporter assays, quantitative real time-polymerase chain reaction, Western blot, and TUNEL staining. Noteworthy, miR-155 was also found to be upregulated in the plasma of patients with septic cardiac dysfunction compared to sepsis patients without cardiac dysfunction, indicating a potential clinical relevance of miR-155. The receiver-operator characteristic curve indicated that plasma miR-155 might be a biomarker for sepsis patients developing cardiac dysfunction. Therefore, inhibition of miR-155 represents a novel therapy for septic myocardial dysfunction.Sepsis-induced myocardial dysfunction represents a major cause of death in intensive care units. Dysregulated microRNAs (miR)-155 has been implicated in multiple cardiovascular diseases and miR-155 can be induced by lipopolysaccharide (LPS). However, the role of miR-155 in LPS-induced cardiac dysfunction is unclear. Septic cardiac dysfunction in mice was induced by intraperitoneal injection of LPS (5 mg/kg) and miR-155 was found to be significantly increased in heart challenged with LPS. Pharmacological inhibition of miR-155 using antagomiR improved cardiac function and suppressed cardiac apoptosis induced by LPS in mice as determined by echocardiography, terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) assay, and Western blot for Bax and Bcl-2, while overexpression of miR-155 using agomiR had inverse effects. Pea15a was identified as a target gene of miR-155, mediating its effects in controlling apoptosis of cardiomyocytes as evidenced by luciferase reporter assays, quantitative real time-polymerase chain reaction, Western blot, and TUNEL staining. Noteworthy, miR-155 was also found to be upregulated in the plasma of patients with septic cardiac dysfunction compared to sepsis patients without cardiac dysfunction, indicating a potential clinical relevance of miR-155. The receiver-operator characteristic curve indicated that plasma miR-155 might be a biomarker for sepsis patients developing cardiac dysfunction. Therefore, inhibition of miR-155 represents a novel therapy for septic myocardial dysfunction.

MicroRNAs in Liver Regeneration.

Liver maintains a unique tremendous regeneration capacity in response to partial hepatectomy (PH) or injury. Hepatocyte proliferation critically contributes to the process of liver regeneration (LR), which is regulated by various cytokines and growth factors. However, the molecular basis of LR remains unclear. Emerging evidence indicates that microRNAs (miRNAs, miRs) are involved in controlling hepatocyte proliferation during LR. In this review, an overview is provided to cover recent achievements in studies on the roles of miRNAs in LR. Studies on the regulatory effects of miRNAs and associated molecular mechanisms in LR will help enhance the understanding of the regenerative process and open up a new prospect for liver transplantation.

Telocytes in exercise‐induced cardiac growth

Exercise can induce physiological cardiac growth, which is featured by enlarged cardiomyocyte cell size and formation of new cardiomyocytes. Telocytes (TCs) are a recently identified distinct interstitial cell type, existing in many tissues and organs including heart. TCs have been shown to form a tandem with cardiac stem/progenitor cells in cardiac stem cell niches, participating in cardiac regeneration and repair. Although exercise‐induced cardiac growth has been confirmed as an important way to promote cardiac regeneration and repair, the response of cardiac TCs to exercise is still unclear. In this study, 4 weeks of swimming training was used to induce robust healthy cardiac growth. Exercise can induce an increase in cardiomyocyte cell size and formation of new cardiomyocytes as determined by Wheat Germ Lectin and EdU staining respectively. TCs were identified by three immunofluorescence stainings including double labelling for CD34/vimentin, CD34/platelet‐derived growth factor (PDGF) receptor‐α and CD34/PDGF receptor‐β. We found that cardiac TCs were significantly increased in exercised heart, suggesting that TCs might help control the activity of cardiac stem/progenitor cells, cardiomyocytes or endothelial cells. Adding cardiac TCs might help promote cardiac regeneration and renewal.

Targeting microRNAs in Pathological Hypertrophy and Cardiac Failure.

MicroRNAs (miRNAs) are a novel class of endogenous, short, non-coding, posttranscriptional RNAs, which play important roles in regulating lots of important biological functions. Evidences show that altered expression of miRNAs are involved in pathological hypertrophy and cardiac failure, making it possible to target miRNAs as a novel therapy. In this review, we focus on very recent progresses in the regulation of miRNAs in pathological hypertrophy and cardiac failure. In addition, we also discuss the potential of using miRNAs as a new therapy for pathological hypertrophy and cardiac failure.

miR‐149 controls non‐alcoholic fatty liver by targeting FGF‐21

Non‐alcoholic fatty liver disease (NAFLD), a lipid metabolism disorder characterized by the accumulation of intrahepatic fat, has emerged as a global public health problem. However, its underlying molecular mechanism remains unclear. We previously have found that miR‐149 was elevated in NAFLD induced by high‐fat diet mice model, whereas decreased by a 16‐week running programme. Here, we reported that miR‐149 was increased in HepG2 cells treated with long‐chain fatty acid (FFA). In addition, miR‐149 was able to promote lipogenesis in HepG2 cells in the absence of FFA treatment. Moreover, inhibition of miR‐149 was capable of inhibiting lipogenesis in HepG2 cells in the presence of FFA treatment. Meanwhile, fibroblast growth factor‐21 (FGF‐21) was identified as a target gene of miR‐149, which was demonstrated by the fact that miR‐149 could negatively regulate the protein expression level of FGF‐21, and FGF‐21 was also responsible for the effect of miR‐149 inhibitor in decreasing lipogenesis in HepG2 cells in the presence of FFA treatment. These data implicate that miR‐149 might be a novel therapeutic target for NAFLD.

Cardiac cell proliferation is not necessary for exercise-induced cardiac growth but required for its protection against ischaemia/reperfusion injury

The adult heart retains a limited ability to regenerate in response to injury. Although exercise can reduce cardiac ischaemia/reperfusion (I/R) injury, the relative contribution of cardiac cell proliferation including newly formed cardiomyocytes remains unclear. A 4‐week swimming murine model was utilized to induce cardiac physiological growth. Simultaneously, the antineoplastic agent 5‐fluorouracil (5‐FU), which acts during the S phase of the cell cycle, was given to mice via intraperitoneal injections. Using EdU and Ki‐67 immunolabelling, we showed that exercise‐induced cardiac cell proliferation was blunted by 5‐FU. In addition, the growth of heart in size and weight upon exercise was unaltered, probably due to the fact that exercise‐induced cardiomyocyte hypertrophy was not influenced by 5‐FU as demonstrated by wheat germ agglutinin staining. Meanwhile, the markers for pathological hypertrophy, including ANP and BNP, were not changed by either exercise or 5‐FU, indicating that physiological growth still developed in the presence of 5‐FU. Furthermore, we showed that CITED4, a key regulator for cardiomyocyte proliferation, was blocked by 5‐FU. Meanwhile, C/EBPβ, a transcription factor responsible for both cellular proliferation and hypertrophy, was not altered by treatment with 5‐FU. Importantly, the effects of exercise in reducing cardiac I/R injury could be abolished when cardiac cell proliferation was attenuated in mice treated with 5‐FU. In conclusion, cardiac cell proliferation is not necessary for exercise‐induced cardiac physiological growth, but it is required for exercise‐associated protection against I/R injury.

miR-21 suppression prevents cardiac alterations induced by d-galactose and doxorubicin

d-galactose (d-gal)-induced cardiac alterations and Doxorubicin (Dox)-induced cardiomyocyte senescence are commonly used models to study cardiac aging. Accumulating evidence has suggested that microRNAs (miRNAs, miRs) are critically involved in the regulation of cellular and organismal aging and age-related diseases. However, little has been revealed about the roles of miRNAs in cardiac alterations induced by d-gal and Dox. In this study, we used miRNA arrays to investigate the dysregulated miRNAs in heart samples from 15month-old versus 2month-old male C57BL/6 mice and further validated them in d-gal-induced pseudo-aging mouse model and Dox-induced cardiomyocyte senescence in vitro model. We confirmed a significant increase of miR-21 in all these models by quantitative reverse transcription polymerase chain reactions. We further demonstrated that miR-21 was able to promote Dox-induced cardiomyocyte senescence whereas suppression of miR-21 could prevent that, as determined by percentage of β-gal-positive cells and gene markers of aging. Phosphatase and tensin homolog (PTEN) was identified as a target gene of miR-21, mediating its effect in increasing cardiomyocyte senescence. Finally, we found that miR-21 knockout mice were resistant to d-gal-induced alterations in aging-markers and cardiac function. Collectively, this study provides direct evidence that inhibition of miR-21 is protective against d-gal-induced cardiac alterations and Dox-induced cardiomyocyte senescence via targeting PTEN. Inhibition of miR-21 might be a novel strategy to combat cardiac aging.