Cloning,characterization, and expression of glucose transporter 2 in the freeze-tolerant wood frog, Rana sylvatica

Background

The essential role of glucose transporter 2 (GLUT2) in glucose homeostasis has been extensively studied in mammals; however, little is known about this important protein in lower vertebrates. The freeze-tolerant wood frog (Rana sylvatica), which copiously mobilizes glucose in response to freezing, represents an excellent system for the study of glucose transport in amphibians.

Methods

GLUT2 was sequenced from northern and southern phenotypes of R. sylvatica, as well as the freeze-intolerant Rana pipiens. These proteins were expressed and functionally characterized in Xenopus oocytes. Abundance of GLUT2 in tissues was analyzed using immunoblotting techniques.

Results

GLUT2s cloned from these anurans encoded proteins with high sequence homologies to known vertebrate GLUT2s and had similar transport properties, although, notably, transport of the glucose analog 3-O-methyl-d-glucose (3-OMG) was strongly inhibited by 150 mM urea. Proteins from all study subjects had similar affinity constants (~ 12 mM) and other kinetic properties; however, GLUT2 abundance in liver was 3.5-fold greater in northern R. sylvatica than in the southern conspecific and R. pipiens.

Conclusion

Our results indicate that amphibian GLUT2s are structurally and functionally similar to their homologs in other vertebrates, attesting to the conserved nature of this transport protein. The greater abundance of this protein in the northern phenotype of R. sylvatica suggests that these transporters contribute importantly to freezing survival.

General significance

This study provides the first functional characterization of any GLUT isoform from an anuran amphibian and novel insights into the role of these proteins in glucose homeostasis and cryoprotectant mobilization in freeze-tolerant vertebrates.     

Molecular targeting of Akt by thymoquinone promotes G1 arrest through translation inhibition of cyclin D1 and induces apoptosis in breast cancer cells

Aim

Thymoquinone (TQ), the predominant bioactive constituent of black seed oil (Nigella Sativa), has been shown to possess antineoplastic activity against multifarious tumors. However, the meticulous mechanism of TQ on Akt mediated survival pathway is still unrevealed in breast cancer. Here, we investigated TQ's mechanism of action against PI3K/Akt signaling and its downstream targets by modulating proteins translational machinery, leading to apoptosis in cancer cells.

Main methods

MDA-MB-468 and T-47D cells were treated with TQ and evaluated for its anticancer activity through phase distribution and western blot. Modulatory effects of TQ on Akt were affirmed through kinase and drug potential studies.

Key findings

Studies revealed G₁ phase arrest till 24 h incubation with TQ while extended exposure showed phase shift to subG₁ indicating apoptosis, supported by suppression of cyclin D1, cyclin E and cyclin dependent kinase inhibitor p27 expression. Immunoblot and membrane potential studies revealed mitochondrial impairment behind apoptotic process with upregulation of Bax, cytoplasmic cytochrome c and procaspase-3, PARP cleavage along with Bcl-2, Bcl-xL and survivin downregulation. Moreover, we construed the rationale behind mitochondrial dysfunction by examining the phosphorylation status of PDK1, PTEN, Akt, c-raf, GSK-3β and Bad in TQ treated cells, thus ratifying the involvement of Akt in apoptosis. Further, the consequential effect of Akt inhibition by TQ is proven by translational repression through deregulated phosphorylation of 4E-BP1, eIF4E, S6R and p70S6K.

Significance

Our observations for the first time may provide a new insight for the development of novel therapies for Akt overexpressed breast cancer by TQ.     

Hepatoprotective effects of berberine on liver fibrosis via activation of AMP-activated protein kinase

Aims

We investigated the protective effect of berberine (BBR) on chronic liver fibrosis in mice and the potential mechanism underlying the activation of AMP-activated protein kinase (AMPK) pathway.

Main methods

CCl4-induced chronic liver fibrosis model in mice was established and activated rat hepatic stellate cell was treated with BBR. Cell viability was evaluated by SRB assay and protein expressions were detected by Western blot.

Key findings

Our results showed that BBR ameliorated the liver fibrosis in mice with CCl4-induced liver injury and inhibited the proliferation of hepatic stellate cell in dose- and time-dependent manner. BBR decreased the enzyme release of ALT, AST, and ALP in serum, elevated SOD and reduced MDA content of liver tissue in CCl4-induced liver fibrosis model. BBR delayed the formation of regenerative nodules and reduced necrotic areas compared to CCl4 group. Moreover, BBR treatment activated AMPK, decreased the protein expression of Nox4, TGF-β1 and the phosphorylated Akt. The expression of smooth muscle actin (α-SMA), the marker of activated hepatic stellate cell, was also reduced by BBR treatment.

Significance

Our studies firstly demonstrated that BBR exerted hepatoprotective effects possibly via activation of AMPK, blocking Nox4 and Akt expression. Our findings may benefit the development of new strategies in the prevention of chronic liver disease.     

Bioinformatics prediction of miR-30a targets and its inhibition of cell proliferation of osteosarcoma by up-regulating the expression of PTEN

Background

MiRNAs are frequently abnormally expressed in the progression of human osteosarcoma. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is one of the tumor suppressors in various types of human cancer. In the present study, we detected how hsa-miR-30a-3p regulated PTEN and further tested the role of hsa-miR-30a-3p in the cell proliferation of osteosarcoma cells.

Methods

The levels of miR-30a were determined by real time PCR. The expression of PTEN was tested by western blotting analysis. Cell distribution of PTEN was observed with confocal laser scanning microscope. Cell viability was determined by MTT assay.

Results

The expression of miR-30a and PTEN was obviously decreased in MG-63, 143B and Saos-2 cells compared with primary osteoblasts. TargetScan analysis data showed miR-30a might bind with position 30-57 of 3’UTR of PTEN. Transfection with miR-30a-3p increased the level of PTEN in MG-63 cells, while transfection with miR-30a-3p inhibitor significantly decreased the expression of PTEN in osteosarcoma cells. Transfection with miR-30a-3p significantly inhibited cell proliferation of osteosarcoma cells, while miR-30a inhibitor obviously promoted cell viability of MG63 cells and Saos-2 cells. Inhibition of PTEN eliminated the proliferation inhibitory effect of miR-30a-3p.

Conclusion

Thus, all these findings revealed the anti-tumor effects of miR-30a in human osteosarcoma cells, which could be mediated by regulating the level of PTEN.

     

High uric acid directly inhibits insulin signalling and induces insulin resistance

Background and aim

Accumulating clinical evidence suggests that hyperuricemia is strongly associated with abnormal glucose metabolism and insulin resistance. However, how high uric acid (HUA) level causes insulin resistance remains unclear. We aimed to determine the direct role of HUA in insulin resistance in vitro and in vivo in mice.

Methods

An acute hyperuricemia mouse model was created by potassium oxonate treatment, and the impact of HUA level on insulin resistance was investigated by glucose tolerance test, insulin tolerance test and insulin signalling, including phosphorylation of insulin receptor substrate 1 (IRS1) and Akt. HepG2 cells were exposed to HUA treatment and N-acetylcysteine (NAC), reactive oxygen species scavenger; IRS1 and Akt phosphorylation was detected by Western blot analysis after insulin treatment.

Results

Hyperuricemic mice showed impaired glucose tolerance with insulin resistance. Hyperuricemia inhibited phospho-Akt (Ser473) response to insulin and increased phosphor-IRS1 (Ser307) in liver, muscle and fat tissues. HUA induced oxidative stress, and the antioxidant NAC blocked HUA-induced IRS1 activation and Akt inhibition in HepG2 cells.

Conclusion

This study supplies the first evidence of HUA directly inducing insulin resistance in vivo and in vitro. Increased uric acid level may inhibit IRS1 and Akt insulin signalling and induce insulin resistance. The reactive oxygen species pathway plays a key role in HUA-induced insulin resistance.     

Anti-miR-197 inhibits migration in HCC cells by targeting KAI 1/CD82

Aim

To investigate the metastatic effects and mechanisms of miR-197 in hepatocellular carcinoma (HCC).

Methods and results

The levels of miR-197 increased in HCC cells and tissues compared with a normal hepatic cell line (LO2) and adjacent nontumorous liver tissues, respectively. miR-197 expression negatively correlated with CD82 mRNA expression in these cell lines and tissues. Dual luciferase reporter assay and Western blot confirmed a direct interaction between miR-197 and CD82 3′UTR sequences. After miR-197 was silenced in HCC cells, CD82 expression increased. In the presence of human hepatocyte growth factor (HGF), cells silenced for anti-miR-197 exhibited elongated cellular tails and diminished lamellipodia due to reductions in both ROCK activity and the levels of Rac 1 protein. Downregulation of miR-197 along with the upregulation of CD82 in HCC cells resulted in the inhibition of HCC migration and invasion in vitro and in vivo.

Conclusion

Taken together, these data suggest that anti-miR-197 suppresses HCC migration and invasion by targeting CD82. The regulation of the miR-197/CD82 axis could be a novel therapeutic target in future HCC effective therapy.     

MiR-124 protects human hepatic L02 cells from H2O2-induced apoptosis by targeting Rab38 gene

Background

Hepatic ischemia reperfusion injury (IRI) is an inevitable clinical problem for liver surgeons. Because microRNAs (miRNAs) participate in various hepatic pathophysiological processes, this study aimed to explore the role and potential mechanism of miR-124 in hepatic IRI.

Methods

A liver IRI model was established in rats. The differential expression of miRNAs was detected using microarrays, and the expression of miR-124 was measured by qRT-PCR. A hydrogen peroxide (H₂O₂)-induced oxidative stress apoptosis model was also established. Cell apoptosis was detected by flow cytometry, and viability was detected by CCK8. The expression of Rab38 was detected by Western blotting and qRT-PCR, and a luciferase reporter assay was used to verify the expression of the miR-124 target gene.

Results

The miRNA spectrum changes dramatically after hepatic IRI in rats, and miR-124 is significantly down-regulated after liver IRI. MiR-124 decreases the H₂O₂-induced apoptosis of human hepatic L02 cells by up-regulating the activation of the AKT pathway. Rab38 is a target gene of miR-124 and is involved in H₂O₂-induced apoptosis. Interference with the expression of the Rab38 gene can protect hepatic L02 from H₂O₂-induced apoptosis by increasing the phosphorylation of AKT. These protective effects of miR-124 are attenuated by over-expression of Rab38.

Conclusions

Many miRNAs are involved in hepatic IRI in rats, and miR-124 is significantly decreased in this model. MiR-124 significantly decreases the H₂O₂-induced apoptosis of human hepatic L02 cells by targeting the Rab38 gene and activating the AKT pathway.     

Mitochondrial dysfunction enhances the migration of vascular smooth muscles cells via suppression of Akt phosphorylation

Background

Atherosclerosis is one of the major complications of diabetes, which may result from insulin resistance via mitochondrial dysfunction. Although a strong association between insulin resistance and cardiovascular disease has been suggested, it is not clear yet whether stress-inducing factors damage mitochondria and insulin signaling pathway in cardiovascular tissues.

Methods

We investigated whether stress-induced mitochondrial dysfunction might alter the insulin/Akt signaling pathway in A10 rat vascular smooth muscle cells (VSMC).

Results

The treatment of oxidized low density lipoprotein (oxLDL) decreased ATP contents, mitochondrial respiration activity, mRNA expressions of OXPHOS subunits and IRS-1/2 and insulin-mediated phosphorylations of Akt and AMP-activated protein kinase (AMPK). Similarly, dideoxycytidine (ddC), the mtDNA replication inhibitor, or rotenone, OXPHOS complex I inhibitor, inhibited the insulin-mediated pAkt while increased pAMPK regardless of insulin. Reciprocally, an inhibitor of Akt, triciribine (TCN), decreased cellular ATP contents. Overexpression of Akt dominant positive reversed the oxLDL- or ddC-mediated ATP decrease but AMPK activator did not. Akt activation also normalized the aberrant VSMC migration induced by ddC.

Conclusions

Defective insulin signaling and mitochondrial function may collectively contribute to developing cardiovascular disease.

General significance

Akt may be a possible therapeutic target for treating insulin resistance-associated atherosclerosis.     

miR-204/miR-211 downregulation contributes to Candidemia-induced kidney injuries via derepression of Hmx1 expression

Aims

This study was aimed to exploit the role of heme oxygenase Hmx1 and the potential miRNA mechanisms in the kidney injuries induced by urinary tract infection by Candida species/Candidemia.

Main methods

We employed a mouse model of systemic Candidiasis by injection of the Candida albicans strain SC5314 into C57BL/6 mice. Kidney injuries were assessed by measuring serum cystatin C (CysC), serum β₂-microglobulin (β₂-MG) and blood urea nitrogen (BUN). Validation of miRNA target gene was conducted by luciferase reporter gene assay, Western blot analysis and real-time RT-PCR.

Key findings

We showed here that Candidemia caused significant downregulation of microRNAs miR-204 and miR-211. In sharp contrast, Hmx1 expression was remarkably upregulated, particularly at the protein level. Computational analysis predicted Hmx1 as a target gene for both miR-204 and miR-211 that share the same seed site sequence. We then experimentally validated the targeting relationship between miR-204/miR-211 and Hmx1, which explains the reciprocal changes of expression of miR-204/miR-211 and Hmx1 in Candidemia. Administration of miR-204/miR-211 mimics substantially downregulated Hmx1 and mitigated the severity of the kidney injuries induced by Candidemia, as reflected by improved renal glomerular filtration rate (GFR) determined by serum cystatin C (CysC), serum β₂-microglobulin (β₂-MG) and blood urea nitrogen (BUN). Knockdown of miR-204/miR-211 worsened while forced expression of miR-204/miR-211 ameliorated kidney injuries in mice with systemic Candidiasis.

Significance

Our findings indicate that miR-204/miR-211 downregulation accounts at least partially for the Hmx1 upregulation and the miR-204/miR-211–Hmx1 signaling axis may contribute to immune-suppression in the host thereby the Candidemia-induced kidney dysfunction.     

High expression of miR-210 predicts poor survival in patients with breast cancer: A meta-analysis

Background

Many microRNAs (miRNAs) exhibit altered expression levels in cancers, and they may be considered as valuable prognostic biomarkers for cancers. Here we aimed to summarize the recent advances in miR-210 involvement in human breast cancer and analyze the predicting role of miR-210 for survival.

Methods

A meta-analysis was performed by searching PubMed, Cochrane Library, and Science Direct databases. Data were extracted from studies comparing survival in patients with breast cancer having higher expression of miR-210 with those having lower expression. Pooled hazard ratios (HRs) and 95% confidence intervals (CI) were calculated.

Results

A total of 511 cases of breast cancer were involved for this global meta-analysis. For post-operational survival, the HR of higher miR-210 expression in breast cancer tissue was 3.39 (95% CI: 2.04–5.63, P < 0.05), which could significantly predict poorer survival.

Conclusions

High expression of miR-210 might predict poor survival in patients with breast cancer.     

Over-expression of microRNA-494 up-regulates hypoxia-inducible factor-1 alpha expression via PI3K/Akt pathway and protects against hypoxia-induced apoptosis

Background

Hypoxia-inducible factor-1 alpha (HIF-1α) is one of the key regulators of hypoxia/ischemia. MicroRNA-494 (miR-494) had cardioprotective effects against ischemia/reperfusion (I/R)-induced injury, but its functional relationship with HIF-1α was unknown. This study was undertaken to determine if miR-494 was involved in the induction of HIF-1α.

Results

Quantitative RT-PCR showed that miR-494 was up-regulated to peak after 4 hours of hypoxia in human liver cell line L02. To investigate the role of miR-494, cells were transfected with miR-494 mimic or miR-negative control, followed by incubation under normoxia or hypoxia. Our results indicated that overexpression of miR-494 significantly induced the expression of p-Akt, HIF-1α and HO-1 determined by qRT-PCR and western blot under normoxia and hypoxia, compared to negative control (p < 0.05). While {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 treatment markedly abolished miR-494-inducing Akt activation, HIF-1α and HO-1 increase under both normoxic and hypoxic conditions (p < 0.05). Moreover, apoptosis detection using Annexin V indicated that overexpression of miR-494 significantly decreased hypoxia-induced apoptosis in L02 cells, compared to control (p < 0.05). MiR-494 overexpression also decreased caspase-3/7 activity by 1.27-fold under hypoxia in L02 cells.

Conclusions

Overexpression of miR-494 upregulated HIF-1α expression through activating PI3K/Akt pathway under both normoxia and hypoxia, and had protective effects against hypoxia-induced apoptosis in L02 cells. Thus, these findings suggested that miR-494 might be a target of therapy for hepatic hypoxia/ischemia injury.     

MicroRNA-33a functions as a bone metastasis suppressor in lung cancer by targeting parathyroid hormone related protein

Background

Bone is a common site of metastasis for lung cancer, and is associated with significant morbidity and a dismal prognosis. MicroRNAs (miRNAs) are increasingly implicated in regulating the progression of malignancies.

Methods

The efficacy of miR-33a or anti-miR-33a plasmid was assessed by Real-time PCR. Luciferase assays were using One-Glo Luciferase Assay System. Measurement of secreted factors was determined by ELISA kit.

Results

We have found that miR-33a, which is downregulated in lung cancer cells, directly targets PTHrP (parathyroid hormone-related protein), a potent stimulator of osteoclastic bone resorption, leading to decreased osteolytic bone metastasis. We also found that miR-33a levels are inversely correlated with PTHrP expression between human normal bronchial cell line and lung cancer cell lines. The reintroduction of miR-33a reduces the stimulatory effect of A549 on the production of osteoclastogenesis activator RANKL (receptor activator of nuclear factor kappa-B ligand) and M-CSF (macrophage colony-stimulating factor) on osteoblasts, while the expression of PTHrP is decreased in A549 cells. miR-33a overexpression also reduces the inhibitory activity of A549 on the production of OPG (osteoprotegerin), an osteoclastogenesis inhibitor. In addition, miR-33a-mediated PTHrP downregulation results in decreased IL-8 secretion in A549, which contributes to decreased lung cancer-mediated osteoclast differentiation and bone resorption.

Conclusions

These findings have led us to conclude that miR-33a may be a potent tumor suppressor, which inhibits direct and indirect osteoclastogenesis through repression of PTHrP.

General significance

miR-33a may even predict a poor prognosis for lung cancer patients.     

Berberine and S allyl cysteine mediated amelioration of DEN + CCl4 induced hepatocarcinoma

Background

Diethylnitrosamine (DEN) and carbon tetrachloride (CCl4) have been used as initiator and promoter respectively to establish an animal model for investigating molecular events appear to be involved in development of liver cancer. Use of herbal medicine in therapeutics to avoid the recurrence of hepatocarcinoma has already generated considerable interest among oncologists. In this context studies involving S-allyl-cysteine (SAC) and berberine have come up with promising results. Here we have determined the individual effect of SAC and berberine on the biomolecules associated with DEN + CCl4 induced hepatocarcinoma. Effective therapeutic value of combined treatment has also been estimated.

Methods

ROS accumulation was analyzed by FACS following DCFDA incubation. Bcl2-Bax and HDAC1‐pMdm2 interaction were demonstrated by co-immunoprecipitation. Immunosorbent assay was performed to analyze PP2A and caspase3 activities. MMP was determined cytofluorimetrically by investigating JC-1 fluorescence. AnnexinV binding was demonstrated by labeling the cells with AnV-FITC followed by flow cytometry.

Results

CytochromeP4502E1 mediated bioactivation of DEN + CCl4 induced Akt dependent pMdm2‐HDAC1 interaction that led to p53 deacetylation, probable cause of its degradation. In parallel, oxidative stress dependent Nrf2‐HO1 activation increased Bcl2 expression which in turn stimulated cell proliferation. SAC in combination with berberine inhibited Akt mediated cell proliferation. Activation of PP2A as well as inhibition of JNK resulted in induction of apoptosis after 30 days of treatment. Extension of combined treatment reverted tissue physiology towards control. Co-treated group displayed normal tissue structure.

Conclusion and general significance

SAC and berberine mediated HDAC1/Akt inhibition implicates the efficacy of combined treatment in the amelioration of DEN + CCl4 induced hepatocarcinoma.     

MicroRNA-34a induces apoptosis in the human glioma cell line,A172, through enhanced ROS production and NOX2 expression

Background

MicroRNA is a type of non-coding small RNA involved in regulating genes and signaling pathways through incomplete complementation with target genes. Recent research supports key roles of miRNA in the formation and development of human glioma.

Methods

The relative quantity of miR-34a was initially determined in human glioma A172 cells and glioma tissues. Next, we analyzed the impact of miR-34a on A172 cell viability with the MTT assay. The effects of miR-34a overexpression on apoptosis were confirmed with flow cytometry and Hoechst staining experiments. We further defined the target genes of miR-34a using immunofluorescence and Western blot.

Results

MiR-34a expression was significantly reduced in human glioma A172 cells and glioma tissue, compared with normal glial cells and tissue samples. Our MTT data suggest that up-regulation of miR-34a inhibits cell viability while suppression of miR-34a enhances cell viability. Flow cytometry and Hoechst staining results revealed increased rates of apoptosis in A172 human glioma cells overexpressing miR-34a. Using immunofluorescence and Western blot analyses, we identified NOX2 as a target of miR-34a in A172 cells.

Conclusion

MiR-34a serves as a tumor suppressor in human glioma mainly by decreasing NOX2 expression.