Seasonal expression of extracellular signal regulated kinases in the colon of wild ground squirrels (Spermophilus dauricus)

BACKGROUND

The purpose of the experiment was to explore the localization and seasonal expression of extracellular signal regulated kinase (ERK) in the colonic tissue of wild ground squirrels (Spermophilus dauricus).

METHODS AND RESULTS

Hematoxylin-eosin staining, immunohistochemistry, real-time quantitative PCR and Western blotting were used in this experiment. The histological results showed that the diameter of the colon lumen enlarged and the number of glandular cells increased in the non-breeding season. It was found in the immunochemical results that both ERK1/2 and pERK1/2 were expressed in the cytoplasm of goblet cells and intestinal epithelial cells, while pERK1/2 was also expressed in the nucleus of them. The immune localization of both was more obvious in the non-breeding season, especially in intestinal epithelial cells. Real-time quantitative PCR and Western blotting showed that ERK1/2 and pERK1/2 were seasonally highly expressed in the non-breeding season.

CONCLUSIONS

The expression of ERK1/2 and pERK1/2 was seasonal changes and had significant increases in the non-breeding season. This study revealed that ERK1/2 had potential roles in the colon to the adaptation of seasonal changes in wild ground squirrels.

ERK inhibition in glioblastoma is associated with autophagy activation and tumorigenesis suppression

PURPOSE

Autophagy-dependent tumorigenic growth is one of the most commonly reported molecular mechanisms in glioblastoma (GBM) progression. However, the mechanistic correlation between autophagy and GBM is still largely unexplored, especially the roles of autophagy-related genes involved in GBM oncogenesis. In this study, we aimed to explore the genetic alterations that interact with both autophagic activity and GBM tumorigenesis, and to investigate the molecular mechanisms of autophagy involved in GBM cell death and survival.

METHOD

For this purpose, we systematically explored the alterations of autophagic molecules at the genome level in human GBM samples through deep RNA sequencing. The effect of genetic and pharmacologic inhibition of ERK on GBM growth in vitro and in vivo was researched. An image-based tracking analysis of LC3 using mCherry-eGFP-LC3 plasmid, and transmission electron microscopy were utilized to monitor autophagic flux. Immunoblot analysis was used to measure the related proteins.

RESULTS

MAPK ERK expression was identified as one of the most probable autophagy-related transcriptional responses during GBM growth. The genetic and pharmacologic inhibition of ERK in vivo and in vitro led to cell death, demonstrating its critical role for GBM proliferation and survival. To our surprise, autophagic activities were excessively activated and resulted in cytodestructive effects on GBM cells upon ERK inhibitor treatment. Furthermore, based on the observation of downregulation of mTOR signaling, we speculated the ERK inhibitor-induced GBM cells death might depend on mTOR-mediated pathway, leading to autophagy dysregulation. Accordingly, the in vivo and in vitro experiments revealed that the mTOR inhibitor rapamycin further increased cell mortality and exhibited enhanced antitumor effect on GBM cells when co-treated with the ERK inhibitor.

CONCLUSION

Our data creatively demonstrated that the autophagy-related regulator ERK maintains autophagic activity during GBM tumorigenesis via mTOR signaling pathway. The pharmacologic inhibition of both mTOR and ERK signaling exhibited synergistic therapeutic effect on GBM growth in vivo and in vitro, which has certain novelty and may provide a potential therapeutic approach for GBM treatment in the future.

Dracocephalum moldavica attenuates scopolamine-induced cognitive impairment through activation of hippocampal ERK-CREB signaling in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Dracocephalum moldavica (Moldavian balm) has been traditionally used for the treatment of intellectual disabilities, migraines and cardiovascular problems in East Asia. Recent scientific studies have demonstrated the usefulness of this plant to treat neurodegenerative disorders, including Alzheimer's disease.

AIM OF THE STUDY

This study aimed to investigate the effects of the ethanolic extract of D. moldavica leaves (EEDM) on scopolamine-induced cognitive impairment in mice and the underlying mechanisms of action.

MATERIALS AND METHODS

The behavioral effects of EEDM were examined using the step-through passive avoidance and Morris water maze tasks. To elucidate the underlying mechanism, we tested whether EEDM affects acetylcholinesterase activity and the expression of memory-related signaling molecules including extracellular signal-regulated kinase (ERK) and cAMP response element-binding protein (CREB) in the hippocampus.

RESULTS

EEDM (25, 50 or 100 mg/kg) significantly ameliorated the scopolamine-induced step-through latency reduction in the passive avoidance task in mice. In the Morris water maze task, EEDM (50 mg/kg) significantly attenuated scopolamine-induced memory impairment. Furthermore, the administration of EEDM increased the phosphorylation levels of ERK and CREB in the hippocampus but did not alter acetylcholinesterase activity.

CONCLUSIONS

These findings suggest that EEDM significantly attenuates scopolamine-induced memory impairment in mice and may be a promising therapeutic agent for improving memory impairment.

Phosphorylation mechanisms in dopamine transporter regulation

The dopamine transporter (DAT) is a plasma membrane phosphoprotein that actively translocates extracellular dopamine (DA) into presynaptic neurons. The transporter is the primary mechanism for control of DA levels and subsequent neurotransmission, and is the target for abused and therapeutic drugs that exert their effects by suppressing reuptake. The transport capacity of DAT is acutely regulated by signaling systems and drug exposure, providing neurons the ability to fine-tune DA clearance in response to specific conditions. Kinase pathways play major roles in these mechanisms, and this review summarizes the current status of DAT phosphorylation characteristics and the evidence linking transporter phosphorylation to control of reuptake and other functions. Greater understanding of these processes may aid in elucidation of their possible contributions to DA disease states and suggest specific phosphorylation sites as targets for therapeutic manipulation of reuptake.

Pioglitazone improves the ability of learning and memory via activating ERK1/2 signaling pathway in the hippocampus of T2DM rats

OBJECTIVE

To explore the correlation between effect of PIO (pioglitazone, PIO) on learning as well as memory and ERK1/2 (extracellular signal regulated kinase 1/2, ERK1/2) pathway in T2DM (type 2 diabetes mellitus, T2DM) rats, further to elucidate the potential mechanism of PIO in improvement of learning and memory.

METHODS

12-week-old male SD rats (number of 10 per group) were randomly divided into control group (CON), T2DM group (DM) and T2DM +PIO group (DM+PG). Rats in DM and DM+PG groups were given high fat diet for 20 weeks, then treated with Streptozotocin (27mg/kg) by intraperitoneal injection at 21week. After 72h, the FBG (fasting blood glucose, FBG) was greater than 7.0mmol/L can considered T2DM rats. DM+PG group was treated with PIO (10 mg·kg^-1·d^-1) by gavage daily. After Hyperinsulinemic-Euglycemic Clamp Study and Morris water maze test at 30-week, all of animals were sacrificed. The expressions of RKIP (Raf-1 kinase inhibitor protein, RKIP) and ERK1/2 in hippocampus were detected using Western Blot and real-time PCR.

RESULTS

The FBG level: DM group (7.68±0.54mmol/L) was higher than CON group (5.35±0.63mmol/L) and DM+PG group (6.07±0.84mmol/L), the differences were considered statistically significant (P <0.05). Hyperinsulinemic-Euglycemic Clamp Studies: GIR (glucose infusion rate, GIR) of DM group (21.02±5.10 mg·kg^-1·d^-1) was less than CON group (27.64±3.87 mg·kg^-1·d^-1) and DM+PG group (26.04 ±5.41 mg·kg^-1·d^-1), the differences were considered statistically significant (P <0.05). Morris water maze training: The escape latencies and searching platform performance of DM group (24.54±5.02s) decreased significantly compared with CON group (16.73±4.02s) and DM+PG group (18.05±4.12s) (P <0.05). Changes of RKIP, ERK, p-ERK protein relative content in rat hippocampus: Compared with CON groupand DM+PG group, the relative content of RKIP in DM group remarkably increased (P<0.01); ERK protein levels were not considered statistically significant among the three groups (P>0.05); The relative content of p-ERK1/2 protein in CON group and DM+PG group rats dorsal were higher than those in group DM, the difference was considered statistically significant (P<0.01). Changes in hippocampus of rat RKIP and ERK gene relative content: Compared with CON group and DM+PG group, levels of RKIP mRNA in DM group were significantly increased (P<0.01); ERK mRNA levels were not considered statistically significant among the three groups (P>0.05).

CONCLUSION

Activation of ERK1/2 signal transduction pathway via reducing RKIP in the hippocampus may be one of the mechanisms of PIO to improve the learning and memory of the T2DM rats.

Potential role of andrographolide in the proliferation of osteoblasts mediated by the ERK signaling pathway

The aim of the present study was to explore the effects of andrographolide (AG) and the ERK signaling pathway on the proliferation of osteoblasts (OBs) in vitro. The calvarial OBs from Sprague Dawley (SD) rats were collected and treated at different concentrations of AG and U0126. The concentrations of AG were measured by colorimetry. Based on different treatment methods, the cells were separated into four groups: control group, U0126 group, AG group, and AG+U0126 group. The cells were cultured for 24h, 48h and 72h. An inverted phase contrast microscope was used to observe the morphologies of treated OBs. The MTT assay was performed to plot OB proliferation curves, and to measure the changes in alkaline phosphatase and hydroxyproline contents after U0126 treatments. The expressions of proliferating cell nuclear antigen (PCNA), Ki67, core binding factor alpha-1 (Cbfa1), type I collagen (Col I), osterix (OSX), p38, extracellular signal regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) were measured by fluorescent quantitative polymerase chain reaction (PCR) and Western blotting. In different cell groups, the in vitro proliferation rates of OBs reached the highest at an AG concentration of 20μmol/L, and the amounts of alkaline phosphatase, hydroxyproline, PCNA, Ki67, Cbfa1, Col I, OSX, and ERK were significantly higher than at other concentrations (all P<0.05). U0126 intervention significantly decreased the expressions of these factors (all P<0.05). At the meantime, p38 and JNK were not affected by AG and were only inhibited by U0126. In conclusion, ERK played an important role in mediating the functions of AG in the proliferation of OBs, indicating that the ERK signaling pathway may be the main pathway through which AG exerts its effects.

Influence of Biejiajian pill on PDGF and Ras signaling pathways in hepatic fibrosis in rats

AIM: To explore the anti-fibrotic mechanism of Biejiajian pill, a traditional Chinese medicine for activating blood circulation and eliminating stasis, in rats with hepatic fibrosis.

METHODS: Hepatic fibrosis was induced in rats by subcutaneous injection of CCl₄. SD rats were randomly divided into five groups: a control group, a model group, low-, medium- and high-dose Biejiajian pill treatment groups. The three treatment groups were given Biejiajian pill 0.55, 1.10, and 2.20 g/(kg•d), respectively, while the normal control group and model group were treated with equal volume of normal saline by gavage. At the 11^th week, hepatic pathological changes were observed. The immunohistochemical technique was applied to analyze the expression of extracellular signal regulated kinase 1 (ERK1) in hepatic tissue. RT-PCR was applied to analyze the expression of platelet derivative growth factor (PDGF) and Ras mRNAs in hepatic tissue.

RESULTS: Compared with the control group, the expression levels of ERK1 protein and PDGF and Ras mRNAs increased significantly in the model group (0.19 ± 0.001 vs 0.71 ± 0.018, 0.12 ± 0.000 vs 0.42 ± 0.006, 0.12 ± 0.000 vs 0.44 ± 0.017, P < 0.05). Compared with the model group, Biejiajian pill significantly improved hepatic pathological changes and decreased the expression of ERK1 protein and PDGF and Ras mRNAs, and the efficacy of high-dose Biejiajian pill was the best.

CONCLUSION: Biejiajian pill can improve hepatic pathological changes in rats with hepatic fibrosis possibly via mechanisms associated with activating the Ras/ERK signaling pathway.

Effects of rosuvastatin on expression of angiotensin-converting enzyme 2 after vascular balloon injury in rats

Objective

To investigate the effects and mechanisms of rosuvastatin on angiotensin -converting enzyme 2 (ACE2) in the process of neointimal formation after vascular balloon injury in rats, and to explore the effects of ACE2 and rosuvastatin in restenosis.

Methods

Thirty-six Wistar rats were randomly allocated into three groups: control group (n = 12), surgery group (n = 12), and statin group (n = 12). Aortic endothelial denudation of rats was performed using 2F balloon catheters. At days 14 and 28 after injury, aortic arteries were harvested to examine the following. Intimal thickening was examined by hematoxylin and eosin staining. We measured angiotensin II (Ang II) and angiotensin 1-7 (Ang-[1–7]) levels by a radioimmunological method or enzyme-linked immunosorbent assay. Protein and mRNA expression of ACE2 and Ang II type 1 receptor (AT₁) were investigated by immunohistochemistry, Western blots, and Reverse transcriptase-polymerase chain reaction (RT-PCR). We measured changes in proliferating cell nuclear antigen (PCNA) by immunohistochemistry. The level of phosphorylated extracellular signal regulated kinase 1/2 (P-ERK1/2) was evaluated by Western blotting.

Results

Proliferation of vascular smooth muscle cells (VSMC) and intimal thickening were higher at day 14 after vascular balloon injury in the surgery group compared with the control group. Proliferation of VSMC was decreased by day 28 after injury, while intimal thickening continued. With rosuvastatin treatment, the extent of VSMC proliferation and intimal thickening was reduced at day 14 and 28 after injury. Ang II and P-ERK levels were significantly increased, Ang-(1–7) levels were significantly decreased, mRNA and protein expressions of ACE2 were significantly decreased, and AT₁ expression was significantly increased at days 14 and 28 after vascular balloon injury in the surgery group compared with the control group. PCNA expression was higher in the surgery group than in the control group, and it was significantly decreased after being given rosuvastatin. Expression of ACE2 mRNA and protein, and Ang-(1–7) levels were significantly increased, while AT₁ expression and levels of Ang II and P-ERK were significantly decreased in the statin group compared with the surgery group.

Conclusions

Expression of ACE2 mRNA and protein is decreased in the process of intimal thickening after balloon injury. The inhibitory effect of rosuvastatin on intimal thickening is related to upregulation of ACE2, an increase in Ang-(1–7), downregulation of AT₁, and activation of the P-ERK pathway.

Sorafenib inhibits growth and metastasis of hepatocellular carcinoma by blocking STAT3

AIM: To investigate the inhibitory role and the underlying mechanisms of sorafenib on signal transducer and activator of transcription 3 (STAT3) activity in hepatocellular carcinoma (HCC).

METHODS: Human and rat HCC cell lines were treated with sorafenib. Proliferation and STAT3 dephosphorylation were assessed. Potential molecular mechanisms of STAT3 pathway inhibition by sorafenib were evaluated. In vivo antitumor action and STAT3 inhibition were investigated in an immunocompetent orthotopic rat HCC model.

RESULTS: Sorafenib decreased STAT3 phosphorylation at the tyrosine and serine residues (Y705 and S727), but did not affect Janus kinase 2 (JAK2) and phospha-tase shatterproof 2 (SHP2), which is associated with growth inhibition in HCC cells. Dephosphorylation of S727 was associated with attenuated extracellular signal-regulated kinase (ERK) phosphorylation, similar to the effects of a mitogen-activated protein kinase (MEK) inhibitor U0126, suggesting that sorafenib induced S727 dephosphorylation by inhibiting MEK/ERK signaling. Meanwhile, sorafenib could also inhibit Akt phosphorylation, and both the phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002 and Akt knockdown resulted in Y705 dephosphorylation, indicating that Y705 dephosphorylation by sorafenib was mediated by inhibiting the PI3K/Akt pathway. Finally, in the rat HCC model, sorafenib significantly inhibited STAT3 activity, reducing tumor growth and metastasis.

CONCLUSION: Sorafenib inhibits growth and metastasis of HCC in part by blocking the MEK/ERK/STAT3 and PI3K/Akt/STAT3 signaling pathways, but independent of JAK2 and SHP2 activation.