Li Mien Chen

IGF-II/mannose-6-phosphate receptor signaling induced cell hypertrophy and atrial natriuretic peptide/BNP expression via Gαq interaction and protein kinase C-α/CaMKII activation in H9c2 cardiomyoblast cells

The role played by IGF-II in signal transduction through the IGF-II/mannose-6-phosphate receptor (IGF2R) in heart tissue has been poorly understood. In our previous studies, we detected an increased expression of IGF-II and IGF2R in cardiomyocytes that had undergone pathological hypertrophy. We hypothesized that after binding with IGF-II, IGF2R may trigger intracellular signaling cascades involved in the progression of pathologically cardiac hypertrophy. In this study, we used immunohistochemical analysis of the human cardiovascular tissue array to detect expression of IGF2R. In our study of H9c2 cardiomyoblast cell cultures, we used the rhodamine phalloidin staining to measure the cell hypertrophy and western blot to measure the expression of cardiac hypertrophy markers atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in cells treated with IGF-II. We found that a significant association between IGF2R overexpression and myocardial infarction. The treatment of H9c2 cardiomyoblast cells with IGF-II not only induced cell hypertrophy but also increased the protein level of ANP and BNP. Using Leu27IGF-II, an analog of IGF-II which interacts selectively with the IGF2R, to specifically activate IGF2R signaling cascades, we found that binding of Leu27IGF-II to IGF2R led to an increase in the phosphorylation of protein Kinase C (PKC)-alpha and calcium/calmodulin-dependent protein kinase II (CaMKII) in a Galphaq-dependent manner. By the inhibition of PKC-alpha/CaMKII activity, we found that IGF-II and Leu27IGF-II-induced cell hypertrophy and upregulation of ANP and BNP were significantly suppressed. Taken together, this study provides a new insight into the effects of the IGF2R and its downstream signaling in cardiac hypertrophy. The suppression of IGF2R signaling pathways may be a good strategy to prevent the progression of pathological hypertrophy.

Endothelin-1 promotes MMP-13 production and migration in human chondrosarcoma cells through FAK/PI3K/Akt/mTOR pathways

Tumor malignancy is associated with several cellular properties including proliferation and ability to metastasize. Endothelin‐1 (ET‐1) the most potent vasoconstrictor plays a crucial role in migration and metastasis of human cancer cells. We found that treatment of human chondrosarcoma (JJ012 cells) with ET‐1 increased migration and expression of matrix metalloproteinase (MMP)‐13. ET‐1‐mediated cell migration and MMP‐13 expression were reduced by pretreatment with inhibitors of focal adhesion kinase (FAK), phosphatidylinositol 3‐kinase (PI3K), Akt, and mammalian target of rapamycin (mTOR), as well as the NF‐κB inhibitor and the IκB protease inhibitor. In addition, ET‐1 treatment induced phosphorylation of FAK, PI3K, AKT, and mTOR, and resulted in increased NF‐κB‐luciferase activity that was inhibited by a specific inhibitor of PI3K, Akt, mTOR, and NF‐κB cascades. Taken together, these results suggest that ET‐1 activated FAK/PI3K/AKT/mTOR, which in turn activated IKKα/β and NF‐κB, resulting in increased MMP‐13 expression and migration in human chondrosarcoma cells. J. Cell. Physiol. 227: 3016–3026, 2012.

Eccentric cardiac hypertrophy was induced by long‐term intermittent hypoxia in rats

It is unclear whether cardiac hypertrophy and hypertrophy‐related pathways will be induced by long‐term intermittent hypoxia. Thirty‐six Sprague–Dawley rats were randomly assigned into three groups: normoxia, and long‐term intermittent hypoxia (12% O2, 8 h per day) for 4 weeks (4WLTIH) or for 8 weeks (8WLTIH). Myocardial morphology, trophic factors and signalling pathways in the three groups were determined by heart weight index, histological analysis, Western blotting and reverse transcriptase‐polymerase chain reaction from the excised left ventricle. The ratio of whole heart weight to body weight, the ratio of left ventricular weight to body weight, the gross vertical cross‐section of the heart and myocardial morphological changes were increased in the 4WLTIH group and were further augmented in the 8WLTIH group. In the 4WLTIH group, tumour necrosis factor‐α(TNFα), insulin‐like growth factor (IGF)‐II, phosphorylated p38 mitogen‐activated protein kinase (P38), signal transducers and activators of transcription (STAT)‐1 and STAT‐3 were significantly increased in the cardiac tissues. However, in the 8WLTIH group, in addition to the above factors, interleukin‐6, mitogen‐activated protein kinase (MEK)5 and extracellular signal‐regulated kinase (ERK)5 were significantly increased compared with the normoxia group. We conclude that cardiac hypertrophy associated with TNFα and IGF‐II was induced by intermittent hypoxia. The longer duration of intermittent hypoxia further activated the eccentric hypertrophy‐related pathway, as well as the interleukin 6‐related MEK5–ERK5 and STAT‐3 pathways, which could result in the development of cardiac dilatation and pathology.

RANKL increases migration of human lung cancer cells through intercellular adhesion molecule‐1 up‐regulation

Invasion of distant tissues by tumor cells is the primary cause of therapeutic failure in the treatment of malignant lung cancer cells. Receptor activator of nuclear factor‐κB ligand (RANKL) and its receptor, RANK, play a key role in osteoclastogenesis and tumor metastasis. Intercellular adhesion molecule‐1 (ICAM‐1, also called CD54), a member of the immunoglobulin supergene family, is an inducible surface glycoprotein that mediates adhesion‐dependent cell‐to‐cell interactions. The effects of RANKL on cell migration and ICAM‐1 expression in human lung cancer cells are largely unknown. We found that RANKL directed the migration and increased ICAM‐1 expression in human lung cancer (A549) cells. Pretreatment of A549 cells with the MAPK kinase (MEK) inhibitor PD98059 or U0126 inhibited RANKL‐mediated migration and ICAM‐1 expression. Stimulation of cells with RANKL increased the phosphorylation of MEK and extracellular signal‐regulating kinase (ERK). In addition, an NF‐κB inhibitor (PDTC) and IκB protease inhibitor (TPCK) also inhibited RANKL‐mediated cell migration and ICAM‐1 up‐regulation. Taken together, these results suggest that the RANKL and RANK interaction acts through MEK/ERK, which in turn activates NF‐κB, resulting in the activation of ICAM‐1 and contributing to the migration of human lung cancer cells. J. Cell. Biochem. 112: 933–941, 2011.

Activation of Insulin-Like Growth Factor II Receptor Induces Mitochondrial-Dependent Apoptosis through Gαq and Downstream Calcineurin Signaling in Myocardial Cells

In previous studies, we have found that IGF-II and IGF-II receptor (IGF-IIR) dose dependently correlated with the progression of pathological hypertrophy after complete abdominal aorta ligation, which may play a critical role in angiotensin II-induced cardiomyocyte apoptosis. However, the detail mechanisms of IGF-IIR in the regulation of cell apoptosis in response to IGF-II remain unclear. By using IGF-IR short hairpin RNA to inhibit IGF-IR expression and using Leu27 IGF-II analog to activate specifically the IGF-IIR, we investigated the role of IGF-II/IGF-IIR activation and its downstream signaling. Our results revealed that IGF-II synergistically increased the cell apoptosis induced by suppressing of IGF-IR in neonatal rat ventricular myocytes. After binding of Leu27IGF-II, IGF-IIR became associated with alpha-q polypeptide, acted like a protein-coupled receptor to activate calcineurin, led to the translocation of Bad into mitochondria and release of cytochrome c into cytoplasm, and contributed to mitochondrial-dependent apoptosis in neonatal rat ventricular myocytes. Furthermore, inhibition of IGF-IIR, alpha-q polypeptide, or calcineurin by RNA interference could block the Leu27IGF-II-induced cell apoptosis. Together, this study provides a new insight into the effects of the IGF-IIR and its downstream signaling in myocardial apoptosis. Suppression of IGF-IIR signaling pathways may be a good strategy for both the protection against myocardial cell apoptosis and the prevention of heart failure progression.

Lipopolysaccharide upregulates uPA, MMP-2 and MMP-9 via ERK1/2 signaling in H9c2 cardiomyoblast cells

Upregulation of urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA), and matrix metallopeptidases (MMPs) is associated with the development of myocardial infarction (MI), dilated cardiomyopathy, cardiac fibrosis, and heart failure (HF). Evidences suggest that lipopolysaccharide (LPS) participates in the inflammatory response in the cardiovascular system; however, it is unknown if LPS is sufficient to upregulate expressions and/or activity of uPA, tPA, MMP-2, and MMP-9 in myocardial cells. In this study, we treated H9c2 cardiomyoblasts with LPS to explore whether LPS upregulates uPA, tPA, MMP-2, and MMP-9, and further to identify the precise molecular and cellular mechanisms behind this upregulatory responses. Here, we show that LPS challenge increased the protein levels of uPA, MMP-2 and MMP-9, and induced the activity of MMP-2 and MMP-9 in H9c2 cardiomyoblasts. However, LPS showed no effects on the expression of tissue inhibitor of metalloproteinase-1, -2, -3, and -4 (TIMP-1, -2, -3, and -4). After administration of inhibitors including U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor), CsA (calcineurin inhibitor), and QNZ (NFκB inhibitor), the LPS-upregulated expression and/or activity of uPA, MMP-2, and MMP-9 in H9c2 cardiomyoblasts are markedly inhibited only by ERK1/2 inhibitors, U0126. Collectively, these results suggest that LPS upregulates the expression and/or activity of uPA, MMP-2, and MMP-9 through ERK1/2 signaling pathway in H9c2 cardiomyoblasts. Our findings further provide a link between the LPS-induced cardiac dysfunction and the ERK1/2 signaling pathway that mediates the upregulation of uPA, MMP-2 and MMP-9.

p38α MAPK mediates 17β-estradiol inhibition of MMP-2 and -9 expression and cell migration in human lovo colon cancer cells†

Epidemiological studies demonstrate that the incidence and mortality rates of colorectal cancer in women are lower than in men. However, it is unknown if 17β‐estradiol (E2) treatment is sufficient to inhibit cell proliferation and cell migration in human colon cancer cells. Up‐regulation of urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA), and matrix metallopeptidases (MMPs) is reported to associate with the development of cancer cell mobility, metastasis, and subsequent malignant tumor. In the present study, we treated human LoVo colon cancer cells with E2 to explore whether E2 down‐regulates cell proliferation and migration, and to identify the precise molecular and cellular mechanisms behind the down‐regulatory responses. Here, we found that E2 treatment decreased cell proliferation and cell cycle‐regulating factors such as cyclin A, cyclin D1 and cyclin E. At the same time, E2 significantly inhibited cell migration and migration‐related factors such as uPA, tPA, MMP‐2, and MMP‐9. However, E2 treatment showed no effects on upregulating expression of plasminogen activator inhibitor‐1 (PAI‐1), tissue inhibitor of metalloproteinase‐1, ‐2, ‐3, and ‐4 (TIMP‐1, ‐2, ‐3, and ‐4). After administration of inhibitors including QNZ (NFκB inhibitor), LY294002 (Akt activation inhibitor), U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor) or SP600125 (JNK1/2 inhibitor), E2‐downregulated cell migration and expression of MMP‐2 and MMP‐9 in LoVo cells is markedly inhibited only by p38 MAPK inhibitors, SB203580. Application of specific target gene siRNA (ERα, ERβ, p38α, and p38β) to LoVo cells further confirmed that p38 MAPK mediates E2/ERs inhibition of MMP‐2 and ‐9 expression and cell motility in LoVo cells.

PP2A mediates diosmin p53 activation to block HA22T cell proliferation and tumor growth in xenografted nude mice through PI3K–Akt–MDM2 signaling suppression

Hepatocellular carcinoma is a common type of cancer with poor prognosis. This study examines the in vitro and in vivo mechanisms of diosmin on human hepato-cellular carcinoma HA22T cell proliferation inhibition. HA22T cells were treated with different diosmin concentrations and analyzed with Western blot analysis, MTT assay, wound healing, flow cytometry, siRNA transfection assays and co-immuno-precipitation assay. The HA22T-implanted xeno-graft nude mice model was applied to confirm the cellular effects. Diosmin showed strong HA22T cell viability inhibition in a dose dependent manner and significantly reduced the cell proliferative proteins as well as inducing cell cycle arrest in the G2/M phase through p53 activation and PI3K-Akt-MDM2 signaling pathway inhibition. However, protein phosphatase 2A (PP2A) siRNA or PP2A inhibitor totally reversed the diosmin effects. The HA22T-implanted nude mice model further confirmed that diosmin inhibited HA22T tumor cell growth and down regulated the PI3K-Akt-MDM2 signaling and cell cycle regulating proteins, as well as activating PP2A and p53 proteins. Our findings indicate that HA22T cell proliferation inhibition and tumor growth suppression by diosmin are mediated through PP2A activation.

Thymoquinone induces apoptosis in oral cancer cells through p38β inhibition

Oral cancer is a common malignancy associated with high morbidity and mortality. While p38 MAPK is reported to be involved in different cellular activities such as proliferation and differentiation, reports rarely define the roles of the individual members of the p38 MAPK family in cancer. We used two unique cell lines developed by our lab representing chemically induced oral cancer cells (T28) and non-tumor cells (N28) obtained from tissues surrounding the induced cancer as a model to screen out whether p38 MAPK is involved in the malignant transformation processes. The results suggest an association between p38β not p38α and oral cancer development. Additionally, the anti-cancer activity of thymoquinone (TQ) was screened out and we found evidences suggesting that the anti-tumor activity of TQ may be attributed to the downregulation of p38β MAPK.

Leu27IGF2 plays an opposite role to IGF1 to induce H9c2 cardiomyoblast cell apoptosis via Gaq signaling

This study examines the role of IGF2/mannose 6-phosphate receptor (IGF2R) signaling in the signaling transduction regulation and cell apoptosis in H9c2 cardiomyoblast cells. However, it is difficult to recognize the distinct activation of IGF2 signaling without interfacing with IGFI receptor (IGF1R) after exposure to IGF2. Leu27IGF2, an analog of IGF2 that interacts selectively with the IGF2R, was used to specifically activate IGF2R signaling in this study. DNA fragmentation and TUNEL assay revealed that in contrast to IGF1 treatment preventing angiotensin II and AG1024-induced cell apoptosis, Leu27IGF2 appears to synergistically increase apoptosis in those cells. We further found cell apoptosis induction and an increase in the active form of caspase 3 in the treatment of cells with Leu27IGF2, but not IGF1. To detect the interaction between IGF2R and Galphaq using the immunoprecipitation assay, we found that IGF2R could directly interact with Galphaq and after treatment with Leu27IGF2 the binding ability of Galphaq to IGF2R had increased. This sequentially resulted in the phosphorylation of phospholipase C-beta, a key downstream modulator of Galphaq, on serine 537. Moreover, disruption of the Galphaq protein by small interferon RNA reduced the cell apoptosis induced by Leu27IGF2. Our findings demonstrate that IGF2R activation appears to induce cell apoptosis via Galphaq-deriving signaling cascades and its effect is completely different from IGF1R survival signaling.