Chung Jung Liu

Akt mediates 17β-estradiol and/or estrogen receptor-α inhibition of LPS-induced tumor necresis factor-α expression and myocardial cell apoptosis by suppressing the JNK1/2-NFκB pathway

Evidence shows that women have lower tumour necrosis factor‐α (TNF‐α) levels and lower incidences of heart dysfunction and sepsis‐related morbidity and mortality. To identify the cardioprotective effects and precise cellular/molecular mechanisms behind estrogen and estrogen receptors (ERs), we investigated the effects of 17β‐estradiol (E2) and estrogen receptor α (ERα) on LPS‐induced apoptosis by analyzing the activation of survival and death signalling pathways in doxycycline (Dox)‐inducible Tet‐On/ERα H9c2 myocardial cells and ERα‐transfected primary cardiomyocytes overexpressing ERα. We found that LPS challenge activated JNK1/2, and then induced IκB degradation, NFκB activation, TNF‐α up‐regulation and subsequent myocardial apoptotic responses. In addition, treatments involving E2, membrane‐impermeable BSA‐E2 and/or Dox, which induces ERα overexpression, significantly inhibited LPS‐induced apoptosis by suppressing LPS‐up‐regulated JNK1/2 activity, IκB degradation, NFκB activation and pro‐apoptotic proteins (e.g. TNF‐α, active caspases‐8, t‐Bid, Bax, released cytochrome c, active caspase‐9, active caspase‐3) in myocardial cells. However, the cardioprotective properties of E2, BSA‐E2 and ERα overexpression to inhibit LPS‐induced apoptosis and promote cell survival were attenuated by applying LY294002 (PI3K inhibitor) and PI3K siRNA. These findings suggest that E2, BSA‐E2 and ERα expression exert their cardioprotective effects by inhibiting JNK1/2‐mediated LPS‐induced TNF‐α expression and cardiomyocyte apoptosis through activation of Akt.

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.

Lipopolysaccharide induces cellular hypertrophy through calcineurin/NFAT-3 signaling pathway in H9c2 myocardiac cells

Evidences suggest that lipopolysaccharide (LPS) participates in the inflammatory response in the cardiovascular system; however, it is unknown if LPS is sufficient to cause the cardiac hypertrophy. In the present study, we treated H9c2 myocardiac cells with LPS to explore whether LPS causes cardiac hypertrophy, and to identify the precise molecular and cellular mechanisms behind hypertrophic responses. Here we show that LPS challenge induces pathological hypertrophic responses such as the increase in cell size, the reorganization of actin filaments, and the upregulation of hypertrophy markers including atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) in H9c2 cells. LPS treatment significantly promotes the activation of GATA-4 and the nuclear translocation of NFAT-3, which act as transcription factors mediating the development of cardiac hypertrophy. After administration of inhibitors including U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor), CsA (calcineurin inhibitor), FK506 (calcineurin inhibitor), and QNZ (NFκB inhibitor), LPS-induced hypertrophic characteristic features, such as increases in cell size, actin fibers, and levels of ANP and BNP, and the nuclear localization of NFAT-3 are markedly inhibited only by calcineurin inhibitors, CsA and FK506. Collectively, these results suggest that LPS leads to myocardiac hypertrophy through calcineurin/NFAT-3 signaling pathway in H9c2 cells. Our findings further provide a link between the LPS-induced inflammatory response and the calcineurin/NFAT-3 signaling pathway that mediates the development of cardiac hypertrophy.

Cardiomyoblast apoptosis induced by insulin-like growth factor (IGF)-I resistance is IGF-II dependent and synergistically enhanced by angiotensin II

Objective: This study explores the synergistic effect of cardiomyoblast apoptosis induced by angiotensin II (Ang II) and Insulin-like growth factor (IGF)-I resistance, and elucidates the role of IGF-II via IGF-II receptor (R) and calcineurin pathways in apoptosis induced by Ang II and IGF-I resistance. Methods: Apoptosis of cultured cardiomyoblast H9c2 cells was assessed by DNA fragmentation on agarose gel electrophoresis, nuclear condensation stained with DAPI, and Western blot analysis of pro-apoptotic Bad and cytochrome c in various combinations of control, Ang II, antisense IGF (I or II), IGF (I or II) antibody, IGF (I or II) receptor (R) antibody, or calcineurin inhibitor (Cyclosporine A, (CsA)). Results: We found the following: (1) The combination of Ang II and IGF-I deficiencies had a synergistic effect on apoptosis, confirmed by DNA fragmentation, nuclei condensation, and increases in such pro-apoptotic proteins as Bad, cytochrome c, caspase 9, and caspase 3 in H9c2 cells. (2) IGF-II and IGF-IIR protein products were increased by antisense IGF-I and IGF-I resistance, but these IGF-II protein products were not affected by sense IGF-I and non-specific antibody IgG in H9c2 cells. (3) The alteration of Bad protein level and the release of cytochrome c, both induced by treatments containing combinations of Ang II and antisense IGF-I, IGF-I antibody or IGF-IR antibody, were inhibited by IGF-II antibody. (4) DNA fragmentation, Bad, and cytochrome c which was induced by treatments combining IGF-IR antibody with Ang II or combining IGF-IR antibody with IGF-II were remarkably attenuated by CsA. Conclusion: IGF-I deficiency and/or IGF-IR resistance induced apoptosis in cardiomyoblast cells. The apoptosis, which might have been caused by the upregulation of IGF-II and IGF-IIR genes possibly activated the downstream calcineurin pathway, was synergistically augmented by Ang II.

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.

JNK suppression is essential for 17β-Estradiol inhibits prostaglandin E2-Induced uPA and MMP-9 expressions and cell migration in human LoVo colon cancer cells

BackgroundEpidemiological 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 treatment is sufficient to inhibit prostaglandin E2 (PGE2)-induced cellular motility in human colon cancer cells.MethodsWe analyzed the protein expression of urokinase plasminogen activator (uPA), tissue plasminogen activator (tPA), matrix metallopeptidases (MMPs), plasminogen activator inhibitor-1 (PAI-1) and tissue inhibitor of metalloproteinases (TIMPs), and the cellular motility in PGE2-stimulated human LoVo cells. 17β-Estradiol and the inhibitors including LY294002 (Akt activation inhibitor), U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor), QNZ (NFκB inhibitor) and ICI 182 780 were further used to explore the inhibitory effects of 17β-estradiol on PGE2-induced LoVo cell motility. Students t-test was used to analyze the difference between the two groups.ResultsUpregulation 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. After administration of inhibitors including LY294002, U0126, SB203580, SP600125 or QNZ, we found that PGE2 treatment up-regulated uPA and MMP-9 expression via JNK1/2 signaling pathway, thus promoting cellular motility in human LoVo cancer cells. However, PGE2 treatment showed no effects on regulating expression of tPA, MMP-2, plasminogen activator inhibitor-1 (PAI-1), tissue inhibitor of metalloproteinase-1, -2, -3 and -4 (TIMP-1, -2, -3 and -4). We further observed that 17β-estradiol treatment inhibited PGE2-induced uPA, MMP-9 and cellular motility by suppressing activation of JNK1/2 in human LoVo cancer cells.ConclusionsCollectively, these results suggest that 17β-estradiol treatment significantly inhibits PGE2-induced motility of human LoVo colon cancer cells.

17β-Estradiol inhibits prostaglandin E2-induced COX-2 expressions and cell migration by suppressing Akt and ERK1/2 signaling pathways 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 treatment is sufficient to inhibit prostaglandin E2 (PGE2)-induced cellular motility in human colon cancer cells. Upregulation of cyclooxygenase-2 (COX-2) is reported to associate with the development of cancer cell mobility, metastasis, and subsequent malignant tumor. After administration of inhibitors including LY294002 (Akt activation inhibitor), U0126 (ERK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), SP600125 (JNK1/2 inhibitor), or QNZ (NFκB inhibitor), we found that PGE2 treatment increases COX-2 via Akt and ERK1/2 pathways, thus promoting cellular motility in human LoVo cancer cells. We further observed that 17β-estradiol treatment inhibits PGE2-induced COX-2 expression and cellular motility via suppressing activation of Akt and ERK1/2 in human LoVo cancer cells. Collectively, these results suggest that 17β-estradiol treatment dramatically inhibits PGE2-induced progression of human LoVo colon cancer cells.