Catalytic Domain ; genetics ; Dual Specificity Phosphatase 3 ; chemistry ; genetics ; metabolism ; Genetic Code ; Humans ; Mutation ; Phosphorylation ; Protein Conformation ; Signal Transduction ; genetics ; Structure-Activity Relationship ; Tyrosine ; analogs & derivatives ; chemistry ; genetics

BACKGROUNDSildenafil is one of the selective phosphodiesterase 5 inhibitors that has been proven by many investigators to suppress growth factor stimulated (e.g. platelet-derived growth factor (PDGF) or epidermal growth factor (EGF)) proliferation and hypertrophy of pulmonary artery smooth muscle cells (PASMCs) via cGMP/cGKIa pathway. Serotonin promotes cell cycle progression leading to cell mitogenesis and plays a key role in the pathogenesis of pulmonary artery hypertension. The role of sildenafil in proliferation of PASMCs induced by serotonin has not been investigated so far. In this study we explored the underlying mechanism of the effect of sildenafil on serotonin induced proliferation of porcine PASMCs.

METHODSPASMCs were cells from primary cultures by the explant method from the pulmonary artery of swine and cells at passage 3 - 5 were used in this study. MTT colorimetric assay and flow cytometry analysis were used to evaluate the cell proliferation and alterations in cell cycle progression respectively. Western blotting analysis was applied to determine the expression of phosphorylated extracellular signal-regulated kinase (ERK), proliferating cell nuclear antigen (PCNA) and mitogen activated protein kinase (MAPK) phosphatase-1 (MKP-1).

RESULTSSerotonin (10 µmol/L) induced the upregulation of phosphorylation of ERK1/ERK2 and PCNA, an increase in the percentage of cells in S phase and subsequent cell proliferation. Pretreatment with 1 µmol/L sildenafil potentiated the phosphorylation of ERK1/ERK2, an increase in the percentage of cells in S phase and cell proliferation, compared with serotonin stimulation alone (P < 0.05). Furthermore, 30-minute pretreatment with 10 µmol/L U0126, specific antagonist for ERK kinase (MEK) prevented the increase in phosphorylation of ERK1/ERK2 and abolished cell cycle progression and the proliferation of PASMCs induced by sildenafil.

CONCLUSIONThis study shows that sildenafil potentiated the proliferative effect of serotonin on PASMCs via phosphorylation of ERK1/ERK2.

Animals ; Blotting, Western ; Cell Proliferation ; drug effects ; Cells, Cultured ; Dual Specificity Phosphatase 1 ; metabolism ; Mitogen-Activated Protein Kinase 1 ; metabolism ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Myocytes, Smooth Muscle ; cytology ; Phosphorylation ; drug effects ; Piperazines ; pharmacology ; Proliferating Cell Nuclear Antigen ; metabolism ; Pulmonary Artery ; cytology ; Purines ; pharmacology ; Serotonin ; pharmacology ; Sildenafil Citrate ; Sulfones ; pharmacology ; Swine

AIM AND METHODSTo investigate the role of mitogen-activated protein kinase phosphatase-1 (MKP-1) in the regulation of cells proliferation, the expression of MKP-1 and extracellular signal-regulated kinase-1 (ERK-1) in heart and aorta of spontaneous hypertensive rat (SHR) and WKY were studied. We also investigated the effect of MKP-1 genes,which were transfected into vascular smooth muscle cells (VSMC) using the classical calcium phosphate coprecipitation technique, on the incorporation of 3H-TdR in VSMC stimulated by angiotensin II (Ang II).

RESULTS(1) Compared with that of WKY, MKP-1 expression in heart and aorta were significantly decreased by 53% (P < 0.01) and 45% (P < 0.01) in SHR, respectively. While the expression of ERK-1 in heart and aorta of SHR were higher than that of WKY (P < 0.01). The ratio of ERK-1/MKP-1 in heart and aorta of SHR were significantly higher than that of WKY. (2) 3H-TdR incorporation in VSMC stimulated by Ang II (10(-7) mol/L) was increased by 207% (P < 0.01), compared with control group. In the transfected cells with wild MKP-1 gene, Ang II-induced incorporation of 3H-TdR lowered 63%, compared with untransfected cells (P < 0.05). There were no marked inhibitive role between mutant MKP-1-transfected cells and blank vector-transfected cells in response to Ang II, compared with Ang II group (P > 0.05).

CONCLUSIONThese results showed that the expression of ERK-1 in heart and aorta isolated from SHR, which stimulated proliferation and hypertrophy of cells, is higher than that of MKP-1 which dephosphorylates and inactivated ERK-1. In addition, MKP-1 significantly inhibits Ang II-stimulated proliferation of VSMC.

Angiotensin II ; pharmacology ; Animals ; Aorta ; cytology ; enzymology ; Cell Proliferation ; Cells, Cultured ; Dual Specificity Phosphatase 1 ; metabolism ; Heart ; Hypertension ; metabolism ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Muscle, Smooth, Vascular ; cytology ; Myocardium ; cytology ; enzymology ; Myocytes, Smooth Muscle ; drug effects ; metabolism ; Rats ; Rats, Inbred SHR ; Rats, Inbred WKY

OBJECTIVETo investigate the effects of protein tyrosine phosphatase-SHP2 and dual-specificity MAPK phosphatase-MKP5 on the activation of MAPKs and cell invasion induced by P2Y purinergic receptor in human prostate cancer cell lines with different metastatic potentials.

METHODSThe wide type (-wt) SHP2, mutant type (-cs) SHP2 and wide type (-wt) MKP5 cDNA expression vectors were constructed and stably transfected into 1E8 cells (highly metastatic) and/or 2B4 cells (non-metastatic). The tyrosine phosphorylation of SHP2 was examined by immunoprecipitation. The activation of ERK1/2 and p38 induced by P2Y receptor agonist ATP was analyzed by Western blot with phospho-specific antibodies against the dually phosphorylated, active forms of ERK1/2 and p38. The in-vitro invasive ability through Matrigel was measured by boyden-chamber assay.

RESULTSATP induced significant SHP2 phosphorylation, which was stronger and lasted longer in 1E8 than in 2B4. SHP2-wt enhanced the ERK1/2 activation induced by ATP in 2B4 cells, while SHP2-cs delayed and decreased this effect in 1E8 cells. Both SHP2-wt and SHP2-cs had no obvious influence on p38 activation. ATP stimulated cell invasion of both 1E8 and 2B4, while transfection of SHP2-wt into 2B4 cells further increased the invasive-stimulating ability of ATP (18.7% increase compared with ATP treatment alone). Transfection of SHP2-cs into 1E8 cells, however, antagonized the invasive-stimulating ability of ATP (40.9% decrease compared with ATP treated group). Up-regulation of MKP5-wt inhibited phosphorylation of p38 by ATP and reduced cell invasion stimulated by ATP (22.4% and 28.7% decrease compared with ATP treated group of 1E8 and 2B4, respectively).

CONCLUSIONSBoth SHP2 and MKP5 play some roles in P2Y receptor-mediated activation of MEK/ERK, p38 signaling pathways and prostate cancer invasion. SHP2 positively regulates ERK activation and prostate cancer invasion, whereas MKP5 inhibits the invasion by suppressing p38 activation.

Adenosine Triphosphate ; pharmacology ; Cell Line, Tumor ; DNA, Complementary ; genetics ; Dual-Specificity Phosphatases ; Genetic Vectors ; Humans ; Intracellular Signaling Peptides and Proteins ; genetics ; metabolism ; Male ; Mitogen-Activated Protein Kinase 1 ; metabolism ; Mitogen-Activated Protein Kinase 3 ; metabolism ; Mitogen-Activated Protein Kinase Phosphatases ; Neoplasm Invasiveness ; Phosphorylation ; Prostatic Neoplasms ; metabolism ; pathology ; Protein Tyrosine Phosphatase, Non-Receptor Type 11 ; Protein Tyrosine Phosphatases ; genetics ; metabolism ; Receptors, Purinergic P2 ; physiology ; Signal Transduction ; Transfection ; p38 Mitogen-Activated Protein Kinases ; metabolism