OBJECTIVETo discuss the important role of actin polymerization in calcium ionophore A23187-induced human acrosome reaction and its mechanism.

METHODSEach spermatozoon specimen was divided into five groups, treated with A23187 3 micromol/L in Group A, Phalloidin 40 micromol/L and A23187 3 micromol/L in Group B, SLO 0.5 U/ml and A23187 3 micromol/L in Group C, SLO 0.5 U/ ml, Phalloidin 40 micromol/L and A23187 3 micromol/L in Group D, and nothing added in Grpup E. Then the percentage of the human acrosome reaction was assessed with Rhodamine-PSA (10 microg/ml).

RESULTSThe difference of the human spermatozoon acrosome reaction was significant (P < 0.01) among the 5 groups with or without SLO, Phalloidin and calcium ionophore A23187 but not between Groups A and B (P > 0.01).

CONCLUSIONPhalloidin does not work on the acrosome reaction of intact human spermatozoa, but in an SLO-permeabilized human spermatozoal model, it can obviously decrease the percentage of human spermatozoon acrosome reaction, which indicates that the polymerization of actin plays an important role in the course of human spermatozoon acrosome reaction, and mostly acts on the acrosome inside.

Acrosome Reaction ; drug effects ; Actins ; physiology ; Bacterial Proteins ; pharmacology ; Calcimycin ; pharmacology ; Cells, Cultured ; Humans ; Ionophores ; pharmacology ; Male ; Phalloidine ; pharmacology ; Spermatozoa ; drug effects ; physiology ; Streptolysins ; pharmacology

The present study aimed to explore whether the stretch of ischemic myocardium could modulate the electrophysiological characteristics via mechanoelectric feedback (MEF), as well as the effect of phalloidin on the electrophysiological changes. Thirty-two Wistar rats were randomly divided into 4 groups: control group (n=9), phalloidin group (n=7), myocardial infarction (MI) group (n=9), MI + phalloidin group (n=7). The acute myocardial infarction (AMI) was conducted by ligation of the left anterior descending (LAD) coronary artery for 30 min in isolated rat heart. The volume alternation of a water-filled latex balloon in the left ventricle produced the stretch of myocardium. After perfused on Langendorff, the isolated hearts were stretched for 5 s by an inflation of 0.1, 0.2 and 0.3 mL separately and the effect of stretch was observed for 30 s, including the left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), ±dp/dt(max), monophasic action potential duration at 90% repolarization (MAPD90), and occurrence of premature ventricular beats (PVB) and ventricular tachycardia (VT). The stretch caused an increase of MAPD(90) in both control and MI rats (P<0.05, P<0.01). Moreover, MAPD(90) in MI group increased more significantly than that in the control group at the same degree of stretch (P<0.05, P<0.01). Phalloidin (1 μmol/L) had no effect on MAPD(90) in basal state. After stretch, MAPD(90) in phalloidin group slightly increased but was not significantly different from that in the control group. However, phalloidin reduced MAPD(90) in infarcted myocardium, especially when ΔV=0.3 mL (P<0.05). The incidence rates of PVB and VT in MI group were higher than that in the control group (both P<0.01). And there was no significant difference in the incidence rates of PVB and VT between phalloidin group and control group. Phalloidin inhibited the occurrence of PVB and VT in infarcted hearts (both P<0.01). LVSP and +dp/dt(max) in MI group obviously decreased (P<0.01 vs control). With application of phalloidin, LVSP slightly, but not significantly increased in infarcted hearts, while -dp/dt(max) significantly increased (P<0.05). It is suggested that MI facilitates the generation and maintenance of malignant arrhythmias, while phalloidin obviously inhibits the occurrence of arrhythmias.
Action Potentials ; Animals ; Arrhythmias, Cardiac ; prevention & control ; Coronary Vessels ; Heart ; drug effects ; physiopathology ; Heart Ventricles ; Myocardial Infarction ; physiopathology ; Phalloidine ; pharmacology ; Rats ; Rats, Wistar

Brain ; Cholesterol ; chemistry ; Cytoskeleton ; drug effects ; Endothelial Cells ; cytology ; metabolism ; Hemolysin Proteins ; chemistry ; pharmacology ; Humans ; Phalloidine ; pharmacology ; Pseudopodia ; drug effects ; Stress Fibers ; drug effects ; rac1 GTP-Binding Protein ; metabolism ; rhoA GTP-Binding Protein ; metabolism

OBJECTIVETo investigate the dose and time-dependent effects of lipopolysaccharide (LPS) on cytoskeletal F-acitn and G-actin reorganizations by visualizing their distribution and measuring their contents in human umbilical vein endothelial cell line ECV-304.

METHODSF-actin was labeled with rhodamine-phalloidin and G-actin with deoxyribonuclease I (DNase I)conjugated with fluorescein isothiocyanate (FITC). Contents of cytoskeletal proteins were obtained by flow cytometry.

RESULTSF-actin was mainly distributed peripherally in endothelial cells under normal conditions. LPS stimulation caused the formation of stress fibers and filopodia. G-actin was normally seen in perinuclear and nuclear areas in control ECV-304 cells. Under LPS stimulation, G-actin dots appeared in the cytoplasmic region. The actin disorganization was accompanied by the time- and dose- dependent decrease in F-actin pool and increase in G-actin pool.

CONCLUSIONSLPS can induce characteristic morphological alterations of actin cytoskeleton and formation of intercellular gap in endothelial cells, accompanied by changes in F-actin and G-actin pools.

Actins ; drug effects ; Analysis of Variance ; Cells, Cultured ; Deoxyribonuclease I ; Dose-Response Relationship, Drug ; Endothelial Cells ; chemistry ; Escherichia coli ; Fluorescein-5-isothiocyanate ; Fluorescent Dyes ; Humans ; Lipopolysaccharides ; pharmacology ; Phalloidine ; Rhodamines ; Umbilical Veins ; cytology

The present study aimed to determine the role of Rho/Rho kinase (Rho/ROCK) phosphorylation on advanced glycation end products (AGEs)-induced morphological and functional changes in human dermal microvascular endothelial cells (HMVECs). HMVECs were respectively incubated with different concentrations of AGEs-modified human serum albumin (AGEs-HSA) for different time. In some other cases, HMVECs were pretreated with ROCK inhibitors (H-1152 or Y-27632). The morphological changes of F-actin cytoskeleton were visualized by rhodamine-phalloidin staining and the phosphorylation of Rho and ROCK were determined by Western blot. Endothelial monolayer permeability was assessed by measuring the flux of FITC-albumin across the endothelial cells. The results showed that the distribution of F-actin was significantly altered by AGEs-HSA in time and dose-dependent patterns. These effects were inhibited by ROCK inhibitors. The phosphorylation of Rho and RCOK was remarkably increased by AGEs-HSA treatment while total Rho and ROCK protein levels were not affected. The permeability of endothelial monolayer was dramatically increased by AGEs-HSA, and both ROCK inhibitors (H-1152 or Y-27632) attenuated these hyperpermeability responses. The results obtained suggest that the phosphorylation of Rho/ROCK plays an important role in AGEs-induced morphological and functional alterations in HMVECs.
1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine ; analogs & derivatives ; pharmacology ; Actin Cytoskeleton ; metabolism ; Actins ; metabolism ; Amides ; pharmacology ; Endothelial Cells ; metabolism ; Endothelium, Vascular ; cytology ; Fluorescein-5-isothiocyanate ; analogs & derivatives ; metabolism ; Glycation End Products, Advanced ; pharmacology ; Humans ; Phalloidine ; analogs & derivatives ; Phosphorylation ; Pyridines ; pharmacology ; Rhodamines ; Serum Albumin ; metabolism ; pharmacology ; Serum Albumin, Human ; Signal Transduction ; rho-Associated Kinases ; metabolism

CD98, a disulfide-linked 125-kDa heterodimeric type II transmembrane glycoprotein, regulates beta 1 integrin- mediated cell adhesion. However, the molecular mechanisms underlying CD98-mediated activation of beta 1 integrin are presently unclear. In this study, the effects of CD98 signaling on the expression and clustering of beta 1 integrin were investigated. Activation of CD98 augmented surface expression of beta 1 integrin on MCF-7 cells. Cross-linking CD98 induced clustering of beta 1 integrins. Inhibition of phosphorylation of focal adhesion kimase (FAK) by PP2, an inhibitor of Src family kinase, reduced cell-extracellular matrix adhesion, but not surface expression and clustering of beta1 integrin on MCF-7 cells. This result was confirmed by over-expression of dominant negative forms of FAK. In addition, phalloidin or cytochalasin D inhibited CD98-mediated induction of cell-ECM adhesion, but not surface expression and clustering of b1 integrins. The inhibitory effects of PP2, cytochalasin D or phalloidin on CD98-stimulated cell adhesion were diminished by pretreatment of cells with Mn2+, which is shown to induce conformational change of integrins. These results provide the first evidence that CD98 activation increases not only beta1 integrin affinity but also its surface expression and clustering and the latter is independent of FAK/Src and cytoskeleton.
Antigens, CD29/*biosynthesis/genetics ; Antigens, CD98/agonists/*metabolism ; Cell Line, Tumor ; Cytochalasin D/pharmacology ; Cytoskeleton/drug effects/enzymology ; Focal Adhesion Kinase 2/genetics/*metabolism ; Focal Adhesions/drug effects/enzymology ; Humans ; Microscopy, Confocal ; Multiprotein Complexes/*biosynthesis/genetics ; Mutant Proteins/genetics/metabolism ; Phalloidine/pharmacology ; Phosphorylation/drug effects ; Protein Binding ; Pyrimidines/pharmacology ; Signal Transduction/physiology ; Transfection