cytochalasin-d and Coronary-Disease

Genetic factors are believed to influence the development of arterial thromboses. Because integrin alpha(IIb)beta(3) plays a crucial role in thrombus formation, we analyzed receptor adhesive properties using Chinese hamster ovary and human kidney embryonal 293 cells overexpressing the Pl(A1) or Pl(A2) polymorphic forms of alpha(IIb)beta(3). Soluble fibrinogen binding was no different between Pl(A1) and Pl(A2) cells, either in a resting state or when alpha(IIb)beta(3) was activated with anti-LIBS6. Pl(A1) and Pl(A2) cells bound equivalently to immobilized fibronectin. In contrast, significantly more Pl(A2) cells bound to immobilized fibrinogen in an alpha(IIb)beta(3)-dependent manner than did Pl(A1) cells. Disruption of the actin cytoskeleton by cytochalasin D abolished the increased binding of Pl(A2) cells. Compared with Pl(A1) cells, Pl(A2) cells exhibited a greater extent of polymerized actin and cell spreading, enhanced tyrosine phosphorylation of pp125(FAK), and greater fibrin clot retraction. These adhesion differences appear to depend on a signaling mechanism sensitive to receptor occupancy. Thus, the Pl(A2) polymorphism altered integrin-mediated functions of adhesion, spreading, actin cytoskeleton rearrangement, and clot retraction.

Topics: Actins; Alleles; Amino Acid Substitution; Animals; Antigens, Human Platelet; Biopolymers; Cell Adhesion Molecules; Cell Line; Cell Size; CHO Cells; Clot Retraction; Coronary Disease; Cricetinae; Cricetulus; Cytochalasin D; Cytoskeleton; Female; Fibrinogen; Focal Adhesion Kinase 1; Focal Adhesion Protein-Tyrosine Kinases; Genetic Predisposition to Disease; Humans; Kidney; Male; Phosphorylation; Platelet Aggregation; Platelet Glycoprotein GPIIb-IIIa Complex; Point Mutation; Polymorphism, Genetic; Protein Isoforms; Protein Processing, Post-Translational; Protein-Tyrosine Kinases; Risk Factors; Signal Transduction

Recovery from ischaemia in heart tissue can be accelerated by addition of precursors of ATP such as AMP to the coronary circulation. Endocytosis in capillary endothelia is also stimulated by AMP; therefore endocytosis may be important in the transport of AMP from the circulation into myocytes. Alternatively, the increase in endocytotic transport itself could be responsible for accelerated recovery, irrespective of the stimulating agent. The effects of sham, AMP, cytochalasin-D (an inhibitor of endocytosis), and cytochalasin-D + AMP infusates given prior to, during, and following a 15 min ischaemic episode, were examined. AMP accelerated biochemical and functional recovery after episodes of ischaemia and stimulated endocytosis in coronary capillaries. Cytochalasin-D strongly inhibited contractility before, during, and after ischaemia, and similarly depressed ATP and creatine phosphate levels. Cytochalasin-D also strongly inhibited endocytosis and caused swelling of the capillary endothelium. When cytochalasin-D and AMP were provided together, the beneficial effects of AMP were only partially inhibited by cytochalasin-D. In fact, AMP was able to reverse most of the effects of cytochalasin-D including the inhibition of endocytosis. This suggests accelerated recovery of ischaemic myocytes requires precursors of ATP such as AMP, and the stimulation of endocytosis may abet transport of these precursors, or may be a spurious phenomenon.

Topics: Adenosine Monophosphate; Adenosine Triphosphate; Animals; Coronary Disease; Cytochalasin D; Cytochalasins; Dogs; Endocytosis; Heart; Microscopy, Electron; Myocardium; Phosphocreatine