EFFECTS OF SHEAR STRESS ON PLATELET - POLYMORPHONUCLEAR LEUKOCYTE INTERACTIONS (LTB(4), AGGREGATION)

[摘要] The effects of shear stress on platelet - polymorphonuclear leukocyte (PMNL) interactions were studied to ascertain whether mechanical trauma induces PMNL aggregation or degranulation. PMNL suspensions were exposed to shear stresses up to 150 dynes/cm(;;2) at room temperature for 1 minute. PMNL responses were monitored by the following measurements. The large particle percentage was calculated from Coulter counter data to indicate shear-induced aggregation. (beta)-glucuronidase in the extracellular fluid was assayed to indicate azurophilic granule release. Lactate dehydrogenase (LDH) release was measured to indicate cell lysis. PMNL suspensions in buffer showed no aggregate formation or enzyme release at shear stresses below 150 dynes/cm(;;2) for an exposure time of 1 minute. However, supernatant plasma from sheared platelet rich plasma (PRP) initiated PMNL aggregation and (beta)-glucuronidase release at this shear stress. In contrast, platelet release factors, such as ADP and serotonin did not cause PMNL aggregation. The use of a cyclooxygenase inhibitor (aspirin) did not suppress the aggregation of PMNLs after shear. However, preincubation with lipoxygenase inhibitors (U-60257 and nordihydroguaiaretic acid) suppressed aggregation and enzyme release. The shear-induced enzyme release was enhanced by cytochalasin B and heparinized samples showed greater effects than citrated samples. The effects of shear stress on whole blood aggregation also were studied. The total aggregate volume and mean channel number were calculated. Blood samples sheared at 37(DEGREES)C showed much less aggregation than those sheared at room temperature. The total aggregate volume and mean aggregate size were decreased at the increased temperature. Heparinized blood was more sensitive to shear stress than citrated samples. A cyclooxygenase inhibitor (aspirin) was ineffective in reducing shear-induced aggregation. However, a lipoxygenase inhibitor (nordihydroguaiaretic acid) was effective in reducing aggregate size. The formation of arachidonic acid metabolities activated by shear stress was documented by reversed phase - high performance liquid chromatography (RP-HPLC). Thus, an interaction between C-12 and C-5 lipoxygenase enzymes can promote the formation of leukotriene B(,4)(LTB(,4)) and these data support the possibility of cooperation between platelet and PMN leukocyte arachidonic acid metabolites leading to a mechanically induced cell activation. (Abstract shortened with permission of author.)

[发布机构] Rice University