ABSTRACT
Objective To explore the activate process of lymphocyte function-associated antigen 1 (LFA-1) triggered by chemokine under shear stresses. Methods Jurkat cells were perfused over ICAM-1 in the parallel-plate flow under 10-30 mPa shear stresses. The effects of soluble and immobilized Chemokines on transient adhesion behavior of Jurkat cells were observed and analyzed to obtain their tether characteristics. Results The immobilized CXCL12 could mediate brief tether (0.13-0.2 s) of Jurkat cells under flow. Only immobilized CXCL12 could effectively activate LFA-1 on Jurkat cells to bind ICAM-1, and then enhance cell adhesion fraction and greatly prolong the tether time (0.8-1.2 s). Two distinct activation states of LFA-1/ICAM-1 were reflected by their dissociation rate k1 (1.09-1.24 s-1) and k2 (0.28-0.7 s-1), respectively. The shear stress would affect the transient adhesion behavior of cells through regulation of k2 and β (the contribution ratio of high affinity to total tether time). Conclusions Shear stress can rapidly trigger LFA-1 activation in 0.2 s through G protein coupled receptors induced by chemokine CXCL12, and further regulate the whole adhesion process of leukocyte. These research findings will contribute to further understanding the integrin activation mechanism of chemokine-force cooperative regulation.
ABSTRACT
Objective To explore the activate process of lymphocyte function-associated antigen 1 (LFA-1) triggered by chemokine under shear stresses.Methods Jurkat cells were perfused over ICAM-1 in the parallel-plate flow under 10-30 mPa shear stresses.The effects of soluble and immobilized Chemokines on transient adhesion behavior of Jurkat cells were observed and analyzed to obtain their tether characteristics.Results The immobilized CXCL12 could mediate brief tether (0.13-0.2 s) of Jurkat cells under flow.Only immobilized CXCL12 could effectively activate LFA-1 on Jurkat cells to bind ICAM-1,and then enhance cell adhesion fraction and greatly prolong the tether time (0.8-1.2 s).Two distinct activation states of LFA-1/ICAM-1 were reflected by their dissociation rate k1 (1.09-1.24 s-1) and k2 (0.28-0.7 s-1),respectively.The shear stress would affect the transient adhesion behavior of cells through regulation of k2 andβ (the contribution ratio of high affinity to total tether time).Conclusions Shear stress can rapidly trigger LFA-1 activation in 0.2 s through G protein coupled receptors induced by chemokine CXCL12,and further regulate the whole adhesion process of leukocyte.These research findings will contribute to further understanding the integrin activation mechanism of chemokine-force cooperative regulation.
ABSTRACT
Objective To reveal the mechanical regulation mechanism for activation of lymphocyte function-associated antigen 1 (LFA-1). Methods The LFA-1 expressed on Jurkat cell surface was pre-activated by Mg2+ from quiescent-to intermediate-affinity state, and the tether events of Jurkat cells under different wall shear stresses (4.5-10 mPa) were observed and analyzed by flow chamber experiment. Meanwhile, a probabilistic model of integrin affinity jumping was established. Results The affinity jumping model was well fitted with the data obtained from flow chamber experiment. Under flowing loads, LFA-1 from intermediate to high-affinity state was observed, with prolonging of the adhesion bonds. The probability of tether event was 15%-26%. LFA-1 at high-affinity state contributed a significant fraction (about 26%-40%) of the bond lifetime. The off-rate of LFA-1 at high-affinity state was slower by 19%-65% as compared to that at intermediate-affinity state. Dissociating of ICAM-1 from LFA-1 was force-dependent and governed either by slip-bond at intermediate-affinity state or by catch-slip bond at high-affinity state. Conclusions The force-induced activation of LFA-1 mediates the slower rolling and firm adhesion of the cells. This research finding will further the understanding of inflammatory response events of circulating leukocytes, and contribute to the discovery of new antibody drug targets for the associated diseases.