[Effects of mechanical force on expressions of intercellular adhesion molecule-1 in cultured human alveolar type 2...

To explore the expression of intercellular adhesion molecule-1 (ICAM-1) in cultured human alveolar type 2 cells (A549) stimulated by mechanical force in vitro.

Cells were divided into 3 groups: a tensile stress group, a compressive stress group and a control group. The four-point bending system was used to stimulate A549 cells. The cells were stimulated by tensile stress or compressive stress respectively at the same magnitude of 1000 microstrain for 6 h. Sham cells in control group were not subjected to mechanical loading. The protein level and mRNA level of ICAM-1 were measured by Western blot and RT-PCR. Then an inhibitor was added to further explore the possible mechanism. The cells were divided into a tensile stress+inhibitor group, a compressive stress + inhibitor group and a control group. The cells were pretreated with PD98059, a specific inhibitor of extracellular signal-regulated kinase (ERK) for 60 min, and then stimulated respectively by tensile stress or compressive stress at the same magnitude of 1000 microstrain for 6 h or were not subjected to mechanical loading. ICAM-1 protein and mRNA concentrations were determined by Western blot and RT-PCR, respectively. The data were analyzed by one-way ANOVA and Student-Newman-Keuls were used to compare 2 means.

The expression of ICAM-1 protein in the tensile stress group (1.16+/-0.07) or the compressive stress group (1.05+/-0.02) were significantly higher than that of the control group (0.78+/-0.07, F=3.31, P<0.05), and the expression of ICAM-1 mRNA in the tensile stress group (1.42+/-0.05) or the compressive stress group (1.27+/-0.05) were also significantly higher than that of the control group (0.13+/-0.04, F=23.1, P<0.01). After pretreated with PD98059 for 60 min, the expression of ICAM-1 protein in the tensile stress group (1.62+/-0.10) was significantly higher than that of the control group (0.50+/-0.03, q=3.75, P<0.05), while there was no significant difference between the compressive stress group (0.60+/-0.03, q=0.32, P>0.05) and the control group. At the transcription level, the expression of ICAM-1 in the tensile stress group (1.57+/-0.03) was significantly higher than that of the control group (0.35+/-0.29, q=3.51, P<0.05), while there was no significant difference between the compressive stress group (0.46+/-0.03, q=0.32, P>0.05) and the control group.

Mechanical forces upregulate the expression of ICAM-1 in A549 cells. PD98059 partly inhibits the upregulation of ICAM-1 induced by mechanical forces. ERK pathway may be partly involved in signal transduction of mechanical force induced expression of ICAM-1 in A549 cells.