机械牵张诱发肺泡Ⅱ型上皮细胞黏附相关的抗损伤机制研究

Mechanical stretch induced anti-injury mechanism of alveolar typeⅡ cells through cell adhesion changing

目的通过对大鼠原代肺泡Ⅱ型上皮(ATⅡ)细胞进行机械牵张研究,探讨在牵张过程中黏附相关的抗损伤机制。方法采用活性荧光染色测定机械牵张所致ATⅡ细胞的死亡率,采用黏着斑染色相对定量法测定细胞的黏附水平,通过改变细胞外二价阳离子及黏附中和抗体调节细胞的黏附水平后,测定牵张后细胞死亡率。结果过度牵张导致细胞的死亡发生在牵张的早期(P<0.05),且不随时间的延长而累积(P>0.05),同时在牵张早期细胞黏着斑快速解聚,细胞表现出明显的回缩,黏附水平下降,推测牵张后细胞的黏附改变可能是细胞的抗损伤机制;通过调节细胞的黏附状态发现细胞黏附增强,牵张后细胞死亡率明显增加(P<0.01),而一定程度的黏附降低,牵张后细胞的死亡率明显下降(P<0.01)。结论黏附与细胞外基质的应力传递密切相关,牵张后ATⅡ细胞利用脱黏过程卸载应力以避免细胞应力损伤。

Objective To investigate the role of primary rat alveolar typeⅡ（ATⅡ）cells adhesion in avoiding mechanical stretch-induced cell injury.Methods The isolated ATⅡ cells were subjected to tonic stretch of37%increase in surface area（△SA）biaxial strain.Tonic stretch-induced cell death with increasing time was detected by the viability staining assay.The cell morphologic remodeling and level of focal adhesion（FA）were detected by the immunofluorescence assay.In addition,we changed cells adhesion by altering bivalent cation levels in the culture medium and applying an integrin neutralizing antibody.Stretch-induced cell death with different level of cell adhesion was detected by the viability staining assay.Results The viability assay showed that ATⅡ cell death was not increasing with time under tonic stretch（P〉0.05）.Immunofluorescence assay showed that ATⅡ cells experienced an expansion-contraction-reexpansion response to tonic stretch and cells′partial FA disassembled during contraction.Moreover,the viability assay of changing cells adhesion showed that facilitated adhesion affinity promoted cell death under tonic stretch（P〈0.01）,while lower level of adhesion protected the cells from stretch-induced stress failure（P〈0.01）.Conclusion These results indicate that ATⅡ cells adhesion play an important role in cell anti-injury mechanism.ATⅡ cells may avoid stress failure via cells′transiently disassembling FAs to unload mechanical forces in tonic stretch.