Objective
The mechanisms of lung injury in acute respiratory distress syndrome (ARDS) are not well understood.Piezo1 was recently identified as a mechanotransduction protein. The present study found the expression of Piezo1 in type II pneumocytes and investigated its role in mediating ARDS-related lung injury.
Methods
Sprague-Dawley rats were used to establish an ARDS model, the expression of Piezo1,lung injuries, apoptosis as well as calcium influx were assessed.
Results
Piezo1 was expressed in type II pneumocytes as shown by immunofluorescence staining and expression was increased in the ARDS model. Knockdown of Piezo1 reduced apoptosis which was related to the elevation of Bcl-2.Calcium influx played a vital role in Piezo1-induced apoptosis.
Conclusion
Piezo1 was expressed in type II pneumocytes. Mechanical stretch of alveoli during ARDS induced activation of the Piezo1 channel,which resulted in calcium influx. The increased intracellular Ca2+ induced the apoptosis of type II pneumocytes, which may be related to the Bcl-2 pathway.
Electronic supplementary material
The online version of this article (10.1186/s12931-019-1083-1) contains supplementary material, which is available to authorized users.
In this paper, a novel prefabricated reinforced concrete (PC) self-sustaining beam-column connection for momentresisting frames was developed to achieve the targets of short erection time, high construction efficiency, low-cost and satisfactory seismic performance. The connection design eliminates the need of temporary supports for the PC beams and slabs during the assembly process in site, and reduces the amount of lateral supports for PC multi-storey columns and formwork for cast-in-place concrete. As the designed thickness of PC U-shells at the beam ends was about 1/3 of the beam width, there could be a marked effect on the achieved integrity of such connections, especially under seismic loading.To investigate the seismic performance of this PC connection, five large-scale PC self-sustaining beam-column connections specimens and one reference conventional RC connection were designed and tested under reverse cyclic loading. The test parameters included the length and area of the flexural reinforcing bars placed at the bottom of PC Ushells, and the anchorage measures (stirrups) inside the PC U-shell. The five precast specimens exhibited similar crack distributions and failure patterns due to the gap-opening between the PC beams and column surface, which was attributed to the reduced effective width and depth of beam cross-section. The test results showed that the use of longer flexural reinforcing bars had little influence on the load-carrying capacity, but contributed to the initial stiffness and energy dissipation capacity. The load-carrying capacity increased by 24% when the area of flexural reinforcing bars increased by 50% in the U-shell region. The incorporation of stirrups in the overlapping region of beam flexural reinforcing bars and longitudinal rebars improved their bond-slip behaviour in specimen PC-S. Compared with specimen PC-C, the energy dissipation capacity of specimen PC-S was improved by 16.5%. Finally, the failure pattern and load-carrying capacity of
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