Role of CaN/NFATc4 signaling pathway in ventilator-induced lung injury

Objective To evaluate the role of calcineurin (CaN)/nuclear factor of activated T cell cytoplasmic 4 protein (NFATc4) signaling pathway in inflammatory responses in lung tissues of rats with ventilator-induced lung injury (VILI). Methods Twenty-four clean-grade healthy male Wistar rats, aged 5-8 weeks, weighing 220-250 g, were divided into 3 groups (n=8 each) using a random number table method: control C (group C), VILI group and cyclosporine A plus VILI group (group CsA+ VILI). The animals were anesthetized with pentobarbital and tracheostomized. The rats were mechanically ventilated for 6 h with the tidal volume set at 40 ml/kg and respiratory rate at 40 breaths/min to establish the model of VILI.The rats kept spontaneous breathing in group C. CaN specific inhibitor cyclosporine A 10 mg/kg was intraperitoneally injected at 1 h before ventilation in group CsA+ VILI.Rats were sacrificed immediately after ventilation, lung tissues were obtained and stained with hematoxylin and eosin to evaluate lung injury, broncho-alveolar lavage fluid was collected for determination of tumor necrosis factor-alpha (TNF-α), interleukin-1beta (IL-1β) and IL-6 concentrations by enzyme-linked immunosorbent assay, and the lungs were removed for determination of the wet to dry weight ratio (W/D ratio), expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) (by real-time polymerase chain reaction), and expression of calcineurin and NFATc4 in lung tissues (using Western blot). Results Compared with group C, the W/D ratio, lung injury scores and concentrations of IL-1β, IL-6 and TNF-α in BALF were significantly increased, and the expression of CaN, NFATc4, ICAM-1 mRNA and VCAM-1 mRNA was up-regulated in group VILI (P<0.05). Compared with group VILI, the W/D ratio, lung injury scores and concentrations of IL-1β, IL-6 and TNF-α in BALF were significantly decreased, and the expression of CaN, NFATc4, ICAM-1 mRNA and VCAM-1 mRNA was down-regulated in group CsA+ VILI (P<0.05). Conclusion CaN/NFATc4 signaling pathway mediates inflammatory responses in lung tissues of rats with VILI. Key words: Ventilator-induced lung injury; Calcineurin; NFATC transcription factors; Inflammation