Knockdown CD44 promote the inflammatory response through the autophagy pathway in mouse models of pulmonary contusion.

Background: The effects of CD44, via the anti-inflammatory functions of autophagy, on lung injuries following pulmonary contusion (PC) and cell apoptosis were investigated.

Methods: Acute lung injury (ALI) mouse models were established by inducing lung injury via PC. This injury was verified using hematoxylin and eosin (H&E) staining, following which bronchoalveolar lavage fluid (BALF) was collected from these mice for analysis and further experimentation. CD44, LC3 I/II ratio, Beclin-1, and p62 expression levels in A549 cells were determined using immunohistochemistry, and western blot assays. CCK-8, flow cytometry, and acridine orange/ethidium bromide (AO/EB) fluorescence staining were used to quantify cell growth induced by BALF. LC3 II and LC3 I expression was determined through immunofluorescence. CD44-knockdown mice were used to demonstrate lung function after PC.

Results: The successful establishment of the ALI mouse models, created via PC was confirmed by an enhanced inflammatory response in the lung tissue, markers of cell autophagy. The ALI mice were found to have elevated CD44 expression. The viability of A549 cells exposed to BALF was downregulated, while the knockdown of CD44 promoted this effect. AO/EB and flow cytometry also indicated that the knockdown of CD44 promoted the cell apoptosis induced by BALF. Western blot analysis showed that knockdown of CD44 can inhibit LC3 I/II, p62, and Beclin-1 expression induced by BALF exposure. Additionally, knockdown of CD44 in mice was found to promote PC-induced lung injury through the attenuation of autophagy.

Conclusions: Knockdown CD44 was shown to inhibit cell growth and induced cell apoptosis via autophagy signaling pathways, promote mice with ALI induced by PC in vivo and in vitro.