Store-operated calcium entry enhances the polarization and chemotaxis of neutrophils in the peripheral venous blood of patients with bronchial asthma by upregulating ERM protein

Background: Neutrophils can be rapidly recruited and are largely abundant in the airways of patients with asthma. However, whether the polarization and chemotaxis of neutrophils in patients with asthma are abnormal, and the underlying mechanisms, have not been clarified. Pseudopods formation is the initial step of neutrophils' polarization, ezrin, radixin and moesin (ERM) play an important role in the polarization of neutrophils. As an important signaling molecule in cell physiological processes, Ca2+ has been shown to be involved in the polarity changes of neutrophils. This study thus aimed to explore polarization and chemotaxis of neutrophils in patients with asthma and the underlying mechanism. Methods: Fresh neutrophils were isolated using standard separation protocols. The polarization and chemotactic activity of neutrophils were observed using Zigmond chamber and Transwell migration assay under linear concentration gradients of N-formyl-methionine-leucine-phenylalanine (fMLP) or interleukin (IL)-8. The distribution of calcium, ERMs and F-actin in neutrophils were observed by confocal laser scanning microscope. The expression of the main components of ERMs (moesin and ezrin) was detected with reverse transcription-polymerase chain reaction (RT-PCR). Results: Compared with those in the healthy control group, the polarization and chemotaxis of neutrophils in the venous blood of patients with asthma were significantly increased, and the expression and distribution of cytoskeletal proteins F-actin and ezrin were abnormal. The expression and function of key components of store-operated calcium entry (SOCE), stromal interaction molecule 1 (STIM1), STIM2, and Orai1 of neutrophils in patients with asthma were significantly increased. Conclusions: The polarization and chemotaxis of neutrophils in the venous blood of patients with asthma are increased. This may be due to the abnormal expression and distribution of ERM and F-actin as a result of abnormal SOCE function.