Long non-coding RNA growth arrest specific-5: a potential biomarker for early diagnosis of severe asthma

BACKGROUND: The diagnosis of severe asthma (SA) is difficult due to a necessary long-term treatment history currently, while there are few studies on biomarkers in the diagnosis of SA. Long non-coding RNA (lncRNA) growth arrest specific-5 (GAS5) has the potential of playing this role because its binding with glucocorticoid receptor (GR). The purpose of this article is to explore the possibility of lncRNA GAS5 acting as a biomarker for early diagnosis of severe asthma (SA). METHODS: Peripheral blood was obtained from healthy volunteers, patients with non-severe asthma (nSA) and SA, and peripheral blood mononuclear cells (PBMCs) were separated. Twenty-four female BALB/c mice (aged 6 weeks) were randomly and averagely divided into 3 groups, i.e., control group, asthma group and dexamethasone group. The mice were sensitized and challenged with ovalbumin (OVA) and lipopolysaccharide (LPS) to establish a murine model of steroid-insensitive asthma. Human bronchial epithelial cells (HBECs) were cultured, transfected with miR-9 mimics, JNK1 inhibitor and treated with interleukin (IL)-2 + IL-4 and dexamethasone. Western blot was used to detect glucocorticoid receptor phosphorylation at serine 226 (GR(ser226)), and quantitative real-time PCR was used to detect GAS5 level. RESULTS: The level of GAS5 in PBMCs from nSA group elevated 20-fold higher after dexamethasone treatment in vitro, while it reduced 15-fold lower in SA group (P<0.001). The expression of GR(ser226) in PBMCs from SA group was significantly higher than that from control group and nSA group after dexamethasone treatment (P<0.001). In the lung tissue of mice, the GAS5 level of dexamethasone group was lower than that of asthma group (P<0.001) and control group (P<0.05). Both treatment with IL-2 + IL-4 and transfection of miR-9 mimics could increase the expression of GR(ser226) in HBECs (P<0.001). The GAS5 level in HBECs after IL-2 + IL-4 + Dexamethasone treatment was lower than that in HBECs only treated with IL-2 + IL-4 (P<0.001). Similarly, dexamethasone treatment also decreased the level of GAS5 in HBECs transfected with miR-9 mimics (P<0.05). Moreover, transfecting with JNK1 inhibitor could reverse the expression of GAS5 in HBECs transfected with miR-9 mimics and treated with dexamethasone. However, the level of GAS5 in HBECs interfered with IL-2 + IL-4 + Dexamethasone was not affected by JNK1 inhibitor. CONCLUSIONS: The expression of GAS5 is different in PBMCs between nSA and SA, and is affected by glucocorticoids treatment, which is due to GR(ser226) phosphorylation. GAS5 can be used as a potential biomarker for diagnosis of severe asthma by comparing GAS5 level in PBMCs from patients before and after glucocorticoids treatment in vitro.