Title : Grape seed proanthocyanidin extract ameliorates glucocorticoid insensitivity in severe asthma
Objective: To explore the role and mechanism of grape seed proanthocyanidin extract (GSPE) in the regulation of glucocorticoid sensitivity in a mouse model of asthma and peripheral blood mononuclear cells (PBMCs) of severe asthmatic patients.
Methods: We recruited 20 healthy controls and 40 patients with severe asthma, and the PBMCs were isolated. BALB/c mice were sensitized with ovalbumin (OVA) and challenged with OVA and lipopolysaccharide (LPS) to establish a mouse model of steroid-insensitive asthma. The PBMCs and mice were treated with dexamethasone (DXM) or DXM combined GSPE in vitro and in vivo, respectively. The levels of interleukin (IL)-8 and monocyte chemotactic protein (MCP)-1 were measured by enzyme linked immunosorbent assay (ELISA). And the protein and mRNA expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), inducible nitric oxide synthase (iNOS), histone deacetylase 2 (HDAC2) and glutamatecysteine ligase modifier subunit (GCLM) were detected by Western blot and qRT-PCR respectively. The Nrf2-antioxidant response element (ARE) binding ability and expression of glutathione (GSH) in PBMCs, and airway inflammation and airway hyperresponsiveness in mice were also examined.
Results: Glucocorticoid resistance exists in patients with severe asthma, which is the main reason why severe asthma is difficult to treat. The mechanisms of glucocorticoid resistance are complex and remain unclear. In this study, we examined the relationship between Nrf2-iNOS-HDAC2 axis and severe asthma, and discussed the role of GSPE in glucocorticoid resistance. We found that the Nrf2-iNOS-HDAC2 axis was related to glucocorticoid resistance. Further studies showed that IL-8, MCP-1 and iNOS were positively correlated with severe asthma, while Nrf2, HDAC2, GSH, GCLM and Nrf2-ARE binding ability were negatively correlated with severe asthma. GSPE could relieve glucocorticoid resistance by targeting the Nrf2-iNOS-HDAC2 axis, and increased the therapeutic sensitivity of severe asthma.
Conclusion: Nrf2-iNOS-HDAC2 axis was involved in the mechanisms of glucocorticoid resistance of severe asthma, and GSPE could relieve glucocorticoid resistance.