Backgroud To explore the Effect of grape seed proanthocyanidin extract(GSPE) in peripheral blood mononuclear cells of severe asthmatic patients. Methods 40 severe asthmatic patients were randomly and averagely divided into 2 groups: DXM group (n=20) and GSPE+DXM group (n=20), and 20 healthy volunteers as control gorup. Heparinized peripheral venous blood from each subject was collected in a sterile vacuum tube. The levels of interleukin (IL)-8 and monocyte chemotactic protein (MCP)-1 were detected by ELISA. The protein and mRNA expressions of Nuclear factor erythroid 2-related factor 2 (Nrf2), glutamatecysteine ligase modifier subunit (GCLM) inducible nitric oxide synthase (iNOS) and inactivation of histone deacetylase-2 (HDAC2) were detected by Western blot and qRT-PCR respectively. Glutathion(GSH) was measured by using Glutathione Fluorometric Detection Kit, and Nrf2-ARE binding ability was measured by using TransAM Nrf2 Transcription Factor ELISA Kit. Results The results showed that the levels of IL-8 and MCP-1 in normal control group were lower than those in severe asthma group (P <0.05). Treatment with GSPE+DXM reduced the levels of IL-8 and MCP-1 significantly when compared with DXM only ( P <0.05).The mRNA expression of iNOS in DXM group was significantly higher than that in control group. However, after adding GSPE treatment, the expression dramatically decreased ( P <0.001). On the contrary, lower mRNA expressions of Nrf2, GCLM and HDAC2 were found in DXM group than in control group ( P <0.001). Accordingly, when treated with GSPE, these expressions elevated and reached a statistical significance ( P <0.05). Consistently, the results from western blot analysis confirmed the role of GSPE on the protein expressions of iNOS, Nrf2, GCLM and HDAC2 in PBMCs of patients with severe asthma ( P <0.001). The PBMCs from patients with severe asthma exhibited lower Nrf2-ARE binding ability and produced less GSH than normal controls. GSPE treatment effectively augmented the Nrf2-ARE binding ability and the expression of GSH, which demonstrated the biological antioxidant potential of GSPE ( P <0.001). Conclusion GSPE can alleviate glucocorticoid resistance by regulating Nrf2-iNOS-HDAC2 signaling pathway in severe asthma, suggesting that GSPE have potential clinical application prospects in the treatment of severe asthma.