RAC1 and chronic obstructive pulmonary disease: As the phosphorylation of Akt is the downsteam target of PI3K, while the elevation level of GTP-bound form of Rac1 also suggests the activation of Rac1, our data thus indicated that the activation of TLR2/PI3K signaling pathway was impaired in COPD rats in response to Aspergillus in a Rac1-dependent manner (Fig. 5b–d; *P < 0.05, #P < 0.01).