ObjectiveTo investigate the anti-inflammatory and antioxidant effects of baicalin for treating chronic obstructive pulmonary disease （COPD） in rats and decipher the molecular mechanisms via the nuclear factor-kappa B （NF-κB）/nuclear factor erythroid 2-related factor 2 （Nrf2） signaling pathway. MethodsSixty SPF-grade male Sprague-Dawley rats were randomly assigned into six groups： normal control， COPD model， low-dose baicalin， medium-dose baicalin， high-dose baicalin， and budesonide. The normal control group received no treatment， whereas COPD was modeled in other groups with a combined modeling approach involving intratracheal lipopolysaccharide instillation and passive cigarette smoke exposure. The model establishment was evaluated through behavioral observation combined with pathological examination. Hematoxylin-eosin （HE） staining was performed to assess histopathological changes in the lung. Serum levels of inflammatory cytokines ［interleukin （IL）-6， IL-8， IL-17， IL-22， tumor necrosis factor （TNF）-α， and transforming growth factor （TGF）-β）］， reactive oxygen species （ROS）， and vascular endothelial growth factor （VEGF） were quantified by enzyme-linked immunosorbent assay （ELISA）. Meanwhile， the levels of IL-6， IL-17， and IL-22 in the bronchoalveolar lavage fluid （BALF） and IL-10， IL-22， and TNF-α in the lung tissue were measured via ELISA. Immunohistochemistry （IHC） was employed to detect the expression of histone deacetylase 2 （HDAC2） and Nrf2. Western blot was performed to evaluate the expression of phosphoinositide 3-kinase （PI3K）， protein kinase B （Akt）， glucocorticoid receptor （GR）， NF-κB， HDAC2， and Nrf2 in the lung tissue. Additionally， real-time PCR was conducted to assess the mRNA levels of PI3K， Akt， HDAC2， Nrf2， GR， and NF-κB in the lung tissue. ResultsHE staining revealed that the airway mucosal epithelium in the COPD model group appeared extensive shedding， structural disorganization， and diffuse infiltration of inflammatory cells within the lumen. And goblet cells showed compensatory proliferation with pathological hypertrophy of mucus glands. In contrast， inflammatory infiltration and alveolar overdistension were significantly alleviated in the medium- and high-dose baicalin groups. The COPD model group exhibited mucus plug formation within the terminal bronchioles， along with fibrotic narrowing of the bronchial wall. Moreover， the smooth muscle bundles of the bronchial wall were hypertrophic， with concomitant collagen deposition. Progressive dissolution and rupture of alveolar septa were observed， leading to the formation of abnormally enlarged air-filled cavities. However， the bronchial wall structure was largely restored with only mild thickening of the smooth muscle layer in the baicalin groups. Compared with the COPD model group， the medium- and high-dose baicalin groups showed declined ROS and VEGF levels （P<0.05）， and all the baicalin groups presented lowered levels of IL-6， IL-8， IL-17， IL-22， TGF-β， and TNF-α and elevated level of IL-10 （P<0.05）. Baicalin upregulated the protein levels of HDAC2， Nrf2， GR， PI3K， and Akt， while suppressing the protein level of NF-κB （P<0.05）. Furthermore， baicalin increased the mRNA levels of Nrf2 and GR while down-regulating the mRNA level of NF-κB （P<0.05）. ConclusionBaicalin exerts anti-inflammatory and antioxidant effects by inhibiting the pro-inflammatory factor NF-κB while enhancing the expression of the anti-inflammatory factor HDAC2 and activating the antioxidant factor Nrf2， thereby alleviating the lung tissue damage in COPD rats. The therapeutic effects of baicalin may be closely associated with its regulatory role in the NF-κB/Nrf2 signaling pathway.

ObjectiveTo investigate the anti-inflammatory and antioxidant effects of baicalin for treating chronic obstructive pulmonary disease （COPD） in rats and decipher the molecular mechanisms via the nuclear factor-kappa B （NF-κB）/nuclear factor erythroid 2-related factor 2 （Nrf2） signaling pathway. MethodsSixty SPF-grade male Sprague-Dawley rats were randomly assigned into six groups： normal control， COPD model， low-dose baicalin， medium-dose baicalin， high-dose baicalin， and budesonide. The normal control group received no treatment， whereas COPD was modeled in other groups with a combined modeling approach involving intratracheal lipopolysaccharide instillation and passive cigarette smoke exposure. The model establishment was evaluated through behavioral observation combined with pathological examination. Hematoxylin-eosin （HE） staining was performed to assess histopathological changes in the lung. Serum levels of inflammatory cytokines ［interleukin （IL）-6， IL-8， IL-17， IL-22， tumor necrosis factor （TNF）-α， and transforming growth factor （TGF）-β）］， reactive oxygen species （ROS）， and vascular endothelial growth factor （VEGF） were quantified by enzyme-linked immunosorbent assay （ELISA）. Meanwhile， the levels of IL-6， IL-17， and IL-22 in the bronchoalveolar lavage fluid （BALF） and IL-10， IL-22， and TNF-α in the lung tissue were measured via ELISA. Immunohistochemistry （IHC） was employed to detect the expression of histone deacetylase 2 （HDAC2） and Nrf2. Western blot was performed to evaluate the expression of phosphoinositide 3-kinase （PI3K）， protein kinase B （Akt）， glucocorticoid receptor （GR）， NF-κB， HDAC2， and Nrf2 in the lung tissue. Additionally， real-time PCR was conducted to assess the mRNA levels of PI3K， Akt， HDAC2， Nrf2， GR， and NF-κB in the lung tissue. ResultsHE staining revealed that the airway mucosal epithelium in the COPD model group appeared extensive shedding， structural disorganization， and diffuse infiltration of inflammatory cells within the lumen. And goblet cells showed compensatory proliferation with pathological hypertrophy of mucus glands. In contrast， inflammatory infiltration and alveolar overdistension were significantly alleviated in the medium- and high-dose baicalin groups. The COPD model group exhibited mucus plug formation within the terminal bronchioles， along with fibrotic narrowing of the bronchial wall. Moreover， the smooth muscle bundles of the bronchial wall were hypertrophic， with concomitant collagen deposition. Progressive dissolution and rupture of alveolar septa were observed， leading to the formation of abnormally enlarged air-filled cavities. However， the bronchial wall structure was largely restored with only mild thickening of the smooth muscle layer in the baicalin groups. Compared with the COPD model group， the medium- and high-dose baicalin groups showed declined ROS and VEGF levels （P<0.05）， and all the baicalin groups presented lowered levels of IL-6， IL-8， IL-17， IL-22， TGF-β， and TNF-α and elevated level of IL-10 （P<0.05）. Baicalin upregulated the protein levels of HDAC2， Nrf2， GR， PI3K， and Akt， while suppressing the protein level of NF-κB （P<0.05）. Furthermore， baicalin increased the mRNA levels of Nrf2 and GR while down-regulating the mRNA level of NF-κB （P<0.05）. ConclusionBaicalin exerts anti-inflammatory and antioxidant effects by inhibiting the pro-inflammatory factor NF-κB while enhancing the expression of the anti-inflammatory factor HDAC2 and activating the antioxidant factor Nrf2， thereby alleviating the lung tissue damage in COPD rats. The therapeutic effects of baicalin may be closely associated with its regulatory role in the NF-κB/Nrf2 signaling pathway.