The Effect of Sodium Ferulate in Experimental Pulmonary Fibrosis via NALP3 Inflammasome

Objective To investigate the activation of NALP3 inflammasome in the process of experimental pulmonary fibrosis (PF), and evaluate the effect of sodium ferulate (SF) in the relationship of NALP3 and PF. Methods Establishing PF experimental model via bleomycin (BLM) intratracheal injection (BLM group, SF group), treated with SF daily (SF group) or PBS 〔BLM group, control (CON) group〕 and mice were executed on day 21. Ashcroft score was used to assess lung fibrosis in mice PF model. The content of hydroxyproline (HYP) in lung tissue was determined by alkaline hydrolysis. Fibroblast NIH-3T3 was treated with H₂O₂ to trigger cell oxidative stress in vitroexperiments (H₂O₂group). Cell was pre-administrated with SF 2 h before H₂O₂ stimulation in H₂O₂+SF group. Blank group without any treatments, was set as control. Real time-PCR was used to investigate the expressions of three elements of inflammasome〔NALP3, caspase-1, apoptosis-associated speck-like protein (ASC〕, collagen-1 and α smooth muscle actin (α-SMA) mRNA in both lung tissue and fibroblast. Western blot was used to detect protein level of NALP3 in mice lung tissue and collagen-1, α-SMA in fibroblast as well. Meanwhile, IL-1β content in lung tissue and cell supernatant was measured by ELISA. Results in vitro experiment, SF treated mice showed lower Ashcroft score and HYP content and decreased NALP3, ASC,caspase-1 mRNA expressions and IL-1β production, NALP3 protein level compared with BLM group (P<0.05). in vitroexperiment, H₂O₂ increased NALP3 (P<0.05), ASC (P<0.01), caspase-1 (P<0.05) expressions and IL-1β releasing (P<0.05)and promoted the expressions of collagen-1 and α-SMA in both gene and protein levels (P<0.05) in NIH-3T3. NALP3 activation was partly inhibited in H₂O₂+SF group (P<0.05). The mRNA expression levels of collagen-1 and α-SMA were reduced in H₂O₂+SF group (P<0.05) and the protein expressions of α-SMA and collagen-1 were decreased (P<0.05) compared with those of H₂O₂ group. Conclusion Sodium ferulate may suppress oxidative stress mediated NALP3 activation to inhibit fibroblast activation in the anti-fibrosis effect.