OBJECTIVETo investigate the therapeutic effect of C-phycocyanin (C-PC) from Spirulina platensis on paraquat (PQ)-induced pulmonary fibrosis in rats.

METHODSA total of 90 healthy Wistar rats were randomly and equally divided into normal control group, model group (PQ group), and C-PC treatment group (C-PC group). Each rat in the PQ group and C-PC group were orally administered with a single dose of PQ (50 mg/kg) to establish a rat model of PQ poisoning. Then, the rats in the normal control group and PQ group were orally given saline solution (1 ml/100 g) every day, and the rats in the C-PC group were orally given C-PC (50 mg/kg) every day. Six rats were randomly selected from each group on days 1, 3, 7, 14, and 28. The inferior lobe of each rat's right lung was homogenized for the measurement of hydroxyproline (HYP) and maleic dialdehyde (MDA) levels and superoxide dismutase (SOD) activity. Parts of each rat's left lung were subject to HE staining and Masson staining for pathological observation, and the expression of transforming growth factor-β(1) (TGF-β(1)), nuclear factor-kappa B p65 (NF-κB p65), and tumor necrosis factor-α (TNF-α) in lung tissue was measured by immunohistochemistry.

RESULTSThe HYP levels on days 1, 3, 7, 14, and 28 and MDA levels on days 14 and 28 were significantly lower in the C-PC group than in the PQ group (P < 0.05, P < 0.01). The SOD activity was significantly higher in the C-PC group than in the PQ group on days 1, 7, 14, and 28 (P < 0.05, P < 0.01). The protein content of TGF-β(1) and the activities of NF-κB p65 and TNF-α in the PQ group and C-PC group were significantly higher than those in the normal control group, while the indices in the C-PC group were significantly lower than those in the PQ group (P < 0.05, P < 0.01). The pathological observation showed that C-PC could alleviate pulmonary alveolitis and fibrosis in rats with PQ poisoning.

CONCLUSIONC-PC can significantly inhibit PQ-induced pulmonary alveolitis and fibrosis in rats.