Phycocyanin attenuates X-ray-induced pulmonary inflammation via the TLR2-MyD88-NF-κB signaling pathway

Abstract

Phycocyanin (PC), a natural algal protein, is reported for having anti-oxidant and antiinflammatory properties. We investigated its ability to attenuate lung inflammation in mice subjected to X-ray radiation. Male C57BL/6 mice were assigned to the control, total body irradiation, PC pretreatment, and PC treatment groups. Mice in the PC pretreatment group were gavaged with 200 mg/kg PC for 7 consecutive days before irradiation, and those in the PC treatment group were gavaged with 200 mg/kg PC for 7 consecutive days after irradiation. Lungs were collected on Day 7 after irradiation exposure. Hematoxylin and eosin staining of mouse lung sections showed considerable inflammation damage 7 days after irradiation compared with the control lung but a reduction in pathological injury in the PC treatment group. Pretreatment or treatment with PC significantly decreased levels of interleukin-6 and tumor necrosis factor-α in the lung, and also increased the relative mRNA expression of superoxide dismutase and glutathione. In vivo, PC significantly reduced the expression of Toll-like receptor TLR2, myeloid differentiation primary response Myd88, and nuclear factor NF-κB, at both the transcriptional and translation level. Taken together, these data indicated that PC attenuated lung inflammatory damage induced by radiation by blocking the TLR2-MyD88-NF-κB signaling pathway. Therefore, PC could be a protective agent against radiation-induced inflammatory damage in normal tissues.