Polyhexamethylene guanidine phosphate-induced necrosis may be linked to pulmonary fibrosis

Following the humidifier disinfectant incident in Korea, polyhexamethylene guanidine phosphate (PHMG-P) has been used to establish lung fibrosis model animals. Herein, we investigated time-dependent changes after a single PHMG-P instillation (22 μg/lung) to identify the underlying pathogenesis and immune response involved in PHMG-P-induced lung fibrosis. Compared to control mice, body weight loss and blood biochemical and hematological changes were more remarkable in PHMG-P-instilled mice, an increase of total cell counts, infiltration of macrophages and neutrophils and necrotic cell death were also more notable in the lungs of PHMG-P-instilled mice. Pathological lesions were detected from Day 1 after exposure, deteriorating with time. In addition, secretion of anti-inflammatory mediators was rapidly inhibited from 6 h after exposure, and level of IL-24, a tissue repair-related cytokine, was up-regulated in the lungs of PHMG-P-instilled mice until Day 21 post-exposure. In vitro tests using BEAS-2B cells showed that PHMG-P disturbed structural and functional homeostasis of organelles and that intracellular ROS increase was considered as an important cause of PHMG-P-induced cell death. Additionally, co-culture with DNA, a polyanionic compound, clearly inhibited PHMG-P-induced necrosis, and increased IL-1β and TNF-α level and decreased IL-6 and IL-8 levels were observed following exposure to PHMG-P. Meanwhile, IL-8 secretion increased in cells exposed to PHMG-P-induced cell debris. Therefore, we suggest that necrotic cell debris may importantly contribute to the PHMG-P-induced inflammatory response and pathogenesis. In addition, PHMG-P-induced necrosis may be initiated by high affinity between PHMG-P and cell membrane.