Associations of cold‐inducible RNA‐binding protein with bacterial load, proinflammatory cytokines and mortality from pneumonia

Abstract Cold‐inducible RNA‐binding protein (CIRP) is a damage‐associated molecular pattern that plays a critical role in triggering inflammatory responses. It remains unknown whether CIRP is strongly associated with bacterial load, inflammatory response, and mortality in sepsis model. Pneumonia was induced in specific pathogen‐free 8–9‐week old male rats by injecting bacteria via puncture of the tracheal cartilage. The expressions of CIRP and proinflammatory cytokines [tumor necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6) and IL‐1β] in lung tissues, alveolar macrophages (AMs), plasma, and bronchoalveolar lavage fluid (BALF) were determined by reverse transcription‐polymerase chain reaction, western blotting, and enzyme‐linked immunosorbent assay. The numbers of bacteria recovered from the lungs were correlated with the bacterial loads injected and mortality. The expressions of CIRP increased sharply as the bacterial loads increased in the lung tissues and AMs. The amounts of TNF‐α, IL‐6 and IL‐1β proteins synthesized were dependent on the bacterial load in the lung tissues. Releases of CIRP, TNF‐α, IL‐6, and IL‐1β increased with the bacterial load in the blood plasma. The proteins confirmed similar patterns in the BALF. CIRP was strongly associated with the releases of TNF‐α, IL‐6, and IL‐1β in the lung tissues, blood plasma, and BALF, and showed a close correlation with mortality. CIRP demonstrated a strong association with bacterial load, which is new evidence, and close correlations with proinflammatory cytokines and mortality of pneumonia in rats, suggesting that it might be an interesting pneumonic biomarker for monitoring host response and predicting mortality, and a promising target for immunotherapy.