Objective: To examine the effect of suppressive oligodeoxynucleotides (ODNs) on the pulmonary inflammation induced by immunostimulatory CpG DNA.
Design: Prospective, randomized, controlled study.
Setting: Research laboratories.
Subjects: RAW 264.7 murine macrophage-like cell line and BALB/c mice.
Interventions: RAW 264.7 cells were incubated with bacterial DNA or CpG ODN, alone or combined with suppressive ODN. The in vivo effect of suppressive ODN was determined using an acute lung injury model. CpG ODN alone or combined with suppressive ODN was instilled into the mouse lung.
Measurements and main results: Production of tumor necrosis factor (TNF)-alpha and macrophage inflammatory protein (MIP)-2 by RAW 264.7 cells were measured by enzyme-linked immunosorbent assay (ELISA), whereas their messenger RNA levels were determined by reverse transcriptase-polymerase chain reaction. Synthetic ODN containing CpG motifs (CpG ODN) mimicked the ability of bacterial DNA to stimulate the production of TNF-alpha and MIP-2. Suppressive ODN significantly inhibited the activation of RAW 264.7 cells by both bacterial DNA and CpG ODN. In the lung injury model, production of proinflammatory cytokines (TNF-alpha and IL-6) and chemokines (MIP-2 and KC) in bronchoalveolar lavage (BAL) fluids was measured by ELISA. Neutrophil accumulation in the alveolar spaces was also evaluated. Instillation of CpG ODN into the lungs of normal mice triggered the synthesis of TNF-alpha, IL-6, MIP-2, and KC. Suppressive ODN significantly blocked the production of these proinflammatory cytokines and chemokines and also reduced neutrophil mobilization into the alveolar spaces by CpG DNA.
Conclusions: Proinflammatory cytokines and chemokines are up-regulated by CpG motifs in bacterial DNA. Suppressive ODN significantly inhibits the inflammatory response induced by CpG DNA in murine macrophages and the lung. This study supports the use of suppressive ODN to reduce the deleterious inflammatory responses induced by bacterial DNA.