Enhanced expression of single immunoglobulin IL-1 receptor-related molecule ameliorates LPS-induced acute lung injury in mice.

Single Ig IL-1 receptor-related molecule (SIGIRR) is one of the members of the Toll-like receptor (TLR)-IL-1 receptor superfamily. Previous studies demonstrated that SIGIRR can function as a negative regulator of IL-1 and LPS signaling. The purpose of this study was to evaluate the effect of enhanced expression of SIGIRR on LPS-induced acute lung injury. We constructed a recombinant adenoviral vector expressing murine SIGIRR (Ad.mSIGIRR) and a control adenoviral vector containing no transgene (Ad.V). A total of 4 × 10⁷ plaque-forming units of Ad.mSIGIRR or Ad.V adenoviral vector were administered intranasally to BALB/c mice. Forty-eight hours later, all the mice were administered a single dose of LPS via i.p. injection to induce lung injury. Lungs and blood were harvested at several time points. The expression of SIGIRR in lung, the histological changes in the lung, the levels of TNF-α in serum and lung, the concentration of nitric monoxide (NO) in lung, and the activity of myeloperoxidase and nuclear transcription factor κB in the lung were examined. A second cohort of mice was followed for survival for 7 days. Administration of Ad.mSIGIRR increased the expression of SIGIRR in lung tissue, as determined by reverse transcription-polymerase chain reaction, Western blot, and immunohistochemistry. Administration of Ad.mSIGIRR significantly suppressed the inflammatory reaction to LPS, attenuated the lung pathological changes, and improved the survival of mice, relative to a control adenovirus. These findings suggest that modulating the expression level of SIGIRR may be a promising potential treatment for acute lung injury.