Cardiac physiologic and genetic predictors of hyperoxia-induced acute lung injury in mice

Exposure of mice to hyperoxia produces pulmonary toxicity similar to acute lung injury/acute respiratory distress syndrome, but little is known about the interactions within the cardiopulmonary system. This study was designed to characterize the cardiopulmonary response to hyperoxia, and to identify candidate susceptibility genes in mice. Electrocardiogram and ventilatory data were recorded continuously from 4 inbred and 29 recombinant inbred strains during 96 hours of hyperoxia (100% oxygen). Genome-wide linkage analysis was performed in 27 recombinant inbred strains against response time indices (TIs) calculated from each cardiac phenotype. Reductions in minute ventilation, heart rate (HR), low-frequency (LF) HR variability (HRV), high-frequency HRV, and total power HRV were found in all mice during hyperoxia exposure, but the lag time before these changes began was strain dependent. Significant (chromosome 9) or suggestive (chromosomes 3 and 5) quantitative trait loci were identified for the HRTI and LFTI. Functional polymorphisms in several candidate susceptibility genes were identified within the quantitative trait loci and were associated with hyperoxia susceptibility. This is the first study to report highly significant interstrain variation in hyperoxia-induced changes in minute ventilation, HR, and HRV, and to identify polymorphisms in candidate susceptibility genes that associate with cardiac responses. Results indicate that changes in HR and LF HRV could be important predictors of subsequent adverse outcome during hyperoxia exposure, specifically the pathogenesis of acute lung injury. Understanding the genetic mechanisms of these responses may have significant diagnostic clinical value.