Effects of elevated CO(2) levels on lung immune response to organic dust and lipopolysaccharide

Workplaces with elevated organic dust levels such as animal feed barns also commonly have elevated levels of gasses, such as CO(2). Workers exposed to such complex environments often experience respiratory effects that may be due to a combination of respirable factors. We examined the effects of CO(2) on lung innate immune responses in mice co-exposed to the inflammatory agents lipopolysaccharide (LPS) and organic dust. We evaluated CO(2) levels at the building recommended limit (1000 ppm) as well as the exposure limit (5000 ppm). Mice were nasally instilled with dust extracts or LPS and immediately put into chambers with a constant flow of room air (avg. 430 ppm CO(2)), 1000 ppm, or 5000 ppm CO(2) enriched air. Results reveal that organic dust exposures tended to show decreased inflammatory responses with 1000 ppm CO(2) and increased responses at 5000 ppm CO(2). Conversely, LPS with addition of CO(2) as low as 1000 ppm tended to inhibit several inflammatory markers. In most cases saline treated animals showed few changes with CO(2) exposure, though some changes in mRNA levels were present. This shows that CO(2) as low as 1000 ppm CO(2) was capable of altering innate immune responses to both LPS and organic dust extracts, but each response was altered in a different fashion.