Gasoline and Diesel Exhaust Exposure in Mice

Twelve-week-old male Apo E^−/− mice (strain B6.129P2-Apoetm1Unc N11, on a C57Bl6 background, backcrossed for 10 generations; Taconic, Oxnard, CA) were placed on a high fat diet (TD88137 Custom Research Diet, Harlan Teklad, Madison, WI; 21.2% fat content by weight, 1.5 g/kg cholesterol content) beginning 30 days prior to initiation of exposure protocol or normal rodent chow. Mice were then randomly grouped to be exposed by whole-body inhalation to a mixture of whole gasoline engine exhaust and diesel engine exhaust (MVE: 30 μg PM/m³ gasoline engine emissions + 70 μg PM/m³ diesel engine, n = 20) or filtered-air (controls, n = 20) for 6 h/d for a period of 30 days. In a separate study, 12-week old male C57Bl6 wildtype mice (Jackson Labs, Bar Harbor, Maine) fed a standard mouse chow diet, were exposed by the same methods to either filtered air (n = 8) or MVE (n = 8). MVE was created by combining exhaust from a 1996 GM gasoline engine and a Yanmar diesel generator system, as previously reported [42 (link),59 (link),60 (link)]. Mice were housed in standard shoebox cages within an Association for Assessment and Accreditation of Laboratory Animal Care International-approved rodent housing facility (2 m³ exposure chambers) for the entirety of the study, which maintained constant temperature (20–24°C) and humidity (30–60% relative humidity). Mice had access to chow and water ad libitum throughout the study period, except during daily exposures when chow was removed. All procedures were approved by the Lovelace Respiratory Research Institute’s Animal Care and Use Committee and conform to the Guide for the Care and Use of Laboratory Animals published by the US National Institutes of Health (NIH Publication No. 85–23, revised 1996).