Respiratory effects caused by exposure to diesel exhaust particles during moderate exercise: a murine model

Abstract

Aerobic exercise is an increasing trend worldwide. However, people are increasingly exercising outdoors, alongside roadways where heavy vehicles release diesel exhaust. We analyzed respiratory effects caused by inhaled diesel particulate emitted by vehicles adhering to Brazilian legislation, PROCONVE Phase P7 (equivalent to EURO 5), as well the effects of exposure during moderate-intensity aerobic exercise. Male C57BL/6 mice were divided into 4 groups for a 4-week treadmill protocol: CE (n=8) received intranasal sterile physiological saline and then performed moderate-intensity exercise (control), CS (n=10) received saline and then remained stationary on the treadmill (control), DS (n=9) received intranasal diesel exhaust particles and then remained stationary, and DE (n=10) was exposed to diesel exhaust and then exercised at moderate intensity. Mice were subsequently connected to a mechanical ventilator (SCIREQ{copyright, serif} flexiVent®, Canada) to analyze the following respiratory mechanics parameters: tissue resistance, elastance, inspiratory capacity, static compliance, Newtonian resistance, and pressure-volume loop area. After euthanasia, peripheral pulmonary tissue strips were extracted and subjected to force-length tests to evaluate parenchymal elastic and mechanical properties, using oscillations applied by a computer-controlled force transducer system; parameters obtained were tissue resistance, elastance, and hysteresivity. DS displayed impaired respiratory mechanics for all parameters, in comparison to CS. DE exhibited significantly reduced inspiratory capacity and static compliance, and increased Newtonian resistance when compared to CE. Exposure to diesel exhaust, both during exercise and rest, still exerts harmful pulmonary effects, even at current legislation limits. These results justify further changes in environmental standards, to reduce the health risks caused by traffic-related pollution.