Identification of organic fractions of diesel exhaust particulate (DEP) which inhibit nitric oxide (NO) production from a murine macrophage cell line.

Diesel exhaust particulates (DEPs) can constitute a large component of the particulate air pollution in urban areas and is a health concern. The effects of DEP on nitric oxide (NO) production by a murine macrophage cell line (RAW264.7) in response to interferon-gamma (INFgamma), lipopolysaccharide, (LPS) and Bacillus Calmette-Guerin (BCG) were studied. The DEP was fractionated into organic and inorganic fractions (carbonaceous core). The organic portion was further divided into asphaltene, saturates, less polar aromatics, more polar aromatics and resins-containing fractions. Each fraction was tested for the ability to suppress NO production from BCG-stimulated macrophages. DEP crude organic extract, more polar aromatic hydrocarbon, and resin fractions dose-dependently inhibited BCG-stimulated NO production. It is concluded that the responsiveness of the macrophages to stimuli, such as BCG, is suppressed by DEP and that this activity is most predominant in the polar aromatic hydrocarbons and resins-containing fractions.

Effect of diesel exhaust particulate on bacillus Calmette-Guerin lung infection in mice and attendant changes in lung interstitial lymphoid subpopulations and IFNgamma response.

The effect of exposure to diesel exhaust particulate (DEP) on bacillus Calmette-Guerin (BCG) lung infection in mice was studied. C57Bl/6J female mice were infected with BCG (2.5 x 104 bacteria/mouse) by intrapulmonary instillation, with or without coadministration of DEP (100 microg/mouse). Five weeks later, mice exposed to DEP + BCG had about a four-fold higher BCG load in the lungs than mice exposed only to BCG (p < 0.05). DEP treatment alone had no effect on the total number of lung lymphocytes or numbers of T, B, or NK cells recovered from lungs. In contrast, BCG infection significantly increased (p< 0.05) recovery levels of all types of lymphocytes from lungs. Coexposure to DEP + BCG further increased the recovery of lymphocytes from lungs of BCG-infected mice. The pulmonary lymphocyte subpopulation expressing the greatest levels of mRNA for IFNgamma after BCG infection was CD4+ T cells. Expression levels were similar in mice exposed to BCG or BCG + DEP and were elevated as compared to noninfected mice and mice treated with DEP alone. Recovery of IFNgamma-secreting lymphocytes and IFNgamma-secreting T cells was significantly higher (p < 0.05) from lungs of BCG-infected mice as compared to control or DEP-exposed mice. BCG and BCG + DEP groups of mice did not differ significantly in the numbers of IFNgamma-secreting lymphocytes in lungs. Taken together, these results indicated that coexposure to DEP + BCG did not significantly affect the level of IFNgamma response of mice to BCG infection. However, DEP treatment was found to inhibit IFNgamma-induced nitric oxide (NO) production by mouse alveolar macrophages in vitro. Our results indicate that DEP exposure did not alter the IFNgamma response to BCG infection, but reduced responsiveness of alveolar macrophages to IFNgamma. Reduced sensitivity of DEP-exposed alveolar macrophages to IFNgamma may contribute to a greater load of BCG in the lungs of BCG-infected mice given DEP.