H. Tran1, C. O’Driscoll1, E. Hoffmann1, J. Fechner1, J. Mezrich1 1University Of Wisconsin,Transplant/Surgery/SMPH,Madison, WI, USA
Introduction: Autoimmune diseases have been dramatically increasing in incidence worldwide with over 80 recognized diseases. Particulate matter (PM) from airborne pollution has been strongly associated with aggravating autoimmunity in humans, but it has been difficult to characterize mechanisms for aggravation of disease and identify which exposures are most pathological. Our group studies the role the aryl hydrocarbon receptor (AHR) on T-cell differentiation and effector function. Our previous studies suggest that inhalation of polycyclic aromatic hydrocarbons (PAHs) found in PMs may impact autoimmune disease through the AHR. We hypothesized that different pollution samples will induce varying, yet predictable effects on autoimmune disease depending on the balance of the fractions of chemicals in the sample. To characterize this, mice were exposed to inhaled pollution samples (urban dust particle (UDP) and two diesel emission particles (DEP1 and DEP2)) and control two weeks prior to induction of experimental autoimmune encephalomyelitis (EAE). Inhalation of both diesel samples significantly aggravated EAE, while exposure to UDP trended towards ameliorating disease. In this study we explored in vitro assays that could characterize the pathologic effects of different exposures.
Methods: Splenocytes of 2D2 mice, transgenic for a T-cell receptor specific to MOG (the antigen that mice respond to in EAE), were stimulated with MOG peptide and LPS (to mature DCs). Dilutions of the three samples were added to the cells. The cells were cultured for 4-5 days and the supernatants of the cultures were harvested. ELISA was used to measure IFNg and IL-17 levels, as measures of immune activation. Cytokine bead arrays were also used to measure additional cytokines. We cultured bone-marrow derived dendritic cells (BMDC) in another assay, exposed them in culture for 24 hours with pollutants or control, and assayed them for cytokine production.
Results: In the MOG assay, all three PMs led to decreased levels of IL-6. Diesel exposure increased IFNg, but decreased IL-10 expression, a cytokine known to suppress immune responses. In contrast, UDP had no effect on IFNg expression, but increased IL-17 and IL-10 expression. In the BMDC assay, exposure to UDP increased levels of IL-10 production while the diesel samples did not. UDP also increased IDO expression in DCs, an enzyme involved in the production of regulatory T cells.
Conclusion: The current data suggests that the in vitro assays may have potential for screening the autoimmune promoting activity in samples of pollution. UDP, which is made up of multiple different sources of pollution, is known to include a complex mixture of chemicals, which may affect many different cell-types, whereas diesel samples, derived from single sources of pollution, may have more predictable and specific consequences on T-cell differentiation and disease. Further characterization of this will allow improved strategies for avoidance and remediation of polluted environments.