Key Points Exosome complex components are endogenous suppressors of erythroid cell maturation. GATA-1 and Foxo3 transcriptionally repress exosome complex components, thus abrogating the erythroid maturation blockade.

BackgroundExposure to particulate matter (PM) has been associated with increased incidence and severity of autoimmune disease. Diesel PM is primarily composed of an elemental carbon core and adsorbed organic compounds such as polycyclic aromatic hydrocarbons (PAHs) and contributes up to 40% of atmospheric PM. The organic fraction (OF) of PM excludes all metals and inorganics and retains most organic compounds, such as PAHs. Both PM and OF increase inflammation in vitro and aggravate autoimmune disease in humans. PAHs are known aryl hydrocarbon receptor (AHR) ligands. The AHR modulates T cell differentiation and effector function in vitro and in experimental autoimmune encephalomyelitis (EAE), a murine model of autoimmune disease. This study aims to identify whether the total mass or active components of PM are responsible for activating pathways associated with exposure to PM and autoimmune disease. This study tests the hypothesis that active components present in diesel PM and their OF enhance effector T cell differentiation and aggravate autoimmune disease.ResultsTwo different diesel samples, each characterized for their components, were tested for their effects on autoimmunity. Both diesel PM enhanced effector T cell differentiation in an AHR-dose-dependent manner and suppressed regulatory T cell differentiation in vitro. Both diesel PM aggravated EAE in vivo. Fractionated diesel OFs exhibited the same effects as PM in vitro, but unlike PM, only one diesel OF aggravated EAE. Additionally, both synthetic PAH mixtures that represent specific PAHs found in the two diesel PM samples enhanced Th17 differentiation, however one lost this effect after metabolism and only one required the AHR.ConclusionsThese findings suggest that active components of PM and not total mass are driving T cell responses in vitro, but in vivo the PM matrix and complex mixtures adsorbed to the particles, not just the OF, are contributing to the observed EAE effects. This implies that examining OF alone may not be sufficient in vivo. These data further suggest that bioavailability and metabolism of organics, especially PAHs, may have an important role in vivo.Electronic supplementary materialThe online version of this article (10.1186/s12989-018-0271-3) contains supplementary material, which is available to authorized users.

Bacterial infection is one known etiology of prostatic inflammation. Prostatic inflammation is associated with prostatic collagen accumulation and both are linked to progressive lower urinary tract symptoms in men. We characterized a model of prostatic inflammation utilizing transurethral instillations of E. coli UTI89 in C57BL/6J male mice with the goal of determining the optimal instillation conditions, understanding the impact of instillation conditions on urinary physiology, and identifying ideal prostatic lobes and collagen 1a1 prostatic cell types for further analysis. The smallest instillation volume tested (50 µL) distributes exclusively to bladder, 100 and 200 µL volumes distributes to bladder and prostate, and a 500 µL volume distributes to bladder, prostate and ureter. A threshold optical density (OD) of 0.4 E. coli UTI89 in the instillation fluid is necessary for significant (p < 0.05) prostate colonization. E. coli UTI89 infection results in a low frequency, high volume spontaneous voiding pattern. This phenotype is due to exposure to E. coli UTI89, not catheterization alone, and is minimally altered by a 50 µL increase in instillation volume and doubling of E. coli concentration. Prostate inflammation is isolated to the dorsal prostate and is accompanied by increased collagen density. This is partnered with increased density of PTPRC+, ProCOL1A1+ co-positive cells and decreased density of ACTA2+, ProCOL1A1+ co-positive cells. Overall, we determined that this model is effective in altering urinary phenotype and producing prostatic inflammation and collagen accumulation in mice.

Atmospheric particulate matter (PM) is a complex component of air pollution that is a composed of inorganic and organic constituents. The chemically-extracted organic fraction (OF) of PM excludes inorganics but retains most organic constituents like polycyclic aromatic hydrocarbons (PAHs). PAHs are ubiquitous environmental toxicants and known aryl hydrocarbon receptor (AHR) ligands. The AHR is a ligand activated transcription factor that responds to endogenous ligands and exogenous ligands including PAHs. Activation of the AHR leads to upregulation of cytochrome P450 (CYP) metabolizing enzymes which are important for the biotransformation of toxicants to less toxic, or in the case of PAHs, more toxic intermediates. Additionally, the AHR plays an important role in balancing regulatory and effector T cell responses. This study aimed to determine whether PAHs present in PM aggravate inflammation by driving inflammatory T cell and dendritic cell (DC) responses and their mechanism of action. This study tests the hypothesis that PAHs present in PM activate the AHR and alter the immune balance shifting from regulation to inflammation. To test this, the effects of SRM1649b OF on T cell differentiation and DC function were measured in vitro. SRM1649b OF enhanced Th17 differentiation in an AHR and CYP-dependent manner and increased the percent of IFNγ positive DCs in an AHR-dependent manner. SRM1649b PAH mixtures enhanced Th17 differentiation in an AHR-dependent but CYP-independent manner and increased the percent of IFNγ positive DCs. Cumulatively, these results suggest that PAHs present in PM are active components that contribute to immune responses in both T cells and BMDCs through the AHR and CYP metabolism. Understanding the role of AHR and CYP metabolism of PAHs in immune cells after PM exposure will shed light on new targets that will shift the immune balance from inflammation to regulation.