IBIMOL   23987
INSTITUTO DE BIOQUIMICA Y MEDICINA MOLECULAR PROFESOR ALBERTO BOVERIS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The exposure to a transition metal-rich environmental particulate matter surrogate induces acute inflammatory leukocyte recruitment by boosting endothelial and myeloid cell activation
Autor/es:
MARCHINI, TIMOTEO; ANTO MICHEL, NATHALY; TASAT, DEBORAH; WOLF, DENNIS; BODE, CHRISTOPH; EVELSON, PABLO; ZIRLIK, ANDREAS
Lugar:
Chascomús, Buenos Aires
Reunión:
Congreso; Fourth Latin American Meeting on Biological Inorganic Chemistry; 2014
Institución organizadora:
Society of Biological Inorganic Chemistry
Resumen:
INTRODUCTION The exposure to environmental particulate matter (PM) is associated with increased morbidity and mortality rates, mainly due to cardiovascular diseases1. Local and systemic inflammation has been suggested to play a predominant role in this scenario, even though little is known about the underling mechanism. Interestingly, the presence of soluble transition metals as PM constituents seems to enhance the inflammatory response, due to increased production of reactive oxygen species (ROS) via Fenton-like chemical reactions2. Residual Oil Fly Ash (ROFA) is the inorganic residue that remains after the incomplete oxidation of fossil fuel combustion during power generation and industrial processes, and significantly contributes to PM in urban air3. Diverse PM surrogates have been assayed in animal models in order to study the biological effects of PM exposure. Among them, ROFA has been particularly useful given that it is especially rich in soluble transition metals, and because of its low concentration of organic compounds. Therefore, ROFA is the most frequently used combustion-derived particle in order to evaluate the contribution of such metals on air pollution toxicity2. By the use of a transition metal-rich PM surrogate (ROFA), the aim of this study was to clarify the mechanisms of PM-induced inflammation in an in vivo animal model of acute exposure to PM. EXPERIMENTAL METHODS ROFA particles. ROFA particles were collected from Boston Edison, Mystic Power Plant, Mystic, US. ROFA constituents mainly consist of vanadium, nickel and iron, present as water-soluble sulfates4. Particle mean aerodynamic diameter is 2.06 ± 1.57 μm. ROFA samples were freshly prepared by suspending ROFA in sterile saline solution (1 mg/mL). Animal model. C57BL/6 mice were exposed to ROFA (1 mg/kg body weight) or saline solution (control group) in a single dose by intranasal instillation. Intravital microscopy. Leukocyte trafficking was imaged on mesenteric venules, 3 h after the ROFA exposure. Sterile peritonitis. A peritoneal lavage was performed 4 h after an i.p. injection of thioglycollate broth, and peritoneal exudate cells (PECs) were quantified. Flow cytometry. Plasma cytokine profile, and endothelial cells (EC) and leukocyte subtypes activation and apoptosis were evaluated. ELISA. Plasma markers of EC activation (soluble I-CAM and V-CAM) were measured. In vitro assays. EC, neutrophils, monocytes, and macrophages were isolated from non-exposed mice, and incubated for 24 h with plasma from saline- and ROFA-exposed mice (1% v/v), ROFA particles, ROFA soluble fraction, and ROFA washed particles (1 μg/mL). RESULTS AND DISCUSSION Leukocyte rolling and adhesion in mesenteric vessels was significantly increased in mice exposed to ROFA in comparison with the control group (Fig. 1). Fig. 1: Intravital microscopy on mice mesenteric venules, 3 h after an acute ROFA exposure. PECs were also increased in ROFA-exposed mice, by 75%. Increased levels of activated Mac-1 were observed in neutrophils and inflammatory monocytes in this group, together with increased sI-CAM and sV-CAM in plasma by 25% and 21%, respectively. These results indicate that an acute exposure to ROFA induces the activation and trafficking of inflammatory leukocytes by the up-regulation of adhesion molecules in EC and myeloid cells. Increased plasma levels of TNFα, IL-6 and MCP-1 were found in ROFA-exposed mice, indicating a systemic inflammatory response triggered by intranasal instillation of ROFA. Plasma samples from this group proved to increase I-CAM and V-CAM expression in EC, as well as Mac-1 activation and L-Selectin expression in myeloid cells in vitro, when compared to the incubation with plasma from saline-exposed mice. Pre-incubation of plasma with blocking antibodies confirmed that TNFα and IL-6 account for most of the effect, meaning that pro-inflammatory cytokines present in plasma from ROFA-exposed mice are able to potentiate EC and leukocyte activation. When EC and neutrophils were incubated in vitro with ROFA particles, no effect was observed on cell activation, cytokine secretion or apoptosis induction, suggesting a lack of a direct effect of ROFA over this cell types. However, ROFA particles induced Mac-1 activation, L-Selectin expression, and pro-inflammatory cytokine secretion (TNFα and IL-6) in monocytes and macrophages in culture. Interestingly, when these cells were incubated with washed ROFA particles, the up-regulation of adhesion molecules was significantly diminished, while a small effect was observed when ROFA soluble fraction was assayed. In addition to EC and myeloid cells activation by pro-inflammatory cytokines present in plasma from ROFA-exposed mice, these findings suggest that there is also a direct effect of ROFA particles over monocytes and macrophages. Moreover, this effect seems to be dependent on the presence of transition metals as ROFA constituents, given that the expression and activation of adhesion molecules was significantly reduced when washed ROFA particles were tested. CONCLUSION The present findings indicate that an acute exposure to environmental PM triggers a systemic inflammatory response characterized by the up-regulation of adhesion molecules in EC and myeloid cells. This effect is induced by pro-inflammatory cytokines and, at least in part, transition metals present as PM constituents. As a consequence of PM exposure, macrophage activation and cytokine release might drive the systemic inflammatory response leading to PM-associated adverse cardiovascular effects. REFERENCES 1. Brook, R.D. et al., Circulation (2010), 121: 2331-2378. 2. Chen, L.C. et al., Inhal. Toxicol. (2009), 21:1-31. 3. Ghio, A.J. et al., Environ. Health Perspect. (2002), 110:89-94. 4. Ostachuk, A. et al., Environ. Res. (2008), 107:170?177. ACKNOWLEDGMENTS The authors would like to thank the German Academic Exchange Service (DAAD) for providing financial support to this project. TM is a fellow from CONICET.