Pro-inflammatory potential of ultrafine particles in mono- and co-cultures of primary cardiac cells

Abstract

Inhalation of particulate air pollution has been associated with increased risks for cardiovascular mortality and morbidity, but the underlying mechanisms are still under discussion. One possible pathway may be that inhaled particles cross the air–blood barrier and interact directly with cardiac tissue. The aim of the present study was to examine the pro-inflammatory potential of particles in cardiac cells. Mono- and co-cultures of primary adult male Wistar (Han) rat cardiomyocytes (CMs) and cardiofibroblasts (CFs) were exposed to increasing concentrations of ultrafine (<100 nm) carbon black particles (Printex 90). Expression and release of cytokines (IL-6, IL-1β and TNF-α) were measured by using quantitative real-time PCR and ELISA, respectively. Cytotoxicity was estimated by measuring cellular release of lactate dehydrogenase (LDH). A particle concentration-dependent increase in IL-6 release was observed in both CM mono- and co-cultures (EC 50 ≈ 57 μg/ml). Furthermore, IL-6 levels detected in both control and particle-exposed co-cultures were synergistically increased compared to mono-cultures (10–19-fold, dependent on the exposure). Experiments with contact and non-contact co-cultures indicate that direct cellular contact is of key importance for the enhanced release of IL-6 in co-cultures. An apparent particle-induced release of IL-1β was only detected in co-cultures. The release of TNF-α was low and did not seem notably influenced by particle exposure. Treatment with an IL-1 receptor antagonist apparently eliminated the particle-induced release of IL-6. In conclusion, ultrafine particles have a pro-inflammatory potential in primary cardiac cells. Furthermore, IL-1 seems critical in triggering particle-induced release of IL-6. These pro-inflammatory responses may be elicited when particles are translocated into the pulmonary circulation upon inhalation or administered intravascularly during medical procedures.