Expression of adhesion molecules, monocyte interactions and oxidative stress in human endothelial cells exposed to wood smoke and diesel exhaust particulate matter

Toxicological effects of wood smoke particles are less investigated than traffic-related combustion particles. We investigated the effect of wood smoke particles, generated by smouldering combustion conditions, on human umbilical endothelial cells (HUVECs) co-cultured with or without monocytic THP-1 cells. Standard reference material (SRM) 2975 diesel exhaust particles were used as benchmark particles. Wood smoke particles at 50 μg/ml or 100 μg/ml caused adhesion of THP-1 monocytes onto HUVECs in co-cultures, whereas SRM2975 had no such effect. Both types of particles from 1 μg/ml increased VCAM-1 expression on HUVECs in mono-cultures. However, only the exposure to wood smoke particles was associated with increased expression of TNF and IL8 mRNA in THP-1 cells. We found no effect on the intracellular production of reactive oxygen species by the fluorescent probe DCFH-DA, whereas especially the wood smoke particles caused increased level of DNA strand breaks and oxidised guanines at concentrations with low cytotoxicity. In conclusion, our results indicate that the adherence of monocytes on endothelial cells in wood smoke particle exposed cultures depend on activation of both cell types.

► We exposed HUVECs and monocytes in co-culture to wood smoke or SRM2975. ► Monocytes exposed to wood smoke particles had increased expression of IL8 and TNF. ► HUVECs had increased VCAM1 expression after exposure to both type of particles. ► Monocyte adhesion on HUVECS was only seen in co-cultures exposed to wood smoke particles. ► Particle-induced adhesion depends on activation of both endothelial cells and monocytes.