The effect of squalane-dissolved fullerene-C60 on adipogenesis-accompanied oxidative stress and macrophage activation in a preadipocyte-monocyte co-culture system

Effects of squalane-dissolved fullerene-C60 (Sql-fullerene) on macrophage activation and adipose conversion with oxidative stress were studied using an inflammatory adipose-tissue equivalent (ATE) and OP9 mouse stromal preadipocyte-U937 lymphoma cell co-culture systems. Differentiation of OP9 cells was initiated by insulin-rich serum replacement (SR) as an adipogenic stimulant, and then followed by accumulation of intracellular lipid droplets and reactive oxygen species (ROS), both of which were significantly inhibited by Sql-fullerene. In the OP9-U937 cell co-culture system, U937 cells rapidly differentiated to macrophage-like cells during SR-induced adipogenesis in OP9 cells. The ROS accumulation was in the co-culture more marked than in OP9 cells alone, suggesting that the interaction between adipocytes and monocytes/macrophages promotes inflammatory responses. Sql-fullerene significantly inhibited macrophage activation and low-grade adipogenesis in the OP9-U937 co-culture system. We developed a three-dimensional inflammatory adipose-tissue model “ATE” consisting of, characteristically, U937 cells in the culture-wells, and, in addition, mounted a culture insert containing OP9 cells-populated collagen gel. ATE is enabled with suitable stimulation to represent the pathology of inflammatory disorders, such as macrophage infiltration in adipose tissue. Five-day culturing of ATE in SR medium occurred U937 macrophage migration and intracellular oil-droplet accumulation that were significantly inhibited by Sql-fullerene. Our results suggest that Sql-fullerene might be explored as a potential medicine for the treatment of metabolic syndrome or other obesity-related disorders.