Silica nanoparticles trigger phosphatidylserine exposure in red blood cells and induce thrombosis risk

Silica nanoparticles (SiNPs) have attracted increasing attention for their health effects due to the increased risk of exposure to human bodies via diverse routes. Considering that SiNPs enter the circulatory system and inevitably encounter red blood cells (RBCs), it is necessary to investigate their risk of causing erythrocytotoxicity. In this study, three sizes of SiNPs (SiNP-60, SiNP-120, and SiNP-200) were tested for their effects on mouse RBCs. The results showed that SiNPs could induce hemolysis, morphological changes, and phosphatidylserine (PS) exposure in RBCs in a particulate size-related manner. Further investigations on the underlying mechanism indicated that SiNP-60 exposure increased intracellular reactive oxidative species (ROS) generation and subsequently caused the phosphorylation of p38 and ERK1/2 in RBCs. The addition of antioxidants or inhibitors of mitogen-activated protein kinase (MAPK) signaling significantly attenuated PS exposure in RBCs and ameliorated SiNP-induced erythrocytotoxicity. Moreover, ex vivo assays using platelet-rich plasma (PRP) showed that SiNP-60-induced PS exposure in RBCs could trigger thrombin-dependent platelet activation. The contrary evidence from the assays of PS blockage and thrombin inhibition further confirmed that SiNP-60-induced platelet activation was dependent on PS externalization in RBCs, concomitantly with thrombin formation. These findings revealed the procoagulant and prothrombotic effects of SiNPs through the regulation of PS externalization in RBCs, and may be of great help in bridging the knowledge gap on the potential cardiovascular hazards of particulate silica from both artificial and naturally occurring origins.