Amorphous nanosilica particles evoke vascular relaxation through PI 3K/Akt/ eNOS signaling

There have been several reported studies on the distribution and/or toxicity of nanosilica particles. However, the influence of these particles on blood vessels through which they are distributed is poorly understood. Hence, we investigated the effects of nano‐ and micromaterials on blood vessel shrinkage and relaxation. Nanosilica particles with diameters of 70 nm ( nSP 70) were used as the nanomaterial, and particles of 300 and 1000 nm ( nSP 300 and mSP 1000, respectively) were used as micromaterials. A rat thoracic aorta was used as the test blood vessel. The nano‐ and micromaterials had no effect on vessel shrinkage. Of the nano‐ and micromaterials tested, only nSP 70 strongly evoked vascular relaxation. Vascular relaxation evoked by nSP 70 was almost completely inhibited by the phosphoinositide 3‐kinase ( PI 3K) inhibitor wortmannin. In addition, the selective nitric oxide synthesis inhibitor NG ‐nitro‐ l ‐arginine methyl ester, which inhibits endothelial nitric oxide synthase ( eNOS ) downstream of PI 3K signaling, inhibited vascular relaxation evoked by nSP 70. In an analysis using bovine aortic endothelial cells ( bAEC s), nSP 70 phosphorylated protein kinase B ( AKT ) and eNOS acted downstream of PI 3K signaling. PI 3K inhibition by wortmannin reduced AKT and eNOS phosphorylation. These results demonstrated that 70‐nm amorphous nanosilica particles evoked vascular relaxation through PI 3K/Akt/ eNOS signaling. Moreover, it was suggested that nanomaterials, in general, control or disrupt vascular function by activating a known signal cascade.