Aspirin rectifies calcium homeostasis, decreases reactive oxygen species, and increases NO production in high glucose-exposed human endothelial cells.

Aspirin's pharmacological action is mainly related to its property to inhibit prostaglandin synthesis; apart from this, aspirin has some beneficial side effects that are not completely understood, yet. Since aspirin possesses antioxidant properties and antioxidants prevent high d-glucose enhanced endothelial [Ca(2+)](i), we questioned whether aspirin also has an effect on this process as well as on high-glucose-impaired nitric oxide (NO) production. For these purposes, human endothelial cells (HECs) were cultured in normal concentration (5 mM) glucose (NG) or high concentration (33 mM) glucose (HG) and after confluence, exposed for 48 h to HG in the absence or presence of 1 mM aspirin. Then, the [Ca(2+)](i) was measured fluorimetrically using fura-2, NO production was determined by Griess reaction, superoxide anions (O(2)) was evaluated by ferricytochrome c reduction, the intracellular reactive oxygen species (ROS) were evaluated by fluorimetry, and the levels of protein kinase C (PKC) by Western blot. The results showed that HECs exposed to HG displayed: (i) increased [Ca(2+)](i); (ii) enhanced O(2) release; (iii) augmented level of intracellular ROS; and (iv) PKC translocation to the membrane fraction. By comparison, exposure to cells grown in HG to 1 mM aspirin resulted in: (i) a reduction of histamine stimulated [Ca(2+)](i) release to control level and of [Ca(2+)](i) entry by 30%; (ii) a twofold increase in NO production; (iii) a decrease of O(2)(-) accumulation in both culture medium and cell homogenate (by 60.4% and 70%, respectively); (iv) a decline of ROS to the control levels; and (v) a reduction of PKC translocation to the control levels. These data indicate that aspirin corrects the high-glucose-induced changes in cellular Ca(2+) homeostasis and NO production, via a mechanism involving the reduction of the O(2)(-) levels possible by acting on PKC-induced NADPH activity.