Role of ERK1/2 in platelet lysate-driven endothelial cell repair

Mechanisms of endothelial repair induced by a platelet lysate (PL) were studied on human (HuVEC, HMVEC-c) and non-human (PAOEC, bEnd5) endothelial cells. A first set of analyses on these cells showed that 20% (v/v) PL promotes scratch wound healing, with a maximum effect on HuVEC. Further analyses made on HuVEC showed that the ERK inhibitor PD98059 maximally inhibited the PL-induced endothelial repair, followed in order of importance by the calcium chelator BAPTA-AM, the PI3K inhibitor wortmannin and the p38 inhibitor SB203580. The PL exerted a chemotactic effect on HuVEC, which was abolished by all the above inhibitors, and induced a PD98059-sensitive increase of cell proliferation rate. Confocal calcium imaging of fluo-3-loaded HuVEC showed that PL was able to induce cytosolic free Ca(2+) oscillations, visible also in Ca(2+)-free medium, suggesting an involvement of Ins3P-dependent Ca(2+) release. Western blot analysis on scratch wounded HuVEC showed that PL induced no activation of p38, a transient activation of AKT, and a sustained activation of ERK1/2. The complex of data indicates that, although different signalling pathways are involved in PL-promoted endothelial repair, the process is chiefly under the control of ERK1/2.