Platelet hyperaggregability might contribute to vascular complications associated with type 2 diabetes mellitus
(DM2).Experimental evidence supports a direct link between altered Ca2+ entry and hyperaggregability in DM2 patients.
Objectives: We aimed to investigate whether altered immunophilin expression and function are involved in the abnormal
Ca2+ entry observed in platelets from DM2 patients. Results: Inhibition of immunophilins by tacrolimus (FK506) and sirolimus
(rapamycin) reduced Ca2+ entry in platelets from healthy donors and DM2 patients. Similarly, immunophilin inhibitors
reduced platelet degranulation in both healthy and DM2 subjects. Nevertheless, α-granule secretion reduction was
greater than that observed for dense granules in platelets from DM2 patients. However, no difference was observed in the
inhibition of secretion in platelets from healthy subjects. Additionally, altered expression of FK506 binding protein-52
(FKBP52) and coupling to Ca2+ channels were found in platelets from DM2 patients compared to healthy subjects. Finally,
reduction in platelet function from healthy subjects and DM2 patients in the presence of immunophilin antagonists
was observed, being this dysfunction more evident in platelets from DM2 patients. Conclusions: We suggest that, among
others, FKBP52 expression and function are altered in platelets from DM2 patients, contributing to the altered Ca2+ entry
and hyperaggregability in these cells.