Engulfment of platelets delays endothelial cell aging via girdin and its phosphorylation

Abstract

Endothelial cells are critical in angiogenesis and maintain the homeostasis of the blood‑brain barrier (BBB). Platelets (PLTs) are essential in vascular biology, including angiogenesis. The present study aimed to investigate the effect of PLTs on the aging of endothelial cells. Human brain microvascular endothelial cells (HBMECs) and human astrocytes were co‑cultured to mimic the BBB. Transmission electron microscopy was used to observe the engulfment of PLTs. Confocal microscopy was used to observe the co‑localization of PLTs, girders of actin filament (girdin) and phosphorylated (p‑)girdin. Senescence‑associated β‑galactosidase (β‑gal) staining, 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide and flow cytometry were performed to examine the cell senescence, viability and apoptosis, respectively. Transwell assays were performed to examine cell invasion and migration. Western blot analysis was performed to detect the expression of girdin, AKT and p‑AKT. PLTs delayed senescence, and promoted the viability and resistance to apoptosis of the HBMECs. Cell invasion and migration were enhanced by PLTs. In addition, girdin and p‑girdin were essential to the engulfment of HBMECs to PLTs. Mechanically, the inhibition of AKT signals reversed the effect of PLTs on HBMECs by increasing the activity of β‑gal, decreasing the cell viability, and inhibiting the invasion and migration of the HBMECs. The engulfment of PLTs assisted in delaying the aging of endothelial cells via girdin and p‑girdin, in which the AKT signal was involved. The present study indicated a potential strategy for delaying endothelial cell aging in the treatment of central nervous system diseases.

SIRT1-induced deacetylation of Akt expedites platelet phagocytosis and delays HEMEC aging

“…27,28 Akt signaling pathway has also been shown to be related to phagocytosis. 8 Other previous studies also showed that SIRT1 and Akt were both involved in aging and platelet phagocytosis, 9,15 and our results provide additional evidence showing the critical roles of SIRT1 and Akt in HEMEC aging.…”

“…These results are consistent with previous studies showing that platelet phagocytosis by endothelial cells has a variety of cellular functions, such as inhibiting cell aging and apoptosis and accelerating cell viability. 8,9 Likewise, erythrocyte phagocytosis by ECs has been demonstrated to be facilitated by aging and glycation, 26 suggesting the implication of phagocytosis in cell aging. More importantly, we found that SIRT1 was responsible for diminished cell aging.…”

“…8 More interestingly, platelet phagocytosis by endothelial cells has been suggested to inhibit endothelial cell aging and apoptosis. 9 Therefore, we attempted to further our understanding of the mechanism underlying the antiaging effects of platelet phagocytosis by human endometrial microvascular endothelial cells (HEMECs). Sirtuin1 (SIRT1) is an enzyme that deacetylates proteins and therefore functions as a hub regulator of antiaging genes in cells.…”

“…14 More importantly, activation of Akt signaling has been shown to enhance platelet phagocytosis by endothelial cells. 9 Based on previous studies showing that SIRT1 and Akt are both involved in aging and platelet phagocytosis, 10,15 we sought to determine if Akt activation would be responsible for platelet phagocytosis-mediated aging in HEMECs.…”

“…As the direct downstream mediator of Akt signaling, 16,17 GIRDIN may be involved in Akt-mediated platelet phagocytosis. 9 Additionally, GIRDIN can augment epithelial polarity under energetic stress and hence affect aging, cancer, and dysbiosis. 18 Based on these previous findings, we examined the role of GIRDIN on Akt-mediated platelet phagocytosis and cell aging.…”