Protein kinase A determines platelet life span and survival by regulating apoptosis
Lili Zhao, Jun Liu, Chunyan He, Rong Yan, Kangxi Zhou, Qingya Cui, Xingjun Meng, Xiaodong Li, Yang Zhang, Yumei Nie, Yang Zhang, Renping Hu, Yancai Liu, Lian Zhao, Mengxing Chen, Weiling Xiao, Jingluan Tian, Yunxiao Zhao, Lijuan Cao, Ling Zhou, Anning Lin, Changgeng Ruan, Kesheng Dai
Lili Zhao, Jun Liu, Chunyan He, Rong Yan, Kangxi Zhou, Qingya Cui, Xingjun Meng, Xiaodong Li, Yang Zhang, Yumei Nie, Yang Zhang, Renping Hu, Yancai Liu, Lian Zhao, Mengxing Chen, Weiling Xiao, Jingluan Tian, Yunxiao Zhao, Lijuan Cao, Ling Zhou, Anning Lin, Changgeng Ruan, Kesheng Dai
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Research Article Hematology

Protein kinase A determines platelet life span and survival by regulating apoptosis

Abstract

Apoptosis delimits platelet life span in the circulation and leads to storage lesion, which severely limits the shelf life of stored platelets. Moreover, accumulating evidence indicates that platelet apoptosis provoked by various pathological stimuli results in thrombocytopenia in many common diseases. However, little is known about how platelet apoptosis is initiated or regulated. Here, we show that PKA activity is markedly reduced in platelets aged in vitro, stored platelets, and platelets from patients with immune thrombocytopenia (ITP), diabetes, and bacterial infections. Inhibition or genetic ablation of PKA provoked intrinsic programmed platelet apoptosis in vitro and rapid platelet clearance in vivo. PKA inhibition resulted in dephosphorylation of the proapoptotic protein BAD at Ser155, resulting in sequestration of prosurvival protein BCL-XL in mitochondria and subsequent apoptosis. Notably, PKA activation protected platelets from apoptosis induced by storage or pathological stimuli and elevated peripheral platelet levels in normal mice and in a murine model of ITP. Therefore, these findings identify PKA as a homeostatic regulator of platelet apoptosis that determines platelet life span and survival. Furthermore, these results suggest that regulation of PKA activity represents a promising strategy for extending platelet shelf life and has profound implications for the treatment of platelet number-related diseases and disorders.

Authors

Lili Zhao, Jun Liu, Chunyan He, Rong Yan, Kangxi Zhou, Qingya Cui, Xingjun Meng, Xiaodong Li, Yang Zhang, Yumei Nie, Yang Zhang, Renping Hu, Yancai Liu, Lian Zhao, Mengxing Chen, Weiling Xiao, Jingluan Tian, Yunxiao Zhao, Lijuan Cao, Ling Zhou, Anning Lin, Changgeng Ruan, Kesheng Dai

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Figure 8

PKA activation protects pathologically stimulated platelets from apoptosis in vitro and clearance in vivo.

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PKA activation protects pathologically stimulated platelets from apoptos...
(A and B) Washed human platelets were incubated with forskolin (20 μM) or vehicle at 37°C for 30 minutes and further incubated with serum from ITP patients or healthy controls (1:1 volume) for 12 hours. Δψm Depolarization (A) and PS exposure (B) are shown. *P < 0.05; #P < 0.001, Mann-Whitney U test for control versus ITP. **P < 0.01; #P < 0.001, Wilcoxon matched-pairs signed rank test for ITP versus ITP plus forskolin. (C) ICR mice were injected with 8-Br-cAMP or vehicle and further injected with 2.4G2. After 10 minutes, R300 was injected into the mice (n = 6). Data are represented as mean of normalized platelet counts (time point 0: 100%) ± SD from 3 independent experiments. *P < 0.05; **P < 0.01; #P < 0.001, 2-way ANOVA. (D and E) Human platelets were incubated with forskolin (5 μM) or vehicle at 37°C for 15 minutes and further incubated with S. aureus (1:20) or vehicle for 90 minutes. Data are represented as mean ± SD of Δψm depolarization (D) and PS exposure (E) from 3 independent experiments. *P < 0.05; **P < 0.01, Student’s t test. (F) Δψm depolarization of platelets incubated with forskolin and serum from diabetes patients or healthy controls. *P < 0.05, Student’s t test.