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 6

PKA inhibitor causes acute thrombocytopenia, and PKA activator elevates peripheral platelets.

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PKA inhibitor causes acute thrombocytopenia, and PKA activator elevates ...
(A and B) Male ICR mice were injected with a single dose of Rp-cAMPS (50 mg/kg) through the tail vein. Platelet counts (A and B) and reticulated platelet counts (B) were determined at the indicated time points. #P < 0.001, compared with control, 2-way ANOVA. (C) Male ICR mice were intraperitoneally injected with a single dose of anti-platelet antibody (R300, 0.15 mg/kg) to synchronize platelet production. The antibody induced severe thrombocytopenia. The newly synthesized platelets were released into the circulation, as indicated by reticulated platelets (right axis) increasing. The number of platelets (left axis) became stable from day 4. (D and E) Male ICR mice were intraperitoneally injected with a single dose of anti-platelet antibody (R300, 0.2 mg/kg) and then injected with Rp-cAMPS (50 mg/kg) through the tail vein 2 or 7 days afterwards. Reticulated platelet counts (D) and platelet counts (E) were determined prior to or 8 hours after injection of Rp-cAMPS. The left panels show representative flow cytometric profiles of thiazole-orange–stained platelets prior to or 8 hours after Rp-cAMPS injection. (F and G) Male ICR mice were injected daily with PKA activator 8-Br-cAMP (2.5 mg/kg) or vehicle control (PBS) through the tail vein. Platelet counts (F) and reticulated platelet counts (G) were determined at day 8. Data in each panel represent mean ± SD of 5 to 6 mice at each time point. *P < 0.05; **P < 0.01; #P < 0.001, compared with control, Student’s t test (D–G).