PB0768 - Mitochondrial calcium uniporter as a key regulator in the generation of procoagulant COAT platelets

Monday, June 24, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Presenting Author(s)

DS

Durre Shehwar

PhD Scholar
Quaid-i-Azam University
Islamabad, Islamabad, Pakistan

Co-Author(s)

Alessandro Aliotta, PhD

Research Associate
Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Lausanne, Geneve, Switzerland
SB

Saima Barki

PhD Scholar
Department of Biochemistry, Quaid-i-Azam University, Islamabad, Pakistan
Islamabad, Islamabad, Pakistan
Debora Bertaggia Calderara

Research Associate
Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Lausanne, Vaud, Switzerland
Lucas Veuthey

PhD student
Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Lausanne, Vaud, Switzerland
CP

Cindy Pereira Portela

MD Student
Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Lausanne, Vaud, Switzerland
MA

Muhammad Rizwan Alam

Associate Professor
Department of Biochemistry, Quaid-i-Azam University, Islamabad, Pakistan
Islamabad, Islamabad, Pakistan
LA

Lorenzo Alberio

Chief Physician and Associate Professor
Division of Hematology and Central Hematology Laboratory, Lausanne University Hospital (CHUV) and University of Lausanne (UNIL), Lausanne, Switzerland
Lausanne, Vaud, Switzerland

Background: Procoagulant platelets represent a subpopulation of platelets that are phenotypically and functionally different from aggregating platelets. The combined activation of platelets with collagen-plus-thrombin induces the formation of procoagulant COAT platelets, which exhibit an elevated surface exposure of phosphatidylserine. This dual agonist stimulation causes high level of cytosolic calcium, which is taken up by mitochondria through mitochondrial calcium uniporter (MCU). A significant rise in mitochondrial calcium results in the depolarization of mitochondrial membrane potential, which triggers opening of mitochondrial permeability transition pore (mPTP) that results in supramaximal cytosolic calcium concentration required for PS exposure. MCU is a n active area of investigation in procoagulant platelets formation.

Aims: The aim is to explore the function of MCU in the generation and modulation of procoagulant COAT platelets.

Methods: Platelets were activated with 0.5 U/ml thrombin (THR), 500 ng/ml convulxin (CVX, collagen GPVI agonist), or a combination of these. Flow cytometry was employed to monitor procoagulant and aggregatory properties of platelets using Annexin-V and PAC-1 binding, respectively. Function of MCU was determined with specific inhibitors, namely mitoxantrone (MTX) or Ru265.

Results: Our results demonstrated that THR stimulation alone triggered only a small increase in PS exposure that was not inhibited by MTX. In contrast, CVX alone generated moderate procoagulant platelets and MTX showed a significant inhibition (35% ± 8.09). Furthermore, when platelets were co-stimulated with THR-plus-CVX, MTX achieved a significant decrease (23% ± 1.26) in Annexin V positive platelets that was associated with a reciprocal increase (36% ± 4.6) in PAC-1 positive platelets. Data were replicated and validated by blocking MCU with Ru265.

Conclusion(s): Altogether, the present study revealed that the signaling pathway downstream of GPVI involved in the formation of procoagulant platelets depends on MCU-driven mitochondrial calcium uptake. We identified MCU as a key regulator in the collagen-dependent generation of procoagulant platelets.