Inflammasome-Independent Mechanism Of NLRP3 Critical For Platelet GPIb-Ⅸ And Thrombo-Inflammation

Platelets are derived from mature megakaryocytes in bone marrow,which are important for hemostasis.However recent studies have shown that,besides hemostasis and coagulation,platelets are also participated in immunity.The diversity of these functions enables us to link thrombosis and inflammation through platelets.Considering that thrombo-inflammatory disease is one of the main causes of global death,clarifying the mechanism of platelet in it will help us to analyze the occurrence of disease from a new perspective and provide effective treatment strategies.NLRP3 is a member of the NOD（nucleoside binding oligomerization domain）like receptor family.Its main function is to recognize pathogen-associated molecular patterns and danger-associated molecular patterns.The activation of NLRP3 inflammasome and the production of IL-1βhave been proved to play a key role in many inflammatory diseases such as sepsis,Alzheimer’s disease and osteoarthritis.Normal NLRP3inflammasome function contributes to the stability of immune system,while NLRP3mutation can lead to immune disorders and autoimmune diseases,such as cryopyrin-associated periodic syndromes.As immune cells,platelet NLRP3 inflammasome plays an important role in the treatment of dengue fever infection.Although recent studies have shown thart NLRP3 inflammasome and IL-1βcontribute to platelet activation,the mechanism is still unclear.Whether platelet activation is dependent on the activation of inflammsome remains to be further verified.Here we report that platelets employ NLRP3 to regulate the major adhesion receptor Glycoprotein（GP）Ib-IX,without involving NLRP3 inflammasome assembly and interleukin（IL）-1β.NLRP3^-/-mice,but not ASC^-/-,caspase-1^-/-,or Nlrp3^A350V/+Cre PF4mice where the inflammasome assembly is either missing or enhanced,presented severely impaired thrombosis or hemostasis,as well as hampered platelet functions specific to GPIb-IX.Underpinning the regulation of NLRP3 in platelet,a decreased c AMP/PKA activity leads to the decreased phosphorylation of Ser 291 on NLRP3,resulting in a NLRP3-filamin A interaction,subsequently enabling a 14-3-3ζ-dependent upregulation of GPIb-IX affinity.Finally,the regulatory roles of GPIb-IX and NLRP3 in thrombo-inflammatory disease models were also confirmed as largely overlapping.Our study thus unveiled a cell type-specific mechanism of NLRP3 in platelet and may help to shape a better strategy for the management of thrombo-inflammatory diseases.In conclusion,NLRP3 targets GPIb-IX-V for the regulation of platelet function,independent of its canonical role in inflammasome assembly and IL-1βproduction.Platelet NLRP3 may be an important target for preventing thrombo-inflammatory diseases.