Interaction Between Mac-1 And ICAM-1 To Mediate NETs Formation

Neutrophils are the first cells to respond to inflammatory stimuli,reach the site of inflammation,and exert their immune function.They are sterilized by phagocytosis,degranulation,and release of extracellular traps?NETs?.NETs are a network structure composed of DNA fibers and histones and a variety of antibacterial proteins attached to the DNA fibers.They play an important role in many infectious and non-infectious diseases,including atherosclerosis,cancer and sepsis,and some scholars even speculated that NETs also played an important role in the process of new coronavirus pneumonia?COVID-19?.Among them,the generation of NETs is closely related to thrombosis.When a thrombus is formed,NETs are generated in blood vessels,providing a network framework for blood cell adhesion,and can activate platelets,thereby promoting thrombosis.In addition,studies have shown that?2 integrin on neutrophils is involved in the formation of NETs.At present,there are two main types of NETs:"suicidal NETs"that takes about 4 hours to form and"vital NETs"that can be quickly formed.The former requires the participation of ROS.However,people do not fully understand the mechanism of NETs formed by neutrophils adhered to the blood vessel wall when thrombosis is formed,and the elimination of thrombus,especially systemic thrombosis,is still a big problem in the medical community.This paper investigates the mechanism of interaction between neutrophils and vascular endothelial cells to mediate the formation of NETs.Using fluorescence microscopy,LPS was used to stimulate neutrophils stably adhered to the surface of ICAM-1,and the formation and regulation mechanism of NETs were investigated.The results show that:?1?neutrophils stably attached to the surface of ICAM-1 produce a large number of NETs after 1 hour of LPS stimulation,and increase with the stimulation time;?2?In this case,The generated NETs depend on the integrin Mac-1,but not on the integrin LFA-1;?3?Surprisingly,this process does not depend on ROS,which is a key molecule in the process of generating NETs;?4?Ca²⁺plays a very important role in the function of neutrophils,it has an effect on integrin activation,cytoskeletal rearrangement and leukocyte migration.This study found that both intracellular Ca²⁺and extracellular Ca²⁺play an important role in the formation of NETs.This study reveals the mechanism by which LPS stimulates the formation of neutrophil NETs that stably adhere to the surface of ICAM-1:The combined effect of LPS stimulation and Mac-1's outside-in signal causes the upregulation of intracellular Ca²⁺in neutrophils and the influx of extracellular Ca²⁺,which may directly activate PAD4,which in turn leads to the formation of NETs.This study is helpful to deeply understand the pathophysiological process of intravascular NETs formation,which leads to thrombosis,and provides new ideas for the treatment and control of related diseases?such as sepsis,COVID-19,etc.?.