Role Of Injury Induced Electric Field In Initial Platelet Accumulation In Primary Hemostasis

Platelets are vital components in early process of primary hemostasis by virtue of their capacity to adhere and aggregate to the injured blood vessel wall.Also,the blood vessel wall has played the important role to the arrest of bleeding.Most types of cells circulating in the blood and vascular endothelial cell(VEC)are negatively charged.The negative charge of them are contributed mainly by the surface exposed sialic acids of the membrane.Some experiments characterizing the electrical properties of blood vessels have been carried out.Some of the experiments were done to determine the possible existence,magnitude,and polarity of the normal potential difference across the vessel wall using in vivo and in vitro preparations.It has been shown that the vascular endothelial cells carry high-density negative charge,there is a potential gradient between the intima of blood vessel and the adventitia,which is about 3～5mV,we called Transvascular electric potential(TVEP).Thus,The contribution of the negative charge prevents the adhesion of circulating platelets from intima of blood vessel.After the injury of the vascular wall,the inside and outside of the vascular wall at the injury site are connected to produce ion flow,the potential gradient decreases or disappears,and the local endogenous electric field(defined as injury induced electric field,IIEF)is formed between the injury site inside the vascular wall(potential 0 mV)and the adjacent uninjured site(potential-3～-5mv).By far,the role of electrical signal in initial platelet adhesion in hemostasis has been less well defined.Here,we show that the injury induced electric field(IIEF)plays an important role in initial platelets accumulation,which is prior to the onset of platelet accumulation.By using electrophysiological method,we show that punctured injury results in an IIEF.The electric field with the strength of the IIEF is large enough to cause highly directional movement of platelets in vitro with field strength dependence.With intravital imaging technique,we demonstrate that an external applied electric field(EAEF)that mimics the IIEF affect transient platelet deposition for uninjured vessels at the site beneath the anode at millisecond time scale,which is confirmed by fluorescent-labeled platelet accumulation.when the EAEF was removed,the fluorescent intensity was decreased and the accumulated platelets were floating away with the circulating blood flow,indicating that the the role of electrical signal could not make the platelets adhere to the blood vessel wall firmly.For injured vessels,the platelet accumulation at the injured site can be delayed if the IIEF is suppressed by the EAEF with physiological strength,while it is accelerated if the IIEF is enhanced.Furthermore,platelets cannot accumulate at all in the injured area if larger EAEF is applied.To study the role of the endogenous IIEF in the platelet accumulation under physiological condition,we manipulated the endogenous IIEF by altering the endogenous TVEP with chemical agents.The results suggest that alteration in endogenous IIEF could exert marked effect on the initial platelet accumulation.In addition,the electrical signal can still induce platelet accumulation even when the platelet adhesion,activation and aggregation are blocked by using aspirin,bivalirudin,lopidogrel,suramin,Aurin tricarboxylic acid(ATA),tirofiban.These findings suggests that the IIEF is the earlier factor that is responsible for forcing the fast moving platelets to accumulate at the injured site.Taken together,we suggest a new reinterpretation of the mechanisms of driving platelet accumulation in hemostasis and provide a new theoretical basis for the hemostatic drugs and antithrombotic therapies.