The Effect Of JAK/STAT3 Pathway Inhibitor On The Function Of Extensor Digitorum Longus And Diaphragm In Severely Burned Rats

Objective:To observe the functional changes of extensor digitorum longus and diaphragm in rats after severe burns,and to explore the effect of JAK/STAT3 pathway inhibitor on extensor digitorum longus and diaphragm function and its possible mechanism.MethodsⅠ:120 male Wistar rats（8 weeks old,300 grams）were randomly divided into control group,burn group and burns+JAK/STAT3 inhibitor（Ruxolitinib）treatment group（the treatment group for short）of 40 per group.The burn group rat was given 50%of the surface area III degrees burns,and after the treatment group rats gave the same burns to the burn group,the abdominal injection inhibitor was given 60mg/kg/d,2 times/d,at intervals of 12h and used continuously 5d.On 0,1,4,7and 14d after injury extensor digitorum longus muscle of rats was cut completely,The contractile function（specific force）,force frequency relationship and fatigue period specific force of extensor digitorum longus muscle were measured by the electrophysiological instrument with ex-vivo automatic organ bath incubation system.The content of carbonyl compounds in extensor digitorum longus protein was measured by UV spectrophotometry,and the content of ATP in extensor digitorum longus muscle was measured by micro method.MethodsⅡ:A total of 240 Wistar male rats were used in this part of the experiment.120 male Wistar rats（8 weeks old,≈300 g）were randomly divided into control group,burn group and burn JAK/STAT3 inhibitor（Ruxolitinib）therapy group（abbreviated as therapy group）,40 rats in each group.The rats in the burn group were given 50%total body surface area III degree,and the rats in the therapy group were given the same scald in the burn group.After the burn group was given the same scald,the inhibitor of intraperitoneal injection was given 60 mg/kg/d,2 times/d,interval 12 h and continued use for 5 d.The rat diaphragm was completely cut in the 0、1、4、7 and 14d after injury.The contractile function（specific force）,force-frequency relationship,fatigue phase specific force,fatigue index was measured by multi-channel electrophysiological instrument.The content of carbonyl compounds in diaphragmatic protein was measured by UV spectrophotometry,and the content of ATP in diaphragmatic was measured by micro method.Meanwhile,120 rats were taken to prepare copy of the above three groups of experimental animals,PowerLab 8/35 measurement of Pdi,Pdimax and Pdi/Paimax ratio;Ultrahigh resolution small animal ultrasound imaging system was used to detect the DTei,DTee,DTmax,DTF and DE.ResultsⅠ:（1）Compared to the control group,in addition to the 4d 20Hz frequency,The strength of extensor digitorum longus muscle contraction in the burn group decreased significantly under electrical stimulation of 0 to 7d frequencies（P<0.05 or P<0.01）,while only 20 to 40Hz was significantly lower than in the control group after 14d（P<0.05 or P<0.01）;Compared with the burn group,in addition to the 1d 20Hz frequency,1to 14d after injury at different frequency electrical stimulation,extensor digitorum longus muscle contraction specific force significantly increased（P<0.05 or P<0.01）,while after the injury 0d different frequency stimulation was no significant difference（P>0.05）.（2）Compared to the control group,The maximum muscle specific force of the extensor digitorum longus muscle in the burn group decreased significantly from 0 to 7d（P<0.05 or P<0.01）,and there was no significant difference in 14d after injury（P>0.05）;Compared with the burn group,the maximum muscle specific force of extensor digitorum longus muscle increased significantly from 1 to 14d（P<0.05 or P<0.01）,and there was no significant difference at 0d after injury（P>0.05）.（3）Compared with the control group,there was no significant difference in the fatigue specific force of the extensor digitorum longus muscle in the burn group only at7d at 240s of electrical stimulation（P>05）,while the fatigue period of the other time points decreased significantly（P<0.05 or P<0.01）;Compared with the burn group,60s,300s,in the treatment group compared to the burn group,60s,300s,There was no significant difference in the 4d fatigue period 240s electrical stimulation（P>0.05）,while the specific force of 1 to 14d other fatigue periods increased significantly after injury（P<0.05 or P<0.01）.（4）Compared with the control group,the levels of carbonyl compounds in extensor digitorum longus muscle were significantly increased in the burn group from 0 to 14d increased significantly after the burn group（P<0.01）;Compared with the burn group,The levels of carbonyl compounds in the treatment group were significantly decreased（P<0.05 or P<0.01）.（5）Compared to the control group,The ATP content in the 0-14d extensor digitorum longus muscle of the burn group was decreased significantly（P<0.05 or P<0.01）;Compared with the burn group,the ATP content in the extensor digitorum longus muscle of the burn group was decreased significantly（P<0.05 or P<0.01）,and there was no significant difference in 0d after injury（P>0.05）.ResultsⅡ:（1）Compared with the control group,the pH of rats in burn group decreased significantly at 0,1d（P<0.01）,then gradually recovered,there was no significant difference at 4,14d（P>0.05）;Therapy group compared with burn group,pH returned to normal at 1 d（P<0.01）,lower than burn group at 7d（P<0.05）,but no significant difference at 0,4,14d（P>0.05）.Compared with the control group,SaO₂ decreased significantly in burn group rats at all time points（P<0.05 or P<0.01）;Therapy group compared with burn group,SaO₂ increased significantly 1-7d（P<0.05 or P<0.01）,No significant difference at 0,14d（P<0.05）.Compared with the control group,PaO₂ in the burn group increased significantly at 0,1d（P<0.01）,Significantly decreased at4-14d（P<0.05 or P<0.01）;Therapy group compared with burn group,PaO₂ was not significantly difference at 0,1d（P>0.05）,4-14 days still higher than the burn group（P<0.05）.Compared with the control group,PaCO₂ in burn group rats decreased significantly at 0,1,4d（P<0.05 or P<0.01）,then significantly higher than the normal range at 7d（P<0.01）,and returned to normal range at 14d（P<0.05）;Therapy group compared with burn group,PaCO₂ increased significantly at 1-4d（P<0.05 or P<0.01）,There was no significant difference at 0,14d（P>0.05）.Compared with the control group,HCO₃^-in burn group rats decreased significantly at 0,1d（P<0.01）,then it increased significantly and was higher than 27 mmol/L at 4-14d（P<0.01）.Therapy group compared with burn group,HCO₃^-increased significantly at 1 d（P<0.01）,and maintained at 24 to 27 mmol/L at 4-14 d,and there was no significant difference at 0d（P>0.05）.Compared with the control group,The LAC in burn group rats increased significantly at 0-14d（P<0.05 or P<0.01）;Therapy group compared with burn group,LAC decreased significantly at 0-14d（P<0.05 or P<0.01）.（2）Compared with the control group,the contractile force of the diaphragm muscle in burn group rats decreased significantly in 20Hz at 0d after injury（P<0.05）,then minimized at 1d（P<0.01）,There was no significant difference in 20Hz electrical stimulation at 7d after injury,in 20,40,50,60,80,100,140,160Hz electrical stimulation at 14d after injury（P>0.05）.Therapy group compared with burn group,Diaphragm contractility increased significantly at 1-14d（P<0.05 or P<0.01）,and there was no significant difference under different frequency electrical stimulation at 0d（P>0.05）.Compared with the control group,the maximum diaphragm specific force in the burn group rats decreased significantly at 0-7d after injury（P<0.01）,and there was no significant difference at 14d（P>0.05）;Therapy group compared with burn group,the maximum diaphragm specific force was significantly increased at 1-14 days（P<0.01）,and there was no significant difference at 0d（P>0.05）.（3）Compared with the control group,the specific force of the diaphragm in the burn group was significantly decreased during fatigue at 0-7d（P<0.05 or P<0.01）,there were significant difference in 0s,120s Electrical stimulation time at 14d after injury（P<0.05）;Therapy group compared with burn group,the specific force of the diaphragm was increased significantly during fatigue at 1-14d after injury（P<0.05 or P<0.01）,but no significant difference was found at all electrical stimulation sites at 0d after injury（P>0.05）.Compared with the control group,diaphragm fatigue index in burn group rats decreased significantly in 180s electrical stimulation time at 1d,in 30s,60s,120s,180s,240,300s electrical stimulation time at 4d,in 20s,60s,120s,180s electrical stimulation time at 7d and in 180s,300s electrical stimulation time at 14d after injury.（P<0.01）,the other was no significant difference（P>0.05）;Therapy group compared with burn group,the fatigue index of rats was significantly increased in 60s,120s,180s at 1d,in 30s,60s,180s at 4d,in 20s,30s,60s,120s,180s,240s,300s at 7d,in 60s,120s,180s at 14d.（P<0.05 or P<0.01）,there was no significant difference in other electrical stimulations（P>0.05）.（4）Compared with the control group,the Pdi in burn group rats decreased significantly at all days after injury（P<0.05 or P<0.01）;Therapy group compared with burn group,Pdi increased significantly at all days after injury.Compared with the control group,the Pdimax in the burn group rats decreased significantly at all days after injury（P<0.05 or P<0.01）;Therapy group compared with burn group,Pdimax increased significantly at 1-14d after injury（P<0.05 or P<0.01）,but there was no significant difference at 0d after injury（P>0.05）.Compared with the control group,Pdi/Pdimax ratio in burn group rats increased significantly 4-14d after injury（P<0.05 or P<0.01）,but there was no significant difference at 0,1d after injury（P>0.05）;Therapy group compared with burn group,Pdi/Pdimax ratio increased at 4d after injury（P<0.05）,and the Pdi/Pdimax ratio decreased significantly at 7,14d after injury（P<0.05）.There was no significant difference at 0,1d after injury（P>0.05）.（5）Compared with the control group,DTei in the burn group decreased significantly at 0-14d after injury（P<0.01）;Therapy group compared with burn group,DTei significantly increased at all days after injury（P<0.05 or P<0.01）.Compared with the control group,,DTee decreased significantly in the burn group at 0-14d（P<0.05 or P<0.01）;Therapy group compared with burn group,DTee increased significantly at 1,7 and14d after injury（P<0.01）,and there was no significant difference 0d,4d（P>0.05）.Compared with the control group,DTmax in the burn group decreased significantly at0-14d after injury（P<0.05 or P<0.01）;Therapy group compared with burn group,DTmax increased significantly at 0-14d after injury（P<0.05 or P<0.01）,but there was no significant difference at 0d（P>0.05）.Compared with the control group,DTF in burn group rats decreased significantly at 0-7d（P<0.05 or P<0.01）,but there was no significant difference at 14 days（P>0.05）;Therapy group compared with burn group,DTF increased significantly at 0-7d after injury（P<0.05）,but there was no significant difference at 14d（P>0.05）.Compared with the control group,DE in burn group rats decreased significantly at 0-14d（P<0.01）;Therapy group compared with burn group,DE increased significantly at 1-14d（P<0.05 or P<0.01）,but there was no significant difference at 0d（P>0.05）.（6）Compared with the control group,the carbonyl compounds levels of diaphragmatic protein in the burn group rats increased significantly at 0-14d after injury（P<0.01）;Therapy group compared with burn group,the carbonyl compounds levels of diaphragmatic protein decreased significantly at 1-14d（P<0.01）,but there was no significant difference at 0 d（P>0.05）.（7）Compared with the control group,the ATP content of diaphragm decreased significantly in burn group after injury（P<0.05 or P<0.01）;Therapy group compared with burn group,ATP content of diaphragm increased significantly at 1-14d（P<0.05 or P<0.01）,but there was no significant difference at 0 days（P>0.05）.Conclusion:The specific force and maximum specific force of the diaphragm decreased significantly under different frequency electrical stimulation after severe burn,and it was easy to fatigue;Meanwhile,the Pdi,Diaphragm thickness,DTF and DE decreased.while blocking the JAK/STAT3 signaling pathway can reduce the oxidative stress of myoprotein and increase the ATP content,and then alleviate the decrease of muscle contractility,Pdi and Diaphragm thickness caused by burns and improve their fatigue degree.