Effect Of High Mobility Group Box 1 On Burn-wound Progression In The Early Stage

Objective: To observe the role of HMGB1 in the early progression of burns and to explore its possible mechanism.Method: The brass comb probe with four 10x20 mm rectangular prongs,separated by three 5x10 mm wide grooves,was used to induce thermal contact burns,that produces 4 distinctive burns sites separated by 3“interspaces” of unburned skin.The interspaces represent the zone of stasis or ischemia.Twenty-four SPrague-Dawley rats were randomly assigned to tree groups,including the control group(burn+PBS 0.2ml subcutaneously,n=8),the HMGB1 group(burn+HMGB1 200 ng subcutaneously,n=8)and the antagonist group(burn+Box A 400 ng subcutaneously,n=8)and sacrificed at 1h、12h、24h、72h post burn.The relevant indicators are as follows:(1)At different time point after injury,the burn were observed for the necrosis in the unburned interspaces,and the percentage of necrotic area was calculated by software.(2)To observe the pathological changes in the unburned interspace sites and the progress of tissue necrosis,tissues were harvested to accept H&E and masson staining at different time points among the three groups.(3)The expression of HIF-1α and CD 45 was detected by immunohistochemistry and western blot.Results:(1)According to the visual observation,the necrotic area of the group was gradually increased with the development of time,but the area of the unburned interspaces undergoing necrosis of HMGB1 treatment group was smaller compared with the control group,and the necrotic area of Box A group was relatively wider.The percentage of interspaces undergoing necrosis in the HMGB1 treatment group,control group,and Box A group were18+10%,34+8%,47 +10%(HMGB1 vs control group,P<0.05;Box A vs control group,P<0.05;HMGB1 vs Box A,P<0.05)at 24 hours after burn,and were 36+12%,59+6%,68+15%(HMGB1 vs control group,P<0.05;Box A vs control group,P>0.05;HMGB1 vs Box A,P<0.05)at 72 hours after burn respectively.(2)Under H&E and Mason stains,it was shown that,with the development of time,the residual length of survived interspace epidermis was getting shorter,the interval between two adjacent necrosis zone was more and more narrow,and tend to merge.The survived interspace epidermics in the H M G B 1 t r e a t m e n t g r o u p,c o n t r o l g r o u p,a n d B o x A g r o u p w e r e 3.10+0.25 mm,2.74+0.27 mm,2.35+0.30mm(HMGB1 vs control group,P<0.05;Box A vs control group,P<0.05;HMGB1 vs Box A,P<0.05)at 24 hours after burn,and were 2.62+0.33 mm,1.84+0.63 mm,1.56+0.66mm(HMGB1 vs control group,P<0.05;Box A vs control group,P>0.05;HMGB1 vs Box A,P<0.05)at 72 hours after burn respectively.At the same time,when compared to control group,the HMGB1-treated interspaces showed a marked increase in epidemis and dermis destruction and discoloration,residual hair follicles and sweat glands,and reduced vascular thrombosis.While the Box A-accepted interspaces showed a marked decrease in epidemis and dermis destruction and discoloration,residual hair follicles and sweat glands,and reduced vascular thrombosis.Note the increased width of interspace and overall rate of necrosis after HMGB1-treatment,and the decreased width of interspace and overall rate of necrosis after Box A-administration.(3)The expression of HIF-1α in the HMGB1 group was significantly higher than that in the control group.The expression level of HIF-1α in the Box A group was significantly decreased.At the same time,with reference to the control group,HMGB1 treatment could promote the expression of factor CD45 at multiple time points.Box A intervention significantly inhibited the expression of factor CD45.Conclusion:(1)Early topical application of HMGB1 improved thermal injury-induced histology changes in the unburned interspace and alleviate wound deepening.(2)Systermic application of HMGB1 on the zone of stasis can improve the expression of HIF-1α in the site,and we observed that the process HMGB1 preventing progression of burn may be associated with the increased expression of HIF-1α,and that the induced HIF-1α was significantly reduced by inhibiting HMGB1 activity.(3)HMGB1 can also promote the expression of CD45 in the unburned interspace and improve the wound inflammatory response in the early stage of burn.However,there was no further progression of the zone of stasis to necrosis.The in vivo inhibition of HMGB1 was accomplished using the Box A,which suppresses the expression of CD45 factor,did not save the zone of stasis.This is probably related to the appropriately promoted inflammatory infiltrate accelerating wound repair at the burn site in the early stage.