Effects Of Mitochondrial Unfolded Protein Response On The Formation Of Deep Tissue Pressure Injury And Its Mechanism

ObjectiveTo observe the dynamic changes of protein levels of HSP60,CHOP,CLpP,p-AKT and caspase-3 in the form of deep tissue pressure injury（DTPI）at different time points,and to investigate the effects of mitochondrial unfolded protein response(UPR^mt)and its related signal pathway on this injury.MethodsConstruction of pressure injury model of rat deep tissue:randomly 40 male SD rats were divided into normal control group and experimental group.The experimental group was divided into 1 cycle group（impose 2-h compression and subsequently release 0.5-h）,3 cycle group（Repeat“1 cycle group”three times）,6 cycle group（Repeat“1 cycle group”three times for two days）and 9 cycle group（Repeat“1 cycle group”three times for three days）,according to the different compression degrees（n=8）.22.47kPa was applied to the thin muscle of the hind limbs of the rat with two magnets.After the model was completed,the rats were killed and the muscle tissues were collected for examination.HE staining was carried out to observe the pathological changes,and Hoechst 33258staining was used to show the number of apoptotic nuclei in the compressed muscle tissue.The expression level of HSP60,CLpP,CHOP,p-AKT and caspase-3 were detected by Western blotting.ResultsThe skin changes of the compressed part were observed by naked eye.The 1compression cycle group began to appear erythema with constant pressure.The color gradually deepened,it showed a deep red with continuous finger pressure and a silt.The skin surface was always intact.With the extension of the compression cycle period,the morphological observation of HE staining showed that compared with the normal muscle tissue,the compressed muscle tissue of the compressed circulation group showed more pathological changes,such as degeneration of muscle fibers,more and more inflammatory cell infiltration and vacuolar degeneration.Furthermore,with the prolongation of compression,the number of apoptotic nuclei were increased,nuclei stained by Hoechst 33258 showed dense condensation and white granular fluorescence.Western Blot detected that compared with the normal group,protein expression of HSP60,CLpP,p-AKT and CHOP of 1 compression cycle group were significantly increased（P<0.01）,HSP60,CLpP and p-AKT protein expression peaked at 1 cycle group,and after that the compression cycle group decreased as much as normal group.The protein level of CHOP in the 3 compression cycle is increased than control（P<0.05）and peaked at 9compression cycle group（P<0.01）.The protein level of caspase-3 decreased in 1compression cycle group（P<0.05）,increased gradually in 3 cycle groups（P<0.01）and slightly decreased in the 6 cycle groups and the highest in the 9 cycle groups（P<0.01）.Conclusion（1）In the early stage（1 cycle）,the related protein expression of unfolded protein response increased significantly,indicating that the unfolded protein reaction of mitochondria may play an important role in the early stage of deep tissue pressure injury.（2）The early protective effect of mitochondrial unfolded protein response on deep tissue pressure injury may also be achieved by activating the PI3K/AKT pathway.After losing the protection,it promotes cell apoptosis probably by up-regulating protein expression of CHOP and caspase-3.