Ischemia Caused Shedding Of Endothelial Glycoalyx Is Protected By Sevoflurane

AimHealthy vascular endothelium is coated by the endothelial glycocalyx, diminution of which increases capillary permeability. The aims of this study is to evaluate the extent of glycocalyx shedding caused by ischemia-reperfusion injury and try to find its mechanism, to observe the effect of sevoflurane on shedding of endothelial glycocalyx caused by ischemia-reperfusion injury and try to find its mechanism, and to assess the effects of different models of sevoflurane treatment on endothelial glycocalyx.Materials and methodsIsolated guinea pig hearts were perfused with modified Krebs-Henseleit (K-H) buffer, the perfusion pressure was maintained at 70 cmH20. The experiment was separated to two parts. The first part,42 healthy male guinea pigs were separated into 6 groups, isolated langendorff model was established on each of them. Group A was time-control group, group B was time-control group with sevoflurane treatment, group C was ischemia-reperfusion group, group D was ischemia-reperfusion injury group with sevoflurane pretreatment, group E was ischemia-reperfusion injury group with sevoflurane post-treatment, group F was ischemia-reperfusion group with sevoflurane pre-and post-treatment. Global warm ischemia (37℃) was induced for 20min in hearts of ischemia-reperfusion group, followed by 40min of reperfusion. In the last 20 min of reperfusion, hearts were perfused with Modified K-H buffer plus 1% of hydroxyethyl starch (130kd). Sevoflurane pretreatment was performed for 15min just before ischemia. Sevoflurane post-treatment was performed thought the whole reperfusion period. Coronary net fluid filtration was evaluated by measuring transudate formation on the epicedial surface. Hearts were perfusion fixed after the end of reperfusion to show the glycocalyx. Baseline measurements of coronary effluent and transudate were performed in the last 3 min before ischemia. Samples of effluent were also collected between minutes 0-5,5-10,10-20,35-40 after the onset of reperfusion. Transudate samples were collected over 5-min time intervals after start of reperfusion. Parameters including the concentration of shedding of components of glycocalyx (sydecan-1, heparan sulfate, and hyaluronan), lactate, purine, uric acid in effluent; the concentration of histamine, creatine kinase, hydroxyethyl starch in transudate. Electron microscopy of hearts to visible glycocalyx was performed and immunohistochemical characterization of hearts was conducted to gain insight into the composition of the glycocalyx. The second part, 12 healthy male guinea pigs were separated into 2 groups, isolated langendorff model was established as the first part. Group C was ischemia-reperfusion group, group S was ischemia-reperfusion group with sevoflurane pre-and post-treatment. Parameters including volume of transudate and effluent, concentrations of cathepsin-B, tryptase and tryptase without thrombin in transudate and effluent. Results1,Compared with time control group A and B, there was more transudate and less effluent in group C. Ischemia-reperfusion injury significantly increased the concentration of lactate, purine, uric acid, syndecan-1, heparan sulfate and hyluronic acid in effluent. Furthermore, concentration of histamine, creatin kinase, HES were significantly higher in group C.2,Immunohistochemical staining showed that ischemia-reperfusion injury caused negative staining of syndecan-1 and heparin sulfate on endovascular surface, electron microscopy with lanthanum staining to visible endothelial glycocalyx showed severe shedding of glycocalyx on endovascular surface in ischemia-reperfusion injury group.3,Application of sevoflurane reduced the volume of transudate, HES and creatine kinase levels in transudate but had no significant impact on the level of histamine. Sevoflurane increased the amount of effluent, but the lactic acid, purine, uric acid release in effluent was not significantly changed. Sevoflurane reduced the release of major components of glycocalyx in the effluent, so immunohistochemical staining of syndecan-1 and heparan sulfate enhanced, and electron microscopy showed that shedding of glycocalyx decreased.4,Sevoflurane also reduced the release of cathepsin B in effluent, but had no significant effect on the release of the tryptase and tryptase without thrombin.5,There is no significant difference among groups with sevoflurane pretreatment, posttreatment and pre-plus post-treatment. Conclusions1,Ischemia-reperfusion cause shedding of endothelial glycocalyx, thus increase the permeability of vascular. It also induce significant increases in myocardial oxidative stress, anaerobic metabolism, release of creatine kinase in myocardial cell and histamine in mast cell, thus reduce the cardiac function.2,Sevoflurane significantly reduce shedding of the endothelial glycocalyx, thus reduce the permeability of small vessels and decrease the extravasation of HES, reduce the release of creatine kinase and improve post-reperfusion cardiac function. However, sevoflurane has no significant effect on oxidative stress and myocardial metabolism, nor prevente the release of histamine in mast cells. In this experiment time frame, compared to sevoflurane pretreatment, sevoflurane pre-plus post-treatment can not enhanced the protective effect.3,The protective mechanism of sevoflurane on endothelial glycocalyx in this isolated guinea pig hearts maybe via binding of sevoflurane to the glycocalyx or to unknown proteinase(s) prevents enzymatic shedding during postischemia reperfusion of the heart, thus inhibited the release of protease or decrease the activity of protease. Sevoflurane has no significant effect on main cell degranulation.