Sevoflurane mitigates shedding of hyaluronan from the coronary endothelium, also during ischemia/reperfusion: an ex vivo animal study

Heparanase as active player in endothelial glycocalyx remodeling

The surface of all animal cells is coated with a layer of carbohydrates linked in various ways to the outer side of the plasma membrane. These carbohydrates are mainly bound to proteins in the form of glycoproteins and proteoglycans and together with the glycolipids constitute the so-called glycocalyx. In particular, the endothelial glycocalyx that covers the luminal layer of the endothelium is composed of glycosaminoglycans (heparan sulphate -HS and hyaluronic acid -HA), proteoglycans (syndecans and glypicans) and adsorbed plasma proteins. Thanks to its ability to absorb water, this structure contributes to making the surface of the vessels slippery but at the same time acts by modulating the mechano-transduction of the vessels, the vascular permeability and the adhesion of leukocytes in thus regulating several physiological and pathological events. Among the various enzymes involved in the degradation of the glycocalyx, heparanase (HPSE) has been shown to be particularly involved. This enzyme is responsible for the cutting of heparan sulfate (HS) chains at the level of the proteoglycans of the endothelial glycocalyx whose dysfunction appears to have a role in organ fibrosis, sepsis and viral infection. In this mini-review, we describe the mechanisms by which HPSE contributes to glycocalyx remodeling and then examine the role of glycocalyx degradation in the development of pathological conditions and pharmacological strategies to preserve glycocalyx during disease pathogenesis.

Cox-2 Antagonizes the Protective Effect of Sevoflurane on Hypoxia/Reoxygenation-Induced Cardiomyocyte Apoptosis through Inhibiting the Akt Pathway

Objective

To uncover the protective role of sevoflurane on hypoxia/reoxygenation-induced cardiomyocyte apoptosis through the protein kinase B (Akt) pathway.

Methods

An in vitro hypoxia/reoxygenation (H/R) model was established in cardiomyocyte cell line H9c2. Sevoflurane (SEV) was administrated in H9c2 cells during the reoxygenation period. Viability, layered double hydroxide (LDH) release, and apoptosis in H9c2 cells were determined to assess H/R-induced cell damage. Relative levels of apoptosis-associated genes were examined. Moreover, phosphorylation of Akt was determined.

Results

H/R injury declined viability and enhanced LDH release and apoptotic rate in H9c2 cells. Cyclooxygenase-2 (Cox-2) was upregulated following H/R injury, which was partially reversed by SEV treatment. In addition, SEV treatment reversed changes in viability and LDH release owing to H/R injury in H9c2 cells, which were further aggravated by overexpression of Cox-2. The Akt pathway was inhibited in H9c2 cells overexpressing Cox-2.

Conclusions

Sevoflurane protects cardiomyocyte damage following H/R via the Akt pathway, and its protective effect was abolished by overexpression of Cox-2.

The Endothelial Glycocalyx and Organ Preservation-From Physiology to Possible Clinical Implications for Solid Organ Transplantation

The endothelial glycocalyx is a thin layer consisting of proteoglycans, glycoproteins and glycosaminoglycans that lines the luminal side of vascular endothelial cells. It acts as a barrier and contributes to the maintenance of vascular homeostasis and microperfusion. During solid organ transplantation, the endothelial glycocalyx of the graft is damaged as part of Ischemia Reperfusion Injury (IRI), which is associated with impaired organ function. Although several substances are known to mitigate glycocalyx damage, it has not been possible to use these substances during graft storage on ice. Normothermic machine perfusion (NMP) emerges as an alternative technology for organ preservation and allows for organ evaluation, but also offers the possibility to treat and thus improve organ quality during storage. This review highlights the current knowledge on glycocalyx injury during organ transplantation, presents ways to protect the endothelial glycocalyx and discusses potential glycocalyx protection strategies during normothermic machine perfusion.

Molecular Aspects of Volatile Anesthetic-Induced Organ Protection and Its Potential in Kidney Transplantation

Ischemia reperfusion injury (IRI) is inevitable in kidney transplantation and negatively impacts graft and patient outcome. Reperfusion takes place in the recipient and most of the injury following ischemia and reperfusion occurs during this reperfusion phase; therefore, the intra-operative period seems an attractive window of opportunity to modulate IRI and improve short- and potentially long-term graft outcome. Commonly used volatile anesthetics such as sevoflurane and isoflurane have been shown to interfere with many of the pathophysiological processes involved in the injurious cascade of IRI. Therefore, volatile anesthetic (VA) agents might be the preferred anesthetics used during the transplantation procedure. This review highlights the molecular and cellular protective points of engagement of VA shown in in vitro studies and in vivo animal experiments, and the potential translation of these results to the clinical setting of kidney transplantation.

Endothelial cells, neutrophils and platelets: getting to the bottom of an inflammatory triangle

Severe fibrotic and thrombotic events permeate the healthcare system, causing suffering for millions of patients with inflammatory disorders. As late-state consequences of chronic inflammation, fibrosis and thrombosis are the culmination of pathological interactions of activated endothelium, neutrophils and platelets after vessel injury. Coupling of these three cell types ensures a pro-coagulant, cytokine-rich environment that promotes the capture, activation and proliferation of circulating immune cells and recruitment of key pro-fibrotic cell types such as myofibroblasts. As the first responders to sterile inflammatory injury, it is important to understand how endothelial cells, neutrophils and platelets help create this environment. There has been a growing interest in this intersection over the past decade that has helped shape the development of therapeutics to target these processes. Here, we review recent insights into how neutrophils, platelets and endothelial cells guide the development of pathological vessel repair that can also result in underlying tissue fibrosis. We further discuss recent efforts that have been made to translate this knowledge into therapeutics and provide perspective as to how a compound or combination therapeutics may be most efficacious when tackling fibrosis and thrombosis that is brought upon by chronic inflammation.

Immediate effects of whole blood donation on the endothelial surface layer and glycocalyx shedding

BACKGROUND

The endothelium plays a pivotal role in regulating microvascular function, especially in situations associated with acute blood loss. Whether blood donation and the associated volume loss affects the dimensions of the endothelial surface layer (ESL) and glycocalyx integrity remains unknown.

MATERIALS AND METHODS

This study was designed to determine real-time ESL and perfusion measurements of the sublingual microcirculation using sidestream dark field imaging performed in healthy subjects shortly before and after a donation of 500 mL whole blood. A novel image acquisition and analysis software (GlycoCheck™) automatically calculated the perfused boundary region (PBR), an inverse parameter for red blood cell (RBC) penetration into the ESL, in vessels between 5 and 25 μm in diameter. Microvascular perfusion was measured by RBC filling percentage. Soluble glycocalyx components were determined in the peripheral circulation.

RESULTS

There was no significant immediate effect of whole blood donation on PBR and RBC filling percentage. Linear regression analysis revealed a distinct association between change in PBR and change in RBC filling percentage (regression coefficient β: -0.040; 95% confidence interval: -0.049 to -0.030; p<0.001). A significant reduction in plasma heparan sulphate (1,329±316 vs 1,237±275 ng/mL, p=0.005) and hyaluronan (94±18 vs 90±16 ng/mL, p=0.002) was noted, while syndecan-1 levels (30 [23-50] vs 29 [24-46] ng/mL, p=0.282) remained unchanged.

DISCUSSION

Dimensions and integrity of the ESL appear to remain stable following a 500 mL whole blood donation and reflect its ability to ensure microvascular function and perfusion.

A review on the physiological and pathophysiological role of endothelial glycocalyx

The glycocalyx is a gel-like layer covering the luminal surface of vascular endothelial cells. It comprises of membrane-attached proteoglycans, glycosaminoglycan chains, glycoproteins, and adherent plasma proteins. The glycocalyx maintains homeostasis of the vasculature, which includes controlling vascular permeability and microvascular tone, preventing microvascular thrombosis, and regulating leukocyte adhesion. In the past decades, the number of studies on endothelial glycocalyx has steadily grown. Glycocalyx emerged as an essential part of blood vessels involved in multiple physiological functions. Damage to glycocalyx is associated with many types of diseases. The structure and physiology and pathophysiology of the glycocalyx, as well as the clinical effects of glycocalyx degradation, are addressed throughout this study. We strive in particular to define therapeutic approaches for the survival or reparation of the glycocalyx.

Effect of sevoflurane and propofol on tourniquet-induced endothelial damage: a pilot randomized controlled trial for knee-ligament surgery

BACKGROUND

The glycocalyx layer is a key structure in the endothelium. Tourniquet-induced ischemic periods are used during orthopedic surgery, and the reactive oxygen species generated after ischemia-reperfusion may mediate the shedding of the glycocalyx. Here, we describe the effects of tourniquet-induced ischemia-reperfusion and compare the effects of sevoflurane and propofol on the release of endothelial biomarkers after ischemia-reperfusion in knee-ligament surgery.

METHODS

This pilot, single-center, blinded, randomized, controlled trial included 16 healthy patients. After spinal anesthesia, hypnosis was achieved with sevoflurane or propofol according to randomization. During the perioperative period, five venous blood samples were collected for quantification of syndecan-1, heparan sulfate, and thrombomodulin from blood serum by using ELISA assays kits. Sample size calculation was performed to detect a 25% change in the mean concentration of syndecan-1 with an alpha of 0.05 and power of 80%.

RESULTS

For our primary outcome, a two-way ANOVA with post-hoc Bonferroni correction analysis showed no differences in syndecan-1 concentrations between the sevoflurane and propofol groups at any time point. In the sevoflurane group, we noted an increase in syndecan-1 concentrations 90 min after tourniquet release in the sevoflurane group from 34.6 ± 24.4 ng/mL to 47.9 ± 29.8 ng/mL (Wilcoxon test, p < 0.01) that was not observed in patients randomized to the propofol group. The two-way ANOVA showed no intergroup differences in heparan sulfate and thrombomodulin levels.

CONCLUSIONS

Superficial endothelial damage without alterations in the cell layer integrity was observed after tourniquet knee-ligament surgery. There was no elevation in serum endothelial biomarkers in the propofol group patients. Sevoflurane did not show the protective effect observed in in vitro and in vivo studies.

TRIAL REGISTRATION

The trial was registered in www.clinicaltrials.gov (ref: NCT03772054, Registered 11 December 2018).

Fluid resuscitation in sepsis: the great 30 mL per kg hoax

Large volume fluid resuscitation is currently viewed as the cornerstone of the treatment of septic shock. The surviving sepsis campaign (SSC) guidelines provide a strong recommendation to rapidly administer a minimum of 30 mL/kg crystalloid solution intravenously in all patients with septic shock and those with elevated blood lactate levels. However, there is no credible evidence to support this recommendation. In fact, recent findings from experimental, observational and randomized clinical trials demonstrate improved outcomes with a more restrictive approach to fluid resuscitation. Accumulating evidence suggests that aggressive fluid resuscitation is harmful. Paradoxically, excess fluid administration may worsen shock. In this review, we critically evaluate the scientific evidence for a weight-based fluid resuscitation approach. Furthermore, the potential mechanisms and consequences of harm associated with fluid resuscitation are discussed. Finally, we recommend an individualized, conservative and physiologic guided approach to fluid resuscitation.

On-the-Scene Hyaluronan and Syndecan-1 Serum Concentrations and Outcome after Cardiac Arrest and Resuscitation

Background

It is not predictable which patients will develop a severe inflammatory response after successful cardiopulmonary resuscitation (CPR), also known as “postcardiac arrest syndrome.” This pathology affects only a subgroup of cardiac arrest victims. Whole body ischemia/reperfusion and prolonged shock states after return of spontaneous circulation (ROSC) may both contribute to this devastating condition. The vascular endothelium with its glycocalyx is especially susceptible to initial ischemic damage and may play a detrimental role in the initiation of postischemic inflammatory reactions. It is not known to date if an immediate early damage to the endothelial glycocalyx, detected by on-the-scene blood sampling and measurement of soluble components (hyaluronan and syndecan-1), precedes and predicts multiple organ failure (MOF) and survival after ROSC.

Methods

15 patients after prehospital resuscitation were included in the study. Serum samples were collected on the scene immediately after ROSC and after 6 h, 12 h, 24 h, and 48 h. Hyaluronan and syndecan-1 were measured by ELISA. We associated the development of multiple organ failure and 30-day survival rates with these serum markers of early glycocalyx damage.

Results

Immediate serum hyaluronan concentrations show significant differences depending on 30-day survival. Further, the hyaluronan level is significantly higher in patients developing MOF during the initial and intermediate resuscitation period. Also, the syndecan-1 levels are significantly different according to MOF occurrence.

Conclusion

Serum markers of glycocalyx shedding taken immediately on the scene after ROSC can predict the occurrence of multiple organ failure and adverse clinical outcome in patients after cardiac arrest.

Anesthesia-Associated Relative Hypovolemia: Mechanisms, Monitoring, and Treatment Considerations

Although the utility and benefits of anesthesia and analgesia are irrefutable, their practice is not void of risks. Almost all drugs that produce anesthesia endanger cardiovascular stability by producing dose-dependent impairment of cardiac function, vascular reactivity, and compensatory autoregulatory responses. Whereas anesthesia-related depression of cardiac performance and arterial vasodilation are well recognized adverse effects contributing to anesthetic risk, far less emphasis has been placed on effects impacting venous physiology and venous return. The venous circulation, containing about 65–70% of the total blood volume, is a pivotal contributor to stroke volume and cardiac output. Vasodilation, particularly venodilation, is the primary cause of relative hypovolemia produced by anesthetic drugs and is often associated with increased venous compliance, decreased venous return, and reduced response to vasoactive substances. Depending on factors such as patient status and monitoring, a state of relative hypovolemia may remain clinically undetected, with impending consequences owing to impaired oxygen delivery and tissue perfusion. Concurrent processes related to comorbidities, hypothermia, inflammation, trauma, sepsis, or other causes of hemodynamic or metabolic compromise, may further exacerbate the condition. Despite scientific and technological advances, clinical monitoring and treatment of relative hypovolemia still pose relevant challenges to the anesthesiologist. This short perspective seeks to define relative hypovolemia, describe the venous system’s role in supporting normal cardiovascular function, characterize effects of anesthetic drugs on venous physiology, and address current considerations and challenges for monitoring and treatment of relative hypovolemia, with focus on insights for future therapies.

Targeting the endothelial glycocalyx in acute critical illness as a challenge for clinical and laboratory medicine

The purpose of this manuscript is to review the role of endothelial glycocalyx (EG) in the field of critical and perioperative medicine and to discuss possible future directions for investigations in this area. Under physiological conditions, EG has several well-defined functions aimed to prevent the disruption of vessel wall integrity. Under pathological conditions, the EG represent one of the earliest sites of injury during inflammation. EG structure and function distortion contribute to organ dysfunction related to sepsis, trauma, or global ischemia of any origin. Discovering new therapeutic approaches (either pharmacological or non-pharmacological) aimed to protect the EG against injury represents a promising direction in clinical medicine. Further, the currently-used common interventions in the acutely ill - fluids, blood products, nutritional support, organ-supporting techniques (e.g. continuous renal replacement therapy, extracorporeal circulation), temperature modulation and many others - should be re-evaluated during acute illness in terms of their EG "friendliness". To assess new therapies that protect the EG, or to evaluate the effect of currently-used interventions on EG integrity, a relevant marker or method to determine EG damage is needed. Such marker or method should be available to clinicians within hours, preferably in the form of a point-of-care test at the bedside. Collaborative research between clinical disciplines and laboratory medicine is warranted, and targeting the EG represents major challenges for both.