Glycocalyx Degradation in Ischemia-Reperfusion Injury

Circulating glycocalyx shedding products as biomarkers for evaluating prognosis of patients with out-of-hospital cardiac arrest after return of spontaneous circulation

The endothelial glycocalyx is damaged in postcardiac arrest syndrome (PCAS), but the prognostic value is unknown. We aimed to observe the expression and prognostic value of glycocalyx shedding products, including syndecan-1 (SDC-1), hyaluronan (HA), and heparan sulfate (HS) in PCAS. Data on clinical and 28-day outcomes of seventy-one consecutive patients with out-of-hospital cardiac arrest (OHCA) after the return of spontaneous circulation (ROSC) were collected. SDC-1, HA, and HS were measured on days 0, 1, and 3 after ROSC. Thirty healthy individuals were controls. Glycocalyx shedding was observed in human umbilical vein endothelial cells (HUVECs) stimulated during hypoxia and reoxygenation in vitro. Within 4 h of ROSC, SDC-1 and HA levels, significantly increased. In the 28-day non-survivors, HA levels showed a gradual upward trend, SDC-1 remained at a high level, and HS levels first increased, then decreased. Kaplan-Meier curves and binary logistic regression analysis showed the prognostic value of SDC-1 levels on days 0, 1, and 3, HA levels on days 1 and 3, and HS levels on day 1. Only HS levels on day 1 showed a prognostic value for 28-day neurological outcomes. SDC-1 and HA levels were positively correlated with the no-flow time. In vitro, HUVECs showed shedding of SDC-1 and HS during a prolonged duration of hypoxia. After ROSC, SDC-1, HA, and HS levels may predict the 28-day survival after PCAS, and HS levels are associated with functional outcomes.

Role of endothelial glycocalyx in central nervous system diseases and evaluation of the targeted therapeutic strategies for its protection: a review of clinical and experimental data

Central nervous system (CNS) diseases, such as stroke, traumatic brain injury, dementia, and demyelinating diseases, are generally characterized by high morbidity and mortality, which impose a heavy economic burden on patients and their caregivers throughout their lives as well as on public health. The occurrence and development of CNS diseases are closely associated with a series of pathophysiological changes including inflammation, blood-brain barrier disruption, and abnormal coagulation. Endothelial glycocalyx (EG) plays a key role in these changes, making it a novel intervention target for CNS diseases. Herein, we review the current understanding of the role of EG in common CNS diseases, from the perspective of individual pathways/cytokines in pathophysiological and systematic processes. Furthermore, we emphasize the recent developments in therapeutic agents targeted toward protection or restoration of EG. Some of these treatments have yielded unexpected pharmacological results, as previously unknown mechanisms underlying the degradation and destruction of EG has been brought to light. Furthermore, the anti-inflammatory, anticoagulative, and antioxidation effects of EG and its protective role exerted via the blood-brain barrier have been recognized.

Dysregulated complement activation during acute myocardial infarction leads to endothelial glycocalyx degradation and endothelial dysfunction via the C5a:C5a-Receptor1 axis

Introduction

Complement-mediated damage to the myocardium during acute myocardial infarction (AMI), particularly the late components of the terminal pathway (C5-convertase and C5b-9), have previously been characterized. Unfortunately, only few studies have reported a direct association between dysregulated complement activation and endothelial function. Hence, little attention has been paid to the role of the anaphylatoxin C5a. The endothelial glycocalyx (eGC) together with the cellular actin cortex provide a vasoprotective barrier against chronic vascular inflammation. Changes in their nanomechanical properties (stiffness and height) are recognized as hallmarks of endothelial dysfunction as they correlate with the bioavailability of vasoactive substances, such as nitric oxide (NO). Here, we determined how the C5a:C5aR1 axis affects the eGC and endothelial function in AMI.

Methods

Samples of fifty-five patients with ST-elevation myocardial infarction (STEMI) vs. healthy controls were analyzed in this study. eGC components and C5a levels were determined via ELISA; NO levels were quantified chemiluminescence-based. Endothelial cells were stimulated with C5a or patient sera (with/without C5a-receptor1 antagonist "PMX53") and the nanomechanical properties of eGC quantified using the atomic force microscopy (AFM)-based nanoindentation technique. To measure actin cytoskeletal tension regulator activation (RhoA and Rac1) G-LISA assays were applied. Vascular inflammation was examined by quantifying monocyte-endothelium interaction via AFM-based single-cell-force spectroscopy.

Results

Serum concentrations of eGC components and C5a were significantly increased during STEMI. Serum and solely C5a stimulation decreased eGC height and stiffness, indicating shedding of the eGC. C5a enhanced RhoA activation, resulting in increased cortical stiffness with subsequent reduction in NO concentrations. Monocyte adhesion to the endothelium was enhanced after both C5a and stimulation with STEMI serum. eGC degradation- and RhoA-induced cortical stiffening with subsequent endothelial dysfunction were attenuated after administering PMX53.

Conclusion

This study demonstrates that dysregulated C5a activation during AMI results in eGC damage with subsequent endothelial dysfunction and reduced NO bioavailability, indicating progressively developing vascular inflammation. This could be prevented by antagonizing C5aR1, highlighting the role of the C5a:C5a-Receptor1 axis in vascular inflammation development and endothelial dysfunction in AMI, offering new therapeutic approaches for future investigations.

Protective effects of Ruscus extract in combination with ascorbic acid and hesperidine methylchalcone on increased leukocyte-endothelial interaction and macromolecular permeability induced by ischemia reperfusion injury

BACKGROUND

Despite the well-recognized effectiveness of Ruscus aculetus extract combined or not with ascorbic acid (AA) and hesperidine methyl chalcone (HMC) on ischemia reperfusion (I/R) injury protection, little is known about the contribution of each constituent for this effect.

OBJECTIVE

To investigate the effects of AA and HMC combined or not with Ruscus extract on increased macromolecular permeability and leukocyte-endothelium interaction induced by I/R injury.

METHODS

Hamsters were treated daily during two weeks with filtered water (placebo), AA (33, 100 and 300 mg/kg/day) and HMC (50, 150 and 450 mg/kg/day) combined or not with Ruscus extract (50, 150 and 450 mg/kg/day). On the day of experiment, the cheek pouch microcirculation underwent 30 min of ischemia, and the number of rolling and adherent leukocytes and leaky sites were evaluated before ischemia and during 45 min of reperfusion.

RESULTS

Ruscus extract combined with AA and HMC (Ruscus extract mixture) significantly prevented post-ischemic increase in leukocyte rolling and adhesion and macromolecular permeability compared to placebo and these effects were more prominent than AA and HMC alone on leukocyte adhesion and macromolecular leakage.

CONCLUSION

Ruscus extract mixture were more effective than its isolated constituents in protect the hamster cheek pouch microcirculation against I/R injury.

A low androgenic state inhibits erectile function by suppressing endothelial glycosides in the penile cavernous tissue of rats

Background

The endothelial glycocalyx is an important barrier that protects the structure and function of endothelial cells. Androgen deficiency is a common factor that causes structural and functional impairment of endothelial cells.

Aim

To investigate changes in the endothelial glycocalyx in the penile corpus cavernosum of the rat with low androgen status and its relationship with erection function.

Methods

Eighteen 10-week-old Sprague-Dawley male rats were randomly divided into 3 groups (n = 6 each): sham operation, castration, and castration + testosterone replacement. The maximum intracavernosal pressure/mean arterial pressure of the penis was measured after modeling for 4 weeks. The expression levels of endothelial nitric oxide synthase (eNOS), phospho-eNOS, syndecan 1, heparanase, and nitric oxide in penile cavernous tissue and the serum levels of heparan sulfate, hyaluronic acid, tumor necrosis factor α, and interleukin 6 were determined. Transmission electron microscopy was used to observe the ultrastructure of the endothelial glycocalyx in penile tissue.

Outcomes

The thickness of the endothelial glycocalyx in the penile corpus cavernosum of castrated rats was significantly lower than that of the control group.

Results

In the castrated rats, the endothelial glycocalyx thickness, syndecan 1 level, ratio of phospho-eNOS to eNOS, nitric oxide level, and maximum intracavernosal pressure/mean arterial pressure (3 V, 5 V) were significantly lower than those in the sham group (P < .05). The expression of heparanase and the serum levels of tumor necrosis factor α and interleukin 6 were significantly higher in the castrated group than in the sham group (P < .05).

Clinical Translation

Upregulating the expression of the endothelial glycocalyx in the penile corpus cavernosum may be a new method for treating erectile dysfunction caused by low androgen levels.

Strengths and Limitations

This study confirms that low androgen status promotes the breakdown of the endothelial glycocalyx. However, further research is needed to determine whether androgens are related to the synthesis of the endothelial glycocalyx.

Conclusion

Low androgen status may suppress the level of nitric oxide in the cavernous tissue of the penis via impairment of the endothelial glycocalyx, resulting in inhibited erection function in rats.

Sedation with propofol and isoflurane differs in terms of microcirculatory parameters: A randomized animal study using dorsal skinfold chamber mouse model

OBJECTIVE

This study aimed to explore the effects of sedative doses of propofol and isoflurane on microcirculation in septic mice compared to controls. Isoflurane, known for its potential as a sedation drug in bedside applications, lacks clarity regarding its impact on the microcirculation system. The hypothesis was that propofol would exert a more pronounced influence on the microvascular flow index, particularly amplified in septic conditions.

MATERIAL AND METHODS

Randomized study was conducted from December 2020 to October 2021 involved 60 BALB/c mice, with 52 mice analyzed. Dorsal skinfold chambers were implanted, followed by intraperitoneal injections of either sterile 0.9 % saline or lipopolysaccharide for the control and sepsis groups, respectively. Both groups received propofol or isoflurane treatment for 120 min. Microcirculatory parameters were obtained via incident dark-field microscopy videos, along with the mean blood pressure and heart rate at three time points: before sedation (T0), 30 min after sedation (T30), and 120 min after sedation (T120). Endothelial glycocalyx thickness and syndecan-1 concentration were also analyzed.

RESULTS

In healthy controls, both anesthetics reduced blood pressure. However, propofol maintained microvascular flow, differing significantly from isoflurane at T120 (propofol, 2.8 ± 0.3 vs. isoflurane, 1.6 ± 0.9; P < 0.001). In the sepsis group, a similar pattern occurred at T120 without statistical significance (propofol, 1.8 ± 1.1 vs. isoflurane, 1.2 ± 0.7; P = 0.023). Syndecan-1 levels did not differ between agents, but glycocalyx thickness index was significantly lower in the isoflurane-sepsis group than propofol (P = 0.001).

CONCLUSIONS

Propofol potentially offers protective action against microvascular flow deterioration compared to isoflurane, observed in control mice. Furthermore, a lower degree of sepsis-induced glycocalyx degradation was evident with propofol compared to isoflurane.

Insights into the Molecular Mechanism of Endothelial Glycocalyx Dysfunction during Heart Surgery

The endothelial glycocalyx (EGC) is a layer of proteoglycans (associated with glycosaminoglycans) and glycoproteins, which adsorbs plasma proteins on the luminal surface of endothelial cells. Its main function is to participate in separating the circulating blood from the inner layers of the vessels and the surrounding tissues. Physiologically, the EGC stimulates mechanotransduction, the endothelial charge, thrombocyte adhesion, leukocyte tissue recruitment, and molecule extravasation. Hence, severe impairment of the EGC has been implicated in various pathological conditions, including sepsis, diabetes, chronic kidney disease, inflammatory disorders, hypernatremia, hypervolemia, atherosclerosis, and ischemia/reperfusion injury. Moreover, alterations in EGC have been associated with altered responses to therapeutic interventions in conditions such as cardiovascular diseases. Investigation into the function of the glycocalyx has expanded knowledge about vascular disorders and indicated the need to consider new approaches in the treatment of severe endothelial dysfunction. This review aims to present the current understanding of the molecular mechanisms underlying cardiovascular diseases and to elucidate the impact of heart surgery on EGC dysfunction.

The endothelium: gatekeeper to lung ischemia-reperfusion injury

The success of lung transplantation is limited by the high rate of primary graft dysfunction due to ischemia-reperfusion injury (IRI). Lung IRI is characterized by a robust inflammatory response, lung dysfunction, endothelial barrier disruption, oxidative stress, vascular permeability, edema, and neutrophil infiltration. These events are dependent on the health of the endothelium, which is a primary target of IRI that results in pulmonary endothelial barrier dysfunction. Over the past 10 years, research has focused more on the endothelium, which is beginning to unravel the multi-factorial pathogenesis and immunologic mechanisms underlying IRI. Many important proteins, receptors, and signaling pathways that are involved in the pathogenesis of endothelial dysfunction after IR are starting to be identified and targeted as prospective therapies for lung IRI. In this review, we highlight the more significant mediators of IRI-induced endothelial dysfunction discovered over the past decade including the extracellular glycocalyx, endothelial ion channels, purinergic receptors, kinases, and integrins. While there are no definitive clinical therapies currently available to prevent lung IRI, we will discuss potential clinical strategies for targeting the endothelium for the treatment or prevention of IRI. The accruing evidence on the essential role the endothelium plays in lung IRI suggests that promising endothelial-directed treatments may be approaching the clinic soon. The application of therapies targeting the pulmonary endothelium may help to halt this rapid and potentially fatal injury.

Peripheral blood syndecan-1 levels after mechanical thrombectomy can predict the clinical prognosis of patients with acute ischemic stroke

BACKGROUND

Previously, we revealed noticeable dynamic fluctuations in syndecan-1 levels in the peripheral blood of post-stroke patients. We further investigated the clinical prognostic value of syndecan-1 as a biomarker of glycoprotein damage in patients with acute ischaemic stroke (AIS).

METHODS

We examined 105 patients with acute large vessel occlusion in the anterior circulation, all of whom underwent mechanical thrombectomy (MT). Peripheral blood syndecan-1 levels were measured 1 day after MT, and patients were categorised into favourable and unfavourable prognostic groups based on the 90-day modified Rankin Scale (mRS) score. Additionally, we compared the clinical outcomes between groups with high and low syndecan-1 concentrations.

RESULTS

The findings revealed a significantly lower syndecan-1 level in the group with an unfavourable prognosis compared to those with a favourable prognosis (p < 0.01). In the multivariable logistic regression analysis, lower syndecan-1 levels were identified as a predictor of unfavourable prognosis (odds ratio (OR) = 0.965, p = 0.001). Patients displaying low syndecan-1 expression in the peripheral blood (< 29.51 ng/mL) experienced a > twofold increase in the rates of unfavourable prognosis and mortality.

CONCLUSIONS

Our study demonstrates that syndecan-1, as an emerging, easily detectable stroke biomarker, can predict the clinical outcomes of patients with AIS. After MT, low levels of syndecan-1 in the peripheral blood on the first day emerged as an independent risk factor for an unfavourable prognosis, suggesting that lower syndecan-1 levels might signify worse clinical presentation and outcomes in stroke patients undergoing this procedure.

Potential Mechanisms for Organoprotective Effects of Exogenous Nitric Oxide in an Experimental Study

Performing cardiac surgery under cardiopulmonary bypass (CPB) and circulatory arrest (CA) provokes the development of complications caused by tissue metabolism, microcirculatory disorders, and endogenous nitric oxide (NO) deficiency. This study aimed to investigate the potential mechanisms for systemic organoprotective effects of exogenous NO during CPB and CA based on the assessment of dynamic changes in glycocalyx degradation markers, deformation properties of erythrocytes, and tissue metabolism in the experiment. A single-center prospective randomized controlled study was conducted on sheep, n = 24, comprising four groups of six in each. In two groups, NO was delivered at a dose of 80 ppm during CPB ("CPB + NO" group) or CPB and CA ("CPB + CA + NO"). In the "CPB" and "CPB + CA" groups, NO supply was not carried out. NO therapy prevented the deterioration of erythrocyte deformability. It was associated with improved tissue metabolism, lower lactate levels, and higher ATP levels in myocardial and lung tissues. The degree of glycocalyx degradation and endothelial dysfunction, assessed by the concentration of heparan sulfate proteoglycan and asymmetric dimethylarginine, did not change when exogenous NO was supplied. Intraoperative delivery of NO provides systemic organoprotection, which results in reducing the damaging effects of CPB on erythrocyte deformability and maintaining normal functioning of tissue metabolism.

Blood endothelium transition and phenotypic plasticity: A key regulator of integrity/permeability in response to ischemia

In the human body, the 1013 blood endothelial cells (ECs) which cover a surface of 500-700 m2 (Mai et al., 2013) are key players of tissue homeostasis, remodeling and regeneration. Blood vessel ECs play a major role in the regulation of metabolic and gaz exchanges, cell trafficking, blood coagulation, vascular tone, blood flow and fluid extravasation (also referred to as blood vascular permeability). ECs are heterogeneous in various capillary beds and have the exquisite capacity to cope with environmental changes by regulating their gene expression. Ischemia has major detrimental effects on the endothelium and ischemia-induced regulation of vascular integrity is of paramount importance for human health, as small amounts of fluid accumulation in the interstitium may be responsible for major effects on organ functions and patients outcome. In this review, we will here focus on the stimuli and the molecular mechanisms that control blood endothelium maintenance and phenotypic plasticity/transition involved in controlling blood capillary leakage that might open new avenues for therapeutic applications.

Mass intraoperative endothelial glycocalyx shedding affects postoperative systemic inflammation response

BACGROUND

Off-pump coronary artery bypass graft (OPCABG) has a high incidence of postoperative systemic inflammation response syndrome (SIRS), and perioperative endothelial glycocalyx layer (EGL) disruption can be one of the predisposing factors. We hypothesized that EGL shedding happened earlier in OPCABG which can influence on postoperative SIRS, and sevoflurane might preserve EGL better than propofol.

METHODS

We randomly allocated 50 patients undergoing OPCABG to receive either sevoflurane-sufentanil or propofol-sufentanil anesthesia. Plasma syndecan-1, heparan sulfate (HS), atrial natriuretic peptide (ANP), IL-6, and cardiac troponin I (cTnI) were measured. Blood samples were collected at 6 timepoints: induction (T1), before grafting (T2), after grafting(T3), surgery done (T4), postoperative day1 (POD1,T5) and POD2 (T6). SIRS criteria and sequential organ failure assessment (SOFA) score were examined.

RESULTS

There were neither differences of syndecan-1, HS, IL-6 nor of SIRS criteria or SOFA score between the sevoflurane and propofol groups. All patients were pooled as a single group for further statistical analyses, plasma syndecan-1 (P < 0.001) and IL-6 (P < 0.001) increased significantly as a function of time; syndecan-1 increasing correlated significantly with the duration of coronary graft anastomosis (r = 0.329, P = 0.026). Syndecan-1(T3) correlated significantly with ANP(T3) (r = 0.0.354, P = 0.016) and IL-6 (T5) (r = 0.570, P < 0.001). The maximum value of IL-6 correlated significantly with SIRS (r = 0.378, P = 0.010), the maximum value of SOFA score (r = 0.399, P = 0.006) and ICU days (r = 0.306, P = 0.039). The maximum value of SOFA score correlated significantly with the occurrence of SIRS (r = 0.568, P < 0.001) and ICU days (r = 0.338, P = 0.022).

CONCLUSIONS

OPCABG intraoperative early EGL shedding caused of grafts anastomosis greatly affected postoperative SIRS and SOFA score, sevoflurane did not clinically preserve EGL better.

TRIAL REGISTRATION

ChiCTR-IOR-17012535. Registered on 01/09/2017.

A systematic review and meta-analysis on the effect of goal-directed fluid therapy on postoperative outcomes in renal transplantation surgeries

Introduction

This systematic review and meta-analysis investigated the impact of intraoperative goal-directed therapy (GDT) compared with conventional fluid therapy on postoperative outcomes in renal transplantation recipients, addressing this gap in current literature.

Method

A systematic search of patients aged ≥18 years who have undergone single-organ primary renal transplantations up to June 2022 in PubMed, Embase, Scopus and CINAHL Plus was performed. Primary outcome examined was postoperative renal function. Secondary outcomes assessed were mean arterial pressure at graft reperfusion, intraoperative fluid volume and other postoperative complications. Heterogeneity was tested using I² test. The study protocol was registered on PROSPERO.

Results

A total of 2459 studies were identified. Seven eligible studies on 607 patients were included. Subgroup assessments revealed potential renal protective benefits of GDT, with patients receiving cadaveric grafts showing lower serum creatinine on postoperative days 1 and 3, and patients monitored with arterial waveform analysis devices experiencing lower incidences of postoperative haemodialysis. Overall analysis found GDT resulted in lower incidence of tissue oedema (risk ratio [RR] 0.34, 95% CI 0.15-0.78, P=0.01) and respiratory complications (RR 0.39, 95% CI 0.17-0.90, P=0.03). However, quality of data was deemed low given inclusion of non-randomised studies, presence of heterogeneities and inconsistencies in defining outcomes measures.

Conclusion

While no definitive conclusions can be ascertained given current limitations, this review highlights potential benefits of using GDT in renal transplantation recipients. It prompts the need for further standardised studies to address limitations discussed in this review.

Ischemic Preconditioning Alleviates Cerebral Ischemia-Reperfusion Injury by Interfering With Glycocalyx

Ischemic preconditioning (IPC) could protect the blood-brain barrier (BBB), but the underlying mechanism is not well understood. This preclinical study aimed to investigate whether glycocalyx could be involved in the neuroprotective effect of IPC on cerebral ischemia-reperfusion injury (IRI) and the possible mechanism in rat middle cerebral artery occlusion/reperfusion (MCAO/R) model. Neurological deficit scores, infarct volume, and brain edema were measured to assess the neuroprotection of IPC. Several serum biomarkers related to glycocalyx damage, such as hyaluronic acid (HA), heparan sulfate (HS), and syndecan-1 (SYND1), were evaluated, and their changes were normalized to the ratio of postoperative/preoperative concentration. Western blot and immunofluorescence were used to evaluate the content and cellular location of HA-related metabolic enzymes. This study found that (1) IPC improved brain infarction and edema, neurological impairment, and BBB disruption in IRI rats; (2) IPC significantly up-regulated HA ratio and down-regulated HS ratio, but did not affect SYND1 ratio compared with the IRI group. Moreover, the increased HA ratio was negatively related to brain edema and neurological deficit score. (3) IPC affected HA metabolism by up-regulating hyaluronate synthase-1 and matrix metalloproteinase-2, and down-regulating hyaluronidase-1 in brain tissue. Together, this is the first report that the neuroprotective effect of IPC on IRI may be mediated through interfering with glycocalyx in the MCAO/R model.

The impact of vascular endothelial glycocalyx on the pathogenesis and treatment of disseminated intravascular coagulation

Disseminated intravascular coagulation (DIC) is a complex disorder characterized by widespread activation of blood clotting mechanisms throughout the body. Understanding the role of vascular endothelial glycocalyx in the pathogenesis and treatment of DIC is crucial for advancing our knowledge in this field. The vascular endothelial glycocalyx is a gel-like layer that coats the inner surface of blood vessels. It plays a significant role in maintaining vascular integrity, regulating fluid balance, and preventing excessive clotting. In the pathogenesis of DIC, the disruption of the vascular endothelial glycocalyx is a key factor. Pathological conditions trigger the activation of enzymes, including heparanase, hyaluronase, and matrix metalloproteinase. This activation leads to glycocalyx degradation, subsequently exposing endothelial cells to procoagulant stimuli. Additionally, the ANGPTs/Tie-2 signaling pathway plays a role in the imbalance between the synthesis and degradation of VEG, exacerbating endothelial dysfunction and DIC. Understanding the mechanisms behind glycocalyx degradation and its impact on DIC can provide valuable insights for the development of targeted therapies. Preservation of the glycocalyx integrity may help prevent the initiation and propagation of DIC. Strategies such as administration of exogenous glycocalyx components, anticoagulant agents, or Tie-2 antibody agents have shown promising results in experimental models. In conclusion, the vascular endothelial glycocalyx plays a crucial role in the pathogenesis and treatment of DIC. Further research in this field is warranted to unravel the complex interactions between the glycocalyx and DIC, ultimately leading to the development of novel therapies.

HYAL1 deficiency attenuates lipopolysaccharide-triggered renal injury and endothelial glycocalyx breakdown in septic AKI in mice

BACKGROUND

Renal dysfunction and disruption of renal endothelial glycocalyx are two important events during septic acute kidney injury (AKI). Here, the role and mechanism of hyaluronidase 1 (HYAL1) in regulating renal injury and renal endothelial glycocalyx breakdown in septic AKI were explored for the first time.

METHODS

BALB/c mice were injected with lipopolysaccharide (LPS, 10 mg/kg) to induce AKI. HYAL1 was blocked in vivo using lentivirus-mediated short hairpin RNA targeting HYAL1 (LV-sh-HYAL1). Biochemical assays were performed to measure the levels and concentrations of biochemical parameters associated with AKI as well as levels of inflammatory cytokines. Renal pathological lesions were determined by hematoxylin-eosin (HE) staining. Cell apoptosis in the kidney was detected using terminal-deoxynucleoitidyl transferase-mediated nick end labeling (TUNEL) assay. Immunofluorescence and immunohistochemical (IHC) staining assays were used to examine the levels of hyaluronic acid in the kidney. The protein levels of adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling, endothelial glycocalyx, and autophagy-associated indicators were assessed by western blotting.

RESULTS

The knockdown of HYAL1 in LPS-subjected mice by LV-sh-HYAL1 significantly reduced renal inflammation, oxidative stress, apoptosis and kidney dysfunction in AKI, as well as alleviated renal endothelial glycocalyx disruption by preventing the release of hyaluronic acid to the bloodstream. Additionally, autophagy-related protein analysis indicated that knockdown of HYAL1 significantly enhanced autophagy in LPS mice. Furthermore, the beneficial actions of HYAL1 blockade were closely associated with the AMPK/mTOR signaling.

CONCLUSION

HYAL1 deficiency attenuates LPS-triggered renal injury and endothelial glycocalyx breakdown in septic AKI in mice.

The role of glycosaminoglycans in blood pressure regulation

Essential hypertension (HT) is the global health problem and is a major risk factor for the development of cardiovascular and kidney disease. High salt intake has been associated with HT and impaired kidney sodium excretion is considered to be a major mechanism for the development of HT. Although kidney has a very important role in regulation of BP, this traditional view of BP regulation was challenged by recent findings suggesting that nonosmotic tissue sodium deposition is very important for BP regulation. This new paradigm indicates that sodium can be stored and deposited nonosmotically in the interstitium without water retention and without increased BP. One of the major determinants of this deposition is glycosaminoglycans (GAGs). By binding to GAGs found in the endothelial surface layer (ESL) which contains glycocalyx, sodium is osmotically inactivated and not induce concurrent water retention. Thus, GAGs has important function for homeostatic BP and sodium regulation. In the current review, we summarized the role of GAGs in ESL and BP regulation.

Prolonged Door-to-Balloon Time Leads to Endothelial Glycocalyx Damage and Endothelial Dysfunction in Patients with ST-Elevation Myocardial Infarction

Damage to the endothelial glycocalyx (eGC) has been reported during acute ischemic events like ST-elevation myocardial infarction (STEMI). In STEMI, a door-to-balloon time (D2B) of <60 min was shown to reduce mortality and nonfatal complications. Here, we hypothesize that eGC condition is associated with D2B duration and endothelial function during STEMI. One hundred and twenty-six individuals were analyzed in this study (STEMI patients vs. age-/sex-matched healthy volunteers). After stimulating endothelial cells with patient/control sera, the eGC's nanomechanical properties (i.e., height/stiffness) were analyzed using the atomic force microscopy-based nanoindentation technique. eGC components were determined via ELISA, and measurements of nitric oxide levels (NO) were based on chemiluminescence. eGC height/stiffness (both p < 0.001), as well as NO concentration (p < 0.001), were reduced during STEMI. Notably, the D2B had a strong impact on the endothelial condition: a D2B > 60 min led to significantly higher serum concentrations of eGC components (syndecan-1: p < 0.001/heparan sulfate: p < 0.001/hyaluronic acid: p < 0.0001). A D2B > 60 min led to the pronounced loss of eGC height/stiffness (both, p < 0.001) with reduced NO concentrations (p < 0.01), activated the complement system (p < 0.001), and prolonged the hospital stay (p < 0.01). An increased D2B led to severe eGC shedding, with endothelial dysfunction in a temporal context. eGC components and pro-inflammatory mediators correlated with a prolonged D2B, indicating a time-dependent immune reaction during STEMI, with a decreased NO concentration. Thus, D2B is a crucial factor for eGC damage during STEMI. Clinical evaluation of the eGC condition might serve as an important predictor for the endothelial function of STEMI patients in the future.

Knowledge mapping and emerging trends of ferroptosis in ischemia reperfusion injury research: A bibliometric analysis (2013-2022)

Objective

Ischemia/reperfusion (I/R) injury is an inevitable dilemma when previously ischemic multiple organs and tissues are returned to a state of blood flow, with confirming a critical role of ferroptosis in molecular, pathway mechanisms, subcellular structure. Discovering the potential relationship may provide useful approaches for the clinical treatment and prognosis of the pathophysiological status of IRI. Therefore, a comprehensive visualization and scientometric analysis were conducted to systematically summarize and discuss the "ferroptosis in ischemia reperfusion injury" research to demonstrate directions for scholars in this field.

Methods

We retrieved all publications focusing on I/R injury and ferroptosis from the Web of Science Core Collection (WoSCC), published from 2013 to October 2022. Next, scientometric analysis of different items was performed using various bibliometrics softwares to explore the annual trends, countries/regions, institutions, journals, authors and their multi-dimensional relationship pointing to current hotspots and future advancement in this field.

Results

We included a total of 421 English articles in set timespan. The number of publications increased steadily annually. China produced the highest number of publications, followed by the United States. Most publications were from Central South University, followed by Sichuan University and Wuhan University. The most authoritative academic journal was Oxidative Medicine and Cellular Longevity. Cell occupied the first rank of co-cited journal list. Andreas Linkermann and Scott J Dixon may have the highest influence in this intersected field with the highest number of citations and co-cited references respectively. The essential biological reactions such as oxidative stress response, lipid peroxidation metabolism, anti-inflammmatory and pro-inflammatory procedure, and related molecular pathways were knowledge base and current hotspots. Molecules pathways exploration, effective inhibition of I/R injury and promising strategy of improving allografts may become future trends and focuses.

Conclusions

Research on ferroptosis in I/R injury had aroused great interest recently. This first bibliometric study comprehensively analyzed the research landscape of ferroptosis and I/R injury, and also provided a reliable reference for related scholars to facilitate further advancement in this field.

Resuscitating the Endothelial Glycocalyx in Trauma and Hemorrhagic Shock

The endothelium is lined by a protective mesh of proteins and carbohydrates called the endothelial glycocalyx (EG). This layer creates a negatively charged gel-like barrier between the vascular environment and the surface of the endothelial cell. When intact the EG serves multiple functions, including mechanotransduction, cell signaling, regulation of permeability and fluid exchange across the microvasculature, and management of cell-cell interactions. In trauma and/or hemorrhagic shock, the glycocalyx is broken down, resulting in the shedding of its individual components. The shedding of the EG is associated with increased systemic inflammation, microvascular permeability, and flow-induced vasodilation, leading to further physiologic derangements. Animal and human studies have shown that the greater the severity of the injury, the greater the degree of shedding, which is associated with poor patient outcomes. Additional studies have shown that prioritizing certain resuscitation fluids, such as plasma, cryoprecipitate, and whole blood over crystalloid shows improved outcomes in hemorrhaging patients, potentially through a decrease in EG shedding impacting downstream signaling. The purpose of the following paragraphs is to briefly describe the EG, review the impact of EG shedding and hemorrhagic shock, and begin entertaining the notion of directed resuscitation. Directed resuscitation emphasizes transitioning from macroscopic 1:1 resuscitation to efforts that focus on minimizing EG shedding and maximizing its reconstitution.

Loss of Endothelial Glycocalyx During Normothermic Machine Perfusion of Porcine Kidneys Irrespective of Pressure and Hematocrit

Normothermic machine perfusion (NMP) is a promising modality for marginal donor kidneys. However, little is known about the effects of NMP on causing endothelial glycocalyx (eGC) injury. This study aims to evaluate the effects of NMP on eGC injury in marginal donor kidneys and whether this is affected by perfusion pressures and hematocrits.

Methods

Porcine slaughterhouse kidneys (n = 6/group) underwent 35 min of warm ischemia. Thereafter, the kidneys were preserved with oxygenated hypothermic machine perfusion for 3 h. Subsequently, 4 h of NMP was applied using pressure-controlled perfusion with an autologous blood-based solution containing either 12%, 24%, or 36% hematocrit. Pressures of 55, 75, and 95 mm Hg were applied in the 24% group. Perfusate, urine, and biopsy samples were collected to determine both injury and functional parameters.

Results

During NMP, hyaluronan levels in the perfusate increased significantly (P < 0.0001). In addition, the positivity of glyco-stained glycocalyx decreased significantly over time, both in the glomeruli (P = 0.024) and peritubular capillaries (P = 0.003). The number of endothelial cells did not change during NMP (P = 0.157), whereas glomerular endothelial expression of vascular endothelial growth factor receptor-2 decreased significantly (P < 0.001). Microthrombi formation was significantly increased after NMP. The use of different pressures and hematocrits did not affect functional parameters during perfusion.

Conclusions

NMP is accompanied with eGC and vascular endothelial growth factor receptor-2 loss, without significant loss of endothelial cells. eGC loss was not affected by the different pressures and hematocrits used. It remains unclear whether endothelial injury during NMP has harmful consequences for the transplanted kidney.

A historical literature review of coronary microvascular obstruction and intra-myocardial hemorrhage as functional/structural phenomena

The analysis of experimental data demonstrates that platelets and neutrophils are involved in the no-reflow phenomenon, also known as microvascular obstruction (MVO). However, studies performed in the isolated perfused hearts subjected to ischemia/reperfusion (I/R) do not suggest the involvement of microembolization and microthrombi in this phenomenon. The intracoronary administration of alteplase has been found to have no effect on the occurrence of MVO in patients with acute myocardial infarction. Consequently, the major events preceding the appearance of MVO in coronary arteries are independent of microthrombi, platelets, and neutrophils. Endothelial cells appear to be the target where ischemia can disrupt the endothelium-dependent vasodilation of coronary arteries. However, reperfusion triggers more pronounced damage, possibly mediated by pyroptosis. MVO and intra-myocardial hemorrhage contribute to the adverse post-infarction myocardial remodeling. Therefore, pharmacological agents used to treat MVO should prevent endothelial injury and induce relaxation of smooth muscles. Ischemic conditioning protocols have been shown to prevent MVO, with L-type Ca ²⁺ channel blockers appearing the most effective in treating MVO.

Intravenous Polyethylene Glycol Alleviates Intestinal Ischemia-Reperfusion Injury in a Rodent Model

Intestinal ischemia-reperfusion injury (IRI) is a common clinical entity, and its outcome is unpredictable due to the triad of inflammation, increased permeability and bacterial translocation. Polyethylene glycol (PEG) is a polyether compound that is extensively used in pharmacology as an excipient in various products. More recently, this class of products have shown to have potent anti-inflammatory, anti-apoptotic, immunosuppressive and cell-membrane-stabilizing properties. However, its effects on the outcome after intestinal IRI have not yet been investigated. We hypothesized that PEG administration would reduce the effects of intestinal IRI in rodents. In a previously described rat model of severe IRI (45 min of ischemia followed by 60 min of reperfusion), we evaluated the effect of IV PEG administration at different doses (50 and 100 mg/kg) before and after the onset of ischemia. In comparison to control animals, PEG administration stabilized the endothelial glycocalyx, leading to reduced reperfusion edema, bacterial translocation and inflammatory reaction as well as improved 7-day survival. These effects were seen both in a pretreatment and in a treatment setting. The fact that this product is readily available and safe should encourage further clinical investigations in settings of intestinal IRI, organ preservation and transplantation.

Glycocalyx-Sodium Interaction in Vascular Endothelium

The glycocalyx generally covers almost all cellular surfaces, where it participates in mediating cell-surface interactions with the extracellular matrix as well as with intracellular signaling molecules. The endothelial glycocalyx that covers the luminal surface mediates the interactions of endothelial cells with materials flowing in the circulating blood, including blood cells. Cardiovascular diseases (CVD) remain a major cause of morbidity and mortality around the world. The cardiovascular risk factors start by causing endothelial cell dysfunction associated with destruction or irregular maintenance of the glycocalyx, which may culminate into a full-blown cardiovascular disease. The endothelial glycocalyx plays a crucial role in shielding the cell from excessive exposure and absorption of excessive salt, which can potentially cause damage to the endothelial cells and underlying tissues of the blood vessels. So, in this mini review/commentary, we delineate and provide a concise summary of the various components of the glycocalyx, their interaction with salt, and subsequent involvement in the cardiovascular disease process. We also highlight the major components of the glycocalyx that could be used as disease biomarkers or as drug targets in the management of cardiovascular diseases.

Peptide-Based Nanoparticles for Systemic Extrahepatic Delivery of Therapeutic Nucleotides

Peptide-based nanoparticles (PBN) for nucleotide complexation and targeting of extrahepatic diseases are gaining recognition as potent pharmaceutical vehicles for fine-tuned control of protein production (up- and/or down-regulation) and for gene delivery. Herein, we review the principles and mechanisms underpinning self-assembled formation of PBN, cellular uptake, endosomal release, and delivery to extrahepatic disease sites after systemic administration. Selected examples of PBN that have demonstrated recent proof of concept in disease models in vivo are summarized to offer the reader a comparative view of the field and the possibilities for clinical application.

Endothelial Dysfunction in Patients Undergoing Cardiac Surgery: A Narrative Review and Clinical Implications

Cardiac surgery is one of the highest-risk procedures, usually involving cardiopulmonary bypass and commonly inducing endothelial injury that contributes to the development of perioperative and postoperative organ dysfunction. Substantial scientific efforts are being made to unravel the complex interaction of biomolecules involved in endothelial dysfunction to find new therapeutic targets and biomarkers and to develop therapeutic strategies to protect and restore the endothelium. This review highlights the current state-of-the-art knowledge on the structure and function of the endothelial glycocalyx and mechanisms of endothelial glycocalyx shedding in cardiac surgery. Particular emphasis is placed on potential strategies to protect and restore the endothelial glycocalyx in cardiac surgery. In addition, we have summarized and elaborated the latest evidence on conventional and potential biomarkers of endothelial dysfunction to provide a comprehensive synthesis of crucial mechanisms of endothelial dysfunction in patients undergoing cardiac surgery, and to highlight their clinical implications.

Albumin protects the ultrastructure of the endothelial glycocalyx of coronary arteries in myocardial ischemia-reperfusion injury in vivo

Myocardial ischemia-reperfusion (I/R) injury induces endothelial glycocalyx (GCX) degradation. Several candidate GCX-protective factors including albumin have been identified, few have been demonstrated in in vivo studies and most albumins used to date have been heterologous. Albumin is a carrier protein for sphingosine 1-phosphate (S1P), which has protective effects on the cardiovascular system. However, changes inhibited by albumin in the endothelial GCX structure in I/R in vivo via the S1P receptor has not been reported. In this study, we aimed to determine whether albumin prevents the shedding of endothelial GCX in response to I/R in vivo. Rats were divided into four groups: control (CON), I/R, I/R with albumin preload (I/R + ALB), and I/R + ALB with S1P receptor agonist fingolimod (I/R + ALB + FIN). FIN acts as an initial agonist of S1P receptor 1 and downregulates the receptor in an inhibitory manner. The CON and I/R groups received saline and I/R + ALB and I/R + ALB + FIN groups received albumin solution before left anterior descending coronary artery ligation. Our study used rat albumin. Shedding of endothelial GCX was evaluated in the myocardium by electron microscopy, and the concentration of serum syndecan-1 was measured. Thus, albumin administration maintained the structure of endothelial GCX and prevented shedding of endothelial GCX via the S1P receptor in myocardial I/R, and FIN annihilated the protective effect of albumin against I/R injury.

Endothelial Glycocalyx and Cardiomyocyte Damage Is Prevented by Recombinant Syndecan-1 in Acute Myocardial Infarction

The outer layer of endothelial cells (ECs), consisting of the endothelial glycocalyx (eGC) and the cortex (CTX), provides a protective barrier against vascular diseases. Structural and functional impairments of their mechanical properties are recognized as hallmarks of endothelial dysfunction and can lead to cardiovascular events, such as acute myocardial infarction (AMI). This study investigated the effects of AMI on endothelial nanomechanics and function and the use of exogenous recombinant syndecan-1 (rSyn-1), a major component of the eGC, as recovering agent. ECs were exposed in vitro to serum samples collected from patients with AMI. In addition, in situ ECs of ex vivo aorta preparations derived from a mouse model for AMI were employed. Effects were quantified by using atomic force microscopy-based nanoindentation measurements, fluorescence staining, and histologic examination of the mouse hearts. AMI serum samples damaged eGC/CTX and augmented monocyte adhesion to the endothelial surface. In particular, the anaphylatoxins C3a and C5a played an important role in these processes. The impairment of endothelial function could be prevented by rSyn-1 treatment. In the mouse model of myocardial infarction, pretreatment with rSyn-1 alleviated eGC/CTX deterioration and reduced cardiomyocyte damage in histologic analyses. However, echocardiographic measurements did not indicate a functional benefit. These results provide new insights into the underlying mechanisms of AMI-induced endothelial dysfunction and perspectives for future studies on the benefit of rSyn-1 in post-AMI treatment.

Effect of albumin solutions on endothelial oxidant injury: A microfluidic study

BACKGROUND

Studies have suggested a beneficial effect of early plasma-based resuscitation in patients following trauma-hemorrhagic shock. The underlying mechanism(s) are unknown but may be owing to protective effects of plasma components on the endothelium and its glycocalyx layer. Albumin, the major protein in plasma, influences vascular integrity and has antioxidant properties in vivo. Sphingosine 1-phosphate is a bioactive sphingolipid with diverse signaling functions, which include endothelial barrier protection in part owing to preservation of the glycocalyx. Sphingosine 1-phosphate is bound mainly to albumin and high-density lipids in the plasma. Debate continues about the beneficial effect of albumin solutions in shock resuscitation. Pharmacologic preparations may modify constituents of albumin solutions for clinical use. We examined the relative effects of sphingosine 1-phosphate concentrations in albumin solutions on the endothelial-glycocalyx barrier in an in vitro microfluidic platform.

METHODS

Endothelial cell monolayers were established in microfluidic perfusion devices and exposed to control or biomimetic shock conditions followed by 5% plasma or different albumin solutions ± exogenous sphingosine 1-phosphate perfusion. Biomarkers of endothelial and glycocalyx activation, damage, and oxidant injury were then determined.

RESULTS

Endothelial cell and glycocalyx barriers were damaged after biomimetic shock conditions. Plasma and sphingosine 1-phosphate loaded albumin solutions protected against barrier injury. Modest protective effects were noted with albumin alone; the efficacy varied with sphingosine 1-phosphate content of the albumin solution.

CONCLUSION

The protective effect of albumin on the endothelia-glycocalyx barrier against oxidant injury was dependent on its sphingosine 1-phosphate concentration. Our data may help explain the discrepancies regarding the effectiveness of albumin solutions in shock resuscitation.

Protective Effect of Oxygen and Isoflurane in Rodent Model of Intestinal Ischemia-Reperfusion Injury

Animal research in intestinal ischemia-reperfusion injury (IRI) is mainly performed in rodent models. Previously, intraperitoneal (I.P.) injections with ketamine-xylazine mixtures were used. Nowadays, volatile anesthetics (isoflurane) are more common. However, the impact of the anesthetic method on intestinal IRI has not been investigated. We aim to analyze the different anesthetic methods and their influence on the extent of intestinal IRI in a rat model. Male Sprague-Dawley rats were used to investigate the effect of I.P. anesthesia on 60 min of intestinal ischemia and 60 min of reperfusion in comparison to hyperoxygenation (100% O₂) and volatile isoflurane anesthesia. In comparison to I.P. anesthesia with room air (21% O₂), supplying 100% O₂ improved 7-day survival by cardiovascular stabilization, reducing lactic acidosis and preventing vascular leakage. However, this had no effect on the intestinal epithelial damage, permeability, and inflammatory response observed after intestinal IRI. In contrast to I.P. + 100% O₂, isoflurane anesthesia reduced intestinal IRI by preventing ongoing low-flow reperfusion hypotension, limiting intestinal epithelial damage and permeability, and by having anti-inflammatory effects. When translating the aforementioned results of this study to clinical situations, such as intestinal ischemia or transplantation, the potential protective effects of hyperoxygenation and volatile anesthetics require further research.

Dynamic changes in the glycocalyx and clinical outcomes in patients undergoing endovascular treatments for large vessel occlusion

Purpose

We aimed to verify the prognostic value of the glycocalyx as a marker of blood-brain barrier damage in patients with acute ischemic stroke undergoing endovascular therapy.

Methods

We recruited patients with large vessel occlusion who were undergoing recanalization and tested their glycocalyx at multiple time points. On the basis of the 90-day follow-up data, the patients were divided into a survivor group and a nonsurvivor group. In addition, neurological function was tracked, and patients were divided into a neurological deterioration group and a group without neurological deterioration. Associations between outcomes and dynamic changes in the glycocalyx were determined using a linear mixed model, and significant factors were used as covariates.

Results

Nonsurvivors and patients with neurological deterioration had significantly higher syndecan-1 concentrations than survivors and patients without neurological deterioration, and syndecan-1 tended to decline after endovascular therapy (p < 0.05). The increased level of syndecan-1 at 36 h after endovascular treatment was positively correlated with the National Institute of Health Stroke Scale score for neurological deterioration (r = 0.702, p = 0.005). However, there was no significant difference in the level of hyaluronic acid or heparan sulfate in the plasma of patients with different clinical outcomes.

Conclusion

Pre-reperfusion syndecan-1 levels in patients with large vessel occlusion stroke are associated with 90-day mortality and the re-degradation of syndecan-1 is positively associated with neurological deterioration.

Setting the stage for universal pharmacological targeting of the glycocalyx

All cells in the human body are covered by a complex meshwork of sugars as well as proteins and lipids to which these sugars are attached, collectively termed the glycocalyx. Over the past few decades, the glycocalyx has been implicated in a range of vital cellular processes in health and disease. Therefore, it has attracted considerable interest as a therapeutic target. Considering its omnipresence and its relevance for various areas of cell biology, the glycocalyx should be a versatile platform for therapeutic intervention, however, the full potential of the glycocalyx as therapeutic target is yet to unfold. This might be attributable to the fact that glycocalyx alterations are currently discussed mainly in the context of specific diseases. In this perspective review, we shift the attention away from a disease-centered view of the glycocalyx, focusing on changes in glycocalyx state. Furthermore, we survey important glycocalyx-targeted drugs currently available and finally discuss future steps. We hope that this approach will inspire a unified, holistic view of the glycocalyx in disease, helping to stimulate novel glycocalyx-targeted therapy strategies.

Diabetic Proteinuria Revisited: Updated Physiologic Perspectives

Albuminuria, a hallmark of diabetic nephropathy, reflects not only injury and dysfunction of the filtration apparatus, but is also affected by altered glomerular hemodynamics and hyperfiltration, as well as by the inability of renal tubular cells to fully retrieve filtered albumin. Albuminuria further plays a role in the progression of diabetic nephropathy, and the suppression of glomerular albumin leak is a key factor in its prevention. Although microalbuminuria is a classic manifestation of diabetic nephropathy, often progressing to macroalbuminuria or overt proteinuria over time, it does not always precede renal function loss in diabetes. The various components leading to diabetic albuminuria and their associations are herein reviewed, and the physiologic rationale and efficacy of therapeutic interventions that reduce glomerular hyperfiltration and proteinuria are discussed. With these perspectives, we propose that these measures should be initiated early, before microalbuminuria develops, as substantial renal injury may already be present in the absence of proteinuria. We further advocate that the inhibition of the renin–angiotensin axis or of sodium–glucose co-transport likely permits the administration of a normal recommended or even high-protein diet, highly desirable for sarcopenic diabetic patients.

The Protective Effects on Ischemia–Reperfusion Injury Mechanisms of the Thoracic Aorta in Daurian Ground Squirrels (Spermophilus dauricus) over the Torpor–Arousal Cycle of Hibernation

Hibernators are a natural model of vascular ischemia–reperfusion injury; however, the protective mechanisms involved in dealing with such an injury over the torpor–arousal cycle are unclear. The present study aimed to clarify the changes in the thoracic aorta and serum in summer-active (SA), late-torpor (LT) and interbout-arousal (IBA) Daurian ground squirrels (Spermophilus dauricus). The results show that total antioxidant capacity (TAC) was unchanged, but malondialdehyde (MDA), hydrogen peroxide (H₂O₂), interleukin-1β (IL-1β) and tumor necrosis factor α (TNFα) were significantly increased for the LT group, whereas the levels of superoxide dismutase (SOD) and interleukin-10 (IL-10) were significantly reduced in the LT group as compared with the SA group. Moreover, the levels of MDA and IL-1β were significantly reduced, whereas SOD and IL-10 were significantly increased in the IBA group as compared with the SA group. In addition, the lumen area of the thoracic aorta and the expression of the smooth muscle cells (SMCs) contractile marker protein 22α (SM22α) were significantly reduced, whereas the protein expression of the synthetic marker proteins osteopontin (OPN), vimentin (VIM) and proliferating cell nuclear antigen (PCNA) were significantly increased in the LT group as compared with the SA group. Furthermore, the smooth muscle layer of the thoracic aorta was significantly thickened, and PCNA protein expression was significantly reduced in the IBA group as compared with the SA group. The contractile marker proteins SM22α and synthetic marker protein VIM underwent significant localization changes in both LT and IBA groups, with localization of the contractile marker protein α-smooth muscle actin (αSMA) changing only in the IBA group as compared with the SA group. In tunica intima, the serum levels of heparin sulfate (HS) and syndecan-1 (Sy-1) in the LT group were significantly reduced, but the serum level of HS in the IBA group increased significantly as compared with the SA group. Protein expression and localization of endothelial nitric oxide synthase (eNOS) was unchanged in the three groups. In summary, the decrease in reactive oxygen species (ROS) and pro-inflammatory factors and increase in SOD and anti-inflammatory factors during the IBA period induced controlled phenotypic switching of thoracic aortic SMCs and restoration of endothelial permeability to resist ischemic and hypoxic injury during torpor of Daurian ground squirrels.

Need for a Paradigm Shift in the Treatment of Ischemic Stroke: The Blood-Brain Barrier

Blood-brain barrier (BBB) integrity is essential to maintaining brain health. Aging-related alterations could lead to chronic progressive leakiness of the BBB, which is directly correlated with cerebrovascular diseases. Indeed, the BBB breakdown during acute ischemic stroke is critical. It remains unclear, however, whether BBB dysfunction is one of the first events that leads to brain disease or a down-stream consequence. This review will focus on the BBB dysfunction associated with cerebrovascular disease. An added difficulty is its association with the deleterious or reparative effect, which depends on the stroke phase. We will first outline the BBB structure and function. Then, we will focus on the spatiotemporal chronic, slow, and progressive BBB alteration related to ischemic stroke. Finally, we will propose a new perspective on preventive therapeutic strategies associated with brain aging based on targeting specific components of the BBB. Understanding BBB age-evolutions will be beneficial for new drug development and the identification of the best performance window times. This could have a direct impact on clinical translation and personalised medicine.

Anti-inflammatory effects of a SERP 30 polysaccharide from the residue of Sarcandra glabra against lipopolysaccharide-induced acute respiratory distress syndrome in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Sarcandra glabra (Thunb.) Nakai, a valuable dietetic Chinese herb, is still widely used today. Multiple ingredients of S. glabra with a variety of activities such as anti-inflammatory, antiviral, and antitumor were studied. However, the Sarcandra glabra (Thunb.) Nakai polysaccharide hasn't been reported for its anti-inflammatory effect.

AIM OF THE STUDY

In this study, the anti-inflammatory activity of Sarcandra glabra (Thunb.) Nakai polysaccharide was assessed in LPS-induced ARDS mice.

MATERIALS AND METHODS

A polysaccharide coded as SERP 30 was obtained by water extraction, alcohol precipitation, and gel filtration. After the physicochemical properties determination and structural characterization, LPS induced-mice ARDS model was used to evaluate the anti-inflammatory and associated antioxidant activities of SERP 30. H&E staining was used to observe the seriousness of lung injury in mice. The ELISA method was used to measure the expression of inflammatory factors (TNF-α and IL-6) in the serum of the mice. The TBA method and the WST-1 method were used to evaluate the oxidative stress injury. Immunohistochemistry was used to distinguish the expression of metalloproteinase-9 (MMP-9), heparinase (HPA), syndecan-1, and decorin in ARDS-mice lung tissue. Western blotting was used to confirm the expression of related proteins in mouse lung tissue.

RESULTS

SERP 30 had a potential role in improving lung damage, reducing inflammation, and preventing oxidative stress. Moreover, SERP 30 significantly attenuated the damage to the endothelial glycocalyx and maintained the integrity of the glycocalyx. The western blotting result implied that the main anti-inflammatory mechanism is directed towards NF-κB and MAPK signaling pathways with inhibiting the activation of associated proteins.

CONCLUSION

This research provides a theoretical basis for treating ARDS by using a byproduct from food resource.

Tranexamic acid: Beyond antifibrinolysis

Tranexamic acid (TXA) is a popular antifibrinolytic drug widely used in hemorrhagic trauma patients and cardiovascular, orthopedic, and gynecological surgical patients. TXA binds plasminogen and prevents its maturation to the fibrinolytic enzyme plasmin. A number of studies have demonstrated the broad life-saving effects of TXA in trauma, superior to those of other antifibrinolytic agents. Besides preventing fibrinolysis and blood loss, TXA has been reported to suppress posttraumatic inflammation and edema. Although the efficiency of TXA transcends simple inhibition of fibrinolysis, little is known about its mechanisms of action besides the suppression of plasmin maturation. Understanding the broader effects of TXA at the cell, organ, and organism levels are required to elucidate its potential mechanisms of action transcending antifibrinolytic activity. In this article, we provide a brief review of the current clinical use of TXA and then focus on the effects of TXA beyond antifibrinolytics such as its anti-inflammatory activity, protection of the endothelial and epithelial monolayers, stimulation of mitochondrial respiration, and suppression of melanogenesis.

Glycocalyx heparan sulfate cleavage promotes endothelial cell angiopoietin-2 expression by impairing shear stress-related AMPK/FoxO1 signaling

Angiopoietin-2 (Ang-2) is a key mediator of vascular disease during sepsis, and elevated plasma levels of Ang-2 are associated with organ injury scores and poor clinical outcomes. We have previously observed that biomarkers of endothelial glycocalyx (EG) damage correlate with plasma Ang-2 levels, suggesting a potential mechanistic linkage between EG injury and Ang-2 expression during states of systemic inflammation. However, the cell signaling mechanisms regulating Ang-2 expression following EG damage are unknown. In the current study, we determined the temporal associations between plasma heparan sulfate (HS) levels as a marker of EG erosion and plasma Ang-2 levels in children with sepsis and in mouse models of sepsis. Secondly, we evaluated the role of shear stress-mediated 5'-adenosine monophosphate-activated protein kinase (AMPK) signaling in Ang-2 expression following enzymatic HS cleavage from the surface of human primary lung microvascular endothelial cells (HLMVEC). We found that plasma HS levels peak prior to plasma Ang-2 levels in children and mice with sepsis. Further, we discovered that impaired AMPK signaling contributes to increased Ang-2 expression following HS cleavage from flow conditioned HLMVECs, establishing a novel paradigm by which Ang-2 may be upregulated during sepsis.

Resveratrol inhibits the inflammatory response and oxidative stress induced by uterine ischemia reperfusion injury by activating PI3K-AKT pathway

Uterus transplantation is a complex surgical procedure. Uterine ischemia reperfusion (I/R) injury that occurs during this process may cause a loss of function of the uterus and the failure of transplantation. Resveratrol (RSV) is a naturally occurring polyphenol found abundantly in the skin of grapes and red wine, and it has also been used as a dietary supplement in clinical practice. RSV possesses strong anti-inflammatory and anti-oxidative effects, and exhibits a role in immune system regulation. However, the role of RSV in protecting the uterus against I/R-induced injury is yet to be fully elucidated. The aim of the present study was to investigate the effects and mechanisms underlying RSV in I/R-induced uterus injury. A total of 48 Sprague-Dawley rats were randomly divided into four groups: Control (sham operation) group, the uterus I/R group, the 20 mg/kg RSV-pre-treated I/R (I/R+RSV/20) group and the 40 mg/kg RSV-pre-treated I/R (I/R+ RSV/40) group. A regular I/R model was established to induce uterus injury in rats. RSV at 20 or 40 mg/kg was intraperitoneally administrated into rats in both I/R+ RSV groups once per day for five consecutive days prior to ischemia. The control and I/R only groups received an intraperitoneal injection of the vehicle (ethanol) for the same period prior to ischemia. Samples from blood and uterine horns were collected 3 h after reperfusion. Changes in the levels of malondialdehyde, interleukin (IL)-6, tumor necrosis factor-α, IL-10 and IL-37 were determined using ELISA, the activity levels of myeloperoxidase, catalase, and superoxidase dismutase were also determined using ELISA, the protein expression levels of PI3K, phosphorylated (p)-PI3K, AKT and p-AKT were determined using western blot analysis, and the uterine histology was investigated using H&E staining. Results of the present study demonstrated that treatment with RSV increased the capacity of antioxidants and suppressed uterine oxidative injury induced by I/R. Moreover, treatment with RSV decreased the levels of pro-inflammatory cytokines and increased the levels of anti-inflammatory cytokines. In addition, RSV promoted the phosphorylation of PI3K and AKT, thus activating the PI3K-AKT signaling pathway. Therefore, administration of RSV prior to uterine I/R effectively alleviated inflammatory response and oxidative stress via activation of the PI3K-AKT pathway, suggesting that RSV may play a protective role in I/R-induced uterus injury.

Vascular Endothelial Glycocalyx Damage and Potential Targeted Therapy in COVID-19

COVID-19 is a highly infectious respiratory disease caused by a new coronavirus known as SARS-CoV-2. COVID-19 is characterized by progressive respiratory failure resulting from diffuse alveolar damage, inflammatory infiltrates, endotheliitis, and pulmonary and systemic coagulopathy forming obstructive microthrombi with multi-organ dysfunction, indicating that endothelial cells (ECs) play a central role in the pathogenesis of COVID-19. The glycocalyx is defined as a complex gel-like layer of glycosylated lipid–protein mixtures, which surrounds all living cells and acts as a buffer between the cell and the extracellular matrix. The endothelial glycocalyx layer (EGL) plays an important role in vascular homeostasis via regulating vascular permeability, cell adhesion, mechanosensing for hemodynamic shear stresses, and antithrombotic and anti-inflammatory functions. Here, we review the new findings that described EGL damage in ARDS, coagulopathy, and the multisystem inflammatory disease associated with COVID-19. Mechanistically, the inflammatory mediators, reactive oxygen species (ROS), matrix metalloproteases (MMPs), the glycocalyx fragments, and the viral proteins may contribute to endothelial glycocalyx damage in COVID-19. In addition, the potential therapeutic strategies targeting the EGL for the treatment of severe COVID-19 are summarized and discussed.

Application of Adsorptive Blood Purification Techniques during Cardiopulmonary Bypass in Cardiac Surgery

By reason of surgical demand, the majority of cardiovascular procedures still depend on the use of cardiopulmonary bypass (CPB). Due to the nonphysiological state of CPB, it can cause complex and unpredictable inflammatory response, which may lead to significant morbidity and mortality. Unfortunately, the pharmacological and mechanical strategies that currently exist do not offer significant advantages in controlling inflammatory response and improving patient outcomes. The best strategy to reduce inflammation in CPB is still uncertain. In recent years, adsorptive blood purification techniques (BPTs) have emerged, among which CytoSorb is the latest representative device. Currently, the primary application area of adsorptive BPTs is in the control and treatment of systemic hyperinflammatory states, such as refractory septic shock patients. However, the evidences on efficacy and safety of adsorptive BPTs application during CPB surgery are still inconclusive, so we summarize the relevant evidences here and suggest future potential research areas.

The Endothelial Glycocalyx: A Possible Therapeutic Target in Cardiovascular Disorders

The physiological, anti-inflammatory, and anti-coagulant properties of endothelial cells (ECs) rely on a complex carbohydrate-rich layer covering the luminal surface of ECs, called the glycocalyx. In a range of cardiovascular disorders, glycocalyx shedding causes endothelial dysfunction and inflammation, underscoring the importance of glycocalyx preservation to avoid disease initiation and progression. In this review we discuss the physiological functions of the glycocalyx with particular focus on how loss of endothelial glycocalyx integrity is linked to cardiovascular risk factors, like hypertension, aging, diabetes and obesity, and contributes to the development of thrombo-inflammatory conditions. Finally, we consider the role of glycocalyx components in regulating inflammatory responses and discuss possible therapeutic interventions aiming at preserving or restoring the endothelial glycocalyx and therefore protecting against cardiovascular disease.

The Effect of Hypothermic Machine Perfusion to Ameliorate Ischemia-Reperfusion Injury in Donor Organs

Hypothermic machine perfusion (HMP) has become the new gold standard in clinical donor kidney preservation and a promising novel strategy in higher risk donor livers in several countries. As shown by meta-analysis for the kidney, HMP decreases the risk of delayed graft function (DGF) and improves graft survival. For the liver, HMP immediately prior to transplantation may reduce the chance of early allograft dysfunction (EAD) and reduce ischemic sequelae in the biliary tract. Ischemia-reperfusion injury (IRI), unavoidable during transplantation, can lead to massive cell death and is one of the main causes for DGF, EAD or longer term impact. Molecular mechanisms that are affected in IRI include levels of hypoxia inducible factor (HIF), induction of cell death, endothelial dysfunction and immune responses. In this review we have summarized and discussed mechanisms on how HMP can ameliorate IRI. Better insight into how HMP influences IRI in kidney and liver transplantation may lead to new therapies and improved transplant outcomes.

Shear stress induced by acute heat exposure is not obligatory to protect against endothelial ischemia-reperfusion injury in humans

Acute heat exposure protects against endothelial ischemia-reperfusion (I/R) injury in humans. However, the mechanism/s mediating this protective effect remain unclear. We tested the hypothesis that inhibiting the increase in shear stress induced by acute heat exposure would attenuate the protection of endothelial function following I/R injury. Nine (3 women) young healthy participants were studied under three experimental conditions: 1) thermoneutral control; 2) whole body heat exposure to increase body core temperature by 1.2°C; and 3) heat exposure + brachial artery compression to inhibit the temperature-dependent increase in shear stress. Endothelial function was assessed via brachial artery flow-mediated dilatation before (pre-I/R) and after (post-I/R) 20 min of arm ischemia followed by 20 min of reperfusion. Brachial artery shear rate was increased during heat exposure (681 ± 359 s^-1), but not for thermoneutral control (140 ± 63 s^-1; P < 0.01 vs. heat exposure) nor for heat + brachial artery compression (139 ± 60 s^-1; P < 0.01 vs. heat exposure). Ischemia-reperfusion injury reduced flow-mediated dilatation following thermoneutral control (pre-I/R, 5.5 ± 2.9% vs. post-I/R, 3.8 ± 2.9%; P = 0.06), but was protected following heat exposure (pre-I/R, 5.8 ± 2.9% vs. post-I/R, 6.1 ± 2.9%; P = 0.5) and heat + arterial compression (pre-I/R, 4.4 ± 2.8% vs. post-I/R, 5.8 ± 2.8%; P = 0.1). Contrary to our hypothesis, our findings demonstrate that shear stress induced by acute heat exposure is not obligatory to protect against endothelial I/R injury in humans.NEW & NOTEWORTHY Acute heat exposure protects against endothelial ischemia-reperfusion injury in humans. However, the mechanism/s mediating this protective effect remain unclear. We utilized arterial compression to inhibit the temperature-dependent increase in brachial artery blood velocity that occurs during acute heat exposure to isolate the contribution of shear stress to the protection of endothelial function following ischemia-reperfusion injury. Our findings demonstrate that shear stress induced by acute heat exposure is not obligatory to protect against endothelial I/R injury.

Endothelial glycocalyx degradation during sepsis: Causes and consequences

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The endothelial glycocalyx is a ubiquitous intravascular structure essential for vascular homeostasis.

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During sepsis, the glycocalyx is degraded via the collective action of a variety of redundant sheddases, the regulation of which remains the focus of active investigation.

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Septic loss of the glycocalyx imparts both local vascular injury (leading to acute respiratory distress syndrome and acute kidney injury) as well as the systemic consequences of circulating glycosaminoglycan fragments (leading to cognitive dysfunction).

•

Glycocalyx degradation during sepsis is potentially shaped by clinically-modifiable factors, suggesting opportunities for therapeutic intervention to mitigate the end-organ consequences of sepsis.

The glycocalyx is a ubiquitous structure found on endothelial cells that extends into the vascular lumen. It is enriched in proteoglycans, which are proteins attached to the glycosaminoglycans heparan sulfate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and hyaluronic acid. In health and disease, the endothelial glycocalyx is a central regulator of vascular permeability, inflammation, coagulation, and circulatory tonicity. During sepsis, a life-threatening syndrome seen commonly in hospitalized patients, the endothelial glycocalyx is degraded, significantly contributing to its many clinical manifestations. In this review we discuss the intrinsically linked mechanisms responsible for septic endothelial glycocalyx destruction: glycosaminoglycan degradation and proteoglycan cleavage. We then examine the consequences of local endothelial glycocalyx loss to several organ systems and the systemic consequences of shed glycocalyx constituents. Last, we explore clinically relevant non-modifiable and modifiable factors that exacerbate or protect against endothelial glycocalyx shedding during sepsis.

Multiple inducers of endothelial NOS (eNOS) dysfunction in sickle cell disease

A characteristic aspect of the robust, systemic inflammatory state in sickle cell disease is dysfunction of endothelial nitric oxide synthase (eNOS). We identify 10 aberrant endothelial cell inputs, present in the specific sickle context, that are known to have the ability to cause eNOS dysfunction. These are: endothelial arginase depletion, asymmetric dimethylarginine, complement activation, endothelial glycocalyx degradation, free fatty acids, inflammatory mediators, microparticles, oxidized low density lipoproteins, reactive oxygen species, and Toll‐like receptor 4 signaling ligands. The effect of true eNOS dysfunction on clinical testing using flow‐mediated dilation can be simulated by two known examples of endothelial dysfunction mimicry (hemoglobin consumption of NO; and oxidation of smooth muscle cell soluble guanylate cyclase). This lends ambiguity to interpretation of such clinical testing. The presence of these multiple perturbing factors argues that a therapeutic approach targeting only a single injurious endothelial input (or either example of mimicry) would not be sufficiently efficacious. This would seem to argue for identifying therapeutics that directly protect eNOS function or application of multiple therapeutic approaches.

Sublingual microcirculatory alterations during the immediate and early postoperative period: A systematic review and meta-analysis

BACKGROUND

The incidence of postoperative microcirculatory flow alterations and their effect on outcome have not been studied extensively.

OBJECTIVE

This systematic review and meta-analysis was designed to investigate the presence of sublingual microcirculatory flow alterations during the immediate and early postoperative period and their correlation with complications and survival.

METHODS

A systematic search of PubMed, Scopus, Embase, PubMed Central, and Google Scholar was conducted for relevant articles from January 2000 to March 2021. Eligibility criteria were randomized controlled and non-randomized trials. Case reports, case series, review papers, animal studies and non-English literature were excluded. The primary outcome was the assessment of sublingual microcirculatory alterations during the immediate and early postoperative period in adult patients undergoing surgery. Risk of bias was assessed with the Ottawa-Newcastle scale. Standard meta-analysis methods (random-effects models) were used to assess the difference in microcirculation variables.

RESULTS

Thirteen studies were included. No statistically significant difference was found between preoperative and postoperative total vessel density (p = 0.084; Standardized Mean Difference (SMD): -0.029; 95%CI: -0.31 to 0.26; I2 = 22.55%). Perfused vessel density significantly decreased postoperatively (p = 0.035; SMD: 0.344; 95%CI: 0.02 to 0.66; I2 = 65.66%), while perfused boundary region significantly increased postoperatively (p = 0.031; SMD: -0.415; 95%CI: -0.79 to -0.03; I2 = 37.21%). Microvascular flow index significantly decreased postoperatively (p = 0.028; SMD: 0.587; 95%CI: 0.06 to 1.11; I2 = 86.09%), while no statistically significant difference was found between preoperative and postoperative proportion of perfused vessels (p = 0.089; SMD: 0.53; 95%CI: -0.08 to 1.14; I2 = 70.71%). The results of the non-cardiac surgery post-hoc analysis were comparable except that no statistically significant difference in perfused vessel density was found (p = 0.69; SMD: 0.07; 95%CI: -0.26 to 0.39; I2 = 0%).

LIMITATIONS

The included studies investigate heterogeneous groups of surgical patients. There were no randomized controlled trials.

CONCLUSIONS

Significant sublingual microcirculatory flow alterations are present during the immediate and early postoperative period. Further research is required to estimate the correlation of sublingual microcirculatory flow impairment with complications and survival.