Sphingosine-1-Phosphate Reduces Hemorrhagic Shock and Resuscitation-Induced Microvascular Leakage by Protecting Endothelial Mitochondrial Integrity

Glabridin ameliorates hemorrhagic shock induced acute kidney injury by activating Nrf2/HO-1 pathway

Glabridin, a bioactive compound extracted from licorice, exhibits anti-inflammatory and antioxidative stress effects. It has rarely been reported in hemorrhagic shock (HS)-induced acute kidney injury (AKI). Here, the effects and potential mechanisms of Glabridin on HS-induced kidney injury was investigated. The active ingredient target network of licorice for HS-induced acute kidney injury was analyzed using network pharmacology. The study also examined the target gene-related biological processes and signaling pathways. To explore the impact of Glabridin on the kidney, a HS-induced rat model was established by femoral artery bleeding following tail vein injection of Glabridin. Glabridin improved kidney function evidenced by reduced levels of creatinine, urea nitrogen, neutrophil gelatinase-associated lipocalin in the serum, and the urinary protein/creatinine ratio in HS rats. This was inseparable from the inhibitory effect on apoptosis and kidney tubule injury. In addition, the protection of Glabridin on mitochondrial function was evident in the improvement of mitochondrial morphology, reduction of reactive oxygen species, increase in adenosine triphosphate, and upregulation of peroxisome proliferator-activated receptor γ coactivator 1-alph. These effects help reduce inflammation in kidney tissue. Hypoxia/reoxygenation-induced HK-2 cells were studied in vitro, and the same results were obtained in the cell model. Mechanically, Glabridin activated the Nrf2/HO-1 signaling pathway in vivo and in vitro, which may be a potential mechanism through which Glabridin protects kidney tissue. This study revealed the preventive effect of Glabridin on the kidney of HS rats, and provided insights for the development of Glabridin as a small molecule drug.

Hemorrhagic Shock and Mitochondria: Pathophysiology and Therapeutic Approaches

Severe injuries and some pathologies associated with massive bleeding, such as maternal hemorrhage, gastrointestinal and perioperative bleeding, and rupture of an aneurysm, often lead to major blood loss and the development of hemorrhagic shock. A sharp decrease in circulating blood volume triggers a vicious cycle of vasoconstriction and coagulopathy leading to ischemia of all internal organs and, in severe decompensated states, ischemia of the brain and heart. The basis of tissue damage and dysfunction in hemorrhagic shock is an interruption in the supply of oxygen and substrates for energy production to the cells, making the mitochondria a source and target of oxidative stress and proapoptotic signaling. Based on these mechanisms, different strategies are proposed to treat the multiple organ failure that occurs in shock. The main direction of such treatment is to provide the cells with a sufficient amount of substrates that utilize oxidative phosphorylation at different stages and increase the efficiency of energy production by the mitochondria. These strategies include restoring the efficiency of mitochondrial complexes, for example, by restoring the nicotinamide adenine dinucleotide (NAD) pool. Another direction is approaches to minimize oxidative stress as well as apoptosis, which are primarily dependent on the mitochondria. There are also a number of other methods to reduce mitochondrial dysfunction and improve the quality of the mitochondrial population. In this review, we consider such strategies for the treatment of hemorrhagic shock and show the promise of therapeutic approaches aimed at restoring the bioenergetic functions of the cell and protecting mitochondria.

Protective effect of 8-Gingerol, a potent constituent of ginger, on acute lung injury following hemorrhagic shock in rats

Acute lung injury (ALI) is a common complication after hemorrhagic shock (HS), which is associated with HS-induced inflammatory response, oxidative stress, and cell apoptosis. This study aimed to investigate the therapeutic efficacy of 8-Gingerol, a constituent extracted from ginger, on ALI after HS in rats. We established a fixed press hemorrhage model in SD rats, in which the HS rats were administered 15 or 30 mg/kg of 8-Gingerol by intraperitoneal injection before fluid resuscitation. Hematoxylin and eosin (H&E) and TUNEL staining were performed to evaluate histopathological changes and cell apoptosis in lung tissues, respectively. Quantitative reverse transcription PCR and western blot were used to measure gene and protein expression. Pro-inflammatory cytokines were detected by ELISA kits. Immunofluorescence of myeloperoxidase was used to evaluate neutrophil infiltration. 8-Gingerol reduced pulmonary edema, alveolar wall thickness, and cell apoptosis in lung tissues of HS rats. Regarding inflammatory responses, 8-Gingerol attenuated neutrophil infiltration in lung tissues, reduced pro-inflammatory cytokines in lung tissues and bronchoalveolar lavage fluid, and decreased the levels of NLR family, pyrin domain containing 3 (NLRP3), PYD and CARD domain containing (ASC), and Cleaved-Caspase 1 (Asp296), p20 (Cleaved Caspase 1) in lung tissues. Additionally, 8-Gingerol ameliorated oxidative stress in lung tissues as evidenced by increased antioxidant indicators (SOD and GSH) and decreased production of malondialdehyde (MDA) and reactive oxygen species (ROS). The therapeutic effects of 8-Gingerol were associated with the regulation of mitogen-activated protein kinase (MAPK) and Nrf2/HO-1 pathways. These results support 8-Gingerol as a promising drug for the treatment of HS-induced ALI.

Endothelial dysfunction is dampened by early administration of fresh frozen plasma in a rodent burn shock model

BACKGROUND

Endothelial dysfunction has been implicated in the pathogenesis of burn shock affecting patients with large thermal injury. In response to injury, glycocalyx components like Syndecan-1 (SDC-1) are shed into circulation and have been used as markers of endothelial damage. Previous work in our laboratory has shown that plasma inclusive resuscitation (PIR) with fresh frozen plasma (FFP) ameliorates endothelial damage. However, there remains a paucity of information regarding optimal timing and dosing of PIR as well as organ-specific endothelial responses to shock. We aimed to examine the impact of PIR on endothelial dysfunction using clinically translatable timing and dosing.

METHODS

Sprague-Dawley rats were used to create thermal burns. Rats were subjected to 40% total body surface area scald burns and were resuscitated with lactated Ringer's (LR) only, LR plus albumin, and LR plus early 1 mL boluses of FFP at 0, 2, 4, and 8 hours postinjury. A late group also received LR plus FFP starting at hour 10 postinjury. Syndecan-1 levels were quantified by enzyme-linked immunosorbent assay, and quantitative real-time polymerase chain reaction analysis characterized transcription of glycocalyx components and inflammatory cytokines in the lung and spleen. Evan's blue dye was used to quantify amount of vascular leakage.

RESULTS

Lactated Ringer's plus early FFP reduced Evan's blue dye extravasation when compared with LR only groups, while late FFP did not. When comparing LR only versus LR plus early FFP, SDC-1 levels were reduced in the LR plus early FFP group at hours 8, 12, and 24 (5.23 vs. 2.07, p < 0.001; 4.49 vs. 2.05, p < 0.01; and 3.82 vs. 2.08, p < 0.05, respectively). Lactated Ringer's only groups had upregulation of Exostosin-1 and SDC-1 in the lung compared with LR plus early FFP groups ( p < 0.01 and p < 0.05) and upregulation of cytokines interluekin-10 and interferon γ ( p < 0.001 and p < 0.001).

CONCLUSION

Early administration of LR plus FFP reduces the magnitude of SDC-1 shedding and dampens the cytokine response to injury. The upregulation of glycocalyx components as a response to endothelial injury is also decreased in the lung and spleen by LR plus early FFP administration.

Shenfu injection alleviate gut ischemia/reperfusion injury after severe hemorrhagic shock through improving intestinal microcirculation in rats

Background

Shenfu (SF) injection, a traditional Chinese medication, would improve microcirculation in cardiogenic shock and infectious shock. This study was aimed to explore the therapeutic potential of the SF injection in gut ischemia-reperfusion (I/R) injury after severe hemorrhagic shock (SHS) and resuscitation. Furthermore, we also investigated the optimal adm？ inistration timing.

Methods

Twenty-four male SD rats were randomly divided into four groups: Sham group (sham, n = 6), Control group (n = 6), SF injection group (SF, n = 6), and Delayed Shenfu injection administration group (SF-delay, n = 6). In SHS and resuscitation model, rats were induced by blood draw to a mean arterial pressure (MAP) of 40 ± 5 mmHg within 1 h and then maintained for 40 min; HR, MAP 'were recorded, microcirculation index [De Backer score, perfused small vessel density (PSVD), total vessel density (TVD), microcirculation flow index score (MFI), flow heterogeneity index (HI)] were analyzed. The blood gas index was detected, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), diamine oxidase (DAO), malondialdehyde (MDA) were measured by ELISA; ZO-1, and claudin-1 were measured by Western blotting. In addition, hematoxylin-eosin (HE) and periodic acid schiff (PAS) staining pathological sections of the intestinal mucosal tissues were also performed.

Results

SF injection increased the MAP, relieved the metabolic acidosis degree associated with the hypoperfusion, and improved the intestinal microcirculatory density and perfusion quality after I/R injury. The expression of DAO, MDA in intestinal tissue, and plasma IL-6, TNF-α significantly decreased in the SF injection group compared to the control group. The concentration of ZO-1 and claudin-1 is also higher in the SF injection group. In addition, the HE and PAS staining results also showed that SF injection could decrease mucosal damage and maintain the structure. In the SF-delay group, the degree of intestinal tissue damage was intermediate between that of the control group and SF injection group.

Conclusions

SF injection protect the intestine from I/R injury induced by SHS and resuscitation, the mechanism of which might be through improving intestinal microcirculation, reducing the excessive release of inflammatory factors and increasing intestinal mucosal permeability. Furthermore, the protection effect is more pronounced if administration during the initial resuscitation phase.

Evaluation of Glycolysis and Mitochondrial Function in Endothelial Cells Using the Seahorse Analyzer

Endothelial bioenergetics have emerged as a key regulator of endothelial barrier function. Glycolytic parameters have been linked to barrier enhancement, and interruption with mitochondrial complexes was shown to disrupt endothelial barrier. Therefore, a new technology that has been introduced to assess bioenergetics and metabolism has also made it possible to determine roles of specific energy production pathways in endothelial health. The Seahorse extracellular flux analysis by Agilent technologies is a state of the art tool that has been more frequently used to evaluate bioenergetics of endothelial cells. This chapter includes details about different assays that can be used to study endothelial cells using the Seahorse analyzer and how interpretation of the results can provide novel insight about endothelial metabolism.

Microvascular Endothelial Glycocalyx Surface Layer Visualization and Quantification

As a primary interface between the blood and underlying vascular wall, the endothelial glycocalyx layer is common to all blood vessels and covers the luminal surface of all endothelial cells. The endothelial glycocalyx has important roles as a regulator of microvascular endothelial functions such as mechanotransduction, leukocyte adhesion, and microvascular permeability. Disruption of the molecular structure of the endothelial glycocalyx disturbs physiological, and hemodynamic processes associated with the microvascular wall leads to microvascular hyperpermeability. Studying the glycocalyx is challenging because cultured cells present aberrant glycocalyx structure and tissue fixation techniques lead to the degradation and loss of this fine and delicate layer. Therefore, studying the glycocalyx requires in vivo imaging of the microcirculation. Here we describe two techniques for direct imaging and assessment of the glycocalyx surface layer integrity using intravital microscopy (IVM), a method widely used in the study of the dynamic changes that occur in the microcirculation during inflammation or injury.

Determination of Solute Permeability of Microvascular Endothelial Cell Monolayers In Vitro

The microvascular endothelium has a critical role in regulating the delivery of oxygen, nutrients, and water to the surrounding tissues. Under inflammatory conditions that accompany acute injury or disease, microvascular permeability becomes elevated. When microvascular hyperpermeability becomes uncontrolled or chronic, the excessive escape of plasma proteins into the surrounding tissue disrupts homeostasis and ultimately leads to organ dysfunction. Much remains to be learned about the mechanisms that control microvascular permeability. In addition to in vivo and isolated microvessel methods, the cultured endothelial cell monolayer protocol is an important tool that allows for understanding the specific, endothelial subcellular mechanisms that determine permeability of the endothelium to plasma proteins. In this chapter, two variations of the popular Transwell culture methodology to determine permeability to using fluorescently labeled tracers are presented. The strengths and weaknesses of this approach are also discussed.

Edema and lymphatic clearance: molecular mechanisms and ongoing challenges

Resolution of edema remains a significant clinical challenge. Conditions such as traumatic shock, sepsis, or diabetes often involve microvascular hyperpermeability, which leads to tissue and organ dysfunction. Lymphatic insufficiency due to genetic causes, surgical removal of lymph nodes, or infections, leads to varying degrees of tissue swelling that impair mobility and immune defenses. Treatment options are limited to management of edema as there are no specific therapeutics that have demonstrated significant success for ameliorating microvascular leakage or impaired lymphatic function. This review examines current knowledge about the physiological, cellular, and molecular mechanisms that control microvascular permeability and lymphatic clearance, the respective processes for interstitial fluid formation and removal. Clinical conditions featuring edema, along with potential future directions are discussed.

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.

Sphingosine-1-Phosphate Signaling in Cardiovascular Diseases

Sphingosine-1-phosphate (S1P) is an important sphingolipid molecule involved in regulating cardiovascular functions in physiological and pathological conditions by binding and activating the three G protein-coupled receptors (S1PR1, S1PR2, and S1PR3) expressed in endothelial and smooth muscle cells, as well as cardiomyocytes and fibroblasts. It exerts its actions through various downstream signaling pathways mediating cell proliferation, migration, differentiation, and apoptosis. S1P is essential for the development of the cardiovascular system, and abnormal S1P content in the circulation is involved in the pathogenesis of cardiovascular disorders. This article reviews the effects of S1P on cardiovascular function and signaling mechanisms in different cell types in the heart and blood vessels under diseased conditions. Finally, we look forward to more clinical findings with approved S1PR modulators and the development of S1P-based therapies for cardiovascular diseases.

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.

Overview and New Insights into the Metabolic Syndrome: Risk Factors and Emerging Variables in the Development of Type 2 Diabetes and Cerebrocardiovascular Disease

Metabolic syndrome (MetS) is considered a metabolic disorder that has been steadily increasing globally and seems to parallel the increasing prevalence of obesity. It consists of a cluster of risk factors which traditionally includes obesity and hyperlipidemia, hyperinsulinemia, hypertension, and hyperglycemia. These four core risk factors are associated with insulin resistance (IR) and, importantly, the MetS is known to increase the risk for developing cerebrocardiovascular disease and type 2 diabetes mellitus. The MetS had its early origins in IR and syndrome X. It has undergone numerous name changes, with additional risk factors and variables being added over the years; however, it has remained as the MetS worldwide for the past three decades. This overview continues to add novel insights to the MetS and suggests that leptin resistance with hyperleptinemia, aberrant mitochondrial stress and reactive oxygen species (ROS), impaired folate-mediated one-carbon metabolism with hyperhomocysteinemia, vascular stiffening, microalbuminuria, and visceral adipose tissues extracellular vesicle exosomes be added to the list of associated variables. Notably, the role of a dysfunctional and activated endothelium and deficient nitric oxide bioavailability along with a dysfunctional and attenuated endothelial glycocalyx, vascular inflammation, systemic metainflammation, and the important role of ROS and reactive species interactome are discussed. With new insights and knowledge regarding the MetS comes the possibility of new findings through further research.

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.

The Microvascular-Lymphatic Interface and Tissue Homeostasis: Critical Questions That Challenge Current Understanding

Lymphatic and blood microvascular networks play critical roles in the clearance of excess fluid from local tissue spaces. Given the importance of these dynamics in inflammation, tumor metastasis, and lymphedema, understanding the coordinated function and remodeling between lymphatic and blood vessels in adult tissues is necessary. Knowledge gaps exist because the functions of these two systems are typically considered separately. The objective of this review was to highlight the coordinated functional relationships between blood and lymphatic vessels in adult microvascular networks. Structural, functional, temporal, and spatial relationships will be framed in the context of maintaining tissue homeostasis, vessel permeability, and system remodeling. The integration across systems will emphasize the influence of the local environment on cellular and molecular dynamics involved in fluid flow from blood capillaries to initial lymphatic vessels in microvascular networks.

PTPRO knockdown protects against inflammation in hemorrhage shock-induced lung injury involving the NF-κB signaling pathway

BACKGROUND

Hemorrhage shock (HS) is characterized by decreased tissue oxygenation and organ damage due to severe blood loss. Protein tyrosine phosphatase receptor type O (PTPRO) is abnormally up-regulated in the rat lungs after trauma/HS.

METHODS

To elucidate the regulatory mechanism of PTPRO in lung inflammation following HS, we established a rat model of HS via withdrawing blood by a catheter inserted into the femoral artery followed by resuscitation. The rats were infected with lentivirus harboring short hairpin RNA (shRNA) targeting PTPRO by intratracheal instillation.

RESULTS

PTPRO was significantly up-regulated in rat lungs after HS. PTPRO knockdown enhanced epithelial integrity and reduced capillary leakage by up-regulating tight junction proteins zonula occludens-1 (ZO-1) and occludin (OCC) in the lungs. Besides, HS-induced myeloperoxidase activity and inflammatory cell infiltration was mitigated by PTPRO knockdown. The expression of inflammatory cytokines/chemokines (TNF-α, IL-6, MIP-2, MCP-1, and KC) in the lungs and bronchoalveolar lavage fluid was regressed after PTPRO knockdown. The nuclear factor kappa B (NF-κB) pathway was involved in HS-induced lung inflammation. PTPRO down-regulation inhibited the NF-κB pathway activation by suppressing the phosphorylation of NF-κB and its translocation from the cytoplasm into the nucleus in HS.

CONCLUSION

Taken together, we demonstrated that PTPRO knockdown may contribute to attenuating inflammation in HS-induced lung injury via inhibiting NF-κB pathway activation.

Methods to evaluate vascular function: a crucial approach towards predictive, preventive, and personalised medicine

Endothelium, the gatekeeper of our blood vessels, is highly heterogeneous and a crucial physical barrier with the ability to produce vasoactive and protective mediators under physiological conditions. It regulates vascular tone, haemostasis, vascular inflammation, remodelling, and angiogenesis. Several cardio-, reno-, and cerebrovascular diseases begin with the dysfunction of endothelial cells, and more recently, COVID-19 was also associated with endothelial disease highlighting the need to monitor its function towards prevention and reduction of vascular dysfunction. Endothelial cells are an important therapeutic target in predictive, preventive, and personalised (3P) medicine with upmost importance in vascular diseases. The development of novel non-invasive techniques to access endothelial dysfunction for use in combination with existing clinical imaging modalities provides a feasible opportunity to reduce the burden of vascular disease. This review summarises recent advances in the principles of endothelial function measurements. This article presents an overview of invasive and non-invasive techniques to determine vascular function and their major advantages and disadvantages. In addition, the article describes mechanisms underlying the regulation of vascular function and dysfunction and potential new biomarkers of endothelial damage. Recognising these biomarkers is fundamental towards a shift from reactive to 3P medicine in the vascular field. Identifying vascular dysfunction earlier with non-invasive or minimally invasive techniques adds value to predictive diagnostics and targeted prevention (primary, secondary, tertiary care). In addition, vascular dysfunction is a potential target for treatments tailored to the person.

The Mighty Mitochondria Are Unifying Organelles and Metabolic Hubs in Multiple Organs of Obesity, Insulin Resistance, Metabolic Syndrome, and Type 2 Diabetes: An Observational Ultrastructure Study

Mitochondria (Mt) are essential cellular organelles for the production of energy and thermogenesis. Mt also serve a host of functions in addition to energy production, which include cell signaling, metabolism, cell death, and aging. Due to the central role of Mt in metabolism as metabolic hubs, there has been renewed interest in how Mt impact metabolic pathways and multiple pathologies. This review shares multiple observational ultrastructural findings in multiple cells and organs to depict aberrant mitochondrial (aMt) remodeling in pre-clinical rodent models. Further, it is intended to show how remodeling of Mt are associated with obesity, insulin resistance, metabolic syndrome (MetS), and type 2 diabetes mellitus (T2DM). Specifically, Mt remodeling in hypertensive and insulin-resistant lean models (Ren2 rat models), lean mice with streptozotocin-induced diabetes, obesity models including diet-induced obesity, genetic leptin-deficient ob/ob, and leptin receptor-deficient db/db diabetic mice are examined. Indeed, aMt dysfunction and damage have been implicated in multiple pathogenic diseases. Manipulation of Mt such as the induction of Mt biogenesis coupled with improvement of mitophagy machinery may be helpful to remove leaky damaged aMt in order to prevent the complications associated with the generation of superoxide-derived reactive oxygen species and the subsequent reactive species interactome. A better understanding of Mt remodeling may help to unlock many of the mysteries in obesity, insulin resistance, MetS, T2DM, and the associated complications of diabetic end-organ disease.

Targeting repair of the vascular endothelium and glycocalyx after traumatic injury with plasma and platelet resuscitation

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Endothelial glycocalyx shedding is a key instigator of the endotheliopathy of trauma.

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Plasma and platelet transfusions preserve vascular integrity in pre-clinical models.

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However, platelets may be less effective than plasma in preserving the glycocalyx.

Severely injured patients with hemorrhagic shock can develop endothelial dysfunction, systemic inflammation, and coagulation disturbances collectively known as the endotheliopathy of trauma (EOT). Shedding of the endothelial glycocalyx occurs early after injury, contributes to breakdown of the vascular barrier, and plays a critical role in the pathogenesis of multiple organ dysfunction, leading to poor outcomes in trauma patients. In this review we discuss (i) the pathophysiology of endothelial glycocalyx and vascular barrier breakdown following hemorrhagic shock and trauma, and (ii) the role of plasma and platelet transfusion in maintaining the glycocalyx and vascular endothelial integrity.

Plasma components to protect the endothelial barrier after shock: A role for sphingosine 1-phosphate

BACKGROUND

Hemorrhagic shock leads to endothelial glycocalyx shedding, endothelial cellular inflammation, and increased vascular permeability. Early plasma administration improves survival in severely injured patients; this may be due in part to its ability to ameliorate this trauma-induced endotheliopathy. The protective effect of early plasma administration may be due to its sphingosine 1-phosphate content. Principle carriers of plasma sphingosine 1-phosphate include apolipoprotein M and albumin. The relative roles of these carriers on sphingosine 1-phosphate protective effects are unknown and were studied in an in vitro model of microcirculation.

METHODS

Endothelial cell monolayers were established in microfluidic perfusion devices and exposed to control or biomimetic shock conditions. Sphingosine 1-phosphate, albumin + sphingosine 1-phosphate, or apolipoprotein M + sphingosine 1-phosphate were added later to the perfusate. Biomarkers of endothelial and glycocalyx activation and damage were then determined.

RESULTS

Sphingosine 1-phosphate preserved endothelial and glycocalyx barrier function after exposure to conditions of shock in the microcirculation. The protective effect was related to sphingosine 1-phosphate chaperones; the apolipoprotein M loaded with sphingosine 1-phosphate had the most profound effect.

CONCLUSION

Carrier-based sphingosine 1-phosphate may be a useful adjunct in early hemorrhagic shock resuscitation.

Therapeutically Targeting Microvascular Leakage in Experimental Hemorrhagic SHOCK: A Systematic Review and Meta-Analysis

BACKGROUND

Microvascular leakage is proposed as main contributor to disturbed microcirculatory perfusion following hemorrhagic shock and fluid resuscitation, leading to organ dysfunction and unfavorable outcome. Currently, no drugs are available to reduce or prevent microvascular leakage in clinical practice. We therefore aimed to provide an overview of therapeutic agents targeting microvascular leakage following experimental hemorrhagic shock and fluid resuscitation.

METHODS

PubMed, EMBASE.com, and Cochrane Library were searched in January 2021 for preclinical studies of hemorrhagic shock using any therapeutic agent on top of standard fluid resuscitation. Primary outcome was vascular leakage, defined as edema, macromolecule extravasation, or glycocalyx degradation. Drugs were classified by targeting pathways and subgroup analyses were performed per organ.

RESULTS

Forty-five studies, published between 1973 and 2020, fulfilled eligibility criteria. The included studies tested 54 different therapeutics mainly in pulmonary and intestinal vascular beds. Most studies induced trauma besides hemorrhagic shock. Forty-four therapeutics (81%) were found effective to reduce microvascular leakage, edema formation, or glycocalyx degradation in at least one organ. Targeting oxidative stress and apoptosis was the predominantly effective strategy (SMD: -2.18, CI [-3.21, -1.16], P < 0.0001). Vasoactive agents were found noneffective in reducing microvascular leakage (SMD: -0.86, CI [-3.07, 1.36], P = 0.45).

CONCLUSION

Pharmacological modulation of pathways involved in cell metabolism, inflammation, endothelial barrier regulation, sex hormones and especially oxidative stress and apoptosis were effective in reducing microvascular leakage in experimental hemorrhagic shock with fluid resuscitation. Future studies should investigate whether targeting these pathways can restore microcirculatory perfusion and reduce organ injury following hemorrhagic shock.

SYSTEMATIC REVIEW REGISTRATION NUMBER

CRD42018095432.

Shenfu injection improves cerebral microcirculation and reduces brain injury in a porcine model of hemorrhagic shock

BACKGROUND

Shenfu injection (SFI) is a traditional Chinese herbal medicine which has been clinically used for treatment of septic shock and cardiac shock. The aim of this study was to clarify effects of SFI on cerebral microcirculation and brain injury after hemorrhagic shock (HS).

METHODS

Twenty-one domestic male Beijing Landrace pigs were randomly divided into three groups: SFI group (SFI, n = 8), saline group (SA, n = 8) or sham operation group (SO, n = 5). In the SFI group, animals were induced to HS by rapid bleeding to a mean arterial pressure of 40 mmHg within 10 minutes and maintained at 40±3 mmHg for 60 minutes. Volume resuscitation (shed blood and crystalloid) and SFI were given after 1 hour of HS. In the SA group, animals received the same dose of saline instead of SFI. In the SO group, the same surgical procedure was performed but without inducing HS and volume resuscitation. The cerebral microvascular flow index (MFI), nitric oxide synthase (NOS) expression, aquaporin-4 expression, interleukin-6, tumor necrosis factor-α (TNF-α) and ultrastructural of microvascular endothelia were measured.

RESULTS

Compared with the SA group, SFI significantly improved cerebral MFI after HS. SFI up regulated cerebral endothelial NOS expression, but down regulated interleukin-6, TNF-α, inducible NOS and aquaporin-4 expression compared with the SA group. The cerebral microvascular endothelial injury and interstitial edema in the SFI group were lighter than those in the SA group.

CONCLUSIONS

Combined application of SFI with volume resuscitation after HS can improve cerebral microcirculation and reduce brain injury.

The Glycocalyx and Its Role in Vascular Physiology and Vascular Related Diseases

Purpose

In 2007 the two senior authors wrote a review on the structure and function of the endothelial glycocalyx layer (Weinbaum in Annu Rev Biomed Eng 9:121–167, 2007). Since then there has been an explosion of interest in this hydrated gel-like structure that coats the luminal surface of endothelial cells that line our vasculature due to its important functions in (A) basic vascular physiology and (B) vascular related diseases. This review will highlight the major advances that have occurred since our 2007 paper.

Methods

A literature search mainly focusing on the role of the glycocalyx in the two major areas described above was performed using electronic databases.

Results

In part (A) of this review, the new formulation of the century old Starling principle, now referred to as the Michel–Weinbaum glycoclayx model or revised Starling hypothesis, is described including new subtleties and physiological ramifications. New insights into mechanotransduction and release of nitric oxide due to fluid shear stress sensed by the glycocalyx are elaborated. Major advances in understanding the organization and function of glycocalyx components, and new techniques for measuring both its thickness and spatio-chemical organization based on super resolution, stochastic optical reconstruction microscopy (STORM) are presented. As discussed in part (B) of this review, it is now recognized that artery wall stiffness associated with hypertension and aging induces glycocalyx degradation, endothelial dysfunction and vascular disease. In addition to atherosclerosis and cardiovascular diseases, the glycocalyx plays an important role in lifestyle related diseases (e.g., diabetes) and cancer. Infectious diseases including sepsis, Dengue, Zika and Corona viruses, and malaria also involve the glycocalyx. Because of increasing recognition of the role of the glycocalyx in a wide range of diseases, there has been a vigorous search for methods to protect the glycocalyx from degradation or to enhance its synthesis in disease environments.

Conclusion

As we have seen in this review, many important developments in our basic understanding of GCX structure, function and role in diseases have been described since the 2007 paper. The future is wide open for continued GCX research.

PRE-084 as a tool to uncover potential therapeutic applications for selective sigma-1 receptor activation

The discovery of a highly selective putative sigma-1 (σ1) receptor agonist, PRE-084, has revealed the numerous potential uses of this receptor subtype as a therapeutic target. While much work has been devoted to determining the role of σ1 receptors in normal and pathophysiological states in the nervous system, recent work suggests that σ1 receptors may be important for modulating functions of other tissues. These discoveries have provided novel insights into σ1 receptor structure, function, and importance in multiple intracellular signaling mechanisms. These discoveries were made possible by σ1 receptor-selective agonists such as PRE-084. The chemical properties and pharmacological actions of PRE-084 will be reviewed here, along with the expanding list of potential therapeutic applications for selective activation of σ1 receptors.

Sigma-1 receptor activation-induced glycolytic ATP production and endothelial barrier enhancement

OBJECTIVE

We tested the hypothesis that σ1 modulates endothelial barrier function due to its influence on endothelial bioenergetics.

METHODS

Cultured HUVEC monolayers were used to model the endothelial barrier. ECIS, Transwell assays, and immunofluorescence labeling of junctional proteins were used to evaluate endothelial barrier function. Endothelial cell bioenergetics was determined using extracellular flux analysis and direct ATP level measurements. The endothelial-specific contribution of σ1 was tested using the σ1-selective agonist, PRE-084, and with targeted knockdown of σ1 expression using siRNA.

RESULTS

Activation of σ1 with PRE-084 significantly enhanced endothelial barrier function and decreased permeability to albumin and dextran. Knockdown of σ1 with siRNA reduced barrier function and abolished PRE-084-induced endothelial barrier enhancement. PRE-084 upregulated endothelial glycolysis and glycolytic ATP production, but this response was abolished by siRNA-mediated knockdown of σ1 expression. PRE-084 also reduced the degree of endothelial barrier dysfunction caused by the mitochondrial oxidative phosphorylation uncoupler CCCP.

CONCLUSION

Activation of σ1 enhances endothelial barrier function and modulates the ratio of glycolytic versus mitochondrial ATP production. These novel findings suggest that endothelial σ1 may prove beneficial as a novel therapeutic target for reducing microvascular hyperpermeability and counteracting mitochondrial dysfunction.

Significance of sphingosine-1-phosphate in cardiovascular physiology and pathology

Sphingosine-1-phosphate (S1P) is a signaling lipid, synthetized by sphingosine kinases (SPHK1 and SPHK2), that affects cardiovascular function in various ways. S1P signaling is complex, particularly since its molecular action is reliant on the differential expression of its receptors (S1PR1, S1PR2, S1PR3, S1PR4, S1PR5) within various tissues. Significance of this sphingolipid is manifested early in vertebrate development as certain defects in S1P signaling result in embryonic lethality due to defective vasculo- or cardiogenesis. Similar in the mature organism, S1P orchestrates both physiological and pathological processes occurring in the heart and vasculature of higher eukaryotes. S1P regulates cell fate, vascular tone, endothelial function and integrity as well as lymphocyte trafficking, thus disbalance in its production and signaling has been linked with development of such pathologies as arterial hypertension, atherosclerosis, endothelial dysfunction and aberrant angiogenesis. Number of signaling mechanisms are critical - from endothelial nitric oxide synthase through STAT3, MAPK and Akt pathways to HDL particles involved in redox and inflammatory balance. Moreover, S1P controls both acute cardiac responses (cardiac inotropy and chronotropy), as well as chronic processes (such as apoptosis and hypertrophy), hence numerous studies demonstrate significance of S1P in the pathogenesis of hypertrophic/fibrotic heart disease, myocardial infarction and heart failure. This review presents current knowledge concerning the role of S1P in the cardiovascular system, as well as potential therapeutic approaches to target S1P signaling in cardiovascular diseases.

The effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion injury in the isolated rat heart

OBJECTIVE

Sphingosine-1-phosphate is a natural metabolite that is cardioprotective, but its effects on endothelial glycocalyx damage during ischemia-reperfusion are unknown. Therefore, we investigated the effect of sphingosine-1-phosphate on the endothelial glycocalyx during ischemia-reperfusion.

METHODS

Isolated hearts from Wistar rats were perfused on a Langendorff system with Krebs-Henseleit buffer and pretreated with sphingosine-1-phosphate (10 nmol/L) before ischemia-reperfusion. Infarct size was measured by triphenyl tetrazolium chloride staining (n ≥ 6 per group). Cardiac edema was assessed by calculating total water content (n = 7 per group) and histologically quantifying the interstitial compartment (n ≥ 3 per group). The post-ischemic coronary release of syndecan-1 was quantified using ELISA. Syndecan-1 immunostaining intensity was assessed in perfusion-fixed hearts (n ≥ 3 per group).

RESULTS

Pretreatment with sphingosine-1-phosphate decreased infarct size in isolated hearts subjected to ischemia-reperfusion (P = .01 vs ischemia-reperfusion). However, sphingosine-1-phosphate had no effect on syndecan-1 levels in the coronary effluent or on the intensity of the syndecan-1 immunostaining signal in cardiac tissue. Heart total water content was not significantly different between control and ischemic groups but was significantly decreased in hearts treated with sphingosine-1-phosphate alone.

CONCLUSION

These results suggest that sphingosine-1-phosphate-induced cardioprotection against ischemia-reperfusion injury is not mediated by the maintenance of syndecan-1 in the endothelial glycocalyx.

Endothelial glycocalyx in acute care surgery - what anaesthesiologists need to know for clinical practice

The endothelial glycocalyx (EG) is the thin sugar-based lining on the apical surface of endothelial cells. It has been linked to the physiological functioning of the microcirculation and has been found to be damaged in critical illness and after acute care surgery. This review aims to describe the role of EG in severely injured patients undergoing surgery, discuss specific situations (e.G. major trauma, hemorrhagic shock, trauma induced coagulopathy) as well as specific interventions commonly applied in these patients (e.g. fluid therapy, transfusion) and specific drugs related to perioperative medicine with regard to their impact on EG.EG in acute care surgery is exposed to damage due to tissue trauma, inflammation, oxidative stress and inadequate fluid therapy. Even though some interventions (transfusion of plasma, human serum albumin, hydrocortisone, sevoflurane) are described as potentially EG protective there is still no specific treatment for EG protection and recovery in clinical medicine.The most important principle to be adopted in routine clinical practice at present is to acknowledge the fragile structure of the EG and avoid further damage which is potentially related to worsened clinical outcome.

RS, Yuan SY. Role of Neutrophil Extracellular Traps and Vesicles in Regulating Vascular Endothelial Permeability

The microvascular endothelium serves as the major barrier that controls the transport of blood constituents across the vessel wall. Barrier leakage occurs during infection or sterile inflammation, allowing plasma fluid and cells to extravasate and accumulate in surrounding tissues, an important pathology underlying a variety of infectious diseases and immune disorders. The leak process is triggered and regulated by bidirectional communications between circulating cells and vascular cells at the blood-vessel interface. While the molecular mechanisms underlying this complex process remain incompletely understood, emerging evidence supports the roles of neutrophil-endothelium interaction and neutrophil-derived products, including neutrophil extracellular traps and vesicles, in the pathogenesis of vascular barrier injury. In this review, we summarize the current knowledge on neutrophil-induced changes in endothelial barrier structures, with a detailed presentation of recently characterized molecular pathways involved in the production and effects of neutrophil extracellular traps and extracellular vesicles. Additionally, we discuss the therapeutic implications of altering neutrophil interactions with the endothelial barrier in treating inflammatory diseases.