Selective Cannabinoid 2 Receptor Agonists as Potential Therapeutic Drugs for the Treatment of Endotoxin-Induced Uveitis

(1) Background: The cannabinoid 2 receptor (CB₂R) is a promising anti-inflammatory drug target and development of selective CB₂R ligands may be useful for treating sight-threatening ocular inflammation. (2) Methods: This study examined the pharmacology of three novel chemically-diverse selective CB₂R ligands: CB₂R agonists, RO6871304, and RO6871085, as well as a CB₂R inverse agonist, RO6851228. In silico molecular modelling and in vitro cell-based receptor assays were used to verify CB₂R interactions, binding, cell signaling (ß-arrestin and cAMP) and early absorption, distribution, metabolism, excretion, and toxicology (ADMET) profiling of these receptor ligands. All ligands were evaluated for their efficacy to modulate leukocyte-neutrophil activity, in comparison to the reported CB₂R ligand, HU910, using an in vivo mouse model of endotoxin-induced uveitis (EIU) in wild-type (WT) and CB₂R^-/- mice. The actions of RO6871304 on neutrophil migration and adhesion were examined in vitro using isolated neutrophils from WT and CB₂R^-/- mice, and in vivo in WT mice with EIU using adoptive transfer of WT and CB₂R^-/- neutrophils, respectively. (3) Results: Molecular docking studies indicated that RO6871304 and RO6871085 bind to the orthosteric site of CB₂R. Binding studies and cell signaling assays for RO6871304 and RO6871085 confirmed high-affinity binding to CB₂R and selectivity for CB₂R > CB₁R, with both ligands acting as full agonists in cAMP and ß-arrestin assays (EC₅₀s in low nM range). When tested in EIU, topical application of RO6871304 and RO6871085 decreased leukocyte-endothelial adhesion and this effect was antagonized by the inverse agonist, RO6851228. The CB₂R agonist, RO6871304, decreased in vitro neutrophil migration of WT neutrophils but not neutrophils from CB₂R^-/-, and attenuated adhesion of adoptively-transferred leukocytes in EIU. (4) Conclusions: These unique ligands are potent and selective for CB₂R and have good immunomodulating actions in the eye. RO6871304 and RO6871085, as well as HU910, decreased leukocyte adhesion in EIU through inhibition of resident ocular immune cells. The data generated with these three structurally-diverse and highly-selective CB₂R agonists support selective targeting of CB₂R for treating ocular inflammatory diseases.

Inflammatory Response to Different Toxins in Experimental Sepsis Models

Sepsis is defined as life-threatening organ dysfunction caused by the dysregulated host response to infection. Despite serious mortality and morbidity, no sepsis-specific drugs exist. Endotoxemia is often used to model the hyperinflammation associated with early sepsis. This model classically uses lipopolysaccharide (LPS) from Gram-negative pathogens to activate the immune system, leading to hyperinflammation, microcirculatory disturbances and death. Other toxins may also be used to activate the immune system including Gram-positive peptidoglycan (PG) and lipoteichoic acid (LTA). In addition to these standard toxins, other bacterial components can induce inflammation. These molecules activate different signaling pathways and produce different physiological responses which can be taken advantage of for sepsis modeling. Endotoxemia modeling can provide information on pathways to inflammation in sepsis and contribute to preclinical drug development.

Monoacylglycerol lipase inhibition as potential treatment for interstitial cystitis

Interstitial cystitis is a chronic inflammatory condition of the urinary bladder with an unclear etiology. Currently, there are no widely accepted long-term treatment options available for patients with IC, with the European Association of Urology (EAU, 2017 guidelines), American Urology Association (AUA, 2014 guidelines), and the Royal College of Obstetricians and Gynaecologists (RCOG, 2016 guidelines) all suggesting various different conservative, pharmacological, intravesical, and surgical interventions. The endocannabinoid system represents a potential target for IC treatment and management. Activation of cannabinoid receptor 2 (CBR2) with various agonists has previously been shown to reduce leukocyte differentiation and migration, in addition to inhibiting the release of pro-inflammatory cytokines at the site of inflammation. These receptors have been identified in the detrusor and sensory nerves of the urothelium in various mammalian species, including humans. We hypothesize that by inhibiting the enzymes responsible for the catabolism of endogenous cannabinoids locally, bladder concentrations of CBR2 agonists will increase, particularly 2-arachidonyl glycerol, resulting in a diminished inflammatory response.

Possible Impact of Spinal Anesthesia and Phenylephrine on Sublingual Microcirculation of Cesarean Delivery Patients

Background

This study was a proof of concept of a novel means to evaluate microcirculatory changes during spinal anesthesia for cesarean delivery. It sought to examine the distributive circulatory effects of spinal anesthesia and evaluate the impact of phenylephrine administration on the microcirculation of these women.

Methods

After Research Ethics Board approval, healthy, non-laboring pregnant women with singleton, term pregnancies scheduled for elective cesarean delivery were recruited. Participants were randomly assigned to receive either phenylephrine infusion or phenylephrine bolus. Spinal anesthesia was standardized. A sidestream dark-field (SDF) MicroScan^® video microscope was applied to the sublingual mucosa to obtain microcirculation videos in five different visual fields. Videos were made before and after spinal anesthesia. The resultant videos were analyzed randomly and blindly. The mean microvascular flow index (MFI) values were compared before and after spinal anesthesia. The difference in MFI following spinal anesthesia was compared between phenylephrine infusion and bolus groups.

Results

Thirty-two patients were recruited for the study; 22 patients had complete video sets for analysis. Baseline characteristics were similar between the two groups, including preoperative hemodynamics. There were no significant differences between pre- and post-spinal MFI. The post-spinal MFI within the infusion group (mean ± standard deviation: 2.74 ± 0.21) was not significantly different from the bolus group (2.56 ± 0.42, P = 0.22).

Conclusion

Despite theoretical physiological implications of spinal anesthesia and phenylephrine on the microcirculation, significant alteration of the MFI was not observed between pre- and post-spinal anesthesia (within group). Additionally, despite an eight-fold larger phenylephrine dose for continuous infusion prophylaxis used in this group of women, this did not result in a significant alteration of the microcirculation compared to those who received phenylephrine treatment for hypotension (between groups).

Inhibition of GPR 55 improves dysregulated immune response in experimental sepsis

Sepsis is a medical condition caused by dysregulated systemic inflammatory response against infection, resulting in high mortality. Despite intensive research over the last few decades, the results from multiple clinical trials targeting specific inflammatory mediators have been disappointing. In the present study, we investigated the role of G protein-coupled receptor GPR55 modulation on immune response in an experimental sepsis model (endotoxemia). Immune response was evaluated by analyzing leukocyte-endothelial interactions and capillary perfusion in the intestinal microcirculation using intravital microscopy. In addition, the levels of plasma inflammatory cytokines were measured. The results demonstrated that GPR55 inhibition using antagonists, CID16020046 or O-1918, significantly reduced leukocyte adherence in intestinal submucosal venules and decreased proinflammatory cytokine TNF-α and IL-6 production. These data suggest that GPR55 inhibition may be a novel therapeutic target for attenuating hyperinflammation during sepsis.

Pretreatment human immunodeficiency virus type 1 (HIV-1) drug resistance in transmission clusters of the Cologne-Bonn region, Germany

OBJECTIVES

In Germany, previous reports have demonstrated transmitted human immunodeficiency virus type 1 (HIV-1) drug-resistance mutations (DRM) in 11% of newly diagnosed individuals, highlighting the importance of drug-resistance screening before the initiation of antiretroviral therapy (ART). Here, we sought to understand the molecular epidemiology of HIV DRM transmission in the Cologne-Bonn region of Germany, given one of the highest rates of new HIV diagnoses in western Europe (13.7 per 100 000 habitants).

METHODS

We analysed 714 HIV-1 ART-naive infected individuals diagnosed at the University Hospitals Cologne and Bonn between 2001 and 2016. Screening for DRM was performed according to the Stanford University Genotypic Resistance Interpretation. Shared DRM were defined as any DRM present in genetically linked individuals (<1.5% genetic distance). Phylogenetic and network analyses were performed to infer putative relationships and shared DRM.

RESULTS

The prevalence of any DRM at time of diagnosis was 17.2% (123/714 participants). Genetic transmission network analyses showed comparable frequencies of DRM in clustering versus non-clustering individuals (17.1% (85/497) versus 17.5% (38/217)). The observed rate of DRM in the region was higher than previous reports 10.8% (87/809) (p < 0.001), revealing the need to reduce onward transmission in this area. Genetically linked individuals harbouring shared DRM were more likely to live in suburban areas (24/38) than in central Cologne (1/38) (p < 0.001).

CONCLUSION

The rate of DRM was exceptionally high. Network analysis elucidated frequent cases of shared DRM among genetically linked individuals, revealing the potential spread of DRM and the need to prevent onward transmission of DRM in the Cologne-Bonn area.

Iron Chelation as Novel Treatment for Interstitial Cystitis

Interstitial cystitis (IC) is a highly prevalent debilitating disease, with its cardinal symptoms being severe pain, urinary urgency and frequency. The associated pain may eventually lead as a last resort to removal of the bladder. Though the initial trigger for IC remains largely unknown, we propose novel iron chelators as a possible new treatment for this disease. Iron is a mandatory component for the generation of reactive oxygen species (ROS). A substantial decrease in ROS production and thus inflammation can be achieved by effectively sequestering host iron, which we believe may improve outcome and quality of life in IC patients. Novel iron chelators could be used via the intravesical route to reduce or attenuate inflammation by effectively sequestering host iron, thus preventing the production of ROS via the Fenton and Haber-Weiss reactions.

Sweet SIGNs: IgG glycosylation leads the way in IVIG-mediated resolution of inflammation

A hallmark of many chronic inflammatory and autoimmune diseases is that there is an impaired resolution of inflammation and return to the steady state. The infusion of high doses of pooled serum IgG preparations from thousands of donors [intravenous immunoglobulin (IVIG) therapy] has been shown to induce resolution of inflammation in a variety of chronic inflammatory and autoimmune diseases, suggesting that IgG molecules can instruct the immune system to stop inflammatory processes and initiate the return to the steady state. The aim of this review is to discuss how insights into the mechanism of IVIG activity may help to understand the molecular and cellular pathways underlying resolution of inflammation. We will put a special emphasis on pathways dependent on the IgG FC domain and IgG sialylation, as several recent studies have provided new insights into how this glycosylation-dependent pathway modulates innate and adaptive immune responses through different sets of C-type or I-type lectins.

Modulation of the Endocannabinoid System Following Central Nervous System Injury

Central nervous system (CNS) injury, such as stroke or trauma, is known to increase susceptibility to various infections that adversely affect patient outcomes (CNS injury-induced immunodepression-CIDS). The endocannabinoid system (ECS) has been shown to have immunoregulatory properties. Therefore, the ECS might represent a druggable target to overcome CIDS. Evidence suggests that cannabinoid type 2 receptor (CB₂R) activation can be protective during the early pro-inflammatory phase after CNS injury, as it limits neuro-inflammation and, therefore, attenuates CIDS severity. In the later phase post CNS injury, CB₂R inhibition is suggested as a promising pharmacologic strategy to restore immune function in order to prevent infection.

Impact of Intravenous Fluid Challenge Infusion Time on Macrocirculation and Endothelial Glycocalyx in Surgical and Critically Ill Patients

(i) Purpose. The fluid challenge (FC) is a well-established test of preload reserve. Only limited data exist in regard to the FC efficacy based on infusion time. Slow administration may be associated with lack of effect based on fluid redistribution and external conditions changes. On the contrary, fast administration may lead to brisk fluid overload and damage to the endothelium and endothelial glycocalyx (EG). The aim of this trial was to compare the FC infusion time on its hemodynamic effects and EG. (ii) Methods. Prospective randomized single-center trial of fast (5-10 minutes) versus slow (20-30 minutes) administration of 500ml balanced crystalloid FC in spinal surgery (cohort OR) and septic shock (cohort SEP) patients. Hemodynamic response was assessed using standard monitoring and blood flow measurements; damage to EG was assessed using the perfused boundary region (PBR) via intravital microscopy monitoring in the sublingual region within relevant time points ranging up to 120 minutes. (iii) Results. Overall, 66 FCs in 50 surgical and 16 septic patients were assessed. Fluid administration was associated with increase of PBR in general (1.9 (1.8-2.1) vs. 2.0 (1.8-2.2); p= 0.008). These changes were transient in OR cohort whereas they were long-lasting in septic fluid responders. The rate of fluid responsiveness after fast versus slow administration was comparable in global population (15 (47%) vs. 17 (50%); p=0.801) as well as in both cohorts. (iv) Conclusions. Fluid challenge administration was associated with increased PBR (and presumable EG volume changes) which normalized within the next 60 minutes in surgical patients but remained impeded in septic fluid responders. The fluid responsiveness rate after fast and slow FC was comparable, but fast administration tended to induce higher, though transient, response in blood pressure.

Clinical assessment of arthritic knee pain by infrared thermography

Background Infrared thermography (IRT) provides accurate measurements of surface temperatures. In inflammatory conditions such as arthritis, tissue temperature is elevated, which can be measured on the periarticular skin surface by IRT. The aim of this review is to evaluate the evidence for the relationship between skin temperature (measured by IRT) and arthritic knee pain and discuss the limitations of IRT in clinical settings of arthritis. Method To reach this goal, a mini-review of all the relevant papers indexed in PubMed was conducted. Results Several studies suggest a significant correlation between skin temperature assessed by IRT and the severity of arthritic knee pain (especially in osteoarthritis and rheumatoid arthritis). Conclusion IRT is a reliable technique to assess inflammatory arthritis pain.

Selective sensitivity of the gut microbiome to iron chelators in polybacterial abdominal sepsis

Iron chelation has been proposed as a potential therapy for polybacterial abdominal sepsis. Treatment with iron chelation is known to be able to attenuate bacterial growth. It is hypothesized that the different types of bacteria will exhibit variations in their sensitivity to iron chelation based on differences in their iron metabolism. Bacteria with weaker iron access systems might have their growth reduced initially, but stronger species may also be suppressed. Gram-positive and Gram-negative bacteria are known to possess different iron acquisition systems, which may affect their response to iron chelation. Bacteria which can produce siderophores are at a particular advantage for iron acquisition. Novel iron chelators, which do not act as xenosiderophores, may be effective in depriving these bacteria of iron. This has implications for the treatment of polybacterial sepsis, which might be enhanced if the sensitivity to iron chelation of the primary causative agents is known.

To prescribe, or not to prescribe: decision making in HIV-1 post-exposure prophylaxis

OBJECTIVES

We investigated the trend in usage of post-exposure prophylaxis (PEP) after HIV-1 risk exposure and evaluated PEP prescription decision making of physicians according to guidelines.

METHODS

All PEP consultations from January 2014 to December 2016 in patients presenting at the University Hospital of Cologne (Germany) were retrospectively analysed. HIV risk contacts included sexual and occupational exposure. The European AIDS Clinical Society (EACS) Guidelines for HIV PEP (version 9.0, 2017) were used for assessment.

RESULTS

A total of 649 patients presented at the emergency department (ED) or the clinic for infectious diseases (IDC) for PEP consultations. A continuous increase in the number of PEP requests was recorded: 189 in 2014, 208 in 2015 and 252 in 2016. PEP consultations in men who have sex with men (MSM) showed a remarkable increase in 2016 (2014, n = 96; 2015, n = 101; 2016, n = 152). Decisions taken by physicians with a specialization in infectious diseases (n = 547) included 61 (11%) guideline-discordant prescriptions [2014: 14% (n = 22); 2015: 9% (n = 16); 2016: 11% (n = 23)]. Among these, sexual exposure accounted for 45 (74%) cases, including 15 cases of nonconsensual sex, while occupational exposure accounted for 14 (23%) cases and other exposure two cases (3%). The main reason for guideline-discordant PEP prescriptions was emotional stress of the patient (n = 37/61).

CONCLUSIONS

PEP prescriptions are increasing and decision making is influenced by patients' emotional stress, but PEP prescriptions should be strictly administered according to risk assessment.

The Ongoing Challenge of Acute Mesenteric Ischemia

Background

The lethality of acute mesenteric ischemia (AMI) remains quite high with 50-70%. The main reasons for that are the fact that AMI is rarely taken into consideration by the differential diagnosis of acute abdomen, the time-consuming diagnostic process, and the lack of a standardized therapeutic concept. The present interdisciplinary review aims to increase awareness among physicians and to help improve clinical outcomes.

Methods

This clinical therapeutic review is based on author expertise as well as a selective literature survey in PubMed based on the term 'mesenteric ischemia', combined with the terms 'arterial', 'clinical presentation', 'diagnosis', 'therapy', 'surgery', and 'interventional radiology'. Based on these search results as well as on the guidelines of the German Society of Vascular Surgery, the American College of Cardiology, and the American Heart Association, we present an interdisciplinary treatment concept.

Results

AMI is a vascular emergency that can be successfully treated only within the first hours after the onset of symptoms. Computed tomography angiography is the diagnostic method of choice. Intensive care unit treatment can prevent the occurrence of multiple organ failure. Treatment primarily consists of the revascularization of the mesenteric arteries. Endovascular techniques should be given priority, whereas signs of peritonitis or a central arterial occlusion with high thrombus load primarily require a surgical approach in order to save time and increase patient safety. Additional bowel resections can play a significant role in the treatment of intestinal sepsis.

Conclusion

Prompt and goal-oriented diagnosis and consistent treatment of AMI within 4-6 h from the onset of symptoms can be decisive for the reduction of AMI-associated lethality. In order for this to happen, a standardized concept of emergency treatment needs to be implemented.

Impact of lipid modulation on the intestinal microcirculation in experimental sepsis

It has been observed, that patients who were treated medically for dyslipoproteinemia had a potentially lower risk of complications during infection and sepsis, regarding both morbidity and mortality. Aim of this study in experimental sepsis was to elucidate the impact of lipid metabolism modulation by simvastatin, HDL, or bezafibrate, respectively, on the intestinal microcirculation which plays a crucial role in the development of multiple organ failure in sepsis. Experimental sepsis was induced in Lewis rats by intravenous lipopolysaccharide (LPS) administration. Animals were treated with simvastatin, HDL or bezafibrate. By means of intestinal intravital microscopy (IVM), the inflammatory response in the microcirculation was studied by leukocyte adherence assessment (LA) and functional capillary density (FCD) measurements. In addition, plasma levels of pro-inflammatory cytokines were determined. Bezafibrate treatment led to a reduction in leukocyte adherence, improved functional capillary density (FCD), and a reduction in interleukin-1α (IL-1α), tumour necrosis factor α (TNF-α) and granulocyte macrophage colony stimulating factors (GM-CSF) plasma levels in experimental sepsis. Contrary to this, the administration of HDL increased leukocyte adherence as well as the number of rolling leukocytes. Only IL-1α plasma levels were decreased by HDL. No significant changes were observed following simvastatin treatment. In summary, only bezafibrate showed anti-inflammatory effects in endotoxemia. This effect cannot be explained by the HDL-enhancing effect of the bezafibrate, since the direct administration of HDL showed opposite effects. Bezafibrate induced reduction of inflammation in sepsis should be investigated in further studies.

Impact of insulin on the intestinal microcirculation in a model of sepsis-related hyperglycemia

BACKGROUND

Sepsis involves dysfunctional glucose metabolism. Among patients with sepsis, hyperglycemia is frequent and insulin administration has been evaluated for glycemic control to improve patient outcomes. Only few studies have examined the hyperglycemic microcirculation and the impact of insulin on the microvasculature in sepsis.

OBJECTIVE

To study the functional capillary density (FCD) and leukocyte activation within the intestinal microcirculation in endotoxin-induced experimental sepsis.

METHODS

In 50 male Lewis rats, endotoxemia was induced with lipopolysaccharide (LPS; 5 mg/kg). Low dose (LD) glucose was administered to avoid insulin-induced hypoglycemia. High dose (HD) glucose was administered to model sepsis-related hyperglycemia. Animals in LD and HD glucose groups received an insulin bolus (1.4 IU/kg). Two hours after LPS administration, intravital microscopy (IVM) of the terminal ileum was performed, and FCD and leukocyte adherence were measured in a blinded fashion. Blood glucose levels were measured every 30 min following the onset of endotoxemia. Plasma samples were collected 3 h after the onset of endotoxemia to measure IFN-γ, TNF-α, IL-1α, IL-4, GM-CSF and MCP-1 levels using multiplex bead immunoassay.

RESULTS

Endotoxemia significantly reduced FCD and increased leukocyte adherence within the intestinal microvasculature. LD and HD glucose administration combined with insulin improved the FCD and decreased the adherence of leukocytes in endotoxemic animals as did HD glucose administration alone. Consistent with these results, IL-4, IL-1α, GM-CSF and IFN-γ levels were decreased following combined HD glucose and insulin administration in endotoxemic animals.

CONCLUSIONS

Insulin administration, as well as an endogenous insulin response triggered by HD glucose administration, improved the FCD and decreased leukocyte activation in endotoxemic rats. The results of this study give insight into the immune and vaso-modulatory role of insulin administration during experimental endotoxemia, and may be extrapolated for clinical sepsis and other critical illnesses with marked microcirculatory dysfunction.

Anti-inflammatory effects of a novel iron chelator, DIBI, in experimental sepsis

BACKGROUND

Iron catalyzes the generation of reactive oxygen species (ROS) as part of the innate antimicrobial defense. During sepsis, the dysregulated systemic inflammatory response to infection, iron homeostasis becomes disrupted, generating an excess of ROS causing damage to tissues. This can be potentially suppressed using iron chelators that selectively bind iron to prevent its participation in ROS-related inflammatory reactions.

OBJECTIVE

We hypothesize that administration of DIBI, a novel iron-chelator, attenuates the dysregulated systemic immune response and reduces tissue damage in experimental endotoxemia.

METHODS

Five groups of animals (n = 5-10) were included in this study: control, untreated endotoxemia, and endotoxemia animals treated with either DIBI-A, MAHMP, or DIBI-B. Intravital microscopy was performed on the intestine of anesthesized mice to observe leukocyte endothelial interactions and evaluate the intestinal microcirculation.

RESULTS

Treatment of endotoxemic mice with DIBI-B reduced the number of adhering leukocytes in submucosal collecting (V1) venules by 68%. DIBI-B, MAHMP, and DIBI-A were able to restore functional capillary density (FCD) in the intestinal muscle layer by 74%, 44%, and 11%, respectively.

CONCLUSIONS

DIBI-B reduces leukocyte recruitment and improves FCD in experimental endotoxemia, outperforming other chelators tested. These findings suggest a potential role for DIBI-B as a candidate drug for sepsis treatment.

Preliminary clinical evaluation of automated analysis of the sublingual microcirculation in the assessment of patients with septic shock: Comparison of automated versus semi-automated software

INTRODUCTION

The outcome of patients in septic shock has been shown to be related to changes within the microcirculation. Modern imaging technologies are available to generate high resolution video recordings of the microcirculation in humans. However, evaluation of the microcirculation is not yet implemented in the routine clinical monitoring of critically ill patients. This is mainly due to large amount of time and user interaction required by the current video analysis software. The aim of this study was to validate a newly developed automated method (CCTools®) for microcirculatory analysis of sublingual capillary perfusion in septic patients in comparison to standard semi-automated software (AVA3®).

METHODS

204 videos from 47 patients were recorded using incident dark field (IDF) imaging. Total vessel density (TVD), proportion of perfused vessels (PPV), perfused vessel density (PVD), microvascular flow index (MFI) and heterogeneity index (HI) were measured using AVA3® and CCTools®.

RESULTS

Significant differences between the numeric results obtained by the two different software packages were observed. The values for TVD, PVD and MFI were statistically related though.

CONCLUSION

The automated software technique successes to show septic shock induced microcirculation alterations in near real time. However, we found wide degrees of agreement between AVA3® and CCTools® values due to several technical factors that should be considered in the future studies.

Microcirculation research in community hospitals - challenges and chances

Community hospitals provide ideal conditions for large clinical studies because of the high volume of unselected patients admitted every year. With regard to microcirculatory studies, there are still some feasibility problems which are not solved yet. First of all, the lack of reliable automated software to analyze microcirculatory images represents the most important issue. Secondly, hardware aspects still need improvements regarding portability and miniaturization. Finally, to conduct studies of the microcirculation in a community hospital is also always a funding issue. The cost of the measurement device is hereby only one factor. Main cost factor is the personnel.

Glycocalyx in vivo measurement

The endothelial glycocalyx (EG) lining the endoluminal surface of the capillaries has been proposed as a key component of the microcirculation and a major player in microvascular pathology. Recent advances in the understanding of its physiological role and clinical significance have been made upon the development of methods allowing EG assessment in clinical medicine. Laboratory methods can assess the amount of EG damage by measuring levels of its degradation products (e.g. syndecan-1, heparan sulphate and hyaluronan sulphate), mostly in the plasma, however, their physiological turnover disqualifies them from being the reliable index of EG damage. At the bedside, in vivo video microscopy tools technologies (e.g. Side-stream Dark Field imaging technology) allow indirect assessment of EG thickness in sublingual microcirculation by measuring the penetration extent (called Perfused Boundary Region) of flowing red blood cells into the EG.