Interleukin 22 mitigates endothelial glycocalyx shedding after lipopolysaccharide injury

Microfluidics as a Powerful Tool to Investigate Microvascular Dysfunction in Trauma Conditions: A Review of the State-of-the-Art

Skeletal muscle trauma such as fracture or crush injury can result in a life-threatening condition called acute compartment syndrome (ACS), which involves elevated compartmental pressure within a closed osteo-fascial compartment, leading to collapse of the microvasculature and resulting in necrosis of the tissue due to ischemia. Diagnosis of ACS is complex and controversial due to the lack of standardized objective methods, which results in high rates of misdiagnosis/late diagnosis, leading to permanent neuro-muscular damage. ACS pathophysiology is poorly understood at a cellular level due to the lack of physiologically relevant models. In this context, microfluidics organ-on-chip systems (OOCs) provide an exciting opportunity to investigate the cellular mechanisms of microvascular dysfunction that leads to ACS. In this article, the state-of-the-art OOCs designs and strategies used to investigate microvasculature dysfunction mechanisms is reviewed. The differential effects of hemodynamic shear stress on endothelial cell characteristics such as morphology, permeability, and inflammation, all of which are altered during microvascular dysfunction is highlighted. The article then critically reviews the importance of microfluidics to investigate closely related microvascular pathologies that cause ACS. The article concludes by discussing potential biomarkers of ACS with a special emphasis on glycocalyx and providing a future perspective.

Dimethyl sulfoxide as a novel therapy in a murine model of acute lung injury

INTRODUCTION

The endothelial glycocalyx on the luminal surface of endothelial cells contributes to the permeability barrier of the pulmonary vasculature. Dimethyl sulfoxide (DMSO) has a disordering effect on plasma membranes, which prevents the formation of ordered membrane domains important in the shedding of the endothelial glycocalyx. We hypothesized that DMSO would protect against protein leak by preserving the endothelial glycocalyx in a murine model of acute respiratory distress syndrome (ARDS).

METHODS

C57BL/6 mice were given ARDS via intratracheally administered lipopolysaccharide (LPS). Dimethyl sulfoxide (220 mg/kg) was administered intravenously for 4 days. Animals were sacrificed postinjury day 4 after bronchoalveolar lavage (BAL). Bronchoalveolar lavage cell counts and protein content were quantified. Lung sections were stained with fluorescein isothiocyanate-labeled wheat germ agglutinin to quantify the endothelial glycocalyx. Human umbilical vein endothelial cells (HUVECs) were exposed to LPS. Endothelial glycocalyx was measured using fluorescein isothiocyanate-labeled wheat germ agglutinin, and co-immunoprecipitation was performed to measure interaction between sheddases and syndecan-1.

RESULTS

Dimethyl sulfoxide treatment resulted in greater endothelial glycocalyx staining intensity in the lung when compared with sham (9,641 vs. 36,659 arbitrary units, p < 0.001). Total BAL cell counts were less for animals receiving DMSO (6.93 × 10 6 vs. 2.49 × 10 6 cells, p = 0.04). The treated group had less BAL macrophages (189.2 vs. 76.9 cells, p = 0.02) and lymphocytes (527.7 vs. 200.0 cells, p = 0.02). Interleukin-6 levels were lower in DMSO treated. Animals that received DMSO had less protein leak in BAL (1.48 vs. 1.08 μg/μL, p = 0.02). Dimethyl sulfoxide prevented LPS-induced endothelial glycocalyx loss in HUVECs and reduced the interaction between matrix metalloproteinase 16 and syndecan-1.

CONCLUSION

Systemically administered DMSO protects the endothelial glycocalyx in the pulmonary vasculature, mitigating pulmonary capillary leak after acute lung injury. Dimethyl sulfoxide also results in decreased inflammatory response. Dimethyl sulfoxide reduced the interaction between matrix metalloproteinase 16 and syndecan-1 and prevented LPS-induced glycocalyx damage in HUVECs. Dimethyl sulfoxide may be a novel therapeutic for ARDS.

Dimethyl malonate protects the lung in a murine model of acute respiratory distress syndrome

BACKGROUND

Succinate is a proinflammatory citric acid cycle metabolite that accumulates in tissues during pathophysiological states. Oxidation of succinate after ischemia-reperfusion leads to reversal of the electron transport chain and generation of reactive oxygen species. Dimethyl malonate (DMM) is a competitive inhibitor of succinate dehydrogenase, which has been shown to reduce succinate accumulation. We hypothesized that DMM would protect against inflammation in a murine model of ARDS.

METHODS

C57BL/6 mice were given ARDS via 67.7 μg of intratracheally administered lipopolysaccharide. Dimethyl malonate (50 mg/kg) was administered via tail vein injection 30 minutes after injury, then daily for 3 days. The animals were sacrificed on day 4 after bronchoalveolar lavage (BAL). Bronchoalveolar lavage cell counts were performed to examine cellular influx. Supernatant protein was quantified via Bradford protein assay. Animals receiving DMM (n = 8) were compared with those receiving sham injection (n = 8). Cells were fixed and stained with FITC-labeled wheat germ agglutinin to quantify the endothelial glycocalyx (EGX).

RESULTS

Total cell counts in BAL was less for animals receiving DMM (6.93 × 10 6 vs. 2.46 × 10 6 , p = 0.04). The DMM group had less BAL macrophages (168.6 vs. 85.1, p = 0.04) and lymphocytes (527.7 vs. 248.3; p = 0.04). Dimethyl malonate-treated animals had less protein leak in BAL than sham treated (1.48 vs. 1.15 μg/μl, p = 0.03). Treatment with DMM resulted in greater staining intensity of the EGX in the lung when compared with sham (12,016 vs. 15,186 arbitrary units, p = 0.03). Untreated animals had a greater degree of weight loss than treated animals (3.7% vs. 1.1%, p = 0.04). Dimethyl malonate prevented the upregulation of monocyte chemoattractant protein-1 (1.66 vs. 0.92 RE, p = 0.02) and ICAM-1 (1.40 vs. 1.01 RE, p = 0.05).

CONCLUSION

Dimethyl malonate reduces lung inflammation and capillary leak in ARDS. This may be mediated by protection of the EGX and inhibition of monocyte chemoattractant protein-1 and ICAM-1. Dimethyl malonate may be a novel therapeutic for ARDS.

EXOSOMES AND MICROVESICLES FROM ADIPOSE-DERIVED MESENCHYMAL STEM CELLS PROTECTS THE ENDOTHELIAL GLYCOCALYX FROM LPS INJURY

ABSTRACT

Introduction: Endothelial glycocalyx damage occurs in numerous pathological conditions and results in endotheliopathy. Extracellular vesicles, including exosomes and microvesicles, isolated from adipose-derived mesenchymal stem cells (ASCs) have therapeutic potential in multiple disease states; however, their role in preventing glycocalyx shedding has not been defined. We hypothesized that ASC-derived exosomes and microvesicles would protect the endothelial glycocalyx from damage by LPS injury in cultured endothelial cells. Methods : Exosomes and microvesicles were collected from ASC conditioned media by centrifugation (10,000 g for microvesicles, 100,000 g for exosomes). Human umbilical vein endothelial cells (HUVECs) were exposed to 1 μg/mL lipopolysaccharide (LPS). LPS-injured cells (n = 578) were compared with HUVECS with concomitant LPS injury plus 1.0 μg/mL of exosomes (n = 540) or microvesicles (n = 510) for 24 hours. These two cohorts were compared with control HUVECs that received phosphate-buffered saline only (n = 786) and HUVECs exposed to exosomes (n = 505) or microvesicles (n = 500) alone. Cells were fixed and stained with FITC-labeled wheat germ agglutinin to quantify EGX. Real-time quantitative reverse-transcription polymerase chain reaction was used on HUVECs cell lystate to quantify hyaluron synthase-1 (HAS1) expression. Results: Exosomes alone decreased endothelial glycocalyx staining intensity when compared with control (4.94 vs. 6.41 AU, P < 0.001), while microvesicles did not cause a change glycocalyx staining intensity (6.39 vs. 6.41, P = 0.99). LPS injury resulted in decreased glycocalyx intensity as compared with control (5.60 vs. 6.41, P < 0.001). Exosomes (6.85 vs. 5.60, P < 0.001) and microvesicles (6.35 vs. 5.60, P < 0.001) preserved endothelial glycocalyx staining intensity after LPS injury. HAS1 levels were found to be higher in the exosome (1.14 vs. 3.67 RE, P = 0.02) and microvesicle groups (1.14 vs. 3.59 RE, P = 0.02) when compared with LPS injury. Hyaluron synthase-2 and synthase-3 expressions were not different in the various experimental groups. Conclusions: Exosomes alone can damage the endothelial glycocalyx. However, in the presence of LPS injury, both exosomes and microvesicles protect the glycocalyx layer. This effect seems to be mediated by HAS1. Level of Evidence : Basic science study.

Succinate metabolism and membrane reorganization drives the endotheliopathy and coagulopathy of traumatic hemorrhage

Acute hemorrhage commonly leads to coagulopathy and organ dysfunction or failure. Recent evidence suggests that damage to the endothelial glycocalyx contributes to these adverse outcomes. The physiological events mediating acute glycocalyx shedding are undefined, however. Here, we show that succinate accumulation within endothelial cells drives glycocalyx degradation through a membrane reorganization-mediated mechanism. We investigated this mechanism in a cultured endothelial cell hypoxia-reoxygenation model, in a rat model of hemorrhage, and in trauma patient plasma samples. We found that succinate metabolism by succinate dehydrogenase mediates glycocalyx damage through lipid oxidation and phospholipase A2-mediated membrane reorganization, promoting the interaction of matrix metalloproteinase 24 (MMP24) and MMP25 with glycocalyx constituents. In a rat hemorrhage model, inhibiting succinate metabolism or membrane reorganization prevented glycocalyx damage and coagulopathy. In patients with trauma, succinate levels were associated with glycocalyx damage and the development of coagulopathy, and the interaction of MMP24 and syndecan-1 was elevated compared to healthy controls.

Glycocalyx degradation and the endotheliopathy of viral infection

The endothelial glycocalyx (EGX) contributes to the permeability barrier of vessels and regulates the coagulation cascade. EGX damage, which occurs in numerous disease states, including sepsis and trauma, results in endotheliopathy. While influenza and other viral infections are known to cause endothelial dysfunction, their effect on the EGX has not been described. We hypothesized that the H1N1 influenza virus would cause EGX degradation. Human umbilical vein endothelial cells (HUVECs) were exposed to varying multiplicities of infection (MOI) of the H1N1 strain of influenza virus for 24 hours. A dose-dependent effect was examined by using an MOI of 5 (n = 541), 15 (n = 714), 30 (n = 596), and 60 (n = 653) and compared to a control (n = 607). Cells were fixed and stained with FITC-labelled wheat germ agglutinin to quantify EGX. There was no difference in EGX intensity after exposure to H1N1 at an MOI of 5 compared to control (6.20 vs. 6.56 Arbitrary Units (AU), p = 0.50). EGX intensity was decreased at an MOI of 15 compared to control (5.36 vs. 6.56 AU, p<0.001). The degree of EGX degradation was worse at higher doses of the H1N1 virus; however, the decrease in EGX intensity was maximized at an MOI of 30. Injury at MOI of 60 was not worse than MOI of 30. (4.17 vs. 4.47 AU, p = 0.13). The H1N1 virus induces endothelial dysfunction by causing EGX degradation in a dose-dependent fashion. Further studies are needed to characterize the role of this EGX damage in causing clinically significant lung injury during acute viral infection.

Dimethyl malonate slows succinate accumulation and preserves cardiac function in a swine model of hemorrhagic shock

BACKGROUND

Succinate (SI) is a citric acid cycle metabolite that accumulates in tissues during hemorrhagic shock (HS) due to electron transport chain uncoupling. Dimethyl malonate (DMM) is a competitive inhibitor of SI dehydrogenase, which has been shown to reduce SI accumulation and protect against reperfusion injury. Whether DMM can be therapeutic after severe HS is unknown. We hypothesized that DMM would prevent SI buildup during resuscitation (RES) in a swine model of HS, leading to better physiological recovery after RES.

METHODS

The carotid arteries of Yorkshire pigs were cannulated with a 5-Fr catheter. After placement of a Swan-Ganz catheter and femoral arterial line, the carotid catheters were opened and the animals were exsanguinated to a mean arterial pressure (MAP) of 45 mm. After 30 minutes in the shock state, the animals were resuscitated to a MAP of 60 mm using lactated ringers. A MAP above 60 mm was maintained throughout RES. One group received 10 mg/kg of DMM (n = 6), while the control received sham injections (n = 6). The primary end-point was SI levels. Secondary end-points included cardiac function and lactate.

RESULTS

Succinate levels increased from baseline to the 20-minute RES point in control, while the DMM cohort remained unchanged. The DMM group required less intravenous fluid to maintain a MAP above 60 (450.0 vs. 229.0 mL; p = 0.01). The DMM group had higher pulmonary capillary wedge pressure at the 20-minute and 40-minute RES points. The DMM group had better recovery of cardiac output and index during RES, while the control had no improvement. While lactate levels were similar, DMM may lead to increased ionized calcium levels.

DISCUSSION

Dimethyl malonate slows SI accumulation during HS and helps preserve cardiac filling pressures and function during RES. In addition, DMM may protect against depletion of ionized calcium. Dimethyl malonate may have therapeutic potential during HS.

Interleukin-22 mitigates acute respiratory distress syndrome (ARDS)

BACKGROUND

The goal of this study was to determine if IL-22:Fc would Acute Respiratory Distress Syndrome (ARDS).

SUMMARY BACKGROUND DATA

No therapies exist for ARDS and treatment is purely supportive. Interleukin-22 (IL-22) plays an integral component in recovery of the lung from infection. IL-22:Fc is a recombinant protein with a human FC immunoglobulin that increases the half-life of IL-22.

STUDY DESIGN

ARDS was induced in C57BL/6 mice with intra-tracheal lipopolysaccharide (LPS) at a dose of 33.3 or 100 ug. In the low-dose LPS group (LDG), IL-22:FC was administered via tail vein injection at 30 minutes (n = 9) and compared to sham (n = 9). In the high-dose LPS group (HDG), IL-22:FC was administered (n = 11) then compared to sham (n = 8). Euthanasia occurred after bronchioalveolar lavage (BAL) on post-injury day 4.

RESULTS

In the LDG, IL-22:FC resulted in decreased protein leak (0.15 vs. 0.25 ug/uL, p = 0.02). BAL protein in animals receiving IL-22:Fc in the HDG was not different. For the HDG, animals receiving IL-22:Fc had lower BAL cell counts (539,636 vs 3,147,556 cells/uL, p = 0.02). For the HDG, IL-6 (110.6 vs. 527.1 pg/mL, p = 0.04), TNF-α (5.87 vs. 25.41 pg/mL, p = 0.04), and G-CSF (95.14 vs. 659.6, p = 0.01) levels were lower in the BAL fluid of IL-22:Fc treated animals compared to sham.

CONCLUSIONS

IL-22:Fc decreases lung inflammation and lung capillary leak in ARDS. IL-22:Fc may be a novel therapy for ARDS.