Vascular biology in sepsis: pathophysiological and therapeutic significance of vascular dysfunction

Myeloid ACE2 protects against septic hypotension and vascular dysfunction through Ang-(1-7)-Mas-mediated macrophage polarization

Angiotensin converting enzyme 2 (ACE2) is a new identified member of the renin-angiotensin-aldosterone system (RAAS) that cleaves angiotensin II (Ang II) to Ang (1-7), which exerts anti-inflammatory and antioxidative activities via binding with Mas receptor (MasR). However, the functional role of ACE2 in sepsis-related hypotension remains unknown. Our results indicated that sepsis significantly reduced blood pressure and led to disruption between ACE-Ang II and ACE2-Ang (1-7) balance. ACE2 knock-in mice exhibited improved sepsis-induced mortality, hypotension and vascular dysfunction, while ACE2 knockout mice exhibited the opposite effects. Bone marrow transplantation and in vitro experiments confirmed that myeloid ACE2 exerted a protective role by suppressing oxidative stress, NO production and macrophage polarization via the Ang (1-7)-MasR-NF-κB and STAT1 pathways. Thus, ACE2 on myeloid cells could protect against sepsis-mediated hypotension and vascular dysfunction, and upregulating ACE2 may represent a promising therapeutic option for septic patients with hypotension.

Circulating protein and lipid markers of early sepsis diagnosis and prognosis: a scoping review

PURPOSE OF REVIEW

Sepsis is the extreme response to infection associated with high mortality, yet reliable biomarkers for its identification and stratification are lacking.

RECENT FINDINGS

Our scoping review of studies published from January 2017 to September 2022 that investigated circulating protein and lipid markers to inform non-COVID-19 sepsis diagnosis and prognosis identified interleukin (IL)-6, IL-8, heparin-binding protein (HBP), and angiopoietin-2 as having the most evidence. Biomarkers can be grouped according to sepsis pathobiology to inform biological data interpretation and four such physiologic processes include: immune regulation, endothelial injury and coagulopathy, cellular injury, and organ injury. Relative to proteins, the pleiotropic effects of lipid species' render their categorization more difficult. Circulating lipids are relatively less well studied in sepsis, however, low high-density lipoprotein (HDL) is associated with poor outcome.

SUMMARY

There is a lack of robust, large, and multicenter studies to support the routine use of circulating proteins and lipids for sepsis diagnosis or prognosis. Future studies will benefit from standardizing cohort design as well as analytical and reporting strategies. Incorporating biomarker dynamic changes and clinical data in statistical modeling may improve specificity for sepsis diagnosis and prognosis. To guide future clinical decisions at the bedside, point-of-care circulating biomarker quantification is needed.

Neutrophil membrane-mimicking nanodecoys with intrinsic anti-inflammatory properties alleviate sepsis-induced acute liver injury and lethality in a mouse endotoxemia model

Sepsis-induced acute liver injury often develops in the early stages of sepsis and can exacerbate the pathology by contributing to multiple organ dysfunction and increasing lethality. No specific therapies for sepsis-induced liver injury are currently available; therefore, effective countermeasures are urgently needed. Considering the crucial role of neutrophils in sepsis-induced liver injury, herein, neutrophil membrane-mimicking nanodecoys (NM) were explored as a biomimetic nanomedicine for the treatment of sepsis-associated liver injury. NM administration exhibited excellent biocompatibility and dramatically decreased the plasma levels of inflammatory cytokines and liver injury biomarkers, including aspartate aminotransferase, alanine aminotransferase, and direct bilirubin, in a sepsis mouse model. NM treatment also reduced hepatic malondialdehyde content, myeloperoxidase activity, and histological injury, and ultimately improved survival in the septic mice. Further in vitro studies showed that NM treatment neutralized the neutrophil chemokines and inflammatory mediators and directly mitigated neutrophil chemotaxis and adhesion. Additionally, NM also markedly weakened lipopolysaccharide-induced reactive oxygen species generation, cyclooxygenase-2 expression, nitric oxide secretion, and subsequent hepatocyte injury. Thus, this study provides a promising therapeutic strategy for the management of sepsis-induced acute liver injury.

Hemodynamic Effects of Ketamine Compared With Propofol or Dexmedetomidine as Continuous ICU Sedation

BACKGROUND

Ketamine has seen increased use for sedation in the intensive care unit. In contrast to propofol or dexmedetomidine, ketamine may provide a positive effect on hemodynamics.

OBJECTIVE

The objective of this study was to compare the development of clinically significant hypotension or bradycardia (ie, negative hemodynamic event) between critically ill adults receiving sedation with ketamine and either propofol or dexmedetomidine.

METHODS

This was a retrospective cohort study of adults admitted to an intensive care unit at an academic medical center between January 2016 and January 2021.

RESULTS

Patients in the ketamine group (n = 78) had significantly less clinically significant hypotension or bradycardia compared with those receiving propofol or dexmedetomidine (n = 156) (34.6% vs 63.5%; P < 0.001). Patients receiving ketamine also experienced smaller degree of hypotension observed by percent decrease in mean arterial pressure (25.3% [17.4] vs 33.8% [14.5]; P < 0.001) and absolute reduction in systolic blood pressure (26.5 [23.8] vs 42.0 [37.8] mm Hg; P < 0.001) and bradycardia (15.5 [24.3] vs 32.0 [23.0] reduction in beats per minute; P < 0.001). In multivariate logistic regression modeling, receipt of propofol or dexmedetomidine was the only independent predictor of a negative hemodynamic event (odds ratio [OR]: 3.3, 95% confidence interval [CI], 1.7 to 6.1; P < 0.001).

CONCLUSION AND RELEVANCE

Ketamine was associated with less clinically relevant hypotension or bradycardia when compared with propofol or dexmedetomidine, in addition to a smaller absolute decrease in hemodynamic parameters. The clinical significance of these findings requires further investigation.

Anti-Inflammatory Effects of the Fraction from the Leaves of Pyrus pyrifolia on LPS-Stimulated THP-1 Cells

Pyrus pyrifolia Nakai (P. pyrifolia) has been traditionally used in East Asia to treat diseases such as phlegm, cough, hangover, and fever. However, there is no investigation that evaluates the biological activities of the leaves of P. pyrifolia. This study aims at describing the anti-inflammatory effects of PP, a bioactive fraction from the leaves of P. pyrifolia, in lipopolysaccharide (LPS)-stimulated THP-1 cells. Initially, PP decreased the protein and RNA expression of TNF-α, MCP-1, IL-8, and IL-6 induced by LPS. Moreover, PP attenuated the phosphorylation of p38, JNK, and ERK. In addition, after stimulation with LPS, the degradation of IκB-α was suppressed by PP, and the phosphorylation of IκB-α and p65 was suppressed by PP. Additionally, PP increased HO-1, which controls the production of inflammatory molecules, by activating Nrf2. These results indicated that PP could be used as an anti-inflammatory drug to promote wellness.

Ethanol consumption increases renal dysfunction and mortality in a mice model of sub-lethal sepsis

Chronic ethanol consumption and sepsis cause oxidative stress and renal dysfunction. This study aimed to examine whether chronic ethanol consumption sensitizes the mouse kidney to sub-lethal cecal ligation and puncture (SL-CLP) sepsis, leading to impairment of renal function by tissue oxidative and inflammatory damage. Male C57BL/6J mice were treated for 9 weeks with ethanol (20%, v/v) before SL-CLP was induced. Systolic blood pressure (SBP), survival rate, creatinine plasma, oxidative stress, and inflammatory parameters, inducible nitric oxide synthase (iNOS), cytokines, and metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) levels were evaluated. Chronic ethanol consumption increased SBP, plasma creatinine, O₂^.-, H₂O₂, lipid peroxidation, catalase activity, Nox4, IL-6, and TNF-α levels, and MMP-9/TIMP-1 ratio. SL-CLP decreased SBP, increased creatinine, lipid peroxidation, IL-6, TNF-α, nitrate/nitrite (NOx), and iNOS levels, and MMP-2/TIMP-2 ratio, and decreased catalase activity. SL-CLP mice previously treated with ethanol showed a similar decrease in SBP but higher mortality and creatinine levels than SL-CLP alone. These responses were mediated by increased O₂^-, lipid peroxidation, IL-6, TNF-α, NOx, iNOS, MMP-2, and MMP-9 levels, and MMP-9/TIMP-1 and MMP-2/TIMP-2 ratios. Our findings demonstrated that previous oxidative stress and inflammatory damage caused by ethanol consumption sensitizes the kidney to SL-CLP injury, resulting in impaired kidney function and sepsis prognosis.

Disrupted eNOS activity and expression account for vasodilator dysfunction in different stage of sepsis

AIMS

Sepsis is a severe endothelial dysfunction syndrome. The role of endothelial nitric oxide synthase (eNOS) in endothelial dysfunction induced by sepsis is controversial. To explore the role of eNOS in vascular dysfunction.

MAIN METHODS

The effect of sepsis on vasodilation and eNOS levels was examined in septic mouse arteries and in cell models.

KEY FINDINGS

In early sepsis mouse arteries, endothelium-dependent relaxation decreased and phosphorylation of the inhibitory Thr495 site in endothelial nitric oxide synthase increased. Mechanically, the phosphorylation of endothelial nitric oxide synthase at Thr497 in bovine aortic endothelial cells occurred in a protein kinase C-α dependent manner. In late sepsis, both nitric oxide-dependent relaxation responses and endothelial nitric oxide synthase levels were decreased in septic mice arteries. Endothelial nitric oxide synthase levels expression levels decreased in tumor necrosis factor-α-treated human umbilical vein endothelial cells and this could be prevented by the ubiquitin proteasome inhibitor (MG-132). MG-132 could reverse the decrease in endothelial nitric oxide synthase expression and improve nitric oxide-dependent vasodilator dysfunction in septic mice arteries.

SIGNIFICANCE

These data indicate that vasodilator dysfunction is induced by the increased phosphorylation of endothelial nitric oxide synthase in early sepsis and its degradation in late sepsis.

Deletion of the adenosine A2A receptor increases the survival rate in a mice model of polymicrobial sepsis

We aim to investigate the role of A_2A receptor in peritonitis-related sepsis by injection of a fecal solution (FS) as a model of polymicrobial infection. C57/black J6 wild-type (WT) and A_2A-deficient mice (A_2AKO) were exposed to sepsis induced by intraperitoneal injection of a FS (FS-induced peritonitis) or instead was injected with saline buffer (Sham). Survival rate and sepsis score were measured up to 48 h. The presence of bacteria in tissue homogenates was analyzed. Telemetry and speckle laser Doppler were used for systemic blood pressure and peripheral blood perfusion analysis, respectively. Histological analysis and identification of active caspase 3 were performed in selected organs, including the liver. The survival rate of A_2AKO mice exposed to FS-induced peritonitis was significantly higher, and the sepsis score was lower than their respective WT counterpart. Injection of FS increases (50 to 150 folds) the number of colonies forming units in the liver, kidney, blood, and lung in WT mice, while these effects were significantly attenuated in A_2AKO mice exposed to FS-induced peritonitis. A significant reduction in both systolic and diastolic blood pressure, as well as in the peripheral perfusion was observed in WT and A_2AKO mice exposed to FS-induced peritonitis. Although, these last effects were significantly attenuated in A_2AKO mice. Histological analysis showed a large perivascular infiltration of polymorphonuclear in the liver of WT and A_2AKO mice exposed to FS-induced peritonitis, but again, this effect was attenuated in A_2AKO mice. Finally, high expression of active caspase 3 was found only in the liver of WT mice exposed to FS-induced peritonitis. The absence of the A_2A receptor increases the survival rate in mice exposed to polymicrobial sepsis. This outcome was associated with both hemodynamic compensation and enhanced anti-bacterial response.

Interleukin-17 Reduces βENaC via MAPK Signaling in Vascular Smooth Muscle Cells

Degenerin proteins, such as the beta epithelial Na⁺ channel (βENaC), are essential in the intracellular signaling of pressure-induced constriction, an important vascular smooth muscle cell (VSMC) function. While certain cytokines reduce ENaC protein in epithelial tissue, it is unknown if interleukin-17 (IL-17), a potent pro-inflammatory cytokine, directly mediates changes in membrane-associated βENaC in VSMCs. Therefore, we tested the hypothesis that exposure to IL-17 reduces βENaC in VSMCs through canonical mitogen-activated protein kinase (MAPK) signaling pathways. We treated cultured rat VSMCs (A10 cell line) with IL-17 (1–100 ng/mL) for 15 min to 16 h and measured expression of βENaC, p38MAPK, c-jun kinase (JNK), and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB). IL-17 reduced βENaC protein expression in a concentration-dependent fashion and increased phosphorylation of p38MAPK by 15 min and JNK by 8 h. NFκB was unaffected by IL-17 in VSMCs. IL-17 treatment reduced VSMC viability but had no effect on cell death. To determine the underlying signaling pathway involved in this response, VSMCs were treated before and during IL-17 exposure with p38MAPK or JNK inhibitors. We found that JNK blockade prevented IL-17-mediated βENaC protein suppression. These data demonstrate that the pro-inflammatory cytokine IL-17 regulates VSMC βENaC via canonical MAPK signaling pathways, raising the possibility that βENaC-mediated loss of VSMC function may occur in inflammatory disorders.

Hemodynamic Effects of Propofol and Dexmedetomidine in Septic Patients Without Shock

Background: Use of nonbenzodiazepine agents propofol and dexmedetomidine are first line for sedation in the intensive care unit (ICU). These agents have been implicated in the development of bradycardia and hypotension in critical illness. Objectives: To compare the development of clinically significant hypotension and/or bradycardia (ie, negative hemodynamic event) in adults with sepsis yet to require vasopressors receiving either propofol or dexmedetomidine for continuous sedation. Methods: This was a retrospective multicenter cohort study of adults with non-vasopressor-dependent sepsis admitted to an ICU at two academic medical centers between July 2013-September 2017. Results: Patients in the propofol (n = 64) and dexmedetomidine (n = 31) groups developed a clinically significant negative hemodynamic event at statistically similar frequencies (34.4% vs 16.1%, P = 0.065). Patients receiving propofol developed a larger degree of hypotension (47.3 vs 34.7 mm Hg reduction, P = 0.031). In multivariable logistic regression modeling, independent predictors of a negative hemodynamic event were a past medical history of chronic kidney disease (odds ratio [OR] = 3.8; 95% CI = 1.17-12.2; P = 0.027) and baseline heart rate (OR = 1.02; 95% CI = 1.00-1.10; P = 0.036). Conclusions and Relevance: A minority of patients with sepsis who received either propofol or dexmedetomidine experienced an event. Patients with sepsis without shock receiving continuous infusions of propofol and dexmedetomidine experienced a negative hemodynamic event at similar frequencies, though the degree of hypotension seen with propofol was greater. The clinical significance of these adverse effects requires cautious use in sepsis and further investigation.

Identification of a transcriptome profile associated with improvement of organ function in septic shock patients after early supportive therapy

Background

Septic shock is the most severe complication of sepsis and this syndrome is associated with high mortality. Treatment of septic shock remains largely supportive of hemodynamics and tissue perfusion. Early changes in organ function assessed by the Sequential Organ Function Assessment (SOFA) score are highly predictive of the outcome. However, the individual patient’s response to supportive therapy is very heterogeneous, and the mechanisms underlying this variable response remain elusive. The aim of the study was to investigate the transcriptome of whole blood in septic shock patients with different responses to early supportive hemodynamic therapy assessed by changes in SOFA scores within the first 48 h from intensive care unit (ICU) admission.

Methods

We performed whole blood RNA sequencing in 31 patients: 17 classified as responders (R) and 14 as non-responders (NR). Gene expression was investigated at ICU admission (time point 1, or T1), comparing R with NR [padj < 0.01; Benjamini–Hochberg (BH)] and over time from T1 to T2 (48 h later) in R and NR independently (paired analysis, padj < 0.01; BH). Then the differences in gene expression trends over time were evaluated (Mann–Whitney, P <0.01). To identify enriched biological processes, we performed an over-representation analysis based on a right-sided hypergeometric test with Bonferroni step-down as multiple testing correction (padj < 0.05).

Results

At ICU admission, we did not identify differentially expressed genes (DEGs) between the two groups. In the transition from T1 to T2, the activation of genes involved in T cell–mediated immunity, granulocyte and natural killer (NK) cell functions, and pathogen lipid clearance was noted in the R group. Genes involved in acute inflammation were downregulated in both groups.

Conclusions

Within the limits of a small sample size, our results could suggest that early activation of genes of the adaptive immune response is associated with an improvement in organ function.

Electronic supplementary material

The online version of this article (10.1186/s13054-018-2242-3) contains supplementary material, which is available to authorized users.

Disseminated Intravascular Coagulation: An Update on Pathogenesis, Diagnosis, and Therapeutic Strategies

Disseminated intravascular coagulation (DIC) is an acquired clinicobiological syndrome characterized by widespread activation of coagulation leading to fibrin deposition in the vasculature, organ dysfunction, consumption of clotting factors and platelets, and life-threatening hemorrhage. Disseminated intravascular coagulation is provoked by several underlying disorders (sepsis, cancer, trauma, and pregnancy complicated with eclampsia or other calamities). Treatment of the underlying disease and elimination of the trigger mechanism are the cornerstone therapeutic approaches. Therapeutic strategies specific for DIC aim to control activation of blood coagulation and bleeding risk. The clinical trials using DIC as entry criterion are limited. Large randomized, phase III clinical trials have investigated the efficacy of antithrombin (AT), activated protein C (APC), tissue factor pathway inhibitor (TFPI), and thrombomodulin (TM) in patients with sepsis, but the diagnosis of DIC was not part of the inclusion criteria. Treatment with APC reduced 28-day mortality of patients with severe sepsis, including patients retrospectively assigned to a subgroup with sepsis-associated DIC. Treatment with APC did not have any positive effects in other patient groups. The APC treatment increased the bleeding risk in patients with sepsis, which led to the withdrawal of this drug from the market. Treatment with AT failed to reduce 28-day mortality in patients with severe sepsis, but a retrospective subgroup analysis suggested possible efficacy in patients with DIC. Clinical studies with recombinant TFPI or TM have been carried out showing promising results. The efficacy and safety of other anticoagulants (ie, unfractionated heparin, low-molecular-weight heparin) or transfusion of platelet concentrates or clotting factor concentrates have not been objectively assessed.

Nucleic-acid based gene therapy approaches for sepsis

Despite advances in overall medical care, sepsis and its sequelae continue to be an embarrassing clinical entity with an unacceptably high mortality rate. The central reason for high morbidity and high mortality of sepsis and its sequelae is the lack of an effective treatment. Previous clinical trials have largely failed to identify an effective therapeutic target to improve clinical outcomes in sepsis. Thus, the key goal favoring the outcome of septic patients is to devise innovative and evolutionary therapeutic strategies. Gene therapy can be considered as one of the most promising novel therapeutic approaches for nasty disorders. Since a number of transcription factors, such as nuclear factor-κB (NF-κB) and activator protein-1 (AP-1), play a pivotal role in the pathophysiology of sepsis that can be characterized by the induction of multiple genes and their products, sepsis may be regarded as a gene-related disorder and gene therapy may be considered a promising novel therapeutic approach for treatment of sepsis. In this review article, we provide an up-to-date summary of the gene-targeting approaches, which have been developed in animal models of sepsis. Our review sheds light on the molecular basis of sepsis pathology for the development of novel gene therapy approaches and leads to the conclusion that future research efforts may fully take into account gene therapy for the treatment of sepsis.

Experimental Cannabinoid 2 Receptor Inhibition in CNS Injury-Induced Immunodeficiency Syndrome

OBJECTIVE

Severe CNS injury, such as stroke, traumatic brain injury, or spinal cord injury, is known to increase susceptibility to infections. The increased susceptibility to infection is due to an impaired immune response and is referred to as CIDS. The CB2 receptor on immune cells presents a potential therapeutic target in CIDS as activation of this receptor has been shown to be involved in immunosuppression. The main purpose of this study was to determine the impact of CB2 receptor inhibition on leukocyte activation within the microcirculation following endotoxin challenge in an experimental stroke model.

METHODS

Five experimental groups (male C57BL/6 mice, age: 6-8 weeks) were subjected to the following treatments: control; endotoxemia (LPS 5 mg/kg, i.v.); transient cerebral hypoxia-ischemia (HI) + endotoxemia; HI + endotoxemia + CB2 receptor antagonist (AM630 2.5 mg/kg, i.v.). HI was induced by unilateral carotid artery occlusion, followed by 50 minute exposure to a low oxygen atmosphere (8% O2 ). The CB2 receptor antagonist was given 15 min prior to LPS administration. Intravital microscopy (IVM) was carried out 2h after LPS administration. Brains were extracted and stained with tetrazolium chloride (TTC) to measure infarct volume.

RESULTS

Compared to endotoxemic animals without CNS injury, mice subjected to HI displayed reduced leukocyte activation in intestinal submucosal venules indicative of CIDS. Administration of the CB2 receptor antagonist in animals with CIDS challenged with endotoxin restored peripheral leukocyte recruitment without a detrimental impact on infarct size.

CONCLUSION

We conclude that the ECS is involved in the impaired immune response following CNS injury. Future studies should further explore the CB2 receptor pathway to develop novel therapies for CIDS.

Hyperglycemia induced testicular damage in type 2 diabetes mellitus rats exhibiting microcirculation impairments associated with vascular endothelial growth factor decreased via PI3K/Akt pathway

As an endocrine disease, type 2 diabetes mellitus (T2DM) can cause testicular damage which induces male infertility. However, the underlying mechanism is still not clear. We prove that T2DM induced testicular microcirculation impairment involves the decrease of VEGF and these actions are regulated by PI3K/Akt pathway. In our study, rats were divided into three groups (n=8): control group, diabetes group and diabetes + VEGF group. Intraperitoneal injection of streptozotocin (STZ, 65mg/Kg, at 9^th week) and daily high-fat diet were used to establish T2DM rat model. Serum glucose in diabetes group and diabetes + VEGF group obviously exceeded 13mmol/L after STZ injection. Immunohistochemical studies indicated that VEGF level in diabetes group significantly decreased. In diabetes group, testicular blood velocity and vascular area reduced evaluated by Doppler and FITC. Furthermore, atrophic testicular morphology and increasing apoptosis cells were evaluated by haematoxylin and eosin staining and TUNEL assay. In diabetes + VEGF group, the administration of VEGF (intraperitoneally, 10mg/kg) can significantly alleviated hyperglycemia-induced impairment of testes in above aspects. Finally, we used Western blot to analyze the mechanism of hyperglycemia-induced testicular VEGF decrease. The results indicated that hyperglycemia-induced VEGF decreased is regulated by PI3K/Akt pathway in Rats testicular sertoli cells (RTSCs). Together, we demonstrate that T2DM can reduce testicular VEGF expression, which results in testicular microcirculation impairment, and then induces testicular morphological disarrangement and functional disorder. These actions are triggered by PI3K/Akt pathway. Our findings provide solid evidence for VEGF becoming a therapeutic target in T2DM related male infertility.

Blood platelets and sepsis pathophysiology: A new therapeutic prospect in critically [corrected] ill patients?

Beyond haemostasis, platelets have emerged as versatile effectors of the immune response. The contribution of platelets in inflammation, tissue integrity and defence against infections has considerably widened the spectrum of their role in health and disease. Here, we propose a narrative review that first describes these new platelet attributes. We then examine their relevance to microcirculatory alterations in multi-organ dysfunction, a major sepsis complication. Rapid progresses that are made on the knowledge of novel platelet functions should improve the understanding of thrombocytopenia, a common condition and a predictor of adverse outcome in sepsis, and may provide potential avenues for management and therapy.

A calpain inhibitor protects against fractalkine production in lipopolysaccharide-treated endothelial cells

Background

Fractalkine (CX3CL1) is a chemokine with a unique CX3C motif and is produced by endothelial cells stimulated with lipopolysaccharide (LPS), tumor necrosis factor (TNF)-α, interleukin (IL)-1, and interferon-γ. There have been several reports that the caspase/calpain system is activated in endotoxemia, which leads to cellular apoptosis and acute inflammatory processes. We aimed to determine the role of the caspase/calpain system in cell viability and regulation of fractalkine production in LPS-treated endothelial cells.

Methods

Human umbilical vein endothelial cells (HUVECs) were stimulated with 0.01–100 μg/mL of LPS to determine cell viability. The changes of CX3CL1 expression were compared in control, LPS (1 μg/mL)-, IL-1α (1 μg/mL)-, and IL-1β (1 μg/mL)-treated HUVECs. Cell viability and CX3CL1 production were compared with 50 μM of inhibitors of caspase-1, caspase-3, caspase-9, and calpain in LPS-treated HUVECs.

Results

Cell viability was significantly decreased from 1 to 100 μg/mL of LPS. Cell viability was significantly restored with inhibitors of caspase-1, caspase-3, caspase-9, and calpain in LPS-treated HUVECs. The expression of CX3CL1 was highest in IL-1β-treated HUVECs. CX3CL1 production was highly inhibited with a calpain inhibitor and significantly decreased with the individual inhibitors of caspase-1, caspase-3, and caspase-9.

Conclusion

The caspase/calpain system is an important modulator of cell viability and CX3CL1 production in LPS-treated endothelial cells.

Inflammation and Arterial Stiffness in Chronic Kidney Disease: Findings From the CRIC Study

BACKGROUND

Chronic kidney disease (CKD) and arterial stiffness are associated with increased cardiovascular morbidity and mortality. Inflammation is proposed to have a role in the development of arterial stiffness, and CKD is recognized as a proinflammatory state. Arterial stiffness is increased in CKD, and cross-sectional data has suggested a link between increased inflammatory markers in CKD and higher measures of arterial stiffness. However, no large scale investigations have examined the impact of inflammation on the progression of arterial stiffness in CKD.

METHODS

We performed baseline assessments of 5 inflammatory markers in 3,939 participants from the chronic renal insufficiency cohort (CRIC), along with serial measurements of arterial stiffness at 0, 2, and 4 years of follow-up.

RESULTS

A total of 2,933 participants completed each of the follow-up stiffness measures. In cross-sectional analysis at enrollment, significant associations with at least 2 measures of stiffness were observed for fibrinogen, interleukin-6, high-sensitivity C-reactive protein, proteinuria, and composite inflammation score after adjustment for confounders. In longitudinal analyses, there were few meaningful correlations between baseline levels of inflammation and changes in metrics of arterial stiffness over time.

CONCLUSION

In a large cohort of CKD participants, we observed multiple significant correlations between initial markers of inflammation and metrics of arterial stiffness, but baseline inflammation did not predict changes in arterial stiffness over time. While well-described biologic mechanisms provide the basis for our understanding of the cross-sectional results, continued efforts to design longitudinal studies are necessary to fully elucidate the relationship between chronic inflammation and arterial stiffening.

Investigation of novel LPS-induced differentially expressed long non-coding RNAs in endothelial cells

The molecular mechanisms responsible for sepsis-induced endothelial dysfunction leading to an elevated risk of cardiovascular diseases remain undefined. Endotoxic or septic shock is a potentially lethal complication of systemic infection by Gram-negative bacteria. Lipopolysaccharide (LPS) is a critical glycolipid component of the outer wall of Gram-negative bacteria, and many of the sepsis-associated cellular signals by Gram-negative bacteria are attributed to LPS. Given that LPS has an established role in the pathophysiology of sepsis and long non-coding RNAs (lncRNAs) have been reported to critically regulate vascular homeostasis, a systematic transcriptional survey was conducted to evaluate the impact of LPS stimulation on human endothelial lncRNAs and protein-coding transcripts (mRNAs). LncRNAs and mRNAs from LPS-treated (100 ng/mL; 24 h) human umbilical vein endothelial cells (HUVECs) were profiled with the Arraystar Human lncRNA Expression Microarray V3.0. Of the 30,584 lncRNAs screened, 871 were significantly upregulated and 1068 significantly downregulated (p < 0.05) in response to LPS. In the same HUVEC samples, 733 of the 26,106 mRNAs screened were upregulated and 536 were downregulated. Among the differentially expressed lncRNAs, AL132709.5 was the most upregulated (~70 fold) and CTC-459I6.1 the most downregulated (~28 fold). Bioinformatics analyses indicated that the differentially expressed upregulated mRNAs are primarily enriched in cytokine-cytokine receptor interaction, infectious diseases, TNF signaling pathway, FoxO signaling pathway, and pathways in cancer. This is the first lncRNA and mRNA transcriptome profile of LPS-mediated changes in human endothelial cells. These observations may reveal novel endothelial targets of LPS that may be involved in the vascular pathology of sepsis.

Upregulation of Transient Receptor Potential Canonical Channels Contributes to Endotoxin-Induced Pulmonary Arterial Stenosis

Background

Septic shock is a pathologic condition caused by endotoxin-producing bacteria, and often associated with severe pulmonary hypertension. Inflammation is a major systemic response to endotoxin; however, it is unknown whether endotoxin has a direct impact on pulmonary arteries that contributes to pathogenesis of pulmonary hypertension.

Material/Methods

Rat pulmonary arteries and primary pulmonary arterial smooth muscle cells (PASMCs) were cultured in vitro and treated with lipopolysaccharide (LPS) and blockers of transient receptor potential canonical (TRPC) channels. Neointimal growth and arterial stenosis were observed on cryosections of cultured pulmonary arteries. Proliferation of PASMCs was examined by a WST-1 (water-soluble tetrazolium salt) assay. Expression of TRPC genes in pulmonary arteries and PASMCs were detected and quantified by real-time polymerase chain reaction and Western blotting.

Results

LPS significantly induced neointimal growth and stenosis of pulmonary arteries and promoted proliferation of PASMCs. TRPC channel blockers 2-aminoethoxydiphenyl borate and SKF-96365 inhibited LPS-induced remodeling of pulmonary arteries and PASMC proliferation. Expression of TRPC1/3/4/6 was detected in pulmonary arteries and PASMCs. LPS treatment dramatically increased the expression of TRPC3 and TRPC4 at both messenger RNA and protein levels.

Conclusions

LPS stimulates stenosis of pulmonary arteries through enhancement of TRPC-mediated Ca²⁺ entry into PASMCs, which is caused by upregulation of TRPC3 and TRPC4 channels.

Modulatory effects of vagal stimulation on neurophysiological parameters and the cellular immune response in the rat brain during systemic inflammation

Background

Stimulation of the vagus nerve has modulating, anti-inflammatory effects on the cellular immune response in the blood and the spleen, stabilizing brain function. Here, we aimed to investigate its potential effects on immune-to-brain communication focusing on neurophysiological readouts and leukocyte migration to the brain during severe sepsis-like endotoxemia.

Methods

Systemic inflammation was induced by intravenous administration of lipopolysaccharide (LPS; 5 mg/kg). Animals received either no manipulation of the vagus nerve, vagotomy, or vagotomy plus vagus nerve stimulation of the distal trunk. Somatosensory evoked potentials and evoked flow velocity response were measured for 4.5 h as indicators of brain function and neurovascular coupling, respectively. In addition, brain areas with (cortex) and without (hypothalamus) tight blood-brain barrier were studied separately using immunohistochemistry and RT-PCR. Moreover, plasma cytokine and leptin levels were analyzed by ELISA.

Results

LPS induced a decline of both neurophysiological parameters, which was prevented by vagus nerve stimulation. As for peripheral organs, LPS-stimulated neutrophil counts increased in the brain and colocalized in the brain with endothelial intercellular adhesion molecule (ICAM)-1. Interestingly, vagal stimulation reduced this colocalization and decreased nuclear translocation of the brain cell activation marker nuclear factor interleukin 6 (NF-IL6). Furthermore, it reduced the gene expression of inflammatory markers and extravasation signals (IL-6, CXCL-1, ICAM-1) in the hypothalamus but not the cortex linked to a moderate decrease in circulating cytokine levels (interleukin 6, tumor necrosis factor alpha) as well as lower plasma leptin concentration.

Conclusions

Our data suggest beneficial effects of anti-inflammatory vagus nerve stimulation on brain function by reducing the interaction of neurotrophil granulocytes with the brain endothelium as well as attenuating inflammatory responses in brain areas lacking a blood-brain barrier.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-016-0091-4) contains supplementary material, which is available to authorized users.

Lipopolysaccharide potentiates endothelin-1-induced proliferation of pulmonary arterial smooth muscle cells by upregulating TRPC channels

Lipopolysaccharide (LPS) and endothelin-1 (ET-1) are critical pathogenic factors in sepsis-induced pulmonary hypertension; however it is unknown whether they have a coordinated action in the pathogenesis of this disease. Here we found that although LPS did not change the contractility of rat pulmonary arterial smooth muscle cells (PASMCs) in response to ET-1, it significantly promoted ET-1-induced PASMC proliferation. Measurement of ET-1-evoked Ca(2+) transients in PASMCs showed that LPS dramatically enhanced Ca(2+) influx mediated by transient receptor potential canonical (TRPC) channels. LPS did not directly activate TRPC channels, instead it selectively upregulated the expression of TRPC3 and TRPC4 in pulmonary arteries. Small interfering RNA (siRNA) and chemical blockers against TRPC channels abolished LPS-induced PASMC proliferation. LPS-induced cell proliferation and TRPC expression was mediated by the Ca(2+)-dependent calcineurin/NFAT signaling pathway. We suggest that blocking TRPC channels could be an effective strategy in controlling pulmonary arterial remodeling after endotoxin exposure.

Suppression of transient receptor potential melastatin 4 expression promotes conversion of endothelial cells into fibroblasts via transforming growth factor/activin receptor-like kinase 5 pathway

OBJECTIVE

To study whether transient receptor potential melastatin 4 (TRPM4) participates in endothelial fibrosis and to investigate the underlying mechanism.

METHODS

Primary human endothelial cells were used and pharmacological and short interfering RNA-based approaches were used to test the transforming growth factor beta (TGF-β)/activin receptor-like kinase 5 (ALK5) pathway participation and contribution of TRPM7 ion channel.

RESULTS

Suppression of TRPM4 expression leads to decreased endothelial protein expression and increased expression of fibrotic and extracellular matrix markers. Furthermore, TRPM4 downregulation increases intracellular Ca levels as a potential condition for fibrosis. The underlying mechanism of endothelial fibrosis shows that inhibition of TRPM4 expression induces TGF-β1 and TGF-β2 expression, which act through their receptor, ALK5, and the nuclear translocation of the profibrotic transcription factor smad4.

CONCLUSION

TRPM4 acts to maintain endothelial features and its loss promotes fibrotic conversion via TGF-β production. The regulation of TRPM4 levels could be a target for preserving endothelial function during inflammatory diseases.

Alert cell strategy in SIRS-induced vasculitis: sepsis and endothelial cells

Sepsis refers to systemic inflammatory response syndrome and organ failure resulting from infection. Inflammatory receptors (e.g., Toll-like receptors and nucleotide oligomerization domain) recognize bacterial components as inflammatory ligands. These are expressed not only in leukocytes but also in major organs and vascular endothelial cells. "Alert cell" is defined as the cell that expresses the inflammatory receptor and intracellular signaling system to produce inflammatory mediators such as inflammatory cytokines, chemokines, nitric oxide, and prostanoids in organs and the vasculature. NF-κB and AP-1, which are the transcriptional factors of these inflammatory molecules, are important regulators of multiple organ failure in sepsis and systemic inflammation. The vascular endothelial injury would induce multiple organ failure as tissue ischemia and organ death. Drug discovery targeted at alert cells holds a promise for therapy of inflammation including sepsis.

Hydrogen-Rich Medium Attenuated Lipopolysaccharide-Induced Monocyte-Endothelial Cell Adhesion and Vascular Endothelial Permeability via Rho-Associated Coiled-Coil Protein Kinase

Sepsis is the leading cause of death in critically ill patients. In recent years, molecular hydrogen, as an effective free radical scavenger, has been shown a selective antioxidant and anti-inflammatory effect, and it is beneficial in the treatment of sepsis. Rho-associated coiled-coil protein kinase (ROCK) participates in junction between normal cells, and regulates vascular endothelial permeability. In this study, we used lipopolysaccharide to stimulate vascular endothelial cells and explored the effects of hydrogen-rich medium on the regulation of adhesion of monocytes to endothelial cells and vascular endothelial permeability. We found that hydrogen-rich medium could inhibit adhesion of monocytes to endothelial cells and decrease levels of adhesion molecules, whereas the levels of transepithelial/endothelial electrical resistance values and the expression of vascular endothelial cadherin were increased after hydrogen-rich medium treatment. Moreover, hydrogen-rich medium could lessen the expression of ROCK, as a similar effect of its inhibitor Y-27632. In addition, hydrogen-rich medium could also inhibit adhesion of polymorphonuclear neutrophils to endothelial cells. In conclusion, hydrogen-rich medium could regulate adhesion of monocytes/polymorphonuclear neutrophils to endothelial cells and vascular endothelial permeability, and this effect might be related to the decreased expression of ROCK protein.

Paricalcitol attenuates lipopolysaccharide-induced myocardial inflammation by regulating the NF-κB signaling pathway

Vitamin D deficiency is associated with an increased risk of cardiovascular disease, diabetes, colon and breast cancer, infectious diseases and allergies. Vascular alterations are an important pathophysiological mechanism of sepsis. Experimental data suggest that paricalcitol, a vitamin D2 analogue, exerts beneficial effects on renal inflammation and fibrosis. In the present study, we aimed to investigate the effects of paricalcitol on lipopolysaccharide (LPS)-induced myocardial inflammation and to elucidate the underlying mechanisms. We used primary cultured human umbilical vein endothelial cells for in vitro experiments, in which stimulation with tumor necrosis factor (TNF)-α was used to induce endothelial cell inflammation. For in vivo experiments, myocardial inflammation was induced by an intraperitoneal injection of 15 mg/kg LPS into C57BL6 mice pre-treated with or without 0.2 µg/kg paricalcitol. Treatment with paricalcitol suppressed the TNF-α-induced increase in the protein expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1) and fractalkine in endothelial cells. Treatment with paricalcitol also decreased the TNF-α-induced nuclear factor (NF)-κB binding activity. In a mouse model of LPS-induced myocardial inflammation, pre-treatment with paricalcitol prevented the LPS-induced increase in the expression of myocardial ICAM-1, phosphorylated p65 and myocardial TNF-α. Pre-treatment with paricalcitol also alleviated endotoxemia‑induced microvascular leakage in the myocardium. The findings of our study suggest that paricalcitol exerts a protective effect against LPS-induced myocardial inflammation by regulating the expression of cell adhesion molecules and TNF-α, and by improving myocardial permeability.

Dietary Apigenin Exerts Immune-Regulatory Activity in Vivo by Reducing NF-κB Activity, Halting Leukocyte Infiltration and Restoring Normal Metabolic Function

The increasing prevalence of inflammatory diseases and the adverse effects associated with the long-term use of current anti-inflammatory therapies prompt the identification of alternative approaches to reestablish immune balance. Apigenin, an abundant dietary flavonoid, is emerging as a potential regulator of inflammation. Here, we show that apigenin has immune-regulatory activity in vivo. Apigenin conferred survival to mice treated with a lethal dose of Lipopolysaccharide (LPS) restoring normal cardiac function and heart mitochondrial Complex I activity. Despite the adverse effects associated with high levels of splenocyte apoptosis in septic models, apigenin had no effect on reducing cell death. However, we found that apigenin decreased LPS-induced apoptosis in lungs, infiltration of inflammatory cells and chemotactic factors’ accumulation, re-establishing normal lung architecture. Using NF-κB luciferase transgenic mice, we found that apigenin effectively modulated NF-κB activity in the lungs, suggesting the ability of dietary compounds to exert immune-regulatory activity in an organ-specific manner. Collectively, these findings provide novel insights into the underlying immune-regulatory mechanisms of dietary nutraceuticals in vivo.

Redox signaling and splicing dependent change in myosin phosphatase underlie early versus late changes in NO vasodilator reserve in a mouse LPS model of sepsis

Microcirculatory dysfunction may cause tissue malperfusion and progression to organ failure in the later stages of sepsis, but the role of smooth muscle contractile dysfunction is uncertain. Mice were given intraperitoneal LPS, and mesenteric arteries were harvested at 6-h intervals for analyses of gene expression and contractile function by wire myography. Contractile (myosin and actin) and regulatory [myosin light chain kinase and phosphatase subunits (Mypt1, CPI-17)] mRNAs and proteins were decreased in mesenteric arteries at 24 h concordant with reduced force generation to depolarization, Ca(2+), and phenylephrine. Vasodilator sensitivity to DEA/nitric oxide (NO) and cGMP under Ca(2+) clamp were increased at 24 h after LPS concordant with a switch to Mypt1 exon 24- splice variant coding for a leucine zipper (LZ) motif required for PKG-1α activation of myosin phosphatase. This was reproduced by smooth muscle-specific deletion of Mypt1 exon 24, causing a shift to the Mypt1 LZ+ isoform. These mice had significantly lower resting blood pressure than control mice but similar hypotensive responses to LPS. The vasodilator sensitivity of wild-type mice to DEA/NO, but not cGMP, was increased at 6 h after LPS. This was abrogated in mice with a redox dead version of PKG-1α (Cys42Ser). Enhanced vasorelaxation in early endotoxemia is mediated by redox signaling through PKG-1α but in later endotoxemia by myosin phosphatase isoform shifts enhancing sensitivity to NO/cGMP as well as smooth muscle atrophy. Muscle atrophy and modulation may be a novel target to suppress microcirculatory dysfunction; however, inactivation of inducible NO synthase, treatment with the IL-1 antagonist IL-1ra, or early activation of α-adrenergic signaling did not suppressed this response.

Endothelial (NOS3 E298D) and inducible (NOS2 exon 22) nitric oxide synthase polymorphisms, as well as plasma NOx, influence sepsis development

INTRODUCTION

Nitric oxide (NO) influences susceptibility to infection and hemodynamic failure (HF) in sepsis. NOS3 and NOS2 SNPs might modify plasma nitrite/nitrate (NOx) levels, sepsis development, hemodynamics and survival.

METHODS

90 severely septic and 91 non-infected ICU patients were prospectively studied. NOS3 (E298D), NOS3 (-786 T/C), NOS3 (27 bp-VNTR), and NOS2A (exon 22) SNPs and plasma NOx levels were assessed.

RESULTS

21 patients (11.6%) died, 7 with sepsis. TT homozygotes and T allele carriers of NOS3 (E298D) and AG carriers of the NOS2A (exon 22) SNPs were more frequent among septic compared to non-infected ICU patients (p < 0.05). Plasma NOx was higher in septic, especially in septic with hemodynamic failure (HF) or fatal outcome (p < 0.006). Plasma NOx was higher in carriers of the T allele of the NOS3 (E298D) SNP (p = 0.006). Sepsis independently associated with HF, increased NOx, peripheral neutrophils, and fibrinogen levels, decreased prothrombin and the presence of the NOS3 (E298D) and NOS2A (exon 22) SNPs. A low APACHE II score was the only variable associated with sepsis survival. NOx was independently associated with sepsis, HF, decreased neutrophils and higher APACHE.

CONCLUSIONS

NOS3 (E298D) and NOS2A (exon 22) SNPs, individually and in combination, and plasma NOx, associated with sepsis development. NOx associated with HF and fatal outcome.

The role of ATP-sensitive potassium channels in cellular function and protection in the cardiovascular system

ATP-sensitive potassium channels (K(ATP)) are widely distributed and present in a number of tissues including muscle, pancreatic beta cells and the brain. Their activity is regulated by adenine nucleotides, characteristically being activated by falling ATP and rising ADP levels. Thus, they link cellular metabolism with membrane excitability. Recent studies using genetically modified mice and genomic studies in patients have implicated K(ATP) channels in a number of physiological and pathological processes. In this review, we focus on their role in cellular function and protection particularly in the cardiovascular system.

Neuronal nitric oxide synthase and its interaction with soluble guanylate cyclase is a key factor for the vascular dysfunction of experimental sepsis

OBJECTIVE

Vascular dysfunction plays a central role in sepsis, and it is characterized by hypotension and hyporesponsiveness to vasoconstrictors. Nitric oxide is regarded as a central element of sepsis vascular dysfunction. The high amounts of nitric oxide produced during sepsis are mainly derived from the inducible isoform of nitric oxide synthase 2. We have previously shown that nitric oxide synthase 2 levels decrease in later stages of sepsis, whereas levels and activity of soluble guanylate cyclase increase. Therefore, we studied the putative role of other relevant nitric oxide sources, namely, the neuronal (nitric oxide synthase 1) isoform, in sepsis and its relationship with soluble guanylate cyclase. We also studied the consequences of nitric oxide synthase 1 blockade in the hyporesponsiveness to vasoconstrictors.

DESIGN

Randomized controlled prospective experimental study.

SETTING

Academic research laboratory.

SUBJECTS

Female Wistar rats submitted to cecal ligation and puncture method.

INTERVENTIONS

1) Six, 12, and 24 hours after cecal ligation and puncture, vascular reactivity to phenylephrine (3 and 30 nmol/kg) before and after 7-nitroindazole (45 μmol/kg, s.c.) or aminoguanidine (30 μmol/kg, s.c.) administration was evaluated. 2) Protein levels and interaction between nitric oxide synthase 1 and soluble guanylate cyclase were determined. 3) Six, 12, and 24 hours after cecal ligation and puncture, thoracic aorta segments were stimulated with phenylephrine in the presence or absence of 7-nitroindazole and cyclic guanosine monophosphate accumulation was determined. 4) After 24 hours of cecal ligation and puncture, norepinephrine was infused (10 μg/kg/min) in the presence or absence of 7-nitroindazole or S-methyl-L-thiocitrulline (1 μmol/kg, IV) and mean arterial pressure was registered.

MEASUREMENTS AND MAIN RESULTS

1) Both nitric oxide synthase 1 and soluble guanylate cyclase are expressed in higher levels in vascular tissues during sepsis; 2) both proteins physically interact and nitric oxide synthase 1 blockade inhibits cyclic guanosine monophosphate production; 3) pharmacological blockade of nitric oxide synthase 1 using 7-nitroindazole or S-methyl-L-thiocitrulline reverts the hyporesponsiveness to phenylephrine and increases the vasoconstrictor effect of norepinephrine and phenylephrine.

CONCLUSIONS

Sepsis induces increased expression and physical association of nitric oxide synthase 1/soluble guanylate cyclase and a higher production of cyclic guanosine monophosphate that together may help explain sepsis-induced vascular dysfunction. In addition, selective inhibition of nitric oxide synthase 1 restores the responsiveness to vasoconstrictors. Therefore, inhibition of nitric oxide synthase 1 (and possibly soluble guanylate cyclase) may represent a valuable alternative to restore the effectiveness of vasopressor agents during late sepsis.

Endotoxin-induced endothelial fibrosis is dependent on expression of transforming growth factors β1 and β2

During endotoxemia-induced inflammatory disease, bacterial endotoxins circulate in the bloodstream and interact with endothelial cells (ECs), inducing dysfunction of the ECs. We previously reported that endotoxins induce the conversion of ECs into activated fibroblasts. Through endotoxin-induced endothelial fibrosis, ECs change their morphology and their protein expression pattern, thereby suppressing endothelial markers and upregulating fibrotic proteins. The most commonly used fibrotic inducers are transforming growth factor β1 (TGF-β1) and TGF-β2. However, whether TGF-β1 and TGF-β2 participate in endotoxin-induced endothelial fibrosis remains unknown. We have shown that the endotoxin-induced endothelial fibrosis process is dependent on the TGF-β receptor, ALK5, and the activation of Smad3, a protein that is activated by ALK5 activation, thus suggesting that endotoxin elicits TGF-β production to mediate endotoxin-induced endothelial fibrosis. Therefore, we investigated the dependence of endotoxin-induced endothelial fibrosis on the expression of TGF-β1 and TGF-β2. Endotoxin-treated ECs induced the expression and secretion of TGF-β1 and TGF-β2. TGF-β1 and TGF-β2 downregulation inhibited the endotoxin-induced changes in the endothelial marker VE-cadherin and in the fibrotic proteins α-SMA and fibronectin. Thus, endotoxin induces the production of TGF-β1 and TGF-β2 as a mechanism to promote endotoxin-induced endothelial fibrosis. To the best of our knowledge, this is the first report showing that endotoxin induces endothelial fibrosis via TGF-β secretion, which represents an emerging source of vascular dysfunction. These findings contribute to understanding the molecular mechanism of endotoxin-induced endothelial fibrosis, which could be useful in the treatment of inflammatory diseases.

Endotoxin induces fibrosis in vascular endothelial cells through a mechanism dependent on transient receptor protein melastatin 7 activity

The pathogenesis of systemic inflammatory diseases, including endotoxemia-derived sepsis syndrome, is characterized by endothelial dysfunction. It has been demonstrated that the endotoxin lipopolysaccharide (LPS) induces the conversion of endothelial cells (ECs) into activated fibroblasts through endothelial-to-mesenchymal transition mechanism. Fibrogenesis is highly dependent on intracellular Ca2+ concentration increases through the participation of calcium channels. However, the specific molecular identity of the calcium channel that mediates the Ca2+ influx during endotoxin-induced endothelial fibrosis is still unknown. Transient receptor potential melastatin 7 (TRPM7) is a calcium channel that is expressed in many cell types, including ECs. TRPM7 is involved in a number of crucial processes such as the conversion of fibroblasts into activated fibroblasts, or myofibroblasts, being responsible for the development of several characteristics of them. However, the role of the TRPM7 ion channel in endotoxin-induced endothelial fibrosis is unknown. Thus, our aim was to study whether the TRPM7 calcium channel participates in endotoxin-induced endothelial fibrosis. Using primary cultures of ECs, we demonstrated that TRPM7 is a crucial protein involved in endotoxin-induced endothelial fibrosis. Suppression of TRPM7 expression protected ECs from the fibrogenic process stimulated by endotoxin. Downregulation of TRPM7 prevented the endotoxin-induced endothelial markers decrease and fibrotic genes increase in ECs. In addition, TRPM7 downregulation abolished the endotoxin-induced increase in ECM proteins in ECs. Furthermore, we showed that intracellular Ca2+ levels were greatly increased upon LPS challenge in a mechanism dependent on TRPM7 expression. These results demonstrate that TRPM7 is a key protein involved in the mechanism underlying endotoxin-induced endothelial fibrosis.

The endothelium, a protagonist in the pathophysiology of critical illness: focus on cellular markers

The endotheliumis key in the pathophysiology of numerous diseases as a result of its precarious function in the regulation of tissue homeostasis. Therefore, its clinical evaluation providing diagnostic and prognostic markers, as well as its role as a therapeutic target, is the focus of intense research in patientswith severe illnesses. In the critically ill with sepsis and acute brain injury, the endothelium has a cardinal function in the development of organ failure and secondary ischemia, respectively. Cellular markers of endothelial function such as endothelial progenitor cells (EPC) and endothelialmicroparticles (EMP) are gaining interest as biomarkers due to their accessibility, although the lack of standardization of EPC and EMP detection remains a drawback for their routine clinical use. In this paper we will review data available on EPC, as a general marker of endothelial repair, and EMP as an equivalent of damage in critical illnesses, in particular sepsis and acute brain injury. Their determination has resulted in new insights into endothelial dysfunction in the critically ill. It remains speculative whether their determination might guide therapy in these devastating acute disorders in the near future.

Neutrophils from critically ill septic patients mediate profound loss of endothelial barrier integrity

Introduction

Sepsis is characterized by systemic immune activation and neutrophil-mediated endothelial barrier integrity compromise, contributing to end-organ dysfunction. Studies evaluating endothelial barrier dysfunction induced by neutrophils from septic patients are lacking, despite its clinical significance. We hypothesized that septic neutrophils would cause characteristic patterns of endothelial barrier dysfunction, distinct from experimental stimulation of normal neutrophils, and that treatment with the immunomodulatory drug β-glucan would attenuate this effect.

Methods

Blood was obtained from critically ill septic patients. Patients were either general surgery patients (Primary Sepsis (PS)) or those with sepsis following trauma (Secondary Sepsis (SS)). Those with acute respiratory distress syndrome (ARDS) were identified. Healthy volunteers served as controls. Neutrophils were purified and aliquots were untreated, or treated with fMLP or β-glucan. Endothelial cells were grown to confluence and activated with tissue necrosis factor (TNF)-α . Electric Cell-substrate Impedance Sensing (ECIS) was used to determine monolayer resistance after neutrophils were added. Groups were analyzed by two-way analysis of variance (ANOVA).

Results

Neutrophils from all septic patients, as well as fMLP-normal neutrophils, reduced endothelial barrier integrity to a greater extent than untreated normal neutrophils (normalized resistance of cells from septic patients at 30 mins = 0.90 ± 0.04; at 60 mins = 0.73 ± 0.6 and at 180 mins = 0.56 ± 0.05; p < 0.05 vs normal). Compared to untreated PS neutrophils, fMLP-treated PS neutrophils caused further loss of barrier function at all time points; no additive effect was noted in stimulation of SS neutrophils beyond 30 min. Neutrophils from ARDS patients caused greater loss of barrier integrity than those from non-ARDS patients, despite similarities in age, sex, septic source, and neutrophil count. Neutrophils obtained after resolution of sepsis caused less barrier dysfunction at all time points. β-glucan treatment of septic patients’ neutrophils attenuated barrier compromise, rendering the effect similar to that induced by neutrophils obtained once sepsis had resolved.

Conclusions

Neutrophils from septic patients exert dramatic compromise of endothelial barrier integrity. This pattern is mimicked by experimental activation of healthy neutrophils. The effect of septic neutrophils on the endothelium depends upon the initial inflammatory event, correlates with organ dysfunction and resolution of sepsis, and is ameliorated by β-glucan.

Vasoplegia in septic shock: do we really fight the right enemy?

Vasoplegia is a key factor for the death of patients with septic shock in intensive care unit owing to persistent and irreversible hypotension. Impairment of vascular reactivity has been attributed to a combination of endothelial injury, arginine-vasopressin system dysfunction, release of other vasodilatory inflammatory mediators, and muscle hyperpolarizaton. Nitric oxide induced by a Ca(+2) independent isoform of nitric oxide synthase has been suggested to play an important role in sepsis-induced vasoplegia. However, inhibition of nitric oxide synthase only partially restores the endotoxin-induced vascular hyporeactivity. The aim of this review is to discuss in detail the recent suggested alternative mechanisms of vasoplegia and to briefly outline the current therapeutic strategies and the novel therapeutic options based on those mechanisms.

Monocytes, peripheral blood mononuclear cells, and THP-1 cells exhibit different cytokine expression patterns following stimulation with lipopolysaccharide

THP-1 cells are widely applied to mimic monocytes in cell culture models. In this study, we compared the cytokine release from THP-1, peripheral blood mononuclear cells (PBMC), monocytes, or whole blood after stimulation with lipopolysaccharide (LPS) and investigated the consequences of different cytokine profiles on human umbilical vein endothelial cell (HUVEC) activation. While Pseudomonas aeruginosa-stimulated (10 ng/mL) THP-1 secreted similar amounts of tumor necrosis factor alpha (TNF- α ) as monocytes and PBMC, they produced lower amounts of interleukin(IL)-8 and no IL-6 and IL-10. Whole blood required a higher concentration of Pseudomonas aeruginosa (1000 ng/mL) to induce cytokine release than isolated monocytes or PBMC (10 ng/mL). HUVEC secreted more IL-6 and IL-8 after stimulation with conditioned medium derived from whole blood than from THP-1, despite equal concentrations of TNF- α in both media. Specific adsorption of TNF- α or selective cytokine adsorption from the conditioned media prior to HUVEC stimulation significantly reduced HUVEC activation. Our findings show that THP-1 differ from monocytes, PBMC, and whole blood with respect to cytokine release after stimulation with LPS. Additionally, we could demonstrate that adsorption of inflammatory mediators results in reduced endothelial activation, which supports the concept of extracorporeal mediator modulation as supportive therapy for sepsis.

Lipopolysaccharide induces a fibrotic-like phenotype in endothelial cells

Endothelial dysfunction is crucial in endotoxaemia-derived sepsis syndrome pathogenesis. It is well accepted that lipopolysaccharide (LPS) induces endothelial dysfunction through immune system activation. However, LPS can also directly generate actions in endothelial cells (ECs) in the absence of participation by immune cells. Although interactions between LPS and ECs evoke endothelial death, a significant portion of ECs are resistant to LPS challenge. However, the mechanism that confers endothelial resistance to LPS is not known. LPS-resistant ECs exhibit a fibroblast-like morphology, suggesting that these ECs enter a fibrotic programme in response to LPS. Thus, our aim was to investigate whether LPS is able to induce endothelial fibrosis in the absence of immune cells and explore the underlying mechanism. Using primary cultures of ECs and culturing intact blood vessels, we demonstrated that LPS is a crucial factor to induce endothelial fibrosis. We demonstrated that LPS was able and sufficient to promote endothelial fibrosis, in the absence of immune cells through an activin receptor-like kinase 5 (ALK5) activity-dependent mechanism. LPS-challenged ECs showed an up-regulation of both fibroblast-specific protein expression and extracellular matrix proteins secretion, as well as a down-regulation of endothelial markers. These results demonstrate that LPS is a crucial factor in inducing endothelial fibrosis in the absence of immune cells through an ALK5-dependent mechanism. It is noteworthy that LPS-induced endothelial fibrosis perpetuates endothelial dysfunction as a maladaptive process rather than a survival mechanism for protection against LPS. These findings are useful in improving current treatment against endotoxaemia-derived sepsis syndrome and other inflammatory diseases.