Sepsis-induced elevation in plasma serotonin facilitates endothelial hyperpermeability

Complementary and alternative medicine on cognitive defects and neuroinflammation after sepsis

Sepsis-associated encephalopathy (SAE) is a common manifestation of sepsis, ranging from mild confusion and delirium to severe cognitive impairment and deep coma. SAE is associated with higher mortality and long-term outcomes, particularly substantial declines in cognitive function. The mechanisms of SAE probably include neuroinflammation that is mediated by systemic inflammation and ischemic lesions in the brain, a disrupted blood-brain barrier, oxidative stress, neurotransmitter dysfunction, and severe microglial activation. Increasing evidence suggests that complementary and alternative medicine, especially Traditional Chinese Medicine (TCM), is favorable in alleviating cognitive decline after sepsis. Here, we summarized the studies of traditional herbal remedies, TCM formulas and acupuncture therapy in animal models of neurological dysfunctions after sepsis in recent decades and reviewed their potential mechanisms.

Activated Platelets Autocrine 5-Hydroxytryptophan Aggravates Sepsis-Induced Acute Lung Injury by Promoting Neutrophils Extracellular Traps Formation

Excessive neutrophil extracellular trap (NET) formation is an important contributor to sepsis-induced acute lung injury (ALI). Recent reports indicate that platelets can induce neutrophil extracellular trap formation. However, the specific mechanism remains unclear. Tph1 gene, which encodes the rate-limiting enzyme for peripheral 5-hydroxytryptophan (5-HT) synthesis, was knocked out in mice to simulate peripheral 5-HT deficiency. Cecal ligation and puncture (CLP) surgery was performed to induce sepsis. We found that peripheral 5-HT deficiency reduced NET formation in lung tissues, alleviated sepsis-induced lung inflammatory injury, and reduced the mortality rate of CLP mice. In addition, peripheral 5-HT deficiency was shown to reduce the accumulation of platelets and NETs in the lung of septic mice. We found that platelets from wild-type (WT), but not Tph1 knockout (Tph1^−/−), mice promote lipopolysaccharide (LPS)-induced NET formation. Exogenous 5-HT intervention increased LPS-induced NET formation when Tph1^−/− platelets were co-cultured with WT neutrophils. Therefore, our study uncovers a mechanism by which peripheral 5-HT aggravated sepsis-induced ALI by promoting NET formation in the lung of septic mice.

Basic research and clinical progress of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE), a major cerebral complication of sepsis, occurs in 70% of patients admitted to the intensive care unit (ICU). This condition can cause serious impairment of consciousness and is associated with a high mortality rate. Thus far, several experimental screenings and radiological techniques (e.g., electroencephalography) have been used for the non-invasive assessment of the structure and function of the brain in patients with SAE. Nevertheless, the pathogenesis of SAE is complicated and remains unclear. In the present article, we reviewed the currently available literature on the epidemiology, clinical manifestations, pathology, diagnosis, and management of SAE. However, currently, there is no ideal pharmacological treatment for SAE. Treatment targeting mitochondrial dysfunction may be useful in the management of SAE.

Serotonin-induced vascular permeability is mediated by transient receptor potential vanilloid 4 in the airways and upper gastrointestinal tract of mice

Endothelial and epithelial cells form physical barriers that modulate the exchange of fluid and molecules. The integrity of these barriers can be influenced by signaling through G protein-coupled receptors (GPCRs) and ion channels. Serotonin (5-HT) is an important vasoactive mediator of tissue edema and inflammation. However, the mechanisms that drive 5-HT-induced plasma extravasation are poorly defined. The Transient Receptor Potential Vanilloid 4 (TRPV4) ion channel is an established enhancer of signaling by GPCRs that promote inflammation and endothelial barrier disruption. Here, we investigated the role of TRPV4 in 5-HT-induced plasma extravasation using pharmacological and genetic approaches. Activation of either TRPV4 or 5-HT receptors promoted significant plasma extravasation in the airway and upper gastrointestinal tract of mice. 5-HT-mediated extravasation was significantly reduced by pharmacological inhibition of the 5-HT2A receptor subtype, or with antagonism or deletion of TRPV4, consistent with functional interaction between 5-HT receptors and TRPV4. Inhibition of receptors for the neuropeptides substance P (SP) or calcitonin gene-related peptide (CGRP) diminished 5-HT-induced plasma extravasation. Supporting studies assessing treatment of HUVEC with 5-HT, CGRP, or SP was associated with ERK phosphorylation. Exposure to the TRPV4 activator GSK1016790A, but not 5-HT, increased intracellular Ca2+ in these cells. However, 5-HT pre-treatment enhanced GSK1016790A-mediated Ca2+ signaling, consistent with sensitization of TRPV4. The functional interaction was further characterized in HEK293 cells expressing 5-HT2A to reveal that TRPV4 enhances the duration of 5-HT-evoked Ca2+ signaling through a PLA2 and PKC-dependent mechanism. In summary, this study demonstrates that TRPV4 contributes to 5-HT2A-induced plasma extravasation in the airways and upper GI tract, with evidence supporting a mechanism of action involving SP and CGRP release.

Apoptosis signal-regulating kinase 1 regulates immune-mediated thrombocytopenia, thrombosis, and systemic shock

BACKGROUND

Immune complexes (ICs) bind to and activate platelets via FcγRIIA, causing patients to experience thrombocytopenia, as well as an increased risk of forming occlusive thrombi. Although platelets have been shown to mediate IC-induced pathologies, the mechanisms involved have yet to be fully elucidated. We identified that apoptosis signal-regulating kinase 1 (ASK1) is present in both human and mouse platelets and potentiates many platelet functions.

OBJECTIVES

Here we set out to study ASK1's role in regulating IC-mediated platelet functions in vitro and IC-induced pathologies using an in vivo mouse model.

METHODS

Using human platelets treated with an ASK1-specific inhibitor and platelets from FCGR2A/Ask1-/- transgenic mice, we examined various platelet functions induced by model ICs in vitro and in vivo.

RESULTS

We found that ASK1 was activated in human platelets following cross-linking of FcγRIIA using either anti-hCD9 or IV.3 + goat-anti-mouse. Although genetic deletion or inhibition of ASK1 significantly attenuated anti-CD9-induced platelet aggregation, activation of the canonical FcγRIIA signaling targets Syk and PLCγ2 was unaffected. We further found that anti-mCD9-induced cPla2 phosphorylation and TxA2 generation is delayed in Ask1 null transgenic mouse platelets leading to diminished δ-granule secretion. In vivo, absence of Ask1 protected FCGR2A transgenic mice from thrombocytopenia, thrombosis, and systemic shock following injection of anti-mCD9. In whole blood microfluidics, platelet adhesion and thrombus formation on fibrinogen was enhanced by Ask1.

CONCLUSIONS

These findings suggest that ASK1 inhibition may be a potential target for the treatment of IC-induced shock and other immune-mediated thrombotic disorders.

Role of Resveratrol on Indoxyl Sulfate-Induced Endothelial Hyperpermeability via Aryl Hydrocarbon Receptor (AHR)/Src-Dependent Pathway

Resveratrol (RES), a dietary polyphenol compound, has been shown to possess health benefits due to its anti-inflammatory, antioxidative, and antiatherosclerosis properties. Tryptophan metabolite-derived indoxyl sulfate (IS) is identified as one of the uremic toxins and physiological endogenous ligand/activator of aryl hydrocarbon receptor (AHR), associated with atherosclerosis in chronic kidney disease (CKD) patients. Studies have shown that a high serum level of IS causes deleterious effects on health primarily by inducing oxidative stress and endothelial dysfunction. However, the precise mechanisms are still unclear. Here, we investigated the underlying mechanism of IS effect on endothelial permeability and the role of RES on IS-induced endothelial hyperpermeability via the AHR/Src-dependent pathway. Bovine aorta endothelial cells (BAECs) were cultured and incubated with IS in the presence or absence of RES, and transendothelial electrical resistance (TEER) and permeability of cells were measured. Alongside, AHR, Src kinase, and Vascular Endothelial Cadherin (VE-Cadherin) activation were examined. Our data showed that IS reduced TEER of cells resulting in increased permeability. VE-Cadherin, a vital regulator of endothelial permeability, was also significantly activated in response to IS, which appeared to be associated with changes of endothelial permeability and AHR/Src kinase. Interestingly, in this setting, RES reversed the effect of IS and inhibited the increased activation of Src induced by IS-activated AHR and modulated VE-Cadherin and permeability. CH223191, an inhibitor of AHR, significantly inhibits IS-induced endothelial hyperpermeability. Further analysis with treatment of PP2, an inhibitor of Src abolishing Src activation, suggests downstream factors. All our data indicated that IS upregulated the AHR/Src kinase pathway, and increased endothelial permeability and phosphorylation of VE-Cadherin may be represented and provide new strategies for addressing protective properties of RES against Src kinase involved in AHR-mediated endothelial hyperpermeability. The findings may be crucial for managing diseases in which endothelial permeability is compromised, and the dietary polyphenols are involved.

Effects of salbutamol and phlorizin on acute pulmonary inflammation and disease severity in experimental sepsis

Respiratory infection can be exacerbated by the high glucose concentration in the airway surface liquid (ASL). We investigated the effects of salbutamol and phlorizin on the pulmonary function, oxidative stress levels and SGLT1 activity in lung, pulmonary histopathological damages and survival rates of rats with sepsis. Sepsis was induced by cecal ligation and puncture surgery (CLP). Twenty-four hours after surgery, CLP rats were intranasally treated with saline, salbutamol or phlorizin. After 2 hours, animals were anesthetized and sacrificed. Sepsis promoted atelectasis and bronchial inflammation, and led to increased expression of SGLT1 on cytoplasm of pneumocytes. Salbutamol treatment reduced bronchial inflammation and promoted hyperinsuflation in CLP rats. The interferon-ɤ and Interleucin-1β concentrations in bronchoalveolar lavage (BAL) were closely related to the bronchial inflammation regulation. Salbutamol stimulated SGLT1 in plasma membrane; whereas, phlorizin promoted the increase of SGLT1 in cytoplasm. Phlorizin reduced catalase activity and induced a significant decrease in the survival rate of CLP rats. Taken together, sepsis promoted atelectasis and lung inflammation, which can be associated with SGLT1 inhibition. The loss of function of SGLT1 by phlorizin are related to the augmented disease severity, increased atelectasis, bronchial inflammation and a significant reduction of survival rate of CLP rats. Alternatively salbutamol reduced BAL inflammatory cytokines, bronchial inflammation, atelectasis, and airway damage in sepsis. These data suggest that this selective β2-adrenergic agonist may protect lung of septic acute effects.

Adjunctive granisetron therapy in patients with sepsis or septic shock (GRANTISS): Study protocol for a randomized controlled trial

INTRODUCTION

The incidence, mortality, and treatment costs of sepsis are high and, thus, present a major challenge for critical care medicine. Our previous studies suggest that intestinal metabolite granisetron has a potential therapeutic effect on sepsis. Granisetron is a clinically widely used antiemetic, which is safe, inexpensive, and reliable. However, its value in the treatment of sepsis remains unclear. This study aims to explore the efficacy and safety of granisetron in the treatment of sepsis.

METHODS AND ANALYSIS

A single-center, single-blind, randomized, controlled clinical trial will be conducted on 154 patients with sepsis. Patients who meet sepsis 3.0 diagnostic criteria, aged ≥18 and ≤80 years, with PCT ≥ 2 ng/mL will be recruited. Patients will be randomized to receive intravenous granisetron 3 mg every 8 hours (n = 77) or an equal volume of normal saline (n = 77) for a treatment period of 4 days or to ICU discharge. The primary outcome is 28-day all-cause mortality. Secondary outcome measures include requirements for organ function support, changes of organ function, changes in infection biomarkers, changes in inflammatory and immune biomarkers, and the proportion of new organ failure. Adverse events and serious adverse events also will be observed closely.

ETHICS AND DISSEMINATION

The study was approved by the Clinical Ethics Committee of Zhujiang Hospital of Southern Medical University (2018-ZZJHZX-009). The trial results will be disseminated at national and international conferences and through peer-reviewed journal.

TRIAL REGISTRATION

NCT03924518.URL: www.clinicaltrials.gov.

PROTOCOL DATE

1 May 2019. version 2.1.

The role of platelets in acute kidney injury

Acute kidney injury (AKI), a major public health problem associated with high mortality and increased risk of progression towards end-stage renal disease, is characterized by the activation of intra-renal haemostatic and inflammatory processes. Platelets, which are present in high numbers in the circulation and can rapidly release a broad spectrum of bioactive mediators, are important acute modulators of inflammation and haemostasis, as they are the first cells to arrive at sites of acute injury, where they interact with endothelial cells and leukocytes. Diminished control of platelet reactivity by endothelial cells and/or an increased release of platelet-activating mediators can lead to uncontrolled platelet activation in AKI. As increased platelet sequestration and increased expression levels of the markers P-selectin, thromboxane A₂, CC-chemokine ligand 5 and platelet factor 4 on platelets have been reported in kidneys following AKI, platelet activation likely plays a part in AKI pathology. Results from animal models and some clinical studies highlight the potential of antiplatelet therapies in the preservation of renal function in the context of AKI, but as current strategies also affect other cell types and non-platelet-derived mediators, additional studies are required to further elucidate the extent of platelet contribution to the pathology of AKI and to determine the best therapeutic approach by which to specifically target related pathogenic pathways.

Role of vimentin in modulating immune cell apoptosis and inflammatory responses in sepsis

New diagnostic biomarkers or therapeutic targets for sepsis have substantial significance for critical care medicine. In this study, 192 differentially expressed proteins were selected through iTRAQ. Based on cluster analysis of protein expression dynamics and protein-protein interactions, hemopexin, vimentin, and heat shock protein 90 were selected for further investigation. It was demonstrated that serum vimentin (VIM) levels were significantly increased in patients with sepsis and septic shock compared to controls and that VIM expression was significantly increased in lymphocytes isolated from septic shock and sepsis patients compared to controls. Moreover, a nonsurvivor group had higher serum VIM levels and VIM expression in lymphocytes. Caspase-3 was significantly upregulated in Jurkat T cells lacking VIM and when exposed to LPS compared to control cells. In contrast, caspase-3 was reduced nearly 40% in cells over-expressing VIM. IL-2, IL-10 and IFN-α levels were significantly decreased in cells lacking VIM compared to control cells, whereas they were not significantly altered in cells over-expressing VIM. These findings suggest that VIM modulates lymphocyte apoptosis and inflammatory responses and that VIM could be a new target for the diagnosis and prognostic prediction of patients with sepsis or septic shock.

Responses of Plasma Catecholamine, Serotonin, and the Platelet Serotonin Transporter to Cigarette Smoking

Cigarette smoking is one of the major causes of coronary heart disease with a thirty percent mortality rate in the United States. Cigarette smoking acting on the central nervous system (CNS) to stimulate the sympathetic nervous system (SNS) through, which facilitates the secretion of serotonin (5-HT) and catecholamines to supraphysiological levels in blood. The enhanced levels of 5-HT and catecholamines in smokers’ blood are associated with increases in G protein-coupled receptor signaling and serotonylation of small GTPases, which in turn lead to remodeling of cytoskeletal elements to enhance granule secretion and promote unique expression of sialylated N-glycan structures on smokers’ platelets. These mechanisms enhance aggregation and adhesion of smokers’ platelets relative to those of non-smokers. This review focuses on the known mechanisms by which 5-HT and SERT, in coordinated signaling with catecholamines, impacts cigarette smokers’ platelet biology.

Post-translational modifications of serotonin transporter

The serotonin transporter (SERT) is an oligomeric glycoprotein with two sialic acid residues on each of two complex oligosaccharide molecules. Studies using in vivo and in vitro model systems demonstrated that diverse post-translational modifications, including phosphorylation, glycosylation, serotonylation, and disulfide bond formation, all favorably influences SERT conformation and allows the transporter to function most efficiently. This review discusses the post-translational modifications and their importance on the structure, maturation, and serotonin (5-HT) uptake ability of SERT. Finally, we discuss how these modifications are altered in diabetes mellitus and subsequently impairs the 5-HT uptake ability of SERT.

Quantitative measurement of selected protein biomarkers of endothelial dysfunction in plasma by micro-liquid chromatography-tandem mass spectrometry based on stable isotope dilution method

The aim of this study was to develop and validate the novel microLC/MS-MRM method for the simultaneous quantification of six proteins: angiopoietin 2 (Angpt-2), soluble form of fms-like tyrosine kinase 1 (sFLT-1), plasminogen activator inhibitor 1 (PAI-1), tissue plasminogen activator (t-PA), endocan (ESM-1), soluble form of E-selectin (sE-sel), and one peptide: adrenomedullin (ADM) in mouse plasma. Two approaches were compared: a stable isotope dilution (SID) method- used as a reference and a modified SID (mSID) procedure. In SID strategy the calibration curves were used, whereas in mSID the ratio between the chromatogram peak area of endogenous tryptic peptides at unknown concentration to chromatogram peak area of exogenous, stable isotope-labelled internal standards (SISs) added to the sample at known concentration was calculated. The microLC/MS-MRM method in the SID approach was linear from 0.250 pmol/mL to 250 pmol/mL for Angpt-2; 5 pmol/mL to 5000 pmol/mL for sFLT-1; 2.5 pmol/mL to 5000 pmol/mL for PAI-1; 0.375 pmol/mL to 250 pmol/mL for t-PA; 0.375 pmol/mL to 187.5 pmol/mL for ESM-1; 2.5 pmol/mL to 5000 pmol/mL for sE-sel and 0.375 pmol/mL to 250 pmol/mL for ADM. LPS-induced changes in plasma assessed based on SID and mSID approaches gave comparable quantitative results and featured LPS-induced dysregulation of endothelial permeability (Angpt-2, sFLT-1), glycocalyx injury (SDC-1) accompanied by a pro-thrombotic response (PAI-1). In addition, we applied microLC/MS-MRM method with mSID strategy to analyze human plasma samples from patients with chronic myeloid leukemia (CML) and obstructive sleep apnoea (OSA) and demonstrated usefulness of the method to characterize endothelial function in humans. In conclusion, the microLC/MS-MRM method with mSID strategy applied for simultaneous quantification of protein biomarkers of endothelial function in plasma represents a novel targeted proteomic platform for the comprehensive evaluation of endothelial function in mice and humans.

Autocrine and paracrine regulatory functions of platelet serotonin

Platelets serotonin (5-hydroxytrytamine, 5-HT) uptake and storage in dense granules is tightly regulated by the serotonergic transport system in the blood. Several 5-HT transporters (5-HTTs) have been identified in the vasculature and blood cells, beyond them 5-HTT is the major 5-HT transporter in platelets. Abnormal 5-HT concentrations in the blood plasma or increased platelet 5-HT uptake or abnormal release contribute to the development of various diseases in the vasculature. Consequently, several clinical trials suggested the positive therapeutic effects of 5-HTT blockade in the circulation. Inhibition of 5-HT strongly attenuates autocrine and paracrine functions of platelets, influencing platelet aggregation, vascular contraction, permeability, tissue repair, wound healing, immunity and cancer. Here, we highlight the current state of basic biological research regarding the hemostatic and non-hemostatic functions of platelet-derived 5-HT in normal and disease conditions. We also describe the physiological consequences of targeting platelet 5-HT functions in thrombosis, stroke, inflammation and cancer to overcome common health problems.

Thymulin, free or bound to PBCA nanoparticles, protects mice against chronic septic inflammation

In the present work, we aimed to study the effects of free and polybutylcyanoacrylate nanoparticle-bound thymulin on immune cell activity in mice with chronic inflammation. NF-κB, MAPK, and PKC-θ signaling pathway activity was assessed, alongside Hsp72, Hsp90-α, and TLR4 expression and levels of apoptosis. In addition, plasma cytokines and blood and brain melatonin and serotonin levels were measured. In mice treated with gradually raised doses of lipopolysaccharide, significant increases in the activity of the signaling pathways tested, heat-shock protein and TLR4 expression, lymphocyte apoptosis, and plasma proinflammatory cytokine levels were noted. Moreover, we observed significantly heightened serotonin concentrations in the plasma and especially the brains of mice with inflammation. In contrast, melatonin levels were reduced in the tissues examined, particularly so in the brain. Treatment of these mice with thymulin alleviated fever, reduced apoptosis, increased splenic cell number, and decreased cytokine production, Hsp72, Hsp90, and TLR4 expression, and the activity of the signaling pathways examined. In addition, thymulin partially restored brain and blood serotonin and melatonin levels. Thus, thymulin suppressed the proinflammatory response in LPS-treated mice, indicating the potential of thymulin co-therapy in the treatment of sepsis. Nanoparticle-bound thymulin was more effective in several respects.

Platelets release pathogenic serotonin and return to circulation after immune complex-mediated sequestration

There is a growing appreciation for the contribution of platelets to immunity; however, our knowledge mostly relies on platelet functions associated with vascular injury and the prevention of bleeding. Circulating immune complexes (ICs) contribute to both chronic and acute inflammation in a multitude of clinical conditions. Herein, we scrutinized platelet responses to systemic ICs in the absence of tissue and endothelial wall injury. Platelet activation by circulating ICs through a mechanism requiring expression of platelet Fcγ receptor IIA resulted in the induction of systemic shock. IC-driven shock was dependent on release of serotonin from platelet-dense granules secondary to platelet outside-in signaling by αIIbβ3 and its ligand fibrinogen. While activated platelets sequestered in the lungs and leaky vasculature of the blood-brain barrier, platelets also sequestered in the absence of shock in mice lacking peripheral serotonin. Unexpectedly, platelets returned to the blood circulation with emptied granules and were thereby ineffective at promoting subsequent systemic shock, although they still underwent sequestration. We propose that in response to circulating ICs, platelets are a crucial mediator of the inflammatory response highly relevant to sepsis, viremia, and anaphylaxis. In addition, platelets recirculate after degranulation and sequestration, demonstrating that in adaptive immunity implicating antibody responses, activated platelets are longer lived than anticipated and may explain platelet count fluctuations in IC-driven diseases.

The role of metabolomic markers for patients with infectious diseases: implications for risk stratification and therapeutic modulation

INTRODUCTION

Metabolomics is a rapidly growing area of research. Metabolomic markers can provide information about the interaction of different organ systems, and thereby improve the understanding of physio-pathological processes, disease risk, prognosis and therapy responsiveness in a variety of diseases. Areas covered: In this narrative review of recent clinical studies investigating metabolomic markers in adult patients presenting with acute infectious disease, we mainly focused on patients with sepsis and lower respiratory tract infections. Currently, there is a growing body of literature showing that single metabolites from distinct metabolic pathways, as well as more complex metabolomic signatures are associated with disease severity and outcome in patients with systemic infections. These pathways include, among others, metabolomic markers of oxidative stress, steroid hormone and amino acid pathways, and nutritional markers. Expert commentary: Metabolic profiling has great potential to optimize patient management, to provide new targets for individual therapy and thereby improve survival of patients. At this stage, research mainly focused on the identification of new predictive signatures and less on metabolic determinants to predict treatment response. The transition from observational studies to implementation of novel markers into clinical practice is the next crucial step to prove the usefulness of metabolomic markers in patient care.

Clinical implications of the plasma EphA2 receptor level in critically ill patients with septic shock

The Eph/ephrin receptor ligand system is known to play a role in inflammation induced by infection, injury, and inflammatory diseases. The present study aimed to evaluate plasma EphA2 receptor levels in critically ill patients with sepsis. This study was a prospective cohort study evaluating samples and clinical data from the medical intensive care unit (MICU) of a 2000-bed university tertiary referral hospital in South Korea. Positive correlations of the plasma EphA2 receptor level with the acute physiology and chronic health evaluation (APACHE) II score and the sequential organ failure assessment (SOFA) score were observed. The area under the curve (AUC) for the plasma EphA2 receptor level on a receiver operating characteristic curve was 0.690 (95% confidence interval [CI], 0.608-0.764); the AUCs for the APACHE II score and SOFA scores were 0.659 (95% CI, 0.576-0.736) and 0.745 (95% CI, 0.666-0.814), respectively. A Cox proportional hazard model identified an association between an increased plasma EphA2 receptor level (>51.5 pg mL-1) and increased risk of 28-day mortality in the MICU (hazard ratio = 3.22, 95% CI, 1.709-6.049). An increased plasma EphA2 receptor level was associated with sepsis severity and 28-day mortality among sepsis patients.

Peripheral serotonin regulates postoperative intra-abdominal adhesion formation in mice

The aim of the present study is to investigate the role and potential mechanisms of peripheral serotonin in postoperative intra-abdominal adhesion formation in mice. The caecum-rubbing operations were conducted for intra-abdominal adhesion formation modelling in wild-type and Tph1−/− mice. The deficiency of serotonin significantly decreased the adhesion scores, weight loss, and adhesion thickness as well as levels of collagen fibres and hydroxyproline in the adhesive tissues. The Tph1−/− mice exhibited a milder inflammatory response and oxidative stress in the adhesive tissues than did the wild-type mice. Moreover, the deficiency of serotonin reduced the levels of PAI-1 and fibrinogen, and raised the t-PA and t-PA/PAI levels in the peritoneal fluids. Moreover, the expressions of CD34, VEGF, TGF-β and 5-HT_2B receptor in the adhesive tissues were significantly decreased in the Tph1−/− group mice. Furthermore, the Tph1−/− +5-HTP group showed more severe adhesions than did the Tph1−/− group mice, and the p-chlorophenylalanine (PCPA) could markedly alleviated the adhesion formation in the WT mice. In conclusion, the present study showed that peripheral serotonin regulated postoperative intra-abdominal adhesion formation by facilitating inflammation, oxidative stress, disorder of the fibrinolytic system, angiopoiesis and TGF-β1 expression via the 5-HT_2B receptor in the adhesive tissues.

DT-13 Ameliorates TNF-α-Induced Vascular Endothelial Hyperpermeability via Non-Muscle Myosin IIA and the Src/PI3K/Akt Signaling Pathway

DT-13(25(R,S)-ruscogenin-1-O-[β-d-glucopyranosyl-(1→2)][β-d-xylopyranosyl-(1→3)]-β-d-fucopyranoside) has been identified as an important factor in TNF-α-induced vascular inflammation. However, the effect of DT-13 on TNF-α-induced endothelial permeability and the potential molecular mechanisms remain unclear. Hence, this study was undertaken to elucidate the protective effect of DT-13 on TNF-α-induced endothelial permeability and the underlying mechanisms in vivo and in vitro. The in vivo results showed that DT-13 could ameliorate endothelial permeability in mustard oil-induced plasma leakage in the skin and modulate ZO-1 organization. In addition, the in vitro results showed that pretreatment with DT-13 could increase the transendothelial electrical resistance value and decrease the sodium fluorescein permeability coefficient. Moreover, DT-13 altered the mRNA and protein levels of ZO-1 as determined by real-time PCR, Western blotting, and immunofluorescence analyses. DT-13 treatment decreased the phosphorylations of Src, PI3K, and Akt in TNF-α-treated human umbilical vein endothelial cells (HUVECs). Further analyses with PP2 (10 µM, inhibitor of Src) indicated that DT-13 modulated endothelial permeability in TNF-α-induced HUVECs in an Src-dependent manner. LY294002 (10 µM, PI3K inhibitor) also had the same effect on DT-13 but did not affect phosphorylation of Src. Following decreased expression of non-muscle myosin IIA (NMIIA), the effect of DT-13 on the phosphorylations of Src, PI3K, and Akt was abolished. This study provides pharmacological evidence showing that DT-13 significantly ameliorated the TNF-α-induced vascular endothelial hyperpermeability through modulation of the Src/PI3K/Akt pathway and NMIIA, which play an important role in this process.

Activation of the tryptophan/serotonin pathway is associated with severity and predicts outcomes in pneumonia: results of a long-term cohort study

BACKGROUND

As part of the immune defense during infection, an increase in enzyme activity of indoleamine 2,3-dioxygenase (IDO) leads to a breakdown of tryptophan to kynurenine. In previous animal studies, therapeutic antagonism of IDO resulted in reduced sepsis mortality. We investigated the prognostic ability of tryptophan, serotonin, kynurenine and IDO (represented by the ratio of kynurenine/tryptophan) to predict adverse clinical outcomes in patients with community-acquired pneumonia (CAP).

METHODS

We measured tryptophan, serotonin and kynurenine on admission plasma samples from CAP patients included in a previous multicenter trial by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We studied their association with inflammation (C-reactive protein), infection (procalcitonin) and clinical outcome.

RESULTS

Mortality in the 268 included patients was 45% within 6 years of follow-up. IDO and kynurenine showed a strong positive correlation with markers of infection (procalcitonin) and inflammation (C-reactive protein) as well as sepsis and CAP severity scores. Tryptophan showed similar, but negative correlations. In a multivariate regression analysis adjusted for age and comorbidities, higher IDO activity and lower tryptophan levels were strongly associated with short-term adverse outcome defined as death and/or ICU admission within 30 days with adjusted odds ratios of 9.1 [95% confidence interval (CI) 1.4-59.5, p=0.021] and 0.11 (95% CI 0.02-0.70, p=0.021). Multivariate analysis did not reveal significant associations for kynurenine and serotonin.

CONCLUSIONS

In hospitalized CAP patients, higher IDO activity and lower tryptophan levels independently predicted disease severity and short-term adverse outcome. Whether therapeutic modulation of IDO has positive effects on outcome needs further investigation.

Circulating levels of the angiogenesis mediators endoglin, HB-EGF, BMP-9 and FGF-2 in patients with severe sepsis and septic shock

PURPOSE

Endothelial barrier dysfunction is a hallmark of sepsis, and is at least partially mediated by pathways that regulate endothelial barrier assembly during angiogenesis. Not surprisingly, increased levels of key angiogenic proteins such as VEGF-A and Angiopoietin-2 have been described in sepsis. The purpose of this study was to investigate if additional pathways that regulate endothelial barrier integrity during angiogenesis could also be involved in the host response of sepsis.

MATERIAL AND METHODS

We evaluated circulating levels of four proteins involved in angiogenesis, not previously studied in sepsis, in a cohort of 50 patients with severe sepsis and septic shock.

RESULTS

Circulating levels of BMP-9 and FGF-2 were similar in patients and healthy volunteers. In contrast, patients with septic shock presented 1.5-fold higher levels of endoglin (P=0.004), and 2-fold lower levels of Heparin-Binding EGF-like growth factor (HB-EGF) (P=0.002) when compared to healthy individuals. Of note, HB-EGF deficiency has been recently demonstrated to be detrimental to survival in a murine model of sepsis.

CONCLUSIONS

Endoglin and HB-EGF could be involved in the host response of sepsis. Additional studies are warrant to investigate their role as biomarker or therapeutic targets in sepsis.

Systemic blockade of P2X7 receptor protects against sepsis-induced intestinal barrier disruption

Sepsis, during which the intestinal epithelial barrier is frequently disrupted, remains a challenging and life-threatening problem in clinical practice. The P2X7 receptor (P2X7R) is a non-selective adenosine triphosphate-gated cation channel present in macrophages that is involved in inflammatory responses. However, little is known about the role of P2X7R in macrophages during sepsis-induced intestinal barrier disruption. In this study, mice were treated with the P2X7R antagonist A740003 or the agonist BzATP by intra-peritoneal injection after the induction of gut-origin sepsis. The survival rates, inflammatory responses, intestinal barrier integrity, macrophage marker expression, and ERK and NF-κB activities were evaluated. Intestinal macrophages were also isolated and studied after exposure to Brilliant Blue G or BzATP. We found that a systemic P2X7R blockade downregulated sepsis-induced inflammatory responses and attenuated intestinal barrier dysfunction based on the evidence that mice in the A740003-treated group exhibited alleviated pro-inflammatory cytokine synthesis, intestinal hyperpermeability, epithelial apoptosis rates and tight junction damage compared with the septic mice. These changes were partly mediated by the inhibition of M1 macrophages activation via ERK/NF-κB pathways. Our data presented herein show that a P2X7R blockade could be a potential therapeutic target for the treatment of sepsis-induced intestinal barrier dysfunction.

5-HT Drives Mortality in Sepsis Induced by Cecal Ligation and Puncture in Mice

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection with a high mortality. 5-Hydroxytryptamine (5-HT) is an important regulatory factor in inflammation. The aim of this study is to investigate the role of 5-HT on cecal ligation and puncture- (CLP-) induced sepsis in the mouse model. CLP was performed on C57B/6 wild-type (WT) mice and tryptophan hydroxylase 1 (TPH1) knockout (KO) mice. The results showed that the 5-HT-sufficient group mice had a significantly lower survival rate than the 5-HT-deficient group in CLP-induced sepsis and septic shock. The KO-CLP sepsis group received a lower clinical score than the WT-CLP sepsis group. Meanwhile, the body temperature of mice in the KO-CLP sepsis group was higher than that in the WT-CLP sepsis group and was much closer to the normal body temperature 24 hours after CLP. The tissue histopathology analysis revealed that 5-HT markedly exacerbated histological damages in the peritoneum, lung, liver, kidney, intestinal tissue, and heart in sepsis. Moreover, significant lower levels of TNF-α, IL-6, bacterial loads, MPO, and ROS were discovered in the KO-CLP sepsis group in contrast to the WT-CLP sepsis group. In conclusion, 5-HT drives mortality and exacerbates organ dysfunction by promoting serum cytokines and bacterial loads as well as facilitating oxidative stress in the process of sepsis.

Cigarette Smoking-Associated Alterations in Serotonin/Adrenalin Signaling Pathways of Platelets

Background

Cigarette smoking plays a major role in cardiovascular diseases. The acute effects of cigarette smoking produce central nervous system–mediated activation of the sympathetic nervous system. The overactive sympathetic nervous system stimulates the secretion of serotonin (5‐HT) and catecholamine into blood at supraphysiological levels. The correlation between these pathological conditions induced by smoking and the increased risk of thrombosis has not been thoroughly investigated. The goal of our study was to explore cigarette smoking–associated changes in platelet biology mediated by elevated 5‐HT and catecholamine levels in blood plasma.

Methods and Results

Using blood samples collected from healthy nonsmokers and smokers (15 minutes after smoking), we determined that cigarette smoking increased the plasma 5‐HT/catecholamine concentration by several fold and the percent aggregation of platelets 2‐fold. Liquid chromatography–tandem mass spectrometry analysis of proteins eluted from platelet plasma membranes of smokers and nonsmokers demonstrated that GTPase‐activating proteins and proteins participating in the actin cytoskeletal network were differentially and significantly elevated in smokers' platelet membranes compared with those of nonsmokers. Interestingly, Matrix‐assisted laser desorption/ionization–mass spectrometry analyses of the glycans eluted from platelet plasma membranes of the smokers demonstrated that the level and structures of glycans are different from the nonsmokers' platelet surface glycans. Pharmacological blockade of 5‐HT or catecholamine receptors counteracted the 5‐HT/catecholamine‐mediated aggregation and altered the level and composition of glycan on platelet surfaces.

Conclusions

Based on our findings, we propose that smoking‐associated 5‐HT/catecholamine signaling accelerates the trafficking dynamics of platelets, and this remodels the surface proteins and glycans and predisposes platelets to hyperactive levels. Smokers' platelets also had correspondingly higher resting concentrations of intracellular calcium and transglutaminase activity. These findings suggest a link among smoking, platelet 5‐HT, catecholamine signaling, and their downstream effectors—including phospholipase C and inositol‐1,4,5‐triphosphate pathways—resulting in an increased tonic level of platelet activation in smokers.

Activation of the Serotonin Pathway is Associated with Poor Outcome in COPD Exacerbation: Results of a Long-Term Cohort Study

BACKGROUND/INTRODUCTION

Indoleamine 2,3-dioxygenase (IDO) metabolizes tryptophan to kynurenine. An increase of its activity is associated with severity in patients with pneumonia. In chronic obstructive pulmonary disease (COPD) patients, an elevation of serotonin has been reported. Experimental models showed that cigarette smoke inhibits monoamine oxidase (MAO) leading to higher levels of serotonin. We investigated the prognostic ability of tryptophan, serotonin, kynurenine, IDO, and tryptophan hydroxylase (TPH) to predict short- and long-term outcomes in patients with a COPD exacerbation.

METHODS

We measured tryptophan, serotonin, and kynurenine on admission plasma samples in patients with a COPD exacerbation from a previous trial by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). IDO and TPH were calculated as ratios of kynurenine over tryptophan, and serotonin over tryptophan, respectively. We studied their association with parameters measured in clinical routine at emergency department admission representing inflammation (C-reactive protein [CRP]), infection (procalcitonin [PCT]), oxygenation (SpO₂), as well as patients' clinical outcome, confirmed by structured phone interviews.

RESULTS

Mortality in the 149 included patients was 53.7% within six years of follow-up. While IDO activity showed strong positive correlations, tryptophan was negatively correlated with CRP and PCT. For 30-day adverse outcome defined as death and/or intensive care unit (ICU) admission, a multivariate regression analysis adjusted for age and comorbidities found strong associations for IDO activity (adjusted odds ratios of 31.4 (95%CI 1.1-857), p = 0.041) and TPH (adjusted odds ratios 27.0 (95%CI 2.2-327), p = 0.010). TPH also showed a significant association with mortality at 18 months, (hazard ratio 2.61 (95%CI 1.2-5.8), p = 0.020).

CONCLUSION

In hospitalized patients with a COPD exacerbation, higher IDO and TPH activities independently predicted adverse short-term outcomes and TPH levels were also predictive of 18-month mortality. Whether therapeutic modulation of the serotonin pathway has positive effects on outcome needs further investigation.

Serotonin transporter protects the placental cells against apoptosis in caspase 3-independent pathway

Serotonin (5-HT) and its specific transporter, SERT play important roles in pregnancy. Using placentas dissected from 18d gestational SERT-knock out (KO), peripheral 5-HT (TPH1)-KO, and wild-type (WT) mice, we explored the role of 5-HT and SERT in placental functions in detail. An abnormal thick band of fibrosis and necrosis under the giant cell layer in SERT-KO placentas appeared only moderately in TPH1-KO and minimally present in WT placentas. The majority of the changes were located at the junctional zone of the placentas in SERT. The etiology of these findings was tested with TUNEL assays. The placentas from SERT-KO and TPH1-KO showed 49- and 8-fold increase in TUNEL-positive cells without a concurrent change in the DNA repair or cell proliferation compared to WT placentas. While the proliferation rate in the embryos of TPH1-KO mice was 16-fold lower than the rate in gestational age matched embryos of WT or SERT-KO mice. These findings highlight an important role of continuous 5-HT signaling on trophoblast cell viability. SERT may contribute to protecting trophoblast cells against cell death via terminating the 5-HT signaling which changes cell death ratio in trophoblast as well as proliferation rate in embryos. However, the cell death in SERT-KO placentas is in caspase 3-independent pathway.

Endothelial Response to Glucocorticoids in Inflammatory Diseases

The endothelium plays a crucial role in inflammation. A balanced control of inflammation requires the action of glucocorticoids (GCs), steroidal hormones with potent cell-specific anti-inflammatory properties. Besides the classic anti-inflammatory effects of GCs on leukocytes, recent studies confirm that endothelial cells also represent an important target for GCs. GCs regulate different aspects of endothelial physiology including expression of adhesion molecules, production of pro-inflammatory cytokines and chemokines, and maintenance of endothelial barrier integrity. However, the regulation of endothelial GC sensitivity remains incompletely understood. In this review, we specifically examine the endothelial response to GCs in various inflammatory diseases ranging from multiple sclerosis, stroke, sepsis, and vasculitis to atherosclerosis. Shedding more light on the cross talk between GCs and endothelium will help to improve existing therapeutic strategies and develop new therapies better tailored to the needs of patients.