Lipopolysaccharide (LPS)-binding protein and soluble CD14 function as accessory molecules for LPS-induced changes in endothelial barrier function, in vitro

Spatial Mass Cytometry-Based Single-Cell Imaging Reveals a Disrupted Epithelial-Immune Axis in Prurigo Nodularis

Prurigo nodularis (PN) is a chronic, inflammatory skin condition that disproportionately affects African Americans and features intensely pruritic, hyperkeratotic nodules on the extremities and trunk. PN is understudied compared with other inflammatory skin diseases, with the spatial organization of the cutaneous infiltrate in PN yet to be characterized. In this work, we employ spatial imaging mass cytometry to visualize PN lesional skin inflammation and architecture with single-cell resolution through an unbiased machine learning approach. PN lesional skin has increased expression of caspase 3, NF-kB, and phosphorylated signal transducer and activator of transcription 3 compared with healthy skin. Keratinocytes in lesional skin are subdivided into CD14+CD33+, CD11c+, CD63+, and caspase 3-positive innate subpopulations. CD14+ macrophage populations expressing phosphorylated extracellular signal-regulated kinase 1/2 correlate positively with patient-reported itch (P = .006). Hierarchical clustering reveals a cluster of patients with PN with greater atopy, increased NF-kB+ signal transducer and activator of transcription 3-positive phosphorylated extracellular signal-regulated kinase 1/2-positive monocyte-derived myeloid dendritic cells, and increased vimentin expression (P < .05). Neighborhood analysis finds interactions between CD14+ macrophages, CD3+ T cells, monocyte-derived myeloid dendritic cells, and keratinocytes expressing innate immune markers. These findings highlight phosphorylated extracellular signal-regulated kinase-positive CD14+ macrophages as contributors to itch and suggest an epithelial-immune axis in PN pathogenesis.

Inhibitory effects of aloin on lipopolysaccharide-induced severe inflammatory responses

Aloin is the main anthraquinone glycoside from Aloe species. Here, the anti-inflammatory functions of aloin against lipopolysaccharide (LPS)-induced vascular inflammatory responses were tested in endothelial cells or mice such as permeability, expressions of cell adhesion molecule (CAM), migration of leukocytes and lethality. Aloin was found to inhibit LPS-induced barrier disruption, CAM expression, and neutrophil adhesion/transendothelial migration to endothelial cells. Furthermore, aloin inhibited LPS-induced hyperpermeability, leukocyte migration, lethality in vivo. These results suggest that aloin has anti-inflammatory activities against LPS, thereby supporting its usefulness as a treatment for vascular inflammatory.

Gut microbiome alterations and gut barrier dysfunction are associated with host immune homeostasis in COVID-19 patients

BACKGROUND

COVID-19 is an infectious disease characterized by multiple respiratory and extrapulmonary manifestations, including gastrointestinal symptoms. Although recent studies have linked gut microbiota to infectious diseases such as influenza, little is known about the role of the gut microbiota in COVID-19 pathophysiology.

METHODS

To better understand the host-gut microbiota interactions in COVID-19, we characterized the gut microbial community and gut barrier function using metagenomic and metaproteomic approaches in 63 COVID-19 patients and 8 non-infected controls. Both immunohematological parameters and transcriptional profiles were measured to reflect the immune response in COVID-19 patients.

RESULTS

Altered gut microbial composition was observed in COVID-19 patients, which was characterized by decreased commensal species and increased opportunistic pathogenic species. Severe illness was associated with higher abundance of four microbial species (i.e., Burkholderia contaminans, Bacteroides nordii, Bifidobacterium longum, and Blautia sp. CAG 257), six microbial pathways (e.g., glycolysis and fermentation), and 10 virulence genes. These severity-related microbial features were further associated with host immune response. For example, the abundance of Bu. contaminans was associated with higher levels of inflammation biomarkers and lower levels of immune cells. Furthermore, human-origin proteins identified from both blood and fecal samples suggested gut barrier dysfunction in COVID-19 patients. The circulating levels of lipopolysaccharide-binding protein increased in patients with severe illness and were associated with circulating inflammation biomarkers and immune cells. Besides, proteins of disease-related bacteria (e.g., B. longum) were detectable in blood samples from patients.

CONCLUSIONS

Our results suggest that the dysbiosis of the gut microbiome and the dysfunction of the gut barrier might play a role in the pathophysiology of COVID-19 by affecting host immune homeostasis.

Endothelial Senescence and Chronic Fatigue Syndrome, a COVID-19 Based Hypothesis

Myalgic encephalomyelitis/chronic fatigue syndrome is a serious illness of unknown etiology, characterized by debilitating exhaustion, memory impairment, pain and sleep abnormalities. Viral infections are believed to initiate the pathogenesis of this syndrome although the definite proof remains elusive. With the unfolding of COVID-19 pandemic, the interest in this condition has resurfaced as excessive tiredness, a major complaint of patients infected with the SARS-CoV-2 virus, often lingers for a long time, resulting in disability, and poor life quality. In a previous article, we hypothesized that COVID-19-upregulated angiotensin II triggered premature endothelial cell senescence, disrupting the intestinal and blood brain barriers. Here, we hypothesize further that post-viral sequelae, including myalgic encephalomyelitis/chronic fatigue syndrome, are promoted by the gut microbes or toxin translocation from the gastrointestinal tract into other tissues, including the brain. This model is supported by the SARS-CoV-2 interaction with host proteins and bacterial lipopolysaccharide. Conversely, targeting microbial translocation and cellular senescence may ameliorate the symptoms of this disabling illness.

Protective Effect of Tetrahydroquinolines from the Edible Insect Allomyrina dichotoma on LPS-Induced Vascular Inflammatory Responses

The larva of Allomyrina dichotoma (family Scarabaeidae) is an edible insect that is registered in the Korean Food Standards Codex as a food resource. The chemical study on the larvae of A. dichotoma resulted in the isolation of three new tetrahydroquinolines, allomyrinaines A-C (1-3), one new dopamine derivative, allomyrinamide A (4), and four known compounds (5-8). The structures were elucidated on the basis of 1D and 2D nuclear magnetic resonance (NMR) and MS spectroscopic data analysis. Allomyrinaines A-C (1-3) possessed three stereogenic centers at C-2, C-3, and C-4, whose relative configurations were determined by analyses of the coupling constants and the nuclear Overhauser enhancement spectroscopy (NOESY) data, as well as DP4+ calculation. The anti-inflammatory effects of compounds 1-4 were evaluated in human endothelial cells. Allomyrinaines A-C (1-3) could stabilize vascular barrier integrity on lipopolysaccharide (LPS)-induced vascular inflammation via inhibition of the nuclear factor-κB (NF-κB) pathway. The physiologically relevant concentration was confirmed by Q-TOF-MS-based quantitative analysis on allomyrinaines A-C in crude extract. This study suggests that allomyrinaines A-C (1-3) are bioactive constituents of A. dichotoma to treat vascular inflammatory disorder.

Genetic inactivation of the phospholipase A2 activity of peroxiredoxin 6 in mice protects against LPS-induced acute lung injury

Peroxiredoxin 6 (Prdx6) is a multifunctional enzyme that serves important antioxidant roles by scavenging hydroperoxides and reducing peroxidized cell membranes. Prdx6 also plays a key role in cell signaling by activating the NADPH oxidase, type 2 (Nox2) through its acidic Ca2+-independent phospholipase A2 (aiPLA2) activity. Nox2 generation of O2·-, in addition to signaling, can contribute to oxidative stress and inflammation such as during sepsis-induced acute lung injury (ALI). To evaluate a possible role of Prdx6-aiPLA2 activity in the pathophysiology of ALI associated with a systemic insult, wild-type (WT) and Prdx6-D140A mice, which lack aiPLA2 but retain peroxidase activity were administered intraperitoneal LPS. LPS-treated mutant mice had increased survival compared with WT mice while cytokines in lung lavage fluid and lung VCAM-1 expression, nitrotyrosine levels, PMN infiltration, and permeability increased in WT but not in mutant mice. Exposure of mouse pulmonary microvascular endothelial cells in primary culture to LPS promoted phosphorylation of Prdx6 and its translocation to the plasma membrane and increased aiPLA2 activity as well as increased H2O2 generation, nitrotyrosine levels, lipid peroxidation, NF-κB nuclear localization, and nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3) inflammasome assembly; these effects were not seen in Nox2 null cells, Prdx6-D140A cells, or WT cells pretreated with MJ33, an inhibitor of aiPLA2 activity. Thus aiPLA2 activity is needed for Nox2-derived oxidant stress associated with LPS exposure. Since inactivation of aiPLA2 reduced mortality and prevented lung inflammation and oxidative stress in this animal model, the aiPLA2 activity of Prdx6 could be a novel target for prevention or treatment of sepsis-induced ALI.

Inhibitory Effect of Pelargonidin on Secretory Group IIA Phospholipase A2

The expression of secretory group IIA phospholipase A2 (sPLA2-IIA) has been shown to be elevated in various inflammatory diseases, and lipopolysaccharide (LPS) up-regulates the expression of sPLA2-IIA in human umbilical vein endothelial cells (HUVECs). Pelargonidin (PEL) is a well-known red pigment found in plants, and has been reported as having important biological activities that are potentially beneficial for human health. Here, PEL was examined for its effects on the expression and activity of sPLA2-IIA in HUVECs and mouse. Post treatment of cells or mouse with PEL inhibited LPS-induced expression and activity of sPLA2-IIA. Therefore, these results suggest that PEL inhibited LPS mediated expression of sPLA2-IIA.

Anti-inflammatory effects of dabrafenib in vitro and in vivo

The screening of bioactive compound libraries can be an effective approach for repositioning FDA-approved drugs or discovering new treatments for human diseases (drug repositioning). Drug repositioning refers to the development of existing drugs for new indications. Dabrafenib (DAB) is a B-Raf inhibitor and initially used for the treatment of metastatic melanoma therapy. Here, we tested the possible use of DAB in the treatment of lipopolysaccharide (LPS)-mediated vascular inflammatory responses. The anti-inflammatory activities of DAB were determined by measuring permeability, neutrophils adhesion and migration, and activation of pro-inflammatory proteins in LPS-activated human umbilical vein endothelial cells (HUVECs) and mice. We found that DAB inhibited LPS-induced barrier disruption, expression of cell adhesion molecules (CAMs), and adhesion and transendothelial migration of neutrophils to human endothelial cells. DAB also suppressed LPS-induced hyperpermeability and leukocytes migration in vivo. Furthermore, DAB suppressed the production of tumor necrosis factor-α (TNF-α) or interleukin (IL)-6 and the activation of nuclear factor-κB (NF-κB) or extracellular regulated kinases (ERK) 1/2 by LPS. Moreover, treatment with DAB resulted in reduced LPS-induced lethal endotoxemia. These results suggest that DAB possesses anti-inflammatory functions by inhibiting hyperpermeability, expression of CAMs, and adhesion and migration of leukocytes, thereby endorsing its usefulness as a therapy for vascular inflammatory diseases.

Inhibitory Effect of Zingerone on Secretory Group IIA Phospholipase A2

The expression of secretory group IIA phospholipase A2 (sPLA2-IIA) has been shown to be elevated in various inflammatory diseases, and lipopolysaccharide (LPS) up-regulates the expression of sPLA2-IIA in human umbilical vein endothelial cells (HUVECs). Zingerone (ZGR), a phenolic alkanone isolated from ginger, has been reported to have various pharmacological activities. Here, we examined the effects of ZRG on the expression and activity of sPLA2-IIA in LPS-activated HUVECs and in mouse models of endotoxemia and sepsis. Treatment of cells or mice with ZRG inhibited LPS-induced expression and activity of sPLA2-IIA. In addition, ZRG suppressed LPS-mediated activation of cytosolic phospholipase A2 (cPLA2) and extracellular signal-regulated kinase (ERK) 1/2. These results suggest that ZRG inhibits LPS-mediated activation of sPLA2-IIA expression by suppressing cPLA2 and ERK 1/2.

Three diketopiperazines from marine-derived bacteria inhibit LPS-induced endothelial inflammatory responses

Diketopiperazine is a natural products found from bacteria, fungi, marine sponges, gorgonian and red algae. They are cyclic dipeptides possessing relatively simple and rigid structures with chiral nature and various side chains. Endothelial dysfunction is a key pathological feature of many inflammatory diseases, including sepsis. In the present study, three (1-3) of diketopiperazines were isolated from two strains of marine-derived bacteria. The compounds were investigated for their effects against lipopolysaccharide (LPS)-mediated endothelial inflammatory responses in vitro and in vivo. From 1 μM, 1-3 inhibited LPS-induced hyperpermeability, adhesion, and migration of leukocytes across a human endothelial cell monolayer and in mice in a dose-dependent manner suggesting that 1-3 may serve as potential scaffolds for the development of therapeutic agents to treat vascular inflammatory disorders.

Inhibitory Effect of FXa on Secretory Group IIA Phospholipase A2

It is well known that the expression level of secretory group IIA phospholipase A2 (sPLA2-IIA) is elevated in inflammatory diseases and lipopolysaccharide (LPS) upregulates the expression of sPLA2-IIA in human umbilical vein endothelial cells (HUVECs). Activated factor X (FXa) is an important enzyme in the coagulation cascade responsible for thrombin generation, and it influences cell signaling in various cell types by activating protease-activated receptors (PARs). Here, FX or FXa was examined for its effects on the expression and activity of sPLA2-IIA in HUVECs and mouse. Prior treatment of cells or mouse with FXa inhibited LPS-induced expression and activity of sPLA2-IIA via interacting with FXa receptor (effective cell protease receptor-1, EPR-1). And FXa suppressed the activation of cytosolic phospholipase A2 (cPLA2) and extracellular signal-regulated kinase (ERK) 1/2 by LPS. Therefore, these results suggest that FXa may inhibit LPS-mediated expression of sPLA2-IIA by suppression of cPLA2 and ERK 1/2.

Inhibitory effect of polyozellin on secretory group IIA phospholipase A2

The expression of secretory group IIA phospholipase A2 (sPLA2-IIA) is enhanced by development of inflammatory disorders. In this study, sPLA2-IIA expression was induced in the lipopolysaccharide (LPS)-stimulated human umbilical vein endothelial cells and mice to evaluate the effect of polyozellin. Polyozellin, a major constituent of a Korea edible mushroom Polyozellus multiplex, has been known to exhibit the biological activities such as anti-oxidative and anti-inflammatory effects. Polyozellin remarkably suppressed the LPS-mediated protein expression and activity of sPLA2-IIA via inhibition of phosphorylation of cytosolic phospholipase A2 and extracellular signal-regulated kinase 1/2. These results demonstrated that polyozellin might play an important role in the modulation of sPLA2-IIA expression and activity in response to the inflammatory diseases.

Anti-inflammatory effects of Baicalin, Baicalein, and Wogonin in vitro and in vivo

Here, three structurally related polyphenols found in the Chinese herb Huang Qui, namely baicalin, baicalein, and wogonin, were examined for its effects on inflammatory responses by monitoring the effects of baicalin, baicalein, and wogonin on lipopolysaccharide (LPS)-mediated vascular inflammatory responses. We found that each compound inhibited LPS-induced barrier disruption, expression of cell adhesion molecules (CAMs), and adhesion/transendothelial migration of monocytes to human endothelial cells. Each compound induced potent inhibition of phorbol-12-myristate 13-acetate and LPS-induced endothelial cell protein C receptor shedding. It also suppressed LPS-induced hyperpermeability and leukocytes migration in vivo. Furthermore, each compound suppressed the production of tumor necrosis factor-α or interleukin-6 and the activation of nuclear factor-κB or extracellular regulated kinases 1/2 by LPS. Moreover, treatment with each compound resulted in reduced LPS-induced lethal endotoxemia. These results suggest that baicalin, baicalein, and wogonin posses anti-inflammatory functions by inhibiting hyperpermeability, expression of CAMs, and adhesion and migration of leukocytes, thereby endorsing its usefulness as a therapy for vascular inflammatory diseases.

Novel insight into drug repositioning: Methylthiouracil as a case in point

Drug repositioning refers to the development of existing drugs for new indications. These drugs may have (I) failed to show efficacy in late stage clinical trials without safety issues; (II) stalled in the development for commercial reasons; (III) passed the point of patent expiry; or (IV) are being explored in new geographic markets. Over the past decade, pressure on the pharmaceutical industry caused by the 'innovation gap' owing to rising development costs and stagnant product output have become major reasons for the growing interest in drug repositioning. Companies that offer a variety of broad platforms for identifying new indications have emerged; some have been successful in building their own pipelines of candidates with reduced risks and timelines associated with further clinical development. The business models and platforms offered by these companies will be validated if they are able to generate positive proof-of-concept clinical data for their repositioned compounds. This review describes the strategy of biomarker-guided repositioning of chemotherapeutic drugs for inflammation therapy, considering the repositioning of methylthiouracil (MTU), an antithyroid drug, as a potential anti-inflammatory reagent.

Nox2-dependent glutathionylation of endothelial NOS leads to uncoupled superoxide production and endothelial barrier dysfunction in acute lung injury

Microvascular barrier integrity is dependent on bioavailable nitric oxide (NO) produced locally by endothelial NO synthase (eNOS). Under conditions of limited substrate or cofactor availability or by enzymatic modification, eNOS may become uncoupled, producing superoxide in lieu of NO. This study was designed to investigate how eNOS-dependent superoxide production contributes to endothelial barrier dysfunction in inflammatory lung injury and its regulation. C57BL/6J mice were challenged with intratracheal LPS. Bronchoalveolar lavage fluid was analyzed for protein accumulation, and lung tissue homogenate was assayed for endothelial NOS content and function. Human lung microvascular endothelial cell (HLMVEC) monolayers were exposed to LPS in vitro, and barrier integrity and superoxide production were measured. Biopterin species were quantified, and coimmunoprecipitation (Co-IP) assays were performed to identify protein interactions with eNOS that putatively drive uncoupling. Mice exposed to LPS demonstrated eNOS-dependent increased alveolar permeability without evidence for altered canonical NO signaling. LPS-induced superoxide production and permeability in HLMVEC were inhibited by the NOS inhibitor nitro-l-arginine methyl ester, eNOS-targeted siRNA, the eNOS cofactor tetrahydrobiopterin, and superoxide dismutase. Co-IP indicated that LPS stimulated the association of eNOS with NADPH oxidase 2 (Nox2), which correlated with augmented eNOS S-glutathionylation both in vitro and in vivo. In vitro, Nox2-specific inhibition prevented LPS-induced eNOS modification and increases in both superoxide production and permeability. These data indicate that eNOS uncoupling contributes to superoxide production and barrier dysfunction in the lung microvasculature after exposure to LPS. Furthermore, the results implicate Nox2-mediated eNOS-S-glutathionylation as a mechanism underlying LPS-induced eNOS uncoupling in the lung microvasculature.

Vascular barrier protective effects of pellitorine in LPS-induced inflammation in vitro and in vivo

Pellitorine (PT), an active amide compound, is well known to possess insecticidal, antibacterial and anticancer properties. In this study, we first investigated the possible barrier protective effects of pellitorine against pro-inflammatory responses induced by lipopolysaccharide (LPS) and the associated signaling pathways in vitro and in vivo. The barrier protective activities of PT were determined by measuring permeability, monocyte adhesion and migration, and activation of pro-inflammatory proteins in LPS-activated human umbilical vein endothelial cells (HUVECs) and in mice. We found that PT inhibited LPS-induced barrier disruption, expression of cell adhesion molecules (CAMs) and adhesion/transendothelial migration of monocytes to human endothelial cells. PT also suppressed LPS-induced hyperpermeability and leukocyte migration in vivo. Further studies revealed that PT suppressed the production of tumor necrosis factor-α (TNF-α) or Interleukin (IL)-6 and activation of nuclear factor-κB (NF-κB) or extracellular regulated kinases (ERK) 1/2 by LPS. Moreover, treatment with PT resulted in reduced LPS-induced lethal endotoxemia. These results suggest that PT protects vascular barrier integrity by inhibiting hyperpermeability, expression of CAMs, and adhesion and migration of leukocytes, thereby endorsing its usefulness as a therapy for vascular inflammatory diseases.

Chitosan oligosaccharides block LPS-induced O-GlcNAcylation of NF-κB and endothelial inflammatory response

It is known that chitosan oligosaccharides (COS) suppress LPS-induced vascular endothelial inflammatory response by mechanism involving NF-κB blockade. It remains unknown how COS inhibit NF-κB. We provided evidence both in cultured endothelial cells and mouse model supporting a new mechanism. Regardless of the endothelial cell types, the LPS-induced NF-κB-dependent inflammatory gene expression was suppressed by COS, which was associated with reduced NF-κB nucleus translocation. LPS enhanced O-GlcNAc modification of NF-κB/p65 and activated NF-κB pathway, which could be prevented either by siRNA knockdown of O-GlcNAc transferase (OGT) or pretreatment with COS. Inhibition of either mitogen-activated protein kinase or superoxide generation abolishes LPS-induced NF-κB O-GlcNAcylation. Consistently, aortic tissues from LPS-treated mice presented enhanced NF-κB/p65 O-GlcNAcylation in association with upregulated gene expression of inflammatory cytokines in vascular tissues; however, pre-administration of COS prevented these responses. In conclusion, COS decreased OGT-dependent O-GlcNAcylation of NF-κB and thereby attenuated LPS-induced vascular endothelial inflammatory response.

Blockade of NOX2 and STIM1 signaling limits lipopolysaccharide-induced vascular inflammation

During sepsis, acute lung injury (ALI) results from activation of innate immune cells and endothelial cells by endotoxins, leading to systemic inflammation through proinflammatory cytokine overproduction, oxidative stress, and intracellular Ca2+ overload. Despite considerable investigation, the underlying molecular mechanism(s) leading to LPS-induced ALI remain elusive. To determine whether stromal interaction molecule 1-dependent (STIM1-dependent) signaling drives endothelial dysfunction in response to LPS, we investigated oxidative and STIM1 signaling of EC-specific Stim1-knockout mice. Here we report that LPS-mediated Ca2+ oscillations are ablated in ECs deficient in Nox2, Stim1, and type II inositol triphosphate receptor (Itpr2). LPS-induced nuclear factor of activated T cells (NFAT) nuclear accumulation was abrogated by either antioxidant supplementation or Ca2+ chelation. Moreover, ECs lacking either Nox2 or Stim1 failed to trigger store-operated Ca2+ entry (SOCe) and NFAT nuclear accumulation. LPS-induced vascular permeability changes were reduced in EC-specific Stim1-/- mice, despite elevation of systemic cytokine levels. Additionally, inhibition of STIM1 signaling prevented receptor-interacting protein 3-dependent (RIP3-dependent) EC death. Remarkably, BTP2, a small-molecule calcium release-activated calcium (CRAC) channel blocker administered after insult, halted LPS-induced vascular leakage and pulmonary edema. These results indicate that ROS-driven Ca2+ signaling promotes vascular barrier dysfunction and that the SOCe machinery may provide crucial therapeutic targets to limit sepsis-induced ALI.

TRAF6 protein couples Toll-like receptor 4 signaling to Src family kinase activation and opening of paracellular pathway in human lung microvascular endothelia

Gram-negative bacteria release lipopolysaccharide (LPS) into the bloodstream. Here, it engages Toll-like receptor (TLR) 4 expressed in human lung microvascular endothelia (HMVEC-Ls) to open the paracellular pathway through Src family kinase (SFK) activation. The signaling molecules that couple TLR4 to the SFK-driven barrier disruption are unknown. In HMVEC-Ls, siRNA-induced silencing of TIRAP/Mal and overexpression of dominant-negative TIRAP/Mal each blocked LPS-induced SFK activation and increases in transendothelial [(14)C]albumin flux, implicating the MyD88-dependent pathway. LPS increased TRAF6 autoubiquitination and binding to IRAK1. Silencing of TRAF6, TRAF6-dominant-negative overexpression, or preincubation of HMVEC-Ls with a cell-permeable TRAF6 decoy peptide decreased both LPS-induced SFK activation and barrier disruption. LPS increased binding of both c-Src and Fyn to GST-TRAF6 but not to a GST-TRAF6 mutant in which the three prolines in the putative Src homology 3 domain-binding motif (amino acids 461-469) were substituted with alanines. A cell-permeable decoy peptide corresponding to the same proline-rich motif reduced SFK binding to WT GST-TRAF6 compared with the Pro → Ala-substituted peptide. Finally, LPS increased binding of activated Tyr(P)(416)-SFK to GST-TRAF6, and preincubation of HMVEC-Ls with SFK-selective tyrosine kinase inhibitors, PP2 and SU6656, diminished TRAF6 binding to c-Src and Fyn. During the TRAF6-SFK association, TRAF6 catalyzed Lys(63)-linked ubiquitination of c-Src and Fyn, whereas SFK activation increased tyrosine phosphorylation of TRAF6. The TRAF6 decoy peptide blocked both LPS-induced SFK ubiquitination and TRAF6 phosphorylation. Together, these data indicate that the proline-rich Src homology 3 domain-binding motif in TRAF6 interacts directly with activated SFKs to couple LPS engagement of TLR4 to SFK activation and loss of barrier integrity in HMVEC-Ls.

Silencing of C5a receptor gene with siRNA for protection from Gram-negative bacterial lipopolysaccharide-induced vascular permeability

Endothelial barrier dysfunction leading to increased permeability and vascular leakage is an underlying cause of several pathological conditions. Whereas these changes have been shown to be associated with activation of the complement system, leading to the release of C5a and interaction of C5a-C5a receptor (C5aR), the role of C5aR in endothelial cells remain(s) ill-defined. Here, we report an essential role of C5aR in endothelial cell injury and vascular permeability through silencing of the C5aR gene using siRNA. In the cultured mouse dermal microvascular endothelial cells (MEMECs) monolayer transfected with C5aR-siRNA, endotoxin-induced cell injury by evaluated as transendothelial flux, cell detachment, and cytoskeletal disorganization was inhibited. Upregulation of vascular cell adhesion molecule-1 (VCAM-1) was also suppressed. Studies exploring the underlying mechanism of siRNA-mediated suppression in VCAM-1 expression were related to reduction of NF-kappaB activation and nuclear localization of both p50 and p65. The effect was associated with inhibition in activation of protein kinase Cdelta(PKC-delta) and induction of PKC-mediated mitogen-activated protein kinase phosphatases-1 (MKP-1) leading to the increased activity of p42/p44 mitogen-activated protein (MAP) kinase cascade. In the model of mice administrated with C5aR-siRNA, endotoxin-induced plasma leakage was inhibited in local abdominal skin. Systemic administration of endotoxin to mice resulted in increased microvascular permeability in multiple organs was reduced. These studies demonstrate that the C5aR responsible for vascular endothelial cell injury and plasma permeability is an important factor, and that blockade of C5aR may be useful therapeutic targets for the prevention of vascular permeability in pathogenic condition.

Probiotics and dietary counselling contribute to glucose regulation during and after pregnancy: a randomised controlled trial

Balanced glucose metabolism ensures optimal fetal growth with long-term health implications conferred on both mother and child. We examined whether supplementation of probiotics with dietary counselling affects glucose metabolism in normoglycaemic pregnant women. At the first trimester of pregnancy 256 women were randomised to receive nutrition counselling to modify dietary intake according to current recommendations or as controls; the dietary intervention group was further randomised to receive probiotics (Lactobacillus rhamnosus GG and Bifidobacterium lactis Bb12; diet/probiotics) or placebo (diet/placebo) in a double-blind manner, whilst the control group received placebo (control/placebo). Blood glucose concentrations were lowest in the diet/probiotics group during pregnancy (baseline-adjusted means 4.45, 4.60 and 4.56 mmol/l in diet/probiotics, diet/placebo and control/placebo, respectively; P = 0.025) and over the 12 months' postpartum period (baseline-adjusted means 4.87, 5.01 and 5.02 mmol/l; P = 0.025). Better glucose tolerance in the diet/probiotics group was confirmed by a reduced risk of elevated glucose concentration compared with the control/placebo group (OR 0.31 (95 % CI 0.12, 0.78); P = 0.013) as well as by the lowest insulin concentration (adjusted means 7.55, 9.32 and 9.27 mU/l; P = 0.032) and homeostasis model assessment (adjusted means 1.49, 1.90 and 1.88; P = 0.028) and the highest quantitative insulin sensitivity check index (adjusted means 0.37, 0.35 and 0.35; P = 0.028) during the last trimester of pregnancy. The effects observed extended over the 12-month postpartum period. The present study demonstrated that improved blood glucose control can be achieved by dietary counselling with probiotics even in a normoglycaemic population and thus may provide potential novel means for the prophylactic and therapeutic management of glucose disorders.

CD14: a soluble pattern recognition receptor in milk

An innate immune system capable of distinguishing among self, non-self, and danger is a prerequisite for health. Upon antigenic challenge, pattern recognition receptors (PRRs), such as the Toll-like receptor (TLR) family of proteins, enable this system to recognize and interact with a number of microbial components and endogenous host proteins. In the healthy host, such interactions culminate in tolerance to self-antigen, dietary antigen, and commensal microorganisms but in protection against pathogenic attack. This duality implies tightly regulated control mechanisms that are not expected of the inexperienced neonatal immune system. Indeed, the increased susceptibility of newborn infants to infection and to certain allergens suggests that the capacity to handle certain antigenic challenges is not inherent. The observation that breast-fed infants experience a lower incidence of infections, inflammation, and allergies than formula-fed infants suggests that exogenous factors in milk may play a regulatory role. There is increasing evidence to suggest that upon exposure to antigen, breast milk educates the neonatal immune system in the decision-making processes underlying the immune response to microbes. Breast milk contains a multitude of factors such as immunoglobulins, glycoproteins, glycolipids, and antimicrobial peptides that, qualitatively or quantitatively, may modulate how neonatal cells perceive and respond to microbial components. The specific role of several of these factors is highlighted in other chapters in this book. However, an emerging concept is that breast milk influences the neonatal immune system's perception of "danger." Here we discuss how CD14, a soluble PRR in milk, may contribute to this education.

Anti-vascular permeability of the cleaved reactive center loop within the carboxyl-terminal domain of C1 inhibitor

C1 inhibitor (C1INH), a member of the serine proteinase inhibitor (serpin) family, functions as an inhibitor of the complement and contact systems. Cleavage of the reactive center loop (RCL) within the carboxyl-terminal domain of C1INH (iC1INH), lacking of serpin function, induces a conformational change in the molecule. Our previous data demonstrated that active, intact C1INH prevents vascular permeability induced by gram-negative bacterial lipopolysaccharide (LPS). In this study, we investigate the role of RCL-cleaved, inactive C1INH (iC1INH) in vascular endothelial activation. In the cultured primary human umbilical vein endothelial cell (HUVEC) monolayer, iC1INH blocked LPS-induced cell injury by evaluated as transendothelial flux, cell detachment, and cytoskeletal disorganization. LPS-induced upregulation of vascular cell adhesion molecule-1 (VCAM-1) could be suppressed by treatment with iC1INH. Studies exploring the underlying mechanism of iC1INH-mediated suppression in VCAM-1 expression were related to reduction of NF-kappaB activation and nuclear translocation in an I kappa B alpha-dependent manner. The inhibitory effect was associated with stabilization of the NF-kappaB inhibitor I kappa B and reduction of inhibitor I kappa B kinase activity. In the model of endotoxin-induced mice, increased plasma leakage in local abdominal skin in response to LPS was reversed by treatment with iC1INH. Furthermore, systemic administration of LPS to mice resulted in increased microvascular permeability in multiple organs, which was reduced by iC1INH. These data provide evidence that iC1INH has an anti-vascular permeability independent on the serpin function.

The intrinsic apoptotic pathway is required for lipopolysaccharide-induced lung endothelial cell death

LPS has been implicated in the pathogenesis of endothelial cell death associated with Gram-negative bacterial sepsis. The binding of LPS to the TLR-4 on the surface of endothelial cells initiates the formation of a death-inducing signaling complex at the cell surface. The subsequent signaling pathways that result in apoptotic cell death remain unclear and may differ among endothelial cells in different organs. We sought to determine whether LPS and cycloheximide-induced cell death in human lung microvascular endothelial cells (HmVECs) was dependent upon activation of the intrinsic apoptotic pathway and the generation of reactive oxygen species. We found that cells overexpressing the anti-apoptotic protein Bcl-X(L) were resistant to LPS and cycloheximide-induced death and that the proapoptotic Bcl-2 protein Bid was cleaved following treatment with LPS. The importance of Bid was confirmed by protection of Bid-deficient (bid(-/-)) mice from LPS-induced lung injury. Neither HmVECs treated with the combined superoxide dismutase/catalase mimetic EUK-134 nor HmVECs depleted of mitochondrial DNA (rho(0) cells) were protected against LPS and cycloheximide-induced death. We conclude that LPS and cycloheximide-induced death in HmVECs requires the intrinsic cell death pathway, but not the generation of reactive oxygen species.

CD44 regulates hepatocyte growth factor-mediated vascular integrity. Role of c-Met, Tiam1/Rac1, dynamin 2, and cortactin

The preservation of vascular endothelial cell (EC) barrier integrity is critical to normal vessel homeostasis, with barrier dysfunction being a feature of inflammation, tumor angiogenesis, atherosclerosis, and acute lung injury. Therefore, agents that preserve or restore vascular integrity have important therapeutic implications. In this study, we explored the regulation of hepatocyte growth factor (HGF)-mediated enhancement of EC barrier function via CD44 isoforms. We observed that HGF promoted c-Met association with CD44v10 and recruitment of c-Met into caveolin-enriched microdomains (CEM) containing CD44s (standard form). Treatment of EC with CD44v10-blocking antibodies inhibited HGF-mediated c-Met phosphorylation and c-Met recruitment to CEM. Silencing CD44 expression (small interfering RNA) attenuated HGF-induced recruitment of c-Met, Tiam1 (a Rac1 exchange factor), cortactin (an actin cytoskeletal regulator), and dynamin 2 (a vesicular regulator) to CEM as well as HGF-induced trans-EC electrical resistance. In addition, silencing Tiam1 or dynamin 2 reduced HGF-induced Rac1 activation, cortactin recruitment to CEM, and EC barrier regulation. We observed that both HGF- and high molecular weight hyaluronan (CD44 ligand)-mediated protection from lipopolysaccharide-induced pulmonary vascular hyperpermeability was significantly reduced in CD44 knock-out mice, thus validating these in vitro findings in an in vivo murine model of inflammatory lung injury. Taken together, these results suggest that CD44 is an important regulator of HGF/c-Met-mediated in vitro and in vivo barrier enhancement, a process with essential involvement of Tiam1, Rac1, dynamin 2, and cortactin.

Dietary counseling and probiotic supplementation during pregnancy modify placental phospholipid fatty acids

It has previously been shown that maternal nutrition affects the fetal environment, with consequences for the infant's health. From early pregnancy onwards participants here received a combination of dietary counseling and probiotics (Lactobacillus GG and Bifidobacterium lactis Bb12; n = 10), dietary counseling with placebo (n = 12), or placebo alone (n = 8). The major differences in placental fatty acids were attributable to a higher concentration of n-3 polyunsaturated fatty acids in both intervention arms than in controls. Further, dietary counseling with probiotics resulted in higher concentrations of linoleic (18:2n-6) and dihomo-gamma-linolenic acids (20:3n-6) compared with dietary counseling with placebo or controls.

Suppression of complement regulatory protein C1 inhibitor in vascular endothelial activation by inhibiting vascular cell adhesion molecule-1 action

Increased expression of adhesion molecules by activated endothelium is a critical feature of vascular inflammation associated with the several diseases such as endotoxin shock and sepsis/septic shock. Our data demonstrated complement regulatory protein C1 inhibitor (C1INH) prevents endothelial cell injury. We hypothesized that C1INH has the ability of an anti-endothelial activation associated with suppression of expression of adhesion molecule(s). C1INH blocked leukocyte adhesion to endothelial cell monolayer in both static assay and flow conditions. In inflammatory condition, C1INH reduced vascular cell adhesion molecule (VCAM-1) expression associated with its cytoplasmic mRNA destabilization and nuclear transcription level. Studies exploring the underlying mechanism of C1INH-mediated suppression in VCAM-1 expression were related to reduction of NF-kappaB activation and nuclear translocation in an IkappaBalpha-dependent manner. The inhibitory effects were associated with reduction of inhibitor IkappaB kinase activity and stabilization of the NF-kappaB inhibitor IkappaB. These findings indicate a novel role for C1INH in inhibition of vascular endothelial activation. These observations could provide the basis for new therapeutic application of C1INH to target inflammatory processes in different pathologic situations.

Attenuation of vascular permeability by methylnaltrexone: role of mOP-R and S1P3 transactivation

Endothelial cell (EC) barrier dysfunction (i.e., increased vascular permeability) is observed in inflammatory states, tumor angiogenesis, atherosclerosis, and both sepsis and acute lung injury. Therefore, agents that preserve vascular integrity have important clinical therapeutic implications. We examined the effects of methylnaltrexone (MNTX), a mu opioid receptor (mOP-R) antagonist, on human pulmonary EC barrier disruption produced by edemagenic agents including morphine, the endogenous mOP-R agonist DAMGO, thrombin, and LPS. Pretreatment of EC with MNTX (0.1 muM, 1 h) or the uncharged mOP-R antagonist naloxone attenuated morphine- and DAMGO-induced barrier disruption in vitro. However, MNTX, but not naloxone, pretreatment of EC inhibited thrombin- and LPS-induced barrier disruption, indicating potential mOP-R-independent effects of MNTX. In addition, intravenously delivered MNTX attenuated LPS-induced vascular hyperpermeability in the murine lung. We next examined the mechanistic basis for this MNTX barrier protection and observed that silencing of mOP-R attenuated the morphine- and DAMGO-induced EC barrier disruption, but not the permeability response to either thrombin or LPS. Because activation of the sphingosine 1-phosphate receptor, S1P(3), is key to a number of barrier-disruptive responses, we examined the role of this receptor in the permeability response to mOP-R ligation. Morphine, DAMGO, thrombin, and LPS induced RhoA/ROCK-mediated threonine phosphorylation of S1P(3), which was blocked by MNTX, suggesting S1P(3) transactivation. In addition, silencing of S1P(3) receptor expression (siRNA) abolished the permeability response to each edemagenic agonist. These results indicate that MNTX provides barrier protection against edemagenic agonists via inhibition of S1P(3) receptor activation and represents a potentially useful therapeutic agent for syndromes of increased vascular permeability.

Modulation of endothelial monolayer permeability induced by plasma obtained from lipopolysaccharide-stimulated whole blood

The aim of this study was to elucidate the time course of the permeability response of endothelial monolayers after exposure to plasma obtained from lipopolysaccharide (LPS)-treated human whole blood; to investigate the role of apoptosis in monolayer permeability, and to inhibit the permeability increase, particularly after addition of the plasma stimulus. Human umbilical vein endothelial cells (HUVEC) were cultured on semiporous membranes and the permeability for albumin was measured after exposure, according to different schedules, to LPS-conditioned plasma. Apoptotic HUVEC were measured by both flow cytometry and ELISA. A variety of agents, including antibodies against cytokines, inhibitors of NF-kappaB, and a caspase inhibitor, were added to HUVEC, either prior to or after the stimulus. A maximum increase of the permeability was achieved after 4-6 h of exposure to LPS-conditioned plasma. This response was not accompanied by an increase in the number of apoptotic HUVEC. Administration of antibodies against both Tumour Necrosis Factor-alpha (TNF-alpha) and Interleukin-1beta (IL-1beta) to HUVEC within 1 h after stimulation significantly reduced the permeability increase. Similarly, pyrollidine di-thiocarbamate (PDTC), but not N-acetylcysteine, could prevent the permeability response, and was still effective when added within 2 h after LPS-conditioned plasma. The TNF-alpha/IL-1beta signal present in LPS-conditioned plasma appears to increase endothelial permeability through intracellular pathways that very likely involve the activation of NF-kappaB. Although poststimulatory inhibition of the permeability response proves to be possible with agents such as PDTC, the window of opportunity appears very small if placed in a clinical perspective.

Breast milk fatty acids may link innate and adaptive immune regulation: analysis of soluble CD14, prostaglandin E2, and fatty acids

In addition to its role in sensing intraluminal microbial antigens, soluble (s)CD14 may regulate immune responses by its lesser known function as a lipid carrier with possible influences in the production of fatty acid-derived eicosanoids. We investigated the interrelations of fatty acids, prostaglandin E2 (PGE2), and sCD14 and their role in infant atopic eczema during the first year of life. Serum and breast milk samples from mothers and serum samples from their infants were collected at infant's age 3 mo and analyzed for sCD14 and PGE2 concentrations and for fatty acid compositions. The main correlation of sCD14 was with arachidonic acid (20:4n-6) (AA). Dihomo-gamma-linolenic acid (20:3n-6) (DHGLA) and the ratio of n-6 to n-3 fatty acids correlated positively and docosahexaenoic acid (22:6n-3) (DHA) and sum of n-3 fatty acid negatively with PGE2 in mother's serum and linoleic acid (LA) negatively with PGE2 in breast milk. Soluble CD14 tended to be higher and LA, total polyunsaturated fatty acid (PUFA), and sum of n-6 fatty acids were lower in breast milk received by infants with atopic eczema compared with those without. These results suggest that fatty acids contribute to the regulation of innate and adaptive immune responses and link intraluminal exposures, mother's diet, and microbes.

Soluble CD14 receptor expression and monocyte heterogeneity but not the C-260T CD14 genotype are associated with severe acute pancreatitis

OBJECTIVE

Soluble CD14 is derived from a membrane glycoprotein, and it enhances endothelial cytokine responses to lipopolysaccharide. We studied the role of soluble CD14 in the pathogenesis of the systemic inflammatory response associated with acute pancreatitis, to determine whether altered expression was due to a functional C-260T polymorphism in the CD14 promoter gene or altered monocyte heterogeneity.

DESIGN

Prospective case-matched study.

SETTING

Tertiary pancreatic treatment unit in the United Kingdom.

SUBJECTS

Patients with pancreatitis and controls.

INTERVENTIONS

DNA from 117 patients with pancreatitis (34 severe) and 263 controls underwent CD14 genotyping using restriction fragment length polymorphism-polymerase chain reaction.

MEASUREMENTS AND MAIN RESULTS

Peripheral venous blood samples at 24 and 72 hrs after the onset of abdominal pain were analyzed for sCD14 levels. Isolated peripheral blood mononuclear cells were phenotyped for CD14/CD16 receptor expression using immunofluorescence flow cytometry. Disease severity was assessed using Atlanta criteria, Acute Physiology Scores, and C-reactive protein.Soluble CD14 levels were higher in severe (24-hr median, 66.6 ng/mL; 72-hr median, 72.2 ng/mL) compared with mild attacks (24-hr median, 50.7 ng/mL; 72-hr median, 49.7 ng/mL, p < .001), although the latter was similar to controls (median, 51 ng/mL). Furthermore, soluble CD14 levels correlated with Acute Physiology Scores (p < .001) and C-reactive protein (p = .01).Peripheral blood mononuclear cells CD14++ (p = .008), CD14+/16+ (p = .003), and CD16++ (p = .015) receptor densities were all increased in severe attacks at 24 hrs. Early CD14+/16+ receptor density correlated with sCD14 (p < .001), Acute Physiology Scores (p < .001), and C-reactive protein (p = 0.006). The CD14 genotype prevalence in acute pancreatitis was similar to controls and failed to correlate with any variables studied.

CONCLUSIONS

Increased soluble CD14 expression is associated with the systemic inflammatory response to acute pancreatitis and an expansion of the proinflammatory CD14+/CD16+ monocyte subset. Its targeted disruption may afford some benefit in preventing the development of systemic complications.

C1 inhibitor prevents Gram-negative bacterial lipopolysaccharide-induced vascular permeability

Gram-negative bacterial endotoxemia may lead to the pathological increase of vascular permeability with systemic vascular collapse, a vascular leak syndrome, multiple organ failure (MOF), and/or shock. Previous studies demonstrated that C1 inhibitor (C1INH) protects mice from lipopolysaccharide (LPS)-induced lethal septic shock via a direct interaction with LPS. Here, we report that C1INH blocked the LPS-induced increase in transendothelial flux through an endothelial monolayer. In addition, LPS-mediated detachment of cultured endothelial cells was prevented with C1INH. C1INH also inhibited LPS-induced endothelial cell apoptosis as demonstrated by suppression of DNA fragmentation and annexin V expression. As illustrated by laser scanning confocal microscopy, C1INH completely blocked the binding of fluorescein isothiocyanate (FITC)-LPS to human umbilical vein endothelial cells (HUVECs). C1INH protected from localized LPS-induced increased plasma leakage in C57BL/6J mice and in C1INH-deficient mice. Local vascular permeability in response to LPS was increased to a greater extent in C1INH-deficient mice compared with wild-type littermate controls and was reversed by treatment with C1INH. Systemic administration of LPS to mice resulted in increased vascular permeability, which was reduced by C1INH. Therefore, these studies demonstrate that C1INH, in addition to its role in suppression of LPS-mediated macrophage activation, may play an important role in the prevention of LPS-mediated increased vascular permeability, endothelial cell injury, and multiple organ failure.

Mechanisms of bacterial lipopolysaccharide-induced endothelial apoptosis

Gram-negative bacterial sepsis remains a common, life-threatening event. The prognosis for patients who develop sepsis-related complications, including the development of acute respiratory distress syndrome (ARDS), remains poor. A common finding among patients and experimental animals with sepsis and ARDS is endothelial injury and/or dysfunction. A component of the outer membrane of gram-negative bacteria, lipopolysaccharide (LPS) or endotoxin, has been implicated in the pathogenesis of much of the endothelial cell injury and/or dysfunction associated with these disease states. LPS is a highly proinflammatory molecule that elicits a wide array of endothelial responses, including the upregulation of cytokines, adhesion molecules, and tissue factor. In addition to activation, LPS induces endothelial cell death that is apoptotic in nature. This review summarizes the evidence for LPS-induced vascular endothelial injury and examines the molecular signaling pathways that activate and inhibit LPS-induced endothelial apoptosis. Furthermore, the role of apoptotic signaling molecules in mediating LPS-induced activation of endothelial cells will be considered.

Bacterial lipopolysaccharide decreases thrombomodulin expression in the sinusoidal endothelial cells of rats -- a possible mechanism of intrasinusoidal microthrombus formation and liver dysfunction

BACKGROUND/AIMS

To elucidate the mechanism of liver dysfunction occurring in patients with sepsis, we evaluated the effect of bacterial lipopolysaccharide (LPS) on the expression of thrombomodulin (TM) in rat sinusoidal endothelial cells (SECs) and the therapeutic efficacy of exogenous recombinant TM.

METHODS

We induced endotoxemia in rats by bolus intraperitoneal injection of LPS. TM antigen levels within tissues were assessed by immunohistochemistry. We measured TM in cultured SECs by enzyme immunoassay, functional analysis and real-time polymerase chain reaction (PCR).

RESULTS

TM antigen and activity levels were significantly decreased in SECs isolated from LPS-treated rats after 3 and 6 h treatment, and recovered after 12 h treatment, correlating with immunohistochemical observations. In contrast, TM messenger RNA was decreased after 6 and 12 h treatment, and slightly recovered after 24 h treatment. TM expression in cultured SECs isolated from normal rats was also reduced after treatment with LPS and tumor necrosis factor (TNF)-alpha in vitro. The increased levels of serum fibrin degradation products (FDP), fibrin deposition within liver sinusoids, injury of SECs and liver dysfunction induced by LPS in our rat model was improved by recombinant TM treatment.

CONCLUSIONS

Decreased TM expression in SECs of LPS-treated rats may result in intrasinusoidal microthrombus formation and subsequent liver dysfunction during sepsis.

Endotoxin and its binding proteins in chronic liver disease: the effect of transjugular intrahepatic portosystemic shunting

BACKGROUND

Gut-derived endotoxin is insufficiently cleared by the diseased liver, and thus, is elevated in plasma of patients with chronic liver disease (CLD). Endotoxin action might be modified by binding to soluble CD14 (sCD14) and lipopolysaccharide-binding protein (LBP), both of which have not yet been sufficiently studied in CLD.

METHODS

Endotoxin, sCD14 and LBP have been determined in peripheral blood of 72 patients and 39 control subjects, and in portal and hepatic venous blood of 12 patients during transjugular intrahepatic portosystemic shunt (TIPS) implantation.

RESULTS

Peripheral endotoxin (average 3-fold increased compared to controls), LBP, and sCD14 plasma levels were elevated in chronic liver disease irrespective of Child stage m, preserve/absence of cirrhosis or aetiology. LBP, and sCD14. Furthermore, endotoxin levels in the portal vein (38.1 +/- 6.1 pg/ml) were only slightly elevated compared to the hepatic vein (29.2 +/- 4.4 pg/ml), and peripheral endotoxin levels did not increase after TIPS.

CONCLUSIONS

Decreased hepatocellular function rather than hepatic blood shunting might be responsible for endotoxemia. The elevation in LBP and sCD14 levels may be a consequence of endotoxemia.

Tumor necrosis factor-alpha and interleukin-1beta mediate endothelial permeability induced by lipopolysaccharide-stimulated whole blood

OBJECTIVE

To investigate the role of endotoxin-induced inflammatory mediators in blood on the permeability of endothelial monolayers.

DESIGN

Whole blood of healthy volunteers was treated with bacterial lipopolysaccharide (Escherichia coli, B55:05), and the resultant plasma was added to human umbilical venular endothelial cells (HUVEC) cultured on semipermeable membrane inserts (Transwells).

SETTING

University hospital laboratory.

SUBJECTS

Whole blood of healthy volunteers.

INTERVENTIONS

Donor plasma was treated with excess antibodies against either tumor necrosis factor-alpha, interleukin-1beta, or both, before the incubation on HUVEC.

MEASUREMENTS AND MAIN RESULTS

The permeability of HUVEC monolayers to fluorescent-labeled albumin and dextran was measured over a 6-hr period, after removal of the stimulus. The production of tumor necrosis factor-alpha and interleukin-1beta in lipopolysaccharide-treated whole blood was determined by radioimmunoassay. Individually, lipopolysaccharide (10 microg/mL), tumor necrosis factor-alpha (10 ng/mL), and interleukin-1beta (50 ng/mL) all increased endothelial permeability by about 2.5-fold. A much larger increase could be achieved by preincubation of lipopolysaccharide (10 microg/mL) in whole blood: the resultant plasma induced a ten-fold increase of the permeability. The permeability response after preincubation of lipopolysaccharide in whole blood was time- and dose-dependent. Moreover, this treatment increased the sensitivity of endothelial monolayers to lipopolysaccharide by a factor of several thousand-fold: Whereas high doses of lipopolysaccharide were required for direct stimulation of the permeability, picomolar amounts of lipopolysaccharide in whole blood induced a similar increase. Significant amounts of tumor necrosis factor-alpha and interleukin-1beta were produced in blood at similar doses of lipopolysaccharide. The addition of antibodies against tumor necrosis factor-alpha or interleukin-1beta to plasma partially but significantly abrogated the permeability increase. However, a complete inhibition could be achieved by the simultaneous addition of anti-tumor necrosis factor-alpha and anti-interleukin-1beta to plasma.

CONCLUSIONS

Although lipopolysaccharide is capable of directly inducing endothelial permeability, blood-borne tumor necrosis factor-alpha and interleukin-1beta mediate lipopolysaccharide-induced endothelial permeability at low endotoxin concentrations. These findings support the idea that multifactorial inhibition of inflammatory mediators may improve survival in septic patients.

Human keratinocytes express functional CD14 and toll-like receptor 4

CD14 and the toll-like receptor 4 have been known to play an important role in lipopolysaccharide-induced cellular responses in bacterial infections. Although CD14 and toll-like receptor 4 expression has been demonstrated in a number of myeloid cells, much less is known about the expression and function of these lipopolysaccharide receptors on nonleukocytes. In this study, we demonstrate that human keratinocytes are capable of expressing functional CD14 and toll-like receptor 4. Keratinocytes were found to constitutively express CD14 and toll-like receptor 4 mRNA that was augmented by exposure to lipopolysaccharide. Cell surface expression of keratinocyte CD14 and toll-like receptor 4 was detected by flow cytometry. Lipopolysaccharide binding to keratinocyte CD14 and toll-like receptor 4 resulted in a rapid intracellular Ca2+ response, nuclear factor-kappaB nuclear translocation, and the secretion of proinflammatory cytokines and chemokines. These results have important implications for our understanding of cutaneous innate immunity to bacterial infections of the skin.

An improved endothelial barrier model to investigate dengue haemorrhagic fever

A cell culture model suitable for studies of dengue haemorrhagic fever was developed, based on culture of primary human umbilical vein endothelial cells (HUVECs) on a permeable membrane. By electron microscopy, cultured HUVECs at day 11 resembled morphologically microvascular endothelium. Endothelial barrier function was assessed by measuring transendothelial flux of albumin. Instead of using a labelled tracer molecule, an enzyme-linked immunosorbent assay (ELISA) was developed to measure concentrations of native human albumin. The permeability characteristics of the HUVEC monolayer were found to be improved significantly (approximately 1 log reduction in permeability coefficient for albumin) by culturing HUVECs in human serum rather than fetal calf serum. Permeability coefficients for albumin in the range 1-4 x 10(-7) cm/s were achieved, which is an improvement on previous in vitro models of the endothelial barrier. Comparison of transendothelial flux of albumin and urea provided evidence of molecular sieving by the HUVEC monolayer. Moreover, tumour necrosis factor-alpha induced a dose-dependent, reversible increase in permeability of the HUVEC monolayer. This endothelial barrier model thus has many important characteristics that resembled human microvascular endothelium and is an improvement on the previous model proposed for studies of dengue haemorrhagic fever.

The essential role of lipopolysaccharide-binding protein in protection of mice against a peritoneal Salmonella infection involves the rapid induction of an inflammatory response

Acute and chronic hyperinflammation are of major clinical concern, and many treatment strategies are therefore directed to inactivating parts of the inflammatory system. However, survival depends on responding quickly to pathogen attack, and since the adaptive immune system requires several days to adequately react, we rely initially on a range of innate defenses, many of which operate by activating parts of the inflammatory network. For example, LPS-binding protein (LBP) can transfer the LPS of Gram-negative bacteria to CD14 on the surface of macrophages, and this initiates an inflammatory reaction. However, the importance of this chain of events in infection is unclear. First, the innate system is redundant, and bacteria have many components that may serve as targets for it. Second, LBP can transfer LPS to other acceptors that do not induce inflammation. In this study, we show that innate defense against a lethal peritoneal infection with Salmonella requires a direct proinflammatory involvement of LBP, and that this is a major nonredundant function of LBP in this infection model. This emphasizes that blocking the LBP-initiated inflammatory cascade disables an essential defense pathway. Any anti-inflammatory protection that may be achieved must be balanced against the risks inherent in blinding the innate system to the presence of Gram-negative pathogens.

Endotoxin causes phosphorylation of MARCKS in pulmonary vascular endothelial cells

Protein kinase C (PKC) has been implicated in lipopolysaccharide (LPS)-induced endothelial cell (EC) monolayer permeability. Myristoylated alanine-rich C kinase substrate (MARCKS), as a specific PKC substrate, appears to mediate PKC signaling by PKC-dependent phosphorylation of MARCKS and subsequent modification of the association of MARCKS with filamentous actin and calmodulin (CaM). Therefore, in the present study, we investigated LPS-induced MARCKS phosphorylation in bovine pulmonary artery EC (BPAEC). LPS potentiated MARCKS phosphorylation in BPAEC in a time- and dose-dependent manner. The PKC inhibitor, calphostin C, significantly decreased LPS-induced phosphorylation of MARCKS. In addition, downregulation of PKC with phorbol 12-myristate 13-acetate (PMA) did not affect the LPS-induced MARCKS phosphorylation, suggesting that LPS and PMA activate different isoforms of PKC. Pretreatment with SB203580, a specific inhibitor of p38 MAP kinase, or genistein, a tyrosine kinase inhibitor, prevented LPS-induced MARCKS phosphorylation. Phosphorylation at appropriate sites will induce translocation of MARCKS from the cell membrane to the cytosol. However, LPS, in contrast to PMA, did not generate MARCKS translocation in BPAEC, suggesting that MARCKS translocation may not play a role in LPS-induced actin rearrangement and EC permeability. LPS also enhanced both thrombin- and PMA-induced phosphorylation of MARCKS, suggesting that LPS was able to prime these signaling pathways in BPAEC. Because the CaM-dependent phosphorylation of myosin light chains (MLC) results in EC contraction, we studied the effect of LPS on MLC phosphorylation in BPAEC. LPS induced diphosphorylation of MLC in a time-dependent manner, which occurred at lower doses of LPS, than those required to induce MARCKS phosphorylation. In addition, there was no synergism between LPS and thrombin in the induction of MLC phosphorylation. These data indicate that MLC phosphorylation is independent of MARCKS phosphorylation. In conclusion, LPS stimulated MARCKS phosphorylation in BPAEC. This phosphorylation appears to involve activation of PKC, p38 MAP kinase, and tyrosine kinases. Further studies are needed to explore the role of MARCKS phosphorylation in LPS-induced actin rearrangement and EC permeability.