Polyphosphate elicits pro-inflammatory responses that are counteracted by activated protein C in both cellular and animal models

The Protein Scaffolding Functions of Polyphosphate

Inorganic polyphosphate (polyP), one of the first high-energy compound on earth, defies its extreme compositional and structural simplicity with an astoundingly wide array of biological activities across all domains of life. However, the underlying mechanism of such functional pleiotropy remains largely elusive. In this review, we will summarize recent studies demonstrating that this simple polyanion stabilizes protein folding intermediates and scaffolds select native proteins. These functions allow polyP to act as molecular chaperone that protects cells against protein aggregation, as pro-amyloidogenic factor that accelerates both physiological and disease-associated amyloid formation, and as a modulator of liquid-liquid phase separation processes. These activities help to explain polyP's known roles in bacterial stress responses and pathogenicity, provide the mechanistic foundation for its potential role in human neurodegenerative diseases, and open a new direction regarding its influence on gene expression through condensate formation. We will highlight critical unanswered questions and point out potential directions that will help to further understand the pleiotropic functions of this ancient and ubiquitous biopolymer.

Chain-length dependent effects of inorganic polyphosphate on endothelial function and nucleotide pool

Endothelial cells (ECs) are the first line that comes into contact with blood pathogens, pathogen-derived molecules, and factors that stimulate coagulation and inflammation. Inorganic polyphosphate (polyP) - a polymer of orthophosphate units synthesized by bacteria under stress and released by platelets upon their activation is among these factors. Bacterial and platelet polyPs differ in length, and both variants elicit different effects in eukaryotes. This study aimed to investigate how bacterial-like long-chain polyP (Lc-polyP) and platelet-like short-chain polyP (Sc-polyP) affect the functionality of cultured endothelial cells. Murine immortalized heart endothelial cells (H5V) were exposed to polyP of different chain lengths to assess the effects of these stimuli on intracellular energetics, permeability, and endothelial adhesion. We observed varying effects between Lc-polyP and Sc-polyP treatments. Lc-polyP more potently disturbs the intracellular ATP pool, a parameter strongly connected with vascular injury, whereas Sc-polyP robustly stimulates cellular adhesion to the endothelium. Both polymers similarly enhance endothelial permeability, suggesting potent immunomodulatory properties. This study provides evidence that polyP elicits profound cellular responses in endothelium depending on the polymer's length.

In-vivo functions and regulation of polyphosphate in the vascular system

PURPOSE OF REVIEW

Polyphosphate, an inorganic polymer consisting of linearly linked phosphate subunits, is ubiquitously found in living organisms. Functions and regulation of the polymer have been analyzed in plants, bacteria and yeast; however, the roles of polyphosphate in mammals are still emerging.

RECENT FINDINGS

In contrast to synthetic polyphosphate that has been extensively utilized in ex-vivo studies, natural polyphosphate is complexed with bivalent cations (mostly Ca 2+ ) and regardless of chain length, forms microparticles that are retained on the surface of procoagulant platelets, platelet-derived microparticles and cancer extracellular vesicles. On cell surfaces, these Ca 2+ /polyphosphate aggregates initiate the factor XII-driven contact system, triggering proinflammatory and procoagulant reactions through the kallikrein kinin system and intrinsic pathway of coagulation, respectively. Polyphosphate inhibitors interfere with thrombosis while sparing hemostasis, replicating the effect of factor XII neutralizing agents. Furthermore, polyphosphate binds to platelet factor 4, which has implications for autoimmune thrombotic diseases, such as heparin-induced thrombocytopenia (HIT) and vaccine-induced thrombotic thrombocytopenia (VITT), potentially contributing to their pathogenesis. The metabolism and organ-specific distribution of the polymer remain incompletely defined and is the topic of ongoing research.

SUMMARY

Polyphosphate acts as a procoagulant and proinflammatory mediator. Neutralizing polyphosphate provides well tolerated thromboprotection, mimicking the effects of factor XII deficiency.

Polyphosphate as an antithrombotic target and hemostatic agent

Polyphosphate (PolyP) is a polymer comprised of linear phosphate units connected by phosphate anhydride bonds. PolyP exists in a diverse range of eukaryotes and prokaryotes with varied chain lengths ranging from six to thousands of phosphate units. Upon activation, human platelets and neutrophils release short-chain PolyP, along with other components, to initiate the coagulation pathway. Long-chain PolyP derived from cellular or bacterial organelles exhibits higher proinflammatory and procoagulant effects compared to short-chain PolyP. Notably, PolyP has been identified as a low-hemorrhagic antithrombotic target since neutralizing plasma PolyP suppresses the thrombotic process without impairing the hemostatic functions. As an inorganic polymer without uniform steric configuration, PolyP is typically targeted by cationic polymers or recombinant polyphosphatases rather than conventional antibodies, small-molecule compounds, or peptides. Additionally, because of its procoagulant property, PolyP has been incorporated in wound-dressing materials to facilitate blood hemostasis. This review summarizes current studies on PolyP as a low-hemorrhagic antithrombotic target and the development of hemostatic materials based on PolyP.

Inhibitors of Polyphosphate and Neutrophil Extracellular Traps

The contact pathway of blood clotting has received intense interest in recent years as studies have linked it to thrombosis, inflammation, and innate immunity. Because the contact pathway plays little to no role in normal hemostasis, it has emerged as a potential target for safer thromboprotection, relative to currently approved antithrombotic drugs which all target the final common pathway of blood clotting. Research since the mid-2000s has identified polyphosphate, DNA, and RNA as important triggers of the contact pathway with roles in thrombosis, although these molecules also modulate blood clotting and inflammation via mechanisms other than the contact pathway of the clotting cascade. The most significant source of extracellular DNA in many disease settings is in the form of neutrophil extracellular traps (NETs), which have been shown to contribute to incidence and severity of thrombosis. This review summarizes known roles of extracellular polyphosphate and nucleic acids in thrombosis, with an emphasis on novel agents under current development that target the prothrombotic activities of polyphosphate and NETs.

Bioenergetics of the polyphosphates accumulation in Pseudomonas aeruginosa via polyphosphate kinase activation by choline in a lung colonization model

Pseudomonas aeruginosa is an ubiquitous and opportunistic bacteria found in water, soil, plants, and immunocompromised humans. Cystic fibrosis (CF) patients are the most vulnerable population to lung colonization by these bacteria. Upon infection, choline and succinate are released from the CF lungs and are catabolized by P. aeruginosa. The bacteria accumulate inorganic polyphosphates, rather than succinate, when choline is catabolized, producing physiological and morphological changes leading to ineradicable infection. Thus, we sought to quantify the enzymes responsible for polyphosphate accumulation and to determine how choline catabolism affects energy flow and storage. Subcellular fractions showed that exo-polyphosphate phosphatase (PPX) activity resides mainly in the periplasm, and three isoenzymes of 24, 70, and 200 KD were found. The PPX activity in the periplasm of bacteria grown with choline was inhibited in an anti-competitive manner from Km 0.5 to 1 μM, and their Vmax increased from 50 to 100 nmol PO 4 ≡ /min/g of protein in succinate medium. Since PPX inhibition by choline did not explain the 3.8-fold increase in polyphosphates, we quantified the polyphosphate kinase activity, and its significant 2.4-fold increase was consistent with the accumulation. Furthermore, intracellular ATP concentration directly correlated with the energetic yield of the carbon source and was significantly higher for succinate, suggesting that the restriction of energy caused by choline catabolism may induce morphological and physiological changes to the swarm form thus facilitating their migration and tissue colonization.

Inorganic Polyphosphate—Regulator of Cellular Metabolism in Homeostasis and Disease

Inorganic polyphosphate (polyP), a simple anionic polymer consisting of even hundreds of orthophosphate units, is a universal molecule present in both simple and complex organisms. PolyP controls homeostatic processes in animals, such as blood coagulation, tissue regeneration, and energy metabolism. Furthermore, this polymer is a potent regulator of inflammation and influences host immune response in bacterial and viral infections. Disturbed polyP systems have been related to several pathological conditions, including neurodegeneration, cardiovascular disorders, and cancer, but we lack a full understanding of polyP biogenesis and mechanistic insights into the pathways through which polyP may act. This review summarizes recent studies that describe the role of polyP in cell homeostasis and show how disturbances in polyP levels may lead to disease. Based on the collected findings, we highlight the possible usage of this polymer as a promising therapeutic tool in multiple pathologies.

Effect of long-chain inorganic polyphosphate treated with wheat phytase on IL-8 signaling in HT-29 cells

Objective

This study was performed to investigate the potential effect of wheat phytase on long-chain inorganic polyphosphate (polyP)-mediated interleukin 8 (IL-8) signaling in an intestinal epithelial cell line, HT-29 cells.

Methods

Cell viability and the release of the pro-inflammatory cytokine IL-8 in HT-29 cells exposed to polyP1150 (average of 1,150 phosphate residues) treated with or without wheat phytase were measured by the EZ-CYTOX kit and the IL-8 ELISA kit, respectively. Also, the activation of cellular inflammatory factors NF-κB and MAPK (p38 and ERK 1/2) in HT-29 cells was investigated using ELISA kits.

Results

PolyP1150 negatively affected the viability of HT-29 cells in a dose-dependent manner. However, 100 mM polyP1150 dephosphorylated by wheat phytase increased cell viability by 1.4-fold over that of the intact substrate. Moreover, the 24 h exposure of cells to enzyme-treated 50 mM polyP1150 reduced the secretion of IL-8 and the activation of NF-κB by 9% and 19%, respectively, compared to the intact substrate. PolyP1150 (25 and 50 mM) dephosphorylated by the enzyme induced the activation of p38 MAPK via phosphorylation to 2.3 and 1.4-fold, respectively, compared to intact substrate, even though it had little effect on the expression of ERK 1/2 via phosphorylation.

Conclusion

Wheat phytase could attenuate polyP1150-induced IL-8 release in HT-29 cells through NF-κB, independent of MAP kinases p38 and ERK. Thus, wheat phytase may alleviate inflammatory responses including hypercytokinemia caused by bacterial polyP infection in animals. Therefore, wheat phytase has the potential as an anti-inflammatory therapeutic supplement in animal husbandry.

Effects of Polyphosphate on Leukocyte Function

Leukocytes are immune cells derived from hematopoietic stem cells of the bone marrow which play essential roles in inflammatory and immune responses. In contrast to anucleate platelets and erythrocytes, leukocytes are differentiated from other blood cells by the presence of a nucleus, and consist of monocytes, neutrophils, lymphocytes, basophils, and eosinophils. Factors released from platelets mediate immune responses in part by recruitment and regulation of leukocyte activity. Platelet dense granules contain the highly anionic polymer polyphosphate (polyP) with monomer chain lengths of approximately 60-100 phosphates long, which are released into the microenvironment upon platelet activation. Recent studies suggest that polyP released from platelets plays roles in leukocyte migration, recruitment, accumulation, differentiation, and activation. Furthermore, bacterial-derived polyphosphate, generally consisting of phosphate monomer lengths in the hundreds to thousands, appear to play a role in pathogenic evasion of the host immune response. This review will discuss the effects of host and pathogenic-derived polyphosphate on leukocyte function.

2,4,6-Trihydroxy-3-geranyl acetophenone suppresses vascular leakage and leukocyte infiltration in lipopolysaccharide-induced endotoxemic mice

CONTEXT

Lipopolysaccharide (LPS) exacerbates systemic inflammatory responses and causes excessive fluid leakage. 2,4,6-Trihydroxy-3-geranyl acetophenone (tHGA) has been revealed to protect against LPS-induced vascular inflammation and endothelial hyperpermeability in vitro.

OBJECTIVE

This study assesses the in vivo protective effects of tHGA against LPS-induced systemic inflammation and vascular permeability in endotoxemic mice.

MATERIALS AND METHODS

BALB/c mice were intraperitoneally pre-treated with tHGA for 1 h, followed by 6 h of LPS induction. Evans blue permeability assay and leukocyte transmigration assay were performed in mice (n = 6) pre-treated with 2, 20 and 100 mg/kg tHGA. The effects of tHGA (20, 40 and 80 mg/kg) on LPS-induced serum TNF-α secretion, lung dysfunction and lethality were assessed using ELISA (n = 6), histopathological analysis (n = 6) and survivability assay (n = 10), respectively. Saline and dexamethasone were used as the negative control and drug control, respectively.

RESULTS

tHGA significantly inhibited vascular permeability at 2, 20 and 100 mg/kg with percentage of inhibition of 48%, 85% and 86%, respectively, in comparison to the LPS control group (IC₅₀=3.964 mg/kg). Leukocyte infiltration was suppressed at 20 and 100 mg/kg doses with percentage of inhibition of 73% and 81%, respectively (IC₅₀=17.56 mg/kg). However, all tHGA doses (20, 40 and 80 mg/kg) failed to prevent endotoxemic mice from lethality because tHGA could not suppress TNF-α overproduction and organ dysfunction.

DISCUSSION AND CONCLUSIONS

tHGA may be developed as a potential therapeutic agent for diseases related to uncontrolled vascular leakage by combining with other anti-inflammatory agents.

An update on factor XII-driven vascular inflammation

The plasma protein factor XII (FXII) is the liver-derived zymogen of the serine protease FXIIa that initiates an array of proteolytic cascades. Zymogen activation, enzymatic FXIIa activity and functions are regulated by interactions with cell receptors, negatively charged surfaces, other serine proteases, and serpin inhibitors, which bind to distinct protein domains and regions in FXII(a). FXII exerts mitogenic activity, while FXIIa initiates the pro-inflammatory kallikrein-kinin pathway and the pro-thrombotic intrinsic coagulation pathway, respectively. Growing evidence indicates that FXIIa-mediated thrombo-inflammation plays a crucial role in various pathological states besides classical thrombosis, such as endothelial dysfunction. Consistently, increased FXIIa levels are associated with hypercholesterolemia and hypertriglyceridemia. In contrast, FXII deficiency protects from thrombosis but is otherwise not associated with prolonged bleeding or other adverse clinical manifestations. Here, we review current concepts for FXII(a)-driven vascular inflammation focusing on endothelial hyperpermeability, receptor signaling, atherosclerosis and immune cell activation.

Metformin inhibits polyphosphate-induced hyper-permeability and inflammation

Circulating inflammatory factor inorganic polyphosphate (polyP) released from activated platelets could enhance factor XII and bradykinin resulted in increased capillary leakage and vascular permeability. PolyP induce inflammatory responses through mTOR pathway in endothelial cells, which is being reported in several diseases including atherosclerosis, thrombosis, sepsis, and cancer. Systems and molecular biology approaches were used to explore the regulatory role of the AMPK activator, metformin, on polyP-induced hyper-permeability in different organs in three different models of polyP-induced hyper-permeability including local, systemic short- and systemic long-term approaches in murine models. Our results showed that polyP disrupts endothelial barrier integrity in skin, liver, kidney, brain, heart, and lung in all three study models and metformin abrogates the disruptive effect of polyP. We also showed that activation of AMPK signaling pathway, regulation of oxidant/anti-oxidant balance, as well as decrease in inflammatory cell infiltration constitute a set of molecular mechanisms through which metformin elicits it's protective responses against polyP-induced hyper-permeability. These results support the clinical values of AMPK activators including the FDA-approved metformin in attenuating vascular damage in polyP-associated inflammatory diseases.

The promises of lysine polyphosphorylation as a regulatory modification in mammals are tempered by conceptual and technical challenges

Polyphosphate (polyP) is a ubiquitous biomolecule thought to be present in all cells on Earth. PolyP is deceivingly simple, consisting of repeated units of inorganic phosphates polymerized in long energy-rich chains. PolyP is involved in diverse functions in mammalian systems-from cell signaling to blood clotting. One exciting avenue of research is a new nonenzymatic post-translational modification, termed lysine polyphosphorylation, wherein polyP chains are covalently attached to lysine residues of target proteins. While the modification was first characterized in budding yeast, recent work has now identified the first human targets. There is significant promise in this area of biomedical research, but a number of technical issues and knowledge gaps present challenges to rapid progress. In this review, the current state of the field is summarized and existing roadblocks related to the study of lysine polyphosphorylation in higher eukaryotes are introduced. It is discussed how limited methods to identify targets of polyphosphorylation are further impacted by low concentration, unknown regulatory enzymes, and sequestration of polyP into compartments in mammalian systems. Furthermore, suggestions on how these obstacles could be addressed or what their physiological relevance may be within mammalian cells are presented.

Supplementary research on K150del variant of activated protein C

Activated protein C (APC) is an anticoagulant with potent cytoprotective and anti-inflammatory effects. K150del, a natural variant of APC, is associated with reduced anticoagulant activity. We performed a comprehensive study to analyze the functional alterations of the K150del mutant. Transcriptome analysis of HEK 293T cells treated with wild and mutant APC revealed differentially expressed genes enriched in inflammatory, apoptotic, and virus defense-related signaling pathways. Both wild and mutant APC displayed concentration-dependent cytoprotective effects. Low concentrations of K150del mutant resulted in decreased anti-inflammatory and anti-apoptotic activities, whereas its higher concentrations restored these effects. Expression of virus defense-related genes improved in mouse lung tissues after repeated administration of the APC variant. These results suggest that the APC K150del mutant could help clinicians to accurately predict disease risks and serve as a potential auxiliary therapeutic in viral infections, including 2019 coronavirus disease (COVID-19).

The emerging role of phosphorus in human health

Phosphorus, an essential nutrient, performs vital functions in skeletal and non-skeletal tissues and is pivotal for energy production. The last two decades of research on the physiological importance of phosphorus have provided several novel insights about its dynamic nature as a nutrient performing functions as a phosphate ion. Phosphorous also acts as a signaling molecule and induces complex physiological responses. It is recognized that phosphorus homeostasis is critical for health. The intake of phosphorus by the general population world-wide is almost double the amount required to maintain health. This increase is attributed to the incorporation of phosphate containing food additives in processed foods purchased by consumers. Research findings assessed the impact of excessive phosphorus intake on cells' and organs' responses, and highlighted the potential pathogenic consequences. Research also identified a new class of bioactive phosphates composed of polymers of phosphate molecules varying in chain length. These polymers are involved in metabolic responses including hemostasis, brain and bone health, via complex mechanism(s) with positive or negative health effects, depending on their chain length. It is amazing, that phosphorus, a simple element, is capable of exerting multiple and powerful effects. The role of phosphorus and its polymers in the renal and cardiovascular system as well as on brain health appear to be important and promising future research directions.

Platelets: Underestimated Regulators of Autoinflammation in Psoriasis

Platelets have long been known as mediators of hemostasis and, more recently, as mediators of thromboinflammation, although their physiopathological role has mostly been investigated in the context of disease of internal organs, such as liver and kidney, or systemic disorders. Of late, exciting recent data suggest that platelets may also play a role in inflammation at distal sites such as the skin: recent studies show that platelets, by engaging polymorphonuclear neutrophils (PMNs), contribute to local inflammation in the frequent skin disorder, psoriasis. In an experimental model, systemic depletion of platelets drastically attenuated skin inflammation by preventing PMN infiltration of the skin. A broader role of platelets in different types of skin inflammation is therefore likely, and in this paper, we specifically review recent advances in psoriasis. Special emphasis is given to the crosstalk with systemic platelet effects, which may be of interest in psoriasis-related cardiovascular comorbidities. Furthermore, we discuss the potential for platelet-centered interventions in the therapy for psoriasis.

Is there a link between inorganic polyphosphate (polyP), mitochondria, and neurodegeneration?

Mitochondrial dysfunction - including increased apoptosis, calcium and protein dyshomeostasis within the organelle, and dysfunctional bioenergetics and oxidative status - is a common, early feature in all the major neurodegenerative diseases, including Alzheimer's Disease (AD) and Parkinson's Disease (PD). However, the exact molecular mechanisms that drive the organelle to dysfunction and ultimately to failure in these conditions are still not well described. Different authors have shown that inorganic polyphosphate (polyP), an ancient and well-conserved molecule, plays a key role in the regulation of mitochondrial physiology under basal conditions. PolyP, which is present in all studied organisms, is composed of chains of orthophosphates linked together by highly energetic phosphoanhydride bonds, similar to those found in ATP. This polymer shows a ubiquitous distribution, even if a high co-localization with mitochondria has been reported. It has been proposed that polyP might be an alternative to ATP for cellular energy storage in different organisms, as well as the implication of polyP in the regulation of many of the mitochondrial processes affected in AD and PD, including protein and calcium homeostasis. Here, we conduct a comprehensive review and discussion of the bibliography available regarding the role of polyP in the mitochondrial dysfunction present in AD and PD. Taking into account the data presented in this review, we postulate that polyP could be a valid, innovative and, plausible pharmacological target against mitochondrial dysfunction in AD and PD. However, further research should be conducted to better understand the exact role of polyP in neurodegeneration, as well as the metabolism of the polymer, and the effect of different lengths of polyP on cellular and mitochondrial physiology.

Suppressive effects of aloin on polyphosphate-mediated vascular inflammatory responses

Human endothelial cells-derived polyphosphate (PolyP) is one of the pro-inflammatory mediators as suggested by the previous reports. Aloin is the major anthraquinone glycoside obtained from the Aloe species and exhibits anti-inflammatory and anti-oxidative activities. Aloin inhibits PolyP-mediated barrier disruption, the expressions of cell adhesion molecules, and adhesion/migration of leukocyte to HUVEC. PolyP-induced NF-κB activation and the productions of TNF-α and IL-6 were inhibited by aloin in HUVECs. These anti-inflammatory functions of aloin were confirmed in PolyP-injected mice. In conclusion, based on the anti-inflammatory effects of aloin in PolyP-mediated septic response, aloin has therapeutic potential for various systemic inflammatory diseases.

Platelet polyphosphate induces fibroblast chemotaxis and myofibroblast differentiation

BACKGROUND

Platelets secrete many pro-wound healing molecules such as growth factors and cytokines. We found that releasates from activated human platelets induced the differentiation of cultured murine and human fibroblasts into a myofibroblast phenotype. Surprisingly, most of this differentiation-inducing activity was heat-stable, suggesting it was not due to the protein component of the releasates. Inorganic polyphosphate is a major constituent of platelet-dense granules and promotes blood coagulation and inflammation.

OBJECTIVES

We aim to investigate the contribution of polyphosphate on myofibroblast differentiating activity of platelet releasates.

METHODS

Using NIH-3T3 cells and primary human fibroblasts, we examined the effect of human platelet releasates and chemically synthesized polyphosphate on fibroblast differentiation and migration.

RESULTS

We found that the myofibroblast-inducing activity of platelet releasates was severely attenuated after incubation with a polyphosphate-degrading enzyme, and that fibroblasts responded to platelet-sized polyphosphate by increased levels of α-smooth muscle actin, stress fibers, and collagen. Furthermore, fibroblasts were chemotactic toward polyphosphate.

CONCLUSIONS

These findings indicate that platelet-derived polyphosphate acts as a cell signaling molecule by inducing murine and human fibroblasts to differentiate into myofibroblasts, a cell type known to drive both wound healing and fibrosing diseases. Polyphosphate therefore not only promotes early wound responses through enhancing fibrin clot formation, but also may play roles in the later stages of wound healing, and, potentially, progression of fibrotic diseases, by recruiting fibroblasts and inducing their differentiation into myofibroblasts.

Membrane Phospholipids and Polyphosphates as Cofactors and Binding Molecules of SERPINA12 (vaspin)

Visceral adipose tissue derived serine protease inhibitor (vaspin) is a member of the serpin family and has been shown to have beneficial effects on glucose tolerance, insulin stability as well as adipose tissue inflammation, parameters seriously affected by obesity. Some of these effects require inhibition of target proteases such as kallikrein 7(KLK7) and many studies have demonstrated vaspin-mediated activation of intracellular signaling cascades in various cells and tissues. So far, little is known about the exact mechanism how vaspin may trigger these intracellular signaling events. In this study, we investigated and characterized the interaction of vaspin with membrane lipids and polyphosphates as well as their potential regulatory effects on serpin activity using recombinant vaspin and KLK7 proteins and functional protein variants thereof. Here, we show for the first time that vaspin binds to phospholipids and polyphosphates with varying effects on KLK7 inhibition. Vaspin binds strongly to monophosphorylated phosphatidylinositol phosphates (PtdInsP) with no effect on vaspin activation. Microscale thermophoresis (MST) measurements revealed high-affinity binding to polyphosphate 45 (K_D: 466 ± 75 nM) and activation of vaspin in a heparin-like manner. Furthermore, we identified additional residues in the heparin binding site in β-sheet A by mutating five basic residues resulting in complete loss of high-affinity heparin binding. Finally, using lipid overlay assays, we show that these residues are additionally involved in PtdInsP binding. Phospholipids play a major role in membrane trafficking and signaling whereas polyphosphates are procoagulant and proinflammatory agents. The identification of phospholipids and polyphosphates as binding partners of vaspin will contribute to the understanding of vaspins involvement in membrane trafficking, signaling and beneficial effects associated with obesity.

Inorganic polyphosphate potentiates lipopolysaccharide-induced macrophage inflammatory response

Inorganic polyphosphate (polyP) is a linear polymer of orthophosphate units that are linked by phosphoanhydride bonds and is involved in various pathophysiological processes. However, the role of polyP in immune cell dysfunction is not well-understood. In this study, using several biochemical and cell biology approaches, including cytokine assays, immunofluorescence microscopy, receptor-binding assays with quartz crystal microbalance, and dynamic light scanning, we investigated the effect of polyP on in vitro lipopolysaccharide (LPS)-induced macrophage inflammatory response. PolyP up-regulated LPS-induced production of the inflammatory cytokines, such as tumor necrosis factor α, interleukin-1β, and interleukin-6, in macrophages, and the effect was polyP dose- and chain length-dependent. However, orthophosphate did not exhibit this effect. PolyP enhanced the LPS-induced intracellular macrophage inflammatory signals. Affinity analysis revealed that polyP interacts with LPS, inducing formation of small micelles, and the polyP-LPS complex enhanced the binding affinity of LPS to Toll-like receptor 4 (TLR4) on macrophages. These results suggest that inorganic polyP plays a critical role in promoting inflammatory response by enhancing the interaction between LPS and TLR4 in macrophages.

Mechanisms for Reducing Neuropathic Pain

Injury typically results in the development of neuropathic pain, but the pain normally decreases and disappears in paralleled with wound healing. The pain results from cells resident at, and recruited to, the injury site releasing pro-inflammatory cytokines and other mediators leading to the development of pro-inflammatory environment and causing nociceptive neurons to develop chronic ectopic electrical activity, which underlies neuropathic pain. The pain decreases as some of the cells that induce pro-inflammation, changing their phenotype leading to the blocking the release of pro-inflammatory mediators while releasing anti-inflammatory mediators, and blocking nociceptive neuron chronic spontaneous electrical activity. Often, despite apparent wound healing, the neuropathic pain becomes chronic. This raises the question of how chronic pain can be eliminated. While many of the cells and mediators contributing to the development and maintenance of neuropathic pain are known, a better understanding is required of how the injury site environment can be controlled to permanently eliminate the pro-inflammatory environment and silence the chronically electrically active nociceptive neurons. This paper examines how methods that can promote the transition of the pro-inflammatory injury site to an anti-inflammatory state, by changing the composition of local cell types, modifying the activity of pro- and anti-inflammatory receptors, inducing the release of anti-inflammatory mediators, and silencing the chronically electrically active nociceptive neurons. It also examines the hypothesis that factors released from platelet-rich plasma applied to chronic pain sites can permanently eliminate chronic inflammation and its associated chronic pain.

Injury-Induced Effectors of Neuropathic Pain

Injuries typically result in the development of neuropathic pain, which decreases in parallel with wound healing. However, the pain may remain after the injury appears to have healed, which is generally associated with an ongoing underlying pro-inflammatory state. Injury induces many cells to release factors that contribute to the development of a pro-inflammatory state, which is considered an essential first step towards wound healing. However, pain elimination requires a transition of the injury site from pro- to anti-inflammatory. Therefore, developing techniques that eliminate chronic pain require an understanding of the cells resident at and recruited to injury sites, the factors they release, that promote a pro-inflammatory state, and promote the subsequent transition of that site to be anti-inflammatory. Although a relatively large number of cells, factors, and gene expression changes are involved in these processes, it may be possible to control a relatively small number of them leading to the reduction and elimination of chronic neuropathic pain. This first of two papers examines the roles of the most salient cells and mediators associated with the development and maintenance of chronic neuropathic pain. The following paper examines the cells and mediators involved in reducing and eliminating chronic neuropathic pain.

Inhibition of IP6K1 suppresses neutrophil-mediated pulmonary damage in bacterial pneumonia

The significance of developing host-modulating personalized therapies to counteract the growing threat of antimicrobial resistance is well-recognized because such resistance cannot be overcome using microbe-centered strategies alone. Immune host defenses must be finely controlled during infection to balance pathogen clearance with unwanted inflammation-induced tissue damage. Thus, an ideal antimicrobial treatment would enhance bactericidal activity while preventing neutrophilic inflammation, which can induce tissue damage. We report that disrupting the inositol hexakisphosphate kinase 1 (Ip6k1) gene or pharmacologically inhibiting IP6K1 activity using the specific inhibitor TNP [N2-(m-(trifluoromethyl)benzyl) N6-(p-nitrobenzyl)purine] efficiently and effectively enhanced host bacterial killing but reduced pulmonary neutrophil accumulation, minimizing the lung damage caused by both Gram-positive and Gram-negative bacterial pneumonia. IP6K1-mediated inorganic polyphosphate (polyP) production by platelets was essential for infection-induced neutrophil-platelet aggregate (NPA) formation and facilitated neutrophil accumulation in alveolar spaces during bacterial pneumonia. IP6K1 inhibition reduced serum polyP levels, which regulated NPAs by triggering the bradykinin pathway and bradykinin-mediated neutrophil activation. Thus, we identified a mechanism that enhances host defenses while simultaneously suppressing neutrophil-mediated pulmonary damage in bacterial pneumonia. IP6K1 is, therefore, a legitimate therapeutic target for such disease.

Schistosomes can hydrolyze proinflammatory and prothrombotic polyphosphate (polyP) via tegumental alkaline phosphatase, SmAP

Schistosoma mansoni is a long-lived intravascular trematode parasite that can infect humans causing the chronic debilitating disease, schistosomiasis. We hypothesize that the action of host-interactive proteins found at the schistosome surface allows the worms to maintain a safe, anti-thrombotic and anti-inflammatory environment around them in the bloodstream. One such protein is the ˜60 kDa alkaline phosphatase SmAP which is known to be expressed in the outer tegument of all intravascular life stages. We demonstrate in this work that the parasites (schistosomula as well as adult males and females) can hydrolyze polyphosphate (polyP) - an anionic, linear polymer of inorganic phosphates that is produced and released by immune cells as well as by activated platelets and that induce proinflammatory and prothrombotic pathways. Purified recombinant SmAP can likewise cleave polyP and with a Km of 6.9 ± 1 mM. Finally, parasites whose SmAP gene has been suppressed by RNAi are significantly impaired in their ability to hydrolyze polyP. SmAP-mediated cleavage of polyP may contribute to the armamentarium of schistosomes that promotes their survival in the hostile intravascular habitat. This is the first report of any pathogen cleaving this bioactive metabolite.

Polyphosphate as a Target for Interference With Inflammation and Thrombosis

Activated platelets and mast cells expose the inorganic polymer, polyphosphate (polyP) on their surfaces. PolyP initiates procoagulant and proinflammatory reactions and the polymer has been recognized as a therapeutic target for interference with blood coagulation and vascular hyperpermeability. PolyP content and chain length depend on the specific cell type and energy status, which may affect cellular functions. PolyP metabolism has mainly been studied in bacteria and yeast, but its roles in eukaryotic cells and mammalian systems have remained enigmatic. In this review, we will present an overview of polyP functions, focusing on intra- and extracellular roles of the polymer and discuss open questions that emerge from the current knowledge on polyP regulation.

Microvascular Mechanisms of Polyphosphate-Induced Neutrophil-Endothelial Cell Interactions in vivo

BACKGROUND

Polyphosphates (PolyPs) have been reported to exert pro-inflammatory effects. However, the molecular mechanisms regulating PolyP-provoked tissue accumulation of leukocytes are not known. The aim of the present investigation was to determine the role of specific adhesion molecules in PolyP-mediated leukocyte recruitment.

METHODS

PolyPs and TNF-α were intrascrotally administered, and anti-P-selectin, anti-E-selectin, anti-P-selectin glycoprotein ligand-1 (PSGL-1), anti-membrane-activated complex-1 (Mac-1), anti-lymphocyte function antigen-1 (LFA-1), and neutrophil depletion antibodies were injected intravenously or intraperitoneally. Intravital microscopy of the mouse cremaster microcirculation was used to examine leukocyte-endothelium interactions and recruitment in vivo.

RESULTS

Intrascrotal injection of PolyPs increased leukocyte accumulation. Depletion of neutrophils abolished PolyP-induced leukocyte-endothelium interactions, indicating that neutrophils were the main leukocyte subtype responding to PolyP challenge. Immunoneutralization of P-selectin and PSGL-1 abolished PolyP-provoked neutrophil rolling, adhesion, and emigration. Moreover, immunoneutralization of Mac-1 and LFA-1 had no impact on neutrophil rolling but markedly reduced neutrophil adhesion and emigration evoked by PolyPs.

CONCLUSION

These results suggest that P-selectin and PSGL-1 exert important roles in PolyP-induced inflammatory cell recruitment by mediating neutrophil rolling. In addition, our data show that Mac-1 and LFA-1 are necessary for supporting PolyP-triggered firm adhesion of neutrophils to microvascular endothelium. These novel findings define specific molecules as potential targets for pharmacological intervention in PolyP-dependent inflammatory diseases.

Inorganic polyphosphate, a multifunctional polyanionic protein scaffold

Polyphosphate (polyP) consists of a linear arrangement of inorganic phosphates and defies its structural simplicity with an astounding number of different activities in the cell. Already well known for its ability to partake in phosphate, calcium, and energy metabolism, polyP recently gained a new functional dimension with the discovery that it serves as a stabilizing scaffold for protein-folding intermediates. In this review, we summarize and discuss the recent studies that have identified polyP not only as a potent protein-like chaperone that protects cells against stress-induced protein aggregation, but also as a robust modifier of amyloidogenic processes that shields neuronal cells from amyloid toxicity. We consider some of the most pressing questions in the field, the obstacles faced, and the potential avenues to take to provide a complete picture about the working mechanism and physiological relevance of this intriguing biopolymer.

Inorganic polyphosphate protects against lipopolysaccharide-induced lethality and tissue injury through regulation of macrophage recruitment

Sepsis is an etiologically complex and often fatal inflammatory process involving a multitude of cytokine signaling pathways. Tumor necrosis factor α (TNFα) acts as a central regulator of the acute-phase inflammatory response by recruiting immune cells, including circulating monocyte/macrophages, to sites of infection or tissue damage. Inorganic polyphosphate (polyP), a linear polymer of orthophosphate residues, has been found in almost all cells and tissues, but its functions in immunity remain largely unknown. In this study, we show that pre- or post-treatment of mice with polyP₁₅₀ (average chain length of 150 phosphate residues) markedly increases survival from lipopolysaccharide (LPS)-induced shock and inhibits macrophage recruitment to the liver and lungs, resulting in protection against tissue injury. In accord with these in vivo results, pretreatment of cultured peritoneal macrophages with polyP₁₅₀ inhibited chemotaxis and actin polarization in response to TNFα. PolyP₁₅₀ also inhibited phosphorylation of stress-activated protein kinases c-Jun N-terminal kinase (JNK) and p38, two downstream signaling molecules of the TNFα cascade, thereby preventing cyclooxygenase-2 gene expression by macrophages. These findings suggest that polyP₁₅₀ inhibits recruitment of macrophages into organs by regulating the TNFα-JNK/p38 pathway, which may, in turn, protect against multi-organ dysfunction and lethality induced by LPS. Our findings identify polyP regulation as a novel therapeutic target for sepsis.

From underlying chemistry to therapeutic potential: open questions in the new field of lysine polyphosphorylation

Polyphosphorylation is a newly described non-enzymatic post-translational modification wherein long chains of inorganic phosphates are attached to lysine residues. The first targets of polyphosphorylation identified were S. cerevisiae proteins Nsr1 and Top1. Building on this theme, we recently exploited functional genomics tools in yeast to identify 15 new targets, including a conserved network of nucleolar proteins implicated in ribosome biogenesis. We also described the polyphosphorylation of six human proteins, suggesting that this unique post-translational modification could be conserved throughout eukaryotes. The study of polyphosphorylation seems poised to uncover novel modes of protein regulation in pathways spanning diverse biological processes. In this review, we establish a framework for future work by outlining critical questions related to the biochemistry of polyphosphorylation, its therapeutic potential, and everything in between.

Vascular Permeability and Remodelling Coincide with Inflammatory and Reparative Processes after Joint Bleeding in Factor VIII-Deficient Mice

Vascular remodelling is a prominent feature of haemophilic arthropathy (HA) that may underlie re-bleeding, yet the nature of vascular changes and underlying mechanisms remain largely unknown. Here, we aimed to characterize synovial vascular remodelling and vessel integrity after haemarthrosis, as well as temporal changes in inflammatory and tissue-reparative pathways. Thirty acutely painful joints in patients with haemophilia (PWH) were imaged by musculoskeletal ultrasound with Power Doppler (MSKUS/PD) to detect vascular abnormalities and bloody effusions. Nineteen out of 30 painful joint episodes in PWH were associated with haemarthrosis, and abnormal vascular perfusion was unique to bleeding joints. A model of induced haemarthrosis in factor VIII (FVIII)-deficient mice was used for histological assessment of vascular remodelling (α-smooth muscle actin [αSMA] expression), and monitoring of in vivo vascular perfusion and permeability by MSKUS/PD and albumin extravasation, respectively. Inflammatory (M1) and reparative (M2) macrophage markers were quantified in murine synovium over a 10-week time course by real-time polymerase chain reaction. The abnormal vascular perfusion observed in PWH was recapitulated in FVIII-deficient mice after induced haemarthrosis. Neovascularization and increased vessel permeability were apparent 2 weeks post-bleed in FVIII-deficient mice, after a transient elevation of inflammatory macrophage M1 markers. These vascular changes subsided by week 4, while vascular remodelling, evidenced by architectural changes and pronounced αSMA expression, persisted alongside a reparative macrophage M2 response. In conclusion, haemarthrosis leads to transient inflammation coupled with neovascularization and associated vascular permeability, while subsequent tissue repair mechanisms coincide with vascular remodelling. Together, these vascular changes may promote re-bleeding and HA progression.

Isolation, Synthesis, and Antisepsis Effects of a C-Methylcoumarinochromone Isolated from Abronia nana Cell Culture

Only a few isoflavones have been isolated from plants of the genus Abronia. The biological properties of compounds isolated from Abronia species have not been well established, and their antisepsis effects have not been reported yet. In the present study, a new C-methylcoumarinochromone, was isolated from Abronia nana suspension cultures. Its structure was deduced as 9,11-dihydroxy-10-methylcoumarinochromone (boeravinone Y, 1) by spectroscopic data analysis and verified by chemical synthesis. The potential inhibitory effects of 1 against high mobility group box 1 (HMGB1)-mediated septic responses were investigated. Results showed that 1 effectively inhibited lipopolysaccharide-induced release of HMGB1 and suppressed HMGB1-mediated septic responses, in terms of reduction of hyperpermeability, leukocyte adhesion and migration, and cell adhesion molecule expression. In addition, 1 increased the phagocytic activity of macrophages and exhibited bacterial clearance effects in the peritoneal fluid and blood of mice with cecal ligation and puncture-induced sepsis. Collectively, these results suggested that 1 might have potential therapeutic activity against various severe vascular inflammatory diseases via inhibition of the HMGB1 signaling pathway.

Translational Implications of Platelets as Vascular First Responders

Platelets play a vital role in normal hemostasis to stem blood loss at sites of vascular injury by tethering and adhering to sites of injury, recruiting other platelets and blood cells to the developing clot, releasing vasoactive small molecules and proteins, and assembling and activating plasma coagulation proteins in a tightly regulated temporal and spatial manner. In synchrony with specific end products of coagulation, primarily cross-linked fibrin, a stable thrombus quickly forms. Far beyond physiological hemostasis and pathological thrombosis, emerging evidence supports platelets playing a pivotal role in vascular homeostasis, inflammation, cellular repair, regeneration, and wide range of autocrine and paracrine functions. In essence, platelets play both structural and functional roles as reporters, messengers, and active transporters surveying the vasculature for cues of environmental or developmental stimuli and participating as first responders.1 In this review, we will provide a contemporary perspective of platelet physiology, including fundamental, translational, and clinical constructs that apply directly to human health and disease.

Amorphous polyphosphate, a smart bioinspired nano-/bio-material for bone and cartilage regeneration: towards a new paradigm in tissue engineering

Physiological amorphous polyphosphate nano/micro-particles, injectable and implantable, attract and stimulate MSCs into implants for tissue regeneration.

Antiseptic effects of dabrafenib on TGFBIp-induced septic responses

Transforming growth factor-β-induced protein (TGFBIp), an extracellular protein, is expressed on several cell types in response to TGF-β stimulation. Human umbilical vein endothelial cell (HUVEC)-derived TGFBIp functions as a mediator of sepsis. Screening of bioactive compound libraries is an effective approach for repositioning FDA-approved drugs or discovering new treatments for human diseases (drug repositioning). Dabrafenib (DAB), a B-Raf inhibitor, was initially used for treating metastatic melanoma. The present study determined whether DAB modulated TGFBIp-mediated septic responses in HUVECs and in mice. Antiseptic functions of DAB were examined by measuring permeability, leukocyte adhesion and migration, and proinflammatory protein activation in TGFBIp-stimulated HUVECs and mice. In addition, beneficial effects of DAB on survival rate were examined using a mouse model of sepsis. We found that DAB inhibited TGFBIp-induced vascular barrier disruption, cell adhesion molecule (CAM) expression, and neutrophil adhesion/transendothelial migration toward human endothelial cells. DAB also suppressed TGFBIp-induced hyperpermeability and leukocyte migration in vivo. These results suggest that DAB exerts anti-inflammatory effects by inhibiting hyperpermeability, CAM expression, and leukocyte adhesion and migration, indicating its utility for treating vascular inflammatory diseases.

Role of moesin in HMGB1-stimulated severe inflammatory responses

Sepsis is a life-threatening condition that arises when the body’s response to infection causes systemic inflammation. High-mobility group box 1 (HMGB1), as a late mediator of sepsis, enhances hyper-permeability, and it is therefore a therapeutic target. Despite extensive research into the underlying mechanisms of sepsis, the target molecules controlling vascular leakage remain largely unknown. Moesin is a cytoskeletal protein involved in cytoskeletal changes and para-cellular gap formation. The objectives of this study were to determine the roles of moesin in HMGB1-mediated vascular hyperpermeability and inflammatory responses and to investigate the mechanisms of action underlying these responses. Using siRNA knockdown of moesin expression in primary human umbilical vein endothelial cells (HUVECs), moesin was found to be required in HMGB1-induced F-actin rearrangement, hyperpermeability, and inflammatory responses. The mechanisms involved in moesin phosphorylation were analysed by blocking the binding of the HMGB1 receptor (RAGE) and inhibiting the Rho and MAPK pathways. HMGB1-treated HUVECs exhibited an increase in Thr558 phosphorylation of moesin. Circulating levels of moesin were measured in patients admitted to the intensive care unit with sepsis, severe sepsis, and septic shock; these patients showed significantly higher levels of moesin than healthy controls, which was strongly correlated with disease severity. High blood moesin levels were also observed in cecal ligation and puncture (CLP)-induced sepsis in mice. Administration of blocking moesin antibodies attenuated CLP-induced septic death. Collectively, our findings demonstrate that the HMGB1-RAGE-moesin axis can elicit severe inflammatory responses, suggesting it to be a potential target for the development of diagnostics and therapeutics for sepsis.

In vivo activation and functions of the protease factor XII

Combinations of proinflammatory and procoagulant reactions are the unifying principle for a variety of disorders affecting the cardiovascular system. Factor XII (FXII, Hageman factor) is a plasma protease that initiates the contact system. The biochemistry of the contact system in vitro is well understood; however, its in vivo functions are just beginning to emerge. The current review concentrates on activators and functions of the FXII-driven contact system in vivo. Elucidating its physiologic activities offers the exciting opportunity to develop strategies for the safe interference with both thrombotic and inflammatory diseases.

Suppressive Effects of Sulforaphane on TGFBIp-mediated Sepsis

Sulforaphane (SFN) is produced when the enzyme myrosinase transforms glucoraphanin upon damage to the plant such as from chewing and effective in preventing carcinogenesis, diabetes, and inflammatory responses. Transforming growth factor β-induced protein (TGFBIp) is an extracellular matrix protein whose expression in several cell types is greatly increased by TGF-β. TGFBIp is released by human umbilical vein endothelial cells (HUVECs) and functions as a mediator of experimental sepsis. We hypothesized that SFN could reduce TGFBIp-mediated severe inflammatory responses in human endothelial cells and mice. Here, we investigated the anti-septic effects and underlying mechanisms of SFN against TGFBIp-mediated septic responses. SFN effectively inhibited lipopolysaccharide-induced release of TGFBIp and suppressed TGFBIp-mediated septic responses. In addition, SFN suppressed cecal ligation and puncture (CLP)-induced sepsis lethality and pulmonary injury. In conclusion, SFN suppressed TGFBIp-mediated and CLP-induced septic responses. Therefore, SFN could be a potential therapeutic agent for treatment of various severe vascular inflammatory diseases via inhibition of the TGFBIp signaling pathway.

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.

Role of MiR-126a-3p in Endothelial Injury in Endotoxic Mice

OBJECTIVE

Sepsis poses a serious global health problem with an overall mortality rate of 30%, in which the vascular injury is a major contributor. The study is to determine the expression profile of micro-RNAs in endotoxic vascular walls and their potential roles in sepsis-related vascular injury.

DESIGN

Prospective randomized study.

SETTING

Laboratory investigation.

SUBJECTS

Male C57BL/6 mice, average weight 26.5 ± 1.8 g.

INTERVENTIONS

Endotoxemia was induced in mice via lipopolysaccharide injection (20 mg/kg, intraperitoneal) (Sigma, St. Louis, MO). The control mice were injected with the same amount of saline (500 μL, intraperitoneal). In a subgroup of mice, a high dose of lipopolysaccharide (30 mg/kg, intraperitoneal) was applied to induce endotoxin-related death.

MEASUREMENTS AND MAIN RESULTS

The mi-RNA expression profiles in aortas from lipopolysaccharide-induced endotoxic mice were determined. The result demonstrated that some micro-RNAs were aberrantly expressed in endotoxic mouse arteries. Among them, the endothelial cell-enriched/endothelial cell-specific miR-126a-3p was significantly down-regulated in endotoxic mouse arteries, septic human vessels, as well as vascular endothelial cells isolated from endotoxic mice or treated with lipopolysaccharide. The down-regulation of miR-126a-3p occurred at transcriptional level via the decreased expression of Krüppel-like factor 2, which could be inhibited by Krüppel-like factor 2 over-expression via adenovirus expressing Krüppel-like factor 2. The down-regulation of miR-126a-3p in endothelial cells resulted in the increased apoptosis, and decreased proliferation and migration, which were inhibited by miR-126a-3p mimics. In vivo, over-expression of miR-126a-3p via lentivirus attenuated endotoxemia-induced injuries on endothelial function and vascular permeability. We found that SPRED1 and VCAM-1 were two direct target genes of miR-126a-3p related to miR-126a-3p-mediated effects in endotoxemia. Finally, the survival rate of endotoxic mice was significantly increased by the over-expression of miR-126a-3p.

CONCLUSIONS

The results suggest that vascular micro-RNAs such as miR-126a-3p may represent novel mechanisms and new therapeutic targets for endotoxemia-induced vascular injury and endotoxic mortality.

Anti-inflammatory effects of pelargonidin on TGFBIp-induced responses

Transforming growth factor β induced protein (TGFBIp) is an extracellular matrix protein expressed in several cell types in response to TGF-β. TGFBIp is released by human umbilical vein endothelial cells (HUVECs) and functions as a mediator of experimental sepsis. 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. This study was undertaken to investigate whether PEL can modulate TGFBIp-mediated inflammatory responses in HUVECs and in mice. The anti-inflammatory activities of PEL were determined by measuring permeability, leukocyte adhesion and migration, and activation of proinflammatory proteins in TGFBIp-activated HUVECs and mice. In addition, the beneficial effects of PEL on survival rate in a mouse sepsis model were tested. We found that PEL inhibited TGFBIp-induced barrier disruption, expression of cell adhesion molecules and adhesion/transendothelial migration of neutrophils to human endothelial cells. PEL also suppressed TGFBIp-induced hyperpermeability and leukocyte migration in vivo. These results suggest that PEL possesses anti-inflammatory properties that result in inhibition of hyperpermeability, expression of cell adhesion molecules, and adhesion and migration of leukocytes, thereby endorsing its usefulness as a therapy for vascular inflammatory diseases.