Activation of CXCR2 by extracellular matrix degradation product acetylated Pro-Gly-Pro has therapeutic effects against sepsis

Cell-liposome delivery system based on neuroinflammation to target the amygdala for ameliorating depressive-like behaviors

Depression is a serious psychiatric disorder with unsatisfactory outcomes due to difficulties in delivering therapeutic molecules from the periphery to the brain. Neuroinflammation plays a key role in neurobiology and the treatment of depression. Neutrophils can cross the blood-brain barrier (BBB) and infiltrate key brain regions related to the pathophysiology of depression during neuroinflammation. N-Acetyl Pro-Gly-Pro (PGP) peptides efficiently bind to CXCR2 receptors on the surface of neutrophils. The neuropeptide oxytocin demonstrated antidepressant properties in preclinical and clinical studies, but its inability to penetrate the BBB hampers its therapeutic applications. In this study, we established a novel drug delivery system based on neutrophil infiltration in key brain regions during neuroinflammation. PGP was used to modify oxytocin-loaded liposomes (PGP-OTL) as the target ligand. Systematic administration of PGP-OTL exhibited enhanced antidepressant properties resulting from elevated oxytocin concentrations, especially in the amygdala, a crucial depression-implicated brain region. Enhanced antidepressant effects of PGP-OTL, similar to the ones caused by central oxytocin infusion, were observed in behavioral measurement including forced swim and tail suspension tests. Our study demonstrated that PGP-OTL can "hitchhike" neutrophils and enhance delivery of therapeutics into the brain, thus providing the means for developing novel cell-liposome-based drug delivery strategies for depression therapy.

The immunological function of CXCR2 in the liver during sepsis

Background

The chemokine receptor CXCR2 and its ligands, especially CXCL8, are crucial mediators for the progression of liver inflammation and liver failure in sepsis. Neutrophils have the highest CXCR2 expression in mice and humans, and their activation via CXCL8 facilitates their migration to the inflamed liver for the clearance of the pathogens and, in turn, the inflammation.

Main body

In sepsis, the inflammatory insult causes extensive neutrophil migration to the liver that overwhelms the immune response. To compensate for the strong receptor activation, CXCR2 desensitizes, incapacitating the immune cells to efficiently clear pathogens, causing further life-threatening liver damage and uncontrolled pathogen spread.

Conclusion

CXCR2 function during infection strongly depends on the expressing cell type. It signals pro- and anti-inflammatory effects that may prompt novel cell-type-specific CXCR2-directed therapeutics.

Highway to heal: Influence of altered extracellular matrix on infiltrating immune cells during acute and chronic lung diseases

Environmental insults including respiratory infections, in combination with genetic predisposition, may lead to lung diseases such as chronic obstructive pulmonary disease, lung fibrosis, asthma, and acute respiratory distress syndrome. Common characteristics of these diseases are infiltration and activation of inflammatory cells and abnormal extracellular matrix (ECM) turnover, leading to tissue damage and impairments in lung function. The ECM provides three-dimensional (3D) architectural support to the lung and crucial biochemical and biophysical cues to the cells, directing cellular processes. As immune cells travel to reach any site of injury, they encounter the composition and various mechanical features of the ECM. Emerging evidence demonstrates the crucial role played by the local environment in recruiting immune cells and their function in lung diseases. Moreover, recent developments in the field have elucidated considerable differences in responses of immune cells in two-dimensional versus 3D modeling systems. Examining the effect of individual parameters of the ECM to study their effect independently and collectively in a 3D microenvironment will help in better understanding disease pathobiology. In this article, we discuss the importance of investigating cellular migration and recent advances in this field. Moreover, we summarize changes in the ECM in lung diseases and the potential impacts on infiltrating immune cell migration in these diseases. There has been compelling progress in this field that encourages further developments, such as advanced in vitro 3D modeling using native ECM-based models, patient-derived materials, and bioprinting. We conclude with an overview of these state-of-the-art methodologies, followed by a discussion on developing novel and innovative models and the practical challenges envisaged in implementing and utilizing these systems.

IM156, a new AMPK activator, protects against polymicrobial sepsis

IM156, a novel biguanide with higher potency of AMP‐activated protein kinase activation than metformin, has inhibitory activity against angiogenesis and cancer. In this study, we investigated effects of IM156 against polymicrobial sepsis. Administration of IM156 significantly increased survival rate against caecal ligation and puncture (CLP)‐induced sepsis. Mechanistically, IM156 markedly reduced viable bacterial burden in the peritoneal fluid and peripheral blood and attenuated organ damage in a CLP‐induced sepsis model. IM156 also inhibited the apoptosis of splenocytes and the production of inflammatory cytokines including IL‐1β, IL‐6 and IL‐10 in CLP mice. Moreover, IM156 strongly inhibited the generation of reactive oxygen species and subsequent formation of neutrophil extracellular traps in response to lipopolysaccharide in neutrophils. Taken together, these results show that IM156 can inhibit inflammatory response and protect against polymicrobial sepsis, suggesting that IM156 might be a new treatment for sepsis.

Placement of Tyrosine Residues as a Design Element for Tuning the Phase Transition of Elastin-peptide-containing Conjugates: Experiments and Simulations

Elastin-like polypeptides (ELP) have been widely used in the biomaterials community due to their controllable, thermoresponsive properties and biocompatibility. Motivated by our previous work on the effect of tryptophan (W) substitutions on the LCST-like transitions of short ELPs, we studied a series of short ELPs containing tyrosine (Y) and/or phenylalanine (F) guest residues with only 5 or 6 pentapeptide repeat units. A combination of experiments and molecular dynamics (MD) simulations illustrated that the substitution of F with Y guest residues impacted the transition temperature (Tt) of short ELPs when conjugated to collagen-like-peptides (CLP), with a reduction in the transition temperature observed only after substitution of at least two residues. Placement of the Y residues near the N-terminal end of the ELP, away from the tethering point to the CLP, resulted in a lower Tt than that observed for peptides with the Y residues near the tethering point. Atomistic and coarse-grained MD simulations indicated an increase in intra- and inter- peptide hydrogen bonds in systems containing Y guest residues that are suggested to enhance the ability of the peptides to coacervate, with a concomitantly lower Tt. Simulations also revealed that the placement of Y-containing pentads near the N-terminus (i.e., away from CLP tethering point) versus C-terminus of the ELP led to more π-π stacking interactions at low temperatures, in agreement with our experimental observations of a lower Tt. Overall, this study provides mechanistic insights into the driving forces for the LCST-like transitions of ELPs and offers additional means for tuning the Tt of short ELPs for biomedical applications such as on-demand drug delivery and tissue engineering.

A membrane-tethering pepducin derived from formyl peptide receptor 3 shows strong therapeutic effects against sepsis

Formyl peptide receptors (FPRs) are G protein-coupled receptors mainly expressed in inflammatory myeloid cells. Previous reports demonstrated that human neutrophils express only FPR1 and FPR2 but not FPR3. Here, we found that FPR3 is expressed in sepsis patient derived neutrophils and Fpr3 is expressed in the mouse neutrophils. To test the role of Fpr3 in neutrophil activity, we synthesized Fpr3 pepducins and successfully developed an agonistic pepducin that stimulates Fpr3, eliciting calcium increase and chemotactic migration of neutrophils. We also found that administration of an Fpr3 pepducin in an experimental mouse sepsis model significantly increased the survival rate. The pepducin markedly inhibited lung injury, splenocyte apoptosis, and inflammatory cytokine production. Bacterial counts were significantly decreased by the pepducin in septic mice. Based on these results, we suggest that FPR3 can be regarded as a new target to control sepsis, and the newly generated Fpr3-based pepducin can be used for the development of anti-septic agents.

Therapeutic Targeting of Apoptosis Inhibitor of Macrophage/CD5L in Sepsis

The factors involved in disturbing host homeostasis during sepsis are largely unknown. We sought to determine the immunopathological role of apoptosis inhibitor of macrophage (AIM)/CD5L in sepsis. Here, we show that blockade of AIM led to significantly increased survival after experimental sepsis, and it decreased local and systemic inflammation, reduced tissue injury, and inhibited bacterial dissemination in the blood, in particular at later time points. Supplementation of recombinant AIM in sepsis resulted in increased tissue injury, amplified inflammation, increased bacteremia, and worsened mortality. Interestingly, the most important difference in the production of cytokines and chemokines after in vivo AIM blockade or AIM administration during sepsis was IL-10. In vitro, AIM enhanced IL-10 production from macrophages, neutrophils, or lymphocytes. In vivo, the beneficial effects of AIM blockade and the detrimental effects of AIM addition on experimental sepsis were ablated by treatment with recombinant IL-10 and neutralizing anti-IL-10 antibodies, respectively. This study is the first to identify AIM as an important mediator in disturbing host homeostasis in sepsis.

Proline-containing peptides-New insight and implications: A Review

The family of regulatory proline-containing peptides (PCPs), also known as glyprolines, exhibit significant biological activity. The group of glyprolines includes Gly-Pro (GP), Pro-Gly-Pro (PGP), cyclic Gly-Pro (cGP), as well as PGP derivatives, for example, N-acetylated PGP (N-a-PGP) and N-methylated PGP (N-m-PGP). PCPs are engaged in various biological processes including the proinflammatory neutrophil chemoattraction in lung diseases, inflammatory bowel diseases or ischemic stroke. Glyprolines have been also postulated to play an important role as atheroprotective and anticoagulant agents, exhibit neuroprotective effects in Parkinson's disease, as well as regulate insulin-like growth factor (IGF) homeostasis. It was also noticed that PCPs inhibit proliferation and migration of keratinocytes in wound healing, protection of the gastric mucosa and stimulation of its regeneration. The regulatory glyprolines are derived from endogenous and exogenous sources. Most PCPs are derived from collagen or diet protein degradation. Recently, great interest is concentrated on short proline-rich oligopeptides derived from IGF-1 degradation. The mechanism of PCPs biological activity is not fully explained. It involves receptor-mediated mechanisms, for example, N-a-PGP acts as CXCR1/2 receptor ligand, whereas cGP regulates IGF-1 bioavailability by modifying the IGF-1 binding to the IGF-1 binding protein-3. PGP has been observed to interact with collagen-specific receptors. The data suggest a promising role of PGP as a target of various diseases therapy. This review is focused on the effect of PCPs on metabolic processes in different tissues and the molecular mechanism of their action as an approach to pharmacotherapy of PCPs-dependent diseases.

Flagellin attenuates experimental sepsis in a macrophage-dependent manner

Background

Sepsis is the leading cause of death among critically ill patients, and no specific therapeutic agent is currently approved for the treatment of sepsis.

Methods

We assessed the effects of flagellin administration on survival, bacterial burden, and tissue injury after sepsis. In addition, we examined the effects on phagocytosis and bacterial killing in monocytes/macrophages.

Results

Therapeutic administration of flagellin increased bacterial clearance, decreased organ inflammation and injury, and reduced immune cell apoptosis after experimental sepsis, in a Toll-like receptor 5 (TLR5)–dependent manner. Macrophages, but not neutrophils, mediated the beneficial effects of flagellin on experimental sepsis, and flagellin induced macrophage polarization into M1 in septic mice. Flagellin treatment could directly enhance phagocytosis and bacterial killing of macrophages, but not neutrophils. Subsequent studies demonstrated that flagellin could promote phagosome formation and increase reactive oxygen species (ROS) levels in macrophages. Finally, we found that the expression of TLR5 was significantly elevated on the surface of circulating monocytes, but not neutrophils, from patients with sepsis. Higher expression levels of TLR5 on monocytes were associated with increased mortality, documented bacteremia, and higher Sequential Organ Failure Assessment scores of the septic patients. Moreover, flagellin treatment rescued the impaired phagocytosis and bacterial killing ability of monocytes/macrophages from patients who died of sepsis.

Conclusions

These novel findings not only established the potential value of application of flagellin as an immunoadjuvant in treating sepsis, but also provided new insights into targeted therapeutic strategy on the basis of monocyte TLR5 expression in septic patients.

Electronic supplementary material

The online version of this article (10.1186/s13054-019-2408-7) contains supplementary material, which is available to authorized users.

Role of CXCR2 in the Ac-PGP-Induced Mobilization of Circulating Angiogenic Cells and its Therapeutic Implications

Circulating angiogenic cells (CACs) have been implicated in the repair of ischemic tissues, and their mobilization from bone marrow is known to be regulated by the activations of chemokine receptors, including CXCR2 and CXCR4. This study was conducted to investigate the role of N‐acetylated proline‐glycine‐proline (Ac‐PGP; a collagen‐derived chemotactic tripeptide) on CAC mobilization and its therapeutic potential for the treatment of peripheral artery diseases. Ac‐PGP was administered daily to a murine hind limb ischemia model, and the effects of Ac‐PGP on blood perfusion and CAC mobilization (Sca1⁺Flk1⁺ cells) into peripheral blood were assessed. Intramuscular administration of Ac‐PGP significantly improved ischemic limb perfusion and increased limb salvage rate by increasing blood vessel formation, whereas Ac‐PGP‐induced blood perfusion and angiogenesis in ischemic limbs were not observed in CXCR2‐knockout mice. In addition, Ac‐PGP‐induced CAC mobilization was found to occur in wild‐type mice but not in CXCR2‐knockout mice. Transplantation of bone marrow from green fluorescent protein (GFP) transgenic mice to wild‐type mice showed bone marrow‐derived cells homed to ischemic limbs after Ac‐PGP administration and that GFP‐positive cells contributed to the formation of ILB4‐positive capillaries and α smooth muscle actin (α‐SMA)‐positive arteries. These results suggest CXCR2 activation in bone marrow after Ac‐PGP administration improves blood perfusion and reduces tissue necrosis by inducing CAC mobilization. These findings suggest a new pharmaceutical basis for the treatment of critical limb ischemia. stem cells translational medicine2019;8:236&246

Activation of formyl peptide receptor 2 by WKYMVm enhances emergency granulopoiesis through phospholipase C activity

Emergency granulopoiesis is a very important strategy to supply efficient neutrophil number in response to infection. However, molecular mechanism involved in this process remains unclear. Here, we found that administration of WKYMVm, an immune modulating peptide, to septic mice strongly increased neutrophil number through augmented emergency granulopoiesis. WKYMVm-induced emergency granulopoiesis was blocked not only by a formyl peptide receptor 2 (FPR2) antagonist (WRW4), but also by FPR2 deficiency. As progenitors of neutrophils, Lin⁻c-kit⁺Sca-1⁻ cells expressed FPR2. WKYMVm-induced emergency granulopoiesis was also blocked by a phospholipase C inhibitor (U-73122). These results suggest that WKYMVm can stimulate emergency granulopoiesis via FPR2 and phospholipase C enzymatic activity.

Surface modification of PGP for a neutrophil-nanoparticle co-vehicle to enhance the anti-depressant effect of baicalein

Exploiting cells as vehicles combined with nanoparticles combined with therapy has attracted increasing attention in the world recently. Red blood cells, leukocytes and stem cells have been used for tumor immunotherapy, tissue regeneration and inflammatory disorders, and it is known that neutrophils can accumulate in brain lesions in many brain diseases including depression. N-Acetyl Pro-Gly-Pro (PGP) peptide shows high specific binding affinity to neutrophils through the CXCR2 receptor. In this study, PGP was used to modify baicalein-loaded solid lipid nanoparticles (PGP-SLNs) to facilitate binding to neutrophils in vivo. Brain-targeted delivery to the basolateral amygdala (BLA) was demonstrated by enhanced concentration of baicalein in the BLA. An enhanced anti-depressant effect was observed in vitro and in vivo. The mechanism involved inhibition of apoptosis and a decrease in lactate dehydrogenase release. Behavioral evaluation carried out with rats demonstrated that anti-depression outcomes were achieved. The results indicate that PGP-SLNs decrease immobility time, increase swimming time and climbing time and attenuate locomotion in olfactory-bulbectomized (OB) rats. In conclusion, PGP modification is a strategy for targeting the brain with a cell-nanoparticle delivery system for depression therapy.

Inflammation-Generated Extracellular Matrix Fragments Drive Lung Metastasis

Mechanisms explaining the propensity of a primary tumor to metastasize to a specific site still need to be unveiled, and clinical studies support a link between chronic inflammation and cancer dissemination to specific tissues. Using different mouse models, we demonstrate the role of inflammation-generated extracellular matrix fragments ac-PGP (N-acetyl-proline-glycine-proline) on tumor cells dissemination to lung parenchyma. In mice exposed to cigarette smoke or lipopolysaccharide, lung neutrophilic inflammation produces increased levels of MMP-9 (matrix metalloproteinase 9) that contributes to collagen breakdown and allows the release of ac-PGP tripeptides. By silencing CXCR2 gene expression in tumor cells, we show that these generated ac-PGP tripeptides exert a chemotactic activity on tumor cells in vivo by binding CXCR2.

Cereblon deficiency confers resistance against polymicrobial sepsis by the activation of AMP activated protein kinase and heme-oxygenase-1

Cereblon (CRBN) has a pleiotropic role in important cellular processes and is a potential therapeutic target in several diseases, including mental retardation, cancer, and metabolic disorders. The role of CRBN in polymicrobial sepsis induced by cecal ligation and puncture (CLP) was investigated using CRBN-deficient (KO) mice. Survival following CLP was significantly higher in KO mice compared to wild-type (WT) controls (50% vs 0% at day 6 after CLP). The improved survival of KO mice was accompanied by reduced peripheral blood bacterial load and lung injury. Serum tumor necrosis factor (TNF)-α and high mobility group box 1 (HMGB1) concentrations were significantly lower in KO mice than in WT mice. Peritoneal macrophages from KO mice with CLP-induced septic mouse had higher levels of activation of AMPK and heme oxygenase-1 (HO-1). Forced expression of CRBN in macrophage of KO mice suppressed activation of 5' adenosine monophosphate-activated protein kinase (AMPK) and HO-1 and augmented expression of TNF-α and HMGB1 as inhibition of AMPK by compound C. These studies demonstrate the contribution of CRBN expression to the pathogenesis of CLP-induced sepsis and peritoneal macrophage responses and suggest a novel therapeutic modality for polymicrobial sepsis.

Contribution of Progranulin to Protective Lung Immunity During Bacterial Pneumonia

Background

Progranulin (PGRN) is an important immunomodulatory factor in a variety of inflammatory diseases. However, its role in pulmonary immunity against bacterial infection remains unknown.

Methods

Pneumonia was induced in PGRN-deficient and normal wild-type mice using Pseudomonas aeruginosa or Staphylococcus aureus, and we assessed the effects of PGRN on survival, bacterial burden, cytokine and chemokine production, and pulmonary leukocyte recruitment after bacterial pneumonia.

Results

Patients with community-acquired pneumonia displayed elevated PGRN levels. Likewise, mice with Gram-negative and Gram-positive pneumonia had increased PGRN production in the lung and circulation. Progranulin deficiency led to increased bacterial growth and dissemination accompanied by enhanced lung injury and mortality in bacterial pneumonia, which was associated with impaired recruitment of macrophages and neutrophils in the lung. The reduced number of pulmonary macrophages and neutrophils observed in PGRN-deficient mice was related to a reduction of CCL2 and CXCL1 in the lungs after bacterial pneumonia. Importantly, therapeutic administration of PGRN improved mortality in severe bacterial pneumonia.

Conclusions

This study supports a novel role for PGRN in pulmonary immunity and suggests that treatment with PGRN may be a viable therapy for bacterial pneumonia.

Direct Macromolecular Drug Delivery to Cerebral Ischemia Area using Neutrophil-Mediated Nanoparticles

Delivery of macromolecular drugs to the brain is impeded by the blood brain barrier. The recruitment of leukocytes to lesions in the brain, a typical feature of neuroinflammation response which occurs in cerebral ischemia, offers a unique opportunity to deliver drugs to inflammation sites in the brain. In the present study, cross-linked dendrigraft poly-L-lysine (DGL) nanoparticles containing cis-aconitic anhydride-modified catalase and modified with PGP, an endogenous tripeptide that acts as a ligand with high affinity to neutrophils, were developed to form the cl PGP-PEG-DGL/CAT-Aco system. Significant binding efficiency to neutrophils, efficient protection of catalase enzymatic activity from degradation and effective transport to receiver cells were revealed in the delivery system. Delivery of catalase to ischemic subregions and cerebral neurocytes in MCAO mice was significantly enhanced, which obviously reducing infarct volume in MCAO mice. Thus, the therapeutic outcome of cerebral ischemia was greatly improved. The underlying mechanism was found to be related to the inhibition of ROS-mediated apoptosis. Considering that neuroinflammation occurs in many neurological disorders, the strategy developed here is not only promising for treatment of cerebral ischemia but also an effective approach for various CNS diseases related to inflammation.

Progranulin Plays a Central Role in Host Defense during Sepsis by Promoting Macrophage Recruitment

RATIONALE

Progranulin, a widely expressed protein, has multiple physiological functions. The functional role of progranulin in the host response to sepsis remains unknown.

OBJECTIVES

To assess the role of progranulin in the host response to sepsis.

METHODS

Effects of progranulin on host response to sepsis were determined.

MEASUREMENTS AND MAIN RESULTS

Progranulin concentrations were significantly elevated in adult (n = 74) and pediatric (n = 26) patients with sepsis relative to corresponding healthy adult (n = 36) and pediatric (n = 17) control subjects, respectively. By using a low-lethality model of nonsevere sepsis, we observed that progranulin deficiency not only increased mortality but also decreased bacterial clearance during sepsis. The decreased host defense to sepsis in progranulin-deficient mice was associated with reduced macrophage recruitment, with correspondingly impaired chemokine CC receptor ligand 2 (CCL2) production in peritoneal lavages during the early phase of sepsis. Progranulin derived from hematopoietic cells contributed to host defense in sepsis. Therapeutic administration of recombinant progranulin not only rescued impaired host defense in progranulin-deficient mice after nonsevere sepsis but also protected wild-type mice against a high-lethality model of severe sepsis. Progranulin-mediated protection against sepsis was closely linked to improved peritoneal macrophage recruitment. In addition, CCL2 treatment of progranulin-deficient mice improved survival and decreased peritoneal bacterial loads during sepsis, at least in part through promotion of peritoneal macrophage recruitment.

CONCLUSIONS

This proof-of-concept study supports a central role of progranulin-dependent macrophage recruitment in host defense to sepsis, opening new opportunities to host-directed therapeutic strategy that manipulate host immune response in the treatment of sepsis.

N-Acetylated Proline-Glycine-Proline Accelerates Cutaneous Wound Healing and Neovascularization by Human Endothelial Progenitor Cells

Human endothelial progenitor cells (hEPCs) are promising therapeutic resources for wound repair through stimulating neovascularization. However, the hEPCs-based cell therapy has been hampered by poor engraftment of transplanted cells. In this study, we explored the effects of N-acetylated Proline-Glycine-Proline (Ac-PGP), a degradation product of collagen, on hEPC-mediated cutaneous wound healing and neovascularization. Treatment of hEPCs with Ac-PGP increased migration, proliferation, and tube-forming activity of hEPCs in vitro. Knockdown of CXCR2 expression in hEPCs abrogated the stimulatory effects of Ac-PGP on migration and tube formation. In a cutaneous wound healing model of rats and mice, topical application of Ac-PGP accelerated cutaneous wound healing with promotion of neovascularization. The positive effects of Ac-PGP on wound healing and neovascularization were blocked in CXCR2 knockout mice. In nude mice, the individual application of Ac-PGP treatment or hEPC injection accelerated wound healing by increasing neovascularization. Moreover, the combination of Ac-PGP treatment and hEPC injection further stimulated wound healing and neovascularization. Topical administration of Ac-PGP onto wound bed stimulated migration and engraftment of transplanted hEPCs into cutaneous dermal wounds. Therefore, these results suggest novel applications of Ac-PGP in promoting wound healing and augmenting the therapeutic efficacy of hEPCs.

Effect of Prolyl-Glycyl-Proline (PGP) and Its Acetylated Form (N-AcPGP) on Calcium Level in the Cytoplasm of Rat Peritoneal Mast Cells

Tripeptide glycyl-prolyl-proline (PGP), a regulatory peptide of the glyproline family, possesses a pronounced anti-inflammatory effect primarily due to its ability to prevent secretion of the proinflammatory mediator histamine by rat peritoneal mast cells. Activation of mast cell with synacthen (ACTH1-24) and substance 48/80 leads to an increase in intracellular calcium concentration. Pretreatment of mast cells with PGP prevented calcium entry into the cytoplasm from both intercellular space and intracellular stores. Acetylated peptide (N-AcPGP) produced a similar effect on histamine release and intracellular calcium content in mast cells activated with synacthen. These findings indicate that both forms of the peptide can stabilize mast cells and prevent intracellular calcium increase.

Antimicrobial peptide scolopendrasin VII, derived from the centipede Scolopendra subspinipes mutilans, stimulates macrophage chemotaxis via formyl peptide receptor 1

In this study, we report that one of the antimicrobial peptides scolopendrasin VII, derived from Scolopendra subspinipes mutilans, stimulates actin polymerization and the subsequent chemotactic migration of macrophages through the activation of ERK and protein kinase B (Akt) activity. The scolopendrasin VII-induced chemotactic migration of macrophages is inhibited by the formyl peptide receptor 1 (FPR1) antagonist cyclosporine H. We also found that scolopendrasin VII stimulate the chemotactic migration of FPR1-transfected RBL-2H3 cells, but not that of vector-transfected cells; moreover, scolopendrasin VII directly binds to FPR1. Our findings therefore suggest that the antimicrobial peptide scolopendrasin VII, derived from Scolopendra subspinipes mutilans, stimulates macrophages, resulting in chemotactic migration via FPR1 signaling, and the peptide can be useful in the study of FPR1-related biological responses. [BMB Reports 2015; 48(8): 479-484]

Anti-septic activity of α-cubebenoate isolated from Schisandra chinensis

Sepsis is a life-threatening, infectious, systemic inflammatory disease. In this study, we investigated the therapeutic effect of α-cubebenoate, a novel compound isolated from Schisandra chinensis against polymicrobial sepsis in a cecal ligation and puncture (CLP) experimental model. Administration of α-cubebenoate strongly enhanced survival in the CLP model. α-cubebenoate administration also markedly blocked CLP-induced lung inflammation and increased bactericidal activity by enhancing phagocytic activity and hydrogen peroxide generation in mouse bone marrow-derived macrophages and neutrophils. Expression of two important inflammatory cytokines, IL-1β and IL-6, was strongly increased in the CLP model, and this was dramatically blocked by α-cubebenoate. Lymphocyte apoptosis and caspase-3 activation, which are associated with immune paralysis during sepsis, were markedly attenuated by α-cubebenoate. Taken together, our findings indicate that α-cubebenoate, a natural compound isolated from Schisandra chinensis, is a powerful potential anti-septic agent.

Matrikines are key regulators in modulating the amplitude of lung inflammation in acute pulmonary infection

Bioactive matrix fragments (matrikines) have been identified in a myriad of disorders, but their impact on the evolution of airway inflammation has not been demonstrated. We recently described a pathway where the matrikine and neutrophil chemoattractant proline–glycine–proline (PGP) could be degraded by the enzyme leukotriene A₄ hydrolase (LTA₄H). LTA₄H classically functions in the generation of pro-inflammatory leukotriene B₄, thus LTA₄H exhibits opposing pro- and anti-inflammatory activities. The physiological significance of this secondary anti-inflammatory activity remains unknown. Here we show, using readily resolving pulmonary inflammation models, that loss of this secondary activity leads to more pronounced and sustained inflammation and illness owing to PGP accumulation. PGP elicits an exacerbated neutrophilic inflammation and protease imbalance that further degrades the extracellular matrix, generating fragments that perpetuate inflammation. This highlights a critical role for the secondary anti-inflammatory activity of LTA₄H and thus has consequences for the generation of global LTA₄H inhibitors currently being developed.

Proteases degrade extracellular matrix during inflammation, releasing peptides that can recruit neutrophils. Here the authors show that degradation of such bioactive peptide by the enzyme leukotriene A4 hydrolase is critical to limit pulmonary inflammation during bacterial infection in mice.

Phospholipase D2 drives mortality in sepsis by inhibiting neutrophil extracellular trap formation and down-regulating CXCR2

Lee et al. find that phospholipase D2 deficiency increases survival and decreases organ damage during experimental sepsis in mice which could be reversed with a CXCR2 antagonist. Thus, targeting PLD2 may offer therapeutics for septic patients.

We determined the function of phospholipase D2 (PLD2) in host defense in highly lethal mouse models of sepsis using PLD2^−/− mice and a PLD2-specific inhibitor. PLD2 deficiency not only increases survival but also decreases vital organ damage during experimental sepsis. Production of several inflammatory cytokines (TNF, IL-1β, IL-17, and IL-23) and the chemokine CXCL1, as well as cellular apoptosis in immune tissues, kidney, and liver, are markedly decreased in PLD2^−/− mice. Bactericidal activity is significantly increased in PLD2^−/− mice, which is mediated by increased neutrophil extracellular trap formation and citrullination of histone 3 through peptidylarginine deiminase activation. Recruitment of neutrophils to the lung is markedly increased in PLD2^−/− mice. Furthermore, LPS-induced induction of G protein–coupled receptor kinase 2 (GRK2) and down-regulation of CXCR2 are markedly attenuated in PLD2^−/− mice. A CXCR2-selective antagonist abolishes the protection conferred by PLD2 deficiency during experimental sepsis, suggesting that enhanced CXCR2 expression, likely driven by GRK2 down-regulation in neutrophils, promotes survival in PLD2^−/− mice. Furthermore, adoptively transferred PLD2^−/− neutrophils significantly protect WT recipients against sepsis-induced death compared with transferred WT neutrophils. We suggest that PLD2 in neutrophils is essential for the pathogenesis of experimental sepsis and that pharmaceutical agents that target PLD2 may prove beneficial for septic patients.

Mouse neutrophils express functional umami taste receptor T1R1/T1R3

Neutrophils play an important role in the initiation of innate immunity against infection and injury. Although many different types of G-protein coupled receptors are functionally expressed in neutrophils, no reports have demonstrated functional expression of umami taste receptor in these cells. We observed that mouse neutrophils express the umami taste receptor T1R1/T1R3 through RNA sequencing and quantitative RT-PCR analysis. Stimulation of mouse neutrophils with L-alanine or L-serine, which are ligands for the umami taste receptor, elicited not only ERK or p38 MAPK phosphorylation but also chemotactic migration. Moreover, addition of L-alanine or L-serine markedly reduced the production of several cytokines including TNF-α induced by lipopolysaccharide (LPS) through inhibition of NF-κB activity or STAT3 phosphorylation in neutrophils. Our findings demonstrate that neutrophils express the umami taste receptor, through which tastants stimulate neutrophils, resulting in chemotactic migration, and attenuation of LPS-induced inflammatory response.

AP-1-Targeted Anti-Inflammatory Activities of the Nanostructured, Self-Assembling S5 Peptide

Peptide-based therapeutics have received increasing attention in medical research. However, the local delivery of such therapeutics poses unique challenges. Self-assembling peptides that use decorated nanofibers are one approach by which these therapeutics may be delivered. We previously found that the self-assembling K5 peptide affects the anti-inflammatory response. The aim of the present study was to investigate another self-assembling peptide, S5. Unlike the K5 peptide which has a positive charge, the S5 peptide has a free hydroxyl (-OH) group. We first examined whether the S5 peptide regulates the inflammatory response in primary cells and found that the S5 peptide reduced the production of prostaglandin E₂ (PGE₂) and tumor necrosis factor (TNF)-α in lipopolysaccharide- (LPS-) treated bone marrow-derived macrophages. Moreover, the S5 peptide significantly downregulated cyclooxygenase- (COX-) 2, TNF-α, and interleukin- (IL-) 1β expression by blocking the nuclear translocation of c-Jun. Consistent with this finding, the S5 peptide diminished the activation of inflammatory signaling enzymes related to p38. The S5 peptide also inhibited the formation of the p38/c-Jun signaling complex in RAW264.7 cells. Similarly, p38 and MKK3/6 were inhibited by the S5 peptide in LPS-activated peritoneal macrophages. Taken together, these results strongly suggest that the S5 peptide could exert anti-inflammatory effects by inhibiting the c-Jun/p38 signaling pathway.

Neonatal infections in Saudi Arabia: Association with cytokine gene polymorphisms

In recent years, many studies have reported potential associations between cytokine gene polymorphisms and the development, course, and outcome of sepsis, often with apparently conflicting results. The objective of this study was to investigate single nucleotide polymorphism (SNP) in the interleukin (IL)-1β –31 T/C, IL-6 –174 G/C, tumor necrosis factor α (TNF-α) –308 G/A, and interferon γ (IFN-γ) +874 A/T genes for their possible association with susceptibility to early onset sepsis (EOS) in Saudi newborn infants. A total of 205 newborn infants aged 1-2 days were consecutively enrolled onto the study having met the inclusion criteria (as per the research protocol). DNA was extracted from filter papers using the Chelex-100 method. The cytokines SNP were genotyping using Taqman 5’ nuclease allelic discrimination. For cytokine measurements we used the commercially available Enzyme-Linked Immunosorbent Assay (ELISA) kit. Our results show that the circulating IL-1β, IL-6, TNF-α, and IFN-γ were significantly (p < 0.001) elevated in EOS patients compared to suspected and sepsis-free control groups; and IL-1β –31C, IL-6 –174G, TNF-α –308G, and IFN-γ +874A alleles were associated with EOS in Saudi infants. In conclusion, analysis of cytokines concentrations and SNP for the four tested genes can be used as a predictor of sepsis outcome in newborns.

The matrikine PGP as a potential biomarker in COPD

The lack of a well-characterized biomarker for the diagnosis of chronic obstructive pulmonary disease (COPD) has increased interest toward finding one, because this would provide potential insight into disease pathogenesis and progression. Since persistent neutrophilia is an important hallmark in COPD Pro-Gly-Pro (PGP), an extracellular matrix-derived neutrophil chemoattractant, has been suggested to be a potential biomarker in COPD. The purpose of this review is to critically examine both biological and clinical data related to the role of PGP in COPD, with particular focus on its role as a clinical biomarker and potential therapeutic target in disease. The data provided in this review will offer insight into the potential use of PGP as end point for future clinical studies in COPD lung disease. Following PGP levels during disease might serve as a guide for the progression of lung disorders.

MMP generated matrikines

Matrikines originate from the fragmentation of extracellular matrix proteins and regulate cellular activities by interacting with specific receptors. Matrikines are implicated in inflammation, immune responses, organ development, wound repair, angiogenesis, atherosclerosis, tumor progression and metastasis due to their ability to alter cellular migration, chemotaxis, and mitogenesis. Matrix metalloproteinases (MMPs) degrade extracellular matrix components under normal circumstances and in disease processes. Of the 20 MMPs identified, MMP-1, MMP-2, MMP-8, MMP-9, and MMP-12 have been implicated in regulating the matrikines Val-Gly-Val-Ala-Pro-Gly (elastin peptide) and proline-glycine-proline (PGP). Elastin peptide fragments are generated by elastolytic enzymes and have implications in atherosclerosis, neovascularization, chronic obstructive pulmonary disease, skin disease, as well as tumor invasion and spread. PGP is produced through a multistep pathway that liberates the tripeptide fragment from extracellular collagen. PGP is best described for its role in neutrophil chemotaxis and is implicated in the pathogenesis of corneal ulcers and in chronic lung conditions. In chronic cigarette smoke related lung disease, the PGP pathway can become a self-propagating cycle of inflammation through cigarette-smoke mediated inhibition of leukotriene A4 hydrolase, the enzyme responsible for degrading PGP and halting acute inflammation. This review highlights the roles of MMPs in generating these important matrikines.

Oxidized low-density lipoprotein-induced foam cell formation is mediated by formyl peptide receptor 2

The increased level of LDL and its modification into oxLDL has been regarded as an important risk factor for the development of cardiovascular diseases such as atherosclerosis. Although some scavenger receptors including CD36 and RAGE have been considered as target receptors for oxLDL, involvement of other receptors should be investigated for oxLDL-induced pathological responses. In this study, we found that oxLDL-induced foam cell formation was inhibited by formyl peptide receptor 2 (FPR2) antagonist WRW(4). oxLDL also stimulated calcium signaling and chemotactic migration in FPR2-expressing RBL-2H3 cells but not in vector-expressing RBL-2H3 cells. Moreover, oxLDL stimulated TNF-α production, which was also almost completely inhibited by FPR2 antagonist. Our findings therefore suggest that oxLDL stimulates macrophages, resulting in chemotactic migration, TNF-α production, and foam cell formation via FPR2 signaling, and thus likely contributes to atherogenesis.

α-Iso-cubebene, a natural compound isolated from Schisandra chinensis fruit, has therapeutic benefit against polymicrobial sepsis

α-Iso-cubebene, a natural compound isolated from Schisandra chinensis fruit, strongly enhanced survival rate in cecal ligation and puncture (CLP) challenge-induced sepsis. The mechanism involved the marked reduction of viable bacteria in the peritoneal fluid, by virtue of increased phagocytic activity and production of hydrogen peroxide. α-Iso-cubebene also significantly attenuated lung inflammation and widespread immune cell apoptosis in a mouse CLP sepsis model, and inhibited the production of proinflammatory cytokines including tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 in CLP mice and lipopolysaccharide-stimulated splenocytes. The results indicate that α-iso-cubebene can reverse the progression of toxic shock by triggering multiple protective downstream signaling pathways to enhance microbial killing and maintain organ function and leukocyte survival.

Nanostructured, self-assembling peptide K5 blocks TNF-α and PGE₂ production by suppression of the AP-1/p38 pathway

Nanostructured, self-assembling peptides hold promise for a variety of regenerative medical applications such as 3D cell culture systems, accelerated wound healing, and nerve repair. The aim of this study was to determine whether the self-assembling peptide K5 can be applied as a carrier of anti-inflammatory drugs. First, we examined whether the K5 self-assembling peptide itself can modulate various cellular inflammatory responses. We found that peptide K5 significantly suppressed the release of tumor-necrosis-factor- (TNF-) α and prostaglandin E₂ (PGE₂) from RAW264.7 cells and peritoneal macrophages stimulated by lipopolysaccharide (LPS). Similarly, there was inhibition of cyclooxygenase- (COX-) 2 mRNA expression assessed by real-time PCR, indicating that the inhibition is at the transcriptional level. In agreement with this finding, peptide K5 suppressed the translocation of the transcription factors activator protein (AP-1) and c-Jun and inhibited upstream inflammatory effectors including mitogen activated protein kinase (MAPK), p38, and mitogen-activated protein kinase kinase 3/6 (MKK 3/6). Whether this peptide exerts its effects via a transmembrane or cytoplasmic receptor is not clear. However, our data strongly suggest that the nanostructured, self-assembling peptide K5 may possess significant anti-inflammatory activity via suppression of the p38/AP-1 pathway.

Targeting of a common receptor shared by CXCL8 and N-Ac-PGP as a therapeutic strategy to alleviate chronic neutrophilic lung diseases

Persistent neutrophilia is implicated in the pathology of several chronic lung diseases and consequently targeting the signals that drive the recruitment of these cells offers a plausible therapeutic strategy. The tripeptide Pro-Gly-Pro (PGP) is a neutrophil chemoattractant derived from extracellular matrix collagen and implicated in diseases such as COPD and cystic fibrosis. It was anticipated that PGP exerts its chemoatactic activity by mimicking key sequences found within classical neutrophil chemokines, such as CXCL8, and binding their receptors, CXCR1/2. Recently, however, the role of CXCR1/2 as the receptors for PGP has been questioned. In this issue of European Journal of Pharmacology, three studies address this controversy and demonstrate CXCR1/2 to be a common receptor for CXCL8 and PGP. Accordingly, these studies demonstrate the therapeutic potential of targeting this shared receptor to simultaneously alleviate neutrophilic inflammation driven by multiple neutrophil chemoattractants.