Phospholipase D1 mediates TNFalpha-induced inflammation in a murine model of TNFalpha-induced peritonitis

Immunomodulatory effect of a proprietary polyherbal formulation on healthy participants: A single- blind, randomized, placebo- controlled, exploratory clinical study

Context

Clinical study for immunity.

Aims

The present study aimed to assess the effect of proprietary polyherbal formulation (PPHF), labelled as Kofol immunity tablets (KIT) on innate and adaptive immune responses in healthy individuals, on the backdrop of COVID-19 pandemic.

Settings and Design

Single-blind, randomized, placebo-controlled, exploratory study in institutional setting.

Materials and Methods

Post Ethics Committee permission, screened healthy individuals of either sex aged 18-35 years were randomized to PPHF/Placebo for 2 months. Major assessment variables included peak expiratory flow rate (PEFR), questionnaire-based immune status, perceived stress, and quality of life (QOL) with immune-specific cell counts (CD4+, CD8+), cytokines (interferon gamma [IFN-γ], tumor necrosis factor-alpha [TNF-α], interleukin 10 [IL-10]), and oxidative stress in red blood cells (RBCs) (malondialdehyde (MDA), glutathione peroxidase [GPx]), done at day 60.

Statistical Analysis Used

Mean ± standard deviation and paired/unpaired t-test for parametric data analysis while median (range) and Wilcoxon Rank sum test/Mann-Whitney test for nonparametric data analysis, were done. Categorical data was analyzed using Chi-square test. GraphPad InStat software, version 9 was used with p < 0.05, as the level of statistical significance.

Results

Of 52 recruited, 28 individuals completed the study. PPHF significantly increased PEFR, improved immune status along with QOL compared to baseline. It also decreased perceived stress from moderate and severe grade to mild. Serum IFN-γ levels remained almost constant post-PPHF treatment. PPHF significantly decreased MDA and increased GPx in RBCs. Significant decrease and increase in TNF-α and IL-10, respectively, were seen in PPHF group. The safety parameters post-PPHF treatment remained within normal reference ranges.

Conclusions

PPHF is an efficacious and safe formulation with immunomodulatory potential.

Endothelial STING controls T cell transmigration in an IFNI-dependent manner

The stimulator of IFN genes (STING) protein senses cyclic dinucleotides released in response to double-stranded DNA and functions as an adaptor molecule for type I IFN (IFNI) signaling by activating IFNI-stimulated genes (ISG). We found impaired T cell infiltration into the peritoneum in response to TNF-α in global and EC-specific STING-/- mice and discovered that T cell transendothelial migration (TEM) across mouse and human endothelial cells (EC) deficient in STING was strikingly reduced compared with control EC, whereas T cell adhesion was not impaired. STING-/- T cells showed no defect in TEM or adhesion to EC, or immobilized endothelial cell-expressed molecules ICAM1 and VCAM1, compared with WT T cells. Mechanistically, CXCL10, an ISG and a chemoattractant for T cells, was dramatically reduced in TNF-α-stimulated STING-/- EC, and genetic loss or pharmacologic antagonisms of IFNI receptor (IFNAR) pathway reduced T cell TEM. Our data demonstrate a central role for EC-STING during T cell TEM that is dependent on the ISG CXCL10 and on IFNI/IFNAR signaling.

Phospholipase D as a Potential Modulator of Metabolic Syndrome: Impact of Functional Foods

Significance: Cardiometabolic disorders (CMD) are composed of a plethora of metabolic dysfunctions such as dyslipidemia, nonalcoholic fatty liver disease, insulin resistance, and hypertension. The development of these disorders is highly linked to inflammation and oxidative stress (OxS), two metabolic states closely related to physiological and pathological conditions. Given the drastically rising CMD prevalence, the discovery of new therapeutic targets/novel nutritional approaches is of utmost importance. Recent Advances: The tremendous progress in methods/technologies and animal modeling has allowed the clarification of phospholipase D (PLD) critical roles in multiple cellular processes, whether directly or indirectly via phosphatidic acid, the lipid product mediating signaling functions. In view of its multiple features and implications in various diseases, PLD has emerged as a drug target. Critical Issues: Although insulin stimulates PLD activity and, in turn, PLD regulates insulin signaling, the impact of the two important PLD isoforms on the metabolic syndrome components remains vague. Therefore, after outlining PLD1/PLD2 characteristics and functions, their role in inflammation, OxS, and CMD has been analyzed and critically reported in the present exhaustive review. The influence of functional foods and nutrients in the regulation of PLD has also been examined. Future Directions: Available evidence supports the implication of PLD in CMD, but only few studies emphasize its mechanisms of action and specific regulation by nutraceutical compounds. Therefore, additional investigations are first needed to clarify the functional role of nutraceutics and, second, to elucidate whether targeting PLDs with food compounds represents an appropriate therapeutic strategy to treat CMD. Antioxid. Redox Signal. 34, 252-278.

Targeting of Phospholipase D1 Ameliorates Collagen-Induced Arthritis via Modulation of Treg and Th17 Cell Imbalance and Suppression of Osteoclastogenesis

Phospholipase D1 (PLD1) plays a crucial role in various inflammatory and autoimmune diseases. Rheumatoid arthritis (RA) is a chronic and systemic autoimmune disease. However, the role of PLD1 in the pathogenesis of RA remains unknown. Here, we first investigated the role and effects of PLD1 in collagen-induced arthritis (CIA) and found that genetic and pharmacological inhibition of PLD1 in DBA1/J mice with CIA reduced the incidence of CIA, decreased the clinical score, and abrogated disease symptoms including infiltration of leukocytes, synovial inflammation, bone erosion, and cartilage destruction. Moreover, ablation and inhibition of PLD1 suppressed the production of type II collagen-specific IgG2a autoantibody and proinflammatory cytokines, accompanied by an increase in the regulatory T (Treg) cell population and a decrease in the Th17 cell population in CIA mice. The PLD1 inhibitor also promoted differentiation of Treg cells and suppressed differentiation of Th17 cells in vitro. Furthermore, the PLD1 inhibitor attenuated pathologic bone destruction in CIA mice by suppressing osteoclastogenesis and bone resorption. Thus, our findings indicate that the targeting of PLD1 can ameliorate CIA by modulating the imbalance of Treg and Th17 cells and suppressing osteoclastogenesis, which might be a novel strategy to treat autoimmune diseases, such as RA.

Phospholipase D and the Mitogen Phosphatidic Acid in Human Disease: Inhibitors of PLD at the Crossroads of Phospholipid Biology and Cancer

Lipids are key building blocks of biological membranes and are involved in complex signaling processes such as metabolism, proliferation, migration, and apoptosis. Extracellular signaling by growth factors, stress, and nutrients is transmitted through receptors that activate lipid-modifying enzymes such as the phospholipases, sphingosine kinase, or phosphoinositide 3-kinase, which then modify phospholipids, sphingolipids, and phosphoinositides. One such important enzyme is phospholipase D (PLD), which cleaves phosphatidylcholine to yield phosphatidic acid and choline. PLD isoforms have dual role in cells. The first involves maintaining cell membrane integrity and cell signaling, including cell proliferation, migration, cytoskeletal alterations, and invasion through the PLD product PA, and the second involves protein-protein interactions with a variety of binding partners. Increased evidence of elevated PLD expression and activity linked to many pathological conditions, including cancer, neurological and inflammatory diseases, and infection, has motivated the development of dual- and isoform-specific PLD inhibitors. Many of these inhibitors are reported to be efficacious and safe in cells and mouse disease models, suggesting the potential for PLD inhibitors as therapeutics for cancer and other diseases. Current knowledge and ongoing research of PLD signaling networks will help to evolve inhibitors with increased efficacy and safety for clinical studies.

Involvement of miRNA polymorphism in mucositis development in childhood acute lymphoblastic leukemia treatment

Aim: Mucositis, linked to methotrexate, daunorubicin or cyclophosphamide, is a frequent childhood acute lymphoblastic leukemia (ALL) therapy side effect. miRNAs regulate the expression of pharmacokinetic/pharmacodynamic pathway genes. SNPs in miRNAs could affect their levels or function, and affect their pharmacokinetic/pharmacodynamic pathway target genes. Our aim was to determine the association between miRNA genetic variants targeting mucositis-related genes and mucositis-developing risk. Patients & methods: We analyzed 160 SNPs in 179 Spanish children with B-cell precursor ALL homogeneously treated with LAL/SHOP protocols. Results: We identified three SNPs in miR-4268, miR-4751 and miR-3117 associated with mucositis, diarrhea and vomiting, respectively. Conclusion: The effect of these SNPs on genes related to drug pharmacokinetics/pharmacodynamics could explain mucositis, diarrhea and vomiting development during ALL therapy.

Enzymatic Activity Is Not Required for Phospholipase D Mediated TNF-α Regulation and Myocardial Healing

Phospholipase D1 is a regulator of tumor necrosis factor-α expression and release upon LPS-induced sepsis and following myocardial infarction (MI). Lack of PLD1 leads to a reduced TNF-α mediated inflammatory response and to enhanced infarct size with declined cardiac function 21 days after ischemia reperfusion (I/R) injury. Deficiency of both PLD isoforms PLD1 and PLD2 as well as pharmacological inhibition of the enzymatic activity of PLD with the PLD inhibitor FIPI protected mice from arterial thrombosis and ischemic brain infarction. Here we treated mice with the PLD inhibitor FIPI to analyze if pharmacological inhibition of PLD after myocardial ischemia protects mice from cardiac damage. Inhibition of PLD with FIPI leads to reduced migration of inflammatory cells into the infarct border zone 24 h after experimental MI in mice, providing first evidence for immune cell migration to be dependent on the enzymatic activity of PLD. In contrast to PLD1 deficient mice, TNF-α plasma level was not altered after FIPI treatment of mice. Consequently, infarct size and left ventricular (LV) function were comparable between FIPI-treated and control mice 21 days post MI. Moreover, cell survival 24 h post I/R was not altered upon FIPI treatment. Our results indicate that the enzymatic activity of PLD is not responsible for PLD mediated TNF-α signaling and myocardial healing after I/R injury in mice. Furthermore, reduced TNF-α plasma levels in PLD1 deficient mice might be responsible for increased infarct size and impaired cardiac function 21 days post MI.

Phospholipase D1 regulation of TNF-alpha protects against responses to LPS

Sepsis is a systemic inflammatory disorder with organ dysfunction and represents the leading cause of mortality in non-coronary intensive care units. A key player in septic shock is Tumor Necrosis Factor-alpha (TNF-α). Phospholipase (PL)D1 is involved in the regulation of TNF-α upon ischemia/reperfusion injury in mice. In this study we analyzed the impact of PLD1 in the regulation of TNF-α, inflammation and organ damage in experimental sepsis. PLD1 deficiency increased survival of mice and decreased vital organ damage after LPS injections. Decreased TNF-α plasma levels and reduced migration of leukocytes and platelets into lungs was associated with reduced apoptosis in lung and liver tissue of PLD1 deficient mice. PLD1 deficient platelets contribute to preserved outcome after LPS-induced sepsis because platelets exhibit an integrin activation defect suggesting reduced platelet activation in PLD1 deficient mice. Furthermore, reduced thrombin generation of PLD1 deficient platelets might be responsible for reduced fibrin formation in lungs suggesting reduced disseminated intravascular coagulation (DIC). The analysis of Pld1^fl/fl-PF4-Cre mice revealed that migration of neutrophils and cell apoptosis in septic animals is not due to platelet-mediated processes. The present study has identified PLD1 as a regulator of innate immunity that may be a new target to modulate sepsis.

Polymerase delta-interacting protein 2 deficiency protects against blood-brain barrier permeability in the ischemic brain

BACKGROUND

Polymerase δ-interacting protein 2 (Poldip2) is a multifunctional protein that regulates vascular extracellular matrix composition and matrix metalloproteinase (MMP) activity. The blood-brain barrier (BBB) is a dynamic system assembled by endothelial cells, basal lamina, and perivascular astrocytes, raising the possibility that Poldip2 may be involved in maintaining its structure. We investigated the role of Poldip2 in the late BBB permeability induced by cerebral ischemia.

METHODS

Transient middle cerebral artery occlusion (tMCAO) was induced in Poldip2+/+ and Poldip2+/- mice. The volume of the ischemic lesion was measured in triphenyltetrazolium chloride-stained sections. BBB breakdown was evaluated by Evans blue dye extravasation. Poldip2 protein expression was evaluated by western blotting. RT-PCR, zymography, and ELISAs were used to measure mRNA levels, activity, and protein levels of cytokines and MMPs. Cultured astrocytes were transfected with Poldip2 siRNA, and mRNA levels of cytokines were evaluated as well as IκBα protein degradation.

RESULTS

Cerebral ischemia induced the expression of Poldip2. Compared to Poldip2+/+ mice, Poldip2+/- animals exhibited decreased Evans blue dye extravasation and improved survival 24 h following stroke. Poldip2 expression was upregulated in astrocytes exposed to oxygen and glucose deprivation (OGD) and siRNA-mediated downregulation of Poldip2 abrogated OGD-induced IL-6 and TNF-α expression. In addition, siRNA against Poldip2 inhibited TNF-α-induced IκBα degradation. TNF-α, IL-6, MCP-1, VEGF, and MMP expression induced by cerebral ischemia was abrogated in Poldip2+/- mice. The protective effect of Poldip2 depletion on the increased permeability of the BBB was partially reversed by systemic administration of TNF-α.

CONCLUSIONS

Poldip2 is upregulated following ischemic stroke and mediates the breakdown of the BBB by increasing cerebral cytokine production and MMP activation. Therefore, Poldip2 appears to be a promising novel target for the development of therapeutic strategies to prevent the development of cerebral edema in the ischemic brain.

Phospholipases: An Overview

Phospholipases are lipolytic enzymes that hydrolyze phospholipid substrates at specific ester bonds. Phospholipases are widespread in nature and play very diverse roles from aggression in snake venom to signal transduction, lipid mediator production, and metabolite digestion in humans. Phospholipases vary considerably in structure, function, regulation, and mode of action. Tremendous advances in understanding the structure and function of phospholipases have occurred in the last decades. This introductory chapter is aimed at providing a general framework of the current understanding of phospholipases and a discussion of their mechanisms of action and emerging biological functions.

Effects of Autologous Fat and ASCs on Swine Hypertrophic Burn Scars: A Multimodal Quantitative Analysis

Background:

Hypertrophic scar formation is unpredictable and poorly understood, afflicting both the pediatric and adult populations. Treatment methods with conservative and invasive approaches have low rates of compliance and high rates of morbidity. The purpose of this study was to test a reproducible scar model and investigate a new technique of scar modification through the use of adipose- derived progenitor stromal cells (ASCs).

Methods:

Twenty thermal deep-partial thickness contact burns were created on the dorsum of three 8-week-old domestic swine and allowed to mature for 10 weeks. Scars were then injected with 2 cc saline, expanded autologous ASCs, or 2 cc fresh lipoaspirate and sampled at 2 week intervals up to 10 weeks postinjection. Volumetric analysis with a 3-D scanner, mechanical elasticity testing through negative pressure transduction, and standardized photography evaluation with Image J was performed. RNA sequencing was performed on scar tissue samples, cultured cells, and fresh lipoaspirate to determine relevant gene transcription regulation. Immunohistochemistry was used to verify expression level changes within the scars.

Results:

Volumetric analysis demonstrates a reduction in average scar thickness at 6 weeks when injected with ASCs (−1.6 cc³) and autologous fat (−1.95 cc³) relative to controls (−0.121 cc³; P < 0.05). A decrease in overall tissue compliance is observed with fat or ASC injection when compared with unburned skin at 8 weeks (35.99/37.94 versus 49.36 mm Hg × mm; P < 0.01). RNA sequencing demonstrates altered regulation of fibroblast gene expression and a decreased inflammatory profile when scars are injected with autologous fat/ASCs over controls.

Conclusion:

Early results suggest that autologous fat and/or ASCs may improve healing of hypertrophic scarring by altering the cellular and structural components during wound remodeling up to 20 weeks after injury. This may have beneficial applications in early treatment of large or cosmetically sensitive immature burn scars.

Phospholipase D1 is a regulator of platelet-mediated inflammation

Glycoprotein (GP)Ib is not only required for stable thrombus formation but for platelet-mediated inflammatory responses. Phospholipase (PL)D1 is essential for GPIb-dependent aggregate formation under high shear conditions while nothing is known about PLD1-induced regulation of GPIb in platelet-mediated inflammation and the underlying mechanisms. This study aimed to investigate the relevance of PLD1 for platelet-mediated endothelial and leukocyte recruitment and activation in vitro and in vivo. Pld1^-/- platelets showed strongly reduced adhesion to TNFα stimulated endothelial cells (ECs) under high shear conditions ex vivo. Normal cytoskeletal reorganization of Pld1^-/- platelets but reduced integrin activation after adhesion to inflamed ECs confirmed that defective integrin activation is responsible for reduced platelet adhesion to ECs. This, together with significantly reduced CD40L expression on platelets led to reduced chemotactic and adhesive properties of ECs in vitro. Under flow conditions, recruitment of leukocytes to collagen-adherent platelets was reduced. Under inflammatory conditions in vivo, reduced platelet and leukocyte recruitment and arrest to the injured carotid artery was observed in Pld1^-/- mice. In a second in vivo model of venous thrombosis, platelet adhesion to activated endothelial cells was reduced while leukocyte recruitment was attenuated in PLD1 deficient mice. Mechanistically, PLD1 modulates PLCγ2 phosphorylation and integrin activation via Src kinases without affecting vWF binding to GPIb. Thus, PLD1 is important for GPIb-induced inflammatory processes of platelets and might be a promising target to reduce platelet-mediated inflammation.

Angiopoietin-Like Protein 7 Promotes an Inflammatory Phenotype in RAW264.7 Macrophages Through the P38 MAPK Signaling Pathway

Angiopoietin-like protein 7 (Angptl7) has been extensively studied for decades, but its potential immune functions have not been characterized. Hence, we investigated the relationship between Angptl7 and inflammation by using RAW264.7 monocyte/macrophage cells. The expression of genes encoding inflammation-associated factors cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, IL-10, and transforming growth factor beta 1 (TGF-β1)) decreased after RAW264.7 cells were treated with anti-Angptl7 polyclonal antibody but increased after the cells were transfected with an Angptl7-expressing plasmid. Angptl7 overexpression enhanced phagocytosis and inhibited the proliferation of RAW264.7 cells. In addition, Angptl7 antagonized the anti-inflammatory effects of TGF-β1 and dexamethasone. Pathway analysis showed that Angptl7 promoted the phosphorylation of both p65 and p38, but only the P38 mitogen-activated protein kinase (MAPK) signaling pathway mediated Angptl7-associated inflammatory functions. Additionally, after 1 week of daily intraperitoneal injections of recombinant TNF-α in a mouse model of peripheral inflammation, Angptl7 expression increased in the mouse eyes. Thus, Angptl7 is a factor that promotes pro-inflammatory responses in macrophages through the P38 MAPK signaling pathway and represents a potential therapeutic target for treatment of inflammatory diseases.

Expression of Phospholipase D in Periodontitis and Its Role in the Inflammatory and Osteoclastic Response by Nicotine- and Lipopolysaccharide-Stimulated Human Periodontal Ligament Cells

BACKGROUND

The aim of the present study is to investigate the expression of phospholipase D (PLD) 1 and PLD2 in periodontal patients and in human periodontal ligament cells (HPDLCs) exposed to nicotine plus lipopolysaccharide (LPS) from Porphyromonas gingivalis (Toll-like receptor 2 ligand). Furthermore, the effects of PLD isoform inhibition on the inflammatory response and osteoclast differentiation and its mechanisms were determined.

METHODS

Proinflammatory mediators were examined by reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. To silence the gene expression of the PLD isoforms, cells were transfected with small interfering RNA (siRNA) targeting PLD1 or PLD2. Mouse bone marrow-derived macrophages (BMMs) were used as osteoclast precursor cells for in vitro osteoclastogenesis. Western blot analysis and immunofluorescence were used to assess signaling pathways.

RESULTS

Chronic smokers with periodontitis exhibited significantly higher PLD1 and PLD2 messenger RNA (mRNA) expression than non-smokers with periodontitis and healthy controls. Nicotine and LPS upregulated PLD1 and PLD2 mRNA expression in a dose-dependent manner in HPDLCs. Pharmacologic and siRNA-mediated inhibition of PLD1 and PLD2 attenuated the nicotine- and LPS-induced upregulation of inducible nitric oxide (NO) synthase and cyclooxygenase-2, production of NO, and prostaglandin E2, and mRNA expression and secretion of tumor necrosis factor-α, interleukin (IL)-1β, and IL-8. The conditioned media from HPDLCs treated with PLD isoform inhibitors or siRNA against PLD inhibited receptor activator of nuclear factor-κB (NF-κB) ligand-mediated osteoclast differentiation, as well as protein expression of nuclear factor of activated T cells c1 and c-Fos, in BMMs. In addition, PLD isoform inhibitors and siRNA inhibited the nicotine- and LPS-induced activation of phosphoinositide 3-kinase, protein kinase C, p38, extracellular signal-regulated kinase, c-Jun N-terminal protein kinase, mitogen-activated protein kinase, and NF-κB.

CONCLUSION

To the best of the authors' knowledge, this study is the first to demonstrate that PLD isoform inhibition has anti-inflammatory and antiosteoclastogenic effects and thus may be a therapeutic target for the treatment of periodontitis.

Pivotal role of phospholipase D1 in tumor necrosis factor-α-mediated inflammation and scar formation after myocardial ischemia and reperfusion in mice

Myocardial inflammation is critical for ventricular remodeling after ischemia. Phospholipid mediators play an important role in inflammatory processes. In the plasma membrane they are degraded by phospholipase D1 (PLD1). PLD1 was shown to be critically involved in ischemic cardiovascular events. Moreover, PLD1 is coupled to tumor necrosis factor-α signaling and inflammatory processes. However, the impact of PLD1 in inflammatory cardiovascular disease remains elusive. Here, we analyzed the impact of PLD1 in tumor necrosis factor-α-mediated activation of monocytes after myocardial ischemia and reperfusion using a mouse model of myocardial infarction. PLD1 expression was highly up-regulated in the myocardium after ischemia/reperfusion. Genetic ablation of PLD1 led to defective cell adhesion and migration of inflammatory cells into the infarct border zone 24 hours after ischemia/reperfusion injury, likely owing to reduced tumor necrosis factor-α expression and release, followed by impaired nuclear factor-κB activation and interleukin-1 release. Moreover, PLD1 was found to be important for transforming growth factor-β secretion and smooth muscle α-actin expression of cardiac fibroblasts because myofibroblast differentiation and interstitial collagen deposition were altered in Pld1(-/-) mice. Consequently, infarct size was increased and left ventricular function was impaired 28 days after myocardial infarction in Pld1(-/-) mice. Our results indicate that PLD1 is crucial for tumor necrosis factor-α-mediated inflammation and transforming growth factor-β-mediated collagen scar formation, thereby augmenting cardiac left ventricular function after ischemia/reperfusion.

Identification of TNF-α-responsive promoters and enhancers in the intestinal epithelial cell model Caco-2

The Caco-2 cell line is one of the most important in vitro models for enterocytes, and is used to study drug absorption and disease, including inflammatory bowel disease and cancer. In order to use the model optimally, it is necessary to map its functional entities. In this study, we have generated genome-wide maps of active transcription start sites (TSSs), and active enhancers in Caco-2 cells with or without tumour necrosis factor (TNF)-α stimulation to mimic an inflammatory state. We found 520 promoters that significantly changed their usage level upon TNF-α stimulation; of these, 52% are not annotated. A subset of these has the potential to confer change in protein function due to protein domain exclusion. Moreover, we locate 890 transcribed enhancer candidates, where ∼50% are changing in usage after TNF-α stimulation. These enhancers share motif enrichments with similarly responding gene promoters. As a case example, we characterize an enhancer regulating the laminin-5 γ2-chain (LAMC2) gene by nuclear factor (NF)-κB binding. This report is the first to present comprehensive TSS and enhancer maps over Caco-2 cells, and highlights many novel inflammation-specific promoters and enhancers.

Functional regulation of phospholipase D expression in cancer and inflammation

Phospholipase D (PLD) regulates downstream effectors by generating phosphatidic acid. Growing links of dysregulation of PLD to human disease have spurred interest in therapeutics that target its function. Aberrant PLD expression has been identified in multiple facets of complex pathological states, including cancer and inflammatory diseases. Thus, it is important to understand how the signaling network of PLD expression is regulated and contributes to progression of these diseases. Interestingly, small molecule PLD inhibitors can suppress PLD expression as well as enzymatic activity of PLD and have been shown to be effective in pathological mice models, suggesting the potential for use of PLD inhibitors as therapeutics against cancer and inflammation. Here, we summarize recent scientific developments regarding the regulation of PLD expression and its role in cancer and inflammatory processes.

Integrative study of physiological changes associated with bacterial infection in Pacific oyster larvae

Background

Bacterial infections are common in bivalve larvae and can lead to significant mortality, notably in hatcheries. Numerous studies have identified the pathogenic bacteria involved in such mortalities, but physiological changes associated with pathogen exposure at larval stage are still poorly understood. In the present study, we used an integrative approach including physiological, enzymatic, biochemical, and molecular analyses to investigate changes in energy metabolism, lipid remodelling, cellular stress, and immune status of Crassostrea gigas larvae subjected to experimental infection with the pathogenic bacteria Vibrio coralliilyticus.

Findings

Our results showed that V. coralliilyticus exposure induced (1) limited but significant increase of larvae mortality compared with controls, (2) declined feeding activity, which resulted in energy status changes (i.e. reserve consumption, β-oxidation, decline of metabolic rate), (3) fatty acid remodeling of polar lipids (changes in phosphatidylinositol and lysophosphatidylcholine composition`, non-methylene–interrupted fatty acids accumulation, lower content of major C₂₀ polyunsaturated fatty acids as well as activation of desaturases, phospholipase and lipoxygenase), (4) activation of antioxidant defenses (catalase, superoxide dismutase, peroxiredoxin) and cytoprotective processes (heat shock protein 70, pernin), and (5) activation of the immune response (non-self recognition, NF-κκ signaling pathway, haematopoiesis, eiconosoids and lysophosphatidyl acid synthesis, inhibitor of metalloproteinase and antimicrobial peptides).

Conclusion

Overall, our results allowed us to propose an integrative view of changes induced by a bacterial infection in Pacific oyster larvae, opening new perspectives on the response of marine bivalve larvae to infections.

Lung-targeted overexpression of the NF-κB member RelB inhibits cigarette smoke-induced inflammation

Acute lung inflammation can be caused by a variety of respirable agents, including cigarette smoke. Long-term cigarette smoke exposure can cause chronic obstructive pulmonary disease (COPD), a serious illness that affects >10 million Americans. Cigarette smoke is a known inducer of inflammation and is responsible for approximately 90% of all COPD cases. RelB, a member of the NF-κB family, attenuates cigarette smoke-induced inflammatory mediator production in mouse lung fibroblasts in vitro. We hypothesized that overexpression of RelB in the airways of mice would dampen acute smoke-induced pulmonary inflammation. Mice received a recombinant adenovirus encoding RelB by intranasal aspiration to induce transient RelB overexpression in the lungs and were subsequently exposed to mainstream cigarette smoke. Markers of inflammation were analyzed after smoke exposure. Neutrophil infiltration, normally increased by smoke exposure, was significantly and potently decreased after RelB overexpression. Cigarette smoke-induced proinflammatory cytokine and chemokine production, cyclooxygenase-2 expression, and prostaglandin E(2) production were also significantly decreased in the context of RelB overexpression. The expression of intercellular adhesion molecule 1, an NF-κB-dependent protein, was decreased, indicating a potential mechanism through which RelB can regulate inflammatory cell migration. Therefore, increased expression and/or activation of RelB could be a novel therapeutic strategy against acute lung inflammation caused by respirable agents and possibly against chronic injury, such as COPD.

Dissecting the role of the S1P/S1PR axis in health and disease

Sphingosine-1-phosphate (S1P) is a pleiotropic sphingophospholipid generated from the phosphorylation of sphingosine by sphingosine kinases (SPHKs). S1P has been experimentally demonstrated to modulate an array of cellular processes such as cell proliferation, cell survival, cell invasion, vascular maturation, and angiogenesis by binding with any of the five known G-protein-coupled sphingosine 1 phosphate receptors (S1P1-5) on the cell surface in an autocrine as well as a paracrine manner. Recent studies have shown that the S1P receptors (S1PRs) and SPHKs are the key targets for modulating the pathophysiological consequences of various debilitating diseases, such as cancer, sepsis, rheumatoid arthritis, ulcerative colitis, and other related illnesses. In this article, we recapitulate these novel discoveries relative to the S1P/S1PR axis, necessary for the proper maintenance of health, as well as the induction of tumorigenic, angiogenic, and inflammatory stimuli that are vital for the development of various diseases, and the novel therapeutic tools to modulate these responses in oral biology and medicine.