Dependence of resolvin-induced increases in corneal epithelial cell migration on EGF receptor transactivation

Restoration of corneal epithelial barrier function: A possible target for corneal neovascularization

Corneal neovascularization (CoNV) is the second leading common cause of vision impairment worldwide and is a blinding pathological alteration brought on by ocular trauma, infection, and other factors. There are some limitations in the treatment of CoNV, hence it's critical to look into novel therapeutic targets. The corneal epithelial barrier, which is the initial barrier of the ocular surface, is an important structure that shields the eye from changes in the internal environment or invasion by the external environment. This study sought to collate evidence on the regulation of corneal epithelial barrier injury on the activation of vascular endothelial cells (VECs), basement membrane (BM) degradation, differentiation, migration, and proliferation of VECs, vascular maturation and stability, and other key processes in CoNV, so as to provide a novel concept for CoNV therapy targeting corneal epithelial barrier repair.

Amino Acid-Based Protein-Mimic Hydrogel Incorporating Pro-Regenerative Lipid Mediator and Microvascular Fragments Promotes the Healing of Deep Burn Wounds

Pro-regenerative lipid mediator 1 (PreM1) is a specialized pro-resolving lipid mediator that promotes wound healing and regenerative functions of mesenchymal stem cells (MSCs), endothelial cells, and macrophages. The healing of third-degree (3°) burns and regenerative functions of MSCs are enhanced by ACgel1, an arginine-and-chitosan-based protein-mimic hybrid hydrogel. Adipose-tissue derived microvascular fragments (MVFs) are native vascularization units and a rich source of MSCs, endothelial cells, and perivascular cells for tissue regeneration. Here we describe an innovative PreM1-MVFs-ACgel1 construct that incorporated PreM1 and MVFs into ACgel1 via optimal design and fabrication. This construct delivered PreM1 to 3°-burn wounds at least up to 7 days-post-burn (dpb), and scaffolded and delivered MVFs. PreM1-MVFs-ACgel1 promoted the healing of 3°-burns in mice, including vascularization and collagen formation. The re-epithelization and closure of 3° burn wounds were promoted by ACgel1, MVFs, PreM1, MVFs-ACgel1, PreM1-ACgel1, or PreM1-MVFs-ACgel1 at certain time-point(s), while PreM1-MVFs-ACgel1 was most effective with 97% closure and 4.69% relative epithelial gap at 13 dpb compared to saline control. The PreM1-ACgel1 and MVFs-ACgel1 also promoted blood vessel regeneration of 3°-burns although PreM1-MVFs-ACgel1 is significantly more effective. These PreM1- and/or MVF-functionalized ACgel1 have nonexistent or minimal graft-donor requirements and are promising adjuvant therapeutic candidates for treating deep burns.

The effect of resolvin D1n-3 DPA on primary oral epithelial cell migration in vitro

Specialized pro-resolving lipid mediators (SPMs) are known for their anti-inflammatory and pro-resolving actions. The aim of the present study was to find new functions of the SPM resolvin D1n-3 DPA (RvD1n-3 DPA) on oral epithelial cells. As a starting point, we used a dataset obtained by RNA high-throughput sequencing of oral epithelial cells exposed to TNF-α and RvD1n-3 DPA versus TNF-α alone. GOrilla enrichment analysis showed that the actin cytoskeleton was significantly overrepresented after adjustment for multiple hypothesis testing. As actin, amongst others, is closely related to cell migration, we then explored whether RvD1n-3 DPA can modulate oral epithelial cell migration. To this end, we used an in vitro cell migration model, including TNF-α treatment, to mimic an inflammatory cell state. The analysis revealed that RvD1n-3 DPA increased oral epithelial cell migration in the presence but not in the absence of TNF-α. Addition of RvD1n-3 DPA also induced F actin accumulation around the cell nucleus, indicating that RvD1n-3 DPA potentially can mediate processes of intracellular transport. This indicates that this lipid mediator may be a promising therapeutic candidate in oral mucosal wound healing.

Elucidating the mechanism of corneal epithelial cell repair: unraveling the impact of growth factors

The repair mechanism for corneal epithelial cell injuries encompasses migration, proliferation, and differentiation of corneal epithelial cells, and extracellular matrix remodeling of the stromal structural integrity. Furthermore, it involves the consequential impact of corneal limbal stem cells (LSCs). In recent years, as our comprehension of the mediating mechanisms underlying corneal epithelial injury repair has advanced, it has become increasingly apparent that growth factors play a pivotal role in this intricate process. These growth factors actively contribute to the restoration of corneal epithelial injuries by orchestrating responses and facilitating specific interactions at targeted sites. This article systematically summarizes the role of growth factors in corneal epithelial cell injury repair by searching relevant literature in recent years, and explores the limitations of current literature search, providing a certain scientific basis for subsequent basic research and clinical applications.

Maresin-2 promotes mucosal repair and has therapeutic potential when encapsulated in thermostable nanoparticles

Resolution of inflammation and mucosal wound healing are crucial processes required to re-establish homeostasis following injury of mucosal tissues. Maresin-2 (MaR2), a lipid specialized pro-resolving mediator derived from omega-3 polyunsaturated fatty acid, has been reported to promote resolution of inflammation. However, a potential role for MaR2 in regulating mucosal repair remains undefined. Using lipidomic analyses, we demonstrate biosynthesis of MaR2 in healing intestinal mucosal wounds in vivo. Importantly, administration of exogenous MaR2 promoted mucosal repair following dextran sulfate sodium-induced colitis or biopsy-induced colonic mucosal injury. Functional analyses revealed that MaR2 promotes mucosal wound repair by driving intestinal epithelial migration through activation of focal cell-matrix adhesion signaling in primary human intestinal epithelial cells. Because of its labile nature, MaR2 is easily degradable and requires ultracold storage to maintain functionality. Thus, we created thermostable polylactic acid MaR2 nanoparticles that retain biological activity following extended storage at 4 °C or above. Taken together, these results establish MaR2 as a potent pro-repair lipid mediator with broad therapeutic potential for use in promoting mucosal repair in inflammatory diseases.

The role of the PI3K/AKT signalling pathway in the corneal epithelium: recent updates

Phosphatidylinositol 3 kinase (PI3K)/AKT (also called protein kinase B, PKB) signalling regulates various cellular processes, such as apoptosis, cell proliferation, the cell cycle, protein synthesis, glucose metabolism, and telomere activity. Corneal epithelial cells (CECs) are the outermost cells of the cornea; they maintain good optical performance and act as a physical and immune barrier. Various growth factors, including epidermal growth factor receptor (EGFR) ligands, insulin-like growth factor 1 (IGF1), neurokinin 1 (NK-1), and insulin activate the PI3K/AKT signalling pathway by binding their receptors and promote antiapoptotic, anti-inflammatory, proliferative, and migratory functions and wound healing in the corneal epithelium (CE). Reactive oxygen species (ROS) regulate apoptosis and inflammation in CECs in a concentration-dependent manner. Extreme environments induce excess ROS accumulation, inhibit PI3K/AKT, and cause apoptosis and inflammation in CECs. However, at low or moderate levels, ROS activate PI3K/AKT signalling, inhibiting apoptosis and stimulating proliferation of healthy CECs. Diabetes-associated hyperglycaemia directly inhibit PI3K/AKT signalling by increasing ROS and endoplasmic reticulum (ER) stress levels or suppressing the expression of growth factors receptors and cause diabetic keratopathy (DK) in CECs. Similarly, hyperosmolarity and ROS accumulation suppress PI3K/AKT signalling in dry eye disease (DED). However, significant overactivation of the PI3K/AKT signalling pathway, which mediates inflammation in CECs, is observed in both infectious and noninfectious keratitis. Overall, upon activation by growth factors and NK-1, PI3K/AKT signalling promotes the proliferation, migration, and anti-apoptosis of CECs, and these processes can be regulated by ROS in a concentration-dependent manner. Moreover, PI3K/AKT signalling pathway is inhibited in CECs from individuals with DK and DED, but is overactivated by keratitis.

Immune regulation of the ocular surface

Despite constant exposure to various environmental stimuli, the ocular surface remains intact and uninflamed while maintaining the transparency of the cornea and its visual function. This 'immune privilege' of the ocular surface is not simply a result of the physical barrier function of the mucosal lining but, more importantly, is actively maintained through a variety of immunoregulatory mechanisms that prevent the disruption of immune homeostasis. In this review, we focus on essential molecular and cellular players that promote immune quiescence in steady-state conditions and suppress inflammation in disease-states. Specifically, we examine the interactions between the ocular surface and its local draining lymphoid compartment, by encompassing the corneal epithelium, corneal nerves and cornea-resident myeloid cells, conjunctival goblet cells, and regulatory T cells (Treg) in the context of ocular surface autoimmune inflammation (dry eye disease) and alloimmunity (corneal transplantation). A better understanding of the immunoregulatory mechanisms will facilitate the development of novel, targeted immunomodulatory strategies for a broad range of ocular surface inflammatory disorders.

Utility of the Specialized Pro-Resolving Mediators as Diagnostic and Prognostic Biomarkers in Disease

A precision medicine approach is widely acknowledged to yield more effective therapeutic strategies in the treatment of patients with chronic inflammatory conditions than the prescriptive paradigm currently utilized in the management and treatment of these patients. This is because such an approach will take into consideration relevant factors including the likelihood that a patient will respond to given therapeutics based on their disease phenotype. Unfortunately, the application of this precision medicine paradigm in the daily treatment of patients has been greatly hampered by the lack of robust biomarkers, in particular biomarkers for determining early treatment responsiveness. Lipid mediators are central in the regulation of host immune responses during both the initiation and resolution of inflammation. Amongst lipid mediators, the specialized pro-resolving mediators (SPM) govern immune cells to promote the resolution of inflammation. These autacoids are produced via the stereoselective conversion of essential fatty acids to yield molecules that are dynamically regulated during inflammation and exert potent immunoregulatory activities. Furthermore, there is an increasing appreciation for the role that these mediators play in conveying the biological actions of several anti-inflammatory therapeutics, including statins and aspirin. Identification and quantitation of these mediators has traditionally been achieved using hyphenated mass spectrometric techniques, primarily liquid-chromatography tandem mass spectrometry. Recent advances in the field of chromatography and mass spectrometry have increased both the robustness and the sensitivity of this approach and its potential deployment for routine clinical diagnostics. In the present review, we explore the evidence supporting a role for specific SPM as potential biomarkers for patient stratification in distinct disease settings together with methodologies employed in the identification and quantitation of these autacoids.

Experimental Pharmacotherapy for Dry Eye Disease: A Review

Dry eye disease (DED) is a complex multifactorial disease showing heterogenous symptoms, including dryness, photophobia, ocular discomfort, irritation and burning but also pain. These symptoms can affect visual function leading to restrictions in daily life activities and reduction in work productivity with a consequently high impact on quality of life. Several pathological mechanisms contribute to the disease: evaporative water loss leads to impairment and loss of tear homeostasis inducing either directly or indirectly to inflammation, in a self-perpetuating vicious cycle. Dysregulated ocular immune responses result in ocular surface damage, which further contributes to DED pathogenesis. Currently, DED treatment is based on a flexible stepwise approach to identify the most beneficial intervention. Although most of the available treatments may control to a certain extent some signs and symptoms of DED, they show significant limitations and do not completely address the needs of patients suffering from DED. This review provides an overview of the emerging experimental therapies for DED. Several promising therapeutic strategies are under development with the aim of dampening inflammation and restoring the homeostasis of the ocular surface microenvironment. Results from early phase clinical trials, testing the effects of EnaC blockers, TRPM8 agonist or mesenchymal stem cells in DED patients, are especially awaited to demonstrate their therapeutic value for the treatment of DED. Moreover, the most advanced experimental strategies in the pipeline for DED, tivanisiran, IL-1R antagonist EBI-005 and SkQ1, are being tested in Phase III clinical trials, still ongoing. Nevertheless, although promising results, further studies are still needed to confirm efficacy and safety of the new emerging therapies for DED.

Omega 3 Fatty Acid and Skin Diseases

Humans are exposed to various external environmental factors. Food intake is one of the most influential factors impacting daily lifestyle. Among nutrients obtained from foods, omega-3 polyunsaturated fatty acids (PUFAs) have various beneficial effects on inflammatory diseases. Furthermore, omega-3 PUFA metabolites, including resolvins, are known to demonstrate strong anti-inflammatory effects during allergic and inflammatory diseases; however, little is known regarding the actual impact of these metabolites on skin diseases. In this review, we focused on metabolites that have strong anti-inflammatory actions in various inflammatory diseases, as well as those that present antitumor actions in malignancies, in addition to the actual effect of omega-3 PUFA metabolites on various cells.

Resolvin E1 accelerates pulp repair by regulating inflammation and stimulating dentin regeneration in dental pulp stem cells

Background

Unresolved inflammation and tissue destruction are considered to underlie the failure of dental pulp repair. As key mediators of the injury response, dental pulp stem cells (DPSCs) play a critical role in pulp tissue repair and regeneration. Resolvin E1 (RvE1), a major dietary omega-3 polyunsaturated fatty-acid metabolite, is effective in resolving inflammation and activating wound healing. However, whether RvE1 facilitates injured pulp-tissue repair and regeneration through timely resolution of inflammation and rapid mobilization of DPSCs is unknown. Therefore, we established a pulp injury model and investigated the effects of RvE1 on DPSC-mediated inflammation resolution and injured pulp repair.

Methods

A pulp injury model was established using 8-week-old Sprague-Dawley rats. Animals were sacrificed on days 1, 3, 7, 14, 21, and 28 after pulp capping with a collagen sponge immersed in PBS with RvE1 or PBS. Hematoxylin-eosin and Masson’s trichrome staining, immunohistochemistry, and immunohistofluorescence were used to evaluate the prohealing properties of RvE1. hDPSCs were incubated with lipopolysaccharide (LPS) to induce an inflammatory response, and the expression of inflammatory factors after RvE1 application was measured. Effects of RvE1 on hDPSC proliferation, chemotaxis, and odontogenic differentiation were evaluated by CCK-8 assay, transwell assay, alkaline phosphatase (ALP) staining, alizarin red staining, and quantitative PCR, and possible signaling pathways were explored using western blotting.

Results

In vivo, RvE1 reduced the necrosis rate of damaged pulp and preserved more vital pulps, and promoted injured pulp repair and reparative dentin formation. Further, it enhanced dentin matrix protein 1 and dentin sialoprotein expression and accelerated pulp inflammation resolution by suppressing TNF-α and IL-1β expression. RvE1 enhanced the recruitment of CD146⁺ and CD105⁺ DPSCs to the damaged molar pulp mesenchyme. Isolated primary cells exhibited the mesenchymal stem cell immunophenotype and differentiation. RvE1 promoted hDPSC proliferation and chemotaxis. RvE1 significantly attenuated pro-inflammatory cytokine (TNF-α, IL-1β, and IL-6) release and enhanced ALP activity, nodule mineralization, and especially, expression of the odontogenesis-related genes DMP1, DSPP, and BSP in LPS-stimulated DPSCs. RvE1 regulated AKT, ERK, and rS6 phosphorylation in LPS-stimulated DPSCs.

Conclusions

RvE1 promotes pulp inflammation resolution and dentin regeneration and positively influences the proliferation, chemotaxis, and differentiation of LPS-stimulated hDPSCs. This response is, at least partially, dependent on AKT, ERK, and rS6-associated signaling in the inflammatory microenvironment. RvE1 has promising application potential in regenerative endodontics.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02141-y.

The potential of lipid mediator networks as ocular surface therapeutics and biomarkers

In the last twenty years an impressive body of evidence in diverse inflammatory animal disease models and human tissues, has established polyunsaturated fatty acids (PUFA) derived specialized-pro-resolving mediators (SPM), as essential mediators for controlling acute inflammation, immune responses, wound healing and for resolving acute inflammation in many non-ocular tissues. SPM pathways and receptors are highly expressed in the ocular surface where they regulate wound healing, nerve regeneration, innate immunity and sex-specific regulation of auto-immune responses. Recent evidence indicates that in the eye these resident SPM networks are important for maintaining ocular surface health and immune homeostasis. Here, we will review and discuss evidence for SPMs and other PUFA-derived mediators as important endogenous regulators, biomarkers for ocular surface health and disease and their therapeutic potential.

The Role of Specialized Pro-Resolving Mediators in Cystic Fibrosis Airways Disease

Cystic Fibrosis (CF) is a recessive genetic disease due to mutations of the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene encoding the CFTR chloride channel. The ion transport abnormalities related to CFTR mutation generate a dehydrated airway surface liquid (ASL) layer, which is responsible for an altered mucociliary clearance, favors infections and persistent inflammation that lead to progressive lung destruction and respiratory failure. The inflammatory response is normally followed by an active resolution phase to return to tissue homeostasis, which involves specialized pro-resolving mediators (SPMs). SPMs promote resolution of inflammation, clearance of microbes, tissue regeneration and reduce pain, but do not evoke unwanted immunosuppression. The airways of CF patients showed a decreased production of SPMs even in the absence of pathogens. SPMs levels in the airway correlated with CF patients' lung function. The prognosis for CF has greatly improved but there remains a critical need for more effective treatments that prevent excessive inflammation, lung damage, and declining pulmonary function for all CF patients. This review aims to highlight the recent understanding of CF airway inflammation and the possible impact of SPMs on functions that are altered in CF airways.

Resolvin E1 is a pro-repair molecule that promotes intestinal epithelial wound healing

Resolution of intestinal inflammation and wound repair are active processes that mediate epithelial healing at mucosal surfaces. Lipid molecules referred to as specialized proresolving mediators (SPMs) play an important role in the restorative response. Resolvin E1 (RvE1), a SPM derived from omega-3 fatty acids, has been reported to dampen intestinal inflammation by promoting anti-inflammatory responses including increased neutrophil spherocytosis and macrophage production of IL-10. Despite these observations, a role for RvE1 in regulating intestinal epithelial cell migration and proliferation during mucosal wound repair has not been explored. Using an endoscopic biopsy-based wound healing model, we report that RvE1 is locally produced in response to intestinal mucosal injury. Exposure of intestinal epithelial cells to RvE1 promoted wound repair by increasing cellular proliferation and migration through activation of signaling pathways including CREB, mTOR, and Src-FAK. Additionally, RvE1-triggered activation of the small GTPase Rac1 led to increased intracellular reactive oxygen species (ROS) production, cell-matrix adhesion, and cellular protrusions at the leading edge of migrating cells. Furthermore, in situ administration of RvE1-encapsulated synthetic targeted polymeric nanoparticles into intestinal wounds promoted mucosal repair. Together, these findings demonstrate that RvE1 functions as a prorepair lipid mediator by increasing intestinal epithelial cell migration and proliferation, and highlight potential therapeutic applications for this SPM to promote mucosal healing in the intestine.

A signalling cascade involving receptor-activated phospholipase A2, glycerophosphoinositol 4-phosphate, Shp1 and Src in the activation of cell motility

Background

Shp1, a tyrosine-phosphatase-1 containing the Src-homology 2 (SH2) domain, is involved in inflammatory and immune reactions, where it regulates diverse signalling pathways, usually by limiting cell responses through dephosphorylation of target molecules. Moreover, Shp1 regulates actin dynamics. One Shp1 target is Src, which controls many cellular functions including actin dynamics. Src has been previously shown to be activated by a signalling cascade initiated by the cytosolic-phospholipase A₂ (cPLA₂) metabolite glycerophosphoinositol 4-phosphate (GroPIns4P), which enhances actin polymerisation and motility. While the signalling cascade downstream Src has been fully defined, the mechanism by which GroPIns4P activates Src remains unknown.

Methods

Affinity chromatography, mass spectrometry and co-immunoprecipitation studies were employed to identify the GroPIns4P-interactors; among these Shp1 was selected for further analysis. The specific Shp1 residues interacting with GroPIns4P were revealed by NMR and validated by site-directed mutagenesis and biophysical methods such as circular dichroism, isothermal calorimetry, fluorescence spectroscopy, surface plasmon resonance and computational modelling. Morphological and motility assays were performed in NIH3T3 fibroblasts.

Results

We find that Shp1 is the direct cellular target of GroPIns4P. GroPIns4P directly binds to the Shp1-SH2 domain region (with the crucial residues being Ser 118, Arg 138 and Ser 140) and thereby promotes the association between Shp1 and Src, and the dephosphorylation of the Src-inhibitory phosphotyrosine in position 530, resulting in Src activation. As a consequence, fibroblast cells exposed to GroPIns4P show significantly enhanced wound healing capability, indicating that GroPIns4P has a stimulatory role to activate fibroblast migration. GroPIns4P is produced by cPLA₂ upon stimulation by diverse receptors, including the EGF receptor. Indeed, endogenously-produced GroPIns4P was shown to mediate the EGF-induced cell motility.

Conclusions

This study identifies a so-far undescribed mechanism of Shp1/Src modulation that promotes cell motility and that is dependent on the cPLA₂ metabolite GroPIns4P. We show that GroPIns4P is required for EGF-induced fibroblast migration and that it is part of a cPLA₂/GroPIns4P/Shp1/Src cascade that might have broad implications for studies of immune-inflammatory response and cancer.

Electronic supplementary material

The online version of this article (10.1186/s12964-019-0329-3) contains supplementary material, which is available to authorized users.

Resolvins and aliamides: lipid autacoids in ophthalmology - what promise do they hold?

Resolvins are a novel class of lipid-derived endogenous molecules (autacoids) with potent immunomodulating properties, which regulate the resolution phase of an active immune response. These modulating factors are locally produced, influencing the function of cells and/or tissues, which are produced on demand and subsequently metabolized in the same cells and/or tissues. This review is focused on certain lipid autacoids with putative relevance for ophthalmology in general and for dry eye more specifically. We also briefly investigate the concept of aliamides and the role of palmitoylethanolamide in ophthalmology, and analyze in more detail the putative role and the preclinical and clinical development of resolvins as emerging treatments for dry eye and related disorders, with a focus on one of the lead resolvin derivatives – RX-10045.

In vitro effects of docosahexaenoic and eicosapentaenoic acid on human meibomian gland epithelial cells

To investigate the effect of ω-3 fatty acids on human meibomian gland epithelial cells (HMGECs, cell line) in vitro. HMGECs were stimulated with docosahexaenoic acid (DHA) or combinations with eicosapentaenoic acid (EPA) and acetyl sialic acid (ASA). Sudan III fat staining, viability and proliferation assays, electric cell-substrate impedance sensing, real-time PCR for gene expression of cyclooxygenase-2 and 15-lipoxygenase and ELISAs for resolvin D1 (RvD1), IFNγ, TNFα and IL-6 were applied. Lipid droplet accumulation and viability was increased by 100 μM DHA in the presence or absence of EPA in serum cultured HMGECs. In contrast, HMGECs cultured with DHA and EPA under serum-free conditions showed minimal lipid accumulation, decreased proliferation and viability. Normalized impedance was significantly reduced in serum-free cultured HMGECs when stimulated with DHA and EPA. HMGECs cultured in serum containing medium showed increased normalized impedance under DHA and EPA stimulation compared to DHA or EPA alone or controls. IL-6 and IFNγ were downregulated in HMGECs treated for 72 h with DHA and EPA. In general, TNFα, IFNγ and IL-6 levels were decreased after 72 h compared to 24 h in serum containing medium with or without DHA or EPA. The concentration of RvD1 was elevated 2-fold after DHA treatment. Cyclooxygenase-2 gene expression decreased compared to controls during DHA stimulation after 72 h. Treatment with DHA and ASA revealed a decreased 15-lipoxygenase gene expression which was reduced after three days of DHA incubation. DHA and EPA supplementation affected HMGECs in vitro and supported anti-inflammatory effects by influencing cytokine levels, decreasing COX-2 expression and increasing the production of RvD1.

Progress in corneal wound healing

Corneal wound healing is a complex process involving cell death, migration, proliferation, differentiation, and extracellular matrix remodeling. Many similarities are observed in the healing processes of corneal epithelial, stromal and endothelial cells, as well as cell-specific differences. Corneal epithelial healing largely depends on limbal stem cells and remodeling of the basement membrane. During stromal healing, keratocytes get transformed to motile and contractile myofibroblasts largely due to activation of transforming growth factor-β (TGF-β) system. Endothelial cells heal mostly by migration and spreading, with cell proliferation playing a secondary role. In the last decade, many aspects of wound healing process in different parts of the cornea have been elucidated, and some new therapeutic approaches have emerged. The concept of limbal stem cells received rigorous experimental corroboration, with new markers uncovered and new treatment options including gene and microRNA therapy tested in experimental systems. Transplantation of limbal stem cell-enriched cultures for efficient re-epithelialization in stem cell deficiency and corneal injuries has become reality in clinical setting. Mediators and course of events during stromal healing have been detailed, and new treatment regimens including gene (decorin) and stem cell therapy for excessive healing have been designed. This is a very important advance given the popularity of various refractive surgeries entailing stromal wound healing. Successful surgical ways of replacing the diseased endothelium have been clinically tested, and new approaches to accelerate endothelial healing and suppress endothelial-mesenchymal transformation have been proposed including Rho kinase (ROCK) inhibitor eye drops and gene therapy to activate TGF-β inhibitor SMAD7. Promising new technologies with potential for corneal wound healing manipulation including microRNA, induced pluripotent stem cells to generate corneal epithelium, and nanocarriers for corneal drug delivery are discussed. Attention is also paid to problems in wound healing understanding and treatment, such as lack of specific epithelial stem cell markers, reliable identification of stem cells, efficient prevention of haze and stromal scar formation, lack of data on wound regulating microRNAs in keratocytes and endothelial cells, as well as virtual lack of targeted systems for drug and gene delivery to select corneal cells.

In vitro anti-osteoclastogenic activity of p38 inhibitor doramapimod via inhibiting migration of pre-osteoclasts and NFATc1 activity

The mitogen activated protein kinase p38 plays a role in the receptor activator of NF-ĸB ligand (RANKL)-induced osteoclast differentiation. In this study, we investigated the effect of p38 inhibitor doramapimod on the osteoclast differentiation. Doramapimod significantly inhibited the osteoclastogenesis of bone marrow macrophages (BMMs) via attenuating the activation of p38 induced by M-CSF and RANKL. Importantly, doramapimod blocked the migration and fusion in pre-osteoclasts via the down-regulating NFATc1. The inhibitory effect of doramapimod on the migration/fusion of pre-osteoclasts via inhibiting NFATc1 activity were confirmed by measuring NFATc1 luciferase activity and evaluating the mRNA expression of NFATc1-responsive genes related to the osteoclastic migration/fusion. These results suggested anti-osteoclastogenic activity of doramapimod via inhibiting migration/fusion of pre-osteoclasts and NFATc1 activity.

Resolvin E1 analog RX-10045 0.1% reduces corneal stromal haze in rabbits when applied topically after PRK

PURPOSE

To perform a masked study to determine whether resolvin E1 (RvE1), a lipid-derived immunomodulator, could regulate the development of corneal haze and opacity-related myofibroblasts after opacity-generating high correction photorefractive keratectomy (PRK) in rabbits.

METHODS

Three groups of eight rabbits each were included in the study. Nine diopter (D) PRK for myopia was performed in each test cornea, and the eyes were treated with 30 µl of topical solution every 4 h (six times a day) for 5 days starting immediately after PRK. Group 1 was treated with 0.1% RX-10045, a prodrug of an RvE1 analog; group 2 was treated with 0.01% RX-10045; and group 3 was treated with vehicle control solution. At 1 month after PRK, haze was graded at the slit-lamp by a masked observer. Immunohistochemistry for α-smooth muscle actin (SMA) was performed on the central cornea of each test eye to determine the anterior stromal myofibroblast density.

RESULTS

Corneal opacity was significantly lower in the 0.1% RX-10045 group, but not the 0.01% RX-10045 group, compared to the vehicle control group (p=0.029), at 1 month after -9.0D PRK. At 1 month after -9.0D PRK, SMA+ myofibroblast densities in the anterior stroma were not statistically significantly different among the three groups, although a trend toward lower myofibroblast generation was noted in the 0.1% RX-10045 group.

CONCLUSIONS

Topical 0.1% RX-10045, a prodrug of an RvE1 analog, reduces corneal opacity after haze-generating PRK in rabbits. Further studies are needed to determine the precise points at which RvE1 decreases corneal opacity after injury.

Roles of resolvins in the resolution of acute inflammation

Resolution is an active process that terminates inflammatory response to maintain health. Acute inflammation and its timely resolution are important in host response to danger signals. Unresolved inflammation is associated with widely recurrent diseases. Resolvins, including the D and E series, are endogenous lipid mediators generated during the resolution phase of acute of inflammation from the ω-3 PUFAs, DHA, and EPA. They have anti-inflammatory and pro-resolving properties that have been determined in many inflammation studies in animal models. In this review, we provide an updated overview of biosynthesis, actions, and signaling pathways of resolvins, thereby underscoring their diverse protective roles and introducing novel therapeutic strategies for inflammation-associated diseases.

Resolvin D1 and aspirin-triggered resolvin D1 regulate histamine-stimulated conjunctival goblet cell secretion

Resolution of inflammation is an active process mediated by pro-resolution lipid mediators. As resolvin (Rv) D1 is produced in the cornea, pro-resolution mediators could be effective in regulating inflammatory responses to histamine in allergic conjunctivitis. Two key mediators of resolution are the D-series resolvins RvD1 or aspirin-triggered RvD1 (AT-RvD1). We used cultured conjunctival goblet cells to determine whether histamine actions can be terminated during allergic responses. We found cross-talk between two types of G protein-coupled receptors (GPRs), as RvD1 interacts with its receptor GPR32 to block histamine-stimulated H1 receptor increases in intracellular [Ca(2+)] ([Ca(2+)]i) preventing H1 receptor-mediated responses. In human and rat conjunctival goblet cells, RvD1 and AT-RvD1 each block histamine-stimulated secretion by preventing its increase in [Ca(2+)]i and activation of extracellular regulated-protein kinase (ERK)1/2. We suggest that D-series resolvins regulate histamine responses in the eye and offer new treatment approaches for allergic conjunctivitis or other histamine-dependent pathologies.

Resolution of inflammation: mechanisms and opportunity for drug development

Inflammation is a beneficial host reaction to tissue damage and has the essential primary purpose of restoring tissue homeostasis. Inflammation plays a major role in containing and resolving infection and may also occur under sterile conditions. The cardinal signs of inflammation dolor, calor, tumor and rubor are intrinsically associated with events including vasodilatation, edema and leukocyte trafficking into the site of inflammation. If uncontrolled or unresolved, inflammation itself can lead to further tissue damage and give rise to chronic inflammatory diseases and autoimmunity with eventual loss of organ function. It is now evident that the resolution of inflammation is an active continuous process that occurs during an acute inflammatory episode. Successful resolution requires activation of endogenous programs with switch from production of pro-inflammatory towards pro-resolving molecules, such as specific lipid mediators and annexin A1, and the non-phlogistic elimination of granulocytes by apoptosis with subsequent removal by surrounding macrophages. These processes ensure rapid restoration of tissue homeostasis. Here, we review recent advances in the understanding of resolution of inflammation, highlighting the pharmacological strategies that may interfere with the molecular pathways which control leukocyte survival and clearance. Such strategies have proved beneficial in several pre-clinical models of inflammatory diseases, suggesting that pharmacological modulation of the resolution process may be useful for the treatment of chronic inflammatory diseases in humans.

Understanding resolvin signaling pathways to improve oral health

The discovery of resolvins has been a major breakthrough for understanding the processes involved in resolution of inflammation. Resolvins belong to a family of novel lipid mediators that possess dual anti-inflammatory and pro-resolution actions. Specifically, they protect healthy tissue during immune-inflammatory responses to infection or injury, thereby aiding inflammation resolution and promoting tissue healing. One of the major concerns in modern medicine is the management and treatment of oral diseases, as they are related to systemic outcomes impacting the quality of life of many patients. This review summarizes known signaling pathways utilized by resolvins to regulate inflammatory responses associated with the oral cavity.

Resolvin E1 (RX-10001) reduces corneal epithelial barrier disruption and protects against goblet cell loss in a murine model of dry eye

PURPOSE

Resolvin E1 (RvE1; RX-10001) belongs to a new class of endogenous immunoregulating mediators, originally identified as a metabolite of the omega-3 polyunsaturated fatty acid, eicosapentaenoic acid. Based on its proven efficacy in models of chronic inflammation, this study investigated the efficacy of resolvin E1 in a murine model of dry eye.

METHODS

C57/B6 mice, aged 6 to 8 weeks, were treated with systemic scopolamine and exposed to air draft and low humidity for 16 hours/day for 5 days and allocated to the following groups: unexposed controls, disease controls, treatment with vehicle or RvE1 delivered topically as its methyl ester prodrug, RX-10005, to enhance corneal surface penetration. Treatment was initiated at the time of desiccating stress induction. Treatment efficacy was assessed by corneal permeability using Oregon Green Dextran and by conjunctival goblet cell density using periodic acid-Schiff reagent.

RESULTS

RvE1 reduced the increase in corneal staining by 80% compared with untreated disease controls. Goblet cell density was reduced by 20% in disease controls but fully maintained in the group receiving RvE1.

CONCLUSIONS

RvE1, delivered as its methyl ester prodrug, improved the outcome measures of corneal staining and goblet cell density in this murine model of dry eye, indicating the potential utility of endogenous resolvins and resolvin analogues in the treatment of dry eye.

Chemical mediators of inflammation and resolution in post-operative abdominal aortic aneurysm patients

Temporal-metabolomic studies of local mediators during inflammation and its resolution uncovered novel pathways and mediators, e.g., lipoxins, resolvins, and protectins that stimulate key resolution responses. Since these studies were carried out with isolated human cells and in animal models, it is important to determine in humans whether temporal profiles between pro-inflammatory mediators and pro-resolving mediators are demonstrable in vivo. To this end, we examined patients undergoing abdominal aortic aneurysm (AAA) surgery. Profiles of mediators including eicosanoids were assessed in addition to pro-resolving mediators. The results demonstrate temporal relationships for local-acting peptides (e.g., VEGF, IL-10, TGF(β)) and lipid mediators (leukotrienes and resolvins). In addition, profiles obtained for AAA patients divided into two groups based on their temporal profile: one group consistent with a pro-inflammatory and another with a resolving profile. Together, these translational metabolomic profiles demonstrate for the first time the temporal relationships between local mediators in humans relevant in inflammation resolution.

Resolvin D1 prevents TNF-α-mediated disruption of salivary epithelial formation

Sjögren's syndrome is a chronic autoimmune disorder characterized by inflammation of salivary glands resulting in impaired secretory function. Our present studies indicate that chronic exposure of salivary epithelium to TNF-α and/or IFN-γ alters tight junction integrity, leading to secretory dysfunction. Resolvins of the D-series (RvDs) are endogenous lipid mediators derived from DHA that regulate excessive inflammatory responses leading to resolution and tissue homeostasis. In this study, we addressed the hypothesis that activation of the RvD1 receptor ALX/FPR2 in salivary epithelium prevents and/or resolves the TNF-α-mediated disruption of acinar organization and enhances monolayer formation. Our results indicate that 1) the RvD1 receptor ALX/FPR2 is present in fresh, isolated cells from mouse salivary glands and in cell lines of salivary origin; and 2) the agonist RvD1 (100 ng/ml) abolished tight junction and cytoskeletal disruption caused by TNF-α and enhanced cell migration and polarity in salivary epithelium. These effects were blocked by the ALX/FPR2 antagonist butyloxycarbonyl-Phe-Leu-Phe-Leu-Phe. The ALX/FPR2 receptor signals via modulation of the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathways since, in our study, blocking PI3K activation with LY294002, a potent and selective PI3K inhibitor, prevented RvD1-induced cell migration. Furthermore, Akt gene silencing with the corresponding siRNA almost completely blocked the ability of Par-C10 cells to migrate. Our findings suggest that RvD1 receptor activation promotes resolution of inflammation and tissue repair in salivary epithelium, which may have relevance in the restoration of salivary gland dysfunction associated with Sjögren's syndrome.

The role of eIF5A in epidermal growth factor-induced proliferation of corneal epithelial cell association with PI3-k/Akt activation

PURPOSE

After excimer laser surgery, epidermal growth factor (EGF) plays an important role in injured corneal epithelial cell on myofibroblastic cell formation in corneal stroma. The purpose of the study is to investigate the precise mechanism of EGF on corneal wound healing, particularly on epithelial proliferation and migration.

METHODS

In this study we applied small interference RNA (siRNA) to knock down the expression of eukaryotic translation initiation factor 5A (eIF5A) in corneal epithelial cells. The relative mRNA and protein expression of matrix metallopeptidase 9 (MMP9) and proliferating cell nuclear antigen (PCNA) was determined via real-time PCR and western blot analysis. The proliferative potential of EGF was evaluated via a proliferation assay using the measurement of (3)H-thymidine incorporation ((3)H-TdR). HCEpiC apoptosis was subjected to flow cytometric analysis.

RESULTS

The results showed eIF5A expression was enhanced and there was a statistically significant increase in EGF treatment compared to the control group. Real-time PCR, western blot analysis, and the proliferation assay demonstrated significantly lower MMP9 and PCNA expression and proliferation cell counts in eIF5A siRNA-treated groups versus significantly higher levels in EGF plus eIF5A siRNA-treated groups. The data analysis showed that eIF5A, MMP9, and PCNA expression decreased as a result of the inhibitor LY294002. Apoptotic cells were increased in the EGF plus eIF5A siRNA, EGF plus LY294002, and EGF plus eIF5A siRNA plus LY294002 groups as compared with the EGF siRNA group.

CONCLUSIONS

These results indicate that EGF-induced upregulation of eIF5A stimulates corneal epithelial cell proliferation in vitro. EGF stimulation of corneal epithelial proliferation was through the phosphatidylinositol 3-kinase (PI3-k)/protein kinase B (Akt) signaling pathway.

Controlling herpes simplex virus-induced ocular inflammatory lesions with the lipid-derived mediator resolvin E1

Stromal keratitis (SK) is a chronic immunopathological lesion of the eye caused by HSV-1 infection and a common cause of blindness in humans. The inflammatory lesions are primarily perpetuated by neutrophils with the active participation of CD4(+) T cells. Therefore, targeting these immune cell types represents a potentially valuable form of therapy to reduce the severity of disease. Resolvin E1 (RvE1), an endogenous lipid mediator, was shown to promote resolution in several inflammatory disease models. In the current report, we determined whether RvE1 administration begun at different times after ocular infection of mice with HSV could influence the severity of SK lesions. Treatment with RvE1 significantly reduced the extent of angiogenesis and SK lesions that occurred. RvE1-treated mice had fewer numbers of inflammatory cells that included Th1 and Th17 cells as well as neutrophils in the cornea. The mechanisms by which RvE1 acts appear to be multiple. These included reducing the influx of neutrophils and pathogenic CD4(+) T cells, increasing production of the anti-inflammatory cytokine IL-10, and inhibitory effects on the production of proinflammatory mediators and molecules, such as IL-6, IFN-γ, IL-17, KC, VEGF-A, MMP-2, and MMP-9, that are involved in corneal neovascularization and SK pathogenesis. These findings are, to our knowledge, the first to show that RvE1 treatment could represent a novel approach to control lesion severity in a virally induced immunopathological disease.

Novel lipid mediators promote resolution of acute inflammation: impact of aspirin and statins

The resolution of acute inflammation is a process that allows for inflamed tissues to return to homeostasis. Resolution was held to be a passive process, a concept now overturned with new evidence demonstrating that resolution is actively orchestrated by distinct cellular events and endogenous chemical mediators. Among these, lipid mediators, such as the lipoxins, resolvins, protectins, and newly identified maresins, have emerged as a novel genus of potent and stereoselective players that counter-regulate excessive acute inflammation and stimulate molecular and cellular events that define resolution. Given that uncontrolled, chronic inflammation is associated with many cardiovascular pathologies, an appreciation of the endogenous pathways and mediators that control timely resolution can open new terrain for therapeutic approaches targeted at stimulating resolution of local inflammation, as well as correcting the impact of chronic inflammation in cardiovascular disorders. Here, we overview and update the biosynthesis and actions of proresolving lipid mediators, highlighting their diverse protective roles relevant to vascular systems and their relation to aspirin and statin therapies.