VIP promotes resistance in the Pseudomonas aeruginosa-infected cornea by modulating adhesion molecule expression

Age-Related Differences in the Mouse Corneal Epithelial Transcriptome and Their Impact on Corneal Wound Healing

Purpose

Aging is a risk factor for dry eye. We sought to identify changes in the aged mouse corneal epithelial transcriptome and determine how age affects corneal sensitivity, re-epithelialization, and barrier reformation after corneal debridement.

Methods

Corneal epithelium of female C57BL/6J (B6) mice of different ages (2, 12, 18, and 24 months) was collected, RNA extracted, and bulk RNA sequencing performed. Cornea sensitivity was measured with an esthesiometer in 2- to 3-month-old, 12- to 13-month-old, 18- to 19-month-old, and 22- to 25-month-old female and male mice. The 2-month-old and 18-month-old female and male mice underwent unilateral corneal debridement using a blunt blade. Wound size and fluorescein staining were visualized and photographed at different time points, and a re-epithelialization rate curve was calculated.

Results

There were 157 differentially expressed genes in aged mice compared with young mice. Several pathways downregulated with age control cell migration, proteoglycan synthesis, and collagen trimerization, assembly, biosynthesis, and degradation. Male mice had decreased corneal sensitivity compared with female mice at 12 and 24 months of age. Aged mice, irrespective of sex, had delayed corneal re-epithelialization in the first 48 hours and worse corneal fluorescein staining intensity at day 14 than young mice.

Conclusions

Aged corneal epithelium has an altered transcriptome. Aged mice regardless of sex heal more slowly and displayed more signs of corneal epithelial defects after wounding than young mice. These results indicate that aging significantly alters the corneal epithelium and its ability to coordinate healing.

A Novel Combination Therapy Tβ4/VIP Protects against Hyperglycemia-Induced Changes in Human Corneal Epithelial Cells

Despite the prevalence of diabetic retinopathy, the majority of adult diabetic patients develop visually debilitating corneal complications, including impaired wound healing. Unfortunately, there is limited treatment for diabetes-induced corneal damage. The current project investigates a novel, peptide-based combination therapy, thymosin beta-4 and vasoactive intestinal peptide (Tβ4/VIP), against high-glucose-induced damage to the corneal epithelium. Electric cell-substrate impedance sensing (ECIS) was used for real-time monitoring of barrier function and wound healing of human corneal epithelial cells maintained in either normal glucose (5 mM) or high glucose (25 mM) ± Tβ4 (0.1%) and VIP (5 nM). Barrier integrity was assessed by resistance, impedance, and capacitance measurements. For the wound healing assay, cell migration was also monitored. Corneal epithelial tight junction proteins (ZO-1, ZO-2, occludin, and claudin-1) were assessed to confirm our findings. Barrier integrity and wound healing were significantly impaired under high-glucose conditions. However, barrier function and cell migration significantly improved with Tβ4/VIP treatment. These findings were supported by high-glucose-induced downregulation of tight junction proteins that were effectively maintained similar to normal levels when treated with Tβ4/VIP. These results strongly support the premise that Tβ4 and VIP work synergistically to protect corneal epithelial cells against hyperglycemia-induced damage. In addition, this work highlights the potential for significant translational impact regarding the treatment of diabetic patients and associated complications of the cornea.

Ferroptosis in the Lacrimal Gland Is Involved in Dry Eye Syndrome Induced by Corneal Nerve Severing

Purpose

Dry eye syndrome (DES) is a prevalent postoperative complication after myopic corneal refractive surgeries and the main cause of postoperative dissatisfaction. Although great efforts have been made in recent decades, the molecular mechanism of postoperative DES remains poorly understood. Here, we used a series of bioinformatics approaches and experimental methods to investigate the potential mechanism involved in postoperative DES.

Methods

BALB/c mice were randomly divided into sham, unilateral corneal nerve cutting (UCNV) + saline, UCNV + vasoactive intestinal peptide (VIP), and UCNV + ferrostatin-1 (Fer-1, inhibitor of ferroptosis) groups. Corneal lissamine green dye and tear volume were measured before and two weeks after the surgery in all groups. Lacrimal glands were collected for secretory function testing, RNA sequencing, ferroptosis verification, and inflammatory factor detection.

Results

UCNV significantly induced bilateral decreases in tear secretion. Inhibition of the maturation and release of secretory vesicles was observed in bilateral lacrimal glands. More importantly, UCNV induced ferroptosis in bilateral lacrimal glands. Furthermore, UCNV significantly decreased VIP, a neural transmitter, in bilateral lacrimal glands, which increased Hif1a, the dominant transcription factor of transferrin receptor protein 1 (TfR1). Supplementary VIP inhibited ferroptosis, which decreased the inflammatory reaction and promoted the maturation and release of secretory vesicles. Supplementary VIP and Fer-1 improved tear secretion.

Conclusions

Our data suggest a novel mechanism by which UCNV induces bilateral ferroptosis through the VIP/Hif1a/TfR1 pathway, which might be a promising therapeutic target for DES-induced by corneal refractive surgeries.

Immunomodulatory Role of Neuropeptides in the Cornea

The transparency of the cornea along with its dense sensory innervation and resident leukocyte populations make it an ideal tissue to study interactions between the nervous and immune systems. The cornea is the most densely innervated tissue of the body and possesses both immune and vascular privilege, in part due to its unique repertoire of resident immune cells. Corneal nerves produce various neuropeptides that have a wide range of functions on immune cells. As research in this area expands, further insights are made into the role of neuropeptides and their immunomodulatory functions in the healthy and diseased cornea. Much remains to be known regarding the details of neuropeptide signaling and how it contributes to pathophysiology, which is likely due to complex interactions among neuropeptides, receptor isoform-specific signaling events, and the inflammatory microenvironment in disease. However, progress in this area has led to an increase in studies that have begun modulating neuropeptide activity for the treatment of corneal diseases with promising results, necessitating the need for a comprehensive review of the literature. This review focuses on the role of neuropeptides in maintaining the homeostasis of the ocular surface, alterations in disease settings, and the possible therapeutic potential of targeting these systems.

USP22 promotes pro‑inflammatory responses in Pseudomonas aeruginosa‑induced keratitis by targeting TRAF6

Pseudomonas aeruginosa (PA)‑induced keratitis is characterized by inflammatory epithelial edema, stromal infiltration, corneal ulceration and can lead to vision loss. The present study aimed to study the effect of ubiquitin‑specific protease 22 (USP22) on PA‑induced keratitis. Using RT‑qPCR and western blotting, significantly increased expression of USP22 was identified in mouse corneas and cultured RAW264.7 cells following PA stimulation. In addition, the results of in vivo experiments, western blot assay and ELISA suggested that the silencing of USP22 attenuated disease progression, downregulated the NF‑κB pathway and suppressed the expression of pro‑inflammatory cytokines following PA stimulation. Notably, it was identified that the expression of tumor necrosis factor receptor‑associated factor 6 (TRAF6) was decreased by silencing of USP22 and USP22 was found to remove lysine 48‑linked poly‑ubiquitination chains from TRAF6 to stabilize TRAF6 expression and these effects were clearly aggravated following PA infection.

Immunity and pain in the eye: focus on the ocular surface

Most ocular diseases are associated with pain. While pain has been generally considered a mere (deleterious) additional symptom, it is now emerging that it is a key modulator of innate/adaptive immunity. Because the cornea receives the highest nerve density of the entire body, it is an ideal site to demonstrate interactions between pain and the immune response. Indeed, most neuropeptides involved in pain generation are also potent regulators of innate and adaptive leukocyte physiology. On the other hand, most inflammatory cells can modulate the generation of ocular pain through release of specific mediators (cytokines, chemokines, growth factors, and lipid mediators). This review will discuss the reciprocal role(s) of ocular surface (and specifically: corneal) pain on the immune response of the eye. Finally, we will discuss the clinical implications of such reciprocal interactions in the context of highly prevalent corneal diseases.

Research Progress on the Mechanism of the Acupuncture Regulating Neuro-Endocrine-Immune Network System

As one of the conventional treatment methods, acupuncture is an indispensable component of Traditional Chinese Medicine. Currently, acupuncture has been partly accepted throughout the world, but the mechanism of acupuncture is still unclear. Since the theory of the neuro-endocrine-immune network was put forward, new insights have been brought into the understanding of the mechanism of acupuncture. Studies have proven that acupuncture is a mechanical stimulus that can activate local cell functions and neuroreceptors. It also regulates the release of related biomolecules (peptide hormones, lipid hormones, neuromodulators and neurotransmitters, and other small and large biomolecules) in the microenvironment, where they can affect each other and further activate the neuroendocrine-immune network to achieve holistic regulation. Recently, growing efforts have been made in the research on the mechanism of acupuncture. Some researchers have transitioned from studying the mechanism of acupuncture as a single linear pathway to using systems approaches, including metabolomics, genomics, proteomics and biological pathway analysis. This review summarizes the research progress on the neuro-endocrine-immune network related mechanism of acupuncture and discusses its current challenges and future directions.

Mammalian Neuropeptides as Modulators of Microbial Infections: Their Dual Role in Defense versus Virulence and Pathogenesis

The regulation of infection and inflammation by a variety of host peptides may represent an evolutionary failsafe in terms of functional degeneracy and it emphasizes the significance of host defense in survival. Neuropeptides have been demonstrated to have similar antimicrobial activities to conventional antimicrobial peptides with broad-spectrum action against a variety of microorganisms. Neuropeptides display indirect anti-infective capacity via enhancement of the host’s innate and adaptive immune defense mechanisms. However, more recently concerns have been raised that some neuropeptides may have the potential to augment microbial virulence. In this review we discuss the dual role of neuropeptides, perceived as a double-edged sword, with antimicrobial activity against bacteria, fungi, and protozoa but also capable of enhancing virulence and pathogenicity. We review the different ways by which neuropeptides modulate crucial stages of microbial pathogenesis such as adhesion, biofilm formation, invasion, intracellular lifestyle, dissemination, etc., including their anti-infective properties but also detrimental effects. Finally, we provide an overview of the efficacy and therapeutic potential of neuropeptides in murine models of infectious diseases and outline the intrinsic host factors as well as factors related to pathogen adaptation that may influence efficacy.

Regulation of LOX-1 on adhesion molecules and neutrophil infiltration in mouse Aspergillus fumigatus keratitis

AIM

To determine whether lectin-like ox-LDL receptor (LOX-1) regulates adhesion molecules expression and neutrophil infiltration in Aspergillus fumigatus (A. fumigatus) keratitis of C57BL/6 mice.

METHODS

C57BL/6 mice were pretreated with a neutralizing antibody to LOX-1 (5 µg/5 µL) or control nonspecific IgG (5 µg/5 µL), LOX-1 inhibitor Poly-I (2 µg/5 µL) or PBS by subconjunctival injection. Fungal keratitis (FK) mouse models of C57BL/6 mice were established by scraping corneal central epithelium, smearing A. fumigatus on the corneal surface and covering the eye with contact lenses. The corneal response to infection was assessed via clinical score. The mRNA levels of the adhesion molecules intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), P-selectin and E-selectin were tested in control and infected corneas by reverse transcription-polymerase chain reaction (RT-PCR). The protein levels of ICAM-1 were evaluated by immunofluorescence (IF) and Western blot. Neutrophils were extracted from the abdominal cavity of C57BL/6 mice followed by pretreatment using antibody to LOX-1 (10 µg/mL) or control nonspecific IgG (10 µg/mL), the Poly-I (4 µg/mL) or PBS. The cells were then stimulated with A. fumigatus and tested mRNA and protein levels of lymphocyte function-associated antigen-1 (LFA-1) using RT-PCR and Western blot. IF and myeloperoxidase (MPO) assays were used to assess neutrophil infiltration in mice corneas.

RESULTS

Pretreatment of LOX-1 antibody or the Poly-I reduced the degree of inflammation of cornea and decreased the clinical FK score compared with pretreatment of IgG or PBS (both P<0.01). And these pretreatment also displayed an obvious decline in the mRNA levels of ICAM-1, VCAM-1, P-selectin, E-selectin and LFA-1 expression compared with control groups (all P<0.01). Furthermore, pretreated with LOX-1 antibody or Poly-I, the protein levels of ICAM-1 and LFA-1 also decreased compared with control groups (all P<0.05). Neutrophil infiltration in the cornea was significantly reduced after pretreatment of LOX-1 antibody or Poly-I compared with control groups by IF and MPO assays (both P<0.01).

CONCLUSION

Inhibition of LOX-1 can decrease the expression of adhesion molecules and reduce neutrophil infiltration in A. fumigatus infected corneas of C57BL/6 mice.

Retinoprotective Effects of TAT-Bound Vasoactive Intestinal Peptide and Pituitary Adenylate Cyclase Activating Polypeptide

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) belong to the same peptide family and exert a variety of biological functions. Both PACAP and VIP have protective effects in several tissues. While PACAP is known to be a stronger retinoprotective peptide, VIP has very potent anti-inflammatory effects. The need for a non-invasive therapeutic approach has emerged and PACAP has been shown to be retinoprotective when administered in the form of eye drops as well. The cell penetrating peptide TAT is composed of 11 amino acids and tagging of TAT at the C-terminus of neuropeptides PACAP/VIP can enhance the traversing ability of the peptides through the biological barriers. We hypothesized that TAT-bound PACAP and VIP could be more effective in exerting retinoprotective effects when given in eye drops, by increasing the traversing efficacy and enhancing the activation of the PAC1 receptor. Rats were subjected to bilateral carotid artery occlusion (BCCAO), and retinas were processed for histological analysis 14 days later. The efficiency of the TAT-bound peptides to reach the retina was assessed as well as their cAMP increasing ability. Our present study provides evidence, for the first time, that topically administered PACAP and VIP derivatives (PACAP-TAT and VIP-TAT) attenuate ischemic retinal degeneration via the PAC1 receptor presumably due to a multifactorial protective mechanism.

Degeneration of Corneal Sensation and Innervation in Patients with Facial Paralysis: A Cross-Sectional Study Using in Vivo Confocal Microscopy

Purpose: Facial paralysis (FP) leads to diverse periocular complications which threats visual acuity and affects corneal nerve functionally and morphologically. This study aims to summarize the clinical ophthalmic outcomes, corneal sensation, and morphological alterations of subbasal nerve and dendritic cells (DCs) in patients with facial paralysis.Methods: We performed a cross-sectional study of 48 consecutive patients with facial paralysis at one tertiary hospital. Forty-eight healthy participants were enrolled as controls. The images of corneal nerves and epithelial DCs were detected by in vivo confocal microscopy (IVCM). Each patient received thorough ophthalmic examination, tear film function tests, corneal fluorescence staining and Cochet-Bonnet esthesiometry test. Clinical and morphologic data were compared with controls.Results: Forty patients (83.3%) showed corneal injuries from punctate epithelial defects to corneal ulcers and scars. Visual impairment and eyelid malposition were observed. Corneal sensitivity remarkably decreased (25.1 ± 23.8 mm) in the affected eyes and was correlated to diminished subbasal nerve density (P = .019, r = 0.387). Numbers of corneal main nerve trunks and branches were significantly reduced (P < .0001) while DCs were increased (P < .0001) in patients with FP when compared with controls. Nerve fiber density showed inverse association with DC density (P = .019, r = -0.389).Conclusions: Ocular complications including corneal erosions, loss of corneal sensation, visual impairment and eyelid malposition have largely affected patients with facial paralysis. Morphological changes of diminished corneal subbasal nerve and increased DCs were detected by IVCM. Corneal epithelial defect, corneal opacity, corneal sensation, dendritic cell density are factors associated with corneal subbasal nerve density. Patients with FP are suggested to have complete ophthalmic evaluation and early instruction on ocular prevention.

VIP modulates the ALX/FPR2 receptor axis toward inflammation resolution in a mouse model of bacterial keratitis

Vasoactive intestinal peptide (VIP) has been shown to regulate corneal inflammation. Formyl peptide receptor 2 (FPR2) is a transmembrane protein belonging to the GPCR family. Ligands include pro-resolving lipids, lipoxin A4 (LXA4) and resolvin D1 (RvD1). The current study focuses on the effect of VIP regarding the FPR2 receptor axis in improving disease outcome in a mouse model of bacterial keratitis. Infection was induced in C57BL/6 (B6) mice using P. aeruginosa (PA) ATCC 19660. Mice received topical treatment (VIP or PBS) 3× daily after infection. Mean clinical scores, bacterial plate counts, Griess and myeloperoxidase (MPO) assays indicate that topical VIP effectively abrogates the disease response. Findings also reveal that VIP influences FPR2 pathway activation independent of archetypal VIP receptors. Exploring the immunoresolving role of FPR2, its ligand RvD1 and related enzymes (5-LOX, 12/15-LOX), our results suggest a mechanism by which VIP treatment influences the disease response in bacterial keratitis, which could offer a therapeutic point of intervention for enhancing this pro-resolving circuit.

Retinoprotective Effects of TAT-Bound Vasoactive Intestinal Peptide and Pituitary Adenylate Cyclase Activating Polypeptide

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide (PACAP) belong to the same peptide family and exert a variety of biological functions. Both PACAP and VIP have protective effects in several tissues. While PACAP is known to be a stronger retinoprotective peptide, VIP has very potent anti-inflammatory effects. The need for a non-invasive therapeutic approach has emerged and PACAP has been shown to be retinoprotective when administered in the form of eye drops as well. The cell penetrating peptide TAT is composed of 11 amino acids and tagging of TAT at the C-terminus of neuropeptides PACAP/VIP can enhance the traversing ability of the peptides through the biological barriers. We hypothesized that TAT-bound PACAP and VIP could be more effective in exerting retinoprotective effects when given in eye drops, by increasing the traversing efficacy and enhancing the activation of the PAC1 receptor. Rats were subjected to bilateral carotid artery occlusion (BCCAO), and retinas were processed for histological analysis 14 days later. The efficiency of the TAT-bound peptides to reach the retina was assessed as well as their cAMP increasing ability. Our present study provides evidence, for the first time, that topically administered PACAP and VIP derivatives (PACAP-TAT and VIP-TAT) attenuate ischemic retinal degeneration via the PAC1 receptor presumably due to a multifactorial protective mechanism.

Role of vasoactive intestinal peptide in Aspergillus fumigatus-infected cornea

AIM

To investigate the anti-inflammatory role of vasoactive intestinal peptide (VIP) in Aspergillus fumigatus (A. fumigatus) ketatitis.

METHODS

Expression of VIP was tested by polymerase chain reaction (PCR) in C57BL/6 and BALB/c normal and A. fumigatus infected corneas. C57BL/6 mice were pretreated with recombinant (r) VIP, while BALB/c mice were pretreated with VIP antagonist, and then infected with A. fumigatus. Clinical score was recorded. Expression of pro- and anti-inflammatory cytokines, toll-like receptor 4 (TLR4), lectin-like oxidized low-density lipoprotein receptor 1 (LOX-1), and neutrophil infiltration were tested by PCR, enzyme-linked immunosorbent assay (ELISA), and myeloperoxidase (MPO) assay.

RESULTS

VIP mRNA expression in BALB/c cornea was higher than C57BL/6 cornea at 1 and 3d post infection (p.i.). rVIP treatment of C57BL/6 mice showed alleviated disease and down-regulated expression of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), while IL-10 expression was up-regulated. Neutrophil infiltration and TLR4, IL-17 expression were decreased after rVIP treatment, while LOX-1 expression was up-regulated in C57BL/6. VIP antagonist pretreatment showed increased disease and higher IL-1β, TNF-α, TLR4, IL-17 and MPO levels, while IL-10 and LOX-1 levels were down-regulated in BALB/c mice.

CONCLUSION

rVIP alleviate disease response of C57BL/6 mice. VIP antagonist resulted in worsened disease of BALB/c mice. VIP proposed anti-inflammatory role in A. fumigatus keratitis.

VIP protects human retinal microvascular endothelial cells against high glucose-induced increases in TNF-α and enhances RvD1

PURPOSE

The purpose of our study was to evaluate the therapeutic effect of VIP on human retinal endothelial cells (HREC) under high glucose conditions. Diabetes affects almost 250 million people worldwide. Over 40% of diabetics are expected to develop diabetic retinopathy, which remains the leading cause of visual impairment/blindness. Currently, treatment is limited to late stages of retinopathy with no options available for early stages. To this end, the purpose of the current study is to evaluate the therapeutic effect of vasoactive intestinal peptide (VIP) on HREC under high glucose conditions.

METHODS

Primary HREC were cultured in normal (5mM) or high (25mM) glucose medium +/- VIP treatment. Protein levels of TNF-α, resolvin D1 (RvD1), formyl peptide receptor 2 (FPR2), G protein-coupled receptor 32 (GPR32), VEGF, and VIP receptors, VPAC1 and VPAC2 were measured.

RESULTS

High glucose-induced changes in TNF-α and RvD1 were restored to control levels with VIP treatment. RvD1 receptors, ALX/FPR2 and GPR32, were partially rescued with VIP treatment. VPAC2 expression appeared to be the major receptor involved in VIP signaling in HREC, as VPAC1 receptor was not detected. In addition, VIP did not induce HREC secretion of VEGF under high glucose conditions.

CONCLUSIONS

Our results demonstrate that VIP's therapeutic effect on HREC, occurs in part, through the balance between the pro-inflammatory cytokine, TNF-α, and the pro-resolving mediator, RvD1. Although VPAC1 is considered the major VIP receptor, VPAC2 is predominantly expressed on HREC under both normal and high glucose conditions.

Efficacy of VIP as Treatment for Bacteria-Induced Keratitis Against Multiple Pseudomonas aeruginosa Strains

PURPOSE

Previous studies have demonstrated the efficacy of vasoactive intestinal peptide (VIP) treatment in regulating inflammation following bacterial keratitis induced by the P. aeruginosa strain 19660. However, in the current study we assessed whether disease outcome is specific to 19660 or if VIP treatment is effective against multiple P. aeruginosa strains.

METHODS

B6 mice received daily IP injections of VIP from -1 through 5 days post injection (p.i.). Control mice were similarly injected with PBS. Corneal infection was induced using PA 19660, PAO1 or KEI 1025. Disease response was documented and bacterial plate counts and myeloperoxidase assays were performed. Expression of select inflammatory mediators as well as enzymes associated with lipid mediator production was assessed after VIP treatment. KEI 1025 was characterized by cytotoxicity and invasion assays and then confirmed for ExoS/ExoU expression.

RESULTS

VIP treatment converted the susceptible response to resistant for the three P. aeruginosa strains tested. Disease response was significantly reduced with no corneal perforation. Anti-inflammatory mediators were enhanced after VIP treatment, while pro-inflammatory molecules were reduced compared to controls. Furthermore, VIP reduced inflammatory cell persistence in the cornea after infection with each of the P. aeruginosa strains.

CONCLUSIONS

VIP treatment is effective at ameliorating disease pathogenesis for multiple P. aeruginosa strains, both cytotoxic and invasive. This study is also the first to indicate a possible role for VIP regarding lipid mediator expression in the eye. In addition, the clinical isolate, KEI 1025, was characterized as an invasive strain. Overall, this study strengthens the preclinical development of VIP as a therapeutic agent for ocular infectious disease.

Effects of VIP on corneal reconstitution and homeostasis following Pseudomonas aeruginosa induced keratitis

PURPOSE

Studies from our laboratory have demonstrated that vasoactive intestinal peptide (VIP) directly converts the normally susceptible C57BL/6J (B6) mouse to resistant after ocular infection through modulation of the inflammatory response. This study examines mechanisms by which VIP influences the healing phase following infection--specifically reconstitution of the extracellular matrix (ECM).

METHODS

B6 mice received daily intraperitoneal (IP) injections of VIP, while control mice were similarly injected with sterile phosphate buffered saline (PBS). Real-time RT-PCR, ELISA, and immunofluorescent staining were used to assess the effects of VIP treatment on ECM molecule expression after Pseudomonas aeruginosa-induced keratitis. We also compared the effect of VIP treatment on lipopolysaccharide (LPS)-stimulated B6- and BALB/c-derived fibroblasts.

RESULTS

In vivo analyses revealed that VIP treatment of P. aeruginosa-infected B6 corneas led to a significant increase in ECM molecules associated with healing/homeostasis, while those associated with ECM degradation were significantly down-regulated when compared to wild-type (WT) controls. In vitro studies revealed that VIP treatment of lipopolysaccharide-stimulated fibroblasts derived from susceptible B6 and resistant BALB/c mice expressed distinct differences in ECM molecule expression, whereby the latter expressed higher levels of ECM molecules aimed at reconstitution. Furthermore, differential expression of VIP receptor-1/VIP receptor-2 (VIPR1/VIPR2) was observed between B6 and BALB/c after VIP treatment of LPS-stimulated fibroblasts.

CONCLUSIONS

VIP treatment functions to enhance ECM reconstitution, which appears to be carried out in large part by fibroblasts via VIPR2. Overall, the data from this study suggest that VIP not only regulates disease pathogenesis, but also functions to restore integrity of the corneal stroma.

Differential changes in Substance P, VIP as well as neprilysin levels in patients with gastritis or ulcer

The protective effect of capsaicin-sensitive sensory nerve (CSSN) activation was recently demonstrated in human gastric mucosa. We here examined changes in neuropeptides, specifically Substance P (SP), calcitonin-gene related peptide (CGRP) and vasoactive intestinal peptide (VIP) in patients with chronic gastritis or ulcer. Furthermore changes in neprilysin levels, which hydrolyse these neuropeptides, were determined. Gastric biopsies were obtained from both lesion- and normal-appearing mucosa of 57 patients. The presence of H. pylori infection was verified with rapid urease assay. Neuronal and non-neuronal levels of SP, VIP, CGRP and neprilysin activity were determined in freshly frozen biopsies. Immunohistochemical localization of neprilysin was performed in 30 paraffin embedded specimens. We here found that neuronal SP levels decreased significantly in normally appearing mucosa of patients with gastritis while levels of non-neuronal SP increased in diseased areas of gastritis and ulcer. The presence of H. pylori led to further decreases of SP levels. The content of VIP in both disease-involved and uninvolved mucosa, and expression of neprilysin, markedly decreased in patients with gastritis or ulcer. Since VIP, as well as SP fragments, formed following hydrolysis with neprilysin is recognized to have gastroprotective effects, decreased levels of VIP, SP and neprilysin may predispose to cellular damage.

Inflammation and the nervous system: the connection in the cornea in patients with infectious keratitis

PURPOSE

To study the density and morphologic characteristics of epithelial dendritic cells, as correlated to subbasal corneal nerve alterations in acute infectious keratitis (IK) by in vivo confocal microscopy (IVCM).

METHODS

IVCM of the central cornea was performed prospectively in 53 eyes with acute bacterial (n = 23), fungal (n = 13), and Acanthamoeba (n = 17) keratitis, and in 20 normal eyes, by using laser in vivo confocal microscopy. Density and morphology of dendritic-shaped cells (DCs) of the central cornea, corneal nerve density, nerve numbers, branching, and tortuosity were assessed and correlated. It should be noted that due to the "in vivo" nature of the study, the exact identity of these DCs cannot be specified, as they could be monocytes or tissue macrophages, but most likely dendritic cells.

RESULTS

IVCM revealed the presence of central corneal DCs in all patients and controls. The mean DC density was significantly higher in patients with bacterial (441.1 ± 320.5 cells/mm(2); P < 0.0001), fungal (608.9 ± 812.5 cells/mm(2); P < 0.0001), and Acanthamoeba keratitis (1000.2 ± 1090.3 cells/mm(2); P < 0.0001) compared with controls (49.3 ± 39.6 cells/mm(2)). DCs had an increased size and dendrites in patients with IK. Corneal nerves were significantly reduced in eyes with IK compared with controls across all subgroups, including nerve density (674.2 ± 976.1 vs. 3913.9 ± 507.4 μm/frame), total nerve numbers (2.7 ± 3.9 vs. 20.2 ± 3.3), main trunks (1.5 ± 2.2 vs. 6.9 ± 1.1), and branching (1.2 ± 2.0 vs. 13.5 ± 3.1; P < 0.0001). A strong association between the diminishment of corneal nerves and the increase of DC density was observed (r = -0.44; P < 0.0005).

CONCLUSIONS

IVCM reveals an increased density and morphologic changes of central epithelial DCs in infectious keratitis. There is a strong and significant correlation between the increase in DC numbers and the decreased subbasal corneal nerves, suggesting a potential interaction between the immune and nervous system in the cornea.