vasoactive-intestinal-peptide and Corneal-Diseases

Diabetic keratopathy, a sight-threatening corneal disease, comprises several symptomatic conditions including delayed epithelial wound healing, recurrent erosions, and sensory nerve (SN) neuropathy. We investigated the role of neuropeptides in mediating corneal wound healing, including epithelial wound closure and SN regeneration. Denervation by resiniferatoxin severely impaired corneal wound healing and markedly upregulated proinflammatory gene expression. Exogenous neuropeptides calcitonin gene-related peptide (CGRP), substance P (SP), and vasoactive intestinal peptide (VIP) partially reversed resiniferatoxin's effects, with VIP specifically inducing interleukin-10 expression. Hence, we focused on VIP and observed that wounding induced VIP and VIP type 1 receptor (VIPR1) expression in normal (NL) corneas, but not corneas from mice with diabetes mellitus (DM). Targeting VIPR1 in NL corneas attenuated corneal wound healing, dampened wound-induced expression of neurotrophic factors, and exacerbated inflammatory responses, while exogenous VIP had the opposite effects in DM corneas. Remarkably, wounding and diabetes also affected the expression of Sonic Hedgehog (Shh) in a VIP-dependent manner. Downregulating Shh expression in NL corneas decreased while exogenous Shh in DM corneas increased the rates of corneal wound healing. Furthermore, inhibition of Shh signaling dampened VIP-promoted corneal wound healing. We conclude that VIP regulates epithelial wound healing, inflammatory response, and nerve regeneration in the corneas in an Shh-dependent manner, suggesting a therapeutic potential for these molecules in treating diabetic keratopathy.

Topics: Animals; Corneal Diseases; Cytokines; Diabetes Mellitus, Experimental; Epithelium, Corneal; Extracellular Signal-Regulated MAP Kinases; Female; Hedgehog Proteins; Mice; Mice, Inbred C57BL; Nerve Regeneration; Neutrophil Infiltration; Receptors, Vasoactive Intestinal Polypeptide, Type I; Signal Transduction; Vasoactive Intestinal Peptide; Wound Healing

Corneal infection with Pseudomonas aeruginosa perforates the cornea in susceptible C57BL/6 (B6), but not resistant BALB/c, mice. To determine whether vasoactive intestinal peptide (VIP) played a role in development of the resistant response, protein expression levels were tested by immunocytochemistry and enzyme immunoassay in BALB/c and B6 corneas. Both mouse strains showed constitutive expression of corneal VIP protein and nerve fiber distribution. However, disparate expression patterns were detected in the cornea after infection. VIP protein was elevated significantly in BALB/c over B6 mice at 5 and 7 days postinfection. Therefore, B6 mice were injected with rVIP and subsequently demonstrated decreased corneal opacity and resistance to corneal perforation compared with PBS controls. rVIP- vs PBS-treated B6 mice also demonstrated down-regulation of corneal mRNA and/or protein levels for proinflammatory cytokines/chemokines: IFN-gamma, IL-1beta, MIP-2, and TNF-alpha, whereas anti-inflammatory mediators, IL-10 and TGF-beta1, were up-regulated. Treatment with rVIP decreased NO levels and polymorphonuclear neutrophil (PMN) number. To further define the role of VIP, peritoneal macrophages (Mphi) and PMN from BALB/c and B6 mice were stimulated with LPS and treated with rVIP. Treatment of LPS-stimulated Mphi from both mouse strains resulted in decreased IL-1beta and MIP-2 protein levels; PMN responded similarly. Both cell types also displayed a strain-dependent differential response to rVIP, whereby B6 Mphi/PMN responded only to a higher concentration of VIP compared with cells from BALB/c mice. These data provide evidence that neuroimmune regulation of the cytokine network and host inflammatory cells functions to promote resistance against P. aeruginosa corneal infection.

Topics: Animals; Corneal Diseases; Cytokines; Female; Macrophages; Mice; Neutrophils; Pseudomonas aeruginosa; Receptors, Vasoactive Intestinal Polypeptide, Type I; Retinal Perforations; RNA, Messenger; Vasoactive Intestinal Peptide

To delineate the clinical features and alterations in innervation and substance P (SP) content in spontaneous chronic corneal epithelial defects (SCCED) in dogs and to conduct a preliminary investigation evaluating the efficacy of topical SP, with or without insulin-like growth factor (IGF)-1, in the treatment of this disorder.. Complete ophthalmic examinations, including Cochet-Bonnet aesthesiometry, were performed in 45 canine patients that had spontaneous corneal epithelial defects of at least 3 weeks' duration and with no identifiable cause. Eighteen patients had superficial keratectomies performed, and the corneal nerves were labeled immunohistochemically with antibodies against protein gene product (PGP)-9.5, SP, vasoactive intestinal peptide (VIP), and tyrosine hydroxylase (TH). Relative fiber densities were assessed qualitatively and quantitatively. Corneal epithelial cell and tear SP contents were determined in affected and normal dogs by an enzyme immunoassay. A preliminary open-label treatment trial of topical SP, with and without IGF-1, was conducted in 21 dogs.. The duration of the erosion before admittance into the study was a mean of 9.22 weeks (range, 3-52). The average patient was middle aged (mean, 9.25 +/- 1.85 years [SD]); no sex predisposition of the disease was identified. Boxers, golden retrievers, and keeshonds were overrepresented when compared with the normal hospital population. Corneal sensation was normal. Marked alterations in corneal innervation were identified in affected dogs with abnormal increased SP and calcitonin gene-related peptide (CGRP)-immunoreactive nerve plexuses identified surrounding the periphery of the epithelial defect. The SP content of epithelial cells surrounding the defect increased, whereas the tear SP content remained unchanged. Of the canine patients treated with SP, with or without IGF-1, 70% to 75% had complete healing of the defect.. This idiopathic spontaneous corneal disease in dogs shares clinical features with chronic epithelial defects in humans. The presence of marked alterations in peptidergic innervation and positive response to topical therapy with SP suggest that SP plays a critical role in corneal wound-healing processes.

Topics: Administration, Topical; Animals; Calcitonin Gene-Related Peptide; Chronic Disease; Corneal Diseases; Dog Diseases; Dogs; Drug Therapy, Combination; Epithelium, Corneal; Female; Fluorophotometry; Immunoenzyme Techniques; Insulin-Like Growth Factor I; Male; Substance P; Thiolester Hydrolases; Trigeminal Nerve; Tyrosine 3-Monooxygenase; Ubiquitin Thiolesterase; Vasoactive Intestinal Peptide