We evaluated the roles of tumor necrosis factor (TNF)-α in alkali-induced corneal neovascularization (CNV).
CNV was induced by alkali injury and compared in wild-type (WT) BALB/c mice, and TNF receptor 1-deficient (TNF-Rp55 KO) counterparts, or in mice treated with TNF-α antagonist and recombinant TNF-α. Angiogenic factor expression and leukocyte accumulation in the early phase after injury were quantified by real-time PCR and immunohistochemical analysis, respectively.
Alkali injury augmented the intraocular mRNA expression of TNF-α and its receptor, together with a transient macrophage and neutrophil infiltration. Compared to WT mice, TNF-Rp55 KO mice exhibited reduced CNV. Intraocular F4/80-positive macrophages and Ly-6G-positive neutrophils infiltration did not change in KO mice compared to WT mice after the injury. Alkali injury induced a massively increased intraocular mRNA expression of angiogenic factors, including vascular endothelial growth factor (VEGF), inducible nitric oxide synthase (iNOS), interleukin (IL)-6, E-selectin, and intercellular adhesion molecule (ICAM)-1 in WT mice, whereas these increments were retarded severely in KO mice. Immunofluorescence analysis demonstrated that F4/80-positive cells expressed VEGF and iNOS. Moreover, TNF-α enhanced VEGF and iNOS expression by peritoneal macrophage from WT, but not KO mice. Topical application of TNF-α antagonist reduced CNV, while topical application of recombinant TNF-α enhanced it.
TNF-Rp55-KO mice exhibited impaired alkali-induced CNV through reduced intracorneal infiltrating macrophage VEGF and iNOS expression.
"Interestingly, Zakaria et al. (2012) have shown from studies of human tears that inflammatory cytokines such as IL-6, IL-8 are positively correlated with the presence of corneal neovascularization. Inhibition of early recruitment or maturation of macrophages by anti-angiogenic agents may also play an important role in later corneal neovascularization (Cursiefen et al., 2004; Lu et al., 2012; Sakurai et al., 2003; Sunderkötter et al., 1994). As expected, VEGF-A expression was suppressed in the treatment groups, alongside with IL-6, a widespread inflammatory cytokine that has been shown to have bidirectional associations with VEGF-A (Tartour et al., 2011; Zakaria et al 2012). "
[Show abstract][Hide abstract] ABSTRACT: Inflammatory angiogenesis is the pathogenic mechanism of various sight-threatening eye diseases, among them corneal neovascularization. Current treatment options include steroids which have undesirable side effects, or anti-VEGF which has only limited efficacy. In an inflammatory environment, however, angiogenesis can be stimulated by numerous factors not directly targeted by anti-VEGF therapy. The aim of this study was to induce corneal inflammation leading to angiogenesis, and investigate the early, differential effects of steroid and anti-VEGF therapy at the cellular, tissue, and gene expression levels. Fifty-two Wistar rats received a single intrastromal corneal suture to induce a controlled inflammatory angiogenic response. Rats were subsequently treated with dexamethasone, rat specific anti-VEGF, or goat IgG (control), topically 4 times daily for 7 days. In vivo confocal microscopy of the cornea was performed longitudinally from 5 h up to 7 d to investigate morphology at the cellular and tissue-level. In vivo photographic vessel analysis and immunohistochemistry were also performed. RT-PCR for VEGF-A, FGF-2, IL-6, TNF-α, CXCL2, CCL2, CCL3 and DLL4 was performed at 24 h, and for VEGF-A, IL-6, TNF-α, FGF-2, CXCL2, CCL2, and CCL3 at 7 days. Early infiltration of CD11b + myeloid cells into the cornea at 5 h post-suture was delayed by both treatments relative to controls; however neither treatment was able to suppress accumulation of myeloid cells at day 2 or 7. Limbal vessel dilation was inhibited at 5 h by both treatments, but only dexamethasone showed sustained effect until day 2. Early macrophage recruitment was also suppressed by dexamethasone (but not by anti-VEGF) until day 2. Dexamethasone furthermore suppressed corneal neovascularization at day 7 by over 90%, whereas suppression by anti-VEGF was 14%. Despite differential suppression of vessel dilation, macrophage recruitment, and vascular invasion, anti-VEGF and dexamethasone both down-regulated VEGF-A and IL-6 expression at 24 h with sustained effect to 7 d. They also both down regulated FGF-2 and TNF-α at 24 h and CCL2 at 7 d. In conclusion, anti-angiogenic treatments influence early, pre-angiogenic tissue activity such as limbal vessel dilation, inflammatory cell infiltration of the stroma, and macrophage recruitment. Importantly, the differential effects of steroids and anti-VEGF treatment in suppressing neovascular growth could not be attributed to differential inhibition of several major angiogenic and inflammatory factors in the early pre-sprouting phase, including IL-6, VEGF-A, FGF-2, TNF-α, CCL2, CCL3, CXCL2, or DLL4.
Experimental Eye Research 01/2014; 125:118–127. · 2.71 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To evaluate the safety/efficacy of topical infliximab, an anti-TNF-α monoclonal antibody, in a mouse model of ocular surface scarring.
Twenty alkali burn mice were treated with infliximab (10 mg/mL) topically 6 times a day, while 20 alkali burn mice received saline for 7 days. Corneal opacity, epithelial wound healing, and ocular phimosis were examined at the slit-lamp. Tear production was quantified with phenol red thread test. Immunofluorescence for infliximab penetration, TNF-α localization, CD45+ cell infiltration, PAS, and Masson's trichrome staining were evaluated on ocular globes and eyelids. TNF-α and IL-1β expression levels were measured on treated murine corneas and eyelids. Finally, quantification of corneal CD31+ blood vessels and LYVE1+ lymphatic vessels were evaluated on 10 additional alkali burn mice receiving either infliximab or saline, after 14 days.
Topical infliximab penetrated the cornea and the conjunctiva and was not toxic (negative fluorescein stain). Its molecular target, TNF-α, was detected in the cornea after injury. Infliximab significantly reduced corneal perforation, opacity index, phimosis, leukocyte infiltration, and fibrosis in the eyelids. It also significantly prevented goblet cell infiltration in epithelial cornea and loss in the conjunctiva (P < 0.05), improved tear secretion and epithelial healing (P < 0.05). Finally, it significantly reduced both corneal hem- (P < 0.05) and lymphangiogenesis (P < 0.01).
Infliximab penetrates the cornea and is safe to the ocular surface in an animal model of ocular surface scarring. We suggest that topical application of infliximab may be a useful treatment in ocular caustications.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
To evaluate the effect of thalidomide analogue CC-3052 on corneal neovascularization in the rabbit model.
Corneal neovascularization was induced in 15 rabbits by a silk suture in the corneal stroma. At 1 week after suturing, 30 eyes were divided into 5 groups of 6 eyes each. Three groups were treated with topical CC-3052 at 3 different concentrations: 0.25% (group 1), 0.5% (group 2), and 1.0% (group 3). All treatments were performed twice a day for a week. A 0.5% concentration of CC-3052 was injected subconjunctivally once in group 4. In group 5, a topical balanced salt solution was added twice a day for a week as the experimental control group. Rabbit corneas were photographed by a digital camera and examined by the operating microscope. Half of the corneal specimens were analyzed histopathologically, and the other half were used to measure the concentration of tumor necrosis factor α and vascular endothelial growth factor (VEGF) messenger RNA by reverse transcriptase-polymerase chain reaction.
The neovascularized area was decreased in all treatment groups compared with the control group. There was a significant difference in the percentage and score of corneal neovascularization between the control and all treatment groups. Inflammation, fibroblast, neovascularization, and anti-VEGF antibody intensities were significantly lower in the control group. The concentration of VEGF and tumor necrosis factor α was significantly lower in the control group. There was no difference between the treatment groups.
Topical and subconjunctival administration of thalidomide analogue CC-3052 was found to be effective for the inhibition of corneal neovascularization.
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