Interleukin-1-beta changes the expression of metalloproteinases in the vitreous humor and induces membrane formation in eyes containing preexisting retinal holes.

PURPOSE: Proliferative vitreoretinopathy occurs when cells migrate into the vitreous humor, where they proliferate and produce a membrane composed of extracellular matrix. Interleukin-1-beta (IL-1-beta) may be involved in these processes because it is chemotactic and mitogenic, and it stimulates metalloproteinase production. In the present study, the effects of intravitreally injected IL-1-beta on retinal membrane formation and the associated changes in metalloproteinase content of vitreous humor were examined. METHODS: Rabbit eyes were injected with IL-1-beta in a buffer, with or without the prior creation of retinal holes. Control eyes received the buffer alone or no injection, with or without retinal holes. Animals were examined by slit lamp biomicroscopy and indirect ophthalmoscopy for 1 month. Zymography was performed on a portion of vitreous humor to assess collagenase content, and the remaining tissue was subjected to histologic analysis. RESULTS: Intraocular IL-1-beta induced perilimbal vessel engorgement, keratic precipitates, synechiae, flare, lens deposits, optic disk hyperemia, and granulomatous formations that gradually subsided during the first week. Intravitreal injection of IL-1-beta in eyes with preexisting retinal holes additionally induced membrane formation. Zymographic analysis of vitreous humor from animals sacrificed 24 hours after IL-1-beta injection showed a 100-kd and a 65-kd gelatinase, whereas control vitreous humor contained predominantly a single gelatinase species of approximately 65 kd. Retinal holes did not affect IL-1-beta induction of the 100-kd gelatinase. CONCLUSIONS: IL-1-beta induces a 100-kd gelatinase in the vitreous humor and epiretinal membrane formation in eyes containing preexisting retinal holes. The presence of retinal holes and abnormal production of cytokines may lead to a cascade of events, including aberrant extracellular matrix remodeling, that result in proliferative diseases of the eye.

Cytokines cause cultured retinal pigment epithelial cells to secrete metalloproteinases and to contract collagen gels.

PURPOSE: Because retinal pigment epithelial cells in epiretinal membranes remodel and contract their surrounding extracellular matrix, investigations were performed to determine if these cells can produce matrix metalloproteinases and contract collagen gels in vitro in the presence of serum or cytokines. METHODS: Cells were grown on collagen gels and their production of metalloproteinases was measured using zymography. RESULTS: Cells grown in a three-dimensional collagen gel culture system produce several latent metalloproteinases that are secreted into the gel and the surrounding medium. These include molecules of 49, 56, 66, and 100 kD. In addition, an enzyme that is probably the active form of the 66 kD enzyme is present. When interleukin 1 beta is added to the cultures, latent 49 kD and 100 kD gelatinase production is greatly stimulated and an active form of both enzymes is also observed in the medium. In contrast, transforming growth factor beta has no stimulatory effect. The cells contract the collagen gel but this is small without cytokines; however, contraction is greatly enhanced in the presence of serum or interleukin 1 beta plus transforming growth factor beta. Contraction is unlikely to be the result of metalloproteinase action on the underlying extracellular matrix because complete inhibition of these enzymes has little effect. CONCLUSIONS: These results show that cytokines can cause cultured retinal pigment epithelial cells to produce metalloproteinases that can, when activated, degrade most collagens and other structural molecules in extracellular matrix. In addition, they can stimulate the contraction of extracellular matrix constituents but there is not a simple causal relationship between matrix remodeling and contraction.

Polypeptide profiles of normal and inflamed rabbit aqueous humor: identification of catabolic products of immunoglobulin G in the normal eye.

The anterior segment of the eye is isolated from the bloodstream by anatomic barriers. These barriers break down during inflammation elicited by muramyl dipeptide (MDP), a component of the cell walls of bacteria. The protein composition of normal aqueous humor and inflamed aqueous were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The presence of transferrin, albumin, IgG and IgM were demonstrated in normal and inflamed aqueous. Normal aqueous additionally contained seven polypeptides (35, 31, 29, 25, 22, 21 and 19 kDa, respectively) that were not observed in inflamed aqueous. Four of these peptides (31, 29, 25 and 19 kDa) were identified as fragments of IgG heavy chains based on their reactivity with anti-IgG antibodies and staphylococcal protein A. Immunoglobulin catabolism has been noted to occur in tissues diffusely throughout the body; this is the first report of it occurring in the eye. This phenomenon appears to be circumvented on breakdown of the blood-aqueous barrier. These observations may relate to the immunoprivilege of the eye and its modulation in inflammation.