Cyclic GMP in the pig vitreous and retina after experimental retinal detachment

Purpose: Earlier studies have revealed a decreased level of cGMP in vitreous fluid obtained from patients with a retinal detachment. To further investigate this phenomenon, we developed an experimental retinal detachment model in pigs. Methods: Experimental unilateral retinal detachments were induced in pig eyes by subretinal injection of 0.25% sodium hyaluronate. Fourteen days later the vitreous and retinas were analyzed for cGMP expression. Following enucleation, the retinas were incubated in the presence of a nonselective phosphodiesterase inhibitor (IBMX), and the particulate guanylyl cyclase stimulator atrial natriuretic peptide (ANP) or the soluble guanylyl cyclase stimulator sodium nitroprusside (SNP). cGMP was visualized in retinal wholemounts by immunochemistry combined with a computer based stereology system. cGMP levels in vitreous were determined by ELISA. Results: The mean vitreous cGMP level in pig eyes with a retinal detachment (1.45 pmol/ml) was significantly lower compared to the mean level of cGMP in healthy pig eyes (4.61 pmol/ml; p= 0.028 was considered significant). In the inner retina, ANP as well as SNP induced cGMP immunoreactivity in both detached and healthy retinas. After incubation with ANP, cGMP could also be detected in the outer nuclear layer of the detached retina, whereas this was not the case in the normal retina. Conclusions: Experimental retinal detachment in the pig eye leads to a decrease of cGMP levels in vitreous similar to that observed in clinical studies. This model may be helpful to analyze the mechanisms involved in cGMP dynamics following retinal detachment

Interleukin and Growth Factor Levels in Subretinal Fluid in Rhegmatogenous Retinal Detachment: A Case-Control Study

BACKGROUND: Rhegmatogenous retinal detachment (RRD) is a major cause of visual loss in developed countries. Proliferative vitreoretinopathy (PVR), an eye-sight threatening complication of RRD surgery, resembles a wound-healing process with inflammation, scar tissue formation, and membrane contraction. This study was performed to determine the possible involvement of a wide range of cytokines in the future development of PVR, and to identify predictors of PVR and visual outcome. METHODOLOGY: A multiplex immunoassay was used for the simultaneous detection of 29 different cytokines in subretinal fluid samples from patients with primary RRD. Of 306 samples that were collected and stored in our BioBank between 2001 and 2008, 21 samples from patients who developed postoperative PVR were compared with 54 age-, sex-, and storage-time-matched RRD control patients who had an uncomplicated postoperative course during the overall follow-up period. FINDINGS: Levels of IL-1α, IL-2, IL-3, IL-6, VEGF, and ICAM-1 were significantly higher (P<0.05) in patients who developed postoperative PVR after reattachment surgery than in patients with an uncomplicated postoperative course, whereas levels of IL-1β, IL-4, IL-5, IL-7, IL-9, IL-10, IL-11, IL-12p70, IL-13, IL-15, IL-17, IL-18, IL-21, IL-22, IL-23, IL-25, IL-33, TNF-α, IFN-γ, IGF-1, bFGF, HGF, and NGF were not (P>0.05). Multivariate logistic regression analysis revealed that IL-3 (P = 0.001), IL-6 (P = 0.047), ICAM-1 (P = 0.010), and preoperative visual acuity (P = 0.026) were independent predictors of postoperative PVR. Linear regression analysis showed that ICAM-1 (P = 0.005) and preoperative logMAR visual acuity (P = 0.001) were predictive of final visual outcome after primary RRD repair. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that after RRD onset an exaggerated response of certain cytokines may predispose to PVR. Sampling at a time close to the onset of primary RRD may thus provide clues as to which biological events may initiate the development of PVR and, most importantly, may provide a means for therapeutic control

Two autocrine pathways to regulate cyclic GMP synthesis in cultured human retinal pigment epithelial cells

AIM: To investigate the role of two separate enzymatic pathways [soluble (sGC) vs. particulate (pGC) guanylyl cyclase] in the synthesis of cyclic GMP (cGMP) in cultured human retinal pigment epithelial (RPE) cells. METHODS: cGMP accumulation was evaluated by quantitative analysis of cGMP immunoreactivity. RPE cells were also stained for inducible nitric oxide synthase (iNOS), ANP and beta(1)- and alpha(2)-subunits of sGC. RESULTS: We showed nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity and iNOS immunoreactivity in RPE cells. Incubation of the cells in the presence of 1 mM IBMX to inhibit phosphodiesterase activity, and the simultaneous inhibition of NOS activity with L-NAME suggested the involvement of sGC in maintaining a low level of cGMP in the RPE cells. The involvement of sGC was further supported by detection of the beta(1)- and alpha(2)-subunits of sGC. Incubation of the cells in the presence of atrial natriuretic peptide (ANP) to stimulate pGC strongly increased cGMP immunoreactivity. We also demonstrated the presence of ANP in all RPE cells. CONCLUSION: Cultured human RPE cells are capable of producing cGMP after stimulation of sGC or pGC. The presence of iNOS and ANP in all cells suggests two different autocrine pathways of stimulating cGMP production in these cells. The possible role of cGMP in the regulation iNOS gene expression and in the regulation of ANP is discussed