Ahmed M. Abu El-Asrar

Cyclooxygenase-2 in Human and Experimental Ischemic Proliferative Retinopathy

Background—Intravitreal neovascular diseases, as in ischemic retinopathies, are a major cause of blindness. Because inflammatory mechanisms influence vitreal neovascularization and cyclooxygenase (COX)–2 promotes tumor angiogenesis, we investigated the role of COX-2 in ischemic proliferative retinopathy. Methods and Results—We describe here that COX-2 is induced in retinal astrocytes in human diabetic retinopathy, in the murine and rat model of ischemic proliferative retinopathy in vivo, and in hypoxic astrocytes in vitro. Specific COX-2 but not COX-1 inhibitors prevented intravitreal neovascularization, whereas prostaglandin E2, mainly via its prostaglandin E receptor 3 (EP3), exacerbated neovascularization. COX-2 inhibition induced an upregulation of thrombospondin-1 and its CD36 receptor, consistent with the observed antiangiogenic effects of COX-2 inhibition; EP3 stimulation reversed effects of COX-2 inhibitors on thrombospondin-1 and CD36. Conclusion—These findings point to an important role for COX-2 in ischemic proliferative retinopathy, as in diabetes.

Expression of the inducible isoform of nitric oxide synthase in the retinas of human subjects with diabetes mellitus

PURPOSE Inducible nitric oxide synthase has been implicated in the pathogenesis of cerebral ischemic damage, in the angiogenic process and in diabetic vascular damage. This study was undertaken to determine whether inducible nitric oxide synthase is present in the retinas from human subjects with diabetes mellitus. METHODS This was an experimental immunohistochemical prospective study. Ten postmortem eyes from five subjects with diabetes mellitus, 10 eyes from five subjects without diabetes and without known ocular disease, and two eyes from one subject with unilateral ocular ischemic syndrome secondary to severe carotid artery obstruction were examined. We used immunohistochemical techniques and antibodies directed against inducible nitric oxide synthase, glial fibrillary acidic protein, and vimentin. The main outcome measure was immunoreactivity for these antibodies. RESULTS Immunoreactivity for inducible nitric oxide synthase was not observed in retinas from all subjects without diabetes and without ocular disease. Six retinas from three subjects with diabetes and nonproliferative retinopathy, and the retina from the eye with ocular ischemic syndrome showed immunoreactivity for inducible nitric oxide synthase in cells with elongated processes. Based on morphology and on glial fibrillary acidic protein and vimentin immunoreactivity, this inducible nitric oxide synthase immunoreactivity appeared to localize to retinal Müller glial cells. CONCLUSIONS These observations suggest that Müller cells may be involved in the microvascular remodeling of the diseased retina and that high concentrations of nitric oxide produced by inducible nitric oxide synthase could contribute to neurotoxicity and angiogenesis that occur in diabetic retinopathy.

Monocyte Chemotactic Protein-1 in Proliferative Vitreoretinal Disorders

PURPOSE To investigate whether the chemokines monocyte chemotactic protein-1 (MCP-1) and interleukin-8 (IL-8) are involved in the pathogenesis of proliferative vitreoretinal disorders and to study their possible interaction with IL-6. METHODS In a prospective study of 125 consecutive patients (125 eyes), vitreous and paired serum samples were obtained and were assayed for MCP-1 and IL-8. Levels of IL-6 were determined by proliferation of the IL-6-dependent hybridoma cell line 7TD1. RESULTS Monocyte chemotactic protein-1 was detected in 13 (48%) of 27 vitreous samples from patients with retinal detachment, in five (63%) of eight samples from patients with macular pucker, in 31 (72%) of 43 samples from patients with proliferative vitreoretinopathy, and in 32 (76%) of 42 samples from patients with proliferative diabetic retinopathy, but not in samples from five patients with idiopathic epiretinal membrane. There was a significant (P = .049) correlation between the incidence of MCP-1 detection in retinal detachment, macular pucker, and proliferative vitreoretinopathy groups and the severity of proliferation. Interleukin-8 was detected in two vitreous samples from eyes with retinal detachment, in two samples from eyes with proliferative vitreoretinopathy, and in three samples from eyes with proliferative diabetic retinopathy. Monocyte chemotactic protein-1 levels in the vitreous samples were positively correlated with IL-6 levels (r = .31, P = .01). Interleukin-6 levels were significantly (P = .0097) greater in vitreous samples with than without detectable levels of MCP-1. CONCLUSION Monocyte chemotactic protein-1 is present in a substantial percent of vitreous samples from eyes with proliferative vitreoretinal disorders and may help in stimulating the infiltration of monocytes and macrophages into eyes with these disorders.

Single-dose Azithromycin in the Treatment of Trachoma: A Randomized, Controlled Study

PURPOSE To compare the safety and efficacy of single oral-dose azithromycin with a 7-week topical tetracycline ointment course in the treatment of active trachoma. METHODS A total of 64 patients with active trachoma were selected randomly to receive azithromycin (20 mg/kg) in a single dose or topical tetracycline eye ointment for 6 weeks. Clinical assessments were made before and at 4, 8, 12, and 24 weeks after treatment. Conjunctival scrapings were obtained before and after 24 weeks after treatment and fixed for Giemsa and direct immunofluorescence staining. RESULTS Trachoma resolved in 17 (63.3%) patients who received azithromycin compared with 19 (65.4%) who were treated with tetracycline ointment. There were no significant differences in treatment effect or baseline characteristics between the treatment groups. Both treatments were well tolerated, and no adverse events were noted. CONCLUSION Single-dose azithromycin is as effective as a 6-week course of topical tetracycline ointment in the treatment of active trachoma. The findings may help establish high compliance in treating trachoma and could contribute to the control of trachoma worldwide.

Recent advances in understanding the biochemical and molecular mechanism of diabetic retinopathy

One of the major complications in patients with diabetes is diabetic retinopathy (DR), a leading cause of blindness worldwide. It takes several years before any clinical signs of retinopathy appear in diabetic patients, which gives an ample opportunity for scientists to uncover biochemical and molecular mechanism implicated early in the development and progression of the disease. During the past few decades, research progress has been made in investigating the pathophysiology of the disease; however, due to nonavailability of human retinal samples at different stages of the disease and also due to lack of a proper animal model of DR, the exact molecular mechanism has not been elucidated, making therapeutic a difficult task. In this review article, we have discussed a number of diabetes-induced metabolites such as glucose, lipids, amino acids, and other related factors and molecules that are implicated in the pathophysiology of the DR. Furthermore, we have highlighted neurodegeneration and regulation of neurotrophic factors, being recognized as early events that may be involved in the pathology of the disease in the course of DR. An understanding of the biochemical and molecular changes especially early in the diabetic retina may lead to new and effective therapies towards prevention and amelioration of DR, which is important for the millions of individuals who already have or are likely to develop the disease before a cure becomes available.

Retinopathy as a predictor of other diabetic complications

Purpose: Early predictors of diabetic complications may aid in the prevention and/or management of these complications. The aim of this cross-sectional study was to determine the predictive value of retinopathy for the presence of other diabetic complications.Methods: The population studied comprised 648 patients with diabetes mellitus assessed by our service. There were 210 patients (32.4%) with insulin-dependent diabetes mellitus (IDDM), and 438 patients (67.6%) with non-insulin-dependent diabetes mellitus (NIDDM).Results: Univariate analyses revealed that retinopathy significantly predicted the presence of neuropathy (odds ratio [OR] = 2.23; 95% confidence interval [CI] = 1.56–3.18; p < 0.00l), nephropathy (OR = 5.68; 95% CI = 3.06–10.62; p < 0.00l), and cerebrovascular disease (OR = 6.6; 95% CI = 1.16–67.21; p = 0.0239) in the total group. Similar associations were observed both in subjects with IDDM and NIDDM. The associations between retinopathyseverity level and the prevalence rate of nephropathy were significant in the total group (p = 0.0001), in patients with IDDM (p = 0.0113), and in patients with NIDDM (p = 0.01). In patients with mild to moderate non-proliferative retinopathy (NPDR), nephropathy was present in 17.2% of patients with IDDM, and in 11.4% of patients with NIDDM. In patients with severe NPDR, nephropathy was present in 23.3% in patients with IDDM, and in 11.8% of patients with NIDDM. In patients with proliferative retinopathy (PDR), nephropathy was present in 50% in patients with IDDM, and in 45.5% in patients with NIDDM. In multivariate logistic regression analyses, nephropathy was the only significant complication to be independently associated with retinopathy in patients with IDDM (OR = 8.02; 95% CI = 1.95–33), and in patients with NIDDM (OR = 2.48;95% CI = 1.02–6.03).Conclusions: Retinopathy, especially the presence of PDR, is an independent predictor for nephropathy. The predictive value of retinopathy for nephropathy is stronger in patients with IDDM than in those with NIDDM. Ophthalmologists should refer patients with retinopathy for regular medical evaluations.

Chemokines in the limbal form of vernal keratoconjunctivitis

BACKGROUND/AIMS Chemokines are a family of low molecular weight cytokines that attract and activate leucocytes. The CC chemokines act on eosinophils, basophils, monocytes, and lymphocytes, suggesting that they play an important part in allergic diseases. The aims of this study were to investigate the expression of the CC chemokines, RANTES, eotaxin, monocyte chemotactic protein (MCP) 1, MCP-2, and MCP-3 in the conjunctiva of patients with vernal keratoconjunctivitis (VKC) and to determine the cellular source of these chemokines. METHODS Conjunctival biopsy specimens from nine subjects with active VKC, and six control subjects were studied by immunohistochemical techniques using a panel of monoclonal and polyclonal antibodies directed against RANTES, eotaxin, MCP-1, MCP-2, and MCP-3. The phenotype of inflammatory cells expressing chemokines was examined by sequential double immunohistochemistry. RESULTS In the normal conjunctiva, superficial epithelial cells showed a constitutive, weak cytoplasmic expression of eotaxin. Few inflammatory cells in the perivascular areas expressed RANTES, MCP-1, MCP-2, and MCP-3. In VKC specimens, the epithelium showed intense cytoplasmic eotaxin staining in all cells, and cytoplasmic RANTES staining mainly in the superficial layers. Furthermore, RANTES and eotaxin were expressed on the vascular endothelium mainly in the upper substantia propria. Compared with normal controls, VKC specimens showed significantly more inflammatory cells expressing RANTES, eotaxin, MCP-1, and MCP-3 (p<0.001, 0.0028, 0.0092, and <0.001, respectively). In VKC specimens, the numbers of inflammatory cells expressing RANTES were significantly higher than the numbers of inflammatory cells expressing eotaxin, MCP-1, and MCP-2 (all p values <0.001). Colocalisation studies revealed that the majority of inflammatory cells expressing chemokines were CD68 positive monocytes/macrophages. CONCLUSIONS These results demonstrate an increase in the expression of RANTES, eotaxin, MCP-1, and MCP-3 in the conjunctiva of patients with VKC compared with control subjects. These data suggest a potential role for these chemokines in the pathogenesis of VKC. Antagonists of chemokine receptors may provide new therapeutic modalities in VKC.

Patterns of Uveitis in Patients admitted to a University hospital in Riyadh, saudi arabia

Purpose: To analyze clinical patterns, causes, and systemic disease associations among patients with uveitis admitted to King Abdulaziz University Hospital. Methods: The authors retrospectively reviewed the medical records of 351 patients (600 eyes). Results: The study subjects consisted of 183 (52.1%) males and 168 (47.9%) females, with a mean age of 39.9 ± 14.2 years at presentation. The most common anatomic diagnosis was panuveitis (68.6%), followed by posterior uveitis (12.7%), anterior uveitis (12.7%), and intermediate uveitis (6.0%). The most common identifiable specific diagnoses were presumed tuberculous uveitis (PTU) (28.2%), Vogt-Koyanagi-Harada (VKH) disease (19.4%), Behçet disease (BD) (12.5%), and toxoplasmosis (8.2%). After a mean follow-up period of 29.5 ± 22.1 months, 63.5% of the eyes achieved visual acuity of 20/40 or better. Eyes from patients with PTU had the worst final visual outcome. Conclusions: The most common anatomic diagnosis was panuveitis. PTU, VKH disease, BD, and toxoplasmosis were the most frequent specific diagnoses.

Expression of hypoxia-inducible factor-1α and the protein products of its target genes in diabetic fibrovascular epiretinal membranes

Aims: To investigate the expression of the hypoxia-inducible factor-1α (HIF-1α) and the protein products of its target genes vascular endothelial growth factor (VEGF), erythropoietin (Epo) and angiopoietins (Angs), and the antiangiogenic pigment epithelium-derived factor (PEDF) in proliferative diabetic retinopathy (PDR) epiretinal membranes. Methods: Sixteen membranes were studied by immunohistochemical techniques. Results: Vascular endothelial cells expressed HIF-1α, Ang-2 and VEGF in 15 (93.75%), 6 (37.5%) and 9 (56.25%) membranes, respectively. There was no immunoreactivity for Epo, Ang-1 and PEDF. There were significant correlations between the number of blood vessels expressing the panendothelial marker CD34 and the numbers of blood vessels expressing HIF-1α (r = 0.554; p = 0.026), Ang-2 (r = 0.830; p<0.001) and VEGF (r = 0.743; p = 0.001). The numbers of blood vessels expressing Ang-2 and VEGF in active membranes were higher than that in inactive membranes (p = 0.015 and 0.028, respectively). Conclusions: HIF-1α, Ang-2 and VEGF may play an important role in the pathogenesis of PDR. The findings suggest an adverse angiogenic milieu in PDR epiretinal membranes favouring aberrant neovascularisation and endothelial abnormalities.

Adhesion molecules in vernal keratoconjunctivitis

AIMS/BACKGROUND Adhesion molecules play a key role in the selective recruitment of different leucocyte population to inflammatory sites. The purpose of the present study was to investigate the presence and distribution of adhesion molecules in the conjunctiva of patients with vernal keratoconjunctivitis (VKC). METHODS The presence and distribution of adhesion molecules were studied in 14 conjunctival biopsy specimens from seven patients with active VKC and in four normal conjunctival biopsy specimens. We used a panel of specific monoclonal antibodies (mAbs) directed against intercellular adhesion molecule-1 (ICAM-1), intercellular adhesion molecule-3 (ICAM-3), lymphocyte function associated antigen-1 (LFA-1), very late activation antigen-4 (VLA-4), vascular cell adhesion molecule-1 (VCAM-1), and endothelial leucocyte adhesion molecule-1 (ELAM-1). In addition, a panel of mAbs were used to characterise the composition of the inflammatory infiltrate. RESULTS In the normal conjunctiva, ICAM-1 was expressed on the vascular endothelium only, LFA-1 and ICAM-3 on epithelial and stromal mononuclear cells , and VLA-4 on stromal mononuclear cells. The expression of VCAM-1 and ELAM-1 was absent. The number of cells expressing adhesion molecules was found to be markedly increased in all VKC specimens. This was concurrent with a heavy inflammatory infiltrate. Strong ICAM-1 expression was induced on the basal epithelial cells, and vascular endothelial cells. Furthermore, ICAM-1 was expressed on stromal mononuclear cells. LFA-1 and ICAM-3 were expressed on the majority of epithelial and stromal infiltrating mononuclear cells. VLA-4 expression was noted on stromal mononuclear cells. Compared with controls, VKC specimens showed significantly more ICAM-3+, LFA-1+, and VLA-4+ cells. VCAM-1 and ELAM-1 were induced on the vascular endothelial cells. CONCLUSIONS Increased expression of adhesion molecules may play an important role in the pathogenesis of VKC.