Biochemical Changes in Anterior Chamber of the Eye in Diabetic Patients-A Review

This article aims to provide a comprehensive review of the biochemical changes observed in the anterior chamber of the eye in diabetic patients. The increased levels of inflammatory markers, alterations in antioxidant defense mechanisms, and elevated levels of advanced glycation end products (AGEs) in the aqueous humor (AH) are explored. Additionally, the impact of these biochemical changes on diabetic retinopathy progression, increased intraocular pressure, and cataract formation is discussed. Furthermore, the diagnostic and therapeutic implications of these findings are presented. This study explores potential biomarkers for detecting diabetic eye disease at an early stage and monitoring its progression. An investigation of the targeting of inflammatory and angiogenic pathways as a potential treatment approach and the role of antioxidant agents in managing these biochemical changes is performed.

EVALUATION OF THE EFFECT OF TOPICAL INTERFERON α2b AS A COMPLEMENTARY TREATMENT OF MACULAR EDEMA OF PATIENTS WITH DIABETIC RETINOPATHY: A Double-Blind Placebo-Controlled Randomized Clinical Trial Study

PURPOSE

The objective of this study is to evaluate the effect of the topical interferon α2b (IFNα2b) as an adjunctive therapy in the treatment of diabetic macular edema.

METHOD

This was a randomized controlled clinical trial performed on patients with diabetic macular edema. Fifty eyes of 50 patients (one eye/patient) who were receiving treatment for diabetic macular edema were randomly assigned to get topical IFNα2b 1 MU/mL or artificial tear eye drop as an adjunctive therapy. The primary measure outcomes were best-corrected visual acuity and central macular thickness; the secondary goals were to assess the effect of topical IFNα2b on the intraocular pressure and its potential side effects.

RESULTS

Baseline demographic data of the two groups were similar. The improvement in visual acuity of patients on IFN was more than the patients on artificial tear by the end of the fourth week (6.85 and 1.45 Early Treatment Diabetic Retinopathy Study letters, respectively, P = 0.001) and the eighth week (6.75 and 1.05 Early Treatment Diabetic Retinopathy Study letters, respectively, P = 0.005). The central macular thickness was also decreased correspondingly by the end of fourth week (53.1 ± 153 µm for patients on IFN and 26.6 ± 119.1 µm for patients on artificial tear, P = 0.497) and eighth week (27.9 ± 67.7 for patients on IFN and 29.2 ± 98 µm for patients on artificial tear, P = 0.957), but it was not statistically significant. Intraocular pressure was decreased on the fourth week in IFN group for 1.7 mmHg ±3 and increased for 0.1 mmHg ±2.3 in the artificial tear group (P = 0.018). No significant side effect was detected with topical IFN drop.

CONCLUSION

This study evaluated the short-term effects of topical IFNα2b 1 MU/mL. The drug was well tolerated and may have an effect on improvement of best-corrected visual acuity in patients with diabetic macular edema. It also had an intraocular pressure lowering effect on the studied eyes. However, further studies are needed to confirm this finding.

Interferon Alpha 2a and 2b in Ophthalmology: A Review

Interferon alpha (IFN-α) is a glycoprotein with antitumor, antiviral, and immunomodulatory activity, used widely in the treatment of viral infections (hepatitis B and C, condylomata acuminata, herpes zoster, etc.), hematological disorders (leukemia, multiple myeloma, T cell lymphoma, and essential thrombocythemia), and solid tumors (clear cell carcinoma in the metastatic stage, melanoma, hepatocellular carcinoma, and cervical neoplasia). Studies have proven the effectiveness of IFN-α in the treatment of ophthalmic disorders involving the anterior segment of the eye (conjunctival papilloma, squamous neoplasia, conjunctival mucosa-associated lymphoid tissue, Mooren's ulcer, and vernal keratoconjunctivitis) and the posterior segment of the eye (serpiginous choroidopathy, posterior uveitis, pseudophakic and diabetic cystoid macular edema, and proliferative diabetic retinopathy). The therapy with IFN-α remains a promising alternative in cases of a failing response to conventional therapy, helping to maintain or improve visual acuity, prevent vision loss, and ameliorate the prognosis of the patient. However, clinicians who decide to use IFN-α in their patients must be aware of general and ophthalmological side effects and inform their patients to undergo a systemic evaluation such as a physical examination, blood and serological tests, and a chest X-ray before the beginning of treatment. This review presents the current knowledge of the use of IFN-α, its efficacy, and properties in ophthalmological diseases, and thus may encourage clinicians to administer this drug as a treatment modality in ophthalmological diseases in the future.

Assessment of biomarkers using multiplex assays in aqueous humor of patients with diabetic retinopathy

Background

With the high prevalence of type 2 diabetes, diabetic retinopathy (DR) has become a leading health problem worldwide. The pathogenesis of DR is complex and several vascular, inflammatory, and neuronal mechanisms are involved. The purpose of this study was to assess the levels of immune and inflammatory biomarkers in the aqueous humor of patients with different severities of DR and to analyze the correlations between Interleukin-6 (IL-6) and these biomarkers, and between IL-6 and the severity of the disease.

Methods

Aqueous humor samples were obtained from 51 non-diabetic patients and 151 diabetic patients. Levels of 45 different cytokines, chemokines, and growth factors were measured using a multiplex bead immunoassay.

Results

IL-6, IL-8, Inducible Protein-10 (IP-10), leukemia inhibitory factor (LIF), hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF)-A were significantly higher (p < 0.05) in the aqueous humor of the DR patients compared to the non-diabetic patients, while the concentrations of IL-1α, IL-4, IL-9, IL-21, IL-23, IL-27, IL-31, RANTES, interferon-α, growth regulated oncogene (GRO), and tumor necrosis factor (TNF)-α were significantly lower (p < 0.05) in the DR patients. The IL-6 levels increased as the severity of DR increased. In addition, the IL-6 level positively correlated with the IL-8, HGF and LIF levels, while negatively with the IL-31and GRO levels.

Conclusions

These findings suggest that inflammation and immune response may contribute to the pathogenesis of DR, and these biomarkers may potentially be new therapeutic targets for DR.

Subtenon injection of natural leukocyte interferon α-2a in diabetic macular edema: a case report

BACKGROUND

To report the effect of subtenon injections of natural leukocyte interferon α-2a (IFNα) on best corrected visual acuity (BCVA) and central macular thickness (CMT) in a patient with diabetic macular edema (DME).

CASE PRESENTATION

A 66-year-old man affected by DME, with glycated hemoglobin (HbA1c) at 6.9%, refractory to laser grid treatment and intravitreal injections of triamcinolone, was selected to receive a cycle of three subtenon injections/week of IFNα (1×106 IU/ml). BCVA and CMT, using spectral domain ocular coherence tomography (SD-OCT), were evaluated preoperatively and at 1 week, 1 month, 4 months, and 1 year postoperatively. BCVA and CMT were significantly improved at 1 week after the three injections (20/200 vs. 20/40 and 498 μm vs. 237 μm, respectively). BCVA remained stable during the 1-year follow-up. CMT was slightly increased, but was still lower than the baseline value (215 μm, 255 μm, and 299 μm during the follow-up visits). No adverse events were recorded, with the exception of mild subconjunctival hemorrhage at the injection site.

CONCLUSIONS

IFNα, with its immunomodulatory, anti-proliferative and anti-angiogenic actions, was effective in improving BCVA and reducing CMT in refractory DME. Further randomized controlled studies are required to assess the effect of IFNα alone or in combination with other therapies for DME treatment.

The immunological basis of degenerative diseases of the eye

It has become clear that disorders that were once considered "degenerative" have complex mechanisms, with many having been shown to have immune mediation as part of the disease process. These include arteriosclerotic heart disease and Alzheimer's disease. Indeed, several ocular disorders that once fell into the "degenerative" category meet this criterion as well. Immune mediation has been shown to be a part of many of the most common ocular disorders, and not just that of uveitis, or ocular inflammatory disease.

Premature vascular damage in systemic lupus erythematosus: an imbalance of damage and repair?

Systemic lupus erythematosus (SLE) is associated with an increase in the risk of premature cardiovascular complications caused by accelerated atherosclerosis, which significantly contributes to morbidity and mortality. Standard Framingham risk factors seem to be less important predictors of cardiovascular events than the presence of active SLE, and the immune dysregulation characteristic of lupus seems to play a dominant role in atherogenesis. Although both SLE-specific and nonspecific mechanisms have been proposed to play a prominent role in the induction of premature vascular damage in this disease, the exact etiology remains unclear. This review summarizes some of the proposed mechanisms that may promote accelerated vascular damage in lupus and explores potential targets for cardiovascular risk prevention in this patient population.

Interferon-alpha promotes abnormal vasculogenesis in lupus: a potential pathway for premature atherosclerosis

Individuals with systemic lupus erythematosus (SLE) have a striking increase in premature atherosclerosis of unclear etiology. Accelerated endothelial cell apoptosis occurs in SLE and correlates with endothelial dysfunction. Endothelial progenitor cells (EPCs) and myelomonocytic circulating angiogenic cells (CACs) are crucial in blood vessel repair after vascular damage, and decreased levels or abnormal function of EPCs/CACs are established atherosclerosis risk factors. We investigated if vascular repair is impaired in SLE. We report that SLE patients display abnormal phenotype and function of EPCs/CACs. These abnormalities are characterized by significant decreases in the number of circulating EPCs (310 +/- 50 EPCs/mL of blood in SLE versus 639 +/- 102 in controls) and significant impairments in the capacity of EPCs/CACs to differentiate into mature ECs and synthesize adequate levels of the proangiogenic molecules vascular endothelial growth factor (VEGF) and hepatic growth factor (HGF). These abnormalities are triggered by interferon-alpha (IFN-alpha), which induces EPC and CAC apoptosis and skews myeloid cells toward nonangiogenic phenotypes. Lupus EPCs/CACs have increased IFN-alpha expression and their supernatants promote higher induction of IFN-inducible genes. Importantly, neutralization of IFN pathways restores a normal EPC/CAC phenotype in lupus. SLE is characterized by an imbalance between endothelial cell damage and repair triggered by type I IFNs, which might promote accelerated atherosclerosis.

Current and future pharmacological intervention for diabetic retinopathy

Diabetic retinopathy (DR) is a potentially visually devastating complication of chronic hyperglycaemia. Prospective, randomised clinical trials have delineated the standard prevention protocols, including intensive glycaemic, blood pressure, and lipid control, and laser photocoagulation treatment for neovascularisation and clinically significant macular oedema. However, despite these interventions, vision loss from DR still occurs at an alarming rate. Researchers have directed their efforts towards better understanding the specific biological and chemical changes occurring in DR to develop more targeted pharmacological prevention and treatment strategies. This review of diabetic retinopathy will primarily detail the therapies in development at present, including aldose reductase inhibitors, advanced glycosylation end product inhibitors, antioxidants, supplemental oxygen, growth factor modulators including vascular endothelial growth factor inhibitors and protein kinase C inhibitors, extracellular matrix modifiers including corticosteroids, and vitreous modulators. The experimental therapies alter several different pathways that lead to DR. Future research will further delineate these pathways, and therapy is likely to involve arresting several different promoters of DR.

Pharmacotherapy for diabetic retinopathy

PURPOSE OF REVIEW

Diabetic retinopathy (DR) is a potentially visually devastating complication of chronic hyperglycemia and other associated systemic abnormalities. Numerous large, prospective, randomized clinical trials have delineated the current standard prevention and treatment protocols including intensive glycemic and blood pressure control and laser photocoagulation for neovascularization and clinically significant macular edema. However, despite standard intervention, vision loss from DR still occurs at an alarming rate. Thus, more recently, researchers have directed their efforts towards better understanding the microscopic changes occurring in DR to develop more effective pharmacologic prevention and treatment strategies.

RECENT FINDINGS

Phase II and III clinical studies involving antivascular endothelial growth factor (VEGF) and protein kinase C (PKC) inhibitors for the management of diabetic macular edema are underway. Researchers recently found elevated pigment endothelium-derived factor (PEDF) associated with active neovascularization, a finding that counteracts prior claims of endogenous anti-angiogenic properties. Other clinical trials are underway to evaluate the efficacy of octreotide, celecoxib, and candesartan on DR. Small clinical studies have suggested beneficial treatment effects for triamcinolone acetonide, interferon alpha-2a, and supplemental oxygen; however, other studies involving losartan, vitamins C and E, and atorvastatin failed to show any benefit.

SUMMARY

Over the past decade, numerous animal models have led to a more thorough understanding of the early microvascular alterations and later neovascularization and edema observed in DR. These discoveries and subsequent human clinical studies involving direct and indirect growth factor modulation, extracellular matrix alteration, vitreolysis, and alternative DR pathways including dyslipidemia, hypoxia, and sorbitol are reviewed in this manuscript.