NOD-like Receptors in the Eye: Uncovering Its Role in Diabetic Retinopathy

Diabetic retinopathy (DR) is an ocular complication of diabetes mellitus (DM). International Diabetic Federations (IDF) estimates up to 629 million people with DM by the year 2045 worldwide. Nearly 50% of DM patients will show evidence of diabetic-related eye problems. Therapeutic interventions for DR are limited and mostly involve surgical intervention at the late-stages of the disease. The lack of early-stage diagnostic tools and therapies, especially in DR, demands a better understanding of the biological processes involved in the etiology of disease progression. The recent surge in literature associated with NOD-like receptors (NLRs) has gained massive attraction due to their involvement in mediating the innate immune response and perpetuating inflammatory pathways, a central phenomenon found in the pathogenesis of ocular diseases including DR. The NLR family of receptors are expressed in different eye tissues during pathological conditions suggesting their potential roles in dry eye, ocular infection, retinal ischemia, cataract, glaucoma, age-related macular degeneration (AMD), diabetic macular edema (DME) and DR. Our group is interested in studying the critical early components involved in the immune cell infiltration and inflammatory pathways involved in the progression of DR. Recently, we reported that NLRP3 inflammasome might play a pivotal role in the pathogenesis of DR. This comprehensive review summarizes the findings of NLRs expression in the ocular tissues with special emphasis on its presence in the retinal microglia and DR pathogenesis.

Anti-fumarase antibody promotes the dropout of photoreceptor inner and outer segments in diabetic macular oedema

AIMS/HYPOTHESIS

In diabetic macular oedema (DMO), blood components passing through the disrupted blood-retinal barrier cause neuroinflammation, but the mechanism by which autoantibodies induce neuroglial dysfunction is unknown. The aim of this study was to identify a novel autoantibody and to evaluate its pathological effects on clinically relevant photoreceptor injuries.

METHODS

Biochemical purification and subsequent peptide fingerprinting were applied to identify autoantigens. The titres of autoantibodies in DMO sera were quantified and their associations with clinical variables were evaluated. Two animal models (i.e. passive transfer of autoantibodies and active immunisation) were characterised with respect to autoimmune mechanisms underlying photoreceptor injuries.

RESULTS

After screening serum IgG from individuals with DMO, fumarase, a Krebs cycle enzyme expressed in inner segments, was identified as an autoantigen. Serum levels of anti-fumarase IgG in participants with DMO were higher than those in diabetic participants without DMO (p < 0.001) and were related to photoreceptor damage and visual dysfunction. Passively transferred fumarase IgG from DMO sera in concert with complement impaired the function and structure of rodent photoreceptors. This was consistent with complement activation in the damaged photoreceptors of mice immunised with fumarase. Fumarase was recruited to the cell surface by complement and reacted to this autoantibody. Subsequently, combined administration of anti-fumarase antibody and complement elicited mitochondrial disruption and caspase-3 activation.

CONCLUSIONS/INTERPRETATION

This study has identified anti-fumarase antibody as a serum biomarker and demonstrates that the generation of this autoantibody might be a pathological mechanism of autoimmune photoreceptor injuries in DMO.

Aqueous Humor Cytokine Levels in Diabetic Macular Edema Patients with Cotton-Wool Spots

PURPOSE

To determine the characteristics of diabetic macular edema (DME) patients with cotton-wool spots (CWS).

METHODS

We classified 80 treatment-naïve DME patients according to whether or not they had CWS involving macula and then compared the concentrations of interleukin- (IL-) 1β, IL-6, IL-8, IL-10, IL-17, placental growth factor, vascular endothelial growth factor (VEGF), and intercellular adhesion molecule (ICAM)-1 in the aqueous humor between the groups, as well as optical coherence tomography (OCT) findings, baseline characteristics, and intravitreal bevacizumab responsiveness.

RESULTS

Aqueous levels of ICAM-1 and VEGF in the group with CWS were significantly higher than those in the non-CWS (control) group (p < 0.001 and p = 0.006, respectively). In multiple logistic regression analysis to identify factors associated with CWS, the aqueous ICAM-1 (≥0.36 ng/mL) was significantly associated with CWS (odds ratio = 13.26, p < 0.001). Based on OCT, ellipsoid zone (EZ) disruption distribution was significantly different between the two groups (p = 0.038). Regarding responsiveness to treatment, although there was no significant difference in central subfield thickness between the two groups after treatments, the best-corrected visual acuity was worse in the group with CWS.

CONCLUSIONS

The presence of CWS was accompanied by higher levels of aqueous ICAM-1. Based on OCT, EZ disruption was greater in DME patients with CWS, and their short-term visual prognosis was poorer.

[A Case of Diabetic Macular Edema with Improvement in Severity of Diabetic Retinopathy following Frequent Anti-Vascular Endothelial Growth Factor Treatment]

Background: Intravitreal anti-vascular endothelial growth factor (VEGF) drug injections are the gold standard for the treatment of diabetic macular edema (DME). We report a case of DME in which frequent anti-VEGF treatment resulted in improvement of diabetic retinopathy. Case: A 73-year old woman with DME who had previously undergone bilateral posterior subtenon injections of triamcinolone acetonide and vitrectomy OD presented at Kyushu University Hospital. Best corrected visual acuity was 0.1 OD and 0.15 OS. The central macular thickness was 1570 μm OD and 578 μm OS. We performed focal macular laser photocoagulation OU but the DME was not resolved. Subsequent intravitreal anti-VEGF drug injections(approximately 20 times/2 years)resulted in an improvement of the best corrected visual acuity (0.3 OD, 0.6 OS) and CMT (1570 μm OD, 578 μm OS). There was an improvement of 2 steps in the Diabetic Retinopathy Severity Scale (DRSS) score OU. Conclusion: Frequent anti-VEGF treatment can improve the severity of diabetic retinopathy.

Aqueous cytokine levels are associated with reduced macular thickness after intravitreal ranibizumab for diabetic macular edema

Purpose

It is controversial whether the administration of anti-vascular endothelial growth factor drugs for diabetic macular edema (DME) affects intraocular inflammatory cytokines. In this study, we measured cytokine concentration in aqueous humor before and after intravitreal injection of ranibizumab (IVR). The aim was to determine changes in cytokine concentration and their effects on DME reduction.

Methods

Twelve patients (13 eyes) with DME received two IVR (0.5 mg) with a 1 month interval, and a total of 26 aqueous humor samples were obtained. Macular thickness was measured with an optical coherence tomography (OCT) using thickness-map mode with an Early Treatment Diabetic Retinopathy Study (ETDRS) 9-zone grid that was divided into two zones: a central circle with a diameter of 1 mm (zone1); and an outer circle with a diameter of 6 mm (zone2).

Results

The concentration of eotaxin-1 in aqueous humor samples decreased significantly after IVR. Baseline cytokine concentration was associated with IVR-induced DME reduction. In zone1, higher baseline concentration of interferon-induced protein (IP)-10, and in zone 2, higher baseline concentration of granulocyte-macrophage colony-stimulating factor, IP-10, and tumor necrosis factor (TNF) α; and lower baseline concentration of eotaxin-1, interleukin (IL)-5, and IL-8 were associated with improved DME. Cytokine changes were associated with IVR-induced DME reduction. In zone1, lower concentration of IP-10 compared to baseline or higher concentration of macrophage inflammatory protein (MIP) -α, and in zone 2, lower concentration of IL-5 compared to baseline, IL-8, and IP-10 or higher concentration of eotaxin-1 and MIP-1β were associated with improved DME.

Conclusions

These findings suggest that ranibizumab affects the concentration of cytokines in aqueous humor. Various cytokines contribute to a decrease in retinal thickness, both in the center of the macula and in a larger area of the retina.

Diabetic Macular Edema Pathophysiology: Vasogenic versus Inflammatory

Diabetic macular edema (DME) can cause blindness in diabetic patients suffering from diabetic retinopathy (DR). DM parameters controls (glycemia, arterial tension, and lipids) are the gold standard for preventing DR and DME. Although the vascular endothelial growth factor (VEGF) is known to play a role in the development of DME, the pathological processes leading to the onset of this disease are highly complex and the exact sequence in which they occur is still not completely understood. Angiogenesis and inflammation have been shown to be involved in the pathogenesis of this disease. However, it still remains to be clarified whether angiogenesis following VEGF overexpression is a cause or a consequence of inflammation. This paper provides a review of the data currently available, focusing on VEGF, angiogenesis, and inflammation. Our analysis suggests that angiogenesis and inflammation act interdependently during the development of DME. Knowledge of DME etiology seems to be important in treatments with anti-VEGF or anti-inflammatory drugs. Current diagnostic techniques do not permit us to differentiate between both etiologies. In the future, diagnosing the physiopathology of each patient with DME will help us to select the most effective drug.

Comparison of intravitreal injection of bevacizumab and triamcinolone acetonide in the treatment of uveitic macular edema

BACKGROUND

Cystoid Macular Edema (CME) is one of the most common and sight threatening complications of uveitis. Intravitreal injection of corticosteroids and Anti-VEGF are two routine options for treatment.

OBJECTIVE

To compare the effects of intravitreal injections of Bevacizumab and Triamcinolone Acetonide for the treatment of persistent macular edema in non-infectious uveitis.

METHODS

In a randomized clinical trial, sixty eyes of 55 patients were enrolled in the study. Patients were divided into two groups with randomized digits table. 29 eyes received 4 mg of intravitreal triamcinolone acetonide, and 31 eyes received 1.25 mg of intravitreal bevacizumab. Two main outcome measures were changes in visual acuity, measured with logarithm of minimal angle of resolution, and central macular thickness, measured with optical coherence tomography.

RESULTS

The mean follow-up was 25.3 weeks. The best visual acuities were achieved 6 months after injection in both groups. Improvement in visual acuity at 6 months was achieved in 28/29 (96%) of eyes in Triamcinolone group and in 26/31 (83%) eyes in Bevacizumab group (p=0.196). None of the eyes showed worsening of visual acuity after 6 months. Mean of central macular thickness in the pre-injection time for intravitreal triamcinolone acetonide (IVTA) group was 295.62 μ, and 309.87 μ in intravitreal bevacizumab (IVB) group, which were decreased after six months to 199.27 μ and 221.06 μ, respectively (p<0.001).

CONCLUSION

This study shows that IVT and IVB are both effective in improving vision in uveitic CME. Although effects of triamcinolone on Central Macular Thickness (CMT) are more apparent, this superiority is not seen on Best Corrected Visual Acuity (BCVA).

[Behcet disease -- case report]

Behçet's Disease is a chronic, systemic, relapsing disease, an occlusive vasculitis which is immune complex mediated. Ocular involvement is usually bilateral, often asymmetric, associated with the loss of visual functions. This case presentation is a way to reveal an uncommon debut and evolution of the pathology using diagnostic criteria for Behçet's Disease.

Visual prognosis and vitreous cytokine levels after arteriovenous sheathotomy in branch retinal vein occlusion associated with macular oedema

PURPOSE

To investigate the relationship between vitreous levels of cytokines, including interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF), and visual prognosis after pars plana vitrectomy (PPV) with arteriovenous sheathotomy in patients with branch retinal vein occlusion (BRVO) associated with macular oedema.

METHODS

We studied 60 patients with logMAR visual acuity (VA) scores of < 0.3 and visual impairment secondary to BRVO-associated macular oedema. All patients underwent PPV with arteriovenous sheathotomy. At the time of PPV, vitreous samples were collected from the operated eye and vitreous levels of VEGF and IL-6 were measured. Best corrected VA (BCVA) (using a logMAR chart) and foveal thickness (FT) (using optical coherence tomography) were monitored for up to 6 months after PPV.

RESULTS

Both BCVA and FT significantly improved after PPV. According to multiple regression analysis, both the improvement in BCVA and decrease in FT were closely related to the vitreous level of IL-6 but not to that of VEGF. The vitreous level of VEGF was strongly correlated with duration of BRVO.

CONCLUSIONS

Both improvement in BCVA and decrease in FT were observed after PPV in BRVO patients with macular oedema. Interestingly, these visual prognoses strongly correlate with the vitreous level of IL-6, whereas the duration of BRVO strongly correlates with the vitreous level of VEGF.

Intravitreal triamcinolone acetonide for the treatment of immune recovery uveitis macular edema

PURPOSE

To evaluate the use of intravitreal triamcinolone (IVTA) for the treatment of macular edema secondary to immune recovery uveitis (IRU) in patients with AIDS.

DESIGN

Prospective, consecutive, interventional case series.

PARTICIPANTS

Eight eyes of 7 patients receiving 13 injections.

METHODS

Prospective, consecutive, interventional case series of 13 injections involving 8 eyes in 7 patients who underwent an intravitreal injection of 20 mg decanted triamcinolone acetate for fluorescein angiographically proven IRU-related macular edema.

MAIN OUTCOME MEASURES

The primary outcome measure was vision (using the Early Treatment Diabetic Retinopathy Study chart). Other outcome measures included fluorescein angiography and optical coherence tomography.

RESULTS

Visual acuity improved at all time points and was statistically significant at the 1-month and 3-month follow-up examinations. The average visual improvement was 3 lines at 3 months. Retinal volume and thickness improvement were statistically significant at all time points. All patients had a minimum follow-up of 9 months, and there were no cases of cytomegalovirus reactivation.

CONCLUSIONS

Previous studies showed that treatment with sub-Tenon repository steroids for the treatment of macular edema of IRU was only marginally effective. However, the current study shows that IVTA can be an effective short-term treatment for macular edema secondary to IRU in patients with AIDS. Longer follow-up is needed to assess the durability of the effect and to monitor for longer-term complications and outcomes.

Cytomegalovirus retinitis after intravitreous triamcinolone in an immunocompetent patient

PURPOSE

To report the case of a 75-year-old man with diabetes who developed cytomegalovirus (CMV) retinitis after intravitreous injection of triamcinolone acetonide (IVTA).

DESIGN

Observational case report.

METHODS

Review of medical records.

RESULTS

A 75-year-old man with diabetic macular edema developed arcuate retinal whitening after IVTA. A presumptive diagnosis of viral retinitis was made, and a vitrectomy was performed. Polymerase chain reaction of the vitreous was positive for CMV DNA. An infectious disease consultant found no signs of systemic CMV infection, and laboratory examination revealed that the patient was HIV negative. The patient responded well to intravitreal ganciclovir and oral valganciclovir, but when therapy was discontinued, the retinitis recurred and CMV DNA was again detected in the vitreous. The retinitis once again responded to antiviral therapy.

CONCLUSIONS

CMV retinitis can occur after local immunosuppression with IVTA. Clinicians should be aware of this rare complication of IVTA.

[Non-steroidal anti-inflammatory drugs and ocular inflammation]

BACKGROUND

Ocular inflammation is regulated by complicated mechanism that are responsible for the rupture of the blood-ocular barrier and the attraction of leukocytes towards the eye. This cellular trafficking is regulated by the liberation of inflammatory mediators and cytokines.

MATERIALS AND METHODS

The main effects of prostaglandins that are described in the literature were reviewed.

RESULTS

Despite the fact that the inhibitory action of aspirin and NSAIDs on prostaglandins secretion is known since 1971, it is quite recently that two isoenzymes of cyclooxygenase were discovered. The Cyclooxygenase-1 (COX-1) is constitutive and is responsible for the production of PGE2. This prostaglandin is related to the housekeeping functions such as gastric protection, platelet aggregation and maintenance of renal function. The expression of the cyclooxygenase 2 (COX-2) is induced by inflammation. The presence of COX-2 could be demonstrated in many ocular tissues (corneal epithelium and endothelium, pigmentary epithelium etc. ...). The use of NSAIDs in clinical practice allows a good control of ocular inflammation, of pain, of the maintenance of a good mydriasis during surgery and are impending the onset of postoperative cystoid macular edema.

CONCLUSION

Prostaglandins are potent anti-inflammatory agents but their use is limited in the presence of severe dry eye syndrome or allergy towards NSAIDs.

Immune-recovery uveitis in patients with cytomegalovirus retinitis taking highly active antiretroviral therapy

PURPOSE

To investigate the clinical features associated with immune recovery in human immunodeficiency virus (HIV)-infected patients with cytomegalovirus retinitis who are taking highly active antiretroviral therapy.

METHODS

Sixteen patients were evaluated prospectively at the National Eye Institute, Bethesda, Maryland. Evaluation included a medical history and a complete ophthalmologic examination. The examination included best-corrected visual acuity score measured by means of logarithmic charts, slit-lamp biomicroscopy, dilated retinal examination, retinal photography, and fluorescein angiography. Immune-recovery uveitis was defined as the ocular inflammation associated with clinical immune recovery in patients taking potent antiretroviral regimens. The ophthalmic characteristics of immune-recovery uveitis were identified, and their effect on visual acuity was statistically analyzed.

RESULTS

The mean CD4+ T-lymphocyte count for the 16 patients taking highly active antiretroviral therapy at the time of evaluation was 393 cells/microl (range, 97-1,338 cells/microl). Immune-recovery uveitis was characterized by vitreitis and optic disk and macular edema. Clinically important complications of immune-recovery uveitis included cataract and epiretinal membrane formation. The visual acuity scores were significantly worse in the 23 eyes with cytomegalovirus retinitis (mean, 67.2 letters, 20/50) than in the nine eyes without cytomegalovirus retinitis (mean, 89.8 letters, 20/16) (P <.001). Regression analysis showed that a lower visual acuity score was associated with the presence of moderate to severe macular edema on fluorescein angiography and vitreous haze (P < or =. 001).

CONCLUSIONS

Immune-recovery uveitis is an important cause of visual morbidity in HIV-infected patients with cytomegalovirus retinitis in the era of highly active antiretroviral therapy. Although immune recovery associated with highly active antiretroviral therapy has allowed some patients to discontinue specific anticytomegalovirus therapy, the rejuvenated immune response can be associated with sight-threatening inflammation.

[Antiretinal antibodies associated with cystoid macular edema]

AIM

Recently, anti-Enolase and anti-carbonic anhydrase antibodies have been observed in over 60% of patients with retinitis pigmentosa (RP) and cystoid macular oedema (CME). We investigated the presence of these antibodies in a series of patients with CME due to different pathologies.

METHODS

In 10 patients with CME serum antibodies against Carbonic anhydrase (CA) II (30 kD) and Enolase (46 kD) were sought using Western Blots, Dot Blots as well as ELISA.

RESULTS

Western and dot blotting showed anti-CA II antibodies in all and anti-Enolase antibodies in six of the 10 patients. The average titer measured with ELISA was 0.9 +/- 0.08 OD Units (0.35-1.4) with a dilution of 1:400.

CONCLUSION

The presence of anti-retinal antibodies in the serum of all patients confirms the high prevalence of these antibodies in patients with CME. This may suggest that a dysfunction of CA and enolase activity in the retinal pigment epithelium may lie at the root of oedema formation, whereas other mechanisms may be responsible in the absence of these antibodies.

Association of antiretinal antibodies and cystoid macular edema in patients with retinitis pigmentosa

PURPOSE

To report the association of antiretinal antibodies in patients with bilateral cystoid macular edema and retinitis pigmentosa.

METHODS

In a prospective study, 30 consecutive patients with bilateral cystoid macular edema and retinitis pigmentosa were tested for antiretinal antibodies. As control subjects, 30 consecutive patients with retinitis pigmentosa who did not have cystoid macular edema and 50 normal subjects without retinitis pigmentosa or cystoid macular edema were tested for antiretinal antibodies. Laboratory personnel performing the antiretinal antibody testing were masked regarding the diagnosis of each patient.

RESULTS

Twenty-seven (90%) of 30 patients with retinitis pigmentosa with cystoid macular edema had antiretinal protein antibody activity, compared with three (6%) of 50 normal controls (P < .001) and only four (13%) of 30 control patients with retinitis pigmentosa (P < .001).

CONCLUSIONS

We found a significant association between cystoid macular edema and the presence of circulating antiretinal antibodies in patients who presented with retinitis pigmentosa and cystoid macular edema. This study suggests that patients with retinitis pigmentosa with cystoid macular edema may have an autoimmune process that is contributing to the formation of cystoid macular edema in retinitis pigmentosa, but to date, there is no direct evidence that the cystoid macular edema is caused by the antiretinal antibodies.

[Bilateral cystoid macular edema after successful treatment of AIDS-associated cytomegalovirus retinitis]

BACKGROUND

Cystoid macular edema (CME) in AIDS patients with inactive cytomegalovirus (CMV) retinitis is an uncommon but potentially sight-threatening complication. The pathogenesis of CME in these patients is unclear. This study tries to identify possible risk factors by analyzing the charts of five patients.

METHODS

Ten eyes of 5 patients that finally developed CME were followed for an average of 18 months. The initial retinal lesions, their response to antiviral treatment, the development of CME, and the patients' immune status were prospectively monitored.

RESULTS

CMV retinitis was diagnosed at a median CD4+ count of 3 cells/mm3 (range 0-11). All eyes responded to the initial systemic anti-viral treatment. At the onset of CME, CMV retinitis was controlled by antiviral maintenance therapy in all patients [ganciclovir (n = 2), cidofovir (n = 2), foscarnet (n = 1)]. The median time between diagnosis of CMV retinitis and onset of CME was 11.5 months (range 5-24). Development of CME was associated with significant visual loss: acuity ranged from 0.05 to 0.7 when CME was first noticed, compared to 0.8-1.25 at diagnosis of CMV retinitis. Duration of inflammation, size or zone of retinal necrosis did not favor the development of CME, neither did the antiviral therapy. A weak correlation of CME development and immune status (expressed as increase of CD4+ cells) was found. Due to systemic corticosteroids CME resolved.

CONCLUSIONS

CME is a new visual threat to AIDS-patients with CMV retinitis whose immune status improved under the latest combined antiretroviral therapy. Therapy with oral corticosteroids may positively influence this condition.

Investigations of antiretinal antibodies in pigmentary retinopathy and other retinal degenerations

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