Changes in aqueous and vitreous inflammatory cytokine levels in diabetic macular oedema: a systematic review and meta-analysis

Rationale of Basic and Cellular Mechanisms Considered in Updating the Staging System for Diabetic Retinal Disease

Purpose

Hyperglycemia is a major risk factor for early lesions of diabetic retinal disease (DRD). Updating the DRD staging system to incorporate relevant basic and cellular mechanisms pertinent to DRD is necessary to better address early disease, disease progression, the use of therapeutic interventions, and treatment effectiveness.

Design

We sought to review preclinical and clinical evidence on basic and cellular mechanisms potentially pertinent to DRD that might eventually be relevant to update the DRD staging system.

Participants

Not applicable.

Methods

The Basic and Cellular Mechanisms Working Group (BCM-WG) of the Mary Tyler Moore Vision Initiative carefully and extensively reviewed available preclinical and clinical evidence through multiple iterations and classified these.

Main Outcome Measures

Classification was made into evidence grids, level of supporting evidence, and anticipated future relevance to DRD.

Results

A total of 40 identified targets based on pathophysiology and other parameters for DRD were grouped into concepts or evaluated as specific candidates. VEGFA, peroxisome proliferator-activated receptor-alpha related pathways, plasma kallikrein, and angiopoietin 2 had strong agreement as promising for use as biomarkers in diagnostic, monitoring, predictive, prognostic, and pharmacodynamic responses as well as for susceptibility/risk biomarkers that could underlie new assessments and eventually be considered within an updated DRD staging system or treatment, based on the evidence and need for research that would fit within a 2-year timeline. The BCM-WG found there was strong reason also to pursue the following important concepts regarding scientific research of DRD acknowledging their regulation by hyperglycemia: inflammatory/cytokines, oxidative signaling, vasoprotection, neuroprotection, mitophagy, and nutrients/microbiome.

Conclusion

Promising targets that might eventually be considered within an updated DRD staging system or treatment were identified. Although the BCM-WG recognizes that at this stage little can be incorporated into a new DRD staging system, numerous potential targets and important concepts deserve continued support and research, as they may eventually serve as biomarkers and/or therapeutic targets with measurable benefits to patients with diabetes.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Aqueous humour interleukin-6 and vision outcomes with anti-vascular endothelial growth factor therapy

BACKGROUND

This analysis evaluated aqueous humour (AH) interleukin (IL)-6 concentrations and the association between AH IL-6 and visual outcomes in patients with neovascular age-related macular degeneration (nAMD) or diabetic macular oedema (DMO) receiving anti-vascular endothelial growth factor (VEGF) monotherapy.

METHODS

Post hoc analysis of the multicentre, double-masked, randomised HARBOR (NCT00891735) and READ-3 (NCT01077401) trials. HARBOR enrolled treatment-naïve nAMD patients. READ-3 enrolled treatment-naïve/previously treated DMO patients. HARBOR patients received ranibizumab 0.5 or 2.0 mg monthly or as needed; AH samples were collected at month 2, after two previous intravitreal injections. READ-3 patients received ranibizumab 0.5 or 2.0 mg as needed; AH samples were collected at baseline and months 3, 6, 9, and 12.

MAIN OUTCOME MEASURE

association between AH IL-6 concentrations and month 24 best-corrected visual acuity (BCVA).

RESULTS

In both trials (HARBOR, N = 36; READ-3, N = 137), patients with higher AH IL-6 concentrations had worse visual outcomes. HARBOR patients with low AH IL-6 concentrations at month 2 had a mean (95% CI) BCVA change at month 24 of +2.9 (-2.6, 8.3) letters, whereas patients with high AH concentrations had a mean (95% CI) BCVA change of -9.0 (-22.7, 4.7) letters. READ-3 patients with low AH concentrations at baseline had a mean (95% CI) BCVA change at month 12 of +9.3 (7.4, 11.3) letters, whereas patients with high AH concentrations had a mean (95% CI) BCVA change of +5.6 (2.2, 9.1) letters.

CONCLUSIONS

Higher IL-6 AH concentrations may predict suboptimal visual responses to anti-VEGF monotherapy in patients with nAMD/DMO.

Interferons in vitreoretinal diseases; a review on their clinical application, and mechanism of action

PURPOSE

This review investigates the therapeutic benefits of interferons (IFNs) in vitreoretinal diseases, focusing on their regulatory roles in innate immunological reactions and angiogenesis. The study aims to categorize the clinical outcomes of IFN applications and proposes a molecular mechanism underlying their action.

METHODS

A systematic review was conducted using MEDLINE/PubMed, Web of Science, EMBASE, and Google Scholar databases to identify randomized clinical trials, case series, and case-control studies related to IFNs' impact on vitreoretinal diseases (1990-2022). The data synthesis involved an in-depth analysis of the anti-inflammatory and anti-angiogenesis effects of IFNs across various studies.

RESULTS

Our findings indicate that IFNs exhibit efficacy in treating inflammation-associated vitreoretinal disorders. However, a lack of sufficient evidence exists regarding the suitability of IFNs in angiogenesis-associated vitreoretinal diseases like choroidal neovascularization and diabetic retinopathies. The synthesis of data suggests that IFNs may not be optimal for managing advanced stages of angiogenesis-associated disorders.

CONCLUSION

While IFNs emerge as promising therapeutic candidates for inflammation-related vitreoretinal diseases, caution is warranted in their application for angiogenesis-associated disorders, especially in advanced stages. Further research is needed to elucidate the nuanced molecular pathways of IFN action, guiding their targeted use in specific vitreoretinal conditions.

Aflibercept Off-Target Effects in Diabetic Macular Edema: An In Silico Modeling Approach

Intravitreal aflibercept injection (IAI) is a treatment for diabetic macular edema (DME), but its mechanism of action (MoA) has not been completely elucidated. Here, we aimed to explore IAI's MoA and its multi-target nature in DME pathophysiology with an in silico (computer simulation) disease model. We used the Therapeutic Performance Mapping System (Anaxomics Biotech property) to generate mathematical models based on the available scientific knowledge at the time of the study, describing the relationship between the modulation of vascular endothelial growth factor receptors (VEGFRs) by IAI and DME pathophysiological processes. We also undertook an enrichment analysis to explore the processes modulated by IAI, visualized the effectors' predicted protein activity, and specifically evaluated the role of VEGFR1 pathway inhibition on DME treatment. The models simulated the potential pathophysiology of DME and the likely IAI's MoA by inhibiting VEGFR1 and VEGFR2 signaling. The action of IAI through both signaling pathways modulated the identified pathophysiological processes associated with DME, with the strongest effects in angiogenesis, blood-retinal barrier alteration and permeability, and inflammation. VEGFR1 inhibition was essential to modulate inflammatory protein effectors. Given the role of VEGFR1 signaling on the modulation of inflammatory-related pathways, IAI may offer therapeutic advantages for DME through sustained VEGFR1 pathway inhibition.

Study of aqueous humour inflammatory mediators' levels in a cohort of Egyptian patients with diabetic macular oedema

BACKGROUND

The aim was to study aqueous humour inflammatory mediators' levels in a cohort of Egyptian patients with diabetic macular oedema (DMO).

METHODS

This was a case-control prospective study conducted on 2 groups: 25 eyes of 22 (11 females) patients seeking treatment for DMO as patients group, and 10 eyes of 10 (4 females) cataract patients as a control group. Aqueous humour was aspirated before intravitreal injection (patients' group) or cataract surgery (control group). Inflammatory mediators in aqueous humour were measured using a multiplex bead immunoassay kit of 27 pre-mixed cytokines.

RESULTS

Eotaxin, interferon gamma-induced protein 10 (IP-10), monocyte chemoattractant protein-1 (MCP-1/CCL2) and interleukin-8 (IL-8/CXCL8) were found significantly higher in patients' group compared to control group (p = 0.043, 0.037, 0.001, 0.015 respectively). On the contrary, interferon-gamma (IFN-gamma) and granulocyte colony-stimulating factor (G-CSF) were found significantly higher in control group than patients' group (p = 0.003, 0.019 respectively). Basic fibroblast growth factor (Basic-FGF/FGF-2) and interleukin-1 receptor antagonist (IL-1ra) were found higher (but not statistically significant) in controls (p = 0.100 and 0.070 respectively). Additionally, a negative and significant correlation was found between Eotaxin level in aqueous humour and central macular thickness.

CONCLUSIONS

Some mediators might be implicated in the pathogenesis of DMO either augmenting or suppressing role. Eotaxin, IP-10, MCP-1 and IL-8 might have a role in cases not responding to standard anti-vascular endothelial growth factor (VEGF) therapy. IL-1ra might have a protective role; therefore, the effectiveness of intravitreal injection of IL-1ra homologue needs to be studied in future clinical trials.

Early detection and correlation of tear fluid inflammatory factors that influence angiogenesis in premature infants with and without retinopathy of prematurity

Purpose

To measure the levels of inflammatory factors in tear fluid of pre-term infants with and without retinopathy of prematurity (ROP).

Methods

The cross-sectional pilot study included 29 pre-term infants undergoing routine ROP screening. Pre-term infants were grouped as those without ROP (no ROP; n = 14) and with ROP (ROP; n = 15). Sterile Schirmer's strips were used to collect the tear fluid from pre-term infants. Inflammatory factors such as interleukin (IL)-6, IL-8, MCP1 (Monocyte Chemoattractant Protein 1; CCL2), RANTES (Regulated on Activation, Normal T Cell Expressed and Secreted; CCL5), and soluble L-selectin (sL-selectin) were measured by cytometric bead array using a flow cytometer.

Results

Birth weight (BW) and gestation age (GA) were significantly (P < 0.05) lower in pre-term infants with ROP compared with those without ROP. Higher levels of RANTES (P < 0.05) and IL-8 (P = 0.09) were observed in the tear fluid of pre-term infants with ROP compared with those without ROP. Lower levels of tear fluid IL-6 (P = 0.14) and sL-selectin (P = 0.18) were measured in pre-term infants with ROP compared with those without ROP. IL-8 and RANTES were significantly (P < 0.05) higher in the tear fluid of pre-term infants with stage 3 ROP compared with those without ROP. Tear fluid RANTES level was observed to be inversely associated with GA and BW of pre-term infants with ROP and not in those without ROP. Furthermore, the area under the curve and odds ratio analysis demonstrated the relevance of RANTES/BW (AUC = 0.798; OR-7.2) and RANTES/MCP1 (AUC = 0.824; OR-6.8) ratios in ROP.

Conclusions

Distinct changes were observed in the levels of tear inflammatory factors in ROP infants. The status of RANTES in ROP suggests its possible role in pathobiology and warrants further mechanistic studies to harness it in ROP screening and management.

Interleukin-6 and Macular Edema: A Review of Outcomes with Inhibition

This paper describes the current literature on the molecular pathophysiology of interleukin-6 (IL-6) in the genesis of macular edema and on the outcomes with IL-6 inhibitors in the treatment of non-infectious macular edema. The role of IL-6 in the development of macular edema has been well elucidated. IL-6 is produced by multiple cells of the innate immune system and leads to a higher likelihood of developing autoimmune inflammatory diseases, such as non-infectious uveitis, through a variety of mechanisms. These include increasing the helper T-cell population over the regulatory T-cell population and leading to the increased expression of inflammatory cytokines, such as tumor necrosis factor-alpha. In addition to being key in the generation of uveitis and subsequent macular edema through these inflammatory pathways, IL-6 also can lead to the development of macular edema through other pathways. IL-6 induces the production of vascular endothelial growth factor (VEGF) and facilitates vascular leakage by downregulating tight junction proteins in retinal endothelial cells. Clinically, the use of IL-6 inhibitors has been found to be efficacious primarily in the context of treatment-resistant non-infectious uveitis and secondary macular edema. IL-6 is a key cytokine in retinal inflammation and macular edema. It is thus not surprising that the use of IL-6 inhibitors in treatment-resistant macular edema in the setting of non-infectious uveitis has been well documented as an effective treatment option. The use of IL-6 inhibitors in macular edema secondary to non-uveitic processes has only begun to be explored.

Vitreous humor proteome: unraveling the molecular mechanisms underlying proliferative and neovascular vitreoretinal diseases

Proliferative diabetic retinopathy (PDR), proliferative vitreoretinopathy (PVR), and neovascular age-related macular degeneration (nAMD) are among the leading causes of blindness. Due to the multifactorial nature of these vitreoretinal diseases, omics approaches are essential for a deeper understanding of the pathophysiologic processes underlying the evolution to a proliferative or neovascular etiology, in which patients suffer from an abrupt loss of vision. For many years, it was thought that the function of the vitreous was merely structural, supporting and protecting the surrounding ocular tissues. Proteomics studies proved that vitreous is more complex and biologically active than initially thought, and its changes reflect the physiological and pathological state of the eye. The vitreous is the scenario of a complex interplay between inflammation, fibrosis, oxidative stress, neurodegeneration, and extracellular matrix remodeling. Vitreous proteome not only reflects the pathological events that occur in the retina, but the changes in the vitreous itself play a central role in the onset and progression of vitreoretinal diseases. Therefore, this review offers an overview of the studies on the vitreous proteome that could help to elucidate some of the pathological mechanisms underlying proliferative and/or neovascular vitreoretinal diseases and to find new potential pharmaceutical targets.

Diabetes mellitus associated neurovascular lesions in the retina and brain: A review

Diabetes mellitus (DM) is now recognized as a system-wide, autoimmune, inflammatory, microvascular disorder, which, in the retina and brain results in severe multifocal injury now recognized as a leading cause, world-wide, of progressive vision loss and dementia. To address this problem, resulting primarily from variations in glycemia in the prediabetic and overt diabetic states, it must be realized that, although some of the injury processes associated with diabetes may be system wide, there are varying responses, effector, and repair mechanisms that differ from organ to organ or within varying cell structures. Specifically, within the retina, and similarly within the brain cortex, lesions occur of the "neurovascular unit", comprised of focal microvascular occlusions, inflammatory endothelial and pericyte injury, with small vessel leakage resulting in injury to astrocytes, Müller cells, and microglia, all of which occur with progressive neuronal apoptosis. Such lesions are now recognized to occur before the first microaneurysms are visible to imaging by fundus cameras or before they result in detectable symptoms or signs recognizable to the patient or clinician. Treatments, therefore, which currently are not initiated within the retina until edema develops or there is progression of vascular lesions that define the current staging of retinopathy, and in the brain only after severe signs of cognitive failure. Treatments, therefore are applied relatively late with some reduction in progressive cellular injury but with resultant minimal vision or cognitive improvement. This review article will summarize the multiple inflammatory and remediation processes currently understood to occur in patients with diabetes as well as pre-diabetes and summarize as well the current limitations of methods for assessing the structural and functional alterations within the retina and brain. The goal is to attempt to define future screening, monitoring, and treatment directions that hopefully will prevent progressive injury as well as enable improved repair and attendant function.

Deletion of the Pedf gene leads to inflammation, photoreceptor loss and vascular disturbances in the retina

Retinal diseases are often accompanied by inflammation, vascular abnormalities, and neurodegeneration that decrease vision. Treatment with exogenous PEDF is widely shown to alleviate these conditions leading us to hypothesize that loss of function of the PEDF gene disrupts these pathways and leads to visual loss. Measurements were carried out by detailed phenotyping of PEDF null mice to assess expression of immunomodulators, glia activation, systemic inflammation, vascular disturbances, and visual sensitivity often associated with retinal pathologies. With a deletion of the Pedf gene, there was increased expression of several immune modulators in Pedf^-/- retinas and serum with IL-2 and GM-CSF upregulated in both. Increases in retina glia activation and macrophage infiltration, levels of serum c-reactive protein (CRP), numbers of white and red blood cells and platelets and decreased blood glucose levels were all features associated with PEDF null mice. With PEDF gene deletion, there was also a notable increase in apoptosis in early developing retinas (PN3), reduced thickness of the photoreceptor layer, swelling of the inner plexiform layer, reduced retinal sensitivity and steady-state reduced activation of Erk and Akt, two signaling pathways used by PEDF. There is a substantial body of animal data emphasizing utility of PEDF treatment in homeostatic regulation of retinal diseases, including diabetic retinopathy and age-related macular degeneration but there is little agreement or evidence on the role of endogenous PEDF in retinal diseases. Our findings strongly support the concept that a deletion of the PEDF gene makes the retina vulnerable to diseases, and argue that endogenous PEDF plays a critical role in limiting pathological events in the retina.

Vitreous Inflammatory Cytokines and Chemokines, Not Altered After Preoperative Adjunctive Conbercept Injection, but Associated With Early Postoperative Macular Edema in Patients With Proliferative Diabetic Retinopathy

Purpose

To investigate the influence of preoperative adjunctive anti-VEGF drug (Conbercept) on vitreous inflammatory cytokines and chemokines profiles and whether those cytokines were associated with early macular edema (ME) after surgery for patients with proliferative diabetic retinopathy (PDR).

Methods

In this post hoc analysis of the CONCEPT clinical trial, subjects with PDR underwent vitrectomy were included and vitreous samples were collected at the start of vitrectomy. Levels of vitreous VEGF, 17 inflammatory cytokines, and 11 chemokines were measured using Luminex multiplex technology. Subjects were then divided into groups based on with (Pre-IV) or without (No-Pre-IV) preoperative intravitreous injection of Conbercept; with or without early ME after surgery.

Results

There was no difference between Pre-IV (13/30) and No-Pre-IV (7/29) concerning the ratio of patients with early ME (p = 0.17). After preoperative intravitreous injection of Conbercept, VEGF level dramatically decreased (p = 0.001), TNF-α (p = 0.002), and IP-10 (p = 0.018) increased in Pre-IV group. In patients with early ME after surgery, however, a number of cytokines increased, including IL-1β (p = 0.008), IL-2 (p = 0.023), IL-4 (p = 0.030), IL-9 (p = 0.02), IL-10 (p = 0.002), IL-12 (p = 0.001), IL-13 (p = 0.031), IL-17A (p = 0.008), TNF-α (p = 0.012), CXCL9 (p = 0.023), G-CSF (p = 0.019), MCP-1 (p = 0.048), and RANTES (p = 0.016).

Conclusion

We found the preoperative adjunctive Conbercept injection has limited influence on the levels of vitreous inflammatory cytokines and chemokines in PDR. The elevated levels of a series of cytokines might be associated with early inflammation after vitrectomy, which may lead to postoperative ME.