Clinical validation of a link between TNF-alpha and the glycosylation enzyme core 2 GlcNAc-T and the relationship of this link to diabetic retinopathy

Retinal microglia - A key player in healthy and diseased retina

Microglia, the resident immune cells of the brain and retina, are constantly engaged in the surveillance of their surrounding neural tissue. During embryonic development they infiltrate the retinal tissues and participate in the phagocytosis of redundant neurons. The contribution of microglia in maintaining the purposeful and functional histo-architecture of the adult retina is indispensable. Within the retinal microenvironment, robust microglial activation is elicited by subtle changes caused by extrinsic and intrinsic factors. When there is a disturbance in the cell-cell communication between microglia and other retinal cells, for example in retinal injury, the activated microglia can manifest actions that can be detrimental. This is evidenced by activated microglia secreting inflammatory mediators that can further aggravate the retinal injury. Microglial activation as a harbinger of a variety of retinal diseases is well documented by many studies. In addition, a change in the microglial phenotype which may be associated with aging, may predispose the retina to age-related diseases. In light of the above, the focus of this review is to highlight the role played by microglia in the healthy and diseased retina, based on findings of our own work and from that of others.

Intravitreal Bevacizumab in Refractory Uveitic Macular Edema: One-year Follow-up

Purpose

Uveitis is a major cause of ocular morbidity in developed countries. It has been demonstrated that macular edema is a significant cause of decreased visual acuity and macular edema in these patients. In this article, we evaluate the long-term outcome of intravitreal bevacizumab in the treatment of refractory uveitic macular edema.

Methods

In this retrospective, noncomparative, interventional case series, uveitic patients with macular edema who were refractory to conventional therapy and who were treated with intravitreal bevacizumab were identified and assessed. Best-corrected visual acuity and optical coherence tomography central macular thickness measurements were collected and analyzed with correlative statistical analysis, including the use of Student paired t-test, Kaplan-Meier, and linear regression analysis.

Results

Twenty-nine eyes of 27 patients with diverse uveitic etiologies were analyzed and followed up at 1 year. Thirteen patients received a single intravitreal bevacizumab injection. Six patients required a second intravitreal bevacizumab injection, while 10 patients received combination therapy of intravitreal bevacizumab and triamcinolone acetonide. Baseline mean logMAR visual acuity was −0.59. At 1 year, the mean logMAR visual acuity was −0.42± 0.36 (p=0.0045). Baseline mean central macular thickness was 383.66 μm. At 1 year, the mean thickness was 294.32±110.87 (p=0.0007).

Conclusions

Intravitreal bevacizumab is a useful and therapeutically beneficial agent in the treatment of refractory uveitic macular edema. Some patients will require adjunctive intravitreal bevacizumab injections or the use of combination therapy with intravitreal triamcinolone acetonide.

Correlation between RAGE gene promoter methylation and diabetic retinal inflammation

The methylation status of the receptor for advanced glycation end products (RAGE) gene promoter in peripheral blood mononuclear cells (PBMCs) of type 2 diabetic retinopathy (DR) patients was evaluated to investigate the correlation between RAGE gene promoter methylation and diabetic retinal inflammation. Eighty patients admitted and diagnosed as type 2 DR in Qilu Hospital, Shandong University during the period from October, 2013 to October, 2015 were enrolled in this study. They were the observation group and 40 healthy subjects were enrolled in the control group. PBMCs were collected from patients using density gradient centrifugation, and the methylation status of RAGE gene promoters was detected using methylation-specific PCP (MSP). Interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) levels of in the serum were measured using enzyme-linked immunosorbent assay (ELISA). PBMCs in patients with positive RAGE gene promoter methylation were isolated and cultured and RAGE gene promoter methylation was inhibited using the demethylating agent, 5′-aza-2′-deoxycytidine (5-aza-dC). The methylation status of RAGE gene promoters in PBMCs was detected via MSP. IL-1β, IL-6 and TNF-α levels in the supernatant of PBMC culture solution were evaluated using ELISA. MSP results showed that there were 26 cases (32.50%) of RAGE gene promoter methylation in PBMCs in DR patients. RAGE gene promoters were methylated in all normal healthy subjects. IL-1β, IL-6 and TNF-α levels in serum for positive RAGE gene promoter methylation group were significantly lower than those in negative RAGE gene promoter methylation group (p<0.01). 5-aza-dC inhibited the RAGE gene promoter methylation of PBMCs in patients with positive RAGE gene promoter methylation. The inhibition of methylation in RAGE gene promoter increased the levels of IL-1β, IL-6 and TNF-α in supernatant of culture solution. In conclusion, RAGE gene promoter hypomethylation was detected in DR patients, indicating that RAGE gene promoter methylation could inhibit the diabetic retinal inflammation.

Antimyeloperoxidase antibody is a biomarker for progression of diabetic retinopathy

AIM

To study the correlation between serum antimyeloperoxidase (MPO) antibody levels with severity of diabetic retinopathy (DR).

METHODS

Study subjects included 60 consecutive cases of type 2 diabetes mellitus (DM): no diabetic retinopathy (NODR, n=20); nonproliferative DR (NPDR, n=20); proliferative DR (PDR, n=20) and 20 healthy controls. Best corrected visual acuity (BCVA) was measured on logMAR scale. Serum anti-MPO antibody levels were evaluated using ELISA IgG kit. Serum urea and creatinine was measured using standard protocol. Data were analysed statistically.

RESULTS

Mean serum anti-MPO antibody (RU/ml) was 16.94 ± 4.85 in controls, 17.66 ± 4.78 in NODR, 21.51 ± 5.27 in NPDR and 37.27 ± 11.92 in PDR groups. On ANOVA, significant difference in visual acuity was found among the study groups (F=73.46, p<0.001). Serum anti-MPO antibody was correlated significantly with decrease in visual acuity (F=48.40, p<0.001), increase in serum urea (F=128.13, p<0.001) and creatinine (F=77.10, p<0.001).

CONCLUSION

Increase in serum anti-MPO antibody levels correlate with increased severity of DR. Serum anti-MPO antibody may be a noteworthy biochemical marker for progression of retinopathy from nonproliferative to proliferative stage.

The role of microglia in diabetic retinopathy

There is growing evidence that chronic inflammation plays a role in both the development and progression of diabetic retinopathy. There is also evidence that molecules produced as a result of hyperglycemia can activate microglia. However the exact contribution of microglia, the resident immune cells of the central nervous system, to retinal tissue damage during diabetes remains unclear. Current data suggest that dysregulated microglial responses are linked to their deleterious effects in several neurological diseases associated with chronic inflammation. As inflammatory cytokines and hyperglycemia disseminate through the diabetic retina, microglia can change to an activated state, increase in number, translocate through the retina, and themselves become the producers of inflammatory and apoptotic molecules or alternatively exert anti-inflammatory effects. In addition, microglial genetic variations may account for some of the individual differences commonly seen in patient's susceptibility to diabetic retinopathy.

Profile of intraocular tumour necrosis factor-α and interleukin-6 in diabetic subjects with different degrees of diabetic retinopathy

PURPOSE

To assess and correlate the levels of inflammatory mediators in the eyes from non-diabetic and diabetic subjects without retinopathy (NDR), with non-proliferative diabetic retinopathy (NPDR) or with proliferative diabetic retinopathy (PDR) to corresponding erum levels.

METHODS

The levels of interleukin 1β, interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) were analysed by an ELISA-mimicking technique in the vitreous from 26 diabetic subjects with active PDR and 27 non-diabetic subjects, or by a multiplex bead assay in the aqueous humour from 35 diabetic subjects with NDR/NPDR and 40 non-diabetic subjects. Intraocular protein production was estimated in vitreous specimens by calculating a vitreous/serum ratio.

RESULTS

In the vitreous, IL-6 was higher in diabetic [157.5 (25.0-1401.0) pg/ml; median (min-max)] than in non-diabetic subjects [44.0 (5.0-4425) pg/ml; p = 0.021]. The vitreous/serum ratio was high (55.5:1 and 16:1, respectively), suggesting intraocular production. TNF-α was lower in diabetic [18.0 (8.0-46.0) pg/ml] than in non-diabetic subjects [22.0 (13.0-47.0) pg/ml; p = 0.034], but the vitreous/serum ratio was elevated in both groups (2:1 and 3.4:1, respectively). TNF-α levels were higher in serum from diabetic subjects [9.0 (5.0-53.0) pg/ml versus 6.7 (3.0-11.0) pg/ml; p < 0.001]. Aqueous levels of inflammatory mediators did not differ between diabetic subjects with NDR/NPDR and non-diabetic subjects despite elevated TNF-α in serum [27.8 (6.8-153.7) pg/ml versus 16.4 (4.1-42.4) pg/ml; p = 0.021].

CONCLUSION

Intraocular inflammation seems to be involved in PDR but does not seem to be prominent in early retinopathy stages, i.e. NDR or NPDR. Diabetic subjects have an overall increased inflammatory activity compared to non-diabetic subjects, as demonstrated by increased serum levels of TNF-α.

Prospective study of inflammatory biomarkers and risk of diabetic retinopathy in the diabetes control and complications trial

IMPORTANCE

This study demonstrates that increasing quintiles of baseline high-sensitivity C-reactive protein (hsCRP) level may be associated with higher risk of incident clinically significant macular edema, the leading cause of vision loss in working-aged individuals in North America.

OBJECTIVE

To determine whether baseline levels of hsCRP and intercellular adhesion molecule 1 (ICAM-1) predict development and progression of diabetic retinopathy (DR), clinically significant macular edema (CSME), retinal hard exudates, and proliferative DR in the Diabetes Control and Complications Trial (DCCT) cohort.

DESIGN

The DCCT was a large multicenter randomized controlled clinical trial.

SETTING

Twenty-nine medical centers in the United States and Canada.

PARTICIPANTS

The DCCT population consisted of 1441 subjects with type 1 diabetes mellitus aged 13 to 39 years at study entry.

INTERVENTION

We measured levels of hsCRP, ICAM-1, vascular cell adhesion molecule 1, and tumor necrosis factor α receptor 1 in stored baseline blood samples.

MAIN OUTCOME MEASURES

We assessed the association of levels of hsCRP, ICAM-1, vascular cell adhesion molecule 1, and tumor necrosis factor α receptor 1 with incident DR end points ascertained from grading of standardized 7-field stereoscopic retinal color photographs taken at baseline and every 6 months during follow-up.

RESULTS

After adjustment for randomized treatment assignment and other factors, we observed a statistically significant association between hsCRP and risk of CSME, with a relative risk (RR) for the top vs bottom quintile of 1.83 (95% CI, 0.94-3.55; P for trend = .01). Similarly, for the development of retinal hard exudates, the RR for the top vs bottom quintile of hsCRP level was 1.78 (95% CI, 0.98-3.25; P for trend = .004), whereas for ICAM-1 level, the RR comparing the top vs bottom quintiles was 1.50 (95% CI, 0.84-2.68; P for trend = .05). There were no statistically significant associations between baseline VCAM-1 or tumor necrosis factor α receptor 1 levels and risk of any of the DR end points.

CONCLUSIONS AND RELEVANCE

After adjusting for known risk factors, increasing quintiles of baseline hsCRP level may be associated with higher risk of incident CSME and macular hard exudate in the DCCT cohort. Circulating levels of ICAM-1 may also be associated with the development of retinal hard exudates.

Selective and pan-blockade agents in the anti-angiogenic treatment of proliferative diabetic retinopathy: a literature summary

Diabetes mellitus is a major health concern in the modern world. Several sight-threatening ocular conditions are included in the array of health problems associated with this disease. Understandably, 2 of the more sight-threatening problems, proliferative diabetic retinopathy (PDR) and diabetic macular edema (DME), have received a great deal of attention in recent years. Pivotal studies, such as the Early Treatment Diabetic Retinopathy Study and the Diabetic Retinopathy Study, have established laser photocoagulation as the accepted treatment modality. The last decade has seen a surge in clinical data supporting the use of pharmacologic therapy in place of the often damaging laser therapy. Supporting data are based on the establishment of vascular endothelial growth factor (VEGF) as a key facilitator of disease progression in diabetic retinopathy. We will discuss the advantages and disadvantages of both selective and pan-blockade anti-VEGF agents available today in an effort to help guide physicians wishing to use these agents to treat PDR and DME.

Diabetic macular oedema: physical, physiological and molecular factors contribute to this pathological process

Diabetic macular oedema (DMO) is an important cause of vision loss in patients with diabetes mellitus. The underlying mechanisms of DMO, on both macrocellular and microcellular levels, are discussed in this review. The pathophysiology of DMO can be described as a process whereby hyperglycaemia leads to overlapping and inter-related pathways that play a role not only in the initial vascular events, but also in the continued tissue insult that leads to chronic DMO. On a macrocellular level, DMO is believed to be in part caused by alterations in hydrostatic pressure, oxygen tension, oncotic pressure and shear stress. Three key components of the microvascular pathways include angiogenic factor expression, inflammation and oxidative stress. These molecular mediators, acting in conjunction with macrocellular factors, which are all stimulated in part by the hyperglycaemia and hypoxia, can have a direct endothelial effect leading to hyperpermeability, disruption of vascular endothelial cell junctions, and leukostasis. The interactions, signalling events and feedback loops between the various molecules are complicated and are not completely understood. However, by attempting to understand the pathways involved in DMO, we can help guide new treatment options targeted towards specific factors or mediators.

TNF-alpha is an independent serum marker for proliferative retinopathy in type 1 diabetic patients

PURPOSE

This study aimed to determine if there are any associations between serum levels of inflammatory markers and proliferative retinopathy (PDR) in type 1 diabetic patients.

DESIGN

A cross-sectional design was utilized for this study.

METHODS

One hundred twenty-eight type 1 diabetic patients underwent stereo fundus photography according to the Early Treatment Diabetic Retinopathy Study and were divided into two retinopathy groups: no or nonproliferative retinopathy (NDR/NPDR; n=62) and PDR (n=66). Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, IL-6, soluble vascular cellular adhesion molecule-1 (sVCAM-1), soluble intercellular adhesion molecule-1 (sICAM-1), P-selectin, and high-sensitivity C-reactive protein (hsCRP) were analyzed. Statistical analysis was performed using nonparametric Mann-Whitney U test and multivariate logistic regression analysis.

RESULTS

Patients with PDR had higher levels of TNF-alpha [7.0 pg/ml (<4-17) vs. 6.0 pg/ml (<4-25); P=.009], sVCAM-1 [860 ng/ml (360-2120) vs. 700 ng/ml (310-1820); P<.001], and P-selectin [180 ng/ml (39-400) vs. 150 ng/ml (42-440); P=.017; figures are expressed as median (range)]. There were no differences in serum levels of sICAM-1 or hsCRP. IL-1 beta was not detectable in any patient, and IL-6 was detectable in only 22.7% of the patients. In multivariate logistic regression analysis, TNF-alpha was the single, persistent, independent determinant inflammatory marker for PDR.

CONCLUSION

The association between TNF-alpha and PDR in type 1 diabetic patients suggests that inflammation might play a role in the pathogenesis of proliferative diabetic retinopathy.

Can electrons act as antioxidants? A review and commentary

A previous study demonstrated that connecting the human body to the earth during sleep (earthing) normalizes the daily cortisol rhythm and improves sleep. A variety of other benefits were reported, including reductions in pain and inflammation. Subsequent studies have confirmed these earlier findings and documented virtually immediate physiologic and clinical effects of grounding or earthing the body. It is well established, though not widely known, that the surface of the earth possesses a limitless and continuously renewed supply of free or mobile electrons as a consequence of a global atmospheric electron circuit. Wearing shoes with insulating soles and/or sleeping in beds that are isolated from the electrical ground plane of the earth have disconnected most people from the earth's electrical rhythms and free electrons. The most reasonable hypothesis to explain the beneficial effects of earthing is that a direct earth connection enables both diurnal electrical rhythms and free electrons to flow from the earth to the body. It is proposed that the earth's diurnal electrical rhythms set the biological clocks for hormones that regulate sleep and activity. It is also suggested that free electrons from the earth neutralize the positively charged free radicals that are the hallmark of chronic inflammation. A relationship between cortisol and inflammation was established in the pioneering work of H. Selye published in the 1950s. Current biomedical research has led to an inflammation hypothesis that is establishing chronic inflammation as the culprit behind almost every modern chronic illness. The research summarized here and in subsequent reports provides a basis for a number of earthing technologies that restore and maintain natural electrical contact between the human body and the earth throughout the day and night in situations where going barefoot on the earth is impractical. It is proposed that free or mobile electrons from the earth can resolve chronic inflammation by serving as natural antioxidants.