Brilliant Blue G as protective agent against trypan blue toxicity in human retinal pigment epithelial cells in vitro

Membrane Blue Dual Protects Retinal Pigment Epithelium Cells/Ganglion Cells-Like through Modulation of Mitochondria Function

Although recent data highlight the greater protective effects exerted by Membrane Blue Dual (MBD), a precise analysis of the mechanisms of action is missing. We examined the effects of MBD with/without polyethylene glycol (PEG) on both human retinal pigment epithelial cells (ARPE-19) and retinal ganglion cells-like (RGC-5) cultured in the presence/absence of ultraviolet B (UVB) treatment on mitochondria function, oxidants, and apoptosis. In ARPE-19/RGC-5 cells either treated or not with UVB, the effects of MBD with/without PEG were evaluated by specific assays for viability, mitochondrial membrane potential and mitochondrial reactive oxygen species (mitoROS) release. Annexin V was used to detect apoptosis, whereas trypan blue and the scratch assay were used for proliferation/migration. In both physiologic conditions and in the presence of UVB, MBD with/without PEG increased cell viability, mitochondrial membrane potential, proliferation and migration in both ARPE-19 and RGC-5 cells. In general, the effects of MBD with PEG were greater than those caused by MBD without PEG. Our results suggest that, in particular, MBD with PEG is a safe and effective dye for vitreoretinal surgery through the modulation of mitochondrial function.

Atypical Retinal Hemorrhages after Vitrectomy for Idiopathic Macular Hole: Possible Toxicity of Brilliant Blue G

Purpose

To describe the development of multiple retinal hemorrhages after uncomplicated macular hole (MH) surgery, and to determine the associated factors.

Methods

The medical records of 163 patients (167 eyes) diagnosed with idiopathic MHs and who underwent surgery at Pusan National University Hospital between March 2016 and July 2018 were retrospectively reviewed. The development of retinal hemorrhages was evaluated using ultra-widefield fundus photographs. Multiple retinal hemorrhages were defined as three or more dot or blot hemorrhages that had not been observed before and during the surgery. The patients were divided into two groups according to the presence of multiple retinal hemorrhages. The variable parameters were compared between the two groups to find the risk factors. The associated factors were evaluated further for the independent factor using multiple logistic regression analysis.

Results

Multiple retinal hemorrhages were observed in 31 eyes (18.6%) after MH surgery. The associated factors were the surgical induction of posterior vitreous detachment (PVD) (p = 0.003), use of the internal limiting membrane flap technique (p = 0.028), and staining with Brilliant Blue G (BBG) (p = 0.003). Retinal hemorrhages were exclusively observed in eyes in which BBG was used. Surgical PVD induction was the only independent risk factor (odds ratio, 13.099; p = 0.013). No statistically significant differences were observed between the two groups in the postoperative visual outcomes and MH closure rate. Additionally, patients who underwent surgery for idiopathic epiretinal membrane during the study period were reviewed to validate the above findings. Multiple retinal hemorrhages were noted in only one case (0.4%) in which BBG was used after surgical induction of PVD.

Conclusions

Multiple retinal hemorrhages after MH surgery appear to be related to the intravitreal use of BBG in eyes that sustained mechanical damage because of surgical induction of PVD; however, they did not affect surgical outcomes.

Toxicity and phototoxicity in human ARPE-19 retinal pigment epithelium cells of dyes commonly used in retinal surgery

PURPOSE

To compare, for the first time, systematically the toxicity and phototoxicity of dyes and dye combinations used in vitreoretinal surgery. The dyes were trypan blue, brilliant blue G, trypan blue + brilliant blue G, indocyanine green, bromophenol blue, bromophenol blue + brilliant blue G, and acid violet 17, in clinically used concentrations.

METHODS

Human ARPE retinal pigment epithelium cells were exposed to the dyes for 30 min. For phototoxicity, the cells were exposed for 15 min to high-intensity light from a light emitting diode source with an intensity similar to surgical conditions. Toxicity was assayed either directly after exposure to either dye alone or dye and light, or with a delay of 24 h.

RESULTS

None of the dyes or their combinations was toxic when cells were exposed to them at ambient light. Acid violet led to a reduction viability by 90% already immediately after light exposure. Bromophenol blue and its combination with brilliant blue G showed strong phototoxicity (reduction of viability by 83%) when assayed with delay. Indocyanine green with different agents to adjust osmolarity (balanced salt solution, glucose, and mannitol) was not found to be toxic.

CONCLUSION

The strong immediate phototoxicity of acid violet reflects its clinical toxicity. Bromophenol blue might also be disadvantageous for patient outcome because of its delayed phototoxicity. The other dyes (trypan blue, brilliant blue g, and indocyanine green) were not found to be toxic neither with exposure to ambient light nor after exposure to light of intensities used in surgery.

Impact of Vital Dyes on Cell Viability and Transduction Efficiency of AAV Vectors Used in Retinal Gene Therapy Surgery: An In Vitro and In Vivo Analysis

Purpose

Treatment of inherited retinal degenerations using adeno-associated viral (AAV) vectors involves delivery by subretinal injection. In the latter stages, alteration of normal anatomy may cause difficulty in visualizing the retinotomy, retinal detachment extension, and vector diffusion. Vital dyes may be useful surgical adjuncts, but their safety and impact on AAV transduction are largely unknown.

Methods

The effects of Sodium Fluorescein (SF), Membrane Blue (MB), and Membrane Blue Dual (DB) at a range of dilutions were assessed on human embryonic kidney cells in vitro using an AAV2-green fluorescent protein (GFP) reporter at different multiplicities of infection. Flow cytometry analysis was performed to assess both cell viability and transduction efficiency. The effect on quantitative (q)PCR titer was determined. Balanced salt solution (BSS) or dilute DB (1:5 in BSS) were delivered subretinally into left/right eyes of C57BL/6J mice (n = 12). Retinal structure and function were analyzed by optical coherence tomography, autofluorescence, dark-and light-adapted full-field electroretinography.

Results

DB and MB were not toxic at any concentration tested, SF only when undiluted. The presence of dyes did not adversely affect the genomic titer. DB even increased the values, due to presence of surfactant in the formulation. AAV2-GFP transduction efficiency was not reduced by the dyes. No structural and functional toxic effects were observed following subretinal delivery of DB.

Conclusions

Only undiluted SF affected cell viability. No effects on qPCR titer and transduction efficiency were observed. DB does not appear toxic when delivered subretinally and improves titer accuracy. DB may therefore be a safe and helpful adjunct during gene therapy surgery.

Translational Relevance

This paper might be of interest to the retinal gene therapy community: it is a “bench to bedside” research paper about the potential use of dyes as a surgical adjunct during the gene therapy surgery. We have tested the potential toxicity and impact on transduction efficiency in an in vitro and in vivo model.

Brilliant Blue Dyes in Daily Food: How Could Purinergic System Be Affected?

Dyes were first obtained from the extraction of plant sources in the Neolithic period to produce dyed clothes. At the beginning of the 19th century, synthetic dyes were produced to color clothes on a large scale. Other applications for synthetic dyes include the pharmaceutical and food industries, which are important interference factors in our lives and health. Herein, we analyzed the possible implications of some dyes that are already described as antagonists of purinergic receptors, including special Brilliant Blue G and its derivative FD&C Blue No. 1. Purinergic receptor family is widely expressed in the body and is critical to relate to much cellular homeostasis maintenance as well as inflammation and cell death. In this review, we discuss previous studies and show purinergic signaling as an important issue to be aware of in food additives development and their correlations with the physiological functions.

Preoperative and intraoperative prognostic factors of epiretinal membranes using chromovitrectomy and internal limiting membrane peeling

BACKGROUND AND OBJECTIVE

To evaluate the preoperative and intraoperative findings as prognostic indicators of functional and anatomic results of idiopathic epiretinal membrane (ERM) surgery.

PATIENTS AND METHODS

Vitrectomies included ERM and internal limiting membrane (ILM) removal with vital dyes. Best corrected visual acuity (BCVA), optical coherence tomography (OCT), fluorescein angiography, and autofluorescence were performed at baseline and postoperatively. Intraoperative ILM status after ERM removal was also evaluated.

RESULTS

Thirty-one eyes were monitored for a mean of 16.78 months. BCVA and central foveal thickness (CFT) improved significantly (P < .001) from baseline at 3 and 12 months. Preoperative hyperautofluorescence was associated with greater CFT reduction (P < .005). ILM status after ERM peeling did not influence visual recovery but was associated with anatomical results as measured by OCT.

CONCLUSION

Preoperative poor initial BCVA and RPE defects by FAF may not be bad prognostic factors. Preoperative hyperautofluorescence was associated with greater CFT reduction. Intraoperative classification of ILM status after ERM and ILM staining/peeling was reported and may be useful for future studies, though it was not associated neither with preoperative nor postoperative BCVA.

Reduction of cytotoxicity of benzalkonium chloride and octenidine by Brilliant Blue G

The irritative effects of preservatives found in ophthalmologic solution, or of antiseptics used for skin disinfection is a consistent problem for the patients. The reduction of the toxic effects of these compounds is desired. Brilliant Blue G (BBG) has shown to meet the expected effect in presence of benzalkonium chloride (BAK), a well known preservative in ophthalmic solutions, and octenidine dihydrochloride (Oct), used as antiseptic in skin and wound disinfection. BBG shows a significant protective effect on human corneal epithelial (HCE) cells against BAK and Oct toxicity, increasing the cell survival up to 51 % at the highest BAK or Oct concentration tested, which is 0.01 %, both at 30 min incubation. Although BBG is described as a P2x7 receptor antagonist, other selective P2x7 receptor antagonists, OxATP (adenosine 5’-triphosphate-2’,3’-dialdehyde) and DPPH (N’-(3,5-dichloropyridin-4-yl)-3-phenylpropanehydrazide), did not reduce the cytotoxicity of neither BAK nor Oct. Therefore we assume that the protective effect of BBG is not due to its action on the P2x7 receptor. Brilliant Blue R (BBR), a dye similar to BBG, was also tested for protective effect on BAK and Oct toxicity. In presence of BAK no significant protective effect was observed. Instead, with Oct a comparable protective effect was seen with that of BBG. To assure that the bacteriostatic effect is not affected by the combinations of BAK/BBG, Oct/BBG and Oct/BBR, bacterial growth inhibition was analyzed on different Gram-negative and Gram-positive bacteria. All combinations of BAK or Oct with BBG hinder growth of Gram-positive bacteria. The combinations of 0.001 % Oct and BBR above 0.025 % do not hinder the growth of B. subtilis. For Gram-negative bacteria, BBG and BBR reduce, but do not abolish, the antimicrobial effect of BAK nor of Oct. In conclusion, the addition of BBG at bacterial inhibitory concentrations is suggested in the ready-to-use ophthalmic preparations and antiseptic solutions.