LASU: An efficient and stable phthalocyanine dye with tolerable safety profile for self-disinfecting anti-COVID textiles activated by ambient light

BACKGROUND

Recent COVID crisis has demonstrated that modern society urgently needs an accessible protection against mass infections, especially viruses, as the new strains are appearing at an ever-increasing pace and cause severe harm to the population and the world economy.

METHODS

We have developed an efficient phthalocyanine photosensitizer LASU, that is suitable for dyeing textiles and allows to prepare reusable self-disinfecting fabrics with strong antiviral properties. The safety profile of LASU was evaluated in accredited laboratories by several in vitro assays according to the OECD-guidelines.

RESULTS

The textiles impregnated with LASU phthalocyanine showed a significant antiviral photodynamic effect even under moderate indoor and outdoor light. The dye did not show any genotoxic potential in human lymphocyte micronucleus assay. It showed a possible indication for eye irritation in human EpiOcular™ model and was phototoxic when tested in mouse BALB/c 3T3 cell test in the presence and absence of UVA-irradiation.

CONCLUSION

Novel phthalocyanine-dyed textiles are suitable for general use as self-disinfecting antiviral barriers and materials in hospitals, households, and public places. The safety profile of LASU is the phototoxic effect which is related to LASU´s mode of action.

The Safety Assessment of Cosmetic Perfumes by Using In Chemico and In Vitro Methods in Combination with GC-MS/MS Analysis

Animal testing has been prohibited for the safety assessment of cosmetic ingredients or finished products. Thus, alternative non-animal methods, followed by confirmatory clinical studies on human volunteers, should be used as the sole legally acceptable approach within the EU. The safety assessment of cosmetic products requires the involvement of multiple scientific disciplines, including analytical chemistry and biomedicine, as well as in chemico, in vitro and in silico toxicology. Recent data suggest that fragrance components may exert multiple adverse biological effects, e.g. cytotoxicity, skin sensitisation, (photo)genotoxicity, mutagenicity, reprotoxicity and endocrine disruption. Therefore, a pilot study was conducted with selected samples of fragrance-based products, such as deodorant, eau de toilette and eau de parfum, with the aim of integrating results from a number of alternative non-animal methods suitable for the detection of the following toxicological endpoints: cytotoxicity (with 3T3 Balb/c fibroblasts); skin sensitisation potential (in chemico method, DPRA); skin sensitisation potential (LuSens in vitro method, based on human keratinocytes); genotoxicity potential (in vitro Comet assay with 3T3 Balb/c cells); and endocrine disruption (in vitro YES/YAS assay). The presence of twenty-four specific known allergens in the products was determined by using GC-MS/MS. The strategies for estimation of the NOAEL of a mixture of allergens, which were proposed by the Scientific Committee on Consumer Products in their 'Opinion on Tea tree oil' document and by the Norwegian Food Safety Authority in their 'Risk Profile of Tea tree oil' report, were used as models for the NOAEL estimation of the mixtures of allergens that were identified in the individual samples tested in this study.

Toxic Indoor Air Is a Potential Risk of Causing Immuno Suppression and Morbidity—A Pilot Study

We aimed to establish an etiology-based connection between the symptoms experienced by the occupants of a workplace and the presence in the building of toxic dampness microbiota. The occupants (5/6) underwent a medical examination and urine samples (2/6) were analyzed by LC-MS/MS for mycotoxins at two time-points. The magnitude of inhaled water was estimated. Building-derived bacteria and fungi were identified and assessed for toxicity. Separate cytotoxicity tests using human THP-1 macrophages were performed from the office’s indoor air water condensates. Office-derived indoor water samples (n = 4/4) were toxic to human THP-1 macrophages. Penicillium, Acremonium sensu lato, Aspergillus ochraceus group and Aspergillus section Aspergillus grew from the building material samples. These colonies were toxic in boar sperm tests (n = 11/32); four were toxic to BHK-21 cells. Mycophenolic acid, which is a potential immunosuppressant, was detected in the initial and follow-up urine samples of (2/2) office workers who did not take immunosuppressive drugs. Their urinary mycotoxin profiles differed from household and unrelated controls. Our study suggests that the presence of mycotoxins in indoor air is linked to the morbidity of the occupants. The cytotoxicity test of the indoor air condensate is a promising tool for risk assessment in moisture-damaged buildings.

Comparison of methods used for evaluation of mutagenicity/genotoxicity of model chemicals - parabens

Growing worldwide efforts to replace (reduce) animal testing and to improve alternative in vitro tests which may be more efficient in terms of both time, cost and scientific validity include also genotoxicity/mutagenicity endpoints. The aim of the review article was to summarize currently available in vitro testing approaches in this field, their regulatory acceptance and recommended combinations for classification of chemicals. A study using the combination of Comet Assay performed on two cell lines and the Chromosomal Aberration test on human peripheral lymphocytes was performed with the aim to predict the genotoxic potential of selected paraben esters, serving as a model chemical group. Parabens are widely used in consumer products as preservatives and have been reported to exhibit inconclusive results in numerous genotoxicity studies. The Comet Assay identified Ethylparaben and Benzylparaben as potentially genotoxic. The Chromosomal Aberration test revealed weak genotoxic potential in case of Ethylparaben and positive genotoxicity in case of Butylparaben, Propylparaben and Isopropylparaben. The main reasons for variability seem to be limited water solubility of parabens, determining their bioavailability at the cellular level, and absence of metabolic activation in the Comet Assay. The results confirmed that the Comet Assay should serve as a screening test and should not be used as a stand-alone method for classification of genotoxicity. The weight of evidence approach in risk assessment should be supported with data generated with the use of human relevant in vitro methods based on cells / tissues of human origin.

Human BJ Fibroblasts is an Alternative to Mouse BALB/c 3T3 Cells in In Vitro Neutral Red Uptake Assay

The OECD GD 129 BALB/c 3T3 neutral red uptake (NRU) assay is a standardized test method for estimating starting dose for an acute oral systemic toxicity test in rodents. Mouse BALB/c 3T3 fibroblasts are the most commonly used cells in the NRU assay. We have previously transferred and validated BALB/c 3T3 NRU assay in our GLP laboratory. Subsequently, in order to obtain more human-relevant cytotoxicity data, we performed an intralaboratory validation using human BJ fibroblasts in the NRU assay instead of mouse BALB/c 3T3 fibroblasts. Here, we present comparative cytotoxicity data of 26 different test chemicals (pharmaceuticals, industrial chemicals, pesticides and food additives) produced with both BALB/c 3T3 NRU and BJ NRU assays.

Intra-laboratory validated human cell-based in vitro vasculogenesis/angiogenesis test with serum-free medium

Vasculogenesis and angiogenesis are the processes by which new blood vessels are formed. We have developed a serum-free human adipose stromal cell and umbilical cord vein endothelial cell based vasculogenesis/angiogenesis test. In this study, the test was validated in our GLP laboratory following the OECD Guidance Document 34 [1] using erlotinib, acetylic salicylic acid, levamisole, 2-methoxyestradiol, anti-VEGF, methimazole, and D-mannitol to show its reproducibility, repeatability, and predictivity for humans. The results were obtained from immunostained tubule structures and cytotoxicity assessment. The performance of the test was evaluated using 26 suspected teratogens and non-teratogens. The positive predictive value was 71.4% and the negative predictive value was 50.0%, indicating that inhibition of vasculogenesis is a significant mechanism behind teratogenesis. In conclusion, this test has great potential to be a screening test for prioritization purposes of chemicals and to be a test in a battery to predict developmental hazards in a regulatory context.

Multilaboratory evaluation of 15 bioassays for (eco)toxicity screening and hazard ranking of engineered nanomaterials: FP7 project NANOVALID

Within EU FP7 project NANOVALID, the (eco)toxicity of 7 well-characterized engineered nanomaterials (NMs) was evaluated by 15 bioassays in 4 laboratories. The highest tested nominal concentration of NMs was 100 mg/l. The panel of the bioassays yielded the following toxicity order: Ag > ZnO > CuO > TiO₂>MWCNTs > SiO₂>Au. Ag, ZnO and CuO proved very toxic in the majority of assays, assumingly due to dissolution. The latter was supported by the parallel analysis of the toxicity of respective soluble metal salts. The most sensitive tests/species were Daphnia magna (towards Ag NMs, 24-h EC₅₀=0.003 mg Ag/l), algae Raphidocelis subcapitata (ZnO and CuO, 72-h EC₅₀=0.14 mg Zn/l and 0.7 mg Cu/l, respectively) and murine fibroblasts BALB/3T3 (CuO, 48-h EC₅₀=0.7 mg Cu/l). MWCNTs showed toxicity only towards rat alveolar macrophages (EC₅₀=15.3 mg/l) assumingly due to high aspect ratio and TiO₂ towards R. subcapitata (EC₅₀=6.8 mg Ti/l) due to agglomeration of TiO₂ and entrapment of algal cells. Finally, we constructed a decision tree to select the bioassays for hazard ranking of NMs. For NM testing, we recommend a multitrophic suite of 4 in vitro (eco)toxicity assays: 48-h D. magna immobilization (OECD202), 72-h R. subcapitata growth inhibition (OECD201), 30-min Vibrio fischeri bioluminescence inhibition (ISO2010) and 48-h murine fibroblast BALB/3T3 neutral red uptake in vitro (OECD129) representing crustaceans, algae, bacteria and mammalian cells, respectively. Notably, our results showed that these assays, standardized for toxicity evaluation of “regular” chemicals, proved efficient also for shortlisting of hazardous NMs. Additional assays are recommended for immunotoxicity evaluation of high aspect ratio NMs (such as MWCNTs).

Toxicity of silver nanoparticle in rat ear and BALB/c 3T3 cell line

Background

Silver nanoparticles (AgNPs) displayed strong activities in anti-bacterial, anti-viral, and anti-fungal studies and was reportedly efficient in treating otitis media .The potential impact of AgNPs on the inner ear was missing.

Objective

Attempted to evaluate the potential toxicity of AgNPs in the inner ear, middle ear, and external ear canal after transtympanic injection in rats.

Results

In in vitro studies, the IC₅₀ for AgNPs in neutral red uptake assay was lower than that in NAD(P)H-dependent cellular oxidoreductase enzyme assay (WST-1) and higher than that in total cellular ATP and nuclear membrane integrity (propidium iodide) assessments. In in vivo experiments, magnetic resonance imaging (MRI) showed that significant changes in the permeability of biological barriers occurred in the middle ear mucosa, the skin of the external ear canal, and the inner ear at 5 h post-transtympanic injection of AgNPs at concentrations ranging from 20 μg/ml to 4000 μg/ml. The alterations in permeability showed a dosage-response relationship, and were reversible. The auditory brainstem response showed that 4000 μg/ml AgNPs induced hearing loss with partial recovery at 7 d, whereas 20 μg/ml caused reversible hearing loss. The functional change in auditory system was in line with the histology results. In general, the BALB/c 3T3 cell line is more than 1000 times more sensitive than the in vivo studies. Impairment of the mitochondrial function was indicated to be the mechanism of toxicity of AgNPs.

Conclusion

These results suggest that AgNPs caused significant, dose-dependent changes in the permeability of biological barriers in the middle ear mucosa, the skin of the external ear canal, and the inner ear. In general, the BALB/c 3T3 cell line is more than 1000 times more sensitive than the in vivo studies. The rat ear model might be expended to other engineered nanomaterials in nanotoxicology study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12951-014-0052-6) contains supplementary material, which is available to authorized users.

Intra-Laboratory Pre-Validation of a Human Cell Based in vitro Angiogenesis Assay for Testing Angiogenesis Modulators

The developed standardized human cell based in vitro angiogenesis assay was intra-laboratory pre-validated to verify that the method is reliable and relevant for routine testing of modulators of angiogenesis, e.g., pharmaceuticals and industrial chemicals. This assay is based on the earlier published method but it was improved and shown to be more sensitive and rapid than the previous assay. The performance of the assay was assessed by using six reference chemicals, which are widely used pharmaceuticals that inhibit angiogenesis: acetyl salicylic acid, erlotinib, 2-methoxyestradiol, levamisole, thalidomide, and anti-vascular endothelial growth factor. In the intra-laboratory pre-validation, the sensitivity of the assay (upper and lower limits of detection and linearity of response in tubule formation), batch to batch variation in tubule formation between different Master cell bank batches, and precision as well as the reliability of the assay (reproducibility and repeatability) were tested. The pre-set acceptance criteria for the intra-laboratory pre-validation study were met. The relevance of the assay in man was investigated by comparing the effects of reference chemicals and their concentrations to the published human data. The comparison showed a good concordance, which indicates that this human cell based angiogenesis model predicts well the effects in man and has the potential to be used to supplement and/or replace of animal tests.

The combined use of human neural and liver cell lines and mouse hepatocytes improves the predictability of the neurotoxicity of selected drugs

The cytotoxicity of amitriptyline (0-100microM), selegiline (0-4.5microM), carbamazepine (0-420microM) and paracetamol (0-10mM) was studied in metabolically competent mouse hepatocytes, metabolically incompetent human hepatoblastoma (HepG2) cells, and in neuroblastoma (SH-SY5Y) and astrocytoma (U-373 MG) cells, by using luminescence-based ATP measurement as an endpoint of cell toxicity. The aim was to evaluate the potential of the selected cell cultures to recognize metabolism-induced toxicity of the test compounds, and to predict further hepatic and neural toxicity. In SH-SY5Y cells amitriptyline was severely toxic, while selegiline and paracetamol failed to show any toxic effect, and carbamazepine was only slightly toxic at the highest concentration. In U-373 MG cells the onset of amitriptyline toxicity started earlier than in SH-SY5Y cells. However, the highest amitriptyline concentration resulted in approximately 100% decrease in the viability of the SH-SY5Y cells, whereas the decrease in the viability of the U-373 MG cells was only approximately 30%. Selegiline, carbamazepine and paracetamol were toxic in mouse hepatocytes (but not in HepG2 cells), which suggests that these drugs may show metabolism-dependent (neuro)toxicity. In conclusion, compared to the use of neurons alone, better estimations of neurotoxicity can be made by the combined use of metabolically competent hepatocytes and glial cells (e.g. U-373 MG) together with neuronal cells (e.g. SH-SY5Y).

D-Glucose uptake in fish hepatocytes: mediated by transporter in rainbow trout (Oncorhynchus mykiss), but only by diffusion in prespawning lamprey (Lampetra fluviatilis) and in RTH-149 cell line

The transport of D-glucose into rainbow trout (Oncorhynchus mykiss) and river lamprey (Lampetra fluviatilis) hepatocytes, as well as into rainbow trout hepatoblastoma cell line RTH-149 was studied using tracer methods. The half-time for D-glucose equilibration was 15 s for rainbow trout. The half-times for the non-metabolizable D-glucose analog, 3-O-methyl-D-glucose equilibration were 8 s, 37 s and 38 s for rainbow trout, lamprey and RTH-149 cells, respectively. The 3-O-methyl-D-glucose was taken up by rainbow trout hepatocytes by facilitated diffusion in addition to simple diffusion. The uptake showed saturation kinetics with the K(m) of 37 mM and V(max) of 62 mmol kg(-1) cells min(-1). The uptake was sensitive to phloretin and cytochalasin B, but not affected by ouabain. The 3-O-methyl-D-glucose uptake by lamprey hepatocytes and RTH-149 cells showed no indication of saturation up to 160 mM, and was not affected by phloretin, cytochalasin B or ouabain, which suggests the mode of transport to be by passive diffusion. However, immunocytochemical stainings revealed the existence of mammalian type GLUT1 and GLUT2 transporters in all cells studied. The lack of a functioning carrier-mediated glucose uptake in lamprey hepatocytes might be due to its physiological state (prespawning starvation). The minor 3-O-methyl-D-glucose uptake into RTH-149 cells compared to freshly isolated rainbow trout hepatocytes might reflect low metabolic activity of the cell lines. Under the conditions applied the RTH-149 cell line is no suitable in vitro model for glucose transport in fish cells.

Toxicity of selected cationic drugs in retinoblastomal cultures and in cocultures of retinoblastomal and retinal pigment epithelial cell lines

Tamoxifen and toremifene are antiestrogenic drugs successfully used in the therapy of breast cancer. Rheumatoid arthritis and malaria have been treated with chloroquine for decades. Unfortunately, tamoxifen and chloroquine are reported to induce retinal changes as a side effect. We now studied the effects of tamoxifen, toremifene, and chloroquine on the viability of the human retinoblastomal cell line Y79, using the WST-1 test or measurement of the cellular ATP content. The studies were made on Y79 cell cultures and on cocultures of Y79 cells and retinal pigment epithelial cell line ARPE-19. The cocultures were used to clarify the effect of retinal pigment epithelium on toxicity to Y79 cells. In the coculture, the drugs were applied to ARPE-19 cells growing in the culture inserts on top of Y79 cells and the viability of ARPE-19 and Y79 cells was assessed separately. Tamoxifen, toremifene, and chloroquine reduced dose-dependently the viability of Y79 cells after 24-h exposure. The ARPE-19 cells proved to be protective after chloroquine exposure in the coculture. The results shed light on the toxicity of tamoxifen and chloroquine in Y79 cells in vitro. With the coculture we were able to simulate the in vivo route of chloroquine to the retina via the retinal pigment epithelium.

Modulation of glucose uptake in glial and neuronal cell lines by selected neurological drugs

Glucose is the main energy source of brain cells. The transport of glucose across the cell membrane is the first step of its utilization. Any modification in glucose uptake capacity may cause deleterious effects on neural cell functions. In the present study, 3-O-methyl-D-glucose (3-OMG) uptake and its modulation by selected neurological drugs (amitriptyline, selegiline, carbamazepine and phenytoin) were studied in differentiated (with retinoic acid and 12-O-tetradecanoyl phorbol 13-acetate) and undifferentiated neuroblastoma SH-SY5Y and astrocytoma U-373 MG cell lines, using tracer methods. The expression of glucose transporters was studied by immunocytochemistry. SH-SY5Y and U-373 MG cells showed differences both in their glucose uptake properties and in the modulation of glucose uptake by the drugs, which might reflect different specialization of neuronal and glial cells in vivo. While selegiline and amitriptyline had a minor and variable effect on 3-OMG uptake in all cell cultures, the anticonvulsants carbamazepine and phenytoin increased 3-OMG uptake in U-373 MG cells, but decreased that in SH-SY5Y cells. Differentiated SH-SY5Y cells were more sensitive to the effects of the anticonvulsants than undifferentiated SH-SY5Y cells. The results suggest that, the cell lines are promising neural models for the evaluation of drug side effects due to disturbances in glucose uptake.

Development of an in vitro blood–brain barrier model—cytotoxicity of mercury and aluminum

In this study, in vitro blood-brain barrier (BBB) models composed of two different cell types were compared. The aim of our study was to find an alternative human cell line that could be used in BBB models. Inorganic and organic mercury and aluminum were studied as model chemicals in the testing of the system. BBB models were composed of endothelial RBE4 cell line or retinal pigment epithelial (RPE) cell line ARPE-19 and neuronal SH-SY5Y cells as target cells. Glial U-373 MG cells were included in part of the tests to induce the formation of a tighter barrier. Millicell CM filter inserts were coated with rat-tail collagen, and RBE4 or ARPE-19 cells were placed on the filters at the density of 3.5-4 x 10(5) cells/filter. During culture, the state of confluency was microscopically observed and confirmed by the measurement of electrical resistance caused by the developing cell layer. The target cells, SH-SY5Y neuroblastoma cells, were plated on the bottom of cell culture wells at the density of 100000 cells/cm(2). In part of the studies, glial U-373 MG cells were placed on the under side of the membrane filter. When confluent filters with ARPE-19 or RBE4 cells were placed on top of the SH-SY5Y cells, different concentrations of mercuric chloride, methyl mercury chloride, and aluminum chloride were added into the filter cups along with a fluorescent tracer. Exposure time was 24 h, after which the cytotoxicity in the SH-SY5Y cell layer, as well as in the ARPE-19 or RBE4 cell layer, was evaluated by the luminescent measurement of total ATP. The leakage of the fluorescent tracer was also monitored. The results showed that both barrier cell types were induced by glial cells. Inorganic and organic mercury caused a leakage of the dye and cytotoxicity in SH-SY5Y cells. Especially, methyl mercury chloride could exert an effect on target cells before any profound cytotoxicity in barrier cells could be seen. Aluminum did not cause any leakage in the barrier cell layer, and even the highest concentration (1 mM) of aluminum did not cause any cytotoxicity in the SH-SY5Y cells. In conclusion, BBB models composed of RBE4 and ARPE-19 cells were able to distinguish between different toxicities, and ARPE-19 cells are thus promising candidates for studies of drug penetration through the blood-brain barrier.

Glutamate uptake is inhibited by tamoxifen and toremifene in cultured retinal pigment epithelial cells

The systemic drugs chloroquine and tamoxifen have caused retinal defects in human eye. The aim of our study was to investigate the effects of the amphiphilic drug tamoxifen, of its homologue toremifene, and of chloroquine on the glutamate uptake in retinal pigment epithelial (RPE) cells. Cultured human RPE cell line D407 and pig RPE cells were used in the study. Glutamate uptake was characterised and the glutamate transporters of pig RPE cells and the human RPE cell line D407 were compared to each other. The uptake of glutamate was studied using L-[3H]glutamate as a tracer. The radioactivity in the solubilised RPE was measured with a liquid scintillation counter. In the uptake experiments, the cells were exposed to the test drugs, to the selected glutamate receptor antagonists, and to the glutamate transporter inhibitors. Both RPE cell types exhibited a high-affinity transport system for glutamate. The glutamate transporter in RPE exhibited features characteristic of the uptake systems of neurotransmitters. The transport was Na+-dependent, and L- and D-aspartate were transported into the cell by the same transporter. Chloroquine had no effect on glutamate uptake, but tamoxifen and toremifene decreased the glutamate uptake of RPE cells dose-dependently both in pig RPE cells and in human RPE cell line. The IC50 values of tamoxifen and toremifene were lower for pig RPE cells, compared to the human RPE cell line D407. The glutamate uptake was a sensitive target for the effects of tamoxifen and toremifene, and disturbances in this function could be considered as one of the possible mechanisms of retinal defects.

Evaluation of the cytotoxicity of selected systemic and intravitreally dosed drugs in the cultures of human retinal pigment epithelial cell line and of pig primary retinal pigment epithelial cells

The cytotoxicity of the selected systemic and intravitreally dosed drugs tamoxifen, toremifene, chloroquine, 5-fluorouracil, gentamicin and ganciclovir was studied in retinal pigment epithelium (RPE) in vitro. The cytotoxicity was assayed in the human RPE cell line D407 and the pig RPE cell culture using the WST-1 test, which is an assay of cell proliferation and viability. The effects of experimental conditions on the WST-1 test (cell density, serum content in the culture medium, the exposure time) were evaluated. The EC50 values in tamoxifen-treated D407 cells ranged between 6.7 and 8.9 micromol/l, and in pig RPE cells between 10.1 and 12.2 micromol/l, depending on the cell density used. The corresponding values for toremifene were 7.4 to 11.1 micromol/l in D407 cells and 10.0 to 11.6 micromol/l in pig RPE cells. In chloroquine-treated cells, the EC50 values were 110.0 micromol/l for D407 cells and 58.4 micromol/l for pig RPE cells. Gentamicin and ganciclovir did not show any toxicity in micromolar concentrations. The exposure time was a significant factor, especially when the drug did not induce cell death, but was antiproliferative (5-fluorouracil). Serum protected the cells from the toxic effects of the drugs. Both cell cultures were most sensitive to tamoxifen and toremifene, and next to chloroquine. The drug toxicities obtained in the present study were quite similar in both cell types; that is, the pig RPE cells and the human D 407 cell line, despite the differences in, for example, the growth rate and melanin contents of the cell types. Owing to the homeostatic functions important for the whole neuroretina, RPE is an interesting in vitro model for the evaluation of retinal toxicity, but, in addition to the WST-1 test, more specific tests and markers based on the homeostatic functions of the RPE are needed.

Comparison of an immortalized human corneal epithelial cell line and rabbit corneal epithelial cell culture in cytotoxicity testing

The cytotoxicity of benzalkonium chloride (BAC) and disodium edetate (EDTA) was evaluated in vitro in rabbit corneal epithelial primary cells and in the immortalized human corneal epithelial cell line SV40. Cell injury was assessed by lactate dehydrogenase (LDH) leakage and by reduction of the tetrazolium salt WST-1 to formazan by mitochondrial metabolic activity. Cell cultures were exposed to test compounds both in serum-free and in serum-containing medium. Although WST-1 and LDH tests measured different physiological endpoints, they yielded comparable results. However, the LDH test seemed less reliable due to great variation. The use of serum was found to result in lower toxicity of the compounds in both tests. The rabbit primary cell culture and the human corneal cell line were quite similar in their responses to BAC and EDTA. The human cell line is a promising in vitro alternative in oculotoxicity testing.

The phagocytosis of rod outer segments is inhibited by selected drugs in retinal pigment epithelial cell cultures

The effects of tamoxifen, toremifene and chloroquine on the phagocytosis of rod outer segments by retinal pigment epithelium were evaluated in human retinal pigment epithelial cell line D407 and pig retinal pigment epithelial cell culture. Retinal pigment epithelial cells were exposed to different concentrations of tamoxifen (1-20 microM), toremifene (1-20 microM) and chloroquine (1-1000 microM), and challenged with FITC-labeled rod outer segments for 24 hr. The phagocytized (bound and ingested) rod outer segments were measured fluorometrically, and the effect of the drugs on the phagocytosis was determined. The cytotoxicity of the drugs was evaluated by measuring their effects on mitochondrial enzyme activities (WST-1-test). The results showed that the test compounds inhibited the phagocytosis of rod outer segments in both D407 and pig retinal pigment epithelial cells. The phagocytic activity was more sensitive to tamoxifen (EC(50) 7.2 microM for D407 cells and 3.6 microM for pig retinal pigment epithelial cells) and toremifene (EC(50) 6.2 microM and 3.1 microM respectively) than to chloroquine (EC(50) 77.2 microM for D407 cells). The inhibition of rod outer segment phagocytosis in both cell cultures started at lower dose levels of test compounds than the cytotoxicity indicated by the WST-1-test. The experiments were carried out both in serum-free medium and serum-containing medium. Serum seemed to be a critical factor in the medium and caused difficulties in the interpretation of the results.