Chronic exposure of human glioblastoma tumors to low concentrations of a pesticide mixture induced multidrug resistance against chemotherapy agents

Glyphosate-based herbicide as a potential risk factor for breast cancer

Breast cancer is the most common neoplasm in women worldwide, with both genetic and environmental factors playing a role in its development. Glyphosate, the active ingredient in widely used agricultural herbicides, is recognized as a potential carcinogen and endocrine disruptor, making it a candidate for inducing epigenetic modifications linked to breast cancer. This study investigates the effects of the glyphosate-based herbicide Roundup® on non-tumorigenic (MCF10A) and tumorigenic (MCF7 and MDA-MB-231) breast cell lines, focusing on the expression of key breast cancer-related genes. Additionally, the study examines the association with epigenetic modifications and the use of epidrugs to reverse potential alterations, aiming to understand the risks and mechanisms of herbicide action. Results indicate that Roundup® affects cells through a non-estrogenic mechanism, impacting both hormone-dependent and -independent cells with varying toxic and proliferative effects depending on dose and exposure time. Moreover, it altered the expression of breast cancer-related genes such as BRCA1 and BRCA2 at low doses. The use of epigenetic modulators was able to reverse some Roundup®-induced changes, suggesting the herbicide's role in epigenetic modifications. Overall, these findings highlight the importance of understanding glyphosate-based herbicide mechanisms in humans, which could enable personalized prevention strategies to mitigate breast cancer risks.

Extended sub-chronic exposure to heavy metal mixture induced multidrug resistance against chemotherapy agents in ovarian cancer cells

Recent scientific findings suggest that persistent, minimal quantity exposure to heavy metals combinations can instigate negative reactions across various cell types, tissues, and organs. However, the interplay between heavy metals present in blood and cancerous cells remains largely unclear. We aimed to examine the capability of a Pb, Cd, and Co at very low concentrations blend to trigger multidrug resistance against chemotherapeutic remedies such as cisplatin, 5-fluorouracil, and doxorubicin in the NIH-Ovcar3 human ovarian cancer cell line. Additionally, we sought to dissect the molecular mechanisms bolstering this resistance. Our results illustrate that consistent administration of the heavy metal mixture at extraordinarily low concentrations fosters pronounced chemotherapy resistance in Ovcar3 cells via cross resistance. This resistance endured and was propagated through ensuing cell generations. We observed that ATP-binding cassette (ABC) membrane transporters, specifically P-gp/ABCB1, BRCP/ABCG2, and ABCC1-type cellular detoxification functions, were markedly overexpressed, playing a crucial role in multidrug resistance. This finding supports the molecular evidence of the acquired multidrug resistance phenotype and provides preliminary insights into the potential resistance mechanism. We also found decreased mortality rates in the resistant ovarian cancer cells, with the mitochondrial apoptosis pathway activating at a reduced rate post-chemotherapy relative to the non-resistant control cells. Furthermore, multidrug-resistant cells exhibited increased motility and enhanced wound-healing abilities, hinting at a higher metastatic potential. These findings suggest that analysing P-gp, BRCP, and ABCC1 multidrug resistance gene expression and/or protein levels within biopsy samples from ovarian cancer patients at risk of heavy metal exposure could prove advantageous in determining chemotherapy dosage and prolonging patient lifespan.

Significance of GSTM1 and GSTT1 Gene Deletions in Glioma Patients in Polish Population: Pilot Study

Background

Detoxification enzymes of the glutathione S-transferase (GST) family are cytosolic phase II detoxification enzymes and play an important role in the normal functioning of the human antioxidant system. When the normal function of GST is disturbed or absent, there can be disturbances in cell metabolism, proliferation, and apoptosis. Deletions in the GSTM1 and GSTT1 genes have been observed in several different diseases as well as in the development of cancer. There is a need to analyze the relationship between glioma and GSTM1 and GSTT1 gene deletion to better understand the relationship between brain tumors and GST polymorphisms, which is crucial for adopting a multidisciplinary approach to prognosis and treatment of brain tumors.

Methods

In a cross-sectional clinical-laboratory study, gene deletions were examined in 34 patients with brain tumors originating from glial cells-gliomas and 88 healthy individuals. All participants were of Polish nationality and were not related.

Results

An increase in GSTM1 and GSTT1 gene deletions was observed in glioma patients compared with the control group. The greatest increase showing a marked rise of 10 times (11.8% vs 1.14%, P < .05) is in the null genotype of both genes (GSTM1-/GSTT1) [odds ratio [OR] = 0.86; 95% confidence interval [CI] = 0.09-0.802] but less in the genotype with deletion of 1 GST gene (GSTM1-/GSTT1+ and GSTM1+/GSTT1-). In addition, the findings indicated a decrease in the non-deletion genotype of both genes (GSTM1+/GSTT1+) in healthy individuals. This study showed a higher frequency of GST gene deletion in glioma patients in the studied population.

Conclusions

Based on the obtained findings, it can be said that the examination of the selected detoxification enzymes can be a useful marker in the diagnosis of glioblastoma.

Long-term chronic exposure to benzo[a]pyrene and catechol induced multidrug resistance in lung cancer cells

Multiple studies have raised concerns about the impact of long-term exposure to environmental pollutants on the occurrence and progression of cancer, but little is known about how these compounds affect the treatment of cancer patients. In this work, two common pollutants including benzo [a]pyrene (B [a]P) and catechol (CL) were tested for their chronic effects on the efficacy of common chemotherapeutic drug in lung cancer (A549) cells. Both pollutants were unlikely to be the substrates of ABC transporters, as their toxicity was unaffected by ABC transporter inhibitors. However, their repeated exposure led to the generation of chemoresistance to doxorubicin (DOX) and cisplatin (CDDP), indicating the formation of multidrug-resistance (MDR) cells. Compared with DOX-resistant cells, decreased expression of ABC transporters but increased responses were found in pollutants-resistant cells. In addition, pollutants-resistant cells were more potent in up-regulating anti-apoptosis, proliferation, and migration pathways, which were confirmed by the wound-healing and apoptosis assays. Overall, these results indicated a distinct MDR mechanism induced by non-substrate pollutants, and could be beneficial for understanding the environmental risk of pollutants in their "safe" concentrations.

Overview of human health effects related to glyphosate exposure

Glyphosate is a chemical compound derived from glycine, marketed as a broad-spectrum herbicide, and represents one of the most widely used pesticides in the world. For a long time, it was assumed that glyphosate was harmless, either due to its selective enzymatic acting method on plants, and because commercial formulations were believed to contain only inert chemicals. Glyphosate is widely spread in the environment, the general population is daily exposed to it via different routes, including the consumption of both plant, and non-plant based foods. Glyphosate has been detected in high amounts in workers' urine, but has been detected likewise in bodily fluids, such as blood and maternal milk, and also in 60%-80% of general population, including children. Considering its massive presence, daily exposure to glyphosate could be considered a health risk for humans. Indeed, in 2015, the IARC (International Agency for Research on Cancer) classified glyphosate and its derivatives in Group 2A, as probable human carcinogens. In 2022, nevertheless, EFSA (European Food Safety Authority) stated that the available data did not provide sufficient evidence to prove the mutagenic/carcinogenic effects of glyphosate. Therefore, the European Commission (EC) decided to renew the approval of glyphosate for another 10 years. The purpose of this review is to examine the scientific literature, focusing on potential risks to human health arising from exposure to glyphosate, its metabolites and its commercial products (e.g., Roundup®), with particular regard to its mutagenic and carcinogenic potential and its effects as endocrine disrupter (ED) especially in the human reproductive system.

Glyphosate modifies the gene expression and migration of trophoblastic cells without altering the process of angiogenesis or the implantation of blastocysts in vitro

Adverse pregnancy outcomes have been associated with the presence of glyphosate (G) in umbilical cord, serum, and urine samples from pregnant women. Our aim was to study the effect of G on blastocyst implantation using an in vitro mouse model, and the migration and acquisition of endothelial phenotype of the human trophoblastic HTR8/SVneo (H8) cells. In mouse blastocysts, no differences in attachment time and implantation outgrowth area were observed after G exposure. H8 cell migration was stimulated by 0.625 μM G without cytotoxicity. After 6 h, the mRNA expression of vascular endothelial growth factor (VEGF) and C-C motif chemokine ligand 2 (CCL2) was upregulated in H8 cells exposed to 1.25 μM G when compared vehicle-treated cells (p ≤ 0.05). No differences were observed in interleukin 11, VEGF receptor 1, and coagulation factor II thrombin receptor in H8 cells exposed to different concentrations of G for 6 h compared to the vehicle. Interestingly, exposure to G did not alter angiogenesis as measured by a tube formation assay. Taken all together, these results suggest that G exposure may contribute as a risk factor during pregnancy, due to its ability to alter trophoblast migration and gene expression.

Glyphosate-induced glioblastoma cell proliferation: Unraveling the interplay of oxidative, inflammatory, proliferative, and survival signaling pathways

The aim of the present study was to investigate the impacts of glyphosate herbicide on the survival and proliferation of glioblastoma cells and to explore the molecular mechanisms underlying such effects. For this, cultured human glioblastoma cell line, A172, was exposed to the glyphosate analytical standard, a glyphosate-based herbicide formulation (GBH), or the metabolite aminomethylphosphonic acid (AMPA). The three compounds induced A172 cytotoxicity after 24 h of exposure, with more prominent cytotoxic effects after 48 and 72 h of treatment. Further experiments were performed by treating A172 cells for 6 h with glyphosate, GBH, or AMPA at 0.5 mg/L, which corresponds to the maximum residue limits for glyphosate and AMPA in drinking water in Brazil. Colony forming units (CFU) assay showed that AMPA increased the number of CFU formed, while glyphosate and GBH increased the CFU sizes. The three compounds tested altered the cell cycle and caused DNA damage, as indicated by the increase in γ-H2AX. The mechanisms underlying the pesticide effects involve the activation of Akt and mitogen-activated protein kinases (MAPKs) signaling pathways, oxidative imbalance, and inflammation. Glyphosate led to NLRP3 activation culminating in caspase-1 recruitment, while AMPA decreased NLRP3 immunocontent and GBH did not alter this pathway. Results of the present study suggest that exposure to glyphosate (isolated or in formulation) or to its metabolite AMPA may affect cell signaling pathways resulting in oxidative damage and inflammation, giving glioblastoma cells an advantage by increasing their proliferation and growth.

Pesticides and Bladder Cancer: Mechanisms Leading to Anti-Cancer Drug Chemoresistance and New Chemosensitization Strategies

Multiple risk factors have been associated with bladder cancer. This review focuses on pesticide exposure, as it is not currently known whether agricultural products have a direct or indirect effect on bladder cancer, despite recent reports demonstrating a strong correlation. While it is known that pesticide exposure is associated with an increased risk of bladder cancer in humans and dogs, the mechanism(s) by which specific pesticides cause bladder cancer initiation or progression is unknown. In this narrative review, we discuss what is currently known about pesticide exposure and the link to bladder cancer. This review highlights multiple pathways modulated by pesticide exposure with direct links to bladder cancer oncogenesis/metastasis (MMP-2, TGF-β, STAT3) and chemoresistance (drug efflux, DNA repair, and apoptosis resistance) and potential therapeutic tactics to counter these pesticide-induced affects.

Nanopesticides in comparison with agrochemicals: Outlook and future prospects for sustainable agriculture

Agrochemicals are products of advanced technologies that use inorganic pesticides and fertilizers. Widespread use of these compounds has adverse environmental effects, leading to acute and chronic exposure. Globally, scientists are adopting numerous green technologies to ensure a healthy and safe food supply and a livelihood for everyone. Nanotechnologies significantly impact all aspects of human activity, including agriculture, even if synthesizing certain nanomaterials is not environmentally friendly. Numerous nanomaterials may therefore make it easier to create natural insecticides, which are more effective and environmentally friendly. Nanoformulations can improve efficacy, reduce effective doses, and extend shelf life, while controlled-release products can improve the delivery of pesticides. Nanotechnology platforms enhance the bioavailability of conventional pesticides by changing kinetics, mechanisms, and pathways. This allows them to bypass biological and other undesirable resistance mechanisms, increasing their efficacy. The development of nanomaterials is expected to lead to a new generation of pesticides that are more effective and safer for life, humans, and the environment. This article aims to express at how nanopesticides are being used in crop protection now and in the future. This review aims to shed some light on the various impacts of agrochemicals, their benefits, and the function of nanopesticide formulations in agriculture.

Nanoparticle-induced chemoresistance: the emerging modulatory effects of engineered nanomaterials on human intestinal cancer cell redox metabolic adaptation

The widespread use of engineered nanomaterials (ENMs) in food products necessitates the understanding of their impact on the gastrointestinal tract (GIT). Herein, we screened several representative food-borne comparator ENMs (i.e. ZnO, SiO₂ and TiO₂ nanoparticles (NPs)) and report that human colon cancer cells can insidiously exploit ZnO NP-induced adaptive response to acquire resistance against several chemotherapeutic drugs. By employing a conditioning and challenge treatment regime, we demonstrate that repeated exposure to a non-toxic dose of ZnO NPs (20 μM) could dampen the efficacy of cisplatin, paclitaxel and doxorubicin by 10-50% in monolayer culture and 3D spheroids of human colon adenocarcinoma cells. Structure-activity relationship studies revealed a complex interplay between nanoparticle surface chemistry and cell type in determining the chemoresistance-inducing effect, with silica coated ZnO NPs having a negligible influence on the anticancer treatment. Mechanistically, we showed that the pro-survival paracrine signaling was potentiated and propagated by a subset of ZnO NP "stressed" (Zn²⁺+/ROS+) cells to the surrounding "bystander" (Zn²⁺+/ROS-) cells. Transcriptome profiling, bioinformatics analysis and siRNA gene knockdown experiments revealed the nuclear factor erythroid 2-related factor 2 (Nrf2) as the key modulator of the ZnO NP-induced drug resistance. Our findings suggest that a ROS-inducing ENM can emerge as a nano-stressor, capable of regulating the chemosensitivity of colon cancer cells.

Tumor spheroids accelerate persistently invading cancer cells

Glioblastoma brain tumors form in the brain’s white matter and remain one of the most lethal cancers despite intensive therapy and surgery. The complex morphology of these tumors includes infiltrative growth and gain of cell motility. Therefore, various brain-mimetic model systems have been developed to investigate invasion dynamics. Despite this, exactly how gradients of cell density, chemical signals and metabolites influence individual cells’ migratory behavior remains elusive. Here we show that the gradient field induced by the spheroid—accelerates cells’ invasion of the extracellular matrix. We show that cells are pushed away from the spheroid along a radial gradient, as predicted by a biased persistent random walk. Thus, our results grasp in a simple model the complex behavior of metastasizing cells. We anticipate that this well-defined and quantitative assay could be instrumental in the development of new anti-cancer strategies.

Characterization and comparison of human glioblastoma models

Glioblastoma (GBM) is one of the deadliest cancers. Treatment options are limited, and median patient survival is only several months. Translation of new therapies is hindered by a lack of GBM models that fully recapitulate disease heterogeneity. Here, we characterize two human GBM models (U87-luc2, U251-RedFLuc). In vitro, both cell lines express similar levels of luciferase and show comparable sensitivity to temozolomide and lapatinib exposure. In vivo, however, the two GBM models recapitulate different aspects of the disease. U87-luc2 cells quickly grow into large, well-demarcated tumors; U251-RedFLuc cells form small, highly invasive tumors. Using a new method to assess GBM invasiveness based on detecting tumor-specific anti-luciferase staining in brain slices, we found that U251-RedFLuc cells are more invasive than U87-luc2 cells. Lastly, we determined expression levels of ABC transporters in both models. Our findings indicate that U87-luc2 and U251-RedFLuc GBM models recapitulate different aspects of GBM heterogeneity that need to be considered in preclinical research.

Epidemiology of Glioblastoma Multiforme-Literature Review

Glioblastoma multiforme (GBM) is one of the most aggressive malignancies, with a median overall survival of approximately 15 months. In this review, we analyze the pathogenesis of GBM, as well as epidemiological data, by age, gender, and tumor location. The data indicate that GBM is the higher-grade primary brain tumor and is significantly more common in men. The risk of being diagnosed with glioma increases with age, and median survival remains low, despite medical advances. In addition, it is difficult to determine clearly how GBM is influenced by stimulants, certain medications (e.g., NSAIDs), cell phone use, and exposure to heavy metals.

Stress-induced miRNAs isolated from wheat have a unique therapeutic potential in ultraviolet-stressed human keratinocyte cells

Increasing evidence supports the existence of cross-kingdom gene regulation. However, the therapeutic potential of stress-specific plant miRNAs and their role in UV-related pathologies in human tissue remain largely unexplored. The aim of this study was to investigate the therapeutic potential and mechanisms of action of stress-induced miRNA cocktails (SI-WmiRs) from Einkorn wheat (Triticum monococcum L.) on human keratinocyte (HaCaT) cells exposed to a high dose of UV-B radiation. We used a biofactory approach and irradiated wheatgrass with UV-C for 240 min to obtain the specific SI-WmiRs that wheat produces to recover from UV stress. We followed the plant with molecular and biochemical analyses and extracted our SI-WmiRs at the most appropriate time (0 h and 6 h after UV-C application). Then, we applied the SI-WmiR cocktail to HaCaT cells exposed to high-dose of UV-B radiation. Our results show that UV-B radiation induced lipid peroxidation and DNA damage, as demonstrated by increased malondialdehyde (MDA) levels and changes in the RAPD band profile, respectively. UV stress also impaired IL6/JAK2/STAT3 signalling and activated the inflammatory mediators IL6 and TNF-α in HaCaT cells, leading to significant induction of apoptotic cell death. We found that SI-WmiR transfection prevents lipid peroxidation and oxidative stress-related DNA damage by increasing antioxidant (CuZn-SOD, Mn-SOD) and DNA repair (EXO1, SMUG1 and XRCC3) gene expression. In addition, SI-WmiRs regulated IL6/JAK2/STAT3 signalling by reducing JAK2 and STAT3 gene expression and phosphorylated protein levels compared to the control treatments. Moreover, SI-WmiRs inhibited pro-apoptotic BAX, Caspase 3 and Caspase 8 gene expression and protein levels to prevent apoptosis of UV-stressed HaCaT cells. Our results demonstrate that stress-induced wheat miRNAs produced using a biofactory approach have strong potential as a novel and effective alternative therapy for UV stress-related skin damage.

Pleiotropic Outcomes of Glyphosate Exposure: From Organ Damage to Effects on Inflammation, Cancer, Reproduction and Development

Glyphosate is widely used worldwide as a potent herbicide. Due to its ubiquitous use, it is detectable in air, water and foodstuffs and can accumulate in human biological fluids and tissues representing a severe human health risk. In plants, glyphosate acts as an inhibitor of the shikimate pathway, which is absent in vertebrates. Due to this, international scientific authorities have long-considered glyphosate as a compound that has no or weak toxicity in humans. However, increasing evidence has highlighted the toxicity of glyphosate and its formulations in animals and human cells and tissues. Thus, despite the extension of the authorization of the use of glyphosate in Europe until 2022, several countries have begun to take precautionary measures to reduce its diffusion. Glyphosate has been detected in urine, blood and maternal milk and has been found to induce the generation of reactive oxygen species (ROS) and several cytotoxic and genotoxic effects in vitro and in animal models directly or indirectly through its metabolite, aminomethylphosphonic acid (AMPA). This review aims to summarize the more relevant findings on the biological effects and underlying molecular mechanisms of glyphosate, with a particular focus on glyphosate's potential to induce inflammation, DNA damage and alterations in gene expression profiles as well as adverse effects on reproduction and development.

Prolonged sub-lethal exposure to galaxolide (HHCB) and tonalide (AHTN) promotes the metastatic potential of glioblastoma tumor spheroids

Galaxolide and tonalide are well-known polycyclic musks whose intensive use without limitations in numerous cleaning, hygiene, and personal care products has resulted in widespread direct human exposure via absorption, inhalation, and oral ingestion. Latest data shows that long-term, low-dose exposure to toxic chemicals can induce unpredictable harmful effects in a variety of living systems, however, interactions between synthetic musks and brain tumours remain largely unexplored. Glioblastoma (GB) accounts for nearly half of all tumours of the central nervous system and is characterized by very poor prognosis. The aims of this study were (1) to investigate the potential effect of long-term (20-generation) single and combined application of galaxolide and tonalide at sub-lethal doses (5-2.5 u M) on the angiogenesis, invasion, and migration of human U87 cells or tumour spheroids, and (2) to explore the underlying molecular mechanisms. Random amplified polymorphic DNA assays revealed significant DNA damage and increased total mutation load in galaxolide- and/or tonalide-treated U87 cells. In those same groups, we also detected remarkable tumour spheroid invasion and up-regulation of both HIF1-α/VEGF/MMP9 and IL6/JAK2/STAT3 signals, known to have important roles in hypoxia-related angiogenesis and/or proliferation. Prolonged musk treatment further altered angio-miRNA expression in a manner consistent with poor prognosis in GB. We also detected significant over-expression of the genes Slug, Snail, ZEB1, and Vimentin, which are biomarkers of epithelial to mesenchymal transition. In addition, matrigel, transwell, and wound healing assays clearly showed that long-term sub-lethal exposure to galaxolide and/or tonalide induced invasion and migration proposing a high metastatic potential. Our results suggest that assessing expression of HIF-1a, VEGF, STAT3, and the miR-17-92 cluster in biopsy samples of GB patients who have a history of possible long-term exposure to galaxolide or tonalide could be beneficial for deciding a therapy regime. Additionally, we recommend that extensively-used hygiene and cleaning materials be selected from synthetic musk-free products, especially when used in palliative care processes for GB patients.

The role of melatonin in angio-miR-associated inhibition of tumorigenesis and invasion in human glioblastoma tumour spheroids

Micro-RNA (miRNA)-based regulation of hypoxia, angiogenesis and tumour growth provides promising targets for effective therapy in malignant glioblastoma multiforme (GBM). Accumulating evidence suggests a potential role of melatonin in miRNA expression in cancer cells. Despite these findings, the melatonin-miRNA interaction in GBM and the effect of this interaction on GBM tumour development and invasion are not clearly understood. The aim of the present study was to evaluate the effects of melatonin on human GBM tumour spheroid tumorigenesis and invasion in vitro, and to analyse the interaction between 36 angio-miRNAs and the HIF1/VEGF/MMP9 axis, which is known to be associated with the antitumour effect of melatonin. We found that melatonin is able to selectively induce cell death in single-layer U87-MG cells (a GBM cell line) in a dose- and time-dependent manner, as characterized by MTT assay. The use of tumour spheroids and a Matrigel invasion assay revealed that melatonin impairs tumorigenesis, and it significantly reduced both the tumour spheroid area and invasion rate, especially at the 0.5 mM and 1 mM concentrations. This inhibition was accompanied by strong reductions in hypoxia-inducible factor 1-α (HIF1-α) and vascular endothelial growth factor (VEGF) gene expression and protein levels in GBM tumour spheroids. In addition, melatonin significantly reduced the relative gene expression and protein levels of matrix metalloproteinase-9 (MMP-9). This study revealed that six differentially expressed angio-miRs (miR-15b, miR-18a-5p, miR-23a-3p, miR-92a-3p, miR-130a-5p, miR-200b-3p) may play important roles in GBM tumorigenesis and invasion, and all respond to melatonin therapy. Our results suggest that melatonin inhibits tumorigenesis and invasion of human GBM tumour spheroids, possibly by suppressing HIF1-α/VEGF/MMP9 signalling via regulation of angio-miRNAs.

Melatonin prevents blood-retinal barrier breakdown and mitochondrial dysfunction in high glucose and hypoxia-induced in vitro diabetic macular edema model

Diabetic macular edema (DME) is a leading cause of blindness in diabetic retinopathy. Prolonged hyperglycemia plus hypoxia contributes to DME pathogenesis. Retinal pigmented epithelial cells comprise the outer blood-retinal barrier and are essential for maintaining physiological functioning of the retina. Melatonin acts as an antioxidant and regulator of mitochondrial bioenergetics and has a protective effect against ocular diseases. However, the role of mitochondrial dysfunction and the therapeutic potential of melatonin in DME remain largely unexplored. Here, we used an in vitro model of DME to investigate blood-retinal barrier integrity and permeability, angiogenesis, mitochondrial dynamics, and apoptosis signaling to evaluate the potential protective efficacy of melatonin in DME. We found that melatonin prevents cell hyper-permeability and outer barrier breakdown by reducing HIF-1α, HIF-1β and VEGF and VEGF receptor gene expression. In addition, melatonin reduced the expression of genes involved in mitochondrial fission (DRP1, hFis1, MIEF2, MFF), mitophagy (PINK, BNip3, NIX), and increased the expression of genes involved in mitochondrial biogenesis (PGC-1α, NRF2, PPAR-γ) to maintain mitochondrial homeostasis. Moreover, melatonin prevented apoptosis of retinal pigmented epithelial cells. Our results suggest that mitochondrial dysfunction may be involved in DME pathology, and melatonin may have therapeutic value in DME, by targeting signaling in mitochondria.