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Here, one hundred patients (50 smokers and 50 non-smokers) clinically diagnosed with COVID-19 were studied. Yet, bioinformatics was used to predict epitopes on Tobacco mosaic virus coat protein (TMV-CP) to produce antibodies towards SARS-CoV-2. Death was three times higher in non-smokers than in smokers. However, biochemical parameters did not separate the groups. Bioinformatics analysis predicted the presence of B-cell epitopes in TMV-CP, suggesting the production of antibodies anti-TMV-CP in smoker patients. Smokers may develop severe forms of COVID-19, but survival was superior in the evaluated group than in non-smokers. Anti-TMV-CP antibodies, potentially present in smokers, might act as a pro-immune agent against SARS-CoV-2 at earlier stages of infection. These data are helpful for future studies assessing COVID-19 in smokers.

Chronic Myeloid Leukemia (CML) is characterized by the increased and unregulated growth of myeloid cells in bone marrow and accumulation of these cells in blood. Its occurrence during pregnancy is a very rare condition and the correct management is not well stablished yet. We present a case of a 21-year-old female diagnosed with CML during pregnancy. The protocol chose by the doctor was hydroxyurea on second trimester, and interferon-alpha on third trimester. The baby was born healthy and at the expected time. After giving birth, the patient started Imatinib Mesilate (IM) 400mg/day treatment and was able to control the disease.

Aim: This study aimed to analyze the phylogenetic relationships between the ACE2 of humans and other animals and investigate the potential interaction between SARS-CoV-2 RBD and ACE2 of different species. Materials & methods: The phylogenetic construction and molecular interactions were assessed using computational models. Results & conclusion: Despite the evolutionary distance, 11 species had a perfect fit for the interaction between their ACE2 and SARS-CoV-2 RBD ( Chinchilla lanigera, Neovison vison, Rhinolophus sinicus, Emballonura alecto, Saccopteryx bilineata, Numida meleagris). Among them, the avian N. meleagris was reported for the first time in this study as a probable SARS-CoV-2 host due to the strong molecular interactions. Therefore, predicting potential hosts for SARS-CoV-2 for understanding the epidemiological cycle and proposal of surveillance strategies.

The Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) disease has had a catastrophic impact on the world resulting in several deaths. Since World Health Organization declared the pandemic status of the disease, several molecular diagnostic kits have been developed to help the tracking of viruses spread.This review aims to describe and evaluate the currently reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) diagnosis kit. Several processes used in COVID-19 diagnostic procedures are detailed in further depth to demonstrate optimal practices. Therefore, we debate the main factors that influence the viral detection of SARS-COV-2 and how they can affect the diagnosis of patients.Here is highlighted and discussed several factors that can interfere in the RT-PCR analysis, such as the viral load of the sample, collection site, collection methodology, sample storage, transport, primer, and probe mismatch/dimerization in different brand kits. This is a pioneer study to discuss the factor that could lead to the wrong interpretation of RT-qPCR diagnosis of SARS-CoV-2. This study aimed to help the readers to understand what very likely is behind a bad result of SARS-CoV-2 detection by RT-PCR and what could be done to reach a reliable diagnosis.

Cryptococcus neoformans is a multidrug-resistant human pathogenic yeast responsible for infections in immunocompromised patients. Here, Itraconazole (ITR), a commercial antifungal drug with low effectiveness against C. neoformans, was combined with different synthetic peptides Mo-CBP3-PepII, RcAlb-PepII, RcAlb-PepIII, PepGAT, and PepKAA. The mechanisms of action responsible for the synergistic effect were evaluated for the best combinations by Fluorescence Microscopy (FM). The synthetic peptides enhanced the activity of ITR by 10-fold against C. neoformans. Our results demonstrated that the combinations could induce pore formation in the membrane and overaccumulation of ROS on C. neoformans cells. Our findings indicate that our peptides successfully potentialize the activity of ITR by reducing it by 10-fold to reach antifungal activity against C. neoformans. Therefore, synthetic peptides are potential molecules to act as co-adjuvant agents in treating Cryptococcal infections.

Klebsiella pneumoniae is a multidrug-resistant opportunistic human pathogen related to various infections. As such, synthetic peptides have emerged as potential alternative molecules. Mo-CBP3-PepI has presented great activity against K. pneumoniae by presenting an MIC50 at a very low concentration (31.25 µg mL-1). Here, fluorescence microscopy and proteomic analysis revealed the alteration in cell membrane permeability, ROS overproduction, and protein profile of K. pneumoniae cells treated with Mo-CBP3-PepI. Mo-CBP3-PepI led to ROS overaccumulation and membrane pore formation in K. pneumoniae cells. Furthermore, the proteomic analysis highlighted changes in essential metabolic pathways. For example, after treatment of K. pneumoniae cells with Mo-CBP3-PepI, it was seen a reduction in the abundance of protein related to DNA and protein metabolism, cytoskeleton and cell wall organization, redox metabolism, regulation factors, ribosomal proteins, and resistance to antibiotics. These reductions lead to the inhibition of DNA repair, inhibition of cell wall turnover, protein turnover, and ROS accumulation leading to cell death. Our findings indicated that Mo-CBP3-PepI might have mechanisms of action against K. pneumoniae cells, mitigating the development of resistance and thus being a potent molecule to be employed in producing new drugs against K. pneumoniae infections.

Colorectal cancer (CRC) is estimated as the third most incident cancer and second in mortality worldwide. Moreover, CRC metastasis reduces patients' survival rates. Thus, the study and identification of new compounds with anticancer activity selectively to tumor cells are encouraged in the CRC treatment. Naphtoquinones are compounds with several pharmacologic activities, including antitumoral properties. Therefore, this study aimed to investigate the anticancer mechanism of synthetic 8-Hydroxy-2-(P-Nitrothiophenol)-1,4-Naphthoquinone (CNN16) in colon cancer cell line HCT-116. CNN16 showed an IC

Gastric cancer (GC) remains the third leading cause of cancer-related death despite several improvements in targeted therapy. There is therefore an urgent need to investigate new treatment strategies, including the identification of novel biomarkers for patient stratification. In this study, we evaluated the effect of FDA-approved kinase inhibitors on GC. Through a combination of cell growth, migration and invasion assays, we identified dasatinib as an efficient inhibitor of GC proliferation. Mass-spectrometry-based selectivity profiling and subsequent knockdown experiments identified members of the SRC family of kinases including SRC, FRK, LYN and YES, as well as other kinases such as DDR1, ABL2, SIK2, RIPK2, EPHA2, and EPHB2 as dasatinib targets. The expression levels of the identified kinases were investigated on RNA and protein level in 200 classified tumor samples from patients, who had undergone gastrectomy, but had received no treatment. Levels of FRK, DDR1 and SRC expression on both mRNA and protein level were significantly higher in metastatic patient samples regardless of the tumor stage, while expression levels of SIK2 correlated with tumor size. Collectively, our data suggest dasatinib for treatment of GC based on its unique property, inhibiting a small number of key kinases (SRC, FRK, DDR1 and SIK2), highly expressed in GC patients.

Gastric cancer (GC) is among the deadliest cancers worldwide despite available therapies, highlighting the need for novel therapies and pharmacological agents. Metabolic deregulation is a potential study area for new anticancer targets, but the in vitro metabolic studies are controversial, as different ranges of glucose used in the culture media can influence results. In this study, we evaluated cellular viability, glucose uptake, and LDH activity in gastric cancer cell lines when exposed to different glucose concentrations: high (HG, 25mM), low (LG, 5.5mM), and free (FG, 0mM) glucose media. Moreover, we evaluated how glucose variations may influence cellular phenotype and the expression of genes related to epithelial-mesenchymal transition (EMT), metabolism, and cancer development in metastatic GC cells (AGP-01). Results showed that metastatic cells exposed to FG medium evidenced higher alterations when compared to other cell lines. Most phenotypic assays did not show difference when exposed to either HG or LG media. However, gene expression profile of cells exposed to LG revealed differences in mRNA levels of metabolism-related genes when compared to HG medium. According to our results, we recommend using LG medium for metabolic studies since the glucose concentration is closer to physiological levels. These findings point out new relevant targets in metabolic reprogramming that can be alternatives to current chemotherapies in patients with metastatic GC.

Aims Swietenia macrophylla have been considered for the treatment of various diseases, including anticancer activity. This study aimed to investigate the anticancer activity of S. macrophylla leaves extract and its isolated compound towards human colorectal cancer cell line. Main methods Hexanic extract of S. macrophylla leaves demonstrated relevant cytotoxicity only against colon cancer cell line HCT116. Key findings Our results showed significant DNA damage and apoptosis after treatment with the hexanic extract of S. macrophylla. Moreover, no toxicity was noticed for the animal model. The isolated compound limonoid L1 showed potent cytotoxicity against cancer cell lines with IC50 at 55.87 μg mL−1. Limonoid L1 did not trigger any cell membrane rupture in the mice erythrocytes suggesting no toxicity. The antiproliferative effect of L1 was confirmed in colorectal cancer cells by clonogenic assay, inducing G2/M arrest, apoptosis, and DNA damage in cancer-type cells. Significance L1 reduced BCL2 and increased ATM, CHK2, TP53, ARF, CDK1, CDKN1A, and CASP3 in the colorectal cancer cell line. These findings suggest that limonoid L1 isolated from S. macrophylla can be a promising anticancer agent in managing colorectal cancer.

Gastric cancer is one of the most common and deadly types of cancer in the world, and poor prognosis with treatment failure is widely reported in the literature. In this context, kinases have been considered a relevant choice for targeted therapy in gastric cancer. Here, we explore the antiproliferative and antimigratory effects of the AURKA inhibitor and the prognostic and therapeutic value as a biomarker of gastric cancer. A total of 145 kinase inhibitors were screened to evaluate the cytotoxic or cytostatic effects in the gastric cancer cell line. Using the Alamar Blue assay, flow cytometry, quantitative polymerase chain reaction, and observation of caspase 3/7 activity and cell migration, we investigated the antiproliferative, proapoptotic, and antimigratory effects of the AURKA inhibitor. Moreover, AURKA overexpression was evaluated in the gastric cell lines and the gastric tumor tissue. Out of the 145 inhibitors, two presented the highest antiproliferative effect. Both molecules can induce apoptosis by the caspases 3/7 pathway in addition to inhibiting cancer cell migration, mainly the AURKA inhibitor. Moreover, molecular docking analysis revealed that GW779439X interacts in the active site of the AURKA enzyme with similar energy as a well-described inhibitor. Our study identified AURKA overexpression in the gastric cancer cell line and gastric tumor tissue, revealing that its overexpression in patients with cancer is correlated with low survival. Therefore, it is feasible to suggest AURKA as a potential marker of gastric cancer, besides providing robust information for diagnosis and estimated survival of patients. AURKA can be considered a new molecular target used in the prognosis and therapy of gastric cancer.

BACKGROUND/AIM Overexpression of human telomerase reverse transcriptase (hTERT) allows disordered proliferation and immortality of malignant cells, which has been of interest for the development of targeted therapies. The present study aimed to characterize hTERT gene expression in a series of cancer cell lines. MATERIALS AND METHODS Leukemia cell lines K-562, its vincristine-resistant derivative K-562-Lucena1 and daunorubicin-resistant derivative FEPS; gastric adenocarcinoma lines AGP01, ACP02 and ACP03; melanoma SK-Mel-103 cells; and MN01 and MRC5, two non-neoplastic cell lines were analyzed by real-time polymerase chain reaction in order to evaluate hTERT gene expression. RESULTS In leukemia cells, hTERT gene expression was significantly increased only in K-562 (p

Three coronaviruses (CoVs) have threatened the world population by causing outbreaks in the last two decades. In late 2019, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) emerged and caused the coronaviruses to disease 2019 (COVID-19), leading to the ongoing global outbreak. The other pandemic coronaviruses, SARS-CoV and Middle East respiratory syndrome CoV (MERS-CoV), share a considerable level of similarities at genomic and protein levels. However, the differences between them lead to distinct behaviors. These differences result from the accumulation of mutations in the sequence and structure of spike (S) glycoprotein, which plays an essential role in coronavirus infection, pathogenicity, transmission, and evolution. In this review, we brought together many studies narrating a sequence of events and highlighting the differences among S proteins from SARS-CoV, MERS-CoV, and SARS-CoV-2. It was performed here, analysis of S protein sequences and structures from the three pandemic coronaviruses pointing out the mutations among them and what they come through. Additionally, we investigated the receptor-binding domain (RBD) from all S proteins explaining the mutation and biological importance of all of them. Finally, we discuss the mutation in the S protein from several new isolates of SARS-CoV-2, reporting their difference and importance. This review brings into detail how the variations in S protein that make SARS-CoV-2 more aggressive than its relatives coronaviruses and other differences between coronaviruses.

Ethnopharmacological relevance 22β-hydroxytingenone (22-HTG) is a quinonemethide triterpene isolated from Salacia impressifolia (Miers) A. C. Smith (family Celastraceae), which has been used in traditional medicine to treat a variety of diseases, including dengue, renal infections, rheumatism and cancer. However, the anticancer effects of 22-HTG and the underlying molecular mechanisms in melanoma cells have not yet been elucidated. Aim of the study The present study investigated apoptosis induction and antimetastatic potencial of 22-HTG in SK-MEL-28 human melanoma cells. Materials and methods First, the in vitro cytotoxic activity of 22-HTG in cultured cancer cells was evaluated. Then, cell viability was determined using the trypan blue assay in melanoma cells (SK-MEL-28), which was followed by cell cycle, annexin V-FITC/propidium iodide assays (Annexin/PI), as well as assays to evaluate mitochondrial membrane potential, production of reactive oxygen species (ROS) using flow cytometry. Fluorescence microscopy using acridine orange/ethidium bromide (AO/BE) staining was also performed. RT-qPCR was carried out to evaluate the expression of BRAF, NRAS, and KRAS genes. The anti-invasiveness potential of 22-HTG was evaluated in a three-dimensional (3D) model of reconstructed human skin. Results 22-HTG reduced viability of SK-MEL-28 cells and caused morphological changes, as cell shrinkage, chromatin condensation, and nuclear fragmentation. Furthermore, 22-HTG caused apoptosis, which was demonstrated by increased staining with AO/BE and Annexin/PI. The apoptosis may have been caused by mitochondrial instability without the involvement of ROS production. The expression of BRAF, NRAS, and KRAS, which are important biomarkers in melanoma development, was reduced by the 22-HTG treatment. In the reconstructed skin model, 22-HTG was able to decrease the invasion capacity of melanoma cells in the dermis. Conclusions Our data indicate that 22-HTG has anti-tumorigenic properties against melanoma cells through the induction of cell cycle arrest, apoptosis and inhibition of invasiveness potential, as observed in the 3D model. As such, the results provide new insights for future work on the utilization of 22-HTG in malignant melanoma treatment.

Aurora kinases (AURKA and AURKB) are mitotic kinases with an important role in the regulation of several mitotic events, and in hematological malignancies, AURKA and AURKB hyperexpression are found in patients with cytogenetic abnormalities presenting a unfavorable prognosis. The aim of this study was evaluated the mRNA expression profile of pediatric Acute Lymphoblastic Leukaemia (ALL) patients and the efficacy of two AURKA and AURKB designed inhibitors (GW809897X and GW806742X) in a leukemia cell line as a potential novel therapy for ALL patients. Cellular experiments demonstrated that both inhibitors induced cell death with caspase activation and cell cycle arrest, however only the GW806742X inhibitor decreased with more efficacy AURKA and AURKB expression in K-562 leukemia cells. In ALL patients both AURKA and AURKB showed a significant overexpression, when compared to health controls. Moreover, AURKB expression level was significant higher than AURKA in patients, and predicted a poorer prognosis with significantly lower survival rates. No differences were found in AURKA and AURKB expression between gene fusions, immunophenotypic groups, white blood cells count, gender or age. In summary, the results in this study indicates that the AURKA and AURKB overexpression are important findings in pediatric ALL, and designed inhibitor, GW806742X tested in vitro were able to effectively inhibit the gene expression of both aurora kinases and induce apoptosis in K-562 cells, however our data clearly shown that AURKB proves to be a singular finding and potential prognostic biomarker that may be used as a promising therapeutic target to those patients.

Overexpression of human telomerase reverse transcriptase (hTERT) allows disordered proliferation and immortality of malignant cells, which has been of interest for the development of targeted therapies. The present study aimed to characterize hTERT gene expression in a series of cancer cell lines.Leukemia cell lines K-562, its vincristine-resistant derivative K-562-Lucena1 and daunorubicin-resistant derivative FEPS; gastric adenocarcinoma lines AGP01, ACP02 and ACP03; melanoma SK-Mel-103 cells; and MN01 and MRC5, two non-neoplastic cell lines were analyzed by real-time polymerase chain reaction in order to evaluate hTERT gene expression.In leukemia cells, hTERT gene expression was significantly increased only in K-562 (p0.05) and K-562-Lucena1 (p0.001) when compared to the calibrator MRC5. For solid tumor types, only ACP03 presented a significant hTERT gene expression when compared to ACP02 (p0.05). hTERT gene expression in K-562 and K-562-L ucena was significantly increased (p0.05 to p0.001) compared to all other cell lines except ACP03.In leukemia cell lines, hTERT gene overexpression was shown to be a potential target for pharmacological assays for drugs aiming to inhibit telomerase activity and control cell proliferation in oncohematological diseases.

Background/aim: Chronic myeloid leukaemia (CML) is a myeloproliferative disorder characterized by the presence of breakpoint cluster region–Abelson murine leukemia (BCR–ABL1) gene fusion as a hallmark that is expressed as two major transcripts b2a2 and b3a2. The aim of this study was to compare the BCR–ABL transcripts in the blood cells of patients with CML, and in chemoresistant and chemosensitive CML cell lines to validate their use as a good method to elucidate CML biology. Materials and Methods: Twelve patients with CML and CML cell lines (K562, K562-LUCENA and FEPS) were analyzed by real-time polymerase chain reaction to evaluate gene expression of BCR–ABL transcripts. Results: All patients had the same expression levels of b2a2 and b3a3 transcripts, however, CML cell lines presented only b3a2 expression. There were no significant differences in absolute b3a2 expression between patients and CML cell lines. Conclusion: CML cell lines provide a good in vitro alternative in that they have the same BCR–ABL expression as patients.

Federal University of Par?. Biological Science Institute. Laboratory of Experimental Neuropathology. Bel?m, PA, Brazil. Federal University of Cear?. Drug Research and Development Center. Laboratory of Pharmacogenetics. Fortaleza, CE, Brazil. Federal University of Par?. Biological Science Institute. Laboratory of Human Cytogenetics. Bel?m, PA, Brazil. Federal University of Cear?. Drug Research and Development Center. Laboratory of Pharmacogenetics. Fortaleza, CE, Brazil. Federal University of Par?. Laboratory of Structural and Functional Biology Science. Bel?m, PA, Brazil / Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Laborat?rio de Cultura Celular e Citogen?tica. Ananindeua, PA, Brasil. Minist?rio da Sa?de. Secretaria de Vigil?ncia em Sa?de. Instituto Evandro Chagas. Laborat?rio de Cultura Celular e Citogen?tica. Ananindeua, PA, Brasil. Federal University of Par?. Biological Science Institute. Laboratory of Human Cytogenetics. Bel?m, PA, Brazil. Federal University of Cear?. Drug Research and Development Center. Laboratory of Pharmacogenetics. Fortaleza, CE, Brazil. The objective of study was to examine the role of MBZ on malignant ascites cells and the involvement of C-MYC. Comet assay was used to assess the genotoxic effects of MBZ in AGP01 cells and human lymphocytes; differential staining by ethidium bromide and acridine orange, caspase 3/7 and flow cytometry assay was done to access the mechanisms of apoptosis and cell cycle analysis of MBZ in AGP01 cells. C-MYC amplification, C-MYC mRNA and C-MYC protein expression were evaluated by FISH, RT-qPCR and Western blotting, respectively. In addition, cytotoxicity of MBZ was evaluated in AGP01 and AGP01 shRNA MYC by MTT. MBZ significantly increased the damage index and no produced in human lymphocytes. MBZ caused remarkable cell cycle arrest in G0/G1 and G2/M phases at 0.5?M and 1.0??M, respectively and induced significantly apoptosis in higher concentrations. Additionally, MBZ (0.5??M and 1.0??M) increased caspase 3 and 7 activities. MBZ decreased signals, C-MYC mRNA and C-MYC protein expression in AGP01 cells. MBZ induced lower cell viability in AGP01 cells compared AGP01 shRNA MYC in the same concentration. Therefore, our results show the evidence of C-MYC gene as one of the pathways by which MBZ induces cell death in gastric cancer cells.

Gastric cancer has been considering one of the worst cancer types since it is diagnosed in advanced stages, currently in the metastatic stage. Therefore, the challenge is to find out a biomarker and a pharmacology target that would help face this worldwide health issue. In this sense, the mitogen-activated protein kinase (MAPK) signaling pathway has become an important aim of the studies in several cancers. Therefore, we evaluated the role of MAPK14 (p38α) inhibitor SB-245392 in the cellular process, such as proliferation, cell death, and cell migration, and whether MAPK14 gene could be a potential biomarker in gastric cancer models. The results clearly suggest that p38α inhibition significantly impairs the cell proliferation, induces modest apoptosis and strongly inhibits cell migration of gastric cancer cell (AGP-01). Gene expression analysis showed that c-MYC level was decreased and TP53 was increased after SB-245392 treatment. Furthermore, MAPK14 was found in high levels in gastric cancer samples compared to normal samples in the TCGA database, especially in advanced stages (stage 3 and 4), which is significantly associated with low rate survival of the patients. In conclusion, the MAPK14 could be a potential biomarker for advanced gastric cancer as well as a pharmacological target, which could improve the survival rate of patients.

Melanoma is a skin cancer with high invasive potential and high lethality. Considering that quinonemethide triterpenes are described as promising anticancer agents, the aim of this study was to evaluate the effect of 22β-hydroxytingenone (22-HTG) against human melanoma cells. Alamar blue assay was performed in order to evaluate its cytotoxic effect. Thus, subtoxic concentrations (1.0, 2.0, and 2.5 μM) were used to evaluate the effect of this compound on proliferation, migration, metabolism, and invasion. IC50 value against SK-MEL-28 cell line was 4.35, 3.72, and 3.29 μM after 24, 48, and 72 h of incubation, respectively. 22-HTG reduced proliferation, migration and invasion by melanoma cells, with decreased activity of metalloproteinases (MMP-2 and MMP-9). Futhermore, 22-HTG decreased expression of lactate dehydrogenase (LDHA), an enzyme associated with cell metabolism. Howerver, the small reduction in LDHA enzyme activity must have occurred by the cytotoxic effect of 22-HTG. According to the results, 22-HTG interferes with important characteristics of cancer, with anti-proliferative, and anti-invasive effect against melanoma cells. The data suggest that 22-HTG is an effective substance against melanoma cells and it should be considered as a potential anticancer agent.

Chemo-resistance has been reported as a relevant barrier for the efficiency of gastric cancer treatment. Therefore, the development of effective and safe drugs for cancer chemotherapy is still a challenge. The purpose of this study was to evaluate the anticancer potential of (E)-2-(((2-(benzo[d]thiazo-2-yl)hydrazono)methyl)-4-nitrophenol) (AFN01) against gastric cancer cell lines. Our results showed promising anticancer activity against gastric cancer cells ACP-02 (IC50 = 1.0 μM) and mild activity against other cell lines including non-malignant gastric cell MNP-01 (IC50 = 3.4 μM). This compound significantly induced S phase cell cycle arrest, prevented cell migration and triggered apoptosis in a concentration-dependent manner. Moreover, AFN01 was significantly more genotoxic against tumoral cell ACP-02, when compared to non-malignant cells, such as MNP-01 and healthy peripheral mononuclear blood cells. AFN01 also synergistically interacts with doxorubicin suppressing cell proliferation and c-MYC gene expression in gastric cancer cell line model, with remarkable c-MYC overexpression. Although further pre-clinical and clinical studies are required to explore its safety and efficiency, AFN01 may represent a promising lead anticancer agent for the treatment of gastric cancer.

Dopamine quinone is substrate of the NRH: Quinone Reductase enzyme (QR2) in the retina. The capability of accumulates endogenous dopamine in a neural tissue explains the association of certain neuropsychiatric diseases with polymorphisms in the QR2 promoter that causes overexpression via loss of the capability to bind repressors. However, QR2 doubly reduce other small compounds present in neural and non-neural tissues, being its physiology tissue dependent. In this context, the function of the neurohormone melatonin and analogues in the active site of this multifunctional enzyme is discussed in this mini review.

NRH:quinone reductase (QR2) is present in the retinas of embryonic and post-hatched (PH) chicks. 5-Methoxycarbonylamino-N-acetyltryptamine (5-MCA-NAT) is a QR2 ligand that increases cAMP levels in developing retinas, but it does not affect cAMP levels in CHO-QR2 cells. The dopamine quinone reductase activity of QR2 retrieves dopamine, which increases cAMP levels in developing retinas. The objective of the present study was to investigate whether 5-MCA-NAT increases endogenous dopamine levels in retinas from chick embryos and post-hatched chicks. Endogenous dopamine was measured by enzyme-linked immunosorbent assay (ELISA). 5-MCA-NAT increased retinal endogenous dopamine levels at all developmental stages studied and in PH chicks (-logEC50=11.62±0.34 M). This effect was inhibited by non-selective antagonists of receptors and melatonin binding sites N-acetyl-2-benzyltryptamine (luzindole, 5 μM), but it was not inhibited by the Mel1b melatonin receptor antagonist 4-phenyl-2-propionamidotetralin (4-P-PDOT, 10 nM). The QR2 cosubstrate, N-methyl-dihydronicotinamide (NMH) (-logEC50=6.74±0.26 M), increased endogenous dopamine levels in controls and in retinas stimulated with 5-MCA-NAT (3 nM). The QR2 inhibitor benzo[e]pyrene inhibited endogenous dopamine levels in both control (-logIC50=7.4±0.28 M) and NMH-stimulated (at 100 nM and 1 μM benzo[e]pyrene concentrations) retinas. Theoretical studies using Molegro Virtual Docking software corroborated these experimental results. We conclude that 5-MCA-NAT increases the level of endogenous dopamine via QR2. We suggest that this enzyme triggers double reduction of the dopamine quinone, recovering dopamine in retinal development.