RESUMO
B-N-methylamino-L-alanine (BMAA), a cyanotoxin produced by most cyanobacteria, has been proposed to cause long term damages leading to neurodegenerative diseases, including Amyotrophic Lateral Sclerosis/Parkinsonism Dementia complex (ALS/PDC) and retinal pathologies. Previous work has shown diverse mechanisms leading to BMAA-induced degeneration; however, the underlying mechanisms of toxicity affecting retina cells are not fully elucidated. We here show that BMAA treatment of rat retina neurons in vitro induced nuclear fragmentation and cell death in both photoreceptors (PHRs) and amacrine neurons, provoking mitochondrial membrane depolarization. Pretreatment with the N-Methyl-D-aspartate (NMDA) receptor antagonist MK-801 prevented BMAA-induced death of amacrine neurons, but not that of PHRs, implying activation of NMDA receptors participated only in amacrine cell death. Noteworthy, BMAA stimulated a selective axonal outgrowth in amacrine neurons, simultaneously promoting growth cone destabilization. BMAA partially decreased the viability of Müller glial cells (MGC), the main glial cell type in the retina, induced marked alterations in their actin cytoskeleton and impaired their capacity to protect retinal neurons. BMAA also induced cell death and promoted axonal outgrowth in differentiated rat pheochromocytoma (PC12) cells, implying these effects were not limited to amacrine neurons. These results suggest that BMAA is toxic for retina neurons and MGC and point to the involvement of NMDA receptors in amacrine cell death, providing new insight into the mechanisms involved in BMAA neurotoxic effects in the retina.
Assuntos
Diamino Aminoácidos/toxicidade , Células Ependimogliais/efeitos dos fármacos , Agonistas de Aminoácidos Excitatórios/toxicidade , Doenças Retinianas/induzido quimicamente , Neurônios Retinianos/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Sobrevivência Celular/efeitos dos fármacos , Toxinas de Cianobactérias , Fragmentação do DNA/efeitos dos fármacos , Maleato de Dizocilpina/farmacologia , Células Ependimogliais/patologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Potencial da Membrana Mitocondrial/efeitos dos fármacos , Ratos , Ratos Wistar , Espécies Reativas de Oxigênio/metabolismo , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Doenças Retinianas/metabolismo , Doenças Retinianas/prevenção & controle , Neurônios Retinianos/patologiaRESUMO
Background: Multi-resistant strains multiply daily, populate farms, hospitals and other ecological niches around the world, and cause serious infections in animals and humans, often leading to a fatal outcome. Researchers of all profiles are investigating intensively to find new substances with antimicrobial activity. In the period between 1981 and 2002, 163 new chemical compounds were approved for use as drugs. Synthesized compounds have become much more interesting than the natural ones in the production of new antimicrobial agents. Some of these synthesized compounds are Copper (II) complex. The antimicrobial properties of copper were known in ancient Egypt (2000 BC), where it was used to sterilize water and wounds. Copper is still interesting for today's research. Materials, Methods & Results: Antimicrobial activity was tested using a microdilution method according to Clinical and Laboratory Standards Institute. The percentage of surviving bacteria was calculated in comparison to the number of bacteria placed in each well. Based on these results, using the Excel software package from Microsoft Office 2007, graphs were generated that showed the percentage of surviving bacteria depending on the corresponding effective concentrations of the tested substance. The function, which was used to approximate the experimental results, was determined using the Power Trendline supplement from the Microsoft Excel program. Cytotoxicity (growth inhibition) was evaluated by tetrazolium colorimetric MTT assay, after exposure of cells to the tested compound for 48 h. Inhibition of growth was expressed as a percentage of cytotoxicity and calculated according to the following equation: (1-A test/A control) x 100. MBC99.9 and MIC99 of the test substance were lowest for Arcanobacterium haemolyticum being 0.2 mg/L and 0.0054 mg/L, respectively. The highest values were obtained for Arcanobacterium pyogenes and methicillin-resistant Staphylococcus aureus (MRSA) 488.002 mg/L and 20.2 mg/L. MIC80 for all four strains ranged from 0.00002 to 0.0023 mg/L. Measured values for MIC99 are 0.00545 mg/L for A. haemolyticum, 0.0443199 mg/L for R. equi, 0.0520712 mg/L for S. aureus and 2.36378 mg/L for A. pyogenes. Values for MIC99.9 ranged from 0.236134 to 488,002 mg/L. Most of the MIC values obtained in this study are significantly lower than those reported by other researchers. The values we obtained were lower as compared to MIC values for standard antibiotics, which were considered acceptable by the relevant institutions. This speaks in favor of a stronger antibacterial effect of our tested substances. In regards to cytotoxicity, the obtained MIC80 doses were lower than toxic, whereas MIC90 could be classified as low-toxic (less than 0.0625 µM), except of Arcanobacterium pyogenes only. According to the IC50 values, the compound Cu (L) Br2·MeOH was 6.4-fold and 4.8-fold more potent against HCT116 cells compared to normal lung fi broblasts and SW620 cells, respectively. Discussion: Copper (II) complex with an arylpyrazole ligand exhibits strong antibacterial properties, and it shows bacteriostatic effect at concentrations where there is no cytotoxic effect in normal human cells. The emergence of multi-resistant strains of pathogenic bacteria is a growing problem worldwide. Therefore, each new compound with potential antimicrobial activity, especially if it is not cytotoxic in effective dosage, deserves the attention of the scientific community. In this paper, we presented a newly synthesized substance with such properties.
Assuntos
Staphylococcus aureus/efeitos dos fármacos , Rhodococcus equi/efeitos dos fármacos , Cobre/toxicidade , Cobre/uso terapêutico , Arcanobacterium/efeitos dos fármacos , Diamino Aminoácidos/toxicidade , Diamino Aminoácidos/uso terapêutico , Anti-Infecciosos/análiseRESUMO
In the mountains of Peru, globular colonies of Nostoc commune (Nostocales) are collected in the highland lakes by the indigenous people, who call them llullucha. They are consumed locally, traded for maize, or sold, eventually entering the folk markets of Cusco and other neighboring cities. Throughout highland Peru, Nostoc commune is highly salient as a seasonal dietary item, being eaten alone, or in picante -- a local stew -- and is said to be highly nutritious. Nostoc commune has been known to produce unusual amino acids, including those of the mycosporine group, which possibly function to prevent UV damage. We analyzed 21 different Nostoc commune spherical colonies from 7 different market collections in the Cusco area for the presence of beta-N-methylamino-L-alanine (BMAA), a neurotoxic amino acid produced by diverse taxa of cyanobacteria, using four different analytical techniques (HPLC-FD, UPLC-UV, UPLC/MS, LC/MS/MS). We found using all four techniques that BMAA was present in the samples purchased in the Peruvian markets. Since BMAA has been putatively linked to neurodegenerative illness, it would be of interest to know if the occurrence of ALS, Alzheimer's, or Parkinson's Disease is greater among individuals who consume llullucha in Peru.
Assuntos
Diamino Aminoácidos/metabolismo , Neurotoxinas/metabolismo , Nostoc commune/química , Diamino Aminoácidos/análise , Diamino Aminoácidos/toxicidade , Cromatografia Líquida de Alta Pressão/métodos , Cromatografia Líquida/métodos , Toxinas de Cianobactérias , Suplementos Nutricionais , Medicina Tradicional , Neurotoxinas/análise , Neurotoxinas/toxicidade , Peru , Espectrometria de Massas em Tandem/métodosRESUMO
Over the last 60 years an abnormally high prevalence of atypical Parkinsonism has been reported in 5 different geographic isolates. It was first described on Guam, later in New Guinea and in the Kii peninsula, on Guadeloupe, and in New Caledonia. We investigated the phenotype of atypical Parkinsonism in three of these foci and observed several similarities with dementia in most and amyotrophic lateral sclerosis in some. This disappearance of this disease in two places--Guam and New Guinea--suggested an environmental origin which has not been clarified before the disease ended. The exposure to annonaceae acetogenins and/or rotenone has been documented in four of these places, and experimental studies in animals demonstrated annonaceae acetogenins neurotoxicity, which is similar to rotenone neurotoxicity. Simultaneous exposure to acetogenins and rotenone could produce a synergistic toxicity on neurons.