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Post-translational modifications (PTMs) of proteins are a diverse source of variability that impacts on their functions, localisation, regulation, and lifetime. However, one of the main pitfalls in their study is that they appear in rather low frequencies and/or are only transiently observed. To overcome this issue and ease the study in vitro of stress-related protein PTMs, several methods have been proposed to model stress conditions and chemically introduce them. These techniques employ the combination of peroxides with transition metal ions or haem-containing proteins, as well as other possibilities such as peroxy radicals or UV radiation. However, their control, reproducibility and undesired secondary reactions that reduce the process yield are often a matter of concern. Here we introduce a photo-tuneable method that selectively targets nitration of aromatic residues. We initially present the adaptation of an oxidation method based on the photosensitiser tris(2,2'-bipyridine)-Ruthenium(II) chloride complex and ammonium persulfate, in which we employ an alternative radical neutralisation/trapping pathway that uses nitrite ions for the nitration of free l-Tyrosine and L-Tryptophan amino acids. After analysing the effect of several factors, we report the application of the photo-tuneable protein nitration (PTPN) method to four different model proteins in which we evaluate the nitration and oxidation of residues in each case. A mass spectrometry label-free quantitation of Tyr and Trp nitration is also described in order to compare the degree of modification and the accessibility of these residues. The method described could be employed to scale up the production of proteins with a selected range of oxidative PTMs for their characterisation, the assessment of their pathophysiological roles, and the development of detection and quantification methods to validate these PTMs as novel biomarkers associated with oxidative stress-related pathologies, such as in cardiovascular or neurodegenerative diseases.

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ABSTRACT Objective: Lumbar spine fusion is indicated in patients who are refractory to traditional treatment for degenerative disc disease. The aim of this study was to compare the perioperative and postoperative results of conventional open surgery versus minimally invasive surgery (MIS) in posterior 360° lumbar fusion with pedicle screw instrumentation. Methods: A total of 25 patients underwent MIS and 40 underwent open surgery between 2015 and 2017. Perioperative variables and lumbar and radicular pain values were compared using a visual analogue scale (VAS) and the Oswestry disability index (ODI) until 12 months after surgery. Results: The MIS cohort presented less blood loss (140 vs 345 ml; p=0.001), shorter hospital stay (1.1 vs 2.2 days; p=0.001), longer operative time (113 vs 94 minutes; p=0.001) and greater X-ray exposure (80 vs 6 seconds; p=0.001), compared to the open surgery group. The MIS cohort showed better results in the ODI and lumbar VAS scores. No significant differences were observed in radicular VAS. Conclusion: MIS surgery showed advantages over the open surgery technique; however, the learning curve should be improved in order to reduce operative time. Level of Evidence III; Retrospective descriptive observational study.

RESUMO Objetivo: A fusão espinhal lombar é indicada para pacientes refratários ao tratamento tradicional da doença degenerativa do disco. O objetivo do presente estudo consistia em comparar os resultados peri- e pós-operatórios da cirurgia aberta convencional versus a cirurgia minimamente invasiva (MIS) na fusão lombar de 360º por via posterior com instrumentação de parafuso pedicular. Métodos: Foram estudados 25 pacientes submetidos à técnica de MIS e 40 submetidos à cirurgia aberta entre 2015 e 2017. As variáveis perioperatórias e os valores da dor lombar e dor radicular foram comparados com a escala visual analógica (EVA) e Oswestry Disability Index (ODI) até 12 meses após a cirurgia. Resultados: O grupo MIS apresentou menores índices de perda sanguínea (140 vs 345 ml; p = 0,001) e menor permanência hospitalar (1,1 vs. 2,2 dias; p = 0,001), maior tempo de cirurgia (113 vs. 94 minutos; p = 0,001) e maior exposição às radiografias (80 vs 6 seg; p = 0,001) em relação ao grupo de cirurgia aberta. O grupo MIS apresentou melhores resultados nos escores de ODI e EVA lombar. Na EVA radicular não foram observadas diferenças significativas. Conclusão: A cirurgia minimamente invasiva apresentou vantagens em relação à técnica da cirurgia aberta, embora a curva de aprendizagem deva ser otimizada para reduzir o tempo de cirurgia. Nível de Evidência III; Estudo retrospectivo descritivo observacional.

RESUMEN Objetivo: La fusión espinal lumbar es indicada para pacientes refractarios al tratamiento tradicional de la enfermedad degenerativa del disco. El objetivo del presente estudio consistía en comparar los resultados peri y postoperatorios de la cirugía abierta convencional versus la cirugía mínimamente invasiva (MIS) en la fusión lumbar de 360º por vía posterior con instrumentación de tornillo pedicular. Métodos: Se estudiaron 25 pacientes sometidos a la técnica MIS y 40 sometidos a la cirugía abierta entre 2015 y 2017. Se compararon las variables perioperatorias y los valores del dolor lumbar y dolor radicular con la escala visual analógica (EVA) e índice de incapacidad de Oswestry (ODI) hasta los 12 meses post cirugía. Resultados: El grupo MIS presentó menores índices de pérdida sanguínea (140 vs 345 ml; p=0,001) y menor permanencia hospitalaria (1,1 vs 2,2 días; p=0,001), mayor tiempo de cirugía (113 vs 94 minutos; p=0,001) y exposición a las radiografías (80 vs 6 seg; p=0,001) con relación al grupo de cirugía abierta. El grupo MIS presentó mejores resultados en las puntuaciones de ODI y EVA lumbar. En la EVA radicular no se observaron diferencias significativas. Conclusión: La cirugía mínimamente invasiva presentó ventajas con relación a la técnica de la cirugía abierta, aunque la curva de aprendizaje deba ser optimizada para reducir el tiempo de cirugía. Nivel de Evidencia III; Estudio retrospectivo descriptivo observacional.

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Fatty acids (FAs) are typically associated with structural and metabolic roles, as they can be stored as triglycerides, degraded by ß-oxidation or used in phospholipids' synthesis, the main components of biological membranes. It has been shown that these lipids exhibit also regulatory functions in different cell types. FAs can serve as secondary messengers, as well as modulators of enzymatic activities and substrates for cytokines synthesis. More recently, it has been documented a direct activity of free FAs as ligands of membrane, cytosolic, and nuclear receptors, and cumulative evidence has emerged, demonstrating its participation in a wide range of physiological and pathological conditions. It has been long known that the central nervous system is enriched with poly-unsaturated FAs, such as arachidonic (C20:4ω-6) or docosohexaenoic (C22:6ω-3) acids. These lipids participate in the regulation of membrane fluidity, axonal growth, development, memory, and inflammatory response. Furthermore, a whole family of low molecular weight compounds derived from FAs has also gained special attention as the natural ligands for cannabinoid receptors or key cytokines involved in inflammation, largely expanding the role of FAs as precursors of signaling molecules. Nutritional deficiencies, and alterations in lipid metabolism and lipid signaling have been associated with developmental and cognitive problems, as well as with neurodegenerative diseases. The molecular mechanism behind these effects still remains elusive. But in the last two decades, different families of proteins have been characterized as receptors mediating FAs signaling. This review focuses on different receptors sensing and transducing free FAs signals in neural cells: (1) membrane receptors of the family of G Protein Coupled Receptors known as Free Fatty Acid Receptors (FFARs); (2) cytosolic transport Fatty Acid-Binding Proteins (FABPs); and (3) transcription factors Peroxisome Proliferator-Activated Receptors (PPARs). We discuss how these proteins modulate and mediate direct regulatory functions of free FAs in neural cells. Finally, we briefly discuss the advantages of evaluating them as potential targets for drug design in order to manipulate lipid signaling. A thorough characterization of lipid receptors of the nervous system could provide a framework for a better understanding of their roles in neurophysiology and, potentially, help for the development of novel drugs against aging and neurodegenerative processes.