Areas of focus
The production of reactive oxygen/nitrogen species (RONS) and the occurrence of antioxidants are critically involved in the redox regulation of cell functions but their steady-state levels and dynamics may be connected to selective responses, including the extensive oxidative damage to biomolecules (oxidative and nitrosative stresses), leading to cell death, either by turning off vital processes or by upregulating toxic cascades. That is why radicals have been implicated in the ethiology of several diseases, including cardiovascular, neurological, inflammatory, cancer and as well in aging, and is also why antioxidants, molecules counteracting free radical-mediated oxidations, namely the polyphenols present in the diet, have been suggested to exhibit health-promoting effects.
More recently, it has been realized that free radicals are not only toxic compounds but participate in the regulation of cell functions and are, therefore, critical molecules in the homeostasis. The term redox regulation refers to the radical and oxidant-mediated cell signaling pathways.
A radical synthesized in vivo with multiple bioactivities is nitric oxide. This gaseous free radical, known for a long time as an atmospheric pollutant, diffuses throughout the cells and is a crucial player in the plastic phenomena occurring in our brain (memory, learning, etc), and is also responsible for the relaxation of blood vessels.
Because nitric oxide is an atypical messenger that crosses cell membranes and does not interact with specific receptors, the information it carries is associated with the spatiotemporal profile of change in a biological setting.
Nitric Oxide Concentration Dynamics in the Brain
In the nervous system, nitric oxide is produced upon activation of the NMDA-type of glutamate receptor. Nitric oxide can act as a neuromodulator, regulating neuromolecular phenomena associated with memory and aging. Additionally, nitric oxide has been implicated in pathophysiological processes underlying neurodegenerative disorders (Alzheimer’s disease, Parkinson’s disease, among others).
Our group is interested in the understanding of nitric oxide concentration dynamics in the hippocampus and how different concentration profiles effect critical phenomena such as tissue oxygen concentration, usage and distribution and regulation vascular tone by neuronal activity (neurovascular coupling).
To address this questions experimentally, we perform real-time and simultaneous recording of nitric oxide, oxygen and/or blood flow both in ex vivo models (ex: hippocampal slices) and in vivo (wild type healthy animals and in disease models).
The Nitrite-to-Nitric Oxide Pathway in the Gastric Compartment
We established the proof of concept that, in the presence of nitrite, polyphenol-containing dietary products induce a strong increase of nitric oxide in the stomach of humans, which, in turn, may diffuse the gastric wall reaching mucosal blood vessels, and elicit local relaxation. This points to a diet-dependent production of the ubiquitous cell modulator, nitric oxide.
In our lab we use a range of experimental strategies, ranging from in vitro biochemistry to in vivo animal models and experiments on humans to better understand this pathway of nitric oxide production out of canonic enzymatic control, as well as gain further insight into the physiological and pathophysiological outcome in the gastric compartment.
Polyphenols, Endothelial Function and Atherosclerosis
The endothelium appears to be a central player in atherogenesis, which is a chronic inflammatory process where overproduction of oxidative species and apoptosis are implicated in disease progression. Beyond their antioxidant properties, polyphenols (e.g., malvidin-3-glucoside) inhibit peroxynitrite-triggered endothelial cell apoptosis disrupting the mitochondrial pathway through modulation of Bcl-2 intracellular levels and by up-regulating cellular nitric oxide and down-regulating NF-kB. Using cellular models (BAEC), a line of research is aimed to determine how polyphenols found in our diet can afford protection against peroxynitrite-promoted endothelial cell toxicity.
Our research incorporates both, scientific and technological components. The development of selective microelectrodes for nitric oxide to be inserted in the rat brain (in vivo and ex vivo) has been carried out in collaboration with the Center for Microlectrode Technology, University of Kentuky (CenMet, Lexington, USA), of which our lab became the Coimbra Lab Division of CenMet.