Peptides as quorum sensing molecules : measurement techniques and obtained levels in vitro and in vivo

The expression of certain bacterial genes is regulated in a cell-density dependent way, a phenomenon called quorum sensing. Both Gram-negative and Gram-positive bacteria use this type of communication, though the signal molecules (auto-inducers) used by them differ between both groups: Gram-negative bacteria use predominantly N-acyl homoserine lacton (AHL) molecules (autoinducer-1, AI-1) while Gram-positive bacteria use mainly peptides (autoinducer peptides, AIP or quorum sensing peptides). These quorum sensing molecules are not only involved in the inter-microbial communication, but can also possibly cross-talk directly or indirectly with their host. This review summarizes the currently applied analytical approaches for quorum sensing identification and quantification with additionally summarizing the experimentally found in vivo concentrations of these molecules in humans

Nutrition and the ageing brain: moving towards clinical applications

The global increases in life expectancy and population have resulted in a growing ageing population and with it a growing number of people living with age-related neurodegenerative conditions and dementia, shifting focus towards methods of prevention, with lifestyle approaches such as nutrition representing a promising avenue for further development. This overview summarises the main themes discussed during the 3 Symposium on "Nutrition for the Ageing Brain: Moving Towards Clinical Applications" held in Madrid in August 2018, enlarged with the current state of knowledge on how nutrition influences healthy ageing and gives recommendations regarding how the critical field of nutrition and neurodegeneration research should move forward into the future. Specific nutrients are discussed as well as the impact of multi-nutrient and whole diet approaches, showing particular promise to combatting the growing burden of age-related cognitive decline. The emergence of new avenues for exploring the role of diet in healthy ageing, such as the impact of the gut microbiome and development of new techniques (imaging measures of brain metabolism, metabolomics, biomarkers) are enabling researchers to approach finding answers to these questions. But the translation of these findings into clinical and public health contexts remains an obstacle due to significant shortcomings in nutrition research or pressure on the scientific community to communicate recommendations to the general public in a convincing and accessible way. Some promising programs exist but further investigation to improve our understanding of the mechanisms by which nutrition can improve brain health across the human lifespan is still required

Stimulatory and Toxic Effects of Neurotransmitters on the lux Operon-Dependent Bioluminescence of Escherichia coli K12 TGI

Background: The normal functioning of the brain requires neuromediators, i.e., substances that transmit messages between nervous cells. Neurochemicals also function as signals that are involved in communication among the microorganisms that inhabit the human organism. While the impact of “classical” neurotransmitters including catecholamines, serotonin, and histamine on microorganisms has been investigated in a number of recent publications, this work provides evidence for the stimulatory and inhibitory (toxic) effects of some other important neurochemicals that have not received sufficient attention in the literature.Methods: The biosensor was based on a GM Escherichia coli K12 strain (TGI) that contained the lux operon of the luminescent soil bacterium Photorhabdus luminescencens ZMI. The biosensor was exposed to the action of the tested neurotransmitters for 15 mins to 144 hrs. The intensity of bacterial luminescence (counts / second) was monitored in the control and the experimental samples with an 1251 BioOrbit luminometer (Finland).Results: Neurochemicals such as putrescine, acetylcholine, taurin, and indole were found to stimulate, at low concentrations (0.1-10 µM), the luminescence of the strain E. coli K12 TGI containing the lux operon from Photorhabdus luminescencens ZMI. At higher concentrations, putrescine, taurin, and indole exerted a weak toxic influence, i.e. they marginally attenuated the luminescence of E. coli K12 TGI.Conclusions: Based on the data obtained, a regulatory, presumably receptor-dependent, effect is exerted by the tested neurochemicals on the bacterium E. coli K12 TGI, in an analogy to their impact on nervous, immune, and other specialized types of eukaryotic cells. However, high neurochemical concentrations are likely to produce nonspecific effects on the bacterial luciferase system and/or on membrane phosphorylation

Detecting Biogenic Amines in Food and Drug Plants with HPLC: Medical and Nutritional Implications

Background: This work reports the results of the initial stage of the project aimed at detecting neuroactive substances in tropical plants that are widely used as food and/or drugs.Methods: The content of neuroactive biogenic amines, e.g, dopamine (DA), norepinephrine (NE), epinephrine (E), serotonin (5-HT), and others was determined using high-performance liquid chromatography (HPLC) with amperometric detection in leaf samples from Plumeria rubra L. cv. acutifolia, Syzigium jambos (L.) Alston, Buxus megistophylla (or Euonymus japonicas cv. aureoma), and Cinnamomum bodinieri Levl.Results: The total fraction of disintegrated leaves contained (sub)micromolar concentrations of DA, NE, and 5-HT. They lacked E and the catecholamine precursor 2,3-dihydrophenylalanine (DOPA).Conclusions: From the data obtained, it is evident that heretofore unexplored tropical plants used in drug preparations (P. rubra and S. jambos) and as desserts (S. jambos) and spices (C. bodinieri) contain physiologically active concentrations of neurochemicals. The neurochemicals are expected to produce a significant effect on the people who consume preparations and food additives made from the aforementioned plants. Moreover, such plant preparations can potentially be used as psychoactive drugs for the purpose of intentionally manipulating human behavior