Wouter De Haes

Metformin promotes lifespan through mitohormesis via the peroxiredoxin PRDX-2

Significance Recently it has been suggested that metformin, the most commonly used antidiabetic drug, might also possess general health-promoting properties. Elucidating metformin’s mode of action will vastly increase its application range and will contribute to healthy aging. We reveal a signaling cascade in which metformin is able to extend lifespan by increasing the production of reactive oxygen species (ROS). This allowed us to further work at the crossroads of human disease and aging research, identifying a key molecule that is able to translate the ROS signal into a prolongevity cue: an antioxidant peroxiredoxin is also able to activate a lifespan-promoting signaling cascade, here described in detail. Continued research efforts in this field lead toward a targeted improvement of aging-related complications. The antiglycemic drug metformin, widely prescribed as first-line treatment of type II diabetes mellitus, has lifespan-extending properties. Precisely how this is achieved remains unclear. Via a quantitative proteomics approach using the model organism Caenorhabditis elegans, we gained molecular understanding of the physiological changes elicited by metformin exposure, including changes in branched-chain amino acid catabolism and cuticle maintenance. We show that metformin extends lifespan through the process of mitohormesis and propose a signaling cascade in which metformin-induced production of reactive oxygen species increases overall life expectancy. We further address an important issue in aging research, wherein so far, the key molecular link that translates the reactive oxygen species signal into a prolongevity cue remained elusive. We show that this beneficial signal of the mitohormetic pathway is propagated by the peroxiredoxin PRDX-2. Because of its evolutionary conservation, peroxiredoxin signaling might underlie a general principle of prolongevity signaling.

Structure-activity studies of Drosophila adipokinetic hormone (AKH) by a cellular expression system of dipteran AKH receptors.

Structure-activity studies for the adipokinetic hormone receptor of insects were for the first time performed in a cellular expression system. A series of single amino acid replacement analogues for the endogenous adipokinetic hormone of Drosophila melanogaster (pGlu-Leu-Thr-Phe-Ser-Pro-Asp-Trp-NH(2)) were screened for activity with a bioluminescence cellular assay, expressing the G-protein coupled receptor. For this series of peptide analogues, one amino acid of the N-terminal tetrapeptide was successively replaced by alanine, while those of the C-terminal tetrapeptide were successively substituted by glycine; other modifications included the blocked N- and C-termini that were replaced by an acetylated alanine and a hydroxyl group, respectively. The analogue series was tested on the AKH receptors of two dipteran species, D. melanogaster and Anopheles gambiae. The blocked termini of the AKH peptide probably play a minor role in receptor interaction and activation, but are considered functionally important elements to protect the peptide against exopeptidases. In contrast, the amino acids at positions 2, 3, 4 and 5 from the N-terminus all seem to be crucial for receptor activation. This can be explained by the potential presence of a β-strand in this part of the peptide that interacts with the receptor. The inferred β-strand is probably followed by a β-turn in which the amino acids at positions 5-8 are involved. In this β-turn, the residues at positions 6 and 8 seem to be essential, as their substitutions induce only a very low degree of receptor activation. Replacement of Asp(7), by contrast, does not influence receptor activation at all. This implies that its side chain is folded inside the β-turn so that no interaction with the receptor occurs.

Functional neuropeptidomics in invertebrates

Neuropeptides are key messengers in almost all physiological processes. They originate from larger precursors and are extensively processed to become bioactive. Neuropeptidomics aims to comprehensively identify the collection of neuropeptides in an organism, organ, tissue or cell. The neuropeptidome of several invertebrates is thoroughly explored since they are important model organisms (and models for human diseases), disease vectors and pest species. The charting of the neuropeptidome is the first step towards understanding peptidergic signaling. This review will first discuss the latest developments in exploring the neuropeptidome. The physiological roles and modes of action of neuropeptides can be explored in two ways, which are largely orthogonal and therefore complementary. The first way consists of inferring the functions of neuropeptides by a forward approach where neuropeptide profiles are compared under different physiological conditions. Second is the reverse approach were neuropeptide collections are used to screen for receptor-binding. This is followed by localization studies and functional tests. This review will focus on how these different functional screening methods contributed to the field of invertebrate neuropeptidomics and expanded our knowledge of peptidergic signaling. This article is part of a Special Issue entitled: Neuroproteomics: Applications in Neuroscience and Neurology.

The Fading Electricity Theory of Ageing: The missing biophysical principle?

Since a few years convincing data are accumulating showing that some of the premises of the master integrative theory of ageing, namely Harmans Reactive Oxygen Species or free radical theory, are less well founded than originally assumed. In addition, none of the about another dozen documented ageing mechanisms seems to hold the final answer as to the ultimate cause and evolutionary significance of ageing. This review raises the question whether, perhaps, something important has been overlooked, namely a biophysical principle, electrical in nature. The first cell on earth started to be alive when its system for generating its own electricity, carried by inorganic ions, became operational. Any cell dies at the very moment that this system irreversibly collapses. In between birth and death, the system is subject to wear and tear because any cells overall repair system is not 100 percent waterproof; otherwise adaptation would not be an option. The Fading Electricity Theory of Ageing has all necessary properties for acting as a universal major integrative concept. The advent of novel methods will facilitate the study of bioelectrical phenomena with molecular biological methods in combination with optogenetics, thereby offering challenging possibilities for innovative research in evo-gero.

Royalactin extends lifespan of Caenorhabditis elegans through epidermal growth factor signaling.

Royalactin is a glycoprotein essential for the development of long-lived queen honeybees. Only larvae fed with royal jelly, containing royalactin, develop into queens. Royalactin plays a central role in this process by switching on the epidermal growth factor (EGF) receptor signaling pathway which ultimately leads to epigenetic changes and a long-lived queen phenotype. Recently it was shown that royalactin by itself also extends lifespan in Drosophila melanogaster. Yet, the mechanism by which royalactin promotes longevity remains largely unknown. We set out to characterize the effects of royalactin on Caenorhabditis elegans lifespan, and clarify the possible involvement of EGF signaling in this process. We demonstrate that royalactin extends lifespan of this nematode and that both EGF (LIN-3) and its receptor (LET-23) are essential to this process. To our knowledge, this is the first report of royalactin-mediated lifespan extension in a non-insect species. Additionally, we show that royalactin enhances locomotion in adult nematodes, implying that royalactin also influences healthspan. Our results suggest that royalactin is an important lifespan-extending factor in royal jelly and acts by promoting EGF signaling in C. elegans. Further work will now be needed to clarify which (secondary) signaling pathways are activated by royalactin, and how this ultimately translates into an extended health- and lifespan.

Integrating -Omics: Systems Biology as Explored Through C. elegans Research

-Omics data have become indispensable to systems biology, which aims to describe the full complexity of functional cells, tissues, organs and organisms. Generating vast amounts of data via such methods, researchers have invested in ways of handling and interpreting these. From the large volumes of -omics data that have been gathered over the years, it is clear that the information derived from one -ome is usually far from complete. Now, individual techniques and methods for integration are maturing to the point that researchers can focus on network-based integration rather than simply interpreting single -ome studies. This review evaluates the application of integrated -omics approaches with a focus on Caenorhabditis elegans studies, intending to direct researchers in this field to useful databases and inspiring examples.

Fast and Reliable Quantitative Peptidomics with labelpepmatch

The use of stable isotope tags in quantitative peptidomics offers many advantages, but the laborious identification of matching sets of labeled peptide peaks is still a major bottleneck. Here we present labelpepmatch, an R-package for fast and straightforward analysis of LC-MS spectra of labeled peptides. This open-source tool offers fast and accurate identification of peak pairs alongside an appropriate framework for statistical inference on quantitative peptidomics data, based on techniques from other -omics disciplines. A relevant case study on the desert locust Schistocerca gregaria proves our pipeline to be a reliable tool for quick but thorough explorative analyses.

A pharmacological study of NLP-12 neuropeptide signaling in free-living and parasitic nematodes

NLP-12a and b have been identified as cholecystokinin/sulfakinin-like neuropeptides in the free-living nematode Caenorhabditis elegans. They are suggested to play an important role in the regulation of digestive enzyme secretion and fat storage. This study reports on the identification and characterization of an NLP-12-like peptide precursor gene in the rat parasitic nematode Strongyloides ratti. The S. ratti NLP-12 peptides are able to activate both C. elegans CKR-2 receptor isoforms in a dose-dependent way with affinities in the same nanomolar range as the native C. elegans NLP-12 peptides. The C-terminal RPLQFamide sequence motif of the NLP-12 peptides is perfectly conserved between free-living and parasitic nematodes. Based on systemic amino acid replacements the Arg-, Leu- and Phe- residues appear to be critical for high-affinity receptor binding. Finally, a SAR analysis revealed the essential pharmacophore in C. elegans NLP-12b to be the pentapeptide RPLQFamide.

Beyond ROS clearance: Peroxiredoxins in stress signaling and aging

Antioxidants were long predicted to have lifespan-promoting effects, but in general this prediction has not been well supported. While some antioxidants do seem to have a clear effect on longevity, this may not be primarily as a result of their role in the removal of reactive oxygen species, but rather mediated by other mechanisms such as the modulation of intracellular signaling. In this review we discuss peroxiredoxins, a class of proteinaceous antioxidants with redox signaling and chaperone functions, and their involvement in regulating longevity and stress resistance. Peroxiredoxins have a clear role in the regulation of lifespan and survival of many model organisms, including the mouse, Caenorhabditis elegans and Drosophila melanogaster. Recent research on peroxiredoxins - in these models and beyond - has revealed surprising new insights regarding the interplay between peroxiredoxins and longevity signaling, which will be discussed here in detail. As redox signaling is emerging as a potentially important player in the regulation of longevity and aging, increased knowledge of these fascinating antioxidants and their mode(s) of action is paramount.

Signaling properties of the human chemokine receptors CXCR4 and CXCR7 by cellular electric impedance measurements

The chemokine receptor 4 (CXCR4) and 7 (CXCR7) are G-protein-coupled receptors involved in various diseases including human cancer. As such, they have become important targets for therapeutic intervention. Cell-based receptor assays, able to detect agents that modulate receptor activity, are of key importance for drug discovery. We evaluated the potential of cellular electric impedance for this purpose. Dose-dependent and specific stimulation of CXCR4 was detected upon addition of its unique chemokine ligand CXCL12. The response magnitude correlated with the CXCR4 expression level. Gαi coupling and signaling contributed extensively to the impedance response, whereas Gαq- and Gβγ-related events had only minor effects on the impedance profile. CXCR7 signaling could not be detected using impedance measurements. However, increasing levels of CXCR7 expression significantly reduced the CXCR4-mediated impedance readout, suggesting a regulatory role for CXCR7 on CXCR4-mediated signaling. Taken together, cellular electric impedance spectroscopy can represent a valuable alternative pharmacological cell-based assay for the identification of molecules targeting CXCR4, but not for CXCR7 in the absence of CXCR4.