Pharynx mitochondrial [Ca2+] dynamics in live C. elegans worms during aging

Olive oil tyrosols reduce α-synuclein aggregation in vitro and in vivo after ingestion in a Caenorhabditis elegans Parkinson's model

Parkinson's disease is the neurodegenerative motor disorder with the highest incidence worldwide. Among other factors, Parkinson's disease is caused by the accumulation of α-synuclein aggregates in a patient's brain. In this work, five molecules present in the diet are proposed as possible nutraceuticals to prevent and/or reduce the formation of α-synuclein oligomers that lead to Parkinson's disease. The olive oil polyphenols tyrosol, hydroxytyrosol (HT), hydroxytyrosol acetate (HTA) and dihydroxyphenyl acetic acid (DOPAC) besides vitamin C were tested using a cellular model of α-synuclein aggregation and a Caenorhabditis elegans Parkinson's disease animal model. Levodopa was included in the assays as the main drug prescribed to treat the disease as well as dopamine, its direct metabolite. HTA and DOPAC completely hindered α-synuclein aggregation in vitro, while dopamine reduced the aggregation by 28.7%. The Parallel Artificial Membrane Permeability Assay (PAMPA) showed that HTA had the highest permeability through brain lipids among the compounds tested. Furthermore, the C. elegans Parkinson's disease model made it possible to assess the chosen compounds in vivo. The more effective substances in vivo were DOPAC and HTA which reduced the αS aggregation inside the animals by 79.2% and 76.2%, respectively. Moreover, dopamine also reduced the aggregates by 67.4% in the in vivo experiment. Thus, the results reveal the potential of olive oil tyrosols as nutraceuticals against α-synuclein aggregation.

An expandable FLP-ON::TIR1 system for precise spatiotemporal protein degradation in Caenorhabditis elegans

The auxin-inducible degradation system has been widely adopted in the Caenorhabditis elegans research community for its ability to empirically control the spatiotemporal expression of target proteins. This system can efficiently degrade auxin-inducible degron (AID)-tagged proteins via the expression of a ligand-activatable AtTIR1 protein derived from A. thaliana that adapts target proteins to the endogenous C. elegans proteasome. While broad expression of AtTIR1 using strong, ubiquitous promoters can lead to rapid degradation of AID-tagged proteins, cell type-specific expression of AtTIR1 using spatially restricted promoters often results in less efficient target protein degradation. To circumvent this limitation, we have developed an FLP/FRT3-based system that functions to reanimate a dormant, high-powered promoter that can drive sufficient AtTIR1 expression in a cell type-specific manner. We benchmark the utility of this system by generating a number of tissue-specific FLP-ON::TIR1 drivers to reveal genetically separable cell type-specific phenotypes for several target proteins. We also demonstrate that the FLP-ON::TIR1 system is compatible with enhanced degron epitopes. Finally, we provide an expandable toolkit utilizing the basic FLP-ON::TIR1 system that can be adapted to drive optimized AtTIR1 expression in any tissue or cell type of interest.

Polyphenols from traditional Chinese medicine and Mediterranean diet are effective against Aβ toxicity in vitro and in vivo in Caenorhabditis elegans

The potential of naturally occurring polyphenols as nutraceuticals to prevent and/or treat Alzheimer's disease is studied. Five structurally related flavones and four tyrosols were tested in vitro in human amyloid-β peptide aggregation assays. The most promising compounds were two flavones, scutellarein and baicalein, and two tyrosols hydroxytyrosol and hydroxytyrosol acetate. These compounds caused a dose-dependent reduction of Aβ-peptide aggregation up to 90% for the flavones and 100% for the tyrosols, at concentrations of 83.3 μM and 33.3 mM, respectively. The IC₅₀ value obtained for scutellarein was 22.5 μM, and was slightly higher for baicalein, 25.9 μM, while for hydroxytyrosol and hydroxytyrosol acetate they were 0.57 mM and 0.62 mM. Given these results, the compounds were selected to conduct in vivo assays with the Caenorhabditis elegans animal model of Alzheimer's disease. The amyloid anti-aggregation ability of these polyphenols was demonstrated in in vivo aggregation assays in which 1 mM hydroxytyrosol reduced the amyloid plaques in the mutant strain CL2331 by 43%. The neuroprotective effect was evaluated in chemotaxis experiments carried out with transgenic strain CL2355 that expresses the human amyloid-β peptide in the neurons. The chemotaxis index was improved by 240% when the neuron-impaired animals were treated with 1 mM hydroxytyrosol. The results indicate that the four molecules would be viable candidates to develop nutraceuticals that interfere in amyloid-β peptide aggregation and, consequently, prevent and/or treat Alzheimer's disease.

Lighting Up Ca2+ Dynamics in Animal Models

Calcium (Ca2+) signaling coordinates are crucial processes in brain physiology. Particularly, fundamental aspects of neuronal function such as synaptic transmission and neuronal plasticity are regulated by Ca2+, and neuronal survival itself relies on Ca2+-dependent cascades. Indeed, impaired Ca2+ homeostasis has been reported in aging as well as in the onset and progression of neurodegeneration. Understanding the physiology of brain function and the key processes leading to its derangement is a core challenge for neuroscience. In this context, Ca2+ imaging represents a powerful tool, effectively fostered by the continuous amelioration of Ca2+ sensors in parallel with the improvement of imaging instrumentation. In this review, we explore the potentiality of the most used animal models employed for Ca2+ imaging, highlighting their application in brain research to explore the pathogenesis of neurodegenerative diseases.

The Mitochondrial Na+/Ca2+ Exchanger Inhibitor CGP37157 Preserves Muscle Structure and Function to Increase Lifespan and Healthspan in Caenorhabditis elegans

We have reported recently that the mitochondrial Na⁺/Ca²⁺ exchanger inhibitor CGP37157 extends lifespan in Caenorhabditis elegans by a mechanism involving mitochondria, the TOR pathway and the insulin/IGF1 pathway. Here we show that CGP37157 significantly improved the evolution with age of the sarcomeric regular structure, delaying development of sarcopenia in C. elegans body wall muscle and increasing the average and maximum speed of the worms. Similarly, CGP37157 favored the maintenance of a regular mitochondrial structure during aging. We have also investigated further the mechanism of the effect of CGP37157 by studying its effect in mutants of aak-1;aak-2/AMP-activated kinase, sir-2.1/sirtuin, rsks-1/S6 kinase and daf-16/FOXO. We found that this compound was still effective increasing lifespan in all these mutants, indicating that these pathways are not involved in the effect. We have then monitored pharynx cytosolic and mitochondrial Ca²⁺ signalling and our results suggest that CGP37157 is probably inhibiting not only the mitochondrial Na⁺/Ca²⁺ exchanger, but also Ca²⁺ entry through the plasma membrane. Finally, a transcriptomic study detected that CGP37157 induced changes in lipid metabolism enzymes and a four-fold increase in the expression of ncx-6, one of the C. elegans mitochondrial Na⁺/Ca²⁺ exchangers. In summary, CGP37157 increases both lifespan and healthspan by a mechanism involving changes in cytosolic and mitochondrial Ca²⁺ homeostasis. Thus, Ca²⁺ signalling could be a promising target to act on aging.

Mitochondrial Ca2+ Dynamics in MCU Knockout C. elegans Worms

Mitochondrial [Ca²⁺] plays an important role in the regulation of mitochondrial function, controlling ATP production and apoptosis triggered by mitochondrial Ca²⁺ overload. This regulation depends on Ca²⁺ entry into the mitochondria during cell activation processes, which is thought to occur through the mitochondrial Ca²⁺ uniporter (MCU). Here, we have studied the mitochondrial Ca²⁺ dynamics in control and MCU-defective C. elegans worms in vivo, by using worms expressing mitochondrially-targeted YC3.60 yellow cameleon in pharynx muscle. Our data show that the small mitochondrial Ca²⁺ oscillations that occur during normal physiological activity of the pharynx were very similar in both control and MCU-defective worms, except for some kinetic differences that could mostly be explained by changes in neuronal stimulation of the pharynx. However, direct pharynx muscle stimulation with carbachol triggered a large and prolonged increase in mitochondrial [Ca²⁺] that was much larger in control worms than in MCU-defective worms. This suggests that MCU is necessary for the fast mitochondrial Ca²⁺ uptake induced by large cell stimulations. However, low-amplitude mitochondrial Ca²⁺ oscillations occurring under more physiological conditions are independent of the MCU and use a different Ca²⁺ pathway.

Electrophysiological Measures of Aging Pharynx Function in C. elegans Reveal Enhanced Organ Functionality in Older, Long-lived Mutants

The function of the pharynx, an organ in the model system Caenorhabditis elegans, has been correlated with life span and motility (another measure of health) since 1980. In this study, in order to further understand the relationship between organ function and life span, we measured the age-related decline of the pharynx using an electrophysiological approach. We measured and analyzed electropharyngeograms (EPG) of wild type animals, short-lived hsf-1 mutants, and long-lived animals with genetically decreased insulin signaling or increased heat shock pathway signaling; we recorded a total of 2,478 EPGs from 1,374 individuals. As expected, the long-lived daf-2(e1370) and hsf-1OE(uthIs235) animals maintained pharynx function relatively closer to the youthful state during aging, whereas the hsf-1(sy441) and wild type animals' pharynx function deviated significantly further from the youthful state at advanced age. Measures of the amount of variation in organ function can act as biomarkers of youthful physiology as well. Intriguingly, the long-lived animals had greater variation in the duration of pharynx contraction at older ages.

The Role of Ca2+ Signaling in Aging and Neurodegeneration: Insights from Caenorhabditis elegans Models

Ca²⁺ is a ubiquitous second messenger that plays an essential role in physiological processes such as muscle contraction, neuronal secretion, and cell proliferation or differentiation. There is ample evidence that the dysregulation of Ca²⁺ signaling is one of the key events in the development of neurodegenerative processes, an idea called the "calcium hypothesis" of neurodegeneration. Caenorhabditis elegans (C. elegans) is a very good model for the study of aging and neurodegeneration. In fact, many of the signaling pathways involved in longevity were first discovered in this nematode, and many models of neurodegenerative diseases have also been developed therein, either through mutations in the worm genome or by expressing human proteins involved in neurodegeneration (β-amyloid, α-synuclein, polyglutamine, or others) in defined worm tissues. The worm is completely transparent throughout its whole life, which makes it possible to carry out Ca²⁺ dynamics studies in vivo at any time, by expressing Ca²⁺ fluorescent probes in defined worm tissues, and even in specific organelles such as mitochondria. This review will summarize the evidence obtained using this model organism to understand the role of Ca²⁺ signaling in aging and neurodegeneration.

Targeting Mitochondria to Counteract Age-Related Cellular Dysfunction

Senescence is related to the loss of cellular homeostasis and functions, which leads to a progressive decline in physiological ability and to aging-associated diseases. Since mitochondria are essential to energy supply, cell differentiation, cell cycle control, intracellular signaling and Ca²⁺ sequestration, fine-tuning mitochondrial activity appropriately, is a tightrope walk during aging. For instance, the mitochondrial oxidative phosphorylation (OXPHOS) ensures a supply of adenosine triphosphate (ATP), but is also the main source of potentially harmful levels of reactive oxygen species (ROS). Moreover, mitochondrial function is strongly linked to mitochondrial Ca²⁺ homeostasis and mitochondrial shape, which undergo various alterations during aging. Since mitochondria play such a critical role in an organism’s process of aging, they also offer promising targets for manipulation of senescent cellular functions. Accordingly, interventions delaying the onset of age-associated disorders involve the manipulation of mitochondrial function, including caloric restriction (CR) or exercise, as well as drugs, such as metformin, aspirin, and polyphenols. In this review, we discuss mitochondria’s role in and impact on cellular aging and their potential to serve as a target for therapeutic interventions against age-related cellular dysfunction.