Biophysical analysis of drug efficacy on C. elegans models for neurodegenerative and neuromuscular diseases

C. elegans: a prominent platform for modeling and drug screening in neurological disorders

INTRODUCTION

Human neurodevelopmental and neurodegenerative diseases (NDevDs and NDegDs, respectively) encompass a broad spectrum of disorders affecting the nervous system with an increasing incidence. In this context, the nematode C. elegans, has emerged as a benchmark model for biological research, especially in the field of neuroscience.

AREAS COVERED

The authors highlight the numerous advantages of this tiny worm as a model for exploring nervous system pathologies and as a platform for drug discovery. There is a particular focus given to describing the existing models of C. elegans for the study of NDevDs and NDegDs. Specifically, the authors underscore their strong applicability in preclinical drug development. Furthermore, they place particular emphasis on detailing the common techniques employed to explore the nervous system in both healthy and diseased states.

EXPERT OPINION

Drug discovery constitutes a long and expensive process. The incorporation of invertebrate models, such as C. elegans, stands as an exemplary strategy for mitigating costs and expediting timelines. The utilization of C. elegans as a platform to replicate nervous system pathologies and conduct high-throughput automated assays in the initial phases of drug discovery is pivotal for rendering therapeutic options more attainable and cost-effective.

Exploring Caenorhabditis elegans as Parkinson's Disease Model: Neurotoxins and Genetic Implications

Parkinson's disease (PD) is the second most common neurodegenerative disease in the world, the first being Alzheimer's disease. Patients with PD have a loss of dopaminergic neurons in the substantia nigra of the basal ganglia, which controls voluntary movements, causing a motor impairment as a result of dopaminergic signaling impairment. Studies have shown that mutations in several genes, such as SNCA, PARK2, PINK1, DJ-1, ATP13A2, and LRRK2, and the exposure to neurotoxic agents can potentially increase the chances of PD development. The nematode Caenorhabditis elegans (C. elegans) plays an important role in studying the risk factors, such as genetic factors, aging, exposure to chemicals, disease progression, and drug treatments for PD. C. elegans has a conserved neurotransmission system during evolution; it produces dopamine, through the eight dopaminergic neurons; it can be used to study the effect of neurotoxins and also has strains that express human α-synuclein. Furthermore, the human PD-related genes, LRK-1, PINK-1, PDR-1, DJR-1.1, and CATP-6, are present and functional in this model. Therefore, this review focuses on highlighting and discussing the use of C. elegans an in vivo model in PD-related studies. Here, we identified that nematodes exposed to the neurotoxins, such as 6-OHDA, MPTP, paraquat, and rotenone, had a progressive loss of dopaminergic neurons, dopamine deficits, and decreased survival rate. Several studies have reported that expression of human LRRK2 (G2019S) caused neurodegeneration and pink-1, pdr-1, and djr-1.1 deletion caused several effects PD-related in C. elegans, including mitochondrial dysfunctions. Of note, the deletion of catp-6 in nematodes caused behavioral dysfunction, mitochondrial damage, and reduced survival. In addition, nematodes expressing α-synuclein had neurodegeneration and dopamine-dependent deficits. Therefore, C. elegans can be considered an accurate animal model of PD that can be used to elucidate to assess the underlying mechanisms implicated in PD to find novel therapeutic targets.

Palladium (II) compounds containing oximes as promising antitumor agents for the treatment of osteosarcoma: An in vitro and in vivo comparative study with cisplatin

Drug resistance, evasion of cell death and metastasis are factors that contribute to the low cure rate and disease-free survival in osteosarcomas (OS). In this study, we demonstrated that a new class of oxime-containing organometallic complexes called Pd-BPO (O3) and Pd-BMO (O4) are more cytotoxic than cisplatin (CDDP) for SaOS-2 and U2OS cells using the MTT assay. Annexin-FITC/7-AAD staining demonstrated a greater potential for palladium-oxime complexes to induce death in SaOS-2 cells than CDDP, an event confirmed using the pan-caspase inhibitor Z-VAD-FMK. Compared to CDDP, only palladium-oxime complexes eradicated the clonogenicity of SaOS-2 cells after 7 days of treatment. The involvement of the lysosome-mitochondria axis in the cell death-inducing properties of the complexes was also evaluated. Using LysoTracker Red to label the acidic organelles of SaOS-2 cells treated with the O3 and O4 complexes, a decrease in the fluorescence intensity of this probe was observed in relation to CDDP and the control. Lysosomal membrane permeabilization (LMP) was also induced by the O3 and O4 complexes in an assay using acridine orange (A/O). The greater efficiency of the complexes in depolarizing the mitochondrial membrane compared to SaOS-2 cells treated with CDDP was also observed using TMRE (tetramethyl rhodamine, ethyl ester). For in vivo studies, C. elegans was used and demonstrated that both complexes reduce body bends and pharyngeal pumping after 24 h of treatment to the same extent as CDDP. We conclude that both palladium-oxime complexes are more effective than CDDP in inducing tumor cell death. The toxicity of these complexes to C. elegans was like that induced by CDDP. These results encourage preclinical studies aimed at developing more effective drugs for the treatment of osteosarcoma (OS). Furthermore, we propose palladium-oxime complexes as a new class of antineoplastic agents.

Microfluidic techniques for mechanical measurements of biological samples

The use of microfluidics to make mechanical property measurements is increasingly common. Fabrication of microfluidic devices has enabled various types of flow control and sensor integration at micrometer length scales to interrogate biological materials. For rheological measurements of biofluids, the small length scales are well suited to reach high rates, and measurements can be made on droplet-sized samples. The control of flow fields, constrictions, and external fields can be used in microfluidics to make mechanical measurements of individual bioparticle properties, often at high sampling rates for high-throughput measurements. Microfluidics also enables the measurement of bio-surfaces, such as the elasticity and permeability properties of layers of cells cultured in microfluidic devices. Recent progress on these topics is reviewed, and future directions are discussed.

Contrasting dose response relationships of neuroactive antidepressants on the behavior of C. elegans

Antidepressant prescriptions are on a rise worldwide and this increases the concerns for the impacts of these pharmaceuticals on nontarget organisms. Antidepressants are neuroactive compounds that can affect organism's behavior. Behavior is a sensitive endpoint that may also propagate effects at a population level. Another interesting aspect of antidepressants is that they have shown to induce non-monotonic dose-response (NMDR) curves. While such NMDR relationships may have clear implications for the environmental risk, the resolution of current studies is often too coarse to be able to detect relevant NMDR. Therefore, the current study was performed into the behavioral effects (activity, feeding and chemotaxis) in Caenorhabditis elegans as the model organism of the selective serotonin reuptake inhibitors fluoxetine and sertraline and the acetylcholinesterase inhibiting pesticide chlorpyrifos, using a wide range of concentrations (ng/l to mg/l). In order to statistically examine the non-monotonicity, nonlinear regression models were applied to the results. The results showed a triphasic dose-response relationship for activity and chemotaxis after exposure to fluoxetine, but not to sertraline or chlorpyrifos. Effects of fluoxetine already occurred at low concentrations in the range of ng/l while sertraline only showed effects at concentrations in the μg/l range, similar to chlorpyrifos. The different responses between fluoxetine and sertraline, both SSRIs, indicate that response patterns may not always be extrapolated from chemicals with the same primary mode of action. The effects of fluoxetine at low concentrations, in a non-monotonic manner, confirm the relevance of examining such responses at low concentrations.

Using a Caenorhabditis elegans Parkinson's Disease Model to Assess Disease Progression and Therapy Efficiency

Despite Parkinson's Disease (PD) being the second most common neurodegenerative disease, treatment options are limited. Consequently, there is an urgent need to identify and screen new therapeutic compounds that slow or reverse the pathology of PD. Unfortunately, few new therapeutics are being produced, partly due to the low throughput and/or poor predictability of the currently used model organisms and in vivo screening methods. Our objective was to develop a simple and affordable platform for drug screening utilizing the nematode Caenorhabditis elegans. The effect of Levodopa, the "Gold standard" of PD treatment, was explored in nematodes expressing the disease-causing α-synuclein protein. We focused on two key hallmarks of PD: plaque formation and mobility. Exposure to Levodopa ameliorated the mobility defect in C. elegans, similar to people living with PD who take the drug. Further, long-term Levodopa exposure was not detrimental to lifespan. This C. elegans-based method was used to screen a selection of small-molecule drugs for an impact on α-synuclein aggregation and mobility, identifying several promising compounds worthy of further investigation, most notably Ambroxol. The simple methodology means it can be adopted in many labs to pre-screen candidate compounds for a positive impact on disease progression.

Structured Long-Chain Omega-3 Fatty Acids for Improvement of Cognitive Function during Aging

Although the human lifespan has increased in the past century owing to advances in medicine and lifestyle, the human healthspan has not kept up the same pace, especially in brain aging. Consequently, the role of preventive health interventions has become a crucial strategy, in particular, the identification of nutritional compounds that could alleviate the deleterious effects of aging. Among nutrients to cope with aging in special cognitive decline, the long-chain omega-3 polyunsaturated fatty acids (ω-3 LCPUFAs) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), have emerged as very promising ones. Due to their neuroinflammatory resolving effects, an increased status of DHA and EPA in the elderly has been linked to better cognitive function and a lower risk of dementia. However, the results from clinical studies do not show consistent evidence and intake recommendations for old adults are lacking. Recently, supplementation with structured forms of EPA and DHA, which can be derived natural forms or targeted structures, have proven enhanced bioavailability and powerful benefits. This review summarizes present and future perspectives of new structures of ω-3 LCPUFAs and the role of "omic" technologies combined with the use of high-throughput in vivo models to shed light on the relationships and underlying mechanisms between ω-3 LCPUFAs and healthy aging.