Plate-Based Respirometry to Assess Thermal Sensitivity of Zebrafish Embryo Bioenergetics in situ

Photodynamic therapy photosensitizers and photoactivated chemotherapeutics exhibit distinct bioenergetic profiles to impact ATP metabolism

Energy is essential for all life, and mammalian cells generate and store energy in the form of ATP by mitochondrial (oxidative phosphorylation) and non-mitochondrial (glycolysis) metabolism. These processes can now be evaluated by extracellular flux analysis (EFA), which has proven to be an indispensable tool in cell biology, providing previously inaccessible information regarding the bioenergetic landscape of cell lines, complex tissues, and in vivo models. Recently, EFA demonstrated its utility as a screening tool in drug development, both by providing insights into small molecule-organelle interactions, and by revealing the peripheral and potentially undesired off-target effects small molecules have within cells. Surprisingly, technologies to quantify cellular bioenergetics have not been systematically applied in phototherapy development, leaving open several questions about how the mechanism of action of a compound can impact essential cellular functions. Here, we utilized the Seahorse analyzer to address this question for photosensitizers (PSs) for photodynamic therapy (PDT) and contrast these systems to molecules that photo-release a ligand and thus act as photocages or photoactivated chemotherapeutics (PACT), intending to understand the influence these two classes of compounds have on cellular bioenergetics. EFA results show that acute treatment of A549 lung adenocarcinoma cells with PDT agents induces a quiescent bioenergetic response as a result of mitochondrial respiration shutdown. The loss of oxidative phosphorylation is followed by disruption of glycolysis, which occurs after an initial increase in glycolytic respiration is unable to compensate for the interruption of the electron transport chain (ETC). In contrast, the PACT agents tested had little impact on cellular respiration, and the minor inhibition of these metabolic processes was not related to the mechanism of action, as reflected by a lack of correlation with photoejection efficiency. Notably, a system capable of both generating 1O2 and photo-releasing a ligand exhibited the dominant profile of a PDT agent and induced the quiescent bioenergetic state, indicating potential implications on cellular bioenergetics for so-called dual-action agents. These findings are presented with the aim to provide the necessary groundwork for expanding the application and utility of EFA to phototherapeutics and to highlight the role of metabolic alterations in PDT.

Polystyrene nanoplastics impact the bioenergetics of developing zebrafish and limit molecular and physiological adaptive responses to acute temperature stress

Plastic pollution is a growing environmental concern due to its ubiquitous impact on aquatic ecosystems. Nanoplastics can be generated from the breakdown of plastic waste and interact with organisms at the cellular level, potentially disrupting cellular physiology. We investigated the effects of 44 nm polystyrene nanoparticles (44 nm NanoPS) on the development and physiology of zebrafish (Danio rerio) in the presence of sublethal heat stress (32 °C vs control, 28 °C). We hypothesized that the simultaneous exposure to nanoplastics and rising temperatures seriously threaten developing fish. This combination could create a critical imbalance: rising temperatures may lead to heightened energy demands, while nanoplastic exposure reduces energy production, threatening animal survival. As expected, 32 °C increased markers associated with animal metabolism and developmental timing, such as growth, hatching, heart rate, and feeding. Changes in apoptosis dynamics, oxygen consumption rates, and a decrease in mitochondrial content were detected as adaptive processes to temperature. 44 nm NanoPS alone did not alter development but decreased mitochondrial efficiency in ATP production and increased apoptosis in the heart. Surprisingly, exposure to 44 nm NanoPS at 32 °C did not cause major implications to survival, developmental success, or morphology. Still, 44 nm NanoPS mitigated the temperature-driven change in heart rate, increased oxidative stress, and decreased the coupling efficiency of the less abundant and highly active mitochondria under heat stress. We highlight the interplay between temperature and nanoplastics exposure and suggest that the combined impact of nanoplastics and temperature stress results in a scenario where physiological adaptations are strained, potentially leading to compromised development. This research underscores the need for further investigation into the metabolic costs of plastic pollution, particularly in the context of global warming, to better understand its long-term implications for aquatic life.

SCAR32: Functional characterization and expansion of the clinical-genetic spectrum

OBJECTIVE

Biallelic mutations in PRDX3 have been linked to autosomal recessive spinocerebellar ataxia type 32. In this study, which aims to contribute to the growing body of knowledge on this rare disease, we identified two unrelated patients with mutations in PRDX3. We explored the impact of PRDX3 mutation in patient skin fibroblasts and the role of the gene in neurodevelopment.

METHODS

We performed trio exome sequencing that identified mutations in PRDX3 in two unrelated patients. We also performed functional studies in patient skin fibroblasts and generated a "crispant" zebrafish (Danio rerio) model to investigate the role of the gene during nervous system development.

RESULTS

Our study reports two additional patients. Patient 1 is a 19-year-old male who showed a novel homozygous c.525_535delGTTAGAAGGTT (p. Leu176TrpfsTer11) mutation as the genetic cause of cerebellar ataxia. Patient 2 is a 20-year-old male who was found to present the known c.425C>G/p. Ala142Gly variant in compound heterozygosity with the p. Leu176TrpfsTer11 one. While the fibroblast model failed to recapitulate the pathological features associated with PRDX3 loss of function, our functional characterization of the prdx3 zebrafish model revealed motor defects, increased susceptibility to reactive oxygen species-triggered apoptosis, and an impaired oxygen consumption rate.

CONCLUSIONS

We identified a new variant, thereby expanding the genetic spectrum of PRDX3-related disease. We developed a novel zebrafish model to investigate the consequences of prdx3 depletion on neurodevelopment and thus offered a potential new tool for identifying new treatment opportunities.

Aspartame Causes Developmental Defects and Teratogenicity in Zebra Fish Embryo: Role of Impaired SIRT1/FOXO3a Axis in Neuron Cells

Aspartame, a widely used artificial sweetener, is present in many food products and beverages worldwide. It has been linked to potential neurotoxicity and developmental defects. However, its teratogenic effect on embryonic development and the underlying potential mechanisms need to be elucidated. We investigated the concentration- and time-dependent effects of aspartame on zebrafish development and teratogenicity. We focused on the role of sirtuin 1 (SIRT1) and Forkhead-box transcription factor (FOXO), two proteins that play key roles in neurodevelopment. It was found that aspartame exposure reduced the formation of larvae and the development of cartilage in zebrafish. It also delayed post-fertilization development by altering the head length and locomotor behavior of zebrafish. RNA-sequencing-based DEG analysis showed that SIRT1 and FOXO3a are involved in neurodevelopment. In silico and in vitro analyses showed that aspartame could target and reduce the expression of SIRT1 and FOXO3a proteins in neuron cells. Additionally, aspartame triggered the reduction of autophagy flux by inhibiting the nuclear translocation of SIRT1 in neuronal cells. The findings suggest that aspartame can cause developmental defects and teratogenicity in zebrafish embryos and reduce autophagy by impairing the SIRT1/FOXO3a axis in neuron cells.

The enhanced mitochondrial dysfunction by cantleyoside confines inflammatory response and promotes apoptosis of human HFLS-RA cell line via AMPK/Sirt 1/NF-κB pathway activation

OBJECTIVE

Cantleyoside (CA) is a kind of iridoid glycosides in Pterocephalus hookeri (C. B. Clarke) Höeck. The purpose of this study was to investigate the effects of CA on human rheumatoid arthritis fibroblast synovial cells (HFLS-RA).

METHODS

Cell proliferation of HFLS-RA was assessed by CCK-8. ELISA was used to detect cytokines NO, TNF-α, IL-1β/6, MCP-1, MMP-1/3/9 and metabolism-related ATPase activities and ATP levels. JC-1, DCFH-DA, Fluo-3 AM and Calcein AM probes were used to detect mitochondrial membrane potential (MMP), reactive oxygen species (ROS), Ca²⁺ and mitochondrial permeability conversion pore (MPTP), respectively. Isolated mitochondria assay was used to detect mitochondrial swelling. Oxygen consumption rate (OCR), extracellular acidification rate (ECAR) and real-time ATP production were measured using a Seahorse analyzer. Apoptosis was detected by TUNEL and Hoechst staining. Western blot was used to detect the expressions of AMPK/p-AMPK, Sirt 1, IκBα, NF-κB p65/p-NF-κB p65, Bcl-2 and Bax. Cytoplasmic nuclear isolation was also performed to detect the translocation of NF-κB.

RESULTS

CA significantly suppressed cell proliferation and the levels of NO, TNF-α, IL-1β/6, MCP-1 and MMP-1/3/9 in HFLS-RA. In addition, CA promoted the apoptosis of HFLS-RA by increasing TUNEL and Hoechst positive cells and the ratio of Bax/Bcl-2. Inhibition of energy metabolism in HFLS-RA by CA reduced OCR, ECAR and real-time ATP generation rate. Importantly, CA promoted p-AMPK and Sirt 1 expression, inhibited IκBα degradation to reduce p-NF-κB and translocation.

CONCLUSION

The results suggest that CA activates the AMPK/Sirt 1/NF-κB pathway by promoting mitochondrial dysfunction, thereby exerting anti-inflammatory and pro-apoptotic effects.

Physiological Performance Curves: When Are They Useful?

This review serves as an introduction to a special issue of Frontiers in Physiology, focused on the importance of physiological performance curves across phylogenetic and functional boundaries. Biologists have used performance curves to describe the effects of changing environmental conditions on animal physiology since the late 1800s (at least). Animal physiologists have studied performance curves extensively over the past decades, and there is a good foundation to understanding how the environment affects physiological functions of individuals. Our goal here was to build upon this research and address outstanding questions regarding the mutability and applicability of performance curves across taxonomic groups and levels of biological organization. Performance curves are not fixed at a taxonomic, population, or individual level – rather they are dynamic and can shift in response to evolutionary pressures (e.g., selection) and epigenetic programming (e.g., plasticity). The mechanisms underlying these shifts are being increasingly used to predict the efficacy with which plasticity and heritability of performance curves can render individuals and populations less vulnerable to climate change. Individual differences in physiological performance curves (and plasticity of performance curves) can also have cascading effects at higher levels of biological organization. For instance, individual physiology likely influences group behaviors in non-additive ways. There is a need therefore to extend the concept of performance curves to social interactions and sociality. Collectively, this special issue emphasizes the power of how within- and between-individual shifts in performance curves might scale up to the population-, species-, and community-level dynamics that inform conservation management strategies.