Pyruvate Dehydrogenase Kinase Protects Dopaminergic Neurons from Oxidative Stress in Drosophila DJ-1 Null Mutants

PDH Inhibition in Drosophila Ameliorates Sensory Dysfunction Induced by Vincristine Treatment in the Chemotherapy-Induced Peripheral Neuropathy Models

Background/Objectives: Chemotherapy-induced peripheral neuropathy (CIPN) is a significant dose-limiting side effect of many effective anticancer agents, including vincristine. While CIPN adversely affects both oncological outcomes and the quality of life for cancer patients, the in vivo mechanisms behind CIPN pathology remain largely unknown, and effective treatments have yet to be developed. In this study, we established a novel Drosophila model of CIPN using vincristine to explore the molecular mechanisms underlying this condition. Methods: We assessed the impact of vincristine exposure on thermal nociception in Drosophila larvae using a programmable heat probe. Additionally, we investigated vincristine-induced mitochondrial dysfunction and dendritic abnormalities in class IV dendritic arborization (C4da) neurons with various fluorescent protein markers. Results: We found a dose-dependent increase in thermal hypersensitivity, accompanied by changes in the sensory dendrites of C4da neurons in vincristine-treated fly larvae. Moreover, vincristine significantly enhanced mitochondrial ROS production and mitophagy-a selective autophagy that targets dysfunctional mitochondria-indicating vincristine-induced mitochondrial dysfunction within C4da neurons. Surprisingly, inhibiting the pyruvate dehydrogenase complex (PDH), a key mitochondrial metabolic enzyme complex, effectively rescued the mitochondrial and sensory abnormalities caused by vincristine. Conclusions: Findings from this first Drosophila model of vincristine-induced peripheral neuropathy (VIPN) suggest that mitochondrial dysfunction plays a critical role in VIPN pathology, representing PDH as a potential target for the treatment of VIPN.

Investigating the link between microplastic exposure (benzyl butyl phthalate) and neurodegenerative diseases using high-performance computational toxicology

Background

Microplastics are tiny plastic particles, typically less than 5 mm in size, formed from the breakdown of larger plastic products. This breakdown releases additives, including benzyl butyl phthalate (BBP), into the environment. Humans can be exposed to BBP through contaminated food and water, inhalation, and dermal contact.

Aim

Research suggests that BBP, like other phthalates, may have neurotoxic effects, potentially contributing to neurodevelopmental disorders, though its specific toxic targets are not yet clear.

Methodology

In this study, high-performance computational methods were used to identify potential neurotoxic targets of BBP. The findings indicate that BBP has a strong potential to interact with Parkin (PRKN) and Pyruvate dehydrogenase lipoamide kinase isozyme 1 (PDK1), with binding scores of -5.35 kcal/mol, -5.56 kcal/mol, respectively. The PRKN and PDK1 BBP complexes were stable throughout the simulation period, as evidenced by the system's backbone exhibiting slight fluctuations and binding energies confirmed by molecular dynamics (MD) simulation trajectories.

Results

The MMPBSA analysis revealed free binding energies of -21.29 kcal/mol and - 27.06 kcal/mol for the PRKN and PDK1 BBP complexes, respectively. The interaction energies of BBP with PRKN and PDK1 were also within an acceptable range, at -113.68 ± 3.1 kJ/mol and - 117.54 ± 6.2 kJ/mol, respectively. Additionally, density-functional theory (DFT) based optimization showed negative values for the highest occupied molecular orbital (HOMO) -6.934 eV and lowest unoccupied molecular orbital (LUMO) -1.562 eV, indicating that BBP is energetically stable, which is crucial for forming a stable ligand-protein complex.

Conclusion

Overall, the computational investigation reveals that BBP has the potential to interact with PRKN and PDK1, leading to neurodegeneration.

Pyruvate dehydrogenase kinases: key regulators of cellular metabolism and therapeutic targets for metabolic diseases

Pyruvate dehydrogenase kinases (PDKs) can regulate the conversion of pyruvate to acetyl coenzyme A through the mitochondrial pyruvate dehydrogenase complex (PDHC). As the rate-limiting enzymes of PDHC, PDKs link glycolysis to the tricarboxylic acid cycle. Pathological changes in many diseases involve alterations in cellular metabolism, which are partly reflected in changes in mitochondrial function. The intermediate role of PDKs in metabolic processes allows for the influence of both glycolysis and oxidative phosphorylation. Recent studies have shown that PDKs play a crucial role in regulating metabolic reprogramming, mitochondrial function and cellular activities in both oncological studies and various non-oncological diseases. This paper aims to clarify the molecular regulatory mechanisms of PDKs; review the relationship of PDKs with cellular metabolic reprogramming, regulation of ROS, and apoptosis; and the present status of research on PDKs in osteoporosis, diabetes mellitus, and vascular diseases. With this review, we have increased our understanding and insight at the molecular level, providing new insights into targeting PDKs to reverse metabolism-related diseases.

The Double-Edged Sword of Total Antioxidant Capacity: Clinical Significance and Personal Experience

Oxidative stress (OS) could be a condition underlying several human diseases, despite the physiological role of reactive oxygen species (oxidative eustress). Therefore, antioxidant compounds could represent a modulatory mechanism for maintaining a proper redox balance and redox signaling. When antioxidants are insufficient or overwhelmed, OS ensues, causing multiple damages at molecular, tissue, and cellular levels. This study focuses on the role of total antioxidant capacity (TAC) as a biomarker to be interpreted according to several clinical scenarios. After a brief description of various assay methods to elucidate terminology and physiopathological roles, we focus on the hormonal influence on TAC in blood plasma and other biological fluids, as different endocrine systems can modulate the antioxidant response. Furthermore, OS characterizes several endocrinopathies through different mechanisms: an inadequate antioxidant response to an increase in reducing equivalents (reductive distress) or a marked consumption of antioxidants (oxidative distress), which leads to low TAC values. An increased TAC could instead represent an adaptive mechanism, suggesting a situation of OS. Hence, the clinical context is fundamental for a correct interpretation of TAC. This review aims to provide the reader with a general overview of oxidative stress in several clinical examples of endocrine relevance, such as metabolic syndrome, non-thyroid illness syndrome, hypopituitarism, and infertility. Finally, the impact of dietary and surgical interventions on TAC in the model of metabolic syndrome is highlighted, along with personal experience.

The alpha-ketoacid dehydrogenase complexes of Drosophila melanogaster

The conserved family of alpha-ketoacid dehydrogenase complexes (AKDHCs) catalyze essential reactions in central metabolism and their dysregulation is implicated in several human diseases. Drosophila melanogaster provides an excellent model system to study the genetics and functions of these complexes. However, a systematic account of Drosophila AKDHCs and their composition has been lacking. Here, I identify and classify the genes encoding all Drosophila AKDHC subunits, update their functional annotations and integrate this work into the FlyBase database.

A comparison study of pathological features and drug efficacy between Drosophila models of C9orf72 ALS/FTD

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease with a complex genetic basis, presenting both in familial and sporadic forms. The hexanucleotide (G4C2) repeat expansion in the C9orf72 gene, which triggers distinct pathogenic mechanisms, has been identified as a major contributor to familial and sporadic Amyotrophic lateral sclerosis cases. Animal models have proven pivotal in understanding these mechanisms; however, discrepancies between models due to variable transgene sequence, expression levels, and toxicity profiles complicate the translation of findings. Herein, we provide a systematic comparison of 7 publicly available Drosophila transgenes modeling the G4C2 expansion under uniform conditions, evaluating variations in their toxicity profiles. Further, we tested 3 previously characterized disease-modifying drugs in selected lines to uncover discrepancies among the tested strains. Our study not only deepens our understanding of the C9orf72 G4C2 mutations but also presents a framework for comparing constructs with minute structural differences. This work may be used to inform experimental designs to better model disease mechanisms and help guide the development of targeted interventions for neurodegenerative diseases, thus bridging the gap between model-based research and therapeutic application.

Function and regulation of nitric oxide signaling in Drosophila

Nitric oxide (NO) serves as an evolutionarily conserved signaling molecule that plays an important role in a wide variety of cellular processes. Extensive studies in Drosophila melanogaster have revealed that NO signaling is required for development, physiology, and stress responses in many different types of cells. In neuronal cells, multiple NO signaling pathways appear to operate in different combinations to regulate learning and memory formation, synaptic transmission, selective synaptic connections, axon degeneration, and axon regrowth. During organ development, elevated NO signaling suppresses cell cycle progression, whereas downregulated NO leads to an increase in larval body size via modulation of hormone signaling. The most striking feature of the Drosophila NO synthase is that various stressors, such as neuropeptides, aberrant proteins, hypoxia, bacterial infection, and mechanical injury, can activate Drosophila NO synthase, initially regulating cellular physiology to enable cells to survive. However, under severe stress or pathophysiological conditions, high levels of NO promote regulated cell death and the development of neurodegenerative diseases. In this review, I highlight and discuss the current understanding of molecular mechanisms by which NO signaling regulates distinct cellular functions and behaviors.

Cumulus Cell and Oocyte Gene Expression in Prepubertal Gilts and Sows Identifies Cumulus Cells as a Prime Informative Parameter of Oocyte Quality

Cumulus cells (CCs) are pivotal during oocyte development. This study aimed to identify novel marker genes for porcine oocyte quality by examining the expression of selected genes in CCs and oocytes, employing the model of oocytes from prepubertal animals being of reduced quality compared to those from adult animals. Total RNA was extracted either directly after follicle aspiration or after in vitro maturation, followed by RT-qPCR. Immature gilt CCs accumulated BBOX1 transcripts, involved in L-carnitine biosynthesis, to a 14.8-fold higher level (p < 0.05) relative to sows, while for CPT2, participating in fatty acid oxidation, the level was 0.48 (p < 0.05). While showing no differences between gilt and sow CCs after maturation, CPT2 and BBOX1 levels in oocytes were higher in gilts at both time points. The apparent delayed lipid metabolism and reduced accumulation of ALDOA and G6PD transcripts in gilt CCs after maturation, implying downregulation of glycolysis and the pentose phosphate pathway, suggest gilt cumulus-oocyte complexes have inadequate ATP stores and oxidative stress balance compared to sows at the end of maturation. Reduced expression of BBOX1 and higher expression of CPT2 in CCs before maturation and higher expression of G6PD and ALDOA after maturation are new potential markers of oocyte quality.

Suboptimal Mitochondrial Activity Facilitates Nuclear Heat Shock Responses for Proteostasis and Genome Stability

Thermal stress induces dynamic changes in nuclear proteins and relevant physiology as a part of the heat shock response (HSR). However, how the nuclear HSR is fine-tuned for cellular homeostasis remains elusive. Here, we show that mitochondrial activity plays an important role in nuclear proteostasis and genome stability through two distinct HSR pathways. Mitochondrial ribosomal protein (MRP) depletion enhanced the nucleolar granule formation of HSP70 and ubiquitin during HSR while facilitating the recovery of damaged nuclear proteins and impaired nucleocytoplasmic transport. Treatment of the mitochondrial proton gradient uncoupler masked MRP-depletion effects, implicating oxidative phosphorylation in these nuclear HSRs. On the other hand, MRP depletion and a reactive oxygen species (ROS) scavenger non-additively decreased mitochondrial ROS generation during HSR, thereby protecting the nuclear genome from DNA damage. These results suggest that suboptimal mitochondrial activity sustains nuclear homeostasis under cellular stress, providing plausible evidence for optimal endosymbiotic evolution via mitochondria-to-nuclear communication.

The pyruvate dehydrogenase complex: Life's essential, vulnerable and druggable energy homeostat

Found in all organisms, pyruvate dehydrogenase complexes (PDC) are the keystones of prokaryotic and eukaryotic energy metabolism. In eukaryotic organisms these multi-component megacomplexes provide a crucial mechanistic link between cytoplasmic glycolysis and the mitochondrial tricarboxylic acid (TCA) cycle. As a consequence, PDCs also influence the metabolism of branched chain amino acids, lipids and, ultimately, oxidative phosphorylation (OXPHOS). PDC activity is an essential determinant of the metabolic and bioenergetic flexibility of metazoan organisms in adapting to changes in development, nutrient availability and various stresses that challenge maintenance of homeostasis. This canonical role of the PDC has been extensively probed over the past decades by multidisciplinary investigations into its causal association with diverse physiological and pathological conditions, the latter making the PDC an increasingly viable therapeutic target. Here we review the biology of the remarkable PDC and its emerging importance in the pathobiology and treatment of diverse congenital and acquired disorders of metabolic integration.

α-Synuclein Disrupts Vesicle Fusion by Two Mutant-Specific Mechanisms

Synaptic accumulation of α-synuclein (α-Syn) oligomers and their interactions with VAMP2 have been reported to be the basis of synaptic dysfunction in Parkinson's disease (PD). α-Syn mutants associated with familial PD have also been known to be capable of interacting with VAMP2, but the exact mechanisms resulting from those interactions to eventual synaptic dysfunction are still unclear. Here, we investigate the effect of α-Syn mutant oligomers comprising A30P, E46K, and A53T on VAMP2-embedded vesicles. Specifically, A30P and A53T oligomers cluster vesicles in the presence of VAMP2, which is a shared mechanism with wild type α-Syn oligomers induced by dopamine. On the other hand, E46K oligomers reduce the membrane mobility of the planar bilayers, as revealed by single-particle tracking, and permeabilize the membranes in the presence of VAMP2. In the absence of VAMP2 interactions, E46K oligomers enlarge vesicles by fusing with one another. Our results clearly demonstrate that α-Syn mutant oligomers have aberrant effects on VAMP2-embedded vesicles and the disruption types are distinct depending on the mutant types. This work may provide one of the possible clues to explain the α-Syn mutant-type dependent pathological heterogeneity of familial PD.