The Peculiar Facets of Nitric Oxide as a Cellular Messenger: From Disease-Associated Signaling to the Regulation of Brain Bioenergetics and Neurovascular Coupling

Investigating hormesis, aging, and neurodegeneration: From bench to clinics

Mitochondria-derived reactive oxygen species production at a moderate physiological level plays a fundamental role in the anti-aging signaling, due to their action as redox-active sensors for the maintenance of optimal mitochondrial balance between intracellular energy status and hormetic nutrients. Iron regulatory protein dysregulation, systematically increased iron levels, mitochondrial dysfunction, and the consequent oxidative stress are recognized to underlie the pathogenesis of multiple neurodegenerative diseases, such as Parkinson's disease and Alzheimer's disease. Central to their pathogenesis, Nrf2 signaling dysfunction occurs with disruption of metabolic homeostasis. We highlight the potential therapeutic importance of nutritional polyphenols as substantive regulators of the Nrf2 pathway. Here, we discuss the common mechanisms targeting the Nrf2/vitagene pathway, as novel therapeutic strategies to minimize consequences of oxidative stress and neuroinflammation, generally associated to cognitive dysfunction, and demonstrate its key neuroprotective and anti-neuroinflammatory properties, summarizing pharmacotherapeutic aspects relevant to brain pathophysiology.

Integrated multi-omics profiling highlights the benefits of resveratrol hydroxypropyl-β-cyclodextrin inclusion complex for A53T transgenic mice through the microbiota-gut-brain axis

Parkinson's disease (PD) is a neurological disorder characterized by motor and gastrointestinal dysfunctions. Resveratrol is a potent antioxidant and anti-inflammatory phytoalexin known for its health-promoting benefits. However, little is known about its potential in treating PD by modulating the microbial gut-brain axis, and its clinical application has been limited due to poor water solubility, rapid metabolism, and limited systemic bioavailability. Our study aimed to evaluate the therapeutic potential of RHSD, a resveratrol-cyclodextrin inclusion complex, in treating PD through the gut-brain axis in human SNCA-transgenic (A53T) mice PD models. Building on our previous study, we prepared RHSD and compared its efficacy with uncoated resveratrol for PD treatment. The study results demonstrated that RHSD exhibited several advantages in improving motor function, alleviating cognitive impairment, restoring intestinal barrier function, and inhibiting neuropathy. Subsequently, a series of analyses, including fecal microbiota metagenomic sequencing, non-target metabolic assays, host transcriptome sequencing, and integrative analysis were performed to reveal the potential therapeutic pathways of RHSD in A53T mice. The metagenomic sequencing results indicated a significant increase in the levels of Lactobacillus murinus, Lactobacillus reuteri, Enterorhabduscaecimuris, Lactobacillus taiwanensis, and Lactobacillus animals following RHSD administration. Furthermore, metabolomics profiling showed that the levels of gut microbiome metabolites were reversed after RHSD treatment, and differential metabolites were significantly correlated with motor function and intestinal function in PD mice. The integrated analysis of microbial metabolites and host transcriptomics suggested that abnormal amino acid metabolism, mitochondrial dysfunction, oxidative stress, and neuroinflammation in the PD model were associated with the diffusion of abnormal metabolites. This study illustrates the profound impact of RHSD administration on rectifying gut microbiota dysbiosis and improving the A53T mouse model. Notably, we observed significant alterations in the proliferation and metabolism of multiple probiotic strains of Lactobacillus. Furthermore, our research supports the hypothesis that microbiota-related metabolites may regulate the transcription of host genes, including dopamine receptors and calcium stabilization. Consequently, our findings underscore the potential of RHSD as a promising therapeutic candidate for the treatment of PD through the modulation of several signaling pathways within the microbiota-gut-brain axis.

S-Nitrosylation-mediated dysfunction of TCA cycle enzymes in synucleinopathy studied in postmortem human brains and hiPSC-derived neurons

A causal relationship between mitochondrial metabolic dysfunction and neurodegeneration has been implicated in synucleinopathies, including Parkinson disease (PD) and Lewy body dementia (LBD), but underlying mechanisms are not fully understood. Here, using human induced pluripotent stem cell (hiPSC)-derived neurons with mutation in the gene encoding α-synuclein (αSyn), we report the presence of aberrantly S-nitrosylated proteins, including tricarboxylic acid (TCA) cycle enzymes, resulting in activity inhibition assessed by carbon-labeled metabolic flux experiments. This inhibition principally affects α-ketoglutarate dehydrogenase/succinyl coenzyme-A synthetase, metabolizing α-ketoglutarate to succinate. Notably, human LBD brain manifests a similar pattern of aberrantly S-nitrosylated TCA enzymes, indicating the pathophysiological relevance of these results. Inhibition of mitochondrial energy metabolism in neurons is known to compromise dendritic length and synaptic integrity, eventually leading to neuronal cell death. Our evidence indicates that aberrant S-nitrosylation of TCA cycle enzymes contributes to this bioenergetic failure.

Nitric Oxide/Nitric Oxide Synthase System in the Pathogenesis of Neurodegenerative Disorders-An Overview

Nitric oxide, a ubiquitous molecule found throughout the natural world, is a key molecule implicated in many central and benefic molecular pathways and has a well-established role in the function of the central nervous system, as numerous studies have previously shown. Dysregulation of its metabolism, mainly the upregulation of nitric oxide production, has been proposed as a trigger and/or aggravator for many neurological affections. Increasing evidence supports the implication of this molecule in prevalent neurodegenerative diseases, such as Parkinson's disease, Alzheimer's disease, or amyotrophic lateral sclerosis. The mechanisms proposed for its neurotoxicity mainly center around the increased quantities of nitric oxide that are produced in the brain, their cause, and, most importantly, the pathological metabolic cascades created. These cascades lead to the formation of neuronal toxic substances that impair the neurons' function and structure on multiple levels. The purpose of this review is to present the main causes of increased pathological production, as well as the most important pathophysiological mechanisms triggered by nitric oxide, mechanisms that could help explain a part of the complex picture of neurodegenerative diseases and help develop targeted therapies.

Metabolic Signature of Energy Metabolism Alterations and Excess Nitric Oxide Production in Culture Media Correlate with Low Human Embryo Quality and Unsuccessful Pregnancy

Notwithstanding the great improvement of ART, the overall rate of successful pregnancies from implanted human embryos is definitely low. The current routine embryo quality assessment is performed only through morphological criteria, which has poor predictive capacity since only a minor percentage of those in the highest class give rise to successful pregnancy. Previous studies highlighted the potentiality of the analysis of metabolites in human embryo culture media, useful for the selection of embryos for implantation. In the present study, we analyzed in blind 66 human embryo culture media at 5 days after in vitro fertilization with the aim of quantifying compounds released by cell metabolism that were not present as normal constituents of the human embryo growth media, including purines, pyrimidines, nitrite, and nitrate. Only some purines were detectable (hypoxanthine and uric acid) in the majority of samples, while nitrite and nitrate were always detectable. When matching biochemical results with morphological evaluation, it was found that low grade embryos (n = 12) had significantly higher levels of all the compounds of interest. Moreover, when matching biochemical results according to successful (n = 17) or unsuccessful (n = 25) pregnancy, it was found that human embryos from the latter group released higher concentrations of hypoxanthine, uric acid, nitrite, and nitrate in the culture media. Additionally, those embryos that developed into successful pregnancies were all associated with the birth of healthy newborns. These results, although carried out on a relatively low number of samples, indicate that the analysis of the aforementioned compounds in the culture media of human embryos is a potentially useful tool for the selection of embryos for implantation, possibly leading to an increase in the overall rate of ART.

Proteomic Assessment of C57BL/6 Hippocampi after Non-Selective Pharmacological Inhibition of Nitric Oxide Synthase Activity: Implications of Seizure-like Neuronal Hyperexcitability Followed by Tauopathy

Nitric oxide (NO) is a small gaseous signaling molecule responsible for maintaining homeostasis in a myriad of tissues and molecular pathways in neurology and the cardiovasculature. In recent years, there has been increasing interest in the potential interaction between arterial stiffness (AS), an independent cardiovascular risk factor, and neurodegenerative syndromes given increasingly epidemiological study reports. For this reason, we previously investigated the mechanistic convergence between AS and neurodegeneration via the progressive non-selective inhibition of all nitric oxide synthase (NOS) isoforms with N(G)-nitro-L-arginine methyl ester (L-NAME) in C57BL/6 mice. Our previous results showed progressively increased AS in vivo and impaired visuospatial learning and memory in L-NAME-treated C57BL/6 mice. In the current study, we sought to further investigate the progressive molecular signatures in hippocampal tissue via LC–MS/MS proteomic analysis. Our data implicate mitochondrial dysfunction due to progressive L-NAME treatment. Two weeks of L-NAME treatment implicates altered G-protein-coupled-receptor signaling in the nerve synapse and associated presence of seizures and altered emotional behavior. Furthermore, molecular signatures implicate the cerebral presence of seizure-related hyperexcitability after short-term (8 weeks) treatment followed by ribosomal dysfunction and tauopathy after long-term (16 weeks) treatment.

Physiological roles of hydrogen sulfide in mammalian cells, tissues and organs

H2S belongs to the class of molecules known as gasotransmitters, which also includes nitric oxide (NO) and carbon monoxide (CO). Three enzymes are recognized as endogenous sources of H2S in various cells and tissues: cystathionine g-lyase (CSE), cystathionine β-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (3-MST). The current article reviews the regulation of these enzymes as well as the pathways of their enzymatic and non-enzymatic degradation and elimination. The multiple interactions of H2S with other labile endogenous molecules (e.g. NO) and reactive oxygen species are also outlined. The various biological targets and signaling pathways are discussed, with special reference to H2S and oxidative posttranscriptional modification of proteins, the effect of H2S on channels and intracellular second messenger pathways, the regulation of gene transcription and translation and the regulation of cellular bioenergetics and metabolism. The pharmacological and molecular tools currently available to study H2S physiology are also reviewed, including their utility and limitations. In subsequent sections, the role of H2S in the regulation of various physiological and cellular functions is reviewed. The physiological role of H2S in various cell types and organ systems are overviewed. Finally, the role of H2S in the regulation of various organ functions is discussed as well as the characteristic bell-shaped biphasic effects of H2S. In addition, key pathophysiological aspects, debated areas, and future research and translational areas are identified A wide array of significant roles of H2S in the physiological regulation of all organ functions emerges from this review.

Updates on Versatile Role of Putative Gasotransmitter Nitric Oxide: Culprit in Neurodegenerative Disease Pathology

Nitric oxide (NO) is a versatile gasotransmitter that contributes in a range of physiological and pathological mechanims depending on its cellular levels. An appropriate concentration of NO is essentially required for cellular physiology; however, its increased level triggers pathological mechanisms like altered cellular redox regulation, functional impairment of mitochondrion, and modifications in cellular proteins and DNA. Its increased levels also exhibit post-translational modifications in protein through S-nitrosylation of their thiol amino acids, which critically affect the cellular physiology. Along with such modifications, NO could also nitrosylate the endoplasmic reticulum (ER)-membrane located sensors of ER stress, which subsequently affect the cellular protein degradation capacity and lead to aggregation of misfolded/unfolded proteins. Since protein aggregation is one of the pathological hallmarks of neurodegenerative disease, NO should be taken into account during development of disease therapies. In this Review, we shed light on the diverse role of NO in both cellular physiology and pathology and discussed its involvement in various pathological events in the context of neurodegenerative diseases.