Mitochondria and Reactive Oxygen Species Contribute to Neurogenic Hypertension

Empowering mitochondrial metabolism: Exploring L-lactate supplementation as a promising therapeutic approach for metabolic syndrome

Mitochondrial dysfunction plays a critical role in the pathogenesis of metabolic syndrome (MetS), affecting various cell types and organs. In MetS animal models, mitochondria exhibit decreased quality control, characterized by abnormal morphological structure, impaired metabolic activity, reduced energy production, disrupted signaling cascades, and oxidative stress. The aberrant changes in mitochondrial function exacerbate the progression of metabolic syndrome, setting in motion a pernicious cycle. From this perspective, reversing mitochondrial dysfunction is likely to become a novel and powerful approach for treating MetS. Unfortunately, there are currently no effective drugs available in clinical practice to improve mitochondrial function. Recently, L-lactate has garnered significant attention as a valuable metabolite due to its ability to regulate mitochondrial metabolic processes and function. It is highly likely that treating MetS and its related complications can be achieved by correcting mitochondrial homeostasis disorders. In this review, we comprehensively discuss the complex relationship between mitochondrial function and MetS and the involvement of L-lactate in regulating mitochondrial metabolism and associated signaling pathways. Furthermore, it highlights recent findings on the involvement of L-lactate in common pathologies of MetS and explores its potential clinical application and further prospects, thus providing new insights into treatment possibilities for MetS.

Investigating the Ischaemic Phase of Skin NADH Fluorescence Dynamics in Recently Diagnosed Primary Hypertension: A Time Series Analysis

The reduced form of nicotinamide adenine dinucleotide (NADH) is crucial in cellular metabolism. During hypoxia, NADH accumulation results from anaerobic cytoplasmic glycolysis and impaired mitochondrial function. This study aimed to compare the dynamic changes in the 460-nm forearm skin fluorescence, which reflects cellular NADH content, during transient ischaemia between healthy individuals and patients with newly diagnosed, untreated essential hypertension (HA). Sixteen healthy volunteers and sixty-five patients with HA underwent non-invasive measurement of forearm skin NADH content using the Flow Mediated Skin Fluorescence (FMSF) method at rest and during a 100-s transient ischaemia induced by inflation of the brachial cuff. The fluorescent signal was sampled at 25 Hz. All samples were normalised to the end of the ischaemic phase, which is the most stable phase of the whole recording. Slope values of 1 s linear regressions were determined for every 25-sample neighbouring set. The 1-s slopes in the early phase of skin ischaemia, indicating quicker hypoxia-induced NADH accumulation in skin, were significantly higher in patients with HA than in healthy individuals. These findings suggest that some protecting mechanisms postponing the early consequences of early cellular hypoxia and premature NADH accumulation during skin ischaemia are impaired in patients with untreated HA. Further studies are needed to investigate this phenomenon.

Role of Bioactive Compounds in the Regulation of Mitochondrial Dysfunctions in Brain and Age-Related Neurodegenerative Diseases

Mitochondria are multifunctional organelles that participate in a wide range of metabolic processes, including energy production and biomolecule synthesis. The morphology and distribution of intracellular mitochondria change dynamically, reflecting a cell’s metabolic activity. Oxidative stress is defined as a mismatch between the body’s ability to neutralise and eliminate reactive oxygen and nitrogen species (ROS and RNS). A determination of mitochondria failure in increasing oxidative stress, as well as its implications in neurodegenerative illnesses and apoptosis, is a significant developmental process of focus in this review. The neuroprotective effects of bioactive compounds linked to neuronal regulation, as well as related neuronal development abnormalities, will be investigated. In conclusion, the study of secondary components and the use of mitochondrial features in the analysis of various neurodevelopmental diseases has enabled the development of a new class of mitochondrial-targeted pharmaceuticals capable of alleviating neurodegenerative disease states and enabling longevity and healthy ageing for the vast majority of people.

Molecular Interactions of Arterial Hypertension in Its Target Organs

Arterial hypertension (AH) is a major risk factor for the development of cardiovascular diseases. It is estimated that the disease affects between 10% and 20% of the adult population and is responsible for 5.8% of all deaths worldwide. Several pathophysiologic factors are crucial in AH, including inappropriate activation of the renin-angiotensin-aldosterone system, oxidative stress and inflammation. The heart, kidney, brain, retina and arterial blood vessels are prime targets of hypertensive damage. Uncontrolled and untreated AH accelerates the damage to these organs and could cause their failure. Damage to these organs could also manifest as coronary heart disease, cognitive impairment, retinopathy or optic neuropathy. For better understanding, it is important to analyze molecular factors which take part in pathogenesis of AH and hypertension-related target organ damage. In our paper, we would like to focus on molecular interactions of AH in the heart, blood vessels, brain and kidneys. We focus on matrix metalloproteinases, the role of immune system, the renin-angiotensin-aldosterone system and oxidative stress in hypertensive induced organ damage.

Mitochondrial contributions to vascular endothelial dysfunction, arterial stiffness, and cardiovascular diseases

Cardiovascular disease (CVD) affects one in three adults and remains the leading cause of death in America. Advancing age is a major risk factor for CVD. Recent plateaus in CVD-related mortality rates in high-income countries after decades of decline highlight a critical need to identify novel therapeutic targets and strategies to mitigate and manage the risk of CVD development and progression. Vascular dysfunction, characterized by endothelial dysfunction and large elastic artery stiffening, is independently associated with an increased CVD risk and incidence and is therefore an attractive target for CVD prevention and management. Vascular mitochondria have emerged as an important player in maintaining vascular homeostasis. As such, age- and disease-related impairments in mitochondrial function contribute to vascular dysfunction and consequent increases in CVD risk. This review outlines the role of mitochondria in vascular function and discusses the ramifications of mitochondrial dysfunction on vascular health in the setting of age and disease. The adverse vascular consequences of increased mitochondrial-derived reactive oxygen species, impaired mitochondrial quality control, and defective mitochondrial calcium cycling are emphasized, in particular. Current evidence for both lifestyle and pharmaceutical mitochondrial-targeted strategies to improve vascular function is also presented.

The Crosstalk Between Pathological Tau Phosphorylation and Mitochondrial Dysfunction as a Key to Understanding and Treating Alzheimer's Disease

Alzheimer's disease (AD) is the most common progressive neurodegenerative disorder. A defining hallmark of the AD brain is the presence of intraneuronal neurofibrillary tangles (NFTs) which are made up of abnormally modified tau, with aberrant phosphorylation being the most studied posttranslational modification (PTM). Although the accumulation of tau as NFTs is an invariant feature of the AD brain, it has become evident that these insoluble aggregates are likely not the primary pathogenic form of tau, rather soluble forms of tau with abnormal PTMs are the mediators of toxicity. The most prevalent PTM on tau is phosphorylation, with the abnormal modification of specific residues on tau playing a key role in its toxicity. Even though it is widely accepted that tau with aberrant PTMs facilitates neurodegeneration, the precise cellular mechanisms remain unknown. Nonetheless, there is an evolving conceptual framework that an important contributing factor may be selective pathological tau species compromising mitochondrial biology. Understanding the mechanisms by which tau with site-specific PTM impacts mitochondria is crucial for understanding the role tau plays in AD. Here, we provide a brief introduction to tau and its phosphorylation and function in a physiological context, followed by a discussion of the impact of soluble phosphorylated tau species on neuronal processes in general and mitochondria more specifically. We also discuss how therapeutic strategies that attenuate pathological tau species in combination with treatments that improve mitochondrial biology could be a potential therapeutic avenue to mitigate disease progression in AD and other tauopathies.

Mitochondrial dysfunction and pancreatic islet β-cell failure (Review)

Pancreatic β-cells are the only source of insulin in humans. Mitochondria uses pyruvate to produce ATP as an intermediate link between glucose intake and insulin secretion in β-cells, in a process known as glucose-stimulated insulin secretion (GSIS). Previous studies have demonstrated that GSIS is negatively regulated by various factors in the mitochondria, including tRNA^Leu mutations, high p58 expression, reduced nicotinamide nucleotide transhydrogenase activity, abnormal levels of uncoupling proteins and reduced expression levels of transcription factors A, B1 and B2. Additionally, oxidative stress damages mitochondria and impairs antioxidant defense mechanisms, leading to the increased production of reactive oxygen species, which induces β-cell dysfunction. Inflammation in islets can also damage β-cell physiology. Inflammatory cytokines trigger the release of cytochrome c from the mitochondria via the NF-κB pathway. The present review examined the potential factors underlying mitochondrial dysfunction and their association with islet β-cell failure, which may offer novel insights regarding future strategies for the preservation of mitochondrial function and enhancement of antioxidant activity for individuals with diabetes mellitus.

Mitochondrial dysfunction in cardiovascular disease: Current status of translational research/clinical and therapeutic implications

Mitochondria provide energy to the cell during aerobic respiration by supplying ~95% of the adenosine triphosphate (ATP) molecules via oxidative phosphorylation. These organelles have various other functions, all carried out by numerous proteins, with the majority of them being encoded by nuclear DNA (nDNA). Mitochondria occupy ~1/3 of the volume of myocardial cells in adults, and function at levels of high-efficiency to promptly meet the energy requirements of the myocardial contractile units. Mitochondria have their own DNA (mtDNA), which contains 37 genes and is maternally inherited. Over the last several years, a variety of functions of these organelles have been discovered and this has led to a growing interest in their involvement in various diseases, including cardiovascular (CV) diseases. Mitochondrial dysfunction relates to the status where mitochondria cannot meet the demands of a cell for ATP and there is an enhanced formation of reactive-oxygen species. This dysfunction may occur as a result of mtDNA and/or nDNA mutations, but also as a response to aging and various disease and environmental stresses, leading to the development of cardiomyopathies and other CV diseases. Designing mitochondria-targeted therapeutic strategies aiming to maintain or restore mitochondrial function has been a great challenge as a result of variable responses according to the etiology of the disorder. There have been several preclinical data on such therapies, but clinical studies are scarce. A major challenge relates to the techniques needed to eclectically deliver the therapeutic agents to cardiac tissues and to damaged mitochondria for successful clinical outcomes. All these issues and progress made over the last several years are herein reviewed.

Cerebrovascular function in hypertension: Does high blood pressure make you old?

The majority of individuals over an age of 60 have hypertension. Elevated blood pressure and older age are associated with very similar changes in brain structure and function. We review the parallel brain changes associated with increasing age and blood pressure. This review focuses on joint associations of aging and elevated blood pressure with neuropsychological function, regional cerebral blood flow responses to cognitive and metabolic challenges, white matter disruptions, grey matter volume, cortical thinning, and neurovascular coupling. Treatment of hypertension ameliorates many of these changes but fails to reverse them. Treatment of hypertension itself appears more successful with better initial brain function. We show evidence that sympathetic and renal influences known to increase blood pressure also impact brain integrity. Possible central mechanisms contributing to the course of hypertension and aging are then suggested. An emphasis is placed on psychologically relevant factors: stress, cardiovascular reactions to stress, and diet/obesity. The contribution of some of these factors to biological aging remains unclear and may provide a starting point for defining the independent and interacting effects of aging and increasing blood pressure on the brain.

Oxidative Stress: A Unifying Paradigm in Hypertension

The etiology of hypertension involves complex interactions among genetic, environmental, and pathophysiologic factors that influence many regulatory systems. Hypertension is characteristically associated with vascular dysfunction, cardiovascular remodelling, renal dysfunction, and stimulation of the sympathetic nervous system. Emerging evidence indicates that the immune system is also important and that activated immune cells migrate and accumulate in tissues promoting inflammation, fibrosis, and target-organ damage. Common to these processes is oxidative stress, defined as an imbalance between oxidants and antioxidants in favour of the oxidants that leads to a disruption of oxidation-reduction (redox) signalling and control and molecular damage. Physiologically, reactive oxygen species (ROS) act as signalling molecules and influence cell function through highly regulated redox-sensitive signal transduction. In hypertension, oxidative stress promotes posttranslational modification (oxidation and phosphorylation) of proteins and aberrant signalling with consequent cell and tissue damage. Many enzymatic systems generate ROS, but NADPH oxidases (Nox) are the major sources in cells of the heart, vessels, kidneys, and immune system. Expression and activity of Nox are increased in hypertension and are the major systems responsible for oxidative stress in cardiovascular disease. Here we provide a unifying concept where oxidative stress is a common mediator underlying pathophysiologic processes in hypertension. We focus on some novel concepts whereby ROS influence vascular function, aldosterone/mineralocorticoid actions, and immunoinflammation, all important processes contributing to the development of hypertension.

Butyrate regulates inflammatory cytokine expression without affecting oxidative respiration in primary astrocytes from spontaneously hypertensive rats

Neurons and glia exhibit metabolic imbalances in hypertensive animal models, and loss of metabolic homeostasis can lead to neuroinflammation and oxidative stress. The objective of this study was to determine the effects of the microbial metabolite butyrate on mitochondrial bioenergetics and inflammatory markers in mixed brainstem and hypothalamic primary cultures of astrocytes between normotensive (Sprague-Dawley, S-D) and spontaneously hypertensive (SHR) rats. Bioenergetics of mitochondria in astrocytes from normotensive S-D rats were modified with butyrate, but this was not the case in astrocytes derived from SHR, suggesting aberrant mitochondrial function. Transcripts related to oxidative stress, butyrate transporters, butyrate metabolism, and neuroinflammation were quantified in astrocyte cultures treated with butyrate at 0, 200, 600, and 1000 μmol/L. Butyrate decreased catalase and monocarboxylate transporter 1 mRNA in astrocytes of S-D rats but not in the SHR. Moreover, while butyrate did not directly regulate the expression of 3-hydroxybutyrate dehydrogenase 1 and 2 in astrocytes of either strain, the expression levels for these transcripts in untreated cultures were lower in the SHR compared to S-D. We observed higher levels of specific inflammatory cytokines in astrocytes of SHR, and treatment with butyrate decreased expression of Ccl2 and Tlr4 in SHR astrocytes only. Conversely, butyrate treatment increased expression of tumor necrosis factor in astrocytes from SHR but not from the S-D rats. This study improves our understanding of the role of microbial metabolites in regulating astrocyte function, and provides support that butyrate differentially regulates both the bioenergetics and transcripts related to neuroinflammation in astrocytes from SHR versus S-D rats.