Hypoxia induces rapid, STAT3 and ROS dependent, mitochondrial translocation of RelA(p65) and IκBα

Mitochondrial RelA empowers mtDNA G-quadruplex formation for hypoxia adaptation in cancer cells

Mitochondrial DNA (mtDNA) G-quadruplexes (G4s) have important regulatory roles in energy metabolism, yet their specific functions and underlying regulatory mechanisms have not been delineated. Using a chemical-genetic screening strategy, we demonstrated that the JAK/STAT3 pathway is the primary regulatory mechanism governing mtDNA G4 dynamics in hypoxic cancer cells. Further proteomic analysis showed that activation of the JAK/STAT3 pathway facilitates the translocation of RelA, a member of the NF-κB family, to the mitochondria, where RelA binds to mtDNA G4s and promotes their folding, resulting in increased mtDNA instability, inhibited mtDNA transcription, and subsequent mitochondrial dysfunction. This binding event disrupts the equilibrium of energy metabolism, catalyzing a metabolic shift favoring glycolysis. Collectively, the results provide insights into a strategy employed by cancer cells to adapt to hypoxia through metabolic reprogramming.

MiR-34a promotes mitochondrial pathway of apoptosis in human salivary gland epithelial cells by activating NF-κB signaling

To investigate the potential molecular mechanism of miR-34a in Sjögren's syndrome (SS). Transmission electron microscopy was used to observe the salivary gland tissues of mild and severe SS patients. SS mouse model was constructed and injected with miR-34a antagonist. HSGE cells were transfected with miR-34a mimic. Starbase predicted miR-34a binding sites and validated them with dual-luciferase reporter assays. Immunohistochemistry, HE staining, CCK-8, TUNEL assay, flow cytometry, immunofluorescence and Western Blot were used to investigate the effects of miR-34a on NF-κB signaling and mitochondrial pathway of apoptosis in HSGE cells. Severe SS patients showed obvious mitochondrial damage and apoptosis in salivary glands. MiR-34a was overexpressed and NF-κB signaling is activated in salivary glands of severe SS patients. Inhibition of miR-34a alleviated salivary gland injury in SS mice, as well as inhibited the activation of NF-κB signaling and mitochondrial pathway of apoptosis. In conclusion, miR-34a promoted NF-κB signaling by targeting IκBα, thereby causing mitochondrial pathway apoptosis and aggravating SS-induced salivary gland damage.

Biological role of mitochondrial TLR4-mediated NF-κB signaling pathway in central nervous system injury

Previous studies suggested that central nervous system injury is often accompanied by the activation of Toll-like receptor 4/NF-κB pathway, which leads to the upregulation of proapoptotic gene expression, causes mitochondrial oxidative stress, and further aggravates the inflammatory response to induce cell apoptosis. Subsequent studies have shown that NF-κB and IκBα can directly act on mitochondria. Therefore, elucidation of the specific mechanisms of NF-κB and IκBα in mitochondria may help to discover new therapeutic targets for central nervous system injury. Recent studies have suggested that NF-κB (especially RelA) in mitochondria can inhibit mitochondrial respiration or DNA expression, leading to mitochondrial dysfunction. IκBα silencing will cause reactive oxygen species storm and initiate the mitochondrial apoptosis pathway. Other research results suggest that RelA can regulate mitochondrial respiration and energy metabolism balance by interacting with p53 and STAT3, thus initiating the mitochondrial protection mechanism. IκBα can also inhibit apoptosis in mitochondria by interacting with VDAC1 and other molecules. Regulating the biological role of NF-κB signaling pathway in mitochondria by targeting key proteins such as p53, STAT3, and VDAC1 may help maintain the balance of mitochondrial respiration and energy metabolism, thereby protecting nerve cells and reducing inflammatory storms and death caused by ischemia and hypoxia.

Multiple Actions of Telomerase Reverse Transcriptase in Cell Death Regulation

Telomerase reverse transcriptase (TERT), a core part of telomerase, has been known for a long time only for its telomere lengthening function by reverse transcription of RNA template. Currently, TERT is considered as an intriguing link between multiple signaling pathways. The diverse intracellular localization of TERT corresponds to a wide range of functional activities. In addition to the canonical function of protecting chromosome ends, TERT by itself or as a part of the telomerase complex participates in cell stress responses, gene regulation and mitochondria functioning. Upregulation of TERT expression and increased telomerase activity in cancer and somatic cells relate to improved survival and persistence of such cells. In this review, we summarize the data for a comprehensive understanding of the role of TERT in cell death regulation, with a focus on the interaction of TERT with signaling pathways involved in cell survival and stress response.

Molecular Regulation of the Response of Brain Pericytes to Hypoxia

The brain needs sufficient oxygen in order to function normally. This is achieved by a large vascular capillary network ensuring that oxygen supply meets the changing demand of the brain tissue, especially in situations of hypoxia. Brain capillaries are formed by endothelial cells and perivascular pericytes, whereby pericytes in the brain have a particularly high 1:1 ratio to endothelial cells. Pericytes not only have a key location at the blood/brain interface, they also have multiple functions, for example, they maintain blood-brain barrier integrity, play an important role in angiogenesis and have large secretory abilities. This review is specifically focused on both the cellular and the molecular responses of brain pericytes to hypoxia. We discuss the immediate early molecular responses in pericytes, highlighting four transcription factors involved in regulating the majority of transcripts that change between hypoxic and normoxic pericytes and their potential functions. Whilst many hypoxic responses are controlled by hypoxia-inducible factors (HIF), we specifically focus on the role and functional implications of the regulator of G-protein signaling 5 (RGS5) in pericytes, a hypoxia-sensing protein that is regulated independently of HIF. Finally, we describe potential molecular targets of RGS5 in pericytes. These molecular events together contribute to the pericyte response to hypoxia, regulating survival, metabolism, inflammation and induction of angiogenesis.

Integrated network pharmacology and experimental validation to explore the mechanisms underlying naringenin treatment of chronic wounds

Naringenin is a citrus flavonoid with various biological functions and a potential therapeutic agent for skin diseases, such as UV radiation and atopic dermatitis. The present study investigates the therapeutic effect and pharmacological mechanism of naringenin on chronic wounds. Using network pharmacology, we identified 163 potential targets and 12 key targets of naringenin. Oxidative stress was confirmed to be the main biological process modulated by naringenin. The transcription factor p65 (RELA), alpha serine/threonine-protein kinase (AKT1), mitogen-activated protein kinase 1 (MAPK1) and mitogen-activated protein kinase 3 (MAPK3) were identified as common targets of multiple pathways involved in treating chronic wounds. Molecular docking verified that these four targets stably bound naringenin. Naringenin promoted wound healing in mice in vivo by inhibiting wound inflammation. Furthermore, in vitro experiments showed that a low naringenin concentration did not significantly affect normal skin cell viability and cell apoptosis; a high naringenin concentration was cytotoxic and reduced cell survival by promoting apoptosis. Meanwhile, comprehensive network pharmacology, molecular docking and in vivo and in vitro experiments revealed that naringenin could treat chronic wounds by alleviating oxidative stress and reducing the inflammatory response. The underlying mechanism of naringenin in chronic wound therapy involved modulating the RELA, AKT1 and MAPK1/3 signalling pathways to inhibit ROS production and inflammatory cytokine expression.

Shedding Light on NF-κB Functions in Cellular Organelles

NF-κB is diffusely recognized as a transcriptional factor able to modulate the expression of various genes involved in a broad spectrum of cellular functions, including proliferation, survival and migration. NF-κB is, however, also acting outside the nucleus and beyond its ability to binds to DNA. NF-κB is indeed found to localize inside different cellular organelles, such as mitochondria, endoplasmic reticulum, Golgi and nucleoli, where it acts through different partners in mediating various biological functions. Here, we discuss the relationship linking NF-κB to the cellular organelles, and how this crosstalk between cellular organelles and NF-κB signalling may be evaluated for anticancer therapies.

Hypoxia as a Modulator of Inflammation and Immune Response in Cancer

A clear association between hypoxia and cancer has heretofore been established; however, it has not been completely developed. In this sense, the understanding of the tumoral microenvironment is critical to dissect the complexity of cancer, including the reduction in oxygen distribution inside the tumoral mass, defined as tumoral hypoxia. Moreover, hypoxia not only influences the tumoral cells but also the surrounding cells, including those related to the inflammatory processes. In this review, we analyze the participation of HIF, NF-κB, and STAT signaling pathways as the main components that interconnect hypoxia and immune response and how they modulate tumoral growth. In addition, we closely examine the participation of the immune cells and how they are affected by hypoxia, the effects of the progression of cancer, and some innovative applications that take advantage of this knowledge, to suggest potential therapies. Therefore, we contribute to the understanding of the complexity of cancer to propose innovative therapeutic strategies in the future.

Protective Effects of Flavonoids Against Mitochondriopathies and Associated Pathologies: Focus on the Predictive Approach and Personalized Prevention

Multi-factorial mitochondrial damage exhibits a “vicious circle” that leads to a progression of mitochondrial dysfunction and multi-organ adverse effects. Mitochondrial impairments (mitochondriopathies) are associated with severe pathologies including but not restricted to cancers, cardiovascular diseases, and neurodegeneration. However, the type and level of cascading pathologies are highly individual. Consequently, patient stratification, risk assessment, and mitigating measures are instrumental for cost-effective individualized protection. Therefore, the paradigm shift from reactive to predictive, preventive, and personalized medicine (3PM) is unavoidable in advanced healthcare. Flavonoids demonstrate evident antioxidant and scavenging activity are of great therapeutic utility against mitochondrial damage and cascading pathologies. In the context of 3PM, this review focuses on preclinical and clinical research data evaluating the efficacy of flavonoids as a potent protector against mitochondriopathies and associated pathologies.

Structure, mechanism, and regulation of mitochondrial DNA transcription initiation

Mitochondria are specialized compartments that produce requisite ATP to fuel cellular functions and serve as centers of metabolite processing, cellular signaling, and apoptosis. To accomplish these roles, mitochondria rely on the genetic information in their small genome (mitochondrial DNA) and the nucleus. A growing appreciation for mitochondria's role in a myriad of human diseases, including inherited genetic disorders, degenerative diseases, inflammation, and cancer, has fueled the study of biochemical mechanisms that control mitochondrial function. The mitochondrial transcriptional machinery is different from nuclear machinery. The in vitro re-constituted transcriptional complexes of Saccharomyces cerevisiae (yeast) and humans, aided with high-resolution structures and biochemical characterizations, have provided a deeper understanding of the mechanism and regulation of mitochondrial DNA transcription. In this review, we will discuss recent advances in the structure and mechanism of mitochondrial transcription initiation. We will follow up with recent discoveries and formative findings regarding the regulatory events that control mitochondrial DNA transcription, focusing on those involved in cross-talk between the mitochondria and nucleus.

Mutual regulation of metabolic processes and proinflammatory NF-κB signaling

The nuclear factor kappa B (NF-κB) signaling system, a key regulator of immunologic processes, also affects a plethora of metabolic changes associated with inflammation and the immune response. NF-κB-regulating signaling cascades, in concert with NF-κB-mediated transcriptional events, control the metabolism at several levels. NF-κB modulates apical components of metabolic processes including metabolic hormones such as insulin and glucagon, the cellular master switches 5' AMP-activated protein kinase and mTOR, and also numerous metabolic enzymes and their respective regulators. Vice versa, metabolic enzymes and their products also exert multilevel control of NF-κB activity, thereby creating a highly connected regulatory network. These insights have resulted in the identification of the noncanonical IκB kinase kinases IκB kinase ɛ and TBK1, which are upregulated by overnutrition, and may therefore be suitable potential therapeutic targets for metabolic syndromes. An inhibitor interfering with the activity of both kinases reduces obesity-related metabolic dysfunctions in mouse models and the encouraging results from a recent clinical trial indicate that targeting these NF-κB pathway components improves glucose homeostasis in a subset of patients with type 2 diabetes.