How the Disruption of Mitochondrial Redox Signalling Contributes to Ageing.

In the past, mitochondrial reactive oxygen species (mtROS) were considered a byproduct of cellular metabolism. Due to the capacity of mtROS to cause oxidative damage, they were proposed as the main drivers of ageing and age-related diseases. Today, we know that mtROS are cellular messengers instrumental in maintaining cellular homeostasis. As cellular messengers, they are produced in specific places at specific times, and the intensity and duration of the ROS signal determine the downstream effects of mitochondrial redox signalling. We do not know yet all the processes for which mtROS are important, but we have learnt that they are essential in decisions that affect cellular differentiation, proliferation and survival. On top of causing damage due to their capacity to oxidize cellular components, mtROS contribute to the onset of degenerative diseases when redox signalling becomes dysregulated. Here, we review the best-characterized signalling pathways in which mtROS participate and those pathological processes in which they are involved. We focus on how mtROS signalling is altered during ageing and discuss whether the accumulation of damaged mitochondria without signalling capacity is a cause or a consequence of ageing.

L-Arginine Ameliorates Defective Autophagy in GM2 Gangliosidoses by mTOR Modulation.

AIMS: Tay-Sachs and Sandhoff diseases (GM2 gangliosidosis) are autosomal recessive disorders of lysosomal function that cause progressive neurodegeneration in infants and young children. Impaired hydrolysis catalysed by ß-hexosaminidase A (HexA) leads to the accumulation of GM2 ganglioside in neuronal lysosomes. Despite the storage phenotype, the role of autophagy and its regulation by mTOR has yet to be explored in the neuropathogenesis. Accordingly, we investigated the effects on autophagy and lysosomal integrity using skin fibroblasts obtained from patients with Tay-Sachs and Sandhoff diseases. RESULTS: Pathological autophagosomes with impaired autophagic flux, an abnormality confirmed by electron microscopy and biochemical studies revealing the accelerated release of mature cathepsins and HexA into the cytosol, indicating increased lysosomal permeability. GM2 fibroblasts showed diminished mTOR signalling with reduced basal mTOR activity. Accordingly, provision of a positive nutrient signal by L-arginine supplementation partially restored mTOR activity and ameliorated the cytopathological abnormalities. INNOVATION: Our data provide a novel molecular mechanism underlying GM2 gangliosidosis. Impaired autophagy caused by insufficient lysosomal function might represent a new therapeutic target for these diseases. CONCLUSIONS: We contend that the expression of autophagy/lysosome/mTOR-associated molecules may prove useful peripheral biomarkers for facile monitoring of treatment of GM2 gangliosidosis and neurodegenerative disorders that affect the lysosomal function and disrupt autophagy.

Inhibition of the NLRP3 inflammasome improves lifespan in animal murine model of Hutchinson-Gilford Progeria.

Inflammation is a hallmark of aging and accelerated aging syndromes such as Hutchinson-Gilford progeria syndrome (HGPS). In this study, we present evidence of increased expression of the components of the NLRP3 inflammasome pathway in HGPS skin fibroblasts, an outcome that was associated with morphological changes of the nuclei of the cells. Lymphoblasts from HGPS patients also showed increased basal levels of NLRP3 and caspase 1. Consistent with these results, the expression of caspase 1 and Nlrp3, but not of the other inflammasome receptors was higher in the heart and liver of Zmpste24-/- mice, which phenocopy the human disease. These data were further corroborated in LmnaG609G/G609G mice, another HGPS animal model. We also showed that pharmacological inhibition of the NLRP3 inflammasome by its selective inhibitor, MCC950, improved cellular phenotype, significantly extended the lifespan of progeroid animals, and reduced inflammasome-dependent inflammation. These findings suggest that inhibition of the NLRP3 inflammasome is a potential therapeutic approach for the treatment of HGPS.

Inhibition of the NLRP3 inflammasome prevents ovarian aging.

Inflammation is a hallmark of aging and is negatively affecting female fertility. In this study, we evaluate the role of the NLRP3 inflammasome in ovarian aging and female fertility. Age-dependent increased expression of NLRP3 in the ovary was observed in WT mice during reproductive aging. High expression of NLRP3, caspase-1, and IL-1ß was also observed in granulosa cells from patients with ovarian insufficiency. Ablation of NLRP3 improved the survival and pregnancy rates and increased anti-Müllerian hormone levels and autophagy rates in ovaries. Deficiency of NLRP3 also reduced serum FSH and estradiol levels. Consistent with these results, pharmacological inhibition of NLRP3 using a direct NLRP3 inhibitor, MCC950, improved fertility in female mice to levels comparable to those of Nlrp3-/- mice. These results suggest that the NLRP3 inflammasome is implicated in the age-dependent loss of female fertility and position this inflammasome as a potential new therapeutic target for the treatment of infertility.

Potential Role of the Mitochondria for the Dermatological Treatment of Papillon-Lefèvre.

The Papillon-Lefèvre syndrome (PLS) is a rare autosomal recessive disorder caused by mutations in the Cathepsin C (CTSC) gene, characterized by periodontitis and palmoplantar hyperkeratosis. The main inflammatory deficiencies include oxidative stress and autophagic dysfunction. Mitochondria are the main source of reactive oxygen species; their impaired function is related to skin diseases and periodontitis. The mitochondrial function has been evaluated in PLS and mitochondria have been targeted as a possible treatment for PLS. We show for the first time an important mitochondrial dysfunction associated with increased oxidative damage of mtDNA, reduced CoQ10 and mitochondrial mass and aberrant morphologies of the mitochondria in PLS patients. Mitochondrial dysfunction, determined by oxygen consumption rate (OCR) in PLS fibroblasts, was treated with CoQ10 supplementation, which determined an improvement in OCR and a remission of skin damage in a patient receiving a topical administration of a cream enriched with CoQ10 0.1%. We provide the first evidence of the role of mitochondrial dysfunction and CoQ10 deficiency in the pathophysiology of PLS and a future therapeutic option for PLS.

A Network of Macrophages Supports Mitochondrial Homeostasis in the Heart.

Cardiomyocytes are subjected to the intense mechanical stress and metabolic demands of the beating heart. It is unclear whether these cells, which are long-lived and rarely renew, manage to preserve homeostasis on their own. While analyzing macrophages lodged within the healthy myocardium, we discovered that they actively took up material, including mitochondria, derived from cardiomyocytes. Cardiomyocytes ejected dysfunctional mitochondria and other cargo in dedicated membranous particles reminiscent of neural exophers, through a process driven by the cardiomyocyte's autophagy machinery that was enhanced during cardiac stress. Depletion of cardiac macrophages or deficiency in the phagocytic receptor Mertk resulted in defective elimination of mitochondria from the myocardial tissue, activation of the inflammasome, impaired autophagy, accumulation of anomalous mitochondria in cardiomyocytes, metabolic alterations, and ventricular dysfunction. Thus, we identify an immune-parenchymal pair in the murine heart that enables transfer of unfit material to preserve metabolic stability and organ function. VIDEO ABSTRACT.

The Absence of NLRP3-inflammasome Modulates Hepatic Fibrosis Progression, Lipid Metabolism, and Inflammation in KO NLRP3 Mice during Aging.

Aging is associated with metabolic changes and low-grade inflammation in several organs, which may be due to NLRP3 inflammasome activation. Methods: Here, we asked whether age-related liver changes such as lipid metabolism and fibrosis are reduced in aged mice lacking the NLRP3 inflammasome. We report reduced protein levels of lipid markers (MTP, FASN, DGAT1), SOD activity, oxidative stress marker PTPRG, and the fibrotic markers TPM2ß, COL1-α1 associated with increased GATA4, in NLRP3 deficient mice. Fibrotic, lipid, and oxidative reduction in liver tissues of mice was more pronounced in those old KO NLRP3 mice than in the younger ones, despite their greater liver damage. These results suggest that absence of the NLRP3 inflammasome attenuates age-related liver fibrotic pathology in mice, suggesting that pharmacological targeting may be beneficial.

Nutraceutical Compounds Targeting Inflammasomes in Human Diseases.

The macromolecular complex known as "inflammasome" is defined as an intracellular multi-protein complex composed of a sensor receptor (PRR), an adaptor protein and an effector enzyme (caspase-1), which oligomerize when they sense danger, such as how the NLR family, AIM-2 and RIG-1 receptors protect the body against danger via cytokine secretion. Within the NLR members, NLRP3 is the most widely known and studied inflammasome and has been linked to many diseases. Nowadays, people's interest in their lifestyles and nutritional habits is increasing, mainly due to the large number of diseases that seem to be related to both. The term "nutraceutical" has recently emerged as a hybrid term between "nutrition" and "pharmacological" and it refers to a wide range of bioactive compounds contained in food with relevant effects on human health. The relationship between these compounds and diseases based on inflammatory processes has been widely exposed and the compounds stand out as an alternative to the pathological consequences that inflammatory processes may have, beyond their defense and repair action. Against this backdrop, here we review the results of studies using several nutraceutical compounds in common diseases associated with the inflammation and activation of the NLRP3 inflammasomes complex. In general, it was found that there is a wide range of nutraceuticals with effects through different molecular pathways that affect the activation of the inflammasome complex, with positive effects mainly in cardiovascular, neurological diseases, cancer and type 2 diabetes.

Integrated molecular signaling involving mitochondrial dysfunction and alteration of cell metabolism induced by tyrosine kinase inhibitors in cancer.

Cancer cells have unlimited replicative potential, insensitivity to growth-inhibitory signals, evasion of apoptosis, cellular stress, and sustained angiogenesis, invasiveness and metastatic potential. Cancer cells adequately adapt cell metabolism and integrate several intracellular and redox signaling to promote cell survival in an inflammatory and hypoxic microenvironment in order to maintain/expand tumor phenotype. The administration of tyrosine kinase inhibitor (TKI) constitutes the recommended therapeutic strategy in different malignancies at advanced stages. There are important interrelationships between cell stress, redox status, mitochondrial function, metabolism and cellular signaling pathways leading to cell survival/death. The induction of apoptosis and cell cycle arrest widely related to the antitumoral properties of TKIs result from tightly controlled events involving different cellular compartments and signaling pathways. The aim of the present review is to update the most relevant studies dealing with the impact of TKI treatment on cell function. The induction of endoplasmic reticulum (ER) stress and Ca2+ disturbances, leading to alteration of mitochondrial function, redox status and phosphatidylinositol 3-kinase (PI3K)-protein kinase B (Akt)-mammalian target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK) signaling pathways that involve cell metabolism reprogramming in cancer cells will be covered. Emphasis will be given to studies that identify key components of the integrated molecular pattern including receptor tyrosine kinase (RTK) downstream signaling, cell death and mitochondria-related events that appear to be involved in the resistance of cancer cells to TKI treatments.

Blockade of the NLRP3 inflammasome improves metabolic health and lifespan in obese mice.

Aging is the major risk factor for many metabolic chronic diseases. Several metabolic pathways suffer a progressive impairment during aging including body composition and insulin resistance which are associated to autophagy dysfunction and increased inflammation. Many of these alterations are aggravated by non-healthy lifestyle such as obesity and hypercaloric diet which have been shown to accelerate aging. Here, we show that the deleterious effect of hypercaloric diets is reverted by the NLRP3 inflammasome inhibition. NLRP3 deficiency extends mean lifespan of adult mice fed a high-fat diet. This lifespan extension is accompanied by metabolic health benefits including reduced liver steatosis and cardiac damage, improved glucose and lipid metabolism, and improved protein expression profiles of SIRT-1, mTOR, autophagic flux, and apoptosis. These findings suggest that the suppression of NLRP3 prevented many age-associated changes in metabolism impaired by the effect of hypercaloric diets.

NLRP3 inflammasome suppression improves longevity and prevents cardiac aging in male mice.

While NLRP3-inflammasome has been implicated in cardiovascular diseases, its role in physiological cardiac aging is largely unknown. During aging, many alterations occur in the organism, which are associated with progressive impairment of metabolic pathways related to insulin resistance, autophagy dysfunction, and inflammation. Here, we investigated the molecular mechanisms through which NLRP3 inhibition may attenuate cardiac aging. Ablation of NLRP3-inflammasome protected mice from age-related increased insulin sensitivity, reduced IGF-1 and leptin/adiponectin ratio levels, and reduced cardiac damage with protection of the prolongation of the age-dependent PR interval, which is associated with atrial fibrillation by cardiovascular aging and reduced telomere shortening. Furthermore, old NLRP3 KO mice showed an inhibition of the PI3K/AKT/mTOR pathway and autophagy improvement, compared with old wild mice and preserved Nampt-mediated NAD+ levels with increased SIRT1 protein expression. These findings suggest that suppression of NLRP3 prevented many age-associated changes in the heart, preserved cardiac function of aged mice and increased lifespan.

NLRP3 Inflammasome Inhibition by MCC950 in Aged Mice Improves Health via Enhanced Autophagy and PPARα Activity.

The NLRP3 inflammasome has emerged as an important regulator of metabolic disorders and age-related diseases in NLRP3-deficient mice. In this article, we determine whether, in old mice C57BL6J, the NLRP3 inflammasome inhibitor MCC950 is able to attenuate age-related metabolic syndrome to providing health benefits. We report that MCC950 attenuates metabolic and hepatic dysfunction in aged mice. In addition, MCC950 inhibited the Pi3K/AKT/mTOR pathway, enhanced autophagy, and activated peroxisome proliferator-activated receptor-α in vivo and in vitro. The data suggest that MCC950 mediates the protective effects by the mammalian target of rapamycin inhibition, thus activating autophagy and peroxisome proliferator-activated receptor-α. In conclusion, pharmacological inhibition of NLRP3 in aged mice has a significant impact on health. Thus, NLRP3 may be a therapeutic target of human age-related metabolic syndrome.

Inflammasomes in Clinical Practice: A Brief Introduction.

Inflammasomes are multiprotein complexes formed and activated after exposure to pathogenic microbes and host danger signals that control the maturation and production of IL-1ß and IL-18. Their implication in different diseases such as cardiovascular, neurodegenerative, psychiatric, and metabolic diseases opens a door to developing new therapeutic perspectives. However, the rapid increase in the knowledge about inflammasomes is associated with their involvement in clinical practice. Two topics open the way to future lines of research: a clinical trial with the new specific inhibitors and the development of diagnostic tools.

Autophagic dysfunction in patients with Papillon-Lefèvre syndrome is restored by recombinant cathepsin C treatment.

BACKGROUND: Cathepsin C (CatC) is a lysosomal enzyme involved in activation of serine proteases from immune and inflammatory cells. Several loss-of-function mutations in the CatC gene have been shown to be the genetic mark of Papillon-Lefèvre syndrome (PLS), a rare autosomal recessive disease characterized by severe early-onset periodontitis, palmoplantar hyperkeratosis, and increased susceptibility to infections. Deficiencies or dysfunction in other cathepsin family proteins, such as cathepsin B or D, have been associated with autophagic and lysosomal disorders. OBJECTIVES: Here we characterized the basis for autophagic dysfunction in patients with PLS by analyzing skin fibroblasts derived from patients with several mutations in the CatC gene and reduced enzymatic activity. METHODS: Skin fibroblasts were isolated from patients with PLS assessed by using genetic analysis. Authophagic flux dysfunction was evaluated by examining accumulation of p62/SQSTM1 and a bafilomycin assay. Ultrastructural analysis further confirmed abnormal accumulation of autophagic vesicles in mutant cells. A recombinant CatC protein was produced by a baculovirus system in insect cell cultures. RESULTS: Mutant fibroblasts from patients with PLS showed alterations in oxidative/antioxidative status, reduced oxygen consumption, and a marked autophagic dysfunction associated with autophagosome accumulation. These alterations were accompanied by lysosomal permeabilization, cathepsin B release, and NLR family pyrin domain containing 3 (NLRP3) inflammasome activation. Treatment of mutant fibroblasts with recombinant CatC improved cell growth and autophagic flux and partially restored lysosomal permeabilization. CONCLUSIONS: Our data provide a novel molecular mechanism underlying PLS. Impaired autophagy caused by insufficient lysosomal function might represent a new therapeutic target for PLS.

Stress-Induced NLRP3 Inflammasome in Human Diseases.

Stress is a complex event that induces disturbances to physiological and psychological homeostasis, and it may have a detrimental impact on certain brain and physiological functions. In the last years, a dual role of the stress effect has been studied in order to elucidate the molecular mechanism by which can induce physiological symptoms after psychological stress exposition and vice versa. In this sense, inflammation has been proposed as an important starring. And in the same line, the inflammasome complex has emerged to give responses because of its role of stress sensor. The implication of the same complex, NLRP3 inflammasome, in different diseases such as cardiovascular, neurodegenerative, psychiatric, and metabolic diseases opens a door to develop new therapeutic perspectives.