Does NLRP1 Inflammasome Activation in Immune Cells in Kidney Transplantation Relate with Donor Organ Age?

Inflammation causes a wide range of health disorders. In this process, the formation of inflammasome complexes plays a key role. Although inflammasomes have been extensively studied during kidney disease, their role in kidney transplantation has not been fully elucidated. In this study, we evaluate the gene and protein expression of several components of the inflammasome pathway before and at several time points after kidney transplantation in a cohort of patients of different ages and receiving an organ from older or younger donors. Our findings indicate the activation of the NLRP1 inflammasome in several immune cell population, monocytes and CD4+ and CD8+ cells mainly, in renal transplant, and its level increases gradually in patients who receive an older organ, whereas it has the opposite effect on older patients who receive a younger organ. Despite treatment with immunosuppressants, inflammation persists in some patients. These results lead to the hypothesis that the donor's age is a critical factor in post-transplant inflammasome activation and that specific NLRP1 inflammasome inhibitors should be considered to increase the success of kidney transplantation long-term.

Does Donor Age Have Effects on Senescence Biomarkers in Kidney-Transplanted Patients?

Renal transplantation is an effective treatment for severe chronic kidney diseases. However, young patients often face a scarcity of kidneys from donors of similar age, resulting in the transplantation of older organs, which increase the risk of graft rejection and several complications compared with older individuals who receive kidneys from donors of similar age or younger. This article focuses on studying different senescence biomarkers in donors and patients who received kidneys from various age ranges complying with the STROBE requirements. We studied 61 patients subjected to renal transplant isolating blood samples 24 h before, and 24 h, 3 days, 7 days, 3 months, and 6 months after transplant. The patients were divided into three groups: older donor than the patient (Old Donor), younger donor than the patient (Young Donor), and similar age (Matched). We studied different senescence markers such as p16, p21, interleukin 6 (IL-6), and senescence-associated secretory phenotype (SASP) release. Young patients who receive older organs showed increased mRNA and protein expression of the senescence makers. Hence, increased SASP release was also observed in patients from older donor. In contrast, older patients who receive younger organs showed a slow but consistent improvement in their initial senescent phenotype. In addition, macrophage cell model treated with blood-derived serum from patients 6 months after the transplant showed a pro-senescence environment in macrophages proposed by the SASP from the patients. These results lead the hypothesis that senolytics could reduce the presence of senescent cells and mitigate the complications associated with the transplantation of older organs in young patients.

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.

NLRP1 inflammasome modulates senescence and senescence-associated secretory phenotype.

Senescence is a cellular aging-related process triggered by different stresses and characterized by the secretion of various inflammatory factors referred to as the senescence-associated secretory phenotype (SASP). Here, we present evidence that the inflammasome sensor, NLRP1, is a key mediator of senescence induced by irradiation both in vitro and in vivo. The NLRP1 inflammasome promotes senescence by regulating the expression of p16, p21, p53, and SASP in Gasdermin D (GSDMD)-dependent manner as these responses are reduced in conditions of NLRP1 insufficiency or GSDMD inhibition. Mechanistically, the NLRP1 inflammasome is activated downstream of the cytosolic DNA sensor cGMP-AMP (cGAMP) synthase (cGAS) in response to genomic damage. These findings provide a rationale for inhibiting the NLRP1 inflammasome-GSDMD axis to treat senescence-driven disorders.

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.

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.

Is AMP-Activated Protein Kinase Associated to the Metabolic Changes in Primary Ovarian Insufficiency?

Primary ovarian insufficiency (POI) is a critical fertility defect characterized by anticipated impairment of the follicular reserve, which pathophysiological mechanisms have not yet been identified. We have investigated the possible relationship between AMP-activated protein kinase (AMPK) and the pathophysiology of POI. We studied 35 POI patients with altered levels of follicle-stimulating hormone (FSH) and estradiol and increased percentage of overweight compared with 20 healthy women. Blood mononuclear cells from POI patients showed reduced levels of phosphorylated AMPK, adenosine triphosphate, and high serum levels of leptin and tumor necrosis factor-alpha. All these alterations were also observed in granulosa cells, a more closer environment of the ovary. Significant negative correlations between AMPK and body mass index, FSH and leptin levels, and a positive correlation between AMPK and estradiol levels were observed. Oral metformin supplementation restored biochemical parameters. Interestingly, AMPK levels from patients were negatively correlated with age, suggesting an accelerated aging in POI mediated by the impairment of AMPK. These results lead to the hypothesis that an impairment of AMPK could be implicated in the metabolic pathophysiology of POI indicating at AMPK induction as a possible new therapeutic target.

A Diet Rich in Saturated Fat and Cholesterol Aggravates the Effect of Bacterial Lipopolysaccharide on Alveolar Bone Loss in a Rabbit Model of Periodontal Disease.

Increasing evidence connects periodontitis with a variety of systemic diseases, including metabolic syndrome, atherosclerosis, and non-alcoholic fatty liver disease (NAFLD). The proposal of this study was to evaluate the role of diets rich in saturated fat and cholesterol in some aspects of periodontal diseases in a lipopolysaccharide (LPS)-induced model of periodontal disease in rabbits and to assess the influence of a periodontal intervention on hyperlipidemia, atherosclerosis, and NAFLD progression to non-alcoholic steatohepatitis. Male rabbits were maintained on a commercial standard diet or a diet rich in saturated fat (3% lard w/w) and cholesterol (1.3% w/w) (HFD) for 40 days. Half of the rabbits on each diet were treated 2 days per week with intragingival injections of LPS from Porphyromonas gingivalis. Morphometric analyses revealed that LPS induced higher alveolar bone loss (ABL) around the first premolar in animals receiving standard diets, which was exacerbated by the HFD diet. A higher score of acinar inflammation in the liver and higher blood levels of triglycerides and phospholipids were found in HFD-fed rabbits receiving LPS. These results suggest that certain dietary habits can exacerbate some aspects of periodontitis and that bad periodontal health can contribute to dyslipidemia and promote NAFLD progression, but only under certain conditions.

Molecular inflammation and oxidative stress are shared mechanisms involved in both myocardial infarction and periodontitis.

BACKGROUND AND OBJECTIVE: Our aims were to improve the understanding of the pathogenic relationship between cardiovascular diseases and periodontitis and to generate new perspectives in the prevention and treatment of acute myocardial infarction (AMI) and periodontitis. The present study evaluates possible differences in inflammation, oxidative stress, and autophagy markers among subject suffering AMI, periodontitis, or both, to explore possible common pathogenic mechanisms. MATERIAL AND METHODS: A total of 260 subjects were enrolled in the study: 106 subjects that survived to a first AMI (AMI group) and 154 subjects had no cardiac events in their clinical record (control group). A questionnaire was used to assess age, height, weight, blood pressure, and heart rate. The clinical probing depth, clinical attachment loss, number of remaining teeth, and average number of sites with bleeding on probing were assessed. Lipid peroxidation and protein levels of phosphorylated AMP-activated protein kinase (p-AMPK) and microtubule-associated proteins 1A/1B-light chain 3-II (LC3-II) were determined in isolated peripheral blood mononuclear cells by thiobarbituric acid reactive substances (TBARS) assay and Western blot, respectively. Plasma levels of interleukin-1ß were determined using a commercial ELISA kit. All the obtained variables were compared between subjects suffering an AMI with or without periodontitis and control subject periodontal healthy or with periodontitis. RESULTS: A higher proportion of subjects suffering AMI + periodontitis than only AMI (without periodontitis) was found. Higher levels of TBARS were found in subjects with periodontitis than in subjects without periodontitis in both AMI and control subjects. Positive correlations between IL-1ß levels and TBARS and between IL-1ß levels and LC3-II were found only in control subjects. CONCLUSION: Results from the present study are consistent with the suggestion of periodontitis as a potential risk factor for AMI. Periodontitis association with circulating lipid peroxides in both AMI and control subjects were found. The absence of differences in IL-1ß levels between AMI subjects (only AMI vs AMI + periodontitis) suggests that oxidative stress could be the main pathogenic link between AMI and periodontitis.

Mitochondrial Adaptations in the Growing Heart.

The heart pumps blood throughout the whole life of an organism, without rest periods during which to replenish energy or detoxify. Hence, cardiomyocytes, the working units of the heart, have mechanisms to ensure constitutive production of energy and detoxification to preserve fitness and function for decades. Even more challenging, the heart must adapt to the varying conditions of the organism from fetal life to adulthood, old age, and pathological stress. Mitochondria are at the nexus of these processes by producing not only energy but also metabolites and oxidative byproducts that can activate alarm signals and be toxic to the cell. We review basic concepts about cardiac mitochondria with a focus on their remarkable adaptations, including elimination, throughout the mammalian lifetime.

Sequential Changes of NLRP3 Inflammasome Activation in Sepsis and its Relationship With Death.

INTRODUCTION: Inflammasomes are recognized as key components of the innate immune response in sepsis. We aimed to describe the transcriptional expression of nucleotide-binding domain, leucine-rich repeat-containing receptor, pyrin domain-containing-3 (NLRP3), and serum interleukin-1ß (IL-1 ß) in critically ill patients, their changes over the first week and their prognostic value in septic patients. METHODS: Prospective study including patients with sepsis based on Sepsis-3 definitions and a control group of critically ill patients without sepsis. We measured the circulating levels of IL-1ß as well as the transcriptional expression of NLRP3 at admission and on days 3 and 7. Caspase-1 and caspase-3 activation was analyzed in a matched cohort of patients with septic shock (four dead and four survivors). RESULTS: Fifty-five septic patients and 11 non-septic patients were studied. Levels on day 0 and 3 of IL-1 ß and NLRP3 inflammasome expression were significantly higher in patients with sepsis than in controls. NLRP3 was significantly higher in septic patients who survived at day 7 without significant difference between survivors and non-survivors at baseline and on day 3. In survivors, an increased caspase-1 protein expression with reduced expression caspase-3 was observed with the opposite pattern in those who died. CONCLUSIONS: NLRP3 is activated in critically ill patients but this up-regulation is more intense in patients with sepsis. In sepsis, a sustained NLRP3 activation during the first week is protective and sepsis. An increased caspase-1 protein expression with reduced expression caspase-3 is the pattern observed in septic shock patients who survive.

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.