Ubiquitination as a key regulatory mechanism for O3-induced cutaneous redox inflammasome activation

NLRP1 is one of the major inflammasomes modulating the cutaneous inflammatory responses and therefore linked to a variety of cutaneous conditions. Although NLRP1 has been the first inflammasome to be discovered, only in the past years a significant progress was achieved in understanding the molecular mechanism and the stimuli behind its activation. In the past decades a crescent number of studies have highlighted the role of air pollutants as Particulate Matter (PM), Cigarette Smoke (CS) and Ozone (O3) as trigger stimuli for inflammasomes activation, especially via Reactive Oxygen Species (ROS) mediators. However, whether NLRP1 can be modulated by air pollutants via oxidative stress and the mechanism behind its activation is still poorly understood. Here we report for the first time that O3, one of the most toxic pollutants, activates the NLRP1 inflammasome in human keratinocytes via oxidative stress mediators as hydrogen peroxide (H2O2) and 4-hydroxy-nonenal (4HNE). Our data suggest that NLRP1 represents a target protein for 4HNE adduction that possibly leads to its proteasomal degradation and activation via the possible involvement of E3 ubiquitin ligase UBR2. Of note, Catalase (Cat) treatment prevented inflammasome assemble and inflammatory cytokines release as well as NLRP1 ubiquitination in human keratinocytes upon O3 exposure. The present work is a mechanistic study that follows our previous work where we have showed the ability of O3 to induce cutaneous inflammasome activation in humans exposed to this pollutant. In conclusion, our results suggest that O3 triggers the cutaneous NLRP1 inflammasome activation by ubiquitination and redox mechanism

Sirtuins as potential therapeutic targets for mitigating OxInflammation in typical Rett syndrome: plausible mechanisms and evidence

Rett syndrome (RTT), a monogenic neurodevelopmental disorder mainly affecting female, is caused by mutations in X-linked MECP2 gene, an ubiquitous epigenetic regulator. In addition to neurological issues, RTT patients show a variety of multisystem manifestations and impairment of different signalling and metabolic pathways, including compromised mitochondrial function, altered redox homeostasis, improper cholesterol metabolism and subclinical inflammation. The sirtuin family (SIRTs), comprising seven members, catalyses the NAD+-dependent deacetylation, ADP-ribosylation and deacylation of a wide range of targets and works as sensors of cellular energetic status. In addition, SIRTs can modulate activities and gene expression of proteins involved in cellular stress responses related to oxidative stress, mitochondrial dysfunctions and inflammation, in both physiological and pathological conditions. Given some shared molecular aspects, herein, we revised the current scientific literature and hypothesized the possible relationship of SIRTs signalling involvement in RTT pathogenesis and OxInflammation. Although further research is needed, uncovering the possible involvement of SIRTs in RTT could reveal new potential pharmacological targets for the disorder. In light of this, SIRT-enhancing compounds could likely represent a new option to be tested as co-adjuvant alternatives to the current therapies

13-HODE, 9-HODE and ALOX15 as potential players in Rett syndrome OxInflammation

Mutations in the MECP2 gene are the main cause of Rett syndrome (RTT), a pervasive neurodevelopmental disorder, that shows also multisystem disturbances associated with a metabolic component. The aim of this study was to investigate whether an increased production of oxidized linoleic acid metabolites, specifically 9- and 13-hydroxyoctadecadienoic acids (HODEs), can contribute to the altered the redox and immune homeostasis, suggested to be involved in RTT. Serum levels of 9- and 13-HODEs were elevated in RTT and associated with the expression of arachidonate 15-Lipoxygenase (ALOX15) in peripheral blood mononuclear cells (PBMCs). Omega-3 polyunsaturated fatty acids supplementation has shown to lower HODEs levels in RTT. Statistically significant correlation was demonstrated between the increased plasma HODEs levels and the lipoprotein-associated phospholipase A2 (Lp-PLA2) activity. Collectively, these findings reinforce the concept of the key role played by lipid peroxidation in RTT, and the possible ability of omega-3 polyunsaturated fatty acids supplementation in improving the oxinflammation status in RTT

Inactivation of two genes located in the GPL biosynthetic locus leads to morphological changes in Mycobacterium smegmatis

Glycopeptidolipids (GPLs) are surface exposed molecules found either in saprophytic or in clinically-relevant non-tuberculous mycobacteria. These molecules, which may represent more than 70% of total surface lipids, are required for cell aggregation, sliding motility and biofilm formation and seem to act as surface antigens stimulating host macrophages response. The GPLs structure is conserved among mycobacteria and is made by a common glycosylated lpopeptide core that is variably modified by O-methylation and O-acetylation. In the fast growing Mycobacterium smegmatis, all the genes necessary for GPL biosynthesis are clustered in a single region of 65 kb and most of them have been identified experimentally or by in silico prediction. Here we report the isolation of two mutant strains of M. smegmatis, carrying null mutations in genes coding for two hypothetical proteins. The two genes (MSMEG_0412; MSMEG_0394) belong to the GPL gene cluster. Preliminary experiments show that inactivation of both genes has drastic impact on bacterial surface properties. Both mutants display rough phenotype, lack of sliding motility, altered biofilm formation and increased antimicrobial susceptibility. GPLs analysis by TLC and MALDI-TOF is in progress to assess whether the observed phenotypes arise from GPLs deficiency and/or structural modification

The complexity of Rett syndrome models: primary fibroblasts as a disease-in-a-dish reliable approach

Rett syndrome (RTT) is a progressive neurodevelopmental disease, which affects almost exclusively the female gender (prevalence of about 1:10,000). RTT symptoms are usually characterized by loss of purposeful hand skills, mental retardation and motor impairment, resulting in a plethora of other systemic co-morbidities. Mutations in the methyl-CpG binding protein 2 gene (MECP2) are the main genetic cause of the disorder, however molecular mechanisms leading from MeCP2 defects to this complicated pathology still need to be clarified. To investigate this and other aspects of RTT, several experimental models have been generated that include animal models, and in vitro approaches. In this article we briefly summarized the main models used for RTT investigations, and special focus is given to the use of primary fibroblasts isolated from RTT patients, since they represent a reliable disease-in-a-dish model, which can help researcher to elucidate cellular and molecular mechanisms of this disease

SIRT1-Dependent Upregulation of Antiglycative Defense in HUVECs Is Essential for Resveratrol Protection against High Glucose Stress

Uncontrolled accumulation of methylglyoxal (MG) and reactive oxygen species (ROS) occurs in hyperglycemia-induced endothelial dysfunction associated with diabetes. Resveratrol (RSV) protects the endothelium upon high glucose (HG); however, the mechanisms underlying such protective effects are still debated. Here we identified key molecular players involved in the glycative/oxidative perturbations occurring in endothelial cells exposed to HG. In addition, we determined whether RSV essentially required SIRT1 to trigger adaptive responses in HG-challenged endothelial cells. We used primary human umbilical vein endothelial cells (HUVECs) undergoing a 24-h treatment with HG, with or without RSV and EX527 (i.e., SIRT1 inhibitor). We found that HG-induced glycative stress (GS) and oxidative stress (OS), by reducing SIRT1 activity, as well as by diminishing the efficiency of MG- and ROS-targeting protection. RSV totally abolished the HG-dependent cytotoxicity, and this was associated with SIRT1 upregulation, together with increased expression of GLO1, improved ROS-scavenging efficiency, and total suppression of HG-related GS and OS. Interestingly, RSV failed to induce effective response to HG cytotoxicity when EX527 was present, thus suggesting that the upregulation of SIRT1 is essential for RSV to activate the major antiglycative and antioxidative defense and avoid MG- and ROS-dependent molecular damages in HG environment