Cigarette Smoke Affects Keratinocytes SRB1 Expression and Localization via H2O2 Production and HNE Protein Adducts Formation

Scavenger Receptor B1 (SR-B1), also known as HDL receptor, is involved in cellular cholesterol uptake. Stratum corneum (SC), the outermost layer of the skin, is composed of more than 25% cholesterol. Several reports support the view that alteration of SC lipid composition may be the cause of impaired barrier function which gives rise to several skin diseases. For this reason the regulation of the genes involved in cholesterol uptake is of extreme significance for skin health. Being the first shield against external insults, the skin is exposed to several noxious substances and among these is cigarette smoke (CS), which has been recently associated with various skin pathologies. In this study we first have shown the presence of SR-B1 in murine and human skin tissue and then by using immunoblotting, immunoprecipitation, RT-PCR, and confocal microscopy we have demonstrated the translocation and the subsequent lost of SR-B1 in human keratinocytes (cell culture model) after CS exposure is driven by hydrogen peroxide (H2O2) that derives not only from the CS gas phase but mainly from the activation of cellular NADPH oxidase (NOX). This effect was reversed when the cells were pretreated with NOX inhibitors or catalase. Furthermore, CS caused the formation of SR-B1-aldheydes adducts (acrolein and 4-hydroxy-2-nonenal) and the increase of its ubiquitination, which could be one of the causes of SR-B1 loss. In conclusion, exposure to CS, through the production of H2O2, induced post-translational modifications of SR-B1 with the consequence lost of the receptor and this may contribute to the skin physiology alteration as a consequence of the variation of cholesterol uptake

Refining the Role of Left Atrial Strain in Heart Failure with Reduced Ejection Fraction

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Cigarette smoke affects SRB1 levels in human keratynocites via H202 production

The pathological effects of cigarette smoke (CS) have been extensively documented and many diseases such as emphysema and lung cancer are directly linked to the consequences of chronic smoke exposure. The combustion of CS produces over 4,000 different compounds in gaseous and particulate states that are able to induce oxidative stress to the cells exposed to the tobacco smoke. In addition, side stream smoke has been shown to be nearly as toxic as direct stream, therefore CS present two-fold heath problem to both passive and active smokers. Skin acts as a first line of defense against environmental trauma. The upper layer of the skin, the stratum corneum (SC), is composed by lipid barrier that contains unsaturated lipids that are susceptible to oxidation. The alteration of the skin lipids composition by the exposure to environmental stressors such as CS can affect the capacity of the SC to protect us from dehydration and external dangers. Scavenger Receptor B1 (SR-B1), one of the large family of scavenger receptors, has been shown to be involved in the uptake of cholesterol from HDL to peripheral tissues via apo A-1 mediated processes and also to be important in the delivery of tocopherol to the cells, therefore its role in skin homeostasis is crucial. In the present studies the effects of CS and of products related to CS such as acrolein, 4HNE and H2O2 on SR-B1 expression in human keratinocytes were assessed. CS exposure induced a significant decrease of SR-B1 expression and the formation of acrolein and 4NHE protein adducts. On the other hand, cells treated with several doses of acrolein or 4HNE or H2O2 did not affect SR-B1 levels. The treatment with glucose oxidase induces the same effect of CS as to concern SR-B1 levels and this was reversed when cells were treated with catalase. In addition, CS induced the activation of NADPH oxidase measured as p67 translocation from the cytoplasm to the membrane. The data from this study show that CS decreases the levels of SR-B1 in human keratinocytes and this effect is mainly driven by the production of H2O2 (exogenous and endogenous). The decrease of SR-B1 could lead to the disturbance of the skin lipid barrier affecting skin physiology and be a possible cause to skin disorders such as skin aging and wound healing linked to CS exposure

Correction: Cigarette Smoke Affects Keratinocytes SRB1 Expression and Localization via H2O2 Production and HNE Protein Adducts Formation.

[This corrects the article DOI: 10.1371/journal.pone.0033592.]

Alteration of serum lipid profile, SRB1 loss, and impaired Nrf2 activation in CDKL5 disorder

CDKL5 mutation is associated with an atypical Rett syndrome (RTT) variant. Recently, cholesterol homeostasis perturbation and oxidative-mediated loss of the high-density lipoprotein receptor SRB1 in typical RTT have been suggested. Here, we demonstrate an altered lipid serum profile also in CDKL5 patients with decreased levels of SRB1 and impaired activation of the defensive system Nrf2. In addition, CDKL5 fibroblasts showed an increase in 4-hydroxy-2-nonenal- and nitrotyrosine-SRB1 adducts that lead to its ubiquitination and probable degradation. This study highlights a possible common denominator between two different RTT variants (MECP2 and CDKL5) and a possible common future therapeutic target. © 2015 Elsevier Inc

Alteration of serum lipid profile, SRB1 loss, and impaired Nrf2 activation in CDKL5 disorder

CDKL5 mutation is associated with an atypical Rett syndrome (RTT) variant. Recently, cholesterol homeostasis perturbation and oxidative-mediated loss of the high-density lipoprotein receptor SRB1 in typical RTT have been suggested. Here, we demonstrate an altered lipid serum profile also in CDKL5 patients with decreased levels of SRB1 and impaired activation of the defensive system Nrf2. In addition, CDKL5 fibroblasts showed an increase in 4-hydroxy-2-nonenal- and nitrotyrosine-SRB1 adducts that lead to its ubiquitination and probable degradation. This study highlights a possible common denominator between two different RTT variants (MECP2 and CDKL5) and a possible common future therapeutic target

Alteration of serum lipid profile, SRB1 loss, and impaired Nrf2 activation in CDKL5 disorder.

CDKL5 mutation is associated with an atypical Rett syndrome (RTT) variant. Recently, cholesterol homeostasis perturbation and oxidative-mediated loss of the high-density lipoprotein receptor SRB1 in typical RTT have been suggested. Here, we demonstrate an altered lipid serum profile also in CDKL5 patients with decreased levels of SRB1 and impaired activation of the defensive system Nrf2. In addition, CDKL5 fibroblasts showed an increase in 4-hydroxy-2-nonenal- and nitrotyrosine-SRB1 adducts that lead to its ubiquitination and probable degradation. This study highlights a possible common denominator between two different RTT variants (MECP2 and CDKL5) and a possible common future therapeutic target

Cigarette Smoke exposure induces changes in SR-B1 levels and localization in human keratinocytes.

<p>Immunocytochemistry of HaCaT cells showing localization of SR-B1 (green) before and after CS exposure for different time points. Images are merged and are representative of at least 100 cells viewed in each experiments (n = 5). Nuclei (blue) were stained with DAPI. A) Cells overview at different time points 40×; B) Representative Western blot of proteins extracted from the membranes of cells exposed to Cigarette Smoke at different time points. The signals of SR-B1 protein levels were determined by densitometric analysis of the scanned images (bottom panel). Data are expressed in arbitrary units and are averages of the values for five different experiments. (*p<0.05).</p

GO treatment decreased SR-B1 levels.

<p>Cells were treated with GO for 50 min and then harvested at different time points (0–24 hrs). A) Representative Western blot of five independent experiments is shown in the top panel. Quantification of the SRB1 bands, average of the five independent experiments, is shown in the bottom panel. Data are expressed in arbitrary units (**p<0.01). β-actin was used as loading control. B) Concentration of H₂O₂ level in cell treated with GO. Data are presented as average of triplicate measurements from each sample and expressed as arbitrary units.</p

Possible mechanism involved in the degradation of SR-B1.

<p>Among the components present in CS there are acrolein and H₂O₂ that beside to react with the membrane lipids (1) are able to cross the cell membrane (2), once H₂O₂ is inside the cells, there will be the formation of OH. (Fenton reaction) (3) that will react with the cytosolic membrane lipids and the formation of lipid peroxidation products such as ACR and HNE (4). ACR and HNE can from SR-B1 adducts (5 and 6) and HNE can also activate NOX by inducing the translocation of the cytoplasmic submit to the membrane (7). Activation of NOX lead to the increased production of O₂⁻ that can be dismutated (SOD) in H₂O₂ (8) that via Fenton reaction will further increase the level of peroxidation (9). The formation of HNE-SR-B1 adducts is recognized by the ubiquitination apparatus of the cell (10) that will ubiquitinate the protein that subsequent will be dregraded by the proteosome (11).</p