OxLDL upregulates caveolin-1 expression in macrophages: Role for caveolin-1 in the adhesion of oxLDL-treated macrophages to endothelium

Gene and Protein Accumulation Changes Evoked in Porcine Aorta in Response to Feeding with Two Various Fructan Sources

In this study, two different ITFs sources were incorporated into a cereal-based diet to evaluate possible aortic protein and gene changes in nursery pigs. The animals were fed two different experimental diets from the 10th day of life, supplemented with either 4% of dried chicory root (CR) or with 2% of native inulin (IN). After a 40-day dietary intervention trial, pigs were sacrificed at day 50 and the aortas were harvested. Our data indicate that dietary ITFs have the potential to influence several structural and physiological changes that are reflected both in the mRNA and protein levels in porcine aorta. In contrast to our hypothesis, we could not show any beneficial effects of a CR diet on vascular functions. The direction of changes of several proteins and genes may indicate disrupted ECM turnover (COL6A1 and COL6A2, MMP2, TIMP3, EFEMP1), increased inflammation and lipid accumulation (FFAR2), as well as decreased activity of endothelial nitric oxide synthase (TXNDC5, ORM1). On the other hand, the IN diet may counteract a highly pro-oxidant environment through the endothelin-NO axis (CALR, TCP1, HSP8, PDIA3, RCN2), fibrinolytic activity (ANXA2), anti-atherogenic (CAVIN-1) and anti-calcification (LMNA) properties, thus contributing to the maintenance of vascular homeostasis.

5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone Inhibits LPS-Induced Vascular Inflammation by Targeting the Cav1 Protein

Vascular inflammation is directly responsible for atherosclerosis. 5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone (TDD), a synthetic bromophenol derivative, exhibits anti-atherosclerosis and anti-inflammatory effects. However, the underlying pathways are not yet clear. In this study, we first examined the effects of TDD on toll-like receptor-4 (TLR4) activity, the signaling receptor for lipopolysaccharide (LPS), and found that TDD does not inhibit LPS-induced TLR4 expression in EA.hy926 cells and the vascular wall in vivo. Next, we investigated the global protein alterations and the mechanisms underlying the action of TDD in LPS-treated EA.hy926 cells using an isobaric tag for the relative and absolute quantification technique. Western blot analysis revealed that TDD inhibited NF-κB activation by regulating the phosphorylation and subsequent degradation IκBα. Among the differentially expressed proteins, TDD concentration-dependently inhibited Caveolin 1(Cav1) expression. The interaction between Cav1 and TDD was determined by using biolayer interference assay, UV-vis absorption spectra, fluorescence spectrum, and molecular docking. We found that TDD can directly bind to Cav1 through hydrogen bonds and van der Waals forces. In conclusion, our results showed that TDD inhibited LPS-induced vascular inflammation and the NF-κB signaling pathway by specifically targeting the Cav1 protein. TDD may be a novel anti-inflammatory compound, especially for the treatment of atherosclerosis.

Effectiveness of a new rutin Cu(II) complex in the prevention of lipid peroxidation and hepatotoxicity in hypercholesterolemic rats

A new rutin copper(II) complex (R-Cu2) was prepared and characterized by spectroscopic methods and elemental analysis. The effects of rutin and R-Cu2 were evaluated on the prevention of hypercholesterolemia in animals feed with high-cholesterol diet (HCD) for 8 weeks. The animals (n = 5) were neither fed with HCD nor treated (control group), or were treated with vehicle, 10 mg/kg simvastatin, rutin (16 and 160 μmol/kg), and R-Cu2 (16 and 160 μmol/kg) administered orally. Total cholesterol (TC) levels were significantly increased (p < .01) in all HCD groups. In rutin and R-Cu2 groups, it was observed a discrete, but not significant, TC and LDL-induced increase inhibition compared with vehicle-treated group. R-Cu2 treatment significantly decreased (p < .05) plasma triglycerides compared with the vehicle-treated group. All groups receiving treatments maintained the malondialdehyde at normal levels. Serum NO levels were reduced in animals treated with rutin and R-Cu2 compared with the vehicle-treated group. In addition, the results also showed that the groups treated with rutin and R-Cu2 reduced significantly (p < .01), the number of neutrophils and prevented histological changes in all evaluated liver zones. R-Cu2 group maintained the ALT, AST, and ALP enzymes at normal levels. Thus, the effects of R-Cu2 in modulating inflammation and protecting liver damage were confirmed. PRACTICAL APPLICATIONS: Rutin, a plant-derived flavonoid, is one of phenolic compounds well known as a nutraceutical due to its antioxidant and anti-inflammatory properties. Findings of this study demonstrate the effects of both rutin and R-Cu2 in modulating inflammation and protecting liver damage in hypercholesterolemic rats. However, some effects analyzed became more evident in R-Cu2. Thereby, it was shown that the synthesis of a new flavonoid compound (R-Cu2) could be applied as a nutraceutical benefit option to prevent hypercholesterolemia condition.

The Potential Contribution of Caveolin 1 to HIV Latent Infection

Combinatorial antiretroviral therapy (cART) suppresses HIV replication to undetectable levels and has been effective in prolonging the lives of HIV infected individuals. However, cART is not capable of eradicating HIV from infected individuals mainly due to HIV’s persistence in small reservoirs of latently infected resting cells. Latent infection occurs when the HIV-1 provirus becomes transcriptionally inactive and several mechanisms that contribute to the silencing of HIV transcription have been described. Despite these advances, latent infection remains a major hurdle to cure HIV infected individuals. Therefore, there is a need for more understanding of novel mechanisms that are associated with latent infection to purge HIV from infected individuals thoroughly. Caveolin 1(Cav-1) is a multifaceted functional protein expressed in many cell types. The expression of Cav-1 in lymphocytes has been controversial. Recent evidence, however, convincingly established the expression of Cav-1 in lymphocytes. In lieu of this finding, the current review examines the potential role of Cav-1 in HIV latent infection and provides a perspective that helps uncover new insights to understand HIV latent infection.

Water-soluble fraction of particulate matter <2.5 μm promoted lung epithelia cells apoptosis by regulating the expression of caveolin-1 and Krüppel-like factor 5

Ambient fine particulate matter of <2.5 μm (PM2.5) has been linked to morbidity and mortality from respiratory and cardiovascular diseases. Lung epithelial cells bear the brunt of PM2.5 exposure. In the present study, we found that exposure of A549 cells to the water-soluble fraction of PM2.5 (WS-PM2.5) promoted the expression and internalization of caveolin-1. Caveolin-1 knockdown restrained the endocytosis of WS-PM2.5. In addition, WS-PM2.5 accumulation in the cells induced the phosphorylation of serine/threonine protein kinase B (AKT) and nuclear factor κ-light-chain enhancer of activated B cells (NFκB), as well as the expression of Krüppel-like factor 5 (KLF5). Inhibiting activation of AKT and NFκB also partly reduced WS-PM2.5 concentration in cells, but KLF5 knockdown did not affect the intracellular accumulation of WS-PM2.5. KLF5 knockdown suppressed cytochrome P450 family 1 subfamily A member 1 (CYP1A1) expression and activated caspase 3. Luciferase reporter assay and chromatin immunoprecipitation assay showed that KLF5 positively regulated the transcription of KLF5. These results suggested that caveolin-1 was required for the endocytosis of WS-PM2.5. Intracellular accumulation of WS-PM2.5 activated AKT and NFκB, which facilitated WS-PM2.5 endocytosis. WS-PM2.5 accumulation also induced KLF5 expression, increasing the transcriptional expression of CYP1A1, which contributed to activate caspase 3.

Maternal chronic intermittent hypoxia in rats causes early atherosclerosis with increased expression of Caveolin-1 in offspring

OBJECTIVE

The objective of our research was to explore the effects of maternal and postpartum chronic intermittent hypoxia (CIH) exposure on atherosclerosis in adulthood offspring of rats, and the role of Caveolin-1 in the course.

METHODS

Sixteen rats were assigned to two groups (n = 8), maternal normoxia and CIH group. After delivery, two male pups per litter were selected and breastfed for 1 month, which then randomly received postpartum normoxia or CIH. Thus, 4 groups were created as follows (n = 8): (1) maternal normoxia and postpartum normoxia group, (2) maternal CIH and postpartum normoxia group, (3) maternal CIH and postpartum CIH group, and (4) maternal normoxia and postpartum CIH group. The offspring were weighed at birth and weaning. After the duration of 12-week experiment, morphological changes, the expression of Caveolin-1 and NF-κB p65 in the aorta were detected.

RESULTS

Maternal CIH resulted in significantly lower body weight and thicker intima (P < 0.001). CIH upregulated the expression of Caveolin-1 and NF-κB p65 significantly (P < 0.01). There was a synergistic effect of maternal and postpartum CIH on the thickening of intima (P < 0.05), also on the expression of Caveolin-1 and NF-κB p65 (P < 0.01).

CONCLUSIONS

The results demonstrate that maternal CIH exposure causes a postpartum catch-up growth and early atherosclerotic changes followed by upregulating Caveolin-1 expression. Besides, maternal CIH enhances the atherosclerotic changes caused by postpartum CIH. Oxidative stress probably implicates in above effects.

oxLDL-mediated cellular senescence is associated with increased NADPH oxidase p47phox recruitment to caveolae

Atherosclerosis develops as a consequence of inflammation and cell senescence. In critical factors involved in the atherosclerotic changes, reactive oxygen species (ROS) generation is considered a leading cause. While NADPH oxidases, particularly NOX2, are the main sources of ROS, how they are regulated in the disease is incompletely understood. In addition, how caveolae, the membrane structure implicated in oxLDL deposition under vascular endothelia, is involved in the oxLDL-mediated ROS production remains mostly elusive. We report here that macrophages exposed to oxLDL up-regulate its caveolin-1 expression, and the latter in turn up-regulates NOX2 p47phox level. This combination effect results in increased cellular senescence. Interestingly, oxLDL treatment causes the p47phox residing in the cytosol to translocate to the caveolae. Immunoprecipitation assays confirms that cavelin-1 is in high degree association with p47phox. These results suggest caveolin-1 may serve as the membrane target for p47phox and as a switch for ROS production following oxLDL exposure. Our results reveal a previously unknown molecular event in oxLDL-mediated cellular ageing, and may provide a target for clinical intervention for atherosclerosis.

The ω-carboxyl group of 7-ketocholesteryl-9-carboxynonanoate mediates the binding of oxLDL to CD36 receptor and enhances caveolin-1 expression in macrophages

CD36 signal transduction modulates the uptake of oxidized low-density lipoprotein (oxLDL) and foam cell formation. We previously observed that 7-ketocholesteryl-9-carboxynonanoate (oxLig-1), the lipid moiety of oxLDL, activates the CD36-Src-JNK/ERK1/2 signalling pathway. In this study, we assessed the role of the ω-carboxyl group in the binding of oxLig-1 to CD36 and investigated whether the binding of the ω-carboxyl group to CD36 triggers CD36-mediated signalling, thereby resulting in the upregulation of caveolin-1 expression. Our results showed that oxLig-1 bound to CD36 and that the ω-carboxyl group was critical for this binding. Furthermore, immunoprecipitation and Western blot analyses showed that interaction between the ω-carboxyl group of oxLig-1 and CD36 triggered intracellular Src-JNK/ERK1/2 signal transduction. Moreover, the binding of the ω-carboxyl group to CD36 induced caveolin-1 expression and translocation to the membrane in macrophages. Additionally, inhibitors of Src, JNK and ERK and siRNA targeting CD36 and NF-κB significantly suppressed the enhanced caveolin-1 expression induced by oxLig-1. In conclusion, these observations suggest that oxLig-1 is a critical epitope of oxLDL that mediates the binding of oxLDL to CD36 and activates downstream Src-JNK/ERK1/2-NF-κB signal transduction, resulting in upregulation of caveolin-1 expression in macrophages.

The Role of Caveolin 1 in HIV Infection and Pathogenesis

Caveolin 1 (Cav-1) is a major component of the caveolae structure and is expressed in a variety of cell types including macrophages, which are susceptible to human immunodeficiency virus (HIV) infection. Caveolae structures are present in abundance in mechanically stressed cells such as endothelial cells and adipocytes. HIV infection induces dysfunction of these cells and promotes pathogenesis. Cav-1 and the caveolae structure are believed to be involved in multiple cellular processes that include signal transduction, lipid regulation, endocytosis, transcytosis, and mechanoprotection. Such a broad biological role of Cav-1/caveolae is bound to have functional cross relationships with several molecular pathways including HIV replication and viral-induced pathogenesis. The current review covers the relationship of Cav-1 and HIV in respect to viral replication, persistence, and the potential role in pathogenesis.

NOR-1 modulates the inflammatory response of vascular smooth muscle cells by preventing NFκB activation

Recent work has highlighted the role of NR4A receptors in atherosclerosis and inflammation. In vascular smooth muscle cell (VSMC) proliferation, however, NOR-1 (neuron-derived orphan receptor-1) exerts antagonistic effects to Nur77 and Nurr1. The aim of this study was to analyse the effect of NOR-1 in VSMC inflammatory response. We assessed the consequence of a gain-of-function of this receptor on the response of VSMC to inflammatory stimuli. In human VSMC, lentiviral over-expression of NOR-1 reduced lipopolysaccharide (LPS)-induced up-regulation of cytokines (IL-1β, IL-6 and IL-8) and chemokines (MCP-1 and CCL20). Similar effects were obtained in cells stimulated with TNFα or oxLDL. Conversely, siRNA-mediated NOR-1 inhibition significantly increased the expression of pro-inflammatory mediators. Interestingly, in the aortas from transgenic mice that over-express human NOR-1 in VSMC (TgNOR-1), the up-regulation of cytokine/chemokine by LPS was lower compared to wild-type littermates. Similar results were obtained in VSMC from transgenic animals. NOR-1 reduced the transcriptional activity of NFκB sensitive promoters (in transient transfections), and the binding of NFκB to its responsive element (in electrophoretic mobility shift assays). Furthermore, NOR-1 prevented the activation of NFκB pathway by decreasing IκBα phosphorylation/degradation and inhibiting the phosphorylation and subsequent translocation of p65 to the nucleus (assessed by Western blot and immunocytochemistry). These effects were associated with an attenuated phosphorylation of ERK1/2, p38 MAPK and Jun N-terminal kinase, pathways involved in the activation of NFκB. In mouse challenged with LPS, the activation of the NFκB signalling was also attenuated in the aorta from TgNOR-1. Our data support a role for NOR-1 as a negative modulator of the acute response elicited by pro-inflammatory stimuli in the vasculature.

Role of aquaglyceroporins and caveolins in energy and metabolic homeostasis

Aquaglyceroporins and caveolins are submicroscopic integral membrane proteins that are particularly abundant in many mammalian cells. Aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) encompass a subfamily of aquaporins that allow the movement of water, but also of small solutes, such as glycerol, across cell membranes. Glycerol constitutes an important metabolite as a substrate for de novo synthesis of triacylglycerols and glucose as well as an energy substrate to produce ATP via the mitochondrial oxidative phosphorylation. In this sense, the control of glycerol influx/efflux in metabolic organs by aquaglyceroporins plays a crucial role with the dysregulation of these glycerol channels being associated with metabolic diseases, such as obesity, insulin resistance, non-alcoholic fatty liver disease and cardiac hypertrophy. On the other hand, caveolae have emerged as relevant plasma membrane sensors implicated in a wide range of cellular functions, including endocytosis, apoptosis, cholesterol homeostasis, proliferation and signal transduction. Caveolae-coating proteins, namely caveolins and cavins, can act as scaffolding proteins within caveolae by concentrating signaling molecules involved in free fatty acid and cholesterol uptake, proliferation, insulin signaling or vasorelaxation, among others. The importance of caveolae in whole-body homeostasis is highlighted by the link between homozygous mutations in genes encoding caveolins and cavins with metabolic diseases, such as lipodystrophy, dyslipidemia, muscular dystrophy and insulin resistance in rodents and humans. The present review focuses on the role of aquaglyceroporins and caveolins on lipid and glucose metabolism, insulin secretion and signaling, energy production and cardiovascular homeostasis, outlining their potential relevance in the development and treatment of metabolic diseases.

oxLDL induces injury and defenestration of human liver sinusoidal endothelial cells via LOX1

Non-alcoholic fatty liver disease is associated with hepatic microangiopathy and liver inflammation caused by type 2 diabetes mellitus. Oxidised LDL (oxLDL) is involved in proinflammatory and cytotoxic events in various microcirculatory systems. The lectin-like oxLDL receptor 1 (LOX1) plays a crucial role in oxLDL-induced pathological transformation. However, the underlying mechanism of oxLDL's effects on liver microcirculation disturbances remains unclear. In this study, we investigated the effects of oxLDL on LOX1 (OLR1) expression and function, as well as on the fenestration features of human liver sinusoidal endothelial cells (HLSECs) in vitro. Primary HLSECs were obtained and cultured. The cells were treated with various concentrations of oxLDL (25, 50, 100 and 200  μg/ml), and the cytotoxicity and expression of LOX1 were examined. Furthermore, LOX1 knockdown was performed using siRNA technology, and the changes in intracellular reactive oxygen species (ROS), NFκB, p65, (p65), endothelin 1 (ET1 (EDN1)), eNOS (NOS3) and caveolin 1 (CAV1) levels were measured. Cells were treated with 100  μg/ml oxLDL, and the fenestra morphology was visualised using scanning electron microscopy. oxLDL significantly increased LOX1 expression at both the mRNA and protein levels in HLSECs in a dose- and time-dependent manner. oxLDL stimulation increased ROS generation and NFκB activation, upregulated ET1 and caveolin 1 expression, downregulated eNOS expression and reduced the fenestra diameter and porosity. All of these oxLDL-mediated effects were inhibited after LOX1 knockdown. These results reveal a mechanism by which oxLDL stimulates the production of LOX1 through the ROS/NFκB signalling pathway and by which LOX1 mediates oxLDL-induced endothelial injury and the defenestration of HLSECs.

Significance of caveolin-1 regulators in pancreatic cancer

Caveolin-1 is a scaffold protein on the cell membrane. As the main component of caveolae, caveolin-1 is involved in many biological processes that include substance uptake and transmembrane signaling. Many of these processes and thus caveolin-1 contribute to cell transformation, tumorigenesis, and metastasis. Of particular interest are the dual rolesof tumor suppressor and oncogene that caveolin-1 appear to play in different malignancies, including pancreatic cancer. Therefore, analyzing caveolin-1 regulators and understanding their mechanisms of actionis key to identifying novel diagnostic and therapeutic tools for pancreatic cancer. This review details the mechanisms of action of caveolin-1 regulators and the potential significance for pancreatic cancer treatment.

Curcumin inhibits oxLDL-induced CD36 expression and foam cell formation through the inhibition of p38 MAPK phosphorylation

The uptake of oxidized low density lipoprotein (oxLDL) via scavenger receptors transforms macrophages into foam cells, which are a hallmark of atherosclerosis. OxLDL markedly increases the expression of the CD36 scavenger receptor. Here, we investigated whether curcumin modulate CD36 expression in oxLDL-treated RAW 264.7 murine macrophages. Our results showed that curcumin dramatically inhibits CD36 expression and foam cell formation. Furthermore, oxLDL-induced expression and activity of peroxisome proliferator-activated receptor-gamma (PPAR-γ), which is involved in CD36 expression, is also blocked in curcumin-treated cells. OxLDL activates the mitogen-activated protein kinase (MAPK) signaling transduction pathway, and p38 MAPK is associated with oxLDL-induced CD36 and PPAR-γ expression. Overexpression of dominant negative p38 MAPK blocks oxLDL-induced CD36 and PPAR-γ expression. Furthermore, curcumin markedly inhibits p38 MAPK phosphorylation. Taken together, our results suggest that curcumin modulates oxLDL-induced CD36 expression and foam cell formation via the inhibition of p38 MAPK phosphorylation in RAW 264.7 murine macrophages.

Caveolin-1 plays a critical role in the differentiation of monocytes into macrophages

OBJECTIVE

Monocyte to macrophage differentiation is an essential step in atherogenesis. The structure protein of caveolae, caveolin-1, is increased in primary monocytes after its adhesion to endothelium. We explore the hypothesis that caveolin-1 plays a role in monocyte differentiation to macrophages.

METHODS AND RESULTS

Both phorbol myristate acetate-induced THP-1 and colony-stimulating factor-induced primary monocyte differentiation was associated with an increase in cellular caveolin-1 expression. Overexpression of caveolin-1 by transfection increased macrophage surface markers and inflammatory genes, whereas caveolin-1 knockdown by small interfering RNA or knockout reduced these. Also, caveolin-1 knockdown inhibited the differentiation-induced nuclear translocation of early growth response 1 (EGR-1) through extracellular signal-regulated kinase phosphorylation, further decreased the binding of EGR-1 to CD115 promoter, thus decreasing EGR-1 transcriptional activity. In functional assays, caveolin-1 inhibited transmigration but promoted phagocytosis in the monocyte-macrophage lineage. Decreasing caveolin-1 inhibited the uptake of modified low-density lipoprotein and reduced cellular lipid content. Finally, we showed that caveolin-1 knockout mice displayed less monocyte differentiation than wild-type mice and that EGR-1 transcription activity was also decreased in these mice because of the inhibition of extracellular signal-regulated kinase phosphorylation.

CONCLUSIONS

Caveolin-1 promotes monocyte to macrophage differentiation through the regulation of EGR-1 transcriptional activity, suggesting that phagocytic caveolin-1 may be critical for atherogenesis.

Oxidized low-density lipoprotein as a biomarker of in vivo oxidative stress: from atherosclerosis to periodontitis

Oxidized low-density lipoprotein is known as an important factor in the development of atherosclerosis. The introduction of a sensitive procedure for the determination of oxidized low-density lipoprotein in human circulating plasma using a monoclonal antibody recognizing oxidized phosphatidylcholines has opened new fields of research based on in vivo oxidized low-density lipoprotein. The plasma oxidized low-density lipoprotein levels are significantly elevated in patients with acute myocardial infarction, cerebral infarction or chronic renal failure accompanied by hemodialysis. It was found that the plasma oxidized low-density lipoprotein level increased prior to aortic atherosclerotic lesion enlargement in apolipoprotein E-knockout mice. Recent studies have pointed out that oxidized low-density lipoprotein is transferrable between vessel wall tissue and the circulation, so it is a reasonable hypothesis that plasma oxidized low-density lipoprotein levels reflect the oxidative status at local sites of atherogenesis. Oxidized low-density lipoprotein measurement has been applied to human gingival crevicular fluids, which can be collected easily and safely, and relatively high levels of oxidized low-density lipoprotein were shown to be present. These findings, together with recent clinical follow-up studies, suggest that oxidized low-density lipoprotein is a predictive biomarker of a variety of diseases related to oxidative stress. This review summarizes the current understanding of in vivo oxidized low-density lipoprotein and its potential significance as a biomarker of disease.

Regulation of SGLT expression and localization through Epac/PKA-dependent caveolin-1 and F-actin activation in renal proximal tubule cells

This study demonstrated that exchange proteins directly activated by cAMP (Epac) and protein kinase A (PKA) by 8-bromo (8-Br)-adenosine 3',5'-cyclic monophosphate (cAMP) stimulated [(14)C]-α-methyl-D-glucopyranoside (α-MG) uptake through increased sodium-glucose cotransporters (SGLTs) expression and translocation to lipid rafts in renal proximal tubule cells (PTCs). In PTCs, SGLTs were colocalized with lipid raft caveolin-1 (cav-1), disrupted by methyl-β-cyclodextrin (MβCD). Selective activators of Epac or PKA, 8-Br-cAMP, and forskolin stimulated expressions of SGLTs and α-MG uptake in PTCs. In addition, 8-Br-cAMP-induced PKA and Epac activation increased phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase (MAPK), and nuclear factor kappa B (NF-κB), which were involved in expressions of SGLTs. Furthermore, 8-Br-cAMP stimulated SGLTs translocation to lipid rafts via filamentous actin (F-actin) organization, which was blocked by cytochalasin D. In addition, cav-1 and SGLTs stimulated by 8-Br-cAMP were detected in lipid rafts, which were blocked by cytochalasin D. Furthermore, 8-Br-cAMP-induced SGLTs translocation and α-MG uptake were attenuated by inhibition of cav-1 activation with cav-1 small interfering RNA (siRNA) and inhibition of F-actin organization with TRIO and F-actin binding protein (TRIOBP). In conclusion, 8-Br-cAMP stimulated α-MG uptake via Epac and PKA-dependent SGLTs expression and trafficking through cav-1 and F-actin in PTCs.

Caveolin-1 and integrin β1 regulate embryonic stem cell proliferation via p38 MAPK and FAK in high glucose

The involvement of caveolin-1 (Cav-1) and integrin β1 (IN β1) in regulation of embryonic stem (ES) cell growth by high glucose is by no means clear cut. Therefore, the aim of this study was to examine the influence of high glucose on Cav-1 and IN β1 expression in mouse ES cells and their signaling pathways to modulate proliferation. High glucose significantly increased Cav-1 and IN β1 expression. In addition, increased IN β1 expression was inhibited by Cav-1 small interfering RNA (siRNA). High glucose caused reactive oxygen species generation and p38 mitogen-activated protein kinase (MAPK) phosphorylation. Inhibition of p38 MAPK blocked high glucose-induced Cav-1 and fibronectin (FN) expression. Moreover, phosphorylation of both Src and focal adhesion kinase (FAK) were increased by high glucose, which were inhibited by IN β1 antibody. In addition, high glucose increased the expression levels of PINCH1/2, integrin-linked kinase (ILK), and α-parvin [PIP] complex proteins, which were all inhibited by the FAK siRNA and Src specific inhibitor (PP2, 10(-7)  M). High glucose also increased F-actin expression, which was inhibited by ILK, PINCH1/2, and α-parvin siRNAs. Finally, high glucose-induced increase of ES cell proliferation was inhibited by TRIO and F-actin binding protein (TRIOBP) siRNA. The results demonstrate that high glucose-induced Cav-1 and IN β1 activation can stimulate ES cell proliferation through the modification of focal adhesion signaling pathways.

The role of caveolae in endothelial cell dysfunction with a focus on nutrition and environmental toxicants

Complications of vascular diseases, including atherosclerosis, are the number one cause of death in Western societies. Dysfunction of endothelial cells is a critical underlying cause of the pathology of atherosclerosis. Lipid rafts, and especially caveolae, are enriched in endothelial cells, and down-regulation of the caveolin-1 gene may provide protection against the development of atherosclerosis. There is substantial evidence that exposure to environmental pollution is linked to cardiovascular mortality, and that persistent organic pollutants can markedly contribute to endothelial cell dysfunction and an increase in vascular inflammation. Nutrition can modulate the toxicity of environmental pollutants, and evidence suggests that these affect health and disease outcome associated with chemical insults. Because caveolae can provide a regulatory platform for pro-inflammatory signalling associated with vascular diseases such as atherosclerosis, we suggest a link between atherogenic risk and functional changes of caveolae by environmental factors such as dietary lipids and organic pollutants. For example, we have evidence that endothelial caveolae play a role in uptake of persistent organic pollutants, an event associated with subsequent production of inflammatory mediators. Functional properties of caveolae can be modulated by nutrition, such as dietary lipids (e.g. fatty acids) and plant-derived polyphenols (e.g. flavonoids), which change activation of caveolae-associated signalling proteins. The following review will focus on caveolae providing a platform for pro-inflammatory signalling, and the role of caveolae in endothelial cell functional changes associated with environmental mediators such as nutrients and toxicants, which are known to modulate the pathology of vascular diseases.

Caveolae: a regulatory platform for nutritional modulation of inflammatory diseases

Dietary intervention strategies have proven to be an effective means of decreasing several risk factors associated with the development of atherosclerosis. Endothelial cell dysfunction influences vascular inflammation and is involved in promoting the earliest stages of lesion formation. Caveolae are lipid raft microdomains abundant within the plasma membrane of endothelial cells and are responsible for modulating receptor-mediated signal transduction, thus influencing endothelial activation. Caveolae have been implicated in the regulation of enzymes associated with several key signaling pathways capable of determining intracellular redox status. Diet and plasma-derived nutrients may modulate an inflammatory outcome by interacting with and altering caveolae-associated cellular signaling. For example, omega-3 fatty acids and several polyphenolics have been shown to improve endothelial cell function by decreasing the formation of ROS and increasing NO bioavailability, events associated with altered caveolae composition. Thus, nutritional modulation of caveolae-mediated signaling events may provide an opportunity to ameliorate inflammatory signaling pathways capable of promoting the formation of vascular diseases, including atherosclerosis.

Caveolae and caveolin-1 mediate endocytosis and transcytosis of oxidized low density lipoprotein in endothelial cells

AIM

To explore the mechanisms involved in ox-LDL transcytosis across endothelial cells and the role of caveolae in this process.

METHODS

An in vitro model was established to investigate the passage of oxidized low density lipoprotein (ox-LDL) through a tight monolayer of human umbilical vein endothelial cells (HUVEC) cultured on a collagen-coated filter. Passage of DiI-labeled ox-LDL through the monolayer was measured using a fluorescence spectrophotometer. The uptake and efflux of ox-LDL by HUVEC were determined using fluorescence microscopy and HPLC.

RESULTS

Caveolae inhibitors - carrageenan (250 μg/mL), filipin (5 μg/mL), and nocodazole (33 μmol/L)-decreased the transport of ox-LDL across the monolayer by 48.9%, 72.4%, and 79.8% as compared to the control group. In addition, they effectively decreased ox-LDL uptake and inhibited the efflux of ox-LDL. Caveolin-1 and LOX-1 were up-regulated by ox-LDL in a time-dependent manner and decreased gradually after depletion of ox-LDL (P<0.05). After treatment HUVEC with ox-LDL and silencing caveolin-1, NF-κB translocation to the nucleus was blocked and LOX-1 expression decreased (P<0.05).

CONCLUSION

Caveolae can be a carrier for ox-LDL and may be involved in the uptake and transcytosis of ox-LDL by HUVEC.

HIV infection upregulates caveolin 1 expression to restrict virus production

Caveolin 1 (Cav-1) is a major protein of a specific membrane lipid raft known as caveolae. Cav-1 interacts with the gp41 of the human immunodeficiency virus (HIV) envelope, but the role of Cav-1 in HIV replication and pathogenesis is not known. In this report, we demonstrate that HIV infection in primary human monocyte-derived macrophages (MDMs), THP-1 macrophages, and U87-CD4 cells results in a dramatic upregulation of Cav-1 expression mediated by HIV Tat. The activity of p53 is essential for Tat-induced Cav-1 expression, as our findings show enhanced phosphorylation of serine residues at amino acid positions 15 and 46 in the presence of Tat with a resulting Cav-1 upregulation. Furthermore, inhibition of p38 mitogen-activated protein kinase (MAPK) blocked phosphorylation of p53 in the presence of Tat. Infection studies of Cav-1-overexpressing cells reveal a significant reduction of HIV production. Taken together, these results suggest that HIV infection enhances the expression of Cav-1, which subsequently causes virus reduction, suggesting that Cav-1 may contribute to persistent infection in macrophages.