Genomic changes in regenerated porcine coronary arterial endothelial cells

Cytoplasmic fatty acid-binding proteins in metabolic diseases and cancers

Cytoplasmic fatty acid-binding proteins (FABPs) are multipurpose proteins that can modulate lipid fluxes, trafficking, signaling, and metabolism. FABPs regulate metabolic and inflammatory pathways, its inhibition can improve type 2 diabetes mellitus and atherosclerosis. In addition, FABPs are involved in obesity, metabolic disease, cardiac dysfunction, and cancers. FABPs are promising tissue biomarkers in solid tumors for diagnostic and/or prognostic targets for novel therapeutic strategies. The signaling responsive elements of FABPs and determinants of FABP-mediated functions may be exploited in preventing or treating these diseases.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

Endothelial Recovery in Bare Metal Stents and Drug-Eluting Stents on a Single-Cell Level

[Figure: see text].

Significance of urinary fatty acid-binding protein 4 level as a possible biomarker for the identification of minimal change disease in patents with nephrotic-range proteinuria

Background

Fatty acid-binding protein 4 (FABP4), but not FABP1 (liver-type FABP), is ectopically induced in injured glomerular endothelial cells, and urinary FABP4 (U-FABP4) level is associated with proteinuria and renal dysfunction in a general population.

Methods

The clinical significance of U-FABP4 was investigated in 81 patients (male/female: 43/38, age: 57 ± 17 years) who underwent kidney biopsy.

Results

U-FABP4 was negatively correlated with estimated glomerular filtration rate (eGFR) (r = − 0.56, P < 0.01) and was positively correlated with age, blood pressure, triglycerides, proteinuria (r = 0.58, P < 0.01), plasma FABP4 and urinary FABP1 (U-FABP1) (r = 0.52, P < 0.01). Multivariable regression analysis showed that eGFR, proteinuria and U-FABP1 were independent predictors of U-FABP4. The level of U-FABP4, but not that of proteinuria, eGFR or U-FABP1, in minimal change nephrotic syndrome (MCNS) was significantly lower than the level in membranous nephropathy (MN) and that in diabetic nephropathy. Receiver operating characteristic curve analysis indicated that U-FABP4 level ≤ 0.78 μg/gCr predicted MCNS in patients who had nephrotic-range proteinuria with a high level of accuracy. When divided by the median value of U-FABP4 at baseline in 33 of the 81 patients who could be followed up, the yearly change (post–pre) in eGFR in the low U-FABP4 group was significantly greater than that in the high U-FABP4 group (median: 11.0 vs. -5.0 mL/min/1.73m²/year).

Conclusions

U-FABP4 level is independently associated with proteinuria and renal dysfunction in patients with glomerular kidney disease. A low U-FABP4 level may predict MCNS in patients with nephrotic syndrome and would be a useful biomarker for differential diagnosis of MCNS and MN, which are common causes of nephrotic syndrome.

Supplementary Information

Supplementary information accompanies this paper at 10.1186/s12882-020-02122-y.

Unraveling the transcriptional determinants of liver sinusoidal endothelial cell specialization

Liver sinusoidal endothelial cells (LSECs) are the first liver cells to encounter waste macromolecules, pathogens, and toxins in blood. LSECs are highly specialized to mediate the clearance of these substances via endocytic scavenger receptors and are equipped with fenestrae that mediate the passage of macromolecules toward hepatocytes. Although some transcription factors (TFs) are known to play a role in LSEC specialization, information about the specialized LSEC signature and its transcriptional determinants remains incomplete.Based on a comparison of liver, heart, and brain endothelial cells (ECs), we established a 30-gene LSEC signature comprising both established and newly identified markers, including 7 genes encoding TFs. To evaluate the LSEC TF regulatory network, we artificially increased the expression of the 7 LSEC-specific TFs in human umbilical vein ECs. Although Zinc finger E-box-binding protein 2, homeobox B5, Cut-like homolog 2, and transcription factor EC (TCFEC) had limited contributions, musculoaponeurotic fibrosarcoma (C-MAF), GATA binding protein 4 (GATA4), and MEIS homeobox 2 (MEIS2) emerged as stronger inducers of LSEC marker expression. Furthermore, a combination of C-MAF, GATA4, and MEIS2 showed a synergistic effect on the increase of LSEC signature genes, including liver/lymph node-specific ICAM-3 grabbing non-integrin (L-SIGN) (or C-type lectin domain family member M (CLEC4M)), mannose receptor C-Type 1 (MRC1), legumain (LGMN), G protein-coupled receptor 182 (GPR182), Plexin C1 (PLXNC1), and solute carrier organic anion transporter family member 2A1 (SLCO2A1). Accordingly, L-SIGN, MRC1, pro-LGMN, GPR182, PLXNC1, and SLCO2A1 protein levels were elevated by this combined overexpression. Although receptor-mediated endocytosis was not significantly induced by the triple TF combination, it enhanced binding to E2, the hepatitis C virus host-binding protein. We conclude that C-MAF, GATA4, and MEIS2 are important transcriptional regulators of the unique LSEC fingerprint and LSEC interaction with viruses. Additional factors are however required to fully recapitulate the molecular, morphological, and functional LSEC fingerprint.NEW & NOTEWORTHY Liver sinusoidal endothelial cells (LSECs) are the first liver cells to encounter waste macromolecules, pathogens, and toxins in the blood and are highly specialized. Although some transcription factors are known to play a role in LSEC specialization, information about the specialized LSEC signature and its transcriptional determinants remains incomplete. Here, we show that Musculoaponeurotic Fibrosarcoma (C-MAF), GATA binding protein 4 (GATA4), and Meis homeobox 2 (MEIS2) are important transcriptional regulators of the unique LSEC signature and that they affect the interaction of LSECs with viruses.

Why the endothelium? The endothelium as a target to reduce diabetes-associated vascular disease

Over the past 66 years, our knowledge of the role of the endothelium in the regulation of cardiovascular function and dysfunction has advanced from the assumption that it is a single layer of cells that serves as a barrier between the blood stream and vascular smooth muscle to an understanding of its role as an essential endocrine-like organ. In terms of historical contributions, we pay particular credit to (1) the Canadian scientist Dr. Rudolf Altschul who, based on pathological changes in the appearance of the endothelium, advanced the argument in 1954 that "one is only as old as one's endothelium" and (2) the American scientist Dr. Robert Furchgott, a 1998 Nobel Prize winner in Physiology or Medicine, who identified the importance of the endothelium in the regulation of blood flow. This review provides a brief history of how our knowledge of endothelial function has advanced and now recognize that the endothelium produces a plethora of signaling molecules possessing paracrine, autocrine, and, arguably, systemic hormone functions. In addition, the endothelium is a therapeutic target for the anti-diabetic drugs metformin, glucagon-like peptide I (GLP-1) receptor agonists, and inhibitors of the sodium-glucose cotransporter 2 (SGLT2) that offset the vascular disease associated with diabetes.

Fine air pollution particles induce endothelial senescence via redox-sensitive activation of local angiotensin system

Fine dust (FD) is a form of air pollution and is responsible for a wide range of diseases. Specially, FD is associated with several cardiovascular diseases (CVDs); long-term exposure to FD was shown to decrease endothelial function, but the underlying mechanism remains unclear. We investigated whether exposure to FD causes premature senescence-associated endothelial dysfunction in endothelial cells (ECs) isolated from porcine coronary arteries. The cells were treated with different concentrations of FD and senescence associated-beta galactosidase (SA-β-gal) activity, cell cycle progression, expression of endothelial nitric oxide synthase (eNOS), oxidative stress level, and vascular function were evaluated. We found that FD increased SA-β-gal activity, caused cell cycle arrest, and increased oxidative stress, suggesting the premature induction of senescence; on the other hand, eNOS expression was downregulated and platelet aggregation was enhanced. FD exposure impaired vasorelaxation in response to bradykinin and activated the local angiotensin system (LAS), which was inhibited by treatment with the antioxidant N-acetyl cysteine (NAC) and angiotensin II receptor type 1 (AT₁) antagonist losartan (LOS). NAC and LOS also suppressed FD-induced SA-β-gal activity, increased EC proliferation and eNOS expression, and improved endothelial function. These results demonstrate that FD induces premature senescence of ECs and is associated with increased oxidative stress and activation of LAS. This study can serve as a pharmacological target for prevention and/or treatment of air pollution-associated CVD.

Isolation of fresh endothelial cells from porcine heart for cardiovascular studies: a new fast protocol suitable for genomic, transcriptomic and cell biology studies

Background

Endothelial cells (ECs) play a key role in tissue homeostasis, in several pathological conditions, and specifically in the control of vascular functions. ECs are frequently used as in vitro model systems for cardiovascular studies and vascular biology. The porcine model is commonly used in human clinical cardiovascular studies. Currently, however, there is no robust protocol for the isolation of porcine heart ECs. We have developed a fast isolation protocol, which is cost effective, takes only 1–2 h, and produces EC purity of over 97%. This protocol is optimized for porcine hearts but can be adapted for use with other large animals.

Methods

Heart is washed by flushing with PBS, whereafter endothelial cells are detached by collagenase incubation and the cells can then be collected immediately after the incubation and plated within an hour after the heart is isolated from a pig.

Results

The swiftness of the protocol limits changes in the phenotype and RNA expression profile of the cells. Cells were identified as ECs with CD31 (PECAM-1) antibody immunostaining. Functionality of ECs were ensured with in vitro angiogenesis assay. The purity of the ECs was verified by using fluorescence assisted cell sorting (FACS) with the CD31 antibody.

Conclusion

We developed a new, fast, and cost-effective isolation method for pig heart ECs. Successful isolation of pure ECs is a prerequisite for several cardiovascular and vascular biology studies.

Effects of host fatty acid-binding protein 4 on Eimeria tenella sporozoites invasion of cells

In our previous study, proteomics analyses of host cells infected with Eimeria tenella sporozoites coupled with isobaric tags for relative and absolute quantitation, identified several host proteins related to Eimeria invasion. In this study, A 458-bp Gallus gallus fatty acid-binding protein 4 (FABP4) gene was cloned and subcloned to pET-28c(+) vector to construct the prokaryotic recombinant expression plasmid pET-28c(+)-FABP4. The 18.5 kDa recombinant FABP4 protein (rFABP4) was expressed and identified by western blotting. Expression of FABP4 in E. tenella sporozoite-infected DF-1 cells was downregulated significantly than in non-infected cells detected by western blotting and immunohistochemistry. The antibody inhibition assay showed that antibodies against FABP4 at 50, 100, 200, 300, and 400 μg/mL had no significant effect on sporozoite invasion. BMS-309403 and transforming growth factor-β3 (TGF-β3) was used to inhibit and improve the expression of FABP4 in DF-1 cells, respectively, and their effect on the sporozoite invasion of cells was detected by flow cytometry. Sporozoite invasion rate in the BMS-309403-treated group was not significantly affected; however, the invasion rate in the TGF-β3-treated group declined significantly. These results show that host FABP4 plays a negative role in Eimeria invasion. However, further studies are needed to elucidate the exact mechanism of how FABP4 negatively regulates Eimeria invasion.

Fatty Acid-Binding Protein 4 in Cardiovascular and Metabolic Diseases

Fatty acid-binding proteins (FABPs), a family of lipid chaperones, contribute to systemic metabolic regulation via several lipid signaling pathways. Fatty acid-binding protein 4 (FABP4), known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays important roles in the development of insulin resistance and atherosclerosis in relation to metabolically driven low-grade and chronic inflammation, referred to as ‘metaflammation’. FABP4 is secreted from adipocytes in a non-classical pathway associated with lipolysis and acts as an adipokine for the development of insulin resistance and atherosclerosis. Circulating FABP4 levels are associated with several aspects of metabolic syndrome and cardiovascular disease. Ectopic expression and function of FABP4 in cells and tissues are also related to the pathogenesis of several diseases. Pharmacological modification of FABP4 function by specific inhibitors, neutralizing antibodies or antagonists of unidentified receptors would be novel therapeutic strategies for several diseases, including obesity, diabetes mellitus, atherosclerosis and cardiovascular disease. Significant roles of FABP4 as a lipid chaperone in physiological and pathophysiological conditions and the possibility of FABP4 being a therapeutic target for metabolic and cardiovascular diseases are discussed in this review.

Lessons from Cre-Mice and Indicator Mice

The adult human adipose tissue is predominantly composed of white adipocytes. However, within certain depots, adipose tissue contains thermogenically active brown-like adipocytes, which have been evolutionarily conserved in mammals. This chapter will give a brief overview on the methods used to genetically target and trace both white and brown adipocytes using techniques such as bacterial artificial chromosome (BAC) cloning to create transgenic mouse models and the tools with which genetic recombination is mediated in vivo (e.g., Cre-loxP, CreERT, and Tet-On). The chapter furthermore critically discusses the strength and limitation of the various systems used to target mature white and brown adipocytes (ap2-Cre, Adipoq-Cre, and Ucp1-Cre). Based on these systems, it is evident that our knowledge of mature adipocyte categorization into brown, white, brite, or beige adipocytes is strongly influenced by the use of the various genetic mouse models described in this chapter. Our evaluation of different studies using the aforementioned systems focuses on key genes, which have been reported to maintain adipocyte's function (insulin receptor, Raptor, or Atgl).

Ectopic Fatty Acid-Binding Protein 4 Expression in the Vascular Endothelium is Involved in Neointima Formation After Vascular Injury

Background

Fatty acid‐binding protein 4 (FABP4) is expressed in adipocytes, macrophages, and endothelial cells of capillaries but not arteries. FABP4 is secreted from adipocytes in association with lipolysis, and an elevated circulating FABP4 level is associated with obesity, insulin resistance, and atherosclerosis. However, little is known about the link between FABP4 and endovascular injury. We investigated the involvement of ectopic FABP4 expression in endothelial cells in neointima hyperplasia after vascular injury.

Methods and Results

Femoral arteries of 8‐week‐old male mice were subjected to wire‐induced vascular injury. After 4 weeks, immunofluorescence staining showed that FABP4 was ectopically expressed in endothelial cells of the hyperplastic neointima. Neointima formation determined by intima area and intima to media ratio was significantly decreased in FABP4‐defficient mice compared with that in wild‐type mice. Adenovirus‐mediated overexpression of FABP4 in human coronary artery endothelial cells (HCAECs) in vitro increased inflammatory cytokines and decreased phosphorylation of nitric oxide synthase 3. Furthermore, FABP4 was secreted from HCAECs. Treatment of human coronary smooth muscle cells or HCAECs with the conditioned medium of Fabp4‐overexpressed HCAECs or recombinant FABP4 significantly increased gene expression of inflammatory cytokines and proliferation‐ and adhesion‐related molecules in cells, promoted cell proliferation and migration of human coronary smooth muscle cells, and decreased phosphorylation of nitric oxide synthase 3 in HCAECs, which were attenuated in the presence of an anti‐FABP4 antibody.

Conclusions

Ectopic expression and secretion of FABP4 in vascular endothelial cells contribute to neointima formation after vascular injury. Suppression of ectopic FABP4 in the vascular endothelium would be a novel strategy against post‐angioplasty vascular restenosis.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

Electrospinning of Bioactive Wound-Healing Nets

The availability of appropriate dressings for treatment of wounds, in particular chronic wounds, is a task that still awaits better solutions than provided by currently applied materials. The method of electrospinning enables the fabrication of novel materials for wound dressings due to the high surface area and porosity of the electrospun meshes and the possibility to include bioactive ingredients. Recent results show that the incorporation of biologically active inorganic polyphosphate microparticles and microspheres and synergistically acting retinoids into electrospun polymer fibers yields biocompatible and antibacterial mats for potential dressings with improved wound-healing properties. The underlying principles and the mechanism of these new approaches in the therapy wounds, in particular wounds showing impaired healing, as well as for further applications in skin regeneration/repair, are summarized.

Gene Expression Profile of Persistent Postoperative Hypertension Patients with Aldosterone-producing Adenomas

Background:

Hypertension often persists after adrenalectomy for primary aldosteronism (PA). Many studies have analyzed the outcomes of adrenalectomy for aldosterone-producing adenomas (APA) to identify predictive factors for persistent hypertension. However, differentially expressed genes in persistent postoperative hypertension remain unknown. Our aim was to describe gene expression profile of persistent postoperative hypertension patients with APA.

Methods:

In this study, we described and compared gene expression profiles in persistent postoperative hypertension and postoperative normotension in Chinese patients with APA using microarray analysis. Confirmation was performed with quantitative real time-polymerase chain reaction analysis. Bioinformatic analysis (gene ontology analysis, pathway analysis and network analysis) was used for further research.

Results:

Microarray analysis identified a total of 99 differentially expressed genes, including 18 up-regulated and 81 down-regulated genes. Among the dysregulated genes were fat atypical cadherin 1 as well as fatty acid binding protein 4 and other genes that have not been previously studied in persistent postoperative hypertension with APA. Bioinformatics analysis indicated that differentially expressed genes were associated with lipid metabolic process, metal ion binding, and cell differentiation. Pathway analysis determined that five pathways corresponded to the dysregulated transcripts. The mRNAs-ncRNAs co-expression network was composed of 49 network nodes and 72 connections between 18 coding genes and 31 noncoding genes.

Conclusions:

This study revealed differentially expressed genes in persistent postoperative hypertension with APA and provided a resource of candidate genes for exploration of possible drug targets and prognostic markers.

Reduction of circulating FABP4 level by treatment with omega-3 fatty acid ethyl esters

Background

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) mainly expressed in adipocytes is secreted and acts as an adipokine. Increased circulating FABP4 level is associated with obesity, insulin resistance and atherosclerosis. However, little is known about the modulation of serum FABP4 level by drugs including anti-dyslipidemic agents.

Methods

Patients with dyslipidemia were treated with omega-3 fatty acid ethyl esters (4 g/day; n = 14) containing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) for 4 weeks. Serum FABP4 level was measured before and after treatment. Expression and secretion of FABP4 were also examined in mouse 3T3-L1 adipocytes treated with EPA or DHA.

Results

Treatment with omega-3 fatty acid ethyl esters significantly decreased triglycerides and serum FABP4 level (13.5 ± 1.5 vs. 11.5 ± 1.1 ng/ml, P = 0.017). Change in FABP4 level by omega-3 fatty acids was negatively correlated with change in levels of EPA + DHA (r = −0.643, P = 0.013), EPA (r = −0.540, P = 0.046) and DHA (r = −0.650, P = 0.011) but not change in the level of triglycerides or other fatty acid composition. Treatment of 3T3-L1 adipocytes with EPA or DHA had no effect on short-term (2 h) secretion of FABP4. However, gene expression and long-term (24 h) secretion of FABP4 were significantly reduced by treatment with EPA or DHA.

Conclusions

Omega-3 fatty acids decrease circulating FABP4 level, possibly by reducing expression and consecutive secretion of FABP4 in adipocytes. Reducing FABP4 level might be involved in suppression of cardiovascular events by omega-3 fatty acids.

Reduction of serum FABP4 level by sitagliptin, a DPP-4 inhibitor, in patients with type 2 diabetes mellitus

Fatty acid binding protein 4 (FABP4), also known as adipocyte FABP or aP2, is secreted from adipocytes in association with lipolysis as a novel adipokine, and elevated serum FABP4 level is associated with obesity, insulin resistance, and atherosclerosis. However, little is known about the modulation of serum FABP4 level by therapeutic drugs. Sitagliptin (50 mg/day), a dipeptidyl peptidase 4 (DPP-4) inhibitor that increases glucagon-like peptide 1 (GLP-1), was administered to patients with type 2 diabetes (n = 24) for 12 weeks. Treatment with sitagliptin decreased serum FABP4 concentration by 19.7% (17.8 ± 1.8 vs. 14.3 ± 1.5 ng/ml, P < 0.001) and hemoglobin A1c without significant changes in adiposity or lipid variables. In 3T3-L1 adipocytes, sitagliptin or exendin-4, a GLP-1 receptor agonist, had no effect on short-term (2 h) secretion of FABP4. However, gene expression and long-term (24 h) secretion of FABP4 were significantly reduced by sitagliptin, which was not mimicked by exendin-4. Treatment with recombinant DPP-4 increased gene expression and long-term secretion of FABP4, and the effects were cancelled by sitagliptin. Furthermore, knockdown of DPP-4 in 3T3-L1 adipocytes decreased gene expression and long-term secretion of FABP4. In conclusion, sitagliptin decreases serum FABP4 level, at least in part, via reduction in the expression and consecutive secretion of FABP4 in adipocytes by direct inhibition of DPP-4.

Electrospun bioactive mats enriched with Ca-polyphosphate/retinol nanospheres as potential wound dressing

Background

While electrospun materials have been frequently used in tissue engineering no wound dressings exist that significantly improved wound healing effectively.

Methods

We succeeded to fabricate three-dimensional (3D) electrospun poly(D,l-lactide) (PLA) fiber mats into which nanospheres, formed from amorphous calcium polyphosphate (polyP) nanoparticles (NP) and encapsulated retinol (“retinol/aCa-polyP-NS” nanospheres [NS]), had been incorporated.

Results

Experiments with MC3T3-E1 cells revealed that co-incubation of the cells with Ca-polyP together with retinol (or incubation with retinol/aCa-polyP-NS) resulted in a significant synergistic effect on cell growth compared with particle-free polyP complexed with Ca²⁺ or amorphous Ca-polyP NPs and retinol alone. Incubation of the cells in the presence of the retinol/aCa-polyP NSs also caused a significant increase of the expression levels of the genes encoding for the fatty acid binding protein 4 (FABP4), as well as of the genes encoding for leptin and the leptin receptor. In contrast, the single components, soluble Na-polyP, complexed to Ca²⁺, or retinol-free aCa-polyP NPs, and retinol, had no significant effect on the expression of these genes.

Conclusions

These results indicate that the PLA fibers, supplemented with aCa-polyP-NP or retinol/aCa-polyP-NS, elicit morphogenetic activity, suggesting that these fiber mats, along with the antibacterial effect of polyP, have a beneficial potential as wound dressings combining antimicrobial and regenerative (wound healing) properties.

General significance

The PLA-based fiber mats, containing retinol and polyP nanoparticles, provide promising bioactive meshes that are urgently needed as dressings for chronic wounds.

• Effect of PLA fiber mats with polyphosphate/retinol nanospheres on gene expression.

• Increased expression of FABP4, leptin and leptin receptor in MC3T3-E1 cells.

• Application as wound dressings, combining antimicrobial and regenerative properties.

Fatty Acid-Binding Protein 4 (FABP4): Pathophysiological Insights and Potent Clinical Biomarker of Metabolic and Cardiovascular Diseases

Over the past decade, evidences of an integration of metabolic and inflammatory pathways, referred to as metaflammation in several aspects of metabolic syndrome, have been accumulating. Fatty acid-binding protein 4 (FABP4), also known as adipocyte FABP (A-FABP) or aP2, is mainly expressed in adipocytes and macrophages and plays an important role in the development of insulin resistance and atherosclerosis in relation to metaflammation. Despite lack of a typical secretory signal peptide, FABP4 has been shown to be released from adipocytes in a non-classical pathway associated with lipolysis, possibly acting as an adipokine. Elevation of circulating FABP4 levels is associated with obesity, insulin resistance, diabetes mellitus, hypertension, cardiac dysfunction, atherosclerosis, and cardiovascular events. Furthermore, ectopic expression and function of FABP4 in several types of cells and tissues have been recently demonstrated. Here, we discuss both the significant role of FABP4 in pathophysiological insights and its usefulness as a biomarker of metabolic and cardiovascular diseases.

Ectopic expression of fatty acid-binding protein 4 in the glomerulus is associated with proteinuria and renal dysfunction

BACKGROUND/AIMS

Fatty acid-binding proteins (FABPs) are a family of intracellular lipid chaperones. Among FABPs, FABP1 (liver FABP) is expressed in proximal tubular epithelial cells in the kidney, and urinary FABP1 has been reported to reflect damage of proximal tubular epithelial cells. However, roles of other FABP isoforms in renal pathologies have not been reported. Recently, FABP4 (adipocyte FABP/aP2) was reported to be expressed in peritubular capillaries (PTCs), but not in glomerular capillaries in the normal kidney. We examined the hypothesis that pathological conditions alter the level and localization of FABP4 expression in the kidney, which mediates renal dysfunction.

METHODS

A total of 112 consecutive patients who underwent renal biopsy were retrospectively enrolled. Expression of FABP4 protein and mRNA in the kidney was examined by immunohistochemistry and in situ hybridization, respectively. The ratio of FABP4-positive area to total area within glomeruli (G-FABP4-Area), urinary protein level (U-Protein), and change in estimated glomerular filtration rate (eGFR) 1 year after biopsy were examined.

RESULTS

FABP4 protein and mRNA were expressed not only in PTCs, but also in endothelial cells and macrophages in the glomerulus. G-FABP4-Area was correlated with U-Protein (r = 0.497, p < 0.001). As a subanalysis, in patients with IgA nephropathy (n = 34), G-FABP4-Area was significantly larger in cases with an endocapillary proliferative lesion, and change in eGFR was negatively correlated with G-FABP4-Area at baseline (r = -0.537, p = 0.008).

CONCLUSION

Ectopic FABP4 expression in the glomerulus is induced by renal diseases and is closely associated with proteinuria and renal dysfunction.

Urinary excretion of fatty acid-binding protein 4 is associated with albuminuria and renal dysfunction

Background

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2) is expressed in not only adipocytes and macrophages but also peritubular capillaries in the normal kidney. We recently demonstrated that ectopic expression of FABP4, but not FABP1 known as liver FABP (L-FABP), in the glomerulus is associated with progression of proteinuria and renal dysfunction. However, urinary excretion of FABP4 has not been investigated.

Methods

Subjects who participated in the Tanno-Sobetsu Study, a study with a population-based cohort design, in 2011 (n = 392, male/female: 166/226) were enrolled. Urinary FABP4 (U-FABP4) and urinary albumin-to-creatinine ratio (UACR) were measured. Change in estimated glomerular filtration rate (eGFR) was followed up one year later.

Results

In 93 (23.7%) of the 392 subjects, U-FABP4 level was below the sensitivity of the assay. Subjects with undetectable U-FABP4 were younger and had lower UACR and higher eGFR levels than subjects with measurable U-FABP4. U-FABP4 level was positively correlated with age, systolic blood pressure and levels of serum FABP4 (S-FABP4), triglycerides, hemoglobin A1c (HbA1c), urinary FABP1 (U-FABP1) and UACR (r = 0.360, p<0.001). Age, S-FABP4, U-FABP1 and UACR were independent predictors of U-FABP4. On the other hand, systolic blood pressure, HbA1c and U-FABP4 were independently correlated with UACR. Reduction in eGFR after one year was significantly larger in a group with the highest tertile of baseline U-FABP4 than a group with the lowest tertile.

Conclusions

Urinary FABP4 level is independently correlated with level of albuminuria and possibly predicts yearly decline of eGFR. U-FABP4 would be a novel biomarker of glomerular damage.

Protective effects of histamine on Gq-mediated relaxation in regenerated endothelium

In the porcine coronary artery, regenerated endothelium is dysfunctional as regards the responses to endothelium-dependent agonists. The current study aimed to determine the possible involvement of histamine in such dysfunction. Pigs were treated chronically with pyrilamine (H1 receptor inhibitor, 2 mg·kg−1·day−1) with part of their coronary endothelium and allowed to regenerate for 28 days after balloon denudation. The results showed a reduction in relaxation to bradykinin (Gq protein dependent) only in the pyrilamine-treated group (area under the curve, 269.7 ± 13.4 vs. 142.0 ± 31.0, native endothelium vs. regenerated endothelium) but not in the control group (253.0 ± 22.1 vs. 231.9 ± 29.5, native endothelium vs. regenerated endothelium). The differences in the relaxation to serotonin (Gi protein dependent) between native and regenerated endothelium were not affected by the pyrilamine treatment (control group, 106.3 ± 17.0 vs. 55.61 ± 12.7; and pyrilamine group, 106.0 ± 8.20 vs. 49.30 ± 6.31, native endothelium vs. regenerated endothelium). These findings indicate that during regeneration of the endothelium, the activation of H1 receptors by endogenous histamine may be required to maintain the endothelium-dependent Gq protein-mediated relaxation to bradykinin, suggesting a beneficial role of the monoamine in the process of endothelial regeneration.

Airway epithelium-derived relaxing factor: myth, reality, or naivety?

The presence of a healthy epithelium can moderate the contraction of the underlying airway smooth muscle. This is, in part, because epithelial cells generate inhibitory messages, whether diffusible substances, electrophysiological signals, or both. The epithelium-dependent inhibitory effect can be tonic (basal), synergistic, or evoked. Rather than a unique epithelium-derived relaxing factor (EpDRF), several known endogenous bronchoactive mediators, including nitric oxide and prostaglandin E2, contribute. The early concept that EpDRF diffuses all the way through the subepithelial layers to directly relax the airway smooth muscle appears unlikely. It is more plausible that the epithelial cells release true messenger molecules, which alter the production of endogenous substances (nitric oxide and/or metabolites of arachidonic acid) by the subepithelial layers. These substances then diffuse to the airway smooth muscle cells, conveying epithelium dependency.

A-FABP and oxidative stress underlie the impairment of endothelium-dependent relaxations to serotonin and the intima-medial thickening in the porcine coronary artery with regenerated endothelium

Experiments were designed to determine the cause of the selective dysfunction of G(i) proteins, characterized by a reduced endothelium-dependent relaxation to serotonin (5-hydroxytryptamine), in coronary arteries lined with regenerated endothelial cells. Part of the endothelium of the left anterior descending coronary artery of female pigs was removed in vivo to induce regeneration. The animals were treated chronically with vehicle (control), apocynin (antioxidant), or BMS309403 (A-FABP inhibitor) for 28 days before functional examination and histological analysis of segments of coronary arteries with native or regenerated endothelium of the same hearts. Isometric tension was recorded in organ chambers and cumulative concentration-relaxation curves obtained in response to endothelium-dependent [serotonin (G(i) protein mediated activation of eNOS) and bradykinin (G(q) protein mediated activation of eNOS)] and independent [detaNONOate (cGMP-mediated), isoproterenol (cAMP-mediated)] vasodilators. The two inhibitors tested did not acutely affect relaxations of preparations with either native or regenerated endothelium. In the chronically treated groups, however, both apocynin and BMS309403 abolished the reduction in relaxation to serotonin in segments covered with regenerated endothelium and prevented the intima-medial thickening caused by endothelial regeneration, without affecting responses to bradykinin or endothelium-independent agonists (detaNONOate and isoproterenol). Thus, inhibition of either oxidative stress or A-FABP likely prevents both the selective dysfunction of G(i) protein mediated relaxation to serotonin and the neointimal thickening resulting from endothelial regeneration.

Methods to investigate the role of SIRT1 in endothelial senescence

Sirtuins are a family of proteins with NAD(+)-dependent deacetylase or mono-ADP-ribosyltransferase activity. SIRT1, the mammalian ortholog most closely related to Sir2 (the first gene of this family discovered in yeast), exhibits anti-senescence activity in a wide range of mammalian cells. Here, we describe the use of an ex vivo senescence model to study SIRT1 function in primary endothelial cells isolated from the porcine aorta. The methods can be applied to the investigation of the role of SIRT1 in the development of endothelial senescence and atherosclerosis.

Deficiency in pulmonary surfactant proteins in mice with fatty acid binding protein 4-Cre-mediated knockout of the tuberous sclerosis complex 1 gene

New findings

Tuberous sclerosis complex 1 (TSC1) forms a heterodimmer with tuberous sclerosis complex 2, to inhibit signalling by the mammalian target of rapamycin (mTOR) complex 1 (mTORC1). The mTORC1 stimulates cell growth by promoting anabolic cellular processes, such as gene transcription and protein translation, in response to growth factors and nutrient signals. Originally designed to test the role of TSC1 in adipocyte function, mice in which the gene for TSC1 was specifically deleted by the fatty acid binding protein 4 (FABP4)-Cre (Fabp4-Tsc1cKO mice) died prematurely within 48 h after birth. The Fabp4-Tsc1cKO mouse revealed a much smaller phenotype relative to the wild-type littermates. Maternal administration of rapamycin, a classical mTOR inhibitor, significantly increased the survival time of Fabp4-Tsc1cKO mice for up to 23 days. Both macroscopic and microscopic haemorrhages were observed in the lungs of Fabp4-Tsc1cKO mice, while other tissues showed no significant changes. Levels of surfactant proteins A and B demonstrated a significant decrease in the Fabp4-Tsc1cKO mice, which was rescued by maternal injection of rapamycin. Co-localization of FABP4 or TSC1 with surfactant protein B was also detected in neonatal pulmonary tissues. Our study suggests that TSC1–mTORC1 may be critical for the synthesis of surfactant proteins A and B.

Elevation of fatty acid-binding protein 4 is predisposed by family history of hypertension and contributes to blood pressure elevation

Background

Fatty acid-binding protein 4 (FABP4/A-FABP/aP2), a lipid chaperone, is expressed in both adipocytes and macrophages. Recent studies have shown secretion of FABP4 from adipocytes and association of elevated serum FABP4 level with obesity, insulin resistance, and atherosclerosis. However, little is known about the role of FABP4 in essential hypertension.

Methods

We first examined serum FABP4 concentrations in 18 normotensives (NT) and 30 nontreated essential hypertensives (EHT). The EHT were divided into 18 insulin-sensitive EHT (EHT-S) and 12 insulin-resistant EHT (EHT-R) based on their insulin-sensitivity index, the M value, determined by the hyperinsulinemic–euglycemic clamp technique. In the second study, we determined FABP4 levels in 30 young NT men with or without a family history of hypertension (FH⁺ and FH^–, respectively; n = 15 each).

Results

Serum FABP4 level was significantly higher in the EHT-R than in the NT, whereas elevation of FABP4 level in the EHT-S was not statistically significant. FABP4 level was positively correlated with age, body mass index (BMI), blood pressure, and triglycerides and negatively correlated with the M value. FABP4 level was an independent predictor of mean arterial pressure after adjustment of age, gender, and adiposity. The FH⁺ group had a significantly lower level of M value and higher level of FABP4 than did the FH^– group, and FABP4 concentration was an independent determinant of the M value.

Conclusions

FABP4 contributes to blood pressure elevation and atherogenic metabolic phenotype in hypertensives, and the elevation of FABP4 is predisposed by a family history of hypertension.

Cyclin-dependent kinase 5-mediated hyperphosphorylation of sirtuin-1 contributes to the development of endothelial senescence and atherosclerosis

BACKGROUND

Endothelial senescence represents one of the major characteristics of vascular aging and promotes the development of atherosclerosis. Sirtuin-1 (SIRT1) is an NAD-dependent deacetylase possessing antiaging activities. During the occurrence of endothelial senescence, both the expression and activity of SIRT1 are downregulated. The present study was designed to investigate the molecular mechanisms contributing to the loss-of-SIRT1 function in senescent endothelial cells.

METHODS AND RESULTS

After repetitive passages, primary cultures of porcine aortic endothelial cells exhibited a severe senescence phenotype. Western blotting revealed that phosphorylation of SIRT1 at serine 47 (S47) was significantly enhanced in senescent endothelial cells. S47 phosphorylation was stimulated by agents promoting senescence and attenuated by drugs with antisenescence properties. Mutation of S47 to nonphosphorable alanine (S47A) enhanced whereas replacing S47 with phospho-mimicking aspartic acid (S47D) abolished the antisenescent, growth-promoting, and LKB1-downregulating actions of SIRT1. Phosphorylation at S47 was critically involved in the nuclear retention of SIRT1 but abolished its association with the telomeric repeat-binding factor 2-interacting protein 1. Cyclin-dependent kinase 5 (CDK5) was identified as an SIRT1 kinase modulating S47 phosphorylation. Knockdown or inhibition of CDK5 reduced the number of senescent endothelial cells, promoted nuclear exportation of SIRT1, and attenuated the expression of inflammatory genes in porcine aortic endothelial cells. The truncated regulatory subunit of CDK5, P25, accumulated in senescent porcine aortic endothelial cells and atherosclerotic aortas. Long-term treatment with roscovitine, a CDK5 inhibitor, blocked the development of cellular senescence and atherosclerosis in aortas of hypercholesterolemic apolipoprotein E-deficient mice.

CONCLUSION

CDK5-mediated hyperphosphorylation of SIRT1 facilitates the development of endothelial senescence and atherosclerosis.

The endothelium: influencing vascular smooth muscle in many ways

The endothelium, although only a single layer of cells lining the vascular and lymphatic systems, contributes in multiple ways to vascular homeostasis. Subsequent to the 1980 report by Robert Furchgott and John Zawadzki, there has been a phenomenal increase in our knowledge concerning the signalling molecules and pathways that regulate endothelial - vascular smooth muscle communication. It is now recognised that the endothelium is not only an important source of nitric oxide (NO), but also numerous other signalling molecules, including the putative endothelium-derived hyperpolarizing factor (EDHF), prostacyclin (PGI(2)), and hydrogen peroxide (H(2)O(2)), which have both vasodilator and vasoconstrictor properties. In addition, the endothelium, either via transferred chemical mediators, such as NO and PGI(2), and (or) low-resistance electrical coupling through myoendothelial gap junctions, modulates flow-mediated vasodilatation as well as influencing mitogenic activity, platelet aggregation, and neutrophil adhesion. Disruption of endothelial function is an early indicator of the development of vascular disease, and thus an important area for further research and identification of potentially new therapeutic targets. This review focuses on the signalling pathways that regulate endothelial - vascular smooth muscle communication and the mechanisms that initiate endothelial dysfunction, particularly with respect to diabetic vascular disease.

Differential genomic changes caused by cholesterol- and PUFA-rich diets in regenerated porcine coronary endothelial cells

Endothelial regeneration and dyslipidemia impair endothelium-dependent relaxation, while supplementation with fish oil (FO) prevents it. The genomic impact of different diets was compared in primary cultures derived from native and regenerated endothelial cells. Pigs were fed with high-cholesterol (CHL) or FO-rich diet. Partial in vivo removal of endothelium was performed to induce endothelial regeneration. Native and regenerated cells were harvested, cultured, and prepared for genomic (microarray experiments, real-time PCR) and proteomic (Western blotting) analysis. The analysis identified genomic changes induced by chronic CHL diet in native cultures resembling those induced by in vivo regeneration, as well as those that could be prevented by FO diet. At the protein level, the reduced and increased presences of endothelial nitric oxide synthase and F2, respectively, observed after regeneration combined with CHL diet were alleviated by FO. The comparison of the differential changes induced by regeneration in vivo in endothelial cells from both diet groups revealed a limited number of genes as the most likely contributors to reduction in endothelium-dependent relaxations in porcine coronary arteries lined with regenerated endothelium.

Small lipid-binding proteins in regulating endothelial and vascular functions: focusing on adipocyte fatty acid binding protein and lipocalin-2

Dysregulated production of adipokines from adipose tissue plays a critical role in the development of obesity-associated cardiovascular abnormalities. A group of adipokines, including adipocyte fatty acid binding protein (A-FABP) and lipocalin-2, possess specific lipid-binding activity and are up-regulated in obese human subjects and animal models. They act as lipid chaperones to promote lipotoxicity in endothelial cells and cause endothelial dysfunction under obese conditions. However, different small lipid-binding proteins modulate the development of vascular complications in distinctive manners, which are partly attributed to their specialized structural features and functionalities. By focusing on A-FABP and lipocalin-2, this review summarizes recent advances demonstrating the causative roles of these newly identified adipose tissue-derived lipid chaperones in obesity-related endothelial dysfunction and cardiovascular complications. The specific lipid-signalling mechanisms mediated by these two proteins are highlighted to support their specialized functions. In summary, A-FABP and lipocalin-2 represent potential therapeutic targets to design drugs for preventing vascular diseases associated with obesity.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Lipid chaperones and metabolic inflammation

Over the past decade, a large body of evidence has emerged demonstrating an integration of metabolic and immune response pathways. It is now clear that obesity and associated disorders such as insulin resistance and type 2 diabetes are associated with a metabolically driven, low-grade, chronic inflammatory state, referred to as “metaflammation.” Several inflammatory cytokines as well as lipids and metabolic stress pathways can activate metaflammation, which targets metabolically critical organs and tissues including adipocytes and macrophages to adversely affect systemic homeostasis. On the other hand, inside the cell, fatty acid-binding proteins (FABPs), a family of lipid chaperones, as well as endoplasmic reticulum (ER) stress, and reactive oxygen species derived from mitochondria play significant roles in promotion of metabolically triggered inflammation. Here, we discuss the molecular and cellular basis of the roles of FABPs, especially FABP4 and FABP5, in metaflammation and related diseases including obesity, diabetes, and atherosclerosis.

Chronic administration of BMS309403 improves endothelial function in apolipoprotein E-deficient mice and in cultured human endothelial cells

BACKGROUND AND PURPOSE

Adipocyte fatty acid-binding protein (A-FABP) is up-regulated in regenerated endothelial cells and modulates inflammatory responses in macrophages. Endothelial dysfunction accompanying regeneration is accelerated by hyperlipidaemia. Here, we investigate the contribution of A-FABP to the pathogenesis of endothelial dysfunction in the aorta of apolipoprotein E-deficient (ApoE(-/-) ) mice and in cultured human endothelial cells.

EXPERIMENTAL APPROACH

A-FABP was measured in aortae of ApoE(-/-) mice and human endothelial cells by RT-PCR, immunostaining and immunoblotting. Total and phosphorylated forms of endothelial nitric oxide synthase (eNOS) were measured by immunoblotting. Changes in isometric tension were measured in rings of mice aortae

KEY RESULTS

A-FABP was expressed in aortic endothelium of ApoE(-/-) mice aged 12 weeks and older, but not at 8 weeks or in C57 wild-type mice. Reduced endothelium-dependent relaxations to acetylcholine, UK14304 (selective α(2) -adrenoceptor agonist) and A23187 (calcium ionophore) and decreased protein presence of phosphorylated and total eNOS were observed in aortae of 18 week-old ApoE(-/-) mice compared with age-matched controls. A 6 week treatment with the A-FABP inhibitor, BMS309403, started in 12 week-old mice, improved endothelial function, phosphorylated and total eNOS and reduced plasma triglyceride levels but did not affect endothelium-independent relaxations. The beneficial effect of BMS309403 on UK14304-induced relaxations was attenuated by Pertussis toxin. In cultured human microvascular endothelial cells, lipid-induced A-FABP expression was associated with reduced phosphorylated eNOS and NO production and was reversed by BMS309403.

CONCLUSIONS AND IMPLICATIONS

Elevated expression of A-FABP in endothelial cells contributes to their dysfunction both in vivo and in vitro.

miR-146a is modulated in human endothelial cell with aging

BACKGROUND

Increasing evidence has demonstrated that the senescence of vascular endothelial cells has critical roles in the pathogenesis of vascular dysfunction such as atherosclerosis and thrombosis. MicroRNA (miR) are small non-coding RNAs that inhibit gene expression by binding to complementary sequences in the 3'UTR of their target mRNAs. MiRs modulate a variety of biological functions such as cell development, cell differentiation, and apoptosis. Moreover, several miRs involved in endothelial cell function have been identified.

METHODS AND RESULTS

Through a microarray approach, we have identified a miR-146a that is progressively modulated in endothelial cells with aging. In young human umbilical vein endothelial cells, this miR is involved in a premature senescence-like phenotype through direct targeting of the NOX4 protein, implicated in cell senescence and aging.

CONCLUSIONS AND GENERAL SIGNIFICANCE

Finding important factors that regulate endothelial cell senescence, like miR-146a, will help provide novel therapeutic strategies for vascular disorders.

Secretoneurin facilitates endothelium-dependent relaxations in porcine coronary arteries

Secretoneurin enhances the adhesion and transendothelial migration properties of monocytes and is a part of the peptide family encoded by the secretogranin II gene. The expression of the secretogranin II gene is upregulated in senescent endothelium. The present study was designed to examine the effects of secretoneurin on endothelium-dependent responsiveness. Isometric tension was measured in rings (with or without endothelium) of porcine coronary arteries. Secretoneurin did not induce contraction of quiescent or contracted rings. In preparations contracted by U-46619, relaxation was observed with high concentrations of the peptide. This relaxation was endothelium dependent and reduced by the nitric oxide synthase inhibitor N(ω)-nitro-l-arginine methyl ester (l-NAME). It was abolished when the preparations were incubated with l-NAME in combination with the cyclooxygenase inhibitor indomethacin. The relaxation was not affected by the combination of 1-[(2-chlorophenyl)diphenylmethyl]-1H-pyrazole (TRAM-34) and 6,12,19,20,25,26-hexahydro-5,27:13,18:21,24-trietheno-11,7-etheno-7H-dibenzo[b,m][1,5,12,16]tetraazacyclotricosine-5,13-diiumditrifluoroacetate hydrate (UCL 1684), which abrogates endothelium-dependent hyperpolarizations. These results indicate that secretoneurin acutely induces relaxation through the activation of endothelial nitric oxide synthase (eNOS) and cyclooxygenase, with nitric oxide playing the dominant role. Prolonged (24 h) incubation with physiological concentrations of secretoneurin enhanced the relaxations to bradykinin and to the calcium ionophore A-23187, but this difference was not observed in preparations incubated with l-NAME or the calmodulin antagonist calmidazolium. Under these conditions, the relaxation to sodium nitroprusside remained unchanged. Incubation with secretoneurin significantly augmented the expression of eNOS and calmodulin as well as the dimerization of eNOS in cultures of porcine coronary arterial endothelial cells. These observations suggest that secretoneurin not only acutely causes but also, upon prolonged exposure, enhances endothelium-dependent relaxations.

SIRT1 Promotes Proliferation and Prevents Senescence Through Targeting LKB1 in Primary Porcine Aortic Endothelial Cells

Rationale : Endothelial senescence causes endothelial dysfunction, promotes atherogenesis and contributes to age-related vascular disorders. SIRT1 is a conserved NAD + -dependent deacetylase possessing beneficial effects against aging-related diseases, despite that the detailed functional mechanisms are largely uncharacterized.

Objective : The present study is designed to evaluate the protective effects of SIRT1 on endothelial senescence and to elucidate the underlying mechanisms.

Methods and Results : An in vitro senescence model was established by prolonged culture of primary endothelial cells isolated from porcine aorta. The freshly isolated “young” cells gradually underwent senescence during 1 month of repetitive passages. Both mRNA and protein expressions of SIRT1 were progressively decreased. In contrast, the protein levels of LKB1, a serine/threonine kinase and tumor suppressor, and the phosphorylation of its downstream target AMPK(Thr172) were dramatically increased in senescent cells. Overexpression of LKB1 promoted cellular senescence and retarded endothelial proliferation, which could be blocked by increasing SIRT1 levels. Knocking down of SIRT1 induced senescence and elevated the protein levels of LKB1 and phosphorylated AMPK(Thr172). Regardless of the nutritional status, hyperactivation of AMPK was able to induce endothelial senescence. SIRT1 antagonized LKB1-dependent AMPK activation through promoting the deacetylation, ubiquitination and proteasome-mediated degradation of LKB1. The survival signaling of Akt was also found to be modulated by SIRT1 and LKB1, and could cross-regulate AMPK activity.

Conclusions : SIRT1 and LKB1/AMPK are the 2 key sensor systems for regulating endothelial cell survival, proliferation and senescence. The protective activities of SIRT1 may be achieved at least in part by fine tuning the acetylation/deacetylation status and stabilities of LKB1 protein.

Cellular signaling and NO production

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor is nitric oxide (NO), which is synthesized by the endothelial isoform of nitric oxide synthase (eNOS). Endothelium-dependent relaxations involve both pertussis-toxin-sensitive G(i) (e.g., responses to serotonin, sphingosine 1-phosphate, alpha(2)-adrenergic agonists, and thrombin) and pertussis-toxin-insensitive G(q) (e.g., adenosine diphosphate and bradykinin) coupling proteins. eNOS undergoes a complex pattern of intracellular regulation, including post-translational modifications involving enzyme acylation and phosphorylation. eNOS is reversibly targeted to signal-transducing plasmalemmal caveolae where the enzyme interacts with a number of regulatory proteins, many of which are modified in cardiovascular disease states. The release of nitric oxide by the endothelial cell can be up- (e.g., by estrogens, exercise, and dietary factors) and down-regulated (e.g. oxidative stress, smoking, and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g., diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis-toxin-sensitive pathway for NO release which favors vasospasm, thrombosis, penetration of macrophages, cellular growth, and the inflammatory reaction leading to atherosclerosis. The unraveling of the complex interaction of the pathways regulating the presence and the activity of eNOS will enhance the understanding of the perturbations in endothelium-dependent signaling that are seen in cardiovascular disease states, and may lead to the identification of novel targets for therapeutic intervention.

Prostaglandins in action indispensable roles of cyclooxygenase-1 and -2 in endothelium-dependent contractions

Endothelium regulates local vascular tone by means of releasing relaxing and contracting factors, of which the latter have been found to be elevated in vascular pathogenesis of hypertension, diabetes, hypercholesterolemia, and aging. Endothelium-derived contracting factors (EDCFs) are mainly metabolites of arachidonic acid generated by cyclooxygenase (COX), as vasodilatations in patients with hypertension, metabolic diseases, or advancing age are improved by acute treatment with COX inhibitor indomethacin. COX is presented in two isoforms, COX-1 and COX-2, with the former regarded as constitutive and the latter mainly expressed upon induction. Experiments with animal models of vascular dysfunctions, however, reveal that both isoforms have similar capacity to participate in endothelium-dependent contractions, with augmented expression and activity. COX-derived prostaglandin (PG) H(2), PGF(2α), PGE(2), prostacyclin (PGI(2)), and thromboxane A(2) (TxA(2)) are the proposed EDCFs that mediate endothelium-dependent contractions via the activation of thromboxane-prostanoid (TP) receptor in various vascular beds from different species. Although COX inhibition seems to be a possible strategy in combating COX-associated vascular complications, the incidence of adverse cardiovascular effects of Vioxx has greatly antagonized this concept. Further review of COX inhibitors is required, especially toward the selectivity of coxibs and whether it directly inhibits prostacyclin synthase activity. Meanwhile, TP receptor antagonism may emerge as a therapeutic alternative to reverse prostanoid-mediated vascular dysregulations.

Fatty acid binding protein 4 is a target of VEGF and a regulator of cell proliferation in endothelial cells

Fatty acid binding protein 4 (FABP4) plays an important role in maintaining glucose and lipid homeostasis. FABP4 has been primarily regarded as an adipocyte- and macrophage-specific protein, but recent studies suggest that it may be more widely expressed. We found strong FABP4 expression in the endothelial cells (ECs) of capillaries and small veins in several mouse and human tissues, including the heart and kidney. FABP4 was also detected in the ECs of mature human placental vessels and infantile hemangiomas, the most common tumor of infancy and ECs. In most of these cases, FABP4 was detected in both the nucleus and cytoplasm. FABP4 mRNA and protein levels were significantly induced in cultured ECs by VEGF-A and bFGF treatment. The effect of VEGF-A on FABP4 expression was inhibited by chemical inhibition or short-hairpin (sh) RNA-mediated knockdown of VEGF-receptor-2 (R2), whereas the VEGFR1 agonists, placental growth factors 1 and 2, had no effect on FABP4 expression. Knockdown of FABP4 in ECs significantly reduced proliferation both under baseline conditions and in response to VEGF and bFGF. Thus, FABP4 emerged as a novel target of the VEGF/VEGFR2 pathway and a positive regulator of cell proliferation in ECs.

Recent advances in arginine metabolism: roles and regulation of the arginases

As arginine can serve as precursor to a wide range of compounds, including nitric oxide, creatine, urea, polyamines, proline, glutamate and agmatine, there is considerable interest in elucidating mechanisms underlying regulation of its metabolism. It is now becoming apparent that the two isoforms of arginase in mammals play key roles in regulation of most aspects of arginine metabolism in health and disease. In particular, work over the past several years has focused on the roles and regulation of the arginases in vascular disease, pulmonary disease, infectious disease, immune cell function and cancer. As most of these topics have been considered in recent review articles, this review will focus more closely on results of recent studies on expression of the arginases in endothelial and vascular smooth muscle cells, post-translational modulation of arginase activity and applications of arginase inhibitors in vivo.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.