Pivotal Role of Protein Kinase C δ in Angiotensin II–Induced Endothelial Cyclooxygenase-2 Expression: A Link to Vascular Inflammation

Evolving concepts in the pathophysiology of atherosclerosis: from endothelial dysfunction to thrombus formation through multiple shades of inflammation

Atherosclerosis is the anatomo-pathological substrate of most cardio, cerebro and vascular diseases such as acute and chronic coronary syndromes, stroke and peripheral artery diseases. The pathophysiology of atherosclerotic plaque and its complications are under continuous investigation. In the last 2 decades our understanding on the formation, progression and complication of the atherosclerotic lesion has greatly improved and the role of immunity and inflammation is now well documented and accepted. The conventional risk factors modulate endothelial function determining the switch to a proatherosclerotic phenotype. From this point, lipid accumulation with an imbalance from cholesterol influx and efflux, foam cells formation, T-cell activation, cytokines release and matrix-degrading enzymes production occur. Lesions with high inflammatory rate become vulnerable and prone to rupture. Once complicated, the intraplaque thrombogenic material, such as the tissue factor, is exposed to the flowing blood, thus inducing coagulation cascade activation, platelets aggregation and finally intravascular thrombus formation that leads to clinical manifestations of this disease. Nonconventional risk factors, such as gut microbiome, are emerging novel markers of atherosclerosis. Several data indicate that gut microbiota may play a causative role in formation, progression and complication of atherosclerotic lesions. The gut dysbiosis-related inflammation and gut microbiota-derived metabolites have been proposed as the main working hypothesis in contributing to disease formation and progression. The current evidence suggest that the conventional and nonconventional risk factors may modulate the degree of inflammation of the atherosclerotic lesion, thus influencing its final fate. Based on this hypothesis, targeting inflammation seems to be a promising approach to further improve our management of atherosclerotic-related diseases.

Cyclooxygenase-2 is a critical determinant of angiotensin II-induced vascular remodeling and stiffness in resistance arteries of ouabain-treated rats

OBJECTIVE

To investigate the role of angiotensin II/AT 1 receptor signaling and/or cyclooxygenase-2 (COX-2) activation on vascular remodeling and stiffening of the mesenteric resistance arteries (MRA) of ouabain-treated rats.

METHODS

Ouabain-treated (OUA, 30 μg kg/day for 5 weeks) and vehicle (VEH)-treated Wistar rats were co-treated with losartan (LOS, AT 1 R antagonist), nimesulide (NIM, COX-2 inhibitor) or hydralazine hydrochloride plus hydrochlorothiazide. MRA structure and mechanics were assessed with pressure myography and histology. Picrosirius red staining was used to determine the total collagen content. Western blotting was used to detect the expression of collagen I/III, MMP-2, Src, NFκB, Bax, Bcl-2 and COX-2. Reactive oxygen species (ROS) and plasma angiotensin II levels were measured by fluorescence and ELISA, respectively.

RESULTS

Blockade of AT 1 R or inhibition of COX-2 prevented ouabain-induced blood pressure elevation. Plasma angiotensin II level was higher in OUA than in VEH. LOS, but not hydralazine hydrochloride with hydrochlorothiazide, prevented inward hypotrophic remodeling, increased collagen deposition and stiffness, and oxidative stress in OUA MRA. LOS prevented the reduction in the total number of nuclei in the media layer and the Bcl-2 expression induced by OUA in MRA. The higher pSrc/Src ratio, NFκB/IκB ratio, and COX-2 expression in OUA MRA were also prevented by LOS. Likewise, COX-2 inhibition prevented vascular remodeling, mechanical changes, oxidative stress and inflammation in OUA MRA.

CONCLUSION

The results suggest that, regardless of hemodynamic adjustments, the angiotensin II/AT 1 R/pSrc/ROS/NFκB/COX-2 pathway is involved in the development of MRA inward hypotrophic remodeling and stiffness in ouabain-treated rats.

Tripeptide IRW Protects MC3T3-E1 Cells against Ang II Stress in an AT2R Dependent Manner

Multiple strategies including the use of bioactive peptides and other nutraceuticals are being adopted to maintain bone health. This study provides an improved and deeper understanding of the pharmacological effects that a bioactive peptide IRW (Ile-Arg-Trp) extends on bone health. Our results showed that IRW treatment protects osteoblasts against Ang II induced decline in cell proliferation and restores protein levels of collagen type I alpha 2 chain (COL1A2) and alkaline phosphatase (ALP) levels in MC3T3-E1 cells (p < 0.05). Apart from augmentation of these mineralization factors, the angiotensin II (Ang II) induced apoptotic stress in osteoblasts was mitigated by IRW as well. At the molecular level, IRW abolished the cytochrome-c release via modulation of pro-and anti-apoptotic genes in MC3T3-E1 cells (p < 0.05). Interestingly, IRW also increased cellular levels of cytoprotective local RAAS factors such as MasR, Ang (1−7), ACE2, and AT2R, and lowered the levels of Ang II effector receptor (AT1R). Further, our results indicated a lower content of inflammation and osteoclastogenesis biomarkers such as cyclooxygenase 2 (COX2), nuclear factor kappa B (NF-κB), and receptor activator of nuclear factor kappa-B ligand (RANKL) following IRW treatment in MC3T3-E1 cells (p < 0.05). The use of an antagonist-guided cell study indicated that IRW contributed to the process of cytoprotection and proliferation of osteoblasts via Runt-related transcription factor 2 (RUNX2) in face of Ang II stress in an AT2R dependent manner. The key findings of our study showed that IRW could potentially have a therapeutic role in the treatment and/or prevention of bone disorders.

Targeting endothelial dysfunction and inflammation

Vascular endothelium maintains vascular homeostasis through liberating a spectrum of vasoactive molecules, both protective and harmful regulators of vascular tone, structural remodeling, inflammation and atherogenesis. An intricate balance between endothelium-derived relaxing factors (nitric oxide, prostacyclin and endothelium-derived hyperpolarizing factor) and endothelium-derived contracting factors (superoxide anion, endothelin-1 and constrictive prostaglandins) tightly regulates vascular function. Disruption of such balance signifies endothelial dysfunction, a critical contributor in aging and chronic cardiometabolic disorders, such as obesity, diabetes, hypertension, dyslipidemia and atherosclerotic vascular diseases. Among many proposed cellular and molecular mechanisms causing endothelial dysfunction, oxidative stress and inflammation are often the pivotal players and they are naturally considered as useful targets for intervention in patients with cardiovascular and metabolic diseases. In this article, we provide a recent update on the therapeutic values of pharmacological agents, such as cyclooxygenase-2 inhibitors, renin-angiotensin-system inhibitors, bone morphogenic protein 4 inhibitors, peroxisome proliferator-activated receptor δ agonists, and glucagon-like peptide 1-elevating drugs, and the physiological factors, particularly hemodynamic forces, that improve endothelial function by targeting endothelial oxidative stress and inflammation.

Effects of Arachidonic Acid Metabolites on Cardiovascular Health and Disease

Arachidonic acid (AA) is an essential fatty acid that is released by phospholipids in cell membranes and metabolized by cyclooxygenase (COX), cytochrome P450 (CYP) enzymes, and lipid oxygenase (LOX) pathways to regulate complex cardiovascular function under physiological and pathological conditions. Various AA metabolites include prostaglandins, prostacyclin, thromboxanes, hydroxyeicosatetraenoic acids, leukotrienes, lipoxins, and epoxyeicosatrienoic acids. The AA metabolites play important and differential roles in the modulation of vascular tone, and cardiovascular complications including atherosclerosis, hypertension, and myocardial infarction upon actions to different receptors and vascular beds. This article reviews the roles of AA metabolism in cardiovascular health and disease as well as their potential therapeutic implication.

A GLP-1 analog lowers ER stress and enhances protein folding to ameliorate homocysteine-induced endothelial dysfunction

Hyperhomocysteinemia (HHcy) is an independent risk factor for cardiovascular diseases and increases mortality in type 2 diabetic patients. HHcy induces endoplasmic reticulum (ER) stress and oxidative stress to impair endothelial function. The glucagon-like peptide 1 (GLP-1) analog exendin-4 attenuates endothelial ER stress, but the detailed vasoprotective mechanism remains elusive. The present study investigated the beneficial effects of exendin-4 against HHcy-induced endothelial dysfunction. Exendin-4 pretreatment reversed homocysteine-induced impairment of endothelium-dependent relaxations in C57BL/6 mouse aortae ex vivo. Four weeks subcutaneous injection of exendin-4 restored the impaired endothelial function in both aortae and mesenteric arteries isolated from mice with diet-induced HHcy. Exendin-4 treatment lowered superoxide anion accumulation in the mouse aortae both ex vivo and in vivo. Exendin-4 decreased the expression of ER stress markers (e.g., ATF4, spliced XBP1, and phosphorylated eIF2α) in human umbilical vein endothelial cells (HUVECs), and this change was reversed by cotreatment with compound C (CC) (AMPK inhibitor). Exendin-4 induced phosphorylation of AMPK and endothelial nitric oxide synthase in HUVECs and arteries. Exendin-4 increased the expression of endoplasmic reticulum oxidoreductase (ERO1α), an important ER chaperone in endothelial cells, and this effect was mediated by AMPK activation. Experiments using siRNA-mediated knockdown or adenoviral overexpression revealed that ERO1α mediated the inhibitory effects of exendin-4 on ER stress and superoxide anion production, thus ameliorating HHcy-induced endothelial dysfunction. The present results demonstrate that exendin-4 reduces HHcy-induced ER stress and improves endothelial function through AMPK-dependent ERO1α upregulation in endothelial cells and arteries. AMPK activation promotes the protein folding machinery in endothelial cells to suppress ER stress.

Calcitriol inhibits COX-1 and COX-2 expressions of renal vasculature in hypertension: Reactive oxygen species involved?

Vitamin D modulates about 3% human gene transcription besides the classical action on calcium/phosphorus homeostasis. The blood pressure-lowing and other protective action on cardiovascular disease have been reported. The present study aims to examine whether COX-1 and COX-2 were implicated in endothelial dysfunction in hypertension and calcitriol, an active form of vitamin D preserved endothelial function through regulating COX expression. Isometric study demonstrated the impaired endothelium-dependent relaxation (EDR) in renal arteries from spontaneously hypertensive rats were reversed by 12 h-calcitriol treatment and COX-1 and COX-2 inhibitors. Combined uses of COX-1 and COX-2 inhibitor induced more improved relaxations. Exaggerated expressions of COX-1 and COX-2 in renal artery from SHR were inhibited by 12 h-administration of calcitriol, NADPH oxidase inhibitor DPI, or reactive oxygen species (ROS) scavenger tempol. Furthermore, in normotensive WKY rats, calcitriol prevents against the blunted EDR in renal arteries by 12 h-Ang II exposure, with similar improvements by COX-1 and COX-2 inhibitors. Accordingly, increased COX-1 and COX-2 expressions by Ang II exposure were corrected by losartan, DPI, or tempol. Studies on human renal artery also revealed the beneficial action of calcitriol is mediated by suppressing COX-1 and COX-2 expressions, dependent on vitamin D receptor (VDR) activation. Taken together, our findings showed that COX-1 and COX-2 are positively involved in the renovascular dysfunction in hypertension and via VDR, calcitriol benefits renovasular function by suppressing COX-1 and COX-2 expressions. Furthermore, ROS is involved in the COX-1 and COX-2 up-regulations of renal arteries, maybe serving as a mediator in the inhibitory action of calcitriol on COX expression.

AT2 receptor interacting protein 1 (ATIP1) mediates COX-2 induction by an AT2 receptor agonist in endothelial cells

Angiotensin II (Ang II) type 2 receptor (AT2R) is one of the major components of the renin-angiotensin-aldosterone system. Nevertheless, the physiological role is not well defined compared to the understanding of the Ang II type 1 receptor (AT1R), which is a well characterized G-protein coupled receptor in the cardiovascular system. While the AT2R signaling pathway remains unclear, AT2 receptor interacting protein 1 (ATIP1) has been identified as a candidate molecule for interacting with the C-terminal region of AT2R. In this study, we investigated the ATIP1 dependent AT2R inducible genes in human umbilical vein endothelial cells (HUVECs). CGP42112A, an AT2R specific agonist, resulted in an upregulation of inflammatory genes in HUVECs, which were inhibited by knocking down ATIP1 with siRNA (siATIP1). Among them, we confirmed by quantitative PCR that the induction of COX-2 mRNA expression was significantly downregulated by siATIP1. COX-2 was also upregulated by Ang II stimulation. This upregulation was suppressed by treatment with the AT2R specific antagonist PD123319, which was not replicated by the AT1R antagonist telmisartan.

These findings suggest that ATIP1 plays an important role in AT2R dependent inflammatory responses. This may provide a new approach to the development of cardio-protective drugs.

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Only the AT2 receptor interacting protein 1 (ATIP1) of ATIP isoforms expresses in endothelial cells.

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A novel anti-ATIP monoclonal antibody detected endogenous ATIP1 and revealed ATIP1 localization in endothelial cells.

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AT2 receptor (AT2R) agonist stimulation induced inflammatory gene expression via ATIP1 in endothelial cells.

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An AT2R specific inhibitor blocks the Ang II induction of COX-2 mRNA in endothelial cells.

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There is the AT2R-ATIP1 related pathway of COX-2 induction in endothelial cells.

Isoliquiritigenin protects against angiotensin II-induced fibrogenesis by inhibiting NF-κB/PPARγ inflammatory pathway in human Tenon's capsule fibroblasts

PURPOSE

To examine the protective effects of Isoliquiritigenin (ISL) in angiotensin II (ANG II)-induced inflammation and fibrosis on Human Tenon's capsule Fibroblasts (HTFs) and Mouse Peritoneal Macrophages (MPMs). This study also investigated the potential mechanism of action of ISL.

METHOD

Methyl-thiazolyl tetrazolium (MTT) assay was used to test ISL toxicity. An ELISA and an RT-qPCR assay detected the inflammatory cytokines (TNF-α, IL-6, COX-2, and ICAM-1). A Western blot investigated the expression levels of inflammation-related signals [nuclear factor-κB (NF-κB), peroxisome proliferator-activated receptor γ (PPARγ)], and fibrogenesis, including fibronectin and alpha-smooth muscle actin (α-SMA)]. Protein expressions of α-SMA were measured by immunofluorescence.

RESULTS

Pre-treatment with ISL (10 or 20 μM) dose-dependently decreased the mRNA levels of TNF-α, IL-6, ICAM-1, and COX-2 induced by ANG II (1 μg/ml) in both MPMs and HTFs. ANG II remarkably increased the amount of P65 in the nuclei and decreased the amount of P65 in the cytoplasm. Additionally, ANG II reduced PPARγ expression levels in a time-dependent manner. Furthermore, these effects which were induced by ISL were remarkably neutralized by ISL pre-treatment. Finally, ANG II markedly elevated the expression of fibronectin and α-SMA.

CONCLUSION

ISL could alleviate ANG II-induced fibrogenesis by inhibiting the NF-κB/PPARγ inflammatory pathway. In addition, ISL may be a potential agent for the treatment of conjunctival fibrosis. Most importantly, the NF-κB/PPARγ signaling pathway could be an effective therapeutic target for the prevention and treatment of conjunctival fibrosis after glaucoma surgery.

A specific small-molecule inhibitor of protein kinase CδI activity improves metabolic dysfunction in human adipocytes from obese individuals

The metabolic consequences and sequelae of obesity promote life-threatening morbidities. PKCδI is an important elicitor of inflammation and apoptosis in adipocytes. Here we report increased PKCδI activation via release of its catalytic domain concurrent with increased expression of proinflammatory cytokines in adipocytes from obese individuals. Using a screening strategy of dual recognition of PKCδI isozymes and a caspase-3 binding site on the PKCδI hinge domain with Schrödinger software and molecular dynamics simulations, we identified NP627, an organic small-molecule inhibitor of PKCδI. Characterization of NP627 by surface plasmon resonance (SPR) revealed that PKCδI and NP627 interact with each other with high affinity and specificity, SPR kinetics revealed that NP627 disrupts caspase-3 binding to PKCδI, and in vitro kinase assays demonstrated that NP627 specifically inhibits PKCδI activity. The SPR results also indicated that NP627 affects macromolecular interactions between protein surfaces. Of note, release of the PKCδI catalytic fragment was sufficient to induce apoptosis and inflammation in adipocytes. NP627 treatment of adipocytes from obese individuals significantly inhibited PKCδI catalytic fragment release, decreased inflammation and apoptosis, and significantly improved mitochondrial metabolism. These results indicate that PKCδI is a robust candidate for targeted interventions to manage obesity-associated chronic inflammatory diseases. We propose that NP627 may also be used in other biological systems to better understand the impact of caspase-3-mediated activation of kinase activity.

Regulation of YAP by Mammalian Target of Rapamycin Complex 1 in Endothelial Cells Controls Blood Pressure Through COX-2/mPGES-1/PGE2 Cascade

Endothelial cells regulate vascular tone by producing both relaxing and contracting factors to control the local blood flow. Hypertension is a common side effect of mTORC1 (mammalian target of rapamycin complex 1) inhibitors. However, the role of endothelial mTORC1 in hypertension remains elusive. The present study aimed to determine the role of endothelial mTORC1 in Ang II (angiotensin II)-induced hypertension and the underlying mechanism. Endothelial mTORC1 activity was increased by Ang II both in vitro and in vivo. Blood pressure was higher in Tie-2-Cre-mediated regulatory associated protein of mTOR (mammalian target of rapamycin; Raptor) heterozygous-deficient (Tie2Cre-Raptor^KD) mice than control mice both before and after Ang II infusion. Acetylcholine-evoked endothelium-dependent relaxation of mesenteric arteries was impaired in Tie2Cre-Raptor^KD mice. Treatment with indomethacin or a specific COX (cyclooxygenase)-2 inhibitor, NS-398, but not L-NG-nitroarginine methyl ester reduced endothelium-dependent relaxation in Raptor^flox/- mice to a similar extent as in Tie2Cre-Raptor^KD mice. Metabolomic profiling revealed that the plasma content of prostaglandin E₂ was reduced in Tie2Cre-Raptor^KD mice with or without Ang II infusion. In endothelial cells, reduction of the protein level of YAP (yes-associated protein) with siRNA-mediated RPTOR deficiency was autophagy dependent and transcriptionally regulated the expression of COX-2 and mPGES-1 (microsomal prostaglandin E synthase-1). Hence, overexpression of YAP in endothelial cells enhanced the mRNA and protein levels of COX-2 and mPGES-1 and reversed the endothelial dysfunction and hypertension in Tie2Cre-Raptor^KD mice. The present results demonstrate that suppression of mTORC1 activity in endothelial cells reduces prostaglandin E₂ production and causes hypertension by reducing YAP-mediated COX-2/mPGES-1 expression.

Regulatory T cells protected against abdominal aortic aneurysm by suppression of the COX-2 expression

CD4⁺CD25⁺ regulatory T cells (Tregs) have been shown to protect against the development of abdominal aortic aneurysm (AAA). Cyclooxygenase‐2 (COX‐2), a pro‐inflammatory protein, can convert arachidonic acid into prostaglandins (PGs). The present study was aimed to investigate the effect of Tregs on COX‐2 expression in angiotension II (Ang II)‐induced AAA in ApoE^−/− mice. Tregs were injected via tail vein in every 2 weeks. Ang II was continuously infused by a micropump for 28 days to induce AAA. In vivo, compared with the control group, adoptive transfer of Tregs significantly reduced the incidence of AAA, maximal diameter, and the mRNA and protein expression of COX‐2 in mice. Immunofluorescence showed that Tregs treatment reduced COX‐2 expression both in smooth muscle cells (SMCs) and macrophages in AAA. In vitro, the Western blot analysis showed that Tregs reduced Ang II‐induced COX‐2 expression in macrophages and SMCs. Meanwhile, ELISA showed that Tregs reduced Ang II‐induced prostaglandin E₂ (PGE₂) secretion. Moreover, Tregs increased SMC viability and induced transition of macrophages phenotype from M1 to M2. In conclusion, Tregs treatment dramatically decreased the expression of COX‐2 in vivo and in vitro, suggesting that Tregs could protect against AAA through inhibition of COX‐2. The study may shed light on the immune treatment of AAA.

Blockade of AT1 receptor restore the migration of vascular smooth muscle cells in high sodium medium

The present study aimed to test the hypothesis that increased sodium concentration affects the migratory phenotype of vascular smooth muscle cells (VSMCs) independently of the haemodynamic factors. Cell migration was evaluated by wound-healing assay under the following conditions: high sodium (HS, 160 mM) and control (CT, 140 mM). Cell viability was assessed by annexin V and propidium iodide labeling. Cyclooxygenase-2 (COX-2) gene expression was analysed by reverse transcription polymerase chain reaction. ERK1/2 phosphorylation was assessed by western blot. Exposure of VSMCs to HS reduced migration, and AT1R blockade prevented this response. HS increased COX-2 gene expression, and COX-2 blockade prevented the reduction in VSMC migration induced by HS. HS also increased ERK1/2 phosphorylation, and ERK1/2 inhibition recovered VSMC migration as well as blocked COX-2 gene expression. The TXA₂ receptor blocker, but not the prostacyclin receptor blocker, prevented the HS-induced VSMCs migration decrease. HS reduces the migration of VSMCs by increasing COX-2 gene expression via AT1R-ERK1/2 phosphorylation. In addition, increased COX-2 by HS seems to modulate the reduction of VSMCs migration by the TXA₂ receptor.

The Role of Tyrosine Phosphorylation of Protein Kinase C Delta in Infection and Inflammation

Protein Kinase C (PKC) is a family composed of phospholipid-dependent serine/threonine kinases that are master regulators of inflammatory signaling. The activity of different PKCs is context-sensitive and these kinases can be positive or negative regulators of signaling pathways. The delta isoform (PKCδ) is a critical regulator of the inflammatory response in cancer, diabetes, ischemic heart disease, and neurodegenerative diseases. Recent studies implicate PKCδ as an important regulator of the inflammatory response in sepsis. PKCδ, unlike other members of the PKC family, is unique in its regulation by tyrosine phosphorylation, activation mechanisms, and multiple subcellular targets. Inhibition of PKCδ may offer a unique therapeutic approach in sepsis by targeting neutrophil-endothelial cell interactions. In this review, we will describe the overall structure and function of PKCs, with a focus on the specific phosphorylation sites of PKCδ that determine its critical role in cell signaling in inflammatory diseases such as sepsis. Current genetic and pharmacological tools, as well as in vivo models, that are used to examine the role of PKCδ in inflammation and sepsis are presented and the current state of emerging tools such as microfluidic assays in these studies is described.

Biological Evaluation and Molecular Docking Studies of Dimethylpyridine Derivatives

Cyclooxygenase inhibitors as anti-inflammatory agents can be used in chemoprevention. Many in vitro and in vivo studies on human and animal models have explained the mechanisms of the chemopreventive effect of COX inhibitors such as: induction of apoptosis, inhibition of neoplasia, angiogenesis suppression, induction of cell cycle inhibition and inhibition of the expression of peroxisome proliferator-activated receptors. Here, biological evaluation of twelve different Schiff base derivatives of N-(2-hydrazine-2-oxoethyl)-4,6-dimethyl-2-sulfanylpyridine- 3-carboxamide are presented. Their in vitro anti-COX-1/COX-2, antioxidant and anticancer activities were studied. The molecular docking study was performed in order to understand the binding interaction of compounds in the active site of cyclooxygenases. Compounds PS18 and PS33 showed a significant inhibitory activity on COX-1 at lower concentrations compared to meloxicam and piroxicam. The IC₅₀ of COX-1 of these compounds was 57.3 µM for PS18 and 51.8 µM for PS33. Out of the tested compounds, the highest therapeutic index was demonstrated by PS18, PS19, PS33, PS40 and PS41. Lower molar concentrations of these compounds inhibit the growth of cancer cells while not inhibiting the healthy cells. Compounds PS18, PS19 and PS33 simultaneously demonstrated a statistically-significant inhibition of COX-1 or COX-2. This opens up the possibility of applying these compounds in the chemoprevention of cancer.

Dose-Effect of Irbesartan on Cyclooxygenase-2 and Matrix Metalloproteinase-9 Expression in Rabbit Atherosclerosis

Irbesartan has previously shown antiatherosclerotic effects on human carotid atherosclerotic plaques. Our study aimed to assess the dose-effect of irbesartan on cyclooxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) in rabbit atherosclerotic aorta. New Zealand rabbits were randomly divided into 6 groups: normal control (NC), high cholesterol (HC), low-dose (10 mg·kg·day), medium-dose (20 mg·kg·d), and high-dose (30 mg·kg·d) irbesartan and celecoxib (20 mg·kg·d). Except for the NCs, rabbits were fed a HC diet for 14 weeks to induce atherosclerosis. Aortic atherosclerotic lesions and messenger RNA and protein expression of COX-2, MMP-9, and nuclear factor-κB (NF-κB) were subsequently measured. The surface area of aortic atherosclerotic lesions was visibly larger in the HC group than in NCs (P < 0.01), but showed considerable reduction with medium- and high-dosage irbesartan and celecoxib treatments (P < 0.01). In medium- and high-dosage irbesartan and celecoxib groups, COX-2 and MMP-9 expression and NF-κB activity were significantly lower than in the high-cholesterol group (P < 0.01). No significant differences in treatment effects were observed between the high-dosage irbesartan and celecoxib groups (P > 0.05). Our results indicate that medium and high doses of irbesartan and celecoxib have antiatherosclerotic effects in aortic plaques via inhibition of COX-2 and MMP-9 by suppressing NF-κB activation. High-dose irbesartan has effects similar to celecoxib.

Maternal high-sodium intake affects the offspring' vascular renin-angiotensin system promoting endothelial dysfunction in rats

Perinatal sodium overload induces endothelial dysfunction in adult offspring, but the underlying mechanisms are not fully known. The involvement of tissue renin-angiotensin system on high sodium-programmed endothelial dysfunction was examined. Acetylcholine and angiotensin I and II responses were analyzed in aorta and mesenteric resistance arteries from 24-week-old male offspring of normal-salt (O-NS, 1.3% NaCl) and high-salt (O-HS, 8% NaCl) fed dams. COX-2 expression, O₂^- production and angiotensin converting enzyme (ACE) activity were determined. A separated O-HS was treated with losartan (15 mg kg^-1/day) for eight weeks. Compared to O-NS, O-HS were normotensive. Acetylcholine-induced relaxation was impaired in O-HS arteries, which was improved by tempol, apocynin or indomethacin. The angiotensin I-induced contraction was greater in O-HS arteries, whereas the angiotensin II responses were unchanged. ACE activity, O₂^- production and COX-2 expression were increased in O-HS arteries. In this group, the increased O₂^- production was inhibited by apocynin or losartan. Chronic losartan decreased COX-2 expression and restored the endothelium-dependent vasodilation in O-HS. Our findings reiterate that perinatal sodium overload programs endothelial dysfunction in adult offspring through a blood pressure-independent mechanism. Our results also suggest that vascular angiotensin II is the main mediator of high sodium-programmed endothelial dysfunction, promoting COX-2 expression and oxidative stress.

Correlations between gene expression highlight a different activation of ACE/TLR4/PTGS2 signaling in symptomatic and asymptomatic plaques in atherosclerotic patients

Inflammation has a key role and translates the effects of many known risk factors for the disease in atherosclerotic vulnerable plaques. Aiming to look into the elements that induce the development of either a vulnerable or stable atherosclerotic plaque, and considering that inflammation has a central role in the progression of lesions, we analyzed the expression of genes involved in the ACE/TLR4/PTGS2 signaling in carotid plaques of symptomatic and asymptomatic patients. Patients with internal carotid artery stenosis undergoing carotid endarterectomy at Verona University Hospital were included in this study. A total of 71 patients was considered for gene expression analysis (29 atherothrombotic stroke patients and 42 asymptomatic patients). Total RNA was extracted from the excised plaques and expression of PTGS2, ACE, TLR4, PTGER4, PTGER3, EPRAP and ACSL4 genes was analyzed by real-time PCR. The correlation between the pair of genes was studied by Spearman coefficient. From the analyzed genes, we did not observe any individual difference in gene expression but the network of co-expressed genes suggests a different activation of pathways in the two groups of plaques.

Study of insulin vascular sensitivity in aortic rings and endothelial cells from aged rats subjected to caloric restriction: Role of perivascular adipose tissue

The prevalence of metabolic syndrome is dramatically increasing among elderly population. Metabolic syndrome in aged individuals is associated with hyperinsulinemia and insulin resistance both in metabolic tissues and in the cardiovascular system, with this fact being associated with the cardiometabolic alterations associated to this condition. Caloric restriction (CR) improves insulin sensitivity and is one of the dietetic strategies most commonly used to enlarge life and to prevent aging induced cardiovascular alterations. The aim of this study was to analyze the possible beneficial effects of CR in aging-induced vascular insulin resistance both in aortic rings and in primary culture of endothelial cells. In addition, the inflammatory profile of perivascular adipose tissue (PVAT) and its possible role in the impairment of vascular insulin sensitivity associated with aging was also assessed. Three experimental groups of male Wistar rats were used: 3 (3m), 24 (24m) fed ad libitum and 24months old rats subjected to 20% CR during their three last months of life (24m-CR). Aorta rings surrounded or not by PVAT were mounted in an organ bath and precontracted with phenylephrine (10^-7.5M). Changes in isometric tension were recorded in response to cumulative insulin concentrations (10^-8-10^-5.5M) in the presence or absence of L-NAME (10^-4M). Aortic rings and primary aortic endothelial cells were incubated in presence/absence of insulin (10^-7M) and the activation of the PI3K/Akt and MAPK pathways as well as nitrite and nitrates concentrations and the mRNA levels of eNOS, insulin receptor, and GLUT-4 were assessed. CR prevented the aging-induced decrease in the vasodilator response to insulin and the aging-induced increase in the vasoconstrictor response to high insulin concentrations. Changes between 24m and 24m-CR aorta rings were abolished in the presence of L-NAME. CR induced-improvement in insulin vascular sensitivity was related with activation of the PI3K/Akt both in aortic rings and in aortic endothelial cells in response to insulin. CR attenuated the overexpression of iNOS, TNF-α and IL-1β in the PVAT of aged rats although aortic rings surrounded by PVAT from 24m rats showed and increased vasorelaxation in response to insulin compared to aortic rings from 3m and 24m-CR rats. In conclusion, a moderate protocol of CR improves insulin vascular sensitivity and prevents the aging induced overexpression of pro-inflammatory cytokines in PVAT.

Losartan reverses COX-2-dependent vascular dysfunction in offspring of hyperglycaemic rats

AIMS

This study examined whether chronic treatment with losartan, an angiotensin II type 1 receptor (AT₁R) antagonist, might reverse COX-2-mediated vascular dysfunction in mesenteric resistance arteries (MRA) from offspring of hyperglycaemic rats.

MATERIALS AND METHODS

Male 12-month-old offspring of hyperglycaemic (O-DR) and normoglycaemic (O-CR) rats were treated with losartan (15mg·kg·day^-1) during 2months. Third order MRA of untreated and losartan-treated O-DR and O-CR were mounted in wire myograph for isometric tension measurements. COX-2 expression was analyzed by Western blot; TxA₂, PGE₂ and PGF_2α release was measured using commercial kits.

KEY FINDINGS

O-DR showed increased blood pressure, impaired acetylcholine-induced vasodilation and increased noradrenaline-induced vasoconstriction than O-CR. All these parameters were normalized by losartan in O-DR. Pre-incubation of MRA with indomethacin (COX-1/2 inhibitor), NS-398 (COX-2 inhibitor) or tempol (superoxide dismutase mimetic) increased relaxation to acetylcholine and reduced contraction to noradrenaline only in O-DR. COX-2 expression, TxA₂, PGE₂ and PGF_2α release were increased in O-DR. In losartan-treated O-DR, NS-398, indomethacin or tempol failed to produce any effect on acetylcholine or noradrenaline responses. Losartan treatment reduced COX-2 expression, TxA₂, PGE₂ and PGF_2α release in O-DR.

SIGNIFICANCE

The present results reveal that chronic losartan administration in O-DR normalizes endothelial function in MRA by correcting the existing COX-2 overexpression and the imbalance between endothelium-derived relaxing and contracting factors. These findings not only support the beneficial effects of AT₁ receptor antagonist in O-DR, but also suggest the implication of angiotensin II as a putative mediator of hyperglycemia-programmed vascular dysfunction in rats.

Treatment with salvianolic acid B restores endothelial function in angiotensin II-induced hypertensive mice

Salvianolic acid B (Sal B) is one of the most abundant phenolic acids derived from the root of Danshen with potent anti-oxidative properties. The present study examined the vasoprotective effect of Sal B in hypertensive mice induced by angiotensin II (Ang II). Sal B (25mg/kg/day) was administered via oral gavage for 11days to Ang II (1.2mg/kg/day)-infused C57BL/6J mice (8-10weeks old). The vascular reactivity (both endothelium-dependent relaxations and contractions) in mouse arteries was examined by wire myography. The production of reactive oxygen species (ROS), protein level and localization of angiotensin AT₁ receptors and the proteins involved in ROS formation were evaluated using dihydroethidium (DHE) fluorescence, lucigenin-enhanced chemiluminescence, immunohistochemistry and Western blotting, respectively. The changes of ROS generating proteins were also assessed in vitro in human umbilical vein endothelial cells (HUVECs) exposed to Ang II with and without co-treatment with Sal B (0.1-10nM). Oral administration of Sal B reversed the Ang II-induced elevation of arterial systolic blood pressure in mice, augmented the impaired endothelium-dependent relaxations and attenuated the exaggerated endothelium-dependent contractions in both aortas and renal arteries of Ang II-infused mice. In addition, Sal B treatment normalized the elevated levels of AT₁ receptors, NADPH oxidase subunits (NOx-2 and NOx-4) and nitrotyrosine in arteries of Ang II-infused mice or in Ang II-treated HUVECs. In summary, the present study provided additional evidence demonstrating that Sal B treatment for 11days reverses the impaired endothelial function and with a marked inhibition of AT₁ receptor-dependent vascular oxidative stress. This vasoprotective and anti-oxidative action of Sal B most likely contributes to the anti-hypertensive action of the plant-derived compound.

Demethoxycurcumin Preserves Renovascular Function by Downregulating COX-2 Expression in Hypertension

Hypertension-associated endothelial dysfunction is largely due to the exaggerated vasoconstrictor generation by cyclooxygenase-2 (COX-2). COX-2 is induced under inflammatory condition. Demethoxycurcumin (DMC) is a major component of Curcuma longa L, which possesses anti-inflammatory action. This study aimed to examine whether DMC protects endothelial function in hypertension by modulating COX-2. Changes in isometric tension showed that in vivo and ex vivo treatment with DMC rescued the attenuated endothelium-dependent relaxations (EDRs) and elevated endothelium-dependent contractions (EDCs) in the renal arteries of SHR, which were also corrected by acute usage of the COX-2 inhibitor celecoxib. The restoration of renovascular activity by DMC was accompanied by the normalization of COX-2 expression. The enhanced COX-2 expression observed in the renal arteries of hypertensive patients was suppressed by incubation of excised arteries with DMC for 12 hrs. In the renal arteries of Wistar-Kyoto rats (WKY), DMC prevented the endothelial dysfunction caused by angiotensin II. The reduction in the generation of nitric oxide (NO) and expression of eNOS phosphorylation (Ser1177) in human umbilical vein endothelial cells caused by angiotensin II (Ang II) were restored by DMC or celecoxib. Our findings suggest that DMC may decrease COX-2 expression and improve endothelial function in hypertension.

Role of COX-2-derived PGE2 on vascular stiffness and function in hypertension

BACKGROUND AND PURPOSE

Prostanoids derived from COX-2 and EP receptors are involved in vascular remodelling in different cardiovascular pathologies. This study evaluates the contribution of COX-2 and EP1 receptors to vascular remodelling and function in hypertension.

EXPERIMENTAL APPROACH

Spontaneously hypertensive rats (SHR) and angiotensin II (AngII)-infused (1.44 mg · kg(-1) · day(-1), 2 weeks) mice were treated with the COX-2 inhibitor celecoxib (25 mg · kg(-1) · day(-1) i.p) or with the EP1 receptor antagonist SC19220 (10 mg · kg(-1) · day(-1) i.p.). COX-2(-/-) mice with or without AngII infusion were also used.

KEY RESULTS

Celecoxib and SC19220 treatment did not modify the altered lumen diameter and wall : lumen ratio in mesenteric resistance arteries from SHR-infused and/or AngII-infused animals. However, both treatments and COX-2 deficiency decreased the augmented vascular stiffness in vessels from hypertensive animals. This was accompanied by diminished vascular collagen deposition, normalization of altered elastin structure and decreased connective tissue growth factor and plasminogen activator inhibitor-1 gene expression. COX-2 deficiency and SC19220 treatment diminished the increased vasoconstrictor responses and endothelial dysfunction induced by AngII infusion. Hypertensive animals showed increased mPGES-1 expression and PGE2 production in vascular tissue, normalized by celecoxib. Celecoxib treatment also decreased AngII-induced macrophage infiltration and TNF-α expression. Macrophage conditioned media (MCM) increased COX-2 and collagen type I expression in vascular smooth muscle cells; the latter was reduced by celecoxib treatment.

CONCLUSIONS AND IMPLICATIONS

COX-2 and EP1 receptors participate in the increased extracellular matrix deposition and vascular stiffness, the impaired vascular function and inflammation in hypertension. Targeting PGE2 receptors might have benefits in hypertension-associated vascular damage.

Protective Effects of Glucagon-like Peptide 1 on Endothelial Function in Hypertension

Vascular endothelial cells play a major role in maintaining cardiovascular homeostasis. Endothelial dysfunction, characterized by reduced endothelium-dependent relaxations or accompanied by enhanced endothelium-dependent contractions, is a hallmark of and plays a pivotal role in the pathogenesis of hypertension. Endothelial dysfunction in hypertension has been linked to decreases in nitric oxide (NO) bioavailability, reflecting the impaired generation of NO and/or the enhanced inactivation of NO by reactive oxygen species. Many of these conditions can be improved by glucagon-like peptide 1 (GLP-1), a proglucagon-derived hormone secreted by intestinal endocrine L-type cells, which is rapidly inactivated by an enzyme dipeptidyl peptidase 4 in circulation. On one hand, GLP-1 analogues or dipeptidyl peptidase 4 inhibitors upregulate endothelial nitric oxide synthase expression and increase endothelial nitric oxide synthase phosphorylation, resulting in improved production of NO and thus endothelium-dependent relaxations. On the other hand, GLP-1 and related agents attenuate endothelium-dependent contractions by reducing reactive oxygen species generation and cyclooxygenase-2 expression. GLP-1 elevating agents and GLP-1 receptor agonists improve endothelial function in hypertension, suggesting that GLP-1 signaling could be a therapeutic target in hypertension-related vascular events.

Biodistribution and Efficacy of Targeted Pulmonary Delivery of a Protein Kinase C-δ Inhibitory Peptide: Impact on Indirect Lung Injury

Sepsis and sepsis-induced lung injury remain a leading cause of death in intensive care units. We identified protein kinase C-δ (PKCδ) as a critical regulator of the acute inflammatory response and demonstrated that PKCδ inhibition was lung-protective in a rodent sepsis model, suggesting that targeting PKCδ is a potential strategy for preserving pulmonary function in the setting of indirect lung injury. In this study, whole-body organ biodistribution and pulmonary cellular distribution of a transactivator of transcription (TAT)-conjugated PKCδ inhibitory peptide (PKCδ-TAT) was determined following intratracheal (IT) delivery in control and septic [cecal ligation and puncture (CLP)] rats to ascertain the impact of disease pathology on biodistribution and efficacy. There was negligible lung uptake of radiolabeled peptide upon intravenous delivery [<1% initial dose (ID)], whereas IT administration resulted in lung retention of >65% ID with minimal uptake in liver or kidney (<2% ID). IT delivery of a fluorescent-tagged (tetramethylrhodamine-PKCδ-TAT) peptide demonstrated uniform spatial distribution and cellular uptake throughout the peripheral lung. IT delivery of PKCδ-TAT at the time of CLP surgery significantly reduced PKCδ activation (tyrosine phosphorylation, nuclear translocation and cleavage) and acute lung inflammation, resulting in improved lung function and gas exchange. Importantly, peptide efficacy was similar when delivered at 4 hours post-CLP, demonstrating therapeutic relevance. Conversely, spatial lung distribution and efficacy were significantly impaired at 8 hours post-CLP, which corresponded to marked histopathological progression of lung injury. These studies establish a functional connection between peptide spatial distribution, inflammatory histopathology in the lung, and efficacy of this anti-inflammatory peptide.

Chronic Losartan Treatment Up-Regulates AT1R and Increases the Heart Vulnerability to Acute Onset of Ischemia and Reperfusion Injury in Male Rats

Inhibition of angiotensin II type 1 receptor (AT1R) is an important therapy in the management of hypertension, particularly in the immediate post-myocardial infarction period. Yet, the role of AT1R in the acute onset of myocardial ischemia and reperfusion injury still remains controversial. Thus, the present study determined the effects of chronic losartan treatment on heart ischemia and reperfusion injury in rats. Losartan (10 mg/kg/day) was administered to six-month-old male rats via an osmotic pump for 14 days and hearts were then isolated and were subjected to ischemia and reperfusion injury in a Langendorff preparation. Losartan significantly decreased mean arterial blood pressure. However, heart weight, left ventricle to body weight ratio and baseline cardiac function were not significantly altered by the losartan treatment. Of interest, chronic in vivo losartan treatment significantly increased ischemia-induced myocardial injury and decreased post-ischemic recovery of left ventricular function. This was associated with significant increases in AT1R and PKCδ expression in the left ventricle. In contrast, AT2R and PKCε were not altered. Furthermore, losartan treatment significantly increased microRNA (miR)-1, -15b, -92a, -133a, -133b, -210, and -499 expression but decreased miR-21 in the left ventricle. Of importance, addition of losartan to isolated heart preparations blocked the effect of increased ischemic-injury induced by in vivo chronic losartan treatment. The results demonstrate that chronic losartan treatment up-regulates AT1R/PKCδ and alters miR expression patterns in the heart, leading to increased cardiac vulnerability to ischemia and reperfusion injury.

Cyclooxygenase-2-dependent oxidative stress mediates palmitate-induced impairment of endothelium-dependent relaxations in mouse arteries

Palmitic acid, one of the saturated free fatty acids, impairs cardiovascular function as manifested by inducing vascular inflammation, apoptosis and over-production of reactive oxygen species (ROS) although the origin for ROS remains unclear. The present study investigated the cellular mechanisms underlying palmitate-induced impairment of endothelial function. Ex vivo treatment in tissue culture with palmitate concentration-dependently attenuated acetylcholine-induced endothelium-dependent relaxations, up-regulated the expression of cyclooxygenase-2 (COX-2) and elevated superoxide formation in mouse aortic endothelial cells (MAECs) measured by dihydroethidium (DHE) staining and electron paramagnetic resonance (EPR) spectroscopy. Superoxide scavengers, COX-2 inhibitor and thromboxane prostanoid (TP) receptor antagonist, but not COX-1 inhibitor reversed the harmful effects of palmitate. Furthermore, palmitate impaired acetylcholine-induced relaxations and raised superoxide in en face endothelium of aortas only from COX-1(-/-) mice but not from COX-2(-/-) mice. Palmitate increased the production and release of TXB2, a stable thromboxane A2 metabolite in mouse aortas, which was abolished by COX-2 inhibitor. Superoxide scavenger did not affect palmitate-induced up-regulated expression of COX-2 in MAECs. Both real time PCR and luciferase reporter gene assay confirmed COX-2 up-regulation in palmitate-treated MAECs and NF-κB was substantially involved in this up-regulation. The present study provides novel evidence that palmitate up-regulates COX-2 through NF-κB-dependent mechanism and resultant COX-2-associated oxidative stress impairs endothelium-dependent relaxations in mouse aortas.

New roles for old pathways? A circuitous relationship between reactive oxygen species and cyclo-oxygenase in hypertension

Elevated production of prostanoids from the constitutive (COX-1) or inducible (COX-2) cyclo-oxygenases has been involved in the alterations in vascular function, structure and mechanical properties observed in cardiovascular diseases, including hypertension. In addition, it is well known that production of ROS (reactive oxygen species) plays an important role in the impaired contractile and vasodilator responses, vascular remodelling and altered vascular mechanics of hypertension. Of particular interest is the cross-talk between NADPH oxidase and mitochondria, the main ROS sources in hypertension, which may represent a vicious feed-forward cycle of ROS production. In recent years, there is experimental evidence showing a relationship between ROS and COX-derived products. Thus ROS can activate COX and the COX/PG (prostaglandin) synthase pathways can induce ROS production through effects on different ROS generating enzymes. Additionally, recent evidence suggests that the COX-ROS axis might constitute a vicious circle of self-perpetuating vasoactive products that have a pathophysiological role in altered vascular contractile and dilator responses and hypertension development. The present review discusses the current knowledge on the role of oxidative stress and COX-derived prostanoids in the vascular alterations observed in hypertension, highlighting new findings indicating that these two pathways act in concert to induce vascular dysfunction.

Angiotensin-generated reactive oxygen species in brain and pathogenesis of cardiovascular diseases

SIGNIFICANCE

Overproduction of angiotensin II (Ang II) in brain contributes to the pathogenesis of cardiovascular diseases. One of the most promising theses that emerged during the last decade is that production of reactive oxygen species (ROS) and activation of redox-dependent signaling cascades underlie those Ang II actions. This review summarizes our status of understanding on the roles of ROS and redox-sensitive signaling in brain Ang II-dependent cardiovascular diseases, using hypertension and heart failure as illustrative examples.

RECENT ADVANCES

ROS generated by NADPH oxidase, mitochondrial electron transport chain, and proinflammatory cytokines activates mitogen-activated protein kinases and transcription factors, which in turn modulate ion channel functions and ultimately increase neuronal activity and sympathetic outflow in brain Ang II-dependent cardiovascular diseases. Antioxidants targeting ROS have been demonstrated to be beneficial to Ang II-induced hypertension and heart failure via protection from oxidative stress in brain regions that subserve cardiovascular regulation.

CRITICAL ISSUES

Intra-neuronal signaling and the downstream redox-sensitive proteins involved in controlling the neuronal discharge rate, the sympathetic outflow, and the pathogenesis of cardiovascular diseases need to be identified. The cross talk between Ang II-induced oxidative stress and neuroinflammation in neural mechanisms of cardiovascular diseases also warrants further elucidation.

FUTURE DIRECTIONS

Future studies are needed to identify new redox-based therapeutics that work not only in animal models, but also in patients suffering from the prevalent diseases. Upregulation of endogenous antioxidants in the regulation of ROS homeostasis is a potential therapeutic target, as are small molecule- or nanoformulated conjugate-based antioxidant therapy.

Salidroside improves homocysteine-induced endothelial dysfunction by reducing oxidative stress

Hyperhomocysteinemia is associated with an increased risk for cardiovascular diseases through increased oxidative stress. Salidroside is an active ingredient of the root of Rhodiola rosea with documented antioxidative, antihypoxia and neuroprotective properties. However, the vascular benefits of salidroside against endothelial dysfunction have yet to be explored. The present study, therefore, aimed to investigate the protective effect of salidroside on homocysteine-induced endothelial dysfunction. Functional studies on the rat aortas were performed to delineate the vascular effect of salidroside. DHE imaging was used to evaluate the reactive oxygen species (ROS) level in aortic wall and endothelial cells. Western blotting was performed to assess the protein expression associated with oxidative stress and nitric oxide (NO) bioavailability. Exposure to homocysteine attenuated endothelium-dependent relaxations in rat aortas while salidroside pretreatment rescued it. Salidroside inhibited homocystein-induced elevation in the NOX2 expression and ROS overproduction in both aortas and cultured endothelial cells and increased phosphorylation of eNOS which was diminished by homocysteine. The present study shows that salidroside is effective in preserving the NO bioavailability and thus protects against homocysteine-induced impairment of endothelium-dependent relaxations, largely through inhibiting the NOX2 expression and ROS production. Our results indicate a therapeutic potential of salidroside in the management of oxidative-stress-associated cardiovascular dysfunction.

Calcitriol restores renovascular function in estrogen-deficient rats through downregulation of cyclooxygenase-2 and the thromboxane-prostanoid receptor

Cardiovascular risks increase in postmenopausal women. While vitamin D is supplemented for osteoporosis, it is not known whether it protects renal arterial function during estrogen deficiency. Here we measured changes in renovascular reactivity induced by ovariectomy in rats and examined whether calcitriol, the most active form of vitamin D, was able to correct such changes. The impairment of endothelium-dependent relaxation in renal arteries from ovariectomized rats was effectively reversed by long-term calcitriol treatment. It was also corrected by acute exposure to cyclooxygenase-2 (COX-2) inhibitors and a thromboxane-prostanoid receptor antagonist, respectively. Calcitriol normalized the overexpression of COX-2 and thromboxane-prostanoid receptors in intralobal renal artery segments and aortic endothelial cells isolated from ovariectomized rats. In vitro exposure of the arterial segments to calcitriol for 12 h improved relaxation and downregulated thromboxane-prostanoid receptors. The attenuated nitric oxide production in ovariectomized rat aortic endothelial cells was restored following a 12-h treatment with calcitriol, COX-2 inhibition, or thromboxane-prostanoid receptor antagonism. Thus, impaired endothelium-dependent renal artery relaxation in ovariectomized rats is mediated largely through increased activity and expression of COX-2 and the thromboxane-prostanoid receptor. Calcitriol restores endothelial function through downregulating both signaling proteins during estrogen deficiency.

Reciprocal relationship between reactive oxygen species and cyclooxygenase-2 and vascular dysfunction in hypertension

AIMS

This study evaluates a possible relationship between reactive oxygen species (ROS) and cyclooxygenase (COX)-2-derived products in conductance and resistance arteries from hypertensive animals. Angiotensin II (Ang II)-infused mice or spontaneously hypertensive rats treated with the NAD(P)H Oxidase inhibitor apocynin, the mitochondrion-targeted SOD2 mimetic Mito-TEMPO, the superoxide dismutase analog tempol, or the COX-2 inhibitor Celecoxib were used.

RESULTS

Apocynin, Mito-TEMPO, and Celecoxib treatments prevented Ang II-induced hypertension, the increased vasoconstrictor responses to phenylephrine, and the reduced acetylcholine relaxation. The NOX-2 inhibitor gp91ds-tat, the NOX-1 inhibitor ML171, catalase, and the COX-2 inhibitor NS398 abolished the ex vivo effect of Ang II-enhancing phenylephrine responses. Antioxidant treatments diminished the increased vascular COX-2 expression, prostanoid production, and/or participation of COX-derived contractile prostanoids and thromboxane A(2) receptor (TP) in phenylephrine responses, observed in arteries from hypertensive models. The treatment with the COX-2 inhibitor normalized the increased ROS production (O(2)·(-) and H(2)O(2)), NAD(P)H Oxidase expression (NOX-1, NOX-4, and p22phox) and activity, MnSOD expression, and the participation of ROS in vascular responses in both hypertensive models. Apocynin and Mito-TEMPO also normalized these parameters of oxidative stress. Apocynin, Mito-TEMPO, and Celecoxib improved the diminished nitric oxide (NO) production and the modulation by NO of phenylephrine responses in the Ang II model.

INNOVATION

This study provides mechanistic evidence of circuitous relationship between COX-2 products and ROS in hypertension.

CONCLUSION

The excess of ROS from NAD(P)H Oxidase and/or mitochondria and the increased vascular COX-2/TP receptor axis act in concert to induce vascular dysfunction and hypertension.

From Skeleton to Cytoskeleton

Rationale:

The expression of osteocalcin is augmented in human atherosclerotic lesions. How osteocalcin triggers vascular pathogenesis and remodeling is unclear.

Objective:

To investigate whether osteocalcin promotes transformation of adventitial fibroblast to myofibroblasts and the molecular mechanism involved.

Methods and Results:

Immunohistochemistry indicated that osteocalcin was expressed in the neointima of renal arteries from diabetic patients. Western blotting and wound-healing assay showed that osteocalcin induced fibroblast transformation and migration, which were attenuated by blockers of the renin-angiotensin system and protein kinase Cδ (PKCδ), toll-like receptor 4 (TLR4) neutralizing antibody, and antagonist and inhibitors of free radical production and cyclooxygenase-2. Small interfering RNA silencing of TLR4 and PKCδ abolished fibroblast transformation. Angiotensin II level in the conditioned medium from the osteocalcin-treated fibroblasts was found elevated using enzyme immunoassay. Culturing of fibroblasts in conditioned medium collected from differentiated osteoblasts promoted fibroblast transformation. The expression of fibronectin, TLR4, and cyclooxygenase-2 is augmented in human mesenteric arteries after 5-day in vitro exposure to osteocalcin.

Conclusions:

Osteocalcin transforms adventitial fibroblasts to myofibroblasts through stimulating angiotensin II release and subsequent activation of PKCδ/TLR4/reactive oxygen species/cyclooxygenase-2 signaling cascade. This study reveals that the skeletal hormone osteocalcin cross-talks with vascular system and contributes to vascular remodeling.

PKCδ signalling regulates SR-A and CD36 expression and foam cell formation

AIMS

The formation of foam cells is crucial in the initiation and progression of atherosclerosis. One of the critical steps in foam cell formation is the uptake of low-density lipoprotein (LDL) by macrophages via scavenger receptors (SRs). This study examined the role of protein kinase C (PKC) isoforms on foam cell formation.

METHODS AND RESULTS

The effects of short-hairpin RNA (shRNA) and small interfering RNA (siRNA) against classical PKC and novel PKC isoforms were investigated in THP-1-derived macrophages and primary macrophages. The knockdown of PKCδ inhibited oxidized LDL (OxLDL) uptake and intracellular cholesterol accumulation in both cell models. The reduction of PKCδ resulted in decreased expression of SR-A and CD36. Similar conclusions were obtained in examining the effects of a PKCδ inhibitor, rottlerin. Molecular investigation revealed that a decrease in PKCδ inhibited protein kinase B (PKB/Akt) expression and extracellular-signal-regulated kinase (ERK) phosphorylation. Surprisingly, PKCδ-knockdown selectively decreased protein but not the mRNA level of PKCβI and PKCβII. We showed that the inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt upstream of ERK decreased SR-A and CD36 expression; however, the inhibition of ERK or PKCβ downstream of ERK attenuated SR-A but not CD36 expression. We further demonstrated that PKCδ could be induced by pro-atherogenic mediators, OxLDL and interferon-γ. Notably, PKCδ, phosphorylated ERK, Akt, and SR-A were highly expressed in human atherosclerotic arteries and CD68-positive macrophages as visualized by immunohistochemical staining.

CONCLUSION

Through regulating PI3K/Akt and ERK activity, PKCδ affects SR-A and CD36 expression and foam cell formation. The results suggest PKCδ as a potential target for atherosclerosis therapeutics.