Identification of vascular endothelial genes differentially responsive to fluid mechanical stimuli: cyclooxygenase-2, manganese superoxide dismutase, and endothelial cell nitric oxide synthase are selectively up-regulated by steady laminar shear stress

Emotion recollected in tranquility: lessons learned from the COX-2 saga

Nonsteroidal antinflammatory drugs (NSAIDs) inhibit prostaglandin formation by cyclooxygenases (COX) 1 and 2. NSAIDs selective for inhibition of COX-2 are less likely than traditional drugs to cause serious gastrointestinal adverse effects, but predispose to adverse cardiovascular events, such as heart failure, myocardial infarction, and stroke. Evidence from human pharmacology and genetics, genetically manipulated rodents, and other animal models and randomized trials indicates that this is consequent to suppression of COX-2-dependent cardioprotective prostagladins, particularly prostacyclin. Lessons drawn from how this saga unfolded are relevant to how we approach drug surveillance and regulation, integrate diversifed forms of information and might pursue a more personalized approach to drug efficacy and risk.

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.

The Gordon Wilson lecture. Understanding vascular endothelium: a pilgrim's progress. Endothelial dysfunction, biomechanical forces and the pathobiology of atherosclerosis

These are exciting times for the biomedical sciences, in general, and, in particular, for those who strive to understand the origins of complex human diseases, as we begin to focus with increasing precision on disease mechanisms at the cellular and molecular levels. Armed with the high-through-put technologies of the Post-Genomic Era, we now face the challenge of understanding biological systems at the level of their complex integration, and this will truly bring meaning to the concept of Systems Biology.

Oxidative risk for atherothrombotic cardiovascular disease

In the vasculature, reactive oxidant species, including reactive oxygen, nitrogen, or halogenating species, and thiyl, tyrosyl, or protein radicals may oxidatively modify lipids and proteins with deleterious consequences for vascular function. These biologically active free radical and nonradical species may be produced by increased activation of oxidant-generating sources and/or decreased cellular antioxidant capacity. Once formed, these species may engage in reactions to yield more potent oxidants that promote transition of the homeostatic vascular phenotype to a pathobiological state that is permissive for atherothrombogenesis. This dysfunctional vasculature is characterized by lipid peroxidation and aberrant lipid deposition, inflammation, immune cell activation, platelet activation, thrombus formation, and disturbed hemodynamic flow. Each of these pathobiological states is associated with an increase in the vascular burden of free radical species-derived oxidation products and, thereby, implicates increased oxidant stress in the pathogenesis of atherothrombotic vascular disease.

Implanted microvessels progress through distinct neovascularization phenotypes

We have previously demonstrated that implanted microvessels form a new microcirculation with minimal host-derived vessel investment. Our objective was to define the vascular phenotypes present during neovascularization in these implants and identify post-angiogenesis events. Morphological, functional and transcriptional assessments identified three distinct vascular phenotypes in the implants: sprouting angiogenesis, neovascular remodeling, and network maturation. A sprouting angiogenic phenotype appeared first, characterized by high proliferation and low mural cell coverage. This was followed by a neovascular remodeling phenotype characterized by a perfused, poorly organized neovascular network, reduced proliferation, and re-associated mural cells. The last phenotype included a vascular network organized into a stereotypical tree structure containing vessels with normal perivascular cell associations. In addition, proliferation was low and was restricted to the walls of larger microvessels. The transition from angiogenesis to neovascular remodeling coincided with the appearance of blood flow in the implant neovasculature. Analysis of vascular-specific and global gene expression indicates that the intermediate, neovascular remodeling phenotype is transcriptionally distinct from the other two phenotypes. Therefore, this vascular phenotype likely is not simply a transitional phenotype but a distinct vascular phenotype involving unique cellular and vascular processes. Furthermore, this neovascular remodeling phase may be a normal aspect of the general neovascularization process. Given that this phenotype is arguably dysfunctional, many of the microvasculatures present within compromised or diseased tissues may not represent a failure to progress appropriately through a normally occurring neovascularization phenotype.

Cyclooxygenase and prostaglandin synthases: roles in plaque stability and instability in humans

PURPOSE OF REVIEW

Cyclooxygenase (COX) is the key enzyme of the arachidonic acid metabolism and it plays a major role in development of both coronary and cerebrovascular disease. In this review, we will analyze the role of COX and prostaglandin synthases in plaque stability.

RECENT FINDINGS

As shown by experimental studies based on biochemical measurement of eicosanoid biosynthesis and by the results of clinical trials, COX plays a key role in plaque evolution. Two COX-isozymes have been identified, COX-1 and COX-2, with different tissue distribution, substrate specificity, regulatory mechanism and susceptibility to drugs inhibition. Whereas, the role of platelet COX-1 in acute coronary syndrome and ischemic stroke is definitely established through several large clinical studies with aspirin, the role of COX-2 in these settings is still under investigation because this enzyme was characterized only recently and its inhibitors (coxibs) became available only in 1998. Recent findings seem to suggest that functional consequences of COX-2 expression and inhibition in different clinical settings may depend on different expression of upstream and downstream receptors as well as by genetic polymorphism.

SUMMARY

COX-2 and prostaglandin synthases and their modulation play a major role in plaque homeostasis and in its clinical manifestations.

T-786C polymorphism of the NOS-3 gene and the endothelial cell response to fluid shear stress-a proteome analysis

Endothelial dysfunction is a common denominator of cardiovascular disease. Central to endothelial dysfunction is a decrease in the bioavailability of nitric oxide (NO) synthesized by endothelial NO synthase (NOS-3). In vivo, the level of fluid shear stress (FSS) exerted by the flowing blood determines NOS-3 expression. However, in contrast to the -786T variant of the nos-3 gene, the -786C variant is not sensitive to shear stress. Consequently, cells homozygous for this variant have an inadequate capacity to synthesize NO. Therefore, we have compared shear stress-induced protein expression in human primary cultured endothelial cells with TT or CC genotype. Cells with the CC genotype exhibited a greatly reduced FSS-induced NOS-3 expression as well as a diminished NO synthesis capacity when compared to TT genotype cells. Proteome changes in response to FSS (30 dyn/cm(2) for 24 h) were monitored by 2D-gel electrophoresis/densitometry/mass spectrometry. Of a total of 14 FSS-sensitive proteins, 8 were identically expressed in all cells. Four proteins, all of them part of the NO-dependent endoplasmic reticulum-stress response, were up-regulated by FSS only in cells with TT genotype. In contrast, CC genotype cells responded to FSS with a unique increase in manganese-containing superoxide dismutase expression. These differences in protein expression may (i) reflect the low bioavailability of NO in cells homozygous for the -786C variant of the nos-3 gene and (ii) point to a mechanism by which this deficit is counterbalanced by protecting the less abundant NO from rapid degradation.

Endothelial damage due to impaired nitric oxide bioavailability triggers cerebral aneurysm formation in female rats

OBJECTIVE

Epidemiological data indicate a high incidence of cerebral aneurysms in postmenopausal women. To elucidate the pathogenesis of cerebral aneurysms, we focused on the contribution of endothelial damage in rats.

METHODS

We induced estradiol deficiency by oophorectomy (OVX), hypertension, or both, and hemodynamic stress in 7-week-old female Sprague-Dawley rats. They were then given hormone-replacement therapy with 17beta-estradiol or an angiotensin II type 1 receptor blocker (ARB). The effects of estradiol, angiotensin II type 1 receptor blocker, or both on cultured endothelial cells were also examined.

RESULTS

The number of anomalously shaped endothelial cells was higher in OVX than hypertensive rats (P < 0.05). Rats subjected to hypertension and OVX exhibited a marked increase in the incidence of saccular cerebral aneurysms. Estradiol or angiotensin II type 1 receptor blocker treatment reduced this incidence (P < 0.05). The endothelial nitric oxide synthase (eNOS) mRNA level in the intracranial artery of OVX and hypertensive and OVX rats was low (P < 0.05). Immunohistochemically, the expression of eNOS and estrogen receptor alpha (ERalpha) in the vascular wall of hypertensive and OVX rats was decreased; angiotensin II and the nicotinamide adenine dinucleotide phosphate oxidase subunits nicotinamide adenine dinucleotide phosphate oxidase 4 and p22phox were strongly expressed in cerebral aneurysms. In the absence of estradiol, eNOS was downregulated and nicotinamide adenine dinucleotide phosphate oxidase expression was increased in endothelial cells; angiotensin II augmented these phenomena. The regulation of eNOS was mediated by ERalpha. These results suggest that estrogen deficiency induces endothelial dysfunction and reactive oxygen species generation, triggering endothelial damage that leads to cerebral aneurysms and that hypertension is an additional risk factor.

CONCLUSION

A therapy targeted at the endothelium and management of hypertension may help to prevent cerebral aneurysms.

Molecular mechanisms responsible for the atheroprotective effects of laminar shear stress

The endothelium lining the inner surface of blood vessels of the cardiovascular system is constantly exposed to hemodynamic shear stress. The interaction between endothelial cells and hemodynamic shear stress has critical implications for atherosclerosis. Regions of arterial narrowing, curvatures, and bifurcations are especially susceptible to atherosclerotic lesion formation. In such areas, endothelial cells experience low, or oscillatory, shear stress. Corresponding changes in endothelial cell structure and function make them susceptible to the initiation and development of atherosclerosis. In contrast, blood flow with high laminar shear stress activates signal transductions as well as gene and protein expressions that play important roles in vascular homeostasis. In response to laminar shear stress, the release of vasoactive substances such as nitric oxide and prostacyclin decreases permeability to plasma lipoproteins as well as the adhesion of leukocytes, and inhibits smooth muscle cell proliferation and migration. In summary, different flow patterns directly determine endothelial cell morphology, metabolism, and inflammatory phenotype through signal transduction and gene and protein expression. Thus, high laminar shear stress plays a key role in the prevention of atherosclerosis through its regulation of vascular tone and long-term maintenance of the integrity and function of endothelial cells.

Photo-initiated grafting of gelatin/N-maleic acyl-chitosan to enhance endothelial cell adhesion, proliferation and function on PLA surface

Vascular graft surface properties significantly affect adhesion, growth and function of endothelial cells (ECs). The bulk degradation property of poly(lactic acid) (PLA) makes it possible for it to be replaced by cellular materials and PLA is desirable as a scaffold material for vascular grafts. However, PLA has an unfavorable surface property for EC adhesion and proliferation due to the lack of a selective cell adhesion motif. Photo-initiated surface-grafting polymerization is a promising method for immobilizing certain biomacromolecules on material surfaces without compromising bulk properties. N-Maleic acyl-chitosan (NMCS) is a novel biocompatible amphiphilic derivative of chitosan with double bonds and can be initiated by ultraviolet light. In this study, gelatin was complexed with NMCS via hydrophobic interaction, and gel/NMCS complex thus formed was then grafted on the PLA surface to improve EC biocompatibility. X-ray photoelectron and Fourier transform infrared spectroscopy, and water contact angle measurement confirmed immobilization of the gel/NMCS complex on PLA surface. Moreover, the gel/NMCS modified PLA enhanced human umbilical vein endothelial cell (HUVEC) spreading and flattening, and promoted the expression of more structured CD31 and vWF compared to unmodified PLA film. Compared to the unmodified PLA surface, the HUVECs on the modified PLA surface had elevated uptake of acetylated low-density lipoprotein, and maintained the ability to modulate metabolic activity upon exposure to shear stress at 5dyncm(-2) by up-regulating nitric oxide and prostacyclin production. Cell retention was 1.6 times higher on the gel/NMCS-PLA surface, demonstrating its improved potential for hemocompatibility. These results indicate that photo-initiated surface-grafting of the biomimetic gel/NMCS complex is an effective method to modify material surfaces as vascular grafts.

Activation of the prostaglandin system in response to sleep loss in healthy humans: potential mediator of increased spontaneous pain

Insufficient duration of sleep is a highly prevalent behavioral pattern in society that has been shown to cause an increase in spontaneous pain and sensitivity to noxious stimuli. Prostaglandins (PGs), in particular PGE2, are key mediators of inflammation and pain, and we investigated whether PGE2 is a potential mediator in sleep-loss-induced changes in nociceptive processing. Twenty-four participants (7 females, age 35.1+/-7.1 years) stayed for 7 days in the Clinical Research Center. After two baseline days, participants were randomly assigned to either 3 days of 88 h of sleep deprivation (TSD, N=15) or 8h of sleep per night (N=9), followed by a night of recovery sleep. Participants rated the intensity of various pain-related symptoms every 2h across waking periods on computerized visual analog scales. PGE2 was measured in 24-h-urine collections during baseline and third sleep deprivation day. Spontaneous pain, including headache, muscle pain, stomach pain, generalized body pain, and physical discomfort significantly increased by 5-14 units on a 100-unit scale during TSD, compared to the sleep condition. Urinary PGE2 metabolite significantly increased by about 30% in TSD over sleep condition. TSD-induced increase in spontaneous pain, in particular headache and muscle pain, was significantly correlated with increase in PGE2 metabolite. Activation of the PGE2 system appears to be a potential mediator of increased spontaneous pain in response to insufficient sleep.

SU-8 force sensing pillar arrays for biological measurements

The generation and sensation of mechanical force plays a role in many dynamic biological processes, including touch sensation. This paper presents a two-axis micro strain gauge force sensor constructed from multiple layers of SU-8 and metal on quartz substrates. The sensor was designed to meet requirements for measuring tactile sensitivity and interaction forces exerted during locomotion by small organisms such as the nematode Caenorhabditis elegans. The device is transparent and compatible with light microscopes, allowing behavioral experiments to be combined with quantitative force measurements. For the first time, we have characterized the scale of interaction forces generated in wild-type C. elegans in probing and responding to their environment during locomotion. The device features sub-microN force resolution from 1 Hz to 1 kHz, >25 microN range, kHz acquisition rates and biocompatibility.

A biocompatible endothelial cell delivery system for in vitro tissue engineering

Engineering solid tissues, including cardiac muscle, requires the inclusion of a microvasculature. Prevascularization in vitro will likely be dependent upon coculturing parenchymal cells with vascular cells, on a matrix that is sufficiently porous to allow microvessel formation. In this study, we examined the behavior and function of endothelial cells on a highly porous elastomeric 3D poly(glycerol sebacate) (PGS) scaffold, to provide a flexible and biocompatible endothelial cell delivery system for developing cardiac engineered tissues with neovascularization potential. Both static and perfusion cell seeding methods were used, and the effects of surface treatment of the scaffold with various extracellular matrix components were examined. Endothelial cell adhesion and phenotype on the PGS scaffold under various flow conditions were also determined. Surface coating with laminin markedly improved the endothelial cell adhesion, survival, and proliferation. The anticoagulant phenotype of adhered endothelial cells was further regulated by the application of flow through regulation of nitric oxide expression. By providing a highly porous scaffolding that contains endothelium with anticoagulant properties, the endothelial cell-seeded PGS scaffold could provide a new basis for subsequent coculture studies with various cell types to develop complex engineered tissue constructs with vascularization capacity.

Modelling in congenital heart disease. Art or science?

Despite the advances in imaging modalities and surgical techniques, the management of adults with congenital heart disease (ACHD) over the years has remained largely empirical rather than evidence-based. Animal models have been difficult to develop and very costly, while clinical trials are difficult to design and perform in ACHD, leaving gaps in our understanding of the pathophysiology and treatment of congenital heart disease. Disease modelling, both hypothetical and patient-specific, provides an alternative solution to many of these problems. Advances in cardiovascular imaging and diagnostics have led to the easy acquisition of large quantities of structural and functional information, which cannot be handled "intuitively". Computational modelling introduces mathematical rigour in the analysis and utilisation of these data by quantitative simulation and testing of clinically relevant hypotheses through experimentally validated models. Close multidisciplinary collaboration between bioengineers and clinicians is essential for transforming data and images derived from models of disease into clinically useful information.

Review: Vasoconstrictors for the treatment of portal hypertension

Vasoconstrictors have long been used in an attempt to mitigate the effects of portal hypertension. In this review, we discuss the current understanding of portal hypertension and the use of vasoconstrictors in the management of its sequlae, including variceal hemorrhage, hepatorenal syndrome, and paracentesis-induced circulatory dysfunction. Experimental and clinical evidence for the use of vasoconstrictors is considered, and several exciting recent developments are reviewed.

Induction of Prostacyclin by Steady Laminar Shear Stress Suppresses Tumor Necrosis Factor-α Biosynthesis via Heme Oxygenase-1 in Human Endothelial Cells

Cyclooxygenase (COX)-2 is among the endothelial genes upregulated by uniform laminar shear stress (LSS), characteristically associated with atherosclerotic lesion-protected areas. We have addressed whether the induction of COX-2–dependent prostanoids in endothelial cells by LSS plays a role in restraining endothelial tumor necrosis factor (TNF)-α generation, a proatherogenic cytokine, through the induction of heme oxygenase-1 (HO)-1, an antioxidant enzyme. In human umbilical vein endothelial cells (HUVECs) exposed to steady LSS of 10 dyn/cm 2 for 6 hours, COX-2 protein was significantly induced, whereas COX-1 and the downstream synthases were not significantly modulated. This was associated with significant ( P <0.05) increase of 6-keto-prostaglandin (PG)F 1α (the hydrolysis product of prostacyclin), PGE 2 , and PGD 2 . In contrast, TNF-α released in the medium in 6 hours (3633±882 pg) or detected in cells lysates (1091±270 pg) was significantly ( P <0.05) reduced versus static condition (9100±2158 and 2208±300 pg, respectively). Coincident induction of HO-1 was detected. The finding that LSS-dependent reduction of TNF-α generation and HO-1 induction were abrogated by the selective inhibitor of COX-2 NS-398, the nonselective COX inhibitor aspirin, or the specific prostacyclin receptor (IP) antagonist RO3244794 illuminates the central role played by LSS-induced COX-2–dependent prostacyclin in restraining endothelial inflammation. Carbacyclin, an agonist of IP, induced HO-1. Similarly to inhibition of prostacyclin biosynthesis or activity, the novel imidazole-based HO-1 inhibitor QC15 reversed TNF-α reduction by LSS. These findings suggest that inhibition of COX-2–dependent prostacyclin might contribute to acceleration of atherogenesis in patients taking traditional nonsteroidal antiinflammatory drugs (NSAIDs) and NSAIDs selective for COX-2 through downregulation of HO-1, which halts TNF-α generation in human endothelial cells.

Differential effects of immunosuppressive drugs on COX-2 activity in vitro and in kidney transplant patients in vivo

BACKGROUND

It was hypothesized that calcineurin inhibitors suppress vascular cyclooxygenase (COX)-2 and exert a reciprocal influence on in vivo prostacyclin and thromboxane. This could contribute to cardiovascular morbidity in transplanted patients.

METHODS

The ability of immunosuppressives to suppress vascular COX-2 expression in vitro was studied in cultured human vascular smooth muscle cells. Blood and urine samples were collected from 28 renal transplant patients before and 2, 4 and 6 h after intake of immunosuppressives and from 11 controls. ELISA was used to measure (1) plasma 6-keto-PGF1alpha and TxB2; (2) urine excretion of PGI-M and TxB(2); (3) 6-keto-PGF1alpha in the whole-blood COX-2 assay; and (4) TxB2 in the whole-blood COX-1 assay. Platelet aggregation was measured optically.

RESULTS

COX-2 in cultured vascular smooth muscle cells was suppressed by cyclosporine A (CsA); tacrolimus and rapamycin had no effect. Human renal arteries and vascular smooth muscle expressed calcineurin Abeta and Agamma isoforms. CsA had no effect on plasma 6-keto-PGF1alpha, whole-blood COX-2 activity or PGI-M urine excretion; after rapamycin intake, the former two increased. Plasma TxB2 did not change after drug intake. TxB2 in the COX-1 assay and urine excretion of TxB2 was significantly lower in tacrolimus- and rapamycin-treated patients compared to the CsA group. Platelet aggregation was increased significantly in the CsA group.

CONCLUSIONS

Although CsA suppressed COX-2 in cultured vascular smooth muscle cells, systemic prostacyclin was not suppressed by either CsA or tacrolimus in vivo. Rapamycin and tacrolimus may actively suppress platelet and renal thromboxane formation. Differential changes in prostanoids may have implications for long-term cardiovascular hazard in patients treated with immunosuppressives.

Endothelial dysfunction in mice with streptozotocin-induced type 1 diabetes is opposed by compensatory overexpression of cyclooxygenase-2 in the vasculature

Cardiovascular complications of diabetes result from endothelial dysfunction secondary to persistent hyperglycemia. We investigated potential compensatory mechanisms in the vasculature that oppose endothelial dysfunction in diabetes. BALB/c mice were treated with streptozotocin (STZ) to induce type 1 diabetes (T1D). In mesenteric vascular beds (MVBs), isolated ex vivo from mice treated with STZ for 1 wk, dose-dependent vasorelaxation to acetylcholine (ACh) or sodium nitroprusside was comparable with that in age-matched control mice (CTRL). By contrast, MVBs from mice treated with STZ for 8 wk had severely impaired vasodilator responses to ACh consistent with endothelial dysfunction. Pretreatment of MVBs from CTRL mice with nitric oxide synthase inhibitor nearly abolished vasodilation to ACh. In MVB from 1-wk STZ-treated mice, vasodilation to ACh was only partially impaired by L-N(omega)-arginine methyl ester. Thus, vasculature of mice with T1D may have compensatory nitric oxide-independent mechanisms to augment vasodilation to ACh and oppose endothelial dysfunction. Indeed, pretreatment of MVBs isolated from 1-wk STZ-treated mice with NS-398 [selective cyclooxygenase (COX)-2 inhibitor] unmasked endothelial dysfunction not evident in CTRL mice pretreated without or with NS-398. Expression of COX-2 in MVBs, aortic endothelial cells, and aortic vascular smooth muscle cells from STZ-treated mice was significantly increased (vs. CTRL). Moreover, concentrations of the COX-2-dependent vasodilator 6-keto-prostaglandin F-1alpha was elevated in conditioned media from aorta of STZ-treated mice. We conclude that endothelial dysfunction in a mouse model of T1D is opposed by compensatory up-regulation of COX-2 expression and activity in the vasculature that may be relevant to developing novel therapeutic strategies for diabetes and its cardiovascular complications.

Cyclooxygenase-2–Derived Prostaglandin F 2α Mediates Endothelium-Dependent Contractions in the Aortae of Hamsters With Increased Impact During Aging

Hypertension and vascular dysfunction result in the increased release of endothelium-derived contracting factors (EDCFs), whose identity is poorly defined. We tested the hypothesis that endothelial cyclooxygenase (COX)-2 can generate EDCFs and identified the possible EDCF candidate. Changes in isometric tension of aortae of young and aged hamsters were recorded on myograph. Real-time changes in intracellular calcium concentrations ([Ca 2+ ] i ) in native aortic endothelial cells were measured by imaging. Endothelium-dependent contractions were triggered by acetylcholine (ACh) after inhibition of nitric oxide production and they were abolished by COX-2 but not COX-1 inhibitors or by thromboxane–prostanoid receptor antagonists. 2-Aminoethoxydiphenyl borate (cation channel blocker) eliminated endothelium-dependent contractions and ACh-stimulated rises in endothelial cell [Ca 2+ ] i . RT-PCR and Western blotting showed COX-2 expression mainly in the endothelium. Enzyme immunoassay and high-performance liquid chromatography-coupled mass spectrometry showed release of prostaglandin (PG)F 2α and prostacyclin (PGI 2 ) increased by ACh; only PGF 2α caused contraction at relevant concentrations. COX-2 expression, ACh-stimulated contractions, and vascular sensitivity to PGF 2α were augmented in aortae from aged hamsters. Human renal arteries also showed thromboxane–prostanoid receptor–mediated ACh- or PGF 2α -induced contractions and COX-2–dependent release of PGF 2α . The present study demonstrates that PGF 2α , derived from COX-2, which is localized primarily in the endothelium, is the most likely EDCF underlying endothelium-dependent, thromboxane–prostanoid receptor–mediated contractions to ACh in hamster aortae. These contractions involved increases in endothelial cell [Ca 2+ ] i . The results support a critical role of COX-2 in endothelium-dependent contractions in this species with an increased importance during aging and, possibly, a similar relevance in humans.

Novel signaling pathways promote a paracrine wave of prostacyclin-induced vascular smooth muscle differentiation

The important athero-protective role of prostacyclin is becoming increasingly evident as recent studies have revealed adverse cardiovascular effects in mice lacking the prostacyclin receptor, in patients taking selective COX-2 inhibitors, and in patients in the presence of a dysfunctional prostacyclin receptor genetic variant. We have recently reported that this protective mechanism includes the promotion of a quiescent differentiated phenotype in human vascular smooth muscle cells (VSMC). Herein, we address the intriguing question of how localized endothelial release of the very unstable eicosanoid, prostacyclin, exerts a profound effect on the vascular media, often 30 cell layers thick. We report a novel PKA-, Akt-1- and ERK1/2-dependent prostacyclin-induced prostacyclin release that appears to play an important role in propagation of the quiescent, differentiated phenotype through adjacent arterial smooth muscle cells in the vascular media. Treating VSMC with the prostacyclin analog iloprost induced differentiation (contractile protein expression and contractile morphology), and also up-regulated COX-2 expression, leading to prostacyclin release by VSMC. This paracrine prostacyclin release, in turn, promoted differentiation and COX-2 induction in neighboring VSMC that were not exposed to iloprost. Using siRNA and pharmacologic inhibitors, we report that this positive feedback mechanism, prostacyclin-induced prostacyclin release, is mediated by cAMP/PKA signaling, ERK1/2 activation, and a novel prostacyclin receptor signaling pathway, inhibition of Akt-1. Furthermore, these pathways appear to be regulated by the prostacyclin receptor independently of one another. We conclude that prevention of de-differentiation and proliferation through a paracrine positive feedback mechanism is a major cardioprotective function of prostacyclin.

Vascular endothelial responses to altered shear stress: pathologic implications for atherosclerosis

Atherosclerosis preferentially develops at branches and curvatures of the arterial tree, where blood flow is disturbed from a laminar pattern, and wall shear stress is non-uniform and has an irregular distribution. Vascular endothelial cells (ECs), which form an interface between the flowing blood and the vessel wall, are exposed to blood flow-induced shear stress. There is increasing evidence suggesting that laminar blood flow and sustained high shear stress modulate the expression of EC genes and proteins that function to protect against atherosclerosis; in contrast, disturbed blood flow and the associated low and reciprocating shear stress upregulate proatherosclerotic genes and proteins that promote development of atherosclerosis. Understanding of the effects of shear stress on ECs will provide mechanistic insights into its role in the pathogenesis of atherosclerosis. The aim of this review article is to summarize current findings on the effects of shear stress on ECs, in terms of their signal transduction, gene expression, structure, and function. These endothelial cellular responses have important relevance to understanding the pathophysiological effects of altered shear stress associated with atherosclerosis and thrombosis and their complications.

Molecular beacons can assess changes in expression and 3'-polyadenylation of human eNOS mRNA

The endothelium plays an essential role in maintaining vascular homeostasis, and it fulfills this role by modulating intracellular signaling and gene expression in response to chemical and mechanical stimuli. Assessing changes in endothelial gene expression is essential to understanding how physiological and pathophysiological processes modulate vascular homeostasis. Here we describe the use of molecular beacons to rapidly and quantitatively assess expression and 3'-polyadenylation of a gene that is important for vascular homeostasis, endothelial nitric oxide synthase (eNOS). Single- and dual-fluorescence resonance energy transfer (FRET) molecular beacon hybridization assays were developed to measure changes in mRNA levels and 3'-polyadenylation, respectively, in primary human endothelial cell cultures subjected to laminar shear stress or statin treatment. Optimized beacon hybridization assays took approximately 15 min to perform, and eNOS mRNA levels were validated by quantitative real-time RT-PCR. Competitive inhibition assays and posttranscriptional silencing of eNOS expression were used to verify the specificity of molecular beacon fluorescence. Finally, the dual-FRET method was used to assess eNOS polyadenylation in tissues isolated from mice subjected to exercise training. These data demonstrate that molecular beacons can be used to rapidly and efficiently measure endothelial gene expression and 3'-polyadenylation. This approach could easily be adapted for studies of other endothelial genes and has promise for applications in live endothelial cells.

Endothelial dysfunction in African-Americans

The journey of atherosclerosis begins with endothelial dysfunction and culminates into its most fearful destination producing ischemia, myocardial infarction and death. The excess cardiovascular disease morbidity and mortality in African-Americans is one of the major public health problems. In this review, we discuss vascular endothelial dysfunction as a key element for excess cardiovascular disease burden in this target population. It can be logical window of future atherosclerotic outcomes, and further efforts should be made to detect it at the earliest in African American individuals even if they are appearing healthy as the therapeutic interventions if instituted early, might prevent the subsequent cardiac events.

Nonlinear optical microscopy reveals invading endothelial cells anisotropically alter three-dimensional collagen matrices

The interactions between endothelial cells (ECs) and the extracellular matrix (ECM) are fundamental in mediating various steps of angiogenesis, including cell adhesion, migration and sprout formation. Here, we used a noninvasive and non-destructive nonlinear optical microscopy (NLOM) technique to optically image endothelial sprouting morphogenesis in three-dimensional (3D) collagen matrices. We simultaneously captured signals from collagen fibers and endothelial cells using second harmonic generation (SHG) and two-photon excited fluorescence (TPF), respectively. Dynamic 3D imaging revealed EC interactions with collagen fibers along with quantifiable alterations in collagen matrix density elicited by EC movement through and morphogenesis within the matrix. Specifically, we observed increased collagen density in the area between bifurcation points of sprouting structures and anisotropic increases in collagen density around the perimeter of lumenal structures, but not advancing sprout tips. Proteinase inhibition studies revealed membrane-associated matrix metalloproteinase were utilized for sprout advancement and lumen expansion. Rho-associated kinase (p160ROCK) inhibition demonstrated that the generation of cell tension increased collagen matrix alterations. This study followed sprouting ECs within a 3D matrix and revealed that the advancing structures recognize and significantly alter their extracellular environment at the periphery of lumens as they progress.

Role of oxidative stress in adaptive responses in special reference to atherogenesis

Although lipid peroxidation products have been implicated in oxidative stress-related diseases, pretreatment of cells with such compounds at sublethal concentrations shows significant cytoprotective effects against forthcoming oxidative stress. The adaptive response induced by 4-hydroxynonenal (HNE) is critically mediated by gene expression of cytoprotective proteins via NF-E2-related factor 2/Kelch-like-ECH-associated protein 1 (Nrf2/Keap-1) pathway. The physical or mechanical stimuli such as shear stress also impose adaptive responses by inducing gene expression. Laminar shear stress, anti-atherogenic shear stress activates Nrf2/Keap-1 pathway. The transcriptome analysis using DNA microarray reveal high similarity in gene expression profiles of cells treated with HNE and laminar shear stress, providing insight into molecular mechanisms. These findings suggest a general hormetic effect of diverse stimuli in cell cultures and may lead to a reappraisal of the eventual role of reactive oxygen species and lipid peroxidation in organisms.

Nitric oxide and cardiovascular effects: new insights in the role of nitric oxide for the management of osteoarthritis

Nitric oxide (NO) is an important mediator in both health and disease. In addition to its effects on vascular tone and platelet function, it plays roles in inflammation and pain perception that may be of relevance in osteoarthritis. Many patients with osteoarthritis take nonsteroidal anti-inflammatory drugs (NSAIDs) long term for pain control. Over recent years concern has been raised about the possible cardiovascular side effects of NSAIDs. The reasons for this possible increased cardiovascular risk with NSAIDs are not yet entirely clear, although changes in blood pressure, renal salt handling and platelet function may contribute. Recently, drugs that chemically link a NSAID with a NO donating moiety (cyclo-oxygenase-inhibiting NO-donating drugs [CINODs]) were developed. NO is an important mediator of endothelial function, acting as a vasodilator and an inhibitor of platelet aggregation, and having anti-inflammatory properties. The potential benefits of CINODs include the combination of effective analgesic and anti-inflammatory actions with NO release, which might counterbalance any adverse cardiovascular effects of NSAIDs. Effects of CINODs in animal studies include inhibition of vasopressor responses, blood pressure reduction in hypertensive rats and inhibition of platelet aggregation. CINODs may also reduce ischemic damage to compromised myocardial tissue. In addition, endothelial dysfunction is a recognized feature of inflammatory arthritides, and therefore a drug that might provide slow release of NO to the vasculature while treating pain is an attractive prospect in these conditions. Further studies of the effects of CINODs in humans are required, but these agents represent a potential exciting advance in the management of osteoarthritis.

Critical role of COX-1 in prostacyclin production by human endothelial cells under modification of hydroperoxide tone

We aimed at evaluating the relative contribution of cyclooxygenase (COX) -1 and COX-2 to the synthesis of prostacyclin in endothelial cells under static conditions in the presence or absence of exogenous arachidonic acid and/or altered intracellular redox balance. Selective inhibitors of either COX-1 (SC560 and FR122047) or COX-2 (SC236) concentration dependently (1-300 nM) reduced basal and interleukin (IL) -1beta-induced prostacyclin production in human umbilical vein endothelial cells by 70% or more; compound selectivity was confirmed using a whole-blood assay (IC(50) COX-1/COX-2: 13 nM/930 nM for SC-560; 9 microM/457 nM for SC-236). The observed concomitant formation of isoprostane appeared to be associated with COX enzyme activity, while formation of COX-1/COX-2 heterodimers was detected by immunoprecipitation. In the presence of arachidonic acid and 12-hydroperoxy-eicosatetraenoic acid, either exogenous or provided by platelet activation, or after glutathione depletion, COX-1 inhibition but not COX-2 inhibition concentration dependently decreased prostacyclin production. Both isoforms appear to contribute to basal prostacyclin production by endothelial cells, with COX-2 providing the hydroperoxide tone required for COX-1 activity. Conversely, in the case of intracellular glutathione depletion or enhanced availability of arachidonic acid and hydroperoxides, selective COX-2 inhibition did not significantly affect the production of endothelial prostacyclin. These findings contribute to a better understanding of the effects of cyclooxygenase inhibitors on prostacyclin production.

Nonsteroidal anti-inflammatory drugs: adverse effects and their prevention

OBJECTIVES

To discuss nonsteroidal anti-inflammatory drugs (NSAIDs), their history, development, mode of action, toxicities, strategies for the prevention of toxicity, and future developments.

METHODS

Medline search for articles published up to 2007, using the keywords acetylsalicylic acid, aspirin, NSAIDs, cyclooxygenase 2, adverse effects, ulcer, and cardiovascular.

RESULTS

NSAIDs are 1 of the oldest, most successful drugs known to modern medicine. They are effective for alleviating pain, fever, and inflammation by inhibiting prostaglandin synthesis. Aspirin, by its irreversible inhibition of blood platelet function, is also effective in the prevention of cardiovascular disease. NSAIDs may cause gastrointestinal ulcers, serious cardiovascular events, hypertension, acute renal failure, and worsening of preexisting heart failure. These adverse effects may be prevented by limiting NSAID dosage and duration and by performing individual risk assessments and treating patients accordingly. Those at risk for gastroduodenal ulcers may be treated with concomitant proton-pump inhibitors, misoprostol and/or COX-2 selective NSAIDs. Those at risk for cardiovascular events may be treated with naproxen and a proton-pump inhibitor or misoprostol, but should best avoid NSAID use altogether.

CONCLUSIONS

Physicians should always prescribe the lowest effective dose for the shortest possible time and must take into account both the gastrointestinal and the cardiovascular risks of individual patients when prescribing NSAIDs.

PECAM-1 is a critical mediator of atherosclerosis

Atherosclerosis is a chronic inflammatory disease of large arteries in which lesion development preferentially occurs at vessel sites exposed to rapid changes in flow. We have previously shown that platelet endothelial cell adhesion molecule (PECAM-1), a surface receptor of the immunoglobulin superfamily, is involved in mechanosensing of rapid changes in flow. We wondered whether apolipoprotein E deficient (ApoE(-/-)) mice, predisposed to development of atheromas, would be protected from atherosclerosis by deficiency in PECAM-1. Using double knockout (DKO) mice for both PECAM-1 and ApoE (ApoE(-/-)/PECAM-1(-/-)) we found a significant reduction of sudanophilic lesions in their aortae compared to single knockout (SKO) (ApoE(-/-)/PECAM-1(+/+)) mice maintained on a high-fat Western diet. Immunostaining of aortic sinus cross sections demonstrated significantly lower ICAM-1 expression in DKO lesions compared with SKO lesions, and en face preparations of vessel regions subjected to disturbed and laminar flow showed less disruption of junctional connexin 43 in DKO than in SKO mice. Thus, PECAM-1 deficiency reduced the extent of lesions at the aortic arch and the aortic sinus, and lowered atherogenic indices. These results suggest that PECAM-1 is an important factor in the atherogenic changes seen in the ApoE-deficient mouse model and thus should be considered as a potential target for protection against atherosclerosis.

The role of cellular adaptation to mechanical forces in atherosclerosis

Atherosclerosis is a chronic inflammatory disease that originates at regions of arteries exposed to disturbances in fluid flow and results in progressive plaque formation in those areas. Recent work on cellular responses to flow has identified potential mechanosensors and pathways that may influence disease progression. These results led us to hypothesize that the same mechanisms that mediate adaptive responses in the vasculature become maladaptive at sites of disturbed flow. Subsequent changes in gene expression and matrix remodeling help to entrain these inflammatory pathways. These events synergize with systemic risk factors such as hyperlipidemia, smoking, and diabetes, leading to disease progression.

Segment-specific genetic effects on carotid intima-media thickness: the Northern Manhattan study

BACKGROUND AND PURPOSE

Carotid intima-media thickness (IMT) is a surrogate marker of subclinical atherosclerosis and a strong predictor of stroke and myocardial infarction. The object of this study was to determine the association between carotid IMT and 702 single nucleotide polymorphisms in 145 genes.

METHODS

B-mode carotid ultrasound was performed among 408 Hispanics from the Northern Manhattan Study. The common carotid artery IMT and bifurcation IMT were phenotypes of interest. Genetic effects were evaluated by the multivariate regression model adjusting for traditional vascular risk factors. For each individual, we calculated a gene risk score (GRS) defined as the total number of the significant single nucleotide polymorphisms in different genes. Subjects were then divided into 3 GRS categories using the 2 cutoff points: mean GRS +/-1 SD.

RESULTS

We identified 6 significant single nucleotide polymorphisms in 6 genes for common carotid artery IMT and 7 single nucleotide polymorphisms in 7 genes for bifurcation IMT using the probability value of 0.005 as the significant level. There were no common significant genes for both phenotypes. The most significant genes were the tissue plasminogen activator (P=0.0005 for common carotid artery IMT) and matrix metallopeptidase-12 genes (P=0.0004 for bifurcation IMT). Haplotype analysis did not yield a more significant result. Subjects with GRS >or=9 had significantly increased IMT than those with GRS <or=5 (P<0.001). GRS was an independent predictor of both common carotid artery IMT (P=2.3x10(-9)) and bifurcation MT (P=7.2x10(-8)).

CONCLUSIONS

Multiple genes contributed to the variation in carotid IMT. IMT in different carotid segments may be regulated by different sets of susceptibility genes.

Antiplatelet drugs: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition)

This article about currently available antiplatelet drugs is part of the Antithrombotic and Thrombolytic Therapy: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). It describes the mechanism of action, pharmacokinetics, and pharmacodynamics of aspirin, reversible cyclooxygenase inhibitors, thienopyridines, and integrin alphaIIbbeta3 receptor antagonists. The relationships among dose, efficacy, and safety are thoroughly discussed, with a mechanistic overview of randomized clinical trials. The article does not provide specific management recommendations; however, it does highlight important practical aspects related to antiplatelet therapy, including the optimal dose of aspirin, the variable balance of benefits and hazards in different clinical settings, and the issue of interindividual variability in response to antiplatelet drugs.

Aneurysm growth occurs at region of low wall shear stress: patient-specific correlation of hemodynamics and growth in a longitudinal study

BACKGROUND AND PURPOSE

Evolution of intracranial aneurysmal disease is known to be related to hemodynamic forces acting on the vessel wall. Low wall shear stress (WSS) has been reported to have a negative effect on endothelial cells normal physiology and may be an important contributor to local remodeling of the arterial wall and to aneurysm growth and rupture.

METHODS

Seven patient-specific models of intracranial aneurysms were constructed using MR angiography data acquired at two different time points (mean 16.4+/-7.4 months between the two time points). Numeric simulations of the flow in the baseline geometries were performed to compute WSS distributions. The lumenal geometries constructed from the two time points were manually coregistered, and the radial displacement of the wall was calculated on a pixel-by-pixel basis. This displacement, corresponding to the local growth of the aneurysm, was compared to the time-averaged wall shear stress (WSS TA) through the cardiac cycle at that location. For statistical analysis, radial displacement was considered to be significant if it was larger than half of the MR pixel resolution (0.3 mm).

RESULTS

Mean WSS TA values obtained for the areas with a displacement smaller and greater than 0.3 mm were 2.55+/-3.6 and 0.76+/-1.5 Pa, respectively (P<0.001). A linear correlation analysis demonstrated a significant relationship between WSS TA and surface displacement (P<0.001).

CONCLUSIONS

These results indicate that aneurysm growth is likely to occur in regions where the endothelial layer lining the vessel wall is exposed to abnormally low wall shear stress.

Prostanoid function and cardiovascular disease

Prostanoids, including prostaglandins (PGs) and thromboxanes (TXs) are synthesized from arachidonic acid by the combined action of cyclooxygenases (COXs) and PG and TX synthases. Finally after their synthesis, prostanoids are quickly released to the extracellular medium exerting their effects upon interaction with prostanoid receptors present in the neighbouring cells. These agents exert important actions in the cardiovascular system, modulating vascular homeostasis and participating in the pathogenesis of vascular diseases as thrombosis and atherosclerosis. Among prostanoids, Tromboxane (TX)A(2), a potent platelet activator and vasoconstrictor and prostacyclin (PGI2), a platelet inhibitor and vasodilator, are the most important in controlling vascular homeostasis. Although multiple studies using pharmacological inhibitors and genetically deficient mice have demonstrated the importance of prostanoid-mediated actions on cardiovascular physiology, further analysis on the prostanoid mediated actions in the vascular system are required to better understand the benefits and risks for the use of COX inhibitors in cardiovascular diseases.

The vessel wall and its interactions

Blood cell interactions with the vessel wall were first documented almost 170 years ago. Modern advances have revealed that leukocyte and platelet interactions with the endothelium are at the nexus of complex, dynamic cellular and molecular networks that, when dysregulated, may lead to pathological inflammation and thrombosis, which are major sources of morbidity and mortality in the Western world. In this review, we relate the history of blood cell interactions with the vasculature, discuss recent progress, and raise some unresolved questions awaiting the field.

Noninvasive methods for determining pulmonary vascular function in children with pulmonary arterial hypertension: application of a mechanical oscillator model

OBJECTIVE

Noninvasive diagnostics for pulmonary arterial hypertension (PAH) have traditionally sought to predict main pulmonary artery pressure from qualitative or direct quantitative measures of the flow velocity pattern obtained from spectral Doppler ultrasound examination of the main pulmonary artery. A more detailed quantification of flow velocity patterns in the systemic circuit has been obtained by parameterizing the flow trace with a simple dynamic system model. Here, we investigate such a model's utility as a noninvasive predictor of total right heart afterload and right heart function.

DESIGN

Flow velocity and pressure was measured within the main pulmonary artery during right heart catheterization of patients with normal hemodynamics (19 subjects, 20 conditions) and those with PAH undergoing reactivity evaluation (34 patients, 69 conditions). Our model parameters were obtained by least-squares fitting the model velocity to the measured flow velocity.

RESULTS

Five parameter means displayed significant (P < .05) differences between normotensive and hypertensive groups. The model stiffness parameter correlated to actual pulmonary vascular resistance (r = 0.4924), pulmonary vascular stiffness (r = 0.6811), pulmonary flow (r = 0.6963), and stroke work (r = 0.7017), while the model initial displacement parameter had good correlation to stiffness (r = 0.6943) and flow (r = 0.6958).

CONCLUSIONS

As predictors of total right heart afterload (resistance and stiffness) and right ventricle work, the model parameters of stiffness and initial displacement offer more comprehensive measures of the disease state than previous noninvasive methods and may be useful in routine diagnostic monitoring of patients with PAH.

Nitric oxide and cardiovascular and renal effects

Nitric oxide (NO) has multiple protective effects for regulating the cardiovascular and renal systems. The major functions include endothelium-dependent relaxation, anti-inflammatory effects, as well as antihypertrophic and antithrombotic activities. Many of the activities mediated by NO are systematically antagonized by angiotensin-II (Ang II), a vasconstrictor peptide. Studies described in the review below have demonstrated that the balance between NO and Ang II activities rather than the absolute concentration of each molecule determines their effects on the physiology and pathophysiology of the cardiovascular and renal systems. NO donors have been used for years as therapeutic agents for a range of cardiovascular conditions including angina, myocardial infarction and for the reduction of arterial stiffness. An understanding of the mechanisms underlying the effects of these medications will enable the development of novel therapies to balance the effects of NO in the cardiovascular system.

Salicylideneamino-2-thiophenol inhibits inflammatory mediator genes (RANTES, MCP-1, IL-8 and HIF-1alpha) expression induced by tert-butyl hydroperoxide via MAPK pathways in rat peritoneal macrophages

Salicylideneamino-2-thiophenol (Sal) regulated the redox status and the expression of chemokines induced by tert-butyl hydroperoxide (t-BHP). Sal (100 microM) increased reduced/oxidized glutathione (GSH/GSSG) ratios and thiol (SH) levels by 210 and 157%, respectively, and decreased reactive oxygen species (ROS) levels by 60% in t-BHP-treated macrophages. The inductions of regulated upon activation, normal T-cell expressed and secreted (RANTES), monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8) and hypoxia inducible factor-1alpha (HIF-1alpha) by t-BHP (10 microM) were decreased to 250, 80, 80 and 500% by Sal (100 microM), respectively. In the Sal signaling pathway, c-Jun N-terminal kinases (JNK), extracellular signal-regulated kinases (ERK) and p38 signaling protein modulation were decreased by 67, 69 and 119%, respectively, by Sal at 100 microM. Sal (100 microM) also altered cytosol and nuclear NF-kappaB protein expression by 169 and 5%, respectively. Sal also attenuated NF-kappaB nuclear binding activity. Sal thus has a protective effect against t-BHP-induced inflammation and that this, in part, is due to the inhibition of the production of RANTES, MCP-1, IL-8 and HIF-1alpha via the modulation of the NF-kappaB and mitogen-activated protein kinase (MAPK) pathways.

Safety, efficacy and anti-inflammatory activity of rho iso-alpha-acids from hops

A defined mixture of rho iso-alpha-acids (RIAA), a modified hop extract, was evaluated for anti-inflammatory efficacy and safety. RIAA inhibited LPS-stimulated PGE(2) formation with >200-fold selectivity of COX-2 (IC(50)=1.3 microg/ml) over COX-1 (IC(50)>289 microg/ml). This occurred only when RIAA was added prior to, but not post, LPS stimulation. Consistent with this observation, RIAA produced no physiologically relevant, direct inhibition of COX-1 or COX-2 peroxidase activity. This suggests that RIAA inhibits inducible but not constitutive COX-2. In support, we found RIAA showed minimal PGE(2) inhibition (IC(50)=21mug/ml) relative to celecoxib (IC(50)=0.024 microg/ml), aspirin (IC(50)=0.52 microg/ml) or ibuprofen (IC(50)=0.57 microg/ml) in the AGS gastric mucosal model, where COX-1 and -2 are expressed constitutively. Taken together these results predict RIAA may have lower potential for gastrointestinal and cardiovascular toxicity observed with COX enzyme inhibitors. Following confirmation of bioavailable RIAA administered orally, gastrointestinal safety was assessed using the fecal calprotectin biomarker in a 14-day human clinical study; RIAA (900 mg/day) produced no change compared to naproxen (1000 mg/day), which increased fecal calprotectin 200%. Cardiovascular safety was addressed by PGI-M measurements where RIAA (1000 mg) did not reduce PGI-M or affect the urinary PGI-M/TXB(2) ratio. Drug interaction potential was evaluated against six major CYPs; of relevance, RIAA inhibited CYP2C9. Toxicity was assessed in a 21-day oral, mouse subchronic toxicity study where no dose dependent histopathological effects were noted. Clinically, RIAA (1000 mg/day) produced a 54% reduction in WOMAC Global scores in a 6-week, open-label trial of human subjects exhibiting knee osteoarthritis.

Celecoxib and ankylosing spondylitis

It is now over 100 years since the arrival of aspirin and, from the mid-20th Century onwards, we have seen numerous attempts at providing society with safer and more efficacious nonsteroidal drugs. Ironically, while aspirin went from strength to strength with an ever-increasing pharmaceutical profile, new nonsteroidal anti-inflammatory drugs arrived and disappeared with rapid succession. Finally, there appears to have been a breakthrough with the development of the coxibs but concern has recently developed because of potential toxic cardiovascular reactions. Although originally studied in rheumatoid arthritis and degenerative arthropathy, the coxibs have now been investigated in ankylosing spondylitis and efficacy appears to be favorable and, to date, there is little evidence of toxicity, although problems in the nonspondylarthropathic arena may spill over into the seronegative spondylarthritides.

Accumulation of 15-deoxy-delta(12,14)-prostaglandin J2 adduct formation with Keap1 over time: effects on potency for intracellular antioxidant defence induction

The COX (cyclo-oxygenase) pathway generates the reactive lipid electrophile 15d-PGJ2 (15-deoxy-Delta(12,14)-prostaglandin J2), which forms covalent protein adducts that modulate cell signalling pathways. It has been shown that this regulates important biological responses, including protection against oxidative stress, and supports the proposal that 15d-PGJ2 has pharmacological potential. Protective pathways activated by 15d-PGJ2 include those controlling the synthesis of the intracellular antioxidants GSH and the enzyme HO-1 (haem oxygenase-1). The induction of the synthesis of these intracellular antioxidants is, in large part, regulated by covalent modification of Keap1 (Kelchlike erythroid cell-derived protein with 'capn'collar homologyassociated protein 1) by the lipid and the subsequent activation of the EpRE (electrophile-response element). For the first time, we show that the potency of 15d-PGJ2 as a signalling molecule in endothelial cells is significantly enhanced by the accumulation of the covalent adduct with 15d-PGJ2 and endogenous Keap1 over the time of exposure to the prostaglandin. The consequence of this finding is that signalling initiated by electrophilic lipids differs from agonists that do not form covalent adducts with proteins because the constant generation of very lowconcentrations of 15d-PGJ2 can lead to induction of GSH or HO-1. In the course of these studies we also found that a substantial amount (97-99%) of exogenously added 15d-PGJ2 is inactivated in the medium and does not enter the cells to initiate cell signalling. In summary, we propose that the accumulation of covalent adduct formation with signalling proteins provides a mechanism through which endogenous intracellular formation of electrophilic lipids from COX can exert an anti-inflammatory effect in vivo.

The Hydrodynamically Relevant Endothelial Cell Glycocalyx Observed In Vivo Is Absent In Vitro

In recent years, the endothelial cell surface glycocalyx has emerged as a structure of fundamental importance to a broad range of phenomena that determine cardiovascular health and disease. This new understanding of the functional significance of the glycocalyx has been made possible through recently developed experimental techniques using intravital microscopy that are capable of directly probing the glycocalyx in vivo. Using fluorescent microparticle image velocimetry in venules and endothelialized cylindrical collagen microchannels, we show that the hydrodynamically relevant endothelial cell glycocalyx surface layer observed in microvessels in vivo (0.52±0.28 μm thickness), which is a fundamental determinant of the hydrodynamic and mechanical environment at the endothelial cell surface, is absent from human umbilical vein (0.03±0.04 μm thickness) and bovine aortic (0.02±0.04 μm thickness) endothelial cells grown and maintained under standard cell culture conditions in vitro. An endothelial surface–bound glycosaminoglycan layer, not necessarily indicative of but having similar hydrodynamic properties to the endothelial glycocalyx observed in vivo, was detected (0.21±0.27 μm thickness) only after hyaluronan and chondroitin sulfate were added to the cell culture media at hyperphysiological concentrations (0.2 mg/mL perfused for 75 minutes). The implications of this glycocalyx deficiency under standard cell culture conditions in these pervasive in vitro models broadly impact a myriad of studies involving endothelial cell monolayers in which inferences are made that may depend on endothelial cell surface chemistry. In light of these findings, conclusions drawn from such studies in the areas of microvascular permeability, inflammation, mechanotransduction, and atherosclerosis must be carefully reconsidered.

Review: Endothelial dysfunction: A potential tool in gender related cardiovascular disease

The overwhelming importance of distinctive cardiovascular disease profile in women has stimulated enormous efforts to disclose its cause. In this review, we discuss vascular endothelium as a potential phenotypic marker for the genetic difference. As it is a potentially modifiable factor for cardiovascular disease, every effort should be made to detect it, either directly or indirectly, at the earliest in females who are at risk, so that the future cardiovascular events might be prevented.