COX-2, another important player in the nitric oxide-endothelin cross-talk: good news for COX-2 inhibitors?

Impaired microvascular reactivity in patients treated with 5-fluorouracil chemotherapy regimens: Potential role of endothelial dysfunction

Background

5-fluorouracil (5-FU) is the second most common cancer chemotherapy associated with short- and long-term cardiotoxicity. Although the mechanisms mediating these toxicities are not well understood, patients often present with symptoms suggestive of microvascular dysfunction. We tested the hypotheses that patients undergoing cancer treatment with 5-FU based chemotherapy regimens would present with impaired microvascular reactivity and that these findings would be substantiated by decrements in endothelial nitric oxide synthase (eNOS) gene expression in 5-FU treated human coronary artery endothelial cells (HCAEC).

Methods

We first performed a cross-sectional analysis of 30 patients undergoing 5-FU based chemotherapy treatment for cancer (5-FU) and 32 controls (CON) matched for age, sex, body mass index, and prior health history (excluding cancer). Cutaneous microvascular reactivity was evaluated by laser Doppler flowmetry in response to endothelium-dependent (local skin heating; acetylcholine iontophoresis, ACh) and -independent (sodium nitroprusside iontophoresis, SNP) stimuli. In vitro experiments in HCAEC were completed to assess the effects of 5-FU on eNOS gene expression.

Results

5-FU presented with diminished microvascular reactivity following eNOS-dependent local heating compared to CON (P = 0.001). Iontophoresis of the eNOS inhibitor L-NAME failed to alter the heating response in 5-FU (P = 0.95), despite significant reductions in CON (P = 0.03). These findings were corroborated by lower eNOS gene expression in 5-FU treated HCAEC (P < 0.01) compared to control. Peak vasodilation to ACh (P = 0.58) nor SNP (P = 0.39) were different between groups.

Conclusions

The present findings suggest diminished microvascular function along the eNOS-NO vasodilatory pathway in patients with cancer undergoing treatment with 5-FU-based chemotherapy regimens and thus, may provide insight into the underlying mechanisms of 5-FU cardiotoxicity.

Anti-Inflammatory and Anti-oxidative Effects of Puerarin in Postmenopausal Cardioprotection: Roles of Akt and Heme Oxygenase-1

During menopause, the sharp decline in estrogen levels leads to an increased risk of cardiovascular disease in women. The inflammatory response and oxidative stress are reportedly involved in the development of cardiovascular disorders postmenopause. In this study, we evaluated the cardioprotective effects of puerarin, a phytoestrogen derived from the root of Pueraria lobate, and investigated its underlying molecular mechanisms. Puerarin alleviated cytotoxicity and the production of reactive oxygen species (ROS) in lipopolysaccharide (LPS)- and hydrogen peroxide-stimulated H9c2 cardiomyoblasts. Puerarin scavenges free radicals and reduces apoptosis, thereby suppressing NADPH oxidase-1 and Bax activation to attenuate the production of ROS and restore Bcl-2 expression. Additionally, puerarin inhibited the expression of inducible nitric oxide synthase, cyclooxygenase-2, and nitric oxide production and decreased the hypertrophic phenotype under LPS stimulation. Treatment with puerarin reduced the levels of malondialdehyde and restored glutathione levels when facing oxidative stress. Mechanistically, puerarin inhibited both the LPS-induced Toll-like receptor 4/NF-[Formula: see text]B and mitogen-activated protein kinase signaling pathways. Furthermore, it reversed both the LPS-mediated downregulation of Akt activation and heme oxygenase-1 (HO-1) expression. The cardioprotective effects of puerarin were abolished by inhibitors of Akt and HO-1 and the estrogen receptor antagonist fulvestrant (ICI). This indicated that the estrogen receptor mediated by these two molecules plays important roles in conferring the anti-inflammatory and anti-oxidative functions of puerarin. These results demonstrate the therapeutic potential of puerarin for treating heart disease in postmenopausal women through Akt and HO-1 activation.

The Effects of Exercise, Aspirin, and Celecoxib in an Atherogenic Environment

INTRODUCTION

Optimal vascular function is a hallmark of cardiovascular health. Specifically, the balance of vasoconstricting and vasodilating substances is recognized as a marker of vascular health. One of the greatest challenges to vascular health and vasodilatory balance is tumor necrosis factor alpha (TNFα)-mediated inflammation. Uncovering effective strategies that maintain a vascular environment that is more vasodilatory and antithrombotic in the face of an inflammatory challenge is favorable.

PURPOSE

To test the ability of various antithrombotic and provasodilatory treatments, as well as combinations thereof, to prevent unfavorable changes in markers of endothelial dysfunction in human umbilical vein endothelial cells when presented with an inflammatory challenge.

METHODS

Human umbilical vein endothelial cells were pretreated with exercise-like levels of laminar shear stress (LSS), aspirin, celecoxib, and their combination before a TNFα challenge. Western blot analysis as well as colorimetric assays were used to determine levels of endothelial nitric oxide synthase (eNOS) and prostacyclin (6-keto PGF1α)/thromboxane (TXB2) metabolite ratio, respectively.

RESULTS

Neither aspirin nor celecoxib were effective in preventing TNFα-induced reduction in eNOS. Further, aspirin was unable to maintain baseline levels of prostacyclin/thromboxane ratio in the face of the inflammatory challenge. Laminar shear stress, aspirin/LSS combination, and celecoxib/LSS combination were all able to prevent TNFα-induced alterations in eNOS levels and prostacyclin/thromboxane ratio.

CONCLUSIONS

Effective strategies to maintain a healthy endothelium, and therefore resistance vessel health, need to include exercise-levels of shear stress to be effective.

Transition in the mechanism of flow-mediated dilation with aging and development of coronary artery disease

In microvessels of patients with coronary artery disease (CAD), flow-mediated dilation (FMD) is largely dependent upon the endothelium-derived hyperpolarizing factor H₂O₂. The goal of this study is to examine the influence of age and presence or absence of disease on the mechanism of FMD. Human coronary or adipose arterioles (~150 µm diameter) were prepared for videomicroscopy. The effect of inhibiting COX [indomethacin (Indo) or NOS (L-NAME), eliminating H₂O₂ (polyethylene glycol-catalase (PEG-CAT)] or targeting a reduction in mitochondrial ROS with scavengers/inhibitors [Vitamin E (_mtVitamin E); phenylboronic acid (_mtPBA)] was determined in children aged 0-18 years; young adults 19-55 years; older adults >55 years without CAD, and similarly aged adults with CAD. Indo eliminated FMD in children and reduced FMD in younger adults. This response was mediated mainly by PGI₂, as the prostacyclin-synthase-inhibitor trans-2-phenyl cyclopropylamine reduced FMD in children and young adults. L-NAME attenuated dilation in children and younger adults and eliminated FMD in older adults without CAD, but had no effect on vessels from those with CAD, where mitochondria-derived H₂O₂ was the primary mediator. The magnitude of dilation was reduced in older compared to younger adults independent of CAD. Exogenous treatment with a sub-dilator dose of NO blocked FMD in vessels from subjects with CAD, while prolonged inhibition of NOS in young adults resulted in a phenotype similar to that observed in disease. The mediator of coronary arteriolar FMD evolves throughout life from prostacyclin in youth, to NO in adulthood. With the onset of CAD, NO-inhibitable release of H₂O₂ emerges as the exclusive mediator of FMD. These findings have implications for use of pharmacological agents, such as nonsteroidal anti-inflammatory agents in children and the role of microvascular endothelium in cardiovascular health.

Endothelial Dysfunction in Rheumatoid Arthritis: Mechanistic Insights and Correlation with Circulating Markers of Systemic Inflammation

Objectives

To determine mechanisms involved in endothelial dysfunction (ED) during the course of arthritis and to investigate the link between cytokines, chemokines and osteoprotegerin.

Approach and Results

Experiments were conducted on aortic rings at day 4 (preclinical), day 11 (onset of disease), day 33 (acute disease) and day 90 (chronic disease) after adjuvant-induced arthritis (AIA) in Lewis rats. At day 4, the unique vascular abnormality was a reduced norepinephrine-induced constriction. At day 11, endothelial function assessed by the relaxation to acetylcholine was normal despite increased cyclo-oxygenase-2 activity (COX-2) and overproduction of superoxide anions that was compensated by increased nitric oxide synthase (NOS) activity. At day 33, ED apparition coincides with the normalization of NOS activity. At day 90, ED was only observed in rats with a persisting imbalance between endothelial NOS and COX-2 pathways and higher plasma levels of IL-1β and TNFα. Plasma levels of IL-1β, TNFα and MIP-1α negatively correlated with Ach-induced relaxation throughout the course of AIA.

Conclusions

Our data identified increased endothelial NOS activity as an important compensatory response that opposes the ED in the early arthritis. Thereafter, a cross-talk between endothelial COX-2/NOS pathways appears as an important element for the occurrence of ED. Our results encourage determining the clinical value of IL-1β, TNFα and MIP-1α as biomarkers of ED in RA.

Endothelin ETA receptor/lipid peroxides/COX-2/TGF-β1 signalling underlies aggravated nephrotoxicity caused by cyclosporine plus indomethacin in rats

BACKGROUND AND PURPOSE

Cyclosporine (CSA) and non-steroidal anti-inflammatory drugs (NSAIDs) are co-prescribed for some arthritic conditions. We tested the hypothesis that this combined regimen elicits exaggerated nephrotoxicity in rats via the up-regulation of endothelin (ET) receptor signalling.

EXPERIMENTAL APPROACH

The effects of a 10 day treatment with CSA (20 mg · kg(-1) · day(-1)), indomethacin (5 mg · kg(-1) · day(-1)) or their combination on renal biochemical, inflammatory, oxidative and structural profiles were assessed. The roles of ETA receptor and COX-2 pathways in the interaction were evaluated.

KEY RESULTS

Oral treatment with CSA or indomethacin elevated serum urea and creatinine, caused renal tubular atrophy and interstitial fibrosis, increased renal TGF-β1, and reduced immunohistochemical expressions of ETA receptors and COX-2. CSA, but not indomethacin, increased renal ET-1, the lipid peroxidation product malondialdehyde (MDA) and GSH activity. Compared with individual treatments, simultaneous CSA/indomethacin exposure caused: (i) greater elevations in serum creatinine and renal MDA; (ii) loss of the compensatory increase in GSH; (iii) renal infiltration of inflammatory cells and worsening of fibrotic and necrotic profiles; and (iv) increased renal ET-1 and decreased ETA receptor and COX-2 expressions. Blockade of ETA receptors by atrasentan ameliorated the biochemical, structural, inflammatory and oxidative abnormalities caused by the CSA/indomethacin regimen. Furthermore, atrasentan partly reversed the CSA/indomethacin-evoked reductions in the expression of ETA receptor and COX-2 protein.

CONCLUSIONS AND IMPLICATIONS

The exaggerated oxidative insult and associated dysregulation of the ETA receptor/COX-2/TGF-β1 signalling might account for the aggravated nephrotoxicity caused by the CSA/indomethacin regimen. The potential renoprotective effect of ETA receptor antagonism might be exploited therapeutically.

Human neutrophil peptides upregulate expression of COX-2 and endothelin-1 by inducing oxidative stress

Polymorphonuclear leukocytes (PMNs) play an important role during inflammation in cardiovascular diseases. Human neutrophil peptides (HNPs) are released from PMN granules upon activation and are conventionally involved in microbial killing. Recent studies suggested that HNPs may be involved in the pathogenesis of vascular abnormality by modulating inflammatory responses and vascular tone. Since HNPs directly interact with endothelium upon release from PMNs in the circulation, we tested the hypothesis that the stimulation with HNPs of endothelial cells modulates the expression of vasoactive by-products through altering cyclooxygenase (COX) activity. When human umbilical vein endothelial cells were stimulated with purified HNPs, we observed a time- and dose-dependent increase in the expression of COX-2, whereas COX-1 levels remained unchanged. Despite an increased expression of COX-2 at the protein level, HNPs did not significantly enhance the COX-2 activity, thus the production of the prostaglandin PGI2. HNPs significantly induced the release of endothelin-1 (ET-1) as well as the formation of nitrotyrosine. The HNP-induced COX-2 and ET-1 production was attenuated by the treatment with the oxygen free radical scavenger N-acetyl-L-cysteine and the inhibitors of p38 MAPK and NF-kappaB, respectively. The angiontensin II pathway did not seem to be involved in the HNP-induced upregulation of COX-2 and ET-1 since the use of the angiotensin-converting enzyme inhibitor enalapril had no effect in this context. In conclusion, HNP may play an important role in the pathogenesis of inflammatory cardiovascular diseases by activating endothelial cells to produce vasoactive by-products as a result of oxidative stress.