Experimental mechanisms of diabetic embryopathy and strategies for developing therapeutic interventions

A high frequency of birth defects is seen in infants born to diabetic mothers. The mechanisms by which maternal hyperglycemia, the major teratogenic factor, induces embryonic malformations remain to be addressed. It has been shown that increases in programmed cell death are one of the factors causing embryonic malformations. Hyperglycemia-induced apoptosis is associated with oxidative stress, lipid peroxidation, and decreased antioxidant defense capacity in the embryos. Recent studies have revealed that mitogen-activated protein kinases as intracellular signaling factors are involved in hyperglycemia-induced embryopathy. Based on the findings, interventions to prevent embryonic malformations have been explored. Strategies include supplementation of molecules that are deficient in the embryos under hyperglycemic conditions and antioxidants to alleviate the adverse effects of oxidative stress. The ultimate goal is to develop multi-nutrient dietary supplements to eliminate embryonic abnormalities induced by maternal diabetes.

Poly(ADP-ribose) polymerase-1-deficient mice are protected from angiotensin II-induced cardiac hypertrophy

Poly(ADP-ribose) polymerase-1 (PARP), a chromatin-bound enzyme, is activated by cell oxidative stress. Because oxidative stress is also considered a main component of angiotensin II-mediated cell signaling, it was postulated that PARP could be a downstream target of angiotensin II-induced signaling leading to cardiac hypertrophy. To determine a role of PARP in angiotensin II-induced hypertrophy, we infused angiotensin II into wild-type (PARP(+/+)) and PARP-deficient mice. Angiotensin II infusion significantly increased heart weight-to-tibia length ratio, myocyte cross-sectional area, and interstitial fibrosis in PARP(+/+) but not in PARP(-/-) mice. To confirm these results, we analyzed the effect of angiotensin II in primary cultures of cardiomyocytes. When compared with PARP(-/-) cardiomyocytes, angiotensin II (1 microM) treatment significantly increased protein synthesis in PARP(+/+) myocytes, as measured by (3)H-leucine incorporation into total cell protein. Angiotensin II-mediated hypertrophy of myocytes was accompanied with increased poly-ADP-ribosylation of nuclear proteins and depletion of cellular NAD content. When cells were treated with cell death-inducing doses of angiotensin II (10-20 microM), robust myocyte cell death was observed in PARP(+/+) but not in PARP(-/-) myocytes. This type of cell death was blocked by repletion of cellular NAD levels as well as by activation of the longevity factor Sir2alpha deacetylase, indicating that PARP induction and subsequent depletion of NAD levels are the sequence of events causing angiotensin II-mediated cardiomyocyte cell death. In conclusion, these results demonstrate that PARP is a nuclear integrator of angiotensin II-mediated cell signaling contributing to cardiac hypertrophy and suggest that this could be a novel therapeutic target for the management of heart failure.

Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture)

Endothelial cells synthesize and release various factors that regulate angiogenesis, inflammatory responses, hemostasis, as well as vascular tone and permeability. Endothelial dysfunction has been associated with a number of pathophysiological processes. Oxidative stress appears to be a common denominator underlying endothelial dysfunction in cardiovascular diseases. However, depending on the pathology, the vascular bed studied, the stimulant, and additional factors such as age, sex, salt intake, cholesterolemia, glycemia, and hyperhomocysteinemia, the mechanisms underlying the endothelial dysfunction can be markedly different. A reduced bioavailability of nitric oxide (NO), an alteration in the production of prostanoids, including prostacyclin, thromboxane A2, and/or isoprostanes, an impairment of endothelium-dependent hyperpolarization, as well as an increased release of endothelin-1, can individually or in association contribute to endothelial dysfunction. Therapeutic interventions do not necessarily restore a proper endothelial function and, when they do, may improve only part of these variables.

Cardiac hypertrophy: a risk factor for QT-prolongation and cardiac sudden death

Cardiac hypertrophy was viewed as a compensatory response to hemodynamic stress. However, cumulative evidence obtained from studies using more advanced technologies in human patients and animal models suggests that cardiac hypertrophy is a maladaptive process of the heart in response to intrinsic and extrinsic stimuli. Although hypertrophy can normalize wall tension, it is a risk factor for QT-prolongation and cardiac sudden death. Studies using molecular biology techniques such as transgenic and knockout mice have revealed many important molecules that are involved in the development of heart hypertrophy and have demonstrated signaling pathways leading to the pathogenesis. With the same approach, the consequence of heart hypertrophy has been examined. The significance of hypertrophy in the development of overt heart failure has been demonstrated and several critical molecular pathways involved in the process were revealed. A comprehensive understanding of the threats of heart hypertrophy to patients has helped to develop novel treatment strategies. The recognition of hypertrophy as a major risk factor for QT-prolongation and cardiac sudden death is an important advance in cardiac medicine. Cellular and molecular mechanisms of this risk aspect are currently under extensively exploring. These studies would lead to more comprehensive approaches to prevention of potential life threatening arrhythmia and cardiac sudden death. The adaptation of new approaches such as functional genomics and proteomics will further advance our knowledge of heart hypertrophy.

Cardiac hypertrophy, substrate utilization and metabolic remodelling: cause or effect?

1. Metabolic remodelling in the heart occurs in response to chronically altered workload and substrate availability. Recently, the importance of the metabolic remodelling processes inherent in the hypertrophic growth response (whether primary or secondary) has been recognized. 2. Altered energy demand, shifts in substrate utilization and increased oxidative stress are observed in the hypertrophic heart. Both a shift away from carbohydrate usage (i.e. insulin resistance) and a shift to carbohydrate usage (i.e. pressure loading) are associated with disturbed cardiomyocyte Ca(2+) homeostasis and the development of cardiac hypertrophy. 3. A change in the balance of myocardial usage of fatty acid and glucose substrates must entail a degree of cellular oxidative stress. Increased throughput of any substrate will necessarily involve a regional imbalance between reactive oxygen species (ROS) production and breakdown. 4. In addition to a number of enzyme generators of ROS at various intracellular locations, the heart also contains a number of endogenous anti-oxidants, to restrict steady state ROS levels. The balance between ROS generation and their elimination by endogenous anti-oxidant mechanisms plays a critical role in preserving cardiac function; inappropriate levels of myocardial ROS likely precipitate impairment of myocardial function and abnormalities in cardiac structure. 5. Although different metabolic adaptations are associated with hypertrophic responses of contrasting aetiology, there is accumulating evidence that the joint insults of increased production of ROS and disturbed Ca(2+) handling in the cardiomyocyte comprise the primary lesion. These molecular signals operate together in a feed-forward mode and have the capacity to inflict substantial functional and structural damage on the hypertrophic myocardium.

CO as a cellular signaling molecule

Many biological functions of heme oxygenase (HO), such as cytoprotection against oxidative stress, vasodilation, neurotransmission in the central or peripheral nervous systems, and anti-inflammatory, anti-apoptotic, or anti-proliferative potential, have been attributed to its enzymatic byproduct carbon monoxide (CO), although roles for biliverdin/bilirubin and iron have also been proposed. In addition to these well-characterized effects, recent findings reveal that HO-derived CO may act as an oxygen sensor and circadian modulator of heme biosynthesis. In lymphocytes, CO may participate in regulatory T cell function. A number of the known signaling effects of CO depend on stimulation of soluble guanylate cyclase and/or activation of mitogen-activated protein kinases (MAPK). Furthermore, modulation of caveolin-1 status may serve as an essential component of certain aspects of CO action, such as growth control. In this review, we summarize recent findings of the beneficial or detrimental effects of endogenous CO with an emphasis on the signaling pathways and downstream targets that trigger the action of this gas.

Reactive oxygen species generation is involved in epidermal growth factor receptor transactivation through the transient oxidization of Src homology 2-containing tyrosine phosphatase in endothelin-1 signaling pathway in rat cardiac fibroblasts

Endothelin-1 (ET-1) is implicated in fibroblast proliferation, which results in cardiac fibrosis. Both reactive oxygen species (ROS) generation and epidermal growth factor receptor (EGFR) transactivation play critical roles in ET-1 signal transduction. In this study, we used rat cardiac fibroblasts treated with ET-1 to investigate the connection between ROS generation and EGFR transactivation. ET-1 treatment was found to stimulate the phosphorylation of EGFR and ROS generation, which were abolished by ETA receptor antagonist N-(N-(N-((hexahydro-1H-azepin-1-yl)carbonyl)-L-leucyl)-D-tryptophyl)-D-tryptophan (BQ485). NADPH oxidase inhibitor diphenyleneiodonium chloride (DPI), ROS scavenger N-acetyl cysteine (NAC), and p47phox small interfering RNA knockdown all inhibited the EGFR transactivation induced by ET-1. In contrast, EGFR inhibitor 4-(3'-chloroanilino)-6,7-dimethoxyquinazoline (AG-1478) cannot inhibit intracellular ROS generation induced by ET-1. Src homology 2-containing tyrosine phosphatase (SHP-2) was shown to be associated with EGFR during ET-1 treatment by EGFR coimmunoprecipitation. ROS have been reported to transiently oxidize the catalytic cysteine of phosphotyrosine phosphatases to inhibit their activity. We examined the effect of ROS on SHP-2 in cardiac fibroblasts using a modified malachite green phosphatase assay. SHP-2 was transiently oxidized during ET-1 treatment, and this transient oxidization could be repressed by DPI or NAC treatment. In SHP-2 knockdown cells, ET-1-induced phosphorylation of EGFR was dramatically elevated and is not influenced by NAC and DPI. However, this elevation was suppressed by GM6001 [a matrix metalloproteinase (MMP) inhibitor] and heparin binding (HB)-epidermal growth factor (EGF) neutralizing antibody. Our data suggest that ET-1-ETA-mediated ROS generation can transiently inhibit SHP-2 activity to facilitate the MMP-dependent and HB-EGF-stimulated EGFR transactivation and mitogenic signal transduction in rat cardiac fibroblasts.

Heme oxygenase-1 mediates the anti-inflammatory actions of 2′-hydroxychalcone in RAW 264.7 murine macrophages

Chalcones are a group of plant-derived polyphenolic compounds that belong to the flavonoids family, and possess a wide variety of cytoprotective and modulatory functions. Chalcones exert their cytoprotective actions via activation of specific transcriptional factors and upregulation of endogenous defensive pathways, such as phase II enzymes and the stress protein heme oxygenase-1 (HO-1). In this study, we investigated the anti-inflammatory action of 2′-hydroxychalcone (2-HC) in a model of lipopolysaccharide (LPS)-induced inflammation in RAW 264.7 macrophages and examined the role of HO-1 in this process. Our results demonstrate that 2-HC potently induces HO-1 expression and markedly reduces LPS-mediated nitrite and TNF-α production. These effects are accompanied by inhibition of inducible nitric oxide synthase protein expression and abolished by blockade of heme oxygenase activity with either tin protoporphyrin IX or HO-1 small interfering RNA. By using a pharmacological approach and siRNA technology, we also found that phosphatidylinositol 3-kinase is a major cellular mediator in 2-HC-induced HO-1 expression. These findings strongly suggest that 2-HC exerts anti-inflammatory actions via activation of the HO-1 pathway and help to elucidate the mechanisms underlying the potential therapeutic value of chalcones.

Effects of trans-resveratrol on hypertension-induced cardiac hypertrophy using the partially nephrectomized rat model

trans-Resveratrol (resveratrol) has been shown to have beneficial effects on the cardiovascular system in a number of studies. It is, however, unclear whether this naturally occurring compound can protect against cardiac hypertrophy. The aim of the present study was to investigate the effects of resveratrol on cardiac hypertrophy in vivo and the potential underlying mechanisms involving endothelin (ET), angiotensin (Ang) II and nitric oxide (NO) in partially nephrectomized rats. Animal models bearing cardiac hypertrophy were replicated in male Sprague-Dawley rats following partial nephrectomy (PNX). Resveratrol (10 or 50 mg/kg) was administered to rats by gavage for 4 weeks. Simultaneous PNX and sham operation controls were simultaneously established in the present study. The systolic blood pressure (SBP) of rats was measured at baseline and, along with heart weight, after 4 weeks treatment. Serum ET-1, AngII and NO concentrations were determined. In the present study, it was shown that, compared with rats in the sham-operated group, rats in the PNX group had significantly higher SBP (154.1 +/- 22.7 mmHg), heart weight (1.69 +/- 0.24 g) and serum ET-1 (125.70 +/- 26.27 pg/mL) and AngII serum concentrations (743.63 +/- 86.50 pg/mL), whereas serum NO concentrations were lower (21.1 +/- 6.9 micromol/L; all P < 0.05). These values in the sham control group were 114 +/- 10 mmHg, 1.28 +/- 0.13 g, 52.44 +/- 21.85 pg/mL, 528.7 +/- 158.5 pg/mL and 53.21 +/- 23.87 micromol/L, respectively. After 4 weeks treatment with 50 mg/kg resveratrol, SBP, heart weight and ET-1 and AngII concentrations had decreased to 135.4 +/- 15.8 mmHg, 1.39 +/- 0.15 g, 97.11 +/- 26.74 pg/mL and 629.64 +/- 116.18 pg/mL, respectively. However, the serum NO concentration had increased to 40.1 +/- 14.6 micromol/L. These values were significantly different from those obtained for the PNX group. In conclusion, trans-resveratrol appears to be able to protect against the increase in SBP and subsequent cardiac hypertrophy in vivo and the mechanisms responsible may involve, at least in part, modulation of NO, AngII and ET-1 production.

ERK1/2 pathway is involved in the inhibitory effect of crocetin on angiotensin II-induced vascular smooth muscle cell proliferation

Angiotensin II (Ang II) induces vascular smooth muscle cells (VSMCs) proliferation, which plays an important role in the development and progression of atherosclerosis. Ang II-induced cellular events have been implicated, in part, in the activation of extracellular signal-regulated kinases 1/2 (ERK1/2). Crocetin is a natural carotenoid compound isolated from Gardenia jasminoids Ellis. In the present study, we investigated the effect of crocetin on the Ang II-induced VSMCs proliferation and ERK1/2 activation. 3-[4,5-dimethylthiazol-2-yl]-2,5-dephenyl tetrazolium bromide (MTT) and [3H]thymidine incorporation assay showed that the Ang II-induced VSMCs proliferation was inhibited significantly by crocetin. In-gel kinase assay indicated that Ang II elicited rapid and significant increase of ERK1/2 activity in VSMCs, which was suppressed by crocetin markedly. Western blotting analysis and cell-based enzyme-linked immunosorbent assay (ELISA) demonstrated that crocetin significantly inhibited the phosphorylation and activation of ERK1/2 induced by Ang II. Using the indirect immunofluorescent technique, we also found that crocetin inhibited nuclear translocation of activated ERK1/2 induced by Ang II. These findings suggest that the suppression by crocetin of the Ang II-induced VSMCs proliferation can be attributed, at least in part, to its inhibitory effect on ERK1/2 pathway.

Involvement of Nrf2, p38, B-Raf, and nuclear factor-kappaB, but not phosphatidylinositol 3-kinase, in induction of hemeoxygenase-1 by dietary polyphenols

The highly inducible enzyme, hemeoxygenase-1 (HO-1), metabolizes heme, thereby protecting a variety of cells against oxidative stress and apoptosis. Up-regulation by cancer chemopreventive agents has been reported, but its regulation and function in transformed cells are unclear. We compared induction by two dietary polyphenols, curcumin and epigallocatechin-3-gallate (EGCG), with that by the endogenous substrate hemin in epithelial and endothelial cells and examined the relevance to apoptosis. Curcumin or hemin (20 microM) induced HO-1 in breast cells from 5 to 24 h. Curcumin (5-40 microM) or hemin (5-100 microM) induced HO-1 and nuclear levels of nuclear factor (erythroid-derived 2)-related factor (Nrf2) in a dose-dependent manner. EGCG had no effect in breast cells, but at 30 microM, it induced nuclear translocation of Nrf2 and HO-1 expression in B-lymphoblasts. In all cases, induction was inhibited by pretreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) or the p38 inhibitor 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580). The nuclear factor-kappaB (NF-kappaB)-DNA binding inhibitor helenalin (20 microM) also prevented induction. However, wortmannin had no effect, suggesting that PI3K was not involved. Curcumin and hemin also induced nuclear Nrf2 and HO-1 effectively in wild-type mouse embryo fibroblasts (wt MEFs) and in B-Raf(-/-) MEFs but not in Nrf2(-/-) MEFs. However, EGCG (5-20 microM) induced HO-1 only in wt MEFs. Results suggest that signaling through p38 mitogen-activated protein kinase, NF-kappaB, and Nrf2 as well as other unidentified molecules is involved in HO-1 induction by hemin and both polyphenols, but cell-specific factors also play a role, particularly with respect to EGCG. Induction of HO-1 by curcumin, EGCG, or low concentrations (5-10 microM) of helenalin did not protect MDA-MB468 breast cells or B-lymphoblasts from apoptosis.

Estrogen therapy replenishes vascular tetrahydrobiopterin and reduces oxidative stress in ovariectomized rats

OBJECTIVE

We investigated whether the effect of estrogen therapy on vascular endothelial function is mediated through increasing the bioavailability of tetrahydrobiopterin (BH4) and associated antioxidant capacity in ovariectomized (Ovx) rats.

DESIGN

Aortas of sham-operated, Ovx, and Ovx plus estrogen therapy (Ovx + ET) female Sprague-Dawley rats were used to measure vascular reactivity. Plasma levels of nitric oxide (NO) metabolites, total antioxidant capacity, aortic superoxide anion (O2.), and BH4 contents were determined.

RESULTS

Vascular reactivity, assessed on isolated aortic segments, indicated that phenylephrine-induced contraction in the Ovx group was significantly greater than that in the sham and Ovx + ET groups. The vasodilator responses to acetylcholine (10 to 10 M) and L-arginine (L-Arg; 10 M) in the sham and Ovx + ET groups were significantly greater than those in the Ovx group. Pretreatment with BH4 (10 M) enhanced the vasodilator responses to L-Arg in the Ovx group compared with the untreated Ovx group. An inhibitor of BH4 synthesis, 2,4-diamino-6-hydroxypyrimidine (2 mM), significantly attenuated the vasodilator response to L-Arg in the sham and Ovx + ET groups. In addition, Ovx significantly increased O2. production in aortic tissues and decreased plasma NO metabolites levels, whereas ET significantly prevented these effects. Pretreatment with BH4 also significantly decreased aortic O2. production in the Ovx group; both plasma total antioxidant capacity and aortic BH4 contents in the Ovx group decreased significantly compared with those in the sham group, which were also improved by ET. There were no significant differences in the protein expression of endothelial NO synthase in aortas in these groups.

CONCLUSIONS

ET increases the availability of vascular BH4 to attenuate O2. production and restores total antioxidant capacity, leading to improved NO-mediated vasodilation in Ovx rats.

The positive inotropic effect of angiotensin II: role of endothelin-1 and reactive oxygen species

Many effects believed to be because of angiotensin II (Ang II) are attributable to the action of endothelin (ET)-1, which is released/produced by Ang II. We investigated whether Ang II elicits its positive inotropic effect (PIE) by the action of endogenous ET-1, in addition to the role played by reactive oxygen species (ROS) in this mechanism. Cat cardiomyocytes were used for: (1) sarcomere shortening measurements; (2) ROS measurements by epifluorescence; (3) immunohistochemical staining for preproET-1, BigET-1, and ET-1; and (4) measurement of preproET-1 mRNA by RT-PCR. Cells were exposed to 1 nmol/L Ang II for 15 minutes. This low concentration of Ang II increases sarcomere shortening by 29.2+/-3.7% (P<0.05). This PIE was abrogated by Na+/H+ exchanger or Na+/Ca2+ exchanger reverse mode inhibition. The production of ROS increased in response to Ang II treatment (DeltaROS respect to control: 68+/-15 fluorescence units; P<0.05). The Ang II-induced PIE and ROS production were blocked by the Ang II type 1 receptor blocker losartan, the nonselective ET-1 receptor blocker TAK044, the selective ETA receptor blocker BQ-123, or the ROS scavenger N-(2-mercapto-propionyl)glycine. Exogenous ET-1 (0.4 nmol/L) induced a similar PIE and increase in ROS production to those caused by Ang II. Immunostaining for preproET-1, BigET-1, and ET-1 was positive in cardiomyocytes. The preproET-1 mRNA abundance increased from 100+/-4.6% in control to 241.9+/-39.9% in Ang II-treated cells (P<0.05). We conclude that the PIE after exposure to 1 nmol/L Ang II is due to endogenous ET-1 acting through the ETA receptor and triggering ROS production, Na+/H+ exchanger stimulation, and Na+/Ca2+ exchanger reverse mode activation.

Antiproliferative effect of isosteviol on angiotensin-II-treated rat aortic smooth muscle cells

Isosteviol is a derivative of stevioside, a constituent of Stevia rebaudiana, which is commonly used as a noncaloric sugar substitute in Japan and Brazil. The aims of this study were to examine whether isosteviol alters angiotensin-II-induced cell proliferation in rat aortic smooth muscle cells. Cultured rat aortic smooth muscle cells were preincubated with isosteviol, then stimulated with angiotensin II, after which [(3)H]thymidine incorporation and endothelin-1 secretion were examined. Isosteviol (1-100 micromol/l) inhibits angiotensin-II-induced DNA synthesis and endothelin-1 secretion. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-sensitive fluorescent dye, showed an isosteviol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II. The inductive properties of angiotensin II on extracellular signal-regulated kinase (ERK) phosphorylation were found reversed with isosteviol and antioxidants such as N-acetylcysteine. In summary, we speculate that isosteviol inhibits angiotensin-II-induced cell proliferation and endothelin-1 secretion via attenuation of reactive oxygen species generation. Thus, this study provides important insights that may contribute to the effects of isosteviol on the cardiovascular system.

Antioxidant and heme oxygenase-1 (HO-1)-induced effects of selected Taiwanese plants

Recent studies have shown biological effects of heme oxygenase-1 (HO-1) induction and antioxidation in cardiovascular disorders. The ethanol extracts of leaves of 12 selected indigenous Taiwanese plants were investigated for their antioxidant activities, evaluated using assays of 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, and superoxide radicals scavenging and reducing power activities as well as the induction of heme oxygenase-1 (HO-1). Acer albopurpurascens, Cinnamomum kanehirai, Diospyros discolor, Excoecaria kawakamii, Koelreuteria henryi, and Syzygium formosanum showed better DPPH-scavenging activities than the other plants. IC(50) values ranged from 1.7 to 8.7 microg/mL. Excepting Millettia pulchra var. microphylla and Pittosporum moluccanum, the extracts displayed hydroxyl-scavenging activities (IC(50) of 0.16-0.67 microg/mL). A. albopurpurascens, D. discolor, K. henryi, and S. formosanum also showed good superoxide anion radical scavenging activities and IC(50) values ranged from 12.9 to 28.5 microg/mL. D. discolor, K. henryi, and S. formosanum showed potent reducing power and M. pulchra var. microphylla and S. formosanum exhibited potent HO-1 induced activity. These active plant extracts also contained abundant phenolic constituents. The present results provide candidates to isolate the active constituents and develop natural antioxidants.

Endothelin-1 expression in vascular adventitial fibroblasts

Endothelial cells are a major source of endothelin (ET)-1, but the possibility that vascular adventitial fibroblasts generate ET-1 has not been explored. We hypothesized that aortic adventitial fibroblasts have the ability to produce ET-1, which may contribute to extracellular matrix synthesis. Vascular adventitial fibroblasts were isolated from mouse aorta and incubated with various concentrations of angiotensin II (ANG II). mRNA levels of preproET-1 and type I procollagen were detected with relative RT-PCR. ET-1 levels in culture medium were measured with ELISA. Protein levels of procollagen were detected with Western blotting. ANG II (10 and 100 nM, 1 microM) induced a time- and concentration-dependent increase in preproET-1 mRNA levels (P < 0.05). Induction of preproET-1 mRNA was accompanied by release of immunoreactive peptide ET-1 (P < 0.05). ANG II-evoked increases in preproET-1 mRNA expression and ET-1 release were blocked by losartan (100 microM), an AT1 receptor antagonist, but not PD-123319 (100 microM), an AT2 receptor antagonist. To further confirm our findings, we cloned and then sequenced vascular fibroblast preproET-1 bidirectionally with T7 and M13 reverse sequencing primers. Their nucleotide sequences were identical to preproET-1 cDNA from mouse vascular endothelial cells (accession no. AB081657). Moreover, ANG II-induced type I procollagen mRNA and protein expression were inhibited by BQ-123 (10 microM), an ET(A) receptor inhibitor, but not BQ-788 (10 microM), an ET(B) receptor inhibitor, suggesting a significant role of adventitial ET-1 in regulation of extracellular matrix synthesis. The results demonstrate that vascular adventitial fibroblasts are able to synthesize and release ET-1 in response to ANG II.

Beneficial effects of the bioflavonoids curcumin and quercetin on early function in cadaveric renal transplantation: a randomized placebo controlled trial

BACKGROUND

The bioflavonoids quercetin and curcumin are renoprotective natural antioxidants. We wished to examine their effects on early graft function (EF).

METHODS

Between September 2002 and August 2004, 43 dialysis dependent cadaveric kidney recipients were enrolled into a study using Oxy-Q which contains 480 mg of curcumin and 20 mg of quercetin, started after surgery and taken for 1 month. They were randomized into three groups: control (placebo), low dose (one capsule, one placebo) and high dose (two capsules). Delayed graft function (DGF) was defined as first week dialysis need and slow function (SGF) as Cr >2.5 mg/dl by day 10. Category variables were compared by chi squared and continuous variables by Kruskal-Wallis.

RESULTS

There were four withdrawals: one by patient choice and three for urine leak. The control group had 2/14 patients with DGF vs. none in either treatment group. Incidence of EF was control 43%, low dose 71% and high dose 93% (P=0.013). Serum creatinine was significantly lower at 2 days (control 7.6+/-2.1, low 5.4+/-0.6, high 3.96+/-.35 P=0.0001) and 30 days (control 1.82+/-.16, low 1.65+/-.09, high 1.33 +/-.1, P=0.03). Acute rejection incidence within 6 months was control 14.3%, low dose 14.3% and high dose 0%. Tremor was detected in 13% of high dose patients vs. 46% of others. Urinary HO-1 was higher in bioflavonoid groups.

CONCLUSION

Bioflavonoid therapy improved early graft function. Acute rejection and neurotoxicity were lowest in the high dose group. These bioflavonoids improve early outcomes in cadaveric renal transplantation, possibly through HO-1 induction.

Effects of trans ‐resveratrol on hypertension‐induced cardiac hypertrophy using the partially nephrectomized rat model

Iron-deficiency anaemia, a complication of end-stage renal disease (ESRD), is often treated with parenteral iron therapies that have been shown to produce dose-limiting hypotension in patients. ABT-870 (iron-(III)-hydroxide-oligosaccharide) is comprised of elemental iron complexed with oligosaccharide, a composition that we hypothesised would allow the hypotensive effects of parenteral iron therapy to be overcome, thus allowing a rapid rate of infusion to be well tolerated. Mean arterial pressure (MAP) and heart rate (HR) were monitored in anaesthetized dogs following the infusion of ABT-870 and iron sucrose administered at doses of 7.1 and 21.3 mg/kg using a rapid 30 s infusion. ABT-870 and iron sucrose were also monitored at doses of 7.1, 21.3 and 50 mg/kg administered over a 10 min period. Sodium ferric gluconate complex (SFGC) was administered in an identical fashion at doses of 12.5 and 31.2 mg/kg. A 30 s rapid infusion of ABT-870 at doses of 7.1 and 14.3 mg/kg or a 10 min infusion of ABT-870 at doses of 7.1 and 21.3 mg/kg produced little effect on MAP and HR. Infusion of the highest dose of ABT-870 (50 mg/kg) produced no consistent hypotension, but did produce an increase in HR (maximal increase 35 +/- 9 b.p.m.), an effect that lasted only 15 min. A 30 s rapid infusion of iron sucrose at 7.1 mg/kg produced modest increases in MAP and HR (5 +/- 1 mmHg and 5 +/- 2 b.p.m., respectively). However, rapid infusion of iron sucrose at 14.3 mg/kg produced hypotension (to -8 +/- 1 mmHg below baseline) and exerted variable, biphasic effects on HR ranging from -16 to +50 b.p.m. Although 10 min infusion of iron sucrose at 7.1 mg/kg exerted little effect on MAP and HR, at doses of 21.3 and 50 mg/kg iron sucrose elicited a profound dose-dependent decrease in MAP (-34 +/- 11 and -83 +/- 5 mmHg, respectively) and a pronounced increase in HR ranging from 32 to 49 b.p.m. above baseline. A 10 min infusion of SFGC at doses of 12.5 and 31.2 mg/kg produced a dose-dependent decrease in MAP (-28 +/- 18 and -67 +/- 12 mmHg below baseline) and a marked increase in HR (26 +/- 11 and 94 +/- 15 b.p.m. above baseline). In conclusion, unlike iron sucrose and SFGC, high doses of ABT-870 failed to exert consistent hypotensive effects. These data demonstrate that ABT-870 may have a substantial therapeutic window and considerable clinical potential for iron-replacement therapy.

Sex dimorphism in cardiac pathophysiology: experimental findings, hormonal mechanisms, and molecular mechanisms

The higher cardiovascular risk in men and post-menopausal women implies a protective action of estrogen. A large number of experimental studies have provided strong support to this concept. However, the recent clinical trials with negative outcomes regarding hormone replacement therapy call for "post hoc" reassessment of existing information, models, and research strategies as well as a summary of recent findings. Sex steroid hormones, in particular estrogen, regulate numerous processes that are related to the development and progression of cardiovascular disease through a variety of signaling pathways. Use of genetically modified models has resulted in interesting information on diverse actions mediated by steroid receptors. By focusing on experimental findings, we have reviewed hormonal, cellular, and signaling mechanisms responsible for sex dimorphism and actions of hormone replacement therapy and addressed current limitations and future directions of experimental research.

1,2,3,4,6-penta-O-galloyl-β-D-glucose up-regulates heme oxygenase-1 expression by stimulating Nrf2 nuclear translocation in an extracellular signal-regulated kinase-dependent manner in HepG2 cells

AIM: To examine the potency of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (PGG) as a hepatic heme oxygenase-1 (HO-1) inducer and its regulation in HepG2 cells.

METHODS: Expression of HO-1 and NF-E2-related factor 2 (Nrf2) and activation of mitogen-activated protein (MAP) kinases were analyzed by Western blot, immunofluorescence assay, and flow cytometry. Transfections of HO-1 gene, small interfering RNAs for HO-1 and Nrf2, and dominant-negative gene for MAP/extracellular signal-regulated kinase (ERK) were carried out to dissect the signaling pathways leading to HO-1 expression in HepG 2 cells.

RESULTS: PGG up-regulated HO-1 expression and this expression conferred cytoprotection against oxidative injury induced by t-butyl hydroperoxide. Moreover, PGG induced Nrf2 nuclear translocation, which was found to be an upstream step of PGG-induced HO-1 expression, and ERK activation, of which pathway was involved in PGG-induced Nrf2 nuclear translocation, HO-1 expression and cytoprotection.

CONCLUSION: PGG up-regulates HO-1 expression by stimulating Nrf2 nuclear translocation in an ERK-dependent manner, and HO-1 expression by PGG may serve as one of the important mechanisms for its hepatoprotective effects.

Alterations in the expression of antioxidant genes and the levels of transcription factor NF-Kappa B in relation to diabetic embryopathy in the cohen diabetic rat model

BACKGROUND

We have previously shown that oxidative stress is important in the pathogenesis of diabetes-induced anomalies in Cohen Diabetic sensitive (CDs) rat embryos and seems to interplay with genetic factors. We investigated the role of genetic factors related to the antioxidant defense mechanism in CDs rat embryos.

METHODS

We studied 11.5- and 12.5-day embryos of Cohen Diabetic resistant (CDr) and CDs rats that were fed a regular diet (RD), and hence not diabetic, compared to rats fed a high-sucrose low-copper diet (HSD) where only the CDs animals became diabetic. Embryos were monitored for growth and congenital anomalies. mRNA of catalase (CAT), glutathione peroxidase (GSHpx), CuZn-SOD (SOD-superoxide dismutase), and Mn-SOD and the extent of nuclear factor kappa B (NF-kappaB) activation were assessed.

RESULTS

Embryos of CDs dams fed RD were significantly smaller and had an increased rate of NTDs compared to embryos of CDr dams fed RD. When CDs dams were fed HSD, >50% of the CDs embryos were dead and 44% of the live embryos had NTDs. Live 11.5-day old embryos of CDs dams fed RD had a statistically significant increase in CAT, CuZn-SOD, and GSHpx mRNA levels compared with the levels in the CDr embryos from dams fed RD. CDs embryos from dams fed HSD showed significant overactivation of NF-kappaB compared with CDr embryos from dams fed HSD (in which activation was decreased), without any increase in the expression of SOD, CAT, and GSHpx.

CONCLUSIONS

This study demonstrates that one of the genetic differences between the CDr and CDs strains fed RD is an increased expression of genes encoding for antioxidant enzymes in the CDs but inability for upregulation in diabetes. In addition, while activation of NF-kappaB is decreased in CDr on HSD, it is increased in the CDs. These differences may play a role in the increased sensitivity of the CDs embryos to diabetic-induced teratogenicity.

Time-dependent resveratrol-mediated mRNA and protein expression associated with cell cycle in WR-21 cells containing mutated human c-Ha-Ras

Cancer results from an undesirable imbalance between cellular proliferation and apoptosis. Both processes may be modulated at the level of gene expression, viz., p53 and c-Ha-ras, by dietary bioactive components such as resveratrol. We tested the time-dependent effect of resveratrol on gene and protein expression in WR-21 cells containing a mutated human c-Ha-ras oncogene. We demonstrate cyclic resveratrol-mediated expression of p53, mdm2, p21(cip/waf), Rb, and cyclin G at both the RNA and the protein level at <8 h. However, ras was not differentially expressed at either the RNA or the protein level. p53 was upregulated followed by p21cip/waf, then mdm2, and cyclin G, all downstream p53-activated targets. RNA transcription increased at >8 h for all genes except p53, but protein levels did not suggest uncoupling of transcription and translation. At 24 h, both p53 and Rb expression returned to baseline, suggesting collapse of DNA structure and spindle assembly checkpoints characteristic of mitotic catastrophe. In summary, resveratrol at <8 h induced p53-mediated effects, including apoptosis and cell-cycle arrest (G2/M). However, later, it induced cell-cycle checkpoint dysfunction, indicative of mitotic catastrophe. Thus, future studies should better elucidate the temporal mechanism of the dietary bioactive agent resveratrol on cancer cells.

Perinatal changes in pulmonary vascular endothelial function

The pulmonary endothelium plays a crucial role in lung development and function during the perinatal period. Its 2 most important functions at this time are to help reduce pulmonary vascular resistance (PVR) in order to permit the entire cardiac output to pass through the lungs for the first time and to facilitate the clearance of lung fluid. In response to changes in environmental factors such as oxygen tension, blood flow, circulating cytokines, and growth factors, the endothelium synthesizes and/or extracts many vasoactive mediators such as endothelin-1 (ET-1), norepinephrine, angiotensin 1, thromboxane, prostacyclin (PGI(2)), and the endothelial-derived relaxing factor nitric oxide (NO). The endothelium acts as a transducer conveying information about environmental changes to the underlying smooth muscle cells (SMCs), which helps regulate their reactivity and pulmonary vascular tone. The endothelial layer also acts as a barrier, regulating the exchange of fluids and nutrients between blood components and the surrounding tissues. The purpose of this review is to demonstrate the importance of structural and functional changes in the pulmonary endothelium during the perinatal period and explain their role in the regulation of the pulmonary circulation in health and disease. We also highlight signalling pathways of some of the most important endothelium-derived factors and indicate potential targets for pharmacological intervention.

The interrelation of the angiotensin and endothelin systems on the modulation of NAD(P)H oxidaseThis paper is one of a selection of papers published in this Special issue, entitled Young Investigator's Forum

The NAD(P)H oxidase is an enzyme assembled at the cellular membrane able to produce superoxide anion from NADH or NAD(P)H (nicotinamide adenine dinucleotide phosphate). It is one of the main sources of superoxide anion in cardiovascular tissues and its role in a variety of cardiovascular disorders such as atherosclerosis, cardiac hypertrophy, and endothelial dysfunction was recently proposed. Although, many factors and receptors were shown to lead to the activation of the enzyme, particulary the type 1 angiotensin receptor, the pathways involved are still widely unknown. Despite the identification of factors such as c-Src and protein kinase C implicated in the acute activation of NAD(P)H oxidase, the signalling involved in the sustained activation of the enzyme is probably far more complex than was previously envisioned. In this review, we describe the role of endothelin-1 in NAD(P)H oxidase signalling after a sustained stimulation by angiotensin II. Since most pathologies caused by an NAD(P)H oxidase overactivation develop over a relatively long period of time, it is necessary to better understand the long-term signalling of the enzyme for the development or use of more specific therapeutic tools.

Subdepressor dose of benidipine ameliorates diabetic cardiac remodeling accompanied by normalization of upregulated endothelin system in rats

We investigated whether benidipine, a long-acting calcium channel blocker (CCB), can normalize cardiac expression profiles of the endothelin (ET)-1 system in insulin-resistant diabetes. Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a model of human Type 2 diabetes, were treated for 12 wk with vehicle or benidipine (3 mg.kg(-1).day(-1)). OLETF rats exhibited a significant increase in ET-1 in plasma and left ventricular (LV) tissues compared with nondiabetic controls. Expression of prepro-ET-1, ET-converting enzyme, and ET(A) and ET(B) receptors in LV tissues was also significantly higher in OLETF rats. The two MAPKs, JNK and p38MAPK, both of which are activated by ET-1, were more abundantly expressed in OLETF rat LV tissues. All these alterations were reversed to nondiabetic levels when OLETF rats were treated with the subdepressor dose of benidipine. Furthermore, benidipine therapy resulted in hindering cardiomyocyte hypertrophy and cardiac perivascular fibrosis in OLETF rats. The beneficial actions of benidipine at the subdepressor dose on cardiac remodeling in insulin-resistant diabetes may involve normalization of the upregulated ET-1 system.

Upregulation of heme oxygenase-1 by Epigallocatechin-3-gallate via the phosphatidylinositol 3-kinase/Akt and ERK pathways

Heme oxygenase-1 (HO-1) is a cytoprotective enzyme activated by various phytochemicals and we examined the ability of Epigallocatechin-3-gallate (EGCG), the major constituent of green tea, to upregulate HO-1 expression in endothelial cells (ECs). We demonstrate that EGCG induces HO-1 expression in a concentration- and time-dependent manner. Furthermore, EGCG-mediated HO-1 induction was abrogated in the presence of actinomycin D and cycloheximide, indicating that this upregulation of HO-1 occurred at the transcriptional level. EGCG also upregulates Nrf2 levels in nuclear extracts and increases ARE-luciferase activity. Furthermore, EGCG is the most potent inducer of HO-1 expression of the different green tea constituents that we analyzed, but had no detectable cytotoxic effects over the 25-100 microM dosage range. The inhibition of intracellular ROS production by N-acetylcysteine (NAC), glutathione (GSH), superoxide dismutase (SOD), catalase and the mitochondrial complex I inhibitor, rotenone, results in a decrease in EGCG-dependent HO-1 expression. In addition, we determined that tyrosine kinase is involved in EGCG induction of HO-1 as this is abrogated by genistein. ECs treated with EGCG exhibit activation of Akt and ERK1/2. In addition, pharmacological inhibitors of phosphatidylinositol 3-kinase and MEK1/2, which are upstream of Akt and ERK1/2, respectively, attenuate EGCG-induced HO-1 expression. On the other hand, pretreatment of these cells with EGCG exerts significant cytoprotective effects against H2O2, suggesting that the induction of HO-1 is an important component in the protection against oxidative stress. Hence, EGCG is a novel phytochemical inducer of HO-1 expression and we further identify the principal underlying mechanisms involved in this process.

Antiatherogenic effects of angiotensin receptor antagonism in mild renal dysfunction

Angiotensin II (Ang II) increases atherosclerotic cardiovascular disease. Renal damage that is characterized by activation of Ang II markedly potentiates the risk for atherosclerosis, even in the setting of subtle renal impairment. Therefore, whether antagonism of Ang II actions can modify atherosclerosis in a model of mild renal impairment was examined. Apolipoprotein E-deficient spontaneously hyperlipidemic mice underwent uninephrectomy (UNx) or sham operation (sham) followed by treatment with Ang II receptor antagonist losartan or hydralazine for 12 wk. While UNx did not increase the serum creatinine levels, BP and lipids were higher in UNx mice than in age-matched sham controls with intact kidneys. UNx caused a dramatic increase in the extent and the number of atherosclerotic lesions together with greater macrophage-positive area and more disruption in the elastin component of the extracellular matrix versus sham. Ang II antagonism dramatically decreased the UNx-induced acceleration in atherosclerosis in association with decreased macrophage content, linked to decreased macrophage migration in vitro with losartan but not with hydralazine. Aortae of mice treated with Ang II antagonism had fewer elastin breaks together with less immunostaining for the powerful elastolytic enzyme cathepsin S. None of these benefits was observed in the hydralazine-treated mice despite equivalent reduction in BP. These findings support an important role for endogenous Ang II in accelerated atherosclerosis in renal dysfunction and offer a therapeutic intervention with particular benefit in this setting through mechanisms that include reduced vascular macrophage infiltration and preservation of the elastin component of extracellular matrix.

Luteolin inhibits endothelin-1 secretion in cultured endothelial cells

We discovered that luteolin, a typical flavonoid contained in various kinds of plants, inhibits the secretion and gene expression of endothelin-1 (ET-1), a potent vasoconstrictor regulating blood pressure, in porcine aortic endothelial cells. Its ED50 was about 10 microM. In addition, the inhibition of ET-1 by a glycoside compound of luteolin (luteolin-6-C-glucoside) was weak.

The Cystic Fibrosis Transmembrane Conductance Regulator Is Regulated by a Direct Interaction with the Protein Phosphatase 2A

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-activated chloride channel expressed at the apical surface of epithelia. Although the regulation of CFTR by protein kinases is well documented, channel deactivation by phosphatases is not well understood. We find that the serine/threonine phosphatase PP2A can physically associate with the CFTR COOH terminus. PP2A is a heterotrimeric phosphatase composed of a catalytic subunit and two divergent regulatory subunits (A and B). The cellular localization and substrate specificity of PP2A is determined by the unique combination of A and B regulatory subunits, which can give rise to at least 75 different enzymes. By mass spectrometry, we identified the exact PP2A regulatory subunits associated with CFTR as Aalpha and B'epsilon and find that the B'epsilon subunit binds CFTR directly. PP2A subunits localize to the apical surface of airway epithelia and PP2A phosphatase activity co-purifies with CFTR in Calu-3 cells. In functional assays, inhibitors of PP2A block rundown of basal CFTR currents and increase channel activity in excised patches of airway epithelia and in intact mouse jejunum. Moreover, PP2A inhibition in well differentiated human bronchial epithelial cells results in a CFTR-dependent increase in the airway surface liquid. Our data demonstrate that PP2A is a relevant CFTR phosphatase in epithelial tissues. Our results may help reconcile differences in phosphatase-mediated channel regulation observed for different tissues and cells. Furthermore, PP2A may be a clinically relevant drug target for CF, which should be considered in future studies.

Inhibition of angiotensin II- and endothelin-1-stimulated proliferation by selective MEK inhibitor in cultured rabbit gingival fibroblasts+

We investigated the implication of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in the proliferation stimulated by angiotensin II (Ang II) and endothelin-1 (ET-1) in cultured rabbit gingival fibroblasts (CRGF). Ang II stimulated activation of ERK1/2 and the activation was inhibited by CV-11974, an AT1 antagonist, and saralasin, an AT1/AT2 antagonist, but not by PD123,319, an AT2 antagonist in the CRGF. Ang II-stimulated proliferation was inhibited by PD98059 or U0126, selective MEK inhibitors. Furthermore, ET-1 stimulated proliferation via G-protein-coupled ETA receptors, which were identified by Western blot analysis of membrane protein from the CRGF. ET-1 also stimulated activation of ERK1/2 and the activation was inhibited by BQ-123, an ETA inhibitor, and TAK044, an ETA/ETB inhibitor, but not by BQ-788, an ETB inhibitor. ET-1-stimulated proliferation was inhibited by PD98059 or U0126. These findings suggest that ERK1/2 play a role in the signaling process leading to proliferation stimulated by Ang II and ET-1 via G-protein-coupled receptors, AT1 and ETA in CRGF.

Redox-sensitive transcription factors as prime targets for chemoprevention with anti-inflammatory and antioxidative phytochemicals

Oxidative stress has been implicated in various pathological conditions including cancer. However, the human body has an intrinsic ability to fight against oxidative stress. A wide array of phase 2 detoxifying or antioxidant enzymes constitutes a fundamental cellular defense system against oxidative and electrophilic insults. Transcriptional activation of genes encoding detoxifying and antioxidant enzymes by NF-E2 related factor 2 (Nrf2), a member of the cap'n'collar family of basic leucine zipper transcription factors, may protect cells and tissues from oxidative damage. Many chemopreventive and chemoprotective phytochemicals have been found to enhance cellular antioxidant capacity through activation of this particular transcription factor, thereby blocking initiation of carcinogenesis. A new horizon in chemoprevention research is the recent discovery of molecular links between inflammation and cancer. Components of the cell signaling pathways, especially those that converge on redox-sensitive transcription factors, including nuclear factor-kappaB (NF-kappaB) and activator protein 1 (AP-1) involved in mediating inflammatory response, have been implicated in carcinogenesis. A wide variety of chemopreventive and chemoprotective agents can alter or correct undesired cellular functions caused by abnormal proinflammatory signal transmission mediated by inappropriately activated NF-kappaB and AP-1. The modulation of cellular signaling by anti-inflammatory phytochemicals hence provides a rational and pragmatic strategy for molecular target-based chemoprevention.

Effects of olmesartan medoxomil as an angiotensin II-receptor blocker in chronic hypoxic rats

We established a rat chronic alveolar hypoxia in vivo model to evaluate the efficacy against hypoxic pulmonary hypertension of a new angiotensin II-receptor I blocker, olmesartan medoxomil. Three groups of rats were established: rats exposed for 2-6 weeks to 10% oxygen atmosphere in a normobaric chamber; hypoxic rats treated with olmesartan medoxomil oral administration (5 mg/day) every day; and control rats fed in a normoxic condition. After hypoxia treatment, the presence, etiology and severity of pulmonary hypertension, was echocardiographically evaluated, and expressions of brain natriuretic peptide (BNP), transforming growth factor (TGF-beta) and endothelin-1 genes measured by both immunohistochemical assay and real-time polymerase chain reaction. Olmesartan medoxomil significantly reduced the induction of hypoxic cor pulmonale not only on echocardiographical observations but also in BNP, TGF-beta and endothelin gene expressions in molecular studies. However, systolic blood pressure was independent of olmesartan medoxomil. The present study clearly indicates that the angiotensin II-type I-receptor blocker olmesartan medoxomil has significant efficacy for hypoxic cor pulmonale.

Mechanism of Endothelin-1 Activation of Map Kinases in Neonatal Pulmonary Vascular Smooth Muscle

Mitogen-activated protein kinases (MAPKs) belong to the group of serine-threonine kinases that are rapidly activated in response to growth factor stimulation. In adult mammalian cells, the MAPK family includes extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2 or p44(mapk) and p42(mapk)), which translocate to the nucleus and integrate signals from second messengers leading to cellular proliferation or differentiation, but the specific role of MAPKs in neonatal pulmonary vascular smooth muscle is not well understood. Expression of p44(mapk) and p42(mapk) in primary cultured pulmonary vascular smooth muscle cells from neonatal (1-2 day old) rats was identified by Western immunoblot analysis and treatment with 10 nM endothelin-1 (ET-1), a potent vasoconstrictor with vascular mitogenic properties, induced cell proliferation, and phosphorylation of both p44(mapk) and p42(mapk). The protein kinase C (PKC) isozyme inhibitor (alpha, beta, gamma, delta, zeta) Go 6983, the ET(A) receptor antagonist BQ 123, and the MAPK kinase inhibitor PD98059 blocked the cell proliferation response to ET-1. Also, BQ 123, Go 6983, and PKC inhibitor 20-28 (Myr-N-FARKGAL-RQ-NH2-PKCalpha antagonist) inhibited ET-1-induced phosphorylation of both p44(mapk) and p42(mapk). In contrast, the reactive oxygen species (ROS) inhibitor diphenylene iodonium (DPI), the PKCdelta inhibitor rottlerin, and the ET(B) receptor antagonist BQ 788 did not block ET-1-induced phosphorylation of MAPKs. Collectively, these data demonstrate the expression and phosphorylation of MAPKs by ET-1 and suggests that MAPK activation and cell proliferation by ET-1 occurs via ET(A) receptor stimulation and specific PKC isozyme activation in rat neonatal pulmonary vascular smooth muscle.

Effects of alcohol on intracellular pH regulators and electromechanical parameters in human myocardium

BACKGROUND

Disturbances in intracellular pH (pHi) of the heart can trigger major changes in the strength and rhythm of the heartbeat. It is well known that two extruders, Na+/H+ exchange (NHE) and Na+/HCO3- symporter (NHS), and a monocarboxylic acid transporter (MCT) are involved in acid-equivalent extruding in the human heart. Drinking alcohol has been proven to affect blood pressure and heart contractility and, sometimes, causes cardiac arrhythmia. To assess the effects of alcohol on pHi regulators and electromechanical parameters, various concentrations of alcohol were superfused into human myocardium in the present study.

METHODS

Human atrial myocardium was obtained from hearts of patients undergoing corrective cardiac surgery. Institutional rules for the protection of human subjects were observed. In the whole study, pHi was measured by an epifluorescent, ratiometric microspectrofluorimetry technique with the dye BCECF, while electrophysiological experiments were performed by traditional micropipette. NHE and NHS activities were measured after pHi recovery from intracellular acidosis induced by NH4Cl prepulse, while MCT activity was measured by a lactate adding/removing technique.

RESULTS

In pHi experiments, we demonstrated that alcohol could induce a biphasic, concentration-dependent (30-1000 mM) pHi change (i.e., alkalosis after acidosis) in human atrium in HEPES-buffered Tyrode solution. To a smaller extent, similar results were found when the superfusate was replaced by HCO3- -buffered Tyrode solution. NHE activity was increased by a moderate concentration of alcohol (30 mM), while it was inhibited in a concentration-dependent manner by higher concentrations of alcohol (>100 mM). On the contrary, 30-1000 mM alcohol increased the activity of NHS in a concentration-dependent manner. Surprisingly, MCT activity was not affected by alcohol. In electromechanical experiments, we found that alcohol (30-1000 mM) had a notable concentration-dependent inhibitory effect on the contractile force, while higher concentrations of alcohol (>100 mM) decreased the action potential amplitude, upstroke velocity, duration of repolarization, and force of contractions in a concentration-dependent way. All these alcohol-induced pHi changes and electromechanical inhibitions were reversible.

CONCLUSIONS

To our knowledge, this study provides the first evidence that alcohol can affect pHi in human myocardial tissue by changing the activity of acid extruders (i.e., NHE and NHS).

Chemoprevention of genome, transcriptome, and proteome alterations induced by cigarette smoke in rat lung

Post-genomic methodologies have provided novel tools for evaluating safety and efficacy of cancer chemopreventive agents. We exposed rats to environmental cigarette smoke (ECS) for 28 days, with or without oral administration of N-acetylcysteine (NAC). As assessed by 32P-postlabelling, ECS caused a 10-fold increase of DNA adduct levels, which were significantly reduced by NAC. Of 518 proteins tested by antibody microarray, ECS stimulated 56 activities involved in stress response, protein removal, cell replication, apoptosis, phagocytosis, and immune response. NAC alone did not change the amounts of any protein, whereas it significantly decreased the amounts of 6 ECS-induced proteins. The intensity of expression of 278 related genes, assessed by cDNA microarray, was significantly correlated with protein amounts. These observed molecular alterations, which can be attenuated by NAC, represent in part adaptive responses and in part reflect mechanisms contributing to the pathogenesis of smoke-related diseases, including lung cancer, asthma, chronic bronchitis, and emphysema.

A forkhead in the road to longevity: the molecular basis of lifespan becomes clearer

OBJECTIVE

Although the quest for longevity is as old as civilization itself, only recently have technical and conceptual advances in genomics research brought us to the point of understanding the precise molecular events that make us age. This heralds an era when manipulations of these will enable us to live longer, healthier lives. The present review describes how recent experimental strategies have identified key genes and intracellular pathways that are responsible for ageing and longevity.

FINDINGS

In diverse species transcription factors belonging to the forkhead/winged helix box gene, group O (FOXO) subfamily have been found to be crucial in downstream suppression of the life-shortening effects of insulin/insulin-like growth factor-I receptor signalling pathways that, when upregulated, accelerate ageing by suppression of FOXO. The various adverse processes activated upon FOXO suppression include increased generation of reactive oxygen species (ROS). ROS are pivotal for the onset of various common conditions, including hypertension, atherosclerosis, type 2 diabetes, cancer and Alzheimer's disease, each of which shortens lifespan. In humans, FOXO3a, as well as FOXO1 and -4, and their downstream effectors, could hold the key to counteracting ageing and common diseases. An understanding of the processes controlled by these FOXOs should permit development of novel classes of agents that will more directly counteract or prevent the damage associated with diverse life-threatening conditions, and so foster a life of good health to a ripe old age. Just like caloric restriction, lifespan can be increased in various species by plant-derived polyphenols, such as resveratrol, via activation of sirtuins in cells. Sirtuins, such as SIRT1 in mammals, utilize FOXO and other pathways to achieve their beneficial effects on health and lifespan.

CONCLUSION

Lifespan is tractable and basic mechanisms are now known. Longevity research complements and overlaps research in most major medical disciplines. Current progress bodes well for an ever-increasing length of healthy life for those who adapt emerging knowledge personally (so-called 'longevitarians').

Molecular basis of heme oxygenase-1 induction: implications for chemoprevention and chemoprotection

Heme oxygenase (HO)-1, involved in the heme degradation process, is an important antioxidant enzyme. The induction of HO-1 gene expression, in response to diverse oxidative stimuli, represents a critical event in adaptive cellular response. Experimental models of various diseases, including acute inflammation, atherosclerosis, degenerative diseases, and carcinogenesis, have demonstrated that the induction of HO-1 can prevent or mitigate the symptoms associated with these ailments. Recent progress in our understanding of cellular signaling networks as critical modulators of gene transcription sheds light on the molecular basis of HO-1 gene expression. A panel of redox-sensitive transcription factors such as activator protein-1, nuclear factor- kappaB, and nuclear factor E2-related factor-2, and some of the upstream kinases have been identified as regulators of HO-1 gene induction. The scope of this review is limited to focus on molecular mechanisms underlying HO-1 expression and the significance of targeted induction of HO-1 as a strategy to achieve chemoprevention and chemoprotection.

Reactive oxygen species as signaling molecules in cardiovascular differentiation of embryonic stem cells and tumor-induced angiogenesis

Besides the well known pathophysiological impact of oxidative stress in cardiovascular disease, reactive oxygen species (ROS) generated at low concentrations exert a role as signaling molecules that are involved in signal transduction cascades of numerous growth factor-, cytokine-, and hormone-mediated pathways, and regulate biological effects such as apoptosis, cell proliferation, and differentiation. Embryonic stem cells have the capacity to differentiate into the cardiovascular cell lineage. Furthermore, upon confrontation culture with tumor tissue, they form blood vessel-like structures that induce tumor-induced angiogenesis within tumor tissues. The role of ROS in cardiovascular differentiation of embryonic stem cells appears to be antagonistic. Whereas continuous exposure to ROS results in inhibition of cardiomyogenesis and vasculogenesis, pulse chase exposure to low-level ROS enhances differentiation toward the cardiomyogenic as well as vascular cell lineage. This review summarizes the current knowledge of ROS-induced cardiovascular differentiation of embryonic stem cells as well as the role of ROS in tumor-induced angiogenesis.

Electrical and Structural Remodeling: Role in the Genesis and Maintenance of Atrial Fibrillation

Atrial fibrillation (AF) and congestive heart failure (CHF) are 2 frequently encountered conditions in clinical practice. Both lead to changes in atrial function and structure, an array of processes known as atrial remodeling. This review provides an overview of ionic, electrical, contractile, neurohumoral, and structural atrial changes responsible for initiation and maintenance of AF. In the last decade, many studies have evaluated atrial remodeling due to AF or CHF. Both conditions often coexist, which makes it difficult to distinguish the contribution of each. Because of atrial stretch in the setting of hypertension or CHF, atrial remodeling frequently occurs long before AF arises. Alternatively, AF may lead to electrical remodeling, that is, shortening of refractoriness due to the high atrial rate itself. In many experimental AF or rapid atrial pacing studies, the ventricular rate was uncontrolled. In those studies, atrial stretch due to CHF may have interfered with the high atrial rate to produce a mixed type of electrical and structural remodeling. Other studies have dissected the individual role of AF or atrial tachycardia from the role CHF plays in atrial remodeling. Atrial fibrillation itself does not lead to structural remodeling, whereas this is frequently produced by hypertension or CHF, even in the absence of AF. Primary and secondary prevention programs should tailor treatment to the various types of remodeling.

Src homology 2-containing phosphotyrosine phosphatase regulates endothelin-1-induced epidermal growth factor receptor transactivation in rat renal tubular cell NRK-52E

Epidermal growth factor (EGF) and endothelin-1 (ET-1) have been shown to be involved in proliferation and autoregeneration of renal tubular cells. This study aims to investigate the regulatory mechanism of ET-1-mediated EGF receptor (EGFR) transactivation in rat renal tubular cells (NRK-52E). Exposure of NRK-52E cells to ET-1 was found to stimulate the phosphorylation of EGFR and induce reactive oxygen species (ROS) generation. Both NAD(P)H oxidase inhibitor, diphenyliodonium (DPI) and ROS scavenger N-acetylcysteine (NAC), inhibited EGFR transactivation and extracellular signal-regulated kinase (ERK) phosphorylation caused by ET-1. In contrast, blockade of EGFR by AG1478 inhibited the phosphorylation of ERK but not ROS generation following ET-1 exposure. We found that the catalytic cysteine of Src homology 2-containing phosphotyrosine phosphatase (SHP-2) was transiently oxidized by ET-1 treatment in a modified malachite green phosphatase assay. In EGFR co-immunoprecipitation, SHP-2 was also found to interact with EGFR following ET-1 treatment. In SHP-2 knockdown NRK-52E cells, ET-1-induced EGFR transactivation was dramatically elevated and not influenced by NAC. However, GM6001 (an MMP inhibitor) and heparin binding (HB)-EGF neutralizing antibody suppressed this elevation. Our data suggest that ROS-mediated oxidation of SHP-2 is essential for HB-EGF-mediated EGFR transactivation in ET-1 signaling pathway in NRK-52E cells.

Oxidative stress and atherosclerosis

Understanding of the pathophysiology of atherosclerosis can provide new strategies for the prevention and treatment of patients with this common disease. Clinical, epidemiologic, and basic molecular science studies have identified oxidative stress as a factor contributing to the development and progression of atherosclerosis. Oxidative stress also participates in the pathogenesis of endothelial dysfunction and hypertension, two important factors in many patients with atherosclerosis. Further, it contributes to mechanisms of disease progression such as lipid oxidation and vascular remodeling. This article reviews the role of reactive oxygen species and oxidative stress in atherosclerosis.

Antioxidant and nitric oxide-sparing actions of dihydropyridines and ACE inhibitors differ in human endothelial cells

The effects of dihydropyridine Ca2+ channel blockers (DHP) and ACE inhibitors on superoxide formation and nitric oxide (NO) bioavailability were compared in human EA.Hy926 endothelial cells (EC). EC were stimulated 4 h with angiotensin II (Ang II, 10 nM) +/- study drugs. Specific superoxide formation was measured by lucigenin-enhanced chemiluminescence, reduction of cytochrome c and rhodamine-123 fluorescence. Free NO release was determined with an amperometric NO sensor. NADPH oxidase subunits expression was examined with Western Blot. In untreated EC the intracellular superoxide is -64.3 +/- 6.0% decreased compared to Ang II stimulated EC. Elevated extracellular superoxide formation was on a -43.0 +/- 1.7% lower level in untreated EC. The DHP Ca2+-channel agonist BayK8644 and ACE inhibitors captopril and ramiprilat led extracellular superoxide concentration to control level. Enalaprilat blocked extracellular superoxide, the DHP amlodipine and nisoldipine prevented intracellular increases only (n = 8-9, p < 0.05). Icatibant (HOE 140), a kinin-B2 receptor antagonist, attenuated antioxidant actions of all tested agents except of nisoldipine. Ang II-induced superoxide was elevated by the phorbolester PMA and blocked by the protein kinase C (PKC) inhibitor chelerythrine. Suppression of substance P-evoked NO release by Ang II (>70%, n = 6) was reversed by the PKC inhibitor chelerythrine, the DHP amlodipine and nisoldipine and the ACE inhibitor ramiprilat. Further, Ang II reduces Nox-4 expression by 34.5 +/- 4.9. Nox-2 expression was not regulated. DHP and ACE inhibitors exert different antioxidant effects in human EC stimulated with Ang II, but both improve NO bioavailability via bradykinin and modulation of redox-regulating enzymes.

Nitric oxide inhibits endothelin-1-induced cardiomyocyte hypertrophy through cGMP-mediated suppression of extracellular-signal regulated kinase phosphorylation

Cardiac hypertrophy is a compensatory mechanism in response to a variety of cardiovascular diseases. Recently, reactive oxygen species and nitric oxide (NO) have been demonstrated to be involved in the pathogenesis of atherosclerosis; however, the role of these free radicals in the development of cardiac hypertrophy remains unclear. In this study, we investigate NO modulation of cellular signaling in endothelin-1 (ET-1)-induced cardiomyocyte hypertrophy in culture. ET-1 treatment of cardiomyocytes increased constitutive NO synthase activity and induced NO production via the stimulation of ET-receptor subtype ET(B). Using Northern blot analysis and chloramphenicol acetyltransferase assay, we found that NO suppressed the ET-1-induced increase in c-fos mRNA level and promoter activity. In contrast, ET-1 stimulation of c-fos expression was augmented by depletion of endogenous NO generation with the addition of NO scavenger PTIO into cardiomyocytes. Cells cotransfected with the dominant negative and positive mutants of signaling molecules revealed that the Ras/Raf/extracellular-signal regulated kinase (ERK) signaling pathway is involved in ET-induced c-fos gene expression. Furthermore, NO directly inhibited ET-1-induced ERK phosphorylation and activation in a cGMP-dependent manner, indicating that NO modulates ET-1-induced c-fos expression via its inhibitory effect on ERK signaling pathway. The ET-1-stimulated activator protein-1 (AP-1) DNA binding activity and AP-1-mediated reporter activity were attenuated by NO. In addition, NO also significantly inhibited ET-1-stimulated promoter activity of hypertrophic marker gene beta-myosin heavy chain and the enhanced protein synthesis. Taken together, our findings provide the molecular basis of NO as a negative regulator in ET-1-induced cardiac hypertrophy.

Tetramethylpyrazine downregulates angiotensin II-induced endothelin-1 gene expression in vascular endothelial cells

1. Tetramethylpyrazine (TMP) is one of the active ingredients of the Chinese herb Ligusticum wallichii Franchat. It is well documented that TMP exerts a cardiovascular protective effect. The aims of the present study were to examine whether TMP alters angiotenisn (Ang) II-induced endothelin (ET)-1 gene expression and to identify the putative underlying signalling pathways in vascular endothelial cells. 2. Cultured vascular endothelial cells were pre-incubated with TMP, stimulated with AngII and ET-1 gene expression was then examined. The effects of TMP pretreatment on AngII-induced extracellular signal-regulated kinase (ERK) phosphorylation were investigated to elucidate the intracellular mechanism responsible for the effects of TMP on ET-1 gene expression. 3. Tetramethylpyrazine inhibited AngII-induced ET-1 gene expression, as revealed by nothern blotting and a promoter activity assay. Tetramethylpyrazine also inhibited the AngII-induced increase in intracellular reactive oxygen species (ROS), as measured by the redox sensitive fluorescent dye 2' 7'-dichlorofluorescin diacetate and ERK phosphorylation. 4. In summary, we have demonstrated, for the first time, that TMP inhibits AngII-induced ROS generation, ERK phosphorylation and ET-1 gene expression in vascular endothelial cells. Thus, the present study delivers important new insights into the molecular pathways that may contribute to the proposed beneficial effects of TMP in the cardiovascular system.

Supplement of tetrahydrobiopterin by a gene transfer of GTP cyclohydrolase I cDNA improves vascular dysfunction in insulin-resistant rats

Deficiency of tetrahydrobiopterin (BH4) in the vascular tissue contributes to endothelial dysfunction in the insulin-resistant state. We intended to develop a new gene transfer method by overexpression of its biosynthetic enzyme, GTP cyclohydrolase I (GTP-CH1). The GTP-CH1 cDNA was inserted into a pCAGGS vector, and then plasmid DNA was mixed with atelocollagen, and the aliquot was injected into thigh muscles of insulin-resistant Zucker fatty rats. After 4 weeks, pteridine derivative levels, superoxide anion (O2-), activity of endothelial nitric oxide synthase (eNOS), and endothelium-dependent relaxation were evaluated in the aortas obtained from Zucker lean or fatty rats. The BH4 contents and GTP-CH1 activity in Zucker fatty rats were 50%-55% less than those of Zucker lean rats. However, those impairments were significantly improved by a plasmid DNA injection, and aortic BH4 content reached more than 80% of the level of Zucker lean rats. Increased A23187-stimulated O2- production as well as decreased eNOS activity and endothelial function in insulin-resistant Zucker fatty rats were improved by a plasmid DNA injection to a level similar to that in Zucker lean rats. These findings suggest that intramuscular GTP-CH1 gene transfer using atelocollagen serves as a useful method of long-term systemic delivery of BH4 and the treatment of endothelial dysfunction.

Calcium channel blocker inhibits Western-type diet-evoked atherosclerosis development in ApoE-deficient mice

Calcium channel blockers slow the progression of atherosclerosis. The purpose of the present experiments was to examine the action of lacidipine in a condition that accelerates the development of atherosclerosis in order to test the hypothesis that the protective action of lacidipine in atherosclerosis is unrelated to the reduction of blood pressure. Male ApoE-deficient mice (6 weeks old) were exposed either to normal chow (ND) or to a Western-type diet (WD, adjusted calorie diet containing 42% from fat) for 8 weeks. Western-type diet induced a reduction of nitric oxide (NO)-mediated endothelium-dependent relaxation to acetylcholine (Max relaxation % = 55.8 +/- 2 for ND and 46.6 +/- 2 for WD, n = 8, p < 0.05). Dose-relaxation curves to S-nitroso-N-acetylpenicillamine (SNAP) NO donor were also significantly rightward-shifted (n = 7, ANOVA, p < 0.01) in WD compared with ND arteries. Chronic treatment of WD mice with lacidipine (1 and 3 mg/kg/day) increased significantly the acetylcholine-evoked relaxation (to 76.6 +/- 3.5%, n = 6, ANOVA, p < 0.001) and prevented the loss of responsiveness to SNAP in mice exposed to WD. Plasma renin activity and endothelin-1 plasma levels as well as thiobarbituric acid-reactive substance levels in kidneys were significantly lower in WD mice treated with lacidipine than in untreated ones. In mice exposed to WD lacidipine reduced extension of atherosclerotic lesions, renal injury and increase in blood pressure. Experimental data indicate that inhibition of Western-type diet-evoked alterations is related to both antioxidant and vasoactive properties of lacidipine.