Nitric oxide and cardiac function

Nitric oxide (NO) participates in the control of contractility and heart rate, limits cardiac remodeling after an infarction and contributes to the protective effect of ischemic pre- and postconditioning. Low concentrations of NO, with production of small amounts of cGMP, inhibit phosphodiesterase III, thus preventing the hydrolysis of cAMP. The subsequent activation of a protein-kinase A causes the opening of sarcolemmal voltage-operated and sarcoplasmic ryanodin receptor Ca(2+) channels, thus increasing myocardial contractility. High concentrations of NO induce the production of larger amounts of cGMP which are responsible for a cardiodepression in response to an activation of protein kinase G (PKG) with blockade of sarcolemmal Ca(2+) channels. NO is also involved in reduced contractile response to adrenergic stimulation in heart failure. A reduction of heart rate is an evident effect of NO-synthase (NOS) inhibition. It is noteworthy that the direct effect of NOS inhibition can be altered if baroreceptors are stimulated by increases in blood pressure. Finally, NO can limit the deleterious effects of cardiac remodeling after myocardial infarction possibly via the cGMP pathway. The protective effect of NO is mainly mediated by the guanylyl cyclase-cGMP pathway resulting in activation of PKG with opening of mitochondrial ATP-sensitive potassium channels and inhibition of the mitochondrial permeability transition pores. NO acting on heart is produced by vascular and endocardial endothelial NOS, as well as neuronal and inducible synthases. In particular, while in the basal control of contractility, endothelial synthase has a predominant role, the inducible isoform is mainly responsible for the cardiodepression in septic shock.

Neurovascular protection by ischemic tolerance: role of nitric oxide and reactive oxygen species

Cerebral ischemic preconditioning or tolerance is a powerful neuroprotective phenomenon by which a sublethal injurious stimulus renders the brain resistant to a subsequent damaging ischemic insult. We used lipopolysaccharide (LPS) as a preconditioning stimulus in a mouse model of middle cerebral artery occlusion (MCAO) to examine whether improvements in cerebrovascular function contribute to the protective effect. Administration of LPS 24 h before MCAO reduced the infarct by 68% and improved ischemic cerebral blood flow (CBF) by 114% in brain areas spared from infarction. In addition, LPS prevented the dysfunction in cerebrovascular regulation induced by MCAO, as demonstrated by normalization of the increase in CBF produced by neural activity, hypercapnia, or by the endothelium-dependent vasodilator acetylcholine. These beneficial effects of LPS were not observed in mice lacking inducible nitric oxide synthase (iNOS) or the nox2 subunit of the superoxide-producing enzyme NADPH oxidase. LPS increased reactive oxygen species and the peroxynitrite marker 3-nitrotyrosine in wild-type mice but not in nox2 nulls. The peroxynitrite decomposition catalyst 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrinato iron (III) attenuated LPS-induced nitration and counteracted the beneficial effects of LPS on infarct volume, ischemic CBF, and vascular reactivity. Thus, LPS preserves neurovascular function and ameliorates CBF in regions of the ischemic territory at risk for infarction. This effect is mediated by peroxynitrite formed from iNOS-derived NO and nox2-derived superoxide. The data indicate that preservation of cerebrovascular function is an essential component of ischemic tolerance and suggest that combining neuroprotection and vasoprotection may be a valuable strategy for treating ischemic brain injury.

TheN-Acylethanolamine-Mediated Regulatory Pathway in Plants

While cannabinoids are secondary metabolites synthesized by just a few plant species, N-acylethanolamines (NAEs) are distributed widely in the plant kingdom, and are recovered in measurable, bioactive quantities in many plant-derived products. NAEs in higher plants are ethanolamides of fatty acids with acyl-chain lenghts of C12-C(18) and zero to three C=C bonds. Generally, the most-abundant NAEs found in plants and vertebrates are similar, including NAE 16 : 0, 18 : 1, 18 : 2, and 18 : 3. Like in animal systems, NAEs are formed in plants from N-acylphosphatidylethanolamines (NAPEs), and they are hydrolyzed by an amidase to yield ethanolamine and free fatty acids (FFA). Recently, a homologue of the mammalian fatty acid amide hydrolase (FAAH-1) was identified in Arabidopsis thaliana and several other plant species. Overexpression of Arabidopsis FAAH (AtFAAH) resulted in plants that grew faster, but were more sensitive to biotic and abiotic insults, suggesting that the metabolism of NAEs in plants resides at the balance between growth and responses to environmental stresses. Similar to animal systems, exogenously applied NAEs have potent and varied effects on plant cells. Recent pharmacological approaches combined with molecular-genetic experiments revealed that NAEs may act in certain plant tissues via specific membrane-associated proteins or by interacting with phospholipase D-alpha, although other, direct targets for NAE action in plants are likely to be discovered. Polyunsaturated NAEs can be oxidized via the lipoxygenase pathway in plants, producing an array of oxylipin products that have received little attention so far. Overall, the conservation of NAE occurrence and metabolic machinery in plants, coupled with the profound physiological effects of elevating NAE content or perturbing endogenous NAE metabolism, suggest that an NAE-mediated regulatory pathway, sharing similarities with the mammalian endocannabinoid pathway, indeed exists.

Neuronal apoptosis in neurodegeneration

Apoptosis mediates the precise and programmed natural death of neurons and is a physiologically important process in neurogenesis during maturation of the central nervous system. However, premature apoptosis and/or an aberration in apoptosis regulation is implicated in the pathogenesis of neurodegeneration, a multifaceted process that leads to various chronic disease states, such as Alzheimer's (AD), Parkinson's (PD), Huntington's (HD) diseases, amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), and diabetic encephalopathy. The current review focuses on two major areas (a) the fundamentals of apoptosis, which includes elements of the apoptotic machinery, apoptosis inducers, and emerging concepts in apoptosis research, and (b) apoptotic involvement in neurodegenerative disorders, neuroprotective treatment strategies/modalities, and the mechanisms of, and signaling in, neuronal apoptosis. Current and new experimental models for apoptosis research in neurodegenerative diseases are also discussed.

Impairment of cardiac insulin signaling and myocardial contractile performance in high-cholesterol/fructose-fed rats

Although insulin resistance is recognized as a potent and prevalent risk factor for coronary heart disease, less is known as to whether insulin resistance causes an altered cardiac phenotype independent of coronary atherosclerosis. In this study, we investigated the relationship between insulin resistance and cardiac contractile dysfunctions by generating a new insulin resistance animal model with rats on high cholesterol-fructose diet. Male Sprague-Dawley rats were given high cholesterol-fructose (HCF) diet for 15 wk; the rats developed insulin resistance syndrome characterized by elevated blood pressure, hyperlipidemia, hyperinsulinemia, impaired glucose tolerance, and insulin resistance. The results show that HCF induced insulin resistance not only in metabolic-response tissues (i.e., liver and muscle) but also in the heart as well. Insulin-stimulated cardiac glucose uptake was significantly reduced after 15 wk of HCF feeding, and cardiac insulin resistance was associated with blunted Akt-mediated insulin signaling along with glucose transporter GLUT4 translocation. Basal fatty acid transporter FATP1 levels were increased in HCF rat hearts. The cardiac performance of the HCF rats exhibited a marked reduction in cardiac output, ejection fraction, stroke volume, and end-diastolic volume. It also showed decreases in left ventricular end-systolic elasticity, whereas the effective arterial elasticity was increased. In addition, the relaxation time constant of left ventricular pressure was prolonged in the HCF group. Overall, these results indicate that insulin resistance reduction of cardiac glucose uptake is associated with defects in insulin signaling. The cardiac metabolic alterations that impair contractile functions may lead to the development of cardiomyopathy.

CB2-receptor stimulation attenuates TNF-alpha-induced human endothelial cell activation, transendothelial migration of monocytes, and monocyte-endothelial adhesion

Targeting cannabinoid-2 (CB(2)) receptors with selective agonists may represent a novel therapeutic avenue in various inflammatory diseases, but the mechanisms by which CB(2) activation exerts its anti-inflammatory effects and the cellular targets are elusive. Here, we investigated the effects of CB(2)-receptor activation on TNF-alpha-induced signal transduction in human coronary artery endothelial cells in vitro and on endotoxin-induced vascular inflammatory response in vivo. TNF-alpha induced NF-kappaB and RhoA activation and upregulation of adhesion molecules ICAM-1 and VCAM-1, increased expression of monocyte chemoattractant protein, enhanced transendothelial migration of monocytes, and augmented monocyte-endothelial adhesion. Remarkably, all of the above-mentioned effects of TNF-alpha were attenuated by CB(2) agonists. CB(2) agonists also decreased the TNF-alpha- and/or endotoxin-induced ICAM-1 and VCAM-1 expression in isolated aortas and the adhesion of monocytes to aortic vascular endothelium. CB(1) and CB(2) receptors were detectable in human coronary artery endothelial cells by Western blotting, RT-PCR, real-time PCR, and immunofluorescence staining. Because the above-mentioned TNF-alpha-induced phenotypic changes are critical in the initiation and progression of atherosclerosis and restenosis, our findings suggest that targeting CB(2) receptors on endothelial cells may offer a novel approach in the treatment of these pathologies.

Cannabinoid-2 receptor agonist HU-308 protects against hepatic ischemia/reperfusion injury by attenuating oxidative stress, inflammatory response, and apoptosis

In this study, we have investigated the role of the cannabinoid CB(2) (CB(2)) receptor in an in vivo mouse model of hepatic ischemia/reperfusion (I/R) injury. In addition, we have assessed the role of the CB(2) receptor in TNF-alpha-induced ICAM-1 and VCAM-1 expression in human liver sinusoidal endothelial cells (HLSECs) and in the adhesion of human neutrophils to HLSECs in vitro. The potent CB(2) receptor agonist HU-308, given prior to the induction of I/R, significantly attenuated the extent of liver damage (measured by serum alanine aminotransferase and lactate dehydrogenase) and decreased serum and tissue TNF-alpha, MIP-1alpha, and MIP-2 levels, tissue lipid peroxidation, neutrophil infiltration, DNA fragmentation, and caspase 3 activity. The protective effect of HU-308 against liver damage was also preserved when given right after the ischemic episode. HU-308 also attenuated the TNF-alpha-induced ICAM-1 and VCAM-1 expression in HLSECs, which expressed CB(2) receptors, and the adhesion of human neutrophils to HLSECs in vitro. These findings suggest that selective CB(2) receptor agonists may represent a novel, protective strategy against I/R injury by attenuating oxidative stress, inflammatory response, and apoptosis.

Pharmacological inhibition of CB1 cannabinoid receptor protects against doxorubicin-induced cardiotoxicity

OBJECTIVES

We aimed to explore the effects of pharmacologic inhibition of cannabinoid-1 (CB1) receptor in in vivo and in vitro models of doxorubicin (DOX)-induced cardiotoxicity.

BACKGROUND

Doxorubicin is one of the most potent antitumor agents available; however, its clinical use is limited because of the risk of severe cardiotoxicity. Endocannabinoids mediate cardiodepressive effects through CB1 receptors in various pathophysiological conditions, and these effects can be reversed by CB1 antagonists.

METHODS

Left ventricular function was measured by Millar pressure-volume system. Apoptosis markers, CB1/CB2 receptor expression, and endocannabinoid levels were determined by immunohistochemistry, Western blot, reverse transcription-polymerase chain reaction, real-time polymerase chain reaction, flow cytometry, fluorescent microscopy, and liquid chromatography/in-line mass spectrometry techniques.

RESULTS

Five days after the administration of a single dose of DOX (20 mg/kg intraperitoneally) to mice, left ventricular systolic pressure, maximum first derivative of ventricular pressure with respect to time (+dP/dt), stroke work, ejection fraction, cardiac output, and load-independent indexes of contractility (end-systolic pressure-volume relation, preload-recruitable stroke work, dP/dt-end-diastolic volume relation) were significantly depressed, and the myocardial level of the endocannabinoid anandamide (but not CB1/CB2 receptor expression) was elevated compared with vehicle-treated control mice. Treatment with the CB1 antagonists rimonabant or AM281 markedly improved cardiac dysfunction and reduced DOX-induced apoptosis in the myocardium. Doxorubicin also decreased cell viability and induced apoptosis in the H9c2 myocardial cell line measured by flow cytometry and fluorescent microscopy, which were prevented by the preincubation of the cells with either CB1 antagonist, but not with CB1 and CB2 agonists and CB2 antagonists.

CONCLUSIONS

These data suggest that CB1 antagonists may represent a new cardioprotective strategy against DOX-induced cardiotoxicity.

Top-down and bottom-up mass spectrometric characterization of human myoglobin-centered free radicals induced by oxidative damage

In an effort to determine the utility of top-down mass spectrometric methodologies for the characterization of protein radical adducts, top-down approaches were investigated and compared to the traditional bottom-up approaches. Specifically, the nature of the radicals on human myoglobin induced by the addition of hydrogen peroxide and captured by the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) was investigated. The most abundant ion observed in the electrospray mass spectrum of this reaction mixture corresponds in mass to the human myoglobin plus one DMPO molecule. In addition, a second ion of lower abundance is observed, which corresponds to a second DMPO molecule being trapped on myoglobin. Top-down analyses using Fourier transform ion cyclotron resonance mass spectrometry can be used to characterize proteins and, thus, were performed on several different charge-state ions of both the native and the mono-DMPO nitrone adduct of human myoglobin. Data produced from the top-down analyses are very complex yet information rich. In the case of DMPO-modified human myoglobin, the top-down data localized the DMPO spin trap to residues 97-110 of the myoglobin. The observation of the y43+5 fragment ion arising from C-terminal cleavage to the cysteine-110 residue in the MS/MS spectrum of DMPO-modified myoglobin and not in the unmodified myoglobin implicates a change to this residue, specifically, DMPO adduction. On the other hand, using the traditional bottom-up approach of peptide mapping and MS sequencing methodologies, two DMPO radical adducts on human myoglobin were identified, Cys-110 and Tyr-103. The bottom-up approach is more proven and robust than the top-down methodologies. Nonetheless, the bottom-up and top-down approaches to protein characterization are complementary rather than competitive approaches with each having its own utility.

The peptaibol alamethicin induces an rRNA-cleavage-associated death in Arabidopsis thaliana

The plant-metabolic response to amphipathic peptides produced by the soil fungi of the genus Trichoderma remains largely unknown. The present investigation was undertaken to examine the death process in alamethicin-treated Arabidopsis thaliana plantlets. The rapid death triggered by alamethicin (at 50 microM) was shown to be associated with protein-synthesis arrest and with specific cleavage of 18S and 25S ribosomal RNA. The use of an inhibitor of nitric oxide (NO) synthases and of an NO scavenger suggested that rRNA cleavage was suppressed by NO. Experiments conducted with a synthetic alamethicin analogue, in which all alpha-aminoisobutyric acid (Aib) residues have been replaced by leucine moieties, showed that the non-coded residues are essential for the ability of the peptaibol to induce rRNA cleavage in Arabidopsis. Our data indicate that further investigations on the mode of action of alamethicin in planta could be of great interest to study the death-signaling pathway associated with rRNA degradation in plants.

Effect of nitric oxide on ram sperm motility in vitro

The aim of this study is to investigate the effects of NO on sperm motility of ram. After incubation of normozoospermic samples for 160 min in the presence of L-arginine (NOS substrate), SNP (NO donor), L-NAME (non-selective nitric oxide inhibitor) and packed erythrocytes (NO scavenger), sperm motility assessed in four grades (A, B, C, D). In this study, L-arginine and SNP non-significantly increased progressive motility at low concentration and significantly decreased progressive motility at high concentration. L-NAME and packed erythrocytes dose-dependently decreased progressive sperm motility. It is concluded that sperm motility of ram physiologically depend on nitric oxide action although excess generation of nitric oxide by sperm or exogenous NO could not increase sperm motility and it seems that excess NO provides toxic condition to decrease sperm motility.

Evidence for oxygen as the master regulator of the responsiveness of soluble guanylate cyclase and cytochrome c oxidase to nitric oxide

Haem is used as a versatile receptor for redox active molecules; most notably NO (nitric oxide) and oxygen. Three haem-containing proteins, myoglobin, haemoglobin and cytochrome c oxidase, are now known to bind NO, and in all these cases competition with oxygen plays an important role in the biological outcome. NO also binds to the haem group of sGC (soluble guanylate cyclase) and initiates signal transduction through the formation of cGMP in a process that is oxygen-independent. From biochemical studies, it has been shown that sGC is substantially more sensitive to NO than is cytochrome c oxidase, but a direct comparison in a cellular setting under various oxygen levels has not been reported previously. In this issue of the Biochemical Journal, Cadenas and co-workers reveal how oxygen can act as the master regulator of the relative sensitivity of the cytochrome c oxidase and sGC signalling pathways to NO. These findings have important implications for our understanding of the interplay between NO and oxygen in both physiology and the pathology of diseases associated with hypoxia.

Cytotoxicity of paraquat in microglial cells: Involvement of PKCdelta- and ERK1/2-dependent NADPH oxidase

Excess production of reactive oxygen species (ROS) is an important mechanism underlying the pathogenesis of a number of neurodegenerative diseases including Parkinson's disease (PD) which is characterized by a progressive loss of dopaminergic neurons in the substantia nigra. Exposure to paraquat, an herbicide with structure similar to the dopaminergic neurotoxin, 1-methyl-4-phenylpyridinium (MPP+), has been shown to produce PD-like symptoms. Despite previous focus on the dopaminergic neurons and signaling pathways involved in their cell death, recent studies have implicated microglial cells as a major producer of ROS for damaging neighboring neurons. In this study, we examined the source of ROS and the underlying signaling pathway for paraquat-induced cytotoxicity to BV-2 microglial cells. Paraquat-induced ROS production (including superoxide anions) in BV-2 cells was accompanied by translocation of the p67phox cytosolic subunit of NADPH oxidase to the membrane. Paraquat-induced ROS production was inhibited by NADPH oxidase inhibitors, apocynin and diphenylene iodonium (DPI), but not the xanthine/xanthine oxidase inhibitor, allopurinol. Apocynin and DPI also rescued cells from paraquat-induced toxicity. The inhibitors for protein kinase C delta (PKCdelta) or extracellular signal-regulated kinases (ERK1/2) could partially attenuate paraquat-induced ROS production and cell death. Rottlerin, a selective PKCdelta inhibitor, also inhibited paraquat-induced translocation of p67phox. Taken together, this study demonstrates the involvement of ROS from NADPH oxidase in mediating paraquat cytotoxicity in BV-2 microglial cells and this process is mediated through PKCdelta- and ERK-dependent pathways.

The effect of mild hyperuricemia on urinary transforming growth factor beta and the progression of chronic kidney disease

Although mild hyperuricemia is common in patients with renal disease, it has usually been considered a marker of reduced nephron mass rather than a risk factor for progression of kidney disease. On the other hand, experiments in a rat model demonstrated important deleterious effects of mild hyperuricemia on several aspects of renal structure and function. In the present investigation, the impact of the discontinuation of allopurinol therapy on the control of hypertension and the rate of progression of chronic kidney disease was considered. The present work involved 50 patients, suffering from stage 3 and 4 chronic kidney disease. All of them were on chronic allopurinol therapy for the treatment of mild hyperuricemia. Their blood pressure, serum creatinine and uric acid levels were followed for 12 months following allopurinol withdrawal. Urinary transforming growth factor beta-1 (TGF-beta1) was assayed by a solid-phase enzyme-linked immunosorbent assay. After allopurinol withdrawal, significant worsening of hypertension, significant acceleration of the rate of loss of kidney function and a significant increase in the urinary excretion of TGF-beta1 were observed in the group of patients who were not receiving pharmacological blockers of the renin-angiotensin system. In conclusion, asymptomatic hyperuricemia has a deleterious effect on the progression of chronic kidney disease and the control of hypertension. This effect was blocked by treatment with renin-angiotensin system blockers.

In vitro and in vivo antiproliferative and trypanocidal activities of ruthenium NO donors

BACKGROUND AND PURPOSE

Many compounds liberating NO (NO donors) have been used as therapeutic agents. Here we test two ruthenium nitrosyls, which release NO when activated by biological reducing agents, for their effects in vitro and in vivo against Trypanosoma cruzi, the agent responsible for the American trypanosomiasis (Chagas' disease).

EXPERIMENTAL APPROACH

Ruthenium NO donors were incubated with a partially drug-resistant strain of T. cruzi and the anti-proliferative and trypanocidal activities evaluated. In a mouse model of acute Chagas' disease, trypanocidal activity was evaluated by measuring parasitemia, survival rate of infected mice and elimination of amastigotes in myocardial tissue.

KEY RESULTS

In vitro, the observed anti-proliferative and trypanocidal activities of trans-[Ru(NO)(NH(3))(4)isn](BF(4))(3) and trans-[Ru(NO)(NH(3))(4)imN](BF(4))(3) were due to NO liberated upon reduction of these nitrosyls. Ru(NO)isn had a lower IC(50 epi) (67 microM) than the NO donor, sodium nitroprusside (IC(50 epi)=244 microM) and Ru(NO)imN (IC(50 try)=52 microM) was more potent than gentian violet (IC(50 try)=536 microM), currently used in the treatment of blood. Both ruthenium nitrosyls eliminated, in vivo, extracellular as well as intracellular forms of T. cruzi in the bloodstream and myocardial tissue and allowed survival of up to 80% of infected mice at a dose (100 nmol kg(-1) day(-1)) much lower than the optimal dose for benznidazole (385 micromol kg(-1) day(-1)).

CONCLUSIONS AND IMPLICATIONS

Our data strongly suggest that NO liberated is responsible for the anti-proliferative and trypanocidal activities of the ruthenium NO donors and that these compounds are promising leads for novel and effective anti-parasitic drugs.

Nitric oxide regulation of microvascular oxygen

The role of nitric oxide (NO) as a highly diffusible free radical gaseous vasodilator is intrinsically linked to the control of blood flow and oxygen (O(2)) delivery to tissue. NO also is involved in regulating mitochondrial O(2) metabolism, growth of new blood vessels, and blood oxygenation through control of respiratory ventilation. Hemoglobin and myoglobin may help to conserve NO for subsequent release of a NO-related vasoactive species under hypoxic conditions. NO has a major role in regulating microvascular O(2), and dysfunctional NO signaling is associated with the pathogenesis of metabolic and cardiovascular diseases.

Contribution of poly(ADP-ribose) polymerase to postischemic blood-brain barrier damage in rats

The nuclear enzyme poly(ADP-ribose) polymerase (PARP) is activated by oxidative stress and plays a significant role in postischemic brain injury. We assessed the contribution of PARP activation to the blood-brain barrier (BBB) disruption and edema formation after ischemia-reperfusion. In male Wistar rats, global cerebral ischemia was achieved by occluding the carotid arteries and lowering arterial blood pressure for 20 mins. The animals were treated with saline or with the PARP inhibitor N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-N, N-dimethylacetamide.HCl (PJ34); (10 mg/kg, i.v.) before ischemia. After 40 mins, 24, and 48 h of reperfusion, the permeability of the cortical BBB was determined after Evans Blue (EB) and Na-fluorescein (NaF) administration. The water content of the brain was also measured. The permeability of the BBB for EB increased after ischemia-reperfusion compared with the nonischemic animals after 24 and 48 h reperfusion but PARP inhibition attenuated this increase at 48 h (nonischemic: 170+/-9, saline: 760+/-95, PJ34: 472+/-61 ng/mg tissue). The extravasation of NaF showed similar changes and PJ34 post-treatment attenuated the permeability increase even at 24 h. PARP inhibition decreased the brain edema seen at 48 h. Because PARP has proinflammatory properties, the neutrophil infiltration of the cortex was determined, which showed lower values after PJ34 treatment. Furthermore, PJ34 treatment decreased the loss of the tight junction protein occludin at 24 and 48 h. The inhibition of PARP activity accompanied by reduced post-ischemic BBB disturbance and decreased edema formation suggests a significant role of this enzyme in the development of cerebral vascular malfunction

Relationship between quantum-chemical descriptors of proton dissociation and experimental acidity constants of various hydroxylated coumarins. Identification of the biologically active species for xanthine oxidase inhibition

Quantum-chemical descriptors related to proton dissociation constants of a set of coumarins hydroxylated in various positions have been computed and related to the experimental pK(a) values. An excellent correlation was found between the computed deprotonation energies of hydroxycoumarins in water and their experimental pK(a) values, and the results were used to predict the pK(a) of other hydroxycoumarins. Then, predicted and experimental pK(a) values were used as a basis for interpreting and discussing the variation of xanthine oxidase inhibitory activities within a subset of coumarins, with the aim of identifying the molecular species most relevant for enzyme inhibition.

The many faces of nitric oxide: cytotoxic, cytoprotective or both

Nitric oxide (NO) has emerged as a major modulator of cellular function in health and disease. In addition to its well-known role as a mediator of smooth muscle relaxation, a rapidly developing body of research suggests, paradoxically, that NO can have both cytotoxic and cytoprotective effects. In this issue of Neurogastroenterology and Motility, Choi et al. provide evidence that supports NO has a prosurvival effect on interstitial cells of Cajal in the mouse stomach. The objective of this short review is to place this interesting report in the context of the current literature.

Loss of cardiac tetralinoleoyl cardiolipin in human and experimental heart failure

The mitochondrial phospholipid cardiolipin is required for optimal mitochondrial respiration. In this study, cardiolipin molecular species and cytochrome oxidase (COx) activity were studied in interfibrillar (IF) and subsarcolemmal (SSL) cardiac mitochondria from Spontaneously Hypertensive Heart Failure (SHHF) and Sprague-Dawley (SD) rats throughout their natural life span. Fisher Brown Norway (FBN) and young aortic-constricted SHHF rats were also studied to investigate cardiolipin alterations in aging versus pathology. Additionally, cardiolipin was analyzed in human hearts explanted from patients with dilated cardiomyopathy. A loss of tetralinoleoyl cardiolipin (L(4)CL), the predominant species in the healthy mammalian heart, occurred during the natural or accelerated development of heart failure in SHHF rats and humans. L(4)CL decreases correlated with reduced COx activity (no decrease in protein levels) in SHHF cardiac mitochondria, but with no change in citrate synthase (a matrix enzyme) activity. The fraction of cardiac cardiolipin containing L(4)CL became much lower with age in SHHF than in SD or FBN mitochondria. In summary, a progressive loss of cardiac L(4)CL, possibly attributable to decreased remodeling, occurs in response to chronic cardiac overload, but not aging alone, in both IF and SSL mitochondria. This may contribute to mitochondrial respiratory dysfunction during the pathogenesis of heart failure.

In vitro production of nitrite by low and high density sperm subpopulations of human, bull and ram

The aim of present study was to characterize nitric oxide production via nitrite measurement as its stable metabolite in the different species of spermatozoa (human, bull and ram). Sperm samples were fractionated on the basis of density with the use of a three-layer Percoll gradient. Spermatozoa collected from the various percoll gradient interfaces (50/70 and 70/95%). Results showed that nitrite is produced by human, bull and ram spermatozoa, but in the same sample, there were no significant difference between high density (with higher percentage of motility) sperm subpopulation and low density (with lower percentage of motility) sperm subpopulation Therefore, it seems that spermatozoa with different motility in the one sperm population have the same production of NO in physiological conditionthat is different from pathological condition (e.g., in the subfertile men).

Inhibition of human hair follicle growth by endo- and exocannabinoids

Recent studies strongly suggest that the cannabinoid system is a key player in cell growth control. Since the organ-culture of human hair follicles (HF) offers an excellent, clinically relevant model for complex tissue interaction systems, we have asked whether the cannabinoid system plays a role in hair growth control. Here, we show that human scalp HF, intriguingly, are both targets and sources of endocannabinoids. Namely, the endocannabinoid N-arachidonoylethanolamide (anandamide, AEA) as well as the exocannabinnoid delta (9) -tetrahydrocannabinol dose-dependently inhibited hair shaft elongation and the proliferation of hair matrix keratinocytes, and induced intraepithelial apoptosis and premature HF regression (catagen). These effects were inhibited by a selective antagonist of cannabinoid receptor-1 (CB1). In contrast to CB2, CB1 was expressed in a hair cycle-dependent manner in the human HF epithelium. Since we successfully identified the presence of endocannabinoids in human HF, our data strongly suggest that human HF exploit a CB1-mediated endocannabinoid signaling system for negatively regulating their own growth. Clinically, CB1 agonists may therefore help to manage unwanted hair growth, while CB1 antagonists might counteract hair loss. Finally, human HF organ culture offers an instructive, physiologically relevant new research tool for dissecting "nonclassical" effects of endocannabinoids and their receptor-mediated signaling in general.

Endocannabinoids acting at CB1 receptors mediate the cardiac contractile dysfunction in vivo in cirrhotic rats

Advanced liver cirrhosis is associated with hyperdynamic circulation consisting of systemic hypotension, decreased peripheral resistance, and cardiac dysfunction, termed cirrhotic cardiomyopathy. Previous studies have revealed the role of endocannabinoids and vascular CB(1) receptors in the development of generalized hypotension and mesenteric vasodilation in animal models of liver cirrhosis, and CB(1) receptors have also been implicated in the decreased beta-adrenergic responsiveness of isolated heart tissue from cirrhotic rats. Here we document the cardiac contractile dysfunction in vivo in liver cirrhosis and explore the role of the endocannabinoid system in its development. Rats with CCl(4)-induced cirrhosis developed decreased cardiac contractility, as documented through the use of the Millar pressure-volume microcatheter system, low blood pressure, and tachycardia. Bolus intravenous injection of the CB(1) antagonist AM251 (3 mg/kg) acutely increased mean blood pressure, as well as both load-dependent and -independent indexes of systolic function, whereas no such changes were elicited by AM251 in control rats. Furthermore, tissue levels of the endocannabinoid anandamide increased 2.7-fold in the heart of cirrhotic compared with control rats, without any change in 2-arachidonoylglycerol levels, whereas, in the cirrhotic liver, both 2-arachidonoylglycerol (6-fold) and anandamide (3.5-fold) were markedly increased. CB(1)-receptor expression in the heart was unaffected by cirrhosis, as verified by Western blotting. Activation of cardiac CB(1) receptors by endogenous anandamide contributes to the reduced cardiac contractility in liver cirrhosis, and CB(1)-receptor antagonists may be used to improve contractile function in cirrhotic cardiomyopathy and, possibly, in other forms of heart failure.

The role of mitochondria in protection of the heart by preconditioning

A prolonged period of ischaemia followed by reperfusion irreversibly damages the heart. Such reperfusion injury (RI) involves opening of the mitochondrial permeability transition pore (MPTP) under the conditions of calcium overload and oxidative stress that accompany reperfusion. Protection from MPTP opening and hence RI can be mediated by ischaemic preconditioning (IP) where the prolonged ischaemic period is preceded by one or more brief (2–5 min) cycles of ischaemia and reperfusion. Following a brief overview of the molecular characterisation and regulation of the MPTP, the proposed mechanisms by which IP reduces pore opening are reviewed including the potential roles for reactive oxygen species (ROS), protein kinase cascades, and mitochondrial potassium channels. It is proposed that IP-mediated inhibition of MPTP opening at reperfusion does not involve direct phosphorylation of mitochondrial proteins, but rather reflects diminished oxidative stress during prolonged ischaemia and reperfusion. This causes less oxidation of critical thiol groups on the MPTP that are known to sensitise pore opening to calcium. The mechanisms by which ROS levels are decreased in the IP hearts during prolonged ischaemia and reperfusion are not known, but appear to require activation of protein kinase Cε, either by receptor-mediated events or through transient increases in ROS during the IP protocol. Other signalling pathways may show cross-talk with this primary mechanism, but we suggest that a role for mitochondrial potassium channels is unlikely. The evidence for their activity in isolated mitochondria and cardiac myocytes is reviewed and the lack of specificity of the pharmacological agents used to implicate them in IP is noted. Some K⁺ channel openers uncouple mitochondria and others inhibit respiratory chain complexes, and their ability to produce ROS and precondition hearts is mimicked by bona fide uncouplers and respiratory chain inhibitors. IP may also provide continuing protection during reperfusion by preventing a cascade of MPTP-induced ROS production followed by further MPTP opening. This phase of protection may involve survival kinase pathways such as Akt and glycogen synthase kinase 3 (GSK3) either increasing ROS removal or reducing mitochondrial ROS production.

Iron chelation-afforded cardioprotection against chronic anthracycline cardiotoxicity: A study of salicylaldehyde isonicotinoyl hydrazone (SIH)

Pyridoxal-derived aroylhydrazone iron chelators have been previously shown as effective cardioprotectants against chronic anthracycline cardiotoxicity. In this study we focused on a novel salicylaldehyde analogue (salicylaldehyde isonicotinoyl hydrazone, SIH), which has been recently demonstrated to possess marked and dose-dependent protective effects against oxidative injury of cardiomyocytes. Therefore, in the present study the cardioprotective potential of SIH against daunorubicin (DAU) cardiotoxicity was assessed in vitro (isolated rat ventricular cardiomyocytes; DAU 10 microM, 48 h exposure) as well as in vivo (chronic DAU-induced cardiomyopathy in rabbits; DAU 3mg/kg, i.v. weekly, 10 weeks). In vitro, SIH (3-100 microM) was able to partially, but significantly decrease the LDH leakage from cardiomyocytes. In vivo, SIH co-administration was capable to reduce (SIH dose of 0.5mg/kg, i.v.) or even to completely prevent (1.0mg/kg, i.v.) the DAU-induced mortality. Moreover, the latter dose of the chelator significantly improved the left ventricular function (LV dP/dt(max)=1185+/-80 kPa/s versus 783+/-53 kPa/s in the DAU group; P<0.05) and decreased the severity of the myocardial morphological changes as well as the plasma levels of cardiac troponin T. Unfortunately, further escalation of the SIH dose (to 2.5mg/kg) resulted in a nearly complete reversal of the protective effects as judged by the overall mortality, functional, morphological as well as biochemical examinations. Hence, this study points out that aroylhydrazone iron chelators can induce a significant cardioprotection against anthracycline cardiotoxicity; however, they share the curious dose-response relationship which is unrelated to the chemical structure or the route of the administration of the chelator.

The antioxidant role of coenzyme Q

A number of functions for coenzyme Q (CoQ) have been established during the years but its role as an effective antioxidant of the cellular membranes remains of dominating interest. This compound is our only endogenously synthesized lipid soluble antioxidant, present in all membranes and exceeding both in amount and efficiency that of other antioxidants. The protective effect is extended to lipids, proteins and DNA mainly because of its close localization to the oxidative events and the effective regeneration by continuous reduction at all locations. Its biosynthesis is influenced by nuclear receptors which may give the possibility, in the future, by using agonists or antagonists, of reestablishing the normal level in deficiencies caused by genetic mutations, aging or cardiomyopathy. An increase in CoQ concentration in specific cellular compartments in the presence of various types of oxidative stress appears to be of considerable interest.

Homocysteine induces cell death in H9C2 cardiomyocytes through the generation of peroxynitrite

Homocysteine (HCY) is toxic on blood vessels, but a potential direct toxicity of HCY on the heart is unknown. We addressed this issue by exposing H9C2 cardiomyocytes to HCY (0.1-5 mM) for up to 6h. At these concentrations, HCY reduced cell viability, induced necrosis and apoptosis and triggered the cleavage of caspase-3 and poly(ADP-ribose) polymerase (PARP). This was associated with the intracellular generation of the potent oxidant peroxynitrite. Removing peroxynitrite by the decomposition catalyst FeTPPS considerably reduced LDH release, DNA fragmentation, cleavage of caspase-3 and PARP, and restored normal cell morphology. In additional experiments performed in primary rat ventricular cardiomyocytes, HCY (1 mM, 6h) activated the phosphorylation of the MAP kinases ERK and JNK, two essential stress signaling kinases regulating myocardial apoptosis, hypertrophy and remodeling. These results provide the first demonstration that HCY kills cardiomyocytes through the generation of peroxynitrite and can activate key signaling cascades in the myocardium.

Cannabinoids ameliorate pain and reduce disease pathology in cerulein-induced acute pancreatitis

BACKGROUND & AIMS

The functional involvement of the endocannabinoid system in modulation of pancreatic inflammation, such as acute pancreatitis, has not been studied to date. Moreover, the therapeutic potential of cannabinoids in pancreatitis has not been addressed.

METHODS

We quantified endocannabinoid levels and expression of cannabinoid receptors 1 and 2 (CB1 and CB2) in pancreas biopsies from patients and mice with acute pancreatitis. Functional studies were performed in mice using pharmacological interventions. Histological examination, serological, and molecular analyses (lipase, myeloperoxidase, cytokines, and chemokines) were performed to assess disease pathology and inflammation. Pain resulting from pancreatitis was studied as abdominal hypersensitivity to punctate von Frey stimuli. Behavioral analyses in the open-field, light-dark, and catalepsy tests were performed to judge cannabinoid-induced central side effects.

RESULTS

Patients with acute pancreatitis showed an up-regulation of cannabinoid receptors and elevated levels of endocannabinoids in the pancreas. HU210, a synthetic agonist at CB1 and CB2, abolished abdominal pain associated with pancreatitis and also reduced inflammation and decreased tissue pathology in mice without producing central, adverse effects. Antagonists at CB1- and CB2-receptors were effective in reversing HU210-induced antinociception, whereas a combination of CB1- and CB2-antagonists was required to block the anti-inflammatory effects of HU210 in pancreatitis.

CONCLUSIONS

In humans, acute pancreatitis is associated with up-regulation of ligands as well as receptors of the endocannabinoid system in the pancreas. Furthermore, our results suggest a therapeutic potential for cannabinoids in abolishing pain associated with acute pancreatitis and in partially reducing inflammation and disease pathology in the absence of adverse side effects.

The vanilloid receptor TRPV1: 10 years from channel cloning to antagonist proof-of-concept

The clinical use of TRPV1 (transient receptor potential vanilloid subfamily, member 1; also known as VR1) antagonists is based on the concept that endogenous agonists acting on TRPV1 might provide a major contribution to certain pain conditions. Indeed, a number of small-molecule TRPV1 antagonists are already undergoing Phase I/II clinical trials for the indications of chronic inflammatory pain and migraine. Moreover, animal models suggest a therapeutic value for TRPV1 antagonists in the treatment of other types of pain, including pain from cancer. We argue that TRPV1 antagonists alone or in conjunction with other analgesics will improve the quality of life of people with migraine, chronic intractable pain secondary to cancer, AIDS or diabetes. Moreover, emerging data indicate that TRPV1 antagonists could also be useful in treating disorders other than pain, such as urinary urge incontinence, chronic cough and irritable bowel syndrome. The lack of effective drugs for treating many of these conditions highlights the need for further investigation into the therapeutic potential of TRPV1 antagonists.

S-nitrosoglutathione-containing hydrogel increases dermal blood flow in streptozotocin-induced diabetic rats

BACKGROUND

Endothelial dysfunction is characterized by decreased vasodilatory capacity of the arterioles mainly due to the reduced release of nitric oxide (NO). Application of NO donors may prevent or even reverse the consequences of endothelial dysfunction, such as diabetic leg ulcers.

OBJECTIVES

To investigate the vasodilatory capacity and the possible side-effects of topical application of an NO donor-containing hydrogel in diabetic rats.

METHODS

S-nitrosoglutathione (GSNO) was incorporated in Pluronic F127 hydrogel and applied on the foot sole skin of healthy and streptozotocin-induced diabetic rats. Blood flow was monitored using a laser-Doppler probe. Nitrotyrosine formation, a possible side-effect of GSNO action, was evaluated by Western blotting of skin protein extracts. Systemic circulatory side-effects were investigated by monitoring blood pressure and heart rate during the application.

RESULTS

The hydrogel alone did not induce any changes in microvascular flow, while GSNO-containing hydrogel caused a twofold increase in perfusion. This effect was similar in diabetic and healthy animals. Topical GSNO application did not increase the nitrotyrosine content of skin proteins, nor did it have any effect on blood pressure or heart rate.

CONCLUSIONS

Dermal application of GSNO may be an effective treatment for promoting the local vasodilation in both healthy and diabetic states, without inducing protein nitration or alterations in blood pressure or heart rate.

Simple quantitative detection of mitochondrial superoxide production in live cells

Experiments with isolated mitochondria have established that these organelles are pivotal intracellular sources of superoxide in a variety of pathophysiological conditions. Recently, a novel fluoroprobe MitoSOX Red was introduced for selective detection of superoxide in the mitochondria of live cells and was validated with confocal microscopy. Here we show approximately 3-7 fold dose- and time-dependent increase in mitochondrial superoxide production (measured by MitoSOX using flow cytometry and confocal microscopy) in rat cardiac derived H9c2 myocytes and/or in human coronary artery endothelial cells triggered by Antimycin A, Paraquat, Doxorubicin or high glucose. These results establish a novel, quantitative method for simple detection of mitochondrial superoxide generation simultaneously in a large population of live cells by flow cytometry. This method can also be adapted for immune cell studies with mixed population of T or B cells or their subsets to analyze mitochondrial superoxide levels using multiple labeled surface markers in individual populations.

Cannabinoids as therapeutic agents in cardiovascular disease: a tale of passions and illusions

In addition to their classical known effects, such as analgesia, impairment of cognition and learning and appetite enhancement, cannabinoids have also been related to the regulation of cardiovascular responses and implicated in cardiovascular pathology. Elevated levels of endocannabinoids have been related to the extreme hypotension associated with various forms of shock as well as to the cardiovascular abnormalities that accompany cirrhosis. In contrast, cannabinoids have also been associated with beneficial effects on the cardiovascular system, such as a protective role in atherosclerosis progression and in cerebral and myocardial ischaemia. In addition, it has also been suggested that the pharmacological manipulation of the endocannabinoid system may offer a novel approach to antihypertensive therapy. During the last decades, the tremendous increase in the understanding of the molecular basis of cannabinoid activity has encouraged many pharmaceutical companies to develop more potent synthetic cannabinoid analogues and antagonists, leading to an explosion of basic research and clinical trials. Consequently. not only the synthetic THC dronabinol (Marinol) and the synthetic THC analogue nabilone (Cesamet) have been approved in the United States, but also the standardized cannabis extract (Sativex) in Canada. At least three strategies can be foreseen in the future clinical use of cannabinoid-based drugs: (a) the use of CB(1) receptor antagonists, such as the recently approved rimonabant (b) the use of CB(2)-selective agonists, and (c) the use of inhibitors of endocannabinoid degradation. In this context, the present review examines the effects of cannabinoids and of the pharmacological manipulation of the endocannabinoid system, in cardiovascular pathophysiology.

Poly(ADP-ribose) polymerase inhibition reduces atherosclerotic plaque size and promotes factors of plaque stability in apolipoprotein E-deficient mice: effects on macrophage recruitment, nuclear factor-kappaB nuclear translocation, and foam cell death

BACKGROUND

Poly(ADP-ribose) polymerase (PARP) was suggested to play a role in endothelial dysfunction that is associated with a number of cardiovascular diseases. We hypothesized that PARP may play an important role in atherogenesis and that its inhibition may attenuate atherosclerotic plaque development in an experimental model of atherosclerosis.

METHODS AND RESULTS

Using a mouse (apolipoprotein E [ApoE](-/-)) model of high-fat diet-induced atherosclerosis, we demonstrate an association between cell death and oxidative stress-associated DNA damage and PARP activation within atherosclerotic plaques. PARP inhibition by thieno[2,3-c]isoquinolin-5-one reduced plaque number and size and altered structural composition of plaques in these animals without affecting sera lipid contents. These results were corroborated genetically with the use of ApoE(-/-) mice that are heterozygous for PARP-1. PARP inhibition promoted an increase in collagen content, potentially through an increase in tissue inhibitor of metalloproteinase-2, and transmigration of smooth muscle cells to intima of atherosclerotic plaques as well as a decrease in monocyte chemotactic protein-1 production, all of which are markers of plaque stability. In PARP-1(-/-) macrophages, monocyte chemotactic protein-1 expression was severely inhibited because of a defective nuclear factor-kappaB nuclear translocation in response to lipopolysaccharide. Furthermore, PARP-1 gene deletion not only conferred protection to foam cells against H2O2-induced death but also switched the mode of death from necrosis to apoptosis.

CONCLUSIONS

Our results suggest that PARP inhibition interferes with plaque development and may promote plaque stability, possibly through a reduction in inflammatory factors and cellular changes related to plaque dynamics. PARP inhibition may prove beneficial for the treatment of atherosclerosis.

Decreased age-related cardiac dysfunction, myocardial nitrative stress, inflammatory gene expression, and apoptosis in mice lacking fatty acid amide hydrolase

Recent studies have uncovered important cross talk between inflammation, generation of reactive oxygen and nitrogen species, and lipid metabolism in the pathogenesis of cardiovascular aging. Inhibition of the endocannabinoid anandamide metabolizing enzyme, the fatty acid amide hydrolase (FAAH), is emerging as a promising novel approach for the treatment of various inflammatory disorders. In this study, we have investigated the age-associated decline of cardiac function and changes in inflammatory gene expression, nitrative stress, and apoptosis in FAAH knockout (FAAH(-/-)) mice and their wild-type (FAAH(+/+)) littermates. Additionally, we have explored the effects of anandamide on TNF-alpha-induced ICAM-1 and VCAM-1 expression and monocyte-endothelial adhesion in human coronary artery endothelial cells (HCAECs). There was no difference in the cardiac function (measured by the pressure-volume conductance catheter system) between 2- to 3-mo-old (young) FAAH(-/-) and FAAH(+/+) mice. In contrast, the aging-associated decline in cardiac function and increased myocardial gene expression of TNF-alpha, gp91phox, matrix metalloproteinase (MMP)-2, MMP-9, caspase-3 and caspase-9, myocardial inducible nitric oxide synthase protein expression, nitrotyrosine formation, poly (ADP-ribose)polymerase cleavage and caspase-3/9 activity, observed in 28- to 31-mo-old (aging) FAAH(+/+) mice, were largely attenuated in knockouts. There was no difference in the myocardial cannabinoid CB(1) and CB(2) receptor gene expression between young and aging FAAH(-/-) and FAAH(+/+) mice. Anandamide dose dependently attenuated the TNF-alpha-induced ICAM-1 and VCAM-1 expression, NF-kappaB activation in HCAECs, and the adhesion of monocytes to HCAECs in a CB(1)- and CB(2)-dependent manner. These findings suggest that pharmacological inhibition of FAAH may represent a novel protective strategy against chronic inflammation, oxidative/nitrative stress, and apoptosis associated with cardiovascular aging and atherosclerosis.

Lack of the antioxidant enzyme glutathione peroxidase-1 accelerates atherosclerosis in diabetic apolipoprotein E-deficient mice

BACKGROUND

Recent clinical studies have suggested a major protective role for the antioxidant enzyme glutathione peroxidase-1 (GPx1) in diabetes-associated atherosclerosis. We induced diabetes in mice deficient for both GPx1 and apolipoprotein E (ApoE) to determine whether this is merely an association or whether GPx1 has a direct effect on diabetes-associated atherosclerosis.

METHODS AND RESULTS

ApoE-deficient (ApoE-/-) and ApoE/GPx1 double-knockout (ApoE-/- GPx1-/-) mice were made diabetic with streptozotocin and aortic lesion formation, and atherogenic pathways were assessed after 10 and 20 weeks of diabetes. Aortic proinflammatory and profibrotic markers were determined by both quantitative reverse-transcription polymerase chain reaction analysis after 10 weeks of diabetes and immunohistochemical analysis after 10 and 20 weeks of diabetes. Sham-injected nondiabetic counterparts served as controls. Atherosclerotic lesions within the aortic sinus region, as well as arch, thoracic, and abdominal lesions, were significantly increased in diabetic ApoE-/- GPx1-/- aortas compared with diabetic ApoE-/- aortas. This increase was accompanied by increased macrophages, alpha-smooth muscle actin, receptors for advanced glycation end products, and various proinflammatory (vascular cell adhesion molecule-1) and profibrotic (vascular endothelial growth factor and connective tissue growth factor) markers. Quantitative reverse-transcription polymerase chain reaction analysis showed increased expression of receptors for advanced glycation end products (RAGE), vascular cell adhesion molecule-1, vascular endothelial growth factor, and connective tissue growth factor. Nitrotyrosine levels were significantly increased in diabetic ApoE-/- GPx1-/- mouse aortas. These findings were observed despite upregulation of other antioxidants.

CONCLUSIONS

Lack of functional GPx1 accelerates diabetes-associated atherosclerosis via upregulation of proinflammatory and profibrotic pathways in ApoE-/- mice. Our study provides evidence of a protective role for GPx1 and establishes GPx1 as an important antiatherogenic therapeutic target in patients with or at risk of diabetic macrovascular disease.

The endocannabinoid system: body weight and metabolic regulation

The endocannabinoid system elicits multiple physiologic functions that are not fully understood. Antagonism of cannabinoid type 1 (CB(1)) receptors has been the only successful new pharmacologic treatment approach in Phase III studies in obesity in the last 8 years. Whereas antagonism of (CB(1)) receptors acutely reduces food intake, the long-term effects on weight reduction and metabolic regulation appear to be mediated by stimulation of energy expenditure and by peripheral effects related to liver, skeletal muscle, adipose tissue, and pancreas physiology. For example, in the liver, lipogenic enzymes and fatty acid synthesis are upregulated by endocannabinoids, and in adipose tissue, antagonism of (CB(1)) receptors increases secretion of adiponectin. Some studies suggest that endocannabinoid formation is increased in obesity, perhaps because endocannabinoid degradation is decreased. Although many questions remain unanswered at present, the emerging concept of endocannabinoids as metabolic regulators helps to explain the success of rimonabant (SR141716), an antagonist of (CB(1)) receptors, currently in Phase III studies.

Endocannabinoids and the regulation of their levels in health and disease

PURPOSE OF REVIEW

Endocannabinoids are defined as endogenous agonists of cannabinoid receptors, that is, of the two G-protein-coupled receptors for the Cannabis psychoactive principle Delta-tetra-hydrocannabinol. Two such endogenous mediators have been most thoroughly studied so far: anandamide and 2-arachidonoylglycerol. Here we review the mechanisms for the regulation of their levels under physiological and pathological conditions, and recent findings on their role in disease.

RECENT FINDINGS

It is becoming increasingly clear that, although both anandamide and 2-arachidonoyl-glycerol are produced and degraded 'on demand', the levels of these two compounds appear to be regulated in different, and sometimes even opposing, ways, often using redundant molecular mechanisms. Alterations of endocannabinoid levels have been found in both animal models of pain, neurological and neurodegenerative states, gastrointestinal disorders and inflammatory conditions, and in blood, cerebrospinal fluid and bioptic samples from patients with various diseases.

SUMMARY

Endocannabinoid levels appear to be transiently elevated as an adaptive reaction to re-establish normal homeostasis when this is acutely and pathologically perturbed. In some chronic conditions, however, this system also contributes to the progress or symptoms of the disorder. As a consequence, new therapeutic drugs are being designed from both stimulants and blockers of endocannabinoid action.

Redox control of calcium channels: from mechanisms to therapeutic opportunities

Calcium plays an integral role in cellular function. It is a well-recognized second messenger necessary for signaling cellular responses, but in excessive amounts can be deleterious to function, causing cell death. The main route by which calcium enters the cytoplasm is either from the extracellular compartment or internal addistores via calcium channels. There is good evidence that calcium channels can respond to pharmacological compounds that reduce or oxidize thiol groups on the channel protein. In addition, reactive oxygen species such as hydrogen peroxide and superoxide that can mediate oxidative pathology also mediate changes in channel function via alterations of thiol groups. This review looks at the structure and function of calcium channels, the evidence that changes in cellular redox state mediate changes in channel function, and the role of redox modification of channels in disease processes. Understanding how redox modification of the channel protein alters channel structure and function is providing leads for the design of therapeutic interventions that target oxidative stress responses.

Effect of heating on peroxynitrite scavenging capacity of garlic

The ability to scavenge peroxynitrite (ONOO(-)) was studied in the following aqueous garlic extracts: (a) unheated extract of garlic powder (GP), (b) heated extract of garlic powder (HGP), (c) unheated extract of raw garlic (RG), (d) heated extract of raw garlic (HRG), (e) extract of boiled garlic cloves (BG), (f) extract of microwave-treated garlic cloves (MG), and (g) extract of pickled garlic (PG). All the extracts scavenged ONOO(-) in a concentration-dependent way. IC(50) (mg/mL) values for each extract were 0.30+/-0.02 and 0.35+/-0.04 for GP and HGP, respectively; and 0.84+/-0.08, 0.59+/-0.04, 0.76+/-0.09, 1.71+/-0.19, and 1.45+/-0.07 for RG, HRG, BG, MG, and PG, respectively. The ONOO(-) scavenging capacity (IC(50) values) was not decreased in HGP (vs. GP, p>0.05) and in HRG and BG (p>0.05 vs. RG). In contrast, the ONOO(-) scavenging capacity decreased in MG and PG (vs. RG, p<0.001). The IC(50) values for the reference compounds nordihydroguiaretic acid and penicillamine were 1.1 and 4.5mug/mL. The heating before or after garlic cutting was unable to eliminate the capacity of the extracts to scavenge ONOO(-); this capacity was significantly decreased in PG and MG.

Cirrhotic cardiomyopathy

Cirrhotic cardiomyopathy is the term used to describe a constellation of features indicative of abnormal heart structure and function in patients with cirrhosis. These include systolic and diastolic dysfunction, electrophysiological changes, and macroscopic and microscopic structural changes. The prevalence of cirrhotic cardiomyopathy remains unknown at present, mostly because the disease is generally latent and shows itself when the patient is subjected to stress such as exercise, drugs, hemorrhage and surgery. The main clinical features of cirrhotic cardiomyopathy include baseline increased cardiac output, attenuated systolic contraction or diastolic relaxation in response to physiologic, pharmacologic and surgical stress, and electrical conductance abnormalities (prolonged QT interval). In the majority of cases, diastolic dysfunction precedes systolic dysfunction, which tends to manifest only under conditions of stress. Generally, cirrhotic cardiomyopathy with overt severe heart failure is rare. Major stresses on the cardiovascular system such as liver transplantation, infections and insertion of transjugular intrahepatic portosystemic stent-shunts (TIPS) can unmask the presence of cirrhotic cardiomyopathy and thereby convert latent to overt heart failure. Cirrhotic cardiomyopathy may also contribute to the pathogenesis of hepatorenal syndrome. Pathogenic mechanisms of cirrhotic cardiomyopathy are multiple and include abnormal membrane biophysical characteristics, impaired β-adrenergic receptor signal transduction and increased activity of negative-inotropic pathways mediated by cGMP. Diagnosis and differential diagnosis require a careful assessment of patient history probing for excessive alcohol, physical examination for signs of hypertension such as retinal vascular changes, and appropriate diagnostic tests such as exercise stress electrocardiography, nuclear heart scans and coronary angiography. Current management recommendations include empirical, nonspecific and mainly supportive measures. The exact prognosis remains unclear. The extent of cirrhotic cardiomyopathy generally correlates to the degree of liver insufficiency. Reversibility is possible (either pharmacological or after liver transplantation), but further studies are needed.

Cannabidiol attenuates high glucose-induced endothelial cell inflammatory response and barrier disruption

A nonpsychoactive cannabinoid cannabidiol (CBD) has been shown to exert potent anti-inflammatory and antioxidant effects and has recently been reported to lower the incidence of diabetes in nonobese diabetic mice and to preserve the blood-retinal barrier in experimental diabetes. In this study we have investigated the effects of CBD on high glucose (HG)-induced, mitochondrial superoxide generation, NF-kappaB activation, nitrotyrosine formation, inducible nitric oxide synthase (iNOS) and adhesion molecules ICAM-1 and VCAM-1 expression, monocyte-endothelial adhesion, transendothelial migration of monocytes, and disruption of endothelial barrier function in human coronary artery endothelial cells (HCAECs). HG markedly increased mitochondrial superoxide generation (measured by flow cytometry using MitoSOX), NF-kappaB activation, nitrotyrosine formation, upregulation of iNOS and adhesion molecules ICAM-1 and VCAM-1, transendothelial migration of monocytes, and monocyte-endothelial adhesion in HCAECs. HG also decreased endothelial barrier function measured by increased permeability and diminished expression of vascular endothelial cadherin in HCAECs. Remarkably, all the above mentioned effects of HG were attenuated by CBD pretreatment. Since a disruption of the endothelial function and integrity by HG is a crucial early event underlying the development of various diabetic complications, our results suggest that CBD, which has recently been approved for the treatment of inflammation, pain, and spasticity associated with multiple sclerosis in humans, may have significant therapeutic benefits against diabetic complications and atherosclerosis.

Role of oxidative stress in cardiac dysfunction of PPARalpha-/- mice

This study was designed to determine the effects of PPARalpha lack on cardiac mechanical performance and to identify potential intracellular mechanisms linking PPARalpha pathway deficiency to cardiac contractile dysfunction. Echocardiography, ex vivo papillary muscle assays, and in vitro motility assays were used to assess global, intrinsic ventricular muscle performance and myosin mechanical properties, respectively, in PPARalpha(-/-) and age-matched wild-type mice. Three-nitrotyrosine formation and 4-hydroxy-2-nonenal protein-adducts, both markers of oxidative damage, were analyzed by Western blot analysis and immunolabeling. Radical scavenging capacity was analyzed by measuring protein levels and/or activities of the main antioxidant enzymes, including catalase, glutathione peroxidase, and manganese and copper-zinc superoxide dismutases. Echocardiographic left ventricular fractional shortening in PPARalpha(-/-) was 16% lower than that in wild-type. Ex vivo left ventricular papillary muscle exhibited reduced shortening velocity and isometric tension (three- and twofold, respectively). In vitro myosin-based velocity was approximately 20% slower in PPARalpha(-/-), indicating that myosin itself was involved in the contractile dysfunction. Staining of 3-nitrotyrosine was more pronounced in PPARalpha(-/-), and myosin heavy chain was the main nitrated protein. Formation of 3-nitrotyrosine myosin heavy chain was twofold higher in PPARalpha(-/-) and 4-hydroxy-2-nonenal protein-adducts were threefold higher. The expression and activity of manganese superoxide dismutase were respectively 33% and 50% lower in PPARalpha(-/-), with no changes in copper-zinc superoxide dismutase, catalase, or glutathione peroxidase. These findings demonstrate that PPARalpha pathway deficiency impairs cardiac function and also identify oxidative damage to myosin as a link between PPARalpha deficiency and contractile dysfunction.

The cannabinoid system and its pharmacological manipulation--a review, with emphasis upon the uptake and hydrolysis of anandamide

Although cannabis has been used both recreationally and for medicinal purposes since ancient times, it was not until the 1990s that the receptors responsible for many of the actions of Delta(9)-tetrahydrocannabinol, the main psychoactive ingredient of cannabis, were cloned. Since then, our knowledge of the endogenous cannabinoid system, its physiology, pharmacology and therapeutic potential have expanded enormously. In the present review, the cannabinoid system is described, with particular emphasis on the mechanisms of removal and metabolism of the endocannabinoid signalling molecule anandamide. The current literature shows that cells can accumulate anandamide, and that this process can be disrupted pharmacologically, but that the nature of the mechanism(s) involved remains a matter of some debate. The main enzyme for the hydrolysis of anandamide, fatty acid amide hydrolase, is well characterized, and molecules selectively inhibiting this enzyme have potential therapeutic utility in a number of areas, in particular for the treatment of pain conditions.

Protein tyrosine nitration and poly(ADP-ribose) polymerase activation in N-methyl-N-nitro-N-nitrosoguanidine-treated thymocytes: implication for cytotoxicity

1-Methyl-3-nitro-1-nitrosoguanidine (MNNG) is a DNA alkylating agent. DNA alkylation by MNNG is known to trigger accelerated poly(ADP-ribose) metabolism. Various nitroso compounds release nitric oxide (NO). Therefore, we set out to investigate whether MNNG functions as NO donor and whether MNNG-derived NO or secondary NO metabolites such as peroxynitrite contribute to MNNG-induced cytotoxicity. MNNG in aqueous solutions resulted in time- and concentration-dependent NO release and nitrite/nitrate formation. Moreover, various proteins in MNNG-treated thymocytes were found to be nitrated, indicating that MNNG-derived NO may combine with cellular superoxide to form peroxynitrite, a nitrating agent. MNNG also caused DNA breakage and increased poly(ADP-ribose) polymerase activity and cytotoxicity in thymocytes. MNNG-induced DNA damage (measured by the comet assay) and thymocyte death (measured by propidium iodide uptake) was prevented by the PARP inhibitor PJ-34 and by glutathione (GSH) or N-acetylcysteine (NAC). The cytoprotection provided by PJ-34 against necrotic parameters was paralleled by increased outputs in apoptotic parameters (caspase activity, DNA laddering) indicating that PARP activation diverts apoptotic death toward necrosis. As MNNG-induced cytotoxicity showed many similarities to peroxynitrite-induced cell death, we tested whether peroxynitrite was responsible for at least part of the cytotoxicity induced by MNNG. Cell-permeable enzymic antioxidants (superoxide dismutase and catalase), the NO scavenger cPTIO or the peroxynitrite decomposition catalyst FP15 failed to inhibit MNNG-induced DNA breakage and cytotoxicity. In conclusion, MNNG induces tyrosine nitration in thymocytes. Furthermore, MNNG damages DNA by a radical mechanism that does not involve NO or peroxynitrite.

Poly(ADP-ribose) polymerase inhibition improves endothelial dysfunction induced by reactive oxidant hydrogen peroxide in vitro

Reactive oxygen species, such as hydrogen peroxide (H(2)O(2)) induce oxidative stress and DNA-injury. The subsequent activation of poly(ADP-ribose) polymerase (PARP) has been implicated in the pathogenesis of various cardiovascular diseases including ischaemia-reperfusion injury, circulatory shock, diabetic complications and atherosclerosis. We investigated the effect of PARP-inhibition on endothelial dysfunction induced by H(2)O(2). In vascular reactivity measurements on isolated rat aortic rings we investigated the phenylephrine-induced contraction, and endothelium-dependent and -independent vasorelaxation by using cumulative concentrations of acetylcholine and sodium nitroprusside. Endothelial dysfunction was induced by exposing the rings to H(2)O(2) (200 and 400 muM) for 30 min. In the treatment group, rings were preincubated with the potent PARP-inhibitor INO-1001. DNA strand breaks were assessed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method. Immunohistochemical analysis was performed for poly(ADP-ribose) (the enzymatic product of PARP) and for apoptosis inducing factor (a pro-apoptotic factor regulated by PARP). Exposure to H(2)O(2) resulted in reduced contraction forces and a dose-dependent impairment of endothelium-dependent vasorelaxation of aortic rings (maximal relaxation to acetylcholine: 86.21+/-1.574% control vs. 72.55+/-1.984% H(2)O(2) 200 muM vs. 66.86+/-1.961% H(2)O(2) 400 muM; P<0.05). PARP-inhibition significantly improved the acetylcholine-induced vasorelaxation (77.75+/-3.019% vs. 66.86+/-1.961%; P<0.05), while the contractility remained unaffected. The dose-response curves of endothelium-independent vasorelaxation to sodium nitroprusside did not differ in any groups studied. In the H(2)O(2) groups immunohistochemical analysis showed enhanced PARP-activation and nuclear translocation of apoptosis inducing factor, which were prevented by INO-1001. Our results demonstrate that PARP activation contributes to the pathogenesis of H(2)O(2)-induced endothelial dysfunction, which can be prevented by PARP inhibitors.