Cryopreserved veins in myocardial revascularization: possible mechanism for their increased failure

Opioids and matrix metalloproteinases: the influence of morphine on MMP-9 production and cancer progression

Opioids are widely administered to alleviate pain, including chronic pain in advanced cancer patients. Among opioids, morphine is one of the most clinically effective drugs for the palliative management of severe pain. In the last few decades, there has been a debate around the possible influence of opioids such as morphine on tumour growth and metastasis. Whilst several in vitro and in vivo studies suggest the possible modulatory effects of morphine on tumour cells, little is known about the impact of this analgesic drug on other mediators such as matrix metalloproteinases (MMPs) that play a key role in the control of cancer cell invasion and metastasis. MMP-9 has been considered as one of the principal mediators in regulation of not only the initial steps of cancer but during the invasion and spreading of cancer cells to distant organs. Herein, current studies regarding the direct and indirect effects of morphine on regulation of MMP-9 production are discussed. In addition, drawing from previous in vivo and in vitro studies on morphine action in regulating MMP-9 production, the potential roles of several underlying factors are summarised, including nuclear factor kappa-B and intracellular molecules such as nitric oxide.

Vascular dysfunction associated with type 2 diabetes and Alzheimer's disease: a potential etiological linkage

The endothelium performs a crucial role in maintaining vascular integrity leading to whole organ metabolic homeostasis. Endothelial dysfunction represents a key etiological factor leading to moderate to severe vasculopathies observed in both Type 2 diabetic and Alzheimer’s Disease (AD) patients. Accordingly, evidence-based epidemiological factors support a compelling hypothesis stating that metabolic rundown encountered in Type 2 diabetes engenders severe cerebral vascular insufficiencies that are causally linked to long term neural degenerative processes in AD. Of mechanistic importance, Type 2 diabetes engenders an immunologically mediated chronic pro-inflammatory state involving interactive deleterious effects of leukocyte-derived cytokines and endothelial-derived chemotactic agents leading to vascular and whole organ dysfunction. The long term negative consequences of vascular pro-inflammatory processes on the integrity of CNS basal forebrain neuronal populations mediating complex cognitive functions establish a striking temporal comorbidity of AD with Type 2 diabetes. Extensive biomedical evidence supports the pivotal multi-functional role of constitutive nitric oxide (NO) production and release as a critical vasodilatory, anti-inflammatory, and anti-oxidant, mechanism within the vascular endothelium. Within this context, we currently review the functional contributions of dysregulated endothelial NO expression to the etiology and persistence of Type 2 diabetes-related and co morbid AD-related vasculopathies. Additionally, we provide up-to-date perspectives on critical areas of AD research with special reference to common NO-related etiological factors linking Type 2 diabetes to the pathogenesis of AD.

Reciprocal regulation of cellular nitric oxide formation by nitric oxide synthase and nitrite reductases

Our mini-review focuses on dual regulation of cellular nitric oxide (NO) signaling pathways by traditionally characterized enzymatic formation from L-arginine via the actions of NO synthases (NOS) and by enzymatic reduction of available cellular nitrite pools by a diverse class of cytosolic and mitochondrial nitrite reductases. Nitrite is a major metabolic product of NO and is found in all cell and tissue types that utilize NO signaling processes. Xanthine oxidoreductase (XOR) has been previously characterized as a housekeeping enzyme responsible for cellular uric acid formation via enzymatic conversion of hypoxanthine and xanthine. It has become apparent that XOR possesses multi-functional enzymatic activities outside the realm of xanthine metabolism and a small but significant literature also established a compelling functional association between administered sodium nitrite, XOR activation, and pharmacologically characterized NO transductive effects in positive cardiovascular function enhanced pulmonary perfusion, and protection against ischemia/reperfusion injury and hypoxic damage and oxidative stress. Similar positive vascular and cellular effects were observed to be functionally associated with mitochondrial aldehyde dehydrogenase and cytochrome c/cytochrome c oxidase. The profound implications of a reciprocal regulatory mechanism responsible for cytosolic and mitochondrial NO production are discussed below.

The presence of endogenous morphine signaling in animals

Recent empirical findings have contributed valuable mechanistic information in support of a regulated de novo biosynthetic pathway for chemically authentic morphine and related morphinan alkaloids within animal cells. Importantly, we and others have established that endogenously expressed morphine represents a key regulatory molecule effecting local circuit autocrine/paracrine cellular signaling via a novel mu(3) opiate receptor coupled to constitutive nitric oxide production and release. The present report provides an integrated review of the biochemical, pharmacological, and molecular demonstration of mu(3) opiate receptors in historical linkage to the elucidation of mechanisms of endogenous morphine production by animal cells and organ systems. Ongoing research in this exciting area provides a rare window of opportunity to firmly establish essential biochemical linkages between dopamine, a morphine precursor, and animal biosynthetic pathways involved in morphine biosynthesis that have been conserved throughout evolution.

Endogenous morphine/nitric oxide-coupled regulation of cellular physiology and gene expression: implications for cancer biology

Cancer is a simplistic, yet complicated, process that promotes uncontrolled growth. In this regard, this unconstrained proliferation may represent primitive phenomena whereby cellular regulation is suspended or compromised. Given the new empirical evidence for a morphinergic presence and its profound modulatory actions on several cellular processes it is not an overstatement to hypothesize that morphine may represent a key chemical messenger in the process of modulating proliferation of diverse cells. This has been recently demonstrated by the finding of a novel opiate-alkaloid selective receptor subtype in human multilineage progenitor cells (MLPC). Adding to the significance of morphinergic signaling are the findings of its presence in plant, invertebrate and vertebrate cells, which also have been shown to synthesize this messenger as well. Interestingly, we and others have shown that some cancerous tissues contain morphine. Furthermore, in medullary histolytic reticulosis, which is exemplified by cells having hyperactivity, the mu3 (mu3) opiate select receptor was not present. Thus, it would appear that morphinergic signaling has inserted itself in many processes taking a long time to evolve, including those regulating the proliferation of cells across diverse phyla.

Endogenous morphine: opening new doors for the treatment of pain and addiction

Nitric oxide (NO) signalling is at the forefront of intense research interest because its many effects remain controversial and seemingly contradictory. This paper examines its role as a potential mediator of pain and tolerance. Within this context discussion covers endogenous morphine, documenting its ability to be made in animal tissues, including nervous tissue, and in diverse animal phyla. Supporting morphine as an endogenous signalling molecule is the presence of the newly cloned mu3 opiate receptor subtype found in animal (including human) immune, vascular and neural tissues, which is coupled to NO release. Importantly, this mu opiate receptor subtype is morphine-selective and opioid peptide-insensitive, further highlighting the presence of morphinergic signalling coupled to NO release. These findings provide novel insights into pain and tolerance as morphinergic signalling exhibits many similarities with NO actions. Taken together, a select morphinergic signalling system utilising NO opens the gate for the development of novel pharmaceuticals and/or the use of old pharmaceuticals in new ways.

Human white blood cells synthesize morphine: CYP2D6 modulation

Human plasma contains low, but physiologically significant, concentrations of morphine that can increase following trauma or exercise. We now demonstrate that normal, human white blood cells (WBC), specifically polymorphonuclear cells, contain and have the ability to synthesize morphine. We also show that WBC express CYP2D6, an enzyme capable of synthesizing morphine from tyramine, norlaudanosoline, and codeine. Significantly, we also show that morphine can be synthesized by another pathway via l-3,4-dihydroxyphenylalanine (L-DOPA). Finally, we show that WBC release morphine into their environment. These studies provide evidence that 1) the synthesis of morphine by various animal tissues is more widespread than previously thought and now includes human immune cells. 2) Moreover, another pathway for morphine synthesis exists, via L-DOPA, demonstrating an intersection between dopamine and morphine pathways. 3) WBC can release morphine into the environment to regulate themselves and other cells, suggesting involvement in autocrine signaling since these cells express the mu3 opiate receptor subtype.

Molecular identification and functional expression of mu 3, a novel alternatively spliced variant of the human mu opiate receptor gene

Studies from our laboratory have revealed a novel mu opiate receptor, mu 3, which is expressed in both vascular tissues and leukocytes. The mu 3 receptor is selective for opiate alkaloids and is insensitive to opioid peptides. We now identify the mu 3 receptor at the molecular level using a 441-bp conserved region of the mu 1 receptor. Sequence analysis of the isolated cDNA suggests that it is a novel, alternatively spliced variant of the mu opiate receptor gene. To determine whether protein expressed from this cDNA exhibits the biochemical characteristics expected of the mu 3 receptor, the cDNA clone was expressed in a heterologous system. At the functional level, COS-1 cells transfected with the mu 3 receptor cDNA exhibited dose-dependent release of NO following treatment with morphine, but not opioid peptides (i.e., Met-enkephalin). Naloxone was able to block the effect of morphine on COS-1 transfected cells. Nontransfected COS-1 cells did not produce NO in the presence of morphine or the opioid peptides at similar concentrations. Receptor binding analysis with [(3)H]dihydromorphine further supports the opiate alkaloid selectivity and opioid peptide insensitivity of this receptor. These data suggest that this new mu opiate receptor cDNA encodes the mu 3 opiate receptor, since it exhibits biochemical characteristics known to be unique to this receptor (opiate alkaloid selective and opioid peptide insensitive). Furthermore, using Northern blot, RT-PCR, and sequence analysis, we have demonstrated the expression of this new mu variant in human vascular tissue, mononuclear cells, polymorphonuclear cells, and human neuroblastoma cells.

The biochemical substrate of nitric oxide signaling is present in primitive non-cognitive organisms

Nitric oxide has been shown to have diverse actions in the mammalian nervous, immune and vascular systems. These include antimicrobial and antiviral activities as well as the modulation of cell adherence. In the nervous system, nitric oxide modulates neurotransmitter release, neurosecretion and behavioral activities such as feeding. In the present review, we discuss the finding that invertebrate organisms also contain nitric oxide and that they appear to use this multidimensional molecule in a similar manner as noted for mammals. Therefore, nitric oxide signaling appears to have emerged first in these primitive non-cognitive organisms. We conclude that basal nitric oxide functioning was established in these organisms and that this molecule was later employed in man, including its involvement in cognitive neural processes.

Effect of central and peripheral administration of a nitric oxide synthase inhibitor on morphine hyperthermia in rats

The effect of central and peripheral administration of a nitric oxide synthase inhibitor, N-nitro-L-arginine methyl ester (L-NAME), on morphine hyperthermia was studied in male Sprague-Dawley rats. The first series of experiments examined the effect of subcutaneous (s.c.) administration of L-NAME on the hyperthermia induced by morphine given s.c. in doses of 4 and 15 mg/kg. L-NAME, at a s.c. dose of 50 mg/kg, per se, had no influence on body temperature (T(b)). Coadministration of L-NAME (50 mg/kg, s.c.) with the higher dose of morphine (15 mg/kg, s.c.) caused a significant suppression of morphine hyperthermia during the first 30 min and then produced hypothermia. In contrast, s.c. injection of L-NAME (50 mg/kg, s.c.) failed to alter the hyperthermic response induced by the lower dose of morphine (4 mg/kg). In the second series of experiments, we investigated the effect of intracerebroventricular (i.c.v.) administration of L-NAME on the hyperthermia induced by morphine given s.c. L-NAME, itself, given i.c.v. at a dose of 1 mg did not evoke any change in T(b). Intracerebroventricular administration of L-NAME (1 mg) blocked the hyperthermia induced by 15 mg/kg morphine during the first 30 min and induced a slight hypothermia but did not alter the hyperthermia induced by 4 mg/kg morphine. The results indicate that either central or peripheral NO synthesis is required for the production of hyperthermia induced by 15 mg/kg of morphine. However, NO synthesis does not seem to be involved in the hyperthermic process induced by 4 mg/kg of morphine.

Human vascular and cardiac endothelia express mu opiate receptor transcripts

Pharmacologic and immunologic evidence suggests that nitric oxide-coupled mu-subtype opiate receptors are expressed in human vascular endothelium. In this study, we present molecular evidence of mu opiate receptor expression. Using primers derived from the human neuronal mu1 opiate receptor, we used RT-PCR to detect expression of mu transcripts from human endothelia. Sequence analysis of the RT-PCR products revealed 100% identity with the neuronal human mu1 receptor. We further show that pretreatment of human internal thoracic artery and cardiac atrial endothelium with the proinflammatory cytokines interleukin-1-alpha and -beta led to a significant increase in both the expression of the mu transcript and in morphine-stimulated nitric oxide release measured amperometrically. Taken together, these studies provide molecular evidence that mu-type opiate receptors are expressed in human vascular endothelia and that their expression can be upregulated by proinflammatory cytokines.

Nitric oxide inhibits norepinephrine stimulated contraction of human internal thoracic artery and rat aorta

The effect of nitric oxide (NO) on norepinephrine-induced vascular contraction was evaluated using segments of rat aorta and human internal thoracic artery (ITA) and the NO donor, SNAP. NO levels were measured directly using an amperometric probe. Concentrations of NO greater than 2 nM were required to reduce vascular contraction induced by 100 nM norepinephrine (NE). Exposure of the aortic rings to SNAP prior to, or after NE addition, resulted in a similar attenuation of NE-induced contraction. In contrast, increased relaxation of ITA segments in response to SNAP was observed relative to that of rat aorta and significant development of contractile tone following NE addition was not observed. Evaluation of cytoskeletal actin demonstrated marked loss of F-actin content in smooth muscle cells following NO exposure, suggesting that NO may have direct and indirect effects on contractile tone. These data taken together suggest that vascular responsiveness to contractile agents may be significantly attenuated by prior or subsequent exposure to NO, and mechanisms in addition to vascular relaxation are likely to contribute to this effect.

Evidence that Alzheimer's disease is a microvascular disorder: the role of constitutive nitric oxide

Evidence is fast accumulating which indicates that Alzheimer's disease is a vascular disorder with neurodegenerative consequences rather than a neurodegenerative disorder with vascular consequences. It is proposed that two factors need to be present for AD to develop: (1) advanced ageing, (2) presence of a condition that lowers cerebral perfusion, such as a vascular-risk factor. The first factor introduces a normal but potentially insidious process that lowers cerebral blood flow in inverse relation to increased ageing; the second factor adds a crucial burden which further lowers brain perfusion and places vulnerable neurons in a state of high energy compromise leading to a cascade of neuronal metabolic turmoil. Convergence of the two factors above will culminate in a critically attained threshold of cerebral hypoperfusion (CATCH). CATCH is a hemodynamic microcirculatory insufficiency that will destabilize neurons, synapses, neurotransmission and cognitive function, creating in its wake a neurodegenerative state characterized by the formation of senile plaques, neurofibrillary tangles, amyloid angiopathy and in some cases, Lewy bodies. Since any of a considerable number of vascular-related conditions must be present in the ageing individual for cognition to be disturbed, CATCH identifies an important aspect of the heterogeneic disease profile assumed to be present in the AD syndrome. It is proposed that CATCH initiates AD by distorting regional brain capillary structure involving endothelial cell shape changes and impairment of nitric oxide (NO) release which affect signaling between the immune, cardiovascular and nervous systems. Evidence is presented that in many tissues there is a basal level of NO being produced and that the actions of several signaling molecules may initiate increases in basal NO levels. Moreover, these temporary increases in basal NO levels exert inhibitory cellular actions, via cellular conformational changes. Findings indicate that (a) constitutive NO is responsible for a basal or 'tonal' level of NO; (b) this NO keeps particular types of cells in a state of inhibition and (c) activation of these cells occurs through disinhibition. Consequently, tissues not maintaining a basal NO level are more prone to excitatory, immune, vascular and neural influences. Under such circumstances, these tissues cannot be down-regulated to normal basal levels, thus prolonging their excitatory state. Thus, the clinical convergence of advanced ageing in the presence of a chronic, pre-morbid vascular risk factor, can, in time, contribute to an endotheliopathy involving basal NO deficit, to the degree where regional metabolic dysfunction leads to cognitive meltdown and to progressive neurodegeneration characteristic of Alzheimer's disease.

Morphine suppresses complement receptor expression, phagocytosis, and respiratory burst in neutrophils by a nitric oxide and mu(3) opiate receptor-dependent mechanism

We investigated whether morphine and fentanyl influence surface receptor expression, phagocytic activity and superoxide anion generation of neutrophils in a whole blood flow cytometric assay. Morphine suppressed complement and Fcgamma receptor expression and neutrophil function in a concentration- and time-dependent manner. Morphine-induced changes were similar to those caused by the nitric oxide (NO) donor S-nitroso-N-acetyl-penicillamine and were abolished by preincubation with the NO synthase inhibitor N-nitro-L-arginine as well as naloxone. Fentanyl had no immunosuppressive effects. These results suggest that these neutrophil functions are inhibited by morphine-stimulated NO release mediated by the mu(3) opiate receptor subtype found on immunocytes.

Suggested treatment protocol for improving patency of femoral-infrapopliteal cryopreserved saphenous vein allografts

PURPOSE

Cryopreserved saphenous vein allografts are used for femoral-infrapopliteal bypass graft purposes when adequate autogenous vein is unavailable. Anticoagulation, immunosuppression therapy, or both have been suggested means for improving allograft patency. Immunosuppression has significant cost and morbidity and has produced variable results. Our successful treatment of luminal surface hypercoagulability associated with certain endovascular procedures prompted the use of an anticoagulation protocol prospectively to improve graft patency and limb salvage for patients receiving femoral-infrapopliteal cryopreserved saphenous vein allografts.

METHODS

Between September 1995 and October 1999, 24 patients (15 men and nine women) were enrolled in a prospective clinical trial for salvage of 26 severely ischemic lower limbs with femoral-infrapopliteal cryopreserved saphenous vein allograft bypass grafts. All patients were treated with a protocol (aspirin, low-dose heparin, low molecular weight dextran 40, dipyridamole, and warfarin), and no immunosuppressive agents were used. The cryopreserved saphenous vein allografts were matched to patients by ABO and Rh compatibility. Indications for revascularization were ischemic rest pain (n = 8), nonhealing ulcer (n = 13), or focal gangrene (n = 5), and no usable autogenous vein was available. Follow-up ranged from 2 to 35 months (mean, 19 months). We studied the location and type of outflow anastomosis, specific outflow vessel, morbidity, death, secondary procedures (digital/transmetatarsal amputation), and complications related to the treatment protocol. Life table analyses of primary graft patency and limb salvage were compared with other current reported data.

RESULTS

Primary graft patency with Kaplan-Meier life table analysis was 96% at 6 months, 87% at 12 months, and 82% at 18 and 24 months. There were no reoperations for acute graft occlusion. One graft underwent late segmental aneurysmal degeneration and rupture. There were no procedure-related deaths or bleeding complications. During late follow-up, anticoagulation was discontinued in three patients (12%) because of gastrointestinal bleeding. Limb salvage was 88% at 6 months and 80% at 12, 18, and 24 months. Patients returned to ambulatory status that was limited only by their other comorbidities.

CONCLUSION

Femoral-infrapopliteal bypass graft for limb salvage with a cryopreserved saphenous vein allograft can be an acceptable alternative when autogenous vein is not available. Our treatment protocol substantially improved allograft patency and limb salvage when compared with current published data.

Rebound from nitric oxide inhibition triggers enhanced monocyte activation and chemotaxis

Exposure of human peripheral blood monocytes to the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP) resulted in a rapid shift in cellular conformation of spontaneously activated cells from ameboid to round. The population of activated cells, approximately 7. 1 +/- 1.2%, was reduced 7-fold to 1.1 +/- 0.4% following 0.5 h exposure to SNAP. Observation of monocytes for 6 h demonstrated a gradual release from NO inhibition initiating at 2.5 h following SNAP treatment and a period of hyperactivity that was maximal at approximately 5 h following SNAP exposure. During the rebound from the NO inhibition phase, there was a significant increase in the population of activated monocytes and an increased responsiveness to chemotactic agents such as IL-1, IL-8, and fMLP relative to that of cells treated with the chemotactic agents alone. Conformational changes induced by SNAP were associated with a reduction in F-actin and loss of filopodial extension. The loss and recovery of F-actin staining paralleled changes in cell activity, suggesting that NO may alter cellular activity by modulation of cytoskeletal actin. These data taken together suggest that inhibition of monocyte activity by NO results in an excitatory phase observed subsequent to release from NO inhibition and increased sensitivity to chemotactic agents. We propose that this rebound from NO inhibition may provide increased immunosurveillance to rectify immunological problems that have been encountered during the period of inhibition.

Estradiol-stimulated nitric oxide release in human granulocytes is dependent on intracellular calcium transients: evidence of a cell surface estrogen receptor

We tested the hypothesis that estrogen acutely stimulates constitutive nitric oxide synthase activity in human granulocytes by acting on a cell surface estrogen receptor (ER). The release of nitric oxide was measured in real time with an amperometric probe. Exposure of granulocytes to 17β-estradiol stimulated NO release within seconds in a concentration-dependent manner. The NO release was also stimulated by 17β-estradiol conjugated to bovine serum albumin (E2-BSA), which suggests mediation by a cell surface receptor. Tamoxifen, an ER inhibitor, antagonized the action of both 17β-estradiol and E2-BSA, whereas ICI 182,780, an inhibitor of the nuclear ER, had no effect. Using dual emission microfluorometry in a calcium-free medium, the 17β-estradiol–stimulated release of NO from granulocytes was shown to be dependent on intracellular calcium ([Ca2+]i) transients in a tamoxifen-sensitive process. Exposure to BAPTA-AM (1,2bis-(-aminophenoxy)ethans-N,N,N′,N′-tetraacetic acid tetra(acetoxyymethyl) ester), a [Ca2+]i chelator, reduced [Ca2+]i in response to E2-BSA, and depleting [Ca2+]i stores abolished the effect of 17β-estradiol on NO release. Confocal photomicrographs using E2-BSA–FITC (fluorescein isothiocyanate) revealed cell membrane reactivity. Estrogen-stimulated NO release had an immunosuppressive effect, and it initiated granulocyte rounding and loss of adherence in a tamoxifen-sensitive manner. Finally, using reverse transcriptase–polymerase chain reaction, human neutrophil granulocytes expressed ER but not ERβ, suggesting that ER may be the membrane receptor for 17β-estradiol. The study demonstrated that a physiological dose of estrogen down-regulates granulocyte activity by acutely stimulating NO release via the activation of a cell surface ER which is coupled to increases in [Ca2+]i.

Estradiol-stimulated nitric oxide release in human granulocytes is dependent on intracellular calcium transients: evidence of a cell surface estrogen receptor

We tested the hypothesis that estrogen acutely stimulates constitutive nitric oxide synthase activity in human granulocytes by acting on a cell surface estrogen receptor (ER). The release of nitric oxide was measured in real time with an amperometric probe. Exposure of granulocytes to 17β-estradiol stimulated NO release within seconds in a concentration-dependent manner. The NO release was also stimulated by 17β-estradiol conjugated to bovine serum albumin (E2-BSA), which suggests mediation by a cell surface receptor. Tamoxifen, an ER inhibitor, antagonized the action of both 17β-estradiol and E2-BSA, whereas ICI 182,780, an inhibitor of the nuclear ER, had no effect. Using dual emission microfluorometry in a calcium-free medium, the 17β-estradiol–stimulated release of NO from granulocytes was shown to be dependent on intracellular calcium ([Ca2+]i) transients in a tamoxifen-sensitive process. Exposure to BAPTA-AM (1,2bis-(-aminophenoxy)ethans-N,N,N′,N′-tetraacetic acid tetra(acetoxyymethyl) ester), a [Ca2+]i chelator, reduced [Ca2+]i in response to E2-BSA, and depleting [Ca2+]i stores abolished the effect of 17β-estradiol on NO release. Confocal photomicrographs using E2-BSA–FITC (fluorescein isothiocyanate) revealed cell membrane reactivity. Estrogen-stimulated NO release had an immunosuppressive effect, and it initiated granulocyte rounding and loss of adherence in a tamoxifen-sensitive manner. Finally, using reverse transcriptase–polymerase chain reaction, human neutrophil granulocytes expressed ER but not ERβ, suggesting that ER may be the membrane receptor for 17β-estradiol. The study demonstrated that a physiological dose of estrogen down-regulates granulocyte activity by acutely stimulating NO release via the activation of a cell surface ER which is coupled to increases in [Ca2+]i.

Cell-surface estrogen receptors mediate calcium-dependent nitric oxide release in human endothelia

BACKGROUND

Although estrogen replacement therapy has been associated with reduction of cardiovascular events in postmenopausal women, the mechanism for this benefit remains unclear. Because nitric oxide (NO) is considered an important endothelium-derived relaxing factor and may function to protect blood vessels against atherosclerotic development, we investigated the acute effects of physiological levels of estrogen on NO release from human internal thoracic artery endothelia and human arterial endothelia in culture.

METHODS AND RESULTS

We tested the hypothesis that estrogen acutely stimulates constitutive NO synthase activity in human endothelial cells by acting on a cell-surface receptor. NO release was measured in real time with an amperometric probe. 17beta-Estradiol exposure to internal thoracic artery endothelia and human arterial endothelia in culture stimulated NO release within seconds in a concentration-dependent manner. 17beta-Estradiol conjugated to bovine serum albumin also stimulated NO release, suggesting action through a cell-surface receptor. Tamoxifen, an estrogen receptor inhibitor, antagonized this action. We further showed with the use of dual emission microfluorometry that 17beta-estradiol-stimulated release of endothelial NO was dependent on the initial stimulation of intracellular calcium transients.

CONCLUSIONS

Physiological doses of estrogen immediately stimulate NO release from human endothelial cells through activation of a cell-surface estrogen receptor that is coupled to increases in intracellular calcium.

Basal nitric oxide limits immune, nervous and cardiovascular excitation: human endothelia express a mu opiate receptor

Nitric oxide (NO) is a major signaling molecule in the immune, cardiovascular and nervous systems. The synthesizing enzyme, nitric oxide synthase (NOS) occurs in three forms: endothelial (e), neuronal (n) and inducible (i) NOS. The first two are constitutively expressed. We surmise that in many tissues there is a basal level of NO and that the actions of several signaling molecules initiate increases in cNOS-derived NO to enhance momentary basal levels that exerts inhibitory cellular actions, via cellular conformational changes. It is our contention that much of the literature concerning the actions of NO really deal with i-NOS-derived NO. We make the case that cNOS is responsible for a basal or 'tonal' level of NO; that this NO keeps particular types of cells in a state of inhibition and that activation of these cells occurs through disinhibition. Furthermore, naturally occurring signaling molecules such as morphine, anandamide, interleukin-10 and 17-beta-estradiol appear to exert, in part, their beneficial physiological actions, i.e., immune and endothelial down regulation by the stimulation of cNOS. In regard to opiates, we demonstrate the presence of a human endothelial mu opiate receptor by RT-PCR and sequence determination, further substantiating the role of opiates in vascular coupling to NO release. Taken together, cNOS derived NO enhances basal NO actions, i.e., cellular activation state, and these actions are further enhanced by iNOS derived NO.

Functional assessment of disease-free saphenous vein grafts at redo coronary artery bypass grafting

BACKGROUND

Reoperations for coronary artery bypass grafting are on the rise. The general rule of replacing all saphenous vein grafts (SVGs) older than 5 years of age at the time of reoperation has recently been challenged on clinical grounds. This study provides functional data of endothelial behavior in long-term vein grafts.

METHODS

Previously placed SVGs were removed at the time of redo operations. Nitric oxide (NO) measurements in real time were carried out before and after stimulation with morphine. The measurements were compared to the angiographic appearance of the grafts obtained prior to operation. Grafts were categorized into 3 groups: disease-free, moderately diseased, and severely diseased.

RESULTS

Sixteen grafts were analyzed. Five were angiographically disease-free, 4 had moderate, and 7 severe disease. In the disease-free group, peak NO production after 10(-6) mol/L morphine stimulation was 35 mol/L, equivalent to the production of native saphenous vein. The severely diseased group did not demonstrate an increase in NO production, and the moderately diseased group produced a small rise in production.

CONCLUSIONS

Measurement of NO release of old SVGs, when angiographically pristine, equals that of native saphenous vein. These findings support the recent clinical observations that long-term angiographically disease-free vein grafts are biologically privileged.

Vitreous cryopreservation maintains the function of vascular grafts

Avoidance of ice formation during cooling can be achieved by vitrification, which is defined as solidification in an amorphous glassy state that obviates ice nucleation and growth. We show that a vitrification approach to storing vascular tissue results in markedly improved tissue function compared with a standard method involving freezing. The maximum contractions achieved in vitrified vessels were >80% of fresh matched controls with similar drug sensitivities, whereas frozen vessels exhibited maximal contractions below 30% of controls and concomitant decreases in drug sensitivity. In vivo studies of vitrified vessel segments in an autologous transplant model showed no adverse effects of vitreous cryopreservation compared with fresh tissue grafts.

Human aortocoronary grafts and nitric oxide release: relationship to pulsatile pressure

BACKGROUND

Short and long-term failure of saphenous vein grafts continues to be a significant problem for cardiac surgeons. The purpose of this study was to elucidate the early adaptive changes of human artery and vein conduits with respect to nitric oxide (NO) production under various pressure and pulsatile distention conditions.

METHODS

Real-time amperometric NO determinations were made in an in vitro model using human saphenous vein segments (n = 12) and internal thoracic artery segments (n = 8) between 70 and 170 mm Hg, under static conditions recorded with a pressure transducer. Exposing the tissue to morphine (10(-6) M) also stimulated NO release. Under conditions in which the conduits were exposed to the respective pressures for 1 hour, they were then examined for their granulocyte-adhering potential using computer-assisted imaging techniques.

RESULTS

A pressure-dependent decrease of NO release was found after 32 minutes of pulsatile pressure (170 mm Hg) in artery and vein, the latter of which appeared to be affected more negatively (p < 0.05; because many more observation points differed significantly after 32 minutes compared to 110 mm Hg values). In vessels maintained for 1 hour at these different pressures and then exposed to morphine (1 microM), stimulated NO release significantly diminished in the veins (artery 37.4 nM NO versus vein 18.1 nM NO; p < 0.05). Increased pressures also correlated with an increase in granulocyte adhesion to veins that could not be reduced following morphine exposure.

CONCLUSIONS

Increased pressure and cyclic distention lead to loss of NO release and increased immunocyte adhesion, which are significantly more pronounced in saphenous vein than in internal thoracic artery, suggesting that in the long term this may contribute to the failure of saphenous vein conduits in coronary revascularization.

Mu3 opiate receptor expression in lung and lung carcinoma: ligand binding and coupling to nitric oxide release

The mu3 opiate receptor subtype is expressed in human surgical specimens of both normal lung and non-small-cell lung carcinoma. Nitric oxide (NO) release is mediated through the mu3 receptor, and in lung carcinoma, morphine-stimulated NO release is significantly higher and prolonged than in normal lung. Using reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blot analysis we show that specific mu opioid receptor transcripts are present in lung carcinoma and other cells with the mu3 profile. Our findings identify a unique role for the mu3 opiate receptor in opiate-mediated NO release and suggest that endogenous opiates, through their release of NO, may play a role in cancer progression.

Opiate, cannabinoid, and eicosanoid signaling converges on common intracellular pathways nitric oxide coupling

Scientific fields as they emerge initially appear to be unrelated to other projects even if they are in a similar area of interest. This is especially true in the case of opiate, cannabinoid, and eicosanoid signaling processes. In this limited speculative review, we attempt to examine aspects of their intracellular cascading signaling systems for their commonalities. We find intracellular calcium mobilization, nuclear factor kappa B involvement, adenylate cyclase activity, and, finally, constitutive nitric oxide release to be converging points for these signaling processes, occurring by separate and distinct receptor-mediated effector systems. Phosphokinase C, mitogen activated protein kinase, and cytosolic phospholipase A2 also represent points of common impact. In this regard, aspirin also appears to be involved in an aspect of this signaling convergence. We conclude that many of the physiological observations regarding the actions of these signaling molecules, for example, immunosuppression, neurotransmission, vasodilation, cellular adherence, and cytotoxicity, can now be understood by considering their converging biochemical cascades.

Long-term exposure of human blood vessels to HIV gp120, morphine, and anandamide increases endothelial adhesion of monocytes: uncoupling of nitric oxide release

Acute exposure of human saphenous vein or internal thoracic artery endothelium to either morphine [27.4 +/- 3.7 and 35.4 +/- 4.1 nM nitric oxide (NO), respectively] or anandamide (18.3 +/- 2.2 and 24.3 +/- 3.0 nM, respectively) results in NO release, whereas exposure to the human immunodeficiency virus envelope protein gp120 does not. After the short-term exposure of the vessel endothelium, monocyte adherence is diminished with morphine and anandamide treatment (jointly by -80%), whereas it is enhanced with that of gp120 (approximately 40%), indicating that gp120 enhances the ability of the endothelium to adhere monocytes. Long-term or continuous exposure of the endothelia to all agents results in a significant enhancement of monocyte adherence (p < 0.05), which is further increased when exposed to either morphine and anandamide plus gp120. This is caused by a desensitization of the endothelium to further NO release after the initial exposure to either anandamide or morphine. The results serve to indicate that in individuals abusing opiates and or cannabinoids, a tissue [i.e., central nervous system (CNS)] viral load may be higher, and acquired immunodeficiency syndrome (AIDS) may progress more rapidly because monocyte adherence and mobility is significantly increased, indicating a higher level of transmembrane migration.

Antagonism of LPS and IFN-gamma induction of iNOS in human saphenous vein endothelium by morphine and anandamide by nitric oxide inhibition of adenylate cyclase

Nitric oxide (NO) production regulates vasodilation in many blood vessels. Additionally, constitutive NO release is being associated with positive biomedical phenomena, whereas inducible NO synthase (iNOS)-associated NO release with detrimental consequences in regard to endothelial inflammatory activities. As yet, an important link demonstrating why one is activated over the other is not available. Previous studies have demonstrated that morphine and anandamide effector processes are coupled to NO release in human endothelial cells (ECs). This study now extends this observation in that these endogenous signaling molecules may use NO directly to inhibit adenylate cyclase activity. Activation of human ECs, obtained from the saphenous vein, with morphine- or anandamide-stimulated NO release (35 nM and 28 nM, respectively) that peaked within 5 min and returned to basal levels within 10 min of agonist stimulation, consistent with constitutive NO synthase (cNOS) activation. Significant release of NO from ECs stimulated with lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) occurred after 2 h after exposure and remained significantly increased over basal levels for 24-48 h (28 nM), consistent with iNOS activation. Preincubation of ECs with morphine or anandamide before, but not after, the addition of LPS + IFN, blocked iNOS activity. Exposure of ECs to the NO donor, SNAP, before the addition of LPS + IFN, blocked iNOS induction, whereas preincubation of ECs with inhibitors of NOS, before morphine or anandamide exposure, restored LPS + IFN induction of iNOS, suggesting a direct impact of NO on the regulation of iNOS activity. Morphine and anandamide stimulation of ECs did not stimulate cyclic adenosine monophosphate (cAMP) accumulation, whereas a marked increase in cAMP was observed in ECs treated with LPS + IFN (8.2 to 33 pmol/mg protein). Treatment of ECs with LPS + IFN did not induce cAMP accumulation in ECs treated with morphine, anandamide, or SNAP before LPS + IFN exposure. These data suggest that cAMP is required for the induction of iNOS in ECs and that NO may directly impair adenylate cyclase activity, preventing iNOS activation.

Aspirin inhibits granulocyte and monocyte adherence to saphenous vein endothelia in a process not mediated by nitric oxide

We examined the effects of aspirin on human immunocyte adherence to human saphenous vein preparations in vitro. Monocytes and granulocytes were analyzed by phase-contrast microscopy in conjunction with a time-lapse video recording system for cell counting in the medium. Saphenous vein samples taken from five volunteer subjects during their elective coronary artery bypass grafting procedures were used for an in vitro experiment in which each subject's immune cells were added to his/her respective endothelial tissues. In addition, aspirin or morphine was added to the preparations. After 30 min the endothelium and the medium were examined for cell numbers using feature color detection software. The endothelium exposed to a 10 min preincubation with 10 mmol/l aspirin was found to have significantly fewer monocytes and granulocytes attached. The saphenous vein preparations were examined for nitric oxide (NO) release using an NO-selective amperometric microprobe. Aspirin at its immunocyte inhibitory concentrations did not induce NO release from the endothelium, whereas morphine, which is known to stimulate NO production by endothelium, did so. These findings demonstrate that the administration of aspirin in high doses can diminish human granulocyte and monocyte adherence to saphenous vein endothelium in vitro through an NO-independent mechanism.

Morphine's immunoregulatory actions are not shared by fentanyl

Fentanyl is a commonly used narcotic agent in anesthesia. It has strong analgesic properties which it shares with morphine. Unlike morphine, it does not possess the ability to bind to the mu3 receptor, and therefore does not have the ability to influence nitric oxide release as measured amperometrically. Cell adhesion also is not influenced. As a result, it also lacks the ability to downregulate the inflammatory response associated with surgery, especially cardiopulmonary bypass.

Delta2 opioid receptor subtype on human vascular endothelium uncouples morphine stimulated nitric oxide release

We demonstrate the presence of both delta and mu opioid receptors on the endothelium of human saphenous vein and internal thoracic artery. Displacement analysis revealed that a variety of opioid peptides were found to be ineffective in displacing specifically bound 3H dihydromorphine and only delta2 ligands were effective in regard to 3H Ala2-met5 enkephalinamide (DAMA), indicating the presence of mu3 and delta2 opioid receptor sites, respectively. Confirming the presence of both mu and delta sites we demonstrated positive immunostaining with anti-delta and anti-mu receptor antibodies. Exposure of these vessels to DAMA significantly enhances granulocyte adherence (P<0.01) even in vessels 5 min later exposed to 10(-6) M morphine. Unlike morphine, DAMA did not stimulate nitric oxide from either blood vessel and human granulocytes. Additionally, DAMA preadministered before morphine exposure to the endothelium or granulocytes, inhibited the morphine-stimulated release of NO in a dose-dependent manner. The data indicate that opioid peptides and opiate alkaloids regulate endothelial function in an antagonistic manner thereby influencing the microvascular environment.

Pharmacological evidence for anandamide amidase in human cardiac and vascular tissues

The present report demonstrates the presence of antianandamide and anticannabinoid receptor 1 immunopositive material on the saphenous vascular endothelium. The endogenous cannabinoid, anandamide, in a dose-dependent manner stimulated the release of nitric oxide (NO) from saphenous vein, internal thoracic artery and right atrium tissue segments in vitro. This process can be antagonized by the nitric oxide synthase (NOS) inhibitor, N-omega-nitro-L-arginine methyl ester (L-NAME) (10(-4) M; 3.4+/-0.9 nM NO; P<0.01 compared to anandamide alone), as well as by the cannabinoid receptor I antagonist SR 141716A (2.9+/-1.0 nM NO; P<0.01). Furthermore, in the presence of varying concentrations of methylarachidonylfluorophosphonate, an anandamide amidase inhibitor, 10(-8) M anandamide stimulates a higher peak level of NO that remains elevated for a longer period of time (P<0.05) compared to anandamide alone, demonstrating the presence of anandamide amidase in human vascular tissues. Morphine, as anandamide, can stimulate the release of NO from right atria. This process can be inhibited by the opiate receptor antagonist naloxone and the NOS inhibitor L-NAME. As expected SR 141716A (10(-6) M; 26+3.8 NO nM in the presence of 10(-7) M morphine) did not antagonize morphine's ability to release NO. Taken together, the data demonstrate that cannabinoid signalling is involved with the regulation of the microvascular environment.

Macrophage behavior associated with acute and chronic exposure to HIV GP120, morphine and anandamide: endothelial implications

We demonstrate that immediate exposure to gp120 (5 min; 0.1 microg/ml) results in a significant shift of the macrophage population to an amoeboid and motile category (P<0.01; 91.7+/-5.5 vs. a control value of 42.4+/-4.2) and prior exposure with anti-gp120 antagonizes this shift. Acute exposure of the macrophages to morphine (10(-6) M) or anandamide (10(-6) M) resulted in the cells rounding up (shape factors of 0.84 and 0.87 respectively) and becoming non-motile. The action is blocked by prior treatment with the specific antagonists naloxone and SR 141716A. Chronic exposure (6 h) of the cells to all three agents resulted in a random migration pattern. Further, all agents blocked chemotaxis induced by DAMA and IL-1. Observation of the cells behavior during chronic exposure revealed a sporadic activity pattern with gp120 whereas morphine and anandamide first induced a period of inactivity which is followed by a period of activity (chemokinesis). Recent work from our laboratory has demonstrated that both morphine and anandamide acutely stimulate constitutive macrophage nitric oxide (NO) release, which then induces macrophage rounding and inactivity. It was therefore of interest to examine their behavior by exposing macrophages to the NO-donor SNAP. In a concentration dependent manner SNAP exhibited the same behavioral actions as both substances of abuse. Given this, we next determined if macrophages exposed to gp120 would release NO. We demonstrated that NO was released only when exposed to morphine and anandamide not gp120. Thus. the chemokinetic inducing activities of these agents may be the basis for excitotoxin liberation in neural tissues and/or a higher viral load in various organ systems since cellular adherence and random migration are stimulated.

Morphine and anandamide coupling to nitric oxide stimulates GnRH and CRF release from rat median eminence: neurovascular regulation

Nitric oxide (NO) is involved in neurohormonal secretion from median eminence neuroendocrine nerve terminals. We report that stimulation of NO release from median eminence fragments including vascular tissues occurs by mu3 receptor activation by morphine, or by cannabinoid type 1 receptor activation by anandamide. The released levels of NO are lower after anandamide than after morphine stimulation. These processes can be blocked by L-NAME, a specific nitric oxide synthase inhibitor, by naloxone for the morphine-stimulated NO release, or SR 141716A, a specific CB1 receptor inhibitor, for the anandamide-stimulated NO release. Furthermore, morphine and anandamide, by this NO dependent process, influences neurohormonal release from median eminence nerve terminals within 10 min. Via this NO dependent process, morphine stimulates both GnRH and CRF release, whereas anandamide selectively stimulates GnRH release. These observations together with previous data suggest that morphine and the anandamide-stimulated NO originates from the vascular endothelium of the portal plexus. These results indicate that endothelial cells of the median eminence may be involved in the release of neurohormones.

Autoimmunovascular regulation: morphine and anandamide and ancondamide stimulated nitric oxide release

The hypothesis concerning morphine as an endogenous signal molecule has been strengthened with the recent discovery of a new opiate receptor subtype, designated mu3. This opiate receptor is opiate alkaloid sensitive and opioid peptide insensitive, including peptides previously shown to have affinities for mu opiate receptors. This receptor is coupled to nitric oxide release in human endothelial cells, granulocytes and monocytes and in invertebrate immunocytes and microglia. In relation to the endothelium, it has also been coupled to vasodilation via nitric oxide. Given the known influence of nitric oxide in downregulating cell adhesion, the role of this compound has now been investigated in also diminishing endothelial-immunocyte interaction. Morphine, via nitric oxide, has the potential to diminish adhesion molecule expression and in so doing calm an inflammatory process between immunocytes and the endothelial surface. In this regard, the potential for abuse is also present.

Endogenous morphine levels increase following cardiac surgery as part of the antiinflammatory response?

Exogenous morphine downregulates the activity of immunocompetent cells such as lymphocytes, granulocytes and macrophages. Furthermore, morphine increases the secretion of CRH, ACTH and glucocorticoids, i.e. substances with inhibitory effects on the immune system. In the present study we tested the hypothesis that endogenous morphine production is increased as part of the antiinflammatory response to cardiac surgery. Sixteen patients submitted to elective coronary artery bypass grafting (CABG) surgery were randomized to either thoracic epidural analgesia combined with general anaesthesia (group I) or high-dose fentanyl anaesthesia (group II). Patients in group I did not receive morphine while patients in group II received systemic morphine for postoperative pain relief. From each patient 18 blood samples were taken perioperatively and tested for morphine. Furthermore, monocyte function with respect to motility and shape was determined by computer-assisted image analysis. A steep increase in plasma morphine concentrations was demonstrated on the first postoperative day in patients in group I (not given morphine). Plasma morphine levels remained significantly elevated during the following five postoperative days. Patients in group II given morphine as pain treatment showed a larger and earlier morphine peak related to the morphine administration. Computer-assisted image analysis of leukocyte behaviour revealed a biphasic increase in cell motility. In conclusion, we demonstrate for the first time that endogenous morphine levels increase after the trauma of surgery. We surmise that morphine is part of the antiinflammatory response to cardiac surgery.

Nitric oxide inhibits the dopamine-induced K+ current via guanylate cyclase in Aplysia neurons

Nitric oxide (NO) is produced by the enzyme nitric oxide synthase (NOS) and has been implicated in inter- and intracellular communication in the nervous system. The present study was undertaken to assess the effects of sodium nitroprusside (SNP) and hydroxylamine (HOA), NO donors, on a dopamine (DA)-induced K+ current in identified Aplysia neurons using voltage-clamp and pressure ejection techniques. Bath-applied SNP (10-25 microM) reduced the DA-induced K+ current without affecting the resting membrane conductance and holding current. The DA-induced K+ current also was inhibited by the focal application of 200 microM HOA to the neuron somata. The DA-induced K+ current suppressing effects of SNP and HOA are completely reversible. Pretreatment with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ; 1 microM), a specific inhibitor of NO-stimulated guanylate cyclase, and hemoglobin (50 microM), a nitric oxide scavenger, decreased the SNP-induced inhibition of the DA-induced current. In contrast, intracellular injection of 1 mM guanosine 3',5'-cyclic monophosphate (cGMP) or bath-applied 3-isobutyl-1-methylxanthine (IBMX; 50 microM), a non-specific phosphodiesterase inhibitor, inhibited the DA-induced current, mimicking the effect of the NO donors. These results demonstrate that SNP and HOA inhibit the DA-induced K+ current and that the mechanism of NO inhibition of the DA-induced current involves cGMP-dependent protein kinase.