Communication between animal cells and the plant foods they ingest: phyto-zooidal dependencies and signaling (Review)

The beneficial effect of plant foods on human health is unmistakable. Time and time again, studies have found foods of plant origin to reduce the risk of most major chronic illnesses suffered by the human population. Possible mechanisms for the preventative effects of these foods are discussed. Each of the plant groups reviewed was found to reduce the risk of one or more of the following: cardiovascular disease, cancer (lung, breast, colon, rectal, prostate, epithelial, stomach, esophageal, oral, pharynx, larynx, urinary tract, endometrium, pancreas, thyroid, liver, ovary, gallbladder, bladder, and kidney), diabetes, hypertension, bone degeneration, diverticulitis, constipation, gallstones, age-related blindness. Almost no evidence was found to suggest a negative effect on health due to consumption of these plant foods. Based on this material and a review of conserved animal signaling molecules we surmise that animals require these chemicals to enhance specific mammalian cellular processes, demonstrating phyto-zooidal signaling. Further, this diet dependency coupling between plants and animals probably evolved because of the abundance of a particular plant material in a local environment, which is now broken because of technological advances. In conclusion, the overwhelming majority of evidence shows that people may significantly decrease their risks of the aforementioned diseases by increasing their intake of these foods since they represent a natural method to enhance animal processes and signaling.

Effect of in vivo and in vitro stimulation of delta1-opioid receptors on myocardial resistance to arrhythmogenic action of ischemia and reperfusion

Preliminary intravenous injection of peptide agonist of delta1-opioid receptors DPDPE (0.5 mg/kg) decreased the incidence of occlusion (10 min) and reperfusion (10 min) arrhythmias in rats. By contrast, delta2-opioid receptor agonist DSLET produced no effect on the incidence of arrhythmias provoked by coronary occlusion and reperfusion. Preliminary injection of selective delta-receptor antagonist ICI 174,864 (2.5 mg/kg) or TIPP[y] (0.5 mg/kg) completely abolished the antiarrhythmic effect of DPDPE. Stimulation of cardiac delta1-opioid receptors with DPDPE added to perfusion saline in concentrations of 0.1 and 0.5 mg/liter decreased the incidence of reperfusion arrhythmias. Addition of DPDPE to perfusion saline in a concentration of 0.1 mg/liter prevented reoxygenation destruction of cardiomyocytes. By contrast, no cardioprotective effect of this peptide was observed at a concentration of 0.5 mg/liter in perfusion saline or when it was injected intravenously. It is concluded that the cardioprotective and antiarrhythmic effects of DPDPE are caused by activation of cardiac delta1-opioid receptors.

Immune processes in the pathogenesis of Parkinson's disease - a potential role for microglia and nitric oxide

It has been known for many years that immune system alterations occur in Parkinson's disease (PD). Changes in lymphocyte populations in cerebrospinal fluid and blood, immunoglobulin synthesis, and cytokine and acute phase protein production have been observed in patients with PD. In this regard, PD patients exhibit a lower frequency of infections and cancer, suggesting that immune system stimulation may occur. This hypothesis is further supported by the observation of T-cell activation leading to the production of interferon gamma in PD. As in other CNS degenerative diseases, in damaged regions in the brains of PD patients, there is evidence of inflammation, characterized by glial reaction (especially microglia), as well as increased expression of HLA-DR antigens, cytokines, and components of complement. These observations suggest that immune system mechanisms are involved in the pathogenesis of neuronal damage in PD. The cellular mechanisms of primary injury in PD have not been clarified, however, but it is likely that mitochondrial mutations, oxidative stress and apoptosis play a role. Furthermore, inflammation initiated by neuronal damage in the striatum and the substantia nigra in PD may aggravate the course of the disease. These observations suggest that treatment with anti-inflammatory drugs may act to slow progression of PD.

Presence of isoquinoline alkaloids in molluscan ganglia

Tetrahydropapaveroline and reticuline, isoquinoline alkaloids, were purified and identified in the pedal ganglia of the marine mollusk Mytilus edulis.

OBJECTIVES

To determine the presence of tetrahydropapaveroline and reticuline, isoquinoline alkaloids, in animal tissues previously shown to express opiate receptors.

METHODS AND RESULTS

This was achieved by high performance liquid chromatography coupled with electrochemical detection and finally identified by electro-spray ionization quadrupole time of flight mass spectrometry (Q-TOF). The expression of these two terahydroisoquinoline alkaloids in the animals neural tissue is at the level of 2.5+/-0.64 ng/ganglion and 1.8+/-0.52 ng/ganglion, respectively.

CONCLUSION

This finding suggests that morphine biosynthesis may occur in Mytilus neural tissues, and that the biosynthesis pathway may be similar to that reported in the poppy plant.

The role of protease inhibition with emphasis on the effects of inflammation and vascular immune phenomena

This review discusses the role of protease inhibition with emphasis on the effects of inflammation and vascular immune phenomena in non-immunocompromised hosts. A vast body of knowledge elucidating the role of protease inhibition and hemostasis has accumulated in recent years. The two subjects are intimately linked, but the focus of this review is limited to the anti-inflammatory effects of protease inhibitors. In light of the particular expertise of the present authors, this review will focus on human studies and often cite work related to open-heart surgery, since in recent years this is the area in which a large effort has been concentrated worldwide.

Cyclic nitric oxide release by human granulocytes, and invertebrate ganglia and immunocytes: nano-technological enhancement of amperometric nitric oxide determination

BACKGROUND

Various tissues from vertebrates and invertebrates respond to external signal molecules by rapid release of nitric oxide (NO) mediated by constitutive nitric oxide synthase.

MATERIAL/METHODS

Invertebrate immunocytes were collected from maintained stock and human granulocytes were isolated from leukocyte-enriched blood obtained from the Long Island Blood Services. The invertebrate ganglionic tissue was either extracted or exposed for ex vivo and in vivo evaluation. Nitric oxide release was measured using a newly developed NO-selective nanoprobe, exhibiting enhanced sensitivity.

RESULTS

Evaluation of NO release from the pedal ganglia of the marine bivalve, Mytilus edulis, demonstrated in vitro release of NO that fluctuated from 969 to 1003 pM, with a mean change in NO of 35 pM/cycle and a mean cycle time of approximately 4 minutes. Basal release of NO/cycle from the ganglia in vivo was increased significantly to approximately 65 pM (P<0.05) with an increase in cycle time to approximately 7 minutes. Exposure of the ganglia to morphine in vivo resulted in a significant increase in NO release and a lack of NO pulsations. The fluctuation in NO release from immunocytes of Mytilus edulis was approximately 27 pM per cycle with a cycle time of 4 minutes whereas human granulocytes release fluctuated approximately 23 pM with a cycle time of 6 minutes.

CONCLUSIONS

These data demonstrate that basal release of NO from various tissues is released in a cyclic manner and the cycle time and magnitude is subject to regulation by external stimuli.

The role of stress in neurodegenerative diseases and mental disorders

OBJECTIVE

Evidence for a connection between stress and selected neurodegenerative diseases as well as mental disorders is analyzed. Does stress cause or exacerbate related pathophysiological disease processes?

METHOD

The stress phenomenon is illustrated and the impact of stress on the nervous system, neurodegenerative diseases, and mental disorders is examined. The connection between stress and the hippocampus - and its association with memory functions - is described. In particular, the pathophysiological significance of stress in Alzheimer's disease, multiple sclerosis, anxiety, depression, posttraumatic stress disorder, and schizophrenia is investigated.

RESULTS

Stress plays a major role in various (patho)physiological processes associated with neurodegenerative diseases and mental disorders. In principle, stress has the potency to exert either ameliorating or detrimental effects. The specific outcome depends on multiple variables. However, the amount of stress experienced in relation to activated physiological processes that aim at successful coping and positive adjustments (i.e., stress response) most often is overwhelming - and may thus become detrimental in the long-term. Moreover, the hippocampus is sensitive to stress, and its involvement in neurodegeneration - in the course of stress-related disease processes - may account for severe clinical disabilities (e.g., memory loss).

DISCUSSION/CONCLUSION

Stress has a major impact upon neurodegenerative diseases and mental disorders. It plays a significant role in susceptibility, progress, and actual outcome. Also, subjective or individual differences have to be taken into account. However, stress - especially 'adequate' acute stress (stress that is not overwhelming) - may even improve performance/biological functions and be beneficial in certain cases.

Stress-related diseases -- a potential role for nitric oxide

Nitric oxide (NO) is involved in stress physiology and stress-related disease processes. Like stress, NO seems to be capable of principally exerting either beneficial or deleterious effects. The actual distinction depends on a multitude of factors. Moreover, NO counteracts norepinephrine (NE) activity and sympathetic responsivity. Thus, NO and the stress (patho)physiology are closely connected and molecular mechanisms or pathways may be shared under certain conditions. NO is involved in immunological, cardiovascular, and neurodegenerative diseases/ mental disorders. It represents a 'double-edged sword', since small quantities produced by constitutive enzymes may predominantly mediate physiological effects, whereas the expression of inducible NO synthases may lead to larger quantities of NO, a situation that may be associated with cytotoxic and detrimental effects of NO. The key step for normally useful physiological mechanisms becoming pathophysiological may be represented by the loss of balance, the loss of control over the different pathways induced. A failure to terminate or shift originally protective mechanisms may lead to a vicious cycle of disease-supporting pathophysiological pathways.

CONCLUSIONS

Profound connections between stress and various disease processes exist. Thereby, common pathophysiological pathways in stress-related diseases have been described, and they involve stress hormone (cortisol, NE) and, in particular, NO activity. Thus, NO has detrimental capacities. However, NO not only exerts deleterious but also strongly ameliorating effects. The balance between both properties is crucial. Yet, nitric oxide involvement in stress-related diseases represents a common pathway, with various pathophysiological analogies, that may be accessible for strategies using stress management and relaxation response techniques.

Effects of morphine on tumour growth

Endogenous opiate alkaloids, such as morphine, and their peptide counterparts have been implicated in a wide variety of pharmacological and physiological functions. In addition to their use in the treatment of pain, opioids, appears to be important in the growth regulation of normal and neoplastic tissue. This review will focus on the influence of endogenous and exogenous opioids on tumour growth, with emphasis on immunoregulatory and antiproliferative mechanisms.

[Anandamide and R-(+)-methanandamide prevent development of ischemic and reperfusion arrhythmia in rats by stimulation of CB2-receptors]

It has been found that prior intravenous administration of the endocannabinoid anandamide (10 mg/kg) or its synthetic analogue R-(+)-methanadamide (5 mg/kg) prevents a development of ischemic and reperfusion arrhythmias in rats. The prior injection of the CB1 receptor antagonist, SR 141716A (3 mg/kg), did no affect the antiarrhythmic action of both cannabinoids. Pretreatment with the CB2 receptor antagonist, SR 144528 (1 mg/kg), completely abolished antiarrhythmic effect of anandamide and R-(+)-methanandamide. Both CB antagonist had no effect on the arrhythmias itself. Pretreatment with the NO-synthase inhibitor, L-NAME (50 mg/kg), had no effect on the antiarrhythmic action of cannabinoids. We therefore conclude that CB2 receptor stimulation increases the heart tolerance to ischemic and reperfusion arrhythmias.

Stress in cardiovascular diseases

OBJECTIVE

Evidence for a connection between stress and selected cardiovascular diseases is analyzed. Does stress cause or exacerbate cardiovascular diseases?

METHOD

The stress phenomenon is illustrated and the impact of stress on the circulatory system is examined. In particular, the pathophysiological significance of stress in hypertension, atherosclerosis, coronary artery disease, myocardial infarction (and others) is described.

RESULTS

Stress plays a major role in various (patho)physiological processes associated with the circulatory system. Thereby, it potentially has ameliorating or detrimental capacities. However, with regard to cardiovascular diseases, stress most often is related to deleterious results. The specific outcome depends on multiple variables (amount of stress, duration of its influence, patient's history/predisposition, genetic components -- as they all may alter functions of the basic stress response components: the hypothalamic-pituitary-adrenal axis and the sympathoadrenal medullary system).

CONCLUSIONS

Stress has a major impact upon the circulatory system. It plays a significant role in susceptibility, progress, and outcome of cardiovascular diseases. Subjective or individual differences have also to be taken into account. Stress, especially 'adequate' acute stress - stress that is not 'overwhelming' - may improve performance and thus be beneficial in certain cases. The close relationship between stress and cardiovascular diseases may represent an important aspect of modern medicine. New therapeutic strategies have to be set in place.

[Increase of the heart arrhythmogenic resistance and decrease of the myocardial necrosis zone during activation of cannabinoid receptors]

We have found that intravenous administration of cannabinoid receptor (CB) agonist HU-210 (0.05 mg/kg), increases cardiac resistance against arrhythmogenic effect of epinephrine, aconitine, coronary artery occlusion and reperfusion in rats. Pretreatment with CB2-receptor antagonist, SR144528 (1 mg/kg), completely abolished the antiarrhythmic effect of HU-210. However this effect of HU-210 was not attenuated by pretreatment with CB1-receptor antagonist, SR141716A (3 mg/kg). We also found that HU-210 (0.05 mg/kg) decreased the relationship between infarction size and area of ischemia. It is concluded that CB2 receptor stimulation promotes an increase in the cardiac resistance against arrhythmogenic influences and probably increases myocardial tolerance of both ischemic and reperfusion damages in rats.

Morphine down regulates human vascular tissue estrogen receptor expression determined by real-time RT-PCR

Human vascular endothelial cells express the estrogen receptor-beta (ER-beta), which can be modulated by the opiate alkaloid morphine.

OBJECTIVES

To determine if morphine is capable of down regulating the ER-beta receptor in a similar fashion as the mu opiate receptor since they are both coupled to constitutive nitric oxide synthase derived nitric oxide release.

METHODS AND RESULTS

Endothelial cells obtain from human vascular tissues (saphenous vein, atria and primary saphenous vein cells) were treated with 1 uM morphine plus or minus the mu opiate receptor antagonist naloxone or CTOP (10 uM) for 24 h at 37 degrees C. Total RNA was isolated from treated and untreated primary endothelial cells, and specific primers and a probe were used to determine the ER-beta gene expression by real-time RT-PCR. Cells treated with morphine exhibited a down-regulation of ER-beta, whereas naloxone and CTOP were able to partially block the morphine effect. In addition, the 266 bp fragment generated by RT-PCR using the same primers as in the real-time PCR was sequenced and revealed a 100% sequence identity as the authentic ER-beta gene sequence.

CONCLUSIONS

These results indicate that ER-beta is expressed in human vascular endothelial cells, and morphine appears to regulate this receptor in a similar fashion as the mu opiate receptor.

Dracunculus medinensis and Schistosoma mansoni contain opiate alkaloids

The results of analysis, by high-performance liquid chromatography coupled with electrochemical detection and by nano-electrospray-ionization, double quadrupole/orthogonal-acceleration, time-of-flight mass spectrometry, indicate that adult Dracunculus medinensis and Schistosoma mansoni both contain the opiate alkaloid morphine and that D. medinesis also contains the active metabolite of morphine, morphine 6-glucuronide. From these and previous observations, it would appear that many helminths are probably using opiate alkaloids as potent immunosuppressive and antinociceptive signal molecules, to down-regulate immunosurveillance responsiveness and pain signalling in their hosts.

The blueprint for stress can be found in invertebrates

Through an extremely complicated equilibrium called homeostasis, all living organisms maintain their survival in the face of both externally and internally generated "stimuli". This apparent harmony is constantly challenged. Survival through successful adaptation is maintained as close to steady state as possible by adaptive responses, which may also be called perturbation responses since they have a constitutively defined dynamic capacity, i.e., an immediate limit, in a series of balancing and feedback activities reflecting an astounding array of biological, psychological and sociological behaviors. The broad spectrum of stimuli capable of engaging this protective response is remarkable. We define stress as a type of stimulation that is stronger and lasts for a longer duration, upsetting a typical perturbation response given its dynamic parameters. The stress response, which evolves out of the perturbation response, involves inducible signal molecules, i.e., cytokines. We surmise that the ability to exist in an ever-changing environment was a requirement for all life forms, including invertebrates and single celled organisms. It would be expected that these organisms exhibit both perturbation and stress responses. In this regard, we demonstrate that these organisms have mammalian-like signal molecule systems, i.e., opioid, and corresponding behaviors that are similar to those found in mammals with regard to both perturbation and stress responses. Thus, it would appear that these responses evolved first in simpler organisms and were then maintained and enhanced during evolution.

Morphine 6 glucuronide stimulates nitric oxide release in mussel neural tissues: evidence for a morphine 6 glucuronide opiate receptor subtype

We have previously demonstrated that Mytilus edulis pedal ganglia contain opiate alkaloids, i.e., morphine and morphine 6 glucuronide (M6G), as well as mu opiate receptor subtype fragments exhibiting high sequence similarity to those found in mammals. Now we demonstrate that M6G stimulates pedal ganglia constitutive nitric oxide (NO) synthase (cNOS)-derived NO release at identical concentrations and to similar peak levels as morphine. However, the classic opiate antagonist, naloxone, only blocked the ability of morphine to stimulate cNOS-derived NO release and not that of M6G. CTOP, a mu-specific antagonist, blocked the ability of M6G to induce cNOS-derived NO release as well as that of morphine, suggesting that a novel mu opiate receptor was present and selective toward M6G. In examining a receptor displacement analysis, both opiate alkaloids displaced [3H]-dihydromorphine binding to the mu opiate receptor subtype. However, morphine exhibited a twofold higher affinity, again suggesting that a novel mu opiate receptor may be present.

Cold stress alters Mytilus edulis pedal ganglia expression of mu opiate receptor transcripts determined by real-time RT-PCR and morphine levels

Previous pharmacological, biochemical and molecular evidence prove that mu-subtype opiate receptors and opiate alkaloids, i.e. morphine, are present in the ganglionic nervous system of the mollusk Mytilus edulis (bivalve). We now present molecular evidence on the effect of rapid temperature changes on mu opiate receptor expression and morphine levels. Using primers, a labeled Taq-Man probe derived from the human neuronal mu1 opiate receptor, and real-time RT-PCR to measure the expression of mu transcripts from Mytilus pedal ganglia, we observe, in animals placed in cold water from room temperature, an enhanced morphine and morphine 6 glucuronide level in addition to a decrease in mu opiate receptor gene expression. This study provides further evidence that mu-type opiate receptors and morphine are expressed in mollusk ganglia and appear to be involved in physiological processes responding to thermal stress.

A hormonal role for endogenous opiate alkaloids: vascular tissues

The distribution of morphine-containing cells in the central nervous system, adrenal gland, and its presence in blood may serve to demonstrate that this signal molecule can act as a hormone besides its role in cell-to-cell signaling within the brain. This speculative review is the result of a literature evaluation with an emphasis on studies from our laboratory. Opioid peptides and opiate alkaloids have been found to influence cardiac and vascular function. They have also been reported to promote ischemic preconditioning protection in the heart. Given the presence of morphine and the novel mu(3) opiate receptor on vascular endothelial cells, including cardiac and vascular endothelial cells in the median eminence, it would appear that endogenous opiate alkaloids are involved in modulating cardiac function, possible at the hormonal level. This peripheral target tissue, via nitric oxide coupling to mu opiate receptors, may serve to down regulate the excitability of this tissue given the heart's high performance state as compared to that of the saphenous vein, a passive resistance conduit. With this in mind, morphine and other endogenous opiate alkaloids may function as a hormone.

Direct assessment and diminished production of morphine stimulated NO by diabetic endothelium from saphenous vein

AIM

To directly measure in real time basal and stimulated levels of NO released from human saphenous vein endothelium and to quantify the expression of the mu opiate receptor, which has been linked with NO release.

METHODS

Saphenous vein segments from patients with type 2 diabetes (n=12) and patients without diabetes (n=8) were obtained. The release of NO was measured directly from the endothelium using a NO-specific amperometric probe. N(Omega)-nitro-L-arginine methyl ester (L-NAME, 0.1 mmol/L), a NO synthase (NOS) inhibitor, or morphine (1 mumol/L), a stimulant, was administered and the measurements were repeated. Values were reported relative to the mean initial measurement of NO release from diabetic endothelium, which was defined as the relative zero level of NO release. A RT-PCR was then performed on the endothelium to measure mu opiate receptor expression.

RESULTS

Diabetic patients (n=12) showed a relative and significantly diminished basal level of released NO, (0.049+/-0.012) nmol/L, compared with non diabetic patients (n=8), (0.42+/-0.12) nmol/L (P<0.05). Application of L-NAME to nonstimulated tissues resulted in no change in NO release from the diabetic group and a decrease in NO release of (0.21+/-0.09) nmol/L from the non diabetic group (P<0.05). Morphine stimulation of the diabetic endothelium resulted in a lower peak and shorter duration of NO release compared to the non-diabetic tissue, (21+/-6) nmol/L vs (38+/-4) nmol/L and (7.3+/-1.4) min vs (12.2+/-2.2) min, respectively (P<0.01). Lastly, evaluation of the mu opiate receptor expression was found to be diminished in the diabetics by 59.1 %.

CONCLUSION

Maturity-onset diabetes attenuates both the constitutive basal and morphine stimulated NO release from human saphenous vein endothelium. In this study, after NOS inhibition, the actual basal NO release in diabetes was negligible. One explanation for the impaired capacity of diabetic endothelium to release NO was the diminished mu opiate receptor that was seen in diabetic endothelium.

The endocannabinoid system in invertebrates

What is the role of the cannabinoid system in invertebrates and can it tell us something about the human system? We discuss in this review the possible presence of the cannabinoid system in invertebrates. Endocannabinoid processes, i.e., enzymatic hydrolysis, as well as cannabinoid receptors and endocannabinoids, have been identified in various species of invertebrates. These signal molecules appear to have multiple roles in invertebrates; diminishing sensory input, control of reproduction, feeding behavior, neurotransmission and antiinflammatory actions. We propose that since this system worked so well, it was retained during evolution, and that invertebrates can serve as a model to study endogenous cannabinoid signaling.

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.

Morphine inhibits indolactam V-induced U937 cell adhesion and gelatinase secretion

We demonstrate that indolactam V, a non-phorbol protein kinase C activator, promotes U937 cell attachment to fibronectin, type IV collagen and laminin. In the absence of indolactam V, 2-4% of U937 cells attach to all test substrates, however, in the presence of 100 nM indolactam V, 25, 16 and 11% of U937 cells attach to fibronectin, type IV collagen and laminin, respectively. When added concomitantly, 90 microM H-7, a protein kinase C inhibitor, reduces indolactam V-induced U937 cell adhesion to fibronectin by 91%. Monoclonal antibodies directed against both the beta1 and alpha 5 integrin subunits inhibit indolactam V-induced U937 cell adhesion to fibronectin by 62 and 52%, respectively. Indolactam V also promotes homotypic aggregation in U937 cells, which is blocked with either anti-ICAM or anti-LFA-1 antibodies. In addition, indolactam V promotes U937 cell secretion of a 92 kDa gelatinase as demonstrated by zymography. In the presence of low levels of morphine (10 nM-1.0 microM), the U937 cell attachment to matrix proteins was not significantly affected. However, in the presence of 10 microM morphine, the indolactam V treated cells exhibit a 71-74% reduction in cell adhesion to the matrix proteins. Further, 10 microM morphine also blocks indolactam V-induced homotypic aggregation and gelatinase secretion. The inhibitory effect of morphine on cell-matrix adhesion and gelatinase secretion was not inhibited by the opiate receptor antagonist naloxone (1 microM). While 10 microM naloxone did partially counteract the effect of 10 microM morphine on U937 cell attachment, this effect was likely non-specific since 10 microM naloxone alone increased cell adhesion. Supporting this conclusion, PCR analysis revealed that U937 cells do not express the mu high affinity morphine receptor. Also, indolactam V did not induce mu receptor expression, suggesting that morphine acts on U937 cells in a non-specific fashion.

Real-time RT-PCR measurement of the modulation of Mu opiate receptor expression by nitric oxide in human mononuclear cells

BACKGROUND

In previous studies, we have attributed opiate alkaloid selectivity to a subtype of the neuronal mu receptor known as mu3, expressed on human blood cells. Opiate alkaloid activation of this receptor subtype leads to the release of constitutively derived nitric oxide. In this report, we show by real-time RT-PCR that the NO donor S-nitroso-N-acetyl-penicillamine (SNAP) initiates the down regulation of mu receptor gene expression in human mononuclear cells after 30 minutes. Superoxide dismutase, a free radical scavenger, blocks the effect of SNAP.

MATERIAL AND METHODS

Human mononuclear cells isolated from whole blood were treated with SNAP (100 microM), and also with SNAP plus superoxide dismutase (100 U/ml) at different time points. Real-time RT-PCR with total RNA extracted from the cells was used to analyze expression of the mu opiate receptor.

RESULTS

Mu opiate receptor gene expression was significantly down regulated in cells treated with SNAP at 30 min, and superoxide dismutase blocked the effect of SNAP. At 2 and 6 hours, a rebound effect was observed as noted by an increase in mu receptor expression, and at 24 hours mu receptor expression returned to control levels in the SNAP-treated cells.

CONCLUSIONS

This study confirms that human mononuclear cells express the mu opiate receptor transcript and demonstrates that nitric oxide is involved in regulation of its expression.

Ischemic preconditioning - an opiate constitutive nitric oxide molecular hypothesis

Coronary artery disease is the number one cause of adult mortality due to a medical illness in the United States. Exciting new studies are looking at the role transient ischemia may play in preconditioning the myocardium to reduce the degree of infarction following a sustained ischemic insult. In this speculative review, we surmise ischemic preconditioning and the resulting protection afforded by it in response to abnormal insults arises from an already existing physiological process that may be associated with exercise. A brief ischemic episode mimics the cells response to normal dips in ATP levels caused by metabolic demand. In so doing, via constitutive nitric oxide synthase derived nitric oxide, it temporarily down regulates a cells excitatory state, thus protecting it from the next insult. Within this context, opiate and opioid actions can be incorporated into the protection scenario, as can other signal molecules since they may release nitric oxide. Instead of ischemia inducing nitric oxide release via a drop of ATP levels, various signal molecules, such as opiate alkaloids, have their cell surface receptors coupled to constitutive nitric oxide synthase thereby releasing nitric oxide, initiating associated cell activity dampening action. In conclusion, it appears as though endogenous nitric oxide stimulators offer their selective preconditioning protection by joining an already existing process that limits activation following normal physical exertion.