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

Mobility Coupled with Motivation Promotes Survival: The Evolution of Cognition as an Adaptive Strategy

Morphine plays a critical regulatory role in both simple and complex plant species. Dopamine is a critical chemical intermediate in the morphine biosynthetic pathway and may have served as a primordial agonist in developing catecholamine signaling pathways. While dopamine remains the preeminent catecholamine in invertebrate neural systems, epinephrine is the major product of catecholamine synthetic pathways in vertebrate species. Given that the enzymatic steps leading to the generation of morphine are similar to those constraining the evolutionary adaptation of the biosynthesis of catecholamines, we hypothesize that the emergence of these more advanced signaling pathways was based on conservation and selective "retrofitting" of pre-existing enzyme activities. This is consistent with observations that support the recruitment of enzymatically synthesized tetrahydrobiopterin (BH4), which is a cofactor for tyrosine hydroxylase, the enzyme responsible for dopamine production. BH4 is also an electron donor involved in the production of nitric oxide (NO). The links that coordinate BH4-mediated NO and catecholaminergic-mediated processes provide these systems with the capacity to regulate numerous downstream signaling pathways. We hypothesize that the evolution of catecholamine signaling pathways in animal species depends on the acquisition of a mobile lifestyle and motivationally driven feeding, sexual, and self-protective responses.

The Breast Cancer Protooncogenes HER2, BRCA1 and BRCA2 and Their Regulation by the iNOS/NOS2 Axis

The expression of inducible nitric oxide synthase (iNOS; NOS2) and derived NO in various cancers was reported to exert pro- and anti-tumorigenic effects depending on the levels of expression and the tumor types. In humans, the breast cancer level of iNOS was reported to be overexpressed, to exhibit pro-tumorigenic activities, and to be of prognostic significance. Likewise, the expression of the oncogenes HER2, BRCA1, and BRCA2 has been associated with malignancy. The interrelationship between the expression of these protooncogenes and oncogenes and the expression of iNOS is not clear. We have hypothesized that there exist cross-talk signaling pathways between the breast cancer protooncogenes, the iNOS axis, and iNOS-mediated NO mutations of these protooncogenes into oncogenes. We review the molecular regulation of the expression of the protooncogenes in breast cancer and their interrelationships with iNOS expression and activities. In addition, we discuss the roles of iNOS, HER2, BRCA1/2, and NO metabolism in the pathophysiology of cancer stem cells. Bioinformatic analyses have been performed and have found suggested molecular alterations responsible for breast cancer aggressiveness. These include the association of BRCA1/2 mutations and HER2 amplifications with the dysregulation of the NOS pathway. We propose that future studies should be undertaken to investigate the regulatory mechanisms underlying the expression of iNOS and various breast cancer oncogenes, with the aim of identifying new therapeutic targets for the treatment of breast cancers that are refractory to current treatments.

Arterial stiffness is associated with oxidative stress and endothelial activation among persons with treated HIV in Zambia

BACKGROUND

Cardiovascular disease (CVD) prevalence is rising among persons with HIV (PLWH) in sub-Saharan Africa. Oxidative stress and endothelial activation, resulting in reduced vascular compliance, are contributors to CVD risk. However, there is a paucity of vascular health data in this population.

OBJECTIVES

To assess the relationships of oxidative stress and endothelial activation with vascular stiffness among PLWH.

METHOD

Fifty-four PLWH on antiretroviral therapy > 5 years and 57 HIV-negative controls, all aged 18-45 years, were enrolled from the University Teaching Hospital, Lusaka, Zambia. Oxidative stress was measured by nitrotyrosine, a peroxynitrite biomarker, and endothelial activation by soluble intercellular adhesion molecule-1 (sICAM-1) plasma levels. Vascular compliance was measured using carotid-radial pulse wave velocity (crPWV) and arterial stiffness index (crASI).

RESULTS

PLWH had higher sICAM-1 levels (median 345 ng/mL) compared to controls (275 ng/mL, p < 0.01), as well as higher nitrotyrosine levels (297 versus 182 nM; p = 0.02). Median crPWV was similar between the groups, but PLWH had higher crASI (2.4 versus 2.2 cm/ms; p < 0.05). After adjusting for age, fat mass, and blood pressure, the estimated effect of a one unit increase in nitrotyrosine on crPWV were twofold higher in the PLWH, but neither reached significance. In a model pooling all participants, there were significant differences in the relationship of nitrotyrosine with crPWV and crASI by HIV status.

CONCLUSION

PLWH in sub-Saharan Africa had significantly greater oxidative stress and endothelial activation compared to HIV-negative individuals. These factors may contribute to increased arterial stiffness and higher CVD prevalence in this population.

Maternal morphine intake during pregnancy and lactation affects the circadian clock of rat pups

Early-life morphine exposure causes a variety of behavioural and physiological alterations observed later in life. In the present study, we investigated the effects of prenatal and early postnatal morphine on the maturation of the circadian clockwork in the suprachiasmatic nucleus and the liver, and the rhythm in aralkylamine N-acetyltransferase activity in the pineal gland. Our data suggest that the most affected animals were those born to control, untreated mothers and cross-fostered by morphine-exposed dams. These animals showed the highest mesor and amplitude in the rhythm of Per2, Nr1d1 but not Per1 gene expression in the suprachiasmatic nuclei (SCN) and arrhythmicity in AA-NAT activity in the pineal gland. In a similar pattern to the rhythm of Per2 expression in the SCN, they also expressed Per2 in a higher amplitude rhythm in the liver. Five of seven specific genes in the liver showed significant differences between groups in their expression. A comparison of mean relative mRNA levels suggests that this variability was caused mostly by cross-fostering, animals born to morphine-exposed dams that were cross-fostered by control mothers and vice versa differed from both groups of natural mothers raising offspring. Our data reveal that the circadian system responds to early-life morphine administration with significant changes in clock gene expression profiles both in the SCN and in the liver. The observed differences between the groups suggest that the dose, timing and accompanying stress events such as cross-fostering may play a role in the final magnitude of the physiological challenge that opioids bring to the developing circadian clock.

Editorial: The Pathogenesis of Long-Term Neuropsychiatric COVID-19 and the Role of Microglia, Mitochondria, and Persistent Neuroinflammation: A Hypothesis

Persistent comorbidities occur in patients who initially recover from acute coronavirus disease 2019 (COVID-19) due to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). ‘Long COVID’ involves the central nervous system (CNS), resulting in neuropsychiatric symptoms and signs, including cognitive impairment or ‘brain fog’ and chronic fatigue syndrome. There are similarities in these persistent complications between SARS-CoV-2 and the Ebola, Zika, and influenza A viruses. Normal CNS neuronal mitochondrial function requires high oxygen levels for oxidative phosphorylation and ATP production. Recent studies have shown that the SARS-CoV-2 virus can hijack mitochondrial function. Persistent changes in cognitive functioning have also been reported with other viral infections. SARS-CoV-2 infection may result in long-term effects on immune processes within the CNS by causing microglial dysfunction. This short opinion aims to discuss the hypothesis that the pathogenesis of long-term neuropsychiatric COVID-19 involves microglia, mitochondria, and persistent neuroinflammation.

Endothelial dysfunction and body mass index: is there a role for plasma peroxynitrite?

BACKGROUND

Endothelial function is dependent on the balance between vasoconstrictive and vasodilatory substances. The endothelium ability to produce nitric oxide is one of the most crucial mechanisms in regulating vascular tone. An increase in inducible nitric oxide synthase contributes to endothelial dysfunction in overweight persons, while in underweight persons, oxidative stress contributes to the conversion of nitric oxide to peroxynitrite (measured as nitrotyrosine in vivo). The objective of this study was to elucidate the interaction of body composition and oxidative stress on vascular function and peroxynitrite. This was done through an experimental design with three weight groups (underweight normal weight and overweight), with four treatment arms in each. Plasma nitrotyrosine levels were measured 15-20 hours post lipopolysaccharide (LPS) treatment, as were aortic ring tension changes. Acetylcholine (ACh) and sodium nitroprusside (SNP) challenges were used to observe endothelial dependent and independent vascular relaxation after pre-constriction of aortic rings with phenylephrine.

RESULTS

Nitrotyrosine levels in saline-treated rats were similar among the weight-groups. There was a significant increase in nitrotyrosine levels between saline-treated rats and those treated with the highest lipopolysaccharide doses in each of the weight groups. In response to ACh challenge, Rmax (percentage reduction in aortic tension) was lowest in overweight rats (112%). In response to SNP, there was an insignificantly lower Rmax in the underweight (106%) compared to the normal weight (112%). Overweight rats had a significant decrease in Rmax (83%) in response to SNP, signifying involvement of a more chronic process in tension reduction changes. A lower Rmax accompanied an increase in peroxynitrite after acetylcholine challenge in all weight-groups.

CONCLUSIONS

Endothelial dysfunction, observed as an impairment in the ability to reduce tension, is associated with increased plasma peroxynitrite levels across the spectrum of body mass. In higher-BMI rats, an additional role is played by vascular smooth muscle in the causation of endothelial dysfunction.

Dysregulation of Nitric Oxide Signaling in Microglia: Multiple Points of Functional Convergence in the Complex Pathophysiology of Alzheimer Disease

Current critical thinking has displaced the elaborated beta amyloid theory as the underlying unitary mechanism of Alzheimer disease (AD) in favor of concerted, long-term disruption or dysregulation of broad-based physiological processes. We present a critical discussion in which a chronic state of systemic proinflammation sustained over the course of several decades and engendered by ongoing metabolic or autoimmune disease is predicted to promote severe disruptions of central neurological processes. Specifically, long-term functional rundown of microglial-mediated phagocytic activity in concert with aberrant expression and cellular deposition of beta amyloid and tau protein facilitates formation of senile plaques and neurofibrillary tangles. Within this functional context, we hypothesize that early initiation events in the pathophysiology of AD may operationally involve a convergence of dysregulated peripheral and central constitutive nitric oxide signaling pathways resulting from a chronic state of systemic proinflammation and leading to severely dysfunctional “hyperactivated” microglia.

Aripiprazole prevents from development of vincristine-induced neuropathic nociception by limiting neural NOS overexpression and NF-kB hyperactivation

PURPOSE

Increased nitric oxide (NO) synthesis and NF-kB activation have been shown as critical players in the pathophysiology of vincristine-induced peripheral neuropathy. Consistently, neural nitric oxide synthase (nNOS) inhibitors alleviated the neuropathic pain. Previous studies demonstrated that aripiprazole is capable of modulating NO synthesis and also has been reported its modulatory effect on NF-kB activity.

METHODS

Aripiprazole was administered daily to the male Wistar rats at the same time with establishing neuropathic model by I.P. injection of vincristine every 2 days, over 2 weeks. Efficacy of aripiprazole in suppressing the development of neuropathy was evaluated by assessing changes in body weight, mechanical threshold, withdrawal latency, sciatic nerve conduction velocity (SNCV), and compound motor action potential (CMAP) characteristics. Expression of nNOS and NF-kB activation were evaluated by western blotting RESULTS: Rats receiving aripiprazole during neuropathy establishment period demonstrated a normal weight gain pattern, a significantly higher mechanical withdrawal threshold, and SNCV compared to vincristine-treated group. Furthermore, the amplitude and area of CMAP were significantly higher in aripiprazole group. Western blotting demonstrated a significantly reduced expression of nNOS and NF-kB activation in dorsal root ganglia of aripiprazole co-treated rats.

CONCLUSION

In conclusion, aripiprazole effectively prevents from vincristine-induced neuropathy by limiting nNOS overexpression and NF-kB hyperactivation.

Potential Immunoregulatory and Antiviral/SARS-CoV-2 Activities of Nitric Oxide

Nitric oxide (NO) represents a key signaling molecule in multiple regulatory pathways underlying vascular, metabolic, immune, and neurological function across animal phyla. Our brief critical discussion is focused on the multiple roles of the NO signaling pathways in the maintenance of basal physiological states of readiness in diverse cell types mediating innate immunological functions and in the facilitation of proinflammatory-mediated adaptive immunological responses associated with viral infections. Prior studies have reinforced the critical importance of constitutive NO signaling pathways in the homeostatic maintenance of the vascular endothelium, and state-dependent changes in innate immunological responses have been associated with a functional override of NO-mediated inhibitory tone. Accordingly, convergent lines of evidence suggest that dysregulation of NO signaling pathways, as well as canonical oxidative effects of inducible NO, may provide a permissive cellular environment for viral entry and replication. In immunologically compromised individuals, functional override and chronic rundown of inhibitory NO signaling systems promote aberrant expression of unregulated proinflammatory pathways resulting in widespread metabolic insufficiencies and structural damage to autonomous cellular and organ structures. We contend that restoration of normative NO tone via combined pharmaceutical, dietary, or complex behavioral interventions may partially reverse deleterious physiological conditions brought about by viral infection linked to unregulated adaptive immune responses.

Chromosomal Processes in Mind-Body Medicine: Chronic Stress, Cell Aging, and Telomere Length

Stress affects cellular aging and inflammatory and chromosomal processes, including telomere length, thereby potentially compromising health and facilitating disease onset and progression. Stress-related diseases and strategies to manage stress usually require integrative or behavioral therapeutic approaches that also operate on cellular levels. Mind-body medicine (MBM) uses the interaction between the mind, body, behavior, and the environment to correct physical and psychological malfunctions, thus ameliorating disease states and improving health. The relaxation response (RR) is a physiological opponent of stress and the stress response (SR) (i.e., fight-or-flight response), also invoking molecular anti-stress processes. Techniques that elicit the RR are at the core of practically all MBM interventions. We surmise that these techniques can also affect chromosomal and telomere processes, molecular aging, and the modulation of inflammatory states on cellular levels.

Alkaloids, Nitric Oxide, and Nitrite Reductases: Evolutionary Coupling as Key Regulators of Cellular Bioenergetics with Special Relevance to the Human Microbiome

Typical alkaloids expressed by prokaryotic and eukaryotic cells are small heterocyclic compounds containing weakly basic nitrogen groups that are critically important for mediating essential biological activities. The prototype opiate alkaloid morphine represents a low molecular mass heterocyclic compound that has been evolutionarily fashioned from a relatively restricted role as a secreted antimicrobial phytoalexin into a broad spectrum regulatory molecule. As an essential corollary, positive evolutionary pressure has driven the development of a cognate 6-transmembrane helical (TMH) domain μ3 opiate receptor that is exclusively responsive to morphine and related opiate alkaloids. A key aspect of “morphinergic” signaling mediated by μ3 opiate receptor activation is its functional coupling with regulatory pathways utilizing constitutive nitric oxide (NO) as a signaling molecule. Importantly, tonic and phasic intra-mitochondrial NO production exerts profound inhibitory effects on the rate of electron transport, H+ pumping, and O2 consumption. Given the pluripotent role of NO as a selective, temporally-defined chemical regulator of mitochondrial respiration and cellular bioenergetics, the expansion of prokaryotic denitrification systems into mitochondrial NO/nitrite cycling complexes represents a series of evolutionary modifications of existential proportions. Presently, our short review provides selective discussion of evolutionary development of morphine, opiate alkaloids, μ3 opiate receptors, and NO systems, within the perspectives of enhanced mitochondrial function, cellular bioenergetics, and the human microbiome.

Nitric oxide pathway presumably does not contribute to antianxiety and memory retrieval effects of losartan

Nitric oxide (NO) and angiotensin (AT) receptors have demonstrated well-established interactions in various physiological phenomena. AT1 receptors can play a part in stress-induced activation of the hypothalamic-pituitary-adrenal axis; also, angiotensinergic neurotransmission plays a pivotal role in stress-evoked physiological responses. On the basis of the stress-modulating characteristics of NO, AT1, and AT2 receptors, the present study evaluated the roles of NO and AT1 receptors in the attenuation of stress-induced anxiety-like behaviors after administration of losartan, an AT1 antagonist. Male Wistar rats were exposed to the communication stress box, using a novel method to induce physical or emotional stress, and losartan (10 mg/kg), losartan+L-NG-nitroargininemethyl ester (L-NAME), L-NAME (1, 10, and 100 mg/kg), and normal saline-treated groups were compared. Losartan had reduced behavioral changes induced by both types of stressor and enhanced memory retrieval. Anxiety-like behaviors were significantly attenuated by administration of losartan, to a greater extent in the emotional rather than physical stress group. None of the injected dosages of L-NAME reversed the antianxiety and memory retrieval effects of losartan. Our results indicate that losartan probably improves memory retrieval and lessens anxiety-like behaviors through mechanisms other than the NO pathway.

AIE-active conjugated polymer nanoparticles with red-emission for in vitro and in vivo imaging

Novel AIE-active conjugated polymer nanoparticles with bright fluorescence emission and excellent photostability have been prepared for imaging in cells and zebrafish.

Morphine stimulates nitric oxide release in human mitochondria

The expression of morphine by plants, invertebrate, and vertebrate cells and organ systems, strongly indicates a high level of evolutionary conservation of morphine and related morphinan alkaloids as required for life. The prototype catecholamine, dopamine, serves as an essential chemical intermediate in morphine biosynthesis, both in plants and animals. We surmise that, before the emergence of specialized plant and animal cells/organ systems, primordial multi-potential cell types required selective mechanisms to limit their responsiveness to environmental cues. Accordingly, cellular systems that emerged with the potential for recruitment of the free radical gas nitric oxide (NO) as a multi-faceted autocrine/paracrine signaling molecule, were provided with extremely positive evolutionary advantages. Endogenous morphinergic signaling, in concert with NO-coupled signaling systems, has evolved as an autocrine/paracrine regulator of metabolic homeostasis, energy metabolism, mitochondrial respiration and energy production. Basic physiological processes involving morphinergic/NO-coupled regulation of mitochondrial function, with special emphasis on the cardiovascular system, are critical to all organismic survival. Key to this concept may be the phenomenon of mitochondrial enslavement in eukaryotic evolution via endogenous morphine.

Role of nitric oxide in the radiation-induced bystander effect

Cells that are not irradiated but are affected by “stress signal factors” released from irradiated cells are called bystander cells. These cells, as well as directly irradiated ones, express DNA damage-related proteins and display excess DNA damage, chromosome aberrations, mutations, and malignant transformation. This phenomenon has been studied widely in the past 20 years, since its first description by Nagasawa and Little in 1992, and is known as the radiation-induced bystander effect (RIBE). Several factors have been identified as playing a role in the bystander response. This review will focus on one of them, nitric oxide (NO), and its role in the stimulation and propagation of RIBE. The hydrophobic properties of NO, which permit its diffusion through the cytoplasm and plasma membranes, allow this signaling molecule to easily spread from irradiated cells to bystander cells without the involvement of gap junction intercellular communication. NO produced in irradiated tissues mediates cellular regulation through posttranslational modification of a number of regulatory proteins. The best studied of these modifications are S-nitrosylation (reversible oxidation of cysteine) and tyrosine nitration. These modifications can up- or down-regulate the functions of many proteins modulating different NO-dependent effects. These NO-dependent effects include the stimulation of genomic instability (GI) and the accumulation of DNA errors in bystander cells without direct DNA damage.

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Ionizing radiation stimulates generation of nitric oxide (NO).

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NO stimulates genomic instability by inhibiting BRCA1 protein expression.

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NO can diffuse and stimulate genomic instability in the bystander cells.

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Propagation of NO from cell-to-cell creates a “mutator fields”.

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Definition of the “mutator filed” is proposed.

Hypoxia defined as a common culprit/initiation factor in mitochondrial-mediated proinflammatory processes

In mammals and invertebrates, the activities of neuro- and immuno-competent cells, e.g., glia, which are present in nervous tissues, are deemed of critical importance to normative neuronal function. The responsiveness of invertebrate and vertebrate immuno-competent glia to a common set of signal molecules, such as nitric oxide and endogenous morphine, is functionally linked to physiologically driven innate immunological and neuronal activities. Importantly, the presence of a common, evolutionarily conserved, set of signal molecules in comparative animal groups strongly suggests an expansive intermediate metabolic profile dependent on high output mitochondrial ATP production and utilization. Normative bidirectional neural-immune communication across invertebrate and vertebrate species requires common anatomical and biochemical substrates and pathways involved in energy production and mitochondrial integrity. Within this closed-loop system, abnormal perturbation of the respective tissue functions will have profound ramifications in functionally altering associated nervous and vascular systems and it is highly likely that the initial trigger to the induction of a physiologically debilitating pro-inflammatory state is a micro-environmental hypoxic event. This is surmised by the need for an unwavering constant oxygen supply. In this case, temporal perturbations of normative oxygen tension may be tolerated for short, but not extended, periods and ischemic/hypoxic perturbations in oxygen delivery represent significant physiological challenges to overall cellular and multiple organ system viability. Hence, hypoxic triggering of multiple pro-inflammatory events, if not corrected, will promote pathophysiological amplification leading to a deleterious cascade of bio-senescent cellular and molecular signaling pathways, which converge to markedly impair mitochondrial energy utilization and ATP production.

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.

Identification of chicken eNOS gene and differential expression in highland versus lowland chicken breeds

Nitric oxide (NO), an endothelium-derived relaxing factor, is synthesized from l-arginine by endothelial nitric oxide synthase (eNOS) in the endothelium. The objective of the present study was to preliminarily illuminate the expression of the eNOS gene in hypoxic adaptation of chicken embryonic development. The eNOS expression profiles between the Tibet and Shouguang chickens incubated under both normoxic and hypoxic conditions were detected by TaqMan real-time PCR. In this study, the chicken eNOS gene was found by both in silico cloning and RACE approaches. From the eNOS gene, we obtained a 3,310-bp mRNA sequence and a 10,666-bp DNA sequence and discovered that it was located on chicken chromosome 2 and had 7 unique transcripts. eNOS mRNA was detected in abundant amounts in some chick embryo organs (i.e., heart, liver, chorio-allantoic membrane, and lung), and expressed stably with the lowest levels in the brain. We observed that when exposed to hypoxia (13% O(2)) different embryo organ tissues had various sensitivities to hypoxia as determined by their eNOS expression profiles. Compared with the Shouguang chicken, the eNOS expression in the Tibet chicken was higher in the lung and liver, lower in the heart, and similar in the brain. In chorio-allantoic membranes, eNOS expression was higher in the Shouguang chicken than the Tibet chicken under hypoxic conditions, but not markedly different under normoxic conditions. The differences of eNOS expression between the 2 breeds may be relative to the hypoxic adaptation ability in Tibet chickens during embryonic development. This work will provide reference for future studies on the role of eNOS in hypoxic adaptation and response.

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.

Opioid receptor subtypes: fact or artifact?

There is a vast amount of pharmacological evidence favouring the existence of multiple subtypes of opioid receptors. In addition to the primary classification of µ (mu: MOP), δ (delta: DOP), κ (kappa: KOP) receptors, and the nociceptin/orphanin FQ peptide receptor (NOP), various groups have further classified the pharmacological µ into µ(1-3), the δ into δ(1-2)/δ(complexed/non-complexed), and the κ into κ(1-3). From an anaesthetic perspective, the suggestions that µ(1) produced analgesia and µ(2) produced respiratory depression are particularly important. However, subsequent to the formal identification of the primary opioid receptors (MOP/DOP/KOP/NOP) by cloning and the use of this information to produce knockout animals, evidence for these additional subtypes is lacking. Indeed, knockout of a single gene (and hence receptor) results in a loss of all function associated with that receptor. In the case of MOP knockout, analgesia and respiratory depression is lost. This suggests that further sub-classification of the primary types is unwise. So how can the wealth of pharmacological data be reconciled with new molecular information? In addition to some simple misclassification (κ(3) is probably NOP), there are several possibilities which include: (i) alternate splicing of a common gene product, (ii) receptor dimerization, (iii) interaction of a common gene product with other receptors/signalling molecules, or (iv) a combination of (i)-(iii). Assigning variations in ligand activity (pharmacological subtypes) to one or more of these molecular suggestions represents an interesting challenge for future opioid research.

Morphine sensitization in the pentylenetetrazole-induced clonic seizure threshold in mice: role of nitric oxide and μ receptors

Behavioral sensitization occurs after repeated administration of μ-opioid receptor agonists following a drug-free period. It seems that the changes in dopaminergic systems induced by μ-opioid receptor agonists play a crucial role in behavioral sensitization to opioids. Nitric oxide also plays a role in some behavioral effects of morphine, including sensitization to the locomotor-stimulating effect. This study investigated whether morphine sensitization appears in seizure threshold and the possible role of μ-opioid receptor and nitric oxide in this sensitization. Sensitization was produced by daily injections of morphine (0.1, 0.5, 1, 5, 15, or 30 mg/kg), followed by a 10-day washout period. Then the challenge test was performed using morphine (0.1, 0.5, 1, 5, 15, or 30 mg/kg) in different groups. To assess clonic seizure threshold, pentylenetetrazole (PTZ) was administered intravenously. Subcutaneous administration of morphine (0.1 and 0.5 mg/kg) induced sensitization in PTZ-induced clonic seizures in mice. Intraperitoneal administration of L-NAME (20 mg/kg), a nonselective inhibitor of nitric oxide synthase, or naltrexone (10 mg/kg), an opioid receptor antagonist, along with morphine inhibited morphine-induced sensitization in PTZ-induced seizure threshold. In conclusion, at low doses, morphine induces sensitization in PTZ-induced clonic seizures in mice probably as a result of the interaction with μ-receptors and nitric oxide.

Mutagenicity of PFOA in mammalian cells: role of mitochondria-dependent reactive oxygen species

Mutagenicity is often a prerequisite to the development of malignancy. Evidences have shown that exposure to perfluorooctanoic acid (PFOA) results in various cancer inductions. However, whether any mutagenic base exists is still puzzling. In the present study, we exposed exponentially growing AL cells to PFOA and assayed the cells for survival, mutation induction, and caspase-3/7, -9 activities. Mitochondrial-DNA deficient human-hamster hybrid (ρ(0) AL) cells and reactive oxygen species (ROS) inhibitor were used to elucidate the possible mechanism. Our results showed that treatment of AL cells with PFOA for 16 days induced significant mutagenic effects together with the increment of ROS, superoxide anions (O2(.-)), and nitrogen oxide (NO) levels, while treatment of ρ(0) AL cells did not have much change. Concurrent treatment of AL cells with ROS inhibitor significantly decreased the mutagenic potential of PFOA. In addition, caspase activities in AL cells were increased by PFOA exposure and suppressed by ROS/RNS (reactive oxygen/nitrogen species) inhibitors. Our results suggest that exposure to PFOA lead to mutagenicity induction in AL cells, and mitochondria-dependent ROS plays an important role in this process. This provides a direct base for PFOA mediated cancer induction.

Interactive effects of endogenous morphine, nitric oxide, and ethanol on mitochondrial processes

Positive evolutionary pressure has preserved the ability to synthesize chemically authentic morphine, albeit in homeopathic concentrations, throughout animal phyla. The prototype catecholamine dopamine (DA) serves as an essential chemical intermediate in morphine biosynthesis both in plants and animals, thereby providing considerable insight into the roles reciprocal "morphinergic" and catecholamine regulation of diverse physiological processes. Primordial, multi-potential cell types, before the emergence of specialized plant and animal cells/organ systems, required selective mechanisms to limit their responsiveness to environmental noise. Accordingly, cellular systems that emerged with the potential for recruitment of the free radical gas nitric oxide (NO) as a multi-faceted autocrine/paracrine signaling molecule were provided with extremely positive evolutionary advantages. Endogenous "morphinergic" in concert with NO-coupled signaling systems have evolved as autocrine/paracrine regulators of metabolic homeostasis, energy metabolism, mitochondrial respiration and energy production. Basic physiological processes involving "morphinergic"/NO-coupled regulation of cardiovascular mitochondrial function, with special emphasis on the interactive effects of ethanol, are discussed within the context of our review.

Nitric oxide mediated DNA double strand breaks induced in proliferating bystander cells after alpha-particle irradiation

Low-dose alpha-particle exposures comprise 55% of the environmental dose to the human population and have been shown to induce bystander responses. Previous studies showed that bystander effect could induce stimulated cell growth or genotoxicity, such as excessive DNA double strand breaks (DSBs), micronuclei (MN), mutation and decreased cell viability, in the bystander cell population. In the present study, the stimulated cell growth, detected with flow cytometry (FCM), and the increased MN and DSB, detected with p53 binding protein 1 (53BP1) immunofluorescence, were observed simultaneously in the bystander cell population, which were co-cultured with cells irradiated by low-dose alpha-particles (1-10 cGy) in a mixed system. Further studies indicated that nitric oxide (NO) and transforming growth factor beta1 (TGF-beta1) played very important roles in mediating cell proliferation and inducing MN and DSB in the bystander population through treatments with NO scavenger and TGF-beta1 antibody. Low-concentrations of NO, generated by spermidine, were proved to induce cell proliferation, DSB and MN simultaneously. The proliferation or shortened cell cycle in bystander cells gave them insufficient time to repair DSBs. The increased cell division might increase the probability of carcinogenesis in bystander cells since cell proliferation increased the probability of mutation from the mis-repaired or un-repaired DSBs.

Dopamine, morphine, and nitric oxide: an evolutionary signaling triad

Morphine biosynthesis in relatively simple and complex integrated animal systems has been demonstrated. Key enzymes in the biosynthetic pathway have also been identified, that is, CYP2D6 and COMT. Endogenous morphine appears to exert highly selective actions via novel mu opiate receptor subtypes, that is, mu3,-4, which are coupled to constitutive nitric oxide release, exerting general yet specific down regulatory actions in various animal tissues. The pivotal role of dopamine as a chemical intermediate in the morphine biosynthetic pathway in plants establishes a functional basis for its expansion into an essential role as the progenitor catecholamine signaling molecule underlying neural and neuroendocrine transmission across diverse animal phyla. In invertebrate neural systems, dopamine serves as the preeminent catecholamine signaling molecule, with the emergence and limited utilization of norepinephrine in newly defined adaptational chemical circuits required by a rapidly expanding set of physiological demands, that is, motor and motivational networks. In vertebrates epinephrine, emerges as the major end of the catecholamine synthetic pathway consistent with a newly incorporated regulatory modification. Given the striking similarities between the enzymatic steps in the morphine biosynthetic pathway and those driving the evolutionary adaptation of catecholamine chemical species to accommodate an expansion of interactive but distinct signaling systems, it is our overall contention that the evolutionary emergence of catecholamine systems required conservation and selective "retrofit" of specific enzyme activities, that is, COMT, drawn from cellular morphine expression. Our compelling hypothesis promises to initiate the reexamination of clinical studies, adding new information and treatment modalities in biomedicine.

Biochemical and genomic analysis of the denitrification pathway within the genus Neisseria

Since Neisseria gonorrhoeae and Neisseria meningitidis are obligate human pathogens, a comparison with commensal species of the same genus could reveal differences important in pathogenesis. The recent completion of commensal Neisseria genome draft assemblies allowed us to perform a comparison of the genes involved in the catalysis, assembly and regulation of the denitrification pathway, which has been implicated in the virulence of several bacteria. All species contained a highly conserved nitric oxide reductase (NorB) and a nitrite reductase (AniA or NirK) that was highly conserved in the catalytic but divergent in the N-terminal lipid modification and C-terminal glycosylation domains. Only Neisseria mucosa contained a nitrate reductase (Nar), and only Neisseria lactamica, Neisseria cinerea, Neisseria subflava, Neisseria flavescens and Neisseria sicca contained a nitrous oxide reductase (Nos) complex. The regulators of the denitrification genes, FNR, NarQP and NsrR, were highly conserved, except for the GAF domain of NarQ. Biochemical examination of laboratory strains revealed that all of the neisserial species tested except N. mucosa had a two- to fourfold lower nitrite reductase activity than N. gonorrhoeae, while N. meningitidis and most of the commensal Neisseria species had a two- to fourfold higher nitric oxide (NO) reductase activity. For N. meningitidis and most of the commensal Neisseria, there was a greater than fourfold reduction in the NO steady-state level in the presence of nitrite as compared with N. gonorrhoeae. All of the species tested generated an NO steady-state level in the presence of an NO donor that was similar to that of N. gonorrhoeae. The greatest difference between the Neisseria species was the lack of a functional Nos system in the pathogenic species N. gonorrhoeae and N. meningitidis.

Transcriptional profiling identifies the metabolic phenotype of gonococcal biofilms

Neisseria gonorrhoeae, the etiologic agent of gonorrhea, is frequently asymptomatic in women, often leading to chronic infections. One factor contributing to this may be biofilm formation. N. gonorrhoeae can form biofilms on glass and plastic surfaces. There is also evidence that biofilm formation may occur during natural cervical infection. To further study the mechanism of gonococcal biofilm formation, we compared transcriptional profiles of N. gonorrhoeae biofilms to planktonic profiles. Biofilm RNA was extracted from N. gonorrhoeae 1291 grown for 48 h in continuous-flow chambers over glass. Planktonic RNA was extracted from the biofilm runoff. In comparing biofilm with planktonic growth, 3.8% of the genome was differentially regulated. Genes that were highly upregulated in biofilms included aniA, norB, and ccp. These genes encode enzymes that are central to anaerobic respiratory metabolism and stress tolerance. Downregulated genes included members of the nuo gene cluster, which encodes the proton-translocating NADH dehydrogenase. Furthermore, it was observed that aniA, ccp, and norB insertional mutants were attenuated for biofilm formation on glass and transformed human cervical epithelial cells. These data suggest that biofilm formation by the gonococcus may represent a response that is linked to the control of nitric oxide steady-state levels during infection of cervical epithelial cells.

Functional analysis of NsrR, a nitric oxide-sensing Rrf2 repressor in Neisseria gonorrhoeae

Nitric oxide (NO) has been shown to be an important component of the human immune response, and as such, it is important to understand how pathogenic organisms respond to its presence. In Neisseria gonorrhoeae, recent work has revealed that NsrR, an Rrf2-type transcriptional repressor, can sense NO and control the expression of genes responsible for NO metabolism. A highly pure extract of epitope-tagged NsrR was isolated and mass spectroscopic analysis suggested that the protein contained a [2Fe-2S] cluster. NsrR/DNA interactions were thoroughly analysed in vitro. Using EMSA analysis, NsrR::FLAG was shown to interact with predicted operators in the norB, aniA and nsrR upstream regions with a K(d) of 7, 19 and 35 nM respectively. DNase I footprint analysis was performed on the upstream regions of norB and nsrR, where NsrR was shown to protect the predicted 29 bp binding sites. The presence of exogenously added NO inhibited DNA binding by NsrR. Alanine substitution of C90, C97 or C103 in NsrR abrogated repression of norB::lacZ and inhibited DNA binding, consistent with their presumed role in co-ordination of a NO-sensitive Fe-S centre required for DNA binding.

Differences in nitric oxide steady states between arginine, hypoxanthine, uracil auxotrophs (AHU) and non-AHU strains of Neisseria gonorrhoeae during anaerobic respiration in the presence of nitrite

Neisseria gonorrhoeae can grow by anaerobic respiration using nitrite as an alternative electron acceptor. Under these growth conditions, N. gonorrhoeae produces and degrades nitric oxide (NO), an important host defense molecule. Laboratory strain F62 has been shown to establish and maintain a NO steady-state level that is a function of the nitrite reductase/NO reductase ratio and is independent of cell number. The nitrite reductase activities (122-197 nmol NO2 reduced x min(-1) x OD600(-1)) and NO reductase activities (88-155 nmol NO reduced x min(-1) x OD600(-1)) in a variety of gonococcal clinical isolates were similar to the specific activities seen in F62 (241 nmol NO2 reduced x min(-1) x OD600(-1) and 88 nmol NO reduced x min(-1) x OD600(-1), respectively). In seven gonococcal strains, the NO steady-state levels established in the presence of nitrite were similar to that of F62 (801-2121 nmol x L-1 NO), while six of the strains, identified as arginine, hypoxanthine, and uracil auxotrophs (AHU), that cause asymptomatic infection in men had either two- to threefold (373-579 nmol x L-1 NO) or about 100-fold (13-24 nmol x L-1 NO) lower NO steady-state concentrations. All tested strains in the presence of a NO donor, 2,2'-(hydroxynitrosohydrazono)bis-ethanimine/NO, quickly lowered and maintained NO levels in the noninflammatory range of NO (<300 nmol x L-1). The generation of a NO steady-state concentration was directly affected by alterations in respiratory control in both F62 and an AHU strain, although differences in membrane function are suspected to be responsible for NO steady-state level differences in AHU strains.

Variants of neural nitric oxide synthase in the spinal cord of neuropathic rats and their effects on nuclear factor-kappaB (NF-kappaB) activity in PC12 cells

Neuropathic pain due to nerve injury is associated with overactivity of spinal N-methyl-D-aspartate (NMDA) receptors and nitric oxide synthases (NOS). Spinal NOS and NMDA receptors could act in a concerted manner to excite each other in nociceptive signaling. Among the 3 major NOS isoforms, neuronal NOS (nNOS) has the most functional relationship with NMDA receptors through a PDZ-PDZ (PSD-95, Dlg, ZO-1 homology) postsynapse interaction. However, some nNOS variants lack the PDZ domain, which may result in the changes in the interaction with the NMDA receptor and subsequent localization and enzymatic activity. The aim of this study was to determine which nNOS variants are expressed in the spinal cord in neuropathic rats and deduce their role in neuropathic pain by testing the effects of these kinds of nNOS on nuclear factor-kappaB (NF-kappaB) activity in PC12 cells. Western blot analysis revealed that there were at least 3 bands of nNOS (155, 135, and 125 kDa) in the spinal cord and, moreover, that nNOS at 135 kDa decreased significantly after development of neuropathic pain. 5'-RACE-PCR and Southern blots determined that the nNOS at 155 and 135 kDa corresponded to nNOSalpha and nNOSbeta, respectively, which was confirmed by RT-PCR. PC12 cells transfected with the nNOSalpha gene had no effect on NF-kappaB activity, but nNOSbeta without the PDZ domain significantly decreased that in PC12 cells. Considering the importance of spinal NF-kappaB signaling in neuropathic rat, it could be concluded that changes in spinal nNOS variants and quantity after peripheral nerve injury implicate nNOS in the generation of neuropathic pain.

PERSPECTIVE

This article presents data demonstrating that nNOS variants change in the spinal cord of the rats after neuropathic pain and result in differential effects on NF-kappaB activity in PC12 cells. These changes in nNOS variants and their different characteristics may account for the spinal NO paradox role in neuropathic pain. Furthermore, these data suggest that nNOSbeta may represent a new therapeutic target for the treatment of chronic neuropathic pain.

The use of osteopathic manipulative treatment as adjuvant therapy in patients with peripheral arterial disease

Peripheral arterial disease (PAD) is a manifestation of systemic atherosclerosis associated with impaired endothelial function and intermittent claudication is the hallmark symptom. Hypothesizing that osteopathic manipulative treatment (OMT) may represent a non-pharmacological therapeutic option in PAD, we examined endothelial function and lifestyle modifications in 15 intermittent claudication patients receiving osteopathic treatment (OMT group) and 15 intermittent claudication patients matched for age, sex and medical treatment (control group). Compared to the control group, the OMT group had a significant increase in brachial flow-mediated vasodilation, ankle/brachial pressure index, treadmill testing and physical health component of life quality (all p<0.05) from the beginning to the end of the study. At univariate analysis in the OMT group there was a negative correlation between changes in brachial flow-mediated vasodilation and IL-6 levels (r=-0.30; p=0.04) and a positive one between claudication pain time and physical function score (r=0.50; p=0.05). In conclusion, despite the relatively few patients in our study, these results suggest that OMT significantly improves endothelial function and functional performance in intermittent claudication patients along with benefits in quality of life. This novel treatment combined with drug and lifestyle modification might be an effective alternative to traditional training based on exercise.

Nitrergic response to cyclophosphamide treatment in blood and bone marrow

Daily intraperitoneal injection of cyclophosphamide (CPA) (50 mgkg(-1) of body weight) for 5 days resulted in reduced levels of marrow and blood cellularity, which was most pronounced in 18 days post-treatment (pt). On day 18 after CPA treatment the enhancedlevels of nitric oxide (NO) precursors and metabolites (L-arginine, L-citrulline, reactive nitrogen species (RNS)) of marrow and blood cells (platelet, neutrophil, lymphocyte and monocyte) resulted from up-regulation of Ca(II)/calmodulin(CaM)-independent "inducible" NO synthase (iNOS), with a lessercontribution of Ca(II)/CaM-dependent "constitutive" cNOS isoforms to systemic NO.Biphasic response to CPA of marrow nitrergic system, i.e. both iNOS and cNOS showed significantly depressed activities, as well as diminished levels of NO metabolites on day 9 pt, suggested that signals in addition to NO might be involved in CPA-induced inhibition of hematopoesis, while a gradual increase of neutrophil and platelet NOS activity appeared to be contributed to a CPA-induced development of granulopenia, thrombocytopenia and hemorrhage.

cis- and trans-acting elements involved in regulation of norB (norZ), the gene encoding nitric oxide reductase in Neisseria gonorrhoeae

The ability of Neisseria gonorrhoeae to reduce nitric oxide (NO) may have important immunomodulatory effects on the host during infection. Therefore, a comprehensive understanding of the regulatory mechanism of the nitric oxide reductase gene (norB) needs to be elucidated. To accomplish this, we analysed the functional regions of the norB upstream region. The promoter contains an extended -10 motif (TGNTACAAT) that is required for high-level expression. Deletion and substitution analysis of the norB upstream region revealed that no sequence upstream of the -10 motif is involved in norB regulation under anaerobic conditions or in the presence of NO. However, replacement of a 29 bp inverted repeat sequence immediately downstream of the extended -10 motif gave high levels of aerobic expression of a norB : : lacZ fusion. Insertional inactivation of gonococcal nsrR, predicted to bind to this inverted repeat sequence, resulted in the loss of norB repression and eliminated NO induction capacity. Single-copy complementation of nsrR in trans restored regulation of both norB transcription and NorB activity by NO. In Escherichia coli, expression of a gonococcal nsrR gene repressed gonococcal norB; induction of norB occurred in the presence of exogenously added NO. NsrR also regulates aniA and dnrN, as well as its own expression. We also determined that Fur regulates norB by a novel indirect activation method, by preventing the binding of a gonococcal ArsR homologue, a second repressor whose putative binding site overlaps the Fur binding site.

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.

Is immunomodulation by opioid drugs of clinical relevance?

PURPOSE OF REVIEW

There has been a growing interest in elucidating the immune consequences of opioid administration for the management of pain. Several studies in vitro and in vivo have demonstrated an immunomodulating effect of opioids. The neuro-endocrine interactions observed after opioid application contribute to this effect as well as direct alterations of immune effector cells. Opioid-induced immunomodulation is mediated by opioid receptors found on immunocytes and in the central nervous system. This review will elucidate the molecular mechanisms of central and peripheral immunomodulation by opioids with special emphasis on the clinical significance of these findings.

RECENT FINDINGS

Recent research has focused on the cellular signaling cascades associated with opioid receptor activation. The crosstalk between chemokine and opioid receptors on leukocytes has opened new insights into the molecular mechanisms involved in opioid-induced immunomodulation. Heterologous desensitization and phosphorylation of chemokine receptors by opioids may not only mediate the immunosuppressive effects of opioids but may also modulate the perception of pain.

SUMMARY

Although immunomodulating effects of opioids are well established, a final statement regarding the clinical relevance cannot be made, since the existing clinical and experimental data are preliminary and inconclusive. Therefore, further clinical studies are mandatory to elucidate the influence of opioid treatment on immune regulation in different clinical settings. Further investigations may help to provide sufficient analgesia by application of opioids, as well as assessing the advantages and disadvantages on immune function.

Endomorphin 1 activates nitric oxide synthase 2 activity and downregulates nitric oxide synthase 2 mRNA expression

Endomorphins 1 and 2 are newly discovered opioid tetrapeptides whose structure is more resistant to enzymatic degradation than that of other opioid peptides. Endomorphins 1 and 2 are considered as endogenous ligands with a high affinity for mu receptors. A number of studies have shown that opioid peptides per se can induce release of nitric oxide from rodent and human immune cells. Endomorphins seemed to be involved in the process of vasodilatation by stimulating release of nitric oxide. In our study we stimulated in vitro J774 macrophages with different concentrations of endomorphin 1 or 2 for measuring nitric oxide release and nitric oxide synthase 2 (NOS 2) mRNA expression. Results showed that 48 h incubation did not enhance nitric oxide release when measured with the Griess method. On the other hand, using real-time amperometric detection of nitric oxide release shortly after challenge with endomorphins, we showed that only 10(-6) M endomorphin 1 was able to stimulate nitric oxide release from a J774 macrophage cell line by activation of NOS 2 isoenzyme. The peak release was 1000-1500 s after stimulation and was in the range of nitric oxide release stimulated with 10 microg/ml lipopolysaccharide. In contrast to this, endomorphin 2 failed to induce nitric oxide release in all tested concentrations. Using a specific inhibitor of nitric oxide synthase 2 (N-(3-[aminomethyl]benzyl)acetamidine, 1400W) we eliminated the stimulatory effect of endomorphin 1 on nitric oxide release. The expression of mRNA for NOS 2 in J774 macrophages, after 30 min incubation with either lipopolysaccharide or 10(-6) M endomorphin 1 was not upregulated. As expected, lipopolysaccharide induced de novo NOS 2 transcription within 4 h. At the same time, in contrast to lipopolysaccharide, mRNA expression of cells treated with endomorphin 1 was downregulated. Since a mu-opioid receptor specific antagonist beta-funaltrexamine hydrochloride inhibited nitric oxide release from endomorphin 1-treated cells, the effect seemed to be mu-opioid receptor mediated.

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.

Constitutive nitric oxide acting as a possible intercellular signaling molecule in the initiation of radiation-induced DNA double strand breaks in non-irradiated bystander cells

The initiation and propagation of the early processes of bystander signaling induced by low-dose alpha-particle irradiation are very important for understanding the underlying mechanism of the bystander process. Our previous investigation showed that the medium collected from cell culture exposed to low-dose alpha-particle rapidly induced phosphorylated form of H2AX protein foci formation among the non-irradiated medium receptor cells in a time-dependent manner. Using N(G)-methyl-L-arginine, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate and N(omega)-nitro-L-arginine (L-NNA) treatment before exposure to 1 cGy alpha-particle, we showed in the present study that nitric oxide (NO(*)) produced in the irradiated cells was important and necessary for the DNA double strand break inducing activity (DIA) of conditioned medium and the generation of NO(*) in irradiated confluent AG1522 cells is in a time-dependent manner and that almost all NO(*) was generated within 15 min post-irradiation. Concurrently, the kinetics of NO(*) production in the medium of irradiated cells after irradiation was rapid and in a time-dependent manner as well, with a maximum yield observed at 10 min after irradiation with electron spin resonance analysis. Furthermore, our results that 7-Nitroindazole and L-NNA, but not aminoguanidine hemisulfate, treatment before exposure to 1 cGy alpha-particle significantly decrease the DIA of the conditioned medium suggested that constitutive NO(*) from the irradiated cells possibly acted as an intercellular signaling molecule to initiate and activate the early process (<or=30 min) of bystander response after low-dose irradiation.

Neuronal Nitric Oxide Synthase Immunopositivity in Motoneurons of the Rabbit's Spinal Cord After Transient Ischemia/Reperfusion Injury

1. Motoneurons in the spinal cord are especially vulnerable to ischemic injury and selectively destroyed after transient ischemia. To evaluate the role of nitric oxide (NO) in the pathophysiology of the spinal cord ischemia, the expression of neuronal nitric oxide synthase (nNOS) in the motoneurons of the lumbosacral spinal cord was examined in the rabbit model of transient abdominal aorta occlusion. 2. The aim of the present study was to find if there is any consensus between the duration of transient abdominal aorta occlusion, nNOS positivity of the motoneurons and neurological hind limb impairment. 3. According to the degree of neurological damage (i.e., from the group with almost no sign of damage to a group with fully developed paraplegia), the experimental animals were divided into three groups. The respective spinal cord segments of each experimental group were compared to the control group. 4. Spinal cord ischemia (15 min) was induced by Fogarty arterial embolectomy catheter occlusion of abdominal aorta with a reperfusion period of 7 days. On seventh day, the sections of lumbosacral segments were immunohistochemically treated and L1-L7, and S1-S2 segment sections were monitored using light microscopy.

Cross-talk between constitutive and inducible NO synthase: an update

Inducible nitric oxide synthase (iNOS) is expressed upon exposure of some cell types to bacterial lipopolysaccharides (LPS) and/or a variety of proinflammatory cytokines. The authors present an overview of some of the recent findings further supporting the notion that this response takes place after an early decline in constitutive nitric oxide (NO) levels (i.e., NO released by constitutive NOS, cNOS). This response is indeed critical for allowing activation of the transcription factor NF-kappaB. Thus, generation of NO by cNOS represents a limiting factor for iNOS expression. Some of the physiological and pathological implications of the cross-talk between these two NOS isoforms are discussed. In addition, the results of recent studies are summarized, suggesting possible mechanisms whereby LPS and/or proinflammatory cytokines may cause inhibition of cNOS.

Norlaudanosoline and Nicotine Increase Endogenous Ganglionic Morphine Levels: Nicotine Addiction

1. Given the presence of morphine, its metabolites and precursors, e.g., norlaudanosoline, in mammalian and invertebrate tissues, it became important to determine if exposing normal excised ganglia to norlaudanosoline would result in increasing endogenous morphine levels. 2. Mytilus edulis pedal ganglia contain 2.2 +/- 0.41 ng/g wet weight morphine as determined by high pressure liquid chromatography coupled to electrochemical detection and radioimmunoassay. 3. Incubation of M. edulis pedal ganglia with norlaudanosoline, a morphine precursor, resulted in a concentration- and time-dependent statistical increase in endogenous morphine levels (6.9 +/- 1.24 ng/g). 4. Injection of animals with nicotine also increased endogenous morphine levels in a manner that was antagonized by atropine, suggesting that nicotine addiction may be related to altering endogenous morphine levels in mammals. 5. We surmise that norlaudanosoline is being converted to morphine, demonstrating that invertebrate neural tissue can synthesize morphine.

Determinants of nitric oxide steady-state levels during anaerobic respiration by Neisseria gonorrhoeae

Nitric oxide (NO) is an important host defence molecule that varies its immune stimulatory effects depending on the concentrations at which it is produced, with low concentrations (< 1 microM) promoting an anti-inflammatory host response while higher concentrations (>1 microM) lead to inflammatory responses. Neisseria gonorrhoeae grows anaerobically by anaerobic respiration using nitrite reductase (Nir) to convert nitrite to NO and nitric oxide reductase (Nor) to convert NO to nitrous oxide. As N. gonorrhoeae can both produce and degrade NO, we have begun a study of NO metabolism in this bacterium to understand how gonococcal manipulation of NO concentration may influence the inflammatory response during infection. N. gonorrhoeae has an apparent Nir Km of 33 microM nitrite and an apparent Nor Km of 1.2 microM NO. The maximum specific activities for Nir and Nor were 135 nmoles nitrite reduced per minute per OD600 (pH 6.7) and 270 nmoles NO reduced per minute per OD600 (pH 7.5) respectively. N. gonorrhoeae established a steady-state concentration of NO after nitrite addition that was dependent on the nitrite concentration until saturation at 1 mM nitrite. The NO steady-state level decreased as pH increased, and the ratio of activities of Nir and Nor correlated to the NO steady-state level. When the NO donor DETA/NO was used to simulate host NO production, N. gonorrhoeae also established a NO steady-state level. The concentration of NO at steady state was found to be a function of the concentration of NO generated by DETA/NO, with N. gonorrhoeae reducing the NO from proinflammatory (>1 microM) to anti-inflammatory (approximately 100 nM) concentrations. The implications of the ability of N. gonorrhoeae to maintain an anti-inflammatory NO concentration is discussed in relation to asymptomatic infection in women.

The involvement of nitric oxide in the enhanced expression of mu-opioid receptors during intestinal inflammation in mice

Intestinal inflammation enhances the potency of mu-opioid receptor (MOR) agonists inhibiting gastrointestinal transit and increases the expression of MOR in mice intestine. The precise mechanisms implicated in the increased expression of MOR during intestinal inflammation are not known. The aim of the study is to evaluate if nitric oxide released during intestinal inflammation could modulate MOR gene expression and affect gastrointestinal transit. Intestinal inflammation was induced by the intragastric administration of croton oil. In CD-1 mice, with and without inflammation, we evaluated the anti-transit effects of morphine in animals treated with NOS inhibitors (L-NAME and L-NIL) and the intestinal levels of iNOS enzyme mRNA. The anti-transit effects of morphine and the expression of MOR mRNA in the gut of wild-type (WT) and iNOS-/- mice were also assessed. Gastrointestinal transit was measured with charcoal meal and mRNA levels determined by real-time PCR. In CD-1 mice, inflammation induced a 10-fold increase (P<0.0001) in iNOS mRNA levels in the gut. The absence of iNOS gene and treatment of CD-1 mice with L-NAME or L-NIL abolished the increased antitransit effects of morphine observed during inflammation. Moreover, although the basal levels of MOR mRNA were similar in WT and iNOS animals (-/-), intestinal inflammation only increased the MOR expression in the gut of WT (P<0.01) but not in iNOS-/- mice. The results suggest that nitric oxide derived from the increased expression of iNOS is implicated in the enhanced effects of morphine and in the upregulation of MOR gene transcription observed during intestinal inflammation.