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Biomedical subjects

G B Stefano

Publications and source records attributed to G B Stefano.

At least 73 records · Page 4Linked to original sources
PubMed1999

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

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

Animals↗
PubMed1999

IL-10 as a mediator in the HPA axis and brain.

Certain functional interactions between the nervous, endocrine, and immune systems are mediated by cytokines. The pro-inflammatory cytokines, interleukin-1 (IL-1) and tumor necrosis factor (TNF) were among the first to be recognized in this regard. A modulator of these cytokines, IL-10, has been shown to have a wide range of activities in the immune system; in this review, we describe its production and actions in the hypothalamic-pituitary-adrenal (HPA) axis. IL-10 is produced in pituitary, hypothalamic, and neural tissues in addition to lymphocytes. IL-10 enhances corticotropin releasing factor (CRF) and corticotropin (ACTH) production in hypothalamic and pituitary tissues, respectively. Further downstream in the HPA axis endogenous IL-10 has the potential to contribute to regulation of glucocorticosteroid production both tonically and following stressors. Our studies and those of others reviewed here indicate that IL-10 may be an important endogenous regulator in HPA axis activity and in CNS pathologies such as multiple sclerosis. Thus, in addition to its more widely recognized role in immunity, IL-10's neuroendocrine activities described here point to its role as an important regulator in communication between the immune and neuroendocrine systems.

Adrenocorticotropic Hormone↗
PubMed1999

Morphine coupling to invertebrate immunocyte nitric oxide release is dependent on intracellular calcium transients.

Morphine significantly stimulated invertebrate immunocyte intracellular calcium level increases in a concentration-dependent manner in cells preloaded with Fura 2/AM. Morphine's action was blocked by prior exposure of the cells to the opiate receptor antagonist naloxone. Various opioid peptides did not exhibit this ability, indicating a morphine-mu 3 mediated process. In comparing the sequence of events concerning morphine's action in stimulating both [Ca2+]i and NO production in these cells, we found that the first event precedes the second by 42 +/- 7 s. The opiate stimulation of [Ca2+]i- was attenuated in cells leached of calcium. strongly suggesting that intracellular calcium levels regulate cNOS activity in invertebrate immunocytes.

Animals↗
PubMed1999

Definitive evidence for the existence of morphological plasticity in the external zone of the median eminence during the rat estrous cycle: implication of neuro-glio-endothelial interactions in gonadotropin-releasing hormone release.

Despite intense investigation, the demonstration of morphological plasticity in the external zone of the median eminence concerning the gonadotropin-releasing hormone system has never been reported. In this study, we investigate whether dynamic transformations of the gonadotropin-releasing hormone nerve terminals and/or tanycytes in the external zone of the median eminence of the hypothalamus occurred during the rat estrous cycle, by following individual gonadotropin-releasing hormone-immunoreactive nerve terminals on serial ultrathin sections observed by electron microscopy. Female rats were killed at 16.00 diestrus II (n = 3), i.e. when estrogen levels are basal and gonadotropin-releasing hormone release is low, and at 16.00 proestrus (n = 4), i.e. when estrogen levels peak and the preovulatory gonadotropin-releasing hormone surge occurs. Our results show that, in the median eminence obtained from proestrus rats, 12+/-2% of the gonadotropin-releasing hormone nerve terminals were observed to make physical contact with the parenchymatous basal lamina, i.e. the pericapillary space. In the median eminence obtained from diestrus II rats, no contacts were observed. On proestrus, numerous physical contacts between gonadotropin-releasing hormone nerve terminals and the basal lamina occurred by evagination of the basal lamina and/or by emerging processes from gonadotropin-releasing hormone nerve terminals. The quantification of the evagination of the basal lamina revealed that the basal lamina was at least twofold more tortuous in appearance during proestrus. These results demonstrate for the first time the existence of dynamic plastic changes in the external zone of the median eminence, allowing gonadotropin-releasing hormone nerve terminals to contact the pericapillary space on the day of proestrus, thus facilitating the release of the neurohormone into the pituitary portal blood.

Animals↗
PubMed1999

Morphine and anandamide stimulate intracellular calcium transients in human arterial endothelial cells: coupling to nitric oxide release.

Both morphine and anandamide significantly stimulated cultured endothelial intracellular calcium level increases in a concentration-dependent manner in cells pre-loaded with fura 2/AM. Morphine is more potent than anandamide (approximately 275 vs. 135 nM [Ca]i), and the [Ca]i for both ligands was blocked by prior exposure of the cells to their respective receptor antagonist, i.e., naloxone and SR 171416A. Various opioid peptides did not exhibit this ability, indicating a morphine-mu3-mediated process. In comparing the sequence of events concerning morphine's and anandamide's action in stimulating both [Ca]i and nitric oxide production in endothelial cells, we found that the first event precedes the second by 40+/-8 sec. The opiate and cannabinoid stimulation of [Ca]i was attenuated in cells leeched of calcium, strongly suggesting that intracellular calcium levels regulate cNOS activity.

Analgesics, Opioid↗
PubMed1999

Estradiol coupling to endothelial nitric oxide stimulates gonadotropin-releasing hormone release from rat median eminence via a membrane receptor.

The median eminence (ME), which is the common termination field for adenohypophysiotropic systems, has been shown to produce nitric oxide (NO), a signaling molecule involved in neuroendocrine secretion. Using an ex vivo technique, 17beta-estradiol exposure to ME fragments, including vascular tissues, stimulated NO release within seconds in a concentration-dependent manner, whereas 17alpha-estradiol or testosterone had no effect. 17Beta-estradiol conjugated to BSA (E2-BSA) also stimulated NO release, suggesting mediation by a membrane surface receptor. Tamoxifen, an estrogen receptor inhibitor, antagonized the action of both 17beta-estradiol and E2-BSA. Furthermore, estradiol-stimulated NO stimulates GnRH release. This was demonstrated by hemoglobin (a NO scavenger), N(omega)-nitro-L-arginine methyl ester, and L-N5-(1-iminoethyl)ornithine (nitric oxide synthase inhibitors) inhibition of estradiol stimulated NO and GnRH release. In this regard, L-N5-(1-iminoethyl)ornithine, specific for endotheliol constitutive nitric oxide synthase, was significantly more potent, suggesting that the estradiol-stimulated NO release arose from vascular endothelial cells. Additionally, the NO-stimulated GnRH release occurs via guanylyl cyclase activation in GnRH nerve terminals, as ODQ, a potent and selective inhibitor of NO-sensitive guanylyl cyclase, abolished the estradiol-stimulated GnRH release. The results suggest that at physiological concentrations, 17beta-estradiol may have immediate actions on ME endothelial cells via nongenomic signaling pathways leading to NO-stimulated GnRH release.

Animals↗
PubMed1999

Substance abuse and HIV-gp120: are opiates protective?

There has long been a popular conceptual linkage between human immunodeficiency virus (HIV) acquisition and substance abuse involving "needles". Indeed, in vitro studies demonstrate that these substances promote the replication of HIV. Included in these in vitro studies is a linkage or association of tissue damage and viral load with the actions HIV envelope protein gp120 with substances of abuse. However, detailed epidemiological studies have not supported this association of substance abuse and HIV acquisition, viral load and exacerbated tissue damage. It is with this understanding that we undertake a reevaluation of the in vitro studies within the context of the microvascular immune environment. In this regard, a counter-intuitive hypothesis emerges, namely, that specific substances of abuse may afford a degree of protection from HIV infection. This new hypothesis involves the neural, immune, and vascular signaling molecule nitric oxide.

Animals↗
PubMed1999

Inhibition of microglial egress in excised ganglia by human interleukin 10: implications for its activity in invertebrates.

We studied the effects of recombinant human interleukin-10 (IL-10) on invertebrate immunocytes and microglia. The present report demonstrates that the spontaneous activation of invertebrate immunocytes can be specifically inhibited by recombinant human IL-10. Induced immunocyte activation by fMLP can also be significantly diminished by IL-10. This inhibition becomes apparent over hours and causes ameboid cells to become round and nonmobile. Furthermore, Mytilus edulis pedal ganglia maintained in culture, over the course of 24 hours, emit microglia. IL-10 significantly reduces this microglial egress, an action that can be diminished by concomitant exposure of the excised ganglia to an antibody specific to IL-10 as well as IL-10. The anti-IL-10 alone is without effect. Active-ameboid microglia that egress become round and inactive following IL-10 exposure, an action prevented by anti-IL-10. Lastly, a substance immunoreactively similar to human IL-10 can be detected in pedal ganglia homogenates. Taken together, and since the immunocytes and microglia are responding to IL-10, it implies that an IL-10-like substance could be present in invertebrates. In conclusion, the study demonstrates that both invertebrate immunocytes and microglia respond to IL-10, suggesting an early evolution of this generally inhibitory cytokine.

Animals↗
PubMed1999

Acupuncture: pain management coupled to immune stimulation.

The phenomenon of acupuncture is both complex and dynamic. Recent information demonstrates that acupuncture may exert its actions on pain and immune processes. The coupling of these two systems occurs via common signaling molecules, i.e., opioid peptides. In this regard, we surmise that opioid activation leads to the processing of opioid peptides from their precursor, proenkephalin, and the simultaneous release of antibacterial peptides contained within the precursor as well. Thus, central nervous system pain circuits may be coupled to immune enhancement. Furthermore, acupuncture needle manipulation elicited signal increases bilaterally in the region of the primary and secondary somatosensory corticies in human brain as determined by magnetic resonance imaging. The maps reveal marked signal decreases bilaterally in multiple limbic and deep gray structures including the nucleus accumbens, amygdala, hypothalamus, hippocampus, and ventral tegmental area. Taken together, we surmise a major central nervous system pathway as well as local pain and immune modulation during acupuncture.

Acupuncture Analgesia↗
PubMed1998

Amino-acid-sequence determination and biological activity of tessulin, a naturally occurring trypsin-chymotrypsin inhibitor isolated from the leech Theromyzon tessulatum.

We purified a new trypsin-chymotrypsin inhibitor, designated tessulin, from the rhynchobdellid leech Theromyzon tessulatum. This 9-kDa peptide was purified to apparent homogeneity by gel-permeation and anion-exchange chromatographies followed by reverse-phase HPLC. The structure of tessulin was determined by reduction, S-beta-pyridylethylation, trypsin digestion, automated Edman degradation and matrix-assisted laser desorption mass spectrometry (m/z 8985 Da). The 81-amino-acid peptide possesses 16 cysteines and exhibits a 16% sequence similarity with antistasin-type inhibitors. Tessulin inhibits trypsin (Ki 1 pM) and chymotrypsin (Ki 150 pM) and exhibits no activity with thrombin, factor Xa, cathepsin G and elastase. This is the first trypsin-chymotrypsin inhibitor isolated from leeches that does not inhibit elastase or cathepsin G, except for cytin and therin. Furthermore, tessulin, in conjunction with other serine-protease inhibitors isolated from Theromyzon (therin, theromin), significantly diminishes the level of human granulocyte and monocyte activation induced by lipopolysaccharides (10 microg). The combined level of inhibition is higher than that of aprotinin, another serine-protease inhibitor used biomedically. Thus, tessulin may be clinically significant in reducing inflammatory events.

Adjuvants, Immunologic↗
PubMed1998

Interleukin-10 stimulation of corticotrophin releasing factor median eminence in rats: evidence for dependence upon nitric oxide production.

Following treatment with interleukin-10 (IL-10), basal corticotrophin releasing factor (CRF) levels from rat hypothalamic median eminence (ME) were found to be increased. Our data show: (1) the specificity of stimulation of CRF through the use of recombinant IL-10 and its blockage by monoclonal anti-IL-10 antibody; (2) the requirement of NO in this process through the use of N(omega)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor; (3) the blockage of IL-10 stimulated NO production by anti-IL-10; and, (4) the presence of IL-10 transcripts in hypothalamic poly A+ mRNA. These results provide the first evidence of IL-10 acting in the ME to influence CRF levels and further support our earlier findings of a potential for IL-10 in the hypothalamic-pituitary axis.

Animals↗
PubMed1998

Putative leech dopamine1-like receptor molecular characterization: sequence homologies between dopamine and serotonin leech CNS receptors explain pharmacological cross-reactivities.

The biochemical characterization of a serotonin (5HT) receptor and the cloning of a dopamine (DA) receptor in the central nervous system (CNS) of the leech, Theromyzon tessulatum, is presented. Additionally, DA and 5HT binding sites were examined in the CNS by Scatchard analysis which showed a single, relatively high-affinity binding site with a Kd 1.1 nM and a Bmax 126+18 fmol/mg protein for [3H]DA and a Kd 2.1 nM and a Bmax 225 fmol/mg protein for [3H]5HT. The first 88 amino acids of the 5HT receptor, isolated by a 5HT-affinity column followed by anion exchange chromatography and C3 reverse-phase HPLC exhibited a 43% sequence homology with Lymnaea stagnalis 5HT-receptor. The isolated DA receptor revealed a single protein of 45 kDa with an anti-D1-R in Western blot. The first 80 N-terminal amino acid residues and a trypsin digested fragment of 31 residues were obtained, and based on these sequencing data, a molecular biology strategy using reverse transcriptase-polymerase chain reaction, was developed. An amplified 1-kb segment was obtained. The complete deduced sequence of 416 amino acid residues exhibited about 30.6% sequence homology with the vertebrate D1 receptor family. Moreover, we further demonstrate that the leech 5HT and DA receptors also exhibit 30% sequence identity with each other, explaining their pharmacological cross-reactivity. Finally, anti-D1-R immunocytochemistry revealed positive structures in the peripheral and central nervous system, e.g., neurons, sensory fibers and immune cells. This is the first biochemical and molecular characterization of a DA receptor in leeches.

Amino Acid Sequence↗
PubMed1998

Amino acid sequence determination and biological activity of therin, a naturally occuring specific trypsin inhibitor from the leech Theromyzon tessulatum.

We purified a trypsin inhibitor, designated therin, from the rhynchobdellid leech Theromyzon tessulatum. Therin was purified to apparent homogeneity by gel-permeation and anion-exchange chromatography followed by reverse-phase HPLC. By a combination of reduction and S-beta-pyridylethylation, Edman degradation and electrospray mass spectrometry measurement, the complete sequence of therin (48 amino acid residues; m/z, 5376.35 +/- 0.22 Da) was determined. Therin exhibits an approximately 30% sequence similarity with peptides of the antistasin-type inhibitors family, i.e. the first and second domains of antistasin, hirustasin, ghilanthen and guamerins (I, II). Therin is a tight-binding inhibitor of trypsin (Ki, 45 +/- 12 pM) and has no action towards elastase or cathepsin G. Furthermore, therin (10(-6) M) in conjunction with theromin, a Theromyzon thrombin inhibitor (10(-6) M) significantly diminish the level of human leucocytes activation induced by lipopolysaccharide (10 microg) in a manner similar to that of aprotinin. These data suggest a leech trypsin inhibitor with possible biomedical significance.

Adjuvants, Immunologic↗
PubMed1998

Anandamide amidase inhibition enhances anandamide-stimulated nitric oxide release in invertebrate neural tissues.

Anandamide, an endogenous cannabinoid signaling molecule, in a concentration dependent manner, initiates the release of nitric oxide (NO) from leech and mussel ganglia. SR 141716A, a cannabinoid antagonist, blocks the anandamide stimulated release of NO from these tissues. Methyl arachidonyl fluorophosphonate (MAFP), a specific anandamide amidase inhibitor, when administered to either ganglia with anandamide (10-6 M) did not increase the peak level of NO release but did significantly extend NO release from 12 to 18 min (P<0.05). Lower levels of anandamide (10-8 and 10-7 M) do not stimulate the release of significant amounts of NO from these tissues. However, in the presence of MAFP (2.5 nM), the lower anandamide concentrations were able to release significant peak amounts of NO. In mussel neural tissues, the peak NO release increased from 2.2+/-1.3 nM to 8.6+/-2.1 nM. Taken together, the results indirectly demonstrate the presence of anandamide amidase in these tissues, suggesting that the enzyme may serve as an endogenous regulator of anandamide action.

Amidohydrolases↗
PubMed1998

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

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

Analysis of Variance↗
PubMed1998

Pharmacological evidence for anandamide amidase in human cardiac and vascular tissues.

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

Amidohydrolases↗