Opioid-mediated suppression of cultured peripheral blood mononuclear cell respiratory burst activity

Opiate addiction and stress have been associated with altered immune responses. In this study, we evaluated the influence of morphine and the stress responsive opioid peptide beta-endorphin (beta-END) on O-2 and H2O2 production by cultured human peripheral blood mononuclear cells. Exposure of these cells during 48 hr of culture to morphine and beta-END at pharmacologically (10(-8) M) and physiologically (10(-12) M) relevant concentrations, respectively, markedly suppressed peripheral blood mononuclear cell O-2 and H2O2 release in response to the respiratory burst stimuli opsonized zymosan and phorbol myristate acetate. Both opioids also induced a minimal, but statistically significant, increase in resting O-2 and H2O2 generation. The modulatory effects of morphine and beta-END on peripheral blood mononuclear cell oxygen metabolism appeared to involve a classical opioid receptor, because opioid activity was blocked by naloxone and was not observed with N-acetylated-beta-END. Using purified lymphocyte and monocyte preparations, we determined that although opioids directly increase monocyte-resting oxygen metabolism, lymphocytes are the primary target cell in opioid-mediated suppression of monocyte respiratory burst activity. The release of a suppressive product from opioid-triggered lymphocytes was inhibited by cyclosporine. Based on the results of this study, we propose that opioid-mediated suppression of mononuclear phagocyte respiratory burst activity is another factor to be considered in the immunodeficiency of opiate addiction and stress.     

Proopiomelanocortin (POMC) products in the central regulation of sympathetic and cardiovascular dynamics: studies on melanocortin and opioid interactions

The proopiomelanocortin (POMC)-derived peptides are important regulators in a number of central nervous system pathways especially as they relate to food intake as well as metabolic and autonomic responses. In this study, we investigated the sympathetic nervous and cardiovascular responses to intracerebroventricular (i.c.v.) administration of alpha melanocyte stimulating hormone (alphaMSH), beta-endorphin (beta-END) and adrenal corticotrophic hormone (ACTH) alone or in the presence of a melanocortin antagonist, or an opioid antagonist, in normal animals. The i.c.v. administration of alphaMSH and ACTH resulted in a significant increase in the lumbar sympathetic nerve activity (LSNA) that was accompanied by an increase in mean arterial pressure (MAP). On the other hand i.c.v. administration of beta-END decreased the LSNA and MAP. The pretreatment of animals with the melanocortin-4 (MC-4) receptor antagonist, agouti protein, significantly antagonized the response to alphaMSH and also, paradoxically, not only antagonized the response to beta-END but converted its inhibitory responses on both the LSNA and MAP to a sympathetic activated and pressor response. Pretreatment with the opioid antagonist, naloxone, significantly antagonized the sympathetic nervous and cardiovascular response to beta-END. It partially but significantly antagonized the MAP response to alphaMSH, but the sympathetic response was unaffected. Neither agouti protein nor naloxone altered the sympathetic nervous and cardiovascular response to ACTH. From these studies, we conclude that i.c.v. administration of alphaMSH and ACTH increases the LSNA and cardiovascular dynamics, whereas beta-END decreases it. And, the MC-4 receptor antagonist reverses the endorphin response and the opioid antagonist attenuates the alphaMSH response suggesting possible receptor or central neural pathway interactions between MC-4 and the opioid receptor mediated effects.     

Delta opioidmimetic antagonists: prototypes for designing a new generation of ultraselective opioid peptides.

BACKGROUND: Tyr-Tic (1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid) and Tyr-Tic-Ala were the first peptides with delta opioid antagonist activity lacking Phe, considered essential for opioid activity based on the N-terminal tripeptide sequence (Tyr-D-Xaa-Phe) of amphibian skin opioids. Analogs were then designed to restrain the rotational flexibility of Tyr by the substitution of 2,6-dimethyl-L-tyrosine (Dmt). MATERIALS AND METHODS: Tyr and Dmt peptides were synthesized by solid phase and solution methods using Fmoc technology or condensing Boc-Dmt-OH or Boc-Tyr(But)-OH with H-L-Tic-OBut or H-D-Tic-OBut, respectively. Peptides were purified (> 99%) by HPLC and characteristics determined by 1H-NMR, FAB-MS, melting point, TLC, and amino acid analyses. RESULTS: H-Dmt-Tic-OH had high affinity (Ki delta = 0.022 nM) and extraordinary selectivity (Ki mu/Ki delta = 150,000); H-Dmt-Tic-Ala-OH had a Ki delta = 0.29 nM and delta selectivity = 20,000. Affinity and selectivity increased 8700- and 1000-fold relative to H-Tyr-Tic-OH, respectively. H-Dmt-Tic-OH and H-Dmt-Tic-NH2 fitted one-site receptor binding models (eta = 0.939-0.987), while H-Dmt-Tic-ol, H-Dmt-Tic-Ala-OH and H-Dmt-Tic-Ala-NH2 best fitted two-site models (eta = 0.708-0.801, F 18.9-26.0, p < 0.0001). Amidation increased mu affinity by 10- to 100-fold and acted synergistically with D-Tic2 to reverse selectivity (delta-->mu). Dmt-Tic di- and tripeptides exhibited delta antagonist bioactivity (Ke = 4-66 nM) with mouse vas deferens and lacked agonist mu activity (> 10 microM) in guinea-pig ileum preparations. Dmt-Tic analogs weakly interacted with kappa receptors in the 1 to > 20 microM range. CONCLUSIONS: Dmt-Tic opioidmimetic peptides represent a highly potent class of opioid peptide antagonists with greater potency than the nonopioid delta antagonist naltrindole and have potential application as clinical and therapeutic compounds.     

Effect of atrial natriuretic peptide on the release of beta-endorphin from rat hypothalamo-neurohypophysial complex

The aim of this study was to determine whether atrial natriuretic peptide (ANP) alters beta-endorphin (beta-END) secretion from rat intermediate pituitary and whether this effect is a direct action on the intermediate pituitary or an indirect one mediated by hypothalamic factor(s). We studied the release of beta-END from rat neuro-intermediate lobes of the pituitary (NIL) and from the hypothalamo-neurohypophysial complex (HNC), which consists of the hypothalamus, pituitary stalk, intermediate and posterior lobes of the pituitary, by means of an in vitro perifusion system. NIL and HNC were prepared from male Wistar rats and individually perifused for 30 min with perifusion medium followed by 20 min perifusion with medium containing alpha-rat ANP and/or dopamine (DA). Samples of perifusion medium were collected every 5 min and subjected to RIA for beta-END. The basal release of beta-END from NIL was 180% of that from HNC (p less than 0.01), which provides further support for the presence of hypothalamic factors that inhibit beta-END release from the intermediate pituitary. The perifusion of HNC with ANP at 10(-7) and 10(-6) M increased the beta-END concentration by 25 and 50%, respectively (p less than 0.01). In contrast, ANP (10(-8) to 10(-6) M) had no effect on beta-END release from NIL. The inhibitory effect of DA (10(6) M) on beta-END release from NIL and HNC (51% and 50% of the basal release, respectively, p less than 0.01) was confirmed. However, this inhibitory effect was not reversed by ANP.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protection of mice from malaria after co-administration of recombinant mouse granulocyte-macrophage colony- stimulating factor and methionine-enkephalin

The protective effect of co-administration of recombinant mouse granulocyte-macrophage colony-stimulating factor (rmGM-CSF) and synthetic peptide met-enkephalin (M-ENK) against blood-induced Plasmodium berghei infection in Swiss mice was investigated. Mice co-administered with rmGM-CSF (10.0 mug/kg) and M-ENK (2.0 mg/kg) x 3/day, i.p., beginning on day -1 and continuing through day +4 after the initiation of infection, showed significant suppression (p < 0.05) (sometimes even complete elimination) of parasitaemia compared to vehicle-treated controls. However, when administered separately, neither of these agents induced any detectable protective effect. Surprisingly, mice similarly co-administered with rmGM-CSF (10.0 mug/kg) and higher doses of M-ENK (10.0 mg/kg), showed no protection. Polyclonal neutralizing (100%) antibody to rmGM-CSF abrogated the combined protective effect of these agents. Additionally, naloxone (10.0 mg/kg/day x 6, i.p.), a non-selective, opioid receptor antagonist, also blocked the combined protection. Mice that survived the challenge showed a significant increase (p < 0.05) in total circulating leukocytes counts, and the pool-size and the phagocytic activity of both the peritoneal and splenic macrophages, ex vivo. Silica (3.0 mg/mouse, i.v.) abrogated the combined protective effect of rmGM-CSF and M-ENK. These results indicate that co-administration of rmGM-CSF and dose dependent quantities of M-ENK in P. berghei-infected mice can protect against malaria, apparently through macrophage-mediated mechanisms.     

Peripheral and Hepatic Vein Cytokine Levels in Correlation with Non-Alcoholic Fatty Liver Disease (NAFLD)-Related Metabolic,Histological, and Haemodynamic Features

Background

Haemodynamic impairment, inflammatory mediators and glucose metabolism disturbances have been implicated in the pathogenesis of Non-Alcoholic Fatty Liver Disease (NAFLD).

Aim

To investigate the cytokine profile in NAFLD patients in peripheral (P) and hepatic venous (HV) blood and to compare with histology, haemodynamic and metabolic parameters.

Methods

40 obese patients with an indication for a transjugular liver biopsy were enrolled. Besides an extended liver and metabolic work-up, interleukin (IL) 1B, IL4, IL6, IL10, IL23, tumour necrosis factor (TNF) α and interferon (INF) γ were measured in plasma obtained from P and HV blood by means of multiplex immunoassay. The T helper (Th)1/Th2, the macrophage M1/M2 and the IL10/IL17a ratios were calculated.

Results

A decrease of the P-IL10/IL17-ratio and an increase of the P-M1/M2-ratio (p<0.05) were observed in NASH versus no-NASH patients. A P-M1/M2-ratio increase was detected also in patients with portal hypertension in comparison with patients without it (p<0.05). Moreover diabetic patients showed an increase of the P-Th1/Th2-ratio in comparison with non-diabetic ones (p<0.05). The P-M1/M2 ratio positively correlated with steatosis grade (r = 0.39, p = 0.02) and insulin (r = 0.47, p = 0.003). The HV-M1/M2 ratio positively correlated with fasting insulin and Hepatic Venous Pressure Gradient (r = 0.47, p = 0.003). IL6 correlated with the visceral fat amount (r = 0.36, p = 0.02). The P- and HV-IL10/IL17 ratios negatively correlated with fasting insulin (respectively r = -0.4, p = 0.005 and r = 0.4, p = 0.01).

Conclusions

A proinflammatory cytokine state is associated with more disturbed metabolic, histological, and haemodynamic features in NAFLD obese patients. An increase of the M1/M2 ratio and a decrease of the IL10/IL17 ratio play a key role in this process.     

Association between the C.1161G>A and C.1779C>G Genetic Variants of XRCC1 Gene and Hepatocellular Carcinoma Risk in Chinese Population

The human X-ray repair complementing group 1 gene (XRCC1) is an important candidate gene influencing hepatocellular carcinoma (HCC) susceptibility. The objective of this study was to detect the association between c.1161G>A and c.1779C>G variants of XRCC1 gene and HCC risk. This study was conducted in Chinese population consisting of 623 HCC cases and 639 controls. These two genetic variants could be genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. The association of XRCC1 gene variants with the risk of HCC was investigated under different genetic models. Our findings suggested that the genotypes/alleles from c.1161G>A and c.1779C>G genetic variants were statistically associated with HCC risk. As for the c.1161G>A, the AA genotype was statistically associated with the increased risk of HCC compared to GG wild genotype (OR = 2.36, 95% CI 1.63-3.40, P < 0.001). As for the c.1779C>G, the risk of HCC was significantly higher for GG genotype compared to CC wild genotype (OR = 2.17, 95% CI 1.51-3.12, P < 0.001). Furthermore, significant differences in the risk of HCC were also detected in other genetic models for these two variants. The allele-A of c.1161G>A and allele-G of c.1779C>G variants may contribute to the susceptibility of HCC (A versus G: OR = 1.48, 95% CI 1.26-1.75, P < 0.001 and G versus C: OR = 1.51, 95% CI 1.28-1.78, P < 0.001). Our data indicated that these two variants of XRCC1 gene were statistically associated with HCC risk in Chinese population.     

Activity of the neuroendocrine axes in patients with polymyalgia rheumatica before and after TNF-α blocking etanercept treatment

Introduction

In this study, we evaluated the activity of the neuroendocrine axes in patients with polymyalgia rheumatica (PMR) before and after tumor necrosis factor (TNF)-α-blocking etanercept treatment, which previously has been shown to reduce interleukin 6 (IL-6) and C-reactive protein (CRP) markedly in PMR.

Methods

Plasma samples were collected from 10 glucocorticoid-naïve patients with PMR and 10 matched controls before and after etanercept treatment (25 mg biweekly for 2 weeks). The primary end points were pre- and posttreatment levels of adrenocorticotropic hormone (ACTH), cortisol, adrenaline, thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH), prolactin, and insulin-like growth factor 1 (IGF-1).

Results

Before TNF-α-blocking treatment, plasma TNF-α, ACTH, and cortisol levels were higher in patients versus controls (P < 0.05 and P < 0.001, respectively); during TNF-α blockade in patients, levels of both hormones decreased (P < 0.05 and P < 0.01, respectively), whereas levels in controls increased (P < 0.05), abolishing the pretreatment differences. Pretreatment adrenaline levels were more than twice as high in patients than in controls (P < 0.01); after treatment in patients, levels had decreased (P < 0.05) but remained higher versus controls (P < 0.05). Levels of the other hormones never differed significantly between groups (P > 0.05).

Conclusions

In PMR, TNF-α may increase the activities of the hypothalamic-pituitary-adrenal and the hypothalamic-sympthoadrenomedullary axes. Secretion of TSH, FSH, prolactin, and IGF-1 is not clearly changed in PMR.

Trial registration

ClinicalTrials.gov ({"type":"clinical-trial","attrs":{"text":"NCT00524381","term_id":"NCT00524381"}}NCT00524381).     

The possible involvement of endogenous ligands for mu-, delta- and kappa-opioid receptors in modulating morphine-induced CPP expression in rats

Previous studies suggested that electroacupuncture (EA) can suppress opioid dependence by the release of endogenous opioid peptides. To explore the site of action and the receptors involved, we tried to inject highly specific agonists for μ-, δ- and κ-opioid receptors into the CNS to test whether it can suppress morphine-induced conditioned place preference (CPP) in the rat. Male Sprague–Dawley rats were trained with 4 mg/kg morphine, i.p. for 4 days to establish the CPP model. This CPP can be prevented by (a) i.p. injection of 3 mg/kg dose of morphine, (b) intracerebroventricular (i.c.v.) injection of micrograms doses of the selective μ-opioid receptor agonist DAMGO, δ-agonist DPDPE or κ-agonist U-50,488H or (c) microinjection of DAMGO, DPDPE or U50488H into the shell of the nucleus accumbens (NAc). The results suggest that the release of endogenous μ-, δ- and κ-opioid agonists in the NAc shell may play a role for EA suppression of opiate addiction.     

Does melatonin modulate beta-endorphin, corticosterone, and pain threshold?

Converging lines of evidence suggest that the pineal hormone, melatonin, may regulate changes in pain threshold by modulating fluctuations in opioid receptor expression and levels of beta-endorphin (beta-END). This study investigated whether the circadian oscillation in plasma melatonin is involved in the modulation of plasma beta-END immunoreactivity (beta-END-ir), and whether fluctuations in pain threshold measured using the hotplate test are contingent upon the fluctuation of these two hormones in Rattus Norvegicus. The role of melatonin was explored using light-induced functional pinealectomy (LFPX) to suppress nocturnal melatonin release. Pinealectomized rats were found to have significantly elevated levels of beta-END-ir compared to control animals at both photophase (398 +/- 89 pg/ml versus 180 +/- 23 pg/ml) and scotophase (373 +/- 45 pg/ml versus 203 +/- 20 pg/ml) test-periods, thus supporting the putative melatonin-opioid axis. Similarly, latency to pain threshold of LFPX rats was significantly longer when compared to control animals at photophase (7.3 +/- 1.4 sec versus 4.8 +/- 0.7 sec) and scotophase (6.3 +/- 0.7 sec versus 5.1 +/- 0.7 sec). Previous studies have produced conflicting data regarding the role of the pineal system in modulating levels of corticosterone (CORT). We observed a moderate, but non-significant, increase in the CORT concentration of LFPX rats during the photophase test period.     

Morphine Induces Hyperalgesia without Involvement of μ-Opioid Receptor or Morphine-3-glucuronide

Opioid-induced hyperalgesia (OIH) is a paradoxical increase in pain perception that may manifest during opioid treatment. For morphine, the metabolite morphine-3-glucuronide (M3G) is commonly believed to underlie this phenomenon. Here, in three separate studies, we empirically assess the role of M3G in morphine-induced hyperalgesia. In the first study, CD-1 mice injected with morphine (15 mg/kg subcutaneously) after pretreatment with the opioid receptor antagonist naltrexone (NTX) (15 mg/kg) showed tail withdrawal latency reductions indicative of hyperalgesia (2.5 ± 0.1 s at t = 30 min, P < 0.001 versus baseline). In these mice, the morphine/M3G concentration ratios versus effect showed a negative correlation (r_p = −0.65, P < 0.001), indicating that higher morphine relative to M3G concentrations are associated with increased OIH. In the second study, similar hyperalgesic responses were observed in mice lacking the multidrug resistance protein 3 (MRP3) transporter protein (Mrp3^−/− mice) in the liver and their wild-type controls (FVB mice; latency reductions: 3.1 ± 0.2 s at t = 30 min, P < 0.001 versus within-strain baseline). In the final study, the pharmacokinetics of morphine and M3G were measured in Mrp3^−/− and FVB mice. Mrp3^−/− mice displayed a significantly reduced capacity to export M3G into the systemic circulation, with plasma M3G concentrations just 7% of those observed in FVB controls. The data confirm previous literature that morphine causes hyperalgesia in the absence of opioid receptor activation but also indicate that this hyperalgesia may occur without a significant contribution of hepatic M3G. The relevance of these data to humans has yet to be demonstrated.     

Age-related differentiations of Th1/Th2 cytokines in newborn infants

OBJECTIVE: To evaluate age-related differentiation of immune response in newborns by measuring serum concentrations of interleukin-2 (IL-2), interleukin-4 (IL-4) and interferon-gamma (IFN-gamma) during the perinatal period. SUBJECTS AND METHODS: Fifty-seven healthy term neonates, their mothers and 25 healthy adults (controls) age-matched to the mothers were included in the study. Cytokine concentrations were measured in the umbilical cord (UC), and in first-day (1N) and fifth-day (5N) neonatal samples, compared with those in maternal serum (MS) and control serum samples. RESULTS: Serum IL-2 concentrations in the UC were markedly elevated compared with those in MS and controls (p < 0.0001), decreasing significantly thereafter up to 5N (p < 0.001). IL-4 serum concentrations did not differ significantly between the UC, 1N and 5N samples; they were, however, markedly elevated compared with those in MS (p < 0.001, p < 0.0007 and p < 0.0001, respectively) and controls (p < 0.05, p < 0.01 and p < 0.006, respectively). IFN-gamma serum concentrations were significantly lower in the UC compared with those in controls (p < 0.04), increasing significantly up to 5N (p < 0.03). Both IFN-gamma/IL-2 and IFN-gamma/IL-4 ratios increased significantly in 5N, compared with those in the UC (p < 0.001 and p < 0.03). CONCLUSION: Our findings indicate a differential cytokine balance at birth with enhanced expression of IL-2 and IL-4 against IFN-gamma. However, a regularization of immune response seems to proceed quickly during the early neonatal life.     

Opioid agonist/antagonist effect of naloxone in modulating rabbit jejunum contractility in vitro.

Opioid peptides are the most effective drugs in controlling pain; their action is elicited by binding to specific membrane receptors. The gastrointestinal tract represents, after the nervous system, the site in which the opioid receptors are expressed at high levels. The opioid agonist morphine has a significant inhibitory effect on intestinal motility, this action is blocked by naloxone an opioid antagonist mainly active at mu and kappa receptors. In this study the presence of mu opioid receptor on rabbit jejunum was investigated by western blot. The effects of beta-endorphin, the endogenous opioid peptide with the highest affinity to the mu opioid receptor and those of naloxone on spontaneous rabbit jejunum contractions were evaluated. Beta-endorphin (10(-6) M) showed a relaxant effect on jejunum contractility while naloxone showed a dual effect inducing an increase of spontaneous contractility at low concentrations (10(-6) M, 10(-7) M, 10(-8) M) and a decrease when high concentrations (10(-3) M, 10(-4) M, 10(-5) M) were utilized. The obtained results demonstrate that mu opioid receptor is expressed in rabbit jejunum and suggest that this receptor may be involved in mediating the effects of both opioid agonist and antagonist on jejunum contractions.     

beta-Endorphin-like peptide SLTCLVKGFY is a selective agonist of nonopioid beta-endorphin receptor

It has been found that beta-endorphin (beta-END) and a synthetic beta-END-like decapeptide Ser-Leu-Thr-Cys-Leu-Val-Lys-Gly-Phe-Tyr (termed immunorphin, IMN) corresponding to the sequence 364-373 of human IgG heavy chain stimulate Con A-induced proliferation of T lymphocytes from the blood of healthy donors. [Met(5)]enkephalin ([Met(5)]ENK) and an antagonist of opioid receptors naloxone (NAL) tested in parallel were not active. The stimulating effect of beta-END and IMN on T lymphocyte proliferation was not inhibited by NAL. Studies on receptor binding of (125)I-labeled IMN to T lymphocytes revealed that it binds with high affinity to NAL-insensitive binding sites (K(d) = 7.0 +/- 0.3 nM). Unlabeled beta-END completely inhibited the specific binding of (125)I-labeled IMN to NAL-insensitive binding sites on T lymphocytes (K(i) = 1.1 +/- 0.2 nM). Thus, beta-END and IMN bind to common NAL-insensitive binding sites on T lymphocytes and enhance Con A-induced proliferation of these cells.     

Opioid agonist modulation of cytoplasmic free Ca2+ level in concanavalin A-stimulated mouse lymphocytes.

In this study the influence of mu-, delta-, and kappa-selective opioid agonists (DAMGO, DSLET, and dynorphin A (1-13)) on cytoplasmic free Ca2+ ([Ca2+]i) level in normal and concanavalin-A (Con A)-activated mouse lymphocytes was investigated. [Ca2+]i was measured using the fluorescent dye FURA-2AM. The opioid peptides at 10-12-10-7 M induced some increase in [Ca2+]i in non-activated lymphocytes. However, DAMGO and DSLET (10-13-10-7 M) considerably inhibited a Con A-induced increase in [Ca2+]i. The inhibiting effect of both peptides was higher after 20-min preincubation compare to 2-h preincubation. The effect of the kappa-agonist dynorphin A (1-13) was significantly different depending on the duration of cell pretreatment and the concentration of the peptide used. After preincubation for 20 min at low concentrations (10-12-10-11 M) it slightly stimulated, while at higher (10-10-10-7 M) concentrations it inhibited lymphocyte response to Con A. After preincubation for 2 h, pronounced stimulation of mitogen-induced Ca2+ flux was observed at peptide concentration 10-9 M. The effects of opioids were antagonized by naloxone. These data indicate that functionally active opioid receptors expressed on lymphocytes could be involved in early stages of mitogen activation.     

Isosteviol has beneficial effects on palmitate-induced α-cell dysfunction and gene expression

Background

Long-term exposure to high levels of fatty acids impairs insulin secretion and exaggerates glucagon secretion. The aim of this study was to explore if the antihyperglycemic agent, Isosteviol (ISV), is able to counteract palmitate-induced α-cell dysfunction and to influence α-cell gene expression.

Methodology/Principal Findings

Long-term incubation studies with clonal α-TC1–6 cells were performed in the presence of 0.5 mM palmitate with or without ISV. We investigated effects on glucagon secretion, glucagon content, cellular triglyceride (TG) content, cell proliferation, and expression of genes involved in controlling glucagon synthesis, fatty acid metabolism, and insulin signal transduction. Furthermore, we studied effects of ISV on palmitate-induced glucagon secretion from isolated mouse islets. Culturing α-cells for 72-h with 0.5 mM palmitate in the presence of 18 mM glucose resulted in a 56% (p<0.01) increase in glucagon secretion. Concomitantly, the TG content of α-cells increased by 78% (p<0.01) and cell proliferation decreased by 19% (p<0.05). At 18 mM glucose, ISV (10⁻⁸ and 10⁻⁶ M) reduced palmitate-stimulated glucagon release by 27% (p<0.05) and 27% (p<0.05), respectively. ISV (10⁻⁶ M) also counteracted the palmitate-induced hypersecretion of glucagon in mouse islets. ISV (10⁻⁶ M) reduced α-TC1–6 cell proliferation rate by 25% (p<0.05), but ISV (10⁻⁸ and 10⁻⁶ M) had no effect on TG content in the presence of palmitate. Palmitate (0.5 mM) increased Pcsk2 (p<0.001), Irs2 (p<0.001), Fasn (p<0.001), Srebf2 (p<0.001), Acaca (p<0.01), Pax6 (p<0.05) and Gcg mRNA expression (p<0.05). ISV significantly (p<0.05) up-regulated Insr, Irs1, Irs2, Pik3r1 and Akt1 gene expression in the presence of palmitate.

Conclusions/Significance

ISV counteracts α-cell hypersecretion and apparently contributes to changes in expression of key genes resulting from long-term exposure to palmitate. ISV apparently acts as a glucagonostatic drug with potential as a new anti-diabetic drug for the treatment of type 2 diabetes.     

Modulation of excitation transfer in the intracardiac ganglionic system by the opioid peptide dermorphin

The aim of the study was to determine whether opioid peptides could modulate the intracardiac ganglionic excitation. It has been shown that postganglionic impulse activity recorded in the frog intracardiac nerve was inhibited by endogenous amphibian opioid peptide-dermorphin (10(-12)-10(-6) M). The inhibition was blocked by naloxone (10(-5) M). Dermorphin (10(-6) M) had no influence on transitory impulse activity in the intracardiac postganglionic sympathetic fibers. It is suggested that opioid peptides take part in the mediatory process in the intracardiac ganglia.