Decreased plasma levels of orexin-A in sleep apnea

BACKGROUND

Orexin-A, also known as hypocretin, is a neuropeptide implicated in appetite and sleep regulation. Because the obstructive sleep apnea syndrome (OSAS) is characterized by obesity and excessive daytime sleepiness, we hypothesized that orexin-A levels may be abnormal in patients with OSAS. Further, since treatment with continuous positive airway pressure (CPAP) in patients with OSAS is very effective in normalizing daytime sleepiness, we also hypothesized that the chronic use of CPAP may influence plasma levels of orexin-A in these patients.

OBJECTIVE

To evaluate plasma levels of orexin-A in patients with OSAS and the effect of CPAP treatment.

PATIENTS AND METHODS

We compared the plasma levels of orexin-A in 13 healthy controls, 27 untreated patients with OSAS and 14 patients treated with CPAP during at least 1 year (4.5 +/- 0.5 h/night; mean +/- SEM). All patients had severe OSAS (apnea-hypopnea index, 57 +/- 4 h(-1)).

RESULTS

Orexin-A plasma levels were significantly lower in untreated (9.4 +/- 1.9 pg.ml(-1), p < 0.01) and treated patients with OSAS (4.2 +/- 1.5 pg.ml(-1), p < 0.001) than in healthy subjects (20.6 +/- 4.5 pg.ml(-1)). In untreated patients, orexin-A levels were not significantly related to daytime somnolence assessed by Epworth scale (r = -0.18, p = 0.37) or the body mass index (r = -0.13, p = 0.52).

CONCLUSIONS

Orexin-A plasma levels are abnormally low in patients with OSAS, independently of the level of somnolence and/or presence of obesity. These results suggest that these low orexin-A levels may be related to the pathogenesis of OSAS.

NF-kappaB activation and iNOS upregulation in skeletal muscle of patients with COPD and low body weight

BACKGROUND

Weight loss, mostly due to skeletal muscle atrophy, is a frequent and clinically relevant problem in patients with chronic obstructive pulmonary disease (COPD). The molecular mechanisms underlying this phenomenon are unclear. This study sought to investigate whether activation of the nuclear transcription factor NF-kappaB and upregulation of the inducible form of nitric oxide synthase (iNOS) occur in the skeletal muscle of patients with COPD and low body weight as potential molecular mechanisms leading to cachexia

METHODS

NF-kappaB DNA binding activity was determined by electromobility shift assay and the immunoreactivity of its inhibitory subunit IkappaB-kappa and that of iNOS by Western blot analysis in biopsy specimens of the quadriceps femoris muscle of seven COPD patients with normal body mass index (BMI, 27.5 (1) kg/m(2)) and seven patients with low BMI (18.5 (1) kg/m(2)).

RESULTS

Compared with patients with normal body weight, those with low BMI showed a 30% increase in NF-kappaB DNA binding activity, a lower expression of IkappaB-alpha (3.37 (0.47) IOD v 5.96 (0.75) IOD, p<0.05; mean difference 2.59; 95% CI -4.53 to -0.65) and higher iNOS expression (1.51 (0.29) IOD v 0.78 (0.11) IOD, p<0.05; mean difference 0.74; 95% CI 0.04 to 1.42).

CONCLUSIONS

NF-kappaB activation and iNOS induction occur in skeletal muscle of COPD patients with low body weight. These changes might contribute to the molecular pathogenesis of cachexia in COPD.

Fragile-X syndrome and skewed X-chromosome inactivation within a family: a female member with complete inactivation of the functional X chromosome

Fragile X syndrome is the most common form of inherited mental retardation. It is caused by the increase in length of a stretch of CGG triplet repeats within the FMR1 gene. A full mutation (> 200 repeats) leads to methylation of the CpG island and silencing of the FMR1 gene. We present here two sisters that are compound heterozygotes for a full mutation and a 53 repeat intermediate allele, one of them showing mental retardation and clinical features of an affected male (speech delay, hyperactivity, large ears, prominent jaw, gaze aversion), while the other is borderline normal (mild delay). Southern blot and FMRP expression analysis showed that the sister with mental retardation had the normal FMR1 gene totally methylated and no detectable protein, while her sister had 70% of her cells with the normal FMR1 gene unmethylated and normal FMRP levels. We found that the observed phenotypic differences between both sisters who are cytogenetically normal, are caused by extreme skewed X-chromosome inactivation. Analysis of the extended family showed that most of the other female family members that carry a pre-mutation or a full mutation showed some degree of skewing in their X-chromosome inactivation. The presence of several family members with skewed X inactivation and the direction and degree of skewing is inconsistent with a mere selection during development, and suggests a genetic origin for this phenomenon.

Weight loss in chronic obstructive pulmonary disease. Mechanisms and implications

Weight loss occurs frequently in patients with chronic obstructive pulmonary disease (COPD). Although the precise cellular mechanisms underlying weight loss in COPD are unclear, this is a clinically relevant phenomenon because it contributes to limit the exercise capacity of these patients and, therefore, it jeopardizes their quality of life. More importantly, it is a negative prognostic factor that is independent of the degree of lung function impairment present. Thus, weight loss in COPD constitutes a new therapeutic target. This article reviews the mechanisms and potential consequences of weight loss in COPD and highlights areas that needed future research. It is hoped that a better understanding of its pathogenesis may eventually contribute to the development of new therapeutic strategies that contribute to improve the well-being and/or long-term prognosis of patients suffering from this devastating disease and, potentially, from others characterized also by unexplained weight loss.

Systemic effects of chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is characterised by an inappropriate/excessive inflammatory response of the lungs to respiratory pollutants, mainly tobacco smoking. Recently, besides the typical pulmonary pathology of COPD (i.e. chronic bronchitis and emphysema), several effects occurring outside the lungs have been described, the so-called systemic effects of COPD. These effects are clinically relevant because they modify and can help in the classification and management of the disease. The present review discusses the following systemic effects of chronic obstructive pulmonary disease: 1) systemic inflammation; 2) nutritional abnormalities and weight loss; 3) skeletal muscle dysfunction; and 4) other potential systemic effects. For each of these, the potential mechanisms and clinical implications are discussed and areas requiring further research are highlighted.

Skeletal muscle apoptosis and weight loss in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) often lose weight during the course of their disease. We hypothesized that this may be due to skeletal muscle apoptosis. To investigate this possibility, we obtained quadriceps femoris biopsies in 15 patients with COPD (8 with normal body mass index [BMI] and 7 with low [< 20 kg/m(2)] BMI), 8 healthy volunteers, and 6 sedentary subjects undergoing orthopedic surgery (both groups with normal BMI). Skeletal muscle apoptosis was assessed by the transferase-mediated dUTP nick end labeling (TUNEL) technique and the immunodetection of poly-(ADP-ribose)-polymerase proteolytic fragments. Exercise tolerance on a cycloergometer was also determined in patients with COPD. We found that skeletal muscle apoptosis (by both techniques) was increased in patients with COPD and low BMI as compared with the other three groups (p < 0.005). In patients with COPD, BMI was inversely related to skeletal muscle apoptosis (TUNEL, p = 0.009), and it was better correlated with exercise capacity (p = 0.006) than with the degree of airflow obstruction present (p = 0.02). Markers of skeletal muscle apoptosis were not related to any of the measured lung function variables. This study shows that skeletal muscle apoptosis (1) is increased in patients with COPD having low BMI; and (2) is associated with a lower exercise tolerance despite a similar degree of lung function impairment.

[Systemic inflammation during exacerbations of chronic obstructive pulmonary disease]

OBJECTIVE

The circulating blood levels of several inflammatory cytokines and acute phase proteins are higher in patients with stable chronic obstructive pulmonary disease (COPD). However, whether or not these inflammatory markers increase during COPD exacerbation or are modified by corticosteroid treatment has not been investigated. The objective of this study was therefore 1) to describe changes in several inflammatory markers in systemic circulation during COPD exacerbation, and 2) to assess the potential effects of corticosteroid treatment during exacerbation.

METHODS

Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin 6 (IL-6), interleukin 8 (IL-8) and C-reactive protein (CRP) were determined for 10 patients (65 2 years old) with severe COPD (FEV1 35 4% reference) who were hospitalized for acute respiratory failure (PaO2 57 2 mm Hg; PaCO2 48 3 mm Hg). Blood samples were obtained in the emergency room (before starting intravenous corticosteroid treatment), during the first 24 hours of admission, upon discharge and two months later. Eight healthy non-smokers of a similar age (54 3 years) were also studied as control subjects.

RESULTS

The COPD patients had higher concentrations of IL-6 (5.1 1.6 vs. 1.8 0.5 pg/mL, p < 0.05) and CRP (2.2 0.4 vs. 0.6 0.2 mg/dL, p < 0.005) than did controls, but the concentrations of IL-8 were similar (29 11.3 vs. 34.7 10.3 pg/mL, p = ns). No statistically significant changes were seen either during recovery, in spite of intravenous corticosteroid treatment, or two months after discharge.The ELISA test used was unable to detect TNF-alpha in any of the samples obtained from either patients or controls.

CONCLUSION

The results show that 1) there is evidence of systemic inflammation during exacerbation of COPD, and 2) such systemic inflammation does not appear to be influenced significantly by intravenous corticosteroid treatment.

Enhanced neutrophil response in chronic obstructive pulmonary disease

BACKGROUND

Neutrophils are likely to play a major role in the inflammatory response seen in chronic obstructive pulmonary disease (COPD). This study sought to address the hypothesis that an enhanced neutrophil response to proinflammatory agents in COPD may contribute to their recruitment and activation in the lungs.

METHODS

Circulating neutrophils were obtained from 10 patients with COPD, eight long term smokers with normal lung function, and eight healthy never smoking controls. The in vitro production of reactive oxygen species (ROS) was measured by the NADPH oxidase method (respiratory burst) and the surface expression of several adhesion molecules (Mac-1, LFA-1 and L-selectin) was measured by flow cytometry. Measurements were obtained under basal conditions and after stimulation with phorbol myristate acetate (PMA) and tumour necrosis factor alpha (TNFalpha). mRNA levels of p22-phox (a subunit of NADPH oxidase) and Mac-1 (CD11b) were also determined by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Patients with COPD showed enhanced respiratory burst compared with smokers with normal lung function, both under basal conditions (mean (SE) fluorescence intensity (MFI) 15.1 (0.5) v 11.6 (0.5); mean difference -3.4 (95% CI of the difference -5.1 to -1.8), p<0.01) and after PMA stimulation (MFI 210 (7) v 133 (10); mean difference -77 (95% CI of the difference -102 to -52), p<0.01). Mac-1 surface expression was also enhanced in patients with COPD, both under basal conditions (MFI 91 (5) v 45 (3); mean difference -46 (95% CI of the difference -61 to -31), p<0.001) and after stimulation with TNFalpha (MFI 340 (15) v 263 (11); mean difference -77 (95% CI of the difference -119 to -34), p=0.001). These differences were also apparent when patients with COPD were compared with non-smokers (p<0.05). The mRNA levels of p22-phox and Mac-1 (CD11b) were similar in patients with COPD and smokers with normal lung function, suggesting that the observed differences were due to post-transcriptional regulation.

CONCLUSIONS

These results demonstrate an enhanced neutrophil response to proinflammatory agents in patients with COPD which may contribute to their enhanced recruitment and activation in the lungs of these patients. These findings support those of other studies which have indicated that the neutrophil is likely to play a major role in the pathogenesis of this disease.

Enhanced neutrophil response in chronic obstructive pulmonary disease

BACKGROUND

Neutrophils are likely to play a major role in the inflammatory response seen in chronic obstructive pulmonary disease (COPD). This study sought to address the hypothesis that an enhanced neutrophil response to proinflammatory agents in COPD may contribute to their recruitment and activation in the lungs.

METHODS

Circulating neutrophils were obtained from 10 patients with COPD, eight long term smokers with normal lung function, and eight healthy never smoking controls. The in vitro production of reactive oxygen species (ROS) was measured by the NADPH oxidase method (respiratory burst) and the surface expression of several adhesion molecules (Mac-1, LFA-1 andl-selectin) was measured by flow cytometry. Measurements were obtained under basal conditions and after stimulation with phorbol myristate acetate (PMA) and tumour necrosis factor alpha (TNFα). mRNA levels of p22-phox (a subunit of NADPH oxidase) and Mac-1 (CD11b) were also determined by reverse transcriptase polymerase chain reaction (RT-PCR).

RESULTS

Patients with COPD showed enhanced respiratory burst compared with smokers with normal lung function, both under basal conditions (mean (SE) fluorescence intensity (MFI) 15.1 (0.5) v 11.6 (0.5); mean difference –3.4 (95% CI of the difference –5.1 to –1.8), p<0.01) and after PMA stimulation (MFI 210 (7) v 133 (10); mean difference –77 (95% CI of the difference –102 to –52), p<0.01). Mac-1 surface expression was also enhanced in patients with COPD, both under basal conditions (MFI 91 (5)v 45 (3); mean difference –46 (95% CI of the difference –61 to –31), p<0.001) and after stimulation with TNFα (MFI 340 (15) v 263 (11); mean difference –77 (95% CI of the difference –119 to –34), p=0.001). These differences were also apparent when patients with COPD were compared with non-smokers (p<0.05). The mRNA levels of p22-phox and Mac-1 (CD11b) were similar in patients with COPD and smokers with normal lung function, suggesting that the observed differences were due to post-transcriptional regulation.

CONCLUSIONS

These results demonstrate an enhanced neutrophil response to proinflammatory agents in patients with COPD which may contribute to their enhanced recruitment and activation in the lungs of these patients. These findings support those of other studies which have indicated that the neutrophil is likely to play a major role in the pathogenesis of this disease.

Brain alpha(2)-adrenoceptors in monoamine-depleted rats: increased receptor density, G coupling proteins, receptor turnover and receptor mRNA

1. This study was designed to assess the molecular and cellular events involved in the up-regulation (and receptor supersensitivity) of brain alpha(2)-adrenoceptors as a result of chronic depletion of noradrenaline (and other monoamines) by reserpine. 2. Chronic reserpine (0.25 mg kg(-1) s.c., every 48 h for 6 - 14 days) increased significantly the density (B(max) values) of cortical alpha(2)-adrenoceptor agonist sites (34 - 48% for [(3)H]-UK14304, 22 - 32% for [(3)H]-clonidine) but not that of antagonist sites (11 - 18% for [(3)H]-RX821002). Competition of [(3)H]-RX821002 binding by (-)-adrenaline further indicated that chronic reserpine was associated with up-regulation of the high-affinity state of alpha(2)-adrenoceptors. 3. In cortical membranes of reserpine-treated rats (0.25 mg kg(-1) s.c., every 48 h for 20 days), the immunoreactivities of various G proteins (Galphai(1/2), Galphai(3), Galphao and Galphas) were increased (25 - 34%). Because the high-affinity conformation of the alpha(2)-adrenoceptor is most probably related to the complex with Galphai(2) proteins, these results suggested an increase in signal transduction through alpha(2)-adrenoceptors (and other monoamine receptors) induced by chronic reserpine. 4. After alpha(2)-adrenoceptor alkylation, the analysis of receptor recovery (B(max) for [(3)H]-UK14304) indicated that the increased density of cortical alpha(2)-adrenoceptors in reserpine-treated rats was probably due to a higher appearance rate constant of the receptor ((Delta)r=57%) and not to a decreased disappearance rate constant ((Delta)k=7%). 5. Northern- and dot-blot analyses of RNA extracted from the cerebral cortex of saline- and reserpine-treated rats (0.25 mg kg(-1), s.c., every 48 h for 20 days) revealed that reserpine markedly increased the expression of alpha(2a)-adrenoceptor mRNA in the brain (125%). This transcriptional activation of the receptor gene expression appears to be the cellular mechanism by which reserpine induces up-regulation in the density of brain alpha(2)-adrenoceptors.

Changes induced by oxygen in rat liver proteins identified by high-resolution two-dimensional gel electrophoresis

Molecular oxygen (O2) regulates the expression of a variety of genes. Several of the proteins that respond to changes in oxygen concentration have been identified in a variety of cell lines. We extend these previous studies by analyzing the effect of oxygen on the entire protein expression profile of an intact organ using high-resolution two-dimensional gel electrophoresis. To this end, we used an isolated, in vitro perfused organ preparation to produce two groups of rat livers perfused with high (95% O2, 5% CO2) or low (95% N2, 5% CO2) oxygen concentrations. Using two-dimensional gel electrophoresis we compared the protein expression profiles of both groups of livers. Computer analysis of the files obtained after laser densitometry of the two-dimensional gels revealed two spots that were strongly up-regulated in high PO2 perfused livers compared with low PO2 perfused livers. These spots were analyzed by peptide mass fingerprinting analysis. These spots were identified as arginase 1 (liver-type arginase; EC 3.5.3.1) and mitochondrial enoyl-CoA hydratase 1 (EC 4.2.1.17). The possible role of these proteins in its new context of oxygen availability is discussed.

Regulation of iNOS expression and glutathione levels in rat liver by oxygen tension

Molecular oxygen (O(2)) regulates the expression of a variety of genes. We hypothesized that O(2) tension may regulate iNOS expression in rat liver through the production of reactive oxygen species (ROS) and the reduction of intracellular glutathione (GSH) levels. To investigate this hypothesis, we determined the effects of hyperoxia upon iNOS induction (both at the protein and mRNA level) and the intracellular concentration of GSH in an isolated in vitro perfused rat liver preparation. To study the potential involvement of ROS in the intracellular signaling pathway linking changes in oxygen tension to gene expression, we repeated these determinations in the presence of the thiol antioxidant N-acetyl-L-cysteine (NAC). We found that 95% O(2) tension caused a significant induction of the iNOS protein and mRNA levels paralleled by a significant fall in intracellular GSH concentration. The addition of NAC (1 mM) to the perfusate during hyperoxia blocked the induction of iNOS and restored GSH levels. These results indicate that molecular O(2) regulates the expression of iNOS in rat liver at the transcriptional level, most likely through the production of ROS and the reduction of intracellular GSH levels.

Expression of adhesion molecules and G proteins in circulating neutrophils in chronic obstructive pulmonary disease

We investigated the expression of adhesion molecules in circulating neutrophils (lymphocyte function-associated antigen-1 [LFA-1], Mac-1, and L-selectin) and endothelial cells (soluble intercellular adhesion molecule-1[sICAM-1]) in 23 patients with stable chronic obstructive pulmonary disease (COPD), 18 subjects with exacerbated COPD, and 23 healthy volunteers. Also, in these circulating neutrophils, we assessed the expression of two G protein subunits (Galphas and Galphai1/2). Compared with control subjects, patients with stable COPD showed increased expression of Mac-1 (p < 0.001) and lower levels of sICAM-1 (p = 0.002); LFA-1 and L-selectin expression was similar in patients and control subjects. During exacerbations, compared with stable patients, the expression of Mac-1 and LFA-1 was reduced (p < 0.001). Finally, the expression of Galphas (but not Galphai1/2) was also reduced (p < 0.001) in circulating neutrophils of patients with COPD, irrespective of the clinical condition of the patient. These results indicate that in patients with COPD: (1) the expression of some neutrophil adhesion molecules (Mac-1) is abnormal, and that this pattern changes during exacerbations; (2) there may be a form of endothelial dysfunction, as suggested by the low sICAM-1 levels; (3) the expression of G protein subunit (Galphas) in circulating neutrophils is downregulated, irrespective of their clinical conditions. Overall, these results indicate the presence of significant systemic abnormalities in COPD.

Density of guanine nucleotide-binding proteins in platelets of patients with major depression: increased abundance of the G alpha i2 subunit and down-regulation by antidepressant drug treatment

The aim of this study was to quantitate the density of guanine nucleotide-binding (G) protein subunits (inhibitory G alpha i, stimulatory G alpha s, G alpha q/11, and G beta) in platelets of unipolar depressed patients to assess the status of these signal transduction proteins in depression and the effects of antidepressant drug treatment. Blood platelets were collected from 22 drug-free depressed patients and 22 age- and sex-matched healthy controls. The levels of the various G protein subunits were assessed by immunoblotting techniques. The immunoreactivity of G alpha 12 was increased (41%) and that of G alpha i3 decreased (25%) in platelets of depressed patients. The levels of other G protein subunits (G alpha s, G alpha q/11, G beta) did not change significantly with respect to those of control subjects. Chronic administration of cyclic antidepressant drugs (citalopram, clomipramine, imipramine) decreased the immunoreactivity of the up-regulated G alpha i2 protein (31%). Since platelet G alpha i2 is in line with the existence of supersensitivity of these receptors in major depression.

Marked decrease of immunolabelled 68 kDa neurofilament (NF-L) proteins in brains of opiate addicts

NEUROFILAMENT (NF) proteins, the major components of the neuronal cytoskeleton, have been shown to represent previously unknown targets for the chronic effects of morphine in rats. This study was designed to evaluate the abundance of immunoreactive NF-L (68 kDa) proteins in post-mortem brains of chronic opiate addicts who had died of a heroin or methadone overdose. Levels of NF-L proteins were assessed by immunoblotting techniques. Levels of immunoreactive NF-L proteins were markedly decreased (47%, n = 17) in the frontal cortex. The reduced abundance of brain NF-L proteins was not related to the post-mortem delay or to the plasma concentrations of opiates, suggesting that the observed changes represent a specific long-term effect of opiate drugs. Because of the functions associated with NF proteins (e.g. axonal transport), this finding suggests that opiate drugs may induce neuronal damage after chronic abuse in humans.

Regulation of immunolabelled mu-opioid receptors and protein kinase C-alpha and zeta isoforms in the frontal cortex of human opiate addicts

To assess the status of opioid receptors in the human brain during the process of opiate addiction, the abundance of immunoreactive mu-opioid receptors was quantitated in postmortem brains of chronic opiate addicts who had died of a heroin or methadone overdose. The immunoreactive levels of the associated enzyme protein kinase C (PKC-alpha and zeta isoforms) and G proteins (G alpha(i1/2) subunits) were also assessed in the same brains. In the frontal cortex of opiate addicts, the abundance of mu-opioid receptors was not different from that obtained in matched controls. The level of Ca2+-dependent PKC-alpha was decreased (25%), whereas that of the atypical PKC-zeta remained unchanged. The density of G alpha(i1/2) proteins also was found to be increased (40%). The results indicate that opiate addiction in humans does not appear to be associated with a reduced density of brain mu-opioid receptors. The sustained down-regulation of PKC-alpha in the brain of opiate addicts would allow the up-regulation of G alpha(i1/2) proteins aimed at compensating the postulated desensitization of the mu-opioid receptor system.

Modulation of immunoreactive protein kinase C-alpha and beta isoforms and G proteins by acute and chronic treatments with morphine and other opiate drugs in rat brain

The abundance of protein kinase C-alpha and beta isoforms (PKC-alphabeta), PKC-alpha messenger (m) RNA and guanine nucleotide-binding G protein subunits (G alpha(i1/2), G alpha(o), and G beta) were quantitated in the rat cerebral cortex after acute and chronic treatments with various opiate drugs. Acute (100 mg/kg for 2 h) and chronic (10 to 100 mg/kg for 5 days) treatment with morphine decreased similarly the immunoreactivity of PKC-alphabeta (28% and 32%, respectively). Acute (2 h) and chronic treatment (5 days) with other mu-agonists heroin (30 mg/kg and 10 to 30 mg/kg) and methadone (30 mg/kg and 5 to 30 mg/kg) also induced similar decreases of PKC-alphabeta (acute: 25% and 23%; chronic: 28% and 18%). After the chronic treatments, spontaneous (48 h) or naloxone (2 mg/kg)-precipitated opiate withdrawal (2 h) resulted in up-regulation of PKC-alphabeta above control levels (30-38%), and in the case of morphine withdrawal in a concomitant marked increase in the expression of PKC-alpha mRNA levels (2.3-fold). Acute (2 h) treatments with pentazocine (80 mg/kg, mixed kappa/delta-agonist and mu-antagonist), spiradoline (30 mg/kg, selective kappa-agonist) and [D-Pen2, D-Pen5] enkephalin (14 nmol i.c.v., selective delta-agonist) induced significant decreases of PKC-alphabeta (19-33%). Chronic (5 days) treatment with pentazocine (10 to 80 mg/kg), but not spiradoline (2 to 30 mg/kg), also induced a similar decrease of PKC-alphabeta (35%). In pentazocine- or spiradoline-dependent rats, naloxone (2 mg/kg) did not induce up-regulation of brain PKC-alphabeta. Acute (10 mg/kg for 2 h) and chronic (2x10 mg/kg for 5 and 14 days) treatment with naloxone did not alter PKC-alphabeta immunoreactivity. Chronic, but not acute, treatment with mu-agonists (morphine, heroin and methadone) increased the immunoreactivities of G alpha(i1/2) (33-37%), G alpha(o), (25-41%) and G beta (10-33%) protein subunits. In heroin- and methadone-dependent rats naloxone (2 mg/kg)-precipitated withdrawal (2 h) did not modify the up-regulation of these G proteins induced by chronic mu-opiate treatment. In marked contrast to mu-agonists, chronic treatment with high doses of pentazocine and spiradoline or acute treatment with [D-Pen2, D-Pen5] enkephalin did not result in up-regulation of these G protein subunits. After chronic treatment with mu-agonists, significant negative correlations were found when the percentage changes in immunoreactivity of PKC-alphabeta were related to the percentage changes in immunoreactivity of G alpha(i1/2), (r = -0.53, n = 29) and G beta (r = -0.41, n = 24) in the same brains. PKC-alphabeta abundance did not correlate significantly with the density of G alpha(o) (r = -0.21, n = 28). Together the results indicate that the brain PKC-alphabeta system may play a major regulatory role in opiate tolerance and dependence. Moreover, the possible in vivo cross-communication between this regulatory enzyme and specific inhibitory G proteins may also be of relevance in the cellular and molecular processes of opiate addiction.

Naloxone-precipitated withdrawal in morphine-dependent rats increases the expression of alpha 2a-adrenoceptor mRNA in brain

Opiate withdrawal has been associated with up-regulation of alpha 2-adrenoceptors (mainly the alpha 2A-subtype) in brain. The modulation of these inhibitory receptors regulating norepinephrine release appears to be a relevant mechanism by which the opiate abstinence syndrome might be counteracted. The aim of this study was to investigate possible changes in alpha 2a-adrenoceptor gene expression as the molecular mechanism underlying the opiate withdrawal-induced up-regulation of alpha 2A-adrenoceptors. In morphine-dependent rats (10-100 mg/kg for 5 days), naloxone (2 mg/kg)-precipitated withdrawal induced a rapid (2 h) and marked up-regulation (111%, P < 0.001) in the expression of alpha 2a-adrenoceptor mRNA (Northern and dot-blot analyses) in the cerebral cortex. Acute and chronic morphine treatments did not alter significantly the expression of cortical alpha 2a-adrenoceptor mRNA. The results indicate that the opiate abstinence syndrome is associated with a transcriptional activation of the alpha 2a-adrenoceptor mRNA which can explain the up-regulation of brain alpha 2A-adrenoceptors during opiate withdrawal.

Platelet imidazoline receptors and regulatory G proteins in patients with major depression

The newly discovered imidazoline receptors have been found to be upregulated in patients with major depression (platelet 45 kDa and 35 kDa proteins) and in suicide victims (brain 45 kDa protein). The signalling pathways coupled to these receptors are not known however. The aim of this study was to quantify, in platelets of depressed patients, the density of various G proteins to assess possible associations with the abundance of imidazoline proteins. There were positive correlations between the immunoreactivities of 45 kDa imidazoline receptors and those of G alpha q/11 (r = 0.64, n = 19, p < 0.005), G alpha i2 (r = 0.46, n = 22, p < 0.05) and G beta (r = 0.62, n = 18, p < 0.01) proteins. The relationship with regulatory G alpha q/11 proteins suggests that this 45 kDa protein (putative I1 imidazoline receptor) may couple to phosphoinositide pathway in platelets. This finding might be of relevance in understanding the functional implications of the abnormal higher expression of imidazoline receptors (45 kDa protein) in the pathogenesis of major depression.

Immunodetection and quantitation of imidazoline receptor proteins in platelets of patients with major depression and in brains of suicide victims

BACKGROUND

Imidazoline receptors are a newly discovered family of receptors, some of which, like alpha 2-adrenoceptors, have a presynaptic inhibitory effect on the release of norepinephrine. The aim of this study was to identify by immunodetection imidazoline receptor proteins in human platelets and the brain to assess their status in depression and suicide.

METHODS

Platelets were collected from 26 drug-free depressed patients and 26 controls. Specimens of frontal cortex (Brodmann area 9) were collected from 13 suicide victims and 11 controls. Levels of imidazoline receptor proteins were assessed by immunoblotting techniques. Solubilized imidazoline receptors were separated by gel electrophoresis, transferred to nitrocellulose membranes, labeled with a specific anti-imidazoline receptor antiserum, and quantitated by image analysis.

RESULTS

Platelet and brain membranes expressed similar 45-kd imidazoline receptor proteins, and their mean +/- SEM immunoreactivities were found to be increased in depressed patients (platelets, 40% +/- 5%) and suicide victims (brain, 51% +/- 14%). Platelets also expressed a 35-kd imidazoline receptor protein that was also found to be up-regulated in depressed patients (21% +/- 4%). In contrast, brain membranes did not express this 35-kd protein but revealed a 29/30-kd imidazoline receptor protein that was found to be down-regulated in suicide victims (19% +/- 3%). In a subset of depressed patients who underwent antidepressant treatment, a change in the immunoreactivity of the up-regulated 45-kd platelet imidazoline receptor protein (-35% +/- 5%), but not of the 35-kd protein, was observed.

CONCLUSION

The results support a role for the newly discovered imidazoline receptors (mainly the 45-kd receptor expressed in the brain and platelets) in the pathogenesis of depression.