Proteinase 3, the major autoantigen of Wegener's granulomatosis, enhances IL-8 production by endothelial cells in vitro

Proteinase 3 is the major target antigen of antineutrophil cytoplasmic autoantibodies (ANCA) in Wegener's granulomatosis and is contained in the azurophilic granules of polymorphonuclear neutrophils, the dominant cell type in vascular lesions during the early stages of systemic vasculitis. This study questioned whether neutrophil lysosomal enzymes, once released at the site of inflammation, are able to potentiate the influx of additional neutrophils by enhancing the production of the chemotactic cytokine interleukin-8 (IL-8) by endothelial cells. Therefore, human umbilical vein endothelial cells in culture were incubated with varying concentrations of highly purified proteinase 3, human neutrophil elastase, and cathepsin G for different time periods. The supernatants were subsequently assessed for IL-8 antigen by using a sandwich ELISA. The presence of both proteinase 3 and elastase resulted in an increased production of IL-8, up to 15.6- and 4.2-fold, respectively, in a dose- and time-dependent fashion. Cathepsin G did not influence IL-8 production. Although the addition of an alpha 1-proteinase inhibitor completely abrogated elastase-mediated IL-8 production, it did not significantly influence the effect of proteinase 3. Both proteinase 3-and elastase-mediated production of IL-8 was inhibited by cycloheximide, indicating de novo synthesis. This was supported by the finding of increased IL-8 mRNA levels in proteinase 3-treated human umbilical vein endothelial cells by using Northern blot analysis. Taken together, the neutrophil lysosomal enzymes proteinase 3 and human neutrophil elastase may contribute to a self-perpetuating process of neutrophil recruitment in acute inflammation by increasing de novo synthesis of IL-8 by endothelial cells. The studies presented here also show that proteinase 3 mediates its effect independently of its enzymatic activity, indicating a hitherto unknown mode of action on endothelial cells.

Evidence for the involvement of phospholipase A2 mechanisms in the development of stimulant sensitization

Evidence suggests that phospholipase A2 (PLA2) activation is involved in numerous neuroplastic phenomena, including long-term potentiation. Considering the pharmacological similarities between long-term potentiation and stimulant sensitization, it seems possible that PLA2 inhibition activity also might have a role in the induction of stimulant sensitization. In this study, we have investigated whether PLA2 inhibition, by quinacrine, has any effects on stimulant-induced behavioral sensitization. Both locomotor and stereotypic behavioral sensitization were dose-dependently blocked in rats pretreated with quinacrine (8-25 mg/kg i.p.) 15 min before cocaine (30 mg/kg i.p.), when tested with cocaine (15 mg/kg i.p) 72 hr later. Similar results also were found with d-amphetamine (2 mg/kg i.p.) sensitization using a 10-day treatment regimen with testing on day 11. The ability of PLA2 activation, by melittin, to produce cocaine sensitization also was tested. Local injections of melittin (0.1 microgram/0.4 microliter) into the ventral tegmental area sensitized the subsequent stimulation of locomotor activity, stereotypy and nucleus accumbens dopamine release by cocaine, when tested 72 hr later. Local injections of melittin (0.1-1.0 microgram/0.8 microliter) into the nucleus accumbens had a moderate sensitizing effect on locomotion. Quinacrine (16 mg/kg) pretreatment 45 min before intraventral tegmental area melittin injection significantly decreased melittin-induced sensitization of the locomotor and stereotypy response to cocaine. These results indicate that PLA2 activation may play a role in the induction of stimulant sensitization. It is proposed that PLA2 activity in mesolimbic dopamine neurons, at the level of the cell bodies and perhaps the nerve terminals, is involved in the biochemical mechanisms mediating the development of stimulant sensitization.

Haloperidol antagonism of cue-elicited cocaine craving

BACKGROUND

Studies of cocaine-dependent subjects have shown that re-exposure to environmental cues previously associated with cocaine use produces a strong conditioned response characterised by autonomic hyperarousal and increases in subjective measures of cocaine craving.

METHODS

To evaluate the role of dopamine release by such cues, 20 cocaine-dependent inpatients were randomised in a single-dose, crossover, placebo-controlled design, to haloperidol (4 mg by mouth) and placebo. Plasma homovanillic acid (HVA, a dopamine metabolite), adrenocorticotropic hormone (ACTH), and cortisol were assayed before and after cue exposure. Craving and anxiety were measured before and after cues with visual analogue scales for desire to use cocaine now and for mood changes.

FINDINGS

Cocaine cues significantly increased anxiety, ACTH, cortisol, and HVA. Increases in anxiety and craving resulting from cue exposure were significantly antagonised by pretreatment with haloperidol.

INTERPRETATION

It has long been hypothesised that increases in extracellular concentrations of dopamine mediate the acute reinforcing effects of cocaine. Our data suggest that dopamine release may also mediate some of the conditioned responses to cocaine cues.

The effects of the kappa agonist U-50,488 on cocaine-induced conditioned and unconditioned behaviors and Fos immunoreactivity

The ability of kappa opioid agonists to modulate dopamine-mediated behavior and Fos immunoreactivity was assessed in adult rats. It was predicted that kappa agonist treatment would block the unconditioned and conditioned behaviors produced by cocaine (an indirect dopamine agonist). In the initial experiments, cocaine-induced locomotor activity was assessed after either acute or chronic injections of the kappa receptor agonist U-50,488 (5 mg/kg, SC). As expected, U-50,488 decreased cocaine-induced activity, while leaving baseline activity levels unaffected. Interestingly, chronic treatment with U-50,488 did not induce behavioral tolerance. The conditioned effects of cocaine (20 mg/kg, IP) were assessed using the conditioned place preference (CPP) paradigm. As expected, rats showed a preference for the cocaine-paired compartment, an effect blocked by U-50,488 (5 mg/kg, SC). One hour after CPP testing, rats were killed and Fos immunoreactivity was assessed. Rats conditioned with cocaine, but not U-50,488, showed increased Fos activity in the anterior cingulate cortex, piriform cortex, lateral septal area, and olfactory tubercles. When considered together, these results suggest that U-50,488 was effective at blocking the unconditioned and conditioned effects of cocaine, as well as cocaine-induced neuronal activity (as measured by Fos induction).

Radiation inactivation studies of the dopamine reuptake transporter protein

Using radiation inactivation, we have estimated the target size for the neuronal dopamine transporter protein. The specific binding of several radioligands previously shown to label the dopamine transporter was determined in an irradiated striatal membrane preparation. The apparent target size of the 1-[1-(2-[3H]benzo[b]thienyl)cyclohexyl]piperidine site was approximately 98 kDa. However, the apparent target size of the "cocaine binding site," as measured with the cocaine analogue 2 beta-[3H]carbomethoxy-3 beta-(4-fluorophenyl)tropane in the same assays, was approximately 140 kDa. Radiation inactivation of the binding of other ligands (GBR-12935 and mazindol) led to target size estimates in the same range (94 kDa and 133 kDa, respectively). All of these target sizes are significantly larger than the estimate of 70 kDa derived from the deduced amino acid sequence for the cloned dopamine reuptake transporter cDNA. Larger target sizes than expected have also been reported for ligand binding to the sodium-dependent serotonin transporter and glucose transporter. The estimated sizes for the ligand binding site(s) associated with the dopamine transporter protein are difficult to reconcile with a single transporter protein of 70 kDa. We conclude that the dopamine transporter protein is a homo- or hetero-oligomer when occupied in situ by uptake-blocking drugs like cocaine.

Photoaffinity labeling of the dopamine reuptake carrier protein with 3-azido[3H]GBR-12935

A high affinity tritiated azido-diphenylpiperazine derivative, 3-azido[3H]GBR-12935, was synthesized as a potential photoaffinity probe of the dopamine transporter. Initially, the reversible binding of 3-azido[3H]GBR-12935 to crude synaptosomal membranes from the rat striatum was characterized. Specific binding was sodium dependent and inhibited by a variety of drugs that are known to potently inhibit dopamine uptake. Other neurotransmitter uptake inhibitors, as well as cis-flupenthixol, a potent inhibitor of [3H]GBR-12935 binding to piperazine binding sites, failed to inhibit specific binding at concentrations of less than or equal to 10 microM. A good correlation was observed between the relative potencies of these drugs in inhibiting dopamine uptake into synaptosomes and in inhibiting specific 3-azido[3H]GBR-12935 binding to rat striatal membranes (r = 0.95, p less than 0.01). These data suggest that 3-azido[3H]GBR-12935, like other diphenylpiperazines such as [3H]GBR-12935 and [3H]GBR-12909, binds primarily to the dopamine transporter under defined assay conditions. After UV photolysis of crude synaptosomal membranes preincubated with 3-azido[3H]GBR-12935 (1-2 nM), a single radiolabeled polypeptide with an apparent molecular mass of 80 kDa was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography. Photoincorporation of 3-azido[3H]GBR-12935 into this polypeptide was inhibited selectively by compounds that inhibit the uptake of dopamine (but not other biogenic amines) and was completely dependent on the presence of Na+. No photolabeled proteins were observed when cerebellar membranes were substituted for striatal membranes. Essentially complete adsorption of the radiolabeled 80-kDa polypeptide to wheat germ agglutinin and elution with N-acetyl-D-glucosamine strongly suggest that the dopamine transporter polypeptide photolabeled by 3-azido[3H]GBR-12935 is glycosylated.

Iterative image restoration

The projection method of solving a set of linear equations was used to restore linearly degraded images. The advantages of this method are that it always converges, it can readily make use of a priori information about the image, and it does not need excessive computation time. Experimental results indicate that this method could potentially achieve superresolution.