| pA2 online © Copyright 2004 The British Pharmacological Society |
164P
GKT, University of London Winter Meeting December 2003 |
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Plasticity
of the endocannabinoid system in the neocortex of rats treated with
human immunodeficiency virus type 1 (HIV-1) coat glycoprotein GP120 |
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Print abstractSubchronic intracerebroventricular (i.c.v.) injection of HIV-1 coat protein gp120 causes delayed neuronal apoptosis in the brain neocortex of rat (see Corasaniti et al., 2001). Here, we report the original observation that in rat gp120 enhances the activity of anandamide (AEA)-hydrolyzing enzyme fatty acid amide hydrolase (FAAH) and decreases AEA in the neocortex suggesting that this endocannabinoid is endowed with neuroprotective properties.
Anaesthesised (chloral hydrate, 400 mgkg-1 i.p.) male Wistar rats (250-280 g) were implanted with a guide cannula in to one lateral cerebral ventricle under stereotaxic guidance (see Bagetta et al., 1999). After 4 days recovery, the animals received, for 7 consecutive days, a daily dose of gp120 (100 ng i.c.v.; 2 µl volume; 1µlmin-1 rate) given alone or preceded (1h beforehand) by i.c.v. injection of SR141716, SR144528 or capsazepine, CB1, CB2 or VR1 receptor antagonists, respectively. Assessment of apoptosis, carried out in coronal tissue sections (n=6 per brain) from the brain of rats killed 24h after the last injection of gp120 by using the TUNEL method and haematoxylin and eosin (H&E) staining, and quantitation of apoptotic cells (TUNEL+ cells [1161 mm2]-1) were according to Bagetta et al. (1999). Endogenous AEA and FAAH activity were assayed as detailed elsewhere (see Maccarrone et al., 2003) by gas chromatography-electron impact spectrometry and by reverse phase HPLC, respectively, in brain cortical tissue preparations. Subchronic treatment with gp120 increased the activity of FAAH up to ~300% over control (set to 100%=950±100 pmolmin-1mg-1 protein; p< 0.01 Mann-Whitney U test) (n=6). FAAH activity increase was paralleled by an ~45% decrease of endogenous levels of AEA (100%=234±40 pmolmg-1 protein; p<0.01) (n=6). Antagonism studies show that CB1, CB2 and VR1 receptor antagonists failed to afford neuroprotection and this is at variance with the protection by the FAAH inhibitor methyl-arachidonoyl fluorophosphonate (MAFP) (Table 1) suggesting that cannabinoid or vanilloid receptors may not be involved in the neuroprotective action of AEA.
Table 1. The FAAH inhibitor MAFP prevents gp120-induced neocortical apoptosis
|
Treatment
(i.c.v.)
|
N° of rats
|
TUNEL+
cells(mean±s.e.m.)
|
|
|
|
T
|
U
|
|
| gp120 (100 ng) |
10
|
5.7±0.3
|
1.0±0.1
|
| + SR141716 (100 nmol) |
5
|
5.2±0.4
|
0.5±0.3
|
| + SR144528 (100 nmol) |
5
|
5.5±0.5
|
0.5±0.2
|
| + capsazepine (100 nmol) |
5
|
5.0±0.4
|
0.7±0.3
|
| + MAFP(100 nmol) |
3
|
1.9
±0.3*
|
0.8
±
0.2
|
U=untreated side; T=treated side. * P<0.01 vs gp120 (Tukey-Kramer test).
Bagetta G. et al.,
(1999) Neuroscience 89, 1051-1066.
Corasaniti M.T. et al. (2001) J. Neurochem. 79, 1-8.
Maccarrone M. et al. (2003) J. Neurochem. 85, 1018-1025.
Supported by the II AIDS Programme (to A. F-A.), ISS, FIRB (to G.B.) and by COFIN'2002 (to M.M.), MIUR, Rome