Dietary essential oil components in the prevention of hypoperfusion/reperfusion-induced tissue damage in the rat cerebral cortex

To extend our previous observations on the beneficial effect of dietary Pistacia lentiscus L. essential oil during cerebral bilateral common carotid artery occlusioninduced injury, we evaluated the activity of one of its major components, beta-caryophyllene (BCP), already known to possess peculiar biological activities, in Wistar rat cerebral cortex. Cerebral hypoperfusion was produced by a 30 min bilateral common carotid artery occlusion followed by 60 min reperfusion (BCCAO/R). Animals were starved for 12 hours before surgery and, 6 hours prior to hypoperfusion, BCP (40 mg/kg/0, 45 ml of sunflower oil as vehicle) was administered via gavage. Biological samples of brain tissue, plasma and cerebrospinal fluid (CSF) were examined by HPLC, western blot, gel zymography and immunohistochemistry and analyzed for fatty acids, expression of the enzyme ciclooxygenase-2 (COX-2), CB receptors for endocannabinoids (eCBs), and peroxisome proliferator-activated receptor (PPAR)-alpha and enzymatic activity of matrix-metalloprotease-9 (MMP9). Data obtained indicate that BCP appears to influence the outcome of BCCAO/R cerebral injury by modulating changes in levels of polyunsaturated fatty acids, biosynthesis of eCBs and eCB congeners, expression of CB1 and CB2 receptors, COX-2 protein levels and enzymatic activity of MMP9. Brain tissue response to the hypoperfusion/reperfusion-induced cerebral insult is modulated by dietary administration of BCP, suggesting the possible use of this molecule as nutritional treatment in neuroprevention. Work funded by Fondazione Banco di Sardegna

Adenosine A2A and dopamine receptor interactions in basal ganglia of dopamine denervated rats

In the unilateral 6-hydroxydopamine-lesioned rat model of Parkinson's disease, blockade of A2A receptors facilitates L-dopa-induced turning behavior by antagonism of A2A transmission, which is increased after dopamine depletion. After long-term intermittent administration of doses that produced the same effect on turning behavior, SCH 58261 (5 mg/kg) + L-dopa (3 mg/kg) induced a stable turning behavior, whereas L-dopa (6 mg/kg) alone induced a sensitized turning behavior. Behavioral studies were correlated to changes in dynorphin and enkephalin mRNAs in the striatum and in glutamic acid decarboxylase 67 (GAD67) mRNA in the striatum, globus pallidus, and substantia nigra. The expression of dynorphin and, to a lesser extent, enkephalin mRNAs was increased in the lesioned striatum of rats that received long-term L-dopa treatment but not in rats that received long-term SCH 58261 + L-dopa treatment. Similarly, GAD67 mRNA was increased in the striatum and globus pallidus by long-term L-dopa administration but not by long-term SCH 58261 + L-dopa administration. GAD67 mRNA was strongly reduced in the lesioned substantia nigra after long-term L-dopa treatment, whereas the reduction of GAD67 mRNA was less marked after SCH 58261 + L-dopa treatment. By increasing L-dopa turning behavior, A2A receptor antagonism allows the utilization of doses of L-dopa that do not produce sensitization of turning behavior, an effect correlated with the dyskinetic potential of dopamine agonist drugs. Moreover, the combination of SCH 58261 + L-dopa produces little or no change in the striatal, pallidal, and nigral expression of markers correlated with dopamine agonist dyskinetic potential

Caffeine sensitization and cross-sensitization with amphetamine: association to post-synaptic changes in rat striatal neurons

Acute administration of caffeine, the most widely diffused psychostimulant drug, increases motor behavior, whereas continuous administration produces tolerance. In order to study whether, similar to other psychostimulant drugs, subchronic intermittent administration of caffeine induces sensitization of motor behavior and promotes cross-sensitization to amphetamine effects, rats were treated with caffeine (15 mg=kg i.p.) on alternate days for 14 days. Three days after discontinuation of treatment, a challenge of caffeine (15 mg=kg i.p.) or amphetamine (0.5, 1mg=kg s.c.) was given. Caffeine induced a sensitizedmotor behavioral response, associated with a decrease of adenosine A2A receptor and zif-268 mRNA levels in striatum and nucleus accumbens. Amphetamine administration produced a higher motor response in caffeine – than vehicle-pretreated rats, associated with a more pronounced increase of zif-268 mRNA levels in the medial striatum but not in the nucleus accumbens. The potentiation of amphetamine effects was not associated with modifications of amphetamine-induced dopamine release in nucleus accumbens in caffeine-pretreated rats compared to vehiclepretreated rats. The results demonstrate that intermittent pre-exposure to caffeine sensitizes the motor stimulant effects of both caffeine and amphetamine in rats. Sensitization to caffeine and cross-sensitization to amphetamine appear to be associated to post-synaptic neuroadaptive changes and to be related to the medial striatum rather than the nucleus accumbens

Neuroprotective and anti-inflammatory properties of a novel non-thiazolidinedione PPARγ agonist in vitro and in MPTP-treated mice

Peroxisome proliferator-activated receptor (PPAR)γ is a potential pharmacological target for disease-modification in Parkinson's disease (PD), mainly acting by modulating the neuroinflammatory response. However, currently available agonists thiazolidinediones (TZDs) present limitations due to safety concerns. We evaluated a novel thiobarbituric-like compound MDG548, which acts as a functional PPARγ agonist displaying higher and selective binding affinity as compared to TZDs. Neuroprotection by MDG548 was tested in vitro and in a mouse MPTP model of PD, and neuroinflammation was investigated as a putative underlying mechanism. Viability assay on rat cortical neurons showed lack of cytotoxic effect in the dose-range of 100nM-10μM, which was therefore used for testing in vitro protection against H2O2 and MPP+ neurotoxicity. MDG548 dose-dependently increased cell viability of rat cortical neurons co-treated with H2O2 or pre-exposed to MDG548 prior to H2O2. Moreover, MDG548 induced neuroprotection in MPP+-treated PC12 cells. NF-kB activation was investigated to assess anti-inflammatory activity. MDG548 dose-dependently decreased NF-kB activation induced by LPS (100ng/100ml) in HEK-Blue-hTLR4 cells. Given the supposed cancer risk of other PPARγ agonists, Ames test for genotoxicity was performed in Salmonella typhimurium TA100 and TA98 strains, showing that MDG548 was not genotoxic. In vivo, BL/6J mice were treated with MPTP (20mg/kg i.p. once/day for 4days) in association with saline or MDG548 (2, 5, 10mg/kg i.p.). Stereological counting showed that MDG548 prevented the MPTP-induced reduction in TH-positive cells in the substantia nigra compacta (SNc) at all doses tested. Moreover, MDG548 reduced reactive microglia and iNOS induction in the SNc. MDG548, being a non-TZD compound with high PPARγ affinity, void of genotoxicity, and with in vitro as well as in vivo neuroprotective properties, provides a promising alternative in the search for safer PPARγ agonists to be tested as potential disease-modifying drugs in PD