Effect of subacute and chronic immobilisation stress on the outcome of permanent focal cerebral ischaemia in rats.

The aim of this study was to determine the effect of mood disorders, including psychological distress and depression, on stroke outcome. Male Fischer rats were exposed to immobilisation stress, an animal paradigm of psychological stress, major depression and post-traumatic stress disorder. Either a subacute (1 h for 7 days) or a chronic (6 h for 21 days) exposure to stress was applied 24 h before permanent middle cerebral artery occlusion (MCAO). Stroke outcome was assessed by measurement of infarct size and behavioural characterisation. Serum glutamate and brain ATP levels as well as brain glutamate transporter function and expression were studied in the search for the molecular mechanisms involved. Subacute stress exposure increased infarct size and decreased behavioural scores after stroke. On the contrary, chronic stress exposure decreased infarct size. Peak serum glutamate levels correlated with infarct size after MCAO. Expression of glutamate transporters was decreased by subacute stress, whereas the expression of EAAT1, a glial glutamate carrier, was increased after the chronic stress protocol. Our results indicate that distinct patterns of stress determine different stroke outcomes, and that expressional changes of brain glutamate transporters, able to affect glutamate release after stroke, are involved.

Neuroprotective effect of aspirin by inhibition of glutamate release after permanent focal cerebral ischaemia in rats.

Aspirin reduces the size of infarcts after ischaemic stroke. Although this fact has been attributed to its anti-platelet actions, direct neuroprotective effects have also been reported. We have recently demonstrated that aspirin is neuroprotective by inhibiting glutamate release in 'in vitro' models of brain ischaemia, via an increase in ATP production. The present study was designed to determine whether the inhibition of glutamate release induced by aspirin might be protective in a whole-animal model of permanent focal brain ischaemia. Focal brain ischaemia was produced in male adult Fischer rats by occluding both the common carotid and middle cerebral arteries. Central and serum glutamate levels were determined at fixed intervals after occlusion. The animals were then killed and infarct volume was measured. Aspirin (30 mg/kg i.p. administered 2 h before the occlusion) produced a significant reduction in infarct volume, an effect that correlated with the inhibition caused by aspirin on ischaemia-induced increase in brain and serum glutamate concentrations after the onset of the ischaemia. Aspirin also inhibited ischaemia-induced decrease in brain ATP levels. Our present findings show a novel mechanism for the neuroprotective effects of aspirin, which takes place at concentrations in the anti-aggregant-analgesic range, useful in the management of patients with risk of ischaemic events.

Implication of TNF-alpha convertase (TACE/ADAM17) in inducible nitric oxide synthase expression and inflammation in an experimental model of colitis.

Tumour necrosis factor-alpha (TNF-alpha) is a pro-inflammatory cytokine which is shed in its soluble form by a disintegrin and metalloproteinase (ADAM) called TNF-alpha convertase (TACE; ADAM17). TNF-alpha plays a role in inflammatory bowel disease (IBD) and is involved in the expression of inducible nitric oxide synthase (iNOS) which has also been implicated in IBD. The study was designed to investigate whether colitis induced by trinitrobenzene sulphonic acid (TNBS) in rats produces an increase in TACE activity and/or expression and whether its pharmacological inhibition reduces TNF-alpha levels, iNOS expression and colonic damage in this model. TNBS (30 mg in 0.4 ml of 50% ethanol) was instilled into the colon of female Wistar rats. Saline or TACE inhibitor BB1101 (10 mg/kg/day) was administered intraperitoneally 5 days after TNBS instillation. On day 10, colons were removed and assessed for pathological score, myeloperoxidase (MPO), NO synthase (NOS), TACE enzymatic activity and protein levels, colonic TNF-alpha and NOx- levels. Instillation of TNBS caused an increase in TACE activity and expression and the release of TNF-alpha. TNBS also resulted in iNOS expression and colonic damage. BB1101 blocked TNBS-induced increase in TACE activity, TNF-alpha release and iNOS expression. Concomitantly, BB1101 ameliorated TNBS-induced colonic damage and inflammation. TNBS causes TNF-alpha release by an increase in TACE activity and expression and this results in the expression of iNOS and subsequent inflammation, suggesting that TACE inhibition may prove useful as a therapeutic means in IBD.

Mechanisms of the neuroprotective effect of aspirin after oxygen and glucose deprivation in rat forebrain slices.

Acetylsalicylic acid (ASA, Aspirin) is an anti-inflammatory drug with a wide spectrum of pharmacological activities and multiple sites of action. Apart from its preventive actions against stroke due to its antithrombotic properties, recent data in the literature suggest that high concentrations of ASA also exert direct neuroprotective effects. We have used an in vitro model of brain ischaemia using rat forebrain slices deprived of oxygen and glucose to test ASA neuroprotective properties. We have found that ASA inhibits neuronal damage at concentrations lower than those previously reported (0.1-0.5 mM), and that these effects correlate with the inhibition of excitatory amino acid release, of NF-kappaB translocation to the nucleus and iNOS expression caused by ASA. All of these three mechanisms may mediate the neuroprotective effects of this drug. Our results also show that the effects of ASA are independent of COX inhibition. Taken together, our present findings show that ASA is neuroprotective in an in vitro model of brain ischaemia at doses close to those recommended for its antithrombotic effects.