Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Final Activity Report Summary - CCMST (In vitro techniques for the identification of novel treatment strategies for brain and spinal cord traumatic injury)

The project was designed with the aim of helping researchers in less favoured regions of the EU to increase their competitiveness. This was achieved, among other ways, through the support of visiting researchers who bring useful techniques that are then taught to the host scientists. In the case of the present project, this has been done to understand further changes in the endocannabinoid (EC) system following cerebral insult.

Mention the word "cannabis" and most people instantly think of debates as to whether (or not) cannabis should be legalised, or whether (or not) "medical marijuana" has a place in our medical arsenal. The role of cannabinoid system in the body, however, is far more wide-ranging these debates would suggest. The main psychoactive ingredient of cannabis exerts its effects in the body by binding to receiver molecules called CB receptors. There are two types of CB receptors, of which CB1 is of most interest here since it is found in the brain. Of course, the body does not produce CB receptors in the expectation that the host will be exposed to cannabis, but rather as receivers of information conveyed by endogenous molecules, "endocannabinoids". These are involved in processes as diverse as control of pain, appetite and gastrointestinal function. The EC system is believed to act to limit the damage produced by cerebral insults such as trauma and stroke. In order to explore this exciting possibility further, we learnt two techniques, one dealing with tissue culture and the second dealing with the function of CB1 receptors. The latter technique takes advantage of the way in which CB1 receptors associate with other proteins following their activation.

We have used this technique to test a hypothesis that a residual deficit in CB1 receptor function (and hence a reduced protection) occurs after oxygen deficit. We found that there is indeed a deficit in the number of receptors, but that the functional response of the receptor population to stimulation was not affected. This is good news, since it means in theory that the EC system can be targeted even following a stroke, to reduce the consequences of a second stroke. Both techniques are generic, i.e. they are not restricted to CB receptors alone but can be applied to other receptors and to other scientific problems. We have started to explore this avenue in different ways, for example in order to see whether an orphan receptor called GPR55 can be activated in its natural state.

The term "orphan receptors" designates receptors whose naturally occurring ligands have not been identified. It has been proposed that a lipid called lysophosphatidylinositol is the endogenous activator for GPR55, although most work has been undertaken using artificial systems. We found that the response to lysophosphatidylinositol was negligible in the brain. We have also explored the usefulness of different in vitro cell culture systems to model the blood brain barrier, a naturally occurring defence against brain penetration by toxic compounds. The blood brain barrier is a natural barrier produced by endothelial cells in the brain blood capillaries. The cells are tightly packed, so that many substances cannot enter the brain. However, following cerebral insult, or following exposure to certain toxic substances, the blood brain barrier becomes less effective, and allows the passage of immune cells into the brain, where they can be highly damaging. Our aim was to model in vitro the blood brain barrier, with the aim of using it to identify novel protective molecules in a simple system. Two cultured cell systems were utilised, and both found to be wanting.

The first model did not produce a strong enough barrier, whilst the second model, although it produced a good barrier, did not behave in the appropriate manner after the cell cultures were exposed to an agent known to affect barrier function. Although negative, these studies are useful since they give information to researchers about which model systems should not be utilised, thereby allowing the researchers to focus on other, potentially more useful systems.

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