Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Ghosh, A.
Basic aspects of neuroinflammation
PhD-Studium (Doctor of Philosophy); Humanmedizin; [ Dissertation ] Medical University of Graz; 2014. pp. 106
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- Autor*innen der Med Uni Graz:
- Ghosh Arijit
- Betreuer*innen:
- Pieber Thomas
- Sattler Wolfgang
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- Abstract:
- Neuroinflammation is a devastating condition characterised by an increased level of pro-inflammatory cytokines in the CNS leading to an alteration of the blood-brain barrier (BBB) and an infiltration of the immune cells in the brain. Recently, it has been linked to many neurodegenerative diseases such as Amyotrophic lateral sclerosis, Alzheimer’s disease, Multiple sclerosis and Parkinson’s disease. The production of the pro-inflammatory cytokines in the brain is mainly caused by the activation of microglia and astroglia. The activation of the glial cells occurs in response to various stimuli such as trauma, toxins, chemicals and drugs. So far, many techniques have been developed to track different chemical substances in the brain extracellular fluid with the purpose of monitoring disease processes such as brain inflammation, but their applications are mostly limited. For example, micro-dialysis is one of the techniques which are widely used in both experimental and clinical set-up. However, this particular technique has a number of drawbacks such as limited application time - it is also unsuitable for substances with a large molecular weight and causes glial scar formation. We, therefore, propose the cerebral Open Flow Microperfusion (cOFM), a novel in vivo technique, as an alternative to microdialysis. The design of the cOFM probe is unique in that it features no membrane and is, therefore, capable of recovering large molecules from the brain interstitial fluid regardless of the molecular weight and lipophilicity. In this present study, we utilized albumin bound Evans blue, a known large molecular weight marker used in permeability studies, and demonstrated that the BBB integrity re-establishes 11 d after the cOFM probe implantation. In addition, we also tested the BBB intactness during sampling of the brain interstitial fluid with a low molecular weight marker sodium fluorescein. We performed the sampling over a 5 h period 15 d after the implantation of the cOFM probe and showed that the cOFM is suitable for monitoring substance transport across the intact BBB. Here we also evaluated the tissue reaction surrounding the implanted cOFM probe. Contemporary microdialysis studies have shown that a glial scar forms around the implanted microdialysis probe which then acts as a mechanical barrier and reduces probe efficiency over time. Since the main cellular components of glial scars are microglia and astroglia we used Iba-1 and GFAP to detect both cell types in the brain tissues surrounding the cOFM probe. On examination we found a significant increase in the number of microglia cells in the close vicinity of the cOFM probe track 15 d after the probe implantation which was probably due to the implantation trauma. Furthermore, in contrast to the 15 d group, the 30 d group showed a minor Iba-1 reactivity surrounding the probe. The results obtained from the non-perfused group were comparable to those of the perfused group indicating that repeated sampling is possible in one individual animal. Moreover, none of the tested animals developed a continuous layer of GFAP positive glial cells surrounding the cOFM probe at any time point during the experiment. In another study, we measured the time dependent changes in the intracerebral cytokine (17 – 26 kDa) concentration as well as changes in BBB permeability. Here we adopted a LPS induced model of systemic inflammation to study neuroinflammation. Our results showed that a pro-inflammatory cytokine TNF-alpha plays an important role in LPS induced increase in BBB permeability that results in neuroinflammation. Further, we demonstrated that the cOFM is suitable for detecting and recovering substances with a large molecular weight such as signalling proteins from the brain interstitial fluid.