ABSTRACT
Brain tumour oedema is coupled with blood-brain barrier damage and alteration in water flow. Aquaporin-4 (AQP4) is involved in the development and resolution of brain oedema, and it is strongly upregulated in glioblastoma multiforme (GBM). Here, we evaluated AQP4 expression and content in GBM and correlated with VEGF-VEGFR-2 expression. In the relapse after chemotherapy and radiotherapy, AQP4 content reduced in parallel with VEGF-VEGFR-2, as compared with primary tumours, and in the peripheral areas of relapsed tumours AQP4 mimicked normal findings of perivascular rearrangement. After immunogold electron microscopy, gold particles were attached on the glial membrane facing the perivascular side, likewise AQP4 gold labelling of the vessels of the control areas. In primary tumours the peripheral vessels appeared faintly marked by AQP4, while the perivascular tumour cells showed a strong expression. The vasculature of the inner tumour areas was unlabelled by AQP4, while tumour cells were labelled, in both primary and relapsing tumours. Relapsed tumours after radiotherapy alone showed slight AQP4 reduction and perivascular restoring in the peripheral areas of the tumour. These data indicate that in GBM chemotherapy and radiotherapy induce a down-regulation in AQP4 expression restoring its perivascular rearrangement suggesting its potential role in the resolution of brain oedema.
Subject(s)
Aquaporin 4/metabolism , Blood-Brain Barrier/metabolism , Brain Edema/metabolism , Brain Neoplasms/metabolism , Glioblastoma/metabolism , Aquaporin 4/drug effects , Aquaporin 4/radiation effects , Blood-Brain Barrier/pathology , Body Water/metabolism , Brain Edema/pathology , Brain Neoplasms/pathology , Brain Neoplasms/therapy , Capillary Permeability , Cerebrovascular Circulation , Combined Modality Therapy , Down-Regulation/drug effects , Down-Regulation/radiation effects , Glioblastoma/pathology , Glioblastoma/therapy , Humans , Up-Regulation , Vascular Endothelial Growth Factor Receptor-2/metabolism , Vascular Endothelial Growth Factors/metabolismABSTRACT
AIM: To determine whether exposure to mobile telephone radiofrequency (RF) fields, either acutely or long-term, produces up-regulation of the water channel protein, aquaporin-4 (AQP-4). METHODS: Using a purpose-designed exposure system at 900 MHz, mice were given a single, far-field whole body exposure at a specific absorption rate of 4 W/kg for 60 minutes or a similar exposure on 5 successive days/week for 104 weeks. Control mice were sham-exposed or freely mobile in a cage to control for any stress caused by restraint in the exposure module. A positive control group was given a clostridial toxin known to cause microvascular endothelial injury, severe vasogenic oedema and upregulation of AQP-4. Brains were perfusion fixed with 4% paraformaldehyde, coronal sections cut from six levels, and immunostained for the principal water channel protein in brain, AQP-4. RESULTS: There was no increase in AQP-4 expression in brains exposed to mobile phone microwaves compared to control (sham exposed and freely moving caged mice) brains after short or protracted exposure, while AQP-4 was substantially upregulated in the brains of mice given the clostridial toxin. CONCLUSION: Brains exposed to mobile telephone RF fields for a short (60 minutes) or long (2 years) duration did not show any immunohistochemically detectable up-regulation of the water channel protein, AQP-4, suggesting that there was no significant increase in blood-brain barrier permeability
