Aquaporin-4 expression is increased in oedematous human brain tumours.
Aquaporin-4 (AQP4) is a highly conserved water channel protein. In rats, AQP4 is expressed in astrocyte foot processes and is important in brain water homeostasis. AQP4 expression has not been investigated in non-neoplastic human brain or oedematous brain tumours, where water homeostasis is disrupted. Therefore, immunohistochemistry was used to study AQP4 expression in non-neoplastic and neoplastic human brain and blood-brain barrier permeability was assessed using contrast enhanced computed tomograms. AQP4 was present around microvessels in five specimens of non-neoplastic brain and five low grade (Daumas-Duport I or II) astrocytomas. AQP4 was massively upregulated in four and absent in one high grade (Daumas-Duport III or IV) astrocytoma. Massive upregulation of AQP4 was also found in reactive astrocytes in five metastatic adenocarcinomas. There was significant (p<0.0001) correlation between blood-brain barrier opening and upregulated AQP4 expression. Increased AQP4 expression in high grade astrocytomas and adenocarcinomas may facilitate the flow of oedema fluid.
Saadoun
S
S
Department of Anatomy and Developmental Biology, St George's Hospital Medical School, London SW17 0RE, UK.
Papadopoulos
M C
MC
Davies
D C
DC
Krishna
S
S
Bell
B A
BA
D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary; D000328:Adult; D000368:Aged; D051401:Aquaporin 4; D020346:Aquaporins / Q000032:analysis*; D001253:Astrocytes / Q000473:pathology; D001254:Astrocytoma / Q000473:pathology*; D001812:Blood-Brain Barrier / Q000502:physiology; D001921:Brain / Q000473:pathology; D001929:Brain Edema / Q000473:pathology*; D001932:Brain Neoplasms / Q000473:pathology* / Q000556:secondary; D002199:Capillary Permeability / Q000502:physiology; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000032:analysis; D006801:Humans; D008297:Male; D008833:Microcirculation / Q000473:pathology; D008875:Middle Aged; D014882:Water-Electrolyte Balance / Q000502:physiology
C496030:AQP4 protein, human; D051401:Aquaporin 4; D020346:Aquaporins; D005904:Glial Fibrillary Acidic Protein