title: Inhibition of aquaporin-4 expression in astrocytes by RNAi determines alteration in cell morphology, growth, and water transport and induces changes in ischemia-related genes.
abstract: Recent studies indicate a key role of aquaporin (AQP) 4 in astrocyte swelling and brain edema and suggest that AQP4 inhibition may be a new therapeutic way for reducing cerebral water accumulation. To understand the physiological role of AQP4-mediated astroglial swelling, we used 21-nucleotide small interfering RNA duplexes (siRNA) to specifically suppress AQP4 expression in astrocyte primary cultures. Semiquantitative RT-PCR experiments and Western blot analysis showed that AQP4 silencing determined a progressive and parallel reduction in AQP4 mRNA and protein. AQP4 gene suppression determined the appearance of a new morphological cell phenotype associated with a strong reduction in cell growth. Water transport measurements showed that the rate of shrinkage of AQP4 knockdown astrocytes was one-half of that of controls. Finally, cDNA microarray analysis revealed that the gene expression pattern perturbed by AQP4 gene silencing concerned ischemia-related genes, such as GLUT1 and hexokinase. Taken together, these results indicate that 1) AQP4 seems to be the major factor responsible for the fast water transport of cultured astrocytes; 2) as in skeletal muscle, AQP4 is a protein involved in cell plasticity; 3) AQP4 alteration may be a primary factor in ischemia-induced cerebral edema; and 4) RNA interference could be a new potent tool for studying AQP pathophysiology in those organs and tissues where they are expressed.
authors.affiliation: Department of General and Environmental Physiology and Center of Excellence in Comparative Genomics (CEGBA), University of Bari, I-70126 Bari, Italy.
authors.forename: Grazia Paola
authors.initials: GP
authors.lastname: Nicchia
authors.forename: Antonio
authors.initials: A
authors.lastname: Frigeri
authors.forename: Grazia Maria
authors.initials: GM
authors.lastname: Liuzzi
authors.forename: Maria
authors.initials: M
authors.lastname: Svelto
mesh_terms: D000818:Animals; D051401:Aquaporin 4; D020346:Aquaporins / Q000096:biosynthesis / Q000235:genetics* / Q000502:physiology*; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D001692:Biological Transport; D001921:Brain / Q000166:cytology*; D001929:Brain Edema / Q000235:genetics / Q000378:metabolism; D002545:Brain Ischemia / Q000235:genetics / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D034622:RNA Interference; D014867:Water / Q000378:metabolism*
chemical_list: D051401:Aquaporin 4; D020346:Aquaporins; D014867:Water