Objective: 

Contribution of Aquaporin-1 (AQP1) to gas permeation through the membrane has been demonstrated. Recent experiments indicated that expression of this protein is upregulated by hypoxic conditions. In the present work we want to confirm the regulation by hypoxia of AQP1 and to explore the molecular mechanism underlying this regulatory process.

Methods: 

Levels of Aqp1 mRNA and protein were measured by RT-qPCR in mouse brain and lung and in a culture cell line (rat gliosarcoma, 9L). Stopped-flow light-scattering experiments were used for water permeability (Pf) measurements and transcriptional activity of AQP1 promoter was evaluated in vitro by transient transfections into mouse endothelial cells with a 1297 bp 5' proximal Aqp1 promoter-luciferase construct.

Results: 

An increment on AQP1 mRNA and protein expression, as well as increase on the Pf of cells exposed to hypoxia was confirmed. Incubation at low oxygen tension produced a dose and time dependent induction on the luciferase activity-AQP1 promoter derived that was obtained also after treatments with hypoxia mimetics (DMOG and CoCl2) and by overexpressing mutated forms of HIF-1a. Single mutations or full deletions of the three putative HIF binding domains present in the promoter significantly reduced its hypoxia response, and transfection with siRNA of Hif-1a decreased the in vivo hypoxic induction on the Aqp1 mRNA and protein levels.

Conclusions: 

HIF-1a participates in the hypoxic induction of AQP1 expression, although other transcription factors might also contribute on it. Physiological relevance of this regulation in different human pathologies can be presumed but further studies are necessaries.