Visit our Expo - Redox and Inflammation signaling 2012

Session XIV : Transcriptional and translational control Poster XIV, 12
Mechanisms of hypoxia inducible factor HIF-1alpha regulation in airway smooth muscle
cells
Georgia Chachami1, 2, George Simos2, Apostolia Hatziefthimiou1, Panagiotis Liakos2,
Sophia Bonanou2, Paschalis-Adam Molyvdas1 and Efrosyni Paraskeva1
1Laboratory of Physiology and 2Laboratory of Biochemistry, Department of Medicine,
University of Thessaly, Larissa, Greece. E-mail:fparaskeva@med.uth.gr
Hypoxia inducible factor 1alpha (HIF-1alpha) is the regulatory subunit of HIF-1, the key
mediator of the cellular response to hypoxia. HIF-1alpha is induced by hypoxia but also at
normoxic conditions by exposure to heavy metals, treatment with growth factors or oncogenic
transformation. We investigate the role of HIF-1 in the physiology of the respiratory tract by
the use of primary cultures of airway smooth muscle (ASM) cells derived from rabbit trachea.
Smooth muscle cells are not terminally differentiated and dynamically exhibit distinct
contractile and proliferative phenotypes with unique morphological, biochemical, functional
and gene expression characteristics. ASM cells in primary cultures maintained in full growth
medium that contains fetal bovine serum (FBS) have the tendency to acquire the proliferative
phenotype. However, prolonged serum deprivation allows a subset of cells to re-acquire the
morphological and functional characteristics of contractile cells within intact tissues.
Exposure of “proliferative” ASM cells to low oxygen concentration as well as to cobalt can
cause a rapid increase of the intracellular levels of HIF-1alpha. The use of specific inhibitors
reveals that induction of HIF-1alpha by cobalt is due to an increase of both HIF-1alpha
stabilization and active protein synthesis and involves the phosphatidylinositol 3-kinase
(PI3K) pathway and the production of reactive oxygen species.
We are currently investigating the induction of HIF-1alpha in serum-deprived quiescent
“contractile” cells and the cellular pathways involved. Cobalt induces HIF-1alpha in
“contractile” cells by affecting predominantly its protein stability. On the other hand, readdition
of serum to these cells also causes HIF-1alpha induction, which is not due to
increased protein stability, but rather requires on-going transcription, active protein synthesis
and is PI3K-dependent. Interestingly, the simultaneous incubation of “contractile” cells with
cobalt and serum results in an additive induction of HIF-1alpha protein levels and more
efficient nuclear localization. Moreover, simultaneous incubation of rabbit trachea strips with
cobalt and serum changes their contractile properties by increasing their responsiveness to
acetylcholine.
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