Hypoxia represents an inadequate
oxygen supply to tissues, which can modulate cell functions, primarily through the
hypoxia-inducible
transcription factor HIF-1α. Dendritic cells (DC) are professional antigen-presenting cells and their migration maybe affected by
hypoxia, since the local microenvironment in lymphoid organs, as well as in inflamed and
tumor tissues, is characterized by low
oxygen tensions. In this study we observed an enhanced migratory capability of human monocyte-derived DC, using in vitro migration assays performed under hypoxic conditions. Such enhancement was independent on either the
chemoattractants involved or the maturation level of DC. However, HIF-1α appeared to be crucial for the migration only of immature DC and not for mature DC under
hypoxia, as indicated by HIF-1α
siRNA approaches. Furthermore, we observed that while Akt phosphorylation was enhanced in both immature and mature DC exposed to
hypoxia, other signaling pathways, such as p38 and p42/
p44 MAPK, were differently affected during hypoxic treatment. More interestingly, aspecific and specific inhibition of PI3K/Akt indicated that such pathway was relevant for the migration of both immature and matured DC under
hypoxia, even when DC were transfected with HIF-1α
siRNA. Our results indicate that, besides HIF-1α, several other pathways, including PI3K/Akt, may be involved in the response to
hypoxia of immature and, more specifically, of mature DC to sustain their trafficking and functions within hypoxic microenvironments.