CD36 mediates H2O2-induced calcium influx in lung microvascular endothelial cells
AJP Lung Cellular and Molecular Physiology
Published online on December 02, 2016
Abstract
Elevated levels of reactive oxygen species (ROS) and intracellular Ca2+ play a key role in endothelial barrier dysfunction in acute lung injury (ALI). We previously showed that H2O2-induced increases in intracellular calcium concentrations ([Ca2+]i) in LMVECs involve the membrane Ca2+ channel, transient receptor potential vanilloid-4 (TRPV4), and that inhibiting this channel attenuated H2O2-induced barrier disruption in vitro. We also showed that phosphorylation of TRPV4 by the Src family kinase, Fyn, contributes to H2O2-induced Ca2+ influx in LMVEC. In endothelial cells, Fyn is tethered to the cell membrane by CD36, a fatty acid transporter. In this study, we assessed the effect of genetic loss or pharmacologic inhibition of CD36 on Ca2+ responses to H2O2. H2O2-induced Ca2+ influx was attenuated in LMVEC isolated from mice lacking CD36 (CD36-/-). TRPV4 expression and function was unchanged in LMVEC isolated from WT and CD36-/- mice, as well as mice with deficiency for Fyn (Fyn-/-). TRPV4 immunoprecipitated with Fyn, but this interaction was decreased in CD36-/- LMVEC. The amount of phosphorylated TRPV4 was decreased in LMVEC from CD36-/- mice compared to WT controls. Loss of CD36 altered subcellular localization of Fyn, while inhibition of CD36 fatty acid transport with succinimidyl oleate (SSO) did not attenuate H2O2-induced Ca2+ influx. Lastly, we found that CD36-/- mice were protected from ischemia-reperfusion injury in vivo. In conclusion, our data suggest that CD36 plays an important role in H2O2-mediated lung injury and that the mechanism may involve CD36-dependent scaffolding of Fyn to the cell membrane in order to facilitate TRPV4 phosphorylation.