IL-4 induces protection of vascular endothelial cells against killing by complement and melittin through lipid biosynthesis.
We have shown previously that cytokines IL-4 and IL-13 induce protection in porcine vascular endothelial cells (EC) against killing by the membrane attack complex (MAC) of human complement. This protection is intrinsic, not due to changes in complement regulatory proteins, and requires activation of Akt and sterol receptor element binding protein-1 (SREBP-1), which regulates fatty acid and phospholipid synthesis. Here we report that, compared to EC incubated in medium, IL-4-treated EC had a profound reduction in complement-mediated ATP loss and in killing assessed by vital dye uptake, but only a slight reduction in permeability disruption measured by calcein release. While controls exposed to complement lost mitochondrial membrane potential and subsequently died, protected EC maintained mitochondrial morphology and membrane potential, and remained alive. SREBP-1 and fatty acid synthase activation were required for protection and fatty acid and phospholipid synthesis, including cardiolipin, were increased after IL-4 stimulation, without increase in cholesterol content or cell proliferation. IL-4 also induced protection of EC from killing by the channel forming protein melittin, similar to protection observed for the MAC. We conclude that IL-4 induced activation of Akt/SREBP-1/lipid biosynthesis in EC, resulting in protection against MAC and melittin, in association with mitochondrial protection.
Black
Sylvester M
SM
Department of Surgery, Medical School, University of Minnesota, Minneapolis, MN 55455, USA.
Schott
Megan E
ME
Batdorf
Bjorn H
BH
Benson
Barbara A
BA
Rutherford
Mark S
MS
Levay-Young
Brett K
BK
Dalmasso
Agustin P
AP
D000818:Animals; D015153:Blotting, Western; D002463:Cell Membrane Permeability; D002469:Cell Separation; D015938:Complement Membrane Attack Complex / Q000187:drug effects; D003165:Complement System Proteins / Q000187:drug effects*; D042783:Endothelial Cells / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D005434:Flow Cytometry; D015847:Interleukin-4 / Q000378:metabolism / Q000494:pharmacology*; D008055:Lipids / Q000096:biosynthesis*; D008555:Melitten / Q000009:adverse effects*; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D051780:Sterol Regulatory Element Binding Protein 1 / Q000187:drug effects / Q000378:metabolism; D013552:Swine
D015938:Complement Membrane Attack Complex; D008055:Lipids; D051780:Sterol Regulatory Element Binding Protein 1; D008555:Melitten; D015847:Interleukin-4; D003165:Complement System Proteins; D051057:Proto-Oncogene Proteins c-akt