Hydrogen peroxide-induced VCAM-1 expression in pancreatic islets and beta-cells through extracellular Ca2+ influx.
BACKGROUND
The use of porcine islets as alternatives to transplantable human islets is hampered by xenotransplant rejection. To identify molecular mechanisms that would allow subversion of xenoislet rejection, we investigated the role of H2O2 in vascular cell adhesion molecule-1 (VCAM-1) expression by porcine and mouse islets and beta-cell lines.


METHODS
Porcine islets were treated with H2O2, tumor necrosis factor alpha, interferon-gamma, interleukin-1beta, and lipopolysaccharide, to assess the effects of inflammatory stimulators on VCAM-1 expression using flow cytometry. The role of Ca2+ in H2O2-induced VCAM-1 expression was investigated in beta-cell lines using an extracellular Ca2+ chelator and Ca2+-depleted media. Furthermore, H2O2-induced VCAM-1 expression was measured in beta-cells, pretreated with inhibitors of protein kinase C, phospholipase D, and phosphatidylinositol-3 kinase/Akt. Finally, H2O2-induced VCAM-1 expression was evaluated in porcine islets and rodent beta-cell lines infected with an adenovirus encoding catalase, a H2O2-removing enzyme.


RESULTS
H2O2 was most potent inflammatory stimulator of VCAM-1 expression in porcine islets and had the greatest effect on VCAM-1 expression by beta-cells. Signaling pathway analysis demonstrated that extracellular Ca2+ influx was critical to H2O2-mediated VCAM-1 expression; however, protein kinase C, phospholipase D, and phosphatidylinositol-3 kinase/Akt activation were not required for VCAM-1 expression. Finally, catalase overexpression inhibited H2O2-induced VCAM-1 expression by islets and beta-cell lines.


CONCLUSIONS
An extracellular calcium-dependent H2O2 pathway is the critical mediator of VCAM-1 expression by pancreatic islets and beta-cells. Inhibition of this pathway by catalase overexpression in donor islets can be exploited to protect against xenoislet immune responses.
Lee
Sukmook
S
Clinical Research Institute, Seoul National University Hospital, Seoul, Korea.
Ha
In Su
IS
Kim
Jae Hyeon
JH
Park
Kyong Soo
KS
Han
Kyu Hyun
KH
Kim
Sun-Hee
SH
Chae
Young Chan
YC
Kim
Sun Hee
SH
Kim
Yun Hee
YH
Suh
Pann-Ghill
PG
Ryu
Sung Ho
SH
Kim
Jung-Eun
JE
Bang
Kitae
K
Hwang
Jong-Ik
JI
Yang
Jaeseok
J
Park
Kwang-Wook
KW
Chung
Junho
J
Ahn
Curie
C
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002374:Catalase / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D006084:Graft Rejection; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism*; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism; D013552:Swine; D013556:Swine, Miniature; D014183:Transplantation, Heterologous; D015854:Up-Regulation / Q000187:drug effects; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism*
D019010:Vascular Cell Adhesion Molecule-1; D006861:Hydrogen Peroxide; D002374:Catalase; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C; D010739:Phospholipase D; D002118:Calcium