Endothelial-specific expression of mitochondrial thioredoxin promotes ischemia-mediated arteriogenesis and angiogenesis.
OBJECTIVE
Thioredoxin-2 (Trx2), a major antioxidant protein in mitochondria, enhances nitric oxide bioavailability and inhibits ASK1-dependent apoptosis in endothelial cells (ECs). However, the in vivo role of Trx2 in angiogenesis has not been defined. Here we used EC-specific transgenesis of Trx2 (Trx2-TG) in mice to determine the in vivo function of Trx2 in arteriogenesis and angiogenesis.


RESULTS
In a femoral artery ligation model, Trx2-TG mice had enhanced capacity in limb perfusion recovery and ischemic reserve capacity compared to the nontransgenic littermates. Ischemia-initiated arteriogenesis in the upper limb was augmented in Trx2-TG mice. Trx2-TG mice also showed significantly enhanced capillary formation and maturation in the lower limb. In nontransgenic limb, ischemia specifically induced a downregulation of Trx2 protein, leading to increased oxidative stress, ASK1 activation, and EC apoptosis. In contrast, Trx2-TG maintained a constitutive level of Trx2, reducing the ischemia-induced deleterious responses. We then defined the mechanism by which Trx2 increases angiogenesis using ECs isolated from Trx2-TG mice. Trx2-TG ECs showed increased NO and NO-dependent migration. In addition, these cells were more resistant to oxidative stress-induced activation of ASK1 signaling and apoptosis. Moreover, Trx2-augmented EC survival is NO-independent. To define the relative contributions of Trx2-increased NO and Trx2-reduced ASK1 apoptotic activity to angiogenesis in vivo, we examined Trx2 effects on ischemia-induced angiogenesis in eNOS-deficient mice. The eNOS deletion caused severe impairment in the functional flow recovery in response to ischemia. Trx2 expression in eNOS-KO mice still dramatically inhibited ischemia-induced ASK1 and EC apoptosis, leading to an enhanced functional flow recovery.


CONCLUSIONS
These in vivo and in vitro data support that Trx2 maintains EC function by two parallel pathways-scavenging ROS to increase NO bioavailability and inhibiting ASK1 activity to enhance EC survival, facilitating ischemia-mediated arteriogenesis and angiogenesis.
Dai
Shengchuan
S
Interdepartmental Program in Vascular Biology and Therapeutics, Yale University School of Medicine, New Haven, CT 06520, USA.
He
Yun
Y
Zhang
Haifeng
H
Yu
Luyang
L
Wan
Ting
T
Xu
Zhe
Z
Jones
Dennis
D
Chen
Hong
H
Min
Wang
W
D000818:Animals; D017209:Apoptosis; D001158:Arteries / Q000254:growth & development; D001783:Blood Flow Velocity; D002465:Cell Movement; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000201:enzymology / Q000378:metabolism*; D006614:Hindlimb; D007511:Ischemia / Q000378:metabolism* / Q000503:physiopathology; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D008928:Mitochondria / Q000378:metabolism; D018482:Muscle, Skeletal / Q000098:blood supply*; D018919:Neovascularization, Physiologic; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress; D017382:Reactive Oxygen Species / Q000378:metabolism; D012039:Regional Blood Flow; D015398:Signal Transduction; D013879:Thioredoxins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D013879:Thioredoxins; D048031:JNK Mitogen-Activated Protein Kinases; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse