Prolonged mechanical ventilation alters the expression pattern of angio-neogenetic factors in a pre-clinical rat model.
OBJECTIVE
Mechanical ventilation (MV) is a life saving intervention for patients with respiratory failure. Even after 6 hours of MV, diaphragm atrophy and dysfunction (collectively referred to as ventilator-induced diaphragmatic dysfunction, VIDD) occurs in concert with a blunted blood flow and oxygen delivery. The regulation of hypoxia sensitive factors (i.e. hypoxia inducible factor 1α, 2α (HIF-1α,-2α), vascular endothelial growth factor (VEGF)) and angio-neogenetic factors (angiopoietin 1-3, Ang) might contribute to reactive and compensatory alterations in diaphragm muscle.


METHODS
Male Wistar rats (n = 8) were ventilated for 24 hours or directly sacrificed (n = 8), diaphragm and mixed gastrocnemius muscle tissue was removed. Quantitative real time PCR and western blot analyses were performed to detect changes in angio-neogenetic factors and inflammatory markers. Tissues were stained using Isolectin (IB 4) to determine capillarity and calculate the capillary/fiber ratio.


RESULTS
MV resulted in up-regulation of Ang 2 and HIF-1α mRNA in both diaphragm and gastrocnemius, while VEGF mRNA was down-regulated in both tissues. HIF-2α mRNA was reduced in both tissues, while GLUT 4 mRNA was increased in gastrocnemius and reduced in diaphragm samples. Protein levels of VEGF, HIF-1α, -2α and 4 did not change significantly. Additionally, inflammatory cytokine mRNA (Interleukin (IL)-6, IL-1β and TNF α) were elevated in diaphragm tissue.


CONCLUSIONS
The results demonstrate that 24 hrs of MV and the associated limb disuse induce an up-regulation of angio-neogenetic factors that are connected to HIF-1α. Changes in HIF-1α expression may be due to several interactions occurring during MV.
Department of Anesthesiology, University Hospital of the RWTH Aachen, Aachen, Germany. cbruells@ukaachen.de
Christian S
CS
Bruells
Karen
K
Maes
Rolf
R
Rossaint
Debby
D
Thomas
Nele
N
Cielen
Christian
C
Bleilevens
Ingmar
I
Bergs
Ursina
U
Loetscher
Agnes
A
Dreier
Ghislaine
G
Gayan-Ramirez
Brad J
BJ
Behnke
Joachim
J
Weis
D042702:Angiopoietin-2 / Q000235:genetics*; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics; D003964:Diaphragm / Q000378:metabolism; D015536:Down-Regulation; D005786:Gene Expression Regulation; D051275:Glucose Transporter Type 4 / Q000235:genetics; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics*; D053583:Interleukin-1beta / Q000235:genetics; D015850:Interleukin-6 / Q000235:genetics; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D012121:Respiration, Artificial; D016211:Transforming Growth Factor alpha / Q000235:genetics; D015854:Up-Regulation; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics*; D012122:Ventilators, Mechanical; D000099162:Endothelial PAS Domain-Containing Protein 1
D042702:Angiopoietin-2; D051792:Basic Helix-Loop-Helix Proteins; D051275:Glucose Transporter Type 4; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053583:Interleukin-1beta; D015850:Interleukin-6; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D042461:Vascular Endothelial Growth Factor A; D000099162:Endothelial PAS Domain-Containing Protein 1