Critical role for leukocyte hypoxia inducible factor-1alpha expression in post-myocardial infarction left ventricular remodeling.
BACKGROUND
Hypoxia inducible factor (HIF)-1alpha is a transcription factor stabilized by hypoxia. It regulates cytokines involved in the inflammatory response after ischemia and affects white blood cell (WBCs) function. The effect of HIF-1alpha on WBC function and inflammation following myocardial infarction (MI) is unknown.


OBJECTIVE
We assessed peritoneal and myocardial inflammation in the setting of low WBC HIF-1alpha expression through bone marrow transplantation of hematopoietic stem cells transfected with scramble or HIF-1alpha small interfering (si)RNA.


RESULTS
Rosa hematopoietic stem cells (lin(-), cKit(+)) were transfected with a green fluorescent protein (GFP) reporter lentivirus encoding a siRNA to HIF-1alpha or scramble. Irradiated 6- to 8-week-old C57/BL6J mice received 50 000 GFP(+) HIF-1alpha or scramble siRNA-transfected hematopoietic stem cells. Peritonitis or myocardial infarction via left anterior descending coronary artery ligation was induced 6 weeks after bone marrow transplantation. In the peritonitis model, HIF-1alpha siRNA group exhibited a significant decrease in neutrophil and monocyte entry to the peritoneum compared to scramble mice. Similarly neutrophil infiltration into the infarct zone was decreased in the HIF-1alpha siRNA group. No difference of myocardial infarct size was observed between groups. Interestingly, the ejection fraction were similar in both groups at baseline and 3 days post-MI but increased significantly in the HIF-1alpha siRNA group compared to control beginning 7 days after MI. Gene array studies demonstrated that downregulation of WBC HIF-1alpha was associated with decreased WBC CCR1, -2, and -4 expression. Chemotaxis assay results confirmed that decreased monocyte migration induced by downregulation of HIF-1alpha was partially reversed by overexpression of CCR2.


CONCLUSIONS
Downregulation of leukocyte HIF-1alpha expression resulted in decreased recruitment of WBC to the sites of inflammation and improvement in cardiac function following MI. Downregulation of HIF-1alpha suppressed WBC cytokine receptors CCR1, -2, and -4, which are necessary for WBC mobilization and recruitment to inflammatory cytokines following MI. The effects of downregulation of leukocyte HIF-1alpha on WBC migration are attributable, at least in part, to the decreased CCR2 expression. These results demonstrate that WBC infiltration into the newly injured myocardium plays a significant role in left ventricular remodeling, but not infarct size.
Dong
Feng
F
Skirball Laboratory for Cardiovascular Cellular Therapeutics, Center for Cardiovascular Cell Therapy, Department of Cardiovascular Medicine, Cleveland Clinic, NE3, 9500 Euclid Ave, Cleveland, OH 44195, USA.
Khalil
Mazen
M
Kiedrowski
Matt
M
O'Connor
Caitlin
C
Petrovic
Erin
E
Zhou
Xiaorong
X
Penn
Marc S
MS
D000818:Animals; D016026:Bone Marrow Transplantation; D043422:Carboxypeptidases A / Q000096:biosynthesis / Q000235:genetics; D018932:Chemokine CCL2 / Q000096:biosynthesis / Q000235:genetics; D002634:Chemotaxis, Leukocyte / Q000502:physiology; D015536:Down-Regulation; D020869:Gene Expression Profiling; D055785:Gene Knockdown Techniques; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D007962:Leukocytes / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009203:Myocardial Infarction / Q000473:pathology / Q000503:physiopathology*; D009504:Neutrophils / Q000502:physiology; D020411:Oligonucleotide Array Sequence Analysis; D010538:Peritonitis / Q000503:physiopathology; D034741:RNA, Small Interfering / Q000235:genetics; D011828:Radiation Chimera; D011897:Random Allocation; D054389:Receptors, CCR1 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D054390:Receptors, CCR2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D054398:Receptors, CCR4 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D020257:Ventricular Remodeling / Q000235:genetics / Q000502:physiology*
C491768:Ccl2 protein, mouse; C515301:Ccr1 protein, mouse; C515335:Ccr2 protein, mouse; C515355:Ccr4 protein, mouse; D018932:Chemokine CCL2; C497443:Hif1a protein, mouse; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D034741:RNA, Small Interfering; D054389:Receptors, CCR1; D054390:Receptors, CCR2; D054398:Receptors, CCR4; D043422:Carboxypeptidases A; C503326:Cpa3 protein, mouse