Endothelial PGC-1α mediates vascular dysfunction in diabetes Reporter: Yaqi Zhou Date: 04/14/2014
Outline I. Introduction II. Research route & Results III. Summary
Diabetes the Epidemic of the 21st Century 1 out of 10 adults will have diabetes in 2035 Number of people with diabetes in different areas by IDF Region, 2013
Diabetes - Endothelial dysfunction Principle mechanisms responsible for endothelial dysfunction in diabetes.
PGC-1α PGC 1α, a transcriptional regulator related to energy metabolism, belongs to a small family of coactivators, comprised of PGC 1α, PGC 1β, and the more distant PRC.
PGC-1α & Angiogenesis PGC-1α Myocyte HIF-1 VEGF PGC-1α Endothelial cell
Research Route Diabetes PGC-1α Endothelial dysfunction Over-Expression Knock-Out Migration Transwell assay Scratch assay Notch signaling Tube formation Angiogenesis
1. Diabetes induces PGC-1α expression in ECs Figure 1.1. Diabetes induces PGC-1α expression in ECs in vivo both in mice and in humans. (A) Relative PGC 1α mrna abundance in ECs freshly isolated from mouse models of type 1 (STZ) and type 2 (HFD, ob/ob, and db/db) diabetes. NC indicates normal chow. (B) Relative PGC 1α mrna abundance in vasculogenic circulating CD34 + cells and cultured endothelial lprogenitor cells (EPCs) isolated from patients with diabetes, versus matched normal subjects.
1. Diabetes induces PGC-1α expression in ECs Figure 1.2. Diabetes, via hyperglycemia, induces PGC-1α expression in ECs. (C) Relative PGC 1α mrna abundance in mouse muscle ECs (MMECs) at the indicated times after changing from hyperglycemia to normal glucose levels. (D) Relative PGC 1α mrna abundance in MMECs in absence or presence of 2 deoxyglucose (2DG) for 24 hr. (E) Relative PGC 1α mrna abundance in mouse heart ECs (MHECs) 2 and 4 hr after exposing cells to hyperglycemia or hyperosmolarity (mannitol).
Conclusion Ⅰ Diabetes, likely at least in part via hyperglycemia, induces PGC-1α expression in ECs in vivo.
Research Route Diabetes PGC-1α Endothelial dysfunction Over-Expression Knock-Out Migration Transwell assay Scratch assay Notch signaling Tube formation Angiogenesis
2. PGC-1α inhibits endothelial migration Figure 2.1. PGC-1α inhibits endothelial migration. (A) Mouse heart ECs (MHECs) were affinity purified from STZ treated mice and cultured to passage 2 (left). The migrated cells were less than those in control, coincident with increased expression of PGC 1α mrna (ih) (right).
2. PGC-1α inhibits endothelial migration Figure 2.2. PGC-1α inhibits endothelial migration. Reduced migration of mouse lung ECs (MLECs) isolated from db/db mice toward S1P (B) and cultured Endothelial progenitor cells(epcs) isolated from diabetic patients (C). (D) Reduced migration (left) of MHECs isolated from mice that overexpress PGC 1α (i (right) h)in ECs.
2. PGC-1α inhibits endothelial migration Figure 2.3 PGC-1α inhibits endothelial migration. (E G) Stable expression of PGC 1α inhibits migration of HUVECs in scratch assays (E) and in Transwell assays stimulated by 10 ng/ml VEGF (F) or 100 nm S1P (G).
2. PGC-1α inhibits endothelial migration Figure 2.4. PGC-1α inhibits endothelial migration. (H) Stable expression of PGC 1α inhibits the tube forming activity of HUVECs.
2. PGC-1α inhibits endothelial migration Figure 2.5. PGC-1α inhibits endothelial migration. PGC 1α inhibits cortical F actin (green) polymerization in response to VEGF and S1P (I), mimicking the impaired F actin (red) accumulation to the same stimuli in db/db mouse lung ECs (J). Arrowheads denote lamellipodia. Scale bars are 50mm in (I) and 20mm in (J).
2. PGC-1α inhibits endothelial migration VEGF and S1P act through distinct cell surface receptors but converge on at least two intracellular l signaling cascades: the ERK and AKT pathways. Endothelial lcell cytoskeletal l activation occurs in large part in response to Rac/Akt/eNOS signaling. Figure 2.6. PGC-1α inhibits endothelial migration. PGC 1α blocks activation of Akt and enos (but not Erk) by VEGF and S1P ([K], with densitometric quantification at 0 and 5 min in[l]) in human endothelial colony forming cells (ECFCs).
Conclusion Ⅱ PGC-1α inhibits endothelial migration and Akt/eNOS proangiogenic pathway.
Research Route Diabetes PGC-1α Endothelial dysfunction Over-Expression Knock-Out Migration Transwell assay Scratch assay Notch signaling Tube formation Angiogenesis
Notch signaling pathway Notch signaling is increasinglyi recognized as a powerful inhibitor of endothelial l migration and angiogenesis. The Notch cell surface receptor is sequentially cleaved by matrix metalloproteinase and γ secretase, leading to nuclear localization of the Notch intracellular domain (NICD).
3. PGC-1α activates Notch signaling to inhibit endothelial migration Figure 3.1. PGC-1α activates Notch signaling both in culture and in vivo. (A) Expression of PGC 1α in HUVECs activates Notch signaling, as assessed by western blotting of the Notch intracellular domain (NICD). (B) mrna expression of known Notch target genes in the endothelial compartment of the mouse skeletal muscle from EC specific PGC 1α overexpressing mice, versus controls.
3. PGC-1α activates Notch signaling to inhibit endothelial migration Figure 3.2. PGC-1α activates Notch signaling to inhibit endothelial migration. (C) Inhibition of Notch signaling with DAPT (2.5mM) rescues inhibition of migration in HUVECs retrovirally transduced with PGC 1α. DAPT, an inhibitor of γ secretase. (D) Inhibition of Notch signaling with DAPT (2.5mM) rescues inhibition of capillary formation in mouse aortic explants from EC specific PGC 1α overexpressing mice.
3. PGC-1α activates Notch signaling to inhibit endothelial migration Figure 3.3. PGC-1α activates Notch signaling to inhibit endothelial migration. (E) DAPT (2.5 mm) and pan MMP inhibitor GM6001 (25mM) equally inhibited the upregulation of Notch downstream gene mrna expression in HUVECs retrovirally transduced with PGC 1α. GM6001, a pan MMP inhibitor.
3. PGC-1α activates Notch signaling to inhibit endothelial migration Figure 3.4. PGC-1α activates Notch signaling to inhibit endothelial migration. (F) Increased mrna abundance of ADAMTS10 in the MHECs isolated from EC specific PGC 1α transgenic mice, the endothelial compartment of STZ induced diabetic mouse lung, cultured EPCs from diabetic patients, and human dermal microvascular ECs treated with high glucose for 24 hr. ADAMTS10, an ADAM like MMP.
3. PGC-1α activates Notch signaling to inhibit endothelial migration Figure 3.5. PGC-1α activates Notch signaling to inhibit endothelial migration. (G) Gene knockdown efficiency by lentiviral transduction of HUVECs with short hairpin RNA targeting ADAMTS10. (H and I) Knockdown of ADAMTS10 with shrna blocked the mrna expression of Notch target genes (H) and reduced the inhibition of endothelial migration toward S1P (I) by retroviral overexpression of PGC 1α in HUVECs.
Conclusion Ⅲ PGC-1α inhibits endothelial migration at least in part via activation of Notch signaling.
4. Loss of PGC-1α activates EC migration Figure 4.1. Angiogenic stimuli inhibits endothelial PGC-1α expression. (A) Relative PGC 1α mrna abundance in human dermal microvascular ECs stimulated with VEGF (10 ng/ml), S1P (100 nm), or S nitrosoglutathione (GSNO,100mM). GSNO, an NO donor.
4. Loss of PGC-1α activates EC migration Figure 4.2. Loss of PGC-1a activates EC migration. (B and C) Isolated MHECs from PGC 1α / (KO) mice are hypermigratory in scratch assays (B) and Transwell migration assays (C). (D) Capillary formation of KO (n = 31) and wild type (WT) (n = 16) mouse aortic explants.
4. Loss of PGC-1α activates EC migration Figure 4.3. Loss of PGC-1α inhibits Notch target genes expression. (E) mrna expression of Notch target genes was depressed in ECs isolated from KO mice, versus wild type controls.
4. Loss of PGC-1α activates EC migration Figure 4.4. High expression of Rac1 in PGC-1α KO ECs. (F) GTP Rac1 pull down assay in WT and KO MHECs. (G) VEGF (10 ng/ml) induced Transwell migration of KO and WT MHECs, with or without DPI (10mM), L NAME, or Rac inhibitor (NSC23766, 30mM).
Conclusion Ⅳ PGC-1α powerfully inhibits Rac/Akt/eNOS signaling and migration in ECs.
Research Route Diabetes PGC-1α Endothelial dysfunction Over-Expression Knock-Out Migration Transwell assay Scratch assay Notch signaling Tube formation Angiogenesis
5. Endothelial PGC-1α inhibits angiogenesis in vivo Figure 5.1. Overexpression of endothelial PGC-1α blunts the formation of new blood vessels. (A) In vivo vasculogenesis assay using mesenchymal progenitor cells and human endothelial colony forming cells (ECFCs) expressing PGC 1α coinjected nude mice versus control vector. Left, sample appearance of the Matrigel plugs. Middle, hematoxylin and eosin staining of plug sections. Right, quantification of vessel density.
5. Endothelial PGC-1α inhibits angiogenesis in vivo Figure 5.2. Induced expression of PGC-1α in ECs. (B) Schema of Tet off and Tet on tetracycline inducible, endothelial specific PGC 1α transgenic (Tg) mice. (C) mrna abundance of PGC 1α in freshly isolated lung ECs from Tet on mouse versus control.
5. Endothelial PGC-1α inhibits angiogenesis in vivo Figure 5.3. Transgenic expression of PGC-1α inhibits re-endothelialization. Quantification (D) and representative images (E) of re endothelialization following wire injury of mouse carotid arteries in Tet off transgenic animals.
5. Endothelial PGC-1α inhibits angiogenesis in vivo Figure 5.4. Transgenic expression of PGC-1α inhibits wound healing. Quantification (F) and representative images (G) of skin wound healing in Tet off transgenic animals.
5. Endothelial PGC-1α inhibits angiogenesis in vivo Figure 5.5. Transgenic expression of PGC-1α inhibits the rate of blood flow recovery in hindlimb ischemia models. Quantification of blood flow recovery (H) and necrotic toes (I) after induced hindlimb ischemia in Tet on animals.
Conclusion Ⅴ Expression of PGC-1α in ECs in vivo mimics multiple aspects of diabetic EC dysfunction.
6. Loss of endothelial PGC-1α rescues diabetic endothelial dysfunction Figure 6.1. Loss of endothelial PGC-1α accelerates wound healing in diabetic mice. (A) Skin wound healing in endothelial specific PGC 1α knockout (EC KO) and control mice, either nondiabetic or rendered diabetic by treatment with STZ. (B) Skin wound healing in EC KO and control mice that were fed dhfdf for 12 months.
6. Loss of endothelial PGC-1α rescues diabetic endothelial dysfunction Figure 6.2. Loss of endothelial PGC-1α recovers blood flow and decreases the number of necrotic toes. Recovery of blood flow after surgical induction of hindlimb ischemia in type 1 diabetic EC KO mice: (C) representative day 14 laser Doppler perfusion images, (D) quantification of blood perfusion recovery in the ischemic limbs, (E) number of necrotic toes in the ischemic i foot at day 28, and (F) representative appearance of diabetic i mouse ischemic i limbs at day 14.
6. Loss of endothelial PGC-1α rescues diabetic endothelial dysfunction Figure 6.3. Loss of endothelial PGC-1α recovers blood flow and decreases the number of necrotic toes. Recovery of blood flow after hind limb ischemia in type 2 diabetic EC KO mice: (G) quantification of blood perfusion recovery in the ischemic limbs and (H) number of necrotic toes in the ischemic foot at day 21.
Conclusion Ⅵ Deletion of PGC-1α in ECs in large part rescues numerous aspects of endothelial dysfunction in diabetes.
Summary
Significance Supporting the notionthatthat induction ofpgc 1α in ECs mediates endothelial dysfunction and vascular complications in diabetes. Identifying an important relationship between angiogenesis and a central regulator of metabolism. Revealing theopposingeffects ofpgc 1α in different cells which Revealing the opposing effects of PGC 1α in different cells which stresses the need for caution in therapies aimed at PGC 1α in this and other contexts.