Objective
Reduced plasma adiponectin (APN) in diabetic patients is associated with endothelial dysfunction. However, APN knockout animals manifest modest systemic dysfunction unless metabolically challenged. The protein family CTRPs (C1q/TNF-related proteins) has recently been identified as APN paralogs and some CTRP members share APN’s metabolic regulatory function. However, the vasoactive properties of CTRPs remain completely unknown.
Methods and Results
The vasoactivity of currently identified murine CTRP members was assessed in aortic vascular rings and underlying molecular mechanisms was elucidated in HUVECs. Of eight CTRPs, CTRPs 3, 5, and 9 caused significant vasorelaxation. The vasoactive potency of CTRP9 exceeded that of APN (3-fold), and is endothelium-dependent and nitric oxide (NO) mediated. Mechanistically, CTRP9 increased AMPK/Akt/eNOS phosphorylation and increased NO production. AMPK knockdown completely blocked CTRP9-induced Akt/eNOS phosphorylation and NO production. Akt knockdown had no significant effect upon CTRP9-induced AMPK phosphorylation, but blocked eNOS phosphorylation and NO production. Adiponectin receptor 1 (AdipoR1), but not receptor 2, knockdown blocked CTRP9-induced AMPK/Akt/eNOS phosphorylation and NO production. Finally, pre-incubating vascular rings with an AMPK-inhibitor abolished CTRP9-induced vasorelaxive effects.
Conclusion
We have provided the first evidence that CTRP9 is a novel vasorelaxive adipocytokine which may exert vasculoprotective effects via the AdipoR1/AMPK/eNOS dependent/NO mediated signaling pathway.
Background
Obesity/diabetes adversely affects post-ischemic heart remodeling via incompletely understood underlying mechanisms. C1q/TNF-related protein-3 (CTRP3) is a newly identified adipokine exerting beneficial metabolic regulation, similar to adiponectin. The current study determined whether CTRP3 may regulate post-ischemic cardiac remodeling and cardiac dysfunction, and, if so, sought to elucidate the involved underlying mechanisms.
Methods and Results
Male adult mice were subjected to myocardial infarction (MI) via left anterior descending (LAD) coronary artery occlusion. Both the effect of MI upon endogenous CTRP3 expression/production and the effect of exogenous CTRP3 (adenovirus or recombinant CTRP3) replenishment upon MI injury were investigated. MI significantly inhibited adipocyte CTRP3 expression and reduced plasma CTRP3 level, reaching nadir 3 days post-MI. CTRP3 replenishment improved survival rate (P<0.05), restored cardiac function, attenuated cardiomyocyte apoptosis, increased revascularization, and dramatically reduced interstitial fibrosis (P values all <0.01). CTRP3 replenishment had no significant effect upon cardiac AMP-activated protein kinase (AMPK) phosphorylation, but significantly increased Akt phosphorylation and expression of hypoxia inducing factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF). Surprisingly, treatment of human umbilical vascular endothelial cells (HUVECs) with CTRP3 did not directly affect NO production or tube formation. However, pre-conditioned medium from CTRP3-treated cardiomyocytes significantly enhanced HUVEC tube formation, an effect blocked by either pre-treatment of cardiomyocytes with a PI3K inhibitor, or pre-treatment of HUVECs with a VEGF inhibitor. Finally, pre-conditioned medium from CTRP3-knockdown 3T3 cells significantly enhanced hypoxia-induced cardiomyocyte injury.
Conclusions
CTRP3 is a novel anti-apoptotic, pro-angiogenic, and cardioprotective adipokine, whose expression is significantly inhibited following MI.
In patients undergoing multiple valve replacement and prolonged cardiopulmonary bypass, administration of nitric oxide decreased the incidence of acute kidney injury, transition to stage 3 chronic kidney disease, and major adverse kidney events at 30 days, 90 days, and 1 year. Clinical trial registered with ClinicalTrials.gov (NCT01802619).
Transcatheter device closure and surgical repair are effective interventions with excellent midterm results for treating pmVSD in children. Transcatheter device closure has a lower incidence of myocardial injury, less blood transfused, faster recovery, shorter hospital stay, and lower medical expenses. (Transcatheter Closure Versus Surgery of Perimembranous Ventricular Septal Defects; NCT00890799).
Since Notch signaling plays a critical role in stem cells and oncogenesis, we hypothesized that Notch signaling might play roles in cancer stem cells and cancer cells with a stem cell phenotype. In this study, we accessed potential functions of the Notch pathway in the formation of cancer stem cells using human glioma. Using RT-PCR, we found that most human astrogliomas of different grades expressed moderate to high level of Notch receptors and ligands. mRNA of Hes5 but not Hes1, both of which are major downstream molecules of the Notch pathway, was also detected. In human glioma cell lines BT325, U251, SHG-44, and U87, mRNA encoding different types of Notch receptors were detected, but active form of Notch1 (NIC) was only detected in SHG-44 and U87 by Western blot. Interestingly, proliferation of these two glioma cell lines appeared faster than that of the other two lines in which NIC was not detected. We have over-expressed NIC of Notch1 in SHG-44 cells by constitutive transfection to evaluate the effects of Notch signaling on glioma cells. Our results showed that over-expression of NIC in SHG-44 cells promoted the growth and the colony-forming activity of SHG-44 cells. Interestingly, over-expression of NIC increased the formation neurosphere-like colonies in the presence of growth factors. These colonies expressed nestin, and could be induced to cells expressing neuron-, astrocyte-, or oligodendrocyte-specific markers, consistent with phenotypes of neural stem cells. These data suggest that Notch signaling promote the formation of cancer stem cell-like cells in human glioma.
Diabetes exacerbates ischemic heart disease morbidity and mortality via incompletely understood mechanisms. Although adiponectin (APN) reduces myocardial ischemia/reperfusion (MI/R) injury in nondiabetic animals, whether APN's cardioprotective actions are altered in diabetes, a pathologic condition with endogenously reduced APN, has never been investigated. High-fat diet (HD)-induced diabetic mice and normal diet (ND) controls were subjected to MI via coronary artery ligation, and given vehicle or APN globular domain (gAPN, 2 mg/g) 10 min before reperfusion. Compared to ND mice (where gAPN exerted pronounced cardioprotection), HD mice manifested greater MI/R injury, and a tripled gAPN dose was requisite to achieve cardioprotective extent seen in ND mice (i.e., infarct size, apoptosis, and cardiac function). APN reduces MI/R injury via AMPactivated protein kinase (AMPK)-dependent metabolic regulation and AMPK-independent antioxidative/ antinitrative pathways. Compared to ND, HD mice manifested significantly blunted gAPN-induced AMPK activation, basally and after MI/R ( p < 0.05). Although both low-and high-dose gAPN equally attenuated MI/ R-induced oxidative stress (i.e., NADPH oxidase expression and superoxide production) and nitrative stress (i.e., inducible nitric oxide synthase expression, nitric oxide production, and peroxynitrite formation) in ND mice, only high-dose gAPN efficaciously did so in HD mice. We demonstrate for the first time that HD-induced diabetes diminished both AMPK-dependent and AMPK-independent APN cardioprotection, suggesting an unreported diabetic heart APN resistance. Antioxid. Redox Signal. 15, 1779-1788.
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