MicroRNA-24 targets Notch and other vascular morphogens to regulates post-ischemic microvascular responses in limb muscles

MicroRNAs (miRs) regulate complex processes, including angiogenesis, by targeting multiple mRNAs. miR-24-3p-3p directly represses eNOS, GATA2, and PAK4 in endothelial cells (ECs), thus inhibiting angiogenesis during development and in the infarcted heart. miR-24-3p is widely expressed in cardiovascular cells, suggesting that it could additionally regulate angiogenesis by acting on vascular mural cells. Here, we have investigated: (1) new miR-24-3p targets; (2) the expression and the function of miR-24-3p in human vascular ECs; (3) the impact of miR-24-3p inhibition in the angiogenesis reparative response to limb ischemia in mice. Using bioinformatics target prediction platforms and 3′-UTR luciferase assays, we newly identified Notch1 and its Delta-like ligand 1 (Dll1) to be directly targeted by miR-24-3p. miR-24-3p was expressed in human ECs and pericytes cultured under normal conditions. Exposure to hypoxia increased miR-24-3p in ECs but not in pericytes. Transfection with a miR-24-3p precursor (pre-miR-24-3p) increased miR-24-3p expression in ECs, reducing the cell survival, proliferation, and angiogenic capacity. Opposite effects were caused by miR-24-3p inhibition. The anti-angiogenic action of miR-24-3p overexpression could be prevented by simultaneous adenovirus (Ad)-mediated delivery of constitutively active Notch intracellular domain (NICD) into cultured ECs. We next demonstrated that reduced Notch signalling contributes to the anti-angiogenic effect of miR-24-3p in vitro. In a mouse unilateral limb ischemia model, local miR-24-3p inhibition (by adenovirus-mediated miR-24-3p decoy delivery) restored endothelial Notch signalling and increased capillary density. However, the new vessels appeared disorganised and twisted, worsening post-ischemic blood perfusion recovery. To better understand the underpinning mechanisms, we widened the search for miR-24-3p target genes, identifying several contributors to vascular morphogenesis, such as several members of the Wingless (Wnt) signalling pathway, β-catenin signalling components, and VE-cadherin, which synergise to regulate angiogenesis, pericytes recruitment to neoformed capillaries, maturation, and stabilization of newly formed vessels. Among those, we next focussed on β-catenin to demonstrate that miR-24-3p inhibition reduces β-catenin expression in hypoxic ECs, which is accompanied by reduced adhesion of pericytes to ECs. In summary, miR-24-3p differentially targets several angiogenesis modulators and contributes to autonomous and non-autonomous EC crosstalk. In ischemic limbs, miR-24-3p inhibition increases the production of dysfunctional microvessels, impairing perfusion. Caution should be observed in therapeutic targeting of miR-24-3p

Enhanced immunological recovery with early start of antiretroviral therapy during acute or early HIV infection–results of Italian Network of ACuTe HIV InfectiON (INACTION) retrospective study

ABSTRACT Background: Viral load peak and immune activation occur shortly after exposure during acute or early HIV infection (AEHI). We aimed to define the benefit of early start of antiretroviral treatment (ART) during AEHI in terms of immunological recovery, virological suppression, and treatment discontinuation. Setting: Patients diagnosed with AEHI (Fiebig stages I-V) during 2008-2014 from an analysis of 20 Italian centers. Methods: This was an observational, retrospective, and multicenter study. We investigated the ef- fect of early ART (defined as initiation within 3 months from AEHI diagnosis) on time to virolog- ical suppression, optimal immunological recovery (defined as CD4 count ≥ 500/μL, CD4 ≥ 30%, and CD4/CD8 ≥ 1), and first-line ART regimen discontinuation by Cox regression analysis. Results: There were 321 patients with AEHI included in the study (82.9% in Fiebig stage III-V). At diagnosis, the median viral load was 5.67 log10 copies/mL and the median CD4 count was 456 cells/μL. Overall, 70.6% of patients started early ART (median time from HIV diagnosis to ART initiation 12 days, IQR 6-27). Higher baseline viral load and AEHI diagnosis during 2012-2014 were independently associated with early ART. HBV co-infection, baseline CD4/CD8 ≥ 1, lower baseline HIV-RNA, and AEHI diagnosis in recent years (2012-2014) were independently associ- ated with a shorter time to virological suppression. Early ART emerged as an independent predic- tor of optimal immunological recovery after adjustment for baseline CD4 (absolute and percent- age count) and CD4/CD8 ratio. The only independent predictor of first-line ART discontinuation was an initial ART regimen including > 3 drugs. Conclusions: In a large cohort of well-characterized patients with AEHI, we confirmed the ben- eficial role of early ART on CD4+ T-cell recovery and on rates of CD4/CD8 ratio normalization. Moreover, we recognized baseline CD4/CD8 ratio as an independent factor influencing time to virological response in the setting of AEHI, thus giving new insights into research of immunolog- ical markers associated with virological control

Local inhibition of microRNA-24 improves reparative angiogenesis and left ventricle remodeling and function in mice with myocardial infarction

Myocardial infarction (MI) is the leading cause of death worldwide. MicroRNAs regulate the expression of their target genes, thus mediating a plethora of pathophysiological functions. Recently, miRNA-24 emerged as an important but controversial miRNA involved in post-MI responses. Here, we aimed at clarifying the effect of adenovirus-mediate intra-myocardial delivery of a decoy for miRNA-24 in a mouse MI model and to investigate the impact of miRNA-24 inhibition on angiogenesis and cardiovascular apoptosis. After MI induction, miRNA-24 expression was lower in the peri-infarct tissue and its resident cardiomyocytes and fibroblasts; while it increased in endothelial cells (ECs). Local adenovirus-mediated miRNA-24 decoy delivery increased angiogenesis and blood perfusion in the peri-infarct myocardium, reduced infarct size, induced fibroblast apopotosis and overall improved cardiac function. Notwithstanding these beneficial effects, miRNA-24 decoy increased cardiomyocytes apoptosis. In vitro, miRNA-24 inhibition enhanced ECs survival, proliferation and networking in capillary-like tubes and induced cardiomyocyte and fibroblast apoptosis. Finally, we identified eNOS as a novel direct target of miR-24 in human cultured ECs and in vivo. Our findings suggest that miRNA-24 inhibition exerts distinct biological effects on ECs, cardiomyocytes and fibroblasts. The overall result of post-infarction local miRNA-24 inhibition appears to be therapeutic

EZH2 modulates angiogenesis in vitro and in a mouse model of limb ischemia

Epigenetic mechanisms may regulate the expression of pro-angiogenic genes, thus affecting reparative angiogenesis in ischemic limbs. The enhancer of zest homolog-2 (EZH2) induces thtrimethylation of lysine 27 on histone H3 (H3K27me3), which represses gene transcription. We explored (i) if EZH2 expression is regulated by hypoxia and ischemia; (ii) the impact of EZH2 on the expression of two pro-angiogenic genes: eNOS and BDNF; (iii) the functional effect of EZH2 inhibition on cultured endothelial cells (ECs); (iv) the therapeutic potential of EZH2 inhibition in a mouse model of limb ischemia (LI). EZH2 expression was increased in cultured ECs exposed to hypoxia (control: normoxia) and in ECs extracted from mouse ischemic limb muscles (control: absence of ischemia). EZH2 increased the H3K27me3 abundance onto regulatory regions of eNOS and BDNF promoters. In vitro RNA silencing or pharmacological inhibition by 3-deazaneplanocin (DZNep) of EZH2 increased eNOS and BDNF mRNA and protein levels and enhanced functional capacities (migration, angiogenesis) of ECs under either normoxia or hypoxia. In mice with experimentally induced LI, DZNep increased angiogenesis in ischaemic muscles, the circulating levels of pro-angiogenic hematopoietic cells and blood flow recovery. Targeting EZH2 for inhibition may open new therapeutic avenues for patients with limb ischemia