S100A1 Deficiency Impairs Postischemic Angiogenesis Via Compromised Proangiogenic Endothelial Cell Function and Nitric Oxide Synthase Regulation

Abstract

Rationale Mice lacking the EF-hand Ca2+ sensor S100A1 display endothelial dysfunction due to distorted Ca2+ activated NO generation. Objective To determine the pathophysiological role of S100A1 in endothelial cell (EC) function in experimental ischemic revascularization. Methods and Results Patients with chronic critical lower limb ischemia (CLI) showed almost complete loss of S100A1 expression in hypoxic tissue. Ensuing studies in S100A1 knockout (SKO) mice subjected to femoral artery resection (FAR) unveiled insufficient perfusion recovery and high rates of autoamputation. Defective in vivo angiogenesis prompted cellular studies in SKO ECs and human ECs with siRNA-mediated S100A1 knockdown demonstrating impaired in vitro and in vivo proangiogenic properties (proliferation, migration, tube formation), and attenuated vascular endothelial growth factor (VEGF)- and hypoxia-stimulated eNOS activity. Mechanistically, S100A1 deficiency compromised eNOS activity in ECs both by interrupted stimulatory S100A1/eNOS interaction and PKC hyperactivation that resulted in inhibitory eNOS phosphorylation and enhanced VEGF-receptor 2 (VEGFR2) degradation with attenuated VEGF signaling. Ischemic SKO tissue recapitulated the same molecular abnormalities with insufficient in vivo NO generation. Unresolved ischemia entailed excessive VEGF accumulation in SKO mice with aggravated VEGFR2 degradation and blunted in vivo signaling through the proangiogenic PI3K/Akt/eNOS cascade. NO supplementation strategies rescued defective angiogenesis and salvaged limbs in SKO mice post-FAR. Conclusions Our study shows for the first time downregulation of S100A1 expression in patients with CLI and identifies S100A1 as critical for EC function in postnatal ischemic angiogenesis. These findings link its pathological plasticity in CLI to impaired neovascularization prompting further studies to probe S100A1’s microvascular therapeutic potential.

Bioactive Nanoparticles Improve Calcium Handling in Failing Cardiac Myocytes

“…Thus, our GlcNAc nanoparticles are a viable system for delivery of cargo proteins to CMs for therapeutic effects and also have the potential for dose-dependent delivery into the intact myocardium. Furthermore, the positive effects seen on other cells of the heart such as cardiac fibroblasts [21] and cardiac endothelial cells [22] with S100A1 therapy gives our GlcNAc delivery system the potential to be more comprehensive of a therapy that viral-based therapies that are engineered to specifically express in CMs.…”

Controlled nitric oxide release for tissue repair and regeneration

“…Administration of exogenous NO to elevate NO levels has been recognized as a strategy for tissue regeneration. Increasing evidence suggests that NO is a key mediator in different phases of tissue reparative processes, including collagen deposition (Han et al, 2012), fibroblast migration (Han et al, 2012), and angiogenesis (Kazakov et al, 2012;Most et al, 2013). …”

Induction of microRNA‐138 by pro‐inflammatory cytokines causes endothelial cell dysfunction

“…Previously, we were able to show that S100A1 directly interacts with eNOS, prevents PKC‐mediated phosphorylation of the eNOS inhibitory Thr‐495 site and augments eNOS enzymatic activity in ECs [11]. S100A1 levels are rapidly lost in hypoxic ECs or in ischemic tissues and this correlates with a loss of stimulus‐induced NO production [11]. We recently published that endothelial cell‐type specific regulation of S100A1 in response to hypoxia is achieved via the HIF1‐α dependent induction of miR‐138, which specifically targets a conserved 22 nucleotide sequence in the 3′UTR of S100A1.…”

“…S100A1 is a small EF‐hand Ca 2+ binding protein that relays intracellular Ca 2+ oscillations and regulates vascular tone [7–10]. Previously, we were able to show that S100A1 directly interacts with eNOS, prevents PKC‐mediated phosphorylation of the eNOS inhibitory Thr‐495 site and augments eNOS enzymatic activity in ECs [11]. S100A1 levels are rapidly lost in hypoxic ECs or in ischemic tissues and this correlates with a loss of stimulus‐induced NO production [11].…”