Fibroblast Growth Factor Signaling Mediates Pulmonary Endothelial Glycocalyx Reconstitution.

The endothelial glycocalyx is a heparan sulfate (HS)-rich endovascular structure critical to endothelial function. Accordingly, endothelial glycocalyx degradation during sepsis contributes to tissue edema and organ injury. We determined the endogenous mechanisms governing pulmonary endothelial glycocalyx reconstitution, and if these reparative mechanisms are impaired during sepsis. We performed intravital microscopy of wild-type and transgenic mice to determine the rapidity of pulmonary endothelial glycocalyx reconstitution after nonseptic (heparinase-III mediated) or septic (cecal ligation and puncture mediated) endothelial glycocalyx degradation. We used mass spectrometry, surface plasmon resonance, and in vitro studies of human and mouse samples to determine the structure of HS fragments released during glycocalyx degradation and their impact on fibroblast growth factor receptor (FGFR) 1 signaling, a mediator of endothelial repair. Homeostatic pulmonary endothelial glycocalyx reconstitution occurred rapidly after nonseptic degradation and was associated with induction of the HS biosynthetic enzyme, exostosin (EXT)-1. In contrast, sepsis was characterized by loss of pulmonary EXT1 expression and delayed glycocalyx reconstitution. Rapid glycocalyx recovery after nonseptic degradation was dependent upon induction of FGFR1 expression and was augmented by FGF-promoting effects of circulating HS fragments released during glycocalyx degradation. Although sepsis-released HS fragments maintained this ability to activate FGFR1, sepsis was associated with the downstream absence of reparative pulmonary endothelial FGFR1 induction. Sepsis may cause vascular injury not only via glycocalyx degradation, but also by impairing FGFR1/EXT1-mediated glycocalyx reconstitution.

A model-specific role of microRNA-223 as a mediator of kidney injury during experimental sepsis.

Sepsis outcomes are heavily dependent on the development of septic organ injury, but no interventions exist to interrupt or reverse this process. microRNA-223 (miR-223) is known to be involved in both inflammatory gene regulation and host-pathogen interactions key to the pathogenesis of sepsis. The goal of this study was to determine the role of miR-223 as a mediator of septic kidney injury. Using miR-223 knockout mice and multiple models of experimental sepsis, we found that miR-223 differentially influences acute kidney injury (AKI) based on the model used. In the absence of miR-223, mice demonstrated exaggerated AKI in sterile models of sepsis (LPS injection) and attenuated AKI in a live-infection model of sepsis (cecal ligation and puncture). We demonstrated that miR-223 expression is induced in kidney homogenate after cecal ligation and puncture, but not after LPS or fecal slurry injection. We investigated additional potential mechanistic explanations including differences in peritoneal bacterial clearance and host stool virulence. Our findings highlight the complex role of miR-223 in the pathogenesis of septic kidney injury, as well as the importance of differences in experimental sepsis models and their consequent translational applicability.

First-in-Class Phosphorylated-p68 Inhibitor RX-5902 Inhibits ß-Catenin Signaling and Demonstrates Antitumor Activity in Triple-Negative Breast Cancer.

RX-5902 is a first-in-class anticancer agent targeting phosphorylated-p68 and attenuating nuclear shuttling of ß-catenin. The purpose of this study was to evaluate the efficacy of RX-5902 in preclinical models of triple-negative breast cancer (TNBC) and to explore effects on ß-catenin expression. A panel of 18 TNBC cell lines was exposed to RX-5902, and changes in proliferation, apoptosis, cellular ploidy, and effector protein expression were assessed. Gene expression profiling was used in sensitive and resistant cell lines with pathway analysis to explore pathways associated with sensitivity to RX-5902. The activity of RX-5902 was confirmed in vivo in cell line and patient-derived tumor xenograft (PDX) models. RX-5902 demonstrated potent antiproliferative activity in vitro against TNBC cell lines with an average IC50 of 56 nmol/L in sensitive cell lines. RX-5902 treatment resulted in the induction of apoptosis, G2-M cell-cycle arrest, and aneuploidy in a subset of cell lines. RX-5902 was active in vivo against TNBC PDX models, and treatment resulted in a decrease in nuclear ß-catenin. RX-5902 exhibited dose-proportional pharmacokinetics and plasma and tumor tissue in nude mice. Pathway analysis demonstrated an increase in the epithelial-to-mesenchymal transformation (EMT), TGFß, and Wnt/ß-catenin pathways associated with sensitivity to RX-5902. RX-5902 is active against in vitro and in vivo preclinical models of TNBC. Target engagement was confirmed with decreases in nuclear ß-catenin and MCL-1 observed, confirming the proposed mechanism of action. This study supports the continued investigation of RX-5902 in TNBC and combinations with immunotherapy.

Circulating Heparan Sulfate Fragments Attenuate Histone-Induced Lung Injury Independently of Histone Binding.

Extracellular histones are cationic damage-associated molecular pattern molecules capable of directly inducing cellular injury via charge-mediated interactions with plasma membranes. Accordingly, histones released into the plasma during critical illness are known to contribute to the onset and propagation of lung injury. Vascular injury (with consequent degradation of the endothelial glycocalyx) simultaneously releases anionic heparan sulfate fragments (hexa- to octasaccharides in size) into the plasma. It is unknown whether this endogenous release of heparan sulfate fragments modulates charge-dependent histone cytotoxicity, or if exogenous heparan sulfate fragments could therapeutically attenuate histone-induced lung injury. Using isothermic calorimetry, we found that extracellular histones only bind to heparan sulfate fragments ≥ 10 saccharides in size, suggesting that glycocalyx-derived heparan sulfate hexa/octasaccharides are incapable of intercepting/neutralizing circulating histones. However, we found that even heparan sulfate fragments incapable of histone binding (e.g., tetrasaccharides) attenuated histone-induced lung injury in vivo, suggesting a direct, size-independent protective effect of heparan sulfate. We found that histones had no effect on human neutrophils ex vivo but exerted toll-like receptor-independent cytotoxicity on human pulmonary microvascular endothelial cells in vitro. This cytotoxicity could be prevented by either the addition of negatively charged (i.e., highly sulfated) heparan sulfate tetrasaccharides (incapable of binding histones) or decasaccharides (capable of binding histones). Taken together, our findings suggest that heparan sulfate oligosaccharides may directly exert pulmonary endothelial-protective effects that attenuate histone-mediated lung injury.