Dengue Virus NS1 Disrupts the Endothelial Glycocalyx, Leading to Hyperpermeability

Abstract

Dengue is the most prevalent arboviral disease in humans and a major public health problem worldwide. Systemic plasma leakage, leading to hypovolemic shock and potentially fatal complications, is a critical determinant of dengue severity. Recently, we and others described a novel pathogenic effect of secreted dengue virus (DENV) non-structural protein 1 (NS1) in triggering hyperpermeability of human endothelial cells in vitro and systemic vascular leakage in vivo. NS1 was shown to activate toll-like receptor 4 signaling in primary human myeloid cells, leading to secretion of pro-inflammatory cytokines and vascular leakage. However, distinct endothelial cell-intrinsic mechanisms of NS1-induced hyperpermeability remained to be defined. The endothelial glycocalyx layer (EGL) is a network of membrane-bound proteoglycans and glycoproteins lining the vascular endothelium that plays a key role in regulating endothelial barrier function. Here, we demonstrate that DENV NS1 disrupts the EGL on human pulmonary microvascular endothelial cells, inducing degradation of sialic acid and shedding of heparan sulfate proteoglycans. This effect is mediated by NS1-induced expression of sialidases and heparanase, respectively. NS1 also activates cathepsin L, a lysosomal cysteine proteinase, in endothelial cells, which activates heparanase via enzymatic cleavage. Specific inhibitors of sialidases, heparanase, and cathepsin L prevent DENV NS1-induced EGL disruption and endothelial hyperpermeability. All of these effects are specific to NS1 from DENV1-4 and are not induced by NS1 from West Nile virus, a related flavivirus. Together, our data suggest an important role for EGL disruption in DENV NS1-mediated endothelial dysfunction during severe dengue disease.

Dengue: knowledge gaps, unmet needs, and research priorities

“…142 NS1 was also shown to induce hyperpermeability in human endothelial cell monolayers independent of cytokines via disruption of the glycocalyx layer that lines the endothelium. 143 These findings identify new potential targets for dengue therapeutics and support inclusion of NS1 in dengue vaccines.…”

Heparanase Upregulation Contributes to Porcine Reproductive and Respiratory Syndrome Virus Release

“…Processing and activation of heparanase occur after proteolytic processing by cathepsin L, a characteristic lysosomal cysteine proteinase of the papain superfamily of peptidases that is implicated in multiple physiological and pathological processes (23)(24)(25). To investigate whether PRRSV infection activates heparanase via cathepsin L, cathepsin L activity in Marc-145 cells was initially assessed at various times or MOIs after PRRSV infection using a Magic Red cathepsin L detection kit.…”

“…Since HS is used by many viruses for initial attachment to target cells, it is reasonable to assume that heparanase might be involved in the pathogenesis of other viruses as well. It has been reported that dengue virus nonstructural protein 1 (NS1) disrupts the endothelial glycocalyx layer on human pulmonary microvascular endothelial cells by NS1-induced expression of sialidases and heparanase (23). Furthermore, heparanase is upregulated in numerous human diseases such as cancer, diabetes, renal disease, and Alzheimer's disease (35,36).…”

Transient Monocytosis Subjugates Low Platelet Count in Adult Dengue Patients

“…Patients with DHF had both the lowest platelet count and highest aPTT on day 5, which might render them the most likely to have bleeding episodes after day 5 [1]. However, bleeding episodes depend on several factors, including vasculopathy, thrombocytopenia, platelet capacity, prothrombin-complex deficiency, and dengue viral NS1 protein [46]. Experimental ex vivo investigations revealed that platelets upon exposure to DENV enhanced the capacity of engulfment by monocytes, which altered the phenotypes toward macrophages or dendritic-like cells after the phagocytosis of the DENV-activated platelets.…”