Effects of therapeutic plasma exchange on the endothelial glycocalyx in septic shock

Abstract

Background Disruption of the endothelial glycocalyx (eGC) is observed in septic patients and its injury is associated with multiple-organ failure and inferior outcomes. Besides this biomarker function, increased blood concentrations of shedded eGC constituents might play a mechanistic role in septic organ failure. We hypothesized that therapeutic plasma exchange (TPE) using fresh frozen plasma might influence eGC-related pathology by removing injurious mediators of eGC breakdown while at the time replacing eGC protective factors. Methods We enrolled 20 norepinephrine-dependent (NE > 0.4 μg/kg/min) patients with early septic shock (onset < 12 h). Sublingual assessment of the eGC via sublingual sidestream darkfield (SDF) imaging was performed. Plasma eGC degradation products, such as heparan sulfate (HS) and the eGC-regulating enzymes, heparanase (Hpa)-1 and Hpa-2, were obtained before and after TPE. A 3D microfluidic flow assay was performed to examine the effect of TPE on eGC ex vivo. Results were compared to healthy controls. Results SDF demonstrated a decrease in eGC thickness in septic patients compared to healthy individuals (p = 0.001). Circulating HS levels were increased more than sixfold compared to controls and decreased significantly following TPE [controls: 16.9 (8–18.6) vs. septic patients before TPE: 105.8 (30.8–143.4) μg/ml, p < 0.001; vs. after TPE: 70.7 (36.9–109.5) μg/ml, p < 0.001]. The Hpa-2 /Hpa-1 ratio was reduced in septic patients before TPE but normalized after TPE [controls: 13.6 (6.2–21.2) vs. septic patients at inclusion: 2.9 (2.1–5.7), p = 0.001; vs. septic patients after TPE: 13.2 (11.2–31.8), p < 0.001]. Ex vivo stimulation of endothelial cells with serum from a septic patient induced eGC damage that could be attenuated with serum from the same patient following TPE. Conclusions Septic shock results in profound degradation of the eGC and an acquired deficiency of the protective regulator Hpa-2. TPE removed potentially injurious eGC degradation products and partially attenuated Hpa-2 deficiency. Trial registration clinicaltrials.gov NCT04231994, retrospectively registered 18 January 2020

Targeting the “sweet spot” in septic shock – A perspective on the endothelial glycocalyx regulating proteins Heparanase-1 and -2

“…In contrast, we and others recently also observed reduced Hpa-1 concentrations in severe septic shock [64] , [65] , which might be due to close binding of Hpa-1′s soluble form to the eGC during HS shedding and therefore, results in lower serum concentrations [66] . Apart from these divergent data on Hpa-1 concentration, Hpa-1 activity is found significantly elevated in diverse septic conditions and has been explored in different tissues, most extensively in the pulmonary microcirculation [38] , [60] .…”

“…In conclusion, the ratio between injurious Hpa-1 and protective Hpa-2 appears crucial for local HS turnover and eGC degradation [22] , [65] . A concurrent increase in Hpa-1 and a reduction in Hpa-2, resulting in an imbalanced Hpa-1/Hpa-2 ratio, may play a crucial role in the pathological host response in sepsis [22] , [65] , [103] .…”

“…Heterogeneous findings concerning Hpa-1 in sepsis exist, all demonstrating elevated Hpa-1 activity but different Hpa-1 concentrations [63] , [64] , [65] . In contrast, a substantial acquired Hpa-2 deficiency has been demonstrated in both murine sepsis models (LPS and CLP) as well as septic patients [22] , [65] .…”

“…Heterogeneous findings concerning Hpa-1 in sepsis exist, all demonstrating elevated Hpa-1 activity but different Hpa-1 concentrations [63] , [64] , [65] . In contrast, a substantial acquired Hpa-2 deficiency has been demonstrated in both murine sepsis models (LPS and CLP) as well as septic patients [22] , [65] . Recently, our group was able to show that Hpa-2 is also decreased in critically ill patients with COVID-19, a disease that can be complicated by overwhelming systemic inflammation and endotheliopathy [103] , [104] , [105] .…”

“…An acquired deficiency of the natural Hpa-1 antagonist Hpa-2 has been demonstrated in both preclinical and clinical investigations in sepsis [22] , [65] . Supplementation with exogenous Hpa-2 attenuates Hpa-1 induced eGC breakdown and subsequent inflammation in septic mice (see above) [22] .…”