Association between plasma glycocalyx component levels and poor prognosis in severe influenza type A (H1N1)

Predictive role of glycocalyx components and MMP-9 in cardiopulmonary bypass patients for ICU stay

Background

Shedding of glycocalyx is relevant to worse prognosis in surgical patients, and elevated levels of serum matrix metalloproteinase-9 (MMP-9) are associated with this phenomenon. This study aimed to investigate the dynamic alterations of serum glycocalyx components and MMP-9 during cardiopulmonary bypass (CPB), and evaluate their predictive capacities for prolonged intensive care unit (ICU) stay, as well as their correlation with coagulation dysfunction.

Methods

This retrospective study analyzed serum levels of syndecan-1, heparan sulfate (HS), and MMP-9 at different time points during CPB, and assessed their association with prolonged ICU stay and coagulation dysfunction.

Results

Syndecan-1, HS, and MMP-9 exhibited divergent changes during CPB. Serum levels of syndecan-1 (AUC = 78.0 %) and MMP-9 (AUC = 78.4 %) were validated as reliable predictors for prolonged ICU stay, surpassing the predictive value of creatinine (AUC = 70.0 %). Syndecan-1 (rho = 0.566, P < 0.01 at T1 and rho = 0.526, P < 0.01 at T2) and HS (rho = 0.403, P < 0.05 at T4) exhibited correlations with activated partial thromboplastin time (APTT) ratio beyond the normal range.

Conclusions

Our findings advocate the potential efficacy of serum glycocalyx components and MMP-9 as early predictive indicators for extended ICU stay following cardiac surgery with CPB. Additionally, we observed a correlation between glycocalyx disruption during CPB and coagulation dysfunction. Further studies with expansive cohorts are warranted to consolidate our findings and explore the predictive potential of other glycocalyx components.

Circulating hyaluronic acid signature in CAP and ARDS - the role of pneumolysin in hyaluronic acid shedding

Shedding of hyaluronan (HA), the component of endothelial cell (EC) glycocalyx, has been associated with acute lung injury. HA degradation allows plasma proteins and fluid to penetrate across the vascular wall leading to lung edema formation and leukocyte recruitment. Here, we analyzed sHA levels and size in patients with community-acquired pneumonia (CAP) and acute respiratory distress syndrome (ARDS), correlated them to disease severity, and evaluated the impact of pneumolysin (PLY), the Streptococcus pneumoniae (S.p.) exotoxin, on HA shedding from human pulmonary microvascular EC (HPMVEC). sHA levels were elevated in CAP and ARDS and correlated with the CRB65 severity score and with markers of inflammation (interleukin-6), EC activation (E-selectin), and basement membrane destruction (collagen IV). Furthermore, sHA levels were associated with an increase in 28-day mortality. Small and large sHA fragments were detected in plasma of most severe CAP or ARDS patients, and the presence of large sHA fragments was accompanied by the elevated levels of circulating collagen IV. In vitro, PLY induced sHA release from HPMVEC. This effect was dependent on reactive oxygen species (ROS) production and was not associated with endothelial barrier dysfunction. Conversely, HA shedding was impaired following HPMVEC infection with a S.p. PLY-deficient mutant. Our study identifies association between the severity of CAP and ARDS and the levels and size of sHA in plasma. It links sHA levels with, inflammation, EC activation status and basement membrane disassembly in ARDS and provides insights into the mechanism of HA shedding during infection.

Glycocalyx degradation and the endotheliopathy of viral infection

The endothelial glycocalyx (EGX) contributes to the permeability barrier of vessels and regulates the coagulation cascade. EGX damage, which occurs in numerous disease states, including sepsis and trauma, results in endotheliopathy. While influenza and other viral infections are known to cause endothelial dysfunction, their effect on the EGX has not been described. We hypothesized that the H1N1 influenza virus would cause EGX degradation. Human umbilical vein endothelial cells (HUVECs) were exposed to varying multiplicities of infection (MOI) of the H1N1 strain of influenza virus for 24 hours. A dose-dependent effect was examined by using an MOI of 5 (n = 541), 15 (n = 714), 30 (n = 596), and 60 (n = 653) and compared to a control (n = 607). Cells were fixed and stained with FITC-labelled wheat germ agglutinin to quantify EGX. There was no difference in EGX intensity after exposure to H1N1 at an MOI of 5 compared to control (6.20 vs. 6.56 Arbitrary Units (AU), p = 0.50). EGX intensity was decreased at an MOI of 15 compared to control (5.36 vs. 6.56 AU, p<0.001). The degree of EGX degradation was worse at higher doses of the H1N1 virus; however, the decrease in EGX intensity was maximized at an MOI of 30. Injury at MOI of 60 was not worse than MOI of 30. (4.17 vs. 4.47 AU, p = 0.13). The H1N1 virus induces endothelial dysfunction by causing EGX degradation in a dose-dependent fashion. Further studies are needed to characterize the role of this EGX damage in causing clinically significant lung injury during acute viral infection.

Heparan Sulfate and Sialic Acid in Viral Attachment: Two Sides of the Same Coin?

Sialic acids and heparan sulfates make up the outermost part of the cell membrane and the extracellular matrix. Both structures are characterized by being negatively charged, serving as receptors for various pathogens, and are highly expressed in the respiratory and digestive tracts. Numerous viruses use heparan sulfates as receptors to infect cells; in this group are HSV, HPV, and SARS-CoV-2. Other viruses require the cell to express sialic acids, as is the case in influenza A viruses and adenoviruses. This review aims to present, in a general way, the participation of glycoconjugates in viral entry, and therapeutic strategies focused on inhibiting the interaction between the virus and the glycoconjugates. Interestingly, there are few studies that suggest the participation of both glycoconjugates in the viruses addressed here. Considering the biological redundancy that exists between heparan sulfates and sialic acids, we propose that it is important to jointly evaluate and design strategies that contemplate inhibiting the interactions of both glycoconjugates. This approach will allow identifying new receptors and lead to a deeper understanding of interspecies transmission.