PULMONARY VASCULAR ENDOTHELIAL GLYCOCALYX DEGRADATION CONTRIBUTES TO ACUTE LUNG INJURY IN EXPERIENCING HEATSTROKE

<jats:title>ABSTRACT</jats:title> <jats:p> <jats:bold>Objectives:</jats:bold> This study investigated the role and potential involvement of pulmonary vascular glycocalyx degradation in acute lung injury in rats with severe heatstroke (HS). <jats:bold>Methods:</jats:bold> Rats in an established HS model were exposed to a heated environment for 60 min in an incubator (temperature, 40°C ± 2°C; humidity, 65% ± 5%). Following pretreatment with heparanase III (HPSE III) or heparin, pathological lung injury, arterial blood gas, alveolar barrier disruption, and hemodynamic changes were evaluated. The vascular endothelial structures of the lungs were examined using electron microscopy. The concentration of Evans blue dye in the lungs and arterial blood gas were assessed. An enzyme-linked immunosorbent assay was used to quantify the plasma concentration of heparan sulfate proteoglycan. The expression of glypican-1 and syndecan-1 in pulmonary vessels was measured using immunofluorescence. Western blots were used to detect the expression of TNF-α, IL-6, and vascular endothelial biomarkers in the rat lungs. Pulmonary apoptosis was assessed using a TUNEL (terminal dUTP nick end labeling) assay, and the concentrations of malondialdehyde were measured. <jats:bold>Results:</jats:bold> Glycocalyx shedding aggravated lung injuries. Severe histopathological damage was observed, and indexes of lung function deviated from abnormal ranges. In addition, pulmonary vascular endothelial cells were disrupted. Compared with the HS group, the plasma concentration of heparan sulfate proteoglycan significantly increased in the HPSE group (<jats:italic toggle="yes">P</jats:italic> < 0.05). The expression of glypican-1 and syndecan-1 decreased, and the extravasation of Evans blue dye increased (<jats:italic toggle="yes">P</jats:italic> < 0.01). Endothelial biomarker expression increased in the lung tissue, whereas occludin expression decreased. Moreover, TNF-α and IL-6 were overexpressed following heat stress. Furthermore, apoptosis of pulmonary tissues and the concentration of malondialdehyde in rat lungs increased in the HS and HPSE groups. <jats:bold>Conclusions</jats:bold>: Heatstroke induced pulmonary glycocalyx degradation, which increased vascular permeability and aggravated vascular endothelial dysfunction, contributing to apoptosis, inflammation, and oxidation in the pulmonary tissues.</jats:p>