[Mechanism of heparin-binding protein increasing vascular permeability in early burn].

OBJECTIVE

To investigate the effect of heparin-binding protein (HBP) on the damage of vascular permeability in early burn.

METHODS

(1) Clinical research: 12 patients with severe burns admitted to Suzhou Hospital of Nanjing Medical University from January 1st to August 30th in 2019 were enrolled. Eight patients with severe trauma admitted to the same hospital during the same period were also enrolled as controls to explain the specificity of burn injury. Whole blood samples were obtained within 0.5 hour after admission. The white blood cell count (WBC), absolute value and ratio of neutrophils, and serum HBP levels were measured. Serum samples of 12 patients with severe burn were collected within 9 days after admission, and enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of metabolism products of glycocalyx including syndecan-1 and hyaluronic acid (HA). The correlation between HBP and neutrophils ratio, syndecan-1 and HA were analyzed by linear correlation. (2) Basic research: a 30% total body surface area (TBSA) III degree angle burn model of Sprague-Dawley (SD) rat aged 6-8 weeks was prepared. In low molecular weight heparin (LMWH) intervention group (n = 5), 200 U/kg LMWH was injected subcutaneously immediately and every 2 hours after injury for 4 times in total; the burn group (n = 5) was given the same amount of normal saline. No intervention was given to the normal control group (n = 5). The peripheral venous blood was collected at 0, 2, 4, and 8 hours after injury, and the serum levels of HBP, syndecan-1 and HA were measured; the injury of glycocalyx on pulmonary vascular endothelial cells was observed under transmission electron microscope.

RESULTS

(1) Clinical research results: the WBC, neutrophils absolute value and ratio, and HBP levels were increased in 12 patients with severe burn and 8 patients with severe trauma. There was no significant difference in the WBC, absolute value and ratio of neutrophils between severe burn and severe trauma patients [WBC (×10/L): 14.5±6.1 vs. 10.8±3.6, the absolute value of neutrophils (×10/L): 12.0±5.9 vs. 9.0±4.0, the ratio of neutrophils: 0.81±0.10 vs. 0.79±0.14, all P > 0.05], but the HBP levels in the burn patients were significantly higher than those in the trauma patients (μg/L: 192.92±61.73 vs. 51.17±23.05, P < 0.01). Twelve patients with severe burns had a sharp increase in serum syndecan-1 and HA levels after burns, which continued to maintain high levels and peaked at the 9th day [syndecan-1 (μg/L): 16.02±0.39, HA (μg/L): 106.83±4.90]. The analysis showed that HBP was positively correlated with neutrophils ratio, syndecan-1 and HA in severe burn patients at the 1st day after admission (r values were 0.805, 0.732 and 0.900, respectively, all P < 0.01). It indicated that the sharp increase of neutrophils after the burn released a lot of HBP, and the glycocalyx of the vascular endothelium was severely damaged. (2) Basic research results: the levels of serum HBP, syndecan-1 and HA in the burn group were increased sharply as compared with the normal control group, and continued to increase with time, reaching a peak at 8 hours after burn. In the LMWH intervention group, the serum levels of HBP, syndecan-1 and HA were significantly lower than those in the burn group, and the difference was still statistically significant after 8 hours [HBP (μg/L): 6.47±0.25 vs. 12.48±0.08, syndecan-1 (μg/L): 19.06±1.48 vs. 25.92±3.34, HA (μg/L): 35.76±2.10 vs. 54.91±2.64, all P < 0.01]. The results of transmission electron microscopy showed that in the normal control group, the glycocalyx pulmonary vascular endothelial cells was continuous, evenly distributed and dense. The glycocalyx on pulmonary vascular endothelial cells of rats were significantly damaged and shed 2 hours after burn in the burn group, and no glycocalyx was observed at 8 hours. In the LMWH intervention group, the glycocalyx on pulmonary vascular endothelial cells was damaged and the phenomenon of shedding was significantly relieved, and the glycocalyx could be observed 8 hours after the injury.

CONCLUSIONS

The massive exudation of body fluids and the significant increase of vascular permeability in patients in early burns may be related to the destruction of the glycocalyx on endothelial cells by HBP released from increased neutrophils.