Intraluminal tranexamic acid inhibits intestinal sheddases and mitigates gut and lung injury and inflammation in a rodent model of hemorrhagic shock

Abstract

Background: Intravenous tranexamic acid (TXA) is an effective adjunct after hemorrhagic shock (HS) because of its antifibrinolytic properties. TXA is also a serine protease inhibitor, and recent laboratory data demonstrated that intraluminal TXA into the small bowel inhibited digestive proteases and protected the gut. A Disintegrin And Metalloproteinase 17 (ADAM-17) and tumor necrosis factor α (TNF-α) are effective sheddases of intestinal syndecan-1, which when shed, exposes the underlying intestinal epithelium to digestive proteases and subsequent systemic insult. We therefore hypothesized that intraluminal TXA as a serine protease inhibitor would reduce intestinal sheddases and syndecan-1 shedding, mitigating gut and distant organ (lung) damage.

Methods: Mice underwent 90 minutes of HS to a mean arterial pressure of 35 ± 5 mm Hg followed by the intraluminal administration of TXA or vehicle. After 3 hours, the small intestine, lung, and blood were collected for analysis.

Results: Intraluminal TXA significantly reduced gut and lung histopathologic injury and inflammation compared with HS alone. Gut, lung, and systemic ADAM-17 and TNF-α were significantly increased by HS but lessened by TXA. In addition, gut and lung syndecan-1 immunostaining were preserved and systemic shedding lessened after TXA. TXA reduced ADAM-17 and TNF-α, but not syndecan-1, in TXA-sham animals compared with sham vehicles.

Conclusion: Results of the present study demonstrate a beneficial effect of intraluminal TXA in the gut and lung after experimental HS in part because of the inhibition of the syndecan-1 shedding by ADAM-17 and TNF-α. Further studies are needed to determine if orally administered TXA could provide similar intestinal protection and thus be of potential benefit to patients with survivable hemorrhage at risk for organ injury. This is particularly relevant in patients or soldiers who may not have access to timely medical care.

Figure 1. Intraluminal tranexamic acid reduces gut injury and inflammation following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, small intestine was analyzed for histopathologic injury expressed as the % of injured villi with representative images shown. Inflammation was assessed by measuring myeloperoxidase activity. Results are expressed as mean ± SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA-tranexamic acid

Figure 2. Intraluminal tranexamic acid reduces pulmonary injury and inflammation following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, lungs were analyzed for histopathologic injury using a three point scoring system; representative photomicrographs are shown. Myeloperoxidase immunofluorescence staining was used to assess lung inflammation; representative images shown along with the corresponding images. Results are expressed as mean SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA- tranexamic acid; MPO=myeloperoxidase; RFU= relative fluorescent units

Figure 3. Intestinal ADAM-17 lessened by intraluminal tranexamic acid following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, small intestine was analyzed for A. Intestinal ADAM-17 protein and B. Intestinal ADAM-17 activity. Results are expressed as mean ± SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA= tranexamic acid; ADAM-17= A disintegrin and metalloproteinase

Figure 3. Intestinal ADAM-17 lessened by intraluminal tranexamic acid following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, small intestine was analyzed for A. Intestinal ADAM-17 protein and B. Intestinal ADAM-17 activity. Results are expressed as mean ± SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA= tranexamic acid; ADAM-17= A disintegrin and metalloproteinase

Figure 4. Intestinal syndecan-1 was preserved by intraluminal tranexamic acid following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, small intestine was immunostained for intestinal syndecan-1. Shown are immunostained images (100x magnification) and the corresponding quantitation. Results are expressed as mean ± SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA= tranexamic acid; RFU= relative fluorescent units

Figure 5. Pulmonary ADAM-17 is reduced by intraluminal tranexamic acid following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, lungs were analyzed for A. Pulmonary ADAM-17 protein and B. Pulmonary ADAM-17 activity. Results are expressed as mean ± SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA= tranexamic acid; ADAM-17= A disintegrin and metalloproteinase;

Figure 6. Pulmonary syndecan-1 is maintained by intraluminal tranexamic acid following hemorrhagic shock

C57BL/6J mice underwent 90 minutes of hemorrhagic shock followed by the intraluminal injection of tranexamic acid into the small intestine. Three hours later, lungs were analyzed for pulmonary syndecan-1. Shown are immunostained images (100x magnification) and the corresponding quantitation. . Results are expressed as mean ± SE; n=8/group. Abbreviations: HS= hemorrhagic shock; TXA= tranexamic acid; RFU= relative fluorescent units.