Platelet-Specific Deletion of Cyclooxygenase-1 Ameliorates Dextran Sulfate Sodium–Induced Colitis in Mice

Abstract

Inflammatory bowel disease (IBD) is associated with an increased risk for thromboembolism, platelet activation, and abnormalities in platelet number and size. In colitis, platelets can extravasate into the colonic interstitium. We generated a mouse with a specific deletion of cyclooxygenase (COX)-1 in megakaryocytes/platelets [(COX-1 conditional knockout (cKO)] to clarify the role of platelet activation in the development of inflammation and fibrosis in dextran sodium sulfate (DSS)induced colitis. The disease activity index was assessed, and colonic specimens were evaluated for histologic features of epithelial barrier damage, inflammation, and fibrosis. Cocultures of platelets and myofibroblasts were performed. We found that the specific deletion of COX-1 in platelets, which recapitulated the human pharmacodynamics of low-dose aspirin, that is, suppression of platelet thromboxane (TX)A 2 production associated with substantial sparing of the systemic production of prostacyclin, resulted in milder symptoms of colitis, in the acute phase, and almost complete recovery from the disease after DSS withdrawal. Reduced colonic accumulation of macrophages and myofibroblasts and collagen deposition was found. Platelet-derived TXA 2 enhanced the ability of myofibroblasts to proliferate and migrate in vitro, and these effects were prevented by platelet COX-1 inhibition or antagonism of the TXA 2 receptor. Our findings allow a significant advance in the knowledge of the role of platelet-derived TXA 2 in the development of colitis and fibrosis in response to intestinal damage and provide the rationale to investigate the potential efficacy of the antiplatelet agent low-dose aspirin in limiting the inflammatory response and fibrosis associated with IBD. SIGNIFICANCE STATEMENT Inflammatory bowel disease (IBD) is characterized by the development of a chronic inflammatory response, which can lead to intestinal fibrosis for which currently there is no medical treatment. Through the generation of a mouse with specific deletion of cyclooxygenase-1 in megakaryocytes/platelets, which recapitulates the human pharmacodynamics of lowdose aspirin, we demonstrate the important role of plateletderived thromboxane A 2 in the development of experimental colitis and fibrosis, thus providing the rationale to investigate the potential efficacy of low-dose aspirin in limiting the inflammation and tissue damage associated with IBD.

The Roles of Various Prostaglandins in Fibrosis: A Review

“…In both human and murine platelets, the production of TXA2 is associated with COX-1 activity. COX-1 deletion in mouse platelets along with a deficiency of TXA2 highlights the role of platelet-derived TXA2 in the development of colitis and fibrosis induced by epithelial damage by inhibiting the proliferation and migration of myofibroblasts [ 102 ]. Due to the profibrotic effect of TXA2, various TP receptor antagonists have been used in antifibrosis research.…”

The antiplatelet agent revacept prevents the increase of systemic thromboxane A2 biosynthesis and neointima hyperplasia

“…Collectively our findings sustain the distinct roles of platelets beyond their fundamental participation in primary hemostasis. As previously shown in cocultures with myofibroblasts, platelet-derived TXA 2 induces morphological changes and enhances their capacity to proliferate and migrate, thus contributing to tissue fibrosis 23 . Moreover, we have shown that the interaction of platelets with colon cancer cells translates into the overexpression of COX-2, a hallmark of malignancy, and the induction of marker genes of epithelial-mesenchymal transition 21 .…”

“…Cell lysates were mixed with sodium dodecyl sulfate (SDS)(Sigma-Aldrich) sample buffer and heated to 95 °C for 5 min. Proteins (15 μg) were analyzed by SDS polyacrylamide gel electrophoresis (SDS-PAGE) 21,23 . Anti-COX-2, anti-COX-1 polyclonal antibodies (1:1000, Cayman Chemical), GAPDH polyclonal antibody (1:1000, Santa Cruz Biotechnology), or anti-β-actin polyclonal antibody (1:1000, Santa Cruz Biotechnology) were used 21,23 .…”

“…Proteins (15 μg) were analyzed by SDS polyacrylamide gel electrophoresis (SDS-PAGE) 21,23 . Anti-COX-2, anti-COX-1 polyclonal antibodies (1:1000, Cayman Chemical), GAPDH polyclonal antibody (1:1000, Santa Cruz Biotechnology), or anti-β-actin polyclonal antibody (1:1000, Santa Cruz Biotechnology) were used 21,23 . Quantification of optical density (OD) of different specific bands was carried out using Alliance 4.7 and Alliance 1 D software (UVITEC, Cambridge, UK) and normalized to the OD of β-actin or GAPDH.…”

Multifaceted Functions of Platelets in Cancer: From Tumorigenesis to Liquid Biopsy Tool and Drug Delivery System

“…In colonic mucosa, these events induce a tissue microenvironment promoting intestinal neoplasia [8]. Enhanced levels of TXA 2 activate fibroblasts, which acquire proliferative and migratory properties [38]. Moreover, plateletderived molecules can induce angiogenesis [39].…”