Evidence of Endothelial Dysfunction and Activation of RhoA/Rho Kinase Pathway in Inflammatory Bowel Disease

Background. Inflammatory bowel diseases (IBD) comprise two chronic relapsing intestinal disorders: Crohn's disease (CD) and ulcerative colitis (UC). IBD are the result of an abnormal inflammatory response to intestinal microbes in a genetically susceptible host. Clinically, rectal bleeding, severe diarrhea, weight loss and abdominal pain characterize IBD. Moreover, IBD are associated with a variety of extraintestinal manifestations (EIM). Increased risk of arterial and venous thrombosis in IBD patients, with a 3-fold higher risk for development venous thromboembolism is one of the most important EIM in terms of morbidity and mortality. Although the mechanisms underlying the increased thrombotic risk in IBD are not completely understood, there is evidence of abnormalities in coagulation, fibrinolysis and platelet function. However, in this context, the contribution of the vessel wall has been less explored. Endothelial dysfunction (ED) and abnormal activation of RhoA/Rho kinase (ROCK) pathway have been shown to participate in multiple pathological processes associated with thrombotic complications. We hypothesize that in IBD, the chronic inflammatory process settles the conditions for a chronic endothelial stimulation and increased ROCK activation contributing to the pathogenesis of thrombotic complications in IBD.

Objectives. The main objective of this work was to demonstrate evidence of ED in patients with IBD and activation of RhoA/Rho kinase pathway.

Methods. We studied 67 IBD patients (aged 18-77 years, mean age 37 years) who met inclusion criteria and age and healthy controls (aged 24-65 years, mean age 32 years). Diagnosis was based on standard clinical, radiological, endoscopic, and histological criteria. Activity of the disease was assessed by Mayo or Harvey Bradshaw Score (UC and CD, respectively). Endothelial cell damage was determined by enumerating circulating endothelial cells (CECs) and levels of circulating biomarkers: soluble intercellular adhesion molecule (sICAM) and vascular cell adhesion molecule (sVCAM) by ELISA. Rho-kinase activity was assessed by the levels of phosphorylated to total myosin light chain phosphatase 1 (MYPT1-P/T) in circulating leukocytes.

Results. IBD patients showed significantly elevated number of CECs compared to the controls (23, 3±15 vs 9, 6±4, 4 cells/mL; p<0.01; respectively). Plasma levels of sICAM (170±83 ng/mL) and sVCAM (523±125 ng/mL) were also increased in IBD patients compared to the controls (136±52 and 489±52, respectively; p< 0.05). In the control subjects, leukocyte mean MYPT1-P/T ratio was 0.6 ± 0.1 whereas in IBD patients were significantly increased (1.2 ± 0.15; p: 0.009). Interestingly, the number of CECs was directly related to the degree of disease activity (20±3.0, 30±4.0 and 33±6.0 cells/mL for mild, moderate and severe, respectively; p: 0.006).

Conclusions: We found that patients with IBD exhibit evidence of endothelial dysfunction related to the degree of disease activity and abnormal activation of the ROCK pathway. Collectively, these data suggest that activation of ROCK could contribute to the increased risk for thrombotic complications in IBD patients. Inhibition of ROCK has proven to be of potential therapeutic benefit for a variety of diseases. In the case of IBD, the use of ROCK inhibitors (e.g. statins) may provide a novel tool to target the thrombotic risk in patients with IBD.