Abstract 13336: Investigating the Effects of Physiological Shear Stress on Monocyte Phenotype for Therapeutic Development in Atherosclerosis

Abstract

Introduction: Monocytes are highly plastic immune cells which play a significant role in atherosclerosis development and progression. Monocyte phenotype is modulated by stimuli including physical parameters like the shear stress induced by blood flow. Atherosclerotic plaque formation impedes blood flow thereby impacting the shear stress applied to monocytes. The altered shear stress could contribute to the abnormal monocyte phenotype populations in atherosclerotic patients. Aim: To understand the relationship between monocyte phenotypic response to varying physiological shear stresses. Methods: To investigate the dynamics of monocytes under inflammatory stresses, THP-1wt cells were exposed to 40 dyne/cm 2 and 5 dyne/cm 2 which represent above normal and below-normal, atherosclerotic shear stress conditions respectively. Monocytes were either untreated or stimulated with lipopolysaccharide (LPS) to simulate low-grade inflammation. To evaluate the phenotypic response, ELISA and qPCR measurements of pro-inflammatory (TNF-α IL-12, NOS2, MAC-1, CCL2, CD40), anti-inflammatory (IL-10), and adhesion molecules (ICAM-1, VCAM-1, CCR2) were taken directly after, and four hours post shearing. Results: Shear stresses of 5 dyne/cm 2 or 40 dyne/cm 2 show differential response profiles in monocytes. At both stresses, THP-1wt cells downregulated expression of inflammatory and adhesion molecules after 4hrs. However, pre-stimulation with LPS resulted in either maintained or increased levels of expression. Notably, LPS stimulation for both shear stresses saw a 40-fold or greater increase in TNF-α, CCL2, CD40, and VCAM-1 after 4-hour incubation. In all conditions angiotensin converting enzyme 2 (ACE2), a molecule important for blood pressure regulation, was downregulated. Conclusion: The data concludes that shear stress has an impact on the activation of monocytes in both unstimulated and stimulated conditions. LPS data suggests that monocytes which are already in proinflammatory conditions are more susceptible to sustained activation from shear stress.