Activated Protein C Attenuates Experimental Autoimmune Encephalomyelitis Progression by Enhancing Vascular Integrity and Suppressing Microglial Activation.

Ravi Kant,Richard Milner,John H Griffin,Jose A Fernández,Sebok K Halder

doi:10.3389/fnins.2020.00333

Abstract

BackgroundActivated protein C (APC), a serine protease with antithrombotic effects, protects in animal models of ischemic stroke by suppressing inflammation and enhancing vascular integrity, angiogenesis, neurogenesis and neuroprotection. A small number of animal studies suggest it might also have therapeutic potential in multiple sclerosis (MS), though results have been mixed. Based on these conflicting data, the goals of this study were to clarify the therapeutic potential of APC in the experimental autoimmune encephalomyelitis (EAE) model of MS and to determine mechanistically how APC mediates this protective effect.MethodsThe protective potential of APC was examined in a chronic progressive model of EAE. Vascular breakdown, tight junction protein expression and vascular expression of fibronectin and α5β1 integrin as well as vascularity and glial activation were analyzed using immunofluorescence (IF) of spinal cord sections taken from mice with established EAE. The direct influence of APC on microglial activation was evaluated in vitro by a combination of morphology and MMP-9 expression.ResultsAPC attenuated the progression of EAE, and this was strongly associated at the histopathological level with reduced levels of leukocyte infiltration and concomitant demyelination. Further analysis revealed that APC reduced vascular breakdown which was associated with maintained endothelial expression of the tight junction protein zonula occludens-1 (ZO-1). In addition, APC suppressed microglial activation in this EAE model and in vitro studies revealed that APC strongly inhibited microglial activation at both the morphological level and by the expression of the pro-inflammatory protease MMP-9.ConclusionThese findings build on the work of others in demonstrating strong therapeutic potential for APC in the treatment of inflammatory demyelinating disease and suggest that enhancement of vascular integrity and suppression of microglial activation may be important mediators of this protection.

Highlights

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) and is the most common neurological disease in the young to middle age population, affecting more than 400,000 people in the United States (Wingerchuk and Carter, 2014; Doshi and Chataway, 2017)
The main findings from our studies were as follows: (1) Activated protein C (APC) suppressed the progression of EAE, both at the clinical and pathological level, resulting in reduced levels of leukocyte infiltration and concomitant protection against loss of myelin, (2) while APC had no effect on angiogenic remodeling in the EAE model, it prevented loss of vascular integrity which was concomitant with maintained endothelial expression of the tight junction protein Zonula occludens-1 (ZO-1), and (3) APC suppressed microglial activation both in vivo and in vitro
These findings build on the work of others in demonstrating strong therapeutic potential for APC in the treatment of inflammatory demyelinating disease and suggest that enhancement of vascular integrity and suppression of microglial activation may be important mediators of this protection

Summary

Introduction

Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS) and is the most common neurological disease in the young to middle age population, affecting more than 400,000 people in the United States (Wingerchuk and Carter, 2014; Doshi and Chataway, 2017). Because MS is such a common disease that strikes relatively early in life, the last 30 years has witnessed intensive research activity seeking to understand disease pathogenesis. This activity has generated a large number of disease-modifying therapies (DMTs), several of which are effective at suppressing the inflammatory aspect of MS. A small number of animal studies suggest it might have therapeutic potential in multiple sclerosis (MS), though results have been mixed Based on these conflicting data, the goals of this study were to clarify the therapeutic potential of APC in the experimental autoimmune encephalomyelitis (EAE) model of MS and to determine mechanistically how APC mediates this protective effect

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