Raw MRI imaging for "In Vivo Neuroprotection in Ischemic Stroke by Activated Protein C Requires β-Arrestin 2"

<p><span>The protease, activated protein C (APC) and its variants provide pharmacological benefits in many murine preclinical injury models, including neuroprotection for ischemic stroke and mortality reduction for sepsis.<span>&nbsp; </span>The <em>in vivo</em> mechanism of action for APC in ischemic stroke and sepsis injury models, similar to extensive in vitro studies using cultured cells, involves protease activated receptor (PAR) 1-mediated biased signaling. Cell culture studies showed that APC/PAR1 signaling requires &beta;-Arrestin 2, an intracellular scaffold protein, and that &beta;-Arrestin 2-dependent, APC-initiated signaling can distinctly alter a wide variety of intracellular signaling pathways.<span>&nbsp; </span>It is unclear whether <em>in vitro</em> studies can be extrapolated to <em>in vivo</em> mechanisms of action.<span>&nbsp; </span>This study employed a proximal transient Middle Cerebral Artery Occlusion model to study the neuroprotective actions of the signaling-selective APC variant, 3K3A-APC, in &beta;-arrestin 2 deficient (<em>Arrb2</em>^-/-) mice. Based on the size and shape of brain injury areas, 3K3A-APC significantly limited brain injury in control mice to a relatively small, localized area whereas these protective effects were lost in <em>Arrb2^-/-</em> mice. Thus, these data indicate that the major <em>in vitro</em> mechanism of action that requires &beta;-arrestin 2 for APC/PAR1 biased signaling is central to the <em>in vivo</em> mechanism of action for APC&rsquo;s neuroprotection. </span></p>