Involvement of Renin-Angiotensin system (RAS) components in mild traumatic brain injury

Abstract

The Renin Angiotensin System (RAS) plays a pathophysiological role in traumatic brain injury (TBI) but the evidence of its involvement in mild TBI (mTBI) is still limited. We aimed at investigating the levels of components from both the classical and counter-regulatory axis of the RAS in a mTBI animal model. Mice with mTBI displayed enhanced ACE/Ang II/AT₁R axis ipsilateral- and contralaterally to the trauma in the hippocampus and prefrontal cortex during acute (24 and 72 h) and later (30 days) timepoints. Increase in Ang-(1-7) levels alongside reduction in Mas receptor expression in hippocampus and prefrontal cortex was also observed after injury. Conversely, mTBI-mice presented higher expression of AT₂ receptor in the contralateral hippocampus and the ipsilateral prefrontal cortex. Importantly, treatment with telmisartan, an AT₁R blocker, and perindopril, an ACE inhibitor, were able to prevent mTBI-associated locomotor activity impairment and anxiety-like behavior, corroborating the involvement of RAS in the pathophysiology of mTBI. We provided original evidence that components of classical and alternative RAS axes undergo alterations in key brain areas following a mTBI in a time and hemisphere dependent manner. Our findings also open new avenues for investigating the therapeutic potential of RAS components in mTBI.

Keywords: Angiotensin II; Mas receptor; Mild traumatic brain injury; Renin angiotensin system; Weight-drop model.