Effect of Diminazene Aceturate, an ACE2 activator, on platelet CD40L signaling induced glial activation in rat model of hypertension

Abstract

Hypertension causes platelet activation and adhesion in the brain resulting in glial activation and neuroinflammation. Further, activation of Angiotensin-Converting Enzyme 2/Angiotensin (1-7)/Mas Receptor (ACE2/Ang (1-7)/MasR) axis of central Renin-Angiotensin System (RAS), is known to reduce glial activation and neuroinflammation, thereby exhibiting anti-hypertensive and anti-neuroinflammatory properties. Therefore, in the present study, the role of ACE2/Ang (1-7)/MasR axis was studied on platelet-induced glial activation and neuroinflammation using Diminazene Aceturate (DIZE), an ACE2 activator, in astrocytes and microglial cells as well as in rat model of hypertension. We found that the ACE2 activator DIZE, independently of its BP-lowering properties, efficiently prevented hypertension-induced glial activation, neuroinflammation, and platelet CD40-CD40L signaling via upregulation of ACE2/Ang (1-7)/MasR axis. Further, DIZE decreased platelet deposition in the brain by reducing the expression of adhesion molecules on the brain endothelium. Activation of ACE2 also reduced hypertension-induced endothelial dysfunction by increasing eNOS bioavailability. Interestingly, platelets isolated from hypertensive rats or activated with ADP had significantly increased sCD40L levels and induced significantly more glial activation than platelets from DIZE treated group. Therefore, injection of DIZE pre-treated ADP-activated platelets into normotensive rats strongly reduced glial activation compared to ADP-treated platelets. Moreover, CD40L-induced glial activation, CD40 expression, and NFкB-NLRP3 inflammatory signaling are reversed by DIZE. Furthermore, the beneficial effects of ACE2 activation, DIZE was found to be significantly blocked by MLN4760 (ACE2 inhibitor) as well as A779 (MasR antagonist) treatments. Hence, our study demonstrated that ACE2 activation reduced the platelet CD40-CD40L induced glial activation and neuroinflammation, hence imparted neuroprotection.

Keywords: Angiotensin Converting Enzyme 2; CD40L; Hypertension; Neuroinflammation; Platelet activation.