Mdivi-1 Protects Against Ischemic Brain Injury via Elevating Extracellular Adenosine in a cAMP/CREB-CD39-Dependent Manner

Abstract

This study aimed to examine whether the neuroprotective effects of Mdivi-1 are attributable to extracellular ATP and adenosine. Mdivi-1 was administered prior to or post middle cerebral artery occlusion (MCAO). The extracellular adenosine was measured by in vivo microdialysis and high-pressure liquid chromatography (HPLC) in MCAO mouse model. Western blot was done to determine the influence of Mdivi-1 on the expression of CD39 and CREB phosphorylation both in vivo and in the cultured astrocytes. Intracellular cAMP and protein kinase A (PKA) activity were detected in primary astrocytes. Results showed that Mdivi-1 significantly reduced infarct volume and neurological scores when administered either prior to or post MCAO. Interestingly, pretreatment with Mdivi-1 resulted in marked increase of extracellular adenosine and concomitant decrease in ATP. The expression of CD39, but not CD73, was upregulated by Mdivi-1, which was associated with the elevated phosphorylated cAMP response element-binding protein (CREB), a transcription factor potentially regulating CD39 expression. In primary astrocytes, Mdivi-1 treatment induced increases in intracellular cAMP, PKA activity and CREB phosphorylation, and PKA-specific inhibitor completely reversed Mdivi-1-induced CD39 expression. Our results demonstrate that Mdivi-1 protects against ischemic brain injury through increasing extracellular adenosine, a process involving elevated CD39 expression that is likely modulated by cAMP/PKA/CREB cascade. Figure Potential mechanisms by which Mdivi-1 mediates the neuroprotection on cerebral ischemic stroke. Results from the present study indicate that Mdivi-1 protects against ischemic brain injury through increasing extracellular adenosine, a process involving elevated CD39 expression that is likely modulated by the cAMP/PKA/CREB cascades.

Mitochondrial fission – a drug target for cytoprotection or cytodestruction?

“…Cui et al. () demonstrated that Mdivi‐1 increases release of the neuroprotective agent, adenosine, through the cAMP/PKA/CREB pathway. Under oxidative stress, ROS trigger apoptotic cell death by increasing intracellular calcium levels and promoting outer mitochondrial membrane permeabilization, leading, in turn, to the release of cytochrome c and activation of the caspase cascade (Cardoso et al.…”

Mitochondrial fission and fusion in secondary brain damage after CNS insults

“…41 Treatment with Mdivi was shown to significantly decrease the infarct volume, apoptotic neuronal death and neurological deficits following transient middle cerebral artery occlusion (MCAO) in adult mice and rats. 18,41,43 Inhibition of Drp1-dependent mitochondrial fission was also shown to provide neuroptotection by activating cyclic adenosine monophosphate (cAMP), protein kinase A (PKA) and cAMP response element binding (CREB) pathway leading to increased adenosine levels and thus increased cerebral blood flow to the ischemic tissue. 41 Inhibition of Drp1 by Mdivi-1 was also shown to improve hippocampal-dependent learning and memory and decrease lesion volume in mice and rats following TBI.…”

“…18,41,43 Inhibition of Drp1-dependent mitochondrial fission was also shown to provide neuroptotection by activating cyclic adenosine monophosphate (cAMP), protein kinase A (PKA) and cAMP response element binding (CREB) pathway leading to increased adenosine levels and thus increased cerebral blood flow to the ischemic tissue. 41 Inhibition of Drp1 by Mdivi-1 was also shown to improve hippocampal-dependent learning and memory and decrease lesion volume in mice and rats following TBI. 20,47 Taken together, these studies strongly suggest that Drp1 plays an important role in regulating neuronal death during CNS insults.…”

Ischemic Cerebroprotection Conferred by Myeloid Lineage-Restricted or Global CD39 Transgene Expression

“…It is this initial pro-inflammatory signal of ATP, which occurs with even minor perturbations of the cellular membrane, that the activity of CD39 is positioned to dissipate. The apyrase activity of CD39 cleaves ATP and ADP to AMP, and the co-expressed partner enzyme of CD39, CD73, completes the cleavage of AMP to adenosine, which modulates inflammation and may protect against ischemic injury 39–42 . Combined with our work which uses a permanent occlusion model, this suggests that CD39 or its downstream signaling pathway has a high therapeutic potential to limit ischemic brain injury.…”