Title:A Mechanistic Rationale for PDE-4 Inhibitors to Treat Residual Cognitive Deficits in Acquired Brain Injury
Volume: 18
Issue: 3
Author(s): Rudy Schreiber*, Romain Hollands and Arjan Blokland
Affiliation:
- Faculty of Psychology and Neuroscience, Section Neuropsychology and Psychopharmacology, Maastricht University, PO BOX 616, 6200 MD Maastricht,Netherlands
Keywords:
Blood brain barrier, cell adhesion molecules, cyclic adenosine monophosphate, cytokines, neuroinflammation,
traumatic brain injury.
Abstract: Patients with acquired brain injury (ABI) suffer from cognitive deficits that interfere
significantly with their daily lives. These deficits are long-lasting and no treatment options are
available. A better understanding of the mechanistic basis for these cognitive deficits is needed to
develop novel treatments. Intracellular cyclic adenosine monophosphate (cAMP) levels are decreased
in ABI. Herein, we focus on augmentation of cAMP by PDE4 inhibitors and the potentially
synergistic mechanisms in traumatic brain injury. A major acute pathophysiological event in ABI is
the breakdown of the blood-brain-barrier (BBB). Intracellular cAMP pathways are involved in the
subsequent emergence of edema, inflammation and hyperexcitability. We propose that PDE4 inhibitors
such as roflumilast can improve cognition by modulation of the activity in the cAMPPhosphokinase
A-Ras-related C3 botulinum toxin substrate (RAC1) inflammation pathway. In addition,
PDE4 inhibitors can also directly enhance network plasticity and attenuate degenerative processes
and cognitive dysfunction by increasing activity of the canonical cAMP/phosphokinase-
A/cAMP Responsive Element Binding protein (cAMP/PKA/CREB) plasticity pathway. Doublecourtin
and microtubule-associated protein 2 are generated following activation of the
cAMP/PKA/CREB pathway and are decreased or even absent after injury. Both proteins are involved
in neuronal plasticity and may consist of viable markers to track these processes. It is concluded
that PDE4 inhibitors may consist of a novel class of drugs for the treatment of residual
symptoms in ABI attenuating the pathophysiological consequences of a BBB breakdown by their
anti-inflammatory actions via the cAMP/PKA/RAC1 pathway and by increasing synaptic plasticity
via the cAMP/PKA/CREB pathway. Roflumilast improves cognition in young and elderly humans
and would be an excellent candidate for a proof of concept study in ABI patients.