Inhibition of CAMP- and cGMP-Phosphodiesterases
CAMP and cGMP act as intracellular second messengers and mediate numerous potentially
neuroprotective actions. For example, cAMP mediates vasodilatation, inhibition
of platelet aggregation, and inhibition of leukocyte and macrophage or microglia
activation (including depression of free radical and cytokine release), as well as enhancement
of the formation of neurotrophic factors such as NGF. It has also been
demonstrated that CAMP inhibits activation of protein kinase C and the successive release
of Ca2+ from intracellular stores, which may be an important factor in the pathophysiological
cascade of brain ischemia. Both cAMP and cGMP are also involved in
the molecular mechanisms underlying hippocampal long-term potentiation (LTP).
Propentofylline enhanced plasma cAMP levels in mice in a dose-dependent fashion
[single intravenous (i.v.) injections of 1 to 25 mg/kg] and potentiated the cAMP
increase induced by isoproterenol (48). A high concentration propentofylline
(0.75 mM) was also shown to increase adenosine-stimulated cAMP accumulation in
rat hippocampal slices (16).