zaprinast and Brain-Injuries

We recently reported that administration of the non-selective cyclic GMP-phosphodiesterase (cGMP-PDE) inhibitor zaprinast to cortically cryoinjured rats results three days post-lesion in reduced neuronal cell death that was associated to decreased macrophage/microglial activation and oxidative stress and increased astrogliosis and angiogenesis. Similar effects have been observed in cryoinjured animals overexpressing metallothioneins I/II (MT-I/II), metal-binding cysteine-rich proteins that are up-regulated in response to injury. In this work we have examined the effect of administration of the selective PDE5 inhibitor sildenafil (10mg/kg, sc) 2h before and 24 and 48h after induction of cortical cryolesion in wild-type and MT-I/II-deficient mice. Our results show that in wild-type animals sildenafil induces similar changes in glial reactivity, angiogenesis and antioxidant and antiapoptotic effects in the cryolesioned cortex as those observed in rats with zaprinast, indicating that inhibition of PDE5 is responsible for the neuroprotective actions. However, these effects were not observed in mice deficient in MT-I/II. We further show that sildenafil significantly increases MT-I/II protein levels in homogenates of lesioned cortex and MT-I/II immunostaining in glial cells around the lesion. Taken together these results indicate that cGMP-mediated pathways regulate expression of MT-I/II and support the involvement of these proteins in the neuroprotective effects of sildenafil in focal brain lesion.

Topics: Animals; Apoptosis; Blotting, Western; Brain Injuries; Cerebral Cortex; Cold Temperature; Cyclic Nucleotide Phosphodiesterases, Type 5; Enzyme-Linked Immunosorbent Assay; Gliosis; Immunohistochemistry; Macrophage Activation; Metallothionein; Mice; Mice, Knockout; Microglia; Neovascularization, Physiologic; Neuroprotective Agents; Oxidative Stress; Phosphodiesterase Inhibitors; Piperazines; Purines; Purinones; Sildenafil Citrate; Sulfones; Up-Regulation

Recent evidence obtained in cultured glial cells indicates that cGMP-mediated pathways regulate cytoskeleton dynamics, glial fibrillary acidic protein expression and motility in astrocytes, as well as inflammatory gene expression in microglia, suggesting a role in the regulation of the glial reactive phenotype. The aim of this work was to examine if cGMP regulates the glial inflammatory response in vivo following CNS damage caused by a focal cryolesion onto the cortex in rats. Results show that treatment with the cGMP phosphodiesterase inhibitor zaprinast (10 mg/kg i.p.) 2 h before and 24 and 48 h after the lesion results 3 days post-lesion in notably enhanced astrogliosis manifested by increased glial fibrillary acidic protein immunoreactivity and protein levels around the lesion. In contrast, zaprinast decreased the number of round/ameboid lectin-positive cells and the expression of the activated microglia/macrophage markers Iba-1 and CD11b indicating decreased recruitment and activation of these cells. This altered inflammatory response is accompanied by a decrease in protein oxidative stress, apoptotic cell death and neuronal degeneration. In addition, zaprinast enhanced angiogenesis in the lesioned cortex probably as a result of vascular endothelial growth factor expression in reactive astrocytes. These results suggest that regulation of the glial inflammatory response may contribute to the reported neuroprotective effects of cGMP-phosphodiesterase inhibitors in brain injury.

Topics: Animals; Brain Injuries; Calcium-Binding Proteins; CD11b Antigen; Cell Count; Cell Death; Cerebral Cortex; Cryosurgery; Disease Models, Animal; Drug Administration Schedule; In Situ Nick-End Labeling; Lectins; Male; Microfilament Proteins; Neovascularization, Physiologic; Nerve Degeneration; Neuroglia; Oxidative Stress; Phosphodiesterase Inhibitors; Purinones; Rats; Rats, Sprague-Dawley; Time Factors; Vascular Endothelial Growth Factor A