SUN11602-induced hyperexpression of calbindin D-28k is pivotal for the survival of hippocampal neurons under neurotoxic conditions.

Basic fibroblast growth factor (FGF-2/bFGF) possesses neuroprotective activity and promotes cell proliferation. In this study, the novel synthetic compound 4-({4-[[(4-amino-2,3,5,6-tetramethylanilino)acetyl](methyl)amino]-1-piperidinyl}methyl)benzamide (SUN11602) exhibited neuroprotective activities similar to those of FGF-2 without promoting cell proliferation. In primary cultures of hippocampal neurons, stimulation with SUN11602 or FGF-2 increased calbindin D-28k (CalB) gene expression and prevented glutamate-induced neuronal death. These effects were abolished by pretreatment with PD166866 (FGF receptor 1 [FGFR1] tyrosine kinase-specific inhibitor). This indicated that FGFR1 activation and increased CalB expression were involved in SUN11602-mediated neuroprotection. However, receptor-binding assays revealed that unlike FGF-2, SUN11602 did not alter the binding of (125)I-labeled FGF-2 to FGFR1. To investigate the possible proliferative activity of SUN11602, we utilized BHK21 and SKN cells expressing endogenous FGFR1. FGF-2 promoted cell proliferation whereas SUN11602 did not. In in vivo studies, wild-type (WT) and CalB-deficient (CalB(-/-)) mice were injected with aggregated Aß1-40 and ibotenate (NMDA receptor agonist) to severely damage the hippocampal tissue. Treatment with SUN11602 (orally) or FGF-2 (intraparenchymally) at the midpoint of Aß1-40 and ibotenate injections prevented the hippocampal damage in WT mice, however this effect was abolished in CalB(-/-) mice. Thus, SUN11602 exerted protective effects on hippocampal neurons through activation of FGFR1 and increased CalB expression. Moreover, the neuroprotective effects of SUN11602 depended upon the various biological activities of FGF-2.

SUN11602 has basic fibroblast growth factor-like activity and attenuates neuronal damage and cognitive deficits in a rat model of Alzheimer's disease induced by amyloid ß and excitatory amino acids.

Basic fibroblast growth factor (bFGF/FGF-2) is known to possess neuroprotective and neurite outgrowth activity properties. In this study, the effects of a novel synthetic compound that mimics the neuroprotective properties of bFGF - SUN11602 - were examined in vitro and in vivo. SUN11602 promoted neurite outgrowth of primarily cultured rat hippocampal neurons. For the in vivo study, an Alzheimer's disease (AD) model with severe damage to the hippocampal tissue was constructed by injecting the hippocampi of rats with aggregated Aß1-40, followed 48 h later by an injection of ibotenate [an agonist for N-methyl-d-aspartate (NMDA) receptor]. Oral administration of SUN11602 at the midpoint of Aß1-40 and ibotenate injections attenuated short-term memory impairment in the Y-maze test, as well as spatial learning deficits in the water maze task. In addition, the SUN11602 treatment inhibited the increase of peripheral-type benzodiazepine-binding sites (PTBBS), which are a marker for gliosis. A negative correlation was found between PTBBS numbers and learning capacity in the water maze task. These results suggest that SUN111602 improved memory and learning deficits in the hippocampally lesioned rats by preventing neuronal death and/or promotion of neurite outgrowth. Taken together, these results indicate that SUN11602, a bFGF-like compound with neuroprotective and neurite outgrowth activity, may be beneficial for the treatment of progressive neurodegenerative diseases such as AD.

SUN11602, a novel aniline compound, mimics the neuroprotective mechanisms of basic fibroblast growth factor.

Basic fibroblast growth factor (bFGF) offers some measure of protection against excitotoxic neuronal injuries by upregulating the expression of the calcium-binding protein calbindin-D28k (Calb). The newly synthesized small molecule 4-({4-[[(4-amino-2,3,5,6-tetramethylanilino)acetyl](methyl)amino]-1-piperidinyl}methyl)benzamide (SUN11602) mimics the neuroprotective effects of bFGF, and thus, we examined how SUN11602 exerts its actions on neurons in toxic conditions of glutamate. In primary cultures of rat cerebrocortical neurons, SUN11602 and bFGF prevented glutamate-induced neuronal death. This neuroprotection, which occurred in association with the augmented phosphorylation of the bFGF receptor-1 (FGFR-1) and the extracellular signal-regulated kinase-1/2 (ERK-1/2), was abolished by pretreatment with PD166866 (a FGFR-1 tyrosine kinase-specific inhibitor) and PD98059 (a mitogen-activated protein kinase [MAPK]/[ERK-1/2] kinase [MEK] inhibitor). In addition, SUN11602 and bFGF increased the levels of CALB1 gene expression in cerebrocortical neurons. Whether this neuroprotection was linked to Calb was investigated with primary cultures of cerebrocortical neurons from homozygous knockout (Calb(-/-)) and wild-type (WT) mice. In WT mice, SUN11602 and bFGF increased the levels of newly synthesized Calb in cerebrocortical neurons and suppressed the glutamate-induced rise in intracellular Ca(2+). This Ca(2+)-capturing ability of Calb allowed the neurons to survive severe toxic conditions of glutamate. In contrast, Calb levels remained unchanged in Calb(-/-) mice after exposure to SUN11602 or bFGF, and due to a loss of function of the gene, these neurons were no longer resistant to toxic conditions of glutamate. These findings indicated that SUN11602 activated a number of cellular molecules (FGFR-1, MEK/ERK intermediates, and Calb) and consequently contributed to intracellular Ca(2+) homeostasis as observed in the case of bFGF.

Effect of bFGF on neuronal damage induced by sequential treatment of amyloid ß and excitatory amino acid in vitro and in vivo.

Effects of basic fibroblast growth factor (bFGF), a potent neurotrophin, on neuronal damage induced by sequential treatment of amyloid ß (Aß) peptide and excitatory amino acid were examined in vitro and in vivo. Treatment of rat primary cortical neurons with glutamate (10µM, 30µM) resulted in neuronal damage, and pretreatment of the neurons with Aß(25-35) (1.0µM) at 48h before glutamate stimulation augmented the susceptibility of the cells to the glutamate-induced neurotoxicity. Application of bFGF (0.3, 1, 3ng/ml) and MK-801 (1, 3, 10, 30nM) to the culture at 24h before glutamate stimulation markedly decreased the neuronal damage elicited by Aß(25-35) and glutamate. In a rat model of Alzheimer's disease, in which aggregated Aß(1-40) (4µg/1µl) was injected into the hippocampus, followed by an injection of ibotenate (an NMDA receptor agonist, 0.3µg/0.5µl) into the same sites at 48h later, significant neuronal damage and learning deficit was induced. Administration of bFGF (25ng/1µl) into the hippocampus at 24h before ibotenate inhibited the neuronal damage and demonstrated a trend of attenuating spatial learning deficits. These results suggest that bFGF might be a useful agent for treatment of Alzheimer's disease in which Aß peptide and glutamate would be involved as causative substances.

The PDE10A inhibitor, papaverine, differentially activates ERK in male and female rat striatal slices.

The phosphodiesterase 10A (PDE10A) is highly expressed within dopaminoreceptive medium spiny neurons (MSNs) of the striatum, which are implicated in various neurodegenerative diseases and psychiatric disorders, such as Huntington's disease and schizophrenia. With its dual action on cAMP and cGMP, PDE10A has been proposed to affect several signaling cascades in the corticostriatothalamic circuits. In particular, papaverine, a selective PDE10A inhibitor has been shown to activate/phosphorylate ERK in striatum. We used acute rat striatal slices to further characterize the effects of papaverine on ERK activation/phosphorylation in D1- and D2-responsive striatal neurons. Incubation of striatal slices from male rats with papaverine increased the levels of phospho-ERK1/2 (p-ERK), an effect enhanced with a D1 agonist or a D2 antagonist, but decreased with a D1 receptor antagonist or a D2 receptor agonist. Papaverine-induced increase in p-ERK was localized in striatal neurons receiving D1-enriched presynaptic terminals, as well as in postsynaptic D2-enriched neurons in striatal slices. Interestingly, papaverine had almost no stimulatory effects on ERK1/2 phosphorylation in slices prepared from female rats. In striatal slices prepared from ovariectomized female rats, papaverine treatment stimulated ERK1/2 phosphorylation to levels similar to those in slices from male rats. Moreover, estrogen was found to regulate the levels of D2 but not D1 receptors in striatum. These results indicate that circulating levels of female hormones, and in particular estrogen, regulate the effects of PDE10A inhibition on ERK1/2 phosphorylation in medium spiny neurons, an effect possibly linked to estrogen's regulation of D2 receptors. Considering the variety of events modulated by ERK1/2 activity, these findings suggest that sex difference needs to be taken into consideration for the further investigation of the effects of PDE10A inhibitors.