Recent reports have indicated that some low-molecular-weight compounds mimic neurotrophic factors inducing neurite outgrowth and neuroprotection. Carnosic acid (CA) promotes neurite outgrowth through the activation of Nrf2 in PC12 cells. CA also protects neurons via the keap/Nrf2 transcriptional pathway from oxidative stress. Forskolin-induced neurite outgrowth is mediated by activation of the PKA signalling pathway and this PKA-mediated neurite outgrowth is achieved by the expression of nur77 in PC12 cells. In addition, forskolin at its low concentration is closely related to the cAMP-induced protective function against L-DOPA-induced cytotoxicity in PC12 cells. A HDAC inhibitor trichostatin A (TSA) increases neurite length via p53 acetylation in rat cultured cerebellar granule neurons and in cerebral cortical neurons, and also protects neurons against glutathione depletion-induced oxidative stress. Recently, it was revealed that Nrf2 and p53 bind to CBP/p300 directly, and Nur77 is acetylated in vivo and in vitro by CBP/p300. Acetylation of Nrf2, p53 and Nur77 by CBP/p300 may constitute a novel similar regulatory mechanism for low-molecular-weight compounds with neurotrophic activities.

Following endoplasmic reticulum (ER) stress, cerebral infarctions have been reported to involve an apoptotic process, including the activation of the caspase cascade. To confirm whether fragmented caspase-12, which is activated by cleavage and is detectable during ER stress, is also involved in embolic cerebral infarctions in rats, we adopted an autologous blood clot model for the analysis of cerebral infarctions. We performed experiments in rats with brain infarctions, which are closely related to embolic cerebral infarctions. We utilized a homologous blood clot, i.e., natural materials, to form the infarct area. Our findings reveal that caspase-12 is fragmented when infarct areas form in cerebral cortical neurons. Interestingly, we observed that these fragments translocated to the nuclei of not only cerebral cortical neurons but hippocampal neurons. We further found that glucose-regulated protein 78 (GRP78), a marker of ER stress, is up-regulated in both cerebral cortical and hippocampal neurons during cerebral infarction. This result suggests that the fragmentation of caspase-12 and the subsequent nuclear translocation of these fragments are involved in the brain infarction process in rats.

The characteristics of the inhibitory effect of calcium ion (Ca2+)/calmodulin (CaM) on specific [125I]-omega-conotoxin GVIA (125I-omega-CTX) binding and on the labeling of 125I-omega-CTX to crude membranes from chick brain were investigated. The inhibitory effect of Ca2+/CaM depended on the concentrations of free Ca2+ and CaM. The IC50 values for free Ca2+ and CaM were about 2.0 x 10(-8) M and 3.0 microg protein/ml, respectively. The inhibitory effect of Ca2+/CaM was attenuated by the CaM antagonists W-7, prenylamine and CaM-kinase II fragment (290-309), but not by the calcineurin inhibitor FK506. Ca2+/CaM also inhibited the labeling of a 135-kDa band (which was considered to be part of N-type Ca2+ channel alpha1 subunits) with 125I-omega-CTX using a cross-linker. These results suggest that Ca2+/CaM affects specific 125I-omega-CTX binding sites, probably N-type Ca2+ channel alpha1 subunits, in crude membranes from chick whole brain.

The effect of Ca2+/calmodulin (CaM) on the specific binding of [125I]omega-conotoxin GVIA (125I-omega-CTX) to crude membranes from chick brain was investigated. When we examined the effects of the activation of various endogenous protein kinases on specific [125I]omega-CTX binding to crude membranes, we observed that Ca2+/CaM had an inhibitory effect regardless of whether or not the standard medium contained ATP (0.5 mM). Ca2+/CaM also had an inhibitory effect in a simple binding-assay medium containing HEPES-HCl buffer, BSA, Ca2+ and CaM, and this effect was dependent on the concentration of Ca2+. The effect of Ca2+/CaM was attenuated by the CaM antagonists W-7 and CaM-kinase II fragment (290-309). An experiment with modified ELISA using purified anti omega-CTX antibody indicated that Ca2+/CaM did not affect the direct binding of [125I]omega-CTX and CaM. These results suggest that Ca2+/CaM either directly or indirectly affects specific [125I]omega-CTX binding sites, probably N-type Ca2+ channels in crude membranes from chick whole brain.

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