Gene expression profile of human colon cancer cells treated with cross-reacting material 197, a diphtheria toxin non-toxic mutant.

Cross-Reacting Material 197 (CRM197) is a diphtheria toxin non-toxic mutant that has shown antitumor activity in mice and humans. It is still unclear whether this anti-tumorigenic effect depends on its strong inflammatory-immunological property, its ability to inhibit heparin-binding epidermal growth factor (HB-EGF), or even its possible weak toxicity. CRM197 is utilized as a specific inhibitor of HB-EGF that competes for the epidermal growth factor receptor (EGFR), overexpressed in colorectal cancer and implicated in its progression. In this study we evaluate the effects of CRM197 on HT-29 human colon cancer cell line behaviour and, for CRM197 recognized ability to inhibit HB-EGF, its possible influence on EGFR activation. In particular, while HT-29 does not show any reduction of viability after CRM197 treatment (MTT modified assay), or changes in cell cycle distribution (flow cytometry), in EGFR localization, phospho-EGFR detected signals (immunohistochemistry) or in morphology (scanning electron microscopy, SEM) they show a change in the gene expression profile by microarray analysis (cDNA microarray SS-H19k8). The overexpression of genes like protein phosphatase 2, catalytic subunit, alpha isozyme (PPP2CA), guanine nucleotide-binding protein G subunit alpha-1(GNAI1) and butyrophilin, subfamily 2, member A1 (BTN2A1) has been confirmed with real-time-qPCR. This is the first study where the CRM197 treatment on HT-29 shows a possible scarce implication of endogenous HB-EGF on EGFR expression and cancer cell development. At the same time, our results show the alteration of a specific and selected number of genes.

Nafadotride administration increases D1 and D1/D2 dopamine receptor mediated behaviors.

The administration of nafadotride, given at doses known to block the D3 dopamine receptors (0.75, 1.5, 3 mg/kg i.p.) increased locomotor activity both in naive and habituated rats and counteracted the hypothermia but not the hypomotility induced by a low dose of the putative D3 dopamine agonist (+/-)-7-hydroxy-2-(di-N-propylamino)-tetralin (7-OH-DPAT; 0.04 mg/kg). Nafadotride did not antagonize either the motor effects induced by different doses of the D2 agonist quinpirole (0.05 and 0.3 mg/kg) or the hypermotility induced by 7-OH-DPAT given at a dose (0.32 mg/kg) stimulating D2 dopamine receptors. The same nafadotride doses potentiated the grooming behavior induced by the D1 dopamine agonist SKF 38393 (10 mg/kg i.p.) as well as the stereotyped response to the D1/D2 agonist apomorphine (0.5 mg/kg s.c.). Stereotyped behavior was also observed in rats concomitantly treated with nafadotride and the D2 agonist quinpirole. As the activation of D1 dopamine receptors plays an important role in the occurrence of stereotypies, the results suggest that the blockade of D3 receptors by nafadotride could have favored D1/D2 dopamine receptor-mediated behaviors by potentiating D1 receptor function.

The activation of serotonin receptors prevents glutamate-induced neurotoxicity and NMDA-stimulated cGMP accumulation in primary cortical cell cultures.

In the present study, we performed experiments on primary cell cultures from rat neocortex to assess the effects of the selective serotonergic 5HT(1A), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) or 5HT(2), (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) agonists on neuronal death induced by 15min exposure to (-)glutamate (300 microM) as measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT). The results show that both drugs attenuated (-)glutamate-induced neurotoxicity and this effect was fully antagonized by the selective antagonists of 5HT(1) (NAN-190) or 5HT(2) (ketanserin) receptors.The effects of the selective serotonergic agonists on the production of cyclic GMP (cGMP) accumulation induced by N-methyl-D-aspartate (NMDA) in the same neuronal preparation were also evaluated. Only the 5HT(2) agent, but not 8-OH-DPAT, per se, decreased basal cGMP levels. In contrast, both drugs attenuated the NMDA-induced cGMP accumulation in this cell preparation. The unexpected similar behavior of 5HT(1) and 5HT(2) agonists towards glutamate-induced neurotoxicity and NMDA-induced cGMP accumulation in primary cell cultures is discussed. It is concluded that primary cell cultures from rat cerebral cortex could represent a suitable experimental model to search novel neuroleptics which exert their effects via 5HT receptors.

Anticonvulsant preclinical profile of CHF 3381: dopaminergic and glutamatergic mechanisms.

Following intraperitoneal or oral administrations, CHF 3381 ([n-(2-indanyl)-glycinamide hydrochloride]) protected rats against maximal electroshock (MES) test seizures. As glutamatergic pathways play a pivotal role in epilepsy, to better characterize the molecular mechanisms of action of CHF 3381, the drug effects on the binding of the excitatory amino acid antagonist [3H]-MK-801 in the presence of n-methyl-D-aspartate (NMDA), spermidine, or the combination of both ligands, were studied. CHF 3381 inhibited the [3H]-MK-801 specific binding in a noncompetitive fashion in respect to NMDA and polyamines recognition sites. CHF 3381 failed to change the kinetic characteristic of glycine B receptors labeled with [3H]-glycine; in contrast, it significantly increased K(d) values when the receptors were labeled with the more specific compound [3H]-MDL 105,519. CHF 3381 antagonized dopamine (DA)-induced behavioral responses and inhibited, in a glycine-dependent manner, the NMDA-induced [3H]-DA release from rat striatal slices, but it failed to change either the kinetic characteristics of D1, D2, or D3 receptors in synaptic plasma membranes (SPM) or the [3H]-DA uptake from striatal synaptosomes. Moreover, in primary cell cultures of cortical neurons, this drug exhibited glycine-independent neuroprotective effects against glutamate-induced excitotoxicity. It is concluded that this compound could have a potential use in several disease states where a pathological high level of NMDA receptor activation is thought to occur.

Inhibition of free radical production or free radical scavenging protects from the excitotoxic cell death mediated by glutamate in cultures of cerebellar granule neurons.

Glutamate kills sensitive neurons through several steps downstream to receptor activation: increased free Ca2+ levels, activation of various enzymes and accumulation of reactive oxygen species (ROS). We have evaluated in a well established model of neuronal cultures the neuroprotective effects of blocking these mechanisms, either singularly or by combining multiple enzyme inhibition and/or ROS scavenging. In vitro cultures of cerebellar granule cells exposed to a toxic concentration of glutamate (100 microM for 15 min in the absence of Mg2+) combined with several pharmacological treatments. Inhibition of nitric oxide synthase (NOS) and phospholipase A2 (PLA2) were effective in decreasing cell death and the combined treatments showed some degree of additivity. By contrast, inhibition of xanthine oxidase (XO) with allopurinol was uneffective. Antioxidants (in particular vitamin e or vitamin E analogs). protected neurons up to more than 50%. A synergistic effect was demonstrated by the combination of vitamin E and C. On the other hand, antioxidants did not increase the protection granted by enzyme inhibitors, suggesting that they act downstream to NOS and PLA2. In conclusion, NOS and PLA2 activated by Ca2+ influx give rise to reactive oxygen species whose deleterious action can be counteracted either by inhibiting these enzymes or by scavenging the excess of free radicals produced by them. Finally, a moderate protection was obtained by blocking protein synthesis with cycloheximide, suggesting a partial contribution of apoptotic mechanisms to the excitotoxic cell death.