Caffeine Neuroprotective Mechanism Against β-Amyloid Neurotoxicity in SHSY5Y Cell Line: Involvement of Adenosine, Ryanodine, and N-Methyl-D-Aspartate Receptors

Purpose: Some reports have shown neuroprotective effects of caffeine in several neurodegenerative disorders. However, its mechanism of action is not completely clear. Therefore, the aim of this study was to explore the interference of ryanodine, N-methyl-D-aspartate (NMDA) and adenosine modulators with the neuroprotective effects of caffeine against β-amyloid (Aβ) neurotoxicity in the SHSY5Y cells.

Methods: The SHSY5Y cells were treated with Aβ23-35 (20µM) and/or caffeine (0.6 and 1mM), or both for 24 hours. Adenosine (20, 40, 60, 80, 100µM), NMDA (20, 50, 70, 90µM), dantrolene (2, 4, 6, 8, 10µM) were also added to the medium and incubated for 24 hours. The cell viability was measured via the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) method. The data were analyzed using one-way ANOVA followed by Bonferroni test.

Results: Caffeine at all the used concentrations (0.6, 0.8, 0.9, 1, and 3mM) significantly protected neuronal cells against Aβ neurotoxicity. Adenosine at the concentrations of 20, 40, 80 and 100μM diminished the neuroprotective effects of caffeine (0.6 and 1mM) against Aβ neurotoxicity. NMDA at the concentrations of 20, 50, 70 and 90μM blocked caffeine (0.6 and 1mM) neuroprotective effects. Dantrolene at the concentration of 2, 4, 6, 8 and 10μM diminished the neuroprotective effects of caffeine (0.6mM) and at the concentrations of 2 and 10μM impede caffeine (1mM) neuroprotection against Aβ neurotoxicity.

Conclusion: Caffeine produced neuroprotective effect against Aβ neurotoxicity. Blockade of adenosine and NMDA receptors, as well as the activation of ryanodine receptors, may contribute to the neuroprotective effects of caffeine.

Preference for high-fat diet is developed by young Swiss CD1 mice after short-term feeding and is prevented by NMDA receptor antagonists

Obesity is a worldwide epidemic that is increasing at an alarming rate. One of its causes is the increased availability and consumption of diets rich in fat. In the present study, we investigated the effects of short-term consumption of a high fat diet (HFD) on dietary preferences in Swiss CD1 mice and its relation in time to specific metabolic effects. Mice that were weaned 21days postpartum and fed a chow diet for one week were afterward subjected to a diet preference test for 5days, exposed to both a regular diet (RD) and HFD. We found that mice did not show any preferences. In a second experiment, two groups of mice that were weaned 21days postpartum and subjected to a chow diet for one week were fed either RD or HFD for 18days, and a diet preference test was performed for 5days. After this short-term consumption of HFD, mice preferred HFD, while mice subjected to RD did not show any preference. Importantly, no differences in blood glucose levels were found between the groups prior to and after the experiments. The results support our hypothesis that the preference for HFD is not a spontaneous behavior in CD1 mice, but it can be observed after short-term consumption; additionally, this preference develops before metabolic effects appear. Finally, this preference for HFD could not be observed when the mice were i.p. injected daily with low doses of the NMDA receptor antagonists, ketamine, ifenprodil or MK-801 during the HFD feeding period. These data suggest that acquisition of dietary preference for HFD is a NMDA receptor-dependent learning process.

Extending therapeutic use of psychostimulants: focus on serotonin-1A receptor

INTRODUCTION

Despite a number of medicinally important pharmacological effects, the therapeutic use of psychostimulants is limited because of abuse potential and psychosis following long term use. Development of pharmacological agents for improving and extending therapeutic use of psychostimulants in narcolepsy, attention deficit hyperactivity disorder, Parkinson's disease, obesity and as cognitive enhancer is an important research imperative. In this regard, one potential target system is the 5-hydroxytryptamine (5-HT; serotonin) neurotransmitter system. The focus of the present article is to evaluate a potential role of 5-HT-1A receptor in the alleviation of abuse potential and psychosis-induced by prescription psychostimulants amphetamines and apomorphine.

METHOD

Synaptic contacts between dopamine systems and 5-HT-1A receptors are traced. Studies on serotonin-1A influences on the modulation of dopamine neurotransmission and psychostimulant-induced behavioral sensitization are accumulated.

RESULTS

Inhibition of amphetamine and apomorphine-induced behavioral sensitization by co administration of 5-HT-1A agonists cannot be explained in terms of direct activation of 5-HT-1A receptors, because activation of pre- as well as postsynaptic 5-HT-1A receptors tends to increase dopamine neurotransmission.

CONCLUSION

Long term use of amphetamine and apomorphine produces adaptive changes in 5-HT-1A receptor mediated functions, which are prevented by the co-use of 5-HT-1A agonists. In view of extending medicinal use of psychostimulants, it is important to evaluate the effects of co-use of 5-HT-1A agonists on potential therapeutic profile of amphetamine and apomorphine in preclinical research. It is also important to evaluate the functional significance of 5-HT-1A receptors on psychostimulant-induced behaviors in other addiction models such as drug self-administration and reinstatement of drug seeking behavior.