Neuroprotective effects of caffeine against complex I inhibition–induced apoptosis are mediated by inhibition of the Atm/p53/E2F‐1 path in cerebellar granule neurons

Abstract

The aim of the present study was to evaluate the neuroprotective effects of caffeine, an inhibitor of ataxia telangiectasia mutated (ATM) enzyme and an antagonist of adenosine receptors, in two models of apoptosis in cerebellar granule neurons (CGNs): the inhibition of mitochondrial complex I by the neurotoxin MPP(+) and serum and potassium deprivation. We used cerebellar granule neurons because of low glial contamination. Cell viability was measured by the MTT method, and apoptosis was evaluated by assessing DNA fragmentation with flow cytometry or quantification of nuclear condensation. Our data indicate that the neuroprotective effects of caffeine in the MPP+ model of apoptosis are mediated through activation of the ATM/p53 pathway. In addition, caffeine decreased the expression of cyclin D and the transcription factor E2F-1, a regulator of apoptosis in neurons. Caffeine-mediated neuroprotection was not mediated through blockade of adenosine receptors because DPCPX and CGS-15943, two antagonists of these receptors, failed to attenuate apoptosis produced by MPP+ treatment. In addition, caffeine did not exert neuroprotective effects after serum and potassium withdrawal, a p53-independent model of apoptosis. Taken together, our findings indicate that DNA damage/ATM activation is a key component of MPP+-induced apoptosis in CGNs through activation of p53 and reentry into the cell cycle, specifically expression of the transcription factor E2F-1.

Caffeine Inhibits Suicidal Erythrocyte Death

“…Similarly, the effect of caffeine may involve mechanisms other than purinergic receptor stimulation. Along those lines, the antiapoptotic effect of caffeine in neurons was similarly independent of adenosine receptors [47]. In theory, caffeine could be effective through inhibition of the phosphodiesterase [43].…”

“…The present experiments were performed to determine whether caffeine, which is known to interact with adenosine receptors, phosphodiesterases, channels, and intracellular Ca 2+ release [43][44][45][46] similarly influences eryptosis. Caffeine has been shown to inhibit [47][48][49] or to stimulate [50][51][52][53] apoptosis of nucleated cells, an effect depending on the cell type and the presence of other challenges.…”

Role of cdk5 on ATM Phosphorylation in Neuronal Death Induced by DNA Damage

“…Cdk5 is a cyclindependent kinase and its activation could cause cell death [12]. Recent findings have established that unrepaired DNA damage can trigger apoptosis, which is mediated by ATM [6,7]. Thus, it has been hypothesized that DNA damage participates in neuronal death in many neurodegenerative diseases, such as Parkinson's and Alzheimer's diseases [13,14].…”

“…The activation of ataxia-telangiectasia mutated protein (ATM), a phosphoinositol-3-kinase, by DNA damage regulates phosphorylation of different proteins related to cell cycle checkpoint control, DNA repair and apoptosis [2][3][4]. ATM plays a key role in DNA damage-induced apoptosis in postmitotic neurons by regulating p53 activity and cell cycle re-entry [5][6][7]. Although different studies aimed to clarify how ATM is activated by DNA damage, the data obtained until now are controversial [8][9][10][11].…”

Cell Cycle and DNA Damage Response in Postmitotic Neurons

“…This may amplify DNA damage and generate apoptotic signaling. The functional link between neuronal cell cycle reentry, DDR, cell cycle checkpoints and apoptosis is supported by data demonstrating that both cell cycle activation and apoptosis in postmitotic neurons exposed to DSB-inducing agents are ATM-dependent (Alvira et al, 2007;Kruman et al, 2004;Otsuka et al, 2004). There is no evidence of entry of neurons under conditions of DNA damage-induced apoptosis into mitosis, although they may progress through DNA synthesis and G2 (Athanasiou et al, 1998;Becker & Bonni, 2004;Feddersen et al, 1992;).…”