GABAergic striatal neurons exhibit caspase‐independent, mitochondrially mediated programmed cell death

Abstract

1These authors contributed equally to this work.Abbreviations used: [Ca 2+ ] i, intracellular calcium level; 3-NP, 3-nitropropionic acid; AIF, apoptosis-inducing factor; cyt c, cytochrome c; DHPG, 3,5-dihydroxyphenylglycine; div, days in vitro; HD, Huntington's disease; HSP60, heat-shock protein 60; HtrA2, high temperature requirement protein A2; IMS, intermembrane space; OMM, outer mitochondrial membrane; PCD, programmed cell death; PI, propidium iodide; SIN-1, 3-morpholinosydnonimine; Smac/DIABLO, second mitochondrial activator of caspases/direct inhibitor of apoptosis protein binding protein of low isoelectric point; STS, staurosporine; TUNEL, terminal transferase-mediated deoxyuridine triphosphate-biotin nick end labeling; DY m, mitochondrial transmembrane potential. AbstractGABAergic striatal neurons are compromised in basal ganglia pathologies and we analysed how insult nature determined their patterns of injury and recruitment of the intrinsic mitochondrial pathway during programmed cell death (PCD). Stressors affecting targets implicated in striatal neurodegeneration [3-morpholinylsydnoneimine (SIN-1), 3-nitropropionic acid (3-NP), NMDA, 3,5-dihydroxyphenylglycine (DHPG), and staurosporine (STS)] were compared in cultured GABAergic neurons from murine striatum by analyzing the progression of injury and its correlation with mitochondrial involvement, the redistribution of intermembrane space (IMS) proteins, and patterns of protease activation. Stressors produced PCD exhibiting slow-onset kinetics with time-dependent annexin-V labeling and eventual DNA fragmentation. IMS proteins including cytochrome c were differentially distributed, although stressors except STS produced early redistribution of apoptosis-inducing factor and Omi, suggestive of early recruitment of both caspase-dependent and caspase-independent signaling. In general, Bax mobilization to mitochondria appeared to promote IMS protein redistribution. Caspase 3 activation was prominent after STS, whereas NMDA and SIN-1 produced mainly calpain activation, and 3-NP and DHPG elicited a mixed profile of protease activation. PCD and redistribution of IMS proteins in striatal GABAergic neurons were canonical and insult-dependent, reflecting differential interplay between the caspase cascade and alternate cell death pathways.

Neuroprotective effects of mGluR II and III activators against staurosporine- and doxorubicin-induced cellular injury in SH-SY5Y cells: New evidence for a mechanism involving inhibition of AIF translocation

“…Our results on cytosolic AIF level showed an increase after St and Dox treatment with a higher effect in the former model. These observations are in line with previous data demonstrating the participation of AIF translocation in the St-and Dox-evoked cell damage in various cellular systems, including neuronal cell cultures (Beart et al, 2007;Diwakarla et al, 2009;Grishchuk et al, 2011;Pucci et al, 2008;Wu et al, 2004;Yuste et al, 2005). Interestingly, we showed that the tested mGluR II/III agents attenuated the St-or Dox-evoked increase in cytosolic AIF level (Fig.…”

“…Moreover, Movsesyan et al (2004) demonstrated that mGluR5 agonist, CHPG was protective against the β-amyloid-induced cell death in primary cortical neurons and that effect was connected to the inhibition of caspase-3 activity and nuclear AIF translocation induced by the used proapoptotic factor. On the other hand it has been shown that DHPG (5 mM) could evoke neuronal cell death by mechanism engaging caspase-3 and calpain activation, as well AIF nuclear translocation (Diwakarla et al, 2009).…”

“…However, a cautionary note here is the linkage of mGluR I to IP3-sensitive calcium pools which could under some conditions exaggerate the neuronal cell death (Nicoletti et al, 1999;Pshenichkin et al, 2008;Werner et al, 2007) as it has been shown for example for DHPG (20 μM) in a model of neuronal cell death induced by oxygen-glucose deprivation (Allen et al, 2000). Moreover, it has been shown that higher concentration of DHPG (5 mM) could induce cell death in striatal neurons, which is executed by apoptotic-and necrotic-like mechanisms (Diwakarla et al, 2009). Accordingly, the II and III groups of mGluRs could be considered as a safer target for neuroprotection, especially in light of the fact that subtype-specific positive allosteric modulators (PAMs) with improved potency, solubility, and pharmacokinetic properties have been recently developed (Acher et al, 1997;Conn et al, 2009;Flor and Acher, 2012;Nickols and Conn, 2014;Nicoletti et al, 2011;Niswender et al, 2008;Robichaud et al, 2011).…”

Oxidative Stress: Emerging Mitochondrial and Cellular Themes and Variations in Neuronal Injury

“…The reversible complex II inhibitor malonate induces a similar pattern of injury to 3NP by a mechanism involving exacerbation of excitotoxicity. Our data in cultured striatal GABAergic neurons reveal that 3NP induces a profile of PCD more consistent with programmed necrosis with early redistribution of AIF involving activation of both calpain and caspase-3 [75]. Mutant Htt has reported effects, both NMDA-mediated and calcium-mediated, on ∆ψ m .…”

Autophagic activity in cortical neurons under acute oxidative stress directly contributes to cell death

“…However, Beclin-1 was not found to be cleaved in these neurons after STS treatment (data not shown). While caspase activity has been reported here, only a low number of neurons were scored positive for caspase-9 and -3 activity [26] relative to the total number of dead cells after 24 h. Thus, it is possible that another caspase-independent pathway to cell death may be operative within a subpopulation of STS-treated neurons [54], without involvement of Beclin 1. Overall, the differential involvement of Beclin 1 and Atg7 highlights the complexity of neuronal cell death and the significance of interaction between the different types of cell death.…”