DHCR24 exerts neuroprotection upon inflammation-induced neuronal death

Abstract

BackgroundDHCR24, involved in the de novo synthesis of cholesterol and protection of neuronal cells against different stress conditions, has been shown to be selectively downregulated in neurons of the affected brain areas in Alzheimer’s disease.MethodsHere, we investigated whether the overexpression of DHCR24 protects neurons against inflammation-induced neuronal death using co-cultures of mouse embryonic primary cortical neurons and BV2 microglial cells upon acute neuroinflammation. Moreover, the effects of DHCR24 overexpression on dendritic spine density and morphology in cultured mature mouse hippocampal neurons and on the outcome measures of ischemia-induced brain damage in vivo in mice were assessed.ResultsOverexpression of DHCR24 reduced the loss of neurons under inflammation elicited by LPS and IFN-γ treatment in co-cultures of mouse neurons and BV2 microglial cells but did not affect the production of neuroinflammatory mediators, total cellular cholesterol levels, or the activity of proteins linked with neuroprotective signaling. Conversely, the levels of post-synaptic cell adhesion protein neuroligin-1 were significantly increased upon the overexpression of DHCR24 in basal growth conditions. Augmentation of DHCR24 also increased the total number of dendritic spines and the proportion of mushroom spines in mature mouse hippocampal neurons. In vivo, overexpression of DHCR24 in striatum reduced the lesion size measured by MRI in a mouse model of transient focal ischemia.ConclusionsThese results suggest that the augmentation of DHCR24 levels provides neuroprotection in acute stress conditions, which lead to neuronal loss in vitro and in vivo.Electronic supplementary materialThe online version of this article (10.1186/s12974-017-0991-6) contains supplementary material, which is available to authorized users.

Extracellular prolyl oligopeptidase derived from activated microglia is a potential neuroprotection target

“…Activated BV‐2 cells secrete pro‐inflammatory cytokines and nitric oxide and induced a significant 50% decrease in neuronal viability as compared to vehicle‐treated samples (LSD post hoc: P < 0.001 No LPS+IFNγ vs control, Figure A). Positive controls IL‐10 and 1400 W worked as described previously . IL‐10 decreased TNF‐α levels ~60%, while 1400 W reduced NO levels ~90% and restored neuronal viability to the same level with vehicle‐treated samples (data not shown).…”

“…Positive controls IL-10 and 1400 W worked as described previously. 27,28 IL-10 decreased TNF-α levels~60%, while 1400 W reduced NO levels~90% and restored neuronal viability to the same level with vehicle-treated samples (data not shown). There was a trend towards dose-dependent neuroprotection by the PREP inhibitor KYP-2047 (0.1-10 μmol/L), and at 10-μmol/L concentration, KYP-2047 significantly protected neurons against microglial toxicity (overall effect of treatment: one-way ANOVA: F 4,80 = 27.308, P < 0.001; LSD post hoc vs control: 1 μmol/L P = 0.078; 10 μmol/L P < 0.001; Figure 4A).…”

“…Thus, we performed a pharmacological PREP inhibitor study in a coculture model of mouse primary neurons and BV‐2 cells. The detailed characteristics of the model have been published by Martiskainen et al BV‐2 cells were added to the mouse cortical neuron cultures after 5 DIV at the ratio 1:5, and neuroinflammation was induced using LPS and IFNγ. Activated BV‐2 cells secrete pro‐inflammatory cytokines and nitric oxide and induced a significant 50% decrease in neuronal viability as compared to vehicle‐treated samples (LSD post hoc: P < 0.001 No LPS+IFNγ vs control, Figure A).…”

“…This coculture model was established based on the method described by Gresa‐Arribas et al with minor modifications. Preparation and characterization of the cocultures have been described previously . Briefly, mouse cortical neurons for the cocultures were isolated and cultured in 48‐well plates as described above.…”

“…Preparation and characterization of the cocultures have been described previously. [26][27][28] Briefly, mouse cortical neurons for the cocultures were isolated and cultured in 48well plates as described above. BV-2 microglial cells were seeded at a 1:5 ratio onto the primary cortical cultures on DIV5.…”