Differentiation impairs Bach1 dependent HO-1 activation and increases sensitivity to oxidative stress in SH-SY5Y neuroblastoma cells

Abstract

Neuronal adaptation to oxidative stress is crucially important in order to prevent degenerative diseases. The role played by the Nrf2/HO-1 system in favoring cell survival of neuroblastoma (NB) cells exposed to hydrogen peroxide (H2O2) has been investigated using undifferentiated or all-trans retinoic acid (ATRA) differentiated SH-SY5Y cells. While undifferentiated cells were basically resistant to the oxidative stimulus, ATRA treatment progressively decreased cell viability in response to H2O2. HO-1 silencing decreased undifferentiated cell viability when exposed to H2O2, proving the role of HO-1 in cell survival. Conversely, ATRA differentiated cells exposed to H2O2 showed a significantly lower induction of HO-1, and only the supplementation with low doses of bilirubin (0,5–1 μM) restored viability. Moreover, the nuclear level of Bach1, repressor of HO-1 transcription, strongly decreased in undifferentiated cells exposed to oxidative stress, while did not change in ATRA differentiated cells. Furthermore, Bach1 was displaced from HO-1 promoter in undifferentiated cells exposed to H2O2, enabling the binding of Nrf2. On the contrary, in ATRA differentiated cells treated with H2O2, Bach1 displacement was impaired, preventing Nrf2 binding and limiting HO-1 transcription. In conclusion, our findings highlight the central role of Bach1 in HO-1-dependent neuronal response to oxidative stress.

HO‐1 downregulation favors BRAFV600 melanoma cell death induced by Vemurafenib/PLX4032 and increases NK recognition

“…Interestingly, while HO-1 protein levels were almost undetectable by means of a standard WB technique in untreated MeOV-1 and MeTA cells, HO-1 mRNA was detectable. Similar results have been obtained by our group in neuroblastoma cells 29,30 and by other authors in podocytes 31 and macrophages 32 highlighting the involvement of specific miRNA in the regulation of HO-1 protein expression. This aspect has not been evaluated in the present study.…”

“…Indeed, PLX4032 specifically inhibits BRAF V600 significantly improving the patient survival rate. Similar results have been obtained by our group in neuroblastoma cells 29,30 and by other authors in podocytes 31 and macrophages 32 highlighting the involvement of specific miRNA in the regulation of HO-1 protein expression. 27 We took into consideration HO-1 as possible limiting factor of PLX4032 efficacy.…”

Heme Oxygenase 1 in the Nervous System: Does It Favor Neuronal Cell Survival or Induce Neurodegeneration?

“…In this context, we recently showed that HO-1 dependent endogenous generation of bilirubin is responsible for neuroblastoma cell resistance to H 2 O 2 but the efficiency of HO-1 induction decreases with neuronal differentiation, underlining the idea that neuronal commitment can reduce HO-1 dependent adaptability [64]. Other authors proved that CO inhibits the activation of AMP-activated protein kinase (AMPK) which is implicated in the β-amyloid induced toxicity [65].…”

Cannabidiol Protects Dopaminergic Neurons in Mesencephalic Cultures against the Complex I Inhibitor Rotenone Via Modulation of Heme Oxygenase Activity and Bilirubin

“…Therefore, the effect of CBD-mediated HO inhibition will result in further increased stress, triggering HO-1 induction. HO inhibition or silencing has been shown to sensitize cells towards an additional (oxidative) stressor [85,86]; but at the same time inhibition of HO activity acts as a HO-1 inducing stimulus [84]. Such stress-triggered super-induction may increase stress tolerance in surviving cells via HO super-induction.…”