Heme oxygenase 1 (HO-1) up-regulation is recognized as a pivotal mechanism of cell adaptation to stress. Under control of different transcription factors but with a prominent role played by Nrf2, HO-1 induction is crucial also in nervous system response to damage. However, several lines of evidence have highlighted that HO-1 expression is associated to neuronal damage and neurodegeneration especially in Alzheimer’s and Parkinson’s diseases. In this review, we summarize the current literature regarding the role of HO-1 in nervous system pointing out different molecular mechanisms possibly responsible for HO-1 up-regulation in nervous system homeostasis and neurodegeneration.

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.

Heme oxygenase 1 (HO-1) is crucially involved in cell adaptation to oxidative stress and has been demonstrated to play an important role in cancer progression and resistance to therapies. We recently highlighted that undifferentiated neuroblastoma (NB) cells are prone to counteract oxidative stress through the induction of HO-1. Conversely, differentiated NB cells were more sensitive to oxidative stress since HO-1 was scarcely upregulated. In this work, we investigated the role played by miR-494, which has been proved to be involved in cancer biology and in the modulation of oxidative stress, in the upregulation of HO-1. We showed that NB differentiation downregulates miR-494 level. In addition, endogenous miR-494 inhibition in undifferentiated cells impairs HO-1 induction in response to exposure to 500 µM H2O2, reducing the number of viable cells. The analysis of Bach1 expression did not reveal any significant modifications in any experimental conditions tested, proving that the impairment of HO-1 induction observed in cells treated with miR-494 inhibitor and exposed to H2O2 is independent from Bach1. Our results underline the role played by miR-494 in favoring HO-1 induction and cell adaptation to oxidative stress and contribute to the discovery of new potential pharmacological targets to improve anticancer therapies.

Long non-coding RNAs (lncRNAs) can affect multiple layers of gene expression to control crucial cellular functions. We have previously demonstrated that the lncRNA EPR, by controlling gene expression at different levels, affects cell proliferation and migration in cultured mammary gland cells and impairs breast tumor formation in an orthotopic transplant model in mice. Here, we used ChIRP-Seq to identify EPR binding sites on chromatin of NMuMG mammary gland cells overexpressing EPR and identified its trans binding sites in the genome. Then, with the purpose of relating EPR/chromatin interactions to the reshaping of the epitranscriptome landscape, we profiled histone activation marks at promoter/enhancer regions by ChIP-Seq. Finally, we integrated data derived from ChIRP-Seq, ChIP-Seq as well as RNA-Seq in a comprehensive analysis and we selected a group of bona fide direct transcriptional targets of EPR. Among them, we identified a subset of EPR targets whose expression is controlled by TGF-β with one of them—Arrdc3—being able to modulate Epithelial to Mesenchymal Transition. This experimental framework allowed us to correlate lncRNA/chromatin interactions with the real outcome of gene expression and to start defining the gene network regulated by EPR as a component of the TGF-β pathway.

EPR is a long non-coding RNA (lncRNA) that controls cell proliferation in mammary gland cells by regulating gene transcription. Here, we report on Mettl7a1 as a direct target of EPR. We show that EPR induces Mettl7a1 transcription by rewiring three-dimensional chromatin interactions at the Mettl7a1 locus. Our data indicate that METTL7A1 contributes to EPR-dependent inhibition of TGF-β signaling. METTL7A1 is absent in tumorigenic murine mammary gland cells and its human ortholog (METTL7A) is downregulated in breast cancers. Importantly, re-expression of METTL7A1 in 4T1 tumorigenic cells attenuates their transformation potential, with the putative methyltransferase activity of METTL7A1 being dispensable for its biological functions. We found that METTL7A1 localizes in the cytoplasm whereby it interacts with factors implicated in the early steps of mRNA translation, associates with ribosomes, and affects the levels of target proteins without altering mRNA abundance. Overall, our data indicates that METTL7A1—a transcriptional target of EPR—modulates translation of select transcripts.

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