The transcription factor, nuclear factor erythroid 2 p45-related factor 2 (Nrf2), acts as a sensor of oxidative or electrophilic stresses and plays a pivotal role in redox homeostasis. Oxidative or electrophilic agents cause a conformational change in the Nrf2 inhibitory protein Keap1 inducing the nuclear translocation of the transcription factor which, through its binding to the antioxidant/electrophilic response element (ARE/EpRE), regulates the expression of antioxidant and detoxifying genes such as heme oxygenase 1 (HO-1). Nrf2 and HO-1 are frequently upregulated in different types of tumours and correlate with tumour progression, aggressiveness, resistance to therapy, and poor prognosis. This review focuses on the Nrf2/HO-1 stress response mechanism as a promising target for anticancer treatment which is able to overcome resistance to therapies.

The upregulation of heme oxygenase-1 (HO-1) is one of the most important mechanisms of cell adaptation to stress. Indeed, the redox sensitive transcription factor Nrf2 is the pivotal regulator of HO-1 induction. Through the antioxidant, antiapoptotic, and antinflammatory properties of its metabolic products, HO-1 plays a key role in healthy cells in maintaining redox homeostasis and in preventing carcinogenesis. Nevertheless, several lines of evidence have highlighted the role of HO-1 in cancer progression and its expression correlates with tumor growth, aggressiveness, metastatic and angiogenetic potential, resistance to therapy, tumor escape, and poor prognosis, even though a tumor- and tissue-specific activity has been observed. In this review, we summarize the current literature regarding the pro-tumorigenic role of HO-1 dependent tumor progression as a promising target in anticancer strategy.

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.

Purpose The purpose of this paper is to assess the reliability of questionnaires as a method of quantifying household food waste (FW), thus providing context regarding the validity of existing Italian estimates. Design/methodology/approach A total of 30 households were involved in a diary study that was conducted for one week. The participating households were first asked about their FW quantities in a questionnaire. Half of the households who filled their diaries properly were then audited through waste sorting analysis performed on their garbage. Non-parametric tests were used to test for differences in FW estimates between audited and non-audited households, as well as differences among estimates obtained through different quantification methodologies. Findings Edible FW was estimated to be 489 grams per week based on questionnaires, and 1,035 grams per week based on diaries. In the audited sub-sample of households, FW estimates were 334 grams per week based on questionnaires, 818 grams per week based on diaries and 1,058 grams per week based on waste sorting analysis. Research limitations/implications Given the small sample size in the present study, future studies can utilize larger samples to assess whether the differences identified in estimates can be replicated. Future studies can also inquire into the behavioral biases that led consumers to underestimate their FW. Practical implications Results of the present study point against the use of questionnaires to quantify household FW, hence raising some doubt on the reliability of existent Italian estimates. Where waste sorting is unfeasible, the use of adjustment methods or diaries is suggested to better inform policies. Originality/value This study is one of the first on FW quantification that tests three different methodologies on the same sample, and is the first to do so in Italy, where estimates are still very poor.

RAGE is a multiligand receptor able to bind advanced glycation end-products (AGEs), amphoterin, calgranulins, and amyloid-beta peptides, identified in many tissues and cells, including neurons. RAGE stimulation induces the generation of reactive oxygen species (ROS) mainly through the activity of NADPH oxidases. In neuronal cells, RAGE-induced ROS generation is able to favor cell survival and differentiation or to induce death through the imbalance of redox state. The dual nature of RAGE signaling in neurons depends not only on the intensity of RAGE activation but also on the ability of RAGE-bearing cells to adapt to ROS generation. In this review we highlight these aspects of RAGE signaling regulation in neuronal cells.

The activation of Nrf2 has been demonstrated to play a crucial role in cancer cell resistance to different anticancer therapies. The inhibition of proteasome activity has been proposed as a chemosensitizing therapy but the activation of Nrf2 could reduce its efficacy. Using the highly chemoresistant neuroblastoma cells HTLA-230, here we show that the strong reduction in proteasome activity, obtained by using low concentration of bortezomib (BTZ, 2.5 nM), fails in reducing cell viability. BTZ treatment favours the binding of Nrf2 to the ARE sequences in the promoter regions of target genes such as heme oxygenase 1 (HO-1), the modulatory subunit of γ-glutamylcysteine ligase (GCLM) and the transporter for cysteine (x-CT), enabling their transcription. GSH level is also increased after BTZ treatment. The up-regulation of Nrf2 target genes is responsible for cell resistance since HO-1 silencing and GSH depletion synergistically decrease BTZ-treated cell viability. Moreover, cell exposure to all-trans-Retinoic acid (ATRA, 3 μM) reduces the binding of Nrf2 to the ARE sequences, decreases HO-1 induction and lowers GSH level increasing the efficacy of bortezomib. These data suggest the role of Nrf2, HO-1 and GSH as molecular targets to improve the efficacy of low doses of bortezomib in the treatment of malignant neuroblastoma.

High-risk neuroblastoma (NB) is characterized by the development of chemoresistance, and bortezomib (BTZ), a selective inhibitor of proteasome, has been proposed in order to overcome drug resistance. Considering the involvement of the nuclear factor-erythroid-derived 2-like 2 (Nrf2) and heme oxygenase-1 (HO-1) in the antioxidant and detoxifying ability of cancer cells, in this study we have investigated their role in differently aggressive NB cell lines treated with BTZ, focusing on the modulation of HO-1 to improve sensitivity to therapy. We have shown that MYCN amplified HTLA-230 cells were slightly sensitive to BTZ treatment, due to the activation of Nrf2 that led to an impressive up-regulation of HO-1. BTZ-treated HTLA-230 cells down-regulated p53 and up-regulated p21, favoring cell survival. The inhibition of HO-1 activity obtained by Zinc (II) protoprophyrin IX (ZnPPIX) was able to significantly increase the pro-apoptotic effect of BTZ in a p53- and p21-independent way. However, MYCN non-amplified SH-SY5Y cells showed a greater sensitivity to BTZ in relation to their inability to up-regulate HO-1. Therefore, we have shown that HO-1 inhibition improves the sensitivity of aggressive NB to proteasome inhibition-based therapy, suggesting that HO-1 up-regulation can be used as a marker of chemoresistance in NB. These results open up a new scenario in developing a combined therapy to overcome chemoresistance in high-risk neuroblastoma.

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