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

Heme oxygenase 1 (HO-1) plays a pivotal role in preventing cell damage. Indeed, through the antioxidant, antiapoptotic and anti-inflammatory properties of its metabolic products, it favors cell adaptation against different stressors. However, HO-1 induction has also been related to the gain of resistance to therapy in different types of cancers and its involvement in cancer immune-escape has been hypothesized. We have investigated the role of HO-1 expression in Vemurafenib-treated BRAFV600 melanoma cells in modulating their susceptibility to NK cell-mediated recognition. Different cell lines, isolated in house from melanoma patients, have been exposed to 1-10 µM PLX4032, which efficiently reduced ERK phosphorylation. In three lines, Vemurafenib was able to induce only a limited decrease in cell viability, while HO-1 expression was upregulated. HO-1 silencing/inhibition was able to induce a further significant reduction of Vemurafenib-treated melanoma viability. Moreover, while NK cell degranulation and killing activity were decreased upon interaction with melanoma exposed to Vemurafenib, HO-1 silencing was able to completely restore NK cell ability to degranulate and kill. Furthermore, melanoma cell treatment with Vemurafenib downregulated the expression of ligands of NKp30 and NKG2D activating receptors, and HO-1 silencing/inhibition was able to restore their expression. Our results indicate that HO-1 downregulation can both improve the efficacy of Vemurafenib on melanoma cells and favor melanoma susceptibility to NK cell-mediated recognition and killing.

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

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.

HO-1 up-regulation: a key point in high-risk neuroblastoma resistance to bortezomib.

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.

Diet and Nutraceutical Supplementation in Dyslipidemic Patients: First Results of an Italian Single Center Real-World Retrospective Analysis.

BACKGROUND: Dyslipidemias are a heterogeneous group of metabolic disorders mainly characterized by an increased risk of atherosclerotic cardiovascular disease (ASCVD) or other conditions, such as acute pancreatitis in hypertriglyceridemia. The aim of this study was to evaluate the effect of diet treatment and nutraceutical (NUTs) supplementation on the plasma lipid profile in outpatient dyslipidemic subjects, considering the influence of several factors (i.e., gender, age, body mass index, alcohol consumption, and smoking habits). METHODS: 487 dyslipidemic patients spanning from 2015 to 2019 were treated with a Mediterranean diet or NUTs in a real-word setting and were retrospectively analyzed. General characteristics and lipid profile at baseline and after the follow-up period were evaluated. RESULTS: Diet alone reduced total cholesterol (-19 mg/dL, -7.7%), LDL cholesterol (-18 mg/dL, -10.1%), and triglycerides (-20 mg/dL, -16.7%). Triglycerides (TG) decreased more in men, while women were associated with higher reduction of LDL cholesterol (LDL-C). Different types of NUTs further ameliorate lipid profiles when associated with diet. Nevertheless, most patients at low ASCVD risk (222 out of 262, 81.6%) did not achieve the 2019 ESC/EAS guidelines recommended LDL-C goals (i.e., LDL-C < 116 mg/dL). CONCLUSION: Lipid-lowering diet improves lipid profile, and NUTs can boost its efficacy, but taken together they are mainly unsatisfactory with respect to the targets imposed by 2019 EAS/ESC guidelines.

microRNA-494 Favors HO-1 Expression in Neuroblastoma Cells Exposed to Oxidative Stress in a Bach1-Independent Way.

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.

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

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 Induction in Cancer Progression: A Matter of Cell Adaptation.

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-derived bilirubin protects endothelial cells against high glucose-induced damage.

Hyperglycemia and diabetes are associated with endothelial cell dysfunction arising from enhanced oxidative injury, leading to the progression of diabetic vascular pathologies. The redox-sensitive transcription factor nuclear factor-E2-related factor 2 (Nrf2) is a master regulator of antioxidant genes, such as heme oxygenase-1 (HO-1), involved in cellular defenses against oxidative stress. We have investigated the pathways involved in high glucose-induced activation of HO-1 in endothelial cells and examined the molecular mechanisms underlying cytoprotection. Elevated d-glucose increased intracellular generation of reactive oxygen species (ROS), leading to nuclear translocation of Nrf2 and HO-1 expression in bovine aortic endothelial cells, with no changes in cell viability. Superoxide scavenging and inhibition of endothelial nitric oxide synthase (eNOS) abrogated upregulation of HO-1 expression by elevated glucose. Inhibition of HO-1 increased the sensitivity of endothelial cells to high glucose-mediated damage, while addition of bilirubin restored cell viability. Our findings establish that exposure of endothelial cells to high glucose leads to activation of endogenous antioxidant defense genes via the Nrf2/ARE pathway. Upregulation of HO-1 provides cytoprotection against high glucose-induced oxidative stress through the antioxidant properties of bilirubin. Modulation of the Nrf2 pathway in the early stages of diabetes may thus protect against sustained damage by hyperglycemia during progression of the disease.

Monomeric Aß1-42 and RAGE: key players in neuronal differentiation.

The aggregation of amyloid-ß (Aß) peptides plays a crucial role in the onset and progression of Alzheimer's disease. Monomeric form of Aß, indeed, could exert a physiological role. Considering the anti-oligomerization property of all-trans retinoic acid (ATRA), the involvement of monomeric Aß1-42 in ATRA-induced neuronal differentiation has been investigated. Four-day ATRA treatment increases ß-secretase 1 (BACE1) level, Aß1-42 production, and receptor for advanced glycation end-products (RAGE) expression. RAGE is a well-recognized receptor for Aß, and the block of both RAGE and Aß1-42 with specific antibodies strongly impairs neurite formation in ATRA-treated cells. The involvement of Aß1-42 and RAGE in ATRA-induced morphologic changes has been confirmed treating undifferentiated cells with different molecular assemblies of peptide: 1 µM monomeric, but not oligomeric, Aß1-42 increases RAGE expression and favors neurite elongation. The block of RAGE completely prevents this effect. Furthermore, our data underline the involvement of the RAGE-dependent adhesion molecule amphoterin-induced gene and open reading frame-1 as downstream effector of both ATRA and Aß1-42. In conclusion, our findings identify a novel physiological role for monomeric Aß1-42 and RAGE in neuronal differentiation.