Hypoxia inducible factor-1 (HIF-1) is the main transcriptional activator of the cellular response to hypoxia and an important target of anticancer therapy. Phosphorylation by ERK1 and/or ERK2 (MAPK3 and MAPK1, respectively; hereafter ERK) stimulates the transcriptional activity of HIF-1α by inhibiting its CRM1 (XPO1)-dependent nuclear export. Here, we demonstrate that phosphorylation by ERK also regulates the association of HIF-1α with a so-far-unknown interaction partner identified as mortalin (also known as GRP75 and HSPA9), which mediates non-genomic involvement of HIF-1α in apoptosis. Mortalin binds specifically to HIF-1α that lacks modification by ERK, and the HIF-1α-mortalin complex is localized outside the nucleus. Under hypoxia, mortalin mediates targeting of unmodified HIF-1α to the outer mitochondrial membrane, as well as association with VDAC1 and hexokinase II, which promotes production of a C-terminally truncated active form of VDAC1, denoted VDAC1-ΔC, and protection from apoptosis when ERK is inactivated. Under normoxia, transcriptionally inactive forms of unmodified HIF-1α or its C-terminal domain alone are also targeted to mitochondria, stimulate production of VDAC1-ΔC and increase resistance to etoposide-or doxorubicin-induced apoptosis. These findings reveal an ERK-controlled, unconventional and anti-apoptotic function of HIF-1α that might serve as an early protective mechanism upon oxygen limitation and promote cancer cell resistance to chemotherapy.

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Proliferation of cells under hypoxia is facilitated by metabolic adaptation, mediated by the transcriptional activator Hypoxia Inducible Factor-1 (HIF-1). HIF-1α, the inducible subunit of HIF-1 is regulated by oxygen as well as by oxygen-independent mechanisms involving phosphorylation. We have previously shown that CK1δ phosphorylates HIF-1α in its N-terminus and reduces its affinity for its heterodimerization partner ARNT. To investigate the importance of this mechanism for cell proliferation under hypoxia, we visually monitored HIF-1α interactions within the cell nucleus using the in situ proximity ligation assay (PLA) and fluorescence recovery after photobleaching (FRAP). Both methods show that CK1δ-dependent modification of HIF-1α impairs the formation of a chromatin binding HIF-1 complex. This is confirmed by analyzing expression of lipin-1, a direct target of HIF-1 that mediates hypoxic neutral lipid accumulation. Inhibition of CK1δ increases lipid droplet formation and proliferation of both cancer and normal cells specifically under hypoxia and in an HIF-1α- and lipin-1-dependent manner. These data reveal a novel role for CK1δ in regulating lipid metabolism and, through it, cell adaptation to low oxygen conditions.

The objective of this study was to assess the resting values of the physiological oxidative stress exhibited by lambs and kids reared in Greece, and the potential correlations between redox biomarker levels in blood and other tissues (liver, diaphragm, quadriceps, psoas major muscle). For this purpose, lambs and kids at different developmental stages (d.s.) were used. The latter corresponded to four live weight categories (LWC), each representing 25%, 35%, 70% and 100% of mature body weight. In each of the above tissues, the levels of five common redox biomarkers were determined: glutathione (GSH), catalase (CAT), total antioxidant capacity (TAC), thiobarbituric reactive substances (TBARS), and protein carbonyls (CARBS). The results revealed that lambs and kids belonging to the 35% LWC had weaker endogenous antioxidant pools, while animals in the 70% and 100% LWC had elevated intrinsic antioxidant defense systems. Blood redox biomarkers were associated with the respective ones measured in the diaphragm, liver, quadriceps, and psoas major of both species. Importantly, TBARS levels in blood of animals in the 25% and 100% LWC are correlated with the TBARS levels in all other tissues tested. Blood antioxidant parameters might be used as potential biomarkers to predict the antioxidant status of tissues that affect meat quality. The latter would facilitate quality assessment prior to slaughter, allowing for timely nutritional interventions that can improve meat products.

The two crucial cellular insults that take place during cerebral ischemia are the loss of oxygen and loss of glucose, which can both activate a cascade of events leading to neuronal death. In addition, the toxic overactivation of neuronal excitatory receptors, leading to Ca2+ overload, may contribute to ischemic neuronal injury. Brain ischemia can be simulated in vitro by oxygen/glucose deprivation, which can be reversible by the re-establishment of physiological conditions. Accordingly, we examined the effects of glucose deprivation on the PI3K/Akt survival signaling pathway and its crosstalk with HIF-1α and Ca2+ homeostasis in SH-SY5Y human neuroblastoma cells. It was found that glucose withdrawal decreased HIF-1α protein levels even in the presence of the ischemia-mimicking CoCl2. On the contrary, and despite neuronal death, we identified a strong activation of the master pro-survival kinase Akt, a finding that was also confirmed by the increased phosphorylation of GSK3, a direct target of p-Akt. Remarkably, the elevated Ca2+ influx recorded was found to promptly trigger the activation of Akt, while a re-addition of glucose resulted in rapid restoration of both Ca2+ entry and p-Akt levels, highlighting the plasticity of neurons to respond to ischemic challenges and the important role of glucose homeostasis for multiple neurological disorders.

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Honey is a natural product derived from the insect Apis mellifera . Approximately 200 different compounds are included, making it a complex mixture with antimicrobial, antioxidant, and antidiabetic activity. Flavonoids and phenolic acids contained in honey are associated with its antioxidant capacity via mechanisms such as hydrogen donation and metallic ion chelation, although the exact antioxidant mechanism remains unknown. The aim of the present study was to: i) Estimate the antioxidant activity of a natural honey-based gel, commercially available under the trade name of ‘Bear Strength honey gel’ and to ii) assess the physiological and redox adjustments obtained after its consumption in healthy adult participants. For this purpose, 20 healthy participants (10 men and 10 women) included in their habitual diet 70 g of the honey-based gel for 14 days in a row. Pre- and post-consumption, physiological [weight, height, body mass index, body fat, waist-to-hip ratio, resting heart rate and blood pressure (BP)] and hematological (complete blood count) data were evaluated, along with the levels of five redox biomarkers: Glutathione (GSH), catalase (CAT), total antioxidant capacity (TAC), protein carbonyls (PCARBS) and thiobarbituric reactive substances (TBARS). The results revealed that the honey-based gel decreased the diastolic and mean arterial BP, especially in women, without affecting the rest of the physiological and hematological variables. Regarding the changes observed in antioxidant status variables, GSH was increased both in the total and women's group, while TAC was increased in all groups post-consumption. No changes were detected in the levels of CAT. Regarding oxidative stress, a decrease in the levels of TBARS in the total and women's group, was observed. PCARBS levels were decreased post-consumption only in the women's group. In conclusion, the present study demonstrated the potential positive effects of a honey-based gel on BP and redox status of healthy adults in a sex-specific manner.