Neuroinflammation and endoplasmic reticulum stress are coregulated by cyclo(His-Pro) to prevent LPS neurotoxicity.

Many neurological and neurodegenerative diseases are associated with oxidative stress and glial inflammation, all related to endoplasmic reticulum stress. Cyclo(His-Pro) is an endogenous cyclic dipeptide that exerts cytoprotection by interfering with the Nrf2-NF-κB systems, the former presiding the antioxidant and the latter the pro-inflammatory cellular response. Here we investigated whether the cyclic dipeptide inhibits glial inflammation thus reducing the detrimental effect of inflammatory neurotoxins on neurons. We found that systemic administration of cyclo(His-Pro) exerts in vivo anti-inflammatory effects in the central nervous system by down-regulating hepatic and cerebral TNFα expression thereby counteracting LPS-induced gliosis. Mechanistic studies indicated that the cyclic dipeptide-mediated effects are achieved through the activation of Nrf2-driven antioxidant response and the inhibition of the pro-inflammatory NF-κB pathway. Moreover, by up-regulating Bip, cyclo(His-Pro) increases the ER stress sensitivity and triggers the unfolded protein response to alleviate the ER stress. These results unveil a novel potential therapeutic use of cyclo(His-Pro) against neuroinflammatory-related diseases and we might now consider its potential anti-inflammatory role in other neuropathological conditions.

α-Tocopheryl succinate pre-treatment attenuates quinone toxicity in prostate cancer PC3 cells.

α-Tocopheryl succinate is one of the most effective analogues of vitamin E for inhibiting cell proliferation and inducing cell death in a variety of cancerous cell lines while sparing normal cells or tissues. αTocopheryl succinate inhibits oxidative phosphorylation at the level of mitochondrial complexes I and II, thus enhancing reactive oxygen species generation which, in turn, induces the expression of Nrf2-driven antioxidant/detoxifying genes. The cytoprotective role of Nrf2 downstream genes/proteins prompted us to investigate whether and how α-tocopheryl succinate increases resistance of PC3 prostate cancer cells to pro-oxidant damage. A 4h α-tocopheryl succinate pre-treatment increases glutathione intracellular content, indicating that the vitamin E derivative is capable of training the cells to react to an oxidative insult. We found that α-tocopheryl succinate pre-treatment does not enhance paraquat-/hydroquinone-induced cytotoxicity whereas it exhibits an additional/synergistic effect on H2O2₋/docetaxel-induced cytotoxicity. While glutathione and heme oxygenase-1 are not involved in α-tocopheryl succinate-induced adaptive response to paraquat, NAD(P)H: quinone oxidoreductase seems to be responsible, at least in part, for the lack of the additional response. Silencing the gene and/or the inhibition of NAD(P)H: quinone oxidoreductase activity counteracts the α-tocopheryl succinate-induced adaptive response. In conclusion, the adaptive response to α-tocopheryl succinate shows that the activation of Nrf2 can promote the survival of cancer cells in an unfavourable environment.

Inhibition of NF-κB nuclear translocation via HO-1 activation underlies α-tocopheryl succinate toxicity.

α-Tocopheryl succinate (α-TOS) inhibits oxidative phosphorylation at the level of mitochondrial complex I and II, thus promoting cancer cell death through mitochondrial reactive oxygen species (ROS) generation. Redox imbalance activates NF-E2 p45-related factor 2 (Nrf2), a transcription factor involved in cell protection and detoxification responses. Here we examined the involvement of heme oxygenase-1 (HO-1) in the regulation of nuclear factor κB (NF-κB) signaling by short exposure to α-TOS in prostate cancer cells. A short-term (4 h) exposure to α-TOS causes a significant reduction in cell viability (76%±9%) and a moderate rise in ROS production (113%±8%). α-TOS alters glutathione (GSH) homeostasis by inducing a biphasic effect, i.e., an early (1 h) decrease in intracellular GSH content (56%±20%) followed by a threefold rise at 4 h. α-TOS increases nuclear translocation and electrophile-responsive/antioxidant-responsive elements binding activity of Nrf2, resulting in up-regulation of downstream genes cystine-glutamic acid exchange transporter and HO-1, while decreasing NF-κB nuclear translocation. This effect is suppressed by the pharmacological inhibition of HO-1 and mimicked by the end-products of HO activity, i.e., bilirubin and carbon monoxide. Results suggest a little understood mechanism for α-TOS-induced inhibition of NF-κB nuclear translocation due to HO-1 up-regulation.

Protective effects of Commiphora erythraea resin constituents against cellular oxidative damage.

By bioguided fractionation of the hexane extract of Commiphora erythraea resin we isolated four furanosesquiterpenoids that were tested for their protective activity against oxidative stress. Furanodienone and 1,10(15)-furanogermacra-dien-6-ones showed to be potent inhibitors of lipid peroxidation (IC(50) of -0.087 µM), being more active than the methoxylated analogues. Furthermore, using BV2 microglial cells, we found that furanodienone from C. erythraea is able to counteract LPS-induced cell death and decrease LPS-induced NO generation thus protecting microglial cells from LPS-induced cytotoxicity. Finally, docking studies were undertaken to gain insight into the possible binding mode of the isolated compounds at 5-LOX binding site.

Nrf2 and NF-κB and Their Concerted Modulation in Cancer Pathogenesis and Progression.

Reactive oxygen species, produced by oxidative stress, are implicated in the initiation, promotion, and malignant conversion of carcinogenesis through activation/suppression of redox-sensitive transcription factors. NF-E2-related factor 2 (Nrf2) encodes for antioxidant and general cytoprotection genes, while NF-κB regulates the expression of pro-inflammatory genes. A variety of anti-inflammatory or anti-carcinogenic phyto-chemicals suppress NF-κB signalling and activate the Nrf2-ARE pathway. In this review we consider the role of Nrf2 and NF-κB in cancer pathogenesis and progression, focusing on their concerted modulation and potential cross-talk.