Influence of Bilberry Extract on Neuronal Cell Toxicity.

Increased intake of dietary antioxidants such as anthocyanins, which are enriched in colourful fruits, is a promising alternative to reduce the risk of degenerative diseases such as Alzheimer's Disease (AD). Since Amyloid ß (Aß) is one of the key components contributing to AD pathology, probably by reactive oxygen species (ROS) induction, this study investigated the preventive effect of anthocyanin-rich bilberry extract (BE) and its anthocyanin fraction (ACN) on ROS generation and cell toxicity. The results showed a significant and concentration-dependent decrease in neuroblastoma cell (SH-SY5Y) viability by BE or ACN, whereas no cell toxicity was observed in HeLa cells. Incubation with BE and ACN for 24 h diminished the generation of induced ROS levels in SH-SY5Y and HeLa cells. In addition, low concentrations of BE (1-5 µg/mL) showed protective effects against Aß-induced cytotoxicity in SH-SY5Y cells. In conclusion, our results suggest antioxidant and protective effects of BE and ACN, which could potentially be used to delay the course of neurodegenerative diseases such as AD. Further studies are needed to clarify the high potential of anthocyanins and their in vivo metabolites on neuronal function.

Endogenous anti-tumorigenic nitro-fatty acids inhibit the ubiquitin-proteasome system by directly targeting the 26S proteasome.

Nitro-fatty acids (NFAs) are endogenous lipid mediators causing a spectrum of anti-inflammatory effects by covalent modification of key proteins within inflammatory signaling pathways. Recent animal models of solid tumors have helped demonstrate their potential as anti-tumorigenic therapeutics. This study evaluated the anti-tumorigenic effects of NFAs in colon carcinoma cells and other solid and leukemic tumor cell lines. NFAs inhibited the ubiquitin-proteasome system (UPS) by directly targeting the 26S proteasome, leading to polyubiquitination and inhibition of the proteasome activities. UPS suppression induced the unfolded protein response, resulting in tumor cell death. The NFA-mediated effects were substantial, specific, and enduring, representing a unique mode of action for UPS suppression. This study provides mechanistic insights into the biological actions of NFAs as possible endogenous tumor-suppressive factors, indicating that NFAs might be key structures for designing a novel class of direct proteasome inhibitors.

Analyzing the Effects of HDAC Inhibitors on DNA Damage and Associated Cytotoxicity in Primary Hepatocytes.

Primary hepatocytes are the gold standard in pharmaco- and toxicokinetic studies during preclinical development of drug candidates. Such cells are a valuable tool to identify potential hepatotoxicity, an important adverse drug reaction. Primary hepatocytes can be obtained not only from wild-type mice but also from genetically engineered knockout mouse strains. Liver perfusion yields murine primary hepatocytes (mpH) with high vitality, expressing an array of metabolic enzymes and transporters that are impaired or even absent in established liver cell lines. Furthermore, mpH display no genetic alterations and are proficient in the DNA damage response pathway. This makes mpH a suitable model to analyze the effects of histone deacetylase inhibitors on DNA damage and cell viability. Here, we report an efficient and fast protocol for the isolation of mpH by liver perfusion. These mpH can be used for downstream applications such as the detection of the DNA damage marker γH2AX by confocal laser scanning microscopy.

p53 triggers mitochondrial apoptosis following DNA damage-dependent replication stress by the hepatotoxin methyleugenol.

Liver cancer is one of the most frequent tumor entities worldwide, which is causally linked to viral infection, fatty liver disease, life-style factors and food-borne carcinogens, particularly aflatoxins. Moreover, genotoxic plant toxins including phenylpropenes are suspected human liver carcinogens. The phenylpropene methyleugenol (ME) is a constituent of essential oils in many plants and occurs in herbal medicines, food, and cosmetics. Following its uptake, ME undergoes Cytochrome P450 (CYP) and sulfotransferase 1A1 (SULT1A1)-dependent metabolic activation, giving rise to DNA damage. However, little is known about the cellular response to the induced DNA adducts. Here, we made use of different SULT1A1-proficient cell models including primary hepatocytes that were treated with 1'-hydroxymethyleugenol (OH-ME) as main phase I metabolite. Firstly, mass spectrometry showed a concentration-dependent formation of N2-MIE-dG as major DNA adduct, strongly correlating with SULT1A1 expression as attested in cells with and without human SULT1A1. ME-derived DNA damage activated mainly the ATR-mediated DNA damage response as shown by phosphorylation of CHK1 and histone 2AX, followed by p53 accumulation and CHK2 phosphorylation. Consistent with these findings, the DNA adducts decreased replication speed and caused replication fork stalling. OH-ME treatment reduced viability particularly in cell lines with wild-type p53 and triggered apoptotic cell death, which was rescued by pan-caspase-inhibition. Further experiments demonstrated mitochondrial apoptosis as major cell death pathway. ME-derived DNA damage caused upregulation of the p53-responsive genes NOXA and PUMA, Bax activation, and cytochrome c release followed by caspase-9 and caspase-3 cleavage. We finally demonstrated the crucial role of p53 for OH-ME triggered cell death as evidenced by reduced pro-apoptotic gene expression, strongly attenuated Bax activation and cell death inhibition upon genetic knockdown or pharmacological inhibition of p53. Taken together, our study demonstrates for the first time that ME-derived DNA damage causes replication stress and triggers mitochondrial apoptosis via the p53-Bax pathway.