Sara Tagliaferri

Antiglycative and neuroprotective activity of colon-derived polyphenol catabolites

SCOPE Dietary flavonoids and allied phenolic compounds are thought to be beneficial in the control of diabetes and its complications, because of their ability to inhibit oxidative stress, protein glycation and to act as neuroprotectants. Following ingestion by humans, polyphenolic compounds entering the large intestine undergo extensive metabolism by interaction with colonic microbiota and it is metabolites and catabolites of the parent compounds that enter the circulatory system. The aim of this study was to investigate the inhibitory activity of some colonic microbiota-derived polyphenol catabolites against advanced glycation endproducts formation in vitro and to determine their ability, at physiological concentrations, to counteract mild oxidative stress of cultured human neuron cells. METHODS AND RESULTS This study demonstrated that ellagitannin-derived catabolites (urolithins and pyrogallol) are the most effective antiglycative agents, whereas chlorogenic acid-derived catabolites (dihydrocaffeic acid, dihydroferulic acid and feruloylglycine) were most effective in combination in protecting neuronal cells in a conservative in vitro experimental model. CONCLUSION Some polyphenolic catabolites, generated in vivo in the colon, were able in vitro to counteract two key features of diabetic complications, i.e. protein glycation and neurodegeneration. These observations could lead to a better control of these events, which are usually correlated with hyperglycemia.

A mechanistic view of polybrominated diphenyl ether (PBDE) developmental neurotoxicity.

Polybrominated diphenyl ethers (PBDEs), extensively used in the past few decades as flame retardants in a variety of consumer products, have become world-wide persistent environmental pollutants. Levels in North America are usually higher than those in Europe and Asia, and body burden is 3-to-9-fold higher in infants and toddlers than in adults. The latter has raised concern for potential developmental toxicity and neurotoxicity of PBDEs. Experimental studies in animals and epidemiological observations in humans suggest that PBDEs may be developmental neurotoxicants. Pre- and/or post-natal exposure to PBDEs may cause long-lasting behavioral abnormalities, particularly in the domains of motor activity and cognition. The mechanisms underlying the developmental neurotoxic effects of PBDEs are not known, though several hypotheses have been put forward. One general mode of action relates to the ability of PBDEs to impair thyroid hormone homeostasis, thus indirectly affecting the developing brain. An alternative or additional mode of action involves a direct effect of PBDEs on nervous system cells; PBDEs can cause oxidative stress-related damage (DNA damage, mitochondrial dysfunction, apoptosis), and interfere with signal transduction (particularly calcium signaling), and with neurotransmitter systems. Important issues such as bioavailability and metabolism of PBDEs, extrapolation of results to low level of exposures, and the potential effects of interactions among PBDE congeners and between PBDEs and other contaminants also need to be taken into account.

Production of Wnt Inhibitors by Myeloma Cells: Potential Effects on Canonical Wnt Pathway in the Bone Microenvironment

Osteoblast impairment occurs within multiple myeloma cell infiltration into the bone marrow. Canonical Wnt signaling activation in osteoprogenitor cells is involved in osteoblast formation through the stabilization of dephosphorylated beta-catenin and its nuclear translocation. The effects of multiple myeloma cells on Wnt signaling in human mesenchymal/osteoprogenitor cells are unclear. In 60 multiple myeloma patients checked, we found that among the Wnt inhibitors, Dickkopf-1 and secreted frizzled-related protein-3 were produced by multiple myeloma cells. However, although multiple myeloma cells or multiple myeloma bone marrow plasma affected expression of genes in the canonical Wnt signaling and inhibited beta-catenin stabilization in murine osteoprogenitor cells, they failed to block the canonical Wnt pathway in human mesenchymal or osteoprogenitor cells. Consistently, Wnt3a stimulation in human osteoprogenitor cells did not blunt the inhibitory effect of multiple myeloma cells on osteoblast formation. Consequently, despite the higher Wnt antagonist bone marrow levels in osteolytic multiple myeloma patients compared with nonosteolytic ones, beta-catenin immunostaining was not significantly different. Our results support the link between the production of Wnt antagonists by multiple myeloma cells and the presence of bone lesions in multiple myeloma patients but show that myeloma cells do not inhibit canonical Wnt signaling in human bone microenvironment.

Low concentrations of the brominated flame retardants BDE-47 and BDE-99 induce synergistic oxidative stress-mediated neurotoxicity in human neuroblastoma cells.

Polybrominated diphenyl ether (PBDE) flame retardants have become widespread environmental contaminants. The highest body burden has been found in toddlers and infants, due to their exposure through breast milk and house dust, and the current concern for potential adverse health effects of PBDEs relates to their developmental neurotoxicity. The mechanisms underlying the neurotoxicity of PBDEs are largely not understood, though there is evidence that PBDEs may elicit oxidative stress. In this study, two different mathematical models were used to evaluate the interaction between BDE-47 and BDE-99 on viability of neuronal cells. The combined exposure to these compounds induced synergistic effects at concentrations of BDE-47 below its threshold doses, and in a wide range of BDE-99 concentrations below its IC(50). In contrast, at concentrations of BDE-47 near its IC(50) value, and in a wide range of BDE-99 concentrations, antagonistic effects were observed. The interactions observed on cell viability were confirmed by an assessment of induction of oxidative stress. The finding that co-exposure to BDE-47 and BDE-99 could induce synergistic neurotoxic effects, in particular at low doses of BDE-47, is of much toxicological interest, as humans are exposed to mixtures of PBDEs, most notably tetra- and penta-BDE congeners.

Everolimus restores gefitinib sensitivity in resistant non-small cell lung cancer cell lines

The epidermal growth factor receptor (EGFR) is a validated target for therapy in non-small cell lung cancer (NSCLC). Most patients, however, either do not benefit or develop resistance to specific inhibitors of the EGFR tyrosine kinase activity, such as gefitinib or erlotinib. The mammalian target of rapamycin (mTOR) is a key intracellular kinase integrating proliferation and survival pathways and has been associated with resistance to EGFR tyrosine kinase inhibitors. In this study, we assessed the effects of combining the mTOR inhibitor everolimus (RAD001) with gefitinib on a panel of NSCLC cell lines characterized by gefitinib resistance and able to maintain S6K phosphorylation after gefitinib treatment. Everolimus plus gefitinib induced a significant decrease in the activation of MAPK and mTOR signaling pathways downstream of EGFR and resulted in a growth-inhibitory effect rather than in an enhancement of cell death. A synergistic effect was observed in those cell lines characterized by high proliferative index and low doubling time. These data suggest that treatment with everolimus and gefitinib might be of value in the treatment of selected NSCLC patients that exhibit high tumor proliferative activity.

Synergistic interactions between PBDEs and PCBs in human neuroblastoma cells

Polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants. Exposure to these chemicals has been associated with developmental neurotoxicity, endocrine dysfunction, and reproductive disorders. Humans and wildlife are generally exposed to a mixture of these environmental pollutants, highlighting the need to evaluate the potential effects of combined exposures. In this study, we investigated the cytotoxic effects of the combined exposure to two PBDEs and two PCBs in a human neuronal cell line. 2,2′,4,4′‐Tetrabromodiphenyl ether, 2,2′,4,4′,5‐pentabromodiphenyl ether, PCB‐126 (3,3′,4,4′,5‐pentachlorobiphenyl; a dioxin‐like PCB), and PCB‐153 (2,2′,4,4′,5,5′‐hexachlorobiphenyl; a non‐dioxin‐like PCB) were chosen, because their concentrations are among the highest in human tissues and the environment. The results suggest that the nature of interactions is related to the PCB structure. Mixtures of PCB‐153 and both PBDEs had a prevalently synergistic effect. In contrast, mixtures of each PBDE congener with PCB‐126 showed additive effects at threshold concentrations, and synergistic effects at higher concentrations. These results emphasize the concept that the toxicity of xenobiotics may be affected by possible interactions, which may be of significance given the common coexposures to multiple contaminants.

Dose-response or dose-effect curves in in vitro experiments and their use to study combined effects of neurotoxicants.

Interactions among neurotoxicants in in vitro models, where the molecular mechanisms of toxicity are generally studied, represent today an emerging field in the experimental neurotoxicology. In this chapter, we define some general concepts about the optimization of in vitro experiments to assess the dose/concentration-effect/response relationships and to extrapolate the functions describing them. After describing the available models to study interactions (the Bliss independence criterion and the Loewe additivity model), we present a method to practically apply these models to experimental data. Finally, we provide some examples of the theory of interactions among neurotoxicants in in vitro models.

Targeting pathways mediating bone disease.

Multiple myeloma (MM) is a plasma cell malignancy characterized by the high capacity to induce osteolytic bone lesions. Bone destruction in MM mainly depends on the increase of osteoclast formation and activity that occurs in close contact with myeloma cells infiltration. The histomorphometric studies, performed in MM patients, have demonstrated that MM patients with high plasma cell infiltrate are also characterized by a lower number of osteoblasts and a decreased bone formation that contributes, to the development of bone lesion. In the last years the progress in acknowledge of the pathophysiology of MM-induced osteolysis leaded to identify new therapeutics targets in MM bone disease and developed new drugs in the treatment of patients with skeletal involvement.

Inter- and intra-subject variability of kinetics of airway exhalation and deposition of particulate matter in indoor polluted environments

PM(2.5) generated by indoor combustion activities can contribute significantly to personal PM exposure. The aims of this study were: (1) to validate a device specifically designed to study the kinetics of particle exhalation and the percentage of airway particle deposition (%DEP) in polluted indoor environments (welding fumes, environmental tobacco smoke - ETS) and (2) to assess the intra- and inter-subject variability of the signal. The device was tested on 14 subjects exposed to welding fumes and 10 subjects exposed to environmental tobacco smoke (ETS), performing repeated measures at different environmental PM concentrations. The intra-subject variability of the signal for particles with diameter 0.3-1.0 μm showed a geometric mean of %CV always below 6%, despite the values of %DEP. In the welding fume study, the increase in airborne 0.5-1.0 μm PM concentrations between the consulting room and production department was explainable in terms of increased density due to the metallic composition of particles. The %DEP of 0.3-1.0 μm ETS particles decreased with airborne PM concentration due to the technical limits of a laser particle counter and the perturbation induced by the physical characteristics of ETS PM. However, also at those extreme conditions, the signal remained repeatable and the individual susceptibility to PM remained substantially unaltered. In conclusion, the versatility and portability of our device, together with the repeatability of the signal, confirmed that the kinetics of exhaled particles and %DEP could be routinely measured in polluted environments and used to define individual susceptibility to airborne particles.

Adverse Events of Proton Pump Inhibitors: Potential Mechanisms

OBJECTIVE We aimed at summarizing current evidence about mechanisms for potentially harmful effects of Proton Pump Inhibitors (PPIs). METHODS A Pubmed search was performed, and 207 studies concerning the relationship between use of PPIs and cardiovascular diseases, kidney impairment, nutritional disorders, fractures, infections, functional decline, and mortality were selected and reviewed. RESULTS PPIs may cause potentially harmful effects by several mechanisms, including endothelial dysfunction, hypomagnesemia, drug interactions, reduced absorption of selected nutrients, increased gastric microbiota and small intestine bacterial overgrowth, reduced immune response, tubular-interstitial inflammation, increased bone turnover, accumulation of amyloid in the brain. Clinical and epidemiologic evidence is not consistent in regard to some negative outcomes during PPI treatment. Data from randomized clinical trials seem to deny most of them, but they are usually designed to investigate efficacy of drugs in ideal conditions and are not powered enough to detect adverse events. Besides being at special risk of experiencing negative outcomes during long-term treatment with PPIs, older and complex patients treated with polypharmacy regimens are persistently excluded from randomized clinical trials. Thus, large observational studies involving real-world patients should be considered as an important informative source about potential risks related to PPIs. CONCLUSIONS Current evidence suggests that use of PPIs may be associated with negative outcomes by eliciting several different pathophysiologic mechanisms. While short-term PPIs could be considered effective and safe in adult patients with acid-related disorders, their long-term and often inappropriate use in patients carrying vulnerability to adverse events and/or high risk of drug-interactions should be avoided.