Sara De Biasi

Quercetin and Cancer Chemoprevention

Several molecules present in the diet, including flavonoids, can inhibit the growth of cancer cells with an ability to act as “chemopreventers”. Their cancer-preventive effects have been attributed to various mechanisms, including the induction of cell-cycle arrest and/or apoptosis as well as the antioxidant functions. The antioxidant activity of chemopreventers has recently received a great interest, essentially because oxidative stress participates in the initiation and progression of different pathological conditions, including cancer. Since antioxidants are capable of preventing oxidative damage, the wide use of natural food-derived antioxidants is receiving greater attention as potential anti-carcinogens. Among flavonoids, quercetin (Qu) is considered an excellent free-radical scavenging antioxidant, even if such an activity strongly depends on the intracellular availability of reduced glutathione. Apart from antioxidant activity, Qu also exerts a direct, pro-apoptotic effect in tumor cells, and can indeed block the growth of several human cancer cell lines at different phases of the cell cycle. Both these effects have been documented in a wide variety of cellular models as well as in animal models. The high toxicity exerted by Qu on cancer cells perfectly matches with the almost total absence of any damages for normal, non-transformed cells. In this review we discuss the molecular mechanisms that are based on the biological effects of Qu, and their relevance for human health.

Interfering with ROS Metabolism in Cancer Cells: The Potential Role of Quercetin

A main feature of cancer cells, when compared to normal ones, is a persistent pro-oxidative state that leads to an intrinsic oxidative stress. Cancer cells have higher levels of reactive oxygen species (ROS) than normal cells, and ROS are, in turn, responsible for the maintenance of the cancer phenotype. Persistent ROS stress may induce adaptive stress responses, enabling cancer cells to survive with high levels of ROS and maintain cellular viability. However, excessive ROS levels render cancer cells highly susceptible to quercetin, one of the main dietary flavonoids. Quercetin depletes intracellular glutathione and increases intracellular ROS to a level that can cause cell death.

Circulating mitochondrial DNA increases with age and is a familiar trait: Implications for “inflamm‐aging”

Mitochondrial components, including mitochondrial DNA (mtDNA), when released extracellularly, can act as “damage‐associated molecular pattern” (DAMP) agents and cause inflammation. As many elderly people are characterized by a low‐grade, chronic inflammatory status defined “inflamm‐aging,” we evaluated if circulating mtDNA can contribute to this phenomenon. Eight hundred and thirty‐one Caucasian subjects were enrolled in the study, including 429 siblings aged 90–104 (90+ siblings). mtDNA plasma levels increased gradually after the fifth decade of life. In 90+ subjects, mtDNA values of two members of the same sibling relationship were directly correlated, suggesting a role for familiar/genetic background in controlling the levels of circulating mtDNA. The subjects with the highest mtDNA plasma levels had the highest amounts of TNF‐α, IL‐6, RANTES, and IL‐1ra; the subjects with the lowest mtDNA levels had the lowest levels of the same cytokines. In vitro stimulation of monocytes with mtDNA concentrations similar to the highest levels observed in vivo resulted in an increased production of TNF‐α, suggesting that mtDNA can modulate the production of proinflammatory cytokines. Our findings therefore show that circulating mtDNA increases with age, and can significantly contribute to the maintenance of the low‐grade, chronic inflammation observed in elderly people.

Human Dental pulp stem cells (hDPSCs): isolation, enrichment and comparative differentiation of two sub-populations

BackgroundHuman dental pulp represents a suitable alternative source of stem cells for the purpose of cell-based therapies in regenerative medicine, because it is relatively easy to obtain it, using low invasive procedures. This study characterized and compared two subpopulations of adult stem cells derived from human dental pulp (hDPSCs). Human DPSCs, formerly immune-selected for STRO-1 and c-Kit, were separated for negativity and positivity to CD34 expression respectively, and evaluated for cell proliferation, stemness maintenance, cell senescence and multipotency.ResultsThe STRO-1+/c-Kit+/CD34+ hDPSCs showed a slower proliferation, gradual loss of stemness, early cell senescence and apoptosis, compared to STRO-1+/c-Kit+/CD34− hDPSCs. Both the subpopulations demonstrated similar abilities to differentiate towards mesoderm lineages, whereas a significant difference was observed after the neurogenic induction, with a greater commitment of STRO-1+/c-Kit+/CD34+ hDPSCs. Moreover, undifferentiated STRO-1+/c-Kit+/CD34− hDPSCs did not show any expression of CD271 and nestin, typical neural markers, while STRO-1+/c-Kit+/CD34+ hDPSCs expressed both.ConclusionsThese results suggest that STRO-1+/c-Kit+/CD34− hDPSCs and STRO-1+/c-Kit+/CD34+ hDPSCs might represent two distinct stem cell populations, with different properties. These results trigger further analyses to deeply investigate the hypothesis that more than a single stem cell population resides within the dental pulp, to better define the flexibility of application of hDPSCs in regenerative medicine.

Increased plasma levels of extracellular mitochondrial DNA during HIV infection: a new role for mitochondrial damage-associated molecular patterns during inflammation.

HIV infection is characterized by a chronic inflammatory state. Recently, it has been shown that mitochondrial DNA (mtDNA) released from damaged or dead cells can bind Toll like receptor-9 (TLR9), an intracellular receptor that responds to bacterial or viral DNA molecules. The activation of TLR9 present within monocytes or neutrophils results in a potent inflammatory reaction, with the production of proinflammatory cytokines. We measured plasma levels of mtDNA in different groups of HIV(+) patients, i.e., those experiencing an acute HIV infection (AHI), long term non progressors (LTNP), late presenters (LP) taking antiretroviral therapy for the first time, and healthy controls. We found that in AHI and LP mtDNA plasma levels were significantly higher than in healthy individuals or in LTNP. Plasma mtDNA levels were not correlated to peripheral blood CD4(+) T cell count, nor to markers of immune activation, but had a significant correlation with plasma viral load, revealing a possible role for mtDNA in inflammation, or as a biomarker of virus-induced damage.

The protease inhibitor atazanavir triggers autophagy and mitophagy in human preadipocytes.

Background:The association between HAART and lipodystrophy is well established, but lipodystrophy pathogenesis is still poorly understood. Drugs, and in particular protease inhibitors, accumulate in adipose tissue affecting adipocyte physiology and gene expression by several mechanisms. Recent studies have identified autophagy as another process affected by these classes of drugs, but no studies have been performed in adipose cells. Methods:SW872 preadipocytic human cell line was used to evaluate changes induced by amprenavir (APV), ritonavir (RTV), or atazanavir (ATV), all used at 10–200 &mgr;mol/l. A subline was stably transfected with murine stem cell virus (pMSCV)-enhanced green fluorescent protein (EGFP)-LC3 plasmid (to obtain a fluorescent LC3 protein) and treated with ATV at different doses. The distribution of LC3 and the colocalization of mitochondria, lysosome, and autophagosome were assessed by confocal microscopy. Transmission electron microscopy of ATV-treated cells was also performed. The cellular content of lysosomes was assessed using Lysotracker Green; apoptosis was evaluated by annexin V/propidium iodide staining, and mitochondrial superoxide anion (mtO2-) was analyzed by mitoSOX red. Lysosomes, apoptosis, and mtO2- were studied by flow cytometry and multispectral imaging flow cytometry. Results:In SW872 cells, RTV caused massive apoptosis, more than autophagy, whereas APV was almost ineffective. ATV induced both apoptosis (high doses) and autophagy (low doses). ATV-treated cells displayed LC3-specific punctae, suggesting the formation of autophagosomes that enclosed mitochondria, as revealed by electron microscopy. At low doses, ATV promoted mitochondrial superoxide generation, whereas at high doses, it induced mitochondrial membrane depolarization. Conclusion:Autophagy/mitophagy can be considered a mechanism triggered by ATV in SW872 preadipocytes.

Natural Compounds Modulating Mitochondrial Functions

Mitochondria are organelles responsible for several crucial cell functions, including respiration, oxidative phosphorylation, and regulation of apoptosis; they are also the main intracellular source of reactive oxygen species (ROS). In the last years, a particular interest has been devoted to studying the effects on mitochondria of natural compounds of vegetal origin, quercetin (Qu), resveratrol (RSV), and curcumin (Cur) being the most studied molecules. All these natural compounds modulate mitochondrial functions by inhibiting organelle enzymes or metabolic pathways (such as oxidative phosphorylation), by altering the production of mitochondrial ROS and by modulating the activity of transcription factors which regulate the expression of mitochondrial proteins. While Qu displays both pro- and antioxidant activities, RSV and Cur are strong antioxidant, as they efficiently scavenge mitochondrial ROS and upregulate antioxidant transcriptional programmes in cells. All the three compounds display a proapoptotic activity, mediated by the capability to directly cause the release of cytochrome c from mitochondria or indirectly by upregulating the expression of proapoptotic proteins of Bcl-2 family and downregulating antiapoptotic proteins. Interestingly, these effects are particularly evident on proliferating cancer cells and can have important therapeutic implications.

Functional characterization of the promoter of the human Lon protease gene

Lon, a nuclear-encoded mitochondrial enzyme, degrades oxidized proteins of the mitochondrial (mt) matrix, and participates in the replication of mtDNA. Lon is upregulated in the presence of substances such as stavudine (d4T), D-deoxyribose (dRib), that increase the intracellular reactive oxygen species (ROS) levels, or in the presence of H(2)O(2.) Here we show the promoter region -623/+1 is essential for response to ROS, and that in SW872, HepG2 and WI-38 cell lines the region -1230/-623 represses transcription, while the region -2023/-1230 increases promoter activity. D4T upregulates Lon promoter activity in all cell lines while dRib upregulates Lon mainly in HepG2 cells, and in shorter incubation times. These data confirm that Lon can be considered a stress responsive protein.

Silencing of mitochondrial Lon protease deeply impairs mitochondrial proteome and function in colon cancer cells

Lon is a nuclear‐encoded, mitochondrial protease that assists protein folding, degrades oxidized/damaged proteins, and participates in maintaining mtDNA levels. Here we show that Lon is up‐regulated in several human cancers and that its silencing in RKO colon cancer cells causes profound alterations of mitochondrial proteome and function, and cell death. We silenced Lon in RKO cells by constitutive or inducible expression of Lon shRNA. Lon‐silenced cells displayed altered levels of 39 mitochondrial proteins (26% related to stress response, 14.8% to ribosome assembly, 12.7% to oxidative phosphorylation, 8.5% to Krebs cycle, 6.3% to β‐oxidation, and 14.7% to crista integrity, ketone body catabolism, and mtDNA maintenance), low levels of mtDNA transcripts, and reduced levels of oxidative phosphorylation complexes (with >90% reduction of complex I). Oxygen consumption rate decreased 7.5‐fold in basal conditions, and ATP synthesis dropped from 0.25 ± 0.04 to 0.03 ± 0.001 nmol/mg proteins, in the presence of 2‐deoxy‐D‐glucose. Hydrogen peroxide and mitochondrial superoxide anion levels increased by 3‐ and 1.3‐fold, respectively. Mitochondria appeared fragmented, heterogeneous in size and shape, with dilated cristae, vacuoles, and electrondense inclusions. The triterpenoid 2‐cyano‐3,12‐dioxooleana‐1,9,‐dien‐28‐oic acid, a Lon inhibitor, partially mimics Lon silencing. In summary, Lon is essential for maintaining mitochondrial shape and function, and for survival of RKO cells.—Gibellini, L., Pinti, M., Boraldi, F., Giorgio, V., Bernardi, P., Bartolomeo, R., Nasi, M., De Biasi, S., Missiroli, S., Carnevale, G., Losi, L., Tesei, A., Pinton, P., Quaglino, D., Cossarizza, A., Silencing of mitochondrial Lon protease deeply impairs mitochondrial proteome and function in colon cancer cells. FASEB J. 28, 5122–5135 (2014). www.fasebj.org

Endoscopic Third Ventriculostomy in Obstructive Infantile Hydrocephalus: Remarks about the So-Called ‘Unsuccessful Cases’

Background: The failure rate following endoscopic third ventriculostomy (ETV) in infants younger than 2 years of age has been reported to be higher compared with that of older children, and it is unclear whether ETV might be superior to shunt placement in this age group. Methods: Between 2003 and 2009, 23 patients younger than 6 months and without a previous history of shunting underwent ETV in our institution. A review of the literature was performed on the basis of publications presenting detailed data on age and etiology in every single patient. Results: In our own patients, total success rate was 39.1%. In the successful cases, median age was 140 days, whereas in the unsuccessful cases it was 47 days. The difference between the two groups was statistically significant (p = 0.01). The median ages of both successful and unsuccessful groups corresponded to data gained from an analysis of the literature (p = 0.04). At a median follow-up of 47 months, 2 out of 14 patients shunted after a failed ETV were revised for ventriculoperitoneal shunt malfunction. Conclusion: The impact of age on ETV failure in infants is clear and becomes crucial during the first 2 months of life, even when excluding etiological factors. Nevertheless, age cannot be considered the only parameter of the decision-making process, especially in these very young patients. Probably, the definition of ‘unsuccessful ETV’ should be reevaluated in light of decreased risk of shunt malfunction observed after a failed ETV.