Pierpaola Davalli

ROS, Cell Senescence, and Novel Molecular Mechanisms in Aging and Age-Related Diseases

The aging process worsens the human body functions at multiple levels, thus causing its gradual decrease to resist stress, damage, and disease. Besides changes in gene expression and metabolic control, the aging rate has been associated with the production of high levels of Reactive Oxygen Species (ROS) and/or Reactive Nitrosative Species (RNS). Specific increases of ROS level have been demonstrated as potentially critical for induction and maintenance of cell senescence process. Causal connection between ROS, aging, age-related pathologies, and cell senescence is studied intensely. Senescent cells have been proposed as a target for interventions to delay the aging and its related diseases or to improve the diseases treatment. Therapeutic interventions towards senescent cells might allow restoring the health and curing the diseases that share basal processes, rather than curing each disease in separate and symptomatic way. Here, we review observations on ROS ability of inducing cell senescence through novel mechanisms that underpin aging processes. Particular emphasis is addressed to the novel mechanisms of ROS involvement in epigenetic regulation of cell senescence and aging, with the aim to individuate specific pathways, which might promote healthy lifespan and improve aging.

Clusterin (SGP-2) transient overexpression decreases proliferation rate of SV40-immortalized human prostate epithelial cells by slowing down cell cycle progression

Clusterin is a highly conserved, widely distributed glycoprotein whose biological significance is still debated. Involved in many biological processes and disease states, clusterin is induced by cell injury and tissue regression, but is repressed during cell proliferation. We have previously reported that clusterin mRNA induction is associated with epithelial cell atrophy in the rat prostate and both clusterin transcript and protein accumulated in quiescent normal human skin fibroblasts. Here we show that transient clusterin overexpression, in SV40-immortalized human prostate epithelial cells (PNT2), resulted in increased accumulation of cells in the G0/G1 phases of the cell cycle, accompanied by slowdown of cell cycle progression and decrease of DNA synthesis. The activities of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC), and the level of histone H3 mRNA (markers of cell proliferation) concomitantly decreased, while Gas1 mRNA (a marker of cell quiescence) accumulated. Thus it appears that clusterin, by opposing the effect of SV40 on the proliferation rate of PNT2 cells, acts as an anti-oncogene in the prostate, suggesting a role for this gene in controlling proliferation of normal and transformed prostate epithelial cells.

Polyamines, Ornithine Decarboxylase, and Diamine Oxidase in the Substantia Nigra and Striatum of the Male Rat After Hemitransection

Partial hemitransection at the mesodiencephalic junction in the rat increased striatal and nigral putrescine concentrations on the lesioned side for at least 168 h, with maximal increases between 24 and 48 h. Spermidine and spermine levels declined at 24 h in the striatum, rising above control values at 48 h and further at 168 h. In the substantia nigra, they remained unchanged for the first 48 h and then increased by 168 h. Cadaverine in the striatum also increased at 48 h. On the intact side putrescine increased but to a much lesser extent (at 48 h in the striatum and at 24 and 48 h in the substantia nigra). Ornithine decarboxylase and diamine oxidase activities showed maximal increases at 24 h in the striatum of the lesioned side, whereas in the substantia nigra ornithine decarboxylase attained a very high value as early as 4 h after the operation and diamine oxidase activity peaked at 48 h. The enzyme activities returned toward the basal values at 168 h. On the intact side, ornithine decarboxylase showed a small increase starting at 4 h and diamine oxidase was enhanced at 48 h. These results indicate that the stimulation of biosyn‐thetic and degradative enzymes of polyamine metabolism accompanied by marked and prolonged increases in putrescine may be essential events in the early phases of neuronal response to mechanical injury in the CNS.

Coordinate changes of polyamine metabolism regulatory proteins during the cell cycle of normal human dermal fibroblasts

In human dermal fibroblasts, brought to quiescence (G0) by serum starvation, the S phase peaked 24 h and G2/M phases 36 h after serum re‐addition. Under the same conditions, ornithine decarboxylase mRNA peaked at 12 h, decreased markedly in S phase and remained low until 48 h. Conversely, ornithine decarboxylase antizyme transcript dropped to its lowest level at 12 h, while reaching its highest values between 24 and 48 h. Ornithine decarboxylase activity followed essentially the pattern of its mRNA, but relative changes were much greater. S‐Adenosylmethionine decarboxylase transcript and enzyme activity also peaked at around 12 h, decreasing thereafter. Spermidine/spermine N 1‐acetyltransferase mRNA and activity reached the highest values at 36–48 h. Putrescine concentration increased up to 18 h and fell dramatically in the S phase, remaining low thereafter. Both spermidine and spermine reached peaks at 18 h and decreased in the S phase, but not nearly as much as putrescine. We discuss how this comprehensive study may help to understand the involvement of polyamines in the control of cell proliferation.

Anticancer Activity of Green Tea Polyphenols in Prostate Gland

Numerous evidences from prevention studies in humans, support the existence of an association between green tea polyphenols consumption and a reduced cancer risk. Prostate cancer is one of the most frequently diagnosed male neoplasia in the Western countries, which is in agreement with this gland being particularly vulnerable to oxidative stress processes, often associated with tumorigenesis. Tea polyphenols have been extensively studied in cell culture and animal models where they inhibited tumor onset and progression. Prostate cancer appears a suitable target for primary prevention care, since it grows slowly, before symptoms arise, thus offering a relatively long time period for therapeutic interventions. It is, in fact, usually diagnosed in men 50-year-old or older, when even a modest delay in progression of the disease could significantly improve the patients quality of life. Although epidemiological studies have not yet yielded conclusive results on the chemopreventive and anticancer effect of tea polyphenols, there is an increasing trend to employ these substances as conservative management for patients diagnosed with less advanced prostate cancer. Here, we intend to review the most recent observations relating tea polyphenols to human prostate cancer risk, in an attempt to outline better their potential employment for preventing prostate cancer.

Upregulation of clusterin in prostate and DNA damage in spermatozoa from bisphenol A-treated rats and formation of DNA adducts in cultured human prostatic cells.

Among endocrine disruptors, the xenoestrogen bisphenol A (BPA) deserves particular attention due to widespread human exposure. Besides hormonal effects, BPA has been suspected to be involved in breast and prostate carcinogenesis, which share similar estrogen-related mechanisms. We previously demonstrated that administration of BPA to female mice results in the formation of DNA adducts and proteome alterations in the mammary tissue. Here, we evaluated the ability of BPA, given with drinking water, to induce a variety of biomarker alterations in male Sprague-Dawley rats. In addition, we investigated the formation of DNA adducts in human prostate cell lines. In BPA-treated rats, no DNA damage occurred in surrogate cells including peripheral blood lymphocytes and bone marrow erythrocytes, where no increase of single-strand DNA breaks was detectable by comet assay and the frequency of micronucleated cells was unaffected by BPA. Liver cells were positive at transferase dUTP nick end labeling assay, which detects both single-strand and double-strand breaks and early stage apoptosis. BPA upregulated clusterin expression in atrophic prostate epithelial cells and induced lipid peroxidation and DNA fragmentation in spermatozoa. Significant levels of DNA adducts were formed in prostate cell lines treated either with high-dose BPA for 24 h or low-dose BPA for 2 months. The BPA-related increase of DNA adducts was more pronounced in PNT1a nontumorigenic epithelial cells than in PC3 metastatic carcinoma cells. On the whole, these experimental findings support mechanistically the hypothesis that BPA may play a role in prostate carcinogenesis and may, potentially, affect the quality of sperm.

Genetic inactivation of ApoJ/clusterin: effects on prostate tumourigenesis and metastatic spread

ApoJ/Clusterin (CLU) is a heterodimeric protein localized in the nucleus, cytoplasm or secretory organelles and involved in cell survival and neoplastic transformation. Its function in human cancer is still highly controversial. In this study, we examined the prostate of mice in which CLU has been genetically inactivated. Surprisingly, we observed transformation of the prostate epithelium in the majority of CLU knockout mice. Either PIN (prostate intraepithelial neoplasia) or differentiated carcinoma was observed in 100 and 87% of mice with homozygous or heterozygous deletion of CLU, respectively. Crossing CLU knockout with TRAMP (prostate cancer prone) mice results in a strong enhancement of metastatic spread. Finally, CLU depletion causes tumourigenesis in female TRAMP mice, which are normally cancer free. Mechanistically, deletion of CLU induces activation of nuclear factor-kB, a potentially oncogenic transcription factor important for the proliferation and survival of prostate cells.

Effects of neurotoxic and mechanical lesions of the mesostriatal dopamine pathway on striatal polyamine levels in the rat: Modulation by chronic ganglioside GM1 treatment

In male rats, partial hemitransections but not 6-hydroxydopamine (6-OHDA)-induced lesions of the mesostriatal dopamine (DA) pathway produce after 7 days a marked and a modest increase of striatal putrescine and spermidine levels, respectively, on the lesioned side. Following chronic ganglioside GM1 treatment of partially hemitransected rats, an increase of striatal polyamine levels was observed also on the intact side. It is suggested that retrograde cell body changes produced by hemitransection may induce striatal ornithine decarboxylase activity and in this way increase striatal putrescine levels, favoring regenerative mechanisms. The increase of striatal polyamine levels by GM1 treatment on the intact side of both 6-OHDA and mechanically lesioned rats compared with intact unoperated rats may also reflect an increased synthesis of striatal polyamines.

GENE RELAXATION AND AGING : CHANGES IN THE ABUNDANCE OF RAT VENTRAL PROSTATE SGP-2 (CLUSTERIN) AND ORNITHINE DECARBOXYLASE MRNAS

Sulfated glycoprotein 2 (SGP‐2) mRNA progressively increased in the ventral prostate of the aging rat, reaching, at 24 months, 4‐fold higher than at 3 months. Ornithine decarboxylase (ODC) mRNA peaked at 6 months (4‐fold increase), and at 12 and 24 months was maintained at higher levels than at 3 months. ODC enzymatic activity was enhanced at 6 months to a much smaller extent than its own mRNA, the values at 12 and 24 months dropping to below those at 3 months. Putrescine (Put), spermidine (Spd) and spermine (Sp) concentrations also peaked at 6 months (100% increase for Put, 50% for Sp and Spd). At 24 months, Put and Spd were diminished, and Sp was unchanged with respect to the 3‐month values. Under the same conditions, glyceraldehyde‐3‐phosphate dehydrogenase mRNA did not undergo significant alterations.

Different localization of spermidine/spermine N1-acetyltransferase and ornithine decarboxylase transcripts in the rat kidney.

In situ hybridization histochemistry of transverse sections from male rat kidney showed that the mRNA of the regulatory enzyme of polyamine degradation, spermidine/spermine N1 acetyltransferase, has a spotty distribution in the cortex, is low and diffused in the outer stripe and high and diffused in the inner stripe of the outer medulla. At the cellular level, this mRNA is solely expressed by the epithelium of the distal straight and convoluted nephron tubules. Since biosynthetic ornithine decarboxylase mRNA is solely found in the proximal straight tubules, it is proposed that polyamine biosynthesis and degradation occur at separate sites along the nephron.