Alba Minelli

Oxidative stress-related aging: A role for prostate cancer?

Prostate cancer has the highest prevalence of any non-cutaneous cancer in the human body and essentially all men with circulating androgens will develop microscopic prostate cancer if they live long enough. Aging, considered as an impairment of body functions over time, caused by the accumulation of molecular damage in DNA, proteins and lipids, is also characterized by an increase in intracellular oxidative stress due to the progressive decrease of the intracellular ROS scavenging. The aging damage may eventually appear in age-related health issues, which have a significant impact on the independence, general well-being and morbidity of the elderly. The association of aging with prostate cancer is undisputable as well as the association of aging with oxidative stress. Nevertheless, supportive evidence linking an increase in oxidative stress with prostate cancer is still scarce. This review is a comprehensive, literature-based analysis of the association of human prostate cancer with oxidative stress. The objective was to examine the involvement of reactive oxygen species in the mechanisms of prostatic carcinogenesis since the understanding of risk factors for prostate cancer has practical importance for public health, genetic and nutritional education, and chemoprevention.

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.

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.

Effect of seminal plasma on the characteristics and fertility of rabbit spermatozoa.

The effects of different dilutions of seminal plasma (SP) on the qualitative characteristics of rabbit spermatozoa and on their fertilising ability were analysed. Ejaculated semen was centrifuged twice and the sperm resuspended in media with decreasing ratios of SP/Tris: (1/2; 1/5; 1/10; 1/20; 1/30; 1/100) until the complete substitution was with SP. The control constituted sperm in undiluted SP. Samples were maintained at 37 degrees C and kinetic analysis done at fixed intervals (0-6h). Also the thiobarbituric reactive substances (TBA-RS) values were determined. Rabbit sperm suspended in Tris, or with extremely low content of SP, lost motility and viability within 1-3h, while sperm suspended in SP either undiluted or diluted up to 10-fold, showed similar motility during the 6h period (from 39 to 49%). Further dilutions of SP (1/20-1/30) had no effect during the initial 2h of storage but thereafter the decline of motility was more marked (after 6h: from 0 to 17%). Kinetic parameters followed the same trend and differences were particularly marked after storage: the highest values were in samples diluted up to 1/10; a sharp decline in motility characteristics was observed at higher dilutions. The addition of SP (1/2 v/v) to immotile sperm reactivated 35.5% of cells. However, SP did not significantly affect fertility rate or litter size possible involving an interaction with the female reproductive tract. SP reduced lipid oxidation (TBA-RS) of semen only after storage. A positive correlation between final TBA-RS and cell viability indicated that peroxidation was one of the cause of rabbit sperm deterioration during conservation.

Spectral properties of the coenzyme bound to dopa decarboxylase from pig kidney

1. Introduction DOPA decarboxylase (EC 4.1.1.26) has been ex- tensively studied, particularly regarding its distribution, specificity and inhibition; unfortunately, not much is known about its mechanism of action, and the mode of binding of the coenzyme (pyridoxal-S’-phos- phate) and the substrates. A study of the absorbance properties of the enzyme in the 300-500 mn range, where the bound coenzyme should show its charac- teristic absorption band, would be highly desirable, since similar studies have provided a good deal of in- formation in other pyridoxal phosphate dependent enzymes [

The chymotryptic phosphopyridoxyl peptide of DOPA decarboxylase from pig kidney

The amino acid sequence of the coenzyme-binding site of DOPA-decarboxylase from pig kidney has been determined. A sample of enzyme was reduced with NABH4, aminoethylated and then digested with chymotrypsin. A single phosphopyridoxyl peptide was isolated and its sequence proved to be: Asn-Phe-Asn-Pro-His-Lys(Pxy)-Trp. Sequence homologies at the active site of various pyridoxalphosphate enzymes, and particularly of the bacterial decarboxylase, are discussed, with some emphasis on the constant presence of a histidine residue adjacent to the phosphopyridoxyl-lysine.

Focus on cyclo(His-Pro): history and perspectives as antioxidant peptide

Summary.Cyclo(His-Pro) is an endogenous cyclic dipeptide structurally related to tyreotropin-releasing hormone that was originally discovered in brain. In the central nervous system it has been described to exert multiple biological activities, which seem to be related to a presynaptic dopaminergic mechanism and include among the others a leptin-like function. It can be found in several body fluids and in the gastrointestinal tract where it has been suggested to act as a gut peptide with influence on the entero-insular axis. The oral administration of cyclo(His-Pro) and zinc was described to improve with a synergistic mechanism the glycaemic control in diabetes.The most intriguing function of this cyclic dipeptide is related with its neuroprotective role that was first reported in traumatic injuries of the spinal cord, and then confirmed in other models of experimental injuries of the nervous system. The mechanism that lies behind the neuroprotective activity of cyclo(His-Pro) remain poorly understood. Recent in vitro studies on rat pheochromocytoma PC12 cells have shown that it is a protective factor against stress stimuli and there is early pre-clinical evidence strongly suggesting that it enhances the expression of small heat shock proteins and antioxidant protection at the cellular level.Future research is underway to better characterize the possible use of this cyclic dipeptide in the therapy of neurodegenerative and metabolic disorders.

Cyclo(His-Pro) up-regulates heme oxygenase 1 via activation of Nrf2-ARE signalling.

Paraquat (1,1′‐dimethyl‐4,4′‐bipyridinium), a widely used non‐selective herbicide, is a redox cycling agent with adverse effects on dopamine systems. Epidemiological data have shown that exposure to paraquat is one of the several risk factors for Parkinson’s disease. We have already shown that cyclo(His‐Pro), an endogenous cyclic dipeptide produced by the cleavage of the thyrotropin releasing hormone, has a cytoprotective effect through a mechanism involving Nrf2 activation that decreases production of reactive oxygen species and increases glutathione synthesis. Using primary neuronal cultures and PC12 cells as targets of paraquat neurotoxicity, we addressed whether and how cyclo(His‐Pro) causes cellular protective response against paraquat‐mediated cell death. We found that cyclo(His‐Pro) attenuated reactive oxygen species production, and prevented glutathione depletion by up‐regulating Nrf2 gene expression, triggering its nuclear accumulation and activating the expression of heme oxygenase1. These protective effects were abolished by RNA interference‐mediated Nrf2 knock down whereas were unaffected by RNA interference‐mediated Keap1 knock down. Inhibition of heme oxygenase activity decreased cyclo(His‐Pro)‐induced neuroprotection. These results suggest that cyclo(His‐Pro), acting as a selective activator of the brain modulable Nrf2 pathway, may be a promising candidate as neuroprotective agent that act through induction of phase II genes.

Immunolocalization of A1 Adenosine Receptors in Mammalian Spermatozoa

The presence of A1 adenosine receptors (A1AR) in mammalian spermatozoa was previously demonstrated by radiochemical and immunochemical detection. This study was performed to investigate the cellular location of the A1AR to determine whether these receptors were somehow connected with ecto-adenosine deaminase and to evaluate their function in calcium uptake. By immunofluorescence staining we showed that in mammalian spermatozoa A1AR were constantly localized in the acrosomal region. This finding was confirmed by immunogold detection. Confocal analyses with anti-A1 and anti-ADA antibodies showed a high degree of co-localization. Calcium loading assay showed that this association was functional and affected calcium accumulation in mammalian spermatozoa. Therefore, we concluded that the acrosomal localization of A1AR was a constant feature in mammalian sperm. Moreover, these A1 receptors were functionally coupled to ecto-ADA and were able to modulate calcium uptake into an IP3-gated store.

Cyclo(His-Pro) exerts anti-inflammatory effects by modulating NF-κB and Nrf2 signalling.

Cyclo(His-Pro) is an endogenous cyclic dipeptide that exerts oxidative damage protection by selectively activating the transcription factor Nrf2 signalling pathway. Given the existence of a tight interplay of the Nrf2/NF-κB systems and that the pro-inflammatory response is governed by transcription factor NF-κB, here we sought to investigate whether and how cyclo(His-Pro) interferes with the cross-talk between the antioxidant Nrf2/heme oxygenase-1 and the pro-inflammatory NF-κB pathways. By knocking down the Nrf2 gene, we confirmed that cyclo(His-Pro) inhibits NF-κB nuclear accumulation induced by paraquat in rat pheochromocytoma PC12 cells via the Nrf2/heme oxygenase-1 pathway. The protection required functional heme oxygenase-1 activity, since zinc protoporphyrin IX, a heme oxygenase-1 inhibitor, prevented NF-κB inhibition, and the presence of exogenous carbon monoxide and bilirubin afforded cytoprotection against paraquat-induced toxicity by preventing NF-κB activation. Cyclooxygenase-2 and matrix metalloproteinase 3, two gene products governed by NF-κB, were down-regulated by cyclo(His-Pro) and up-regulated in heme oxygenase-1 knock-down cells. We validated the general mechanism underlying the anti-inflammatory effects by treating PC12 and murine microglial BV2 cells with different pro-inflammatory agents. Finally, cyclo(His-Pro) reduced 12-otetradecanoylphorbol-13-acetate-induced oedema in mouse ear inflammation model. Results, by showing that cyclo(His-pro) suppresses the pro-inflammatory NF-κB signalling via the Nrf2-mediated heme oxygenase-1 activation, contribute to the understanding of essential cellular pathways and allow the proposal of cyclo(His-Pro) as an in vivo anti-inflammatory compound.