Sox-2 Positive Neural Progenitors in the Primate Striatum Undergo Dynamic Changes after Dopamine Denervation.

The existence of endogenous neural progenitors in the nigrostriatal system could represent a powerful tool for restorative therapies in Parkinson's disease. Sox-2 is a transcription factor expressed in pluripotent and adult stem cells, including neural progenitors. In the adult brain Sox-2 is expressed in the neurogenic niches. There is also widespread expression of Sox-2 in other brain regions, although the neurogenic potential outside the niches is uncertain. Here, we analyzed the presence of Sox-2+ cells in the adult primate (Macaca fascicularis) brain in naïve animals (N = 3) and in animals exposed to systemic administration of 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine to render them parkinsonian (N = 8). Animals received bromodeoxyuridine (100 mg/kg once a day during five consecutive days) to label proliferating cells and their progeny. Using confocal and electron microscopy we analyzed the Sox-2+ cell population in the nigrostriatal system and investigated changes in the number, proliferation and neurogenic potential of Sox-2+ cells, in control conditions and at two time points after MPTP administration. We found Sox-2+ cells with self-renewal capacity in both the striatum and the substantia nigra. Importantly, only in the striatum Sox-2+ was expressed in some calretinin+ neurons. MPTP administration led to an increase in the proliferation of striatal Sox-2+ cells and to an acute, concomitant decrease in the percentage of Sox-2+/calretinin+ neurons, which recovered by 18 months. Given their potential capacity to differentiate into neurons and their responsiveness to dopamine neurotoxic insults, striatal Sox-2+ cells represent good candidates to harness endogenous repair mechanisms for regenerative approaches in Parkinson's disease

The transcription factor Nrf2 as a new therapeutic target in Parkinson's disease

In recent years, it has been accepted that oxidative stress is critically involved in the etiopathology of Parkinson's disease(PD) and as a result new therapeutic targets for reduction of oxidant injury and neuroprotection can be defined. Here we discuss the potential use of the transcription factor nuclear factor erythroid-2-related factor 2(Nrf2), as a pharmacological target for neuroprotective therapy in PD. Data generated by various groups indicate that Nrf2 induces the expression of a group of cytoprotective, antixenobiotic and antioxidant enzymes that include heme oxygenase-1, NAD(P)H:quinone oxidoreductase and enzymes of glutathione(GSH) metabolism such as γ-glutamyl cysteine ligase, GSH transferases and so on. Two strategies are known to increase Nrf2 transcriptional activity in PD: i) use of certain catechol-derived quinones for selective inhibition of the Nrf2 repressor Kelch-like ECH-associated protein to increase of Nrf2 protein levels; and ii) use of glycogen synthase kinase 3β inhibitors to maintain high protein and activity levels of Nrf2 in the nucleus. This review provides a rationale for drug design of appropriate molecules that might endorse a neuroprotective strategy to PD on the basis of attenuation of oxidative stress. © 2009 Informa UK Ltd. All rights reserved.Peer Reviewe

Snake venom disintegrins: novel dimeric disintegrins and structural diversification by disulphide bond engineering.

We report the isolation and amino acid sequences of six novel dimeric disintegrins from the venoms of Vipera lebetina obtusa (VLO), V. berus (VB), V. ammodytes (VA), Echis ocellatus (EO) and Echis multisquamatus (EMS). Disintegrins VLO4, VB7, VA6 and EO4 displayed the RGD motif and inhibited the adhesion of K562 cells, expressing the integrin alpha5beta1 to immobilized fibronectin. A second group of dimeric disintegrins (VLO5 and EO5) had MLD and VGD motifs in their subunits and blocked the adhesion of the alpha4beta1 integrin to vascular cell adhesion molecule 1 with high selectivity. On the other hand, disintegrin EMS11 inhibited both alpha5beta1 and alpha4beta1 integrins with almost the same degree of specificity. Comparison of the amino acid sequences of the dimeric disintegrins with those of other disintegrins by multiple-sequence alignment and phylogenetic analysis, in conjunction with current biochemical and genetic data, supports the view that the different disintegrin subfamilies evolved from a common ADAM (a disintegrin and metalloproteinase-like) scaffold and that structural diversification occurred through disulphide bond engineering

Survival Mechanisms of Metastatic Melanoma Cells: The Link between Glucocorticoids and the Nrf2-Dependent Antioxidant Defense System

Circulating glucocorticoids increase during stress. Chronic stress, characterized by a sustained increase in serum levels of cortisol, has been associated in different cases with an increased risk of cancer and a worse prognosis. Glucocorticoids can promote gluconeogenesis, mobilization of amino acids, fat breakdown, and impair the body’s immune response. Therefore, conditions that may favor cancer growth and the acquisition of radio- and chemo-resistance. We found that glucocorticoid receptor knockdown diminishes the antioxidant protection of murine B16-F10 (highly metastatic) melanoma cells, thus leading to a drastic decrease in their survival during interaction with the vascular endothelium. The BRAFV600E mutation is the most commonly observed in melanoma patients. Recent studies revealed that VMF/PLX40-32 (vemurafenib, a selective inhibitor of mutant BRAFV600E) increases mitochondrial respiration and reactive oxygen species (ROS) production in BRAFV600E human melanoma cell lines. Early-stage cancer cells lacking Nrf2 generate high ROS levels and exhibit a senescence-like growth arrest. Thus, it is likely that a glucocorticoid receptor antagonist (RU486) could increase the efficacy of BRAF-related therapy in BRAFV600E-mutated melanoma. In fact, during early progression of skin melanoma metastases, RU486 and VMF induced metastases regression. However, treatment at an advanced stage of growth found resistance to RU486 and VMF. This resistance was mechanistically linked to overexpression of proteins of the Bcl-2 family (Bcl-xL and Mcl-1 in different human models). Moreover, melanoma resistance was decreased if AKT and NF-κB signaling pathways were blocked. These findings highlight mechanisms by which metastatic melanoma cells adapt to survive and could help in the development of most effective therapeutic strategies

Snake venom disintegrins: novel dimeric disintegrins and structural diversification by disulphide bond engineering

We report the isolation and amino acid sequences of six novel dimeric disintegrins from the venoms of Vipera lebetina obtusa (VLO), V. berus (VB), V. ammodytes (VA), Echis ocellatus (EO) and Echis multisquamatus (EMS). Disintegrins VLO4, VB7, VA6 and EO4 displayed the RGD motif and inhibited the adhesion of K562 cells, expressing the integrin a5b1 to immobilized fibronectin. A second group of dimeric disintegrins (VLO5 and EO5) had MLD and VGD motifs in their subunits and blocked the adhesion of the a4b1 integrin to vascular cell adhesion molecule 1 with high selectivity. On the other hand, disintegrin EMS11 inhibited both a5b1 and a4b1 integrins with almost the same degree of specificity. Comparison of the amino acid sequences of the dimeric disintegrins with those of other disintegrins by multiple-sequence alignment and phylogenetic analysis, in conjunction with current biochemical and genetic data, supports the view that the different disintegrin subfamilies evolved from a common ADAM (a disintegrin and metalloproteinase-like) scaffold and that structural diversification occurred through disulphide bond engineering

N-Acetylcysteine Promotes Metastatic Spread of Melanoma in Mice

N-acetylcysteine (NAC) is a direct Cys donor and a promoter of glutathione (GSH) synthesis. GSH regulates melanoma growth and NAC has been suggested to increase melanoma metastases in mice. We found that high therapeutic doses of NAC do not increase the growth of melanoma xenografts, but can cause metastatic spread and distant metastases. Nevertheless, this is not due to an antioxidant effect since NAC, in fact, increases the generation of reactive oxygen species in the growing metastatic melanoma. Trolox, an antioxidant vitamin E derivative, administered in vivo, decreased metastatic growth. Metastatic cells isolated from NAC-treated mice showed an increase in the nuclear translocation of Nrf2, as compared to controls. Nrf2, a master regulator of the antioxidant response, controls the expression of different antioxidant enzymes and of the γ-glutamylcysteine ligase (the rate-limiting step in GSH synthesis). Cystine uptake through the xCT cystine-glutamate antiporter (generating intracellular Cys) and the γ-glutamylcysteine ligase activity are key to control metastatic growth. This is associated to an increase in the utilization of L-Gln by the metastatic cells, another metastases promoter. Our results demonstrate the potential of NAC as an inducer of melanoma metastases spread, and suggest that caution should be taken when administering GSH promoters to cancer patients

Survival Mechanisms of Metastatic Melanoma Cells: The Link between Glucocorticoids and the Nrf2-Dependent Antioxidant Defense System

Circulating glucocorticoids increase during stress. Chronic stress, characterized by a sustained increase in serum levels of cortisol, has been associated in different cases with an increased risk of cancer and a worse prognosis. Glucocorticoids can promote gluconeogenesis, mobilization of amino acids, fat breakdown, and impair the body’s immune response. Therefore, conditions that may favor cancer growth and the acquisition of radio- and chemo-resistance. We found that glucocorticoid receptor knockdown diminishes the antioxidant protection of murine B16-F10 (highly metastatic) melanoma cells, thus leading to a drastic decrease in their survival during interaction with the vascular endothelium. The BRAFV600E mutation is the most commonly observed in melanoma patients. Recent studies revealed that VMF/PLX40-32 (vemurafenib, a selective inhibitor of mutant BRAFV600E) increases mitochondrial respiration and reactive oxygen species (ROS) production in BRAFV600E human melanoma cell lines. Early-stage cancer cells lacking Nrf2 generate high ROS levels and exhibit a senescence-like growth arrest. Thus, it is likely that a glucocorticoid receptor antagonist (RU486) could increase the efficacy of BRAF-related therapy in BRAFV600E-mutated melanoma. In fact, during early progression of skin melanoma metastases, RU486 and VMF induced metastases regression. However, treatment at an advanced stage of growth found resistance to RU486 and VMF. This resistance was mechanistically linked to overexpression of proteins of the Bcl-2 family (Bcl-xL and Mcl-1 in different human models). Moreover, melanoma resistance was decreased if AKT and NF-κB signaling pathways were blocked. These findings highlight mechanisms by which metastatic melanoma cells adapt to survive and could help in the development of most effective therapeutic strategies

Correction: Sox-2 Positive Neural Progenitors in the Primate Striatum Undergo Dynamic Changes after Dopamine Denervation.

[This corrects the article on p. e66377 in vol. 8.]

Cell renewal and differentiation dynamics of progenitors in the striatum.

<p>Schematic representation of hypothetic dynamics of endogenous striatal progenitors and the effects of MPTP. <b>A.</b> For reference we represented on top, the results of fate mapping of Sox-2⁺ cells in the murine dentate gyrus showing that non-radial Sox-2⁺ progenitors have self-renew potential and give rise to both neurons and astrocytes <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0066377#pone.0066377-Muotri1" target="_blank">[26]</a>. <b>B, C.</b> Similarly, we propose than in the normal situation, Sox-2⁺ striatal progenitors (Sox-2⁺/GFAP^−/CR^–) divide to generate new Sox-2⁺ progenitors. Moreover, some Sox-2⁺ progenitors give rise to astrocytes and (few) Sox-2⁺/CR⁺ neurons that after several maturation steps could switch off Sox-2 expression and give rise to different mature phenotypes (including TH⁺). Following MPTP administration the number of Sox-2⁺ progenitors increases while the number of CR⁺ cells that express Sox-2 is decreased. Possible mechanisms are A) MPTP favours gliogenesis from Sox2 progenitors at the expense of neurogenesis. B) MPTP (or lack of dopamine) accelerates maturation of Sox-2⁺/CR⁺ cells. C) Sox-2⁺/CR⁺ cells are susceptible to MPTP toxicity. Abbreviations: 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine: MPTP; calretinin: CR; tyrosine hydroxylase: TH.</p

MPTP effect on the nigrostriatal system.

<p>Midbrain sections at the level of the 3rd nerve from a control (<b>A</b>), a MPTP short-term (<b>B</b>) and a MPTP long-term treated monkey (<b>C</b>) immunostained for TH. Note the severe reduction of TH immunoreactivity in the SNpc of the lesioned monkeys. Scale bar = 1 cm. <b>D.</b> Stereological quantification of TH⁺ neurons in the SNpc. Data represent median and quartiles, N = 3, *p≤0.05. Images of precommisural striatum sections from a control monkey (<b>E</b>), a MPTP short-term monkey (<b>F</b>) and a MPTP long-term monkey (<b>G</b>) immunostained for TH. Note the loss of TH⁺ fibers in the lesioned monkeys. Scale bar = 1 cm. Representative striatal sections of a control <b>(e’)</b> a MPTP short-term monkey (<b>f’</b>) and a MPTP long-term monkey (<b>g’</b>), at higher magnification showing the intrinsic TH⁺ neurons (arrows). Scale bar = 300 µm. <b>H.</b> Quantification of striatal TH⁺ neurons. There was a significant increase in the density of TH⁺ neurons after MPTP administration in both groups. Data represent median and quartiles, N = 3, *p≤0.05. <b>I.</b> Western blot to assess striatal TH levels showing a reduction in the MPTP-short term group and a partial recovery in the MPTP-long term group with respect to controls. Data represent median and quartiles, N = 3, *p≤0.05. Abbreviations: 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine: MPTP; tyrosine hydroxylase: TH; substantia nigra pars compacta: SNpc.</p