Fragile X mental retardation protein (FMRP) and metabotropic glutamate receptor subtype 5 (mGlu5) control stress granule formation in astrocytes.

Fragile X syndrome (FXS) is a common form of intellectual disability and autism caused by the lack of Fragile X Mental Retardation Protein (FMRP), an RNA-binding protein involved in RNA transport and protein synthesis. Upon cellular stress, global protein synthesis is blocked and mRNAs are recruited into stress granules (SGs), together with RNA-binding proteins including FMRP. Activation of group-I metabotropic glutamate (mGlu) receptors stimulates FMRP-mediated mRNA transport and protein synthesis, but their role in SGs formation is unexplored. To this aim, we pre-treated wild type (WT) and Fmr1 knockout (KO) cultured astrocytes with the group-I-mGlu receptor agonist (S)-3,5-Dihydroxyphenylglycine (DHPG) and exposed them to sodium arsenite (NaAsO2), a widely used inducer of SGs formation. In WT cultures the activation of group-I mGlu receptors reduced SGs formation and recruitment of FMRP into SGs, and also attenuated phosphorylation of eIF2α, a key event crucially involved in SGs formation and inhibition of protein synthesis. In contrast, Fmr1 KO astrocytes, which exhibited a lower number of SGs than WT astrocytes, did not respond to agonist stimulation. Interestingly, the mGlu5 receptor negative allosteric modulator (NAM) 2-methyl-6-(phenylethynyl)pyridine (MPEP) antagonized DHPG-mediated SGs reduction in WT and reversed SGs formation in Fmr1 KO cultures. Our findings reveal a novel function of mGlu5 receptor as modulator of SGs formation and open new perspectives for understanding cellular response to stress in FXS pathophysiology.

Fragile X mental retardation protein (FMRP) interacting proteins exhibit different expression patterns during development.

Fragile X syndrome is caused by the lack of expression of fragile X mental retardation protein (FMRP), an RNA-binding protein involved in mRNA transport and translation. FMRP is a component of mRNA ribonucleoprotein complexes and it can interact with a range of proteins either directly or indirectly, as demonstrated by two-hybrid selection and co-immunoprecipitation, respectively. Most of FMRP-interacting proteins are RNA-binding proteins such as FXR1P, FXR2P and 82-FIP. Interestingly, FMRP can also interact directly with the cytoplasmic proteins CYFIP1 and CYFIP2, which do not bind RNA and link FMRP to the RhoGTPase pathway. The interaction with these different proteins may modulate the functions of FMRP by influencing its affinity to RNA and by affecting the FMRP ability of cytoskeleton remodeling through Rho/Rac GTPases. To better define the relationship of FMRP with its interacting proteins during brain development, we have analyzed the expression pattern of FMRP and its interacting proteins in the cortex, striatum, hippocampus and cerebellum at different ages in wild type (WT) mice. FMRP and FXR2P were strongly expressed during the first week and gradually decreased thereafter, more rapidly in the cerebellum than in the cortex. FXR1P was also expressed early and showed a reduction at later stages of development with a similar developmental pattern in these two regions. CYFIP1 was expressed at all ages and peaked in the third post-natal week. In contrast, CYFIP2 and 82-FIP (only in forebrain regions) were moderately expressed at P3 and gradually increased after P7. In general, the expression pattern of each protein was similar in the regions examined, except for 82-FIP, which exhibited a strong expression at P3 and low levels at later developmental stages in the cerebellum. Our data indicate that FMRP and its interacting proteins have distinct developmental patterns of expression and suggest that FMRP may be preferentially associated to certain proteins in early and late developmental periods. In particular, the RNA-binding and cytoskeleton remodeling functions of FMRP may be differently modulated during development.

Antioxidant activity of timolol on endothelial cells and its relevance for glaucoma course.

PURPOSE: A growing evidence in the scientific literature suggests that oxidative damage plays a pathogenic role in primary open-angle glaucoma. Therefore, it is of interest to test whether drugs effective against glaucoma display antioxidant activity. We test the hypothesis that the classic beta-blocker therapy for glaucoma with timolol involves the activation of antioxidant protective mechanisms towards endothelial cells. METHODS: Oxidative stress was induced in cultured human endothelial cells by iron/ascorbate with or without timolol pretreatment. Analysed parameters included cell viability (neutral red uptake and tetrazolium salt tests), lipid peroxidation (thiobarbituric reactive substances), and occurrence of molecular oxidative damage to DNA (8-hydroxy-2'-deoxyguanosine). RESULTS: Oxidative stress decreased 1.8-fold cell viability, increased 3.0-fold lipid peroxidation and 64-fold oxidative damage to DNA. In the presence of timolol, oxidative stress did not modify cell viability, whereas lipid peroxidation was increased 1.3-fold, and DNA oxidative damage 3.6-fold only. CONCLUSIONS: The obtained results indicate that timolol exerts a direct antioxidant activity protecting human endothelial cells from oxidative stress. These cells employ mechanisms similar to those observed in the vascular endothelium. It is hypothesized that this antioxidant activity is involved in the therapeutic effect of this drug against glaucoma.

Oxidative stress and apoptosis in immune diseases.

Antigenic stimuli increase ROS that influence T-cell activation by interfering with the oxidant-antioxidant balance. Oxidative stress takes place when excess of ROS production is not counterbalanced by antioxidant mechanisms and bcl-2 gene product that inhibits apoptosis by interacting with mitochondrial superoxide dismutase. ROS Excess induces apoptosis both by activation of NF-kB-dependent genes and DNA damage. The latter has been shown to elicit the activation of poly-ADP-ribose transferase and the accumulation of p53, thus determining apoptosis. Additionally, oxidative stress may induce formation of cell membrane oxidized lipids, potent inducers of apoptosis. Oxidative stress is also involved in immune diseases. In AIDS, ROS excess and deficiency of antioxidants lead to apoptosis and virus activation. ROS produced at sites of chronic inflammation, have genotoxic effects. As a consequence, abnormalities of the p53 genes might explain the conversion from an inflammatory phase into autonomous progression of rheumatoid arthritis or other chronic inflammatory disorders.

IL-2-driven natural killer cell generation: role of anti-H-2b monoclonal antibodies and stromal cells in controlling quantitative and repertoire changes.

To investigate the role of major histocompatibility complex class I and bone marrow stromal cells on in vitro differentiation of natural killer cells, a CD44(low/-) CD2- population was isolated from mouse bone marrow. This NK-1.1- CD3- LFA-3+ B220+ population, when stimulated with IL-2 and co-cultured with supportive syngeneic stromal cells, generated populations of NK-1.1+ Ly49A+ Ly49C/I+ CD3- mature natural killer cells. The effect of anti-H-2b monoclonal antibodies (mAbs) on this phenomenon was assayed. Pre-adhesion of anti-H-2b mAbs to the stromal cells did not exert any effect, whereas when the same mAbs were pre-adhered to progenitors, there was a inhibition of natural killer cell generation that was maximum when the mAbs were added directly to cultures. In addition, the anti-H-2b mAbs did not inhibit the IL-2-induced proliferation of mature natural killer cells. Allogeneic but not H-2b-deficient stromal cells decreased the expression of Ly-49C/I but not Ly49A, thus suggesting that stromal cell haplotypes qualitatively influence the expression of Ly49s repertoire.

Effect of interleukin-2 on generation of natural killer cells: role of major histocompatibility complex class I in B6 and TAP-1-/- mice.

Long-term bone marrow cultures were used to investigate the effect of IL-2, a cytokine widely used in immunotherapy, on natural killer cell differentiation. Specifically, the role of MHC was evaluated by comparing normal B6 and class I-deficient TAP-1-/- mice. The number of cells generated after a 13-day culture was the same in cell cultures from TAP-1-/- or B6 mice but the relative number of natural killer cells, identified as NK-1.1+CD3- cells by flow cytometry analysis, was increased in TAP-1-/- compared to B6 cultures (74.4% and 63.9%, respectively). Addition of an anti-class I mAb determined a strong inhibition of natural killer cell generation in B6 cultures, and its effect was specific since no effect was seen in TAP-1-/- cell cultures. TAP-1-/- natural killer cells or the few natural killer cells escaping the inhibitory effect of anti-class I mAb, were less cytotoxic than total B6 natural killer cells against target cell lines of different haplotype.

Cytotoxic and antiproliferative activity of the CMF regimen administered in association with tamoxifen as primary chemotherapy in breast cancer patients.

Seventy six consecutive patients with T2-4, N0-1, M0 primary breast cancer (BC) received a median of 3 cycles of CMF (cyclophosphamide, methotrexate, 5-fluorouracil) regimen. Tamoxifen was concomitantly administered in patients with estrogen receptor positive (ER+) BC. Ki67 antigen was evaluated immunohistochemically in tumor specimens obtained before chemotherapy and at mastectomy. At post chemotherapy evaluation, tumor shrinkage greater than 50% was obtained in 60 patients (78.9%), 21 of them being complete responders (27.6%). As a whole, primary chemotherapy significantly decreased the number of Ki67 positive cells. More than 50% decrease in Ki67 expression was observed in 78.9% of patients attaining a clinical complete response (CR), in 44.7% of patients with partial remission (PR) and in 50.0% of non-responders, while an increase (>25%) in Ki67 expression was found in 5.3%, 18.4% and 18.7% of patients with CR, PR and non-response, respectively. Both CR and PR rates were superimposable in patients with ER+ and ER- primary BC, while the reduction in Ki67 expression was mainly found in ER+ cases. Patients with increased Ki67 expression from baseline, at the end of primary chemotherapy, had a shorter disease-free interval (70 months) with respect to patients with no change (88+ months) or decrease (87+ months), p<0. 05. To conclude, the activity of CMF + tamoxifen in primary BC does not seem superior to that expected administering CMF alone. The reduction in Ki67 expression, as a whole, correlated with clinical CR, but some individual discrepancies between tumor shrinkage and Ki67 pattern have been observed. The Ki67 reduction mainly confined to the ER+ primary BC suggests that tumor response in this subset may be linked to the reduction in proliferation activity, whereas other mechanisms such as apoptosis might be responsible for the tumor shrinkage in ER- tumors. Since the increase in proliferation activity after primary chemotherapy was associated with a greater recurrence rate and lower disease free interval, irrespective of tumor response, changes in proliferation activity after primary chemotherapy may represent a potentially available parameter that, in addition to the tumor response, can discriminate patients who would benefit from the cytotoxic treatment from patients who would not.