Proteomics and transcriptomics analyses of ataxia telangiectasia cells treated with Dexamethasone.

Ataxia telangiectasia (A-T) is an incurable and rare hereditary syndrome. In recent times, treatment with glucocorticoid analogues has been shown to improve the neurological symptoms that characterize this condition, but the molecular mechanism of action of these analogues remains unknown. Hence, the aim of this study was to gain insight into the molecular mechanism of action of glucocorticoid analogues in the treatment of A-T by investigating the role of Dexamethasone (Dexa) in A-T lymphoblastoid cell lines. We used 2DE and tandem MS to identify proteins that were influenced by the drug in A-T cells but not in healthy cells. Thirty-four proteins were defined out of a total of 746±63. Transcriptome analysis was performed by microarray and showed the differential expression of 599 A-T and 362 wild type (WT) genes and a healthy un-matching between protein abundance and the corresponding gene expression variation. The proteomic and transcriptomic profiles allowed the network pathway analysis to pinpoint the biological and molecular functions affected by Dexamethasone in Dexa-treated cells. The present integrated study provides evidence of the molecular mechanism of action of Dexamethasone in an A-T cellular model but also the broader effects of the drug in other tested cell lines.

ATM splicing variants as biomarkers for low dose dexamethasone treatment of A-T.

BACKGROUND: Ataxia Telangiectasia (AT) is a rare incurable genetic disease, caused by biallelic mutations in the Ataxia Telangiectasia-Mutated (ATM) gene. Treatment with glucocorticoid analogues has been shown to improve the neurological symptoms that characterize this syndrome. Nevertheless, the molecular mechanism underlying the glucocorticoid action in AT patients is not yet understood. Recently, we have demonstrated that Dexamethasone treatment may partly restore ATM activity in AT lymphoblastoid cells by a new ATM transcript, namely ATMdexa1. RESULTS: In the present study, the new ATMdexa1 transcript was also identified in vivo, specifically in the PMBCs of AT patients treated with intra-erythrocyte Dexamethasone (EryDex). In these patients it was also possible to isolate new "ATMdexa1 variants" originating from canonical and non-canonical splicing, each containing the coding sequence for the ATM kinase domain. The expression of the ATMdexa1 transcript family was directly related to treatment and higher expression levels of the transcript in patients' blood correlated with a positive response to Dexamethasone therapy. Neither untreated AT patients nor untreated healthy volunteers possessed detectable levels of the transcripts. ATMdexa1 transcript expression was found to be elevated 8 days after the drug infusion, while it decreased 21 days after treatment. CONCLUSIONS: For the first time, the expression of ATM splicing variants, similar to those previously observed in vitro, has been found in the PBMCs of patients treated with EryDex. These findings show a correlation between the expression of ATMdexa1 transcripts and the clinical response to low dose dexamethasone administration.

Dexamethasone improves redox state in ataxia telangiectasia cells by promoting an NRF2-mediated antioxidant response.

Ataxia telangiectasia (A-T) is a rare incurable neurodegenerative disease caused by biallelic mutations in the gene for ataxia-telangiectasia mutated (ATM). The lack of a functional ATM kinase leads to a pleiotropic phenotype, and oxidative stress is considered to have a crucial role in the complex physiopathology. Recently, steroids have been shown to reduce the neurological symptoms of the disease, although the molecular mechanism of this effect is largely unknown. In the present study, we have demonstrated that dexamethasone treatment of A-T lymphoblastoid cells increases the content of two of the most abundant antioxidants [glutathione (GSH) and NADPH] by up to 30%. Dexamethasone promoted the nuclear accumulation of the transcription factor nuclear factor (erythroid-derived 2)-like 2 to drive expression of antioxidant pathways involved in GSH synthesis and NADPH production. The latter effect was via glucose 6-phosphate dehydrogenase activation, as confirmed by increased enzyme activity and enhancement of the pentose phosphate pathway rate. This evidence indicates that glucocorticoids are able to potentiate antioxidant defenses to counteract oxidative stress in ataxia telangiectasia, and also reveals an unexpected role for dexamethasone in redox homeostasis and cellular antioxidant activity.

Effect of FSH and progesterone on human spermatozoa cytosolic calcium.

Ejaculated spermatozoa must undergo a number of modifications before fertilizing the oocyte: among these the capacitation and the acrosome reaction. Calcium signals play an essential role in these functional and structural modifications. Mature spermatozoa have few organelles and a very small cytoplasmic volume but maintain the homeostasis of [Ca(2+)](c) with great accuracy. We study Ca(2+) mobilization in human spermatozoa exposed to FSH and progesterone by measuring the [Ca(2+)](c) with the FURA-2AM method and report for the first time that the exposure to FSH (up to 98ng/ml) produced an increase of [Ca(2+)](c) to an extent comparable to that observed with 1muM progesterone. FSH and progesterone increase the spermatozoa [Ca(2+)](c) by acting primarily on calcium entry from the external medium. The effects of the two hormones on [Ca(2+)](c) were similar but not identical; the pre-treatment of progesterone blocks the effects of FSH, but not vice-versa. The increase of [Ca(2+)](c) due to FSH was more sensitive to nifedipine (VOCCs inhibitor) than that of progesterone. The effects of these hormones on calcium homeostasis may be relevant for sperm activation.