Age and albumin D site-binding protein control tissue plasminogen activator levels: neurotoxic impact.

ABSTRACT: Recombinant tissue-type plasminogen activator (tPA) is the fibrinolytic drug of choice to treat stroke patients. However, a growing body of evidence indicates that besides its beneficial thrombolytic role, tPA can also have a deleterious effect on the ischaemic brain. Although ageing influences stroke incidence, complications and outcome, age-dependent relationships between endogenous tPA and stroke injuries have not been investigated yet. Here, we report that ageing is associated with a selective lowering of brain tPA expression in the murine brain. Moreover, our results show that albumin D site-binding protein (DBP) as a key age-associated regulator of the neuronal transcription of tPA. Additionally, inhibition of DBP-mediated tPA expression confers in vitro neuroprotection. Accordingly, reduced levels of tPA in old mice are associated with smaller excitotoxic/ischaemic injuries and protection of the permeability of the neurovascular unit during cerebral ischaemia. Likewise, we provide neuroradiological evidence indicating the existence of an inverse relationship between age and the volume of the ischaemic lesion in patients with acute ischaemic stroke. Together, these results indicate that the relationship among DBP, tPA and ageing play an important role in the outcome of cerebral ischaemia. For each stage (4 months and 21 months), samples were prepared by pooling an equal amount of the 3 individual RNA. Five M-BM-5g of total RNA from each pool were reverse-transcribed in the presence of 7.5M-BM-5M random hexamers (GE Healthcare), 75M-BM-5M aminoallyl-dUTP (Sigma-Aldrich) and 100U Rtases Reverse-iT Blend (Thermo scientific) overnight at 37M-BM-0C. Aminoallyl cDNAs were then labelled with Cy5 or Cy3 mono-Reactive Dye (GE Healthcare) according to the manusfacturerM-bM-^@M-^Ys instructions. Labelled cDNAs were then purified on Qiaquick PCR prurification kit (Qiagen) and hybridized to the RNG-MRC_MM25k_EVRY microarrays (Le brigand et al., NAR, 2006) according to the RNG procedures (http://www.microarray.fr:8080/merge/index). Each pool was hybridized in duplicate dye-swap independent experiments. After hybridization, median signal and median background intensities were extracted using Genepix 4.1 software (Axon Instruments). We have first evaluated the level of expression of each gene by calculating the mean ratio M-bM-^@M-^\signal/backgroundM-bM-^@M-^] for each corresponding spot from the 2 dye-swap experiments. Genes were considered to be expressed if their mean ratio was higher or equal to 1.2. Genes with mean ratio < 1.2 in the 2 conditions were not used for further analysis. These filtered data were then submitted to VARAN (http//:www. bionet. espci.fr) for normalization by lowess fit and differential expression analysis (Golfier et al., 2004). Normalized log2ratio 21 months/4 months were then used for further statistical analysis by SAM software (Tusher et al., 2001) and t-test with a p-value equal to 5% using TIGR Multiexperiment Viewer (TM4:MeV, http://www.tm4.org/mev.html). The final list of differentially expressed genes was established by comparing the results obtained with the 3 methods.

ORGANISM(S): Mus musculus

SUBMITTER: Benoit Roussel 

PROVIDER: E-GEOD-9004 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress