We conclude that imbalance of monocyte activation profiles and impaired M2 expression, are key factors in development of relapses. Our study opens new perspectives for therapeutic applications in MS.

No abstract

BackgroundVasogenic edema dynamically accumulates in many brain disorders associated with brain inflammation, with the critical step of edema exacerbation feared in patient care. Water entrance through blood-brain barrier (BBB) opening is thought to have a role in edema formation. Nevertheless, the mechanisms of edema resolution remain poorly understood. Because the water channel aquaporin 4 (AQP4) provides an important route for vasogenic edema resolution, we studied the time course of AQP4 expression to better understand its potential effect in countering the exacerbation of vasogenic edema.MethodsFocal inflammation was induced in the rat brain by a lysolecithin injection and was evaluated at 1, 3, 7, 14 and 20 days using a combination of in vivo MRI with apparent diffusion coefficient (ADC) measurements used as a marker of water content, and molecular and histological approaches for the quantification of AQP4 expression. Markers of active inflammation (macrophages, BBB permeability, and interleukin-1β) and markers of scarring (gliosis) were also quantified.ResultsThis animal model of brain inflammation demonstrated two phases of edema development: an initial edema build-up phase during active inflammation that peaked after 3 days (ADC increase) was followed by an edema resolution phase that lasted from 7 to 20 days post injection (ADC decrease) and was accompanied by glial scar formation. A moderate upregulation in AQP4 was observed during the build-up phase, but a much stronger transcriptional and translational level of AQP4 expression was observed during the secondary edema resolution phase.ConclusionsWe conclude that a time lag in AQP4 expression occurs such that the more significant upregulation was achieved only after a delay period. This change in AQP4 expression appears to act as an important determinant in the exacerbation of edema, considering that AQP4 expression is insufficient to counter the water influx during the build-up phase, while the second more pronounced but delayed upregulation is involved in the resolution phase. A better pathophysiological understanding of edema exacerbation, which is observed in many clinical situations, is crucial in pursuing new therapeutic strategies.

In vitro selection was performed in a DNA library, made of oligonucleotides with a 30-nucleotide random sequence, to identify ligands of the human immunodeficiency virus type-1 trans-activation-responsive (TAR) RNA element. Aptamers, extracted after 15 rounds of selection-amplification, either from a classical library of sequences or from virtual combinatorial libraries, displayed an imperfect stem-loop structure and presented a consensus motif 5ACTCCCAT in the apical loop. The six central bases of the consensus were complementary to the TAR apical region, giving rise to the formation of RNA-DNA kissing complexes, without disrupting the secondary structure of TAR. The RNA-DNA kissing complex was a poor substrate for Escherichia coli RNase H, likely due to steric and conformational constraints of the DNA/RNA heteroduplex. 2-O-Methyl derivatives of a selected aptamer were binders of lower efficiency than the parent aptamer in contrast to regular sense/antisense hybrids, indicating that the RNA/DNA loop-loop region adopted a non-canonical heteroduplex structure. These results, which allowed the identification of a new type of complex, DNA-RNA kissing complex, demonstrate the interest of in vitro selection for identifying non-antisense oligonucleotide ligands of RNA structures that are of potential value for artificially modulating gene expression.In the antisense strategy, a DNA oligonucleotide is designed to hybridize to an RNA sequence, in order to inhibit specifically the reading of the encoded genetic information (1). Although RNA is a single chain nucleic acid, it adopts secondary and tertiary structures, which can prevent the hybridization of the antisense sequence. This is one of the likely explanations of the poor inhibition efficiency, if any, induced by some antisense oligonucleotides. The aptamer strategy has been successfully used for the selection of ligands against a large range of targets, such as proteins and small molecules (nucleotides, amino acids, dyes) (see Ref. 2 for a review). This methodology offers an alternative way for designing nucleic acid ligands against an RNA structure. Indeed, we previously demonstrated that in vitro selection of DNA ligands (aptamers) against DNA secondary structures led to the identification of sequences able to recognize the DNA targets through base pair formation and additional unidentified interactions (3, 4). This might be of high potential interest, as numerous RNA structures display a regulatory function through interaction either with proteins (such as the iron-responsive element interacting with the ironresponsive element-binding protein (5), the HIV trans-activation-responsive (TAR) 1 element binding to the viral protein Tat (6), or the HIV Rev-responsive element promoting the export of retroviral RNA from the nucleus due to the binding with the viral protein Rev (6)) or with nucleic acids (like the dimerization-initiating sequence of HIV (7)). The binding of an oligonucleotide to such structures could prevent the interaction of the RNA with the regulator...