Les modèles animaux de la maladie veineuse chronique

PARIS-BIUP (751062107) / SudocSudocFranceF

Cytosolic RNA:DNA Duplexes Generated by Endogenous Reverse Transcriptase Activity as Autonomous Inducers of Skin Inflammation in Psoriasis

International audiencePsoriasis is a chronic skin disease of unknown ætiology. Recent studies suggested that a large amount of cytosolic DNA (cyDNA) in keratinocytes is breaking keratinocytes DNA tolerance and promotes self-sustained inflammation in the psoriatic lesion. We investigated the origin of this cyDNA. We show that, amongst all the possible DNA structures, the cyDNA could be present as RNA:DNA duplexes in keratinocytes. We further show that endogenous reverse transcriptase activities generate such duplexes and consequently activate the production of Th1-inflammatory cytokines. These observations open a new research avenue related to endogenous retroelements for the aetiology of psoriasis and probably of other human chronic inflammatory diseases

Detection of RNA:DNA duplexes in psoriatic lesions, healed psoriatic lesions and normal skin.

<p>Using indirect immunofluorescence, staining was observed in the epidermis of lesional psoriatic skin (A, MAb clone S9.6; C, MAb clone D5H6), but not DNase1 pretreated skin section (D) or in non lesional psoriatic skin (E) or in atopic dermatitis (F). Focal staining was noted in skin section from a formally lesional psoriatic skin, both in the epidermis and in the underlying residual inflammation (B). Negative control is shown in panel G. The bar represents 80 μm.</p

Detection of <i>in situ</i> RT activities in lesional psoriatic skins and normal skin.

<p>On-going RT reactions were visualized by the detection of a tagged nucleotide, biotinylated dCTP and revealed by immunohistochemistry (ACEFG), or DIG-11-dUTP revealed by immunofluorescence (BD). Mn²⁺-dependent RT is shown in ABE while Mg²⁺-dependent RT is shown in CDFG. AC, BD and EF were issued from the same biopsies. GP+E-86 packaging cell line was used as positive control. Negative controls consisted of the same procedure but with omission of the primary antibody. They are shown as insert of each panel.</p

RNA:DNA duplexes and cytokine secretion.

<p>Human keratinocytes were incubated with 1.25 μg/ml of AzaC, then stained with MAb clone S9.6 and revealed by immunohistochemistry. A shows induction of RNA:DNA synthesis when compared to control experiment (B). Nuclei were counterstained with Hoescht 33258. Molecular quantification by real time PCR was next performed on two target genes, namely <i>HERV-K</i> (C) and <i>LINE-1</i> (D). Keratinocytes were treated by AzaC (1.25 μg/ml) or by IdU (200 μg/ml) and total nucleic acid were extracted. Both diagrams show the evolution of the ratio target gene to <i>GAPDH</i> over 72 hours. Cytokine concentrations were measured in the supernatant of the above treated cells at 48 hours (E).</p