Background α-MSH is a neuropeptide with several biological functions including down regulation of pro-inflammatory pathways and inhibition of the development of some experimental rheumatic diseases. Although pristane-induced SLE murine has clinical and serological similarities to human disease, cellular characteristics that contributes to autoimmunity and the effect of α-MSH in this model remains unknown.

Objectives To analyze, in pristane-induced SLE balb/c mice, the expressions of CD69 activation receptor on CD4 Tcells and of CD4⁺CD25⁺FoxP3⁺ peripheral Treg cells; and to evaluate the potential therapeutic effects of an α-MSH analogue (NDP-α-MSH) this model.

Methods Twenty balb/c mice were studied: 15 were injected with a single intraperitoneal (IP) dose of 0.5ml pristane for SLE-like model induction, whereas 5 age/gender matched control mice were given saline. Among the 15 pristane-induced mice (PIM), 5 received daily IP saline and 10 were treated with 1,25mg/kg/d NDP-α-MSH for 90 days. Samples of 200ul heparinized peripheral blood were collected from submandibular area from all 20 animals initially (time 0, T0) and following 90 days (T90). PBMC were isolated by erythrocyte lysis and stained with monoclonal antibodies against CD3, CD4, CD8, CD25, CD69 and FoxP3 molecules (BD Pharmingen™). Cell surface expressions were analyzed by flow cytometry using Guava EasyCyte™ HT (Millipore) and all results are shown as mean ± SD. Kruskal-Wallis test was used for statistical analysis, and P<0.05 considered significant.

Results Untreated PIM compared to control mice had significantly increased expression of CD69 on CD4 Tcells (22.1±2.1% vs 5.3±1.9%, P<0.005) even though the percentage of Treg cells was significantly lower (2.3±0.7% vs 6.9±1.4%, P<0.005). The comparison of NDP-α-MSH treated PIM and untreated PIM revealed similar expression of CD69 on CD4 Tcells (16.5±8.4% vs 22.1±2.1%, P>0.005), whereas treated PIM had significantly higher percentage of peripheral Treg cells (10.2±3.9% vs 2.3±0.7%, P<0.005).

Conclusions Pristane-induced SLE model develops similar expression patterns of activated CD4+CD69+ Tcells and CD4+CD25+FoxP3+ Treg cells to human lupus, which were in part reverted by α-MSH treatment. These murine findings generate new knowledge concerning immunological abnormalities of human SLE contributing to the understanding of this disease, and may indicate a potential therapeutical role for α-MSH.

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Disclosure of Interest None declared