Mouse models, antibodies, and neuroimaging: Current knowledge and future perspectives in neuropsychiatric systemic lupus erythematosus (NPSLE)

As a chronic autoimmune disease systemic lupus erythematosus (SLE) can also affect the central and the peripheral nervous system causing symptoms which are summed up as neuropsychiatric systemic lupus erythematosus (NPSLE). These symptoms are heterogenous including cognitive impairment, seizures, and fatigue, leading to morbidity or even mortality. At present, little is known about the pathophysiological processes involved in NPSLE. This review focuses on the current knowledge of the pathogenesis of NPSLE gained from the investigation of animal models, autoantibodies, and neuroimaging techniques. The antibodies investigated the most are anti-ribosomal P protein antibodies (Anti-rib P) and anti-N-Methyl-D-Aspartic Acid Receptor 2 antibodies (Anti-NR2), which represent a subpopulation of anti-dsDNA autoantibodies. Experimental data demonstrates that Anti-rib P and Anti-NR2 cause different neurological pathologies when applied intravenously (i.v.), intrathecally or intracerebrally in mice. Moreover, the investigation of lupus-prone mice, such as the MRL/MpJ-Faslpr/lpr strain (MRL/lpr) and the New Zealand black/New Zealand white mice (NZB × NZW F1) showed that circulating systemic antibodies cause different neuropsychiatric symptoms compared to intrathecally produced antibodies. Furthermore, neuroimaging techniques including magnetic resonance imaging (MRI) and positron emission tomography (PET) are commonly used tools to investigate structural and functional abnormalities in NPSLE patients. Current research suggests that the pathogenesis of NPSLE is heterogenous, complex and not yet fully understood. However, it demonstrates that further investigation is needed to develop individual therapy in NPSLE.

Characterization of mast cell-derived rRNA-containing microvesicles and their inflammatory impact on endothelial cells

Tissue-resident mast cells (MCs) are well known for their role in inflammatory responses and allergic and anaphylactic reactions, but they also contribute to processes of arterial remodeling. Although ribosomes and cytosolic RNAs are located around secretory granules in mature MCs, their functional role in MC responses remains unexplored. Previous studies by our group characterized extracellular RNA (eRNA) as an inflammatory and pathogenetic factor in vitro and in vivo. In the present study, RNA-containing MCs and eRNA were located in close proximity to growing collateral arteries in vivo. In vitro, various agonists were found to induce the degranulation of MCs and the concomitant release of eRNA in association with microvesicles (MVs). The liberation of eRNA from MCs was abolished by MC stabilizers or by preventing the increase of intracellular Ca²⁺ in MCs. eRNA was found to be mainly contained inside MVs, as demonstrated by electron microscopy and immunocytochemistry. The exposure to and the uptake of MC-released MVs by cultured endothelial cells increased their expression of cytokines, such as monocyte chemoattractant protein or IL-6, in a dose- and time-dependent manner. These results indicate that RNA-containing MC-derived MVs are likely to be involved in inflammatory responses, relevant, for example, to processes of vascular remodeling.-Elsemüller, A.-K., Tomalla, V., Gärtner, U., Troidl, K., Jeratsch, S., Graumann, J., Baal, N., Hackstein, H., Lasch, M., Deindl, E., Preissner, K. T., Fischer, S. Characterization of mast cell-derived rRNA-containing microvesicles and their inflammatory impact on endothelial cells.