Interleukin-1␤ (IL-1) expression is associated with a spectrum of neuroinflammatory processes related to chronic neurodegenerative diseases. The single-bolus microinjection of IL-1 into the central nervous system (CNS) parenchyma gives rise to delayed and localized neutrophil recruitment, transient blood-brain barrier (BBB) breakdown, but no overt damage to CNS integrity. However, acute microinjections of IL-1 do not mimic the chronic IL-1 expression, which is a feature of many CNS diseases. To investigate the response of the CNS to chronic IL-1 expression, we injected a recombinant adenovirus expressing IL-1 into the striatum. At the peak of IL-1 expression (days 8 and 14 post-injection), there was a marked recruitment of neutrophils, vasodilatation, and breakdown of the BBB. Microglia and astrocyte activation was evident during the first 14 days post-injection. At days 8 and 14, extensive demyelination was observed but the number of neurons was not affected by any treatment. Finally, at 30 days, signs of inflammation were no longer present, there was evidence of tissue reorganization, the BBB was intact, and the process of remyelination was noticeable. In summary, our data show that chronic expression of IL-1, in contrast to its acute delivery, can reversibly damage CNS integrity and implicates this cytokine or downstream components as major mediators of demyelination in chronic inflammatory and demyelinating diseases.

Diversity in neuronal signaling is a product not only of differential gene expression, but also of alternative splicing. However, although recognized, the precise contribution of alternative splicing in ion channel transcripts to channel kinetics remains poorly understood. Invertebrates, with their smaller genomes, offer attractive models to examine the contribution of splicing to neuronal function. In this study we report the sequencing and biophysical characterization of alternative splice variants of the sole voltage-gated Na+ gene (DmNav, paralytic), in late-stage embryos of Drosophila melanogaster. We identify 27 unique splice variants, based on the presence of 15 alternative exons. Heterologous expression, in Xenopus oocytes, shows that alternative exons j, e, and f primarily influence activation kinetics: when present, exon f confers a hyperpolarizing shift in half-activation voltage (V1/2), whereas j and e result in a depolarizing shift. The presence of exon h is sufficient to produce a depolarizing shift in the V1/2 of steady-state inactivation. The magnitude of the persistent Na+ current, but not the fast-inactivating current, in both oocytes and Drosophila motoneurons in vivo is directly influenced by the presence of either one of a pair of mutually exclusive, membrane-spanning exons, termed k and L. Transcripts containing k have significantly smaller persistent currents compared with those containing L. Finally, we show that transcripts lacking all cytoplasmic alternatively spliced exons still produce functional channels, indicating that splicing may influence channel kinetics not only through change to protein structure, but also by allowing differential modification (i.e., phosphorylation, binding of cofactors, etc.). Our results provide a functional basis for understanding how alternative splicing of a voltage-gated Na+ channel results in diversity in neuronal signaling.

Summary Background Circadian rhythms regulate physiology and behavior through transcriptional feedback loops of clock genes running within specific pacemaker cells. In Drosophila, molecular oscillations in the small ventral Lateral Neurons (sLNvs) command rhythmic behavior under free-running conditions releasing the neuropeptide PIGMENT DISPERSING FACTOR (PDF) in a circadian fashion. Electrical activity in the sLNvs is also required for behavioral rhythmicity. Yet, how temporal information is transduced into behavior remains unclear. Results Here we developed a new tool for temporal control of gene expression to obtain adult-restricted electrical silencing of the PDF circuit, which led to reversible behavioral arrhythmicity. Remarkably, PER oscillations during the silenced phase remained unaltered, indicating that arrhythmicity is a direct consequence of the silenced activity. Accordingly, circadian axonal remodeling and PDF accumulation were severely affected during the silenced phase. Conclusions Although electrical activity of the sLNvs is not a clock component it coordinates circuit outputs leading to rhythmic behavior.