The interleukin-1 (IL-1) receptor antagonist (IL-1ra) is an endogenous antagonist that blocks the effects of the proinflammatory cytokines IL-1α and IL-1β by occupying the type I IL-1 receptor. Here we describe transgenic mice with astrocyte-directed overexpression of the human secreted IL-1ra (hsIL-1ra) under the control of the murine glial fibrillary acidic protein (GFAP) promoter. Two GFAP-hsIL-1ra strains have been generated and characterized further: GILRA2 and GILRA4. These strains show a brain-specific expression of the hsIL-1ra at the mRNA and protein levels. The hsIL-1ra protein was approximated to ∼50 ng/brain in cytosolic fractions of whole brain homogenates, with no differences between male and female mice or between the two strains. Furthermore, the protein is secreted, inasmuch as the concentration of hsIL-1ra in the cerebrospinal fluid was 13 (GILRA2) to 28 (GILRA4) times higher in the transgenic mice than in the control animals. To characterize the transgenic phenotype, GILRA mice and nontransgenic controls were injected with recombinant human IL-1β (central injection) or lipopolysaccharide (LPS, peripheral injection). The febrile response elicited by IL-1β (50 ng/mouse icv) was abolished in hsIL-1ra-overexpressing animals, suggesting that the central IL-1 receptors were occupied by antagonist. The peripheral LPS injection (25 μg/kg ip) triggered a fever in overexpressing and control animals. Moreover, no differences were found in LPS-induced (100 and 1,000 μg/kg ip; 1 and 6 h after injection) IL-1β and IL-6 serum levels between GILRA and wild-type mice. On the basis of these results, we suggest that binding of central IL-1 to central IL-1 receptors is not important in LPS-induced fever or LPS-induced IL-1β and IL-6 plasma levels.

Expression of the cytokine interleukin la (IL-la) was demonstrated in the rat PC12 pheochromocytoma cell line by (i) immunohistochemistry using rabbit polyclonal antisera raised against the recombinant murine IL-la, (it) an ELISA, and (i) a specific cell conversion bioassay based on the use of LBRM33-1A5 cells. IL-la mRNA was demonstrated in the PC12 cells, by PCR amplification. Constitutive expression of IL-la in PC12 cells was demonstrated in all experiments, although the cellular levels of IL-la-like immunoreactivity varied. The expression of IL-la, as studied at the mRNA level, was inducible by mouse nerve growth factor (7S NGF), and the gene product level was inducible in-a dose-and time-dependent fashion by 7S NGF. The maxmum induction corresponds to a 600% increase in IL-la-like immunoreactivity above the expression level found in noninduced cells and occurred after Interleukin la and 13 (IL-la and IL-1p), the endogenous pyrogen/lymphocyte-activating factors were first identified as products of lipopolysaccharide-stimulated macrophages (1). Both IL-la and IL-1,B have numerous effects on the nervous system besides their role as immune mediators (2). The most important effects of IL-1 on the nervous system include stimulation of corticotropin releasing factor and corticotropin release (3), slow wave sleep (4), and fever (1).We have been focusing on the question of whether the neuronally active substances IL-la and IL-1,B could also be of neuronal origin. Recent reports indicate that IL-1-like immunoreactivity (IL-i-LI) can be found in the human hypothalamus (5) and the rat hippocampus and olfactory bulb (6). IL-1l3 mRNA has been detected in the rat hippocampus upon convulsant treatment (7) and was also found to be colocalized with nerve growth factor (NGF) mRNA in hippocampal pyramidal cells (8).We have earlier shown, by means of immunohistochemistry, that IL-la is localized in peripheral nerves (24) with a distribution closely resembling that of sympathetic noradrenergic innervation and in the noradrenergic chromaffin cells of the rat and mouse adrenal medulla (9). It was also shown that in vivo treatment of rats with cholinergic agonists, known to stimulate the release of the content of the chromaffin cells, caused a significant decline in the adrenal IL-la content. This suggests that IL-la can be released in a similar fashion to catecholamines, neuropeptide Y, and enkephalins (10).To further study the expression and release of IL-la in chromaffin cells, we have turned to the well-established pheochromocytoma PC12 cell line, which has been widely used as a model system in studies of sympathetic neuronal function and development. It also enabled us to examine the regulation of IL-la expression by NGF, which stimulates neurite outgrowth and regulates the expression of a wide variety of proteins in PC12 cells (11-13).The analysis of NGF effects on the expression of IL-1, in relation to the numerous neuronal effects of IL-1, is particularly interesting in view of the demonstration that IL-1 can induce...

Influenza A virus encodes two segments (7 and 8) that produce mRNAs that can be spliced. We have investigated if naturally occurring sequence polymorphisms in the influenza A virus family affects splicing of these viral mRNAs, as that could potentially alter the NS1/NS2- and/or M1/M2-protein ratios. We compared splicing efficiency of segment 7 and 8 mRNAs of A/Brevig Mission/1918/1 (H1N1) and A/Netherlands/178/95 (H3N2), as well as various H5N1 avian strains. Results revealed that both segment 7 and 8 mRNAs of A/Brevig Mission/1918/1 (H1N1) were inefficiently spliced compared to other influenza virus segment 7 and 8 mRNAs. This resulted in production of higher levels of functional NS1 protein, which could potentially contribute to the pathogenic properties of the A/Brevig Mission/1918/1 (H1N1). We also show that A/Brevig Mission/1918/1 (H1N1) segment 8 mRNAs responded differently to overexpression of SR proteins than A/Netherlands/178/95 (H3N2).

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