Ž . Journal of Neuroimmunology 91 1998 43–54 Cultured sympathetic neurons express functional interleukin-1 receptors Yuchen Bai 1 , Ronald P. Hart ) Department of Biological Sciences, Rutgers UniÕersity, 101 Warren St., Newark, NJ 07102-1811, USA Received 30 March 1998; revised 27 May 1998; accepted 28 May 1998 Abstract Ž . Since recent work has identified an apoptotic pathway in sympathetic neurons that is mediated by autocrine interleukin-1 IL-1 , we investigated whether cultured sympathetic neurons possess functional IL-1 receptors. Cultured sympathetic neurons express levels of IL-1RI and IL-1RAcP mRNAs consistent with signal transduction. Neurons stimulated with IL-1 demonstrate enhanced p65 NF-k B nuclear translocation and enhanced NF-k B DNA binding activity, with at least p65 and p50 subunits participating in the DNA binding activity. RNA differential display identified several neuronal mRNAs regulated by IL-1, including a member of the reticulon family. We conclude that IL-1 stimulates a potential component of a neuronal secretory pathway. q 1998 Elsevier Science B.V. All rights reserved. Keywords: Sympathetic neuron; Functional interleukin-1 receptor; IL-1RI; IL-1RAcp 1. Introduction Ž . Interleukin-1 IL-1 receptor signalling has been found to mediate at least some portions of an oxidative stress stimulation of apoptosis in sympathetic neurons and PC12 Ž . cells Friedlander et al., 1996; Troy et al., 1996 . Our previous studies have observed IL-1 receptor signalling in non-neuronal cells of sympathetic ganglia, but not in sym- Ž pathetic neurons Carlson et al., 1996a,b; Carlson and . Hart, 1996c . The involvement of IL-1 in apoptotic path- ways was first suspected after the identification of se- quence homology between the Caenorhabditis elegans ced- Ž .Ž 3 gene and IL-1 converting enzyme ICE Yuan et al., . 1993 . Inhibitors of ICE were sometimes found to inhibit Ž neuronal cell death Gagliardini et al., 1994; Lynch et al., . 1997 . Some experiments found that exogenous IL-1 re- Ž . ceptor antagonist IL-1ra could inhibit some models of Ž . apoptosis Gagliardini et al., 1995 , suggesting that sympa- thetic neurons may be capable of augmenting apoptotic signalling by autocrine stimulation with bioactive IL-1. This hypothesis would require that sympathetic neurons are capable of IL-1 production and IL-1 receptor function. A precise demonstration of the requirement of autocrine IL-1 in apoptosis required an oxidative stress downregula- ) Corresponding author. Tel.: q1 973 3531008; fax: q1 973 3531007; e-mail: rhart@newark.rutgers.edu 1 Present address. 3800 Spruce Street, 139 Rosenthal Hall, University of Pennsylvania, Philadelphia, PA 19104, USA. Ž .Ž . tion of superoxide dismutase SOD Troy et al., 1996 . Ž . Inhibition of IL-1b converting enzyme ICE rescues both PC12 cells and cultured sympathetic neurons after NGF or Ž . serum withdrawal Troy et al., 1996 . IL-1 mRNA is induced in NGF-primed PC12 cells when SOD is down- Ž . regulated Troy et al., 1996 . Addition of IL-1ra to the medium of SOD-downregulated cells lowered the rate of apoptotic cell death. These results further suggest the presence of functional IL-1 receptors on sympathetic neu- rons. Two IL-1 receptor subtypes have been identified that Ž . bind both IL-1a and b reviewed by Dower et al., 1989 . Ž . Type I IL-1 receptor IL-1RI has a molecular mass of about 80 kDa and consists of a single polypeptide chain Ž with a single proposed transmembrane domain Sims et al., . Ž . 1988 . A second receptor subtype, type II IL-1RII , con- tains a single polypeptide chain with a single putative transmembrane domain, but has a much shorter intra- cellular domain, making the observed molecular mass Ž . about 68 kDa McMahan et al., 1991 . However, studies have determined that only IL-1RI is a signal transducer Ž . Sims et al., 1993 and that IL-1RII functions as a ‘decoy’, Ž binding IL-1 ligand but transducing no signal Colotta et . al., 1993 . A sequence homologous to the IL-1 receptors has recently been cloned and is proposed to function by binding with IL-1RI protein and enhancing its affinity for Ž . ligand Greenfeder et al., 1995 . This molecule is named Ž . IL-1 receptor accessory protein IL-1RAcP . IL-1RAcP has been found to be required for IL-1-induced activation 0165-5728r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. Ž . PII: S0165-5728 98 00149-0