Absence of the Cell Cycle Inhibitor p21 Cip1 Reduces LPS-Induced NO Release and Activation of the Transcription Factor NF-B in Mixed Glial Cultures JOSEP MARIA TUSELL, 1 JOSEP SAURA, 2 AND JOAN SERRATOSA 2 * 1 Department of Neurochemistry, Institut d’Investigacions Biome `diques de Barcelona, IIBB-CSIC, IDIBAPS, Barcelona, Spain 2 Department of Pharmacology and Toxicology, Institut d’Investigacions Biome `diques de Barcelona, IIBB-CSIC, IDIBAPS, Barcelona, Spain KEY WORDS glia; astrocytes; microglia; p21 Cip1 ; lipopolysaccharide; glial activation ABSTRACT We have studied possible differences in glial activation between cells from wild-type and p21 Cip1-/- mice. We compared the effect of serum mitogenic stimu- lation on proliferation rate and on the total number of glial cells after 7 days of culture. No differences between wild-type and p21 Cip1-/- glial cells were observed. We also compared the effect of lipopolysaccharide (LPS) from Escherichia coli, an agent widely used to induce glial activation. Nitric oxide (NO) and tumor necrosis factor- (TNF-) release, and nuclear factor kappa-B (NF-B) activation were evaluated as indicators of glial activation. We observed an attenuation of NO release and NF-B activation in p21 Cip1-/- glial cells when compared with glial cells from wild-type mice. In contrast, TNF- release was enhanced in p21 Cip1-/- glia. These results suggest that the cell cycle inhibitor p21 Cip1 plays a role in the inflammatory response induced by LPS. © 2004 Wiley-Liss, Inc. INTRODUCTION Under physiological conditions, glial cells play a key role in the normal function of the central nervous sys- tem (CNS). Astroglial and microglial cells respond to neuronal damage with morphological and functional changes, which is known as glial activation. Reactive astroglial and microglial cells produce a variety of fac- tors— growth factors, cytokines, nitric oxide (NO), and neuropeptides—with known neurotrophic or neuro- toxic properties (Chao et al., 1995; Raivich et al; 1999; Streit et al., 1999; Vitkovic et al., 2000). Reactive glial cells have been detected in experimental models of neuronal injury, such as ischemia (Rischke and Kriegl- stein, 1991; Jorgensen et al., 1993), axotomy (Graeber and Kreutzberg, 1986; Barron et al., 1990), and neuro- toxic insult (Jorgensen et al., 1993; Akiyama et al., 1994; Acarı ´n et al., 1996). Alterations in the functional state of glial cells, including changes in their morphol- ogy, immunophenotype, and proliferative activity have been observed in almost all brain pathologies. Acti- vated microglial cells are able to attack invading mi- croorganisms and remove cell debris and may promote tissue repair by secreting growth factors. Astrocytes also take part in the glial response. Activated astro- cytes are characterized by hypertrophic processes and, as in the case of microglia, they are known to possess neuroprotective as well as neurotoxic properties (Ba- nati et al., 1993; Giulian et al., 1993). In vivo studies in Grant sponsor: Spanish Ministerio de Ciencia y Tecnologı ´a; Grant number: SAF2001-2240; Grant number: Red CIEN. *Correspondence to: Joan Serratosa, Department Farmacologia i Toxicologia IIBB-CSIC, Rossello ´ 161, 6a planta, 08036-Barcelona, Spain. E-mail: jssnmc@iibb.csic.es Received 18 March 2004; Accepted 17 May 2004 DOI 10.1002/glia.20095 Published online 27 July 2004 in Wiley InterScience (www.interscience.wiley. com). GLIA 49:52–58 (2004) © 2004 Wiley-Liss, Inc.