Microglial apolipoprotein E and astroglial apolipoprotein J expression in vitro: opposite effects of lipopolysaccharide Josep Saura,* ,   ,1 Valerie Petegnief,  ,1 Xin Wu, Yanbin Liang and Steven M. Paul* ,   *Department of Pharmacology, Toxicology and Psychiatry, Indiana School of Medicine, Indianapolis, Indiana, USA  Neuroscience Discovery Research, Lilly Research Laboratories, Indianapolis, Indiana, USA Abstract Apolipoprotein E (apoE) and apoJ are lipid carriers produced in the brain primarily by glial cells. A variety of glial-activating stimuli induce a parallel upregulation of both apolipoproteins expression in vivo and in vitro. To further characterize the cell type and mechanisms by which apoE and apoJ expression are upregulated in activated glia, mixed glial cultures from neonatal rat cortex were treated with the endotoxin lipopolysaccharide (LPS). LPS induced dose- dependent increases in apoJ and decreases in apoE expres- sion and secretion with maximum effects at 1–10 ng/mL and 0.1–1 lg/mL, respectively. Experiments with enriched astroglial and microglial cultures demonstrated that apoE and apoJ expression are predominantly microglial and astroglial, respectively. Given the pivotal role that nuclear factor-jB (NF-jB) plays in glial activation, we assessed its possible role in mediating apoE and apoJ expression by activated glia. LPS robustly increased NF-jB activation in mixed glial cultures. Two NF-jB inhibitors, aspirin (10 mM) and MG-132 (0.1 lM), blocked basal apoE and apoJ secretion as well as LPS-induced apoJ secretion. These data demonstrate that glial apoE and apoJ expression are independently regulated by LPS in microglia and astroglia, respectively, and that activated microglia are the predominant source of apoE in mixed glial cultures. The transcription factor NF-jB appears to be a critical mediator of LPS-stimulated apoJ expression from astroglia. Keywords: apolipoprotein E, apolipoprotein J, astrocytes, glial activation, microglia, NF-jB. J. Neurochem. (2003) 85, 1455–1467. Apolipoprotein E (apoE) and apolipoprotein J (apoJ; also known as clusterin among many other names) are compo- nents of plasma and cerebrospinal fluid (CSF) lipoprotein particles (Holtzman et al. 1999b). By binding to specific receptors they direct the utilization and clearance of lipids contained in lipoprotein particles by various cells and tissues. ApoE has recently attracted the attention of neuroscientists as it has been consistently shown to be a major susceptibility gene for late-onset Alzheimer’s disease (AD; Strittmatter et al. 1993). While it is still unclear exactly how apoE contributes to AD pathogenesis, we have recently reported a marked reduction in amyloid-b peptide (Ab) deposition and an almost complete absence of thioflavine-S-positive amyloid in transgenic mice over- expressing a human mutant amyloid precursor protein transgene that lack apoE (Bales et al. 1997, 1999b). Expression of human apoE in these mice suppressed early thioflavine-S-negative Ab deposition (Holtzman et al. 1999a) but resulted in fibrillar Ab deposits at a later age (Holtzman et al. 2000). These data suggest that apoE is critical for Ab fibrillization into amyloid plaques in brain. In line with these findings, it has previously been shown that apoE is an avid Ab binding protein (Wisniewski et al. 1993) and is localized to amyloid plaques in AD brain (Namba et al. 1991; Kida et al. 1994). Interestingly, apoJ is also an Ab binding protein (Wisniewski et al. 1993) and reportedly the major Ab binding protein in human CSF (Golabek et al. 1995). In vitro reports suggest an anti- amyloidogenic role for apoJ as apoJ binding to Ab prevents Ab aggregation and polymerization in vitro (Oda Resubmitted manuscript received February 28, 2003; accepted March 4, 2003. Address correspondence and reprint requests to Steven M. Paul, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285, USA. E-mail: Paul_Steven_M@Lilly.com 1 JS and VP equally contributed to this work. Abbreviations used:Ab, amyloid-b peptide; AD, Alzheimer’s disease; apoE, apolipoprotein E; apoJ, apolipoprotein J; CSF, cerebrospinal fluid; DIV, days in vitro; DTT, dithiothreitol; GFAP, glial fibrillary acidic protein; LDH, lactate dehydrogenase; LDL, low-density lipoprotein; LPS, lipopolysaccharide; NF-jB, nuclear factor-jB; PBS, phosphate- buffered saline; PMSF, phenylmethylsulphonyl fluoride. Journal of Neurochemistry , 2003, 85, 1455–1467 doi:10.1046/j.1471-4159.2003.01788.x Ó 2003 International Society for Neurochemistry, J. Neurochem. (2003) 85, 1455–1467 1455