Neuroscience Letters 391 (2006) 147–149 Effect of the functional toll-like receptor 4 Asp299Gly polymorphism on susceptibility to late-onset Alzheimer’s disease Piercarlo Minoretti, Carmine Gazzaruso, Clara Di Vito, Enzo Emanuele, Marika Bianchi, Enrico Coen, Marta Reino, Diego Geroldi ∗ Interdepartmental Center for Research in Molecular Medicine (CIRMC), University of Pavia, Viale Taramelli 24, I-27100 Pavia, Italy Received 30 July 2005; received in revised form 18 August 2005; accepted 22 August 2005 Abstract Experimental data have shown an upregulated expression of toll-like receptors, particularly toll-like receptor 4 (TLR4), in neurodegeneration. The Asp299Gly polymorphism of the TLR4 gene has been associated with an attenuated receptor signalling and a blunted inflammatory response. In the present study, we sought to determine whether this common genetic variant could influence susceptibility to late-onset Alzheimer’s disease (LOAD) in an Italian population sample. A cohort of 277 LOAD patients and 300 cognitively healthy controls were genotyped for the TLR4 Asp299Gly polymorphism using restriction isotyping. The frequency of the minor 299Gly allele was significantly higher in the controls than in the LOAD cases (7.2% versus 3.1%, respectively, P =0.003). Additionally, the frequency of the variant genotypes (Asp/Gly and Gly/Gly) was 13.0% in the controls and 5.4% in LOAD patients (P = 0.002). After adjustment for age, gender, and the APOE 4 carrier status, the odds ratio for the development of LOAD associated with the Asp/Gly and Gly/Gly versus Asp/Asp genotype was 0.37 (95% CI: 0.20–0.69, P = 0.002). Our data further support a role for innate immunity in neurodegeneration and give the first evidence that the TLR4 Asp299Gly variant may be protective toward the development of LOAD. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Toll-like receptor 4; Late-onset Alzheimer’s disease; Single nucleotide polymorphism; Association study Toll-like receptors (TLRs) represent a series of genetically con- served and stable cell-surface receptors that have emerged as key players in the initiation of cellular innate immune responses [1,19]. In the CNS, constitutive expression of human toll-like receptor 4 (TLR4), a transmembrane glycoprotein that acts as a signal-transducing receptor for the endotoxin lipopolysaccha- ride (LPS) [20], has been reported in microglia but not astrocytes or oligodendrocytes [7]. Of interest, a growing amount of data has recently suggested that TLR4 could play a role in neurode- generative processes. Accordingly, TLR4 signalling pathway has been found to be necessary for LPS-induced oligodendro- cyte injury in a developing neural model [14]. Additionally, in an in vivo model of neurodegeneration, mice bearing a loss-of- function mutation in the TLR4 gene were found to be resistant to LPS-induced damage in different neuronal populations [15]. According to the above data, and in view of a role of innate immunity in the pathogenesis of Alzheimer’s disease [6,16], the ∗ Corresponding author. Tel.: +39 0382 528341; fax: +39 0382 526259. E-mail address: d.geroldi@smatteo.pv.it (D. Geroldi). TLR4 gene might constitute a candidate susceptibility gene for this neurodegenerative disease. A common adenine to guanine substitution in TLR4, 896 nucleotides downstream of the tran- scription start site (+896), causes the replacement of an aspartic acid residue by a glycine at amino acid 299 (Asp299Gly). This missense polymorphism has recently generated great interest as it leads to an attenuated efficacy of LPS signalling and a reduced capacity to elicit inflammation [4]. Notably, several independent investigations have shown that the carriage of at least one minor 299Gly allele is associated with a diminished risk of vascular events [3,13] as well as successful aging in humans [5]. However, in spite of the potential importance of this common genetic variant in neurodegeneration, no investigation of its role in relation to Alzheimer’s disease has been undertaken. Given these considerations, in the present report we sought to evaluate whether the TLR4 Asp299Gly polymorphism could influence susceptibility to late-onset Alzheimer’s disease (LOAD) in an Italian population sample. We examined a total of 277 patients (141 males and 136 females) with LOAD (≥65 years), with a mean age of 76.5 ± 6.3 years and a mean age-at-onset of 73.6 ± 6.2 years. 0304-3940/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2005.08.047