title: Activation of toll-like receptor 4 (TLR4) by in vivo and in vitro exposure of rat epididymis to lipopolysaccharide from Escherichia Coli.
abstract: This study provides the first evidence that rat epididymis is fully capable of initiating an inflammatory response to lipopolysaccharide (LPS) from Escherichia coli through activation of Toll-like receptor 4 (TLR4). TLR4 functionality was demonstrated by in vivo LPS challenge, which induced a time- and dose-dependent activation of the transcription factor nuclear factor kappa B (NFKB) in caput and cauda epididymides. NFKB activation by LPS in caput epididymidis was abrogated when rats were pretreated with the NFKB inhibitor PDTC, confirming the specificity of this response. Within 2 h of LPS treatment (0.01 and 1 mg/kg, i.v.), NFKB activation in caput and cauda was accompanied by upregulation of Il1b, Nfkbia, and Cd14, but not Tlr4, mRNA. These effects, however, were not sustained after 24 h of LPS treatment. Lipopolysaccharide systemic effects were not restricted to epididymides, since Il1b, Nfkbia, and Cd14 mRNAs were also upregulated in other male reproductive tissues from LPS-treated rats (1 mg/kg, i.v., 2 h). Constitutive TLR4 was immunolocalized in some, but not all, epididymal epithelial cells and in interstitial cells, some of them identified as resident ED2-positive macrophages. No change in TLR4 immunostaining pattern was observed when epididymides from control and LPS-treated rats were compared (1 mg/kg, i.v., 2 h and 24 h). Significant NFKB activation was also achieved within 1 min of in vitro incubation of caput epididymidis with LPS (0.01-5 mug/ml), confirming that components for TLR4 signaling cascade activation are fully active in this tissue. This study contributes to a better understanding of the innate immune response in the epididymis and other tissues from the male reproductive tract.
authors.affiliation: Section of Experimental Endocrinology, Department of Pharmacology, Universidade Federal de São Paulo, Escola Paulista de Medicina, São Paulo, São Paulo 04044-020, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Rodrigues
authors.forename: Daniel B C
authors.initials: DB
authors.lastname: Queiróz
authors.forename: Luciana
authors.initials: L
authors.lastname: Honda
authors.forename: Erick José R
authors.initials: EJ
authors.lastname: Silva
authors.forename: Susan H
authors.initials: SH
authors.lastname: Hall
authors.forename: Maria Christina W
authors.initials: MC
authors.lastname: Avellar
mesh_terms: D000818:Animals; D015153:Blotting, Western; D003345:Corticosterone / Q000097:blood; D024202:Electrophoretic Mobility Shift Assay; D004822:Epididymis / Q000187:drug effects* / Q000378:metabolism*; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D053583:Interleukin-1beta / Q000096:biosynthesis / Q000235:genetics; D018950:Lipopolysaccharide Receptors / Q000096:biosynthesis / Q000235:genetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D016328:NF-kappa B / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects; D013739:Testosterone / Q000097:blood; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: D053583:Interleukin-1beta; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D016328:NF-kappa B; D051197:Toll-Like Receptor 4; D013739:Testosterone; D003345:Corticosterone