The effect of endotoxin on hepatocyte nuclear factor 1 nuclear protein binding: potential implications on CYP2E1 expression in the rat

• Published in: Journal of pharmacy and pharmacology Vol. 53; no. 10; p. 1365
• Main Authors: Roe, A L, Poloyac, S M, Howard, G, Shedlofsky, S I, Blouin, R A
• Format: Journal Article
• Language: English
• Published: England 01.10.2001
• Subjects: Animals; Blotting, Western; Cell Nucleus - chemistry; Cytochrome P-450 CYP2E1 - biosynthesis; DNA-Binding Proteins; Electrophoretic Mobility Shift Assay; Endotoxins - pharmacology; Enzyme-Linked Immunosorbent Assay; Gene Expression Regulation, Enzymologic - drug effects; Hepatocyte Nuclear Factor 1; Hepatocyte Nuclear Factor 1-alpha; Hepatocyte Nuclear Factor 1-beta; Lipopolysaccharides - pharmacology; Liver - drug effects; Liver - enzymology; Male; Microsomes, Liver - drug effects; Microsomes, Liver - enzymology; Nuclear Proteins - metabolism; Protein Binding; Rats; Rats, Sprague-Dawley; Transcription Factors - metabolism
• ISSN: 0022-3573
• DOI: 10.1211/0022357011777864

The purpose of this study was to determine if changes in nuclear protein binding of hepatocyte nuclear factor 1 (HNF-1) occur after lipopolysaccharide (LPS) administration. In addition, the time-course of alterations in CYP2E1 regulation were evaluated. Rats were injected with 2.0 mg LPS and euthanized over a 72-h period. Nuclear protein binding to a consensus HNF-1 oligonucleotide was assessed by the electrophoretic mobility shift assay. CYP2E1 activity was analysed using chlorzoxazone as a substrate (60H-CLZ), and CYP2E1 protein concentration was determined by enzyme-linked immunosorbent assay. Endotoxin treatment resulted in decreased nuclear protein binding to an HNF-1 element as early as 1 h after treatment and returned to control levels by 72 h. This reduced binding persisted for 24 h and returned to control values 48 h after LPS administration. In addition, the reduction in binding was primarily attributable to a HNF-1alpha immunoreactive protein. The observed reduction in HNF-1 binding was followed in the time-course by decreases in CYP2E1 activity and protein content with maximal decreases to 50 and 67% of control, respectively, at 48 h after LPS administration. Endotoxin is a potent inducer of the acute phase response (APR). The APR stimulation by endotoxin administration reduced HNF-1alpha binding and decreased the expression of CYP2E1 in the rat liver. The time-course of alterations in HNF-1 and CYP2E1 lend support to the possibility that HNF-1alpha may play a role in the down-regulation of genes that require HNF-1alpha for their constitutive expression. These data serve as an important precedent for future studies evaluating the direct association of decreased HNF-1alpha binding and reduced gene expression after LPS administration.