Tissue-type plasminogen activator (t-PA) is approved for treatment of ischemic stroke patients, but it increases the risk of intracranial bleeding (ICB). Previously, we have shown in a mouse stroke model that stromelysin-1 (matrix metalloproteinase-3 [MMP-3]) induced in endothelial cells was critical for ICB induced by t-PA. In the present study, using bEnd.3 cells, a mouse brain-derived endothelial cell line, we showed that MMP-3 was induced by both ischemic stress and t-PA treatment. This induction by t-PA was prevented by inhibition either of low-density lipoprotein receptor-related protein (LRP) or of nuclear factor-B activation. LRP was upregulated by ischemic stress, both in bEnd.
IntroductionTissue-type plasminogen activator (t-PA) is a thrombolytic agent that degrades fibrin clots through activation of plasminogen to plasmin. 1 Although t-PA given within 3 hours from onset of ischemic stroke improves the clinical outcome in patients, it induces a 10-fold increase of symptomatic intracranial bleeding (ICB). 2 Furthermore, delayed t-PA treatment beyond 3 hours is associated with an increased risk of hemorrhagic transformation and with enhanced brain injury. 3 The increase of ICB by delayed treatment with t-PA was also observed in a mouse stroke model. 4 Matrix metalloproteinases (MMPs), a family of zinc endopeptidases, contribute to tissue remodeling through degradation of extracellular matrix proteins. For ICB associated with ischemic stroke, MMPs have a key role in the degradation of the barrier of blood vessels. 5,6 Previously, we have shown that the increase in ICB caused by t-PA treatment was impaired in mice with gene deficiency of MMP-3 (stromelysin-1) and that a broad-spectrum MMP inhibitor suppressed ICB in wild-type but not in MMP-3-deficient mice. 7 MMP-3 can be activated by plasmin 8 and has a broad-spectrum substrate specificity. 9 Furthermore, t-PA treatment induced MMP-3 selectively in endothelial cells at the ischemic damaged area in a mouse stroke model, 7 suggesting that MMP-3 may be involved in degradation of the barrier of blood vessels and contribute to ICB. However, the mechanism underlying MMP-3 induction by t-PA remained unknown and is the subject of the present study.Low-density lipoprotein receptor-related protein (LRP), a member of the lipoprotein receptor family, is a scavenger receptor that binds a variety of biologic ligands and is thought to be primarily involved in lipoprotein metabolism 10 and in clearance of proteaseinhibitor complexes in the adult brain. 11 Recent reports have shown that t-PA induces MMP-9 in brain endothelial cells 12 and increases the blood-brain barrier permeability via LPR activation, 13 suggesting a role for LRP as a t-PA receptor. It has also been reported that LRP activation by t-PA stimulates the nuclear factor kappa-B (NF-B) pathway. 14 In this study, we have evaluated whether the LRP/NF-B pathway plays a role in MMP-3 induction by t-PA treatment. Therefore, we used bEnd.3 cells, a transformed endothelial cell line derived from mouse brain, as w...
UDP-glucuronosyltransferase (UGT) 1A1 glucuronidates endogenous metabolites, such as bilirubin, and exogenous substances, and plays a critical role in their detoxification and excretion. In a previous article, we described the phenobarbital response activity to a 290-base pair (bp) distal enhancer sequence (Ϫ3499/Ϫ3210) of the human UGT1A1 gene that is activated by the constitutive androstane receptor (CAR). Here, we show that dexamethasone at submicromolar concentrations enhances the pregnane X receptor (PXR) activator-mediated expression of the UGT1A1 gene and protein in HepG2 cells. We investigated the molecular mechanism of UGT1A1 induction by glucocorticoids at submicromolar concentrations and PXR activators and the functional cross-talk between the glucocorticoid receptor (GR) and CAR/PXR. The glucocorticoid-response element (GRE) was characterized by cotransfection experiments, site-directed mutagenesis, and electrophoretic mobility shift assays. Analysis of the human UGT1A1 promoter revealed GREs at Ϫ3404/Ϫ3389 and Ϫ3251/Ϫ3236
ABSTRACT:Inulin enzymatically synthesized from sucrose is a dietary component that completely escapes glucide digestion. Supplementing inulin to a high-fat and high-sucrose diet (HF) ameliorated hypertriglycemia and hepatic steatosis in 8-week-fed rats by suppressing elevated levels of serum triacylglycerols, fatty acids, and glucose, and the accumulation of hepatic triacylglycerols and fatty acids. Inulin intake prevented phenobarbital (PB)-and dexamethasone-induced liver injuries in the HF group. No significant alteration in the baseline expression of CYP2B, CYP2C11, CYP3A, and NADPH-cytochrome P450 (P450) reductase mRNAs and proteins was found. In contrast, baseline and PB-treated expressions of CYP2E1 mRNA were reduced in HF-fed rats. The induction of P450s in response to PB was affected by the nutritional status of the rats; mRNA levels of CYP2B1 and CYP3A1 after PB treatment, as assessed by quantitative real-time polymerase chain reaction analysis were reduced in the inulin-supplemented HF (HF؉I) group, compared with those in the HF group. Western blot analysis detected the corresponding changes of CYP2B and CYP3A proteins. These alterations were correlated with changes in hepatic thiobarbituric acid-reactive substances. Furthermore, no significant difference in the expression of nuclear receptors constitutive androstane receptor, pregnane X receptor, and retinoid X receptor ␣ and coactivator peroxisome proliferator-activated receptor-␥ coactivator 1␣ proteins was found in the hepatic nucleus between the HF and HF؉I groups, but the expression of hepatocyte nuclear factor ␣ (HNF4␣) protein was significantly reduced in the HF؉I group. Taken together, these results indicate that inulin intake ameliorates PB-induced liver injury, associated with a decline in lipid accumulation and PB-induced expression of CYP2B and CYP3A, which may be related by a reduction in the nuclear expression of HNF4␣.
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