The UII/UT system mediates upregulation of proinflammatory cytokines through p38 MAPK and NF-κB pathways in LPS-stimulated Kupffer cells.

The urotensin II (UII)/UII receptor (UT) system is closely related to immune inflammation. In acute liver failure (ALF), the UII/UT system can promote the production and release of proinflammatory cytokines, inducing an inflammatory injury response in liver tissue. However, the mechanism by which the hepatic UII/UT system promotes proinflammatory cytokine production and release is not clear. To solve this problem, we used primary Kupffer cells (KCs) as the model system in the current study. The results showed that after lipopolysaccharide (LPS) stimulation, KCs showed significantly increased expression and release of UII/UT and proinflammatory cytokines tumor necrosis factor α (TNF-α) and interleukin 1ß (IL-1ß). Pretreatment with urantide, which is a UT receptor antagonist, significantly inhibited the LPS-stimulated expression and release of UII/UT, TNF-α, and IL-1ß by KCs. In addition, LPS stimulation induced nuclear p38 mitogen-activated protein kinase (MAPK) protein phosphorylation and expression of the nuclear nuclear factor κB (NF-κB) p65 subunit in KCs and enhanced the binding activity of NF-κB to DNA molecules, whereas urantide pretreatment significantly inhibited the LPS-stimulated nuclear expression and activity of these molecules in KCs. Therefore, our conclusion is that the UII/UT system mediates LPS-stimulated production and release of proinflammatory cytokine by KCs, and this mediating effect at least partially relies on the inflammatory signaling pathway molecules p38 MAPK and NF-κB.

Effects of urotensin-II on cytokines in early acute liver failure in mice.

AIM: To investigate urotensin-II (UII) and its effects on tumor necrosis factor (TNF)-α and interleukin (IL)-1ß in early acute liver failure (ALF). METHODS: We investigated the time-dependent alteration in UII levels and its effects on TNF-α and IL-1ß in liver and blood in the early stage of lipopolysaccharide/D-galactosamine-induced ALF. RESULTS: After lipopolysaccharide/D-galactosamine challenge, UII rose very rapidly and reached a maximal level 0.5 h, and the level remained significantly elevated after 2 h (P < 0.05). Six hours after challenge, UII began to degrade, but remained higher than at 0 h (P < 0.05). Pretreatment with urantide, an inhibitor of the UII receptor, suppressed the degree of UII increase in liver and blood at 6 h after challenge (P < 0.05 vs paired controls). In addition, liver and blood TNF-α increased from 1 to 6 h, and reached a peak at 1 and 2 h, respectively; however, IL-1ß did not rise until 6 h after challenge. Urantide pretreatment inhibited the degree of TNF-α and IL-1ß increase following downregulation of UII post-challenge (all P < 0.05). CONCLUSION: UII plays a role in the pathogenesis and priming of ALF by triggering an inflammatory cascade and driving the early release of cytokines in mice.

Inhibition of UII/UTR system relieves acute inflammation of liver through preventing activation of NF-κB pathway in ALF mice.

Urotensin II (UII) is implicated in immune inflammatory diseases through its specific high-affinity UT receptor (UTR). Enhanced expression of UII/UTR was recently demonstrated in the liver with acute liver failure (ALF). Here, we analysed the relationship between UII/UTR expression and ALF in lipopolysaccharide (LPS)/D-galactosamine (GalN)-challenged mice. Thereafter, we investigated the effects produced by the inhibition of UII/UTR system using urantide, a special antagonist of UTR, and the potential molecular mechanisms involved in ALF. Urantide was administered to mice treated with LPS/GalN. Expression of UII/UTR, releases of proinflammatory cytokines including tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1ß) and interferon-γ (IFN-γ), and activation of nuclear factor κB (NF-κB) signaling pathway were assessed in the lethal ALF with or without urantide pretreatment. We found that LPS/GalN-challenged mice showed high mortality and marked hepatic inflammatory infiltration and cell apoptosis as well as a significant increase of UII/UTR expression. Urantide pretreatment protected against the injury in liver following downregulation of UII/UTR expression. A close relationship between the acutely flamed hepatic injury and UII/UTR expression was observed. In addition, urantide prevented the increases of proinflammatory cytokines such as TNF-α, IL-1ß and IFN-γ, and activation of NF-κB signaling pathway induced by LPS/GalN in mice. Thus, we conclude that UII/UTR system plays a role in LPS/GalN-induced ALF. Urantide has a protective effect on the acutely inflamed injury of liver in part through preventing releases of proinflammatory cytokines and activation of NF-κB pathway.

[Inhibitive mechanisms of Pim-3 affecting fulminant hepatic apoptosis].

To investigate the mechanisms of serine/threonine kinase Pim-3 inhibition of fulminant hepatic apoptosis. Thirty-two rats were randomly divided into four groups (n = 8 each): normal controls (A); pretreatment with Ringer's solution (B), vector plasmid (C), or Pim-3 recombinant plasmid (D) by hydrodynamics-based procedure followed by intraperitoneal injections of lipopolysaccharide (LPS) and D-galactosamine (D-GalN) after one day. At 8 h after the LPS/D-GalN injections, liver tissues were collected from all groups of mice and analyzed for cell apoptosis by detecting caspase-3 activity (measured in relative fluorescence units, RFU). Changes in expression of relevant genes were determined by RT-PCR and Western blotting. Caspase-3 activity was induced in response to LPS/D-GalN injection. Pim-3-pretreated rats showed a lower level of caspase-3 activity than the Ringer's-pretreated or vector plasmid-pretreated rats [(141.7+/-13.7)RFU vs. (508.1+/-32.0) or (493.5+/-33.1) RFU; all P less than 0.01]. High expressions of the liver injury marker gene, iNOS, and the apoptosis-induced genes, p53 and Bax, were found after LPS/D-GalN challenge, and were suppressed by exogenous Pim-3 gene injection. In addition, exogenous Pim-3 gene injection induced high expression of the liver anti-apoptosis protein, Bcl-2, but had no effect on Bax protein expression. The Pim-3 gene can block fulminant hepatic apoptosis by affecting the expression of the iNOS liver injury gene and the p53, Bax and Bcl-2 apoptosis-related genes.

[Effects of urantide, a urotensin receptor inhibitor, on acute hepatocyte apoptosis in mice].

OBJECTIVE: To explore the effects of urantide, a urotensin II receptor (UT) inhibitor, on lipopolysaccharide (LPS)/D-galactosamine (D-GalN)-induced acute hepatocyte apoptosis in mice. METHODS: Male BALB/c mice were randomly divided into 4 groups (n = 6 each): normal control, pre-treatment control, model and pre-treatment model. The pre-treatment control and pre-treatment model groups received urantide (0.6 mg/kg body weight) by a caudal vein injection. At 30 minutes post-injection, the model and pre-treatment model groups were treated with LPS/D-GalN to induce acute hepatocyte apoptosis via an intraperitoneal injection. Hepatocyte apoptosis was examined by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) and caspase-3 colorimetric assay. The expressions of proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-α), interferon-γ (IFN-γ) and interleukin-1 beta (IL-1ß), were detected by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay. RESULTS: Massive hepatocyte apoptosis were detected in the model group. The apoptotic index was clearly reduced in the pre-treatment model group [(26 ± 11)% vs (77 ± 20)%, P < 0.01]. And the activity of caspase-3 was also lower in the pre-treatment model group than that in the model group [(2.50 ± 0.83) pmol · min(-1) · mg(-1) vs (3.76 ± 0.42) pmol · min(-1) · mg(-1), P < 0.01]. In addition, the serum and liver tissue levels of TNF-α, IL-1ß and IFN-γ in the pre-treatment model group were significantly lower than those in the model group[1.69 ± 0.47 vs 3.57 ± 0.79, 0.31 ± 0.02 vs 0.46 ± 0.06, 2.81 ± 0.72 vs 3.35 ± 0.84, (233 ± 36) pg/ml vs (441 ± 157) pg/ml, (228 ± 21) pg/ml vs (364 ± 20) pg/ml, (93.8 ± 5.2) pg/ml vs (180.3 ± 4.3) pg/ml, all P < 0.01]. CONCLUSION: LPS/D-GalN-induced acute hepatocyte apoptosis can be inhibited by a pretreatment of urantide through an inhibition of expression and secretion of proinflammatory cytokines. The UII/UT receptor system plays a pivotal role in the liver immuno-inflammatory injury of acute liver failure (ALF). And it may become a new drug target of ALF therapy.