Thromboxane A₂from Kupffer cells contributes to the hyperresponsiveness of hepatic portal circulation to endothelin-1 in endotoxemic rats

Abstract

We examined the role of thromboxane A2 (TXA2) in LPS-induced hyperresponsiveness of hepatic portal circulation to endothelins (ETs) and whether Kupffer cells are the primary source of TXA2 release in response to ET-1 in endotoxemia. After 6 h of LPS (1 mg/kg body wt ip) or saline (control), liver was isolated and perfused with recirculating Krebs-Henseleit bicarbonate buffer at a constant flow rate (100 ml.min(-1).kg body wt(-1)). ET-1 (10 pmol/min) was infused for 10 min. Portal pressure (PP) was continuously monitored during perfusion. Perfusate was sampled for enzyme immunoassay of thromboxane B2 (TXB2; the stable metabolite of TXA2) and lactate dehydrogenase (LDH) assay. ET-1 infusion resulted in a significantly greater increase of PP in the LPS group than in controls. Both TXA2 synthase inhibitor furegrelate (Fureg) and TXA2 receptor antagonist SQ-29548 (SQ) substantially blocked enhanced increase of PP in the LPS group (4.9 +/- 0.4 vs. 3.6 +/- 0.5 vs. 2.6 +/- 0.6 mmHg for LPS alone, LPS + Fureg, and LPS + SQ, respectively; P < 0.05) while having no significant effect on controls. GdCl3 for inhibition of Kupffer cells had similar effects (4.9 +/- 0.4 mmHg vs. 2.9 +/- 0.4 mmHg for LPS alone and GdCl3 + LPS, respectively; P < 0.05). In addition, the attenuated PP after ET-1 was found concomitantly with significantly decreased releases of TXB2 and LDH in LPS rats treated with Fureg, SQ, and GdCl3 (886.6 +/- 73.4 vs. 110.8 +/- 0.8 vs. 114.8 +/- 54.7 vs. 135.2 +/- 45.2 pg/ml, respectively; P < 0.05). After 6 h of LPS, Kupffer cells in isolated cell preparations released a significant amount of TXA2 in response to ET-1. These results clearly indicate that hyperresponsiveness of hepatic portal circulation to ET-1 in endotoxemia is mediated at least in part by TXA2-induced receptor activation, and Kupffer cells are likely the primary source of increased TXA2 release.

Intraperitoneal LPS amplifies portal hypertension in rat liver fibrosis

“…15,29,30 KCs are highly relevant for the production of vasoconstrictors in the intrahepatic microvasculature. 6,16 The effects observed in this study seem to be predominantly dependent on the KCs, because GdCl 3 pretreatment attenuated TLR4 and MyD88 expression after LPS pretreatment.…”

“…14,15 Therefore, KCs could have a leading role in the regulation of infection-related variceal bleeding, as proposed previously. 16 The activation of KCs is dependent on surface receptors such as Toll-like receptors (TLRs) and intracellular effectors such as MyD88.…”

Altered Endothelin-1 Signaling in Production of Thromboxane A2 in Kupffer Cells from Bile Duct Ligated Rats

“…KCs form one week BLD and sham operated Male Sprague-Dawley rats weighing between 250-400 g were isolated as previously described (9,52). Cells were plated in 24-well plastic culture dishes (Corning, Corning, NY) at a concentration of 1 × 10 6 cells/well and cultured in 1000 l of RPMI 1640 medium (Sigma Chemical, St. Louis, MO) supplemented with 25 mM HEPES, 20% fetal bovine serum (FBS) and antibiotics (0.05% gentamycin sulfate).…”

“…Thromboxane A 2 (TXA 2 ) is a potent cyclooxygenase (COX)-derived vasoconstrictor in the portal circulation and contributes to the overall vascular tone of the hepatic microcirculation (5)(6)(7). Our lab has shown that Kupffer cell (KC)-derived TXA 2 plays significant roles in the development of portal hypertension and hepatocellular injury in early fibrosis using the one-week bile duct ligation (BDL) model (8) and in mediating the hyperresponsiveness of the portal circulation to the vasoconstrictive effect of ET-1 during endotoxemia (9). In the same model, we have also shown that the fibrotic stress primes KCs for the release of TXA 2 by inducing the upregulation of cytosolic phopholipase A 2 (cPLA 2 ), COX-2, and thromboxane synthase (TS) (10), the three key enzymes for its biosynthesis (11)(12)(13)(14)(15)(16).…”

Treatment With the Leukotriene Inhibitor Montelukast for 10 Days Attenuates Portal Hypertension in Rat Liver Cirrhosis

“…2 The morphological and molecular changes that the cirrhotic liver undergoes form the basis for subsequent alterations in the generation, degradation, and the response to vasodilators and vasoconstrictors. Hepatic vascular tone rearrangements originate from an increase in the levels of vasoconstrictors, such as thromboxane (TX) A 2 [3][4][5][6] or cysteinyl leukotrienes (Cys-LTs, leukotrienes C 4 , D 4 , E 4 ), 7,8 and a decrease in the levels of vasodilators. [9][10][11][12][13] One mechanism in addition to the many others for the intrahepatic hyperresponsiveness to vasoconstrictors in the cirrhotic liver is the up-regulation of Rho kinase-mediated contraction.…”