bq-123 and Necrosis

The optimal vasodilator to avoid hepatic artery vasospasm during normothermic ex vivo liver perfusion (NEVLP) is yet to be determined. We compared safety and efficacy of BQ123 (endothelin1 antagonist), epoprostenol (prostacyclin analogue), and verapamil (calcium channel antagonist).. Livers from porcine heart beating donors were perfused for 3 hours and transplanted into recipient pigs. Four groups were compared: group 1, livers perfused with a dose of 1.25 mg of BQ123 at baseline and at 2 hours of perfusion; group 2, epoprostenol at a continuous infusion of 4 mg/h; group 3, verapamil 2.5 mg at baseline and at 2 hours of perfusion; group 4, no vasodilator used during ex vivo perfusion. Liver injury and function were assessed during perfusion, and daily posttransplantation until postoperative day (POD) 3. All groups were compared with a cold storage group for postoperative graft function.. Hepatic artery flow during NEVLP was significantly higher in BQ123 compared with verapamil, epoprostenol, and no vasodilator-treated livers. Aspartate aminotransferase levels were significantly lower with BQ123 and verapamil compared with epoprostenol and control group during perfusion. Peak aspartate aminotransferase levels were lower in pigs receiving BQ123 and verapamil perfused grafts compared with epoprostenol and control group. International Normalized Ratio, alkaline phosphatase, and total bilirubin levels were lower in the BQ123 and verapamil groups compared to epoprostenol group. Cold storage group had increased markers of ischemia reperfusion injury and slower graft function recovery compared to machine perfused grafts.. The use of BQ123, epoprostenol, and verapamil during NEVLP is safe. Livers perfused with BQ123 and verapamil have higher hepatic artery flow and reduced hepatocyte injury during perfusion compared with epoprostenol. Hepatic artery flow is significantly reduced in the absence of vasodilators during NEVLP.

Topics: Animals; Apoptosis; Calcium Channel Blockers; Endothelin Receptor Antagonists; Epoprostenol; Hepatic Artery; Liver; Liver Circulation; Liver Transplantation; Male; Necrosis; Peptides, Cyclic; Perfusion; Reperfusion Injury; Sus scrofa; Vasoconstriction; Vasodilator Agents; Verapamil

Insufficient perfusion of distal flap areas, which may lead to partial necrosis, still represents a challenge in reconstructive surgery. In the process of microvascular and endothelial dysfunction, endothelins (ETs) and their receptors may play an important role. Therefore, the aim of the study was to investigate in a chronic in vivo model the effect of various ET-receptor antagonists in critically perfused flap tissue.. A random pattern musculocutaneous flap was elevated in the back of 25 C57BL/6 mice and fixed into a dorsal skinfold chamber. Repetitive intravital fluorescence microscopy was performed over a 10-day observation period, assessing arteriolar diameter, arteriolar blood flow (aBF), functional capillary density (FCD), the area of tissue necrosis, and the development of newly formed blood vessels. ET-receptor blockers were administrated intraperitoneally 30 min before induction of ischemia, as well as daily during the subsequent 4-day period, including (1) BQ-123, a specific ET-A-receptor antagonist (ET-A = 1 mg/kg), (2) BQ-788, a selective ET-B-receptor antagonist (ET-B = 1 mg/kg), and (3) PD-142893, a nonselective ET-AB-receptor antagonist (ET-AB = 0.5 mg/kg). Animals receiving saline only served as controls (n = 7).. Despite an increase in aBF during the 10-day observation period (day 1 = 1.92 +/- 0.29 nl/s; day 10 = 4.70 +/- 1.64 nl/s), the flaps of saline-treated controls showed a distinct decrease in FCD (94 +/- 12 cm/cm(2)). This perfusion failure resulted in flap necrosis of 52 +/- 3%. Selective blockade of the ET-B receptor caused a further increase in aBF already at day 1 (2.97 +/- 0.42 nl/s), which persisted during the following 10-day observation period (day 10 = 5.74 +/- 0.69 nl/s). Accordingly, adequate FCD could be maintained (day 10 = 215 +/- 8 cm/cm(2); p < 0.05 vs control), resulting in a significant reduction in flap necrosis (day 10 = 25 +/- 4%; p < 0,05). In contrast, neither selective blockade of the ET-A receptor nor nonselective ET-A- and ET-B-receptor blockade were able to significantly affect aBF when compared to controls (day 1 = ET-A = 1.39 +/- 0.10 nl/s; ET-AB = 1.53 +/- 0.80 nl/s; n.s.). Accordingly, flap necrosis after ET-A- and ET-AB-receptor inhibition did not differ from that of controls (day 10 = ET-A: 46 +/- 10%; ET-AB = 51 +/- 7%).. Our data show that only selective ET-B-receptor inhibition is capable of maintaining nutritive perfusion and, hence, reducing necrosis in critically perfused flap tissue. Accordingly, administration of ET-B-receptor antagonists may be considered in the treatment of critically perfused flaps.

Topics: Animals; Arterioles; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Graft Survival; Ischemia; Mice; Mice, Inbred C57BL; Microcirculation; Microscopy, Fluorescence; Models, Animal; Necrosis; Oligopeptides; Peptides, Cyclic; Piperidines; Regional Blood Flow; Surgical Flaps; Time Factors; Venules

Endothelins (ETs) are a group of vasoactive peptides (ET-1, ET-2 and ET-3) produced by many cell types that bind to G-protein-linked transmembrane receptors, ET-A receptors (ET-RAs) and ET-B receptors (ET-RBs). These peptides are expressed in several human tumors, including carcinomas of the breast, and have a mitogenic effect in ovarian cancer cell lines. We investigated ET expression in infiltrating ductal carcinomas (IDCs) of the breast and the relationship between ET and hypoxia. ET staining was increased in human grade II IDC samples compared with normal breast tissue. ET-2 and ET-RB mRNA expression were absent in the majority of normal human breast samples (1 of 5 and 0 of 5, respectively) but was present in the majority of IDC tested (13 of 15 and 12 of 15, respectively). In a murine breast cancer model, HTH-K, ET-2, and ET-RB mRNA were detected in tumor but not normal breast tissue, and ET expression colocalized with areas of hypoxia. In vitro, ET-2, ET-RA, and ET-RB mRNA were increased by incubating HTH-K cells in hypoxia (0.1% oxygen) for 24 h. Hypoxia also up-regulated ET-2 mRNA in several human breast tumor cell lines. ET-2 mRNA increased within 3 h in a hypoxia-inducible factor 1-dependent manner. The ET-RB antagonist BQ-788 increased in hypoxia-associated apoptosis of breast tumor cells in vitro. These effects could be reversed by addition of ET-2 peptide. Intratumoral injection of BQ-788 led to an increase in the development and extent of necrosis within the HTH-K tumor and a decrease in the rate of tumor growth. The ET-RA antagonist, BQ-123, also led to a decrease in tumor growth but without a concomitant increase in necrosis. We propose that modulation of ET-2 production via the hypoxia-inducible factor 1 transcription factor and autocrine signaling via ET-RB is a novel mechanism by which tumor cells can withstand hypoxic stress. Treatment of breast carcinomas with ET receptor antagonists may have a therapeutic benefit.

Topics: Antihypertensive Agents; Blotting, Northern; Breast Neoplasms; Cell Survival; DNA-Binding Proteins; Dose-Response Relationship, Drug; Endothelin-2; Female; Humans; Hypoxia; Hypoxia-Inducible Factor 1; Hypoxia-Inducible Factor 1, alpha Subunit; Necrosis; Nuclear Proteins; Oligopeptides; Ovarian Neoplasms; Peptides, Cyclic; Piperidines; Receptor, Endothelin B; Receptors, Endothelin; RNA, Messenger; Time Factors; Transcription Factors; Tumor Cells, Cultured; Up-Regulation

The endothelin receptor antagonists BQ-610 and BQ-123 were used to clarify the role of endothelin in the pathogenesis of postischemic microvascular incompetence in the myocardium. Forty-five isolated rat hearts were perfused with Krebs-Henseleit buffer (KHB) for 15 min and then subjected to 0, 15, or 60 min of ischemia followed by 5 min of reperfusion with KHB, KHB + BQ-610, or KHB + BQ-123. They were fixed by perfusion with 2.5% glutaraldehyde and then perfused with nuclear track emulsion as an indicator of vascular flow. Transmural sections of resin-embedded myocardium were examined by scanning and transmission electron microscopy. Following 60 min of ischemia, the subendocardial third of the LV wall of hearts treated with BQ-123 showed nearly three times the proportion (P < 0.001) of competent capillaries in untreated hearts. Reperfusion after 15 min of ischemia of hearts treated with BQ-123 showed a 30% increase in the proportion of competent capillaries compared to controls (P < 0. 002). Treatment of corresponding groups with BQ-610 increased the proportion of competent capillaries but these differences were not statistically significant. In addition, both ET-I antagonists dramatically reduced the amount of ultrastructural change evident in myocardium reperfused after 60 min of ischemia. Thus endothelin plays a significant role in the pathogenesis of postischemic microvascular incompetence in the myocardium and, probably by its effects on Ca(2+) uptake, contributes also to the ultrastructural damage to the myocytes and endothelium which follows postischemic reperfusion of irreversibly injured myocardium.

Topics: Animals; Calcium; Capillaries; Coronary Vessels; Drug Evaluation, Preclinical; Endothelin Receptor Antagonists; Endothelins; Heart; Heart Ventricles; Ion Transport; Myocardial Stunning; Myocardium; Necrosis; Oligopeptides; Peptides, Cyclic; Rats; Rats, Inbred WKY; Receptor, Endothelin A; Receptors, Endothelin