Factors mediating the hemodynamic effects of tumor necrosis factor-alpha in portal hypertensive rats

Pathophysiological-based treatments of complications of cirrhosis

Detailed knowledge and understanding of the pathophysiological mechanisms and changes in hepatic and splanchnic function leading to the development of haemodynamic changes and portal hypertension in patients with cirrhosis are essential since it guides the search for targets to ameliorate liver-related abnormalities. Recent research has focused on the gut-liver axis, changes in intestinal permeability, translocation of bacterial products, and inflammation as important drivers of haemodynamic alterations and thereby targets for treatment. Additionally, treatment strategies should focus on microbiotic modulation, antiangiogenics, anti-inflammatory strategies, and modulation of bile acid metabolism. This paper aims to review contemporary pathophysiological-based treatment principles of the major complications of cirrhosis and portal hypertension and future targets for treatment.

Vascular syndromes in liver cirrhosis

Liver cirrhosis is associated with multiple vascular syndromes affecting almost all body systems. Many of these syndromes are directly related to impaired liver function and sometimes reversible after liver transplantation while others arise secondary to portal hypertension and ascites. Altered expression of angiogenic and vasoactive compounds (most importantly nitric oxide), endothelial dysfunction, dysregulated neurohormonal control, and systemic inflammatory state play differential roles in mediating homeostatic instability and abnormal vasogenic response. Important vascular features encountered in liver disease include portal hypertension, splanchnic overflow, abnormal angiogenesis and shunts, portopulmonary syndrome, hepatopulmonary syndrome, and systemic hyperdynamic circulation. Redistribution of effective circulatory volume deviating from vital organs and pooling in splanchnic circulation is also encountered in liver patients which may lead to devastating outcomes as hepatorenal syndrome. Etiologically, vascular syndromes are not isolated phenomena and vascular dysfunction in one system may lead to the development of another in a different system. This review focuses on understanding the pathophysiological factors underlying vascular syndromes related to chronic liver disease and the potential links among them. Many of these syndromes are associated with high mortality, thus it is crucial to look for early biomarkers for these syndromes and develop novel preventive and therapeutic strategies.

The pathophysiology of arterial vasodilatation and hyperdynamic circulation in cirrhosis

Patients with cirrhosis and portal hypertension often develop complications from a variety of organ systems leading to a multiple organ failure. The combination of liver failure and portal hypertension results in a hyperdynamic circulatory state partly owing to simultaneous splanchnic and peripheral arterial vasodilatation. Increases in circulatory vasodilators are believed to be due to portosystemic shunting and bacterial translocation leading to redistribution of the blood volume with central hypovolemia. Portal hypertension per se and increased splanchnic blood flow are mainly responsible for the development and perpetuation of the hyperdynamic circulation and the associated changes in cardiovascular function with development of cirrhotic cardiomyopathy, autonomic dysfunction and renal dysfunction as part of a cardiorenal syndrome. Several of the cardiovascular changes are reversible after liver transplantation and point to the pathophysiological significance of portal hypertension. In this paper, we aimed to review current knowledge on the pathophysiology of arterial vasodilatation and the hyperdynamic circulation in cirrhosis.

Pathogenesis of intracranial aneurysm is mediated by proinflammatory cytokine TNFA and IFNG and through stochastic regulation of IL10 and TGFB1 by comorbid factors

BACKGROUND

Intracranial aneurysm (IA) is often asymptomatic until the time of rupture resulting in subarachnoid hemorrhage (SAH).There is no precise biochemical or phenotype marker for diagnosis of aneurysm. Environmental risk factors that associate with IA can result in modifying the effect of inherited genetic factors and thereby increase the susceptibility to SAH. In addition subsequent to aneurismal rupture, the nature and quantum of inflammatory response might be critical for repair. Therefore, genetic liability to inflammatory response caused by polymorphisms in cytokine genes might be the common denominator for gene and environment in the development of aneurysm and complications associated with rupture.

METHODS

Functionally relevant polymorphisms in the pro- and anti-inflammatory cytokine genes IL-1 complex (IL1A, IL1B, and IL1RN), TNFA, IFNG, IL3, IL6, IL12B, IL1RN, TGFB1, IL4, and IL10] were screened in radiologically confirmed 220 IA patients and 250 controls from genetically stratified Malayalam-speaking Dravidian ethnic population of south India. Subgroup analyses with genetic and environmental variables were also carried out.

RESULTS

Pro-inflammatory cytokines TNFA rs361525, IFNG rs2069718, and anti-inflammatory cytokine IL10 rs1800871 and rs1800872 were found to be significantly associated with IA, independent of epidemiological factors. TGFB1 rs1800469 polymorphism was observed to be associated with IA through co-modifying factors such as hypertension and gender. Functional prediction of all the associated SNPs of TNFA, IL10, and TGFB1 indicates their potential role in transcriptional regulation. Meta-analysis further reiterates that IL1 gene cluster and IL6 were not associated with IA.

CONCLUSIONS

The study suggests that chronic exposure to inflammatory response mediated by genetic variants in pro-inflammatory cytokines TNFA and IFNG could be a primary event, while stochastic regulation of IL10 and TGFB1 response mediated by comorbid factors such as hypertension may augment the pathogenesis of IA through vascular matrix degradation. The implication and interaction of these genetic variants under a specific environmental background will help us identify the resultant phenotypic variation in the pathogenesis of intracranial aneurysm. Identifying genetic risk factors for inflammation might also help in understanding and addressing the posttraumatic complications following the aneurismal rupture.

PUMA mediates ER stress-induced apoptosis in portal hypertensive gastropathy

Mucosal apoptosis has been demonstrated to be an essential pathological feature in portal hypertensive gastropathy (PHG). p53-upregulated modulator of apoptosis (PUMA) was identified as a BH3-only Bcl-2 family protein that has an essential role in apoptosis induced by a variety of stimuli, including endoplasmic reticulum (ER) stress. However, whether PUMA is involved in mucosal apoptosis in PHG remains unclear, and whether PUMA induces PHG by mediating ER stress remains unknown. The aim of the study is to investigate whether PUMA is involved in PHG by mediating ER stress apoptotic signaling. To identify whether PUMA is involved in PHG by mediating ER stress, gastric mucosal injury and apoptosis were studied in both PHG patients and PHG animal models using PUMA knockout (PUMA-KO) and PUMA wild-type (PUMA-WT) mice. The induction of PUMA expression and ER stress signaling were investigated, and the mechanisms of PUMA-mediated apoptosis were analyzed. GES-1 and SGC7901 cell lines were used to further identify whether PUMA-mediated apoptosis was induced by ER stress in vitro. Epithelial apoptosis and PUMA were markedly induced in the gastric mucosa of PHG patients and mouse PHG models. ER stress had a potent role in the induction of PUMA and apoptosis in PHG models, and the apoptosis was obviously attenuated in PUMA-KO mice. Although the targeted deletion of PUMA did not affect ER stress, mitochondrial apoptotic signaling was downregulated in mice. Meanwhile, PUMA knockdown significantly ameliorated ER stress-induced mitochondria-dependent apoptosis in vitro. These results indicate that PUMA mediates ER stress-induced mucosal epithelial apoptosis through the mitochondrial apoptotic pathway in PHG, and that PUMA is a potentially therapeutic target for PHG.

Evidence of an anti-apoptotic effect of qinghuobaiduyin on intestinal mucosa following burn injury

Burn injuries are common in wartime and in times of peace. The prevention and therapy of ischemia-reperfusion injury to the organs, in particular the intestine, during the burn shock and recovery process has become a popular yet challenging area of research. Studies concerning the apoptosis of the cells of the burned intestinal mucosa have gained considerable attention. Qinghuobaiduyin (QHBDY) is a traditional Chinese medicine that has been used as a clinical prescription since 1995 to treat burn patients due to its opsonization function in the immune system and favorable clinical therapeutic effect. The aim of this study was to investigate the effect of QHBDY on the apoptosis of intestinal mucosa following burn injury. An animal model was constructed comprising severely burned rats that were treated with various dosages of QHBDY. Tissues from the small intestine were collected to investigate the apoptosis rate by TUNEL assay and the protein expression levels of heat shock protein 70 (Hsp70) and caspase-3 by immunohistochemistry. In addition, IEC-18 cells treated with QHBDY and burn serum were investigated. The cell apoptosis rate was analyzed by flow cytometry (FCM), the protein expression levels of Hsp70 were measured by western blot analysis and caspase-3 activity was analyzed by a colorimetric assay. The results showed that in animal experiments, compared with the burned group, the apoptosis rates in the treatment group was decreased, the protein expression level of Hsp70 was increased while Caspase-3 was decreased. In cell experiments, after treatment with QHBDY, the cell apoptosis rate was lower than that of the burn serum group. In addition, Hsp70 protein expression was upregulated and caspase-3 activity was decreased. QHBDY may play an important role in the prevention of apoptosis at the whole animal and cellular levels.

Nitric oxide and prostaglandin as mediators in the pathogenesis of hyperkinetic circulatory state in a model of endotoxemia-induced portal hypertension

AIMS

To evaluate the participation of nitric oxide (NO) and prostaglandin (PGI2) on hyperdynamic state in endotoxemia-induced portal hypertension (EIP) induced by chronic endotoxemia.

METHODS

The portal pressure (PP) and mean arterial pressure (MAP) were recorded, in vivo before and after administration of L-NAME (NOS inhibitor) and indomethacin (specific blocker of COX). The vasoactive responses to acetylcholine of thoracic rat aortic rings were studied in vitro before and after nitric oxide and cyclooxygenase blockade using multichannel organ bath. The mRNA expression for isoforms of (cyclooxygenase) COX and nitric oxide synthase (NOS) were analyzed using RT-PCR.

RESULTS

Administration of both L-NAME and indomethacin in EIP rabbits significantly reduced (p < 0.05) the PP and reversed the MAP to normal as compared to sham-operated (SO) rabbits. There was impaired vasodilatory response to acetylcholine in EIP rabbits. L-NAME caused a significant reduction in acetylcholine-induced vasorelaxation in SO rabbits than EIP due to preexisting hyperemia in EIP. Indomethacin partially restored vasoresponsiveness to acetylcholine in EIP group. The mRNA expression of eNOS (endothelial NOS) and COX-1 (constitutive COX) were significantly higher in SO than EIP rabbits. iNOS (inducible NOS) and COX-2 (inducible COX) mRNA expression was seen only in EIP rabbits.

CONCLUSIONS

A significant component of acetylcholine-mediated vasorelaxation in EIP model is modulated by eNOS. There was increased production of contractile prostaglandin in EIP rabbits. iNOS and COX-2 play an important role in the hemodynamic abnormalities of PHT. This novel model of PHT produced by chronic splanchnic endotoxemia in rabbit, mimics impaired vasodilation and vasoreactivity akin to other models of PHT.

Biology of intracranial aneurysms: role of inflammation

Intracranial aneurysms (IAs) linger as a potentially devastating clinical problem. Despite intense investigation, our understanding of the mechanisms leading to aneurysm development, progression and rupture remain incompletely defined. An accumulating body of evidence implicates inflammation as a critical contributor to aneurysm pathogenesis. Intracranial aneurysm formation and progression appear to result from endothelial dysfunction, a mounting inflammatory response, and vascular smooth muscle cell phenotypic modulation producing a pro-inflammatory phenotype. A later final common pathway appears to involve apoptosis of cellular constituents of the vessel wall. These changes result in degradation of the integrity of the vascular wall leading to aneurysmal dilation, progression and eventual rupture in certain aneurysms. Various aspects of the inflammatory response have been investigated as contributors to IA pathogenesis including leukocytes, complement, immunoglobulins, cytokines, and other humoral mediators. Furthermore, gene expression profiling of IA compared with control arteries has prominently featured differential expression of genes involved with immune response/inflammation. Preliminary data suggest that therapies targeting the inflammatory response may have efficacy in the future treatment of IA. Further investigation, however, is necessary to elucidate the precise role of inflammation in IA pathogenesis, which can be exploited to improve the prognosis of patients harboring IA.

Therapeutic effect of captopril, pentoxifylline, and cordyceps sinensis in pre-hepatic portal hypertensive rats

BACKGROUND/AIM

Portal hypertension is an important and potentially fatal complication of liver disease whereby cellular and fibrotic alterations manifest to increase portal venous pressure. The aim of this study is to investigate the effect of captopril, pentoxifylline (PTX), and cordyceps sinensis in pre-hepatic portal hypertensive rats.

SETTINGS AND DESIGN

Wistar male rats were divided at random into 3 main groups: the first group: control rats. The second group: sham-operated rats and the third group: prehepatic portal hypertensive rats (PHPHT) induced by regulated pre-hepatic portal vein ligation. After 14 days, Group 3 was subdivided into 5 subgroups. Subgroup (1): portal vein-ligated (PVL) was killed at once; Subgroup (2): received distilled water for 30 days (untreated PVL group); subgroups 3-5 were treated with captopril (60 mg/kg, orally); PTX (100 mg/kg, orally); and C. sinensis (200 mg/kg, orally), respectively, as a single daily dose for 30 days.

PATIENTS AND METHODS

Portal pressure, nitric oxide (NO), antioxidant enzymes, Liver enzymes, and creatinine levels were measured to evaluate the status of the liver state.

RESULTS

Portal vein ligation produced significant increments in liver enzymes, NO, creatinine and portal pressure concomitant with significant decrements in glutathione content and superoxide dismutase activity. Treatment with captopril, PTX, and C. sinensis resulted in a significant reduction in liver enzymes, NO, creatinine and portal pressure and observable increase in antioxidant enzymes.

CONCLUSIONS

captopril, PTX, and C. sinensis have promising effect in controlling PHPHT and reducing hyperdynamic circulatory state through reduction of portal pressure and NO level.

Downregulation of cyclooxygenase-1 is involved in gastric mucosal apoptosis via death signaling in portal hypertensive rats

Portal hypertension (PHT) gastropathy is a frequent complication of liver cirrhosis and one of the leading causes of death from cirrhosis. Apoptosis is widely considered to be an active energy-dependent mode of cell death and a distinct entity from necrotic cell death. It is unclear whether gastric mucosal apoptosis is involved in PHT gastropathy. Prostaglandins (PGs) produced through cyclooxygenase (COX) are thought to play a key role in protection of the gastrointestinal mucosa from injury and apoptosis. However, the role of COX in PHT gastropathy is still not clearly understood. The aims of this study were to investigate whether (1) gastric mucosal apoptosis is involved in PHT gastropathy and (2) downregulation of COX contributes to this apoptosis. In this study, we show that gastric mucosal apoptosis was remarkably increased while mucosal proliferation was inhibited in PHT rats. Gastric mucosal COX-1 was significantly suppressed at both the mRNA and protein levels, and PGE(2) was reduced in PHT rats. Further, PGE(2) treatment suppressed gastric mucosal apoptosis in PHT rats. However, gastric mucosal COX-2 levels did not differ between sham-operated rats and PHT rats. Gastric mucosal levels of tumor necrosis factor-alpha (TNF-alpha) and Fas ligand, but not TNF-related apoptosis-inducing ligand, were increased, and activated caspase-8 and caspase-3 levels were upregulated in PHT rats. The release of cytochrome c from the mitochondria to the cytosol was not observed in PHT rats. Our data indicate that downregulation of COX-1 is involved in gastric mucosal apoptosis via death signaling-mediated type-I cell death in PHT rats.

TNF-alpha-mediated inflammation in cerebral aneurysms: a potential link to growth and rupture

Intracranial aneurysm (IA) rupture is one of the leading causes of stroke in the United States and remains a major health concern today. Most aneurysms are asymptomatic with a minor percentage of rupture annually. Regardless, IA rupture has a devastatingly high mortality rate and does not have specific drugs that stabilize or prevent aneurysm rupture, though other preventive therapeutic options such as clipping and coiling of incidental aneurysms are available to clinicians. The lack of specific drugs to limit aneurysm growth and rupture is, in part, attributed to the limited knowledge on the biology of IA growth and rupture. Though inflammatory macrophages and lymphocytes infiltrate the aneurysm wall, a link between their presence and aneurysm growth with subsequent rupture is not completely understood. Given our published results that demonstrate that the pro-inflammatory cytokine, tumor necrosis factor-alpha (TNF-alpha), is highly expressed in human ruptured aneurysms, we hypothesize that pro-inflammatory cell types are the prime source of TNF-alpha that initiate damage to endothelium, smooth muscle cells (SMC) and internal elastic lamina (IEL). To gain insights into TNF-alpha expression in the aneurysm wall, we have examined the potential regulators of TNF-alpha and report that higher TNF-alpha expression correlates with increased expression of intracellular calcium release channels that regulate intracellular calcium (Ca2+), and Toll like receptors (TLR) that mediate innate immunity. Moreover, the reduction of tissue inhibitor of metalloproteinase-1 (TIMP-1) expression provides insights on why higher matrix metalloproteinase (MMP) activity is noted in ruptured IA. Because TNF-alpha is known to amplify several signaling pathways leading to inflammation, apoptosis and tissue degradation, we will review the potential role of TNF-alpha in IA formation, growth and rupture. Neutralizing TNF-alpha action in the aneurysm wall may have a beneficial effect in preventing aneurysm growth by reducing inflammation and arterial remodeling.

Tumor necrosis factor-alpha, interleukin-1beta and nitric oxide: induction of liver megamitochondria in prehepatic portal hypertensive rats

It has been shown that portal hypertension in the rat causes microvesicular hepatocytic fatty infiltration. Formation of megamitochondria (MG) is one of the most prominent alterations in steatosis. Because nitric oxide (NO), tumor necrosis factor-alpha (TNFalpha), and interleukin-1beta (IL-1beta) impair mitochondrial function, these mediators have been studied in prehepatic portal hypertensive rats to verify their coexistence with MG and therefore with steatosis. Male Wistar rats were divided into two groups: a control group (n = 7) and a group with partial portal vein hgation (n = 19) at 6 weeks of evolution. TNFalpha and IL-1beta were quantified in liver by enzyme-linked immunosorbent assay, and NO was measured in the portal vein, suprahepatic inferior vena cava, and infrahepatic inferior vena cava by the Griess reaction. In portal hypertensive rats, the serum concentration of NO of hepatic origin increases (132.10 +/- 34.72 vs. 52.44 +/- 11.32 nmol/ml; p < 0.001), as do TNFalpha (2.02 +/- 0.20 vs. 1.12 +/- 0.43 micromol/mg protein) and IL-1beta (18.95 +/- 2.59 vs. 5.48 +/- 1.70 micromol/mg protein) (p = 0.005) in the liver. The most frequent hepatic histologic findings are the presence of MG (p < 0.001), steatosis, and hyperplasia. An increase in hepatic release of NO, TNFalpha and IL-1beta with MG formation is produced in rats with portal hypertension. Therefore these proinflammatory mediators and this morphologic mitochondrial alteration could both be involved in the etiopathogenesis of steatosis.

Proinflammatory liver and antiinflammatory intestinal mediators involved in portal hypertensive rats

Proinflammatory (TNF-alpha , IL-1beta, and NO) and antiinflammatory (IL-10, CO) levels were assayed in serum, liver, and small bowel in order to verify a hypothetic inflammatory etiopathogeny of portal hypertension that could be the cause of its evolutive heterogeneity. Male Wistar rats were divided into one control group (n=11) and one group with a triple stenosing ligation of the portal vein (n=23) after 28 days of evolution. In one subgroup of portal hypertensive rats, portal pressure, collateral venous circulation, mesenteric vasculopathy, and liver and spleen weights were determined. In the remaining rats with portal hypertension TNF-alpha, IL-1beta, and IL-10 were quantified in liver and ileum by enzyme-linked immunosorbent assay. NO synthase activity was studied in liver and ileum. CO and NO were measured in portal and systemic blood by spectrophotometry and Griess reaction, respectively. Portal hypertensive rats with mayor spleen weight show hepatomegaly and mayor development of collateral circulation. Ileum release of IL-10 (0.30 +/- 0.12 versus 0.14 +/- 0.02 pmol/mg protein; P< .01) is associated with a liver production of both proinflammatory mediators (TNF-alpha: 2 +/- 0.21 versus 1.32 +/- 0.60 pmol/mg protein; P< .05, IL-1beta: 19.17 +/- 2.87 versus 5.96 +/- 1.84 pmol/mg protein; P=.005, and NO: 132.10 +/- 34.72 versus 61.05 +/- 8.30 nmol/mL; P=.005) and an antiinflammatory mediator (CO: 6.49 +/- 2.99 versus 3.03 +/- 1.59 pmol/mL; P=.005). In short-term prehepatic portal hypertension a gut-liver inflammatory loop, which could be fundamental in the regulation both of the portal pressure and of its complications, could be proposed.

Expression of TNF-α and VEGF in the esophagus of portal hypertensive rats

AIM: To investigate the expression of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) in the development of esophageal varices in portal hypertensive rats.

METHODS: Thirty male Sprague-Dawley (SD) rats in the model group in which a two-stage ligation of portal vein plus ligation of the left adrenal vein was performed, were divided into three subgroups (M₇, M₁₄, and M₂₁) in which the rats were kiued on the seventh day, the 14^th d and the 21 d after the complete portal ligation. Thirty male SD rats, which underwent the sham operation in the control group, were also separated into three subgroups (C₇, C₁₄ and C₂₁) corresponding to the models. The expression of TNF-α and VEGF in the esophagus of all the six subgroups of rats were measured with immunohistochemical SP technique.

RESULTS: The portal pressure in the three model subgroups was significantly higher than that in the corresponding control subgroups (23.82±1.83 vs 11.61±0.86 cmH₂O, 20.90±3.27 vs 11.43±1.55 cmH₂O and 20.68±2.27 vs 11.87±0.79 cmH₂O respectively, P<0.01), as well as the number (9.3±1.6 vs 5.1±0.8, 11.1±0.8 vs 5.4±1.3 and 11.7±1.5 vs 5.2±1.1 respectively, P<0.01) and the total vascular area (78972.6±3527.8 vs 12993.5±4994.8 μm², 107207.5±46461.4 vs 11862.6±5423.2 μm² and 110241.4±49262.2 vs 11973.7±3968.5 μm² respectively, P<0.01) of submucosal veins in esophagus. Compared to the corresponding controls, the expression of TNF-α and VEGF in M₂₁ was significantly higher (2.23±0.30 vs 1.13±0.28 and 1.65±0.38 vs 0.56±0.30 for TNF-α and VEGF respectively, P <0.01), whereas there was no difference in M₇ (1.14±0.38 vs 1.06±0.27 and 0.67±0.35 vs 0.50±0.24 for TNF-α and VEGF respectively, P>0.05) and M₁₄ (1.20±0.25 vs 1.04±0.26 and 0.65±0.18 vs 0.53±0.25 for TNF-α and VEGF respectively, P>0.05). And the expression of TNF-α and VEGF in M₂₁ was significantly higher than that in M₇ (2.23±0.30 vs 1.14±0.38 and 1.65±0.38 vs 0.67±0.35 for TNF-α and VEGF respectively, P<0.01) and M₁₄ (2.23±0.30 vs 1.20±0.25 and 1.65±0.38 vs 0.65±0.18 for TNF-α and VEGF respectively, P<0.01), but there was no difference between M₇ and M₁₄ (1.14±0.38 vs 1.20±0.25 and 0.67±0.35 vs 0.65±0.18 for TNF-α and VEGF respectively, P >0.05).

CONCLUSION: In the development of esophageal varices in portal hypertensive rats, increased TNF-α and VEGF may be not an early event, and probably play a role in weakening the esophageal wall and the rupture of esophageal varices.

Endothelial COX-1 and -2 differentially affect reactivity of MVB in portal hypertensive rats

Expression of constitutive and inducible cyclooxygenase (COX-1 and COX-2, respectively) and the role of prostanoids were investigated in the aorta and mesenteric vascular bed (MVB) from the portal vein-ligated rat (PVL) as a model of portal hypertension. Functional experiments were carried out in MVB from PVL and sham-operated rats in the absence or presence of the nonselective COX inhibitor indomethacin or the selective inhibitors of COX-1 (SC-560) or COX-2 (NS-398). Western blots of COX-1 and COX-2 proteins were evaluated in aorta and MVB, and PGI(2) production by enzyme immunoassay of 6-keto-PGF(1alpha) was evaluated in the aorta. In the presence of functional endothelium, decreased contraction to norepinephrine (NE) and increased vasodilatation to ACh were observed in MVB from PVL. Exposure of MVB to indomethacin, SC-560, or NS-398 reversed the hyporeactivity to NE and the increased endothelial vasodilatation to ACh in PVL, with NS-398 being more potent than the other two inhibitors. Upregulation of COX-1 and COX-2 expressions was detected in aorta and MVB from PVL portal hypertensive rats, and increased production of 6-keto-PGF(1alpha) was observed in aorta from portal hypertensive rats. These results suggest that generation of endothelial vasodilator prostanoids, from COX-1 and COX-2 isoforms, accounts for the increased mesenteric blood flow in portal hypertension.

Adaptive vasodilatory response after octreotide treatment

Despite the suppression of glucagon release, an adaptive response aimed at maintaining vasodilatation after octreotide treatment may exist in portal hypertension. The present study was undertaken to evaluate the possible interaction between endothelium and non-endothelium-derived vasodilators after 1-wk octreotide administration in cirrhotic rats. Rats were allocated to receive either vehicle or octreotide (30 or 100 microg/kg every 12 h subcutaneously). Hemodynamic values, plasma glucagon levels, endothelium-related vasodilatory activities, and aortic endothelial nitric oxide synthase (eNOS) expression were determined after treatment. Octreotide administration decreased plasma glucagon and increased serum 6-keto-PGF(1 alpha) and NOx levels without affecting the hemodynamic values. In cirrhotic rats receiving octreotide, there was a blunt response to either L-NAME or indomethacin administration alone, but this blunt pressor response disappeared after simultaneous administration of the two drugs. Additionally, an increased aortic eNOS expression was observed in cirrhotic rats receiving 1-wk octreotide. It is concluded that 1-wk octreotide treatment did not correct the hemodynamic derangement in cirrhotic rats. The enhanced endothelium-related vasodilatory activity was noted after octreotide treatment that overcame the octreotide-induced hemodynamic effects in portal hypertension.

TNF-alpha induced bronchial vasoconstriction

The pro-inflammatory characteristics of tumor necrosis factor-alpha (TNF-alpha) have been extensively characterized in in vitro systems. Furthermore, this cytokine has been shown to play a pivotal role in airways inflammation in asthma. Since the airway vasculature also performs an essential function in inflammatory cell transit to the airways, experiments were performed to determine the effects of TNF-alpha on bronchial vascular resistance (BVR). In anesthetized, ventilated sheep, the bronchial artery (BA) was cannulated and perfused with autologous blood. BVR was defined as inflow pressure/flow and averaged 6.3 +/- 0.2 mmHg. ml(-1). min(-1) (+/-SE) for the 25 sheep studied. Recombinant human TNF-alpha (10 microg for 20 or 40 min) infused directly into the BA resulted in a significant decrease in BVR to 87% of baseline (P < 0.05). This vasodilation was followed by a reversal of tone by 120 min and a sustained increase in BVR to 126% of baseline (P < 0.05). Since others have shown TNF-alpha caused coronary vasoconstriction through endothelial release of endothelin-1 (ET-1), an ET-1 antagonist was used to block bronchial vasoconstriction. BQ-123, a selective ET(A) receptor antagonist, was delivered to the bronchial vasculature prior to TNF-alpha challenge. Attenuation of bronchial vasoconstriction was observed at 120 min (P < 0.03). Thus TNF-alpha causes bronchial vasoconstriction by the secondary release of ET-1. Although TNF-alpha exerts pro-inflammatory actions on most cells of the airways, vasoactive properties of this cytokine likely further contribute to the inflammatory status of the airways.