TNF-alpha induces thromboxane receptor signaling-dependent microcirculatory dysfunction in mouse liver

A biologically active lipid, thromboxane, as a regulator of angiogenesis and lymphangiogenesis

Thromboxane (TX) and prostaglandins are metabolites of arachidonic acid, a twenty-carbon unsaturated fatty acid, and have a variety of actions that are exerted via specific receptors. Angiogenesis is defined as the formation of new blood vessels from pre-existing vascular beds and is a critical component of pathological conditions, including inflammation and cancer. Lymphatic vessels play crucial roles in the regulation of interstitial fluid, immune surveillance, and the absorption of dietary fat from the intestine; and they are also involved in the pathogenesis of various diseases. Similar to angiogenesis, lymphangiogenesis, the formation of new lymphatic vessels, is a critical component of pathological conditions. The TP-dependent accumulation of platelets in microvessels has been reported to enhance angiogenesis under pathological conditions. Although the roles of some growth factors and cytokines in angiogenesis and lymphangiogenesis have been well characterized, accumulating evidence suggests that TX induces the production of proangiogenic and prolymphangiogenic factors through the activation of adenylate cyclase, and upregulates angiogenesis and lymphangiogenesis under disease conditions. In this review, we discuss the role of TX as a regulator of angiogenesis and lymphangiogenesis, and its emerging importance as a therapeutic target.

The effect of TNF-α inhibitor treatment on microRNAs and endothelial function in collagen induced arthritis

Chronic inflammation causes dysregulated expression of microRNAs. Aberrant microRNA expression is associated with endothelial dysfunction. In this study we determined whether TNF-α inhibition impacted the expression of miRNA-146a-5p and miRNA-155-5p, and whether changes in the expression of these miRNAs were related to inflammation-induced changes in endothelial function in collagen-induced arthritis (CIA). Sixty-four Sprague-Dawley rats were divided into control (n = 24), CIA (n = 24) and CIA+etanercept (n = 16) groups. CIA and CIA+etanercept groups were immunized with bovine type-II collagen, emulsified in incomplete Freund’s adjuvant. Upon signs of arthritis, the CIA+etanercept group received 10mg/kg of etanercept intraperitoneally, every three days. After six weeks of treatment, mesenteric artery vascular reactivity was assessed using wire-myography. Serum concentrations of TNF-α, C-reactive protein, interleukin-6, vascular adhesion molecule-1 (VCAM-1) and pentraxin-3 (PTX-3) were measured by ELISA. Relative expression of circulating miRNA-146a-5p and miRNA-155-5p were determined using RT-qPCR. Compared to controls, circulating miRNA-155-5p, VCAM-1 and PTX-3 concentrations were increased, and vessel relaxation was impaired in the CIA (all p<0.05), but not in the CIA+etanercept (all p<0.05) groups. The CIA group had greater miRNA-146a-5p expression compared to the CIA+etanercept group (p = 0.005). Independent of blood pressure, miRNA-146a-5p expression was associated with increased PTX-3 concentrations (p = 0.03), while miRNA-155-5p expression was associated with impaired vessel relaxation (p = 0.01). In conclusion, blocking circulating TNF-α impacted systemic inflammation-induced increased expression of miRNA-146a-5p and miRNA-155-5p, which were associated with endothelial inflammation and impaired endothelial dependent vasorelaxation, respectively.

Ibuprofen alters epoxide hydrolase activity and epoxy-oxylipin metabolites associated with different metabolic pathways in murine livers

Over the last decade oxylipins have become more recognized for their involvement in several diseases. Non-steroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen are known to inhibit cyclooxygenase (COX) enzymes, but how NSAIDs affect oxylipins, in addition to COX products, in animal tissues is not well understood. Oxylipins in livers from male and female mice treated with 100 mg/kg/day of ibuprofen for 7 days were investigated. The results showed that ibuprofen treated male livers contained 7 times more altered oxylipins than ibuprofen treated female livers. In male and female livers some prostaglandins were altered, while diols, hydroxy fatty acids and epoxides were significantly altered in male livers. Some soluble epoxide hydrolase (sEH) products, such as 9,10-DiHODE were found to be decreased, while sEH substrates (such as 9(10)-EpODE and 5(6)-EpETrE) were found to be increased in male livers treated with ibuprofen, but not in ibuprofen treated female livers. The enzymatic activities of sEH and microsomal epoxide hydrolase (mEH) were elevated by ibuprofen in both males and females. Analyzing the influence of sex on the effect of ibuprofen on oxylipins and COX products showed that approximately 27% of oxylipins detected were influenced by sex. The results reveal that ibuprofen disturbs not only the COX pathway, but also the CYP450 and lipoxygenase pathways in male mice, suggesting that ibuprofen is likely to generate sex related differences in biologically active oxylipins. Increased sEH activity after ibuprofen treatment is likely to be one of the mechanisms by which the liver reduces the higher levels of EpODEs and EpETrEs.

Ischaemia reperfusion injury in liver transplantation: Cellular and molecular mechanisms

Liver disease causing end organ failure is a growing cause of mortality. In most cases, the only therapy is liver transplantation. However, liver transplantation is a complex undertaking and its success is dependent on a number of factors. In particular, liver transplantation is subject to the risks of ischaemia-reperfusion injury (IRI). Liver IRI has significant effects on the function of a liver after transplantation. The cellular and molecular mechanisms governing IRI in liver transplantation are numerous. They involve multiple cells types such as liver sinusoidal endothelial cells, hepatocytes, Kupffer cells, neutrophils and platelets acting via an interconnected network of molecular pathways such as activation of toll-like receptor signalling, alterations in micro-RNA expression, production of ROS, regulation of autophagy and activation of hypoxia-inducible factors. Interestingly, the cellular and molecular events in liver IRI can be correlated with clinical risk factors for IRI in liver transplantation such as donor organ steatosis, ischaemic times, donor age, and donor and recipient coagulopathy. Thus, understanding the relationship of the clinical risk factors for liver IRI to the cellular and molecular mechanisms that govern it is critical to higher levels of success after liver transplantation. This in turn will help in the discovery of therapeutics for IRI in liver transplantation - a process that will lead to improved outcomes for patients suffering from end-stage liver disease.

Protection from vascular dysfunction in female rats with chronic stress and depressive symptoms

The increasing prevalence and severity of clinical depression are strongly correlated with vascular disease risk, creating a comorbid condition with poor outcomes but demonstrating a sexual disparity whereby female subjects are at lower risk than male subjects for subsequent cardiovascular events. To determine the potential mechanisms responsible for this protection against stress/depression-induced vasculopathy in female subjects, we exposed male, intact female, and ovariectomized (OVX) female lean Zucker rats to the unpredictable chronic mild stress (UCMS) model for 8 wk and determined depressive symptom severity, vascular reactivity in ex vivo aortic rings and middle cerebral arteries (MCA), and the profile of major metabolites regulating vascular tone. While all groups exhibited severe depressive behaviors from UCMS, severity was significantly greater in female rats than male or OVX female rats. In all groups, endothelium-dependent dilation was depressed in aortic rings and MCAs, although myogenic activation and vascular (MCA) stiffness were not impacted. Higher-resolution results from pharmacological and biochemical assays suggested that vasoactive metabolite profiles were better maintained in female rats with normal gonadal sex steroids than male or OVX female rats, despite increased depressive symptom severity (i.e., higher nitric oxide and prostacyclin and lower H₂O₂ and thromboxane A₂ levels). These results suggest that female rats exhibit more severe depressive behaviors with UCMS but are partially protected from the vasculopathy that afflicts male rats and female rats lacking normal sex hormone profiles. Determining how female sex hormones afford partial vascular protection from chronic stress and depression is a necessary step for addressing the burden of these conditions on cardiovascular health. NEW & NOTEWORTHY This study used a translationally relevant model for chronic stress and elevated depressive symptoms to determine how these factors impact conduit and resistance arteriolar function in otherwise healthy rats. While chronic stress leads to an impaired vascular reactivity associated with elevated oxidant stress, inflammation, and reduced metabolite levels, we demonstrated partial protection from vascular dysfunction in female rats with normal sex hormone profiles compared with male or ovariectomized female rats.

Hepatic stellate cells relay inflammation signaling from sinusoids to parenchyma in mouse models of immune-mediated hepatitis

Hepatic stellate cells (HSCs) constitute the liver sinusoid with Kupffer cells and liver sinusoidal endothelial cells. While the sinusoid functions as the gateway to liver inflammation, whether HSCs contribute to liver inflammation and, if so, how they exert such functions remain elusive. Here, we found that mouse as well as human HSCs expressed DP1 receptor for prostaglandin D2 selectively in the liver. Pharmacological stimulation of DP1 by BW245C, a DP1-selective agonist, suppressed the activation of cultured HSCs by tumor necrosis factor-α at least in part through down-regulation of nuclear factor kappa-light-chain-enhancer of activated B cells signaling and inhibition of c-Jun N-terminal kinase phosphorylation. DP1 deficiency or BW245C administration in mice significantly enhanced or suppressed concanavalin A (ConA)-induced hepatitis, respectively. ConA injection induced tumor necrosis factor-α and interferon-γ expression in the sinusoid, which was suppressed by administration of BW245C. Coculture of spleen cells and liver nonparenchymal cells showed that ConA first activated spleen cells and that this activation led to activation of nonparenchymal cells to secondarily produce tumor necrosis factor-α and interferon-γ. Microarray analysis revealed ConA-induced expression of endothelin-1, tissue factor, and chemokines in the liver and inducible nitric oxide synthase in hepatocytes, resulting in flow stagnation, leukocyte adherence and migration to the parenchyma, and hepatocyte death. DP1 stimulation inhibits all these events in the liver. Therefore, HSCs mediate amplification of ConA-induced liver inflammation in the sinusoid, causing direct and indirect hepatocyte injury, and DP1 stimulation inhibits this HSC activation.

CONCLUSIONS

HSCs integrate cytokine-mediated inflammatory responses in the sinusoids and relay them to the liver parenchyma, and these HSC actions are inhibited by DP1 stimulation.

Adhesion of platelets through thromboxane A₂ receptor signaling facilitates liver repair during acute chemical-induced hepatotoxicity

AIMS

Platelets have been suggested to play an important role in liver regeneration and repair after hepatic resection and acute liver injury. However, the underlying mechanisms of liver repair remain elusive. Signaling through thromboxane prostanoid (TP) receptor participates in inflammation and tissue injury through platelet aggregation. On the other hand, TP receptor signaling also is involved in tissue repair and tumor growth through angiogenesis. The present study was examined whether or not TP receptor signaling contributes to liver repair and sinusoidal restoration from acute liver injury through platelet adhesion to the hepatic sinusoids.

MAIN METHODS

Carbon tetrachrolide (CCl4) was used to induce acute liver injury in TP receptor knockout mice (TP(-/-) mice) and their wild-type littermates (WT mice).

KEY FINDINGS

Compared with WT mice, TP(-/-) mice exhibited delayed in liver repair and sinusoidal restoration after CCl4 treatment, which were associated with attenuated hepatic expression of pro-angiogenic factors. Intravital microscopic observation revealed that adhering platelets to the sinusoids was increased in WT livers during the repair phase as compared with TP(-/-) livers, and platelet adhesion was dependent on TP receptor signaling. The levels of hepatocyte growth factor (HGF) in platelets from WT mice treated with CCl4 for 48h were greater than those form TP(-/-) mice, and HGF enhanced the expression of angiogenic factors in cultured human umbilical vein endothelial cells (HUVECs).

SIGNIFICANCE

These results suggested that TP receptor signaling facilitates liver repair and sinusoidal restoration from acute liver injury through HGF release from platelets adhering to the sinusoids.

Regulation of tissue factor gene expression in monocytes and endothelial cells: Thromboxane A2 as a new player

Tissue factor (TF) is the primary activator of the coagulation cascade. Under normal conditions, endothelial cells (ECs) and blood cells, such as monocytes, do not express TF. However, bacterial lipopolysaccharide (LPS) induces TF expression in monocytes and this leads to disseminated intravascular coagulation during endotoxemia and sepsis. A variety of stimuli induce TF expression in ECs in vitro, although it is unclear how much TF is expressed by the endothelium in vivo. LPS induction of TF gene expression in monocytic cells and ECs is mediated by various intracellular signaling pathways and the transcription factors NF-ĸB, AP-1 and Egr-1. In contrast, vascular endothelial cell growth factor (VEGF) induces TF gene expression in ECs via the transcription factors NFAT and Egr-1. Similarly, oxidized phospholipids (such as 1-palmitoyl-2-arachidonyl-sn-glycero-3-phosphorylcholine) induce TF expression in ECs and possibly monocytes via NFAT and Egr-1. Thromboxane A2 (TXA2) can now be added to the list of stimuli that induce TF gene expression in both monocytes and ECs. Interestingly, inhibition of the TX-prostanoid (TP) receptor also reduces TF expression in with tumor necrosis factor (TNF)-α stimulated ECs and LPS stimulated monocytes, which suggests that TP receptor antagonist may be useful in reducing pathologic TF expression in the vasculature and blood.

Involvement of the TP receptor in TNF-α-induced endothelial tissue factor expression

BACKGROUND

Thromboxane (TX) A2, prostaglandin endoperoxides and F2-isoprostanes exert their effects through a TX-prostanoid (TP) receptor, also expressed in endothelial cells. We investigated a role of the TP receptor in the endothelial expression of tissue factor (TF), a key trigger to thrombosis.

METHODS AND RESULTS

Human umbilical vein endothelial cells (HUVEC) exposed to the TP receptor agonist U46619 featured a concentration-dependent increase in TF surface exposure and procoagulant activity. HUVEC pre-incubation with the TP receptor antagonist S18886, followed by stimulation with either U46619 or tumor necrosis factor-α (TNF-α), attenuated TF surface exposure and activity compared with stimulated control. Aspirin or indomethacin, while inhibiting cyclooxygenase (COX)-1 and -2 activities, did not mimic this effect. Probing of underlying mechanisms by selective pharmacological and gene silencing experiments showed that S18886 reduced U46619- or TNF-α-induced TF expression inhibiting ROS production, NAD(P)H oxidase and PKC activation. In addition, S18886 also inhibited ERK activation in the presence of both U46619 and TNF-α alone, while inhibition of JNK activation only occurred in the presence of U46619.

CONCLUSION

The endothelial TP receptor contributes to TF surface exposure and activity induced not only by known TP receptor agonists, but also by TNF-α. Such findings expand the therapeutic potential of TP receptor inhibition.

Evaluation of hepatic tissue blood flow using xenon computed tomography with fibrosis progression in nonalcoholic fatty liver disease: comparison with chronic hepatitis C

AIMS

The present study evaluated the utility of xenon computed tomography (Xe-CT) as a noninvasive diagnostic procedure for the measurement of hepatic tissue blood flow (TBF) in patients with nonalcoholic fatty liver disease (NAFLD) or chronic hepatitis C (CH-C).

METHODS

Xe-CT was performed in 93 patients with NAFLD and in 109 patients with CH-C. Subjects were classified into one of three groups, based on fibrosis stage: group 1, no bridging fibrosis; group 2, bridging fibrosis; and group 3, liver cirrhosis. Correlations between hepatic TBFs in each fibrosis stage were examined.

RESULTS

In group 1, portal venous TBF (PVTBF), hepatic arterial (HATBF), and total hepatic TBF (THTBF) were significantly lower in patients with in nonalcoholic steatohepatitis (NASH) than in those with CH-C (p < 0.001, p < 0.05, p < 0.001, respectively). In group 2, PVTBF and THTBF were significantly lower in patients with in NASH than in those with CH-C (p < 0.001, p < 0.05, respectively). In group 3, hepatic TBFs were not significantly different when comparing patients with NASH and those with CH-C.

CONCLUSIONS

PVTBF decreased due to fat infiltration. Therefore, hemodynamic changes occur relatively earlier in NAFLD than in CH-C. Patients with NASH should be monitored carefully for portal hypertensive complications in the early fibrosis stage.

Prooxidant mechanisms in iron overload cardiomyopathy

Iron overload cardiomyopathy (IOC), defined as the presence of systolic or diastolic cardiac dysfunction secondary to increased deposition of iron, is emerging as an important cause of heart failure due to the increased incidence of this disorder seen in thalassemic patients and in patients of primary hemochromatosis. At present, although palliative treatment by regular iron chelation was recommended; whereas IOC is still the major cause for mortality in patient with chronic heart failure induced by iron-overloading. Because iron is a prooxidant and the associated mechanism seen in iron-overload heart is still unclear; therefore, we intend to delineate the multiple signaling pathways involved in IOC. These pathways may include organelles such as calcium channels, mitochondria; paracrine effects from both macrophages and fibroblast, and novel mediators such as thromboxane A2 and adiponectin; with increased oxidative stress and inflammation found commonly in these signaling pathways. With further understanding on these complex and inter-related molecular mechanisms, we can propose potential therapeutic strategies to ameliorate the cardiac toxicity induced by iron-overloading.

Dual modulation of cyclooxygenase and CYP epoxygenase metabolism and acute vascular inflammation in mice

Cyclooxygenase (COX)-derived prostaglandins and cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids are important regulators of inflammation; however, functional interactions between these pathways in the regulation of vascular inflammation in vivo have not been studied. We investigated the relative and additive effects of endothelial CYP2J2 overexpression (Tie2-CYP2J2-Tr), global sEH disruption (Ephx2(-/-)), and pharmacologic COX inhibition with indomethacin on the acute vascular inflammatory response to endotoxin in mice. Compared to vehicle-treated wild-type C57BL/6 controls, induction of myeloperoxidase (MPO) activity in lung and liver was similarly attenuated in Tie2-CYP2J2-Tr mice, Ephx2(-/-) mice and wild-type mice treated with moderate dose indomethacin. Dual modulation of both pathways, however, did not produce an additive anti-inflammatory effect. These findings demonstrate that both COX and CYP epoxygenase-mediated eicosanoid metabolism are important regulators of the acute vascular inflammatory response in vivo, and suggest that the anti-inflammatory effects of modulating each pathway may be mediated, at least in part, by overlapping mechanisms.

Cytokines are systemic effectors of lymphatic function in acute inflammation

The response of the lymphatic system to inflammatory insult and infection is not completely understood. Using a near-infrared fluorescence (NIRF) imaging system to noninvasively document propulsive function, we noted the short-term cessation of murine lymphatic propulsion as early as 4h following LPS injection. Notably, the effects were systemic, displaying bilateral lymphatic pumping cessation after a unilateral insult. Furthermore, IL-1β, TNF-α, and IL-6, cytokines that were found to be elevated in serum during lymphatic pumping cessation, were shown separately to acutely and systemically decrease lymphatic pulsing frequency and velocity following intradermal administration. Surprisingly, marked lymphatic vessel dilation and leakiness were noted in limbs contralateral to IL-1β intradermal administration, but not in ipsilateral limbs. The effects of IL-1β on lymphatic pumping were abated by pre-treatment with an inhibitor of inducible nitric oxide synthase, L-NIL (N-iminoethyl-L-lysine). The results suggest that lymphatic propulsion is systemically impaired within 4h of acute inflammatory insult, and that some cytokines are major effectors of lymphatic pumping cessation through nitric oxide-mediated mechanisms. These findings may help in understanding the actions of cytokines as mediators of lymphatic function in inflammatory and infectious states.

Pathophysiological analysis of nonalcoholic fatty liver disease by evaluation of fatty liver changes and blood flow using xenon computed tomography: can early-stage nonalcoholic steatohepatitis be distinguished from simple steatosis?

INTRODUCTION

Effective noninvasive tests that can distinguish early-stage nonalcoholic steatohepatitis (NASH) from simple steatosis (SS) have long been sought. Our aim was to determine the possibility of noninvasively distinguishing early-stage NASH from SS.

MATERIALS AND METHODS

We used Fick's principle and the Kety-Schmidt equation to determine the hepatic tissue blood flow (TBF) in 65 NASH patients who underwent xenon computed tomography (Xe-CT). We calculated the lambda value (LV), i.e., Xe gas solubility coefficient, in liver and blood. We assessed the histological severity of fatty changes and fibrosis on the basis of Brunt's classification. Liver biopsy revealed SS in 9 patients and NASH in 56 patients. NASH stages 1 and 2 were classified as early-stage NASH (Ea-NASH; 38 patients) and stages 3 and 4 as advanced-stage NASH (Ad-NASH; 18 patients). We evaluated the differences in LV and TBF among the 3 groups.

RESULTS

LV was significantly lower in the Ad-NASH group than in the SS and Ea-NASH groups. Portal venous TBF (PVTBF) was significantly lower in the Ea-NASH group than in the SS group, and PVTBF was lower in the Ad-NASH group than in the Ea-NASH group. Total hepatic TBF (THTBF) was significantly different between the SS and Ea-NASH groups and between the SS and Ad-NASH groups.

CONCLUSIONS

In conclusion, measurements of TBF and LV are useful for evaluating the pathophysiological progression of NASH. In addition, these measurements can facilitate the differential diagnosis of SS and Ea-NASH, which may not be distinguishable by other means.

Effect of ketamine hydrochloride on the analgesic effects of tramadol hydrochloride in horses with signs of chronic laminitis-associated pain

OBJECTIVE

To investigate the effects of ketamine hydrochloride on the analgesic effects of tramadol hydrochloride in horses with signs of pain associated with naturally occurring chronic laminitis.

ANIMALS

15 client-owned adult horses with chronic laminitis.

PROCEDURES

Each horse received tramadol alone or tramadol and ketamine in a randomized, crossover study (≥ 2 months between treatments). Tramadol (5 mg/kg) was administered orally every 12 hours for 1 week. When appropriate, ketamine (0.6 mg/kg/h) was administered IV for 6 hours on each of the first 3 days of tramadol administration. Noninvasive systemic blood pressure values, heart and respiratory rates, intestinal sounds, forelimb load and off-loading frequency (determined via force plate system), and plasma tumor necrosis factor-α and thromboxane B(2) concentrations were assessed before (baseline) during (7 days) and after (3 days) each treatment.

RESULTS

Compared with baseline data, arterial blood pressure decreased significantly both during and after tramadol-ketamine treatment but not with tramadol alone. Forelimb off-loading frequency significantly decreased during the first 3 days of treatment with tramadol only, returning to baseline frequency thereafter. The addition of ketamine to tramadol treatment reduced off-loading frequency both during and after treatment. Forelimb load did not change with tramadol alone but increased with tramadol-ketamine treatment. Plasma concentrations of tumor necrosis factor-α and thromboxane B(2) were significantly reduced with tramadol-ketamine treatment but not with tramadol alone.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses with chronic laminitis, tramadol administration induced limited analgesia, but this effect was significantly enhanced by administration of subanesthetic doses of ketamine.

Hepatic arterial infusion with tumor necrosis factor-α induces early hepatic hyperperfusion

BACKGROUND

Hepatic arterial infusion (HAI) has been developed for high-dose regional chemotherapy of unresectable liver metastases or primary liver malignancies. While it is well known that high concentrations of tumor necrosis factor (TNF)-α damage tumor blood perfusion, there is no information on whether autochthonous liver perfusion is affected by HAI with TNF-α. Therefore, we investigated the effects of HAI with TNF-α on hepatic macro- and microvascular perfusion.

METHODS

Swabian Hall pigs were randomized into three groups. HAI was performed with either 20 or 40 µg/kg body weight TNF-α (n = 6 each group). Saline-treated animals served as controls (n = 6). Analyses during a 2-hour post-HAI observation period included systemic hemodynamics, portal venous and hepatic arterial blood flow, portal venous pressure, and the blood flow in the hepatic microcirculation.

RESULTS

HAI with TNF-α caused a slight decrease of mean arterial blood pressure (p < 0.001), which was compensated by a moderate increase of heart rate (p < 0.001). No further systemic side effects of TNF-α were observed. HAI with TNF-α further caused a slight but not significant decrease of portal venous blood flow (p = 0.737) in both experimental groups, paralleled by an increase of hepatic arterial blood flow (p = 0.023, 20 µg/kg; p = 0.034, 40 µg/kg) resulting in an overall hepatic hyperperfusion. The hepatic hyperperfusion after HAI with 20 µg/kg TNF-α was more pronounced and associated with a 40% decrease of the blood flow in the hepatic microcirculation (p = 0.009). HAI with 40 µg/kg TNF-α was only associated with a temporary and moderate total hepatic hyperperfusion and did not affect the blood flow in the hepatic microcirculation.

CONCLUSION

HAI with TNF-α causes a decrease of portal venous flow; however, this is overcompensated by an increased hepatic arterial blood flow, resulting in a total hepatic hyperperfusion. Moderate total hepatic hyperperfusion does not affect the blood flow in the hepatic microcirculation, while a persistent and more pronounced hyperperfusion may cause hepatic microcirculatory disturbances.

International Union of Basic and Clinical Pharmacology. LXXXIII: classification of prostanoid receptors, updating 15 years of progress

It is now more than 15 years since the molecular structures of the major prostanoid receptors were elucidated. Since then, substantial progress has been achieved with respect to distribution and function, signal transduction mechanisms, and the design of agonists and antagonists (http://www.iuphar-db.org/DATABASE/FamilyIntroductionForward?familyId=58). This review systematically details these advances. More recent developments in prostanoid receptor research are included. The DP(2) receptor, also termed CRTH2, has little structural resemblance to DP(1) and other receptors described in the original prostanoid receptor classification. DP(2) receptors are more closely related to chemoattractant receptors. Prostanoid receptors have also been found to heterodimerize with other prostanoid receptor subtypes and nonprostanoids. This may extend signal transduction pathways and create new ligand recognition sites: prostacyclin/thromboxane A(2) heterodimeric receptors for 8-epi-prostaglandin E(2), wild-type/alternative (alt4) heterodimers for the prostaglandin FP receptor for bimatoprost and the prostamides. It is anticipated that the 15 years of research progress described herein will lead to novel therapeutic entities.

Hyperoxic ventilation improves survival in pigs during endotoxaemia at the critical hemoglobin concentration

AIM OF THE STUDY

Recently it has been demonstrated that short term hyperoxic ventilation (HV) can improve glucose metabolism, reduce pulmonary and hepatic apoptosis, and improve gastrointestinal perfusion during acute sepsis. However, it is unknown whether additional O(2) improves survival. Therefore we investigated the effects of increased plasma O(2) on survival during extreme anaemia and concomitant endotoxaemia in order to quantify the efficacy of HV.

METHODS

Endotoxaemia (Salmonella abortus equi-LPS) was induced in 14 anesthetized pigs ventilated with room air (FiO(2)=0.21). Simultaneously, animals were haemodiluted by exchange of whole blood for 6% hydroxyethyl starch (200,000:0.5) until the individual critical hemoglobin concentration (Hb(crit)) was achieved (outermost limit of tissue oxygenation). Subsequently, animals were either ventilated with an FiO(2) of 0.21 (NOX, n=7) or an FiO(2) of 1.0 (HOX, n=7), and observed thereafter for 6 h without further intervention.

RESULTS

HV significantly prolonged survival time at Hb(crit) (NOX, 30 [27/35] min; HOX, 172 [111/235] min, p<0.05). In contrast to the NOX group, HV maintained MAP, and improved DO(2) and tissue oxygenation in the HOX group.

CONCLUSION

The improvement of survival, oxygen transport and tissue oxygenation seems to underline the efficacy of HV during endotoxaemia and concomitant acute anaemia. Further studies are needed to transfer these results into daily clinical practice.

Lipid-enriched enteral nutrition controls the inflammatory response in murine Gram-negative sepsis

OBJECTIVES

Controlling the inflammatory cascade during sepsis remains a major clinical challenge. Recently, it has become evident that the autonomic nervous system reduces inflammation through the vagus nerve. The current study investigates whether nutritional stimulation of the autonomic nervous system effectively attenuates the inflammatory response in murine Gram-negative sepsis.

DESIGN

Controlled in vivo and ex vivo experimental study.

SETTINGS

Research laboratory of a university hospital.

SUBJECTS

Male C57bl6 mice.

INTERVENTIONS

Mice were intraperitoneally challenged with lipopolysaccharide derived from Escherichia coli. Before lipopolysaccharide administration, mice were fasted or enterally fed either lipid-rich nutrition or low-lipid nutrition. Antagonists to cholecystokinin receptors or nicotinic receptors were administered before lipopolysaccharide administration. Blood and tissue samples were collected at 90 mins. Mesenteric afferent discharge was determined in ex vivo preparations in response to both nutritional compositions.

MEASUREMENTS AND MAIN RESULTS

Both lipid-rich and low-lipid nutrition dose-dependently reduced lipopolysaccharide-induced tumor necrosis factor-α release (high dose: both 1.4 ± 0.4 ng/mL) compared with fasted mice (3.7 ± 0.8 ng/mL; p < .01). The anti-inflammatory effect of both nutritional compositions was mediated through cholecystokinin receptors (p < .01), activation of mesenteric vagal afferents (p < .05), and peripheral nicotinic receptors (p < .05). Lipid-rich nutrition attenuated the inflammatory response at lower dosages than low-lipid nutrition, indicating that enrichment of enteral nutrition with lipid augments the anti-inflammatory potential. Administration of lipid-rich nutrition prevented endotoxin-induced small intestinal epithelium damage and reduced inflammation in the liver and spleen compared with fasted (all p < .01) and low-lipid nutrition controls (all p < .05).

CONCLUSIONS

The current study demonstrates that lipid-rich nutrition attenuates intestinal damage and systemic as well as organ-specific inflammation in murine Gram-negative sepsis through the nutritional vagal anti-inflammatory pathway. These findings implicate enteral administration of lipid-enriched nutrition as a promising intervention to modulate the inflammatory response during septic conditions.

Intraperitoneal LPS amplifies portal hypertension in rat liver fibrosis

Recent studies have shown that the risk of variceal bleeding in patients with liver cirrhosis increases with infections such as spontaneous bacterial peritonitis (SBP). In this study, we hypothesized that pretreatment with intraperitoneal LPS may escalate portal hypertension. In fibrotic livers (4 weeks after bile duct ligation, BDL), the activation of Kupffer cells (KCs) by zymosan (150 microg/ml) in the isolated non-recirculating liver perfusion system resulted in a transient increase in portal perfusion pressure. Pretreatment with intraperitoneal LPS (1 mg/kg body weight (b.w.) for 3 h) increased basal portal perfusion pressure, and prolonged the zymosan-induced increase from transient to a long-lasting increase that was sustained until the end of the experiments in BDL but not in sham-operated animals. Pretreatment with gadolinium chloride (10 mg/kg b.w.), MK-886 (0.6 mg/kg b.w.), Ly171883 (20 microM) or BM 13.177 (20 microM) reduced the maximal and long-lasting pressure increase in BDL animals by approximately 50-60%. The change in portal perfusion pressure was paralleled by a long-lasting production of cysteinyl leukotriene (Cys-LT) and thromboxane (TX) after LPS pretreatment. However, the response to vasoconstrictors was not altered by intraperitoneal LPS. Western blot analyses showed an increased Toll-like receptor (TLR)4 and MyD88 expression after LPS pretreatment. In vivo experiments confirmed that intraperitoneal LPS increased basal portal pressure, and extended the portal pressure increase produced by intraportal zymosan or by LPS infusion. In conclusion, upregulation of TLR4 and MyD88 expression in fibrotic livers confers hypersensitivity to LPS. This may lead to escalation of portal hypertension by production of TX and Cys-LT after endotoxin-induced KC activation. Therefore, LT inhibitors may represent a promising treatment option in addition to early administration of antibiotics in SBP.

Bone marrow-derived EP3-expressing stromal cells enhance tumor-associated angiogenesis and tumor growth

Recent results suggest that bone marrow (BM)-derived hematopoietic cells are major components of tumor stroma and play crucial roles in tumor growth and angiogenesis. An E-type prostaglandin is known to regulate angiogenesis. We examined the role of BM-derived cells expressing an E-type prostaglandin receptor subtype (EP3) in tumor-induced angiogenesis and tumor growth. The replacement of wild-type (WT) BM with BM cells (BMCs) from green fluorescent protein (GFP) transgenic mice revealed that the stroma developed via the recruitment of BMCs. Selective knockdown of EP3 by recruitment of genetically modified BMCs lacking EP3 receptors was performed by transplantation of BMCs from EP3 knockout (EP3(-/-)) mice. Tumor growth and tumor-associated angiogenesis were suppressed in WT mice transplanted with BMCs from EP3(-/-) mice, but not in mice transplanted with BMCs from either EP1(-/-), EP2(-/-), or EP4(-/-) mice. Immunohistochemical analysis revealed that vascular endothelial growth factor (VEGF) expression was suppressed in the stroma of mice transplanted with BMCs from EP3(-/-) mice. EP3 signaling played a significant role in the recruitment of VEGFR-1- and VEGFR-2-positive cells from the BM to the stroma. These results indicate that the EP3 signaling expressed in bone marrow-derived cells has a crucial role in tumor-associated angiogenesis and tumor growth with upregulation of the expression of the host stromal VEGF together with the recruitment of VEGFR-1/VEGFR-2-positive. The present study suggests that the blockade of EP3 signaling and the recruitment of EP3-expressing stromal cells may become a novel strategy to treat solid tumors.