Cyclooxygenase-2 and inducible nitric oxide synthase in omental arteries harvested from patients with severe liver diseases: immuno-localization and influence on vascular tone

Anti-inflammatory effects of rhaponticin on LPS-induced human endothelial cells through inhibition of MAPK/NF-κβ signaling pathways

The untreated systemic chronic inflammation leads to autoimmune diseases, hyperglycemia, cardiovascular diseases, type 2 diabetes, hypertension, osteoporosis, and so on. Phytochemicals effectively inhibit the inflammation, and numerous studies have proved that the phytocomponents possess anti-inflammatory property via inhibiting the cyclooxygenase and lipoxygenase signaling pathways. Rhaponticin is one such phytochemical obtained from the perennial plant Rheum rhaponticum L. belonging to Polygonaceae family. We assessed the anti-inflammatory potency of rhaponticin in endothelial cells induced with lipopolysaccharides (LPS). Four different endothelial cells induced with LPS were treated with rhaponticin and assessed for the nitric oxide generation. The cytotoxic potency of rhaponticin was evaluated in endothelial cells using the 3-(4,5-dimethylthizaol-2yl)-2,5-diphenyl tetrazolium bromide assay. The tumor necrosis factor-α (TNF-α) synthesis was quantified using the commercially available assay kit. The inflammatory signaling protein gene expression of TNF-α, inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX2), and interleukin-1β (IL-1β) was analyzed with quantitative polymerase chain reaction (PCR) analysis. The gene expression of NADPH oxidase (NOX) cytoplasmic catalytic subunits gp91^phox , p47^phox , and p22^phox was assessed with real-time PCR analysis. Finally, to confirm the anti-inflammatory potency of rhaponticin, the nuclear factor kappa B (NFκB) and mitogen-activated protein kinase (MAPK) signaling protein expression was analyzed with immunoblotting analysis. Rhaponticin treatment significantly decreased the levels of nitric oxide and TNF-α synthesis in LPS-induced endothelial cells. It significantly decreased the gene expression of inflammatory proteins and NOX signaling protein. The protein expression of NFκB and MAPK signaling proteins was drastically decreased in rhaponticin-treated endothelial cells induced with LPS. Overall, our results confirm that rhaponticin effectively inhibited the inflammation triggered by LPS in endothelial cells via downregulating iNOS, COX2, and NFκB and MAPK signaling pathways.

Adrenergic Response of Splanchnic Arteries from Cirrhotic Patients: Role of Nitric Oxide, Prostanoids, and Reactive Oxygen Species

Peripheral and splanchnic vasodilatation in cirrhotic patients has been related to hyporesponsiveness to vasoconstrictors, but studies to examine the vascular adrenergic response provide contradictory results. Hepatic arteries from cirrhotic patients undergoing liver transplantation and mesenteric arteries from liver donors were obtained. Segments 3 mm long from these arteries were mounted in organ baths for testing isometric adrenergic response. The concentration-dependent contraction to noradrenaline (10−8 to 10−4 M) was similar in hepatic and mesenteric arteries, and prazosin (α 1-adrenergic antagonist, 10−6 M), but not yohimbine (α 2-adrenergic antagonist, 10−6 M), produced a rightward parallel displacement of this contraction in both types of arteries. Phenylephrine (α 1-adrenergic agonist, 10−8 to 10−4 M) and clonidine (α 2-adrenergic agonist, 10−8 to 10−4 M) also produced concentration-dependent contractions that were comparable in hepatic and mesenteric arteries. The inhibitor of cyclooxygenase meclofenamate (10−5 M), but not the inhibitor of nitric oxide synthesis Nw-nitro-l-arginine methyl ester (l-NAME, 10−4 M), potentiated the response to noradrenaline in hepatic arteries; neither inhibitor affected the response to noradrenaline in mesenteric arteries. Diphenyleneiodonium (DPI; 5 × 10−6 M), but neither catalase (1000 U/ml) nor tiron (10−4 M), decreased the maximal contraction for noradrenaline similarly in hepatic and mesenteric arteries. Therefore, it is suggested that, in splanchnic arteries from cirrhotic patients, the adrenergic response and the relative contribution of α 1- and α 2-adrenoceptors in this response is preserved, and prostanoids, but not nitric oxide, may blunt that response. Products dependent on NAD(P)H oxidase might contribute to the adrenergic response in splanchnic arteries from control and cirrhotic patients.

Vitamin C exerts beneficial hepatoprotection against Concanavalin A-induced immunological hepatic injury in mice through inhibition of NF-κB signal pathway

The present study was designed to investigate the potential benefits of vitamin C (VC) in treating immunological liver injury induced by Concanavalin A (Con A, 20 mg kg(-1)) in mice. Interestingly, VC administration significantly reduced serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total-bilirubin (T-bilirubin) in Con A-lesioned mice, while serum concentrations of albumin and total-protein (T-protein) were increased. Moreover, inflammatory cytokine profiles, such as interferon-gamma (IFN-γ), interleukin-4 (IL-4), interleukin-6 (IL-6) and interleukin-8 (IL-8), were decreased in liver tissue by VC administration. Morphological examination showed that Con A-induced liver damage was effectively mitigated. As shown in RT-PCR assay, VC administration resulted in down-regulated mRNA expressions of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS). In addition, VC contributed towards the reduction of intrahepatic tumor necrosis factor alpha (TNF-α) and the receptor (TNF-R) protein levels, as well as decreasing IKKβ, p-IκBα, p50 and NF-κB expressions; furthermore, VC blocked intranuclear DNA-binding NF-κB locus. Our findings show that VC effectively attenuates Con A-mediated immunotoxicity in liver tissue, through an underlying mechanism which relates to dampening of the intrahepatic NF-κB signal pathway, thereby reducing cytotoxicity within hepatocytes.

TNF-α signalling and inflammation: interactions between old acquaintances

INTRODUCTION

Inflammation is a very important part of innate immunity and is regulated in many steps. One such regulating step is the cytokine network, where tumor necrosis factor α (TNF-α) plays one of the most important roles.

METHODS

A PubMed and Web of Science databases search was performed for studies providing evidences on the role of TNF-α in inflammation, apoptosis, and cancer.

RESULTS AND CONCLUSION

This review concisely summarizes the role of this pro-inflammatory cytokine during inflammation. It is focused mainly on TNF-α intracellular signaling and its influence on the typical inflammatory features in the organism. Being one of the most important pro-inflammatory cytokines, TNF-α participates in vasodilatation and edema formation, and leukocyte adhesion to epithelium through expression of adhesion molecules; it regulates blood coagulation, contributes to oxidative stress in sites of inflammation, and indirectly induces fever. The connection between TNF-α and cancer is mentioned as well.

Endothelium-derived hyperpolarization factor (EDHF) is up-regulated in a pig model of acute liver failure

BACKGROUND

Acute liver failure (ALF) is hemodynamically characterized by hyperdynamic circulation, but the pathophysiologic mechanisms underlying these disturbances are not known. The purposes of the present experiments were: to study systemic and peripheral hemodynamics in vivo, to measure changes in vascular reactivity in vitro, and to determine the role of endothelium-dependent vasodilator pathways in a well-validated porcine model of ALF.

METHODS

Landrace pigs (24-29 kg) were allocated to sham operation (n=8) or ALF induced by hepatic devascularization (n=9). Systemic and regional hemodynamics were monitored. Femoral artery rings were prepared for isometric tension recordings 8 h after ALF induction. Contractile responses to phenylephrine were assessed in ring segments of endothelium-intact femoral arteries in the absence or presence of inhibitors of endothelium-derived hyperpolarizing factor, nitric oxide synthase, cyclooxygenase and heme oxygenase pathways.

RESULTS

Pigs with ALF developed a hyperdynamic circulation. Cardiac index increased (PGT<0.001), while mean arterial pressure (PGT=0.012) and systemic vascular resistance decreased (PGT<0.001) in this group. Femoral artery blood flow decreased in controls, while it remained unchanged in ALF (PGT=0.010). Accordingly, vascular resistance across the hind leg was significantly decreased (PGT<0.001) in ALF. The combination of Ca2+-activated potassium channel inhibitors charybdotoxin and apamin, which block the release of endothelium-derived hyperpolarizing factor, increased the contraction force (ANOVA, PGT=0.05) and Emax (P=0.01) to phenylephrine in ALF. In contrast, inhibitors of nitric oxide synthase, cyclooxygenase and heme oxygenase pathways did not increase isometric contraction force.

CONCLUSIONS

Endothelium dependent hyperpolarization of vascular smooth muscle contributes to the development of hyperdynamic circulation in ALF.

Stronger inhibition by nonsteroid anti-inflammatory drugs of cyclooxygenase-1 in endothelial cells than platelets offers an explanation for increased risk of thrombotic events

Recent data have suggested that regular consumption of nonsteroid anti-inflammatory drugs (NSAIDs), particularly selective inhibitors of cyclo-oxygenase-2 (COX-2), is associated with an increased risk of thrombotic events. It has been suggested that this is due to NSAIDs reducing the release from the endothelium of the antithrombotic mediator prostaglandin I2 as a result of inhibition of endothelial COX-2. Here, however, we show that despite normal human vessels and endothelial cells containing cyclo-oxygenase-1 (COX-1) without any detectable COX-2, COX-1 in vessels or endothelial cells is more readily inhibited by NSAIDs and COX-2-selective drugs than COX-1 in platelets (e.g., log IC50+/-SEM values for endothelial cells vs. platelets: naproxen -5.59+/-0.07 vs. -4.81+/-0.04; rofecoxib -4.93+/-0.04 vs. -3.75+/-0.03; n=7). In broken cell preparations, the selectivities of the tested drugs toward endothelial cell over platelet COX-1 were lost. These observations suggest that variations in cellular conditions, such as endogenous peroxide tone and substrate supply, and not the isoform of cyclo-oxygenase present, dictate the effects of NSAIDs on endothelial cells vs. platelets. This may well be because the platelet is not a good representative of COX-1 activity within the body as it produces prostanoids in an explosive burst that does not reflect tonic release from other cells. The results reported here can offer an explanation for the apparent ability of NSAIDs and COX-2-selective inhibitors to increase the risk of myocardial infarction and stroke.

Mechanisms of the inflammatory response

The physiological alterations induced by acute inflammation present significant management challenges for anaesthesiologists. Major surgery, trauma, burns and sepsis all have large inflammatory components. Acute inflammation is characterized by vasodilatation, fluid exudation and neutrophil infiltration. These processes are activated and amplified by a series of intracellular and extracellular factors that tightly co-ordinate the inflammatory process. The innate immune system responds rapidly to infection or injury. Macrophages, natural killer cells, CD8 + T-lymphocytes and neutrophils provide an early response to injurious factors in an effort to contain and eliminate harmful stimuli. The adaptive immune response requires prior exposure to microbial antigens, is mediated primarily by CD4 + T-lymphocytes and serves to further amplify acute inflammation. Although acute inflammation is fundamentally beneficial, severe inflammation can precipitate the systemic inflammatory response syndrome. This syndrome is characterized by hyperinflammation and can cause organ injury, shock and death in its most severe forms. Overall, our understanding of inflammation has increased tremendously during the past 20 years. However, these basic science advances have not yet translated into widespread benefit for patients suffering from trauma, sepsis and systemic inflammation.

N/A

N/A