Prostaglandin I(2) and E(2) mediate the protective effects of cyclooxygenase-2 in a mouse model of immune-mediated liver injury

Gamma-Linolenic Acid (GLA) Protects against Ionizing Radiation-Induced Damage: An In Vitro and In Vivo Study

Radiation is pro-inflammatory in nature in view of its ability to induce the generation of reactive oxygen species (ROS), cytokines, chemokines, and growth factors with associated inflammatory cells. Cells are efficient in repairing radiation-induced DNA damage; however, exactly how this happens is not clear. In the present study, GLA reduced DNA damage (as evidenced by micronuclei formation) and enhanced metabolic viability, which led to an increase in the number of surviving RAW 264.7 cells in vitro by reducing ROS generation, and restoring the activities of desaturases, COX-1, COX-2, and 5-LOX enzymes, TNF-α/TGF-β, NF-kB/IkB, and Bcl-2/Bax ratios, and iNOS, AIM-2, and caspases 1 and 3, to near normal. These in vitro beneficial actions were confirmed by in vivo studies, which revealed that the survival of female C57BL/6J mice exposed to lethal radiation (survival~20%) is significantly enhanced (to ~80%) by GLA treatment by restoring altered levels of duodenal HMGB1, IL-6, TNF-α, and IL-10 concentrations, as well as the expression of NF-kB, IkB, Bcl-2, Bax, delta-6-desaturase, COX-2, and 5-LOX genes, and pro- and anti-oxidant enzymes (SOD, catalase, glutathione), to near normal. These in vitro and in vivo studies suggest that GLA protects cells/tissues from lethal doses of radiation by producing appropriate changes in inflammation and its resolution in a timely fashion.

A novel prostaglandin I2 agonist, ONO-1301, attenuates liver inflammation and suppresses fibrosis in non-alcoholic steatohepatitis model mice

BACKGROUND

ONO-1301 is a novel long-lasting prostaglandin (PG) I₂ mimetic with inhibitory activity on thromboxane (TX) A₂ synthase. This drug can also induce endogenous prostaglandin (PG)I2 and PGE2 levels. Furthermore, ONO-1301 acts as a cytokine inducer and can initiate tissue repair in a variety of diseases, such as pulmonary hypertension, pulmonary fibrosis, cardiac infarction, and obstructive nephropathy. In this study, our aim was to evaluate the effect of ONO-1301 on liver inflammation and fibrosis in a mouse model of non-alcoholic steatohepatitis (NASH).

METHODS

The therapeutic effects of ONO-1301 against liver damage, fibrosis, and occurrence of liver tumors were evaluated using melanocortin 4 receptor-deficient (Mc4r-KO) NASH model mice. The effects of ONO-1301 against macrophages, hepatic stellate cells, and endothelial cells were also evaluated in vitro.

RESULTS

ONO-1301 ameliorated liver damage and fibrosis progression, was effective regardless of NASH status, and suppressed the occurrence of liver tumors in Mc4r-KO NASH model mice. In the in vitro study, ONO-1301 suppressed LPS-induced inflammatory responses in cultured macrophages, suppressed hepatic stellate cell (HSC) activation, upregulated vascular endothelial growth factor (VEGF) expression in HSCs, and upregulated hepatocyte growth factor (HGF) and VEGF expression in endothelial cells.

CONCLUSIONS

The results of our study highlight the potential of ONO-1301 to reverse the progression and prevent the occurrence of liver tumors in NASH using in vivo and in vitro models. ONO-1301 is a multidirectional drug that can play a key role in various pathways and can be further analyzed for use as a new drug candidate against NASH.

Inhibition of SUMO2/3 antagonizes isoflurane-induced cancer-promoting effect in hepatocellular carcinoma Hep3B cells

Surgery for patients with complicated liver cancer often results in a long exposure to anesthesia with an increase in side effects. Continued long-term exposure to isoflurane may promote liver cancer progression. Small ubiquitin-like modifier (SUMO) 2 and 3, also known as SUMO2/3, conjugates to substrate proteins when cells undergo acute stress. However, whether or not SUMO2/3 is involved in isoflurane-mediated liver cancer progression is unknown. In the present study, hepatocellular carcinoma (HCC) cells were exposed to 2% isoflurane for 12 h, followed by 36 h of drug withdrawal, and the formation of SUMO2/3 conjugates and cancer behavioral characteristics were studied. The results demonstrated that the formation of SUMO2/3 conjugates was significantly increased following HCC cells being exposed to isoflurane for 0.5 h, and continued to increase for 48 h, even after the drug had been withdrawn. Furthermore, isoflurane-exposed HCC cells exhibited increased proliferation and invasion activity during the subsequent observation period. SUMO specific protease 3 (SENP3), which inhibits the binding of SUMO2/3 to its target proteins, was overexpressed and it was discovered that isoflurane-induced SUMOylation was significantly inhibited, and accordingly, the proliferation and invasion abilities of HCC cells were decreased to a certain extent. These findings indicated that SUMO2/3 is involved in the progression of HCC cells, at least in the Hep3B cell line, induced by the anesthetic isoflurane, and that inhibition of SUMO2/3 may antagonize the response. These results provided a novel target for decreasing the adverse reactions occurring in patients with HCC during anesthesia, particularly those who are exposed to isoflurane for long periods of time.

Mesenchymal stem cell-secreted prostaglandin E2 ameliorates acute liver failure via attenuation of cell death and regulation of macrophage polarization

BACKGROUND

Acute liver failure (ALF) is an acute inflammatory liver disease with high mortality. Previous preclinical and clinical trials have confirmed that mesenchymal stem cell (MSC) is a promising therapeutic approach; however, the effect is not satisfied as the underlying molecular mechanisms of MSC in treating ALF remain unclear.

METHODS

MSC isolated from 4- to 6-week-old C57BL/6 mice were used to treat ALF. Histological and serological parameters were analyzed to evaluate the efficacy of MSC. We explored the molecular mechanism of MSC in the treatment of ALF by detecting liver inflammatory response and hepatocyte death.

RESULTS

In this study, we found that the therapeutic potential of MSC on ALF is dependent on the secretion of prostaglandin E2 (PGE2), a bioactive lipid. MSC-derived PGE2 inhibited TGF-β-activated kinase 1 (TAK1) signaling and NLRP3 inflammasome activation in liver macrophages to decrease the production of inflammatory cytokines. Meanwhile, macrophages in the liver could be induced to anti-inflammatory (M2) macrophages by MSC-derived PGE2 via STAT6 and mechanistic target of rapamycin (mTOR) signaling, which then promote inflammatory resolution and limit liver injury. Finally, administrating EP4 antagonist significantly ameliorated the therapeutic ability of MSC, which promoted liver inflammation and decreased M2 macrophages.

CONCLUSIONS

Our results indicate that PGE2 might be a novel important mediator of MSC in treating ALF, which is through inhibiting the liver inflammatory response and hepatocyte death.

The Tumor Microenvironment-A Metabolic Obstacle to NK Cells' Activity

NK cells have unique capabilities of recognition and destruction of tumor cells, without the requirement for prior immunization of the host. Maintaining tolerance to healthy cells makes them an attractive therapeutic tool for almost all types of cancer. Unfortunately, metabolic changes associated with malignant transformation and tumor progression lead to immunosuppression within the tumor microenvironment, which in turn limits the efficacy of various immunotherapies. In this review, we provide a brief description of the metabolic changes characteristic for the tumor microenvironment. Both tumor and tumor-associated cells produce and secrete factors that directly or indirectly prevent NK cell cytotoxicity. Here, we depict the molecular mechanisms responsible for the inhibition of immune effector cells by metabolic factors. Finally, we summarize the strategies to enhance NK cell function for the treatment of tumors.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Chitinase 3-like-1 promotes intrahepatic activation of coagulation through induction of tissue factor in mice

Coagulation is a critical component in the progression of liver disease. Identification of key molecules involved in the intrahepatic activation of coagulation (IAOC) will be instrumental in the development of effective therapies against liver disease. Using a mouse model of concanavalin A (ConA)-induced hepatitis, in which IAOC plays an essential role in causing liver injury, we uncovered a procoagulant function of chitinase 3-like 1 (Chi3l1). Chi3l1 expression is dramatically elevated after ConA challenge, which is dependent on ConA-induced T cell activation and the resulting interferon γ and tumor necrosis factor α productions. Compared with wild-type mice, Chi3l1-/- mice show less IAOC, reduced tissue factor (TF) expression, and attenuated liver injury. Reconstituting Chi3l1-/- mice with recombinant TF triggers IAOC and augments liver injury.

CONCLUSION

Our data demonstrate that Chi3l1, through induction of TF via mitogen-activated protein kinase activation, promotes IAOC and tissue injury. (Hepatology 2018;67:2384-2396).

Prostaglandin I2 suppresses the development of diet-induced nonalcoholic steatohepatitis in mice

Nonalcoholic steatohepatitis (NASH) is a hepatic manifestation of metabolic syndrome. Although the prostaglandin (PG)I₂ receptor IP is expressed broadly in the liver, the role of PGI₂-IP signaling in the development of NASH remains to be determined. Here, we investigated the role of the PGI₂-IP system in the development of steatohepatitis using mice lacking the PGI₂ receptor IP [IP-knockout (IP-KO) mice] and beraprost (BPS), a specific IP agonist. IP-KO and wild-type (WT) mice were fed a methionine- and choline-deficient diet (MCDD) for 2, 5, or 10 wk. BPS was administered orally to mice every day during the experimental periods. The effect of BPS on the expression of chemokine and inflammatory cytokines was examined also in cultured Kupffer cells. WT mice fed MCDD developed steatohepatitis at 10 wk. IP-KO mice developed steatohepatitis at 5 wk with augmented histologic derangements accompanied by increased hepatic monocyte chemoattractant protein-1 (MCP-1) and TNF-α concentrations. After 10 wk of MCDD, IP-KO mice had greater hepatic iron deposition with prominent oxidative stress, resulting in hepatocyte damage. In WT mice, BPS improved histologic and biochemical parameters of steatohepatitis, accompanied by reduced hepatic concentration of MCP-1 and TNF-α. Accordingly, BPS suppressed the LPS-stimulated Mcp-1 and Tnf-α mRNA expression in cultured Kupffer cells prepared from WT mice. PGI₂-IP signaling plays a crucial role in the development and progression of steatohepatitis by modulating the inflammatory response, leading to augmented oxidative stress. We suggest that the PGI₂-IP system is an attractive therapeutic target for treating patients with NASH.-Kumei, S., Yuhki, K.-I., Kojima, F., Kashiwagi, H., Imamichi, Y., Okumura, T., Narumiya, S., Ushikubi, F. Prostaglandin I₂ suppresses the development of diet-induced nonalcoholic steatohepatitis in mice.

Structure-guided chemical modification of guide RNA enables potent non-viral in vivo genome editing

Efficient genome editing with Cas9-sgRNA in vivo has required the use of viral delivery systems, which have limitations for clinical applications. Translational efforts to develop other RNA therapeutics have shown that judicious chemical modification of RNAs can improve therapeutic efficacy by reducing susceptibility to nuclease degradation. Guided by the structure of the Cas9-sgRNA complex, we identify regions of sgRNA that can be modified while maintaining or enhancing genome-editing activity, and we develop an optimal set of chemical modifications for in vivo applications. Using lipid nanoparticle formulations of these enhanced sgRNAs (e-sgRNA) and mRNA encoding Cas9, we show that a single intravenous injection into mice induces >80% editing of Pcsk9 in the liver. Serum Pcsk9 is reduced to undetectable levels, and cholesterol levels are significantly lowered about 35% to 40% in animals. This strategy may enable non-viral, Cas9-based genome editing in the liver in clinical settings.

Augmented liver targeting of exosomes by surface modification with cationized pullulan

Exosomes are membrane nanoparticles containing biological substances that are employed as therapeutics in experimental inflammatory models. Surface modification of exosomes for better tissue targetability and enhancement of their therapeutic ability was recently attempted mainly using gene transfection techniques. Here, we show for the first time that the surface modification of exosomes with cationized pullulan, which has the ability to target hepatocyte asialoglycoprotein receptors, can target injured liver and enhance the therapeutic effect of exosomes. Surface modification can be achieved by a simple mixing of original exosomes and cationized pullulan and through an electrostatic interaction of both substances. The exosomes modified with cationized pullulan were internalized into HepG2 cells in vitro to a significantly greater extent than unmodified ones and this internalization was induced through the asialoglycoprotein receptor that was specifically expressed on HepG2 cells and hepatocytes. When injected intravenously into mice with concanavalin A-induced liver injury, the modified exosomes accumulated in the liver tissue, resulting in an enhanced anti-inflammatory effect in vivo. It is concluded that the surface modification with cationized pullulan promoted accumulation of the exosomes in the liver and the subsequent biological function, resulting in a greater therapeutic effect on liver injury.

STATEMENT OF SIGNIFICANCE

Exosomes have shown potentials as therapeutics for various inflammatory disease models. This study is the first to show the specific accumulation of exosomes in the liver and enhanced anti-inflammatory effect via the surface modification of exosomes using pullulan, which is specifically recognized by the asialoglycoprotein receptor (AGPR) on HepG2 cells and hepatocytes. The pullulan was expressed on the surface of PKH-labeled exosomes, and it led increased accumulation of PKH into HepG2 cells, whereas the accumulation was canceled by AGPR inhibitor. In the mouse liver injury model, the modification of PKH-labeled exosomes with pullulan enabled increased accumulation of PKH specifically in the injured liver. Furthermore the greater therapeutic effects against the liver injury compared with unmodified original exosomes was observed.

Role of cyclooxygenase-2 in immune response in liver fibrosis and mechanisms involved

Cyclooxygenase-2 (COX-2), an inducible enzyme, is almost not expressed in normal human and rat liver tissues, but is highly expressed in liver tissues of patients with chronic hepatitis and cirrhosis. Inhibition or interference of COX-2 expression can significantly inhibit the formation of hepatic fibrosis in rats, suggesting that COX-2 is involved in the occurrence and development of hepatic fibrosis; however, the underlying mechanism is unclear. Recent studies have shown that the role of COX-2 in the development of hepatic fibrosis may be related to immune response. In this paper, we review the role of COX-2 and its metabolites in the immune response in liver fibrosis, with an aim to provide a theoretical basis for clinical prevention and treatment of hepatic fibrosis.

Leishmania donovani-Induced Prostaglandin E2 Generation Is Critically Dependent on Host Toll-Like Receptor 2-Cytosolic Phospholipase A2 Signaling

Visceral leishmaniasis (VL) is the second-largest parasitic killer disease after malaria. During VL, the protozoan Leishmania donovani induces prostaglandin E2 (PGE2) generation within host macrophages to aid parasite survival. PGE2 significantly influences leishmanial pathogenesis, as L. donovani proliferation is known to be attenuated in PGE2-inhibited macrophages. Here, we report for the first time that signaling via macrophage Toll-like receptor 2 (TLR2) plays an instrumental role in inducing PGE2 release from L. donovani-infected macrophages. This signaling cascade, mediated via the TLR2-phosphatidylinositol 3-kinase (PI3K)-phospholipase C (PLC) signaling pathway, was found to be indispensable for activation of two major enzymes required for PGE2 generation: cytosolic phospholipase A2 (cPLA2) and cyclooxygenase 2 (Cox2). Inhibition of cPLA2, but not secreted phospholipase A2 (sPLA2) or calcium-independent phospholipase A2 (iPLA2), arrested L. donovani infection. During infection, cPLA2 activity increased >7-fold in a calcium-dependent and extracellular signal-regulated kinase (ERK)-dependent manner, indicating that elevation of intracellular calcium and ERK-mediated phosphorylation was necessary for L. donovani-induced cPLA2 activation. For transcriptional upregulation of cyclooxygenase 2, activation of the calcium-calcineurin-nuclear factor of activated T cells (NFAT) signaling was required in addition to the TLR2-PI3K-PLC pathway. Detailed studies by site-directed mutagenesis of potential NFAT binding sites and chromatin immunoprecipitation (ChIP) analysis revealed that the binding of macrophage NFATc2, at the -73/-77 site on the cox2 promoter, induced L. donovani-driven cox2 transcriptional activation. Collectively, these findings highlight the contribution of TLR2 downstream signaling toward activation of cPLA2 and Cox2 and illustrate how the TLR2-PI3K-PLC pathway acts in a concerted manner with calcium-calcineurin-NFATc2 signaling to modulate PGE2 release from L. donovani-infected macrophages.

Hepatic NK cell-mediated hypersensitivity to ConA-induced liver injury in mouse liver expressing hepatitis C virus polyprotein

The role of hepatic NK cells in the pathogenesis of HCV-associated hepatic failure is incompletely understood. In this study, we investigated the effect of HCV on ConA-induced immunological hepatic injury and the influence of HCV on hepatic NK cell activation in the liver after ConA administration. An immunocompetent HCV mouse model that encodes the entire viral polyprotein in a liver-specific manner based on hydrodynamic injection and φC31o integrase was used to study the role of hepatic NK cells. Interestingly, the frequency of hepatic NK cells was reduced in HCV mice, whereas the levels of other intrahepatic lymphocytes remained unaltered. Next, we investigated whether the reduction in NK cells within HCV mouse livers might elicit an effect on immune-mediated liver injury. HCV mice were subjected to acute liver injury models upon ConA administration. We observed that HCV mice developed more severe ConA-induced immune-mediated hepatitis, which was dependent on the accumulated intrahepatic NK cells. Our results indicated that after the administration of ConA, NK cells not only mediated liver injury through the production of immunoregulatory cytokines (IFN-γ, TNF-α and perforin) with direct antiviral activity, but they also killed target cells directly through the TRAIL/DR5 and NKG2D/NKG2D ligand signaling pathway in HCV mice. Our findings suggest a critical role for NK cells in oversensitive liver injury during chronic HCV infection.

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.

Differential Contributions of Alcohol and the Nicotine-Derived Nitrosamine Ketone (NNK) to Insulin and Insulin-Like Growth Factor Resistance in the Adolescent Rat Brain

AIMS

Since epidemiologic studies suggest that tobacco smoke toxins, e.g. the nicotine-derived nitrosamine ketone (NNK) tobacco-specific nitrosamine, can be a co-factor in alcohol-related brain disease (ARBD), we examined the independent and additive effects of alcohol and NNK exposures on spatial learning/memory, and brain insulin/IGF signaling, neuronal function and oxidative stress.

METHODS

Adolescent Long Evans rats were fed liquid diets containing 0 or 26% caloric ethanol for 8 weeks. During weeks 3-8, rats were treated with i.p. NNK (2 mg/kg, 3×/week) or saline. In weeks 7-8, ethanol groups were binge-administered ethanol (2 g/kg; 3×/week). In week 8, at 12 weeks of age, rats were subjected to Morris Water Maze tests. Temporal lobes were used to assess molecular indices of insulin/IGF resistance, oxidative stress and neuronal function.

RESULTS

Ethanol and NNK impaired spatial learning, and NNK ± ethanol impaired memory. Linear trend analysis demonstrated worsening performance from control to ethanol, to NNK, and then ethanol + NNK. Ethanol ± NNK, caused brain atrophy, inhibited insulin signaling through the insulin receptor and Akt, activated GSK-3β, increased protein carbonyl and 3-nitrotyrosine, and reduced acetylcholinesterase. NNK increased NTyr. Ethanol + NNK had synergistic stimulatory effects on 8-iso-PGF-2α, inhibitory effects on p-p70S6K, tau and p-tau and trend effects on insulin-like growth factor type 1 (IGF-1) receptor expression and phosphorylation.

CONCLUSIONS

Ethanol, NNK and combined ethanol + NNK exposures that begin in adolescence impair spatial learning and memory in young adults. The ethanol and/or NNK exposures differentially impair insulin/IGF signaling through neuronal growth, survival and plasticity pathways, increase cellular injury and oxidative stress and reduce expression of critical proteins needed for neuronal function.

HGF-Met Pathway in Regeneration and Drug Discovery

Hepatocyte growth factor (HGF) is composed of an α-chain and a β-chain, and these chains contain four kringle domains and a serine protease-like structure, respectively. Activation of the HGF–Met pathway evokes dynamic biological responses that support morphogenesis (e.g., epithelial tubulogenesis), regeneration, and the survival of cells and tissues. Characterizations of conditional Met knockout mice have indicated that the HGF–Met pathway plays important roles in regeneration, protection, and homeostasis in various cells and tissues, which includes hepatocytes, renal tubular cells, and neurons. Preclinical studies designed to address the therapeutic significance of HGF have been performed on injury/disease models, including acute tissue injury, chronic fibrosis, and cardiovascular and neurodegenerative diseases. The promotion of cell growth, survival, migration, and morphogenesis that is associated with extracellular matrix proteolysis are the biological activities that underlie the therapeutic actions of HGF. Recombinant HGF protein and the expression vectors for HGF are biological drug candidates for the treatment of patients with diseases and injuries that are associated with impaired tissue function. The intravenous/systemic administration of recombinant HGF protein has been well tolerated in phase I/II clinical trials. The phase-I and phase-I/II clinical trials of the intrathecal administration of HGF protein for the treatment of patients with amyotrophic lateral sclerosis and spinal cord injury, respectively, are ongoing.

Helicobacter hepaticus induces an inflammatory response in primary human hepatocytes

Helicobacter hepaticus can lead to chronic hepatitis and hepatocellular carcinoma in certain strains of mice. Until now the pathogenic role of Helicobacter species on human liver tissue is still not clarified though Helicobacter species identification in human liver cancer was successful in case controlled studies. Therefore we established an in vitro model to investigate the interaction of primary human hepatocytes (PHH) with Helicobacter hepaticus. Successful co-culturing of PHH with Helicobacter hepaticus was confirmed by visualization of motile bacteria by two-photon-microscopy. Isolated human monocytes were stimulated with PHH conditioned media. Changes in mRNA expression of acute phase cytokines and proteins in PHH and stimulated monocytes were determined by Real-time PCR. Furthermore, cytokines and proteins were analyzed in PHH culture supernatants by ELISA. Co-cultivation with Helicobacter hepaticus induced mRNA expression of Interleukin-1 beta (IL-1β), Tumor necrosis factor-alpha, Interleukin-8 (IL-8) and Monocyte chemotactic protein-1 (MCP-1) in PHH (p<0.05) resulting in a corresponding increase of IL-8 and MCP-1 concentrations in PHH supernatants (p<0.05). IL-8 and IL-1β mRNA expression was induced in monocytes stimulated with Helicobacter hepaticus infected PHH conditioned media (p<0.05). An increase of Cyclooxygenase-2 mRNA expression was observed, with a concomitant increase of prostaglandin E2 concentration in PHH supernatants at 24 and 48 h (p<0.05). In contrast, at day 7 of co-culture, no persistent elevation of cytokine mRNA could be detected. High expression of intercellular adhesion molecule-1 on PHH cell membranes after co-culture was shown by two-photon-microscopy and confirmed by flow-cytomety. Finally, expression of Cytochrome P450 3A4 and albumin mRNA were downregulated, indicating an impairment of hepatocyte synthesis function by Helicobacter hepaticus presence. This is the first in vitro model demonstrating a pathogenic effect of a Helicobacter spp. on human liver cells, resulting in an inflammatory response with increased synthesis of inflammatory mediators and consecutive monocyte activation.

Lipopeptide nanoparticles for potent and selective siRNA delivery in rodents and nonhuman primates

siRNA therapeutics have promise for the treatment of a wide range of genetic disorders. Motivated by lipoproteins, we report lipopeptide nanoparticles as potent and selective siRNA carriers with a wide therapeutic index. Lead material cKK-E12 showed potent silencing effects in mice (ED50 ∼ 0.002 mg/kg), rats (ED50 < 0.01 mg/kg), and nonhuman primates (over 95% silencing at 0.3 mg/kg). Apolipoprotein E plays a significant role in the potency of cKK-E12 both in vitro and in vivo. cKK-E12 was highly selective toward liver parenchymal cell in vivo, with orders of magnitude lower doses needed to silence in hepatocytes compared with endothelial cells and immune cells in different organs. Toxicity studies showed that cKK-E12 was well tolerated in rats at a dose of 1 mg/kg (over 100-fold higher than the ED50). To our knowledge, this is the most efficacious and selective nonviral siRNA delivery system for gene silencing in hepatocytes reported to date.

The efficacy of parecoxib on systemic inflammatory response associated with cardiopulmonary bypass during cardiac surgery

AIMS

Cardiopulmonary bypass (CPB) during cardiac surgery is well known to be associated with the development of a systemic inflammatory response. The efficacy of parecoxib in attenuating this systemic inflammatory response is still unknown.

METHODS

Patients undergoing elective mitral valve replacement with CPB were assessed, enrolled and randomly allocated to receive parecoxib (80 mg) or placebo. Blood samples were collected in EDTA vials for measuring serum cytokine concentrations, troponin T, creatinekinase myocardial-brain isoenzyme CK-MB concentrations and white cell counts.

RESULTS

Compared with the control group, IL-6 and IL-8-values in the parecoxib group increased to a lesser extent, peaking at 2 h after the end of CPB (IL-6 31.8 pg ml⁻¹ ± 4.7 vs. 77.0 pg ml⁻¹ ± 14.1, 95% CI -47.6, -42.8, P < 0.001; IL-8 53.6 pg ml⁻¹ ± 12.6 vs. 105.7 pg ml⁻¹ ± 10.8, 95% CI -54.8, -49.4, P < 0.001). Peak concentrations of anti-inflammatory cytokine IL-10 occurred immediately after termination of CPB and were higher in the parecoxib group (115.7 pg ml⁻¹ ± 10.5 vs. 88.4 pg ml⁻¹ ± 12.3, 95% CI 24.7, 29.9, P < 0.001). Furthermore, the increase in neutrophil counts caused by CPB during cardiac surgery was inhibited by parecoxib. The increases in serum troponin T and CK-MB concentrations were also significantly attenuated by parecoxib in the early post-operative days. Peak serum concentrations of CK-MB in both groups occurred at 24 h post-CPB (17.4 μg l⁻¹ ± 5.2 vs. 26.9 μg l⁻¹ ± 6.9, 95% CI -10.9, -8.1, P < 0.001). Peak troponin T concentrations occurred at 6 h post-bypass (2 μg l⁻¹ ± 0.62 vs. 3.5 μg l⁻¹ ± 0.78, 95% CI -1.7, -1.3, P < 0.001).

CONCLUSION

Intra-operative parecoxib attenuated the systemic inflammatory response associated with CPB during cardiac surgery and lowered the biochemical markers of myocardial injury.

Multifaceted roles of PGE2 in inflammation and cancer

Prostaglandin E(2) (PGE(2)) is a bioactive lipid that elicits a wide range of biological effects associated with inflammation and cancer. PGE(2) exerts diverse effects on cell proliferation, apoptosis, angiogenesis, inflammation, and immune surveillance. This review concentrates primarily on gastrointestinal cancers, where the actions of PGE(2) are most prominent, most likely due to the constant exposure to dietary and environmental insults and the intrinsic role of PGE(2) in tissue homeostasis. A discussion of recent efforts to elucidate the complex and interconnected pathways that link PGE(2) signaling with inflammation and cancer is provided, supported by the abundant literature showing a protective effect of NSAIDs and the therapeutic efficacy of targeting mPGES-1 or EP receptors for cancer prevention. However, suppressing PGE(2) formation as a means of providing chemoprotection against all cancers may not ultimately be tenable, undoubtedly the situation for patients with inflammatory bowel disease. Future studies to fully understand the complex role of PGE(2) in both inflammation and cancer will be required to develop novel strategies for cancer prevention that are both effective and safe.

PGI2 as a regulator of inflammatory diseases

Prostacyclin, or PGI₂, is an end product derived from the sequential metabolism of arachidonic acid via cyclooxygenase and PGI synthase (PGIS). The receptor for PGI₂, IP, can be found on a variety of cell types and signaling through this receptor exhibits broad physiological effects. Historically, PGI₂ has been understood to play a role in cardiovascular health, specifically having powerful vasodilatory effects via relaxation of smooth muscle and inhibiting of platelet aggregation. For these reasons, PGI₂ has a long history of use for the treatment of pulmonary arterial hypertension (PAH). Only recently, its importance as an immunomodulatory agent has been investigated. PGI₂ regulates both the innate and adaptive immune systems and its effects are, for the most part, thought to be anti-inflammatory or immunosuppressive in nature, which may have implications for its further clinical use.

Suppression of acute hepatic injury by a synthetic prostacyclin agonist through hepatocyte growth factor expression

Previous studies have demonstrated that mice disrupted with the cyclooxygenase-2 gene showed much more severe liver damage compared with wild-type mice after liver injury, and prostaglandins (PGs) such as PGE(1/2) and PGI(2) have decreased hepatic injury, but the mechanisms by which prostaglandins exhibit protective action on the liver have yet to be addressed. In the present study, we investigated the mechanism of the protective action of PGI(2) using the synthetic IP receptor agonist ONO-1301. In primary cultures of hepatocytes and nonparenchymal liver cells, ONO-1301 did not show protective action directly on hepatocytes, whereas it stimulated expression of hepatocyte growth factor (HGF) in nonparenchymal liver cells. In mice, peroral administration of ONO-1301 increased hepatic gene expression and protein levels of HGF. Injections of CCl4 induced acute liver injury in mice, but the onset of acute liver injury was strongly suppressed by administration of ONO-1301. The increases in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) by CCl4 were suppressed by 10 mg/kg ONO-1301 to 39.4 and 33.6%, respectively. When neutralizing antibody against HGF was administered with ONO-1301 and CCl4, the decreases by ONO-1301 in serum ALT and AST, apoptotic liver cells, and expansion of necrotic areas in liver tissue were strongly reversed by neutralization of endogenous HGF. These results indicate that ONO-1301 increases expression of HGF and that hepatoprotective action of ONO-1301 in CCl4-induced liver injury may be attributable to its activity to induce expression of HGF, at least in part. The potential for involvement of HGF-Met-mediated signaling in the hepatotrophic action of endogenous prostaglandins generated by injury-dependent cyclooxygenase-2 induction is considerable.

Immunological tolerance in a mouse model of immune-mediated liver injury induced by 16,16 dimethyl PGE2 and PGE2-containing nanoscale hydrogels

Although immunosuppressive agents play a pivotal role in the success of organ transplantation, chronic toxicity has been a major issue for long-term treatment. The development of therapies that induce donor-specific immunological tolerance remains an important clinical challenge. In the present study, we investigated the underlying mechanisms and applications of prostaglandin (PG) E2 for the induction of immunological tolerance in mice with concanavalin A(Con A)-induced immune-mediated liver injury. The immunological tolerogenic effect of 16,16 dimethyl PGE2 (dmPGE2) pretreatment in C57B/6 male mice with Con A-induced liver injury was observed, and it was revealed that its response was partially associated with the expression of interleukin (IL)-10, an anti-inflammatory cytokine, in Kupffer cells. To apply native eicosanoids of PGE2 for tolerance induction in vivo, PGE2 was incorporated into l-lactic acid oligomer-grafted pullulan of an amphiphilic polymer to form a nano-sized hydrogel (PGE2-nanogel). Pharmacokinetics studies revealed that nanogel incorporation enabled PGE2 to have a prolonged life-time in circulating blood, and a tolerogenic effect was also observed in Con A-induced liver injury, the same as with dmPGE2 pretreatment. Nanogel-based prostaglandin administration might be developed as a therapeutic agent to induce immunological tolerance, which is necessary in allogenic organ and cell transplantation.

Curative effects of hydrogen sulfide against acetaminophen-induced hepatotoxicity in mice

AIMS

Hydrogen sulfide (H(2)S), an endogenous gaseous mediator, plays an important role in regulation of many physiological and pathological processes. On the other hand, acetaminophen overdose is a major cause of drug-induced liver failure. The aim of this study therefore is to evaluate the possible curative effects of H(2)S against acetaminophen-induced hepatotoxicity.

MAIN METHODS

Male Swiss mice were treated with sodium hydrogen sulfide, a H(2)S donor, 30 min after acetaminophen administration. N-acetylcysteine, a therapeutic antidote, was used as a reference drug.

KEY FINDINGS

H(2)S treatment resulted in hepatocurative effects as evident by a significant decrease in serum alanine aminotransferase and hepatic malondialdehyde and nitric oxide levels, with a concurrent increase in hepatic glutathione content compared to acetaminophen-treated group. H(2)S did not alter catalase activity. Additionally, immunohistochemical analysis demonstrated that H(2)S treatment markedly reduced tumor necrosis factor-α expression, while expression of cyclooxygenase-2 was markedly enhanced with nuclear localization into hepatocytes. The curative effects of H(2)S were confirmed by liver histopathological examination and were maintained in the presence of glibenclamide, an antagonist of ATP-sensitive potassium (K(ATP)) channels.

SIGNIFICANCE

H(2)S treatment markedly alleviates acetaminophen hepatotoxicity in mice possibly, in part, through anti-oxidative and anti-inflammatory effects but not likely to be coupled with activation of K(ATP) channels. The hepatocurative effects of H(2)S are comparable to N-acetylcysteine. Hence, H(2)S has a potential therapeutic value for treatment of acetaminophen hepatotoxicity.

Resolution of inflammation in murine autoimmune arthritis is disrupted by cyclooxygenase-2 inhibition and restored by prostaglandin E2-mediated lipoxin A4 production

Acute inflammation follows defined phases of induction, inflammation and resolution, and resolution occurs by an active process that requires cyclooxygenase-2 (COX-2) activity. This study aims to address whether this paradigm extends to recognized model of chronic inflammation. We demonstrated that murine collagen-induced arthritis follows a similar sequential course. Interestingly, COX-2 and its metabolite, the presumably proinflammatory PGE(2), are present in the joints during resolution, and blocking COX-2 activity and PGE(2) production within this period perpetuated, instead of attenuated, inflammation. Repletion with PGE(2) analogs restored homeostasis, and this function is mediated by the proresolving lipoxygenase metabolite, lipoxin A(4), a potent stop signal. Thus, the study provided in vivo evidence for a natural, endogenous link between the cyclooxygenase-lipoxygenase pathways and showed that PGE(2) serves as a feedback inhibitor essential for limiting chronic inflammation in autoimmune arthritis. These findings may explain the enigma regarding why COX-2 inhibitors are palliative rather than curative in humans, because blocking resolution may mitigate the benefit of preventing induction.

Lactoferrin protects against concanavalin A-induced liver injury in mice

BACKGROUND

Liver diseases, caused by viral infection, autoimmune conditions, alcohol ingestion or the use of certain drugs, are a significant health issue, as many can develop into liver failure. Lactoferrin (Lac) is an iron-binding glycoprotein that belongs to the transferrin family. Owing to its multiple biological functions, Lac has been evaluated in a number of clinical trials to treat infections, inflammation and cancer.

AIM

The present study aims to reveal a profound hepatoprotective effect of Lac, using a mouse model of Concanavalin A (Con A)-induced hepatitis, which mimics the pathophysiology of human viral and autoimmune hepatitis.

METHOD

C57Bl/6J mice were injected with bovine Lac following Con A challenge. The effects of Lac on interferon (IFN)-gamma and interleukin (IL)-4 expression were determined. The roles of Lac on T-cell apoptosis and activation, and leukocytes infiltration were examined.

RESULT

The data demonstrated that the protective effect of Lac was attributed to its ability to inhibit T-cell activation and production of IFN-gamma, as well as to suppress IL-4 production by hepatic natural killer T cells.

CONCLUSION

These findings indicate a great therapeutic potential of Lac in treating in treating inflammatory hepatitis and possibly other inflammatory diseases.

COX-2 in liver, from regeneration to hepatocarcinogenesis: What we have learned from animal models?

The use of animals lacking genes or expressing genes under the control of cell-specific promoters has significantly increased our knowledge of the genetic and molecular basis of physiopathology, allowing testing of functional hypotheses and validation of biochemical and pharmacologic approaches in order to understand cell function. However, with unexpected frequency, gene knockout animals and, more commonly, animal models of transgenesis give experimental support to even opposite conclusions on gene function. Here we summarize what we learned on the role of cyclooxygenase 2 (COX-2) in liver and revise the results obtained in 3 independent models of mice expressing a COX-2 transgene specifically in the hepatocyte. Upon challenge with pro-inflammatory stimuli, the animals behave very differently, some transgenic models having a protective effect but others enhancing the injury. In addition, one transgene exerts differential effects on normal liver physiology depending on the transgenic animal model used.

Cyclooxygenase 2 pathway and its therapeutic inhibition in superantigen-induced toxic shock

Bacterial superantigens are a family of exotoxins that are the most potent T-cell activators known. Because of their ability to induce strong immune activation, superantigens have been implicated in a variety of diseases ranging from self-limiting food poisoning to more severe toxic shock syndrome (TSS) and have the potential to be used as agents of bioterrorism. Nonetheless, the precise molecular mechanisms by which T-cell activation by superantigens lead to acute systemic inflammatory response, multiple organ dysfunction, and ultimately death are unclear. Inadequate understanding of the pathogenesis has resulted in lack of development of effective therapy for superantigen-induced TSS. To fill these deficiencies, we systematically dissected the molecular pathogenesis of superantigen-induced TSS using the humanized human leukocyte antigen-DR3 transgenic mouse model by microarray-based gene expression profiling. Splenic expression of prostaglandin-endoperoxide synthase 2 (PTGS-2; also called cyclooxygenase 2 or COX-2) gene was increased by several hundred folds shortly after systemic superantigen (staphylococcal enterotoxin B [SEB]) exposure. In addition, expressions of several genes associated with eicosanoid pathway were significantly modulated by SEB, as analyzed by dedicated software. Given the importance of the COX-2 pathway in inflammation, we examined whether therapeutic inhibition of COX-2 by a highly selective inhibitor, CAY10404, could be beneficial. Our studies showed that i.p. administration of CAY10404 (50 mg/kg) immediately after challenge with 10 microg of SEB was unable to inhibit SEB-induced in vivo cytokine/chemokine production or T-cell activation/proliferation and did not prevent superantigen-associated thymocyte apoptosis.

Hepatoprotective effects of misoprostol and silymarin on carbon tetrachloride-induced hepatic damage in rats

The aim of this study was to investigate the effect of misoprostol, silymarin or the co-administration of misoprostol + silymarin on the carbon tetrachloride (CCl(4))-induced hepatic injury in rats. Misoprostol (10, 100, 1000 microg/kg), silymarin (25 mg/kg) or misoprostol (100 microg/kg) + silymarin (25 mg/kg) was given once daily orally simultaneously with CCl(4) and for 15 days thereafter. The results showed that misoprostol (10, 100 or 1000 microg/kg) conferred significant protection against the hepatotoxic actions of CCl(4) in rats, reducing serum alanine aminotransferase (ALT) levels by 24.7%, 42.6% and 49.4%, respectively compared with controls. Misoprostol, given at 100 or 1000 microg/kg, decreased aspartate aminotransferase (AST) by 28 and 43.6% and alkaline phosphatase (ALP) by 19.3% and 53.4% respectively. Meanwhile, silymarin reduced ALT, AST and ALP levels by 62.7%, 66.1% and 65.1% respectively. The co-administration of misoprostol (100 microg/kg) and silymarin (25 mg/kg) resulted in 61.4%, 66.1% and 57.5% reduction in ALT, AST and ALP levels respectively. Histopathological alterations and depletion of hepatocyte glycogen and DNA content by CCl(4) were markedly reduced after treatment with misoprostol, silymarin or misoprostol + silymarin. Image analysis of liver specimens revealed a marked reduction in liver necrosis; area of damage: 32.4%, 24% and 10.2% after misoprostol (10, 100 or 1000 microg/kg), 7.2% after silymarin and 10.9% after treatment with misoprostol 100 microg/kg + silymarin, compared with CCl(4) control group (46.7%). These results indicate that treatment with misoprostol protects against hepatocellular necrosis induced by CCl(4). This study suggests a potential therapeutic use for misoprostol in liver injury.

Effect of polyI:C cotreatment on halothane-induced liver injury in mice

Drug-induced liver injury (DILI) is a challenging problem in drug development and clinical practice. Patient susceptibility to DILI is multifactorial, making these reactions difficult to predict and prevent. Clinical observations have suggested that concurrent bacterial and viral infections represent an important risk factor in determining patient susceptibility to developing adverse drug reactions, although the underlying mechanism is not clear. In the present study, we employed the viral RNA mimetic (polyinosinic-polycytidylic acid [polyI:C]) to emulate viral infection and examined its effect on halothane-induced liver injury. Although pretreatment of mice with polyI:C attenuated halothane hepatotoxicity due to its inhibitory effect on halothane metabolism, posttreatment significantly exacerbated liver injury with hepatocellular apoptosis being significantly higher than that in mice treated with polyI:C alone or halothane alone. The pan-caspase inhibitor z-VAD-fmk suppressed liver injury induced by polyI:C/posthalothane cotreatment, suggesting that the increased hepatocyte apoptosis contributes to the exacerbation of liver injury. Posttreatment with polyI:C also caused activation of hepatic Kupffer cells (KCs) and natural killer (NK) cells and upregulated multiple proapoptotic factors, including tumor necrosis factor-alpha (TNF-alpha), NK receptor group 2, member D (NKG2D), and Fas ligand (FasL). These factors may play important roles in mediating polyI:C-induced hepatocyte apoptosis.

CONCLUSION

This is the first study to provide evidence that concurrent viral infection can inhibit cytochrome (CYP)450 activities and activate the hepatic innate immune system to proapoptotic factors. DILI may be attenuated or exacerbated by pathogens depending on the time of infection.

Constitutive expression of cyclo-oxygenase 2 transgene in hepatocytes protects against liver injury

The effect of COX (cyclo-oxygenase)-2-dependent PGs (prostaglandins) in acute liver injury has been investigated in transgenic mice that express human COX-2 in hepatocytes. We have used three well-established models of liver injury: in LPS (lipopolysaccharide) injury in D-GalN (D-galactosamine)-preconditioned mice; in the hepatitis induced by ConA (concanavalin A); and in the proliferation of hepatocytes in regenerating liver after PH (partial hepatectomy). The results from the present study demonstrate that PG synthesis in hepatocytes decreases the susceptibility to LPS/D-GalN or ConA-induced liver injury as deduced by significantly lower levels of the pro-inflammatory profile and plasmatic aminotransferases in transgenic mice, an effect suppressed by COX-2-selective inhibitors. These Tg (transgenic) animals express higher levels of anti-apoptotic proteins and exhibit activation of proteins implicated in cell survival, such as Akt and AMP kinase after injury. The resistance to LPS/D-GalN-induced liver apoptosis involves an impairment of procaspase 3 and 8 activation. Protection against ConA-induced injury implies a significant reduction in necrosis. Moreover, hepatocyte commitment to start replication is anticipated in Tg mice after PH, due to the expression of PCNA (proliferating cell nuclear antigen), cyclin D1 and E. These results show, in a genetic model, that tissue-specific COX-2-dependent PGs exert an efficient protection against acute liver injury by an antiapoptotic/antinecrotic effect and by accelerated early hepatocyte proliferation.

Celecoxib exacerbates hepatic fibrosis and induces hepatocellular necrosis in rats treated with porcine serum

Inhibitors against cyclooxygenase-2 (COX-2), an inducible enzyme that catalyzes prostaglandin synthesis, are widely used in clinical. However, the potential hepatic toxicity of COX-2 inhibitors remains incompletely investigated. We report in this study that a clinically available COX-2 inhibitor, celecoxib, exacerbates porcine serum (PS)-induced hepatic fibrosis and induces hepatocellular necrosis in an experimental liver fibrosis model. Histological results revealed that although celecoxib by itself did not cause notable hepatic damages, it markedly enhanced hepatic fibrosis that had been initiated by PS. While PS alone did not cause any necrotic change in liver cells, the addition of celecoxib resulted in hepatocellular necrosis in PS-treated animals. Notably, celecoxib enhanced reduction of plasma prostaglandin E(2) (PGE(2)) levels induced by PS. Taken together, our results indicate that treatment with celecoxib may exacerbate liver fibrosis and cause hepatocellular necrosis. This may be associated with reduction in PGE(2) as an inheritance consequence of inhibition of COX-2.

Prostaglandin D(2) induces contraction via thromboxane A(2) receptor in rat liver myofibroblasts

Increased intrahepatic resistance is one of the major characteristics of cirrhotic liver, in which extravascular cells including liver myofibroblasts (MFs) abnormally contract. Although several studies provided evidence that various prostaglandins (PG) are involved in liver cirrhosis, the role of PGD(2) remains unknown. In this study, we investigated the effect of PGD(2) on the contractile properties of liver MFs. Cultured rat liver MFs were used at passages 4-7. A collagen gel contraction assay was used for the evaluation of the MFs contraction. mRNA expression was assessed by semi-quantitative RT-PCR. Intracellular Ca(2+) concentrations ([Ca(2+)](i)) were measured by monitoring the fluorescence intensity of fura-2. PGD(2) (1-10 microM) induced liver MF contraction in a dose-dependent manner with [Ca(2+)](i) elevation. Pretreatment with 300 nM LaCl(3), a nonselective Ca(2+) channel blocker abolished the 10 microM PGD(2)-induced MFs contraction. RT-PCR revealed that three distinct PGD(2) responsive receptors, prostanoid DP receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) and thromboxane A(2) receptor (prostanoid TP receptor), were expressed in liver MFs. While prostanoid DP receptor agonist and CRTH2 agonist didn't induce contraction, 0.01-1 microM U46619 (11alpha, 9alpha-epoxymethano-PGH(2), prostanoid TP receptor agonist) caused robust contraction with [Ca(2+)](i) elevation. Furthermore, pretreatment with prostanoid TP receptor antagonists ramatroban (1 microM) or SQ29548 ([1S-[1alpha, 2alpha(Z), 3alpha, 4alpha]]-7-[3-[[2-[(phenyl amino)carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid, 1 microM) completely suppressed PGD(2)-induced contraction and [Ca(2+)](i) elevation. Additionally, we observed that BW245C (1-10 microM) decreased basal MF contraction. These results suggest that PGD(2) induces rat liver MF contraction with an increase in [Ca(2+)](i) through prostanoid TP receptor.

Neuroinflammatory response to lipopolysaccharide is exacerbated in mice genetically deficient in cyclooxygenase-2

Background

Cyclooxygenases (COX) -1 and -2 are key mediators of the inflammatory response in the central nervous system. Since COX-2 is inducible by inflammatory stimuli, it has been traditionally considered as the most appropriate target for anti-inflammatory drugs. However, the specific roles of COX-1 and COX-2 in modulating a neuroinflammatory response are unclear. Recently, we demonstrated that COX-1 deficient mice show decreased neuroinflammatory response and neuronal damage in response to lipopolysaccharide (LPS).

Methods

In this study, we investigated the role of COX-2 in the neuroinflammatory response to intracerebroventricular-injected LPS (5 μg), a model of direct activation of innate immunity, using COX-2 deficient (COX-2^-/-) and wild type (COX-2^+/+) mice, as well as COX-2^+/+ mice pretreated for 6 weeks with celecoxib, a COX-2 selective inhibitor.

Results

Twenty-four hours after LPS injection, COX-2^-/- mice showed increased neuronal damage, glial cell activation, mRNA and protein expression of markers of inflammation and oxidative stress, such as cytokines, chemokines, iNOS and NADPH oxidase. Brain protein levels of IL-1β, NADPH oxidase subunit p67^phox, and phosphorylated-signal transducer and activator of transcription 3 (STAT3) were higher in COX-2^-/- and in celecoxib-treated mice, compared to COX-2^+/+ mice. The increased neuroinflammatory response in COX-2^-/- mice was likely mediated by the upregulation of STAT3 and suppressor of cytokine signaling 3 (SOCS3).

Conclusion

These results show that inhibiting COX-2 activity can exacerbate the inflammatory response to LPS, possibly by increasing glial cells activation and upregulating the STAT3 and SOCS3 pathways in the brain.

Human neutrophil peptides upregulate expression of COX-2 and endothelin-1 by inducing oxidative stress

Polymorphonuclear leukocytes (PMNs) play an important role during inflammation in cardiovascular diseases. Human neutrophil peptides (HNPs) are released from PMN granules upon activation and are conventionally involved in microbial killing. Recent studies suggested that HNPs may be involved in the pathogenesis of vascular abnormality by modulating inflammatory responses and vascular tone. Since HNPs directly interact with endothelium upon release from PMNs in the circulation, we tested the hypothesis that the stimulation with HNPs of endothelial cells modulates the expression of vasoactive by-products through altering cyclooxygenase (COX) activity. When human umbilical vein endothelial cells were stimulated with purified HNPs, we observed a time- and dose-dependent increase in the expression of COX-2, whereas COX-1 levels remained unchanged. Despite an increased expression of COX-2 at the protein level, HNPs did not significantly enhance the COX-2 activity, thus the production of the prostaglandin PGI2. HNPs significantly induced the release of endothelin-1 (ET-1) as well as the formation of nitrotyrosine. The HNP-induced COX-2 and ET-1 production was attenuated by the treatment with the oxygen free radical scavenger N-acetyl-L-cysteine and the inhibitors of p38 MAPK and NF-kappaB, respectively. The angiontensin II pathway did not seem to be involved in the HNP-induced upregulation of COX-2 and ET-1 since the use of the angiotensin-converting enzyme inhibitor enalapril had no effect in this context. In conclusion, HNP may play an important role in the pathogenesis of inflammatory cardiovascular diseases by activating endothelial cells to produce vasoactive by-products as a result of oxidative stress.

Respiratory Francisella tularensis live vaccine strain infection induces Th17 cells and prostaglandin E2, which inhibits generation of gamma interferon-positive T cells

Two key routes of Francisella tularensis infection are through the skin and airway. We wished to understand how the route of inoculation influenced the primary acute adaptive immune response. We show that an intranasal inoculation of the F. tularensis live vaccine strain (LVS) with a 1,000-fold-smaller dose than an intradermal dose results in similar growth kinetics and peak bacterial burdens. In spite of similar bacterial burdens, we demonstrate a difference in the quality, magnitude, and kinetics of the primary acute T-cell response depending on the route of inoculation. Further, we show that prostaglandin E(2) secretion in the lung is responsible for the difference in the gamma interferon (IFN-gamma) response. Intradermal inoculation led to a large number of IFN-gamma(+) T cells 7 days after infection in both the spleen and the lung. In contrast, intranasal inoculation induced a lower number of IFN-gamma(+) T cells in the spleen and lung but an increased number of Th17 cells in the lung. Intranasal infection also led to a significant increase of prostaglandin E(2) (PGE(2)) in the bronchoalveolar lavage fluid. Inhibition of PGE(2) production with indomethacin treatment resulted in increased numbers of IFN-gamma(+) T cells and decreased bacteremia in the lungs of intranasally inoculated mice. This research illuminates critical differences in acute adaptive immune responses between inhalational and dermal infection with F. tularensis LVS mediated by the innate immune system and PGE(2).

Cyclooxygenase-2 deficiency enhances Th2 immune responses and impairs neutrophil recruitment in hepatic ischemia/reperfusion injury

Cyclooxygenase-2 (COX-2) is a prostanoid-synthesizing enzyme that is critically implicated in a variety of pathophysiological processes. Using a COX-2-deficient mouse model, we present data that suggest that COX-2 has an active role in liver ischemia/reperfusion (I/R) injury. We demonstrate that COX-2-deficient mice had a significant reduction in liver damage after I/R insult. The inability of COX-2(-/-) to elaborate COX-2 products favored a Th2-type response in these mice. COX-2(-/-) livers after I/R injury showed significantly decreased levels of IL-2, as well as IL-12, a cytokine known to have a central role in Th1 effector cell differentiation. Moreover, such livers expressed enhanced levels of the anti-inflammatory cytokine IL-10, shifting the balance in favor of a Th2 response in COX-2-deficient mice. The lack of COX-2 expression resulted in decreased levels of CXCL2, a neutrophil-activating chemokine, reduced infiltration of MMP-9-positive neutrophils, and impaired late macrophage activation in livers after I/R injury. Additionally, Bcl-2 and Bcl-x(L) were normally expressed in COX-2(-/-) livers after injury, whereas respective wild-type controls were almost depleted of these two inhibitors of cell death. In contrast, caspase-3 activation and TUNEL-positive cells were depressed in COX-2(-/-) livers. Therefore, our data support the concept that COX-2 is involved in the pathogenic events occurring in liver I/R injury. The data also suggest that potential valuable therapeutic approaches in liver I/R injury may result from further studies aimed at identifying specific COX-2-derived prostanoid pathways.