Protective effect of linoleic acid on IFN gamma-induced cellular injury in primary culture hepatocytes

Modulatory Effect of Linoleic Acid During Brucella abortus 544 Infection in Murine Macrophage RAW264.7 Cells and Murine Model BALB/c Mice

In this study, we investigated the effects of linoleic acid (LA) treatment on Brucella abortus infection in professional phagocyte RAW264.7 cells, particularly during the pathogens invasion and intracellular growth in these cells, as well as in murine model BALB/c mice focusing on bacterial splenic proliferation and immunoregulatory activities. LA inhibited the growth of Brucella in a doseand time-dependent manner. The ability of the pathogen to enter the phagocytes was inhibited as was its survival within these cells. This was accompanied by increased nitrite accumulation in these cells at 24 h post-infection. The concentration of LA used in the present study did not affect the total body weight or liver function of the mice. During Brucella infection, the total splenic weight of these animals was not changed; rather, resistance to bacterial proliferation was enhanced in the spleen. Furthermore, mice treated with LA displayed elevated levels of IL-12 and IFN-γ but reduced levels of IL-10 during infection. The findings in this study showed the regulatory role of LA against B. abortus infection suggesting its potential use in designing intervention strategy for brucellosis.

Effects of a new bioactive lipid-based drug carrier on cultured hepatic stellate cells and liver fibrosis in bile duct-ligated rats

In the fibrotic liver, hepatic stellate cells (HSC) produce large amounts of collagen and secrete variety of mediators that promote development of fibrosis in this organ. Therefore, these cells are considered an attractive target for antifibrotic therapies. We incorporated the bioactive lipid dilinoleoylphosphatidylcholine (DLPC) into the membrane of liposomes, and then we evaluated its effect on hepatic stellate cell activation and liver fibrosis. To target DLPC-liposomes to HSC, human serum albumin modified with mannose 6-phosphate (M6P-HSA) was coupled to the surface of these liposomes. In vitro, the effects of the carrier were determined in primary cultures of HSC, Kupffer cells, and liver endothelial cells using real-time reverse transcription-polymerase chain reaction. In vivo DLPC-liposomes were tested in bile duct-ligated rats. Targeted M6P-HSA-DLPC-liposomes and DLPC-liposomes significantly reduced gene expression levels for collagen 1alpha1, alpha-smooth muscle actin (alpha-SMA), and transforming growth factor-beta (TGF-beta) in cultured HSC. In fibrotic livers, DLPC-liposomes decreased gene expression for TGF-beta and collagen 1alpha1 as well as alpha-SMA and collagen protein expression. In contrast, M6P-HSA-DLPC-liposomes enhanced expression of profibrotic and proinflammatory genes in vivo. In cultured Kupffer and endothelial cells M6P-HSA liposomes influenced the expression of proinflammatory genes. Both types of liposomes increased hepatocyte glycogen content in fibrotic livers, indicating improved functionality of the hepatocytes. We conclude that DLPC-containing liposomes attenuate activation of cultured HSC. In fibrotic livers, M6P-HSA-mediated activation of Kupffer and endothelial cells probably counteracts this beneficial effect of DLPC-liposomes. Therefore, these bioactive drug carriers modulate the activity of all liver cells during liver fibrosis.

Direct effects of interleukin-6 on liver progenitor oval cells in culture

Following acute injury, liver is usually regenerated from hepatocytes by a process that is dependent on interleukin (IL)-6. If this pathway is impaired, restoration of the liver mass and ultimately the survival of the animal are dependent on recruitment of cells from a precursor cell population, either a stem cell or an oval cell. Importantly, oval cells are also implicated in tumorigenesis. A carcinogenic choline-deficient ethionine supplemented (CDE) diet is capable of inducing substantial numbers of oval cells that we can isolate and utilize to identify cytokines, which affect oval cell proliferation and differentiation. Currently, a putative role of IL-6 in oval cell biology is suggested by the elevation of IL-6 in liver and serum of mice treated with a CDE diet and knockout mouse studies. Also, when IL-6 is injected into the peritoneal cavity of mice on the CDE diet, oval cell numbers are increased compared to mice on the CDE diet alone. We investigated the role of human IL-6 on p53 null immortalized murine oval cell lines (PIL), finding that they express transcripts for the IL-6 receptor and gp 130, STAT-3 is phosphorylated upon IL-6 stimulation, IL-6 induces IL-6 production, and proliferation is induced by IL-6. In addition, we show that mouse primary oval cells also express IL-6 receptor and gp 130 mRNA. These findings suggest that IL-6 directly stimulates oval cells and an autocrine mechanism may sustain oval cell proliferation.

Linoleic acid epoxide promotes the maintenance of mitochondrial function and active Na+ transport following hypoxia

Low concentrations of arachidonic acid monoepoxides protect against ischemia/reperfusion injury. This study examined whether low concentrations of the linoleic acid monoepoxide, cis-12,13-epoxy-9-octadecenoic acid (12,13-EOA), protect renal cells against decreases in mitochondrial and transport functions induced by hypoxia/reoxygenation. Primary cultures of rabbit renal proximal tubular cells (RPTC) were pretreated with diluent or 1, 5, or 10 microM 12,13-EOA for 1 h and exposed to 2 h hypoxia/0.5 h reoxygenation in the absence of 12,13-EOA. Basal respiration, oligomycin-sensitive oxygen consumption (QO2), and ATP content decreased 31, 35 and 65%, respectively, following hypoxia/reoxygenation. Hypoxia/reoxygenation also increased mitochondrial membrane potential (DeltaPsi(m)). Pretreatment with 12,13-EOA prevented decreases in basal and oligomycin-sensitive QO2s and increases in DeltaPsi(m). Despite the protection against decreases in mitochondrial function, 12,13-EOA pretreatment did not prevent the initial decrease in intracellular ATP content following hypoxia. However, pretreatment did accelerate the recovery of intracellular ATP levels during reoxygenation. Pretreatment with 12,13-EOA also prevented hypoxia-induced decreases in active Na+ transport. Ouabain-sensitive QO2 (a marker of active Na+ transport) decreased 38% following hypoxia/reoxygenation but was maintained in RPTC pretreated with 1, 5 or 10 microM 12,13-EOA prior to hypoxia. Pretreatment of RPTC with the hydrolyzed product of 12,13-EOA, 12,13-dihydroxyoctadecenoic acid, did not have any protective effects against mitochondrial dysfunction and decreases in active Na+ transport. Thus, this is the first report demonstrating that preconditioning of RPTC with low concentrations of 12,13-EOA, but not its hydrolyzed product, maintains mitochondrial respiration, accelerates restoration of ATP levels, and prevents decreases in active Na+ transport following hypoxia/reoxygenation.

Divergent role of gamma interferon in a murine model of pulmonary versus systemic Klebsiella pneumoniae infection

Klebsiella pneumoniae is a leading cause of both community-acquired and nosocomial gram-negative-bacterial pneumonia. A further clinical complication of pulmonary K. pneumoniae infection is dissemination of bacteria from the lung into the peripheral blood, resulting in bacteremia concurrent with the localized pulmonary infection. Here, we report studies detailing the divergent role of gamma interferon (IFN-gamma) in pulmonary versus systemic K. pneumoniae infection. Intratracheal inoculation of IFN-gamma knockout mice resulted in significantly increased mortality compared to that observed for wild-type infected animals. Increased mortality correlated with a 100-fold increase in pulmonary bacteria within 2 days postinfection and upregulation of lung-associated interleukin-10 (IL-10) mRNA. Interestingly, IFN-gamma knockout mice had a twofold reduction in plasma aminospartate transferase activity, indicating diminished liver injury following peripheral blood bacterial dissemination. To study the host response towards blood-borne bacteria in the absence of the ongoing pulmonary infection, intravenous inoculation studies were initiated. IFN-gamma knockout mice were no more susceptible to intravenous infection than their wild-type counterparts. The consistent observation in IFN-gamma knockout mice was for improved survival correlating with increased clearance of blood- and liver-associated bacteria. Intravenous inoculation resulted in a two- to threefold increase in hepatic IL-10 production 24 and 48 h postinfection. Liver injury was also significantly reduced in IFN-gamma knockout mice. These data indicate that IFN-gamma secretion is a critical mediator in the resolution of localized gram-negative pulmonary pneumonia. Surprisingly, host responses towards systemic infection with the same bacteria appear to be IFN-gamma independent.