Leukotriene C4 (LTC4) elicits a respiratory burst in peritoneal macrophages

Synergic pro-apoptotic effects of Ferulic Acid and nanostructured lipid carrier in glioblastoma cells assessed through molecular and Delayed Luminescence studies

Herein, we assessed the effect of Ferulic Acid (FA), a natural antioxidant with anti-cancer effect, on the human glioblastoma cells through molecular and Delayed Luminescence (DL) studies. DL, a phenomenon of ultra-week emission of optical photons, was used to monitor mitochondrial assessment. The effect of FA loaded in nanostructured lipid carriers (NLCs) was also assessed. To validate NLCs as a drug delivery system for glioblastoma treatment, particular attention was focused on their effect. We found that free FA induced a significant decrease in c-Myc and Bcl-2 expression levels accompanied by the apoptotic pathway activation. Blank NLCs, even if they did not induce cytotoxicity and caspase-3 cleavage, decreased Bcl-2, ERK1/2, c-Myc expression levels activating PARP-1 cleavage. The changes in DL intensity and kinetics highlighted a possible effect of nanoparticle matrix on mitochondria, through the involvement of the NADH pool and ROS production that, in turn, activates ERK1/2 pathways. All the effects on protein expression levels and on the activation of apoptotic pathway appeared more evident when the cells were exposed to FA loaded in NLCs. We demonstrated that the observed effects are due to a synergic pro-apoptotic influence exerted by FA, whose bio-availability increases in the glioblastoma cells, and NLCs formulation.

Leukotrienes enhance the bactericidal activity of alveolar macrophages against Klebsiella pneumoniae through the activation of NADPH oxidase

Leukotrienes (LTs) are lipid mediators that participate in inflammatory diseases and innate immune function. We sought to investigate the importance of LTs in regulating the microbicidal activity of alveolar macrophages (AMs) and the molecular mechanisms by which this occurs. The role of LTs in enhancing AM microbicidal activity was evaluated pharmacologically and genetically using in vitro challenge with Klebsiella pneumoniae. Exogenous LTs increased AM microbicidal activity in a dose- and receptor-dependent manner, and endogenous production of LTs was necessary for optimal killing. Leukotriene B4 (LTB4) was more potent than cysteinyl LTs. An important role for nicotinamide adenine dinucleotide (NADPH) oxidase in LT-induced microbicidal activity was indicated by the fact that bacterial killing was abrogated by the NADPH oxidase inhibitor diphenyleneiodonium (DPI; 10 microM) and in AMs derived from gp91phox-deficient mice. By contrast, LT-induced microbicidal activity was independent of the generation of nitric oxide. LTs increased H2O2 production, and LTB4 was again the more potent agonist. Both classes of LTs elicited translocation of p47phox to the cell membrane, and LTB4 induced phosphorylation of p47phox in a manner dependent on protein kinase C-delta (PKC-delta) activity. In addition, the enhancement of microbicidal activity by LTs was also dependent on PKC-delta activity. Our results demonstrate that LTs, especially LTB4, enhanceAM microbicidal activity through the PKC-delta-dependent activation of NADPH oxidase.

Phospholipase A2, an in vivo immunomodulator

Arachidonic acid (AA) can be released from membrane phospholipids by the action of phospholipase A2 (PLA2). There is evidence that unsaturated fatty acids, particularly AA, released from membrane phospholipids are required to activate the respiratory burst of macrophages. The data reported here indicate that peritoneal macrophages harvested 30 min after i.p. injection of PLA2 can phagocytose Candida albicans more efficiently and emit more chemoluminescence (CL) than normal cells when stimulated by zymosan. PLA2 injection also enhances the CL of peritoneal cells from mice already stimulated by immunomodulators such as trehalose dimycolate (TDM), bestatin, or oncostatic drugs such as aclacinomycin (ACM). CL is not sensitive to potassium cyanide (KCN), but is inhibited by catalase, superoxide dismutase (SOD), nordihydroguaiaretic acid (NDGA) and high doses of indomethacin (10(-3) M). In vivo PLA2 treatment stimulates the synthesis of both cyclooxygenase and lipoxygenase derivatives of AA metabolism (PGE2, 6-keto, PGF1 alpha TXB2 and LTC4). Inhibitors of AA metabolism (NDGA, indomethacin) modulate the production of free oxidizing radicals in this experimental model, partly because of their effect on AA metabolism, as determined by the measuring immunoreactive products. However, this work indicates that the effects of these inhibitors, which have been extensively used in CL studies, should be interpreted with caution, since their specificity for AA metabolism is relative.

Recombinant interleukin-1 beta stimulates eicosanoid production in rat primary culture astrocytes

Astrocytes may play a prominent role in the initiation of immunoinflammatory responses in the central nervous system. They can be induced to synthesize eicosanoids but how immunologically relevant molecules modulate this process is not known. We examined the influence of recombinant interleukin-1 (rIL-1), an immunomodulating monokine on the release of arachidonic acid metabolites. IL-1 (1-30 U) induced a dose-related elaboration predominantly of the cyclo-oxygenation products prostaglandin E and thromboxane B2. Preincubation of rIL-1 with a specific antibody abrogated and heat-inactivation destroyed this activity. Both mepacrine and the isoquinolinesulfonamide H7 blocked the stimulatory effect dose-dependently, indicating involvement of protein kinase C in this novel biologic activity of IL-1. In central nervous system inflammation, IL-1-evoked release from astrocytes of arachidonic acid-derived metabolites may influence the severity of phlogistic responses and modulate local immune reactivity.

Leukotriene production by cultured astroglial cells

Astrocytes metabolize arachidonic acid via the cyclooxygenase pathway to prostanoids. We examined whether primary culture astrocytes from neonatal rat brain can be induced to generate and release the lipoxygenase derivative leukotriene C4 (LTC4). While there was only minute constitutive production of immunoreactive LTC4 this metabolite was liberated by astroglial cells in response to calcium ionophore A23187. The phorbol diester 12-O-tetradecanoylphorbol 13-acetate (TPA) failed to precipitate leukotriene release. However, when threshold doses of A23187 were added to astrocyte cultures challenged with TPA, LTC4 was recovered from their supernatants. It is suggested that leukotriene generation by astrocytes bears relevance to immunoinflammatory responses in the central nervous system and may be involved in brain edema formation.

Cyclooxygenase inhibitors promote the leukotriene C4 induced release of beta-glucuronidase from rat peritoneal macrophages: prostaglandin E2 suppresses

The effects of leukotriene C4, indomethacin, aspirin and prostaglandin E2 on macrophage activity were investigated, whereby the release of the lysosomal enzyme beta-glucuronidase was taken as a criterion for cell activity. Leukotriene C4 enhanced the release of beta-glucuronidase as well as the production of prostaglandin E2. Blocking the production of endogenous prostaglandins by adding indomethacin or aspirin resulted in an augmented effect of leukotriene C4. Exogenous prostaglandin E2 could reverse the leukotriene C4 and/or indomethacin induced beta-glucuronidase release. These results support the postulated interaction between leukotriene C4 and prostaglandin E2 with respect to the regulation of macrophage activity, leukotriene C4 being stimulatory, prostaglandin E2 suppressive.

Unsaturated fatty acids stimulate NADPH-dependent superoxide production by cell-free system derived from macrophages

Arachidonic acid (C20:4) and other unsaturated fatty acids are shown to activate superoxide (O2-) production in a cell-free system represented by sonically disrupted guinea pig peritoneal macrophages. The reaction requires a heat-sensitive cellular component and NADPH, is enhanced by flavin adenine dinucleotide (FAD), and is not linked to enzymatic oxidation of the fatty acid. C20:4-elicited O2- formation is dependent on the cooperation between a subcellular component sedimentable at 48,000g (probably containing the O2- -forming enzyme) and a cytosolic factor. This appears to be the first report of O2- generation being elicited in a cell-free system derived from unstimulated cells and supports the idea that unesterified unsaturated fatty acids act as second messengers of O2- formation in intact phagocytes.