Secretion Of Acute Phase Proteins Research Articles

Bioactivity of orange-spotted grouper (Epinephelus coioides) interleukin-6 in innate immunity: Inducing inflammation, antimicrobial peptides, and innate immune molecular gene expression as well as activating phagocytosis of leukocytes and increasing survival under Vibrio and NNV infection

Interleukin-6 (IL-6) is a multifunctional cytokine involved in innate and acquired immunity. In mammals, IL-6 can induce the secretion of acute-phase proteins (APPs) and antimicrobial peptides, activate macrophages and neutrophils, and regulate the expression of inflammatory cytokines in innate immunity, resulting in enhanced resistance to invading pathogens. In teleost fish, the functions of IL-6 are still unclear. In our previous studies using orange-spotted grouper (Epinephelus coioides) as an animal model, we demonstrated that IL-6 induces the Th2 pathway in acquired immunity and enhances antibody production. In the current study, we evaluated in greater detail the mechanisms underlying the functions of IL-6 in innate immunity. In gene expression assays, the expression of fish inflammatory cytokine genes (e.g., ifnγ, ccl4, il1β, tnfα 1, and tnfα 2), antimicrobial peptide genes (e.g., epinecidin 1, hepcidin 1, and hepcidin 2), and genes related to innate immunity (e.g., mx, crp, and complement C3) was higher in fish injected with recombinant IL-6 (rIL-6). The serum from those same fish also presented higher antibacterial activity and higher phagocytosis activity of leukocytes. In a pathogen challenge involving Vibrio campbellii and nervous necrosis virus, fish injected with rIL-6 presented a higher survival rate and lower pathogen count in the body. These results demonstrate that the administration of rIL-6 can activate innate immune responses and enhance resistance against invading bacterial or viral pathogens.

Serum iron concentration as a marker of inflammation in young cows that underwent dehorning surgery

The systemic reaction to proinflammatory cytokines is the production and secretion of acute phase proteins (APPs) by the liver. The common APPs measured in cattle are haptoglobin (Hp), serum amyloid A (SAA), lipopolysaccharide binding protein, alpha(1)-acid glycoprotein, and transferrin. Iron (Fe) plays important roles in many enzymatic activities, and is an essential trace element for the host and pathogen. Previous studies have demonstrated that the serum Fe concentration decreases in acute traumatic reticuloperitonitis and mastitis in cows. Therefore, the relationship between inflammation and the serum Fe concentration may be useful for the evaluation of the host response to inflammation during surgery because measurement of the serum Fe concentration is cheap and easy to perform. However, comparative studies have not been conducted regarding the serum Fe concentration in cattle that underwent surgery. Therefore, the aim of the present study was to measure changes in the serum Fe concentration in cows that underwent dehorning surgery in order to assess the usefulness of the serum Fe concentration as a marker of inflammation.

Haptoglobin improves acute phase response and endotoxin tolerance in response to bacterial LPS

Sepsis is characterized by delayed acute phase response and lowered immune tolerance in patients. Acute phase serum proteins, like Haptoglobin (Hp), have been associated with increased mortality in bacteria mediated acute lung inflammation and sepsis in neonates. However, it’s direct role in modulating the immune response by regulating pro-inflammatory mediators leading to immune tolerant state and if gender affects its expression levels during bacterial infection, especially in blood has not been fully explored. To understand its specific role in endotoxin-mediated immune response, we investigated the correlation between the rise in Hp levels on bacterial infection and its influence on the expression of pro-inflammatory mediators in male and female Whole blood (WHB) and PBMCs. Here, we observed pathogen-specific and gender-specific expression of Hp. Gonadal steroid hormones differentially influenced the Hp expression in LPS-induced WHB, where the addition of Estrogen increased Hp expression, with suppression of TNFα, in both genders. Further on evaluating, the influence of Hp on TNFα expression in endotoxin tolerance (ET), we show that increased Hp levels directly reduced TNFα expression in ET models. Interestingly, blockade of secreted Hp significantly reversed the (ET) state, confirmed by a significant rise in TNFα expression in both ex vivo and in vitro ET models, indicating a possible feedback inhibition by Hp on inflammatory mediators like TNFα. We also investigated the role of PKCδ in the regulation of LPS induced secretion of acute phase proteins (Hp) in serum, where inhibition of PKCδ, reduced secretion of anti-microbial proteins in response to LPS shown by restored bacterial growth. These findings clearly highlight the crucial role of Hp in maintaining immune tolerance via suppressing the pro-inflammatory mediators and also in preventing bacterial proliferation in blood during infection.

Synergistic gene expression during the acute phase response is characterized by transcription factor assisted loading

The cytokines interleukin 1β and 6 (IL-1β, IL-6) mediate the acute phase response (APR). In liver, they regulate the secretion of acute phase proteins. Using RNA-seq in primary hepatocytes, we show that these cytokines regulate transcription in a bifurcated manner, leading to both synergistic and antagonistic gene expression. By mapping changes in enhancer landscape and transcription factor occupancy (using ChIP-seq), we show that synergistic gene induction is achieved by assisted loading of STAT3 on chromatin by NF-κB. With IL-6 treatment alone, STAT3 does not efficiently bind 20% of its coordinated binding sites. In the presence of IL-1β, NF-κB is activated, binds a subset of enhancers and primes their activity, as evidenced by increasing H3K27ac. This facilitates STAT3 binding and synergistic gene expression. Our findings reveal an enhancer-specific crosstalk whereby NF-κB enables STAT3 binding at some enhancers while perturbing it at others. This model reconciles seemingly contradictory reports of NF-κB-STAT3 crosstalk.

Multi-walled carbon nanotube-physicochemical properties predict the systemic acute phase response following pulmonary exposure in mice.

Pulmonary exposure to multi-walled carbon nanotubes (MWCNTs) has been linked to an increased risk of developing cardiovascular disease in addition to the well-documented physicochemical-dependent adverse lung effects. A proposed mechanism is through a strong and sustained pulmonary secretion of acute phase proteins to the blood. We identified physicochemical determinants of MWCNT-induced systemic acute phase response by analyzing effects of pulmonary exposure to 14 commercial, well-characterized MWCNTs in female C57BL/6J mice pulmonary exposed to 0, 6, 18 or 54 μg MWCNT/mouse. Plasma levels of acute phase response proteins serum amyloid A1/2 (SAA1/2) and SAA3 were determined on day 1, 28 or 92. Expression levels of hepatic Saa1 and pulmonary Saa3 mRNA levels were assessed to determine the origin of the acute phase response proteins. Pulmonary Saa3 mRNA expression levels were greater and lasted longer than hepatic Saa1 mRNA expression. Plasma SAA1/2 and SAA3 protein levels were related to time and physicochemical properties using adjusted, multiple regression analyses. SAA3 and SAA1/2 plasma protein levels were increased after exposure to almost all of the MWCNTs on day 1, whereas limited changes were observed on day 28 and 92. SAA1/2 and SAA3 protein levels did not correlate and only SAA3 protein levels correlated with neutrophil influx. The multiple regression analyses revealed a protective effect of MWCNT length on SAA1/2 protein level on day 1, such that a longer length resulted in lowered SAA1/2 plasma levels. Increased SAA3 protein levels were positively related to dose and content of Mn, Mg and Co on day 1, whereas oxidation and diameter of the MWCNTs were protective on day 28 and 92, respectively. The results of this study reveal very differently controlled pulmonary and hepatic acute phase responses after MWCNT exposure. As the responses were influenced by the physicochemical properties of the MWCNTs, this study provides the first step towards designing MWCNT that induce less SAA.

Reaction of human macrophages on protein corona covered TiO2 nanoparticles

The cytokine secretion of primary cells of human macrophages during the interaction of TiO2 nanoparticles (with an average primary size of 100-120nm) is investigated down to concentration levels suggested to be relevant for in vivo conditions. We find that high TiO2 concentrations induce the cytokines Interleukin IL-1β, IL-6, and IL-10 secretion, while at low concentrations only IL-6 secretion is observed. To obtain further evidence on in vivo conditions we investigated the development and structure of the protein corona of the nanoparticles. We demonstrated that the surface of TiO2 particles attract preferably secondary modified proteins which then induce cytokine secretion of macrophages. Our results indicate that concentration of corona covered TiO2 particles below 1μg/ml induce IL-6 secretion which is reported to be responsible for the development of autoimmune diseases as well as for the secretion of acute phase proteins. From the Clinical EditorThis study investigates the effects of protein corona covered titanium dioxide nanoparticles on human macrophages, concluding that concentration of such particles below 1 μg/ml induces IL-6 secretion, which may be responsible for the development of autoimmune diseases as well as for the secretion of acute phase proteins. This finding has important implications on future applications of such nanoparticles.

Associations between resumption of postpartum ovarian activity, uterine health and concentrations of metabolites and acute phase proteins during the transition period in Holstein cows

The resumption of ovarian activity, uterine health, severity of the negative energy balance and the synthesis of inflammatory mediators during the transition period in dairy cows are interrelated. Therefore, the aim of this study was to evaluate the association between the resumption of postpartum ovarian activity and the percentage of polymorphonuclear (PMN) cells in endometrial cytology, lipid mobilization and the secretion of acute phase proteins. For this study, 20 multiparous Holstein cows were used. Blood samples that were collected from 21d before calving to 44d in milk (DIM) were analyzed for serum glucose, non-esterified fatty acids (NEFA), insulin, haptoglobin, albumin, paraoxonase and progesterone. Endometrial cytology was performed at 37±2DIM to evaluate the percentage of PMN cells in the uterine flushing. Cows were divided into two groups: (1) ovulatory cows (n=12), which returned to ovarian activity by 44±2DIM; and (2) anovulatory cows (n=8), which did not resume ovarian activity during this period. Ovulatory cows had a lower (P=0.05) percentage of PMN cells in endometrial cytology than anovulatory cows (26.3±8.3% vs. 53.4±16.9%, respectively). Ovulatory cows had higher serum albumin during the pre- (P=0.03) and postpartum periods (P=0.01), and tended to have lower haptoglobin concentrations in the prepartum period (P=0.07) and higher paraoxonase activity in the postpartum period (P=0.09). In conclusion, cows that resumed ovarian activity early in the postpartum period had higher albumin concentrations in the peripartum period, which were associated with a lower percentage of uterine PMN cells.

Normalization and Statistical Analysis of Multiplexed Bead-based Immunoassay Data Using Mixed-effects Modeling

Multiplexed bead-based flow cytometric immunoassays are a powerful experimental tool for investigating cellular communication networks, yet their widespread adoption is limited in part by challenges in robust quantitative analysis of the measurements. Here we report our application of mixed-effects modeling for the normalization and statistical analysis of bead-based immunoassay data. Our data set consisted of bead-based immunoassay measurements of 16 phospho-proteins in lysates of HepG2 cells treated with ligands that regulate acute-phase protein secretion. Mixed-effects modeling provided estimates for the effects of both the technical and biological sources of variance, and normalization was achieved by subtracting the technical effects from the measured values. This approach allowed us to detect ligand effects on signaling with greater precision and sensitivity and to more accurately characterize the HepG2 cell signaling network using constrained fuzzy logic. Mixed-effects modeling analysis of our data was vital for ascertaining that IL-1α and TGF-α treatment increased the activities of more pathways than IL-6 and TNF-α and that TGF-α and TNF-α increased p38 MAPK and c-Jun N-terminal kinase (JNK) phospho-protein levels in a synergistic manner. Moreover, we used mixed-effects modeling-based technical effect estimates to reveal the substantial variance contributed by batch effects along with the absence of loading order and assay plate position effects. We conclude that mixed-effects modeling enabled additional insights to be gained from our data than would otherwise be possible and we discuss how this methodology can play an important role in enhancing the value of experiments employing multiplexed bead-based immunoassays.

Green tea extract supplementation ameliorates CCl4-induced hepatic oxidative stress, fibrosis, and acute-phase protein expression in rat

We evaluated the long-term effects of green tea extract (GTE) supplementation on oxidative stress, biliary acute phase protein expression, and liver function in CCl(4)-induced chronic liver injury. We evaluated the antioxidant activity of GTE in comparison with those of vitamin C, vitamin E, and β-carotene in vitro by using an ultrasensitive chemiluminescence analyzer. Chronic liver injury was induced by intraperitoneally administering carbon tetrachloride (CCl(4)) (1 mL/kg body weight, twice weekly) to female Wistar rats for 8 weeks. The effects of low (4 mg/kg body weight per day) and high (20 mg/kg body weight per day) doses of intragastric GTE on CCl(4)-induced liver dysfunction and fibrosis were examined by measuring the bile and blood reactive oxygen species levels and biochemical parameters by using Western blot and two-dimensional polyacrylamide gel electrophoresis techniques. GTE has greater scavenging activity against O(2)(-), H(2)O(2), and Hypochlorous acid (HOCl) in vitro than vitamin C, vitamin E, and β-carotene do. In vivo, CCl(4) markedly increased bile and blood reactive oxygen species production, lipid accumulation, number of infiltrated leukocytes, fibrosis, hepatic hydroxyproline content, and plasma alanine aminotransferase and aspartate aminotransferase activities, and reduced plasma albumin levels. Two-dimensional polyacrylamide gel electrophoresis revealed that CCl(4) increased the acute-phase expression of six biliary proteins and decreased hepatic B-cell lymphoma 2 (Bcl-2), catalase, and CuZn superoxide dismutase protein expression. GTE supplementation attenuated CCl(4)-enhanced oxidative stress, levels of biochemical parameters, pathology, and acute-phase protein secretion, and preserved antioxidant/antiapoptotic protein expression. GTE supplementation attenuates CCl(4)-induced hepatic oxidative stress, fibrosis, acute phase protein excretion, and hepatic dysfunction via the antioxidant and antiapoptotic defense mechanisms.

Co-culture of primary rat hepatocytes with rat liver epithelial cells enhances interleukin-6-induced acute-phase protein response.

Three different primary rat hepatocyte culture methods were compared for their ability to allow the secretion of fibrinogen and albumin under basal and IL-6-stimulated conditions. These culture methods comprised the co-culture of hepatocytes with rat liver epithelial cells (CC-RLEC), a collagen type I sandwich culture (SW) and a conventional primary hepatocyte monolayer culture (ML). Basal albumin secretion was most stable over time in SW. Fibrinogen secretion was induced by IL-6 in all cell culture models. Compared with ML, CC-RLEC showed an almost three-fold higher fibrinogen secretion under both control and IL-6-stimulated conditions. Induction of fibrinogen release by IL-6 was lowest in SW. Albumin secretion was decreased after IL-6 stimulation in both ML and CC-RLEC. Thus, cells growing under the various primary hepatocyte cell culture techniques react differently to IL-6 stimulation with regard to acute-phase protein secretion. CC-RLEC is the preferred method for studying cytokine-mediated induction of acute-phase proteins, because of the pronounced stimulation of fibrinogen secretion upon IL-6 exposure under these conditions.

How much is too much? Interleukin-6 and its signalling in atherosclerosis

The importance of inflammation as a driver of pathology is no longer confined to autoimmune and infectious diseases. In line with convincing experimental data as well as abundant clinical findings the current view of atherosclerosis points to inflammation as a critical regulator of atherosclerotic plaque formation and progression leading to the fatal clinical endpoints myocardial infarction, stroke or sudden cardiac death. The underlying mechanisms have been a matter of intense research during the last decades. In this regard, the interleukin-6 (IL-6) cytokines and their signalling events have been shown to contribute to both, atherosclerotic plaque development and plaque destabilisation via a variety of mechanisms. These involve the release of other pro-inflammatory cytokines, oxidation of lipoproteins by phospholipases, stimulation of acute phase protein secretion, the release of prothrombotic mediators, and the activation of matrix metalloproteinases. Moreover, the formation of reactive oxygen species generated by vascular enzyme systems may play a critical role in the regulation of IL-6 indicating a cross talk between vasoactive substances i.e. angiotensin II or adrenalin and pro-inflammatory cytokines such as IL-6. In this review we will summarise and discuss the underlying molecular and cellular mechanisms how IL-6 as an early and central regulator of inflammation contributes to atherosclerosis and how this knowledge can be integrated into the clinical context.

Membrane-remodeling controls the death of microvascular cells engaged by radiotherapy

Aging leads to a decreased ability of liver to metabolize drugs and increased expression and secretion of acute phase proteins, such as serum amyloid A (SAA), C-reactive protein (CRP), and alpha-1-acid glycoprotein (AGP). This phenomenon resembles some aspects of the acute phase response of host to inflammation; however, the molecular basis for the similarity is unclear. Ceramide and sphingosine are second messenger mediators of cellular responses to stress and inflammation. In liver, they play important role in mediating acute phase responses to IL-β. In this study, we use HPLC and thin layer chromatography to evaluate the effects of aging on steady-state level of ceramide and sphingosine. We report that both lipids are elevated in liver of old (24 months) as compared to young (5 months) male Fisher 344 rats. To elucidate the mechanism(s) for ceramide elevation, we test the acidic(ASMase) and neutral sphingomyelinase (NSMase) in vitro using NBD-sphingomyelin as an exogenous substrate. SM synthase is also analyzed in vitro using NBD-ceramide and {3H}-dipalmitoylphosphatidylcholine (DPPC) as exogenous substrates. In accordance with the increases in the mass of ceramide, the activity of acid and neutral SMase is elevated in old animals. Michaelis-Menten analysis of NSMase implies that the apparent activation of this enzyme is caused by an increase in the Vmax of the enzyme. In contrast, SM synthase activity is lower in old animals as compared to young ones. These results show that aging is accompanied by an elevation in SM turnover and a decrease in its synthesis, resulting in accumulation of pro-inflammatory and growth inhibitory second messenger ceramide. Ceramidase, the only enzyme leading to sphingosine generation, is also measured in vitro using NBD-ceramide as a substrate and liver homogenate as an enzyme source. Its activity is higher in the old rats, as compared to young ones. The acid and neutral forms of the enzyme are affected the most, while the changes in the alkaline enzyme are not significant. The increases in the basal levels of ceramide and sphingosine in old animals may contribute to the onset of inflammatory like state in liver during aging, exemplified by decrease P4502C11mRNA expression and chronic induction of acute phase protein expression.

Interleukin‐6 is a direct mediator of T cell migration

Interleukin (IL)-6 is a pleiotropic cytokine involved in the differentiation and proliferation of hematopoietic cells. Hepatocytes respond to IL-6 with the synthesis and secretion of acute-phase proteins. In addition, IL-6 plays a role as a migration factor in vivo. In the present paper, we studied the potential of IL-6 to mediate migration of human primary T cells and T cell-derived cell lines. IL-6 was found to induce migration only in the presence of extracellular matrix, suggesting a cross-talk between the IL-6- and integrin signal transduction pathways. Furthermore, an IL-6 gradient is required for chemotactic migration. This activity is not due to the release of secondary chemotactic activities, but is a direct response to IL-6. T cell migration could also be observed in response to IL-11, but no migration was found after stimulation with leukemia inhibitory factor or oncostatin M, although these cytokines signal through gp130-containing receptor complexes. Finally, we present evidence that activation of the mitogen-activated protein kinase (MAPK) cascade, the phosphatidylinositol 3-kinase as well as the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway is crucial for IL-6-induced migration. Selective activation of the JAK/STAT or the MAPK cascade by mutated receptor proteins shows a crucial role of IL-6-initiated SH2 domain-containing tyrosine phosphatase 2/MAPK activity for migration.

The secretion of acute phase proteins and inflammatory cytokines during Trypanosoma congolense infection is not affected by the absence of the TNF-α gene

Tumor necrosis factor-α (TNF-α) plays a role in the host’s defence against infections with African trypanosomes. It helps to control the blood stream form of the parasite and in Trypanosoma congolense infections, it also prolongs survival. The mechanisms by which this cytokine can influence parasitemia and survival are unknown. Therefore, the levels of acute phase proteins and other inflammatory cytokines were monitored in trypano-tolerant wild-type and TNF-α-deficient mice during a T. congolense infection. The titres of ceruloplasmin (CP), α1-acid glycoprotein (AGP) and serum amyloid P (SAP) increased and reached their peaks at 11 days post-infection, when the first peak of parasitemia was observed. No significant differences were observed in the acute phase protein profiles between the two mouse strains. Also the profiles of serum titres of IFN-γ, IL-1α, IL-6 and IL-10 were not significantly different. Our present results indicate that acute phase protein and cytokine responses can be induced in the absence of TNF-α during a T. congolense infection in mice, and that the susceptibility of the TNF-α-deficient mice is not due to modulation of expression of these molecules.

Allele frequencies of +874T --> A single nucleotide polymorphism at the first intron of IFN-gamma gene in Alzheimer's disease patients.

Inflammation seems to play a role in progressive neurological degenerative diseases such as Alzheimer's disease (AD). Local inflammatory processes can in fact give rise to direct neurotoxicity, interfere with beta-amyloid expression and metabolism, and maintain chronic, intracerebral, acute-phase protein secretion, in turn favoring the formation of beta-amyloid fibrils. Accordingly, recent studies show an increased risk for AD associated with certain polymorphisms in the genes encoding some proinflammatory cytokines and acute-phase proteins. To our knowledge, no data have yet been presented on the association between AD and polymorphisms of the interferon(IFN)-gamma gene, despite the pivotal role that IFN-gamma plays in immune-mediated inflammatory responses. Using the amplification refractory mutation system method, we evaluated the role of IFN-gamma in AD by analyzing, in 111 AD patients and 213 healthy controls, the prevalence of +874T --> A single nucleotide polymorphism (SNP), associated with different IFN-gamma production. Allele ApoE polymorphisms were assessed by the PCR-based method. No statistically significant differences were observed between AD patients and controls in the frequency of +874T --> A SNP, either on analyzing data as a whole or according to gender. As expected, the frequency of the well-known genetic risk factor APOE-epsilon4 allele was significantly increased in AD patients. However, analyzing the results according to the presence or absence of the APOE-epsilon4 allele, no interactions among ApoE, IFN-gamma alleles, gender or age at onset were observed. Our study does not support the hypothesis that IFN-gamma SNP may be a genetic risk factor for AD. Further analysis of recently described IFN-gamma polymorphisms may clarify the role, if any, of IFN-gamma alleles in AD.

Differential effects of pentoxifylline on the hepatic inflammatory response in porcine liver cell cultures: Increase in inducible nitric oxide synthase expression

Pentoxifylline (PTX) has been shown to exert hepatoprotective effects in various liver injury models. However, little information is available about the effect of PTX on the hepatic acute phase response. In the present study, the effect of PTX on a lipopolysaccharide (LPS)-induced acute phase response in primary porcine liver cell cultures was examined. During 72 hr of incubation with or without LPS, the ability of PTX to influence the secretion of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), acute phase proteins, and nitric oxide (NO) was assessed. PTX completely inhibited LPS-induced TNF-α production and attenuated IL-6 only after 48 hr of incubation. In contrast, PTX potentiated NO production and the expression of inducible nitric oxide synthase (iNOS) in hepatocytes after stimulation with LPS. The increased expression of iNOS and concurrent production of NO was also observed when liver cell cultures were incubated with dibutyryl cyclic adenosine monophosphate. No effect of PTX on acute phase protein secretion was observed during 72 hr of incubation. The present results show that PTX differentially affects the endotoxin-induced inflammatory response in primary porcine liver cell cultures by suppressing TNF-α and IL-6 while potentiating NO production.

Activation of sphingolipid turnover and chronic generation of ceramide and sphingosine in liver during aging

Aging leads to a decreased ability of liver to metabolize drugs and increased expression and secretion of acute phase proteins, such as serum amyloid A (SAA), C-reactive protein (CRP), and alpha-1-acid glycoprotein (AGP). This phenomenon resembles some aspects of the acute phase response of host to inflammation; however, the molecular basis for the similarity is unclear. Ceramide and sphingosine are second messenger mediators of cellular responses to stress and inflammation. In liver, they play important role in mediating acute phase responses to IL-β. In this study, we use HPLC and thin layer chromatography to evaluate the effects of aging on steady-state level of ceramide and sphingosine. We report that both lipids are elevated in liver of old (24 months) as compared to young (5 months) male Fisher 344 rats. To elucidate the mechanism(s) for ceramide elevation, we test the acidic(ASMase) and neutral sphingomyelinase (NSMase) in vitro using NBD-sphingomyelin as an exogenous substrate. SM synthase is also analyzed in vitro using NBD-ceramide and { 3H}-dipalmitoylphosphatidylcholine (DPPC) as exogenous substrates. In accordance with the increases in the mass of ceramide, the activity of acid and neutral SMase is elevated in old animals. Michaelis-Menten analysis of NSMase implies that the apparent activation of this enzyme is caused by an increase in the V max of the enzyme. In contrast, SM synthase activity is lower in old animals as compared to young ones. These results show that aging is accompanied by an elevation in SM turnover and a decrease in its synthesis, resulting in accumulation of pro-inflammatory and growth inhibitory second messenger ceramide. Ceramidase, the only enzyme leading to sphingosine generation, is also measured in vitro using NBD-ceramide as a substrate and liver homogenate as an enzyme source. Its activity is higher in the old rats, as compared to young ones. The acid and neutral forms of the enzyme are affected the most, while the changes in the alkaline enzyme are not significant. The increases in the basal levels of ceramide and sphingosine in old animals may contribute to the onset of inflammatory like state in liver during aging, exemplified by decrease P4502C11mRNA expression and chronic induction of acute phase protein expression.

Regulation of cytokine secretion and amyloid precursor protein processing by proinflammatory amyloid beta (A beta).

Neurodegenerative processes in Alzheimer's disease (AD) are thought to be driven, in part, by the deposition of amyloid beta (A beta), a 39-43-aminoacid peptide product resulting from an alternative cleavage of amyloid precursor protein (APP). In addition to its neurotoxic properties, A beta may influence neuropathology by stimulating glial cell cytokine and acute phase protein secretion in affected areas of the brain (e.g., cortex, hippocampus). Using an in vitro human astrocyte model (U-373 MG astrocytoma cells), the effects of A beta treatment on acute phase protein (APP and alpha-1-antichymotrypsin [alpha 1-ACT]) and interleukin-8 (IL-8) were examined. U-373 MG cells secreted increased levels of alpha 1-ACT and neurotrophic/neuroprotective alpha-cleaved APP (alpha APP) after exposure to interleukin-1 beta (IL-1 beta) for 24 hours. A beta treatment resulted in a similar, but modest increase in alpha 1-ACT secretion, a two- to threefold stimulation of IL-8 production, and, conversely, a profound reduction in the levels of secreted alpha APPs. A beta inhibited alpha APP secretion by U-373 MG cells in a concentration- and conformation-dependent manner. Moreover, the reduction in alpha APP secretion was accompanied by an increase in cell-associated APP. Another proinflammatory amyloidogenic peptide, human amylin, similarly affected APP processing in U-373 astrocytoma cells. These data suggest that A beta may contribute to Alzheimer's-associated neuropathology by lowering the production of neuroprotective/neurotrophic alpha APPs. Moreover, the concomitant increase in cell-associated APP may provide increased substrate for the generation of amyloidogenic peptides within astrocytes.

Hematopoietic, immunomodulatory and epithelial effects of interleukin-11.

Interleukin 11 (IL-11) is a pleiotropic cytokine with biological activities on many different cell types. Recombinant human IL-11 (rhIL-11) is produced by recombinant DNA technology in Escherichia coli. Both in vitro and in vivo, rhIL-11 has shown effects on multiple hematopoietic cell types. Its predominant in vivo hematopoietic activity is the stimulation of peripheral platelet counts in both normal and myelosuppressed animals. This activity is mediated through effects on both early and late progenitor cells to stimulate megakaryocyte differentiation and maturation. rhIL-11 has been approved for the treatment of chemotherapy-induced thrombocytopenia. The hematopoietic effects of rhIL-11 are most likely direct effects on progenitor cells and megakaryocytes in combination with other cytokines or growth factors. rhIL-11 also induces secretion of acute phase proteins (ferritin, haptoglobin, C-reactive protein, and fibrinogen) from the liver. The induction of heme oxidase and inhibition of several P450 oxidases have been reported from in vitro studies. In vivo, rhIL-11 treatment decreases sodium excretion by the kidney by an unknown mechanism and induces hemodilution. rhIL-11 also exhibits anti-inflammatory effects in a variety of animal models of acute and chronic inflammation, including inflammatory bowel disease, inflammatory skin disease, autoimmune joint disease, and various infection-endotoxemia syndromes. rhIL-11 has trophic effects on non-transformed intestinal epithelium under conditions of mucosal damage. The mechanism of the anti-inflammatory activity of rhIL-11 has been extensively studied. rhIL-11 directly affects macrophage and T cell effector function. rhIL-11 inhibits tumor necrosis factor-alpha (TNF alpha), interleukin 1beta (IL-1beta), interleukin 12 (IL-12), interleukin 6 (IL-6), and nitric oxide (NO) production from activated macrophages in vitro. The inhibition of cytokine production was associated with inhibition of nuclear translocation of the transcription factor, nuclear factor kappa B (NF-kappaB). The block to NF-kappaB nuclear translocation correlates with the ability of rhIL-11 to maintain or enhance production of the inhibitors of NF-kappaB, IkappaB-alpha and IkappaB-beta. In addition to effects on macrophages, rhIL-11 also reduces CD4+ T cell production of Th1 cytokines, such as IFN gamma induced by IL-12, while enhancing Th2 cytokine production. rhIL-11 also blocks IFN gamma production in vivo. The molecular effects of rhIL-11 have also been studied in a clinical trial. Molecular analysis of skin biopsies of patients with psoriasis before and during rhIL-11 treatment demonstrates a decrease in mRNA levels of TNF alpha, IFN gamma and iNOS. These activities suggest that in addition to its thrombopoietic clinical use, rhIL-11 may also be valuable in the treatment of inflammatory diseases. The clinical utility of the anti-inflammatory properties of rhIL-11 is being investigated in patients with Crohn's disease, psoriasis and rheumatoid arthritis. These diseases are believed to be initiated and maintained by activated CD4+ Th1 cells in conjunction with activated macrophages.

Stress activated protein kinase p38 is involved in IL-6 induced transcriptional activation of STAT3.

The pleiotropic cytokine interleukin-6 (IL-6) induces acute phase protein expression in HepG2 human hepatoma cells and promotes the growth of mouse B9 hybridoma. The signaling cascades leading to these biological functions are only partially known. We analysed the involvement of MAPK homologues in IL-6 transduction pathways and found that interleukin-6 triggered activation of p38 stress-activated protein kinase (p38) but not of jun kinase. p38 activity was required for biological functions including acute phase protein secretion from HepG2 hepatoma and proliferation of B9 hybridoma cells. Using a reporter gene construct containing a 190 bp promoter fragment of the acute phase protein haptoglobin we found that p38 is involved in transcriptional activation of the haptoglobin promoter by STAT3 but not by NF-IL6. Thus, we present evidence for a role of p38 in IL-6 induced functions and a possible cross-talk between this MAPK homologue and the STAT pathway.