Higher Production Of Proinflammatory Cytokines Research Articles

APOE genotype-specific differences in the innate immune response

Apolipoprotein-E protein is an endogenous immunomodulatory agent that affects both the innate and the adaptive immune responses. Since individuals with the APOE4 gene demonstrate worsened pathology and poorer outcomes in many neurological disorders, we examined isoform-specific differences in the response of microglia, the primary cellular component of the brain's innate immune response, in detail. Our data demonstrate that microglia derived from APOE4/ 4 targeted replacement mice demonstrate a pro-inflammatory phenotype that includes altered cell morphology, increased NO production associated with increased NOS2 mRNA levels, and higher pro-inflammatory cytokine production (TNFα, IL-6, IL12p40) compared to microglia derived from APOE3/ 3 targeted replacement mice. The effect is gene dose-dependent and increases with the number of APOE4 gene alleles. The APOE genotype-specific immune profile observed in the microglial immune response is also observed in the cortex of aged APOE3/ 3 and APOE4/ 4 mice treated with lipopolysacchride (LPS) and in peripheral (peritoneal) macrophages. To determine if APOE4's action resulted from an isoform-specific difference in effective levels of the apolipoproteins, we generated mice expressing only a single allele of APOE3. Immune-stimulated macrophages from APOE3/ 0 mice demonstrated an increased inflammatory response compared to APOE3/ 3 mice, but less than in APOE4/ 4 mice. These data suggest that inhibition of inflammation depends upon the dose of apoE3 protein available and that apoE4 protein may alter inflammation partly by dose effects and partly by being qualitatively different than apoE3. Overall, these data emphasize the important role of apolipoprotein E and of the APOE genotype on the immune responses that are evident in most, if not all, neurological disease.

Cytokine gene polymorphisms in acquired bone marrow failure

Some acquired aplastic anemia (AA) results from immune-mediated destruction of hematopoietic stem cells. Cytokine gene polymorphisms are implicated in controlling cytokine production and increasing the susceptibility to some autoimmune diseases. We characterized the IL-6/-174, TNF-alpha/-308, IL-10/-1082, IFN-gamma/+874, TGFbeta1/-509 single nucleotide polymorphisms (SNP's) and the IL1-RA second intron variable number tandem repeat (VNTR) alleles in 73 patients with AA and compared the frequency of genotypes to established control populations. We found that some patients with acquired AA have polymorphisms which are linked to high production of proinflammatory cytokines, particularly TNF-alpha and IFN-gamma.

Trypanosoma cruzi: Populations bearing opposite virulence induce differential expansion of circulating CD3+CD4−CD8− T cells and cytokine serum levels in young and adult rats

The JG strain is the least virulent while the CL-Brener clone is one of the most virulent Trypanosoma cruzi populations in young rats. In this study, we determined that the parasitemia peak values in CL-Brener clone-infected adult rats were 50-fold lower than in young rats and that mortality was null as compared to 45% death in young rats. Low parasitemia, milder and sustained myocarditis and myositis characterized JG infections. CL-Brener clone caused a significantly higher production of pro-inflammatory cytokines and higher expansion of CD3+CD4−CD8−, double-negative (DN) T cells, during the acute phase in both adult and young rats. DN T cell frequencies correlated with IFN-γ levels. These findings may explain the higher inflammation and fast acute phase resolution in CL-Brener infection. In young rats, IL-10 levels were similar in both infections. The IL-10/IFN-γ ratio was higher in JG acute infection in accordance with the milder inflammation and parasite persistence leading to a chronic phase. In conclusion, virulence and pathogenicity depend on T. cruzi ability to induce expansion of DN T cells and production of specific cytokines.

Smad3 Deficiency in Mast Cells Provides Efficient Host Protection against Acute Septic Peritonitis

Mast cells play an important role in innate immunity as well as in allergic reaction. However, regulatory mechanisms underlying mast cell-mediated innate immune responses remain largely unknown. Here we determined whether Smad3, a major signal transducer of TGF-beta, regulates innate immune response by mast cells against Gram-negative bacteria. Bone marrow-derived mast cells (BMMC) obtained from Smad3 null mutant mice showed augmented capacity to produce proinflammatory cytokines upon stimulation with a Gram-negative bacteria-associated product, LPS. In acute septic peritonitis model induced by cecal ligation and puncture, mast cell-deficient W/W(v) mice reconstituted with Smad3 null BMMC had significantly higher survival rate than W/W(v) mice reconstituted with wild-type BMMC, which was associated with higher production of proinflammatory cytokines in the peritoneal cavity. These in vitro and in vivo results suggest that Smad3 in mast cells functions as inhibitory for mast cell-mediated innate immune response against Gram-negative bacteria. Suppression of Smad3 expression in mast cells may thus have therapeutic potential for Gram-negative bacterial infection such as acute septic peritonitis by augmenting innate immune responses of mast cells.

Tumor Necrosis Factor-Alpha and Interleukin-6 Promoter Gene Polymorphisms in Acquired Bone Marrow Failure Syndromes.

Some acquired aplastic anemia (AA) results from immune mediated destruction of the hematopoetic stem cells. Immunosuppressive therapy is successful in majority of AA patients and substantial laboratory data are consistent with an immune pathophysiology. Substantial research has implicated differences in cytokine gene expression profiles and polymorphisms in the genes controlling cytokine expression in other autoimmune diseases such as lupus erythematosus and rheumatoid arthritis. Interlukin-6 (IL-6) and tumor necrosis alpha (TNF-α) are two potent pro-inflammatory cytokines that have implicated in a variety of immune-mediated conditions. TNF-α results in Fas expression and apoptosis of in progenitor cells and the TNF-alpha −308 allele was significantly associated with SLE in Caucasians. Levels both IL-6 and TNF-α have been reported elevated in AA patients. In the promoter region of the IL-6 gene, at position −174, exists a single nucleotide polymorphism (G/C) in close proximity to a glucocorticoid-responsive element; patients homozygous for the G allele have circulating IL-6 concentrations close to twice as high as those homozygous for the C allele. The TNF-α gene, located in the class III region of the major histocompatibility complex (MHC), has a polymorphism at position −308, TNF2, where the presence of adenine instead of guanine is associated with higher cytokine production. In our study, we characterized the IL-6/−174 and the TNF-α/−308 polymorphisms in patients with acquired bone marrow failure syndromes to assess if the higher production genotypes were more prevalent that in established controls. We identified seventy-three patients (age range 3–84) treated at our institution for AA. Following an established protocol for the identification of single nucleotide polymorphisms, genomic DNA was amplified with primers designed for the promoter regions of the IL-6 and TNF-α genes where intentional mismatches were inserted at 1–3 nucleotide positions to incorporate a restriction site for endonucleases. The amplicons were digested with four restriction endonucleases (BlsI, BsaBI, EcoNI, RsaI) then analyzed by electrophoresis in 3% agarose gels. The resulting fragments allowed for the identification and confirmation of the specific nucleotide polymorphism at the 174 and 308 position of the IL-6 and TNF-α promoter, respectively. The frequency of the high cytokine producing genotypes in the cohort was compared to established controls and the statistical significance determined by the two-tailed Fishers exact test. The GG genotype of the IL-6/−174 polymorphism was present in 32 of 73 (44%) of affected patients versus 80 of 250 (32%) historical controls of the control population (p =0.0698) while the AA genotype of the TNF-α/−308 polymorphism was found in 8 of 73 AA patients (11%) and in only 9 of 354 historical controls (2.5%) (p= 0.0034). Three of 73 AA patients had both gene polymophisms p<0.0001. Two patients' BM was cultured and ELISA performed for TNF-α as part of a larger study, which included 20 normal controls and 30 patients with marrow failure; both of these patients demonstrated significant elevations in TNF-α. In conclusion, we showed that some patients with acquired bone marrow failure have cytokine gene polymophisms which are linked to high production of pro-inflammatory cytokines, particularly TNF-α.

Inflammatory response in the elderly.

During ageing there may be the onset of a chronic inflammatory state. This review examines the underlying causes of this phenomenon and the role that genotype plays in its intensity. There are predisposing factors for the chronic inflammation that occurs during ageing. These include increased oxidative stress, a decrease in ovarian function, a decrease in stress-induced glucocorticoid sensitivity of pro-inflammatory cytokine production in men, and an increased incidence of asymptomatic bacteriuria. Obesity induces chronic inflammation. Inflammation is a key factor in the progressive loss of lean tissue and impaired immune function observed in ageing. Polymorphisms in the promoter regions of pro- and anti-inflammatory cytokine genes influence the level of cytokine production and the ageing process. Thus, a genotype for high pro-inflammatory cytokine production results in high cytokine production and may accelerate the rate of tissue loss. Conversely, polymorphisms in the genes for anti-inflammatory cytokines may result in a slowing of tissue loss. In the healthy aged male population, the former polymorphisms are under-represented and the latter over-represented, indicating a genetically determined survival advantage in maintaining inflammation at a low level. Nutrients with anti-inflammatory properties, such as vitamin E and n-3 polyunsaturated fatty acid, may reduce the level of chronic inflammation and thereby ameliorate tissue and functional loss during ageing. New evidence suggests that, for the latter nutrient, gene-nutrient interactions occur that alter the effectiveness of dietary therapy. Ageing is associated with increased levels of chronic inflammation. This plays a major role in the decline in immune function and lean body mass. Anti-inflammatory nutrient therapy may slow the rate of decline. The pro- and anti-inflammatory cytokine genotype is linked negatively and positively, respectively, with life-span, because of its influence on inflammation.

CD14 Receptor Expression and Lipopolysaccharide-Induced Cytokine Production in Preterm and Term Neonates

CD14 expression and the capacity of mononuclear cells (MC) from preterm and term neonates to secrete the proinflammatory cytokines interleukin (IL) 1β, tumor necrosis factor α and IL-6 in response to lipopolysaccharide (LPS) was investigated and compared to that of adults. MC were incubated with various doses of LPS, and the cytokine level in the supernatants was tested. CD14 receptors on MC and the intensity of their expression were analyzed. MC of preterm and term neonates and adults responded to LPS with low, medium and high proinflammatory cytokine production, respectively. CD14 expression was lowest in preterm infants, intermediate in term infants and highest in adults. The difference between term and preterm neonates for both parameters was significant. The results suggest a possible correlation between the lower expression of CD14 receptor on neonatal cells and the reduced secretion of proinflammatory cytokines by these cells. This decreased production may possibly contribute to the low ability of neonates to develop fever.

Maturation of dendritic cells by recombinant human CD40L-trimer leads to a homogeneous cell population with enhanced surface marker expression and increased cytokine production.

Dendritic cells (DC) have been shown to be potent inducers of specific cytotoxic T-cell responses both in vivo and in vitro. Furthermore, exposure to cytokines such as tumour necrosis factor (TNF)-alpha or CD40 triggering changes DC phenotype and cytokine production and may enhance the T-cell activating capacity of the DC. We studied DC phenotype and cytokine production as well as the T-cell proliferation and cytotoxic T lympocyte (CTL) activation induced by DC generated in vitro. In addition, the effect of exposure to recombinant human CD40L-trimer (huCD40LT) on these parameters was investigated. Effective differentiation of monocytes derived from freshly isolated peripheral blood mononuclear cells (PBMC) was obtained with granulocyte macrophage-colony stimulating factor (GM-CSF) and interleukin (IL)-4. The DC expression of human leucocyte antigen (HLA) molecules, CD80, CD83, and CD86 was markedly enhanced by exposure to huCD40LT even compared to TNF-alpha exposure. Only a moderate cytokine production was observed initially, while TNF-alpha addition or CD40 triggering, especially, induced enhanced production of IL-6 and IL-12 p40. Surprisingly, comparable induction of T-cell proliferation by a DC allostimulus or through the presentation of PPD, and influenza M1-peptide specific CTL activity was obtained with nonmaturated (CD83-) and maturated (CD83+) DC. In conclusion, a final maturation of monocyte-derived DC through huCD40LT resulted in a highly homogeneous cell population with enhanced surface marker expression and high production of pro-inflammatory cytokines. In addition, the induction of responses to allo or recall antigens presented by huCD40LT maturated DC was comparable to the responses obtained with the DC maturated through TNF-alpha exposure.

Expression of interleukin-18 and its monokine-directed function in rheumatoid arthritis.

To investigate the expression of and monokine induction by interleukin 18 (IL-18; also called interferon-gamma inducing factor, IGIF), in peripheral blood mononuclear cells (PBMC) and cultured synoviocytes from rheumatoid arthritis (RA) patients. We carried out IL-18 Western blotting and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) of cytokines in PBMC [IL-18, IL-1beta and tumour necrosis factor alpha (TNF-alpha)] and long-term cultured fibroblast-like synoviocytes (FLS) [IL-18, IL-1beta, TNF-alpha, IL-6, interferon gamma (INF-gamma) and [granulocyte-macrophage colony stimulating factor (GM-CSF)] from RA patients and controls. FLS were isolated from RA synovial membranes (FLS(SM)) and RA synovial fluids (FLS(SF)), osteoarthritis (OA) FLS(SM) and FLS(SF) from spondyloarthropathy patients. FLS were characterized by fluorescence-activated cell sorting of the FLS. PBMC and FLS from RA patients and control subjects were stimulated with recombinant human IL-18 and IL-1beta (rHuIL-18/rHuIL-1beta), and TNF-alpha, IL-1beta and MMP-1 were measured by ELISA in supernatants. Constitutive expression of IL-18 mRNA was significantly reduced whereas that of TNF-alpha was enhanced in RA PBMC. Persistent low expression of IL-18, TNF-alpha, GM-CSF and IL-1beta was observed in RA and OA FLS(SM) as well as spondyloarthropathy FLS(SF). In contrast, high constitutive expression of IL-18 in FLS (CD90/Thy-1- and CD54-positive, CD14- and CD86-negative), accompanied by persistent high levels of TNF-alpha, GM-CSF and IL-1beta expression, was restricted to synovial fluid-derived FLS obtained from RA patients. IFN-gamma was not detectable in any culture, but IL-6 mRNA was equally expressed in all FLS cultures. rHuIL-18 was effective in stimulating TNF-alpha and IL-1beta secretion in PBMC from healthy controls, but failed to stimulate TNF-alpha and IL-1beta secretion from PBMC in 11 of 12 RA patients, and all FLS cultures. rHu-IL-1beta, but not rHu-IL-18, induced interstitial collagenase (MMP-1) in FLS. Persistent high production of proinflammatory cytokines in RA-FLS(SF) may be relevant for chronic progression in RA synovitis. Levels of TNF-alpha and IL-1beta expression are increased in RA-FLS(SF), but are independent of IL-18. The pathological function of enhanced IL-18 expression in RA-FLS(SF) remains to be further elucidated.