Serum IL-1beta, IL-2, and IL-6 in insulin-dependent diabetic children

Insulin-dependent diabetes mellitus (IDDM) is a chronic disease characterized by T-cell-dependent autoimmune destruction of the insulin-producing beta cells in the pancreatic islets of Langerhans, resulting in an absolute lack of insulin. T cells are activated in response to islet-dominant autoantigens, the result being the development of IDDM. Insulin is one of the islet autoantigens responsible for the activation of T-lymphocyte functions, inflammatory cytokine production, and development of IDDM. The aim of this study was to investigate serum concentrations of interleukin (IL)-1beta, IL-2, IL-6, and tumor necrosis factor (TNF)-alpha in children IDDM. The study population consisted of 27 children with IDDM and 25 healthy controls. Children with IDDM were divided into three subgroups: (1) previously diagnosed patients (long standing IDDM) (n : 15), (2) newly diagnosed patients with diabetic ketoacidosis (before treatment) (n : 12), and (3) newly diagnosed patients with diabetic ketoacidosis (after treatment for two weeks) (n : 12). In all stages of diabetes higher levels of IL-1beta and TNF-alpha and lower levels of IL-2 and IL-6 were detected. Our data about elevated serum IL-1beta, TNF-alpha and decreased IL-2, IL-6 levels in newly diagnosed IDDM patients in comparison with longer standing cases supports an activation of systemic inflammatory process during early phases of IDDM which may be indicative of an ongoing beta-cell destruction. Persistence of significant difference between the cases with IDDM monitored for a long time and controls in terms of IL-1beta, IL-2, IL-6, and TNF-alpha supports continuous activation during the late stages of diabetes.     

Inhibition of IL-6, TNF-alpha, and cyclooxygenase-2 protein expression by prostaglandin E2-induced IL-10 in bone marrow-derived dendritic cells

Several endogenously produced mediators, including cytokines such as IL-6, IL-10, and TNF-alpha and prostanoids such as prostaglandin E(2) (PGE(2)), regulate dendritic cell (DC) function and contribute to immune homeostasis. In this study, we report that exogenous PGE(2) enhances the production of IL-10 from bone marrow-derived DC (BM-DC). IL-6, but not TNF-alpha, release is enhanced by PGE(2) in the presence of anti-IL-10, suggesting that endogenous IL-10 masks PGE(2)-induced IL-6. Furthermore, both exogenous IL-10 and PGE(2) inhibit LPS-induced IL-6 and TNF-alpha, whereas selective inhibition of cyclooxygenase-2 (COX-2) or addition of anti-IL-10 causes the reverse effects. Exogenous IL-10, but not IL-6, dose-dependently suppresses COX-2 protein expression and PGE(2) production, and TNF-alpha does not reverse this effect. In contrast, anti-IL-10 up-regulates prostanoid production by LPS-stimulated BM-DC. Taken together, our results show that in response to PGE(2), BM-DC produce IL-10, which in turn down-regulates their own production of IL-6-, TNF-alpha-, and COX-2-derived prostanoids, and plays crucial roles in determining the BM-DC pro-inflammatory phenotype.     

Phagocytosis of N-acetyl-D-glucosamine particles, a Th1 adjuvant, by RAW 264.7 cells results in MAPK activation and TNF-alpha, but not IL-10, production

A practical and highly effective Th1 adjuvant should induce Th1 cytokines (IL-12, IL-18, and TNF-alpha) but not the Th2 cytokine IL-10, an inhibitor of Th1 responses. In this study, phagocytosis of N-acetyl-d-glucosamine polymer (chitin) particles by RAW 264.7 cells, a murine macrophage-like cell line, resulted in phosphorylation of MAPK (p38, Erk 1/2, and JNK), and production of relatively high levels of TNF-alpha and COX-2 with increased PGE(2) release. Similar results were observed in response to oligonucleotides with CpG motifs, mycobacterial components and endotoxin. However, these bacterial components also induced a large amount of IL-10. Chitin particles, in contrast, failed to induce detectable levels of IL-10, although the production of high levels of PGE(2) and TNF-alpha and the activation of MAPK's are potentially positive signals for IL-10 production. Thus, our results indicate that chitin particles act as a unique Th1 adjuvant for macrophages without inducing increased production of IL-10.     

Effects of TGF-beta, TNF-alpha, IL-beta and IL-6 alone or in combination, and tyrosine kinase inhibitor on cyclooxygenase expression, prostaglandin E2 production and bone resorption in mouse calvarial bone cells

Cyclooxygenase-2 (COX-2) and tyrosine kinase, which are involved in the biosynthesis of prostaglandin E(2) (PGE(2)) in mouse calvarial osteoblasts, are stimulated by cytokine interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and/or interleukin-6 (IL-6). IL-1beta and IL-6 and, to a lesser extent, TNF-alpha, enhances COX-2 mRNA levels in calvarial osteoblasts. Simultaneous treatment with IL-6 and IL-1beta and TNF-alpha resulted in enhanced COX-2 mRNA levels accompanied by the cooperative stimulation of PGE(2) biosynthesis compared to cells treated with IL-1beta or TNF-alpha or IL-6 alone. In contrast, the presence of TGF-beta reduced COX-2 mRNA level, PGE(2) biosynthesis and bone resorption induced by IL-1beta, TNF-alpha, IL-6 or a combination thereof. However, neither IL-1beta, TNF-alpha, IL-6 nor a combination of IL-1beta, TNF-alpha, IL-6 enhanced COX-1 mRNA levels in calvarial osteoblasts. A novel Src tyrosine kinase inhibitor, Herbimycin A (HERB), reduced COX-2 mRNA levels as well as PGE(2) production induced by IL-1beta, TNF-alpha and IL-6 or a combination of IL-1beta, TNF-alpha, IL-6, whereas COX-1 mRNA levels remained unaffected. Finally, HERB was found to inhibit in vitro bone resorption. These results indicate that the cooperative effects of IL-beta, TNF-alpha, IL-6 on PGE(2) production are due to the enhanced expression of the COX-2 gene and that tyrosine kinase(s) are involved in COX-2 signal transduction in mouse calvarial osteoblasts. Thus, the Src family of kinase inhibitors may be useful in treating diseases associated with elevated bone loss.     

Prostaglandin E(2) receptors, EP2 and EP4, differentially modulate TNF-alpha and IL-6 production induced by lipopolysaccharide in mouse peritoneal neutrophils

The expression and function of prostaglandin (PG) E(2) receptors were examined in mouse neutrophils exudated into the peritoneal cavity by casein treatment. Expressions of the EP2 and EP4 receptors were detected in neutrophils by Northern blot, but those of EP1 and EP3 receptors were not detected by RT-PCR. EP2-selective agonist, ONO-AE1-259, and EP4-selective agonist, ONO-AE1-329, stimulated cAMP formation in the cells. PGE(2) affected the TNF-alpha and IL-6 production in lipopolysaccharide (LPS)-treated neutrophils; it suppressed the TNF-alpha production and enhanced the IL-6 production. The PGE(2) effects were mimicked by dibutyryl cAMP. This is the first study of the enhancement of IL-6 production by cAMP-elevating reagents in neutrophils. Using neutrophils from EP2- and EP4-deficient mice in combination with EP2- and EP4-selective agonists, it was found that the augmentation of IL-6 was mediated mainly by the EP2 receptor and the suppression of TNF-alpha by the EP4 receptor and partially by the EP2 receptor. These findings indicate that casein-induced peritoneal neutrophils express Gs-coupled PGE(2) receptors, EP2 and EP4, which might differentially regulate the LPS-induced production of TNF-alpha and IL-6.     

PGE2 exerts its effect on the LPS-induced release of TNF-alpha, ET-1, IL-1alpha, IL-6 and IL-10 via the EP2 and EP4 receptor in rat liver macrophages

Lipopolysaccharide (LPS) induces a release of tumor necrosis factor (TNF)-alpha, endothelin (ET)-1, interleukin (IL)-1alpha, IL-6 and IL-10 in rat liver macrophages (Kupffer cells). Prostaglandin (PG)E2 inhibits the release of the fibrogenic mediators TNF-alpha, ET-1 and IL-1alpha, and enhances the release of the anti-fibrogenic mediators IL-6 and IL-10. This effect of PGE2 is mimicked by specific agonists for the PGE2 receptors EP2 and EP4; whereas, agonists for the PGE2 receptors EP1 and EP3 are inactive. Rat liver macrophages express mRNA encoding the PGE2 receptors EP2 and EP4 but not the PGE2 receptors EP1 and EP3. These data suggest that PGE2 exerts its anti-fibrogenic effect through the EP2 and EP4 receptor by inhibiting the release of the fibrogenic mediators TNF-alpha, ET-1 and IL-1alpha, and by enhancing the release of the anti-fibrogenic mediators IL-6 and IL-10 in liver macrophages.     

Serum IL-1beta,sIL-2R,IL-6, IL-8 and TNF-alpha in schizophrenic patients,relation with symptomatology and responsiveness to risperidone treatment.

Activation of the inflammatory response system and varied levels of cytokines in acute schizophrenia have been suggested by recent studies. Psychopharmacologic agents can differentially effect cytokine production, which suggests that therapeutic function of neuroleptics may involve immunomodulation. The present study was carried out to examine: (i) serum concentrations of interleukin (IL)-1beta, soluble interleukin-2 receptor (sIL-2R), IL-6, IL-8 and tumour necrosis factor (TNF)-alpha in schizophrenic patients; (ii) their relation with psychopathological assessment; and (iii) the relation of the initial cytokine levels with responsiveness to risperidone therapy. Thirty-four drug-free schizophrenic patients with acute exacerbation and 23 age- and gender-matched healthy controls were recruited for this study. Psychopathological assessments at admission and throughout risperidone treatment for 60 days were recorded. Serum cytokine concentrations were determined with chemilumunescence assays. According to our results, serum IL-1beta, sIL-2R, IL-6, IL-8 and TNF-alpha concentrations adjusted for age, gender, body mass index and smoking were no different in patients with schizophrenia and controls and among subtypes of schizophrenia. However, the initial TNF-alpha concentrations had a significant effect on Brief Psychiatric Rating Scale and Scale Assessment of Positive Symptoms scores. The initial cytokine concentrations of the patients responsive to risperidone were not significantly different from those of non-responsive patients. The present study demonstrates that plasma levels of IL-1beta, sIL-2R, IL-6, IL-8 and TNF-alpha adjusted for confounding factors are not altered in drug-free schizophrenic patients at acute exacerbation. We suggest that, if cytokine production is altered in schizophrenia, these alterations may not be detectable in systemic circulation. According to our results, the therapeutic effect of risperidone is not related to basal levels of the aforementioned cytokines. However, serum TNF-alpha may contribute to symptomatology in schizophrenia     

Endotoxin tolerance in rats: expression of TNF-alpha, IL-6, IL-10, VCAM-1 AND HSP 70 in lung and liver during endotoxin shock.

Endotoxin can induce a state of tolerance against its own pathological effects, commonly referred to as endotoxin tolerance. This phenomenon has been found to be associated with reduced serum levels of cytokines such as TNF-alpha, IL-1, IL-6 and IL-10. In the present study the expression of TNF-alpha, IL-6, IL-10, the adhesion molecule VCAM-1 and the heat shock protein 70 was determined in vivo in lung and liver of LPS-tolerant and naive rats by means of semiquantitative RT-PCR after i.v. LPS injection. TNFalpha, IL-6, IL-10, HSP 70 and VCAM-1 were induced in lung and liver after LPS injection. In liver and lung of endotoxin-tolerant rats TNF-alpha and IL-6 were induced to a lower degree after LPS treatment when compared to non-tolerant controls. The LPS-induced IL-10 expression was also slightly attenuated in the lung of tolerant rats, but in the liver no differences between tolerant and non-tolerant animals were observed. HSP 70 and VCAM-1 were expressed after systemic LPS treatment in liver and lung. The degree of induction, however, was the same in tolerant and untreated controls. The presented data show that endotoxin tolerance is reflected by a reduced cytokine expression in lung and liver in vivo. On the other hand, levels of expression of the adhesion molecule VCAM-1 and the stress protein HSP 70 do not appear to be changed by endotoxin tolerance.     

Microvascular abnormalities in capillaroscopy correlate with higher serum IL-18 and sE-selectin levels in patients with type 1 diabetes complicated by microangiopathy

Microvascular abnormalities are one of the most important causes of persistent diabetic complications. The aim of this study was to compare microvascular changes examined by nailfold capillaroscopy with serum concentrations of soluble E-selectin (sE-selectin) and IL-18 in type 1 diabetic patients with and without microangiopathy. Serum levels of sE-selectin and IL-18 were determined by an enzyme-linked immunosorbent assay in 106 patients with type 1 diabetes and in 40 healthy controls. All diabetic patients were evaluated by extensive clinical, laboratory and capillaroscopic studies. Morphological changes were observed by nailfold capillaroscopy in 86 out of 106 (81%) diabetic patients. Severe capillaroscopic changes were seen in 32 out of 54 (59%) patients with microangiopathy, but in only seven out of 52 (13%) patients without microangiopathy. Higher serum levels of sE-selectin (p < 0.001) and IL-18 (p < 0.05) were demonstrated in diabetic patients compared to controls. Significant differences of sE-selectin (p , 0.001) and IL-18 (p < 0.01) serum concentrations were observed between diabetic patients with microangiopathy and controls. Moreover, comparison between patients with and without microangiopathic complications showed a significantly higher capillaroscopic score and sE-selectin serum concentration in the group with microangiopathy (p < 0.001). Furthermore, diabetic patients with severe microvascular changes in capillaroscopy showed significantly higher IL-18 (p < 0.001) and sE-selectin (p < 0.05) serum levels than subgroups without changes or with mild abnormalities. Our findings suggest that abnormalities in nailfold capillaroscopy may reflect the extent of microvascular involvement and are associated with higher sE-selectin and IL-18 serum levels, as well as with microangiopathic complications in diabetic patients.     

Analysis of serum and cerebrospinal fluid cytokine levels in subacute sclerosing panencephalitis in Papua New Guinea

BACKGROUND: Subacute sclerosing panencephalitis (SSPE) is a rare progressive inflammatory disease characterized by the persistent infection of the brain by the measles virus. However, the immunological pathophysiology of SSPE is still unclear. METHODS: We measured the concentrations of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin-2 (IL-2), IL-4, IL-6, IL-10, and soluble TNF receptor 1 (sTNFR1) in the serum and cerebrospinal fluid (CSF) of 23 patients with SSPE in Papua New Guinea (PNG), a country with a high incidence of SSPE, and Japanese controls by cytometric bead array or ELISA. RESULTS: The serum IL-6 and IL-10 levels of SSPE patients were significantly higher than those of controls (p=0.0075, and p=0.0019, respectively). The serum IL-6 and IL-10 levels of SSPE patients with fever were significantly higher than those without fever (p=0.0107, and p=0.0006, respectively). The CSF IL-6 levels of SSPE patients were significantly higher than those of controls (p=0.0218). The CSF IL-6 levels of SSPE patients with myoclonic jerks were significantly higher than those without myoclonic jerks (p=0.0189). There were no differences in serum IFN-gamma, TNF-alpha, IL-2, IL-4, and sTNFR1, or CSF IFN-gamma, TNF-alpha, IL-2, IL-4, IL-10, and sTNFR1 levels between the affected patients and controls. CONCLUSION: Our present study suggests that serum IL-6 and IL-10 levels are related to fever, and the CSF IL-6 level, myoclonic jerks, in SSPE patients in PNG.     

Hypoglycaemia downregulates endotoxin-induced production of tumour necrosis factor-alpha,but does not affect IL-1beta,IL-6, or IL-10

The aim of the present study was to investigate the effect of hypoglycaemia on the production capacity of the proinflammatory cytokines tumour necrosis factor-alpha (TNFalpha) and interleukin-1beta (IL-1beta) in subjects with and without diabetes. Hyperinsulinaemic (360 pmolm(-2) x min(-1)) stepped hypoglycaemic (5.0-3.5-2.5 mmoll(-1)) glucose clamps were performed in eight diabetic patients and in six non-diabetic subjects, and hyperinsulinaemic normoglycaemia (5.0 mmoll(-1)) control experiments were performed in four non-diabetic subjects. Circulating levels of cytokines and endotoxin-induced production of TNFalpha, IL-1beta, IL-6, and IL-10 were assessed. The effects of insulin and adrenaline were measured in separate in vitro experiments. In non-diabetic subjects, hypoglycaemia downregulated the production capacity of TNFalpha in a concentration-dependent fashion (P=0.007), but not of IL-1beta, IL-6, or IL-10. Compared to controls, the production capacity of TNFalpha in diabetic patients was already suppressed at normoglycaemia (P=0.02) and only fell in response to hypoglycaemic nadir (P=0.04). The downregulation of TNFalpha could not be explained by increased insulin or adrenaline levels. We conclude that hypoglycaemia specifically downregulates TNFalpha production capacity. Diabetic patients already have a suppressed TNFalpha production capacity at non-hypoglycaemic levels.     

Cytokine responses of human gingival fibroblasts to Actinobacillus actinomycetemcomitans cytolethal distending toxin

Actinobacillus actinomycetemcomitans is implicated in the pathogenesis of localized aggressive periodontitis, and has the capacity to express a cytolethal distending toxin (Cdt). Gingival fibroblasts (GF) are resident cells of the periodontium, which can express several osteolytic cytokines. The aims of this study were a) to investigate the role of Cdt in A. actinomycetemcomitans-induced expression of osteolytic cytokines and their cognate receptors in GF and b) to determine if the previously demonstrated induction of receptor activator of NFkappaB ligand (RANKL) by A. actinomycetemcomitans is mediated by these pro-inflammatory cytokines or by prostaglandin E(2) (PGE(2)). A. actinomycetemcomitans clearly induced interleukin (IL)-6, IL-1beta, and to a minimal extent, tumor necrosis factor (TNF)-alpha mRNA expression. At the protein level, IL-6 but not IL-1beta or TNF-alpha expression was stimulated. The mRNA expression of the different receptor subtypes recognizing IL-6, IL-1beta and TNF-alpha was not affected. A cdt-knockout strain of A. actinomycetemcomitans had similar effects on cytokine and cytokine receptor mRNA expression, compared to its parental wild-type strain. Purified Cdt stimulated IL-6, but not IL-1beta or TNF-alpha protein biosynthesis. Antibodies neutralizing IL-6, IL-1 or TNF-alpha, and the PGE(2) synthesis inhibitor indomethacin, did not affect A. actinomycetemcomitans-induced RANKL expression. In conclusion, a) A. actinomycetemcomitans induces IL-6 production in GF by a mechanism largely independent of its Cdt and b) A. actinomycetemcomitans-induced RANKL expression in GF occurs independently of IL-1, IL-6, TNF-alpha, or PGE(2).     

Methylenedioxymethamphetamine (MDMA; Ecstasy) suppresses IL-1beta and TNF-alpha secretion following an in vivo lipopolysaccharide challenge

In this study we examined the effects of methylenedioxymethamphetamine (MDMA) administration on responsiveness to an in vivo immune challenge with lipopolysaccharide (LPS; 100 microg/kg; i.p.). LPS produced an increase in circulating IL-1beta and TNF-alpha in control animals. MDMA (20 mg/kg; i.p.) significantly impaired LPS-induced IL-1beta and TNF-alpha secretion. The suppressive effect of MDMA on IL-1beta secretion was transient and returned to control levels within 3 hours of administration. In contrast, the MDMA-induced suppression of TNF-alpha secretion was evident for up to 12 hours following administration. In a second study we examined the effect of co-administration of MDMA (5, 10 and 20 mg/kg; i.p.) on LPS-induced IL-1beta and TNF-alpha secretion, and demonstrated that all three doses potently suppressed LPS-induced TNF-alpha secretion, but only MDMA 10 and 20 mg/kg suppressed LPS-induced IL-1beta secretion. In addition, serum MDMA concentrations displayed a dose-dependent increase, with the concentrations achieved following administration of 5 and 10 mg/kg being in the range reported in human MDMA abusers. In order to examine the possibility that the suppressive effect of MDMA on IL-1beta and TNF-alpha could be due to a direct effect of the drug on immune cells, the effect of in vitro exposure to MDMA on IL-1beta and TNF-alpha production in LPS-stimulated diluted whole blood was evaluated. However IL-1beta or TNF-alpha production were not altered by in vitro exposure to MDMA. In conclusion, these data demonstrate that acute MDMA administration impairs IL-1beta and TNF-alpha secretion following an in vivo LPS challenge, and that TNF-alpha is more sensitive to the suppressive effects of MDMA than is IL-1beta. However the suppressive effect of MDMA on IL-1beta and TNF-alpha could not be attributed to a direct effect on immune cells. The relevance of these findings to MDMA-induced immunomodulation is discussed.     

Alpha tocopherol supplementation decreases serum C-reactive protein and monocyte interleukin-6 levels in normal volunteers and type 2 diabetic patients

Type 2 diabetic subjects have an increased propensity to premature atherosclerosis. Alpha tocopherol (AT), a potent antioxidant, has several anti-atherogenic effects. There is scanty data on AT supplementation on inflammation in Type 2 diabetic subjects. The aim of the study was to test the effect of RRR-AT supplementation (1200 IU/d) on plasma C-reactive protein (CRP) and interleukin-6 (IL-6) release from activated monocyte in Type 2 diabetic patients with and without macrovascular complications compared to matched controls. The volunteers comprised Type 2 diabetic subjects with macrovascular disease (DM2-MV, n = 23), Type 2 diabetic subjects without macrovascular complications (DM2, n = 24), and matched controls (C, n = 25). Plasma high sensitive CRP (Hs-CRP) and Monocyte IL-6 were assayed at baseline, following 3 months of supplementation and following a 2 month washout phase. DM2-MV subjects have elevated HsCRP and monocyte IL-6 compared to controls. AT supplementation significantly lowered levels of C-reactive protein and monocyte interleukin-6 in all three groups. In conclusion, AT therapy decreases inflammation in diabetic patients and controls and could be an adjunctive therapy in the prevention of atherosclerosis.     

Increased resistance of LFA-1-deficient mice to lipopolysaccharide-induced shock/liver injury in the presence of TNF-alpha and IL-12 is mediated by IL-10: a novel role for LFA-1 in the regulation of the proinflammatory and anti-inflammatory cytokine balance

Challenge with low doses of LPS together with D-galactosamine causes severe liver injury, resulting in lethal shock (low dose LPS-induced shock). We examined the role of LFA-1 in low dose LPS-induced shock. LFA-1(-/-) mice were more resistant to low dose LPS-induced shock/liver injury than their heterozygous littermates, although serum levels of TNF-alpha and IL-12 were higher in these mice. C57BL/6 mice were not rescued from lethal effects of LPS by depletion of NK1(+) cells, granulocytes, or macrophages, and susceptibility of NKT cell-deficient mice was comparable to that of controls. High numbers of platelets were detected in the liver of LFA-1(+/-) mice after low dose LPS challenge, whereas liver accumulation of platelets was only marginal in LFA-1(-/-) mice. Following low dose LPS challenge, serum levels of IL-10 were higher in LFA-1(-/-) mice than in LFA-1(+/-) mice, and susceptibility to low dose LPS-induced shock as well as platelet accumulation in the liver of LFA-1(-/-) mice were markedly increased by IL-10 neutralization. Serum levels of IL-10 in LFA-1(+/-) mice were only marginally affected by macrophage depletion. However, in LFA-1(-/-) mice macrophage depletion markedly reduced serum levels of IL-10, and as a corollary, susceptibility of LFA-1(-/-) mice to low dose LPS-induced shock was markedly elevated despite the fact that TNF-alpha levels were also diminished. We conclude that LFA-1 participates in LPS-induced lethal shock/liver injury by regulating IL-10 secretion from macrophages and that IL-10 plays a decisive role in resistance to shock/liver injury. Our data point to a novel role of LFA-1 in control of the proinflammatory/anti-inflammatory cytokine network.     

Lipoteichoic acid isolated from Lactobacillus plantarum inhibits lipopolysaccharide-induced TNF-alpha production in THP-1 cells and endotoxin shock in mice

In this study, the effect of Lactobacillus plantarum lipoteichoic acid (pLTA) on LPS-induced MAPK activation, NF-kappaB activation, and the expression of TNF-alpha and IL-1R-associated kinase M (IRAK-M) was examined. The expression of the pattern recognition receptor and the survival rate of mice were also examined. pLTA pretreatment inhibited the phosphorylation of ERK, JNK, and p38 kinase. It also inhibited the degradation of IkappaBalpha and IkappaBbeta, as well as the activation of the LPS-induced TNF-alpha factor in response to subsequent LPS stimulation. These changes were accompanied by the suppression of the LPS-induced expression of TLR4, NOD1, and NOD2, and the induction of IRAK-M, with a concurrent reduction of TNF-alpha secretion. Furthermore, the overexpression of pattern recognition receptors such as TLR4, NOD1, and NOD2 and the degradation of IRAK-M by transient transfection were found to reinstate the production of TNF-alpha after LPS restimulation. In addition, the i.p. injection of pLTA suppressed fatality, and decreased the level of TNF-alpha in the blood, in LPS-induced endotoxin shock mice. In conclusion, these data extend our understanding of the pLTA tolerance mechanism, which is related to the inhibition of LPS-induced endotoxin shock, and suggest that pLTA may have promise as a new therapeutic agent for LPS-induced septic shock.     

LPS and proinflammatory cytokines decrease lipin-1 in mouse adipose tissue and 3T3-L1 adipocytes

Infection and inflammation affect adipose triglyceride metabolism, resulting in increased plasma free fatty acid (FFA) and VLDL levels during the acute-phase response. Lipin-1, a multifunctional protein, plays a critical role in adipose differentiation, mitochondrial oxidation, and triglyceride synthesis. Here, we examined whether LPS [a Toll-like receptor (TLR)-4 activator], zymosan (a TLR-2 activator), and proinflammatory cytokines regulate lipin-1 in adipose tissue. LPS administration caused a marked decrease in the levels of lipin-1 mRNA and protein in adipose tissue. The decrease in lipin-1 mRNA levels occurred rapidly and lasted for at least 24 h. In contrast, lipin-2 and -3 mRNA levels did not change, suggesting specific repression of lipin-1. Zymosan similarly decreased lipin-1 mRNA without affecting lipin-2 or lipin-3 mRNA levels. To determine the pathways by which LPS repressed lipin-1, we examined the effect of proinflammatory cytokines on cultured adipocytes. In 3T3-L1 adipocytes, TNF-alpha, IL-1beta, and IFN-gamma, but not LPS or IL-6, caused a decrease in lipin-1 mRNA levels. Furthermore, TNF-alpha and IL-1beta administration also decreased mRNA levels of lipin-1 in adipose tissue in mice. Importantly, the LPS-induced decrease in lipin-1 mRNA levels was significantly but not totally blunted in TNF-alpha/IL-1 receptor-null mice compared with controls, suggesting key roles for TNF-alpha/IL-1beta and other cytokines in mediating LPS-induced repression of lipin-1. Together, our results demonstrate that expression of lipin-1, one of the essential triglyceride synthetic enzymes, was suppressed by LPS, zymosan, and proinflammatory cytokines in mouse adipose tissue and in cultured 3T3-L1 adipocytes, which could contribute to a decrease in the utilization of FFA to synthesize triglycerides in adipose tissue, thus promoting the release of FFA into the circulation.