Cytokine-mediated modulation of leptin and adiponectin secretion during in vitro adipogenesis: evidence that tumor necrosis factor-alpha- and interleukin-1beta-treated human preadipocytes are potent leptin producers

Over the last decade, compelling evidence has been presented that cytokines affect adipocyte tissue formation and function. In this study we explored the effect of pro-inflammatory (i.e. interleukin (IL)-1beta, IL-6, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha) versus anti-inflammatory cytokines (i.e. IL-4, IL-10, and transforming growth factor (TGF)-beta1) on leptin and adiponectin secretion during in vitro human adipogenesis. Confirmative to previous reports, conversion of precursor preadipocytes into mature adipocytes was completely inhibited upon exposure to TNF-alpha, IL-1beta, IFN-gamma, or TGF-beta1. Hence, all these anti-adipogenic cytokines prevented release of adipocyte-specific adiponectin. IFN-gamma also strongly reduced leptin production (> or =85%). However, TNF-alpha, IL-1beta, and TGF-beta1 stimulated leptin production from preadipocytes in the absence of mature adipocytes (20.6+/-5.4 ng/ml, 100.8+/-18.2 ng/ml, and 5.4+/-0.4 ng/ml, respectively, compared to 6.6+/-0.8 ng/ml in control adipocyte cultures on day 21; n=4). IL-4, IL-6 and IL-10 did not, or only slightly, affect adipocyte differentiation and their hormonal secretion. In conclusion, adiponectin and leptin are both synthesized by adipocytes, whereas leptin is also produced by preadipocytes upon TNF-alpha or IL-1beta stimulation. These data suggest that preadipocytes could contribute more to total circulating leptin levels than has been previously considered, especially in diseased conditions were these pro-inflammatory factors play a prominent role.     

IgE-dependent cytokine production by human peripheral blood mononuclear phagocytes.

These studies demonstrate the IgE-dependent production of IL-1 beta and TNF-alpha by circulating blood monocytes. IL-1 beta production was demonstrated biologically as the stimulation of proliferation of the cloned IL-1-dependent murine T cell line D10.G4.1 in the presence of a submitogenic concentration of PHA. In a representative experiment, 3H-thymidine uptake increased from 57826 cpm in the presence of supernatants obtained from unstimulated cells to 200774 cpm with supernatants from monocytes stimulated by IgE/alpha IgE immune complexes. By ELISA, IgE complexes increased IL-1 beta production from 0.54 +/- 0.06 ng (per 10(6) monocytes) to 2.60 +/- 0.62 ng (p less than 0.01; mean of eight experiments) and TNF-alpha production from 0.17 +/- 0.10 ng to 3.00 +/- 0.54 ng (p less than 0.01; mean of four experiments). No IL-1 alpha secretion was observed. RNA hybridization analysis demonstrated that IL-1 beta production represented de novo synthesis of the cytokine. Stimulated RNA production was observed after a minimal 1/2-h incubation and was maximal at 2 h. The IgE-dependent secretion of these pro-inflammatory cytokines by mononuclear phagocytic cells may contribute to the inflammation characteristic of allergic responses.     

Relationship among nitric oxide, leptin, ACTH, corticosterone, and IL-1beta, in the early and late phases of adjuvant arthritis in male Long Evans rats

Leptin, a hormone regulating body weight, food intake, and metabolism, is associated with activation of immune cells and inflammation. In this study we analyzed levels of leptin, adrenocorticotropic hormone (ACTH), corticosterone, interleukin 1beta (IL-1beta), and nitric oxide (NO) production on days 10 and 22 of adjuvant arthritis (AA) in male Long Evans rats to ascertain possible relationship of leptin with its modulators during the early and late phases of chronic inflammation. The circulating leptin levels were significantly reduced already on day 10 of AA compared to controls (1.97+/-0.22 ng/ml vs. 3.08+/-0.25 ng/ml, p<0.05); on day 22 no significant further drop was observed (1.06+/-0.21 ng/ml). Leptin mRNA in epididymal fat tissue was reduced in arthritic animals compared to controls on day 22 (0.61+/-0.09 vs. 1.30+/-0.1 arbU/GAPDH (p<0.01). IL-1beta concentration in spleen was enhanced on day 10 of AA (24.55+/-4.67 pg/100 microg protein vs. 14.33+/-1.71 pg/100 microg protein; p<0.05); on day 22 it did not differ from controls. ACTH and corticosterone levels were significantly elevated only on day 22 of AA (ACTH: 306.17+/-42.22 pg/ml vs. 157.61+/-23.94 pg/ml; p<0.05; corticosterone: 5.24+/-1.38 microg/100 ml vs. 1.05+/-0.23 microg/100 ml; p<0.01). Nitrate levels were enhanced similarly on days 10 (49.86+/-1.83 microM) and 22 of AA (43.58+/-2.17 microM), compared to controls (23.42+/-1.39 microM, p<0.001). These results show that corticosterone does not stimulate leptin production during AA. The suppression of leptin may be a consequence of permanent activation of NO, IL-1beta, and of lower weight gain. Circulating leptin does not seem to play a key role in the progression of chronic arthritis.     

Plasma and urinary cytokine homeostasis and renal function during cardiac surgery without cardiopulmonary bypass

Cardiopulmonary bypass (CPB) significantly contributes to the plasma pro-inflammatory cytokine response at cardiac surgery. Complementary plasma and urinary anti-inflammatory cytokine responses have been described. The pro-inflammatory cytokines interleukin 8 (IL-8), tumour necrosis factor alpha (TNF-alpha) and interleukin 1beta (IL-1beta) have lower molecular weights than the anti-inflammatory cytokines interleukin 10 (IL-10), interleukin 1 receptor antagonist (IL-1ra) and TNF soluble receptor 2 (TNFsr2) and thus undergo glomerular filtration more readily. In vitro work suggests that proximal tubular cells are vulnerable to pro-inflammatory cytokine mediated injury. Accordingly, this study investigated the hypothesis that cardiac surgery without CPB would not have significant changes in plasma and urinary cytokines and proximal renal dysfunction. Eight patients undergoing coronary artery bypass grafting (CABG) without CPB were studied. Blood and urine samples were analysed for pro- and anti-inflammatory cytokines. Proximal tubular dysfunction was measured using urinary Nu-acetyl-beta-D-glucosaminidase (NAG)/creatinine and alpha(1)-microglobulin/creatinine ratios. Plasma IL-8, IL-10, IL-1ra and TNFsr2 were significantly elevated compared with baseline. Urinary IL-1ra and TNFsr2 were significantly elevated, as were urinary NAG/creatinine and alpha(1)-microglobulin/creatinine ratios. Two hours following revascularization, urinary IL-1ra correlated with urinary alpha(1)-microglobulin/creatinine ratios (P<0.05). As previously reported in CABG surgery with CPB, we now report that non-CPB cardiac surgery also has significant changes in plasma and urinary cytokine homeostasis and early proximal tubular injury. The correlation between urinary IL-1ra and alpha(1)-microglobulin/creatinine ratios is consistent with earlier suggestions of a mechanistic link between cytokine changes and proximal tubular dysfunction. The relative roles of CPB and non-CPB processes in producing inflammation still require definition.     

Outer membrane vesicles from Neisseria meningitidis: effects on cytokine production in human whole blood

The Norwegian group B meningococcal outer membrane vesicle (OMV) vaccine consists of outer membrane proteins (OMPs) as main antigens with significant amounts of lipopolysaccharide (LPS; 5-9% relative to protein). We have studied the ability of this OMV vaccine preparation to induce secretion of pro-inflammatory cytokines, tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), interleukin 6 (IL-6), interleukin 8 (IL-8) and anti-inflammatory cytokines, interleukin 4 (IL-4), interleukin 10 (IL-10) and interleukin 13 (IL-13) in a human whole blood model. Plasma levels of TNF-alpha, IL-1beta, IL-6 and IL-8 were massively increased; mean peak levels of TNF-alpha 44 696+/-7764, IL-1beta 38 043+/-5411, IL-6 10 057+/-1619 and IL-8 30 449+/-5397 pg/ml were obtained with an OMV-LPS concentration of 1 microg/ml; corresponding levels in control plasmas were below the detection limit of the assay. Mean maximal level of IL-10 (2540+/-144 pg/ml) was obtained at OMV-LPS concentration of 10 microg/ml, after 24 h; while the level in control plasma was below detection limit. OMV-LPS did not induce release of IL-4 and IL-13 in doses from 0.001-10 microg/ml. The present results show that OMVs from meningococci have potent pro-inflammatory properties and are likely to contribute to the observed local and systemic inflammatory effects.     

Influence of surgery on in-vitro cytokine production by human monocytes

Surgery leads to significant modulation of the immune system, in which cytokines play a major role. Circulating interleukin 6 (IL-6) and IL-1 have been reported following surgery whereas tumor necrosis factor alpha (TNF-alpha) is only found in gut ischemia-associated surgery. We have investigated the consequences of surgery on in-vitro cytokine production by human monocytes stimulated by lipopolysaccharide (LPS) and staphylococcal toxic shock syndrome toxin-1 (TSST-1). Comparisons were made between the responsiveness of cells obtained the day before (D-1), during (D0) and after (D1, D2, D3) surgery. Patients undergoing abdominal aortic surgery (N = 9), carotid surgery (N = 4) and spinal surgery (N = 4) have been studied. A significant decrease of TNF-alpha, IL-1 beta and IL-1 alpha production by monocytes prepared from blood samples taken during the surgery was noticed, whereas IL-6 production was not significantly modified. On D2 a significant increase of monocyte responsiveness was observed and levels of cytokine productions rose back to initial values by the end of the follow up. The diminished in-vitro cytokine production observed during surgery might be the consequence of the effects of anaesthetic drugs, whereas the enhancement observed on D2 might reflect the surgical stress, leading to in-vivo priming of circulating monocytes.     

Effect of pericardial fluid pro-inflammatory cytokines on hemodynamic parameters

We investigated the effects of pro-inflammatory cytokines of pericardial fluid on hemodynamic parameters in patients undergoing coronary artery surgery. Seventy-eight patients were included in the study and they were allocated to three groups: group 1, stable angina pectoris (SAP, n = 15); group 2, unstable angina pectoris (USAP, n = 34); group 3, post-myocardial infarction (PMI, n = 29). Pericardial fluid and arterial blood samples were obtained from all patients and interleukin (IL)-1beta, IL-2 receptor, IL-6, IL-8 and tumor necrosis factor-alpha (TNF-alpha) levels were measured. Pericardial IL-1beta concentration (pg/mL) was significantly higher in the USAP group (26.6 +/- 10.9) compared to the SAP (5.0 +/- 0.1) and PMI (5.8 +/- 1.0) groups. IL-2R, IL-6, IL-8 and TNF-alpha concentrations of pericardial fluid were significantly higher than serum in all groups; difference was more prominent in the PMI group compared to the SAP and the USAP groups. Serum IL-1beta concentrations (pg/mL) were significantly higher in the USAP group (21.8 +/- 3.4) compared to the SAP group (5.0 +/- 0.1) and the PMI group (5.4 +/- 1.6). Cardiac index (CI) before opening the pericardial sac was found to be lower in the USAP group (1.6 +/- 0.3 L/min/m2) compared to the SAP (2.2 +/- 0.5 L/min/m2) and the PMI (2.1 +/- 0.5 L/min/m2) groups (p = 0.028 and p = 0.011, respectively). In the USAP group, there was a relationship between reduction of CI and increase of IL-1beta levels in serum and pericardial fluid.     

Inhibition of inducible NO synthase by TH2 cytokines and TGF beta in rheumatoid arthritic synoviocytes: effects on nitrosothiol production.

The aim of this study was to compare the effects on NO production of IL-4, IL-10, and IL-13 with those of TGF-beta. RA synovial cells were stimulated for 24 h with IL-1 beta (1 ng/ml), TNF-alpha (500 pg/ml), IFN-gamma (10(-4)IU/ml) alone or in combination. Nitrite was determined by the Griess reaction, S-nitrosothiols by fluorescence, and inducible NO synthase (iNOS) by immunofluorescence and fluorescence activated cell sorter analysis (FACS). In other experiments, IL-4, IL-10, IL-13, and TGF beta were used at various concentrations and were added in combination with proinflammatory cytokines. The addition of IL-1 beta, TNF-alpha, and IFN-gamma together increased nitrite production: 257.5 +/- 35.8 % and S-nitrosothiol production : 413 +/- 29%, P < 0.001. None of these cytokines added alone had any significant effect. iNOS synthesis increased with NO production. IL-4, IL-10, IL-13, and TGF beta strongly decreased the NO production caused by the combination of IL-1 beta, TNF-alpha, and IFN-gamma. These results demonstrate that stimulated RA synoviocytes produce S-nitrosothiols, bioactive NO* compounds, in similar quantities to nitrite. IL-4, IL-10, IL-13, and TGF-beta decrease NO production by RA synovial cells. The anti-inflammatory properties of these cytokines may thus be due at least in part to their effect on NO metabolism.     

Proinflammatory liver and antiinflammatory intestinal mediators involved in portal hypertensive rats

Proinflammatory (TNF-alpha , IL-1beta, and NO) and antiinflammatory (IL-10, CO) levels were assayed in serum, liver, and small bowel in order to verify a hypothetic inflammatory etiopathogeny of portal hypertension that could be the cause of its evolutive heterogeneity. Male Wistar rats were divided into one control group (n=11) and one group with a triple stenosing ligation of the portal vein (n=23) after 28 days of evolution. In one subgroup of portal hypertensive rats, portal pressure, collateral venous circulation, mesenteric vasculopathy, and liver and spleen weights were determined. In the remaining rats with portal hypertension TNF-alpha, IL-1beta, and IL-10 were quantified in liver and ileum by enzyme-linked immunosorbent assay. NO synthase activity was studied in liver and ileum. CO and NO were measured in portal and systemic blood by spectrophotometry and Griess reaction, respectively. Portal hypertensive rats with mayor spleen weight show hepatomegaly and mayor development of collateral circulation. Ileum release of IL-10 (0.30 +/- 0.12 versus 0.14 +/- 0.02 pmol/mg protein; P< .01) is associated with a liver production of both proinflammatory mediators (TNF-alpha: 2 +/- 0.21 versus 1.32 +/- 0.60 pmol/mg protein; P< .05, IL-1beta: 19.17 +/- 2.87 versus 5.96 +/- 1.84 pmol/mg protein; P=.005, and NO: 132.10 +/- 34.72 versus 61.05 +/- 8.30 nmol/mL; P=.005) and an antiinflammatory mediator (CO: 6.49 +/- 2.99 versus 3.03 +/- 1.59 pmol/mL; P=.005). In short-term prehepatic portal hypertension a gut-liver inflammatory loop, which could be fundamental in the regulation both of the portal pressure and of its complications, could be proposed.     

Cytokine responses differ by compartment and wasting status in patients with HIV infection and healthy controls

Inflammatory cytokines are implicated in the loss of lean tissue that occurs in patients with inflammatory and infectious diseases, including HIV infection. However, it is not known whether plasma levels or cellular production of cytokines, or their antagonists, are more closely related to lean tissue loss. We studied whether plasma cytokine analysis could substitute for PBMC production assays in studies of nutrition status and disease state, and if cytokine antagonists could offer an alternative in assessing cytokine status. We used a bout of moderately difficult exercise to perturb cytokine production in 12 adults with HIV without wasting, 10 adults with HIV wasting, and nine healthy controls. Plasma and peripheral blood mononuclear cell (PBMC) production of interleukin-1 beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), interleukin-1 receptor antagonist (IL-1ra) and soluble TNF receptor type II (sTNFrII) were measured at baseline and 2, 6, 24 and 168h following exercise. PBMC production of IL-1beta, TNF-alpha and IL-6 were all higher in the HIV-infected patients without wasting than in the controls (P<0.05) or the patients with AIDS wasting (P<0.05). Plasma concentrations of TNF-alpha and IL-6 were higher in the HIV wasted patients than in the controls (P<0.05). Both plasma and PBMC levels of sTNFrII were higher in HIV patients, regardless of wasting, than in controls. These data suggest that the PBMC cytokine compartment is more sensitive to nutritional and metabolic abnormalities than is the plasma compartment. PBMC production of IL-1beta, IL-6 and TNF-alpha best distinguish between HIV patients with and without wasting, while plasma concentrations of IL-6 and TNF-alpha are elevated in AIDS wasting, but do not reliably distinguish patients with wasting from HIV-infected patients without wasting.     

Correlation of neutrophil and monocyte derived interleukin-1 receptor antagonist and interleukin-8 with colitis severity in the rabbit

Activated neutrophils and monocytes produce interleukin (IL)-8, a pro-inflammatory chemokine, but also IL-1 receptor antagonist (IL-1ra), which is an anti-inflammatory cytokine. We were interested to see the profiles of IL-8 and IL-1ra in the colonic tissue and in the peripheral blood leukocytes (PBL) during the development of immune complex induced colitis in rabbits. IL-1ra and IL-8 in PBL were measured in 26 rabbits at time 0 h, 24 h, and 48 h after induction of colitis. The colons were removed at 48 h for measuring myeloperoxidase (MPO), ulcer area, IL-1ra and IL-8. Epithelial damage, crypt abscess formation and leukocyte infiltration of the colonic tissue were major features of this colitis model. During the development of colitis, there was an increase in circulating neutrophils and monocytes (P < 0.0001), but not lymphocytes. Likewise, elevated amounts of IL-1ra (P = 0.0001) and IL-8 (P = 0.0219) production by PBL were observed following induction of colitis. Flow cytometry revealed major source of IL-1ra was monocytes, while the main sources of IL-8 were neutrophils and monocytes. There was correlation between MPO and ulcer area (R_s = 0.6327, P < 0.0001). At 24 h, PBL from MPO^High group (n = 11) showed increased IL-1ra (P = 0.027) and IL-8 (P = 0.0128) levels vs MPO^Low group (n = 15). IL-8 production by PBL showed correlation with tissue MPO (R_s = 0.4273, P = 0.0295). The colitis in this model was associated with an increase in circulating monocytes and neutrophils, which released increased amounts of IL-8 and IL-1ra. Further, IL-8 and IL-1ra showed correlation with the severity of colitis. These observations should significantly further understandings on the role of neutrophils and monocytes in the immunopathogenesis of ulcerative colitis.     

Muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase in human skeletal muscle

Physiological stress associated with muscle damage results in systemic insulin resistance. However, the mechanisms responsible for the insulin resistance are not known; therefore, the present study was conducted to elucidate the molecular mechanisms associated with insulin resistance after muscle damage. Muscle biopsies were obtained before (base) and at 1 h during a hyperinsulinemic-euglycemic clamp (40 mU x kg(-1) x min(-1)) in eight young (age 24+/-1 yr) healthy sedentary (maximal O(2) consumption, 49.7+/-2.4 ml x kg(-1) x min(-1)) males before and 24 h after eccentric exercise (ECC)-induced muscle damage. To determine the role of cytokines in ECC-induced insulin resistance, venous blood samples were obtained before (control) and 24 h after ECC to evaluate ex vivo endotoxin-induced mononuclear cell secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and IL-1beta. Glucose disposal was 19% lower after ECC (P<0.05). Insulin-stimulated insulin receptor substrate (IRS)-1 tyrosine phosphorylation was 45% lower after ECC (P<0.05). Insulin-stimulated phosphatidylinositol (PI) 3-kinase, Akt (protein kinase B) serine phosphorylation, and Akt activity were reduced 34, 65, and 20%, respectively, after ECC (P < 0.05). TNF-alpha, but not IL-6 or IL-1beta production, increased 2.4-fold 24 h after ECC (P<0.05). TNF-alpha production was positively correlated with reduced insulin action on PI 3-kinase (r = 0.77, P = 0.04). In summary, the physiological stress associated with muscle damage impairs insulin stimulation of IRS-1, PI 3-kinase, and Akt-kinase, presumably leading to decreased insulin-mediated glucose uptake. Although more research is needed on the potential role for TNF-alpha inhibition of insulin action, elevated TNF-alpha production after muscle damage may impair insulin signal transduction.     

Obstructive cholestasis induces TNF-alpha- and IL-1 -mediated periportal downregulation of Bsep and zonal regulation of Ntcp, Oatp1a4, and Oatp1b2

Inverse acinar regulation of Mrp2 and 3 represents an adaptive response to hepatocellular cholestatic injury. We studied whether obstructive cholestasis (bile duct ligation) and LPS treatment affect the zonal expression of Bsep (Abcb11), Mrp4 (Abcc4), Ntcp (Slc10a1), and Oatp isoforms (Slco1a1, Slco1a4, and slco1b2) in rat liver, as analyzed by semiquantitative immunofluorescence. Contribution of TNF-alpha and IL-1beta to transporter zonation in obstructive cholestasis was studied by cytokine inactivation. In normal liver Bsep, Mrp4, Ntcp, and Oatp1a1 were homogeneously distributed in the acinus, whereas Oatp1a4 and Oatp1b2 expression increased from zone 1 to 3. Glutamine synthetase-positive pericentral hepatocytes exhibited markedly lower Oatp1a4 expression than the remaining zone 3 hepatocytes. In cholestatic liver Bsep and Ntcp immunofluorescence in periportal hepatocytes significantly decreased to 66 +/- 4% (P < 0.01) and 67 +/- 7% (P < 0.05), whereas it was not altered in pericentral hepatocytes. Oatp1a4 was significantly induced in hepatocytes with a primarily low expression, i.e., in periportal hepatocytes and in glutamine synthetase-positive pericentral hepatocytes. Likewise, Oatp1b2 was upregulated in periportal hepatocytes. Mrp4 zonal induction was homogeneous. Inactivation of TNF-alpha and IL-1beta prevented periportal downregulation of Bsep. Recruitment of neutrophils and polymorphonuclear cells mainly occurred in the periportal zone. Likewise, IL-1beta induction was largely found periportally. No significant transporter zonation was seen following LPS treatment. In conclusion, zonal downregulation of Bsep in obstructive cholestasis is associated with portal inflammation and is mediated by TNF-alpha and IL-1beta. Periportal downregulation of Ntcp and induction of Oatp1a4 and Oatp1b2 may represent adaptive mechanisms to reduce cholestatic injury in hepatocytes with profound downregulation of Bsep and Mrp2.     

Lipopolysaccharide activates an innate immune system response in human adipose tissue in obesity and type 2 diabetes

Type 2 diabetes (T2DM) is associated with chronic low-grade inflammation. Adipose tissue (AT) may represent an important site of inflammation. 3T3-L1 studies have demonstrated that lipopolysaccharide (LPS) activates toll-like receptors (TLRs) to cause inflammation. For this study, we 1) examined activation of TLRs and adipocytokines by LPS in human abdominal subcutaneous (AbdSc) adipocytes, 2) examined blockade of NF-kappaB in human AbdSc adipocytes, 3) examined the innate immune pathway in AbdSc AT from lean, obese, and T2DM subjects, and 4) examined the association of circulating LPS in T2DM subjects. The findings showed that LPS increased TLR-2 protein expression twofold (P<0.05). Treatment of AbdSc adipocytes with LPS caused a significant increase in TNF-alpha and IL-6 secretion (IL-6, Control: 2.7+/-0.5 vs. LPS: 4.8+/-0.3 ng/ml; P<0.001; TNF-alpha, Control: 1.0+/-0.83 vs. LPS: 32.8+/-6.23 pg/ml; P<0.001). NF-kappaB inhibitor reduced IL-6 in AbdSc adipocytes (Control: 2.7+/-0.5 vs. NF-kappaB inhibitor: 2.1+/-0.4 ng/ml; P<0.001). AbdSc AT protein expression for TLR-2, MyD88, TRAF6, and NF-kappaB was increased in T2DM patients (P<0.05), and TLR-2, TRAF-6, and NF-kappaB were increased in LPS-treated adipocytes (P<0.05). Circulating LPS was 76% higher in T2DM subjects compared with matched controls. LPS correlated with insulin in controls (r=0.678, P<0.0001). Rosiglitazone (RSG) significantly reduced both fasting serum insulin levels (reduced by 51%, P=0.0395) and serum LPS (reduced by 35%, P=0.0139) in a subgroup of previously untreated T2DM patients. In summary, our results suggest that T2DM is associated with increased endotoxemia, with AT able to initiate an innate immune response. Thus, increased adiposity may increase proinflammatory cytokines and therefore contribute to the pathogenic risk of T2DM.     

Docosahexaenoic acid induces an anti-inflammatory profile in lipopolysaccharide-stimulated human THP-1 macrophages more effectively than eicosapentaenoic acid

A number of studies have investigated the effects of fish oil on the production of pro-inflammatory cytokines using peripheral blood mononuclear cell models. The majority of these studies have employed heterogeneous blends of long-chain n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which preclude examination of the individual effects of LC n-3 PUFA. This study investigated the differential effects of pure EPA and DHA on cytokine expression and nuclear factor kappaB (NF-kappaB) activation in human THP-1 monocyte-derived macrophages. Pretreatment with 100 microM EPA and DHA significantly decreased lipopolysaccharide (LPS)-stimulated THP-1 macrophage tumor necrosis factor (TNF) alpha, interleukin (IL) 1beta and IL-6 production (P<.02), compared to control cells. Both EPA and DHA reduced TNF-alpha, IL-1beta and IL-6 mRNA expression. In all cases, the effect of DHA was significantly more potent than that of EPA (P<.01). Furthermore, a low dose (25 microM) of DHA had a greater inhibitory effect than that of EPA on macrophage IL-1beta (P<.01 and P<.04, respectively) and IL-6 (P<.003 and P<.003, respectively) production following 0.01 and 0.1 microg/ml LPS stimulation. Both EPA and DHA down-regulated LPS-induced NF-kappaB/DNA binding in THP-1 macrophages by approximately 13% (P< or =.03). DHA significantly decreased macrophage nuclear p65 expression (P< or =.05) and increased cytoplasmic IkappaBalpha expression (P< or =.05). Although similar trends were observed with EPA, they were not significant. Our findings suggest that DHA may be more effective than EPA in alleviating LPS-induced pro-inflammatory cytokine production in macrophages - an effect that may be partly mediated by NF-kappaB. Further work is required to elucidate additional divergent mechanisms to account for apparent differences between EPA and DHA.     

Cytokine and hormone profiles in mice subjected to handling combined with rectal temperature measurement stress and handling only stress

Stress is known to either up or down regulate immunity. In this study, mice were subjected to handling combined with rectal temperature measurement (RTM) stress or handling only stress. We investigated whether there were any significant differences in the effect of handling combined with RTM and handling only on NK cell activity, serum cytokine (IL-1beta, IL-6, and TNF-alpha) and ACTH and beta-endorphin levels, and splenic cytokine (IL-1beta, IL-6, TNF-alpha, IFN-alpha, and IFN-beta) levels. Circulating cytokines and hormones and splenic cytokine mRNA levels were measured in individual mice. NK cell activity was significantly increased in both stress groups when compared to the control group. Handling combined with RTM produced significantly increased serum levels of IL-1beta, IL-6, and beta-endorphin. Serum IL-1beta, ACTH, and beta-endorphin were elevated significantly in the handling only group. Splenic TNFalpha mRNA in both of the stress groups and IL-6 mRNA in handling only group decreased significantly. Our observations are supported by existing literature demonstrating that various stressors have differential effects on immune functions and the neuroendocrine hormones and cytokines, which regulate them.     

Effects of chronic exercise on cytokine production in white adipose tissue and skeletal muscle of rats

White adipose tissue (WAT) is a major source of production of cytokines involved in chronic diseases such as obesity, type 2 diabetes, and atherosclerosis. Long-term exercise has been proposed as a therapy to reduce chronic inflammation. We investigated here the influence of an intense exercise training (over 7 weeks) on several cytokine concentrations including interleukin 1 receptor antagonist (IL-1ra), IL-1beta, and IL-12 in serum, WAT, and skeletal muscle (SM) from non-obese rats. Two groups of 10 rats were investigated: one group was progressively trained (the two last weeks: 120min per day, 25m/min, 7% grade, 5 days per week) and the other age-matched group was used as a sedentary control. Compared to sedentary rats, weight gain was lower in the trained rats (P<0.01). In WAT, concentrations of IL-1ra, IL-1beta, and IL-12 were lower (P<0.001 for IL-1ra and IL-12, P<0.05 for IL-1beta) while they were higher in SM (P<0.01 for IL-1ra, P<0.001 for IL-1beta, P<0.05 for IL-12), and similar in serum. Significant correlations were noted between (i) body weight and WAT concentrations of IL-1ra, IL-1beta, and IL-12 (0.595, 0.450, and 0.481, respectively), (ii) body weight and IL-1beta concentration in SM (-0.526). We also observed significant negative correlations between WAT and SM concentrations of the three cytokines. We show here for the first time that intense exercise training with weight loss reduced concentrations of IL-1ra, IL-1beta, and IL-12 in WAT, while it increased them in SM. These results suggest that exercise could help reduce inflammation in WAT through mobilization of immune cells producing pro- and anti-inflammatory cytokines in SM.