IL-10 Plasma Levels are Elevated After LPS Injection in Splenectomized A/J Mice1

Enhanced Bacteremia in Dextran Sulfate-Induced Colitis in Splenectomy Mice Correlates with Gut Dysbiosis and LPS Tolerance

Because both endotoxemia and gut dysbiosis post-splenectomy might be associated with systemic infection, the susceptibility against infection was tested by dextran sulfate solution (DSS)-induced colitis and lipopolysaccharide (LPS) injection models in splenectomy mice with macrophage experiments. Here, splenectomy induced a gut barrier defect (FITC-dextran assay, endotoxemia, bacteria in mesenteric lymph nodes, and the loss of enterocyte tight junction) and gut dysbiosis (increased Proteobacteria by fecal microbiome analysis) without systemic inflammation (serum IL-6). In parallel, DSS induced more severe mucositis in splenectomy mice than sham-DSS mice, as indicated by mortality, stool consistency, gut barrier defect, serum cytokines, and blood bacterial burdens. The presence of green fluorescent-producing (GFP) E. coli in the spleen of sham-DSS mice after an oral gavage supported a crucial role of the spleen in the control of bacteria from gut translocation. Additionally, LPS administration in splenectomy mice induced lower serum cytokines (TNF-α and IL-6) than LPS-administered sham mice, perhaps due to LPS tolerance from pre-existing post-splenectomy endotoxemia. In macrophages, LPS tolerance (sequential LPS stimulation) demonstrated lower cell activities than the single LPS stimulation, as indicated by the reduction in supernatant cytokines, pro-inflammatory genes (iNOS and IL-1β), cell energy status (extracellular flux analysis), and enzymes of the glycolysis pathway (proteomic analysis). In conclusion, a gut barrier defect after splenectomy was vulnerable to enterocyte injury (such as DSS), which caused severe bacteremia due to defects in microbial control (asplenia) and endotoxemia-induced LPS tolerance. Hence, gut dysbiosis and gut bacterial translocation in patients with a splenectomy might be associated with systemic infection, and gut-barrier monitoring or intestinal tight-junction strengthening may be useful.

Blockade of Microglial Kv1.3 Potassium Channels by the Peptide HsTX1[R14A] Attenuates Lipopolysaccharide-mediated Neuroinflammation

The expression of voltage-gated potassium Kv1.3 channels is increased in activated microglia, with non-selective blockade reported to attenuate microglial-mediated neuroinflammation. In this study, we evaluated the impact of a potent and selective peptidic blocker of Kv1.3 channels, HsTX1[R14A], on microglial-mediated neuroinflammation in vitro and in vivo. Treatment with both 0.1 and 1 µg/mL lipopolysaccharide (LPS) significantly (p < 0.05) increased Kv1.3 abundance on the surface of BV-2 microglia in association with increased levels of mRNA for tumour necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The increased transcription of TNF-α and IL-6 was significantly attenuated (by 24.9 and 20.2%, respectively) by HsTX1[R14A] (100 nM). The concomitant increase in TNF-α and IL-6 release from BV-2 microglia was significantly attenuated by HsTX1[R14A] by 10.7 and 12.6%, respectively. In LPS-treated primary mouse microglia, the levels of TNF-α and nitric oxide were also attenuated by HsTX1[R14A] (26.1 and 20.4%, respectively). In an LPS-induced mouse model of neuroinflammation, both an immediate and delayed subcutaneous dose of HsTX1[R14A] (2 mg/kg) significantly reduced plasma and brain levels of the pro-inflammatory mediators TNF-α, IL-1β and IL-6, with no impact on the anti-inflammatory IL-10. These results demonstrate that HsTX1[R14A] is a promising therapeutic candidate for the treatment of diseases with a neuroinflammatory component.

Role of the End-Point Mediators of Sympathoadrenal and Sympathoneural Stress Axes in the Pathogenesis of Experimental Autoimmune Encephalomyelitis and Multiple Sclerosis

The role of stress effector systems in the initiation and progression of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, has strongly been suggested. To corroborate this notion, alterations in activity of the sympathoadrenal and sympathoneural axes of sympathoadrenal system (a major communication pathway between the central nervous system and the immune system), mirrored in altered release of their end-point mediators (adrenaline and noradrenaline, respectively), are shown to precede (in MS) and/or occur during development of MS and EAE in response to immune cell activation (in early phase of disease) and disease-related damage of sympathoadrenal system neurons and their projections (in late phase of disease). To add to the complexity, innate immunity cells and T-lymphocytes synthesize noradrenaline that may be implicated in a local autocrine/paracrine self-amplifying feed-forward loop to enhance myeloid-cell synthesis of proinflammatory cytokines and inflammatory injury. Furthermore, experimental manipulations targeting noradrenaline/adrenaline action are shown to influence clinical outcome of EAE, in a disease phase-specific manner. This is partly related to the fact that virtually all types of cells involved in the instigation and progression of autoimmune inflammation and target tissue damage in EAE/MS express functional adrenoceptors. Although catecholamines exert majority of immunomodulatory effects through β₂-adrenoceptor, a role for α-adrenoceptors in EAE pathogenesis has also been indicated. In this review, we summarize all aforementioned aspects of immunopathogenetic action of catecholamines in EAE/MS as possibly important for designing new strategies targeting their action to prevent/mitigate autoimmune neuroinflammation and tissue damage.

Beta-adrenergic receptor mediated inflammation control by monocytes is associated with blood pressure and risk factors for cardiovascular disease

Overwhelming data indicate that individuals with even mildly elevated blood pressure (BP) are at great risk for developing clinical hypertension and future cardiovascular disease (CVD). There remains a lack of consensus regarding treatment strategies for mildly elevated BP, termed prehypertension, and the knowledge of pathophysiology and mechanisms of its clinical outcomes remains limited. Our primary aim was to investigate βAR-mediated inflammation control (BARIC) responses of blood monocytes to isoproterenol (Iso) in relation to BP and CVD risk factors, including obesity, depressive mood, fasting glucose, triglycerides, and cholesterol levels in the 64 prehypertensive compared to 84 individuals with normal BP. BARIC was determined by measuring the degree of inhibition in lipopolysaccharides-stimulated monocytic intracellular TNF production by ex vivo Iso treatment (10(-8)M). Depressive mood was assessed by Beck Depression Inventory (BDI). Fasting metabolic and lipid panels were assessed, and plasma levels of inflammatory cytokines TNF, IL-1β, IL-6 were measured in a subset to confirm proinflammatory state of prehypertensive participants. Prehypertensive participants were older, heavier, included more men, and presented higher levels of fasting glucose, triglycerides, cholesterol, and plasma TNF compared to normotensive participants (p's<.05). BARIC was significantly attenuated in the prehypertensive compared to normotensive group (p<.05). BARIC was negatively associated with systolic BP, diastolic BP, age, BMI, fasting glucose, triglycerides, total and low density cholesterol levels, and somatic depressive symptoms in all participants (p's<.0001 to .05). However, among the prehypertensive individuals BARIC was positively associated with SBP even after controlling for the covariates (age, gender, race, BMI, glucose and lipid panel, somatic BDI scores) (p<.05). This differing nature of the BARIC-SBP relationship between the two BP groups may be attributed to moderating factors such as cardiorespiratory fitness or depressive symptoms that could not be clearly deciphered in this current study. Nonetheless, our findings indicate the associations between inflammation dysregulation mediated by sympathoadrenal activation and BP that is observable even among individuals with normal to mildly elevated BP. BARIC may be a useful and sensitive indicator of elevated risk for vascular inflammatory disease that can be detected even at lower BP levels, especially given its associations with traditional CVD risk factors and the critical role of monocytes in atherogenic processes.

High-density lipoprotein increases the uptake of oxidized low density lipoprotein via PPARγ/CD36 pathway in inflammatory adipocytes

Aim: Previous studies have demonstrated that the dysregulated-secretion of adipokines by adipocytes may contribute to obesity-associated atherosclerosis (As) and high density lipoprotein (HDL) may protect against atherogenesis through multiple pathways. This study was to explore the effect of HDL on the oxLDL uptake in inflammatory adipocytes stimulated by endotoxin lipopolysaccharide (LPS) and the possible mechanism.

Methods and Results: 3T3-L1 adipocytes were cultured and induced to differentiation and maturation. Acute inflammation in adipocytes was induced by LPS (100 ng/ml) for 6 hours. The adipocytes were pretreated with HDL in various concentrations (10, 50, 100 μg/ml) for 16 hours or with specific PPARγ antagonist (GW9662, 10 μM) or agonist (Rosiglitazone, 10 μM) for 30 min before administration of LPS. The results showed that LPS significantly increased the release of inflammation-related adipokines, such as monocyte chemoattractant protein-1 (MCP-1), plasminogen activator inhibitor 1 (PAI-1), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-8 and IL-6, while decreasing the release of leptin and adiponectin. Meanwhile, LPS reduced the uptake and degradation of ¹²⁵I-oxLDL, and down-regulated the expression of PPARγ and CD36. Pretreatment with HDL dose-dependently affected the release of IL-8 and IL-6 and the reduced uptake and degradation of oxLDL of adipocytes stimulated by LPS, accompanied with marked upregulation of PPARγ and CD36 expression. Pretreatment with GW9662 markedly inhibited the upregulation of CD36 expression mediated by HDL (100 μg/ml), while the effects of Rosiglitazone were opposite to GW9662.

Conclusions: HDL may increase oxLDL uptake of inflammatory adipocytes stimulated by LPS via upregulation of PPARγ/CD36 pathway, which may be a new mechanism of anti-atherosclerosis mediated by HDL.

Plasma cytokine profiles in preprotachykinin-A knockout mice subjected to polymicrobial sepsis

During the course of polymicrobial sepsis, a range of pro- and antiinflammatory cytokines are produced by the host immune system. Successful recovery from sepsis involves striking a balance between these counteracting cytokines. We herein investigated the circulating cytokine profiles in preprotachykinin-A knockout (PPTA(-/-)) mice, which have been found to be protected significantly against microbial sepsis, by employing multiplexed bead-based suspension arrays for the measurement of 18 plasma cytokines. Four sets of PPTA(-/-) and wild-type mice, each with six mice, were subjected to cecal ligation and puncture-induced sepsis or a sham procedure and were killed at 1, 5, 8 and 24 h post surgery. The cytokine profiles revealed, rather interestingly, that both pro- and antiinflammatory cytokines were elevated in the knockout group in response to a septic challenge. The higher systemic levels of both pro- and antiinflammatory cytokines in PPTA(-/-) septic mice was similar to the increase that we observed earlier in lung tissue of PPTA(-/-) mice after induction of sepsis. Thus, elevated levels of both pro- and antiinflammatory mediators may act simultaneously and help to resolve the infectious assault at the early stages of sepsis without excessively damaging the host tissue in PPTA(-/-) mice. In addition, our results underline the importance of comprehensive clinical analysis of multiple biomarkers to provide a better prognostic tool.

Restoration of endothelin-1-induced impairment in endothelium-dependent relaxation by interleukin-10 in murine aortic rings

Endothelin-1 (ET-1) is implicated in the development of endothelial dysfunction through the generation of reactive oxygen species by NADPH oxidase activation. Interleukin-10 (IL-10) is an antiinflammatory cytokine that stimulates nitric oxide production, decreases superoxide production, and restores endothelial integrity after vascular injury. In this study, we tested whether IL-10 attenuates ET-1-induced endothelial dysfunction by improving acetylcholine (ACh)-induced relaxation of cultured murine aortic rings. Aortic rings (2 mm long) of C57BL/6 mice were incubated in 2 mL DMEM containing 120 U/mL penicillin and 120 microg/mL streptomycin in the presence of one of 4 treatments: vehicle (deionized water), ET-1 (100 nmol/L), recombinant mouse IL-10 (300 ng/mL), or a combination of both ET-1 and IL-10. After incubation at 37 degrees C for either 1 or 6 h (short-term exposure) or 22 h (overnight exposure), rings were mounted in a wire myograph and stretched to a passive force of 5 mN. Endothelium-dependent vasorelaxation was assessed by constructing cumulative concentration-response curves to ACh (0.001-10 micromol/L) during 10 mumol/L phenylephrine (PE)-induced contraction. Short-term exposure of ET-1 did not result in an impairment of ACh-induced relaxation. Overnight exposure of aortic rings to ET-1 resulted in a statistically significant endothelial dysfunction characterized by a reduced maximal relaxation response to ACh compared with that of untreated rings (Emax 57% +/- 3% versus 82% +/- 4%). IL-10 treatment restored ACh-induced relaxation (Emax 77% +/- 3%). Western blotting showed decreased eNOS expression in response to ET-1, whereas vessels treated with a combination of ET-1 and IL-10 showed increased expression of eNOS. Immunohistochemical analysis showed decreased eNOS expression in ET-1-treated vessels compared with those treated with both ET-1 and IL-10. We conclude that, in murine aorta, the antiinflammatory cytokine IL-10 prevents impairment in endothelium-dependent relaxation induced in response to long-term incubation with ET-1 via normalization of eNOS expression.

Interleukin-10 counteracts impaired endothelium-dependent relaxation induced by ANG II in murine aortic rings

ANG II stimulates the production of reactive oxygen species and activates proinflammatory cytokines leading to endothelial dysfunction. We hypothesized that the anti-inflammatory cytokine IL-10 counteracts the impairment in endothelium-dependent ACh relaxation caused by ANG II. Aortic rings of C57BL/6 mice were incubated in DMEM in the presence of vehicle (deionized H(2)O), ANG II (100 nmol/l), recombinant mouse IL-10 (300 ng/ml), or both ANG II and IL-10 for 22 h at 37 degrees C. After incubation, rings were mounted in a wire myograph to assess endothelium-dependent vasorelaxation to cumulative concentrations of ACh. Overnight exposure of aortic rings to ANG II resulted in blunted ACh-induced vasorelaxation compared with that shown in untreated rings (maximal response = 44 +/- 3% vs. 64 +/- 3%, respectively; P<0.05). IL-10 treatment significantly restored this impairment in relaxation (63 +/- 2%). In addition, the NADPH oxidase inhibitor apocynin restored the impairment in relaxation (maximal response = 76 +/- 3%). Western blotting showed increased gp91(phox) expression (a subunit of NADPH oxidase) in response to ANG II. Vessels treated with a combination of ANG II and IL-10 showed decreased expression of gp91(phox). Immunohistochemical analysis showed increased gp91(phox) expression in ANG II-treated vessels compared with those treated with combined ANG II and IL-10. We found that the anti-inflammatory cytokine IL-10 prevents impairment in endothelium-dependent vasorelaxation in response to long-term incubation with ANG II via decreasing NADPH oxidase expression.