Galantamine attenuates autoinflammation in a mouse model of familial mediterranean fever

BACKGROUND

Autoinflammatory diseases, a diverse group of inherited conditions characterized by excessive innate immune activation, have limited therapeutic options. Neuroimmune circuits of the inflammatory reflex control innate immune overactivation and can be stimulated to treat disease using the acetylcholinesterase inhibitor galantamine.

METHODS

We tested the efficacy of galantamine in a rodent model of the prototypical autoinflammatory disease familial Mediterranean fever (FMF). Multiple chronic disease markers were evaluated in animals that received long-term galantamine treatment compared to vehicle.

RESULTS

Long-term treatment with galantamine attenuated the associated splenomegaly and anemia which are characteristic features of this disease. Further, treatment reduced inflammatory cell infiltration into affected organs and a subcutaneous air pouch.

CONCLUSIONS

These findings suggest that galantamine attenuates chronic inflammation in this mouse model of FMF. Further research is warranted to explore the therapeutic potential of galantamine in FMF and other autoinflammatory diseases.

Therapeutic Potential of B-1a Cells in Intestinal Ischemia-reperfusion Injury

BACKGROUND

Acute mesenteric ischemia is a common surgical emergency. Restoration of blood flow is a critical objective of treating this pathology. However, many patients suffer from ischemia-reperfusion (I/R) injuries at the time of revascularization, requiring prolonged hospitalizations. B-1a cells are a subtype of B lymphocytes with roles in regulating inflammation and tissue injury by spontaneous release of natural IgM and IL-10. We hypothesized that treatment with B-1a cells protects mice from intestinal I/R.

METHODS

Mesenteric ischemia was induced in mice by placing a vascular clip on the superior mesenteric artery for 60 minutes. At the time of reperfusion, B-1a cells or PBS control were instilled into the peritoneal cavity (PerC) of mice. PerC lavage, blood, intestine, and lungs were collected 4 h after reperfusion. Serum organ injury and inflammatory markers such as ALT, AST, LDH, lactate, IL-6, as well as lung and gut histology and myeloperoxidase (MPO) were assessed.

RESULTS

In intestinal I/R, B-1a cell frequency and number in the PerC were significantly decreased compared to sham-operated mice. There was an increase in the serum levels of ALT, AST, LDH, lactate, and IL-6 when comparing the vehicle group with the sham group. These increases were significantly reduced in the B-1a cell treated group. B-1a cell treatment significantly decreased the intestine and lung injury scores as well as MPO content, compared to vehicle treated mice. B-1a cell treatment resulted in a reduction of apoptotic cells in these tissues. Serum IgM levels were decreased in intestinal I/R, while treatment with B-1a cells significantly increased their levels towards normal levels.

CONCLUSIONS

B-1a cell treatment at the time of mesenteric reperfusion ameliorates end organ damage and reduces systemic inflammation through the improvement of serum IgM levels. Preserving B-1a cells pool could serve as a novel therapeutic avenue in intestinal I/R injury.

Frontline Science: Extracellular CIRP generates a proinflammatory Ly6G+ CD11bhi subset of low-density neutrophils in sepsis

Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern. Neutrophils present in the mononuclear cell fraction of Ficoll gradient separation are called low-density neutrophils (LDNs). Here we report the novel role of eCIRP on LDNs' heterogeneity in sepsis. Sepsis was induced in male C57BL/6 wild-type (WT) and CIRP^-/- mice by cecal ligation and puncture (CLP). At 20 h after CLP, LDNs in the blood were isolated by Ficoll gradient separation, followed by staining the cells with anti-Ly6G and anti-CD11b Abs and detection by flow cytometry. Sepsis or recombinant murine CIRP (rmCIRP) injection in mice resulted in significant increase in the frequency (%) and number of Ly6G⁺ CD11b^hi and Ly6G⁺ CD11b^lo LDNs in the blood compared to sham- or vehicle-treated mice. At 20 h of CLP, CIRP^-/- mice had significantly lower frequency and number of Ly6G⁺ CD11b^hi and Ly6G⁺ CD11b^lo LDNs in the blood compared to WT mice. In sepsis mice or rmCIRP-injected mice, compared to Ly6G⁺ CD11b^lo LDNs, the expression of CXCR4, ICAM-1, and iNOS and formation of reactive oxygen species, and neutrophil extracellular traps in Ly6G⁺ CD11b^hi LDNs in the blood were significantly increased. Treatment of WT bone marrow-derived neutrophils (BMDNs) with rmCIRP increased Ly6G⁺ CD11b^hi LDN frequency, whereas treatment of TLR4^-/- BMDNs with rmCIRP significantly decreased the frequency of Ly6G⁺ CD11b^hi LDNs. BMDNs' stimulation with rmCIRP increased the expression of transcription factors in LDNs. eCIRP induces the formation of a proinflammatory phenotype Ly6G⁺ CD11b^hi of LDNs through TLR4. Targeting eCIRP may provide beneficial outcomes in sepsis by decreasing proinflammatory Ly6G⁺ CD11b^hi LDNs.

Correction of immunosuppression in aged septic rats by human ghrelin and growth hormone through the vagus nerve-dependent inhibition of TGF-β production

BACKGROUND

Co-administration of human ghrelin and growth hormone (GH) reverse immunosuppression in septic aged animals, but the mechanism remains elusive. Here, we hypothesize that ghrelin and GH co-treatment restores the immune response in aged septic rats by inhibiting the production of transforming growth factor-β (TGF-β), an immunoregulatory cytokine, through the vagus nerve.

METHODS

Male aged Fischer rats (22-23-month-old) were made septic by cecal ligation and puncture (CLP) with or without dissecting the vagus nerve (vagotomy). Human ghrelin and GH or vehicle (PBS) were administrated subcutaneously at 5 h post CLP. After 20 h of CLP, serum and spleens were harvested.

RESULTS

Serum TGF-β levels were increased in septic aged rats, while ghrelin and GH treatment significantly reduced its levels. Expression of TGF-β in the spleen was upregulated after sepsis, while ghrelin and GH treatment significantly inhibited its expression. TNF-α and IL-6 levels were significantly reduced after ex vivo LPS stimulation of splenocytes from rats that underwent CLP compared to sham rats; while these levels were significantly higher in splenocytes from ghrelin and GH-treated CLP rats compared to vehicle-treated CLP rats. Ghrelin and GH treatment reduced program death receptor-1 (PD-1) expression, increased human leukocyte antigen-DR (HLA-DR) expression, attenuated lymphopenia, and cleaved caspase-3 levels in the spleen of septic aged rats. Vagotomy diminished the beneficial effects of ghrelin and GH treatment in septic rats. In vitro, the addition of ghrelin, GH, or ghrelin and GH together had no effect on restoring immune response in splenocytes from CLP rats following LPS stimulation, indicating the requirement of the vagus nerve for ghrelin and GH's effect.

CONCLUSIONS

Ghrelin and GH attenuate immunosuppression in aged septic rats through the vagus nerve-dependent inhibition of TGF-β production.

Inhibition of a triggering receptor expressed on myeloid cells-1 (TREM-1) with an extracellular cold-inducible RNA-binding protein (eCIRP)-derived peptide protects mice from intestinal ischemia-reperfusion injury

BACKGROUND

Intestinal ischemia-reperfusion injury results in morbidity and mortality from both local injury and systemic inflammation and acute lung injury. Extracellular cold-inducible RNA-binding protein is a damage associated molecular pattern that fuels systemic inflammation and potentiates acute lung injury. We recently discovered a triggering receptor expressed on myeloid cells-1 serves as a novel receptor for extracellular cold-inducible RNA-binding protein. We developed a 7-aa peptide, named M3, derived from the cold-inducible RNA-binding protein, which interferes with cold-inducible RNA-binding protein's binding to a triggering receptor expressed on myeloid cells-1. Here, we hypothesized that M3 protects mice against intestinal ischemia-reperfusion injury.

METHODS

Intestinal ischemia was induced in C57BL/6 mice via clamping of the superior mesenteric artery for 60 minutes. At reperfusion, mice were treated intraperitoneally with M3 (10 mg/kg body weight) or normal saline vehicle. Mice were killed 4 hours after reperfusion and blood and lungs were collected for various analysis. A 24-hours survival after intestinal ischemia-reperfusion was assessed.

RESULTS

Serum levels of organ injury markers aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and lactate were increased with intestinal ischemia-reperfusion, while treatment with M3 significantly decreased their levels. Serum, intestinal, and lung levels of proinflammatory cytokines and chemokines were also increased by intestinal ischemia-reperfusion, and treatment with M3 significantly reduced these values. Intestinal ischemia-reperfusion caused significant histological intestinal and lung injuries, which were mitigated by M3. Treatment with M3 improved the survival from 40% to 80% after intestinal ischemia-reperfusion.

CONCLUSION

Inhibition of triggering receptor expressed on myeloid cells-1 by an extracellular cold-inducible RNA-binding protein-derived small peptide (M3) decreased inflammation, reduced lung injury, and improved survival in intestinal ischemia-reperfusion injury. Thus, blocking the extracellular cold-inducible RNA-binding protein-triggering receptor expressed on myeloid cells-1 interaction is a promising therapeutic avenue for mitigating intestinal ischemia-reperfusion injury.

Alteration in TNFα mediates impaired antigen-specific humoral responses in sepsis survivors

Sepsis survivors show impaired responsiveness to antigen (Ag), which is linked to increased susceptibility to infection. Using the cecal ligation and puncture (CLP) model of sepsis, we showed that CLP surviving mice have a reduced antibody response to the T-dependent Ag, NP-CGG, compared to mice that underwent a sham procedure, but an intact response to the T-independent Ag, NP-Ficoll. CLP mice have reduced TNFα levels due to sustained vagus nerve activity. We hypothesized that reduced TNFα production might lead to disruption in follicular dendritic cell (FDC) function and impaired germinal center (GC) responses. FDCs play a key role in GC responses and TNFα is critical for FDC clustering and maturation. Immunofluorescence staining in spleens showed a reduced number of FDC clusters and reduced binding of immune complexes on FDCs in CLP mice compared to sham mice. NP-specific GC B cells sorted from CLP mice immunized with NP-CGG exhibit reduced TNFα, AICDA, and BCL6 mRNA expression compared to sham mice. To confirm the role of the vagus nerve in impaired FDC clusters, CLP mice were subjected to bilateral subdiaphragmatic vagotomy 2 weeks post-CLP. These mice exhibit increased anti-NP IgG levels in response to immunization with NP-CGG compared to non-vagotomized CLP mice. FDC are radioresistant cells; therefore, we lethally irradiated sham and CLP mice and reconstituted them with bone marrow cells from naive mice that never experienced sepsis. CLP mice still show an impaired Ag-specific response confirming involvement of FDCs and vagus nerve signals. In summary, our data suggest that altered vagus nerve activity, low TNFα, and disruption in FDC function contributes to reduced Ag-specific humoral responses in sepsis survivors.

Extracellular CIRP as an endogenous TREM-1 ligand to fuel inflammation in sepsis

Extracellular cold-inducible RNA-binding protein (eCIRP) is a recently discovered damage-associated molecular pattern. Understanding the precise mechanism by which it exacerbates inflammation is essential. Here we identified that eCIRP is a new biologically active endogenous ligand of triggering receptor expressed on myeloid cells-1 (TREM-1), fueling inflammation in sepsis. Surface plasmon resonance revealed a strong binding affinity between eCIRP and TREM-1, and fluorescence resonance energy transfer assay confirmed eCIRP's interaction with TREM-1 in macrophages. Targeting TREM-1 by its siRNA or a decoy peptide, LP17, or by using TREM-1-/- mice dramatically reduced eCIRP-induced inflammation. We developed a potentially novel 7-aa peptide derived from human eCIRP, M3, which blocked the interaction of TREM-1 and eCIRP. M3 suppressed inflammation induced by eCIRP or agonist TREM-1 antibody cross-linking in murine macrophages or human peripheral blood monocytes. M3 also inhibited eCIRP-induced systemic inflammation and tissue injury. Treatment with M3 further protected mice from sepsis, improved acute lung injury, and increased survival. Thus, we have discovered a potentially novel TREM-1 ligand and developed a new peptide, M3, to block eCIRP-TREM-1 interaction and improve outcomes in sepsis.

Extracellular cold inducible RNA-binding protein mediates binge alcohol-induced brain hypoactivity and impaired cognition in mice

BACKGROUND

Alcohol abuse affects the brain regions responsible for memory, coordination and emotional processing. Binge alcohol drinking has shown reductions in brain activity, but the molecular targets have not been completely elucidated. We hypothesized that brain cells respond to excessive alcohol by releasing a novel inflammatory mediator, called cold inducible RNA-binding protein (CIRP), which is critical for the decreased brain metabolic activity and impaired cognition.

METHODS

Male wild type (WT) mice and mice deficient in CIRP (CIRP^-/-) were studied before and after exposure to binge alcohol level by assessment of relative brain glucose metabolism with fluorodeoxyglucose (¹⁸FDG) and positron emission tomography (PET). Mice were also examined for object-place memory (OPM) and open field (OF) tasks.

RESULTS

Statistical Parametric Analysis (SPM) of ¹⁸FDG-PET uptake revealed marked decreases in relative glucose metabolism in distinct brain regions of WT mice after binge alcohol. Regional analysis (post hoc) revealed that while activity in the temporal (secondary visual) and limbic (entorhinal/perirhinal) cortices was decreased in WT mice, relative glucose metabolic activity was less suppressed in the CIRP^-/- mice. Group and condition interaction analysis revealed differing responses in relative glucose metabolism (decrease in WT mice but increase in CIRP^-/- mice) after alcohol in brain regions including the hippocampus and the cortical amygdala where the percent changes in metabolic activity correlated with changes in object discrimination performance. Behaviorally, alcohol-treated WT mice were impaired in exploring a repositioned object in the OPM task, and were more anxious in the OF task, whereas CIRP^-/- mice were not impaired in these tasks.

CONCLUSION

CIRP released from brain cells could be responsible for regional brain metabolic hypoactivity leading to cognitive impairment under binge alcohol conditions.

Constitutive Vagus Nerve Activation Modulates Immune Suppression in Sepsis Survivors

Patients surviving a septic episode exhibit persistent immune impairment and increased mortality due to enhanced vulnerability to infections. In the present study, using the cecal ligation and puncture (CLP) model of polymicrobial sepsis, we addressed the hypothesis that altered vagus nerve activity contributes to immune impairment in sepsis survivors. CLP-surviving mice exhibited less TNFα in serum following administration of LPS, a surrogate for an infectious challenge, than control-operated (control) mice. To evaluate the role of the vagus nerve in the diminished response to LPS, mice were subjected to bilateral subdiaphragmatic vagotomy at 2 weeks post-CLP. CLP-surviving vagotomized mice exhibited increased serum and tissue TNFα levels in response to LPS-challenge compared to CLP-surviving, non-vagotomized mice. Moreover, vagus nerve stimulation in control mice diminished the LPS-induced TNFα responses while having no effect in CLP mice, suggesting constitutive activation of vagus nerve signaling in CLP-survivors. The percentage of splenic CD4⁺ ChAT-EGFP⁺ T cells that relay vagus signals to macrophages was increased in CLP-survivors compared to control mice, and vagotomy in CLP-survivors resulted in a reduced percentage of ChAT-EGFP⁺ cells. Moreover, CD4 knockout CLP-surviving mice exhibited an enhanced LPS-induced TNFα response compared to wild-type mice, supporting a functional role for CD4⁺ ChAT⁺ T cells in mediating inhibition of LPS-induced TNFα responses in CLP-survivors. Blockade of the cholinergic anti-inflammatory pathway with methyllcaconitine, an α7 nicotinic acetylcholine receptor antagonist, restored LPS-induced TNFα responses in CLP-survivors. Our study demonstrates that the vagus nerve is constitutively active in CLP-survivors and contributes to the immune impairment.

Targeting junctional adhesion molecule-C ameliorates sepsis-induced acute lung injury by decreasing CXCR4+ aged neutrophils

Sepsis is a severe inflammatory condition associated with high mortality. Transmigration of neutrophils into tissues increases their lifespan to promote deleterious function. Junctional adhesion molecule-C (JAM-C) plays a pivotal role in neutrophil transmigration into tissues. We aim to study the role of JAM-C on the aging of neutrophils to cause sepsis-induced acute lung injury (ALI). Sepsis was induced in C57BL/6J mice by cecal ligation and puncture (CLP) and JAM-C expression in serum was assessed. Bone marrow-derived neutrophils (BMDN) were treated with recombinant mouse JAM-C (rmJAM-C) ex vivo and their viability was assessed. CLP-operated animals were administrated with either isotype IgG or anti-JAM-C Ab at a concentration of 3 mg/kg and after 20 h, aged neutrophils (CXCR4⁺ ) were assessed in blood and lungs and correlated with systemic injury and inflammatory markers. Soluble JAM-C level in serum was up-regulated during sepsis. Treatment with rmJAM-C inhibited BMDN apoptosis, thereby increasing their lifespan. CLP increased the frequencies of CXCR4⁺ neutrophils in blood and lungs, while treatment with anti-JAM-C Ab significantly reduced the frequencies of CXCR4⁺ aged neutrophils. Treatment with anti-JAM-C Ab significantly reduced systemic injury markers (alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) as well as systemic and lung inflammatory cytokines (IL-6 and IL-1β) and chemokine (macrophage inflammatory protein-2). The blockade of JAM-C improved lung histology and reduced neutrophil contents in lungs of septic mice. Thus, reduction of the pro-inflammatory aged neutrophils by blockade of JAM-C has a novel therapeutic potential in sepsis-induced ALI.

B-1a cells protect mice from sepsis-induced acute lung injury

BACKGROUND

Sepsis morbidity and mortality are aggravated by acute lung injury (ALI) or acute respiratory distress syndrome (ARDS). Mouse B-1a cells are a phenotypically and functionally unique sub-population of B cells, providing immediate protection against infection by releasing natural antibodies and immunomodulatory molecules. We hypothesize that B-1a cells ameliorate sepsis-induced ALI.

METHODS

Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). PBS or B-1a cells were adoptively transferred into the septic mice intraperitoneally. After 20 h of CLP, lungs were harvested and assessed by PCR and ELISA for pro-inflammatory cytokines (IL-6, IL-1β) and chemokine (MIP-2) expression, by histology for injury, by TUNEL and cleaved caspase-3 for apoptosis, and by myeloperoxidase (MPO) assay for neutrophil infiltration.

RESULTS

We found that septic mice adoptively transferred with B-1a cells significantly decreased the mRNA and protein levels of IL-6, IL-1β and MIP-2 in the lungs compared to PBS-treated mice. Mice treated with B-1a cells showed dramatic improvement in lung injury compared to PBS-treated mice after sepsis. We found apoptosis in the lungs was significantly inhibited in B-1a cell injected mice compared to PBS-treated mice after sepsis. B-1a cell treatment significantly down-regulated MPO levels in the lungs compared to PBS-treated mice in sepsis. The protective outcomes of B-1a cells in ALI was further confirmed by using B-1a cell deficient CD19-/- mice, which showed significant increase in the lung injury scores following sepsis as compared to WT mice.

CONCLUSIONS

Our results demonstrate a novel therapeutic potential of B-1a cells to treat sepsis-induced ALI.

Vagal tonic activity modulates immune suppression in sepsis survivors

Sepsis survivors exhibit persistent immune dysfunction and compromised quality of life with premature mortality due to increased vulnerability to infections. Previously we demonstrated in a cecal ligation and puncture (CLP) model, sepsis survivors had a reduced TNFα response to LPS-challenge in vivo. The vagus nerve is known to modulate TNFα production. To evaluate the role of the vagus nerve in the diminished TNFα production, sepsis-surviving mice were subjected to bilateral subdiaphragmatic vagotomy 2 weeks post-CLP. CLP-surviving vagotomized mice exhibit increased (p<0.05) TNFα levels in response to LPS-challenge 4 weeks post surgery compared to CLP. Moreover, vagus nerve stimulation in sham mice dampened (p<0.05) the LPS-induced TNFα response while it had no effect in CLP-surviving mice; suggesting that vagus nerve signaling is constitutively active in CLP-sepsis survivors. To identify whether there was an alteration in the number of acetylcholine-producing T cells that relay the vagus signal to splenic macrophages, we used ChAT-EGFP mice. Our findings show that the frequency of splenic ChAT-EGFP+ cells among memory CD4+CD44highCD62LlowT cells is increased (p<0.001) in CLP-surviving mice compared to sham, and vagotomy in these mice resulted in decreased (p<0.01) frequency of ChAT-EGFP+ cells, buttressing the conclusion that the vagus nerve is constitutively firing action potentials to activate more ChAT+ T cells. Methyllycaconitine, the α7 nicotinic acetylcholine receptor antagonist, increased (p<0.01) LPS-induced TNFα secretion in CLP-surviving mice compared to saline treated-CLP. In summary, our study demonstrates that altered vagus nerve activity contributes to the immune impairment in sepsis survivors.

Connexin 43 Hemichannel as a Novel Mediator of Sterile and Infectious Inflammatory Diseases

Cytoplasmic membrane-bound connexin 43 (Cx43) proteins oligomerize into hexameric channels (hemichannels) that can sometimes dock with hemichannels on adjacent cells to form gap junctional (GJ) channels. However, the possible role of Cx43 hemichannels in sterile and infectious inflammatory diseases has not been adequately defined due to the lack of selective interventions. Here we report that a proinflammatory mediator, the serum amyloid A (SAA), resembled bacterial endotoxin by stimulating macrophages to up-regulate Cx43 expression and double-stranded RNA-activated protein kinase R (PKR) phosphorylation in a TLR4-dependent fashion. Two well-known Cx43 mimetic peptides, the GAP26 and TAT-GAP19, divergently affected macrophage hemichannel activities in vitro, and differentially altered the outcome of lethal sepsis in vivo. By screening a panel of Cx43 mimetic peptides, we discovered that one cysteine-containing peptide, P5 (ENVCYD), effectively attenuated hemichannel activities, and significantly suppressed endotoxin-induced release of ATP and HMGB1 in vitro. In vivo, the P5 peptide conferred a significant protection against hepatic ischemia/reperfusion injury and lethal microbial infection. Collectively, these findings have suggested a pathogenic role of Cx43 hemichannels in sterile injurious as well as infectious inflammatory diseases possibly through facilitating extracellular ATP efflux to trigger PKR phosphorylation/activation.

New melanocortin-like peptide of E. coli can suppress inflammation via the mammalian melanocortin-1 receptor (MC1R): possible endocrine-like function for microbes of the gut

E. coli releases a 33 amino acid peptide melanocortin-like peptide of E. coli (MECO-1) that is identical to the C-terminus of the E. coli elongation factor-G (EF-G) and has interesting similarities to two prominent mammalian melanocortin hormones, alpha-melanocyte-stimulating hormone (alpha-MSH) and adrenocorticotropin (ACTH). Note that MECO-1 lacks HFRW, the common pharmacophore of the known mammalian melanocortin peptides. MECO-1 and the two hormones were equally effective in severely blunting release of cytokines (HMGB1 and TNF) from macrophage-like cells in response to (i) endotoxin (lipopolysaccharide) or (ii) pro-inflammatory cytokine HMGB-1. The in vitro anti-inflammatoty effects of MECO-1 and of alpha-MSH were abrogated by (i) antibody against melanocortin-1 receptor (MC1R) and by (ii) agouti, an endogenous inverse agonist of MC1R. In vivo MECO-1 was even more potent than alpha-MSH in rescuing mice from death due to (i) lethal doses of LPS endotoxin or (ii) cecal ligation and puncture, models of sterile and infectious sepsis, respectively.

Mitigation of sepsis-induced inflammatory responses and organ injury through targeting Wnt/β-catenin signaling

The Wnt/β-catenin pathway has been involved in regulating inflammation in various infectious and inflammatory diseases. Sepsis is a life-threatening condition caused by dysregulated inflammatory response to infection with no effective therapy available. Recently elevated Wnt/β-catenin signaling has been detected in sepsis. However, its contribution to sepsis-associated inflammatory response remains to be explored. In this study, we show that inhibition of Wnt/β-catenin signaling reduces inflammation and mitigates sepsis-induced organ injury. Using in vitro LPS-stimulated RAW264.7 macrophages, we demonstrate that a small-molecule inhibitor of β-catenin responsive transcription, iCRT3, significantly reduces the LPS-induced Wnt/β-catenin activity and also inhibits TNF-α production and IκB degradation in a dose-dependent manner. Intraperitoneal administration of iCRT3 to C57BL/6 mice, subjected to cecal ligation and puncture-induced sepsis, decreases the plasma levels of proinflammatory cytokines and organ injury markers in a dose-dependent manner. The histological integrity of the lungs is improved with iCRT3 treatment, along with reduced lung collagen deposition and apoptosis. In addition, iCRT3 treatment also decreases the expression of the cytokines, neutrophil chemoattractants, as well as the MPO activity in the lungs of septic mice. Based on these findings we conclude that targeting the Wnt/β-Catenin pathway may provide a potential therapeutic approach for treatment of sepsis.

Neuronal Circuits Modulate Antigen Flow Through Lymph Nodes

When pathogens and toxins breech the epithelial barrier, antigens are transported by the lymphatic system to lymph nodes. In previously immunized animals, antigens become trapped in the draining lymph nodes, but the underlying mechanism that controls antigen restriction is poorly understood. Here we describe the role of neurons in sensing and restricting antigen flow in lymph nodes. The antigen keyhole-limpet hemocyanin (KLH) injected into the mouse hind paw flows from the popliteal lymph node to the sciatic lymph node, continuing through the upper lymphatics to reach the systemic circulation. Re-exposure to KLH in previously immunized mice leads to decreased flow from the popliteal to the sciatic lymph node as compared with naïve mice. Administering bupivacaine into the lymph node region restores antigen flow in immunized animals. In contrast, neural activation using magnetic stimulation significantly decreases antigen trafficking in naïve animals as compared with sham controls. Ablating Na_V1.8 + sensory neurons significantly reduces antigen restriction in immunized mice. Genetic deletion of FcγRI/FcεRI also reverses the antigen restriction. Colocalization of PGP9.5-expressing neurons, FcγRI receptors and labeled antigen occurs at the antigen challenge site. Together, these studies reveal that neuronal circuits modulate antigen trafficking through a pathway that requires Na_V1.8 and FcγR.

Blood-Brain Barrier Deterioration and Hippocampal Gene Expression in Polymicrobial Sepsis: An Evaluation of Endothelial MyD88 and the Vagus Nerve

Systemic infection can initiate or exacerbate central nervous system (CNS) pathology, even in the absence of overt invasion of bacteria into the CNS. Recent epidemiological studies have demonstrated that human survivors of sepsis have an increased risk of long-term neurocognitive decline. There is thus a need for improved understanding of the physiological mechanisms whereby acute sepsis affects the CNS. In particular, MyD88-dependent activation of brain microvascular endothelial cells and a resulting loss of blood-brain barrier integrity have been proposed to play an important role in the effects of systemic inflammation on the CNS. Signaling through the vagus nerve has also been considered to be an important component of CNS responses to systemic infection. Here, we demonstrate that blood-brain barrier permeabilization and hippocampal transcriptional responses during polymicrobial sepsis occur even in the absence of MyD88-dependent signaling in cerebrovascular endothelial cells. We further demonstrate that these transcriptional responses can occur without vagus nerve input. These results suggest that redundant signals mediate CNS responses in sepsis. Either endothelial or vagus nerve activation may be individually sufficient to transmit systemic inflammation to the central nervous system. Transcriptional activation in the forebrain in sepsis may be mediated by MyD88-independent endothelial mechanisms or by non-vagal neuronal pathways.

Basal forebrain cholinergic signaling regulates peripheral cytokine responses (INC1P.349)

Brain cholinergic signaling regulates peripheral cytokine release and inflammation (Nat Rev Endocrinol, 2012, 8:743). We have previously shown that the centrally-acting acetylcholinesterase inhibitor galantamine suppresses peripheral pro-inflammatory cytokine release through a brain muscarinic receptor-mediated and vagus nerve-dependent mechanism. Here, we provide insight into the brain mechanisms of this regulation. VAChTNkx21-Cre-flox/flox mice with selective, basal forebrain cholinergic neuron genetic ablation of the vesicular acetylcholine transporter (an important determinant of acetylcholine release), and control VAChTflox/flox mice, were treated with galantamine or saline and subjected to endotoxemia. Galantamine (3mg/kg) i.p. administration suppressed serum TNF levels in control mice only. In addition, serum TNF and IL-10 in VAChTNkx2 1-Cre-flox/flox mice were significantly higher (2.9-fold, P<0.05) and lower (57%, P<0.05) respectively, as compared to control mice. Furthermore, electrical stimulation of the medial septum, an important basal forebrain cholinergic region, significantly lowered serum TNF (79%, P<0.01) and other pro-inflammatory cytokine levels in endotoxemic mice, as compared to sham-stimulation. These results demonstrate a previously unrecognized role of basal forebrain cholinergic signaling in the regulation of peripheral inflammation.

Brain region-specific alterations in the gene expression of cytokines, immune cell markers and cholinergic system components during peripheral endotoxin-induced inflammation

Inflammatory conditions characterized by excessive peripheral immune responses are associated with diverse alterations in brain function, and brain-derived neural pathways regulate peripheral inflammation. Important aspects of this bidirectional peripheral immune-brain communication, including the impact of peripheral inflammation on brain region-specific cytokine responses, and brain cholinergic signaling (which plays a role in controlling peripheral cytokine levels), remain unclear. To provide insight, we studied gene expression of cytokines, immune cell markers and brain cholinergic system components in the cortex, cerebellum, brainstem, hippocampus, hypothalamus, striatum and thalamus in mice after an intraperitoneal lipopolysaccharide injection. Endotoxemia was accompanied by elevated serum levels of interleukin (IL)-1β, IL-6 and other cytokines and brain region-specific increases in Il1b (the highest increase, relative to basal level, was in cortex; the lowest increase was in cerebellum) and Il6 (highest increase in cerebellum; lowest increase in striatum) mRNA expression. Gene expression of brain Gfap (astrocyte marker) was also differentially increased. However, Iba1 (microglia marker) mRNA expression was decreased in the cortex, hippocampus and other brain regions in parallel with morphological changes, indicating microglia activation. Brain choline acetyltransferase (Chat ) mRNA expression was decreased in the striatum, acetylcholinesterase (Ache) mRNA expression was decreased in the cortex and increased in the hippocampus, and M1 muscarinic acetylcholine receptor (Chrm1) mRNA expression was decreased in the cortex and the brainstem. These results reveal a previously unrecognized regional specificity in brain immunoregulatory and cholinergic system gene expression in the context of peripheral inflammation and are of interest for designing future antiinflammatory approaches.

Neutralization of osteopontin attenuates neutrophil migration in sepsis-induced acute lung injury

Introduction

Sepsis refers to severe systemic inflammation leading to acute lung injury (ALI) and death. Introducing novel therapies can reduce the mortality in ALI. Osteopontin (OPN), a secretory glycoprotein produced by immune reactive cells, plays a deleterious role in various inflammatory diseases. However, its role in ALI caused by sepsis remains unexplored. We hypothesize that treatment with an OPN-neutralizing antibody (anti-OPN Ab) protects mice against ALI during sepsis.

Methods

Sepsis was induced in 8-week-old male C57BL/6 mice by cecal ligation and puncture (CLP). Anti-OPN Ab or non-immunized IgG as control, at a dose of 50 μg/mouse, was intravenously injected at the time of CLP. After 20 hours, the expression of OPN and proinflammatory cytokines in tissues and plasma was examined by real-time PCR, Western blot, and ELISA. Plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) and the lung myeloperoxidase (MPO) levels were determined by colorimetric assays. Lung damage and neutrophil infiltrations were determined by histological H&E and Gr-1 staining, respectively. The effect of recombinant mouse OPN (rmOPN) on human neutrophil-like cell (HL-60) migration was performed by Boyden chamber assays and the involvement of intracellular signaling molecules in HL-60 cells was revealed by Western blot.

Results

After 20 hours of sepsis, mRNA and protein levels of OPN were significantly induced in lungs, spleen, and plasma. Treatment with an anti-OPN Ab in septic mice significantly reduced the plasma levels of ALT, AST, and LDH, and the proinflammatory cytokines IL-6, IL-1β and the chemokine MIP-2, compared with the vehicle group. Similarly, the lung mRNA and protein expressions of proinflammatory cytokines and chemokine were greatly reduced in anti-OPN Ab-treated animals. The lung histological architecture, MPO and neutrophil infiltration were significantly improved in anti-OPN Ab-treated mice compared with the vehicle animals. Treatment of rmOPN in HL-60 cells significantly increased their migration, in vitro. The neutrophils treated with rmOPN remarkably increased the levels of phospho focal adhesion kinase (pFAK), phospho extracellular signal-regulated kinase (pERK) and phospho p38.

Conclusions

Our findings clearly demonstrate the beneficial outcomes of anti-OPN Ab treatment in protecting against ALI, implicating a novel therapeutic strategy in sepsis.

Xanomeline suppresses excessive pro-inflammatory cytokine responses through neural signal-mediated pathways and improves survival in lethal inflammation

Inflammatory conditions characterized by excessive immune cell activation and cytokine release, are associated with bidirectional immune system-brain communication, underlying sickness behavior and other physiological responses. The vagus nerve has an important role in this communication by conveying sensory information to the brain, and brain-derived immunoregulatory signals that suppress peripheral cytokine levels and inflammation. Brain muscarinic acetylcholine receptor (mAChR)-mediated cholinergic signaling has been implicated in this regulation. However, the possibility of controlling inflammation by peripheral administration of centrally-acting mAChR agonists is unexplored. To provide insight we used the centrally-acting M1 mAChR agonist xanomeline, previously developed in the context of Alzheimer's disease and schizophrenia. Intraperitoneal administration of xanomeline significantly suppressed serum and splenic TNF levels, alleviated sickness behavior, and increased survival during lethal murine endotoxemia. The anti-inflammatory effects of xanomeline were brain mAChR-mediated and required intact vagus nerve and splenic nerve signaling. The anti-inflammatory efficacy of xanomeline was retained for at least 20h, associated with alterations in splenic lymphocyte, and dendritic cell proportions, and decreased splenocyte responsiveness to endotoxin. These results highlight an important role of the M1 mAChR in a neural circuitry to spleen in which brain cholinergic activation lowers peripheral pro-inflammatory cytokines to levels favoring survival. The therapeutic efficacy of xanomeline was also manifested by significantly improved survival in preclinical settings of severe sepsis. These findings are of interest for strategizing novel therapeutic approaches in inflammatory diseases.

HMGB1 mediates splenomegaly and expansion of splenic CD11b+ Ly-6C(high) inflammatory monocytes in murine sepsis survivors

BACKGROUND

More than 500,000 hospitalized patients survive severe sepsis annually in the USA. Recent epidemiological evidence, however, demonstrated that these survivors have significant morbidity and mortality, with 3-year fatality rates higher than 70%. To investigate the mechanisms underlying persistent functional impairment in sepsis survivors, here we developed a model to study severe sepsis survivors following cecal ligation and puncture (CLP).

METHODS

Sepsis was induced in mice by CLP and survivors were followed for twelve weeks. Spleen and blood were collected and analyzed at different time points post-sepsis.

RESULTS

We observed that sepsis survivors developed significant splenomegaly. Analysis of the splenic cellular compartments revealed a major expansion of the inflammatory CD11b+ Ly-6CHigh pool. Serum high-mobility group box 1 (HMGB1) levels in the sepsis surviving mice were significantly elevated for 4-6 weeks after post-sepsis, and administration of an anti-HMGB1 monoclonal antibody significantly attenuated splenomegaly as well as splenocyte priming. Administration of recombinant HMGB1 to naive mice induced similar splenomegaly, leukocytosis and splenocyte priming as observed in sepsis survivors. Interestingly analysis of circulating HMGB1 from sepsis survivors by mass spectroscopy demonstrated a stepwise increase of reduced form of HMGB1 (with known chemo-attractant properties) during the first 3 weeks, followed by disulphide form (with known inflammatory properties) 4-8 weeks after CLP.

DISCUSSION

Our results indicate that prolonged elevation of HMGB1 is a necessary and sufficient mediator of splenomegaly and splenocyte expansion, as well as splenocyte inflammatory priming in murine severe sepsis survivors.

Positive allosteric modulation of M1 muscarinic acetylcholine receptors suppresses lethal peripheral inflammation (P5082)

Peripheral inflammation can be regulated by activation of brain muscarinic acetylcholine receptor (mAChR)-dependent signaling functionally associated with a vagus-nerve mediated anti-inflammatory circuit (Proc Natl Acad Sci USA, 2006, 5219; Brain Behav Immun, 2009, 23:41). Here, we studied the specific role of the M1 mAChR subtype in this regulation by utilizing BQCA, a highly specific allosteric M1 mAChR activator that crosses the blood-brain barrier. Single drug (5,10 or 20 mg/kg, i.p) administration in mice 1h prior to endotoxin (8 mg/kg, i.p.) dose-dependently reduced serum and splenic TNF levels and significantly improved survival in mice as compared to vehicle-treated controls. Pharmacological blockade of brain mAChRs significantly abolished BQCA anti-inflammatory effects. Furthermore, BQCA (20 mg/kg, i.p.) significantly reduced serum and splenic TNF levels in wild type mice, but failed to alter TNF levels in M1 KO mice. Together these results indicate the anti-inflammatory role of increased functional activity of endogenous acetylcholine on the M1 mAChR by selective allosteric receptor activation. Our findings are of interest for further development of BQCA and other centrally-acting allosteric activators of the M1 mAChR as a novel class of experimental anti-inflammatory therapeutics.

Haptoglobin inhibits the pro-inflammatory activity of HMGB1 (P4177)

HMGB1 is a cytokine mediator in the pathogenesis of inflammatory diseases including sepsis (Yang et al, BBA, 2009). Recently we demonstrated that haptoglobin (Hp), a naturally occurring serum protein, binds to HMGB1 and suppresses HMGB1-stimulated TNF and IL-8 release in cultured macrophages. Hp knockout mice subjected to cecal ligation and puncture (CLP)-induced sepsis had significantly higher serum HMGB1 levels and higher mortality rates compared to wild type animals (75% survival in wild type vs. 34% in Hp knockout mice; P<0.05). Wild type mice subjected to CLP and received injections of Hp were twice as likely to survive (63% survival in Hp-treated vs. 33% in vehicle control; P<0.05), suggesting the therapeutic potential of exogenous Hp in sepsis. Hp is composed of alpha and beta subunits in a polymeric form (Yueh, J. Chromat B Life Sci. 2007). Structure-functional analysis revealed that Hp beta subunit alone is sufficient to recapitulate effects of Hp to neutralize HMGB1 in vitro in macrophages. The survival advantage of Hp in CLP-induced sepsis was also fully reproduced by Hp beta. Surface plasmon resonance analysis showed that Hp beta binds HMGB1 with high affinity (Kd = 29 nM). Thus, our data reveal unexpected roles of Hp as an endogenous antagonist of HMGB1, preventing the harmful HMGB1-induced inflammation in sepsis. The essential domain of Hp maps to the beta subunit, making it a target in the design of therapeutics.

Identification of pigment epithelium-derived factor as an adipocyte-derived inflammatory factor

Obesity is a major risk factor for insulin resistance, type 2 diabetes mellitus and cardiovascular disease. The pathophysiology of obesity is associated with chronic low-grade inflammation. Adipose tissue in obesity is significantly infiltrated by macrophages that secrete cytokines. The mechanisms of interaction between macrophages and adipocytes, leading to macrophage activation and increased cytokine release, remain to be elucidated. We reasoned that an adipocyte-derived factor might stimulate activation of macrophages. We have identified pigment epithelium-derived factor (PEDF) as a mediator of inflammation that is secreted by adipocytes and mediates macrophage activation. Recombinant PEDF activates macrophages to release tumor necrosis factor (TNF) and interleukin-1 (IL-1). The PEDF receptor adipose triglyceride lipase (ATGL) is required for PEDF-mediated macrophage activation. Selective inhibition of ATGL on macrophages attenuates PEDF-induced TNF production, and PEDF enhances the phosphorylation of p38 and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinases. PEDF administration to rats results in increased serum TNF levels, and insulin resistance. Together, these findings suggest that PEDF secreted by adipocytes contributes to the onset and maintenance of chronic inflammation in obesity, and may be a therapeutic target in ameliorating insulin resistance.

HMGB1 mediates cognitive impairment in sepsis survivors

Severe sepsis, a syndrome that complicates infection and injury, affects 750,000 annually in the United States. The acute mortality rate is approximately 30%, but, strikingly, sepsis survivors have a significant disability burden: up to 25% of survivors are cognitively and physically impaired. To investigate the mechanisms underlying persistent cognitive impairment in sepsis survivors, here we developed a murine model of severe sepsis survivors following cecal ligation and puncture (CLP) to study cognitive impairments. We observed that serum levels of high mobility group box 1 (HMGB1), a critical mediator of acute sepsis pathophysiology, are increased in sepsis survivors. Significantly, these levels remain elevated for at least 4 wks after CLP. Sepsis survivors develop significant, persistent impairments in learning and memory, and anatomic changes in the hippocampus associated with a loss of synaptic plasticity. Administration of neutralizing anti-HMGB1 antibody to survivors, beginning 1 wk after onset of peritonitis, significantly improved memory impairments and brain pathology. Administration of recombinant HMGB1 to naïve mice recapitulated the memory impairments. Together, these findings indicate that elevated HMGB1 levels mediate cognitive decline in sepsis survivors, and suggest that it may be possible to prevent or reverse cognitive impairments in sepsis survivors by administration of anti-HMGB1 antibodies.

α7 nicotinic acetylcholine receptor (α7nAChR) expression in bone marrow-derived non-T cells is required for the inflammatory reflex

The immune response to infection or injury coordinates host defense and tissue repair, but also has the capacity to damage host tissues. Recent advances in understanding protective mechanisms have found neural circuits that suppress release of damaging cytokines. Stimulation of the vagus nerve protects from excessive cytokine production and ameliorates experimental inflammatory disease. This mechanism, the inflammatory reflex, requires the α7 nicotinic acetylcholine receptor (α7nAChR), a ligand-gated ion channel expressed on macrophages, lymphocytes, neurons and other cells. To investigate cell-specific function of α7nAChR in the inflammatory reflex, we created chimeric mice by cross-transferring bone marrow between wild-type (WT) and α7nAChR-deficient mice. Deficiency of α7nAChR in bone marrow-derived cells significantly impaired vagus nerve-mediated regulation of tumor necrosis factor (TNF), whereas α7nAChR deficiency in neurons and other cells had no significant effect. In agreement with recent work, the inflammatory reflex was not functional in nude mice, because functional T cells are required for the integrity of the pathway. To investigate the role of T-cell α7nAChR, we adoptively transferred α7nAChR-deficient or WT T cells to nude mice. Transfer of WT and α7nAChR-deficient T cells restored function, indicating that α7nAChR expression on T cells is not necessary for this pathway. Together, these results indicate that α7nAChR expression in bone marrow-derived non-T cells is required for the integrity of the inflammatory reflex.

Haptoglobin inhibits the pro-inflammatory activity of HMGB1. (172.19)

Severe sepsis accounts for over 200,000 deaths in US annually (Angus et al, CCM, 2001). The mechanism involves endogenous molecules that impair organ function. Extracellular hemoglobin is one such factor enhancing tissue damage during sepsis. We designed haptoglobin-coated beads for a perfusion system to remove hemoglobin in an experimental sepsis model. Surprisingly, we observed that in addition to removing hemoglobin, haptoglobin beads also captured large amounts of HMGB1. HMGB1 is a major mediator on the final common pathway to lethality in sepsis (Yang et al, BBA 2009). Addition of haptoglobin suppressed HMGB1-stimulated TNF and IL-8 release in cultured macrophages. Haptoglobin knockout mice subjected to cecal perforation-induced sepsis had significantly higher serum HMGB1 levels and higher mortality compared to wild type animals (75% survival in wild type vs. 34% in haptoglobin knockout mice; n=15/group, P<0.05). Treatment with anti-HMGB1 antibodies significantly reduced the mortality in haptoglobin knockout mice (12% survival in control vs. 56% in animals receiving HMGB1 antibodies; n=16/group, P<0.05). Structure-function analysis revealed that haptoglobin beta subunit alone is sufficient to recapitulate the protective effects observed with haptoglobin. These findings indicate that haptoglobin is an endogenous modulator of HMGB1 that is capable of reducing the toxicity of HMGB1 in sepsis. Supported in part by grants from NIH (RO1GM62508, to KJT and RO1GM098446, to HY).

Choline Acetyltransferase-Expressing T cells are rare in young mice (122.7)

Neural circuits regulate cytokine production to prevent potentially damaging inflammation. A prototypical vagus nerve circuit, the inflammatory reflex, inhibits tumor necrosis factor production in spleen by a mechanism requiring acetylcholine signaling through the α7 nicotinic acetylcholine receptor on macrophages. Nerve fibers in spleen lack the machinery necessary for acetylcholine production. Instead, an acetylcholine-producing, memory phenotype T cell relays the neural signal. These choline acetyltransferase+ (ChAT+) T cells are required for inhibition of cytokine production by vagus nerve stimulation. Thus, action potentials originating in the vagus nerve regulate T cells, which in turn produce the acetylcholine required to control innate immune responses. The understanding of the phenotype of ChAT+ T cells is incomplete. Using flow cytometry, we detected TCRβ+ but no TCRγδ+ ChAT+ T cells. Since acetylcholine-producing T cells are memory cells, we hypothesized that this relay function is acquired, and investigated the splenic ChAT+ T cell population early in life. Indeed, splenic ChAT+ T cells were rare in 2 to 25 days old mice (2%±0.3 of ChAT+ cells) while B cells constituted the majority of the ChAT+ splenocytes (86±5%). In contrast, frequencies of ChAT+ T cells varied considerably in adults and could constitute 1/4 of the ChAT+ population. The infrequency of ChAT+ T cells early in life suggests that the inflammatory reflex may be impaired in young mice.

Acetylcholine-synthesizing T cells relay neural signals in a vagus nerve circuit

Neural circuits regulate cytokine production to prevent potentially damaging inflammation. A prototypical vagus nerve circuit, the inflammatory reflex, inhibits tumor necrosis factor-α production in spleen by a mechanism requiring acetylcholine signaling through the α7 nicotinic acetylcholine receptor expressed on cytokine-producing macrophages. Nerve fibers in spleen lack the enzymatic machinery necessary for acetylcholine production; therefore, how does this neural circuit terminate in cholinergic signaling? We identified an acetylcholine-producing, memory phenotype T cell population in mice that is integral to the inflammatory reflex. These acetylcholine-producing T cells are required for inhibition of cytokine production by vagus nerve stimulation. Thus, action potentials originating in the vagus nerve regulate T cells, which in turn produce the neurotransmitter, acetylcholine, required to control innate immune responses.

Galantamine alleviates inflammation and other obesity-associated complications in high-fat diet-fed mice

Obesity, a serious and growing health threat, is associated with low-grade inflammation that plays a role in mediating its adverse consequences. Previously, we have discovered a role for neural cholinergic signaling in controlling inflammation, and demonstrated that the cholinergic agent galantamine suppresses excessive proinflammatory cytokine release. The main objective of this study was to examine the efficacy of galantamine, a clinically-approved drug, in alleviating obesity-related inflammation and associated complications. After 8 wks on a high-fat diet, C57BL/6J mice were treated with either galantamine (4 mg/kg, intraperitoneally [i.p.]) or saline for 4 wks in parallel with mice on a low-fat diet and treated with saline. Galantamine treatment of obese mice significantly reduced body weight, food intake, abdominal adiposity, plasma cytokine and adipokine levels, and significantly improved blood glucose, insulin resistance and hepatic steatosis. In addition, galantamine alleviated impaired insulin sensitivity and glucose intolerance significantly. These results indicate a previously unrecognized potential of galantamine in alleviating obesity, inflammation and other obesity-related complications in mice. These findings are of interest for studying the efficacy of this clinically-approved drug in the context of human obesity and metabolic syndrome.

In a murine model of sepsis, IL-6 increases early and remains high until week 4, when its decrease may be related to late-phase immunodeficiency. (117.27)

Chronic sepsis survival is still an unchartered territory, where system-wide, sometimes perennial dysfunction occurs, usually with dire consequences. In the present study, polimicrobial abdominal sepsis -or sham surgery- was induced using the CLP model. Long-term survivors (>7 days) were sacrificed at weekly intervals, and blood and spleen were collected. Splenic and circulating leukocyte populations were analyzed by flow cytometry. Cytokines were measured by bead-array assay. We found an early increase in splenic size and weight, followed by massive, significant influx of granulocytes, monocytes, and B-cells. Splenic monocytes and granulocytes remained high until week 4. In contrast, splenic T-cell populations remained stable after sepsis, and B-cells returned to baseline by week 3. In peripheral circulation, we found early increases in IL-6 (25-fold; p=0.01), and TNF (7-fold; p=0.01). Other cytokines, including IL-2, IFN-γ, and IL-17A were not different between groups. Serum IL-6 concentration dropped back to levels similar to those of sham mice by week 4. Strikingly, around this time all surviving mice developed spontaneous abdominal abscesses. This is interesting since IL-6 levels have been shown to be a good predictor of early mortality. The fact that a late-phase decrease may be related to a the development of a state of imunosuppression opens new avenues to understanding CARS syndrome/immunoparalysis state known to be devastating in long term septic patients.

Cholinergic activation by galantamine suppresses obesity-associated inflammation in mice (54.4)

Low-grade systemic inflammation is a central event in obesity and mediates insulin resistance and other complications. Previously we discovered a role for neural cholinergic signaling in controlling inflammation (Nature, 2000, 405, 6785; Proc Natl Acad Sci USA, 2006, 5219) and demonstrated that the acetylcholinesterase inhibitor galantamine suppresses systemic lethal inflammation (Brain Behav Immun, 2009, 4; 1). Here we tested the efficacy of galantamine in alleviating obesity-associated inflammation. C57BL/6J mice with high fat-diet induced (for 8 weeks) obesity were treated with either galantamine (4 mg/kg daily, i.p.), or saline for 4 weeks while on the high-fat diet. Galantamine treatment of obese mice resulted in lower body weight and abdominal adiposity as compared to saline treatment. Galantamine significantly decreased systemic levels of characteristic pro-inflammatory cytokines/adipokines, including IL-6, MCP-1, resistin and leptin and increased adiponectin levels, accompanied by alleviated hyperglycemia, hyperinsulinemia, insulin resistance and hepatosteatosis. These results demonstrate that galantamine reduces obesity-associated inflammation and alleviates obesity-related complications and provide a rationale for further mechanistic studies and novel therapeutic implications. Translational aspects of these studies will be additionally facilitated by the fact that galantamine is a FDA approved (for the treatment of Alzheimer’s disease) cholinergic agent.

Pigment epithelium-derived factor as an inflammatory factor — a new role for an old protein (60.4)

Obesity is a major risk factor for insulin resistance, type 2 diabetes mellitus, and atherosclerosis. A chronic inflammatory state plays a pathogenic role in the development and progression of obesity-related disorders. Adipose tissue is infiltrated with macrophages; however the factors mediating the inflammatory response are not yet clear. Here we have identified and characterized a mediator of inflammation that is secreted by adipocytes. Pigment epithelium-derived factor (PEDF), a non-inhibitory serine protease inhibitor, is expressed by differentiated adipocytes. PEDF induces dose dependent increase in expression of proinflammatory cytokines (TNF, IL1 and IL6) in macrophages. The PEDF receptor, adipose triglyceride lipase (ATGL), is expressed in macrophages, and inhibitors of ATGL attenuated PEDF mediated responses indicating importance of PEDF-ATGL interaction in PEDF mediated inflammatory responses. Analysis of downstream effects demonstrated that p38 and ERK1/2 kinases are phosphorylated following PEDF treatment and consistently, inhibitors of p38 and ERK1/2 kinases attenuate PEDF induced cytokine production. PEDF administration induced increased serum levels of TNF and IL6 in mice, while neutralizing PEDF attenuated inflammatory responses. These studies suggest that PEDF secreted by adipocytes contributes to onset and maintenance of chronic inflammation observed in obesity and may serve as a therapeutic target for treatment of obesity related disorders.

Pigment epithelium-derived factor (PEDF) is an endogenous inflammatory factor (94.6)

Obesity is a major risk factor for conditions ranging from metabolic syndrome and type 2 diabetes mellitus to atherosclerosis. Low grade inflammation leading to insulin resistance is a central feature of the pathophysiology of most obesity-related disorders; however the factors linking these disorders are not well defined. Here a potential mediator of inflammation is identified and characterized in animal models. We identified pigment epithelium-derived factor (PEDF), a noninhibitory serine protease inhibitor, as a mediator released from cultured adipocytes. Adipocyte PEDF levels were elevated after treatment with TNF. Addition of adipocyte-conditioned media to macrophages resulted in increased proinflammatory cytokine production, and this activity was recapitulated by addition of recombinant PEDF to macrophages in culture. PEDF administration to mice mediated increased serum levels of TNF and IL6, and administration of neutralizing PEDF antibodies attenuated this cytokine release. Animals injected with recombinant PEDF developed insulin resistance. Considering these observations, in light of the recently reported elevated levels of circulating PEDF in patients with type 2 diabetes and metabolic syndrome, indicates that adipocyte secreted PEDF may contribute to the development of chronic inflammation and insulin resistance observed in obesity.

Long lasting macrophage cytokine suppression by alpha 7 nAChR requires JAK/STAT (138.23)

The central nervous system regulates innate immunity reflexively, as action potentials transmitted in the vagus nerve suppress cytokine release during endotoxemia. The mechanism of cytokine release by this neural circuit requires signaling through the alpha 7 nicotinic acetylcholine receptor (a7 nAChR), but the duration of this protection is incompletely understood. Electrical vagus nerve stimulation (VNS) in mice significantly inhibited serum TNF levels during endotoxemia, even when endotoxin was given 2, 24 or 48 h after VNS. This inhibition of TNF was abolished in a7 nAChR deficient mice, confirming the mechanism that requires this receptor. One-hour exposure of human macrophages to acetylcholine in vitro reduced endotoxin-induced increases in IKKbeta, IkappaBalpha activity and TNF release for up to 24 h after removal of acetylcholine. Levels of Supressor of Cytokine Signaling 1-3, A20, BCL3, IkappaBNS and IkappaBzeta were not altered in human macrophages 15 min to 8 h after exposure to acetylcholine, but exposure of macrophages to the selective JAK/STAT inhibitor AG490 abolished the cytokine suppressing effect of acetylcholine. Together with previous work indicating that JAK/STAT forms a signaling complex with a7 nAChR, these results suggest that JAK/STAT activation is required for long lasting suppression of macrophage cytokine release after transient exposure to acetylcholine.

Toll-like receptor 4 (TLR4) and interferon-gamma (IFN-r) are required for HMGB1-induced TNF release from macrophages. (34.18)

High mobility group box 1 (HMGB1) has been implicated as a cytokine mediator in the pathogenesis of inflammatory diseases (Yang et al. BBA, 2009). To study mechanisms of HMGB1 action, we produced mammalian HMGB1, devoid of bacterial products, and examined receptor signaling for HMGB1 mediated macrophage cytokine release. HMGB1 induced significant TNF release in macrophages from TLR2 KO, RAGE KO and wild type (WT) mice (n = 4-5 experiments). HMGB1 induced TNF release was completely abolished in TLR4 KO macrophages as compared to WT. Interestingly, we observed that HMGB1 induced TNF mRNA expression, but not TNF protein release, from TLR4 KO mouse macrophages. Pre-treatment of TLR4 KO macrophages with IFN-r restored HMGB1-induced TNF protein release. Thus, our results indicate that TLR4 is required for HMGB1-mediated cytokine release from macrophages, and that IFN-r can restore HMGB1-induced TNF release in TLR4 KO macrophages. (supported in part by grant from NIH, NIGMS, to KJT).

Neural control of acetylcholine release by T cells attenuates TNF production in endotoxemia (138.24)

The cholinergic anti-inflammatory pathway regulates pro-inflammatory cytokine production through vagus nerve signaling via the α7 subunit of the nicotinic acetylcholine receptor expressed on macrophages. Vagus nerve stimulation requires an intact splenic nerve to attenuate TNF production by spleen macrophages. Despite exhaustive search, cholinergic fibers have not been observed in spleen. Here, we used transgenic mice that express enhanced green fluorescent protein (eGFP) under control of transcriptional regulatory elements of choline acetyltransferase, the enzyme that synthesizes acetylcholine. eGFP was detected in spleen B and T cells, some of which were located in close proximity to catecholaminergic nerve endings in the parenchyma of the white pulp. Vagus nerve stimulation significantly increased acetylcholine levels in spleen. In vitro, adrenergic stimulation induced the release of acetylcholine by spleen lymphocytes through a β2 adrenergic receptor dependent mechanism. Vagus nerve stimulation failed to suppress TNF in endotoxemic nude mice, and transfer of CD3+ T cells into nude mice restored vagus nerve control of cytokine production. Together, these data identify T cells as an essential component of the cholinergic anti-inflammatory pathway, and suggest that neural signals increase acetylcholine release from spleen T cells, which in turn attenuates TNF production in spleen via α7 expressed on innate immune cells.

Cholinergic neural signals to the spleen down-regulate leukocyte trafficking via CD11b

The cholinergic anti-inflammatory pathway is a physiological mechanism that inhibits cytokine production and diminishes tissue injury during inflammation. Recent studies demonstrate that cholinergic signaling reduces adhesion molecule expression and chemokine production by endothelial cells and suppresses leukocyte migration during inflammation. It is unclear how vagus nerve stimulation regulates leukocyte trafficking because the vagus nerve does not innervate endothelial cells. Using mouse models of leukocyte trafficking, we show that the spleen, which is a major point of control for cholinergic modulation of cytokine production, is essential for vagus nerve-mediated regulation of neutrophil activation and migration. Administration of nicotine, a pharmacologic agonist of the cholinergic anti-inflammatory pathway, significantly reduces levels of CD11b, a beta(2)-integrin involved in cell adhesion and leukocyte chemotaxis, on the surface of neutrophils in a dose-dependent manner and this function requires the spleen. Similarly, vagus nerve stimulation significantly attenuates neutrophil surface CD11b levels only in the presence of an intact and innervated spleen. Further mechanistic studies reveal that nicotine suppresses F-actin polymerization, the rate-limiting step for CD11b surface expression. These studies demonstrate that modulation of leukocyte trafficking via cholinergic signaling to the spleen is a specific, centralized neural pathway positioned to suppress the excessive accumulation of neutrophils at inflammatory sites. Activating this mechanism may have important therapeutic potential for preventing tissue injury during inflammation.

Brain acetylcholinesterase activity controls systemic cytokine levels through the cholinergic anti-inflammatory pathway

The excessive release of cytokines by the immune system contributes importantly to the pathogenesis of inflammatory diseases. Recent advances in understanding the biology of cytokine toxicity led to the discovery of the "cholinergic anti-inflammatory pathway," defined as neural signals transmitted via the vagus nerve that inhibit cytokine release through a mechanism that requires the alpha7 subunit-containing nicotinic acetylcholine receptor (alpha7nAChR). Vagus nerve regulation of peripheral functions is controlled by brain nuclei and neural networks, but despite considerable importance, little is known about the molecular basis for central regulation of the vagus nerve-based cholinergic anti-inflammatory pathway. Here we report that brain acetylcholinesterase activity controls systemic and organ specific TNF production during endotoxemia. Peripheral administration of the acetylcholinesterase inhibitor galantamine significantly reduced serum TNF levels through vagus nerve signaling, and protected against lethality during murine endotoxemia. Administration of a centrally-acting muscarinic receptor antagonist abolished the suppression of TNF by galantamine, indicating that suppressing acetylcholinesterase activity, coupled with central muscarinic receptors, controls peripheral cytokine responses. Administration of galantamine to alpha7nAChR knockout mice failed to suppress TNF levels, indicating that the alpha7nAChR-mediated cholinergic anti-inflammatory pathway is required for the anti-inflammatory effect of galantamine. These findings show that inhibition of brain acetylcholinesterase suppresses systemic inflammation through a central muscarinic receptor-mediated and vagal- and alpha7nAChR-dependent mechanism. Our data also indicate that a clinically used centrally-acting acetylcholinesterase inhibitor can be utilized to suppress abnormal inflammation to therapeutic advantage.

Modulation of TNF release by choline requires alpha7 subunit nicotinic acetylcholine receptor-mediated signaling

The alpha7 subunit-containing nicotinic acetylcholine receptor (alpha7nAChR) is an essential component in the vagus nerve-based cholinergic anti-inflammatory pathway that regulates the levels of TNF, high mobility group box 1 (HMGB1), and other cytokines during inflammation. Choline is an essential nutrient, a cell membrane constituent, a precursor in the biosynthesis of acetylcholine, and a selective natural alpha7nAChR agonist. Here, we studied the anti-inflammatory potential of choline in murine endotoxemia and sepsis, and the role of the alpha7nAChR in mediating the suppressive effect of choline on TNF release. Choline (0.1-50 mM) dose-dependently suppressed TNF release from endotoxin-activated RAW macrophage-like cells, and this effect was associated with significant inhibition of NF-kappaB activation. Choline (50 mg/kg, intraperitoneally [i.p.]) treatment prior to endotoxin administration in mice significantly reduced systemic TNF levels. In contrast to its TNF suppressive effect in wild type mice, choline (50 mg/kg, i.p.) failed to inhibit systemic TNF levels in alpha7nAChR knockout mice during endotoxemia. Choline also failed to suppress TNF release from endotoxin-activated peritoneal macrophages isolated from alpha7nAChR knockout mice. Choline treatment prior to endotoxin resulted in a significantly improved survival rate as compared with saline-treated endotoxemic controls. Choline also suppressed HMGB1 release in vitro and in vivo, and choline treatment initiated 24 h after cecal ligation and puncture (CLP)-induced polymicrobial sepsis significantly improved survival in mice. In addition, choline suppressed TNF release from endotoxin-activated human whole blood and macrophages. Collectively, these data characterize the anti-inflammatory efficacy of choline and demonstrate that the modulation of TNF release by choline requires alpha7nAChR-mediated signaling.

Splenectomy protects against sepsis lethality and reduces serum HMGB1 levels

High mobility group box 1 (HMGB1) is a critical mediator of lethal sepsis. Previously, we showed that apoptotic cells can activate macrophages to release HMGB1. During sepsis, apoptosis occurs primarily in lymphoid organs, including the spleen and thymus. Currently, it is unclear whether this accelerated lymphoid organ apoptosis contributes to systemic release of HMGB1 in sepsis. In this study, we report that splenectomy significantly reduces systemic HMGB1 release and improves survival in mice with polymicrobial sepsis. Treatment with a broad-spectrum caspase inhibitor reduces systemic lymphocyte apoptosis, suppresses circulating HMGB1 concentrations, and improves survival during polymicrobial sepsis, but fails to protect septic mice following splenectomy. These findings indicate that apoptosis in the spleen is essential to the pathogenesis of HMGB1-mediated sepsis lethality.

Cholinergic agonists attenuate renal ischemia-reperfusion injury in rats

Inflammation plays a significant role in the pathophysiology of renal ischemia-reperfusion injury. Local inflammation is modulated by the brain via the vagus nerve and nicotinic acetylcholine receptors such that electrical or pharmacologic stimulation of this cholinergic anti-inflammatory pathway results in suppression of proinflammatory cytokine production. We examined the effects of cholinergic stimulation using agonists, nicotine or GTS-21, given before or after bilateral renal ischemia-reperfusion injury in rats. Pretreatment of rats with either agonist significantly attenuated renal dysfunction and tubular necrosis induced by renal ischemia. Similarly, tumor necrosis factor-alpha protein expression and leukocyte infiltration of the kidney were markedly reduced following treatment with cholinergic agonists. We found functional nicotinic acetylcholine receptors were present on rat proximal tubule epithelial cells. Cholinergic stimulation significantly decreased tubular necrosis in vagotomized rats after injury, implying an intact vagus nerve is not required for this renoprotective effect.

Transcutaneous vagus nerve stimulation reduces serum high mobility group box 1 levels and improves survival in murine sepsis

OBJECTIVE

Electrical vagus nerve stimulation inhibits proinflammatory cytokine production and prevents shock during lethal systemic inflammation through an alpha7 nicotinic acetylcholine receptor (alpha7nAChR)-dependent pathway to the spleen, termed the cholinergic anti-inflammatory pathway. Pharmacologic alpha7nAChR agonists inhibit production of the critical proinflammatory mediator high mobility group box 1 (HMGB1) and rescue mice from lethal polymicrobial sepsis. Here we developed a method of transcutaneous mechanical vagus nerve stimulation and then investigated whether this therapy can protect mice against sepsis lethality.

DESIGN

Prospective, randomized study.

SETTING

Institute-based research laboratory.

SUBJECTS

Male BALB/c mice.

INTERVENTIONS

Mice received lipopolysaccharide to induce lethal endotoxemia or underwent cecal ligation and puncture to induce polymicrobial sepsis. Mice were then randomized to receive electrical, transcutaneous, or sham vagus nerve stimulation and were followed for survival or euthanized at predetermined time points for cytokine analysis.

MEASUREMENTS AND MAIN RESULTS

Transcutaneous vagus nerve stimulation dose-dependently reduced systemic tumor necrosis factor levels during lethal endotoxemia. Treatment with transcutaneous vagus nerve stimulation inhibited HMGB1 levels and improved survival in mice with polymicrobial sepsis, even when administered 24 hrs after the onset of disease.

CONCLUSIONS

Transcutaneous vagus nerve stimulation is an efficacious treatment for mice with lethal endotoxemia or polymicrobial sepsis.

Alternative chemical modifications reverse the binding orientation of a pharmacophore scaffold in the active site of macrophage migration inhibitory factor

Pharmacophores are chemical scaffolds upon which changes in chemical moieties (R-groups) at specific sites are made to identify a combination of R-groups that increases the therapeutic potency of a small molecule inhibitor while minimizing adverse effects. We developed a pharmacophore based on a carbonyloxime (OXIM) scaffold for macrophage migration inhibitory factor (MIF), a protein involved in the pathology of sepsis, to validate that inhibition of a catalytic site could produce therapeutic benefits. We studied the crystal structures of MIF.OXIM-based inhibitors and found two opposite orientations for binding to the active site that were dependent on the chemical structures of an R-group. One orientation was completely unexpected based on previous studies with hydroxyphenylpyruvate and (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester (ISO-1). We further confirmed that the unexpected binding mode targets MIF in cellular studies by showing that one compound, OXIM-11, abolished the counter-regulatory activity of MIF on anti-inflammatory glucocorticoid action. OXIM-11 treatment of mice, initiated 24 h after the onset of cecal ligation and puncture-induced sepsis, significantly improved survival when compared with vehicle-treated controls, confirming that inhibition of the MIF catalytic site could produce therapeutic effects. The crystal structures of the MIF inhibitor complexes provide insight for further structure-based drug design efforts.