Peripheral Tissue Inflammation Research Articles

The Presence of High Levels of Circulating Trimethylamine N-Oxide Exacerbates Central and Peripheral Inflammation and Inflammatory Hyperalgesia in Rats Following Carrageenan Injection.

Gut microbiota-derived metabolite trimethylamine N-oxide (TMAO) has recently been shown to promote inflammation in peripheral tissues and the central nervous system (CNS), contributing to the pathogenesis of various human diseases. Here, we examined whether the presence of high levels of circulating TMAO would influence central and peripheral inflammation and inflammatory hyperalgesia in a carrageenan (CG)-induced rat model of inflammation. Rats were treated with vehicle or TMAO in drinking water. After 2weeks of treatment, rats received intraplantar injection of saline or CG into the hind paw. Acute nociception was unaltered in TMAO-treated rats that had elevated plasma TMAO. Following CG injection, TMAO-treated rats were significantly more sensitive to thermal and mechanical stimulation of the inflamed paw and displayed greater paw edema. Molecular studies revealed that CG injection induced increases in recruitment of neutrophils/macrophages in the paw and activation of microglia in the spinal cord, along with increased activation of nuclear factor (NF)-kB and production of proinflammatory mediators in both vehicle-treated rats and TMAO-treated rats. However, the increases in the above parameters were more pronounced in TMAO-treated rats. Moreover, TMAO treatment decreased protein levels of anti-inflammatory mediator regulator of G protein signaling (RGS)-10 in both saline-injected rats and CG-injected rats. These findings suggest that the presence of high levels of circulating TMAO downregulates anti-inflammatory mediator RGS10 in both peripheral tissues and the CNS, which may increase the susceptibility to inflammatory challenge-induced NF-kB activity, leading to greater increase in production of inflammatory mediators and consequent exacerbation of peripheral inflammation and inflammatory hyperalgesia.

Antioxidant and anti-inflammatory effects of dexrazoxane on dopaminergic neuron degeneration in rodent models of Parkinson's disease

Emerging evidence has demonstrated that the integrity and the function of blood-brain barrier (BBB) are gradually impaired in the processes of aging and nervous system disorders, including neurodegenerative diseases (e.g. Parkinson's disease, PD). The leakage of BBB contributes to the infiltration of peripheral immune cells and harmful mediators into brain parenchyma, even the drugs that can not cross BBB under physiological conditions. Therefore, PD has been regarded as not only a neurodegenerative disease, but also a systemic disorder. In the present study, we demonstrate for the first time that Dexrazoxane (Dex), a drug clinically used to reduce doxorubicin-induced cardiotoxicity in chemotherapy, can enter into midbrain and striatum through broken BBB in 6-hydroxydopamine (6-OHDA)- and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced rodent models of PD. Unexpectedly, Dex (1.5, 5, 15 mg/kg, i.p.) administration for 3-week significantly ameliorates apomorphine-induced contralateral rotation behavior in 6-OHDA-treated rats and Dex (10 mg/kg, i.p.) treatment for 5-week improves MPTP-induced mouse motor dysfunctions. We find that Dex administration protects dopaminergic neurons against neurotoxin-induced degeneration in SNc, accompanied by the attenuated glial cell activation. Further study indicates that suppression of oxidative stress and endoplasmic reticulum stress, as well as the inhibition of systemic inflammation in both peripheral tissues and brain, contribute to the neuroprotective effects of Dex in PD models. Our study implies that Dex may serve as an effective neuroprotectant to treat neurodegeneration and has potential clinical value in term of PD therapeutics.

Sphingosine-1-Phosphate and Macrophage Biology-How the Sphinx Tames the Big Eater.

The sphingolipid sphingosine-1-phosphate (S1P) is produced by sphingosine kinases to either signal through intracellular targets or to activate a family of specific G-protein-coupled receptors (S1PR). S1P levels are usually low in peripheral tissues compared to the vasculature, forming a gradient that mediates lymphocyte trafficking. However, S1P levels rise during inflammation in peripheral tissues, thereby affecting resident or recruited immune cells, including macrophages. As macrophages orchestrate initiation and resolution of inflammation, the sphingosine kinase/S1P/S1P-receptor axis emerges as an important determinant of macrophage function in the pathogenesis of inflammatory diseases such as cancer, atherosclerosis, and infection. In this review, we therefore summarize the current knowledge how S1P affects macrophage biology.

Protective Effect of Melatonin Against Polymicrobial Sepsis Is Mediated by the Anti-bacterial Effect of Neutrophils.

Sepsis is an infection- or toxin-mediated systemic inflammatory syndrome. Previous studies have shown that melatonin, the primary hormone produced by the pineal gland, attenuates the effect of polymicrobial infection-mediated septic shock in animals. However, the mechanism of the anti-septic effect of melatonin during polymicrobial infection has not been well-studied. In this study, we investigated how melatonin protects mice from polymicrobial sepsis. Melatonin treatment inhibited peripheral tissue inflammation and tissue damage in a cecal ligation puncture (CLP)-induced polymicrobial sepsis model, consequently reducing the mortality of the mice. We found that macrophages and neutrophils expressed melatonin receptors. Upon depletion of neutrophils, melatonin-induced protection against polymicrobial infection failed in the mice, but melatonin treatment in macrophage-depleted mice attenuated the mice mortality resulting from polymicrobial sepsis. Moreover, melatonin treatment promoted the development of the neutrophil extracellular trap (NET), which contributed to anti-bacterial activity during polymicrobial infection, whereas the phagocytic activities of neutrophils were inhibited by melatonin. The data from this study support previously unexplained antiseptic effects of melatonin during a polymicrobial infection and could be potentially useful for human patients with sepsis.

Chrysanthemum Leaf Ethanol Extract Prevents Obesity and Metabolic Disease in Diet-Induced Obese Mice via Lipid Mobilization in White Adipose Tissue.

This study aimed to elucidate the molecular mechanism of Chrysanthemum morifolium Ramat. against obesity and diabetes, by comparing the transcriptional changes in epididymal white adipose tissue (eWAT) with those of the bioactive compound in C. morifolium, luteolin (LU). Male C57BL/6J mice were fed a normal diet, high-fat diet (HFD), and HFD supplemented with 1.5% w/w chrysanthemum leaf ethanol extract (CLE) for 16 weeks. Supplementation with CLE and LU significantly decreased the body weight gain and eWAT weight by stimulating mRNA expressions for thermogenesis and energy expenditure in eWAT via lipid mobilization, which may be linked to the attenuation of dyslipidemia. Furthermore, CLE and LU increased uncoupling protein-1 protein expression in brown adipose tissue, leading to energy expenditure. Of note, CLE and LU supplements enhanced the balance between lipid storage and mobilization in white adipose tissue (WAT), in turn, inhibiting adipocyte inflammation and lipotoxicity of peripheral tissues. Moreover, CLE and LU attenuated hepatic steatosis by suppressing hepatic lipogenesis, thereby ameliorating insulin resistance and dyslipidemia. Our data suggest that CLE helps inhibit obesity and its comorbidities via the complex interplay between liver and WAT in diet-induced obese mice.

CXCL13/CXCR5 signaling contributes to diabetes-induced tactile allodynia via activating pERK, pSTAT3, pAKT pathways and pro-inflammatory cytokines production in the spinal cord of male mice

Painful diabetic neuropathy (PDN) is a severely debilitating chronic pain syndrome. Spinal chemokine CXCL13 and its receptor CXCR5 were recently demonstrated to play a pivotal role in the pathogenesis of chronic pain induced by peripheral tissue inflammation or nerve injury. In this study we investigated whether CXCL13/CXCR5 mediates PDN and the underlying spinal mechanisms. We used the db/db type 2 diabetes mice, which showed obvious hyperglycemia and obese, long-term mechanical allodynia, and increased expression of CXCL13, CXCR5 as well as pro-inflammatory cytokines TNF-α and IL-6 in the spinal cord. Furthermore, in the spinal cord of db/db mice there is significantly increased gliosis and upregulated phosphorylation of cell signaling kinases, including pERK, pAKT and pSTAT3. Mechanical allodynia and upregulated pERK, pAKT and pSTAT3 as well as production of TNF-α and IL-6 were all attenuated by the noncompetitive NMDA receptor antagonist MK-801. If spinal giving U0126 (a selective MEK inhibitor) or AG490 (a Janus kinase (JAK)-STAT inhibitor) to db/db mice, both of them can decrease the mechanical allodynia, but only inhibit pERK (by U0126) or pSTAT3 (by AG490) respectively. Acute administration of CXCL13 in C57BL/6J mice resulted in exacerbated thermal hyperalgesia and mechanical allodynia, activation of the pERK, pAKT and pSTAT3 pathways and increased production of pro-inflammatory cytokines (IL-1β, TNF-α and IL-6), which were all attenuated by knocking out of Cxcr5. In all, our work showed that chemokine CXCL13 and its receptor CXCR5 in spinal cord contribute to the pathogenesis of PDN and may help develop potential novel therapeutic approaches for patients afflicted with PDN.

Patent Highlights December 2018–January 2019

Patent Highlights December 2018–January 2019

High Fat, High Sugar Diet Induces Metabolic Changes in Articular Cartilage that are Reversed with Low Intensity Exercise and Genistein Treatment

High fat, high‐sugar diet (HSFD) has been shown to induce obesity, metabolic dysregulation, and inflammation in peripheral tissues. Inflammation within cartilage tissue is associated with metabolic changes that lead to arthrosis. In this study, we examine the effects of HSFD on expression of col10a and MMP‐13 in articular cartilage of the knee joint. Both of these proteins are markers for inflammation in chondral tissue. In the presence of proinflammatory cytokines, col10a expression by chondrocytes decreases, while MMP‐13 increases. We also examined the effects of low intensity exercise and genistein treatment on cartilage metabolism. Both of these treatments have been shown to improve bone health, but their effects on diet‐induced cartilage inflammation are unclear. We randomly assigned 100 mice to five treatment groups of equal sizes: lean controls, HFSD fed, HFSD + exercise, HFSD + genistein, and HFSD + exercise + genistein. HFSD included 60% fat in chow and 42 g/L sugar in the drinking water. Exercise training included treadmill running for 180 min/week. Genistein was given in the diet at 600 mg/kg. Duration of treatment was 12 weeks. Col10a expression was significantly reduced in mice fed HFSD versus lean controls (P < 0.05). Mice treated with exercise and genistein in combination exhibited decreased col10a expression that was similar to levels expressed in cartilage of lean controls. MMP‐13 expression did not differ significantly among the treatment groups (P > 0.05). Examination of articular cartilage stained with H&E revealed the thickness of the uncalcified zones was significantly reduced in mice fed HFSD in comparison to lean control mice (P < 0.05). Staining in this zone also reflected reduced proteoglycan content in the cartilage of mice in the HFSD treatment group. These findings suggest articular cartilage of mice fed HFSD exhibit signs of inflammation and reduced capacity to resist compression. Treatment with genistein and exercise in combination resulted in articular cartilage that more closely resembles cartilage of lean mice fed a standard diet. Low‐intensity exercise and genistein intake may prove beneficial to joint health in the obese condition.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Hyperactivation of proprioceptors induces microglia-mediated long-lasting pain in a rat model of chronic fatigue syndrome

BackgroundPatients diagnosed with chronic fatigue syndrome (CFS) or fibromyalgia experience chronic pain. Concomitantly, the rat model of CFS exhibits microglial activation in the lumbar spinal cord and pain behavior without peripheral tissue damage and/or inflammation. The present study addressed the mechanism underlying the association between pain and chronic stress using this rat model.MethodsChronic or continuous stress-loading (CS) model rats, housed in a cage with a thin level of water (1.5 cm in depth), were used. The von Frey test and pressure pain test were employed to measure pain behavior. The neuronal and microglial activations were immunohistochemically demonstrated with antibodies against ATF3 and Iba1. Electromyography was used to evaluate muscle activity.ResultsThe expression of ATF3, a marker of neuronal hyperactivity or injury, was first observed in the lumbar dorsal root ganglion (DRG) neurons 2 days after CS initiation. More than 50% of ATF3-positive neurons simultaneously expressed the proprioceptor markers TrkC or VGluT1, whereas the co-expression rates for TrkA, TrkB, IB4, and CGRP were lower than 20%. Retrograde labeling using fluorogold showed that ATF3-positive proprioceptive DRG neurons mainly projected to the soleus. Substantial microglial accumulation was observed in the medial part of the dorsal horn on the fifth CS day. Microglial accumulation was observed around a subset of motor neurons in the dorsal part of the ventral horn on the sixth CS day. The motor neurons surrounded by microglia were ATF3-positive and mainly projected to the soleus. Electromyographic activity in the soleus was two to three times higher in the CS group than in the control group. These results suggest that chronic proprioceptor activation induces the sequential activation of neurons along the spinal reflex arc, and the neuronal activation further activates microglia along the arc. Proprioceptor suppression by ankle joint immobilization significantly suppressed the accumulation of microglia in the spinal cord, as well as the pain behavior.ConclusionOur results indicate that proprioceptor-induced microglial activation may be a key player in the initiation and maintenance of abnormal pain in patients with CFS.

Fine particulate matter (PM2.5) enhances FcεRI-mediated signaling and mast cell function

Persistent exposure to ambient fine particulate matter (PM2.5) can exacerbate allergic diseases in humans. Mast cells play an important role in allergic inflammation in peripheral tissues, such as skin, mucosa, and lung. Engagement of the high-affinity Fc receptor leads to mast cell degranulation, releasing a variety of highly active mediators including histamine, leukotrienes, and inflammatory cytokines. How PM2.5 exposure affects mast cell activation and function remains largely unknown. To characterize the effect of PM2.5 on mast cells, we used bone marrow-derived mast cells (BMMCs) to examine whether PM2.5 affected FcεRI-mediated signaling, cytokine production, and degranulation. Exposure to high doses of PM2.5 caused pronounced apoptosis and death of BMMCs. In contrast, exposure to low doses of PM2.5 enhanced mast cell degranulation and FcεRI-mediated cytokine production. Further analysis showed that PM2.5 treatment increased Syk activation and subsequently phosphorylation of its substrates including LAT, PLC-γ1, and SLP-76. Moreover, PM2.5 treatment led to activation of the PI3K and MAPK pathways. Intriguingly, water-soluble fraction of PM2.5 were found responsible for the enhancement of FcεRI-mediated signaling, mast cell degranulation, and cytokine production. Our data suggest that PM2.5, mainly water-soluble fraction of PM2.5, could affect mast cell activation through enhancing FcεRI-mediated signaling.

Pilose antler polypeptides ameliorate inflammation and oxidative stress and improves gut microbiota in hypoxic-ischemic injured rats

Pilose antler polypeptides (PAP) have recently been found to be effective in the treatment of brain damage in hypoxic-ischemic encephalopathy (HIE). However, the impacts of hypoxic-ischemic (HI)-induced injury on oxidative stress and inflammation in peripheral tissues remain unclear. In the present study, we hypothesized that the administration of PAP might exert a protective effect on HI-induced peripheral tissue dysfunction. To that end, HI-injured rats were administered PAP for 3 weeks, and then the metabolic phenotypes and gut microbiota were evaluated by qPCR and 16S rRNA sequencing analysis. Hepatic lipid accumulation, systemic oxidative stress and inflammation, as well as impaired gut barrier function and altered gut microbiota were found in HI-injured rats, which were reversed by the treatment of PAP. PAP treatment modulated the abundance and composition of gut microbiota, and PICRUSt analyses revealed that PAP treatment also led to a functional change in the microbial communities. These protective effects of PAP were associated with attenuated susceptibility to bacterial infections, decreased antibiotic synthesis and changed cellular processes and signaling, which may cause inflammation, barrier dysfunction, oxidative stress and mitochondria dysfunction in HI rats. In conclusion, these results suggested that PAP protected against HI-induced peripheral tissue damage in rats and therefore might be a potential candidate for the treatment of HIE and its complications.

Hemp seed/evening primrose oil affects expression of STAT3, IL-17, and FOXP3+ in experimental autoimmune encephalomyelitis.

T helper (Th)-17 mediate inflammation in both peripheral tissues and the central nervous system. Signal transducer and activator of transcription factor3 (STAT3) is required for Th-cell pathogenicity and its activation in the brain has been demonstrated during the acute phase of experimental autoimmune encephalomyelitis (EAE) through the mammalian target of rapamycin (mTOR) signaling. Rapamycin (RAPA), an inhibitor of mTOR, can drive Forkhead box P3 (FOXP3+) induction as a regulatory factor. The aim of this study was to determine the effects of hemp seed/evening primrose oils (HSO/EPO) supplement on the expression of FOXP3+, STAT3, and interleukin (IL)-17 genes in EAE lymph nodes. EAE was induced by myelin oligodendrocyte glycoprotein peptide in mice, and then the mice were assigned to three treatment groups compared to two control groups (EAE and naive). The histological findings of the spinal cord were evaluated. To determine the expression of FOXP3+, STAT3, and IL-17 genes in the lymphocytes, qRT-PCR was used. Our results showed that EAE severity was reduced in HSO/EPO mice by reducing the expression of STAT3 and IL-17 genes and increasing the expression of FOXP3+ gene, which was confirmed by slight inflammation in the spinal cord. Histological findings showed a significant improvement in the HSO/EPO group. Our findings suggest that the HSO/EPO treatment can be used to ameliorate the demyelination of spinal cord, which was confirmed by immunological and histological findings.

Implications of Systemic Inflammation and Periodontitis for Major Depression.

Increasing evidence suggests that infection and persistent low-grade inflammation in peripheral tissues are important pathogenic factors in major depression. Major depression is frequently comorbid with systemic inflammatory diseases/conditions such as rheumatoid arthritis, allergies of different types, multiple sclerosis, cardiovascular disease, inflammatory bowel disease, chronic liver disease, diabetes, and cancer, in which pro-inflammatory cytokines are overexpressed. A number of animal studies demonstrate that systemic inflammation induced by peripheral administration of lipopolysaccharide increases the expression of pro-inflammatory cytokines in both the periphery and brain and causes abnormal behavior similar to major depression. Systemic inflammation can cause an increase in CNS levels of pro-inflammatory cytokines associated with glial activation, namely, neuroinflammation, through several postulated pathways. Such neuroinflammation can in turn induce depressive moods and behavioral changes by affecting brain functions relevant to major depression, especially neurotransmitter metabolism. Although various clinical studies imply a causal relationship between periodontitis, which is one of the most common chronic inflammatory disorders in adults, and major depression, the notion that periodontitis is a risk factor for major depression is still unproven. Additional population-based cohort studies or prospective clinical studies on the relationship between periodontitis and major depression are needed to substantiate the causal link of periodontitis to major depression. If such a link is established, periodontitis may be a modifiable risk factor for major depression by simple preventive oral treatment.

Comparison of effects of serine racemase knockout on nociceptive behavior among different models of neuropathic and inflammatory pain

Peripheral nerve injury and tissue inflammation often induce abnormal pain. The activation of N‐methyl‐D‐aspartate (NMDA) receptors mediates the development and maintenance of such abnormal pain. D‐serine co‐localizes with NMDA receptors and acts as an endogenous co‐agonist of the NMDA receptor at the glycine binding site. D‐serine is synthesized from L‐serine by serine racemase (SR), which is an enzyme that is abundant in the central nervous system. It remains unclear how alterations in SR activity are involved in modulation of neuropathic and inflammatory pain behavior. In the present investigation, we compared pain behaviors in SR knockout (KO) mice and wild‐type (WT) mice after subjection to a chronic constriction injury (CCI model of Bennett), partial sciatic nerve ligation (PSL model of Seltzer), spinal nerve ligation (SNL model of Chung), and an inflammatory pain model that was induced by subcutaneous formalin.Seven‐ to nine‐week‐old male WT and SR‐KO mice were used for the experiments. Under halothane anesthesia, the mice were subjected to neuropathic surgery. Three types of nerve ligation were performed, as previously described by Bennett et al. (1988), Kim and Chung (1992), and Seltzer et al. (1990). The left sciatic nerve was tied loosely with four ligatures of chromic gut at the mid‐thigh level (Bennett model), the left L5 and L6 spinal nerves were isolated and ligated tightly with a 4‐0 silk thread (Chung model), and the dorsal one‐third to one‐half of the left sciatic nerve was tightly ligated (Seltzer model). Mechanical allodynia was assessed by measuring the frequency of withdrawal responses using von Frey filaments both before and after ligation. To induce inflammatory pain, paraformaldehyde (50 μL, 25% in distilled water) was injected subcutaneously in the dorsal surface of the left hind paw. The mice were continuously observed for 60 min after the formalin injection, and the number of flinches of the injected paw was measured during the observation period.Behavioral observations showed the following results: 1) The second phase of the formalin‐induced licking response was augmented in SR‐KO mice, while the first phase was not; 2) mechanical allodynia in the Seltzer model was quite similar between SR‐KO mice and WT mice; 3) mechanical allodynia in both the Chung and Bennett models was significantly augmented in SR‐KO mice compared with WT mice.The mechanisms of the presently observed different effects of SR knockout on different pain models are unclear. We are currently investigating how differently synaptic circuit activity in the spinal dorsal horn is affected by SR knockout in different pain models.Support or Funding InformationDokkyo Med Univ Mutual FundThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Notch signaling represents an important checkpoint between follicular T-helper and canonical T-helper 2 cell fate

Type-2 immunity is regulated by two distinct CD4+ T-cell subsets. T follicular helper (Tfh) cells are required for humoral hallmarks of type-2 inflammation. T-helper type-2 (Th2) cells orchestrate type-2 inflammation in peripheral tissues, such as the lung and intestine. Given the importance of Notch signaling in the establishment of other CD4+ T-helper cell subsets, we investigated whether canonical Notch activation could differentially impact Tfh and Th2 cell fate during the induction of type-2 immunity. These studies show that Tfh cell, but not Th2 cell, generation and function is reliant on Notch signaling. While early Tfh cell specification is influenced by functional Notch ligands on classical dendritic cells, functional Notch ligands on cells other than dendritic cells, T cells, B cells, and follicular dendritic cells are sufficient to achieve full Tfh cell commitment. These findings identify Notch signaling as an early lineage-determining factor between Tfh and Th2 cell fate.

Inflammatory-linked changes in CpG island methylation of three opioid peptide genes in a rat model for pain.

Expression of the opioid peptide genes proopiomelanocortin (Pomc), proenkephalin (Penk), and prodynorphin (Pdyn), in immune cells plays a key role in endogenous pain control. In a rat model of painful unilateral paw inflammation, we isolated cells from popliteal lymph nodes and evaluated the role of CpG island C5-methylation on the transcriptional activation of those genes. Using methylated DNA immunoprecipitation, we sorted gDNA into methylated (me) and non-me fractions and then determined the CpG island methylation status of each fraction via quantitative Real Time-PCR (qRT-PCR). In silico analysis by MethPrimer software identified one CpG island in Pdyn and three each in Pomc and Penk. No substantial changes in C5-methylation of any gene were observed. In conclusion, the CpG island methylation status does not seem to be a key regulator of opioid gene activation in immune cells during peripheral tissue inflammation.

Live Images of GLUT4 Protein Trafficking in Mouse Primary Hypothalamic Neurons Using Deconvolution Microscopy.

Type 2 diabetes mellitus (T2DM) is a global health crisis which is characterized by insulin signaling impairment and chronic inflammation in peripheral tissues. The hypothalamus in the central nervous system (CNS) is the control center for energy and insulin signal response regulation. Chronic inflammation in peripheral tissues and imbalances of certain chemokines (such as CCL5, TNFα, and IL-6) contribute to diabetes and obesity. However, the functional mechanism(s) connecting chemokines and hypothalamic insulin signal regulation still remain unclear.In vitro primary neuron culture models are convenient and simple models which can be used to investigate insulin signal regulation in hypothalamic neurons. In this study, we introduced exogeneous GLUT4 protein conjugated with GFP (GFP-GLUT4) into primary hypothalamic neurons to track GLUT4 membrane translocation upon insulin stimulation. Time-lapse images of GFP-GLUT4 protein trafficking were recorded by deconvolution microscopy, which allowed users to generate high-speed, high-resolution images without damaging the neurons significantly while conducting the experiment. The contribution of CCR5 in insulin regulated GLUT4 translocation was observed in CCR5 deficient hypothalamic neurons, which were isolated and cultured from CCR5 knockout mice. Our results demonstrated that the GLUT4 membrane translocation efficiency was reduced in CCR5 deficient hypothalamic neurons after insulin stimulation.

Live Images of GLUT4 Protein Trafficking in Mouse Primary Hypothalamic Neurons Using Deconvolution Microscopy

Type 2 diabetes mellitus (T2DM) is a global health crisis which is characterized by insulin signaling impairment and chronic inflammation in peripheral tissues. The hypothalamus in the central nervous system (CNS) is the control center for energy and insulin signal response regulation. Chronic inflammation in peripheral tissues and imbalances of certain chemokines (such as CCL5, TNFα, and IL-6) contribute to diabetes and obesity. However, the functional mechanism(s) connecting chemokines and hypothalamic insulin signal regulation still remain unclear. In vitro primary neuron culture models are convenient and simple models which can be used to investigate insulin signal regulation in hypothalamic neurons. In this study, we introduced exogeneous GLUT4 protein conjugated with GFP (GFP-GLUT4) into primary hypothalamic neurons to track GLUT4 membrane translocation upon insulin stimulation. Time-lapse images of GFP-GLUT4 protein trafficking were recorded by deconvolution microscopy, which allowed users to generate high-speed, high-resolution images without damaging the neurons significantly while conducting the experiment. The contribution of CCR5 in insulin regulated GLUT4 translocation was observed in CCR5 deficient hypothalamic neurons, which were isolated and cultured from CCR5 knockout mice. Our results demonstrated that the GLUT4 membrane translocation efficiency was reduced in CCR5 deficient hypothalamic neurons after insulin stimulation.

Reprint of “Dual blockade of the pro-inflammatory chemokine CCL2 and the homeostatic chemokine CXCL12 is as effective as high dose cyclophosphamide in murine proliferative lupus nephritis”

Induction therapy of proliferative lupus nephritis still requires the use of unselective immunosuppressive drugs with significant toxicities. In search of more specific drugs with equal efficacy but fewer side effects we considered blocking pro-inflammatory chemokine monocyte chemoattractant protein-1 (MCP-1/CCL2) and homeostatic chemokine stromal cell-derived factor-1 (SDF-1/CXCL12), which both contribute to the onset and progression of proliferative lupus nephritis yet through different mechanisms. We hypothesized that dual antagonism could be as potent on lupus nephritis as the unselective immunosuppressant cyclophosphamide (CYC). We estimated serum levels of CCL2 and CXCL12 in patients with SLE (n=99) and compared the results with healthy individuals (n=21). In order to prove our hypothesis we used l-enantiomeric RNA Spiegelmer® chemokine antagonists, i.e. the CCL2-specific mNOX-E36 and the CXCL12-specific NOX-A12 to treat female MRL/lpr mice from week 12 to 20 of age with either anti-CXCL12 or anti-CCL2 alone or both. SLE patients showed elevated serum levels of CCL2 but not of CXCL12. Female MRL/lpr mice treated with dual blockade showed significantly more effective than either monotherapy in preventing proteinuria, immune complex glomerulonephritis, and renal excretory failure and the results are at par with CYC treatment. Dual blockade reduced leukocyte counts and renal IL-6, IL-12p40, CCL-5, CCL-2 and CCR-2 mRNA expression. Dual blockade of CCL2 and CXCL12 can be as potent as CYC to suppress the progression of proliferative lupus nephritis probably because the respective chemokine targets mediate different disease pathomechanisms, i.e. systemic autoimmunity and peripheral tissue inflammation.

CD1d-Restricted pathways in hepatocytes control local natural killer T cell homeostasis and hepatic inflammation

Invariant natural killer T (iNKT) cells recognize lipid antigens presented by CD1d and play a central role in regulating immunity and inflammation in peripheral tissues. However, the mechanisms which govern iNKT cell homeostasis after thymic emigration are incompletely understood. Here we demonstrate that microsomal triglyceride transfer protein (MTP), a protein involved in the transfer of lipids onto CD1d, regulates liver iNKT cell homeostasis in a manner dependent on hepatocyte CD1d. Mice with hepatocyte-specific loss of MTP exhibit defects in the function of CD1d and show increased hepatic iNKT cell numbers as a consequence of altered iNKT cell apoptosis. Similar findings were made in mice with hepatocyte-specific loss of CD1d, confirming a critical role of CD1d in this process. Moreover, increased hepatic iNKT cell abundance in the absence of MTP is associated with susceptibility to severe iNKT cell-mediated hepatitis, thus demonstrating the importance of CD1d-dependent control of liver iNKT cells in maintaining immunological homeostasis in the liver. Together, these data demonstrate an unanticipated role of parenchymal cells, as shown here for hepatocytes, in tissue-specific regulation of CD1d-restricted immunity and further suggest that alterations in lipid metabolism may affect iNKT cell homeostasis through effects on CD1d-associated lipid antigens.