Decay accelerating factor (CD55) protects neuronal cells from chemical hypoxia-induced injury

Background  

Activated complement system is known to mediate neuroinflammation and neurodegeneration following exposure to hypoxic-ischemic insults. Therefore, inhibition of the complement activation cascade may represent a potential therapeutic strategy for the management of ischemic brain injury. Decay-accelerating factor (DAF, also known as CD55) inhibits complement activation by suppressing the function of C3/C5 convertases, thereby limiting local generation or deposition of C3a/C5a and membrane attack complex (MAC or C5b-9) production. The present study investigates the ability of DAF to protect primary cultured neuronal cells subjected to sodium cyanide (NaCN)-induced hypoxia from degeneration and apoptosis.     

Immunomodulation with CD40 stimulation and interleukin-2 protects mice from disseminated cryptococcosis

Cryptococcus neoformans is a ubiquitous fungus that can cause life-threatening infections during immunosuppressive states such as AIDS and after bone marrow transplantation. In this study we investigated the antifungal efficacy of an agonist antibody to CD40, an important costimulator of immune function, in combination with interleukin 2 (IL-2) in a murine model of disseminated cryptococcosis. Only the combination of anti-CD40 and IL-2 significantly prolonged the survival time of infected mice. This protection was correlated with decreased yeast burdens in the brain and kidney. Increased immune cell populations in the spleens, as well as increased serum gamma interferon (IFN-gamma) and tumor necrosis factor alpha levels were observed in infected mice treated with anti-CD40 and IL-2. Further experiments with IFN-gamma knockout mice demonstrated that the protection induced by anti-CD40 and IL-2 treatment was dependent on IFN-gamma. Depletion of CD4+ T cells did not affect the increased serum IFN-gamma levels induced by anti-CD40 and IL-2 treatment and, importantly, did not affect the antifungal effect of combination therapy. These studies indicate that immunotherapy using anti-CD40 and IL-2 has therapeutic potential in augmenting host resistance to disseminated cryptococcosis and that IFN-gamma is essential for efficacy.     

Interleukin-10 protects against inflammation-mediated degeneration of dopaminergic neurons in substantia nigra

Inflammation has been increasingly recognized to play an important role in the pathogenesis of Parkinson's disease (PD). Using immunocytochemistry and electron microscopy, we found that intranigral injection of lipopolysaccharide (LPS) caused marked microglial activation and a dose-dependent selective loss of dopaminergic neurons, which was mediated by apoptosis as evidenced by prominent TUNEL labeling. RNase protection assays revealed that mRNA for Bax, Fas and the pro-inflammatory cytokines interleukin (IL)-1α, IL-1β, IL-6 and tumor necrosis factor (TNF)-α were significant increased ipsilaterally in LPS-injected side of SN, while expression of the anti-apoptotic gene Bcl-2 was decreased. Osmotic pump infusion of IL-10, a global inhibitor of cytokine synthesis, protected against LPS-induced cell death of dopaminergic neurons, with a corresponding decrease in the number of activated microglia, suggesting that the reduction in microglia-mediated release of inflammatory mediators may contribute to the anti-inflammatory effect of IL-10. Our results provide evidence that LPS induces apoptotic cell death in SNpc, which is likely through the expression of Fas, Bax, caspase-3, and the pro-inflammatory cytokines.     

Galectin-1 deactivates classically activated microglia and protects from inflammation-induced neurodegeneration

Inflammation-mediated neurodegeneration occurs in?the acute and the chronic phases of multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE). Classically activated (M1) microglia are key players mediating this process. Here, we identified Galectin-1 (Gal1), an endogenous glycan-binding protein, as a pivotal regulator of M1 microglial activation that targets the activation of p38MAPK-, CREB-, and NF-κB-dependent signaling pathways and hierarchically suppresses downstream proinflammatory mediators, such as iNOS, TNF, and CCL2. Gal1 bound to core 2 O-glycans on CD45, favoring retention of this glycoprotein on the microglial cell surface and augmenting its phosphatase activity and inhibitory function. Gal1 was highly expressed in the acute phase of?EAE, and its targeted deletion resulted in pronounced inflammation-induced neurodegeneration. Adoptive transfer of Gal1-secreting astrocytes or administration of recombinant Gal1 suppressed EAE through mechanisms involving microglial deactivation. Thus, Gal1-glycan interactions are essential in tempering microglial activation, brain inflammation, and neurodegeneration, with critical therapeutic implications for MS.     

Glycyrrhizin protects mice from concanavalin A-induced hepatitis without affecting cytokine expression.

The administration of concanavalin A (Con A) to mice induces cytokine-dependent hepatitis. In the present study, the effect of glycyrrhizin on Con A-induced hepatitis was examined. Treatment of mice with Con A (0.2 mg/mouse, i.v.) induced elevation of the plasma transaminase activities at 24 h. Mice were treated with glycyrrhizin (100, 200 and 400 mg/kg, i.p.), and glycyrrhizin at the doses of 200 and 400 mg/kg inhibited the Con A-induced elevation of the plasma transaminase activities. At 1 h after Con A treatment, interferon-gamma, tumor necrosis factor-alpha, interleukin-2 and interleukin-6 proteins were released into the plasma. Although treatment with glycyrrhizin at 200 mg/kg inhibited Con A-induced hepatitis, it did not affect the release of any of these Con A-induced cytokines into the plasma. The present results clearly show that glycyrrhizin inhibited Con A-induced hepatitis without affecting cytokine expression.     

Synthetic peptides from the N-terminal regions of CD200 and CD200R1 modulate immunosuppressive and anti-inflammatory effects of CD200-CD200R1 interaction

A series of 15-mer peptides were synthesized defining continuous sequences of the extracellular region of the murine and human CD200 molecule. In addition, peptides mapping to the presumptive CDR1, CDR2 and CDR3 of the human and mouse CD200R1 molecules were synthesized. The ability of these various molecules to block the interaction of CD200 with CD200R1 was studied in a competitive ELISA using plate-bound CD200R1Fc and biotinylated CD200Fc, and by FACS using FITC-conjugated CD200Fc binding to 24-h LPS-activated adherent cells. Results from these data were compared with the functional ability of the same peptides to suppress the inhibition of generation of allo-specific CTL in vitro following inclusion of CD200Fc in mixed leukocyte culture reactions. Peptides defining discrete regions in the N terminal regions of CD200 and CD200R1 were functionally active in these different assays. Moreover, infused in vivo, the same mouse-specific peptides suppressed protection from graft rejection afforded by injection of soluble immunosuppressive CD200Fc. Used alone in vitro, these peptides enhanced alloimmunity.     

Upregulation of miR-137 protects anesthesia-induced hippocampal neurodegeneration

Purpose: Ketamine is commonly used in pediatric anesthesia but may cause neurodegeneration in young brains. The aim of the study is to use an animal model to characterize the role of microRNA 137 (miR-137) in ketamine-induced neurodegeneration in neonatal hippocampus. Methods: Young Sprague-Dawley Rats (1 month old) was systemically administrated with ketamine (75 mg/kg) for 3 days. TUNEL assay was used to assess the ketamine-induced neurodegeneration of hippocampal CA1 neurons, quantitative real-time PCR (qRT-PCR) to assess the expression of miR-137 and Morris water maze test (MWM) to assess the damaged memory function. Alternatively, lentivirus over-expressing miR-137 was injected into hippocampus before ketamine administration, and the subsequent effects of miR-137 upregulation on ketamine-induced hippocampal neurodegeneration and memory dysfunction were investigated. Furthermore, the direct downstream target of miR-137, CDC42, was down-regulated by siRNA injection into hippocampus. The effects of CDC42 inhibition on hippocampal apoptosis and memory function were also investigated. Results: Excessive ketamine treatment resulted in severe apoptosis in hippocampal CA1 neurons, downregulation of miR-137 in hippocampus and significant long-term memory dysfunction. Conversely, pre-treatment of overexpressing miR-137 protected hippocampal neurodegeneration and memory loss. The molecular target of miR-137, CDC42 was down-regulated by ketamine in hippocampus. Knocking down hippocampal CDC42 exerted an apoptotic effect on hippocampal neurons and memory loss, similar to the effect of ketamine treatment. Conclusions: Our results demonstrated that miR-137 played an important role in regulating ketamine induced hippocampal neurodegeneration, possibly through CDC42.     

Effect of CD200 and CD200R1 expression within tissue grafts on increased graft survival in allogeneic recipients

In transgenic mice over-expressing CD200 (CD200^tg) graft survival is associated with increased intra-graft expression of mRNAs for genes associated with altered T cell subset differentiation (Foxp3; TGFβ; IL-10). Grafts are rejected in recipients lacking the inhibitory receptor for CD200, CD200R1.We compared grafts of C57BL/6 skin taken from control, CD200KO, CD200^tg, CD200R1KO or CD200^tg.CD200R1KO C57BL/6 donor mice transplanted to control or CD200^tg BALB/c recipients. Animals received either low-dose rapamycin (0.5 mg/kg), which only enhanced survival in CD200^tg mice, or high dose rapamycin (1.5 mg/kg) which increased graft survival in all recipients. Recipient draining lymph nodes (DLNs) were analyzed at 14 days post grafting in mixed leukocyte cultures (MLCs) with irradiated BL/6 or C3H/HeJ stimulator cells, assaying antigen-specific CTL at day 5. MLC responses were correlated with changes in mRNA gene expression in skin tissue harvested from the same recipients, focusing on genes altered in “graft-accepting” CD200^tg recipients. Tissue histology was used to assess graft infiltrating Foxp3⁺ Tregs, mast cells (MCs) and their degranulation.CD200^tg grafts were accepted in control but not CD200KO/CD200R1KO recipients, along with decreased degranulation in graft MCs, diminished DLN MLC responses, and augmented intragraft Foxp3, TGFβ, IL-10 and mast cell gene expression. Skin grafts from either CD200KO or CD200R1KO donors to control mice were rejected, with no change in DLN MLC responses, no altered graft gene expression from that seen using control skin grafts, and pronounced graft MC degranulation. Our data highlight a role for both graft and host CD200/CD200R expression in increased allograft survival.     

Ibuprofen protects ischemia-induced neuronal injury via up-regulating interleukin-1 receptor antagonist expression

The inflammatory response accompanies and exacerbates the developing injury after cerebral ischemia. Ibuprofen, a non-steroidal anti-inflammatory drug, has been shown to attenuate injuries in animal models of various neurological diseases. In the present study, we investigated ibuprofen's neuroprotective effects in rats exposed to transient forebrain ischemia and in cultures exposed to oxygen glucose deprivation (OGD). Rats treated with ibuprofen after transient forebrain ischemia displayed long-lasting protection of CA1 hippocampal neurons. There were selective increases in interleukin-1 receptor antagonist gene and protein expression in ibuprofen-treated OGD microglia. Furthermore, treatment with ibuprofen in neuron/microglia co-cultures increased the number of surviving HC2S2 neurons against OGD whereas IL-1ra neutralizing antibody reversed the ibuprofen-induced neuroprotection. The data indicate that ibuprofen-induced IL-1ra secretion is involved in neuroprotection against ischemic conditions.     

Thalidomide protects against ischemic neuronal damage induced by focal cerebral ischemia in mice

We aimed to examine whether thalidomide might inhibit the neuronal damage resulting from focal cerebral ischemia, and if so to explore the neuroprotective mechanism. Focal cerebral ischemia was induced by permanent middle cerebral artery occlusion (MCAO) in mice, and thalidomide was intraperitoneally administered a total of three times (at 10 min before, just before, and 1 h after MCAO). Thalidomide significantly reduced (a) the infarct area and volume at 24 and 72 h after MCAO and (b) the neurological score at 72 h after MCAO. Brains were also histochemically assessed for apoptosis and lipid peroxidation using terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) staining and an antibody recognizing 8-hydroxy-2′-deoxyguanosine (8-OHdG), respectively. Thalidomide reduced both the number of TUNEL-positive cells and the oxidative damage. However, post-treatment of thalidomide [20 mg/kg, three times (at just after, 1 h after, 3 h after MCAO)] did not reduce the infarct volume. In an in vitro study, we examined the effects of thalidomide on lipid peroxidation in mouse brain homogenates and on the production of various radical species. Thalidomide inhibited both the lipid peroxidation and the production of H₂O₂ and O₂ · ⁻ (but not HO⁻) radicals. We also measured the brain concentration of TNF-α by ELISA. The TNF-α level in the brain was significantly increased at 9–24 h after MCAO. However, thalidomide did not reduce the elevated TNF-α level at either 12 or 24 h after MCAO. These findings indicate that thalidomide has neuroprotective effects against ischemic neuronal damage in mice, and that an inhibitory action of thalidomide against oxidative stress may be partly responsible for these neuroprotective effects.     

The SLAM family member CD48 (Slamf2) protects lupus-prone mice from autoimmune nephritis

Polymorphisms in the SLAM family of leukocyte cell surface regulatory molecules have been associated with lupus-like phenotypes in both humans and mice. The murine Slamf gene cluster lies within the lupus-associated Sle1b region of mouse chromosome 1. Non-autoreactive C57BL/6 (B6) mice that have had this region replaced by syntenic segments from other mouse strains (i.e. 129, NZB and NZW) are B6 congenic strains that spontaneously produce non-nephritogenic lupus-like autoantibodies. We have recently reported that genetic ablation of the SLAM family member CD48 (Slamf2) drives full-blown autoimmune disease with severe proliferative glomerulonephritis (CD48GN) in B6 mice carrying 129 sequences of the Sle1b region (B6.129CD48^−/−). We also discovered that BALB/c mice with the same 129-derived CD48-null allele (BALB.129CD48^−/−) have neither nephritis nor anti-DNA autoantibodies, indicating that strain specific background genes modulate the effects of CD48 deficiency. Here we further examine this novel model of lupus nephritis in which CD48 deficiency transforms benign autoreactivity into fatal nephritis. CD48GN is characterized by glomerular hypertrophy with mesangial expansion, proliferation and leukocytic infiltration. Immune complexes deposit in mesangium and in sub-endothelial, sub-epithelial and intramembranous sites along the glomerular basement membrane. Afflicted mice have low-grade proteinuria, intermittent hematuria and their progressive renal injury manifests with elevated urine NGAL levels and with uremia. In contrast to the lupus-like B6.129CD48^−/− animals, neither BALB.129CD48^−/− mice nor B6 × BALB/c F1.129CD48^−/− progeny have autoimmune traits, indicating that B6-specific background genes modulate the effect of CD48 on lupus nephritis in a recessive manner.     

Elevated production of interferon-gamma and interleukin 4 by mature T cells from autoimmune lpr mice correlates with Pgp-1 (CD44) expression

The cell surface glycoprotein, Pgp-1 (CD44), has been shown to be a marker of murine memory T lymphocytes. When activated, Pgp-1hi memory T cells produce strikingly higher amounts of interferon-gamma (IFN-gamma) than naive Pgp-1lo T cells, yet both subsets make similar levels of interleukin (IL)2. Whereas Pgp-1hi cells represent only 20%-25% of peripheral T cells from most strains, this marker is expressed by the vast majority (greater than 90%) of T cells from autoimmune MRL mice homozygous for the lymphoproliferation (lpr) gene. The massive lymphadenopathy that develops in lpr/lpr mice is composed of both non-mature (CD4-CD8-) T cells as well as a greatly expanded number (up to 300-fold) of mature (CD4+CD8-,CD4-CD8+) T cells. Paralleling the expression of high levels of Pgp-1, we find that compared to normal mouse T cells, the lpr mature T lymphocyte subsets are also very high producers on a per cell basis of IFN-gamma and, for the CD4+ subset, IL 4. Increased concentrations of IFN-gamma and IL 4 produced by large numbers of lpr Pgp-1hi mature T cells could contribute to the autoimmune syndrome in MRL lpr/lpr mice through the effects of these cytokines on augmenting MHC class II expression and production of certain classes of antibodies.     

A20 expression in dendritic cells protects mice from LPS‐induced mortality

DCs contribute to immune homeostasis under physiological conditions and regulate the immune activation during infection. The deubiquitinase A20 inhibits the activation of NF‐κB‐dependent immune reactions, and prevents the hyperactivation of DCs under steady‐state conditions. However, the role of DC‐specific A20 under pathological conditions is unknown. Here, we demonstrate that upon injection of low‐dose LPS, mice with DC‐specific A20 deletion (CD11c‐Cre A20^fl/fl) died within 6 h, whereas A20^fl/fl controls survived. LPS‐induced mortality in CD11c‐Cre A20^fl/fl mice was characterized by increased serum levels of IL‐2, IL‐10, IL‐12, IFN‐γ, and TNF. Upon LPS stimulation, the activation of NF‐κB and ERK‐NFATc3 pathways were enhanced in A20‐deficient DCs, resulting in an increased production of IL‐2, IL‐12, and TNF both in vitro and in vivo. Targeted inhibition of ERK in A20‐deficient DCs abolished the increased production of IL‐2. A20‐deficient DCs failed to induce LPS tolerance, which was independent of T cells and the intestinal flora, since T‐cell depletion and decolonization of CD11c‐Cre A20^fl/fl mice could not prevent death of LPS‐challenged CD11c‐Cre A20^fl/fl mice. In conclusion, these findings show that DC‐specific A20 preserves immune homeostasis in steady‐state conditions and is also required for LPS tolerance.     

Epicutaneous immunotherapy protects cashew-sensitized mice from anaphylaxis

Background

The prevalence of tree nut allergy has increased worldwide, and cashew has become one of the most common food allergens. More critically, cashew allergy is frequently associated with severe anaphylaxis. Despite the high medical need, no approved treatment is available and strict avoidance and preparedness for prompt treatment of allergic reactions are considered dual standard of care. In the meantime, Phase III study results suggest investigational epicutaneous immunotherapy (EPIT) may be a relevant and safe treatment for peanut allergy and may improve the quality of life for many peanut allergic children.

Objective

We aimed to evaluate the capacity of EPIT to provide protection against cashew-induced anaphylaxis in a relevant mouse model.

Methods

The efficacy of EPIT was evaluated by applying patches containing cashew allergens to cashew-sensitized mice. As negative control, sham mice received patches containing excipient. Following treatment, mice were challenged orally to cashew and anaphylactic symptoms, as well as plasmatic levels of mast-cell proteases (mMCP)-1/7, were quantified.

Results

Of 16 weeks of EPIT significantly protects against anaphylaxis by promoting a faster recovery of challenged mice. This protection was characterized by a significant reduction of temperature drop and clinical symptoms, 60 minutes after challenge. This was associated with a decrease in mast-cell reactivity as attested by the reduction of mMCP-1/7 in plasma, suggesting that EPIT specifically decrease IgE-mediated anaphylaxis.

Conclusion

We demonstrate that EPIT markedly reduced IgE-mediated allergic reactions in a mouse model of cashew allergy, which suggests that EPIT may be a relevant approach to treating cashew allergy.

     

Sulfiredoxin protects mice from lipopolysaccharide-induced endotoxic shock

Peroxiredoxins constitute a major family of cysteine-based peroxide-scavenging enzymes. They carry an intriguing redox switch by undergoing substrate-mediated inactivation via overoxidation of their catalytic cysteine to the sulfinic acid form that is reverted by reduction catalyzed by the sulfinic acid reductase sulfiredoxin (Srx). The biological significance of such inactivation is not understood, nor is the function of Srx1. To address this question, we generated a mouse line with a null deletion of the Srx1-encoding Srxn1 gene. We show here that Srxn1(-/-) mice are perfectly viable and do not suffer from any apparent defects under laboratory conditions, but have an abnormal response to lipopolysaccharide that manifests by increased mortality during endotoxic shock. Microarray-based mRNA profiles show that although the response of Srxn1(-/-) mice to lipopolysaccharide is typical, spanning all spectrum and all pathways of innate immunity, it is delayed by several hours and remains intense when the response of Srxn1(+/+) mice has already dissipated. These data indicate that Srx1 activity protects mice from the lethality of endotoxic shock, adding this enzyme to other host factors, as NRF2 and peroxiredoxin 2, which by regulating cellular reactive oxygen species levels act as important modifiers in the pathogenesis of sepsis.     

Acetaminophen inhibits neuronal inflammation and protects neurons from oxidative stress

Background  

Recent studies have demonstrated a link between the inflammatory response, increased cytokine formation, and neurodegeneration in the brain. The beneficial effects of anti-inflammatory drugs in neurodegenerative diseases, such as Alzheimer's disease (AD), have been documented. Increasing evidence suggests that acetaminophen has unappreciated anti-oxidant and anti-inflammatory properties. The objectives of this study are to determine the effects of acetaminophen on cultured brain neuronal survival and inflammatory factor expression when exposed to oxidative stress.     

Hydrogen sulfide protects HT22 neuronal cells from oxidative stress

Hydrogen sulfide (H2S) is a neuromodulator in the brain and a relaxant for smooth muscle. H2S protects primary cortical neurons from oxidative stress by increasing the intracellular concentrations of glutathione, the major antioxidant in cells. However, changes in glutathione alone are not sufficient to account for full protection in all types of nerve cells. H2S is here shown to protect an immortalized mouse hippocampal cell line from oxidative glutamate toxicity by activating ATP-dependent K+ (KATP) and Cl- channels, in addition to increasing the levels of glutathione. The present study therefore identifies a novel pathway for H2S protection from oxidative stress.