In Vivo Administration of Interleukin 1 to Normal Mice Depresses Their Capacity to Elicit Contact Hypersensitivity Responses: Prostaglandins Are Involved in This Modification of Immune Function

The administration of pyrogenic doses of interleukin 1 (IL-1) to normal mice before contact sensitization with dinitrofluorobenzene (DNFB) resulted in a significant reduction in the intensity of the elicited contact hypersensitivity (CH) responses. Adoptive transfer experiments established no difference between normal and IL-1-pretreated mice regarding their capacity to generate splenic suppressor-cell activity and lymph node effector-cell activity in response to DNFB. However, a marked reduction in the intensity of elicited responses was observed when primed CH-effector cells, obtained from normal donors, were adoptively transferred to IL-1-pretreated recipients. This finding was paralleled by a consistent reduction in the ability of the adoptively transferred cells to infiltrate the tissue sites of antigen challenge in the IL-1-pretreatcd animals. Treatment of mice with indomethacin, a potent inhibitor of prostaglandin production, abrogated the capacity of IL-1 to depress CH responses following skin sensitization with DNFB. Similarly, indomethacin was also capable of abrogating the ability of IL-1 to depress CH responses of adoptive recipients of primed CH-effector cells. Our results indicate that the capacity of IL-1 to depress CH responses in normal mice is due to an indomethacin-sensitive process, presumably mediated through the IL-1-induced generation and action of prostaglandins. This was supported by our finding that treatment of mice with arachidonic acid or prostaglandin E2 caused a similar type of inhibition. The mechanism(s) responsible for this effect appears to act at the efferent level of the CH response, as evidenced by the reduced capacity of CH-effector cells to infiltrate the tissue sites of antigen challenge

Nicotinic Receptor Alpha7 Expression during Tooth Morphogenesis Reveals Functional Pleiotropy

The expression of nicotinic acetylcholine receptor (nAChR) subtype, alpha7, was investigated in the developing teeth of mice that were modified through homologous recombination to express a bi-cistronic IRES-driven tau-enhanced green fluorescent protein (GFP); alpha7GFP) or IRES-Cre (alpha7Cre). The expression of alpha7GFP was detected first in cells of the condensing mesenchyme at embryonic (E) day E13.5 where it intensifies through E14.5. This expression ends abruptly at E15.5, but was again observed in ameloblasts of incisors at E16.5 or molar ameloblasts by E17.5–E18.5. This expression remains detectable until molar enamel deposition is completed or throughout life as in the constantly erupting mouse incisors. The expression of alpha7GFP also identifies all stages of innervation of the tooth organ. Ablation of the alpha7-cell lineage using a conditional alpha7Cre×ROSA26-LoxP(diphtheria toxin A) strategy substantially reduced the mesenchyme and this corresponded with excessive epithelium overgrowth consistent with an instructive role by these cells during ectoderm patterning. However, alpha7knock-out (KO) mice exhibited normal tooth size and shape indicating that under normal conditions alpha7 expression is dispensable to this process. The function of ameloblasts in alpha7KO mice is altered relative to controls. High resolution micro-computed tomography analysis of adult mandibular incisors revealed enamel volume of the alpha7KO was significantly reduced and the organization of enamel rods was altered relative to controls. These results demonstrate distinct and varied spatiotemporal expression of alpha7 during tooth development, and they suggest that dysfunction of this receptor would have diverse impacts upon the adult organ

Apolipoprotein epsilon 3 alleles are associated with indicators of neuronal resilience

<p>Abstract</p> <p>Background</p> <p>Epilepsy is associated with precocious development of Alzheimer-type neuropathological changes, including appearance of senile plaques, neuronal loss and glial activation. As inheritance of <it>APOE ε4 </it>allele(s) is reported to favor this outcome, we sought to investigate neuronal and glial responses that differ according to <it>APOE </it>genotype. With an eye toward defining ways in which <it>APOE ε3 </it>alleles may foster neuronal well-being in epilepsy and/or <it>APOE ε4 </it>alleles exacerbate neuronal decline, neuronal and glial characteristics were studied in temporal lobectomy specimens from epilepsy patients of either <it>APOE ε4,4 </it>or <it>APOE ε3,3 </it>genotype.</p> <p>Methods</p> <p>Tissue and/or cellular expressions of interleukin-1 alpha (IL-1α), apolipoprotein E (ApoE), amyloid β (Aβ) precursor protein (βAPP), synaptophysin, phosphorylated tau, and Aβ were determined in frozen and paraffin-embedded tissues from 52 <it>APOE ε3,3 </it>and 7 <it>APOE ε4,4 </it>(0.25 to 71 years) epilepsy patients, and 5 neurologically normal patients using Western blot, RT-PCR, and fluorescence immunohistochemistry.</p> <p>Results</p> <p>Tissue levels of IL-1α were elevated in patients of both <it>APOE ε3,3 </it>and <it>APOE ε4,4 </it>genotypes, and this elevation was apparent as an increase in the number of activated microglia per neuron (<it>APOE </it>ε<it>3,3 </it>vs <it>APOE ε4,4 </it>= 3.7 ± 1.2 vs 1.5 ± 0.4; <it>P </it>< 0.05). This, together with increases in βAPP and ApoE, was associated with apparent neuronal sparing in that <it>APOE ε4,4 </it>genotype was associated with smaller neuron size (<it>APOE ε4,4 </it>vs <it>APOE ε3,3 </it>= 173 ± 27 vs 356 ± 45; <it>P </it>≤ 0.01) and greater DNA damage (<it>APOE ε4,4 </it>vs <it>APOE ε3,3 </it>= 67 ± 10 vs 39 ± 2; <it>P </it>= 0.01). 3) Aβ plaques were noted at early ages in our epilepsy patients, regardless of <it>APOE </it>genotype (<it>APOE ε4,4 </it>age 10; <it>APOE ε3,3 </it>age 17).</p> <p>Conclusions</p> <p>Our findings of neuronal and glial events, which correlate with lesser neuronal DNA damage and larger, more robust neurons in epilepsy patients of <it>APOE ε3,3 </it>genotype compared to <it>APOE ε4,4 </it>genotype carriers, are consistent with the idea that the <it>APOE </it>ε<it>3,3 </it>genotype better protects neurons subjected to the hyperexcitability of epilepsy and thus confers less risk of AD (Alzheimer's disease).</p> <p>Please see related article: <url>http://www.biomedcentral.com/1741-7015/10/36</url></p

Intrapulmonary interleukin 1 mediates acute immune complex alveolitis in the rat

Interleukin 1[alpha] and [beta] are polypeptide cytokines that possesses a wide variety of immunologic and inflammatory activities. We have examined the role of intrapulmonary interleukin 1 in the pathogenesis of acute IgG immune complex alveolitis in the rat. Intratracheal instillation of IgG anti-bovine serum albumin accompanied by intravenous infusion of bovine albumin results in acute neutrophil and complement-dependent alveolitis. Over the course of evolving lung injury there was a 12-fold increase in bronchoalveolar lavage fluid interleukin 1 activity. Intratracheal instillation of neutralizing anti-interleukin 1[beta] antibodies upon induction of lung injury resulted in a dose-dependent reduction in lung injury as assessed by measurements of pulmonary hemorrhage and vascular permeability. Morphometric analysis and measurements of myeloperoxidase activities in whole lung homogenates from rats that received anti-interleukin 1[beta] revealed a pronounced reduction in neutrophil recruitment compared to positive controls. Incubation of isolated alveolar macrophages with preformed IgG immune complexes resulted in dose-dependent interleukin 1 secretion. These data suggest that intrapulmonary IL-1 activity plays a role in neutrophil recruitment and is necessary for the full development of acute IgG immune complex induced lung injury in the rat.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29418/1/0000494.pd

Neuromodulation of the feedforward dentate gyrus-CA3 microcircuit

The feedforward dentate gyrus-CA3 microcircuit in the hippocampus is thought to activate ensembles of CA3 pyramidal cells and interneurons to encode and retrieve episodic memories. The creation of these CA3 ensembles depends on neuromodulatory input and synaptic plasticity within this microcircuit. Here we review the mechanisms by which the neuromodulators aceylcholine, noradrenaline, dopamine, and serotonin reconfigure this microcircuit and thereby infer the net effect of these modulators on the processes of episodic memory encoding and retrieval

Characterizing low affinity epibatidine binding to α4β2 nicotinic acetylcholine receptors with ligand depletion and nonspecific binding

<p>Abstract</p> <p>Background</p> <p>Along with high affinity binding of epibatidine (<it>K</it>_d1≈10 pM) to α4β2 nicotinic acetylcholine receptor (nAChR), low affinity binding of epibatidine (<it>K</it>_d2≈1-10 nM) to an independent binding site has been reported. Studying this low affinity binding is important because it might contribute understanding about the structure and synthesis of α4β2 nAChR. The binding behavior of epibatidine and α4β2 AChR raises a question about interpreting binding data from two independent sites with ligand depletion and nonspecific binding, both of which can affect equilibrium binding of [³H]epibatidine and α4β2 nAChR. If modeled incorrectly, ligand depletion and nonspecific binding lead to inaccurate estimates of binding constants. Fitting total equilibrium binding as a function of total ligand accurately characterizes a single site with ligand depletion and nonspecific binding. The goal of this study was to determine whether this approach is sufficient with two independent high and low affinity sites.</p> <p>Results</p> <p>Computer simulations of binding revealed complexities beyond fitting total binding for characterizing the second, low affinity site of α4β2 nAChR. First, distinguishing low-affinity specific binding from nonspecific binding was a potential problem with saturation data. Varying the maximum concentration of [³H]epibatidine, simultaneously fitting independently measured nonspecific binding, and varying α4β2 nAChR concentration were effective remedies. Second, ligand depletion helped identify the low affinity site when nonspecific binding was significant in saturation or competition data, contrary to a common belief that ligand depletion always is detrimental. Third, measuring nonspecific binding without α4β2 nAChR distinguished better between nonspecific binding and low-affinity specific binding under some circumstances of competitive binding than did presuming nonspecific binding to be residual [³H]epibatidine binding after adding a large concentration of cold competitor. Fourth, nonspecific binding of a heterologous competitor changed estimates of high and low inhibition constants but did not change the ratio of those estimates.</p> <p>Conclusions</p> <p>Investigating the low affinity site of α4β2 nAChR with equilibrium binding when ligand depletion and nonspecific binding are present likely needs special attention to experimental design and data interpretation beyond fitting total binding data. Manipulation of maximum ligand and receptor concentrations and intentionally increasing ligand depletion are potentially helpful approaches.</p

Granzyme B Cleaves Decorin, Biglycan and Soluble Betaglycan, Releasing Active Transforming Growth Factor-β1

Objective: Granzyme B (GrB) is a pro-apoptotic serine protease that contributes to immune-mediated target cell apoptosis. However, during inflammation, GrB accumulates in the extracellular space, retains its activity, and is capable of cleaving extracellular matrix (ECM) proteins. Recent studies have implicated a pathogenic extracellular role for GrB in cardiovascular disease, yet the pathophysiological consequences of extracellular GrB activity remain largely unknown. The objective of this study was to identify proteoglycan (PG) substrates of GrB and examine the ability of GrB to release PG-sequestered TGF-b1 into the extracellular milieu. Methods/Results: Three extracellular GrB PG substrates were identified; decorin, biglycan and betaglycan. As all of these PGs sequester active TGF-b1, cytokine release assays were conducted to establish if GrB-mediated PG cleavage induced TGF-b1 release. Our data confirmed that GrB liberated TGF-b1 from all three substrates as well as from endogenous ECM and this process was inhibited by the GrB inhibitor 3,4-dichloroisocoumarin. The released TGF-b1 retained its activity as indicated by the induction of SMAD-3 phosphorylation in human coronary artery smooth muscle cells. Conclusion: In addition to contributing to ECM degradation and the loss of tissue structural integrity in vivo, increase