Joseph P. McGillis

Characterization of a calcitonin gene-related peptide (CGRP) receptor on mouse bone marrow cells

Calcitonin gene-related peptide, (CGRP), a vasoactive neuropeptide, is found throughout the peripheral nervous system, and CGRP receptors are present on mature lymphocytes. The current studies describe a CGRP receptor on isolated mouse bone marrow cells. The affinity, distribution and specificity of CGRP receptors were analyzed using radioligand binding assays. [125I]CGRP binding in mouse bone marrow cells was dependent on cell concentration and was stable from 5 to 60 min at room temperature. The average Kd is 3.29 +/- 1.24 nM and the average receptor density is 2796 +/- 365 sites/cell. Competition binding analysis found rat alpha and beta CGRP to be the most inhibitory, (Ki values 0.899 and 0.711 nM, respectively), followed by human alpha CGRP and the antagonist human CGRP8-37. The neuropeptides human and salmon calcitonin did not inhibit [125I]CGRP binding to bone marrow cells. The presence of CGRP receptors on mouse bone marrow cells provides further evidence for a direct role for CGRP in modulating the function and differentiation of cellular components of the immune and inflammatory systems.

Catecholamines decrease lymphocyte adhesion to cytokine-activated endothelial cells.

Numerous studies have shown that catecholamines can modulate lymphocyte migration. This effect may be mediated in part by modulation of lymphocyte-endothelial cell interactions, which is dependent on adhesion molecules expressed on both of these cells. Our results show that catecholamines decreased T-cell binding to IL-1 activated endothelial cells in vitro. The decrease in adhesion was not mediated by a change in adhesion molecule expression as LFA-1 and VLA-4 expression on T-cells and ICAM-1 and VCAM-1 expression on endothelial cells were not changed by catecholamine stimulation. T-cells flatten and enlarge the area of surface contact as they adhere to endothelial cells. Image analysis of the number of T-cells bound and the amount of cell spreading over several time points suggests that catecholamines alter the kinetics of T-cell-endothelial cell adhesion. These results support the hypothesis that catecholamines can alter lymphocyte-endothelial interactions in vivo, which in turn would affect lymphocyte migration.

Plasmin deficiency does not alter endogenous murine amyloid beta levels in mice.

Deposition of amyloid beta (A beta) into extracellular plaques is a pathologic characteristic of Alzheimers disease. Plasmin, neprilysin, endothelin-converting enzyme and insulin-degrading enzyme (IDE) have each been implicated in A beta degradation; data supporting the role of the latter three enzymes have included increased levels of endogenous murine A beta in mice genetically deficient for the respective enzyme. In this study, we sought to determine if plasminogen deficiency increases endogenous A beta. We report that plasminogen deficiency did not result in an A beta increase in the brain or in the plasma of adult mice. Hence, although plasmin is potentially important in the degradation of A beta aggregates, we interpret these data as suggesting that plasmin does not regulate steady-state A beta levels in non-pathologic conditions.

Calcitonin‐gene related peptide (CGRP) inhibits interleukin‐7‐induced pre‐B cell colony formation

Calcitonin gene‐related peptide (CGRP) is a sensory neuropeptide with inflammatory and immunoregulatory activities. Its role in B lymphocyte development was investigated using a pre‐B cell colony‐forming assay. Physiological concentrations of CGRP inhibited pre‐B cell responses to interleukin‐7 (IL‐7). Inhibition was specific in that it was blocked by the CGRP antagonist CGRP8‐37. Adrenomedulin, substance P, and calcitonin had no effect on B cell precursor responses. Similar responses were observed with B220+/IgM− B cell precursors. Inhibition of IL‐7 responses in B220+/IgM− cells suggests that CGRP has a direct effect on B cell precursors. Studies with cultured bone marrow‐adherent cells found that CGRP also has an indirect effect on IL‐7 responses. Cultured bone marrow‐adherent cells were treated with CGRP for 24 h, and anti‐CGRP was added to the supernatants to neutralize CGRP. Concentrations of CGRP as low as 0.01 nM induced a factor that inhibited colony formation. In contrast, CGRP did not induce an inhibitory factor in cultured bone marrow macrophages, suggesting that CGRP induces an inhibitory factor in some adherent cell other than macrophages. The results show that CGRP has both direct and indirect effects on developing B cells and support a role for CGRP as an inhibitor of early B cell development. J. Leukoc. Biol. 67: 669–676; 2000.

Elevated circulating calcitonin gene-related peptide in umbilical cord and infant blood associated with maternal and neonatal sepsis and shock.

The role of the sensory neuropeptide calcitonin gene-related peptide (CGRP) was studied in preterm and term neonates with sepsis and shock. CGRP levels in blood were measured by RIA. The identity of immunoreactive CGRP (irCGRP) in adult and infant human blood was confirmed by reverse phase-HPLC. CGRP levels were analyzed in a total of 189 samples (95 from cord blood and 94 from neonates). The gestational ages ranged from 24 to 43 wk, and the birth weights ranged from 520 to 4445 g. Cord samples were collected immediately after delivery and infant blood samples were collected within 12 h of birth. Samples were coded, and the data were assigned to groups after determination of CGRP levels. There was a weight- and gestation-dependent increase in irCGRP in the newborn population. The direct correlation of circulating CGRP with ascending birth weight and gestation may have significance in the development of the fetus. Infants with and without certain complications were grouped in 500-g intervals. CGRP levels in cord blood were significantly elevated when certain stressful situations existed in the mother. These included culture-positive chorioamnionitis, placental abruption, and severe preeclampsia. There was a similar elevation in CGRP in patient blood in infants with culturepositive sepsis and/or shock with blood pressure <2 SD from the mean for corresponding gestation. CGRP levels did not differ between male and female infants and did not appear to be influenced by type of delivery (vaginal versus cesarean section). There was no significant difference in CGRP level between cord and patient blood in preterm neonates, but at term gestation cord blood levels were slightly higher than those in the patient blood. These results suggest that inflammation and hemodynamic imbalance(e.g. shock) are associated with increased in CGRP levels in the circulation in neonates. Future studies will focus on the biologic effects of elevated CGRP during neonatal complications and will examine the utility of CGRP measurement for diagnosis and treatment of disease in preterm infants.

Sensory neuropeptides, neurogenic inflammation and inflammatory cells

The term neurogenic inflammation was first used to describe the contribution of sensory nerves to local inflammatory responses [1]. There is a large body of research dating back to the last century that documents the role of sensory nerves in vascular aspects of inflammatory responses. The sensory neuropeptides, substance P (SP) and calcitonin gene-related peptide (CGRP) are potent vasoactive peptides found in nociceptive nerve endings. Following a noxious stimulus they are released at local sites where they coordinate the activities of different cells and tissues involved in inflammatory and immune responses. In addition to their vascular effects SP and CGRP also regulate the function of leukocytes involved in immune and inflammatory responses. (The term leukocyte refers collectively to all white blood cells. This includes lymphocytes, monocytes, macrophages and granulocytes.)

Functional characterization of the insulin-like growth factor I receptor on Jurkat T cells

Insulin-like growth factor I (IGF-I) has been shown to be important in the maintenance, development, and proliferation of various types of leukocytes, particularly T cells. Radio-receptor binding assays demonstrate that Jurkat T cells bind 125I-IGF-I with an affinity of 1.77 nM (Kd) and express approximately 230 receptors/cell. Specificity studies show insulin also binds the IGF-I receptor with an affinity 20-fold lower than that of IGF-I. Interaction of IGF-I with its receptor on Jurkat T cells induces the phosphorylation of tyrosine kinase which is detectable by Western blotting. The 95,000 MW protein detected is equivalent to the molecular weight of the beta chain of the IGF-I receptor described in other types of cells. These studies characterize the binding of IGF-I to its receptor on Jurkat T cells, demonstrate that IGF-I binding induces tyrosine phosphorylation, and support the hypothesis that IGF-I is important in the induction of T cell activation.

Calcitonin gene-related peptide induces AP-1 activity by a PKA and c-fos-dependent mechanism in pre-B cells

Calcitonin gene-related peptide (CGRP) is a sensory neuropeptide with regulatory influences on immune and inflammatory responses and early B lymphocyte differentiation. Little is known about its cellular mechanisms. These studies examined whether CGRP induces c-fos. CGRP induced a transient concentration-dependent increase in c-fos in a CGRP receptor expressing pre-B cell line, 70Z/3. CGRP did not induce c-jun, jun B or jun D. A protein kinase A (PKA) inhibitor blocked c-fos induction by CGRP, suggesting that the mechanism depends on cAMP induction of PKA. CGRP induced AP-1 binding activity in the nucleus, indicating that CGRP regulates expression of specific target genes. CGRP also induced c-fos in B220(+) enriched cells from bone marrow. These results suggest that regulatory influences of CGRP on early B cells and in other tissues can involve a cAMP/PKA, c-fos/AP-1-dependent pathway for regulation of specific genes.

[8] Preparation, characterization, and use of human and rodent lymphocytes, monocytes, and neutrophils

Publisher Summary This chapter describes some simple, concise protocols for the preparation, characterization, and use of leukocytes. The model systems used to examine the role of the nervous and endocrine systems in degenerative and inflammatory disease processes have ranged from simple in vitro proliferative assays to complex in vivo systems. Much of the progress that has been made in understanding the mechanisms of neuroimmunomodulation has come from in vitro studies using primary cultures of leukocytes. The chapter also describes methods that can be used to prepare leukocytes for in vitro studies, as well as methods for lymphocyte activation and analysis of second-messenger production. Several factors should be considered when designing a set of experiments. One of the most important is context.

Postmortem elevation in extracellular glutamate in the rat hippocampus when brain temperature is maintained at physiological levels: implications for the use of human brain autopsy tissues

Postmortem alterations in the neuronal cytoskeleton resemble some aspects of the cytoskeletal disruption associated with neurodegenerative disorders, and are also similar to those observed following ischemia and produced by excitotoxins in vivo and in vitro. This suggests the involvement of excitotoxic mechanisms during the postmortem interval. The purpose of this study was to determine if extracellular levels of glutamate are elevated postmortem. Extracellular levels of GABA and taurine were also monitored using in vivo microdialysis. These three amino acids were analyzed using high-performance liquid chromatography. When postmortem rat brain temperature cooled rapidly to near room temperature, dialysate concentrations of glutamate were not increased in the hippocampal CA1 region during a 2-h postmortem interval, although increased extracellular levels of GABA and taurine were observed. In contrast, maintenance of brain temperature at 37 degrees C resulted in a 12-to-40 fold elevation in extracellular glutamate levels 20-120 min postmortem. In addition, the elevation in dialysate taurine concentration was greater than that observed in rats in which postmortem brain temperature was not maintained. Excitatory amino acid antagonists, NBQX (2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline) and MK-801 (dizocilpine, (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cylohepten-5, 10-imine hydrogen maleate blocked the additional elevation in taurine associated with maintaining brain at 37 degrees C, but had less robust effects against glutamate and GABA release. The results indicate that extracellular concentrations of glutamate, taurine and GABA increase in postmortem rat brain when physiologic temperatures are maintained, but that these increases are blunted when brain temperature decreases. After death, the human brain cools much more slowly than does the rat brain. Therefore, extracellular glutamate levels are likely to increase in the postmortem human brain and may contribute to excitotoxic neuronal damage occurring in the interval between death and autopsy.