RANTES stimulation of T lymphocyte adhesion and activation: role for LFA-1 and ICAM-3

CCL5 promotes LFA-1 expression in Th17 cells and induces LCK and ZAP70 activation in a mouse model of Parkinson's disease

Background

Parkinson's disease (PD), which is associated to autoimmune disorders, is characterized by the pathological deposition of alpha-synuclein (α-Syn) and loss of dopaminergic (DA) neurons. Th17 cells are thought to be responsible for the direct loss of DA neurons. C-C chemokine ligand 5 (CCL5) specifically induces Th17 cell infiltration into the SN. However, the specific effect of CCL5 on Th17 cells in PD and the relationship between CCL5 and lymphocyte function-associated antigen-1 (LFA-1) expression in Th17 cells are unknown.

Methods

We evaluated the effects of CCL5 on LFA-1 expression in Th17 cells in mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and examined Th17 cell differentiation upon CCL5 stimulation in vitro. Furthermore, we assessed the effects of CCL5 on tyrosine kinase zeta-chain-associated protein kinase 70 (ZAP70) and lymphocyte-specific protein tyrosine kinase (LCK) activity in CCL5-stimulated Th17 cells in vivo and in vitro.

Results

CCL5 increased the proportion of peripheral Th17 cells in MPTP-treated mice, LFA-1 expression on Th17 cells, and Th17 cell levels in the SN of MPTP-treated mice. CCL5 promoted Th17 cell differentiation and LFA-1 expression in naive T cells in vitro. Moreover, CCL5 increased Th17 cell differentiation and LFA-1 expression by stimulating LCK and ZAP70 activation in naive CD4+ T cells. Inhibiting LCK and ZAP70 activation reduced the proportion of peripheral Th17 cells and LFA-1 surface expression in MPTP-treated mice, and Th17 cell levels in the SN also significantly decreased.

Conclusion

CCL5, which increased Th17 cell differentiation and LFA-1 protein expression by activating LCK and ZAP70, could increase the Th17 cell number in the SN, induce DA neuron death and aggravate PD.

A Single Nucleotide ADA Genetic Variant Is Associated to Central Inflammation and Clinical Presentation in MS: Implications for Cladribine Treatment

In multiple sclerosis (MS), activated T and B lymphocytes and microglial cells release various proinflammatory cytokines, promoting neuroinflammation and negatively affecting the course of the disease. The immune response homeostasis is crucially regulated by the activity of the enzyme adenosine deaminase (ADA), as evidenced in patients with genetic ADA deficiency and in those treated with cladribine tablets. We investigated in a group of patients with MS the associations of a single nucleotide polymorphism (SNP) of ADA gene with disease characteristics and cerebrospinal fluid (CSF) inflammation. The SNP rs244072 of the ADA gene was determined in 561 patients with MS. Disease characteristics were assessed at the time of diagnosis; furthermore, in 258 patients, proinflammatory and anti-inflammatory molecules were measured in the CSF. We found a significant association between rs244072 and both clinical characteristics and central inflammation. In C-carriers, significantly enhanced disability and increased CSF levels of TNF, IL-5 and RANTES was observed. In addition, lower CSF levels of the anti-inflammatory cytokine IL-10 were found. Finally, the presence of the C allele was associated with a tendency of increased lymphocyte count. In MS patients, ADA SNP rs244072 is associated with CSF inflammation and disability. The selective targeting of the ADA pathway through cladribine tablet therapy could be effective in MS by acting on a pathogenically relevant biological mechanism.

N-terminal Backbone Pairing Shifts in CCL5-12AAA14 Dimer Interface: Structural Significance of the FAY Sequence

CC-type chemokine ligand 5 (CCL5) has been known to regulate immune responses by mediating the chemotaxis of leukocytes. Depending on the environment, CCL5 forms different orders of oligomers to interact with targets and create functional diversity. A recent CCL5 trimer structure revealed that the N-terminal conversed F12-A13-Y14 (¹²FAY¹⁴) sequence is involved in CCL5 aggregation. The CCL5-¹²AAA¹⁴ mutant with two mutations had a deficiency in the formation of high-order oligomers. In the study, we clarify the respective roles of F12 and Y14 through NMR analysis and structural determination of the CCL5-¹²AAA¹⁴ mutant where F12 is involved in the dimer assembly and Y14 is involved in aggregation. The CCL5-¹²AAA¹⁴ structure contains a unique dimer packing. The backbone pairing shifts for one-residue in the N-terminal interface, when compared to the native CCL5 dimer. This difference creates a new structural orientation and leads to the conclusion that F12 confines the native CCL5 dimer configuration. Without F12 anchoring in the position, the interfacial backbone pairing is permitted to slide. Structural plasticity occurs in the N-terminal interaction. This is the first case to report this structural rearrangement through mutagenesis. The study provides a new idea for chemokine engineering and complements the understanding of CCL5 oligomerization and the role of the ¹²FAY¹⁴ sequence.

Integrative Model to Coordinate the Oligomerization and Aggregation Mechanisms of CCL5

CC-type chemokine ligand 5 (CCL5) is involved in the pathogenesis of many inflammatory conditions. Under physiological conditions, CCL5 oligomerization and aggregation are considered to be responsible for its inflammatory properties. The structural basis of CCL5 oligomerization remains controversial because the current oligomer models contain no consensus interactions. In this study, NMR and biophysical analyses proposed evidence that the CC-type CCL5 dimer acts as the basic unit to constitute the oligomer and that CCL5 oligomerizes alternatively through E66-K25 and E66-R44/K45 interactions. In addition, a newly determined trimer structure, constituted by CCL5 and the E66S mutant, reported an interfacial interaction through the N-terminal ¹²FAY¹⁴ sequence. The interaction contributes to CCL5 aggregation and precipitation but not to oligomerization. In accordance with the observations, an integrative model explains the CCL5 oligomerization and aggregation mechanism in which CCL5 assembly consists of two types of dimer-dimer interactions and one aggregation mechanism. For full-length CCL5, the molecular accumulation triggers oligomerization through the E66-K25 and E66-R44/K45 interactions, and the ¹²FAY¹⁴ interaction acts as a secondary effect to derive aggregation and precipitation. In contrast, the E66-R44/K45 interaction might dominate in CCL5 N-terminal truncations, and the interaction would lead to the filament-like formation in solution.

Beyond migration-Chemokines in lymphocyte priming, differentiation, and modulating effector functions

Chemokines and their receptors coordinate the positioning of leukocytes, and lymphocytes in particular, in space and time. Discrete lymphocyte subsets, depending on their activation and differentiation status, express various sets of chemokine receptors to be recruited to distinct tissues. Thus, the network of chemokines and their receptors ensures the correct localization of specialized lymphocyte subsets within the appropriate microenvironment enabling them to search for cognate antigens, to become activated, and to fulfill their effector functions. The chemokine system therefore is vital for the initiation as well as the regulation of immune responses to protect the body from pathogens while maintaining tolerance towards self. Besides the well investigated function of orchestrating directed cell migration, chemokines additionally act on lymphocytes in multiple ways to shape immune responses. In this review, we highlight and discuss the role of chemokines and chemokine receptors in controlling cell-to-cell contacts required for lymphocyte arrest on endothelial cells and immunological synapse formation, in lymphocyte priming and differentiation, survival, as well as in modulating effector functions.

Neuroimmune Mechanisms of Depression in Adults with Heart Failure

Heart failure (HF) is a major and costly public health concern, and its prognosis is grim-with high hospitalization and mortality rates. HF affects millions of individuals across the world, and this condition is expected to become "the epidemic" of the twenty-first century (Jessup et al., 2016). It is well documented that individuals with HF experience disproportionately high rates of depression and that those who are depressed have worse clinical outcomes than their nondepressed counterparts. The purpose of this chapter is to introduce the reader to the study of depression in HF, and how psychoneuroimmunologic principles have been applied to further elucidate mechanisms (i.e., neurohormonal and cytokine activation) linking these comorbid disorders.

Elevated expression of platelet-derived chemokines in patients with antiphospholipid syndrome

OBJECTIVE

Platelet factor 4 tetramers (CXCL4 chemokine) form complexes with β2glycoprotein I (β2GPI), recognized by anti-β2GPI antibodies leading to platelet activation in antiphospholipid syndrome (APS), either primary (PAPS) or secondary (SAPS). Increased plasma levels of CXCL4 may favor this process; therefore we measured plasma levels of CXCL4, a CXCL4 variant (CXCL4L1) and as controls, platelet-derived chemokines CXCL7 (NAP-2) and CCL5 (RANTES), in APS, and disease controls such as patients with systemic lupus erythematosus (SLE) coronary artery disease (CAD) and healthy donors (HDs).

METHODS

Plasma samples and platelets were isolated from patients with APS (n = 87), SLE (n = 29), CAD (n = 14) and 54 HDs. Plasma levels of CXCL4, CXCL4L1, CXCL7 and CCL5 as well as intracellular platelet CXCL4 and CXCL4L1 were measured using ELISA. Platelet CXCL4 and CXCL4L1 RNA levels were determined by RT-PCR.

RESULTS

CXCL4, CXCL7 (NAP-2) and CCL5 (RANTES) plasma levels were significantly higher in patients with APS compared to both control groups (SLE, CAD) and HDs. CXCL4L1 plasma levels were also significantly higher in APS than in SLE and HDs, but lower from that of CAD patients. Statistically significant concordance was detected between CXCL4 and CXCL7 (p < 0.0001) or CCL5 (p < 0.0001) plasma levels in patients with APS, either PAPS or SAPS. CXCL4L1 plasma levels were inversely correlated with CXCL4 (P = 0.0027), CXCL7 (p = 0.012) and CCL5 (p = 0.023) in PAPS and positively with CXCL4 (p = 0.0191), CCL5 (p < 0.0001) and CXCL7 (P < 0.0001), in SAPS. Levels of CXCL4, CXCL4L1, CXCL7 and CCL5 were divided in "high" (exceeding a level defined as the mean of HDs and 3 SD) and "low" (below this level); The "CXCL4L1 high" group was characterized by increased IgG aCL, (p = 0.0215), double antibody positivity (either aCL or anti-β2GPI plus LA), (p = 0.0277), triple antibody positivity (aCL plus anti-β2GPI plus LA), (p = 0.0073) and thrombocytopenia (p = 0.0061), as well as with at least 1 thrombotic event or the last 5 years (p = 0.0001), or more than 3 thrombotic events ever (p = 0.0151).

CONCLUSIONS

Chemokines associated with platelet activation and immune cell chemotaxis were found to be elevated in APS patients' plasma and may contribute to the pathogenesis of the syndrome. High CXCL4L1 plasma levels are associated with the clinical expression of APS and should be prospectively evaluated as a biomarker.

An Alternative Phosphorylation Switch in Integrin β2 (CD18) Tail for Dok1 Binding

Integrins are involved in cell migration and adhesion. A large number of proteins interact with the cytoplasmic tails of integrins. Dok1 is a negative regulator of integrin activation and it binds to the phosphorylated membrane proximal NxxY motif in a number of integrin β tails. The β tail of the β2 integrins contains a non-phosphorylatable NxxF motif. Hence it is unclear how Dok1 associates with the β2 integrins. We showed in this study using NMR and cell based analyses that residues Ser745 and Ser756 in the integrin β2 tail, which are adjacent to the NxxF motif, are required for Dok1 interaction. NMR analyses detected significant chemical shift changes and higher affinity interactions between Dok1 phospho-tyrosine binding (PTB) domain and integrin β2 tail peptide containing pSer756 compared to pSer745. The phosphorylated β2 peptide occupies the canonical ligand binding pocket of Dok1 based on the docked structure of the β2 tail-Dok1 PTB complex. Taken together, our data suggest an alternate phosphorylation switch in β2 integrins that regulates Dok1 binding. This could be important for cells of the immune system and their functions.

Characterization of structure, dynamics, and detergent interactions of the anti-HIV chemokine variant 5P12-RANTES

RANTES (CCL5) is a chemokine that recruits immune cells to inflammatory sites by interacting with the G-protein coupled receptor CCR5, which is also the primary coreceptor used together with CD4 by HIV to enter and infect target cells. Ligands of CCR5, including chemokines and chemokine analogs, are capable of blocking HIV entry, and studies of their structures and interactions with CCR5 will be key to understanding and optimizing HIV inhibition. The RANTES derivative 5P12-RANTES is a highly potent HIV entry inhibitor that is being developed as a topical HIV prevention agent (microbicide). We have characterized the structure and dynamics of 5P12-RANTES by solution NMR. With the exception of the nine flexible N-terminal residues, 5P12-RANTES has the same structure as wild-type RANTES but unlike the wild-type, does not dimerize via its N-terminus. To prepare the ground for interaction studies with detergent-solubilized CCR5, we have also investigated the interaction of RANTES and 5P12-RANTES with various commonly used detergents. Both RANTES variants are stable in Cymal-5, DHPC, Anzergent-3-12, dodecyltrimethylammonium chloride, and a DDM/CHAPS/CHS mixture. Fos-Cholines, dodecyldimethylglycine, and sodium dodecyl-sulfate denature both RANTES variants at low pH, whereas at neutral pH the stability is considerably higher. The onset of Fos-Choline-12-induced denaturation and the denatured state were characterized by circular dichroism and NMR. The detergent interaction starts below the critical micelle concentration at a well-defined mixed hydrophobic/positive surface region of the chemokine, which overlaps with the dimer interface. An increase of Fos-Choline-12 concentration above the critical micelle concentration causes a transition to a denatured state with a high α-helical content.

Neuroimmune mechanisms of depression in heart failure

Heart failure (HF) is a major and costly public health concern, and its prognosis is grim-with high hospitalization and mortality rates. It is well documented that HF patients experience disproportionately high rates of depression and that depressed HF patients have worse clinical outcomes than their non-depressed counterparts. The purpose of this chapter is to introduce the reader to the study of depression in HF, and how psychoneuroimmunologic principals have been applied to further elucidate the mechanisms (i.e., neurohormonal and cytokine activation) linking these co-morbid disorders.

Activated platelets and atherosclerosis

Several studies suggest an important role for platelets in atherogenesis, not only as mediators of thrombus formation, but also as inducers of inflammation. Several lines of evidence indicate that platelets are potent inflammatory cells that induce inflammatory responses in adjacent cells such as leukocytes and endothelial cells. Platelets may also themselves respond to inflammatory mediators produced by these neighboring cells. These platelet-mediated inflammatory pathways contribute to atherogenesis in both the early and late stage of the process. The bidirectional interaction between platelets and other cells may also be involved in the nonresolving inflammation characterizing atherosclerosis. In patients with atherosclerotic disorders, platelet-mediated inflammation appears to be operating in spite of the wide use of platelet-inhibiting drugs. This underscores the need for new therapeutic tools that more specifically target the pathways in platelet-mediated inflammation.

HIV-1 Nef-mediated inhibition of T cell migration and its molecular determinants

Lymphocyte trafficking is a multistep, intricate process and involves a number of host factors such as integrins and chemokine receptors on lymphocytes, adhesion molecules on endothelial cells, and chemokines present in the local microenvironment. Previous studies have shown that HIV-1 Nef inhibits T cell chemotaxis in response to the physiological ligand SDF-1alpha [( 1) ]. In this study, we aimed to gain a better understanding of the inhibitory mechanisms and to define the molecular determinants of HIV-1 Nef for this phenotype. We showed that HIV-1 Nef inhibited transwell and transendothelial migration of T cells. Specifically, HIV-1 Nef protein impaired T cell chemotaxis toward SDF-1alpha without altering CXCR4 expression. Moreover, we showed that HIV-1 Nef protein down-modulated LFA-1 expression on T lymphocytes and diminished adhesion and polarization of T lymphocytes and as a result, led to decreased migration across the endothelium. Furthermore, we showed that the myristoylation site and DeltaSD domain played important roles in Nef-mediated inhibition of transwell and transendothelial migration and polarization of T lymphocytes; however, different sites or domains were needed for Nef-mediated LFA-1 down-modulation and impaired adhesion of T lymphocyte. Taken together, these results demonstrated that HIV-1 Nef inhibited T lymphocyte migration at multiple steps and suggest that membrane localization and intracellular signaling events likely contribute to the inhibitory effects of Nef on T cell migration and subsequently, the pathobiology of the HIV-1 Nef protein.

A potential shift from adaptive immune activity to nonspecific inflammatory activation associated with higher depression symptoms in chronic heart failure patients

BACKGROUND

Chronic heart failure (CHF) patients with elevated depression symptoms are at greater risk of morbidity and mortality. The mechanisms linking symptoms of depression with disease progression in CHF are unclear. However, research studies have found evidence of alterations in immune activity associated with depression symptoms that may influence heart function. The present study sought to determine the relationship between depression symptoms and chemotaxis of peripheral blood mononuclear cells (PBMCs) in CHF patients, both at rest and in response to moderate exercise.

METHODS AND RESULTS

Sixty-five patients diagnosed with CHF (mean age, 59.8 +/- 14.5 years) and 45 non-CHF control subjects (mean age, 52.1 +/- 11.6) completed the Beck Depression Inventory (BDI) before undergoing a moderate 20-minute bicycle exercise task. Chemotaxis of PBMCs was examined in vitro to a bacterial peptide f-met leu phe (fMLP) and a physiologic chemokine, stromal cell derived factor-1 (SDF-1) immediately before and after exercise. CHF patients had reduced chemotaxis to SDF-1 (P = .025) compared with non-CHF subjects. Higher BDI scores were associated with reduced baseline chemotaxis to SDF-1 in both CHF and non-CHF subjects (P = .027). In contrast, higher BDI scores were associated with increased chemotaxis to fMLP (P = .049) and SDF-1 (P = .018) in response to exercise in the CHF patients.

CONCLUSION

The present study suggests a shift in immune cell mobility in CHF patients with greater depression symptom severity, with reduced chemotaxis to a physiologically specific chemokine at rest but increased chemotaxis to both nonspecific and specific chemical attractants in response to physical activity. This could have implications for cardiac repair and remodeling in CHF patients and therefore may affect disease progression.

RANTES Modulates TLR4-Induced Cytokine Secretion in Human Peripheral Blood Monocytes

Monocytes are the key regulators of joint inflammation and destruction in rheumatoid arthritis; hence, suppression of their recruitment into the joint may be therapeutically beneficial. Chemokines, including RANTES, are highly expressed in the joints of patient with rheumatoid arthritis, and they promote leukocyte trafficking into the synovial tissue. Because endogenous TLR4 ligands are expressed in the rheumatoid joint, the TLR4 ligand LPS was used to characterize the effects of RANTES on the TLR4-mediated induction of TNF-alpha and IL-6. Using peripheral blood (PB) monocytes, RANTES decreased LPS-induced IL-6 transcriptionally, whereas TNF-alpha was suppressed at the posttranscriptional level. RANTES signaled through p38 MAPK, and this signaling was further enhanced by LPS stimulation in PB monocytes, resulting in the earlier and increased secretion of IL-10. Inhibition of p38 by short-interfering RNA or a chemical inhibitor, as well as neutralization of IL-10, reversed the RANTES-mediated suppression of LPS-induced IL-6 and TNF-alpha. Further, when rheumatoid arthritis synovial fluid was added to PB monocytes, the neutralization of RANTES in fluid reduced the LPS-induced IL-10 and increased TNF-alpha. In conclusion, the results of this study suggest that RANTES down-regulates TLR4 ligation-induced IL-6 and TNF-alpha secretion by enhancing IL-10 production in PB monocytes. These observations suggest that the therapeutic neutralization of RANTES, in addition to decreasing the trafficking of leukocytes, may have a proinflammatory effect at the site of established chronic inflammation.

CCL5-CCR5-mediated apoptosis in T cells: Requirement for glycosaminoglycan binding and CCL5 aggregation

CCL5 (RANTES (regulated on activation normal T cell expressed and secreted)) and its cognate receptor, CCR5, have been implicated in T cell activation. CCL5 binding to glycosaminoglycans (GAGs) on the cell surface or in extracellular matrix sequesters CCL5, thereby immobilizing CCL5 to provide the directional signal. In two CCR5-expressing human T cell lines, PM1.CCR5 and MOLT4.CCR5, and in human peripheral blood-derived T cells, micromolar concentrations of CCL5 induce apoptosis. CCL5-induced cell death involves the cytosolic release of cytochrome c, the activation of caspase-9 and caspase-3, and poly(ADP-ribose) polymerase cleavage. CCL5-induced apoptosis is CCR5-dependent, since native PM1 and MOLT4 cells lacking CCR5 expression are resistant to CCL5-induced cell death. Furthermore, we implicate tyrosine 339 as a critical residue involved in CCL5-induced apoptosis, since PM1 cells expressing a tyrosine mutant receptor, CCR5Y339F, do not undergo apoptosis. We show that CCL5-CCR5-mediated apoptosis is dependent on cell surface GAG binding. The addition of exogenous heparin and chondroitin sulfate and GAG digestion from the cell surface protect cells from apoptosis. Moreover, the non-GAG binding variant, (44AANA47)-CCL5, fails to induce apoptosis. To address the role of aggregation in CCL5-mediated apoptosis, nonaggregating CCL5 mutant E66S, which forms dimers, and E26A, which form tetramers at micromolar concentrations, were utilized. Unlike native CCL5, the E66S mutant fails to induce apoptosis, suggesting that tetramers are the minimal higher ordered CCL5 aggregates required for CCL5-induced apoptosis. Viewed altogether, these data suggest that CCL5-GAG binding and CCL5 aggregation are important for CCL5 activity in T cells, specifically in the context of CCR5-mediated apoptosis.

Macaque trophoblast migration is regulated by RANTES

In human and non-human primates, migratory trophoblasts penetrate the uterine epithelium, invade the endometrium, enter the uterine vasculature, and migrate within the arteries. The mechanisms that regulate this directional migration are unknown. We have used early gestation macaque trophoblasts to test the hypothesis that trophoblast migration is regulated by the chemokine, Regulated on Activation T-Cell Expressed and Secreted (RANTES). Immunohistochemical analysis of cryosections of endometrial tissue showed expression of RANTES by stromal cells and vascular cells. Isolated endothelial cells expressed RANTES as determined by immunocytochemistry and RT-PCR analyses. Immunohistochemical analysis of endometrial cryosections showed that the RANTES receptor, CCR5, was expressed by trophoblasts on anchoring villi and by cells within the trophoblastic shell. Cytokeratin-positive/CCR5-positive cells, consistent with trophoblasts, were also found scattered within the stroma and were often clustered around blood vessels. Isolated trophoblast cells expressed CCR5 as determined by immunocytochemistry and RT-PCR analyses. Isolated trophoblasts migrated towards RANTES when cultured in migration chambers and migration was reduced in the presence of anti-CCR5 antibody. When trophoblasts were cultured on dishes coated with recombinant RANTES, expression of beta1 integrin was increased. The RANTES-induced increase in beta1 integrin expression was inhibited by pertussis toxin. These data suggest a role for RANTES and CCR5 in the regulation of trophoblast migration within the endometrium and within the uterine vasculature.

Rolling of Th1 Cells via P-Selectin Glycoprotein Ligand-1 Stimulates LFA-1-Mediated Cell Binding to ICAM-1

Activated T cells migrate from the blood into nonlymphoid tissues through a multistep process that involves cell rolling, arrest, and transmigration. P-Selectin glycoprotein ligand-1 (PSGL-1) is a major ligand for P-selectin expressed on subsets of activated T cells such as Th1 cells and mediates cell rolling on vascular endothelium. Rolling cells are arrested through a firm adhesion step mediated by integrins. Although chemokines presented on the endothelium trigger integrin activation, a second mechanism has been proposed where signaling via rolling receptors directly activates integrins. In this study, we show that Ab-mediated cross-linking of the PSGL-1 on Th1 cells enhances LFA-1-dependent cell binding to ICAM-1. PSGL-1 cross-linking did not enhance soluble ICAM-1 binding but induced clustering of LFA-1 on the cell surface, suggesting that an increase in LFA-1 avidity may account for the enhanced binding to ICAM-1. Combined stimulation by PSGL-1 cross-linking and the Th1-stimulating chemokine CXCL10 or CCL5 showed a more than additive effect on LFA-1-mediated Th1 cell adhesion as well as on LFA-1 redistribution on the cell surface. Moreover, PSGL-1-mediated rolling on P-selectin enhanced the Th1 cell accumulation on ICAM-1 under flow conditions. PSGL-1 cross-linking induced activation of protein kinase C isoforms, and the increased Th1 cell adhesion observed under flow and also static conditions was strongly inhibited by calphostin C, implicating protein kinase C in the intracellular signaling in PSGL-1-mediated LFA-1 activation. These results support the idea that PSGL-1-mediated rolling interactions induce intracellular signals leading to integrin activation, facilitating Th1 cell arrest and subsequent migration into target tissues.

Differential immune cell chemotaxis responses to acute psychological stress in Alzheimer caregivers compared to non-caregiver controls

OBJECTIVE

Caregiving for a spouse with Alzheimer's disease is associated with alterations in various immune cell responses. Chemotaxis of immune cells to chemokines is an important factor involved in lymphocyte migration, which plays an essential role in inflammatory responses to infection and may also be involved in atherogenesis. However, the effects of chronic stress on chemotaxis have not been investigated. The objective of this study was to examine lymphocyte chemotaxis to chemokines, stromal cell-derived factor-1 (SDF-1), N-formyl-methionyl-leucyl-phenylalanine (FMLP), and a beta-adrenergic agonist, isoproteronol (ISO), in response to an acute stressor in Alzheimer's caregivers. Correlations between immune cell chemotaxis and epinephrine and norepinephrine levels were also examined.

METHODS

Caregivers (n = 18) and noncaregiver controls (n = 9) completed a public speaking task. Blood was drawn before and immediately after the task for changes in chemotaxis to FMLP, SDF-1, and ISO, and for epinephrine and norepinephrine levels.

RESULTS

Caregivers had reduced chemotaxis to FMLP, SDF-1, and ISO in response to the speech task, compared with non-caregivers. Also, the direction of the correlations between chemotaxis to FMLP, SDF-1, and ISO and epinephrine levels differed between groups.

CONCLUSIONS

These findings suggest that immune cells released into circulation in response to acute stress are altered in caregivers. Group differences in immune responses may be due to sympathetically mediated alterations, which may have implications for caregivers' ability to successfully mount viable immune responses, as well as, atherogenesis.

RhoH is required to maintain the integrin LFA-1 in a nonadhesive state on lymphocytes

Lymphocyte function-associated antigen 1 (LFA-1) is relatively nonadhesive on resting lymphocytes; however, the mechanisms underlying changes in its adhesiveness are poorly understood. In this study, we generated a Jurkat T cell clone, J+hi1.14, that contained low amounts of mRNA for RhoH, a leukocyte-specific inhibitory Rho family member. J+hi1.14 cells expressed constitutively adhesive LFA-1 and the cells bound spontaneously to intracellular adhesion molecules 1, 2 and 3. Reconstitution of RhoH mRNA expression in J+hi1.14 cells reverted the adhesion phenotype to that of wild-type. We obtained similar results using RNA interference in peripheral blood lymphocytes. These data demonstrate that RhoH is required for maintenance of lymphocyte LFA-1 in a nonadhesive state.

Identification of tissue transglutaminase as a novel molecule involved in human CD8+ T cell transendothelial migration

During inflammation, T lymphocytes migrate out of the blood across the vascular endothelium in a multistep process. The receptors mediating T cell adhesion to endothelium are well characterized; however, the molecules involved in T cell transendothelial migration (TEM) subsequent to lymphocyte adhesion to the endothelium are less clear. To identify receptors mediating TEM, mAbs were produced against human blood T cells adhering to IFN-gamma-activated HUVEC in mice and tested for inhibition of lymphocyte TEM across cytokine-activated HUVEC. Most of the mAbs were against beta(1) and beta(2) integrins, but one mAb, 6B9, significantly inhibited T cell TEM across IFN-gamma, TNF-alpha, and IFN-gamma plus TNF-alpha-stimulated HUVEC, and did not react with an integrin. 6B9 mAb did not inhibit T cell adhesion to HUVEC, suggesting that 6B9 blocked a novel pathway in T cell TEM. The 6B9 Ag was 80 kDa on SDS-PAGE, and was expressed by both blood leukocytes and HUVEC. Immunoaffinity purification and mass spectrometry identified this Ag as tissue transglutaminase (tTG), a molecule not known to mediate T cell TEM. Treatment of HUVEC with 6B9 was more effective than treatment of T cells. 6B9 blockade selectively inhibited CD4(-), but not CD4(+), T cell TEM, suggesting a role for tTG in recruitment of CD8(+) T lymphocytes. Thus, 6B9 is a new blocking mAb to human tTG, which demonstrates that tTG may have a novel role in mediating CD8(+) T cell migration across cytokine-activated endothelium and infiltration of tissues during inflammation.

Acute psychological stress: effects on chemotaxis and cellular adhesion molecule expression

OBJECTIVE

Activation of a psychological stress response increases autonomic activity and enhances immune function by inducing a significant increase in numbers of leukocytes at sites of inflammation. Chemotaxis and cellular adhesion are thought to mediate leukocyte trafficking. In this study, we examine the effects of an acute psychological stress on chemotactic responses of PBMCs and on CAM expression in relation to measures of sympathetic activation.

METHODS

Subjects underwent either a public speaking task (N = 24) or a control condition (N = 13). Blood was drawn before the task, immediately after, and 20 minutes after, the task for changes in percentage of cells expressing cellular adhesion molecules, chemotaxis to chemokines, HR, blood pressure, and E and NE levels.

RESULTS

In response to the laboratory stressor, increases of PBMC chemotaxis to FMLP and SDF-1 were found, which were coupled with increases in the percentages of lymphocytes expressing the integrin Mac-1. Autonomic activity, including blood pressure and circulating levels of catecholamines, increased after administration of the stressor, and correlated with increases of Mac-1.

CONCLUSIONS

These data show that acute stress induces increase of chemotaxis and expression of CAM expression, which may contribute to increased migration and recruitment of immune cells to sites of infection and/or inflammation.

IFN-gamma reverses the stop signal allowing migration of antigen-specific T cells into inflammatory sites

In humans the majority of endothelial cells (EC) constitutively express MHC class II Ags. We know that in vitro ECs can activate CD45RO(+) B7-independent CD4(+) T cells to proliferate and produce IL-2. The in vivo correlate of this T cell response is not known, and here we have explored whether endothelial expression of MHC class II Ags affects the transendothelial migration of alloreactive CD4(+) CD45RO(+) B7-independent T cells. Alloreactive CD4(+) T cell clones and lines were generated against HLA-DR11, DR13, DR4, and DR1 MHC Ags, and their rates of migration across untreated EC line Eahy.926 (MHC class II negative) or Eahy.926 transfected with CIITA (EahyCIITA) to express DR11 and DR13 were investigated. The migrations of EahyCIITA-specific T cell clones and lines were retarded in a DR-specific manner, and retardation was reversed in the presence of mAb to DR Ag. When investigating the ability of T cells to proliferate in response to EahyCIITA before and after transmigration, migrated cells were still able to proliferate, but the frequency of EahyCIITA-specific cells was much reduced compared with that of nonmigrated cells. The use of fluorescently labeled T cells revealed that specific cells become trapped within the endothelial monolayer. Pretreatment of EahyCIITA with IFN-gamma restored the ability of DR11- or DR13-specific T cells to transmigrate and proliferate, thus abrogating DR-specific retardation. We conclude that cognate interaction between T cells and endothelial MHC class II initiates a stop signal possibly similar to an immunological synapse, but this is overcome in an inflammatory milieu.

Rapid leukocyte integrin activation by chemokines

Chemokines control selective targeting of circulating leukocytes to the microvasculature by triggering inside-out signal transduction pathways leading to integrin-dependent adhesion. Integrin activation by chemokines is very rapid, is downmodulated within minutes and appears to involve both enhanced heterodimer lateral mobility on the plasma membrane, facilitating encounters with dispersed ligand, as well as induction of a high-affinity state. These two modalities of integrin activation by chemokines involve distinct signaling pathways in the cell, yet complement each other functionally, allowing binding of rolling cells under conditions of low as well as high ligand density. Recent data show that chemokines generate both pro- and anti-adhesive intracellular signaling events, whose equilibrium is likely to be relevant to the kinetics of adhesion and de-adhesion, and to cell movement during diapedesis and chemotaxis. Importantly, chemokines utilize different signaling mechanisms to modulate the activity of distinct integrin subtypes. These recent advances suggest that chemokines may regulate adhesive responses of immune cells based not only on patterns of chemokine receptor expression, but also on variable signaling pathways that can modulate the pro-adhesive responses of leukocytes as a function of their differentiated state, and of the local microenvironment.

Interaction of the CC-chemokine RANTES with glycosaminoglycans activates a p44/p42 mitogen-activated protein kinase-dependent signaling pathway and enhances human immunodeficiency virus type 1 infectivity

The interaction of the CC-chemokine RANTES with its cell surface receptors transduces multiple intracellular signals: low concentrations of RANTES (1 to 10 nM) stimulate G-protein-coupled receptor (GPCR) activity, and higher concentrations (1 microM) activate a phosphotyrosine kinase (PTK)-dependent pathway. Here, we show that the higher RANTES concentrations induce rapid tyrosine phosphorylation of multiple proteins. Several src-family kinases (Fyn, Hck, Src) are activated, as is the focal adhesion kinase p125 FAK and, eventually, members of the p44/p42 mitogen-activated protein kinase (MAPK) family. This PTK signaling pathway can be activated independently of known seven-transmembrane GPCRs for RANTES because it occurs in cells that lack any such RANTES receptors. Instead, activation of the PTK signaling pathway is dependent on the expression of glycosaminoglycans (GAGs) on the cell surface, in that it could not be activated by RANTES in GAG-deficient cells. We have previously demonstrated that RANTES can both enhance and inhibit infection of cells with human immunodeficiency virus type 1 (HIV-1). Here we show that activation of both PTK and MAPK is involved in the enhancement of HIV-1 infectivity caused by RANTES in cells that lack GPCRs for RANTES but which express GAGs.

A dominant Jurkat T cell mutation that inhibits LFA-1-mediated cell adhesion is associated with increased cell growth

LFA-1 exists in a low avidity state on resting leukocytes and is believed to adopt a high avidity state when the cells are exposed to a stimulus. Current evidence supports both aggregation of LFA-1 on the cell surface and conformational changes in the reversible acquisition of a high avidity state. We studied this regulation by selecting a Jurkat T cell clone, J-lo1.3, that expresses LFA-1 yet fails to bind to purified ICAM-1 despite treatment of the cells with PMA or Mn2+. Several lines of evidence demonstrated the absence of any changes within LFA-1 itself. LFA-1 protein purified from the J-lo1.3 clone and the wild-type Jurkat clone, Jn.9, were found to be functionally equivalent. The cDNA sequences encoding the LFA-1 alpha- and beta-chains from J-lo1.3 were identical with the published sequences except for nine base pairs. However, these differences were also found in a Jurkat mutant with a constitutively avid phenotype, J+hi1.19 or the wild-type Jn.9 genomic or cDNA. Fusion of J-lo1.3 with Jn.9 yielded hybrids that exhibited the J-lo1.3 adhesion phenotype, which indicated a dominant mutation in J-lo1.3. This phenotype was relatively specific for LFA-1 among all integrins expressed by Jurkat. Interestingly, the J-lo1.3 cells had a 1.2-fold faster doubling time than did the Jn.9 cells. Reversion of J-lo1.3 to the wild-type adhesion phenotype by mutagenesis and selection also decreased the growth rate. These data support a connection between cellular growth and cellular adhesion in lymphocytes.

Augmentation of RANTES-induced extracellular signal-regulated kinase mediated signaling and T cell adhesion by elastase-treated fibronectin

T cells migrating across extracellular matrix (ECM) barriers toward their target, the inflammatory site, should respond to chemoattractant cytokines and to the degradation of ECM by specific enzymes. In this study, we examined the effects of RANTES and ECM proteins treated with human leukocyte elastase on T cell activation and adhesion to the ECM. We found that human peripheral blood T cells briefly suspended with RANTES (0.1-100 ng/ml) had increased phosphorylation of their intracellular extracellular signal-regulated kinase (ERK), a mitogen-activated protein kinase involved in the activation of several intracellular downstream effector molecules implicated in cell adhesion and migration. Consequently, a small portion (12-20%) of the responding cells adhered to fibronectin (FN). However, when the T cells were exposed to RANTES in the presence of native immobilized FN, laminin, or collagen type I, ERK phosphorylation was partially inhibited, suggesting that this form of the ECM proteins can down-regulate RANTES-induced intracellular signaling. In contrast, when the T cells were exposed to RANTES in the presence of elastase-treated immobilized FN, but not to elastase-treated laminin, ERK phosphorylation was markedly increased. Furthermore, a large percentage (30%) of RANTES-activated T cells adhered to the enzymatically treated FN in a beta1 integrin-dependent fashion. Thus, while migrating along chemotactic gradients within the ECM, T cells can adapt their adhesive performance according to the level of cleavage induced by enzymes to the matrix.

The C-class chemokine lymphotactin costimulates the apoptosis of human CD4(+) T cells

Clonal expansion of activated T cells is controlled by homeostatic mechanisms leading to cell death of a large proportion of the cells. The CD3/TcR pathway induces cell death, mostly when triggered in the absence of costimulatory signal. The unique T cell-specific chemokine of the C class, lymphotactin (Lptn), has recently been shown to inhibit the production of Th1-type lymphokines in human CD4(+) T cells. The present study shows the ability of Lptn to costimulate the death of CD4(+) T lymphocytes triggered through CD3/TCR. The Lptn-mediated increased cell death exhibited characteristic features of apoptosis, as mainly determined by DNA fragmentation and exposure of an apoptotic-specific mitochondrial antigen. This apoptosis was dependent on Fas/FasL signaling, was not rescued by addition of interleukin 2, and proceeded with a predominant processing of both initiator procaspase-9 and effector procaspase-7. These caspase activities were further evidenced by specific cleavage of poly(ADP-ribose) polymerase (PARP) and CD3/TCR zeta-chain, but not DNA fragmentation factor (DFF45). This study demonstrates that the functional repertoire of Lptn in the regulation of human CD4(+) T-lymphocyte activation includes the ability to costimulate apoptosis.

RANTES activates antigen-specific cytotoxic T lymphocytes in a mitogen-like manner through cell surface aggregation

RANTES (regulated upon activation, normal T cell expressed and secreted) is released by cytotoxic T lymphocytes (CTL), and is a potent chemoattractant factor for monocytes and T cells, also known for its ability to suppress HIV infection. At micromolar concentration, RANTES is able to activate leukocytes, and, paradoxically, to enhance HIV infection in vitro. These latter properties are dependent on its ability to self-aggregate. In order to understand further the mechanism of RANTES-induced activation, the effects of both aggregated and disaggregated RANTES on antigen-specific CD8(+) clones were studied in comparison with the effects of specific antigens and in the presence of specific inhibitors of RANTES-mediated activation. We observed large amounts of RANTES aggregated on the cell surface, which led to cell activation, including up-regulation of cell surface markers, and secretion of IFN-gamma and macrophage inflammatory protein (MIP)-1beta. Specific inhibitors of RANTES-induced activation, such as soluble glycosaminoglycans, MIP-1alpha and MIP-1beta, acted by preventing the binding of RANTES on the cell surface. These studies suggest that RANTES acted more like a mitogen than an antigen-independent activator.

The C-class chemokine, lymphotactin, impairs the induction of Th1-type lymphokines in human CD4+ T cells

Chemokines are involved in the regulation of leukocyte migration and for some of them, T-cell costimulation. To date, the only direct property of lymphotactin (Lptn), the unique member of the C class of chemokines, consists of T-cell chemoattraction. This report describes a novel function for Lptn in human T-lymphocyte biology, by demonstrating the direct ability of Lptn to both inhibit and costimulate CD4+ and CD8+ T-cell activation, respectively. Lptn but not RANTES inhibited CD4+ T-cell proliferation, through a decreased production of Th1 (interleukin [IL]-2, interferon [IFN]-γ) but not Th2 (IL-4, IL-13) lymphokines, and decreased IL-2R expression. Transfections in Jurkat cells showed a Lptn-mediated transcriptional down-regulation of gene-promoter activities specific for Th1-type lymphokines, as well as of nuclear factor of activated T cells (NF-AT) but not AP-1 or NF-ΚB enhancer activities. This suppressive action of Lptn could be compensated by overexpression of NF-ATc but not NF-ATp. CD4+ T-cell proliferation was completely restored by exogenous IL-2 or reversed by pertussis toxin, wortmannin, and genistein, suggesting the involvement of multiple partners in Lptn signaling. In contrast to CD4+ cells, Lptn exerted a potent costimulatory activity on CD8+ T-cell proliferation and IL-2 secretion. These data provide important insights into the role of Lptn in differential regulation of normal human T-cell activation and its possible implication in immune response disorders.

The C-class chemokine, lymphotactin, impairs the induction of Th1-type lymphokines in human CD4+ T cells

Chemokines are involved in the regulation of leukocyte migration and for some of them, T-cell costimulation. To date, the only direct property of lymphotactin (Lptn), the unique member of the C class of chemokines, consists of T-cell chemoattraction. This report describes a novel function for Lptn in human T-lymphocyte biology, by demonstrating the direct ability of Lptn to both inhibit and costimulate CD4+ and CD8+ T-cell activation, respectively. Lptn but not RANTES inhibited CD4+ T-cell proliferation, through a decreased production of Th1 (interleukin [IL]-2, interferon [IFN]-γ) but not Th2 (IL-4, IL-13) lymphokines, and decreased IL-2R expression. Transfections in Jurkat cells showed a Lptn-mediated transcriptional down-regulation of gene-promoter activities specific for Th1-type lymphokines, as well as of nuclear factor of activated T cells (NF-AT) but not AP-1 or NF-ΚB enhancer activities. This suppressive action of Lptn could be compensated by overexpression of NF-ATc but not NF-ATp. CD4+ T-cell proliferation was completely restored by exogenous IL-2 or reversed by pertussis toxin, wortmannin, and genistein, suggesting the involvement of multiple partners in Lptn signaling. In contrast to CD4+ cells, Lptn exerted a potent costimulatory activity on CD8+ T-cell proliferation and IL-2 secretion. These data provide important insights into the role of Lptn in differential regulation of normal human T-cell activation and its possible implication in immune response disorders.

Human leukemic (HMC-1) mast cells are responsive to 1alpha, 25-dihydroxyvitamin D(3): selective promotion of ICAM-3 expression and constitutive presence of vitamin D(3) receptor

Expression levels of adhesion molecules on HMC-1 mast cells were examined prior to and following administration of 1alpha, 25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. While most receptors (including ICAM-1) remained unchanged by the treatment, solely ICAM-3 expression was promoted in a dose- and time-dependent fashion, peaking at 50 nM of 1,25(OH)(2)D(3) and 72 h, illustrating that like other myeloid cells, human mast cells are 1,25(OH)(2)D(3) responsive, yet in a highly selective manner. Flow cytometric results were confirmed by ELISA, by semiquantitative RT-PCR, and functionally by showing enhanced anti-ICAM-3 mediated homotypic aggregation of 1,25(OH)(2)D(3) pretreated cells. Since cellular responsiveness is conferred by the vitamin D(3) receptor (VDR), we examined human mast cells for its expression. VDR was constitutively present in both HMC-1 and skin mast cells by RT-PCR technique and in nuclear extracts of HMC-1 cells by Western blot analysis. Our data thus suggest that human mast cells are direct targets of 1, 25(OH)(2)D(3) action.

RANTES production and expression is reduced in relapsing-remitting multiple sclerosis patients treated with interferon-beta-1b

RANTES (regulated upon activation, normal T-cell expressed and secreted), a CC chemokine, appears to play a role in the pathogenesis of relapsing-remitting multiple sclerosis (RR-MS), enhancing the inflammatory response within the nervous system. We have demonstrated that RANTES production is increased in RR-MS compared to controls. Interferon-beta-1b (IFN-beta-1b) treatment reduces RANTES production in sera and peripheral blood adherent mononuclear cell (PBAM) supernatants both in relapse and remission. IFN-beta-1b also reduces RANTES expression in PBAM. Our results suggest that RANTES modulation might represent one of the mechanisms of action of IFN-beta-1b in RR-MS.

CX3C-chemokine, fractalkine-enhanced adhesion of THP-1 cells to endothelial cells through integrin-dependent and -independent mechanisms

Leukocyte adhesion and trafficking at the endothelium requires both cellular adhesion molecules and chemotactic factors. A newly identified CX3C chemokine, fractalkine, expressed on activated endothelial cells, plays an important role in leukocyte adhesion and migration. We examined the functional effects of fractalkine on beta1 and beta2 integrin-mediated adhesion using a macrophage-like cell line, THP-1 cells. In this study, we report that THP-1 cells express mRNA encoding a receptor for fractalkine, CX3CR1, determined by Northern blotting. Scatchard analysis using fractalkine-SEAP (secreted form of placental alkaline phosphatase) chimeric proteins revealed that THP-1 cells express a single class of CX3CR1 with a dissociation constant of 30 pM and a mean expression of 440 sites per cell. THP-1 cells efficiently adhered, in a fractalkine-dependent manner, to full-length of fractalkine immobilized onto plastic and to the membrane-bound form of fractalkine expressed on ECV304 cells or TNF-alpha-activated HUVECs. Moreover, soluble-fractalkine enhanced adhesion of THP-1 cells to fibronectin and ICAM-1 in a dose-dependent manner. Pertussis toxin, an inhibitor of Gi, inhibited the fractalkine-mediated enhancement of THP-1 cell adhesion to fibronectin and ICAM-1. Finally, we found that soluble-fractalkine also enhanced adhesion of freshly separated monocytes to fibronectin and ICAM-1. These results indicate that fractalkine may induce firm adhesion between monocytes and endothelial cells not only through an intrinsic adhesion function itself, but also through activation of integrin avidity for their ligands.

Chemokine signaling in inflammation

The events that lead to an inflammatory response are characterized by recognition of the site of injury by inflammatory cells, specific recruitment of subpopulations of leukocytes into tissue, removal of the offending agent and "debridement" of the injured cells/tissue, and repair of the site of injury with attempts to reestablish normal parenchymal, stromal, and extracellular matrix relationship. The molecular regulation of this complex physiologic process involves the interaction between cell surface, extracellular matrix, and soluble mediators, such as chemokines. Chemokine activities are mediated through G-protein coupled receptors. This is the largest known family of cell-surface receptors, which mediate transmission of stimuli as diverse as hormones, peptides, glycopeptides, and chemokines. In this review, we will focus on the signaling pathways involved in the production and function of chemokines as they relate to the inflammatory response.

Pertussis toxin treatment in vivo reduces surface expression of the adhesion integrin leukocyte function antigen-1 (LFA-1)

Pertussis toxin treatment in macaques inhibits lymphocyte extravasation from the blood and leads to transient lymphocytosis and leukocytosis. We examined lymphocyte adhesion molecules known to be involved in the extravasation process to find possible mechanisms for the effects of pertussis toxin treatment. The two subunits of LFA-1, CD11a and CD18, showed decreased surface expression on lymphocytes from pertussis toxin treated animals compared to untreated animals. The adhesion molecule CD44, and the alpha subunit of the integrin VLA-4 (CD49d) were not decreased by pertussis toxin treatment. Lower surface expression of CD11a and CD18 was observed on all lymphocyte subsets and was correlated inversely with the extent of lymphocytosis. The magnitude of lymphocytosis after pertussis toxin treatment was higher in SIV-infected macaques than in uninfected animals. However, changes in LFA-1 levels were similar in both groups. These data show that LFA-1 surface levels are affected by pertussis toxin in vivo and this change may account in part, for the ability of pertussis toxin to induce lymphocytosis.

Increased chemokine receptor CCR7/EBI1 expression enhances the infiltration of lymphoid organs by adult T-cell leukemia cells

Adult T-cell leukemia (ATL) is characterized by infiltration of various tissues by circulating ATL cells, a finding often associated with a poor prognosis. Leukocyte migration from the circulation into tissues depends on integrin-mediated adhesion to the endothelium, and integrins are tightly regulated by several factors, such as chemokines. In this study, we focused on the interaction between chemokines and chemokine receptors on ATL cells to understand factors involved in ATL cell infiltration of lymphoid organs. We compared freshly isolated ATL cells from patients with and without lymphoid organ involvement for the expression of the chemokine receptor CCR7/EBI1, the functional receptor for secondary lymphoid-tissue chemokine (SLC), which is expressed at high levels by high endothelial venules of lymph nodes and Peyer's patches. Reverse transcriptase-polymerase chain reaction and flow cytometric analysis, using anti-CCR7 monoclonal antibody (CCR7.6B3), revealed that ATL cells from patients with lymphoid organ involvement expressed significantly more CCR7/EBI1 than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement. Consequently, significantly more ATL cells from patients with lymphoid organ involvement than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement adhered to surfaces coated with ICAM-1 and SLC or EBI1-ligand chemokine (ELC), another ligand for CCR7/EBI1, under static and flow conditions and migrated toward SLC or ELC at a low concentration (30 ng/ml). These findings suggest that increased CCR7/EBI1 expression plays a role in lymphoid organ infiltration of ATL cells. (Blood. 2000; 30-38)

Increased chemokine receptor CCR7/EBI1 expression enhances the infiltration of lymphoid organs by adult T-cell leukemia cells

Adult T-cell leukemia (ATL) is characterized by infiltration of various tissues by circulating ATL cells, a finding often associated with a poor prognosis. Leukocyte migration from the circulation into tissues depends on integrin-mediated adhesion to the endothelium, and integrins are tightly regulated by several factors, such as chemokines. In this study, we focused on the interaction between chemokines and chemokine receptors on ATL cells to understand factors involved in ATL cell infiltration of lymphoid organs. We compared freshly isolated ATL cells from patients with and without lymphoid organ involvement for the expression of the chemokine receptor CCR7/EBI1, the functional receptor for secondary lymphoid-tissue chemokine (SLC), which is expressed at high levels by high endothelial venules of lymph nodes and Peyer's patches. Reverse transcriptase-polymerase chain reaction and flow cytometric analysis, using anti-CCR7 monoclonal antibody (CCR7.6B3), revealed that ATL cells from patients with lymphoid organ involvement expressed significantly more CCR7/EBI1 than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement. Consequently, significantly more ATL cells from patients with lymphoid organ involvement than control CD4+CD45RO+ T cells and ATL cells from patients without lymphoid organ involvement adhered to surfaces coated with ICAM-1 and SLC or EBI1-ligand chemokine (ELC), another ligand for CCR7/EBI1, under static and flow conditions and migrated toward SLC or ELC at a low concentration (30 ng/ml). These findings suggest that increased CCR7/EBI1 expression plays a role in lymphoid organ infiltration of ATL cells. (Blood. 2000; 30-38)

Identification of surface residues of the monocyte chemotactic protein 1 that affect signaling through the receptor CCR2

The CC chemokine, monocyte chemotactic protein, 1 (MCP-1) functions as a major chemoattractant for T-cells and monocytes by interacting with the seven-transmembrane G protein-coupled receptor CCR2. To identify which residues of MCP-1 contribute to signaling though CCR2, we mutated all the surface-exposed residues to alanine and other amino acids and made some selective large changes at the amino terminus. We then characterized the impact of these mutations on three postreceptor pathways involving inhibition of cAMP synthesis, stimulation of cytosolic calcium influx, and chemotaxis. The results highlight several important features of the signaling process and the correlation between binding and signaling: The amino terminus of MCP-1 is essential as truncation of residues 2-8 ([1+9-76]hMCP-1) results in a protein that cannot stimulate chemotaxis. However, the exact peptide sequence may be unimportant as individual alanine mutations or simultaneous replacement of residues 3-6 with alanine had little effect. Y13 is also important and must be a large nonpolar residue for chemotaxis to occur. Interestingly, both Y13 and [1+9-76]hMCP-1 are high-affinity binders and thus affinity of these mutants is not correlated with ability to promote chemotaxis. For the other surface residues there is a strong correlation between binding affinity and agonist potency in all three signaling pathways. Perhaps the most interesting observation is that although Y13A and [1+9-76]hMCP are antagonists of chemotaxis, they are agonists of pathways involving inhibition of cAMP synthesis and, in the case of Y13A, calcium influx. These results demonstrate that these two well-known signaling events are not sufficient to drive chemotaxis. Furthermore, it suggests that specific molecular features of MCP-1 induce different conformations in CCR2 that are coupled to separate postreceptor pathways. Therefore, by judicious design of antagonists, it should be possible to trap CCR2 in conformational states that are unable to stimulate all of the pathways required for chemotaxis.

Macrophage Inflammatory Protein-3β Enhances IL-10 Production by Activated Human Peripheral Blood Monocytes and T Cells

We report that the addition of human macrophage inflammatory protein-3β (MIP-3β) to cultures of human PBMCs that have been activated with LPS or PHA results in a significant enhancement of IL-10 production. This effect was concentration-dependent, with optimal MIP-3β concentrations inducing more than a 5-fold induction of IL-10 from LPS-stimulated PBMCs and a 2- to 3-fold induction of IL-10 from PHA-stimulated PBMCs. In contrast, no significant effect on IL-10 production was observed when 6Ckine, the other reported ligand for human CCR7, or other CC chemokines such as monocyte chemoattractant protein-1, RANTES, MIP-1α, and MIP-1β were added to LPS- or PHA-stimulated PBMCs. Similar results were observed using activated purified human peripheral blood monocytes or T cells. Addition of MIP-3β to nonactivated PBMCs had no effect on cytokine production. Enhancement of IL-10 production by MIP-3β correlated with the inhibition of IL-12 p40 and TNF-α production by monocytes and with the impairment of IFN-γ production by T cells, which was reversed by addition of anti-IL-10 Abs to the cultures. The ability of MIP-3β to augment IL-10 production correlated with CCR7 mRNA expression and stimulation of intracellular calcium mobilization in both monocytes and T cells. These data indicate that MIP-3β acts directly on human monocytes and T cells and suggest that this chemokine is unique among ligands binding to CC receptors due to its ability to modulate inflammatory activity via the enhanced production of the anti-inflammatory cytokine IL-10.

Aggregation of RANTES is responsible for its inflammatory properties. Characterization of nonaggregating, noninflammatory RANTES mutants

The biology of RANTES (regulated on activation normal T cell expressed) aggregation has been investigated using RANTES and disaggregated variants, enabling comparison of aggregated, tetrameric, and dimeric RANTES forms. Disaggregated variants retain their G(i)-type G protein-coupled receptor-mediated biological activities. A correlation between RANTES aggregation and cellular activation has been demonstrated. Aggregated RANTES, but not disaggregated RANTES, activates human T cells, monocytes, and neutrophils. Dimeric RANTES has lost its cellular activating activity, rendering it noninflammatory. Macrophage inflammatory protein 1alpha, macrophage inflammatory protein-1beta, and erythrocytes are potent natural antagonists of aggregated RANTES-induced cellular activation. There is a clear difference in the signaling properties of aggregated and disaggregated RANTES forms, separating the dual signaling pathways of RANTES and the enhancing and suppressive effects of RANTES on human immunodeficiency virus infection. Disaggregated RANTES will be a valuable tool to explore the biology of RANTES action in human immunodeficiency virus infection and in inflammatory disease.

CD28 co-stimulation results in down-regulation of lymphotactin expression in human CD4(+) but not CD8(+) T cells via an IL-2-dependent mechanism

Chemokines are key molecules in promoting leukocyte migration and, for some of them, T cell adhesion and activation. Lymphotactin, which is the unique known member of the C class of chemokines, is produced by and acts on T lymphocytes, but the requirement of co-stimulatory pathways such as CD28 for its expression is largely unknown. CD28 plays a dominant role in the amplification of T cell proliferation, survival and cytokine production. In this report, we demonstrate that human lymphotactin expression, at both the mRNA and protein levels, is optimally induced by CD3/TCR activation alone, whereas CD28 co-stimulation turns off this expression. This down-regulation is not attributable to secondary activation via CTLA-4, the alternative counter-receptor of B7 ligands. Only the CD4(+) and not the CD8(+) subset is directly affected by this negative regulation. Transcript destabilization can be ruled out as a mechanism by which CD28 down-regulates lymphotactin expression. However, such down-regulation can be partly induced by IL-2 and abrogated by blocking IL-2/IL-2 receptor interaction. This particular profile of lymphotactin expression is not in line with the prevailing dogma of up-regulation of cytokine gene expression by CD28 co-stimulation, and represents a new CD28-mediated regulatory mechanism for lymphotactin expression.

A one-tube polymerase chain reaction protocol demonstrates CC chemokine overexpression in Graves' disease glands

An adaptation of mixed oligonucleotide primed amplification of complementary DNA to detect the profile of CC chemokines in biological samples is presented. By introducing normalization, two correction coefficients, performing a single amplification reaction, and five parallel hybridizations, intrasample and intersample comparisons can be reliably made. This protocol of single tube PCR CC chemokine profiling was applied to tissue samples from an autoimmune thyroid condition, Graves' disease, and from a nonautoimmune condition, multinodular goiter. Results demonstrate overexpression of CC chemokines in Graves' disease, statistically significant for macrophage inflammatory protein-1alpha and -1beta, which correlated with the aberrant human leukocyte antigen class II expression by thyrocytes, as assessed by flow cytometry. Overexpression of CC chemokines probably plays a major role in determining the characteristics of the lymphocytes migrating to the thyroid gland and influences the course of the disease. The study of chemokine profile should be more informative than the study of isolated chemokines and cytokines, and as it can be applied to fine needle aspiration biopsies, it may be useful to clinical research.

Increased levels in vivo of mRNAs for IL-8 and macrophage inflammatory protein-1 alpha (MIP-1 alpha), but not of RANTES mRNA in peripheral blood mononuclear cells of patients with atopic dermatitis (AD)

Chemokines play an important role in the selective movement of leucocytes into inflammatory areas and they also activate various cells in inflamed tissues. However, it is unclear which cells are the main sources of chemokines in actual inflammatory diseases, even though both mononuclear cells and non-inflammatory resident cells are able to produce chemokines in vitro and the former cells are also the main target of chemokines. To clarify the roles of chemokines that are produced by mononuclear cells in AD, we measured levels in vivo of mRNA for IL-8 and MIP-1 alpha, as well as the level of regulated upon activation normal T cell expressed and secreted (RANTES) mRNA in freshly isolated peripheral blood mononuclear cells from patients with AD. We compared the results with those from psoriatic patients, and patients without AD who were suffering from other cutaneous diseases and eosinophilia. Levels of mRNAs were determined by semiquantitative reverse transcriptase-polymerase chain reactions. Levels of IL-8 and MIP-1 alpha mRNA were elevated not only in atopic patients but also in non-atopic patients with inflammatory skin disease associated with eosinophilia, compared with levels in psoriatic patients and healthy controls. Levels of RANTES mRNA were similar in atopic patients but they were lower in the other two groups of patients when compared with levels in healthy controls. In atopic patients, the levels of both IL-8 and MIP-1 alpha mRNAs but not of RANTES mRNA decreased with improvements in symptom scores after therapy. These findings suggest that mononuclear cells are not only the target of chemokines but might also play an important role in the pathogenesis of AD by producing IL-8 and MIP-1 alpha.

Real-time analysis of integrin-mediated chemotactic migration of T lymphocytes within 3-D extracellular matrix-like gels

We have developed a novel 3-D gel reconstituted with major extracellular matrix (ECM) glycoproteins to follow the dynamics of migration of human T cells locomoting, in real-time, on gradients formed by representative chemoattractants: the C-C chemokine RANTES, and the pro-inflammatory cytokine IL-2. In the absence of chemoattractants, none of the T cells migrated directionally and the levels of random migration or cell polarization were low. However, major fractions of T cells placed in IL-2 and RANTES gradients in the gels polarized immediately after exposure to the chemoattractants. Shortly after polarization, 25% of the T cells migrated, in either a random or directional fashion, towards the sources of the chemoattractants; additional 5-10% of the cells remained polarized but stationary. The number of T cells migrating directionally towards RANTES or IL-2 peaked along with the formation of the chemotactic gradients. The directional migration of T cells was increased by a short pre-exposure to low doses of IL-2, which did not alter the level of expression of the beta1 integrins. The directional migration of T cells towards IL-2 and RANTES was mediated by IL-2R and pertussis toxin-sensitive receptors, respectively, and the directional, and to a lesser degree, the random locomotion of T cells induced by both chemoattractants required intact tyrosine kinase signaling and activities of the alpha4, alpha5, and, to a lesser degree, the alpha2 and alpha6 members the beta1 integrins. Our system enables the real-time tracking of individual locomoting lymphocytes and the analysis of their dynamic interactions with ECM components and cytokines.

Adenoviral gene therapy leads to rapid induction of multiple chemokines and acute neutrophil-dependent hepatic injury in vivo

Replication-deficient adenoviruses are known to induce acute injury and inflammation of infected tissues, thus limiting their use for human gene therapy. However, molecular mechanisms triggering this response have not been fully defined. To characterize this response, chemokine expression was evaluated in DBA/2 mice following the intravenous administration of various adenoviral vectors. Administration of adCMVbeta gal, adCMV-GFP, or FG140 intravenously rapidly induced a consistent pattern of C-X-C and C-C chemokine expression in mouse liver in a dose-dependent fashion. One hour following infection with 10(10) PFU of adCMVbeta gal, hepatic levels of MIP-2 mRNA were increased >60-fold over baseline. MCP-1 and IP-10 mRNA levels were also increased immediately following infection with various adenoviral vectors, peaking at 6 hr with >25- and >100-fold expression, respectively. Early induction of RANTES and MIP-1beta mRNA by adenoviral vectors also occurred, but to a lesser degree. The induction of chemokines occurred independently of viral gene expression since psoralen-inactivated adenoviral particles produced an identical pattern of chemokine gene transcription within the first 16 hr of administration. The expression of chemokines correlated as expected with the influx of neutrophils and CD11b+ cells into the livers of infected animals. At high titers, all adenoviral vectors caused significant hepatic necrosis and apoptosis following systemic administration to DBA/2 mice. To investigate the role of neutrophils in this adenovirus-induced hepatic injury, animals were pretreated with neutralizing anti-MIP-2 antibodies or depleted of neutrophils. MIP-2 antagonism and neutrophil depletion both resulted in reduced serum ALT/AST levels and attenuation of the adenovirus-induced hepatic injury histologically, confirming that this early injury is largely due to chemokine production and neutrophil recruitment. Our findings further clarify the early immune response against replication-deficient adenoviral vectors and suggest a strategy to prevent adenovirus-mediated inflammation and tissue injury by interfering with chemokine or neutrophil function.

RANTES stimulates cell-mediated transmission of HIV-1 infection

We wished to determine the effects of the beta-chemokine RANTES in an established system of cell-mediated transmission of HIV-1, that is, normal human umbilical vein endothelial cells (HUVEC) nonproductively infected with HIV-1, cocultivated with CD4+ T cells to rescue productive infection. The results indicate that the addition of RANTES to HUVEC, either before or after HIV-1 infection, stimulates HIV-1 rescue by CD4+ T cells. However, viral DNA is not increased in HUVEC, suggesting that the stimulation exerted by RANTES could be mediated by events following HUVEC infection. The mechanisms of increase seem to be related to the rescue phase, involving membrane interaction of abortively infected HUVEC with permissive T cells. In fact, a strong upregulation and polarization of intercellular adhesion molecule-1 (ICAM-1) is induced in HUVEC by RANTES, and antibodies against ICAM-1 inhibit HIV-1 rescue by T cells. These results indicate that RANTES, similarly to other inflammatory cytokines, may favor HIV-1 spreading and crossing of blood-tissue barriers by indirect mechanisms involving membrane interactions between nonproductively infected and permissive cells.

T lymphocyte adhesion mechanisms within inflamed human kidney: studies with a Stamper-Woodruff assay

Renal inflammatory conditions are characterized by mononuclear cell recruitment to sites of inflammation. We have developed a modified Stamper-Woodruff assay system to analyze mechanisms of functional T cell adhesion to cryostat sections of renal biopsy material from patients with vasculitic glomerulonephritis (GN) and acute allograft rejection. Peripheral blood T cells adhered to intraglomerular, periglomerular, and tubulointerstitial regions of the cortex. Blocking monoclonal antibodies against tissue expressed ICAM-1, VCAM-1, and the CS-1 domain of fibronectin (CS-1Fn) differentially attenuated T cell adhesion. Glomerular adhesion in vasculitic GN and tubulointerstitial adhesion in acute rejection were particularly sensitive to both anti-ICAM-1 and anti-VCAM-1 antibodies, indicating a prominent role for ICAM-1 and VCAM-1 at glomerular sites in vasculitis and at tubulointerstitial sites in rejection. Furthermore, using KL/4 cells (LFA-1 expressing) and Jurkat cells (VLA-4 expressing), we demonstrated specific LFA-1/ICAM-1- and VLA-4/VCAM-1-mediated interactions within glomerular and tubulointerstitial compartments. Jurkat cells also adhered to VCAM-1-free sites, and binding was inhibitable by anti-CS-1Fn antibody, thereby demonstrating a role for VLA-4/fibronectin interactions especially at intraglomerular sites in acute rejection where VCAM-1 is notably absent. We therefore propose a prominent functional role for ICAM-1, VCAM-1, and CS-1 domain fibronectin in T cell recruitment to the inflamed kidney.

Chemokines: understanding their role in T-lymphocyte biology

The chemokines are a complex superfamily of small, secreted proteins that were initially characterized through their chemotactic effects on a variety of leucocytes. The superfamily is divided into families based on structural and genetic considerations and have been termed the CXC, CC, C and CX3C families. Chemokines from these families have a key role in the recruitment and function of T lymphocytes. Moreover, T lymphocytes have also been identified as a source of a number of chemokines. T lymphocytes also express most of the known CXC and CC chemokine receptors to an extent that depends on their state of activation/differentiation and/or the activating stimuli. The expression of two chemokine receptors, namely CXCR4 and CCR5, together with the regulated production of their respective ligands, appears to be extremely important in determining sensitivity of T cells to HIV-1 infection. The intracellular events which mediate the effects of chemokines, particularly those elicited by the CC chemokine RANTES, include activation of both G-protein- and protein tyrosine kinase-coupled signalling pathways. The present review describes our current understanding of the structure and expression of chemokines and their receptors, the effects of chemokines on T-cell function(s), the intracellular signalling pathways activated by chemokines and the role of certain chemokines and chemokine receptors in determining sensitivity to HIV-1 infection.