Age-related changes in cytokine production by leukocytes in rhesus monkeys

Using a variety of experimental rodent and human models, age-related alterations in cytokine production by immune cells have been described extensively. While the precise mechanism(s) responsible for such age-related changes in cytokine responses remain unclear, it seems likely that these changes may have a significant effect on immune cell function. In an attempt to clarify such changes in aging primates, we examined cytokine production by white cells derived from a controlled colony of rhesus monkeys (Macaca mulatta). Non-fractionated whole blood and peripheral blood mononuclear cells (PBMCs) were obtained from male monkeys of different ages (6-28 years), and were subsequently evaluated for their ability to express mRNA and protein for the cytokines, IL-10, IL-6, IFNgamma, IL-1beta, and TNFalpha, following in vitro stimulation with polyclonal mitogens. Our results suggest that white blood cells derived from aged rhesus monkeys exhibit a significant increase in their ability to produce the Th2-associated cytokine, IL-10, upon stimulation with lipopolysaccharide (LPS) when compared to white cells derived from younger counterparts. Similarly, a significant age-related decrease in the expression of the Th1-associated cytokine, IFNgamma, was also observed using phytohemagglutinin (PHA)-stimulated PBMCs. No significant age-related differences in the production of IL-1beta or TNFalpha were observed in response to any stimulation, but there was limited evidence of an age-related increase in IL-6 production. Overall, our results suggest that a possible systemic change from a Th0/Th1 to a Th2-like cytokine profile occurs in circulating leukocytes derived from aging primates. We believe that such age-related alterations in cytokine production may play a role in the reduced immune responses observed in elderly human populations.

Early local generation of C5a initiates the elicitation of contact sensitivity by leading to early T cell recruitment

We have shown previously that an early complement C5-dependent cascade is required to recruit T cells to elicit 24-h contact sensitivity (CS) responses. In this paper, we have characterized molecular events of this early required cascade by biochemically analyzing extracts of mouse ears undergoing elicitation of CS. Chemotactic activity was found after local Ag challenge, in CS ear extracts early (by 1 h), in CS ear extracts late (through 24 h), in previously immunized mice, but not in ears of vehicle-immunized or non-immune-challenged mice. The early chemotactic activity at 2 h was likely caused by C5a, because it was neutralized in vitro by anti-C5a Ab, was inactive on C5aR-deficient (C5aR-/-) macrophages, and was absent in C5-deficient mice. The activity was present in T cell-deficient mice, but elaboration was Ag-specific. This T cell-independent, Ag-specific elaboration of C5a early in CS ear responses likely led to T cell recruitment, because subsequent local IFN-gamma mRNA and protein expression, as markers of T cell arrival and activation, began by 4 h after Ag challenge. In contrast to early C5a chemotactic activity, late chemotactic activity 24 h after Ag challenge was unaffected by anti-C5, was active on C5aR-/- macrophages, was T cell-dependent, and by ELISA appeared largely due to chemokines (macrophage-inflammatory protein-1alpha and -1beta, IFN-gamma-inducible protein-10, and monocyte chemoattractant protein-1). Importantly, early generation of C5a was required for T cell recruitment because C5aR-/- mice had absent 24-h CS. Taken together, these findings indicate an important linkage of C5a as a component of early activated innate immunity that is required for later elicitation of acquired T cell immunity, probably by facilitating the initial recruitment of T cells into the Ag-challenged local site in CS responses.

Identification and characterization of a potent, selective, and orally active antagonist of the CC chemokine receptor-1

The CC chemokine receptor-1 (CCR1) is a prime therapeutic target for treating autoimmune diseases. Through high capacity screening followed by chemical optimization, we identified a novel non-peptide CCR1 antagonist, R-N-[5-chloro-2-[2-[4-[(4-fluorophenyl)methyl]-2-methyl-1-piperazinyl ]-2-oxoethoxy]phenyl]urea hydrochloric acid salt (BX 471). Competition binding studies revealed that BX 471 was able to displace the CCR1 ligands macrophage inflammatory protein-1alpha (MIP-1alpha), RANTES, and monocyte chemotactic protein-3 (MCP-3) with high affinity (K(i) ranged from 1 nm to 5.5 nm). BX 471 was a potent functional antagonist based on its ability to inhibit a number of CCR1-mediated effects including Ca(2+) mobilization, increase in extracellular acidification rate, CD11b expression, and leukocyte migration. BX 471 demonstrated a greater than 10,000-fold selectivity for CCR1 compared with 28 G-protein-coupled receptors. Pharmacokinetic studies demonstrated that BX 471 was orally active with a bioavailability of 60% in dogs. Furthermore, BX 471 effectively reduces disease in a rat experimental allergic encephalomyelitis model of multiple sclerosis. This study is the first to demonstrate that a non-peptide chemokine receptor antagonist is efficacious in an animal model of an autoimmune disease. In summary, we have identified a potent, selective, and orally available CCR1 antagonist that may be useful in the treatment of chronic inflammatory diseases.

CXC and CC chemokine receptors on coronary and brain endothelia

BACKGROUND

Chemokine receptors on leukocytes play a key role in inflammation and HIV-1 infection. Chemokine receptors on endothelia may serve an important role in HIV-1 tissue invasion and angiogenesis.

MATERIALS AND METHODS

The expression of chemokine receptors in human brain microvascular endothelial cells (BMVEC) and coronary artery endothelial cells (CAEC) in vitro and cryostat sections of the heart tissue was determined by light and confocal microscopy and flow cytometry with monoclonal antibodies. Chemotaxis of endothelia by CC chemokines was evaluated in a transmigration assay.

RESULTS

In BMVEC, the chemokine receptors CCR3 and CXCR4 showed the strongest expression. CXCR4 was localized by confocal microscopy to both the cytoplasm and the plasma membrane of BMVEC. In CAEC, CXCR4 demonstrated a strong expression with predominantly periplasmic localization. CCR5 expression was detected both in BMVEC and CAEC but at a lower level. Human umbilical cord endothelial cells (HUVEC) expressed strongly CXCR4 but only weakly CCR3 and CCR5. Two additional CC chemokines, CCR2A and CCR4, were detected in BMVEC and CAEC by immunostaining. Immunocytochemistry of the heart tissues with monoclonal antibodies revealed a high expression of CXCR4 and CCR2A and a low expression of CCR3 and CCR5 on coronary vessel endothelia. Coronary endothelia showed in vitro a strong chemotactic response to the CC chemokines RANTES, MIP-1alpha, and MIP-1beta.

CONCLUSIONS

The endothelia isolated from the brain display strongly both the CCR3 and CXCR4 HIV-1 coreceptors, whereas the coronary endothelia express strongly only the CXCR4 coreceptor. CCR5 is expressed at a lower level in both endothelia. The differential display of CCR3 on the brain and coronary endothelia could be significant with respect to the differential susceptibility of the heart and the brain to HIV-1 invasion. In addition, CCR2A is strongly expressed in the heart endothelium. All of the above chemokine receptors could play a role in endothelial migration and repair.

Phenotypic and functional characterization of lymphocytes derived from normal and HIV-1-infected human lymph nodes

Lymph nodes are the major site of cell-to-cell transmission and replication of HIV-1. Trafficking of CD4+ T lymphocytes into lymph nodes provides a continual supply of susceptible target lymphocytes, and conversely, recruitment of CD8+ T lymphocytes may be critical for the host response that attempts to control HIV-1 replication. The present study was undertaken as no detailed assessment of lymphocyte subpopulations in HIV-1-infected lymph nodes has previously been reported. Peripheral blood and single-cell suspensions prepared from lymph nodes of patients with HIV-1 and control subjects were analysed using three-colour flow cytometry. Approximately 80% of the lymphocytes in control lymph nodes were CD3+ T lymphocytes, of which over 65% were CD4+. The majority of the CD4+ and CD8+ T lymphocytes obtained from both lymph nodes and blood of control subjects were immunologically naive (CD45RA+). By contrast, in HIV-1-infected patients there was a significant reduction in the proportion of CD4+ T lymphocytes and an expansion of the CD8+ T lymphocyte subset in both lymph nodes and peripheral blood. Furthermore, a high proportion of these T lymphocytes displayed a marker for immunological memory (CD45RO+). T lymphocytes derived from HIV-1-infected lymph nodes also showed altered expression of the adhesion molecules, L-selectin and very late antigen-4 (VLA-4), but not leucocyte function-associated antigen-1 (LFA-1). In an in vitro adhesion assay, lymphocytes from HIV-1-infected nodes were significantly more adhesive than control lymphocytes on fibronectin, as well as recombinant human intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) substrates. This combination of altered lymphocyte subpopulations in the HIV-1-infected lymph nodes, as well as enhanced adhesion phenotype and function, suggests that T lymphocyte traffic to lymph nodes in HIV disease may be an important determinant of pathogenesis.

Tyrphostin AG-490 inhibits cytokine-mediated JAK3/STAT5a/b signal transduction and cellular proliferation of antigen-activated human T cells

Janus kinase 3 (JAK3) is a cytoplasmic tyrosine kinase required for T cell development and activated by cytokines that utilize the interleukin-2 (IL-2) receptor common gamma chain (gamma(c)). Genetic inactivation of JAK3 is manifested as severe combined immunodeficiency disease (SCID) in humans and mice. These findings have suggested that JAK3 represents a pharmacological target to control certain lymphoid-derived diseases. Here we provide novel evidence that AG-490 potently inhibits the autokinase activity of JAK3 and tyrosine phosphorylation and DNA binding of signal transducer and activator of transcription 5a and 5b (STAT5a/b). Similar inhibitory effects were observed with other cytokines that use gamma(c). AG-490 also inhibited IL-2-mediated proliferative growth in human T cells with an IC50) = 25 microM that was partially recoverable. Moreover, we demonstrate that this inhibitor prevented tetanus toxoid antigen-specific T cell proliferation and expansion but failed to block activation of Zap70 or p56Lck after anti-CD3 stimulation of human T cells. Taken together, these findings suggest that AG-490 inhibits the JAK3-mediated Type II signaling pathway but not the T cell receptor-derived Type I pathway and possesses therapeutic potential for T cell-derived pathologies such as graft-versus-host disease, allergy, and autoimmune disorders.

Cocaine opens the blood-brain barrier to HIV-1 invasion

Cocaine abuse has been associated with vasculitis and stroke, and is suspected to influence the progression of AIDS dementia. Cocaine may enhance HIV-1 neuroinvasion by actions directed at the blood-brain barrier. HIV-1 appears to penetrate the human brain microvascular endothelial cell barrier by a paracellular route breached by tumor necrosis factor-alpha (TNF-alpha). Cocaine's effects on the blood-brain barrier were investigated using human brain microvascular endothelial cells and peripheral blood monocytes. Cocaine (10(-5) M and 10(-6) M) increased molecular permeability of the barrier and viral invasion by the macrophage-tropic HIV-1(JR-FL) into the brain chamber. Cocaine also augmented apoptosis of brain endothelial cells and monocytes, increased secretion of four chemokines (interleukin-8, interferon-inducible protein-10, macrophage inflammatory protein-1alpha, and monocyte chemoattractant protein-1) and the cytokine, TNF-alpha, by human monocytes. TNF-alpha enhanced invasion of the brain compartment by macrophage-tropic, lymphotropic, and bitropic HIV-1 strains. These data indicate that HIV-1 neuroinvasion can be increased by (a) cocaine's direct effects on brain microvascular endothelial cells and (b) paracrine effects of cocaine-induced pro-inflammatory cytokines and chemokines on the blood-brain barrier.

Tyrosine kinase-deficient Wv c-kit induces mast cell adhesion and chemotaxis

W/Wv mice are deficient in tissue mast cells, and mast cells cultured from these mice do not proliferate in response to the c-kit ligand, stem cell factor (SCF). In this paper, we report that mouse bone marrow cultured mast cells derived from W/Wv mice do adhere to fibronectin in the presence of SCF and exhibit chemotaxis to SCF, and we explore this model for the understanding of c-kit-mediated signaling pathways. Both in vitro and in vivo (in intact cells) phosphorylation experiments demonstrated a low residual level of W/Wv c-kit protein phosphorylation. SCF-induced responses in W/Wv mast cells were abolished by the tyrosine kinase inhibitor herbimycin A and by the phospatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin but were not affected by protein kinase C inhibitors. These observations are consistent with the conclusions that Wv c-kit initiates a signaling process that is PI 3-kinase dependent and that mutated Wv c-kit retains the ability to initiate mast cell adhesion and migration.

Predictors and outcome of admission for invasive Streptococcus pneumoniae infections at a Canadian children's hospital

Rates of admission for invasive Streptococcus pneumoniae infection in children vary considerably between institutions. We performed a retrospective study to investigate factors used in the decision to admit patients with invasive S. pneumoniae infection to Alberta Children's Hospital. Of 254 patients who were initially assessed in the emergency department, 38.2% were admitted to the hospital. Significant risk factors for admission as determined by a logistic regression model included murmur (odds ratio [OR], 18.98; 95% confidence interval [CI], 4.08-88.23), focal infection (OR, 11.41; 95% CI, 5.07-25.67), and older age (OR, 2.72; 95% CI, 1.03-7.17). Higher hemoglobin level (OR, 0.96; 95% CI, 0.93-0.99) and temperature of > 38.5 degrees C (OR, 0.39; 95% CI, 0.18-0.85) were associated with a lower risk of admission. Two patients died (case-fatality rate, 0.7%). Despite the low rate of admission for invasive S. pneumoniae infections at our hospital, the mortality rate was comparable with those at institutions with higher rates of admission, thus suggesting that the factors we identified may be useful in deciding whether to admit patients with (or who are at high risk for) invasive S. pneumoniae infections.

Amyloid-beta induces chemokine secretion and monocyte migration across a human blood--brain barrier model

BACKGROUND

Aside from numerous parenchymal and vascular deposits of amyloid beta (A beta) peptide, neurofibrillary tangles, and neuronal and synaptic loss, the neuropathology of Alzheimer's disease is accompanied by a subtle and chronic inflammatory reaction that manifests itself as microglial activation. However, in Alzheimer's disease, alterations in the permeability of the blood-brain barrier and chemotaxis, in part mediated by chemokines and cytokines, may permit the recruitment and transendothelial passage of peripheral cells into the brain parenchyma.

MATERIALS AND METHODS

Human monocytes from different donors were tested for their capacity to differentiate into macrophages and their ability to secrete cytokines and chemokines in the presence of A beta 1-42. A paradigm of the blood-brain barrier was constructed utilizing human brain endothelial and astroglial cells with the anatomical and physiological characteristics observed in vivo. This model was used to test the ability of monocytes/macrophages to transmigrate when challenged by A beta 1-42 on the brain side of the blood-brain barrier model.

RESULTS

In cultures of peripheral monocytes, A beta 1-42 induced the secretion of proinflammatory cytokines TNF-alpha, IL-6, IL-1 beta, and IL-12, as well as CC chemokines MCP-1, MIP-1 alpha, and MIP-1 beta, and CXC chemokine IL-8 in a dose-related fashion. In the blood-brain barrier model, A beta 1-42 and monocytes on the brain side potentiated monocyte transmigration from the blood side to the brain side. A beta 1-42 stimulated differentiation of monocytes into adherent macrophages in a dose-related fashion. The magnitude of these proinflammatory effects of A beta 1-42 varied dramatically with monocytes from different donors.

CONCLUSION

In some individuals, circulating monocytes/macrophages, when recruited by chemokines produced by activated microglia and macrophages, could add to the inflammatory destruction of the brain in Alzheimer's disease.

Neuronal apoptosis induced by HIV-1 gp120 and the chemokine SDF-1 alpha is mediated by the chemokine receptor CXCR4

CXCR4, a seven transmembrane domain G-protein-coupled receptor for the Cys-X-Cys class of chemokines, is one of several chemokine receptors that can act as a co-receptor with CD4 for the human immunodeficiency virus (HIV-1) glycoprotein gp120 [1-3]. CXCR4 can mediate the entry of HIV-1 strains that specifically infect T cells, such as the IIB strain (see [4] for review). Recent reports indicate that gp120 can signal through CXCR4 [5] and it has been suggested that signal transduction, mediated by the viral envelope, might influence viral-associated cytopathicity or apoptosis [6]. Neuronal apoptosis is a feature of HIV-1 infection in the brain [7,8], although the exact mechanism is unknown. Here, we address the possible role of CXCR4 in inducing apoptosis using cells of the hNT human neuronal cell line; these cells resemble immature post-mitotic cholinergic neurons and have a number of neuronal characteristics [9-15]. We have previously shown that gp120 from the HIV-1 IIIB strain binds with high affinity to CXCR4 expressed on hNT neurons [15]. We now find that both IIIB gp120 and the Cys-X-Cys chemokine SDF-1 alpha can directly induce apoptosis in hNT neurons in the absence of CD4 and in a dose-dependent manner. To our knowledge, this is the first report of a chemokine and an HIV-1 envelope glycoprotein eliciting apoptotic responses through a chemokine receptor.

Identification and characterization of the CXCR4 chemokine receptor in human T cell lines: ligand binding, biological activity, and HIV-1 infectivity

The CXCR4 chemokine receptor has been shown to respond to the C-X-C chemokine stromal-derived factor (SDF-1) and has recently been shown to be an important coreceptor for HIV-1 infection. In the present paper we have tested a number of human lymphocyte cell lines, including Jurkat, HUT78, CEM, and Sup-T1 for the presence of CXCR4 receptors. We found that these T cell lines bind SDF-1alpha and SDF-1beta with high affinity. The CXCR4 Ab 12G5 inhibited both SDF-1 binding and HIV-1LAI-mediated fusion of CEM. Scatchard analysis revealed the presence of approximately 150,000 SDF-1alpha-binding sites per cell with a Kd between 5 and 10 nM. Cross-competition experiments using unlabeled SDF-1alpha and SDF-1beta revealed that both chemokines are equally capable of displacing their radiolabeled counterparts. Internalization studies with [125]I-SDF-1alpha revealed that Jurkat cells internalized greater than 90% of the ligand by 2 h at 37 degrees C. SDF-1alpha was also chemotactic for Jurkat cells and caused an increase in the rate of extracellular acidification that was half-maximal at 18 nM SDF-1alpha and could be inhibited by pretreatment with the SDF-1 proteins, pertussis toxin, or the Ab 12G5. Finally, SDF-1alpha also caused an increase in the cytosolic Ca2+ concentration in Sup-T1 cells that was abolished by preincubating the cells with pertussis toxin or PMA and inhibited by the Ab 12G5. This molecular characterization of CXCR4 receptors should prove useful in clarifying receptor interaction with SDF-1 proteins and with HIV-1 glycoprotein, with the ultimate aim of targeting the viral interaction for therapeutic intervention.

The CC chemokine I-309 inhibits CCR8-dependent infection by diverse HIV-1 strains

Using a chemokine receptor model based on known receptor sequences, we identified several members of the seven transmembrane domain G-protein superfamily as potential chemokine receptors. The orphan receptor ChemR1, which has recently been shown to be a receptor for the CC chemokine I-309, scored very high in our model. We have confirmed that I-309, but not a number of other chemokines, can induce a transient Ca2+ flux in cells expressing CCR8. In addition, the human erythroleukemic cell line K562 responded chemotactically in a dose-responsive manner to this chemokine. Since several chemokine receptors have been shown to be required as coreceptors for HIV-1 infection, we asked whether human immunodeficiency virus type 1 (HIV-1) could efficiently utilize CCR8. Here we show that the CCR8 receptor can serve as a coreceptor for diverse T-cell tropic, dual-tropic, and macrophage-tropic HIV-1 strains and that I-309 was a potent inhibitor of HIV-1 envelope-mediated cell-cell fusion and virus infection. Furthermore, we show by flow cytometry and immunohistochemistry that antibodies generated against the CCR8 receptor amino-terminal peptide cross-reacted with U-87 MG cells stably expressing CCR8, THP-1 cells, HL-60 cells, and human monocytes, a target cell for HIV-1 infectivity in vivo.

Chemokines in acute anterior uveitis

PURPOSE

The aim of this study was to define the expression of chemoattractant cytokines (chemokines) in human aqueous humor, obtained from patients with idiopathic acute anterior uveitis (AU). The chemokines assayed included macrophage inflammatory proteins-1 alpha and -1 beta (MIP-1 alpha and -1 beta), monocyte chemoattractant protein-1 (MCP-1), interleukin-8 (IL-8), interferon-inducible protein-10 (IP-10), and regulated on activation, normal T-expressed and secreted (RANTES).

METHODS

We studied fifteen patients (7 females) with idiopathic acute AU, at various stages of disease activity, and two control subjects undergoing elective cataract extraction. Aqueous humor was collected under aseptic conditions, after obtaining informed consent. Chemokine concentrations were measured using specific ELISA. Correlation was sought between chemokine concentrations and disease activity, evaluated by slit lamp biomicroscopy and graded using a standardized scale of disease severity.

RESULTS

IL-8 was detected (35.9 +/- 13.6, mean +/- SE) in three of seven subjects in active, untreated stages of AU (clinical score 2-4), and it was undetectable in subjects sampled in the quiescent phase of the disease. IP-10 had a mean concentration of 40.6 ng/ml +/- 20.9 in the active group (N = 7), declining to 0.8 ng/ml +/- 0.3 in the samples from patients with inactive disease (N = 7, P = 0.001). Similarly, substantial expression of MCP-1 was noted, with a maximum concentration of 145 ng/ml, in acute (active) AU (N = 6), (26.7 +/- 19.7), falling to undetectable levels in those with inactive disease, and in control subjects (P = 0.001). MIP-1 beta (N = 7), (3.4 +/- 1.5, P = 0.001) and RANTES (N = 7, 8.8 +/- 4.2) levels were significantly increased in acute disease (P = 0.001) and related to the activity of the disease, although the concentrations were not as high as MCP-1, IP-10 and IL-8. IP-10, RANTES and MIP-1 beta were detected at low concentrations in the aqueous humor of the control subjects.

CONCLUSIONS

This is the first study of chemokine concentrations in the aqueous humor of patients with acute anterior uveitis. The concentration of chemokines: IL-8, IP-10, MCP-1, RANTES and MIP-1 beta were significantly increased during the active stages of AU, and correlated with the clinical severity of the disease. These chemoattractant cytokines probably play a critical role in leucocyte recruitment in acute AU.

Regulation of C-C chemokine production by murine T cells by CD28/B7 costimulation

C-C chemokines play an important role in recruitment of T lymphocytes to inflammatory sites. T lymphocytes secrete chemokines, but the activation requirements for chemokine production by T cells are uncertain. We studied the regulation of C-C chemokine production by CD28 costimulatory signals by murine T lymphocytes. Splenocytes from BALB/c mice cultured with anti-CD3 mAb expressed macrophage-inflammatory protein (MIP)-1alpha mRNA and secreted MIP-1alpha, which was inhibited by anti-B7-1 plus anti-B7-2 mAbs. MIP-1alpha production by Ag-stimulated T cells from DO.11.10 TCR transgenic mice was augmented by anti-CD28 mAb and increased compared with DO.11.10/CD28(-/-) cells. When T cell costimulation was provided by IL-2, MIP-1alpha was not enhanced. Studies with IL-2, IL-4, STAT4, and STAT6 knock-out mice suggested that chemokine production is controlled by pathways different from those regulating T cell differentiation. Thus, CD28 costimulation may amplify an immune response by stimulating T cell survival, proliferation, and production of chemokines that recruit T cells to inflammatory sites.