The orphan mouse receptor interleukin (IL)-8R beta binds N51. Structure-function analysis using N51/IL-8 chimeric molecules

The Female Response to Seminal Fluid

Seminal fluid is often assumed to have just one function in mammalian reproduction, delivering sperm to fertilize oocytes. But seminal fluid also transmits signaling agents that interact with female reproductive tissues to facilitate conception and .pregnancy. Upon seminal fluid contact, female tissues initiate a controlled inflammatory response that affects several aspects of reproductive function to ultimately maximize the chances of a male producing healthy offspring. This effect is best characterized in mice, where the female response involves several steps. Initially, seminal fluid factors cause leukocytes to infiltrate the female reproductive tract, and to selectively target and eliminate excess sperm. Other signals stimulate ovulation, induce an altered transcriptional program in female tract tissues that modulates embryo developmental programming, and initiate immune adaptations to promote receptivity to implantation and placental development. A key result is expansion of the pool of regulatory T cells that assist implantation by suppressing inflammation, mediating tolerance to male transplantation antigens, and promoting uterine vascular adaptation and placental development. Principal signaling agents in seminal fluid include prostaglandins and transforming growth factor-β. The balance of male signals affects the nature of the female response, providing a mechanism of ‟cryptic female choiceˮ that influences female reproductive investment. Male-female seminal fluid signaling is evident in all mammalian species investigated including human, and effects of seminal fluid in invertebrates indicate evolutionarily conserved mechanisms. Understanding the female response to seminal fluid will shed new light on infertility and pregnancy disorders and is critical to defining how events at conception influence offspring health.

Safrole-2',3'-oxide induces atherosclerotic plaque vulnerability in apolipoprotein E-knockout mice

Safrole-2',3'-oxide (SFO) is the major electrophilic metabolite of safrole (4-allyl-1, 2-methylenedioxybenzene), a natural plant constituent found in essential oils of numerous edible herbs and spices and in food containing these herbs, such as pesto sauce, cola beverages and bologna sausages. The effects of SFO in mammalian systems, especially the cardiovascular system, are little known. Disruption of vulnerable atherosclerotic plaques in atherosclerosis, a chronic inflammatory disease, is the main cause of cardiovascular events. In this study, we investigated SFO-induced atherosclerotic plaque vulnerability (possibility of rupture) in apolipoprotein E-knockout (apoE(-/-)) mice. Lipid area in vessel wall reached 59.8% in high dose SFO (SFO-HD) treated group, which is only 31.2% in control group. SFO treatment changed the lesion composition to an unstable phenotype, increased the number of apoptotic cells in plaque and the endothelium in plaques was damaged after SFO treatment. Furthermore, compared with control groups, the plaque endothelium level of p75(NTR) was 3-fold increased and the liver level of p75(NTR) was 17.4-fold increased by SFO-HD. Meanwhile, the serum level of KC (a functional homolog of IL-8 and the main proinflammatory alpha chemokine in mice) in apoE(-/-) mice was up to 357pg/ml in SFO-HD treated group. Thus, SFO contributes to the instability of atherosclerotic plaque in apoE(-/-) mice through activating p75(NTR) and IL-8 and cell apoptosis in plaque.

Cutting edge: critical role for mesothelial cells in necrosis-induced inflammation through the recognition of IL-1 alpha released from dying cells

Endogenous danger signals released from necrotic cells are thought to be sensed by phagocytes leading to secretion of IL-1alpha and neutrophilic recruitment. However, the mechanisms for IL-1alpha production and IL-1alpha-mediated sterile inflammation remain poorly understood. We report here that necrotic cell extracts elicited little secretion of CXCL1 and IL-6 from macrophages but robust production in mesothelial cells. The induction of CXCL1 as well as activation of NF-kappaB and MAPKs by cytosolic extracts required the presence of IL-1alpha in the necrotic cell. Conversely, expression of IL-1R and MyD88 but not IL-1alpha, RICK, TLR2, TLR4, TRIF, or inflammasome components in mesothelial cells was critical for the production of CXCL1. Furthermore, IL-1alpha was critical to induce the recruitment of neutrophils in the peritoneal cavity via CXCR2. These studies show that IL-1alpha is a key danger signal released from necrotic cells to trigger CXCL1 secretion and recruitment of neutrophils via IL-1R/MyD88 on neighboring mesothelial cells.

Effects of acute global venous obstruction and unfractionated heparin on muscle cytokine synthesis

Phlegmasia cerulea dolens is a devastating complication of massive deep venous thrombosis, which is clinically characterized by massive lower extremity tissue edema and subsequent arterial insufficiency. These experiments evaluated the local tissue effects of acute global venous obstruction combined with partial arterial ischemia. Experiments were performed to assess the effects of heparin on the cytokine response to simultaneous venous and partial arterial obstruction. Murine hind limbs were subjected to conditions of unilateral venous occlusion and partial tourniquet limb ischemia, which was confirmed by laser Doppler imaging (LDI). Mice underwent either hind limb venous obstruction with intravenous unfractionated heparin (200IU/kg) or intravenous saline 5min before venous occlusion. Sham-treated mice were subjected to anesthesia alone without venous occlusion. After 3hr, the mice were killed and tissue was harvested for measurement of edema (wet to dry weight ratio, W/D), muscle viability, indices of local thrombosis (thrombin-antithrombin complex [TAT]), and cytokine analysis for growth-related oncogene-1 (GRO-1) and interleukin-6 (IL-6, protein via enzyme-linked immunoassay and mRNA via reverse transcriptase polymerase chain reaction). Bleeding time and volume were documented in saline- and heparin-treated mice to confirm systemic anticoagulation. Administration of intravenous heparin resulted in a marked increase in bleeding time and volume. LDI confirmed venous obstruction and ongoing arterial inflow. Venous obstruction resulted in severe visible edema that correlated with a significantly higher W/D ratio but was not associated with a significant decrease in muscle viability. GRO-1 and IL-6 protein and mRNA levels were significantly elevated in the venous occlusion group compared to sham. Heparin therapy significantly decreased TAT3 levels but did not alter the profile of GRO-1 or IL-6 protein levels seen with venous occlusion. Venous occlusion with partial ischemia induces a unique and potent local cytokine expression. Heparin therapy did not ameliorate the cytokine response. These data indicate that heparin therapy does not modulate the cytokine response to venous obstruction.

Release of interleukins and other inflammatory cytokines by human adipose tissue is enhanced in obesity and primarily due to the nonfat cells

The white adipose tissue, especially of humans, is now recognized as the central player in the mild inflammatory state that is characteristic of obesity. The question is how the increased accumulation of lipid seen in obesity causes an inflammatory state and how this is linked to the hypertension and type 2 diabetes that accompanies obesity. Once it was thought that adipose tissue was primarily a reservoir for excess calories that were stored in the adipocytes as triacylglycerols. In times of caloric deprivation these stored lipids were mobilized as free fatty acids and the insulin resistance of obesity was attributed to free fatty acids. It is now clear that in humans the expansion of adipose tissue seen in obesity results in more blood vessels, more connective tissue fibroblasts, and especially more macrophages. There is an enhanced secretion of some interleukins and inflammatory cytokines in adipose tissue of the obese as well as increased circulating levels of many cytokines. The central theme of this chapter is that human adipose tissue is a potent source of inflammatory interleukins plus other cytokines and that the majority of this release is due to the nonfat cells in the adipose tissue except for leptin and adiponectin that are primarily secreted by adipocytes. Human adipocytes secrete at least as much plasminogen activator inhibitor-1 (PAI-1), MCP-1, interleukin-8 (IL-8), and IL-6 in vitro as they do leptin but the nonfat cells of adipose tissue secrete even more of these proteins. The secretion of leptin, on the other hand, by the nonfat cells is negligible. The amount of serum amyloid A proteins 1 & 2 (SAA 1 & 2), haptoglobin, nerve growth factor (NGF), macrophage migration inhibitory factor (MIF), and PAI-1 secreted by the adipocytes derived from a gram of adipose tissue is 144%, 75%, 72%, 37%, and 23%, respectively, of that by the nonfat cells derived from the same amount of human adipose tissue. However, the release of IL-8, MCP-1, vascular endothelial growth factor (VEGF), TGF-beta1, IL-6, PGE(2), TNF-alpha, cathepsin S, hepatocyte growth factor (HGF), IL-1beta, IL-10, resistin, C-reactive protein (CRP), and interleukin-1 receptor antagonist (IL-1Ra) by adipocytes is less than 12% of that by the nonfat cells present in human adipose tissue. Obesity markedly elevates the total release of TNF-alpha, IL-6, and IL-8 by adipose tissue but only that of TNF-alpha is enhanced in adipocytes. However, on a quantitative basis the vast majority of the TNF-alpha comes from the nonfat cells. Visceral adipose tissue also releases more VEGF, resistin, IL-6, PAI-1, TGF-beta1, IL-8, and IL-10 per gram of tissue than does abdominal subcutaneous adipose tissue. In conclusion, there is an increasing recognition that adipose tissue is an endocrine organ that secretes leptin and adiponectin along with a host of other paracrine and endocrine factors in addition to free fatty acids.

Strain differences influence murine pulmonary responses to Stachybotrys chartarum

When the fungus Stachybotrys chartarum is inhaled, its mycotoxins may cause lung injury and inflammation. The severity of human responses to S. chartarum in both occupational and home settings varies widely. To explore these differences, we intratracheally instilled C3H/HeJ, BALB/c, and C57BL/6J mice with S. chartarum spores suspended in saline. One day later, the mice were humanely killed, bronchoalveolar lavage (BAL) was performed, and biochemical and cellular indicators of lung injury and inflammation were measured. BALB/c mice showed the highest myeloperoxidase activity, albumin and hemoglobin levels, and neutrophil numbers in their BAL among the three strains. BALB/c was the only strain to show significant increases in keratinocyte-derived cytokine (KC), monocyte chemotactic protein (MCP)-1, MCP-3, macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, MIP-1gamma, MIP-2, RANTES, IL-1alpha, IL-1beta, IL-3, IL-6, IL-18, leukemia inhibitory factor, macrophage colony-stimulating factor, and TNF-alpha. A model of allergen-induced airway inflammation was examined to assess whether underlying allergic inflammation might contribute to increased susceptibility to S. chartarum-induced pulmonary inflammation and injury. Surprisingly, in BALB/c mice, ovalbumin-induced airway inflammation produced a protective effect against some S. chartarum-induced pulmonary responses. This is the first report of mammalian strain differences affecting responses to S. chartarum. These responses differ from those reported for LPS and other fungi. Analogous underlying genetic differences may contribute to the wide range of sensitivity to Stachybotrys among humans.

Induction of the CXCL1 (KC) chemokine in mouse astrocytes by infection with the murine encephalomyelitis virus of Theiler

In the present study, we focused on the production of the chemokine CXCL1, also termed KC, by cultured Theiler murine encephalomyelitis virus (TMEV)-infected mouse astrocytes. cRNA from mock- and TMEV-infected cells was hybridized to the Affymetrix murine genome U74v2 DNA microarray. Hybridization data analysis demonstrated upregulation of two sequences coding for IL-8 and related to the GRO 1 oncogene MGSA. The murine counterpart of the above human genes has been reported to be the chemokine CXCL1 or KC, and therefore we studied its regulation, confirming its mRNA increase by Northern blots. The presence of CXCL1 in the supernatants of infected cells was further demonstrated by a specific ELISA and its intracellular accumulation by flow cytometry. This secreted CXCL1 was biologically active in a non species-specific way as it induces chemoattraction on human neutrophils and monocyte/macrophages, but not on CD3 positive lymphocytes. Its induction does not follow the MAP kinase pathway which transcripts are decrease in infected cells compared with uninfected astrocytes. Two inflammatory cytokines, IL-1alpha and TNF-alpha, which are also induced by TMEV in astrocytes, were potent inducers of CXCL1. Nevertheless, both mechanisms of induction follow different pathways as antibodies to both cytokines fail to inhibit TMEV-induced CXCL1 upregulation. Spinal cords but not brains from TMEV-infected SJL/J animals contain CXCL1 at the start of clinical signs of the disease. As no CXCL1 induction can be detected neither in cultured BALB/c astrocytes nor in nervous tissue, we propose an important role for CXCL1 in this experimental model of multiple sclerosis as a chemoattractant of destructive immune cells.

Lactobacillus johnsonii La1 attenuates Helicobacter pylori-associated gastritis and reduces levels of proinflammatory chemokines in C57BL/6 mice

In clinical settings, Lactobacillus johnsonii La1 administration has been reported to have a favorable effect on Helicobacter pylori-associated gastritis, although the mechanism remains unclear. We administered, continuously through the water supply, live La1 to H. pylori-infected C57BL/6 mice and followed colonization, the development of H. pylori-associated gastritis in the lamina propria, and the levels of proinflammatory chemokines macrophage inflammatory protein 2 (MIP-2) and keratinocyte-derived cytokine (KC) in the serum and gastric tissue over a period of 3 months. We documented a significant attenuation in both lymphocytic (P=0.038) and neutrophilic (P=0.003) inflammatory infiltration in the lamina propria as well as in the circulating levels of anti-H. pylori immunoglobulin G antibodies (P=0.003), although we did not observe a suppressive effect of La1 on H. pylori colonizing numbers. Other lactobacilli, such as L. amylovorus DCE 471 and L. acidophilus IBB 801, did not attenuate H. pylori-associated gastritis to the same extent. MIP-2 serum levels were distinctly reduced during the early stages of H. pylori infection in the La1-treated animals, as were gastric mucosal levels of MIP-2 and KC. Finally, we also observed a significant reduction (P=0.046) in H. pylori-induced interleukin-8 secretion by human adenocarcinoma AGS cells in vitro in the presence of neutralized (pH 6.8) La1 spent culture supernatants, without concomitant loss of H. pylori viability. These observations suggest that during the early infection stages, administration of La1 can attenuate H. pylori-induced gastritis in vivo, possibly by reducing proinflammatory chemotactic signals responsible for the recruitment of lymphocytes and neutrophils in the lamina propria.

Theiler's virus induces the MIP-2 chemokine (CXCL2) in astrocytes from genetically susceptible but not from resistant mouse strains

The murine encephalomyelitis virus of Theiler (TMEV) induces demyelination in susceptible strains of mice by a CD4(+) Th1 T cell mediated immunopathologic process. We focused on the production of one chemokine, the macrophage inflammatory protein-2 (MIP-2 or CXCL2), by cultured mouse astrocytes infected with the BeAn strain of TMEV. Analysis of a murine genome DNA hybridized with cRNA from mock- and TMEV-infected astrocytes, revealed up-regulation of three sequences encoding MIP-2. Northern blot analysis indicated increased MIP-2 mRNA expression. Levels of MIP-2 in the supernatants of infected cells as detected by ELISA, varied directly with the multiplicity of infection used. This secreted CXCL2 was biologically active inducing chemoattraction of neutrophils but not of lymphocytes. CXCL2 was specifically induced by TMEV infection, since induction was inhibited by anti TMEV antibodies. The inflammatory cytokines, IL-1alpha and TNF-alpha, which are also induced in astrocytes by TMEV, were very potent inducers of CXCL2. Nevertheless, both mechanisms of induction follows different pathways as antibodies to both cytokines fails to inhibit TMEV-induced CXCL2 up-regulation. Sera from TMEV-infected SJL/J mice with chronic demyelination, but not from BALB/c TMEV-resistant mice, revealed CXCL2 at the peak of clinical disease. Our main novel finding is the strain-dependent differences in CXCL2 expression both in vitro and in vivo. This suggest an role for this chemokine in attracting immune cells within the CNS, which in turn, might trigger demyelination in this experimental model of MS.

Production of chemokine CXCL1/KC by okadaic acid through the nuclear factor-kappaB pathway

The murine chemokine CXCL1/KC is known as a chemoattractant for neutrophil infiltration and as a promoter of tumor growth. To determine its relevance in tumorigenesis, we first asked whether okadaic acid (OKA), a natural tumor promoter and a potent protein phosphatase 1 and 2A inhibitor, stimulates KC expression and if it does, through what pathway, in a promotable mouse epidermal-like JB6 cell line commonly used for studying molecules related to tumor promotion. We found that OKA stimulated the de novo synthesis of KC mRNA and protein in a dose- and time-dependent manner. To determine the mechanism by which OKA stimulated the expression of KC at the transcriptional level, transient transfection assays using serially deleted sections of KC promoter fused to luciferase reporter gene were performed. These studies showed that transactivation of KC promoter by OKA specifically involved the region between -104 and -59 containing the two nuclear factor-kappaB (NF-kappaB) response elements (kappaB1 and kappaB2). Further analyses using the mutated NF-kappaB response elements kappaB1 and kappaB2 indicated that both regions were required for optimum transactivation of KC by OKA with the former NF-kappaB response element playing a more significant role in regulating KC expression. Gel-shift and supershift analyses demonstrated the involvement of three NF-kappaB subunits, p65, p50 and c-Rel, with p65 as the major subunit in the NF-kappaB dimer complex. Additionally, immunohistochemistry and western blot analyses confirmed the presence of p65 in the nucleus with its transactivation domain phosphorylated at serine 536. In summary, this is the first report to show that the tumor promoter OKA can stimulate the de novo synthesis and secretion of KC, and that this stimulation is mediated through the NF-kappaB pathway in JB6 cells.

Chemokine Amplification in Mesangial Cells

Mesangial cells are specialized cells of the renal glomerulus that share some properties of vascular smooth muscle cells and macrophages. They are implicated in the pathogenesis of many forms of nephritis. The murine CXC-chemokines macrophage inflammatory protein-2 (MIP-2) and KC induce migration of mouse mesangial cells. Mesangial cells also exhibit a unique chemokine feedback mechanism. Treatment with nanomolar concentrations of MIP-2 or KC markedly up-regulates monocyte chemoattractant protein-1 and RANTES expression in mesangial cells. Autoinduction of MIP-2 and KC mRNA was also noted. Low levels of MIP-1α, MIP-1β, and IFN-γ-inducible protein-10 were induced following treatment with higher doses of MIP-2 or KC. These effects are specific to mesangial cells, as MIP-2 or KC treatment of renal cortical epithelial cells or peritoneal macrophages failed to induce chemokine production. This cascade of chemokine interactions may contribute to renal infiltration and leukocyte activation. The abilities of MIP-2 or KC to stimulate their own synthesis may also contribute to the maintenance and chronic course of glomerular inflammation. The mesangial cell receptor for MIP-2 and/or KC is unknown but is not CXC-chemokine receptor-2.

Expression of the Neutrophil Chemokine KC in the Colon of Mice with Enterocolitis and by Intestinal Epithelial Cell Lines: Effects of Flora and Proinflammatory Cytokines

IL-10 plays an important role in preventing excessive inflammation to the normal flora in the intestinal lumen. The purpose of this study was to compare the effect of normal flora on inflammation in mice in which the IL-10 gene was disrupted. IL-10 knock-out mice housed in germfree conditions remained healthy while those housed in conventional conditions developed colitis after weaning, suggesting that IL-10 inhibits the adverse responses to luminal Ag. Crypt abscesses were present in virtually all of the diseased animals as evidenced by flattening of the epithelial cells and a large number of neutrophils in the lumen of the crypt. Since KC is a chemokine that is capable of recruiting neutrophils in mice, mRNA and protein for KC was measured. Increased levels of both KC mRNA and protein were detected in the colon of diseased mice. To determine whether the epithelial cells were capable of synthesizing KC and contributing to neutrophil accumulation in the crypts, a murine intestinal epithelial cell line (Mode-K) was shown to express mRNA and protein for KC. Two cytokines induced in association with colitis in these mice, TNF-α and IFN-γ, increased the expression of KC mRNA and protein in murine epithelial cells. However, IL-10 was incapable of decreasing the induction of KC, even though the cells expressed the IL-10 receptor. These results suggest that the neutrophil chemokine KC is produced by gastrointestinal epithelial cells in response to inflammatory mediators that are expressed following exposure to normal flora in animals lacking IL-10.

CXC Chemokines Suppress Proliferation of Myeloid Progenitor Cells by Activation of the CXC Chemokine Receptor 2

IL-8 is one of the major mediators of the transendothelial migration of neutrophils from the circulation to the site of injury and infection. In this work we demonstrate that the CXC or α-chemokines, IL-8 and melanoma growth stimulatory activity (MGSA) induce myeloid suppression via direct action on progenitor cells, mediated by activation of the murine homologue of the CXC chemokine receptor-2 (CXCR2) or IL-8R B. We first show that proliferation of the IL-3-dependent murine myeloid progenitor cell line 32D is suppressed by human IL-8 and the functionally and structurally related peptide, MGSA. Second, we show for the first time the high endogenous expression of the murine CXCR2 in 32D cells, as demonstrated by Northern blot analysis, binding to [125I]macrophage inflammatory protein-2, and macrophage inflammatory protein-2-induced calcium responses in 32D cells. Third, we demonstrate that IL-8 and MGSA induce a rise in intracellular calcium in 32D cells. The IL-8-induced Ca2+ response is desensitizing, since a second dose of IL-8 did not trigger a second calcium response. Other chemokines, including neutrophil-activating protein-2, platelet factor-4, RANTES, and macrophage chemotactic protein-1, neither suppressed the proliferation of 32D cells nor induced a rise in intracellular calcium. Finally, the IC50 of IL-8- and MGSA-dependent suppression of proliferation of 32D cells is in good agreement with the EC50 of IL-8- and MGSA-dependent activation of neutrophil Mac-1 up-regulation and chemotaxis. Our studies are consistent with the idea that IL-8 and MGSA suppress the proliferation of 32D cells by activation of murine CXCR2.

Hypercholesterolemia exacerbates transplant arteriosclerosis via increased neointimal smooth muscle cell accumulation: studies in apolipoprotein E knockout mice

BACKGROUND

Hypercholesterolemia is thought to be a significant risk factor for coronary vasculopathy in cardiac transplant recipients.

METHODS AND RESULTS

We examined the development of arteriosclerosis in mouse carotid artery loops allografted from B.10A(2R) (H-2h2) donors to normocholesterolemic C57BL/6J (H-2h) recipients and hypercholesterolemic C57BL/6J recipients in which the apolipoprotein (apo) E gene had been knocked out. Luminal occlusion and cross-sectional neointimal area were greater in arteries allografted into hypercholesterolemic recipients at 15 and 30 days after transplantation. We also measured cellular and extracellular matrix components of the neointima by computerized planimetry of the fractional areas subtended by smooth muscle cells (anti-alpha-actin stain), collagen (Masson's trichrome), lipid (oil red O), and leukocytes (anti-CD45). The neointimal area stained for smooth muscle cells was significantly greater in hypercholesterolemic recipients than in normocholesterolemic recipients at 15 and 30 days after allografting. Lipid contributed to neointimal area to a lesser degree, and there was no significant increase in the contribution of collagen or leukocytes.

CONCLUSIONS

Smooth muscle cell accumulation appears to be the principal contributor to the increase in neointimal area observed in arteries allografted into hypercholesterolemic mice.

Human chemokines: an update

Interleukin 8, the first chemokine to be characterized, was discovered nearly ten years ago. Today, more than 30 human chemokines are known. They are often upregulated in inflammation and act mainly on leukocytes inducing migration and release responses. The present review deals largely with the new developments of the last three years. Several structural studies have shown that most chemokines form dimers. The dimers, however, dissociate upon dilution, and the monomers constitute the biologically active form. Chemokine activities are mediated by seven-transmembrane-domain, G protein coupled receptors, five of which were discovered in the past three years. The primary receptor-binding domain of all chemokines is near the NH2 terminus, and antagonists can be obtained by truncation or substitutions in this region. Major progress has been made in the understanding of chemokine actions on T lymphocytes that respond to several CC chemokines but also to IP10 and Mig, two CXC chemokines that selectively attract T cells via a novel receptor. Effects of chemokines on angiogenesis and tumor growth have been reported, but the data are still contradictory and the mechanisms unknown. Of considerable interest is the recent discovery that some chemokines function as HIV-suppressive factors by interacting with chemokine receptors which, together with CD4, were recognized as the binding sites for HIV-1.

Neutrophil infiltration, glial reaction, and neurological disease in transgenic mice expressing the chemokine N51/KC in oligodendrocytes

Chemokines (pro-inflammatory chemoattractant cytokines) are expressed in pathological conditions of the central nervous system (CNS). Previous studies suggested that the CNS is relatively resistant to leukocyte diapedesis after chemokine injection, leaving their functional role unresolved. The CNS function of N51/KC, a neutrophil-selective chemokine, was addressed by expressing N51/KC under control of the myelin basic protein (MBP) promoter in transgenic (tg) mice (MBP-N51/KC mice). CNS-specific N51/KC expression produced remarkable neutrophil infiltration into perivascular, meningeal, and parenchymal sites, demonstrating that this chemokine exerts the multiple functions in vivo required to recruit leukocytes into the CNS. MBP-N5 1/KC mice represent an incisive model for the molecular dissection of neutrophil entry into the CNS. Unexpectedly, MBP-N51/KC mice developed a neurological syndrome of pronounced postural instability and rigidity at high frequency beginning at 40 days of age, well after peak chemokine expression. 68/182 mice in one tg fine were found dead before one year of age, with prominent neurological symptoms premortem in 26 (38%). Florid microglial activation and blood-brain barrier disruption without dysmyelination were the major neuropathological alterations. Late-onset neurological symptoms in MBP-N51/KC mice may indicate unanticipated consequences of CNS chemokine expression.

N51 competes 125I-interleukin (IL)-8 binding to IL-8R beta but not IL-8R alpha. Structure-function analysis using N51/IL-8 chimeric molecules

We have demonstrated that the mouse chemokine N51, also known as KC, can compete for 125I-human interleukin-8 (IL-8) binding to NIH 3T3 cells expressing the human IL-8 receptor beta (NIH-IL-8R beta) but not the IL-8 receptor alpha (NIH-IL-8R alpha). In addition, we used the chimeras between N51 and IL-8 described previously (Heinrich, J. N., O'Rourke, E. C., Chen, L., Gray, H., Dorfman, K. S., and Bravo, R. (1994) Mol. Cell. Biol. 14, 2849-2861; Heinrich, J. N., and Bravo, R. (1995) J. Biol. Chem. 270, 4987-4989) to evaluate possible contributions of equivalent domains from each chemokine to binding and specificity. Specifically, the amino acid sequences between cysteines 2 and 3 or between cysteines 3 and 4 or the alpha-helical C-terminal end (domains I, II, and III, respectively) of one of the chemokines was exchanged with the corresponding sequence of the other and vice versa. Chimeras of IL-8 containing either domain II or III of N51 behaved similarly, but not identically, to IL-8 in competing 125I-IL-8 binding with both NIH-IL-8R alpha cells and NIH-IL-8R beta cells. The IL-8 chimera containing domain I of N51 did not compete. On the other hand, N51 competes 125I-IL-8 binding with NIH-IL-8R beta but not NIH-IL-8R alpha cells. The N51 chimera containing domain I of IL-8 was an agonist with NIH-IL-8R alpha cells and was an even more potent agonist with NIH-IL-8R beta cells. On the latter cells it was more potent than either IL-8 or N51. The N51 chimera containing domain II of IL-8, compared with N51, was a partial agonist with NIH-IL-8R alpha cells but was equivalent to N51 with NIH-IL-8R beta cells. However, N51 chimera containing domain III of IL-8 was a partial agonist with both cells. The results are consistent with the observations we originally made with human neutrophils and the NIH mouse IL-8R beta cells, i.e. domain I confers binding specificity for IL-8 and domains II and III of IL-8 and N51 may be interchangeable but they are not equivalent. Although we originally hypothesize that domains II and III confer binding specificity to N51, these results emphasize the role of domain III.