GPCR Pharmacological Profiling of Aaptamine from the Philippine Sponge Stylissa sp. Extends Its Therapeutic Potential for Noncommunicable Diseases

We report the first isolation of the alkaloid aaptamine from the Philippine marine sponge Stylissa sp. Aaptamine possessed weak antiproliferative activity against HCT116 colon cancer cells and inhibited the proteasome in vitro at 50 µM. These activities may be functionally linked. Due to its known, more potent activity on certain G-protein coupled receptors (GPCRs), including α-adrenergic and δ-opioid receptors, the compound was profiled more broadly at sub-growth inhibitory concentrations against a panel of 168 GPCRs to potentially reveal additional targets and therapeutic opportunities. GPCRs represent the largest class of drug targets. The primary screen at 20 µM using the β-arrestin functional assay identified the antagonist, agonist, and potentiators of agonist activity of aaptamine. Dose-response analysis validated the α-adrenoreceptor antagonist activity of aaptamine (ADRA2C, IC₅₀ 11.9 µM) and revealed the even more potent antagonism of the β-adrenoreceptor (ADRB2, IC₅₀ 0.20 µM) and dopamine receptor D4 (DRD4, IC₅₀ 6.9 µM). Additionally, aaptamine showed agonist activity on selected chemokine receptors, by itself (CXCR7, EC₅₀ 6.2 µM; CCR1, EC₅₀ 11.8 µM) or as a potentiator of agonist activity (CXCR3, EC₅₀ 31.8 µM; CCR3, EC₅₀ 16.2 µM). These GPCRs play a critical role in the treatment of cardiovascular disease, diabetes, cancer, and neurological disorders. The results of this study may thus provide novel preventive and therapeutic strategies for noncommunicable diseases (NCDs).

Modulation of the chemokine/chemokine receptor axis as a novel approach for glioma therapy

Chemokines are a large subfamily of cytokines known for their ability to facilitate cell migration, most notably leukocytes, throughout the body. Chemokines are necessary for a functioning immune system in both health and disease and have received considerable attention for their roles in orchestrating temporal-spatial regulation of immune cell populations in cancer. Gliomas comprise a group of common central nervous system (CNS) primary tumors that are extremely challenging to treat. Immunotherapy approaches for highly malignant brain tumors offer an exciting new avenue for therapeutic intervention but so far, have seen limited successful clinical outcomes. Herein we focus on important chemokine/chemokine receptor systems in the regulation of pro- and anti-tumor mechanisms, highlighting potential therapeutic advantages of modulating these systems in malignant gliomas and other cancers.

Gene Expression Analysis in Sinonasal Polyposis before and after Oral Corticosteroids: A Preliminary Investigation

OBJECTIVE: To characterize gene expression in sinonasal polyps and to gain insight into change in expression after oral corticosteroid treatment.

STUDY DESIGN AND METHODS: Nasal polyps were obtained before and after oral corticosteroid treatment and gene expression was analyzed with a focused gene array technique.

RESULTS: Pretreated sinonasal polyps demonstrated high gene expression for chemokine and leukotriene receptor genes (CCR2, CCR5, CX3CL1, and LTB4R) in all patients. After treatment, the global effects of corticosteroids were evident on gene expression.

CONCLUSIONS: Gene array techniques hold promise as a research method in sinonasal polyposis. The potential benefits, as well as the potential challenges, in using these research methods will be discussed.

Chemokines and squamous cancer of the head and neck: targets for therapeutic intervention?

The biological properties of squamous carcinoma cells are intimately regulated by a multitude of cytokines and growth factors; the most well studied of these include epidermal growth factor receptor agonists and members of the transforming growth factor-beta family. The recent explosion of research in the field of chemokine function as a mediator of tumor progression has led to the possibility that these small, immunomodulatory proteins also play key roles in squamous carcinogenesis and may, therefore, be potential targets for novel therapeutic approaches.

[Curcumin down-regulates CX3CR1 expression in spinal cord dorsal horn and DRG in neuropathic pain rats]

OBJECTIVE

To investigate the effects of curcumin on the behavior of chronic constrictive injury (CCI) rats and the CX3CR1 expression in spinal cord dorsal horn and dorsal root ganglia (DRG).

METHOD

Seventy-two male SD rats were randomly divided into 4 groups: 1) Sham operation group (Sham); 2) Chronic constrictive injury group (CCI); 3) Curcumin treated group (Cur), administrated with curcumin 100 mg x kg(-1) x d(-1) ip for 14 days after CCI; 4) Solvent contrast group (SC), administrated with an equal volume of solvent for 14 days after CCI. Paw thermal withdrawal (PTWL) and paw mechanical withdrawal threshold (PMWT) were measured on 2 pre-operative and 1, 3, 5, 7, 10, 14 post-operative days respectively. The lumbar segments L4-5 of the spinal cord and the L4, L5 DRG were removed at 3, 7, 14 days after surgery. The expression of CX3CR1 was determined by immunohistochemical staining.

RESULT

Compared with Sham group, PTWL and PMWT in CCI group were significantly lower on each post-operative day (P<0.01), which reached a nadir on the 3rd day after CCI (PTWL was 6.5 +/- 1.1, PMWT was 22.6 +/- 5.1), and the expression of CX3CR1 were markedly increased in spinal cord dorsal horn and DRG. In Cur group, PTWL were higher than in CCI group on 7, 10, 14 post-operative day (P<0.05), and PMWT were higher than those in CCI group on 10 and 14 post-operative day (P<0.05). The administration of curcumin could significantly attenuate the activation of CX3CR1 induced by CCI.

CONCLUSION

The study suggests that curcumin ameliorates the CCI-induced neuropathic pain, probably by attenuating the expression of CX3CR1 in spinal cord dorsal horn and dorsal root ganglia.

[The viral acceptor antagonist to entrapment ligand H9 in vitro activeness and the function to human acceptor CX3-CR1]

AIM

To clarify the activeness of H9 in vitro and internalization and modulation of the surface chemokine receptor CX3CR1 induced by H9, To discuss the influence of H9 on the chemokine receptor CX3CR1.

METHODS

Inhibition by chemotactic peptide on the physiological detection of chemokine induced cell migration activity. Flowcytometry examined the effection of H9 on intracellular calcium. Laser scanning confocal microscopy and flow cytometry were used to determine the quality and quantity of CX3CR1 internalization.

RESULTS

H9 was able to block the migration induced by chemokine receptor. In the chemoattraction test, H9 was unable to induce the chemotactic movement, and it does not affect the signal transduction and activeness of cells. It was found that H9 could induce internalization with a maximal rate of 70%, at the concentration of 200 ng/mL. The internalized CX3CR1 molecules could recycled to the cell surface.

CONCLUSION

H9 makes human CX3CR1 internalize. After internalizing, the CX3CR1 receptor recirculates the cell surface. It does not affect CX3CR1 physiology function. H9 could be used as a specificity anti-virus peptide.

Progesterone treatment reduces disease severity and increases IL-10 in experimental autoimmune encephalomyelitis

Ovarian hormones, including progesterone, are known to have immunomodulatory and neuroprotective effects which may alter the disease course of experimental autoimmune encephalomyelitis (EAE). In the current study, we examined the treatment potential of progesterone beginning at the onset of EAE symptoms. Progesterone treated animals showed reduced peak disease scores and cumulative disease indices, and decreased inflammatory cytokine secretion (IL-2 and IL-17). In addition, increased production of IL-10 was accompanied by increased numbers of CD19+ cells and an increase in CD8+ cells. Decreased chemokine and chemokine receptor expression in the spinal cord also contributed to decreased lesions in the spinal cord.

HIV entry inhibitors: progress in development and application

This review discusses recent progress in the development of anti-HIV agents, with emphasis on small molecule HIV-1 entry inhibitors. The entry inhibitors primarily target HIV-1 envelope glycoproteins or the cellular receptors, CD4 and chemokine receptors. Two of the entry inhibitors, enfuvirtide and maraviroc, have been approved by the US FDA for AIDS therapy. The drug resistance associated with some of the entry inhibitors will also be discussed.

Chemokines and chemokine receptors as therapeutic targets in chronic kidney disease

As other cytokine families, chemokines have multiple roles in local and systemic immune responses. In the kidney, the temporal and spatial expression of chemokines correlates with local renal damage. Chemokines play important roles in leukocyte trafficking and leukocyte activation, hence, blocking chemokines can effectively reduce renal leukocyte recruitment and subsequent renal damage. However, recent data indicate that blocking chemokine or chemokine receptor activity in renal disease may also exacerbate renal inflammation under certain conditions. An increasing amount of data indicate that additional roles of chemokines in the regulation of innate and adaptive immune responses may adversely affect the outcome of interventional studies. This review summarizes available in vivo studies on the blockade of chemokines and chemokine receptors in kidney diseases, with a special focus on the therapeutic potential and possible adverse effects of anti-chemokine strategies in renal inflammation.

Compound library design for target families

Chemogenomics is a modern approach to analysis of the biological effect of a wide array of small molecule compounds on a large set of homologous receptors or other macromolecular drug targets. However, the relative productivity of the method and the extremely high-cost procedure jointly force the scientist to use additional computational tools for rational compound library design and selection. The present chapter will focus specifically on application of a predictive mapping computational technology in the context of the fundamental principles of chemogenomic approach to foster rational drug design and derive information from the simultaneous biological evaluation of multiple compounds on a set of coherent biological targets.

Chemokines and their receptors: drug targets in immunity and inflammation

The chemokine system coordinates leukocyte migration in immunity and inflammation and is implicated in the pathogenesis of many human diseases. Although several successful strategies have been identified to develop drugs targeting chemokines and their receptors, this has not yet resulted in many new therapeutics. This is likely due to a complexity of the chemokine system, which was not initially appreciated, that is characterized by redundancy, pleiotropy, and differences among species. Nevertheless, our understanding of chemokine biology is continuing to grow and several promising drugs are currently being tested in late-stage clinical trials. In this review, we examine the role of chemokines in health and diseases and discuss strategies to target the chemokine system.

Ex vivo nicotine stimulation augments the efficacy of therapeutic bone marrow-derived dendritic cell vaccination

PURPOSE

To explore the preventive and therapeutic antitumor effects of nicotine-treated immature dendritic cells (imDC).

EXPERIMENTAL DESIGN

First, bone marrow-derived imDCs were stimulated with nicotine in vitro, and nicotinic acetylcholine receptor, costimulator molecules, chemokine receptor, and endocytosis ability of imDCs were detected by flow cytometry. Second, the DC-dependent antigen-specific T-cell proliferation, CTL priming, and interleukin-12 secretion were determined by flow cytometry, enzyme-linked immunospot assay, and ELISA, respectively. Finally, preventive and therapeutic antitumor effects of such imDCs were determined by i.p. transfer against tumor challenge or implantation in mice.

RESULTS

Nicotine could up-regulate expression of nicotinic acetylcholine receptor, costimulatory molecules, such as CD80, CD86, and CD40, adhesion molecule CD11b, and chemokine receptor CCR7 and enhance endocytosis ability of imDCs. In addition, nicotine could promote imDC-dependent CTL priming and interleukin-12 secretion in vitro. Most importantly, systemic transfer of ex vivo nicotine-stimulated imDCs could reveal preventive and therapeutic effect on tumor development.

CONCLUSIONS

Ex vivo nicotine stimulation can significantly improve the efficacy of imDCs for adaptive therapy of cancer and nicotine-treated imDCs may be considered as a potential candidate for preventive and therapeutic tumor vaccination.

Immunomodulatory mediators from pollen enhance the migratory capacity of dendritic cells and license them for Th2 attraction

The immune response of atopic individuals against allergens is characterized by increased levels of Th2 cytokines and chemokines. However, the way in which the cytokine/chemokine profile is matched to the type of invading allergen, and why these profiles sometimes derail and lead to disease, is not well understood. We recently demonstrated that pollen modulates dendritic cell (DC) function in a way that results in an enhanced capacity to initiate Th2 responses in vitro. Here, we examined the effects of aqueous birch pollen extracts (Bet.-APE) on chemokine receptor expression and chemokine production by human monocyte-derived DCs. Bet.-APE strongly induced expression and function of CXCR4 and reduced CCR1 and CCR5 expression on immature DCs. In addition, DC treatment with Bet.-APE significantly reduced LPS-induced production of CXCL10/IP-10, CCL5/RANTES; induced CCL22/macrophage-derived chemokine; and did not significantly change release of CCL17/thymus and activation-regulated chemokine. At a functional level, Bet.-APE increased the capacity of LPS-stimulated DCs to attract Th2 cells, whereas the capacity to recruit Th1 cells was reduced. Bet.-APE significantly and dose-dependently enhanced intracellular cAMP, suggesting that water-soluble factors from pollen grains bind a G(alphas)-protein-coupled receptor. E(1)-Phytoprostanes were identified to be one player in the Th2-polarizing potential of aqueous pollen extracts. In summary, our results demonstrate that pollen itself releases regulatory mediators which generate a Th2-promoting micromilieu with preferential recruitment of Th2 cells to the site of pollen exposure.

Role of chemokines in tumor growth

Chemokines play a paramount role in the tumor progression. Chronic inflammation promotes tumor formation. Both tumor cells and stromal cells elaborate chemokines and cytokines. These act either by autocrine or paracrine mechanisms to sustain tumor cell growth, induce angiogenesis and facilitate evasion of immune surveillance through immunoediting. The chemokine receptor CXCR2 and its ligands promote tumor angiogenesis and leukocyte infiltration into the tumor microenvironment. In harsh acidic and hypoxic microenvironmental conditions tumor cells up-regulate their expression of CXCR4, which equips them to migrate up a gradient of CXCL12 elaborated by carcinoma-associated fibroblasts (CAFs) to a normoxic microenvironment. The CXCL12-CXCR4 axis facilitates metastasis to distant organs and the CCL21-CCR7 chemokine ligand-receptor pair favors metastasis to lymph nodes. These two chemokine ligand-receptor systems are common key mediators of tumor cell metastasis for several malignancies and as such provide key targets for chemotherapy. In this paper, the role of specific chemokines/chemokine receptor interactions in tumor progression, growth and metastasis and the role of chemokine/chemokine receptor interactions in the stromal compartment as related to angiogenesis, metastasis, and immune response to the tumor are reviewed.

CXCR3 axis: role in inflammatory bowel disease and its therapeutic implication

There is a great need for new intervention and prevention strategies against Crohn's disease (CD), a chronic, relapsing tissue-destructive inflammatory bowel disease (IBD). Estimates indicate more than 1 million cases of IBD in the United States occur annually, with 50% involving CD. The clinical features of CD correlate with certain mouse models of colitis, including the spontaneous colitis observed in interleukin-10 deficient (IL-10(-/-)), senescence accelerated mice (SAMP1/Yit) and trinitrobenzene sulfonic acid (TNBS)-treated mice. Chemokines undoubtedly play a pivotal role in the regulation (i.e., initiation, maintenance, and suppression) of mucosal inflammation and tissue destruction. A number of key advances have led to greater understanding of the steps responsible for colitis and the roles played by chemokines. In fact, CXCR3 and the ligands for this chemokine receptor, monokine-induced by interferon-gamma (IFN-gamma) (MIG/CXCL9), IFN-gamma-inducible 10 kDa protein (IP-10/CXCL10), and IFN-gamma-inducible T cell alpha-chemoattractant (I-TAC/CXCL11) are differentially expressed at sites of colitis in IL-10(-/-) mice and in clinical cases of CD. While we have demonstrated that antibodies directed against CXCL10 could both prevent the onset and cure of pre-existing colitis in IL-10(-/-) mice, studies by other investigators have shown the efficacy of CXCR3 blockade to mitigate colitis and other inflammatory diseases. This review describes the hallmarks of IBD, CXCL9-11, and CXCR3 expression during murine colitis and IBD, gives an overview of the antagonist therapies targeting the CXCR3 axis, details current and pending bio-therapies for IBD, and discusses what is known about the cellular and CXCR3-mediated mechanisms of colitis.

Immunoreactive cycloimmunogen design based on conformational epitopes derived from human immunodeficiency virus type 1 coreceptors: cyclic dodecapeptides mimic undecapeptidyl arches of extracellular loop-2 in chemokine receptor and inhibit human immunodeficiency virus type 1 infection

Human immunodeficiency virus type 1 (HIV-1) requires a chemokine receptor (CCR5 or CXCR4) as a coreceptor not only for initiate viral entry but also protecting highly conserved neutralization epitopes from the attack of neutralizing antibodies. Over the past decade, many studies have provided new insights into the HIV entry mechanism and have focused on developing an effective vaccine strategy. However, to date, no vaccine that can provide protection from HIV-1 infection has been developed. One reason for the disappointing results has been the inability of current vaccine candidates to elicit a broadly reactive immunity to viral proteins such as the envelope (env) protein. Here, we propose that chemokine receptors are attractive targets of vaccine development because their structures are highly conserved and that our synthetic cycloimmunogens can mimic conformational-specific epitopes of undecapeptidyl arches (UPAs: R(168)-C(178) in CCR5, N(176)-C(186) in CXCR4) and be useful for HIV-1 novel vaccine development.

Inhibition of Chemokine Receptor CCR2 and CCR5 Expression Contributes to Simvastatin-induced Attenuation of Cardiac Allograft Vasculopathy

BACKGROUND

Accumulating evidence reveals that statins possess pleiotropic properties beyond cholesterol reduction, which may contribute to the attenuation of cardiac allograft vasculopathy (CAV). Recent in vitro data suggest that statins could down-regulate chemokine receptors. This study was designed to test the hypothesis that simvastatin ameliorates CAV development via the inhibition of chemokine receptor expression in an inbred rat model of cardiac transplantation.

METHODS

Animals were divided into four groups: isograft; control (cyclosporine [CsA] + vehicle); low-dose simvastatin (LSIM; CsA + 5 mg/kg simvastatin); and high-dose simvastatin (HSIM; CsA + 10 mg/kg simvastatin). Donor hearts from Fisher 344 rats were transplanted heterotopically into Lewis rat recipients. CsA was administered at 1.5 mg/kg/day for 2 weeks post-operatively. In addition, recipients were treated daily with simvastatin or vehicle for 8 weeks. Donor hearts were harvested for histopathologic and immunohistochemical examination. Intragraft concentration of chemokines and chemokine receptor expression were analyzed using enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively.

RESULTS

Both low and high doses of simvastatin significantly decreased the CAV score; inhibited recruitment of T lymphocytes and macrophages; reduced levels of intragraft MCP-1 (monocyte chemoattractant protein-1), RANTES (regulated on activation, normal T-cell expressed and secreted) protein and IP-10 (interferon-inducible protein-10); and down-regulated expression of chemokine receptors CCR2 and CCR5. CXCR3 expression was not affected by simvastatin treatment.

CONCLUSIONS

Our results demonstrate that simvastatin may attenuate CAV development, possibly through retarding intragraft chemokine accumulation and chemokine receptor expression.

Chemokines and their receptors as potential targets for the treatment of asthma

Asthma is a chronic and sometimes fatal disease, which affects people of all ages throughout the world. Important hallmarks of asthma are airway inflammation and remodelling, with associated bronchial hyperresponsiveness and variable airflow obstruction. These features are orchestrated by cells of both the innate (eosinophils, neutrophils and mast cells) and the adaptive (T(H)2 T cells) immune system, in concert with structural airway cells. Chemokines are important for the recruitment of both immune and structural cells to the lung, and also for their microlocalisation within the lung tissue. Specific blockade of the responses elicited by chemokines and chemokine receptors responsible for the pathological migration of airway cells could therefore be of great therapeutic interest for the treatment of asthma.

Rapid heterologous desensitization of antinociceptive activity between mu or delta opioid receptors and chemokine receptors in rats

Previous studies have shown pretreatment with chemokines CCL5/RANTES (100 ng) or CXCL12/SDF-1alpha (100 ng) injected into the periaqueductal grey (PAG) region of the brain, 30 min before the mu opioid agonist DAMGO (400 ng), blocked the antinociception induced by DAMGO in the in vivo cold water tail-flick (CWT) antinociceptive test in rats. In the present experiments, we tested whether the action of other agonists at mu and delta opioid receptors is blocked when CCL5/RANTES or CXCL12/SDF-1alpha is administered into the PAG 30 min before, or co-administered with, opioid agonists in the CWT assay. The results showed that: (1) CXCL12/SDF-1alpha (100 ng, PAG) or CCL5/RANTES (100 ng, PAG), given 30 min before the opioid agonist morphine, or selective delta opioid receptor agonist DPDPE, blocked the antinociceptive effect of these drugs; (2) CXCL12/SDF-1alpha (100 ng, PAG) or CCL5/RANTES (100 ng, PAG), injected at the same time as DAMGO or DPDPE, significantly reduced the antinociceptive effect induced by these drugs. These results demonstrate that the heterologous desensitization is rapid between the mu or delta opioid receptors and either CCL5/RANTES receptor CCR5 or CXCL12/SDF-1alpha receptor CXCR4 in vivo, but the effect is greater if the chemokine is administered before the opioid.

Sphingosine kinase inhibitor suppresses dendritic cell migration by regulating chemokine receptor expression and impairing p38 mitogen-activated protein kinase

The migration of dendritic cells (DCs) to secondary lymphoid organs plays a crucial role in the initiation of adaptive immune responses. Although lipopolysaccharide enhances chemokine receptor 7 (CCR7) expression on DCs, the second signal for the migration of DCs toward the chemokine CCL19 remains unknown. In this study, we show that sphingosine kinase inhibitor (SKI) inhibits the migration of DCs toward CCL19 through the down-regulation of CCR7. Inhibition of p38 mitogen-activated protein kinase (MAPK) activation by SKI may be responsible for the SKI-mediated effects on the regulation of chemokine receptor expression. Impairment of DC migration by the inhibition of p38 MAPK and down-regulation of CCR7 expression may contribute to the protective effects of SKI in DC-related disorders. These results suggest that sphingosine kinase-mediated signalling plays a role in the innate and adaptive immune responses by altering DC migration.

Diaryl substituted pyrazoles as potent CCR2 receptor antagonists

We have identified and synthesized a series of diaryl substituted pyrazoles as potent antagonists of the chemokine receptor subtype 2. Structure-activity relationship studies directed toward improving the potency led to the discovery of 23 (IC50 = 6 nM).

Chemokine inhibition in inflammatory arthritis

Synovial inflammation in rheumatoid arthritis (RA) and other arthritides is, in part, dependent on migration of inflammatory cells as well as retention of these cells at the site of inflammation. Chemokines play a critical role in these processes and represent an attractive target for therapeutic intervention. Animal models of RA have shown that it is possible to induce clinical improvement by specifically targeting chemokines or their receptors. Although at present only very limited data exist, initial data suggest that it may be possible to reduce synovial inflammation in patients with RA by specific chemokine blockade. Innovative trial design may help to screen for potentially interesting chemokine antagonists in an early stage of development.

Effects of the Angiotensin II Type 1 Receptor Antagonist Telmisartan on Monocyte Adhesion and Activation in Patients with Essential Hypertension

Circulating monocytes from hypertensive patients show elevated secretion patterns of pro-inflammatory cytokines, an increased expression of adhesion molecules, and an increased adhesion to vascular endothelial cells. We tested the hypothesis that telmisartan, an angiotensin II type 1 (AT(1)) receptor antagonist, reduces the activation of circulating monocytes from hypertensive patients and diminishes the monocyte-endothelial cell adhesion. Monocytes of 20 hypertensive patients and 20 normotensive controls were isolated by density gradient centrifugation and Dynabeads, and the monocyte adhesion to human aortic endothelial cell monolayers was measured by adhesion assays. To characterize monocyte activation we assessed the expression of activity-related cell surface markers that are also involved in monocyte adhesion to endothelial cells, such as CD11a/b and CD54, as well as the chemokine receptors CCR1, CCR2 and CCR5 before and after telmisartan therapy using flow cytometry. Spontaneous adhesion of monocytes from hypertensive patients and the adhesion after stimulation with angiotensin II were significantly increased compared with those in normotensive controls (p<0.05). Treatment of hypertensive patients with the AT(1) receptor antagonist telmisartan significantly diminished the adhesion of circulating monocytes to human endothelial cells (p=0.02) despite the increase in the expressions of CD11b, CD54 and CCR5 after telmisartan therapy. Reducing monocyte adhesion may be a novel beneficial effect of the AT(1) receptor antagonist telmisartan helping to prevent vascular alterations in hypertension. The mechanism of action remains to be elucidated, since reduction in monocyte adhesion was not attributable to changes in adhesion molecule expression.

Minocycline modulates chemokine receptors but not interleukin-10 mRNA expression in hypoxic-ischemic neonatal rat brain

Hypoxic-ischemic (HI) brain injury in the perinatal period causes significant morbidity. Minocycline (MN) is a tetracycline derivative that has reduced brain injury in various animal models of neurodegeneration, including perinatal ischemia. To determine whether MN can modulate the expression of chemokine receptors and interleukin-10 (IL10) in a model of neonatal brain injury, we produced an HI insult to the right cerebral hemisphere (ipsilateral) of the 7-day-old rat (PD7) by right common carotid artery ligation and 2.25 hr of hypoxia in 8% oxygen. MN (45 mg/kg, i.p.) or vehicle (PBS) was injected twice: 2 days and immediately before the HI insult. At 0, 1, 3, and 24 hr and 14 days after HI, total RNA from the ipsilateral and contralateral (exposed to hypoxia only) hemispheres was extracted, reverse transcribed, and amplified with gene-specific primers using a semiquantitative RT-PCR for macrophage inflammatory protein-1alpha), interferon-inducible protein (IP-10), C-C chemokine receptor 5 (CCR5; MIP-1alpha receptor), C-X-C chemokine receptor 3 (CXCR3; IP-10 receptor), and IL10. We found that, in the ipsilateral hemisphere, a significant (P < 0.05) increase in MIP-1alpha, IP-10, CCR5, and CXCR3 mRNA levels was observed. MN treatment decreased mRNA levels for CCR5 and CXCR3. In contrast, the levels of antiinflammatory cytokine IL10 were markedly decreased as a result of HI insult. Treatment with MN, however, had no effect on IL10. We conclude that MN decreased proinflammatory chemokine receptor expression but had little or no influence on the expression of antiinflammatory cytokine IL10. These effects confirm the antiinflammatory effect of MN in neonatal HI brain injury.

α-Aminothiazole-γ-aminobutanoic amides as potent, small molecule CCR2 receptor antagonists

A series of racemic and homochiral alpha-aminothiazole-gamma-aminobutyroamides that display high affinities for human and murine CCR2 and functional antagonism by inhibition of monocyte recruitment are described. A representative example is (2S)-2-[2-(acetylamino)-1,3-thiazol-4-yl]-N-[3-methyl-5-(trifluoromethyl)benzyl]-4-(4-phenylpiperidin-1-yl)butanamide, which shows 5 nM affinity for human monocytes and CHO cells expressing the human CCR2b receptor. It also inhibited MCP-1 initiated chemotaxis of human monocytes with an IC50 of 0.69 nM.

Inducible functional expression of Bcl-2 in human astrocytes derived from NTera-2 cells

Astrocytes provide structural support for neurons and may also play important roles in both neuroprotection and neurodegeneration. We, here report that human astrocytes derived from on NTera-2 (NT2) cell line expressing a functional anti-apoptotic protein bcl-2 under the control of a tetracycline responsive promoter using the Tet-On and Tet-Off expression systems. NT2 cells were transfected with the Tet On or Tet Off vectors followed by pTRE carrying human bcl-2. Drug resistant cells were differentiated into astrocytes under retinoic acid exposure. These astrocyte lines were found to express astrocyte specific markers such glial fibrillary acidic protein and chemokine receptors (CCR5, CXCR4) but not CCR3 and CD4. Furthermore, NT2 astrocytes expressing bcl-2 showed rapid response to doxycycline presence in the Tet On and Tet off system. The inducible expression of bcl-2 was found to be tightly regulated by doxycycline concentration in the NT2 astrocytes. We also showed that the induction of bcl-2 expression prevented NT2 astrocytes from camptothecin-induced cellular damage. These results indicate that this system may be useful for the study of specific effects of bcl-2 gene expression on astrocyte function(s) and cellular damage.

Targeting leukocyte trafficking to inflamed skin - still an attractive therapeutic approach?

Research into leukocyte trafficking and its therapeutic exploitation appears to be a multistep process, just like the trafficking cascade itself. The initial euphoria evoked by an early understanding of the trafficking steps was followed by considerable disappointment following the clinical failure of the first selectin antagonist Cylexin (CY-1503), a sialyl Lewis(X) mimetic. The research area recovered and identified additional attractive pharmacological targets such as chemokine receptors and integrins. However, after lack of efficacy in anti-chemokine trials and the fatalities associated with anti VLA-4 therapy (Tysabri), the question arose again whether targeting leukocyte trafficking is really promising or whether such a complex, multistep process with many redundant and/or functionally overlapping molecules is simply too challenging to deal with. In this article, we delineate some pros and cons of this approach followed by a brief update on where we stand in the field and where we might move in the future.

Activation of the CXCR3 Chemokine Receptor through Anchoring of a Small Molecule Chelator Ligand between TM-III, -IV, and -VI

Seven transmembrane segment (7TM) receptors are activated through a common, still rather unclear molecular mechanism by a variety of chemical messengers ranging from monoamines to large proteins. By introducing a His residue at position III:05 in the CXCR3 receptor a metal ion site was built between the extracellular ends of transmembrane (TM) III and TM-IV to anchor aromatic chelators at a location corresponding to the presumed binding pocket for adrenergic receptor agonists. In this construct, free metal ions had no agonistic effect in accordance with the optimal geometry of the metal ion site in molecular models built over the inactive form of rhodopsin. In contrast, the aromatic chelators bipyridine or phenanthrolene in complex with Zn(II) or Cu(II) acted as potent agonists displaying signaling efficacies similar to or even better than the endogenous chemokine agonists. Molecular modeling and molecular simulations combined with mutational analysis indicated that the metal ion site-anchored chelators act as agonists by establishing an aromatic-aromatic, second-site interaction with TyrVI:16 on the inner face of TM-VI. It is noteworthy that this interaction required that the extracellular segment of TM-VI moves inward in the direction of TM-III, whereby TyrVI:16 together with the chelators complete an "aromatic zipper" also comprising PheIII:08 (corresponding to the monoamine receptor anchoring point) and TyrVII:10 (corresponding to the retinal attachment site in rhodopsin). Chemokine agonism was independent of this aromatic zipper. It is proposed that in rhodopsin-like 7TM receptors, small-molecule compounds in general act as agonists in a similar manner as here demonstrated with the artificial, metal ion site anchored chelators, by holding TM-VI bent inward.

Activation and coreceptor expression of T lymphocytes induced by highly active antiretroviral therapy in Chinese HIV/AIDS patients

BACKGROUND

At the end of 2005, 650,000 people lived with human immunodeficiency virus type-1 (HIV-1) in China, of whom 75 000 were AIDS patients. Many AIDS patients received highly active antiretroviral therapy (HAART) supported by the "China CARES" program but the immune responses of HAART were seldom reported. This study investigated the effect of HAART on the activation and coreceptor expression of T lymphocytes in Chinese HIV/AIDS patients and evaluated its effect on immune reconstitution.

METHODS

Seventeen HIV/AIDS patients were enrolled and three-color-flow cytometry was used to detect the activation of HLA-DR CD38 and the coreceptor CCR5, CXCR4 expression on T lymphocytes in whole blood samples taken from the patients before and after 3- or 6-month HAART.

RESULTS

The activation percents of CD4(+), CD8(+) T lymphocytes were significantly higher before therapy than the normal controls (HLA-DR/CD4: 40.47 +/- 18.85 vs 11.54 +/- 4.10; CD38/CD4: 81.34 +/- 10.86 vs 53.34 +/- 11.44; HLA-DR/CD8: 63.94 +/- 12.71 vs 25.67 +/- 9.18; CD38/CD8: 86.56 +/- 11.41 vs 58.84 +/- 6.16, all P < 0.01). After 6-month combined antiretroviral treatment, the activation of T lymphocytes in HIV/AIDS patients was significantly decreased (HLA-DR/CD4: 28.31 +/- 13.48; CD38/CD4: 69.88 +/- 12.64; HLA-DR/CD8: 46.56 +/- 18.64; CD38/CD8: 70.17 +/- 14.54, all P < 0.01 compared with the pre-treatment values). Before the treatment, CCR5 expression on CD8(+) T lymphocytes was up-regulated while CXCR4 expression on CD8(+) T lymphocytes downregulated in HIV/AIDS patients compared with the normal controls (CD8/CCR5: 70.91 +/- 10.03 vs 52.70 +/- 7.68; CD8/CXCR4: 24.14 +/- 11.08 vs 50.05 +/- 11.68, all P < 0.01). After 6-month HAART, CCR5 expression on CD8(+) T lymphocytes significantly decreased (56.35 +/- 12.96, P < 0.01), while CXCR4 expression on CD8(+) T lymphocytes increased (36.95 +/- 9.96, P < 0.05) compared with the pre-treatment and the normal controls. A significant statistical relationship was observed between the expression of activation markers, CCR5 and the CD4(+) T lymphocyte counts after HAART (P < 0.05).

CONCLUSIONS

Reduced activation of T lymphocytes and a normalization of coreceptor expression were observed in Chinese HIV/AIDS patients after HAART. Immunity can be restored in HIV/AIDS patients receiving HAART.

Immolina, a high-molecular-weight polysaccharide fraction of Spirulina, enhances chemokine expression in human monocytic THP-1 cells

INTRODUCTION

Spirulina (Spirulina platensis) is a dietary supplement valued for its immune-enhancing properties. We previously reported that the immunostimulatory effect of spirulina can be traced to a high-molecular- weight polysaccharide fraction. This fraction, labeled Immolina, activates nuclear factor kappa-B in human monocytic THP-1 cells and increases expression of proinflammatory cytokines.

OBJECTIVE

To characterize further the immunostimulatory effects of Immolina on THP-1 cells, we evaluated its effect on genes encoding the chemokines interleukin (IL)-8, MCP-1, MIP-1alpha, MIP-1beta, IP-10, the cytokines tumor necrosis factor (TNF)-alpha, IL-1beta, and the enzyme cyclo-oxygenase-2 (COX-2).

METHODS

THP-1 cells were exposed to concentrations of Immolina ranging from 1 ng/mL to 100 microg/mL and changes in gene expression were assessed by reverse transcriptase-polymerase chain reaction (RT-PCR). For comparison, THP-1 cells were activated with 1 ng/mL of TNF-alpha, 10 ng/mL of IL-1beta, or 10 ng/mL of lipopolysaccharide using the same assay conditions. To assess the response of THP-1 cells to Immolina at the protein level, we probed culture supernatants using a cytokine array immunoblot assay.

RESULTS

RT-PCR analysis revealed that Immolina dose-dependently increased the expression of all 5 chemokines tested as well as the expression of TNF-alpha, IL-1beta, and COX-2. The cytokine array immunoblot assay revealed an increase in the chemokines IL-8 and MIP-1beta. Thymidine uptake experiments verified that Immolina did not affect the viability and growth rate of THP-1 cells.

CONCLUSIONS

The results of the experiments demonstrate that Immolina activates THP-1 cells in a manner that is consistent with the recruitment of diverse populations of leukocytes in response to inflammatory and infectious signals.

PI3Kgamma inhibition: towards an 'aspirin of the 21st century'?

Class IB phosphatidylinositol 3-kinase p110gamma (PI3Kgamma) has gained increasing attention as a promising drug target for the treatment of inflammatory disease. Extensive target-validation data are available, which are derived from studies using both pharmacological and genetic tools. More recent findings have uncovered further therapeutic applications for PI3Kgamma inhibitors, opening up potentially huge opportunities for these drugs. Several companies have been pursuing small-molecule PI3Kgamma inhibitor projects, but none of them has progressed to the clinic yet. Here, we discuss the insights gained so far and the main challenges that are emerging on the path to developing PI3Kgamma inhibitors for the treatment of human disease.

Heparin Displaces Interferon-γ–Inducible Chemokines (IP-10, I-TAC, and Mig) Sequestered in the Vasculature and Inhibits the Transendothelial Migration and Arterial Recruitment of T Cells

Background— Heparin, used clinically as an anticoagulant, also has antiinflammatory properties and has been described to inhibit interferon (IFN)-γ responses in endothelial cells. We investigated the effects of heparin on the IFN-γ–inducible chemokines IP-10/CXCL10, I-TAC/CXCL11, and Mig/CXCL9, which play important roles in the vascular recruitment of IFN-γ–producing Th1 cells through interactions with their cognate receptor, CXCR3.

Methods and Results— Patients undergoing coronary artery bypass grafting were studied because coronary atherosclerosis is recognized as a Th1-type inflammatory disease and the subjects required systemic heparinization. Plasma levels of IP-10, I-TAC, and Mig increased immediately after heparin administration and diminished promptly after heparin antagonism with protamine. These effects were independent of detectable circulating IFN-γ or the IFN-γ inducer interleukin-12. We confirmed previous reports that heparin inhibits the IFN-γ–dependent production of CXCR3 chemokine ligands using atherosclerotic coronary arteries in organ culture. In addition to prolonged treatment decreasing chemokine secretion, heparin rapidly displaced membrane-associated IP-10 from cultured endothelial cells that did not express CXCR3 and reduced the IP-10–dependent transendothelial migration of T helper cells under conditions of venular shear stress. Finally, heparin administration to immunodeficient mouse hosts decreased both the recruitment and accumulation of memory T cells within allogeneic human coronary arteries.

Conclusions— Besides inhibiting IFN-γ responses, heparin has further immunomodulatory effects by competing for binding with IP-10, I-TAC, and Mig on endothelial cells. Disruption of CXCR3 + Th1 cell trafficking to arteriosclerotic arteries may contribute to the therapeutic efficacy of heparin in inflammatory arterial diseases, and nonanticoagulant heparin derivatives may represent a novel antiinflammatory strategy.

Sarcoptes scabiei (Acari: Sarcoptidae) mite extract modulates expression of cytokines and adhesion molecules by human dermal microvascular endothelial cells

The inflammatory and immune responses seen with the worldwide disease scabies, caused by the mite Sarcoptes scabiei (De Geer) (Acari: Sarcoptidae), are complex. Clinical symptoms are delayed for weeks in patients when they are infested with scabies for the first time. This study was undertaken to elucidate the role of the human dermal microvascular endothelial cell (HMVEC-D) in modulating the inflammatory and immune responses in the skin to S. scabiei. Extracts of S. scabiei were incubated with HMVEC-D and the expression of adhesion molecules and chemokine receptors on the cells and the secretion of selected cytokines were determined by enzyme-linked immunosorbent assay. S. scabiei extract was found to inhibit HMVEC-D expression of E-selectin and vascular cell adhesion molecule-1, although not intercellular adhesion molecule-1. The secretion of interleukin-8 also was inhibited by S. scabiei extract. S. scabiei extract increased expression of the chemokine receptor CXCR-1 and both down-regulated and up-regulated expression of CXCR-2, depending on the concentration tested. These findings help explain the delayed inflammatory reaction to infestation with S. scabiei.

Role for macrophage metalloelastase in glomerular basement membrane damage associated with alport syndrome

Alport syndrome is a glomerular basement membrane (GBM) disease caused by mutations in type IV collagen genes. A unique irregular thickening and thinning of the GBM characterizes the progressive glomerular pathology. The metabolic imbalances responsible for these GBM irregularities are not known. Here we show that macrophage metalloelastase (MMP-12) expression is >40-fold induced in glomeruli from Alport mice and is markedly induced in glomeruli of both humans and dogs with Alport syndrome. Treatment of Alport mice with MMI270 (CGS27023A), a broad spectrum MMP inhibitor that blocks MMP-12 activity, results in largely restored GBM ultrastructure and function. Treatment with BAY-129566, a broad spectrum MMP inhibitor that does not inhibit MMP-12, had no effect. We show that inhibition of CC chemokine receptor 2 (CCR2) receptor signaling with propagermanium blocks induction of MMP-12 mRNA and prevents GBM damage. CCR2 receptor is expressed in glomerular podocytes of Alport mice, suggesting MCP-1 activation of CCR2 on podocytes may underlie induction of MMP-12. These data indicate that the irregular GBM that characterizes Alport syndrome may be mediated, in part, by focal degradation of the GBM due to MMP dysregulation, in particular, MMP-12. Thus, MMP-12/CCR2 inhibitors may provide a novel and effective therapeutic stra-tegy for Alport glomerular disease.

CCR2 mediates increases in glial activation caused by exposure to HIV-1 Tat and opiates

To assess the role of CCL2/MCP-1 in opiate drug abuse and HIV-1 comorbidity, the effects of systemic morphine and intrastriatal HIV-1 Tat on macrophage/microglial and astroglial activation were assessed in wild type and CCR2 null mice. Tat and/or morphine additively increased the proportion of CCL2 immunoreactive astroglia. The effects of morphine were prevented by naltrexone. Glial activation was significantly reduced in CCR2-/- versus wild-type mice following Tat or morphine plus Tat exposure. Thus, CCR2 contributes to local glial activation caused by Tat alone or in the presence of opiates, implicating CCR2 signaling in HIV-1 neuropathogenesis in drug abusers and non-abusers.

Mechanisms of apoptosis induction by the HIV-1 envelope

The envelope glycoprotein complex (Env) of human immunodeficiency virus-1 (HIV-1) can induce apoptosis by a cornucopia of distinct mechanisms. A soluble Env derivative, gp120, can kill cells through signals that are transmitted by chemokine receptors such as CXCR4. Cell surface-bound Env (gp120/gp41), as present on the plasma membrane of HIV-1-infected cells, can kill uninfected bystander cells expressing CD4 and CXCR4 (or similar chemokine receptors, depending on the Env variant) by at least three different mechanisms. First, a transient interaction involving the exchange of lipids between the two interacting cells ('the kiss of death') may lead to the selective death of single CD4-expressing target cells. Second, fusion of the interacting cells may lead to the formation of syncytia which then succumb to apoptosis in a complex pathway involving the activation of several kinases (cyclin-dependent kinase-1, Cdk1; checkpoint kinase-2, Chk2; mammalian target of rapamycin, mTOR; p38 mitogen-activated protein kinase, p38 MAPK; inhibitor of NF-kappaB kinase, IKK), as well as the activation of several transcription factors (NF-kappaB, p53), finally resulting in the activation of the mitochondrial pathway of apoptosis. Third, if the Env-expressing cell is at an early stage of imminent apoptosis, its fusion with a CD4-expressing target cell can precipitate the death of both cells, through a process that may be considered as contagious apoptosis and which does not involve Cdk1, mTOR, p38 nor p53, yet does involve mitochondria. Activation of some of the above- mentioned lethal signal transducers have been detected in patients' tissues, suggesting that HIV-1 may indeed trigger apoptosis through molecules whose implication in Env-induced killing has initially been discovered in vitro.

Structure activity relationships of monocyte chemoattractant proteins in complex with a blocking antibody

Monocyte chemoattractant proteins (MCPs) are cytokines that direct immune cells bearing appropriate receptors to sites of inflammation or injury and are therefore attractive therapeutic targets for inhibitory molecules. 11K2 is a blocking mouse monoclonal antibody active against several human and murine MCPs. A 2.5 A structure of the Fab fragment of this antibody in complex with human MCP-1 has been solved. The Fab blocks CCR2 receptor binding to MCP-1 through an adjacent but distinct binding site. The orientation of the Fab indicates that a single MCP-1 dimer will bind two 11K2 antibodies. Several key residues on the antibody and on human MCPs were predicted to be involved in antibody selectivity. Mutational analysis of these residues confirms their involvement in the antibody-chemokine interaction. In addition to mutations that decreased or disrupted binding, one antibody mutation resulted in a 70-fold increase in affinity for human MCP-2. A key residue missing in human MCP-3, a chemokine not recognized by the antibody, was identified and engineering the preferred residue into the chemokine conferred binding to the antibody.

Chemokine expression in human erythroid leukemia cell line AS-E2: macrophage inflammatory protein-3alpha/CCL20 is induced by inflammatory cytokines

OBJECTIVE

Normal and malignant hematopoietic cells are shown to express and secrete various cytokines and chemokines, some of which are believed to play an important role in normal and abnormal hematopoiesis in an autocrine/paracrine manner. To explore the possibility of a cytokine/chemokine network participating in the pathophysiology of anemic disorders, we evaluated the ability of inflammatory cytokines to induce chemokine expression using erythroid progenitor cells.

METHODS

Erythropoietin-dependent human leukemia cell line AS-E2 was used as a model of erythroid colony-forming unit (CFU-E) cells. The expression of mRNA of 8 chemokines was examined using RT-PCR, before and after TNF-alpha, IFN-gamma, and IL-1beta stimulation. For MIP-3alpha, the promoter activity was analyzed by luciferase assay and secretion was confirmed by ELISA. The expression of CCR6, the specific receptor for MIP-3alpha, was analyzed by RT-PCR and flow cytometry.

RESULTS

Unstimulated AS-E2 cells constitutively expressed transcripts for MCP-4, IP-10, PF-4, IL-8, and MIP-3alpha. Stimulation with TNF-alpha, IFN-gamma, and IL-1beta upregulated MIP-3alpha mRNA expression and induced its protein secretion. Luciferase assay revealed that these cytokines could upregulate promoter activity of the MIP-3alpha gene, possibly through the NF-kappaB pathway. CCR6 mRNA was detected and its intracellular expression was confirmed.

CONCLUSION

These data suggest that inflammatory cytokine-stimulated erythroid progenitors secrete MIP-3alpha, which may function in an autocrine/paracrine manner. Furthermore, the existence of intracellular CCR6 suggests the involvement in cytokine signaling of a MIP-3alpha-dependent internal autocrine mechanism. These mechanisms may play a role in pathophysiology of anemic disorders, such as secondary anemia and bone marrow failure syndromes.

Chemokines as potential therapeutic targets in atherosclerosis

Atherosclerosis is a chronic disease with high morbidity and mortality around the globe. It is characterized by chronic inflammation of the vessel wall, which is perpetuated by the continuous migration of cells to and within the atherosclerotic lesion. Chemokines (CK) and chemokine receptors (CKR) together with other chemoattractants and adhesion molecules are major mediators facilitating this process. Many CK/CKR (CC, CX3C and CXC) and other chemoattractants (e.g. leukotrienes) have been implicated in atherogenesis, but only a few have been validated as pathogenic by in vitro assays, in vivo experiments using gene-targeted animal models and genetic studies. Promising attempts are currently made to inhibit CK-dependent cell recruitment to lesion by using neutralizing antibodies, mutant proteins, viral and synthetic inhibitors or receptor antagonists. Some of the therapeutics have already entered clinical trials for other conditions and are about to be tested in human atherosclerosis. However, our limited understanding of the complex CK system and the functional specialization of individual CK/CKR, translatability of animal research into human population, limitations of current imaging techniques and surrogate markers for evaluation of the benefits of potential anti-CK compounds are still hampering therapeutic exploitation of the CK system in atherosclerosis. Hopefully we will be able to solve many of these issues in the near future and use this approach to control atherosclerotic disease in man.

Lymphoproliferative disorders and chemokines

Chemokines are low molecular weight cytokines specialized in leukocyte recruitment. Recent studies have shown that tumor cells of hematopoietic and non hematopoietic origin express different chemokine receptors that may be involved in neoplastic cell growth, metastasis and angiogenesis. Human lymphoproliferative disorders arise from the malignant transformation of normal lymphoid cells frozen at discrete maturational stages. Studies performed with acute or chronic lymphoproliferative disorders have shown that CXCR4, the unique receptor for CXCL12, is up-regulated in many B and T cells malignancies and may be involved in metastatic localization of the neoplastic elements. Additional chemokine receptors are expressed in the individual lymphoproliferative disorders, but some of these are often non functional. Here we shall review the state of the art on chemokine receptor expression and function in human lymphoproliferative disorders, stressing the potential value of chemokines receptors as novel therapeutic targets. In this respect, small antagonistic peptides are being produced by pharmaceutical companies and hold great promise for clinical application.

Kidney diseases and chemokines

Infiltrating inflammatory cells into the kidney mediate the initiation and progression of damage by direct cytotoxicity, the secretion of soluble factors such as cytokines and proteases, or by the subsequent induction of further immune response. Before leukocytes can exert their effects on renal damage or repair, they have to reach the site of injury. It has become clear in recent years that a group of small proteins called chemokines are the chemotactic cytokines considered to be the main regulators of directional leukocyte trafficking under homeostatic and inflammatory conditions. In this review, we summarize available in vivo studies on the neutralization of chemokines and chemokine receptors in renal inflammatory disease, and especially focus on the potential therapeutic effects of chemokine blockade in glomerulonephritis and renal transplantation. Although interference with chemokine expression holds great promises for the treatment of inflammatory renal diseases, it has been shown that such an approach may actually worsen in diseases under certain circumstances. This suggests that inhibition of chemokine expression and action must be time and compartment specific to provide therapeutic benefit for renal structure and function.

Adenosine A2a receptors induce heterologous desensitization of chemokine receptors

Adenosine, released by cells in an injurious or hypoxic environment, possesses potent anti-inflammatory effects by inhibiting the production of proinflammatory cytokines and superoxide anions (O2-). We hypothesized that adenosine compounds also induced heterologous desensitization of chemokine receptors, which played a critical role in leukocyte trafficking. Our studies using adenosine receptor subtype-specific agonists revealed that pretreatment with adenosine compounds suppressed RANTES-induced chemotaxis and Ca2+ flux through activation of A2a adenosine receptor. Adenosine compounds also desensitized IL-8- and MCP-1-induced chemotaxis, but not that induced by fMLP. Activation of protein kinase A (PKA), a component of the signaling pathway induced by the A2a receptor, was sufficient to desensitize RANTES-induced chemotaxis. Inhibition of PKA reversed the desensitization effects of adenosine compounds, suggesting that PKA was necessary for A2a receptor-mediated heterologous desensitization. In a mouse model, prior activation of A2a receptors blocked RANTES-induced recruitment of leukocytes in an air pouch. Moreover, the A2a receptor-induced cross-desensitization also reduced the susceptibility of monocytes to infection by an R5 strain of HIV-1. Our results suggest that activation of A2a adenosine receptors suppresses chemokine receptor function, and such receptor cross-talk was based on the simple mechanism of PKA-mediated heterologous desensitization, thus contributing to the antiinflammatory activity of adenosine.

Induction of surface CCR4 and its functionality in mouse Th2 cells is regulated differently during Th2 development

T helper cell type 1 (Th1) and Th2 cells express distinct sets of chemokine receptors. In contrast to Th1 chemokine receptors, it is largely unknown how Th2 chemokine receptors such as CC chemokine receptor 4 (CCR4) are induced during Th2 differentiation. Here, we investigated the induction of CCR4 surface expression and ligand responsiveness evaluated by functional assays such as chemokine binding and chemotaxis. This was done in comparison with those of a Th1 chemokine receptor, CXC chemokine receptor 3 (CXCR3). Resting T cells expressed neither CXCR3 nor CCR4. CXCR3 expression and ligand responsiveness were observed when resting T cells were stimulated with anti-CD3 plus anti-CD28 in the presence of [interleukin (IL)-12+anti-IL-4] and then recultured without T cell receptor (TCR) stimulation. Unlike CXCR3, CCR4 was induced immediately after anti-CD3/anti-CD28 stimulation in the presence of (IL-4+anti-interferon-gamma+anti-IL-12). However, these CCR4-positive cells failed to exhibit chemokine binding and chemotaxis. Although the levels of surface CCR4 expression were not increased after the subsequent reculture in the absence of TCR stimulation, CCR4 responsiveness was induced in this stage of Th2 cells. The induction of CCR4 expression and the acquisition of CCR4 responsiveness did not occur in IL-4-deficient (IL-4(-/-)) and signal transducer and activator of transcription (STAT)6(-/-) T cells. CCR4 expression and functionality were regained in IL-4(-/-) but not in STAT6(-/-) T cells by the addition of recombinant IL-4. Although surface expression and functionality of CCR4 are induced depending on the IL-4/STAT6 signaling pathway, the present results indicate that the functionality of CCR4 does not correlate with CCR4 expression but emerges at later stages of Th2 differentiation.

Eosinophils, but not eosinophil peroxidase or major basic protein, are important for host protection in experimental Brugia pahangi infection

The attenuation of eosinophilia by the administration of monoclonal antibodies to CCR3 consistently correlates with impairment in worm elimination following primary intraperitoneal Brugia pahangi infections in mice. Host protection was unimpaired in mice deficient in eosinophil peroxidase (EPO) or major basic protein 1 (MBP-1), suggesting that eosinophils are essential in host protection but that neither EPO nor MBP-1 alone is.

Cocaine and sigma-1 receptors modulate HIV infection, chemokine receptors, and the HPA axis in the huPBL-SCID model

Cocaine is associated with an increased risk for, and progression of, clinical disease associated with human immunodeficiency virus (HIV) infection. A human xenograft model, in which human peripheral blood mononuclear cells were implanted into severe combined immunodeficiency mice (huPBL-SCID) and infected with a HIV reporter virus, was used to investigate the biological interactions between cocaine and HIV infection. Systemic administration of cocaine (5 mg/kg/d) significantly increased the percentage of HIV-infected PBL (two- to threefold) and viral load (100- to 300-fold) in huPBL-SCID mice. Despite the capacity for cocaine to increase corticosterone and adrenocorticotropic hormone levels in control mice, the hypothalamic-pituitary-adrenal axis was suppressed in HIV-infected animals, and corticosterone levels were further decreased when animals were exposed to HIV and cocaine. Activating huPBL in vitro in the presence of 10(-8) M cocaine increased expression of CC chemokine receptor 5 (CCR5) and CXC chemokine receptor 4 (CXCR4) coreceptors. Expression of CCR5 was also increased at early time-points in the huPBL-SCID model following systemic exposure to cocaine (54.1+/-9.4% increase over control, P<0.01). This effect preceded the boost in viral infection and waned as HIV infection progressed. Cocaine has been shown to mediate immunosuppressive effects by activating sigma-1 receptors in immune cells in vitro and in vivo. Consistent with these reports, a selective sigma-1 antagonist, BD1047, blocked the effects of cocaine on HIV replication in the huPBL-SCID mouse. Our results suggest that systemic exposure to cocaine can enhance HIV infection in vivo by activating sigma-1 receptors and by modulating the expression of HIV coreceptors.

Eosinophilic differentiation is promoted by blockage of Notch signaling with a gamma-secretase inhibitor

Although increasing evidence supports the inhibitory role of Notch in granulocyte differentiation, the direct effects of Notch on the differentiation and maturation of eosinophils, one type of granulocyte, have not yet been studied. We investigated whether a blockage of Notch signaling promoted the differentiation of eosinophils from umbilical cord blood (UCB) cells. Freshly isolated UCB cells were cultured with IL-3, IL-5 and GM-CSF in the presence or absence of a gamma-secretase inhibitor L-685,458, and examined for the expression of major basic protein (MBP). Freshly isolated UCB cells expressed mRNA and proteins for Notch 1, Notch 2, Delta 1, and Jagged 1. MBP expression in cultures with the inhibitor was significantly increased, as compared with the cultures in the absence of the inhibitor. Treatment with the inhibitor was accompanied by a decrease in Hes 1 mRNA expression, indicative of Notch-mediated signaling for the inhibitor effect. UCB cells cultured with the inhibitor for 28 days displayed similar levels of CCR3, a late marker of eosinophil development, as compared with the cells cultured without the inhibitor, but almost completely lost chemotaxis response to eotaxin. Our data suggest that Notch signaling may modulate eosinophil migration at the mature stage as well as inhibit eosinophil differentiation.

All-trans-retinoic acid suppresses interferon-gamma and tumor necrosis factor-alpha; a possible therapeutic agent for rheumatoid arthritis

OBJECTIVES

To study the effects of all-trans-retinoic acid (ATRA), we determined the proliferation and cytokine production by peripheral blood mononuclear cells (PBMCs) and CD4+ T cells in healthy volunteers and patients with rheumatoid arthritis (RA), and explored the possibility of using ATRA as a therapeutic agent for autoimmune diseases.

METHODS

Proliferation of these cells was determined by modified MTT assay, and expression of CC chemokine receptors 4 (CCR4) and CCR5 was determined by flow cytometry. Production and expression of interferon (IFN)-gamma, interleukin (IL)-2, IL-4, and tumor necrosis factor (TNF)-alpha was determined by Enzyme-Linked Immunosorbent Assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR). The presence of STAT6 protein was determined by Western blot analysis.

RESULTS

ATRA did not affect the proliferation or production of IL-2 and IL-4. We did not detect STAT6 protein, and saw no evidence of the differentiation of PBMCs to Th1 or Th2 cells. In contrast, ATRA suppressed the production of IFN-gamma and TNF-alpha significantly. There were no significant differences between the healthy volunteers and RA patients.

CONCLUSIONS

ATRA was demonstrated to affect the cytokine production of IFN-gamma and TNF-alpha. ATRA might be useful in the treatment of autoimmune diseases such as RA.

Distribution of receptor targets in the lung

Most of the drugs that are currently used to treat airway diseases interact with receptors expressed by cells in the airways. This makes inhaled delivery efficient because it reaches the key target cells and has a low risk of systemic side effects. Both beta(2)-agonists and anticholinergics target autonomic receptors on airway smooth muscle of large and small airways. Inhaled beta(2)-agonists also interact with beta(2)-receptors expressed on other important target cells, including mast cells and postcapillary venules. Anticholinergic bronchodilators target M(3) muscarinic receptors on airway smooth muscle, which in small airways may be activated by extraneuronal acetylcholine. Corticosteroids target glucocorticoid receptors (GR), which are widely distributed so that they are best given by inhalation to interact with intracellular GR in the respiratory tract and to avoid side effects from activation of GR in extrapulmonary tissues such as bone. By contrast, cysteinyl-leukotriene 1 receptors are mainly expresses in airway smooth muscle so that antileukotrienes are less effective clinically than beta(2)-agonists and corticosteroids, but oral delivery is possible as there are minimal side effects. There are many other receptor targets in lung and for several of these receptors, such as receptors for chemotactic agonists, selective antagonists are in clinical development. For drugs that inhibit chemotactic receptors, systemic delivery is more appropriate to prevent the inflammatory cells that bear these receptors from being recruited into the airways by locally released chemotactic factors. Many novel receptors, including orphan receptors, have now been identified as these may be future targets for developing novel therapies for asthma and chronic obstructive pulmonary disease.