Local delivery of protease-resistant stromal cell derived factor-1 for stem cell recruitment after myocardial infarction

BACKGROUND

Local delivery of chemotactic factors represents a novel approach to tissue regeneration. However, successful chemokine protein delivery is challenged by barriers including the rapid diffusion of chemokines and cleavage of chemokines by proteases that are activated in injured tissues. Stromal cell-derived factor-1 (SDF-1) is a well-characterized chemokine for attracting stem cells and thus a strong candidate for promoting regeneration. However, SDF-1 is cleaved by exopeptidases and matrix metalloproteinase-2, generating a neurotoxin implicated in some forms of dementia.

METHODS AND RESULTS

We designed a new chemokine called S-SDF-1(S4V) that is resistant to matrix metalloproteinase-2 and exopeptidase cleavage but retains chemotactic bioactivity, reducing the neurotoxic potential of native SDF-1. To deliver S-SDF-1(S4V), we expressed and purified fusion proteins to tether the chemokine to self-assembling peptides, which form nanofibers and allow local delivery. Intramyocardial delivery of S-SDF-1(S4V) after myocardial infarction recruited CXCR4+/c-Kit+ stem cells (46+/-7 to 119+/-18 cells per section) and increased capillary density (from 169+/-42 to 283+/-27 per 1 mm2). Furthermore, in a randomized, blinded study of 176 rats with myocardial infarction, nanofiber delivery of the protease-resistant S-SDF-1(S4V) improved cardiac function (ejection fraction increased from 34.0+/-2.5% to 50.7+/-3.1%), whereas native SDF-1 had no beneficial effects.

CONCLUSIONS

The combined advances of a new, protease-resistant SDF-1 and nanofiber-mediated delivery promoted recruitment of stem cells and improved cardiac function after myocardial infarction. These data demonstrate that driving chemotaxis of stem cells by local chemokine delivery is a promising new strategy for tissue regeneration.

In vitro reconstitution and preparative purification of complexes between the chemokine receptor CXCR4 and its ligands SDF-1alpha, gp120-CD4 and AMD3100

CXCR4 belongs to the family of G protein-coupled receptors and mediates the various developmental and regulatory effects of the chemokine SDF-1alpha. In addition, CXCR4 acts as a co-receptor along with CD4 for the HIV-1 viral glycoprotein gp120. Recently, there has also been a small molecule described that antagonizes both SDF-1 and gp120 binding to CXCR4. The structural and mechanistic basis for this dual recognition ability of CXCR4 is unknown largely due to the technical challenges of biochemically producing the components of the various complexes. We expressed the human CXCR4 receptor using a modified baculovirus expression vector that facilitates a single step antibody affinity purification of CXCR4 to >80% purity from Hi5 cells. The recombinant receptor undergoes N-linked glycosylation, tyrosine sulfation and is recognized by the 12G5 conformation specific antibody against human CXCR4. We are able to purify CXCR4 alone as well as complexed with its endogenous ligand SDF-1, its viral ligand gp120, and a small molecule antagonist AMD3100 by ion-exchange chromatography. We anticipate that the expression and purification scheme described in this paper will facilitate structure-function studies aimed at elucidating the molecular basis for CXCR4 recognition of its endogenous chemokine and viral ligands.

CC and CXC chemokines in breastmilk are associated with mother-to-child HIV-1 transmission

INTRODUCTION

CC and CXC chemokines may play a role in mother-to-child HIV-1 transmission by blocking HIV-1 binding to chemokine receptors and impeding viral entry into cells.

METHODS

To define correlates of breastmilk chemokines and associations with infant HIV-1 acquisition, chemokines in breastmilk and infant HIV-1 infection risk were assessed in an observational, longitudinal cohort study. We measured MIP-1alpha, MIP-1beta, RANTES, and SDF-1 in month 1 breastmilk specimens from HIV-1-infected women in Nairobi and HIV-1 viral load was calculated in maternal plasma and breastmilk at delivery and 1 month postpartum. Infant infection status was determined at birth and months 1, 3, 6, 9, and 12.

RESULTS

Among 281 breastfeeding women, 60 (21%) of their infants acquired HIV-1 during follow-up, 39 (65%) of whom became infected intrapartum or after birth. MIP-1alpha, MIP-1beta, RANTES, and SDF-1 were all positively correlated with breastmilk HIV-1 RNA (P<0.0005). Women with clinical mastitis had 50% higher MIP-1alpha and MIP-1beta levels (P<0.001 and P=0.006, respectively) and women with subclinical mastitis (breastmilk Na(+)/K(+)>1) had approximately 70% higher MIP-1alpha, MIP-1beta and RANTES (P<0.002 for all) compared to women without mastitis. Independent of breastmilk HIV-1, increased MIP-1beta and SDF-1 were associated with reduced risk of infant HIV-1 (RR=0.4; 95% CI 0.2-0.9; P=0.03 and RR=0.5; 95% CI=0.3-0.9; P=0.02, respectively) and increased RANTES was associated with higher transmission risk (RR=2.3; 95% CI 1.1- 5.3; P=0.04).

CONCLUSIONS

These observations suggest a complex interplay between virus levels, breastmilk chemokines, and mother-to-child HIV-1 transmission and may provide insight into developing novel strategies to reduce infection across mucosal surfaces.

[Expression and purification of mouse B lymphocyte chemoattractant]

A DNA fragment encoding mouse B Lymphocyte Chemoattractant (BLC, MV10Kda) was obtained by PCR. The amplified fragment was inserted into prokaryotic expression vector PQE30. Recombinant protein was expressed in E. Coli XL-1 blue and purified by affinity chromatography on a nickel-nitrilotriacetic acid gel matrix. Then it was identified by sequence analysis and Western blot analysis. The fragment inserted into prokaryotic expression vector PQE30 was identified to be BLC gene fragment by sequence analysis. And a specfic band was shown by Western blot analysis. These findings provide the evidence that the recombinant protein obtained and purified in this study using gene engineering method is mouse B Lymphocyte Chemoattractant.

Serum inactivation contributes to the failure of stromal-derived factor-1 to block HIV-I infection in vivo

The chemokine stromal-derived factor-1 (SDF-1) can block human immunodeficiency virus type 1 (HIV-1) infection in vitro by binding to the CXC chemokine receptor, CXCR-4, which serves as a coreceptor for T cell tropic HIV-1. In spite of being constitutively expressed in vivo, SDF-1 does not appear to block HIV-1 infection and spread in vivo. We report that SDF-1 is consistently measured in normal serum (15.4+/-3.0 ng/ml; mean+/-sd) and in serum from AIDS patients (16.6+/-3.7 ng/ml). However, we find that circulating SDF-1 is modified to an inactive form. When exposed to serum, recombinant SDF-1 is specifically and rapidly altered to yield an apparently smaller chemokine that does not bind to SDF-1 receptor-expressing cells, does not have chemoattractive or pre-B cell stimulatory activity, and does not block HIV-1 infection. Thus, serum modification and inactivation contribute to the failure of SDF-1 to block HIV-1 infection and spread in man. The inactivation of circulating SDF-1 may be critical in permitting local gradients to develop and direct cell trafficking.

Isolation and characterization of a novel CXC chemokine in common carp (Cyprinus carpio L.)

A novel CXC chemokine was identified for the first time in fish from common carp (Cyprinus carpio L.). The gene was obtained from the head kidney (HK) stimulated with LPS and Con A. The cDNA consists of 619 bp with a 37 bp 5' UTR and a 287 bp 3' UTR. An open reading frame of 368 bp encodes a 97 amino acid peptide, with a putative signal peptide of 20 aa. The gene has four cysteines residues, which are conserved, with first two cysteines separated with phenylalanine. By homology and phylogenetic analysis, the chemokine was found to be closer to human IP-10. Identities were significantly low to the CXC chemokines cloned from lamprey (Lampetra fluviatilis), flounder (Paralichthys olivaceus), rainbow trout (Onchorhynchus mykiss) and zebrafish (Danio rerio). The carp CXC chemokine contains three exons interrupted by two introns. The gene was transcribed from an early time point by stimulation with LPS and Con A. Organs in resting phase as well as stimulated expressed the gene.

A CXC chemokine sequence isolated from the rainbow trout Oncorhynchus mykiss resembles the closely related interferon-gamma-inducible chemokines CXCL9, CXCL10 and CXCL11

A sequence encoding a CXC - type chemokine from rainbow trout was found to most resemble members of the CXCL9/CXCL10/CXCL11 sub-family. In mammals, all 3 chemokines are regulated by IFN-gamma and are chemotactic for activated T lymphocytes. The trout chemokine (gammaIP1), with a message of 787 nucleotides, contains 100 amino acids in a typical non-ELR CXC chemokine arrangement. A second sequence (gammaIP2), with 6 nucleotide differences in the coding region when compared to the first, was also identified although it is not known whether this is a second functional gene or a second allele. The gene is separated onto 4 exons, and the introns intervene in conserved positions according to the mammalian equivalents. The sequence encoded by the second exon shares the highest amino acid identity (37%) with CXCL10, with lower values of identity to other CXC chemokines (17-31%). Furthermore, phylogenetic analysis groups the trout chemokine with mammalian CXCL9, CXCL10 and CXCL11 peptides. Constitutive expression of gammaIP is seen in trout gill and low level expression in spleen, head kidney and liver. In RTS-11 cells, gammaIP expression can be induced with poly I:C, but not by LPS, suggesting virus-mediated regulation of gammaIP. Intraperitoneal injection of recombinant trout TNF-alpha caused elevation in gammaIP mRNA levels in trout head kidney.

Isolation and characterization of mouse homolog of the neutrophil activating peptide-2

In the presence of thrombopoietin (TPO), megakaryocytes mature by polyploidization and cytoplasmic maturation, and the matured megakaryocytes induce drastic morphological change and proplatelet formation and release a number of platelets. However, the regulatory mechanism of this unique differentiation process is still obscure. We therefore attempted to identify the factors, expression of which is induced by TPO stimulation in mouse bone marrow megakaryocytes. We isolated the mouse homolog of the neutrophil activating peptide-2 (NAP-2). Mouse NAP-2 cDNA encodes a predicted sequence of 113 amino acids and contains the Cys motif (CXC) found in other members of the alpha-chemokine family. At the amino acid level, the predicted mouse NAP-2 has 50.4%, 51.8%, and 72.6% identity with the predicted human, pig, and rat NAP-2, respectively. Northern blot analysis demonstrates that mouse NAP-2 is expressed only in spleen. Furthermore, the RT-PCR technique shows that the mouse NAP-2 gene is clearly upregulated by TPO stimulation in mouse megakaryocytes.

Processing of natural and recombinant CXCR3-targeting chemokines and implications for biological activity

Chemokines comprise a class of peptides with chemotactic activity towards leukocytes. The potency of different chemokines for the same receptor often varies as a result of differences in primary structure. In addition, post-translational modifications have been shown to affect the effectiveness of chemokines. Although in several studies, natural CXCR3-targeting chemokines have been isolated, detailed information about the proteins and their possible modifications is lacking. Using a combination of liquid chromatography and mass spectrometry we studied the protein profile of CXCR3-targeting chemokines expressed by interferon-gamma-stimulated human keratinocytes. The biological implications of one of the identified modifications was studied in more detail using calcium mobilization and chemotaxis assays. We found that the primary structure of human CXCL10 is different from the generally accepted sequence. In addition we identified a C-terminally truncated CXCL10, lacking the last four amino acids. Native CXCL11 was primarily found in its intact mature form but we also found a mass corresponding to an N-terminally truncated human CXCL11, lacking the first two amino acids FP, indicating that this chemokine is a substrate for dipeptidylpeptidase IV. Interestingly, this same truncation was found when we expressed human CXCL11 in Drosophila S2 cells. The biological activity of this truncated form of CXCL11 was greatly reduced, both in calcium mobilization (using CXCR3 expressing CHO cells) as well as its chemotactic activity for CXCR3-expressing T-cells. It is concluded that detailed information on chemokines at the protein level is important to characterize the exact profile of these chemotactic peptides as modifications can severely alter their biological activity.

Solution studies of recombinant human stromal-cell-derived factor-1

Stromal-cell-derived factor-1 (SDF-1alpha) is an 8-kDa chemokine that is constitutively expressed in bone-marrow-derived stromal cells and has been identified as a ligand for the CXCR4 receptor. We produced the chemokine recombinantly as methionine-SDF-1alpha in Escherichia coli without the leader peptide sequence. The protein was denatured, refolded, and further purified by reversed-phase HPLC. SDF-1alpha was shown to be >95% pure as judged by SDS-PAGE. The final yield of purified and refolded SDF-1alpha was 1-2 mg per gram of wet cell paste. The refolded protein is a ligand for the CXCR4 receptor and has been used to block HIV-mediated cell fusion and downmodulates the CXCR4 receptor. Our ability to purify hundreds of milligrams of refolded protein allowed us to conduct detailed studies of the biophysical properties of the protein. We have used a combination of biophysical techniques to study the solution properties of SDF-1alpha. The average mass of SDF-1alpha, as determined by static light scattering, gave us the first indications that the chemokine may self-associate. Further investigation with sedimentation velocity ultracentrifugation confirmed the existence of two species. The measured s(20, W) values defined two masses corresponding to monomer and dimer. Finally, sedimentation equilibrium ultracentrifugation and dynamic light scattering yielded a composite value of 150 +/- 30 microM for the dimerization constant. We conclude that SDF-1alpha exists in a monomer-dimer equilibrium.

Human recombinant interferon-inducible protein-10: intact disulfide bridges are not required for inhibition of hematopoietic progenitors and chemotaxis of T lymphocytes and monocytes

Human recombinant interferon-inducible protein-10 (rIP-10), a C-X-C chemokine, inhibits proliferation of human hematopoietic progenitors responsive to co-stimulation by recombinant steel factor (rSLF), is chemotactic for human monocytes and T-lymphocytes, and promotes T-lymphocyte adhesion to endothelial cells. Because chemokines have four conserved cysteines forming two intramolecular disulfide bridges, we decided to investigate their contribution in the biological activity of rIP-10. Since amino acid residues 22-98 of the sequence predicted by the cDNA constitute the naturally occurring IP-10, they were cloned after an initiating methionine into expression vector pET-3d. Subsequently rIP-10 was purified by enzymatic cell lysis, solubilization of refractile bodies with guanidine hydrochloride, renaturation by dialysis against dilute acetic acid, and sequential ion-exchange and reverse-phase high-performance liquid chromatography. Purified rIP-10 was reduced with 20 mM dithiothreitol, and chemically modified with 100 mM iodoacetamide (IAA), or S-methyl-methanethiosulfonate (MMTS), or N-methylmaleimide (NMM). Radiolabeling experiments demonstrated that 95% of the rIP-10 thiols were modified, and this was confirmed with SDS-PAGE. The biological activity of modified rIP-10 was determined in vitro by inhibition of rSLF-responsive human bone marrow hematopoietic progenitor proliferation and by chemotaxis assays using human T-lymphocytes and monocytes. In both assay systems, the biological activity was evident at rIP-10 concentrations of 20-100 ng/ml. The activity was preserved after modification of rIP-10 by IAA or MMTS, but was abolished after modification by NMM. We conclude that disulfide bridges are not essential for the biological activity of rIP-10.

Biochemical and biological characterization of neutrophil chemotactic protein, a novel rabbit CXC chemokine from alveolar macrophages

The role of interleukin-8 (IL-8) and related CXC chemokines has been demonstrated in many human diseases. However, more profound studies, e.g., by blocking the effect of these inflammatory mediators, request animal models and hence the identification of all human counterparts for commonly used laboratory animals. In this study, we describe the identification of a novel neutrophil chemotactic protein (NCP) of the rabbit. Intact and NH(2)-terminally truncated NCP forms and IL-8 were isolated from LPS-stimulated rabbit alveolar macrophages and purified to homogeneity by a four-step purification procedure. Determination of the complete primary structure of NCP by mass spectrometry and NH(2)-terminal sequencing of natural protein revealed high structural homology with human epithelial cell-derived neutrophil attractant-78 (ENA-78) and granulocyte chemotactic protein-2 (GCP-2), two related ELR(+)CXC chemokines. Intact NCP(1-76) was found to be 10-fold less potent than truncated NCP(7, 8-76) at inducing neutrophil chemotaxis. NCP(7,8-76) was equally potent as intact rabbit IL-8 at chemoattracting human neutrophils and at inducing calcium fluxes in rabbit neutrophils, 1 ng/mL being the minimal effective concentration. However, like IL-8, NCP failed to induce monocyte or eosinophil migration at 300-fold higher concentrations. IL-8 desensitized the calcium increase induced by NCP and vice versa. Finally, intradermal injection of NCP induced a dose-dependent and significant infiltration of neutrophils in mice skin. It can be concluded that NCP is a novel rabbit CXC chemokine that is, like IL-8, implicated in animal models used to study various human disorders in which neutrophils play an important role.

Intraallograft chemokine RNA and protein during rejection of MHC-matched/multiple minor histocompatibility-disparate skin grafts

Chemokines direct leukocyte recruitment into sites of tissue inflammation and may facilitate recruitment of leukocytes into allografts following transplantation. Although the expression of chemokines during rejection of MHC-disparate allografts has been examined, chemokine expression in MHC-matched/multiple minor histocompatibility Ag-disparate allografts has not been tested. The intraallograft RNA expression of several C-X-C and C-C chemokines was tested during rejection of full thickness skin grafts from B10. D2 donors on control Ig-, anti-CD4 mAb-, and anti-CD8 mAb-treated BALB/c recipients. In all recipients, two patterns of intragraft chemokine expression were observed during rejection of these grafts: 1) macrophage-inflammatory protein-1alpha, macrophage-inflammatory protein-1beta, GRO-alpha (KC), JE, and IFN-gamma-inducible protein (IP-10) were expressed at equivalent levels in allo- and isografts for 2-4 days posttransplant and then returned to low or undetectable levels; and 2) IP-10 and monokine induced by IFN-gamma (Mig) were expressed in the allografts 3 days before rejection was completed, suggesting a possible role in recruiting primed T cells into the allograft. Three days before completion of rejection, intraallograft IP-10 protein was restricted to the epidermis, whereas Mig was located in the lower dermis and associated with the intense infiltration of mononuclear cells. Treatment of B10.D2 recipients with rabbit antiserum to Mig, but not to IP-10, delayed rejection of the allografts 3-4 days. The results suggest that Mig mediates optimal recruitment of T cells into MHC-matched/multiple minor histocompatibility Ag-disparate allografts during rejection.

Expression of IFN-inducible T cell alpha chemoattractant by human endothelial cells is cyclosporin A-resistant and promotes T cell adhesion: implications for cyclosporin A-resistant immune inflammation

IFN-inducible T cell alpha chemoattractant (I-TAC) is a recently discovered member of the CXC chemokine family. It is a potent T cell chemoattractant expressed by IFN-gamma-treated astrocytes, monocytes, keratinocytes, bronchial epithelial cells, and neutrophils. In this study, we show that I-TAC is also expressed by IFN-gamma-treated endothelial cells (EC), both at the mRNA and protein levels. Induction of the I-TAC message is rapid and sustained over 24 h. TNF-alpha does not induce I-TAC mRNA alone, but does act synergistically with IFN-gamma. Blocking Abs to I-TAC, or to its receptor, CXCR3, reduce T cell adhesion to EC monolayers demonstrating that the expressed protein is functional. Finally, the expression of I-TAC by EC is resistant to the immunosuppressive drug cyclosporin A, suggesting that I-TAC may contribute to the chronic immune inflammation characteristic of graft arteriosclerosis.

Identification of unique truncated KC/GRO beta chemokines with potent hematopoietic and anti-infective activities

SK&F 107647, a previously described synthetic immunomodulatory peptide, indirectly stimulates bone marrow progenitor cells and phagocytic cells, and enhances host defense effector mechanisms in bacterial and fungal infection models in vivo. In vitro, SK&F 107647 induces the production of a soluble mediator that augments colony forming cell (CFU-GM) formation in the presence of CSFs. In this paper we purified and sequenced the stromal cell-derived hematopoietic synergistic factors (HSF) secreted from both murine and human cell lines stimulated with SK&F 107647. Murine HSF is an N-terminal 4-aa truncated form of the CXC chemokine, KC, while human HSF was identified as an N-terminal 4-aa truncated form of the CXC chemokine, GRO beta. In comparison to their full-length forms, truncated KC and truncated GRO beta were 10 million times more potent as synergistic growth stimulants for CFU-GM. Enhanced potency of these novel truncated chemokines relative to their full-length forms was also demonstrated in respiratory burst assays, CD11b Ag expression, and intracellular killing of the opportunistic pathogen, Candida albicans. Administration of truncated KC significantly enhanced survival of mice lethally infected with C. albicans. The results reported herein delineate the biological mechanism of action of SK&F 107647, which functions via the induction of unique specific truncated forms of the chemokines KC and GRO beta. To our knowledge, this represents the first example where any form of KC or GRO beta were purified from marrow stromal cells. Additionally, this is the first demonstration of in vivo efficacy of a CXC chemokine in an animal infectious fungal disease model.

NH2- and COOH-terminal truncations of murine granulocyte chemotactic protein-2 augment the in vitro and in vivo neutrophil chemotactic potency

Chemokines are important mediators of leukocyte migration during the inflammatory response. Post-translational modifications affect the biological potency of chemokines. In addition to previously identified NH2-terminally truncated forms, COOH-terminally truncated forms of the CXC chemokine murine granulocyte chemotactic protein-2 (GCP-2) were purified from conditioned medium of stimulated fibroblasts. The truncations generated 28 natural murine GCP-2 isoforms containing 69-92 residues, including most intermediate forms. Both NH2- and COOH-terminal truncations of GCP-2 resulted in enhanced chemotactic potency for human and murine neutrophils in vitro. The truncated isoform GCP-2(9-78) was 30-fold more potent than intact GCP-2(1-92)/LPS-induced CXC chemokine (LIX) at inducing an intracellular calcium increase in human neutrophils. After intradermal injection in mice, GCP-2(9-78) was also more effective than GCP-2(1-92)/LIX at inducing neutrophil infiltration. Similar to human IL-8 and GCP-2, murine GCP-2(9-78) and macrophage inflammatory protein-2 (MIP-2) induced calcium increases in both CXCR1 and CXCR2 transfectants. Murine GCP-2(9-78) could desensitize the calcium response induced by MIP-2 in human neutrophils and vice versa. Furthermore, MIP-2 and truncated GCP-2(9-78), but not intact GCP-2(1-92)/LIX, partially desensitized the calcium response to human IL-8 in human neutrophils. Taken together, these findings point to an important role of post-translationally modified GCP-2 to replace IL-8 in the mouse.

High-performance liquid chromatographic purification and capillary electrophoresis quantification of the chemokine stromal cell-derived factor-1

Chemokines are members of the chemotactic cytokines family implicated in various immunoregulatory functions. The CXC-chemokine stromal cell derived factor-1 (SDF-1alpha) was purified from the culture medium of murine bone marrow stromal cell line (MS-5) by affinity and reversed-phase liquid chromatography. Yield and purity were assessed by capillary electrophoresis (CE) with reference to the human SDF-1alpha from recombinant DNA technology. CE technique was useful to evaluate the purity of human SDF-1alpha from chemical synthesis and to resolve murine and human SDF-1alpha, differing by only one amino acid. Chemotactic activity of the murine SDF-1alpha was tested on the basis of CE quantification.

Pertussis toxin-sensitive signal controls the trafficking of thymocytes across the corticomedullary junction in the thymus

We investigated a role of chemokines in thymocyte trafficking. Genes encoding stromal cell-derived factor-1 and its receptor CXCR4 were detected in the cortex by in situ hybridization. Early immigrant cells did not express CXCR4, whereas their descendant CD44+CD25+CD4-CD8- cells did. CXCR4 expression was down-modulated when CD4+CD8+ double-positive cells became CD4+CD8- or CD4-CD8+ single-positive (SP) cells. Positively selected CD69+CD3intermediate cells gained CCR4, of which ligand, thymus activation-regulated chemokine, was expressed in the medulla. At the next developmental stage, CD69-CD3high cells lost CCR4 but gained CCR7. These results suggest that thymocytes use different chemokines along with their development. Blockade of chemokine receptor-mediated signaling by pertussis toxin perturbed the normal distribution of SP cells and resulted in the accumulation of SP cells in the cortex. Thus, a pertussis toxin-sensitive event controls the trafficking of SP cells across the corticomedullary junction.

Isolation of the CXC chemokines ENA-78, GRO alpha and GRO gamma from tumor cells and leukocytes reveals NH2-terminal heterogeneity. Functional comparison of different natural isoforms

Chemokines are a family of chemotactic peptides affecting leukocyte migration during the inflammatory response. Post-translational modification of chemokines has been shown to affect their biological potency. Here, the isolation and identification of natural isoforms of the neutrophil chemoattractants GRO alpha and GRO gamma and the epithelial-cell-derived neutrophil attractant-78 (ENA-78), is reported. Cultured tumor cells produced predominantly intact chemokine forms, whereas peripheral blood monocytes secreted mainly NH2-terminally truncated forms. The order of neutrophil chemotactic potency of these CXC chemokines was GRO alpha > GRO gamma > ENA-78 both for intact and truncated forms. However, truncated GRO alpha (4,5,6-73), GRO gamma (5-73) and ENA-78(8,9-78) were 30-fold, fivefold and threefold more active than the corresponding intact chemokine. As a consequence, truncated GRO alpha (4,5,6-73) was 300-fold more potent than intact ENA-78 indicating that both the type of chemokine and its mode of processing determine the chemotactic potency. Similar observations were made when intact and truncated GRO alpha, GRO gamma and ENA-78 were compared for their capacity to induce an increase in the intracellular calcium concentration in neutrophilic granulocytes, and to desensitize the calcium response towards the CXC chemokine granulocyte chemotactic protein-2 (GCP-2). It must be concluded that physiological proteolytic cleavage of CXC chemokines in general enhances the inflammatory response, whereas for CC chemokines NH2-terminal processing mostly results in reduced chemotactic potency.

Chemokine IP-10 expression in cultured human keratinocytes

IP-10, a member of the CXC family of chemokines, is considered to play an important role in inflammation via its T-cell chemotactic and adhesion-promoting properties. Elevated IP-10 levels in the epidermis of psoriasis, delayed-type hypersensitivity reactions, cutaneous T-cell lymphoma and fixed drug eruptions prompted us to study its expression in keratinocytes. IP-10 mRNA could be detected using the sensitive RT-PCR method, but not by Northern blotting in RNA preparations from unstimulated normal cultured keratinocytes, indicating a low steady-state level of IP-10 mRNA. Upon stimulation with IFN-gamma, IP-10 mRNA was found to accumulate in high amounts in a time- and dose-dependent manner. Superexpression was found with the combination of IFN-gamma and TNF-alpha or IL-1, although these latter cytokines by themselves did not induce accumulation of IP-10 mRNA. Nuclear run-on experiments performed to investigate the regulation of IP-10 mRNA expression, showed a very high constitutive transcriptional activity of the IP-10 gene in unstimulated keratinocytes, which was not affected by stimulation with IFN-gamma, TNF-alpha, or a combination of IFN-gamma and TNF-alpha. Protein kinase C (PKC) was shown to be involved in IP-10 mRNA expression since the PKC inhibitor H7 decreased IP-10 mRNA accumulation. A protein was isolated from culture supernatants of stimulated keratinocytes using HPLC techniques and, by sequence analysis, was found to be identical to IP-10. The dynamics of secretion of IP-10 protein as monitored by ELISA was shown to parallel the mRNA expression.

Large quantity production with extreme convenience of human SDF-1alpha and SDF-1beta by a Sendai virus vector

We describe a robust expression of human stromal cell-derived factor-1alpha (SDF-1alpha) and SDF-1beta, the members of CXC-chemokine family, with a novel vector system based upon Sendai virus, a non-segmented negative strand RNA virus. Recombinant SDF-1alpha and SDF-1beta were detected as a major protein species in culture supernatants, reached as high as 10 microg/ ml. This remarkable enrichment of the products allowed us to use even the crude supernatants as the source for biological and antiviral assays without further concentration nor purification and will thus greatly facilitate to screen their genetically engineered derivatives.