Anti-HIV activity and conformational studies of peptides derived from the C-terminal sequence of SDF-1

Crosstalk between CXCL12/CXCR4/ACKR3 and the STAT3 Pathway

The reciprocal modulation between the CXCL12/CXCR4/ACKR3 axis and the STAT3 signaling pathway plays a crucial role in the progression of various diseases and neoplasms. Activation of the CXCL12/CXCR4/ACKR3 axis triggers the STAT3 pathway through multiple mechanisms, while the STAT3 pathway also regulates the expression of CXCL12. This review offers a thorough and systematic analysis of the reciprocal regulatory mechanisms between the CXCL12/CXCR4/ACKR3 signaling axis and the STAT3 signaling pathway in the context of diseases, particularly tumors. It explores the potential clinical applications in tumor treatment, highlighting possible therapeutic targets and novel strategies for targeted tumor therapy.

An emerging paradigm of CXCL12 involvement in the metastatic cascade

The chemokine CXCL12, also known as stromal cell-derived factor 1 (SDF1), has emerged as a pivotal regulator in the intricate molecular networks driving cancer progression. As an influential factor in the tumor microenvironment, CXCL12 plays a multifaceted role that spans beyond its traditional role as a chemokine inducing invasion and metastasis. Indeed, CXCL12 has been assigned functions related to epithelial-to-mesenchymal transition, cancer cell stemness, angiogenesis, and immunosuppression, all of which are currently viewed as specialized biological programs contributing to the "metastatic cascade" among other cancer hallmarks. Its interaction with its cognate receptor, CXCR4, initiates a cascade of events that not only shapes the metastatic potential of tumor cells but also defines the niches within the secondary organs that support metastatic colonization. Given the profound implications of CXCL12 in the metastatic cascade, understanding its mechanistic underpinnings is of paramount importance for the targeted elimination of rate-limiting steps in the metastatic process. This review aims to provide a comprehensive overview of the current knowledge surrounding the role of CXCL12 in cancer metastasis, especially its molecular interactions rationalizing its potential as a therapeutic target.

In-situ wound healing by SDF-1-mimic peptide-loaded click crosslinked hyaluronic acid scaffold

Endogenous stem cell-based in-situ tissue regeneration has recently gained considerable attention. In this study, we investigated the potential of a chemokine, SDF-1-mimic peptide (SMP), to promote endogenous stem cell-based in-situ wound healing. Our approach involved the development of a click crosslinked hyaluronic acid scaffold loaded with SMP (Cx-HA + SMP) to release SMP in a wound site. The Cx-HA scaffold maintained its structural integrity throughout the wound healing process and also captured endogenous stem cells. Gradual SMP release from the Cx-HA + SMP scaffold established a concentration gradient at the wound site. In animal wound experiments, Cx-HA + SMP exhibited faster wound contraction compared to Cx-HA + SDF-1. Additionally, Cx-HA + SMP resulted in approximately 1.2-1.6 times higher collagen formation compared to Cx-HA + SDF-1. SMP released from the Cx-HA + SMP scaffold promoted endogenous stem cell migration to the wound site 1.5 times more effectively than Cx-HA + SDF-1. Moreover, compared to Cx-HA + SDF-1, Cx-HA + SMP exhibited higher expression of CXCR4 and CD31, as well as the positive markers CD29 and CD44 for endogenous stem cells. The endogenous stem cells that migrated through Cx-HA + SMP regenerated into wound skin with minimal scar granule formation, similar to the normal tissue. In conclusion, SMP peptide offers greater convenience, while efficiently attracting migrating endogenous stem cells compared to the SDF protein. Our findings suggest that Cx-HA + SMP scaffolds hold promise as a strategy to enhance endogenous stem cell-based in-situ wound healing.

Expression and function of the stromal cell-derived factor-1 (SDF-1) and CXC chemokine receptor 4 (CXCR4) in the swine ovarian follicle

The most characterized stromal cell-derived factor-1 (SDF-1) variants are the isoform α, which is the predominant one but undergoes rapid proteolysis, and the β isoform, which is more resistant. Through the interaction with a specific chemokine receptor called CXCR4, SDF-1 is able to regulate different physiological processes. The aim of this study was to verify the expression and potential functional role of SDF-1 and CXCR4 in the porcine ovary. Firstly, the expression of SDF-1 and its receptor in different ovarian districts was verified for the first time. Thereafter, the effect of SDF-1 β isoform (51-72) fragment on functional parameters, such as proliferation, metabolic activity, redox status, nitric oxide production, and steroidogenic activity, was assessed on granulosa cells collected from follicles. In addition, the potential effect of this protein in vascular events was verified through investigations on porcine aortic (AOC) endothelial cells, such as the production of nitric oxide and viability tests. The proliferation and metabolic activity were not affected by treatment with the cytokine. As regard to steroidogenesis, the peptide stimulated both estrogen (P = 0.049) and progesterone production (P = 0.039). Redox status was affected by the examined substance since superoxide anion was inhibited (P = 0.001), while antioxidant power (P = 0.034), as well as nitric oxide generation, were stimulated (P = 0.034). Tests performed on AOCs showed significant stimulation of nitric oxide production (P = 0.004) by the examined peptide, while cell viability was unaffected. Therefore, the potential role of cytokine in the mechanisms involved in the regulation of follicular function can be hypothesized.

Sitagliptin, a dipeptidyl peptidase-4 inhibitor, increases the number of circulating CD34⁺CXCR4⁺ cells in patients with type 2 diabetes

We investigated the effects of sitagliptin, a dipeptidyl peptidase (DPP)-4 inhibitor, on the number of circulating CD34(+)CXCR4(+)cells, a candidate for endothelial progenitor cells (EPCs), plasma levels of stromal cell-derived factor (SDF)-1α, a ligand for CXCR4 receptor and a substrate for DPP-4, and plasma levels of interferon-inducible protein (IP)-10, for a substrate for DPP-4, in patients with type 2 diabetes. We studied 30 consecutive patients with type 2 diabetes who had poor glycemic control despite treatment with metformin and/or sulfonylurea. Thirty diabetic patients were randomized in a 2:1 ratio into a sitagliptin (50 mg/day) treatment group or an active placebo group (glimepiride 1 mg/day) for 12 weeks. Both groups showed similar improvements in glycemic control. The number of circulating CD34(+)CXCR4(+) cells was increased from 30.5 (20.0, 47.0)/10(6) cells at baseline to 55.5 (31.5, 80.5)/10(6) cells at 12 weeks of treatment with 50 mg/day sitagliptin (P = 0.0014), while showing no significant changes in patients treated with glimepiride. Plasma levels of SDF-1α and IP-10, both physiological substrates of endogenous DPP-4 and chemokines, were significantly decreased at 12 weeks of sitagliptin treatment. In conclusion, treatment with sitagliptin increased the number of circulating CD34(+)CXCR4(+) cells by approximately 2-fold in patients with type 2 diabetes.

Oversulfated chondroitin sulfate binds to chemokines and inhibits stromal cell-derived factor-1 mediated signaling in activated T cells

Oversulfated chondroitin sulfate (OSCS), a member of the glycosaminoglycan (GAG) family, was a contaminant in heparin that was linked to the 2008 heparin adverse events in the US. Because of its highly negative charge, OSCS can interact with many components of the contact and immune systems. We have previously demonstrated that OSCS inhibited the complement classical pathway by binding C1 inhibitor and potentiating its interaction with C1s. In the present study, by using surface plasmon resonance, we found OSCS interacts with T cell chemokines that can impact adaptive immunity. The binding of OSCS to stromal cell-derived factor-1 (SDF-1) chemokines, SDF-1α and SDF-1β, caused a significant change in the secondary structures of these chemokines as detected by far-ultraviolet circular dichroism spectra analysis. Functionally, OSCS binding profoundly inhibited SDF-1-induced calcium mobilization and T cell chemotaxis. Imaging flow cytometry revealed T cell morphological changes mediated by SDF-1α were completely blocked by OSCS. We conclude that the OSCS, a past contaminant in heparin, has broad interactions with the components of the human immune system beyond the contact and complement systems, and that may explain, in part, prior OSCS-related adverse events, while suggesting potentially useful therapeutic applications for related GAGs in the control of inflammation.

Chemokine receptor CXCR4: role in gastrointestinal cancer

Chemokines (CK)s, small proinflammatory chemoattractant cytokines that bind to specific G-protein coupled seven-span transmembrane receptors, are major regulators of cell trafficking and adhesion. The CXCL12 [stromal cell-derived factor-1 (SDF-1)] binds primarily to CXC receptor 4 (CXCR4; CD184). The binding of CXCL12 to CXCR4 induces intracellular signaling through several divergent pathways initiating signals related to chemotaxis, cell survival and/or proliferation, increase in intracellular calcium, and gene transcription. CXCR4 is expressed on multiple cell types including lymphocytes, hematopoietic stem cells, endothelial and epithelial cells, and cancer cells. One of the most intriguing and perhaps important roles that CKs and the CK receptors have is in regulating metastasis. Here, CK receptors may potentially facilitate tumor dissemination at each of the key steps of metastasis, including adherence of tumor cells to endothelium, extravasation from blood vessels, metastatic colonization, angiogenesis, proliferation, and protection from the host response via activation of key survival pathways such as ERK/MAPK, PI-3K/Akt/mTOR, or Jak/STAT, etc. In addition, it is increasingly recognized that CKs play an important role in facilitating communication between cancer cells and non-neoplatic cells in the tumor microenvironment (TME), including endothelial cells and fibroblasts, promoting the infiltration, activation of neutrophils, and tumor-associated macrophages within the TME. In this review, we mainly focus on the roles of chemokines CXCL12 and its cognate receptors CXCR4 as they pertain to cancer progression. In particular, we summarizes our current understanding regarding the contribution of CXCR4 and SDF-1 to gastrointestinal tumor behavior and its role in local progression, dissemination, and immune evasion of tumor cells. Also, describes recent therapeutic approaches that target these receptors or their ligands.

Cardiomyocytes in vitro adhesion is actively influenced by biomimetic synthetic peptides for cardiac tissue engineering

Scaffolds for tissue engineering must be designed to direct desired events such as cell attachment, growth, and differentiation. The incorporation of extracellular matrix-derived peptides into biomaterials has been proposed to mimic biochemical signals. In this study, three synthetic fragments of fibronectin, vitronectin, and stromal-derived factor-1 were investigated for the first time as potential adhesive sequences for cardiomyocytes (CMs) compared to smooth muscle cells. CMs are responsive to all peptides to differing degrees, demonstrating the existence of diverse adhesion mechanisms. The pretreatment of nontissue culture well surfaces with the (Arginine-Glycine-Aspartic Acid) RGD sequence anticipated the appearance of CMs' contractility compared to the control (fibronectin-coated well) and doubled the length of cell viability. Future prospects are the inclusion of these sequences into biomaterial formulation with the improvement in cell adhesion that could play an important role in cell retention during dynamic cell seeding.

CXCL12 / CXCR4 / CXCR7 chemokine axis and cancer progression

Chemokines, small pro-inflammatory chemoattractant cytokines that bind to specific G-protein-coupled seven-span transmembrane receptors, are major regulators of cell trafficking and adhesion. The chemokine CXCL12 (also called stromal-derived factor-1) is an important α-chemokine that binds primarily to its cognate receptor CXCR4 and thus regulates the trafficking of normal and malignant cells. For many years, it was believed that CXCR4 was the only receptor for CXCL12. Yet, recent work has demonstrated that CXCL12 also binds to another seven-transmembrane span receptor called CXCR7. Our group and others have established critical roles for CXCR4 and CXCR7 on mediating tumor metastasis in several types of cancers, in addition to their contributions as biomarkers of tumor behavior as well as potential therapeutic targets. Here, we review the current concepts regarding the role of CXCL12 / CXCR4 / CXCR7 axis activation, which regulates the pattern of tumor growth and metastatic spread to organs expressing high levels of CXCL12 to develop secondary tumors. We also summarize recent therapeutic approaches to target these receptors and/or their ligands.

Structure-activity relationships of polybiguanides with activity against human immunodeficiency virus type 1

Previous investigations showing that polydisperse biguanide (PDBG) molecules have activity against human immunodeficiency virus type 1 (HIV-1) also suggested a relationship between PDBG biologic activity and the lengths of hydrocarbon linkers surrounding the positively charged biguanide unit. To better define structure-activity relationships, PDBG molecules with select linker lengths were evaluated for cytotoxicity, anti-HIV-1 activity, and in vivo toxicity. Results of the in vitro experiments demonstrated that increases in linker length (and, therefore, increases in compound lipophilicity) were generally associated with increases in cytotoxicity and antiviral activity against HIV-1. However, a relationship between linker length asymmetry and in vitro therapeutic index (TI) suggested structural specificity in the mechanism of action against HIV-1. Polyethylene hexamethylene biguanide (PEHMB; biguanide units spaced between alternating ethylene and hexamethylene linkers) was found to have the highest in vitro TI (CC₅₀/IC₅₀) among the compounds examined. Recent improvements in PEHMB synthesis and purification have yielded preparations of PEHMB with in vitro TI values of 266 and 7000 against HIV-1 strains BaL and IIIB, respectively. The minimal toxicity of PEHMB relative to polyhexamethylene biguanide (PHMB; biguanide units alternating with hexamethylene linkers) in a murine model of cervicovaginal microbicide toxicity was consistent with considerable differences in cytotoxicity between PEHMB and PHMB observed during in vitro experiments. These structure-activity investigations increase our understanding of PDBG molecules as agents with activity against HIV-1 and provide the foundation for further preclinical studies of PEHMB and other biguanide-based compounds as antiviral and microbicidal agents.

Specific interactions between the viral coreceptor CXCR4 and the biguanide-based compound NB325 mediate inhibition of human immunodeficiency virus type 1 infection

The present studies were conducted to better define the mechanism of action of polyethylene hexamethylene biguanide (PEHMB) (designated herein as NB325), which was shown in previous studies to inhibit infection by the human immunodeficiency virus type 1 (HIV-1). Fluorescence-activated flow cytometric analyses of activated human CD4(+) T lymphocytes exposed to NB325 demonstrated concentration-dependent reductions in CXCR4 epitope recognition in the absence of altered recognition of selected CD4 or CD3 epitopes. NB325 also inhibited chemotaxis of CD4(+) T lymphocytes induced by the CXCR4 ligand CXCL12. However, NB325 did not cause CXCR4 internalization (unlike CXCL12) and did not interfere with CXCL12 binding. Additional flow cytometric analyses using antibodies with distinct specificities for extracellular domains of CXCR4 demonstrated that NB325 specifically interfered with antibody binding to extracellular loop 2 (ECL2). This interaction was confirmed using competitive binding analyses, in which a peptide derived from CXCR4 ECL2 competitively inhibited NB325-mediated reductions in CXCR4 epitope recognition. Collectively, these results demonstrate that the biguanide-based compound NB325 inhibits HIV-1 infection by specifically interacting with the HIV-1 coreceptor CXCR4.

A naturally occurring splice variant of CXCL12/stromal cell-derived factor 1 is a potent human immunodeficiency virus type 1 inhibitor with weak chemotaxis and cell survival activities

CXCL12/stromal cell-derived factor 1 is a member of the CXC family of chemokines that plays an important role in hematopoiesis and signals through CXCR4 and CXCR7. Two splice variants of human CXCL12 (CXCL12alpha and CXCL12beta) induce chemotaxis of CXCR4(+) cells and inhibit X4 infection. Recent studies described four other novel splice variants of human CXCL12; however, their antiviral activities were not investigated. We constructed and expressed all of the CXCL12 splice variants in Escherichia coli. Recombinant proteins were purified through a His affinity column, and their biological properties were analyzed. All six CXCL12 variants induced chemotaxis of CXCR4(+) and CXCR7(+) cell lines. Enhancement of survival and replating capacity of human hematopoietic progenitor cells were observed with CXCL12alpha, CXCL12beta, and CXCL12epsilon but not with the other variants. CXCL12gamma showed the greatest antiviral activity in X4 inhibition assays and the weakest chemotaxis activity through CXCR4. The order of potency in X4 inhibition assays was as follows: CXCL12gamma > CXCL12beta > CXCL12alpha > CXCL12theta > CXCL12epsilon > CXCL12delta. The order of anti-human immunodeficiency virus (HIV) activity was associated with the number of BBXB motifs present in each variant; the most potent inhibitor was CXCL12gamma, with five BBXB domains. The results suggest that the different C termini of CXCL12 variants may contain important molecular determinants for the observed differences in antiviral effects and other biological functions. These studies implicate CXCL12gamma as a potent HIV-1 entry inhibitor with significantly reduced chemotaxis activity and small or absent effects on progenitor cell survival or replating capacity, providing important insight into the structure-function relationships of CXCL12.

Peptide, Peptidomimetic and Small-molecule Drug Discovery Targeting HIV-1 Host-cell Attachment and Entry through gp120, gp41, CCR5 and CXCR4+

This review highlights selected examples of peptide, peptidomimetic and small-molecule drug discovery targeting HIV-1 to advance novel anti-HIV pharmaceuticals that inhibit initial stages of the viral cycle; namely, attachment and entry. Some of these approaches have culminated in the development of peptide-based drugs, while other have exploited peptides as enabling tools toward the identification of small-molecule lead compounds. Both of these conceptually different approaches have facilitated lead optimization of molecules with complementary and often surprising anti-HIV pharmacological properties, supporting their role in pharmaceutical development. Furthermore, such molecules enabled mechanistic elucidation of viral attachment and entry and provided additional insights toward achieving the desired drug profile.

Identification of carboxypeptidase N as an enzyme responsible for C-terminal cleavage of stromal cell-derived factor-1alpha in the circulation

The chemokine stromal-derived factor-1alpha (SDF-1alpha) is an essential regulator of hematopoiesis, lymphocyte homing, pre-B-cell growth, and angiogenesis. As SDF-1alpha is constitutively expressed in many tissues, chemokine function is mostly regulated by proteolytic degradation. Human serum cleaves the 68-amino acid chemokine, SDF-1alpha, at both termini. The enzyme or enzymes responsible for the removal of the carboxy-terminal lysine from SDF-1alpha, leading to significant reduction in biologic activity, have not been identified. Using a new biochemical assay for measuring the carboxy-terminal cleavage activity, we purified from serum and plasma a peptidase that specifically removes the carboxy-terminal lysine from SDF-1alpha and identified it as carboxypeptidase N (CPN, also known as kininase I, arginine carboxypeptidase, and anaphylotoxin inactivator). We demonstrate that SDF-1alpha in serum and plasma lacks the carboxy terminal lysine, and depletion of CPN from serum and plasma significantly reduces the SDF-1alpha carboxypeptidase activity. Purified CPN effectively and specifically removes the carboxy-terminal lysine from SDF-1alpha and significantly reduces the chemokine's biologic activity as a pre-B-cell growth factor and chemoattractant. Thus, in addition to its role as a regulator of the biologic activity of kinins and anaphylatoxins, CPN is an important regulator of the biologic activity of SDF-1alpha by reducing the chemokine-specific activity.