Pathological roles of the homeostatic chemokine CXCL12

CXCL12 is a CXC chemokine that traditionally has been classified as a homeostatic chemokine. It contributes to physiological processes such as embryogenesis, hematopoiesis and angiogenesis. In contrast to these homeostatic functions, increased expression of CXCL12 in general, or of a specific CXCL12 splicing variant has been demonstrated in various pathologies. In addition to this increased or differential transcription of CXCL12, also upregulation of its receptors CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3) contributes to the onset or progression of diseases. Moreover, posttranslational modification of CXCL12 during disease progression, through interaction with locally produced molecules or enzymes, also affects CXCL12 activity, adding further complexity. As CXCL12, CXCR4 and ACKR3 are broadly expressed, the number of pathologies wherein CXCL12 is involved is growing. In this review, the role of the CXCL12/CXCR4/ACKR3 axis will be discussed for the most prevalent pathologies. Administration of CXCL12-neutralizing antibodies or small-molecule antagonists of CXCR4 or ACKR3 delays disease onset or prevents disease progression in cancer, viral infections, inflammatory bowel diseases, rheumatoid arthritis and osteoarthritis, asthma and acute lung injury, amyotrophic lateral sclerosis and WHIM syndrome. On the other hand, CXCL12 has protective properties in Alzheimer's disease and multiple sclerosis, has a beneficial role in wound healing and has crucial homeostatic properties in general.

Delivery of stromal cell-derived factor 1α for in situ tissue regeneration

In situ tissue regeneration approach aims to exploit the body's own biological resources and reparative capability and recruit host cells by utilizing cell-instructive biomaterials. In order to immobilize and release bioactive factors in biomaterials, it is important to engineer the load effectiveness, release kinetics and cell recruiting capabilities of bioactive molecules by using suitable bonding strategies. Stromal cell-derived factor 1α (SDF-1α) is one of the most potent chemokines for stem cell recruitment, and SDF-1α-loaded scaffolds have been used for the regeneration of many types of tissues. This review summarizes the strategies to incorporate SDF-1α into scaffolds, including direct loading or adsorption, polyion complexes, specific heparin-mediated interaction and particulate system, which may be applied to the immobilization of other chemokines or growth factors. In addition, we discuss the application of these strategies in the regeneration of tissues such as blood vessel, myocardium, cartilage and bone.

CXCL12 regulates platelet activation via the regulator of G-protein signaling 16

The regulators of G protein signaling (RGS) protein superfamily negatively controls G protein-coupled receptor signal transduction pathways. One of the members of this family, RGS16, is highly expressed in megakaryocytes and platelets. Studies of its function in platelet and megakaryocyte biology have been limited, in part, due to lack of pharmacological inhibitors. For example, RGS16 overexpression inhibited CXC chemokine receptor 4 (CXCR4)-mediated megakaryocyte migration. More recent studies showed that the chemokine stromal cell-derived factor (SDF1α or CXCL12) regulates platelet function via CXCR4. Based on these considerations, the present study investigated the capacity of RGS16 to regulate CXCL12-dependent platelet function, using the RGS16 knockout mouse model (Rgs16(-/-)). RGS16-deficient platelets had increased protease activated receptor 4 and collagen-induced aggregation, as well as increased CXCL12-dependent agonist-induced aggregation, dense and alpha granule secretion, integrin αIIbβ3 activation and phosphatidylserine exposure compared to those from WT littermates. CXCL12 alone did not stimulate aggregation or secretion in either RGS16-deficient or WT platelets. Furthermore, platelets from Rgs16(-/-) mice displayed enhanced phosphorylation of ERK and Akt following CXCL12 stimulation relative to controls. Finally, we also found that PKCδ is involved in regulating CXCL12-dependent activation of ERK and Akt, in the Rgs16-deficient platelets. Collectively, our findings provide the first evidence that RGS16 plays an important role in platelet function by modulating CXCL12-dependent platelet activation.

Primordial germ cell migration in the yellowtail kingfish (Seriola lalandi) and identification of stromal cell-derived factor 1

Primordial germ cells (PGCs) are progenitors of the germ cell lineage, giving rise to either spermatogonia or oogonia after the completion of gonadal differentiation. Currently, there is little information on the mechanism of PGCs migration leading to the formation of the primordial gonad in perciform fish. Yellowtail kingfish (Seriola lalandi) (YTK) (order Perciforms) inhabit tropical and temperate waters in the southern hemisphere. Fundamental details into the molecular basis of larval development in this species can be easily studied in Australia, as they are commercially cultured and readily available. In this study, histological analysis of YTK larvae revealed critical time points for the migration of PGCs to the genital ridge, resulting in the subsequent development of the primordial gonad. In YTK larvae at 3, 5, 7 and 10 days post hatch (DPH), PGCs were not yet enclosed by somatic cells, indicating the primordial gonad had not yet started to form. While at 15, 18 and 20 DPH PGCs had already settled at the genital ridge and started to become enclosed by somatic cells indicating the primordial gonad had started to develop. A higher number of PGCs were observed in the larvae at 15 and 18 DPH indicating PGCs proliferation, which corresponds with them becoming enclosed by the somatic cells. Directional migration of PGCs toward the genital ridge is a critical event in the subsequent development of a gonad. In zebrafish, mouse and chicken, stromal-cell derived factor (SDF1) signalling is one of the key molecules for PGC migration. We subsequently isolated from YTK the SDF1 (Slal-SDF1) gene, which encodes for a 98-residue precursor protein with a signal peptide at the N-terminus. There is spatial conservation between fish species of four cysteine residues at positions C9, C11, C34 and C49, expected to form disulphide bonds and stabilize the SDF structure. In YTK, Slal-SDF1 gene expression analyses shows that this gene is expressed in larvae from 1 to 22 DPH and demonstrates distinct spatial localisation in the larvae at 7 DPH. These results provide a platform for further studies into the molecular machinery of PGC migration in yellowtail kingfish, as well as other perciform fish species.

Serum ENA78/CXCL5, SDF-1/CXCL12, and their combinations as potential biomarkers for prediction of the presence and distant metastasis of primary gastric cancer

BACKGROUND

Chemokines play important roles in cancer development and progression. Epithelial-derived neutrophil-activating peptide-78 (ENA78/CXCL5) and stromal cell-derived factor (SDF-1/CXCL12) supposedly contribute to gastric cancer (GC) development and progression. This study aims to evaluate serum levels of ENA78/CXCL5 and SDF-1/CXCL12 along the GC carcinogenesis, and analyze their clinical significance, and diagnostic potentials through human serum samples.

METHODS

A total of 300 subjects were enrolled in this study. Serum levels of ENA78/CXCL5 and SDF-1/CXCL12, measured by chemiluminescent immunoassay, were compared among 4 disease groups; normal, high-risk (intestinal metaplasia and adenoma), early GC (EGC), and advanced GC (AGC) groups in both training (n=25 per group) and validation dataset (n=70, 30, 50, 50, respectively) by ANOVA test (post hoc Bonferroni). Correlations between serum ENA78/CXCL5 or SDF-1/CXCL12 levels and clinicopathological parameters of GC patients were evaluated (Spearman's correlation; γs). To validate the diagnostic accuracy, receiver operating characteristic (ROC) curve and logistic regression analysis was performed.

RESULTS

Serum ENA78/CXCL5 and SDF-1/CXCL12 levels were significantly higher in AGC groups than EGC, high-risk and normal groups in both training and validation dataset (Bonferroni, from p<0.01 to p<0.001). Clinicopathologically, serum ENA78/CXCL5 was correlated with T-stage (γs=0.231, p=0.021) and distant metastasis (γs=0.357, p<0.001), while serum SDF-1/CXCL12 was correlated with lymph node (γs=0.220, p=0.029) and distant (γs=0.425, p<0.001) metastasis. ROC curve and logistic regression demonstrated that serum ENA78/CXCL5 and SDF-1/CXCL12 showed higher diagnostic accuracy compared with carcinoembryonic antigen (CEA) in predicting GC. Serum ENA78/CXCL5 could predict both the presence of GC and distant metastasis, while serum SDF-1/CXCL12 could mainly predict its distant metastasis. All combination of serum ENA78/CXCL5, SDF-1/CXCL12, and CEA achieved 92.8% specificity at 75.0% sensitivity to predict distant metastasis of GC.

CONCLUSIONS

Combinations of initial serum ENA78/CXCL5, SDF-1/CXCL12, and CEA before any treatment for GC can produce valuable serum biomarker panels to predict the presence and distant metastasis of GC.