In the present study we
In the present study, we identified that SDF-1α could significantly elevate the expression of p-P65 in the NF-κB signaling pathway and p-Akt in the PI3K-Akt signaling pathway, while significantly reducing the expression of p-IκB in the NF-κB signaling pathway. AMD3100 and hesperidin antagonized the effect induced by SDF-1α, suggesting that hesperidin inhibited the migration of A549 (±)-Bay K 8644 by blocking the SDF-1/CXCR-4 signaling pathway. Furthermore, the present results demonstrated that hesperidin promoted the activation of the NF-κB signaling pathway. However, our results indicated that hesperidin could increase the level of p-IκB, which is contrary to previous studies in human hepatocellular carcinoma cells and Ramos cells [35,36], suggesting different effects of hesperidin treatment in different tumor types. In addition, the results demonstrated that hesperidin inhibited the migration and invasion of A549 NSCLC cells in a time- and dose-dependent manner, as demonstrated by wound-healing and Transwell assays, which provides a theoretical basis for further trials on NSCLC cell metastasis in rat models.
EMT, the process of cohesive epithelial cells converting to a migratory mesenchymal phenotype, is regarded as a contributing factor in the metastasis of tumor cells [7,37]. Our results indicated that the expression of CK-19, a cytoskeletal protein specifically expressed in epithelial cells, was evidently upregulated in hesperidin-treated A549 cells. Similarly, the protein expression of Vimentin, a mesenchymal marker, and of MMP-9, a mesenchyme-associated molecular marker that serves a vital role in digesting the extracellular matrix to promote tumor cell metastasis  [38,39], was downregulated compared with the control group. This indicated that hesperidin may prevent tumor metastasis by inhibiting the EMT phenotype transformation. In addition, EMT-related proteins were previously reported to be the regulatory targets for downstream molecules of the SDF-1/CXCR-4 axis . Therefore, the inhibition of EMT by hesperidin is of great interest for the treatment of tumors.
Competing financial interests
Acknowledgements This work was supported by the Guizhou Provincial Department of Education Natural Science Research Tender Project Fund (grant no.,  375). We graciously thank Professor Ming Zhang Qian (Department of Biochemistry, Zunyi Medical College) and Dr. Ming Zhuo (University of Texas M. D. Anderson Cancer Center) for their technical assistance.
Introduction Leucocytes play critical roles in innate and adaptive immune systems. During this process, the movement of leucocytes is mediated primarily by the chemokine system, including the chemokine receptors, which interact with a group of peptide ligands and are indispensable for the coordination of migration in diverse physiological processes, such as development, angiogenesis, immune defense and neuroendocrine regulation [, , ]. Based on which ligand they bind, the chemokine receptors can be classified into four subfamilies, including CC chemokine receptors (CCRs), CXCRs, XCRs, and CX3CRs [4,5]. They belong to the largest rhodopsin family of G protein-coupled receptors (GPCRs) and inherited the majority of the repertoires of GPCRs . Structurally, the CXCRs possess seven transmembrane domains (TM1–7), an extracellular N-terminal region, three extracellular hydrophilic loops (ECL1–3), three intracellular loops (ICL1–3) and an intracellular C-terminal region . C-X-C chemokine receptor type 1 (CXCR1) and CXCR2, which mediate leukocyte migration, activation and regulation, have been well characterized in vertebrates [8,9]. CXCR1 primarily binds with CXCL6 and CXCL8 , while CXCR2 interacts with CXCL1–3 and CXCL5–8 . Recent studies have shown that CXCR1 predominantly couples to GPK2, whereas CXCR2 interacts with GPK6 to negatively regulate receptor sensitization and trafficking to influence cell signaling and angiogenesis . This can lead to functional differences. One CXCR2 and two CXCR1 (termed CXCR1a and CXCR1b) homologs have been identified in a wide range of teleost fish species, including common carp , rainbow trout  and zebrafish [15,16]. In mammals, a single CXCR3 has been identified; however, alternative splicing gives rise to two transcript variants . CXCR3 is highly expressed on effector T cells and plays an important role in T cell trafficking and function . CXCR3 can be activated by CXCL9–11 . In teleost fish, two apparent CXCR3 genes are found, termed CXCR3a and CXCR3b [14,20,21]. Among the CXCRs, CXCR4 is the most well studied receptor because of its critical roles in development, and its association with health and disease [22,23]. CXCR4, as well as CXCR5 and CXCR6/Bonzo, has been reported as a coreceptor of HIV and SIV for entry into host cells [, , ]. CXCR4 can bind to CXCL12 to exert its various functions . In recent years, CXCR4 has been characterized with respect to its innate immune role in certain fish species [, , , , ]. Despite reports of these CXCRs in teleost fish, the function of fish CXCR1–4 are largely unknown, especially in economically important fish species, such as the Asian swamp eel (Monopterus albus).