Characterization of interleukin-8 receptors in non-human primates

Cellular Efficacy of Fattigated Nanoparticles and Real-Time ROS Occurrence Using Microfluidic Hepatocarcinoma Chip System: Effect of Anticancer Drug Solubility and Shear Stress

The objective of this study was to evaluate the effectiveness of organ-on-chip system investigating simultaneous cellular efficacy and real-time reactive oxygen species (ROS) occurrence of anticancer drug-loaded nanoparticles (NPs) using hepatocarcinoma cells (HepG2) chip system under static and hepatomimicking shear stress conditions (5 dyne/cm2). Then, the role of hepatomimetic shear stress exposed to HepG2 and drug solubility were compared. The highly soluble doxorubicin (DOX) and poorly soluble paclitaxel (PTX) were chosen. Fattigated NPs (AONs) were formed via self-assembly of amphiphilic albumin (HSA)-oleic acid conjugate (AOC). Then, drug-loaded AONs (DOX-AON or PTX-AON) were exposed to a serum-free HepG2 medium at 37 °C and 5% carbon dioxide for 24 h using a real-time ROS sensor chip-based microfluidic system. The cellular efficacy and simultaneous ROS occurrence of free drugs and drug-loaded AONs were compared. The cellular efficacy of drug-loaded AONs varied in a dose-dependent manner and were consistently correlated with real-time of ROS occurrence. Drug-loaded AONs increased the intracellular fluorescence intensity and decreased the cellular efficacy compared to free drugs under dynamic conditions. The half-maximal inhibitory concentration (IC50) values of free DOX (13.4 μg/mL) and PTX (54.44 μg/mL) under static conditions decreased to 11.79 and 38.43 μg/mL, respectively, under dynamic conditions. Furthermore, DOX- and PTX-AONs showed highly decreased IC50 values of 5.613 and 21.86 μg/mL, respectively, as compared to free drugs under dynamic conditions. It was evident that cellular efficacy and real-time ROS occurrence were well-correlated and highly dependent on the drug-loaded nanostructure, drug solubility and physiological shear stress.

Monkey-based research on human disease: the implications of genetic differences

Assertions that the use of monkeys to investigate human diseases is valid scientifically are frequently based on a reported 90-93% genetic similarity between the species. Critical analyses of the relevance of monkey studies to human biology, however, indicate that this genetic similarity does not result in sufficient physiological similarity for monkeys to constitute good models for research, and that monkey data do not translate well to progress in clinical practice for humans. Salient examples include the failure of new drugs in clinical trials, the highly different infectivity and pathology of SIV/HIV, and poor extrapolation of research on Alzheimer's disease, Parkinson's disease and stroke. The major molecular differences underlying these inter-species phenotypic disparities have been revealed by comparative genomics and molecular biology - there are key differences in all aspects of gene expression and protein function, from chromosome and chromatin structure to post-translational modification. The collective effects of these differences are striking, extensive and widespread, and they show that the superficial similarity between human and monkey genetic sequences is of little benefit for biomedical research. The extrapolation of biomedical data from monkeys to humans is therefore highly unreliable, and the use of monkeys must be considered of questionable value, particularly given the breadth and potential of alternative methods of enquiry that are currently available to scientists.

Functional characterization of chimpanzee cytomegalovirus chemokine, vCXCL-1(CCMV)

Human cytomegaloviruses (HCMVs) are important pathogens in immunocompromised patients and newborns. The viral chemokine, vCXCL-1, of the Toledo (Tol) strain of HCMV has been implicated in HCMV virulence. Chimpanzee CMV (CCMV) has several genes with similarity to the vCXCL-1(Tol) gene, UL146. In order to test whether the CCMV viral chemokine, vCXCL-1(CCMV), is similar to vCXCL-1(Tol), we characterized its function in vitro. Receptor binding, activation, chemotaxis, signaling, and apoptosis in neutrophils were compared between vCXCL-1(Tol) and vCXCL-1(CCMV) and host chemokines. Although the homologues had similar activation potentials, chemotactic properties, and signaling, vCXCL-1(CCMV) had a approximately 70-fold lower affinity for CXCR2 and displayed differences in integrin upregulation and neutrophil apoptosis. These data demonstrate that in spite of extensive amino acid variability in vCXCL-1, CCMV may provide a model for assessing the role of vCXCL-1 in CMV pathogenesis in vivo.

Rabbit neutrophil chemotactic protein (NCP) activates both CXCR1 and CXCR2 and is the functional homologue for human CXCL6

Neutrophil chemotactic protein (NCP) is a rabbit CXC chemokine with activating and chemotactic properties on neutrophilic granulocytes. Although its selective activity on neutrophils is demonstrated, its interactions with specific chemokine receptors are not defined. For further functional characterization, NCP was chemically synthesized and was found to be equipotent as natural NCP in neutrophil chemotaxis. To identify its human homologue, we separately expressed two potential rabbit NCP receptors (CXCR1 and CXCR2) in Jurkat cells. Pure synthetic NCP was equally efficient to promote chemotaxis through either rabbit CXCR1 or CXCR2. Moreover, chemotaxis assays on rabbit CXCR1 and CXCR2 transfectants showed that NCP uses the same receptors as interleukin-8 (IL-8), a major rabbit CXC chemokine, but not rabbit GROalpha, which only recognized CXCR2. In addition, specific inhibitors for CXCR1 or CXCR2 reduced rabbit neutrophil chemotaxis induced by NCP and rabbit IL-8. Furthermore, NCP and the structurally related human CXCR1/CXCR2 agonist CXCL6/GCP-2 (granulocyte chemotactic protein-2) cross-desensitized each other in intracellular calcium release assays on human neutrophils, further indicating that both chemokines share the same receptors. The inflammatory role of NCP was also evidenced by its potent granulocytosis inducing capacity in rabbits upon systemic administration. This study provides in vitro and in vivo evidences that NCP is the functional rabbit homologue for human CXCL6/GCP-2 rather than the most related CXCR2 agonist CXCL5/ENA-78 (epithelial cell-derived neutrophil activating peptide-78). It is concluded that the rabbit is a better model to study human neutrophil activation compared to mice, which lack CXCL8/IL-8.

Molecular cloning and genomic structure of an interleukin-8 receptor-like gene from homozygous clones of rainbow trout (Oncorhynchus mykiss)

Chemokines are small proteins (70-100 amino acids) which play an important role in recruitment and activation of leucocytes to migrate to the site of inflammation. Based on the position of the first two conserved cysteines, chemokines are classified into four subfamilies: C, CC, CXC and CX3C. To date, many members of CC and CXC have been found and studied extensively [1]. Chemokines exert effects on their target cell via chemokine receptors, which are G-protein coupled receptors containing seven transmembrane domains with an extracellular N-terminus and an intracellular C-terminus [2]. Interleukin 8 (IL-8) belongs to the CXC chemokine subfamily. It can activate and attract migratory neutrophils to an inflammation site. Two IL-8 receptors, CXCR1 and CXCR2, have been identified in mammals [3-6]; both of these receptors have high affinity for IL-8 and are expressed on the neutrophil. CXCR1 just binds IL-8; however, CXCR2 binds IL-8 and other structurally related chemokines such as growth-related oncogene (GRO) a, GRObeta, GROgamma, neutrophil-activating peptide-2 (NAP-2) and epithelial cell-derived neutrophil activating peptide-78 (ENA-78) [7, 8]. Several studies on fish chemokine receptors have been reported [9-11]. Thus far, however, IL-8 and CXCR1 and CXCR2 proteins from rainbow trout have not been reported: however, the sequence of a rainbow trout IL-8 has been noted (GenBank Accession No. AJ279069 [12]). Cloning of the IL-8 receptor is important to study the function of IL-8/CXCR1 and (CXCR2) in inflammation and signal transduction in fish. This paper reports the molecular cloning and genomic structure of an IL-8 receptor-like gene from four homozygous clones of rainbow trout: Oregon State University (OSU), Hot Creek (HC), Arlee (AR) and Swanson (SW).

Molecular evolution of the N-formyl peptide and C5a receptors in non-human primates

N-formyl peptides (FMLP) and complement fragment C5a are neutrophil chemoattractants. In humans, a single-copy gene was identified for the C5a receptor, and the receptor for FMLP (FPR1) is encoded by a single gene that shows 53% amino acid similarity to the C5aR. Two other human FPR1 homologues, FPR-like 1 (FPR2/FPRL1) and FPR-like 2 (FPRL2) have been cloned. The human C5aR, FPR1, FPRL1, and FPRL2 are physically linked. By direct sequencing or by sequencing plasmid clones we studied the C5aR and FPR genes from four non-human primates (chimpanzee, gorilla, orangutan, and macaque). The sequences showed 95% - 99% similarity to the human homologues, with the major divergences observed in macaque. In these genes, the transmembrane and the cytoplasmic domains are highly conserved, while the highest divergence corresponded to the extracellular loops involved in ligand binding. Additionally, we constructed a physical map of these genes in non-human primates. In all species the four genes were physically linked and we defined the relative orientation of the four genes in primates: C5aR>FPR1>FPR2 (FPRL1)>FPRL2.