Microglia-Neutrophil Interactions Drive Dry AMD-like Pathology in a Mouse Model

In dry age-related macular degeneration (AMD), inflammation plays a key role in disease pathogenesis. Innate immune cells such as microglia and neutrophils infiltrate the sub-retinal space (SRS) to induce chronic inflammation and AMD progression. But a major gap in our understanding is how these cells interact with each other in AMD. Here, we report a novel concept of how dynamic interactions between microglia and neutrophils contribute to AMD pathology. Using well-characterized genetically engineered mouse models as tools, we show that in the diseased state, retinal pigmented epithelial (RPE) cells trigger pro-inflammatory (M1) transition in microglia with diminished expression of the homeostatic marker, CX3CR1. Activated microglia localize to the SRS and regulate local neutrophil function, triggering their activation and thereby inducing early RPE changes. Ligand receptor (LR)-loop analysis and cell culture studies revealed that M1 microglia also induce the expression of neutrophil adhesion mediators (integrin β1/α4) through their interaction with CD14 on microglia. Furthermore, microglia-induced neutrophil activation and subsequent neutrophil-mediated RPE alterations were mitigated by inhibiting Akt2 in microglia. These results suggest that the Akt2 pathway in microglia drives M1 microglia-mediated neutrophil activation, thereby triggering early RPE degeneration and is a novel therapeutic target for early AMD, a stage without treatment options.

In vitro and in vivo effects of AVA4746, a novel competitive antagonist of the ligand binding of VLA-4, in B-cell acute lymphoblastic leukemia

Treatment of resistant or recurrent acute lymphoblastic leukemia (ALL) remains a challenge. It was previously demonstrated that the adhesion molecule integrin α4, referred to hereafter as α4, mediates the cell adhesion-mediated drug resistance (CAM-DR) of B-cell ALL by binding to vascular cell adhesion molecule-1 (VCAM-1) on bone marrow stroma. In addition, it was previously observed that the blockade of α4 with natalizumab or inhibition using the small molecule antagonist TBC3486 sensitized relapsed ALL cells to chemotherapy. However, α4-targeted therapy is not clinically available for the treatment of leukemia to date. In the present study, the use of a novel non-peptidic small molecule integrin α4 antagonist, AVA4746, as a potential new approach to combat drug-resistant B-ALL was explored. An in vitro co-culture = model of primary B-ALL cells and an in vivo xenograft model of patient-derived B-ALL cells were utilized for evaluation of AVA4746. VLA-4 conformation activation, cell adhesion/de-adhesion, endothelial tube formation, in vivo leukemia cell mobilization and survival assays were performed. AVA4746 exhibited high affinity for binding to B-ALL cells, where it also efficiently blocked ligand-binding to VCAM-1. In addition, AVA4746 caused the functional de-adhesion of primary B-ALL cells from VCAM-1. Inhibition of α4 using AVA4746 also prevented angiogenesis in vitro and when applied in combination with chemotherapy consisting of Vincristine, Dexamethasone and L-asparaginase, it prolonged the survival of ~33% of the mice in an in vivo xenograft model of B-ALL. These data implicate the potential of targeting the α4-VCAM-1 interaction using AVA4746 for the treatment of drug-resistant B-lineage ALL.

Circulating integrin α4 β7 + CD4 T cells are enriched for proliferative transcriptional programs in HIV infection

HIV preferentially infects α₄ β₇ ⁺ CD4 T cells, forming latent reservoirs that contribute to HIV persistence during antiretroviral therapy. However, the properties of α₄ β₇ ⁺ CD4 T cells in blood and mucosal compartments remain understudied. Employing two distinct models of HIV infection, HIV-infected humans and simian-human immunodeficiency virus (SHIV)-infected rhesus macaques, we show that α₄ β₇ ⁺ CD4 T cells in blood are enriched for genes regulating cell cycle progression and cellular metabolism. Unlike their circulating counterparts, rectal α₄ β₇ ⁺ CD4 T cells exhibited a core tissue-residency gene expression program. These features were conserved across primate species, indicating that the environment influences memory T-cell transcriptional networks. Our findings provide an important molecular foundation for understanding the role of α₄ β₇ in HIV infection.

Disruption of integrin α4 in zebrafish leads to cephalic hemorrhage during development

Integrins, transmembrane molecules that facilitate cell-to-cell and cell-to-extracellular matrix interactions, are heterodimers that consist of an α- and β-subunit. The integrin α4 gene (itgα4) is expressed in various type of cells and tissues. Its biochemical functions and physiological roles have been revealed using cultured cell assays. In contrast, the primary effect caused by itgα4 deletion on vertebrate development is poorly understood, because knockout mice exhibit multiple defects that can lead to embryonic lethality in the uterus. Zebrafish are a convenient vertebrate model to investigate morphogenesis during embryogenesis, because of their external fertilization and subsequent development outside the female's body. Here, we generated a zebrafish mutant line named itgα4 ^ko108 using the CRISPR/Cas9 genome editing system; the mutant genome harbored an approximately 2.0-kb deletion in the itgα4 locus. A truncated transcript was detected in itgα4 (+/-) or (-/-) fish but not in (+/+) fish. The mutant transcript was hypothesized to encode a truncated Itgα4 protein due to a premature stop codon. itgα4 (-/-) embryos obtained from the mating of heterozygous parents exhibited no apparent phenotype during development at 24 hours post-fertilization (hpf). However, approximately half of them exhibited cephalic hemorrhage at 48 hpf. The incidence ratio was significantly higher than that in (+/+) or (+/-) embryos. Embryonic hemorrhage has also been reported previously in Itgα4 knockout mice. In contrast, embryonic lethality with the other defects reported in the knockout mice was not observed in our zebrafish model. Therefore, the mutant line itgα4 ^ko108 should be a useful model to investigate a physiological function for Itgα4 in the blood circulation system.

Development of α4 integrin DNA aptamer as a potential therapeutic tool for multiple sclerosis

One of the most important molecules for multiple sclerosis pathogenesis is α4 integrin, which is responsible for autoreactive leukocytes migration into the brain. The monoclonal antibody, natalizumab, was introduced to market for blocking the extravasation of autoreactive leukocytes via inhibition of α4 integrin. However, the disadvantages of antibodies provided a suitable background for other agents to be replaced with antibodies. Considering the profound advantages of aptamers over antibodies, aptamer isolation against α4 integrin was intended in the current study. The α4 integrin-specific aptamers were selected using cell-systematic evolution of ligands by exponential enrichment (SELEX) method with human embryonic kidney (HEK)-293T overexpressing α4 integrin and HEK-293T as target and control cells, respectively. Evaluation of selected aptamer was performed through flow cytometric analysis. The selected clones were then sequenced and analyzed for any possible secondary structure and affinity. The results of this study led to isolation of 13 different single-stranded DNA clones in 11 rounds of selection which were categorized to three clusters based on common structural motifs and the equilibrium dissociation constant (K _d ) of the most stable structure was calculated. The evaluation of SELEX progress showed growth in aptamer affinity with increasing of the number of cycles. Taken together, the findings of this study demonstrated the isolation of α4-specific single-stranded DNA aptamers with suitable affinity for ligand, which can further be replaced with natalizumab.

Do the expressions of epithelial-mesenchymal transition proteins, periostin, integrin-α4 and fibronectin correlate with clinico-pathological features and prognosis of metastatic castration-resistant prostate cancer?

Development of metastatic castration-resistant prostate cancer is a result of the lack of an apoptotic response by the tumor cells and loss of the ability to stick to adjacent cells through epithelial-mesenchymal transition. Although there are several strongly recommended biomarkers for determining prognosis of metastatic castration-resistant prostate cancer, only few of them may help decide the selection of the optimal treatment option. The mode of treatment sequencing in metastatic castration-resistant prostate cancer will be based on the individual characteristics of the patient. In this study, we aimed to explain the correlation between the expression characteristics of periostin, integrin-α4, and fibronectin in metastatic castration-resistant prostate cancer patients and their clinico-pathological data comprising Gleason score, PSA levels, and metastatic sites in the process of epithelial-mesenchymal transition. We evaluated by using Western blotting, periostin, integrin-α4, and fibronectin expressions in peripheral blood samples of metastatic castration-resistant prostate cancer patients ( n = 40), benign prostatic hyperplasia patients ( n = 20), and the healthy control group ( n = 20). Associations between changes in the protein expressions and clinico-pathological parameters were also analyzed in the metastatic castration-resistant prostate cancer group. When comparing BPH and healthy groups with the metastatic castration-resistant prostate cancer group, a reduced expression of integrin-α4 was found in metastatic patients, albeit being statistically insignificant ( P > 0.05). Protein expressions of periostin and fibronectin in the metastatic castration-resistant prostate cancer group were higher than those in the BPH and heathy groups ( P < 0.001). Increased periostin expression in metastatic patients was significantly associated with bone metastasis ( P < 0.05). Elevated periostin and fibronectin levels in metastatic castration-resistant prostate cancer patients may be appropriate targets of therapeutic intervention in the future. Impact statement Prostate cancer is the third most common cancer in the world and the most common cancer among men. Development of metastatic castration-resistant prostate cancer (mCRPC) is a result of the lack of an apoptotic response by the tumor cells and loss of the ability to stick to adjacent cells through epithelial-mesenchymal transition (EMT). The present study analyzes for the first time the expressions of EMT marker proteins - periostin, integrin α4, fibronectin - in mCRPC and in benign prostatic hyperplasia (BPH) with the aim to determine the clinical relevance of changes in these three proteins vis-a-vis the PCa aggressive phenotype. In doing so, it sheds light on the molecular mechanism underlying the disease. We concluded that elevated periostin and fibronectin levels in mCRPC patients may be appropriate targets of therapeutic intervention in the future; hence, adopting methods that target these proteins may help treat prostate cancer effectively.

Integrin α4 Induces Lymphangiogenesis and Metastasis via Upregulation of VEGF-C in Human Colon Cancer

Vascular endothelial growth factor-C (VEGF-C) is a key regulator in lymphangiogenesis, and is overexpressed in various malignancies. Integrin α4β1, a new member of the VEGF-C/VEGF receptor pathway, was found to be overexpressed in melanoma tumors. However, little is known regarding the potential role of integrin α4β1 in lymphangiogenesis and other solid tumors. The aim of this study was to investigate the expression patterns of integrin α4 and VEGF-C in relation to lymphangiogenesis and clinicopathological parameters in human colon cancer. The expression of integrin α4, VEGF-C, and VEGFR-3 was assessed in 71 human colon cancer tissues and 30 paracancerous normal tissues by immunohistochemical staining. Lymphatic microvessel density (LMVD) was measured after D2-40-labeling, and the correlations among different factors were statistically analyzed. The expression of integrin α4, VEGF-C, VEGFR-3, and LMVD was higher in colon cancer tissues compared with the normal paracancerous colon tissues. There was a positive correlation between the expression of integrin α4 and VEGF-C. Integrin α4 and VEGF-C were significantly associated with the clinicopathological parameters (LMVD, Duke's stage, and lymph node metastasis). Kaplan-Meier analyses indicated that patients with high integrin α4 or VEGF-C expression had significantly shorter overall survival and tumor-free survival time. Multivariate analyses suggested that integrin α4 and VEGF-C may serve as independent prognostic factors for human colon cancer. Both integrin α4 and VEGF-C are involved in lymphangiogenesis and lymphatic metastasis. Our results demonstrated that integrin α4 is a novel prognostic indicator for human colon cancer. Anat Rec, 299:741-747, 2016. © 2016 Wiley Periodicals, Inc.

Immunoscreening of a cutaneous T-cell lymphoma library for plasma membrane proteins

Cutaneous T-cell lymphomas (CTCL) belong to non-Hodgkin lymphomas, which are primarily manifested in the skin and mostly exhibit a T-helper memory phenotype. Mycosis fungoides (MF) and the leukemic variant Sézary syndrome (SzS) are the most common forms of CTCL. The aim of this study was to identify CTCL surface proteins with a tumor specific expression profile. A plasma membrane enriched fraction of the CTCL cell line HuT78 was used for immunization of two rabbits. Subsequently, a CTCL cDNA phage library was screened by a new variant of the SEREX method (serological identification of antigens by recombinant expression cloning) using the polyspecific rabbit antisera instead of patients' sera. Isolated reactive transfectants were sequenced and 42 different genes identified including four known plasma membrane proteins: Ligatin, HLA-A, integrin alpha4 and MT5-MMP. The level of transcripts of the matrix metalloproteinase MT5-MMP was diminished in MF tumor specimens. MT5-MMP normally occurs in several different protein variants. Western blot analysis revealed that activated MT5-MMPs were reduced in tumor specimens, whereas the amounts of most of the inactivated variants were unchanged. The amount of mRNA coding for the adhesion protein integrin alpha4 was not altered in tumor specimens in comparison to controls when analyzed by quantitative real-time PCR analysis. Ku86, known to be predominantly located in the nucleus and cytosol, was frequently detected during the SEREX screening. Western blot analysis revealed higher protein amounts of Ku86 in HuT78 than in control cells. In addition, we could show, that Ku86 can also be detected in lipid rafts of CTCL cells as it has been described for other tumor types. Thus, Ku86 might be involved in homo- and heterotypic adhesion steps of CTCL tumor cells and might protect these cells against apoptosis triggered by irradiation as it was suggested for multiple myeloma cells. The design of this study enabled screening for all proteins on the plasma membrane, irrespectively of whether these are directly anchored within the membrane or associated with other membrane proteins. Further analysis will unravel whether the list of identified proteins harbors candidates, which might be accessible for antibodies from outside the cell.