Expression of NF-κB p50 in Tumor Stroma Limits the Control of Tumors by Radiation Therapy

Radiation therapy aims to kill cancer cells with a minimum of normal tissue toxicity. Dying cancer cells have been proposed to be a source of tumor antigens and may release endogenous immune adjuvants into the tumor environment. For these reasons, radiation therapy may be an effective modality to initiate new anti-tumor adaptive immune responses that can target residual disease and distant metastases. However, tumors engender an environment dominated by M2 differentiated tumor macrophages that support tumor invasion, metastases and escape from immune control. In this study, we demonstrate that following radiation therapy of tumors in mice, there is an influx of tumor macrophages that ultimately polarize towards immune suppression. We demonstrate using in vitro models that this polarization is mediated by transcriptional regulation by NFκB p50, and that in mice lacking NFκB p50, radiation therapy is more effective. We propose that despite the opportunity for increased antigen-specific adaptive immune responses, the intrinsic processes of repair following radiation therapy may limit the ability to control residual disease

Lymphangiogenesis Is Required for Pancreatic Islet Inflammation and Diabetes

Lymphangiogenesis is a common phenomenon observed during inflammation and engraftment of transplants, but its precise role in the immune response and underlying mechanisms of regulation remain poorly defined. Here we showed that in response to injury and autoimmunity, lymphangiogenesis occurred around islets and played a key role in the islet inflammation in mice. Vascular endothelial growth factors receptor 3 (VEGFR3) is specifically involved in lymphangiogenesis, and blockade of VEGFR3 potently inhibited lymphangiogenesis in both islets and the draining LN during multiple low-dose streptozotocin (MLDS) induced autoimmune insulitis, which resulted in less T cell infiltration, preservation of islets and prevention of the onset of diabetes. In addition to their well-known conduit function, lymphatic endothelial cells (LEC) also produced chemokines in response to inflammation. These LEC attracted two distinct CX3CR1hi and LYVE-1+ macrophage subsets to the inflamed islets and CX3CR1hi cells were influenced by LEC to differentiate into LYVE-1+ cells closely associated with lymphatic vessels. These observations indicate a linkage among lymphangiogenesis and myeloid cell inflammation during insulitis. Thus, inhibition of lymphangiogenesis holds potential for treating insulitis and autoimmune diabetes

Normalization of the Lymph Node T Cell Stromal Microenvironment in lpr/lpr Mice Is Associated with SU5416-Induced Reduction in Autoantibodies

The vascular-stromal elements of lymph nodes can play important roles in regulating the activities of the lymphocytes within. During model immune responses, the vascular-stromal compartment has been shown to undergo proliferative expansion and functional alterations. The state of the vascular-stromal compartment and the potential importance of this compartment in a spontaneous, chronic model of autoimmunity have not been well studied. Here, we characterize the vascular expansion in MRL-lpr/lpr lymph nodes and attempt to ask whether inhibiting this expansion can interfere with autoantibody generation. We show that characteristics of vascular expansion in enlarging MRL-lpr/lpr lymph nodes resemble that of the VEGF-dependent expansion that occurs in wild-type mice after model immunization. Surprisingly, treatment with SU5416, an inhibitor of VEGF and other receptor tyrosine kinases, did not have sustained effects in inhibiting vascular growth, but attenuated the anti-dsDNA response and altered the phenotype of the double negative T cells that are expanded in these mice. In examining for anatomic correlates of these immunologic changes, we found that the double negative T cells are localized within ectopic follicles around a central B cell patch and that these T cell-rich areas lack the T zone stromal protein ER-TR7 as well as other elements of a normal T zone microenvironment. SU5416 treatment disrupted these follicles and normalized the association between T zone microenvironmental elements and T cell-rich areas. Recent studies have shown a regulatory role for T zone stromal elements. Thus, our findings of the association of anti-dsDNA responses, double negative T cell phenotype, and altered lymphocyte microenvironment suggest the possibility that lymphocyte localization in ectopic follicles protects them from regulation by T zone stromal elements and functions to maintain autoimmune responses. Potentially, altering the lymphocyte microenvironment that is set up by the vascular-stromal compartment can be a means by which to control undesired autoimmune responses

Caveolin-1 Plays a Crucial Role in Inhibiting Neuronal Differentiation of Neural Stem/Progenitor Cells via VEGF Signaling-Dependent Pathway

In the present study, we aim to elucidate the roles of caveolin-1(Cav-1), a 22 kDa protein in plasma membrane invaginations, in modulating neuronal differentiation of neural progenitor cells (NPCs). In the hippocampal dentate gyrus, we found that Cav-1 knockout mice revealed remarkably higher levels of vascular endothelial growth factor (VEGF) and the more abundant formation of newborn neurons than wild type mice. We then studied the potential mechanisms of Cav-1 in modulating VEGF signaling and neuronal differentiation in isolated cultured NPCs under normoxic and hypoxic conditions. Hypoxic embryonic rat NPCs were exposed to 1% O2 for 24 h and then switched to 21% O2 for 1, 3, 7 and 14 days whereas normoxic NPCs were continuously cultured with 21% O2. Compared with normoxic NPCs, hypoxic NPCs had down-regulated expression of Cav-1 and up-regulated VEGF expression and p44/42MAPK phosphorylation, and enhanced neuronal differentiation. We further studied the roles of Cav-1 in inhibiting neuronal differentiation by using Cav-1 scaffolding domain peptide and Cav-1-specific small interfering RNA. In both normoxic and hypoxic NPCs, Cav-1 peptide markedly down-regulated the expressions of VEGF and flk1, decreased the phosphorylations of p44/42MAPK, Akt and Stat3, and inhibited neuronal differentiation, whereas the knockdown of Cav-1 promoted the expression of VEGF, phosphorylations of p44/42MAPK, Akt and Stat3, and stimulated neuronal differentiation. Moreover, the enhanced phosphorylations of p44/42MAPK, Akt and Stat3, and neuronal differentiation were abolished by co-treatment of VEGF inhibitor V1. These results provide strong evidence to prove that Cav-1 can inhibit neuronal differentiation via down-regulations of VEGF, p44/42MAPK, Akt and Stat3 signaling pathways, and that VEGF signaling is a crucial target of Cav-1. The hypoxia-induced down-regulation of Cav-1 contributes to enhanced neuronal differentiation in NPCs

The Herpes Simplex Virus-1 Transactivator Infected Cell Protein-4 Drives VEGF-A Dependent Neovascularization

Herpes simplex virus-1 (HSV-1) causes lifelong infection affecting between 50 and 90% of the global population. In addition to causing dermal lesions, HSV-1 is a leading cause of blindness resulting from recurrent corneal infection. Corneal disease is characterized by loss of corneal immunologic privilege and extensive neovascularization driven by vascular endothelial growth factor-A (VEGF-A). In the current study, we identify HSV-1 infected cells as the dominant source of VEGF-A during acute infection, and VEGF-A transcription did not require TLR signaling or MAP kinase activation. Rather than being an innate response to the pathogen, VEGF-A transcription was directly activated by the HSV-1 encoded immediate early transcription factor, ICP4. ICP4 bound the proximal human VEGF-A promoter and was sufficient to promote transcription. Transcriptional activation also required cis GC-box elements common to the VEGF-A promoter and HSV-1 early genes. Our results suggest that the neovascularization characteristic of ocular HSV-1 disease is a direct result of HSV-1's major transcriptional regulator, ICP4, and similarities between the VEGF-A promoter and those of HSV-1 early genes

Cardiac lymphatics in health and disease

The lymphatic vasculature, which accompanies the blood vasculature in most organs, is indispensable in the maintenance of tissue fluid homeostasis, immune cell trafficking, and nutritional lipid uptake and transport, as well as in reverse cholesterol transport. In this Review, we discuss the physiological role of the lymphatic system in the heart in the maintenance of cardiac health and describe alterations in lymphatic structure and function that occur in cardiovascular pathology, including atherosclerosis and myocardial infarction. We also briefly discuss the role that immune cells might have in the regulation of lymphatic growth (lymphangiogenesis) and function. Finally, we provide examples of how the cardiac lymphatics can be targeted therapeutically to restore lymphatic drainage in the heart to limit myocardial oedema and chronic inflammation.Peer reviewe

Profound but dysfunctional lymphangiogenesis via vascular endothelial growth factor ligands from CD11b+ macrophages in advanced ovarian cancer

Severe ascites is a hallmark of advanced ovarian cancer (OVCA), yet the underlying mechanism that creates an imbalance between peritoneal vascular leakage and lymphatic drainage is unknown. Here, we identified and characterized peritoneal lymphatic vessels in OVCA mice, a model generated by implantation of human OVCA cells into athymic nude mice. The OVCA mice displayed substantial lymphangiogenesis and lymphatic remodeling, massive infiltration of CD11b(+)/LYVE-1(+) macrophages and disseminated carcinomatosis in the mesentery and diaphragm, and progressive chylous ascites formation. Functional assays indicated that the abnormally abundant lymphatic vessels in the diaphragm were not conductive in peritoneal fluid drainage. Moreover, lipid absorbed from the gut leaked out from the aberrant mesenteric lymphatic vessels. Our results indicate that vascular endothelial growth factor (VEGF)-C, VEGF-D, and VEGF-A from CD11b(+) macrophages are responsible for producing OVCA-induced dysfunctional lymphangiogenesis, although other cell types contribute to the increased ascites formation. Accordingly, the combined blockade of VEGF-C/D and VEGF-A signaling with soluble VEGF receptor-3 and VEGF-Trap, respectively, markedly inhibited chylous ascites formation. These findings provide additional therapeutic targets to ameliorate chylous ascites formation in patients with advanced OVCA