A novel function for programmed death ligand-1 regulation of angiogenesis

Potential applications of mesenchymal stem cells in ocular surface immune-mediated disorders

We explore the interaction between corneal immunity and mesenchymal stem/stromal cells (MSCs) and their potential in treating corneal and ocular surface disorders. We outline the cornea's immune privilege mechanisms and the immunomodulatory substances involved. In this realm, MSCs are characterized by their immunomodulatory properties and regenerative potential, making them promising for therapeutic application. Therefore, we focus on the role of MSCs in immune-mediated corneal diseases such as dry eye disease, corneal transplantation rejection, limbal stem cell deficiency, and ocular graft-versus-host disease. Preclinical and clinical studies demonstrate MSCs' efficacy in promoting corneal healing and reducing inflammation in these conditions. Overall, we emphasize the potential of MSCs as innovative therapies in ophthalmology, offering promising solutions for managing various ocular surface pathologies.

Mast cells and ocular surface: An update review

Mast cells (MCs), traditionally viewed as key players in IgE-mediated allergic responses, are increasingly recognized for their versatile roles. Situated at critical barrier sites such as the ocular surface, these sentinel cells participate in a broad array of physiological and pathological processes. This review presents a comprehensive update on the immune pathophysiology of MCs, with a particular focus on the mechanisms underlying innate immunity. It highlights their roles at the ocular surface, emphasizing their participation in allergic reactions, maintenance of corneal homeostasis, neovascularization, wound healing, and immune responses in corneal grafts. The review also explores the potential of MCs as therapeutic targets, given their significant contributions to disease pathogenesis and their capacity to modulate immunity. Through a thorough examination of current literature, we aim to elucidate the immune pathophysiology and multifaceted roles of MCs in ocular surface health and disease, suggesting directions for future research and therapeutic innovation.

PD-1/PD-L1 Provides Protective Role in Hypoxia-Induced Pulmonary Vascular Remodeling

BACKGROUND

Hypoxia-induced pulmonary hypertension (HPH) is a T helper 17 cell response-driven disease, and PD-1 (programmed cell death 1)/PD-L1 (programmed cell death-ligand 1) inhibitor-associated pulmonary hypertension has been reported recently. This study is designed to explore whether the PD-1/PD-L1 pathway participates in HPH via regulating endothelial dysfunction and T helper 17 cell response.

METHODS

Lung tissue samples were obtained from eligible patients. Western blotting, immunohistochemistry, and immunofluorescence techniques were used to assess protein expression, while immunoprecipitation was utilized to detect ubiquitination. HPH models were established in C57BL/6 WT (wild-type) and PD-1-/- mice, followed by treatment with PD-L1 recombinant protein. Adeno-associated virus vector delivery was used to upregulate PD-L1 in the endothelial cells. Endothelial cell function was assessed through assays for cell angiogenesis and adhesion.

RESULTS

Expression of the PD-1/PD-L1 pathway was downregulated in patients with HPH and mouse models, with a notable decrease in PD-L1 expression in endothelial cells compared with the normoxia group. In comparison to WT mice, PD-1-/- mice exhibited a more severe HPH phenotype following exposure to hypoxia, However, administration of PD-L1 recombinant protein and overexpression of PD-L1 in lung endothelial cells mitigated HPH. In vitro, blockade of PD-L1 with a neutralizing antibody promoted endothelial cell angiogenesis, adhesion, and pyroptosis. Mechanistically, hypoxia downregulated PD-L1 protein expression through ubiquitination. Additionally, both in vivo and in vitro, PD-L1 inhibited T helper 17 cell response through the PI3K (phosphoinositide 3-kinase)/AKT (protein kinase B)/mTOR (mammalian target of rapamycin) pathway in HPH.

CONCLUSIONS

PD-1/PD-L1 plays a role in ameliorating HPH development by inhibiting T helper 17 cell response through the PI3K/AKT/mTOR pathway and improving endothelial dysfunction, suggesting a novel therapeutic indication for PD-1/PD-L1-based immunomodulatory therapies in the treatment of HPH.

IL-36γ Augments Ocular Angiogenesis by Promoting the Vascular Endothelial Growth Factor-Vascular Endothelial Growth Factor Receptor Axis

Prevention of inflammatory angiogenesis is critical for suppressing chronic inflammation and inhibiting inflammatory tissue damage. Angiogenesis is particularly detrimental to the cornea because pathologic growth of new blood vessels can lead to marked vision impairment and even loss of vision. The expression of proinflammatory cytokines by injured tissues exacerbates the inflammatory cascade, including angiogenesis. IL-36 cytokine, a subfamily of the IL-1 superfamily, consists of three proinflammatory agonists, IL-36α, IL-36β, and IL-36γ, and an IL-36 receptor antagonist (IL-36Ra). Data from the current study indicate that human vascular endothelial cells constitutively expressed the cognate IL-36 receptor. The current investigation, for the first time, characterized the direct contribution of IL-36γ to various angiogenic processes. IL-36γ up-regulated the expression of vascular endothelial growth factors (VEGFs) and their receptors VEGFR2 and VEGFR3 by human vascular endothelial cells, suggesting that IL-36γ mediates the VEGF-VEGFR signaling by endothelial cells. Moreover, by using a naturally occurring antagonist IL-36Ra in a murine model of inflammatory angiogenesis, this study demonstrated that blockade of endogenous IL-36γ signaling results in significant retardation of inflammatory angiogenesis. The current investigation on the proangiogenic function of IL-36γ provides novel evidence of the development of IL-36γ-targeting strategies to hamper inflammatory angiogenesis.

Contemporary clinical trials in pancreatic cancer immunotherapy targeting PD-1 and PD-L1

Pancreatic cancer (PC) is a major gastrointestinal cancer in terms of worldwide incidence and mortality. Despite advances in diagnostic and treatment modalities, the mortality of PC is still a serious concern in both sexes. Immune therapy using inhibitors of immune checkpoints, especially inhibitors of programmed cell death protein 1/programmed cell death ligand-1(PD-1/PD-L1), offer huge benefits to cancer patients. This review describes an up-to-date information on the role of PD-1 and PD-L1 in the development of immune tolerance in PC alongside the current clinical trials and the known outcomes citing the available literature. We also included the details on PD-1/PD-L1-mediated signalling in maintenance of PC stem cells and metastasis. We reviewed the critical information on safety, tolerance, and efficacy of clinically important regimens of PD-1/PD-L1 blocking agents and targeted therapeutics. This review elucidates the underlying mechanisms of PD-1/PD-L1 alliance in tolerance of the immune system, maintenance of stem cells, and metastasis promotion as well as design regimens with high safety and excellent tolerability and efficacy for management of PC in advanced stages.

Immune regulation of the ocular surface

Despite constant exposure to various environmental stimuli, the ocular surface remains intact and uninflamed while maintaining the transparency of the cornea and its visual function. This 'immune privilege' of the ocular surface is not simply a result of the physical barrier function of the mucosal lining but, more importantly, is actively maintained through a variety of immunoregulatory mechanisms that prevent the disruption of immune homeostasis. In this review, we focus on essential molecular and cellular players that promote immune quiescence in steady-state conditions and suppress inflammation in disease-states. Specifically, we examine the interactions between the ocular surface and its local draining lymphoid compartment, by encompassing the corneal epithelium, corneal nerves and cornea-resident myeloid cells, conjunctival goblet cells, and regulatory T cells (Treg) in the context of ocular surface autoimmune inflammation (dry eye disease) and alloimmunity (corneal transplantation). A better understanding of the immunoregulatory mechanisms will facilitate the development of novel, targeted immunomodulatory strategies for a broad range of ocular surface inflammatory disorders.

Programmed death (PD)-1/PD-ligand 1 blockade mediates antiangiogenic effects by tumor-derived CXCL10/11 as a potential predictive biomarker

Immune checkpoint inhibitor (ICI) programmed death (PD)-1/PD-ligand 1 (PD-L1) blockade has been approved for various cancers. However, the underlying antitumor mechanisms mediated by ICIs and the predictive biomarkers remain unclear. We report the effects of anti-PD-L1/PD-1 Ab in tumor angiogenesis. In syngeneic mouse models, anti-PD-L1 Ab inhibited tumor angiogenesis and induces net-like hypoxia only in ICI-sensitive cell lines. In tumor tissue and serum of ICI-sensitive cell line-bearing mice, interferon-γ (IFN-γ) inducible angiostatic chemokines CXCL10/11 were upregulated by PD-L1 blockade. In vitro, CXCL10/11 gene upregulation by IFN-γ stimulation in tumor cell lines correlated with the sensitivity of PD-L1 blockade. The CXCL10/11 receptor CXCR3-neutralizing Ab or CXCL11 silencing in tumor cells inhibited the antiangiogenic effect of PD-L1 blockade in vivo. In pretreatment serum of lung carcinoma patients receiving anti-PD-1 Ab, the concentration of CXCL10/11 significantly correlated with the clinical outcome. Our results indicate the antiangiogenic function of PD-1/PD-L1 blockade and identify tumor-derived CXCL10/11 as a potential circulating biomarker of therapeutic sensitivity.

Corneal lymphangiogenesis as a potential target in dry eye disease - a systematic review

Dry eye disease (DED) is a common ocular surface condition causing symptoms of significant discomfort, visual disturbance, and pain. With recent advancements, DED has become recognized as a chronic self-perpetuating inflammatory condition triggered by various internal and environmental factors. DED has been shown to arise from the activation of both the innate and adaptive immune systems, leading to corneal epithelium and lacrimal gland dysfunction. While the cornea is normally avascular and thus imbued with angiogenic and lymphangiogenic privilege, various DED models have revealed activated corneal antigen-presenting cells in regional lymph nodes, suggesting the formation of new corneal lymphatic vessels in DED. The recent availability of reliable lymphatic cell surface markers such as LYVE-1 has made it possible to study lymphangiogenesis. Accordingly, numerous studies have been published within the last decade discussing the role of lymphangiogenesis in DED pathology. We systematically review the literature to identify and evaluate studies presenting data on corneal lymphangiogenesis in DED. There is considerable evidence supporting corneal lymphangiogenesis as a central mediator of DED pathogenesis. These findings suggest that anti-lymphangiogenic therapeutic strategies may be a viable option for the treatment of DED, a conclusion supported by the limited number of reported clinical trials examining anti-lymphangiogenic modalities in DED.

Corneal Lymphangiogenesis: Current Pathophysiological Understandings and Its Functional Role in Ocular Surface Disease

The cornea is a transparent and avascular tissue that plays a central role in light refraction and provides a physical barrier to the external environment. Corneal avascularity is a unique histological feature that distinguishes it from the other parts of the body. Functionally, corneal immune privilege critically relies on corneal avascularity. Corneal lymphangiogenesis is now recognized as a general pathological feature in many pathologies, including dry eye disease (DED), corneal allograft rejection, ocular allergy, bacterial and viral keratitis, and transient corneal edema. Currently, sizable data from clinical and basic research have accumulated on the pathogenesis and functional role of ocular lymphangiogenesis. However, because of the invisibility of lymphatic vessels, ocular lymphangiogenesis has not been studied as much as hemangiogenesis. We reviewed the basic mechanisms of lymphangiogenesis and summarized recent advances in the pathogenesis of ocular lymphangiogenesis, focusing on corneal allograft rejection and DED. In addition, we discuss future directions for lymphangiogenesis research.

Autoimmunity in dry eye disease - An updated review of evidence on effector and memory Th17 cells in disease pathogenicity

The classic Th1/Th2 dogma has been significantly reshaped since the subsequent introduction of several new T helper cell subsets, among which the most intensively investigated during the last decade is the Th17 lineage that demonstrates critical pathogenic roles in autoimmunity and chronic inflammation - including the highly prevalent dry eye disease. In this review, we summarize current concepts of Th17-mediated disruption of ocular surface immune homeostasis that leads to autoimmune inflammatory dry eye disease, by discussing the induction, activation, differentiation, migration, and function of effector Th17 cells in disease development, highlighting the phenotypic and functional plasticity of Th17 lineage throughout the disease initiation, perpetuation and sustention. Furthermore, we emphasize the most recent advance in Th17 memory formation and function in the chronic course of dry eye disease, a major area to be better understood for facilitating the development of effective treatments in a broader field of autoimmune diseases that usually present a chronic course with recurrent episodes of flare in the target tissues or organs.

Diagnostic utility of programmed cell death ligand 1 (clone SP142) immunohistochemistry for malignant lymphoma and lymphoproliferative disorders: A brief review

The programmed cell death 1 (PD1)/PD1 ligand (PD-L1) axis plays an important role in tumor cell escape from immune control and has been most extensively investigated for therapeutic purposes. However, PD-L1 immunohistochemistry is still not used widely for diagnosis. We review the diagnostic utility of PD-L1 (by clone SP142) immunohistochemistry in large-cell lymphomas, mainly consisting of classic Hodgkin lymphoma (CHL) and diffuse large B-cell lymphoma (DLBCL). Neoplastic PD-L1 (nPD-L1) expression on Hodgkin and Reed-Sternberg cells is well-established among prototypic CHL. Of note, EBV+ CHL often poses a challenge for differential diagnosis from peripheral T-cell lymphoma with EBV+ non-malignant large B-cells; their distinction is based on the lack of PD-L1 expression on large B-cells in the latter. The nPD-L1 expression further provides a good diagnostic consensus for CHL with primary extranodal disease conceivably characterized by a combined pathogenesis of immune escape of tumor cells and immunodeficiency. Compared with CHL, the nPD-L1 expression rate is much lower in DLBCL, highlighting some specific subgroups of intravascular large B-cell lymphoma, primary mediastinal large B-cell lymphoma, and EBV+ DLBCL. They consist of nPD-L1-positive and -negative subgroups, but their clinicopathological significance remains to be elucidated. Microenvironmental PD-L1 positivity on immune cells may be associated with a favorable prognosis in extranodal DLBCL. PD-L1 (by SP142) immunohistochemistry has helped us to understand the immune biology of lymphoid neoplasms possibly related by immune escape and/or immunodeficiency. However, knowledge of these issues remains limited and should be clarified for diagnostic consensus in the future.

Spatial Distribution of Mast Cells Regulates Asymmetrical Angiogenesis at the Ocular Surface

Mast cells, historically known for their function as effector cells in the induction of allergic diseases, reside in all vascularized tissues of the body, particularly, in proximity to blood and lymphatic vessels. Despite being neighboring sentinel cells to blood vessels, whether the spatial distribution of mast cells regulates the degree of angiogenesis remains to be investigated. Herein, an asymmetrical distribution of mast cells was shown at the murine ocular surface, with the higher number of mast cells distributed along the nasal limbus of the cornea compared with the temporal side. Using a well-characterized murine model of suture-induced corneal neovascularization, insult to the nasal side was shown to result in more extensive angiogenesis compared with that to the temporal side. To directly assess the impact of the spatial distribution of mast cell on angiogenesis, neovascularization was induced in mast cell-deficient mice (cKit^w-sh). Unlike the wild-type (C57BL/6) mice, cKit^w-sh mice did not show disproportionate growth of corneal blood vessels following the temporal and nasal insult. Moreover, cromolyn-mediated pharmacologic blockade of mast cells at the ocular surface attenuated the asymmetrical nasal and temporal neovascularization, suggesting that spatial distribution of mast cells significantly contributes to angiogenic response at the ocular surface.

Corneal angiogenic privilege and its failure

The cornea actively maintains its own avascular status to preserve its ultimate optical function. This corneal avascular state is also defined as "corneal angiogenic privilege", which results from a critical and sensitive balance between anti-angiogenic and pro-angiogenic mechanisms. In our review, we aim to explore the complex equilibrium among multiple mediators which prevents neovascularization in the resting cornea, as well as to unveil the evolutive process which leads to corneal angiogenesis in response to different injuries.

Delicate Role of PD-L1/PD-1 Axis in Blood Vessel Inflammatory Diseases: Current Insight and Future Significance

Immune checkpoint molecules are the antigen-independent generator of secondary signals that aid in maintaining the homeostasis of the immune system. The programmed death ligand-1 (PD-L1)/PD-1 axis is one among the most extensively studied immune-inhibitory checkpoint molecules, which delivers a negative signal for T cell activation by binding to the PD-1 receptor. The general attributes of PD-L1's immune-suppressive qualities and novel mechanisms on the barrier functions of vascular endothelium to regulate blood vessel-related inflammatory diseases are concisely reviewed. Though targeting the PD-1/PD-L1 axis has received immense recognition-the Nobel Prize in clinical oncology was awarded in the year 2018 for this discovery-the use of therapeutic modulating strategies for the PD-L1/PD-1 pathway in chronic inflammatory blood vessel diseases is still limited to experimental models. However, studies using clinical specimens that support the role of PD-1 and PD-L1 in patients with underlying atherosclerosis are also detailed. Of note, delicate balances in the expression levels of PD-L1 that are needed to preserve T cell immunity and to curtail acute as well as chronic infections in underlying blood vessel diseases are discussed. A significant link exists between altered lipid and glucose metabolism in different cells and the expression of PD-1/PD-L1 molecules, and its possible implications on vascular inflammation are justified. This review summarizes the most recent insights concerning the role of the PD-L1/PD-1 axis in vascular inflammation and, in addition, provides an overview exploring the novel therapeutic approaches and challenges of manipulating these immune checkpoint proteins, PD-1 and PD-L1, for suppressing blood vessel inflammation.

Activation of ocular surface mast cells promotes corneal neovascularization

PURPOSE

Mast cells, historically known for their effector function in the induction of allergic diseases, reside in all vascularized tissues of the body in particular proximity to blood and lymphatic vessels. As neighboring sentinel cells to blood vessels, mast cells have been associated with angiogenesis. Here we assess the direct contribution of mast cells to neovascularization at the ocular surface.

METHODS

Corneal neovascularization was induced by placing a single figure-of-eight intrastromal suture 1 mm from the limbus in mast cell-deficient (cKit^W-sh), C57BL/6, and Balb/c mice. Corneas were harvested at 6 h post-suture to quantify cKit⁺FcεR1⁺ mast cells using flow cytometry and tear wash was collected within 6 h to measure β-hexosaminidase and tryptase. Neovascularization was assessed using slit-lamp biomicroscope and immunohistochemistry analysis of corneas harvested on day 4 post-suture. To investigate the effects of mast cells on blood vessel growth, mast cells were co-cultured with vascular endothelial cells (VECs), and tube formation and proliferation of VECs were measured. 2% cromolyn was administered locally to inhibit mast cell activation in vivo.

RESULTS

Placement of corneal suture activates ocular surface mast cells, which infiltrate into the cornea adjacent to new vessels. Mast cell-deficient mice develop significantly fewer new vessels following suture placement. Mast cells directly promote VEC proliferation and tube formation, partly through secreting high levels of VEGF-A. Pharmacological inhibition of mast cell activation results in significantly less corneal neovascularization.

CONCLUSION

Our data demonstrate that ocular surface mast cells are critical to corneal neovascularization, suggesting mast cells as a potential therapeutic target in the treatment of corneal neovascularization.

Immunomodulatory Strategies Targeting Dendritic Cells to Improve Corneal Graft Survival

Even though the cornea is regarded as an immune-privileged tissue, transplantation always comes with the risk of rejection due to mismatches between donor and recipient. It is common sense that an alternative to corticosteroids as the current gold standard for treatment of corneal transplantation is needed. Since blood and lymphatic vessels have been identified as a severe risk factor for corneal allograft survival, much research has focused on vessel regression or inhibition of hem- and lymphangiogenesis in general. However, lymphatic vessels have been identified as required for the inflammation's resolution. Therefore, targeting other players of corneal engraftment could reveal new therapeutic strategies. The establishment of a tolerogenic microenvironment at the graft site would leave the recipient with the ability to manage pathogenic conditions independent from transplantation. Dendritic cells (DCs) as the central player of the immune system represent a target that allows the induction of tolerogenic mechanisms by many different strategies. These strategies are reviewed in this article with regard to their success in corneal transplantation.

PD-1 Blockade During Post-partum Involution Reactivates the Anti-tumor Response and Reduces Lymphatic Vessel Density

Post-partum breast cancer patients, or breast cancer patients diagnosed within 10 years of last childbirth, are ~3-5 times more likely to develop metastasis in comparison to non-post-partum, or nulliparous, patients. Additionally, post-partum patients have increased tumor-associated lymphatic vessels and LN involvement, including when controlled for size of the primary tumor. In pre-clinical, immune-competent, mouse mammary tumor models of post-partum breast cancer (PPBC), tumor growth and lymphogenous tumor cell spread occur more rapidly in post-partum hosts. Here we report on PD-L1 expression by lymphatic endothelial cells and CD11b+ cells in the microenvironment of post-partum tumors, which is accompanied by an increase in PD-1 expression by T cells. Additionally, we observed increases in PD-L1 and PD-1 in whole mammary tissues during post-partum mammary gland involution; a known driver of post-partum tumor growth, invasion, and metastasis in pre-clinical models. Importantly, implantation of murine mammary tumor cells during post-partum mammary gland involution elicits a CD8+ T cell population that expresses both the co-inhibitory receptors PD-1 and Lag-3. However, upon anti-PD-1 treatment, during post-partum mammary gland involution, the involution-initiated promotional effects on tumor growth are reversed and the PD-1, Lag-3 double positive population disappears. Consequently, we observed an expansion of poly-functional CD8+ T cells that produced both IFNγ and TNFα. Finally, lymphatic vessel frequency decreased significantly following anti-PD-1 suggesting that anti-PD-1/PD-L1 targeted therapies may have efficacy in reducing tumor growth and dissemination in post-partum breast cancer patients.

The secreted Ly6/uPAR-related protein-1 suppresses neutrophil binding, chemotaxis, and transmigration through human umbilical vein endothelial cells

The secreted Ly-6/uPAR Related Protein-1 (SLURP1) is an immunomodulatory protein that promotes corneal immune- and angiogenic-privilege. Here, we have examined the influence of SLURP1 on neutrophil-vascular endothelial cell interactions using human umbilical vein endothelial cells (HUVEC) and differentiated neutrophil-like HL-60 (dHL-60) cells, or primary human neutrophils. SLURP1 blocked the tumor necrosis factor-alpha (TNF-α)-activated dHL-60 cells (i) binding to TNF-α-activated HUVEC with a concurrent reduction in endothelial cell adhesion molecule E-selectin, (ii) transmigration through TNF-α-activated confluent HUVEC monolayer by stabilizing VE-cadherin and β-catenin on endothelial cell cytoplasmic membranes, (iii) chemotaxis towards chemoattractant formyl Met-Leu-Phe (fMLP) coupled with their decreased polarization, and (iv) TNF-α-stimulated matrix metalloproteinase-9 (MMP9) expression and activity. SLURP1 also suppressed the primary human neutrophil chemotaxis, and interaction with HUVEC. Furthermore, SLURP1 suppressed fMLP-induced phosphorylation of protein kinase-B (AKT) in dHL-60 cells. Collectively, these results provide evidence that SLURP1 suppresses neutrophil (i) docking on HUVEC cells by decreasing endothelial cell adhesion molecule E-Selectin production, (ii) transmigration through HUVEC monolayer by stabilizing endothelial cell membrane localization of VE-cadherin and β-catenin complex and promoting their barrier function, and (iii) chemotaxis by modulating their polarization and TNF-α-stimulated MMP9 production.

Lymph Node Lymphatic Endothelial Cell Expansion and Contraction and the Programming of the Immune Response

Lymphatic endothelial cells (LECs) form the structure of the lymphatic vessels and the sinuses of the lymph nodes, positioning them to be key players in many different aspects of the immune response. Following an inflammatory stimulus, LECs produce chemokines that recruit immune cells to the lymph nodes. The recruitment of immune cells aids in the coordination of both LEC and lymph node expansion and contraction. More recent data has demonstrated that to coordinate LEC division and death, cell surface molecules, such as PD-L1 and interferon receptors, are required. During homeostasis, LECs use PD-L1 to maintain peripheral tolerance by presenting specific peripheral tissue antigens in order to eliminate tissue specific responses. LECs also have the capacity to acquire, present, and exchange foreign antigens following viral infection or immunization. Here we will review how lymph node LECs require immune cells to expand and contract in response to an immune stimulus, the factors involved and how direct LEC-immune cell interactions are important for programming immunity.

In tumor cells, thyroid hormone analogues non-immunologically regulate PD-L1 and PD-1 accumulation that is anti-apoptotic

The PD-1/PD-L1 immune checkpoint involving tumor cells and host immune defense lymphocytes is a well-studied therapeutic target in oncology. That PD-1 and PD-L1 may have additional functions within tumor cells that are independent of the checkpoint is indicated by actions of a thyroid hormone analogue, L-thyroxine (T₄), on these checkpoint components. Acting at a cell surface receptor on plasma membrane integrin αvβ3, T₄ stimulates intracellular accumulation of PD-L1 in cancer cells. In these thyroid hormone-treated cells, T₄-induced PD-L1 is non-immunologically anti-apoptotic, blocking activation of p53. Several laboratories have also described accumulation of PD-1 in a variety of cancer cells, not just immune defense lymphocytes and macrophages. Preliminary observations indicate that T₄ stimulates intracellular accumulation of PD-1 in tumor cells, suggesting that, like PD-L1, PD-1 has non-immunologic roles in the setting of cancer. Where such roles are anti-apoptotic, thyroid hormone-directed cancer cell accumulation of PD-1 and PD-L1 may limit effectiveness of immunologic therapy directed at the immune checkpoint.

Type 1 IFN and PD-L1 Coordinate Lymphatic Endothelial Cell Expansion and Contraction during an Inflammatory Immune Response

Lymph node (LN) expansion during an immune response is a complex process that involves the relaxation of the fibroblastic network, germinal center formation, and lymphatic vessel growth. These processes require the stromal cell network of the LN to act deliberately to accommodate the influx of immune cells to the LN. The molecular drivers of these processes are not well understood. Therefore, we asked whether the immediate cytokines type 1 IFN produced during viral infection influence the lymphatic network of the LN in mice. We found that following an IFN-inducing stimulus such as viral infection or polyI:C, programmed cell death ligand 1 (PD-L1) expression is dynamically upregulated on lymphatic endothelial cells (LECs). We found that reception of type 1 IFN by LECs is important for the upregulation of PD-L1 of mouse and human LECs and the inhibition of LEC expansion in the LN. Expression of PD-L1 by LECs is also important for the regulation of LN expansion and contraction after an IFN-inducing stimulus. We demonstrate a direct role for both type 1 IFN and PD-L1 in inhibiting LEC division and in promoting LEC survival. Together, these data reveal a novel mechanism for the coordination of type 1 IFN and PD-L1 in manipulating LEC expansion and survival during an inflammatory immune response.

When Clarity Is Crucial: Regulating Ocular Surface Immunity

The ocular surface is a unique mucosal immune compartment in which anatomical, physiological, and immunological features act in concert to foster a particularly tolerant microenvironment. These mechanisms are vital to the functional competence of the eye, a fact underscored by the devastating toll of excessive inflammation at the cornea - blindness. Recent data have elucidated the contributions of specific anatomical components, immune cells, and soluble immunoregulatory factors in promoting homeostasis at the ocular surface. We highlight research trends at this distinctive mucosal barrier and identify crucial gaps in our current knowledge.

Improving immunotherapy outcomes with anti-angiogenic treatments and vice versa

Immunotherapies have revolutionized medical oncology following the remarkable and, in some cases, unprecedented outcomes observed in certain groups of patients with cancer. Combination with other therapeutic modalities, including anti-angiogenic agents, is one of the many strategies currently under investigation to improve the response rates and duration of immunotherapies. Such a strategy might seem counterintuitive given that anti-angiogenic agents can increase tumour hypoxia and reduce the number of blood vessels within tumours. Herein, we review the additional effects mediated by drugs targeting VEGF-dependent signalling and other pathways, such as those mediated by angiopoietin 2 or HGF, which might increase the efficacy of immunotherapies. In addition, we discuss the seldom considered possibility that immunotherapies, and immune-checkpoint inhibitors in particular, might increase the efficacy of anti-angiogenic or other types of antivascular therapies and/or promote changes in the tumour vasculature. In short, we propose that interactions between both therapeutic modalities could be considered a 'two-way street'.

Role of Corneal Stromal Cells on Epithelial Cell Function during Wound Healing

Following injury, corneal stromal keratocytes transform into repair-phenotype of activated stromal fibroblasts (SFs) and participate in wound repair. Simultaneously, ongoing bi-directional communications between corneal stromal-epithelial cells also play a vital role in mediating the process of wound healing. Factors produced by stromal cells are known to induce proliferation, differentiation, and motility of corneal epithelial cells, which are also subsequently the main processes that occur during wound healing. In this context, the present study aims to investigate the effect of SFs conditioned medium (SFCM) on corneal epithelial cell function along with substance P (SP). Antibody microarrays were employed to profile differentially expressed cell surface markers and cytokines in the presence of SFCM and SP. Antibody microarray data revealed enhanced expression of the ITGB1 in corneal epithelial cells following stimulation with SP whereas SFCM induced abundant expression of IL-8, ITGB1, PD1L1, PECA1, IL-15, BDNF, ICAM1, CD8A, CD44 and NTF4. All these proteins have either direct or indirect roles in epithelial cell growth, movement and adhesion related signaling cascades during tissue regeneration. We also observed activation of MAPK signaling pathway along with increased expression of focal adhesion kinase (FAK), paxillin, vimentin, β-catenin and vasodilator-stimulated phosphoprotein (VASP) phosphorylation. Additionally, epithelial-to-mesenchymal transition (EMT) regulating transcription factors Slug and ZEB1 expression were enhanced in the presence of SFCM. SP enriched the expression of integrin subunits α4, α5, αV, β1 and β3 whereas SFCM increased α4, α5, αV, β1 and β5 integrin subunits. We also observed increased expression of Serpin E1 following SP and SFCM treatment. Wound healing scratch assay revealed enhanced migration of epithelial cells following the addition of SFCM. Taken together, we conclude that SFCM-mediated sustained activation of ZEB1, Slug in combination with upregulated migration-associated integrins and ERK (Extracellular signal-regulated kinase)-FAK-paxillin axis, may lead to induce type 2 EMT-like changes during corneal epithelial wound healing.

Advancing Immunotherapy in Metastatic Breast Cancer

OPINION STATEMENT

Despite many advances in the treatment of breast cancer, the development of metastatic disease remains an incurable and frequent cause of cancer death for women worldwide. An improved understanding of the role of host immunosurveillance in modulating breast cancer disease biology, as well as impressive survival benefits seen to checkpoint blockade in other malignancies have provided great hope for an expanding role of immunotherapies in breast cancer management. While these novel therapies are currently being investigated in clinical trials, signals of efficacy, and tolerability in early phase studies suggest these will eventually make their way into standard practice algorithms. Ongoing research has highlighted a high degree of intertumoural heterogeneity in tumour lymphocytic infiltrates, suggesting some tumours or subtypes are more immunogenic than others. Furthermore, tumour intrinsic mechanisms of immune evasion are beginning to be uncovered, potentially representing key therapeutic targets to use in combination with checkpoint blockade, exemplifying the emerging concept of personalised medicine approaches to immune therapies. Subsequently, different immunotherapeutic strategies may be required based on stratification by these factors-for the minority of tumours with a high level of pre-existing immunity, immune checkpoint blockade monotherapy may be sufficient. However, for the majority of tumours with lower levels of pre-existing immunity, combination approaches will likely be required to achieve maximal therapeutic effect. Results of ongoing clinical trials including combinations with chemotherapy, radiation therapy, and targeted therapies are eagerly awaited.

Inhibition of HUVEC tube formation via suppression of NFκB suggests an anti-angiogenic role for SLURP1 in the transparent cornea

Previously, we have reported that the Secreted Ly6/uPAR related protein-1 (SLURP1) serves an important immunomodulatory function in the ocular surface. Here, we examine the involvement of SLURP1 in regulating corneal angiogenic privilege. Slurp1 expression detected by QPCR, immunoblots and immunofluorescent stain, was significantly decreased in mouse corneas subjected to alkali burn-induced corneal neovascularization (CNV). Addition of exogenous SLURP1 (6XHis-tagged, E. coli expressed and partially purified using Ni-ion columns) significantly suppressed the tumor necrosis factor-α (TNF-α)-stimulated human umbilical cord vascular endothelial cell (HUVEC) tube formation. SLURP1 suppressed the HUVEC tube length, tube area and number of branch points, without affecting their viability and/or proliferation. Exogenous SLURP1 in HUVEC also suppressed the TNF-α-induced (i) interleukin-8 (IL-8) and TNF-α production, (ii) adhesion to different components of the extracellular matrix, (iii) migration, and (iv) nuclear localization of NFκB. Together, these results demonstrate that SLURP1 suppresses HUVEC tube formation by blocking nuclear translocation of NFκB, and suggest a potential role for SLURP1 in promoting corneal angiogenic privilege.

Alloimmunity and Tolerance in Corneal Transplantation

Corneal transplantation is one of the most prevalent and successful forms of solid tissue transplantation. Despite favorable outcomes, immune-mediated graft rejection remains the major cause of corneal allograft failure. Although low-risk graft recipients with uninflamed graft beds enjoy a success rate ∼90%, the rejection rates in inflamed graft beds or high-risk recipients often exceed 50%, despite maximal immune suppression. In this review, we discuss the critical facets of corneal alloimmunity, including immune and angiogenic privilege, mechanisms of allosensitization, cellular and molecular mediators of graft rejection, and allotolerance induction.

Antiangiogenic Therapy in Advanced Non-small-cell Lung Cancer: A Meta-analysis of Phase III Randomized Trials

We conducted a meta-analysis to evaluate the efficacy of adding any antiangiogenic therapy (AT) to the standard of care in advanced non-small-cell lung cancer (NSCLC). The electronic databases Ovid PubMed, Cochrane Central Register of Controlled Trials, and Embase were searched to identify eligible trials. We included all phase III randomized trials with any line and type of treatment, histology. and AT dose. Pooled hazard ratios (HRs) for overall survival (OS) and progression-free survival (PFS), and pooled odds ratio (OR) for overall response rates (RR) were calculated. We divided the population into 2 subgroups based on the bevacizumab dose. Data of 19,098 patients from 25 phase III trials were analyzed. Compared with the standard of care, the addition of AT did not prolong OS (HR 0.98; 95% confidence interval [CI], 0.96-1.00; P = .1 and HR 0.97; 95% CI, 0.94-1.00; P = .06 for groups 1 and 2, respectively). However, there was a significant improvement in PFS with the addition of AT (HR 0.85; 95% CI, 0.79-0.91; P < .00001 and HR 0.81; 95% CI, 0.75-0.88; P < .00001 for groups 1 and 2, respectively) and overall RR (OR 1.61; 95% CI, 1.30-2.01; P < .0001 and OR 1.72; 95% CI, 1.39-2.14; P < .00001 for groups 1 and 2, respectively). This is the first meta-analysis including only all phase III trials with AT in NSCLC showing no significant effect on OS and an improvement in PFS and RR only. The role of AT in advanced NSCLC is still questionable; strong validated biomarkers are eagerly needed to predict which subgroup might benefit the most from such therapy.

Emerging therapeutic targets in metastatic progression: A focus on breast cancer

Metastasis is the underlying cause of death for the majority of breast cancer patients. Despite significant advances in recent years in basic research and clinical development, therapies that specifically target metastatic breast cancer remain inadequate, and represents the single greatest obstacle to reducing mortality of late-stage breast cancer. Recent efforts have leveraged genomic analysis of breast cancer and molecular dissection of tumor-stromal cross-talk to uncover a number of promising candidates for targeted treatment of metastatic breast cancer. Rational combinations of therapeutic agents targeting tumor-intrinsic properties and microenvironmental components provide a promising strategy to develop precision treatments with higher specificity and less toxicity. In this review, we discuss the emerging therapeutic targets in breast cancer metastasis, from tumor-intrinsic pathways to those that involve the host tissue components, including the immune system.

Corneal Expression of SLURP-1 by Age, Sex, Genetic Strain, and Ocular Surface Health

PURPOSE

Although secreted Ly6/urokinase-type plasminogen activator receptor-related protein-1 (Slurp1) transcript is highly abundant in the mouse cornea, corresponding protein expression remains uncharacterized. Also, SLURP1 was undetected in previous tear proteomics studies, resulting in ambiguity about its baseline levels. Here, we examine mouse corneal Slurp1 expression in different sexes, age groups, strains, and health conditions, and quantify SLURP1 in human tears from healthy or inflamed ocular surfaces.

METHODS

Expression of Slurp1 in embryonic day-13 (E13), E16, postnatal day-1 (PN1), PN10, PN20, and PN70 Balb/C, FVBN, C57Bl/6, and DBA/2J mouse corneas, Klf4Δ/ΔCE corneas with corneal epithelial-specific ablation of Klf4, migrating cells in wild-type corneal epithelial wound edge, and in corneas exposed to pathogen-associated molecular patterns (PAMPs) poly(I:C), zymosan-A, or Pam3Csk4 was examined by QPCR, immunoblots, and immunofluorescent staining. Human SLURP1 levels were quantified by ELISA in tears from 34 men and women aged 18 to 80 years.

RESULTS

Expression of Slurp1, comparable in different strains and sexes, was low in E13, E16, PN1, and PN10 mouse corneas, and increased rapidly after eyelid opening in a Klf4-dependent manner. We found Slurp1 was downregulated in corneas exposed to PAMPs, and in migrating cells at the wound edge. Human SLURP1 expression, comparable in different sexes and age groups, was significantly decreased in tears from inflamed ocular surfaces (0.34%) than those from healthy individuals (0.77%).

CONCLUSIONS

These data describe the influence of age, sex, genetic background, and ocular surface health on mouse corneal expression of Slurp1, establish the baseline for human tear SLURP1 expression, and identify SLURP1 as a useful diagnostic and/or therapeutic target for inflammatory ocular surface disorders.

MicroRNAs in congenital heart disease

Congenital heart disease (CHD) is a broad term which encompasses a spectrum of pathology, the most common phenotypes include atrial septal defects (ASDs), ventricular septal defects (VSDs), patent ductus arteriosus (PAD) and tetralogy of Fallot (TOF). The impact of CHD is profound and it is estimated to be responsible for over 40% of prenatal deaths. MicroRNAs (miRs) are small, highly conserved, non-coding RNAs which have complex roles in a variety of pathophysiological states. miRs are post-transcriptional negative regulators of gene expression. Individual miRs are known to exert effects in multiple target genes, therefore the altered expression of a single miR could influence an entire gene network resulting in complex pathological states. Recent evidences suggest a role in the dysregulation of miRs in CHD. Mouse knock out models have contributed to our knowledge base revealing specific patterns of miR expression in cardiovascular physiology and pathological states. Specific miRs necessary for embryonic cardiac development have been revealed. Dysregulation of these miRs has been shown to cause structural abnormalities in the heart and vasculature, thus furthering our understanding of the processes which result in CHD. These advances have provided new insight into the signalling pathways responsible for CHD. Furthermore, this new appreciation for miRs in the development of CHD has uncovered their potential for new therapeutic targets where modulated miR activity may reduce the burden of disease. Here, we summarize current knowledge of the cause-effect relationships of miRs in CHD and consider their potential as a therapeutic targets and biomarkers in this clinical setting.

Programmed cell death receptor ligand 1 modulates the regulatory T cells' capacity to repress shock/sepsis-induced indirect acute lung injury by recruiting phosphatase SRC homology region 2 domain-containing phosphatase 1

We recently reported that adoptively transferred (AT) exogenous CD4+ CD25+ regulatory T cells (Tregs) to wild-type (WT) mice can directly act to repress shock/sepsis-induced experimental indirect acute lung injury (iALI), and this is mediated in part by programmed cell death receptor 1 (PD-1). In this study, we further determine whether recipient mouse lacking PD-L1, one of the primary ligands for PD-1, contributes to the manipulation of the Tregs' capacity to repress lung injury. To do this, Tregs isolated from the spleen of WT mice were AT into PD-L1 mice subjected to hemorrhagic shock and subsequent to cecal ligation and puncture to induce iALI. Samples were collected for analyses 24 h after cecal ligation and puncture. We found that in PD-L1-recipient mice, AT WT-Tregs lost the ability to reverse the development of iALI seen in WT recipient mice (i.e., no reduction of lung injury indices assessed by histology and vascular leakage, failure to decrease the lung neutrophil influx [myeloperoxidase activity], or the rise in lung apoptosis [caspase 3 activity]). Also, a significant increase in interleukin 1β (IL-1β) and keratinocyte-derived chemokine, but no changes in IL-6, IL-10, and IL-17A levels in lung tissues were seen in these mice compared with iALI mice without AT of Tregs. Furthermore, we noted that the lung tissue tyrosine phosphatase Src homology region 2 domain-containing phosphatase 1 (SHP-1), but not SHP-2, was activated with the AT of Tregs in PD-L1(-/-) iALI mice. Finally, through local depletion of CD4+ T cells or CD25+ (Tregs) in the lung, prior to inducing iALI, we found that SHP-1 activation was associated with the loss of Tregs' protective effects in vivo. Collectively, our data reveal that PD-L1 is a critical modulator of Tregs' ability to suppress iALI, and this appears to involve SHP-1 activation.

SLURP-1 modulates corneal homeostasis by serving as a soluble scavenger of urokinase-type plasminogen activator

PURPOSE

Our previous study revealed the immunomodulatory property of the secreted lymphocyte antigen (Ly6)/urokinase-type plasminogen activator receptor (uPAR)-related protein-1 (SLURP1), abundantly expressed in the cornea and associated with the hyperkeratotic disorder Mal de Meleda. Here, we test the hypothesis that SLURP1 modulates the functions of membrane-tethered uPAR by acting as a soluble scavenger of its ligand urokinase-type plasminogen activator (uPA).

METHODS

Human corneal limbal epithelial (HCLE) and mouse corneal stromal fibroblast MK/T-1 cells were employed to examine the effect of SLURP1 on cell proliferation and migration. Human corneal limbal epithelial cell clones stably expressing SLURP1 under the control of cytomegalovirus (CMV) promoter were generated using lentiviral vectors. Recombinant 6× His-mouse Slurp1 and maltose-binding protein (MBP)-mouse uPA were expressed in Escherichia coli and partially purified using nickel-ion and amylose columns, respectively. Slurp1 interaction with uPA was detected using ligand blots, ELISA, pull-down assays, and immunofluorescent staining.

RESULTS

Stable expression of SLURP1 in HCLE cells was confirmed by immunoblots and immunofluorescent staining. Human corneal limbal epithelial and MK/T-1 cell proliferation and migration rates were suppressed by exogenous SLURP1. Ligand blots, ELISA, and pull-down assays indicated that Slurp1 efficiently interacts with uPA. Immunofluorescent staining demonstrated that exogenous SLURP1 decreased the amount of cell surface-bound uPA in the leading edges of migrating cells. In gap-filling assays, wild-type HCLE cells responded to uPA by increasing their velocity and closing larger area, while the SLURP1-expressing HCLE cells failed to do so.

CONCLUSIONS

SLURP1 modulates corneal homeostasis by serving as a soluble scavenger of uPA and regulating the uPA-dependent functions of uPAR.

The resolvin D1 analogue controls maturation of dendritic cells and suppresses alloimmunity in corneal transplantation

PURPOSE

To analyze the effect of a resolvin D1 (RvD1) analogue (RvD1a) on dendritic cell maturation, T-cell sensitization, and allograft rejection in corneal allotransplantation.

METHODS

The receptor expression of RvD1 (ALX/FPR2) on bone marrow-derived dendritic cells (BMDC) was measured using quantitative real-time PCR. We determined BMDC maturation after treatment with RvD1a using ELISA to measure interleukin (IL)-12 protein expression and flow cytometry to assess the expression of CD40, major histocompatibility complex (MHC) II, CD80, and CD86. After corneal transplantation in BALB/c mice, we analyzed T-cell infiltration in the cornea and the draining lymph nodes using flow cytometry. The enzyme-linked immunospot (ELISPOT) assay was used to measure T-cell sensitization via the direct and indirect pathway. Angiogenesis and lymphangiogenesis in the cornea after transplantation were measured using immunohistochemistry. Graft opacity and survival were evaluated by slit lamp biomicroscopy.

RESULTS

The receptor for RvD1, lipoxin A4/formyl peptide receptor 2 (ALX/FPR2), was expressed at a significantly lower level on immature than mature dendritic cells (DCs), and RvD1a reduced DC expression of MHC II, CD40, and IL-12 following lipopolysaccharide (LPS) stimulation. Using a murine model of corneal transplantation, RvD1a-treated hosts exhibited significantly reduced allosensitization as demonstrated by decreased frequencies of interferon-gamma-secreting T cells in the draining lymph nodes, and reduced T-cell infiltration into the grafts. Graft survival was significantly enhanced and angiogenesis at the graft site was suppressed in RvD1a-treated hosts compared with vehicle-treated hosts.

CONCLUSIONS

These results suggest that RvD1 inhibits DC maturation and reduces alloimmune sensitization following transplantation, thereby establishing a novel connection between resolvin D1 and the regulation of DC-mediated, antigen-specific immunity.

Soluble vascular endothelial growth factor receptor-3 suppresses allosensitization and promotes corneal allograft survival

PURPOSE

To investigate the effect of VEGF-C and VEGF-D blockade via soluble VEGFR-3 (sVEGFR-3) on T cell allosensitization, corneal neovascularization, and transplant survival.

METHODS

Corneal intrastromal suture placement and allogeneic transplantation were performed on BALB/c mice to evaluate the effect of sVEGFR-3 on corneal neovascularization. Soluble VEGFR-3 trap was injected intraperitoneally to block VEGF-C/D (every other day starting the day of surgery). Immunohistochemical staining of corneal whole mounts was performed using anti-CD31 (PECAM-1) and anti-LYVE-1 antibodies to quantify the levels of hem- and lymphangiogenesis, respectively. Mixed lymphocyte reaction (MLR) was performed to assess indirect and direct host T cell allosensitization and the frequencies of IFN-γ-producing T cells in the draining lymph nodes were assessed using flow cytometry. Graft opacity and survival was evaluated by slit-lamp biomicroscopy.

RESULTS

Treatment with sVEGFR-3 resulted in a significant blockade of lymphangiogenesis 2 weeks post-transplantation and significantly prolonged corneal allograft survival compared to the control group at 8 weeks post-transplantation (87.5 % vs. 50 %), and this was associated with significant reduction in the frequencies of allosensitized T cells and decreased frequencies of IFN-γ-producing CD4 T cells.

CONCLUSIONS

Soluble VEGFR-3 suppresses corneal lymphangiogenesis and allograft rejection and may offer a viable therapeutic modality for corneal neovascularization and corneal transplantation.

Corneal Lymphatics: Role in Ocular Inflammation as Inducer and Responder of Adaptive Immunity

The normal cornea is devoid of lymphatic and blood vessels, thus suppressing both the afferent (lymphatic) and efferent (vascular) arms of the immune response–contributing to its ‘immune privilege’. Inflammation, however, negates this unique ‘immune’ and ‘angiogenic’ privilege of the cornea. Abnormal blood vessel growth from pre-existing limbal vessels into the cornea has been studied for many years, but it is only recently that the significance of new lymphatic vessels (lymphangiogenesis) in ocular inflammatory diseases has been demonstrated. Whereas blood vessels in inflamed ocular surface provide a route of entry for immune effector cells to the cornea, lymphatics facilitate the exit of antigen-presenting cells and antigenic material from the cornea to regional lymph nodes, thus promoting induction of adaptive immune response. This review summarizes the current evidence for lymphangiogenesis in the cornea, and describes its molecular mediators; and discusses the interface between corneal lymphangiogenesis and adaptive immunity. Furthermore, the pathophysiologic implications of corneal lymphangiogenesis in the setting of allo- and autoimmune-mediated corneal inflammation are discussed.

Kupffer cells potentiate liver sinusoidal endothelial cell injury in sepsis by ligating programmed cell death ligand-1

PD-1 and PD-L1 have been reported to provide peripheral tolerance by inhibiting TCR-mediated activation. We have reported that PD-L1-/- animals are protected from sepsis-induced mortality and immune suppression. Whereas studies indicate that LSECs normally express PD-L1, which is also thought to maintain local immune liver tolerance by ligating the receptor PD-1 on T lymphocytes, the role of PD-L1 in the septic liver remains unknown. Thus, we hypothesized initially that PD-L1 expression on LSECs protects them from sepsis-induced injury. We noted that the increased vascular permeability and pSTAT3 protein expression in whole liver from septic animals were attenuated in the absence of PD-L1. Isolated LSECs taken from septic animals, which exhibited increased cell death, declining cell numbers, reduced cellular proliferation, and VEGFR2 expression (an angiogenesis marker), also showed improved cell numbers, proliferation, and percent VEGFR2(+) levels in the absence of PD-L1. We also observed that sepsis induced an increase of liver F4/80(+)PD-1(+)-expressing KCs and increased PD-L1 expression on LSECs. Interestingly, PD-L1 expression levels on LSECs decreased when PD-1(+)-expressing KCs were depleted with clodronate liposomes. Contrary to our original hypothesis, we document here that increased interactions between PD-1(+) KCs and PD-L1(+) LSECs appear to lead to the decline of normal endothelial function-essential to sustain vascular integrity and prevent ALF. Importantly, we uncover an underappreciated pathological aspect of PD-1:PD-L1 ligation during inflammation that is independent of its normal, immune-suppressive activity.

Klf4 regulates the expression of Slurp1, which functions as an immunomodulatory peptide in the mouse cornea

PURPOSE

The secreted Ly6/uPAR-related protein-1 (Slurp1), associated with the hyperkeratotic disorder mal de Meleda, is abundantly expressed in corneas. Here, we examine its corneal expression and functions.

METHODS

Gene expression was quantified by quantitative PCR (qPCR), immunoblots, and immunofluorescent staining. Effect of Kruppel-like factor 4 (Klf4) on Slurp1 promoter was evaluated by chromatin immunoprecipitation (ChIP) and transient transfections. Adenoviral vectors were used to express Slurp1 in corneas. Leukocytic infiltration in bacterial lipopolysaccharide (LPS)-, herpes simplex virus type 1 (HSV-1)-, or adenovirus (serotype 5)-treated mouse corneas was characterized by flow cytometry.

RESULTS

Corneal expression of Slurp1 increased sharply upon mouse eyelid opening, concurrent with the elevated expression of Klf4. Slurp1 was significantly decreased in Klf4 conditional null (Klf4CN) corneas that displayed elevated expression of cytokines and cytokine receptors, as well as neutrophil influx consistent with a proinflammatory environment. In additional models of corneal inflammation, Slurp1 expression was abrogated within 24 hours of LPS injection or HSV-1 or adenoviral infection, accompanied by a predominantly neutrophilic infiltrate. Neutrophilic infiltration was enhanced in HSV-1-infected Klf4CN corneas lacking Slurp1. SLURP1 promoter activity was stimulated by KLF4, suppressed by IL-4, IL-13, and TNFα, and unperturbed by IFN-γ. Slurp1 downregulation and neutrophil influx were comparable in HSV-1-infected wild-type (WT) and Ifng-/- mouse corneas. Mouse corneas infected with Slurp1-expressing adenoviral vectors displayed reduced signs of inflammation and restricted neutrophilic infiltration compared with those infected with control vectors.

CONCLUSIONS

Klf4 regulates the expression of Slurp1, a key immunomodulatory peptide that is abundantly expressed in healthy corneas and is downregulated in proinflammatory conditions.

Effects of two mesenchymal cell populations on hepatocytes and lymphocytes

The inflammatory response to liver injury plays an important role in the onset of liver fibrosis, which may ultimately lead to liver failure. The attenuation of inflammation and hepatocyte rescue are, therefore, of the utmost importance for recovery. Mesenchymal stromal cells (MSCs) from adult bone marrow have been shown to rescue hepatocyte function. Here we explore a more plentiful source of neonatal MSCs: human umbilical cord perivascular cells (HUCPVCs). We cocultured HUCPVCs or bone marrow-derived mesenchymal stromal cells (BM-MSCs) with rat hepatocytes or human peripheral blood mononuclear cells in order to identify their effects on hepatocyte functionality and the proliferation of phytohemagglutinin-stimulated peripheral blood mononuclear cells (phaPBMCs). The expression of hepatotrophic factors by both types of MSCs in the presence of hepatocytes and the functional implications of blocking putative MSC anti-inflammatory factors were compared. Both types of MSCs improved albumin secretion, ureagenesis, hepatospecific gene expression, cytochrome P450 (CYP) activity, and functional hepatocyte mass maintenance. However, although HUCPVCs had an improved effect on the maintenance of ureagenesis, BM-MSCs had a strong effect on hepatocyte CYP activity. Additionally, each MSC type differentially expressed putative hepatotrophic factors, whereas phaPBMC proliferation was significantly decreased. Indoleamine 2,3-dioxygenase (IDO) was the main immunosuppressive mechanism used by both types of MSCs, but HUCPVCs exhibited higher expression of programmed death 1 ligands. However, the functional significance of the difference in anti-inflammatory factor expression still remains to be elucidated. Thus, both MSC types can serve as hepatocyte stromal cells and mitigate inflammation with IDO, but they present differences in the manner in which they affect hepatocytes and in the expression of both hepatotrophic and anti-inflammatory factors.

Corneal neovascularization and the utility of topical VEGF inhibition: ranibizumab (Lucentis) vs bevacizumab (Avastin)

Corneal avascularity is necessary for the preservation of optimal vision. The cornea maintains a dynamic balance between pro- and antiangiogenic factors that allows it to remain avascular under normal homeostatic conditions; however, corneal avascularity can be compromised by pathologic conditions that negate the cornea's "angiogenic privilege." The clinical relevance of corneal neovascularization has long been recognized, but management of this condition has been hindered by a lack of safe and effective therapeutic modalities. Herein, the etiology, epidemiology, pathogenesis, and treatment of corneal neovascularization are reviewed. Additionally, the authors' recent findings regarding the clinical utility of topical ranibizumab (Lucentis®) and bevacizumab (Avastin®) in the treatment of corneal neovascularization are summarized. These findings clearly indicate that ranibizumab and bevacizumab are safe and effective treatments for corneal neovascularization when appropriate precautions are observed. Although direct comparisons are not conclusive, the results suggest that ranibizumab may be modestly superior to bevacizumab in terms of both onset of action and degree of efficacy. In order to justify the increased cost of ranibizumab, it will be necessary to demonstrate meaningful treatment superiority in a prospective, randomized, head-to-head comparison study.

Overexpression of programmed death ligand 1 in dendritic cells inhibits allogeneic lymphocyte activation in mice

BACKGROUND

Co-stimulatory molecules are pivotal for T cell activation. It is increasingly recognized that programmed death ligand 1 (PD-L1) is a novel co-stimulatory molecule, which raises the question as to whether PD-L1 regulates T cell responses. This study aimed to investigate the inhibitory effects of PD-L1 on T cell activation.

MATERIALS AND METHODS

We constructed a transgenic vector containing the complete PD-L1 gene, which interacts with the inhibitory receptor PD-1 in T cell-mediated immune activation. Donor dendritic cells (DCs) derived from C57BL/6 mice were transfected with PD-L1 and mixed with allogeneic, recipient T cells from BALB/c mice. The T cell activation was determined by the MTT assay and T cell proliferation was determined using carboxyfluoroscein succinimidyl ester (CFSE)-labeling following in vitro mixed leukocyte reactions.

RESULTS

The expression of PD-L1 protein in PD-L1-transfected DCs was 47.97% ± 1.06%, compared with 4.66% ± 0.76% and 5.30% ± 0.60% in blank and negative controls, respectively (P < 0.05). PD-L1 protein was effectively expressed in DCs. Furthermore, in DCs stably transfected with PD-L1, T cell activation was significantly suppressed and T cell proliferation rate was decreased by 35% compared with untransfected DCs (P < 0.05).

CONCLUSION

PD-L1 delivers an immunoinhibitory signal, suppressing T cell activation. Overexpression of PD-L1 signaling induces tolerance, which presents a promising immunotherapeutic approach for long-term graft acceptance.