Anti-inflammatory effects of alphav integrin antagonism in acute kidney allograft rejection

Looking below the surface: using intravital imaging to decipher inflammatory renal disease and renal cell injury

Renal function can be perturbed by a range of stimuli that cause cellular injury and inflammation in the kidney. These injurious and inflammatory processes are typically dynamic and progressive, involving the actions of highly migratory cells such as leukocytes and cellular responses that occur over time spans ranging from seconds to weeks. Understanding these dynamic responses has entailed the use of imaging technologies that allow visualization and capture of events over different time spans, ideally in intact organs in live, experimental animals. The technique that allows this is intravital imaging. Intravital imaging, particularly multiphoton intravital microscopy, has been crucial to the investigation of dynamic physiological and pathophysiological processes in the kidney for many years, driving key developments in our understanding of renal (patho)physiology. This includes the mechanisms of ultrafiltrate generation, the response to acute kidney injury, and how inflammatory leukocytes are recruited to and cause injury in the kidney. This review describes the key studies that have applied intravital imaging to the investigation of models of inflammatory renal disease. The responses examined include those restricted to the glomerulus and the effects of acute kidney injury on the tubulointerstitium. Future innovations and directions in this field of research are also discussed.

A peptidic network antibody inhibits both angiogenesis and inflammatory response

Corneal neovascularization (CNV) is a global threat to human health. Traditional anti-angiogenesis agent may have therapy effect, while the inflammation in disease area remains unsolved. Herein, we reported two binding-induced fibrillogenesis (BIF) peptides as peptidic network antibodies for high-efficient and long-lasting anti-angiogenesis with reduced inflammatory response. BIF peptides could self-assemble into nanoparticles and further perform BIF behavior through binding Ca2+. In vitro, the migration of integrin αvβ3 highly expressed endothelial cells was inhibited by BIF peptides. In vivo, one BIF peptide (0.012 mg/Kg) exhibited higher anti-angiogenesis effect than monoclonal antibody bevacizumab (0.96 mg/Kg) in a CNV rabbit model on day 14, despite that the dose of BIF was only 1.3% of bevacizumab. Meanwhile, the inflammatory response, such as PI3 kinase/Akt pathway in CNV was successfully inhibited as well. The peptidic network antibody could block integrin αvβ3 via a long-term retention mode, which led to long-term therapeutic effect. The study provides BIF peptides as promising therapeutic agents for both anti-angiogenesis and reduced inflammatory response.

Immune cell behaviour and dynamics in the kidney - insights from in vivo imaging

The actions of immune cells within the kidney are of fundamental importance in kidney homeostasis and disease. In disease settings such as acute kidney injury, anti-neutrophil cytoplasmic antibody-associated vasculitis, lupus nephritis and renal transplant rejection, immune cells resident within the kidney and those recruited from the circulation propagate inflammatory responses with deleterious effects on the kidney. As in most forms of inflammation, intravital imaging - particularly two-photon microscopy - has been critical to our understanding of immune cell responses in the renal microvasculature and interstitium, enabling visualization of immune cell dynamics over time rather than statically. These studies have demonstrated differences in the recruitment and function of these cells from those in more conventional vascular beds, and provided a wealth of information on the actions of blood-borne immune cells such as neutrophils, monocytes and T cells, as well as kidney-resident mononuclear phagocytes, in a range of diseases affecting different kidney compartments. In particular, in vivo imaging has furthered our understanding of leukocyte function within the glomerulus in acute glomerulonephritis, and in the tubulointerstitium and interstitial microvasculature during acute kidney injury and following transplantation, revealing mechanisms of immune surveillance, antigen presentation and inflammation in the kidney.

The Mandible Ameliorates Facial Allograft Rejection and Is Associated with the Development of Regulatory T Cells and Mixed Chimerism

Vascularized composite allografts contain various tissue components and possess relative antigenicity, eliciting different degrees of alloimmune responses. To investigate the strategies for achieving facial allograft tolerance, we established a mouse hemiface transplant model, including the skin, muscle, mandible, mucosa, and vessels. However, the immunomodulatory effects of the mandible on facial allografts remain unclear. To understand the effects of the mandible on facial allograft survival, we compared the diversities of different facial allograft-elicited alloimmunity between a facial osteomyocutaneous allograft (OMC), including skin, muscle, oral mucosa, and vessels, and especially the mandible, and a myocutaneous allograft (MC) including the skin, muscle, oral mucosa, and vessels, but not the mandible. The different facial allografts of a BALB/c donor were transplanted into a heterotopic neck defect on fully major histocompatibility complex-mismatched C57BL/6 mice. The allogeneic OMC (Allo-OMC) group exhibited significant prolongation of facial allograft survival compared to the allogeneic MC group, both in the presence and absence of FK506 immunosuppressive drugs. With the use of FK506 monotherapy (2 mg/kg) for 21 days, the allo-OMC group, including the mandible, showed prolongation of facial allograft survival of up to 65 days, whereas the myocutaneous allograft, without the mandible, only survived for 34 days. The Allo-OMC group also displayed decreased lymphocyte infiltration into the facial allograft. Both groups showed similar percentages of B cells, T cells, natural killer cells, macrophages, and dendritic cells in the blood, spleen, and lymph nodes. However, a decrease in pro-inflammatory T helper 1 cells and an increase in anti-inflammatory regulatory T cells were observed in the blood and lymph nodes of the Allo-OMC group. Significantly increased percentages of donor immune cells were also observed in three lymphoid organs of the Allo-OMC group, suggesting mixed chimerism induction. These results indicated that the mandible has the potential to induce anti-inflammatory effects and mixed chimerism for prolonging facial allograft survival. The immunomodulatory understanding of the mandible could contribute to reducing the use of immunosuppressive regimens in clinical face allotransplantation including the mandible.

Targeting RGD-binding integrins as an integrative therapy for diabetic retinopathy and neovascular age-related macular degeneration

Integrins are a class of transmembrane receptors that are involved in a wide range of biological functions. Dysregulation of integrins has been implicated in many pathological processes and consequently, they are attractive therapeutic targets. In the ophthalmology arena, there is extensive evidence suggesting that integrins play an important role in diabetic retinopathy (DR), age-related macular degeneration (AMD), glaucoma, dry eye disease and retinal vein occlusion. For example, there is extensive evidence that arginyl-glycyl-aspartic acid (Arg-Gly-Asp; RGD)-binding integrins are involved in key disease hallmarks of DR and neovascular AMD (nvAMD), specifically inflammation, vascular leakage, angiogenesis and fibrosis. Based on such evidence, drugs that engage integrin-linked pathways have received attention for their potential to block all these vision-threatening pathways. This review focuses on the pathophysiological role that RGD-binding integrins can have in complex multifactorial retinal disorders like DR, diabetic macular edema (DME) and nvAMD, which are leading causes of blindness in developed countries. Special emphasis will be given on how RGD-binding integrins can modulate the intricate molecular pathways and regulate the underlying pathological mechanisms. For instance, the interplay between integrins and key molecular players such as growth factors, cytokines and enzymes will be summarized. In addition, recent clinical advances linked to targeting RGD-binding integrins in the context of DME and nvAMD will be discussed alongside future potential for limiting progression of these diseases.

AGT haplotype in ITGA4 gene is related to antibody-mediated rejection in heart transplant patients

Introduction

One of the main problems involved in heart transplantation (HT) is antibody-mediated rejection (AMR). Many aspects of AMR are still unresolved, including its etiology, diagnosis and treatment. In this project, we hypothesize that variants in genes involved in B-cell biology in HT patients can yield diagnostic and prognostic information about AMR.

Methods

Genetic variants in 61 genes related to B-cell biology were analyzed by next generation sequencing in 46 HT patients, 23 with and 23 without AMR.

Results

We identified 3 single nucleotide polymorphisms in ITGA4 gene (c.1845G>A, c.2633A>G, and c.2883C>T) that conformed the haplotype AGT-ITGA4. This haplotype is associated with the development of AMR. Moreover, AMR patients with the haplotype AGT-ITGA4 present lower levels of integrin α-4 in serum samples compared to the reference GAC haplotype in control patients.

Conclusion

We can conclude that polymorphisms in genes related to the biology of B-cells could have an important role in the development of AMR. In fact, the AGT haplotype in ITGA4 gene could potentially increase the risk of AMR.

Imaging Leukocyte Responses in the Kidney

The kidney can be negatively affected by a range of innate and adaptive immune responses, resulting in alterations in the functions of the kidney and, in some cases, progression to renal failure. In many of these responses, infiltration of blood-borne leukocytes into the kidney is central to the response. In addition, a large population of mononuclear phagocytes resident in the kidney can modulate these responses. A great deal of research has investigated both the mechanisms of leukocyte recruitment to the kidney and the actions of immune cells resident within the kidney. Because of the dynamic nature of the processes whereby leukocytes enter sites of inflammation, in vivo imaging has been one of the key approaches used for understanding leukocyte recruitment as it occurs throughout the body, and this is also true for kidney. However, imaging this organ and its complicated microvasculature during different forms of renal pathology presents a unique set of challenges. In this review, we examine the approaches used for intravital imaging of the kidney and summarize the insights gained from these studies regarding the mechanisms of leukocyte entry into the kidney during inflammation and the actions of immune cells within this organ.

The disintegrin, trimucrin, suppresses LPS-induced activation of phagocytes primarily through blockade of NF-κB and MAPK activation

In addition to antiplatelet activity, disintegrin, a small-mass RGD-containing polypeptide, has been shown to exert anti-inflammatory effects but the mechanism involved remains unclear. In this study, we report that trimucrin, a disintegrin from the venom of Trimeresurus mucrosquamatus, inhibits lipopolysaccharide (LPS)-induced stimulation of THP-1 and RAW 264.7 cells. We also investigate the underlying mechanism. Trimucrin decreased the release of proinflammatory cytokines including tumor necrosis factor α (TNFα), interleukin-6 (IL-6), nitric oxide, and reactive oxygen species (ROS), and inhibited the adhesion and migration of LPS-activated phagocytes. Trimucrin significantly blocked the expression of nuclear factor kappaB (NF-κB)-related downstream inducible enzymes such as inducible nitric oxide synthase (iNOS) and COX-2. In addition, its anti-inflammatory effect was associated with the decreased mitogen-activated protein kinase (MAPK) phosphorylation. Furthermore, trimucrin concentration dependently inhibited LPS-induced phosphorylation of focal adhesion kinase (FAK), PI3K, and Akt. Trimucrin also reversed the DNA-binding activity of NF-κB by suppressing the LPS-induced nuclear translocation of p65 and the cytosolic IκB release. Flow cytometric analyses showed that trimucrin bound to cells in a concentration-dependent manner. The anti-αVβ3 mAb also specifically decreased the binding of fluorescein isothiocyanate (FITC)-conjugated trimucrin. Binding assays demonstrated that integrin αVβ3 was the binding site for trimucrin on THP-1 and RAW 264.7 cells. In conclusion, we showed that trimucrin decreases the inflammatory reaction through the attenuation of iNOS expression and nitric oxide (NO) production by blocking MAP kinase and the NF-κB activation in LPS-stimulated THP-1 and RAW 264.7 cells.

Improvements in endotoxemic syndromes using a disintegrin, rhodostomin, through integrin αvβ3-dependent pathway

BACKGROUND AND OBJECTIVES

Septic shock is a major cause of morbidity and mortality in intensive care units, but there is still no effective therapy for the patients. We evaluated the effects of rhodostomin (Rn), an Arg-Gly-Asp-containing snake venom disintegrin, on lipopolysaccharide (LPS)-activated phagocytes in vitro and LPS-induced endotoxemia in vivo.

METHODS AND RESULTS

Rn inhibited adhesion, migration, cytokine production and mitogen-activated protein kinase (MAPK) activation of macrophage induced by LPS. Flow cytometric analysis revealed that Rn specifically blocked anti-αv mAb binding to RAW264.7. Besides inhibiting MAPK activation of THP-1, Rn bound to LPS-activated THP-1 and specifically blocked anti-αvβ3 mAb binding to THP-1. Binding assays proved that integrin αvβ3 was the binding site for rhodostomin on phagocytes. Rn reversed the enhancement of fibronectin and vitronectin on LPS-induced monocyte adhesion and cytokine release. Transfection of integrin αv siRNA also inhibited LPS-induced activation of monocyte, and Rn exerted no further inhibitory effect. Furthermore, Rn significantly decreased the production of tumor necrosis factor-α (TNF-a), interleukin (IL)-6, -1β and -10 and attenuated cardiovascular dysfunction, including blood pressure and heart pulse, and thrombocytopenia in LPS-induced endotoxemic mice. Rn also protected against tissue inflammation as evidenced by histological examination.

CONCLUSIONS

Rn may interact with αvβ3 integrin of monocytes/macrophages leading to interfere with the activation of phagocytes triggered by LPS. These results suggest that the protective function of Rn in LPS-induced endotoxemia may be attributed to its anti-inflammation activities in vivo.

αVβ3 integrin regulates macrophage inflammatory responses via PI3 kinase/Akt-dependent NF-κB activation

Controlling macrophage responses to pathogenic stimuli is critical for prevention of and recovery from the inflammatory state associated with the pathogenesis of many diseases. The adhesion receptor αVβ3 integrin is thought to be an important receptor that regulates macrophage differentiation and macrophage responses to external signaling, but it has not been previously identified as a contributor to macrophage-related inflammation. Using an in vitro model of human blood monocytes (Mo) and monocyte-derived macrophages (MDMs) we demonstrate that αVβ3 ligation results in sustained increases of the transcription factor NF-κB DNA-binding activity, as compared with control isotype-matched IgG(1). Activation of NF-κB parallels the increase of NF-κB-dependent pro-inflammatory cytokine mRNA expression in MDMs isolated from individual donors, for example, TNF-α (8- to 28-fold), IL-1β (15- to 30-fold), IL-6 (2- to 4-fold), and IL-8 (5- to 15-fold) whereas there is more than a 10-fold decrease in IL-10 mRNA level occurs. Upon ligation of the αVβ3 receptor, treatment with TNF-α (10 ng/ml) or LPS (200 ng/ml, 1,000 EU) results in the enhanced and synergistic activation of NF-κB and LPS-induced TNF-α secretion. As additional controls, an inhibitor of αVβ3 integrin, cyclic RGD (10 µg/ml; IC(50) = 7.6 µM), attenuates the effects of αVβ3 ligation, and the natural ligand of αVβ3 integrin, vitronectin, reproduces the effects of αVβ3 activation by an immobilizing anti-αVβ3 integrin mAb. We hypothesize that αVβ3 activation can maintain chronic inflammatory processes in pathological conditions and that the loss of αVβ3 ligation will allow macrophages to escape from the inflammatory state.

Targeting the recruitment of monocytes and macrophages in renal disease

Macrophages convert proinflammatory or anti-inflammatory signals of tissue microenvironments into response mechanisms. These response mechanisms largely derive from evolutionary conserved defense programs of innate host defense, wound healing, and tissue homeostasis. Hence, in many settings these programs lead to renal inflammation and tissue remodeling (ie, glomerulonephritis and sclerosis or interstitial nephritis and fibrosis). There is abundant experimental evidence that blocking macrophage recruitment or macrophage activation can ameliorate renal inflammation and fibrosis. In this review we discuss experimental tools to target renal macrophage recruitment by using antagonists against selectins, chemokines, integrins, or other important cytokines that mediate renal injury via macrophage recruitment, some of these already having been used in clinical trials.

Immunologic mechanisms in RCC and allogeneic renal transplant rejection

The tolerance state that exists between renal cell carcinoma (RCC) and the host's immune system would be an ideal situation in the setting of human kidney transplantation, in which graft tolerance is the ultimate goal of immunosuppressive therapy. On the other hand, acute rejection, as it appears in renal allografts, would be the optimal immunologic situation in patients with RCC. Analysis of the underlying mechanisms of acute allograft rejection and local pro-tumor immunosuppression could help to identify potential therapeutic targets for inducing immune tolerance in allograft recipients and immune rejection in RCC patients. Experimental kidney transplantation might be a suitable model in which to analyze these processes. Macrophages are a prominent and vital cell type in the cellular infiltrate seen in both RCC and renal allografts. Depending on their polarization, they can initiate and promote either proinflammatory or pro-tumor responses, which lead to tissue rejection or acceptance, respectively. Improved understanding of macrophage biology could lead to therapeutic modification of their function in order to promote a desirable immunologic response in either RCC or transplant tissue.

Viral macrophage inflammatory protein-II improves acute rejection in allogeneic rat kidney transplants

Purpose

During rejection, leukocytes are recruited from the peripheral circulation into the graft leading to the damage of endothelial cells, capillary perfusion failure and graft loss. Chemokines play a pivotal role in the recruitment of leukocytes to the endothelium. Viral macrophage inflammatory protein-II (vMIP-II), a human herpes virus-8 DNA-encoded protein, is a broad-spectrum chemokine antagonist. The aim of the study was to prove the beneficial activity of vMIP-II treatment on acute rat kidney allograft damage.

Methods

Heterotopic rat kidney transplantation was performed in the Fischer 344 to Lewis transplantation model and animals were treated with vMIP-II (2 × 15 µg or 100 µg/day) for 7 days. Rejection-induced damage was analyzed by histology, and microcirculatory changes within the graft were analyzed by in vivo microscopy.

Results

Viral macrophage inflammatory protein-II significantly improved acute glomerular damage and tubulointerstitial inflammation and lowered the extent of vascular and tubulointerstitial damage of the treated allografts. Functional microcirculation of peritubular capillaries was significantly improved in vivo, and the firm adherence of leukocytes was significantly reduced by vMIP-II treatment.

Conclusions

The administration of the broad-spectrum antagonist vMIP-II improved acute renal allograft damage, mainly by a reduction in leukocyte recruitment with a subsequently improved renal cortical microcirculation in vivo.

A novel CXCL8 protein-based antagonist in acute experimental renal allograft damage

Acute renal allograft damage is caused by early leukocyte infiltration which is mediated in part by chemokines presented by glycosaminoglycan (GAG) structures on endothelial surfaces. CXCL8 can recruit neutrophils and induce the firm arrest of monocytes on activated endothelial cells. A human CXCL8-based antagonist (dnCXCL8) designed to generate a dominant-negative mutant protein with enhanced binding to GAG structures and reduced CXCR1/2 receptor binding ability was tested in models of early allograft injury. The agent displayed enhanced binding to GAG structures in vitro and could antagonize CXCL8-induced firm adhesion of monocytes as well as neutrophils to activated microvascular endothelium in physiologic flow assays. In a rat model of acute renal damage, dnCXCL8 treatment limited proximal tubular damage and reduced granulocyte infiltration. In a Fischer 344 (RT1(lvl)) to Lewis (RT1(l)) rat acute renal allograft model, dnCXCL8 was found to reduce monocyte and CD8+ T-cell infiltration into glomeruli and to limit tubular interstitial inflammation and tubulitis in vivo. Early treatment of allografts with agents like dnCXCL8 may help reduce acute allograft damage and preserve renal morphology and thereby help limit chronic dysfunction.