Cell adhesion molecules for targeted drug delivery

Rapid advancement of the understanding of the structure and function of cell adhesion molecules (i.e., integrins, cadherins) has impacted the design and development of drugs (i.e., peptide, proteins) with the potential to treat cancer and heart and autoimmune diseases. For example, RGD peptides/peptidomimetics have been marketed as anti-thrombic agents and are being investigated for inhibiting tumor angiogenesis. Other cell adhesion peptides derived from ICAM-1 and LFA-1 sequences were found to block T-cell adhesion to vascular endothelial cells and epithelial cells; these peptides are being investigated for treating autoimmune diseases. Recent findings suggest that cell adhesion receptors such as integrins can internalize their peptide ligands into the intracellular space. Thus, many cell adhesion peptides (i.e., RGD peptide) were used to target drugs, particles, and diagnostic agents to a specific cell that has increased expression of cell adhesion receptors. This review is focused on the utilization of cell adhesion peptides and receptors in specific targeted drug delivery, diagnostics, and tissue engineering. In the future, more information on the mechanism of internalization and intracellular trafficking of cell adhesion molecules will be exploited for delivering drug molecules to a specific type of cell or for diagnosis of cancer and heart and autoimmune diseases.     

A Peptide from the Beta-strand Region of CD2 Protein that Inhibits Cell Adhesion and Suppresses Arthritis in a Mouse Model

Cell adhesion molecules play a central role at every step of the immune response. The function of leukocytes can be regulated by modulating adhesion interactions between cell adhesion molecules to develop therapeutic agents against autoimmune diseases. Among the different cell adhesion molecules that participate in the immunologic response, CD2 and its ligand CD58 (LFA-3) are two of the best-characterized adhesion molecules mediating the immune response. To modulate the cell adhesion interaction, peptides were designed from the discontinuous epitopes of the β-strand region of CD2 protein. The two strands were linked by a peptide bond. β-Strands in the peptides were nucleated by inserting a β-sheet-inducing Pro-Gly sequence with key amino acid sequences from CD2 protein that binds to CD58. Using a fluorescence assay, peptides that exhibited potential inhibitory activity in cell adhesion were evaluated for their ability to bind to CD58 protein. A model for peptide binding to CD58 protein was proposed based on docking studies. Administration of one of the peptides, P3 in collagen-induced arthritis in the mouse model, indicated that peptide P3 was able to suppress rheumatoid arthritis in mice.     

Arylalkyl ketones, benzophenones, desoxybenzoins and chalcones inhibit TNF-α induced expression of ICAM-1: structure-activity analysis

The interaction between leukocytes and the vascular endothelial cells (EC) via cellular adhesion molecules plays an important role in the pathogenesis of various inflammatory and autoimmune diseases. Small molecules that block these interactions have been targeted as potential therapeutic agents against acute and chronic inflammatory diseases. In an effort to identify potent intercellular cell adhesion molecule-1 (ICAM-1) inhibitors, a large number of arylalkyl ketones, benzophenones, desoxybenzoins and chalcones and their analogs (54 in total) have been synthesized and screened for their ICAM-1 inhibitory activity. The structure-activity relationship studies of these compounds identified three potent chalcone derivatives and also demonstrated the possible mechanism for their ICAM-1 inhibitory activities. The most active compound was found to be 79.     

脑缺血损伤的炎症免疫机制

脑缺血是指脑循环血流量减少为特征的中枢神经系统疾病 ,因其发病率、致残率和死亡率均较高 ,严重地影响了人类的生存质量。探讨脑缺血损伤的机制 ,对减轻脑缺血损伤和提高人类的生存质量极其重要。脑缺血损伤的炎症免疫机制研究将为临床寻找有效的治疗方法提供重要的思路。脑缺血的炎症免疫损伤是一个复杂的病理过程 ,炎症免疫细胞、免疫因子和NO等都参与了脑缺血损伤的病理过程 ,其中细胞因子首先诱导产生 ,尔后诱导粘附分子和趋化因子的表达 ,促使炎症免疫细胞浸润到损伤组织 ,炎症免疫细胞及其产生的细胞因子又相互诱导激活 ,进一步加重组织损伤。NO及其合酶在脑缺血的炎症免疫损伤中占重要地位     

Two Faces of Inflammation: An Immunopharmacological View

Inflammation is a protective response intended to eliminate pathogens and other offending agents which have potential to cause cell injury, as well as malignant and necrotic cells. However, if the inflammatory response is dysregulated or inappropriately focused, it has considerable potential to cause harm and can lead to development of inflammatory diseases such as allergic and autoimmune diseases. Despite the recent success in cytokine‐targeted therapies, for example by the use of specific biological drugs, there are still considerable unmet needs in the treatment of inflammatory diseases. Further, recent discoveries in many diseases in addition to the classical inflammatory diseases have revealed inflammation to be a major factor participating in the underlying pathophysiological processes, either through activation of inflammatory cells or through triggering of inflammatory signalling mechanisms in the tissue cells. Examples of such diseases and conditions are many cardiovascular, metabolic and degenerative diseases, as well as cancer, obesity and pain. This brings the immunopharmacological approach into a new perspective in the drug development in very wide therapeutic areas. Immunopharmacology investigates mechanisms of inflammation and potential molecules and targets to treat inflammatory diseases. The current issue of Basic and Clinical Pharmacology and Toxicology focuses on some of the novel inflammatory mechanisms with potential in anti‐inflammatory drug development, including kinase pathways, TRP ion channels, eicosanoid system, obesity‐related adipokines, autoantibodies against citrullinated proteins, eosinophils, platelets and pathways connecting nervous and immune systems. The MiniReviews are based on lectures given at the symposium “Novel Drugs and Drug Targets to Treat Inflammation” in Ylläs, Finland, in March 2013.     

Therapeutic benefits of regulating inflammation in autoimmunity

Autoimmunity results from the dysregulation of the immune system leading to tissue damage. Th1 and Th17 cells are known to be cellular mediators of inflammation in autoimmune diseases. The specific cytokine milieu within the site of inflammation or within secondary lymphatic tissues is important during the priming and effector phases of T cell response. In this review, we will address the nature of the inflammatory response in the context of autoimmune disease, specifically we will discuss the role of dendritic cells following stimulation of their innate pathogen recognition receptors in directing the development of T cell responses. We will focus on how dendritic cell subsets change the balance between major players in autoimmunity, namely Th1, Th17 and regulatory T cells. Th17 cells, once thought to only act as pathogenic effectors through production of IL-17, have been shown to have regulatory properties as well with co-production of the anti-inflammatory cytokine IL-10 by a subset now referred to as regulatory Th17 cells. IL-17 is important in the induction of autoimmune diseases such as experimental autoimmune encephalomyelitis (EAE) and inflammatory bowel disease (IBD). Study of the inflammatory process following encounter with agents that stimulate the innate immune responses such as adjuvants opens a new horizon for the discovery of therapeutic agents including those derived from microorganisms. Microbial products such as adjuvants that function as TLR ligands may stimulate the immune system by interacting with Toll-like receptors (TLR) on antigen-presenting cells. Microbial agents such as Bacille Calmette-Guérin (BCG) or Freund's adjuvant (CFA) that induce a Th17 response are protective in models of autoimmune diseases particularly EAE and type 1 diabetes (T1D). The induction of innate immunity by these microbial products alters the balance in the cytokine microenvironment and may be responsible for modulation of the inflammation and protection from autoimmunity.     

Inhibitors of membrane receptors involved with leukocyte extravasation

The migration of leukocytes from the blood stream to sites of infection is a key event in cellular immune response, mediated by multiple types of molecules including several adhesion receptors. The inhibition of adhesion receptors holds great promise for novel therapeutical strategies to treat chronic inflammatory disorders or autoimmune diseases. This review reports on recent advances in adhesion-based therapeutics and focuses on structural classification of selectin and integrin inhibitors.     

Intravenous immunoglobulin in autoimmune disorders: an insight into the immunoregulatory mechanisms

Intravenous immunoglobulin (IGIV) has increasingly been used for the treatment of autoimmune and systemic inflammatory diseases in addition to supportive therapy of immunodeficient patients. IGIV is beneficial in several diseases, including acute and chronic/relapsing diseases, autoimmune diseases and inflammatory disorders. Therapeutic efficacy of IGIV has also been established in a number of dermatologic diseases. Although a considerable progress has been made in understanding the mechanisms by which IGIV exerts immunomodulatory functions in autoimmune diseases, they remain not fully elucidated. The mode of action of IGIV is complex, involving modulation of expression and function of Fc receptors, interference with activation of complement and the cytokine network, modulation of idiotype network, regulation of cell growth, alteration of cellular adhesion process, and effects on the activation differentiation and effector functions of T and B cells and of antigen-presenting cells. The therapeutic effects of IGIV most likely reflect the functions of natural antibodies in maintaining immune homeostasis in healthy people. The ability of IGIV to interact through V regions with complementary V regions of antibodies and antigen receptors as well as with relevant soluble and surface molecules provides the basis for inducing the selection of immune repertoires. Since IGIV is frequently used to treat autoimmune and inflammatory diseases for which evidence of its efficacy is insufficiently documented, controlled trials, particularly of some neurologic and dermatologic diseases, are imperative.     

Future treatments of allergic diseases and asthma

Recent advances in the understanding of the inflammatory and immunological mechanisms of allergic diseases have illuminated many potential therapeutic strategies that may prevent or even reverse the abnormalities of allergic inflammation. As the roles of effector cells, and of signalling and adhesion molecules are better understood, the opportunities to inhibit or prevent the inflammatory cascade have increased. In addition, there have been advances in the synthesis of proteins, monoclonal antibodies and new small molecule chemical entities, which provide further valuable flexibility in the therapeutic approach to asthma. Such new approaches are aimed at prevention of T-cell activation; redressing the imbalance of T helper cell populations thus inhibiting or preventing Th-2-derived cytokine expression; and the inhibition or blockade of the downstream actions of these cytokines such as effects on IgE and eosinophils. Approaches such as these allow both broad and highly specific targeting, and may pave the way towards the prevention and reversal of the immunological and inflammatory processes driving asthma, allergic rhinitis and atopic dermatitis. The development of effective agents with effects beyond those provided by current therapies coupled with lesser side-effects will further address the unmet needs of allergic disease.     

Roles of glycans and glycopeptides in immune system and immune-related diseases

Almost all of the key molecules in organisms involved in the innate and adaptive immune response (including immunoglobulins, cytokines and cytokine receptors, complements, CD molecules, adhesions, T-cell receptors and major histocompatibility complex molecules) are glycoproteins. Besides, foreign antigens, such as many viral envelope proteins, are glycoproteins too. Carbohydrates attached to proteins or peptides are classified by the nature of their linkages to the protein, mostly as either N-linked (N-acetylglucosamine to asparagines) or O-linked (N-acetylgalactosamine to serine or threonine) oligosaccharides. The glycans have three major roles: firstly, the sugars confer stability on the proteins to which they are attached, protecting them from proteases and non-specific protein-protein interactions. Secondly, glycans play key roles in signal transduction, control of cell development and differentiation. Thirdly, specific regions of the oligosaccharide chains provide recognition epitopes, which influence innate and adaptive immune responses. Glycopeptides not only provide specific oligosaccharides, but also have specific information of amino acids sequences. The glycans and glycopeptides not only influence the structure and functions of immune molecules, but also influence the immune response. In addition, changes in glycans or glycopeptides may have a significant role in a variety of human immune-related diseases, such as rheumatoid, autoimmune disease, Wiskott-Aldrich syndrome, infection disease, cancer, etc. In this article, the roles of N-, O-glycans and glycopeptides in immune system and immune-related diseases are discussed. The potential therapeutic significance of the information is also mentioned.     

mTOR--beyond transplantation

mTOR kinase plays a central role in the activation of many cell types, and blocking mTOR function with rapamycin results in arrest of the cell cycle at the G1 phase. Recently, several additional molecules have been identified in the mTOR pathway, providing further opportunities to interfere with cell activation and develop novel therapeutic agents. Under certain conditions and in specific cell types, activation can occur independently of mTOR and in the presence of rapamycin. Selective inhibition of cell activation in the appropriate setting might prove to be beneficial for several autoimmune or inflammatory diseases.     

Interleukin-2 as immunotherapeutic in the autoimmune diseases

Interleukins, also called cytokines are secretory proteins that bind to specific receptors and play a critical role in the intercellular communication between cells of the immune system. Cytokines are mainly produced by T lymphocytes, macrophages and eosinophils. Among its functions are the activation and suppression of immune system responses, induction of cell division and regulation of memory cells. Interleukin 2 (IL-2) is a secretory monomeric glycoprotein composed of 149 amino acids containing a signal peptide of 20 amino acids. It is classified as a member of the type I cytokines family. IL-2 binds to its receptor (IL-2R receptor) with high affinity and its signaling function promotes the activation of various subtypes of lymphocytes during the process of cell differentiation to generate an immune or homeostatic response. The specificity of IL-2 depends on its binding to low, medium or high-affinity receptors. Interleukin 2 acts as a regulator of the proliferation of CD4+ and CD8+ T cells. There is a relationship between IL-2 and autoimmune diseases due to its influence in the differentiation of T helper cells, which in turn directly influence immunological response processes. Therefore, IL-2 is a key element in the control and treatment of those diseases. In recent years, many therapeutic agents based on biomolecules and recombinant chimeric proteins have been developed to treat different autoimmune diseases. In this review, we focus on the use of interleukin 2 as a versatile therapeutic agent, alone or associated with other molecules to increase the efficiency of autoimmune disease treatment.     

Boosting interleukin-10 production: therapeutic effects and mechanisms

More than forty cytokines have been extensively researched on the molecular structure, cell signaling and transduction pathway. With respect to cytokine-regulating therapy in immunological imbalance however, the reported results are conflicting because of the pleiotropic functions and the intricate interactions of the cytokine network. In this review, we outline the observations on interleukin-10 (IL-10) upregulatory therapy. Despite varying opinions on its therapeutic effects for different disorders, IL-10 has been considered a potential anti-inflammatory cytokine. Numerous studies support the view that IL-10 shows a strong suppressive effect on Th1 lymphocytes, antigen presenting cells and the production of inflammatory mediators. It is also noticeable that recent research has revealed the relationship between IL-10 induced antigen specific regulatory CD4+ T cells and antigen specific immune tolerance. This specific regulation was mediated in part through IL-10 secretion, because anti-IL-10 treatment reverted the inhibitory effect of regulatory T cell clones. In different models, these cells were shown to inhibit both Th1 and Th2-type inflammatory responses through the secretion of IL-10. With the presence of IL-10, regulatory T cells may induce peripheral immune tolerance. Exogenous administration, transgenic expression and endogenous stimulative agents of IL-10 have been used for a variety of inflammatory diseases, autoimmune diseases and allograft rejection in patients and experimental models. A therapeutic intervention with drug inducing endogenous IL-10 may be more practical than an exogenous administration of IL-10 with transient effect. Although further investigation on gene regulation of IL-10 is necessary, increasing studies have been reported concerning the attempt to develop the agents, which could promote endogenous IL-10 production for the treatment of immunological disorders and inflammatory diseases. With some unclear mechanisms, these agents have strongly upregulated IL-10 production in vitro or in vivo. Reported IL-10 upregulatory agents have shown promising prospects for remission of autoimmune diseases and inflammatory diseases and have even induced antigen specific immune tolerance. It is interesting that the IL-10 upregulatory effect of several traditional immunosuppressive drugs has been detected, e.g. glucocorticoid, which is considered "not more as an immunosuppressive drug but an immune modulating agent". Approximately twenty IL-10 upregulatory agents as instances are described in the present review. In addition, their therapeutic effects in various diseases are discussed.     

Pharmacological modulation of GITRL/GITR system: therapeutic perspectives

Glucocorticoid-induced TNFR-related (gitr) is a gene coding for a member of the TNF receptor superfamily. GITR activation by its ligand (GITRL) influences the activity of effector and regulatory T cells, thus participating in the development of immune response against tumours and infectious agents, as well as in autoimmune and inflammatory diseases. Notably, treating animals with GITR-Fc fusion protein ameliorates autoimmune/inflammatory diseases while GITR triggering, by treatment with anti-GITR mAb, is effective in treating viral, bacterial and parasitic infections, as well in boosting immune response against tumours. GITR modulation has been indicated as one of the top 25 most promising research areas by the American National Cancer Institute, and a clinical trial testing the efficacy of an anti-GITR mAb in melanoma patients has been started. In this review, we summarize results regarding: (i) the mechanisms by which GITRL/GITR system modulates immune response; (ii) the structural and functional studies clearly demonstrating differences between GITRL/GITR systems of mice and humans; (iii) the molecules with pharmacological activities including anti-GITR mAbs, GITR-Fc and GITRL-Fc fusion proteins, GITRL in monomer or multimer conformation; and (iv) the possible risks deriving from GITRL/GITR system pharmacological modulation. In conclusion, GITR triggering and inhibition could be useful in treating tumours, infectious diseases, as well as autoimmune and inflammatory diseases. However, differences between mouse and human GITRL/GITR systems suggest that further preclinical studies are needed to better understand how safe therapeutic results can be obtained and to design appropriate clinical trials.     

Immunosuppression by Co‐stimulatory Molecules: Inhibition of CD2‐CD48/CD58 Interaction by Peptides from CD2 to Suppress Progression of Collagen‐induced Arthritis in Mice

Targeting co‐stimulatory molecules to modulate the immune response has been shown to have useful therapeutic effects for autoimmune diseases. Among the co‐stimulatory molecules, CD2 and CD58 are very important in the early stages of generation of an immune response. Our goal was to utilize CD2‐derived peptides to modulate protein–protein interactions between CD2 and CD58, thereby modulating the immune response. Several peptides were designed based on the structure of the CD58‐binding domain of CD2 protein. Among the CD2‐derived peptides, peptide 6 from the F and C β‐strand region of CD2 protein exhibited inhibition of cell–cell adhesion in the nanomolar concentration range. Peptide 6 was evaluated for its ability to bind to CD58 in Caco‐2 cells and to CD48 in T cells from rodents. A molecular model was proposed for binding a peptide to CD58 and CD48 using docking studies. Furthermore, in vivo studies were carried out to evaluate the therapeutic ability of the peptide to modulate the immune response in the collagen‐induced arthritis (CIA) mouse model. In vivo studies indicated that peptide 6 was able to suppress the progression of CIA. Evaluation of the antigenicity of peptides in CIA and transgenic animal models indicated that this peptide is not immunogenic.     

Biologic therapy for inflammatory bowel disease

Despite all of the advances in our understanding of the pathophysiology of inflammatory bowel disease (IBD), we still do not know its cause. Some of the most recently available data are discussed in this review; however, this field is changing rapidly and it is increasingly becoming accepted that immunogenetics play an important role in the predisposition, modulation and perpetuation of IBD. The role of intestinal milieu, and enteric flora in particular, appears to be of greater significance than previously thought. This complex interplay of genetic, microbial and environmental factors culminates in a sustained activation of the mucosal immune and non-immune response, probably facilitated by defects in the intestinal epithelial barrier and mucosal immune system, resulting in active inflammation and tissue destruction. Under normal situations, the intestinal mucosa is in a state of 'controlled' inflammation regulated by a delicate balance of proinflammatory (tumour necrosis factor [TNF]-alpha, interferon [IFN]-gamma, interleukin [IL]-1, IL-6, IL-12) and anti-inflammatory cytokines (IL-4, IL-10, IL-11). The mucosal immune system is the central effector of intestinal inflammation and injury, with cytokines playing a central role in modulating inflammation. Cytokines may, therefore, be a logical target for IBD therapy using specific cytokine inhibitors. Biotechnology agents targeted against TNF, leukocyte adhesion, T-helper cell (T(h))-1 polarisation, T-cell activation or nuclear factor (NF)-kappaB, and other miscellaneous therapies are being evaluated as potential therapies for IBD. In this context, infliximab is currently the only biologic agent approved for the treatment of inflammatory and fistulising Crohn's disease. Other anti-TNF biologic agents have emerged, including CDP 571, certolizumab pegol (CDP 870), etanercept, onercept and adalimumab. However, ongoing research continues to generate new biologic agents targeted at specific pathogenic mechanisms involved in the inflammatory process. Lymphocyte-endothelial interactions mediated by adhesion molecules are important in leukocyte migration and recruitment to sites of inflammation, and selective blockade of these adhesion molecules is a novel and promising strategy to treat Crohn's disease. Therapeutic agents that inhibit leukocyte trafficking include natalizumab, MLN-02 and alicaforsen (ISIS 2302). Other agents being investigated for the treatment of Crohn's disease include inhibitors of T-cell activation, peroxisome proliferator-activated receptors, proinflammatory cytokine receptors and T(h)1 polarisation, and growth hormone and growth factors. Agents being investigated for treatment of ulcerative colitis include many of those mentioned for Crohn's disease. More controlled clinical trials are currently being conducted, exploring the safety and efficacy of old and new biologic agents, and the search certainly will open new and exciting perspectives on the development of therapies for IBD.     

Immune deviation strategies in the therapy of psoriasis

The experience with biologicals in currently available animal models suggest that inflammatory autoimmune disease depend on IFN-gamma-producing T helper (Th) cells. Deletion of T cells improves most of these autoimmune diseases but bears the risks of general immunosuppression. Alternatively, selective deviation of the inflammatory, disease-inducing Th cells into an anti-inflammatory Th cell phenotype may be a promising strategy to treat inflammatory autoimmune diseases, such as psoriasis, rheumatoid arthritis, multiple sclerosis or autoimmune diabetes. The common feature of these organ-specific autoimmune diseases is the close association with IFN-gamma-producing Th1 cells, which recognize organ-specific antigens and orchestrate the cells and mediators that ultimately cause the tissue damage. Even though the autoantigens recognized in psoriasis remain enigmatic, it has been the first Th1-mediated autoimmune disease successfully treated in humans by immune deviation. The basis of such an immune intervention therapy has been established in experimental mice with model diseases of multiple sclerosis, rheumatoid arthritis or autoimmune diabetes. In all these autoimmune diseases clinical improvement was associated with the skewing of IFN-gamma producing autoantigen-specific Th1 cells into an IL-4 dominated Th2 phenotype. Such Th2 cells are still reactive to the autoantigen but provide a different cytokine pattern. The most powerful cytokines capable of inducing anti-inflammatory Th2 cells are IL-4 itself or IL-11. Interestingly, another agent that has been used for decades in the therapy of psoriasis in some European countries, fumaric acid esters (FAE), seems also to induce immune deviation. This review focuses on the potential immune deviating strategies based on the use of IL-4, IL-11 or FAE in the therapy of psoriasis, the effects of these agents on the immune system, potential risks and future perspectives for therapeutic intervention by immune deviation replacing immunosuppression.     

Neutrophils: Cinderella of innate immune system

Neutrophils are the first line of innate immune defense against infectious diseases. However, since their discovery by Elie Metchnikoff, they have always been considered tissue-destructive cells responsible for inflammatory tissue damage occurring during acute infections. Now, extensive research in the field of neutrophil cell biology and their role skewing the immune response in various infections or inflammatory disorders revealed their importance in the regulation of immune response. Along with releasing various antimicrobial molecules, neutrophils also release neutrophil extracellular traps (NETs) for the containment of infection and inflammation. Activated neutrophils provide signals for the activation and maturation of macrophages as well as dendritic cells. Neutrophils are also involved in the regulation of T-cell immune response against various pathogens and tumor antigens. Thus, the present review is intended to highlight the emerging role of neutrophils in the regulation of both innate and adaptive immunity during acute infectious or inflammatory conditions.