Causal effects of non-alcoholic fatty liver disease on osteoporosis: a Mendelian randomization study

Background

Osteoporosis (OP) is a systemic skeletal disease characterized by compromised bone strength leading to an increased risk of fracture. There is an ongoing debate on whether non-alcoholic fatty liver disease (NAFLD) is an active contributor or an innocent bystander in the pathogenesis of OP. The aim of this study was to assess the causal association between NAFLD and OP.

Methods

We performed two-sample Mendelian randomization (MR) analyses to investigate the causal association between genetically predicted NAFLD [i.e., imaging-based liver fat content (LFC), chronically elevated serum alanine aminotransferase (cALT) and biopsy-confirmed NAFLD] and risk of OP. The inverse variant weighted method was performed as main analysis to obtain the causal estimates.

Results

Imaging-based LFC and biopsy-confirmed NAFLD demonstrated a suggestive causal association with OP ([odds ratio (OR): 1.003, 95% CI: 1.001-1.004, P < 0.001; OR: 1.001, 95% CI: 1.000-1.002, P = 0.031]). The association between cALT and OP showed a similar direction, but was not statistically significant (OR: 1.001, 95% CI: 1.000-1.002, P = 0.079). Repeated analyses after exclusion of genes associated with confounding factors showed consistent results. Sensitivity analysis indicated low heterogeneity, high reliability and low pleiotropy of the causal estimates.

Conclusion

The two-sample MR analyses suggest a causal association between genetically predicted NAFLD and OP.

Combined therapy of GABA and sitagliptin prevents high-fat diet impairment of beta-cell function

We recently demonstrated that combined therapy of GABA and sitagliptin promoted beta-cell proliferation, and decreased beta-cell apoptosis in a multiple low-dose streptozotocin (STZ)-induced beta-cell injury mouse model. In this study, we examined whether this combined therapy is effective in ameliorating the impairment of beta-cell function caused by high-fat diet (HFD) feeding in mice. Male C57BL/6J mice were fed normal chow diet, HFD, or HFD combined with GABA, sitagliptin, or both drugs. Oral drug daily administration was initiated one week before HFD and maintained for two weeks. After two weeks of intervention, we found that GABA or sitagliptin administration ameliorated the impairment of glucose tolerance induced by HFD. This was associated with improved insulin secretion in vivo. Notably, combined administration of GABA and sitagliptin significantly enhanced these effects as compared to each of the monotherapies. Combined GABA and sitagliptin was superior at increasing beta-cell mass, and associated Ki67⁺ and PDX-1⁺ beta-cell counts. In addition, we found that HFD-induced compensatory beta-cell proliferation was associated with increased activation of unfolded protein response (UPR), as indicated by BiP expression. This could be an important mechanism of compensatory beta-cell proliferation, and beta cells treated with GABA and sitagliptin showed greater UPR activation. Our results suggest that the combined use of these agents produces superior therapeutic outcomes.

Combined use of GABA and sitagliptin promotes human β-cell proliferation and reduces apoptosis

γ-Aminobutyric acid (GABA) and glucagon-like peptide-1 receptor agonist (GLP-1RA) improve rodent β-cell survival and function. In human β-cells, GABA exerts stimulatory effects on proliferation and anti-apoptotic effects, whereas GLP-1RA drugs have only limited effects on proliferation. We previously demonstrated that GABA and sitagliptin (Sita), a dipeptidyl peptidase-4 inhibitor which increases endogenous GLP-1 levels, mediated a synergistic β-cell protective effect in mice islets. However, it remains unclear whether this combination has similar effects on human β-cell. To address this question, we transplanted a suboptimal mass of human islets into immunodeficient NOD-scid-gamma mice with streptozotocin-induced diabetes, and then treated them with GABA, Sita, or both. The oral administration of either GABA or Sita ameliorated blood glucose levels, increased transplanted human β-cell counts and plasma human insulin levels. Importantly, the combined administration of the drugs generated significantly superior results in all these responses, as compared to the monotherapy with either one of them. The proliferation and/or regeneration, improved by the combination, were demonstrated by increased Ki67+, PDX-1+, or Nkx6.1+ β-cell numbers. Protection against apoptosis was also significantly improved by the drug combination. The expression level of α-Klotho, a protein with protective and stimulatory effects on β cells, was also augmented. Our study indicates that combined use of GABA and Sita produced greater therapeutic benefits, which are likely due to an enhancement of β-cell proliferation and a decrease in apoptosis.

Immune-Mediated Tissue Injury (Hypersensitivity Reactions)

Hypersensitivity is synonymous with immune-mediated tissue injury. Hypersensitivity reactions occur in several forms and give rise to numerous conditions including allergies, autoimmune disease, allograft rejection, granulomatous inflammation, and a variety of acute or chronic inflammatory disorders (vasculitis, glomerulonephritis, arthritis, pneumonitis, encephalitis, etc.). While hypersensitivity is usually detrimental, in some cases it represents a normal response to a pathogen (e.g., the granulomatous inflammation of tuberculosis). Several years ago, Gell and Coombs divided hypersensitivity states into four basic types (1), and this classification remains useful today (Table 1). Type I hypersensitivity reactions result from IgE-dependent degranulation of mast cells or basophils. Type II, or "cytotoxic" hypersensitivity, results from the binding of IgG or IgM antibodies to cell membranes or fixed tissue antigens, causing activation of the complement system. Type III, or "immune-complex" hypersensitivity, results from the formation of immune complexes that precipitate in tissues (or form in situ), also with activation of complement. Type IV, or "cell-mediated" reactions, can be subdivided into two basic types: type IV-A is synonymous with delayed-type hypersensitivity (DTH) and usually occurs in response to soluble antigens; type IV-B results from the direct killing of target cells by cytotoxic T lymphocytes (CTL). Stimulation of cells by anti-receptor autoantibodies (such as the anti-TSH receptor antibodies of Graves' disease) has been designated as type V hypersensitivity by some authors. In addition, there are syndromes caused by massive cytokine release that are not usually referred to as hypersensitivity reactions, although (in accord with the definition) they should be included in that category. Examples are anti-CD3 mAb therapy, superantigen- (superAg) induced diseases (toxic shock syndrome, scalded skin syndrome), and shock caused by endotoxins (gram negative septicemia). Despite the occurrence of tissue injury, it should be understood that hypersensitivity mechanisms evolved as a means of fighting infectious agents. The mechanisms underlying these hypersensitivity states will be described and some clinical examples will be mentioned. In particular, the important role of cytokines, which is an area where considerable progress has occurred in recent years, will be emphasized.

GABA requires GLP-1R to exert its pancreatic function during STZ challenge

Gamma-aminobutyric acid (GABA) administration attenuates streptozotocin (STZ)-induced diabetes in rodent models with unclear underlying mechanisms. We found that GABA and Sitagliptin possess additive effect on pancreatic β-cells, which prompted us to ask the existence of common or unique targets of GLP-1 and GABA in pancreatic β-cells. Effect of GABA on expression of thioredoxin-interacting protein (TxNIP) was assessed in the INS-1 832/13 (INS-1) cell line, WT and GLP-1R-/- mouse islets. GABA was also orally administrated in STZ-challenged WT or GLP-1R-/- mice, followed by immunohistochemistry assessment of pancreatic islets. Effect of GABA on Wnt pathway effector β-catenin (β-cat) was examined in INS-1 cells, WT and GLP-1R-/- islets. We found that GABA shares a common feature with GLP-1 on inhibiting TxNIP, while this function was attenuated in GLP-1R-/- islets. In WT mice with STZ challenge, GABA alleviated several 'diabetic syndromes', associated with increased β-cell mass. These features were virtually absent in GLP-1R-/- mice. Knockdown TxNIP in INS-1 cells increased GLP-1R, Pdx1, Nkx6.1 and Mafa levels, associated with increased responses to GABA or GLP-1 on stimulating insulin secretion. Cleaved caspase-3 level can be induced by high-glucose, dexamethasone, or STZ in INS-1 cell, while GABA treatment blocked the induction. Finally, GABA treatment increased cellular cAMP level and β-cat S675 phosphorylation in WT but not GLP-1R-/- islets. We, hence, identified TxNIP as a common target of GABA and GLP-1 and suggest that, upon STZ or other stress challenge, the GLP-1R-cAMP-β-cat signaling cascade also mediates beneficial effects of GABA in pancreatic β-cell, involving TxNIP reduction.

GABAergic regulation of pancreatic islet cells: Physiology and antidiabetic effects

Diabetes occurs when pancreatic β-cell death exceeds β-cell growth, which leads to loss of β-cell mass. An effective therapy must have two actions: promotion of β-cell replication and suppression of β-cell death. Previous studies have established an important role for γ-aminobutyric acid (GABA) in islet-cell hormone homeostasis, as well as the maintenance of the β-cell mass. GABA exerts paracrine actions on α cells in suppressing glucagon secretion, and it has autocrine actions on β cells that increase insulin secretion. Multiple studies have shown that GABA increases the mitotic rate of β cells. In mice, following β-cell depletion with streptozotocin, GABA therapy can restore the β-cell mass. Enhanced β-cell replication appears to depend on growth and survival pathways involving Akt activation. Some studies have also suggested that it induces transdifferentiation of α cells into β cells, but this has been disputed and requires further investigation. In addition to proliferative effects, GABA protects β cells against injury and markedly reduces their apoptosis under a variety of conditions. The antiapoptotic effects depend at least in part on the enhancement of sirtuin-1 and Klotho activity, which both inhibit activation of the NF-κB inflammatory pathway. Importantly, in xenotransplanted human islets, GABA therapy stimulates β-cell replication and insulin secretion. Thus, the intraislet GABAergic system is a target for the amelioration of diabetes therapy, including β-cell survival and regeneration. GABA (or GABAergic drugs) can be combined with other antidiabetic drugs for greater effect.

Novel GLP-1 Analog Supaglutide Stimulates Insulin Secretion in Mouse and Human Islet Beta-Cells and Improves Glucose Homeostasis in Diabetic Mice

Glucagon-like peptide-1 (GLP-1), an incretin hormone plays an important role in regulating glucose homeostasis. The therapeutic use of native GLP-1 is inadequate due to its short in vivo half-life. We recently developed a novel GLP-1 mimetics supaglutide, and demonstrated that this formulation retained native GLP-1 biological activities and possessed long-lasting GLP-1 actions. In this study, we further examined its abilities in regulating blood glucose in diabetic mice. We found that supaglutide stimulated insulin secretion in both mouse and human islets in a dose-dependent fashion. Oral glucose tolerance test conducted in normal ICR mice showed that supaglutide significantly decreased postprandial glucose excursions in a dose-dependent fashion. In type 2 diabetic db/db mice, a single-dose injection of supaglutide significantly decreased blood glucose levels, and this efficacy was lasted for at least 72 h in a dose-dependent fashion. During a 4-weeks intervention course supaglutide (twice injections per week) dose-dependently and significantly decreased fasting and random blood glucose levels in hyperglycemic db/db mice. Supaglutide, at a dose of 1.2 mg/kg, significantly reduced serum fructosamine levels. This was associated with significant enlargement of beta-cell mass, increased pancreatic insulin content, and increased plasma insulin level. Notably, during the intervention course supaglutide significantly reduced body-weight gain in these obese diabetic mice, associated with reduced fat mass (but not the lean mass), improved lipid profile, i.e., declined serum triglyceride, and free fatty acid levels compared to the placebo control. These finding reveals that supaglutide exerts beneficial effects in regulating blood glucose and lipid homeostasis in diabetic db/db mice.

Combined effect of GABA and glucagon-like peptide-1 receptor agonist on cytokine-induced apoptosis in pancreatic β-cell line and isolated human islets

BACKGROUND

Treatment with GABA or glucagon-like peptide-1 (GLP-1) can preserve pancreatic β-cell mass and prevent diabetes. Recently, we reported that the combination of GABA and sitagliptin (a dipeptidyl peptidase-4 inhibitor that increases endogenous GLP-1) was more effective than either agent alone in reducing drug-induced β-cell damage and promoting β-cell regeneration in mice. However, in human islets, it remains unclear whether GABA and GLP-1 exert similar effects.

METHODS

To investigate GABA and GLP-1 interactions, human islets or INS-1 cells were treated with GABA and/or exendin-4, a GLP-1 receptor agonist (GLP-1RA) in clinical use, and incubated with a cytokine mixture for 24 hours. Cleaved caspase-3 and annexin V binding were measured by western blot and flow cytometry analysis, respectively, to investigate effects on cytokine-induced apoptosis.

RESULTS

Cytokine-induced apoptosis was reduced by either GABA or exendin-4 alone. This was markedly improved by combining GABA and exendin-4, resulting in a reversal of apoptosis. The combination notably increased Akt pathway signaling. Furthermore, sirtuin-1 (SIRT1) and α-Klotho, both reported to have protective effects on β-cells, were increased. Importantly, the combination ameliorated insulin secretion by human β-cells.

CONCLUSIONS

The combination of GABA and a GLP-1RA exerted additive effects on β-cell survival and function, suggesting that this combination may be superior to either drug alone in the treatment of diabetes.

Jack of many trades: Multifaceted role of neuropilins in pancreatic cancer

Neuropilins (NRPs) have been described as receptors for class 3 semaphorins and coreceptors for a plethora of ligands, such as members of the vascular endothelial growth factor (VEGF) family of angiogenic cytokines and transforming growth factor (TGF). Initial studies using genetic models have indicated that neuropilin-1 (NRP-1) is essential for axonal guidance during neuronal and cardiovascular development, regulated via semaphorins and VEGF, respectively, whereas the other homolog of neuropilin, NRP-2, has been shown to play a more specific role in neuronal patterning and lymphangiogenesis. Pancreatic ductal adenocarcinoma (PDAC) remains a significant cause of cancer mortality with the lowest five-year survival rate compared to other types of cancer. Recent findings have indicated that NRPs are abundantly expressed in pancreatic cancer cell lines and pancreatic tumor tissues, where they mediate several essential cancer-initiating and cancer-promoting functional responses through their unique ability to bind multiple ligands. Specifically, NRPs have been implicated in numerous biological processes such as cancer cell proliferation, survival, invasion, and tumor growth. More recently, several other protumorigenic roles mediated by NRPs have emerged, advocating NRPs as ideal therapeutic targets against PDAC.

Neuropilin-1 is a receptor for extracellular miRNA and AGO2/miRNA complexes and mediates the internalization of miRNAs that modulate cell function

Extracellular miRNAs are increasingly studied as markers for specific diseases. They are released in biological fluids in a remarkably stable form, and may play a role in intercellular communication. They are thought to be protected against degradation by either encapsulation within microparticles, or by binding to proteins (mostly AGO2). The particulate forms may be internalized by endocytosis or membrane fusion, but the protein-bound forms require a receptor mechanism for their uptake. A major question is whether there are natural cell-membrane receptors that capture and internalize protein-bound functional miRNAs. We examined neuropilin-1 (NRP1), in view of its properties as a receptor for many ligands, including growth factors such as vascular endothelial growth factor (VEGF), and efficiency at mediating ligand internalization. It is expressed by endothelial cells, many other normal cell types, and cancer cells. Here, we report that NRP1 binds miRNAs with high affinity, and promotes their entry into the cell. Furthermore, the internalized miRNAs remain functional, as they specifically regulate proliferation and migration of cancer cells, as well as tube formation by human endothelial cells. Anti-NRP1 antibodies or NRP1 siRNA knockdown block miRNA effects, further confirming NRP1-mediated uptake. VEGF does not compete with miRNAs for binding to NRP1. In addition, NRP1 binds extracellular AGO2 (carrying miRNA or not), and internalizes AGO2/miRNA complexes. Because miRNA bound to AGO2 appears to the most abundant form in body fluids, this may have important physiological and pathological effects.

Novel regulatory role of neuropilin-1 in endothelial-to-mesenchymal transition and fibrosis in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is characterized by an intense fibrotic reaction termed tumor desmoplasia, which is in part responsible for its aggressiveness. Endothelial cells have been shown to display cellular plasticity in the form of endothelial-to-mesenchymal transition (EndMT) that serves as an important source of fibroblasts in pathological disorders, including cancer. Angiogenic co-receptor, neuropilin-1 (NRP-1) actively binds TGFβ1, the primary mediator of EndMT and is involved in oncogenic processes like epithelial-to-mesenchymal transition (EMT). NRP-1 and TGFβ1 signaling have been shown to be aberrantly up-regulated in PDAC. We report herein a positive correlation between NRP-1 levels, EndMT and fibrosis in human PDAC xenografts. Loss of NRP-1 in HUVECs limited TGFβ1-induced EndMT as demonstrated by gain of endothelial and loss of mesenchymal markers, while maintaining endothelial cell architecture. Knockdown of NRP-1 down-regulated TGFβ canonical signaling (pSMAD2) and associated pro-fibrotic genes. Overexpression of NRP-1 exacerbated TGFβ1-induced EndMT and up-regulated TGFβ signaling and expression of pro-fibrotic genes. In vivo, loss of NRP-1 attenuated tumor perfusion and size, accompanied by reduction in EndMT and fibrosis. This study defines a previously unrecognized role of NRP-1 in regulating TGFβ1-induced EndMT and fibrosis, and advocates NRP-1 as a therapeutic target to reduce tumor fibrosis and PDAC progression.

Combined Oral Administration of GABA and DPP-4 Inhibitor Prevents Beta Cell Damage and Promotes Beta Cell Regeneration in Mice

γ-aminobutyric acid (GABA) or glucagon-like peptide-1 based drugs, such as sitagliptin (a dipeptidyl peptidase-4 inhibitor), were shown to induce beta cell regenerative effects in various diabetic mouse models. We propose that their combined administration can bring forth an additive therapeutic effect. We tested this hypothesis in a multiple low-dose streptozotocin (STZ)-induced beta cell injury mouse model (MDSD). Male C57BL/6J mice were assigned randomly into four groups: non-treatment diabetic control, GABA, sitagliptin, or GABA plus sitagliptin. Oral drug administration was initiated 1 week before STZ injection and maintained for 6 weeks. GABA or sitagliptin administration decreased ambient blood glucose levels and improved the glucose excursion rate. This was associated with elevated plasma insulin and reduced plasma glucagon levels. Importantly, combined use of GABA and sitagliptin significantly enhanced these effects as compared with each of the monotherapies. An additive effect on reducing water consumption was also observed. Immunohistochemical analyses revealed that combined GABA and sitagliptin therapy was superior in increasing beta cell mass, associated with increased small-size islet numbers, Ki67⁺ and PDX-1⁺ beta cell counts; and reduced Tunel⁺ beta cell counts. Thus, beta cell proliferation was increased, whereas apoptosis was reduced. We also noticed a suppressive effect of GABA or sitagliptin on alpha cell mass, which was not significantly altered by combining the two agents. Although either GABA or sitagliptin administration delays the onset of MDSD, our study indicates that combined use of them produces superior therapeutic outcomes. This is likely due to an amelioration of beta cell proliferation and a decrease of beta cell apoptosis.

Current indications and surgical approaches to corneal transplants at the University of Toronto: A clinical-pathological study

OBJECTIVE

To determine the most common reasons and surgical approaches for corneal graft surgery at the Kensington Eye Institute (KEI), University of Toronto.

DESIGN

Retrospective cross-sectional study.

PARTICIPANTS

A total of 229 consecutive corneal transplants performed at the KEI.

METHODS

Demographic, clinical, and pathological data on all 2012 and 2013 corneal transplants were collected.

RESULTS

The mean age for corneal transplants was 65 ± 16 years; 39% were full-thickness penetrating keratoplasties (PK) and 61% were partial-thickness. Graft failure (30%), infection (18%), and keratoconus (17%) were the leading indications for PK. Fuchs' dystrophy (40%) and bullous keratopathy (24%) were main causes for partial-thickness procedures. Among partial-thickness approaches, Descemet's stripping automated endothelial keratoplasty (DSAEK), deep anterior lamellar keratoplasty (DALK), and Descemet's membrane endothelial keratoplasty (DMEK) procedures accounted for 68%, 16%, and 16%, respectively. Fuchs' dystrophy (40%) and bullous keratopathy (33%) were the most common indications for DSAEK. Keratoconus (57%) and corneal scarring (35%) were the most common indications for DALK, whereas Fuchs' dystrophy (82%) accounted for most DMEK procedures. The most common reasons for all corneal grafts were Fuchs' dystrophy (25%), bullous keratopathy (21%), graft failure (17%), and keratoconus (12%).

CONCLUSIONS

Almost two-thirds of all corneal transplant procedures at the University of Toronto are partial thickness procedures. A failed graft was found to be the most common indication for full-thickness transplants. Fuchs' dystrophy was the most common indication for a partial-thickness approach, most often treated by DSAEK. Longitudinal data are needed to determine whether partial-thickness surgeries will improve graft survival and reduce the need for regraft.

Study of GABA in Healthy Volunteers: Pharmacokinetics and Pharmacodynamics

Preclinical studies show that GABA exerts anti-diabetic effects in rodent models of type 1 diabetes. Because little is known about its absorption and effects in humans, we investigated the pharmacokinetics and pharmacodynamics of GABA in healthy volunteers. Twelve subjects were subjected to an open-labeled, three-period trial involving sequential oral administration of placebo, 2 g GABA once, and 2 g GABA three times/day for 7 days, with a 7-day washout between each period. GABA was rapidly absorbed (Tmax: 0.5 ~ 1 h) with the half-life (t1/2) of 5 h. No accumulation was observed after repeated oral GABA administration for 7 days. Remarkably, GABA significantly increased circulating insulin levels in the subjects under either fasting (1.6-fold, single dose; 2.0-fold, repeated dose; p < 0.01) or fed conditions (1.4-fold, single dose; 1.6-fold, repeated dose; p < 0.01). GABA also increased glucagon levels only under fasting conditions (1.3-fold, single dose, p < 0.05; 1.5-fold, repeated dose, p < 0.01). However, there were no significant differences in the insulin-to-glucagon ratio and no significant change in glucose levels in these healthy subjects during the study period. Importantly, GABA significantly decreased glycated albumin levels in the repeated dosing period. Subjects with repeated dosing showed an elevated incidence of minor adverse events in comparison to placebo or the single dosing period, most notably transient discomforts such as dizziness and sore throat. However, there were no serious adverse events observed throughout the study. Our data show that GABA is rapidly absorbed and tolerated in human beings; its endocrine effects, exemplified by increasing islet hormonal secretion, suggest potential therapeutic benefits for diabetes.

GABA promotes human β-cell proliferation and modulates glucose homeostasis

γ-Aminobutyric acid (GABA) exerts protective and regenerative effects on mouse islet β-cells. However, in humans it is unknown whether it can increase β-cell mass and improve glucose homeostasis. To address this question, we transplanted a suboptimal mass of human islets into immunodeficient NOD-scid-γ mice with streptozotocin-induced diabetes. GABA treatment increased grafted β-cell proliferation, while decreasing apoptosis, leading to enhanced β-cell mass. This was associated with increased circulating human insulin and reduced glucagon levels. Importantly, GABA administration lowered blood glucose levels and improved glucose excursion rates. We investigated GABA receptor expression and signaling mechanisms. In human islets, GABA activated a calcium-dependent signaling pathway through both GABA A receptor and GABA B receptor. This activated the phosphatidylinositol 3-kinase-Akt and CREB-IRS-2 signaling pathways that convey GABA signals responsible for β-cell proliferation and survival. Our findings suggest that GABA regulates human β-cell mass and may be beneficial for the treatment of diabetes or improvement of islet transplantation.

A site-specific genomic integration strategy for sustained expression of glucagon-like peptide-1 in mouse muscle for controlling energy homeostasis

The incretin hormone glucagon-like peptide-1 (GLP-1) exerts important functions in controlling glucose and energy homeostasis. Endogenous GLP-1 has a very short half-life due to DPP-IV-mediated degradation and renal clearance, which limits the therapeutic use of native GLP-1. We have shown previously that immunoglobulin fragment-fused GLP-1 (GLP-1/Fc) is a structurally stable GLP-1 analog. Here, we report a non-viral GLP-1/Fc gene therapy strategy utilizing a REP78-in-trans and REB-in-cis element system to achieve a site-specific genomic integration. For this purpose, the GLP-1/Fc expression cassette, which is fused with the RBE element, was co-injected with the Rep78 plasmid into the muscles of transgenic mice carrying the AAVS1 locus of human chromosome 19. The Rep protein-mediated site-specific integration was demonstrated by nested PCR, dot-blot, and Southern blotting. We found that this approach reduced weight gain and improved lipid profiles in the AAVS1-mice on high-fat diet challenge. Our observations reveal a new GLP-1 therapeutic strategy with an apparent absence of side effects, which may find applications in diabetes treatment and obesity prevention.

Tranilast treatment decreases cell growth, migration and inhibits colony formation of human breast cancer cells

In the treatment of breast cancer, although a wide of choice of drugs and treatment modalities are available, drug resistance or drug toxicity poses a considerable challenge. Tranilast is a well tolerated drug used in the treatment of allergic disorders. Previous works in various models have shown that tranilast has the potential to be used as an anti-cancer drug. Hence, in this study using human breast cancer cell lines BT-474 and MDA-MB-231, we studied the effect of tranilast on cell growth, migration and ability to prevent colony formation in vitro, properties that are relevant to a possible therapeutic effect in breast cancer. We found that tranilast inhibits the growth of both breast cancer cell lines. In the cell migration experiments, the tumor cells exhibit significantly slower wound closure after tranilast treatment, as well as reduced migration using an insert system. Downregulation of MRTF-A, a global cytoskeleton regulator was observed after tranilast treatment. Additionally, tranilast treatment increased levels of cleaved PARP in both cell lines tested indicating a stimulation of apoptosis. A significant reduction in colony size and number was observed in soft agar clonogenic assays in both cell lines after tranilast treatment. BT-474 cells were more responsive to tranilast treatment compared to MDA-MB-231 cells, suggesting a difference in modes of action, or sensitivity, possibly related to their different receptor status. Based on these changes in cancer cell lines, we conclude that tranilast exerts effects that set a rationale for future preclinical studies in animal models of breast cancer.

Novel GLP-1 fusion chimera as potent long acting GLP-1 receptor agonist

GLP-1 has a variety of anti-diabetic effects. However, native GLP-1 is not suitable for therapy of diabetes due to its short half-life (t1/2<2 min). To circumvent this, we developed a long-lasting GLP-1 receptor agonist by the fusion of GLP-1 with human IgG2 Fc (GLP-1/hIgG2). ELISA-based receptor binding assay demonstrated that GLP-1/hIgG2 had high binding affinity to the GLP-1R in INS-1 cells (Kd = 13.90±1.52 nM). Upon binding, GLP-1/hIgG2 was rapidly internalized by INS-1 cells in a dynamin-dependent manner. Insulin RIA showed that GLP-1/IgG2 dose-dependently stimulated insulin secretion from INS-1 cells. Pharmacokinetic studies in CD1 mice showed that with intraperitoneal injection (i.p.), the GLP-1/hIgG2 peaked at 30 minutes in circulation and maintained a plateau for >168 h. Intraperitoneal glucose tolerance test (IPGTT) in mice showed that GLP-1/hIgG2 significantly decreased glucose excursion. Furthermore, IPGTT performed on mice one week after a single drug-injection also displayed significantly reduced glucose excursion, indicating that GLP-1/hIgG2 fusion protein has long-lasting effects on the modulation of glucose homeostasis. GLP-1/hIgG2 was found to be effective in reducing the incidence of diabetes in multiple-low-dose streptozotocin-induced type 1 diabetes in mice. Together, the long-lasting bioactive GLP-1/hIgG2 retains native GLP-1 activities and thus may serve as a potent GLP-1 receptor agonist.

Abstract LB-290: Tranilast inhibits breast cancer stem cells

Cancer stem cells (CSCs) have increased resistance to anti-cancer drugs, and may be responsible for chemotherapeutic failure. CSCs can be enriched from cancer cell lines by growth with anti-cancer drugs (e.g., doxorubicin, mitoxantrone), and form mammospheres in low-adherence, serum-free cultures. We are studying tranilast, a non-toxic orally active drug in clinical use for allergic diseases in Japan, but that we found also targets cancer cells. Previously, we reported that tranilast exerts multiple anti-cancer effects and protects against breast cancer metastasis. Our recent studies show that tranilast strongly inhibits breast CSCs in several assays, at pharmacologically relevant concentrations. We enriched CSCs from breast cancer cell lines by cell sorting for ALDH-1 positive cells (ALDEFLUOR+), or by growth in mitoxantrone-containing medium to select drug-surviving CSCs. In both cases, CSCs readily formed mammospheres in vitro. Tranilast inhibited mammosphere formation,’ and dissociated formed mammospheres. It was more effective than paclitaxel or etoposide. We recently identified molecular targets of this drug. We found it has aryl hydrocarbon receptor (AHR) agonist activity and this might explain its anti-cancer effects. The AHR is a receptor for toxins such as dioxin and polycyclic aromatic hydrocarbons. It is a transcription factor that exerts a number of ligand-dependent effects, such as cell-cycle arrest, reduced RB phosphorylation, and decreased cytokine and growth factor production. Unlike many AHR ligands, tranilast has very low toxicity (LD50 &gt; 1 gm/kg in rats), and is well tolerated by patients. In accord with a role for the AHR, breast CSCs expressed higher levels of this receptor than the main population of cancer cells, and the effects of tranilast were markedly diminished by an AHR antagonist (alpha-naphthoflavone). Moreover, we found tranilast inhibits some ATP-binding cassette (ABC) multiple drug resistance transporters, and it enhances the effects of other anti-cancer drugs. Our studies show that tranilast is a drug of low toxicity that has potential as an anti-CSC drug.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-290.

Neuropilins bind TGF-beta and its receptor components and promote Smad signaling (88.5)

Neuropilin-1 (Nrp1) and/or neuropilin-2 (Nrp2) are expressed by many tumors, correlating with a poor prognosis. Normally, Nrp1 is expressed by neurons, endothelial cells, dendritic cells (DCs) and Treg cells, while Nrp2 has a more limited distribution. Because neuropilins are coreceptors for VEGF, it has been thought they stimulate tumor angiogenesis, but they may also act otherwise. We recently reported that Nrp1 binds and activates LAP-TGF-beta1 (the latent form) and enhances Treg activity. Here, we report that both Nrp1 and Nrp2 interact with TGF-beta1, as well as TGF-beta receptor components, and induce internalization of the TGF-beta receptor complex. This enhances signaling by the Smad pathway. In accord with this, we found that both Nrp1 and Nrp2 activate latent TGF-beta1 on the membrane of breast cancer cells. The classical TGF-beta receptors (RI, RII and RIII) only bind active TGF-beta, but our data suggest that the neuropilins allow responsiveness to latent TGF-beta by its activation. We also find that TGF-beta competes with VEGF for binding to Nrp1/Nrp2, possibly altering angiogenesis. TGF-beta has been linked to metastasis and, thus, the neuropilins may promote metastasis by capturing and activating latent TGF-beta. Our novel findings are relevant to cancer biology, immune regulation and angiogenesis. This work was funded by the Ontario Institute for Cancer Research, Province of Ontario, Canada.

In vivo expression of GLP-1/IgG-Fc fusion protein enhances beta-cell mass and protects against streptozotocin-induced diabetes

Glucagon-like peptide 1 (GLP-1) and its analogue exendin-4 (Ex4) have displayed potent glucose homeostasis-modulating characteristics in type 2 diabetes (T2D). However, there are few reports of effectiveness in type 1 diabetes (T1D) therapy, where there is massive loss of beta cells. We previously described a novel GLP-1 analogue consisting of the fusion of active GLP-1 and IgG heavy chain constant regions (GLP-1/IgG-Fc), and showed that in vivo expression of the protein, via electroporation-enhanced intramuscular plasmid-based gene transfer, normalized blood glucose levels in T2D-prone db/db mice. In the present study, GLP-1/IgG-Fc and Ex4/IgG-Fc were independently tested in multiple low-dose streptozotocin-induced T1D. Both GLP-1/IgG-Fc and Ex4/IgG-Fc effectively reduced fed blood glucose levels in treated mice and ameliorated diabetes symptoms, where as control IgG-Fc had no effect. Treatment with GLP-1/IgG-Fc or Ex4/IgG-Fc improved glucose tolerance and increased circulating insulin and GLP-1 levels. It also significantly enhanced islet beta-cell mass, which is likely a major factor in the amelioration of diabetes. This suggests that GLP-1/IgG-Fc gene therapy may be applicable to diseases where there is either acute or chronic beta-cell injury.

Plasmid-based gene therapy of diabetes mellitus

Type I diabetes mellitus (T1D) is due to a loss of immune tolerance to islet antigen and thus, there is intense interest in developing therapies that can re-establish it. Tolerance is maintained by complex mechanisms that include inhibitory molecules and several types of regulatory T cells (Tr). A major historical question is whether gene therapy can be employed to generate Tr cells. This review shows that gene transfer of immunoregulatory molecules can prevent T1D and other autoimmune diseases. In our studies, non-viral gene transfer is enhanced by in vivo electroporation (EP). This technique can be used to perform DNA vaccination against islet cell antigens and when combined with appropriate immune ligands results in the generation of Tr cells and protection against T1D. In vivo EP can also be applied for non-immune therapy of diabetes. It can be used to deliver protein drugs such as glucagon-like peptide 1 (GLP-1), leptin or transforming growth factor beta (TGF-beta). These act in T1D or type II diabetes (T2D) by restoring glucose homeostasis, promoting islet cell survival and growth or improving wound healing and other complications. Furthermore, we show that in large animals EP can deliver peptide hormones, such as growth hormone releasing hormone (GHRH). We conclude that the non-viral gene therapy and EP represent a safe and efficacious approach with clinical potential.

Gene therapy of diabetes using a novel GLP-1/IgG1-Fc fusion construct normalizes glucose levels in db/db mice

Glucagon-like peptide (GLP-1), a major physiological incretin, plays numerous important roles in modulating blood glucose homeostasis and has been proposed for the treatment of type 2 diabetes. The major obstacles for using native GLP-1 as a therapeutic agent are that it must be delivered by a parenteral route and has a short half-life. In an attempt to develop a strategy to prolong the physiological t(1/2) and enhance the potency of GLP-1, a fusion protein consisting of active human GLP-1 and mouse IgG(1) heavy chain constant regions (GLP-1/Fc) was generated. A plasmid encoding an IgK leader peptide-driven secretable fusion protein of the active GLP-1 and IgG(1)-Fc was constructed for mammalian expression. This plasmid allows for expression of bivalent GLP-1 peptide ligands as a result of IgG-Fc homodimerization. In vitro studies employing purified GLP-1/Fc indicate that the fusion protein is functional and elevates cAMP levels in insulin-secreting INS-1 cells. In addition, it stimulates insulin secretion in a glucose concentration-dependent manner. Intramuscular gene transfer of the plasmid in db/db mice demonstrated that expression of the GLP-1/Fc peptide normalizes glucose tolerance by enhancing insulin secretion and suppressing glucagon release. This strategy of using a bivalent GLP-1/Fc fusion protein as a therapeutic agent is a novel approach for the treatment of diabetes.

Plasmids encoding membrane-bound IL-4 or IL-12 strongly costimulate DNA vaccination against carcinoembryonic antigen (CEA)

Vaccination with plasmids encoding an antigen of interest (DNA vaccination) is a new strategy to achieve effective immunization against many agents. DNA vaccination can be ameliorated by co-administration of plasmids encoding a cytokine. Thus far, only plasmids encoding soluble cytokines have been used for this purpose. However, these plasmids can induce release of cytokines into the circulation and could potentially cause many undesirable effects. We undertook this study to determine whether membrane-bound cytokines, which would restrict their localization at the site of administration, can act as immunoadjuvants. We and others have previously shown that plasmids encoding soluble IL-4 and IL-12 are effective adjuvants for DNA vaccination. In this study, we demonstrate that DNA co-vaccination with membrane-bound IL-4 (mbIL-4) or membrane-bound IL-12 (mbIL-12) both enhance anti-CEA immunity, as detected by in vitro and in vivo assays. Mice co-injected with plasmids encoding CEA and either type of membrane-bound cytokine rejected transplanted CEA-positive tumor cells strongly. Notably, unlike secreted IL-4, mbIL-4 was the most effective adjuvant for anti-tumor immunity. This study demonstrates that membrane-bound cytokines are suitable adjuvants for DNA vaccination.

Immunopathology and the gene therapy of lupus

Lupus is a chronic autoimmune inflammatory disease with complex clinical manifestations. In humans, lupus, also known as systemic lupus erythematosus (SLE), affects between 40 and 250 individuals, mostly females, in each 100 000 of the population. There are also a number of murine models of lupus widely used in studies of the genetics, immunopathology, and treatment of lupus. Human patients and murine models of lupus manifest a wide range of immunological abnormalities. The most pervasive of these are: (1) the ability to produce pathogenic autoantibodies; (2) lack of T- and B-lymphocyte regulation; and (3) defective clearance of autoantigens and immune complexes. This article briefly reviews immunological abnormalities and disease mechanisms characteristic of lupus autoimmunity and highlight recent studies on the use of gene therapy to target these abnormalities.

Immunoinhibitory DNA vaccine protects against autoimmune diabetes through cDNA encoding a selective CTLA-4 (CD152) ligand

Cytotoxic T lymphocyte antigen 4 (CTLA-4 or CD152) is a strong negative regulator of T cell activity. Like CD28 (a positive regulator) it binds to B7-1 and B7-2, and there is no known natural selective ligand. Monoclonal antibodies to CTLA-4 generally have a masking effect, enhancing rather than suppressing responses. However, a single amino acid substitution in B7-1 (W88 > A; denoted B7-1wa) abrogates binding to CD28 but not to CTLA-4. We constructed plasmids encoding B7-1 or B7-1wa, as cell-surface or Ig fusion proteins. In a bound state, B7-1-Ig enhanced CD3-mediated T cell activation, but B7-1wa-Ig was inhibitory, as expected of a CTLA-4 ligand. To alter immunity in vivo, we inoculated mice intramuscularly (i.m.) with a carcinoembryonic antigen (CEA) plasmid. Gene transfer was amplified by electroporation. Co-injection of a B7-1wa (membrane-bound form) plasmid blocked induction of anti-CEA immunity, whereas a B7-1 plasmid was stimulatory. We studied this DNA covaccination method in nonobese diabetic (NOD) mice with autoimmune diabetes. Delivery of either preproinsulin I (PPIns) or B7-1wa cDNA alone did not suppress the autoimmune anti-insulin response of spleen cells. However, co-delivery of B7-1wa and PPIns cDNA abrogated reactivity to insulin and ameliorated disease. Interferon-gamma and interleukin-4 were both depressed, arguing against a Th2 bias. Reactivity to glutamic acid decarboxylase 65, another major islet autoantigen, was not altered and suppressor cells were not identified, suggesting induction of tolerance to insulin by either T cell anergy or deletion. Selective engagement of CTLA-4 through gene transfer represents a novel and powerful way to block autoimmunity specifically.

Inhibitors of phosphodiesterase isoforms III or IV suppress islet-cell nitric oxide production

The general phosphodiesterase (PDE) inhibitor pentoxifylline (PTX), and the PDE type IV inhibitor rolipram (ROL), both increase intracellular cAMP levels and suppress inflammatory cytokine production by T cells and macrophages. We have previously shown that PTX and ROL protect from autoimmune diabetes in nonobese diabetic (NOD) mice. These drugs may mediate some of their anti-inflammatory effects by blocking nitric oxide (NO) production by macrophages. In this study, we investigated the effect of PDE inhibitors in blocking NO production by insulin-secreting NIT-1 insulinoma cells and mouse islet cells in vitro and in vivo. Insulinoma cells and islet cells produced NO when stimulated with a combination of inflammatory cytokines and lipopolysaccharide (LPS). We found that both PTX and ROL markedly suppressed this induced NO production. Islet cells express PDEs III and IV and, accordingly, the PDE III inhibitor cilostamide (CIL) also suppressed NO production, and a combination of ROL and CIL had a synergistic effect. This suppression appeared to be mediated, at least in part, by elevating cAMP level and was mimicked by other cAMP-elevating agents, ie, membrane-permeable cAMP analogs (dibutyryl cAMP and 8-bromo cAMP) and an adenylate cyclase stimulator (forskolin). PDE inhibitors suppressed the expression of inducible nitric oxide synthase (iNOS) mRNA. In vivo treatment with PTX or ROL prevented iNOS protein expression in the islets of NOD mice with cyclophosphamide-accelerated disease. Our findings suggest that PDE inhibitors can protect islets against autoimmunity.

Anticytokine gene therapy of autoimmune diseases

Viral and nonviral gene therapy vectors have been successfully employed to deliver inflammatory cytokine inhibitors (anticytokines), or anti-inflammatory cytokines, such as transforming growth factor beta-1 (TGF-beta 1), which protect against experimental autoimmune diseases. These vectors carry the relevant genes into a variety of tissues, for either localised or systemic release of the encoded protein. Administration of cDNA encoding soluble IFN-gamma receptor (IFN-gamma R)/IgG-Fc fusion proteins, soluble TNF-alpha receptors, or IL-1 receptor antagonist (IL-1ra), protects against either lupus, various forms of arthritis, autoimmune diabetes, or other autoimmune diseases. These inhibitors, unlike many cytokines, have little or no toxic potential. Similarly, TGF-beta 1 gene therapy protects against numerous forms of autoimmunity, though its administration entails more risk than anticytokine therapy. We have relied on the injection of naked plasmid DNA into skeletal muscle, with or without enhancement of gene transfer by in vivo electroporation. Expression plasmids offer interesting advantages over viral vectors, since they are simple to produce, non-immunogenic and nonpathogenic. They can be repeatedly administered and after each treatment the encoded proteins are produced for relatively long periods, ranging from weeks to months. Moreover, soluble receptors which block cytokine action, encoded by gene therapy vectors, can be constructed from non-immunogenic self elements that are unlikely to be neutralised by the host immune response (unlike monoclonal antibodies [mAbs]), allowing long-term gene therapy of chronic inflammatory disorders.

Immunotherapeutic gene transfer into muscle

Immuno-gene therapy can be advantageously performed with nonviral approaches. Genes that encode regulatory cytokines or inflammatory cytokine inhibitors can be delivered intramuscularly and expressed for weeks or months. This type of gene transfer into muscle has been shown to ameliorate several autoimmune diseases and is relevant to the development of effective DNA vaccines in autoimmune diseases, infectious diseases and cancer.

The phosphodiesterase inhibitors pentoxifylline and rolipram suppress macrophage activation and nitric oxide production in vitro and in vivo

We studied the effects of the phosphodiesterase inhibitors pentoxifylline (PTX) and rolipram (ROL) on nitric oxide (NO) production by macrophages and correlated this with cellular cAMP levels. The RAW 264.7 cell line or mouse peritoneal macrophages were activated with lipopolysaccharide (LPS) and interferon gamma (IFN gamma), with or without ROL, PTX, cAMP analogues, or Forskolin. In vivo, peritoneal macrophages were stimulated with staphylococcal enterotoxin B with or without administration of ROL. Nitrite levels in culture and the total cellular cAMP levels were measured. ROL and PTX suppressed NO production of LPS/IFN gamma-stimulated macrophages. ROL (IC(50) = 68-74 microM) was about 40 times more potent than PTX (IC(50) = 2.4-2.9 mM). The suppression paralleled increased total cellular cAMP level (EC(50) = 68-72 microM) and was mimicked by other cAMP elevating agents. ROL and PTX suppressed inducible NO synthase at the mRNA level. The inhibition of NO production of macrophages by ROL or PTX could be beneficial in NO-mediated inflammatory and/or autoimmune disorders.

IL-12 plasmid-enhanced DNA vaccination against carcinoembryonic antigen (CEA) studied in immune-gene knockout mice

Intramuscular (i.m.) injection of a plasmid encoding human carcinoembryonic antigen (CEA) elicited immunity against transplanted syngeneic (C57BL/6) CEA-positive Lewis lung carcinoma (CEA/LLC) cells, but tumors still appeared in all mice. In wild-type mice, coinjection of an IL-12 plasmid markedly enhanced anti-CEA humoral, T-helper-1 and cytotoxic T lymphocyte (CTL) responses, and resistance to a CEA/LLC tumor challenge such that 80% of mice remained tumor free. Injection of the IL- 12 plasmid alone was not protective. To analyze immune requirements, we immunized gene knockout (KO) mice of C57BL/6 background, deficient in either CD3, CD4, CD8, interferon gamma (IFNgamma), perforin or Fas ligand (FasL). Only CD3+ mice expressing both CD4 and CD8, which appear equally important, as well as IFNgamma and perforin, could fully resist a tumor challenge. IL-12 stimulated CTL activity, which was strictly CD3/CD8/perforin-dependent. FasL-KO mice had normal CTL activity and tumor resistance, indicating that only the perforin lytic pathway was involved. CD4-KO and IFNgamma-KO mice still generated CTLs. CEA-stimulated IFNgamma production occurred in both CD4- or CD8-KO mice and in both cases was augmented by IL-12. In IFNgamma-KO mice, IL-12 still enhanced anti-CEA antibody production but only moderately restored impaired DTH and tumor resistance. We conclude that the immune requirements for tumor rejection are stringent, involving multiple mechanisms which are all enhanced by IL-12.

Treatment of murine lupus with cDNA encoding IFN-gammaR/Fc

IFN-gamma, a pleiotropic cytokine, is a key effector molecule in the pathogenesis of several autoimmune diseases, including lupus. Importantly, deletion of IFN-gamma or IFN-gammaR in several lupus-predisposed mouse strains resulted in significant disease reduction, suggesting the potential for therapeutic intervention. We evaluated whether intramuscular injections of plasmids with cDNA encoding IFN-gammaR/Fc can retard lupus development and progression in MRL-Fas(lpr) mice. Therapy significantly reduced serum levels of IFN-gamma, as well as disease manifestations (autoantibodies, lymphoid hyperplasia, glomerulonephritis, mortality), when treatment was initiated at the predisease stage, particularly when IFN-gammaR/Fc expression was enhanced by electroporation at the injection site. Remarkably, disease was arrested and even ameliorated when this treatment was initiated at an advanced stage. This therapy represents a rare example of disease reversal and makes application of this nonviral gene therapy in humans with lupus (and perhaps other autoimmune/inflammatory conditions) highly promising.

Gene therapy of autoimmune diseases with vectors encoding regulatory cytokines or inflammatory cytokine inhibitors

Gene therapy offers advantages for the immunotherapeutic delivery of cytokines or their inhibitors. After gene transfer, these mediators are produced at relatively constant, non-toxic levels and sometimes in a tissue-specific manner, obviating limitations of protein administration. Therapy with viral or nonviral vectors is effective in several animal models of autoimmunity including Type 1 diabetes mellitus (DM), experimental allergic encephalomyelitis (EAE), systemic lupus erythematosus (SLE), colitis, thyroiditis and various forms of arthritis. Genes encoding transforming growth factor beta, interleukin-4 (IL-4) and IL-10 are most frequently protective. Autoimmune/ inflammatory diseases are associated with excessive production of inflammatory cytokines such as IL-1, IL-12, tumor necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma). Vectors encoding inhibitors of these cytokines, such as IL-1 receptor antagonist, soluble IL-1 receptors, IL-12p40, soluble TNFalpha receptors or IFNgamma-receptor/IgG-Fc fusion proteins are protective in models of either arthritis, Type 1 DM, SLE or EAE. We use intramuscular injection of naked plasmid DNA for cytokine or anticytokine therapy. Muscle tissue is accessible, expression is usually more persistent than elsewhere, transfection efficiency can be increased by low-voltage in vivo electroporation, vector administration is simple and the method is inexpensive. Plasmids do not induce neutralizing immunity allowing repeated administration, and are suitable for the treatment of chronic immunological diseases.

Regulation of T-helper-1 versus T-helper-2 activity and enhancement of tumor immunity by combined DNA-based vaccination and nonviral cytokine gene transfer

Intramuscular (i.m.) injections of a plasmid encoding human carcinoembryonic antigen (CEA) elicited both humoral and cellular immune responses in mice, but only partial inhibition of the growth of transplanted syngeneic CEA-positive P815 tumor cells (CEA/P815). Coinjection of the CEA vector with a vector encoding either interferon-gamma (IFN gamma) or IL-12 promoted IgG2a isotype anti-CEA antibody production, anti-CEA/P815 CTL activity and greater resistance to CEA/P815 tumor challenge. As well, CEA/P815-stimulated IFN gamma secretion in vitro was increased, but IL-4 diminished, consistent with a T-helper type 1 (Th1) response. In contrast, coinjection of the CEA vector with an IL-4 vector increased IgG1 production, but reduced CTL activity and resistance to tumor challenge. The latter treatment inhibited CEA/P815-dependent IFN gamma production but enhanced IL-4 secretion, consistent with a Th type 2 (Th2) response. Antitumor immunity was enhanced when the CEA and IL-12 plasmids were coinjected at the same muscle site, but not at separate sites despite increased serum IL-12 levels. Though the tumor cells expressed neomycin phosphotransferase, mice immunized with vectors encoding that protein (without CEA) were not protected against tumor growth, and produced no CTLs except for low levels when coinjected with an IL-12 vector. Thus, we show that immunity elicited by DNA vaccination against CEA can be biased to a protective type (high Th1 and CTL activity) or nonprotective type (high Th2 and low CTL activity) by i.m. coinjection of cytokine-expressing plasmids. IL-12 appears to act locally, but not systemically, through an adjuvant effect.

The inhibitory effects of transforming growth factor-beta-1 (TGF-beta1) in autoimmune diseases

The importance of transforming growth factor-beta-1 (TGF-beta1) in immunoregulation and tolerance has been increasingly recognized. It is now proposed that there are populations of regulatory T cells (T-reg), some designated T-helper type 3 (Th3), that exert their action primarily by secreting this cytokine. Here, we emphasize the following concepts: (1) TGF-beta1 has multiple suppressive actions on T cells, B cells, macrophages, and other cells, and increased TGF-beta1 production correlates with protection and/or recovery from autoimmune diseases; (2) TGF-beta1 and CTLA-4 are molecules that work together to terminate immune responses; (3) Th0, Th1 and Th2 clones can all secrete TGF-beta1 upon cross-linking of CTLA-4 (the functional significance of this in autoimmune diseases has not been reported, but TGF-beta1-producing regulatory T-cell clones can produce type 1 inflammatory cytokines); (4) TGF-beta1 may play a role in the passage from effector to memory T cells; (5) TGF-beta1 acts with some other inhibitory molecules to maintain a state of tolerance, which is most evident in immunologically privileged sites, but may also be important in other organs; (6) TGF-beta1 is produced by many cell types, is always present in the plasma (in its latent form) and permeates all organs, binding to matrix components and creating a reservoir of this immunosuppressive molecule; and (7) TGF-beta1 downregulates adhesion molecules and inhibits adhesion of leukocytes to endothelial cells. We propose that rather than being passive targets of autoimmunity, tissues and organs actively suppress autoreactive lymphocytes. We review the beneficial effects of administering TGF-beta1 in several autoimmune diseases, and show that it can be effectively administered by a somatic gene therapy approach, which results in depressed inflammatory cytokine production and increased endogenous regulatory cytokine production.

Intramuscular administration of expression plasmids encoding interferon-gamma receptor/IgG1 or IL-4/IgG1 chimeric proteins protects from autoimmunity

BACKGROUND

Interferon gamma (IFNgamma) is an inflammatory cytokine that promotes autoimmune insulitis and diabetes in NOD mice, while interleukin-4 (IL-4) is protective. We constructed plasmids encoding either an IFNgamma receptor/IgG1 (IFNgammaR/IgG1) chimeric protein which inhibits IFNgamma, or an IL-4/IgG1 chimeric protein with IL-4 activity, for therapeutic gene transfer into NOD mice.

METHODS

Murine IFNgammaR/IgG1 and IL-4/IgG1 cDNA segments were cloned into the VICAL VR1255 expression plasmid. Naked plasmid DNA was injected i.m. into young NOD mice, which were then observed for development of insulitis and diabetes.

RESULTS

After transient transfection of COS-7 cells, IFNgammaR/IgG1 and IL-4/IgG1 fusion proteins are secreted in vitro as disulfide-linked homodimers, with the expected biological activity. Intramuscular injection of these vectors results in the production of the respective fusion proteins locally in muscle. In serum, the IFNgammaR/IgG1 protein is present at >200 ng/ml over 130 days after the last of five DNA injections, but IL-4/IgG1 is undetectable in our assays (<10 pg/ml) at all time points. Both vectors protect NOD mice from autoimmune insulitis and diabetes, but the IL-4/IgG1 vector is more effective. Neutralization of IFNgamma with IFNgammaR/IgG1 was most protective when treatment was begun early (3 weeks of age).

CONCLUSION

Gene therapy by i.m. injection of these plasmids protects NOD mice from autoimmunity, and the IL-4/IgG1 vector is more effective despite low circulating protein levels. These chimeric proteins consist of nonimmunogenic self elements and are suitable for long-term therapy of autoimmune disorders.

Prevention of experimental allergic encephalomyelitis by intramuscular gene transfer with cytokine-encoding plasmid vectors

Antiinflammatory cytokines such as transforming growth factor beta1 (TGF-beta1) and interleukin 4 (IL-4) can protect from autoimmune diseases. To study the immunoregulatory effects of these cytokines in vivo, we used a method of gene therapy that permits continuous cytokine delivery over a period of weeks. We injected naked plasmid DNA expression vectors encoding either TGF-beta1 (pVR-TGF-beta1) or an IL-4-IgG1 chimeric protein (pVR-IL-4-IgG1) intramuscularly. This resulted in production of TGF-beta1 or IL-4-IgG1, respectively, and protection from myelin basic protein (MBP)-induced experimental allergic encephalomyelitis (EAE). TGF-beta1 gene delivery had pronounced downregulatory effects on T cell proliferation and production of interferon gamma (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha), on in vitro restimulation with MBP. IL-4-IgG1 vector administration also suppressed these responses, although much less than TGF-beta1, and enhanced secretion of endogenous IL-4. Therapy resulted in a significant decrease in the severity of histopathologic inflammatory lesions. In the CNS, treatment with either vector suppressed IL-12 and IFN-gamma mRNA expression, while IL-4 and TGF-beta1 mRNA levels were increased compared with control mice. Thus, cytokine plasmid treatment appeared to inhibit MBP-specific pathogenic Thl responses, while enhancing endogenous secretion of protective cytokines. We demonstrate that gene therapy with these vectors is an effective therapeutic strategy for EAE.

Alginate-poly-L-lysine microcapsule biocompatibility: a novel RT-PCR method for cytokine gene expression analysis in pericapsular infiltrates

Transplantation of microencapsulated islets of Langerhans is impaired by a pericapsular host reaction that eventually induces graft failure. We are studying the role of cytokines in the pathogenesis of this reaction, using the model of alginate-polylysine microcapsule implantation in rat epididymal fat pads. The objectives were: (1) to develop a method to measure, by semiquantitative PCR, TGF-beta1 gene expression in fat pad pericapsular infiltrates, and (2) to use this method to evaluate TGF-beta1 gene expression 14 days after microcapsule implantation. TGF-beta1 mRNA level was significantly higher in pericapsular infiltrate cells than in nonimplanted tissue cells and saline-injected tissue cells (p < 0.0001 and p < 0.01, respectively). There was no significant difference between the TGF-beta1 mRNA levels of the two types of controls (p = 0.0945). These results suggest that TGF-beta1 plays a role in the pathogenesis of the pericapsular reaction. The method developed can be used to study the role of other fibrogenic cytokines potentially involved. This will shed light on the mechanisms underlying the pericapsular reaction and will serve as a basis for the development of strategies to control this reaction.

Prevention of autoimmune diabetes by intramuscular gene therapy with a nonviral vector encoding an interferon-gamma receptor/IgG1 fusion protein

We report on long-term delivery of an interferon-gamma (IFN gamma) inhibitory protein by intramuscular (i.m.) gene therapy. IFN gamma is a cytokine that plays an important role in many inflammatory disorders, including autoimmune insulin-dependent diabetes mellitus (IDDM) in NOD mice and (in various strains) multiple low-dose streptozotocin (STZ)-induced diabetes (MDSD). By cDNA insertion into plasmid VICAL VR-1255 we constructed an expression vector encoding a soluble IFN gamma receptor/IgG1 heavy chain (all murine) fusion protein (IFN gamma R/IgG1). This protein is secreted as a homodimer and neutralizes IFN gamma in vitro. We show that i.m. injections of this vector as naked DNA in mice results in secretion of IFN gamma R/IgG1, with serum levels exceeding 100 ng/ml for months after treatment. These levels are sufficient to neutralize IFN gamma in vivo, and to prevent either MDSD or cyclophosphamide (CYP)-accelerated diabetes in NOD mice, which are both characterized by systemic release of IFN gamma. In these diseases gene therapy considerably reduces inflammation in the islets of Langerhans (insulitis). Also, circulating IFN gamma R/IgG1 blocked IFN gamma-enhanced nitric oxide production by peritoneal macrophages. The fusion protein is constructed from non-immunogenic self elements, avoiding a neutralizing immune response and making it suitable for prolonged therapy of numerous inflammatory disorders.

TGF-beta1 somatic gene therapy prevents autoimmune disease in nonobese diabetic mice

Nonobese diabetic (NOD) mice develop insulitis and diabetes through an autoimmune process. Since TGF-beta1 down-regulates many immune responses, we hypothesized that TGF-beta1 could prevent disease in NOD mice and that there would be several advantages to cytokine delivery by a somatic gene therapy approach. We opted for i.m. injection of a naked plasmid DNA expression vector encoding murine TGF-beta1 (pCMV-TGF-beta1). Treatment with pCMV-TGF-beta1 resulted in the retention and expression of the vector in muscle cells, associated with a considerable elevation in the plasma levels of TGF-beta1, that was not observed in control vector-treated mice. The levels of TGF-beta1 produced were sufficient to exert immunosuppressive effects. Delayed-type hypersensitivity responses were suppressed, and autoimmunity-prone NOD mice were protected from insulitis and diabetes in models of cyclophosphamide-accelerated and natural course disease. In pCMV-TGF-beta1-treated mice, pancreatic IL-12 and IFN-gamma mRNA expression was depressed, and the ratio of IFN-gamma to IL-4 mRNA was decreased, as determined by semiquantitative reverse-transcription PCR. In contrast, NOD mice injected with a vector encoding the proinflammatory cytokine IFN-gamma developed diabetes earlier. Intramuscular administration of cytokine-encoding plasmid vectors proved to be an effective method of cytokine delivery in these mice, and altered autoimmune disease expression.

The phosphodiesterase inhibitors pentoxifylline and rolipram prevent diabetes in NOD mice

Interleukin (IL)-12, interferon (IFN)-gamma, and other inflammatory cytokines play an important role in the pathogenesis of autoimmune insulitis and diabetes in NOD mice, and inhibition of these cytokines is likely to be beneficial. In this study, we found that Pentoxifylline (PTX) and Rolipram (phosphodiesterase [PDE] inhibitors that induce increased intracellular cAMP) can block inflammatory cytokine production. Inhibition of IL-12 and IFN-gamma secretion was demonstrated in macrophages activated with lipopolysaccharide or T-cells stimulated through the CD3/T-cell receptor complex, respectively. Moreover, strong inhibition of IL-12 was demonstrated in vivo in superantigen-immunized mice. Rolipram was inhibitory at concentrations as low as 10(-8) to 10(-7) mol/l, and on a molar basis, it was 100-fold more effective than PTX. Tumor necrosis factor-alpha was also inhibited, but IL-4 was less sensitive to suppression. In NOD mice, both PTX and Rolipram reduced the severity of insulitis and prevented diabetes, with or without cyclophosphamide administration (which precipitates onset of disease). This protection of NOD mice was still apparent over 10 weeks after withdrawal of the drug treatment. It appears that blocking the activity of type IV PDE is sufficient to mediate the effects reported in this study, since Rolipram inhibits only this isoform, unlike PTX (a general inhibitor). PTX and Rolipram may be effective in the treatment of autoimmune diabetes or other conditions characterized by excessive production of inflammatory cytokines.

Effects of cyclosporin A, rapamycin, and FK520 on peripheral T-cell deletion and anergy

In this study we compare the effects of cyclosporin A (CsA), FK520 (an agent similar to FK506), and rapamycin (RAPA) on peripheral T-cell deletion induced by either superantigens or anti-TCR alpha beta mAb, and on anergy induced by superantigens in mice. CsA enhanced T-cell deletion and blocked anergy induction (in residual T cells), while FK520 and RAPA had no effects on these processes. CsA also enhanced apoptosis of stimulated T cells in vitro, where cell death occurred without prior proliferation and in the absence of phagocytes. Our data suggest that CsA exerts these effects through a calcineurin-independent pathway, and this may be relevant to the development of tolerance in some models.

Quantitative polymerase chain reaction analysis reveals marked overexpression of interleukin-1 beta, interleukin-1 and interferon-gamma mRNA in the lymph nodes of lupus-prone mice

The nature of the stimuli driving autoantibody production in systemic lupus erythematosus (SLE) is unclear, but cytokines are believed to play an important role. Since cytokines primarily appear to act locally at the tissue level, we analysed mRNA expression of several cytokines (IL-1 alpha, IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-10, IFN gamma, TNF alpha, TNF beta and TGF beta 1) in the lymph nodes of lupus-prone mice, in models of early onset disease. We constructed a multispecific competitor fragment that allowed quantification of these cytokine transcripts by competitive PCR assay. The results reveal considerable overexpression of IL-1 beta, IL-10 and IFN gamma transcripts in SLE-prone MRL-lpr/lpr (MRL/l) and BXSB male (BXSBm) mice, but with some strain differences. IFN gamma was most markedly augmented in MRL/l mice (in some cases over 100-fold greater than control mice), IL-1 beta was most severely overexpressed in BXSBm mice while IL-10 was equally increased in both strains. In addition, TGF beta 1 expression was moderately elevated in the lymph nodes of BXSBm (but not MRL/l) mice. We found no abnormality in the expression of the other cytokines. Cytokine transcript levels were only slightly altered at 4 weeks of age, but were elevated from 10 to 22 weeks of age. The latter phase corresponds to a period where lupus-like disease escalates, resulting in frequent mortality. Interestingly, our results do not reveal a clear Th1 or Th2 cytokine expression pattern in these lupus-prone mice. IL-1 beta, IFN gamma and IL-10 are pleiotropic cytokines with pro-inflammatory and B-cell stimulatory effects. These results point to certain cytokines as potential targets for immunotherapy in lupus.

Cyclosporine, tolerance, and autoimmunity

A large number of studies have documented the effects of CsA on immunologic tolerance. Initially, these studies concentrated on the ability of CsA to induce tolerance to allografts, particularly in rats. However, it has become apparent that CsA can sometimes block the induction of tolerance, and provoke or aggravate specific autoimmune diseases in several species (Table 1). CsA can inhibit at least three processes thought to contribute to tolerance (Table 2). In the thymus, CsA has been reported by some investigators to block negative selection, but surprisingly, large numbers of undeleted or "forbidden" T-cells are rarely observed in the periphery. In mature T-cells (extrathymic), CsA can block the induction of anergy which occurs after immunization with superantigens, and in vitro this drug can block anergy induction in Th1 clones which occurs when antigenic peptides are presented by metabolically inactive (treated with a fixative) antigen-presenting cells. However, CsA can also enhance the deletion of peripheral superantigen-reactive T-cells, when the drug is administered at high doses. Thus, responses to superantigens can be either enhanced or inhibited depending on the protocol of CsA administration. Whether or not these phenomena apply to conventional antigens has not been determined. Numerous studies demonstrate that CsA treatment can either enhance or depress suppressor T-cell function in various experimental models. The interpretation of data on suppressor cells is complicated by the current poor understanding of the function of the cells. In CsA-induced syngeneic (or autologous) GVHD, CsA may inhibit both T-cell anergy induction and the generation and/or function of suppressor cells. CsA can alter Th1/Th2 antagonism, such that DTH responses are enhanced. Enhanced Th1 activity could explain the deterioration that CsA sometimes provokes in autoimmune diseases where DTH is important, e.g., collagen-induced arthritis and EAE. CsA can prevent the development of neonatal tolerance. The latter effect may account, at least in part, for the induction of organ-specific autoimmunity observed after treating mice with CsA during the neonatal period. However, in all the situations mentioned the effects of CsA on tolerance cannot be easily explained by a single mechanism. There is redundancy in the immune tolerance mechanism, such that clonal deletion, clonal anergy, and suppressor cells may all be capable of maintaining tolerance to similar antigens. Thus, it is likely that CsA must inhibit more than one of these mechanisms for autoimmunity to occur.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of natural suppressor cells in long-term renal allograft recipients

We have previously reported an abnormal expansion of CD3+Leu7+ (CD57+) large granular lymphocytes in long-term renal allograft recipients. These cells lacked NK activity, T-helper activity and did not respond to T cell mitogens. The following studies were done in order to further define the functional characteristics of these cells. We sorted CD3+Leu7+ T cells from the peripheral blood of 45 recipients (all with good renal allograft function), and found that these cells suppress mixed lymphocyte culture responses and pokeweed mitogen-induced IgG secretion in a non-genetically restricted manner. PWM-induced IgG secretion assays are suppressed by 60-100%, and MLC responses are suppressed by 20-85% at a ratio of 1:10 CD3+Leu7+ cells to responder/effector cells. Supernatants from CD3+Leu7+ cell cultures are also suppressive. On the other hand, unsorted cells and non-CD3+Leu7+ sorted cells either enhance responses or produce less than 10% suppression under the same conditions. Patients who were tested more than once showed a relatively stable percentage and suppressive effect of their CD3+Leu7+ cells over an interval of 6-12 months. These nonspecifically suppressive CD3+Leu7+ large granular lymphocytes are similar in many ways to the natural suppressor cells that have been identified in hematopoietic tissues, in graft-vs.-host disease, and in the lymphoid organs of neonates.

Cyclosporin A markedly enhances superantigen-induced peripheral T cell deletion and inhibits anergy induction

Cyclosporin A (CsA) is a well-known immunosuppressive agent that modulates immune tolerance in many ways. CsA can give rise to a state of long-term nonimmunosuppressed transplantation tolerance, but it can also aggravate autoimmune diseases, and provoke specific forms of autoimmunity. These effects, which are often paradoxical, remain largely unexplained. In this study, we investigated the effects of CsA on superantigen (superAg)-reactive peripheral T cells. The intravenous injection of either staphylococcal enterotoxin B (SEB), or Mls-1a cells into Mls-1b recipients, causes long-term in vitro nonresponsiveness (anergy) and partial elimination of the peripheral T cell receptor (TCR) V beta 8+/CD4+ and -V beta 6+/CD4+ T cell subsets, respectively. We report that CsA markedly enhances the peripheral elimination of SEB- and Mls-1a-reactive T cells such that up to 90% of the targeted CD4+/V beta subpopulations are deleted. The degree of deletion depends on the dose and the schedule of CsA administration, and the number of superAg injections. In situations where the extent of deletion is only moderate, we find that the remaining superAg-reactive T cells fail to develop anergy, unlike the T cells of control superAg-immunized mice. Higher doses of CsA are required to enhance T cell deletion (greater than or equal to 25 mg/kg/d, i.p.) than to impair anergy induction (greater than or equal to 6.25 mg/kg/d, i.p.). In view of these results, it appears that the degree of tolerance in CsA/superAg-treated mice depends on the balance between these opposing effects, i.e., enhancement of peripheral elimination versus the abrogation of anergy. The possibility of enhancing or preventing immune tolerance with a drug may have important clinical implications.

T-cell maturation and clonal deletion in cyclosporine-induced autoimmunity

In some circumstances cyclosporine (CyA) induces autoimmune phenomena, and a lethal form of syngeneic graft-vs-host disease (SGVHD) can be induced in rats by the administration of CyA. Although several rat strains develop this disease, in this study, we report that of six mouse strains tested, only the DBA/2 strain developed SGVHD. A comparison of the effect of CyA on thymocytic and peripheral T-cell populations revealed that CyA-induced alterations were similar in the two species, although more marked in rats. Notably, CyA-treated syngeneic bone marrow chimeras (SBMC) had transiently increased numbers of peripheral CD4+ CD8+ T-cells, expressing a marker normally limited to thymocytes. Examination of T-cell receptor (TCR) V beta expression in CyA-treated mice revealed a normal pattern of clonal deletion in all strains (including disease-prone DBA/2 mice), suggesting that CyA may induce autoimmunity without blocking intrathymic clonal deletion.

Analysis of pancreas-infiltrating T cells in diabetic NOD mice: fusion with BW5147 yields a high frequency of islet-reactive hybridomas

Diabetes in NOD mice is an autoimmune disease which is characterized by the infiltration of islets of Langerhans by large numbers of T cells. Some of these infiltrating T cells are clearly islet-cells-specific; however, many or most of these T cells could be attracted nonspecificity into these lesions. To study NOD pancreas-infiltrating T cells, we fused these cells with BW5147 to make T cell hybridomas. Ninety-four pancreas-derived T hybrids were analyzed of which 12 responded specifically to islet cells by secreting IL-2. Only CD3+, CD4+ hybrids responded to islet cells in our assay, and a large proportion of these hybrids were islet-cell reactive. T cell receptor (TCR) V beta element usage was heterogeneous in islet-reactive hybridomas.