Structural basis of activation and antagonism of receptor signaling mediated by interleukin-27

Interleukin-27 (IL-27) uniquely assembles p28 and EBI3 subunits to a heterodimeric cytokine that signals via IL-27Rα and gp130. To provide the structural framework for receptor activation by IL-27 and its emerging therapeutic targeting, we report here crystal structures of mouse IL-27 in complex with IL-27Rα and of human IL-27 in complex with SRF388, a monoclonal antibody undergoing clinical trials with oncology indications. One face of the helical p28 subunit interacts with EBI3, while the opposite face nestles into the interdomain elbow of IL-27Rα to juxtapose IL-27Rα to EBI3. This orients IL-27Rα for paired signaling with gp130, which only uses its immunoglobulin domain to bind to IL-27. Such a signaling complex is distinct from those mediated by IL-12 and IL-23. The SRF388 binding epitope on IL-27 overlaps with the IL-27Rα interaction site explaining its potent antagonistic properties. Collectively, our findings will facilitate the mechanistic interrogation, engineering, and therapeutic targeting of IL-27.

IL27 Signaling Serves as an Immunologic Checkpoint for Innate Cytotoxic Cells to Promote Hepatocellular Carcinoma

Although inflammatory mechanisms driving hepatocellular carcinoma (HCC) have been proposed, the regulators of anticancer immunity in HCC remain poorly understood. We found that IL27 receptor (IL27R) signaling promotes HCC development in vivo. High IL27EBI3 cytokine or IL27RA expression correlated with poor prognosis for patients with HCC. Loss of IL27R suppressed HCC in vivo in two different models of hepatocarcinogenesis. Mechanistically, IL27R sig-naling within the tumor microenvironment restrains the cytotoxicity of innate cytotoxic lymphocytes. IL27R ablation enhanced their accumulation and activation, whereas depletion or functional impairment of innate cytotoxic cells abrogated the effect of IL27R disruption. Pharmacologic neutralization of IL27 signaling increased infiltration of innate cytotoxic lymphocytes with upregulated cytotoxic molecules and reduced HCC development. Our data reveal an unexpected role of IL27R signaling as an immunologic checkpoint regulating innate cytotoxic lymphocytes and promoting HCC of different etiologies, thus indicating a therapeutic potential for IL27 pathway blockade in HCC.

SIGNIFICANCE

HCC, the most common form of liver cancer, is characterized by a poor survival rate and limited treatment options. The discovery of a novel IL27-dependent mechanism controlling anticancer cytotoxic immune response will pave the road for new treatment options for this devastating disease. This article is highlighted in the In This Issue feature, p. 1825.

Abstract 1137: Determination of a recommended Phase 2 dose (RP2D) for SRF388, a first-in-class IL-27-blocking antibody, in patients with advanced solid tumors

SRF388 is a first-in-class, anti-IL-27 antibody developed to enhance immune responses within the tumor microenvironment. Preclinical studies have demonstrated that IL-27 pathway blockade can inhibit tumor growth in mouse models of liver cancer and lung cancer metastases. There is also evidence that IL-27 pathway inhibition is accompanied by activation of the innate and adaptive arms of the immune system. An ongoing Phase I trial has shown good tolerability at all dose levels tested and preliminary monotherapy antitumor activity with SRF388 (NCT04374877). Here, we describe the preclinical and clinical data used to select a RP2D and characterize cytokine and chemokine changes observed in patients after treatment with SRF388. To guide selection of the RP2D, the relationship between maximal effective dose (MaxED), pharmacokinetics (PK), and whole blood inhibition of IL-27-mediated phosphorylation of STAT1 by SRF388 was evaluated in a mouse model of liver cancer. The concentration of SRF388 associated with optimal antitumor activity was ~20-fold above the concentration needed for complete inhibition (> 90%) of whole blood phosphorylated STAT1 (pSTAT1). These PK and activity relationships were also defined in patients during the dose-escalation phase of the trial and integrated with safety and efficacy data to select a monotherapy RP2D. In patients, PK were linear, no dose-limiting toxicities were reported, complete pSTAT1 inhibition was achieved throughout the first cycle at 0.3 mg/kg, and 1 patient experienced a confirmed partial response per RECIST version 1.1 at a dose of 10 mg/kg. In the MaxED mouse model, the area under the concentration versus time curve (AUC) associated with significant antitumor activity was 1720 day*μg/mL. In patients, the corresponding target AUC was achieved clinically at 10 mg/kg after a single dose of SRF388. Changes in the concentration of several serum cytokines and chemokines were observed after SRF388 treatment including an increase in IL-27, a phenomenon described for other anti-cytokine antibodies due to altered clearance of the cytokine-antibody complex. Changes in a subset of other serum cytokines/chemokines correlated with a reduction in target lesion size. Taken together, these data support the selection of a monotherapy RP2D of 10 mg/kg intravenously every 4 weeks for SRF388. These data highlight how complementary strategies utilizing preclinical and clinical biomarker evaluations can be employed to establish a monotherapy RP2D and assess biological activity of a first-in-class anti-cytokine antibody, SRF388, for patients with cancer.

Citation Format: Jonathan A. Hill, Kerry F. White, Matthew Rausch, Jou-Ku Chung, Amita Patnaik, Aung Naing, Daniel Morgensztern, Charlene M. Mantia, Nizar M. Tannir, Lon S. Smith, Beth Bowers, Alex Alika, Lauren C. Harshman, Benjamin H. Lee. Determination of a recommended Phase 2 dose (RP2D) for SRF388, a first-in-class IL-27-blocking antibody, in patients with advanced solid tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1137.

The Fully human anti-CD47 antibody SRF231 exerts dual-mechanism antitumor activity via engagement of the activating receptor CD32a

Background

CD47 is a broadly expressed cell surface glycoprotein associated with immune evasion. Interaction with the inhibitory receptor signal regulatory protein alpha (SIRPα), primarily expressed on myeloid cells, normally serves to restrict effector function (eg, phagocytosis and immune cell homeostasis). CD47/SIRPα antagonists, commonly referred to as ‘macrophage checkpoint’ inhibitors, are being developed as cancer interventions. SRF231 is an investigational fully human IgG₄ anti-CD47 antibody that is currently under evaluation in a phase 1 clinical trial. The development and preclinical characterization of SRF231 are reported here.

Methods

SRF231 was characterized in assays designed to probe CD47/SIRPα blocking potential and effects on red blood cell (RBC) phagocytosis and agglutination. Additionally, SRF231-mediated phagocytosis and cell death were assessed in macrophage:tumor cell in vitro coculture systems. Further mechanistic studies were conducted within these coculture systems to ascertain the dependency of SRF231-mediated antitumor activity on Fc receptor engagement vs CD47/SIRPα blockade. In vivo, SRF231 was evaluated in a variety of hematologic xenograft models, and the mechanism of antitumor activity was assessed using cytokine and macrophage infiltration analyses following SRF231 treatment.

Results

SRF231 binds CD47 and disrupts the CD47/SIRPα interaction without causing hemagglutination or RBC phagocytosis. SRF231 exerts antitumor activity in vitro through both phagocytosis and cell death in a manner dependent on the activating Fc-gamma receptor (FcγR), CD32a. Through its Fc domain, SRF231 engagement with macrophage-derived CD32a serves dual purposes by eliciting FcγR-mediated phagocytosis of cancer cells and acting as a scaffold to drive CD47-mediated death signaling into tumor cells. Robust antitumor activity occurs across multiple hematologic xenograft models either as a single agent or in combination with rituximab. In tumor-bearing mice, SRF231 increases tumor macrophage infiltration and induction of the macrophage cytokines, mouse chemoattractant protein 1 and macrophage inflammatory protein 1 alpha. Macrophage depletion results in diminished SRF231 antitumor activity, underscoring a mechanistic role for macrophage engagement by SRF231.

Conclusion

SRF231 elicits antitumor activity via apoptosis and phagocytosis involving macrophage engagement in a manner dependent on the FcγR, CD32a.

Abstract 4548: SRF813, a fully human monoclonal antibody targeting the inhibitory receptor CD112R, enhances immune cell activation and demonstrates preclinical in vivo anti-tumor activity

CD112R (PVRIG) is a recently identified inhibitory receptor of the PVR gene family, which includes TIGIT, CD96, and CD226, that is expressed on NK cells and T cells. CD112R suppresses immune cell activation through its association with the cell adhesion molecule CD112 (PVRL2), a ligand that it competes for with the activating receptor CD226. CD112 binding to CD112R induces downstream signaling via recruitment of SHP-1, SHP-2, and SHIP-1 phosphatases to the ITIM in the cytoplasmic tail, resulting in dampened effector cell activation. As CD112 is commonly upregulated on cancer cells and is also expressed on tumor infiltrating myeloid cells, it was hypothesized that disruption of the CD112:CD112R interaction would promote anti-tumor immune responses. Phenotypic screening of a panel of antibodies generated against CD112R led to the identification of SRF813, a high affinity, fully human CD112R antibody that blocks the interaction of CD112R with CD112. To explore the therapeutic potential of CD112R blockade, the ability of SRF813 to increase immune cell activation was evaluated in human peripheral blood mononuclear cells. In vitro assays showed that SRF813 treatment enhanced NK cell activation in response to multiple tumor cell lines. This activation was characterized by upregulation of several cell surface markers, including 4-1BB and ICAM-1, in addition to increased cytokine production and degranulation. The activity of SRF813 was highly dependent on the antibody isotype and Fc receptor engagement. Mechanistically, the enhanced immunologic responses observed in NK cells treated with SRF813 could be reversed in the presence of a CD226 blocking antibody, confirming the role of CD112R in regulating CD226 mediated signaling. Blockade of CD112R in mouse syngeneic tumor models using a murine surrogate of SRF813 demonstrated reduced tumor growth with an accompanying increase in TIL activation following treatment. In the CT-26 tumor model, anti-CD112R treatment resulted in complete tumor regression in a subset of treated mice. These mice rapidly rejected tumors upon re-challenge, signifying the development of an immunologic anti-tumor memory response in these animals. Additional depletion studies highlighted that the anti-tumor efficacy was dependent on both CD8 T cells and NK cells. Moreover, the combination of anti-CD112R with PD-1 blockade led to greater inhibition of tumor growth than either treatment alone. Collectively, these preclinical data demonstrated that CD112R is a negative regulator of immune responses and that CD112R blockade can potentiate anti-tumor responses in cancers that express CD112.

Citation Format: Marisella Panduro, Roy M. Dornbrook, Kshama A. Doshi, Jing Hua, Jamie Strand, Vito J. Palombella, Pamela M. Holland, Jonathan A. Hill, James F. Mohan. SRF813, a fully human monoclonal antibody targeting the inhibitory receptor CD112R, enhances immune cell activation and demonstrates preclinical in vivo anti-tumor activity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4548.

Abstract 558: MERTK-specific antibodies that have therapeutic antitumor activity in mice disrupt the integrity of the retinal pigmented epithelium in cynomolgus monkeys

MERTK, a member of the TAM (TYRO3, AXL, MERTK) family of receptor tyrosine kinases, is a pleiotropic immune modulator that controls efferocytosis. Engagement of MERTK with its ligand GAS6, found anchored to phosphatidylserine exposed on the outer membrane of apoptotic cells, triggers MERTK phosphorylation and signaling events that culminate in the removal of apoptotic debris. Recent studies have highlighted the expression of MERTK on tumor-associated macrophages, and Mertk-deficient mice show reduced tumor cell growth accompanied by inflammatory cytokine production and alterations in macrophage activation. Thus, MERTK has emerged as a promising therapeutic target for augmenting innate antitumor immune responses. MERTK is also expressed in retinal pigmented epithelium (RPE) cells of the eye where it mediates phagocytosis of photoreceptor outer segment fragments. Mutations in MERTK that disrupt its expression or kinase activity lead to marked retinal degeneration and blindness in mice, rats, and humans. Due to known differences in blood-retinal permeability, we explored whether therapeutic antibodies targeting MERTK could inhibit macrophage-mediated efferocytosis and promote antitumor activity while sparing RPE toxicity. A diverse panel of high-affinity antibodies was developed to explore MERTK blockade in vitro and in vivo. Multiple antibodies disrupted MERTK-GAS6 binding and blocked human and murine macrophage-mediated efferocytosis. Two antibodies targeting distinct GAS6 binding epitopes were selected for further characterization. Both antibodies demonstrated antitumor activity in murine CT26 and MC38 syngeneic colorectal cancer models and led to alterations in immune cell-related gene expression. To investigate potential effects on RPE biology with MERTK antibodies, a multi-dose, 4-week cynomolgus monkey study with several in-life and post-mortem ophthalmologic endpoints was designed. While no abnormal ophthalmic or electroretinography (ERG) findings were detected, all animals treated with either MERTK antibody at all doses showed histological abnormalities of the retina, including vacuolation of the outer segments of photoreceptors, displacement of RPE cells, and single cell necrosis of the outer nuclear layer. These data suggest that inhibition of efferocytosis by antibody-mediated blockade of MERTK can promote immune activation and inhibit tumor growth in vivo; however, retinal toxicity consistent with histological observations made in Mertk mutant animals is an on-target effect. As several therapeutics that block MERTK function are currently in preclinical development, a thorough evaluation of retinal toxicity is warranted.

Citation Format: Kerry F. White, Matthew Rausch, Jing Hua, Katherine H. Walsh, Christine E. Miller, Christopher C. Wells, Devapregasan Moodley, Benjamin H. Lee, Scott C. Chappel, Pamela M. Holland, Jonathan A. Hill. MERTK-specific antibodies that have therapeutic antitumor activity in mice disrupt the integrity of the retinal pigmented epithelium in cynomolgus monkeys [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 558.

IL-27 and TCR Stimulation Promote T Cell Expression of Multiple Inhibitory Receptors

Inhibitory receptors (IR) are a diverse group of cell surface molecules that modulate T cell activation, but there are gaps in our knowledge of the cell-extrinsic factors that regulate their expression. The present study found that in vivo overexpression of IL-27 in mice led to increased T cell expression of PD-L1, LAG-3, TIGIT, and TIM-3. In vitro, TCR stimulation alone promoted expression of multiple IRs, whereas IL-27 alone induced expression of PD-L1. However, the combination of intermediate TCR stimulation and IL-27 resulted in synergistic induction of LAG-3, CTLA-4, and TIGIT. In vivo, infection with Toxoplasma gondii resulted in parasite-specific effector T cells that expressed high levels of IR, and at local sites of infection where IL-27 production was highest, IL-27 was required for maximal effector cell expression of PD-L1, LAG-3, CTLA-4, and TIGIT. Together, these results affirm the critical role of TCR signals in the induction of IR expression but find that during infection, IL-27 promotes T cell expression of IR.

Glass formation via structural fragmentation of a 2D coordination network

The structure of a glass obtained by the melt quenching of a two-dimensional (2D) coordination network was examined. X-ray analyses disclosed a 2D-to-0D structural transformation before and after glass formation. The mechanism is unique to coordination compounds, as it is characterized by labile and flexible coordination bonds.

Diverse Gene Expression in Human Regulatory T Cell Subsets Uncovers Connection between Regulatory T Cell Genes and Suppressive Function

Regulatory T (Treg) cells have a critical role in the control of immunity, and their diverse subpopulations may allow adaptation to different types of immune responses. In this study, we analyzed human Treg cell subpopulations in the peripheral blood by performing genome-wide expression profiling of 40 Treg cell subsets from healthy donors. We found that the human peripheral blood Treg cell population is comprised of five major genomic subgroups, represented by 16 tractable subsets with a particular cell surface phenotype. These subsets possess a range of suppressive function and cytokine secretion and can exert a genomic footprint on target effector T (Teff) cells. Correlation analysis of variability in gene expression in the subsets identified several cell surface molecules associated with Treg suppressive function, and pharmacological interrogation revealed a set of genes having causative effect. The five genomic subgroups of Treg cells imposed a preserved pattern of gene expression on Teff cells, with a varying degree of genes being suppressed or induced. Notably, there was a cluster of genes induced by Treg cells that bolstered an autoinhibitory effect in Teff cells, and this induction appears to be governed by a different set of genes than ones involved in counteracting Teff activation. Our work shows an example of exploiting the diversity within human Treg cell subpopulations to dissect Treg cell biology.

Hepatitis due to human herpesvirus 6B after hematopoietic cell transplantation and a review of the literature

Human herpesvirus 6B (HHV-6B) is an opportunistic pathogen associated with a growing number of complications in immunocompromised patients. Multiple reports of HHV-6B-associated hepatitis following primary HHV-6 infection and liver transplantation have appeared, but this has only been well documented in 1 patient after hematopoietic cell transplantation (HCT). This report describes a case of acute hepatitis likely caused by HHV-6B in an HCT recipient who was successfully treated with ganciclovir. HHV-6B DNA was demonstrated in plasma and hepatic tissue using quantitative polymerase chain reaction and immunohistochemical stains. Chromosomal integration was ruled out. We review the literature reporting HHV-6B-associated hepatitis, which may be an underappreciated cause of liver disease after HCT.

A multiply redundant genetic switch 'locks in' the transcriptional signature of regulatory T cells

The transcription factor FoxP3 partakes dominantly in the specification and function of FoxP3⁺CD4⁺ T regulatory cells (Tregs), but is neither strictly necessary nor sufficient to determine the characteristic Treg signature. Computational network inference and experimental testing assessed the contribution of other transcription factors (TF). Enforced expression of Helios or Xbp1 elicited specific signatures, but Eos, Irf4, Satb1, Lef1 and Gata1 elicited exactly the same outcome, synergizing with FoxP3 to activate most of the Treg signature, including key TFs, and enhancing FoxP3 occupancy at its genomic targets. Conversely, the Treg signature was robust to inactivation of any single cofactor. A redundant genetic switch thus locks-in the Treg phenotype, a model which accounts for several aspects of Treg physiology, differentiation and stability.

Gut immune maturation depends on colonization with a host-specific microbiota

Gut microbial induction of host immune maturation exemplifies host-microbe mutualism. We colonized germ-free (GF) mice with mouse microbiota (MMb) or human microbiota (HMb) to determine whether small intestinal immune maturation depends on a coevolved host-specific microbiota. Gut bacterial numbers and phylum abundance were similar in MMb and HMb mice, but bacterial species differed, especially the Firmicutes. HMb mouse intestines had low levels of CD4(+) and CD8(+) T cells, few proliferating T cells, few dendritic cells, and low antimicrobial peptide expression--all characteristics of GF mice. Rat microbiota also failed to fully expand intestinal T cell numbers in mice. Colonizing GF or HMb mice with mouse-segmented filamentous bacteria (SFB) partially restored T cell numbers, suggesting that SFB and other MMb organisms are required for full immune maturation in mice. Importantly, MMb conferred better protection against Salmonella infection than HMb. A host-specific microbiota appears to be critical for a healthy immune system.

Cardiomyocyte death: mechanisms and translational implications

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Although treatments have improved, development of novel therapies for patients with CVD remains a major research goal. Apoptosis, necrosis, and autophagy occur in cardiac myocytes, and both gradual and acute cell death are hallmarks of cardiac pathology, including heart failure, myocardial infarction, and ischemia/reperfusion. Pharmacological and genetic inhibition of autophagy, apoptosis, or necrosis diminishes infarct size and improves cardiac function in these disorders. Here, we review recent progress in the fields of autophagy, apoptosis, and necrosis. In addition, we highlight the involvement of these mechanisms in cardiac pathology and discuss potential translational implications.

Anabolic androgenic steroids and intracellular calcium signaling: a mini review on mechanisms and physiological implications

Increasing evidence suggests that nongenomic effects of testosterone and anabolic androgenic steroids (AAS) operate concertedly with genomic effects. Classically, these responses have been viewed as separate and independent processes, primarily because nongenomic responses are faster and appear to be mediated by membrane androgen receptors, whereas long-term genomic effects are mediated through cytosolic androgen receptors regulating transcriptional activity. Numerous studies have demonstrated increases in intracellular Ca2+ in response to AAS. These Ca2+ mediated responses have been seen in a diversity of cell types, including osteoblasts, platelets, skeletal muscle cells, cardiac myocytes and neurons. The versatility of Ca2+ as a second messenger provides these responses with a vast number of pathophysiological implications. In cardiac cells, testosterone elicits voltage-dependent Ca2+ oscillations and IP3R-mediated Ca2+ release from internal stores, leading to activation of MAPK and mTOR signaling that promotes cardiac hypertrophy. In neurons, depending upon concentration, testosterone can provoke either physiological Ca2+ oscillations, essential for synaptic plasticity, or sustained, pathological Ca2+ transients that lead to neuronal apoptosis. We propose therefore, that Ca2+ acts as an important point of crosstalk between nongenomic and genomic AAS signaling, representing a central regulator that bridges these previously thought to be divergent responses.

Effect of nesiritide in patients with acute decompensated heart failure

BACKGROUND

Nesiritide is approved in the United States for early relief of dyspnea in patients with acute heart failure. Previous meta-analyses have raised questions regarding renal toxicity and the mortality associated with this agent.

METHODS

We randomly assigned 7141 patients who were hospitalized with acute heart failure to receive either nesiritide or placebo for 24 to 168 hours in addition to standard care. Coprimary end points were the change in dyspnea at 6 and 24 hours, as measured on a 7-point Likert scale, and the composite end point of rehospitalization for heart failure or death within 30 days.

RESULTS

Patients randomly assigned to nesiritide, as compared with those assigned to placebo, more frequently reported markedly or moderately improved dyspnea at 6 hours (44.5% vs. 42.1%, P=0.03) and 24 hours (68.2% vs. 66.1%, P=0.007), but the prespecified level for significance (P≤0.005 for both assessments or P≤0.0025 for either) was not met. The rate of rehospitalization for heart failure or death from any cause within 30 days was 9.4% in the nesiritide group versus 10.1% in the placebo group (absolute difference, -0.7 percentage points; 95% confidence interval [CI], -2.1 to 0.7; P=0.31). There were no significant differences in rates of death from any cause at 30 days (3.6% with nesiritide vs. 4.0% with placebo; absolute difference, -0.4 percentage points; 95% CI, -1.3 to 0.5) or rates of worsening renal function, defined by more than a 25% decrease in the estimated glomerular filtration rate (31.4% vs. 29.5%; odds ratio, 1.09; 95% CI, 0.98 to 1.21; P=0.11).

CONCLUSIONS

Nesiritide was not associated with an increase or a decrease in the rate of death and rehospitalization and had a small, nonsignificant effect on dyspnea when used in combination with other therapies. It was not associated with a worsening of renal function, but it was associated with an increase in rates of hypotension. On the basis of these results, nesiritide cannot be recommended for routine use in the broad population of patients with acute heart failure. (Funded by Scios; ClinicalTrials.gov number, NCT00475852.).

Near-infrared fluorescent probe for imaging of pancreatic beta cells

The ability to image and ultimately quantitate beta-cell mass in vivo will likely have far reaching implications in the study of diabetes biology, in the monitoring of disease progression or response to treatment, and for drug development. Here, using animal models, we report on the synthesis, characterization, and intravital microscopic imaging properties of a near-infrared fluorescent exendin-4 analogue with specificity for the GLP-1 receptor on beta cells (E4(K12)-Fl). The agent demonstrated subnanomolar EC(50) binding concentrations, with high specificity and binding that could be inhibited by GLP-1R agonists. Following intravenous administration to mice, pancreatic islets were readily distinguishable from exocrine pancreas, achieving target-to-background ratios within the pancreas of 6:1, as measured by intravital microscopy. Serial imaging revealed rapid accumulation kinetics (with initial signal within the islets detectable within 3 min and peak fluorescence within 20 min of injection), making this an ideal agent for in vivo imaging.

Retinoic acid enhances Foxp3 induction indirectly by relieving inhibition from CD4+CD44hi Cells

CD4(+)Foxp3(+) regulatory T (Treg) cells originate primarily from thymic differentiation, but conversion of mature T lymphocytes to Foxp3 positivity can be elicited by several means, including in vitro activation in the presence of TGF-beta. Retinoic acid (RA) increases TGF-beta-induced expression of Foxp3, through unknown molecular mechanisms. We showed here that, rather than enhancing TGF-beta signaling directly in naive CD4(+) T cells, RA negatively regulated an accompanying population of CD4(+) T cells with a CD44(hi) memory and effector phenotype. These memory cells actively inhibited the TGF-beta-induced conversion of naive CD4(+) T cells through the synthesis of a set of cytokines (IL-4, IL-21, IFN-gamma) whose expression was coordinately curtailed by RA. This indirect effect was evident in vivo and required the expression of the RA receptor alpha. Thus, cytokine-producing CD44(hi) cells actively restrain TGF-beta-mediated Foxp3 expression in naive T cells, and this balance can be shifted or fine-tuned by RA.

Arthritis induced by posttranslationally modified (citrullinated) fibrinogen in DR4-IE transgenic mice

Rheumatoid arthritis (RA) is a common autoimmune disease that afflicts the synovium of diarthrodial joints. The pathogenic mechanisms inciting this disease are not fully characterized, but may involve the loss of tolerance to posttranslationally modified (citrullinated) antigens. We have demonstrated that this modification leads to a selective increase in antigenic peptide affinity for major histocompatibility complex (MHC) class II molecules that carry the RA-associated shared epitope, such as HLA-DRB1*0401 (DR4). We describe the induction of arthritis in DR4-IE transgenic (tg) mice with citrullinated fibrinogen, a protein commonly found in inflamed synovial tissue and a frequent target of autoantibodies in RA patients. The disease induced in these mice was characterized by synovial hyperplasia followed by ankylosis, but lacked a conspicuous polymorphonuclear cell infiltrate. Immunological analysis of these mice through T cell epitope scanning and antibody microarray analysis identified a unique profile of citrulline-specific reactivity that was not found in DR4-IE tg mice immunized with unmodified fibrinogen or in wild-type C57BL/6 mice immunized with citrullinated fibrinogen, two conditions where arthritis was not observed. These observations directly implicate citrullinated fibrinogen as arthritogenic in the context of RA-associated MHC class II molecules.

Foxp3 transcription-factor-dependent and -independent regulation of the regulatory T cell transcriptional signature

The CD4(+)CD25(+) lineage of regulatory T (Treg) cells plays a key role in controlling immune and autoimmune responses and is characterized by a unique transcriptional signature. The transcription factor Foxp3 had been thought to determine the Treg cell lineage, a hypothesis challenged by recent observations. We have performed a cross-sectional analysis of the Treg cell signature in Treg-like cells generated under a number of conditions, with or without Foxp3, to delineate the elements that can be ascribed to T cell activation, interleukin-2, transforming growth factor-beta (TGF-beta) signaling, or Foxp3 itself. These influences synergized to determine many of the signature's components. Much of the Treg cell signature was not ascribable to Foxp3 because it contained gene clusters that are coregulated with, but not transactivated by, Foxp3. Thus, a higher level of regulation upstream of Foxp3 determines the lineage, distinct from elements downstream of Foxp3 that are essential for its regulatory properties.

Notch signalling suppresses apoptosis in adult human and mouse pancreatic islet cells

AIMS/HYPOTHESIS

The pathogenesis of diabetes and the success of islet transplantation depend on the control of pancreatic beta cell fate. The Notch signalling pathway is essential for normal prenatal pancreatic development, but the presence and function of this gene network in adult islets has received much less attention.

METHODS

The presence of Notch signalling components was assessed in vitro using RT-PCR, western blotting and immunofluorescence. The functional consequences of altering Notch signalling on insulin secretion and programmed cell death were examined.

RESULTS

Adult mouse islets, human islets and mouse insulinoma MIN6 cells possess key components of the Notch pathway. RT-PCR, western blotting and immunofluorescence indicated that the Notch target gene, neurogenin3 (Ngn3, also known as Neurog3), is also present in adult islet cells. Inhibiting Notch signalling with N-[N-(3,5-difluorophenacetyl-L-alanyl)]-S-phenylglycine t-butyl ester (DAPT) increased Ngn3 mRNA expression and protein levels in adult islets. The activated notch homologue 1 (NOTCH1) protein level was decreased upon serum withdrawal, as well as after treatment with a phosphatidylinositol 3-kinase inhibitor, or hydroxy-2-naphthalenylmethylphosphonic acid, an insulin receptor inhibitor. While islets cultured in DAPT did not exhibit defects in insulin secretion, indicating that differentiation is unaltered, inhibiting gamma-secretase-dependent Notch activation led to a dose-dependent increase in caspase-3-dependent apoptosis in both MIN6 cells and human islets. Conversely, gamma-secretase overactivity resulted in an accumulation of cleaved NOTCH1 and protection from apoptosis.

CONCLUSIONS/INTERPRETATION

Together these results show that the Notch/Ngn3 signalling network is intact and functional in adult islets. This pathway represents an attractive target for modulating beta cell fate in diabetes, islet transplantation and efforts to derive beta cell surrogates in vitro.

The Influence of MHC Class II Molecules Containing the Rheumatoid Arthritis Shared Epitope on the Immune Response to Aggrecan G1 and Its Peptides

Aggrecan has been implied as an autoantigen in rheumatoid arthritis (RA). Immunization with aggrecan induces arthritis in BALB/c (H-2(d)) mice but not in other strains of mice [e.g. C57BL/6 (H-2(b))]. In humans, the strongest genetic association with RA is to the shared epitope (SE), and aggrecan peptides are predicted to bind to the SE. Therefore, we hypothesized that C57BL/6 mice transgenic (tg) for the RA SE (DR4 tg mice) may be susceptible to aggrecan-induced arthritis. C57BL/6 and DR4 tg mice were immunized with a mixture of SE-binding aggrecan peptides and tested for immune responses to the corresponding peptides as well as aggrecan. Sustained T- and B-cell immune responses to aggrecan and several of its peptides were detected in DR4 tg mice. C57BL/6 mice showed only transient T-cell responses to different immunizing peptides and little B-cell response. Therefore, an immune response to peptides of aggrecan can be induced experimentally in DR4 tg mice as anticipated from the predicted and actual binding affinities of these peptides for the RA SE. Failure to induce arthritis in these DR4 tg mice may be due to a lack of appropriate non-MHC genes.

Treg cells: guardians for life

Regulatory T cells expressing the transcription factor Foxp3 are known to control autoreactivity during and subsequent to the development of the peripheral immune system. New evidence emphasizes the fact that those cells are constant and powerful guardians against the state of 'horror autotoxicus'.

Serum autoantibodies that bind citrullinated fibrinogen are frequently found in patients with rheumatoid arthritis

OBJECTIVE

Autoantibodies that bind citrullinated antigens are a sensitive and specific marker for rheumatoid arthritis (RA). While synthetic cyclic citrullinated peptides (CCP) are typically used to identify these antibodies, little is known about antibody reactivity to the predominant citrullinated protein found in the inflamed synovium, citrullinated fibrinogen (CitFib). We assessed the prevalence of anti-CitFib antibodies in patients with various rheumatic diseases.

METHODS

In total, 65 patients with established RA and 63 patients with other rheumatic diseases were tested for serum IgM rheumatoid factor (RF), IgG anti-CCP2, and IgG anti-CitFib antibodies. This cohort was used to determine optimal positive cutoff values for antibody reactivity to CitFib through receiver operating characteristic curve analysis. The specificity of these assays was confirmed with sera from 49 patients with psoriatic arthritis.

RESULTS

Antibodies to both citrullinated antigens were identified in the majority of RA patients tested. The overall sensitivity and specificity of the assays were: CCP 82%, 96%, CitFib 75%, 98%, and IgM RF 80%, 64%, respectively. All but one patient that was positive for CitFib was also positive for CCP2, and close to half the RF-negative RA patients were positive for CitFib and CCP2.

CONCLUSION

These results suggest that autoimmunity to CitFib is common in patients with RA and may play a role in disease pathogenesis.

Polyglucosan body disease in a mixed-breed dog

AIM

To describe the histopathology of a previously unrecorded canine disease and deduce the cause of the lesions.

METHODS

Formalin-fixed tissues were processed into paraffin wax and epoxy resin for light and electron microscopy of variously stained sections of liver, brain, heart muscle and kidney.

RESULTS

Periodic acid Schiff (PAS) -positive bodies in liver and myocardium were typical of a polyglucosan body disease. Neurons contained coarse granular material that stained similarly to the polyglucosan bodies.

CONCLUSION

The nature, distribution and histochemistry of lesions observed are consistent with a putative diagnosis of Glycogen storage disease type IV, an inherited metabolic defect associated with a deficiency of glycogen-branching enzyme not previously reported in dogs.

The effect of endometriosis, cycle stage, lymphocyte suppression and pregnancy on CA-125 levels in peritoneal fluid and serum in baboons

BACKGROUND

Serum CA-125 during the mid-follicular phase has been reported to be a clinically useful and reproducible marker in the diagnosis of advanced endometriosis in women. This study was undertaken to document the effect of the menstrual cycle, pregnancy and lymphocyte suppression on CA-125 levels in peritoneal fluid (PF) and serum in baboons with a normal pelvis and baboons with endometriosis.

METHODS

CA-125 levels were measured in 264 serum samples that were serially obtained during one menstrual cycle from 10 animals with and without endometriosis. In addition, CA-125 levels were determined in 204 archived samples (serum, n = 112 and PF, n = 92) obtained from 32 female baboons with or without endometriosis. The CA-125 assays were performed by radioimmunoassay using kits from Centocor (Malvern, PA, USA).

RESULTS

Serum CA-125 levels were at their highest during menstruation and decreased progressively during the follicular and luteal phase. PF CA-125 levels were increased during the follicular phase in baboons with a normal pelvis, but no cyclic changes were observed in animals with endometriosis. Serum CA-125 levels were unaffected by induction, lymphocyte suppression or pregnancy. Induction of endometriosis resulted in increased PF CA-125 levels, whereas lymphocyte suppression or pregnancy had no effect.

CONCLUSION

In baboons, serum CA-125 originates mainly from eutopic endometrium whereas the main source of PF CA-125 seems to be the peritoneum or ectopic endometrium. The baboon appears to be a valid model to further study the relationship between endometriosis and CA-125.

Immune modulation by silencing IL-12 production in dendritic cells using small interfering RNA

RNA interference is a mechanism of posttranscriptional gene silencing that functions in most eukaryotic cells, including human and mouse. Specific gene silencing is mediated by short strands of duplex RNA of approximately 21 nt in length (termed small interfering RNA or siRNA) that target the cognate mRNA sequence for degradation. We demonstrate here that RNAi can be used for immune modulation by targeting dendritic cell (DC) gene expression. Transfection of DC with siRNA specific for the IL-12 p35 gene resulted in potent suppression of gene expression and blockade of bioactive IL-12 p70 production without affecting unrelated genes or cellular viability. Inhibition of IL-12 was associated with increased IL-10 production, which endowed the DC with the ability to stimulate production of Th2 cytokines from allogenic T cells in vitro. Furthermore, siRNA-silenced DC lacking IL-12 production were poor allostimulators in MLR. IL-12-silenced and KLH-pulsed DC polarized the immune response toward a Th2 cytokine profile in an Ag-specific manner. These data are the first to demonstrate that RNA interference is a potent and specific tool for modulating DC-mediated immune responses.

Cutting edge: the conversion of arginine to citrulline allows for a high-affinity peptide interaction with the rheumatoid arthritis-associated HLA-DRB1*0401 MHC class II molecule

Rheumatoid arthritis (RA) is genetically associated with MHC class II molecules that contain the shared epitope. These MHC molecules may participate in disease pathogenesis by selectively binding arthritogenic peptides for presentation to autoreactive CD4(+) T cells. The nature of the arthritogenic Ag is not known, but recent work has identified posttranslationally modified proteins containing citrulline (deiminated arginine) as specific targets of the IgG Ab response in RA patients. To understand how citrulline might evoke an autoimmune reaction, we have studied T cell responses to citrulline-containing peptides in HLA-DRB1*0401 transgenic (DR4-IE tg) mice. In this study, we demonstrate that the conversion of arginine to citrulline at the peptide side-chain position interacting with the shared epitope significantly increases peptide-MHC affinity and leads to the activation CD4(+) T cells in DR4-IE tg mice. These results reveal how DRB1 alleles with the shared epitope could initiate an autoimmune response to citrullinated self-Ags in RA patients.

Evolving trends in risk profiles and causes of death after heart transplantation: a ten-year multi-institutional study

BACKGROUND

As therapeutic options evolve for advanced heart failure, the appropriate role for cardiac transplantation will require survival analyses that reflect changing trends in causes of death and patient and institutional risk profiles. Results from multi-institutional studies could be used to monitor progress in individual centers.

METHODS

Between 1990 and 1999, 7290 patients undergoing cardiac transplantation in 42 institutions entered a formal outcomes study. Changing survival, causes of death, and patient risk profiles were analyzed. Multivariable risk-factor equations were applied to a single institution (300 primary heart transplants) to examine differences in risk-adjusted expected versus observed actuarial outcomes over time.

RESULTS

Overall survival in the 42 institutions improved during the decade (P =.02). One- and 3-year cardiac transplant research database survival was as follows: era 1 (1990-1992), 84% and 76%, respectively; era 2 (1993-1995), 85% and 79%, respectively; and era 3 (1996-1999), 85% and 79%, respectively. Causes of death changed over time. Pretransplantation risk profiles increased over time (P =.0001), with increases in reoperations, devices, diabetes, severely ill recipients, pulmonary vascular resistance, sensitization, ischemic times, donor age, and donor inotropic support. Three-year actuarial survival in a single institution was 3% less than risk-adjusted predicted survival in era 1, 1% higher than predicted in era 2, and 7% higher than predicted in era 3.

CONCLUSIONS

Survival after cardiac transplantation is gradually improving, despite increasing risk profiles. Further improvement requires periodic re-evaluation of risk profiles and causes of death to target areas of surveillance, therapy, and research. By using these methods, progress at individual institutions can be assessed in a time-related, risk-adjusted manner that also reflects changing institutional experience, expertise, or both.

The relationship between predicted peptide-MHC class II affinity and T-cell activation in a HLA-DRbeta1*0401 transgenic mouse model

The HLA-DRB1*0401 MHC class II molecule (DR4) is genetically associated with rheumatoid arthritis. It has been proposed that this MHC class II molecule participates in disease pathogenesis by presenting arthritogenic endogenous or exogenous peptides to CD4+ T cells, leading to their activation and resulting in an inflammatory response within the synovium. In order to better understand DR4 restricted T cell activation, we analyzed the candidate arthritogenic antigens type II collagen, human aggrecan, and the hepatitis B surface antigen for T-cell epitopes using a predictive model for determining peptide-DR4 affinity. We also applied this model to determine whether cross-reactive T-cell epitopes can be predicted based on known MHC-peptide-TCR interactions. Using the HLA-DR4-IE transgenic mouse, we showed that both T-cell proliferation and Th1 cytokine production (IFN-gamma) correlate with the predicted affinity of a peptide for DR4. In addition, we provide evidence that TCR recognition of a peptide-DR4 complex is highly specific in that similar antigenic peptide sequences, containing identical amino acids at TCR contact positions, do not activate the same population of T cells.

Induction of transient arthritis by the adoptive transfer of a collagen II specific Th1 clone to HLA-DR4 (B1*0401) transgenic mice

Collagen II arthritis (CIA) represents an animal model of human RA that can be induced in DBA/1J (H-2(q)) but not in C57BL/6 mice (H-2(b)). A vigorous CII specific CD4 Th1-cell response but not IgG2 anti-CII antibody or CIA could be induced in C57BL/6 mice made transgenic for the RA shared epitope DR4 (B1*0401). We developed CD4 Th1-cell clones specific for CII from these transgenic (tg) mice in order to determine if the adoptive transfer of these clones into syngeneic tg C57BL/6 recipients could induce CIA. Three bovine CII specific (bCII) CD4 Th1-cell clones and one T-cell line specific for an immunodominant region of bCII (p261-273) were generated. Among these only one clone that could up-regulate anti-CII, IgG2 antibody in the recipient mice was able to induce transient arthritis. However, this level of IgG2 anti-CII antibody was only one-third of that seen in CII immunized DBA/1J mice that develop persistent arthritis. These results confirm our previous observations that the induction of CIA requires a sustained IgG2 antibody response to CII, an effect difficult to achieve even in DR4 (B1*0401) tg mice reconstituted with CD4 Th1 cells. This suggests that a rate limiting step in the development of human RA among those individuals expressing the RA shared epitope may be the requirement to generate sustained levels of complement fixing antibody to arthritogenic antigens.

The influence of HLA-DR4 (0401) on the immune response to type II collagen and the development of collagen induced arthritis in mice

Rheumatoid arthritis (RA) is an autoimmune disease that is genetically associated with the MHC class II molecule HLA-DRbeta1*0401 (DR4). In order to determine if this MHC can influence the immune response to the candidate autoantigen type II collagen (CII), we have studied collagen induced arthritis (CIA) resistant C57BL/6 mice, made transgenic (Tg) for human DR4. These DR4 Tg mice exhibited a strong T cell proliferative response to CII and its DR4 restricted peptide p261-273 after immunization with these antigens that was not seen in the C57BL/6 wild type mice. DR4 Tg mice also exhibited an increase in IFN-gamma production in response to CII, indicating the activation of Th1 cells. While these Tg mice produced IgM anti-CII antibodies, they failed to produce a detectable level of IgG2a (Th1 type) anti-bCII antibody and did not develop CIA. This study shows that a Th1 type T cell response to CII can be established in CIA non-susceptible mice by introducing the human transgene, DR4. This T cell response, however, is not sufficient to induce an antibody isotype switch to IgG2a, nor is it sufficient for the induction of CIA. These results may help to explain why many individuals expressing HLA-DRbeta1*0401 do not develop RA.

Identification of the white blood cell populations responsible for Th1 immunity to trophoblast and the timing of the response in women with recurrent pregnancy loss

AIM

The purpose of this study was to identify the white blood cell populations responsible for Th1 immunity to trophoblast as evidenced in our in vitro assays following trophoblast activation and the timing of this response.

STUDY DESIGN

Peripheral blood mononuclear cells (PBMC) were isolated from 32 nonpregnant women with a history of at least three prior first trimester spontaneous abortions of unknown etiology except their PBMC secreted Th1 embryotoxic cytokines in response to trophoblast stimulation. White blood cell populations were separated from PBMC by magnetic immunobeads and cultured with and without a trophoblast antigen extract. Supernatants from these cultures were added to two cell mouse embryos and after four days of culture assessment of blastocyst development was made to determine the white blood cell population responsible for embryotoxicity. In separate experiments trophoblast-activated PBMC culture supernatants were prepared over seven time points and individual Th1 cytokines (IL-2, INF-gamma, TNF-alpha) were measured by ELISA to determine the timing of the response to trophoblast stimulation.

RESULTS

The white blood cell (CD45) populations responsible for embryotoxicity in response to trophoblast were T cells (CD3) and NK (CD56) cells. Levels of IL-2 peaked in the first 24 h of culture followed by TNF-alpha and IFN-gamma levels which peaked at 96 h of culture.

CONCLUSIONS

Our data demonstrated that the white blood cell populations responsible for embryotoxicity in our in vitro assays, were both T and NK cells. The kinetics of the cytokine response to trophoblast found in our study parallels the time course of a typical Th1 cytokine response. The profile of secreted cytokines support our hypothesis that trophoblast can produce Th1 immunity in some women with recurrent pregnancy loss that have embryotoxic effects in vitro.

T helper 1-type immunity to trophoblast antigens in women with a history of recurrent pregnancy loss is associated with polymorphism of the IL1B promoter region

Recurrent pregnancy loss (RPL) is a common disorder during early gestation. Recent evidence suggests that T helper 1 (Th1)-type immunity is associated with unsuccessful pregnancy especially in women with RPL of otherwise unknown etiology, while Th2-type immunity is associated with pregnancy success. Interleukin (IL)-1 may influence Th1/Th2 immune responsiveness and has been implicated in the establishment of successful pregnancy. In the present study, we investigated polymorphism of the IL-1beta gene (IL1B) in women with a history of RPL. Significant increases in the frequencies of IL1B promoter region variants IL1-511C and IL1B-31T were found in women with a history of RPL. Increased frequencies of these two variants and their homozygotes were found only in cases having evidence of Th1 immunity to trophoblast as determined by IFN-gamma production of peripheral blood mononuclear cells (PBMCs) stimulated with a trophoblast cell-line extract. Significantly higher IFN-gamma production by PBMCs in response to trophoblast correlated with variant IL1B-511C and its homozygocity in women with RPL. These results suggest that variants -511C and -31T in the IL1B promoter region confer risk for RPL associated with Th1 immunity to trophoblast antigens.

A randomized study comparing Crinone 8% and intramuscular progesterone supplementation in in vitro fertilization-embryo transfer cycles

OBJECTIVE

To compare the efficacy of Crinone 8% intravaginal progesterone gel vs. IM progesterone for luteal phase and early pregnancy support after IVF-ET.

DESIGN

Randomized, open-label study.

SETTING

Academic medical center.

PATIENT(S)

Two hundred and one women undergoing IVF-ET.

INTERVENTION(S)

Women were randomized to supplementation with Crinone 8% (90 mg once daily) or IM progesterone (50 mg once daily) beginning the day after oocyte retrieval.

MAIN OUTCOME MEASURE(S)

Pregnancy, embryo implantation, and live birth rates.

RESULT(S)

The women randomized to luteal phase supplementation with IM progesterone had significantly higher clinical pregnancy (48.5% vs. 30.4%; odds ratio [OR], 2.16; 95% confidence interval [CI], 1.21, 3.87), embryo implantation (24.1% vs. 17.5%; OR, 1.89; 95% CI, 1.08, 3.30), and live birth rates (39.4% vs. 24.5%; OR, 2.00; 95% CI, 1.10, 3.70) than women randomized to Crinone 8%.

CONCLUSION(S)

In women undergoing IVF-ET, once-a-day progesterone supplementation with Crinone 8%, beginning the day after oocyte retrieval, resulted in significantly lower embryo implantation, clinical pregnancy, and live birth rates compared with women supplemented with IM progesterone.

Sperm morphology, motility, and concentration in fertile and infertile men

BACKGROUND

Although semen analysis is routinely used to evaluate the male partner in infertile couples, sperm measurements that discriminate between fertile and infertile men are not well defined.

METHODS

We evaluated two semen specimens from each of the male partners in 765 infertile couples and 696 fertile couples at nine sites. The female partners in the infertile couples had normal results on fertility evaluation. The sperm concentration and motility were determined at the sites; semen smears were stained at the sites and shipped to a central laboratory for an assessment of morphologic features of sperm with the use of strict criteria. We used classification-and-regression-tree analysis to estimate threshold values for subfertility and fertility with respect to the sperm concentration, motility, and morphology. We also used an analysis of receiver-operating-characteristic curves to assess the relative value of these sperm measurements in discriminating between fertile and infertile men.

RESULTS

The subfertile ranges were a sperm concentration of less than 13.5 x 10(6) per milliliter, less than 32 percent of sperm with motility, and less than 9 percent with normal morphologic features. The fertile ranges were a concentration of more than 48.0 x 10(6) per milliliter, greater than 63 percent motility, and greater than 12 percent normal morphologic features. Values between these ranges indicated indeterminate fertility. There was extensive overlap between the fertile and the infertile men within both the subfertile and the fertile ranges for all three measurements. Although each of the sperm measurements helped to distinguish between fertile and infertile men, none was a powerful discriminator. The percentage of sperm with normal morphologic features had the greatest discriminatory power.

CONCLUSIONS

Threshold values for sperm concentration, motility, and morphology can be used to classify men as subfertile, of indeterminate fertility, or fertile. None of the measures, however, are diagnostic of infertility.

Electrical remodeling in pressure-overload cardiac hypertrophy: role of calcineurin

BACKGROUND

Myocyte hypertrophy accompanies many forms of heart disease, but its contribution to electrical remodeling is unknown.

METHODS AND RESULTS

We studied mouse hearts subjected to pressure overload by surgical thoracic aortic banding. In unbanded control hearts, action potential duration (APD) was significantly longer in subendocardial myocytes compared with subepicardial myocytes. Hypertrophy-associated APD prolongation was significantly greater in subendocardial myocytes compared with subepicardial myocytes, indicating stress-induced amplification of repolarization dispersion. To investigate the underlying basis, we performed voltage-clamp recordings on dissociated myocytes. Under control unoperated conditions, subendocardial myocytes exhibited significantly less transient outward current (I(to)) than did subepicardial cells. Hypertrophy was not associated with significant changes in I(to), sustained current, or inward rectifier current densities, but peak L-type Ca(2+) current density (I(Ca,L)) increased 26% (P<0.05). Recovery from I(Ca,L) inactivation was accelerated in hypertrophied myocytes. Inhibition of calcineurin with cyclosporin A prevented increases in heart mass and myocyte size but was associated with an intermediate APD. The hypertrophy-associated increase in I(Ca,L) and the accelerated recovery from inactivation were blocked by cyclosporin A.

CONCLUSIONS

These data reveal regional variation in the electrophysiological response within the left ventricle by way of a mechanism involving upregulated Ca(2+) current and calcineurin. Furthermore, these results reveal partial uncoupling of electrophysiological and structural remodeling in hypertrophy.

Environmental toxins associated with recurrent pregnancy loss

Couples experiencing recurrent pregnancy loss are often concerned that toxins within the environment have contributed to their reproductive difficulty. Questions posed by these couples to their health care providers are difficult to answer because scientifically accurate information regarding the reproductive impact of potential environmental toxins and other teratogens is not readily available. Heavy metals such as lead and mercury, organic solvents, alcohol, and ionizing radiation are confirmed environmental teratogens, and exposure could contribute to pregnancy loss. Caffeine, cigarette smoking, and hyperthermia are suspected teratogens, and the teratogenic impact of pesticides remains unknown. The teratogenic potential of multiple other environmental factors has been studied and is reviewed. Before definitive conclusions can be drawn regarding the teratogenicity of environmental exposures, several clinical factors need to be addressed, including gestational age at the time of exposure, the amount of toxin reaching the conceptus, the duration of exposure, the impact of other factors or agents to which the mother or her conceptus is simultaneously exposed, and the physiological status of the mother and conceptus. In addition, in a given population, the interrelationship between frequency of exposures,frequency of effects, and recognizability of adverse outcomes, such as spontaneous abortion, should be considered.

Maternal-embryonic cross-talk

The human menstrual cycle evolved to prepare the uterus for blastocyst implantation, which is fundamentally under the control of gonadal steroids. Ovarian hormones induce marked morphological, physiological, and biochemical changes within reproductive tissues. These changes in turn induce alterations in the biosynthetic activity and release of a myriad of locally produced proteins into the microenvironment of the reproductive tract. These same factors may be further modified by proteins secreted by the developing embryo and accompanying cumulus cells in intimate contact with reproductive epithelium in a network signaling process. Communication is not one-way, but rather maternal-embryonic cross-talk may occur as maternal proteins are secreted into the microenvironment of the oviduct and uterus, facilitating fertilization and early embryo development and serving as homing beacons for blastocyst nidation. The communicating language facilitating this dialogue includes cytokines, growth factors, angiogenic factors, apoptotic factors, adhesion molecules, and, potentially, homeotic genes.

Sonographic and Doppler characteristics of the corpus luteum: can they predict pregnancy outcome?

OBJECTIVE

To determine whether there is a relationship between gray scale or Doppler characteristics of the corpus luteum and first-trimester pregnancy outcome.

METHODS

We conducted a prospective study of patients with spontaneous singleton pregnancies between 5 and 8 weeks' gestation. The corpus luteum size, sonographic appearance, resistive index, and peak systolic velocity were measured on transvaginal sonography. Maternal use of exogeneous progesterone was recorded. Only patients with known first-trimester outcome were included.

RESULTS

There were 201 study patients. The corpus luteum could be visualized in 197 (98%) and had a mean +/- SD size of 1.9 +/- 0.6 cm, a mean resistive index of 0.50 +/- 0.08, and a peak systolic velocity of 20.5 +/- 11.2 cm/s. There were 151 first-trimester survivors (75.1 %) and 50 spontaneous losses (24.9%). In a comparison of the survivors and losses, there was no significant difference in mean corpus luteum size (1.9 versus 1.7 cm; P = .10, t test), mean resistive index (0.50 versus 0.50; P = .71, t test), peak systolic velocity (21 versus 19 cm/s; P = .29, t test), or sonographic appearance (P = .78, chi2 test). The lack of association between corpus luteum characteristics and outcome persisted when cases were stratified by progesterone use and the presence or absence of a heartbeat on the study sonogram.

CONCLUSION

There is no apparent relationship between the characteristics of the corpus luteum and first-trimester pregnancy outcome.

Targeted replacement of KV1.5 in the mouse leads to loss of the 4-aminopyridine-sensitive component of I(K,slow) and resistance to drug-induced qt prolongation

The K(+) channel mKv1.5 is thought to encode a 4-aminopyridine (4-AP)-sensitive component of the current I(K,slow) in the mouse heart. We used gene targeting to replace mKv1.5 with the 4-AP-insensitive channel rKv1.1 (SWAP mice) and directly test the role of Kv1.5 in the mouse ventricle. Kv1.5 RNA and protein were undetectable, rKv1.1 was expressed, and Kv2.1 protein was upregulated in homozygous SWAP hearts. The density of the K(+) current I(K,slow) (depolarizations to +40 mV, pA/pF) was similar in left ventricular myocytes isolated from SWAP homozygotes (17+/-1, n=27) and littermate controls (16+/-2, n=19). The densities and properties of I(peak), I(to,f), I(to,s), and I(ss) were also unchanged. In homozygous SWAP myocytes, the 50-micromol/L 4-AP-sensitive component of IK,slowwas absent (n=6), the density of the 20-mmol/L tetraethylammonium-sensitive component of I(K,slow) was increased (9+/-1 versus 5+/-1, P<0.05), and no 100- to 200-nmol/L alpha-dendrotoxin-sensitive current was found (n=8). APD(90) in SWAP myocytes was similar to controls at baseline but did not prolong in response to 30 micromol/L 4-AP. Similarly, QTc (ms) was not prolonged in anesthetized SWAP mice (64+/-2, homozygotes, n=9; 62+/-2, controls, n=9), and injection with 4-AP prolonged QTc only in controls (63+/-1, homozygotes; 72+/-2, controls; P<0.05). SWAP mice had no increase in arrhythmias during ambulatory telemetry monitoring. Thus, Kv1.5 encodes the 4-AP-sensitive component of I(K,slow) in the mouse ventricle and confers sensitivity to 4-AP-induced prolongation of APD and QTC: Compensatory upregulation of Kv2.1 may explain the phenotypic differences between SWAP mice and the previously described transgenic mice expressing a truncated dominant-negative Kv1.1 construct.

Outcome of pregnancies in women with uterine leiomyomas identified by sonography in the first trimester

PURPOSE

We assessed the outcome of pregnancies in women with uterine leiomyomas (fibroids) documented by sonography in the first trimester of pregnancy.

METHODS

We collected cases of women who had undergone first-trimester sonography and had uterine fibroids and singleton pregnancies with documented fetal heartbeats. We compared pregnancy loss rates and modes of delivery in these cases to a maternal-age-matched and gestational-age-matched control group of women who had normal uteruses and first-trimester pregnancies with documented fetal heartbeats. Sonograms in patients with fibroids were reviewed to determine the number of fibroids, their sizes, and their locations. Within the group of patients with fibroids, the pregnancy loss rate was also compared based on the number of fibroids and fibroid size and location.

RESULTS

Our study population consisted of 143 women with leiomyomas, and our control group comprised 715 patients with a normal uterus. Among patients with fibroids, 14.7% of pregnancies resulted from assisted conception; in the control group, 6.4% of pregnancies resulted from assisted conception. The rate of spontaneous pregnancy loss in women with fibroids was almost twice the rate in women with normal uteruses (14.0% versus 7.6%; p < 0.05), and the loss rate was higher in women with multiple fibroids than in women with a single leiomyoma (23.6% versus 8.0%, p < 0.05). The loss rate was not significantly associated with fibroid size or location. The rate of cesarean-section delivery was higher in patients with fibroids than in patients with normal uteruses (38% versus 28%, p < 0.05).

CONCLUSIONS

Uterine fibroids are associated with an elevated risk of spontaneous pregnancy loss. The loss rate is higher in patients with multiple fibroids than with a single fibroid. The cesarean-section rate is also higher in patients with fibroids than in patients with a normal uterus.

Cardiac transplantation in a patient with hereditary hemochromatosis: role of adjunctive phlebotomy and erythropoietin

We describe the case of a 36-year-old woman with hereditary hemochromatosis (HH) resulting in end-stage cardiomyopathy and treated successfully with orthotopic cardiac transplantation. Before and after transplantation, the patient underwent aggressive treatment with frequent phlebotomy. We used erythropoietin concomitantly to maintain adequate hematocrit to support continued phlebotomy. We believe that aggressive use of phlebotomy provided the patient hemodynamic benefit and hastened the return of endocrine function post-transplantation. We also believe that the patient's history of high-dose vitamin C usage may have accelerated iron deposition in the heart and other vital organs.

Na+-Ca2+ exchanger remodeling in pressure overload cardiac hypertrophy

Perturbations of Ca(2+) metabolism are central to the pathogenesis of cardiac hypertrophy. The electrogenic Na(+)-Ca(2+) exchanger mediates a substantial component of transmembrane Ca(2+) movement in cardiac myocytes and is up-regulated in heart failure. However, the role of the exchanger in the pathogenesis of cardiac hypertrophy is poorly understood. Thoracic aortic banding in mice induced 50-60% increases in heart mass and cardiomyocyte size. Despite the absence of myocardial dysfunction, steady-state NCX1 transcript and protein levels were increased to an extent similar to that reported in heart failure. As recent studies indicate that calcineurin is critical to the expression of Na(+)-Ca(2+) exchanger genes, we inhibited calcineurin with cyclosporin. Calcineurin inhibition blunted the increases in NCX1 transcript and protein levels and eliminated the increases in heart mass and cell volume normally associated with pressure overload. To examine the functional significance of these changes, we measured Na(+)-Ca(2+) exchanger current in two independent ways. Surprisingly, exchanger current density was decreased in hypertrophied myocytes, and this down-regulation was eliminated by calcineurin inhibition. Together, these data reveal a role for Na(+)-Ca(2+) exchanger current in the electrical remodeling of hypertrophy and implicate calcineurin signaling therein. In addition, these data suggest the Na(+)-Ca(2+) exchanger is functionally regulated in hypertrophy.