Lactate limits CNS autoimmunity by stabilizing HIF-1α in dendritic cells

Dendritic cells (DCs) have a role in the development and activation of self-reactive pathogenic T cells1,2. Genetic variants that are associated with the function of DCs have been linked to autoimmune disorders3,4, and DCs are therefore attractive therapeutic targets for such diseases. However, developing DC-targeted therapies for autoimmunity requires identification of the mechanisms that regulate DC function. Here, using single-cell and bulk transcriptional and metabolic analyses in combination with cell-specific gene perturbation studies, we identify a regulatory loop of negative feedback that operates in DCs to limit immunopathology. Specifically, we find that lactate, produced by activated DCs and other immune cells, boosts the expression of NDUFA4L2 through a mechanism mediated by hypoxia-inducible factor 1α (HIF-1α). NDUFA4L2 limits the production of mitochondrial reactive oxygen species that activate XBP1-driven transcriptional modules in DCs that are involved in the control of pathogenic autoimmune T cells. We also engineer a probiotic that produces lactate and suppresses T cell autoimmunity through the activation of HIF-1α-NDUFA4L2 signalling in DCs. In summary, we identify an immunometabolic pathway that regulates DC function, and develop a synthetic probiotic for its therapeutic activation.

Ornithine aminotransferase supports polyamine synthesis in pancreatic cancer

There is a need to develop effective therapies for pancreatic ductal adenocarcinoma (PDA), a highly lethal malignancy with increasing incidence1 and poor prognosis2. Although targeting tumour metabolism has been the focus of intense investigation for more than a decade, tumour metabolic plasticity and high risk of toxicity have limited this anticancer strategy3,4. Here we use genetic and pharmacological approaches in human and mouse in vitro and in vivo models to show that PDA has a distinct dependence on de novo ornithine synthesis from glutamine. We find that this process, which is mediated through ornithine aminotransferase (OAT), supports polyamine synthesis and is required for tumour growth. This directional OAT activity is usually largely restricted to infancy and contrasts with the reliance of most adult normal tissues and other cancer types on arginine-derived ornithine for polyamine synthesis5,6. This dependency associates with arginine depletion in the PDA tumour microenvironment and is driven by mutant KRAS. Activated KRAS induces the expression of OAT and polyamine synthesis enzymes, leading to alterations in the transcriptome and open chromatin landscape in PDA tumour cells. The distinct dependence of PDA, but not normal tissue, on OAT-mediated de novo ornithine synthesis provides an attractive therapeutic window for treating patients with pancreatic cancer with minimal toxicity.

Engineered probiotics limit CNS autoimmunity by stabilizing HIF-1α in dendritic cells

Dendritic cells (DCs) control the generation of self-reactive pathogenic T cells. Thus, DCs are considered attractive therapeutic targets for autoimmune diseases. Using single-cell and bulk transcriptional and metabolic analyses in combination with cell-specific gene perturbation studies we identified a negative feedback regulatory pathway that operates in DCs to limit immunopathology. Specifically, we found that lactate, produced by activated DCs and other immune cells, boosts NDUFA4L2 expression through a mechanism mediated by HIF-1α. NDUFA4L2 limits the production of mitochondrial reactive oxygen species that activate XBP1-driven transcriptional modules in DCs involved in the control of pathogenic autoimmune T cells. Moreover, we engineered a probiotic that produces lactate and suppresses T-cell autoimmunity in the central nervous system via the activation of HIF-1α/NDUFA4L2 signaling in DCs. In summary, we identified an immunometabolic pathway that regulates DC function, and developed a synthetic probiotic for its therapeutic activation.

Metabolomic Analysis of Coronary Heart Disease in an African American Cohort From the Jackson Heart Study

Importance

African American individuals have disproportionate rates of coronary heart disease (CHD) but lower levels of coronary artery calcium (CAC), a marker of subclinical CHD, than non-Hispanic White individuals. African American individuals may have distinct metabolite profiles associated with incident CHD risk compared with non-Hispanic White individuals, and examination of these differences could highlight important processes that differ between them.

Objectives

To identify novel biomarkers of incident CHD and CAC among African American individuals and to replicate incident CHD findings in a multiethnic cohort.

Design, Setting, and Participants

This analysis targeted plasma metabolomic profiling of 2346 participants in the Jackson Heart Study (JHS), a prospective population-based cohort study that included 5306 African American participants who were examined at baseline (2000-2004) and 2 follow-up visits. Replication of CHD-associated metabolites was sought among 1588 multiethnic participants from the Women's Health Initiative (WHI), a prospective population-based multiethnic cohort study of 161 808 postmenopausal women who were examined at baseline (1991-1995) and ongoing follow-up visits. Regression analyses were performed for each metabolite to examine the associations with incident CHD and CAC scores. Data were collected from the WHI between 1994 and 2009 and from the JHS between 2000 and 2015. All data were analyzed from November 2020 to August 2021.

Exposures

Plasma metabolites.

Main Outcomes and Measures

Incident CHD was defined as definite or probable myocardial infarction or definite fatal CHD in both the JHS and WHI cohorts. In the JHS cohort, silent myocardial infarction between examinations (as determined by electrocardiography) and coronary revascularization were included in the incident CHD analysis. Coronary artery calcium was measured using a 16-channel computed tomographic system and reported as an Agatston score.

Results

Among 2346 African American individuals in the JHS cohort, the mean (SD) age was 56 (13) years, and 1468 individuals (62.6%) were female. Among 1588 postmenopausal women in the WHI cohort, the mean (SD) age was 67 (7) years; 217 individuals (13.7%) self-identified as African American, 1219 (76.8%) as non-Hispanic White, and 152 (9.6%) as other races or ethnicities. In the fully adjusted model including 1876 individuals, 46 of 303 targeted metabolites were associated with incident CHD (false discovery rate q <0.100). Data for 32 of the 46 metabolites were available in the WHI cohort, and 13 incident CHD-associated metabolites from the JHS cohort were replicated in the WHI cohort. A total of 1439 participants from the JHS cohort with available CAC scores received metabolomic profiling. Nine metabolites were associated with CAC scores. Minimal overlap was found between the results from the incident CHD and CAC analyses, with only 3 metabolites shared between the 2 analyses.

Conclusions and Relevance

This cohort study identified metabolites that were associated with incident CHD among African American individuals, including 13 incident CHD-associated metabolites that were replicated in a multiethnic population and 9 novel metabolites that included N-acylamides, leucine, and lipid species. These findings may help to elucidate common and distinct metabolic processes that may be associated with CHD among individuals with different self-identified race.

Abstract PO-028: Pancreatic ductal adenocarcinoma is dependent on an unconventional pathway for polyamine synthesis

Targeting altered metabolism in pancreatic ductal adenocarcinoma (PDAC) has been an area of extensive investigation for over a decade now. A major hurdle however, for most anti-tumor metabolic strategies, is the high risk for toxicity, given the essential roles of metabolic pathways in the maintenance of normal tissue homeostasis. Indeed, this has been the case for targeting polyamines in cancers. Polyamines are small, highly positively charged molecules involved in multiple fundamental processes of cell growth and survival, including the synthesis of nucleic acids, modifications of chromatin structure, gene transcription and mRNA translation. Polyamine levels are significantly increased in many cancers, including PDAC. Prior anti-tumor strategies focused on pharmacological inhibition of the rate-limiting enzyme of polyamine synthesis, ornithine decarboxylase (ODC1) with little success, partially due to risk of harming normal tissues at higher drug doses. In this project, using both in vitro and in vivo mouse models of PDAC, we identified a dependency of PDAC on an unconventional way for the synthesis of the polyamine precursor ornithine, specifically from glutamine via ornithine aminotransferase (OAT); this is in contrast to its synthesis in most adult normal tissues from arginine via arginase (ARG) activity. We also identified potential key players mediating the induction of this metabolic pathway via KRAS, the main oncogenic driver in PDAC and are currently characterizing the downstream effects of polyamines on pancreatic tumor cells. The high dependency of PDAC, compared to normal tissue, on de novo ornithine synthesis via OAT provides an attractive therapeutic window for treating pancreatic cancer patients with minimal toxicity.

Citation Format: Min-Sik Lee, Insia Naqvi, Courtney Dennis, Lucas Dailey, Alireza Lorzadeh, Tamara Zaytouni, Ashley Adler, Daniel S. Hitchcock, Lin Lin, Unmesh Jadhav, Clary B. Clish, Nada Y. Kalaany. Pancreatic ductal adenocarcinoma is dependent on an unconventional pathway for polyamine synthesis [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-028.

Abstract PO-029: Pancreatic cancer-associated cachexia as a 3-stage systemic disease with changes in body composition, tissue-specific wasting across time and alterations in glucose metabolism

Pancreatic ductal adenocarcinoma (PDAC) is a devastating disease that rapidly deteriorates the organism resulting in &lt;10% 5-years survival in humans. Cancer-associated cachexia (CAC) is a multi-organ complex syndrome that accompanies PDAC in 85% of the cases. CAC is often characterized by the loss of body weight, including loss of muscle and fat tissues. Chronic inflammation, myokines and adipokines (released from muscle and fat, respectively), together with few recent tumor-derived factors, have been shown to collectively induce some of the metabolic changes in peripheral tissues that lead to wasting. Those include the synthesis of acute phase proteins in the liver, lipolysis and browning of the white adipose tissues (WAT), and protein degradation in the skeletal muscle. However, how these changes affect systemic metabolism, such as amino-acid utilization for liver gluconeogenesis, the systemic consequences of increased free fatty acids from lipolysis and their final destination for b-oxidation, or the rewiring of glucose metabolism, are processes not fully understood during cachexia. Here we established a 3-stage model of cachexia progression, including pre-, early- and late-CAC stages, in a doxycycline inducible murine model of PDAC (p48(Cre/+);tetKRAS(LSL/+);p53(fl/fl)), in both genders. We have monitored body weight loss, changes in body composition using DEXA scan, food intake and survival, across time since the start of doxycycline administration (i.e. tumor initiation). We have submitted these mice to metabolic cages aiming to distinguish in which of the 3 stages fat consumption starts, as well as monitored the weight of 8 tissue types (pancreas, liver, iWAT, eWAT, brown adipose tissue, quadriceps, gastrocnemius and soleus) over time. Overall, we have defined pre-CAC as “weight-gaining stage, before body weight peaks”, early-CAC as &lt;10% and late-CAC as &gt;10% of body weight loss, together with specific changes in body composition in each stage, food intake only happening at the very end stage, while all non-tumoral tissues present significant reduced weight at early stages. We have performed metabolomics and lipidomics in all peripheral tissues, aiming to identify changes that occur not only at early- but also at the pre-CAC stages, when pancreatic tumors already weighed more than double of the normal pancreas. In addition, glucose tolerance test analyses showed that tumor-bearing mice cleared the glucose more rapidly than control mice, even at pre-CAC stages, opening new avenues to continue studying glucose metabolism in the periphery such as increased liver gluconeogenesis and peripheral insulin resistance. Together, these results allowed us to establish a murine model to study cachexia in 3 stages, similar to what happens in humans. Furthermore, metabolomic data from the peripheral tissues, tumor interstitial fluid (TIF) and plasma, will allow us to identify the metabolic landscape of the entire organism throughout the progression of the disease, and potentially propose new therapeutic windows to target or prevent wasting in cancer.

Citation Format: Blanca Majem, Insia Naqvi, Courtney Dennis, Lucas Dailey, Clary B. Clish, Nada Kalaany. Pancreatic cancer-associated cachexia as a 3-stage systemic disease with changes in body composition, tissue-specific wasting across time and alterations in glucose metabolism [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2021 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2021;81(22 Suppl):Abstract nr PO-029.

Metabolomic Profiles and Heart Failure Risk in Black Adults: Insights From the Jackson Heart Study

BACKGROUND

Heart failure (HF) is a heterogeneous disease characterized by significant metabolic disturbances; however, the breadth of metabolic dysfunction before the onset of overt disease is not well understood. The purpose of this study was to determine the association of circulating metabolites with incident HF to uncover novel metabolic pathways to disease.

METHODS

We performed targeted plasma metabolomic profiling in a deeply phenotyped group of Black adults from the JHS (Jackson Heart Study; n=2199). We related metabolites associated with incident HF to established etiological mechanisms, including increased left ventricular mass index and incident coronary heart disease. Furthermore, we evaluated differential associations of metabolites with HF with preserved ejection fraction versus HF with reduced ejection fraction.

RESULTS

Metabolites associated with incident HF included products of posttranscriptional modifications of RNA, as well as polyamine and nitric oxide metabolism. A subset of metabolite-HF associations was independent of well-established HF pathways such as increased left ventricular mass index and incident coronary heart disease and included homoarginine (per 1 SD increase in metabolite level, hazard ratio, 0.77; P=1.2×10^-3), diacetylspermine (hazard ratio, 1.34; P=3.4×10^-3), and uridine (hazard ratio, 0.79; P, 3×10^-4). Furthermore, metabolites involved in pyrimidine metabolism (orotic acid) and collagen turnover (N-methylproline) among others were part of a distinct metabolic signature that differentiated individuals with HF with preserved ejection fraction versus HF with reduced ejection fraction.

CONCLUSIONS

The integration of clinical phenotyping with plasma metabolomic profiling uncovered novel metabolic processes in nontraditional disease pathways underlying the heterogeneity of HF development in Black adults.

Metabolic Architecture of Acute Exercise Response in Middle-Aged Adults in the Community

BACKGROUND

Whereas regular exercise is associated with lower risk of cardiovascular disease and mortality, mechanisms of exercise-mediated health benefits remain less clear. We used metabolite profiling before and after acute exercise to delineate the metabolic architecture of exercise response patterns in humans.

METHODS

Cardiopulmonary exercise testing and metabolite profiling was performed on Framingham Heart Study participants (age 53±8 years, 63% women) with blood drawn at rest (n=471) and at peak exercise (n=411).

RESULTS

We observed changes in circulating levels for 502 of 588 measured metabolites from rest to peak exercise (exercise duration 11.9±2.1 minutes) at a 5% false discovery rate. Changes included reductions in metabolites implicated in insulin resistance (glutamate, -29%; P=1.5×10-55; dimethylguanidino valeric acid [DMGV], -18%; P=5.8×10-18) and increases in metabolites associated with lipolysis (1-methylnicotinamide, +33%; P=6.1×10-67), nitric oxide bioavailability (arginine/ornithine + citrulline, +29%; P=2.8×10-169), and adipose browning (12,13-dihydroxy-9Z-octadecenoic acid +26%; P=7.4×10-38), among other pathways relevant to cardiometabolic risk. We assayed 177 metabolites in a separate Framingham Heart Study replication sample (n=783, age 54±8 years, 51% women) and observed concordant changes in 164 metabolites (92.6%) at 5% false discovery rate. Exercise-induced metabolite changes were variably related to the amount of exercise performed (peak workload), sex, and body mass index. There was attenuation of favorable excursions in some metabolites in individuals with higher body mass index and greater excursions in select cardioprotective metabolites in women despite less exercise performed. Distinct preexercise metabolite levels were associated with different physiologic dimensions of fitness (eg, ventilatory efficiency, exercise blood pressure, peak Vo2). We identified 4 metabolite signatures of exercise response patterns that were then analyzed in a separate cohort (Framingham Offspring Study; n=2045, age 55±10 years, 51% women), 2 of which were associated with overall mortality over median follow-up of 23.1 years (P≤0.003 for both).

CONCLUSIONS

In a large sample of community-dwelling individuals, acute exercise elicits widespread changes in the circulating metabolome. Metabolic changes identify pathways central to cardiometabolic health, cardiovascular disease, and long-term outcome. These findings provide a detailed map of the metabolic response to acute exercise in humans and identify potential mechanisms responsible for the beneficial cardiometabolic effects of exercise for future study.

Coevolution of HMG domains and homeodomains and the generation of transcriptional regulation by Sox/POU complexes

The highly conserved homeodomains and HMG domains are components of a large number of proteins that play a role in the transcriptional regulation of gene expression during embryogenesis. Both the HMG domain and the homeodomain serve as interfaces for factor interactions with DNA, as well as with other proteins, and it is likely that the high degree of structural and sequence conservation within these domains reflects the conservation of basic aspects of these interactions. Classical HMG domain proteins have an ancient origin, being found in all eukaryotes, and are thought to have given rise to the metazoan-specific class of HMG domain proteins called the Sox proteins. Similarly, the metazoan-specific POU domain proteins are thought to have arisen from genes encoding ancestral homeodomain proteins. In this review, we summarize several examples of different HMG-homeodomain interactions that illustrate not only the ancient origin of each of these protein families, but also their relationship to each other, and discuss how coevolution of HMG and homeodomains may have lead to creation of the specialized Sox/POU protein complexes. Using the FGF-4 gene as an example, we also speculate on how coevolution of regulatory Sox/POU target DNA sequences may have occurred, and how the summation of these changes may have lead to the emergence of new developmental pathways.

Modulation of the activity of multiple transcriptional activation domains by the DNA binding domains mediates the synergistic action of Sox2 and Oct-3 on the fibroblast growth factor-4 enhancer

Fibroblast growth factor (FGF)-4 gene expression in the inner cell mass of the blastocyst and in EC cells requires the combined activity of two transcriptional regulators, Sox2 and Oct-3, which bind to adjacent sites on the FGF-4 enhancer DNA and synergistically activate transcription. Sox2 and Oct-3 bind cooperatively to the enhancer DNA through their DNA-binding, high mobility group and POU domains, respectively. These two domains, however, are not sufficient to activate transcription. We have analyzed a number of Sox2 and Oct-3 deletion mutants to identify the domains within each protein that contribute to the activity of the Sox2 x Oct-3 complex. Within Oct-3, we have identified two activation domains, the N-terminal AD1 and the C-terminal AD2, that play a role in the activity of the Sox2 x Oct-3 complex. AD1 also displays transcriptional activation functions in the absence of Sox2 while AD2 function was only detected within the Sox2 x Oct-3 complex. In Sox2, we have identified three activation domains within its C terminus: R1, R2, and R3. R1 and R2 can potentiate weak activation by Sox2 in the absence of Oct-3 but their deletion has no effect on the Sox2 x Oct-3 complex. In contrast, R3 function is only observed when Sox2 is complexed with Oct-3. In addition, analysis of Oct-1/Oct-3 chimeras indicates that the Oct-3 homeodomain also plays a critical role in the formation of a functional Sox2 x Oct-3 complex. Our results are consistent with a model in which the synergistic action of Sox2 and Oct-3 results from two major processes. Cooperative binding of the factors to the enhancer DNA, mediated by their binding domains, stably tethers each factor to DNA and increases the activity of intrinsic activation domains within each protein. Protein-protein and protein-DNA interactions then may lead to reciprocal conformational changes that expose latent activation domains within each protein. These findings define a mechanism that may also be utilized by other Sox x POU protein complexes in gene activation.

The dhfr oribeta-binding protein RIP60 contains 15 zinc fingers: DNA binding and looping by the central three fingers and an associated proline-rich region

Initiation of DNA replication occurs with high frequency within oribeta, a short region 3' to the Chinese hamster dhfr gene. Homodimers of RIP60 (replication initiation-region protein 60 kDA) purified from nuclear extract bind two ATT-rich sites in oribeta and foster the formation of a twisted 720 bp DNA loop in vitro. Using a one hybrid screen in yeast, we have cloned the cDNA for human RIP60. RIP60 contains 15 C(2)H(2)zinc finger (ZF) DNA binding motifs organized in three clusters, termed hand Z1 (ZFs 1-5), hand Z2 (ZFs 6-8) and hand Z3 (ZFs 9-15). A proline-rich region is located between hands Z2 and Z3. Gel mobility shift and DNase I footprinting experiments show hands Z1 and Z2 independently bind the oribeta RIP60 sites specifically, but with different affinities. Hand Z3 binds DNA, but displays no specificity for RIP60 sites. Ligation enhancement, DNase I footprinting, and atomic force microscopy assays show that hand Z2 and a portion of the associated proline-rich region is sufficient for protein multimerization on DNA and DNA looping in vitro. Polyomavirus origin-dependent plasmid replication assays show RIP60 has weak replication enhancer activity, suggesting that RIP60 does not harbor a transcriptional transactivation domain. Because vertebrate origins of replication have no known consensus sequence, we suggest that sequence-specific DNA binding proteins such as RIP60 may act as accessory factors in origin identification prior to the assembly of pre-initiation complexes.

Ozone effects on the immediate-phase response to allergen in the nasal airways of allergic asthmatic subjects

Epidemiologic and clinical trials have suggested that exposure to ozone increases airway hyperresponsiveness and inflammatory response to inhaled nasal allergen challenge in allergic asthmatic subjects. Previous studies have demonstrated an increased late-phase response to nasal allergen challenge; however, the early-phase response is unknown. We sought to characterize the early-phase response by measuring mast-cell inflammatory mediators and cellular influx at time points immediately following ozone exposure and subsequent allergen challenge. A cohort of mild, asymptomatic dust mite--sensitive asthmatic subjects was identified. Each subject underwent two separate exposures to both 0.4 ppm ozone and clean air in a randomized manner. Nasal lavage was performed before and after each exposure. Nasal allergen was then administered to a defined clinical end point, followed by nasal lavage. Differential cell counts and mast-cell products were identified in each lavage specimen. The mast-cell mediators tryptase and prostaglandin D2 were analyzed, as was a marker of epithelial cell permeability, albumin. Although allergen produced an increase in early-onset mediator release (mast cell-derived), no enhancement was noted after exposure to ozone. Neutrophil and eosinophil inflammatory mediators were not increased after ozone exposure or enhanced after allergen exposure, although ozone did enhance eosinophilic influx after exposure to allergen. Ozone exposure does not promote early-phase--response mediator release or enhance the response to allergen challenge in the nasal airways of extrinsic asthmatic subjects. Ozone, however, may promote an inflammatory cell influx, which helps induce a more significant late-phase response in this population.

Copper-dependent inflammation and nuclear factor-kappaB activation by particulate air pollution

Particulate air pollution causes increased cardiopulmonary morbidity and mortality, but the chemical determinants responsible for its biologic effects are not understood. We studied the effect of total suspended particulates collected in Provo, Utah, an area where an increase in respiratory symptoms in relation to levels of particulate pollution has been well documented. Provo particulates caused cytokine-induced neutrophil chemoattractant-dependent inflammation of rat lungs. Provo particulates stimulated interleukin-6 (IL-6) and IL-8 production, increased IL-8 messenger RNA (mRNA) and enhanced expression of intercellular adhesion molecule-1 (ICAM-1) in cultured BEAS-2B cells, and stimulated IL-8 secretion in primary cultures of human bronchial epithelium. Cytokine secretion was preceded by activation of the transcription factor nuclear factor-kappaB (NF-kappaB) and was reduced by treatment of cultures with superoxide dismutase, deferoxamine, or N-acetylcysteine. These biologic effects were replicated by culturing BEAS cells with quantities of Cu2+ found in Provo extract. IL-8 secretion by BEAS cells could be modified by addition of normal constituents of airway lining fluid to the culture medium. Mucin significantly reduced IL-8 secretion, and ceruloplasmin significantly increased IL-8 secretion and activation of NF-kappaB. These findings suggest that copper ions may cause some of the biologic effects of inhaled particulate air pollution in the Provo region of the United States, and may provide an explanation for the sensitivity of asthmatic individuals to Provo particulates that has been observed in epidemiologic studies.

Synergistic activation of the fibroblast growth factor 4 enhancer by Sox2 and Oct-3 depends on protein-protein interactions facilitated by a specific spatial arrangement of factor binding sites

Octamer binding and Sox factors are thought to play important roles in development by potentiating the transcriptional activation of specific gene subsets. The proteins within these factor families are related by the presence of highly conserved DNA binding domains, the octamer binding protein POU domain or the Sox factors HMG domain. We have previously shown that fibroblast growth factor 4 (FGF-4) gene expression in embryonal carcinoma cells requires a synergistic interaction between Oct-3 and Sox2 on the FGF-4 enhancer. Sox2 and Oct-3 bind to adjacent sites within this enhancer to form a ternary protein-DNA complex (Oct-3*) whose assembly correlates with enhancer activity. We now demonstrate that increasing the distance between the octamer and Sox binding sites by base pair insertion results in a loss of enhancer function. Significantly, those enhancer "spacing mutants" which failed to activate transcription were also compromised in their ability to form the Oct* complexes even though they could still bind both Sox2 and the octamer binding proteins, suggesting that a direct interaction between Sox2 and Oct-3 is necessary for enhancer function. Consistent with this hypothesis, Oct-3 and Sox2 can participate in a direct protein-protein interaction in vitro in the absence of DNA, and both this interaction and assembly of the ternary Oct* complexes require only the octamer protein POU and Sox2 HMG domains. Assembly of the ternary complex by these two protein domains occurs in a cooperative manner on FGF-4 enhancer DNA, and the loss of this cooperative interaction contributes to the defect in Oct-3* formation observed for the enhancer spacing mutants. These observations indicate that Oct-3* assembly results from protein-protein interactions between the domains of Sox2 and Oct-3 that mediate their binding to DNA, but it also requires a specific arrangement of the binding sites within the FGF-4 enhancer DNA. Thus, these results define one parameter that is fundamental to synergistic activation by Sox2 and Oct-3 and further emphasize the critical role of enhancer DNA sequences in the proper assembly of functional activation complexes.

Epithelial cell-conditioned media inhibits degranulation of the RBL-2H3 rat mast cell line

The effect of epithelial cells on mast cell responses was investigated by examination of degranulation of the rat mast cell line RBL-2H3 after overnight culture in media conditioned by the BEAS-2B human bronchial epithelial cell line [epithelial cell-conditioned media (ECM)]. These studies indicate that BEAS-2B cells secrete an inhibitor(s) of immunoglobulin E and A-23187-mediated degranulation of the RBL-2H3 cell line. The inhibitory activities of ECM are recovered after filtration through a 3-kDa cutoff filter. Pharmacological inhibition of cyclooxygenase in the BEAS-2B cells before preparation of ECM has no effect on subsequent inhibition of mast cell degranulation by ECM. However, cycloheximide treatment of the BEAS-2B cells before the conditioning process does preclude development of mast cell inhibitor activity in ECM, suggesting that this activity depends on protein synthesis. The effects of ECM on mast cell function are reversible, demonstrating that these effects do not result from overt cytotoxicity. Finally, media conditioned by primary cultures of human respiratory epithelial cells, but not fibroblasts, influence RBL-2H3 degranulation in a manner similar to ECM, suggesting that secretion of mast cell inhibitors may be somewhat unique to epithelial cells.

Developmental-specific activity of the FGF-4 enhancer requires the synergistic action of Sox2 and Oct-3

Fibroblast growth factor 4 (FGF-4) has been shown to be a signaling molecule whose expression is essential for postimplantation mouse development and, at later embryonic stages, for limb patterning and growth. The FGF-4 gene is expressed in the blastocyst inner cell mass and later in distinct embryonic tissues but is transcriptionally silent in the adult. In tissue culture FGF-4 expression is restricted to undifferentiated embryonic stem (ES) cells and embryonal carcinoma (EC) cell lines. Previously, we determined that EC cell-specific transcriptional activation of the FGF-4 gene depends on a synergistic interaction between octamer-binding proteins and an EC-specific factor, Fx, that bind adjacent sites on the FGF-4 enhancer. Through the cloning and characterization of an F9 cell cDNA we now show that the latter activity is Sox2, a member of the Sry-related Sox factors family. Sox2 can form a ternary complex with either the ubiquitous Oct-1 or the embryonic-specific Oct-3 protein on FGF-4 enhancer DNA sequences. However, only the Sox2/Oct-3 complex is able to promote transcriptional activation. These findings identify FGF-4 as the first known embryonic target gene for Oct-3 and for any of the Sox factors, and offer insights into the mechanisms of selective gene activation by Sox and octamer-binding proteins during embryogenesis.

Modulation of mast cell functions by in vitro ozone exposure

Exposure to ozone has been reported to cause increased immediate bronchial reactivity to inhaled allergen in asthmatics. The purpose of these studies was to determine whether ozone induces either spontaneous physiological degranulation or enhanced immunoglobulin E (IgE)-mediated degranulation of mast cells, thus accounting for the in vivo effects noted in asthmatics. A rat mast cell line (RBL-2H3) was exposed to different levels of ozone (0.1, 0.3, 0.5, and 1.0 ppm), covered by different amounts of buffer, and both cytotoxic and nontoxic exposure conditions were determined. In addition to cytotoxicity, spontaneous release of granule products and prostaglandin D2 (PGD2) associated with ozone exposure were assessed. RBL-2H3 cells were also exposed to ozone under noncytotoxic conditions followed by stimulation with alpha-IgE to cross-link membrane-bound IgE and A23187 so that the effect of ozone on stimulated degranulation could be examined. Only exposure conditions associated with cytotoxicity were associated with spontaneous release of mast cell serotonin, indicating no physiologic degranulation due to ozone exposure. Data presented herein also demonstrate that ozone substantially inhibited both IgE- and A23187-induced degranulation. Neither catalase nor superoxide dismutase protected cells from the inhibitory effect of ozone, indicating that ozone does not act through generation of H2O2 or superoxide. Additionally, ozone caused a modest increase in spontaneous PGD2 generation only under cytotoxic conditions. Thus ozone appears to inhibit mast cell degranulation after IgE- or A23187-mediated stimulation and causes direct release of mast cell granule products and PGD2 only under conditions associated with membrane cytotoxicity.

Interaction between a novel F9-specific factor and octamer-binding proteins is required for cell-type-restricted activity of the fibroblast growth factor 4 enhancer

Understanding how diverse transcription patterns are achieved through common factor binding elements is a fundamental question that underlies much of developmental and cellular biology. One example is provided by the fibroblast growth factor 4 (FGF-4) gene, whose expression is restricted to specific embryonic tissues during development and to undifferentiated embryonal carcinoma cells in tissue culture. Analysis of the cis- and trans-acting elements required for the activity of the previously identified FGF-4 enhancer in F9 embryonal carcinoma cells showed that enhancer function depends on sequences that bind Sp1 and ubiquitous as well as F9-specific octamer-binding proteins. However, sequences immediately upstream of the octamer motif, which conform to a binding site for the high-mobility group (HMG) domain factor family, were also critical to enhancer function. We have identified a novel F9-specific factor, Fx, which specifically recognizes this motif. Fx formed complexes with either Oct-1 or Oct-3 in a template-dependent manner. The ability of different enhancer variants to form the Oct-Fx complexes correlated with enhancer activity, indicating that these complexes play an essential role in transcriptional activation of the FGF-4 gene. Thus, while FGF-4 enhancer function is octamer site dependent, its developmentally restricted activity is determined by the interaction of octamer-binding proteins with the tissue-specific factor Fx.

Hydrogen peroxide effects on rat mast cell function

Oxidant exposure of the airway mucosa may play a significant role in the pathophysiology of asthma and allergic rhinitis. Mast cells play an important role in asthma, and oxidant exposure has been reported to cause direct mast cell degranulation as well as augment immunoglobulin E (IgE)-mediated responses in vivo. H2O2 is an oxidant generated by inflammatory cells and by the interaction of ozone with lipids or aqueous solutions. In this study, the RBL-2H3 mast cell line was used to investigate the ability of H2O2 to induce mast cell responses as well as to effect mast cell responses to IgE and the calcium ionophore A23187. Although cytotoxicity of RBL-2H3 cells at the membrane level was not observed with any concentration of H2O2, DNA damage resulted from exposure to 0.2 and 2.0 mM H2O2, and cell proliferation was inhibited by 0.075-0.2 mM H2O2. RBL cell prostaglandin D2 generation was enhanced after 60- and 120-min exposure to 0.2-20 mM H2O2. Direct serotonin release required 120-min exposures to 2.0 mM and 60-min exposures to 20 mM H2O2. However, degranulation responses induced by either IgE or A23178 were diminished after exposure to 0.2-2.0 mM H2O2. Lesser amounts (0.005-0.02 mM) had no effect on mast cell function. In summary, H2O2-induced responses of RBL cells, as well as modification of responses to IgE and A23187, occurred only at high concentrations of H2O2, which also induced both intracellular damage and inhibition of cell proliferation. Concentrations of H2O2 more likely to be physiologically relevant had no effect on mast cell responses or cytotoxicity.(ABSTRACT TRUNCATED AT 250 WORDS)

RIP60 dimers and multiples of dimers assemble link structures at an origin of bidirectional replication in the dihydrofolate reductase amplicon of Chinese hamster ovary cells

We show assembly of low and high multimers of HeLa cell nuclear protein, RIP60, at the origin of bidirectional replication (OBR) identified by Burhans, Vassilev, Caddle, Heintz and DePamphilis in Chinese hamster ovary cells. RIP60 binds a 5'-ATT-3' reiterated sequence downstream of the OBR and a second, homologous ATT sequence of opposite orientation situated within the OBR zone. Specifically bound structures were studied by conventional electron microscopy (EM) and quantitative scanning transmission electron microscopy (STEM). Dimers and multiples of dimers link the downstream binding site that overlaps a bent DNA sequence and the homologous upstream OBR sequence, looping out 700 bp of intervening DNA. Superposed dimers are found at individual unlinked sites, stabilized presumably through protein-protein interaction, and such superposition appears to occur also in the basic link structure. Along the loop, single crossovers and extended twists are observed by conventional EM. By STEM, loop DNA is laterally compacted, with diameter and mass equivalent to double-duplex DNA strands. Supercoiled 736 bp and 5243 bp circular DNAs assume similar laterally compacted geometries that are mostly absent from relaxed forms. These observations parallel the compacted, interwound superhelices viewed by cryo-electron microscopy in vitrified solutions containing magnesium ions, and provide structural evidence in agreement with that from conventional EM for superhelical tension in RIP60 loop DNA. Loop superhelicity could arise as a topological response to linking and suggests a functional role for link formation.

Eukaryotic replication origins as promoters of bidirectional DNA synthesis

Recent work in yeast shows that eukaryotic origins of DNA replication are multipartite regulatory elements resembling promoters of transcription. As for the regulation of transcription, accessory transcription factors appear to function in concert with basic origin recognition factors to regulate initiation of DNA synthesis at specific subsets of origins. The participation of transcription factors in the regulation of DNA replication may facilitate temporal control of transcription and replication during the cell cycle, as well as providing a mechanism for integrating origin selection with the cellular transcriptional program.

Use of the Green transfer in treatment of patients with spastic cerebral palsy: 17-year experience

We retrospectively reviewed Green procedures and transfer of the flexor carpi ulnaris (FCU) in treatment of spastic forearm pronation, wrist volarflexion, and ulnar deviation deformities. Patient's ages ranged from 3 years 5 months to 16 years 5 months. Surgically, a single volar incision was made and the extensor carpi radialis brevis and/or longus (ECRB, ECRL) were used for insertion. The FCU was tensioned at neutral against gravity and immobilized in 5 degrees of dorsiflexion and 45 degrees of supination. Arc of flexion (47 degrees) did not change but was centered about neutral. Supination improved markedly when operation included a pronator procedure. Quadraplegia athetosis and intellectual impairment did not affect the operative result adversely. Patients aged greater than 12 years showed less functional improvement. Eighty-eight percent had cosmetic improvement, and 79% improved functionally. None had a decreased functional rating.

Purification of RIP60 and RIP100, mammalian proteins with origin-specific DNA-binding and ATP-dependent DNA helicase activities

Replication of the Chinese hamster dihydrofolate reductase gene (dhfr) initiates near a fragment of stably bent DNA that binds multiple cellular factors. Investigation of protein interactions with the dhfr bent DNA sequences revealed a novel nuclear protein that also binds to domain B of the yeast origin of replication, the autonomously replicating sequence ARS1. The origin-specific DNA-binding activity was purified 9,000-fold from HeLa cell nuclear extract in five chromatographic steps. Protein-DNA cross-linking experiments showed that a 60-kDa polypeptide, which we call RIP60, contained the origin-specific DNA-binding activity. Oligonucleotide displacement assays showed that highly purified fractions of RIP60 also contained an ATP-dependent DNA helicase activity. Covalent radiolabeling with ATP indicated that the DNA helicase activity resided in a 100-kDa polypeptide, RIP100. The cofractionation of an ATP-dependent DNA helicase with an origin-specific DNA-binding activity suggests that RIP60 and RIP100 may be involved in initiation of chromosomal DNA synthesis in mammalian cells.

RIP60, a mammalian origin-binding protein, enhances DNA bending near the dihydrofolate reductase origin of replication

Replication of the Chinese hamster dihydrofolate (dhfr) gene initiates near a 281-bp HaeIII fragment of stably bent DNA that binds RIP60, a 60-kDa origin-specific DNA-binding protein that has been purified from HeLa cell nuclear extract (L. Dailey, M. S. Caddle, N. Heintz, and N. H. Heintz, Mol. Cell. Biol. 10:6225-6235, 1990). Circular permutation assays showed that stable DNA bending in the dhfr origin region fragment was due to the presence of five oligo (dA)3-4 tracts, designated bend elements B1 to B5, that are spaced 10 bp apart. DNA bending directed by elements B1 to B5, as assessed by anomolous migration of DNA fragments on polyacrylamide gels, was accentuated at 4 degrees C. Bend element B5, which is in inverse orientation relative to elements B1 to B4, overlaps an ATT-rich motif that comprises the RIP60 protein-binding site. Gel mobility shift assays with circularly permuted bent DNA fragments and purified RIP60 showed that RIP60 markedly enhanced DNA bending of the dhfr origin region sequences. These results suggest that, as in many plasmids, bacteriophages, and eucaryotic viruses, mammalian DNA-binding proteins may enhance DNA bending near origins of replication during initiation of DNA synthesis.

Purification of the human histone H4 gene-specific transcription factors H4TF-1 and H4TF-2

Transcription of the cell-cycle-regulated human histone genes increases approximately fivefold during S phase. One step toward the elucidation of the biochemical mechanisms that govern cell-cycle-regulated expression of these genes is to purify and characterize the transcription factors that regulate these promoters. Here, we describe the purification of two previously identified factors, H4TF-1 and H4TF-2, which bind the human histone H4 promoter. Purification was achieved through a combination of ion-exchange and oligonucleotide affinity chromatography. On the basis of analysis of purified fractions by SDS-polyacrylamide gels and UV cross-linking, we believe that H4TF-1 is two polypeptides of 105 and 110 kD. This factor binds to a GC-rich DNA sequence required for maximal expression of the H4 gene but does not bind to any Sp1 consensus elements tested. H4TF-2 is a 65-kD protein that binds specifically to sequences within that highly conserved H4 subtype-specific consensus promoter element. Both highly purified factors activated transcription in vitro only from H4 promoters that contained their binding sequences, demonstrating that H4TF-1 and H4TF-2 are H4-specific transcription factors that potentiate expression of this gene.

Comparison of pronator tenotomy and pronator rerouting in children with spastic cerebral palsy

Forty-one patients with cerebral palsy and pronation contracture of the forearm were treated with pronator teres rerouting compared with 16 patients who were treated with pronator teres tenotomy. The mean age of patients with pronator tenotomy was 4 years 3 months compared with 7 years 3 months for patients with rerouting. Follow-up averaged 94 months for tenotomy and 21 months for rerouting. Average gain in supination was 78 degrees for rerouting and 54 degrees for tenotomy. No patient lost active range of motion during follow-up. Although pronator teres tenotomy increased active supination of the forearm, greater active supination of the forearm was afforded patients treated with pronator teres rerouting.

RNA polymerase II transcription factors H4TF-1 and H4TF-2 require metal to bind specific DNA sequences

Specific DNA-binding and in vitro transcription activities of H4TF-1 and H4TF-2 are inactivated by chelating agents. Binding activity is restored by addition of Zn2+, and H4TF-2 is also reactivated by Fe2+. In contrast, preformed factor-DNA complexes are resistant to chelators. Therefore, metal ions are a required component of the H4TF-1 and H4TF-2 DNA-binding domains.

Distinct transcription factors bind specifically to two regions of the human histone H4 promoter

Two proteins specifically binding to separate regions of the human histone H4 promoter were identified in nuclear extracts prepared from synchronized S-phase HeLa cells. Competition experiments with H4 promoter mutants and DNase protection assays ("footprinting") demonstrate that these factors bind to regions of the H4 promoter that are essential for maximal expression in vitro. One of these factors (H4TF-1) binds to sequences between -80 and -110 base pairs upstream of the H4 cap site, whereas the other (H4TF-2) binds to the H4 subtype-specific sequence element immediately upstream from the "TATA" homology. Neither of these activities can efficiently bind to any of the other histone gene subtypes or simian virus 40 DNA. Binding of H4TF-1 to the distal region of the pHu4A histone H4 promoter is inhibited competitively with varying efficiency by four of six human histone H4 genes cloned in this laboratory, whereas efficient competition for binding of H4TF-2 is exhibited by five of the six H4 genes. Since both of these factors bind to significant regions of the pHu4A histone H4 promoter and can be bound by several different human H4 genes, we believe that they are important for maximal transcription of the gene and that they may be involved in its regulated expression during the cell cycle.

Common regulatory elements control gene expression from polyoma early and late promoters in cells transformed by chimeric plasmids

In a previous report we showed that transcripts initiating from the late promoter of integrated polyoma plasmids could be detected at significant levels when neomycin resistance (neo) coding sequences were linked to this promoter. In this report we used chimeric plasmids that contain either a limited portion of the polyoma genome or deletions within the polyoma noncoding regulatory region to determine the sequence requirements for late promoter activity in this system. We observed no absolute requirement for either the polyoma early coding region or the origin of DNA replication for Neo-r colony formation. We were therefore able to independently assess the effects of deletions in the polyoma enhancer region on gene activity in both the early and late directions. We measured the ability of cells transfected with plasmids containing deletions in this region to form colonies in either semisolid or G418-containing medium under nonreplicative conditions. Our results indicate that either the PvuII 4 fragment, which contains the simian virus 40 core enhancer sequence, or a region from nucleotides 5099 to 5142, which contains the adenovirus type 5 E1A core enhancer sequence, can be deleted without significantly affecting gene expression in either direction. However, a deletion of nucleotides 5099 to 5172 reduced activities to similar extents in both directions, and a plasmid containing a larger deletion of nucleotides 5055 to 5182 showed a further reduction in activity. Although having no effect by itself, a second origin region deletion of nucleotides 5246 to 127 when present in these mutant backgrounds caused either a further reduction or elimination, respectively, of both G418 and agar colony-forming ability, suggesting the presence of an additional common regulatory element within this region. A comparison of 5' ends of neo transcripts present in cells transformed by these plasmids suggested that the reduction in activity was due to deletion of regulatory rather than structural elements of the late promoter. Our results indicate that the noncoding region of polyoma contains multiple complementing regulatory elements that control the level of both early and late gene expression.

Latissimus dorsi transfer to restore elbow extension in obstetrical palsy

Four patients with weak triceps muscle function, secondary to obstetrical palsy, were treated by transfer of the latissimus dorsi on its neurovascular pedicle to provide effective elbow extension. The average age of the patients at surgery was 10 years, and follow-up ranged from 12 to 53 months. Postoperatively, all patients demonstrated increased strength of elbow extension and improvement in activities of daily living. These satisfactory results support the use of latissimus dorsi transfer in patients with weak elbow extension secondary to obstetrical palsy.

Amplification and excision of integrated polyoma DNA sequences require a functional origin of replication

Cells transformed by Polyoma virus (Py) can undergo a high rate of excision or amplification of integrated viral DNA sequences, and these phenomena require the presence of homology (i.e., repeats) within the viral insertion as well as a functional viral large T antigen (T-Ag). To determine whether the main role of large T-Ag in excision and amplification was replicative or recombination-promoting, we studied transformed rat cell lines containing tandem insertions of a ts-a Py molecule (encoding a thermolabile large T-Ag) with a deletion of the origin of viral DNA replication. Culturing of these cells at the temperature permissive for large T-Ag function did not result in any detectable excision or amplification of integrated Py sequences. We then introduced into origin-defective lines a recombinant plasmid containing the viral origin of replication and the gene coding for resistance to the antibiotic G418. All G418-resistant clones analyzed readily amplified the integrated plasmid molecules when grown under conditions permissive for large T-Ag function, showing that these cells produced viral large T-Ag capable of promoting amplification in trans of DNA sequences containing the Py origin. These observations strongly suggest that Polyoma large T antigen promotes excision or amplification of viral DNA by initiating replication at the integrated origin, providing a favorable substrate for subsequent recombination.

Deletion of the origin of replication impairs the ability of polyomavirus DNA to transform cells and to form tandem insertions

We examined the transforming properties of polyomavirus DNA molecules which can produce a functional large T-antigen but which are cis defective for viral DNA replication. The inability of these molecules to replicate results from the deletion of sequences comprising the viral replication origin. We found that even in the presence of a functional large T-antigen, transformation of rat cells by these viral DNAs was greatly reduced when compared with replication-competent parental DNA, and cells transformed by origin-minus mutants generally contained the integrated viral DNA in a nontandem arrangement. Therefore, polyomavirus large T-antigen promotes the establishment of transformation and tandem integration by interacting with the viral origin of DNA replication. This indicates that viral DNA synthesis is directly involved in these processes.

Requirements for excision and amplification of integrated viral DNA molecules in polyoma virus-transformed cells

The integration of polyoma virus DNA into the genome of transformed rat cells generally takes place in a tandem head-to-tail arrangement. A functional viral large tumor antigen (T-Ag) renders this structure unstable, as manifested by free DNA production and excision or amplification of the integrated viral DNA. All of these phenomena involve the mobilization of precise genomic "units," suggesting that they result from intramolecular homologous recombination events occurring in the repeated viral DNA sequences within the integrated structures. We studied polyoma ts-a-transformed rat cell lines, which produced large T-Ag but contained less than a single copy of integrated viral DNA. In all of these lines, reversion to a normal phenotype (indicative of excision) was extremely low and independent of the presence of a functional large T-Ag. The revertants were either phenotypic or had undergone variable rearrangements of the integrated sequences that seemed to involve flanking host DNA. In two of these cell lines (ts-a 4A and ts-a 3B), we could not detect any evidence of amplification even after 2 months of propagation under conditions permissive for large T-Ag. An amplification event was detected in a small subpopulation of the ts-a R5-1 line after 2 months of growth at 33 degrees C. This involved a DNA fragment of 5.1 kilobases, consisting of the left portion of the viral insertion and about 2.5 kilobases of adjacent host DNA sequences. None of these lines spontaneously produced free viral DNA, but after fusion with 3T3 mouse fibroblasts, R5-1 and 4A produced a low level of heterogeneous free DNA molecules, which contained both viral and flanking host DNA. In contrast, the ts-a 9 cell line, whose viral insertion consists of a partial tandem of approximately 1.2 viral genomes, underwent a high rate of excision or amplification when propagated at temperatures permissive for large T-Ag function. These results indicate that the high rate of excision and amplification of integrated viral genomes observed in polyoma-transformed rat cells requires the presence of regions of homology (i.e., repeats) in the integrated viral sequences. Therefore, these events occur via homologous intramolecular recombination, which is promoted directly or indirectly by the large viral T-Ag.

Amplification of integrated viral DNA sequences in polyoma virus-transformed cells

Polyoma virus (Py) transformation of rat cells requires integration of viral genomes into the host DNA, which generally occurs in a partial or full head-to-tail tandem arrangement. The instability of this structure was previously demonstrated by the high rate of loss of integrated Py genomes in the presence of viral large tumor (T) antigen. We now show that integrated Py DNA sequences can also undergo amplification. We studied two rat cell lines transformed by the ts-a Py mutant, which codes for a thermolabile large T antigen. In a derivative of the ts-a H6A cell line, we have observed loss of full-length Py DNA molecules from the integrated tandem ("curing"), accompanied by the creation of new tandem repeats of two segments of viral DNA corresponding to 38% and 10% of the viral genome, each containing the origin of DNA replication. In the ts-a H3A cell line, which contains an integrated partial tandem of about 1.3 viral genomes with three distinct deletions, propagation at 33 degrees C resulted in the generation of full tandem repeats of a 94% Py DNA "unit" (including two 3% deletions), an 85% "unit" (including a 3% and the 12% deletion), or both. Amplification of integrated viral DNA was not observed in cells propagated at 39.5 degrees C, the nonpermissive temperature for large T antigen function. Amplification of integrated Py DNA sequences thus requires an active large T antigen and can generate a full tandem of integrated viral DNA molecules long after the initial integration event.