A metalloproteinase disintegrin that releases tumour-necrosis factor-alpha from cells

Mammalian cells proteolytically release (shed) the extracellular domains of many cell-surface proteins. Modification of the cell surface in this way can alter the cell's responsiveness to its environment and release potent soluble regulatory factors. The release of soluble tumour-necrosis factor-alpha (TNF-alpha) from its membrane-bound precursor is one of the most intensively studied shedding events because this inflammatory cytokine is so physiologically important. The inhibition of TNF-alpha release (and many other shedding phenomena) by hydroxamic acid-based inhibitors indicates that one or more metalloproteinases is involved. We have now purified and cloned a metalloproteinase that specifically cleaves precursor TNF-alpha. Inactivation of the gene in mouse cells caused a marked decrease in soluble TNF-alpha production. This enzyme (called the TNF-alpha-converting enzyme, or TACE) is a new member of the family of mammalian adamalysins (or ADAMs), for which no physiological catalytic function has previously been identified. Our results should facilitate the development of therapeutically useful inhibitors of TNF-alpha release, and they indicate that an important function of adamalysins may be to shed cell-surface proteins.

Cloning of a T cell growth factor that interacts with the beta chain of the interleukin-2 receptor

A cytokine was identified that stimulated the proliferation of T lymphocytes, and a complementary DNA clone encoding this new T cell growth factor was isolated. The cytokine, designated interleukin-15 (IL-15), is produced by a wide variety of cells and tissues and shares many biological properties with IL-2. Monoclonal antibodies to the beta chain of the IL-2 receptor inhibited the biological activity of IL-15, and IL-15 competed for binding with IL-2, indicating that IL-15 uses components of the IL-2 receptor.

Molecular characterization of murine and human OX40/OX40 ligand systems: identification of a human OX40 ligand as the HTLV-1-regulated protein gp34

A ligand was cloned for murine OX40, a member of the TNF receptor family, using a T cell lymphoma cDNA library. The ligand (muOX40L) is a type II membrane protein with significant identity to human gp34 (gp34), a protein whose expression on HTLV-1-infected human leukemic T cells is regulated by the tax gene. The predicted structures of muOX40L and gp34 are similar to, but more compact than, those of other ligands of the TNF family. Mapping of the muOX40L gene revealed tight linkage to gld, the FasL gene, on chromosome 1. gp34 maps to a homologous region in the human genome, 1q25. cDNAs for human OX40 receptor were cloned by cross-hybridization with muOX40, and gp34 was found to bind the expressed human receptor. Lymphoid expression of muOX40L was detected on activated T cells, with higher levels found on CD4+ rather than CD8+ cells. The cell-bound recombinant ligands are biologically active, co-stimulating T cell proliferation and cytokine production. Strong induction of IL-4 secretion by muOX40L suggests that this ligand may play a role in regulating immune responses. In addition, the HTLV-1 regulation of gp34 suggests a possible connection between virally induced pathogenesis and the OX40 system.

Diabetic peripheral neuropathy: evidence for apoptosis and associated mitochondrial dysfunction

We hypothesized that diabetic sensory neuropathy is associated with activation of apoptosis and concomitant mitochondrial dysfunction. Studies were performed in excised intact and acutely dissociated dorsal root ganglion (DRG) neurons from control and streptozotocin-induced diabetic rats with decreased peripheral nerve conduction velocities (NCV). Apoptosis was increased in acutely dissociated DRG neurons from 3- to 6-week-old diabetic rats. Basal mitochondrial membrane potential (deltapsi) was significantly more positive in DRG neurons from diabetic rats. Depolarization with glutamate resulted in significantly more positive deltapsi and delayed recovery of deltapsi in neurons from diabetic rats. Restoration of euglycemia for 2 weeks with insulin implants normalized NCV, deltapsi, and apoptosis. Intact and acutely dissociated neurons from diabetic rats demonstrated decreased Bcl-2 levels and translocation of cytochrome C from the mitochondria to the cytoplasm. Neither levels of Bax nor levels of Bcl-XL were altered in diabetic neuropathy. Apoptosis associated with mitochondrial dysfunction may contribute to the pathogenesis of diabetic sensory neuropathy.

Resistance-modifying agents. 9. Synthesis and biological properties of benzimidazole inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase

The nuclear enzyme poly(ADP-ribose) polymerase (PARP) facilitates the repair of DNA strand breaks and is implicated in the resistance of cancer cells to certain DNA-damaging agents. Inhibitors of PARP have clinical potential as resistance-modifying agents capable of potentiating radiotherapy and the cytotoxicity of some forms of cancer chemotherapy. The preclinical development of 2-aryl-1H-benzimidazole-4-carboxamides as resistance-modifying agents in cancer chemotherapy is described. 1H-Benzimidazole-4-carboxamides, particularly 2-aryl derivatives, are identified as a class of potent PARP inhibitors. Derivatives of 2-phenyl-1H-benzimidazole-4-carboxamide (23, K(i) = 15 nM), in which the phenyl ring contains substituents, have been synthesized. Many of these derivatives exhibit K(i) values for PARP inhibition < 10 nM, with 2-(4-hydroxymethylphenyl)-1H-benzimidazole-4-carboxamide (78, K(i) = 1.6 nM) being one of the most potent. Insight into structure-activity relationships (SAR) for 2-aryl-1H-benzimidazole-4-carboxamides has been enhanced by studying the complex formed between 2-(3-methoxyphenyl)-1H-benzimidazole-4-carboxamide (44, K(i) = 6 nM) and the catalytic domain of chicken PARP. Important hydrogen-bonding and hydrophobic interactions with the protein have been identified for this inhibitor. 2-(4-Hydroxyphenyl)-1H-benzimidazole-4-carboxamide (45, K(i) = 6 nM) potentiates the cytotoxicity of both temozolomide and topotecan against A2780 cells in vitro (by 2.8- and 2.9-fold, respectively).

The fragile X mental retardation syndrome protein interacts with novel homologs FXR1 and FXR2

Fragile X Mental Retardation Syndrome is the most common form of hereditary mental retardation, and is caused by defects in the FMR1 gene. FMR1 is an RNA-binding protein and the syndrome results from lack of expression of FMR1 or expression of a mutant protein that is impaired in RNA binding. The specific function of FMR1 is not known. As a step towards understanding the function of FMR1 we searched for proteins that interact with it in vivo. We have cloned and sequenced a protein that interacts tightly with FMR1 in vivo and in vitro. This novel protein, FXR2, is very similar to FMR1 (60% identity). FXR2 encodes a 74 kDa protein which, like FMR1, contains two KH domains, has the capacity to bind RNA and is localized to the cytoplasm. The FXR2 gene is located on human chromosome 17 at 17p13.1. In addition, FMR1 and FXR2 interact tightly with the recently described autosomal homolog FXR1. Each of these three proteins is capable of forming heteromers with the others, and each can also form homomers. FXR1 and FXR2 are thus likely to play important roles in the function of FMR1 and in the pathogenesis of the Fragile X Mental Retardation Syndrome.

Toward improved health: disaggregating Asian American and Native Hawaiian/Pacific Islander data

The 2000 census, with its option for respondents to mark 1 or more race categories, is the first US census to recognize the multiethnic nature of all US populations but especially Asian Americans and Native Hawaiians/Pacific Islanders. If Asian Americans and Native Hawaiians/Pacific Islanders have for the most part been "invisible" in policy debates regarding such matters as health care and immigration, it has been largely because of a paucity of data stemming from the lack of disaggregated data on this heterogeneous group of peoples. Studies at all levels should adhere to these disaggregated classifications. Also, in addition to oversampling procedures, there should be greater regional/local funding for studies in regions where Asian American and Native Hawaiian/Pacific Islander populations are substantial.

FXR1, an autosomal homolog of the fragile X mental retardation gene

Fragile X mental retardation syndrome, the most common cause of hereditary mental retardation, is directly associated with the FMR1 gene at Xq27.3. FMR1 encodes an RNA binding protein and the syndrome results from lack of expression of FMR1 or expression of a mutant protein that is impaired in RNA binding. We found a novel gene, FXR1, that is highly homologous to FMR1 and located on chromosome 12 at 12q13. FXR1 encodes a protein which, like FMR1, contains two KH domains and is highly conserved in vertebrates. The 3' untranslated regions (3'UTRs) of the human and Xenopus laevis FXR1 mRNAs are strikingly conserved (approximately 90% identity), suggesting conservation of an important function. The KH domains of FXR1 and FMR1 are almost identical, and the two proteins have similar RNA binding properties in vitro. However, FXR1 and FMR1 have very different carboxy-termini. FXR1 and FMR1 are expressed in many tissues, and both proteins, which are cytoplasmic, can be expressed in the same cells. Interestingly, cells from a fragile X patient that do not have any detectable FMR1 express normal levels of FXR1. These findings demonstrate that FMR1 and FXR1 are members of a gene family and suggest a biological role for FXR1 that is related to that of FMR1.

Hyperglycaemia-induced superoxide production decreases eNOS expression via AP-1 activation in aortic endothelial cells

AIMS/HYPOTHESIS

Hyperglycaemia is a primary cause of vascular complications in diabetes. A hallmark of these vascular complications is endothelial cell dysfunction, which is partly due to the reduced production of nitric oxide. The aim of this study was to investigate the regulation of endothelial nitric oxide synthase (eNOS) activity by acute and chronic elevated glucose.

METHODS

Human aortic endothelial cells were cultured in 5.5 mmol/l (NG) or 25 mmol/l glucose (HG) for 4 h, 1 day, 3 days or 7 days. Mouse aortic endothelial cells were freshly isolated from C57BL/6J control and diabetic db/db mice. The expression and activity of eNOS were measured using quantitative PCR and nitrite measurements respectively. The binding of activator protein-1 (AP-1) to DNA in nuclear extracts was determined using electrophoretic mobility-shift assays.

RESULTS

Acute exposure (4 h) of human aortic endothelial cells to 25 mmol/l glucose moderately increased eNOS activity and eNOS mRNA and protein expression. In contrast, chronic exposure to elevated glucose (25 mmol/l for 7 days) reduced total nitrite levels (46% reduction), levels of eNOS mRNA (46% reduction) and eNOS protein (65% reduction). In addition, AP-1 DNA binding activity was increased in chronic HG-cultured human aortic endothelial cells, and this effect was reduced by the specific inhibition of reactive oxygen species production through the mitochondrial electron transport chain. Mutation of AP-1 sites in the human eNOS promoter reversed the effects of HG. Compared with C57BL/6J control mice, eNOS mRNA levels in diabetic db/db mouse aortic endothelial cells were reduced by 60%. This decrease was reversed by the overexpression of manganese superoxide dismutase using an adenoviral construct.

CONCLUSIONS/INTERPRETATION

In diabetes, the expression and activity of eNOS is regulated through glucose-mediated mitochondrial production of reactive oxygen species and activation of the oxidative stress transcription factor AP-1.

The E6 oncoproteins of high-risk papillomaviruses bind to a novel putative GAP protein, E6TP1, and target it for degradation

The high-risk human papillomaviruses (HPVs) are associated with carcinomas of the cervix and other genital tumors. Previous studies have identified two viral oncoproteins, E6 and E7, which are expressed in the majority of HPV-associated carcinomas. The ability of high-risk HPV E6 protein to immortalize human mammary epithelial cells (MECs) has provided a single-gene model to study the mechanisms of E6-induced oncogenic transformation. In this system, the E6 protein targets the p53 tumor suppressor protein for degradation, and mutational analyses have shown that E6-induced degradation of p53 protein is required for MEC immortalization. However, the inability of most dominant-negative p53 mutants to induce efficient immortalization of MECs suggests the existence of additional targets of the HPV E6 oncoprotein. Using the yeast two-hybrid system, we have isolated a novel E6-binding protein. This polypeptide, designated E6TP1 (E6-targeted protein 1), exhibits high homology to GTPase-activating proteins for Rap, including SPA-1, tuberin, and Rap1GAP. The mRNA for E6TP1 is widely expressed in tissues and in vitro-cultured cell lines. The gene for E6TP1 localizes to chromosome 14q23.2-14q24.3 within a locus that has been shown to undergo loss of heterozygosity in malignant meningiomas. Importantly, E6TP1 is targeted for degradation by the high-risk but not the low-risk HPV E6 proteins both in vitro and in vivo. Furthermore, the immortalization-competent but not the immortalization-incompetent HPV16 E6 mutants target the E6TP1 protein for degradation. Our results identify a novel target for the E6 oncoprotein and provide a potential link between HPV E6 oncogenesis and alteration of a small G protein signaling pathway.

The relation of obesity throughout life to carotid intima-media thickness in adulthood: the Bogalusa Heart Study

OBJECTIVE

Although obese children are at increased risk for coronary heart disease in later life, it is not clear if this association results from the persistence of childhood obesity into adulthood. We examined the relation of adiposity at various ages to the carotid intima-media thickness (IMT) at age 35 y.

DESIGN

Prior to the determination of IMT by B-mode ultrasound, subjects (203 men, 310 women) had, on average, six measurements of body mass index (BMI) and triceps skinfold thickness (TSF) between the ages of 4 and 35 y. Mixed regression models for longitudinal data were used to assess the relation of these characteristics to adult IMT.

RESULTS

Overall, adult IMT was associated with levels of both BMI and TSF (P<0.001), with the magnitudes of the associations with childhood adiposity comparable to those with adult levels of BMI and TSF. Furthermore, adult obesity modified the association between childhood adiposity and IMT: high IMT levels were seen only among overweight (BMI > or =95th percentile) children who became obese (BMI > or =30 kg/m2) adults (P<0.01 for linear trend). In contrast, IMT levels were not elevated among (1) overweight children who were not obese in adulthood, or among (2) thinner children who became obese adults.

CONCLUSIONS

These results emphasize the adverse, cumulative effects of childhood-onset obesity that persists into adulthood. Since many overweight children become obese adults, the prevention of childhood obesity should be emphasized.

Features of the metabolic syndrome after childhood craniopharyngioma

Obesity and multiple pituitary hormone deficiency are common complications after surgery for childhood craniopharyngioma. We hypothesized that post craniopharyngioma surgery, children are at high risk for the metabolic syndrome, including insulin resistance due to excess weight gain and GH deficiency. This study characterized body composition (anthropometry and dual energy x-ray absorptiometry) and metabolic outcomes in 15 children (10 males and 5 females; age, 12.2 yr; range, 7.2-18.5 yr) after surgical removal of craniopharyngioma. In 9 subjects, outcomes were compared with those of healthy age-, sex-, body mass index-, and pubertal stage-matched controls. Insulin sensitivity was measured by 40-min iv glucose tolerance test. Seventy-three percent of subjects were overweight or obese. Sixty-six percent had normal growth velocity without GH treatment. Subjects had increased abdominal adiposity (P = 0.008) compared with controls. However, there was no significant difference in total body fat. Subjects had higher fasting triglycerides (P = 0.02) and lower high density lipoprotein cholesterol to total cholesterol ratio (P = 0.015). Insulin sensitivity was equally reduced for subjects and controls (P = 0.86). After craniopharyngioma removal, patients had more features of the metabolic syndrome compared with controls. This could be a result of hypothalamic damage causing obesity and GH deficiency. Further studies exploring predictors of the metabolic syndrome after craniopharyngioma surgery are required.

Diabetic gastrointestinal motility disorders and the role of enteric nervous system: current status and future directions

BACKGROUND

Gastrointestinal manifestations of diabetes are common and a source of significant discomfort and disability. Diabetes affects almost every part of gastrointestinal tract from the esophagus to the rectum and causes a variety of symptoms including heartburn, nausea, vomiting, abdominal pain, diarrhea and constipation. Understanding the underlying mechanisms of diabetic gastroenteropathy is important to guide development of therapies for this common problem. Over recent years, the data regarding the pathophysiology of diabetic gastroenteropathy is expanding. In addition to autonomic neuropathy causing gastrointestinal disturbances the role of enteric nervous system is becoming more evident.

PURPOSE

In this review, we summarize the reported alterations in enteric nervous system including enteric neurons, interstitial cells of Cajal and neurotransmission in diabetic animal models and patients. We also review the possible underlying mechanisms of these alterations, with focus on oxidative stress, growth factors and diabetes induced changes in gastrointestinal smooth muscle. Finally, we will discuss recent advances and potential areas for future research related to diabetes and the ENS such as gut microbiota, micro-RNAs and changes in the microvasculature and endothelial dysfunction.

Glycogen synthase kinase 3beta and Alzheimer's disease: pathophysiological and therapeutic significance

Alzheimer's disease (AD) is a neurodegenerative disorder associated with cognitive and behavioral dysfunction and is the leading cause of dementia in the elderly. Several studies have implicated molecular and cellular signaling cascades involving the serine-threonine kinase, glycogen synthase kinase beta(GSK-3beta) in the pathogenesis of AD. GSK-3beta may play an important role in the formation of neurofibrillary tangles and senile plaques, the two classical pathological hallmarks of AD. In this review, we discuss the interaction between GSK-3beta and several key molecules involved in AD, including the presenilins, amyloid precursor protein, tau, and beta-amyloid. We identify the signal transduction pathways involved in the pathogenesis of AD, including Wnt, Notch, and the PI3 kinase/Akt pathway. These may be potential therapeutic targets in AD.

Structural characteristics of CD40 ligand that determine biological function

CD40 ligand (CD40L) is a 33 kDa type II glycoprotein which is transiently expressed on the surface of T cells following activation. The demonstration that signals delivered by CD40L are essential for the process of affinity maturation and immunoglobulin isotype switching following antigenic challenge came from the study of X-linked hyper-IgM patients whose T cells cannot express functional CD40L. While some of the biological activities of CD40L, especially on B cells, can be mimicked by monoclonal antibodies (MAb) specific for CD40, it is becoming increasingly clear that CD40L also mediates various functional effects on other cell types. Not only are there distinctions between the activities of CD40L and CD40 MAb, but the manner in which CD40 is ligated appears to play an important part in the biological outcome of signaling through this receptor. In this review, we compare and contrast the activities which can currently be ascribed to CD40L and CD40 MAb and consider the role that ligand oligomerization plays in CD40-mediated signal transduction.

Modulation of the baboon (Papio anubis) uterine endometrium by chorionic gonadotrophin during the period of uterine receptivity

This study was undertaken to determine the modulation of uterine function by chorionic gonadotrophin (CG) in a nonhuman primate. Infusion of recombinant human CG (hCG) between days 6 and 10 post ovulation initiated the endoreplication of the uterine surface epithelium to form distinct epithelial plaques. These plaque cells stained intensely for cytokeratin and the proliferating cell nuclear antigen. The stromal fibroblasts below the epithelial plaques stained positively for alpha-smooth muscle actin (alphaSMA). Expression of alphaSMA is associated with the initiation of decidualization in the baboon endometrium. Synthesis of the glandular secretory protein glycodelin, as assessed by Western blot analysis, was markedly up-regulated by hCG, and this increase was confirmed by immunocytochemistry, Northern blot analysis, and reverse transcriptase-PCR. To determine whether hCG directly modulated these uterine responses, we treated ovariectomized baboons sequentially with estradiol and progesterone to mimic the hormonal profile of the normal menstrual cycle. Infusion of hCG into the oviduct of steroid-hormone-treated ovariectomized baboons induced the expression of alphaSMA in the stromal cells and glycodelin in the glandular epithelium. The epithelial plaque reaction, however, was not readily evident. These studies demonstrate a physiological effect of CG on the uterine endometrium in vivo and suggest that the primate blastocyst signal, like the blastocyst signals of other species, modulates the uterine environment prior to implantation.

Diabetes and the enteric nervous system

Diabetes is associated with several changes in gastrointestinal (GI) motility and associated symptoms such as nausea, bloating, abdominal pain, diarrhoea and constipation. The pathogenesis of altered GI functions in diabetes is multifactorial and the role of the enteric nervous system (ENS) in this respect has gained significant importance. In this review, we summarize the research carried out on diabetes-related changes in the ENS. Changes in the inhibitory and excitatory enteric neurons are described highlighting the role of loss of inhibitory neurons in early diabetic enteric neuropathy. The functional consequences of these neuronal changes result in altered gastric emptying, diarrhoea or constipation. Diabetes can also affect GI motility through changes in intestinal smooth muscle or alterations in extrinsic neuronal control. Hyperglycaemia and oxidative stress play an important role in the pathophysiology of these ENS changes. Antioxidants to prevent or treat diabetic GI motility problems have therapeutic potential. Recent research on the nerve-immune interactions demonstrates inflammation-associated neurodegeneration which can lead to motility related problems in diabetes.

Mitochondrial retrograde signaling induces epithelial-mesenchymal transition and generates breast cancer stem cells

Metastatic breast tumors undergo epithelial-to-mesenchymal transition (EMT), which renders them resistant to therapies targeted to the primary cancers. The mechanistic link between mtDNA (mitochondrial DNA) reduction, often seen in breast cancer patients, and EMT is unknown. We demonstrate that reducing mtDNA content in human mammary epithelial cells (hMECs) activates Calcineurin (Cn)-dependent mitochondrial retrograde signaling pathway, which induces EMT-like reprogramming to fibroblastic morphology, loss of cell polarity, contact inhibition and acquired migratory and invasive phenotype. Notably, mtDNA reduction generates breast cancer stem cells. In addition to retrograde signaling markers, there is an induction of mesenchymal genes but loss of epithelial markers in these cells. The changes are reversed by either restoring the mtDNA content or knockdown of CnAα mRNA, indicating the causal role of retrograde signaling in EMT. Our results point to a new therapeutic strategy for metastatic breast cancers targeted to the mitochondrial retrograde signaling pathway for abrogating EMT and attenuating cancer stem cells, which evade conventional therapies. We report a novel regulatory mechanism by which low mtDNA content generates EMT and cancer stem cells in hMECs.