Sub-clinical dose of bone morphogenetic protein-2 does not precipitate rampant, sustained inflammatory response in bone wound healing

Large bone injuries, defects, and chronic wounds present a major problem for medicine. Several therapeutic strategies are used clinically to precipitate bone including a combination therapy delivering osteoinductive bone morphogenetic protein 2 (rhBMP-2) via an osteoconductive scaffold (absorbable collagen sponge [ACS], i.e., INFUSE). Adverse side effects reportedly associated with rhBMP2 administration include rampant inflammation and clinical failures. Although acute inflammation is necessary for proper healing in bone, inflammatory cascade dysregulation can result in sustained tissue damage and poor healing. We hypothesized that a subclinical dose of rhBMP2 modeled in the murine calvarial defect would not precipitate alterations to inflammatory markers during acute phases of bone wound healing. We utilized the 5 mm critical size calvarial defect in C57BL6 wild-type mice which were subsequently treated with ACS and a subclinical dose of rhBMP2 shown to be optimal for healing. Three and 7-day postoperative time points were used to assess the role that rhBMP-2 plays in modulating inflammation vs. ACS alone by cytokine array and histological interrogation. Data revealed that rhBMP-2 delivery resulted in substantial modulation of several markers associated with inflammation, most of which decreased to levels similar to control by the 7-day time point. Additionally, while rhBMP-2 administration increased macrophage response, this peptide had a little noticeable effect on traditional markers of macrophage polarization (M1-iNOS, M2-Arg1). These results suggest that rhBMP-2 delivered at a lower dose does not precipitate rampant inflammation. Thus, an assessment of dosing for rhBMP-2 therapies may lead to better healing outcomes and less surgical failure.

Early Blood Profile of C57BL/6 Mice Exposed to Chronic Unpredictable Stress

Physiological responses to psychological stressors are protective in acute fight or flight situations; however, there is increasing evidence suggesting the detrimental impact of chronic psychological stress on disease. Chronic stress has been associated with inflammation, poor prognosis, increased morbidity, and poor outcome in many diseases including atherosclerosis, cancer, and pulmonary disease. Given the systemic impact of stress, and the role of the hematopoietic system as a rapid responder to homeostatic insults, we hypothesized that early blood profile changes and biochemical alterations could be detected in a model of chronic stress. To test this hypothesis, a variation of the chronic unpredictable stress (CUS) model was employed. Following 10 days of CUS, C57BL/6 mice exhibited a chronic-stress-associated corticosterone profile. Complete blood count (CBC) revealed mild normochromic, normocytic anemia, and reduced monocyte and lymphocyte count. Serum analysis demonstrated hypoferremia with unchanged total iron binding capacity and serum ferritin levels. These findings are consistent with clinical diagnostic parameters for anemia of chronic disease and indicate that CUS results in significant changes in blood and serum biochemical profile in C57BL/6 mice. These studies identify early changes in blood parameters in response to CUS and identify hematopoietic and biochemical alterations that are often associated with increased morbidity in patients experiencing chronic-stress-associated mental health disease.

Abstract 2234: Dietary-AGE ingestion during puberty modifies the breast microenvironment to alter mammary gland development: Linking diet, development and breast cancer risk

Evidence supports the notion that critical events during mammary development permanently alter developmentally regulated programs which influence the breast microenvironment to increase breast cancer risk. This is analogous to metabolic memory in diabetic patients where early metabolic events have been found to be remembered and affect disease severity later in life.

Advanced glycation end products (AGEs) are highly reactive metabolites that irreversibly accumulate in tissues as we age. AGE accumulation can contribute to pro-inflammatory and -oxidant phenotypes when signaling through the receptor for advanced glycation end products (RAGE). The pathogenic effects of AGE-RAGE signaling include tissue degeneration, protein dysfunction, aberrant cell signaling, and reduced genetic fidelity. AGEs form during normal metabolism but critically, lifestyle factors such as poor diet, a sedentary lifestyle and being obese also contribute to the AGE accumulation pool. The permanence of AGE adducts and their ability to mediate chronic and persistent inflammatory and oxidative stresses is particularly compatible to the concept of metabolic memory.

Our dietary studies in pubertal FVB/n mice fed a high AGE diet show a significant dysregulation of mammary gland development and hyperplastic lesion formation. We observe delayed mammary ductal extension, increased ductal branching and aberrant terminal end-bud (TEB) morphology. The basal myoepithelial cell layer surrounding mammary ducts and TEBs was irregular and epithelial cell proliferation was increased. Molecular characterization of these hyperplastic lesions were defined using DCIS progression markers by histopathological staining and qRT-PCR. Elevated AGE levels accompanied increased RAGE expression and increased macrophage and fibroblast infiltration around the TEBs. In attempt to reverse the effects caused by a high AGE diet, mice were fed a control diet after a pubertal high AGE diet. Hyperplastic lesions persisted despite diet intervention. Importantly, hyperplastic lesions were not observed in mice fed a control diet during puberty, then switched to a high AGE diet. These data indicate that exposure to AGE induced changes during puberty may leave a long-lasting imprint analogous to metabolic memory.

In conclusion, increased AGE consumption during pubertal growth results in significant disruption of normal mammary development and the appearance of hyperplastic lesions by adulthood. Consumption of a high AGE diet despite a control diet intervention, reveals hyperplastic lesions indicative of metabolic memory. We hypothesize that the high AGE diet may leave a metabolic imprint on the mammary gland microenvironment, increasing the risk of future breast cancer development.

Citation Format: Jaime F. Randise, Bradley A. Krisanits, Lourdes M. Nogueira, Kristi L. Helke, Taaliah Campbell, Victoria J. Findlay, David P. Turner. Dietary-AGE ingestion during puberty modifies the breast microenvironment to alter mammary gland development: Linking diet, development and breast cancer risk [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2234.

Tristetraprolin Is Required for Alveolar Bone Homeostasis

Tristetraprolin (TTP) is an RNA-binding protein that targets numerous immunomodulatory mRNA transcripts for degradation. Many TTP targets are key players in the pathogenesis of periodontal bone loss, including tumor necrosis factor-α. To better understand the extent that host immune factors play during periodontal bone loss, we assessed alveolar bone levels, inflammation and osteoclast activity in periodontal tissues, and immune response in draining cervical lymph nodes in TTP-deficient and wild-type (WT) mice in an aging study. WT and TTP-deficient (knockout [KO]) mice were used for all studies under specific pathogen-free conditions. Data were collected on mice aged 3, 6, and 9 mo. Microcomputed tomography (µCT) was performed on maxillae where 3-dimensional images were generated and bone loss was assessed. Decalcified sections of specimens were scored for inflammation and stained with tartrate-resistant acid phosphate (TRAP) to visualize osteoclasts. Immunophenotyping was performed on single-cell suspensions isolated from primary and peripheral lymphoid tissues using flow cytometry. Results presented indicate that TTP KO mice had significantly more alveolar bone loss over time compared with WT controls. Bone loss was associated with significant increases in inflammatory cell infiltration and an increased percentage of alveolar bone surfaces apposed with TRAP+ cells. Furthermore, it was found that the draining cervical lymph nodes were significantly enlarged in TTP-deficient animals and contained a distinct pathological immune profile compared with WT controls. Finally, the oral microbiome in the TTP KO mice was significantly different with age from WT cohoused mice. The severe bone loss, inflammation, and increased osteoclast activity observed in these mice support the concept that TTP plays a critical role in the maintenance of alveolar bone homeostasis in the presence of oral commensal flora. This study suggests that TTP is required to inhibit excessive inflammatory host responses that contribute to periodontal bone loss, even in the absence of specific periodontal pathogens.

Decreased glutathione levels cause overt motor neuron degeneration in hSOD1WT over-expressing mice

Mutations in Cu/Zn-superoxide dismutase (SOD1) cause familial forms of amyotrophic lateral sclerosis (ALS), a fatal disorder characterized by the progressive loss of motor neurons. Several lines of evidence have shown that SOD1 mutations cause ALS through a gain of a toxic function that remains to be fully characterized. A significant share of our understanding of the mechanisms underlying the neurodegenerative process in ALS comes from the study of rodents over-expressing ALS-linked mutant hSOD1. These mutant hSOD1 models develop an ALS-like phenotype. On the other hand, hemizygous mice over-expressing wild-type hSOD1 at moderate levels (hSOD1^WT, originally described as line N1029) do not develop paralysis or shortened life-span. To investigate if a decrease in antioxidant defenses could lead to the development of an ALS-like phenotype in hSOD1^WT mice, we used knockout mice for the glutamate-cysteine ligase modifier subunit [GCLM(-/-)]. GCLM(-/-) mice are viable and fertile but display a 70-80% reduction in total glutathione levels. GCLM(-/-)/hSOD1^WT mice developed overt motor symptoms (e.g. tremor, loss of extension reflex in hind-limbs, decreased grip strength and paralysis) characteristic of mice models over-expressing ALS-linked mutant hSOD1. In addition, GCLM(-/-)/hSOD1^WT animals displayed shortened life span. An accelerated decrease in the number of large neurons in the ventral horn of the spinal cord and degeneration of spinal root axons was observed in symptomatic GCLM(-/-)/hSOD1^WT mice when compared to age-matched GCLM(+/+)/hSOD1^WT mice. Our results show that under conditions of chronic decrease in glutathione, moderate over-expression of wild-type SOD1 leads to overt motor neuron degeneration, which is similar to that induced by ALS-linked mutant hSOD1 over-expression.

Vagus nerve stimulation improves locomotion and neuronal populations in a model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is a progressive, neurodegenerative disorder with no disease-modifying therapies, and symptomatic treatments are often limited by debilitating side effects. In PD, locus coeruleus noradrenergic (LC-NE) neurons degenerate prior to substantia nigra dopaminergic (SN-DA) neurons. Vagus nerve stimulation (VNS) activates LC neurons, and decreases pro-inflammatory markers, allowing improvement of LC targets, making it a potential PD therapeutic.

OBJECTIVE

To assess therapeutic potential of VNS in a PD model.

METHODS

To mimic the progression of PD degeneration, rats received a systemic injection of noradrenergic neurotoxin DSP-4, followed one week later by bilateral intrastriatal injection of dopaminergic neurotoxin 6-hydroxydopamine. At this time, a subset of rats also had vagus cuffs implanted. After eleven days, rats received a precise VNS regimen twice a day for ten days, and locomotion was measured during each afternoon session. Immediately following final stimulation, rats were euthanized, and left dorsal striatum, bilateral SN and LC were sectioned for immunohistochemical detection of monoaminergic neurons (tyrosine hydroxylase, TH), α-synuclein, astrocytes (GFAP) and microglia (Iba-1).

RESULTS

VNS significantly increased locomotion of lesioned rats. VNS also resulted in increased expression of TH in striatum, SN, and LC; decreased SN α-synuclein expression; and decreased expression of glial markers in the SN and LC of lesioned rats. Additionally, saline-treated rats after VNS, had higher LC TH and lower SN Iba-1.

CONCLUSIONS

Our findings of increased locomotion, beneficial effects on LC-NE and SN-DA neurons, decreased α-synuclein density in SN TH-positive neurons, and neuroinflammation suggest VNS has potential as a novel PD therapeutic.

P38 delta MAPK promotes breast cancer progression and lung metastasis by enhancing cell proliferation and cell detachment

The protein p38 mitogen-activated protein kinase delta isoform (p38δ) is a poorly studied member of the MAPK family. Data analysis from The Cancer Genome Atlas (TCGA) database revealed that p38δ is highly expressed in all types of human breast cancers. Using a human breast cancer tissue array, we confirmed elevation in cancer tissue. The breast cancer mouse model, MMTV-PyMT (PyMT), developed breast tumors with lung metastasis; however, mice deleted in p38δ (PyMT/p38δ^−/−) exhibited delayed primary tumor formation and highly reduced lung metastatic burden. At the cellular level, we demonstrate that targeting of p38δ in breast cancer cells, MCF-7 and MDA-MB-231 resulted in a reduced rate of cell proliferation. Additionally, cells lacking p38δ also displayed an increased cell-matrix adhesion and reduced cell detachment. This effect on cell adhesion was molecularly supported by the regulation of the focal adhesion kinase (FAK) by p38δ in the human breast cell lines. These studies define a previously unappreciated role for p38δ in breast cancer development and evolution by regulating tumor growth and altering metastatic properties.

The distinct metabolic phenotype of lung squamous cell carcinoma defines selective vulnerability to glycolytic inhibition

Adenocarcinoma (ADC) and squamous cell carcinoma (SqCC) are the two predominant subtypes of non-small cell lung cancer (NSCLC) and are distinct in their histological, molecular and clinical presentation. However, metabolic signatures specific to individual NSCLC subtypes remain unknown. Here, we perform an integrative analysis of human NSCLC tumour samples, patient-derived xenografts, murine model of NSCLC, NSCLC cell lines and The Cancer Genome Atlas (TCGA) and reveal a markedly elevated expression of the GLUT1 glucose transporter in lung SqCC, which augments glucose uptake and glycolytic flux. We show that a critical reliance on glycolysis renders lung SqCC vulnerable to glycolytic inhibition, while lung ADC exhibits significant glucose independence. Clinically, elevated GLUT1-mediated glycolysis in lung SqCC strongly correlates with high ¹⁸F-FDG uptake and poor prognosis. This previously undescribed metabolic heterogeneity of NSCLC subtypes implicates significant potential for the development of diagnostic, prognostic and targeted therapeutic strategies for lung SqCC, a cancer for which existing therapeutic options are clinically insufficient.

Adenocarcinoma and squamous cell carcinoma are distinct subtypes of non-small cell lung cancer. Here, the authors show that increased glycolytic flux, via increased glucose transporter Glut1 expression, is a core metabolic feature of squamous cell carcinoma that renders it sensitive to glycolysis inhibition.

Deficient Adipogenesis of Scleroderma Patient and Healthy African American Monocytes

Monocytes from systemic sclerosis (SSc, scleroderma) patients and healthy African Americans (AA) are deficient in the regulatory protein caveolin-1 leading to enhanced migration toward chemokines and fibrogenic differentiation. While dermal fibrosis is the hallmark of SSc, loss of subcutaneous adipose tissue is a lesser-known feature. To better understand the etiology of SSc and the predisposition of AA to SSc, we studied the adipogenic potential of SSc and healthy AA monocytes. The ability of SSc and healthy AA monocytes to differentiate into adipocyte-like cells (ALC) is inhibited compared to healthy Caucasian (C) monocytes. We validated that monocyte-derived ALCs are distinct from macrophages by flow cytometry and immunocytochemistry. Like their enhanced fibrogenic differentiation, their inhibited adipogenic differentiation is reversed by the caveolin-1 scaffolding domain peptide (CSD, a surrogate for caveolin-1). The altered differentiation of SSc and healthy AA monocytes is additionally regulated by peroxisome proliferator-activated receptor γ (PPARγ) which is also present at reduced levels in these cells. In vivo studies further support the importance of caveolin-1 and PPARγ in fibrogenesis and adipogenesis. In SSc patients, healthy AA, and mice treated systemically with bleomycin, adipocytes lose caveolin-1 and PPARγ and the subcutaneous adipose layer is diminished. CSD treatment of these mice leads to a reappearance of the caveolin-1+/PPARγ+/FABP4+ subcutaneous adipose layer. Moreover, many of these adipocytes are CD45+, suggesting they are monocyte derived. Tracing experiments with injected EGFP+ monocytes confirm that monocytes contribute to the repair of the adipose layer when it is damaged by bleomycin treatment. Our observations strongly suggest that caveolin-1 and PPARγ work together to maintain a balance between the fibrogenic and adipogenic differentiation of monocytes, that this balance is altered in SSc and in healthy AA, and that monocytes make a major contribution to the repair of the adipose layer.

Effects of antimicrobial use in agricultural animals on drug-resistant foodborne salmonellosis in humans: A systematic literature review

Controversy continues concerning antimicrobial use in food animals and its relationship to drug-resistant infections in humans. We systematically reviewed published literature for evidence of a relationship between antimicrobial use in agricultural animals and drug-resistant meat or dairy-borne non-typhoidal salmonellosis in humans. Based on publications from the United States (U.S.), Canada, and Denmark from January 2010 to July 2014, 858 articles received title and abstract review, 104 met study criteria for full article review with 68 retained for which data are presented. Antibiotic exposure in both cattle and humans found an increased likelihood of Salmonella colonization, whereas in chickens, animals not exposed to antibiotics (organic) were more likely to be Salmonella positive and those that had antibiotic exposure were more likely to harbor antimicrobial resistant Salmonella organisms. In swine literature, only tylosin exposure was examined and no correlation was found among exposure, Salmonella colonization, or antimicrobial resistance. No studies that identified farm antimicrobial use also traced antimicrobial-resistant Salmonella from farm to fork.

Effect of Antimicrobial Use in Agricultural Animals on Drug-resistant Foodborne Campylobacteriosis in Humans: A Systematic Literature Review

Controversy continues concerning antimicrobial use in food animals and its relationship to drug-resistant infections in humans. We systematically reviewed published literature for evidence of a relationship between antimicrobial use in agricultural animals and drug-resistant foodborne campylobacteriosis in humans. Based on publications from the United States (U.S.), Canada and Denmark from 2010 to July 2014, 195 articles were retained for abstract review, 50 met study criteria for full article review with 36 retained for which data are presented. Two publications reported increase in macrolide resistance of Campylobacter coli isolated from feces of swine receiving macrolides in feed, and one of these described similar findings for tetracyclines and fluoroquinolones. A study in growing turkeys demonstrated increased macrolide resistance associated with therapeutic dosing with Tylan® in drinking water. One publication linked tetracycline-resistant C. jejuni clone SA in raw cow's milk to a foodborne outbreak in humans. No studies that identified farm antimicrobial use also traced antimicrobial-resistant Campylobacter from farm to fork. Recent literature confirms that on farm antibiotic selection pressure can increase colonization of animals with drug-resistant Campylobacter spp. but is inadequately detailed to establish a causal relationship between use of antimicrobials in agricultural animals and prevalence of drug-resistant foodborne campylobacteriosis in humans.

Development of a radiofrequency ablation platform in a clinically relevant murine model of hepatocellular cancer

RFA is used in treatment of patients with hepatocellular cancer (HCC); however, tumor location and size often limit therapeutic efficacy. The absence of a realistic animal model and a radiofrequency ablation (RFA) suitable for small animals presents significant obstacles in developing new strategies. To establish a realistic RFA platform that allows the development of effective RFA-integrated treatment in an orthotopic murine model of HCC, a human cardiac radiofrequency generator was modified for murine use. Parameters were optimized and RFA was then performed in normal murine livers and HCCs. The effects of RFA were monitored by measuring the ablation zone and transaminases. The survival of tumor-bearing mice with and without RFA was monitored, ablated normal liver and HCCs were evaluated macroscopically and histologically. We demonstrated that tissue-mimicking media was able to optimize RFA parameters. Utilizing this information we performed RFA in normal and HCC-bearing mice. RFA was applied to hepatic parenchyma and completely destroyed small tumors and part of large tumors. Localized healing of the ablation and normalization of transaminases occurred within 7 days post RFA. RFA treatment extended the survival of small tumor-bearing mice. They survived at least 5 months longer than the controls; however, mice with larger tumors only had a slight therapeutic effect after RFA. Collectively, we performed RFA in murine HCCs and observed a significant therapeutic effect in small tumor-bearing mice. The quick recovery of tumor-bearing mice receiving RFA mimics observations in human subjects. This platform provides us a unique opportunity to study RFA in HCC treatment.

Altered glutamate release in the dorsal striatum of the MitoPark mouse model of Parkinson's disease

Mitochondrial dysfunction has been implicated in the degeneration of dopamine (DA) neurons in Parkinson's disease (PD). In addition, animal models of PD utilizing neurotoxins, such as 6-hydroxydopamine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, have shown that these toxins disrupt mitochondrial respiration by targeting complex I of the electron transport chain, thereby impairing DA neurons in these models. A MitoPark mouse model was created to mimic the mitochondrial dysfunction observed in the DA system of PD patients. These mice display the same phenotypic characteristics as PD, including accelerated decline in motor function and DAergic systems with age. Previously, these mice have responded to L-Dopa treatment and develop L-Dopa induced dyskinesia (LID) as they age. A potential mechanism involved in the formation of LID is greater glutamate release into the dorsal striatum as a result of altered basal ganglia neurocircuitry due to reduced nigrostriatal DA neurotransmission. Therefore, the focus of this study was to assess various indicators of glutamate neurotransmission in the dorsal striatum of MitoPark mice at an age in which nigrostriatal DA has degenerated. At 28 weeks of age, MitoPark mice had, upon KCl stimulation, greater glutamate release in the dorsal striatum compared to control mice. In addition, uptake kinetics were slower in MitoPark mice. These findings were coupled with reduced expression of the glutamate re-uptake transporter, GLT-1, thus providing an environment suitable for glutamate excitotoxic events, leading to altered physiological function in these mice.

Pigs in Toxicology

Both a rodent and a nonrodent species are required for evaluation in nonclinical safety studies conducted to support human clinical trials. Historically, dogs and nonhuman primates have been the nonrodent species of choice. Swine, especially the miniature swine or minipigs, are increasingly being used in preclinical safety as an alternate nonrodent species. The pig is an appropriate option for these toxicology studies based on metabolic pathways utilized in xenobiotic biotransformation. Both similarities and differences exist in phase I and phase II biotransformation pathways between humans and pigs. There are numerous breeds of pigs, yet only a few of these breeds are characterized with regard to both xenobiotic-metabolizing enzymes and background pathology findings. Some specific differences in these enzymes based on breed and sex are known. Although swine have been used extensively in biomedical research, there is also a paucity of information in the current literature detailing the incidence of background lesions and differences between commonly used breeds. Here, the xenobiotic-metabolizing enzymes are compared between humans and pigs, and minipig background pathology changes are reviewed with emphasis on breed differences.

Background Pathological Changes in Minipigs

Swine, especially the miniature swine or minipigs, are increasingly being used in preclinical safety assessment of small molecules, biopharmaceutical agents, and medical devices as an alternate nonrodent species. Although swine have been used extensively in biomedical research, there is a paucity of information in the current literature detailing the incidence of background lesions and differences in incidence between commonly used breeds. This article is a collaborative effort between multiple organizations to define and document lesions found in the common breeds of minipigs used for toxicological risk assessment in North America (NA) and the European Union (EU). We retrospectively assessed 10 years of historical control data from several institutions located in NA and EU, covering the period of 2004–2015. Here we report the background lesions with consideration of breed and geographical location. To our knowledge, this is the first report documenting spontaneous background lesions in commonly used breeds of swine in both NA and EU. This report serves as a resource to pathologists and will aid in interpretation of findings and differentiation of background from test article–related changes.

Biology and Diseases of Swine

Swine are used in biomedical research as models for biomedical research and for teaching. This chapter covers normative biology and behavior along with common and emerging swine diseases. Xenotransplantation is discussed along with similarities and differences of swine immunology.

Effects of aging on glutamate neurotransmission in the substantia nigra of Gdnf heterozygous mice

Glial cell line-derived neurotrophic factor (GDNF) helps protect dopaminergic neurons in the nigrostriatal tract. Although the cause of nigrostriatal degeneration is unknown, one theory is that excess glutamate from the subthalamic nucleus results in excitotoxic events in the substantia nigra (SN). Because dopaminergic degeneration is accompanied by a reduction in GDNF, we examined glutamate neurotransmission in the SN using a Gdnf heterozygous mouse model (Gdnf(+/-)) at 8 and 12 months of age. At 8 months, Gdnf(+/-) mice have greater glutamate release and higher basal glutamate levels, which precede the SN dopaminergic degeneration observed at 12 months of age. However, at 12 months, Gdnf(+/-) mice have lower basal levels of glutamate and less glutamate release than wild-type mice. Also at 8 months, Gdnf(+/-) mice have lower levels of glutamate transporter-1 and greater glial fibrillary acidic protein levels in the SN compared with wild-type mice, differences that increase with age. These data suggest that reduced levels of GDNF induce excess glutamate release and dysregulation of glutamate transporter-1, causing excitotoxicity in the SN that precedes dopaminergic degeneration.

Rho GTPases RhoA and Rac1 mediate effects of dietary folate on metastatic potential of A549 cancer cells through the control of cofilin phosphorylation

Folate, an important nutrient in the human diet, has been implicated in cancer, but its role in metastasis is not established. We have shown previously that the withdrawal of medium folate leads to the inhibition of migration and invasion of A549 lung carcinoma cells. Here we have demonstrated that medium folate regulates the function of Rho GTPases by enabling their carboxyl methylation and translocation to plasma membrane. Conversely, the lack of folate leads to the retention of these proteins in endoplasmic reticulum. Folate also promoted the switch from inactive (GDP-bound) to active (GTP-bound) GTPases, resulting in the activation of downstream kinases p21-activated kinase and LIM kinase and phosphorylation of the actin-depolymerizing factor cofilin. We have further demonstrated that in A549 cells two GTPases, RhoA and Rac1, but not Cdc42, are immediate sensors of folate status: the siRNA silencing of RhoA or Rac1 blocked effects of folate on cofilin phosphorylation and cellular migration and invasion. The finding that folate modulates metastatic potential of cancer cells was confirmed in an animal model of lung cancer using tail vein injection of A549 cells in SCID mice. A folate-rich diet enhanced lung colonization and distant metastasis to lymph nodes and decreased overall survival (35 versus 63 days for mice on a folate-restricted diet). High folate also promoted epithelial-mesenchymal transition in cancer cells and experimental mouse tumors. Our study provides experimental evidence for a mechanism of metastasis promotion by dietary folate and highlights the interaction between nutrients and metastasis-related signaling.

14-3-3 Protein in CSF reflects SIV-mediated pre-synaptic damage

HIV-associated neurocognitive disorders (HAND) remain prevalent despite effective combined anti-retroviral therapy (cART). Cognitive function has been shown to inversely correlate with decreased synaptic and dendritic density. In this study, macaques inoculated with SIV were examined over a 3-month course of infection to characterize the appearance of the neuronal damage marker 14-3-3 protein in CSF and to determine whether CSF 14-3-3 levels directly reflected synaptic alterations. SIV-infected macaques with 14-3-3 in CSF had significantly lower levels of the presynaptic protein synaptophysin in cortical grey matter. Synaptophysin levels were inversely correlated with amount of SIV RNA in the CNS. In contrast, levels of 14-3-3 in CSF did not correspond with either alterations in levels of the postsynaptic protein PSD-95 or viral replication in the brain. These findings suggest that the appearance of 14-3-3 in CSF during asymptomatic infection reflects pre-synaptic damage in SIV-infected macaques and thus may serve as a marker of the early synaptic alterations that underlie HIV-induced neurocognitive impairment.

Essential role of the molecular chaperone gp96 in regulating melanogenesis

Through a process known as melanogenesis, melanocyte produces melanin in specialized organelles termed melanosomes, which regulates pigmentation of the skin, eyes, and hair. Gp96 is a constitutively expressed heat shock protein in the endoplasmic reticulum whose expression is further upregulated upon ultraviolet irradiation. However, the roles and mechanisms of this chaperone in pigmentation biology are unknown. In this study, we found that knockdown of gp96 by RNA interference significantly perturbed melanin synthesis and blocked late melanosome maturation. Gp96 knockdown did not impair the expression of tyrosinase, an essential enzyme in melanin synthesis, but compromised its catalytic activity and melanosome translocation. Further, mice with melanocyte-specific deletion of gp96 displayed decreased pigmentation. A mechanistic study revealed that the defect in melanogenesis can be rescued by activation of the canonical Wnt pathway, consistent with the critical roles of gp96 in chaperoning Wnt-coreceptor LRP6. Thus, this work uncovered the essential role of gp96 in regulating melanogenesis.

Animal models of toxicology testing: the role of pigs

INTRODUCTION

In regulatory toxicological testing, both a rodent and non-rodent species are required. Historically, dogs and non-human primates (NHP) have been the species of choice of the non-rodent portion of testing. The pig is an appropriate option for these tests based on metabolic pathways utilized in xenobiotic biotransformation.

AREAS COVERED

This review focuses on the Phase I and Phase II biotransformation pathways in humans and pigs and highlights the similarities and differences of these models. This is a growing field and references are sparse. Numerous breeds of pigs are discussed along with specific breed differences in these enzymes that are known. While much available data are presented, it is grossly incomplete and sometimes contradictory based on methods used.

EXPERT OPINION

There is no ideal species to use in toxicology. The use of dogs and NHP in xenobiotic testing continues to be the norm. Pigs present a viable and perhaps more reliable model of non-rodent testing.

Defining a role for sphingosine kinase 1 in p53-dependent tumors

p53 is a crucial tumor suppressor that is mutated or deleted in a majority of cancers. Exactly how p53 prevents tumor progression has proved elusive for many years; however, this information is crucial to define targets for chemotherapeutic development that can effectively restore p53 function. Bioactive sphingolipids have recently emerged as important regulators of proliferative, apoptotic and senescent cellular processes. In this study, we demonstrate that the enzyme sphingosine kinase 1 (SK1), a critical enzyme in the regulation of the key bioactive sphingolipids ceramide, sphingosine and sphingosine-1-phosphate (S1P), serves as a key downstream target for p53 action. Our results show that SK1 is proteolysed in response to genotoxic stress in a p53-dependent manner. p53 null mice display elevation of SK1 levels and a tumor-promoting dysregulation of bioactive sphingolipids in which the anti-growth sphingolipid ceramide is decreased and the pro-growth sphingolipid S1P is increased. Importantly, deletion of SK1 in p53 null mice completely abrogated thymic lymphomas in these mice and prolonged their life span by ~30%. Deletion of SK1 also significantly attenuated the formation of other cancers in p53 heterozygote mice. The mechanism of p53 tumor suppression by loss of SK1 is mediated by elevations of sphingosine and ceramide, which in turn were accompanied by increased expression of cell cycle inhibitors and tumor cell senescence. Thus, targeting SK1 may restore sphingolipid homeostasis in p53-dependent tumors and provide insights into novel therapeutic approaches to cancer.

ABCA2 transporter deficiency reduces incidence of TRAMP prostate tumor metastasis and cellular chemotactic migration

In order to study the effects of ATP-binding cassette transporter 2 (ABCA2) deficiency on the progression of prostate cancer, congenic Abca2 knockout (KO) mice were crossed to the transgenic adenocarcinoma of the mouse prostate (TRAMP) model. ABCA2 expression was elevated in wild-type/TRAMP (WT/Tg) dorsal prostate, a region comprising the most aggressive tumors in this model, compared to non-transgenic WT mice. Primary prostate tumor progression was similar in KO/Tg and WT/Tg mice with respect to pathological score, prostate tumor growth, as calculated using MRI volumetry, and proliferative index, as determined by PCNA immunostaining. Vimentin, a marker of the epithelial-mesenchymal transition, was expressed at similar levels in prostate, but elevated in histologically normal seminal vesicles (SV) in KO/Tg mice (P < 0.02), concomitant with an increased SV volume (P < 0.01). These changes in the SV did not exacerbate the metastatic phenotype of this disease model; rather, KO/Tg mice aged 20-25 weeks had no detectable metastases while 38% of WT/Tg developed metastases to lung and/or lymph nodes. The absence of a metastatic phenotype in KO/Tg mice was reprised in stable ABCA2 knockdown (KD) cells where chemotactic, but not random, migration was impaired (P = 0.0004). Expression levels of sphingolipid biosynthetic enzymes were examined due to the established link of the transporter with sphingolipid homeostasis. Galactosylceramide synthase (GalCerS) mRNA levels were over 8-fold higher in KD cells (P = 0.001), while lactosylceramide synthase (LacCerS) and CTP:choline cytidylyltransferase (CCT) were significantly reduced (P < 0.0001 and 0.03, respectively). Overall, we demonstrate that ABCA2-deficiency inhibits prostate tumor metastasis in vivo and decreases chemotactic potential of cells, conceivably due to altered sphingolipid metabolism.

Effects of brain-derived neurotrophic factor on dopaminergic function and motor behavior during aging

Brain-derived neurotrophic factor (BDNF) is critical in synaptic plasticity and in the survival and function of midbrain dopamine neurons. In this study, we assessed the effects of a partial genetic deletion of BDNF on motor function and dopamine (DA) neurotransmitter measures by comparing Bdnf(+/-) with wildtype mice (WT) at different ages. Bdnf(+/-) and WT mice had similar body weights until 12 months of age; however, at 21 months, Bdnf(+/-) mice were significantly heavier than WT mice. Horizontal and vertical motor activity was reduced for Bdnf(+/-) compared to WT mice, but was not influenced by age. Performance on an accelerating rotarod declined with age for both genotypes and was exacerbated for Bdnf(+/-) mice. Body weight did not correlate with any of the three behavioral measures studied. Dopamine neurotransmitter markers indicated no genotypic difference in striatal tyrosine hydroxylase, DA transporter (DAT) or vesicular monoamine transporter 2 (VMAT2) immunoreactivity at any age. However, DA transport via DAT (starting at 12 months) and VMAT2 (starting at 3 months) as well as KCl-stimulated DA release were reduced in Bdnf(+/-) mice and declined with age suggesting an increasingly important role for BDNF in the release and uptake of DA with the aging process. These findings suggest that a BDNF expression deficit becomes more critical to dopaminergic dynamics and related behavioral activities with increasing age.