Liposomal Irinotecan Shows a Larger Therapeutic Index than Non-liposomal Irinotecan in Patient-Derived Xenograft Models of Pancreatic Cancer

INTRODUCTION

Liposomal irinotecan promotes controlled sustained release of irinotecan (CPT-11), therefore, we hypothesize that the therapeutic index (quantitative measurement of the relative efficacy/safety ratio of a drug) will be higher for liposomal than non-liposomal irinotecan.

METHODS

We compared the therapeutic indexes of liposomal and non-liposomal irinotecan in mice bearing subcutaneous patient-derived xenograft (PDX) pancreatic tumors under dosing regimens approximating the clinical setting. Following preliminary drug sensitivity/antitumor activity analyses on three PDX tumor models, one model was selected for analyses of efficacy, biomarker, toxicology, pharmacokinetics in mice receiving liposomal irinotecan (2.5, 10, 50 mg/kg/week) or non-liposomal irinotecan (10, 25, 50 mg/kg/week). The maximum tolerated dose (MTD) for each treatment was 50 mg/kg/week.

RESULTS

Using the selected IM-PAN-001 model at the MTD (both treatments, 50 mg/kg/week), antitumor activity, phospho-histone gamma-H2AX protein staining in cancer cell nuclei, histological tumor regression, and plasma levels of CPT-11 and its active metabolite SN-38 after 24 h were greater with liposomal than non-liposomal irinotecan, but tumor SN-38 levels were similar. At the lowest doses assessed, antitumor activity, histological tumor regression, and jejunum and bone marrow toxicity were similar. Based on these findings, liposomal and non-liposomal irinotecan had therapeutic indexes of 20 and 5, respectively.

CONCLUSION

This non-clinical study showed a fourfold broader therapeutic index with liposomal than non-liposomal irinotecan in mice bearing IM-PAN-001 PDX pancreatic tumors, even at optimal dosing for the two drugs. These findings support the clinical benefit observed with liposomal irinotecan in patients with pancreatic cancer.

Evaluation of Recombinant Botulinum Neurotoxin Type A1 Efficacy in Peripheral Inflammatory Pain in Mice

Well-established efficacy of botulinum neurotoxin type A (BoNT/A) in aesthetic dermatology and neuromuscular hyperactivity disorders relies on canonical interruption of acetylcholine neurotransmission at the neuromuscular junction at the site of the injection. The mechanisms and the site of activity of BoNT/A in pain, on the other hand, remain elusive. Here, we explored analgesic activity of recombinant BoNT/A1 (rBoNT/A1; IPN10260) in a mouse model of inflammatory pain to investigate the potential role of peripheral sensory afferents in this activity. After confirming analgesic efficacy of rBoNT/A1 on CFA-induced mechanical hypersensitivity in C57Bl6J mice, we used GCaMP6s to perform in vivo calcium imaging in the ipsilateral dorsal root ganglion (DRG) neurons in rBoNT/A1 vs. vehicle-treated mice at baseline and following administration of a range of mechanical and thermal stimuli. Additionally, immunohisochemical studies were performed to detect cleaved SNAP25 in the skin, DRGs and the spinal cord. Injection of CFA resulted in reduced mechanical sensitivity threshold and increased calcium fluctuations in the DRG neurons. While rBoNT/A1 reduced mechanical hypersensitivity, calcium fluctuations in the DRG of rBoNT/A1- and vehicle-treated animals were similar. Cleaved SNAP25 was largely absent in the skin and the DRG but present in the lumbar spinal cord of rBoNT/A1-treated animals. Taken together, rBoNT/A1 ameliorates mechanical hypersensitivity related to inflammation, while the signal transmission from the peripheral sensory afferents to the DRG remained unchanged. This strengthens the possibility that spinal, rather than peripheral, mechanisms play a role in the mediation of analgesic efficacy of BoNT/A in inflammatory pain.

Characterization of an interdigitating dendritic cell hyperplasia case in a lymph node of a control C57BL/6 mouse

Interdigitating dendritic cell (IDC) hyperplasia is considered a benign spontaneous condition occasionally observed in the lymph nodes of mice. It has been rarely reported and, to the best of our knowledge, it has never been characterized using immunohistochemistry. The present work describes a spontaneous IDC hyperplasia case in a lymph node of a 16-week-old control female C57BL/6 mouse. Microscopically, the lymph node architecture was completely effaced by the proliferation of eosinophilic spindle cells with an abundant pale cytoplasm forming trabecule admixed lymphocyte infiltrates. The spindle cell population was positive for F4/80, partially positive for S100 calcium-binding protein A4 (S100A4), slightly positive for E-cadherin, and negative for α-Smooth muscle actin (SMA) and cytokeratin. Lymphocytes were positive for CD3, CD4, CD20 and negative for CD8. Spindle cells were considered to be originated from the myeloid lineage, based on the immunohistochemistry (IHC) results, but their precise origin remains unclear (IDC or macrophages); even if macrophage origin is most likely based on F4/80 positivity, this remains to be further clarified using other markers.

A rare case of malignant vagus nerve sheath tumor presenting with multiple cranial nerve dysfunction in a dog

A 5-year-old intact male Gascon Saintongeois dog was presented with a 6-month history of coughing, laryngeal paralysis, a deglutition disorder of gradual onset, and left-sided Horner's syndrome. The dog was admitted as an emergency for acute central vestibular signs. Magnetic resonance images identified a left extra-axial brainstem lesion extending caudally from the medulla to the vagosympathetic trunk. Histological and immunohistological examination revealed a high grade epithelioid malignant peripheral nerve sheath tumor (MPNST). This case report is the first description of a MPNST of the vagus nerve compressing the brainstem and causing multiple cranial nerve dysfunction in a dog. Key clinical message: Nerve sheath tumors have been reported in many locations arising from spinal nerve roots and cranial nerves. Although the trigeminal nerve is the most commonly affected nerve, other cranial nerves such as the vagus can be affected.

Immunohistochemical Characterization of Procaspase-3 Overexpression as a Druggable Target With PAC-1, a Procaspase-3 Activator, in Canine and Human Brain Cancers

Gliomas and meningiomas are the most common brain neoplasms affecting both humans and canines, and identifying druggable targets conserved across multiple brain cancer histologies and comparative species could broadly improve treatment outcomes. While satisfactory cure rates for low grade, non-invasive brain cancers are achievable with conventional therapies including surgery and radiation, the management of non-resectable or recurrent brain tumors remains problematic and necessitates the discovery of novel therapies that could be accelerated through a comparative approach, such as the inclusion of pet dogs with naturally-occurring brain cancers. Evidence supports procaspase-3 as a druggable brain cancer target with PAC-1, a pro-apoptotic, small molecule activator of procaspase-3 that crosses the blood-brain barrier. Procaspase-3 is frequently overexpressed in malignantly transformed tissues and provides a preferential target for inducing cancer cell apoptosis. While preliminary evidence supports procaspase-3 as a viable target in preclinical models, with PAC-1 demonstrating activity in rodent models and dogs with spontaneous brain tumors, the broader applicability of procaspase-3 as a target in human brain cancers, as well as the comparability of procaspase-3 expressions between differing species, requires further investigation. As such, a large-scale validation of procaspase-3 as a druggable target was undertaken across 651 human and canine brain tumors. Relative to normal brain tissues, procaspase-3 was overexpressed in histologically diverse cancerous brain tissues, supporting procaspase-3 as a broad and conserved therapeutic target. Additionally, procaspase-3 expressing glioma and meningioma cell lines were sensitive to the apoptotic effects of PAC-1 at biologically relevant exposures achievable in cancer patients. Importantly, the clinical relevance of procaspase-3 as a potential prognostic variable was demonstrated in human astrocytomas of variable histologic grades and associated clinical outcomes, whereby tumoral procaspase-3 expression was negatively correlated with survival; findings which suggest that PAC-1 might provide the greatest benefit for patients with the most guarded prognoses.

In utero growth restriction and catch-up adipogenesis after developmental di (2-ethylhexyl) phthalate exposure cause glucose intolerance in adult male rats following a high-fat dietary challenge

Phthalates impact adipocyte morphology in vitro, but the sex-specific adipogenic signature immediately after perinatal di(2-ethylhexyl) phthalate (DEHP) exposure and adulthood physiology following a high-fat (HF) dietary challenge are unknown. In the current study, pregnant and lactating dams received DEHP (300 mg/kg body weight) or oil. At weaning [postnatal day (PND) 21], adipose tissue was sampled for real-time polymerase chain reaction. The remaining offspring consumed a control or HF diet. DEHP decreased % fat in males at birth from 13.9%±0.2 to 11.8%±0.6 (mean±S.E.M.), representing a 15.1% decrease in fat by DEHP, and these males caught up in adiposity to controls by PND21. Adult DEHP-exposed males had a 27.5% increase in fat (12.5%±0.9% in controls vs. 15.9%±1.5% in the DEHP group); adipocyte perimeter was increased as well, with fewer small/medium-sized adipocytes, and decreased cell number compared to oil controls. HF diet intake in DEHP-exposed males further increased male energy intake and body weight and led to glucose intolerance. In PND21 males, DEHP increased the expression of adipogenic markers (Pparg1, Cebpa, Adipoq, Ppard, Fabp4, Fasn, Igf1), decreased Lep, and decreased markers of mesenchymal stem cell commitment to the adipogenic lineage (Bmp2, Bmp4, Stat1, Stat5a) compared to oil controls. These data suggest that DEHP may decrease the adipocyte pool at birth, which initially increases adaptive adipocyte maturation and lipid accumulation, but leads to adipose tissue dysfunction in adulthood, decreasing the capacity to adapt to a HF diet, and leading to systemic glucose intolerance.

High-fat diet caused widespread epigenomic differences on hepatic methylome in rat

A high-fat (HF) diet is associated with progression of liver diseases. To illustrate genome-wide landscape of DNA methylation in liver of rats fed either a control or HF diet, two enrichment-based methods, namely methyl-DNA immunoprecipitation assay with high-throughput sequencing (MeDIP-seq) and methylation-sensitive restriction enzyme sequencing (MRE-seq), were performed in our study. Rats fed with the HF diet exhibited an increased body weight and liver fat accumulation compared with that of the control group when they were 12 wk of age. Genome-wide analysis of differentially methylated regions (DMRs) showed that 12,494 DMRs induced by HF diet were hypomethylated and 6,404 were hypermethylated. DMRs with gene annotations [differentially methylated genes (DMGs)] were further analyzed to show gene-specific methylation profile. There were 88, 2,680, and 95 hypomethylated DMGs identified with changes in DNA methylation in the promoter, intragenic and downstream regions, respectively, compared with fewer hypermethylated DMGs (45, 1,623, and 50 in the respective regions). Some of these genes also contained an ACGT cis-acting motif whose DNA methylation status may affect gene expression. Pathway analysis showed that these DMGs were involved in critical hepatic signaling networks related to hepatic development. Therefore, HF diet had global impacts on DNA methylation profile in the liver of rats, leading to differential expression of genes in hepatic pathways that may involve in functional changes in liver development.

Redox-Responsive Self-Assembled Chain-Shattering Polymeric Therapeutics

We report the design and development of redox-responsive chain-shattering polymeric therapeutics (CSPTs). CSPTs were synthesized by condensation polymerization and further modified with poly(ethylene glycol) (PEG) via "Click" reaction. Size-controlled CSPT nanoparticles (NPs) were formed through nanoprecipitation with high drug loading (up to 18%); the particle size increased in a concentration dependent manner. Drug release from particles was well controlled over 48 h upon redox triggering. The anticancer efficacy of the CSPT NPs was validated both in vitro and in vivo.

Developmental bisphenol A (BPA) exposure leads to sex-specific modification of hepatic gene expression and epigenome at birth that may exacerbate high-fat diet-induced hepatic steatosis

Developmental bisphenol A (BPA) exposure increases adulthood hepatic steatosis with reduced mitochondrial function. To investigate the potential epigenetic mechanisms behind developmental BPA-induced hepatic steatosis, pregnant Sprague-Dawley rats were dosed with vehicle (oil) or BPA (100μg/kg/day) from gestational day 6 until postnatal day (PND) 21. After weaning, offspring were either challenged with a high-fat (HF; 45% fat) or remained on a control (C) diet until PND110. From PND60 to 90, both BPA and HF diet increased the fat/lean ratio in males only, and the combination of BPA and HF diet appeared to cause the highest ratio. On PND110, Oil-HF, BPA-C, and BPA-HF males had higher hepatic lipid accumulation than Oil-C, with microvesicular steatosis being marked in the BPA-HF group. Furthermore, on PND1, BPA increased and modified hepatic triglyceride (TG) and free fatty acid (FFA) compositions in males only. In PND1 males, BPA increased hepatic expression of FFA uptake gene Fat/Cd36, and decreased the expression of TG synthesis- and β-oxidation-related genes (Dgat, Agpat6, Cebpα, Cebpβ, Pck1, Acox1, Cpt1a, Cybb). BPA altered DNA methylation and histone marks (H3Ac, H4Ac, H3Me2K4, H3Me3K36), and decreased the binding of several transcription factors (Pol II, C/EBPβ, SREBP1) within the male Cpt1a gene, the key β-oxidation enzyme. In PND1 females, BPA only increased the expression of genes involved in FFA uptake and TG synthesis (Lpl, Fasn, and Dgat). These data suggest that developmental BPA exposure alters and reprograms hepatic β-oxidation capacity in males, potentially through the epigenetic regulation of genes, and further alters the response to a HF diet.

Expression of nociceptive ligands in canine osteosarcoma

Background

Canine osteosarcoma (OS) is associated with localized pain as a result of tissue injury from tumor infiltration and peritumoral inflammation. Malignant bone pain is caused by stimulation of peripheral pain receptors, termed nociceptors, which reside in the localized tumor microenvironment, including the periosteal and intramedullary bone cavities. Several nociceptive ligands have been determined to participate directly or indirectly in generating bone pain associated with diverse skeletal abnormalities.

Hypothesis

Canine OS cells actively produce nociceptive ligands with the capacity to directly or indirectly activate peripheral pain receptors residing in the bone tumor microenvironment.

Animals

Ten dogs with appendicular OS.

Methods

Expression of nerve growth factor, endothelin‐1, and microsomal prostaglandin E synthase‐1 was characterized in OS cell lines and naturally occurring OS samples. In 10 dogs with OS, circulating concentrations of nociceptive ligands were quantified and correlated with subjective pain scores and tumor volume in patients treated with standardized palliative therapies.

Results

Canine OS cells express and secrete nerve growth factor, endothelin‐1, and prostaglandin E2. Naturally occurring OS samples uniformly express nociceptive ligands. In a subset of OS‐bearing dogs, circulating nociceptive ligand concentrations were detectable but failed to correlate with pain status. Localized foci of nerve terminal proliferation were identified in a minority of primary bone tumor samples.

Conclusions and Clinical Importance

Canine OS cells express nociceptive ligands, potentially permitting active participation of OS cells in the generation of malignant bone pain. Specific inhibitors of nociceptive ligand signaling pathways might improve pain control in dogs with OS.

Genistein exposure during the early postnatal period favors the development of obesity in female, but not male rats

Genistein (Gen), the primary isoflavone in soy, has been shown to adversely affect various endocrine-mediated endpoints in rodents and humans. Soy formula intake by human infants has been associated with early age at menarche and decreased female-typical behavior in girls. Adipose deposition and expansion are also hormonally regulated and Gen has been shown to alter these processes. However, little is known about the impact of early-life soy intake on metabolic homeostasis in adulthood. The current study examined the impact of early-life Gen exposure on adulthood body composition (by magnetic resonance imaging) and the molecular signals mediating adipose expansion. From postnatal day (PND) 1 to 22, rat pups were daily orally dosed with 50mg/kg Gen to mimic blood Gen levels in human infants fed soy formula. Female but not male Gen-exposed rats had increased fat/lean mass ratio, fat mass, adipocyte size and number, and decreased muscle fiber perimeter. PND22 Gen-exposed females, but not males, had increased expression of adipogenic factors, including CCAAT/enhancer binding protein alpha (Cebpα), CCAAT/enhancer binding protein beta (Cebpβ), and peroxisome proliferator-activated receptor gamma (Pparγ). Furthermore, Wingless-related MMTV integration site 10b (Wnt10b), a critical regulator of adipogenic cell fate determination, was hypermethylated and had decreased expression in adipose of PND22 Gen-exposed females. These data suggest that developmental Gen exposure in rats has gender-specific effects on adiposity that closely parallel the effects of a postweaning high-fat diet and underscore the importance of considering timing of exposure and gender when establishing safety recommendations for early-life dietary Gen intake.

Chloroquine causes similar electroretinogram modifications, neuronal phospholipidosis and marked impairment of synaptic vesicle transport in albino and pigmented rats

Retinal toxicity of chloroquine has been known for several years, but the mechanism(s) of toxicity remain controversial; some author support the idea that the binding of chloroquine to melanin pigments in the retinal pigmented epithelium (RPE) play a major toxic role by concentrating the drug in the eye. In our study, 12 albinos Sprague-Dawley (SD) and 12 pigmented Brown Norway (BN) rats were treated orally for 3 months with chloroquine to compare functional and pathological findings. On Flash electroretinograms (ERG) performed in scotopic conditions, similar and progressive (time-dependent) delayed onset and decreased amplitudes of oscillatory potentials (from Day 71) and b-waves (on Day 92) were identified in both BN and SD rats. In both strains, identical morphological changes consisted of neuronal phospholipidosis associated with UV auto-fluorescence without evidence of retinal degeneration and gliosis; the RPE did not show any morphological lesions or autofluorescence. IHC analyses demonstrated a decrease in GABA expression in the inner nuclear layer. In addition, a marked accumulation of synaptic vesicles coupled with a marked disruption of neurofilaments in the optic nerve fibers was identified. In conclusion, ERG observations were very similar to those described in humans. Comparable ERG modifications, histopathology and immunohistochemistry findings were observed in the retina of both rat strains suggesting that melanin pigment is unlikely involved. chloroquine-induced impairment of synaptic vesicle transport, likely related to disruption of neurofilaments was identified and non-previously reported. This new mechanism of toxicity may also be responsible for the burry vision described in humans chronically treated with chloroquine.

Comparison of brain PrPd distribution in ovine BSE and scrapie

Scrapie and bovine spongiform encephalopathy (BSE) are both prion diseases affecting ruminants, and these diseases do not share the same public health concerns. Surveillance of the BSE agent in small ruminants has been a great challenge, and the recent identification of diverse prion diseases in ruminants has led to the development of new methods for strain typing. In our study, using immunohistochemistry (IHC), we assessed the distribution of PrP(d) in the brains of 2 experimentally BSE-infected sheep with the ARQ/ARQ genotype. Distribution of PrP(d) in the brain, from the spinal cord to the frontal cortex, was remarkably similar in the 2 sheep despite different inoculation routes and incubation periods. Comparatively, overall PrP(d) brain distribution, evaluated by IHC, in 19 scrapie cases with the ARQ/ARQ, ARQ/VRQ, and VRQ/VRQ genotypes, in some cases showed similarities to the experimentally BSE-infected sheep. There was no exclusive neuroanatomical site with a characteristic and specific PrP(d) type of accumulation induced by the BSE agent. However, a detailed analysis of the topography, types, and intensity of PrP(d) deposits in the frontal cortex, striatum, piriform cortex, hippocampus, mesencephalon, and cerebellum allowed the BSE-affected sheep group to be distinguished from the 19 scrapie cases analyzed in our study. These results strengthen and emphasize the potential interest of PrP(d) brain mapping to help in identifying prion strains in small ruminants.

Spontaneous Metritis Related to the Presence of Vaginal Septum in Pregnant Sprague Dawley Crl:CD(SD) Rats

Recently, 6% of 1,176 Sprague Dawley rats examined in our reproductive toxicity studies presented with dark-red uterine contents with or without fetuses demonstrating delayed development. Sometimes, a high proportion of the litter was found dead, and dystocia with death or preterminal euthanasia of the dam occurred. Microscopic findings in the uterus consisted of necrohemorrhagic and suppurative periplacentitis associated with the presence of bacterial colonies identified as Escherichia coli. In the vagina, similar findings were observed that were associated with mucus accumulation and the presence of a transverse occlusive or partially occlusive thin membrane identified as a vaginal septum. Microscopically, this septum consisted of a thin band of connective tissue covered on both sides by a mucous epithelium that was continuous with vaginal epithelium. In some cases, there was only mucus accumulation retained by a septum in the vagina without evidence of bacterial infection. Serological and histological examinations did not reveal any specific pathogenic agent. The presence of these septa in the vagina most likely favored mucus accumulation, nonspecific ascending bacterial infection, and dystocia.

This colony of rats presented with an unusually high incidence of vaginal septa as it was described in different strains of mice and rats in the past. We hypothesized that the use of an impedance meter by the breeder—to determine the phase of the estrous cycle by introducing a probe in the vagina—likely facilitated gestation by perforating the vaginal septum in some cases.

Is the presence of abnormal prion protein in the renal glomeruli of feline species presenting with FSE authentic?

In a recent paper written by Hilbe et al (BMC vet res, 2009), the nature and specificity of the prion protein deposition in the kidney of feline species affected with feline spongiform encephalopathy (FSE) were clearly considered doubtful. This article was brought to our attention because we published several years ago an immunodetection of abnormal prion protein in the kidney of a cheetah affected with FSE. At this time we were convinced of its specificity but without having all the possibilities to demonstrate it. As previously published by another group, the presence of abnormal prion protein in some renal glomeruli in domestic cats affected with FSE is indeed generally considered as doubtful mainly because of low intensity detected in this organ and because control kidneys from safe animals present also a weak prion immunolabelling. Here we come back on these studies and thought it would be helpful to relay our last data to the readers of BMC Vet res for future reference on this subject.

Here we come back on our material as it is possible to study and demonstrate the specificity of prion immunodetection using the PET-Blot method (Paraffin Embedded Tissue - Blot). It is admitted that this method allows detecting the Proteinase K (PK) resistant form of the abnormal prion protein (PrPres) without any confusion with unspecific immunoreaction. We re-analysed the kidney tissue versus adrenal gland and brain samples from the same cheetah affected with TSE using this PET-Blot method. The PET-Blot analysis revealed specific PrPres detection within the brain, adrenal gland and some glomeruli of the kidney, with a complete identicalness compared to our previous detection using immunohistochemistry. In conclusion, these new data enable us to confirm with assurance the presence of specific abnormal prion protein in the adrenal gland and in the kidney of the cheetah affected with FSE. It also emphasizes the usefulness for the re-examination of any available tissue blocks with the PET-Blot method as a sensitive complementary tool in case of doubtful PrP IHC results.

Immunohistochemical Characterization of a Hepatic Neuroendocrine Carcinoma in a Cat

A hepatic mass was identified in a 5-year-old, female mixed-breed cat that died spontaneously after a clinical history of progressive emaciation, ptyalism, and persistent coryza. At necropsy, a 7-cm-diameter, yellow-brown, firm, multilobulated tumor was identified in the liver. Microscopically, the mass consisted of neoplastic cells arranged in small, closely packed nests within a thin fibrovascular stroma. These cells were of medium sized and polygonal, with fine argyrophilic cytoplasmic granules. Nuclei were predominantly round with finely stippled chromatin and indistinct nucleoli. Mitotic figures were numerous. Immunohistochemically, most of the neoplastic cells were immunoreactive for chromogranin A, neuron-specific enolase (NSE), and cytokeratin AE1/AE3 and weakly labeled for synaptophysin. The tumor was negative for glial fibrillary acidic protein (GFAP), vimentin, and cytokeratins 5, 6, 8, and 17. Vascular emboli and intrahepatic micrometastasis were also identified with chromogranin A. All these features were consistent with a hepatic neuroendocrine carcinoma and emphasized the importance of using a panel of antibodies to diagnose such rare tumors.

Severe Necrotizing Encephalitis in a Yorkshire Terrier: Topographic and Immunohistochemical Study

Necrotizing encephalitis of the Yorkshire terrier is a chronic non-suppurative encephalitis that was reported in approximately 15 cases worldwide. We report the case of a 10-year-old female Yorkshire terrier with gross evidence of severe cortical degeneration and necrosis. Microscopically, affected areas were mainly located in the cortical white matter and in the mesencephalon without implication of the cerebellum. Cavitation necrosis, demyelination, gemistocytic astrocytosis, marked perivascular lymphocytic cuffing with a diffuse lymphocytic/histiocytic/gitter cell infiltration characterized the lesions. Immunohistochemical analysis identified the major infiltration of T lymphocytes and macrophages with implication of some cytotoxic lymphocytes and IgG-producing plasma cells; depositions of IgG in the affected white matter were also observed. Specific stains did not reveal fungal, protozoal or bacterial organisms and reverse transcriptase-polymerase chain reaction analysis for distemper virus was also negative. The lympho-histiocytic inflammation suggests a T-cell-mediated and a delayed-type immune reaction as a possible pathogenic mechanism for this brain disorder.

Peripheral circulation of the prion infectious agent in transgenic mice expressing the ovine prion protein gene in neurons only

BACKGROUND

For prion diseases, even if a large body of evidence indicates that both the lymphoreticular system (LRS) and peripheral nerves are involved in scrapie neuroinvasion, the processes by which prions invade the central nervous system are only partially understood.

METHODS

Transgenic Tg(OvPrP4) mice, which express the ovine prion protein (PrP) gene under the rat neuron-specific enolase promoter on a knockout background, were used to study prion extracerebral circulation after scrapie prions were inoculated via the intracerebral (ic) and the intraperitoneal (ip) route.

RESULTS

Surprisingly, PrP(Sc) was detected in the spleens of mice inoculated ic with prions. Moreover, the absence of the ovine PrP(C) in nonneural tissue at the periphery did not stop neuroinvasion after ip challenge. Additionally, pilot studies performed in Tg(OvPrP4) mice that had undergone splenectomy before ic prion inoculation showed that the time course of the disease is delayed.

CONCLUSIONS

Given that these mice express the ovine PrP gene in neuronal cells but not in nonnervous tissue, our results suggest that PrP(C) expressed by cells of the LRS are not necessary for neuroinvasion or for their ability to accumulate PrP(Sc) and emphasize the importance of extracerebral circulation of PrP(C) or PrP(Sc) for the development of the disease.

BSE inoculation to prion diseases-resistant sheep reveals tricky silent carriers

The possible transmission of bovine spongiform encephalopathy (BSE) agent to sheep contributed to select genetically sheep considered as resistant to prion diseases i.e., with PrP ARR/ARR genotype. Here, we report the infection of two PrP ARR/ARR genotype sheep using the cattle BSE agent inoculated by peripheral routes. Disease-associated prion protein (PrP(d)) was detected in the brain for one case (at 2191 days post-infection (dpi)) and only in the nervous enteric system for the other one (at 673dpi). The electrophoretic pattern of PrP(d) from the obex region in this BSE challenged sheep was shown to be closer from that found in naturally scrapie-affected sheep with regard to the apparent molecular mass of the unglycosylated PrP(d). Importantly, the absence of any clinical symptoms up to 6 years following experimental challenge suggests that silent carriers of the BSE agent may exist among ARR homozygous sheep.

PET-blot analysis contributes to BSE strain recognition in C57Bl/6 mice

Identification of the strain of agent responsible for bovine spongiform encephalopathy (BSE) can be made histologically through the analysis of both distribution and intensity of brain vacuolar lesions after BSE transmission to mouse. Another useful way to distinguish the BSE agent from other prion strains is the study of the distribution of the abnormal prion protein (PrP(res)). For that purpose, paraffin-embedded tissue blot (PET-blot) method was applied on brains from C57Bl/6 mice infected with cattle BSE, experimental sheep BSE, or feline spongiform encephalopathy (FSE) from a cheetah. PrP(res) distribution was comparable, whichever of the three BSE agent sources was considered and was distinct from the PrP(res) distribution in C57Bl/6 mice inoculated with a French scrapie isolate or with a mouse-adapted scrapie strain (C506M3). These data confirm a common origin of infectious agent responsible for the British and French cattle BSE. They also indicate that PET-blot method appears as a precise complementary tool in prion strain studies because it offers easy and quick assessment of the PrP(res) mapping. Advantages and limits of the PET-blot method are discussed and compared with other established and validated methods of strain typing.

Evaluation of the genotoxic potential of 3-monochloropropane-1,2-diol (3-MCPD) and its metabolites, glycidol and beta-chlorolactic acid, using the single cell gel/comet assay

3-monochloropropane-1,2-diol (3-MCPD) is a member of a group of chemicals known as chloropropanols. It is found in many foods and food ingredients as a result of food processing. 3-MCPD is regarded as a rat carcinogen known to induce Leydig-cell and mammary gland tumours in males and kidney tumours in both genders. The aim of our study was to clarify the possible involvement of genotoxic mechanisms in 3-MCPD induced carcinogenicity at the target organ level. For that purpose, we evaluated DNA damages in selected target (kidneys and testes) and non-target (blood leukocytes, liver and bone marrow) male rat organs by the in vivo alkaline single cell gel electrophoresis (comet) assay, 3 and 24 h after 3-MCPD oral administration to Sprague-Dawley and Fisher 344 adult rats. 3-MCPD may be metabolised to a genotoxic intermediate, glycidol, whereas the predominant urinary metabolite in rats following 3-MCPD administration is beta-chlorolactic acid. Therefore, we also studied the DNA damaging effects of 3-MCPD and its metabolites, glycidol and beta-chlorolactic acid, in the in vitro comet assay on CHO cells. Our results show the absence of genotoxic potential of 3-MCPD in vivo in the target as well as in the non-target organs. Glycidol, the epoxide metabolite, induced DNA damages in CHO cells. beta-Chlorolactic acid, the main metabolite of 3-MCPD in rats, was shown to be devoid of DNA-damaging effects in vitro in mammalian cells.

PrP(d) accumulation in organs of ARQ/ARQ sheep experimentally infected with BSE by peripheral routes

To study the pathogenesis of bovine spongiform encephalopathy infection in small ruminants, two Lacaune sheep with the AA136RR154QQ171 and one with the AA136RR154RR171 genotype for the prion protein, were inoculated with a brain homogenate from a French cattle BSE case by peripheral routes. Sheep with the ARQ/ARQ genotype are considered as susceptible to prion diseases contrary to those with the ARR/ARR genotype. The accumulation of disease-associated prion protein (PrP(d)) was analysed by biochemical and immunohistochemical methods. No PrP(d) accumulation was detected in samples from the ARR/ARR sheep 2 years post inoculation. In the two ARQ/ARQ sheep that had scrapie-like clinical symptoms, PrP(d) was found in the central, sympathetic and enteric nervous systems and in lymphoid organs. Remarkably, PrP(d) was also detected in some muscle types as well as in all peripheral nerves that had not been reported previously thus revealing a widespread distribution of BSE-associated PrP(d) in sheep tissues.

PrP(d) accumulation in organs of ARQ/ARQ sheep experimentally infected with BSE by peripheral routes

To study the pathogenesis of bovine spongiform encephalopathy infection in small ruminants, two Lacaune sheep with the AA136RR154QQ171 and one with the AA136RR154RR171 genotype for the prion protein, were inoculated with a brain homogenate from a French cattle BSE case by peripheral routes. Sheep with the ARQ/ARQ genotype are considered as susceptible to prion diseases contrary to those with the ARR/ARR genotype. The accumulation of disease-associated prion protein (PrP(d)) was analysed by biochemical and immunohistochemical methods. No PrP(d) accumulation was detected in samples from the ARR/ARR sheep 2 years post inoculation. In the two ARQ/ARQ sheep that had scrapie-like clinical symptoms, PrP(d) was found in the central, sympathetic and enteric nervous systems and in lymphoid organs. Remarkably, PrP(d) was also detected in some muscle types as well as in all peripheral nerves that had not been reported previously thus revealing a widespread distribution of BSE-associated PrP(d) in sheep tissues.

Abnormal prion protein in genetically resistant sheep from a scrapie-infected flock

The central molecular event in transmissible spongiform encephalopathies, such as scrapie in sheep, is the accumulation in tissues of an abnormal isoform of the cellular prion protein. A previous investigation of 26 sheep showed that the accumulation of PrP(res) in brain correlated more with the prnp genotype than with the severity of the clinical disease. Here, the ability of a sandwich ELISA to detect PrP(res) distribution in the brain was demonstrated. Immunohistochemistry also strongly supported the hypothesis that the dorsal motor nucleus of the vagus nerve is the possible entry site in the brain for the scrapie agent. Remarkably, three asymptomatic (or possibly asymptomatic for scrapie) sheep carrying an allele known to be associated with clinical scrapie resistance (ARR), which were negative for the detection of PrP(res) by Western blotting and immunohistochemistry, were positive for the presence of PrP(res) by ELISA, raising the possibility of carriers resistant to the disease and possibly contributing to the persistence of scrapie in certain flocks.

Comparative molecular analysis of the abnormal prion protein in field scrapie cases and experimental bovine spongiform encephalopathy in sheep by use of Western blotting and immunohistochemical methods

Since the appearance of bovine spongiform encephalopathy (BSE) in cattle and its linkage with the human variant of Creutzfeldt-Jakob disease, the possible spread of this agent to sheep flocks has been of concern as a potential new source of contamination. Molecular analysis of the protease cleavage of the abnormal prion protein (PrP), by Western blotting (PrP(res)) or by immunohistochemical methods (PrP(d)), has shown some potential to distinguish BSE and scrapie in sheep. Using a newly developed enzyme-linked immunosorbent assay, we identified 18 infected sheep in which PrP(res) showed an increased sensitivity to proteinase K digestion. When analyzed by Western blotting, two of them showed a low molecular mass of unglycosylated PrP(res) as found in BSE-infected sheep, in contrast to other naturally infected sheep. A decrease of the labeling by P4 monoclonal antibody, which recognizes an epitope close to the protease cleavage site, was also found by Western blotting in the former two samples, but this was less marked than in BSE-infected sheep. These two samples, and all of the other natural scrapie cases studied, were clearly distinguishable from those from sheep inoculated with the BSE agent from either French or British cattle by immunohistochemical analysis of PrP(d) labeling in the brain and lymphoid tissues. Final characterization of the strain involved in these samples will require analysis of the features of the disease following infection of mice, but our data already emphasize the need to use the different available methods to define the molecular properties of abnormal PrP and its possible similarities with the BSE agent.

Florid plaques in ovine PrP transgenic mice infected with an experimental ovine BSE

The occurrence of the variant Creutzfeldt-Jakob disease (vCJD), related to bovine spongiform encephalopathy (BSE), raises the important question of the sources of human contamination. The possibility that sheep may have been fed with BSE-contaminated foodstuff raises the serious concern that BSE may now be present in sheep without being distinguishable from scrapie. Sensitive models are urgently needed given the dramatic consequences of such a possible contamination on animal and human health. We inoculated transgenic mice expressing the ovine PrP gene with a brain homogenate from sheep experimentally infected with BSE. We found numerous typical florid plaques in their brains. Such florid plaques are a feature of vCJD in humans and experimental BSE infection in macaques. Our observation represents the first description, after a primary infection, of this hallmark in a transgenic mouse model. Moreover, these mice appear to be a promising tool in the search for BSE in sheep.

Autonomic nervous system innervation of lymphoid territories in spleen: a possible involvement of noradrenergic neurons for prion neuroinvasion in natural scrapie

In experimental as well as in natural scrapie, transmissible spongiform encephalopathies (TSEs), the infectious agent, closely related to PrPsc, an abnormal isoform of the cellular prion protein, invades and replicates in lymphoid organs such as spleen before affecting the brain. To clarify the cellular requirements for the possible neuroinvasion of scrapie agent from the spleen to the central nervous system, we have studied the sympathetic innervation within the lymphoid territories of the spleen. These noradrenergic fibers originating from the coeliomesenteric ganglia were examined with regard to PrPsc-associated cells in spleen of adult sheep severely affected with natural scrapie. Using a double immunolabelling strategy, we demonstrated the proximity of noradrenergic endings with PrPsc-accumulating cells, strengthening its possible implication in the neuroinvasion process.

CNA42 monoclonal antibody identifies FDC as PrPsc accumulating cells in the spleen of scrapie affected sheep

Natural scrapie, new variant Creutzfeldt-Jakob disease and murine experimental transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative disorders. The agent responsible for these diseases is closely related to PrPsc, an abnormal isoform of the cellular prion protein. Before reaching the brain, it invades and replicates in lymphoid organs such as spleen, tonsils and lymph nodes. Follicular dendritic cells (FDC) may support the prion replication in lymphoid tissues of sheep as shown in murine models infected with scrapie. In sheep, specific antibodies recognising FDC are lacking. The CNA42 mAb, directed against human FDC was used to identify these cells in sheep spleen. As well as showing that the pre-treatments needed for immunohistochemical detection of PrPsc did not prevent labelling by the CNA42 mAb, accumulation of PrPsc in FDC of spleens of scrapie affected sheep was demonstrated using a double immunolabelling strategy. Thus, the CNA42 antibody represents a suitable tool to identify FDC and investigate their role in natural sheep scrapie.

Close vicinity of PrP expressing cells (FDC) with noradrenergic fibers in healthy sheep spleen

In naturally and experimentally occurring scrapie in sheep, prions invade the immune system and replicate in lymphoid organs. Here we analysed immunohistochemically, in seven spleens of 6-month-old healthy sheep, the nature of the cells expressing prion protein (PrP) potentially supporting prion replication, as well as their relationship with autonomic innervation. PrP was identified using either RB1 rabbit antiserum or 4F2 monoclonal antibody directed against AA 108-123 portion of the bovine and AA 79-92 of human prion protein respectively. Using double labelling analysis, we demonstrated that PrPc is expressed by follicular dendritic cells using a specific monoclonal antibody (CNA42). We also showed the close vicinity of these PrP expressing cells with noradrenergic fibers, using a polyclonal tyrosine hydroxylase antibody. Our results may help the study of the cellular requirements for the possible neuroinvasion from the spleen.