Temporal and regional expression changes and co-staining patterns of metabolic and stemness-related markers during glioblastoma progression

Glioblastomas (GBMs) are characterized by high heterogeneity, involving diverse cell types, including those with stem-like features contributing to GBM's malignancy. Moreover, metabolic alterations promote growth and therapeutic resistance of GBM. Depending on the metabolic state, antimetabolic treatments could be an effective strategy. Against this background, we investigated temporal and regional expression changes and co-staining patterns of selected metabolic markers [pyruvate kinase muscle isozyme 1/2 (PKM1/2), glucose transporter 1 (GLUT1), monocarboxylate transporter 1/4 (MCT1/4)] in a rodent model and patient-derived samples of GBM. To understand the cellular sources of marker expression, we also examined the connection of metabolic markers to markers related to stemness [Nestin, Krüppel-like factor 4 (KLF4)] in a regional and temporal context. Rat tumour biopsies revealed a temporally increasing expression of GLUT1, higher expression of MCT1/4, Nestin and KLF4, and lower expression of PKM1 compared to the contralateral hemisphere. Patient-derived tumours showed a higher expression of PKM2 and Nestin in the tumour centre vs. edge. Whereas rare co-staining of GLUT1/Nestin was found in tumour biopsies, PKM1/2 and MCT1/4 showed a more distinct co-staining with Nestin in rats and humans. KLF4 was mainly co-stained with GLUT1, MCT1 and PKM1/2 in rat and human tumours. All metabolic markers yielded individual co-staining patterns among themselves. Co-staining mainly occurred later in tumour progression and was more pronounced in tumour centres. Also, positive correlations were found amongst markers that showed co-staining. Our results highlight a link between metabolic alterations and stemness in GBM progression, with complex distinctions depending on studied markers, time points and regions.

Incidence of microvascular dysfunction is increased in hyperlipidemic mice, reducing cerebral blood flow and impairing remote memory

Introduction

The development of cognitive dysfunction is not necessarily associated with diet-induced obesity. We hypothesized that cognitive dysfunction might require additional vascular damage, for example, in atherosclerotic mice.

Methods

We induced atherosclerosis in male C57BL/6N mice by injecting AAV-PCSK9DY (2x1011 VG) and feeding them a cholesterol-rich Western diet. After 3 months, mice were examined for cognition using Barnes maze procedure and for cerebral blood flow. Cerebral vascular morphology was examined by immunehistology.

Results

In AAV-PCSK9DY-treated mice, plaque burden, plasma cholesterol, and triglycerides are elevated. RNAseq analyses followed by KEGG annotation show increased expression of genes linked to inflammatory processes in the aortas of these mice. In AAV-PCSK9DY-treated mice learning was delayed and long-term memory impaired. Blood flow was reduced in the cingulate cortex (-17%), caudate putamen (-15%), and hippocampus (-10%). Immunohistological studies also show an increased incidence of string vessels and pericytes (CD31/Col IV staining) in the hippocampus accompanied by patchy blood-brain barrier leaks (IgG staining) and increased macrophage infiltrations (CD68 staining).

Discussion

We conclude that the hyperlipidemic PCSK9DY mouse model can serve as an appropriate approach to induce microvascular dysfunction that leads to reduced blood flow in the hippocampus, which could explain the cognitive dysfunction in these mice.

Epithelial and Mesenchymal-like Pancreatic Cancer Cells Exhibit Different Stem Cell Phenotypes Associated with Different Metastatic Propensities

Pancreatic ductal adenocarcinoma (PDAC) is mostly diagnosed at advanced or even metastasized stages, limiting the prognoses of patients. Metastasis requires high tumor cell plasticity, implying phenotypic switching in response to changing environments. Here, epithelial-mesenchymal transition (EMT), being associated with an increase in cancer stem cell (CSC) properties, and its reversion are important. Since it is poorly understood whether different CSC phenotypes exist along the EMT axis and how these impact malignancy-associated properties, we aimed to characterize CSC populations of epithelial and mesenchymal-like PDAC cells. Single-cell cloning revealed CSC (Holoclone) and non-CSC (Paraclone) clones from the PDAC cell lines Panc1 and Panc89. The Panc1 Holoclone cells showed a mesenchymal-like phenotype, dominated by a high expression of the stemness marker Nestin, while the Panc89 Holoclone cells exhibited a SOX2-dominated epithelial phenotype. The Panc89 Holoclone cells showed enhanced cell growth and a self-renewal capacity but slow cluster-like invasion. Contrarily, the Panc1 Holoclone cells showed slower cell growth and self-renewal ability but were highly invasive. Moreover, cell variants differentially responded to chemotherapy. In vivo, the Panc1 and Panc89 cell variants significantly differed regarding the number and size of metastases, as well as organ manifestation, leading to different survival outcomes. Overall, these data support the existence of different CSC phenotypes along the EMT axis in PDAC, manifesting different metastatic propensities.

Multiscale morphological analysis of bone microarchitecture around Mg-10Gd implants

The utilization of biodegradable magnesium (Mg)-based implants for restoration of bone function following trauma represents a transformative approach in orthopaedic application. One such alloy, magnesium-10 weight percent gadolinium (Mg-10Gd), has been specifically developed to address the rapid degradation of Mg while enhancing its mechanical properties to promote bone healing. Previous studies have demonstrated that Mg-10Gd exhibits favorable osseointegration; however, it exhibits distinct ultrastructural adaptation in comparison to conventional implants like titanium (Ti). A crucial aspect that remains unexplored is the impact of Mg-10Gd degradation on the bone microarchitecture. To address this, we employed hierarchical three-dimensional imaging using synchrotron radiation in conjunction with image-based finite element modelling. By using the methods outlined, the vascular porosity, lacunar porosity and the lacunar-canaliculi network (LCN) morphology of bone around Mg-10Gd in comparison to Ti in a rat model from 4 weeks to 20 weeks post-implantation was investigated. Our investigation revealed that within our observation period, the degradation of Mg-10Gd implants was associated with significantly lower (p < 0.05) lacunar density in the surrounding bone, compared to Ti. Remarkably, the LCN morphology and the fluid flow analysis did not significantly differ for both implant types. In summary, a more pronounced lower lacunae distribution rather than their morphological changes was detected in the surrounding bone upon the degradation of Mg-10Gd implants. This implies potential disparities in bone remodelling rates when compared to Ti implants. Our findings shed light on the intricate relationship between Mg-10Gd degradation and bone microarchitecture, contributing to a deeper understanding of the implications for successful osseointegration.

Maternal microbiota communicates with the fetus through microbiota-derived extracellular vesicles

BACKGROUND

Reports regarding the presence of bacteria in the fetal environment remain limited and controversial. Recently, extracellular vesicles secreted by the human gut microbiota have emerged as a novel mechanism for host-microbiota interaction. We aimed to investigate the presence of bacterial extracellular vesicles in the fetal environment during healthy pregnancies and determine whether extracellular vesicles derived from the gut microbiota can cross biological barriers to reach the fetus.

RESULTS

Bacterial extracellular vesicles were detectable in the amniotic fluid of healthy pregnant women, exhibiting similarities to extracellular vesicles found in the maternal gut microbiota. In pregnant mice, extracellular vesicles derived from human maternal gut microbiota were found to reach the intra-amniotic space.

CONCLUSIONS

Our findings reveal maternal microbiota-derived extracellular vesicles as an interaction mechanism between the maternal microbiota and fetus, potentially playing a pivotal role in priming the prenatal immune system for gut colonization after birth. Video Abstract.

Establishment of a Rodent Glioblastoma Partial Resection Model for Chemotherapy by Local Drug Carriers-Sharing Experience

Local drug delivery systems (LDDS) represent a promising therapy strategy concerning the most common and malignant primary brain tumor glioblastoma (GBM). Nevertheless, to date, only a few systems have been clinically applied, and their success is very limited. Still, numerous new LDDS approaches are currently being developed. Here, (partial resection) GBM animal models play a key role, as such models are needed to evaluate the therapy prior to any human application. However, such models are complex to establish, and only a few reports detail the process. Here, we report our results of establishing a partial resection glioma model in rats suitable for evaluating LDDS. C6-bearing Wistar rats and U87MG-spheroids- and patient-derived glioma stem-like cells-bearing athymic rats underwent tumor resection followed by the implantation of an exemplary LDDS. Inoculation, tumor growth, residual tumor tissue, and GBM recurrence were reliably imaged using high-resolution Magnetic Resonance Imaging. The release from an exemplary LDDS was verified in vitro and in vivo using Fluorescence Molecular Tomography. The presented GBM partial resection model appears to be well suited to determine the efficiency of LDDS. By sharing our expertise, we intend to provide a powerful tool for the future testing of these very promising systems, paving their way into clinical application.

P-315 The importance of treatment features beyond pain reduction associated with gonadotropin-releasing hormone analogues from the patient perspective

Study question

Beyond reducing pain, how do women with moderate-severe-endometriosis pain prioritize treatment features and outcomes associated with gonadotropin-releasing hormone (GnRH) analogues?

Summary answer

Moderate-severe-endometriosis patients prioritized safe long-term treatment, feeling treatment-effects within a few cycles, being able to maintain employment, reducing fatigue, depression, and headaches, and improving libido.

What is known already

The importance of pain management in endometriosis treatment is well-established. Poor health-related quality of life has been attributed to endometriosis pain, with greater impact as the number of endometriosis symptoms and symptom severity increase. Endometriosis treatment options include analgesics for acute pain episodes and surgery in more severe cases, as well as hormone therapies, including GnRH analogues. The potential risks, benefits, and outcomes associated with currently available GnRH analogues for endometriosis treatment can vary. Data are lacking on the patient perspective with respect to potential treatment features and outcomes beyond just pain reduction.

Study design, size, duration

Treatment-naïve patients with moderate-severe-endometriosis pain (rating scale ≥4 for menstrual pain) in the United States completed a cross-sectional online survey. Best-worst scaling (BWS) was used to assess preferences for key non-pain treatment attributes that were identified based on the literature. Cognitive pre-test interviews were conducted to confirm content validity of the questionnaire. Data collection for this ongoing survey was initiated in December 2021.

Participants/materials, setting, methods

Patients (English-speaking, premenopausal, 18-50 years-old) were recruited via healthcare research panel. Eligible patients self-reported laparoscopy-confirmed-endometriosis, no endometriosis/other gynecological surgery in past 3 months, no osteoporosis/bone disease/uterine fibroids history, and healthcare coverage for previous 3 years. Treatment features in the BWS exercise included dosage flexibility, short treatment onset, reversibility of side effects, reducing fatigue, depression, headache, impact on libido, impact on sleep, ability to maintain employment, duration of treatment, and additional need for contraceptive use.

Main results and the role of chance

Overall, 115 patients (31.1±7.5 years-old) were included in the analyses. On a 0 (no pain) to 10 (pain as bad as you can imagine) scale, the mean worst menstrual and non-menstrual pelvic pain (during past month) were 7.7±1.6 and 5.4±2.7, respectively. The most common endometriosis treatments ever used included over-the-counter pain medications (90.4%) and prescription contraceptives (74.8%).

Of 11 BWS features tested, patients prioritized:

“You can safely take the treatment for a long period of time” (relative importance=11.4%) “Your ability to get or maintain a job” (11.1%) “When starting a treatment, you will begin to feel the treatment’s effects within the first few menstrual cycles” (10.9%) “You will be less depressed” (10.8%) “Your interest in sex will not be affected” (10.7%) “Any side-effects you may experience are resolved quickly after treatment stops” (10.1%) “You will be less fatigued or tired” (9.5%) “You will have fewer headaches or migraines” (8.6%)

Least important to patients were:

“Your sleep will not be affected” (6.8%) “Your doctor offers different options for the dose strength and how often you take it, as appropriate to your needs” (5.9%) “You are not required to take additional contraceptives along with the treatment” (4.0%)

Limitations, reasons for caution

The preferences of patients who participated may differ from those who did not participate, thereby reducing the ability to generalize results. All data were self-reported; diagnosis and treatment could not be independently confirmed. The BWS exercise cannot include all possible attributes and outcomes relevant to patients.

Wider implications of the findings

Beyond pain reduction, patients most highly valued having safe long-term treatment, feeling treatment effects within a few cycles, rapid resolution of side effects, being able to work, maintaining libido, and reducing fatigue, depression, and headaches. These factors can help physicians to better align endometriosis treatment decision-making with patient preferences.

Trial registration number

Not applicable

Dynamic in vivo monitoring of fracture healing process in response to magnesium implant with multimodal imaging: Pilot longitudinal study in a rat external fixation model

Rodent models are commonly used in pre-clinical research of magnesium (Mg) -based and other types of biomaterials for fracture treatment. Most studies selected unstable fixation methods, and there is a...

Telmisartan prevents high-fat diet-induced neurovascular impairments and reduces anxiety-like behavior

Angiotensin II receptor blockers (telmisartan) prevent rodents from diet-induced obesity and improve their metabolic status. Hyperglycemia and obesity are associated with reduced cerebral blood flow and neurovascular uncoupling which may lead to behavioral deficits. We wanted to know whether a treatment with telmisartan prevents these changes in obesity.We put young mice on high-fat diet and simultaneously treated them with telmisartan. At the end of treatment, we performed laser speckle imaging and magnetic resonance imaging to assess the effect on neurovascular coupling and cerebral blood flow. Different behavioral tests were used to investigate cognitive function.Mice developed diet-induced obesity and after 16, not 8 weeks of high-fat diet, however, the response to whisker pad stimulation was about 30% lower in obese compared to lean mice. Simultaneous telmisartan treatment increased the response again by 10% compared to obese mice. Moreover, telmisartan treatment normalized high-fat diet-induced reduction of cerebral blood flow and prevented a diet-induced anxiety-like behavior. In addition to that, telmisartan affects cellular senescence and string vessel formation in obesity.We conclude, that telmisartan protects against neurovascular unit impairments in a diet-induced obesity setting and may play a role in preventing obesity related cognitive deficits in Alzheimer's disease.

Tissue responses after implantation of biodegradable Mg alloys evaluated by multimodality 3D micro-bioimaging in vivo

The local response of tissue triggered by implantation of degradable magnesium-based implant materials was investigated in vivo in a murine model. Pins (5.0 mm length by 0.5 mm diameter) made of Mg, Mg-10Gd, and Ti were implanted in the leg muscle tissue of C57Bl/6N mice (n = 6). Implantation was generally well tolerated as documented by only a mild short term increase in a multidimensional scoring index. Lack of difference between the groups indicated that the response was systemic and surgery related rather than material dependent. Longitudinal in vivo monitoring utilizing micro-computed tomography over 42 days demonstrated the highest and most heterogeneous degradation for Mg-10Gd. Elemental imaging of the explants by micro X-ray fluorescence spectrometry showed a dense calcium-phosphate-containing degradation layer. In order to monitor resulting surgery induced and/or implant material associated local cell stress, sphingomyelin based liposomes containing indocyanine green were administered. An initial increase in fluorescent signals (3-7 days after implantation) indicating cell stress at the site of the implantation was measured by in vivo fluorescent molecular tomography. The signal decreased until the 42nd day for all materials. These findings demonstrate that Mg based implants are well tolerated causing only mild and short term adverse reactions.

Utilizing ICG Spectroscopical Properties for Real-Time Nanoparticle Release Quantification <i>In vitro</i> and <i>In vivo</i> in Imaging Setups

BACKGROUND

Nanoparticle imaging and tracking the release of the loaded material from the nanoparticle system have attracted significant attention in recent years. If the release of the loaded molecules could be monitored reliably in vivo, it would speed up the development of drug delivery systems remarkably.

METHODS

Here, we test a system that uses indocyanine green (ICG) as a fluorescent agent for studying release kinetics in vitro and in vivo from the lipid iron nanoparticle delivery system. The ICG spectral properties like its concentration dependence, sensitivity and the fluctuation of the absorption and emission wavelengths can be utilized for gathering information about the change of the ICG surrounding.

RESULTS

We have found that the absorption, fluorescence, and photoacoustic spectra of ICG in lipid iron nanoparticles differ from the spectra of ICG in pure water and plasma. We followed the ICG containing liposomal nanoparticle uptake into squamous carcinoma cells (SCC) by fluorescence microscopy and the in vivo uptake into SCC tumors in an orthotopic xenograft nude mouse model under a surgical microscope.

CONCLUSION

Absorption and emission properties of ICG in the different solvent environment, like in plasma and human serum albumin, differ from those in aqueous solution. Photoacoustic spectral imaging confirmed a peak shift towards longer wavelengths and an intensity increase of ICG when bound to the lipids. The SCC cells showed that the ICG containing liposomes bind to the cell surface but are not internalized in the SCC-9 cells after 60 minutes of incubation. We also showed here that ICG containing liposomal nanoparticles can be traced under a surgical camera in vivo in orthotopic SCC xenografts in mice.

Using Alendronic Acid Coupled Fluorescently Labelled SM Liposomes as a Vehicle for Bone Targeting

Background:

We recently developed a liposomal nanoparticle system that can be used for drug delivery and simultaneously be monitored by optical or photoacoustic imaging devices. Here we tested the efficacy of alendronate as a homing molecule in SM-liposomes for bone targeting.

Methods:

Alendronate was immobilized covalently on the liposomal surface and the fluorescent dye indocyanine green was used as a payload in the liposomes. The indocyanine green delivery was analyzed by 3D optical tomography, optical fluorescence scanner, photoacoustic imaging, and by ex-vivo biodistribution studies.

Results:

The results show that the alendronate, coupled to the liposomal surface, increases sphingomyelin containing liposome targeting up to several-folds.

Conclusion:

The alendronate targeted liposomes open possibilities for an application in active bone targeting.

Lipid-Iron Nanoparticle with a Cell Stress Release Mechanism Combined with a Local Alternating Magnetic Field Enables Site-Activated Drug Release

Most available cancer chemotherapies are based on systemically administered small organic molecules, and only a tiny fraction of the drug reaches the disease site. The approach causes significant side effects and limits the outcome of the therapy. Targeted drug delivery provides an alternative to improve the situation. However, due to the poor release characteristics of the delivery systems, limitations remain. This report presents a new approach to address the challenges using two fundamentally different mechanisms to trigger the release from the liposomal carrier. We use an endogenous disease marker, an enzyme, combined with an externally applied magnetic field, to open the delivery system at the correct time only in the disease site. This site-activated release system is a novel two-switch nanomachine that can be regulated by a cell stress-induced enzyme at the cellular level and be remotely controlled using an applied magnetic field. We tested the concept using sphingomyelin-containing liposomes encapsulated with indocyanine green, fluorescent marker, or the anticancer drug cisplatin. We engineered the liposomes by adding paramagnetic beads to act as a receiver of outside magnetic energy. The developed multifunctional liposomes were characterized in vitro in leakage studies and cell internalization studies. The release system was further studied in vivo in imaging and therapy trials using a squamous cell carcinoma tumor in the mouse as a disease model. In vitro studies showed an increased release of loaded material when stress-related enzyme and magnetic field was applied to the carrier liposomes. The theranostic liposomes were found in tumors, and the improved therapeutic effect was shown in the survival studies.

Comparison of photoacoustic and fluorescence tomography for the in vivo imaging of ICG-labelled liposomes in the medullary cavity in mice

Few reports quantitatively compare the performance of photoacoustic tomography (PAT) versus fluorescence molecular tomography (FMT) in vivo. We compared both modalities for the detection of signals from injected ICG liposomes in the tibial medullary space of 10 BALB/c mice in vivo and ex vivo. Signals significantly correlated between modalities (R² = 0.69) and within each modality in vivo versus ex vivo (PAT: R² = 0.70, FMT: R² = 0.76). Phantom studies showed that signals at 4 mm depth are detected down to 3.3 ng ICG by PAT and 33 ng by FMT, with a nominal spatial resolution below 0.5 mm in PAT and limited to 1 mm in FMT. Our study demonstrates comparable in vivo sensitivity, but superior ex vivo sensitivity and in vivo resolution for our ICG liposomes of the VevoLAZR versus the FMT2500. PAT provides a useful new tool for the high-resolution imaging of bone marrow signals, for example for monitoring drug delivery.

Alpha-MSH Targeted Liposomal Nanoparticle for Imaging in Inflammatory Bowel Disease (IBD)

Background:

The purpose of our study was to find a novel targeted imaging and drug delivery vehicle for inflammatory bowel disease (IBD). IBD is a common and troublesome disease that still lacks effective therapy and imaging options. As an attempt to improve the disease treatment, we tested αMSH for the targeting of nanoliposomes to IBD sites. αMSH, an endogenous tridecapeptide, binds to the melanocortin-1 receptor (MC1-R) and has anti-inflammatory and immunomodulating effects. MC1-R is found on macrophages, neutrophils and the renal tubule system. We formulated and tested a liposomal nanoparticle involving αMSH in order to achieve a specific targeting to the inflamed intestines.

Methods:

NDP-αMSH peptide conjugated to Alexa Fluor™ 680 was linked to the liposomal membrane via NSuccinyl PE and additionally loaded into the lumen of the liposomes. Liposomes without the αMSH-conjugate and free NDP-αMSH were used as a control. The liposomes were also loaded with ICG to track them. The liposomes were tested in DSS treated mice, which had received DSS via drinking water order to develop a model IBD. Inflammation severity was assessed by the Disease Activity Index (DAI) score and ex vivo histological CD68 staining of samples taken from different parts of the intestine. The liposome targeting was analyzed by analyzing the ICG and ALEXA 680 fluorescence in the intestine compared to the biodistribution.

Results:

NPD-αMSH was successfully labeled with Alexa and retained its biological activity. Liposomes were identified in expected regions in the inflamed bowel regions and in the kidneys, where MC1-R is abundant. In vivo liposome targeting correlated with the macrophage concentration at the site of the inflammation supporting the active targeting of the liposomes through αMSH. The liposomal αMSH was well tolerated by animals.

Conclusions:

This study opens up the possibility to further develop an αMSH targeted theranostic delivery to different clinically relevant applications in IBD inflammation but also opens possibilities for use in other inflammations like lung inflammation in Covid 19.

Multimodal Targeted Nanoparticle-Based Delivery System for Pancreatic Tumor Imaging in Cellular and Animal Models

BACKGROUND

Pancreatic ductal adenocarcinoma (PDAC), which ranks forth on the cancer-related death statistics still is both a diagnostic and a therapeutic challenge. Adenocarcinoma of the exocrine human pancreas originates in most instances from malignant transformation of ductal epithelial cells, alternatively by Acinar-Ductal Metaplasia (ADM). RA96 antibody targets to a mucin M1, according to the more recent nomenclature MUC5AC, an extracellular matrix component excreted by PDAC cells. In this study, we tested the usability of multimodal nanoparticle carrying covalently coupled RA96 Fab fragments for pancreatic tumor imaging.

METHODS

In order to make and evaluate a novel, better targeting, theranostic nanoparticle, iron nanoparticles and the optical dye indocyanin green (ICG) were encapsulated into the cationic sphingomyelin (SM) consisting liposomes. RA-96 Fab fragment was conjugated to the liposomal surface of the nanoparticle to increase tumor homing ability. ICG and iron nanoparticle-encapsulated liposomes were studied in vitro with cells and (i) their visibility in magnetic resonance imaging (MRI), (ii) optical, (iii) Magnetic particle spectroscopy (MPS) and (iv) photoacoustic settings was tested in vitro and also in in vivo models. The targeting ability and MRI and photoacoustic visibility of the RA-96-nanoparticles were first tested in vitro cell models where cell binding and internalization was studied. In in vivo experiments liposomal nanoparticles were injected into a tail vain using an orthotopic pancreatic tumor xenograft model and subcutaneous pancreas cancer cell xenografts bearing mice to determine in vivo targeting abilities of RA-96-conjugated liposomes.

RESULTS

Multimodal liposomes could be detected by MRI, MPS and by photoacoustic imaging in addition to optical imaging showing a wide range of imaging utility. The fluorescent imaging of ICG in pancreatic tumor cells Panc89 and Capan-2 revealed increased association of ICG-encapsulated liposomes carrying RA-96 Fab fragments in vitro compared to the control liposomes without covalently linked RA-96. Fluorescent molecular tomography (FMT) studies showed increased accumulation of the RA96-targeted nanoparticles in the tumor area compared to non-targeted controls in vivo. Similar accumulation in the tumor sites could be seen with liposomal ferric particles in MRI. Fluorescent tumor signal was confirmed by using an intraoperative fluorescent imaging system which showed fluorescent labeling of pancreatic tumors.

CONCLUSION

These results suggest that RA-96-targeted liposomes encapsulating ICG and iron nanoparticles can be used to image pancreatic tumors with a variety of optical and magnetic imaging techniques. Additionally, they might be a suitable drug delivery tool to improve treatment of PDAC patients.

Universal membrane-labeling combined with expression of Katushka far-red fluorescent protein enables non-invasive dynamic and longitudinal quantitative 3D dual-color fluorescent imaging of multiple bacterial strains in mouse intestine

BACKGROUND

The human gastrointestinal (GI) tract microbiota has been a subject of intense research throughout the 3rd Millennium. Now that a general picture about microbiota composition in health and disease is emerging, questions about factors determining development of microbiotas with specific community structures will be addressed. To this end, usage of murine models for colonization studies remains crucial. Optical in vivo imaging of either bioluminescent or fluorescent bacteria is the basis for non-invasive detection of intestinal colonization of bacteria. Although recent advances in in vivo fluorescence imaging have overcome many limitations encountered in bioluminescent imaging of intestinal bacteria, such as requirement for live cells, high signal attenuation and 2D imaging, the method is still restricted to bacteria for which molecular cloning tools are available.

RESULTS

Here, we present usage of a lipophilic fluorescent dye together with Katushka far-red fluorescent protein to establish a dual-color in vivo imaging system to monitor GI transit of different bacterial strains, suitable also for strains resistant to genetic labeling. Using this system, we were able to distinguish two different E. coli strains simultaneously and show their unique transit patterns. Combined with fluorescence molecular tomography, these distinct strains could be spatially and temporally resolved and quantified in 3D.

CONCLUSIONS

Developed novel method for labeling microbes and identify their passage both temporally and spatially in vivo makes now possible to monitor all culturable bacterial strains, also those that are resistant to conventional genetic labeling.

Risk of Suicide After a Cancer Diagnosis in England: A Population-Based Study

Background: Previous research has identified an increased risk of suicide among cancer patients, however this has not been investigated at a population level in England. Those subgroups of patients most at risk need to be identified to ensure appropriate access to psychological support. Aim: To examine the variation in suicide risk among individuals diagnosed with cancer in England. Methods: We identified 4,453,547 individuals (21 million person-years at risk) aged 18 to 99 years at diagnosis of cancer during 1995 to 2015 from the national cancer registry, and followed them up until 31 August 2017. The outcomes of interest were both suicide and open verdicts (ICD-10 X60-X84, Y87.0, Y10-Y34 [excluding Y33.9, Y87.2]). Population-based expected deaths were as published by ONS [2]. We calculated standardized mortality ratios (SMRs) and absolute excess risks (AERs), and explored variation in suicide risk by cancer type, age at death, sex, deprivation, ethnicity, and years since cancer diagnosis. Results: 2352 cancer patients died by suicide. This was 0.08% of all deaths. The overall SMR for suicide was 1.19 (95% CI 1.14-1.24) and AER per 10,000 person-years was 0.18 (0.13-0.22). The risk was highest among individuals diagnosed with mesothelioma, with a 4.34-fold risk corresponding to 4.00 extra deaths per 10,000 person-years. This was followed by pancreatic (3.94-fold), esophageal (2.53-fold), lung (2.52-fold), and stomach (2.14-fold) cancer (all significantly elevated). Suicide risk was highest in the first 6 months following cancer diagnosis (SMR: 2.64 [2.42-2.89]), but a significantly increased risk persisted for 2 years (SMR: 1.21 [1.08-1.35]). Conclusion: Despite low numbers, the elevated risk of suicide in patients with certain cancers is a concern, representing potentially preventable deaths. The increased risk in the first 6 months after diagnosis, which is consistent with previous studies, highlights unmet needs for psychological support delivered alongside cancer diagnosis and treatment. Our findings suggest a need for improved risk stratification across cancer services, followed by targeted psychological support.

Liver metastasis of pancreatic cancer: the hepatic microenvironment impacts differentiation and self-renewal capacity of pancreatic ductal epithelial cells

Pancreatic ductal adenocarcinoma (PDAC) is often diagnosed at advanced stages with the liver as the main site of metastases. The hepatic microenvironment has been shown to determine outgrowth of liver metastases. Cancer stem cells (CSCs) are essential for initiation and maintenance of tumors and acquisition of CSC-properties has been linked to Epithelial-Mesenchymal-Transition. Thus, this study aimed at elucidating whether and how the hepatic microenvironment impacts stemness and differentiation of disseminated pancreatic ductal epithelial cells (PDECs). Culture of premalignant H6c7-kras and malignant Panc1 PDECs together with hepatocytes and hepatic stellate cells (HSC) promoted self-renewal capacity of both PDEC lines. This was indicated by higher colony formation compared to cells cocultured with hepatocytes and hepatic myofibroblasts. Different Panc1 colony types derived from an HSC-enriched coculture were expanded and characterized revealing that holoclones exhibited an enhanced colony formation ability, elevated and exclusive expression of the CSC-marker Nestin and a more pronounced mesenchymal phenotype compared to paraclones. Moreover, Panc1 holoclone cells showed an increased tumorigenic potential in vivo leading to formation of undifferentiated tumors in 7/10 animals, while inoculation of paraclone cells only led to formation of tumors in 2/10 animals being smaller in number and size. Holoclone tumors were characterized by elevated expression of mesenchymal markers, complete loss of E-cadherin expression and high expression of Nestin. Finally, Etanercept-mediated TNF-α blocking partly reversed the mesenchymal CSC-phenotype of Panc1 holoclone cells. Overall, these data provide evidence that the hepatic microenvironment determines stemness and differentiation of PDECs, thereby substantially contributing to liver metastases of PDAC.

The hepatic microenvironment essentially determines tumor cell dormancy and metastatic outgrowth of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is often diagnosed when liver metastases already emerged. This study elucidated the impact of hepatic stromal cells on growth behavior of premalignant and malignant pancreatic ductal epithelial cells (PDECs). Liver sections of tumor-bearing KPC mice comprised micrometastases displaying low proliferation located in an unobtrusive hepatic microenvironment whereas macrometastases containing more proliferating cells were surrounded by hepatic myofibroblasts (HMFs). In an age-related syngeneic PDAC mouse model livers with signs of age-related inflammation exhibited significantly more proliferating disseminated tumor cells (DTCs) and micrometastases despite comparable primary tumor growth and DTC numbers. Hepatic stellate cells (HSC), representing a physiologic liver stroma, promoted an IL-8 mediated quiescence-associated phenotype (QAP) of PDECs in coculture. QAP included flattened cell morphology, Ki67-negativity and reduced proliferation, elevated senescence-associated β galactosidase activity and diminished p-Erk/p-p38-ratio. In contrast, proliferation of PDECs was enhanced by VEGF in the presence of HMF. Switching the micromilieu from HSC to HMF or blocking VEGF reversed QAP in PDECs. This study demonstrates how HSCs induce and maintain a reversible QAP in disseminated PDAC cells, while inflammatory HMFs foster QAP reversal and metastatic outgrowth. Overall, the importance of the hepatic microenvironment in induction and reversal of dormancy during PDAC metastasis is emphasized.

Epithelial IL-23R Signaling Licenses Protective IL-22 Responses in Intestinal Inflammation

A plethora of functional and genetic studies have suggested a key role for the IL-23 pathway in chronic intestinal inflammation. Currently, pathogenic actions of IL-23 have been ascribed to specific effects on immune cells. Herein, we unveil a protective role of IL-23R signaling. Mice deficient in IL-23R expression in intestinal epithelial cells (Il23R(ΔIEC)) have reduced Reg3b expression, show a disturbed colonic microflora with an expansion of flagellated bacteria, and succumb to DSS colitis. Surprisingly, Il23R(ΔIEC) mice show impaired mucosal IL-22 induction in response to IL-23. αThy-1 treatment significantly deteriorates colitis in Il23R(ΔIEC) animals, which can be rescued by IL-22 application. Importantly, exogenous Reg3b administration rescues DSS-treated Il23R(ΔIEC) mice by recruiting neutrophils as IL-22-producing cells, thereby restoring mucosal IL-22 levels. The study identifies a critical barrier-protective immune pathway that originates from, and is orchestrated by, IL-23R signaling in intestinal epithelial cells.

Segmental colonic length and mobility

INTRODUCTION

Locoregional variation in the human colon is important in surgical practice; the length and mobility of different colonic regions impacts on laparoscopic and endoscopic colorectal procedures. The aim of this study was to refine anatomical understanding of the colon in terms of segmental length and mobility.

METHODS

The colons of 35 cadavers were examined to determine lengths of caecum as well as ascending, transverse, descending and rectosigmoid colon, and to characterise colonic mobility at each location in terms of the mesenteric attachments. The presence of Jackson's membrane (a congenital peritoneal band of the right colon) was also documented.

RESULTS

The mean total colonic length was 131.2cm (standard deviation [SD]: 13.4cm). There was no correlation with height, age or sex; the best predictor of total colonic length was the length of the rectosigmoid segment. The mean height of the transverse mesocolon was 7.4cm (SD: 3.6cm) and that of the sigmoid mesocolon was 6.3cm (SD: 2.6cm). Two-thirds of the subjects had a mobile portion of the ascending colon and nearly one-third had a mobile descending colon. A mobile ascending colon was significantly more common in females. Jackson's membrane was present in 66% of the subjects.

CONCLUSIONS

This cadaveric study suggests that rectosigmoid length accounts for most of the variability in total colonic length. The significant proportion of colons with mobility of the ascending and descending segments prompts revision of the traditional anatomical teaching of these segments as fixed and retroperitoneal. Mobility of the ascending colon may account for the anecdotal finding that colonoscopy is more challenging in female patients. Jackson's membrane was identified in most colons.

Variation in colorectal cancer treatment and survival: a cohort study covering the East Anglia region

AIM

National guidelines for colorectal cancer management aim to optimize cancer outcomes irrespective of postcode. However, in order to ensure equal performance of cancer services, variation in outcome must be monitored and intelligently assessed. In this study, detailed regional cancer registry data were used to quantify and explore the reasons for variation in colorectal cancer outcomes at nine hospitals in East Anglia.

METHOD

We analysed data on colorectal cancers registered by the Eastern Cancer Registry and Information Centre (ECRIC) between 1999 and 2005. Tumours were grouped by site, in keeping with surgical resection. Multivariable Cox regression models were used to identify the effects of patient, disease and treatment variables on an individual's risk of death.

RESULTS

After adjusting for demographic, disease and treatment variables there were significant differences in survival among hospitals in emergency admissions with cancer of the right colon, in elective admissions with cancer of the left, sigmoid or recto-sigmoid colon and in emergency admissions with cancer of the rectum. There were also differences among hospitals in terms of perioperative death, nonsurgical management and numbers of nodes examined. For rectal cancers, rates of anterior resection compared with abdominoperineal excision differed, as well as the use of neoadjuvant radiotherapy.

CONCLUSION

Detailed analysis of demographic, disease and treatment factors are required when comparing the survival of individuals with colorectal cancer across hospitals. The results imply that cancer management was not consistent across East Anglia in 1999-2005 but the reasons for this are uncertain. Nevertheless, 5-year age-standardized survival with colon cancer in the Anglia Cancer Network region is currently among the best in the UK.

Binding kinetics of a fluorescently labeled bisphosphonate as a tool for dynamic monitoring of bone mineral deposition in vivo

Bone mineral deposition during the modeling of new bone and remodeling of old bone can be perturbed by several pathological conditions, including osteoporosis and skeletal metastases. A site-specific marker depicting the dynamics of bone mineral deposition would provide insight into skeletal disease location and severity, and prove useful in evaluating the efficacy of pharmacological interventions. Fluorescent labels may combine advantages of both radioisotope imaging and detailed microscopic analyses. The purpose of this study was to determine if the fluorescent bisphosphonate OsteoSense could detect localized changes in bone mineral deposition in established mouse models of accelerated bone loss (ovariectomy) (OVX) and anabolic bone gain resulting from parathyroid hormone (PTH) treatment. We hypothesized that the early rate of binding, as well as the total amount of bisphosphonate, which binds over long periods of time, could be useful in evaluating changes in bone metabolism. Evaluation of the kinetic uptake of bisphosphonates revealed a significant reduction in both the rate constant and plateau binding after OVX, whereas treatment with PTH resulted in a 36-fold increase in the bisphosphonate binding rate constant compared with untreated OVX controls. Localization of bisphosphonate binding revealed initial binding at sites of ossification adjacent to the growth plate and, to a lesser extent, along more distal trabecular and cortical elements. Micro-computed tomography (CT) was used to confirm that initial bisphosphonate binding is localized to sites of low tissue mineral density, associated with new bone mineral deposition. Our results suggest monitoring binding kinetics based on fluorescently labeled bisphosphonates represents a highly sensitive, site-specific method for monitoring changes in bone mineral deposition with the potential for translation into human applications in osteoporosis and bone metastatic processes and their treatment.

DSS-induced acute colitis in C57BL/6 mice is mitigated by sulforaphane pre-treatment

The Brassica-derived isothiocyanate sulforaphane (SFN) is known to induce factor erythroid 2-related factor 2 (Nrf2), a transcription factor centrally involved in chemoprevention. Furthermore, SFN exhibits anti-inflammatory properties in vitro and in vivo. However, little is known regarding the anti-inflammatory properties of SFN in severe inflammatory phenotypes. In the present study, we tested if pre-treatment with SFN protects mice from dextran sodium sulphate (DSS)-induced colitis. C57BL/6 mice received either phosphate-buffered saline (control) or 25 mg/kg body weight (BW) SFN per os for 7 days. Subsequently, acute colitis was induced by administering 4% DSS via drinking water for 5 days and BWs, stool consistency and faecal blood loss were recorded. Following endoscopic colonoscopy, mice were sacrificed, the organs excised and spleen weights and colon lengths measured. For histopathological analysis, distal colon samples were fixed in 4% para-formaldehyde, sectioned and stained with hematoxylin/eosin. Inflammatory biomarkers were also measured in distal colon. Treatment with SFN prior to colitis induction significantly minimised both BW loss and the disease activity index compared to control mice. Furthermore, colon lengths in SFN pre-treated mice were significantly longer than in control mice. Both macroscopic and microscopic analysis of the colon revealed attenuated inflammation in SFN pre-treated animals. mRNA analysis of distal colon samples confirmed reduced expression of inflammatory markers and increased expression of Nrf2-dependent genes in SFN pre-treated mice. Our results indicate that pre-treating mice with SFN confers protection from DSS-induced colitis. These protective effects were corroborated macroscopically, microscopically and at the molecular level.

Polo-like kinase 2, a novel ADAM17 signaling component, regulates tumor necrosis factor α ectodomain shedding

ADAM17 (a disintegrin and metalloprotease 17) controls pro- and anti-inflammatory signaling events by promoting ectodomain shedding of cytokine precursors and cytokine receptors. Despite the well documented substrate repertoire of ADAM17, little is known about regulatory mechanisms, leading to substrate recognition and catalytic activation. Here we report a direct interaction of the acidophilic kinase Polo-like kinase 2 (PLK2, also known as SNK) with the cytoplasmic portion of ADAM17 through the C-terminal noncatalytic region of PLK2 containing the Polo box domains. PLK2 activity leads to ADAM17 phosphorylation at serine 794, which represents a novel phosphorylation site. Activation of ADAM17 by PLK2 results in the release of pro-TNFα and TNF receptors from the cell surface, and pharmacological inhibition of PLK2 leads to down-regulation of LPS-induced ADAM17-mediated shedding on primary macrophages and dendritic cells. Importantly, PLK2 expression is up-regulated during inflammatory conditions increasing ADAM17-mediated proteolytic events. Our findings suggest a new role for PLK2 in the regulation of inflammatory diseases by modulating ADAM17 activity.

Metabolic signature of electrosurgical liver dissection

BACKGROUND AND AIMS

High frequency electrosurgery has a key role in the broadening application of liver surgery. Its molecular signature, i.e. the metabolites evolving from electrocauterization which may inhibit hepatic wound healing, have not been systematically studied.

METHODS

Human liver samples were thus obtained during surgery before and after electrosurgical dissection and subjected to a two-stage metabolomic screening experiment (discovery sample: N = 18, replication sample: N = 20) using gas chromatography/mass spectrometry.

RESULTS

In a set of 208 chemically defined metabolites, electrosurgical dissection lead to a distinct metabolic signature resulting in a separation in the first two dimensions of a principal components analysis. Six metabolites including glycolic acid, azelaic acid, 2-n-pentylfuran, dihydroactinidiolide, 2-butenal and n-pentanal were consistently increased after electrosurgery meeting the discovery (p<2.0 × 10(-4)) and the replication thresholds (p<3.5 × 10(-3)). Azelaic acid, a lipid peroxidation product from the fragmentation of abundant sn-2 linoleoyl residues, was most abundant and increased 8.1-fold after electrosurgical liver dissection (preplication = 1.6 × 10(-4)). The corresponding phospholipid hexadecyl azelaoyl glycerophosphocholine inhibited wound healing and tissue remodelling in scratch- and proliferation assays of hepatic stellate cells and cholangiocytes, and caused apoptosis dose-dependently in vitro, which may explain in part the tissue damage due to electrosurgery.

CONCLUSION

Hepatic electrosurgery generates a metabolic signature with characteristic lipid peroxidation products. Among these, azelaic acid shows a dose-dependent toxicity in liver cells and inhibits wound healing. These observations potentially pave the way for pharmacological intervention prior liver surgery to modify the metabolic response and prevent postoperative complications.

Management of young onset colorectal cancer: divergent practice in the East of England

AIM

According to the revised Bethesda Guidelines, colorectal cancer (CRC) occurring under age 50 years should be screened to exclude Lynch syndrome. However, in current practice in East Anglia, tumour screening is initiated only after genetics referral, reserved for those with a strong pedigree. This study aimed to determine how many patients with young-onset CRC undergo tumour screening in hospitals in East Anglia.

METHOD

A retrospective case notes review over 5 years in four hospitals was undertaken to determine what proportion of those with young-onset CRC underwent referral for tumour screening and to assess local practices in terms of patient counselling and management.

RESULTS

One hundred and twenty-two patients were included. There was an average yearly caseload of 6-9 patients per hospital. Documented family history was rare, as was counselling concerning metachronous and extra-colonic tumour risk and CRC risk in relatives. The rate of referral for genetic testing varied from 44% to 65%. Postoperative colonoscopic surveillance was inconsistent.

CONCLUSION

Many patients with young-onset CRC are managed as sporadic cancers, without Lynch syndrome having been excluded. This may have implications for survival of patients and any affected relatives. A streamlined management algorithm for tumour screening and genetics referral is recommended.

A Comparison Between the Short Term and Long Term Benefits of Screening for Abdominal Aortic Aneurysms from the Huntingdon Aneurysm Screening Programme

BACKGROUND

The UK Multicentre Aneurysm Screening Study (MASS) showed a 44% reduction in AAA-related mortality after 4 years and predicted an increased number of deaths prevented in the longer term. We aim to compare the 5 and 13 years benefit from aneurysm screening in the Huntingdon Aneurysm screening programme.

METHODS

Incidence and mortality of ruptured AAA (RAAA) after 5 and 13 years of screening in a population based aneurysm screening program.

RESULTS

Five years of screening resulted in a reduction in the incidence of RAAA of 49% (95% CI: 3-74%). Nine out of 11 ruptures in the invited group did not survive (mortality 82%; 95% CI: 48-98%) compared to 38 non-survivors from 51 ruptures in the control group (mortality 75%; 95% CI: 60-86%). Five years of screening resulted in an RAAA-related mortality reduction of 45% (95% CI: -15 to 74%). After 13 years of screening the incidence of RAAA was reduced by 73% (95% CI: 58-82%). Twenty-one out of 29 ruptures in the invited group did not survive (mortality 72%; 95% CI: 53-87%) compared to 64 non-survivors from 82 ruptures in the control group (mortality 78%; 95% CI: 68-86%). Thirteen years screening resulted in a reduction of mortality from RAAA of 75% (95% CI: 58-84%). The number needed to screen to prevent one death reduced from 1380 after 5 years to 505 after 13 years. The number of elective AAA operations needed to prevent one death reduced from 6 after 5 years to 4 after 13 years.

CONCLUSION

AAA screening becomes increasingly beneficial as screening continues over the longer term. Benefits continue to increase after screening has ceased.

Oxidative DNA damage and mutations induced by a polar photosensitizer, Ro19-8022

The oxidative DNA damage induced by the polar photosensitizer Ro19-8022 in the presence of light was studied and correlated with the associated mutagenicity. Both in isolated DNA and AS52 Chinese hamster ovary cells, photoexcited Ro19-8022 gave rise to a DNA damage profile that was similar to that caused by singlet oxygen: base modifications sensitive to the repair endonuclease Fpg protein, which according to high-performance liquid chromatography (HPLC) analysis were predominantly 8-hydroxyguanine (8-oxoG) residues, were generated in much higher yield than single-strand breaks, sites of base loss (AP sites) and oxidative pyrimidine modifications sensitive to endonuclease III. Fifty percent of the Fpg-sensitive modifications were repaired within 2 h. Under conditions that induced 10 Fpg-sensitive modifications per 10(6) bp (six 8-oxoG residues per 10(6) bp), approximately 60 mutations per 10(6) cells were induced in the gpt locus of the AS52 cells. A rather similar mutation frequency was observed when a plasmid carrying the gpt gene was exposed to Ro19-8022 plus light under cell-free conditions and subsequently replicated in bacteria. Sequence analysis revealed that GC-->TA and GC-->CG transversions accounted for 90% of the base substitutions. A significant generation of micronuclei was detectable in AS52 cells exposed to the photosensitizer plus light as well.

Influence of glutathione levels and heat-shock on the steady-state levels of oxidative DNA base modifications in mammalian cells

The effects of thiols, ascorbic acid and thermal stress on the basal (steady-state) levels of oxidative DNA base modifications were studied. In various types of untreated cultured mammalian cells, the levels of total glutathione were found to be inversely correlated with the levels of DNA base modifications sensitive to the repair endonuclease Fpg protein, which include 8-hydroxyguanine (8-oxoG). A depletion of glutathione by treatment with buthionine sulphoximine increased the steady-state level in AS52 Chinese hamster cells by approximately 50%. However, additional thiols in the culture medium did not reduce the level of Fpg-sensitive base modifications: 0-10 mM N-acetylcysteine had no effect, whereas cysteine ethylester even increased the oxidative DNA damage at concentrations >0.1 mM. Similarly, ascorbic acid (0-20 mM) failed to reduce the steady-state levels. When AS52 cells were grown at elevated temperature (41 degrees C), the steady-state level of the oxidative DNA modifications increased by 40%, in spite of a concomitant 1.6-fold increase of the cellular level of total glutathione. Depletion of glutathione at 41 degrees C nearly doubled the already elevated level of oxidative damage. A constitutive expression of the heat-shock protein Hsp27 in L929 mouse fibrosarcoma cells at 37 degrees C increased the glutathione level by 60%, but had little effect on the level of oxidative DNA damage.

DNA oxidation products determined with repair endonucleases in mammalian cells: types, basal levels and influence of cell proliferation

Purified repair endonucleases such as Fpg protein, endonuclease III and IV allow a very sensitive quantification of various types of oxidative DNA modifications in mammalian cells. By means of these assays, the numbers of base modifications sensitive to Fpg protein, which include 8-hydroxyguanine (8-oxoG), were determined to be less than 0.3 per 10(6) bp in several types of untreated cultured mammalian cells and human lymphocytes and less than 10 per 10(6) bp in mitochondrial DNA from rat and porcine liver. Oxidative 5,6-dihydropyrimidine derivatives sensitive to endonuclease III and sites of base loss sensitive to endonuclease IV or exonuclease III were much less frequent than Fpg-sensitive modifications. Here, we summarize our indications that all Fpg-sensitive modifications are recognized under the assay conditions and that on the other hand there is no artifactual generation of oxidative damage during the analysis. In addition, we show that the steady-state levels of Fpg-sensitive modifications in human lymphocytes and in two mammalian cell lines were higher in proliferating than in resting (confluent) cells. Only some of the Fpg-sensitive base modifications induced by various oxidants are 8-oxoG residues, as demonstrated for the damage under cell-free conditions. The percentage was dependent on the species ultimately responsible for the DNA damage and was approx. 40% in the case of hydroxyl radicals and peroxynitrite, 75% for type II photosensitizers (reacting via singlet oxygen) and only 20-30% in the case of type I photosensitizers such as riboflavin and acridine orange, which are assumed to react directly with the DNA.

Fanconi's anaemia cells have normal steady-state levels and repair of oxidative DNA base modifications sensitive to Fpg protein

Cells from Fanconi's anaemia (FA) patients are abnormally sensitive to oxygen. However, a distinct genetic defect in either the cellular defence against reactive oxygen species (ROS) or in their metabolic generation has not been identified to date. Recently, the gene for the human 8-hydroxyguanine (8-oxoG) glycosylase, which removes this oxidative base modification from the genome, has been localized on chromosome 3p25, i.e., in the same region as the FA complementation group D (FAD) gene. We therefore studied the removal of photosensitization-induced 8-oxoG residues from the DNA of FA cells, using Fpg protein, the bacterial 8-oxoG glycosylase, to quantify the lesions by alkaline elution. Similar repair kinetics (approx. 50% removal within 2 h) were observed in Epstein-Barr virus (EBV) immortalized lymphoid cells from FA complementation groups A, B, C and D and in control cells from normal donors, as well as in primary fetal lung fibroblasts not yet assigned to a specific complementation group. The susceptibility for the induction of oxidative DNA modifications by photosensitization was similar in all cells. In addition, the background (steady-state) levels of Fpg-sensitive oxidative DNA base modifications, which reflect the balance between generation and removal of the lesions, were similar in control and FA cells. It is concluded that both the generation and the overall removal of 8-oxoG residues in nuclear DNA is not impaired in FA cells.

Determination of steady-state levels of oxidative DNA base modifications in mammalian cells by means of repair endonucleases

The alkaline elution technique in combination with various repair endonucleases (Fpg protein, endonuclease III, exonuclease III, T4 endonuclease V) was used to quantify steady-state (background) levels of oxidative base modifications in various types of mammalian cells. In human lymphocytes the number of base modifications sensitive to Fpg protein, which include 8-hydroxyguanine, was 0.25 +/- 0.05 per 10(6) base pairs. Even lower levels (0.07 +/- 0.02 per 10(6) bp) were observed in HeLa cells. The numbers of sites sensitive to the other repair endonucleases were below the detection limit (0.05 per 10(6) bp). In a direct comparison, the background level of Fpg-sensitive modifications determined by alkaline elution was much lower than the background level of 8-hydroxydesoxyguanosine (8-oxodG) determined after enzymatic DNA hydrolysis by HPLC and electrochemical detection. However, the number of additional Fpg-sensitive modifications induced by a photosensitizer plus light was similar to the additional number of 8-oxodG residues determined by HPLC with electrochemical detection. This indicates that the enzyme assay does not systematically underestimate the number of lesions and points to an artefactual generation of 8-oxodG during DNA isolation and hydrolysis.