Three-dimensional identification of microvascular pathology and neurovascular inflammation in severe white matter hyperintensity: a case report

White matter hyperintensities (WMH) are the most prevalent markers of cerebral small vessel disease (SVD), which is the major vascular risk factor for dementia. Microvascular pathology and neuroinflammation are suggested to drive the transition from normal-appearing white matter (NAWM) to WMH, particularly in individuals with hypertension. However, current imaging techniques cannot capture ongoing NAWM changes. The transition from NAWM into WMH is a continuous process, yet white matter lesions are often examined dichotomously, which may explain their underlying heterogeneity. Therefore, we examined microvascular and neurovascular inflammation pathology in NAWM and severe WMH three-dimensionally, along with gradual magnetic resonance imaging (MRI) fluid-attenuated inversion recovery (FLAIR) signal (sub-)segmentation. In WMH, the vascular network exhibited reduced length and complexity compared to NAWM. Neuroinflammation was more severe in WMH. Vascular inflammation was more pronounced in NAWM, suggesting its potential significance in converting NAWM into WMH. Moreover, the (sub-)segmentation of FLAIR signal displayed varying degrees of vascular pathology, particularly within WMH regions. These findings highlight the intricate interplay between microvascular pathology and neuroinflammation in the transition from NAWM to WMH. Further examination of neurovascular inflammation across MRI-visible alterations could aid deepening our understanding on WMH conversion, and therewith how to improve the prognosis of SVD.

A walk in the PARC: developing and implementing 21st century chemical risk assessment in Europe

Current approaches for the assessment of environmental and human health risks due to exposure to chemical substances have served their purpose reasonably well. Nevertheless, the systems in place for different uses of chemicals are faced with various challenges, ranging from a growing number of chemicals to changes in the types of chemicals and materials produced. This has triggered global awareness of the need for a paradigm shift, which in turn has led to the publication of new concepts for chemical risk assessment and explorations of how to translate these concepts into pragmatic approaches. As a result, next-generation risk assessment (NGRA) is generally seen as the way forward. However, incorporating new scientific insights and innovative approaches into hazard and exposure assessments in such a way that regulatory needs are adequately met has appeared to be challenging. The European Partnership for the Assessment of Risks from Chemicals (PARC) has been designed to address various challenges associated with innovating chemical risk assessment. Its overall goal is to consolidate and strengthen the European research and innovation capacity for chemical risk assessment to protect human health and the environment. With around 200 participating organisations from all over Europe, including three European agencies, and a total budget of over 400 million euro, PARC is one of the largest projects of its kind. It has a duration of seven years and is coordinated by ANSES, the French Agency for Food, Environmental and Occupational Health & Safety.

Atomoxetine effects on attentional bias to drug-related cues in cocaine dependent individuals

RATIONALE

Biased attention towards drug-related cues and reduced inhibitory control over the regulation of drug-intake characterize drug addiction. The noradrenaline system has been critically implicated in both attentional and response inhibitory processes and is directly affected by drugs such as cocaine.

OBJECTIVES

We examined the potentially beneficial effects of the noradrenaline reuptake inhibitor atomoxetine in improving cognitive control during two tasks that used cocaine- and non-cocaine-related stimuli.

METHODS

A double-blind, placebo-controlled, and cross-over psycho-pharmacological design was employed. A single oral dose of atomoxetine (40 mg) was administered to 28 cocaine-dependent individuals (CDIs) and 28 healthy controls. All participants performed a pictorial attentional bias task involving both cocaine- and non-cocaine-related pictures as well as a verbal go/no-go task composed of cocaine- and food-related words.

RESULTS

As expected, CDIs showed attentional bias to cocaine-related cues whilst controls did not. More importantly, however, atomoxetine, relative to placebo, significantly attenuated attentional bias in CDIs (F ₂₆ = 6.73, P = 0.01). During the go/no-go task, there was a treatment × trial × group interaction, although this finding only showed a trend towards statistical significance (F ₂₆ = 3.38, P = 0.07).

CONCLUSIONS

Our findings suggest that atomoxetine reduces attentional bias to drug-related cues in CDIs. This may result from atomoxetine's modulation of the balance between tonic/phasic activity in the locus coeruleus and the possibly parallel enhancement of noradrenergic neurotransmission within the prefrontal cortex. Studying how cognitive enhancers such as atomoxetine influence key neurocognitive indices in cocaine addiction may help to develop reliable biomarkers for patient stratification in future clinical trials.

Detection of the mechanism of immunotoxicity of cyclosporine A in murine in vitro and in vivo models

Transcriptomics in combination with in vitro cell systems is a powerful approach to unravel modes of action of toxicants. An important question is to which extent the modes of action as revealed by transcriptomics depend on cell type, species and study type (in vitro or in vivo). To acquire more insight into this, we assessed the transcriptomic effects of the immunosuppressive drug cyclosporine A (CsA) upon 6 h of exposure of the mouse cytotoxic T cell line CTLL-2, the thymoma EL-4 and primary splenocytes and compared these to the effects in spleens of mice orally treated with CsA for 7 days. EL-4 and CTLL-2 cells showed the highest similarities in response. CsA affected many genes in primary splenocytes that were not affected in EL-4 or CTLL-2. Pathway analysis demonstrated that CsA upregulated the unfolded protein response, endoplasmic reticulum stress and NRF2 activation in EL-4 cells, CTLL-2 cells and primary mouse splenocytes but not in mouse spleen in vivo. As expected, CsA downregulated cell cycle and immune response in splenocytes in vitro, spleens in vivo as well as CTLL-2 in vitro. Genes up- and downregulated in human Jurkat, HepG2 and renal proximal tubular cells were similarly affected in CTLL-2, EL-4 and primary splenocytes in vitro. In conclusion, of the models tested in this study, the known mechanism of immunotoxicity of CsA is best represented in the mouse cytotoxic T cell line CTLL-2. This is likely due to the fact that this cell line is cultured in the presence of a T cell activation stimulant (IL-2) making it more suitable to detect inhibitory effects on T cell activation.

Benzo[a]pyrene-induced transcriptomic responses in primary hepatocytes and in vivo liver: toxicokinetics is essential for in vivo-in vitro comparisons

The traditional 2-year cancer bioassay needs replacement by more cost-effective and predictive tests. The use of toxicogenomics in an in vitro system may provide a more high-throughput method to investigate early alterations induced by carcinogens. Recently, the differential gene expression response in wild-type and cancer-prone Xpa (-/-) p53 (+/-) primary mouse hepatocytes after exposure to benzo[a]pyrene (B[a]P) revealed downregulation of cancer-related pathways in Xpa (-/-) p53 (+/-) hepatocytes only. Here, we investigated pathway regulation upon in vivo B[a]P exposure of wild-type and Xpa (-/-) p53 (+/-) mice. In vivo transcriptomics analysis revealed a limited gene expression response in mouse livers, but with a significant induction of DNA replication and apoptotic/anti-apoptotic cellular responses in Xpa (-/-) p53 (+/-) livers only. In order to be able to make a meaningful in vivo-in vitro comparison we estimated internal in vivo B[a]P concentrations using DNA adduct levels and physiologically based kinetic modeling. Based on these results, the in vitro concentration that corresponded best with the internal in vivo dose was chosen. Comparison of in vivo and in vitro data demonstrated similarities in transcriptomics response: xenobiotic metabolism, lipid metabolism and oxidative stress. However, we were unable to detect cancer-related pathways in either wild-type or Xpa (-/-) p53 (+/-) exposed livers, which were previously found to be induced by B[a]P in Xpa (-/-) p53 (+/-) primary hepatocytes. In conclusion, we showed parallels in gene expression responses between livers and primary hepatocytes upon exposure to equivalent concentrations of B[a]P. Furthermore, we recommend considering toxicokinetics when modeling a complex in vivo endpoint with in vitro models.

Duplication and transposition of the NF1 pseudogene regions on chromosomes 2, 14, and 22

Numerous NF1 pseudogenes have been identified in the human genome. Those in 2q21, 14q11, and 22q11 form a subset with a similar genomic organization and a high sequence homology. We have studied, by polymerase chain reaction and fluorescence in situ hybridization, the extent of homology of the regions surrounding these NF1 pseudogenes. Our analyses have demonstrated that a fragment of at least 640 kb is homologous between the three regions. Based on previous studies and these new findings, we propose a model for the spreading of the NF1 pseudogene-containing regions. A fragment of approximately 640 kb was first duplicated in chromosome region 2q21 and transposed to 14q11. Subsequently, this fragment was duplicated in 14q11 and transposed to 22q11. A part of the 640-kb fragment in 14q11, with a length of about 430 kb, was further duplicated to a variable extent in 14q11. In addition, we have identified sequences that may facilitate the duplication and transposition of the 640-kb and 430-kb fragments.

Microsatellite instability and promoter methylation as possible causes of NF1 gene inactivation in neurofibromas

Neurofibromatosis type 1 (NF1) is a frequent hereditary disorder. One of the characteristic features of this disease is the development of neurofibromas. Since the NF1 gene is supposed to be a tumour suppressor gene, these neurofibromas should develop upon inactivation of both NF1 alleles. So far, mutation and deletion have been found to be involved in NF1 gene inactivation. However, these inactivating mechanisms explain the development of only a limited fraction of analysed neurofibromas. In this study, we investigated microsatellite instability (MSI) and promoter methylation as potential contributors to NF1 gene inactivation. As site-specific methylation in the NF1 promoter inhibits binding of transcription factors Sp1 and CREB, we studied the methylation status of their binding sites in particular. We analysed 20 neurofibromas and three neurofibrosarcomas, but did not find evidence for microsatellite instability or NF1 promoter methylation in any of the tumours. Thus, our data suggest that both microsatellite instability and promoter methylation are unlikely to be the major causes of NF1 gene inactivation in these tumours.

Mechanism of spreading of the highly related neurofibromatosis type 1 (NF1) pseudogenes on chromosomes 2, 14 and 22

Neurofibromatosis type 1 (NF1) is a frequent hereditary disorder that involves tissues derived from the embryonic neural crest. Besides the functional gene on chromosome arm 17q, NF1-related sequences (pseudogenes) are present on a number of chromosomes including 2, 12, 14, 15, 18, 21, and 22. We elucidated the complete nucleotide sequence of the NF1 pseudogene on chromosome 22. Only the middle part of the functional gene but not exons 21-27a, encoding the functionally important GAP-related domain of the NF1 protein, is presented in this pseudogene. In addition to the two known NF1 pseudogenes on chromosome 14 we identified two novel variants. A phylogenetic tree was constructed, from which we concluded that the NF1 pseudogenes on chromosomes 2, 14, and 22 are closely related to each other. Clones containing one of these pseudogenes cross-hybridised with the other pseudogenes in this subset, but did not reveal any in situ hybridisation with the functional NF1 gene or with NF1 pseudogenes on other chromosomes. This suggests that their hybridisation specificity is mainly determined by homologous sequences flanking the pseudogenes. Strong support for this concept was obtained by sequence analysis of the flanking regions, which revealed more than 95% homology. We hypothesise that during evolution this subset of NF1 pseudogenes initially arose by duplication and transposition of the middle part of the functional NF1 gene to chromosome 2. Subsequently, a much larger fragment, including flanking sequences, was duplicated and gave rise to the current NF1 pseudogene copies on chromosomes 14 and 22.

Homeobox gene Prx3 expression in rodent brain and extraneural tissues

Different cDNA clones encoding a rat homeobox gene and the mouse homologue OG-12 were cloned from adult rat brain and mouse embryo mRNA, respectively. The predicted amino acid sequences of the proteins belong to the paired-related subfamily of homeodomain proteins (Prx homeodomains). Hence, the gene was named Prx3 and the mouse and rat genes are indicated as mPrx3 and rPrx3, respectively. In the mouse as well as in the rat, the predicted Prx3 proteins share the homeodomain but have three different N termini, a 12-aa residue variation in the C terminus, and contain a 14-aa residue motif common to a subset of homeodomain proteins, termed the "aristaless domain." Genetic mapping of Prx3 in the mouse placed this gene on chromosome 3. In situ hybridization on whole mount 12.5-day-old mouse embryos and sections of rat embryos at 14.5 and 16.5 days postcoitum revealed marked neural expression in discrete regions in the lateral and medial geniculate complex, superior and inferior colliculus, the superficial gray layer of the superior colliculus, pontine reticular formation, and inferior olive. In rat and mouse embryos, nonneuronal structures around the oral cavity and in hip and shoulder regions also expressed the Prx3 gene. In the adult rat brain, Prx3 gene expression was restricted to thalamic, tectal, and brainstem structures that include relay nuclei of the visual and auditory systems as well as other ascending systems conveying somatosensory information. Prx3 may have a role in specifying neural systems involved in processing somatosensory information, as well as in face and body structure formation.

Rhodoquinone is synthesized de novo by Fasciola hepatica

Most adult parasitic helminths have an anaerobic energy metabolism in which fumarate is reduced to succinate by fumarate reductase. Rhodoquinone (RQ) is an essential component of the electron transport associated with this fumarate reduction, whereas ubiquinone (UQ) is used in the aerobic energy metabolism of parasites. Not known yet, however, is the RQ and UQ composition during the entire life cycle nor the origin of RQ in parasitic helminths. This report demonstrates the essential function of RQ in anaerobic energy metabolism during the entire life cycle of Fasciola hepatica, as the amount of RQ present reflected the importance of fumarate reduction in various stages. We also studied the origin of RQ, as earlier studies on the protozoan Euglena gracilis suggested that RQ is synthesized from UQ. Therefore, in parasitic helminths RQ might be synthesized by modification of UQ obtained from the host. However, we demonstrated that in F. hepatica adults RQ was not produced by modification of UQ obtained from the host but that RQ was synthesized de novo, as (i) the chain-length of the quinones of F. hepatica adults was not related to the chain length of the quinone of the host, (ii) despite many attempts we could never detect any in vitro conversion of UQ9 into RQ9 or into UQ10, neither by intact adult flukes nor by homogenates of F. hepatica adults and (iii) F. hepatica adults used mevalonate as precursor for the synthesis of RQ. We also showed that the rate of quinone synthesis in F. hepatica adults was comparable to that in the free-living nematode Caenorhabditis elegans. These results prompted the suggestion that RQ is synthesized via a pathway nearly identical to that of UQ biosynthesis: possibly only the last reaction differs.