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West Nile virus (WNV) is a single-stranded positive-sense RNA virus (+ssRNA) belonging to the genus Orthoflavivirus . Its enzootic cycle involves mosquito vectors, mainly Culex , and wild birds as reservoir hosts, while mammals, such as humans and equids, are incidental dead-end hosts. It was first discovered in 1934 in Uganda, and since 1999 has been responsible for frequent outbreaks in humans, horses and wild birds, mostly in America and in Europe. Virus spread, as well as outbreak severity, can be influenced by many ecological factors, such as reservoir host availability, biodiversity, movements and competence, mosquito abundance, distribution and vector competence, by environmental factors such as temperature, land use and precipitation, as well as by virus genetic factors influencing virulence or transmission. Former studies have investigated WNV factors of virulence, but few have compared viral genetic determinants of pathogenicity in different host species, and even fewer have considered the genetic drivers of virus invasiveness and excretion in Culex vector. In this study, we characterized WNV genetic factors implicated in the difference in virulence observed in two lineage 1 WNV strains from the Mediterranean Basin, the first isolated during a significant outbreak reported in Israel in 1998, and the second from a milder outbreak in Italy in 2008. We used an innovative and powerful reverse genetic tool, e.g., ISA ( infectious subgenomic amplicons ) to generate chimeras between Israel 1998 and Italy 2008 strains, focusing on non-structural (NS) proteins and the 3'UTR non-coding region. We analyzed the replication of these chimeras and their progenitors in mammals, in BALB/cByJ mice, and vector competence in Culex (Cx.) pipiens mosquitoes. Results obtained in BALB/cByJ mice suggest a role of the NS2B/NS3/NS4B/NS5 genomic region in viral attenuation in mammals, while NS4B/NS5/3'UTR regions are important in Cx. pipiens infection and possibly in vector competence., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Fiacre, Nougairède, Migné, Bayet, Cochin, Dumarest, Helle, Exbrayat, Pagès, Vitour, Richardson, Failloux, Vazeille, Albina, Lecollinet and Gonzalez.)

B cell acute lymphoblastic leukemia (B-ALL) is a multistep disease characterized by the hierarchical acquisition of genetic alterations. However, the question of how a primary oncogene reprograms stem cell-like properties in committed B cells and leads to a preneoplastic population remains unclear. Here, we used the PAX5::ELN oncogenic model to demonstrate a causal link between the differentiation blockade, the self-renewal, and the emergence of preleukemic stem cells (pre-LSCs). We show that PAX5::ELN disrupts the differentiation of preleukemic cells by enforcing the IL7r/JAK-STAT pathway. This disruption is associated with the induction of rare and quiescent pre-LSCs that sustain the leukemia-initiating activity, as assessed using the H2B-GFP model. Integration of transcriptomic and chromatin accessibility data reveals that those quiescent pre-LSCs lose B cell identity and reactivate an immature molecular program, reminiscent of human B-ALL chemo-resistant cells. Finally, our transcriptional regulatory network reveals the transcription factor EGR1 as a strong candidate to control quiescence/resistance of PAX5::ELN pre-LSCs as well as of blasts from human B-ALL., (© 2023 Fregona et al.)

Our understanding of the hierarchical structure of acute leukemia has yet to be fully translated into therapeutic approaches. Indeed, chemotherapy still has to take into account the possibility that leukemia-initiating cells may have a distinct chemosensitivity profile compared to the bulk of the tumor, and therefore are spared by the current treatment, causing the relapse of the disease. Therefore, the identification of the cell-of-origin of leukemia remains a longstanding question and an exciting challenge in cancer research of the last few decades. With a particular focus on acute lymphoblastic leukemia, we present in this review the previous and current concepts exploring the phenotypic, genetic and functional heterogeneity in patients. We also discuss the benefits of using engineered mouse models to explore the early steps of leukemia development and to identify the biological mechanisms driving the emergence of leukemia-initiating cells. Finally, we describe the major prospects for the discovery of new therapeutic strategies that specifically target their aberrant stem cell-like functions.

The clinical effectiveness of carbapenem antibiotics such as meropenem is becoming increasingly compromised by the spread of both metallo-β-lactamase (MBL) and serine-β-lactamase (SBL) enzymes on mobile genetic elements, stimulating research to find new β-lactamase inhibitors to be used in conjunction with carbapenems and other β-lactam antibiotics. Herein, we describe our initial exploration of a novel chemical series of metallo-β-lactamase inhibitors, from concept to efficacy, in a survival model using an advanced tool compound (ANT431) in conjunction with meropenem.

Infections caused by carbapenem-resistant Enterobacteriaceae (CRE) are increasingly prevalent and have become a major worldwide threat to human health. Carbapenem resistance is driven primarily by the acquisition of β-lactamase enzymes, which are able to degrade carbapenem antibiotics (hence termed carbapenemases) and result in high levels of resistance and treatment failure. Clinically relevant carbapenemases include both serine β-lactamases (SBLs; e.g., KPC-2 and OXA-48) and metallo-β-lactamases (MBLs), such as NDM-1. MBL-producing strains are endemic within the community in many Asian countries, have successfully spread worldwide, and account for many significant CRE outbreaks. Recently approved combinations of β-lactam antibiotics with β-lactamase inhibitors are active only against SBL-producing pathogens. Therefore, new drugs that specifically target MBLs and which restore carbapenem efficacy against MBL-producing CRE pathogens are urgently needed. Here we report the discovery of a novel MBL inhibitor, ANT431, that can potentiate the activity of meropenem (MEM) against a broad range of MBL-producing CRE and restore its efficacy against an Escherichia coli NDM-1-producing strain in a murine thigh infection model. This is a strong starting point for a chemistry lead optimization program that could deliver a first-in-class MBL inhibitor-carbapenem combination. This would complement the existing weaponry against CRE and address an important and growing unmet medical need., (Copyright © 2018 American Society for Microbiology.)

Tyrosine-hydroxylase (TH)-like immunoreactivity was investigated in normal and oestrogenized rat anterior pituitaries in the light of recent studies showing a TH enzymatic activity in the gland and the presence of TH mRNA in endocrine cells. Sparse TH positive fibres, probably dopaminergic as assessed by the absence of dopamine-beta-hydroxylase (DBH) immunoreactivity, were detected in the anterior pituitary, but the detection of TH immunoreactivity in cells was unsuccessful.

Somatuline, in common with other SRIH analogues, exerts antiproliferative and antisecretory activities on various tumors. Our purpose was to test the effectiveness of a slow-release formulation of somatuline on lactotroph hyperplasia and PRL hypersecretion induced by estrogens (17 beta E2) in rats. Female rats were primed with 17 beta E2 for 6 weeks before receiving somatuline (2 mg/kg) intramuscular injections every 10 days for one month. The mean anterior pituitary weight was 11.22 +/- 0.32 mg (mean +/- SEM) in non-estrogenized rats, 29.62 +/- 1.63 mg in 17 beta E2-primed rats and 23.58 +/- 1.26 mg in 17 beta E2-primed somatuline-treated rats. Mean plasma PRL level was 5.63 +/- 0.97 ng/ml, 182.37 +/- 27.55 ng/ml and 113.89 +/- 15.07 ng/ml in the same groups respectively. Thus, the 17 beta E2-induced pituitary enlargement and hyperprolactinemia were 20% and 38% lower respectively when animals were treated with somatuline during the last month of estrogenization. The 17 beta E2-induced increase in PRL cell density was also reduced by somatuline treatment. We conclude that the slow-release formulation of somatuline impedes 17 beta E2-induced hyperprolactinemia and pituitary enlargement concomittantly, at least in part by acting on lactotroph proliferation.

The anterior pituitary is thought to be unable to synthesize dopamine (DA) except under experimental conditions where a tyrosine hydroxylase (TH) activity, the rate-limiting step of its synthesis, has been demonstrated. In this work, we tested whether the enzyme described as active under particular conditions comes from de novo TH gene transcription or from a pre-existing TH mRNA poorly translated or untranslated under physiological conditions. Therefore, we searched for the presence of TH mRNA in normal female rat pituitary using the polymerase chain reaction following reverse transcription (RT/PCR) and in situ hybridization (ISH). The neurointermediate lobe (NIL) of the hypophysis was used as negative tissue, since it is thought to be unable to synthesize TH. As expected, no ISH labelling could be seen in the neural lobe (NL). However, scarce labelled cells were found in the intermediate lobe (IL) confirming the positive results observed in the NIL by RT/PCR. The anterior lobe (AL) also presented TH mRNA by PCR and ISH. The TH gene expression in sparse cells of the AL is discussed in regard to the ability of the AL to synthesize DA under particular conditions from a pre-existing mRNA.

The amounts of prostaglandin E2 formed in vitro by the median eminences of adult male rats were greater than those produced by the median eminences of immature, 22 day-old rats. However, the amount of leukotriene C4 produced by the adult rat median eminences was lower than that produced by the immature rat median eminences. Analysis of the prostaglandin E2 binding parameters of hypothalamic P2 membrane fractions indicates that there are two binding components, one high affinity (RH) and one low affinity (RL) in both adult and immature rats. The maximal binding capacity of RH from adult rat membranes was significantly lower than that of immature rat membranes, correlating with greater prostaglandin E2 production by the adult rat median eminence. Only one leukotriene C4 binding site was detected in both adult and immature rat membranes. Exogenous prostaglandin E2 and leukotriene C4 both stimulated, the release of luteinizing hormone-releasing hormone to the same extent from both the adult and immature median eminences.

Abstract Prostaglandin E(2), (PGE(2)) is involved in the luteinizing hormone-releasing hormone-stimulated luteinizing hormone surge in female rats and may act via specific membrane receptors. The following studies were performed to determine whether there were any changes in the hypothalamic PGE(2) binding and/or PGE(2) content which were specific to proestrus and not to the rest of the estrous cycle. Groups of female Wistar rats were sacrificed at 3-h intervals throughout the estrous cycle to determine both the circadian and circaestral changes in the hypothalamic PGE(2) content and [(3)H]PGE(2) binding. The hypothalamic PGE(2) content was maximal at 1700 h on each of the 4 consecutive days of the estrous cycle but was independent of the stage of the cycle. [(3)H]PGE(2) binding also displayed a circadian rhythm; the lowest binding occurred near the circadian peak of PGE(2), suggesting that the PGE(2) binding sites were occupied by endogenous PGE(2). Since such circadian rhythms were not observed in the hypothalamus of male rats, they may be under the control of ovarian steroids. Also, since PGE(2) binding and the PGE(2) content both exhibit a diurnal pattern independent of the day of the cycle, there may be changes in the PGE(2) receptor-mediated process coupled to an adenylyl cyclase which could explain the luteinizing hormone surge in proestrus.

We show that the effect of prostaglandin (PG) E2 on luteinizing hormone-releasing hormone (LHRH) release involves a receptor-mediated process coupled to an adenylyl cyclase system. The adenylyl cyclase activity in rat hypothalamus synaptic membrane preparations was stimulated by PGE2 and this stimulation was directly related to the presence of guanine nucleotide (GTP). PGE2 specifically bound to P2 membranes from rat and porcine hypothalami with similar characteristics. Computer-fitted saturation curves provided evidence for two binding components which may be two states of the same receptor (RH and RL). Experiments with Gpp(NH)p, a non-metabolizable analogue of GTP, suggested the interconversion of RH and RL. These results may reflect different states of the ternary complex (hormone-receptor-guanine binding protein). Magnesium (Mg2+) can modify the RH and RL binding parameters, but seems to act directly on the PGE2 receptor site.