Jérôme Leprince

Oxytocin (OT) is a peptide hormone promoting social interactions and reducing anxiety, both core behaviors altered in autism spectrum disorder (ASD)1. Current approaches to boost OT signaling in the brain have, however, had little success2. OT is carried in the blood by immunoglobulin G (IgG), suggesting a new therapeutic target for boosting OT, but its antigenic origin and capacity to influence central OT signaling are unknown3. Here we show that Ligilactobacillus salivarius (LS) 48 kDa enolase (ENO) displays a species-unique structural homology with OT underlying both its OT-like antigenic and ligand properties. While LS ENO was naturally present in human plasma, correlating between members of the same family, its levels were reduced in children of both sexes diagnosed with ASD, starting from the disorder’s onset. Using mice, we show that LS ENO was present in both plasma and brain, and that its levels were lower in BTBR mice, a model of ASD. We further show that LS ENO immunization induced OT-binding IgG, which enhanced OT stability in plasma, increased OT receptor activation, and facilitated OT entry into the brain. Accordingly, LS ENO-immunization boosted OT concentrations in the brain and improved social, repetitive and anxiety-like behavior in BTBR mice. Thus, LS ENO is an OT-like protein which enhances OT signaling and boosts brain OT levels via production of OT-carrier IgG. Reduced plasma levels of LS ENO may, hence, contribute to ASD pathophysiology.

Amphibian skin secretions constitute a rich source of bioactive peptides whose structural diversity is often amplified by post-translational modifications. In this study, we report the discovery and comprehensive characterization of a post-translational modification that has not been described previously in peptides from a vertebrate. Tryptophyllins are a heterogeneous group of short, tryptophan- and proline-containing peptides widely distributed among anuran species and are thought to contribute to skin protection against oxidative and UV-induced damage. Two peptides derived from tryptophyllins, termed tryptolinophyllins, were isolated from skin secretions of the giant gladiator treefrog Boana boans. They are distinguished by the presence of an N-terminal (S)-tryptoline-3-carboxylic acid (Tpi) residue, resulting from the conversion of tryptophan into a tetrahydro-β-carboline moiety via a Pictet–Spengler-type reaction. The primary structures of two tryptolinophyllins were elucidated by high-resolution tandem mass spectrometry and multidimensional NMR spectroscopy, and confirmed through total chemical synthesis of the corresponding diastereoisomers. To our knowledge, this represents the first confirmed tetrahydro-β-carboline post-translational modification in a vertebrate peptide, revealing an unexpected level of chemical innovation in amphibian peptide biosynthesis. Computational analyses of electronic structure identified the Tpi residue as the preferred locus for electron transfer, suggesting a potential role in redox chemistry. ABTS radical-cation scavenging assays demonstrated that the antioxidant activity of the tryptolinophyllins was reduced compared with unmodified tryptophyllins, highlighting a nuanced relationship between post-translational chemical diversification and functional output. Together, these findings expand the known repertoire of naturally occurring peptide modifications in vertebrates and underscore the exceptional chemical plasticity of amphibian skin secretions.

Enterobacterial caseinolytic protease B (ClpB) plays a key role in the development of activity-based anorexia (ABA) in mice due to its mimetism with α-melanocyte-stimulating hormone (α-MSH), an anorexigenic peptide. ClpB immunization stimulates α-MSH cross-reactive IgG influencing ABA outcome depending on IgG binding properties. As such, low affinity IgG blocks melanocortin type 4 receptor (MC4R) activation by ClpB and α-MSH, protecting against ABA. In contrast, higher affinity IgG was associated with increased plasma ClpB and α-MSH, and ABA aggravation. However, it remained unknown if such IgG may influence MC4R signaling and if ClpB and IgG may reach the brain, questions that were addressed in this study. We report here that higher affinity IgG efficiently protects α-MSH from degradation in plasma and enhances MC4R activation by both α-MSH and ClpB. We also reveal that ClpB is present in the brain with higher levels in the hypothalamus. Brain ClpB levels were further increased in mice developing higher affinity IgG who had also increased hypothalamic levels of both ClpB-binding IgG and α-MSH. Opposite effects were observed in ABA mice developing low affinity IgG characterized by the preferential IgG binding to the α-MSH-like epitope of ClpB. We also show that ClpB binds to MC1R, MC3R, MC4R and MC5R. Thus, these results reveal that both ClpB protein and ClpB-binding IgG can reach the brain depending on IgG properties modulating ClpB and α-MSH anorexigenic signaling. These data further clarify the putative role of Enterobacterial ClpB and of ClpB- and α-MSH-binding IgG in the pathophysiology of anorexia nervosa.

Methyl-coenzyme M reductase (MCR) is a crucial enzyme for methanogenesis and harbors several unusual post-translational modifications. Recent studies have identified glutamine C-methyltransferase (QCMT), as a B₁₂-dependent radical SAM enzyme responsible for methylating a glutamine residue within the MCR active site. B₁₂-dependent radical SAM enzymes have the remarkable ability to alkylate unactivated Csp²- and Csp³-atoms in a stereoselective manner. However, the factors influencing the stereo-selectivity and catalytic properties of this emerging superfamily of enzymes remain poorly understood. Here, we report the mechanistic, structural, and biochemical investigation of several QCMTs. Our findings reveal significant differences among them, notably in their ability to bind cobalamin. In addition, our data support that Cα H-atom abstraction and methyl transfer are not concerted but rather independent processes that require motion within the enzyme's active site. We also demonstrate that QCMT catalyzes novel reactions, including the formation of unnatural C-methylated residues, peptide epimerization, reversible H-atom abstraction, and the direct conversion of glycine into D-alanine. Overall, our data are consistent with QCMT being a unique and versatile biocatalyst allowing for the installation of unnatural post-translational modifications and provide a structural and biochemical rationale for the control of the stereochemistry by B₁₂-dependent radical SAM enzymes.

Melatonin is reported to exert two types of actions: those based on its interaction with cognate receptors (characterized by very high affinities—1 nM and below), and those mediated by unknown targets (characterized by high concentrations—100 µM and above). Whereas receptor-mediated activities are known to regulate circadian rhythm, the high-dose effects are reported to be independent of these receptors and to produce literally dozens of beneficial effects in almost all human diseases, including cancer, neurodegenerative disorders, viral infections, obesity and many others. In the present opinion paper, we discuss this extensive set of claims and place them in perspective with a sum of evidence that collectively challenges the validity of these alleged beneficial effects.

Methyl-coenzyme M reductase (MCR) is a crucial enzyme for methanogenesis and harbors several unusual post-translational modifications. Recent studies have identified glutamine C-methyltransferase (QCMT), as a B ₁₂ -dependent radical SAM enzyme responsible for methylating a glutamine residue within the MCR active site. B ₁₂ -dependent radical SAM enzymes have the remarkable ability to alkylate unactivated C sp ² - and Csp ³ -atoms in a stereoselective manner. However, the factors influencing the stereo-selectivity and catalytic properties of this emerging superfamily of enzymes remain poorly understood. In this study, we report the mechanistic, structural, and biochemical investigation of several QCMTs. Our findings reveal significant differences among them, notably in their ability to bind cobalamin. In addition, our data support that Cα H-atom abstraction and methyl transfer are not concerted but rather independent processes that require motion within the enzyme’s active site. We also demonstrate that QCMT can catalyze novel reactions, including the formation of unnatural C -methylated residues, peptide epimerization, reversible H-atom abstraction, and the direct conversion of glycine into d -alanine. Overall, our data are consistent with QCMT being a unique and versatile biocatalyst allowing for the installation of unnatural post-translational modifications and provide a structural and biochemical rationale for the control of the stereochemistry by B ₁₂ -dependent radical SAM enzymes.

Breast cancer remains one of the leading causes of cancer-related mortality among women worldwide. Although cisplatin is widely used in chemotherapy, its clinical efficacy is often limited by adverse effects and resistance. Thus, natural bioactive compounds are gaining attention as complementary therapeutic agents. This study aimed to evaluate the anti-tumor effects of Annona muricata leaf extract on murine breast cancer 4T1 cells, used alone or in combination with cisplatin. Cisplatin induced intrinsic apoptosis through mitochondrial membrane disruption, up-regulation of the Bax gene and inhibition of the PI3K/AKT/mTOR signaling pathway. Cisplatin also promoted hypoxia by HIF1α gene expression, inflammation by TNFα and IL-6 gene expression, and induced cell cycle arrest at the sub-G1 phase by down-regulation of cyclin D1 and cyclin E1 genes. Annona muricata leaf extract triggered autophagy-mediated 4T1 cell death through mainly mTOR down-regulation and increased expression of Beclin1 and LC3 genes. It also induced cell cycle arrest at sub-G1 and S phases in a concentration- and time-dependent manner. When, combined with cisplatin, Annona muricata extract shifts the cell death pathway from intrinsic apoptosis toward autophagy by reduced caspase-3 gene expression and activity and enhanced LC3-I to LC3-II conversion. Moreover, Annona muricata extract attenuated cisplatin-induced inflammation by inhibiting TNFα and IL-6 gene expression and reinforced cell cycle arrest through suppression of the cyclin D1 gene. In conclusion, our results suggest that Annona muricata leaf extract exerts significant anti-tumor activity in breast cancer cells and may enhance cisplatin efficacy by shifting the signaling pathway from intrinsic apoptosis toward autophagy, and attenuating inflammation-related effects, supporting its potential use as a complementary therapeutic strategy.

The Concise Guide to Pharmacology 2025/26 marks the seventh edition in this series of biennial publications in the British Journal of Pharmacology. Presented in landscape format, the guide provides a comparative overview of the pharmacology of drug target families. The concise nature of the Concise Guide refers to the style of presentation, being clear, accessible, and well‐structured, rather than the scope of the content, which spans approximately 500 pages. The Concise Guide summarises the key pharmacological properties of around 1900 human drug targets, and nearly 7000 interactions, involving around 4400 ligands. While the content is a substantially condensed version of the more detailed information and links available at the www.guidetopharmacology.org website, the printed guide serves as a permanent, citable, point‐in‐time record, that remains stable despite ongoing updates to the online database. The full contents of this publication can be found at https://bpspubs.onlinelibrary.wiley.com/doi/10.1111/bph.70230 . The Concise Guides provide expert‐curated recommendations of ‘Gold Standard’ selective pharmacological tools, available either commercially or as donations, which enable the identification of individual drug targets or families of drug targets. While the Concise Guide offers a more streamlined overview, more comprehensive information, including detailed pharmacological profiles and links to multiple online databases, is available through the Guide to Pharmacology website. The 2025/26 edition of the Concise Guide is based on material current as of mid‐2025, and supersedes all previous editions, including the 2023/24 Guide, and earlier Guides to Receptors and Channels. It is produced in close conjunction with the Nomenclature and Standards Committee of the International Union of Basic and Clinical Pharmacology (NC‐IUPHAR), and as such provides official IUPHAR classification and nomenclature for human drug targets, where applicable. G protein‐coupled receptors are one of the six major pharmacological targets into which the Guide is divided, with the others being: ion channels, nuclear hormone receptors, catalytic receptors, enzymes and transporters. Each section includes nomenclature guidance, concise summaries, information of the best available pharmacological tools, key references, and suggestions for further reading.

Parkinson's disease (PD) is a neurodegenerative disorder for which existing therapies are primarily palliative and lack curative efficacy. Octadecaneuropeptide (ODN) is a peptide exclusively produced by astrocytes that protects neurons against oxidative cell damage and apoptosis in in vitro and in vivo models of PD. However, ODN cannot cross the blood-brain barrier (BBB) and requires intracerebroventricular injection to reach the brain, presenting a significant challenge for therapeutic application. This study investigates the neuroprotective efficacy of cyclo(1-8)OP, an ODN analog, delivered via the intranasal (IN) route to bypass the BBB in an in vivo model of PD. Male C57BL/6J mice were used for the experiments and divided into four groups: sham, MPTP- (20 mg/kg body weight, intraperitoneal), cyclo(1-8)OP- (10 ng/10 µL, IN), and MPTP + cyclo(1-8)OP-treated animals. On day 0 (D0), animals received three intraperitoneal injections of 100 µL MPTP solution at 2-h intervals (MPTP- and MPTP + cyclo(1-8)OP-treated mice) or saline solution (sham and cyclo(1-8)OP-treated mice). One hour after the final injection, 10 µL of IN instillation of cyclo(1-8)OP (cyclo(1-8)OP- and MPTP + cyclo(1-8)OP-treated mice) or IN saline solution (sham and MPTP-treated mice) was administered. On D7, a cylinder test was performed to assess motor function. Subsequently, animals were sacrificed, and the striatum was removed and analyzed by RT-qPCR to assess caspase-3 gene expression. Tissue samples were also used to measure antioxidant enzyme activities, reactive oxygen species (ROS), malondialdehyde (MDA), and carbonylated protein abundance. A single IN dose of 10 ng cyclo(1-8)OP, administered 1 h after the final MPTP dose, prevented neurotoxicity in the striatum 7 days post-treatment. Cyclo(1-8)OP-mediated neuroprotection was associated with strong inhibition of caspase-3 expression induced by MPTP in the striatum. Additionally, cyclo(1-8)OP restored the activities of antioxidant enzymes, preventing the accumulation of ROS, lipid peroxidation products, and protein carbonylation in the striatum.

Parkinson's disease (PD) is a neurodegenerative disorder for which existing therapies are primarily palliative and lack curative efficacy. Octadecaneuropeptide (ODN) is a peptide exclusively produced by astrocytes that protects neurons against oxidative cell damage and apoptosis in in vitro and in vivo models of PD. However, ODN cannot cross the blood-brain barrier (BBB) and requires intracerebroventricular injection to reach the brain, presenting a significant challenge for therapeutic application. This study investigates the neuroprotective efficacy of cyclo(1-8)OP, an ODN analog, delivered via the intranasal (IN) route to bypass the BBB in an in vivo model of PD. Male C57BL/6J mice were used for the experiments and divided into four groups: sham, MPTP- (20 mg/kg body weight, intraperitoneal), cyclo(1-8)OP- (10 ng/10 µL, IN), and MPTP + cyclo(1-8)OP-treated animals. On day 0 (D0), animals received three intraperitoneal injections of 100 µL MPTP solution at 2-h intervals (MPTP- and MPTP + cyclo(1-8)OP-treated mice) or saline solution (sham and cyclo(1-8)OP-treated mice). One hour after the final injection, 10 µL of IN instillation of cyclo(1-8)OP (cyclo(1-8)OP- and MPTP + cyclo(1-8)OP-treated mice) or IN saline solution (sham and MPTP-treated mice) was administered. On D7, a cylinder test was performed to assess motor function. Subsequently, animals were sacrificed, and the striatum was removed and analyzed by RT-qPCR to assess caspase-3 gene expression. Tissue samples were also used to measure antioxidant enzyme activities, reactive oxygen species (ROS), malondialdehyde (MDA), and carbonylated protein abundance. A single IN dose of 10 ng cyclo(1-8)OP, administered 1 h after the final MPTP dose, prevented neurotoxicity in the striatum 7 days post-treatment. Cyclo(1-8)OP-mediated neuroprotection was associated with strong inhibition of caspase-3 expression induced by MPTP in the striatum. Additionally, cyclo(1-8)OP restored the activities of antioxidant enzymes, preventing the accumulation of ROS, lipid peroxidation products, and protein carbonylation in the striatum.