Loss of ON-Pathway Function in Mice Lacking Lrit3 Decreases Recovery From Lens-Induced Myopia.

Purpose: To determine whether the Lrit3-/- mouse model of complete congenital stationary night blindness with an ON-pathway defect harbors myopic features and whether the genetic defect influences the recovery from lens-induced myopia. Methods: Retinal levels of dopamine (DA) and 3,4 dihydroxyphenylacetic acid (DOPAC) from adult isolated Lrit3-/- retinas were quantified using ultra performance liquid chromatography after light adaptation. Natural refractive development of Lrit3-/- mice was measured from three weeks to nine weeks of age using an infrared photorefractometer. Susceptibility to myopia induction was assessed using a lens-induced myopia protocol with -25 D lenses placed in front of the right eye of the animals for three weeks; the mean interocular shift was measured with an infrared photorefractometer after two and three weeks of goggling and after one and two weeks after removal of goggles. Results: Compared to wild-type littermates (Lrit3+/+), both DA and DOPAC were drastically reduced in Lrit3-/- retinas. Natural refractive development was normal but Lrit3-/- mice showed a higher myopic shift and a lower ability to recover from induced myopia. Conclusions: Our data consolidate the link between ON pathway defect altered dopaminergic signaling and myopia. We document for the first time the role of ON pathway on the recovery from myopia induction.

Harnessing intestinal tryptophan catabolism to relieve atherosclerosis in mice.

Tryptophan (Trp) is an essential amino acid, whose metabolism is a key gatekeeper of intestinal homeostasis. Yet, its systemic effects, particularly on atherosclerosis, remain unknown. Here we show that high-fat diet (HFD) increases the activity of intestinal indoleamine 2, 3-dioxygenase 1 (IDO), which shifts Trp metabolism from the production of microbiota-derived indole metabolites towards kynurenine production. Under HFD, the specific deletion of IDO in intestinal epithelial cells leads to intestinal inflammation, impaired intestinal barrier, augmented lesional T lymphocytes and atherosclerosis. This is associated with an increase in serotonin production and a decrease in indole metabolites, thus hijacking Trp for the serotonin pathway. Inhibition of intestinal serotonin production or supplementation with indole derivatives alleviates plaque inflammation and atherosclerosis. In summary, we uncover a pivotal role of intestinal IDO in the fine-tuning of Trp metabolism with systemic effects on atherosclerosis, paving the way for new therapeutic strategies to relieve gut-associated inflammatory diseases.

Can Biomarkers Correctly Predict Ventilator-associated Pneumonia in Patients Treated With Targeted Temperature Management After Cardiac Arrest? An Exploratory Study of the Multicenter Randomized Antibiotic (ANTHARTIC) Study.

IMPORTANCE: Ventilator-associated pneumonia (VAP) frequently occurs in patients with cardiac arrest. Diagnosis of VAP after cardiac arrest remains challenging, while the use of current biomarkers such as C-reactive protein (CRP) or procalcitonin (PCT) is debated. OBJECTIVES: To evaluate biomarkers' impact in helping VAP diagnosis after cardiac arrest. DESIGN SETTING AND PARTICIPANTS: This is a prospective ancillary study of the randomized, multicenter, double-blind placebo-controlled ANtibiotherapy during Therapeutic HypothermiA to pRevenT Infectious Complications (ANTHARTIC) trial evaluating the impact of antibiotic prophylaxis to prevent VAP in out-of-hospital patients with cardiac arrest secondary to shockable rhythm and treated with therapeutic hypothermia. An adjudication committee blindly evaluated VAP according to predefined clinical, radiologic, and microbiological criteria. All patients with available biomarker(s), sample(s), and consent approval were included. MAIN OUTCOMES AND MEASURES: The main endpoint was to evaluate the ability of biomarkers to correctly diagnose and predict VAP within 48 hours after sampling. The secondary endpoint was to study the combination of two biomarkers in discriminating VAP. Blood samples were collected at baseline on day 3. Routine and exploratory panel of inflammatory biomarkers measurements were blindly performed. Analyses were adjusted on the randomization group. RESULTS: Among 161 patients of the ANTHARTIC trial with available biological sample(s), patients with VAP (n = 33) had higher body mass index and Acute Physiology and Chronic Health Evaluation II score, more unwitnessed cardiac arrest, more catecholamines, and experienced more prolonged therapeutic hypothermia duration than patients without VAP (n = 121). In univariate analyses, biomarkers significantly associated with VAP and showing an area under the curve (AUC) greater than 0.70 were CRP (AUC = 0.76), interleukin (IL) 17A and 17C (IL17C) (0.74), macrophage colony-stimulating factor 1 (0.73), PCT (0.72), and vascular endothelial growth factor A (VEGF-A) (0.71). Multivariate analysis combining novel biomarkers revealed several pairs with p value of less than 0.001 and odds ratio greater than 1: VEGF-A + IL12 subunit beta (IL12B), Fms-related tyrosine kinase 3 ligands (Flt3L) + C-C chemokine 20 (CCL20), Flt3L + IL17A, Flt3L + IL6, STAM-binding protein (STAMBP) + CCL20, STAMBP + IL6, CCL20 + 4EBP1, CCL20 + caspase-8 (CASP8), IL6 + 4EBP1, and IL6 + CASP8. Best AUCs were observed for CRP + IL6 (0.79), CRP + CCL20 (0.78), CRP + IL17A, and CRP + IL17C. CONCLUSIONS AND RELEVANCE: Our exploratory study shows that specific biomarkers, especially CRP combined with IL6, could help to better diagnose or predict early VAP occurrence in cardiac arrest patients.

Design of a pharmacokinetic/pharmacodynamic model for administration of low dose peripheral norepinephrine during general anaesthesia.

AIMS: Intraoperative hypotension is a risk factor for kidney, heart and cognitive postoperative complications. Literature suggests that the use of low-dose peripheral norepinephrine (NOR) reduces organ dysfunction, yet its administration remains unstandardized. In this work we develop a pharmacokinetic (PK)/pharmacodynamic (PD) model of NOR and its effect on mean arterial pressure (MAP). METHODS: From June 2018 to December 2021, we included patients scheduled for elective neurosurgery and requiring vasopressors for intraoperative hypotension management at Lariboisière Hospital, Paris. Low doses of NOR were administered peripherally, and successive arterial blood samples were collected to track its plasmatic concentration. We used a compartmental modelling approach for NOR PK. We developed and compared 2 models for NOR PD on MAP. Model comparison was done using Bayes information criteria. The resulting PK/PD model parameters were fitted over the entire population and linked to age, weight, height and sex. RESULTS: We included 29 patients (age 52 [46-64] years, 69% female). NOR median time to peak effect on MAP was 74 [53-94] s. After bolus administration, MAP increased by 24% (15-31%). A 2-comparment model with depot best captured NOR PK. NOR PD effect on MAP was well represented by both Emax and Windkessel models, with better results for the former. We found that age, height and weight as well as history of smoking and hypertension were correlated with model parameters. CONCLUSION: We have developed a PK/PD model to accurately track norepinephrine plasma concentration and its effect on MAP over time, which could serve for target-controlled infusion.

Inhibition of circulating dipeptidyl-peptidase 3 by procizumab in experimental septic shock reduces catecholamine exposure and myocardial injury.

BACKGROUND: Dipeptidyl peptidase 3 (DPP3) is a ubiquitous cytosolic enzyme released into the bloodstream after tissue injury, that can degrade angiotensin II. High concentrations of circulating DPP3 (cDPP3) have been associated with worse outcomes during sepsis. The aim of this study was to assess the effect of Procizumab (PCZ), a monoclonal antibody that neutralizes cDPP3, in an experimental model of septic shock. METHODS: In this randomized, open-label, controlled study, 16 anesthetized and mechanically ventilated pigs with peritonitis were randomized to receive PCZ or standard treatment when the mean arterial pressure (MAP) dropped below 50 mmHg. Resuscitation with fluids, antimicrobial therapy, peritoneal lavage, and norepinephrine was initiated one hour later to maintain MAP between 65-75 mmHg for 12 h. Hemodynamic variables, tissue oxygenation indices, and measures of organ failure and myocardial injury were collected. Organ blood flow was assessed using isotopic assessment (99mtechnetium albumin). cDPP3 activity, equilibrium analysis of the renin-angiotensin system and circulating catecholamines were measured. Tissue mRNA expression of interleukin-6 and downregulation of adrenergic and angiotensin receptors were assessed on vascular and myocardial samples. RESULTS: PCZ-treated animals had reduced cDPP3 levels and required less norepinephrine and fluid than septic control animals for similar organ perfusion and regional blood flow. PCZ-treated animals had less myocardial injury, and higher PaO2/FiO2 ratios. PCZ was associated with lower circulating catecholamine levels; higher circulating angiotensin II and higher angiotensin II receptor type 1 myocardial protein expression, and with lower myocardial and radial artery mRNA interleukin-6 expression. CONCLUSIONS: In an experimental model of septic shock, PCZ administration was associated with reduced fluid and catecholamine requirements, less myocardial injury and cardiovascular inflammation, along with preserved angiotensin II signaling.

Circulating Dipeptidyl Peptidase 3 Modulates Systemic and Renal Hemodynamics Through Cleavage of Angiotensin Peptides.

BACKGROUND: High circulating DPP3 (dipeptidyl peptidase 3) has been associated with poor prognosis in critically ill patients with circulatory failure. In such situation, DPP3 could play a pathological role, putatively via an excessive angiotensin peptides cleavage. Our objective was to investigate the hemodynamics changes induced by DPP3 in mice and the relation between the observed effects and renin-angiotensin system modulation. METHODS: Ten-week-old male C57Bl/6J mice were subjected to intravenous injection of purified human DPP3 or an anti-DPP3 antibody (procizumab). Invasive blood pressure and renal blood flow were monitored throughout the experiments. Circulating angiotensin peptides and catecholamines were measured and receptor blocking experiment performed to investigate the underlying mechanisms. RESULTS: DPP3 administration significantly increased renal blood flow, while blood pressure was minimally affected. Conversely, procizumab led to significantly decreased renal blood flow. Angiotensin peptides measurement and an AT1R (angiotensin II receptor type 1) blockade experiment using valsartan demonstrated that the renovascular effect induced by DPP3 is due to reduced AT1R activation via decreased concentrations of circulating angiotensin II, III, and IV. Measurements of circulating catecholamines and an adrenergic receptor blockade by labetalol demonstrated a concomitant catecholamines release that explains blood pressure maintenance upon DPP3 administration. CONCLUSIONS: High circulating DPP3 increases renal blood flow due to reduced AT1R activation via decreased concentrations of circulating angiotensin peptides while blood pressure is maintained by concomitant endogenous catecholamines release.

Impact of IDO activation and alterations in the kynurenine pathway on hyperserotonemia, NAD+ production, and AhR activation in autism spectrum disorder.

Hyperserotonemia is the most replicated biochemical anomaly associated with autism spectrum disorder (ASD) and has been reported in 35-46% of individuals with ASD. Serotonin is synthesised from the essential amino acid tryptophan (TRP). However, the main catabolic route of TRP is the kynurenine pathway (KP), which competes with serotonin synthesis when indoleamine dioxygenase (IDO) is activated. Using the same cohort of individuals with ASD, we used to report extensive studies of the serotonin/melatonin pathway, and found increased kynurenine (KYN), suggesting IDO activation in 58.7% of individuals with ASD (159/271), supported by a strong negative correlation between KYN/TRP ratio and miR-153-3p plasma levels, which negatively regulates IDO. IDO activation was associated with normoserotonemia, suggesting that IDO activation could mask hyperserotonemia which meant that hyperserotonemia, if not masked by IDO activation, could be present in ~94% of individuals with ASD. We also identified several KP alterations, independent of IDO status. We observed a decrease in the activity of 3-hydroxyanthranilate dioxygenase which translated into the accumulation of the aryl hydrocarbon receptor (AhR) selective ligand cinnabarinic acid, itself strongly positively correlated with the AhR target stanniocalcin 2. We also found a deficit in NAD+ production, the end-product of the KP, which was strongly correlated with plasma levels of oxytocin used as a stereotypical neuropeptide, indicating that regulated neuropeptide secretion could be limiting. These results strongly suggest that individuals with ASD exhibit low-grade chronic inflammation that is mediated in most cases by chronic AhR activation that could be associated with the highly prevalent gastrointestinal disorders observed in ASD, and explained IDO activation in ~58% of the cases. Taken together, these results extend biochemical anomalies of TRP catabolism to KP and posit TRP catabolism as a possible major component of ASD pathophysiology.

Organic cation transporter 2 contributes to SSRI antidepressant efficacy by controlling tryptophan availability in the brain.

Selective serotonin reuptake inhibitors (SSRI) are common first-line treatments for major depression. However, a significant number of depressed patients do not respond adequately to these pharmacological treatments. In the present preclinical study, we demonstrate that organic cation transporter 2 (OCT2), an atypical monoamine transporter, contributes to the effects of SSRI by regulating the routing of the essential amino acid tryptophan to the brain. Contrarily to wild-type mice, OCT2-invalidated mice failed to respond to prolonged fluoxetine treatment in a chronic depression model induced by corticosterone exposure recapitulating core symptoms of depression, i.e., anhedonia, social withdrawal, anxiety, and memory impairment. After corticosterone and fluoxetine treatment, the levels of tryptophan and its metabolites serotonin and kynurenine were decreased in the brain of OCT2 mutant mice compared to wild-type mice and reciprocally tryptophan and kynurenine levels were increased in mutants' plasma. OCT2 was detected by immunofluorescence in several structures at the blood-cerebrospinal fluid (CSF) or brain-CSF interface. Tryptophan supplementation during fluoxetine treatment increased brain concentrations of tryptophan and, more discreetly, of 5-HT in wild-type and OCT2 mutant mice. Importantly, tryptophan supplementation improved the sensitivity to fluoxetine treatment of OCT2 mutant mice, impacting chiefly anhedonia and short-term memory. Western blot analysis showed that glycogen synthase kinase-3ß (GSK3ß) and mammalian/mechanistic target of rapamycin (mTOR) intracellular signaling was impaired in OCT2 mutant mice brain after corticosterone and fluoxetine treatment and, conversely, tryptophan supplementation recruited selectively the mTOR protein complex 2. This study provides the first evidence of the physiological relevance of OCT2-mediated tryptophan transport, and its biological consequences on serotonin homeostasis in the brain and SSRI efficacy.

Successful treatment of JAK1-associated inflammatory disease.

BACKGROUND: Gain-of-function variants of JAK1 drive a rare immune dysregulation syndrome associated with atopic dermatitis, allergy, and eosinophilia. OBJECTIVES: This study sought to describe the clinical and immunological characteristics associated with a new gain-of-function variant of JAK1 and report the therapeutic efficacy of Janus kinase (JAK) inhibition. METHODS: The investigators identified a family affected by JAK1-associated autoinflammatory disease and performed clinical assessment and immunological monitoring on 9 patients. JAK1 signaling was studied by flow and mass cytometry in patients' cells at basal state or after immune stimulation. A molecular disease signature in the blood was studied at the transcriptomic level. Patients were treated with 1 of 2 JAK inhibitors: either baricitinib or upadacitinib. Clinical, cellular, and molecular response were evaluated over a 2-year period. RESULTS: Affected individuals displayed a syndromic disease with prominent allergy including atopic dermatitis, ichthyosis, arthralgia, chronic diarrhea, disseminated calcifying fibrous tumors, and elevated whole blood histamine levels. A variant of JAK1 localized in the pseudokinase domain was identified in all 9 affected, tested patients. Hyper-phosphorylation of STAT3 was found in 5 of 6 patients tested. Treatment of patients' cells with baricitinib controlled most of the atypical hyper-phosphorylation of STAT3. Administration of baricitinib to patients led to rapid improvement of the disease in all adults and was associated with reduction of systemic inflammation. CONCLUSIONS: Patients with this new JAK1 gain-of-function pathogenic variant displayed very high levels of blood histamine and showed a variable combination of atopy with articular and gastrointestinal manifestations as well as calcifying fibrous tumors. The disease, which appears to be linked to STAT3 hyperactivation, was well controlled under treatment by JAK inhibitors in adult patients.

The enzymatic and neurochemical outcomes of a mutation in Mexican cavefish MAO reveal teleost-specific aspects of brain monoamine homeostasis.

Monoamine oxidases (MAO; MAO-A and MAO-B in mammals) are enzymes catalyzing the degradation of biogenic amines, including monoamine neurotransmitters. In humans, coding mutations in MAOs are extremely rare and deleterious. Here, we assessed the structural and biochemical consequences of a point mutation (P106L) in the single mao gene of the blind cavefish, Astyanax mexicanus. This mutation decreased mao enzymatic activity by ∼3-fold and affected the enzyme kinetics parameters, in line with potential structure-function alterations. HPLC measurements in brains of four A. mexicanus genetic lines (mutant and non-mutant cavefish, and mutant and non-mutant surface fish) showed major disturbances in serotonin, dopamine, noradrenaline and metabolite levels in mutants and demonstrated that the P106L mao mutation is responsible for monoaminergic disequilibrium in the P106L mao mutant cavefish brain. The outcomes of the mutation were different in the posterior brain (containing the raphe nucleus) and the anterior brain (containing fish-specific hypothalamic serotonergic clusters), revealing contrasting properties in neurotransmitter homeostasis in these different neuronal groups. We also discovered that the effects of the mutation were partially compensated by a decrease in activity of TPH, the serotonin biosynthesis rate-limiting enzyme. Finally, the neurochemical outcomes of the mao P106L mutation differed in many respects from a treatment with deprenyl, an irreversible MAO inhibitor, showing that genetic and pharmacological interference with MAO function are not the same. Our results shed light on our understanding of cavefish evolution, on the specificities of fish monoaminergic systems, and on MAO-dependent homeostasis of brain neurochemistry in general.

Histamine elevation in familial Mediterranean fever: A study from the Juvenile Inflammatory Rheumatism cohort.

BACKGROUND: Familial Mediterranean Fever (FMF) is the most frequent monogenic autoinflammatory disease (AID). Some patients have persistent symptoms despite colchicine intake. Mast cells (MC) are innate immune cells involved in inflammatory conditions including AID. Their activation is responsible for various symptoms such as abdominal pain, bloating and pruritus. OBJECTIVE: Our objective was to evaluate features of a systemic MC activation in FMF adult patients. METHODS: FMF adult patients prospectively filled a MC activation survey and usual MC mediators (tryptase and histamine in whole blood, plasma and urine) were measured. They were compared with a healthy control group (HC) and a systemic mastocytosis (SM) group. When digestive biopsies were realized during follow-up, MC infiltration in digestive mucosa was analyzed in FMF, in comparison with SM, Crohn disease (CD) and normal biopsies. RESULTS: Forty-four FMF patients, 44 HC and 44 SM patients were included. Thirty-one (70%) FMF patients had symptoms of mast cell activation, versus 14 (32%) in the HC group (p = 0.0006). Thirty (68%) FMF patients had at least one elevated MC mediator: mainly whole blood histamine, in 19 (43%) and urinary histamine, in 14 (32%), which were significantly higher than in HC subjects. MC infiltration was comparable in FMF digestive biopsies, biopsies of CD and normal biopsies but was lower than in SM biopsies. CONCLUSION: FMF patients show frequent symptoms of MC activation and an increase of blood or urinary histamine never described before in this disease. This suggests an implication of MC and possibly basophils in FMF pathophysiology.

Mechanisms of Neurorespiratory Toxicity Induced by Fentanyl Analogs-Lessons from Animal Studies.

In 2020, fentanyl and its analogs contributed to ~65% of drug-attributed fatalities in the USA, with a threatening increasing trend during the last ten years. These synthetic opioids used as potent analgesics in human and veterinary medicine have been diverted to recreational aims, illegally produced and sold. Like all opioids, central nervous system depression resulting from overdose or misuse of fentanyl analogs is characterized clinically by the onset of consciousness impairment, pinpoint miosis and bradypnea. However, contrasting with what observed with most opioids, thoracic rigidity may occur rapidly with fentanyl analogs, contributing to increasing the risk of death in the absence of immediate life support. Various mechanisms have been proposed to explain this particularity associated with fentanyl analogs, including the activation of noradrenergic and glutamatergic coerulospinal neurons and dopaminergic basal ganglia neurons. Due to the high affinities to the mu-opioid receptor, the need for more elevated naloxone doses than usually required in morphine overdose to reverse the neurorespiratory depression induced by fentanyl analogs has been questioned. This review on the neurorespiratory toxicity of fentanyl and analogs highlights the need for specific research focused on these agents to better understand the involved mechanisms of toxicity and develop dedicated strategies to limit the resulting fatalities.

Endolysosomal TPCs regulate social behavior by controlling oxytocin secretion.

Oxytocin (OT) is a prominent regulator of many aspects of mammalian social behavior and stored in large dense-cored vesicles (LDCVs) in hypothalamic neurons. It is released in response to activity-dependent Ca2+ influx, but is also dependent on Ca2+ release from intracellular stores, which primes LDCVs for exocytosis. Despite its importance, critical aspects of the Ca2+-dependent mechanisms of its secretion remain to be identified. Here we show that lysosomes surround dendritic LDCVs, and that the direct activation of endolysosomal two-pore channels (TPCs) provides the critical Ca2+ signals to prime OT release by increasing the releasable LDCV pool without directly stimulating exocytosis. We observed a dramatic reduction in plasma OT levels in TPC knockout mice, and impaired secretion of OT from the hypothalamus demonstrating the importance of priming of neuropeptide vesicles for activity-dependent release. Furthermore, we show that activation of type 1 metabotropic glutamate receptors sustains somatodendritic OT release by recruiting TPCs. The priming effect could be mimicked by a direct application of nicotinic acid adenine dinucleotide phosphate, the endogenous messenger regulating TPCs, or a selective TPC2 agonist, TPC2-A1-N, or blocked by the antagonist Ned-19. Mice lacking TPCs exhibit impaired maternal and social behavior, which is restored by direct OT administration. This study demonstrates an unexpected role for lysosomes and TPCs in controlling neuropeptide secretion, and in regulating social behavior.

Shedding light on myopia by studying complete congenital stationary night blindness.

Myopia is the most common eye disorder, caused by heterogeneous genetic and environmental factors. Rare progressive and stationary inherited retinal disorders are often associated with high myopia. Genes implicated in myopia encode proteins involved in a variety of biological processes including eye morphogenesis, extracellular matrix organization, visual perception, circadian rhythms, and retinal signaling. Differentially expressed genes (DEGs) identified in animal models mimicking myopia are helpful in suggesting candidate genes implicated in human myopia. Complete congenital stationary night blindness (cCSNB) in humans and animal models represents an ON-bipolar cell signal transmission defect and is also associated with high myopia. Thus, it represents also an interesting model to identify myopia-related genes, as well as disease mechanisms. While the origin of night blindness is molecularly well established, further research is needed to elucidate the mechanisms of myopia development in subjects with cCSNB. Using whole transcriptome analysis on three different mouse models of cCSNB (in Gpr179-/-, Lrit3-/- and Grm6-/-), we identified novel actors of the retinal signaling cascade, which are also novel candidate genes for myopia. Meta-analysis of our transcriptomic data with published transcriptomic databases and genome-wide association studies from myopia cases led us to propose new biological/cellular processes/mechanisms potentially at the origin of myopia in cCSNB subjects. The results provide a foundation to guide the development of pharmacological myopia therapies.

Investigation of the Mechanisms of Tramadol-Induced Seizures in Overdose in the Rat.

Tramadol overdose is frequently associated with the onset of seizures, usually considered as serotonin syndrome manifestations. Recently, the serotoninergic mechanism of tramadol-attributed seizures has been questioned. This study's aim was to identify the mechanisms involved in tramadol-induced seizures in overdose in rats. The investigations included (1) the effects of specific pretreatments on tramadol-induced seizure onset and brain monoamine concentrations, (2) the interaction between tramadol and γ-aminobutyric acid (GABA)A receptors in vivo in the brain using positron emission tomography (PET) imaging and 11C-flumazenil. Diazepam abolished tramadol-induced seizures, in contrast to naloxone, cyproheptadine and fexofenadine pretreatments. Despite seizure abolishment, diazepam significantly enhanced tramadol-induced increase in the brain serotonin (p < 0.01), histamine (p < 0.01), dopamine (p < 0.05) and norepinephrine (p < 0.05). No displacement of 11C-flumazenil brain kinetics was observed following tramadol administration in contrast to diazepam, suggesting that the observed interaction was not related to a competitive mechanism between tramadol and flumazenil at the benzodiazepine-binding site. Our findings do not support the involvement of serotoninergic, histaminergic, dopaminergic, norepinephrine or opioidergic pathways in tramadol-induced seizures in overdose, but they strongly suggest a tramadol-induced allosteric change of the benzodiazepine-binding site of GABAA receptors. Management of tramadol-poisoned patients should take into account that tramadol-induced seizures are mainly related to a GABAergic pathway.

Prolonged Consumption of Sweetened Beverages Lastingly Deteriorates Cognitive Functions and Reward Processing in Mice.

We investigated the detrimental effects of chronic consumption of sweet or sweetened beverages in mice. We report that consumption of beverages containing small amounts of sucrose during several weeks impaired reward systems. This is evidenced by robust changes in the activation pattern of prefrontal brain regions associated with abnormal risk-taking and delayed establishment of decision-making strategy. Supporting these findings, we find that chronic consumption of low doses of artificial sweeteners such as saccharin disrupts brain regions' activity engaged in decision-making and reward processes. Consequently, this leads to the rapid development of inflexible decisions, particularly in a subset of vulnerable individuals. Our data also reveal that regular consumption, even at low doses, of sweet or sweeteners dramatically alters brain neurochemistry, i.e., dopamine content and turnover, and high cognitive functions, while sparing metabolic regulations. Our findings suggest that it would be relevant to focus on long-term consequences on the brain of sweet or sweetened beverages in humans, especially as they may go metabolically unnoticed.

Mice Lacking Gpr179 with Complete Congenital Stationary Night Blindness Are a Good Model for Myopia.

Mutations in GPR179 are one of the most common causes of autosomal recessive complete congenital stationary night blindness (cCSNB). This retinal disease is characterized in patients by impaired dim and night vision, associated with other ocular symptoms, including high myopia. cCSNB is caused by a complete loss of signal transmission from photoreceptors to ON-bipolar cells. In this study, we hypothesized that the lack of Gpr179 and the subsequent impaired ON-pathway could lead to myopic features in a mouse model of cCSNB. Using ultra performance liquid chromatography, we show that adult Gpr179-/- mice have a significant decrease in both retinal dopamine and 3,4-dihydroxyphenylacetic acid, compared to Gpr179+/+ mice. This alteration of the dopaminergic system is thought to be correlated with an increased susceptibility to lens-induced myopia but does not affect the natural refractive development. Altogether, our data added a novel myopia model, which could be used to identify therapeutic interventions.

The microbial metabolite p-Cresol induces autistic-like behaviors in mice by remodeling the gut microbiota.

BACKGROUND: Autism spectrum disorders (ASD) are associated with dysregulation of the microbiota-gut-brain axis, changes in microbiota composition as well as in the fecal, serum, and urine levels of microbial metabolites. Yet a causal relationship between dysregulation of the microbiota-gut-brain axis and ASD remains to be demonstrated. Here, we hypothesized that the microbial metabolite p-Cresol, which is more abundant in ASD patients compared to neurotypical individuals, could induce ASD-like behavior in mice. RESULTS: Mice exposed to p-Cresol for 4 weeks in drinking water presented social behavior deficits, stereotypies, and perseverative behaviors, but no changes in anxiety, locomotion, or cognition. Abnormal social behavior induced by p-Cresol was associated with decreased activity of central dopamine neurons involved in the social reward circuit. Further, p-Cresol induced changes in microbiota composition and social behavior deficits could be transferred from p-Cresol-treated mice to control mice by fecal microbiota transplantation (FMT). We also showed that mice transplanted with the microbiota of p-Cresol-treated mice exhibited increased fecal p-Cresol excretion, compared to mice transplanted with the microbiota of control mice. In addition, we identified possible p-Cresol bacterial producers. Lastly, the microbiota of control mice rescued social interactions, dopamine neurons excitability, and fecal p-Cresol levels when transplanted to p-Cresol-treated mice. CONCLUSIONS: The microbial metabolite p-Cresol induces selectively ASD core behavioral symptoms in mice. Social behavior deficits induced by p-Cresol are dependant on changes in microbiota composition. Our study paves the way for therapeutic interventions targeting the microbiota and p-Cresol production to treat patients with ASD. Video abstract.

Dopaminergic and serotonergic changes in rabbit fetal brain upon repeated gestational exposure to diesel engine exhaust.

Limited studies in humans and in animal models have investigated the neurotoxic risks related to a gestational exposure to diesel exhaust particles (DEP) on the embryonic brain, especially those regarding monoaminergic systems linked to neurocognitive disorders. We previously showed that exposure to DEP alters monoaminergic neurotransmission in fetal olfactory bulbs and modifies tissue morphology along with behavioral consequences at birth in a rabbit model. Given the anatomical and functional connections between olfactory and central brain structures, we further characterized their impacts in brain regions associated with monoaminergic neurotransmission. At gestational day 28 (GD28), fetal rabbit brains were collected from dams exposed by nose-only to either a clean air or filtered DEP for 2 h/day, 5 days/week, from GD3 to GD27. HPLC dosage and histochemical analyses of the main monoaminergic systems, i.e., dopamine (DA), noradrenaline (NA), and serotonin (5-HT) and their metabolites were conducted in microdissected fetal brain regions. DEP exposure increased the level of DA and decreased the dopaminergic metabolites ratios in the prefrontal cortex (PFC), together with sex-specific alterations in the hippocampus (Hp). In addition, HVA level was increased in the temporal cortex (TCx). Serotonin and 5-HIAA levels were decreased in the fetal Hp. However, DEP exposure did not significantly modify NA levels, tyrosine hydroxylase, tryptophan hydroxylase or AChE enzymatic activity in fetal brain. Exposure to DEP during fetal life results in dopaminergic and serotonergic changes in critical brain regions that might lead to detrimental potential short-term neural disturbances as precursors of long-term neurocognitive consequences.