Amphetamine Modulates Excitatory Neurotransmission through Endocytosis of the Glutamate Transporter EAAT3 in Dopamine Neurons

SummaryAmphetamines modify the brain and alter behavior through mechanisms generally attributed to their ability to regulate extracellular dopamine concentrations. However, the actions of amphetamine are also linked to adaptations in glutamatergic signaling. We report here that when amphetamine enters dopamine neurons through the dopamine transporter, it stimulates endocytosis of an excitatory amino acid transporter, EAAT3, in dopamine neurons. Consistent with this decrease in surface EAAT3, amphetamine potentiates excitatory synaptic responses in dopamine neurons. We also show that the process of internalization is dynamin- and Rho-mediated and requires a unique sequence in the cytosolic C terminus of EAAT3. Introduction of a peptide based on this motif into dopamine neurons blocks the effects of amphetamine on EAAT3 internalization and its action on excitatory responses. These data indicate that the internalization of EAAT3 triggered by amphetamine increases glutamatergic signaling and thus contributes to the effects of amphetamine on neurotransmission

Directed Evolution of a Selective and Sensitive Serotonin Sensor via Machine Learning

Serotonin plays a central role in cognition and is the target of most pharmaceuticals for psychiatric disorders. Existing drugs have limited efficacy; creation of improved versions will require better understanding of serotonergic circuitry, which has been hampered by our inability to monitor serotonin release and transport with high spatial and temporal resolution. We developed and applied a binding-pocket redesign strategy, guided by machine learning, to create a high-performance, soluble, fluorescent serotonin sensor (iSeroSnFR), enabling optical detection of millisecond-scale serotonin transients. We demonstrate that iSeroSnFR can be used to detect serotonin release in freely behaving mice during fear conditioning, social interaction, and sleep/wake transitions. We also developed a robust assay of serotonin transporter function and modulation by drugs. We expect that both machine-learning-guided binding-pocket redesign and iSeroSnFR will have broad utility for the development of other sensors and in vitro and in vivo serotonin detection, respectively

Resources and Geographic Access to Care for Severe Pediatric Pneumonia in Four Resource-limited Settings

Rationale: Pneumonia is the leading cause of death in children worldwide. Identifying and appropriately managing severe pneumonia in a timely manner improves outcomes. Little is known about the readiness of healthcare facilities to manage severe pediatric pneumonia in low-resource settings. Objectives: As part of the HAPIN (Household Air Pollution Intervention Network) trial, we sought to identify healthcare facilities that were adequately resourced to manage severe pediatric pneumonia in Jalapa, Guatemala (J-GUA); Puno, Peru (P-PER); Kayonza, Rwanda (K-RWA); and Tamil Nadu, India (T-IND). We conducted a facility-based survey of available infrastructure, staff, equipment, and medical consumables. Facilities were georeferenced, and a road network analysis was performed. Measurements and Main Results: Of the 350 healthcare facilities surveyed, 13% had adequate resources to manage severe pneumonia, 37% had pulse oximeters, and 44% had supplemental oxygen. Mean (±SD) travel time to an adequately resourced facility was 41 ± 19 minutes in J-GUA, 99 ± 64 minutes in P-PER, 40 ± 19 minutes in K-RWA, and 31 ± 19 minutes in T-IND. Expanding pulse oximetry coverage to all facilities reduced travel time by 44% in J-GUA, 29% in P-PER, 29% in K-RWA, and 11% in T-IND (all P < 0.001). Conclusions: Most healthcare facilities in low-resource settings of the HAPIN study area were inadequately resourced to care for severe pediatric pneumonia. Early identification of cases and timely referral is paramount. The provision of pulse oximeters to all health facilities may be an effective approach to identify cases earlier and refer them for care and in a timely manner

Facing the Realities of Pragmatic Design Choices in Environmental Health Studies: Experiences from the Household Air Pollution Intervention Network Trial

Objective: Household Air Pollution Intervention Network (HAPIN) investigators tested a complex, non-pharmacological intervention in four low- and middle-income countries as a strategy to mitigate household air pollution and improve health outcomes across the lifespan. Intervention households received a liquefied petroleum gas (LPG) stove, continuous fuel delivery and regular behavioral reinforcements for 18 months, whereas controls were asked to continue with usual cooking practices. While HAPIN was designed as an explanatory trial to test the efficacy of the intervention on four primary outcomes, it introduced several pragmatic aspects in its design and conduct that resemble real-life conditions. We surveyed HAPIN investigators and asked them to rank what aspects of the design and conduct they considered were more pragmatic than explanatory. Methods: We used the revised Pragmatic Explanatory Continuum Indicator Summary (PRECIS-2) to survey investigators on the degree of pragmatism in nine domains of trial design and conduct using a five-point Likert rank scale from very explanatory (1) to very pragmatic (5). We invited 103 investigators. Participants were given educational material on PRECIS-2, including presentations, papers and examples that described the use and implementation of PRECIS-2. Results: Thirty-five investigators (mean age 42 years, 51% female) participated in the survey. Overall, only 17% ranked all domains as very explanatory, with an average (±SD) rank of 3.2 ± 1.4 across domains. Fewer than 20% of investigators ranked eligibility, recruitment or setting as very explanatory. In contrast, ≥50% of investigators ranked the trial organization, delivery and adherence of the intervention and follow-up as very/rather explanatory whereas ≤17% ranked them as rather/very pragmatic. Finally, &lt;25% of investigators ranked the relevance of outcomes to participants and analysis as very/rather explanatory whereas ≥50% ranked then as rather/very pragmatic. In-country partners were more likely to rank domains as pragmatic when compared to investigators working in central coordination (average rank 3.2 vs. 2.8, respectively; Wilcoxon rank-sum p &lt; 0.001). Conclusion: HAPIN investigators did not consider their efficacy trial to be rather/very explanatory and reported that some aspects of the design and conduct were executed under real-world conditions; however, they also did not consider the trial to be overly pragmatic. Our analysis underscores the importance of using standardized tools such as PRECIS-2 to guide early discussions among investigators in the design of environmental health trials attempting to measure efficacy.</jats:p

Affordability and Access to Essential Medications for Asthma and Chronic Obstructive Pulmonary Disease in Three Low- and Middle-Income Country Settings

INTRODUCTION: Despite the rising burden of chronic respiratory disease globally, and although many respiratory medications are included in the World Health Organization Essential Medications List (WHO-EML), there is limited information concerning the availability and affordability of treatment drugs for respiratory conditions in low- and middle-income countries (LMICs). METHODS: All public and private pharmacies in catchment areas of the Global Excellence in COPD outcomes (GECo) study sites in Bhaktapur, Nepal, Lima, Peru, and Nakaseke, Uganda, were approached in 2017-2019 to assess pricing and availability of medications for the management of asthma and COPD. RESULTS: We surveyed all 63 pharmacies in respective study areas in Nepal (95.2% private), 104 pharmacies in Peru (94.2% private) and 53 pharmacies in Uganda (98.1% private). The availability of any medication for respiratory disease was higher in private (93.3%) compared to public (73.3%) pharmacies. Salbutamol (WHO-EML) monotherapy in any formulation was the most commonly available respiratory medication among the three sites (93.7% Nepal, 86.5% Peru and 79.2% Uganda) while beclomethasone (WHO-EML) was only available in Peru (33.7%) and Nepal (22%). LABA-LAMA combination therapy was only available in Nepal (14.3% of pharmacies surveyed). The monthly treatment cost of respiratory medications was lowest in Nepal according to several cost metrics: the overall monthly cost, the median price ratio comparing medication costs to international reference prices at time of survey in dollars, and in terms of days' wages of the lowest-paid government worker. For the treatment of intermittent asthma, defined as 100 mcg Salbutamol/Albuterol inhaler, days' wages ranged from 0.47 days in Nepal and Peru to 3.33 days in Uganda. CONCLUSION: The availability and pricing of respiratory medications varied across LMIC settings, with medications for acute care of respiratory diseases being more widely available than those for long-term management

The importance of the excitatory amino acid transporter 3 (EAAT3)

The neuronal excitatory amino acid transporter 3 (EAAT3) is fairly ubiquitously expressed in the brain, though it does not necessarily maintain the same function everywhere. It is important in maintaining low local concentrations of glutamate, where its predominant post-synaptic localization can buffer nearby glutamate receptors and modulate excitatory neurotransmission and synaptic plasticity. It is also the main neuronal cysteine uptake system acting as the rate-limiting factor for the synthesis of glutathione, a potent antioxidant, in EAAT3 expressing neurons, while on GABAergic neurons, it is important in supplying glutamate as a precursor for GABA synthesis. Several diseases implicate EAAT3, and modulation of this transporter could prove a useful therapeutic approach. Regulation of EAAT3 could be targeted at several points for functional modulation, including the level of transcription, trafficking and direct pharmacological modulation, and indeed, compounds and experimental treatments have been identified that regulate EAAT3 function at different stages, which together with observations of EAAT3 regulation in patients is giving us insight into the endogenous function of this transporter, as well as the consequences of altered function. This review summarizes work done on elucidating the role and regulation of EAAT3

Gut microbiota modulates the development of murine Kawasaki disease vasculitis

Alterations of gut microbiota composition and function influence the development of cardiovascular disease, but the role of these aberrations remains poorly understood in Kawasaki Disease (KD), an acute pediatric vasculitis that targets coronary arteries. Using a murine model of KD vasculitis, we found that germ-free and antibiotic-treated mice displayed reduced inflammation and cardiovascular lesions. Development of KD vasculitis in mice was associated with alterations in the composition of the intestinal microbiota, specifically decreased abundance of Akkermansia muciniphila and Faecalibacterium prausnitzii. Supplementation with live or pasteurized A. muciniphila or F. prausnitzii attenuated the severity of KD cardiovascular inflammation. Oral administration of the short-chain fatty acids acetate or butyrate, which are produced by A. muciniphila and F. prausnitzii respectively, or treatment with Amuc_1100, a purified protein isolated from the outer membrane of A. muciniphila, ameliorated the severity of KD cardiovascular lesions. Reduced development of KD vasculitis in mice receiving either pasteurized A. muciniphila or Amuc_1100 was associated with improvements of gut barrier function. These results reveal an underappreciated gut microbiota-cardiovascular inflammation axis during murine KD vasculitis. Our findings may stimulate the development of novel diagnostic tools and therapeutic strategies that modulate the intestinal microbiota composition and function for KD patients