Single-cell transcriptomic atlas of taste papilla aging.

Taste perception is one of the important senses in mammals. Taste dysfunction causes significant inconvenience in daily life, leading to subhealth and even life-threatening condition. Aging is a major cause to taste dysfunction, while the underlying feature related to gustatory aging is still not known. Using single-cell RNA Sequencing, differentially expressed genes between aged and young taste papillae are identified, including upregulated mt-Nd4l and Xist, as well as downregulated Hsp90ab1 and Tmem59. In the Tmem59-/- circumvallate papillae (CVP), taste mature cell generation is impaired by reduction in the numbers of PLCß2+ and Car4+ cells, as well as decreases in expression levels of taste transduction genes. Tmem59-/- mice showed deficits in sensitivities to tastants. Through screening by GenAge and DisGeNET databases, aging-dependent genes and oral disease-associated genes are identified in taste papillae. In the CVP, aging promotes intercellular communication reciprocally between (cycling) basal cell and mature taste cell by upregulated Crlf1/Lifr and Adam15/Itga5 signaling. By transcriptional network analysis, ribosome proteins, Anxa1, Prdx5, and Hmgb1/2 are identified as transcriptional hubs in the aged taste papillae. Chronological aging-associated transcriptional changes throughout taste cell maturation are revealed. Aged taste papillae contain more Muc5b+ cells that are not localized in gustatory gland. Collectively, this study shows molecular and cellular features associated with taste papilla aging.

A single-cell transcriptomic census of mammalian olfactory epithelium aging.

Mammalian olfactory epithelium has the capacity of self-renewal throughout life. Aging is one of the major causes leading to the olfactory dysfunction. Here, we performed single-cell RNA sequencing (scRNA-seq) analysis on young and aged murine olfactory epithelium (OE) and identified aging-related differentially expressed genes (DEGs) throughout 21 cell types. Aging led to the presence of activated horizontal basal cells (HBCs) in the OE and promoted cellular interaction between HBCs and neutrophils. Aging enhanced the expression of Egr1 and Fos in sustentacular cell differentiation from multipotent progenitors, whereas Bcl11b was downregulated during the sensory neuronal homeostasis in the aged OE. Egr1 and Cebpb were predictive core regulatory factors of the transcriptional network in the OE. Overexpression of Egr1 in aged OE organoids promoted cell proliferation and neuronal differentiation. Moreover, aging altered expression levels and frequencies of olfactory receptors. These findings provide a cellular and molecular framework of OE aging at the single-cell resolution.

Neural substrates for regulating self-grooming behavior in rodents. / 啮齿动物自我梳理行为调控的神经基质.

Grooming, as an evolutionarily conserved repetitive behavior, is common in various animals, including humans, and serves essential functions including, but not limited to, hygiene maintenance, thermoregulation, de-arousal, stress reduction, and social behaviors. In rodents, grooming involves a patterned and sequenced structure, known as the syntactic chain with four phases that comprise repeated stereotyped movements happening in a cephalocaudal progression style, beginning from the nose to the face, to the head, and finally ending with body licking. The context-dependent occurrence of grooming behavior indicates its adaptive significance. This review briefly summarizes the neural substrates responsible for rodent grooming behavior and explores its relevance in rodent models of neuropsychiatric disorders and neurodegenerative diseases with aberrant grooming phenotypes. We further emphasize the utility of rodent grooming as a reliable measure of repetitive behavior in neuropsychiatric models, holding promise for translational psychiatry. Herein, we mainly focus on rodent self-grooming. Allogrooming (grooming being applied on one animal by its conspecifics via licking or carefully nibbling) and heterogrooming (a form of grooming behavior directing towards another animal, which occurs in other contexts, such as maternal, sexual, aggressive, or social behaviors) are not covered due to space constraints.

Cholecystokinin-expressing superficial tufted cells modulate odour representation in the olfactory bulb and olfactory behaviours.

In mammals, odour information within the olfactory bulb (OB) is processed by complex neural circuits before being ultimately represented in the action potential activity of mitral/tufted cells (M/Ts). Cholecystokinin-expressing (CCK+) superficial tufted cells (sTCs) are a subset of tufted cells that potentially contribute to olfactory processing in the OB by orchestrating M/T activity. However, the exact role of CCK+ sTCs in modulating odour processing and olfactory function in vivo is largely unknown. Here, we demonstrate that manipulating CCK+ sTCs can generate perception and induce place avoidance. Optogenetic activation/inactivation of CCK+ sTCs exerted strong but differing effects on spontaneous and odour-evoked M/T firing. Furthermore, inactivation of CCK+ sTCs disrupted M/T odour encoding and impaired olfactory detection and odour discrimination. These results establish the role of CCK+ sTCs in odour representation and olfactory behaviours. KEY POINTS: Mice could perceive the activity of CCK+ sTCs and show place avoidance to CCK+ sTC inactivation. Optical activation of CCK+ sTCs increased the percentage of cells with odour response but reduced the odour-evoked response in M/Ts in awake mice. Optical inactivation of CCK+ sTCs greatly decreased spontaneous firing and odour-evoked response in M/Ts. Inactivation of CCK+ sTCs impairs the odour decoding performance of M/Ts and disrupts odour detection and discrimination behaviours in mice. These results indicate that CCK+ sTCs participate in modulating the odour representation and maintaining normal olfactory-related behaviours.

Prediction of Drug-Drug Interactions with Ensartinib as a Time-Dependent CYP3A Inhibitor Using Physiologically Based Pharmacokinetic Model.

Ensartinib (X-396) is a second-generation anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor (TKI) indicated for the treatment of ALK-positive patients with locally advanced or metastatic non-small cell lung cancer. Although in vitro experiments and molecular docking suggested its potential as a cytochrome P450 inhibitor, no further investigation or clinical trials have been conducted to assess its drug-drug interaction (DDI) risk. In this study, we conducted a series of in vitro experiments to elucidate the inhibition mechanism of ensartinib. Furthermore, a physiologically-based pharmacokinetic (PBPK) model was developed based on in vitro, in silico, and in vivo parameters, verified using clinical data, and applied to predict the clinical DDI mediated by ensartinib. The in vitro incubation experiments suggested that ensartinib exhibited strong time-dependent inhibition. Simulation results from the PBPK model indicated a significant increase in the exposure of CYP3A substrates in the presence of ensartinib, with the maximal plasma concentration and area under the plasma concentration-time curve increasing up to 12-fold and 29-fold for sensitive substrates. Based on these findings, it is evident that co-administration of ensartinib and CYP3A substrates requires careful regulatory consideration. SIGNIFICANCE STATEMENT: Ensartinib was found to be a strong time-dependent inhibitor of CYP3A for the first time based on in vitro experiments, but there was no research conducted to estimate the risk of drug-drug interaction (DDI) of ensartinib in clinic. Therefore, the first ensartinib physiologically based pharmacokinetic model was developed and applied to predict various untested scenarios. The simulation result indicated that the exposure of CYP3A substrate increased significantly and urged the further clinical DDI study.

Cisplatin attenuates taste cell homeostasis and induces inflammatory activation in the circumvallate papilla.

Rationale: Gustation is important to several biological functions in mammals. However, chemotherapy drugs often harm taste perception in cancer patients, while the underlying mechanism is still unclear for most drugs and there is no effective way to restore taste function. This study investigated the effects of cisplatin on the taste cell homeostasis and gustatory function. Methods: We used both mice and taste organoid models to study the effect of cisplatin on taste buds. Gustometer assay, gustatory nerve recording, RNA-Sequencing, quantitative PCR, and immunohistochemistry was performed to analyze the cisplatin-induced alteration in taste behavior and function, transcriptome, apoptosis, cell proliferation and taste cell generation. Results: Cisplatin inhibited proliferation and promoted apoptosis in the circumvallate papilla, leading to significant impairment in taste function and receptor cell generation. The transcriptional profile of genes associated with cell cycle, metabolic process and inflammatory response was significantly altered after cisplatin treatment. Cisplatin inhibited growth, promoted apoptosis, and deferred taste receptor cell differentiation in taste organoids. LY411575, a γ-secretase inhibitor, reduced the number of apoptotic cells and increased the number of proliferative cells and taste receptor cells, potentially suggesting as a taste tissue protective agent against chemotherapy. LY411575 treatment could offset the increased number of Pax1+ or Pycr1+ cells induced by cisplatin in the circumvallate papilla and taste organoids. Conclusion: This study highlights the inhibitory effects of cisplatin on taste cell homeostasis and function, identifies critical genes and biological processes regulated by chemotherapy, and proposes potential therapeutic targets and strategy for taste dysfunction in cancer patients.

TMEM59 ablation leads to loss of olfactory sensory neurons and impairs olfactory functions via interaction with inflammation.

The olfactory epithelium undergoes constant neurogenesis throughout life in mammals. Several factors including key signaling pathways and inflammatory microenvironment regulate the maintenance and regeneration of the olfactory epithelium. In this study, we identify TMEM59 (also known as DCF1) as a critical regulator to the epithelial maintenance and regeneration. Single-cell RNA-Seq data show downregulation of TMEM59 in multiple epithelial cell lineages with aging. Ablation of TMEM59 leads to apparent alteration at the transcriptional level, including genes associated with olfactory transduction and inflammatory/immune response. These differentially expressed genes are key components belonging to several signaling pathways, such as NF-κB, chemokine, etc. TMEM59 deletion impairs olfactory functions, attenuates proliferation, causes loss of both mature and immature olfactory sensory neurons, and promotes infiltration of inflammatory cells, macrophages, microglia cells and neutrophils into the olfactory epithelium and lamina propria. TMEM59 deletion deteriorates regeneration of the olfactory epithelium after injury, with significant reduction in the number of proliferative cells, immature and mature sensory neurons, accompanied by the increasing number of inflammatory cells and macrophages. Anti-inflammation by dexamethasone recovers neuronal generation and olfactory functions in the TMEM59-KO animals, suggesting the correlation between TMEM59 and inflammation in regulating the epithelial maintenance. Collectively, TMEM59 regulates olfactory functions, as well as neuronal generation in the olfactory epithelium via interaction with inflammation, suggesting a potential role in therapy against olfactory dysfunction associated with inflamm-aging.

Mimicking the Biological Sense of Taste In Vitro Using a Taste Organoids-on-a-Chip System.

Thanks to the gustatory system, humans can experience the flavors in foods and drinks while avoiding the intake of some harmful substances. Although great advances in the fields of biotechnology, microfluidics, and nanotechnologies have been made in recent years, this astonishing recognition system can hardly be replaced by any artificial sensors designed so far. Here, taste organoids are coupled with an extracellular potential sensor array to form a novel bioelectronic organoid and developed a taste organoids-on-a-chip system (TOS) for highly mimicking the biological sense of taste ex vivo with high stability and repeatability. The taste organoids maintain key taste receptors expression after the third passage and high cell viability during 7 days of on-chip culture. Most importantly, the TOS not only distinguishs sour, sweet, bitter, and salt stimuli with great specificity, but also recognizes varying concentrations of the stimuli through an analytical method based on the extraction of signal features and principal component analysis. It is hoped that this bioelectronic tongue can facilitate studies in food quality controls, disease modelling, and drug screening.

Application of physiologically-based pharmacokinetic/pharmacodynamic models to evaluate the interaction between nifedipine and apatinib.

Aim: It has been found that the co-administration of nifedipine with apatinib could cause exposure changes of nifedipine in vivo. But, whether this pharmacokinetic drug-drug interaction (DDI) between nifedipine and apatinib could enhance the antihypertensive effect of nifedipine, causing sever changes of blood pressure was unknown. Therefore, the aim of the present study was to conduct the pharmacokinetic/pharmacodynamic (PK/PD) modelling to evaluate the effect of pharmacokinetic changes on the antihypertensive effect of nifedipine. Thus, the results could guide the co-administration of these two drugs in clinic. Methods: A physiologically-based pharmacokinetic (PBPK) model was first developed for nifedipine. The pharmacokinetic DDI between nifedipine and apatinib was evaluated. Then the verified PBPK models were linked to a PD model for investigating whether the exposure changes of nifedipine could cause severe changes in blood pressure. Furthermore, the changes in blood pressure caused by combination with apatinib were also assessed in patients with hepatic impairment via the PBPK/PD models. Results: The predicted area under plasma concentration-time profile (AUC), maximum concentration (Cmax), area under effect-time profile (AUE), and maximum reduction in systolic blood pressure (Rmax) are all within 0.5-2.0-fold of the observed data, indicating that the PBPK/PD models for nifedipine are successfully established. The increases of predicted AUC and Cmax of nifedipine in the presence of apatinib are 1.73 and 1.41-fold, respectively. Co-administration of nifedipine with apatinib could cause exposure changes of nifedipine in vivo. However, the predicted AUE and Rmax changes of nifedipine in the presence to the absence of apatinib in cancer patients as well as in patients with hepatic impairment are all within 1.25-fold. The results indicate that the exposure changes of nifedipine caused by combination of apatinib has little effect on the changes of systolic blood pressure both in cancer patients and patients with hepatic impairment. Conclusion: The pharmacokinetic changes of nifedipine caused by co-administration with apatinib has little impact on the antihypertensive effect of nifedipine. Apatinib is unlikely to cause severe pharmacodynamic DDI via inhibition of CYP3A4. It is suggested that nifedipine could be used in combination with apatinib without dose adjustment in clinic.

Extracellular loop 2 of G protein-coupled olfactory receptors is critical for odorant recognition.

G protein-coupled olfactory receptors (ORs) enable us to detect innumerous odorants. They are also ectopically expressed in nonolfactory tissues and emerging as attractive drug targets. ORs can be promiscuous or highly specific, which is part of a larger mechanism for odor discrimination. Here, we demonstrate that the OR extracellular loop 2 (ECL2) plays critical roles in OR promiscuity and specificity. Using site-directed mutagenesis and molecular modeling, we constructed 3D OR models in which ECL2 forms a lid over the orthosteric pocket. We demonstrate using molecular dynamics simulations that ECL2 controls the shape and volume of the odorant-binding pocket, maintains the pocket hydrophobicity, and acts as a gatekeeper of odorant binding. Therefore, we propose the interplay between the specific orthosteric pocket and the variable, less specific ECL2 controls OR specificity and promiscuity. Furthermore, the 3D models created here enabled virtual screening of new OR agonists and antagonists, which exhibited a 70% hit rate in cell assays. Our approach can potentially be generalized to structure-based ligand screening for other G protein-coupled receptors that lack high-resolution 3D structures.