Hypoxia sensing requires H2S-dependent persulfidation of olfactory receptor 78

The Application of Hydrogen Sulfide Fluorescent Probe in Food Preservation, Detection and Evaluation

This work primarily reviewed the response mechanism of fluorescent probes for H2S detection in foodstuffs in recent years, as well as the methodologies employed for detecting foodstuffs. Firstly, the significance of studying H2S gas as an important signaling molecule is introduced. Subsequently, a review of the response mechanism of the scientific community on how to detect H2S in foodstuffs samples by fluorescent probe technology is carried out. Secondly, the methods commonly used for detecting foodstuffs samples are discussed, including the test strip method and the spiking recovery methods. Nevertheless, despite the significant advancements in this field, there remain some research gaps. Finally, the article identifies the remaining issues that require further attention in current research and proposes avenues for future investigation. More importantly, this work identifies the current limitations of research in this field and proposes future applications of fluorescent probes for H2S in assessing food freshness and determining food spoilage. Therefore, this review will provide robust technical support for the protection of consumer health and the advancement of the sustainable development of the food industry and also put forward some new ideas and suggestions for future research.

Intracellular Allosteric Antagonist of the Olfactory Receptor OR51E2

Olfactory receptors are members of class A (rhodopsin-like) family of G protein-coupled receptors (GPCRs). Their expression and function have been increasingly studied in nonolfactory tissues, and many have been identified as potential therapeutic targets. In this manuscript, we focus on the discovery of novel ligands for the olfactory receptor family 51 subfamily E2 (OR51E2). We performed an artificial intelligence-based virtual drug screen of a ∼2.2 million small molecule library. Cell-based functional assay identified compound 80 (C80) as an antagonist and inverse agonist, and detailed pharmacological analysis revealed C80 acts as a negative allosteric modulator by significantly decreasing the agonist efficacy, while having a minimal effect on receptor affinity for agonist. C80 binds to an allosteric binding site formed by a network of nine residues localized in the intracellular parts of transmembrane domains 3, 5, 6, 7, and H8, which also partially overlaps with a G protein binding site. Mutational experiments of residues involved in C80 binding uncovered the significance of the C2406.37 position in blocking the activation-related conformational change and keeping the receptor in the inactive form. Our study provides a mechanistic understanding of the negative allosteric action of C80 on agonist-ctivated OR51E2. We believe the identification of the antagonist of OR51E2 will enable a multitude of studies aiming to determine the functional role of this receptor in specific biologic processes. SIGNIFICANCE STATEMENT: OR51E2 has been implicated in various biological processes, and its antagonists that can effectively modulate its activity have therapeutic potential. Here we report the discovery of a negative allosteric modulator of OR51E2 and provide a mechanistic understanding of its action. We demonstrate that this modulator has an inhibitory effect on the efficacy of the agonist for the receptor and reveal a network of nine residues that constitute its binding pocket, which also partially overlaps with the G protein binding site.

Potential therapeutic effects of traditional Chinese medicine in acute mountain sickness: pathogenesis, mechanisms and future directions

Background and objectives

Acute mountain sickness (AMS) is a pathology with different symptoms in which the organism is not adapted to the environment that occurs under the special environment of high altitude. Its main mechanism is the organism's tissue damage caused by acute hypobaric hypoxia. Traditional Chinese medicine (TCM) theory focuses on the holistic concept. TCM has made remarkable achievements in the treatment of many mountain sicknesses. This review outlines the pathogenesis of AMS in modern and traditional medicine, the progress of animal models of AMS, and summarizes the therapeutic effects of TCM on AMS.

Methods

Using the keywords "traditional Chinese medicine," "herbal medicine," "acute mountain sickness," "high-altitude pulmonary edema," "high-altitude cerebral edema," "acute hypobaric hypoxia," and "high-altitude," all relevant TCM literature published up to November 2023 were collected from Scopus, Web of Science, PubMed, and China National Knowledge Infrastructure databases, and the key information was analyzed.

Results

We systematically summarised the effects of acute hypobaric hypoxia on the tissues of the organism, the study of the methodology for the establishment of an animal model of AMS, and retrieved 18 proprietary Chinese medicines for the clinical treatment of AMS. The therapeutic principle of medicines is mainly invigorating qi, activating blood and removing stasis. The components of botanical drugs mainly include salidroside, ginsenoside Rg1, and tetrahydrocurcumin. The mechanism of action of TCM in the treatment of AMS is mainly through the regulation of HIF-1α/NF-κB signaling pathway, inhibition of inflammatory response and oxidative stress, and enhancement of energy metabolism.

Conclusion

The main pathogenesis of AMS is unclear. Still, TCM formulas and components have been used to treat AMS through multifaceted interventions, such as compound danshen drip pills, Huangqi Baihe granules, salidroside, and ginsenoside Rg1. These components generally exert anti-AMS pharmacological effects by inhibiting the expression of VEGF, concentration of MDA and pro-inflammatory factors, down-regulating NF-κB/NLRP3 pathway, and promoting SOD and Na + -K + -ATPase activities, which attenuates acute hypobaric hypoxia-induced tissue injury. This review comprehensively analyses the application of TCM in AMS and makes suggestions for more in-depth studies in the future, aiming to provide some ideas and insights for subsequent studies.

Overexpression of olfactory receptor 78 ameliorates brain injury in cerebral ischaemia-reperfusion rats by activating Prkaca-mediated cAMP/PKA-MAPK pathway

Ischemic stroke is one of the main causes of disability and death. However, recanalization of occluded cerebral arteries is effective only within a very narrow time window. Therefore, it is particularly important to find neuroprotective biological targets for cerebral artery recanalization. Here, gene expression profiles of datasets GSE160500 and GSE97537 were downloaded from the GEO database, which were related to ischemic stroke in rats. Olfactory receptor 78 (Olfr78) was screened, and which highly associated with Calcium signalling pathway and MAPK pathway. Interacting protein of Olfr78, Prkaca, was predicted by STRING, and their interaction was validated by Co-IP analysis. Then, a rat model of middle cerebral artery occlusion/reperfusion (MCAO/R) and a neuronal cell model stimulated by oxygen-glucose deprivation/reoxygenation (OGD/R) were constructed, and the results showed that expression of Olfr78 and Prkaca was downregulated in MCAO rats and OGD/R-stimulated neurons. Overexpression of Olfr78 or Prkaca inhibited the secretion of inflammatory factors, Ca2+ overload, and OGD/R-induced neuronal apoptosis. Moreover, Overexpression of Prkaca increased protein levels of cAMP, PKA and phosphorylated p38 in OGD/R-stimulated neurons, while SB203580, a p38 inhibitor, treatment inhibited activation of the cAMP/PKA-MAPK pathway and counteracted the effect of Olfr78 overexpression on improvement of neuronal functions. Meanwhile, overexpression of Olfr78 or Prkaca markedly inhibited neuronal apoptosis and improved brain injury in MCAO/R rats. In conclusion, overexpression of Olfr78 inhibited Ca2+ overload and reduced neuronal apoptosis in MCAO/R rats by promoting Prkaca-mediated activation of the cAMP/PKA-MAPK pathway, thereby improving brain injury in cerebral ischaemia-reperfusion.

Transcriptomic Analysis of Postnatal Rat Carotid Body Development

The carotid body (CB), located bilaterally at the carotid artery bifurcations, is the primary sensory organ for monitoring arterial blood O2 levels. Carotid bodies are immature at birth, exhibiting low sensitivity to hypoxia, and become more sensitive with maturation during the first few weeks of neonatal life. To understand the molecular basis for the postnatal developmental hypoxic responses of CB, we isolated CBs from 5-day and 21-day-old Sprague-Dawley rats and performed RNA sequencing, which allows comprehensive analysis of gene expression. Differentially expressed genes (DEGs) were generated using Edge R, while functional enrichment analysis was performed using gene-set enrichment analysis (GSEA). Analysis of RNA-Seq data showed 2604 DEGs of the total 12,696 genes shared between neonates and adults. Of the 2604 DEGs, 924 genes were upregulated, and 1680 genes were downregulated. Further analysis showed that genes related to oxidative phosphorylation (Ox/phos) and hypoxia-signaling pathways were significantly upregulated in neonatal CBs compared to adult CBs, suggesting a possible link to differential developmental hypoxic responses seen in CB. Genes related to cytokine signaling (INFγ and TNFα) and transcription factors (CREB and NFΚB) mediated pathways were enriched in adult CBs, suggesting that expression of these pathways may be linked to developmental regulation. The RNA-Seq results were verified by analyzing mRNA changes in selected genes by qRT-PCR. Our results of enrichment analysis of biological pathways offer valuable insight into CB hypoxic sensing responses related to the development process.

Carotid Body Function in Tyrosine Hydroxylase Conditional Olfr78 Knockout Mice

The Olfr78 gene encodes a G-protein-coupled olfactory receptor that is expressed in several ectopic sites. Olfr78 is one of the most abundant mRNA species in carotid body (CB) glomus cells. These cells are the prototypical oxygen (O2) sensitive arterial chemoreceptors, which, in response to lowered O2 tension (hypoxia), activate the respiratory centers to induce hyperventilation. It has been proposed that Olfr78 is a lactate receptor and that glomus cell activation by the increase in blood lactate mediates the hypoxic ventilatory response (HVR). However, this proposal has been challenged by several groups showing that Olfr78 is not a physiologically relevant lactate receptor and that the O2-based regulation of breathing is not affected in constitutive Olfr78 knockout mice. In another study, constitutive Olfr78 knockout mice were reported to have altered systemic and CB responses to mild hypoxia. To further characterize the functional role of Olfr78 in CB glomus cells, we here generated a conditional Olfr78 knockout mouse strain and then restricted the knockout to glomus cells and other catecholaminergic cells by crossing with a tyrosine hydroxylase-specific Cre driver strain (TH-Olfr78 KO mice). We find that TH-Olfr78 KO mice have a normal HVR. Interestingly, glomus cells of TH-Olfr78 KO mice exhibit molecular and electrophysiological alterations as well as a reduced dopamine content in secretory vesicles and neurosecretory activity. These functional characteristics resemble those of CB neuroblasts in wild-type mice. We suggest that, although Olfr78 is not essential for CB O2 sensing, activation of Olfr78-dependent pathways is required for maturation of glomus cells.

Exploring the Potential of Olfactory Receptor Circulating RNA Measurement for Preeclampsia Prediction and Its Linkage to Mild Gestational Hypothyroidism

Gestational hypothyroidism may lead to preeclampsia development. However, this pathophysiological is unknown. We expect to find a shared mechanism by comparing hypothyroidism and preeclampsia. From our transcriptome data, we recognized olfactory receptors as that fingerprint. The reduction of taste and smell in hypothyroid patients has been known for a long time. Therefore, we decided to look to the olfactory receptors and aimed to identify genes capable of predicting preeclampsia (PEC). Methods: An Ion Proton Sequencer (Thermo Fisher Scientific, Waltham, MA, USA) was used to construct the transcriptome databases. RStudio with packages Limma v.3.50.0, GEOquery v.2.62.2, and umap v.0.2.8.8 were used to analyze the differentially expressed genes in GSE149440 from the Gene Expression Omnibus (GEO). The 7500 Real-Time PCR System (Applied Biosystems, Foster City, CA, USA) was used for RT-qPCR amplification of OR6X1 and OR4E2. Results: Our transcriptomic datasets analysis revealed 25.08% and 26.75% downregulated olfactory receptor (ORs) in mild nontreated gestational hypothyroidism (GHT) and PEC, respectively. In the GSE149440 GEO dataset, we found OR5H1, OR5T3, OR51A7, OR51B6, OR10J5, OR6C6, and OR2AG2 as predictors of early-onset PEC. We also evaluate two chosen biomarkers' responses to levothyroxine. The RT-qPCR demonstrated a difference in OR6X1 and OR4E2 expression between GHT and healthy pregnancy (p < 0.05). Those genes presented a negative correlation with TSH (r: -0.51, p < 0.05; and r: -0.44, p < 0.05), a strong positive correlation with each other (r: 0.89; p < 0.01) and the levothyroxine-treated group had no difference from the healthy one. We conclude that ORs could be used as biomarkers at the beginning of gestation, and the downregulated ORs found in GHT may be improved with levothyroxine treatment.