Gut Microbiota as the Potential Mechanism to Mediate Drug Metabolism Under High-Altitude Hypoxia

The gut microbiota mediates memory impairment under high-altitude hypoxia via the gut-brain axis in mice

Hypoxia is a predominant risk factor at high altitudes, and evidence suggests that high-altitude hypoxia alters the gut microbiota, which plays an essential regulatory role in memory function. However, the causal relationship between the gut microbiota and memory impairment under hypoxic conditions remains unclear. In this study, we employed a high-altitude hypoxia model combined with fecal microbiota transplantation (FMT) approach in mice to explore the effects of the gut microbiota on memory impairment in a hypoxic environment. We observed that high-altitude hypoxia exposure reduced short- and long-term memory and hippocampus-dependent fear memory abilities, along with decreased relative abundance of Ligilactobacillus and Muribaculum. Moreover, hypoxic conditions increased intestinal and blood-brain barrier permeability. FMT from hypoxia-exposed mice into naïve antibiotic-treated mice resulted in similar memory impairments, Ligilactobacillus and Muribaculum abundance changes, and increased intestinal/blood-brain barrier permeability. Correlation analysis showed a robust positive association between Ligilactobacillus and Muribaculum with hippocampus-dependent contextual fear memory. Likewise, Ligilactobacillus was positively correlated with short-term memory. Therefore, Ligilactobacillus and Muribaculum may be key microbes in reducing memory ability in hypoxia, with the intestinal and blood-brain barriers as primary pathways. Our findings provide further evidence for the potential regulatory mechanism by which gut microbiota dysbiosis may contribute to memory impairment in a high-altitude environment.

Exploring cytochrome P450 under hypoxia: potential pharmacological significance in drug metabolism and protection against high-altitude diseases

High-altitude hypoxia affects the human respiratory, central nervous, cardiovascular, and endocrine systems. These outcomes affect the expression of cytochrome P450 (CYP), the most important family of metabolic enzymes in the body that is involved in the metabolism of both exogenous and endogenous substances (such as arachidonic acid, vitamins, and steroids). Hypoxia influences CYP expression and activity, mediating changes in drug and endogenous substance metabolism, with endogenous metabolites playing a significant role in controlling high-altitude diseases. However, the mechanisms regulating CYP changes under hypoxic conditions and the effects of CYP changes on drug and endogenous metabolism remain unclear. We explored how changes in CYP expression and activity during hypoxia affect the metabolism of drugs and endogenous substances, such as arachidonic acid, vitamins, and steroid hormones, and how CYPs are controlled by nuclear receptors, epigenetic modifications, cytokines, and gut microbiota during hypoxia. Special attention will also be given to the complex role of CYP and its metabolites in the pathophysiology of high-altitude diseases to provide valuable insights for plateau medicine research. SIGNIFICANCE STATEMENT: Cytochrome P450 is a class of monooxygenases that metabolize xenobiotics and endogenous substances. Hypoxia affects the expression and activity of cytochrome P450, and this in turn affects the metabolism of drugs and endogenous substances, leading to altered clinical efficacy and the development of hypoxia-associated diseases. A comprehensive understanding of the changes and regulatory mechanisms of cytochrome P450 under hypoxic conditions can improve therapeutic protocols in hypoxic environments and provide new ideas for the targeted treatment of hypoxic diseases.

Resveratrol attenuates non-steroidal anti-inflammatory drug-induced intestinal injury in rats in a high-altitude hypoxic environment by modulating the TLR4/NFκB/IκB pathway and gut microbiota composition

INTRODUCTION

Non-steroidal anti-inflammatory drugs (NSAIDs) are currently the most widely used anti-inflammatory medications, but their long-term use can cause damage to the gastrointestinal tract(GIT). One of the risk factors for GIT injury is exposure to a high-altitude hypoxic environment, which can lead to damage to the intestinal mucosal barrier. Taking NSAIDs in a high-altitude hypoxic environment can exacerbate GIT injury and impact gut microbiota. The aim of this study is to investigate the mechanisms by which resveratrol (RSV) intervention alleviates NSAID-induced intestinal injury in a high-altitude hypoxic environment, as well as its role in regulating gut microbiota.

METHODS

Aspirin was administered orally to rats to construct a rat model of intestinal injury induced by NSAIDs. Following the induction of intestinal injury, rats were administered RSV by gavage, and the expression levels of TLR4, NF-κB,IκB as well as Zonula Occludens-1 (ZO-1) and Occludin proteins in the different treatment groups were assessed via Western blot. Furthermore, the expression of the inflammatory factors IL-10, IL-1β, and TNF-α was evaluated using Elisa.16sRNA sequencing was employed to investigate alterations in the gut microbiota.

RESULTS

The HCk group showed elevated expression of TLR4/NF-κB/IκB pathway proteins, increased expression of pro-inflammatory factors IL-1β and TNF-α, decreased expression of the anti-inflammatory factor IL-10, and expression of intestinal mucosal barrier proteins ZO-1 and Occludin. The administration of NSAIDs drugs in the plateau hypoxic environment exacerbates intestinal inflammation and damage to the intestinal mucosal barrier. After treatment with RSV intervention, the expression of TLR4/NF-κB/IκB signaling pathway proteins would be reduced, thereby lowering the expression of inflammatory factors in the HAsp group. The results of HE staining directly show the damage to the intestines and the repair of intestinal mucosa after RSV intervention. 16sRNA sequencing results show significant differences (P<0.05) in Ruminococcus, Facklamia, Parasutterella, Jeotgalicoccus, Coprococcus, and Psychrobacter between the HCk group and the Ck group. Compared to the HCk group, the HAsp group shows significant differences (P<0.05) in Facklamia, Jeotgalicoccus, Roseburia, Psychrobacter, and Alloprevotella. After RSV intervention, Clostridium_sensu_stricto bacteria significantly increase compared to the HAsp group.

CONCLUSION

Resveratrol can attenuate intestinal damage caused by the administration of NSAIDs at high altitude in hypoxic environments by modulating the TLR4/NF-κB/IκB signaling pathway and gut microbiota composition.

Impact of high-altitude acclimatization and de-acclimatization on the intestinal microbiota of rats in a natural high-altitude environment

Introduction

Intestinal microorganisms play an important role in the health of both humans and animals, with their composition being influenced by changes in the host's environment.

Methods

We evaluated the longitudinal changes in the fecal microbial community of rats at different altitudes across various time points. Rats were airlifted to high altitude (3,650 m) and acclimatized for 42 days (HAC), before being by airlifted back to low altitude (500 m) and de-acclimatized for 28 days (HADA); meanwhile, the control group included rats living at low altitude (500 m; LA). We investigated changes in the gut microbiota at 12 time points during high-altitude acclimatization and de-acclimatization, employing 16S rRNA gene sequencing technology alongside physiological indices, such as weight and daily autonomous activity time.

Results

A significant increase in the Chao1 index was observed on day 14 in the HAC and HADA groups compared to that in the LA group, indicating clear differences in species richness. Moreover, the principal coordinate analysis revealed that the bacterial community structures of HAC and HADA differed from those in LA. Long-term high-altitude acclimatization and de- acclimatization resulted in the reduced abundance of the probiotic Lactobacillus. Altitude and age significantly influenced intestinal microbiota composition, with changes in ambient oxygen content and atmospheric partial pressure being considered key causal factors of altitude-dependent alterations in microbiota composition. High-altitude may be linked to an increase in anaerobic bacterial abundance and a decrease in non-anaerobic bacterial abundance.

Discussion

In this study, the hypobaric hypoxic conditions at high-altitude increased the abundance of anaerobes, while reducing the abundance of probiotics; these changes in bacterial community structure may, ultimately, affect host health. Overall, gaining a comprehensive understanding of the intestinal microbiota alterations during high-altitude acclimatization and de-acclimatization is essential for the development of effective prevention and treatment strategies to better protect the health of individuals traveling between high- and low-altitude areas.

Altitude effect on Propofol Pharmacokinetics in Rats

BACKGROUND

Propofol is an intravenous agent for clinical anesthesia. As the influence of the hypobaric-hypoxic environment (Qinghai-Tibetan region, altitude: 2800-4300 m, PaO2: 15.1-12.4 kPa) on the metabolism of Propofol is complex, the research results on the metabolic characteristics of Propofol in high-altitude areas remain unclear. This study aimed to investigate the pharmacokinetic characteristics of Propofol in a high-altitude hypoxic environment using animal experiments.

METHODS

Rats were randomly divided into three groups: high-altitude, medium-altitude, and plain groups. The time of disappearance and recovery of the rat righting reflex was recorded as the time of anesthesia induction and awakening, respectively. The plasma concentration of Propofol was determined by gas chromatography-mass spectrometry. A pharmacokinetic analysis software was used to analyze the blood-drug concentrations and obtain the pharmacokinetic parameters.

RESULTS

We observed that when Propofol anesthetizes rats, the anesthesia induction time was shortened, and the recovery time was prolonged with increased altitude. Compared with the plain group, the clearance of Propofol decreased, whereas the half-life, area under the concentration-time curve, peak plasma concentration, and average residence time extension increased.

CONCLUSION

The pharmacokinetic characteristics of Propofol are significantly altered in high-altitude hypoxic environments.

Relationship between blood-brain barrier changes and drug metabolism under high-altitude hypoxia: obstacle or opportunity for drug transport?

The blood-brain barrier is essential for maintaining the stability of the central nervous system and is also crucial for regulating drug metabolism, changes of blood-brain barrier's structure and function can influence how drugs are delivered to the brain. In high-altitude hypoxia, the central nervous system's function is drastically altered, which can cause disease and modify the metabolism of drugs in vivo. Changes in the structure and function of the blood-brain barrier and the transport of the drug across the blood-brain barrier under high-altitude hypoxia, are regulated by changes in brain microvascular endothelial cells, astrocytes, and pericytes, either regulated by drug metabolism factors such as drug transporters and drug-metabolizing enzymes. This article aims to review the effects of high-altitude hypoxia on the structure and function of the blood-brain barrier as well as the effects of changes in the blood-brain barrier on drug metabolism. We also hypothesized and explore the regulation and potential mechanisms of the blood-brain barrier and associated pathways, such as transcription factors, inflammatory factors, and nuclear receptors, in regulating drug transport under high-altitude hypoxia.

Regulation of CYP450 and drug transporter mediated by gut microbiota under high-altitude hypoxia

Hypoxia, an essential feature of high-altitude environments, has a significant effect on drug metabolism. The hypoxia–gut microbiota–CYP450/drug transporter axis is emerging as a vital factor in drug metabolism. However, the mechanisms through which the gut microbiota mediates the regulation of CYP450/drug transporters under high-altitude hypoxia have not been well defined. In this study, we investigated the mechanisms underlying gut microbial changes in response to hypoxia. We compared 16S ribosomal RNA gene sequences of the gut microbiota from plain and hypoxic rats. As a result, we observed an altered gut microbial diversity and composition in rats under hypoxia. Our findings show that dysregulated gut microbiota changes CYP3A1 and MDR1 expressions in high-altitude hypoxic environments. Thus, our study reveals a novel mechanism underlying the functioning of the hypoxia–gut microbiota–CYP450/drug transporter axis.