The effects of metronidazole on Cytochrome P450 Activity and Expression in rats after acute exposure to high altitude of 4300m

Effect of High Altitude Environment on Pharmacokinetic and Pharmacodynamic of Warfarin in Rats

BACKGROUND

High altitude environment affects the pharmacokinetic (PK) parameters of drugs and the PK parameters are an important theoretical basis for guiding the rational clinical use of drugs. Warfarin is an oral anticoagulant of the coumarin class commonly used in clinical practice, but it has a narrow therapeutic window and wide individual variation. However, the effect of high altitude environment on PK and pharmacodynamic (PD) of warfarin is unclear.

OBJECTIVE

The objective of this study is to investigate the effect of a high altitude environment on PK and PD of warfarin in rats.

METHOD

Rats were randomly divided into plain group and high altitude group and blood samples were collected through the orbital venous plexus after administration of 2 mg/kg warfarin. Warfarin concentrations in plasma samples were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and PK parameters were calculated by the non-compartment model using WinNonlin 8.1 software. Meanwhile, the expression of PXR, P-gp and CYP2C9 in liver tissues was also determined by western blotting. The effect of high altitude environment on PD of warfarin was explored by measuring activated partial thromboplastin time (APTT) and prothrombin time (PT) values and then calculated international normalized ratio (INR) values based on PT.

RESULTS

Significant changes in PK behaviors and PD of warfarin in high altitude-rats were observed. Compared with the plain-rats, the peak concentration (Cmax) and the area under the plasma concentration-time curve (AUC) increased significantly by 50.9% and 107.46%, respectively. At the same time, high altitude environment significantly inhibited the expression of PXR, P-gp and CYP2C9 in liver tissues. The results of the PD study showed that high altitude environments significantly prolonged PT, APTT and INR values.

CONCLUSION

High altitude environment inhibited the metabolism and increased the absorption of warfarin in rats and increased the effect of anticoagulant effect, suggesting that the optimal dose of warfarin for patients at high altitude should be reassessed.

Effects of high-altitude environment on pharmacokinetic parameters of gliquidone in rats

OBJECTIVE

To investigate the effect of high-altitude hypoxia on the pharmacokinetics parameters of gliquidone.

METHODS

Twelve healthy male Wistar rats were randomly divided into plain group and high-altitude group with 6 rats in each group. Blood samples were collected after intragastric administration of gliquidone (6.3 mg/kg). Ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS) was used to determine the concentration of gliquidone in rat plasma samples. And the expression of CYP2C9 in rat liver tissues was determined by Western blotting.

RESULTS

Compared with the plain group, the peak concentration of gliquidone in the high-altitude rats was significantly increased, the absorption rate constant was decreased, the elimination rate constant and the absorption half-life were increased, the elimination half-life was shortened, the mean residence time and apparent volume of distribution were decreased (all P<0.05). Western blotting showed that the expression of CYP2C9 was significantly up-regulated in the liver tissues of high altitude group rats, compared with the plain group (4.18 ±0.06 vs. 2.13±0.06, t=11.57, P<0.01).

CONCLUSION

Under the high-altitude hypoxia environment, the absorption of gliquidone in rats was reduced and the metabolism was accelerated in rats, which may be related to the up-regulation of CYP2C9 expression in liver tissues.

The Clinical Differences of Patients With Traumatic Brain Injury in Plateau and Plain Areas

Objective

Traumatic brain injury (TBI) is a leading cause of death and disability, which tends to have a worse clinical recovery if it occurs in plateau areas than in plain areas. To explore the underlying cause of this outcome preliminarily, this retrospective study was conducted to compare the clinical differences of patients with TBI in plateau and plain areas.

Methods

In this study, 32 patients with TBI in plateau areas (altitude ≥ 4,000 m) and 32 in plain areas (altitude ≤ 1,000 m) were recruited according to the inclusion and exclusion criteria from June 2020 to December 2021. The collected data and compared parameters include clinical features, head CT presentations and Marshall classifications, hematology profile, lipid profile, coagulation profile, and multiorgan (cardiac, liver, renal) function within 24 h of hospital admission, as well as the treatment method and final outcome.

Results

There were no obvious differences in demographic characteristics, including gender, age, height, and weight, between patients with TBI in plateau and plain areas (all P > 0.05). Compared to patients with TBI in plain areas, the time before hospital admission was longer, heartbeat was slower, systolic blood pressure (SBP) was lower, and hospital stays were longer in patients with TBI in plateau areas (all P < 0.05). More importantly, elevated red blood cells (RBCs) count and hemoglobin (HGB) level, enhanced coagulation function, and higher rates of multiorgan (cardiac, liver, and renal) injury were found in patients with TBI in plateau areas (all P < 0.05).

Conclusion

Patients with TBI in plateau areas presented with altered clinical characteristics, enhanced coagulation function, and aggravated predisposition toward multiorgan (cardiac, liver, and renal) injury, compared to patients with TBI in plain areas. Future prospective studies are needed to further elucidate the influences of high altitude on the disease course of TBI.

Intermittent Hypoxia Inhibits Hepatic CYP1a2 Expression and Delays Aminophylline Metabolism

Purpose

In this study, we aimed to determine the effects of intermittent hypoxia (IH) on hepatic cytochrome P450 1A2 (CYP1A2) expression and the pharmacokinetics of CYP1A2-mediated aminophylline and warfarin in vitro and in a rabbit model of obstructive sleep apnea.

Materials

Human normal liver (LO-2) cells were exposed to 30 min each of 1%, 1–21%, 21%, and 21–1% O₂, and then, CYP1A2 expression and drug concentrations were analyzed. We compared the pharmacokinetic parameters of drugs administered to normoxic rabbits and those exposed to 10 min of IH during which the oxygen level fluctuated from 21% to 8%–10% (n = 10 per group).

Result

s. The expression of CYP1A2 protein in vitro was significantly reduced in the IH compared with the normoxic cells (0.56 ± 0.11 vs. 1.27 ± 0.17, p < 0.001). Aminophylline was more abundant in cell culture supernatants after 48 h of IH than in those under normoxia. The T_1/2, AUC_0–24 h, and Ke values for aminophylline were significantly higher in the IH group.

Conclusion

Intermittent hypoxia inhibits hepatic CYP1A2 expression and delays aminophylline metabolism, suggesting that the impact of IH on the expression of CYP enzymes should be closely monitored in clinical practice.

Changes in CYP3A4 Enzyme Expression and Biochemical Markers Under Acute Hypoxia Affect the Pharmacokinetics of Sildenafil

To investigate the effects of pathological, physiological, biochemical and metabolic enzymes CYP3A4 on the pharmacokinetics of sildenafil under acute hypoxia, rats were randomly divided into the plain group (50 m above sea level), acute plateau group 1 (2300 m above sea level), and acute plateau group 2 (4300 m above sea level), and blood samples and liver tissues were collected. Our results showed that the blood gas, physiological and biochemical indexes of rats changed under acute hypoxia, and the protein expression of CYP3A4 enzyme decreased. The process of absorption, distribution, metabolism and excretion of sildenafil in rats has changed. Compared with the P group, the area under the drug-time curve and the average resident in the H2 group increased to 213.32 and 72.34%, respectively. The half-life and peak concentration increased by 44.27 and 133.67%, respectively. The clearance rate and apparent distribution volume decreased to 69.13 and 46.75%, respectively. There were no statistical differences in the pharmacokinetic parameters between the P group and the H1 group. In conclusion, the pharmacokinetic changes of sildenafil have a multi-factor regulation mechanism, and changes in blood gas, pathology, and biochemical indicators and metabolic enzymes affect the absorption, distribution, excretion, and metabolism of sildenafil, respectively. This study provides experimental evidence and new ideas for the rational use of sildenafil under acute hypoxic conditions.

Analysis of the Reactivity of Aspirin and Clopidogrel and Its Influencing Factors in Patients with Coronary Heart Disease at High Altitude

Objective

To evaluate the efficacy of dual-antiplatelet treatment (DAPT) in patients with coronary heart disease (CHD) at high altitude by using thrombelastogram (TEG) and to analyze the related biochemical factors affecting drug reactivity.

Methods

Totally 118 CHD patients who admitted to the Qinghai People's Hospital from September 2019 to September 2020 were enrolled in the group. Those people have lived in Qinghai for a long time. Seven days after DAPT, venous blood was collected on an empty stomach in the early morning of the next day; blood routine, coagulation function, and biochemical items were tested. Thrombelastogram (TEG) was used to draw curves to calculate platelet, coagulation and fibrinolysis functions, and drug inhibition rate. Patients were divided into the aspirin resistance (AR) group, clopidogrel resistance (CR) group, dual-antiplatelet drug resistance (DAR) group, and drug-sensitive group according to different inhibition rates. The drug efficacy was analyzed, and the clinical data, biochemical indexes, and TEG parameters of each group were compared to identify the risk factors of drug resistance.

Results

Those 118 CHD patients at high altitude were incorporated into the study, ranging from 38 to 84 years of age, including 81 males (68.64%) and 37 females (31.36%). The platelet function and coagulation-fibrinolysis function were detected by TEG, and MA_THROMBI, MA_ADP, and MA_AA were higher than the reference range. There were 82 cases (69.49%) of drug resistance, 36 cases (32.53%) of drug sensitivity, 17 cases (14.41%) of AR alone, and 16 cases (12.71%) of CR alone. There was no significant difference in age, gender, BMI, oxygen saturation, TG, GFR, and history of diabetes and hypertension between ACS and CCS groups (P > 0.05). PLT and FIB in the ACS group were higher than those in the CCS group, and the difference was statistically significant (P < 0.05). In addition, MA_THROMBIN, MA_FIBRIN, E, A, A30, and coagulation composite index were also higher than those in the CCS group, with a statistically significant difference (P < 0.05). Univariate analysis and logistic regression analysis suggested that age, HbA1c, FBG, and diabetes were the main factors of drug resistance.

Conclusion

Antiplatelet drugs aspirin and clopidogrel resistance are associated with increased age, elevated HbA1c and FBG, and diabetes. Therefore, it is necessary to take reasonable treatment measures based on the actual situation of patients.

Effects of Gut Microbiota on Drug Metabolism and Guidance for Rational Drug Use Under Hypoxic Conditions at High Altitudes

BACKGROUND

Modern features of drug development such as low permeability, low solubility, and improved release affect the interplay of the gut microbiota and drug metabolism. In recent years, studies have established the impact of plateau hypoxia on gut microbiota, where drug use by plateau populations is affected by hypoxia- induced changes in intestinal microflora-mediated drug metabolism.

METHODS

In this review, we summarized the effects of gut microbiota on drug metabolism, and of plateau hypoxia on the intestinal flora, with the aim of providing guidance for the rational use of drugs in high-altitude populations.

RESULTS

The evidence clearly shows that alterations in gut microbiota can affect pro-drug activation, drug inactivation, and the biotransformation of xenobiotics. Additionally, plateau hypoxia alters drug metabolism by affecting intestinal flora.

CONCLUSION

This review provides an overview of the effects of gut microbiota on drug metabolism and provides guidance for rational drug use under hypoxic conditions at high altitudes.

Pharmacology of Ivabradine and the Effect on Chronic Heart Failure

Chronic Heart Failure (CHF) is a complex clinical syndrome with a high incidence worldwide. Although various types of pharmacological and device therapies are available for CHF, the prognosis is not ideal, for which, the control of increased Heart Rate (HR) is critical. Recently, a bradycardic agent, ivabradine, is found to reduce HR by inhibiting the funny current (If). The underlying mechanism states that ivabradine can enter the Hyperpolarization-activated Cyclic Nucleotide-gated (HCN) channels and bind to the intracellular side, subsequently inhibiting the If. This phenomenon can prolong the slow spontaneous phase in the diastolic depolarization, and thus, reduce HR. The clinical trials demonstrated the significant effects of the drug on reducing HR and improving the symptoms of CHF with fewer adverse effects. This review primarily introduces the chemical features and pharmacological characteristics of ivabradine and the mechanism of treating CHF. Also, some expected therapeutic effects on different diseases were also concluded. However, ivabradine, as a typical If channel inhibitor, necessitates additional research to verify its pharmacological functions.