Identification and characterization of endogenous biomarkers for hepatic vectorial transport (OATP1B3-P-gp) function using metabolomics with serum pharmacology.

The organic anion-transporting polypeptide 1B3 and P-glycoprotein (P-gp) provide efficient directional transport (OATP1B3-P-gp) from the blood to the bile that serves as a key determinant of hepatic disposition of the drug. Unfortunately, there is still a lack of effective means to evaluate the disposal ability mediated by transporters. The present study was designed to identify a suitable endogenous biomarker for the assessment of OATP1B3-P-gp function in the liver. We established stably transfected HEK293T-OATP1B3 and HEK293T-P-gp cell lines. Results showed that azelaic acid (AzA) was an endogenous substrate for OATP1B3 and P-gp using serum pharmacology combined with metabolomics. There is a good correlation between the serum concentration of AzA and probe drugs of rOATP1B3 and rP-gp when rats were treated with their inhibitors. Importantly, after 5-fluorouracil-induced rat liver injury, the relative mRNA level and expression of rOATP1B3 and rP-gp were markedly down-regulated in the liver, and the serum concentration of AzA was significantly increased. These observations suggest that AzA is an endogenous substrate of both OATP1B3 and P-gp, and may serve as a potential endogenous biomarker for the assessment of the function of OATP1B3-P-gp for the prediction of changes in the pharmacokinetics of drugs transported by OATP1B3-P-gp in liver disease states.

Predictive value of cytokines combined with human neutrophil lipocalinin acute ischemic stroke-associated pneumonia.

OBJECTIVE: To explore the predictive value of interleukin-6 (IL-6) combined with human neutrophil lipocalin (HNL) of stroke-associated pneumonia (SAP) in patients who were diagnosed with acute ischemic stroke (AIS). METHODS: 108patients were divided into two groups: pneumonia group (52 cases) and non-pneumonia group (56 cases), according to whether the patients developed SAP within 7 days of admission. General information was compared between the two groups, like age, gender, history of hypertension, diabetes mellitus, cardiovascular disease, dysphagia, smoking and alcoholhistory. Clinical data were recorded and compared, including lipid profile, interleukin-6 (IL-6), homocysteine (Hcy), National Institutes of Health Stroke Scale (NIHSS) score, and HNL. Multivariate Logistic regression analysis was used to screen the risk factors of AIS-AP, and the predictive value of IL-6 and HNL alone and in combination was evaluated by receiver operating characteristic curve (ROC curve). RESULTS: Logistic regression analysis showed that dysphagia (OR,0.018; 95% CI, 0.001 ~ 0.427; P = 0.013), increased NIHSS scores(OR,0.012; 95% CI, 0.000 ~ 0.434; P = 0.016), and high levels of IL-6 (OR,0.014; 95% CI, 0.000 ~ 0.695; P = 0.032)and HNL (OR,0.006; 95% CI, 0.000 ~ 0.280; P = 0.009) were independent risk factors for SAP with significant difference (all P < 0.05). According to the ROC curve analysis of IL-6, the area under the curve (AUC) was 0.881 (95% CI: 0.820 ~ 0.942), and the optimal cutoff value was 6.89 pg/mL with the sensitivity of 73.1% and specificity of 85.7%. As for the ROC curve analysis of HNL, the AUC was 0.896 (95% CI: 0.839 ~ 0.954), and the best cutoff value was 99.66ng/mL with the sensitivity of 76.9% and specificity of 89.3%. The AUC of the combination of IL-6 and HNL increased to 0.952 (95% CI: 0.914 ~ 0.989), and the sensitivity and specificity increased to 80.8% and 92.9%, respectively. CONCLUSION: In this research, the levels of IL-6 ≥ 6.89 pg/mL and HNL ≥ 99.66ng/mL were considered as risk factors for AIS patients complicated with SAP. The combined detection had higher predictive value for patients with SAP, which may help to identify who were in highrisk.

Identification and characterization of an endogenous biomarker of the renal vectorial transport (OCT2-MATE1).

The renal tubular organic cation transporter 2 (OCT2) and multidrug and toxin extrusion protein 1 (MATE1) mediate the vectorial elimination of many drugs and toxins from the kidney, and endogenous biomarkers for vectorial transport (OCT2-MATE1) would allow more accurate drug dosing and help to characterize drug-drug interactions and toxicity. Human serum uptake in OCT2-overexpressing cells and metabolomics analysis were carried out. Potential biomarkers were verified in vitro and in vivo. The specificity of biomarkers was validated in renal transporter overexpressing cells and the sensitivity was investigated by Km . The results showed that the uptake of thiamine, histamine, and 5-hydroxytryptamine was significantly increased in OCT2-overexpressing cells. In vitro assays confirmed that thiamine, histamine, and 5-hydroxytryptamine were substrates of both OCT2 and MATE1. In vivo measurements indicated that the serum thiamine level was increased significantly in the presence of the rOCT2 inhibitor cimetidine, and the level in renal tissue was increased significantly by the rMATE1 inhibitor pyrimethamine. There were no significant changes in the uptake or efflux of thiamine in cell lines overexpressed OAT1, OAT2, OAT3, MRP4, organic anion transporting polypeptide 4C1, P-gp, peptide transporter 2, urate transporter 1, and OAT4. The Km for thiamine with OCT2 and MATE1 were 71.2 and 10.8 µM, respectively. In addition, the cumulative excretion of thiamine at 2 and 4 h was strongly correlated with metformin excretion (R2  > 0.6). Thus, thiamine is preferentially secreted by the OCT2 and MATE1 in renal tubules and can provide a reference value for evaluating the function of the renal tubular OCT2-MATE1.

Erythropoietin promotes energy metabolism to improve LPS-induced injury in HK-2 cells via SIRT1/PGC1-α pathway.

Acute kidney injury (AKI) is one of frequent complications of sepsis with high mortality. Mitochondria is the center of energy metabolism participating in the pathogenesis of sepsis-associated AKI, and SIRT1/PGC1-α signaling pathway plays a crucial role in the modulation of energy metabolism. Erythropoietin (EPO) exerts protective functions on chronic kidney disease. We aimed to assess the effects of EPO on cell damage and energy metabolism in a cell model of septic AKI. Renal tubular epithelial cells HK-2 were treated with LPS and human recombinant erythropoietin (rhEPO). Cell viability was detected by CCK-8 and mitochondrial membrane potential was determined using JC-1 fluorescent probe. Then the content of ATP, ADP and NADPH, as well as lactic acid, were measured for the assessment of energy metabolism. Oxidative stress was evaluated by detecting the levels of ROS, MDA, SOD and GSH. Pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1ß, were measured with ELISA. Moreover, qRT-PCR and western blot were performed to detect mRNA and protein expressions. shSIRT1 was used to knockdown SIRT1, while EX527 and SR-18292 were applied to inhibit SIRT1 and PGC1-α, respectively, to investigate the regulatory mechanism of rhEPO on inflammatory injury and energy metabolism. In LPS-exposed HK-2 cells, rhEPO attenuated cell damage, inflammation and abnormal energy metabolism, as indicated by the elevated cell viability, the inhibited oxidative stress, cell apoptosis and inflammation, as well as the increased mitochondrial membrane potential and energy metabolism. However, these protective effects induced by rhEPO were reversed after SIRT1 or PGC1-α inhibition. EPO activated SIRT1/PGC1-α pathway to alleviate LPS-induced abnormal energy metabolism and cell damage in HK-2 cells. Our study suggested that rhEPO played a renoprotective role through SIRT1/PGC1-α pathway, which supported its therapeutic potential in septic AKI.

Preventive effect of LCZ696 on hypoxic pulmonary hypertension in rats via regulating the PI3K/AKT signaling pathway.

Hypoxic pulmonary hypertension (HPH) is a devastating disease worldwide; however, effective therapeutic drugs are lacking. This study investigated the effects and underlying mechanisms of LCZ696 treatment on hypoxia-induced pulmonary hypertension. Male Sprague-Dawley (SD) rats were kept in a hypobaric chamber with an oxygen concentration of 5% for 4 weeks. Rats were treated with either LCZ696 (18 mg/kg, 36 mg/kg, and 72 mg/kg) or sildenafil. The mean pulmonary artery pressure (mPAP), right ventricle hypertrophy index (RVHI), and lung system index were measured. Hematoxylin-eosin (HE) staining, Masson staining, and immunofluorescence staining were used for histological analysis. Enzyme linked immunosorbent assay (ELISA) kits were used to determine the concentrations of inflammatory and hypoxia-related factors. Western blotting was used to examine the expression of apoptotic and PI3K/AKT signaling pathway proteins in rat lung tissue. Hypoxia increased mPAP, RVHI, and lung system index and induced pulmonary vascular remodeling, pulmonary arteriomyosis, and pulmonary artery fibrosis. LCZ696 treatment reduced the increase in mPAP, RVHI, and the lung system index and ameliorated the induced pathological changes. Hypoxia upregulated expression of NF-kB, TNF-α, IL-6, HIF-1α, and Vascular endothelial growth factor (VEGF), decreased the ratio of Bax/Bcl-2, and activated the PI3K/AKT signaling pathway in lung tissue, and these effects were partially reversed by treatment with LCZ696. These results demonstrated that LCZ696 can ameliorate hypoxia-induced HPH by suppressing apoptosis, inhibiting the inflammatory response, and inhibiting the PI3K/AKT signaling pathway. It provides a reference for clinical rational drug use and lays a foundation for the study of HPH therapeutic drugs.

Accumulation of Renal Fibrosis in Hyperuricemia Rats Is Attributed to the Recruitment of Mast Cells, Activation of the TGF-ß1/Smad2/3 Pathway, and Aggravation of Oxidative Stress.

Renal fibrosis is relentlessly progressive and irreversible, and a life-threatening risk. With the continuous intake of a high-purine diet, hyperuricemia has become a health risk factor in addition to hyperglycemia, hypertension, and hyperlipidemia. Hyperuricemia is also an independent risk factor for renal interstitial fibrosis. Numerous studies have reported that increased mast cells (MCs) are closely associated with kidney injury induced by different triggering factors. This study investigated the effect of MCs on renal injury in rats caused by hyperuricemia and the relationship between MCs and renal fibrosis. Our results reveal that hyperuricemia contributes to renal injury, with a significant increase in renal MCs, leading to renal fibrosis, mitochondrial structural disorders, and oxidative stress damage. The administration of the MCs membrane stabilizer, sodium cromoglycate (SCG), decreased the expression of SCF/c-kit, reduced the expression of α-SMA, MMP2, and inhibited the TGF-ß1/Smad2/3 pathway, thereby alleviating renal fibrosis. Additionally, SCG reduced renal oxidative stress and mitigated mitochondrial structural damage by inhibiting Ang II production and increasing renal GSH, GSH-Px, and GR levels. Collectively, the recruitment of MCs, activation of the TGF-ß1/Smad2/3 pathway, and Ang II production drive renal oxidative stress, ultimately promoting the progression of renal fibrosis in hyperuricemic rats.

miR-433-3p Targets AJUBA to Inhibit Malignant Progression of Glioma.

INTRODUCTION: Glioma is the most aggressive and malignant type of tumors among primary intracranial tumors. miR-433-3p has been verified to be correlated with the formation and progression of many types of cancers. METHODS: In this study, the effects of miR-433-3p and AJUBA on the proliferation, migration, and invasion of glioma and the molecular mechanisms were investigated. We analyzed bioinformatics databases and conducted cell biology experiments to determine that compared with adjacent tissue and normal cells, the expression level of miR-433-3p in glioma tissue and cells was lower, while the expression level of AJUBA was higher. Overexpressing miR-433-3p could significantly inhibit the proliferation, migration, and invasion of glioma cells and promote cell apoptosis. RESULTS: In addition, after overexpressing miR-433-3p and AJUBA, it was found that overexpressing AJUBA could attenuate the inhibitory effect of overexpressing miR-433-3p on the proliferation, migration, and invasion of glioma cells, which suggested that miR-433-3p regulated the biological function of glioma by downregulating AJUBA expression. CONCLUSION: These results proved that miR-433-3p could target to inhibit the expression of AJUBA, thus inhibiting the biological function and malignant progression of glioma.

Enalapril increases the urinary excretion of metformin in rats by inducing multidrug and toxin excretion protein 1 in the kidney.

Two-thirds of patients with type 2 diabetes mellitus have hypertension, and thus the combination of two or more drugs to treat these diseases is common. It has been shown that the combination of metformin and enalapril has beneficial effects, but few studies have evaluated the interactions between these two drugs. This study investigated the effects of enalapril on the pharmacokinetics and urinary excretion of metformin in rats, with a focus on transporter-mediated drug interactions. Rats were dosed orally with metformin alone (100 mg/kg) or in combination with enalapril (4 mg/kg). The concentration of metformin was measured by high performance liquid chromatography and the level of organic cation transporters (rOCTs) and multidrug and toxin excretion protein 1 (rMATE1), which mediate the uptake and efflux of metformin, respectively, were evaluated by immunoblotting. After single and 7-day dosing, the plasma concentration of metformin in the co-administration group was significantly lower than that in the metformin-only group, and the CL/F and urinary excretion were increased in the co-administration group. Enalapril did not affect the Kp of metformin but reduced renal slice-uptake of metformin. The expression of rMATE1 was increased, whereas rOCT2 expression was decreased in rat kidney. Importantly, long-term co-administration of metformin and enalapril markedly decreased the level of lactic acid and uric acid in the blood. Enalapril increases the urinary excretion of metformin through the up-regulation of rMATE1. This reveals a new mechanism of drug interactions and provides a basis for drug dosage adjustment when these drugs are co-administered.

rhEPO inhibited cell apoptosis to alleviate acute kidney injury in sepsis by AMPK/SIRT1 activated autophagy.

BACKGROUND: Nowadays, people diagnosed sepsis may develop acute kidney injury (AKI), resulting heavy burden of health care. Recombinant human erythroprotein (rhEPO) has been suggested to have multifunction and may be used in the prevention or treatment of AKI, and its underlying mechanism remains largely unknown. METHODS: In our study, cell model induced by LPS-activated cell apoptosis in vitro and AKI animal model caused by lipopolysaccharide (LPS) injection in vivo. MTT assay and Flow Cytometry were conducted to analyze cell viability and apoptosis, respectively. Western bot was used to analyze expressions of apoptosis and autophagy associated proteins, and effects on AMPK/SIRT1 pathway. RESULTS: Our results suggested that rhEPO inhibited LPS-induced cell apoptosis in HK-2 and HEK-293. Moreover, we found that rhEPO activated autophagy to prevented cell apoptosis, changing the expression level of autophagy associated proteins such as LC3-I/LC3-II and P62, and AMPK/SIRT1 pathway was involved in its regulation. Additionally, both EX527 (SIRT1 inhibitor) and Compound C (AMPK inhibitor) blocked the autophagy effects caused by rhEPO and thus reversed the anti-apoptotic effects of rhEPO. Furthermore, our data demonstrated that rhEPO inhibited LPS-induced kidney tubular injury and decreased the expression level of apoptotic proteins by altering the expression level of autophagy related proteins and AMPK/SIRT1 pathway related proteins in vitro. CONCLUSION: Collectively, rhEPO suppressed LPS-induced cell apoptosis via AMPK/SIRT1 pathway mediated autophagy, and modulating their levels may serve as potential way in preventing AKI.

Effect of high uric acid on the disposition of metformin: in vivo and in vitro studies.

Metformin is always used as the baseline antidiabetic therapy for patients with type 2 diabetes mellitus (T2DM) and hyperuricemia. Metformin is excreted into urine through active secretion mediated by rOCTs and rMATE1.The aim of this study was to identify the effects of high uric acid on the disposition and its mechanism. For the in vivo study, a hyperuricemic animal model was induced by intraperitoneal injection of potassium oxonate (250 mg/kg) in rats. Metformin (100 mg/kg) was administered orally to investigate the pharmacokinetics in control and hyperuricemic rats, respectively. For the in vitro study, HEK293 and HepaRG cells were used to investigate the effect of uric acid (15 mg/dl) on the expression of OCT1, OCT2 and MATE1 and the disposition of metformin, respectively. The in vivo study showed that the AUC0 â†’ 600 of metformin was significantly decreased by 33.3%, whereas the cumulative urinary excretion of metformin was increased by 25.4% in hyperuricemic rats compared with that in control rats. The renal rOCT1, rOCT2 and rMATE1 and hepatic rMATE1 levels were increased in hyperuricemic rats compared with those in control rats, respectively. The in vitro study showed that uric acid could upregulate the expression of OCT2 and MATE1 in HEK293 cells and MATE1 in HepaRG cells and increase the intracellular metformin concentration in these two cell lines. These results demonstrated that a high uric acid level promoted urinary metformin excretion and decreased the plasma metformin concentration; the in vivo and in vitro studies provided a possible explanation being that high uric acid could upregulate the expression of renal metformin transporters OCTs and MATE1.

Different lipid profiles, insulin sensitivity, and insulin resistance among Han, Uygur, and Kazak men with normal glucose tolerance in Xinjiang, China.

BACKGROUND: This study aimed to determine the differences in clinical parameters among Han, Uygur, and Kazak men with normal glucose tolerance. METHODS: Participants' data from the China National Diabetes and Metabolic Disorders Study pertaining to Han, Uygur, and Kazak men from the Xinjiang province were used (n = 930). Pearson's correlation was used to examine the relationship between HOMA-IR, Matsuda Index, and clinical characteristics. RESULTS: HOMA-IR of Han men was significantly higher than in Uygurs and Kazaks (P < 0.001). The Matsuda Index of Kazaks was significantly higher than that of Hans and Uygurs (P < 0.001). While Kazaks had the highest BMI, WC, SBP, and DBP; they also had the highest HDL-C and lowest TG (P < 0.001). TG of Uygurs was significantly higher than that of Hans and Kazaks (P < 0.001). In Hans and Kazaks, the TG/HDL-C ratio increased with HOMA-IR quartiles; there was no association in Uygurs. In Hans and Kazaks, the TG/HDL-C ratio decreased with Matsuda index quartiles; there was no association in Uygurs. Multivariate linear regression showed that HOMA-IR was independently associated with ethnicity, BMI and TG/HDL-C ratio (P < 0.01), while Matsuda index was independently associated with ethnicity, BMI, LDL-C levels (P < 0.001) and TG/HDL-C ratio (P < 0.001). CONCLUSIONS: In conclusion, Han, Uygur, and Kazak men had different lipid profiles, BMI, and WC. Han men had the highest insulin resistance while Kazak men had the highest insulin sensitivity.

Alteration of renal excretion pathways in gentamicin-induced renal injury in rats.

The kidney plays a major part in the elimination of many drugs and their metabolites, and drug-induced kidney injury commonly alters either glomerular filtration or tubular transport, or both. However, the renal excretion pathway of drugs has not been fully elucidated at different stages of renal injury. This study aimed to evaluate the alteration of renal excretion pathways in gentamicin (GEN)-induced renal injury in rats. Results showed that serum cystatin C, creatinine and urea nitrogen levels were greatly increased by the exposure of GEN (100 mg kg-1 ), and creatinine concentration was increased by 39.7% by GEN (50 mg kg-1 ). GEN dose-dependently upregulated the protein expression of rOCT1, downregulated rOCT2 and rOAT1, but not affected rOAT2. Efflux transporters, rMRP2, rMRP4 and rBCRP expressions were significantly increased by GEN(100), and the rMATE1 level was markedly increased by GEN(50) but decreased by GEN(100). GEN(50) did not alter the urinary excretion of inulin, but increased metformin and furosemide excretion. However, GEN(100) resulted in a significant decrease of the urinary excretion of inulin, metformin and p-aminohippurate. In addition, urinary metformin excretions in vivo were significantly decreased by GEN(100), but slightly increased by GEN(50). These results suggested that GEN(50) resulted in the induction of rOCTs-rMATE1 and rOAT3-rMRPs pathway, but not changed the glomerular filtration rate, and GEN(100)-induced acute kidney injury caused the downregulated function of glomerular filtration -rOCTs-rMATE1 and -rOAT1-rMRPs pathway.

Multicomponent determination of traditional Chinese medicine preparation yin-zhi-huang injection by LC-MS/MS for screening of its potential bioactive candidates using HepaRG cells.

Yin-zhi-huang (YZH) injection is an injectable multiherbal prescription derived from the ancient Chinese medicine formula of Yin-chen-hao-tang, which is widely used in the clinic for the treatment of jaundice and chronic liver diseases. To date, the systematic study of the components in this multiherbal prescription still lacks suitable analytical methods that are able to simultaneously detect a broad array of components at low concentrations. In this study, a new liquid chromatography-tandem mass spectrometry method using dynamic multiple reaction monitoring mode was developed to determine multiple peaks in traditional Chinese medicine preparation YZH injection. This simple, selective and sensitive method enabled the quantification of 22 components with standard materials with a lower limit of quantification of 1.46-12.5 ng/mL in cell lysates. This method was successfully applied to celluar uptake and binding investigation of components in YZH injection. The results indicated that this strategy might be a useful approach for rapidly screening of the potential bioactive candidates from YZH injection, and the discovered candidates could be used to investigate the pharmacodynamics in further studies.

[Effects of metoprolol or/and pravastatin on the pharmacokinetics of metformin in rats].

This study investigates the effects of metoprolol (METO) or/and pravastatin (PRAV) on the pharmacokinetics of metformin (METF) in rats. Twenty-eight male SD rats were divided into METF group, METF+METO group, METF+PRAV group and METF+METO+PRAV group. Blood samples were collected at 10, 20, 40, 60, 90, 120, 180, 240, 360, 480 and 600 min after oral administration of metformin, and concentration of metformin in plasma was determined by HPLC. Compared to the METF group, Cmax of metformin was significantly decreased (P < 0.01) and MRT0−t , t1/2 and V were significantly increased in the METF+METO group; t1/2 was significantly decreased in the METF+PRAV group; Cmax was significantly decreased and MRT0−t was significantly increased in the METF+METO+PRAV group. Compared to the METF+METO group, MRT0−t of metformin was significantly decreased in the METF+METO+PRAV group. Compared to the METF+PRAV group, Cmax of metformin was significantly decreased (P < 0.01), and MRT0−t , t1/2 and V were significantly increased in the METF+METO+PRAV group. There exist multiple drug interactions of metformin, metoprolol and pravastatin in rats.

Metoprolol decreases the plasma exposure of metformin via the induction of liver, kidney and muscle uptake in rats.

Drug interactions are one of the commonest causes of side effects, particularly in long-term therapy. The aim of the current study was to investigate the possible effects of metoprolol on the pharmacokinetics of metformin in rats and to clarify the mechanism of drug interaction. In this study, rats were treated with metformin alone or in combination with metoprolol. Plasma, urine and tissue concentrations of metformin were determined by HPLC. Western blotting and real-time qPCR were used to evaluate the expression of rOCTs and rMATE1. The results showed that, after single or 7-day repeated administration, the plasma concentrations of metformin in the co-administration group were significantly decreased compared with that in the metformin group. However, the parameter V/F of metformin in the co-administration group was markedly increased compared with that in the metformin group. The hepatic, renal and muscular Kp of metformin were markedly elevated after co-administration with metoprolol. Consistently, metformin uptake in rat kidney slices was significantly induced by metoprolol. In addition, multiple administrations of metoprolol significantly reduced the expression of rMATE1 in rat kidney as well as the urinary excretion of metformin. Importantly, after long-term administration, lactic acid and uric acid levels in the co-administration group were increased by 25% and 26%, respectively, compared with that in the metformin group. These results indicate that metoprolol can decrease the plasma concentration of metformin via the induction of hepatic, renal and muscular uptake, and long-term co-administration of metformin and metoprolol can cause elevated lactic acid and uric acid levels. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of hesperidin on the pharmacokinetics of CPT-11 and its active metabolite SN-38 by regulating hepatic Mrp2 in rats.

The usage of irinotecan hydrochloride (CPT-11) chemotherapy is hindered by its dose-limiting diarrhea which appears to be associated with the intestinal exposure to SN-38, the active metabolite of CPT-11. Hesperidin, a safe and natural food ingredient flavonoid, exhibits various biological properties. Accumulated evidence showed that the regulatory effect of hesperidin on the expression of Mrp2 in the liver may be one of the critical factors controlling the biliary excretion of SN-38. This study examined the effect of hesperidin on the pharmacokinetics of CPT-11 and SN-38 as well as the regulatory effect on the hepatic expression of Mrp2. Compared with the control group, the AUC5-t was increased to 115% of CPT-11 and 122% of SN-38; the CL was decreased to 87% for CPT-11; the tissue concentration was increased in the liver, kidney and colon; and the accumulated biliary excretion was significantly decreased to 77% for CPT-11 and 76% for SN-38 in hesperidin-treated rats. Furthermore, the expression of Mrp2 in the liver was significantly decreased to 37% in the hesperidin-treated rats compared with that of the control group. These results indicate that oral administration of hesperidin significantly increased the AUC5-t and reduced the clearance of CPT-11 and SN-38, possibly by decreasing the hepatic expression of Mrp2, and thus inhibiting the biliary excretion of CPT-11 and SN-38. The results from this present study suggest that hesperidin may reduce the exposure of CPT-11 and SN-38 in the intestine by reducing the amount of biliary excretion of CPT-11 and SN-38. Copyright © 2016 John Wiley & Sons, Ltd.

Serum serotonin reduced the expression of hepatic transporter Mrp2 and P-gp via regulating nuclear receptor CAR in PI-IBS rats.

Hepatic transporters and drug metabolizing enzymes (DMEs) play important roles in the pharmacological effects and (or) side-effects of many drugs, and are regulated by several mediators, including neurotransmitters. This work aimed to investigate whether serum levels of 5-hydroxytryptamine (5-HT) affected the expression of hepatic transporters or DMEs. The expression of hepatic transporters was assessed using the Western-blot technique in a 2,4,6-trinitrobenzenesulfonic-acid-induced rat model of post-infectious irritable bowel syndrome (PI-IBS), in which serum levels of 5-HT were significantly elevated. To further clarify the underlying mechanism, the 5-HT precursor 5-hydroxytryptophan (5-HTP) and the 5-HT depleting agent parachlorophenylalanine (pCPA) were applied to adjust serum levels of 5-HT. Serum levels of 5-HT were measured using LC-MS/MS; the expression of hepatic transporters, DMEs, and nuclear receptors were examined by Western-blot technique. Our results showed that in PI-IBS rats the expression of multidrug resistance protein 2 (Mrp2) was significantly decreased, while colonic enterochromaffin cell density and serum levels of 5-HT were all significantly increased. Moreover, 5-HTP treatment significantly increased serum levels of 5-HT and decreased the expression of Mrp2 and glycoprotein P (P-gp), whereas treatment with pCPA markedly decreased serum levels of 5-HT and increased the expression of Mrp2 and P-gp. Our results indicated that serum 5-HT regulates the expression of Mrp2 and P-gp, and the underlying mechanism may be related to the altered expression of the nuclear receptor constitutive androstane receptor (CAR).

Development of a LC-MS/MS method for simultaneous determination of metoprolol and its metabolites, α-hydroxymetoprolol and O-desmethylmetoprolol, in rat plasma: application to the herb-drug interaction study of metoprolol and breviscapine.

A simple, specific and sensitive LC-MS/MS method was developed and validated for the simultaneous determination of metoprolol (MET), α-hydroxymetoprolol (HMT) and O-desmethylmetoprolol (DMT) in rat plasma. The plasma samples were prepared by protein precipitation, then the separation of the analytes was performed on an Agilent HC-C18 column (4.6 × 250 mm, 5 µm) at a flow rate of 1.0 mL/min, and post-column splitting (1:4) was used to give optimal interface flow rates (0.2 mL/min) for MS detection; the total run time was 8.5 min. Mass spectrometric detection was achieved using a triple-quadrupole mass spectrometer equipped with an electrospray source interface in positive ionization mode. The method was fully validated in terms of selectivity, linearity, accuracy, precision, stability, matrix effect and recovery over a concentration range of 3.42-7000 ng/mL for MET, 2.05-4200 ng/mL for HMT and 1.95-4000 ng/mL for DMT. The analytical method was successfully applied to herb-drug interaction study of MET and breviscapine after administration of breviscapine (12.5 mg/kg) and MET (40 mg/kg). The results suggested that breviscapine have negligible effect on pharmacokinetics of MET in rats; the information may be beneficial for the application of breviscapine in combination with MET in clinical therapy.

[Simultaneous determination of repaglinide and pravastatin sodium in rat plasma by LC-ms/MS and its application on pharmacokinetic interactions study].

The study aims to establish a method for simultaneous determination of repaglinide and pravastatin sodium in rat plasma by LC-MS/MS and to study its pharmacokinetic interactions. Eighteen male SD rats were divided into repaglinide group, pravastatin sodium group and co-administration group. Blood samples were collected at different times after oral administration. Repaglinide and pravastatin sodium in rat plasma were separated by Agilent HC-C18 with the mobile phase consisting of methanol-0.1% formic acid (80 : 20). Detection and quantification were performed by using ESI-MS. The detector was operated in selected Reaction-monitoring mode at m/z 453.3-->230.1 for repaglinide, m/z 447.2-->327.4 for pravastatin sodium and m/z 285.1-->192.9 for diazepam as the internal standard. The calibration curve obtained was linear (R2>0.99) over the concentration range of 9.77-10,000 ng.mL-1 for repaglinide and 4.88-625 ng.mL-1 for pravastatin sodium. Compared with the single administration group, Cmax and AUC0-6h of repaglinide increased significantly (P<0.05) and tmax of pravastatin sodium prolonged (P<0.05) in co-administration group. The method is found to be simple, sensitive and accurate for determining the concentration of repaglinide and pravastatin sodium in rat plasma. There exists pharmacokinetic interactions in the co-administration of repaglinide and pravastatin sodium.

Characterization of the renal tubular transport of creatinine by activity-based protein profiling and transport kinetics.

Serum creatinine is widely used to adjust the dosing of drugs eliminated by the kidney in patients with renal dysfunction, as it is a readily accessible indicator of kidney function. However, there are many limitations for drug dosage adjustment based on serum creatinine levels, one of which is the limited understanding of creatinine's tubular transport. Thus, we aimed to complement and advance the renal tubular transport of creatinine by activity-based protein profiling (ABPP) and transporter-overexpression technology. Renal tubular transporters were not identified via ABPP due to the low-affinity interaction between transporters and creatinine. The uptake of isotopically labeled d3-creatinine was significantly increased in OCT2-overexpressing cell lines (p<0.01), and the Km and Vmax of d3-creatinine uptake mediated by OCT2 was 3.1 mM and 408 pmol/mg protein/min, respectively. In the OCT2-overexpressing cell lines, the IC50 of creatinine for d3-creatinine uptake was 10.3 mM, and that of the OCT2 inhibitor cimetidine for d3-creatinine uptake was 99.04 µM. Different dosages of creatinine did not affect the renal excretion of d3-creatinine in mice (p>0.05), while cimetidine significantly reduced the renal excretion of d3-creatinine (p<0.01) without affecting the glomerular filtration rate. Molecular docking in silico showed that the OCT2 amino acid GLN242 could form a hydrogen bond of 2.5 Å with creatinine, and there may be a π-π interaction between TYR362 and creatinine. A site mutation experiment demonstrated that TYR362 and GLN242 were important sites for the OCT2-creatinine interaction. These results demonstrate that OCT2 mediates the renal tubular secretion of creatinine with low affinity and is a minor contributor to creatinine secretion.