Prediction of metabolic clearance of diclofenac in adjuvant-induced arthritis rats using a substrate depletion assay

Comparative pharmacokinetic study of the five anti-inflammatory active ingredients of Inula cappa in a normal and an LPS-induced inflammatory cell model

Inula cappa is a commonly used medicine in the Miao area of Guizhou Province in China. We established an in vitro inflammatory model of mouse macrophage RAW264.7 cells to study the different pharmacokinetics of five anti-inflammatory active ingredients in the I. cappa extract namely luteolin (LUT), chlorogenic acid (CA), cryptochlorogenic acid (CCA), 3,4-dicaffeoylquinic acid (3,4-DCQA) and 4,5-dicaffeoylquinic acid (4,5-DCQA), in a normal and an inflammatory cell model. First, RAW264.7 cells were treated in vitro with l μg/mL lipopolysaccharide (LPS) for 24 h to establish an inflammatory cell model. Then, the pharmacokinetic characteristics of the five ingredients were compared in normal and inflammatory cells after treatment with 200 μg/ml and 800 μg/ml of I. cappa extracts. After treatment with 1 μg/ml LPS for 24 h, the volume of RAW264.7 cells was increased, the morphology was changed, the antennae were obvious, and the secretion of inflammatory factors nitric oxide and TNF-α was increased. The pharmacokinetics results showed that the five ingredients in normal and inflammatory cells exhibited an increase in C_max and AUC values with increasing doses, and the C_max and AUC values of five ingredients were positively correlated with the extract concentration. Each of these five ingredients presented nonlinear pharmacokinetic characteristics. After treatment with 200 μg/ml of I. cappa extract, the uptake of five ingredients increased in inflammatory cells, T_max was prolonged, MRT and t_1/2 were prolonged, and CL_F and Vz_F were decreased, while after treatment with 800 μg/ml of I. cappa extract, the uptake of five ingredients decreased, T_max was prolonged, absorption was faster, and MRT and t_1/2 were prolonged. The five analyzed components in I. cappa extract exerted different effects on normal cells and LPS-induced inflammatory cells. Compared to normal cells, the uptake of five ingredients in inflammatory cells was faster and the AUC and C_max values increased with increasing doses, showing a dose-dependent nonlinear pharmacokinetic profile. These results indicate that the pharmacokinetic effects of the five analyzed ingredients in I. cappa extract are changed in the inflammatory state.

An HPLC-UV validated bioanalytical method for measurement of in vitro phase 1 kinetics of α-synuclein binding bifunctional compounds

Aggregates of the protein α-synuclein are associated with pathophysiology of Parkinson's disease and are present in Lewy Bodies found in the brains of Parkinson's patients. We previously demonstrated that bifunctional compounds composed of caffeine linked via a six carbon chain to either 1-aminoindan (C₈-6-I) or nicotine (C₈-6-N) bind α-synuclein and protect yeast cells from α-synuclein mediated toxicity.A critical step in development of positron emission tomography (PET) probes for neurodegenerative diseases is evaluation of their metabolic stability. We determined that C₈-6-I, and C₈-6-N both undergo phase 1 P450 metabolism in mouse, rat, and human liver microsomes. We utilised this metabolic information to guide the design of fluorinated analogues for use as PET probes and determined that the fluorine in ¹⁹F-C₈-6-I and ¹⁹F-C₈-6-N is stable to P450 enzymes.We have developed and validated an analytical HPLC-UV method following FDA and EMA guidelines to measure in vitro phase 1 kinetics of these compounds and determine their V_max, K_M and CL_int,u in mouse liver microsomes. We found that C₈-6-I and ¹⁹F-C₈-6-I have a two- to fourfold lower CL_int,u than C₈-6-N, and ¹⁹F-C₈-6-N. Our approach shows a simple, specific, and effective system to design and develop compounds as PET probes.

Protein Kinase N Family Negatively Regulates Constitutive Androstane Receptor-Mediated Transcriptional Induction of Cytochrome P450 2b10 in the Livers of Mice

In receptor-type transcription factors-mediated cytochrome P450 (P450) induction, few studies have attempted to clarify the roles of protein kinase N (PKN) in the transcriptional regulation of P450s. This study aimed to examine the involvement of PKN in the transcriptional regulation of P450s by receptor-type transcription factors, including the aryl hydrocarbon receptor, constitutive androstane receptor (CAR), and pregnane X receptor. The mRNA and protein levels and metabolic activity of P450s in the livers of wild-type (WT) and double-mutant (D) mice harboring both PKN1 kinase-negative knock-in and PKN3 knockout mutations [PKN1 ^T778A/T778A; PKN3 ^-/-] were determined after treatment with activators for receptor-type transcription factors. mRNA and protein levels and metabolic activity of CYP2B10 were significantly higher in D mice treated with the CAR activator phenobarbital (PB) but not with 1,4-bis((3,5-dichloropyridin-2-yl)oxy)benzene compared with WT mice. We examined the CAR-dependent pathway regulated by PKN after PB treatment because the extent of CYP2B10 induction in WT and D mice was notably different in response to treatment with different CAR activators. The mRNA levels of Cyp2b10 in primary hepatocytes from WT and D mice treated with PB alone or in combination with Src kinase inhibitor 1 (SKI-1) or U0126 (a mitogen-activated protein kinase inhibitor) were evaluated. Treatment of hepatocytes from D mice with the combination of PB with U0126 but not SKI-1 significantly increased the mRNA levels of Cyp2b10 compared with those from the corresponding WT mice. These findings suggest that PKN may have inhibitory effects on the Src-receptor for activated C kinase 1 (RACK1) pathway in the CAR-mediated induction of Cyp2b10 in mice livers. SIGNIFICANCE STATEMENT: This is the first report of involvement of PKN in the transcriptional regulation of P450s. The elucidation of mechanisms responsible for induction of P450s could help optimize the pharmacotherapy and improve drug development. We examined whether the mRNA and protein levels and activities of P450s were altered in double-mutant mice harboring both PKN1 kinase-negative knock-in and PKN3 knockout mutations. PKN1/3 negatively regulates CAR-mediated induction of Cyp2b10 through phosphorylation of a signaling molecule in the Src-RACK1 pathway.

Increased brain penetration of diphenhydramine and memantine in rats with adjuvant-induced arthritis

Brain penetration of cationic drugs is an important determinant of their efficacy and side effects. However, the effects of alterations in the activity of uptake transporters in the brain under inflammatory conditions on the brain penetration of cationic drugs are not fully understood. The aim of this study was to examine changes in brain penetration of cationic drugs, including diphenhydramine (DPHM), memantine (MMT), and cimetidine (CMD), and changes in the expression of uptake transporters such as organic cation transporter (Oct) in brain microvascular endothelial cells (BMECs) under inflammatory conditions. To clarify the effects of inflammation on the brain penetration of DPHM, MMT, and CMD, we performed brain microdialysis studies in a rat model of adjuvant-induced arthritis (AA). Further, differences in transporter mRNA expression levels between BMECs from control and AA rats were evaluated. Brain microdialysis showed that the unbound brain-to-plasma partition coefficient (K_p,uu,brain) for DPHM and MMT was significantly lower in AA rats compared with control rats. OCT mRNA levels were increased and proton-coupled organic cation (H⁺/OC) antiporter mRNA levels were decreased in AA rats compared with control rats. Taken together, our findings suggest that inflammation decreases the brain penetration of H⁺/OC antiporter substrates such as DPHM and MMT.

Inhibition of Methotrexate Uptake via Organic Anion Transporters OAT1 and OAT3 by Glucuronides of Nonsteroidal Anti-inflammatory Drugs

Combination therapy of non-steroidal anti-inflammatory drugs (NSAIDs) and methotrexate (MTX) sometimes triggers adverse effects, such as liver injury, renal failure, gastrointestinal disorders, and myelosuppression, owing to the reduction of MTX clearance. Previous reports have suggested that NSAIDs inhibit renal MTX uptake via organic anion transporters (OATs) and reduced folate transporter (RFC)-1 and efflux via multidrug resistance-associated proteins (MRPs). Recently, our laboratory found inhibitory effects of NSAIDs-glucuronide (NSAIDs-Glu), a major metabolite of NSAIDs, on MRP-mediated MTX transport as a new site of interaction between MTX and NSAIDs. However, it remains unclear that whether NSAIDs-Glu inhibit renal uptake of MTX. Therefore, the present study aimed to evaluate inhibitory effects of several NSAIDs-Glu (diclofenac, R- and S-ibuprofen, R- and S-flurbiprofen, and R- and S-naproxen) on human OAT1 and OAT3-mediated MTX transport. In this study, [³H]MTX uptake was observed by using human OAT1 and OAT3-overexpressing HEK293 cells in the presence or absence of NSAIDs-Glu. All examined NSAIDs-Glu exhibited concentration-dependent inhibitory effects on MTX uptake via OAT1 and OAT3. Our results indicated that NSAIDs-Glu are more potent (5- to 15-fold) inhibitors of OAT3 than OAT1. Moreover, stereoselective inhibitory effects of NSAIDs-Glu on OATs-mediated MTX uptake were not observed, unlike on MRPs-mediated transport. These findings suggest that inhibition of OAT1 and OAT3-mediated renal uptake of MTX by plasma NSAIDs-Glu may be one of the competitive sites underlying complex drug interaction between MTX and NSAIDs.

Age-related changes in mRNA levels of hepatic transporters, cytochrome P450 and UDP-glucuronosyltransferase in female rats

Hepatic transporters and metabolic enzymes affect drug pharmacokinetics. Limited information exists on the alteration in mRNA levels of hepatic transporters and metabolic enzymes with aging. We examined the effects of aging on the mRNA levels of representative hepatic drug transporters and metabolic enzymes by analyzing their levels in 10-, 30- and 50-week-old male and female rats. Levels of mRNA of drug transporters including multidrug resistance protein (Mdr)1a, multidrug resistance-associated protein (Mrp)2, breast cancer resistance protein (Bcrp) and organic anion-transporting polypeptide (Oatp)1a1, and the metabolic enzymes cytochrome P450 (CYP)3A1, CYP3A2 and UDP-glucuronosyltransferase (UGT)1A1 were analyzed using real-time reverse transcriptase polymerase chain reaction. The mRNA levels of transporters in male rats did not decrease with age, while the mRNA levels of Bcrp and Oatp1a1 in female rats decreased with age. The mRNA levels of CYP3A1 and CYP3A2 in male rats were higher than those in female rats. The mRNA levels of metabolic enzymes decreased with age in female but not male rats. In particular, the mRNA levels of UGT1A1 in 10-week-old female rats were higher than those in male rats. mRNA expression of hepatic transporters and metabolic enzymes are more susceptible to aging in female than male rats. The age-related decreases in the mRNA levels of Bcrp, Oatp1a1, CYP3A1 and CYP3A2 in female rats may affect the metabolism and transport of substrates. This study showed that aging affected the mRNA expression of hepatic transporters and metabolic enzymes in rats.

Pharmacokinetic comparison of berberine in rat plasma after oral administration of berberine hydrochloride in normal and post inflammation irritable bowel syndrome rats

In the present study, post inflammation irritable bowel syndrome (PI-IBS) rats were firstly established by intracolonic instillation of acetic acid with restraint stress. Then the pharmacokinetics of berberine in the rat plasma were compared after oral administration of berberine hydrochloride (25 mg/kg) to normal rats and PI-IBS rats. Quantification of berberine in the rat plasma was achieved by using a sensitive and rapid UPLC-MS/MS method. Plasma samples were collected at 15 different points in time and the pharmacokinetic parameters were analyzed by WinNonlin software. Compared with the normal group, area under the plasma concentration vs. time curve from zero to last sampling time (AUC_0–t) and total body clearance (CL/F) in the model group significantly increased or decreased, (2039.49 ± 492.24 vs. 2763.43 ± 203.14; 4999.34 ± 1198.79 vs. 3270.57 ± 58.32) respectively. The results indicated that the pharmacokinetic process of berberine could be altered in PI-IBS pathological conditions.

Pharmacokinetic-pharmacodynamic modeling of diclofenac in normal and Freund's complete adjuvant-induced arthritic rats

AIM

To characterize pharmacokinetic-pharmacodynamic modeling of diclofenac in Freund's complete adjuvant (FCA)-induced arthritic rats using prostaglandin E(2) (PGE(2)) as a biomarker.

METHODS

The pharmacokinetics of diclofenac was investigated using 20-day-old arthritic rats. PGE(2) level in the rats was measured using an enzyme immunoassay. A pharmacokinetic-pharmacodynamic (PK-PD) model was developed to illustrate the relationship between the plasma concentration of diclofenac and the inhibition of PGE(2) production. The inhibition of diclofenac on lipopolysaccharide (LPS)-induced PGE(2) production in blood cells was investigated in vitro.

RESULTS

Similar pharmacokinetic behavior of diclofenac was found both in normal and FCA-induced arthritic rats. Diclofenac significantly decreased the plasma levels of PGE(2) in both normal and arthritic rats. The inhibitory effect on PGE(2) levels in the plasma was in proportion to the plasma concentration of diclofenac. No delay in the onset of inhibition was observed, suggesting that the effect compartment was located in the central compartment. An inhibitory effect sigmoid I(max) model was selected to characterize the relationship between the plasma concentration of diclofenac and the inhibition of PGE(2) production in vivo. The I(max) model was also used to illustrate the inhibition of diclofenac on LPS-induced PGE(2) production in blood cells in vitro.

CONCLUSION

Arthritis induced by FCA does not alter the pharmacokinetic behaviors of diclofenac in rats, but the pharmacodynamics of diclofenac is slightly affected. A PK-PD model characterizing an inhibitory effect sigmoid I(max) can be used to fit the relationship between the plasma PGE(2) and diclofenac levels in both normal rats and FCA-induced arthritic rats.