A safety signal for congenital strabismus associated with valproic acid: A pharmacovigilance analysis utilizing the FDA Adverse Event Reporting System database.

This pharmacovigilance study investigated the relationship between antiepileptic drugs and congenital strabismus, utilizing the FDA Adverse Event Report System database between 2014 and 2023. Out of 28 347 889 reports of adverse events in 10 937 764 cases, we identified 1104 reports of strabismus and 67 of congenital strabismus. Valproic acid was the most frequently implicated primary suspect drug (95 and 14 cases, respectively). Ninety-five reports involved transplacental valproic acid exposure, yielding an information component (IC) of 7.06 (IC-2 × standard deviation: 5.50). A multivariate analysis showed that transplacental exposure to valproic acid correlated with strabismus (adjusted odds ratio: 8.47, 95% CI: 6.74-10.65). We revealed a robust safety signal linking valproic acid to congenital strabismus.

Relationship Between Clozapine and Non-Hematological Malignant Tumors: A Pharmacovigilance Analysis Using the FDA Adverse Event Reporting System Database.

BACKGROUND AND OBJECTIVES: Clozapine shows higher efficacy against treatment-resistant schizophrenia than other antipsychotics. This study aimed to investigate whether clozapine is associated with the risk of non-hematological malignant tumors, utilizing the US Food and Drug Administration (FDA) Adverse Event Report System (FAERS) database. METHODS: The records from the first quarter of 2004 to the third quarter of 2012 were used for disproportionality analysis, and patients who developed non-hematological malignant tumors were identified by the Standardized Medical Dictionary for Regulatory Activities Queries (SMQ). RESULTS: Of the 3,641,281 patients with 12,401,586 reports of adverse drug events, 151,904 reports belonged to non-hematological malignant tumors (SMQ). We identified 1668 reports of non-hematological malignant tumors (SMQ) in clozapine users, and the reporting odds ratio (ROR) was calculated to be 1.28 (95% confidence interval (CI): 1.22-1.34). ROR (95% CI) for the relationship between clozapine and the risk of testis cancer was calculated as 10.94 (6.99-17.12), 9.87 (7.42-13.15) for gastrointestinal carcinoma, 7.48 (5.57-10.05) for metastatic lung cancer, 6.71 (4.52-9.97) for throat cancer, 6.12 (4.56-8.21) for metastases to the spine, 5.97 (5.30-6.72) for lung malignant neoplasm, 5.07 (3.69-6.95) for esophageal carcinoma, 1.88 (1.43-2.47) for colon cancer, and 1.65 (1.24-2.21) for metastases to the liver. Colon cancer, esophageal carcinoma, and throat cancer were predominantly reported in males, and metastases to the spine and liver were in females. CONCLUSION: This study detected signals indicating a relationship between clozapine and certain non-hematological malignant tumors, utilizing the FAERS database. Despite the database relying on spontaneous reporting, the current results justify further investigation.

Data Mining for Risks of Clozapine Side Effects, Including Neutropenia, Associated with Lithium Carbonate Administration: Analysis Using the Japanese Adverse Drug Event Report Database.

BACKGROUND AND OBJECTIVE: Clozapine use is associated with development of neutropenia, and lithium carbonate may be co-administered to reduce this risk; however, this has not yet been adequately investigated. The present study examined whether lithium administration is associated with the risks of clozapine side effects, including neutropenia. METHODS: Data on patients taking clozapine, extracted from the Japanese Adverse Drug Event Report (JADER) database, were analyzed. Patients who developed clozapine side effects were identified by the Standardized Medical Dictionary for Regulatory Activities Queries. The relationship between the use of lithium and risk of clozapine side effects was examined using logistic regression analysis. RESULTS: The use of lithium was reported in 530 out of 2,453 clozapine users. Hematopoietic leukopenia, convulsion, and noninfectious myocarditis/pericarditis developed in 109, 87, and seven lithium-treated patients, and in 335, 173, and 62 untreated patients, respectively. Univariate analysis showed no relationship between lithium administration and the risks of hematopoietic leukopenia (adjusted odds ratio (aOR) 1.11; 95% confidence interval (CI) 0.98-1.25), and the association with the risks of convulsion (aOR 1.41; 95% CI 1.23-1.62) and noninfectious myocarditis/pericarditis (aOR 0.63; 95% CI 0.43-0.94). Multivariate analysis revealed that lithium use was independently associated with the risks of convulsion (aOR 1.40; 95% CI 1.21-1.60) and noninfectious myocarditis/pericarditis (aOR 0.62; 95% CI 0.41-0.91). CONCLUSION: The risks of seizure and myocarditis, but not of neutropenia, in clozapine-treated patients may be altered by lithium. Although the JADER database is based on spontaneous reporting, the present results warrant further study.

Risk factors for suicidal behavior/ideation and hostility/aggression in patients with bipolar disorders: An analysis using the Japanese Adverse Drug Event Report database.

The present study attempted to identify risk factors for suicidality and hostility/aggression in patients with bipolar disorders. Data on 3521 patients were extracted from the Japanese Adverse Drug Event Report (JADER) database. There were 134 reports regarding suicidal behavior/ideation, and 129 patients were judged to have it. Standardized Medical Dictionary for Regulatory Activities queries indicated that 248 adverse drug events pertained to hostility/aggression, and 218 patients were considered to show hostility/aggression. A multiple logistic regression analysis revealed the association of the risk for suicidal behavior/ideation with bipolar II disorder [adjusted odds ratio (aOR): 4.55, 95% confidence interval (CI): 1.90-10.9], male sex (aOR: 1.23, 95% CI: 1.02-1.48), age <50 years (aOR: 1.75, 95% CI: 1.43-2.15), the administration of aripiprazole (aOR: 1.27, 95% CI: 1.00-1.60), and akathisia (aOR: 3.05, 95% CI: 1.80-5.18), while lithium carbonate decreased its odds (aOR: 0.664, 95% CI: 0.537-0.821). The risk of hostility/aggression was associated with male sex (aOR: 1.22, 95% CI: 1.06-1.40), lithium carbonate (aOR: 0.823, 95% CI: 0.710-0.953), and carbamazepine (aOR: 0.693, 95% CI: 0.500-0.961). No association between suicidal behavior/ideation and hostility/aggression was recognized. The present study proposes factors related with suicidal behavior/ideation and hostility/aggression in patients with bipolar disorders using the JADER database. Lithium carbonate appeared to decrease the risks of suicidal behavior/ideation and hostility/aggression in patients with bipolar disorders, and akathisia may be associated with the former risk. Further studies are required to evaluate the identified signals.

Relationship between lithium carbonate and the risk of Parkinson-like events in patients with bipolar disorders: A multivariate analysis using the Japanese adverse drug event report database.

The present study attempted to identify risk factors for Parkinson-like events using the Japanese adverse drug event report database. A total of 3521 patients with bipolar disorders were extracted from the database, and Parkinson-like events were detected in 111 (3.15%) using the standardized Medical Dictionary for Regulatory Activities queries. A multiple logistic regression analysis identified age ≥50 years and the use of sodium valproate or aripiprazole as risk factors. Lithium carbonate was not associated with an increased risk of Parkinson-like events, but was related to these events in patients taking sodium valproate.

Antidepressants induce toxicity in human placental BeWo cells.

Selective serotonin reuptake inhibitors (SSRIs), serotonin and noradrenaline reuptake inhibitors (SNRIs), and noradrenergic and specific serotonergic antidepressants (NaSSAs) are broadly used for the treatment of depression. Depression is one of the most common psychiatric disorders in pregnant women and SSRIs are commonly prescribed for depression during pregnancy. The placenta regulates the transport of nutrients and oxygen between the maternal and fetal circulation, and is essential for the survival and growth of the fetus. The present study investigated the effects of antidepressants on human placental BeWo cells. BeWo cell viability was significantly decreased following exposure to sertraline (SSRI), paroxetine (SSRI), fluvoxamine (SSRI), and duloxetine (SNRI), whereas escitalopram (SSRI), venlafaxine (SNRI), and mirtazapine (NaSSA) showed little or no effects. Extracellular lactate dehydrogenase activity was increased by sertraline, paroxetine, fluvoxamine, and duloxetine, indicating toxicity to the cells. Sertraline increased the production of cellular reactive oxygen species (ROS) and decreased the mitochondrial membrane potential. Sertraline decreased the cellular ATP content in a time and concentration-dependent manner. Caspase-3/7 activity and apoptotic cells, detected using the phosphatidylserine-specific fluorescent probe Apotracker Green, were increased by sertraline. Our findings suggest that antidepressants, such as sertraline, paroxetine, fluvoxamine, and duloxetine, induce toxicity in human placental BeWo cells. Sertraline may induce ROS-dependent apoptosis in human placental cells. These results are useful for further studies to determine the optimal dosage of antidepressants for pregnant women.

Amiloride is a suitable fluorescent substrate for the study of the drug transporter human multidrug and toxin extrusion 1 (MATE1).

Human multidrug and toxin extrusion 1 (MATE1; SLC47A1) is highly expressed in the kidneys and the liver. It plays a significant role in drug and endogenous compound disposition, and therefore, a rapid evaluation of its inhibition is important for drug development and for the understanding of renal and hepatic physiology. Amiloride is a potassium-sparing diuretic used for treating hypertension; it also demonstrates strong fluorescence in organic solvent or detergent solutions. In this study, we investigated the transport characteristics of amiloride by human MATE1. Cellular accumulation of amiloride was evaluated in control vector- or MATE1-transfected HEK293 cells. Cells were lysed with 1% sodium dodecyl sulfate, and fluorescence was measured using a microplate reader at wavelengths of 364ex and 409em. With ammonium prepulse-induced intracellular acidification, MATE1 transported amiloride at an extracellular pH of 7.4. The uptake demonstrated an overshoot phenomenon and saturated, with the Km and Vmax being 23.5 µM and 1.01 nmol/mg/min, respectively. MATE1-mediated amiloride transport also presented with a bell-shaped pH profile that reached a maximum pH value of 7.4. The inhibitor sensitivity of MATE1-facilitated amiloride transport was similar to those of known substrates, such as tetraethylammonium and metformin. Among the tested inhibitors, pyrimethamine demonstrated the most potent inhibition with an IC50 value of 0.266 µM. Furthermore, MATE1 was found to be inhibited by fampridine, which was previously considered to be a non-inhibitor of MATE1. This study demonstrates that amiloride is a suitable fluorescent substrate for the in vitro study of the transport activity of MATE1.

Surveillance of drug overdose and identification of its risk factors by a multivariate analysis using the Japanese Adverse Drug Event Report database.

BACKGROUND: Limited information is currently available on drug overdose in Japan. Therefore, the present study examined drug overdose using the Japanese Adverse Drug Event Report (JADER) database. METHODS: The records of drug overdose in patients were extracted from the JADER database. Risk factors for drug overdose in patients with bipolar disorders were examined using a multiple logistic regression analysis. RESULTS: Overdoses of 1327 medicines in 784 patients were registered in the JADER database. An overdose of lithium carbonate was the most frequently reported in 144 patients, followed by zolpidem tartrate in 88, and then quetiapine fumarate, sodium valproate, risperidone, and paroxetine hydrochloride hydrate. The number of overdoses was higher in females, and peaked in patients aged with 30-39 years. The dosages of overdosed lithium carbonate ranged between 1800 and 60,000 mg, with a median of 8400 mg, while those of overdosed zolpidem tartrate ranged between 15 and 600 mg, with a median of 105 mg. Forty-one drug overdose cases were registered in 3521 patients with bipolar disorder, bipolar I disorder, or bipolar II disorder in the JADER database. A multivariate analysis of these cases identified female sex, an age younger than 50 years, and the use of lithium carbonate as risk factors for drug overdose. Lamotrigine reduced its odds, and no relationship was observed with aripiprazole or sodium valproate. CONCLUSION: The present study represented a surveillance of drug overdose, and identified risk factors in patients with bipolar disorders by a multivariate analysis using the JADER database.

Effect of Experimental Fanconi Syndrome on Tubular Reabsorption of Lithium in Rats.

Lithium, administered to patients of bipolar disorders, is mainly excreted into urine, and tubular reabsorption at the proximal tubule is involved in the renal handling of lithium. In this study, we examined the renal excretion of lithium in rats with Fanconi syndrome, characterized by defects of transports of various compounds at the proximal tubules, induced by maleic acid. After maleic acid was intravenously injected, mannitol and lithium chloride were infused in turn. Using samples of plasma and bladder urine during the mannitol infusion, renal parameters were determined. Pharmacokinetic parameters of lithium were obtained using samples during the lithium chloride infusion. Maleic acid decreased creatinine clearance and increased the fractional excretion of glucose and phosphate, suggesting the induction of Fanconi syndrome. In rats with Fanconi syndrome, plasma concentration of lithium was increased, and its renal clearance was decreased. No effect on the fractional excretion of lithium was exhibited. This study represents that the tubular reabsorption of lithium was impaired to the same degree with glomerular filtration in rats with experimental Fanconi syndrome and that the dysfunction of the tubular reabsorption of glucose and phosphate was more severe. It is possible that Fanconi syndrome inhibited the reabsorption of lithium at the proximal tubule and facilitated the reabsorption of lithium from the loop of Henle to the collecting duct.

(-)-Epigallocatechin-3-gallate Inhibits Human and Rat Renal Organic Anion Transporters.

Organic anion transporter 1 (OAT1, SLC22A6) and 3 (OAT3, SLC22A8) are multispecific drug transporters highly expressed on the basolateral membranes of the renal proximal tubules. OAT1 and OAT3 mediate the tubular secretion of clinically significant drugs; thus, they influence the pharmacokinetics of drugs and further determine their efficacy and toxicity. OAT1 and OAT3 are also the target of drug-drug interactions. In this study, we examined the effects of the tea catechin (-)-epigallocatechin-3-gallate (EGCG) on human (h) and rat (r) OAT1 and OAT3 using the fluorescent organic anion 6-carboxyfluorescein (6-CF) and hOAT1-, hOAT3-, rOat1-, or rOat3-expressing HEK293 cells and on renal elimination of 6-CF in rats. 6-CF is transported by hOAT1, hOAT3, rOat1, and rOat3. 6-CF is urinary excreted by Oats in rats. EGCG, a dominant catechin in green tea leaf, inhibits human and rat OAT1 and OAT3 and reduces the renal elimination of 6-CF in rats. Our findings are useful for the assessment of food-drug interactions mediated by renal OATs.

Citrus auraptene induces drug efflux transporter P-glycoprotein expression in human intestinal cells.

P-glycoprotein (encoded by MDR1) is a membrane transport protein expressed in the intestine, liver, kidney, placenta, and blood-brain barrier. It excludes various clinically important drugs from cells, such as verapamil, digoxin, tacrolimus, and vinblastine. Therefore, human P-glycoprotein plays important roles in drug absorption, distribution, and excretion. We reported previously that auraptene, a natural compound occurring widely in citrus fruit (e.g., grapefruit), inhibited P-glycoprotein-mediated drug transport. In this study, we investigated the effects of auraptene and other phenylpropanoids on P-glycoprotein expression using human intestinal epithelial LS174T cells and a reporter plasmid expressing 10.2 kbp of the upstream regulatory region of MDR1. Auraptene (7-geranyloxycoumarin), a prenylated coumarin, and several phenylpropanoids, such as 3-(4'-geranyloxy-3'-methoxyphenyl)-2-trans propenoic acid, derricidin [2'-hydroxy-4'-(prenyloxy)chalcone], and 3-(4'-geranyloxyphenyl)-propanoic acid, induced MDR1 promoter activity in LS174T cells. Overexpression of the nuclear receptor human pregnane X receptor gene (NR1I2) enhanced auraptene-induced MDR1 activation. Nuclear factor-kappaB inhibitors, Bay11-7082 and JSH-23, repressed MDR1 activation by auraptene. Western blot analyses showed the induction of P-glycoprotein expression in the auraptene-treated LS174T cells. The citrus phytochemical auraptene can induce the drug efflux transporter P-glycoprotein in human intestinal cells, and thus has the potential to cause food-drug interactions.

Investigation of Fluorescent Substrates and Substrate-Dependent Interactions of a Drug Transporter Organic Anion Transporting Polypeptide 2B1 (OATP2B1).

PURPOSE: In this study, we investigated organic anion transporting polypeptide 2B1 (OATP2B1)-mediated uptake of fluorescent anions to better identify fluorescent substrates for in vitro OATP2B1 assays. The OATP2B1 is involved in the intestinal absorption and one of the pharmacokinetic determinants of orally administered drugs. METHODS: A microplate reader was used to determine the cellular accumulation of the fluorescent compounds into the OATP2B1 or the empty vector-transfected HEK293 cells. RESULTS: Two types of derivatives were found to be OATP2B1 substrates: heavy halogenated derivatives, such as 4',5'-dibromofluorescein (DBF), and carboxylated derivatives, such as 5-carboxyfluorescein (5-CF). The DBF and 5-CF were transported in a time and concentration-dependent manner. The DBF was transported at a broad pH (pH 6.5-8.0) while 5-CF was transported at an acidic pH (pH 5.5-6.5). The Km values were 0.818 ± 0.067 µM at pH 7.4 for DBF and 8.56 ± 0.41 µM at pH 5.5 for 5-CF. The OATP2B1 inhibitors, including atorvastatin, bromosulfophthalein, glibenclamide, sulfasalazine, talinolol, and estrone 3-sulfate, inhibited the DBF and the 5-CF transport. Contrastively, testosterone, dehydroepiandrosterone sulfate, and progesterone inhibited the DBF transport but stimulated the 5-CF transport. Natural flavonoid aglycones, such as naringenin and baicalein, also exhibited substrate-dependent effects in this manner. CONCLUSION: We found two fluorescein analogs, DBF and 5-CF as the OATP2B1 substrates that exhibited substrate-dependent interactions.

Microtubule-targeting anticancer drug eribulin induces drug efflux transporter P-glycoprotein.

This study examined the effects of microtubule-targeting anticancer drugs (paclitaxel, cabazitaxel, and eribulin) on the expression of drug efflux transporter P-glycoprotein, which is encoded by MDR1. Paclitaxel and eribulin induced MDR1 promoter activity in a concentration-dependent manner, while cabazitaxel had little effect in human intestinal epithelial LS174T cells. Overexpression of the nuclear receptor pregnane X receptor (PXR) gene (NR1I2) enhanced paclitaxel- and eribulin-induced MDR1 activation, but expression of the nuclear receptor co-repressor silencing mediator for retinoid and thyroid receptors (SMRT) gene (NCOR2) repressed MDR1 activation. Eribulin increased the mRNA and protein expression of P-glycoprotein in LS174T cells. Cellular uptake of rhodamine 123 and calcein-acetoxymethyl ester (calcein-AM), P-glycoprotein substrates, decreased in paclitaxel- or eribulin-treated LS174T cells. Eribulin also increased MDR1 promoter activity in human breast cancer MCF7 cells. The results suggest that the microtubule-targeting anticancer drug eribulin can induce the drug efflux transporter P-glycoprotein via PXR in human intestinal and breast cancer cells and thus influence the efficacy of anticancer drugs.

Effect of renal ischemia on urinary excretion of lithium in rats.

Lithium, administered to patients with bipolar disorders, is mainly excreted in the urine, and tubular reabsorption is involved. This study characterized the renal excretion of lithium in rats subjected to renal ischemia for 60 min or 90 min. After intravenous injection of lithium chloride at 25 mg/kg, the pharmacokinetic parameters of lithium were determined. In sham-operated rats, the renal clearance of lithium was calculated to be 1.49 ml/min/kg, and its ratio to creatinine clearance (fractional excretion) was 43.4%. Renal ischemia inhibited the renal excretion of lithium, and did not affect its fractional excretion. The urinary pH of rats with renal ischemia for 90 min was significantly higher than those of the other groups, and the linear regression with the fractional excretion of lithium in rats with renal ischemia showed a moderate correlation (r = 0.650, p = 0.00193). This study demonstrated the effect of renal ischemia on the renal excretion of lithium in rats. It was suggested that not only glomerular filtration but also the reabsorption of lithium was impaired by renal ischemia.

Effects of Natural Polyphenols on the Expression of Drug Efflux Transporter P-Glycoprotein in Human Intestinal Cells.

The drug efflux transporter P-glycoprotein, which is encoded by MDR1 (ABCB1), plays important roles in drug absorption, distribution, and elimination. We previously reported that dietary polyphenols such as quercetin, curcumin, honokiol, magnolol, caffeic acid phenetyl ester (CAPE), xanthohumol, and anacardic acid inhibit P-glycoprotein-mediated drug transport. In the present study, we investigated the effects of polyphenols on the expression of P-glycoprotein using human intestinal epithelial LS174T cells and a reporter plasmid expressing 10.2 kbp of the upstream regulatory region of MDR1. Honokiol, magnolol, CAPE, xanthohumol, and anacardic acid activated the MDR1 promoter in LS174T cells, and the cellular uptake of rhodamine 123 and calcein-AM, fluorescent substrates of P-glycoprotein, decreased in polyphenol-treated LS174T cells. These results suggest that dietary natural polyphenols can induce the drug efflux transporter P-glycoprotein and have the potential to promote food-drug interactions.

Purification and reconstitution of polyspecific H+/organic cation antiporter human MATE1.

Human MATE1 (multidrug and toxin extrusion 1, hMATE1) is a H+/organic cation (OC) exchanger responsible for the final step of toxic organic cation excretion in the kidney and liver. To investigate the mechanism of transport, we have established an in vitro assay procedure that includes its expression in insect cells, solubilization with octyl glucoside, purification, and reconstitution into liposomes. The resultant proteoliposomes containing hMATE1 as the sole protein component took up radiolabeled tetraethylammonium (TEA) in a ∆pH-dependent and electroneutral fashion. Furthermore, lipid-detergent micelle containing hMATE1 showed ∆pH-dependent TEA binding similar to transport. Mutated hMATE1 with replacement E273Q completely lacked these TEA binding and transport. In the case of divalent substrates, transport was electrogenic. These observations indicate that the stoichiometry of OC/H+ exchange is independent of substrate charge. Purification and reconstitution of hMATE1 is considered to be suitable for understanding the detailed molecular mechanisms of hMATE1. The results suggest that Glu273 of hMATE1 plays essential roles in substrate binding and transport.

Nonlinear disposition of lithium in rats and saturation of its tubular reabsorption by the sodium-phosphate cotransporter as a cause.

We previously reported the contribution of sodium-phosphate cotransporter to the tubular reabsorption of lithium in rats. In the present study, the dose dependency of the renal handling of lithium was examined in rats. When lithium chloride at 1.25 mg/kg, 2.5 mg/kg and 25 mg/kg was intravenously injected as a bolus, the areas under the plasma concentration-time curve of lithium until 60 minutes were calculated to be 6.23 mEq·min/l, 8.77 mEq·min/l and 64.6 mEq·min/l, respectively. The renal clearance of lithium and its fractional excretion increased with increments in the dose administered. The renal clearance of lithium strongly correlated with the urinary excretion rate of phosphate in the 1.25 mg/kg group (r = 0.840) and 2.5 mg/kg group (r = 0.773), whereas this correlation was weak in the 25 mg/kg group (r = 0.306). The infusion of foscarnet, a typical inhibitor of sodium-phosphate cotransporter, decreased the fractional reabsorption of lithium in rats administered lithium chloride at 2.5 mg/kg, but did not affect it in rats administered 25 mg/kg. These results demonstrate the nonlinearity of the renal excretion of lithium in rats, with the saturation of lithium reabsorption by the sodium-phosphate cotransporter potentially being involved.

D-Malate decreases renal content of α-ketoglutarate, a driving force of organic anion transporters OAT1 and OAT3, resulting in inhibited tubular secretion of phenolsulfonphthalein, in rats.

d-Malate inhibits a Krebs cycle enzyme and the tubular transport of α-ketoglutarate, an intermediate of the Krebs cycle and the driving force for rat organic anion transporter 1 (rOAT1) and rOAT3 in the kidney. This study examined the effects of d-malate on the rat organic anion transport system. The uptake of 6-carboxyfluorescein by HEK293 cells expressing rOAT1 or rOAT3 was not affected by d-malate and l-malate. Up to 60 min after the intravenous injection of phenolsulfonphthalein (PSP), a typical substrate of the renal organic anion transporters, as a bolus to rats, 47.1% of the dose was recovered in the urine, and its renal clearance was estimated to be 8.60 ml/min/kg. d-Malate but not l-malate interfered with its renal excretion, resulting in the delayed elimination of PSP from plasma. No effect of d-malate was recognized on creatinine clearance or the expression level of rOAT3 in the kidney cortex. d-Malate increased the plasma concentration of α-ketoglutarate. In addition, the compound greatly stimulated the renal excretion of α-ketoglutarate, implying that d-malate inhibited its reabsorption. The content of α-ketoglutarate was significantly decreased in the kidney cortex of rats administered d-malate. Collectively, this study shows that d-malate abrogates the tubular secretion of PSP, and the reduction of the renal content of α-ketoglutarate was proposed to be one of the mechanisms. A relationship between the reabsorption of α-ketoglutarate and the basolateral uptake of organic anion in the kidney is suggested.

Effects of phenylpropanoids on human organic anion transporters hOAT1 and hOAT3.

Human organic anion transporters hOAT1/SLC22A6 and hOAT3/SLC22A8 are highly expressed on the basolateral membrane of renal proximal tubules and mediate tubular uptake of anionic drugs from blood. They play an important role for drug disposition, and therefore close studies of their ligand recognition are important for drug therapy and development. In this study, we performed uptake experiments using HEK293 and fluorescent anion 6-carboxyfluorescein to asses the effects of phenylpropanoids on hOAT1 and hOAT3. We found that phenylpropanoids, 3-(4'-isopentenyloxyphenyl)-benzoic acid (IBA), 3-(4'-isopentenyloxy-3'-methoxyphenyl)-benzoic acid (IMBA), and 3-(4'-geranyloxy-3'-methoxy phenyl)-benzoic acid (GMBA) inhibited hOAT1 and hOAT3. The Ki values for hOAT1 were comparable to that of probenecid, a strong inhibitor of hOAT1 and hOAT3. While IBA demonstrated competitive inhibition, IMBA and GMBA showed mixed-type inhibition. After preincubation and washout, the inhibitory effects remained with IMBA and GMBA but not IBA, suggesting that the functional group at 3'-position is responsible for these differences. In conclusion, IBA, IMBA, and GMBA are inhibitors of hOAT1 and hOAT3.