Effect of endotoxin on doxorubicin transport across blood-brain barrier and P-glycoprotein function in mice

Influence of Escherichia coli lipopolysaccharide-induced endotoxemia on plasma and tissue disposition of florfenicol after intramuscular administration in rabbits

To assess the effects of the acute inflammatory response (AIR) induced by Escherichia coli lipopolysaccharide (LPS) on plasma and tissue disposition of florfenicol (FFC) and its metabolite florfenicol amine (FFC-a), after its intramuscular (IM) administration, twenty-two New Zealand rabbits were randomly distributed in two experimental groups: Group 1 (LPS) was treated with three intravenous doses of 2 μg LPS/kg bw, before an intramuscular dose of 20 mg/kg FFC twenty-four h after the first LPS or SS injection; Group 2 (Control) was treated with saline solution (SS) in equivalent volumes as LPS-treated group. Blood samples were collected before (T0) and at different times after FFC administration. Acute inflammatory response was assessed in a parallel study where significant increases in body temperature, C-reactive protein concentrations and leukopenia were observed in the group treated with LPS. In another two groups of rabbits, 4 h after FFC treatment, rabbits were euthanized and tissue samples were collected for analysis of FFC and FFC-a concentrations. Pharmacokinetic parameters of FFC that showed significantly higher values in LPS-treated rabbits compared with control rabbits were absorption half-life, area under the curve, mean residence time and clearance /F (Cl/F). Elimination half-life and mean residence time of FFC-a were significantly higher in LPS-treated rabbits, whereas the metabolite ratio of FFC-a decreased significantly. Significant differences in tissue distribution of FFC and FFC-a were observed in rabbits treated with LPS. Modifications in plasma and tissue disposition of FFC and FFC-a were attributed mainly to haemodynamic modifications induced by the AIR through LPS administration.

Inflammation Induces Changes in the Functional Expression of P-gp, BCRP, and MRP2: An Overview of Different Models and Consequences for Drug Disposition

The ATP-binding cassette (ABC) transporters play a key role in drug pharmacokinetics. These membrane transporters expressed within physiological barriers can be a source of pharmacokinetic variability. Changes in ABC transporter expression and functionality may consequently affect the disposition of substrate drugs, resulting in different drug exposure. Inflammation, present in several acute and chronic diseases, has been identified as a source of modulation in drug transporter expression leading to variability in drug response. Its regulation may be particularly dangerous for drugs with a narrow therapeutic index. In this context, numerous in vitro and in vivo models have shown up- or downregulation in the expression and functionality of ABC transporters under inflammatory conditions. Nevertheless, the existence of contradictory data and the lack of standardization for the models used have led to a less conclusive interpretation of these data.

Sleep pattern and locomotor activity are impaired by doxorubicin in non-tumor-bearing rats

Purpose

We sought explore the effects of doxorubicin on sleep patterns and locomotor activity. To investigate these effects, two groups were formed: a control group and a Doxorubicin (DOXO) group.

Methods

Sixteen rats were randomly assigned to either the control or DOXO groups. The sleep patterns were examined by polysomnographic recording and locomotor activity was evaluated in an open-field test.

Results

In the light period, the total sleep time and slow wave sleep were decreased, while the wake after sleep onset and arousal were increased in the DOXO group compared with the control group (p<0.05). In the dark period, the total sleep time, arousal, and slow wave sleep were increased, while the wake after sleep onset was decreased in the DOXO group compared with the control group (p<0.05). Moreover, DOXO induced a decrease of crossing and rearing numbers when compared control group (p<0.05).

Conclusions

Therefore, our results suggest that doxorubicin induces sleep pattern impairments and reduction of locomotor activity.

Guggulsterone regulates the function and expression of P-glycoprotein in rat brain microvessel endothelial cells

Our previous studies found that guggulsterone could inhibit P-glycoprotein-mediated multidrug resistance in P-glycoprotein over-expressed human cancer cell lines. However, the effects of guggulsterone on the ;P-glycoprotein function and expression in rat brain microvessel endothelial cells (rBMECs) are poorly understood. In the present study, we investigated whether guggulsterone has a modulative effect on the function and expression of P-glycoprotein in rBMECs. rhodamine 123 acts as a good substrate for P-glycoprotein, and agents that block P-glycoprotein have been found to increase the retention of rhodamine in cells. The results showed that the accumulation of rhodamine 123 in rBMECs was potentiated in a time-dependent manner after incubation with 30, 100 μM guggulsterone (P<0.05). Efflux of intracellular rhodamine 123 was decreased in a time-dependent manner from after 30, 100 μM guggulsterone treatment. The inhibitory effect of guggulsterone on P-glycoprotein function was reversible and remained at 120 min after removal of 30, 100 μM guggulsterone from the medium. Further results showed that guggulsterone (30, 100 μM) down-regulated the expression of P-glycoprotein, and had no influence on the expression of breast cancer resistance protein in rBMECs. In addition, the present study revealed that guggulsterone promoted the activity of P-glycoprotein ATPase in a dose-dependent manner. These results indicated that guggulsterone suppressed the function and expression of P-glycoprotein in rBMECs primary cultures.

[Nitric oxide synthase-mediated alteration of intestinal P-glycoprotein under hyperglycemic stress]

P-glycoprotein (P-gp), one of the important drug-efflux pumps, is known to be affected by pathological conditions such as inflammation or infection. Recently, it is reported that high glucose or hyperglycemia can alter P-gp expression levels at the blood-brain barrier or in kidney, although the details are still unknown. Here, we analyzed the alteration of intestinal P-gp expression and function in the development of diabetes and elucidated the mechanisms. Type 1 diabetes was induced in male ddY mice by an i.p. injection of streptozotocin (STZ) (230 mg/kg). We analyzed ileal P-gp expression and drug efflux activity using western blot analysis and an in situ closed loop method, respectively. Additionally, we analyzed ileal nitric oxide synthase (NOS) activity using colorimetric method. A significant reduction of P-gp expression level in ileum was found on day 9 after STZ administration. In contrast, a remarkable decrease in drug efflux activity was observed on days 3 and 9. Interestingly, NOS activity in ilea was significantly increased on day 9. The decrease of P-gp expression levels observed on day 9 was completely suppressed by L-NG-nitroarginine methyl ester (L-NAME), a broad range NOS inhibitor, or aminoguanidine, a specific inducible NOS (iNOS) inhibitor. In addition, P-gp expression level in ileum was significantly decreased by administration of NOR5, a NO donor. These results indicate the possibility that NO, produced by iNOS in the ileum, is involved in the alteration of ileal P-gp expression and function under STZ-induced diabetic conditions.

Tissue-specific alterations in expression and function of P-glycoprotein in streptozotocin-induced diabetic rats

AIM

To investigate the changes of expression and function of P-glycoprotein (P-GP) in cerebral cortex, hippocampus, liver, intestinal mucosa and kidney of streptozocin-induced diabetic rats.

METHODS

Diabetic rats were prepared via a single dose of streptozocin (65 mg/kg, ip). Abcb1/P-GP mRNA and protein expression levels in tissues were evaluated using quantitative real time polymerase chain reaction (QRT-PCR) analysis and Western blot, respectively. P-GP function was investigated via measuring tissue-to-plasma concentration ratios and body fluid excretion percentages of rhodamine 123.

RESULTS

In 5- and 8-week diabetic rats, Abcb1a mRNA levels were significantly decreased in cerebral cortices and intestinal mucosa, but dramatically increased in hippocampus and kidney. In liver, the level was increased in 5-week diabetic rats, and decreased in 8-week diabetic rats. Abcb1b mRNA levels were increased in cerebral cortex, hippocampus and kidney, but reduced in liver and intestinal mucosa in the diabetic rats. Western blot results were in accordance with the alterations of Abcb1a mRNA levels in most tissues examined. P-GP activity was markedly decreased in most tissues of diabetic rats, except kidney tissues.

CONCLUSION

Alterations in the expression and function of Abcb1/P-GP under diabetic conditions are tissue specific, Abcb1 specific and diabetic duration-dependent.

Effect of cyclosporin A on the brain regional distribution of doxorubicin in rats

Doxorubicin (DOX) is an anthracycline antibiotic that possesses broad-spectrum antineoplastic activity, and is one of the most important anticancer agents. The purpose of this study was to investigate the effects of cyclosporine A (CsA) on the brain regional distribution of DOX and its liposome DOX formulation (Lipo-Dox). Liquid chromatography with tandem mass spectrometry (LC-MS/MS) was used to measure DOX in rat plasma and in various brain regions (cerebral cortex, hippocampus, striatum, midbrain, cerebellum, and the rest of brain). Good linearity was achieved over the 5-5000ng/mL range, with coefficients of correlation greater than 0.995. The limit of quantification for doxorubicin was 5ng/mL. This study was divided into the following four groups: DOX alone, DOX+CsA, Lipo-Dox alone and Lipo-Dox+CsA. After administering DOX (5mg/kg, i.v.) alone and DOX+CsA (10mg/kg, i.v.), it was undetectable in various brain regions. When the same dose of Lipo-Dox (5mg/kg, i.v.) and Lipo-Dox+CsA (10mg/kg, i.v.) were given individually, the plasma level and the brain regional level of DOX were much greater than those of DOX given alone. These results indicate that Lipo-Dox prolongs the DOX level in plasma and enhances brain distribution of DOX. The disposition of DOX might be regulated by P-glycoprotein.

The Role of Size and Charge for Blood–Brain Barrier Permeation of Drugs and Fatty Acids

The lipid bilayer is the diffusion barrier of biological membranes. Highly protective membranes such as the blood-brain barrier (BBB) are reinforced by ABC transporters such as P-glycoprotein (MDR1, ABCB1) and multidrug resistance associated proteins (MRPs, ABCCs). The transporters bind their substrates in the cytosolic lipid bilayer leaflet before they reach the cytosol and flip them to the outer leaflet. The large majority of drugs targeted to the central nervous system (CNS) are intrinsic substrates of these transporters. Whether an intrinsic substrate can cross the BBB depends on whether passive influx is higher than active efflux. In this paper, we show that passive influx can be estimated quantitatively on the basis of Stokesian diffusion, taking into account the ionization constant and the cross-sectional area of the molecule in its membrane bond conformation, as well as the lateral packing density of the membrane. Active efflux by ABC transporters was measured. The calculated net flux is in excellent agreement with experimental results. The approach is exemplified with several drugs and fatty acid analogs. It shows that compounds with small cross-sectional areas (A(D) < 70 A(2)) and/or intermediate or low charge exhibit higher passive influx than efflux and, therefore, cross the BBB despite being intrinsic substrates. Large (A(D) > 70 A(2)) or highly charged compounds show higher efflux than influx. They cannot cross the BBB and are, thus, apparent substrates for ABC transporters. The strict size and charge limitation for BBB permeation results from the synergistic interaction between passive influx and active efflux.

Impaired function and expression of P-glycoprotein in blood-brain barrier of streptozotocin-induced diabetic rats

The aim was to investigate the effect of diabetes mellitus (DM) on P-glycoprotein (P-GP) function and expression in rat blood-brain barrier (BBB). P-GP function in BBB was assessed by measuring the brain-to-plasma concentration ratios (Kp values) of rhodamine 123 (Rho123) and vincristine (VCR), two well-known P-GP substrates, in control rats and 5-week streptozotocin (STZ)-induced diabetic rats. Evans blue (EB) dye was used as a BBB integrity indicator for examining the extravasation from the blood into the brain. P-GP expression in the brain cortex was evaluated with Western blot. The uptakes of Rho123 and VCR by cultured rat brain microvessel endothelial cells (rBMECs) incubated in diabetic and control rat serum for 72 h were also used to examine P-GP function, respectively. It was found that the Kp value of Rho123 (0.022+/-0.005 vs. 0.016+/-0.002 ml/g brain, p=0.033) and VCR (0.072+/-0.028 vs. 0.023+/-0.006 ml/g brain, p=0.006) in diabetic rats was significantly higher than that in control rats. The uptakes of Rho123 and VCR by cultured rBMECs incubated in the diabetic rat serum were higher than that in the control rat serum, respectively. No significant difference of the EB concentration in the brain cortex was found between the diabetic rats and control rats. Electron microscope examination of the brain cortex did not show a clear damage to the endothelial cells of microvessel in diabetic rats. In addition, the protein level of P-GP in the brains of the diabetic rats examined was significantly lower than that of control rats. These results suggested that the function and expression of P-GP might be impaired in the BBB of STZ-induced diabetic rats.

CJZ3, a lomerizine derivative, modulates P-glycoprotein function in rat brain microvessel endothelial cells

AIM

To investigate the modulatory effect of CJZ3, a lomerizine derivative, on P-glycoprotein (P-gp) function in rat brain microvessel endothelial cells (RBMEC).

METHODS

RBMEC were isolated and cultured in Dulbecco modified Eagle medium/F12 (1:1) medium, and the amount of intracellular rhodamine 123 (Rh123) was determined using a fluorescence spectrophotometer to evaluate the modulatory effect of CJZ3 on P-gp function.

RESULTS

The accumulation of Rh123 was potentiated in a concentration-dependent manner after incubation with CJZ3 for RBMEC, but not for human umbilical vein endothelial cells (HUVEC). CJZ3 caused the accumulation of intracellular Rh123 in a time-dependent manner and significantly decreased the efflux of Rh123 from the cells. The inhibitory effect of CJZ3 on P-gp function was reversible and remained for 120 min after CJZ3 (2.5 micromol/L) was removed from the medium.

CONCLUSION

CJZ3 has a potent in vitro effect on the inhibition of P-gp function.

Endotoxin from various gram-negative bacteria has differential effects on function of hepatic cytochrome P450 and drug transporters

The differential effects of endotoxin derived from Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli on hepatic cytochrome P450 (CYP)-dependent drug-metabolizing enzyme activity and on the expression of hepatic CYP3A2, CYP2C11, P-glycoprotein and multidrug resistance-associated protein 2 (Mrp2) was investigated in rats. Endotoxin from all three different pathogens significantly decreased the systemic clearance of antipyrine, reflecting reduced hepatic drug-metabolizing enzyme activity 24 h after intravenous injection (0.5 mg/kg). The degree of the decreased systemic clearance by P. aeruginosa endotoxin was smaller than that by both K. pneumoniae and E. coli endotoxin. Western blot analysis revealed that the down-regulation of CYP3A2 by K. pneumoniae and E. coli endotoxin was greater than that by P. aeruginosa endotoxin. However, the down-regulation of CYP2C11 by all three different endotoxin was almost the same. Both K. pneumoniae and P. aeruginosa endotoxin significantly down-regulated P-glycoprotein, but did not down-regulate Mrp2. E. coli endotoxin had no effect on the expression of either P-glycoprotein or Mrp2, probably due to the low dose used. The down-regulation of CYP3A2 by endotoxin was parallel to the decreased systemic clearance of antipyrine. These results suggest that endotoxin has a differential effect on the hepatic CYP-mediated drug-metabolizing enzyme activity, and on the protein levels of hepatic CYP3A2 and P-glycoprotein, probably due to bacterial source-differences in the production of some proinflammatory mediators. Endotoxin appears to regulate coordinately CYP3A2, CYP2C11 and P-glycoprotein, but not Mrp2.

Modulation of P-glycoprotein function by amlodipine derivatives in brain microvessel endothelial cells of rats

AIM

To investigate whether the amlodipine derivatives, CJX1 and CJX2, have a modulative effect on P-glycoprotein (P-gp) function in rat brain microvessel endothelial cells (RBMEC).

METHODS

Isolated RBMEC were cultured in DMEM/F12 (1:1) medium. The amount of intracellular rhodamine (Rh123) was determined, using a fluorescence spectrophotometer, to evaluate the function of P-gp.

RESULTS

The accumulation of Rh123 in RBMEC was potentiated in a concentration-dependent manner after incubation with CJX1 and CJX2 at 1, 2.5, 5, and 10 micromol/L (P<0.01), but no accumulation of Rh123 was observed in human umbilical vein endothelial cells after incubation with CJX1 and CJX2 10 micromol/L (P>0.05). Accumulation of intracellular Rh123 was increased and efflux of intracellular Rh123 was decreased in a time-dependent manner from 0-100 min after CJX1 and CXJ2 at 10 micromol/L treatment. The inhibitory effect of CJX1 and CJX2 on P-gp function was reversible and remained even at 120 min after removal of CJX1 and CJX2 at 2.5 micromol/L from the medium.

CONCLUSION

CJX1 and CJX2 exhibited a potent effect in the inhibition of P-gp function in vitro.

Altered Brain Penetration of Diclofenac and Mefenamic Acid, but Not Acetaminophen, in Shiga-Like Toxin II-Treated Mice

It is well accepted that bacterial and virus infections elevate the levels of cytokines in serum and cerebrospinal fluids. Such high levels of cytokines might alter the integrity of the blood-brain barrier (BBB) and/or blood-cerebrospinal fluid barrier (BCSFB), subsequently affecting brain penetration of drugs. However, few reports have addressed this issue. Thus, we investigated brain penetration of cyclooxygenase (COX) inhibitors, commonly used as antipyretics, in mice treated with Shiga-like toxin II (SLT-II) derived from E. coli O157:H7, which significantly elevates cytokine levels. As antipyretics, we used diclofenac, mefenamic acid, and acetaminophen. We found that SLT-II significantly increased the brain-to-plasma concentration ratio (Kp) of diclofenac and mefenamic acid, but not of acetaminophen. Moreover, the Kp of diclofenac and mefenamic acid was increased by probenecid, an anionic compound. These results suggest that efflux anion transporters might be involved in the transport of diclofenac and mefenamic acid. Western blot analysis revealed that SLT-II decreased the expression of organic anion transporter-3, an efflux transporter located on the BBB and/or BCSFB. Taken together, these results suggest that SLT-II and/or SLT-II-stimulated cytokines might change brain penetration of drugs and could possibly increase the risk of their side-effects by altering the expression of transporters.

Role of tumor necrosis factor-alpha in down-regulation of hepatic cytochrome P450 and P-glycoprotein by endotoxin

We investigated the role of tumor necrosis factor-alpha (TNF-alpha) in the down-regulation of hepatic P-glycoprotein and cytochrome P450 (CYP) by endotoxin, using TNF-alpha gene-deficient (TNF-alpha-/-) mice. In the case of P-glycoprotein, endotoxin (10 mg/kg) significantly decreased the expression of hepatic P-glycoprotein in wild-type mice 6 h, but not 24 h, after intraperitoneal injection, with no significant differences in the constitutional expression of P-glycoprotein between wild-type mice and TNF-alpha-/- mice. However, endotoxin had no effect on the expression of P-glycoprotein in TNF-alpha-/- mice either 6 or 24 h after injection. When doxorubicin was administered intravenously to TNF-alpha-/- mice treated 6 h earlier with and without endotoxin, no significant differences in the plasma concentrations of doxorubicin 3 h after injection were observed between endotoxin-treated and untreated TNF-alpha-/- mice. These results suggest that TNF-alpha plays a pivotal role in the down-regulation of P-glycoprotein by endotoxin. In the case of CYP, the constitutive expression of hepatic CYP3A2 and CYP2C11 had a tendency to decline in TNF-alpha-/- mice compared with that in wild-type mice. Endotoxin significantly decreased the expression of hepatic CYP3A2 and CYP2C11 in wild-type mice 24 h after injection, and that decreased expression was significantly greater in TNF-alpha-/- mice than wild-type mice. When antipyrine was administered intravenously to wild-type mice and TNF-alpha-/- mice treated 24 h earlier with endotoxin, the plasma concentrations of antipyrine in TNF-alpha-/- mice 3 h after injection were significantly higher than those in wild-type mice. These findings suggest that TNF-alpha plays a key role in endotoxin-induced down-regulation of hepatic P-glycoprotein, as well as plays a protective role in the regulation of hepatic CYP3A2 and CYP2C11 against endotoxin-induced acute inflammatory response. In TNF-alpha-/- mice, other cytokines appear to function as compensation for the lack of endogenous TNF-alpha.

Downregulation of mdr1a expression in the brain and liver during CNS inflammation alters the in vivo disposition of digoxin

1. Inflammation is a pathophysiological event that has relevance for altered drug disposition in humans. Two functions of P-glycoprotein (P-gp) are hepatic drug elimination and prevention of drug entry into the central nervous system (CNS). Our objective was to investigate if localized CNS inflammation induced by Escherichia coli lipopolysaccharide (LPS) would modify mdr1a/P-gp expression and function in the brain and liver. 2. Our major finding was that the CNS inflammation in male rats produced a loss in the expression of mdr1a mRNA in the brain and liver that was maximal 6 h after intracranial ventricle (i.c.v.) administration of LPS. When (3)H-digoxin was used at discrete time points, as a probe for P-gp function in vivo, an increase in brain and liver (3)H-radioactivity and plasma level of parent digoxin was produced 6 and 24 h following LPS treatment compared to the saline controls. Digoxin disposition was similarly altered in mdr1a(+/+) mice but not in mdr1a(-/-) mice 24 h after administering LPS i.c.v. 3. In male rats, the biliary elimination of parent digoxin was reduced at 24 h (60%) and 48 h (40%) after LPS treatment and was blocked by the P-gp substrate cyclosporin A. An observed loss in CYP3A1/2 protein and organic anion transporting polypeptide 2 mRNA in the liver may make a minor contribution to digoxin elimination in male rats after LPS treatment. 4. Conditions which impose inflammation in the CNS produce dynamic changes in mdr1a/P-gp expression/function that may alter hepatic drug elimination and the movement of drugs between the brain and the periphery. The use of experimental models of brain inflammation may provide novel insight into the regulation of P-gp function in that organ.

Shiga-like toxin II modifies brain distribution of a P-glycoprotein substrate, doxorubicin, and P-glycoprotein expression in mice

The effect of Shiga-like toxin II (SLT-II), which was derived from Escherichia coli O157:H7, on doxorubicin transport across the blood-brain barrier (BBB) and P-glycoprotein function, was investigated in ddY mice. Doxorubicin (30 mg kg(-1)) was administered intravenously or fluorescein isothiocyanate labeled dextran (FD-4) was infused (20 microg min(-1)) to the mice, who had received an intravenous injection of SLT-II (0.2 microg/animal) 6 or 24 h earlier. Blood and brain were removed 4 h after injection of doxorubicin or 60 min after infusion of FD-4. SLT-II significantly elevated the brain concentration and brain-to-plasma concentration ratio (K(p)) of doxorubicin and FD-4 24 h after injection, but did not alter 6 h after. Cyclosporin A (200 mg kg(-1)) significantly increased the K(p) value of doxorubicin in the control mice, but did not alter it in mice treated 24 h earlier with SLT-II. Pentoxifylline (100 mg kg(-1)) a TNF-alpha production inhibitor, ameliorated SLT-II-induced increases in the brain concentrations of both drugs and the K(p) value of FD-4, suggesting that TNF-alpha, at least in part, causes damage to the brain capillaries. Western blot analysis revealed that SLT-II increased the protein level of P-glycoprotein in the brain of mice 6 h after injection and the increased level remained unchanged for 24 h. SLT-II did not change ATP content in the brain of mice. These results suggest that the increased P-glycoprotein level cannot explain SLT-II-induced increase in the doxorubicin accumulation in brain. The present findings indicate that SLT-II impairs the BBB function and doxorubicin transport across the BBB, while it overexpresses P-glycoprotein.