Decreased antipyrine clearance following endotoxin administration: in vivo evidence of the role of nitric oxide

Regulation of cytochrome P450 enzyme activity and expression by nitric oxide in the context of inflammatory disease

Many hepatic cytochrome P450 enzymes and their associated drug metabolizing activities are down-regulated in disease states, and much of this has been associated with inflammatory cytokines and their signaling pathways. One such pathway is the induction of inducible nitric oxide synthase (NOS2) and generation of nitric oxide (NO) in many tissues and cells including the liver and hepatocytes. Experiments in the 1990s demonstrated that NO could bind to and inhibit P450 enzymes, and suggested that inhibition of NOS could attenuate, and NO generation could mimic, the down-regulation by inflammatory stimuli of not only P450 catalytic activities but also of mRNA expression and protein levels of certain P450 enzymes. This review will summarize and examine the evidence that NO functionally inhibits and down-regulates P450 enzymes in vivo and in vitro, with a particular focus on the mechanisms by which these effects are achieved.

Inhibition of lipopolysaccharide-induced liver injury in rats treated with a hepatic drug-metabolizing enzyme inducer p,p'-DDT

Hepatocellular hypertrophy in association with drug-metabolizing enzyme induction is considered to be an adaptive change associated with drug metabolism. To improve our understanding of liver hypertrophy, we determined the effect of a single ip injection of either lipopolysaccharide (LPS) or vehicle in male F344 rats with hepatocellular hypertrophy induced by oral delivery of p,p'-DDT for 2 weeks. The rats were sacrificed 3h or 24h after LPS or vehicle injection. LPS induced a focal hepatocellular necrosis in rats fed the control diet. When rats pre-treated with p,p'-DDT were injected with LPS, necrotic foci surrounded by ballooned hepatocytes were observed in the liver. The change was consistent with reduced LPS-mediated increases in plasma hepatic biomarkers, neutrophil influx, and apoptosis, and also associated with hepatic mRNA levels of TNF-α, CYPs, and NOS2. By contrast, when combined with p,p'-DDT and LPS, faint hepatocellular fatty change was extended, together with a synergistic increase in total blood cholesterol. These results suggest that hepatocytes exposed to p,p'-DDT are protected from the cell-lethal toxic effects of an exogenous stimulus, resulting in cell ballooning rather than necrosis in association with reduced inflammation and apoptosis, but compromised by an adverse effect on lipid metabolism.

Oxidative stress and liver monooxygenase function after heart valve surgery

BACKGROUND AND OBJECTIVES

this prospective study was carried out to evaluate oxidative stress and liver monooxygenase function after cardiac surgery in patients with acquired valvular heart disease.

METHODS

97 patients were studied. Oxidative stress was quantified with malondialdehyde, coupled trienes, hepatocuprein, and catalase activity. Liver monooxygenase function was evaluated with antipyrine pharmacokinetics. For statistical analyses, the Dunnett test and Pearson's correlation coefficient were used.

RESULTS

on the 1st-2nd postoperative days, high lipid peroxidation activation (malondialdehyde: 9.6 ± 2.7 vs. 6.9 ± 2.0 nmol mL(-1), p <0.05) and a significant decrease in liver monooxygenase function (antipyrine clearance: 18.3 ± 11.1 vs. 39.0 ± 18.9 mL kg(-1)h(-1), p <0.05) were revealed. On the 3rd-4th and 11th-12th postoperative days, the intensity of oxidative stress decreased and monooxygenase function returned to baseline (antipyrine clearance: 45.6 ± 17.9 vs. 39.0 ± 18.9 mL kg(-1)h(-1)). The analysis showed a negative relationship between oxidative stress and liver monooxygenase function.

CONCLUSION

patients undergoing surgery for acquired valvular heart disease have considerable oxidative stress and a decrease in liver monooxygenase function on the 1st-2nd postoperative days. Activation of lipid peroxidation is one of the main reasons for suppression of microsomal monooxygenases activity. A slowdown of liver microsomal oxidation might change the pharmacokinetic response of patients under drug therapy.

Effect of lipopolysaccharide on P-glycoprotein-mediated intestinal and biliary excretion of rhodamine123 in rats

The effects of lipopolysaccharide (LPS) on the ileal and biliary excretion of rhodamine123 were investigated in rats at different times after intraperitoneal (i.p.) injection (1 mg/kg and 5 mg/kg of body weight). P-gp protein decreased 8h after injection of LPS and returned to the control level 24h after i.p. injection of LPS in the ileum. There was a marked decrease in the expression level of mdr1a mRNA in the ileum and liver 8h after i.p. injection of LPS when compared with the control condition. Also, the ileal and biliary clearance of rhodamine123 significantly decreased 8h after i.p. injection of LPS, but returned to the control levels 24h after i.p. injection of LPS. These results suggest that LPS-induced decreases in P-gp-mediated ileal and biliary excretion of rhodamine123 were probably due to impaired P-gp-mediated transport ability. The levels of iNOS and IL-1beta mRNA in the ileum and liver increased 2 and 8h after i.p. injection of LPS, respectively, and returned to the control levels 24h after injection of LPS. These findings suggest that LPS markedly decreases P-gp-mediated ileal and biliary excretion of rhodamine123, probably by partly decreasing the expression of P-gp protein levels, likely due to increased lipid peroxidation levels through iNOS mRNA and inflammatory mediators such as IL-1beta.

Changes of midazolam pharmacokinetics in Wistar rats treated with lipopolysaccharide: relationship between total CYP and CYP3A2

It has been reported that infection interferes with drug metabolism, resulting in changes in pharmacokinetics. In this study, we investigated the effects of lipopolysaccharide (LPS) on hepatic total cytochrome P450 (CYP), CYP3A2, and CYP2C11 contents in a transient, LPS-induced, endotoxemia model of rats. In addition, to assess the effects on CYP3A2 activities, the pharmacokinetics of midazolam (CYP3A2 substrate) and 1-OH-midazolam (metabolite of midazolam) were investigated. Hepatic total CYP contents were significantly low until day 3 ( P < 0.05) but returned to the control level on day 5. Hepatic CYP3A2 contents were significantly decreased on day 1 until day 5 ( P < 0.05) but returned to the control level on day 7. Hepatic CYP2C11 contents were continuously low until day 7, and lowest on day 3. The AUC of 1-OH-midazolam was significantly decreased on day 1 after LPS administration ( P < 0.01). In conclusion, LPS (5 mg/kg) challenge decreased hepatic total CYP, CYP3A2, and CYP2C11 contents and also decreased the activities of hepatic CYP3A2. It took at least 7 days for hepatic total CYP and CYP3A2 to recover to control levels, and it was suggested that the changes of hepatic total CYP contents might correlate with those of hepatic CYP3A2 contents and activities. Additionally, it is shown that their changes might reflect the recovery process from inflammation.

Association of serum NO( x ) level with clustering of metabolic syndrome components in middle-aged and elderly general populations in Japan

OBJECTIVES

The aim of this study was to determine whether the serum nitrite plus nitrate (NO( x )) level correlates with biomarkers that are known components of the metabolic syndrome (MetS).

METHODS

Serum NO( x ) levels were measured using a commercial kit in 608 Japanese men and women between the ages of 39 and 85 years. Multivariate adjustments for age, smoking status, alcohol consumption and exercise were made in the analysis of covariance (ANCOVA). The components of the metabolic syndrome were defined based on the following criteria: body mass index (BMI) >/=25.0 kg/m(2), glycated hemoglobin (HbA1c) >/=5.6%, systolic blood pressure >/=130 mmHg or diastolic blood pressure >/=85 mmHg, high-density lipoprotein-cholesterol (HDL-C) </=1.03 mmol/l for men and </=1.29 mmol/l for women and triglyceride >/=1.69 mmol/l.

RESULTS

The logarithmically transformed age-adjusted serum NO( x ) (lnNO( x )) value was significantly higher in the low HDL-C group (1.76 +/- 0.05 mumol/l; p < 0.05) than MetS component groups (1.65 +/- 0.01 mumol/l) in men, but no difference was found in women. The means of serum lnNO( x ) after multivariate adjustment were 1.64, 1.65, 1.64, 1.66, and 1.81 mumol/l for 0, 1, 2, 3, and 4-5 MetS components for all subjects, respectively. The results of ANCOVA confirmed that the serum lnNO( x ) level was significantly correlated with the clustering of MetS components in both men and women (p < 0.0001 for trend).

CONCLUSION

Our results suggest that an increase in the clustering of MetS components was associated with the increase in serum NO levels in our general population.

Quality Assurance Assessment of the Use of Linezolid in the Treatment of Thermal Injury Patients at a Community Teaching Hospital

We sought to evaluate the adverse effect profile of linezolid among thermal injury patients requiring treatment for Enterococcus species or other Gram-positive infection warranting treatment with linezolid. Seventy-six inhalation injury and/or thermal injury patients experiencing 94 exposures to linezolid for 48 hours or longer (range, 2-83 days) were included. We evaluated leukocyte count and platelet count for the time period preceding, during, and after therapy with linezolid based on specified time periods of exposure for evaluation of specific adverse effects. Sixty-three of 76 (83%) patient admissions were complicated by inhalation injury. The average TBSA involvement was 34.4% (range, 0-98%). The onset of thrombocytopenia before linezolid therapy was noted in 21 of 57 patients (36.8%), which was attributable to fluid resuscitation and acute platelet consumption. After they were exposure to linezolid, 12 patients developed thrombocytopenia. Platelet counts recovered in 7 of these 12 patients with continued exposure to linezolid; however, thrombocytopenia persisted for more than 9 days after therapy in 9 patients, of whom 6 patients succumbed to sepsis. On average, thrombocytes increased by 102,000/mm3 during linezolid treatment. Leucopenia was rare in thermal injury patients, and persisting thrombocytopenia in this population was associated with sepsis and mortality. Continuing linezolid therapy after the onset of thrombocytopenia among survivors almost always resulted in recovery from thrombocytopenia.

Perinatal lipopolysaccharide exposure downregulates pregnane X receptor and Cyp3a11 expression in fetal mouse liver

The pregnane X receptor (PXR) is a member of the nuclear receptor superfamily that regulates cytochrome P450 3A (CYP3A) gene transcription in a ligand-dependent manner. Lipopolysaccharide (LPS)-induced downregulation on PXR and cyp3a11 in adult mouse liver has been well characterized. In this study, we investigated the effects of maternal LPS exposure on PXR and cyp3a11 expression in fetal mouse liver. Pregnant ICR mice were injected intraperitoneally with different doses of LPS (0.1 approximately 0.5 mg/kg) on gestational day (GD) 17. PXR and cyp3a11 mRNA levels were determined using RT-PCR. Erythromycin N-demethylase (ERND) activity was used as an indicator of CYP3A expression in this study. Results showed that LPS significantly downregulated PXR and cyp3a11 mRNA levels and ERND activity in fetal liver in a dose-dependent manner. LPS-induced downregulation of PXR and cyp3a11 mRNA expression and ERND activity was attenuated after pregnant mice were pretreated with alpha-phenyl-N-t-butylnitrone (PBN), a free radical spin trapping agent. Additional experiment revealed that LPS significantly increased lipid peroxidation in fetal liver, which was also attenuated by PBN pretreatment. Furthermore, LPS-induced downregulation of PXR and cyp3a11 mRNA expression and ERND activity was prevented by maternal pretreatment with N-acetylcysteine (NAC). Maternal pretreatment with NAC also inhibited LPS-initiated lipid peroxidation and GSH depletion in fetal liver. However, maternal LPS treatment did not affect nitrite plus nitrate concentration in fetal liver. Correspondingly, aminoguanidine, a selective inhibitor of inducible nitric oxide synthase (iNOS), has no effect on LPS-induced downregulation of PXR and cyp3a11 expression and ERND activity in fetal liver. These results indicated that maternal LPS exposure downregulates PXR and cyp3a11 in fetal mouse liver. Reactive oxygen species (ROS) may be involved in LPS-induced downregulation of PXR and cyp3a11 in fetal mouse liver.

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.

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.

Effect of pioglitazone on endotoxin-induced decreases in hepatic drug-metabolizing enzyme activity and expression of CYP3A2 and CYP2C11

It has been reported that peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligands ameliorate the expression of inducible nitric oxide synthase (iNOS) by endotoxin. In the present study, we investigated the effect of pioglitazone, a potent PPAR-gamma ligand, on the endotoxin-induced reduction of hepatic drug-metabolizing enzyme activity and on the down-regulation of the expression of hepatic cytochrome P450 (CYP) 3A2 and CYP2C11 proteins in rats. Endotoxin (1 mg/kg) significantly decreased hepatic drug-metabolizing enzyme activity in vivo, as represented by the systemic clearance of antipyrine and protein levels of CYP3A2 and CYP2C11 24 h after intraperitoneal injection. Pretreatment with pioglitazone (10 mg/kg, 4 times at 10-min intervals) significantly protected the endotoxin-induced decreases in the systemic clearance of antipyrine and protein levels of CYP3A2, but not CYP2C11, with no biochemical and histopathological changes in the liver. Pioglitazone alone had no effect on the systemic clearance of antipyrine and protein levels of CYP3A2 or CYP2C11. Pioglitazone significantly protected endotoxin-induced overexpression of iNOS in the liver, but not the overproduction of nitric oxide (NO) in plasma. It is unlikely that the protective effect of pioglitazone against endotoxin-induced decreases in the hepatic drug-metabolizing enzyme activity and protein levels of CYP3A2 in the liver is due to the inhibition of the overproduction of NO.

Down-regulation of cytochrome P450 proteins and its activities by Shiga-like toxin II from Escherichia coli O157:H7

Escherichia coli O157:H7 infection frequently induces clinical complications such as hemolytic uremic syndromes and intestinal dysfunctions. These changes could alter the disposition of drugs, consequently changing their efficacy. However, the possible changes of drug-metabolizing activities by E. coli O157:H7 infection have not been addressed. Thus, we have investigated the effect of Shiga-like toxin type II (SLT-II), derived from E. coli O157:H7, on the hepatic cytochrome P450 (CYP) content and its activity in rats. SLT-II (2microg per animal, i.v.) time-dependently decreased total CYP content and the contents of CYP2C11 and CYP3A2 in hepatic microsomal preparations up to 24hr following injection. Consistently, SLT-II time-dependently decreased CYP activity in vivo, as represented by systemic clearance of antipyrine. An inhibitor of inducible nitric oxide synthase, S-methylisothiourea, restored the decreased systemic clearance of antipyrine by SLT-II, suggesting the involvement of the overproduction of nitric oxide by SLT-II. Moreover, dexamethasone restored the decreased systemic clearance of antipyrine by SLT-II. In the hepatic microsomal preparation, dexamethasone restored the SLT-II-induced decrease of CYP3A2 whereas S-methylisothiourea did not affect both CYP subtypes. Taken together, these results suggest that SLT-II might alter hepatic drug-metabolizing function during E. coli O157 infection and that more than one cytokines induced by SLT-II, including nitric oxide, might make a critical contribution to the decrease of CYP content and its activity.

Experimental demonstration of the unstirred water layer effect on drug transport in Caco-2 cells

We previously demonstrated that P-glycoprotein and MRP2 contribute to the secretory transport of grepafloxacin in the small intestine. Although inhibitors of these secretory transporters increased absorptive transport of grepafloxacin, secretory transport was not altered in Caco-2 cells, as determined by a conventional Transwell method. Because the value of the permeability coefficient of grepafloxacin is high, permeation through the unstirred water layer (UL) might be the rate-limiting step. To examine the possibility that the UL effect may mask the involvement of membrane transporters in the transport of drug with high permeability in Caco-2 cells, transport experiments were performed by agitating the experimental solution to decrease the thickness of the UL, and by lowering the temperature to decrease permeation via active transporters. Under these conditions, the UL effect was not rate limiting, and the inhibitory effects of transporter modulators were reflected in the apparent permeability as a decrease in secretory transport as well as an increase in absorptive transport. In conclusion, it was demonstrated that the UL can be the rate-limiting factor for transport of drugs with high membrane permeability in Caco-2 cells. When the UL affects the apparent permeability in an experimental apparatus in vitro, careful analysis is required to evaluate the contributions of transporters from the apparent permeability of drugs.

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

The aim of this study was to investigate whether Klebsiella pneumoniae endotoxin modifies transport of doxorubicin, a P-glycoprotein substrate, across the blood-brain barrier and P-glycoprotein function in mice. Doxorubicin (30 mg/kg) was administered into the tail vein or fluorescein isothiocyanate-labeled dextran (FD-4) was infused (20 microg/min) into the right jugular vein of mice intravenously injected with endotoxin (10 mg/kg) 6 or 24 h earlier. Blood and brain samples were collected 4 h after injection of doxorubicin or 1 h after infusion of FD-4. We examined using Western blotting the influence of endotoxin on the expression of P-glycoprotein in brains obtained 6, 12 and 24 h after injection. Endotoxin did not change the plasma and brain concentrations and brain-to-plasma concentration ratio (K(p) value) of FD-4. No histopathological changes in brain capillaries were observed. These results suggest that endotoxin does not cause damage to brain capillaries. Plasma and brain concentrations of doxorubicin in mice treated 6 h earlier with endotoxin were significantly higher than those in control and mice treated 24 h earlier. However, endotoxin did not significantly change the K(p) value of doxorubicin. The protein level of P-glycoprotein was significantly, but slightly down-regulated 6 h after endotoxin treatment. However, the levels remained almost unchanged after 12 and 24 h. The present results suggest that Klebsiella pneumoniae endotoxin has no effect on the brain capillary integrity and doxorubicin transport across the blood-brain barrier in mice. It is likely that P-glycoprotein function might be sufficient to transport doxorubicin in spite of decreased levels of P-glycoprotein in the brain.

Shiga-like toxin II derived from Escherichia coli O157:H7 modifies renal handling of levofloxacin in rats

The effect of Shiga-like toxin II (SLT-II) (2 microg/animal), which was derived from Escherichia coli O157:H7, on renal handling of levofloxacin (LVX), a model drug for quinolone antimicrobial agents, was investigated in rats 24 h after intravenous injection. In histopathological examination, acute tubular injury was observed in SLT-II-treated rats, but the glomeruli were not injured. SLT-II significantly increased the steady-state concentration of LVX in plasma to 1.5-fold that of control rats. SLT-II induced significant decreases in the glomerular filtration rate (GFR) and renal clearance (CL(R)) of LVX. SLT-II slightly, but significantly, increased the unbound fraction and decreased renal plasma flow with no change in the extraction ratio of p-aminohippurate. SLT-II significantly increased concentrations of tumor necrosis factor alpha (TNF-alpha) and nitrite and nitrate (NOx) in plasma. The TNF-alpha inhibitor pentoxifylline partly, but significantly, inhibited SLT-II-induced decreases in the GFR and CL(R) of LVX; in contrast, S-methylisothiourea, a selective inhibitor of inducible nitric oxide synthase, did not. Western blotting analysis revealed that SLT-II did not alter the levels of multidrug resistance-associated protein 2 (Mrp2) and P-glycoprotein in kidneys 24 h after injection, assuming the lack of involvement of Mrp2 and P-glycoprotein in SLT-II-induced acute renal tubular injury and renal handling of LVX observed 24 h after SLT-II injection. The present study suggests that SLT-II impairs the renal handling of LVX by decreasing GFR and causing decreased renal plasma flow.

Effect of endotoxin on P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 in rats

The effects of Klebsiella pneumoniae endotoxin on the biliary excretion and renal handling of rhodamine-123 were investigated in rats at different times after intraperitoneal injection (1 mg/kg of body weight). The typical substrates for P glycoprotein, i.e., cyclosporine, colchicine, and erythromycin, inhibited the biliary clearance of rhodamine-123, whereas a substrate for organic cation transporter, cimetidine, did not inhibit clearance, suggesting that rhodamine-123 is transported mainly by P glycoprotein. The biliary, renal, and tubular secretory clearances of rhodamine-123 and the glomerular filtration rate significantly decreased 6 h after injection of endotoxin but returned to control levels by 24 h. These results suggest that endotoxin-induced decreases in P-glycoprotein-mediated biliary excretion and renal handling of rhodamine-123 were probably due to impairment of P-glycoprotein-mediated transport ability. Pretreatment with pentoxifylline (50 mg/kg) significantly inhibited endotoxin-induced increases in tumor necrosis factor alpha (TNF-alpha) levels in plasma, which ameliorated the endotoxin-induced reduction of the biliary excretion of rhodamine-123. It is likely that endotoxin-induced impairment of the transport of rhodamine-123 is caused, in part, by overproduction of TNF-alpha. The effect of endotoxin on the expression of P-glycoprotein mRNA in liver and kidneys of rats was investigated by using a reverse transcriptase PCR. The expression of Mdr1a mRNA in both liver and kidney decreased 6 h after endotoxin injection and returned to control levels after 24 h, whereas the expression of Mdr1b mRNA in liver increased at both times and that in kidney decreased at 24 h. These findings suggest that K. pneumoniae endotoxin dramatically decreases P-glycoprotein-mediated biliary and renal excretion of rhodamine-123 probably by decreasing the expression of Mdr1a, which is likely due to increased plasma TNF-alpha levels.

Endotoxin impairs biliary transport of sparfloxacin and its glucuronide in rats

The effect of endotoxin on glucuronidation and hepatobiliary transport of quinolone antimicrobial agents was investigated in rats using sparfloxacin and p-nitrophenyl glucuronide as model drugs. The biliary clearance experiments were performed 24 h after a single intraperitoneal injection of endotoxin (1 mg/kg). Endotoxin significantly delayed the disappearance of sparfloxacin from plasma and increased plasma concentration of its glucuronide after intravenous injection of sparfloxacin (10 mg/kg). Significant decreases in the systemic clearance of sparfloxacin and the biliary clearance of sparfloxacin and the glucuronide were observed. Endotoxin had no effect on in vitro glucuronidation activity using p-nitrophenol as a substrate. When p-nitrophenyl glucuronide (8 mg/kg) was administered in endotoxin-pretreated rats, significant decreases in the systemic clearance, biliary clearance and renal clearance of p-nitrophenyl glucuronide were observed. These findings suggest that endotoxin decreases the biliary excretion of sparfloxacin and its glucuronide probably due to impairment of their hepatobiliary transport systems and renal handling.