Intestinal inflammation induces adaptation of P-glycoprotein expression and activity

Disease-drug and drug-drug interaction in COVID-19: Risk and assessment

COVID-19 is announced as a global pandemic in 2020. Its mortality and morbidity rate are rapidly increasing, with limited medications. The emergent outbreak of COVID-19 prompted by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) keeps spreading. In this infection, a patient's immune response plays pivotal role in the pathogenesis. This inflammatory factor was shown by its mediators that, in severe cases, reach the cytokine at peaks. Hyperinflammatory state may sparks significant imbalances in transporters and drug metabolic machinery, and subsequent alteration of drug pharmacokinetics may result in unexpected therapeutic response. The present scenario has accounted for the requirement for therapeutic opportunities to relive and overcome this pandemic. Despite the diminishing developments of COVID-19, there is no drug still approved to have significant effects with no side effect on the treatment for COVID-19 patients. Based on the evidence, many antiviral and anti-inflammatory drugs have been authorized by the Food and Drug Administration (FDA) to treat the COVID-19 patients even though not knowing the possible drug-drug interactions (DDI). Remdesivir, favipiravir, and molnupiravir are deemed the most hopeful antiviral agents by improving infected patient’s health. Dexamethasone is the first known steroid medicine that saved the lives of seriously ill patients. Some oligopeptides and proteins have also been using. The current review summarizes medication updates to treat COVID-19 patients in an inflammatory state and their interaction with drug transporters and drug-metabolizing enzymes. It gives an opinion on the potential DDI that may permit the individualization of these drugs, thereby enhancing the safety and efficacy.

Citrobacter rodentium Infection Inhibits Colonic P-glycoprotein Expression

P-glycoprotein (Pgp/MDR1) serves as a biological barrier that protects intestinal epithelial cells (IECs) by transporting out xenobiotics and bacterial toxins. Decreased Pgp function and expression has been seen in mouse models of inflammatory colitis and also in patients with IBD. Pgp knockout mice spontaneously develop severe colitis, which is also seen in human patients with ulcerative colitis. However, whether Pgp is also altered in infectious colitis is not known. Citrobacter rodentium (CR), a murine pathogen has been shown to cause colonic hyperplasia and colitis in mice by attaching to IECs. The current study investigated the direct effects of Citrobacter rodentium infection on intestinal Pgp expression in mice. Mice were challenged with a single dose of C. rodentium (1 × 10⁹ CFU) by oral gavage for 9 days and Pgp expression in the ileum and colon was measured by real time qRT-PCR and immunofluorescence studies. Our results showed that C. rodentium infection significantly decreased Pgp mRNA and protein expression in the colon, although no significant change was observed in the ileum of mice. These findings suggest that inhibition of the efflux protein, Pgp by C. rodentium can cause perturbations in the intestinal epithelial integrity, which could further lead to the pathogenesis of intestinal inflammation as observed in infectious colitis.

Early downregulation of P-glycoprotein facilitates bacterial attachment to intestinal epithelial cells and thereby triggers barrier dysfunction in a rodent model of total parenteral nutrition

Intestinal barrier dysfunction is a major complication of total parenteral nutrition (TPN). Our preliminary study revealed that intestinal P-glycoprotein (P-gp) was significantly downregulated under TPN treatment followed by disruption of barrier function, and thus the significance of early downregulation of P-gp needs to be addressed. Herein, we report a pivotal role of P-gp in the development of intestinal barrier dysfunction under TPN. Functional suppression of P-gp may facilitate bacterial attachment to intestinal epithelial cells (IECs) and thereby induce degradation of tight junctions to trigger barrier dysfunction. By using a rat model of TPN, we found early downregulation of P-gp function in ileum after 3-day TPN, followed by disruption of barrier function after 7-day TPN. By using Escherichia coli (E. coli) k88 and DH5α as type strains, we found significantly increased bacterial attachment to IECs in TPN group compared to sham. By using Caco-2 cells as an IEC model in vitro, we found that functional suppression of P-gp remarkably facilitated bacterial attachment to Caco-2 cells, leading to subsequent disruption of intestinal barrier function. Of note, Occludin was significantly downregulated by bacterial attachment when P-gp was functionally suppressed. Mechanistically, changes on Occludin were attributed to enhanced protein degradation instead of suppressed protein translation. Despite the half-life of Occludin protein being unchanged by DH5α treatment alone, it was decreased by about 40% when P-gp was simultaneously suppressed. Taken together, our findings revealed that early downregulation of intestinal P-gp under TPN may be a potential therapeutic target to prevent the development of barrier dysfunction.

Angiotensin II inhibits P-glycoprotein in intestinal epithelial cells

AIM

P-glycoprotein (Pgp/MDR1) plays a major role in intestinal homeostasis. Decrease in Pgp function and expression has been implicated in the pathogenesis of IBD. However, inhibitory mechanisms involved in the decrease of Pgp in inflammation are not fully understood. Angiotensin II (Ang II), a peptide hormone predominantly expressed in the epithelial cells of the crypt-villus junction of the intestine, has been shown to exert pro-inflammatory effects in the gut. It is increased in IBD patients and animals with experimental colitis. Whether Ang II directly influences Pgp is not known.

METHODS

Pgp activity was measured as verapamil-sensitive 3 H-digoxin flux. Pgp surface expression and exocytosis were measured by cell surface biotinylation studies. Signalling pathways were elucidated by Western blot analysis and pharmacological approaches.

RESULTS

Ang II (10 nM) significantly inhibited Pgp activity at 60 minutes. Ang II-mediated effects on Pgp function were receptor-mediated as the Ang II receptor 1 (ATR1) antagonist, losartan, blocked Pgp inhibition. Ang II effects on Pgp activity appeared to be mediated via PI3 kinase, p38 MAPK and Akt signalling. Ang II-mediated inhibition of Pgp activity was associated with a decrease in the surface membrane expression of Pgp protein via decreased exocytosis and was found to be dependent on the Akt pathway. Short-term treatment of Ang II (2 mg/kg b.wt., 2 hours) to mice also decreased the membrane expression of Pgp protein levels in ileum and colon.

CONCLUSION

Our findings provide novel insights into the role of Ang II and ATR1 in decreasing Pgp expression in intestinal inflammation.

CYP3A4 Activity is Markedly Lower in Patients with Crohn's Disease

BACKGROUND

Disease-dependent changes in the activity of drug metabolizing enzymes and transporters, such as Cytochrome P450 (CYP) 3A4 and P-glycoprotein (P-gp), are thought to have a major influence on the disposition of shared substrates. However, little is known regarding the in vivo relevance of these 2 proteins during drug therapy for gastrointestinal diseases. Our aim was to elucidate the activity of CYP3A4 and P-gp in subjects with Crohn's disease (CD) and to evaluate their influence on budesonide pharmacokinetics.

METHODS

A detailed pharmacokinetic assessment was conducted in 8 individuals diagnosed with CD on stable doses of oral budesonide, a putative shared CYP3A4, and P-gp substrate, where hepatic and intestinal CYP3A4 activity were also assessed using intravenous and oral midazolam. In addition, oral fexofenadine was used as an in vivo probe for P-gp activity.

RESULTS

Budesonide area under the curve was highly variable between subjects but similar to previously reported values in healthy subjects. The hepatic and intestinal extraction ratios for midazolam were 0.11 ± 0.06 and 0.64 ± 0.25, respectively; however, CYP3A4 activity was nearly 5-fold lower in our CD cohort compared with published data among healthy subjects. Multivariate regression revealed that only 25% budesonide clearance could be explained based on midazolam or fexofenadine clearance.

CONCLUSIONS

Midazolam and fexofenadine disposition profile did not predict budesonide clearance. However, we observed a marked reduction in vivo CYP3A4 activity among individuals with CD. Therefore, changes in CYP3A4 activity in disease states such as CD may be a heretofore underappreciated determinant of variation in drug responsiveness in CD.

Lactobacillus acidophilus stimulates intestinal P-glycoprotein expression via a c-Fos/c-Jun-dependent mechanism in intestinal epithelial cells

Our previous studies showed that Lactobacillus acidophilus (LA) culture supernatant (CS) increased P-glycoprotein [Pgp/multidrug resistance 1 (MDR1)] function, expression, and promoter activity in Caco-2 cells. The current studies were designed to elucidate the molecular mechanisms mediating the stimulatory effects of LA CS on Pgp promoter activity. Deletion analysis indicated that the LA CS response element(s) is located in the -172/+428-bp region, and sequence analysis of this region revealed three potential binding sites for c-Fos or c-Jun: proximal activating protein (AP) 1a (-119/-98 bp), distal AP1b (-99/-78 bp), and AP1c (+175/+196 bp). LA CS (24 h) showed an approximately twofold increase in the protein expression of c-Fos and c-Jun in Caco-2 cells. Electrophoretic mobility shift assay showed that LA CS markedly increased the binding of Caco-2 nuclear proteins to AP1a and AP1b, but not AP1c. The DNA-protein complex was completely eliminated by c-Fos antibody, while c-Jun antibody partially eliminated the complex. Chromatin immunoprecipitation analysis also showed that LA CS enhanced the association of c-Fos and c-Jun (by ∼4- and 1.5-fold, respectively) with endogenous Pgp promoter in Caco-2 cells (p-172/+1). Interestingly, overexpression of c-Fos or c-Jun activated Pgp promoter by nearly twofold each. This increase was further enhanced (∼14-fold) when c-Fos and c-Jun were simultaneously overexpressed, suggesting that the presence of one of these transcription factors potentiates the effect of the other. These studies, for the first time, provide evidence for the involvement of c-Fos/c-Jun in stimulation of Pgp gene expression by LA CS in the human intestine.

Downregulation of CYP3A and P-glycoprotein in the secondary inflammatory response of mice with dextran sulfate sodium-induced colitis and its contribution to cyclosporine A blood concentrations

CYP3A and P-glycoprotein (P-gp) play important roles in drug metabolism and excretion; however, their functions in pathological conditions remain unclear. Hepatobiliary abnormalities have been described in patients with ulcerative colitis, which may affect drug metabolism and excretion in the liver and small intestine. We examined the functions of CYP3A and P-gp in the liver and small intestine of mice with dextran sodium sulfate (DSS)-induced colitis. Up to day 7, inflammatory markers were significantly increased in the livers of DSS-treated mice, accompanied by decreased CYP3A. Additionally hepatobiliary transporters and Pregnane X receptor, which regulates the transcriptional activation of CYP3A, were reduced. Both CYP3A and P-gp were significantly decreased in the upper small intestine of DSS-treated mice on day 7. This was associated with the increased expression of inducible nitric oxide synthase, but not changes in nuclear receptor expression. On day 7 of DSS treatment, the concentrations of cyclosporine A (CsA), a substrate of both CYP3A and P-gp, were significantly higher than controls. These results indicated the existence of a second inflammatory response in the liver and upper small intestine of mice with DSS-induced colitis, and bioavailability of CsA was increased by the dysfunction of CYP3A and P-gp in these organs.

Keratinocyte growth factor-2 stimulates P-glycoprotein expression and function in intestinal epithelial cells

Intestinal P-glycoprotein (Pgp/multidrug resistance 1), encoded by the ATP-binding cassette B1 gene, is primarily involved in the transepithelial efflux of toxic metabolites and xenobiotics from the mucosa into the gut lumen. Reduced Pgp function and expression has been shown to be associated with intestinal inflammatory disorders. Keratinocyte growth factor-2 (KGF2) has emerged as a potential target for modulation of intestinal inflammation and maintenance of gut mucosal integrity. Whether KGF2 directly regulates Pgp in the human intestine is not known. Therefore, the present studies were undertaken to determine the modulation of Pgp by KGF2 using Caco-2 cells. Short-term treatment of Caco-2 cells with KGF2 (10 ng/ml, 1 h) increased Pgp activity (~2-fold, P < 0.05) as measured by verapamil-sensitive [(3)H]digoxin flux. This increase in Pgp function was associated with an increase in surface Pgp levels. The specific fibroblast growth factor receptor (FGFR) antagonist PD-161570 blocked the KGF2-mediated increase in Pgp activity. Inhibition of the mitogen-activated protein kinase (MAPK) pathway by PD-98059 attenuated the stimulatory effects of KGF2 on Pgp activity. Small-interfering RNA knockdown of Erk1/2 MAPK blocked the increase in surface Pgp levels by KGF2. Long-term treatment with KGF2 (10 ng/ml, 24 h) also significantly increased PgP activity, mRNA, protein expression, and promoter activity. The long-term effects of KGF2 on Pgp promoter activity were also blocked by the FGFR antagonist and mediated by the Erk1/2 MAPK pathway. In conclusion, our findings define the posttranslational and transcriptional mechanisms underlying stimulation of Pgp function and expression by KGF2 that may contribute to the beneficial effects of KGF2 in intestinal inflammatory disorders.

The effects of natural and modified clinoptilolite on intestinal barrier function and immune response to LPS in broiler chickens

The protection of intestinal barrier function and the anti-inflammatory effects of natural clinoptilolite (NCLI) and modified clinoptilolite (MCLI) were investigated in broilers that were repeatedly challenged with lipopolysaccharide (LPS). A total of 288 1-d-old broiler chicks were divided equally into three treatment groups: control, NCLI-treated (2%) and MCLI-treated (2%). Half of the birds from each treatment group were challenged with 0.9% NaCl solution or LPS (250μg/kg body weight, administered orally) at 16, 18 and 21d of age. The results indicated that, prior to LPS challenge, the diet had no effect on bird growth performance (P>0.05). The oral administration of LPS was also not associated with any significant changes in poultry performance (P>0.05). In LPS-challenged birds that were pretreated with NCLI (2%) or MCLI (2%), the LPS-induced increases in the plasma and intestinal mucosa concentrations of TNF-α, IL-1β, IL-2, IL-6, IL-4 and IL-10 were dramatically attenuated. Additionally, significant decreases in the plasma d-lactic acid and diamine oxidase (DAO) levels were found in birds that were pretreated with NCLI or MCLI. Furthermore, both NCLI and MCLI reduced the sICAM-1 concentration in the intestinal mucosa. In conclusion, NCLI and MCLI are able to prevent the LPS-induced intestinal mucosa damage and inflammatory response in vivo. These beneficial effects suggest that NCLI and MCLI act as anti-inflammatory agents in part by inhibiting neutrophil infiltration and hyperactivation and by suppressing the secretion of various plasma and intestinal mucosa inflammatory mediators.

P-glycoprotein expression in Helicobacter pylori-positive patients: the influence of MDR1 C3435T polymorphism

OBJECTIVE

The aim of this study was to determine whether the presence of Helicobacter pylori (H. pylori) infection and multidrug resistance protein 1 (MDR1) C3435T polymorphism had an influence on P-glycoprotein (P-gp) expression in the upper gastrointestinal tract.

METHODS

A total of 76 patients who underwent upper gastroendoscopy at Sir Charles Gairdner Hospital in Western Australia from October 2010 to July 2011 were enrolled in the study. Antral and duodenal biopsies were collected for P-gp examination. Blood samples were taken and analyzed for MDR1 C3435T polymorphism. H. pylori infection status was confirmed by culture and polymerase chain reaction.

RESULTS

A significant difference was found in P-gp expression between H. pylori-positive and H. pylori-negative patients (P = 0.028). For the MDR1 C3435T polymorphism, the TT genotype had a significantly lower P-gp expression compared with the CC genotype in antral specimens (P = 0.041). The homozygous TT genotype with H. pylori infection was also significantly different in P-gp expression compared with H. pylori-negative patients (P = 0.029).

CONCLUSIONS

P-gp expression in the upper gastrointestinal tract is associated with H. pylori infection, and the TT genotype appeared to be associated with lower P-gp expression than the CC genotype in the stomach.

P-glycoprotein induction by breast milk attenuates intestinal inflammation in experimental necrotizing enterocolitis

P-glycoprotein (Pgp), a product of the multi-drug resistance gene MDR1a, is a broad specificity efflux ATP cassette transmembrane transporter that is predominantly expressed in epithelial tissues. Because mdr1a(-/-) mice tend to develop spontaneous colitis in bacteria-dependent manner, Pgp is believed to have a role in protection of the intestinal epithelium from luminal bacteria. Here we demonstrate that levels of Pgp in the small intestine of newborn rodents dramatically increase during breastfeeding, but not during formula feeding (FF). In rats and mice, levels of intestinal Pgp peak on days 3-7 and 1-5 of breastfeeding, respectively. The mdr1a(-/-) neonatal mice subjected to FF, hypoxia, and hypothermia have significantly higher incidence and pathology, as well as significantly earlier onset of necrotizing enterocolitis (NEC) than congenic wild type mice. Breast-fed mdr1a(-/-) neonatal mice are also more susceptible to intestinal damage caused by the opportunistic pathogen Cronobacter sakazakii that has been associated with hospital outbreaks of NEC. Breast milk, but not formula, induces Pgp expression in enterocyte cell lines in a dose- and time-dependent manner. High levels of ectopically expressed Pgp protect epithelial cells in vitro from apoptosis induced by C. sakazakii. Taken together, these results show that breast milk-induced expression of Pgp may have a role in the protection of the neonatal intestinal epithelium from injury associated with nascent bacterial colonization.

Expression of P-glycoprotein in the intestinal epithelium of dogs with lymphoplasmacytic enteritis

Inflammatory bowel disease (IBD) is an idiopathic chronic inflammatory disease of the stomach, the small intestine and/or the large intestine. Loss of integrity of the intestinal barrier may be an important factor in the pathogenesis of IBD. In dogs, lymphoplasmacytic enteritis (LPE) is one of the recognized forms of IBD. P-glycoprotein (P-gp) is a membrane-bound efflux pump constituting an important component of the intestinal barrier. Changes in P-gp expression at the level of the intestinal barrier may be important in the pathogenesis of canine LPE, as this may lead to variable protection against xenobiotics and bacterial products in the intestine. The aim of the present study was to evaluate the expression of epithelial P-gp in the intestine in dogs with LPE compared with disease-free animals. Formalin-fixed intestinal biopsy samples from 57 dogs with histopathological evidence of LPE were immunolabelled with anti-P-gp antibodies (C494 and C219). Endoscopic biopsy samples of the duodenum and colon from 16 healthy beagles were used as controls. None of the control dogs had P-gp expression in the apical membrane of duodenal enterocytes, but all had P-gp labelling at the colonic epithelial surface. Twenty out of 57 dogs with LPE had P-gp expression at the apical surface membrane of villus epithelial cells in the duodenum, jejunum and/or ileum. Six out of 16 colonic samples from dogs with LPE had decreased P-gp expression at the epithelial surface compared with controls. It is unclear whether these changes in P-gp expression in dogs with LPE are a cause or a consequence of the inflammation. The observed changes could affect bioavailability of therapeutic drugs used in LPE.

Influence of MDR1 polymorphism on H. pylori-related chronic gastritis

BACKGROUND

There is evidence that changes in MDR1 function and/or expression contribute to the pathogenesis of inflammatory disorders of the gastrointestinal tract.

AIMS

We aimed to investigate the effect of C3435T polymorphism of the MDR1 gene on histological chronic gastritis, and on the risk of peptic ulcer diseases.

METHODS

Restriction fragment length polymorphism analysis was performed for polymorphisms at C3435T in the MDR1 gene in 556 cancer-free subjects including 116 gastric and 60 duodenal ulcers, and 380 non-ulcer subjects. Gastritis scores in the antrum were assessed according to the updated Sydney system in 384 subjects.

RESULTS

We did not find a significant association between MDR1 genotype and gastritis scores in any of the 384 subjects. However, the 3435T carrier was significantly associated with a higher degree of neutrophil infiltration in H. pylori-positive subjects (CC vs. T carrier: p=0.0495). When the H. pylori positive subjects were divided according to generation, the 3435T carrier was significantly associated with a higher degree of neutrophil infiltration in subjects more than 65 years of age (CC vs. T carrier: p=0.03). Also, the MDR1 3435 TT genotype was significantly associated with a higher degree of atrophy and intestinal metaplasia in the same generation (atrophy, TT vs. C carrier: p=0.038, intestinal metaplasia, TT vs. C carrier: p=0.016). No association was found between MDR1 genotypes and risk of peptic ulcer diseases.

CONCLUSIONS

It appears that the C3435T polymorphism of MDR1 influences H. pylori-related inflammatory conditions in the stomach, especially in older subjects.

Overexpression of translocator protein in inflammatory bowel disease: potential diagnostic and treatment value

BACKGROUND

Inflammatory bowel diseases (IBDs), such as ulcerative colitis and Crohn's disease, are chronic inflammatory disorders that increase the risk for colorectal cancer. The mitochondrial translocator protein (TSPO) is a high-affinity drug- and cholesterol-binding protein expressed in the colon and its expression is increased in colon cancers. The aim of this study was to investigate TSPO expression in IBD biopsies and to establish an animal model of IBD to examine the role of TSPO. In addition, we evaluated the potential use of TSPO drug ligands in diagnosing and treating IBD.

METHODS

TSPO expression in IBD biopsies was evaluated using immunohistochemistry. IBD was induced in a rat experimental model via treatment with dextran sodium sulfate (DSS). Colon morphology, TSPO expression, and proinflammatory cytokine production were evaluated in addition to the effect of TSPO drug ligands on disease pathology.

RESULTS

TSPO protein levels were elevated in the enterocytes of IBD biopsies. TSPO expression was localized to the enterocyte mitochondria. DSS treatment induced a time-dependent phenotype mimicking IBD with tissue injury and subsequent tissue regeneration. Coadministration of DSS and the TSPO drug ligands PK 11195 or Ro5-4864 increased both the rate of colon ulceration and regeneration, whereas administration of the TSPO drug ligand flunitrazepam partially prevented this pathology. These data correlated with changes in proinflammatory cytokine plasma levels, as well as increased cytokine production and secretion from the colon.

CONCLUSIONS

TSPO may serve as a marker of the IBD repair process, and TSPO drug ligands should be further evaluated for IBD treatment.

ABCB1: the role in Parkinson's disease and pharmacokinetics of antiparkinsonian drugs

ABCB1/P-glycoprotein (P-gp) is an ATP-dependant transmembrane efflux protein widely expressed in human organs and plays a protective role against endogenous and exogenous substances. It is involved in drug pharmacokinetics affecting drug absorption, disposition and elimination. At the BBB level, due to its luminal localisation, ABCB1 limits drug transport and is important in central detoxification. Inter-individual variability has been described in ABCB1 expression and functionality. Recent work suggests that variability may play a role in the pathogenesis of neurological diseases. Furthermore, ABCB1 expression and/or functionality may modify drug efficacy or increase central adverse events. This paper reviews ABCB1 implication in the pathophysiology of Parkinson's disease and its role in the cerebral distribution of drugs.

Pharmacology of morphine in obese patients: clinical implications

Morphine is an analgesic drug used to treat acute and chronic pain. Obesity is frequently associated with pain of various origins (e.g. arthritis, fibromyalgia, cancer), which increases the need for analgesic drugs. Obesity changes drug pharmacokinetics, and for certain drugs, specific modalities of prescription have been proposed for obese patients. However, scant data are available regarding the pharmacokinetics and pharmacodynamics of morphine in obesity. Prescription of morphine depends on pain relief but the occurrence of respiratory adverse effects correlates with obesity, and is not currently taken into account. Variations in the volume of distribution, elimination half-life and oral clearance of morphine, as well as recent advances in the respective roles of drug-metabolizing enzymes, catechol-O-methyltransferase and the mu opioid receptor in morphine pharmacokinetics and pharmacodynamics, may contribute to differences between obese and non-obese patients. In addition, drug-drug interactions may alter the disposition of morphine and its glucuronide metabolites, which may either increase the risk of adverse effects or reduce drug efficacy.

Differential susceptibility of P-glycoprotein deficient mice to colitis induction by environmental insults

BACKGROUND

P-glycoprotein (P-gp), the product of the multidrug resistance gene (MDR), is an ATP-dependent transmembrane pump, which is expressed in multiple cell lineages including epithelial and hematopoetic cells. The human MDR gene is located on chromosome 7 (7q21.1), a susceptibility loci for inflammatory bowel disease (IBD). A significant number of IBD patients carry mutations in this gene and P-gp-deficient FVB/N mice develop a severe spontaneous colitis, characterized by impaired intestinal barrier function and immune reactivity to intestinal bacterial antigens.

METHODS

In this work we explored the role of mouse strain, as well as environmental insults, on the development of colonic inflammation in the absence of P-gp. Among the induction methods utilized, dextran sodium sulfate (DSS) disrupts the intestinal epithelium, while piroxicam is a nonsteroidal antiinflammatory (NSAID) drug that inhibits prostaglandin production and initiates colitis in IL10-deficient animals. Helicobacter bilis is a known mediator of bacterial-induced colitis.

RESULTS

We demonstrate that crossing this mutation onto the C57BL/6 strain confers protection from spontaneous colitis. C57BL/6.mdr1a-deficient animals demonstrated increased histological inflammation, colonic shortening, fecal blood, and reduced body weight after 7 days of treatment with 2.25% DSS. C57BL/6.mdr1a-deficient mice treated with piroxicam or infected with H. bilis showed no weight loss, or alterations in colonic histology.

CONCLUSIONS

These data indicate that the effects of P-gp deficiency are significantly modulated by background strain influences, but that the epithelium continues to have increased susceptibility to chemical injury in the C57BL/6 model.

Regulation of the oligopeptide transporter, PEPT-1, in DSS-induced rat colitis

The effect of colitis induced with dextran sodium sulfate (DSS) in rats on the bioavailability of drugs transported by the oligopeptide transporter PepT-1 was analyzed by studying the pharmacokinetics of PepT-1 substrates: cephalexin and valacyclovir, the prodrug of antiviral acyclovir. Western blot, immunohistochemistry, and real-time PCR were used to determine the PepT-1 protein and gene expression. We observed (1) no significant modification of PepT-1 expression in the duodenum and jejunum; (2) a slight decrease in both PepT-1 mRNA (50%) and protein expression (25%) in the ileum following DSS challenge; and (3) ectopic PepT-1 immunostaining in regenerative hyperplasia segments in the distal colon from DSS-treated rats where focal inflammation is localized. However, no modification of pharmacokinetic parameters (C (max), T (max), AUC) of cephalexin or acyclovir was detected. In conclusion, DSS-induced rat colitis did not alter PepT-1 substrate bioavailability despite certain modifications in PepT-1 expression profile.

Decreased P-glycoprotein (P-gp/MDR1) expression in inflamed human intestinal epithelium is independent of PXR protein levels

BACKGROUND

Altered P-glycoprotein expression (P-gp/MDR1) and/or function may contribute to the pathogenesis of gastrointestinal inflammatory disorders. Low intestinal mRNA levels of the pregnane X receptor (PXR) have been linked to low MDR1 mRNA levels in patients with ulcerative colitis (UC). Here we compared intestinal MDR1 mRNA and protein expression in uninflamed and inflamed intestinal epithelium (IE) of patients with gastrointestinal inflammatory disorders to healthy controls.

METHODS

Intestinal mucosal biopsies were obtained from patients with Crohn's disease (CD, n = 20), UC (n = 10), diverticulitis (n = 3), collagenous colitis (n = 3), and healthy controls (n = 10). MDR1, iNOS, MRP1, CYP3A4, and PXR expression was determined using real-time reverse-transcriptase polymerase chain reaction (RT-PCR), Western blotting, and/or immunohistochemistry. Furthermore, MDR1 expression was determined in human intestinal biopsies and the human colon carcinoma cell line DLD-1 after exposure to cytokines (TNF-alpha, IFN-gamma, and/or IL-1beta).

RESULTS

MDR1 mRNA levels in uninflamed colon of UC patients were comparable to healthy controls, while they were slightly decreased in ileum and slightly increased in colon of CD patients. MDR1 expression, however, was strongly decreased in inflamed IE of CD, UC, collagenous colitis, and diverticulitis patients. A cytokine-dependent decrease of MDR1 expression was observed in human intestinal biopsies, but not in DLD-1 cells. Remarkably, PXR protein levels were equal in uninflamed and inflamed tissue of CD and UC patients despite low PXR mRNA levels in inflamed tissue.

CONCLUSIONS

MDR1 expression is strongly decreased in inflamed IE of patients with gastrointestinal disorders and this is independent of PXR protein levels. Low MDR1 levels may aggravate intestinal inflammation.

Effects of lipopolysaccharide on intestinal P-glycoprotein expression and activity

It is well known that pharmacokinetics is often altered by changing the expression and activity of P-glycoprotein during sepsis. However, there have been few reports about expression and activity of P-glycoprotein in the small intestine during sepsis. We examined the levels of intestinal P-glycoprotein expression and activity using a rat sepsis model induced by lipopolysaccharide (LPS, from Escherichia coli). LPS was administered to male Wistar/ST rats intraperitonealy (i.p.) at 5 mg/kg. The small intestine was excised before and 1, 3 and 7 days after LPS administration, and the intestinal P-glycoprotein expression was determined using Western blot analysis. The activity of P-glycoprotein was evaluated by measuring the efflux of rhodamine-123 (Rho123) in rats using an in situ single perfusion method. The changes of permeability via the paracellular route were evaluated by measuring the amount of fluorescein isothicyanate-dextran 4400 (FD-4) in a similar way. On Day 1 after LPS administration, both the level of P-glycoprotein expression and the total amount of Rho123 excreted into the intestinal lumen decreased significantly, but levels of both AUC2-95 and CLtot were not significantly different as compared with the control group. On Day 3, the total P-glycoprotein, including intestinal P-glycoprotein, might have been induced by sepsis, and then the excretion of P-glycoprotein substrate drugs into the intestinal lumen increased more than that of the control group. On Day 7, all pharmacokinetic parameters returned to the control level. Thus the intestinal P-glycoprotein function recovered within 3 days of LPS administration.

ABCB1 genotype and PGP expression, function and therapeutic drug response: a critical review and recommendations for future research

The product of the ABCB1 gene, P-glycoprotein (PGP), is a transmembrane active efflux pump for a variety of drugs. It is a putative mechanism of multidrug resistance in a range of diseases. It is postulated that ABCB1 polymorphisms contribute to variability in PGP function, and that therefore multidrug resistance is, at least in part, genetically determined. However, studies of ABCB1 genotype or haplotype and PGP expression, activity or drug response have produced inconsistent results. This critical review of ABCB1 genotype and PGP function, including mRNA expression, PGP-substrate drug pharmacokinetics and drug response, highlights methodological limitations of existing studies, including inadequate power, potential confounding by co-morbidity and co-medication, multiple testing, poor definition of disease phenotype and outcomes, and analysis of multiple drugs that might not be PGP substrates. We have produced recommendations for future research that will aid clarification of the association between ABCB1 genotypes and factors related to PGP activity.

Involvement of the multidrug resistance transporters in cisplatin-induced neuropathy in rats. Comparison with the chronic constriction injury model and monoarthritic rats

It has recently been suggested that P-glycoprotein is involved in the genesis and the treatment of the neurotoxic adverse events of anticancer drugs, including vincristine. A lower activity of P-glycoprotein in the peripheral nervous system (PNS) than in the central nervous system could contribute to the neurotoxicity of vincristine. Vincristine treatment is responsible for the induction of multidrug resistance (MDR) gene expression and transporter activity, with deleterious consequences, including a potential decrease in the efficiency of opioid analgesics, antidepressants or antiepileptics. Concerning cisplatin, which is also a strong neurotoxic drug but only an multidrug resistance protein 2 (MRP2) substrate, the same assumption could be suggested for MRP2 nervous function. The aim of this study was to assess MDR gene and protein activity in a rat model of cisplatin-induced neuropathy compared with different peripheral nerve injury models, i.e. mononeuropathy and inflammatory pain (monoarthritis). First, in cisplatin-induced neuropathy, this study demonstrated low MRP2 gene expression in dorsal root ganglia compared with the brain and spinal cord, which could contribute to the strong neurotoxicity of cisplatin in the PNS and particularly the dorsal root ganglia. Thus, gene expression increased in cisplatin-induced neuropathy but decreased in mononeuropathy and remained unchanged in monoarthritis models. Transporter activity of nervous tissues increased in the cisplatin-induced neuropathy, mononeuropathy and monoarthritis to different intensities (3.7-, 1.8- and 1.8-fold, respectively). The development of a MDR in the cisplatin-induced neuropathy is a striking difference with mononeuropathy and monoarthritis models, and characterizes the neuropathies induced by this anticancer drug.

Regional levels of drug transporters along the human intestinal tract: co-expression of ABC and SLC transporters and comparison with Caco-2 cells

A vast number of drugs are subjected to active or facilitated transport and multiple transport mechanism may contribute to the net flux during drug absorption. The main objective of this study was to quantify the regional mRNA expression and determine the co-expression of drug transporters from the ABC (Pgp, BCRP, MRP2, MRP3) and SLC (PEPT1, MCT1, OATPB, OCTN2, OCT1) families along the human intestine (duodenum, jejunum, ileum, and colon). A second objective was to compare the transporter expression between the different intestinal regions and Caco-2 cells. Eight out of nine of the investigated transporters exhibited significant regional differences in expression. OATPB was the only transporter that did not show a region-dependency in the expression along the human intestinal canal. The expression of Pgp, BCRP, OCTN2 and MCT1 differed along the small intestine, but the expression differences were greater than five-fold only for Pgp. The rank order of transcript prevalence was identical in the ileum and the jejunum. Between the ileum and colon, seven transcripts were differentially expressed, and MCT1, OCTN2 and MRP3 were expressed at higher levels in the colon than in the small intestine. The expression of transporters in Caco-2 was closest to the expression pattern in the small intestine, although the expression of OATPB, BCRP and MRP2 differed more than five-fold between the Caco-2 cells and ileum. In conclusion, this study provides quantitative data on the expression of transporters from the ABC and SLC families along the human intestine, which can be useful in the interpretation of clinical studies where more than one intestinal transporter contribute to the net transport and in the computer modelling of drug absorption.