Decreased drug penetration in inflamed tissue related to changed mucosal metabolism in experimental colitis

Protein expression analysis of inflammation-related colon carcinogenesis

Background:

Chronic inflammation is a risk factor for colorectal cancer (CRC) development. The aim of this study was to determine the differences in protein expression between CRC and the surrounding nontumorous colonic tissues in the mice that received azoxymethane (AOM) and dextran sodium sulfate (DSS) using a proteomic analysis.

Materials and Methods:

Male ICR mice were given a single intraperitoneal injection of AOM (10 mg/kg body weight), followed by 2% (w/v) DSS in their drinking water for seven days, starting one week after the AOM injection. Colonic adenocarcinoma developed after 20 weeks and a proteomics analysis based on two-dimensional gel electrophoresis and ultraflex TOF/TOF mass spectrometry was conducted in the cancerous and nontumorous tissue specimens.

Results:

The proteomic analysis revealed 21 differentially expressed proteins in the cancerous tissues in comparison to the nontumorous tissues. There were five markedly increased proteins (beta-tropomyosin, tropomyosin 1 alpha isoform b, S100 calcium binding protein A9, and an unknown protein) and 16 markedly decreased proteins (Car1 proteins, selenium-binding protein 1, HMG-CoA synthase, thioredoxin 1, 1 Cys peroxiredoxin protein 2, Fcgbp protein, Cytochrome c oxidase, subunit Va, ETHE1 protein, and 7 unknown proteins).

Conclusions:

There were 21 differentially expressed proteins in the cancerous tissues of the mice that received AOM and DSS. Their functions include metabolism, the antioxidant system, oxidative stress, mucin production, and inflammation. These findings may provide new insights into the mechanisms of inflammation-related colon carcinogenesis and the establishment of novel therapies and preventative strategies to treat carcinogenesis in the inflamed colon.

Cyclooxygenase-2 inhibitors prevent trinitrobenzene sulfonic acid-induced P-glycoprotein up-regulation in vitro and in vivo

Failed medical therapy is a common problem in inflammatory bowel disease. P-glycoprotein (P-gp), an efflux pump encoded by MDR1 (ABCB1) gene can actively pump drugs out of cells conferring the phenotype of multidrug resistance. Various studies evoked that cyclooxygenase (COX) system may be involved in the regulation of P-gp activity. Since COX-2 isoform is overexpressed in colic inflammatory states, we examined the inhibitory effect of COX-2-inhibitors on P-gp expression and function under COX-2 stimulated conditions mediated by trinitrobenzene sulfonic acid (TNBS) in vitro, in Caco-2 cells, and in TNBS-induced colitis in mice. COX-2 and P-gp expressions were evaluated by real-time PCR and western blot. The activity of P-gp was measured by intracellular accumulation of rhodamine123 (Rho123) in Caco-2 cells and by Rho123 efflux using the intestinal everted loop method in mice. We showed that COX-2 stimulation in Caco-2 cells by 0.1mM TNBS exposure for 24h induced P-gp protein expression and activity. This activation was reversed by simultaneous COX-2-inhibitor treatment. Moreover, this effect was reproduced in vivo, in mice, where an increased P-gp expression and activity were observed 24h post intra-rectal TNBS administration. Induced P-gp expression and activity could be blocked by the oral pre-treatment with indomethacin heptyl ester (IHE) (20mg/kg). Administration of indomethacin heptyl ester had also a protective effect in TNBS-induced colitis. Our observations suggest that the inhibition of P-gp by COX-2-inhibitors could contribute to the improvement of medical response and this finding may have relevance to medical treatment of inflammatory bowel disease patients.

Colonic treatments and targets: issues and opportunities

The colon provides a plethora of therapeutic opportunities. There are multiple disease targets, drug molecules, and colon-specific delivery systems to be explored. Clinical studies highlight the potential for systemic delivery via the colon, and the emerging data on the levels of cell membrane transporters and metabolic enzymes along the gut could prove advantageous for this. Often efflux transporters and metabolic enzyme levels are lower in the colon, suggesting a potential for improved bioavailability of drug substrates at this site. The locoregional distribution of multiple metabolic enzymes (including cytochromes), efflux transporters (including P-glycoprotein and breast cancer resistance proteins), and influx transporters (including the solute carrier family) along the intestine is summarized. Local delivery to the colonic mucosa remains a valuable therapeutic option. New therapies that target inflammatory mediators could improve the treatment of inflammatory bowel disease, and old and new anticancer molecules could, when delivered topically, prove to be beneficial adjuncts to the current systemic or surgical treatments. New issues such as pharmacogenomics, chronotherapeutics, and the delivery of prebiotics and probiotics are also discussed in this review. Targeting drugs to the colon utilizes various strategies, each with their advantages and flaws. The most promising systems are considered in the light of the physiological data which influence their in vivo behavior.