The effect of a selective 5-lipoxygenase inhibitor, zileuton, on tissue damage in acute colonic inflammation in rats

Evaluation of mucosal immune profile associated with Zileuton nanocrystal-formulated BCS-II drug upon oral administration in Sprague Dawley rats

Nanocrystal drug formulation involves several critical manufacturing procedures that result in complex structures to improve drug solubility, dissolution, bioavailability, and consequently the efficacy of poorly soluble Biopharmaceutics Classification System (BCS) II and IV drugs. Nanocrystal formulation of an already approved oral drug may need additional immunotoxic assessment due to changes in the physical properties of the active pharmaceutical ingredient (API). In this study, we selected Zileuton, an FDA-approved drug that belongs to BCS-II for nanocrystal formulation. To evaluate the efficacy and mucosal immune profile of the nanocrystal drug, 10-week-old rats were dosed using capsules containing either API alone or nanocrystal formulated Zileuton (NDZ), or with a physical mixture (PM) using flexible oral gavage syringes. Control groups consisted of untreated, or placebo treated animals. Test formulations were administrated to rats at a dose of 30 mg/kg body weight (bw) once a day for 15 days. The rats treated with NDZ or PM had approximately 4.0 times lower (7.5 mg/kg bw) API when compared to the micron sized API treated rats. At the end of treatment, mucosal (intestinal tissue) and circulating cytokines were measured. The immunological response revealed that NDZ decreased several proinflammatory cytokines in the ileal mucosa (Interleukin-18, Tumor necrosis Factor-α and RANTES [regulated upon activation, normal T cell expressed and secreted]). A similar pattern in the cytokine profile was also observed for the micron sized API and PM treated rats. The cytokine production revealed that there was a significant increase in the production of IL-1β and IL-10 in the females in all experimental groups. Additionally, NDZ showed an immunosuppressive effect on proinflammatory cytokines both locally and systemically, which was similar to the response in micron sized API treated rats. These findings indicate that NDZ significantly decreased several proinflammatory cytokines and it displays less immunotoxicity, probably due to the nanocrystal formulation. Thus, the nanocrystal formulation is more suitable for oral drug delivery, as it exhibited better efficacy, safety, and reduced toxicity.

Attenuation of inflammation and cytokine production in rat colitis by a novel selective inhibitor of leukotriene A4 hydrolase

BACKGROUND AND PURPOSE

Leukotriene B(4) (LTB(4)), formed by the sequential actions of the 5-lipoxygenase (5-LO) and leukotriene A(4) hydrolase (LTA(4)H), is a pro-inflammatory mediator implicated in the pathogenesis of inflammatory bowel disease. However, inhibitors of 5-LO have not proved to be consistent in their therapeutic efficacy in colitis. Another approach to inhibiting LTB(4) synthesis is through the use of inhibitors of LTA(4)H, such as the novel, potent and selective compound, JNJ 26993135.

EXPERIMENTAL APPROACH

The effect of oral administration of JNJ 26993135 has been evaluated in a rat model of colitis provoked by colonic instillation of trinitrobenzenesulphonic acid (TNBS). The extent and severity of the macroscopic inflammatory response, the colonic levels of myeloperoxidase (MPO) and LTB(4) and of the pro-inflammatory cytokines, tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) were measured.

KEY RESULTS

Oral administration of JNJ 26993135 (5, 15 and 30 mg kg(-1), twice a day) dose-dependently reduced both the extent and intensity of the colonic inflammatory damage observed 3 days after TNBS challenge. JNJ 26993135 also dose-dependently reduced the elevated colonic levels of LTB(4), as well as the inflammatory biomarkers, MPO, IL-6 and TNF-alpha. This dosing regimen was supported by the pharmacokinetic profile of JNJ 26993135, along with the demonstration of the inhibition of ex vivo production of LTB(4) in whole blood following oral administration.

CONCLUSIONS AND IMPLICATIONS

These results with JNJ 26993135 in the rat TNBS model support the role of LTB(4) in colitis and the potential value of targeting LTA(4)H for the treatment of inflammatory bowel diseases.

Is administration of n-3 fatty acids by mucosal enema protective against trinitrobenzene-induced colitis in rats?

We investigated the protective role of fish oil (FO-source of n-3 FA) enriched diet (in the first protocol) in 20 rats and FO administration intrarectally (in the second protocol) in 40 rats with trinitrobenzene (TNB) colitis. All colonic specimens were pathologically evaluated, myeloperoxidase enzyme activities were measured, leukotriene B4 (LTB4) and LTC4 levels were determined by radioimmunoassay. In the first protocol 10 rats (group A1) were fed with 8% sunflower and cotton oil enriched diet and (group A2) with 8% FO enriched diet for 6 weeks. At the end of this period, TNB (30 mg in 0.25 ml of 30% ethanol) were intrarectally administered. After 2 weeks, rats were sacrificed. MPO activities (2.47 versus 30.17), LTB4 (34.5 versus 903.3) and LTC4 (77.7 versus 456.0) levels were significantly reduced in group A2 compared with group A1 (P<0.005). There was also a significant difference in pathologic scores (1.55 versus 2.12, P<0.002) between two groups. In the first part of the second protocol, 20 male rats were randomized into two equal groups (B1 and B2) and TNB colitis was induced. After 1 day, 1 ml of saline (group B1) or n-3 FA enemas (group B2) were administered every day for 2 weeks. At the end of this period, rats were sacrificed and evaluated as done for previous groups. Although there was no significant difference between the two groups in comparison with MPO enzyme activities and pathologic scores, the LTB4 (130.1 versus 971.0) and LTC4 (126.0 versus 532.0) levels of FO group were significantly reduced (P<0.005). In the second part of the second protocol, 20 male rats were randomized into two groups. One millilitre of saline (group B3) or FO enemas (group B4) were administered to rats every day for 3 days. At the fourth day, TNB-colitis was induced and after 24 h rats were sacrificed. We could not find any significant difference in MPO activities, pathologic scores, LTB4 and LTC4 levels between groups B3 and B4. In conclusion, FO enriched diet decreased both pathologic damage and tissue LT levels. The second protocol of our study revealed that the long-term FO enemas decreased the LTB4 and LTC4 levels; however, did not have any beneficial effect on the tissue lesions. Short periods of FO enemas did not have a protective role in the occurrence of experimental colitis. The present study showed that FO enemas significantly decreased LT levels. The protective effect of FO (oral and enema) in TNB colitis may open a new insight into the treatment of inflammatory bowel disease.

Differential effects of inhibitors of cyclooxygenase (cyclooxygenase 1 and cyclooxygenase 2) in acute inflammation

The anti-inflammatory activity of drugs more selective for cyclooxgenase isoform inhibition (cyclooxygenase 1, cyclooxygenase 2), were compared in rat carrageenin-induced pleurisy. Suppression of inflammation by cyclooxygenase 2-selective inhibitors, NS-398 (N-[-2-cyclohexyloxy]-4-nitrophenyl methanesulphonamide) and nimesulide (4-nitro-2-phenoxy-methanesulfonanilide), and by piroxicam and aspirin, more selective for cyclooxygenase 1, was measured. Piroxicam and aspirin significantly inhibited inflammatory cell influx, exudate and prostaglandin E2 formation, 6 h after carrageenin injection. Cyclooxygenase 2 inhibitors had little effect on these parameters with NS-398 alone reducing prostaglandin E2 levels, but increasing levels of leukotriene B4. In contrast, at 3 h after carrageenin injection, cyclooxygenase 2 inhibitors significantly inhibited all inflammatory parameters however suppression with piroxicam and aspirin was greater, and more pronounced than at 6 h. NS-398 and nimesulide dosing did not reduce thromboxane B2 production from platelets isolated from rats with carrageenin-induced pleurisy, demonstrating that at the doses used, cyclooxygenase 2 inhibitors did not inhibit cyclooxygenase 1, as platelets contain only this isoform. Therefore, in the rat carrageenin-induced pleurisy, drugs more selective for the inhibition of cyclooxygenase 1 attenuate inflammation over a wider time frame than cyclooxygenase 2-selective drugs, suggesting a significant role for cyclooxygenase 1 in this model. Inhibition of cyclooxygenase 2 by NS-398 however, resulted in an increase in the potent chemoattractant leukotriene B4.