A novel drug interaction between the quinolone antibiotic ciprofloxacin and a chiral metabolite of pentoxifylline.

Pentoxifylline (PTX), a methylxanthine derivative, is metabolized to seven compounds in vivo, with metabolites 1 and 5 possessing biologic activity. Metabolite-1 is a chiral molecule and its S-enantiomer is selectively formed during PTX metabolism in vivo. We have developed a reproducible method of synthesizing a racemic mixture of the chiral metabolite-1 (M-1) of PTX. In this study, we examined the kinetics of racemic M-1 in mice compared to PTX. An interaction between PTX and the quinolone antibiotic ciprofloxacin has been demonstrated. A goal of this study was to determine if a similar interaction occurs between ciprofloxacin and M-1 in vivo. M-1 and PTX had similar absorption and elimination rates. M-1 was rapidly converted to PTX, while very little PTX was converted to M-1 in vivo. The peak concentration of biologically active drug (PTX+M-1) was 36% higher when M-1 was administered compared to PTX. Combination of ciprofloxacin and PTX significantly increased serum concentrations of both PTX and M-1 (2-fold) compared to controls. The combination of M-1 and ciprofloxacin significantly increased serum concentration of M-1 (3-fold) and PTX (2-fold). The ciprofloxacin/M-1 combination produced a significantly higher sera concentration of bioactive drug compared to all other groups suggesting that this combination may enhance the anti-fibrogenic effect.

Cytokines as therapeutic targets for the gastrointestinal manifestations of scleroderma.

Systemic sclerosis (SSc), or scleroderma, is a connective tissue disorder characterized by progressive fibrosis of the skin and internal organs. It has significance for gastroenterologists because the gastrointestinal tract is involved in 90% of SSc patients, who often present with esophageal dysfunction. Though the exact pathogenesis of SSc is unknown, there is increasing evidence supporting an immune mechanism. Cytokines are the soluble mediators of immune activation, altered fibroblast proliferation and extracellular matrix accumulation in SSc and thereby provide important therapeutic targets. In the present review, the involvement of cytokines in SSc is discussed with particular emphasis on cytokines and growth factors that have been implicated in the disease process and likely play an important role in the gastrointestinal manifestations of scleroderma. The role of cytokines as therapeutic targets in scleroderma forms the basis of this timely review.

The effect of pentoxifylline and its metabolite-1 on inflammation and fibrosis in the TNBS model of colitis.

TNBS-induced colitis has characteristics resembling human Crohn's disease including transmural inflammation, ulceration, and fibrosis. Current treatments target acute symptoms but do not necessarily prevent fibrotic complications of the disease. The aim of this study was to determine the effect of pentoxifylline and its primary metabolite (M-1) on fibrosis in the TNBS-induced colitis model. Myeloperoxidase activity and interleukin-18 are indicators of inflammation and were elevated in the TNBS model. The morphology damage score assesses colon damage and was also elevated in the TNBS model. Collagen as the indicator of fibrosis was quantified and visualized by the Sirius Red/Fast Green staining technique and collagen type I was assessed by Western analysis. Collagen was elevated in the TNBS-induced model. Pentoxifylline and M-1 treatment significantly attenuated colon damage and inflammation in TNBS-colitis (P<0.05). M-1 treatment significantly reduced the TNBS-induced increase in colon weight, colon thickness and total collagen content (P<0.05). Results suggest that pentoxifylline and M-1 inhibit intestinal fibrosis in this experimental model and may prove beneficial in the treatment of intestinal fibrosis associated with human Crohn's disease with the added benefit of inhibiting inflammation and ulceration. This is the first study to examine the effects of racemic M-1 in vivo and one of the few studies to examine the effect of drugs on both inflammation and fibrosis in an experimental model of colitis.

Retention of transporter activities in cryopreserved, isolated rat hepatocytes.

The success of cryopreservation of isolated hepatocytes with existing methodologies is assessed with respect to the retentivity of cell integrity/viability (defined by trypan blue) and metabolic activities upon thawing in comparison to those of freshly prepared cells. But the ability of the cryopreserved cells to transport xenobiotics relative to that of freshly prepared cells has not been investigated. In this study, we optimized our previous methodology for cryopreservation and evaluated the metabolism and transport of thawed hepatocytes. Half of the freshly, isolated rat hepatocytes prepared by collagenase perfusion were immediately used for studies of transport of [(14)C]taurocholate, [(3)H]estrone sulfate and [(3)H]estradiol 17beta-D-glucuronide (1 microM) and metabolism of 7-hydroxy-4-(trifluoromethyl)-coumarin (100 microM), (3,4-difluorobenzyloxy)-5,5-dimethyl-4-(4-methylsulfonylphenyl)-(5H)-furan-2-one (250 microM), bufuralol (100 microM), and tolbutamide (100 microM), probes for UDP-glucuronyl transferase (UGT) and CYP3A, CYP2D, and CYP2C, respectively. The remaining half was cryopreserved using an optimized, programmed-freezing protocol, which was developed to minimize the prolonged release of latent heat during freezing. With the exception of the UGT probe, no significant difference (P > 0.05) was found in both metabolism and transport with freshly isolated versus cryopreserved hepatocytes upon thawing. In conclusion, we have demonstrated for the first time that thawed rat hepatocytes cryopreserved by a programmed-freezing protocol retain drug transport activities.